U.S. patent application number 16/463563 was filed with the patent office on 2019-12-12 for refrigeration apparatus.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. The applicant listed for this patent is DAIKIN INDUSTRIES, LTD.. Invention is credited to Azuma KONDOU, Satoru SAKAE.
Application Number | 20190376730 16/463563 |
Document ID | / |
Family ID | 62195825 |
Filed Date | 2019-12-12 |
United States Patent
Application |
20190376730 |
Kind Code |
A1 |
SAKAE; Satoru ; et
al. |
December 12, 2019 |
REFRIGERATION APPARATUS
Abstract
A refrigeration apparatus includes: a usage-side expansion valve
whose opening degree is changed in response to a change in a flow
rate or a pressure of a refrigerant on the upstream side; a first
expansion valve; and a controller. The controller exerts, in an oil
recovery operation, an oil recovery first control on the first
expansion valve to attain a first opening degree (an opening degree
of increasing an opening degree of the usage-side expansion valve
in relation to a reduction in the flow rate or the pressure of the
refrigerant passing through the first expansion valve), to reduce
the flow rate or the pressure of the refrigerant passing through
the first expansion valve. The controller exerts an oil recovery
second control following the oil recovery first control on the
first expansion valve to attain a second opening degree (an opening
degree that allows a liquid refrigerant to flow into a usage-side
heat exchanger before the opening degree of the usage-side
expansion valve is reduced in relation to an increase in the flow
rate or the pressure of the refrigerant passing through the first
expansion valve), to increase the flow rate or the pressure of the
refrigerant passing through the first expansion valve.
Inventors: |
SAKAE; Satoru; (Osaka-shi,
JP) ; KONDOU; Azuma; (Osaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAIKIN INDUSTRIES, LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
62195825 |
Appl. No.: |
16/463563 |
Filed: |
November 21, 2017 |
PCT Filed: |
November 21, 2017 |
PCT NO: |
PCT/JP2017/041855 |
371 Date: |
May 23, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 2700/21175
20130101; F25B 2341/063 20130101; F25B 43/02 20130101; F25B 2400/13
20130101; F25B 2341/0683 20130101; F25B 2600/00 20130101; F25B
2600/21 20130101; F25B 49/02 20130101; F25B 31/004 20130101; F25B
41/062 20130101; F25B 2600/2513 20130101; F25B 2700/21152 20130101;
F25B 5/02 20130101; F25B 2341/0662 20130101; F25B 2341/065
20130101; F25B 2500/16 20130101 |
International
Class: |
F25B 43/02 20060101
F25B043/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 2016 |
JP |
2016-227659 |
Claims
1. A refrigeration apparatus configured to carry out a
refrigeration cycle through a refrigerant circuit including: a heat
source unit including a compressor configured to compress a
refrigerant and a heat-source-side heat exchanger functioning as a
condenser for the refrigerant; and a service unit including a
usage-side heat exchanger functioning as an evaporator for the
refrigerant, the refrigeration apparatus comprising: a mechanical
expansion valve disposed on a refrigerant flow upstream side
relative to the usage-side heat exchanger and configured to
decompress a refrigerant passing through the mechanical expansion
valve in accordance with an opening degree of the mechanical
expansion valve; an electric valve disposed on the refrigerant flow
upstream side relative to the mechanical expansion valve and
configured to adjust a flow rate or a pressure of a refrigerant
passing through the electric valve in accordance with an opening
degree of the electric valve; and a controller configured to
control an operation of a plurality of actuators, wherein the
mechanical expansion valve has an opening degree changed in
response to an increase and a reduction in a flow rate or a
pressure of a refrigerant flowing upstream to the mechanical
expansion valve, the controller executes an oil recovery operation
including a first control and a second control for recovering a
refrigerating machine oil built up in the service unit to the
compressor at a predetermined timing, by the first control, the
electric valve has an opening degree set to a predetermined first
opening degree to reduce the flow rate or the pressure of the
refrigerant passing through the electric valve, by the second
control, after the first control, the electric valve has an opening
degree set to a second opening degree to increase the flow rate or
the pressure of the refrigerant passing through the electric valve,
the first opening degree is an opening degree that causes the
opening degree of the mechanical expansion valve to increase in
relation to a reduction in the flow rate or the pressure of the
refrigerant passing through the electric valve, and the second
opening degree is an opening degree that allows, before the opening
degree of the mechanical expansion valve is reduced in relation to
an increase in the flow rate or the pressure of the refrigerant
passing through the electric valve, a liquid refrigerant to flow
into the usage-side heat exchanger.
2. The refrigeration apparatus according to claim 1, wherein the
controller executes the first control, and executes the second
control after a lapse of a predetermined time from execution of the
first control.
3. The refrigeration apparatus according to claim 1, wherein the
mechanical expansion valve includes a feeler bulb disposed on a
refrigerant flow downstream side relative to the usage-side heat
exchanger, and has an opening degree changed in response to a
detected temperature by the feeler bulb.
4. The refrigeration apparatus according to claim 1, wherein the
electric valve is disposed in the heat source unit.
5. The refrigeration apparatus according to claim 1, wherein the
controller is disposed at the heat source unit and not electrically
connected to any element disposed at the service unit.
6. The refrigeration apparatus according to claim 1, wherein the
refrigerant circuit includes a plurality of the service units.
7. The refrigeration apparatus according to claim 2, wherein the
mechanical expansion valve includes a feeler bulb disposed on a
refrigerant flow downstream side relative to the usage-side heat
exchanger, and has an opening degree changed in response to a
detected temperature by the feeler bulb.
8. The refrigeration apparatus according to claim 2, wherein the
electric valve is disposed in the heat source unit.
9. The refrigeration apparatus according to claim 3, wherein the
electric valve is disposed in the heat source unit.
10. The refrigeration apparatus according to claim 2, wherein the
controller is disposed at the heat source unit and not electrically
connected to any element disposed at the service unit.
11. The refrigeration apparatus according to claim 3, wherein the
controller is disposed at the heat source unit and not electrically
connected to any element disposed at the service unit.
12. The refrigeration apparatus according to claim 4, wherein the
controller is disposed at the heat source unit and not electrically
connected to any element disposed at the service unit.
13. The refrigeration apparatus according to claim 2, wherein the
refrigerant circuit includes a plurality of the service units.
14. The refrigeration apparatus according to claim 3, wherein the
refrigerant circuit includes a plurality of the service units.
15. The refrigeration apparatus according to claim 4, wherein the
refrigerant circuit includes a plurality of the service units.
16. The refrigeration apparatus according to claim 5, wherein the
refrigerant circuit includes a plurality of the service units.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration
apparatus.
BACKGROUND ART
[0002] Conventionally, a refrigeration apparatus including a
refrigerant circuit performing a refrigeration cycle is known. The
refrigerant circuit includes: a heat source unit including a
compressor and a heat-source-side heat exchanger; and a service
unit including a usage-side heat exchanger and a mechanical
expansion valve. Some of such refrigeration apparatuses, for
example, as a refrigeration apparatus disclosed in Patent
Literature 1 (JP 2009-257759 A), perform at a predetermined timing
an oil recovery operation of opening and closing an on-off valve
disposed upstream to a mechanical expansion valve in the service
unit to send a liquid refrigerant to the usage-side heat exchanger
and to recover a refrigerating machine oil built up in the
usage-side heat exchanger.
SUMMARY OF THE INVENTION
Technical Problem
[0003] In the case where a controller for controlling actuators is
disposed outside the service unit, the refrigeration apparatus
which performs the oil recovery operation in the manner disclosed
in Patent Literature 1 necessitates an electric wire for
electrically connecting between the on-off valve in the service
unit and the controller in installation or maintenance. For the
troubles and costs in works and maintenance relating to the
electric wire, such refrigeration apparatus is poor in workability,
maintainability, and economy.
[0004] An object of the present invention is to provide a
refrigeration apparatus which is excellent in workability,
maintainability, and economy.
Solution to Problem
[0005] A refrigeration apparatus according to a first aspect of the
present invention is a refrigeration apparatus configured to carry
out a refrigeration cycle through a refrigerant circuit including a
heat source unit and a service unit. The refrigeration apparatus
includes a mechanical expansion valve, an electric valve, and a
controller. The heat source unit includes a compressor and a
heat-source-side heat exchanger. The compressor is configured to
compress a refrigerant. The heat-source-side heat exchanger
functions as a condenser for a refrigerant. The service unit
includes a usage-side heat exchanger. The usage-side heat exchanger
functions as an evaporator for a refrigerant. The mechanical
expansion valve is disposed on a refrigerant flow upstream side
relative to the usage-side heat exchanger. The mechanical expansion
valve is configured to decompress a refrigerant passing through the
mechanical expansion valve in accordance with an opening degree of
the mechanical expansion valve. The electric valve is disposed on
the refrigerant flow upstream side relative to the mechanical
expansion valve. The electric valve is configured to adjust a flow
rate or a pressure of a refrigerant passing through the electric
valve in accordance with an opening degree of the electric valve.
The controller is configured to control the operation of actuators.
The actuators include the electric valve. The mechanical expansion
valve has its opening degree changed in response to an increase and
a reduction in a flow rate or a pressure of a refrigerant flowing
on an upstream side relative to the mechanical expansion valve. The
controller executes an oil recovery operation at a predetermined
timing. The oil recovery operation includes a first control and a
second control. The first control and the second control are
control for recovering a refrigerating machine oil built up in the
service unit to the compressor. In the first control, the
controller sets the opening degree of the electric valve to a
predetermined first opening degree to reduce the flow rate or the
pressure of the refrigerant passing through the electric valve. The
first opening degree is an opening degree that increases the
opening degree of the mechanical expansion valve in relation to a
reduction in the flow rate or the pressure of the refrigerant
passing through the electric valve. In the second control, after
the first control, the controller sets the opening degree of the
electric valve to a second opening degree to increase the flow rate
or the pressure of the refrigerant passing through the electric
valve. The second opening degree is an opening degree that allows,
before the opening degree of the mechanical expansion valve is
reduced in relation to an increase in the flow rate or the pressure
of the refrigerant passing through the electric valve, a liquid
refrigerant to flow into the usage-side heat exchanger.
[0006] In the refrigeration apparatus according to the first aspect
of the present invention, in the oil recovery operation, the
controller sets the opening degree of the electric valve to the
first opening degree to reduce the flow rate or the pressure of the
refrigerant passing through the electric valve, and thereafter sets
the opening degree of the electric valve to the second opening
degree to increase the flow rate or the pressure of the refrigerant
passing through the electric valve. Thus, in the oil recovery
operation, under the first control, in relation to a reduction in
the flow rate or the pressure of the refrigerant passing through
the electric valve, the opening degree of the mechanical expansion
valve is increased. Thereafter, under the second control, before
the opening degree of the mechanical expansion valve is reduced in
relation to an increase in the flow rate or the pressure of the
refrigerant passing through the electric valve, a liquid
refrigerant is allowed to flow into the usage-side heat exchanger.
As a result, the liquid refrigerant flowing into the usage-side
heat exchanger is compatibilized with a refrigerating machine oil
built up in the usage-side heat exchanger and is delivered toward
the heat source unit side. Thus, the refrigerating machine oil is
recovered to the compressor.
[0007] That is, it is possible to carry out the oil recovery
operation of recovering a refrigerating machine oil in the service
unit to the compressor without the necessity of disposing an on-off
valve for the oil recovery operation in the service unit (or in a
refrigerant flow path downstream to the heat source unit and
upstream to the mechanical expansion valve, the same holds true for
the following). In other words, in performing the oil recovery
operation through the refrigerant circuit including the mechanical
expansion valve upstream to the usage-side heat exchanger, an
on-off valve disposed upstream to the mechanical expansion valve
can be dispensed with. Hence, the refrigeration apparatus can
dispense with an electric wire for electrically connecting between
the controller and the on-off valve in installation or maintenance
and accordingly save any troubles and costs in works and
maintenance relating to the electric wire. Hence, the refrigeration
apparatus is excellent in workability, maintainability, and
economy.
[0008] Note that, while the "refrigerant" as used herein is not
limited, it may be a HFC refrigerant such as R410A or R32, for
example.
[0009] The refrigeration apparatus according to a second aspect of
the present invention is the refrigeration apparatus according to
the first aspect, in which the controller executes the first
control, and executes the second control after a lapse of a
predetermined time from execution of the first control. As used
herein, the predetermined time is a time that is required for the
mechanical expansion valve to have its opening degree increased in
response to a reduction in the flow rate or the pressure of the
refrigerant passing through the electric valve by the first
control.
[0010] Thus, after the opening degree of the mechanical expansion
valve is increased in relation to the first control being executed,
the opening degree of the electric valve is increased by the second
control, whereby a liquid refrigerant by a flow rate suitable for
recovering a refrigerating machine oil flows into the usage-side
heat exchanger. As a result, it is possible to carry out the oil
recovery operation without the necessity of disposing an on-off
valve for the oil recovery operation in the service unit. Thus, any
electric wire for electrically connecting between the controller
and the on-off valve in installation or maintenance can be
dispensed with, and accordingly, the refrigeration apparatus can
save any troubles and costs in works and maintenance relating to
the electric wire.
[0011] The refrigeration apparatus according to a third aspect of
the present invention is the refrigeration apparatus according to
the first or second aspect, in which the mechanical expansion valve
includes a feeler bulb. The feeler bulb is disposed on a
refrigerant flow downstream side relative to the usage-side heat
exchanger. The mechanical expansion valve has its opening degree
changed in response to a temperature detected by the feeler
bulb.
[0012] Thus, using the characteristic of the mechanical expansion
valve including the feeler bulb, a liquid refrigerant is sent to
the usage-side heat exchanger to recover a refrigerating machine
oil. That is, the opening degree of the mechanical expansion valve
is not immediately changed in response to a change in the flow rate
of a refrigerant on the upstream side. Instead, the opening degree
is changed by a delay corresponding to a response time in response
to a change in the flow rate of the refrigerant on the upstream
side (that is, a change in the opening degree of the electric
valve). In other words, the mechanical expansion valve is
characterized by its low-speed responsivity. By virtue of this
characteristic, when the second control is executed following the
first control, the opening degree of the mechanical expansion valve
is not immediately reduced. Hence, after the electric valve is set
to the second opening degree under the second control and until the
mechanical expansion valve has its opening degree reduced in
response thereto, a liquid refrigerant is allowed to flow in by a
flow rate suitable for recovering a refrigerating machine oil to
the usage-side heat exchanger.
[0013] The refrigeration apparatus according to a fourth aspect of
the present invention is the refrigeration apparatus according to
any one of the first to third aspects, in which the electric valve
is disposed in the heat source unit. This eliminates the necessity
of providing an electric wire for connecting between the heat
source unit and the service unit which are generally disposed
spaced apart from each other. This particularly minimizes works and
costs relating to installation or maintenance.
[0014] The refrigeration apparatus according to a fifth aspect of
the present invention is the refrigeration apparatus according to
any one of the first to fourth aspects, in which the controller is
disposed at the heat source unit and not electrically connected to
any element disposed at the service unit. This eliminates the
necessity of providing an electric wire for connecting between the
heat source unit and the service unit which are generally disposed
spaced apart from each other. This particularly minimizes works and
costs relating to installation or maintenance.
[0015] The refrigeration apparatus according to a sixth aspect of
the present invention is the refrigeration apparatus according to
any one of the first to fifth aspects. The refrigerant circuit
includes a plurality of the service units. Thus, even in the case
where a plurality of service units are installed (that is, in the
case where electric wires are required for connecting between the
heat source unit and the service units, which involves particularly
complicated installation works or maintenance works), the
refrigeration apparatus can dispense with any electric wires which
are required by an on-off valve for the oil recovery operation
installed in each of the service units. This particularly minimizes
works and costs relating to installation or maintenance.
Advantageous Effects of Invention
[0016] Without the necessity of disposing an on-off valve for an
oil recovery operation in the service unit, the refrigeration
apparatus according to the first aspect of the present invention
carries out the oil recovery operation of recovering a
refrigerating machine oil in the service unit to the compressor. In
other words, the mechanical expansion valve performing an oil
recovery operation in the refrigerant circuit disposed upstream to
the usage-side heat exchanger does not require an on-off valve
disposed upstream to the mechanical expansion valve. Hence, the
refrigeration apparatus can dispense with an electric wire
electrically connecting between the controller and an on-off valve
in installation or maintenance and, accordingly, the refrigeration
apparatus can save any troubles and costs in works and maintenance
relating to the electric wire. Thus, the refrigeration apparatus is
excellent in workability, maintainability, and economy.
[0017] The refrigeration apparatus according to the second aspect
of the present invention can dispense with an electric wire for
electrically connecting between the controller and an on-off valve
in installation or maintenance and, accordingly, the refrigeration
apparatus can save any troubles and costs in works and maintenance
relating to the electric wire.
[0018] In the refrigeration apparatus according to the third aspect
of the present invention, using the characteristic of the
mechanical expansion valve including the feeler bulb, a liquid
refrigerant is sent to the usage-side heat exchanger to recover the
refrigerating machine oil.
[0019] The refrigeration apparatus according to the fourth or fifth
aspect of the present invention can dispense with an electric wire
for connecting between the heat source unit and the service unit
which are generally disposed spaced apart from each other. This
particularly minimizes works and costs relating to installation or
maintenance.
[0020] The refrigeration apparatus according to the sixth aspect of
the present invention can dispense with an electric wire which is
required for an on-off valve for an oil recovery operation in each
of the service units, even in the case where a plurality of service
units are provided. This particularly minimizes works and costs
relating to installation or maintenance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic configuration diagram of a
refrigeration apparatus according to one embodiment of the present
invention.
[0022] FIG. 2 is a block diagram schematically showing a schematic
configuration of a controller and units connected to the
controller.
[0023] FIG. 3 is a flowchart showing an exemplary flow of processes
at the controller.
DESCRIPTION OF EMBODIMENTS
[0024] In the following, with reference to the drawings, a
description will be given of a refrigeration apparatus 100
according to an embodiment of the present invention. Note that, the
following embodiment is merely a specific example of the present
invention and does not limit the technical scope of the present
invention. Any changes can be made as appropriate within a range
not deviating from the spirit of the invention.
(1) Refrigeration Apparatus 100
[0025] FIG. 1 is a schematic configuration diagram of the
refrigeration apparatus 100 according to an embodiment of the
present invention. The refrigeration apparatus 100 is configured to
cool, by a vapor compression refrigeration cycle, the inside of a
low-temperature warehouse, the inside of a showcase at a shop, the
usage-side space (the target space) formed in a transfer container
or the like. The refrigeration apparatus 100 mainly includes a heat
source unit 10, a plurality of (two in the present embodiment)
service units 30 (30a, 30b), and a controller 50 controlling the
operation of the refrigeration apparatus 100.
[0026] In the refrigeration apparatus 100, a refrigerant circuit RC
is formed by one heat source unit 10 and the service units 30 being
connected to each other via a gas-side connection pipe G1 and a
liquid-side connection pipe L1. The refrigeration apparatus 100
carries out a refrigeration cycle of subjecting a refrigerant
enclosed in the refrigerant circuit RC to compression, cooling or
condensation, decompression, and heating or evaporation, and
thereafter again compression. The refrigerant enclosed in the
refrigerant circuit RC is, for example, an HFC refrigerant such as
R32 or R410A.
(1-1) Heat Source Unit 10
(1-1-1) Circuit Elements Disposed at Heat Source Unit 10
[0027] The heat source unit 10 is connected to the service units 30
via the gas-side connection pipe G1 and the liquid-side connection
pipe L1 to form part of the refrigerant circuit RC. The heat source
unit 10 mainly includes, as circuit elements forming the
refrigerant circuit RC, a plurality of (in the present embodiment,
three) compressors 11 (a first compressor 11a, a second compressor
11b, a third compressor 11c), a heat-source-side heat exchanger 12,
a receiver 13, a subcooling heat exchanger 14, a first expansion
valve 15, a second expansion valve 16, injection valves 17 (a first
injection valve 17a, a second injection valve 17b, a third
injection valve 17c) as many as the compressors 11 (in the present
embodiment, three), a gas-side shutoff valve SV1, and a liquid-side
shutoff valve SV2.
[0028] The compressors 11 take in and compress a low-pressure
refrigerant in a refrigeration cycle, and discharge the compressed
refrigerant as a high-pressure refrigerant. The compressors 11 are
each, for example, a scroll-type compressor, and each have a closed
configuration in which a compression element (not shown) is rotated
as being linked to a compressor motor (not shown) in a casing. In
the present embodiment, the first compressor 11a, the second
compressor 11b, and the third compressor 11c are each a
"variable-capacity compressor" whose operating capacity is
variable, that is, which has, in operation, the number of
revolutions of the compressor motor controlled as appropriate by an
inverter. Alternatively, the second compressor 11b and the third
compressor 11c are each a "constant-capacity compressor" whose
operating capacity is constant, that is, the number of revolutions
of the compressor motor in operation is constant. The first
compressor 11a, the second compressor 11b, and the third compressor
11c are disposed in parallel to one another.
[0029] Note that, while the refrigerating machine oil (the
lubricant of the compressors 11) is not specified, it may be, for
example, an ester oil having an ester bond, a carbonate oil, a
polyalkylene glycol oil (PAG) having an ether bond, or a polyvinyl
ether oil.
[0030] The heat-source-side heat exchanger 12 is a heat exchanger
that functions as a radiator or a condenser for the high-pressure
refrigerant in the refrigeration cycle. The heat-source-side heat
exchanger 12 includes a heat transfer tube (not shown) through
which a refrigerant flows, and is configured to allow the
refrigerant in the heat transfer tube and an air flow generated by
the heat-source-side fan 19 (described later) to exchange heat with
each other.
[0031] The receiver 13 is a container that temporarily stores the
refrigerant flowed out from the heat-source-side heat exchanger 12.
In the receiver 13, a refrigerant reservoir space is formed. The
refrigerant reservoir space has the capacity corresponding to the
amount of the refrigerant enclosed in the refrigerant circuit
RC.
[0032] The subcooling heat exchanger 14 is, for example, a double
pipe heat exchanger. The subcooling heat exchanger 14 is provided
with two refrigerant flow paths (a first flow path 141 and a second
flow path 142). The first flow path 141 is a path through which a
refrigerant flowed out from the receiver 13 passes. The second flow
path 142 is a flow path through which an intermediate-pressure
refrigerant having passed through the first flow path 141 and
thereafter decompressed by the second expansion valve 16 passes.
The subcooling heat exchanger 14 is configured to allow a
refrigerant in the first flow path 141 and a refrigerant in the
second flow path 142 to exchange heat with each other.
[0033] The first expansion valve 15 (corresponding to the "electric
valve" in the claims) is an electric valve whose opening degree is
controllable. In accordance with the opening degree of the first
expansion valve 15, the refrigerant passing therethrough is
decompressed, or the flow rate of the refrigerant passing
therethrough is increased or reduced. The first expansion valve 15
decompresses a high-pressure liquid refrigerant having passed
through the first flow path 141 of the subcooling heat exchanger 14
to provide a low-pressure gas-liquid two-phase refrigerant. The
first expansion valve 15 is disposed on the upstream side in the
liquid-side connection pipe L1 extending to the service units 30,
and adjusts the pressure and the flow rate of the refrigerant sent
to the service units 30 via the liquid-side connection pipe L1.
[0034] The second expansion valve 16 is an electric valve whose
opening degree is controllable. In accordance with the opening
degree of the second expansion valve 16, the refrigerant passing
therethrough is decompressed, or the flow rate of the refrigerant
passing therethrough is increased or reduced. The second expansion
valve 16 decompresses a high-pressure liquid refrigerant having
passed through the first flow path 141 of the subcooling heat
exchanger 14 to provide an intermediate-pressure gas-liquid
two-phase refrigerant or liquid refrigerant (an
intermediate-pressure refrigerant). The second expansion valve 16
is disposed on the refrigerant flow upstream side in the
refrigerant pipe (a twelfth pipe P12 which will be described later)
upstream to the injection valve 17.
[0035] The injection valves 17 are electric expansion valves whose
opening degree is controllable. In accordance with the opening
degree of the injection valves 17, the refrigerant passing
therethrough is decompressed, or the flow rate of the refrigerant
passing therethrough is increased or reduced. The injection valves
17 have their respective one ends connected to corresponding
injection pipes (fourth pipes P4 which will be described later) of
the compressors 11, and adjust the flow rate of the
intermediate-pressure refrigerant passing through. Here, the first
injection valve 17a corresponds to the first compressor 11a and a
fourth pipe P4a (described later). The second injection valve 17b
corresponds to the second compressor 11b and a fourth pipe P4b
(described later). The third injection valve 17c corresponds to the
third compressor 11c and a fourth pipe P4c (described later).
[0036] The gas-side shutoff valve SV1 is a manual valve connected
to one end of the gas-side connection pipe G1. The liquid-side
shutoff valve SV2 is a manual valve connected to one end of the
liquid-side connection pipe L1.
(1-1-2) Refrigerant Pipe Disposed at Heat Source Unit 10
[0037] The heat source unit 10 includes a plurality of refrigerant
pipes connecting between the circuit elements. Specifically, the
heat source unit 10 includes a first pipe P1, second pipes P2 (P2a,
P2b, P2c), third pipes P3 (P3a, P3b, P3c), and fourth pipes P4
(P4a, P4b, P4c) as many as (three) the compressors 11, and a fifth
pipe P5 to a twelfth pipe P12.
[0038] The first pipe P1 connects between one end of the gas-side
shutoff valve SV1 and individual one ends of the second pipes P2
(intake pipes).
[0039] Each of the second pipes P2 corresponds to any of the
compressors 11 and is connected to the intake port of the
corresponding compressor 11. Each second pipe P2 functions as an
intake pipe through which a low-pressure refrigerant flowing into
the corresponding compressor 11 flows. The second pipe P2a
corresponds to the first compressor 11a. The second pipe P2b
corresponds to the second compressor 11b. The second pipe P2c
corresponds to the third compressor 11c.
[0040] Each of the third pipes P3 corresponds to any of the
compressors 11 and is connected to a discharge port of the
corresponding compressor 11. Each third pipe P3 functions as a
discharge pipe through which a high-pressure refrigerant discharged
from the corresponding compressor 11 flows. The third pipe P3a
corresponds to the first compressor 11a. The third pipe P3b
corresponds to the second compressor 11b. The third pipe P3c
corresponds to the third compressor 11c.
[0041] Each of the fourth pipes P4 corresponds to any of the
compressors 11 and is connected to an injection port of the
corresponding compressor 11. Each fourth pipe P4 functions as an
injection pipe that allows an intermediate-pressure refrigerant to
flow into a compression chamber of the corresponding compressor 11.
The fourth pipe P4a corresponds to the first compressor 11a. The
fourth pipe P4b corresponds to the second compressor 11b. The
fourth pipe P4c corresponds to the third compressor 11c.
[0042] The fifth pipe P5 connects between one ends of the third
pipes P3 and the gas side of the heat-source-side heat exchanger
12.
[0043] The sixth pipe P6 connects between the liquid side of the
heat-source-side heat exchanger 12 and a refrigerant inflow port of
the receiver 13.
[0044] The seventh pipe P7 connects between a refrigerant outflow
port of the receiver 13 and one end of the first flow path 141 of
the subcooling heat exchanger 14.
[0045] The eighth pipe P8 connects between other end of the first
flow path 141 of the subcooling heat exchanger 14 and one end of
the first expansion valve 15.
[0046] The ninth pipe P9 connects between other end of the first
expansion valve 15 and one end of the liquid-side shutoff valve
SV2.
[0047] The tenth pipe P10 extends from a point between the opposite
ends of the eighth pipe P8 and is connected to one end of the
second expansion valve 16.
[0048] The eleventh pipe P11 connects between other end of the
second expansion valve 16 and one end of the second flow path 142
of the subcooling heat exchanger 14.
[0049] The twelfth pipe P12 connects between other end of the
second flow path 142 of the subcooling heat exchanger 14 and
individual other ends of the injection valves 17. In more detail,
the twelfth pipe P12 has its one end connected to the second flow
path 142, and its other end branched in three ways and individually
connected to the injection valves 17.
[0050] Note that, in the refrigerant circuit RC, the tenth pipe
P10, the second expansion valve 16, the eleventh pipe P11, the
second flow path 142 of the subcooling heat exchanger 14, the
twelfth pipe P12, the injection valves 17, and the fourth pipes P4
form an injection line J1. The injection line J1 is a refrigerant
flow path for allowing part of the refrigerant flowing through the
eighth pipe P8 to branch and flow (be injected) into the
compressors 11.
(1-1-3) Other Elements Disposed at Heat Source Unit 10
[0051] The heat source unit 10 includes a heat-source-side fan 19
that generates an air flow that flows from the outside of the heat
source unit 10 into the heat source unit 10, passes through the
heat-source-side heat exchanger 12, and then flows to the outside
from the heat source unit 10. The heat-source-side fan 19 is a fan
for supplying the heat-source-side heat exchanger 12 with air as
the cooling source for a refrigerant flowing through the
heat-source-side heat exchanger 12. The heat-source-side fan 19 is,
for example, a propeller fan or a sirocco fan, and rotates as being
linked with a heat-source-side fan motor (not shown).
[0052] The heat source unit 10 further includes various types of
sensors such as a low-pressure side pressure sensor 21, a
high-pressure side pressure sensor 22, an intermediate pressure
sensor 23, and a plurality of discharge temperature sensors 25 (a
first discharge temperature sensor 25a, a second discharge
temperature sensor 25b, a third discharge temperature sensor
25c).
[0053] The low-pressure side pressure sensor 21 is disposed at the
first pipe P1 (a low-pressure-side refrigerant pipe) on the
refrigerant flow upstream side relative to the intake pipes (P2a,
P2b, P2c) of the compressors 11. The low-pressure side pressure
sensor 21 detects a low-pressure-side pressure LP which is the
pressure of the refrigerant passing through the first pipe P1 (that
is, the low-pressure refrigerant on the intake side of the
compressors 11).
[0054] The high-pressure side pressure sensor 22 is disposed at the
fifth pipe P5 on the refrigerant flow downstream side relative to
the discharge pipes (P3a, P3b, P3c) of the compressors 11. The
high-pressure side pressure sensor 22 detects a high-pressure-side
pressure HP which is the pressure of the refrigerant passing
through the fifth pipe P5 (that is, the high-pressure refrigerant
on the discharge side of the compressors 11).
[0055] The intermediate pressure sensor 23 is disposed at the
twelfth pipe P12 (an upstream side common pipe) on the refrigerant
flow upstream side relative to the injection pipes (P4a, P4b, P4c)
of the compressors 11. The intermediate pressure sensor 23 detects
an intermediate pressure MP which is the pressure of the
refrigerant passing through the twelfth pipe P12 (that is, the
intermediate-pressure refrigerant flowing into the injection valves
17).
[0056] The discharge temperature sensors 25 are disposed at the
discharge pipes (P3a, P3b, or P3c) of corresponding ones of the
compressors 11 and detect the temperature of a high-pressure
refrigerant discharged from the corresponding ones of the
compressors 11 (a discharged refrigerant temperature HT). The first
discharge temperature sensor 25a corresponds to the first
compressor 11a. The second discharge temperature sensor 25b
corresponds to the second compressor 11b. The third discharge
temperature sensor 25c corresponds to the third compressor 11c.
(1-2) Service Units 30
[0057] The service units 30 are connected to the heat source unit
10 via the gas-side connection pipe G1 and the liquid-side
connection pipe L1, and form part of the refrigerant circuit RC. In
the present embodiment, to one heat source unit 10, two service
units 30 (30a, 30b) are connected. The service units 30 are
connected in parallel to each other.
[0058] The service units 30 each mainly include, as circuit
elements forming the refrigerant circuit RC, a usage-side expansion
valve 31 and a usage-side heat exchanger 32.
(1-2-1) Usage-Side Expansion Valve 31
[0059] The usage-side expansion valve 31 is a throttling mechanism
that functions as means for decompressing (means for expanding) a
refrigerant sent from the heat source unit 10 (corresponding to the
"mechanical expansion valve" in the claims). In accordance with its
opening degree, the usage-side expansion valve 31 decompresses the
refrigerant that passes therethrough. The usage-side expansion
valve 31 is a thermostatic expansion valve that includes a valve
body 311 formed of a valve element, a diaphragm and the like, a
feeler bulb 312 having enclosed therein a refrigerant similar to
that flowing through the refrigerant circuit RC, and a capillary
tube 313 establishing communication between the valve body 311 and
the feeler bulb 312. The usage-side expansion valve 31 may be a
known general valve as the one disclosed in JP H10-184982 A, for
example. Details of the usage-side expansion valve 31 will be given
later.
(1-2-2) Usage-Side Heat Exchanger 32
[0060] The usage-side heat exchanger 32 is a heat exchanger that
functions as an evaporator for a low-pressure refrigerant in the
refrigeration cycle, to cool the air in the usage-side space. The
usage-side heat exchanger 32 includes a heat transfer tube (not
shown) through which a refrigerant flows, and is configured to
allow the refrigerant in the heat transfer tube and an air flow
generated by a usage-side fan 35 (described later) to exchange heat
with each other.
(1-2-3) Refrigerant Pipes Disposed at Service Units 30
[0061] The service units 30 each include a plurality of refrigerant
pipes connecting between the circuit elements. Specifically, each
service unit 30 includes a thirteenth pipe P13, a fourteenth pipe
P14, and a fifteenth pipe P15.
[0062] The thirteenth pipe P13 connects between other end of the
liquid-side connection pipe L1 and one end of the usage-side
expansion valve 31. Note that, other end of the liquid-side
connection pipe L1 branches in accordance with the number of the
service units 30, to connect to respective thirteenth pipes P13 of
the service units 30.
[0063] The fourteenth pipe P14 connects between other end of the
usage-side expansion valve 31 and a liquid-side gate of the
usage-side heat exchanger 32.
[0064] The fifteenth pipe P15 connects between a gas-side gate of
the usage-side heat exchanger 32 and other end of the gas-side
connection pipe G1. Note that, other end of the gas-side connection
pipe G1 branches in accordance with the number of the service units
30, to connect to respective fifteenth pipes P15 of the service
units 30.
(1-2-4) Other Elements Disposed at Service Units 30
[0065] The service units 30 each include a usage-side fan 35 that
generates an air flow passing through the usage-side heat exchanger
32. The usage-side fan 35 is a fan for supplying the usage-side
heat exchanger 32 with air as the heating source for a refrigerant
flowing through the usage-side heat exchanger 32. The usage-side
fan 35 is, for example, a centrifugal fan or a sirocco fan, and
rotates as being linked to a usage-side fan motor (not shown). The
usage-side fan 35 is electrically connected to an independent power
source (a commercial power source, a storage battery or the like),
and operates by being supplied with power.
(1-3) Controller 50
[0066] The controller 50 is a control unit configured to control
the operation state of the refrigeration apparatus 100 by
controlling the operation of the actuators included in the
refrigeration apparatus 100. The controller 50 includes a
microcomputer which includes a CPU, a memory and the like. In the
present embodiment, the controller 50 is disposed at the heat
source unit 10. The controller 50 is electrically connected to the
actuators included in the refrigeration apparatus 100, to exchange
signals via a predetermined interface. The controller 50 is further
electrically connected to various types of sensors included in the
refrigeration apparatus 100, to receive signals corresponding to
detection results as appropriate. Details of the controller 50 will
be given later.
(2) Flow of Refrigerant in Refrigerant Circuit RC in Cooling
Operation
[0067] In the following, a description will be given of the flow of
the refrigerant in the refrigerant circuit RC in operation. In the
refrigeration apparatus 100, in operation, in accordance with the
required cooling load in the service units 30, the
variable-capacity compressor out of the compressors 11 has its
capacity controlled, and the constant-capacity compressor performs
a rated operation. Specifically, the number of the compressors 11
in operation and the operating capacity of the variable-capacity
compressor are controlled so as to satisfy respective target values
of the low-pressure-side pressure LP, the high-pressure-side
pressure HP, and/or the intermediate pressure MP, which target
values are set in accordance with the required cooling load in the
service units 30. Thus, a cooling operation (a refrigeration cycle
operation) is carried out in which the refrigerant enclosed in the
refrigerant circuit RC mainly circulates, in sequence, any of the
compressors 11 in operation, the heat-source-side heat exchanger
12, the receiver 13, the subcooling heat exchanger 14 (the first
flow path 141), the first expansion valve 15, the usage-side
expansion valve 31, and the usage-side heat exchanger 32.
[0068] In the cooling operation, a refrigerant is taken into the
compressor 11 in operating via the intake pipe (P2a, P2b, or P2c)
to be compressed, and then discharged as a high-pressure
refrigerant. Here, the low pressure in the refrigeration cycle is
the low-pressure-side pressure LP detected by the low-pressure side
pressure sensor 21. The high pressure is the high-pressure-side
pressure HP detected by the high-pressure side pressure sensor 22.
The intermediate pressure is the intermediate pressure MP detected
by the intermediate pressure sensor 23.
[0069] Each of the gas refrigerant discharged from the compressors
11 flows through corresponding ones of discharge pipes (P3a, P3b,
P3c), to merge with each other at the fifth pipe P5 and flows into
the gas-side gate of the heat-source-side heat exchanger 12. Note
that, in each of the operating compressors 11 in operation, an
intermediate-pressure refrigerant is injected into the compression
chamber via the injection pipe (the fourth pipe P4), so as to
control the temperature of the discharged high-pressure refrigerant
to attain the target value.
[0070] The gas refrigerant flowing into the gas-side gate of the
heat-source-side heat exchanger 12 exchanges, in the
heat-source-side heat exchanger 12, heat with air supplied by the
heat-source-side fan 19. Thus, the gas refrigerant radiates heat,
condenses, becomes a liquid refrigerant or a gas-liquid two-phase
refrigerant of a high pressure, and then flows out from the
liquid-side gate of the heat-source-side heat exchanger 12. The
refrigerant flowed out from the liquid-side gate of the
heat-source-side heat exchanger 12 flows into the refrigerant
inflow port of the receiver 13 via the sixth pipe P6. The
refrigerant flowed into the receiver 13 is temporarily stored at
the receiver 13 as a saturated liquid refrigerant, and then flows
out from the refrigerant outflow port of the receiver 13.
[0071] The liquid refrigerant flowed out from an outflow port of
the receiver 13 passes through the seventh pipe P7 to flow into the
first flow path 141 of the subcooling heat exchanger 14. The liquid
refrigerant flowing into the first flow path 141 of the subcooling
heat exchanger 14 exchanges heat with a refrigerant flowing through
the second flow path 142 in the subcooling heat exchanger 14 to be
further cooled. Thus, the liquid refrigerant becomes a subcooled
liquid refrigerant and is discharged from the subcooling heat
exchanger 14.
[0072] The subcooled liquid refrigerant flowed out from the
subcooling heat exchanger 14 flows through the eighth pipe P8. The
refrigerant flowing through the eighth pipe P8 branches into two
flows. In the two flows of the refrigerant branched from the eighth
pipe P8, one flow flows into the first expansion valve 15. The
refrigerant flowing into the first expansion valve 15 is
decompressed in accordance with the opening degree of the first
expansion valve 15, to become a low-pressure gas-liquid two-phase
refrigerant. The gas-liquid two-phase refrigerant having passed
through the first expansion valve 15 passes through the ninth pipe
P9 and the liquid-side shutoff valve SV2, and is discharged from
the heat source unit 10.
[0073] On the other hand, in the flow of the refrigerant branched
from the eighth pipe P8, other flow flows into the injection line
J1. The refrigerant flowing into the injection line J1 passes
through the tenth pipe P10 to flow into the second expansion valve
16. The refrigerant flowing into the second expansion valve 16 is
decompressed in accordance with the opening degree of the second
expansion valve 16, to become a liquid refrigerant or a gas-liquid
two-phase refrigerant of an intermediate pressure. The refrigerant
having passed through the second expansion valve 16 flows through
the eleventh pipe P11 to flow into the second flow path 142 of the
subcooling heat exchanger 14. Note that, the flow rate and the
pressure of the refrigerant flowing through the injection line J1
fluctuate mainly on the basis of the opening degree of the second
expansion valve 16, the opening degree of the injection valves 17,
the frequency of the compressors 11 in operation, and the like.
[0074] The liquid refrigerant flowing into the second flow path 142
of the subcooling heat exchanger 14 exchanges heat with the
refrigerant flowing through the first flow path 141 in the
subcooling heat exchanger 14 thereby heated, to become a gas-liquid
two-phase refrigerant or a gas refrigerant of an intermediate
pressure, and flows out from the subcooling heat exchanger 14. The
gas-liquid two-phase refrigerant or the gas refrigerant of an
intermediate pressure flowed out from the subcooling heat exchanger
14 flows through the twelfth pipe P12. Note that, the flow rate and
the pressure of the refrigerant flowing through the second flow
path 142 of the subcooling heat exchanger 14 and the twelfth pipe
P12 increase or reduce in accordance with the opening degree of the
second expansion valve 16.
[0075] The refrigerant flowing through the twelfth pipe P12
branches into three flows, which flows respectively flow into the
injection valves 17. The refrigerant flowed into the injection
valves 17 is decompressed or has its flow rate adjusted in
accordance with the opening degree of the injection valves 17, and
flows through the injection pipes (the fourth pipes P4) to be
injected into the compression chamber of corresponding ones of the
compressors 11. Note that, this injection is performed for the
purpose of controlling the temperature of the refrigerant
discharged from the compressors 11 to attain the target value.
[0076] The low-pressure two-phase refrigerant flowed out from the
heat source unit 10 passes through the liquid-side connection pipe
L1 to flow into the operating ones of the service units 30. The
refrigerant flowed into each service unit 30 passes through the
thirteenth pipe P13 to flow into the valve body 311 of the
usage-side expansion valve 31, and is decompressed or has its flow
rate adjusted in accordance with the opening degree of the valve
body 311. Note that, the opening degree of the valve body 311
increases or reduces in accordance with the degree of superheating
of a refrigerant in the fifteenth pipe P15 where the feeler bulb
312 is disposed. The refrigerant having passed through the valve
body 311 of the usage-side expansion valve 31 flows through the
fourteenth pipe P14 to flow into the liquid-side gate of the
usage-side heat exchanger 32.
[0077] The refrigerant flowed into the liquid-side gate of the
usage-side heat exchanger 32 exchanges heat with air supplied by
the usage-side fan 35 in the usage-side heat exchanger 32 thereby
evaporated, to become a low-pressure gas refrigerant and flows out
from the gas-side gate of the usage-side heat exchanger 32. The gas
refrigerant flowed out from the gas-side gate of the usage-side
heat exchanger 32 flows through the fifteenth pipe P15 and flows
out from the service unit 30.
[0078] The refrigerant flowed out from each service unit 30 flows
through the gas-side connection pipe G1 and the gas-side shutoff
valve SV1 to flow into the heat source unit 10. The refrigerant
flowing into the heat source unit 10 flows through the first pipe
P1 and the second pipe P2, and again taken into the operating ones
of the compressors 11.
(3) Details of Usage-Side Expansion Valve 31
[0079] In the usage-side expansion valve 31, the valve body 311 is
disposed on the liquid-side gate side (the refrigerant flow
upstream side) relative to the usage-side heat exchanger 32, and
the feeler bulb 312 is disposed on the gas-side gate side (the
refrigerant flow downstream side) relative to the usage-side heat
exchanger 32. In other words, the usage-side expansion valve 31 is
disposed on the refrigerant flow downstream side relative to the
first expansion valve 15.
[0080] The state of the refrigerant in the feeler bulb 312 changes
in accordance with the detected temperature at the feeler bulb 312
(in the present embodiment, the temperature of the refrigerant
flowing out from the gas-side gate of the usage-side heat exchanger
32). The valve body 311 and the feeler bulb 312 communicate with
each other via the capillary tube 313. A diaphragm in the valve
body 311 actuates in accordance with the change in the state of the
refrigerant in the feeler bulb 312. This determines the opening
degree of the valve element. Note that, the valve body 311 includes
therein a spring that biases the valve element. The biasing force
of the spring is adjustable by an adjust screw.
[0081] When the flow rate of the refrigerant flowing into the
service unit 30 reduces, the flow rate of the refrigerant passing
through the valve body 311 reduces. In relation thereto, the degree
of superheating at the usage-side heat exchanger 32 increases. In
response thereto, the opening degree of the valve body 311 is
increased. Here, the flow rate of the refrigerant flowing into the
service unit 30 reduces in response to a reduction in the flow rate
of the refrigerant passing through the first expansion valve 15.
That is, by the opening degree of the first expansion valve 15
being reduced, the flow rate of the refrigerant flowing into the
service unit 30 reduces. In relation thereto, the degree of
superheating at the usage-side heat exchanger 32 increases and the
opening degree of the valve body 311 is increased.
[0082] By the opening degree of the first expansion valve 15 being
reduced, the pressure of the refrigerant passing through the first
expansion valve 15 reduces and the pressure of the refrigerant
flowing into the service unit 30 reduces. That is, when the opening
degree of the first expansion valve 15 is reduced, the flow rate
and the pressure of the refrigerant passing through the first
expansion valve 15 reduce and the degree of superheating at the
usage-side heat exchanger 32 increases, whereby the opening degree
of the valve body 311 is increased. In other words, the usage-side
expansion valve 31 is disposed so that its opening degree is
increased in response to a reduction in the flow rate or the
pressure of the refrigerant flowing through the first expansion
valve 15.
[0083] On the other hand, when the flow rate of the refrigerant
flowing into the service unit 30 increases, the flow rate of the
refrigerant passing through the valve body 311 increases. In
relation thereto, the degree of superheating at the usage-side heat
exchanger 32 reduces. In response thereto, the opening degree of
the valve body 311 is reduced. Here, the flow rate of the
refrigerant flowing into the service unit 30 increases in response
to an increase in the flow rate of the refrigerant passing through
the first expansion valve 15 (that is, an increase in the opening
degree of the first expansion valve 15). Furthermore, by the
opening degree of the first expansion valve 15 being increased, the
pressure of the refrigerant passing through the first expansion
valve 15 increases, and the pressure of the refrigerant flowing
into the service unit 30 increases. That is, by the opening degree
of the first expansion valve 15 being increased, the flow rate and
the pressure of the refrigerant flowing into the service unit 30
increase. In relation thereto, the degree of superheating at the
usage-side heat exchanger 32 reduces, whereby the opening degree of
the valve body 311 is reduced.
[0084] In this manner, the usage-side expansion valve 31 has its
opening degree changed in direct response to an increase or
reduction in the degree of superheating of the refrigerant flowing
out from the usage-side heat exchanger 32 (that is, an increase or
reduction in the flow rate of the refrigerant flowing into the
service unit 30). From a broad view, it can be regarded that the
usage-side expansion valve 31 has its opening degree changed in
response to an increase or reduction in the pressure of the
refrigerant flowing into the service unit 30. That is, the opening
degree of the usage-side expansion valve 31 is changed in response
to an increase or reduction in the opening degree of the first
expansion valve 15.
[0085] Note that, because of its structure, the opening degree of
the usage-side expansion valve 31 is not immediately changed upon a
change in the opening degree of the first expansion valve 15. An
increase or reduction in the degree of superheating at the
usage-side heat exchanger 32 takes place in response to a change in
the opening degree of the first expansion valve 15, and the feeler
bulb 312 detects that change in the degree of superheating. Then,
the opening degree of the usage-side expansion valve 31 is changed.
That is, the opening degree of the usage-side expansion valve 31 is
changed with a delay corresponding to a predetermined response time
for a change in the opening degree of the first expansion valve 15.
This response time varies depending on the configuration of the
usage-side expansion valve 31, the length of the refrigerant pipes,
the capacity of the usage-side heat exchanger 32, the airflow
volume of the usage-side fan 35, and/or the type of the
refrigerant, and the like.
(4) Details of Controller 50
[0086] FIG. 2 is a block diagram schematically showing the
schematic configuration of the controller 50 and units connected to
the controller 50.
[0087] The controller 50 has a plurality of control modes, and
controls the operation of the refrigeration apparatus 100
corresponding to the current control mode. For example, the
controller 50 has, as the control modes, a normal mode in a normal
operation, and an oil recovery control mode to which the controller
50 transitions from the normal mode when an oil recovery operation
start condition (described later) is satisfied.
[0088] The controller 50 is electrically connected to actuators
included in the heat source unit 10 (specifically, the compressors
11, the first expansion valve 15, the second expansion valve 16,
the injection valves 17, the heat-source-side fan 19 and the like),
and various types of sensors (the low-pressure side pressure sensor
21, the high-pressure side pressure sensor 22, the intermediate
pressure sensor 23, the discharge temperature sensors 25 and the
like). The controller 50 is further electrically connected to a
command input apparatus such as a remote controller, which is not
shown. Note that, in the present embodiment, the controller 50 is
not electrically connected to the elements disposed in the service
unit 30.
[0089] The controller 50 mainly includes a storage unit 51, an
input control unit 52, a mode control unit 53, and an actuator
control unit 54. Note that, these units in the controller 50 are
implemented by the elements forming the controller 50 (a CPU,
various types of memory, a communication module, various types of
interfaces, various types of electric components and the like)
organically functioning.
(4-1) Storage Unit 51
[0090] The storage unit 51 is formed of, for example, various types
of memory such as, for example, ROM, RAM, and/or flash memory, and
includes a plurality of storage regions. For example, the storage
unit 51 includes a program storage region 511 for storing a control
program in which processes at the units of the controller 50 are
defined.
[0091] The storage unit 51 further includes a detected value
storage region 512 for storing detected values from various types
of sensors, and a command storage region 513 for storing any input
command.
[0092] The storage unit 51 further includes a characteristic
information storage region 514 for storing the characteristic of
the usage-side expansion valve 31. The characteristic information
storage region 514 stores, for example, information (usage-side
expansion valve characteristic information) on the opening degree
characteristic of the usage-side expansion valve 31 (the
correlation between the degree of superheating of a refrigerant
flowing out from the usage-side heat exchanger 32 or the opening
degree of the first expansion valve 15 and the opening degree of
the usage-side expansion valve 31) and the response characteristic
(for example, the response time of the usage-side expansion valve
31 to a change in the opening degree of the first expansion valve
15).
[0093] The storage unit 51 is provided with a plurality of flags
having predetermined number of bits. For example, the storage unit
51 is provided with a control mode determination flag 515 with
which the current control mode of the controller 50 is determined.
The control mode determination flag 515 includes the number of bits
corresponding to the number of the control modes, and sets a bit
corresponding to the current control mode. This allows the units to
determine the current control mode.
[0094] The storage unit 51 is further provided with an oil recovery
operation first flag 516 for determining whether or not a start
execution condition on an oil recovery operation (an oil recovery
operation start condition) for recovering the refrigerating machine
oil from the service units 30 to the compressors 11 is satisfied
(that is, whether or not to execute the oil recovery operation).
The oil recovery operation first flag 516 is set when the oil
recovery operation start condition is satisfied.
[0095] The storage unit 51 is further provided with an oil recovery
operation second flag 517 for determining whether or not an oil
recovery first control (described later) in the oil recovery
operation has been completed and a start execution condition (a
second control start condition) for an oil recovery second control
(described later) is satisfied (that is, whether or not to execute
the oil recovery second control). The oil recovery operation second
flag 517 is set when the second control start condition is
satisfied.
(4-2) Input Control Unit 52
[0096] The input control unit 52 is a functional unit that
functions as an interface for accepting signals from any elements
connected to the controller 50. For example, the input control unit
52 receives a signal corresponding to a detection result output
from any of the various types of sensors (21-23, 25 and the like),
attaches predetermined identification data thereto and stores the
same individually in the detected value storage region 512. For
example, the input control unit 52 receives a signal from a command
input apparatus which is not shown, and stores the same
individually in the command storage region 513.
(4-3) Mode Control Unit 53
[0097] The mode control unit 53 is a functional unit that switches
the control mode. When the oil recovery operation start condition
is satisfied in the normal mode, the mode control unit 53 sets the
oil recovery operation first flag 516. Thus, the control mode
transitions to the oil recovery control mode, and the oil recovery
first control (described later) is executed.
[0098] The oil recovery operation start condition is a condition
satisfied by the refrigerating machine oil being built up in the
service units 30 (in particular, the usage-side heat exchangers
32). For example, the oil recovery operation start condition is
satisfied by a lapse of a predetermined time (the time indicating
that the refrigerating machine oil has built up in the service
units 30) in a cooling operation. Furthermore, for example, the oil
recovery operation start condition is satisfied by, in a cooling
operation, any detected value of various types of sensors (21, 22,
23, or 25) attaining a predetermined reference value (a value
indicating that the refrigerating machine oil has built up in the
service units 30).
[0099] When the mode control unit 53 is in the oil recovery control
mode, by a predetermined second control start condition being
satisfied, the mode control unit 53 sets the oil recovery operation
second flag 517. This ends the oil recovery first control in the
oil recovery operation, and starts the oil recovery second control
(described later).
[0100] The second control start condition is a condition satisfied
by the oil recovery first control being completed. Specifically,
the second control start condition is a condition satisfied by the
opening degree of the usage-side expansion valve 31 being increased
in response to the first expansion valve 15 set to a first opening
degree under the oil recovery first control which will be described
later. In the present embodiment, the oil recovery operation end
condition is satisfied by, in the oil recovery first control of the
oil recovery operation, a lapse of a predetermined time (a
predetermined first time t1 indicating that the opening degree of
the usage-side expansion valve 31 has attained a maximum opening
degree). The first time t1 is a time which is necessary for the
opening degree of the usage-side expansion valve 31 to be
increased, by the oil recovery first control, in response to a
reduction in the flow rate or the pressure of a refrigerant passing
through the first expansion valve 15. The first time t1 is set on
the basis of the usage-side expansion valve characteristic
information. In the present embodiment, the first time t1 is set to
three minutes.
[0101] When the mode control unit 53 is in the oil recovery control
mode, the mode control unit 53 clears the oil recovery operation
first flag 516 and the oil recovery operation second flag 517 by a
predetermined oil recovery operation end condition being satisfied.
This ends the oil recovery operation.
[0102] The oil recovery operation end condition is a condition
satisfied by the recovery of the refrigerating machine oil in the
service units 30 (particularly the usage-side heat exchangers 32)
to the compressors 11 being completed. In the present embodiment,
the oil recovery operation end condition is satisfied by, in the
oil recovery second control which will be described later, a lapse
of a predetermined time (a second time t2). The second time t2 is a
time which is necessary for the increased opening degree of the
usage-side expansion valve 31 to be reduced, by the oil recovery
second control, to cause the liquid refrigerant to become less
prone to flow into the usage-side heat exchanger 32. The second
time t2 is set on the basis of the usage-side expansion valve
characteristic information. In the present embodiment, the second
time t2 is set to three minutes.
[0103] The mode control unit 53 switches the control mode to the
normal mode, unless the control mode is in the oil recovery control
mode.
(4-4) Actuator Control Unit 54
[0104] The actuator control unit 54 controls, as circumstances
demand in accordance with the control program, the operation of the
actuators included in the refrigeration apparatus 100 (the heat
source unit 10 and the service units 30). For example, the actuator
control unit 54 controls, in real time, the number of revolutions
of the compressors 11, the number of revolutions of the
heat-source-side fan 19 and the usage-side fans 35, the opening
degree of the first expansion valve 15, the opening degree of the
second expansion valve 16, and the opening degree of the usage-side
expansion valves 31 in accordance with the set temperature, the
type of commands, the magnitude of the cooling load, the detected
values of the sensors (21, 22, 23, 25) and the like.
[0105] The actuator control unit 54 includes a plurality of
functional units. For example, the actuator control unit 54
includes a drive signal output unit 55 and a first expansion valve
control unit 56.
(4-4-1) Drive Signal Output Unit 55
[0106] The drive signal output unit 55 is a functional unit that
outputs a predetermined drive signal (drive voltage) to the
actuators (11a to 11c, 15, 16, 17a to 17c, 19 and the like). The
drive signal output unit 55 includes a plurality of inverters (not
shown), and outputs a drive signal via a corresponding one of the
inverters to the first compressor 11a or the heat-source-side fan
19.
(4-4-2) First Expansion Valve Control Unit 56
[0107] The first expansion valve control unit 56 is a functional
unit that controls the opening degree of the first expansion valve
15. The first expansion valve control unit 56 controls, in real
time, the opening degree according to the control program and the
set temperature, load and the like of the service units 30 when
none of the oil recovery operation first flag 516 and the oil
recovery operation second flag 517 are set (that is, when the
control mode is in the normal mode).
[0108] When the oil recovery operation first flag 516 is set (that
is, when the control mode is the oil recovery control mode), the
first expansion valve control unit 56 executes the oil recovery
first control. The oil recovery first control is control for
increasing the opening degree of the usage-side expansion valve 31.
In the oil recovery first control, the first expansion valve
control unit 56 set the opening degree of the first expansion valve
15 to a first opening degree.
[0109] The first opening degree is smaller than an opening degree
of the first expansion valve 15 in the normal mode. When the first
expansion valve 15 is set to the first opening degree, the flow
rate and the pressure of a refrigerant passing through the first
expansion valve 15 reduce and the flow rate and the pressure of the
refrigerant passing through the first expansion valve 15 and
flowing into the service unit 30 reduce, whereby the degree of
superheating at the usage-side heat exchanger 32 increases. In
accordance therewith, the opening degree of the usage-side
expansion valve 31 is increased. In the present embodiment, the
first opening degree is set to a minimum opening degree such that
the opening degree of the usage-side expansion valve 31 attains a
maximum opening degree by the oil recovery first control. In other
words, the first opening degree is an opening degree that causes
the opening degree of the usage-side expansion valve 31 to be
increased in relation to a reduction in the flow rate or pressure
of the refrigerant passing through the first expansion valve
15.
[0110] When the oil recovery operation second flag 517 is set (that
is, when the oil recovery first control has been completed), the
first expansion valve control unit 56 executes the oil recovery
second control. The oil recovery second control is control for
sending a liquid refrigerant for compatibilizing with the
refrigerating machine oil to the usage-side heat exchanger 32. In
the oil recovery second control, the first expansion valve control
unit 56 sets the opening degree of the first expansion valve 15 to
a second opening degree.
[0111] The second opening degree is greater than the opening degree
of the first expansion valve 15 in the oil recovery first control.
When the first expansion valve 15 is set to the second opening
degree, the flow rate and the pressure of the refrigerant passing
through the first expansion valve 15 increase and the flow rate and
the pressure of the refrigerant passing through the first expansion
valve 15 and flowing into the service unit 30 increase, whereby the
degree of superheating at the usage-side heat exchanger 32 reduces.
In accordance therewith, the opening degree of the usage-side
expansion valve 31 is reduced.
[0112] Here, the opening degree of the usage-side expansion valve
31 changes by a delay corresponding to the response time, in
response to the change in the opening degree of the first expansion
valve 15. That is, until that response time elapses since when the
first expansion valve 15 is switched from the first opening degree
to the second opening degree, the opening degree of the usage-side
expansion valve 31 is maintained at the opening degree which has
been increased by the oil recovery first control. Therefore, until
the response time elapses since when the first expansion valve 15
is switched from the first opening degree to the second opening
degree by the oil recovery second control, a liquid refrigerant or
a gas-liquid two-phase refrigerant having passed through the first
expansion valve 15 is sent to the usage-side heat exchanger 32 via
the usage-side expansion valve 31. The liquid refrigerant or the
gas-liquid two-phase refrigerant is compatibilized with a
refrigerating machine oil built up in the usage-side heat exchanger
32, and flows toward the gas side (the first pipe P1) of the heat
source unit 10. Thus, the refrigerating machine oil built up in the
usage-side heat exchanger 32 is recovered to the compressors
11.
[0113] In the present embodiment, the second opening degree of the
first expansion valve 15 is set to the maximum opening degree so as
to facilitate sending the liquid refrigerant or the gas-liquid
two-phase refrigerant to the usage-side heat exchanger 32 by the
oil recovery second control. It can be regarded that the second
opening degree is an opening degree that allows, before the opening
degree of the usage-side expansion valve 31 is reduced in relation
to an increase in the flow rate or the pressure of the refrigerant
passing through the first expansion valve 15, a liquid refrigerant
to flow into the usage-side heat exchanger 32 to be compatibilized
with the refrigerating machine oil.
(5) Flow of Process at Controller 50
[0114] In the following, with reference to FIG. 3, a description
will be given of an exemplary flow of a process at the controller
50. FIG. 3 is a flowchart showing an exemplary flow of processes at
the controller 50.
[0115] When the controller 50 is turned on and receives an
operation start command, the controller 50 carries out processes
according to the flow from steps S101 to S108 shown in FIG. 3. In
FIG. 3, steps S102 to S106 show a process relating to the oil
recovery operation (the oil recovery control mode). Steps S107 to
S108 show a process relating to the cooling operation (the normal
mode). Note that, the process flow shown in FIG. 3 is merely of an
exemplary nature, and may be changed as appropriate. For example,
the order of the steps may be changed unless a contradiction
arises. Part of the steps may be executed in parallel to other
steps.
[0116] In step S101, when the oil recovery operation start
condition is not satisfied (that is, when NO), the controller 50
proceeds to step S107. On the other hand, when the oil recovery
operation start condition is satisfied (when YES), the controller
50 proceeds to step S102.
[0117] In step S102, the controller 50 enters the oil recovery
control mode. Thereafter, the controller 50 proceeds to step
S103.
[0118] In step S103, the controller 50 starts the oil recovery
operation and executes the oil recovery first control.
Specifically, the controller 50 sets, as the oil recovery first
control, the first expansion valve 15 to the first opening degree.
Thus, the flow rate and the pressure of a refrigerant passing
through the first expansion valve 15 reduce and the flow rate and
the pressure of the refrigerant having passed through the first
expansion valve 15 and flowing into the service unit 30 reduce,
whereby the degree of superheating at the usage-side heat exchanger
32 increases. In accordance therewith, the opening degree of the
usage-side expansion valve 31 is increased (in the present
embodiment, the opening degree is set to the maximum opening
degree). Following the start of executing the oil recovery first
control, the controller 50 proceeds to step S104.
[0119] In step S104, when the second control start condition is not
satisfied (in the present embodiment, when the first time t1 has
not elapsed since the start of executing the oil recovery first
control, that is, when NO), the controller 50 stays at step S104.
On the other hand, when the second control start condition is
satisfied (in the present embodiment, when the first time t1 has
elapsed since the start of executing the oil recovery first
control, that is, when YES), the controller 50 proceeds to step
S105.
[0120] In step S105, the controller 50 ends the oil recovery first
control and executes the oil recovery second control. Specifically,
the controller 50 sets, as the oil recovery second control, the
first expansion valve 15 to the second opening degree. Thus, the
flow rate and the pressure of a refrigerant passing through the
first expansion valve 15 increase and the flow rate and the
pressure of the refrigerant having passed through the first
expansion valve 15 and flowing into the service unit 30 increase,
whereby the degree of superheating at the usage-side heat exchanger
32 reduces. In accordance therewith, the opening degree of the
usage-side expansion valve 31 is reduced. Note that, until a
response time elapses since when the first expansion valve 15 is
switched from the first opening degree to the second opening
degree, the opening degree increased by the oil recovery first
control (in the present embodiment, the maximum opening degree) is
maintained. Hence, until the response time elapses since when the
first expansion valve 15 is switched from the first opening degree
to the second opening degree, a liquid refrigerant or a gas-liquid
two-phase refrigerant passes through the first expansion valve 15,
and the liquid refrigerant or the gas-liquid two-phase refrigerant
flows into the usage-side heat exchanger 32. The liquid refrigerant
or the gas-liquid two-phase refrigerant flowing into the usage-side
heat exchanger 32 is compatibilized with a refrigerating machine
oil built up in the usage-side heat exchanger 32, and flows toward
the gas side (the first pipe P1 and the second pipe P2) of the heat
source unit 10. Thus, the refrigerating machine oil built up in the
usage-side heat exchanger 32 is recovered to the compressors 11.
After the start of executing the oil recovery second control, the
controller 50 proceeds to step S106.
[0121] In step S106, when the oil recovery operation end condition
is not satisfied (in the present embodiment, when the second time
t2 has not elapsed since the start of executing the oil recovery
second control, that is, when NO), the controller 50 stays at step
S106. On the other hand, when the oil recovery operation end
condition is satisfied (in the present embodiment, when the second
time t2 has elapsed since the start of executing the oil recovery
second control, that is, when YES), the controller 50 proceeds to
step S107.
[0122] In step S107, the controller 50 enters the normal mode.
Thereafter, the controller 50 proceeds to step S108.
[0123] In step S108, the controller 50 controls in real time the
state of the actuators (11, 15, 16, 17, 19) in accordance with the
set temperature and the detected values of various types of sensors
(20 to 23, 25) to cause them to perform the cooling operation.
Thereafter, the controller 50 returns to step S101.
(6) Oil Recovery Operation
[0124] As has been described above, the refrigeration apparatus 100
in operation performs the oil recovery operation for recovering the
refrigerating machine oil built up in the service units 30 to the
compressors 11 at a predetermined timing (specifically, at a timing
when the oil recovery operation start condition is satisfied). In
the oil recovery operation, the controller 50 successively executes
the oil recovery first control and the oil recovery second
control.
[0125] In the oil recovery first control, by the first expansion
valve 15 having its opening degree reduced to the first opening
degree, the flow rate and the pressure of a refrigerant passing
through the first expansion valve 15 (that is, a refrigerant sent
to the service units 30) reduces. In relation thereto, the flow
rate and the pressure of a refrigerant passing through the
usage-side expansion valve 31 reduce and the flow rate and the
pressure of a refrigerant flowing into the usage-side heat
exchanger 32 reduce. In accordance therewith, the degree of
superheating of the refrigerant at the usage-side heat exchanger 32
increases. As a result, the opening degree of the usage-side
expansion valve 31 is increased.
[0126] In the oil recovery second control, by the first expansion
valve 15 having its opening degree increased to the second opening
degree, the flow rate and the pressure of a refrigerant passing
through the first expansion valve 15 increase. In relation thereto,
the flow rate and the pressure of a refrigerant passing through the
usage-side expansion valve 31 increase and the flow rate and the
pressure of a refrigerant flowing into the usage-side heat
exchanger 32 increase. In accordance therewith, the degree of
superheating of the refrigerant at the usage-side heat exchanger 32
reduces. In response to the reduced degree, the opening degree of
the usage-side expansion valve 31 is reduced. Here, the timing at
which the opening degree of the usage-side expansion valve 31 is
reduced is delayed by a predetermined response time from the timing
where the first expansion valve is set to the second opening
degree. That is, there exists a time lag corresponding to the
response time of the usage-side expansion valve 31 between the
timing where the first expansion valve 15 is set to the second
opening degree and the opening degree of the usage-side expansion
valve 31 is reduced.
[0127] Hence, during the period since when the first expansion
valve 15 is set to the second opening degree until when the opening
degree of the usage-side expansion valve 31 is reduced, the opening
degree of the usage-side expansion valve 31 is maintained in the
increased state by the oil recovery first control. On the other
hand, the flow rate of the refrigerant sent to the usage-side
expansion valve 31 increases by the first expansion valve 15 is
controlled to the second opening degree. Therefore, until the
opening degree of the usage-side expansion valve 31 is reduced, the
liquid refrigerant flowed out from the receiver 13 is sent to the
usage-side heat exchanger 32. This liquid refrigerant transfers the
refrigerating machine oil built up in the usage-side heat exchanger
32 to the heat source unit 10, to be recovered to the compressors
11.
[0128] In the refrigeration apparatus 100, executing the oil
recovery operation including the oil recovery first control and the
oil recovery second control recovers the refrigerating machine oil
built up in the usage-side heat exchanger 32 to the compressors 11,
without the necessity of disposing an on-off valve on the
refrigerant flow upstream side relative to the usage-side expansion
valve 31.
(7) Characteristic of Refrigeration Apparatus 100
[0129] (7-1)
[0130] The refrigeration apparatus 100 according to the
above-described embodiment is excellent in workability,
maintainability, and economy.
[0131] That is, there exists a conventional refrigeration apparatus
which includes an on-off valve disposed upstream to the mechanical
expansion valve. By the on-off valve being turned on or off, a
liquid refrigerant is sent to the usage-side heat exchanger, to
perform an oil recovery operation of recovering a refrigerating
machine oil built up in the usage-side heat exchanger at a
predetermined timing. In the case where a controller for
controlling, actuators is to be disposed outside the service unit,
such a conventional refrigeration apparatus necessitates an
electric wire for electrically connecting between the on-off valve
in the service unit and the controller in installation or
maintenance. For the works relating to the electric wire, and
troubles and costs in maintenance, the conventional refrigeration
apparatus is poor in workability, maintainability, and economy.
[0132] In contrast, in the refrigeration apparatus 100, the
controller 50 executes the oil recovery operation for recovering
the refrigerating machine oil to the compressors 11 at a
predetermined timing. In the oil recovery operation, the opening
degree of the first expansion valve 15 is set to the first opening
degree, to reduce the flow rate and the pressure of a refrigerant
passing through the first expansion valve 15. Thereafter, the
opening degree of the first expansion valve 15 is set to the second
opening degree, to increase the flow rate and the pressure of the
refrigerant passing through the first expansion valve 15. Thus, in
the oil recovery operation, under the oil recovery first control,
in relation to a reduction in the flow rate or the pressure of the
refrigerant passing through the first expansion valve 15, the
opening degree of the usage-side expansion valve 31 is increased.
Thereafter, under the oil recovery second control, before the
opening degree of the usage-side expansion valve 31 is reduced in
relation to the increase in the flow rate or the pressure of the
refrigerant passing through the first expansion valve 15, a liquid
refrigerant flows into the usage-side heat exchanger 32. As a
result, the liquid refrigerant flowing into the usage-side heat
exchanger 32 is compatibilized with a refrigerating machine oil
building up in the usage-side heat exchanger 32 and flows toward
the heat source unit 10 side. Then, the refrigerating machine oil
is recovered to the compressors 11.
[0133] That is, in the refrigeration apparatus 100, the oil
recovery operation of recovering a refrigerating machine oil in the
service units 30 to the compressors 11 is carried out without the
necessity of disposing an on-off valve for the oil recovery
operation in the service units 30 (or in a refrigerant flow path
downstream to the heat source unit 10 and upstream to the
usage-side expansion valve 31; in the present embodiment, the
liquid-side connection pipe L1, the same holds true for the
following). In other words, in the refrigeration apparatus 100, the
refrigerant circuit RC including the usage-side expansion valve 31
upstream to the usage-side heat exchanger 32 performing the oil
recovery operation does not require an on-off valve disposed
upstream to the usage-side expansion valve 31. Hence, the
refrigeration apparatus 100 can dispense with an electric wire for
electrically connecting between the controller 50 and such an
on-off valve in installation and maintenance and, accordingly, the
refrigeration apparatus 100 can save any works relating to the
electric wire and troubles and costs in maintenance. Thus, the
refrigeration apparatus 100 is excellent in workability,
maintainability, and economy.
(7-2)
[0134] In the refrigeration apparatus 100 according to the
above-described embodiment, the controller 50 first executes the
oil recovery first control, and after a lapse of the first time t1,
the controller 50 executes the oil recovery second control. The
first time t1 in the embodiment is a time that is required for the
usage-side expansion valve 31 to have its opening degree increased
in response to a reduction in the flow rate or the pressure of a
refrigerant passing through the first expansion valve 15 by the oil
recovery first control.
[0135] Thus, after the opening degree of the usage-side expansion
valve 31 is increased by the oil recovery first control being
executed, the opening degree of the first expansion valve 15 is
increased by the oil recovery second control, whereby a liquid
refrigerant by a flow rate suitable for recovering a refrigerating
machine oil flows into the usage-side heat exchanger 32. As a
result, the oil recovery operation is realized without the
necessity of disposing an on-off valve for an oil recovery
operation in the service units 30. Thus, any electric wire for
electrically connecting between the controller 50 and such an
on-off valve in installation or maintenance can be dispensed with
and, accordingly, the refrigeration apparatus 100 can save any
works relating to the electric wire and troubles and costs in
maintenance.
(7-3)
[0136] In the refrigeration apparatus 100 according to the
above-described embodiment, the usage-side expansion valve 31
includes the feeler bulb 312 disposed on the refrigerant flow
downstream side relative to the usage-side heat exchanger 32, and
the opening degree of the usage-side expansion valve 31 is changed
in response to the detected temperature by the feeler bulb 312.
[0137] Thus, using the characteristic of the usage-side expansion
valve 31 including the feeler bulb 312, a liquid refrigerant is
sent to the usage-side heat exchanger 32 to recover a refrigerating
machine oil. That is, the opening degree of the usage-side
expansion valve 31 is not immediately changed in response to a
change in the flow rate of a refrigerant sent from the upstream
side (that is, a change in the opening degree of the first
expansion valve 15). Instead, the opening degree is changed by a
delay corresponding to a response time in response to a change in
the flow rate of a refrigerant sent from the upstream side. In
other words, the usage-side expansion valve 31 is characterized by
its low-speed responsivity. By virtue of this characteristic, when
the oil recovery second control is executed following the oil
recovery first control, the opening degree of the usage-side
expansion valve 31 is not immediately reduced. Hence, after the
first expansion valve 15 is set to the second opening degree by the
oil recovery second control and until the usage-side expansion
valve 31 has its opening degree reduced in response thereto, a
liquid refrigerant is allowed to flow in by a flow rate suitable
for recovering a refrigerating machine oil to the usage-side heat
exchanger 32.
(7-4)
[0138] In the refrigeration apparatus 100 according to the
above-described embodiment, the first expansion valve 15 is
disposed in the heat source unit 10. This eliminates the necessity
of providing an electric wire for electrically connecting between
the heat source unit 10 and the service unit 30 disposed separate
from each other. This particularly minimizes works and costs
relating to installation or maintenance.
(7-5)
[0139] In the refrigeration apparatus 100 according to the
above-described embodiment, the controller 50 is disposed at the
heat source unit 10, and not electrically connected to any element
disposed at the service unit 30. This eliminates the necessity of
providing an electric wire for electrically connecting between the
heat source unit 10 and the service unit 30 disposed separate from
each other. This particularly minimizes works and costs relating to
installation or maintenance.
(7-6)
[0140] In the refrigeration apparatus 100 according to the
above-described embodiment, the refrigerant circuit RC includes a
plurality of service units 30. That is, even in the case where a
plurality of service units 30 are installed (that is, in the case
where electric wires are required for electrically connecting
between the heat source unit 10 and the service units 30, which
involves particularly complicated installation works or maintenance
works), the refrigeration apparatus 100 can dispense with any
electric wires required by an on-off valve for the oil recovery
operation installed in each of the service units 30. This
particularly minimizes works and costs relating to installation or
maintenance.
(8) Variations
[0141] The above-described embodiment can be modified as
appropriate as shown in the following variations. Note that, the
variations may be carried out in combination with other variation
unless any contradiction arises.
(8-1) Variation A
[0142] In the above-described embodiment, the second control start
condition in the oil recovery operation is satisfied by a lapse of
the first time t1 in the oil recovery first control. Note that, so
long as the second control start condition is a condition which is
satisfied by the opening degree of the usage-side expansion valve
31 being increased in response to the oil recovery first control,
the second control start condition can be changed as appropriate in
accordance with the design specification or the installation
environment. For example, the second control start condition may be
satisfied by a detected value by any of various types of sensors
(21, 22, 23, or 25) attaining a predetermined reference value (a
value indicating an increase in the opening degree of the
usage-side expansion valve 31) in the oil recovery first
control.
(8-2) Variation B
[0143] In the above-described embodiment, the oil recovery
operation end condition in the oil recovery operation is satisfied
by a lapse of the second time t2 in the oil recovery second
control. Note that, so long as the oil recovery operation end
condition is a condition which is satisfied by the recovery of a
refrigerating machine oil built up in the service unit 30
(particularly, the usage-side heat exchanger 32) being completed,
the oil recovery operation end condition can be changed as
appropriate in accordance with the design specification or the
installation environment. For example, the oil recovery operation
end condition may be satisfied by a detected value by any of
various types of sensors (21, 22, 23, or 25) attaining a
predetermined reference value (a value indicating the complete of
recovery of a refrigerating machine oil built up in the service
unit 30) in the oil recovery second control.
(8-3) Variation C
[0144] In the above-described embodiment, the first time t1 and the
second time t2 are set to three minutes. Note that, the first time
t1 and the second time t2 can be changed as appropriate in
accordance with the installation environment and the design
specification. For example, the first time t1 or the second time t2
may be set to a value less than three minutes (for example, one
minute), or a value greater than three minutes (for example, five
minutes). Furthermore, the first time t1 and the second time t2 may
not be set to an identical value, and may be respectively set to
different values.
(8-4) Variation D
[0145] In the above-described embodiment, the description has been
given of the oil recovery first control under which the first
expansion valve 15 has its opening degree set to a minimum opening
degree as the first opening degree such that the usage-side
expansion valve 31 has its opening degree set to a maximum opening
degree. Note that, the first opening degree is just an opening
degree smaller than an opening degree of the first expansion valve
15 in the normal mode, and may not be a minimum opening degree so
long as it increases the opening degree of the usage-side expansion
valve 31.
[0146] Further, in the oil recovery second control, the description
has been given of the first expansion valve 15 having its opening
degree set to a maximum opening degree as the second opening
degree. Note that, the first opening degree is just an opening
degree greater than the second opening degree, and may not be a
maximum opening degree so long as it allows a liquid refrigerant to
flow into the usage-side heat exchanger 32.
[0147] That is, so long as the object of the oil recovery first
control and the oil recovery second control is achieved, the first
opening degree and the second opening degree should be set as
appropriate in accordance with the design specification and the
installation environment.
(8-5) Variation E
[0148] In the above-described embodiment, the oil recovery
operation is performed when the oil recovery operation start
condition is satisfied in the cooling operation. Note that, the
trigger of the oil recovery operation is not limited thereto, and
may be changed as appropriate. For example, the oil recovery
operation may be performed when the user inputs a predetermined
command instructing the start of the oil recovery operation.
(8-6) Variation F
[0149] The configuration of the refrigerant circuit RC in the
above-described embodiment is not limited to the configuration
shown in FIG. 1, and may be changed as appropriate according, to
the design specification and the installation environment.
[0150] For example, the first expansion valve 15 may not be
disposed in the heat source unit 10. For example, the first
expansion valve 15 may be disposed at the liquid-side connection
pipe L1.
[0151] For example, while three compressors 11 in total are
disposed, the number of the compressors 11 may be changed as
appropriate in accordance with the design specification. For
example, the compressors 11 may be two in number, or four or more
in number. In such cases, the number and allocation of the
variable-capacity compressor and the constant-capacity compressor
should be selected as appropriate.
[0152] For example, the subcooling heat exchanger 14 and the
injection line J1 are not essential, and may be omitted as
appropriate.
(8-7) Variation G
[0153] In the above-described embodiment, the usage-side expansion
valve 31 is a thermostatic expansion valve including the feeler
bulb 312. Note that, so long as the usage-side expansion valve 31
is an automatic regulating valve whose opening degree changes in
response to a change in the flow rate or the pressure of the
refrigerant sent from the upstream side, the usage-side expansion
valve 31 may not be a thermostatic expansion valve and may be other
mechanical expansion valve.
(8-8) Variation H
[0154] In the above-described embodiment, the usage-side fan 35 is
not connected to the controller 50. Note that, the usage-side fan
35 may be electrically connected to the controller 50, and may have
its start, stop or number of revolutions controlled by the
controller 50. The usage-side fan 35 may not be supplied with power
from an independent power source (a commercial power source, a
storage battery or the like), and may be supplied with drive power
from a power source unit shared with the heat source unit 10.
(8-9) Variation I
[0155] The above-described embodiment includes one heat source unit
10 and two service units 30. Note that, the number of the heat
source unit 10 disposed in the refrigeration apparatus 100 is not
limited, and may be two or more. The number of the service units 30
in the refrigeration apparatus 100 is not limited, and may be one,
or three or more.
(8-10) Variation J
[0156] In the above-described embodiment, the controller 50 is
disposed at the heat source unit 10. Note that, the controller 50
may not be disposed at the heat source unit 10. For example, the
controller 50 may be disposed at any unit other than the heat
source unit 10, or may be disposed independently. In such cases,
the controller 50 may be disposed at a remote location connected to
the heat source unit 10 via a communication network.
[0157] The configuration of the controller 50 is not limited to the
configuration in the above-described embodiment, and may be changed
as appropriate in accordance with the design specification or the
installation environment. For example, the elements (the CPU, the
memory, and various types of electric components) forming the
controller 50 may not be disposed at an identical position. The
elements disposed in dispersed locations may be connected to each
other via a communication network to form the controller 50. That
is, so long as the elements forming the controller 50 are
configurable, the configuration of the controller 50 is not
limited.
(8-11) Variation K
[0158] In the above-described embodiment, the present invention is
applied to the refrigeration apparatus 100 that cools a
low-temperature warehouse, the inside of a showcase at a shop, or
the usage-side space in the transfer container. Without being
limited thereto, the present invention is applicable to other
refrigeration apparatus including a refrigerant circuit. For
example, the present invention may be applied to an air
conditioning system (an air conditioner) that realizes air
conditioning by cooling the space inside a building.
INDUSTRIAL APPLICABILITY
[0159] The present invention is applicable to a refrigeration
apparatus including a refrigerant circuit.
REFERENCE SIGNS LIST
[0160] 10: heat source unit [0161] 11: compressor (actuator) [0162]
12: heat-source-side heat exchanger [0163] 13: receiver [0164] 14:
subcooling heat exchanger [0165] 15: first expansion valve
(electric valve, actuator) [0166] 16: second expansion valve
(actuator) [0167] 17: injection valve [0168] 19: heat-source-side
fan (actuator) [0169] 21: low-pressure side pressure sensor [0170]
22: high-pressure side pressure sensor [0171] 23: intermediate
pressure sensor [0172] 25: discharge temperature sensor [0173] 30:
service unit [0174] 31: usage-side expansion valve (mechanical
expansion valve) [0175] 32: usage-side heat exchanger [0176] 35:
usage-side fan [0177] 50: controller [0178] 51: storage unit [0179]
52: input control unit [0180] 53: mode control unit [0181] 54:
actuator control unit [0182] 55: drive signal output unit [0183]
56: first expansion valve control unit [0184] 100: refrigeration
apparatus [0185] 141: first flow path [0186] 142: second flow path
[0187] 311: valve body [0188] 312: feeler bulb [0189] 313:
capillary tube [0190] G1: gas-side connection pipe [0191] J1:
injection line [0192] L1: liquid-side connection pipe [0193] P1 to
P15: first pipe-fifteenth pipe [0194] RC: refrigerant circuit
[0195] SV1: gas-side shutoff valve [0196] SV2: liquid-side shutoff
valve [0197] t1: first time (predetermined time) [0198] t2: second
time
CITATION LIST
Patent Literature
[0198] [0199] Patent Literature 1: JP 2009-257759 A
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