U.S. patent application number 12/667016 was filed with the patent office on 2010-07-15 for refrigeration apparatus.
Invention is credited to Shinichi Kasahara.
Application Number | 20100175400 12/667016 |
Document ID | / |
Family ID | 40225828 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100175400 |
Kind Code |
A1 |
Kasahara; Shinichi |
July 15, 2010 |
REFRIGERATION APPARATUS
Abstract
The present disclosure allows for easy settling of control of
capability of an refrigeration apparatus for performing a
supercritical refrigeration cycle. An air conditioner (10)
includes: a refrigerant circuit (20) sequentially connecting a
compressor (21), an outdoor heat exchanger (23), an outdoor
expansion valve (24), and an indoor heat exchanger (27), and
performing a supercritical refrigeration cycle in which a high
pressure is a supercritical pressure or higher; and a controller
(40) for controlling a plurality of objects of control including at
least the compressor (21) and the outdoor expansion valve (24). The
controller (40) concurrently controls the plurality of objects of
control, thereby concurrently controlling a predetermined physical
value as an index of an ability of the refrigeration apparatus, and
the high pressure of the refrigeration cycle.
Inventors: |
Kasahara; Shinichi; (Osaka,
JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
40225828 |
Appl. No.: |
12/667016 |
Filed: |
June 11, 2008 |
PCT Filed: |
June 11, 2008 |
PCT NO: |
PCT/JP2008/001493 |
371 Date: |
December 28, 2009 |
Current U.S.
Class: |
62/225 ; 62/426;
62/510; 62/513 |
Current CPC
Class: |
F25B 9/008 20130101;
F25B 1/10 20130101; F25B 2313/02741 20130101; F25B 2700/1931
20130101; F25B 2700/2102 20130101; F25B 2313/005 20130101; F25B
2313/0272 20130101; F25B 2309/061 20130101; F25B 2313/0315
20130101; F25B 2400/23 20130101; F25B 41/39 20210101; F25B
2700/1933 20130101; F25B 2600/17 20130101; F25B 49/02 20130101;
F25B 2400/13 20130101; F25B 2600/21 20130101; F25B 2700/2106
20130101; F25B 2600/2513 20130101; F25B 2700/21174 20130101; F25B
2313/0314 20130101; F25B 13/00 20130101; F25B 49/027 20130101; F25B
2700/21152 20130101; F25B 2313/0233 20130101 |
Class at
Publication: |
62/225 ; 62/510;
62/513; 62/426 |
International
Class: |
F25B 41/04 20060101
F25B041/04; F25B 1/10 20060101 F25B001/10; F25B 41/00 20060101
F25B041/00; F25D 17/06 20060101 F25D017/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2007 |
JP |
2007-173372 |
Claims
1. A refrigeration apparatus comprising: a refrigerant circuit (20)
sequentially connecting a compression mechanism (21), a heat source
side heat exchanger (23), an expansion mechanism (24), and a
utilization side heat exchanger (27), and performing a
supercritical refrigeration cycle in which a high pressure is a
supercritical pressure of a refrigerant or higher; and a control
section (40) for controlling a plurality of objects of control
including at least the compression mechanism (21) and the expansion
mechanism (24), wherein the control section (40) concurrently
controls the plurality of objects of control, thereby concurrently
controlling a predetermined physical value as an index of a
capability of the refrigeration apparatus, and the high pressure of
the refrigeration cycle.
2. The refrigeration apparatus of claim 1, wherein the control
section (40) receives the predetermined physical value, and the
high pressure of the refrigeration cycle as inputs, generates
control signals each corresponding to the plurality of objects of
control by associating the physical value and the high pressure
with each other, and outputs the control signals to the
corresponding objects of control, respectively, thereby
concurrently controlling the predetermined physical value, and the
high pressure of the refrigeration cycle.
3. The refrigeration apparatus of claim 1, further comprising: a
heat source side fan (28) for feeding air to the heat source side
heat exchanger (23) in which the refrigerant exchanges heat with
the air, wherein in cooling operation, the predetermined physical
value includes, an evaporating temperature of the refrigerant in
the utilization side heat exchanger (27), and a degree of superheat
of the refrigerant at an outlet of the utilization side heat
exchanger (27), the objects of control further include the heat
source side fan (28), and the control section (40) receives the
evaporating temperature of the refrigerant, the degree of superheat
of the refrigerant, and the high pressure of the refrigeration
cycle as inputs, and concurrently controls the compression
mechanism (21), the expansion mechanism (24), and the heat source
side fan (28), thereby concurrently controlling the evaporating
temperature of the refrigerant, the degree of superheat of the
refrigerant, and the high pressure of the refrigeration cycle.
4. The refrigeration apparatus of claim 1, wherein in heating
operation, the predetermined physical value includes a degree of
superheat of the refrigerant at an outlet of the heat source side
heat exchanger (23), and the control section (40) receives the
degree of superheat of the refrigerant, and the high pressure of
the refrigeration cycle as inputs, and concurrently controls the
compression mechanism (21) and the expansion mechanism (24),
thereby concurrently controlling the degree of superheat of the
refrigerant, and the high pressure of the refrigeration cycle.
5. The refrigeration apparatus of claim 1, wherein the compression
mechanism includes a first compressor (21a) for sucking and
compressing a low pressure refrigerant, and a second compressor
(21b) for further compressing and discharging the refrigerant
discharged from the first compressor (21a), the expansion mechanism
includes a first expansion mechanism (24) for expanding a high
pressure refrigerant, and a second expansion mechanism (26) for
further expanding the refrigerant expanded to an intermediate
pressure refrigerant in the first expansion mechanism (24), in
cooling operation, the predetermined physical value includes an
evaporating temperature of the refrigerant in the utilization side
heat exchanger (27), a degree of superheat of the refrigerant at an
outlet of the utilization side heat exchanger (27), and an
intermediate pressure of the refrigeration cycle, and the control
section (240) receives the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, the
intermediate pressure of the refrigeration cycle, and the high
pressure of the refrigeration cycle as inputs, and concurrently
controls the first and second compressors (21a, 21b), and the first
and second expansion mechanisms (24, 26), thereby concurrently
controlling the evaporating temperature of the refrigerant, the
degree of superheat of the refrigerant, the intermediate pressure
of the refrigeration cycle, and the high pressure of the
refrigeration cycle.
6. The refrigeration apparatus of claim 1, wherein the compression
mechanism includes a first compressor (21a) for sucking and
compressing a low pressure refrigerant, and a second compressor
(21b) for further compressing and discharging the refrigerant
discharged from the first compressor (21a), the expansion mechanism
includes a first expansion mechanism (24) for expanding a high
pressure refrigerant, and a second expansion mechanism (26) for
further expanding the refrigerant expanded to an intermediate
pressure refrigerant in the first expansion mechanism (24), in
heating operation, the predetermined physical value includes, an
evaporating temperature of the refrigerant in the heat source side
heat exchanger (23), a degree of superheat of the refrigerant at an
outlet of the heat source side heat exchanger (23), and a gas
cooler outlet temperature which is a temperature of the refrigerant
at an outlet of the utilization side heat exchanger (27), and the
control section (240) receives the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, the gas
cooler outlet temperature of the refrigerant, and the high pressure
of the refrigeration cycle as inputs, and concurrently controls the
first and second compressors (21a, 21b), and the first and second
expansion mechanisms (24, 26), thereby concurrently controlling the
evaporating temperature of the refrigerant, the degree of superheat
of the refrigerant, the gas cooler outlet temperature of the
refrigerant, and the high pressure of the refrigeration cycle.
7. The refrigeration apparatus of claim 1, wherein a plurality ones
of the utilization side heat exchanger (27a, 27b) are connected in
parallel with each other, the expansion mechanism includes a
plurality of utilization side expansion mechanisms (26a, 26b) each
corresponding to the utilization side heat exchangers (27a, 27b),
and a heat source side expansion mechanism (24) provided between
the utilization side heat exchangers (27a, 27b) and expansion
mechanisms (26a, 26b), and the heat source side heat exchanger
(23), in cooling operation, the predetermined physical value
includes evaporating temperatures of the refrigerant in the
utilization side heat exchangers (27a, 27b), and degrees of
superheat of the refrigerant at the outlets of the utilization side
heat exchangers (27a, 27b), and the control section (340) receives
the evaporating temperatures of the refrigerant, the degrees of
superheat of the refrigerant in the utilization side heat
exchangers (27a, 27b), and the high pressure of the refrigeration
cycle as inputs, and concurrently controls the compression
mechanism (21), the plurality of utilization side heat expansion
mechanisms (26a, 26b), and the heat source side expansion mechanism
(24), thereby concurrently controlling the evaporating temperatures
of the refrigerant, and the degrees of superheat of the refrigerant
in the utilization side heat exchangers (27a, 27b), and the high
pressure of the refrigeration cycle.
8. The refrigeration apparatus of claim 1, wherein a plurality ones
of the utilization side heat exchanger (27a, 27b) are connected in
parallel with each other, the expansion mechanism includes a
plurality of utilization side expansion mechanisms (26a, 26b) each
corresponding to the utilization side heat exchangers (27a, 27b),
and a heat source side expansion mechanism (24) provided between
the utilization side heat exchangers (27a, 27b) and expansion
mechanisms (26a, 26b), and the heat source side heat exchanger
(23), in heating operation, the predetermined physical value
includes a degree of superheat of the refrigerant at an outlet of
the heat source side heat exchanger (23), and gas cooler outlet
temperatures of the refrigerant which are temperatures of the
refrigerant at outlets of the utilization side heat exchangers
(27a, 27b), and the control section (340) receives the degree of
superheat of the refrigerant, the gas cooler outlet temperatures of
the refrigerant in the utilization side heat exchangers (27a, 27b),
and the high pressure of the refrigeration cycle as inputs, and
concurrently controls the compression mechanism (21), the plurality
of utilization side expansion mechanisms (26a, 26b), and the heat
source side expansion mechanism (24), thereby concurrently
controlling the degree of superheat of the refrigerant, the gas
cooler outlet temperatures of the refrigerant in the utilization
side heat exchangers (27a, 27b), and the high pressure of the
refrigeration cycle.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a refrigeration apparatus
including a refrigerant circuit for performing a supercritical
refrigeration cycle.
BACKGROUND ART
[0002] In general, a capability of a refrigeration apparatus
including a refrigerant circuit sequentially connecting a
compression mechanism, a heat source side heat exchanger, an
expansion mechanism, and a utilization side heat exchanger is
controlled by controlling the compression mechanism and the
expansion mechanism. Patent Document 1 shows an example of the
refrigeration apparatus.
[0003] The refrigeration apparatus of the Patent Document 1
includes a compressor capacity controller for controlling the
capacity of a compressor as the compression mechanism, and an
expansion valve controller for controlling the degree of opening of
an expansion valve as the expansion mechanism. The compressor
capacity controller controls the capacity of the compressor based
on a low pressure of a refrigerant flowing in the refrigerant
circuit. The expansion valve controller controls the degree of
opening of the expansion valve based on the temperature of the
refrigerant at an outlet of an evaporator. Then, a control amount
of the expansion valve controller is corrected based on the
capacity of the compressor.
CITATION LIST
[0004] PATENT DOCUMENT 1: Japanese Patent Publication No.
2002-22242
SUMMARY OF THE DISCLOSURE
[0005] Technical Problem
[0006] Even if the refrigeration apparatus is configured to correct
the control amount of the degree of opening of the expansion valve
controlled by the expansion valve controller based on the capacity
of the compressor, change of the degree of opening of the expansion
valve leads to change of a circulation state of the refrigerant,
thereby changing the low pressure of the refrigerant. In response
to the change of the low pressure of the refrigerant, the
compressor capacity controller adjusts the capacity of the
compression mechanism. The change of the capacity of the compressor
involves re-correction of the control amount of the expansion valve
controller. Thus, a sequence of the correction of the control
amount of the expansion valve controller, the change of the low
pressure of the refrigerant, the change of the capacity of the
compressor, and the re-correction of the control amount of the
expansion valve controller occurs in a loop. The control of the low
pressure by the compressor, and the control of the degree of
superheat by the expansion valve cannot be easily settled.
[0007] In particular, a refrigeration apparatus for performing a
supercritical refrigeration cycle in which a high pressure of the
refrigerant is equal to or higher than a critical pressure has a
problem of difficulty in settling the control.
[0008] From this point of view, the present disclosure is intended
to allow for improved settling of the control of the capability of
a refrigeration apparatus for performing the supercritical
refrigeration cycle.
SOLUTION TO THE PROBLEM
[0009] The present disclosure has been achieved by paying attention
to a large variation of enthalpy of the refrigerant at an outlet of
a gas cooler relative to the change of the high pressure of the
supercritical refrigeration cycle. Specifically, in cooling
operation in the supercritical refrigeration cycle, the enthalpy of
the refrigerant at the outlet of the gas cooler may greatly vary
when the high pressure changes due to change of the low pressure.
This leads to an event that is not caused by a subcritical
refrigerant, i.e., the enthalpy of the refrigerant at an inlet of
an indoor heat exchanger varies, thereby changing the degree of
superheat of the refrigerant at an outlet of the indoor heat
exchanger. As a result, the difficulty of settling of the control
increases. Also in heating operation, the enthalpy of the
refrigerant at the outlet of the gas cooler may greatly vary due to
the change of the high pressure. This leads to great fluctuation of
indoor air heating capability, thereby changing the temperature of
the indoor air, and changing a target value of the temperature of
the refrigerant at the outlet of the gas cooler. This vicious
circle further increases the difficulty of settling of the control.
Moreover, CO.sub.2, which is a supercritical refrigerant, shows
greater variation in refrigerant density when it is superheated as
compared with chlorofluorocarbons (e.g., when an evaporating
temperature is 5.degree. C., and the degree of superheat varies
from 0.degree. C. to 5.degree. C., R410A shows a decrease in gas
density of only 3.5%, whereas CO.sub.2 shows a decrease of as much
as 6.5%). Further, the supercritical refrigerant shows great
variation in circulating amount and capability of the apparatus due
to the change of the degree of superheat, thereby greatly affecting
the controllability. In view of this, the present disclosure is
intended to control the high pressure of the refrigeration cycle,
and a predetermined physical value controlled by the control of the
capability of the apparatus in a concurrent manner
[0010] A first aspect of the disclosure is directed to a
refrigeration apparatus including: a refrigerant circuit (20)
sequentially connecting a compression mechanism (21), a heat source
side heat exchanger (23), an expansion mechanism (24), and a
utilization side heat exchanger (27), and performing a
supercritical refrigeration cycle in which a high pressure is a
supercritical pressure of a refrigerant or higher; and a control
section (40) for controlling a plurality of objects of control
including at least the compression mechanism (21) and the expansion
mechanism (24). The control section (40) concurrently controls the
plurality of objects of control, thereby concurrently controlling a
predetermined physical value of the refrigeration apparatus, and
the high pressure of the refrigeration cycle.
[0011] With this configuration, the predetermined physical value is
controlled, while controlling the high pressure of the
refrigeration cycle in the refrigerant circuit (20). Specifically,
a different physical value can be controlled in consideration of
the change of the high pressure of the refrigeration cycle, and the
change of enthalpy of the refrigerant at an outlet of a gas cooler,
due to adjustment of the objects of control. In this way, the
plurality of objects of control are concurrently controlled so as
to concurrently control the high pressure of the refrigeration
cycle and the predetermined physical value, thereby controlling the
objects of control by taking into account the effect of their
changes on the high pressure and the predetermined physical value.
Therefore, an event can be avoided in which the objects of control
are independently controlled, and the corresponding high pressure
of the refrigeration cycle and predetermined physical value are
independently changed, and are affected by each other, thereby
resulting in difficulty in settling the control. This allows for an
improved convergence rate of the control of the predetermined
physical value and the high pressure in the refrigeration
apparatus.
[0012] In a second aspect of the disclosure related to the first
aspect of the disclosure, the control section (40) receives the
predetermined physical value, and the high pressure of the
refrigeration cycle as inputs, generates control signals each
corresponding to the plurality of objects of control by associating
the physical value and the high pressure with each other, and
outputs the control signals to the corresponding objects of
control, respectively, thereby concurrently controlling the
predetermined physical value, and the high pressure of the
refrigeration cycle.
[0013] With this configuration, the control signals for controlling
the plurality of objects of control, respectively, are generated by
associating the input predetermined physical value and high
pressure of the refrigeration cycle with each other. This allows
for controlling the objects of control by taking both of the
predetermined physical value and the high pressure into
consideration, instead of controlling the objects of control by
inputting any one of the predetermined physical value and the high
pressure. Since the plurality of objects of control are
concurrently controlled as described above, a control signal for
one of the objects of control can be generated in consideration of
the effect of adjustment of the other objects of control on the
predetermined physical value and the high pressure.
[0014] In a third aspect of the disclosure related to the first or
second aspect of the disclosure, the refrigeration apparatus
further includes: a heat source side fan (28) for feeding air to
the heat source side heat exchanger (23) in which the refrigerant
exchanges heat with the air, wherein in cooling operation, the
predetermined physical value includes an evaporating temperature of
the refrigerant in the utilization side heat exchanger (27), and a
degree of superheat of the refrigerant at an outlet of the
utilization side heat exchanger (27), the objects of control
further include the heat source side fan (28), and the control
section (40) receives the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, and the
high pressure of the refrigeration cycle as inputs, and
concurrently controls the compression mechanism (21), the expansion
mechanism (24), and the heat source side fan (28), thereby
concurrently controlling the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, and the
high pressure of the refrigeration cycle.
[0015] With this configuration, in the cooling operation, three
objects of control, i.e., the compression mechanism (21), the
expansion mechanism (24), and the heat source side fan (28), are
concurrently controlled, thereby concurrently controlling the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, and the degree of superheat of the refrigerant.
Thus, the evaporating temperature and the degree of superheat of
the refrigerant can be controlled with the high pressure of the
refrigeration cycle stably controlled to a desired target value.
This allows for an improved convergence rate of the control of the
high pressure of the refrigeration cycle, the evaporating
temperature of the refrigerant, and the degree of superheat of the
refrigerant.
[0016] In a fourth aspect of the disclosure related to the first or
second aspect of the disclosure, in heating operation, the
predetermined physical value includes a degree of superheat of the
refrigerant at an outlet of the heat source side heat exchanger
(23), and the control section (40) receives the degree of superheat
of the refrigerant, and the high pressure of the refrigeration
cycle as inputs, and concurrently controls the compression
mechanism (21) and the expansion mechanism (24), thereby
concurrently controlling the degree of superheat of the
refrigerant, and the high pressure of the refrigeration cycle.
[0017] With this configuration, in the heating operation, two
objects of control, i.e., the compression mechanism (21) and the
expansion mechanism (24), are concurrently controlled, thereby
concurrently controlling the high pressure of the refrigeration
cycle, and the degree of superheat of the refrigerant. Thus, the
degree of superheat of the refrigerant can be controlled with the
high pressure of the refrigeration cycle stably controlled to a
desired target value. This allows for an improved convergence rate
of the control of the high pressure of the refrigeration cycle, and
the degree of superheat of the refrigerant.
[0018] In a fifth aspect of the disclosure related to the first or
second disclosure, the compression mechanism includes a first
compressor (21a) for sucking and compressing a low pressure
refrigerant, and a second compressor (21b) for further compressing
and discharging the refrigerant discharged from the first
compressor (21a), the expansion mechanism includes a first
expansion mechanism (24) for expanding a high pressure refrigerant,
and a second expansion mechanism (26) for further expanding the
refrigerant expanded to an intermediate pressure refrigerant by the
first expansion mechanism (24). In cooling operation, the
predetermined physical value includes an evaporating temperature of
the refrigerant in the utilization side heat exchanger (27), a
degree of superheat of the refrigerant at an outlet of the
utilization side heat exchanger (27), and an intermediate pressure
of the refrigeration cycle, and the control section (240) receives
the evaporating temperature of the refrigerant, the degree of
superheat of the refrigerant, the intermediate pressure of the
refrigeration cycle, and the high pressure of the refrigeration
cycle as inputs, and concurrently controls the first and second
compressors (21a, 21b), and the first and second expansion
mechanisms (24, 26), thereby concurrently controlling the
evaporating temperature of the refrigerant, the degree of superheat
of the refrigerant, the intermediate pressure of the refrigeration
cycle, and the high pressure of the refrigeration cycle.
[0019] With this configuration, in the cooling operation, four
objects of control, i.e., the first and second compressors (21a,
21b), and the first and second expansion mechanisms (24, 26), are
concurrently controlled, thereby concurrently controlling the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, the degree of superheat of the refrigerant, and
the intermediate pressure. Thus, the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, and the
intermediate pressure of the refrigeration cycle can be controlled
with the high pressure of the refrigeration cycle stably controlled
to a desired target value. This allows for an improved convergence
rate of the control of the high pressure of the refrigeration
cycle, the evaporating temperature of the refrigerant, the degree
of superheat of the refrigerant, and the intermediate pressure of
the refrigeration cycle.
[0020] In a sixth aspect of the disclosure related to the first or
second aspect of the disclosure, the compression mechanism includes
a first compressor (21a) for sucking and compressing a low pressure
refrigerant, and a second compressor (21b) for further compressing
and discharging the refrigerant discharged from the first
compressor (21a), the expansion mechanism includes a first
expansion mechanism (24) for expanding a high pressure refrigerant,
and a second expansion mechanism (26) for further expanding the
refrigerant expanded to an intermediate pressure refrigerant in the
first expansion mechanism (24). In heating operation, the
predetermined physical value includes an evaporating temperature of
the refrigerant in the heat source side heat exchanger (23), a
degree of superheat of the refrigerant at an outlet of the heat
source side heat exchanger (23), and a gas cooler outlet
temperature which is a temperature of the refrigerant at an outlet
of the utilization side heat exchanger (27), and the control
section (240) receives the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, the gas
cooler outlet temperature of the refrigerant, and the high pressure
of the refrigeration cycle as inputs, and concurrently controls the
first and second compressors (21a, 21b), and the first and second
expansion mechanisms (24, 26), thereby concurrently controlling the
evaporating temperature of the refrigerant, the degree of superheat
of the refrigerant, the gas cooler outlet temperature of the
refrigerant, and the high pressure of the refrigeration cycle.
[0021] With this configuration, in the heating operation, four
objects of control, i.e., the first and second compressors (21a,
21b), and the first and second expansion mechanisms (24, 26), are
concurrently controlled, thereby concurrently controlling the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, the degree of superheat of the refrigerant, and
the gas cooler outlet temperature. Thus, the evaporating
temperature of the refrigerant, the degree of superheat of the
refrigerant, and the gas cooler outlet temperature can be
controlled with the high pressure of the refrigeration cycle stably
controlled to a desired target value. This allows for an improved
convergence rate of the control of the high pressure of the
refrigeration cycle, the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, and the
gas cooler outlet temperature.
[0022] In a seventh aspect of the disclosure related to the first
or second aspect of the disclosure, a plurality ones of the
utilization side heat exchanger (27a, 27b) are connected in
parallel with each other, the expansion mechanism includes a
plurality of utilization side expansion mechanisms (26a, 26b) each
corresponding to the utilization side heat exchangers (27a, 27b),
and a heat source side expansion mechanism (24) provided between
the utilization side heat exchangers (27a, 27b) and expansion
mechanisms (26a, 26b), and the heat source side heat exchanger
(23). In cooling operation, the predetermined physical value
includes evaporating temperatures of the refrigerant in the
utilization side heat exchangers (27a, 27b), and degrees of
superheat of the refrigerant at outlets of the utilization side
heat exchangers (27a, 27b), and the control section (340) receives
the evaporating temperatures of the refrigerant, the degrees of
superheat of the refrigerant in the utilization side heat
exchangers (27a, 27b), and the high pressure of the refrigeration
cycle as inputs, and concurrently controls the compression
mechanism (21), the plurality of utilization side heat expansion
mechanisms (26a, 26b), and the heat source side expansion mechanism
(24), thereby concurrently controlling the evaporating temperatures
of the refrigerant, and the degrees of superheat of the refrigerant
in the utilization side heat exchangers (27a, 27b), and the high
pressure of the refrigeration cycle.
[0023] With this configuration, in the cooling operation, a
plurality of objects of control, i.e., the compression mechanism
(21), the heat source side expansion mechanism (24), and the
plurality of utilization side expansion mechanisms (26a, 26b), are
concurrently controlled, thereby concurrently controlling the high
pressure of the refrigeration cycle, and the evaporating
temperatures of the refrigerant, and the degrees of superheat of
the refrigerant at the utilization side heat exchangers (27a, 27b).
Thus, the evaporating temperatures of the refrigerant, and the
degrees of superheat of the refrigerant at the utilization side
heat exchangers (27a, 27b) can be controlled with the high pressure
of the refrigeration cycle stably controlled to a desired target
value. This allows for an improved convergence rate of the control
the high pressure of the refrigeration cycle, the evaporating
temperatures of the refrigerant, and the degrees of superheat of
the refrigerant at the utilization side heat exchangers (27a,
27b).
[0024] In an eighth aspect of the disclosure related to the first
or second aspect of the disclosure, a plurality ones of the
utilization side heat exchanger (27a, 27b) are connected in
parallel with each other, the expansion mechanism includes a
plurality of utilization side expansion mechanisms (26a, 26b) each
corresponding to the utilization side heat exchangers (27a, 27b),
and a heat source side expansion mechanism (24) provided between
the utilization side heat exchangers (27a, 27b) and expansion
mechanisms (26a, 26b), and the heat source side heat exchanger
(23). In heating operation, the predetermined physical value
includes a degree of superheat of the refrigerant at an outlet of
the heat source side heat exchanger (23), and gas cooler outlet
temperatures of the refrigerant which are temperatures of the
refrigerant at outlets of the utilization side heat exchangers
(27a, 27b), and the control section (340) receives the degree of
superheat of the refrigerant, the gas cooler outlet temperatures of
the refrigerant in the utilization side heat exchangers (27a, 27b),
and the high pressure of the refrigeration cycle as inputs, and
concurrently controls the compression mechanism (21), the plurality
of utilization side expansion mechanisms (26a, 26b), and the heat
source side expansion mechanism (24), thereby concurrently
controlling the degree of superheat of the refrigerant, the gas
cooler outlet temperatures of the refrigerant in the utilization
side heat exchangers (27a, 27b), and the high pressure of the
refrigeration cycle.
[0025] With this configuration, in the heating operation, a
plurality of objects of control, i.e., the compression mechanism
(21), the heat source side expansion mechanism (24), and the
plurality of utilization side expansion mechanisms (26a, 26b), are
concurrently controlled, thereby concurrently controlling the high
pressure of the refrigeration cycle, the degree of superheat of the
refrigerant, and the gas cooler outlet temperatures at the
utilization side heat exchangers (27a, 27b). Thus, the degree of
superheat of the refrigerant, and the gas cooler outlet
temperatures of the refrigerant at the utilization side heat
exchangers (27a, 27b) can be controlled with the high pressure of
the refrigeration cycle stably controlled to a desired target
value. This allows for an improved convergence rate of the control
of the high pressure of the refrigeration cycle, the degree of
superheat of the refrigerant, and the gas cooler outlet
temperatures of the refrigerant at the utilization side heat
exchangers (27a, 27b).
ADVANTAGES OF THE DISCLOSURE
[0026] According to the present disclosure, a plurality of objects
of control are concurrently controlled, thereby concurrently
controlling the predetermined physical value of the refrigeration
apparatus, and the high pressure of the refrigeration cycle.
Therefore, the predetermined physical value, and the high pressure
of the refrigeration cycle can be controlled concurrently while
concurrently considering the predetermined physical value and the
high pressure of the refrigeration cycle, and considering the
effect of the plurality of objects of control on the predetermined
physical value and the high pressure of the refrigeration cycle.
This allows for an improved convergence rate of the control of the
predetermined physical value and the high pressure of the
refrigeration apparatus.
[0027] According to the second aspect of the disclosure, the
control signals for controlling the plurality of objects of
control, respectively, are generated by associating the input
predetermined physical value and high pressure of the refrigeration
cycle with each other. Therefore, a control signal for one of the
objects of control can be generated in concurrent consideration of
the predetermined physical value and the high pressure, and in
consideration of the effect of adjustment of the other objects of
control on the predetermined physical value and the high pressure.
This allows for an improved convergence rate of the control of the
predetermined physical value and the high pressure of the
refrigeration apparatus.
[0028] According to the third aspect of the disclosure, three
objects of control, i.e., the compression mechanism (21), the
expansion mechanism (24), and the heat source side fan (28), are
concurrently controlled in the cooling operation, thereby
concurrently controlling the high pressure of the refrigeration
cycle, the evaporating temperature of the refrigerant, and the
degree of superheat of the refrigerant. This allows for an improved
convergence rate of the control of the high pressure of the
refrigeration cycle, the evaporating temperature of the
refrigerant, and the degree of superheat of the refrigerant.
[0029] According to the fourth aspect of the disclosure, two
objects of control, i.e., the compression mechanism (21) and the
expansion mechanism (24), are concurrently controlled in the
heating operation, thereby concurrently controlling the high
pressure of the refrigeration cycle, and the degree of superheat of
the refrigerant. This allows for an improved convergence rate of
the control of the high pressure of the refrigeration cycle, and
the degree of superheat of the refrigerant.
[0030] According to the fifth aspect of the disclosure, four
objects of control, i.e., the first and second compressors (21a,
21b), and the first and second expansion mechanisms (24, 26), are
concurrently controlled in the cooling operation in the
refrigeration apparatus for performing a two-stage compression
refrigeration cycle, thereby concurrently controlling the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, the degree of superheat of the refrigerant, and
the intermediate pressure of the refrigeration cycle. This allows
for an improved convergence rate of the control of the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, the degree of superheat of the refrigerant, and
the intermediate pressure of the refrigeration cycle.
[0031] According to the sixth aspect of the disclosure, four
objects of control, i.e., the first and second compressors (21a,
21b), and the first and second expansion mechanisms (24, 26), are
concurrently controlled in the heating operation in the
refrigeration apparatus for performing the two-stage compression
refrigeration cycle, thereby concurrently controlling the high
pressure of the refrigeration cycle, the evaporating temperature of
the refrigerant, the degree of superheat of the refrigerant, and
the gas cooler outlet temperature. This allows for an improved
convergence rate of the control of the high pressure of the
refrigeration cycle, the evaporating temperature of the
refrigerant, the degree of superheat of the refrigerant, and the
gas cooler outlet temperature.
[0032] According to the seventh aspect of the disclosure, a
plurality of objects of control, i.e., the compression mechanism
(21), the heat source side expansion mechanism (24), and a
plurality of utilization side expansion mechanisms (26a, 26b), are
concurrently controlled in the cooling operation of a so-called
multi-type refrigeration apparatus including a plurality of indoor
units, thereby concurrently controlling the high pressure of the
refrigeration cycle, the evaporating temperature of the
refrigerant, and the degrees of superheat at the heat utilization
side heat exchangers (27a, 27b). This allows for an improved
convergence rate of the control of the high pressure of the
refrigeration cycle, the evaporating temperature of the
refrigerant, and the degrees of superheat in the utilization side
heat exchangers (27a, 27b).
[0033] According to the eighth aspect of the disclosure, a
plurality of objects of control, i.e., the compression mechanism
(21), the heat source side expansion mechanism (24), and a
plurality of utilization side expansion mechanisms (26a, 26b), are
concurrently controlled in the heating operation in the so-called
multi-type refrigeration apparatus including a plurality of indoor
units, thereby concurrently controlling the high pressure of the
refrigeration cycle, the degree of superheat of the refrigerant,
and the gas cooler outlet temperatures of the refrigerant at the
utilization side heat exchangers (27a, 27b). This allows for an
improved convergence rate of the control of the high pressure of
the refrigeration cycle, the degree of superheat of the
refrigerant, and the gas cooler outlet temperatures of the
refrigerant in the utilization side heat exchangers (27a, 27b).
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a piping diagram illustrating the structure of an
air conditioner of a first embodiment.
[0035] FIG. 2 is a control block diagram of a controller in cooling
operation.
[0036] FIG. 3 is a control block diagram of the controller in
heating operation.
[0037] FIG. 4 is a piping diagram illustrating the structure of an
air conditioner of a second embodiment.
[0038] FIG. 5 is a control block diagram of a controller in cooling
operation.
[0039] FIG. 6 is a control block diagram of the controller in
heating operation.
[0040] FIG. 7 is a piping diagram illustrating the structure of an
air conditioner of a third embodiment.
[0041] FIG. 8 is a control block diagram of a controller in cooling
operation.
[0042] FIG. 9 is a control block diagram of the controller in
heating operation.
[0043] FIG. 10 is a piping diagram illustrating the structure of an
air conditioner of another embodiment.
[0044] FIG. 11 is a piping diagram illustrating the structure of an
air conditioner of still another embodiment.
DESCRIPTION OF EMBODIMENTS
[0045] Embodiments of the present disclosure will be described in
detail with reference to the drawings.
First Embodiment
[0046] A first embodiment of the present disclosure will be
described in detail with reference to the drawings.
[0047] As shown in FIG. 1, an air conditioner (10) of the present
embodiment includes a refrigerant circuit (20), and a controller
(40).
[0048] The refrigerant circuit (20) is a closed circuit filled with
carbon dioxide (CO.sub.2) as a refrigerant. The refrigerant circuit
(20) is configured to perform a vapor compression refrigeration
cycle by circulating the refrigerant. Further, the refrigerant
circuit (20) is configured to perform a supercritical refrigeration
cycle in which a high pressure is equal to or higher than a
supercritical pressure of carbon dioxide (i.e., a refrigeration
cycle in which a vapor pressure is equal to or higher than a
supercritical temperature of carbon dioxide).
[0049] The refrigerant circuit (20) connects a compressor (21), a
four way switching valve (22), an outdoor heat exchanger (23), an
outdoor expansion valve (24), and an indoor heat exchanger
(27).
[0050] Specifically, in the refrigerant circuit (20), a discharge
side of the compressor (21) is connected to a first port of the
four way switching valve (22), and a suction side of the compressor
(21) is connected to a second port of the four way switching valve
(22). In the refrigerant circuit (20), the outdoor heat exchanger
(23), the outdoor expansion valve (24), and the indoor heat
exchanger (27) are sequentially arranged in a path from a third
port to a fourth port of the four way switching valve (22).
[0051] The compressor (21) is configured as a fully sealed variable
capacity compressor. The compressor (21) sucks and compresses the
refrigerant (carbon dioxide) to a supercritical pressure or higher,
and then discharges the compressed refrigerant. Changing a
frequency of AC fed to a motor (not shown) of the compressor (21)
changes a rotation speed, i.e., a capacity, of the compressor (21).
The compressor (21) constitutes a compression mechanism.
[0052] In the outdoor heat exchanger (23), outdoor air sucked by an
outdoor fan (28) exchanges heat with the refrigerant. In the indoor
heat exchanger (27), indoor air sucked by an indoor fan (29)
exchanges heat with the refrigerant. The outdoor heat exchanger
(23) constitutes a heat source side heat exchanger, and the indoor
heat exchanger (27) constitutes a utilization side heat exchanger.
The outdoor fan (28) constitutes a heat source side fan.
[0053] The outdoor expansion valve (24) is comprised of an
electronic expansion valve whose degree of opening is variable, and
whose valve element (not shown) is driven by a pulse motor (not
shown). The outdoor expansion valve (24) constitutes an expansion
mechanism.
[0054] The four way switching valve (22) is switchable between a
first state where the first and third ports communicate with each
other, and the second and fourth ports communicate with each other
(a state indicated by a solid line in FIG. 1), and a second state
where the first and fourth ports communicate with each other, and
the second and third ports communicate with each other (a state
indicated by a broken line in FIG. 1).
[0055] Thus, the air conditioner (10) is able to switchably perform
cooling operation and heating operation by switching the four way
switching valve (22).
[0056] In the cooling operation, the four way switching valve (22)
is set to the first state. When the compressor (21) is operated in
this state, the outdoor heat exchanger (23) functions as a radiator
(a gas cooler), and the indoor heat exchanger (27) functions as an
evaporator to perform the refrigeration cycle. Specifically, the
refrigerant in the supercritical state discharged from the
compressor (21) flows into the outdoor heat exchanger (23), and
dissipates heat to the outdoor air. After the heat dissipation, the
refrigerant expands (decreases in pressure) as it passes through
the outdoor expansion valve (24), and then flows into the indoor
heat exchanger (27). The refrigerant in the indoor heat exchanger
(27) absorbs heat from the indoor air to evaporate, and the cooled
indoor air is fed to the inside of the room. The evaporated
refrigerant is sucked into and compressed in the compressor
(21).
[0057] In the heating operation, the four way switching valve (22)
is set to the second state. When the compressor (21) is operated in
this state, the indoor heat exchanger (27) functions as a radiator
(a gas cooler), and the outdoor heat exchanger (23) functions as an
evaporator to perform the refrigeration cycle. Specifically, the
refrigerant in the supercritical state discharged from the
compressor (21) flows into the indoor heat exchanger (27), and
dissipates heat to the indoor air. The heated indoor air is fed to
the inside of the room. After the heat dissipation, the refrigerant
expands (decreases in pressure) as it passes through the outdoor
expansion valve (24). The refrigerant expanded by the outdoor
expansion valve (24) flows into the outdoor heat exchanger (23),
and absorbs heat from the outdoor air to evaporate. The evaporated
refrigerant is sucked into and compressed in the compressor
(21).
[0058] In the air conditioner (10) configured in this manner, the
refrigerant circuit (20) includes an outdoor temperature sensor
(30), an indoor temperature sensor (31), a low pressure sensor
(32), a discharge temperature sensor (33), a high pressure sensor
(34), a gas cooler outlet temperature sensor (37) for the heating
operation, and a gas cooler outlet temperature sensor (39) for the
cooling operation.
[0059] The outdoor temperature sensor (30) is a temperature sensing
part for sensing the temperature of the outdoor air entering the
outdoor heat exchanger (23). The indoor temperature sensor (31) is
a temperature sensing part for sensing the temperature of the
indoor air entering the indoor heat exchanger (27). The low
pressure sensor (32) is a pressure sensing part for sensing the
pressure of the refrigerant sucked into the compressor (21), i.e.,
the low pressure of the refrigeration cycle in the refrigerant
circuit (20). The discharge temperature sensor (33) is a
temperature sensing part for sensing the temperature of the
refrigerant discharged from the compressor (21). The high pressure
sensor (34) is a pressure sensing part for sensing the pressure of
the refrigerant discharged from the compressor (21), i.e., the high
pressure of the refrigeration cycle in the refrigerant circuit
(20). The gas cooler outlet temperature sensor (37) for the heating
operation is a temperature sensing part for sensing the temperature
of the refrigerant at an outlet of the indoor heat exchanger (27)
when the refrigerant circulates in the refrigerant circuit (20) in
a heating cycle. The gas cooler outlet temperature sensor (39) for
the cooling operation is a temperature sensing part for sensing the
temperature of the refrigerant at an outlet of the outdoor heat
exchanger (23) when the refrigerant circulates in the refrigerant
circuit (20) in a cooling cycle.
[0060] The controller (40) is configured to receive output signals
from the indoor temperature sensor (31), the low pressure sensor
(32), the discharge temperature sensor (33), and the high pressure
sensor (34), and to control an operation frequency of the
compressor (21), the degree of opening of the outdoor expansion
valve (24), and an operation frequency of the outdoor fan (28). The
controller (40) functions as a control section.
[0061] The controller (40) includes, as shown in FIGS. 2 and 3, a
target low pressure calculator (41) for calculating a target low
pressure P1s which is a target value of the low pressure of the
refrigeration cycle, a target high pressure calculator (42) for
calculating a target high pressure Phs which is a target value of
the high pressure of the refrigeration cycle, a target discharge
temperature calculator (43) for calculating a target discharge
temperature T1s which is a target value of the discharge
temperature of the refrigerant, and a control signal generator (49)
for generating control signals transmitted to the compressor (21),
the outdoor expansion valve (24), and the outdoor fan (28). The
controller (40) performs the control in different ways for the
cooling operation and the heating operation. That is, components
operated in the cooling operation are different from those operated
in the heating operation. Therefore, a control block for the
cooling operation is shown in FIG. 2, and a control block for the
heating operation is shown in FIG. 3.
[0062] The target low pressure calculator (41) calculates the
target low pressure P1s based on a temperature deviation et between
a set temperature Ts and the output signal from the indoor
temperature sensor (31) (i.e., an indoor temperature Ta).
[0063] In the cooling operation, the target high pressure
calculator (42) calculates the target high pressure Phs based on
the output signal from the outdoor temperature sensor (30) (i.e.,
an outdoor temperature T0), and the output signal from the gas
cooler outlet temperature sensor (39) for the cooling operation
(i.e., a gas cooler outlet temperature T4). In the heating
operation, the target high pressure calculator (42) calculates the
target high pressure Phs based on the temperature deviation et, and
the output signal from the gas cooler outlet temperature sensor
(37) for the heating operation (i.e., the gas cooler outlet
temperature T4).
[0064] The target discharge temperature calculator (43) calculates
the target discharge temperature T1s based on the temperature
deviation et, the output signal from the low pressure sensor (32)
(i.e., an actual low pressure P1), the output signal from the high
pressure sensor (34) (i.e., an actual high pressure Ph), an
operation frequency fc of the compressor (21), and the outdoor
temperature TO. More specifically, the target discharge temperature
calculator (43) calculates the target discharge temperature T1s
corresponding to a target degree of superheat based on the
temperature deviation et, the actual low pressure P1, the actual
high pressure Ph, the operation frequency fc of the compressor
(21), and the outdoor temperature T0.
[0065] The target low pressure calculator (41), the target high
pressure calculator (42), and the target discharge temperature
calculator (43) have maps and functions, respectively. Each of the
calculators is configured to deliver an output value (a target
value) corresponding to the input.
[0066] Signals input to the control signal generator (49) in the
cooling operation are different from those input to the control
signal generator (49) in the heating operation. The control signal
generator (49) has a plurality of PID control sections (p1a, p2a, .
. . , p1b, p2b, . . . ) each having a control parameter
corresponding to the input signal.
[0067] In the cooling operation, the control signal generator (49)
receives a low pressure deviation el between the target low
pressure P1s calculated by the target low pressure calculator (41)
and the actual low pressure P1 from the low pressure sensor (32), a
high pressure deviation e2 between the target high pressure Phs
calculated by the target high pressure calculator (42) and the
actual high pressure Ph from the high pressure sensor (34), and a
discharge temperature deviation e3 between the target discharge
temperature T1s calculated by the target discharge temperature
calculator (43) and the output signal from the discharge
temperature sensor (33) (i.e., an actual discharge temperature
T1).
[0068] Nine PID control sections (p1a, p2a, . . . ) of the control
signal generator (49) are operated in the cooling operation.
Specifically, the low pressure deviation el input to the control
signal generator (49) is input to the first to third PID control
sections (p1a, p2a, p3a), the high pressure deviation e2 is input
to the fourth to sixth PID control sections (p4a, p5a, p6a), and
the discharge temperature deviation e3 are input to the seventh to
ninth PID control sections (p7a, p8a, p9a).
[0069] Each of the first to ninth PID control sections (p1a, p2a, .
. . ) delivers an output generated by multiplying the input
deviation by a predetermined control parameter. As a result, the
control signal generator (49) generates a compressor frequency
control signal .DELTA.fc by adding the output signals from the
first, fourth, and seventh PID control sections (p1a, p4a, p7a),
generates an expansion valve control signal .DELTA.ev by adding the
output signals from the second, fifth, and eighth PID control
sections (p2a, p5a, p8a), and generates a fan frequency control
signal .DELTA.ff by adding the output signals from the third,
sixth, and ninth PID control sections (p3a, p6a, p9a).
[0070] The compressor frequency control signal .DELTA.fc, the
expansion valve control signal .DELTA.ev, and the fan frequency
control signal .DELTA.ff generated in this manner are output to the
air conditioner (10).
[0071] In the air conditioner (10), a frequency of AC fed to the
motor of the compressor (21) (i.e., the operation frequency) is set
to a value corresponding to the compressor frequency control signal
.DELTA.fc, thereby changing the rotation speed of the compressor
(21). Thus, the capacity of the compressor (21) varies according to
the compressor frequency control signal .DELTA.fc.
[0072] A pulse number of the signal fed to the pulse motor of the
outdoor expansion valve (24) is set to a value corresponding to the
expansion valve control signal .DELTA.ev. Thus, the pulse motor of
the outdoor expansion valve (24) rotates by an angle corresponding
to the pulse number, thereby adjusting the degree of opening of the
valve according to the expansion valve control signal
.DELTA.ev.
[0073] Further, a frequency of AC fed to the motor of the outdoor
fan (28) (i.e., the operation frequency) is set to a value
corresponding to the fan frequency control signal .DELTA.ff,
thereby changing the rotation speed of the outdoor fan (28). Thus,
a flow rate of air fed from the outdoor fan (28) to the outdoor
heat exchanger (23) varies according to the fan frequency control
signal .DELTA.ff.
[0074] The low pressure P1, the discharge temperature T1, and the
high pressure Ph of the air conditioner (10) operated in this
operation state are fed back to the controller (40) through the low
pressure sensor (32), the discharge temperature sensor (33), and
the high pressure sensor (34). In this way, the controller (40)
performs feed back control to set the low pressure P1 (and an
evaporating temperature), the discharge temperature T1 (and the
degree of superheat), and the high pressure Ph to the target values
corresponding to the operation state, respectively.
[0075] As described above, each of the compressor frequency control
signal .DELTA.fc, the expansion valve control signal .DELTA.ev, and
the fan frequency control signal .DELTA.ff is generated by
associating the low pressure deviation e1, the high pressure
deviation e2, and the discharge temperature deviation e3 with each
other. Specifically, for example, unlike a refrigeration apparatus
in which the low pressure of the refrigeration cycle is controlled
by the compressor (21), the discharge temperature of the
refrigerant is controlled by the outdoor expansion valve (24), and
the high pressure of the refrigeration cycle is controlled by the
outdoor fan (28), objects of the control corresponding to the
physical values, respectively, are not controlled independently.
Instead of this, the compressor (21), the outdoor expansion valve
(24), and the outdoor fan (28) are concurrently controlled, thereby
concurrently, or simultaneously controlling the high pressure, the
low pressure, and the discharge temperature. Specifically, each of
the low pressure, the high pressure, and the discharge temperature
is not controlled only by one of the compressor (21), the outdoor
expansion valve (24), and the outdoor fan (28), but is controlled
by all the compressor (21), the outdoor expansion valve (24), and
the outdoor fan (28). More specifically, each of the objects of the
control, i.e., the compressor (21), the outdoor expansion valve
(24), and the outdoor fan (28), is controlled not only based on the
changes of the low pressure, the high pressure, and the discharge
temperature resulting from the control solely of the each of the
objects of control, but is controlled based on the changes of the
low pressure, the high pressure, and the discharge temperature
resulting from the control of the other objects of control (in
other words, the control parameters of the first to nine PID
control sections (p1a, p2a, . . . ) are determined so as to take
these changes into account).
[0076] In the heating operation, the control signal generator (49)
receives the high pressure deviation e2 between the target high
pressure Phs calculated by the target high pressure calculator (42)
and the actual high pressure Ph from the high pressure sensor (34),
and the discharge temperature deviation e3 between the target
discharge temperature T1s calculated by the target discharge
temperature calculator (43) and the actual discharge temperature T1
of the discharge temperature sensor (33).
[0077] In the heating operation, four PID control sections (p1b,
p2b, . . . ) of the control signal generator (49) are operated.
Specifically, the discharge temperature deviation e3 input to the
control signal generator (49) is input to the first and second PID
control sections (p1b, p2b), and the high pressure deviation e2 is
input to the third and fourth PID control sections (p3b, p4b).
[0078] Each of the first to fourth PID control sections (p1b, p2b,
. . . ) delivers an output generated by multiplying the input
deviation by a predetermined control parameter. As a result, the
control signal generator (49) generates the compressor frequency
control signal .DELTA.fc by adding the output signals from the
first and third PID control sections (p1b, p3b), and generates the
expansion valve control signal .DELTA.ev by adding the output
signals from the second and fourth PID control sections (p2b,
p4b).
[0079] The compressor frequency control signal .DELTA.fc and the
expansion valve control signal .DELTA.ev generated in this manner
are output to the air conditioner (10).
[0080] In the air conditioner (10), the capacity of the compressor
(21) varies according to the compressor frequency control signal
.DELTA.fc, and the degree of opening of the outdoor expansion valve
(24) is adjusted according to the expansion valve control signal
.DELTA.ev.
[0081] The discharge temperature T1 and the high pressure Ph of the
air conditioner (10) operated in this operation state are fed back
to the controller (40) through the discharge temperature sensor
(33) and the high pressure sensor (34). In this way, the controller
(40) performs feed back control to set the discharge temperature T1
(and the degree of superheat), and the high pressure Ph to target
values corresponding to the operation state, respectively.
[0082] As described above, each of the compressor frequency control
signal .DELTA.fc and the expansion valve control signal .DELTA.ev
are generated by associating the high pressure deviation e2 and the
discharge temperature deviation e3 with each other. Specifically,
for example, unlike a refrigeration apparatus in which the high
pressure of the refrigeration cycle is controlled by the compressor
(21), and the discharge temperature of the refrigerant is
controlled by the outdoor expansion valve (24), the objects of
control corresponding to the physical values, respectively, are not
controlled independently. Instead of this, the compressor (21) and
the outdoor expansion valve (24) are concurrently controlled,
thereby concurrently, or simultaneously controlling the high
pressure and the discharge temperature. Specifically, each of the
high pressure and the discharge temperature is not controlled by
only one of the compressor (21) and the outdoor expansion valve
(24), but is controlled by both of the compressor (21) and the
outdoor expansion valve (24). More specifically, each of the
objects of control, i.e., the compressor (21) and the outdoor
expansion valve (24), is controlled not only based on the changes
of the high pressure and the discharge temperature resulting solely
from the control of the each of the objects of control, but is
controlled based on the changes of the high pressure and the
discharge temperature resulting from the control of the other
objects of control (in other words, the control parameters of the
first to fourth PID control sections (p1b, p2b, . . . ) are
determined so as to take these changes into account).
[0083] Thus, according to the first embodiment, the plurality of
objects of control (e.g., the compressor (21), the outdoor
expansion valve (24), etc.) are simultaneously controlled in such a
manner that the high pressure of the refrigeration cycle, and the
predetermined physical value of the air conditioner (10) are
adjusted to the predetermined target values corresponding to the
operation state. At the same time, each of the objects of control
is controlled in consideration of the changes of the physical value
and the high pressure of the refrigeration cycle resulting from the
control of the plurality of objects of control. According to these
schemes, the capability of the air conditioner (10) (e.g., the low
pressure, the degree of superheat, etc., in the cooling operation)
can be controlled with the high pressure stably kept to the target
value corresponding to the operation state. This can avoid an event
in which the control of a target physical value cannot be easily
settled, i.e., an event in which adjustment of a first physical
value changes a second physical value, and correction of the change
of the second physical value by adjusting the second physical value
changes a third physical value or the first physical value already
adjusted, thereby involving another adjustment. This allows for an
improved convergence rate of the control of the capability and the
high pressure of the air conditioner (10).
[0084] According to the present embodiment, three physical values,
i.e., the low pressure, the high pressure, and the discharge
temperature, are controlled by three objects of control, i.e., the
compressor (21), the outdoor expansion valve (24), and the outdoor
fan (28), in the cooling operation. In the heating operation, two
physical values, i.e., the high pressure and the discharge
temperature, are controlled by two objects of control, i.e., the
compressor (21) and the outdoor expansion valve (24). However, some
of the objects of control easily have an effect on the physical
values, but some do not. That is, even when one of the objects of
control is changed, some physical values are less susceptible to
the change. In the present embodiment, all the physical values to
be controlled are input, and they are associated with each other to
generate control signals each corresponding to the objects of
control. Instead of this, in generating a control signal for one of
the objects of control to which a certain physical value is less
susceptible, the degree of association of the certain physical
value may be reduced or eliminated (specifically, among the PID
control sections (p1a, p1b, . . .) for generating the control
signal for the object of control to which a certain physical value
is less susceptible, a control parameter of one of the PID control
sections corresponding to the certain physical value may be reduced
or reduced to zero).
Second Embodiment
[0085] A second embodiment of the present disclosure will be
described below. An air conditioner (210) of the second embodiment
is different from the air conditioner (10) of the first embodiment
in that two expansion valves (24, 26) are provided between an
outdoor heat exchanger (23) and an indoor heat exchanger (27) of a
refrigerant circuit (220), and that two compressors (21a, 21b) are
provided to perform a two-stage compression refrigeration
cycle.
[0086] Specifically, as shown in FIG. 4, the air conditioner (210)
includes a refrigerant circuit (220), and a controller (240).
[0087] The refrigerant circuit (220) connects a low pressure first
compressor (21a), a high pressure second compressor (21b), a four
way switching valve (22), an outdoor heat exchanger (23), an
outdoor expansion valve (24), a gas-liquid separator (25), an
indoor expansion valve (26), and an indoor heat exchanger (27).
[0088] Specifically, in the refrigerant circuit (220), a discharge
side of the second compressor (21b) is connected to a first port of
the four way switching valve (22), and a suction side of the first
compressor (21a) is connected to a second port of the four way
switching valve (22). The first compressor (21a) and the second
compressor (21b) are connected through a pipe in such a manner that
the refrigerant compressed in and discharged from the first
compressor (21a) is sucked into the second compressor (21b) for
further compression. In the refrigerant circuit (220), the outdoor
heat exchanger (23), the outdoor expansion valve (24), the
gas-liquid separator (25), the indoor expansion valve (26), and the
indoor heat exchanger (27) are sequentially arranged in a path from
a third port to a fourth port of the four way switching valve (22).
The gas-liquid separator (25) is connected to the pipe connecting
the first compressor (21a) and the second compressor (21b) through
a first intermediate pressure refrigerant pipe (25a).
[0089] The first and second compressors (21a, 21b) are the same as
the compressor of the first embodiment. The first and second
compressors (21a, 21b) constitute a compression mechanism.
[0090] Each of the outdoor expansion valve (24) and the indoor
expansion valve (26) is comprised of an electronic expansion valve
whose degree of opening is variable, and whose valve element (not
shown) is driven by a pulse motor (not shown). The outdoor
expansion valve (24) constitutes a first expansion mechanism, and
the indoor expansion valve (26) constitutes a second expansion
mechanism.
[0091] The gas-liquid separator (25) is a longitudinal, cylindrical
hermetic container. The gas-liquid separator (25) is connected to
the outdoor expansion valve (24) and the indoor expansion valve
(26) through a bridge circuit (50).
[0092] Specifically, the outdoor expansion valve (24) is connected
to one of terminals of the bridge circuit (50) through a second
intermediate pressure refrigerant pipe (25b). The indoor expansion
valve (26) is connected to a second terminal of the bridge circuit
(50) through a third intermediate pressure refrigerant pipe (25c).
An end of a refrigerant inlet pipe (25d) is connected to a third
terminal of the bridge circuit (50), and the other end of the
refrigerant inlet pipe (25d) is connected to the gas-liquid
separator (25). The other end of the refrigerant inlet pipe (25d)
penetrates an upper surface of the hermetic container serving as
the gas-liquid separator (25), and is positioned in an upper
portion of space inside the container. An end of a refrigerant
outlet pipe (25e) is connected to a fourth terminal of the bridge
circuit (50), and the other end of the refrigerant outlet pipe
(25e) is connected to the gas-liquid separator (25). The other end
of the refrigerant outlet pipe (25e) penetrates the upper surface
of the hermetic container of the gas-liquid separator (25), and is
positioned in a lower portion of the space inside the
container.
[0093] An end of the first intermediate pressure refrigerant pipe
(25a) close to the gas-liquid separator (25) penetrates the upper
surface of the hermetic container of the gas-liquid separator (25),
and is positioned in the upper portion of the space inside the
container.
[0094] Like the air conditioner of the first embodiment, the air
conditioner (210) is able to switchably perform cooling operation
and heating operation by switching the four way switching valve
(22).
[0095] In the cooling operation, the four way switching valve (22)
is set to the first state.
[0096] When the first and second compressors (21a, 21b) are driven
in this state, the outdoor heat exchanger (23) functions as a
radiator (a gas cooler), and the indoor heat exchanger (27)
functions as an evaporator to perform the refrigeration cycle.
Specifically, an intermediate pressure refrigerant discharged from
the first compressor (21a) is compressed in the second compressor
(21b) to the supercritical state. The supercritical refrigerant
flows into the outdoor heat exchanger (23), and dissipates heat to
the outdoor air. After the heat dissipation, the high pressure
refrigerant decreases in pressure in the outdoor expansion valve
(24) to become a gas-liquid two phase intermediate pressure
refrigerant, and flows into the gas-liquid separator (25) through
the second intermediate pressure refrigerant pipe (25b), the bridge
circuit (50), and the refrigerant inlet pipe (25d). The
intermediate pressure refrigerant entered the gas-liquid separator
(25) is separated to a liquid refrigerant and a gaseous
refrigerant. The intermediate pressure gaseous refrigerant flows
from the upper portion in the space inside the gas-liquid separator
(25) to the suction side of the second compressor (21b) through the
first intermediate pressure refrigerant pipe (25a), merges with the
intermediate pressure gaseous refrigerant discharged from the first
compressor (21a), and is sucked into the second compressor (21b).
The intermediate pressure liquid refrigerant is temporarily stored
in the lower portion of the space inside the gas-liquid separator
(25), and then exits from the lower portion of the space to pass
through the refrigerant outlet pipe (25e), the bridge circuit (50),
and the third intermediate pressure refrigerant pipe (25c). Then,
the intermediate pressure liquid refrigerant expands (decreases in
pressure) in the indoor expansion valve (26) to become a gas-liquid
two phase low pressure refrigerant, and flows into the indoor heat
exchanger (27). In the indoor heat exchanger (27), the refrigerant
absorbs heat from the indoor air to evaporate, and the cooled
indoor air is fed to the inside of the room. The evaporated
refrigerant is sucked into and compressed in the first compressor
(21a).
[0097] In the heating operation, the four way switching valve (22)
is set to the second state. When the first and second compressors
(21a, 21b) are operated in this state, the indoor heat exchanger
(27) functions as a radiator (a gas cooler), and the outdoor heat
exchanger (23) functions as an evaporator to perform the
refrigeration cycle. Specifically, an intermediate pressure gaseous
refrigerant discharged from the first compressor (21a) is
compressed in the second compressor (21b) to the supercritical
state. The supercritical refrigerant flows into the indoor heat
exchanger (27), and dissipates heat to the indoor air. The heated
indoor air is fed to the inside of the room. After the heat
dissipation, the refrigerant decreases in pressure in the indoor
expansion valve (26) to become a gas-liquid two phase intermediate
pressure refrigerant, and flows into the gas-liquid separator (25)
through the third intermediate pressure refrigerant pipe (25c), the
bridge circuit (50), and the refrigerant inlet pipe (25d). The
intermediate pressure refrigerant entered the gas-liquid separator
(25) is separated into a liquid refrigerant and a gaseous
refrigerant. The intermediate pressure gaseous refrigerant flows
from the upper portion of the space inside the gas-liquid separator
(25) to the suction side of the second compressor (21b) through the
first intermediate pressure refrigerant pipe (25a), merges with the
intermediate pressure gaseous refrigerant discharged from the first
compressor (21a), and is sucked into the second compressor (21b).
The intermediate pressure liquid refrigerant is temporarily stored
in the lower portion of the space inside the gas-liquid separator
(25), and then flows from the lower portion of the space to the
outdoor expansion valve (24) through the refrigerant outlet pipe
(25e), the bridge circuit (50), and the second intermediate
pressure refrigerant pipe (25b). The intermediate pressure liquid
refrigerant expands (decreases in pressure) as it passes through
the outdoor expansion valve (24) to become a gas-liquid two phase
low pressure refrigerant, and flows into the outdoor heat exchanger
(23). In the outdoor heat exchanger (23), the refrigerant absorbs
heat from the outdoor air to evaporate. The evaporated refrigerant
is sucked into and compressed in the first compressor (21a).
[0098] The air conditioner (210) configured in this manner
includes, in the refrigerant circuit (220), an indoor temperature
sensor (31), a low pressure sensor (32), a discharge temperature
sensor (33), a high pressure sensor (34), a suction temperature
sensor (35), an intermediate pressure saturation temperature sensor
(36), a gas cooler outlet temperature sensor (37) for the heating
operation.
[0099] The indoor temperature sensor (31) is a temperature sensing
part for sensing the temperature of the indoor air entering the
indoor heat exchanger (27). The low pressure sensor (32) is a
pressure sensing part for sensing the pressure of the refrigerant
sucked into the first compressor (21a), i.e., the low pressure of
the refrigeration cycle in the refrigerant circuit (220). The
discharge temperature sensor (33) is a temperature sensing part for
sensing the temperature of the refrigerant discharged from the
second compressor (21b). The high pressure sensor (34) is a
pressure sensing part for sensing the pressure of the refrigerant
discharged from the second compressor (21b), i.e., the high
pressure of the refrigeration cycle in the refrigerant circuit
(220). The suction temperature sensor (35) is a temperature sensing
part for sensing the temperature of the refrigerant sucked into the
first compressor (21a). The intermediate pressure saturation
temperature sensor (36) is arranged in the refrigerant outlet pipe
(25e) connecting the bridge circuit (50) and the gas-liquid
separator (25), and functions as a temperature sensing part for
sensing the temperature of the intermediate pressure refrigerant,
i.e., the intermediate pressure saturation temperature of the
refrigeration cycle. The gas cooler outlet temperature sensor (37)
for the heating operation is a temperature sensing part for sensing
the temperature of the refrigerant at an outlet of the indoor heat
exchanger (27) when the refrigerant circulates in the refrigerant
circuit (220) in a heating cycle.
[0100] The controller (240) is configured to receive output signals
from the indoor temperature sensor (31), the low pressure sensor
(32), the high pressure sensor (34), the suction temperature sensor
(35), the intermediate pressure saturation temperature sensor (36),
and the gas cooler outlet temperature sensor (37) for the heating
operation, and to control the operation frequencies of the first
and second compressors (21a, 21b), and the degrees of opening of
the outdoor and indoor expansion valves (24, 26).
[0101] The controller (240) includes, as shown in FIGS. 5 and 6, a
target low pressure calculator (41) for calculating a target low
pressure P1s which is a target value of the low pressure of the
refrigeration cycle, a target high pressure calculator (42) for
calculating a target high pressure Phs which is a target value of
the high pressure of the refrigeration cycle, a target superheat
degree calculator (44) for calculating the target degree of
superheat SHs of the refrigerant which is a target value of the
degree of superheat of the refrigerant, an actual superheat degree
calculator (45) for calculating the actual degree of superheat SH
of the refrigerant, a target intermediate pressure saturation
temperature calculator (46) for calculating a target intermediate
pressure saturation temperature T3s which is a target value of the
intermediate pressure saturation temperature of the refrigerant, a
target gas cooler outlet temperature calculator (47) for
calculating a target gas cooler outlet temperature T4s which is a
target value of the temperature of the refrigerant at an outlet of
the gas cooler in the heating operation, and a control signal
generator (249) for generating control signals transmitted to the
first and second compressors (21a, 21b), and the outdoor and indoor
expansion valves (24, 26). The controller (240) performs the
control in different ways for the cooling operation and the heating
operation. Therefore, a control block for the cooling operation is
shown in FIG. 5, and a control block for the heating operation is
shown in FIG. 6.
[0102] In the cooling operation, the target superheat degree
calculator (44) calculates the target degree of superheat SHs of
one of the outdoor heat exchanger (23) and the indoor heat
exchanger (27) functioning as an evaporator based on a temperature
deviation et between a set temperature Ts and an indoor temperature
Ta from the indoor temperature sensor (31). In the heating
operation, the target superheat degree calculator (44) calculates
the target degree of superheat SHs based on the temperature
deviation et and an outdoor temperature T0 from the outdoor
temperature sensor (30).
[0103] The actual superheat degree calculator (45) calculates the
actual degree of superheat SH of the refrigerant at an outlet of a
heat exchanger functioning as an evaporator of the outdoor heat
exchanger (23) and the indoor heat exchanger (27) based on an
actual low pressure P1 from the low pressure sensor (32) and an
actual suction temperature T2 from the suction temperature sensor
(35).
[0104] The target intermediate pressure saturation temperature
calculator (46) calculates the target intermediate pressure
saturation temperature T3s based on at least one of the outdoor
temperature TO from the outdoor temperature sensor (30), the indoor
temperature Ta from the indoor temperature sensor (31), an actual
high pressure Ph from the high pressure sensor (34), the actual low
pressure P1 from the low pressure sensor (32), the target high
pressure Phs calculated by the target high pressure calculator
(42), and the target low pressure P1s calculated by the target low
pressure calculator (41).
[0105] The target gas cooler outlet temperature calculator (47)
calculates the target gas cooler outlet temperature T4s, which is a
target value of the temperature of the refrigerant at the outlet of
the indoor heat exchanger (27) when the indoor heat exchanger (27)
functions as a radiator, based on the temperature deviation et.
[0106] The target superheat degree calculator (44), the actual
superheat degree calculator (45), and the target intermediate
pressure saturation temperature calculator (46) have maps and
functions, respectively. Each of them is configured to deliver an
output value (a target value) corresponding to the input.
[0107] Signals input to the control signal generator (249) in the
cooling operation are different from those input to the control
signal generator (249) in the heating operation. The control signal
generator (249) has a plurality of PID control sections (p1a, p2a,
p1b, p2b, . . . ) each having a control parameter corresponding to
the input signal.
[0108] In the cooling operation, the control signal generator (49)
receives a low pressure deviation el between the target low
pressure P1s calculated by the target low pressure calculator (41)
and the actual low pressure P1 from the low pressure sensor (32), a
high pressure deviation e2 between the target high pressure Phs
calculated by the target high pressure calculator (42) and the
actual high pressure Ph from the high pressure sensor (34), a
superheat degree deviation e4 between the target degree of
superheat SHs calculated by the target superheat degree calculator
(44) and the actual degree of superheat SH calculated by the actual
superheat degree calculator (45), and an intermediate pressure
saturation temperature deviation e5 between the target intermediate
pressure saturation temperature T3s calculated by the target
intermediate pressure saturation temperature calculator (46) and
the output signal from the intermediate pressure saturation
temperature sensor (36) (i.e., an actual intermediate pressure
saturation temperature T3).
[0109] In the cooling operation, sixteen PID control sections (p1c,
p2c, . . . ) of the control signal generator (249) are operated.
Specifically, the high pressure deviation e2 input to the control
signal generator (249) is input to the first to fourth PID control
sections (p1c-p4c), the intermediate pressure saturation
temperature deviation e5 is input to the fifth to eighth PID
control sections (p5c-p8c), the low pressure deviation el is input
to the ninth to twelfth PID control sections (p9c-p12c), and the
superheat degree deviation e4 is input to the thirteenth to
sixteenth PID control sections (p13c-p16c).
[0110] Each of the first to sixteenth PID control sections (p1c,
p2c, . . . ) delivers an output generated by multiplying the input
deviation by a predetermined control parameter. As a result, the
control signal generator (249) generates a first compressor
frequency control signal .DELTA.fc1 by adding the output signals
from the first, fifth, ninth, and thirteenth PID control sections
(p1c, p5c, p9c, p13c), generates a second compressor frequency
control signal .DELTA.fc2 by adding the output signals from the
second, sixth, tenth, and fourteenth PID control sections (p2c,
p6c, p10c, p14c), generates an outdoor expansion valve control
signal .DELTA.ev1 by adding the output signals from the third,
seventh, eleventh, and fifteenth PID control sections (p3c, p7c,
p11c, p15c), and generates an indoor expansion valve control signal
.DELTA.ev2 by adding the output signals from the fourth, eighth,
twelfth, and sixteenth PID control sections (p4c, p8c, p12c,
p16c).
[0111] The first compressor frequency control signal .DELTA.fc1,
the second compressor frequency control signal .DELTA.fc2, the
outdoor expansion valve control signal .DELTA.ev1, and the indoor
expansion valve control signal .DELTA.ev2 generated in this manner
are output to the air conditioner (210).
[0112] In the air conditioner (210), the capacity of the first
compressor (21a) varies to a value corresponding to the first
compressor frequency control signal Me1, and the capacity of the
second compressor (21b) varies to a value corresponding to the
second compressor frequency control signal .DELTA.fc2.
[0113] The degree of opening of the outdoor expansion valve (24) is
adjusted according to the outdoor expansion valve control signal
.DELTA.ev1, and the degree of opening of the indoor expansion valve
(26) is also adjusted according to the indoor expansion valve
control signal .DELTA.ev2.
[0114] The low pressure P1, the high pressure Ph, the suction
temperature T2, and the intermediate pressure saturation
temperature T3 in the air conditioner (210) operated in this
operation state are fed back to the controller (240) through the
low pressure sensor (32), the high pressure sensor (34), the
suction temperature sensor (35), and the intermediate pressure
saturation temperature sensor (36). Thus, the controller (240)
performs feed back control to set the low pressure P1, the high
pressure Ph, the degree of superheat SH, and the intermediate
pressure saturation temperature T3 to target values corresponding
to the operation state, respectively.
[0115] As described above, each of the first and second compressor
frequency control signals .DELTA.fc1 and .DELTA.fc2, and the
outdoor and indoor expansion valve control signals .DELTA.ev1 and
.DELTA.ev2 are generated by associating the low pressure deviation
e1, the high pressure deviation e2, the superheat degree deviation
e4, and the intermediate pressure saturation temperature deviation
e5 with each other. Specifically, the objects of control each
corresponding to the physical values are not controlled
independently, but the first and second compressors (21a, 21b), and
the outdoor and indoor expansion valves (24, 26) are controlled
concurrently, thereby concurrently, or simultaneously controlling
the low pressure, the high pressure, the degree of superheat, and
the intermediate pressure saturation temperature. That is, each of
the low pressure, the high pressure, the degree of superheat, and
the intermediate pressure saturation temperature is not controlled
only by one of the first and second compressors (21a, 21b), and the
outdoor and indoor expansion valves (24, 26), but is controlled by
all the first and second compressors (21a, 21b), and the outdoor
and indoor expansion valves (24, 26). More specifically, each of
the objects of control, i.e., the first and second compressors
(21a, 21b), and the outdoor and indoor expansion valves (24, 26),
is controlled not only based on the changes of the low pressure,
the high pressure, the degree of superheat, and the intermediate
pressure saturation temperature resulting solely from the control
of the each of the objects of control, but is controlled based on
the changes of the low pressure, the high pressure, the degree of
superheat, and the intermediate pressure saturation temperature
resulting from the control of the other objects of control (in
other words, the control parameters of the first to sixteenth PID
control sections (p1c, p2c, . . . ) are determined so as to take
these changes into account).
[0116] In the heating operation, the control signal generator (249)
receives the high pressure deviation e2 between the target high
pressure Phs calculated by the target high pressure calculator (42)
and the actual high pressure Ph from the high pressure sensor (34),
the superheat degree deviation e4 between the target degree of
superheat SHs calculated by the target superheat degree calculator
(44) and the actual degree of superheat SH calculated by the actual
superheat degree calculator (45), the intermediate pressure
saturation temperature deviation e5 between the target intermediate
pressure saturation temperature T3s calculated by the target
intermediate pressure saturation temperature calculator (46) and
the actual intermediate pressure saturation temperature T3 from the
intermediate pressure saturation temperature sensor (36), and the
gas cooler outlet temperature deviation e6 between the target gas
cooler outlet temperature T4s calculated by the target gas cooler
outlet temperature calculator (47) and the output signal from the
gas cooler output temperature sensor (37) for the heating operation
(i.e., an actual gas cooler outlet temperature T4).
[0117] In the heating operation, sixteen PID control sections (p1d,
p2d, . . . ) of the control signal generator (249) different from
those operated in the cooling operation are operated. Specifically,
the high pressure deviation e2 input to the control signal
generator (249) is input to the first to the fourth PID control
sections (p1d-p4d), the intermediate pressure saturation
temperature deviation e5 is input to the fifth to the eighth PID
control sections (p5d-p8d), the gas cooler outlet temperature
deviation e6 is input to the ninth to twelfth PID control sections
(p9d-p12d), and the superheat degree deviation e4 is input to the
thirteenth to sixteenth PID control sections (p13d-p16d).
[0118] Each of the first to sixteenth PID control sections (p1d,
p2d, . . . ) delivers an output by multiplying the input deviation
by a predetermined control parameter. As a result, the control
signal generator (249) generates a first compressor frequency
control signal .DELTA.fc1 by adding the output signals from the
first, fifth, ninth, and thirteenth PID control sections (p1d, p5d,
p9d, p13d), generates a second compressor frequency control signal
.DELTA.fc2 by adding the output signals from the second, sixth,
tenth, and fourteenth PID control sections (p2d, p6d, p10d, p14d),
generates an outdoor expansion valve control signal .DELTA.ev1 by
adding the output signals from the third, seventh, eleventh, and
fifteenth PID control sections (p3d, p7d, p11d, p15d), and
generates an indoor expansion valve control signal .DELTA.ev2 by
adding the fourth, eighth, twelfth, and sixteenth PID control
sections (p4d, p8d, p12d, p16d).
[0119] The first compressor frequency control signal .DELTA.fc1,
the second compressor frequency control signal .DELTA.fc2, the
outdoor expansion valve control signal .DELTA.ev1, and the indoor
expansion valve control signal .DELTA.ev2 generated in this manner
are output to the air conditioner (210).
[0120] In the air conditioner (210), the capacity of the first
compressor (21a) varies according to the first compressor frequency
control signal .DELTA.fc1, the capacity of the second compressor
(21b) varies according to the second compressor frequency control
signal .DELTA.fc2. The degree of opening of the outdoor expansion
valve (24) is adjusted according to the outdoor expansion valve
control signal .DELTA.ev1, and the degree of opening of the indoor
expansion valve (26) is adjusted according to the expansion valve
control signal .DELTA.ev2.
[0121] The high pressure Ph, the suction temperature T2, the
intermediate pressure saturation temperature T3, and the gas cooler
outlet temperature T4 in the air conditioner (210) operated in this
operation state are fed back to the controller (240) through the
high pressure sensor (34), the suction temperature sensor (35), the
intermediate pressure saturation temperature sensor (36), and the
gas cooler outlet temperature sensor (37) for the heating
operation. Thus, the controller (240) performs feed back control to
set the high pressure Ph, the degree of superheat SH, the
intermediate pressure saturation temperature T3, and the gas cooler
outlet temperature T4 to target values corresponding to the
operation state, respectively.
[0122] The first and second compressor frequency control signals
.DELTA.fc1 and .DELTA.fc2, and the outdoor and indoor expansion
valve control signals .DELTA.ev1 and .DELTA.ev2 are generated by
associating the high pressure deviation e2, the superheat degree
deviation e4, the intermediate pressure saturation temperature
deviation e5, and the gas cooler outlet temperature deviation e6
with each other. Specifically, the objects of control each
corresponding to the physical values are not controlled
independently, but the first and second compressors (21a, 21b), and
the outdoor and indoor expansion valves (24, 26) are concurrently
controlled, thereby concurrently, or simultaneously controlling the
high pressure, the degree of superheat, the intermediate pressure
saturation temperature, and the gas cooler outlet temperature. That
is, each of the high pressure, the degree of superheat, the
intermediate pressure saturation temperature, and the gas cooler
outlet temperature is not controlled only by one of the first and
second compressors (21a, 21b), and the outdoor and indoor expansion
valves (24, 26), but is controlled by all the first and second
compressors (21a, 21b), and the outdoor and indoor expansion valves
(24, 26). More specifically, each of the objects of control, i.e.,
the first and second compressors (21a, 21b), and the outdoor and
indoor expansion valves (24, 26), is controlled not only based on
the changes of the high pressure, the degree of superheat, the
intermediate pressure saturation temperature, and the gas cooler
outlet temperature resulting from the control of the each of the
objects of control, but is controlled based on the changes of the
high pressure, the degree of superheat, the intermediate pressure
saturation temperature, and the gas cooler outlet temperature
resulting from the control of the other objects of control (in
other words, the control parameters of the first to sixteenth PID
control sections (p1c, p2c, . . . ) are determined so as to take
these changes into account).
[0123] Thus, according to the second embodiment, the plurality of
objects of control (e.g., the first compressor (21a), the outdoor
expansion valve (24), etc.) are simultaneously controlled in such a
manner that the high pressure of the refrigeration cycle, and the
predetermined physical value of the air conditioner (210) are
adjusted to the predetermined target values corresponding to the
operation state. At the same time, each of the objects of control
is controlled in consideration of the changes of the physical value
and the high pressure of the refrigeration cycle resulting from the
control of the plurality of objects of control. According to these
schemes, the capability of the air conditioner (210) (e.g., the low
pressure, the degree of superheat, etc., in the cooling operation)
can be controlled with the high pressure stably kept to the target
value corresponding to the operation state. This can avoid an event
in which the control of a target physical value cannot be easily
settled, i.e., an event in which adjustment of a first physical
value changes a second physical value, and correction of the change
of the second physical value by adjusting the second physical value
changes a third physical value or the first physical value already
adjusted, thereby involving another adjustment. This allows for an
improved convergence rate of the control of the capability and the
high pressure of the air conditioner (210).
[0124] According to the present embodiment, four physical values,
i.e., the low pressure, the high pressure , the degree of
superheat, and the intermediate pressure saturation temperature,
are controlled by four objects of control, i.e., the first and
second compressors (21a, 21b), and the outdoor and indoor expansion
valves (24, 26), in the cooling operation. In the heating
operation, four physical values, i.e., the high pressure, the
degree of superheat, the intermediate pressure saturation
temperature, and the gas cooler outlet temperature, are controlled
by four objects of control, i.e., the first and second compressors
(21a, 21b), and the outdoor and indoor expansion valves (24, 26).
However, some of the objects of control easily have an effect on
the physical values, but some do not. That is, even when one of the
objects of control is changed, some physical values are less
susceptible to the change. In the present embodiment, all the
physical values to be controlled are input, and they are associated
with each other to generate control signals each corresponding to
the objects of control. In generating a control signal for one of
the objects of control to which a certain physical value is less
susceptible, the degree of association of the certain physical
value may be reduced or eliminated (specifically, among the PID
control sections (p1c, p1d, . . . ) for generating the control
signal for the object of control to which a certain physical value
is less susceptible, a control parameter of one of the PID control
sections corresponding to the certain physical value may be reduced
or reduced to zero.)
Third Embodiment
[0125] A third embodiment of the present disclosure will be
described below. An air conditioner (310) of the third embodiment
is different from the air conditioner (10) of the first embodiment
in that a plurality of indoor heat exchangers (27a, 27b) are
provided in a refrigerant circuit (320).
[0126] Specifically, the air conditioner (310) includes a
refrigerant circuit (320), and a controller (340) as shown in FIG.
7.
[0127] The refrigerant circuit (320) connects a compressor (21), a
four way switching valve (22), an outdoor heat exchanger (23), an
outdoor expansion valve (24), a receiver (25), a first and second
indoor expansion valves (26a, 26b), and first and second indoor
heat exchangers (27a, 27b). In this refrigerant circuit (320), a
plurality of (two in the present embodiment) indoor heat exchangers
(27a, 27b) are connected in parallel, and an indoor expansion valve
(26a (26b)) is connected to each of the indoor heat exchangers (27a
(27b)).
[0128] Specifically, in the refrigerant circuit (320), a discharge
side of the compressor (21) is connected to a first port of the
four way switching valve (22), and a suction side of the compressor
(21) is connected to a second port of the four way switching valve
(22). In the refrigerant circuit (320), the outdoor heat exchanger
(23), the outdoor expansion valve (24), the receiver (25), the two
indoor expansion valves (26a, 26b), and the two indoor heat
exchangers (27a, 27b) are sequentially arranged in a path from a
third port to a fourth port of the four way switching valve
(22).
[0129] Each of the outdoor expansion valve (24), and the first and
second indoor heat expansion valves (26a, 26b) is comprised of an
electronic expansion valve whose degree of opening is variable, and
whose valve element (not shown) is driven by a pulse motor (not
shown). The outdoor expansion valve (24) constitutes a heat source
side expansion mechanism, and the first and second indoor expansion
valves (26a, 26b) constitute a utilization side expansion
mechanism.
[0130] The first and second indoor heat exchangers (27a, 27b) are
provided with first and second indoor fans (29a, 29b),
respectively.
[0131] Like the air conditioner of the first embodiment, the air
conditioner (310) is able to switchably perform cooling operation
and heating operation by switching the four way switching valve
(22).
[0132] In the cooling operation, the four way switching valve (22)
is set to the first state. When the compressor (21) is operated in
this state, the outdoor heat exchanger (23) functions as a
radiator, and the first and second indoor heat exchangers (27a,
27b) function as evaporators to perform the refrigeration cycle.
Specifically, the refrigerant in the supercritical state discharged
from the compressor (21) flows into the outdoor heat exchanger
(23), and dissipates heat to the outdoor air. After the heat
dissipation, the refrigerant expands (decreases in pressure) as it
passes through the outdoor expansion valve (24). The expanded
refrigerant passes through the receiver (25), and is branched, and
the branched flows of the refrigerant pass through the first and
second indoor expansion valves (26a, 26b). At this time, the
refrigerant further expands (decreases in pressure), and flows into
the first and second indoor heat exchangers (27a, 27b). That is,
the refrigerant flowing between the outdoor expansion valve (24)
and the indoor expansion valves (26a, 26b), and in the receiver
(25) is at an intermediate pressure. In the first and second indoor
heat exchangers (27a, 27b), the refrigerant absorbs heat from the
indoor air to evaporate, and the cooled air is fed to the inside of
the room. The evaporated refrigerant is sucked into and compressed
in the compressor (21).
[0133] In the heating operation, the four way switching valve (22)
is set to the second state. When the compressor (21) is operated in
this state, the first and second indoor heat exchangers (27a, 27b)
function as radiators, and the outdoor heat exchanger (23)
functions as an evaporator to perform the refrigeration cycle.
Specifically, the refrigerant discharged from the compressor (21)
in the supercritical state is branched, and the branched flows of
the refrigerant enter the first and second indoor heat exchangers
(27a, 27b), respectively, and dissipate heat to the indoor air. The
heated indoor air is fed to the inside of the room. After the heat
dissipation, the refrigerant expands (decreases in pressure) as it
passes through the second indoor expansion valves (26a, 26b). The
expanded refrigerant passes through the receiver (25), and then
further expands (decreases in pressure) as it passes through the
outdoor expansion valve (24). That is, the refrigerant flowing
between the first and second indoor expansion valves (26a, 26b) and
the outdoor expansion valve (24), and in the receiver (25) is at
the intermediate pressure. The refrigerant expanded by the outdoor
expansion valve (24) flows into the outdoor heat exchanger (23),
and absorbs heat from the outdoor air to evaporate. The evaporated
refrigerant is sucked into and compressed in the compressor
(21).
[0134] The air conditioner (310) configured in this manner
includes, in the refrigerant circuit (320), first and second indoor
temperature sensors (31a, 31b), a low pressure sensor (32), a high
pressure sensor (34), a suction temperature sensor (35), first and
second gas cooler outlet temperature sensors (37a, 37b) for the
heating operation, first and second evaporator outlet temperature
sensors (38a, 38b), and a gas cooler outlet temperature sensor (39)
for the cooling operation.
[0135] The first and second indoor temperature sensors (31a, 31b)
are sensing parts for sensing the temperatures of the flows of the
indoor air entering the first and second indoor heat exchangers
(27a, 27b), and are provided for the first and second indoor heat
exchangers (27a, 27b), respectively. The first and second gas
cooler outlet temperature sensors (37a, 37b) for the heating
operation are temperature sensing parts for sensing the
temperatures of the refrigerant at the outlets of the first and
second indoor heat exchangers (27a, 27b), respectively, when the
refrigerant circulates in the refrigerant circuit (320) in the
heating cycle. The first and second gas cooler outlet temperature
sensors (37a, 37b) for the heating operation are provided for the
first and second indoor heat exchangers (27a, 27b), respectively.
The first and second evaporator outlet temperature sensors (38a,
38b) are temperature sensing parts for sensing the temperatures of
the refrigerant at the outlets of the first and second indoor heat
exchangers (27a, 27b), respectively, when the refrigerant
circulates in the refrigerant circuit (320) in the cooling cycle,
and are provided for the first and second indoor heat exchangers
(27a, 27b), respectively.
[0136] The controller (340) is configured to receive output signals
from the first and second indoor temperature sensors (31a, 31b),
the low pressure sensor (32), the high pressure sensor (34), the
suction temperature sensor (35), the first and second gas cooler
outlet temperature sensors (37a, 37b) for the heating operation,
and the first and second evaporator outlet temperature sensors
(38a, 38b), and to control the operation frequency of the
compressor (21), and the degrees of opening of the outdoor, first,
and second indoor expansion valves (24, 26a, 26b).
[0137] The controller (340) includes, as shown in FIGS. 8 and 9, a
target low pressure calculator (41) for calculating a target low
pressure P1s which is a target value of the low pressure of the
refrigeration cycle, a target high pressure calculator (42) for
calculating a target high pressure Phs which is a target value of
the high pressure of the refrigeration cycle, an actual superheat
degree calculator (45) for calculating the actual degree of
superheat SH which is the actual degree of superheat of the
refrigerant, a target first superheat degree calculator (44a) for
calculating a target first degree of superheat SHas which is a
target value of the degree of superheat of the refrigerant at the
outlet of the first indoor heat exchanger (27a) in the cooling
operation, a target second superheat degree calculator (44b) for
calculating a target second degree of superheat SHbs which is a
target value of the degree of superheat of the refrigerant at the
outlet of the second indoor heat exchanger (27b) in the cooling
operation, a target first gas cooler outlet temperature calculator
(47a) for calculating a target first gas cooler outlet temperature
T4as which is a target value of the temperature of the refrigerant
at the outlet of the first indoor heat exchanger (27a) in the
heating operation, a target second gas cooler outlet temperature
(47b) for calculating a target second gas cooler outlet temperature
T4bs which is a target value of the temperature of the refrigerant
at the outlet of the second indoor heat exchanger (27b) in the
heating operation, a target superheat degree calculator (44) for
calculating the target degree of superheat SHs which is a target
value of the degree of superheat of the refrigerant at the outlet
of the outdoor heat exchanger (23) in the heating operation, and a
control signal generator (349) for generating control signals
transmitted to the compressor (21), and the outdoor, first, and
second indoor expansion valves (24, 26a, 26b). The controller (340)
performs the control in different ways for the cooling operation
and the heating operation. Therefore, a control block for the
cooling operation is shown in FIG. 8, and a control block for the
heating operation is shown in FIG. 9.
[0138] The target low pressure calculator (41) calculates the
target low pressure P1s of the air conditioner (310) as a whole
based on a temperature deviation eta between a set temperature Tsa
of the first indoor heat exchanger (27a) and an indoor temperature
Taa from the first indoor temperature sensor (31a), and a
temperature deviation etb between a set temperature Tsb of the
second indoor heat exchanger (27b) and an indoor temperature Tab
from the second indoor temperature sensor (31b).
[0139] In the cooling operation, the target high pressure
calculator (42) calculates the target high pressure Phs of the air
conditioner (310) based on an outdoor temperature TO from the
outdoor temperature sensor (30), and a gas cooler outlet
temperature T4 from the gas cooler outlet temperature sensor (39)
for the cooling operation. In the heating operation, the target
high pressure calculator (42) calculates the target high pressure
Phs of the air conditioner (310) based on at least one of the
temperature deviation eta of the first indoor heat exchanger (27a),
the temperature deviation etb of the second indoor heat exchanger
(27b), the target first gas cooler outlet temperature T4as
calculated by the target first gas cooler outlet temperature
calculator (47a), the target second gas cooler outlet temperature
T4bs calculated by the target second gas cooler outlet temperature
calculator (47b), and the first and second gas cooler outlet
temperatures T4a, T4b from the first and second gas cooler outlet
temperature sensors (37a, 37b) for the heating operation.
[0140] The target first superheat degree calculator (44a)
calculates the target first degree of superheat SHas based on the
temperature deviation eta of the first indoor heat exchanger
(27a).
[0141] The target second superheat degree calculator (44b)
calculates the target second degree of superheat SHbs based on the
temperature deviation etb of the second indoor heat exchanger
(27b).
[0142] In the cooling operation, the actual superheat degree
calculator (45) calculates an actual first or actual second degree
of superheat SHa or SHb, which is the actual degree of superheat of
the refrigerant at the outlet of the first or second indoor heat
exchanger (27a, 27b), based on the actual low pressure P1 from the
low pressure sensor (32), and the first or second evaporator outlet
temperature T5a or Tbb from the first or second evaporator outlet
temperature sensor (38a, 38b). In the heating operation, the actual
superheat degree calculator (45) calculates the actual degree of
superheat SH, which is the actual degree of superheat of the
refrigerant at the outlet of the outdoor heat exchanger (23), based
on the actual low pressure P1 from the low pressure sensor (32),
and the actual suction temperature T2 from the suction temperature
sensor (35).
[0143] The target first gas cooler outlet temperature calculator
(47a) calculates the target first gas cooler outlet temperature
T4as based on the temperature deviation eta of the first indoor
heat exchanger (27a).
[0144] The target second gas cooler outlet temperature calculator
(47b) calculates the target second gas cooler outlet temperature
T4bs based on the temperature deviation etb of the second indoor
heat exchanger (27b).
[0145] The target low pressure calculator (41), the target high
pressure calculator (42), the target first superheat degree
calculator (44a), the target second superheat degree calculator
(44b), the target superheat degree calculator (44), the target
first gas cooler outlet temperature calculator (47a), and the
target second gas cooler outlet temperature calculator (47b) have
maps and functions, respectively. Each of them is configured to
output an output value corresponding to the input.
[0146] Signals input to the control signal generator (349) in the
cooling operation are different from those input to the control
signal generator (349) in the heating operation. The control signal
generator (349) has PID control sections (p1e, p2e, p1f, p2f, . . .
) each having a control parameter corresponding to the input
signal.
[0147] In the cooling operation, the control signal generator (349)
receives a low pressure deviation el between the target low
pressure P1s calculated by the target low pressure calculator (41)
and the actual low pressure P1 from the low pressure sensor (32), a
high pressure deviation e2 between the target high pressure Phs
calculated by the target high pressure calculator (42) and the
actual high pressure Ph from the high pressure sensor (34), a first
superheat degree deviation e4a between the target degree of
superheat SHas calculated by the target first superheat degree
calculator (44a) and the actual first degree of superheat SHa of
the first indoor heat exchanger (27a) calculated by the actual
superheat degree calculator (45), and the second superheat degree
deviation e4b between the target degree of superheat SHbs
calculated by the target second superheat degree calculator (44b)
and the actual second degree of superheat SHb of the second indoor
heat exchanger (27b) calculated by the actual superheat degree
calculator (45).
[0148] In the cooling operation, sixteen PID control sections (p1e,
p2e, . . . ) of the control signal generator (349) are operated.
Specifically, the low pressure deviation el input to the control
signal generator (349) is input to the first to fourth PID control
sections (p1e-p4e), the high pressure deviation e2 is input to the
fifth to eighth PID control sections (p5e-p8e), the first superheat
degree deviation e4a is input to the ninth to twelfth PID control
sections (p9e-p12e), and the second superheat degree deviation e4b
is input to the thirteenth to sixteenth PID control sections
(p13e-p16e).
[0149] Each of the first to sixteenth PID control sections (p1e,
p2e, . . . ) delivers an output generated by multiplying the input
deviation by a predetermined control parameter. Specifically, the
control signal generator (349) generates a compressor frequency
control signal .DELTA.fc by adding output signals from the first,
fifth, ninth, and thirteenth PID control sections (p1e, p5e, p9e,
p13e), generates an outdoor expansion valve control signal
.DELTA.ev1 by adding output signals from the second, sixth, tenth,
and fourteenth PID control sections (p2e, p6e, p10e, p14e),
generates a first indoor expansion valve control signal .DELTA.ev2a
by adding output signals from the third, seventh, eleventh, and
fifteenth PID control sections (p3e, p7e, p11e, p15e), and
generates a second indoor expansion valve control signal
.DELTA.ev2b by adding output signals from the fourth, eighth,
twelfth, and sixteenth PID control sections (p4e, p8, p12e,
p16e).
[0150] The compressor frequency control signal .DELTA.fc, the
outdoor expansion valve control signal .DELTA.ev1, the first indoor
expansion valve control signal .DELTA.ev2a, and the second indoor
expansion valve control signal .DELTA.ev2b are output to the air
conditioner (310).
[0151] In the air conditioner (310), the capacity of the compressor
(21) varies to a value corresponding to the compressor frequency
control signal .DELTA.fc.
[0152] The degree of opening of the outdoor expansion valve (24) is
adjusted according to the outdoor expansion valve control signal
.DELTA.ev1, and the degree of opening of the first indoor expansion
valve (26a) is adjusted according to the first indoor expansion
valve control signal .DELTA.ev2a, and the degree of opening of the
second indoor expansion valve (26b) is adjusted according to the
second indoor expansion valve control signal .DELTA.ev2b.
[0153] The low pressure P1, the high pressure Ph, the first
evaporator outlet temperature T5a of the first indoor heat
exchanger (27a), and the second evaporator outlet temperature T5b
of the second indoor heat exchanger (27b) of the air conditioner
(310) operated in this operation state are fed back to the
controller (340) through the low pressure sensor (32), the high
pressure sensor (34), and the first and second evaporator outlet
temperature sensors (38a, 38b). Thus, the controller (340) performs
feed back control to set the low pressure P1, the high pressure Ph,
and the first and second degrees of superheat SHa and SHb to target
values corresponding to the operation state, respectively.
[0154] As described above, each of the compressor frequency control
signal .DELTA.fc, and the outdoor, first indoor, and second indoor
expansion valve control signals .DELTA.ev1, .DELTA.ev2a, and
.DELTA.ev2b is generated by associating the low pressure deviation
e1, the high pressure deviation e2, the first superheat degree
deviation e4a, and the second superheat degree deviation e4b with
each other. Specifically, the objects of control each corresponding
to the physical values are not controlled independently, but the
compressor (21), the outdoor expansion valve (24), and the first
and second indoor expansion valves (26a, 26b) are controlled
concurrently, thereby concurrently, or simultaneously controlling
the low pressure, the high pressure, the first degree of superheat,
and the second degree of superheat. That is, each of the low
pressure, the high pressure, the first degree of superheat, and the
second degree of superheat is not controlled only by one of the
compressor (21), the outdoor expansion valve (24), and the first
and second indoor expansion valves (26a, 26b), but is controlled by
all the compressor (21), the outdoor expansion valve (24), and the
first and second indoor expansion valves (26a, 26b). More
specifically, each of the objects of control, i.e., the compressor
(21), the outdoor expansion valve (24), and the first and second
indoor expansion valves (26a, 26b), is not controlled not only
based on the changes of the low pressure, the high pressure, the
first degree of superheat, and the second degree of superheat
resulting from the control of the each of the objects of control,
but is controlled based on the changes of the low pressure, the
high pressure, the first degree of superheat, and the second degree
of superheat resulting from the control of the other objects of
control (in other words, the control parameters of the first to
sixteenth PID control sections (p1e, p2e, . . . ) are determined so
as to take these changes into account).
[0155] In the heating operation, the control signal generator (349)
receives a high pressure deviation e2 between the target high
pressure Phs calculated by the target high pressure calculator (42)
and the actual high pressure Ph from the high pressure sensor (34),
a superheat degree deviation e4 between the target degree of
superheat SHs calculated by the target superheat degree calculator
(44) and the actual degree of superheat SH calculated by the actual
superheat degree calculator (45), a first gas cooler outlet
temperature deviation e6a between the target first gas cooler
outlet temperature T4as calculated by the target first gas cooler
outlet temperature calculator (47a) and the actual first gas cooler
outlet temperature T4a from the first gas cooler outlet temperature
sensor (37a) for the heating operation, and a second gas cooler
outlet temperature deviation e6b between the target second gas
cooler outlet temperature T4bs calculated by the target second gas
cooler outlet temperature calculator (47b) and the actual second
gas cooler outlet temperature T4b from the second gas cooler outlet
temperature sensor (37b) for the heating operation.
[0156] In the heating operation, sixteen PID control sections (p1f,
p2f, . . . ) of the control signal generator (349) different from
those operated in the cooling operation are operated. Specifically,
the high pressure deviation e2 input to the control signal
generator (349) is input to the first to fourth PID control
sections (p1f-p4f), the first gas cooler outlet temperature
deviation e6a is input to the fifth to the eighth PID control
sections (p5f-p8f), the second gas cooler outlet temperature
deviation e6b is input to the ninth to the twelfth PID control
sections (p9f-p12f), and the superheat degree deviation e4 is input
to the thirteenth to sixteenth PID control sections
(p13f-p16f).
[0157] Each of the first to sixteenth PID control sections (p1f,
p2f, . . . ) delivers an output generated by multiplying the input
deviation by a predetermined control parameter. Specifically, the
control signal generator (349) generates a compressor frequency
control signal .DELTA.fc by adding output signals from the first,
fifth, ninth, and thirteenth PID control sections (p1f, p5f, p9f,
p13f), generates an outdoor expansion valve control signal
.DELTA.ev1 by adding output signals from the second, sixth, tenth,
and fourteenth PID control sections (p2f, p6f, p10f, p14f),
generates a first indoor expansion valve control signal .DELTA.ev2a
by adding output signals from the third, seventh, eleventh, and
fifteenth PID control sections (p3f, p7f, p11f, p15f), and
generates a second indoor expansion valve control signal
.DELTA.ev2b by adding output signals from the fourth, eighth,
twelfth, and sixteenth PID control sections (p4f, p8f, p12f,
p16f).
[0158] The compressor frequency control signal .DELTA.fc, the
outdoor expansion valve control signal .DELTA.ev1, the first indoor
expansion valve control signal .DELTA.ev2a, and the second indoor
expansion valve control signal .DELTA.ev2b generated in this manner
are output to the air conditioner (310).
[0159] In the air conditioner (310), the capacity of the compressor
(21) varies to a value corresponding to the compressor frequency
control signal .DELTA.fc.
[0160] The degree of opening of the outdoor expansion valve (24) is
adjusted according to the outdoor expansion valve control signal
.DELTA.ev1, the degree of the first indoor expansion valve (26a) is
adjusted according to the first indoor expansion valve control
signal .DELTA.ev2a, and the degree of opening of the second indoor
expansion valve (26b) is adjusted according to the second indoor
expansion valve control signal .DELTA.ev2b.
[0161] The low pressure P1, the high pressure Ph, the first gas
cooler outlet temperature T4a of the first indoor heat exchanger
(27a), and the second gas cooler outlet temperature T4b of the
second indoor heat exchanger (27b) in the air conditioner (310)
operated in this operation state are fed back to the controller
(340) through the low pressure sensor (32), the high pressure
sensor (34), and the first and second gas cooler outlet temperature
sensors (37a, 37b) for the heating operation. Thus, the controller
(340) performs feed back control to set the low pressure Pl, the
high pressure Ph, and the first and second degrees of superheat SHa
and SHb to target values corresponding to the operation state,
respectively.
[0162] Each of the compressor frequency control signal .DELTA.fc,
the outdoor expansion valve control signal .DELTA.ev1, and the
first and second indoor expansion valve control signals .DELTA.ev2a
and .DELTA.ev2b is generated by associating the high pressure
deviation e2, the superheat degree deviation e4, the first gas
cooler outlet temperature deviation e6a, and the second gas cooler
outlet temperature deviation e6b with each other. Specifically, the
objects of control each corresponding to the physical values are
not controlled independently, but the compressor (21), the outdoor
expansion valve (24), and the first and second indoor expansion
valves (26a, 26b), are controlled concurrently, thereby
concurrently, or simultaneously controlling the high pressure, the
degree of superheat, the first gas cooler outlet temperature, and
the second gas cooler outlet temperature. That is, each of the high
pressure, the degree of superheat, the first gas cooler outlet
temperature, and the second gas cooler outlet temperature is not
controlled only by one of the compressor (21), the outdoor
expansion valve (24), and the first and second indoor expansion
valves (26a, 26b), but is controlled by all the compressor (21),
the outdoor expansion valve (24), and the first and second indoor
expansion valves (26a, 26b). More specifically, the objects of
control, i.e., the compressor (21), the outdoor expansion valve
(24), and the first and second indoor expansion valves (26a, 26b)
is controlled not only based on the changes of the high pressure,
the degree of superheat, the first gas cooler outlet temperature,
and the second gas cooler outlet temperature resulting from the
control of the each of the objects of control, but is controlled
based on the changes of the high pressure, the degree of superheat,
the first and second gas cooler outlet temperatures resulting from
the control of the other objects of control (in other words, the
control parameters of the first to sixteenth PID control sections
(p1f, p2f, . . . ) are determined so as to take these changes into
account).
[0163] Thus, according to the third embodiment, the plurality of
objects of control (e.g., the compressor (21), the outdoor
expansion valve (24), etc.) are simultaneously controlled in such a
manner that the high pressure of the refrigeration cycle, and the
predetermined physical value of the air conditioner (310) are
adjusted to the predetermined target values corresponding to the
operation state. At the same time, each of the objects of control
is controlled in consideration of the changes of the physical value
and the high pressure of the refrigeration cycle resulting from the
control of the plurality of objects of control. According to these
schemes, the capability of the air conditioner (310) (e.g., the low
pressure, the degree of superheat, etc. in the cooling operation)
can be controlled with the high pressure stably kept to the target
value corresponding to the operation state. This can avoid an event
in which the control of a target physical value cannot be easily
settled, i.e., an event in which adjustment of a first physical
value changes a second physical value, and correction of the change
of the second physical value by adjusting the second physical value
changes a third physical value or the first physical value already
adjusted, thereby involving another adjustment. This allows for
improved settling of the control of the capability and the high
pressure of the air conditioner (310).
[0164] In the present embodiment, four physical values, i.e., the
low pressure, the high pressure, the first degree of superheat, and
the second degree of superheat, are controlled by the four objects
of control, i.e., the compressor (21), the outdoor expansion valve
(24), and the first and second indoor expansion valves (26a, 26b),
in the cooling operation. In the heating operation, four physical
values, i.e., the high pressure, the first gas cooler outlet
temperature, the second gas cooler outlet temperature, and the
degree of superheat, are controlled by four objects of control,
i.e., the compressor (21), the outdoor expansion valve (24), and
the first and second indoor expansion valves (26a, 26b). However,
some of the objects of control easily have an effect on the
physical values, but some do not. That is, even when one of the
objects of control is changed, some physical values are less
susceptible to the change. In the present embodiment, all the
physical values to be controlled are input, and they are associated
with each other to generate control signals each corresponding to
the objects of control. In generating a control signal for one of
the objects of control to which a certain physical value is less
susceptible, the degree of association of the certain physical
value may be reduced or eliminated (specifically, among the PID
control sections (p1e, p1f, . . . ) for generating the control
signal for the object of control to which a certain physical value
is less susceptible, a control parameter of one of the PID control
sections corresponding to the certain physical value may be reduced
or reduced to zero).
Other Embodiments
[0165] The above-described embodiments may be modified in the
following manner.
[0166] Specifically, the present disclosure is not limited to the
refrigerant circuit described in the above embodiments, but is
applicable to any refrigerant circuits. For example, as shown in
FIG. 10, the disclosed technique may be applied to a multi-type air
conditioner (410) which performs a two-stage compression
refrigeration cycle, and includes a plurality of indoor units. In
this case, for example, the high pressure, the low pressure, the
first evaporator outlet temperature, the second evaporator outlet
temperature, and the intermediate pressure saturation temperature
may be input, and these physical values may be associated to
generate control signals for controlling the first and second
compressors (21a, 21b), the first and second indoor expansion
valves (26a, 26b), and the outdoor expansion valve (24),
respectively. As a result, the control signals for the first and
second compressors (21a, 21b), the first and second indoor
expansion valves (26a, 26b), and the outdoor expansion valve (24)
are generated, i.e., the first and second compressors (21a, 21b),
the first and second indoor expansion valves (26a, 26b), and the
outdoor expansion valve (24) are controlled, in such a manner that
the high pressure, the low pressure, the first evaporator outlet
temperature, the second evaporator outlet temperature, and the
intermediate pressure saturation temperature are set to
predetermined target values, respectively, when adjustment of all
the first and second compressors (21a, 21b), the first and second
indoor expansion valves (26a, 26b), and the outdoor expansion valve
(24) is done.
[0167] For example, as shown in FIG. 11, the disclosed technique
may be applied to a multi-type air conditioner (510) which performs
a two-stage compression refrigeration cycle, and includes an
internal heat exchanger (51) between the outdoor heat exchanger
(23) and the outdoor expansion valve (24), and a plurality of
indoor units.
[0168] Specifically, the air conditioner (510) includes a bypass
pipe (53) branched from a connection pipe (52) connecting the
outdoor heat exchanger (23) and the receiver (25), and is connected
to a pipe connecting the first compressor (21a) and the second
compressor (21b). A bypass expansion valve (54) is provided in the
bypass pipe (53). The refrigerant flowing in the bypass pipe (53)
decreases in pressure as it passes through the bypass expansion
valve (54), and becomes an intermediate pressure refrigerant.
[0169] Further, an outdoor expansion valve (24) is provided in the
connection pipe (52) to be positioned closer to the receiver (25)
than to the junction with the bypass pipe (53).
[0170] The internal heat exchanger (51) is provided on the
connection pipe (52) between the junction with the bypass pipe (53)
and the outdoor expansion valve (24), and on the bypass pipe (53)
downstream of the bypass expansion valve (54), thereby performing
heat exchange between the refrigerants flowing the pipes,
respectively. Specifically, in the cooling operation, the
refrigerant flowing in the bypass pipe (53) decreases in pressure
as it passes through the bypass expansion valve (54) to become an
intermediate pressure liquid or an intermediate pressure gas-liquid
two-phase refrigerant. Then, the refrigerant passes through the
internal heat exchanger (51), absorbs heat from the refrigerant
flowing in the connection pipe (52) to become a superheated gaseous
refrigerant, and flows into the suction side of the second
compressor (21b). The refrigerant flowing in the connection pipe
(52) exits from the outdoor heat exchanger (23), flows into the
internal heat exchanger (51), and dissipates heat to the
refrigerant flowing in the bypass pipe (53) to become a supercooled
refrigerant. Then, the refrigerant decreases in pressure in the
outdoor expansion valve (24) to become an intermediate pressure
refrigerant, and flows into the receiver (25).
[0171] A receiver pressure saturation temperature sensor (55) is
arranged at the connection pipe (52) closer to the receiver (25)
than to the outdoor expansion valve (24). An intermediate pressure
saturation temperature sensor (36) is arranged at the bypass pipe
(53) downstream of the internal heat exchanger (51).
[0172] In the air conditioner (510) configured in this manner, for
example, the high pressure, the low pressure, the first evaporator
outlet temperature, the second evaporator outlet temperature, the
intermediate pressure saturation temperature, and an internal
pressure of the receiver sensed by the receiver pressure saturation
temperature sensor (55) are input, and these physical values are
associated with each other to generate control signals for
controlling the first and second compressors (21a, 21b), the first
and second indoor expansion valves (26a, 26b), the outdoor
expansion valve (24), and the bypass expansion valve (54),
respectively. As a result, the control signals for the first and
second compressors (21a, 21b), the first and second indoor
expansion valves (26a, 26b), the outdoor expansion valve (24), and
the bypass expansion valve (54), respectively, are generated, i.e.,
the first and second compressors (21a, 21b), the first and second
indoor expansion valves (26a, 26b), the outdoor expansion valve
(24), and the bypass expansion valve (54) are controlled in such a
manner that the high pressure, the low pressure, the first
evaporator outlet temperature, the second evaporator outlet
temperature, the intermediate pressure saturation temperature, and
the internal pressure of the receiver are set to the predetermined
target values, respectively, when adjustment of all the first and
second compressors (21a, 21b), the first and second indoor
expansion valves (26a, 26b), the outdoor expansion valve (24), and
the bypass expansion valve (54) is done.
[0173] Further, in the second embodiment, two compressors (21a,
21b), and two expansion valves (24, 26) are provided to perform a
two-stage compression refrigeration cycle. However, a single
compressor may be provided, and gas injection may be performed
during the compression in the compressor. In this case, the number
of objects of control is three including the single compressor and
the two expansion valves (24, 26). Therefore, the number of
physical values to be controlled is preferably three in total
(including at least the high pressure of the refrigeration
cycle).
[0174] In the above embodiments, a plurality of physical values is
input, and outputs generated by multiplying the input physical
values by control parameters, respectively, are added to generate a
control signal for one object of control. However, the disclosed
technique is not limited to this configuration. For example, a
plurality of physical values may be input, and they may be
multiplied by a matrix constituted of the control parameters, to
calculate a plurality of control signals as outputs based on a
dynamic model of the refrigeration cycle in each of the refrigerant
circuits. Even in this configuration, the input physical values are
associated with each other to generate the control signal for the
objects of control. Thus, concurrent control of the plurality of
objects of control allows for concurrent control of the plurality
of physical values, thereby allowing for an improved convergence
rate of the control of each of the physical values.
[0175] In the above embodiments, the expansion valve is employed as
the expansion mechanism. However, the disclosed technique is not
limited thereto, and an expansion unit may be used.
[0176] In the first embodiment only, the outdoor fan (28) is
controlled as the object of control. However, in the other
embodiments, the outdoor fan (28) may be used in combination to
perform control of the high pressure and the capability of the
apparatus.
[0177] The above embodiments are merely preferred embodiments in
nature, and are not intended to limit the scope, applications and
use of the disclosed technique.
INDUSTRIAL APPLICABILITY
[0178] As described above, the present disclosure is useful for a
refrigeration apparatus including a refrigerant circuit for
performing a supercritical refrigeration cycle.
DESCRIPTION OF REFERENCE CHARACTERS
[0179] 20 Refrigerant circuit
[0180] 21 Compressor (compression mechanism)
[0181] 21a First compressor (compressor mechanism)
[0182] 21b Second compressor (compressor mechanism)
[0183] 23 Outdoor heat exchanger (heat source side heat
exchanger)
[0184] 24 Outdoor expansion valve (expansion mechanism, first
expansion mechanism, heat source side expansion mechanism)
[0185] 26 Indoor expansion valve (expansion mechanism, second
expansion mechanism)
[0186] 26a First indoor expansion valve (utilization side expansion
mechanism)
[0187] 26b Second indoor expansion valve (utilization side
expansion mechanism)
[0188] 27 Indoor heat exchanger (utilization side heat
exchanger)
[0189] 27a First indoor heat exchanger (utilization side heat
exchanger)
[0190] 27b Second indoor heat exchanger (utilization side heat
exchanger)
[0191] Outdoor fan (heat source side fan)
[0192] 40, 240, 340 Controller (control section)
* * * * *