JP2001133055A - Refrigeration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To store refrigerant efficiently in a receiver through pump down operation. SOLUTION: A refrigeration system comprising a compressor 1, a heat source side heat exchanger 3, a receiver 7, an expansion valve 4 and a using side heat exchanger 5 coupled in series is provided with a bypath 13 connecting the gas phase section of the receiver 7 with a low pressure line 25 on the downstream side of the expansion valve 4, and an on/off valve 14 for opening the bypath 13 only during the period after starting pump down operation before stopping operation of the compressor 1 thus interconnecting the gas phase section of the receiver 7 with the low pressure line 25 on the downstream side of the expansion valve 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus, and more particularly, to a refrigerating apparatus in which liquid refrigerant easily accumulates in a receiver during a pump-down operation.

[0002]

2. Description of the Related Art For example, as shown in FIG.
A four-way switching valve 2, an outdoor heat exchanger (that is, a heat source side heat exchanger) 3, which functions as a condenser during a cooling operation and as an evaporator during a heating operation and is provided with a supercooling heat exchanger 6;
A motor-operated expansion valve 4 serving as a pressure reducing mechanism, and an indoor heat exchanger (that is, a use-side heat exchanger) 5 serving as an evaporator during a cooling operation and serving as a condenser during a heating operation; In the refrigerating apparatus capable of reversing the flow of refrigerant by the switching operation of the switching valve 2, a receiver 7 and a refrigerant flow switching mechanism 8 including four check valves 9 to 12 are additionally provided, and the outdoor heat exchanger is provided. A configuration in which the refrigerant from the indoor heat exchanger 3 or the indoor heat exchanger 5 always flows from the receiver 7 to the electric expansion valve 4 is well known.

In the refrigeration system having the above-described structure, the low-pressure line 25 downstream of the gas phase portion of the receiver 7 and the electric expansion valve 4.
And a bypass path 13 for connecting the
There is another type in which a liquid refrigerant is stored in the receiver 7 during a pump-down operation by interposing a capillary tube 14 '.

In FIG. 5, reference symbol A denotes an outdoor unit, and B denotes an outdoor unit.
Is an indoor unit, 15 is an outside air temperature sensor that detects an outdoor suction temperature (in other words, outside air temperature) To, 16 is an outdoor heat exchange sensor that detects the outdoor heat exchange temperature Tg of the outdoor heat exchanger 3, and 17 is an indoor heat exchange sensor. An indoor temperature sensor for detecting the suction temperature (in other words, the indoor air temperature) Ta, 18 for detecting the indoor heat exchange temperature Tn of the indoor heat exchanger 5, and 19 for detecting the discharge pipe temperature Th. Discharge temperature sensor, 20 is an outdoor fan, 21 is an indoor fan, 22, 23
Is a closing valve, and 24 is a control unit.

In the above pump down operation, FIG.
As shown in the figure, when the stop signal is received, the electric expansion valve 4
The operation of the compressor 1 and the outdoor fan 20 is stopped when a predetermined time PD has elapsed from when the electric expansion valve 4 is fully closed. When the stop signal is received, the discharge pipe temperature Th of the compressor 1 and the opening EVm of the electric expansion valve 4 at that time are set in the control unit 2.
4 is stored.

Further, as shown in FIG. 7, the predetermined time PD is determined in accordance with the discharge pipe temperature Th at the time of receiving the stop signal. When high, PD = 0, and Th ≦ 90 ° C.
In this case, it is set to 5 seconds. That is, only when the discharge pipe temperature Th is 90 ° C. or less, the compressor 1 and the outdoor fan 20 are stopped when 5 seconds have elapsed since the electric expansion valve 4 was fully closed. .

[0007]

However, as described above, the gas phase portion of the receiver 7 and the low pressure line 25 downstream of the electric expansion valve 4 are connected by the bypass passage 13 having the capillary tube 14 '. In such a case, since the flow resistance of the capillary tube 14 'is high, gas is not smoothly discharged from the gas phase part of the receiver 7, and there is a problem that it is difficult to store the liquid refrigerant in the receiver 7. On the other hand, when the system is stopped (that is, when the operation of the compressor 1 is stopped), the receiver 7 is stopped.
The refrigerant may flow out from the gaseous phase portion to the low-pressure side via the capillary tube 14 ′, causing the refrigerant 1 to stagnate into the compressor 1.

If the capillary tube is not provided, there is a possibility that the liquid between the closing valve 22 and the receiver 7 is sealed.

[0009] The present invention has been made in view of the above points, and an object of the present invention is to enable a refrigerant to be efficiently stored in a receiver by a pump-down operation.

[0010]

According to the first aspect of the present invention, there are provided a compressor 1, a heat source side heat exchanger 3, a receiver 7, an expansion valve 4, and a use side heat exchanger 5 as means for solving the above problems. In the refrigerating apparatus, the low-pressure line 25 downstream of the expansion valve 4 and the gas phase of the receiver 7.
And an on-off valve 14 that opens the bypass passage 13 only during the period from the start of the pump-down operation to the stop of the operation of the compressor 1.

With the above configuration, the on-off valve 14 is opened only from the start of the pump-down operation to the stop of the operation of the compressor 1, and the gas phase of the receiver 7 and the expansion valve 4 are opened.
Is connected to the low pressure line 25 on the downstream side of
The liquid refrigerant can be efficiently stored in the receiver 7.
When the system is stopped (that is, when the operation of the compressor 1 is stopped).
The on-off valve 14 is closed, so that the receiver 7
Of refrigerant from the gas phase to the low pressure side of the compressor 1
It is also possible to avoid stagnation or the like of refrigerant.

As in the second aspect of the present invention, the first aspect
In the refrigerating apparatus described above, an electric expansion valve is adopted as the expansion valve 4, and the opening degree of the electric expansion valve 4 is set to correspond to the discharge pipe temperature of the compressor 1 at the start of a pump-down operation. In the case where the valve is fully closed after being maintained at a predetermined opening for a predetermined time before the operation stop of the operation 1, abnormal increase of high pressure and abnormal decrease of low pressure during the pump down operation can be avoided, and the receiver 7 is stopped when the system is stopped. Since the liquid refrigerant is sealed, it is possible to more reliably prevent the refrigerant from falling into the compressor 1 and the like.

As in the invention of claim 3, claim 1
3. In the refrigerating apparatus according to any one of (2) and (3), when the on-off valve 14 employs an electromagnetic on-off valve having a pressure relief mechanism 32 that releases pressure when the pressure rises to a predetermined pressure, the pressure becomes higher than a predetermined pressure. The pressure can be released through the electromagnetic on-off valve 14, and the closing valve 22
It is possible to avoid a liquid seal between the receiver and the receiver 7.

As in the invention of claim 4, in the refrigerating apparatus according to any one of claims 1, 2 and 3, when a compressor having no crankcase heater is employed as the compressor 1, cost reduction is achieved. Can be achieved.

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

This refrigeration system is provided with a refrigerant circuit similar to that described in the section of the prior art, and as shown in FIG. 1, a compressor 1, a four-way switching valve 2, and a condenser during cooling operation. An outdoor heat exchanger (that is, a heat source side heat exchanger) 3 acting as an evaporator during a heating operation, an electric expansion valve 4 acting as a pressure reducing mechanism, and a condenser acting as an evaporator during a cooling operation and during a heating operation The heat exchanger is provided with an indoor-side heat exchanger (that is, a use-side heat exchanger) 5 that functions as a refrigerant, and the refrigerant can be reversibly circulated by the switching operation of the four-way switching valve 2. Reference numeral 6 denotes a subcooling heat exchanger attached to the outdoor heat exchanger 3, reference numeral 7 denotes a receiver, and reference numeral 8 denotes a refrigerant flow switching mechanism.

As the compressor 1, a compressor having no crankcase heater is employed.

The refrigerant flow switching mechanism 8 is composed of four check valves 9 to 12, and the refrigerant from the outdoor heat exchanger 3 or the indoor heat exchanger 5 always receives the refrigerant from the receiver 7 and the electric expansion valve 4. It is to be controlled to flow to

Reference numeral 13 denotes a bypass connecting the gas phase of the receiver 7 to the low pressure line 25 downstream of the electric expansion valve 4. The bypass 13 has a pump-down operation as will be described in detail later. Solenoid on-off valve 1 that is opened only when
4 are interposed.

The compressor 1, the four-way switching valve 2, the outdoor heat exchanger 3, the electric expansion valve 4, the receiver 7, and the refrigerant flow switching mechanism 8 constitute an outdoor unit A, and the indoor heat exchanger 5 is an indoor unit. Unit B is configured.

Reference numeral 15 denotes an outdoor air temperature sensor for detecting an outdoor suction temperature (in other words, outdoor air temperature) To, 16 an outdoor heat exchange sensor for detecting an outdoor heat exchange temperature Tg of the outdoor heat exchanger 3, and 17 an indoor heat exchange sensor. An indoor temperature sensor for detecting the suction temperature (in other words, the indoor air temperature) Ta, 18 for detecting the indoor heat exchange temperature Tn of the indoor heat exchanger 5, and 19 for detecting the discharge pipe temperature Th. Discharge temperature sensor, 20 is an outdoor fan, 21 is an indoor fan, 22, 23
Is a closing valve, and 24 is a control unit.

In this refrigerating apparatus, as shown in FIG. 3, the time from when the pump-down stop signal is received (in other words, when the pump-down operation starts) to the time when the compressor 1 and the outdoor fan 20 stop operating. The opening and closing of the electric expansion valve 4 starts to be reduced from the time when the pump-down stop signal is received (in other words, the time when the pump-down operation is started) while the electromagnetic on-off valve 14 is opened only for a while. The opening of the electric expansion valve 4 is maintained at the predetermined opening ΔP for only 10 seconds before the operation of the outdoor fan 20 is stopped, and thereafter, the electric expansion valve 4 is fully closed. At the time of receiving the pump down stop signal, the control unit 24 determines the discharge pipe temperature Th of the compressor 1 and the opening EVm of the electric expansion valve 4 at that time.
Is stored.

As shown in FIG. 4, the opening ΔP of the electric expansion valve 4 is determined in accordance with the discharge pipe temperature Th at the time of receiving the stop signal. When Th is higher than 90 ° C., ΔP = EVm ×
When the discharge pipe temperature Th is 90 ° C. or less, ΔP = EVm × 0.4.
That is, only when the discharge pipe temperature Th is 90 ° C. or less, the electric expansion valve 4 is reduced to 40% of the opening EVm at the time of receiving the pump-down operation stop signal for 10 seconds before the operation of the compressor 1 is stopped. It is.

As described above, in the present embodiment, the solenoid on-off valve 14 is opened only from the start of the pump-down operation to the stop of the operation of the compressor 1, and the gas phase of the receiver 7 and the expansion valve 4 Since the low pressure line 25 on the downstream side is in communication with the low pressure line 25, the liquid refrigerant can be efficiently stored in the receiver 7. When the system is stopped (that is, when the compressor 1
When the operation is stopped), the solenoid on-off valve 14 is closed, so that the refrigerant does not flow out from the gas phase part of the receiver 7 to the low pressure side, and the refrigerant stagnation into the compressor 1 can be avoided. it can.

Further, the opening of the electric expansion valve 4 is maintained at a predetermined opening for a predetermined time before the operation of the compressor 1 is stopped in correspondence with the temperature of the discharge pipe of the compressor 1 at the start of the pump-down operation. And then fully closed,
Abnormal high pressure and abnormal low pressure during pump down operation can be avoided, and liquid refrigerant is sealed in the receiver 7 when the system is stopped, so that refrigerant stagnation in the compressor 1 and the like are more reliably avoided. be able to.

As described above, in the present embodiment, refrigerant stagnation or the like in the compressor 1 can be avoided. Therefore, as the compressor 1, it is preferable to use a compressor without a crankcase heater. This is desirable for cost reduction.

Further, the solenoid on-off valve 1 in the present embodiment
4, a valve body 26 having an inlet pipe 30 and an outlet pipe 31; a valve body 27 having a ball valve 27a for opening and closing a valve seat 26a of the valve body 26; 27
, And a solenoid 29 for sucking the suction body 28. A spring 32 having a predetermined urging force is provided between the valve body 27 and the suction body 28.
Is interposed. The spring 32 functions as a pressure relief mechanism for releasing the pressure when the pressure on the inlet pipe 30 side rises to a predetermined pressure. When the electromagnetic on-off valve 14 having such a configuration is used, when the pressure of the receiver 7 becomes equal to or higher than a predetermined pressure, the pressure can be released via the electromagnetic on-off valve 14, so that the liquid between the closing valve 22 and the receiver 7 is sealed. Can be avoided.

[0028]

According to the first aspect of the present invention, there is provided a refrigeration apparatus in which a compressor 1, a heat source side heat exchanger 3, a receiver 7, an expansion valve 4, and a use side heat exchanger 5 are sequentially connected. 7 and a low-pressure line 25 downstream of the expansion valve 4.
With an on-off valve 14 that opens only during the period from the start of the pump-down operation to the stop of the operation of the compressor 1,
The on-off valve 14 is opened only from the start of the pump-down operation to the stop of the operation of the compressor 1, so that the gas phase of the receiver 7 and the low-pressure line 25 downstream of the expansion valve 4 are connected. Therefore, there is an effect that the liquid refrigerant can be efficiently stored in the receiver 7. Further, when the system is stopped (that is, when the operation of the compressor 1 is stopped), the on-off valve 14 is closed, so that the refrigerant does not flow out of the gas phase portion of the receiver 7 to the low pressure side. There is also an effect that it is possible to avoid the refrigerant stagnation or the like.

As in the invention of claim 2, claim 1
In the refrigerating apparatus described above, an electric expansion valve is adopted as the expansion valve 4, and the opening degree of the electric expansion valve 4 is set to correspond to the discharge pipe temperature of the compressor 1 at the start of a pump-down operation. In the case where the valve is fully closed after being maintained at a predetermined opening for a predetermined time before the operation stop of the operation 1, abnormal increase of high pressure and abnormal decrease of low pressure during the pump down operation can be avoided, and the receiver 7 is stopped when the system is stopped. Since the liquid refrigerant is sealed, it is possible to more reliably prevent the refrigerant from falling into the compressor 1 and the like.

[0030] As in the invention of claim 3, claim 1
3. In the refrigerating apparatus according to any one of (2) and (3), when the on-off valve 14 employs an electromagnetic on-off valve having a pressure relief mechanism 32 that releases pressure when the pressure rises to a predetermined pressure, the pressure becomes higher than a predetermined pressure. The pressure can be released through the electromagnetic on-off valve 14, and the closing valve 22
It is possible to avoid a liquid seal between the receiver and the receiver 7.

As in the invention of claim 4, in the refrigerating apparatus according to any one of claims 1, 2 and 3, when a compressor having no crankcase heater is adopted as the compressor 1, cost reduction is achieved. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an electromagnetic on-off valve used in the refrigeration apparatus according to the embodiment of the present invention.

FIG. 3 is a time chart illustrating behaviors of an electric expansion valve, a compressor, an electromagnetic on-off valve, and an outdoor fan during a pump-down operation in the refrigeration apparatus according to the embodiment of the present invention.

FIG. 4 is a table for determining an opening of an electric expansion valve during a pump-down operation in the refrigeration apparatus according to the embodiment of the present invention.

FIG. 5 is a refrigerant circuit diagram of a conventional refrigeration apparatus.

FIG. 6 is a time chart illustrating behaviors of an electric expansion valve, a compressor, and an outdoor fan during a pump-down operation of a conventional refrigeration apparatus.

FIG. 7 is a table for determining a time from a stop of a compressor operation to a fully closed state of an electric expansion valve during a pump-down operation of a conventional refrigeration system.

[Explanation of symbols]

1 is a compressor, 3 is a heat source side heat exchanger, 4 is an expansion valve (electric expansion valve), 5 is a use side heat exchanger, 7 is a receiver, 13 is a bypass, 14 is an on-off valve (electromagnetic on-off valve), 22 and 23 are closing valves, 24 is a control unit, 25 is a low pressure line, 32
Is a pressure relief mechanism (spring).

Claims (4)

[Claims] 1. A compressor (1), a heat source side heat exchanger (3),
A refrigeration apparatus in which a receiver (7), an expansion valve (4), and a use side heat exchanger (5) are sequentially connected, wherein a gas phase portion of the receiver (7) and a downstream side of the expansion valve (4). And a switching valve (14) for opening the bypass passage (13) only from the start of the pump-down operation to the stop of the operation of the compressor (1). ). 2. An electric expansion valve is adopted as the expansion valve (4), and an opening degree of the electric expansion valve (4) corresponds to a discharge pipe temperature of the compressor (1) at the start of a pump-down operation. The refrigerating apparatus according to claim 1, wherein the compressor (1) is kept at a predetermined opening for a predetermined time before the operation of the compressor (1) is stopped, and then is fully closed. 3. A pressure relief mechanism (3) for releasing pressure when the pressure rises to a predetermined pressure, as the on-off valve (14).
The refrigeration apparatus according to any one of claims 1 and 2, wherein an electromagnetic on-off valve having (2) is adopted. 4. The refrigerating apparatus according to claim 1, wherein a compressor having no crankcase heater is employed as the compressor (1).