JP3042506B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system having a refrigerant circuit constituting a vapor compression refrigeration cycle, and more particularly to measures for improving the reliability of a compressor.

[0002]

2. Description of the Related Art Conventionally, a refrigerating apparatus having a refrigerant circuit constituting a vapor compression type refrigerating cycle and performing a refrigerating operation is well known. This type of refrigerant circuit is disclosed in
As disclosed in Japanese Patent Publication No. 26739, a compressor generally includes a compressor, a condenser, an expansion valve, and an evaporator connected in this order.

As shown in FIG. 7, a known refrigerant circuit is provided with a compression mechanism (b) formed by connecting two totally hermetic rotary compressors (a, a) in parallel. ing. This type of refrigerant circuit is formed by sequentially connecting the compression mechanism (b), the condenser (c), the expansion valve (d), and the evaporator (e). The compression mechanism (b) switches between an operation for driving both compressors (a, a) and an operation for driving only one of the compressors (a) and stopping the other. The capacity of (b) can be switched in two stages.

Further, the compression mechanism (b) includes an oil equalizing pipe (f) connected to the housing of each compressor (a, a), and lubricating oil stored in the housing of each compressor (a, a). Is made uniform. That is, lubricating oil is discharged from the compressor (a, a) together with the discharged gas refrigerant. The discharged lubricating oil flows through the refrigerant circuit and returns to the compressor together with the low-pressure gas refrigerant. For this reason, the amount of lubricating oil stored in the housing of the compressor is maintained at a certain level or more.

On the other hand, the compression mechanism (b) is composed of two compressors (a, a). Both compressors (a, a)
Have the same capacity, but the capacity of both compressors (a, a) does not completely match, and there is some individual difference. Therefore, even when both compressors (a, a) are operated at the maximum capacity, the amount of the lubricating oil discharged and the amount of the lubricating oil returned are the same for each compressor (a, a). different. Therefore, the amount of the lubricating oil stored in the housings of the two compressors (a, a) is not uniform, and the lubricating oil is biased to one of the compressors (a).

On the other hand, in the compression mechanism (b),
The oil equalizing operation is performed every predetermined operation time, and both compressors (a,
a) The amount of lubricating oil in the housing is made uniform. Specifically, an operation of driving one compressor (a) and stopping the other compressor (a) is performed for a predetermined time, for example, one minute. Thereafter, an operation of stopping one of the driven compressors (a) and driving the other of the stopped compressors (a) is performed for a predetermined time. By this operation, the lubricating oil discharged from the compressor (a, a) together with the discharge gas and accumulated in the refrigerant circuit is collected, and the lubricating oil is passed through the oil equalizing pipe (f) between the two compressors (a, a). And the two compressors (a,
The amount of lubricating oil in the housing a) is made equal.

[0007] In addition, a refrigeration apparatus is conventionally known which is configured to exchange heat between refrigerant in the refrigerant circuit and water or refrigerant outside the circuit in the evaporator of the refrigerant circuit. For example, Japanese Patent Application Laid-Open No. 9-210515 discloses this type of refrigeration apparatus.
There is a binary refrigeration apparatus as disclosed in Japanese Unexamined Patent Publication (Kokai) Publication.

In this binary refrigeration apparatus, a high-temperature side circuit and a low-temperature side circuit are connected via a cascade condenser, and both circuits are constituted by a refrigerant circuit performing a vapor compression type refrigeration cycle operation. . And the evaporator of the low-temperature side circuit is installed inside a freezing warehouse or the like, and the evaporator exchanges heat between the refrigerant of the low-temperature side circuit and the air in the refrigerator, cools the air in the refrigerator, and reduces the temperature in the refrigerator. For example, it is maintained at minus several tens degrees.

In the above-mentioned two-way refrigeration system, the high-temperature side circuit is the refrigerant circuit referred to here, and the cascade condenser is formed in the evaporator of the high-temperature side circuit. In the cascade condenser, heat is exchanged between the refrigerant in the high-temperature side circuit and the refrigerant in the low-temperature side circuit. As this kind of cascade condenser, a so-called double tube heat exchanger is often used, but a plate heat exchanger formed by laminating a number of heat transfer plates may be used.

[0010]

However, in a refrigeration system having a compression mechanism composed of a plurality of compressors, as described above, the compressor is stopped when the capacity of the compression mechanism is changed or the oil leveling operation is performed. Therefore, there is a problem that the reliability of the compressor is reduced. That is, when the compressor is started, it always goes through a transient state and then enters a steady operation state. In this transient state, liquid back and the like are likely to occur, and the possibility of damage to the compressor increases. Specifically, it is said that 70 to 80% of troubles related to the compressor occur in a transient state after starting. On the other hand, in the refrigerating apparatus, the compressor is frequently stopped and started not only at the time of starting or stopping the apparatus, but also during the operation state of the apparatus. Therefore, there is a problem that the chance that the compressor is operated in a transient state at the time of starting is increased, and the probability of occurrence of trouble of the compressor is increased.

On the other hand, it is conceivable to reduce the number of start-ups of the compressor by reducing the frequency of the oil equalizing operation. However, in this case, a sufficient amount of lubricating oil cannot be secured in each compressor. This increases the risk of seizure due to poor lubrication. Also, since only one of the compressors is driven to set the compression mechanism to an intermediate capacity,
Uneven oil occurs between the driven compressor and the stopped compressor,
This may also cause poor lubrication.

Furthermore, when a plate-type heat exchanger is used as an evaporator in the refrigerant circuit, there is a problem that the reliability of the compressor is reduced due to the use of the plate-type heat exchanger. In other words, no matter what type of heat exchanger is used as the evaporator, the liquid refrigerant normally flows in from the lower part of the heat exchanger, evaporates and flows out from the upper part of the heat exchanger. It is. For this reason, generally, in the evaporator, the lubricating oil that has flowed in along with the liquid refrigerant is likely to be accumulated inside the evaporator. On the other hand, in the plate heat exchanger, the refrigerant is caused to flow through a flow passage defined between a number of stacked heat transfer plates. For this reason, the plate-type heat exchanger has a larger cross-sectional area of the flow passage than the double-tube heat exchanger and the like, and the flow velocity of the refrigerant in the flow passage becomes slow. Therefore, when a plate-type heat exchanger is used as an evaporator, the problem that lubricating oil easily accumulates inside the evaporator becomes significant. When a large amount of lubricating oil accumulates in the evaporator, the amount of lubricating oil stored in the compressor decreases, and there is a problem that the risk of seizure due to poor lubrication increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably prevent poor lubrication in a compressor and improve the reliability of the compressor.

[0014]

SUMMARY OF THE INVENTION According to the present invention, poor lubrication of a compressor is prevented by always maintaining the amount of lubricating oil held by the compressor at a predetermined level or more.

[0015] Specifically, the first and second solving means of the present invention include a compressor means (80) comprising a plurality of variable capacity compressors (21a, 21b) connected in parallel, and a condenser means (80). Container (22),
It is premised on a refrigeration apparatus having a refrigerant circuit (20) formed by connecting an expansion mechanism (EV12) and an evaporator (11) in order.
One end is connected to the housing of one compressor (21a, 21b), and the other end is connected to the housing of another compressor (21a, 21b). All compressors (21a, 21a,
21b) Oil equalizer pipes (47,47a,
47b) and a distribution in which one of the plurality of compressors (21a, 21b) is operated with a maximum capacity and the remaining compressors (21a, 21b) are operated with a small capacity smaller than the maximum capacity for a predetermined time. The oil equalizing operation means (71) which switches the compressors (21a, 21b) operated at the maximum capacity and performs the predetermined number of times so that each compressor (21a, 21b) has the maximum capacity at least once. It is provided.

Further, a first solution is to add to the above configuration.
An unload passage (45, 45a, 45b) for returning a part of the gas refrigerant discharged from the compressor (21, 21a, ...) to the suction side of the compressor (21, 21a, ...); Passage (45,45a, 45
b) Unloading passage opening / closing means (SV1, SV1a, SV1
b), the compressor (21, 21a,...) is connected to the unload passages (45, 45a,.
45b) closes to full capacity and unload aisle (45,
45a, 45b), the capacity becomes small and the capacity is variable.

Further , a second solution is to add to the above configuration.
In addition, while the refrigerant circuit (20) is configured as a high-temperature side refrigeration circuit (20), the compressor (31, 31), the condenser (11), the expansion mechanism (EV21) and the evaporator (50) are connected in order. Low-temperature refrigeration circuits (3A, 3B). The condenser (11) of the low-temperature refrigeration circuit (3A, 3B) is connected to the high-temperature refrigeration circuit (2
0) is formed integrally with the evaporator (11) to form a cascade condenser (11,11), and the low-temperature side refrigeration circuit (3A, 3B)
And the high-temperature side refrigeration circuit (20) into a two-stage refrigeration cycle for exchanging heat between the refrigerant of the high-temperature side refrigeration circuit (20) and the refrigerant of the low-temperature side refrigeration circuit (3A, 3B) in the cascade condensers (11, 11). Make up.

A third solution taken by the present invention is a compressor means (80) comprising a plurality of variable capacity compressors (21a, 21b) connected in parallel; a condenser (22); Mechanism (EV12)
And a refrigerant circuit (20) formed by connecting an evaporator (11) in sequence
Is assumed. Then, a capacity control means (A) that adjusts the capacity of the compressors (21a, 21b) to change the capacity of the compressor means (80) so that both the compressors (21a, 21b) are continuously operated. 72).

A fourth solution taken by the present invention is a variable capacity compressor (21), a condenser (22), and an expansion mechanism (EV1).
2) and a refrigerant circuit (2
0) is assumed. The evaporator (11) is constituted by a plate-type heat exchanger formed by stacking a number of heat transfer plates, while the compressor (21) is operated for a small capacity smaller than the maximum capacity for a predetermined time. Continuing the above, the oil return operation means (73) for temporarily collecting the lubricating oil accumulated in the refrigerant circuit (20) to the compressor (21) with the compressor (21) temporarily set to the maximum capacity Is provided.

The fifth solution taken by the present invention is the fifth solution .
In the third or fourth solution, the compressor (21, 21a,...)
Open and close the unload passages (45, 45a, 45b) and the unload passages (45, 45a, 45b) for returning a part of the gas refrigerant discharged from the compressor to the suction side of the compressor (21, 21a,...). Unload circuit (4) having unload passage opening / closing means (SV1, SV1a, SV1b)
6,46a, 46b). Then, the compressor (21, 21a,
..) Have a maximum capacity when the unload passages (45, 45a, 45b) are closed, and have a small capacity when the unload passages (45, 45a, 45b) are opened, so that the capacity is variable.

The sixth solution taken by the present invention is as follows .
In the third or fourth solution, while the refrigerant circuit (20) is configured as a high-temperature side refrigeration circuit (20), the compressor (31,3)
1), condenser (11), expansion mechanism (EV21) and evaporator (5
0) are connected in order to provide a low-temperature refrigeration circuit (3A, 3B). Then, the condenser (1) of the low temperature side refrigeration circuit (3A, 3B)
1) is formed integrally with the evaporator (11) of the high-temperature side refrigeration circuit (20) to constitute a cascade condenser (11, 11), and the low-temperature side refrigeration circuit (3A, 3B) and the high-temperature side refrigeration circuit (2
0) is configured as a dual refrigeration cycle in which the cascade condensers (11, 11) exchange heat with the refrigerant in the high-temperature refrigeration circuit (20) and the refrigerant in the low-temperature refrigeration circuit (3A, 3B).

-Operation- In the first and second solving means, each compressor (21a, 21b)
The high-pressure gas refrigerant discharged from is discharged and condensed in the condenser (22). This liquid refrigerant is used for expansion mechanism (EV12)
After the pressure is reduced by, heat is absorbed by the evaporator (11) to evaporate. Thereafter, the low-pressure gas refrigerant is sucked into the compressors (21a, 21b) and repeats this circulation. As described above, the refrigerant circuit (20) performs a vapor compression refrigeration cycle operation.

On the other hand, even if the design capacity of each of the compressors (21a, 21b) is equal, the actual compressors (21a, 21b)
The dimensional accuracy of the component parts is different in each compressor.
There is an individual difference in the capacity of b). Therefore, all compressors (2
1a, 21b) at the maximum capacity, each compressor (2a, 21b) may have a different capacity due to individual differences in the capacity of each compressor (21a, 21b).
1a, 21b), so-called uneven oil, which is an uneven amount of lubricating oil stored in the housing. On the other hand, in the present solution, the oil equalizing operation means (71) performs a predetermined distribution operation on each of the compressors (21a, 21b). By this distribution operation, the lubricating oil flows in the oil equalizing pipes (47, 47a, 47b), and the uneven oil is eliminated so that the amount of the lubricating oil held by each compressor (21a, 21b) is made uniform.

Further, in the first solving means, the following operation is performed.
Run a business. It should be noted that the operation of the fifth solving means is also
Same as this. Then, in the first and fifth solving means,
Is a gas refrigerant flowing from the compressors (21, 21a,...) To the condenser (22) by opening and closing the unload passages (45, 45a, 45b) by unload passage opening and closing means (SV1, SV1a, SV1b). The amount was changed, which caused the compressor (21, 21a,
...) are configured to be variable in capacity.

In the second solution, the following operation is performed.
Run a business. It should be noted that the operation of the sixth solving means is also
Same as this. Then, in the second and sixth solving means,
Are the low-temperature refrigeration circuits (3A, 3B) and the high-temperature refrigeration circuits (20)
And are connected via cascade capacitors (11,11),
A binary refrigeration cycle is configured in which heat absorbed by the evaporator (50) of the low-temperature refrigeration circuit (3A, 3B) is radiated by the condenser (22) of the high-temperature refrigeration circuit (20).

Specifically, the high-pressure gas refrigerant discharged from the compressor (31, 31) of the low-temperature side refrigeration circuit (3A, 3B) is supplied to the condenser (11) provided in the cascade condenser (11, 11).
Flows to The gas refrigerant that has flowed into the condenser (11) radiates heat by heat exchange with the refrigerant in the high-temperature side refrigeration circuit (20), condenses, and then flows into the receiver (34). The liquid refrigerant in the receiver (34) flows to the expansion mechanism (EV21), and the expansion mechanism (EV21)
After being depressurized in, heat is absorbed by the evaporator (50) to evaporate. Thereafter, the low-pressure gas refrigerant is sucked into the compressor (31, 31) and repeats this circulation.

On the other hand, the compressor (2) of the high-temperature side refrigeration circuit (20)
The high-pressure gas refrigerant discharged from (1, 21a,...) Flows to the condenser (22). The gas refrigerant flowing to the condenser (22) radiates heat and condenses by heat exchange with a cooling medium such as air.
The refrigerant condensed in the condenser (22) flows to the expansion mechanism (EV12), and after being decompressed by the expansion mechanism (EV12), flows to the evaporator (11) provided in the cascade condensers (11, 11).
The refrigerant flowing to the evaporator (11) is sent to the low-temperature side refrigeration circuit (3A, 3A).
It absorbs heat by heat exchange with the refrigerant of B) and evaporates. Thereafter, the low-pressure gas refrigerant is sucked into the compressors (21, 21a,...) And repeats this circulation.

Therefore, the heat absorbed by the refrigerant of the low-temperature refrigeration circuit (3A, 3B) in the evaporator (50) of the low-temperature refrigeration circuit (3A, 3B) is transferred to the low-temperature refrigeration circuit of the cascade condenser (11, 11). (3A, 3B) refrigerant and high temperature side refrigeration circuit (2
0) is given to the refrigerant in the high-temperature refrigeration circuit (20) by heat exchange with the refrigerant, and then radiated from the refrigerant in the high-temperature refrigeration circuit (20) in the condenser (22) of the high-temperature refrigeration circuit (20). You.

[0029] In the third solution, the refrigerant circuit (20) may include the refrigerant circuit (20) of the first and second solutions.
, And performs a vapor compression refrigeration cycle operation. On the other hand, in the present solution, the capacity control means (72) adjusts the capacity of each compressor (21a, 21b) to change the capacity of the compressor means (80).

[0030] In the fourth solution, the refrigerant circuit (20) is the same as the refrigerant circuit (20) of the first or the second solution.
, And performs a vapor compression refrigeration cycle operation. In the present solution, the number of compressors may be one or more.

On the other hand, a plate type heat exchanger is used for the evaporator (11) of the refrigerant circuit (20) of the present invention. Therefore, the lubricating oil discharged together with the gas refrigerant from the compressor (21) is likely to accumulate in the plate heat exchanger. In particular, when the compressor (21) is operated with a small capacity, the amount of refrigerant circulating in the refrigerant circuit (20) decreases, and the flow velocity of the refrigerant inside the plate heat exchanger decreases. Therefore, the lubricating oil accumulated in the plate heat exchanger is hardly recovered by the compressor (21), and the amount of lubricating oil held by the compressor (21) decreases. On the other hand, in the present solution, when the operation of the compressor (21) with a small capacity is performed for a predetermined time or more, the oil return means temporarily operates the compressor (21) with the maximum capacity. Thereby, the lubricating oil collected in the refrigerant circuit (20) including the plate-type heat exchanger is recovered by the compressor (21),
The amount of lubricating oil held by the compressor (21) is maintained at or above a predetermined amount.

[0032]

According to the first and second solutions, each compressor (21a, 21b) is operated by the operation of the oil equalizing means (71).
The uneven oil distribution between the compressors (21a, 21b) can be eliminated, and the amount of lubricating oil stored in the housing of each compressor (21a, 21b) can be made uniform. As a result, it is possible to reliably prevent poor lubrication of the compressors (21a, 21b) due to oil imbalance between the compressors (21a, 21b),
The reliability of the compressors (21a, 21b) can be improved.

Further, according to the oil equalizing operation means (71) of the present invention, all the compressors (21a, 21b) are continuously operated without stopping any of the compressors (21a, 21b). In addition, uneven oil can be eliminated and oil leveling can be performed. As a result, the number of times of starting the compressors (21a, 21b) can be reduced, and the reliability of the compressors (21a, 21b) can also be improved.

According to the third solution, the capacity of each compressor (21a, 21b) is changed by adjusting the capacity of each compressor (21a, 21b).
b) It is possible to reduce uneven oil distribution between the two. That is,
Conventionally, the capacity of the compressor means (80) has been changed by changing the number of compressors to be operated, so that the compressor in the operating state and the compressor in the stopped state are mixed. On the other hand, in the present solution, the capacity of the compressors (21a, 21b) is adjusted while each compressor (21a, 21b) is maintained in the operating state. For this reason, the capacity difference between the compressors (21a, 21b) during operation is reduced, and the compressors (21a, 21b) caused by the capacity difference are reduced.
Oil deviation between them can be reduced. As a result, poor lubrication of the compressors (21a, 21b) due to oil imbalance between the compressors (21a, 21b) can be reliably prevented, and the compressors (21a, 21b)
b) The reliability can be improved.

According to the capacity control means (72) of the present invention, all the compressors (21a, 21b) are continuously operated without stopping any of the compressors (21a, 21b). Meanwhile, the capacity of the compressor means (80) can be changed.
As a result, the number of times of starting the compressors (21a, 21b) can be reduced, and the reliability of the compressors (21a, 21b) can also be improved.

[0036] According to the fourth solution, in the refrigerant circuit (20) using the plate-type heat exchanger as the evaporator (11), the operation of the compressor (21) with a small capacity continues. Even so, the lubricating oil in the refrigerant circuit (20) including the plate-type heat exchanger can be reliably collected in the compressor (21) by the oil return means. As a result, poor lubrication of the compressor (21) due to a decrease in lubricating oil held by the compressor (21) can be reliably prevented, and the reliability of the compressor (21) can be improved.

According to the first and fifth solving means, the unloading circuit (46, 46a, 46b) having a simple structure is connected to the compressor (21, 2).
1a,...), The capacity of the compressors (21, 21a,...) Can be made variable. Therefore, the compressor (21, 21
a, ...) without complicating the structure of the compressor (21,21).
a, ...) can be configured to have variable capacity.

According to the second and sixth solutions, the low-temperature refrigeration circuit (3A, 3B) and the high-temperature refrigeration circuit (20) are connected via the cascade capacitors (11, 11). I have. For this reason, the evaporation temperature of the refrigerant in the evaporator (50) of the low-temperature refrigeration circuits (3A, 3B) can be reduced as compared with the case where one refrigerant circuit is provided. Therefore, the object to be cooled can be cooled to a low temperature state (for example, about several tens of degrees Celsius) by the evaporator (50) of the low-temperature side refrigeration circuit (3A, 3B), and the application range of the refrigeration apparatus is expanded. be able to.

[0039]

Embodiment 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the binary refrigeration system (10) cools a refrigerator or a freezer.
An outdoor unit (1A), a cascade unit (1B), and a cooling unit (1C) are provided. The outdoor unit (1A) and a part of the cascade unit (1B) constitute a high-temperature refrigeration circuit (20). Also,
Two low-temperature side refrigeration circuits (3A, 3B) are constituted by the cascade unit (1B) and the cooling unit (1C).

The high-temperature side refrigeration circuit (20) is configured to be capable of reversible operation by switching the refrigerant circulation direction between a forward cycle and a reverse cycle. And the high temperature side refrigeration circuit (20)
Is a compressor mechanism (80) as a compressor means, and a condenser (22)
And an evaporator of two refrigerant heat exchangers (11, 11). The evaporator of the refrigerant heat exchanger (11, 11) constitutes an evaporator of the high-temperature refrigeration circuit (20).

The compression mechanism (80) includes a first compressor (21)
a) and the second compressor (21b) are connected in parallel. Specifically, each compressor (21a, 21b) is a hermetic rotary compressor. The suction sides of the compressors (21a, 21b) are connected to each other by a suction-side pipe (81). A first oil separator (23a) and a second oil separator (23b) are connected to the discharge side of each compressor (21a, 21b), respectively, while both oil separators (23a, 23b) are connected. Are connected to each other by a discharge side pipe (82). An oil return passage (44) having a capillary tube (CP) is provided between each of the oil separators (23a, 23b) and the suction side of each of the compressors (21a, 21b). Each of the above compressors (21a,
A high pressure switch (HPS1a, HPS1b) that outputs an off signal when the high pressure refrigerant pressure excessively rises to a predetermined high pressure value is provided between each of the oil separators (23a, 23b). Have been.

A first unload circuit (46a) and a second unload circuit (46b) are connected to the compressors (21a, 21b), respectively. And both compressors (21a, 21b)
Has an unloading circuit (46a, 46b) so as to be variable in capacity. Specifically, the first unload circuit (46a) includes a first unload passage (45a), a capillary tube (CP1a), and a first unload on-off valve (SV1).
a). 1st unload passage (4
5a), one end is connected to the discharge side of the first compressor (21a), and the other end is connected to the suction side. The first unload passage (45a) is provided with a capillary tube (CP1a) and a first unload on-off valve (SV1a) in order from the discharge side to the suction side of the first compressor (21a), The space between the capillary tube (CP1a) and the first unloading on-off valve (SV1a) is connected to the first compressor (21a). The second unload circuit (46b) is connected to the second unload passage (45
b), a capillary tube (CP1b) and a second unloading on-off valve (SV1b).
It is configured in the same manner as in a) and is provided in the second compressor (21b). The first and second unloading on-off valves (SV1a, SV1
b) is constituted by unload passage opening / closing means for opening / closing each unload passage (45a, 45b).

Then, unloading on-off valves (SV1a, SV1b)
Open, about half of the gas refrigerant discharged from the compressors (21a, 21b) passes through the unload passages (45a, 45b).
The compressor (21a, 21b) is returned to the suction side of b), and is operated at unload with approximately half of the maximum capacity. When the unloading on-off valves (SV1a, SV1b) are closed, the compressor (21a, 21
The discharge gas refrigerant of b) does not flow to the unload passages (45a, 45b), and the compressors (21a, 21b) operate at full load with the maximum capacity.

Further, an oil equalizing pipe (47) is provided between the two compressors (21a, 21b). Specifically, the oil equalizing pipe (47)
Is connected to the housing of the first compressor (21a),
The other end is connected to the housing of the second compressor (21b). Each end of the oil equalizing pipe (47) is connected to each compressor (21a,
21b) is connected to a predetermined position corresponding to the oil level in the housing. Then, the amount of lubricating oil stored in the housing increases, and the oil level of the lubricating oil increases
When the connection position becomes higher than the connection position of 7), excess lubricating oil is caused to flow to the oil equalizing pipe (47).

A first gas pipe (40) is connected to the discharge pipe (82) of the compression mechanism (80), and a second gas pipe (41) is connected to the suction pipe (81). The first gas pipe (40) connects the compression mechanism (80) and the four-way switching valve (24) in order, and is connected to one end of the condenser (22).
One end of a liquid pipe (42) is connected to the other end of the condenser (22), and the liquid pipe (42) is formed by a main pipe (4a) and two branch pipes (4b, 4c). I have. Each branch pipe (4b, 4c) is connected to each evaporator of the two refrigerant heat exchangers (11, 11).

The main pipe (4a) of the liquid pipe (42) connects the electric expansion valve for defrost (EV11) and the receiver (25) in order from the condenser (22). On the other hand, the above-mentioned branch pipes (4b, 4c) have an electric expansion valve for cooling (EV1
2) is provided.

The second gas pipe (41) is a main pipe (4d)
And two branch pipes (4e, 4f). The main pipe (4d) of the second gas pipe (41) connects the accumulator (26) and the four-way switching valve (24) in order from the compression mechanism (80), while the branch pipes (4e, 4f) Is connected to the evaporator of each refrigerant heat exchanger (11, 11). That is, the evaporating sections of the two refrigerant heat exchangers (11, 11) are connected in parallel in the high-temperature side refrigeration circuit (20).

The branch pipes (4b, 4c, 4e, 4f) of the liquid pipe (42) and the second gas pipe (41) are provided in the cascade unit (1B).

The first gas pipe (40) and the receiver (25)
A gas passage (43) is connected between the two. One end of the gas passage (43) is connected between the four-way switching valve (24) and the condenser (22) in the first gas pipe (40), and the other end is connected to the upper part of the receiver (25). Have been. And
The gas passage (43) is provided with an on-off valve (SV), and is configured to perform high-pressure control during a cooling operation and venting during a defrost operation.

A high-pressure pressure sensor (SPH1) for detecting a high-pressure refrigerant pressure is provided between the compression mechanism (80) and the four-way switching valve (24) in the first gas pipe (40). . Further, a low-pressure pressure sensor (SPL1) for detecting a low-pressure refrigerant pressure is provided between the compression mechanism (80) and the accumulator (26) in the second gas pipe (41).

The high temperature side refrigeration circuit (20) includes a controller (7) having an oil equalizing operation section (71) and a capacity control section (72).
0).

The oil equalizing operation section (71) is an oil equalizing operation means characterized by the present invention, and outputs a predetermined control signal to the compression mechanism (80), A predetermined distribution operation is performed for each of the compressors (21a, 21b) every two hours in the cumulative operation time of one compressor (21a). Specifically, the first unloading on-off valve (SV1a) is opened, and the second unloading on-off valve (SV1b) is closed.
The compressor (21a) is operated at full load, and the second compressor (21a) is operated.
b) Drive with unloading. This state is maintained for about one minute. After that, the first unloading on-off valve (SV1
a) is closed, the second unloading on-off valve (SV1b) is opened, and the first compressor (21a) is operated with unloading,
Operate the compressor (21b) at full load. This state,
Hold for about 1 minute. And oil equalization operation part (71)
Is designed to eliminate uneven oil distribution between the compressors (21a, 21b) by performing the distribution operation as described above.

The capacity control section (72) is a capacity control means characterized by the present invention, and outputs a predetermined control signal to the compression mechanism (80) to change the capacity of the compression mechanism (80). It is configured as follows. Specifically, when operating the compression mechanism (80) at the maximum capacity, the two unload on-off valves (SV1
a, SV1b) is closed and both compressors (21a, 21b) are operated at full load. On the other hand, when operating the compression mechanism (80) at about half the maximum capacity, the two unloading on-off valves (SV1a, SV1
Open b) and operate both compressors (21a, 21b) with unloading. Thus, the capacity control section (72) switches the capacity of the compression mechanism (80) between two stages of 100% and 50%.

On the other hand, the first low temperature side refrigeration circuit (3A)
The refrigerant circulation direction is switched between a forward cycle and a reverse cycle so that reversible operation is possible. The first low-temperature side refrigeration circuit (3A) includes a compressor (31), a condensing section of a first refrigerant heat exchanger (11), and an evaporating heat transfer tube (5a).
The condenser of the refrigerant heat exchanger (11) forms a condenser of the first low-temperature refrigeration circuit (3A).

The discharge side of the compressor (31) is connected to a first refrigerant heat exchanger (11) via a first gas pipe (60) via an oil separator (32) and a four-way switching valve (33). Is connected to one end of the condenser section. The other end of the condenser is connected to a liquid pipe (61)
Evaporating heat transfer tube (5a) via check valve (CV), receiver (34) and cooling expansion valve (EV21) as an expansion mechanism
Is connected to one end. The other end of the evaporating heat transfer tube (5a) is connected to a compressor (31) via a check valve (CV), a four-way switching valve (33) and an accumulator (35) by a second gas pipe (62). Connected to the suction side.

The first refrigerant heat exchanger (11) is a cascade condenser having an evaporator of the high-temperature refrigeration circuit (20) and a condenser of the first low-temperature refrigeration circuit (3A). It consists of a heat exchanger. The first refrigerant heat exchanger (11) is connected to the first low-temperature refrigeration circuit (3
The refrigerant of A) and the refrigerant of the high-temperature refrigeration circuit (20) exchange heat, and the refrigerant of the first low-temperature refrigeration circuit (3A) releases heat and condenses, while the refrigerant of the high-temperature refrigeration circuit (20) Endothermic and evaporate.

The cooling expansion valve (EV21) is a temperature-sensitive expansion valve, and the temperature-sensitive cylinder (TS) is connected to the second gas pipe (62) on the outlet side of the evaporation heat transfer tube (5a). Is provided.

Since the first low-temperature side refrigeration circuit (3A) is configured to perform a reverse cycle defrost operation, it is provided with a drain pan passage (63), a gas bypass passage (64), and a pressure reduction passage (65). I have. The drain pan passage (63) is connected to both ends of a check valve (CV) in the second gas pipe (62), and is provided with a drain pan heater (6a) and a check valve (CV). ) Is configured to flow.

The gas bypass passage (64) is connected to both ends of the cooling expansion valve (EV21) in the liquid pipe (61), and is provided with a check valve (CV). (EV21).

The pressure reducing passage (65) is connected to both ends of the check valve (CV) in the liquid pipe (61), and includes an on-off valve (SV) and an expansion valve for defrost (EV22). It is configured to depressurize the refrigerant. The expansion valve for defrost (EV22) is a temperature-sensitive expansion valve,
A temperature sensing cylinder is provided in the second gas pipe (62) upstream of the accumulator (35).

Further, one end of a gas vent passage (66) is connected to an upper portion of the receiver (34). The gas vent passage (66) is provided with an on-off valve (SV) and a capillary tube (C
P), and the other end is connected to the second gas pipe (62) on the upstream side of the accumulator (35).

An oil return passage (67) having a capillary tube (CP) is connected between the oil separator (32) and the suction side of the compressor (31).

The first gas pipe (60) on the discharge side of the compressor (31) is provided with a high-pressure pressure sensor (SPH2) for detecting the high-pressure refrigerant pressure, and a predetermined high-pressure High pressure switch (HPS2) that outputs an off signal when the value reaches
Are provided. The second gas pipe (62) on the suction side of the compressor (31) is provided with a low pressure sensor (SPL2) for detecting a low pressure refrigerant pressure.

The second low-temperature refrigeration circuit (3B) has substantially the same configuration as the first low-temperature refrigeration circuit (3A), but is configured to perform only the cooling operation without performing the defrost operation. . The second low-temperature side refrigeration circuit (3B) does not include the four-way switching valve (24) in the first low-temperature side refrigeration circuit (3A), and further includes a drain pan passage (63), a gas bypass passage (64), and a pressure reducing passage. The passage (65) is not provided. That is, the second low-temperature side refrigeration circuit (3B) includes the compressor (31), the condensing part of the second refrigerant heat exchanger (11), the receiver (34), the cooling expansion valve (EV21), and the evaporating transmission. Heat tube (5b) and accumulator (3
5) are sequentially connected by a first gas pipe (60), a liquid pipe (61), and a second gas pipe (62).
The condenser of the second refrigerant heat exchanger (11) constitutes a condenser of the second low-temperature refrigeration circuit (3B).

The cooling expansion valve (EV21) is a temperature-sensitive expansion valve, and a temperature-sensitive cylinder is provided in the second gas pipe (62) on the outlet side of the evaporation heat transfer tube (5b). The second refrigerant heat exchanger (11) is a cascade condenser having an evaporator of the high-temperature refrigeration circuit (20) and a condenser of the second low-temperature refrigeration circuit (3B). It consists of an exchanger. Then, this second refrigerant heat exchanger (1
1) is that the refrigerant in the second low-temperature refrigeration circuit (3B) exchanges heat with the refrigerant in the high-temperature refrigeration circuit (20), and the refrigerant in the second low-temperature refrigeration circuit (3B) radiates heat and condenses. Then, the refrigerant in the high-temperature side refrigeration circuit (20) absorbs heat and evaporates.

The evaporator heat transfer tubes (5a, 5b) in the two low-temperature refrigeration circuits (3A, 3B) are constituted by one evaporator (50). The refrigerant in the circuit (3A, 3B) exchanges heat with the air in the refrigerator or the freezer. The evaporator (50), the cooling expansion valve (EV21) and the drain pan passage (63) are provided in the cooling unit (1C), while another compressor (31) is provided in the cascade unit (1B). Have been.

In the first low temperature side refrigeration circuit (3A), a liquid temperature sensor (Th21) for detecting the temperature of the liquid refrigerant is provided in front of the flow divider (51) of the liquid pipe (61). The evaporator (50) is provided with an evaporator temperature sensor (Th22) for detecting the temperature of the evaporator (50).

-Operation of Binary Refrigeration Unit- Next, the operation of the binary refrigeration unit (10) will be described.

First, when performing the cooling operation, the two compressors (21a, 21b) of the compression mechanism (80) of the high temperature side refrigeration circuit (20) and the two compressors of both the low temperature side refrigeration circuits (3A, 3B) are used. Machine (31,31)
Are driven together. In this state, in the high-temperature side refrigeration circuit (20), the four-way switching valve (24) is switched to the solid line in FIG. 1, the electric expansion valve for defrost (EV11) is fully opened, and the electric expansion valve for cooling (EV12) is opened. To control the opening.

In the high-temperature side refrigeration circuit (20), the high-temperature side refrigerant discharged from both compressors (21a, 21b) of the compression mechanism (80) is condensed in the condenser (22) to become a liquid refrigerant, and the cascade unit (1B). And the liquid refrigerant is
It is divided into two branch pipes (4b, 4c), and the pressure is reduced by the electric expansion valve for cooling (EV12). Thereafter, the liquid refrigerant evaporates in each evaporating section of the two refrigerant heat exchangers (11, 11), becomes a gas refrigerant, returns to the compressors (21a, 21b), and repeats this circulation.

On the other hand, in the first low-temperature side refrigeration circuit (3A), the four-way switching valve (33) is switched to the solid line in FIG. 2, while the defrost expansion valve (EV22) is fully closed and the cooling expansion valve (EV2) is closed.
1) control the degree of superheat. In addition, the second low-temperature refrigeration circuit (3
In B), the degree of superheat of the cooling expansion valve (EV21) is controlled.

In the low-temperature side refrigeration circuits (3A, 3B), the low-temperature side refrigerant discharged from the compressors (31, 31) is condensed in the condensing section of the refrigerant heat exchanger (11, 11) to become a liquid refrigerant. ,
This liquid refrigerant is decompressed by the cooling expansion valve (EV21). Thereafter, the liquid refrigerant evaporates in the evaporating heat transfer tubes (5a, 5b) to become a gas refrigerant, returns to the compressors (31, 31), and repeats this circulation.

In the refrigerant heat exchangers (11, 11), the high-temperature refrigerant and the low-temperature refrigerant exchange heat, and the low-temperature refrigerant in the low-temperature refrigeration circuits (3A, 3B) is cooled and condensed. I do. On the other hand, in the evaporator (50), the low-temperature side refrigerant evaporates to generate cooling air, thereby cooling the inside of the refrigerator.

The binary refrigeration system (10) performs a defrost operation. This defrost operation is performed every 6 hours during the refrigeration operation and every 12 hours during the freezing operation. The defrost operation is performed by the second low-temperature refrigeration circuit (3B)
Is stopped, while the refrigerant circulation direction of the first low-temperature refrigeration circuit (3A) and the high-temperature refrigeration circuit (20) is reversed.

Specifically, in the first low-temperature refrigeration circuit (3A), the four-way switching valve (33) is switched to the broken line in FIG.
Control the degree of superheat of the defrost expansion valve (EV22) and fully close the cooling expansion valve (EV21).

The low-temperature side refrigerant discharged from the compressor (31) passes through a drain pan passage (63) through a four-way switching valve (33), and heats a drain pan by a drain pan heater (6a).
Subsequently, the low-temperature-side refrigerant flows through the heat transfer tube for evaporation (5a) to heat the evaporator (50), thereby melting the frost on the evaporator (50). Thereafter, the low-temperature-side refrigerant flowing through the heat transfer tube for evaporation (5a) flows through the gas bypass passage (64), and flows into the receiver (3).
After passing through 4), it flows through the pressure reducing passage (65), and the pressure is reduced by the defrost expansion valve (EV22). Subsequently, the low-temperature side refrigerant evaporates in the condensing section of the refrigerant heat exchanger (11), and the four-way switching valve (33)
And returns to the compressor (31) via the accumulator (35),
This cycle is repeated.

On the other hand, in the high-temperature side refrigeration circuit (20), the four-way switching valve (24) is switched to the dashed line in FIG. 1, while the opening degree of the defrost electric expansion valve (EV11) is controlled, and the cooling electric expansion valve is operated. (EV12) fully open.

The two compressors (21a, 21a) of the compression mechanism (80)
The high-temperature side refrigerant discharged from b) flows through the evaporating section of the first refrigerant heat exchanger (11) via the four-way switching valve (24), and heats the low-temperature side refrigerant of the first low-temperature side refrigeration circuit (3A). I do. Thereafter, the high-temperature side refrigerant flowing through the evaporating section of the refrigerant heat exchanger (11) is
Electric expansion valve for defrost (EV11) via receiver (25)
To reduce pressure. Subsequently, the high-temperature side refrigerant is supplied to the condenser (22)
At the four-way switching valve (24) and accumulator (2
Returning to both compressors (21a, 21b) via 6), this circulation is repeated.

In the above defrost operation, the liquid temperature sensor (Th21) detects the refrigerant temperature of, for example, 10 ° C., or the evaporator temperature sensor (Th22) detects the evaporator temperature of, for example, 20 ° C. Or the first low-temperature side refrigeration circuit (3A)
When the high pressure sensor (SPH2) detects a high pressure refrigerant pressure of, for example, 18 kg / cm ² , the process ends. Note that the above defrost operation ends even with a one-hour guard timer.

In the cooling operation in addition to the defrost operation, the on-off valve (SV) of the gas vent passage (66) in each low-temperature refrigeration circuit (3A, 3B) is opened, and the liquid refrigerant stored in the receiver (34) is opened. To the low temperature side compressor (31).

Further, when the pressure of the high-pressure refrigerant detected by the high-pressure pressure sensor (SPH1) decreases during the cooling operation, the gas passage (43) in the high-temperature side refrigeration circuit (20) becomes, for example, 6 kg / cm ^2. When the pressure drops, the on-off valve (SV) is opened, high-pressure refrigerant is supplied to the receiver (25), and the high-pressure refrigerant pressure is increased. When the pressure of the high-pressure refrigerant increases, for example, to 15 kg / cm ² , the opening of the on-off valve (SV)
finish. Before performing the high-pressure control, the airflow of the outdoor fan of the condenser (22) is reduced to suppress a decrease in the high-pressure pressure. If the high-pressure pressure cannot be suppressed by the fan control, the on-off valve (SV) is opened. .

During the defrost operation, the on-off valve (SV) of the gas passage (43) is opened and the receiver (25) is opened.
Of the gas refrigerant from the compressors (21a, 21a) of the compression mechanism (80).
Returning to b), the liquid refrigerant is stored in the receiver (25). That is, during the defrost operation, the liquid refrigerant is stored in the receiver (25) even when the outside air temperature is high.

Next, the operation during the oil leveling operation, which is a feature of the present invention, will be described with reference to the flowchart of FIG.

First, during the cooling operation of the binary refrigeration system (10), the integrated operation time of the first compressor (21a) is monitored in step ST1. If the integrated operation time is less than 2 hours, the refrigeration operation is performed as it is, and if the integrated operation time is 2 hours, the process proceeds to step ST2 to start the oil equalizing operation.

In step ST2, the first unloading on / off valve (SV1a) is closed and the second unloading on / off valve (SV1b) is closed regardless of the operation state of the compression mechanism (80) before the oil equalization operation starts.
Open . Then, the first compressor (21a) is operated at full load, and the second compressor (21b) is operated at unload. Subsequently, the process proceeds to step ST3, and the operation in step ST2 is performed by 1
Perform for a minute. As described above, the first compressor (21
Perform the distribution operation of a).

Then, the process proceeds to step ST4,
Contrary to T2, the first unload on-off valve (SV1a) is opened and the second unload on-off valve (SV1b) is closed . Then, the first compressor (21a) is operated by unloading, and the second compressor (21b) is operated.
Drive at full load. Then, it moves to step ST5 and performs the operation in step ST4 for one minute.
As described above, the distribution operation of the second compressor (21b) is performed.

Thereafter, the operation proceeds to step ST6, in which the operation state of the compression mechanism (80) is returned to the operation state before the start of the oil leveling operation.
That is, if the compression mechanism (80) was operated at the capacity of 50% before the oil equalizing operation, the process proceeds to step ST7, in which both the first and second unloading on-off valves (SV1a, SV1b) are opened. ,
Both the first and second compressors (21a, 21b) are operated with unloading. Before the oil leveling operation, set the compression mechanism (80) to 100
%, The process proceeds to step ST8, where both the first and second unloading on-off valves (SV1a, SV1b) are closed, and the first and second compressors (21a, 21b) are closed. Drive both at full load.

Further, the lubricating oil discharged together with the discharged gas refrigerant from each compressor (21a, 21b) of the compression mechanism (80) and accumulated in the circuit by the oil equalizing operation as described above is used for the compressor (21).
a, 21b).

That is, when the compression mechanism (80) is operated at a capacity of 50%, the amount of circulating refrigerant decreases and the high-temperature side refrigeration circuit
The flow velocity of the refrigerant in (20) decreases. For this reason, the lubricating oil discharged from each compressor (21a, 21b) tends to accumulate in the high-temperature side refrigeration circuit, making it difficult to return to the compressors (21a, 21b). In particular, in the high-temperature side refrigeration circuit (20), the refrigerant heat exchangers (11, 11) which are plate-type heat exchangers
Is used as the evaporator, so this refrigerant heat exchanger (11,11)
Lubricant tends to accumulate on the surface. Therefore, if the operation of the compression mechanism (80) at 50% capacity is continued for a long time, the lubricating oil held by each compressor (21a, 21b) decreases, and troubles such as seizure occur due to poor lubrication. There is a risk.

On the other hand, in the present embodiment, the oil equalizing operation is performed every time the operation time of the first compressor (21a) becomes 2 hours in total. In this oil leveling operation, as described above, first, the first compressor (21a) is operated at full load. For this reason, the amount of circulating refrigerant increases and the flow velocity of the refrigerant increases, whereby the lubricating oil accumulated in the circuit is collected by the first compressor (21a). The lubricating oil collected by the first compressor (21a) is supplied to the first compressor (21b) when the second compressor (21b) is operated at full load during the distribution operation of the second compressor (21b). 21a) to the second compressor (21b). In this way, the lubricating oil held by both compressors (21a, 21b) is maintained at a predetermined amount.

-Effects of the First Embodiment- According to the first embodiment, the uneven oil distribution between the compressors (21a, 21b) is eliminated by the oil leveling operation section (71) of the controller (70), and each compression is performed. The amount of lubricating oil stored in the housing of the machine (21a, 21b) can be made uniform. As a result,
Insufficient lubrication of the compressors (21a, 21b) due to the uneven oil distribution can be reliably prevented, and the reliability of the compressors (21a, 21b) can be improved.

Further, according to the oil equalizing operation section (71), all the compressors (21a, 21b) are continuously operated without stopping any of the compressors (21a, 21b), and the unbalanced operation is performed. Oil can be eliminated and leveling can be performed. As a result, the compressor (21a, 21b)
Can be reduced, and the reliability of the compressors (21a, 21b) can also be improved.

Further, since the capacity of the compression mechanism (80) is changed by adjusting the capacity of each compressor (21a, 21b), uneven oil distribution between the compressors (21a, 21b) is reduced. be able to. That is, conventionally, since the number of operating compressors is changed to change the capacity of the compression mechanism (80), the operating compressor and the stopped compressor are mixed. On the other hand, in the present embodiment, each compressor (21a,
21b) is operated by unloading. For this reason, the capacity difference between the compressors (21a, 21b) is reduced, and uneven oil distribution between the compressors (21a, 21b) due to the capacity difference can be reduced. As a result, poor lubrication of the compressors (21a, 21b) due to oil imbalance between the compressors (21a, 21b) can be reliably prevented, and the reliability of the compressors (21a, 21b) is improved. be able to.

According to the capacity control section (72) of the controller (70), all the compressors (21a, 21b) are continuously operated without stopping any of the compressors (21a, 21b). Meanwhile, the capacity of the compression mechanism (80) can be changed. As a result, the number of times of starting the compressors (21a, 21b) can be reduced, and the reliability of the compressors (21a, 21b) can also be improved.

Further, the lubricating oil easily accumulates in the refrigerant heat exchanger (11, 11) constituted by the plate-type heat exchanger as described above. On the other hand, the oil leveling operation is performed by the oil leveling operation section (71) every predetermined operation time. Therefore, even when the operation of the compression mechanism (80) at the 50% capacity is continued, the lubricating oil accumulated in the circuit including the refrigerant heat exchanger (11, 11) is removed by the compression mechanism (80). Compressor (21a, 21
b) It is possible to surely collect. As a result, poor lubrication of the compressors (21a, 21b) due to a decrease in lubricating oil held by the compressors (21a, 21b) can be reliably prevented, and the reliability of the compressors (21a, 21b) can be improved. Can be improved.

Modification of First Embodiment In the first embodiment, the compression mechanism (80) is constituted by two compressors (21a, 21b). However, the compression mechanism is constituted by two or more compressors. (80) may be configured.
Regarding the connection of the oil equalizing pipes (47a, 47b) and the oil equalizing operation in this case, an example in which the compression mechanism (80) is configured by three first to third compressors (21a, 21b, 21c) will be described. 4 and 5
It will be described based on. In FIGS. 4 and 5, the oil separator, the oil return passage, the high-pressure switch, and the unload circuit are omitted.

The connection of the oil equalizing pipes (47a, 47b) will be described. As shown in FIG. 4, the first oil equalizing pipe (47a) is connected between the first compressor (21a) and the second compressor (21b). At the same time, a second oil equalizing pipe (47b) is provided between the second compressor (21b) and the third compressor (21c). As shown in FIG. 5, a second oil equalizing pipe (47b) is provided between the second compressor (21b) and the third compressor (21c), while the first oil equalizing pipe (47) is provided.
One end of a) may be connected to the first compressor (21a), and the other end may be connected to the second oil equalizing pipe (47b).

The oil leveling operation is performed by the first compressor (21a)
Is operated at full load, and the second and third compressors (21b, 21c) are operated at unload for 1 minute. Then, the second compressor (21
b) is operated at full load, the first and third compressors (21a, 21c) are operated for 1 minute with unloading, and then the third compressor (21c)
Is operated at full load, and the first and second compressors (21a, 21b) are operated for 1 minute with unload to perform oil-equalizing operation.

[0100]

[Embodiment 2] The second embodiment of the present invention is different from the above-described embodiment in that two compressors (21a, 21a) are connected to the high-temperature side refrigeration circuit (20).
Instead of providing b), as shown in FIG. 6, only one compressor (21) is provided in the high-temperature side refrigeration circuit (20). Accordingly, in the present embodiment, the configuration of the controller (70) is changed.
Other configurations are the same as those in the first embodiment.

That is, an oil separator (23) is provided on the discharge side of the compressor (21), and a first gas pipe (40) is connected to the outlet side of the oil separator (23). I have. A first gas pipe (4) is provided on the suction side of the compressor (21).
0) is connected. The above oil separator (23) and compressor (2
An oil return passageway (44) is provided between the intake side 1) and the intake side as in the first embodiment. The compressor (2
1) is provided with an unload circuit (46) which is composed of an unload opening / closing valve (45), a capillary tube (CP), and an unload passage (45), and is configured in the same manner as in the first embodiment. By opening and closing the unload opening / closing valve (45) of the unload circuit (46), the compressor (21) can be switched between two stages: a full load of 100% capacity and an unload of 50% capacity. Have been.

The controller (70) of the present embodiment
Has a capacity control section (74) and an oil return operation section (73). The capacity control section (74) is configured to perform opening / closing control of the unload opening / closing valve (45) to switch the compressor (21) between full load and unload. The oil return operation section (73) is an oil return operation means characterized by the present invention, in which the unload operation of the compressor (21) is continuously performed, and the duration of this operation is Is set to perform a predetermined oil return operation when the time reaches 2 hours.

This oil return operation is performed by operating the compressor (21) at full load for one minute. That is, when the compressor (21) is operated at full load, the refrigerant circulation amount in the high-temperature side refrigeration circuit (20) increases, and the flow velocity of the refrigerant increases. For this reason, the lubricating oil accumulated in the high-temperature side refrigeration circuit (20), particularly in the refrigerant heat exchangers (11, 11), which are plate-type heat exchangers, flows together with the refrigerant flowing in the circuit, and flows to the compressor (21). Come back.

The binary refrigeration system (10) of this embodiment performs the cooling operation and the defrost operation by operating in the same manner as in the above embodiment, except for the operation of the oil return operation. In this embodiment, since only one compressor (21) is provided in the high-temperature side refrigeration circuit (20), the oil equalizing operation as in the first embodiment is unnecessary.

-Effects of Second Embodiment- In the second embodiment, the operation in which the compressor (21) continues to be unloaded and the lubricating oil easily accumulates in the circuit including the refrigerant heat exchangers (11, 11). When the state continues for a long time, the oil return operation is performed by the oil return operation unit (73). Therefore, the lubricating oil can be reliably returned to the compressor (21), and the lubricating oil held by the compressor (21) can be prevented from being insufficient. As a result, the compressor (2
Insufficient lubrication of the compressor (21) due to a decrease in lubricating oil held by 1) can be reliably prevented, and the reliability of the compressor (21) can be improved.

[0106]

In other embodiments of the present invention, the compressor (21) of the high temperature side refrigeration circuit (20) is provided with an unload passage (45) so that the capacity of the compressor (21) is variable. Like that. On the other hand, the compressor (21) may be configured to have a variable capacity by making the number of revolutions of the compressor (21) variable. That is, an inverter may be provided, and the frequency of the AC power supplied to the compressor motor that drives the compressor (21) may be appropriately changed by the inverter.

Although the compressors (21, 21a,...) Are constituted by rotary compressors, they may be constituted by scroll compressors.

Further, the low-temperature side refrigeration circuit (3A, 3B) and the high-temperature side refrigeration circuit (20) are connected by a refrigerant heat exchanger (11, 11) which is a cascade condenser to form a binary refrigeration cycle. However, an ordinary vapor compression refrigeration cycle (one-way refrigeration cycle) including one refrigerant circuit may be configured.

Although the air in the refrigerator or the freezer is cooled by the refrigeration apparatus (10), the air conditioning in the room of a general building or house may be performed. That is, the refrigeration apparatus (10) may be configured as an air conditioner.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram illustrating a high-temperature side refrigeration circuit according to a first embodiment.

FIG. 2 is a refrigerant circuit diagram illustrating a low-temperature refrigeration circuit according to Embodiment 1.

FIG. 3 is a flowchart showing an operation of the high temperature side refrigeration circuit according to the first embodiment during an oil equalizing operation.

FIG. 4 is a schematic diagram illustrating a configuration of a compression mechanism according to a modification of the first embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of a compression mechanism according to a modification of the first embodiment.

FIG. 6 is a refrigerant circuit diagram illustrating a high-temperature side refrigeration circuit according to a second embodiment.

FIG. 7 is a refrigerant circuit diagram showing a conventional refrigerant circuit having a plurality of compressors.

[Explanation of symbols]

(3A) First low-temperature refrigeration circuit (3B) Second low-temperature refrigeration circuit (11) Refrigerant heat exchanger (cascade condenser, low-temperature refrigeration circuit condenser, high-temperature refrigeration circuit evaporator) (20) High-temperature side Refrigeration circuit (refrigerant circuit) (21) Compressor (21a) First compressor (21b) Second compressor (22) Condenser (45) Unload passage (45a) First unload passage (45b) Second unload Load passage (46) Unload circuit (46a) First unload circuit (46b) Second unload circuit (47) Equalizer pipe (47a) First equalizer pipe (47b) Second equalizer pipe (50) Evaporator (71 ) Oil equalizing operation unit (oil equalizing operation means) (72) Capacity control unit (capacity control means) (73) Oil return operation unit (oil return operation means) (80) Compression mechanism (compressor means) (EV12) For cooling Electric expansion valve (expansion mechanism) (EV21) Cooling expansion valve (expansion mechanism) (SV1) Unload on-off valve (unload Channel opening and closing means) (SV1a) first unloading off valve (unloading channel opening and closing means) (SV1b) first unloading off valve (unloading channel opening and closing means)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 6-5141 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 1/00

Claims (6)

(57) [Claims] 1. A compressor means (80) comprising a plurality of variable capacity compressors (21a, 21b) connected in parallel, and a condenser (22).
And a refrigeration system having a refrigerant circuit (20) formed by connecting an expansion mechanism (EV12) and an evaporator (11) in sequence, wherein one end is connected to the housing of one compressor (21a, 21b), and the other end is connected to the housing. Each of the compressors (21a, 21b) is connected to a housing of the other one of the compressors (21a, 21b), so that the amount of lubricating oil stored in the housing of each of the compressors (21a, 21b) is uniform. Oil equalizing pipes (47, 47a, 47b) for circulating lubricating oil, and one of the plurality of compressors (21a, 21b) having the maximum capacity, and the remaining compressors (21a, 21b) having the maximum capacity. The distribution operation in which the compressors (21a, 21b) are operated at the maximum capacity is switched at least once by the compressor (21a, 21b) by switching the compressor (21a, 21b) operated at the maximum capacity at least once. , And a part of the gas refrigerant discharged from the compressor (21, 21a,...) Unload passage (45 to return to the suction side,
45a, 45b) and an unload circuit (46, 46a, 46b) having unload passage opening / closing means (SV1, SV1a, SV1b) for opening and closing the unload passage (45, 45a, 45b). (21, 21a,...)
a, 45b) to the maximum capacity when the unload passage (4
(5, 45a, 45b) has a small capacity when opened, and is configured to have a variable capacity. 2. A compressor means (80) comprising a plurality of variable capacity compressors (21a, 21b) connected in parallel, and a condenser (22).
And a refrigeration system having a refrigerant circuit (20) formed by connecting an expansion mechanism (EV12) and an evaporator (11) in sequence, wherein one end is connected to the housing of one compressor (21a, 21b), and the other end is connected to the housing. Each of the compressors (21a, 21b) is connected to a housing of the other one of the compressors (21a, 21b), so that the amount of lubricating oil stored in the housing of each of the compressors (21a, 21b) is uniform. Oil equalizing pipes (47, 47a, 47b) for circulating lubricating oil, and one of the plurality of compressors (21a, 21b) having the maximum capacity, and the remaining compressors (21a, 21b) having the maximum capacity. The distribution operation in which the compressors (21a, 21b) are operated at the maximum capacity is switched at least once by the compressor (21a, 21b) by switching the compressor (21a, 21b) operated at the maximum capacity at least once. And a refrigerant circuit (20) is configured as a high-temperature side refrigeration circuit (20). That one compressor (31, 31), the condenser (11), expansion mechanism (EV21) and an evaporator cold side refrigeration circuit (3 formed by connecting the (50) in order
A, 3B), and the condenser (11) of the low-temperature side refrigeration circuit (3A, 3B) is formed integrally with the evaporator (11) of the high-temperature side refrigeration circuit (20). , 11), the low-temperature refrigeration circuit (3A, 3B) and the high-temperature refrigeration circuit (20)
Is characterized in that the cascade condensers (11, 11) constitute a binary refrigeration cycle for exchanging heat between the refrigerant of the high-temperature refrigeration circuit (20) and the refrigerant of the low-temperature refrigeration circuit (3A, 3B). Refrigeration equipment. 3. A compressor means (80) comprising a plurality of variable capacity compressors (21a, 21b) connected in parallel, and a condenser (22).
And a refrigeration system having a refrigerant circuit (20) formed by sequentially connecting an expansion mechanism (EV12) and an evaporator (11) so that both compressors (21a, 21b) are continuously operated. And a capacity control means (72) for changing the capacity of the compressor means (80) by adjusting the capacity of the compressors (21a, 21b). 4. A compressor (21) having a variable capacity and a condenser (2).
2), a refrigeration apparatus having a refrigerant circuit (20) formed by connecting an expansion mechanism (EV12) and an evaporator (11) in order. The evaporator (11) is formed by stacking a number of heat transfer plates. On the other hand, when the operation of reducing the capacity of the compressor (21) smaller than the maximum capacity is continued for a predetermined time or more, the compressor (21) is temporarily turned off. A refrigerating apparatus comprising, as a maximum capacity, oil return operating means (73) for recovering lubricating oil accumulated in the refrigerant circuit (20) to the compressor (21). 5. The refrigerating apparatus according to claim 3 , wherein a part of the gas refrigerant discharged from the compressor (21, 21a,...) Is returned to a suction side of the compressor (21, 21a,...). Road aisle (45,
45a, 45b) and an unload circuit (46, 46a, 46b) having unload passage opening / closing means (SV1, SV1a, SV1b) for opening and closing the unload passage (45, 45a, 45b). (21, 21a,...) Are the unload passages (45, 45).
a, 45b) to the maximum capacity when the unload passage (4
(5, 45a, 45b) has a small capacity when opened, and is configured to have a variable capacity. 6. The refrigeration apparatus according to claim 3, wherein the refrigerant circuit (20) is configured as a high-temperature side refrigeration circuit (20), while the compressor (31, 31), the condenser (11), A low-temperature refrigeration circuit (3) consisting of an expansion mechanism (EV21) and an evaporator (50) connected in order.
A, 3B), and the condenser (11) of the low-temperature side refrigeration circuit (3A, 3B) is formed integrally with the evaporator (11) of the high-temperature side refrigeration circuit (20). , 11), the low-temperature refrigeration circuit (3A, 3B) and the high-temperature refrigeration circuit (20)
Is characterized in that the cascade condensers (11, 11) constitute a binary refrigeration cycle for exchanging heat between the refrigerant of the high-temperature refrigeration circuit (20) and the refrigerant of the low-temperature refrigeration circuit (3A, 3B). Refrigeration equipment.