JP2002081778A - Refrigerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a compressor from sucking wet vapor when reverse cycle defrosting operation is performed. SOLUTION: Before starting defrosting operation, an indoor electronic expansion valve is opened and a refrigerant in an indoor unit side is collected in a liquid receiver (18). Gas refrigerant in the liquid receiver (18) is made to flow into a suction side pipe (28) through a gas bypass pipe (35) by opening a solenoid valve (36) of the gas bypass pipe (35). The solenoid valve (36) of the gas bypass pipe (35) is closed when the superheat degree of the refrigerant sucked by the compressors (11 and 12) become a specified value or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refrigeration system,
In particular, the present invention relates to prevention of liquid back during defrost operation.

[0002]

2. Description of the Related Art In a refrigerating apparatus provided with an indoor heat exchanger and an outdoor heat exchanger, under conditions where the outdoor air temperature is relatively low, for example, in a cold region, frost is formed on the outdoor heat exchanger during a heating operation. May occur. When the frost is formed, the performance of the heat exchanger is reduced, so that the performance of the refrigeration system is reduced. Therefore, conventionally, a defrost operation for melting frost has been performed when frost formation is detected or at regular intervals.

[0003] A so-called reverse cycle defrost is often used as a defrosting method. Reverse cycle defrosting is a method of performing defrosting using high-temperature gas refrigerant discharged from a compressor.At the start of defrosting operation, the refrigeration cycle of the refrigeration system is switched from a heating cycle to a cooling cycle, The discharged gas refrigerant is supplied to the outdoor heat exchanger.

[0004]

In the heating cycle, the refrigerant condenses in the indoor heat exchanger and evaporates in the outdoor heat exchanger. At this time, the pressure distribution of the refrigerant in the refrigerant circuit is such that the indoor heat exchanger side is on the high pressure side and the outdoor heat exchanger side is on the low pressure side. On the other hand, in the cooling cycle, the refrigerant condenses in the outdoor heat exchanger and evaporates in the indoor heat exchanger. The pressure distribution of the refrigerant at this time is such that the indoor heat exchanger side is on the low pressure side and the outdoor heat exchanger side is on the high pressure side. Therefore, when the refrigeration cycle is switched from the heating cycle to the cooling cycle, the indoor heat exchanger and the suction side of the compressor communicate with each other while the condensed liquid refrigerant is present on the indoor heat exchanger. as a result,
Immediately after the start of the defrost operation, there is a possibility that the liquid refrigerant accumulated in the indoor heat exchanger may flow into the suction side of the compressor, causing a reduction in the reliability of the compressor.

[0005] The present invention has been made in view of such a point, and an object of the present invention is to prevent liquid back of a compressor at the start of defrost operation.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention pushes a liquid refrigerant from an indoor heat exchanger to a predetermined location so as not to flow into a suction side of a compressor prior to a defrost operation. I decided that.

Specifically, the refrigeration apparatus according to the first invention comprises a compressor (11, 12), a four-way switching valve (13), an outdoor heat exchanger (1).
4, 20), a liquid receiver (18), a refrigerant circuit (1) having an openable and closable pressure reducing means (7) provided on the indoor side and an indoor heat exchanger (8), at least a heating operation and a reverse cycle A refrigerating apparatus capable of performing a defrost operation, and a bypass passage (3) connecting the liquid receiver (18) and the low pressure part (28) of the refrigerant circuit (1).
5) and a passage opening / closing means provided in the bypass passage (35).
(36), and before starting the reverse cycle defrost operation, the pressure reducing means (7) so as to collect the liquid refrigerant accumulated on the indoor side of the refrigerant circuit (1) in the liquid receiver (18). ) And the passage opening / closing means (36) is opened.

[0008] In the first aspect of the present invention, since the pressure reducing means is opened prior to the reverse cycle defrost operation, the liquid refrigerant on the indoor heat exchanger side passes through the pressure reducing means and flows into the receiver. At this time, since the passage opening / closing means is also opened, the internal pressure of the liquid receiver decreases. Therefore, the refrigerant on the indoor heat exchanger side is efficiently collected in the receiver. Therefore, when the defrost operation is started, the amount of the liquid refrigerant remaining on the indoor heat exchanger side is reduced, and the liquid back of the compressor is prevented.

A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein a temperature detecting means (37) for detecting a refrigerant suction temperature of the compressor (11, 12); Pressure detecting means (38) for detecting the suction refrigerant pressure of the suction refrigerant temperature and the suction refrigerant superheat degree calculated based on the suction refrigerant temperature and the suction refrigerant pressure become a predetermined value or less, the passage opening and closing means (36) It is to be closed.

[0010] As the collection of the liquid refrigerant into the liquid receiver proceeds, the liquid receiver eventually becomes full of the liquid refrigerant, and the low-dry refrigerant flows from the liquid receiver to the suction side of the compressor. Then, the suction superheat degree of the compressor decreases, and when the suction superheat degree becomes equal to or lower than the predetermined temperature, the passage opening / closing means is closed. Therefore, the liquid refrigerant is prevented from flowing from the liquid receiver toward the compressor.

A refrigeration apparatus according to a third aspect of the present invention includes a compressor (11,
12), four-way switching valve (13), outdoor heat exchanger (14, 20), openable and closable decompression means (7) and indoor heat exchanger (8) provided on the indoor side
A refrigeration apparatus comprising a refrigerant circuit (1) having at least a heating operation and a reverse cycle defrost operation, and comprising a pressure detecting means (38) for detecting a low pressure side pressure of the refrigerant circuit (1). Before starting the reverse cycle defrost operation, the pressure reducing means (7) to recover the liquid refrigerant accumulated in the indoor heat exchanger (8) to the outdoor heat exchanger (14, 20) side
Once, then the pressure reducing means (7) is closed, and then the four-way switching valve (13) is switched, so that the refrigerant circuit (1)
The pressure reducing means when the low-pressure side pressure falls below a predetermined value.
(7) is to be released.

In the third aspect of the present invention, since the pressure reducing means is opened prior to the reverse cycle defrost operation, the liquid refrigerant on the indoor heat exchanger side is recovered on the outdoor heat exchanger side. Thereafter, the pressure reducing means is closed and the four-way switching valve is switched, so that the pressure on the indoor heat exchanger side decreases.
Therefore, the small amount of liquid refrigerant remaining on the indoor heat exchanger side is decompressed and evaporates before being sucked into the compressor. Therefore, liquid back of the compressor is prevented.

[0013]

As described above, according to the first aspect of the present invention, the liquid refrigerant on the indoor heat exchanger side is collected in the receiver before the defrost operation, so that when the defrost operation is started, It is possible to prevent the liquid refrigerant from flowing from the indoor heat exchanger toward the compressor. At this time, since the gas refrigerant in the receiver is discharged through the bypass passage, the recovery efficiency of the receiver can be improved. Therefore, the liquid back of the compressor during the defrost operation can be reliably prevented.

According to the second aspect, the bypass passage is shut off when the degree of superheat of the refrigerant sucked into the compressor becomes lower than a predetermined temperature, so that the liquid refrigerant flows from the receiver toward the suction side of the compressor. Inflow can be prevented. Therefore, it is possible to prevent the liquid refrigerant in the receiver from returning to the compressor.

According to the third aspect of the present invention, the decompression means is opened prior to the defrost operation, and the liquid refrigerant in the indoor heat exchanger is recovered in the outdoor heat exchanger. Therefore, when the defrost operation is started. The liquid refrigerant can be prevented from flowing into the compressor from the indoor heat exchanger side. Thereafter, the pressure reducing means is closed until the refrigerant pressure on the suction side of the compressor becomes equal to or lower than a predetermined value. Therefore, even if liquid refrigerant is mixed on the suction side, the liquid refrigerant is reduced in pressure as the suction side pressure decreases. ,Evaporate. Therefore, the refrigerant is prevented from flowing into the compressor in a liquid state. Therefore, the liquid back of the compressor during the defrost operation can be reliably prevented.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> As shown in FIG. 1, a refrigeration apparatus according to an embodiment of the present invention comprises a plurality of outdoor units (2, 2).
This is a multi-type air conditioner including 3) and a plurality of indoor units (4, 4,...), And includes a refrigerant circuit (1). The indoor units (4, 4, ...) are connected to the outdoor units (2, 3) via refrigerant pipes (5, 6), and each indoor unit (4) has an indoor electronic expansion valve (7) and An indoor heat exchanger (8) is provided. The indoor electronic expansion valve (7) can be fully opened or fully closed as well as being able to control the degree of opening, and corresponds to the "openable and closable pressure reducing means" according to the present invention.
The "openable and closable pressure reducing means" is not limited to the electronic expansion valve as long as it has both the function of opening and closing the refrigerant flow path and the function of reducing the pressure of the refrigerant. For example, a combination of an on-off valve (for example, an electromagnetic valve or the like) and a throttle mechanism (a capillary tube or the like) in parallel may be used.

As shown in FIG. 2, the first outdoor unit (2)
Inside, there are a compressor (11, 12), a four-way switching valve (13), a first outdoor heat exchanger (14), a first outdoor blower (15), a first outdoor electronic expansion valve (16), A two outdoor electronic expansion valve (17), a liquid receiver (18), and an accumulator (19) are provided. A second outdoor heat exchanger (20) and a second outdoor blower (21) are provided inside the second outdoor unit (3).

The first port of the four-way switching valve (13) is connected to the compressor (11,
The second port is connected to the refrigerant pipe (23), and the second port is connected to the discharge pipe (22). The refrigerant pipe (23) is branched, one branch pipe is connected to one end of the first outdoor heat exchanger (14), and the other branch pipe is connected to one end of the second outdoor heat exchanger (20). . The other end of the first outdoor heat exchanger (14) is connected to the first outdoor electronic expansion valve (16) via a refrigerant pipe (24). Second
The other end of the outdoor heat exchanger (20) is connected to the second through a refrigerant pipe (25).
It is connected to the outdoor electronic expansion valve (17). The refrigerant pipe (26) connected to the first outdoor electronic expansion valve (16) merges with the refrigerant pipe (27) connected to the second outdoor electronic expansion valve (17), and the liquid receiver (1)
8) is connected to one end. The other end of the liquid receiver (18) is connected to a liquid-side refrigerant pipe (5) connected to the indoor units (4, 4,...). The gas side refrigerant pipe (6) connected to the indoor units (4, 4, ...) is connected to the fourth port of the four-way switching valve (13). The third port of the four-way switching valve (13) is a compressor
(11, 12) are connected to the suction side pipe (28). The suction side pipe (28) is provided with an accumulator (19).
Note that oil dischargers (29, 29) are provided on the discharge side of the compressors (11, 12), respectively. The discharge pipe (22) is provided with a pressure sensor (39) for detecting a discharge refrigerant pressure. A temperature sensor (37) for detecting a suction refrigerant temperature and a pressure sensor (38) for detecting a suction refrigerant pressure are provided in the suction pipe (28) of the compressors (11, 12).

A gas bypass pipe (35) is provided above the liquid receiver (18).
Is connected. The gas bypass pipe (35) is connected to the receiver (18)
This is a bypass passage for bypassing the gas refrigerant in the inside to the suction side pipe (28), and communicates the liquid receiver (18) with the suction side pipe (28). The gas bypass pipe (35) is provided with an electromagnetic valve (36) as a passage opening / closing means.

A bypass pipe (50) is provided between the discharge pipe (22) and the suction pipe (28). Bypass pipe (50)
Is provided with a solenoid valve (54), on the downstream side of which three branch pipes
(51,52,53). The branch pipes (51, 52, 53) are respectively connected to the suction side pipes (28). This bypass pipe
(50) is to supply the high-pressure refrigerant to the suction-side pipe (28) by opening the solenoid valve (54) when the low-pressure side pressure becomes equal to or lower than a predetermined value, thereby preventing an excessive decrease in the low-pressure side pressure. . Thus, the downstream side of the bypass pipe (50) is connected to the three branch pipes (51, 5).
By branching to (2, 53), the amount of refrigerant flowing per bottle is reduced, so that the passing sound of the refrigerant can be reduced.

The first outdoor heat exchanger (14) and the second outdoor heat exchanger (20) are provided with temperature sensors (31, 32), respectively. The temperature sensor (31) is provided at a position on the first outdoor electronic expansion valve (16) side of the first outdoor heat exchanger (14), and the temperature sensor (32)
Is provided at a position of the second outdoor heat exchanger (20) on the side of the second outdoor electronic expansion valve (17). In addition, (33, 34) is a temperature sensor for detecting the outdoor air temperature, and (40) is a controller that executes a defrost preparation operation and a defrost operation described later.

Next, the operation of the air conditioner will be described.

During the cooling operation, the four-way switching valve (13) is set in a state where the first port and the second port communicate with each other, and the third port and the fourth port communicate with each other. The refrigerant is supplied to the compressor (1
After being discharged from (1,12), it is condensed in the outdoor heat exchanger (14,20), decompressed by the indoor electronic expansion valve (7,7, ...), and decompressed in the indoor heat exchanger (8,8, ...). Evaporates and returns to the compressor (11,12).

During the heating operation, the four-way switching valve (13) is set in a state where the first port and the fourth port communicate with each other, and the second port and the third port communicate with each other. The refrigerant is supplied to the compressor (1
After being discharged from (1,12), it condenses in the indoor heat exchangers (8,8, ...), is decompressed by the outdoor electronic expansion valves (16,17), and evaporates in the outdoor heat exchangers (14,20). Return to the compressor (11, 12).

If the temperature detected by the temperature sensors (31, 32) of the outdoor heat exchangers (14, 20) becomes lower than a predetermined temperature during the heating operation, it is determined that frost has occurred and prior to the defrost operation. The following defrost preparation operation is performed.

In the defrost preparation operation, first, all the indoor electronic expansion valves (7, 7,...) Are opened to a half-open state.
As a result, the liquid refrigerant inside or near the indoor heat exchanger (8, 8, ...) flows through the refrigerant pipe (5) without being obstructed by the indoor electronic expansion valves (7, 7, ...). It flows into the outdoor unit (2, 3).
And the liquid refrigerant flowing into the outdoor unit (2, 3) side is
Collected in the receiver (18). When a predetermined time (one minute in this embodiment) has elapsed since the start of the defrost preparation operation, the solenoid valve (36) of the gas bypass pipe (35) is opened. As a result, the gas refrigerant in the receiver (18) passes through the gas bypass pipe (3
The liquid is discharged to the suction pipe (28) through 5), and the internal pressure of the liquid receiver (18) decreases. Therefore, the efficiency of refrigerant recovery of the liquid receiver (18) is improved. The solenoid valve (36) of the gas bypass pipe (35)
It is configured to close automatically when a predetermined time (for example, 60 seconds) elapses after being opened. However, in order to reliably prevent the liquid refrigerant from overflowing from the liquid receiver (18) toward the suction-side pipe (28), the superheat degree of the suction refrigerant of the compressors (11, 12) became lower than a predetermined temperature. In this case, it is preferable to close the solenoid valve (36) even before the predetermined time has elapsed. Therefore, in the present embodiment, the degree of superheat of the suction refrigerant is calculated based on the temperature of the suction refrigerant detected by the temperature sensor (37) and the temperature of the suction refrigerant detected by the pressure sensor (38). When the time becomes below, the electromagnetic valve (36) is closed even before the predetermined time has elapsed.

When two minutes or more have elapsed since the start of the defrost preparation operation and the difference between the high and low pressures of the refrigerant circuit becomes equal to or less than a predetermined value, the defrost preparation operation ends. Thereafter, the four-way switching valve (13) is switched, and the reverse cycle defrost operation is started.

As described above, in the present embodiment, the liquid refrigerant on the indoor unit (4, 4,...) Side is collected in the receiver (18) prior to the defrost operation. The liquid refrigerant on the unit (4,4, ...) side is the compressor (11,1
2) It can be prevented from flowing into the suction side. Therefore, liquid back of the compressors (11, 12) can be prevented, and the reliability of the device can be improved.

Since the gas refrigerant of the receiver (18) is allowed to escape to the suction pipe (28) during the defrost preparation operation, the liquid refrigerant can be efficiently introduced into the receiver (18). it can. Therefore, the liquid refrigerant on the indoor unit (4, 4,...) Side can be efficiently recovered.

<Embodiment 2> Embodiment 2 is based on Embodiment 1.
Is a modification of the defrost preparation operation. In the defrost preparation operation of the second embodiment, first, all the indoor electronic expansion valves (7, 7,...) Are opened and the liquid refrigerant on the indoor unit (4, 4,. Collect to the outdoor unit (2, 3) through the pipe (5). Next, after opening the indoor electronic expansion valves (7, 7,...) For a predetermined time (for example, 50 seconds)
, The indoor electronic expansion valves (7, 7,...) Are closed. When a predetermined time (for example, 10 seconds) elapses after closing the indoor electronic expansion valves (7, 7,...), The four-way switching valve (1
Switch 3). By switching the four-way switching valve (13) in this way, the indoor heat exchanger (8, 8,...) Side becomes the low pressure side of the refrigerant circuit. At this time, since the indoor electronic expansion valves (7, 7, ...) are closed, the internal pressure of the indoor heat exchangers (8, 8, ...) and the suction side pressure of the compressors (11, 12) are: It gradually decreases. Then, the pressure of the suction refrigerant of the compressors (11, 12) is detected by a pressure sensor (38). When the pressure of the suction refrigerant becomes a predetermined value (for example, 2 kg / cm ² ) or less, the indoor electronic expansion valve (7,
7, ...) are opened to an opening suitable for defrost operation,
Defrost operation is started.

As described above, also in the second embodiment, the liquid refrigerant on the indoor unit (4, 4,...) Side is recovered prior to the defrost operation, so that the indoor unit (4, 4,. ) Can be prevented from flowing into the suction side of the compressors (11, 12). Therefore, liquid back of the compressors (11, 12) can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an outdoor unit.

[Explanation of symbols]

 (1) Refrigerant circuit (2) First outdoor unit (3) Second outdoor unit (4) Indoor unit (5) Refrigerant piping (7) Indoor electronic expansion valve (openable and closable pressure reducing means) (8) Indoor heat exchanger (11,12) Compressor (13) Four-way switching valve (14) First outdoor heat exchanger (18) Receiver (20) Second outdoor heat exchanger (35) Gas bypass pipe (bypass passage) (36 ) Solenoid valve (passage opening / closing means)

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Seiji Sakai 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Inside Kanaoka Plant of Sakai Seisakusho Co., Ltd. (72) Keiichi Yamamoto 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries, Ltd. Inside the Sakai Plant Kanaoka Plant (72) Inventor Tsuyoshi Yamada 1304 Kanaokacho, Sakai City, Osaka Daikin Industries Inside the Sakai Plant Kanaoka Plant F-term (reference) 3L092 AA07 BA05 BA23 BA26 BA27 DA19 EA05 FA22 FA23 FA27

Claims (3)

[Claims] A compressor (11, 12), a four-way switching valve (13), an outdoor heat exchanger (14, 20), a liquid receiver (18), an openable and closable pressure reducing means ( 7) and a refrigerant circuit (1) having an indoor heat exchanger (8), a refrigeration apparatus capable of executing at least a heating operation and a reverse cycle defrost operation, wherein the liquid receiver (18) and the refrigerant circuit A bypass passage (35) connecting the low-pressure section (28) of (1), and a passage opening / closing means (36) provided in the bypass passage (35), wherein before starting the reverse cycle defrost operation, The pressure reducing means (7) and the passage opening / closing means so that the liquid refrigerant collected on the indoor side of the refrigerant circuit (1) is collected in the liquid receiver (18).
(36) A refrigeration apparatus characterized by opening. 2. A refrigerating apparatus according to claim 1, wherein a temperature detecting means for detecting a temperature of a refrigerant sucked into the compressor (11, 12).
(37), and pressure detecting means (38) for detecting the suction refrigerant pressure of the compressor (11, 12), the suction refrigerant superheat degree calculated based on the suction refrigerant temperature and the suction refrigerant pressure is A refrigeration system characterized in that when a predetermined value or less is reached, the passage opening / closing means (36) is closed. 3. A compressor (11, 12), a four-way switching valve (13), an outdoor heat exchanger (14, 20), an openable and closable pressure reducing means (7) provided on the indoor side, and an indoor heat exchanger. A refrigeration apparatus comprising a refrigerant circuit (1) having (8), and capable of performing at least a heating operation and a reverse cycle defrost operation, wherein a pressure detecting means for detecting a low pressure side pressure of the refrigerant circuit (1)
Before the reverse cycle defrost operation is started, the liquid refrigerant accumulated in the indoor heat exchanger (8) is removed from the outdoor heat exchanger (14, 20).
The pressure reducing means (7) is once opened so as to be collected on the side, then the pressure reducing means (7) is closed, and then the four-way switching valve (13) is switched, so that the low pressure side pressure of the refrigerant circuit (1) is reduced. A refrigerating device, wherein the pressure reducing means (7) is opened when the pressure becomes equal to or less than a predetermined value.