U.S. patent application number 12/674036 was filed with the patent office on 2011-02-03 for air conditioner.
This patent application is currently assigned to Mitsubishi Electric Corporation. Invention is credited to Tomokazu Kawagoe, Hirofumi Koge, Kazuyoshi Shinozaki.
Application Number | 20110023512 12/674036 |
Document ID | / |
Family ID | 40386787 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110023512 |
Kind Code |
A1 |
Kawagoe; Tomokazu ; et
al. |
February 3, 2011 |
AIR CONDITIONER
Abstract
To obtain an air conditioner which ensures safe operation and
protection of the device and can carry out an operation with
favorable energy efficiency by efficiently compressing the
refrigerant. The air conditioner 100 is capable of performing a
cooling/heating mixed operation, constituting a refrigerant circuit
by piping connection of a heat-source side unit 10 having a
heat-source side heat exchanger 15 and a compressor 11, a plurality
of load-side units 50 having a load-side throttle device 51 and a
load-side heat exchanger 52, and a cooling/heating branch unit 30
having a gas/liquid separator 31. It is further provided with a
bypass pipe 21 forming a bypass for splitting the refrigerant
discharged by the compressor, an opening/closing valve 22 for
bypass for controlling the split of the refrigerant to the bypass
pipe through opening/closing, and control means 40 for executing
processing to split the refrigerant by opening the opening/closing
valve 22 for bypass if it is judged that there is an abnormal rise
or a fear of the abnormal rise in a refrigerant pressure on a
discharge side of the compressor 11 when operating the heat-source
side heat exchanger 15 functioning as an evaporator.
Inventors: |
Kawagoe; Tomokazu; (Tokyo,
JP) ; Shinozaki; Kazuyoshi; (Tokyo, JP) ;
Koge; Hirofumi; (Tokyo, JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Mitsubishi Electric
Corporation
Chiyoda-ku
JP
|
Family ID: |
40386787 |
Appl. No.: |
12/674036 |
Filed: |
August 28, 2007 |
PCT Filed: |
August 28, 2007 |
PCT NO: |
PCT/JP2007/066593 |
371 Date: |
February 18, 2010 |
Current U.S.
Class: |
62/196.1 ;
62/238.6 |
Current CPC
Class: |
F25B 2313/006 20130101;
F25B 13/00 20130101; Y02B 30/70 20130101; F25B 2600/0253 20130101;
F25B 2313/0253 20130101; F25B 2313/02741 20130101; F25B 2400/23
20130101; Y02B 30/741 20130101; F25B 2313/0272 20130101; F25B
49/027 20130101; F25B 2313/0231 20130101; F25B 2313/0233 20130101;
F25B 2600/2501 20130101 |
Class at
Publication: |
62/196.1 ;
62/238.6 |
International
Class: |
F25B 41/00 20060101
F25B041/00; F25B 27/00 20060101 F25B027/00 |
Claims
1. An air conditioner capable of a cooling/heating mixed operation
in which a refrigerant circulates through a refrigerant circuit
formed by connecting, with piping: a heat-source side unit having a
heat-source side heat exchanger and a compressor; a plurality of
load-side units each having a load-side throttle device and a
load-side heat exchanger; and a cooling/heating branch unit having
a gas/liquid separator for supplying a gas refrigerant to said
load-side unit that carries out a heating operation and for
supplying a liquid refrigerant to said load-side unit that carries
out a cooling operation, the air conditioner comprising: a bypass
pipe forming a bypass into which the refrigerant discharged by said
compressor is split; an opening/closing valve for bypass that
controls a split flow of the refrigerant to said bypass pipe by
opening/closing; and control means for executing processing in
which it is judged if there is an abnormal rise or a fear of the
abnormal rise in a refrigerant pressure on the discharge side of
said compressor when a state in which said load-side units involved
in the operation carry out both the heating operation and the
cooling operation and said heat-source side heat exchanger
functions as a condenser is changed to another state in which all
of said load-side units involved in the operation carry out the
heating operation and said heat-source side heat exchanger came to
function as an evaporator, and if it is judged that there is the
abnormal rise or a fear thereof, said opening/closing valve for
bypass is made to open so as to split the refrigerant to said
bypass pipe.
2. (canceled)
3. The air conditioner of claim 1, wherein said plurality of
load-side units are constituted by a high-ability unit and a
low-ability unit; and said control means controls said
opening/closing valve for bypass to be an open state when said
high-ability unit changes to other operation modes except said
cooling operation in a cooling/heating simultaneous operation in
which said low-ability unit performs heating operation and said
high-ability unit performs cooling operation.
4. The air conditioner of claim 1, wherein said control means
judges on the basis of a signal from pressure detection means for
detecting a pressure of the refrigerant on a discharge side of said
compressor if the pressure of the refrigerant on said discharge
side exceeds a predetermined pressure or not so as to judge said
abnormal rise.
5. The air conditioner of claim 1, wherein said control means
judges on the basis of a signal from temperature detection means
for detecting an ambient temperature of said heat-source side unit
if said ambient temperature exceeds a predetermined temperature or
not so as to judge the fear of said abnormal rise.
6. The air conditioner of claim 1, wherein said heat-source side
heat exchanger is constituted by piping connection of a plurality
of heat exchangers in parallel with the refrigerant circuit and one
end of said bypass pipe and the piping to any of said heat
exchangers are made to communicate with each other so that the
refrigerant having passed through said bypass pipe returns to an
intake side of said compressor through any of said plurality of
heat exchangers.
7. The air conditioner of claim 1, wherein said compressor is a
variable-capacity compressor having an inverter circuit for
changing a driving frequency and said control means executes
processing to open said opening/closing valve for bypass and to
split the refrigerant to said bypass pipe in addition to the
judgment on whether there is said abnormal rise or a fear of the
abnormal rise when it is judged that said compressor is driving at
a frequency not more than a predetermined driving frequency.
8. The air conditioner of claim 1, wherein a throttle device for
bypass for controlling an amount of said split refrigerant amount
to be is further provided with said bypass and said control means
controls an opening degree of said throttle device for bypass on
the basis of a pressure of the refrigerant on the discharge side of
said compressor.
9. The air conditioner of claim 1, wherein a capillary tube for
controlling an amount of said split refrigerant to be constant is
further provided with said bypass.
10. The air conditioner of claim 3, wherein said control means
judges on the basis of a signal from pressure detection means for
detecting a pressure of the refrigerant on a discharge side of said
compressor if the pressure of the refrigerant on said discharge
side exceeds a predetermined pressure or not so as to judge said
abnormal rise.
11. The air conditioner of claim 3, wherein said control means
judges on the basis of a signal from temperature detection means
for detecting an ambient temperature of said heat-source side unit
if said ambient temperature exceeds a predetermined temperature or
not so as to judge the fear of said abnormal rise.
12. The air conditioner of claim 4, wherein said control means
judges on the basis of a signal from temperature detection means
for detecting an ambient temperature of said heat-source side unit
if said ambient temperature exceeds a predetermined temperature or
not so as to judge the fear of said abnormal rise.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air conditioner for
carrying out a cooling/heating operation using a refrigerating
cycle (heat pump cycle) for air conditioning. The present invention
particularly relates to an equipment (means) configuration for
restraining an abnormal rise of a refrigerant pressure on a
discharge side of a compressor which can easily occur if a heat
quantity available for heat exchange is small in a load-side unit
provided indoors.
BACKGROUND ART
[0002] In an air conditioner for air conditioning (room temperature
adjustment) indoors or the like by a cooling/heating operation, a
heating operation might be carried out even if a temperature of an
outside air is high such as in the summer. For example, in the air
conditioner capable of a cooling/heating mixed operation in which a
plurality of load-side units carry out cooling and heating
operations in each unit, cooling and heating operations are in many
cases automatically determined to perform operations according to a
set temperature of a remote controller provided in the air
conditioner and a temperature around the load-side unit,
respectively. However, the number of load-side units carrying out
the heating operation is small in general when the temperature of
the outside air is high. An air conditioning load in the loads-side
unit (heat quantity required by the load-side unit. Hereinafter
referred to as a load) carrying out the heating operation is also
small, and the heat quantity for heat exchange becomes smaller in a
heat exchanger provided in the load-sided unit (hereinafter
referred to as a load-side heat exchanger). Moreover, in the air
conditioner capable of the cooling/heating mixed operation as
above, in order to promote size reduction and diversification of
the load-side units, the heat quantity available for heat exchange
by the load-side heat exchanger (hereinafter referred to as a heat
exchange capacity) tends to be small.
[0003] On the other hand, when the heating operation is carried out
in the air conditioner, a heat exchanger `provided in a heat-source
side unit provided outdoors or the like (hereinafter referred to as
a heat-source side heat exchanger) functions as an evaporator. If a
temperature of the outside air is high, the heat quantity (heat
absorbing amount) absorbed by a refrigerant passing through the
heat-source side heat exchanger from the outside air becomes large.
As a result, an over-heating degree of a gas refrigerant on a
secondary side of the heat-source side heat exchanger (to become an
outlet side of the refrigerant when functioning as the evaporator)
is increased and the refrigerant becomes an overheated vapor, and
the compressor takes in the gas refrigerant with a high
temperature. Thus, the compressor is overheated. Since the
temperature of the gas refrigerant is high, the pressure of the
discharged refrigerant can be raised easily.
[0004] As mentioned above, in such a state that the heat exchange
capacity is small and a temperature of the refrigerant to be taken
in is high, the pressure of the refrigerant discharged by the
compressor is abnormally raised, thereby the compressor is further
overheated. As a result, abnormal stop of the compressor might
occur, which deteriorates operation efficiency such as energy
consumption efficiency. An abnormal pressure rise also gives a bad
influence on equipment and piping. Then, using a compressor having
an inverter circuit, a driving frequency of the compressor is
reduced, and a refrigerant amount (per unit time) circulating in
the refrigerating cycle is decreased. A method is proposed in which
a cooling/heating ability according to the load (heat quantity per
hour to be supplied to the load-side unit side. Hereinafter
referred to as ability) is supplied so as to suppress rise in the
pressure on the discharge side (See Patent Document 1).
[0005] [Patent Document 1] Japanese Unexamined Patent Application
Publication No. 5-99519 (FIG. 1)
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0006] Even if the driving frequency of the compressor is reduced
by the inverter circuit, there is a limit in general such that the
compressor has a minimum driving frequency required to keep
driving, for example. If the ability when driving at the minimum
driving frequency cannot be fully processed in the load-side unit,
the refrigerant beyond ability is supplied to be overfed and incurs
rise in the pressure on the discharge side. On the load-side unit,
the heat quantity more than necessary is immediately supplied.
Thus, start, temporary stop and the like of the operation
frequently occur, which raises power consumption and causes drop in
the energy consumption efficiency.
[0007] The present invention was made in order to solve the above
problems. In an air conditioner capable of the cooling/heating
mixed operation, for example, even if the number of the
heating-source side units for heating operation is small and the
heat exchange capacity is small, the ability corresponding to the
load is supplied by circulating an appropriate amount of a
refrigerant. The purpose of the present invention is to obtain an
air conditioner which ensures safe operation and protection of the
device and can carry out an operation with favorable energy
efficiency by efficiently condensing the refrigerant.
Means for Solving the Problems
[0008] An air conditioner according to the present invention is an
air conditioner capable of a cooling/heating mixed operation by
constituting a refrigerant circuit by piping connection of a
heat-source side unit having a heat-source side heat exchanger and
a compressor, a plurality of load: side units each having a
load-side throttle device and a load-side heat exchanger, and a
cooling/heating splitting unit having a gas/liquid, separator for
supplying a gas refrigerant to the load-side unit carrying out a
heating operation and supplying a liquid refrigerant to the
load-side unit carrying out a cooling operation, to circulate the
refrigerant, and is provided with a bypass pipe forming a bypass
into which the refrigerant discharged by the compressor is split,
an opening/closing valve for bypass for controlling a split flow of
the refrigerant to the bypass pipe by opening/closing, and control
means that judges whether there is an abnormal rise or a fear of
the abnormal rise of a refrigerant pressure on the discharge side
of the compressor when performing an operation in which the
heat-source side heat exchanger functions as an evaporator and at
least one of the load-side heat exchangers functions as a
condenser, and if it is judged that there is the abnormal rise or
the fear of the abnormal rise, processing is executed to open the
opening/closing valve for bypass and to split the refrigerant to
the bypass pipe.
Advantages
[0009] As mentioned above, the bypass pipe and the opening/closing
valve for bypass are provided on the heat-source side unit, a
bypass is formed so that the compressor can split the discharged
refrigerant, and when an operation in which at least one of the
load-side heat exchangers functions as a condenser is carried out
as in a heating operation and heating-dominant operation, for
example, if there is a rise or a fear of rise in the refrigerant
pressure on the discharge side of the compressor, the refrigerant
is made to be split into the bypass pipe by the control means, so
that an ability (refrigerant amount) matched with the heat exchange
capacity of the load-side heat exchanger can be supplied, an
abnormal rise of the refrigerant pressure on the discharge side is
suppressed, and temperature rise, abnormal stop of the compressor
caused by overheat can be restrained or prevented. Further, the
energy consumption efficiency can be improved such that the number
of start and stop of operation in a compressor 11 and a load-side
unit 50 is reduced to promote energy saving. Particularly, such an
effect can be demonstrated in the air conditioner capable of
performing cooing/heating mixed operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a configuration diagram of an air conditioner in
an embodiment 1 of the present invention.
[0011] FIG. 2 is a Mollier diagram (p-h diagram) of the present
invention.
[0012] FIG. 3 is a diagram illustrating a flowchart relating to a
high-pressure restraint control in the embodiment 1.
[0013] FIG. 4 is a table illustrating threshold values used in the
control of the present invention.
[0014] FIG. 5 is a diagram illustrating a flowchart relating to a
high-pressure restraint control in an embodiment 2.
[0015] FIG. 6 is a diagram illustrating a flowchart relating to a
high-pressure restraint control in an embodiment 3.
[0016] FIG. 7 is a configuration diagram of an air conditioner in
an embodiment 4 of the present invention.
[0017] FIG. 8 is a diagram illustrating a flowchart relating to a
high-pressure restraint control in an embodiment 4.
[0018] FIG. 9 is a Mother diagram (p-h diagram) showing transition
in the control of the present invention.
REFERENCE NUMERALS
[0019] 1 high-pressure pipe
[0020] 2 low-pressure pipe
[0021] 3a, 3b liquid branch pipe
[0022] 4a, 4b gas branch pipe
[0023] 10 heat-source side unit
[0024] 11 compressor
[0025] 12 flow-passage switching valve
[0026] 13a, 13b, 13c, 13d, 13e, 13f check valve
[0027] 14a, 14b, 14c heat-source side opening/closing valve
[0028] 15a, 15b, 15c heat-source side heat exchanger
[0029] 16a, 16b, 16c check valve
[0030] 17 accumulator
[0031] 18 heat-source side fan
[0032] 19 oil separator
[0033] 20 capillary
[0034] 21 bypass pipe
[0035] 22 opening/closing valve for bypass
[0036] 23 throttle device for bypass
[0037] 24 capillary tube
[0038] 30 cooling/heating branch unit
[0039] 31 gas/liquid separator
[0040] 32, 33 throttle device on the cooling/heating branch unit
side
[0041] 34 opening/closing valve on the cooling/heating branch unit
side
[0042] 40 controller
[0043] 40a control start judgement processing portion
[0044] 40b control start-time processing portion
[0045] 40c during-control processing portion
[0046] 40d control end-time processing portion
[0047] 41 storage device
[0048] 50 load-side unit
[0049] 51 load-side throttle device
[0050] 52 load-side heat exchanger
[0051] 54 load-side controller
[0052] 61 pressure sensor
[0053] 62 temperature sensor
[0054] 100, 100A air conditioner
BEST MODE FOR CARRYING OUT THE INVENTION
Descriptions will be Given to Embodiments of the Present
Invention
Embodiment 1
[0055] FIG. 1 is a diagram illustrating a configuration of an air
conditioner 100 according to an embodiment 1 of the present
invention. On the basis of FIG. 1, means or the like constituting
the air conditioner 100 will be described. The air conditioner 100
carries out a cooling/heating operation using a refrigerating cycle
(heat pump cycle) by a refrigerant circulation. Particularly, the
air conditioner 100 is supposed to be a device capable of
performing a cooling/heating mixed operation.
[0056] The air conditioner 100 of the present embodiment is roughly
constituted by a heat-source side unit (outdoor unit) 10, a
cooling/heating branch unit 30, and load-side units (indoor units)
50a, 50b. The heat-source side unit 10 and the cooling/heating
branch unit 30 are connected by a high-pressure pipe 1 and a
low-pressure pipe 2, which are refrigerant piping. Also, the
cooling/heating branch unit 30 and the load-side unit 50a are
connected by a liquid branch pipe 3a, which is refrigerant piping,
and a gas branch pipe 4a, which is refrigerant piping, and the
cooling/heating branch unit 30 and the load-side unit 50b are
connected by a liquid branch pipe 3b, which is refrigerant piping,
and a gas branch pipe 4b, which is refrigerant piping. By means of
piping connection of the high-pressure pipe 1, the low-pressure
pipe 2, the liquid branch pipes 3a and 3b, and the gas branch pipes
4a and 4b, a refrigerant circulates among the heat-source side unit
10, the cooling/heating branch unit 30, and the load-side unit 50
and constitutes a refrigerant circuit. The cooling/heating branch
unit 30 switchably connects a plurality of the load-side units 50a,
50b in series or in parallel. Here, if the liquid branch pipes 3a,
3b, the gas branch pipes 4a, 4b, and the load-side units 50a, 50b
do not have to be particularly discriminated, they will be
described as a liquid branch pipe 3, a gas branch pipe 4, and a
load-side unit 50 (if the same means are indicated in plural, they
are supposed to be the same in the following). With regard to a
magnitude of the pressure in the present embodiment, it is not
determined by a relation with a pressure to be a reference but
represented as a relative pressure by a pressurization of the
compressor 11, refrigerant passage control of each throttle device
and the like.
[0057] The heat-source side unit 10 of the present embodiment is
constituted by the compressor 11, a four-way valve 12, a check
valve 13 (13a, 13b, 13c, 13d, 13e, 13f), a heat-source side
opening/closing valve 14 (14a, 14b, 14c), a heat-source side heat
exchanger 15 (15a, 15b, 15c), a check valve 16 (16a, 16b, 16c), an
accumulator 17, a heat-source side fan 18, an oil separator 19, a
capillary 20, a bypass pipe 21, an opening/closing valve 22 for
bypass, and a throttle device 23 for bypass.
[0058] The compressor 11 applies a pressure on the taken-in
refrigerant so as to discharge (feed out) it. Though not
particularly limited, the compressor 11 in the present embodiment
is supposed to be a capacity-variable inverter compressor provided
with an inverter circuit (not shown) capable of changing a capacity
(refrigerant discharge amount per unit time) and ability therewith
by arbitrarily changing a driving frequency above a minimum driving
frequency, for example. The oil separator 18 separates refrigerator
oil mixed in the refrigerant discharged from the compressor 11. The
separated refrigerator oil returns to the compressor 11, while its
flow rate being controlled by the capillary tube 19. The four-way
valve 13 switches a valve on the basis of an instruction from a
controller 40 so that a refrigerant path is switched according to a
cooling operation (meaning that all the operating heat-source side
units are carrying out the cooling operation here), a
cooling-dominant operation (operation constituted mainly by the
cooling operation in the cooling/heating mixed operation), a
heating operation (meaning that all the operating heat-source side
units are carrying out the heating operation here), and a
heating-dominant operation (operation constituted mainly by the
heating operation in the cooling/heating mixed operation).
[0059] The heat-source side heat exchanger 15 (15a, 15b, 15c) has a
pipe through which the refrigerant is made to pass and a fin to
enlarge a heat transfer area between the refrigerant flowing
through the pipe and air (outdoor air), for example, carrying out
heat exchange between the refrigerant and the air. For example, in
the heating operation and the heating-dominant operation, the heat
exchanger functions as an evaporator and evaporates and gasifies
the refrigerant. On the other hand, in the cooling operation and
the cooling-dominant operation, the heat exchanger functions as a
condenser and condenses and liquefies the refrigerant. For example,
in the cooling-dominant operation, adjustment is made so that
condensation progresses to a state of two-phase region (gas-liquid
two-phase refrigerant) of liquid and gas. Also, a heat-source side
fan 20 is provided in the vicinity of the heat-source side heat
exchanger 15 for efficient heat exchange between the refrigerant
and the air.
[0060] Here, in the present embodiment, the heat-source side heat
exchanger 15 is constituted in a form divided into three
heat-source side heat exchangers 15a, 15b, 15c connected by piping
in parallel with respect to the refrigerant circuit. The
heat-source side heat exchangers 15a, 15b, 15c can independently
pass the refrigerant to be condensed or evaporated. Though not
particularly limited, in the present embodiment, respective heat
exchange capacities of the heat-source side heat exchangers 15a,
15b, 15c are made to be different. For that purpose, a size or
shape (heat transfer area) of the fins of each of the heat-source
side heat exchangers 15a, 15b, 15c, a path count occupied by a
header from the heat-source side heat exchangers 15a, 15b, 15c
(ratio of the heat transfer area in each heat exchanger at
division), a distance of refrigerant passage in the pipe and the
like are made to be varied. Also, ease of heat exchange with the
air is made to be varied (by making a distance to the heat-source
side fan 20 different so as to change an amount of the air to be
fed for the heat exchange, for example). Particularly, for the
heat-source side heat exchanger 15b, piping (on the heat-source
side heat exchanger 15b side rather than the heat-source side
opening/closing valve 14) leading to a primary side of the
heat-source side heat exchanger 15b (to become an inlet side
through which the refrigerant flows when functioning as the
evaporator) communicates with one end of the bypass pipe 21, which
will be described later, so that the refrigerant having passed
through the bypass pipe 21 can be made to flow into the heat-source
side heat exchanger 15b.
[0061] The heat-source side opening/closing valve 14 (14a, 14b,
14c) carries out an opening/closing operation independently on the
basis of the instruction from the controller 40 in order to control
passage of the refrigerant to the heat-source side heat exchanger
15. The check valve 13 (13a, 13b, 13c, 13d, 13e, 13f) and the check
valve 16 (16a, 16b, 16c) make a circulation path of the refrigerant
changed depending on whether the operation is cooling or heating,
for example, constant according to the respective operation so as
to prevent a backflow. The accumulator 17 reserves an excessive
refrigerant in the refrigerant circuit.
[0062] Moreover, the heat-source side unit 10 of the present
embodiment has the bypass pipe 21, the opening/closing valve 22 for
bypass, and the throttle device 23 for bypass. The bypass pipe 21
forms a bypass (path) from a discharge side (high-pressure side) of
the compressor 11 to between the heat-source side opening/closing
valve 14b and the heat-source side heat exchanger 15b. As mentioned
above, one end thereof communicates with piping communicating with
the primary side of the heat-source side heat exchanger 15b. The
opening/closing valve 22 for bypass is provided at a portion on the
bypass branching from the piping on the discharge side of the
compressor 11 and carries out an opening/closing operation on the
basis of the instruction from the controller 40. While the
opening/closing valve 22 for bypass opens the valve, a part of the
refrigerant discharged from the compressor 11 is branched, split,
and made to pass through the bypass pipe 21. The throttle device 23
for bypass is constituted by electronic expansion valves and the
like capable of changing an opening degree, for example. The
throttle device 23 for bypass is also provided on the bypass,
opened with an opening degree on the basis of the instruction from
the controller 40, splits a flow and controls the refrigerant flow
passing through the bypass pipe 21. The refrigerant having passed
through the bypass constitutes a circuit of another circulation
path passing through the heat-source side heat exchanger 15b and
leading to the compressor 11 via the accumulator 17 (hereinafter
referred to as a bypass circuit) against the regular circulation
path (hereinafter referred to as a refrigerant main circuit).
[0063] The cooling/heating branch unit 30 of the present embodiment
is constituted by the gas/liquid separator 31, the throttle devices
32 and 33 on the cooling/heating branch unit side, and the
opening/closing valve 34 (34a, 34b) for cooling/heating branch
unit. The as/liquid separator 31 separates the refrigerant inflow
in the gas-liquid two-phase state into a gas refrigerant and a
liquid refrigerant. The throttle devices 32 and 33 on the
cooling/heating branch unit side are also constituted by electronic
expansion valves and the like, opened with an opening degree on the
basis of the instruction from the controller 40, and control the
flow of the liquid refrigerant and the refrigerant amount.
[0064] The load-side unit 50 (50a, 50b) of the present embodiment
is constituted by the load-side throttle device 51 (51a, 51b), the
load-side heat exchanger 52 (52a, 52b), the load-side fan 53 (53a,
53b), and the load-side controller 54 (54a, 54b). The load-side
throttle device 51 functions as a pressure reducing valve and an
expansion valve and adjusts a pressure of the refrigerant passing
through the load-side heat exchanger 52. The load-side throttle
device 51 of the present embodiment is also constituted by an
electronic expansion valve and the like capable of changing the
opening degree, for example. The load-side heat exchanger 52
functions as an evaporator in the cooling operation and a condenser
in the heating operation, carries out heat exchange between the
refrigerant and the air (indoor air), and evaporates the
refrigerant so as to gasify it or condenses the refrigerant so as
to liquefy it. The load-side fan 53 also adjusts the air flow to be
used for heat exchange similarly to the heat-source side fan 18.
Here, a rotation speed of the load-side fan 53 is not changed by a
state of the refrigerant circulating in the refrigerant circuit as
the heat-source side fan 18, for example, but is determined by
setting of an indoor user. In the present embodiment, there is no
setting change by the user and the rotation speed is supposed to be
constant. Here, the load-side heat exchanger 52 has a small heat
transfer area since its fan is not so large as the heat-source side
heat exchanger 15 in general. The pipe is short and the distance
through which the refrigerant flows is also short. Further, the
load-side fan 53 has an air volume smaller than the heat-source
side fan 20 in general. Thus, the heat exchange capacity of a
single load-side heat exchanger 52 becomes considerably smaller
than that of the heat-source side heat exchanger 15.
[0065] The load-side controller 54 controls an operation of each of
equipment (means) constituting the load-side unit 50 on the basis
of room temperature setting by the indoor user and the instruction
from the controller 40, for example. The controller transmits a
signal containing various data relating to the load-side unit 50
such as an operation state of the load-side unit 50, a state of
each of the equipment (means), physical amounts (physical
parameters) detected by various sensors provided at the load-side
unit 50 or the like to the control means through a communication
line (not shown). In the present embodiment, the case in which two
units of the load-side unit 50 are provided is shown as an example,
but not limited to that, three or more units of the load-side unit
50 may be provided.
[0066] The controller 40 carries out determination processing on
the basis of a signal transmitted from various sensors (detection
means) provided inside and outside the air conditioner 100 and each
of the equipment of the air conditioner 100, for example. The
controller has a function to operate each of the equipment on the
basis of the determination to control the operation of the entire
air conditioner 100 in an integrated manner. Specifically, the
control includes driving frequency control of the compressor 11,
opening degree control of the load-side throttle device 51, the
throttle devices 32 and 33 on the cooling/heating branch unit side
of the cooling/heating branch unit 30, and opening/closing control
of the opening/closing valve 14, the opening/closing valve 34 for
cooling/heating branch unit or the like. Here, the controller 40 in
the present embodiment is supposed to have a control start
judgement processing portion 40a, a control start-time processing
portion 40b, a during-control processing portion 40c, and a control
end-time processing portion 40d, particularly, in order to execute
a high-pressure restraint control using the bypass mentioned later.
The processing contents executed by these processing portions will
be described later. A storage device 41 stores data, program and
the like required for processing by the controller 40 temporarily
or for a long time.
[0067] Moreover, in the present embodiment, as the detection Means
for detecting a physical quantity with which the controller 40
executes high-pressure restraint control, a pressure sensor 61 and
a temperature sensor 62 are particularly provided. The pressure
sensor 61 is provided in the piping on the discharge side in the
heat-source side unit 10 in order to monitor a pressure PS
(hereinafter referred to as high-pressure PS) of the refrigerant in
the piping on the discharge side (high pressure side) of the
compressor 11 to transmit a signal on the basis of the detection.
The temperature sensor 62 is provided in order to monitor a
temperature (since the heat-source side unit 10 is often placed
outdoors, the temperature is a temperature of the outside air.
Hereinafter, referred to as an ambient temperature T) around the
heat-source side unit 10 to transmit a signal on the basis of the
detection. Though not shown and the description is omitted here,
other various sensors (detection means) for monitoring and
detecting a temperature of the refrigerant discharged from the
compressor 11 and a pressure of the refrigerant, in the piping on
the intake side (low-pressure side) of the compressor 11 may be
provided inside and outside the air conditioner 100.
[0068] Here, the refrigerant used in the air conditioner 100 and
circulating in the refrigerant circuit will be described. The
refrigerant used in the air conditioner 100 includes nonazeotropic
refrigerant mixture, pseudo zeotropic refrigerant mixture, single
refrigerant and the like. The nonazeotropic refrigerant mixture
includes R407C (R32/R125/R134a), which is an HFC
(hydrofluorocarbon) refrigerant. Since the nonazeotropic
refrigerant mixture is a mixture of refrigerants with different
boiling points, it has a characteristic that composition ratios of
a liquid-phase refrigerant and gas-phase refrigerant are different.
The pseudo zeotropic refrigerant mixture includes R410A (R32/R125)
and R404A (R125/R143a/R134a), which are HFC refrigerants. The
pseudo zeotropic refrigerant mixture has a characteristic of an
operation pressure of approximately 1.6 times of R22 in addition to
characteristics similar to the nonazeotropic refrigerant,
mixture.
[0069] A single refrigerant includes R22, which is an HCFC
(hydrochlorofluorocarbon) refrigerant, and R134a, which is an HFC
refrigerant. Since the single refrigerant is not a mixture, it has
a characteristic that handling thereof is easy. Other than the
above, carbon dioxide, propane, isobutane, ammonia and the like,
which are natural refrigerants, may be used. R22 indicates
chlorodifluoromethane, R32 difluoromethane, R125
pentafluoromethane, R134a 1,1,1,2-tetrafluoromethane, and R143a
1,1,1-trifluoroethane, respectively. A refrigerant according to an
application and a purpose of the air conditioner 100 in the above
refrigerants may be used.
[0070] In the air conditioner 100 of the present embodiment, in the
heating operation and heating-dominated operation, when the
compressor 11 is driven at a minimum, driving frequency, for
example, when it is determined that the high-pressure PS becomes a
pressure not less than a predetermined threshold value, the
controller 40 opens the opening/closing valve 22 for bypass. Then,
while the throttle device 23 for bypass adjusts the refrigerant
amount, a part of the gas refrigerant discharged from the
compressor 11 is split and made to pass through the bypass. By
splitting the refrigerant flow, the refrigerant amount flowing to
the load-side unit 50 side is reduced, and the ability of the
compressor 11 to supply it to the load-side unit 50 side is
restrained. As a result, the ability is supplied within a range of
the heat exchange capacity of the load-side heat exchanger 52 so
that condensation according to a load required by the load-side
unit 50 can be carried out.
[0071] On the other hand, the refrigerant having passed through the
bypass is made to further pass through the heat-source side heat
exchanger 15b and to return to the intake side (low-pressure side)
of the compressor 11. By means of pressure regulation (pressure
reduction) by the throttle device 23 for bypass and sensible heat
removal (specific enthalpy reduction) by heat exchange in the
heat-source side heat exchanger 15b, while pressure rise on the
intake side of the compressor 11 is restrained, the refrigerant is
made to return. Here, the sensible heat removal of the split
refrigerant is carried out by the heat-source side heat exchanger
15b in the present embodiment, however, the removal may be carried
out by an exclusive heat exchanger. However, in the operation state
of the air conditioner 100 using the bypass, a load required by the
heat-source side unit 50 is small and it is considered that there
is no need to make all the heat-source side heat exchangers 15a,
15b, 15c to function as condensers. Then, any of the heat-source
side heat exchangers 15 (It may be plural. In the present
embodiment, it is the heat-source side heat exchanger 15b) is
selected as a heat exchanger capable of sensible heat removal by a
heat transfer area or the like, for example, and used also as the
heat exchanger in the refrigerant main circuit.
[0072] Next, a flow of the refrigerant in the refrigerant main
circuit and an operation content of each of the equipment on the
basis of the flow by each operation in the air conditioner 100 will
be described. First, a case in which all the operating load-side
units 50 conduct the cooling operation will be described. In the
heat-source side unit 10, the compressor 11 compresses the taken-in
refrigerant and discharges a high-pressure gas refrigerant. The
refrigerant discharged from the compressor 11 flows through the
four-way valve 12, the check valve 13a, and the opening/closing
valve 14 into the heat-source side heat exchanger 15. While passing
through the heat-source side heat exchanger 15, the high-pressure
gas refrigerant is condensed by heat exchange and becomes a
high-pressure liquid refrigerant and flows through the check valve
16, the check valve 13e into the high-pressure pipe 1 then into the
cooling/heating branch unit 30. In the cooling/heating branch unit
30, the high-pressure liquid refrigerant flowing from the
high-pressure pipe 1 flows through the gas/liquid separator 31 and
the throttle device 32 into the liquid branch pipes 3a and 3b then
into the load-side units 50a and 50b.
[0073] In the load-side units 50a and 50b, the liquid refrigerant
flowing from the liquid branch pipes 3a, 3b, respectively, becomes
the low-pressure gas-liquid two-phase refrigerant or low-pressure
liquid refrigerant by means of pressure regulation through opening
degree adjustment of the load-side throttle devices 51a, 51b and
flows to the load-side heat exchangers 52a, 52b. The low-pressure
gas-liquid two-phase refrigerant or low-pressure liquid refrigerant
is evaporated by heat exchange and becomes a low-pressure gas
refrigerant while passing through the load-side heat exchangers
52a, 52b and flows into the gas branch pipes 4a and 4b. The
low-pressure gas refrigerant flowing from the gas branch pipes 4a
and 4b flows through the opening/closing valve 34 of the
cooling/heating branch unit 30 into the low-pressure pipe 2. The
low-pressure gas refrigerant flowing from the low-pressure pipe 2
flows through the check valve 13b of the heat-source side unit 10,
the four-way valve 12 as a flow-passage switching valve, the
accumulator 17 and is taken into the compressor 11 again and
circulates by discharging as mentioned above. This is a circulation
path in the cooling operation of the refrigerant main circuit.
[0074] Next, the cooling-dominant operation will be described.
Here, the description will be made on the premise that the
load-side unit 50a carries out the cooling operation and the
load-side unit 50b the heating operation. First, in the heat-source
side unit 10, the compressor 11 compresses the taken-in,
refrigerant and discharges a high-pressure gas refrigerant. The
discharged refrigerant flows through the four-way valve 12, the
check valve 13a, and the opening/closing valve 14 to the
heat-source side heat exchanger 15. The high-pressure gas
refrigerant is condensed by heat exchange while passing through the
heat-source side heat exchanger 15 so as to become a high-pressure
gas-liquid two-phase refrigerant and flows through the check valve
16, the check valve 13e to the high-pressure pipe 1 and flows into
the cooling/heating branch unit 30.
[0075] In the cooling/heating branch unit 30, the gas/liquid
separator 31 separates the high-pressure gas-liquid two-phase
refrigerant flowing from the high-pressure pipe 1 into a
high-pressure gas refrigerant and a high-pressure liquid
refrigerant. The high-pressure gas refrigerant flows through the
opening/closing valve 34b to the gas branch pipe 4b. The
high-pressure gas refrigerant is condensed by the heat exchange and
becomes a high-pressure liquid refrigerant while passing through
the load-side heat exchanger 52b and flows to the load-side
throttle device 51b. By means of pressure regulation through the
opening-degree adjustment of the load-side throttle devices 51b,
the refrigerant becomes an intermediate-pressure gas-liquid
two-phase refrigerant or an intermediate-pressure liquid
refrigerant and flows to the liquid branch pipe 3b.
[0076] On the other hand, the high-pressure liquid refrigerant
separated by the gas/liquid separator 31 and the
intermediate-pressure gas-liquid two-phase refrigerant or the
intermediate-pressure liquid refrigerant flowing from the liquid
branch pipe 3b become a low-pressure gas-liquid two-phase
refrigerant or low-pressure liquid refrigerant by means of pressure
regulation through the opening-degree adjustment of the load-side
throttle device 51a and flows into the load-side heat exchanger
52a. The low-pressure gas-liquid two-phase refrigerant or
low-pressure liquid refrigerant is evaporated by the heat exchange
and becomes a low-pressure gas refrigerant while passing through
the load-side heat exchanger 52a and flows to the gas branch pipe
4a. The low-pressure gas refrigerant flowing from the gas branch
pipe 4a flows through the opening/closing valve 34 of the
cooling/heating branch unit 30 to the low-pressure pipe 2.
[0077] Here, if the inflow liquid refrigerant is large in quantity
or the opening degree of the load-side throttle device 51a is
small, for example, an amount of the liquid refrigerant collected
is getting large in a section (hereinafter referred to as a liquid
pipe line) in the load-side throttle devices 51a and 51b, the
liquid branch pipes 3a and 3b, and the throttle devices 32 and 33
on the cooling/heating branch unit side. As the amount of the
liquid refrigerant is getting large, a pressure of the refrigerant
in the liquid pipe line is raised. At this time, in the load-side
unit 50b (load-side heat exchanger 52b), a differential pressure
gets small between the liquid pipe line side (secondary side,
liquid branch pipe 3b side) and the gas branch pipe 4b side. Thus,
the refrigerant amount flowing to the load-side unit 50b is
reduced, and the heating ability is lowered. Then, the device
controller 40 adjusts the opening degree of the throttle device 33
on the cooling/heating branch unit side so as to flow the liquid
collected in the liquid pipe line to the low-pressure pipe 2 and
adjusts the pressure in the liquid pressure line.
[0078] As mentioned above, a low-pressure gas-liquid two-phase
refrigerant flows through the low-pressure pipe 2 in which the
low-pressure gas refrigerant flowing from the gas branch pipe 4a
and the low-pressure liquid refrigerant flowing from the throttle
device 33 on the cooling/heating branch unit side or a two-phase
refrigerant of low-pressure gas and liquid are mixed. In the
heat-source side unit 10, the low-pressure gas-liquid two-phase
refrigerant flowing from the low-pressure pipe 2 flows through the
check valve 13b of the heat-source side unit 10, the four-way valve
12, and the accumulator 17. The gas refrigerant is taken into the
compressor 11 again and circulates by discharging as mentioned
above. This makes a circulation path at the cooling-dominant
operation in the refrigerant main circuit.
[0079] Next, a case in which all the operating load-side units 50
carry out the heating operation will be described. In the
heat-source side unit 10, the compressor 11 compresses and
pressurizes the taken-in refrigerant and discharges the
high-pressure gas refrigerant. The discharged refrigerant flows
through the four-way valve 12 and the check valve 13d to the
high-pressure pipe 1 and flows into the cooling/heating branch unit
30. In the cooling/heating branch unit 30, the high-pressure gas
refrigerant flowing from the high-pressure pipe 1 flows through the
gas/liquid separator 31 and the opening/closing valve 34 to the gas
branch pipes 4a and 4b. The high-pressure gas refrigerant is
condensed by the heat exchange and becomes the high-pressure liquid
refrigerant while passing through the load-side heat exchangers 52a
and 52b and flows into the load-side throttle devices 51a and 51b.
By means of the pressure regulation through the opening-degree
adjustment by the load-side throttle devices 51a and 51b, the
refrigerant becomes a low-pressure gas-liquid two-phase refrigerant
or low-pressure liquid refrigerant and flows to the liquid branch
pipes 3a and 3b. The low-pressure gas-liquid two-phase refrigerant
or low-pressure liquid refrigerant flowing from the liquid branch
pipes 3a and 3b flows through the throttle device 33 of the
cooling/heating branch unit 30 to the low-pressure pipe 2. It
further flows through the check valve 13c of the heat-source side
unit 10, the opening/closing valve 14, the load-side heat exchanger
15, the check valve 16, the check valve 13f, the four-way valve 12,
and the accumulator 17 and is taken into the compressor 11 again
and circulates by being pressurized and discharged as mentioned
above. This makes a circulation path in the heating operation in
the refrigerant main circuit.
[0080] The heating-dominant operation will be described. Here, a
case will be described as well in which the load-side unit 50a
carries out the cooling operation and the load-side unit 50b the
heating operation. In the heat-source side unit 10, the compressor
11 compresses and pressurizes the taken-in refrigerant and
discharges the high-pressure gas refrigerant. The discharged
refrigerant flows through the four-way valve 12 and the check valve
13d to the high-pressure pipe 1. In the cooling/heating branch unit
30, the high-pressure gas refrigerant flowing from the
high-pressure pipe 1 flows through the gas-liquid separator 31 and
the opening/closing valve 34 to the gas branch pipe 4b. The
high-pressure gas refrigerant flowing from the gas branch pipe 4b
is condensed by the heat exchange while passing through the
load-side heat exchanger 52b and becomes a high-pressure liquid
refrigerant and flows into the load-side throttle device 51b. By
means of the pressure regulation through the opening-degree
adjustment by the load-side throttle device 51b, the refrigerant
becomes an intermediate-pressure gas-liquid two-phase refrigerant
or intermediate-pressure liquid refrigerant and flows to the liquid
branch pipe 3b.
[0081] The intermediate-pressure gas-liquid two-phase refrigerant
or intermediate-pressure liquid refrigerant flowing from the liquid
branch pipe 3b flows to the liquid branch pipe 3a. By means of
pressure regulation through the opening degree adjustment by the
load-side throttle device 51a, the refrigerant becomes a
low-pressure gas-liquid two-phase refrigerant or low-pressure
liquid refrigerant and flows into the load-side heat exchanger 52a.
The low-pressure gas-liquid two-phase refrigerant or low-pressure
liquid refrigerant is evaporated by the heat exchange while passing
through the load-side heat exchanger 52a and becomes a low-pressure
gas refrigerant and flows to the gas branch pipe 4a. The
low-pressure gas refrigerant flowing from the gas branch pipe 4a
flows through the opening/closing valve 34 of the cooling/heating
branch unit 30 to the low-pressure pipe 2. Here, in the
heating-dominant operation, since the liquid refrigerant might be
collected in the liquid pipe line as well, the opening degree of
the throttle device 33 on the cooling/heating branch unit side is
adjusted so as to flow the liquid collected in the liquid pipe line
to the low pressure pipe 2 and pressure adjustment is performed in
the liquid pipe line.
[0082] As mentioned above, the low-pressure gas-liquid two-phase
refrigerant flows through the low-pressure pipe 2 in which the
low-pressure gas refrigerant flowing from the gas branch pipe 4a
and the low-pressure liquid refrigerant or low-pressure two-phase
refrigerant of gas and liquid flowing from the throttle device 33
on the cooling/heating branch unit side are mixed. Moreover, the
refrigerant is taken into the compressor 11 again through the check
valve 13c of the heat-source side unit 10, the opening/closing
valve 14, the load-side heat exchanger 15, the check valve 16, the
check valve 13f, the four-way valve 12, and the accumulator 17 and
circulates by being pressurized and discharged as mentioned above.
This makes a circulation path at the heating-dominant operation in
the refrigerant main circuit.
[0083] Next, a case in which the refrigerant is circulated using
the bypass circuit will be described. In the present embodiment, at
the heating operation or heating-dominant operation, a case will be
described in which only the load-side unit 50a having the load-side
heat exchanger 52a with a small heat exchange capacity (load)
carries out the heating operation. Thus, the gas refrigerant
discharged from the compressor 11 is condensed only by the
load-side heat exchanger 52a.
[0084] FIG. 2 is a Mollier diagram (p-h diagram) illustrating a
state of the refrigerant of the air conditioner 100 according to
the present embodiment. For example, even if the driving frequency
of the compressor 11 is set at the minimum, when the ability of
supply by the compressor 11 exceeds the heat exchange capacity in
the load-side unit 50a, the load-side heat exchanger 52a of the
load-side unit 50a cannot fully condense the refrigerant. Thus, a
specific enthalpy difference .DELTA.h between a primary side of the
load-side unit 50a (to be a refrigerant inlet side in the heating
operation) and the liquid pipe line becomes smaller, so that on a
secondary side of the load-side heat exchanger 52a (between the
load-side heat exchanger 52a and the load-side throttle device 51a.
To become a refrigerant outlet side in the heating operation), a
tendency of outflow of the gas-liquid two-phase refrigerant gets
stronger (the Mollier diagram shown by a dot line in FIG. 2).
[0085] On the other hand, the opening degree of the load-side
throttle device 51a of the load-side unit 50a is controlled by the
controller 40 in the load-side unit 50a on the basis of a
supercooling degree (subcool) SC of the liquid refrigerant flowing
out of the load-side heat exchanger 52a. Here, an outflow of the
gas-liquid two-phase refrigerant on the secondary side of the
load-side heat exchanger 52a means that the supercooling degree SC
is smaller than 0. Thus, in order to increase the supercooling
degree SC, the controller 40 decreases the opening degree of the
load-side throttle device 51a.
[0086] As a result, the refrigerant passing through the load-side
throttle device 51a is decreased, while since the refrigerant is
supplied from the compressor 11, the refrigerant density between
the load-side throttle device 51a and the compressor 11 is
increased. Moreover, the time during which the high-pressure gas
refrigerant is shut up inside the load-side heat exchanger 52a of
the load-side unit 50a gets longer. Until it is judged that the
supercooling degree SC in the load-side unit 50a becomes a targeted
supercooling degree SC above 0, the opening degree of the load-side
throttle device 51a is also reduced. From the above, until the
targeted supercooling degree SC is reached, a phenomenon
(hereinafter referred to as high-pressure rise phenomenon) occurs
in which the pressure of the refrigerant on the discharge side
(high pressure side) of the compressor 11 continues to abnormally
rise. Usually, the controller 40 tries to lower the high-pressure
PS by lowering the driving frequency of the compressor 11, but if
the driving frequency of the compressor 11 has reached a limit, the
pressure cannot be lowered by controlling the compressor 11.
[0087] In order to avoid the above-mentioned phenomenon, two
methods are conceivable. The first method is to increase an area of
the heat exchanger of the load-side unit 50a or to increase an air
volume flowing through the load-side unit 50a so as to increase the
heat exchange capacity of the load-side unit 50a (to make
correspond to the ability). The second method is to reduce the
refrigerant amount flowing through the load-side unit 50a (to make
correspond to the heat exchange capacity (load)).
[0088] Using either of the methods, the ability and the heat
exchange capacity (load) are well-balanced and contained in the
range of heat exchange capacity, so that the load-side heat
exchanger 52a can condense the refrigerant. Moreover, the specific
enthalpy difference Ah between the primary side (the inlet side in
the heating operation) of the load-side unit 50a (load-side heat
exchanger 52a) and the liquid pipe line (the secondary side of the
load-side heat exchanger 52a) can be made large, so that the
supercooling degree SC in the load-side unit 50a (the secondary
side of the load-side heat exchanger 52a) can be set as a target.
As a result, the refrigerant density between the throttle device
51a and the compressor 11 is getting low, and the high-pressure PS
can be lowered.
[0089] Here, since the heat transfer area of the load-side heat
exchanger 52a is fixed and the rotation speed of the load-side fan
53a is changed according to users as mentioned above, the heat
exchange capacity is constant. Therefore, the load cannot be
changed in order to control the state of the refrigerant as the
former of the above-mentioned two methods. Thus, the state of the
refrigerant needs to be controlled so that the ability
corresponding to the load is supplied to lower the high-pressure PS
as in the latter method.
[0090] In the present embodiment, the bypass for splitting the
refrigerant by the bypass pipe 21, the opening/closing valve 22 for
bypass, and the throttle device 23 for bypass is branched and
provided from the piping on the discharge side of the compressor
11. By constituting a bypass circuit such that if it is judged that
the high-pressure PS is not less than a predetermined pressure on
the basis of a detection signal from the pressure sensor 61, the
refrigerant discharged by the compressor 11 is split so as to lower
the pressure by the throttle device 23 for bypass and is returned
to the intake side of the compressor 11, the refrigerant amount
flowing through the load-side unit 50 (refrigerant amount flowing
through the refrigerant main circuit) can be reduced without losing
balance of the refrigerating cycle. The refrigerant having passed
through the bypass can be returned to the intake side of the
compressor 11 as it is, but by removing sensible heat by the
heat-source side heat exchanger 15, the pressure on the intake side
(low-pressure side) of the compressor 11 is kept from rising.
[0091] As mentioned above, the refrigerant having passed the bypass
is made to pass through the heat-source side heat exchanger 15b in
the present embodiment. Here, selection of the heat-source side
heat exchanger 15 for removing sensible heat of the split
refrigerant will be described. As shown in FIG. 2, with respect to
the refrigerant of the overheated vapor having passed the bypass
(without raising the pressure on the intake side of the compressor
11,) the refrigerant having the heat exchange capacity that can
remove sensible heat of a difference in the specific enthalpy
(between the refrigerant on the discharge side and the refrigerant
on the intake side of the compressor 11) from the refrigerant is
selected from the heat-source side heat exchanger 15a, the
heat-source side heat exchanger 15b, and the heat-source side heat
exchanger 15c. The difference in the specific enthalpy can be
calculated using values of the targeted high-pressure PS in the
heating operation and heating-dominant operation, pressure on the
intake side, temperature of the compressor 11, and temperature of
the secondary side of the heat-source side heat exchanger 15 (when
functioning as an evaporator, the outlet side), for example, as
physical parameters, and moreover, on the basis of an assumed
amount of the refrigerant passing through the bypass, a heat
quantity for the heat exchange can be calculated. Then, it is only
necessary to make a selection from the heat-source side heat
exchanger 15 having the heat exchange capacity capable of heat
exchange of the calculated heat quantity and to perform piping
connection to have it communicate. Here, for example, the
refrigerant passing through the bypass is made to flow only to the
heat-source side heat exchanger 15b, but if sensible heat cannot be
sufficiently removed by a single heat exchanger, for example, a
plurality of heat-source side heat exchangers 15 may be
combined.
[0092] FIG. 3 is a diagram illustrating a flowchart according to
high-pressure restraint control executed by the controller 40 in
the embodiment 1. The controller 40 has, as mentioned above, the
control start judgment processing portion 40a, the control
start-time processing portion 40b, the during-control processing
portion 40c, and the control end-time processing portion 40d.
Processing executed by each portion will be described on the basis
of FIG. 3.
[0093] The control start judgment processing portion 40a executes
start-condition judgment processing on whether high-pressure
restraint control is to be started or not (S10). In the present
embodiment, it is judged on the basis of four items, namely, an
operation mode when control is effective, values of physical
parameters for judging high-pressure rise, the driving frequency of
the compressor 11, and a state of the opening/closing valve 21 for
the bypass circuit, which are indispensable in start judgment.
[0094] First, since the above problem does not occur when the
heat-source side heat exchanger 15 capable of largely changing the
heat exchange capacity functions as a condenser, it is judged
whether the operation mode is the heating operation or the
heating-dominant operation (S11). Then, it is judged if a
high-pressure rise phenomenon has occurred or not. In the present
embodiment, a physical parameter to perform judgment relating to
the high-pressure rise phenomenon is the high-pressure PS judged on
the basis of the signal transmitted from a pressure sensor 61. It
is judged if a value of the high-pressure PS judged on the basis of
the signal from the pressure sensor 61 is larger than a preset
threshold value P1 (S12). If it is judged that the value is larger
than the threshold value P1, it is regarded that the
above-mentioned high-pressure rise phenomenon has occurred.
[0095] FIG. 4 is a diagram illustrating setting conditions of the
threshold value in the high-pressure restraint control. An
excessive rise of the high-pressure PS causes a failure of the air
conditioner 100 (heat-source side unit 10), its upper limit
(high-pressure design pressure) is set in the design. For the
pressure exceeding the high-pressure design pressure, the
controller 40 executes control to protect the air conditioner 100
(heat-source side unit 10). Since the high-pressure restraint
control may perform processing at a pressure lower than that, the
threshold value P1 is set at a value provided with a margin below
the high-pressure design pressure.
[0096] Also, it is judged if the compressor 11 is driven at the
minimum driving frequency (S15). This is because in order to
execute the high-pressure restraint control in the case where a
large amount of refrigerant flows to the load so as to cause
overcapacity even if the compressor 11 is driven at the minimum
driving frequency. To judge on the basis of the minimum driving
frequency is convenient from the viewpoint of the energy
efficiency. However, it is not necessarily limited to the minimum
driving frequency but an upward margin may be given. Here, the
high-pressure restraint control is to forcedly restrain the ability
(refrigerant amount) to be supplied to the load-side unit 50. If
the margin is too much, the compressor 11 with the largest energy
consumption might be excessively driven with respect to an ability
to be supplied, so that attention should be paid. Moreover, in the
state where the opening/closing valve 22 for bypass is opened, the
high-pressure restraint control has been started, and it is judged
if the opening/closing valve 22 for bypass is in the closed state
or not (S16), and if it is judged that the valve is closed, the
control moves to the control start-time processing by the control
start-time processing portion 40b.
[0097] If it is judged that the control start judgment processing
portion 40a is to start the high-pressure restraint control, the
control start-time processing portion 40b executes the control
start-time processing (S20) that forms a bypass circuit passing
through the opening/closing valve 22 for bypass--the throttle
device 23 for bypass--the bypass pipe 21--the heat-source side heat
exchanger 15b to the intake side of the compressor 11. First,
processing to close the heat-source side opening/closing valve 14b
is executed (S21). Then, processing to open the opening/closing
valve 22 for bypass is executed (S22). If the opening/closing valve
22 for bypass is opened first, the liquid refrigerant passing
through the heat-source side opening/closing valve 14b and the gas
refrigerant passing through the bypass pipe 21 are mixed and
disturb the flow in the refrigerant circuit, therefore, it is
necessary to close the heat-source side opening/closing valve 14b
and thereafter, to open the opening/closing valve 22 for bypass so
as to pass the refrigerant through the bypass. Here, depending on
the selected heat-source side heat exchanger 15, the heat-source
side opening/closing valve 14 to be closed might be the heat-source
side opening/closing valve 14a or 14c instead of the heat-source
side opening/closing valve 14b as mentioned above.
[0098] The during-control processing portion 40c executes the
high-pressure restraint during-control processing when the control
start-time processing portion 40b executes the control start-time
processing (S30). In the high-pressure restraint during-control
processing, opening-degree adjustment control processing and
control end judgment processing are executed. First, regarding the
opening-degree adjustment control processing of the throttle device
23 for bypass, if it is judged that the high-pressure-side pressure
PS judged on the basis of the signal from a pressure sensor 61 is
not less than a threshold value P1 (S31), processing to change and
to increase (open) the opening degree of the throttle device 23 for
bypass is executed so as to increase the amount of the refrigerant
split to the bypass (S32). Here, the opening degree of the throttle
device 23 for bypass will be described. An initial opening degree
of the throttle device 23 for bypass is predetermined when the
opening/closing valve 22 for bypass is opened at the control start
processing. This initial opening degree is determined by the
refrigerant amount to be flown to the bypass in order to set the
targeted high-pressure PS not more than the pressure of the
threshold value P2 on the basis of the parameters such as the
ability supplied by the compressor 11 at the minimum frequency.
Further, an opening-degree change margin of the throttle device 23
for bypass may be set arbitrarily in advance. In the present
embodiment, a change of approximately 10% to 20% increase is made
so that a large amount of the refrigerant is not split rapidly in
order to lower the pressure but the balance of the refrigerating
cycle can be maintained at the steady operation of the air
conditioner 100. Here, the threshold value P2 is, as shown in FIG.
4, set so that the high-pressure PS at a temperature close to a
targeted condensation temperature can be obtained in the load-side
heat exchanger 52a functioning as a condenser in the heating
operation and heating-dominant operation.
[0099] In the control end-time determination processing to be
executed subsequently, determination is judged on the basis of four
items, namely, a value of a physical parameter not requiring a
high-pressure restraint control, the driving frequency of the
compressor 11, the operation mode, and the state of the compressor
11. In the present embodiment, as the physical parameter for
judgment, a high-pressure side pressure PS is used similarly to the
control start-time judgment. It is judged if the high-pressure side
pressure PS is not more than the threshold value P2 or not on the
basis of the signal from the pressure sensor 61 (S33).
[0100] The controller 40 judges the load required by the load-side
unit 10 on the basis of the signal from various sensors, changes
the driving frequency of the compressor 11 by the inverter circuit
and carries out ability supply according to the load. Then, it is
judged if the compressor 11 is driven at the driving frequency not
less than a threshold value F1 due to the increase in the load-side
units 50 for carrying out the heating operation, for example (S34).
Here, as shown in FIG. 4, as the threshold value F1, for example,
the refrigerant amount is set which is discharged at the minimum
driving frequency when the refrigerant is not split, and when the
refrigerant is split, the driving frequency of the compressor 11 is
set that can supply the refrigerant to the heat-source side unit 50
side. That is, at S34, it is judged if the compressor 11 supplies
the refrigerant amount exceeding the refrigerant amount discharged
at the minimum driving frequency to the load-side unit 50 or
not.
[0101] It is judged if the load-side heat exchanger 52 is operated
in the cooling operation or cooling-dominant operation in which the
heat exchanger functions not as a condenser but as an evaporator
(S35). Then, it is judged if the compressor 11 has been stopped or
not (S36). If the during-control processing portion 40c judges that
any one of the judgments at S33 to 336 is satisfied, processing is
moved to the control end-time processing by the control end-time
processing portion 40d. On the other hand, if it is judged that
none of the conditions is satisfied, after waiting for a
predetermined time (S37), the processing returns to 331, where the
opening-degree adjustment control processing and the control end
judgment processing are executed. The predetermined time becomes
time till the subsequent sampling in the control software if the
processing is executed, for example, by the during-control
processing portion 40c (controller 40) with the control program or
the like stored in storage means 45.
[0102] Here, since the two types of control processing executed by
the during-control processing portion 40c do not interfere with
each other as a control process, either of the processing may be
executed first. However, if the control end judgment processing is
executed prior to the opening-degree adjustment control processing,
since it is likely that the control end is judged before the
high-pressure restraint control after the control start-time
processing portion 40b executes the processing, they are preferably
executed in the order of the opening-degree adjustment control
processing and the control end determination processing.
[0103] If the during-control processing portion 40c judges in the
control end determination processing that the control is finished,
the control end-time processing portion 40d executes the control
end-time processing (S40) such that the refrigerant does not pass
through the bypass and is returned to the refrigerant flow before
the control start-time processing. First, processing to close the
opening/closing valve 22 for bypass is executed (S41). Then,
processing to open the heat-source side opening/closing valve 14b
is executed (S42). Here, if the heat-source side opening/closing
valve 14b is opened first, the liquid refrigerant flowing through
the heat-source side opening/closing valve 14b and the gas
refrigerant having passed through the bypass pipe 21 are mixed and
disturb the refrigerant circuit flow, so that the opening/closing
valve 22 for bypass is closed first, and after the refrigerant flow
passing through the bypass is shut off, the heat-source side
opening/closing valve 14b is opened.
[0104] As mentioned above, according to the air conditioner 100 of
the embodiment 1, in the heating operation and heating-dominant
operation, if the controller 40 judges that the high-pressure PS
becomes a pressure not less than a predetermined threshold value P1
on the basis of the signal from the pressure sensor 61 when the
compressor 11 is driven at the minimum driving frequency, the
opening/closing valve 22 for bypass is opened so as to split part
of the refrigerant flow by the bypass pipe 21 and to decrease the
refrigerant amount flowing to the load-side unit 50 side, so that
the ability (refrigerant amount) matching the heat exchange
capacity of the load-side heat exchanger 52 can be supplied from
the heat-source side unit 10 side, the high-pressure rise
phenomenon is restrained, and temperature rise and abnormal stop of
the compressor 11 caused by overheat can be prevented. Further, it
is possible to improve, for example, COP (Coefficient of
Performance), APF (Annual Performance Fact) and the like by
reducing the number of start and stop times of the operation of the
compressor 11 and the load-side unit 50 to promote energy saving.
Since it is highly likely that the pressure rise phenomenon can
occur in the air conditioner 100 capable of the cooling/heating
mixed operation, particularly the above effects can be exerted, in
which the heating operation might be carried out even in summer, so
that the heat exchange capacity of the load-side heat exchanger 52
sometimes might be small.
[0105] FIG. 9 is a diagram illustrating a Mollier diagram (p-h
diagram) varying by control. When the method described in the
embodiment 1 is used, the diagram (p-h diagram) changes as in FIG.
9, thereby if a characteristic is such that an input drop width
(W1-W2) in the compressor 11 is large with respect to ability loss
Qloss by the condenser (load-side heat exchanger 52) of the
load-side unit 50 used as the bypass circuit, the COP and APF are
improved in addition to the above effect. Moreover, by reusing
exhaust heat generated by the Qloss, the COP and APF can be further
improved.
[0106] The cooling/heating branch unit 30 can connect with a
plurality of load-side units 50a and 50b switchably in series or
parallel connection. In this case, when the plurality of the
load-side units 50a and 50b are switched from parallel connection
to series connection, and only the load-side heat exchanger 52 of
the load-side unit 50 on the upstream side with respect to the
refrigerant flow is used as a condenser, for example, and the
high-pressure is raised, since the opening/closing valve 22 for
bypass is controlled to the open state so as to split the
refrigerant, the excessive rise of the high pressure can be
effectively restrained. Particularly, when the load-side unit 50a
(low-performance unit) having the load-side heat exchanger 52a with
a small heat exchange capacity (load) and the load-side unit 50b
(high performance unit) with a large heat exchange capacity are
mixed, it is likely that the high pressure is raised during the
cooling/heating simultaneous operation in which the low-performance
unit carries out the heating operation and the high-performance
unit carries out the cooling operation. However, in the air
conditioner of the present embodiment, since the controller 40
controls the opening/closing valve 22 for bypass to be the open
state so as to spilt the refrigerant, the excessive rise of the
high pressure can be effectively restrained. Thereby, by having the
controller 40 specify the load-side unit 50 carrying out the
heating operation, it is possible to judge that there is a fear of
abnormal rise of the high pressure from its heat exchange ability,
indoor temperature and the like not from a detected pressure value
or using the pressure detected value in combination.
[0107] Since the controller 40 judges the pressure on the basis of
the signal from the pressure sensor 61, the start of the
high-pressure restraint control can be judged directly on the basis
of the rise of the high-pressure PS. With regard to the refrigerant
having passed through the bypass, since it is made to pass through
the heat-source side heat exchanger 15b so as to remove sensible
heat and is returned to the intake side of the compressor 11 to
constitute the bypass circuit, the refrigerant of overheated vapor
with a temperature higher than necessary flows into the intake side
of the compressor 11 not to raise the temperature of the
refrigerant on the intake side. Therefore, the high-pressure rise
phenomenon can be further restrained. At this time, since one end
of the bypass pipe 21 is made to communicate with any of the piping
to the plurality of the heat-source side heat exchangers 15 so as
to remove sensible heat of the refrigerant, space and costs can be
reduced without using an exclusive heat exchanger. Moreover, since
the refrigerant amount to be split by the throttle device 23 for
bypass can be adjusted on the basis of the instruction of the
controller 40 based on the pressure state of the high-pressure PS,
rise of the high pressure can be effectively restrained.
Embodiment 2
[0108] FIG. 5 is a diagram illustrating a flowchart relating to the
high-pressure restraint control executed by the controller 40 in an
embodiment 2. Here, the apparatus configuration of the air
conditioner 100 is the same as in FIG. 1, and since the description
has been already made in the embodiment 1, the description will be
omitted. In the embodiment 1, the control start judgment processing
portion 40a executes the start condition judgment processing on the
basis of the high-pressure PS judged by the signal from the
pressure sensor 61.
[0109] As mentioned above, in the heating operation and
heating-dominant operation, the heat-source side heat exchanger 15
functions as an evaporator. Here, since the higher the temperature,
the larger the heat quantity contained in the air in the case of
the outside air temperature being 20.degree. C. or above as in the
summer, for example, the heat exchange between the refrigerant and
air is facilitated in the heat-source side heat exchanger 15. As a
result, an evaporation temperature of the refrigerant tends to rise
when the outside air temperature is high. This leads to a rise in
the pressure on the intake side of the compressor 11, the
high-pressure PS and constitutes one of the causes of the
high-pressure rise phenomenon. Thus, in the present embodiment, the
control start judgment processing portion 40a executes the start
condition judgment processing on whether or not to start the
high-pressure restraint control on the basis of an ambient
temperature T judged by a signal from the temperature sensor 62. By
making a judgment at a stage in which a factor of the pressure rise
phenomenon occurs, early response is made possible such that the
refrigerant is split to lower the high-pressure PS before rapid
pressure rise to become a pressure higher than a high-pressure
design pressure while the system is stabilized, such a situation
can be prevented that control is executed in order to protect the
air conditioner 100 (heat-source side unit 10).
[0110] In FIG. 5, those given the same step numbers as in FIG. 3
execute the same processing as described in the embodiment 1, so
that the description will be omitted. As mentioned above, at S11,
after the operation mode is judged, the judgment on the
high-pressure rise phenomenon is made, but in the present
embodiment, the physical parameter for the judgment is the ambient
temperature T judged on the basis of the signal transmitted from
the temperature sensor 62. It is judged if the value of the ambient
temperature T judged on the basis of the signal from the
temperature sensor 62 is larger than a preset threshold value T1 or
not (S13). If it is judged as being larger, there is a sign of
occurrence of the above-mentioned high-pressure rise phenomenon.
Here, as shown in FIG. 4, the threshold value T1 is set on the
basis of the outside air temperature in the summer.
[0111] Though it is possible to perform judgment only by the
ambient temperature T, since no high-pressure rise phenomenon
occurs if the load in the heat-source side unit 50 and the ability
supplied by the compressor 11 are well-balanced, for example, by
making only the ambient temperature T be the judgment condition,
even in the operation state in which the high-pressure rise
phenomenon cannot occur, it might be judged that the high-pressure
restraint control is to be started. Therefore, another judgment
condition (particularly condition relating to the load of the
load-side unit 50) is preferably added. Then, processing to judge
the number of load-side units 50 carrying out the heating
operation, for example, is executed. In the present embodiment, the
total of the parameters relating to the heat exchange capacity of
the load-side units 50 carrying out the heating operation is
calculated, and it is judged if the summation is not more than a
threshold value Q1 or not (S14). As shown in FIG. 4, the threshold
value Q1 is set on the basis of the ability that can be supplied to
the heat-source side unit 50 when the compressor 11 is driven at
the minimum driving frequency, for example. With regard to the
parameter relating to the heat exchange capacity in each of the
load-side units 50, for example, the data is stored in the storage
device 41. The control start judgment processing portion 40a judges
the operation state of each of the heat-source side units 50 on the
basis of a signal transmitted from the load-side controller 54 of
each heat-source side unit 50, reads out data of the parameter
relating to the heat exchange capacity of the heat-source side unit
carrying out the heating operation from the storage device 41, and
calculates the summation.
[0112] If it is judged that the summation is not more than the
threshold value Q1, there is a possibility that the high-pressure
rise phenomenon occurs. Here, as mentioned above, start of the
high-pressure restraint control is judged at a stage before the
high-pressure rise phenomenon actually occurs. Thus, if the
threshold value P2 is the same as the embodiment 1, the condition
of being not more than the threshold value P2 might be already
satisfied at a stage when the opening/closing value 22 for bypass
is opened. Then, when the start judgment processing is made on the
basis of the ambient temperature T, the threshold P2 may be set
lower than the case of the embodiment 1.
[0113] As mentioned above, according to the air conditioner of the
embodiment 2, the high-pressure rise phenomenon is restrained,
temperature rise and abnormal stop of the compressor 11 caused by
overheat is prevented and energy saving is promoted as in the
embodiment 1. Since the controller 40 judges the ambient
temperature T on the basis of the signal from the temperature
sensor 62, if the outside air temperature is high such as in the
summer when the high-pressure rise phenomenon can easily occur, the
judgment can be made at a stage in which the factor occurs, so that
early response can be made.
Embodiment 3
[0114] FIG. 6 is a diagram illustrating a flowchart relating to the
high-pressure restraint control executed by the controller 40 in an
embodiment 3. In the present embodiment, since the apparatus
configuration of the air conditioner 100 is the same as in FIG. 1,
the description will be omitted. In FIG. 6, those given the same
step numbers as in FIGS. 3 and 5 execute the same processing as in
the processing described in the embodiments 1 and 2, and the
description will be omitted. In the present embodiment, the start
condition judgment processing is executed by the control start
judgment processing portion 40a on the basis of both the
high-pressure PS judged on the basis of the signal from the
pressure sensor 61 and the ambient temperature T judged on the
basis of the signal from the temperature sensor 62. By increasing
the bases for judgment on whether the high-pressure restraint
control is to be executed or not by the high-pressure PS and the
ambient temperature T, the judgment according to the state of the
air conditioner 100 can be made.
Embodiment 4
[0115] FIG. 7 is a configuration diagram of an air conditioner 100A
according to an embodiment 4. When the refrigerant amount (per unit
time) to be split is determined in advance, for example, the
opening-degree adjustment by the throttle device 22 for bypass is
not needed. Then, in the present embodiment, instead of the
throttle device 22 for bypass, a capillary tube 24 for passing a
certain amount of the refrigerant is used.
[0116] FIG. 8 is a diagram illustrating a flowchart relating to the
high-pressure restraint control executed by the controller 40 in
the embodiment 4. In FIG. 8, since those given the same step
numbers as in FIG. 3 execute the same processing as in the
processing described in the embodiment 1, descriptions will be
omitted. As shown in FIG. 8, in the high-pressure restraint
during-control processing executed by the during-control processing
portion 40c of the controller 40, the processing S31 and S32 to be
the above-mentioned opening-degree adjustment control processing do
not have to be executed. Thus, processing burden of the
during-control processing portion 40c in the controller 40 can be
reduced.
INDUSTRIAL APPLICABILITY
[0117] In the above-mentioned embodiments, application to the air
conditioner capable of cooling/heating mixed operation is
described, but the present invention can also be applied to other
air conditioners capable of the cooling/heating switching
operation. The present invention can be applied to other
refrigerating cycle devices constituting a refrigerant circuit such
as a heat pump device as well.
* * * * *