U.S. patent application number 10/580335 was filed with the patent office on 2007-06-21 for refrigeration system.
Invention is credited to Satoru Sakae, Masaaki Takegami, Kenji Tanimoto.
Application Number | 20070137231 10/580335 |
Document ID | / |
Family ID | 36060027 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137231 |
Kind Code |
A1 |
Takegami; Masaaki ; et
al. |
June 21, 2007 |
Refrigeration system
Abstract
When a guard timer of a compressor (141) expires, an R2 signal
from a control section (140) of an outdoor unit is turned on
(Action I). If a control section (120) of a freezer unit recognizes
from an inside temperature detected by a temperature sensor (124)
that the R2 signal is turned on and a request for a shift to a
freezer thermo-on state is raised (Action II), a freezer
electromagnetic valve (121) is opened (Action III). In general,
when the electromagnetic valve (121) is opened, it is supposed that
an increase in refrigerant suction pressure is detected by a
pressure sensor (146) and then the compressor (141) is actuated.
However, if an outside air temperature is low, the refrigerant
suction pressure remains lower than a predetermined value.
Therefore, the control section (120) actuates a booster compressor
(131) (Action IV) to raise the refrigerant suction pressure of the
compressor (141).
Inventors: |
Takegami; Masaaki; (Osaka,
JP) ; Sakae; Satoru; (Osaka, JP) ; Tanimoto;
Kenji; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
36060027 |
Appl. No.: |
10/580335 |
Filed: |
September 13, 2005 |
PCT Filed: |
September 13, 2005 |
PCT NO: |
PCT/JP05/16830 |
371 Date: |
May 24, 2006 |
Current U.S.
Class: |
62/228.3 ;
62/228.5; 62/510 |
Current CPC
Class: |
F25D 2700/12 20130101;
F25B 1/10 20130101; F25B 2500/31 20130101; F25B 2700/1933 20130101;
F25B 2400/22 20130101; F25B 5/02 20130101; F25B 2600/01
20130101 |
Class at
Publication: |
062/228.3 ;
062/510; 062/228.5 |
International
Class: |
F25B 49/00 20060101
F25B049/00; F25B 1/10 20060101 F25B001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2004 |
JP |
2004-265548 |
Claims
1. A refrigeration system (1) for vapor compression refrigeration
cycle including a heat source circuit provided with a high
temperature compressor (141) and a utilization circuit connected to
the heat source circuit and provided with an evaporator (123) and a
low temperature compressor (131), the refrigeration system (1)
comprising: an operation control means for switching the high
temperature compressor (141) between actuated state and suspended
state based on a refrigerant suction pressure; and an actuation
control means for actuating the low temperature compressor (131) to
increase the refrigerant suction pressure of the high temperature
compressor (141) when the high temperature compressor (141) is
suspended and given conditions including a condition concerning a
request for cooling in the evaporator (123) are met.
2. A refrigeration system (2) for vapor compression refrigeration
cycle comprising: an operation control means for switching a
compressor (241) between actuated state and suspended state based
on a refrigerant suction pressure; and a reference value changing
means for reducing a reference value of the refrigerant suction
pressure for judging whether to actuate the compressor (241) or not
when the compressor (241) is suspended and an outside air
temperature is reduced from a predetermined temperature.
3. The refrigeration system (2) of claim 2, wherein the reference
value changing means is adapted to reduce the reference value in
stages based on the amount of reduction in outside air temperature
from the predetermined temperature.
4. A refrigeration system (3) for vapor compression refrigeration
cycle comprising: an operation control means for switching a
compressor (341) between actuated state and suspended state based
on a refrigerant suction pressure; and a power supply control means
for supplying open phase current to a motor of the compressor (341)
to increase the refrigerant suction pressure increases when the
compressor (341) is suspended, an outside air temperature is
reduced from a predetermined temperature and a condition concerning
a request for cooling in an evaporator (313) is met.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration system,
particularly to a technique for improvement in actuation of a
compressor under low outside air temperature condition.
BACKGROUND ART
[0002] So far, stores such as convenience stores use a
refrigeration system in which a cold storage unit for displaying
and keeping articles at low temperature in a cold storage showcase
and a freezer unit for displaying and freezing articles in a
freezer showcase are connected as a single refrigerant circuit.
[0003] FIG. 15 shows a refrigerant circuit diagram for briefly
explaining the operation of a conventional refrigeration system
(5).
[0004] In the refrigeration system (5), a refrigerant compressed in
a compressor (541) in an outdoor unit (54) placed outdoor is
condensed in a condenser (542) while it dissipates heat. The
condensed liquid refrigerant is divided so that part thereof flows
into a cold storage unit (51) and the other flows into a freezer
unit (52). The refrigerant entered the cold storage unit (51) is
depressurized by an expansion valve (512) and evaporated in a cold
storage evaporator (513) while it absorbs heat of inside air. The
refrigerant entered the freezer unit (52) is depressurized by an
expansion valve (522) and evaporated in a freezer evaporator (523)
while it absorbs heat of inside air.
[0005] Saturation pressure of the refrigerant in the freezer
evaporator (523) is kept lower than that in the cold storage
evaporator (513) by a booster compressor (531) in a booster unit
(53). The evaporating temperature in the freezer evaporator (523)
(about -5.degree. C.) is kept lower than that in the cold storage
evaporator (513) (about 5.degree. C.).
[0006] As the cooling is continued, temperatures in the cold
storage unit (51) and the freezer unit (52) reach predetermined
target temperatures, respectively. Then, an electromagnetic valve
(511) and an electromagnetic valve (521) are closed and the
refrigerant is no longer supplied to the evaporators (513) and
(523) (the cold storage unit and the freezer unit enter a cold
storage thermo-off state and a freezer thermo-off state,
respectively).
[0007] In a control section (540) (including a microprocessor, a
ROM, a RAM and the like for executing certain programs), a pressure
sensor (546) is adapted to detect the pressure of the refrigerant
sucked into the compressor (541). If the detected value is not
higher than a predetermined value (e.g., 0.10 MPa), the control
section (540) suspends the compressor (541) (an outdoor unit
thermo-off state).
[0008] In the outdoor unit thermo-off state, when a certain
temperature difference is observed between inside temperature and
target inside temperature, the electromagnetic valve (511) of the
cold storage unit (51) or the electromagnetic valve (521) of the
freezer unit (52) is opened and a request for a refrigerant supply
to the evaporator (513) or (523) is raised (a cold storage
thermo-on state or a freezer thermo-on state). Further, the
pressure sensor (546) of the control section (540) detects that the
refrigerant suction pressure has increased to or above a
predetermined value (e.g., 0.25 MPa). Accordingly, the control
section (540) actuates the compressor (541) (an outdoor unit
thermo-on state).
[0009] In the refrigeration unit (5) described above, the pressure
sensor (546) makes it possible to determine whether or not it is
necessary to circulate the refrigerant to either one of the
evaporators (513, 523) to maintain the operation of the compressor
(541). Therefore, there is no need of transmitting a signal
indicating that the cooling is required in the cold storage unit
(51) or the freezer unit (52) to the control section (540). Thus,
the compressor (541) is easily switched between actuated state and
suspended state with a simple structure.
[0010] For example, according to a similar refrigeration system of
Japanese Patent Publication No. 2002-228297, the compressor is
suspended when the refrigerant suction pressure is not higher than
a predetermined value to avoid operation in a wet state.
[0011] Problem to Solve
[0012] According to the refrigeration system (5), in order to shift
the outdoor unit from the thermo-off state to the thermo-on state,
the compressor is controlled not to start working if the
refrigerant suction pressure is lower than the predetermined value.
However, if the outside air temperature is as low as -5.degree. C.
or lower, for example, the saturation pressure of the refrigerant
decreases to reduce the refrigerant pressure in the circuit. As a
result, even if the freezer unit (52) requests cooling and the
electromagnetic valve (513, 523) is opened, the refrigerant suction
pressure may possibly remain low and the compressor (541) may not
be actuated.
[0013] Under the circumstances, the present invention has been
achieved. An object of the present invention is to provide a
refrigeration system which makes it possible to actuate a
compressor smoothly even if the outside air temperature is low.
DISCLOSURE OF THE INVENTION
[0014] The present invention solves the problem as described
below.
[0015] A first aspect of the present invention is directed to a
refrigeration system for vapor compression refrigeration cycle
including a heat source circuit provided with a high temperature
compressor (141) and a utilization circuit connected to the heat
source circuit and provided with an evaporator (123) and a low
temperature compressor (131). The refrigeration system includes an
operation control means for switching the high temperature
compressor (141) between actuated state and suspended state based
on a refrigerant suction pressure; and an actuation control means
for actuating the low temperature compressor (131) to increase the
refrigerant suction pressure in the high temperature compressor
(141) when the high temperature compressor (141) is suspended and
given conditions including a condition concerning a request for
cooling in the evaporator (123) are met.
[0016] According to the first aspect of the present invention, the
high temperature compressor (141) is switched between actuated
state and suspended state based on the refrigerant suction
pressure. In the process of restarting the high temperature
compressor (141) in the suspended state, if given conditions
including a condition concerning a request for cooling in the
evaporator (123) are met, the low temperature compressor (131) is
actuated to increase the refrigerant suction pressure in the high
temperature compressor (141).
[0017] A second aspect of the present invention is directed to a
refrigeration system for vapor compression refrigeration cycle. The
refrigeration system includes an operation control means for
switching a compressor (241) between actuated state and suspended
state based on a refrigerant suction pressure; and a reference
value changing means for reducing a reference value of the
refrigerant suction pressure for judging whether to actuate the
compressor (241) or not when the compressor (241) is suspended and
outside air temperature is reduced from a predetermined
temperature.
[0018] According to the second aspect of the present invention, the
compressor (241) is switched between actuated state and suspended
state based on the refrigerant suction pressure. In the process of
restarting the temperature compressor (241) in the suspended state,
if the outside air temperature is reduced from the predetermined
temperature, a reference value of the refrigerant suction pressure
for judging whether to actuate the compressor (241) or not is
reduced.
[0019] According to a third aspect of the present invention related
to the second aspect of the present invention, the reference value
changing means is adapted to reduce the reference value in stages
based on the amount of reduction in outside air temperature from
the predetermined temperature.
[0020] According to the third aspect of the present invention, the
reference value is reduced in stages based on the amount of
reduction in outside air temperature.
[0021] A fourth aspect of the present invention is directed to a
refrigeration system for vapor compression refrigeration cycle. The
refrigeration system includes an operation control means for
switching a compressor (341) between actuated state and suspended
state based on a refrigerant suction pressure; and a power supply
control means for supplying open phase current to a motor of the
compressor (341) to increase the refrigerant suction pressure
increases when the compressor (341) is suspended, an outside air
temperature is reduced from a predetermined temperature and a
condition concerning a request for cooling in an evaporator (313)
is met.
[0022] According to the fourth aspect of the present invention, the
compressor (341) is switched between actuated state and suspended
state based on the refrigerant suction pressure. In the process of
restarting the compressor (341) in the suspended state, if the
outside air temperature is reduced from the predetermined
temperature and the condition concerning a request for cooling in
the evaporator (313) is met, open phase current is supplied to the
motor for driving the compressor (341) to increase the refrigerant
suction pressure.
[0023] Effect
[0024] According to the first aspect of the present invention, in
the process of restarting the high temperature compressor (141), if
given conditions including a condition concerning a request for
cooling in the evaporator (123) are met, the low temperature
compressor (131) is actuated in advance of the actuation of the
high temperature compressor (141) such that the refrigerant suction
pressure of the high temperature compressor (141) increases.
Therefore, even if the outside air temperature is significantly
low, the refrigerant suction pressure of the high temperature
compressor (141) surely increases. Thus, the high temperature
compressor (141) is smoothly actuated.
[0025] According to the second aspect of the present invention, in
the process of restarting the compressor (241), if the outside air
temperature is lower than the predetermined temperature, the value
of a refrigerant suction pressure which is a criterion for judging
whether to actuate the compressor (241) or not is reduced.
Therefore, the compressor (241) is smoothly actuated even if the
refrigerant pressure in the circuit is reduced due to the low
outside air temperature.
[0026] According to the third aspect of the present invention, the
reference value of the refrigerant suction pressure is reduced by a
suitable amount based on the reduced amount of the outside air
temperature, whereby the reduction in refrigerant suction pressure
caused by the reduction in outside air temperature is detected with
accuracy. Thus, the compressor is smoothly actuated in accordance
with the detection result.
[0027] According to the fourth aspect of the present invention, in
the process of restarting the compressor (341), if the condition
concerning a request for cooling in the evaporator (313) is met,
open phase current is supplied to the motor for driving the
compressor (341). Therefore, even if the outside air temperature is
reduced to a significant degree, the sucked refrigerant is heated
to increase its pressure. Thus, the compressor (341) is smoothly
actuated.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a view illustrating the schematic structure of a
refrigeration system according to a first embodiment of the present
invention.
[0029] FIG. 2 is a view illustrating how the refrigeration system
works in a normal state.
[0030] FIG. 3 is a view illustrating a characteristic feature of
the present invention, i.e., how the refrigeration system enters a
freezer thermo-on state under a low outside air temperature.
[0031] FIG. 4 is a block diagram schematically illustrating the
major structure of a control program for entering an outdoor unit
thermo-on state executed by a control section of an outdoor
unit.
[0032] FIG. 5 is a flowchart illustrating the processing steps for
entering a thermo-on state executed by the control section of the
outdoor unit.
[0033] FIG. 6 is a flowchart illustrating the processing steps for
controlling the opening/closing of a cold storage electromagnetic
valve executed by a control section of a cold storage unit.
[0034] FIG. 7 is a flowchart illustrating the processing steps for
controlling the opening/closing of a freezer electromagnetic valve
executed by a control section of a freezer unit.
[0035] FIG. 8 is a flowchart illustrating the processing steps for
controlling the actuation/suspension of a booster compressor
executed by the control section of the freezer unit.
[0036] FIG. 9 is a view illustrating how a refrigeration system of
a second embodiment enters a cold storage thermo-on state under a
low outside air temperature.
[0037] FIG. 10 is a block diagram schematically illustrating the
major structure of a control program for entering an outdoor unit
thermo-on state executed by a control section of an outdoor
unit.
[0038] FIG. 11 is a flowchart illustrating the processing steps for
entering a thermo-on state executed by the control section of the
outdoor unit.
[0039] FIG. 12 is a view illustrating how a refrigeration system of
a third embodiment enters a cold storage thermo-on state under a
low outside air temperature.
[0040] FIG. 13 is a block diagram illustrating the major structure
of a control program for entering an outdoor unit thermo-on state
executed by a control section of an outdoor unit.
[0041] FIG. 14 is a flowchart illustrating the processing steps for
entering a thermo-on state executed by the control section of the
outdoor unit.
[0042] FIG. 15 is a refrigerant circuit diagram schematically
illustrating how a conventional refrigeration system works.
BRIEF EXPLANATION OF REFERENCE NUMERALS
[0043] 1,2,3 Refrigeration system
[0044] 113, 213, 313 Cold storage evaporator
[0045] 123 Freezer evaporator
[0046] 131 Booster compressor
[0047] 141, 241, 341 Variable capacity compressor
BEST MODE FOR CARRYING OUT THE INVENTION
[0048] Hereinafter, a detailed explanation of refrigeration systems
(1, 2, 3) as embodiments of the present invention will be provided
with reference to the drawings.
[0049] FIG. 1 is a view schematically illustrating the structure of
a refrigeration system (1) according to a first embodiment of the
present invention.
[0050] The refrigeration system (1), which is placed in convenience
stores and the like, includes a cold storage unit (11), a freezer
unit (12), a booster unit (13) and an outdoor unit (14) as shown in
FIG. 1.
[0051] The cold storage unit (11) includes a cold storage showcase
for displaying and keeping articles at low temperature and the
freezer unit (12) includes a freezer showcase for displaying and
freezing articles. The booster unit (13) keeps a refrigerant at low
pressure for freezing. The outdoor unit (14) is disposed outdoor
such that the refrigerant dissipates heat to outside air. The cold
storage unit (11), freezer unit (12) and booster unit (13) are
connected in parallel to the outdoor unit (14), thereby providing a
single refrigerant circuit for two-step vapor compression
refrigeration cycle.
[0052] In the cold storage unit (11), a temperature-sensitive
expansion valve (112) for depressurizing the refrigerant is
connected via a pipe with a cold storage evaporator (113) in which
the refrigerant absorbs heat of inside air to evaporate. The cold
storage unit (11) further includes a fan (115) for sending the
inside air cooled in the cold storage evaporator (113) to the cold
storage showcase. The cold storage unit (11) is further provided
with a cold storage electromagnetic valve (111) which is opened or
closed to pass through or block a refrigerant flow to the cold
storage evaporator (113) and a temperature sensor (114) for
detecting inside temperature.
[0053] The cold storage electromagnetic valve (111),
temperature-sensitive expansion valve (112) and cold storage
evaporator (113) are connected in series in this order along the
path from an inlet pipe (201) to an outlet pipe (202).
[0054] Also in the freezer unit (12), a temperature-sensitive
expansion valve (122) is connected via a pipe with a freezer
evaporator (123) in which the refrigerant absorbs heat of inside
air to evaporate. The freezer unit (12) further includes a fan
(125) for sending the inside air cooled in the freezer evaporator
(123) to the freezer showcase. The freezer unit (12) is further
provided with a freezer electromagnetic valve (121) which is opened
or closed to pass through or block a refrigerant flow to the
freezer evaporator (123) and a temperature sensor (124) for
detecting inside temperature.
[0055] The freezer electromagnetic valve (121),
temperature-sensitive expansion valve (122) and freezer evaporator
(123) are connected in series in this order along the path from an
inlet pipe (203) to an outlet pipe (204).
[0056] The booster unit (13) includes a booster compressor (131).
The booster compressor (131) keeps the pressure of the refrigerant
passing through the freezer evaporator (123) lower than the
pressure of the refrigerant passing through the cold storage
evaporator (113).
[0057] The booster unit (13) further includes a bypass (132) having
a check valve (133) for bypassing the booster compressor (131).
When the booster compressor (131) fails to operate properly or
stops, the bypass (132) allows the refrigerant to flow to the
outdoor unit (14) without passing through the booster compressor
(131). In other words, when the booster compressor (14) is working,
the refrigerant does not pass through the bypass (132). The check
valve (133) allows only the passage of the refrigerant flowing from
an inlet pipe (205) to an outlet pipe (206).
[0058] The outdoor unit (14) includes a variable capacity
compressor (141), a condenser (142) and a liquid receiver (143).
The variable capacity compressor (141) is adapted to adjust its
capacity depending on a cooling load of the cold storage unit (11),
for example. The condenser (142) is adapted to allow the
refrigerant dissipate its heat to the outside air for condensation.
The liquid receiver (143) temporarily stores a liquid refrigerant
resulting from the condensation in the condenser (142).
Specifically, in the refrigeration system (1), the variable
capacity compressor (141) functions as a high temperature
compressor and the booster compressor (131) functions as a low
temperature compressor.
[0059] The outdoor unit (14) includes a fan (144) for taking the
outside air into the condenser (142). The outdoor unit (14) further
includes a temperature sensor (145) for detecting outside air
temperature and a pressure sensor (146) for detecting the pressure
of the refrigerant sucked into the variable capacity compressor
(141).
[0060] The variable capacity compressor (141), condenser (142) and
liquid receiver (143) are connected in series in this order along
the path from an inlet pipe (207) to an outlet pipe (208).
[0061] The inlet pipe (207) of the outdoor unit (14) is connected
to the outlet pipe (206) of the booster unit (13) and the outlet
pipe (202) of the cold storage unit (11). The outlet pipe (208) of
the outdoor unit (14) is connected to the inlet pipe (201) of the
cold storage unit (11) and the inlet pipe (203) of the freezer unit
(12). Further, the outlet pipe (204) of the freezer unit (12) is
connected to the inlet pipe (205) of the booster unit (13).
[0062] The outdoor unit (14) is further provided with a control
section (140). The control section (140) controls the capacity of
the variable capacity compressor (141) such that the pressure of
the refrigerant is kept uniform in each of the evaporators (113,
123). The control by the control section (140) according to the
present invention will be explained with reference to FIGS. 4 to
8.
[0063] The refrigeration system (1) works as shown in FIGS. 2 and
3. FIG. 2 shows how the refrigeration system (1) works in a normal
state and FIG. 3 shows a characteristic feature of the present
invention, i.e., how the refrigeration system (1) enters a freezer
thermo-on state under a low outside air temperature.
[0064] As shown in FIG. 2, in the outdoor unit thermo-on state
where the variable capacity compressor (141) is working, the
electromagnetic valves (111, 121) are opened to shift the cold
storage unit (11) to the cold storage thermo-on state and the
freezer unit (12) to the freezer thermo-on state. More
specifically, when the variable capacity compressor (141) is
working, the compressed refrigerant is condensed in the condenser
(142) while it dissipates heat. The condensed refrigerant passes
through the liquid receiver (143) and divided such that part
thereof flows into the cold storage unit (11) and the other flows
into the freezer unit (12).
[0065] In the cold storage unit (11), the refrigerant depressurized
by the expansion valve (112) is evaporated in the cold storage
evaporator (113) while it absorbs heat, thereby cooling the air in
the cold storage showcase. In the freezer unit (12), the
refrigerant depressurized by the expansion valve (122) is
evaporated in the freezer evaporator (123) while it absorbs heat,
thereby cooling the air in the freezer showcase. Then, the
refrigerant coming out of the freezer unit (12) is compressed in
the booster compressor (131). The compressed refrigerant is sucked
into the variable capacity compressor (141) of the outdoor unit
(14) together with the refrigerant coming out of the cold storage
unit (11). In this way, the refrigerant circulation is
repeated.
[0066] When the temperature in the cold storage showcase reaches a
predetermined target temperature, the cold storage electromagnetic
valve (111) is closed to block the refrigerant flow to the cold
storage evaporator (113) (cold storage thermo-off state). In the
same manner, if the temperature in the freezer showcase reaches a
predetermined target temperature, the freezer electromagnetic valve
(121) is closed and the booster compressor (131) is suspended to
block the refrigerant flow to the freezer evaporator (123) (freezer
thermo-off state). Under the cold storage thermo-off state and the
freezer thermo-off state, the variable capacity compressor (141)
decreases in refrigerant suction pressure. Once the reduction in
refrigerant suction pressure is detected, the variable capacity
compressor (141) is suspended to enter the outdoor unit thermo-off
state.
[0067] In the normal state where the outside air temperature is
higher than -5.degree. C., a control section (110) of the control
storage unit (11) automatically performs switching between the cold
storage thermo-on/off states and a control unit (120) of the
freezer unit (12) automatically performs switching between the
freezer thermo-on/off states. Depending on the cold storage
thermo-on/off states and the freezer thermo-on/off states, the
control section (140) of the outdoor unit (14) automatically
performs switching between the outdoor unit thermo-on/off states.
The control sections (110) and (120) will be explained later with
reference to FIG. 4.
[0068] When the difference between the inside temperature of the
freezer unit (12) and the target inside temperature is larger than
a predetermined value, a request for a shift to the freezer
thermo-on state is generated and the freezer electromagnetic valve
(121) is opened. However, if the outside air temperature is as low
as -5.degree. C. or lower, the variable capacity compressor (141)
hardly increases the refrigerant suction pressure. According to a
characteristic feature of the refrigeration system (1) of the
present invention as shown in FIG. 3, the booster compressor (131)
is forcibly actuated before the variable capacity compressor (141)
is driven such that the refrigerant suction pressure of the
variable capacity compressor (141) increases.
[0069] Specifically, when a guard timer of the variable capacity
compressor (141) expires, an R2 signal from the control section
(140) of the outdoor unit (14) to the control section (120) of the
freezer unit (12) is turned on (Action I). Then, if the control
section (120) of the freezer unit (12) recognizes that a request
for a shift to the freezer thermo-on state is raised according to
the value of the inside temperature detected by the temperature
sensor (124) (Action II), the freezer electromagnetic valve (121)
is opened (Action III).
[0070] The guard timer of the variable capacity compressor (41) is
used to prevent damage to the compressor by repetitive on-off
switching in a short term and expires in 1 or 2 minutes after the
suspension of the compressor.
[0071] When the freezer electromagnetic valve (121) is opened under
the normal condition, the refrigerant at the discharge side of the
variable capacity compressor (141) is allowed to flow to the
suction side of the variable capacity compressor (141) through the
bypass (132) of the booster compressor (131). As a result, the
refrigerant suction pressure increases. When the increase in
refrigerant suction pressure is detected by the pressure sensor
(146), the variable capacity compressor (141) is actuated. However,
if the outside air temperature is significantly low, the
refrigerant suction pressure of the variable capacity compressor
(141) remains lower than the predetermined value. Therefore, the
control section (120) of the freezer unit (12) forcibly actuates
the booster compressor (131) (Action IV) to increase the
refrigerant suction pressure of the variable capacity compressor
(141).
[0072] When the increase of the refrigerant suction pressure is
detected by the pressure sensor (146) (Action V), the variable
capacity compressor (141) is actuated in response to the detection
result (Action VI).
[0073] The control processes by the refrigeration system (1) will
be explained in detail with reference to FIGS. 4 to 8.
[0074] FIG. 4 is a block diagram schematically illustrating the
major structure of a control program for entering an outdoor unit
thermo-on state executed by the control section (140) of the
outdoor unit (14) and an input-output relationship between the
control section (140), the control section (110) of the cold
storage unit (11) and the control unit (120) of the freezer unit
(12).
[0075] The control section (140) of the outdoor unit (14) executes
a control program for entering the thermo-on state shown in FIG. 5.
The control section (110) of the cold storage unit (11) executes a
control program for opening/closing the cold storage
electromagnetic valve shown in FIG. 6. The control unit (120) of
the freezer unit (12) executes a control program for
opening/closing the freezer electromagnetic valve and a control
program for actuating/suspending the booster compressor. The
control sections (110, 120, 140) execute the programs
simultaneously.
[0076] The control section (140) of the outdoor unit (14) includes
an electromagnetic valve open/close permission section (1401), a
compressor actuating condition judging section (1402) and a
compressor actuating section (1403).
[0077] The electromagnetic valve open/close permission section
(1401) is adapted to turn on R1 and R2 signals for permitting the
electromagnetic valves (111, 121) to open and the booster
compressor (131) to start working after the guard timer of the
variable capacity compressor (141) has expired. The compressor
actuating condition judging section (1402) is adapted to judge
whether or not refrigerant suction pressure LP detected by the
pressure sensor (146) and outside air temperature Ta detected by
the temperature sensor (145) are within the predetermined ranges,
respectively. The compressor actuating section (1403) is adapted to
actuate the variable capacity compressor (141) when the refrigerant
suction pressure LP and the outside air temperature Ta are within
the predetermined ranges, respectively.
[0078] The control section (110) of the cold storage unit (11)
includes a cooling request judging section (1102) and an
electromagnetic valve opening/closing section (1102).
[0079] The cooling request judging section (1102) judges whether or
not the difference between the inside temperature detected by the
temperature sensor (114) and a predetermined target temperature is
not lower than a predetermined value (whether or not a request for
a shift to the cold storage thermo-on state is raised). The cooling
request judging section (1102) further judges whether the R1 signal
is turned on or not. The electromagnetic valve opening/closing
section (1102) is adapted to open the cold storage electromagnetic
valve (111) when the request for a shift to the cold storage
thermo-on state is raised and the R1 signal is turned on.
[0080] The control section (120) of the freezer unit (12) includes
a cooling request judging section (1201), an electromagnetic valve
opening/closing section (1202) and a booster compressor
actuating/suspending section (1203).
[0081] The cooling request judging section (1201) judges whether or
not the difference between the inside temperature detected by the
temperature sensor (124) and a predetermined target temperature is
not lower than a predetermined value (whether or not a request for
a shift to the freezer thermo-on state is raised). The cooling
request judging section (1201) further judges whether the R2 signal
is turned on or not. The electromagnetic valve opening/closing
section (1202) is adapted to open the cold storage electromagnetic
valve (121) when the request for a shift to the freezer thermo-on
state is raised and the R2 signal is turned on. The booster
compressor actuating/suspending section (1203) is adapted to
actuate the booster compressor (131) when the request for a shift
to the freezer thermo-on state is raised and the R2 signal is
turned on.
[0082] In this case, the compressor actuating condition judging
section (1402) and the compressor actuating section (1403) function
as an operation control means for switching between actuation
(thermo-on state) and suspension (thermo-off state) of the variable
capacity compressor (141). Further, the cooling request judging
section (1201), electromagnetic valve opening/closing section
(1202) and booster compression actuating/suspending section (1203)
function as an actuation control means for actuating the booster
compressor (131) when given conditions are met, such as a request
for cooling in the freezer unit (12) is raised and the guard timer
of the variable capacity compressor (141) expires.
[0083] According to the programs executed by the control sections
(110, 120, 140), even if the refrigerant suction pressure of the
variable capacity compressor (141) is locally reduced due to a low
outside air temperature, the booster compressor (131) is actuated
to forcibly increase the refrigerant suction pressure of the
variable capacity compressor (141). More specifically, the
following processes are executed.
[0084] As shown in FIG. 5, in the control process for entering the
thermo-on state executed by the control section (140) of the
outdoor unit (14), judgment is made as to whether or not the guard
timer of the variable capacity compressor (141) has expired (step
111, hereinafter indicated as ST111). If the guard timer has not
expired (NO in ST111), the process is ended. If the guard timer has
expired (YES in ST111), the R1 signal for permitting the cold
storage electromagnetic valve (111) to open is turned on and the R2
signal for permitting the freezer electromagnetic valve (121) to
open and the booster compressor (131) to start working is turned on
(ST112).
[0085] Subsequently, judgment is made as to whether or not the
refrigerant suction pressure LP of the variable capacity compressor
(141) is higher than 0.25 MPa (ST113). If the refrigerant suction
pressure LP is higher than 0.25 MPa (YES in ST113), the variable
capacity compressor (141) is actuated (ST114) and the process is
ended.
[0086] If the refrigerant suction pressure LP is not higher than
0.25 MPa (NO in ST113), judgment is made as to whether or not the
outside air temperature Ta detected by the temperature sensor (145)
is lower than -5.degree. C. and whether or not the variable
capacity compressor (141) has been suspended for 10 minutes or more
(ST115). If these conditions are met (YES in ST115), the variable
capacity compressor (141) is forcibly actuated in ST114. If the
outside air temperature Ta is not lower than -5.degree. C. or the
variable capacity compressor (141) has been suspended for less than
10 minutes (NO in ST115), the process is ended.
[0087] According to these processes, even if the refrigerant
suction pressure is low and the variable capacity compressor (141)
is not actuated, the R1 and R2 signals are turned on when the guard
timer has expired. Thus, the control sections (110, 120) permit the
electromagnetic valves (111, 121) to open and the booster
compressor (131) to start working.
[0088] As shown in FIG. 6, in the control process for
opening/closing the cold storage electromagnetic valve executed by
the control section (110) of the cold storage unit (11), judgment
is made as to whether or not the difference between the inside
temperature detected by the temperature sensor (114) and a
predetermined target temperature is not lower than a predetermined
value to raise a request for a shift to the cold storage thermo-on
state (ST121). If the request for a shift to the cold storage
thermo-on state is not raised (NO in ST121), the cold storage
electromagnetic valve (111) remains closed (ST122) and the process
is ended.
[0089] If the request for a shift to the cold storage thermo-on
state is raised (YES in STl21), judgment is made as to whether the
R1 signal is turned on or not (ST123). If the R1 signal is not
turned on (NO in ST123), the cold storage electromagnetic valve
(111) remains closed in ST122 and the process is ended. If the R1
signal is turned on (YES in ST123), the cold storage
electromagnetic valve (111) is opened (ST124) and the process is
ended.
[0090] As shown in FIG. 7, in the control process for
opening/closing the freezer electromagnetic valve executed by the
control section (120) of the freezer unit (12), judgment is made in
the same manner as described above. That is, if it is judged from
the inside temperature detected by the temperature sensor (124)
that a request for a shift to the freezer thermo-on state is not
raised (NO in ST131) or the R2 signal is turned off (NO in ST133),
the freezer electromagnetic valve (121) remains closed (ST132) and
the process is ended. If the request for a shift to the freezer
thermo-on state is raised and the R2 signal is turned on (YES in
ST131 and ST133), the freezer electromagnetic valve (121) is opened
(ST134) and the process is ended.
[0091] As shown in FIG. 8, in the control process for
actuating/suspending the booster compressor executed by the control
section (120) of the freezer unit (12), if a request for a shift to
the freezer thermo-on state is not raised (NO in ST141) or the R2
signal is turned off (NO in ST143), the booster compressor (131) is
suspended (ST142) and the process is ended. If the request for a
shift to the freezer thermo-on state is raised and the R2 signal is
turned on (YES in ST141 and ST143), the booster compressor (131) is
actuated (ST144) and the process is ended.
[0092] In general, the freezer electromagnetic valve (121) is
opened by the control process for opening/closing the freezer
electromagnetic valve. Then, when the refrigerant is allowed to
circulate in the refrigeration circuit, the refrigerant suction
pressure of the variable capacity compressor (141) increases and
the variable capacity compressor (141) is actuated according to the
judgment made in ST113 for the control of the thermo-on state.
However, if the outside air temperature is low, the refrigerant
suction pressure hardly increases and the variable capacity
compressor (141) cannot be actuated.
[0093] In such a state, the refrigeration system (1) actuates the
booster compressor (131) by the control process for
actuating/suspending the booster compressor. Accordingly, the
variable capacity compressor (141) increases in refrigerant suction
pressure. As a result, the variable capacity compressor (141) is
surely actuated according to the judgment made in ST113 for the
control of the thermo-on state. Thus, according to the control
processes, the variable capacity compressor (141) is smoothly
actuated even if the outside air temperature is low.
[0094] Now, refrigeration systems (2) and (3) which are second and
third embodiments of the present invention will be explained. The
refrigeration systems (2, 3) are substantially the same as the
refrigeration system of the first embodiment except that the
freezer unit and the booster unit are omitted. In the explanation
of the refrigeration systems (2, 3), the same components as those
of the refrigeration system (1) of the first embodiment are
indicated by the same reference numerals to omit specific
explanation.
[0095] FIG. 9 is a view illustrating how the refrigeration system
(2) enters the cold storage thermo-on state under a low outside air
temperature.
[0096] In the refrigeration system (2), when a guard timer of a
compressor (241) expires, an R1 signal from a control section (240)
of an outdoor unit (24) to a control section (210) of a cold
storage unit (21) is turned on (Action I). If the control section
(210) of the cold storage unit (21) recognizes that a request for a
shift to the cold storage thermo-on state is raised according to
the value of the inside temperature detected by a temperature
sensor (214) (Action II), an electromagnetic valve (211) is opened
(Action III).
[0097] When the outside air temperature detected by a temperature
sensor (245) is low, a threshold value of the refrigerant suction
pressure which is a criterion for judging whether to actuate the
compressor (241) or not is reduced (Action IV). Then, if the
refrigerant suction pressure detected by a pressure sensor (246)
reaches the reduced threshold value (Action V), the compressor
(241) is actuated (Action VI).
[0098] The control as described above is explained in detail with
reference to FIGS. 10 and 11.
[0099] FIG. 10 is a block diagram schematically illustrating the
major structure of a control program for entering an outdoor unit
thermo-on state executed by the control section (240) of the
outdoor unit (24). Specifically, the control section (240) executes
a control program for entering the thermo-on state as shown in FIG.
11 and the control section (210) of the cold storage unit (21)
executes the same control program for opening/closing the
electromagnetic valve as that shown in FIG. 6.
[0100] The control section (240) of the outdoor unit (24) includes
an electromagnetic valve open/close permission section (2401), a
compressor actuating condition changing section (2402), a
compressor actuating condition judging section (2403) and a
compressor actuating section (2404).
[0101] When the guard timer of the compressor (241) expires, the
electromagnetic valve open/close permission section (2401) turns on
an R1 signal for permitting the electromagnetic valve (211) to
open. The compressor actuating condition changing section (2402)
reduces the threshold value of the refrigerant suction pressure for
actuating the compressor (241) based on the outside air temperature
Ta detected by the temperature sensor (245). The compressor
actuating condition judging section (2403) judges as to whether or
not the refrigerant suction pressure LP detected by the pressure
sensor (246) is within the predetermined range. The compressor
actuating section (2404) actuates the compressor (241) when the
refrigerant suction pressure LP is within the predetermined
range.
[0102] The control section (210) of the cold storage unit (21)
includes a cooling request judging section (2101) for judging as to
whether or not a request for a shift to the cold storage thermo-on
state is raised and whether or not the R1 signal is turned on and
an electromagnetic valve opening/closing section (2102) for opening
the electromagnetic valve (211) when the request for a shift to the
cold storage thermo-on state is raised and the R1 signal is turned
on.
[0103] In this case, the compressor actuating condition judging
section (2403) and the compressor actuating section (2404) function
as an operation control means for switching the compressor (241)
between actuated state and suspended state. Further, the compressor
actuating condition changing section (2402) functions as a
reference value changing means for reducing the threshold value of
the refrigerant suction pressure which is a criterion for judging
whether to actuate the compressor (241) or not when the outside air
temperature is lower than the predetermined temperature.
[0104] According to the programs executed by the control sections
(210, 240), even if the refrigerant suction pressure of the
compressor (241) is reduced because of the low outside air
temperature, the compressor (241) is actuated without fail by
reducing the threshold value of the refrigerant suction pressure.
More specifically, the following processes are executed. The
process of controlling the opening/closing of the cold storage
electromagnetic valve by the control section (210) of the cold
storage unit (21) is not explained below because it is the same as
that shown in FIG. 6.
[0105] As shown in FIG. 11, in the control process for entering the
thermo-on state executed by the control section (240) of the
outdoor unit (24), judgment is made as to whether or not the guard
timer of the compressor (241) has expired (ST201). If the guard
timer has not expired (NO in ST201), the process is ended. If the
guard timer has expired (YES in ST201), the R1 signal is turned on
to permit the cold storage electromagnetic valve (211) to open
(ST202).
[0106] Subsequently, judgment is made as to whether or not the
refrigerant suction pressure LP of the compressor (241) is higher
than 0.4 MPa (ST203). If the refrigerant suction pressure LP is
higher than 0.4 MPa (YES in ST203), the compressor (241) is
actuated and the process is ended.
[0107] If the refrigerant suction pressure LP is not higher than
0.4 MPa (NO in ST204), judgment is made as to whether or not the
outside air temperature Ta is lower than 0.degree. C. and whether
or not the refrigerant suction pressure LP is higher than 0.25 MPa
(ST205). If these conditions are met (YES in ST205), the compressor
(241) is actuated in ST204 and the process is ended.
[0108] If the conditions presented in ST205 are not met, i.e., if
the outside air temperature Ta is 0.degree. C. or higher or the
refrigerant suction pressure LP is not higher than 0.25 MPa (NO in
ST205), judgment is made as to whether or not the outside air
temperature Ta is lower than -5.degree. C. and whether or not the
refrigerant suction pressure LP is higher than 0.2 MPa (ST206). If
these conditions are met (YES in ST206), the compressor (241) is
actuated in ST204 and the process is ended. If the outside air
temperature Ta is not lower than -5.degree. C. or the refrigerant
suction pressure LP is not higher than 0.2 MPa (NO in ST206), the
process is ended without actuating the compressor (24).
[0109] In these processes, when the RI signal is turned on in ST202
and the request for a shift to the cold storage unit (21) to the
thermo-on state is raised, the cold storage electromagnetic valve
(211) is opened. However, if the outside air temperature is low,
the refrigerant suction pressure of the compressor (241) remains
low even if the electromagnetic valve (211) is opened. Then, the
threshold value of the refrigerant suction pressure at which the
compressor (241) is actuated is reduced in stages from 0.4 MPa to
0.25 MPa and then to 0.2 MPa in response to the reduction in
outside air temperature from a certain reference temperature to
0.degree. C. and then to -5.degree. C., thereby allowing the
actuation of the compressor (241). According to these control
processes, the compressor (241) is smoothly actuated even if the
outside air temperature is low.
[0110] FIG. 12 is a view illustrating how the refrigeration system
(3) enters the cold storage thermo-on state under a low outside air
temperature.
[0111] In the refrigeration system (3), when a guard timer of a
compressor (341) expires, an R1 signal from a control section (340)
of an outdoor unit (34) to a control section (310) of a cold
storage unit (31) is turned on (Action I). If the control section
(310) of the cold storage unit (31) recognizes from the inside
temperature detected by a temperature sensor (314) that a request
for a shift to the cold storage thermo-on state is raised (Action
II), an electromagnetic valve (311) is opened (Action III).
[0112] When the outside air temperature is low, the saturation
pressure of the refrigerant is reduced. Therefore, the refrigerant
suction pressure of the compressor (341) remains low even if the
cold storage electromagnetic valve (311) is opened. In such a case,
when the outside air temperature is detected low (Action IV), the
refrigeration system (3) begins open phase power supply to a motor
of the compressor (341) (Action V). The open phase power supply is
to apply electric current to the motor while one of three phase
currents is blocked such that the coil of the motor generates heat
without rotating the motor.
[0113] According to the open phase power supply, the refrigerant in
the suspended compressor (341) raises its temperature, thereby
increasing the saturation pressure of the refrigerant near the
suction port of the compressor (341). Accordingly, the refrigerant
suction pressure detected by a pressure sensor (346) increases.
Thus, if the predetermined pressure condition is met (Action VI),
the compressor (341) is actuated (Action VII).
[0114] The control by the refrigeration system (3) is explained
with reference to FIGS. 13 and 14.
[0115] FIG. 13 a block diagram schematically illustrating the major
structure of a control program for entering the thermo-on state
executed by the control section (340) of the outdoor unit (34). The
control section (340) of the outdoor unit (34) executes a control
program for entering the thermo-on state as shown in FIG. 14 and
the control unit (310) of the cold storage unit (31) executes the
same control program for opening/closing the cold storage
electromagnetic valve as that shown in FIG. 6.
[0116] The control section (340) of the outdoor unit (34) includes
an electromagnetic valve open/close permission section (3401), an
open phase power supply instructing section (3402), a compressor
actuating condition judging section (3403) and a compressor
actuating section (3404).
[0117] When the guard timer of the compressor (341) expires, the
electromagnetic valve open/close permission section (3401) turns on
an R1 signal for permitting the cold storage electromagnetic valve
(311) to open. The open phase power supply instructing section
(3402) instructs open phase power supply based on the outside air
temperature Ta detected by the temperature sensor (345). The
compressor actuating condition judging section (3403) judges as to
whether or not the refrigerant suction pressure LP detected by the
pressure sensor (346) is within the predetermined range. The
compressor actuating section (3404) actuates the compressor (341)
when the refrigerant suction pressure LP is within the
predetermined range.
[0118] Similarly to the refrigeration system (1) of the first
embodiment, the control section (310) of the cold storage unit (31)
includes a cooling request judging section (3101) for judging as to
whether or not a request for a shift to the cold storage thermo-on
state is raised and whether or not the R1 signal is turned on and
an electromagnetic valve opening/closing section (3102) for opening
the electromagnetic valve (311) when the request for a shift to the
cold storage thermo-on state is raised and the R1 signal is turned
on.
[0119] In this case, the compressor actuating condition judging
section (3403) and the compressor actuating section (3404) function
as an operation control means for switching the compressor (341)
between actuated state and suspended state. Further, the open phase
power supply instructing section (3404) functions as a power supply
control means for supplying open phase current to a motor of the
compressor (341) when the compressor (341) is suspended, the
outside air temperature is lower than a predetermined temperature
and the request for a shift to the cold storage thermo-on state is
raised such that the refrigerant suction pressure increases.
[0120] Thus, when the refrigerant suction pressure of the
compressor (341) remains low because of the low outside air
temperature even if the cold storage electromagnetic valve (311) is
opened, the programs executed by the control sections (310, 340)
make it possible to forcibly increase the refrigerant suction
pressure of the compressor (341) by applying open phase current to
the motor of the compressor (341). More specifically, the following
processes are executed. The control process for opening/closing the
cold storage electromagnetic valve executed by the control section
(310) of the cold storage unit (31) is not explained below because
it is the same as that shown in FIG. 6.
[0121] As shown in FIG. 14, in the control process for entering the
thermo-on state executed by the control section (340) of the
outdoor unit (34), judgment is made as to whether or not the guard
timer of the compressor (341) has expired (ST301). If the guard
timer has not expired (NO in ST301), the process is ended. If the
guard timer has expired (YES in ST301), the R1 signal is turned on
to permit the cold storage electromagnetic valve (311) to open
(ST302).
[0122] Subsequently, judgment is made as to whether or not the
refrigerant suction pressure LP of the compressor (341) is higher
than 0.25 MPa (ST303). If the refrigerant suction pressure LP is
higher than 0.25 MPa (YES in ST303), the open phase power supply is
prohibited and normal power supply is selected (ST304). Then, the
compressor (341) is actuated (ST305) and the process is ended.
[0123] If the refrigerant suction pressure LP is not higher than
0.25 MPa (NO in ST303), judgment is made as to whether or not the
outside air temperature Ta is lower than -5.degree. C. and whether
or not the open phase power supply has continued for 5 minutes or
more (ST306). If the outer temperature Ta is not lower than
-5.degree. C. and the open phase power supply has continued for
less than 5 minutes (NO in ST306), judgment is made as to whether
the outside air temperature Ta is lower than -5.degree. C. and
whether or not the suspension time of the compressor (341) is not
shorter than 5 minutes (ST307).
[0124] In ST307, if the outside air temperature Ta is lower than
-5.degree. C. and the suspension time of the compressor (341) is
not shorter than 5 minutes (YES in ST307), the open phase power
supply is permitted (ST308) and the process returns to ST301 (back
to the beginning). Then, the process goes through ST301 to ST303
and judgment is made again as to whether or not the refrigerant
suction pressure LP of the compressor (341) is higher than 0.25
MPa. If the refrigerant suction pressure LP is raised higher than
0.25 MPa (YES in ST303) by the open phase power supply, the open
phase power supply is prohibited (ST304) and the compressor (341)
is actuated (ST305) as described above. Thus, the process is
ended.
[0125] Specifically, in ST307, if the outer temperature Ta is lower
than -5.degree. C. and the compressor (341) has passed 5 minutes
since it entered the thermo-off state, it is recognized that the
temperature of the refrigerant in the compressor (341) is
significantly reduced. Accordingly, the open phase power supply is
carried out.
[0126] In ST303, if the refrigerant suction pressure LP is not
higher than 0.25 MPa even if the open phase power supply is carried
out (NO in ST303), judgment is made again in ST306 as to whether or
not the outside air temperature Ta is lower than -5.degree. C. and
whether or not the open phase power supply has continued for 5
minutes or more. If these conditions are met (YES in ST306), the
process goes through ST304 and ST305 to actuate the compressor
(341). Then, the process is ended. Conversely, if these conditions
are not met (NO in ST306), the process returns to ST307.
Specifically, in ST306, the compressor (341) is actuated as long as
the open phase power supply has been carried out for a certain
period of time to raise the refrigerant suction pressure LP to some
degree, though the refrigerant suction pressure LP has not reached
the predetermined value due to the low outside air temperature.
[0127] In ST307, if the outside air temperature is not lower than
-5.degree. C. or the suspension time of the compressor (341) is
less than 5 minutes (NO in ST307), the open phase power supply is
not permitted and the process returns to ST301 (back to the
beginning). After that, the process goes through the steps in the
same manner as described above.
[0128] In these processes, the cold storage electromagnetic valve
(311) is opened when the R1 signal is turned on in ST302 and the
request for a shift to the cold storage thermo-on state is raised.
If the outside air temperature is low, the refrigerant suction
pressure of the compressor (341) remains low. However, if the open
phase current is supplied to the motor of the compressor (341), the
refrigerant suction pressure of the compressor (341) is forcibly
raised, thereby actuating the compressor (341) without fail.
[0129] In the above-described embodiments, the refrigeration system
uses the temperature sensor (145, 245, 345) to detect the outside
air temperature directly for recognizing the temperature reduction.
However, in addition to use of the temperature sensor, the
temperature of the refrigerant may also be detected near the
discharge port of the high pressure dome-shaped compressor (141,
241, 341). In this case, if a refrigerant temperature not higher
than 20.degree. C. detected near the discharge port is regarded as
an indication of low outside air temperature, the reduction in
outside air temperature is surely detected even if one of the two
temperature sensors is broken.
[0130] In the refrigeration system (1, 2, 3) of the above-described
embodiments, the electromagnetic valve and the expansion valve are
used to control the amount of a refrigerant flow in the cold
storage unit (11, 21, 31) and the freezer unit (12). However, these
valves may be replaced with other valves such as an electronic
expansion valve such that the valve is opened in the thermo-on
state. Just like the use of the electromagnetic valve described
above, the use of the electronic expansion valve also makes the
refrigerant circulate in the circuit by merely actuating the
compressor.
[0131] it should be understood that the above-described embodiments
are essentially preferable examples of the present invention and do
not limit the present invention, application thereof and the range
of application.
INDUSTRIAL APPLICABILITY
[0132] As described above, the present invention is useful for a
refrigeration system including a compressor which is switchable
between actuated state and suspended state.
* * * * *