Refrigerator

Details Refrigerator Refrigerator

2001-06-15

2003-09-09

Tanner, Harry B. (Department: 3744)

Refrigeration

Automatic control

Refrigeration producer

C062S324600, C062S509000

Reexamination Certificate

active

06615597

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a refrigeration system, and more particularly to a technique for reducing the amount of refrigerant remaining on the indoor side by trapping the refrigerant on the outdoor side when the system is shut down.
BACKGROUND ART
A refrigeration system known in the art having an outdoor unit and an indoor unit connected to each other via communication pipes is designed to trap the refrigerant on the outdoor unit side when refrigerant leakage is detected and when the system is shut down in order to prevent the refrigerant from leaking into the room. For example, Japanese Laid-Open Patent Publication No. 5-118720 discloses a refrigeration system which performs a pump down operation for trapping the refrigerant on the outdoor unit side in the event of refrigerant leakage.
A conventional refrigeration system which traps the refrigerant in the indoor unit will be described with reference to FIG.
12
. The refrigeration system includes electromagnetic valves (
108
) and (
109
) along communication pipes (
113
) separately from stop valves (
106
) and (
107
) for closing an outdoor unit (
111
) before connecting the outdoor unit (
111
) and an indoor unit (
112
) to each other.
During a cooling operation, the refrigerant discharged from a compressor (
101
) circulates as it passes through a four-way switching valve (
102
), is condensed through an outdoor heat exchanger (
103
), depressurized through an electric expansion valve (
104
) and evaporated through an indoor heat exchanger (
105
), and then returns to the compressor (
101
) via the four-way switching valve (
102
). When the system is shut down, the electromagnetic valve (
109
) on the liquid side (the high pressure side) is first closed while leaving the compressor (
101
) operating. Thus, the pressure on the low pressure side of the refrigerant circuit gradually decreases, and a low pressure switch (
114
) is eventually activated to shut down the compressor (
101
). Simultaneously with the shut down of the compressor (
101
), the electromagnetic valve (
108
) on the gas side (the low pressure side) is closed to close the outdoor unit (
111
), thereby trapping the refrigerant in the outdoor unit (
111
). Through such a pump down operation, substantially no refrigerant exists in the indoor unit (
112
), thereby avoiding leakage of a large amount of refrigerant into the room.
On the other hand, during a heating operation, the refrigerant discharged from the compressor (
101
) circulates as it passes through the four-way switching valve (
102
), is condensed through the indoor heat exchanger (
105
), depressurized through the electric expansion valve (
104
) and evaporated through the outdoor heat exchanger (
103
), and then returns to the compressor (
101
) via the four-way switching valve (
102
). When the system is shut down, the state of the four-way switching valve (
102
) is first switched to another so as to change the circulation path of the refrigerant to that in the cooling operation described above. Then, an operation as the pump down operation in the cooling operation is performed.
However, in the conventional refrigeration system described above, it is necessary to provide the electromagnetic valves (
108
) and (
109
) respectively for the communication pipes (
113
) and (
113
), and these electromagnetic valves (
108
) and (
109
) cause an increase in the cost of the system.
Moreover, when performing the pump down operation in a heating operation, the four-way switching valve (
102
) needs to be switched before performing a refrigerant circulation operation as that in a cooling operation, which lowers the efficiency of the system and may even detract from the comfort in the room.
Especially, where a slightly flammable refrigerant such as R
32
or R
32
/
134
a
is used as the refrigerant, it is particularly desired that the refrigerant is confined in the outdoor unit when the system is shut down because there is a risk of ignition due to the combustion of the refrigerant.
The present invention has been made in view of the above and aims to provide a refrigeration system capable of trapping the refrigerant on the outdoor side while maintaining the high efficiency and the comfort.
DISCLOSURE OF THE INVENTION
In order to achieve the above-described object, the present invention is designed so that a refrigerant of an indoor unit is trapped in an outdoor unit without switching the circulation direction of the refrigerant discharged from a compressor when shutting down either a cooling operation or a heating operation.
Specifically, a refrigeration system according to the present invention includes: an outdoor unit (
1
) including a compressor (
4
), a flow path switching mechanism (
5
) for switching a circulation direction of a refrigerant discharged from the compressor (
4
), an outdoor heat exchanger (
6
), and an expansion valve (
7
) capable of being fully closed; an indoor unit (
2
) including an indoor heat exchanger (
8
); and a communication pipe (
3
) for connecting the outdoor unit (
1
) and the indoor unit (
2
) to each other, wherein: the outdoor unit (
1
) includes: a receiver (
10
) provided upstream of the expansion valve (
7
); a gas vent passageway (
12
) for connecting the receiver (
10
) and a downstream side pipe (
24
) of the expansion valve (
7
) to each other; gas vent opening/closing means (
13
) provided along the gas vent passageway (
12
); and a bridge circuit (
11
), wherein during a cooling operation, the bridge circuit (
11
) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (
6
), to the receiver (
10
) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (
7
), to the indoor heat exchanger (
8
), and during a heating operation, the bridge circuit (
11
) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (
8
), to the receiver (
10
) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (
7
), to the outdoor heat exchanger (
6
); and the refrigeration system further includes control means (
35
) for, before shutting down the compressor (
4
), opening the gas vent opening/closing means (
13
) and closing the expansion valve (
7
) while the compressor (
4
) is left operating, and for closing the gas vent opening/closing means (
13
) upon subsequent shut down of the compressor (
4
).
With the above arrangement, either in a cooling operation or in a heating operation, the condensed refrigerant will be expanded through the expansion valve (
7
) after passing through the receiver (
10
). Moreover, the backflow of refrigerant running from the receiver (
10
) to the bridge circuit (
11
) is prevented. Therefore, when shutting down either of these operations, the refrigerant is trapped in the receiver (
10
) by closing the expansion valve (
7
) without switching the flow path switching mechanism (
5
).
Because the expansion valve (
7
) is closed before the compressor (
4
) is shut down, the refrigerant is trapped in the receiver (
10
). At this time, since the gas vent opening/closing means (
13
) is opened, the gas refrigerant in the receiver (
10
) is discharged through the gas vent passageway (
12
), whereby the liquid refrigerant is efficiently stored in the receiver (
10
). Then, when the compressor (
4
) is shut down based on a predetermined condition, the gas vent opening/closing means (
13
) is closed, and the receiver (
10
) and the vicinity thereof are enclosed with the refrigerant being trapped therein. In this way, the refrigerant is collected into the outdoor unit (
1
) while the backflow thereof into the indoor unit (
2
) is prevented, thereby reducing the amount of refrigerant remaining in the indoor unit (
2
). Note that the control means (
35
) may be configured so as to start its control operation based on a predeterm

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