JP2001235246A - Freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a changing-over mechanism (22) for changing-over a single- stage compressing operation and double-stage compressing operation in a freezer (1) provided with double-stage compressing mechanisms (11, 21), enable a low cost formation to be attained and the circuit to be simplified and further concurrently a changing-over control to be easily carried out. SOLUTION: A changing-over between a single stage compressing operation and double-stage compressing operation is carried out by a four-way changing- over valve (22) in place of a plurality of solenoid valves.

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 two-stage compression mechanism, and more particularly to a technique for simplifying a switching structure between a single-stage compression operation and a two-stage compression operation.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 4-80545
As described in the publication, a two-stage compression refrigeration cycle is employed in a refrigeration system that requires a low evaporation pressure and a high compression ratio operation. The compression mechanism of the two-stage compression refrigeration cycle is composed of a low-stage compressor and a high-stage compressor, and uses a single-stage compression operation using only one compressor and uses both compressors in series. It is configured to be able to switch between two-stage compression operation.

[0003] As a switching mechanism for switching between the single-stage compression operation and the two-stage compression operation, a plurality of solenoid valves are provided on the discharge side and the suction side of each compressor (depending on the circuit configuration of the refrigerant circuit). For example, a total of about two to three are provided, and the number of compression stages is switched by appropriately opening and closing them.

[0004]

However, in such a conventional configuration, a plurality of solenoid valves are required to switch between the single-stage compression operation and the two-stage compression operation. There was a problem that the configuration was complicated. Also, in order to avoid a situation in which all of these solenoid valves are closed during operation, it is necessary to open and close each solenoid valve at the same time when the number of compression stages is switched, thereby ensuring the reliability of the opening and closing control. There was also a need.

The present invention has been made in view of the above problems, and has as its object to simplify a switching mechanism for switching between a single-stage compression operation and a two-stage compression operation to reduce cost. Therefore, the switching control can be easily performed at the same time.

[0006]

According to the present invention, the switching between the single-stage compression operation and the two-stage compression operation is performed by one four-way switching valve instead of a plurality of solenoid valves.

Specifically, a solution taken by the present invention is a two-stage compression mechanism (11, 21) comprising a low-stage compressor (11) and a high-stage compressor (21), and a two-stage compression mechanism. It is premised on a refrigerating apparatus that includes a switching mechanism (22) for switching between operation and single-stage compression operation and performs a refrigeration cycle. Then, the switching mechanism (22) includes a low-stage compressor (11), a high-stage compressor (21), and a predetermined heat exchanger (31).
Connected to the low-stage compressor (11) and the high-stage compressor (21)
And a predetermined heat exchanger (31) in order, and a second communication state in which the low-stage compressor (11) communicates with the predetermined heat exchanger (31). It is constituted by a four-way switching valve.

In the above configuration, the four-way switching valve (22) communicates with the discharge side of the low-stage compressor (11) and the suction side of the high-stage compressor (21) in the first communication state. While the discharge side of the stage side compressor (21) communicates with the predetermined heat exchanger (31), in the second communication state, the discharge side or suction side of the low stage side compressor (11) communicates with the predetermined heat exchanger. (31), and the suction side and the discharge side of the high-stage compressor (21) can be configured to communicate with each other.

Further, in the above configuration, the low-stage compressor is provided.
High-stage compressor (21) in gas line (40G) connected to (11)
An over-pressure release passage (44) connected by bypassing the four-way switching valve (22) is provided in the over-pressure release passage (44) from the high-stage compressor (21) to the gas line (40G). It is preferable to provide a check valve (45) that allows only the flow of the refrigerant to the air.

In the above solution, when the four-way switching valve (22), which is a switching mechanism, is in the first communication state, the discharge gas of the low-stage compressor (11) is supplied to the four-way switching valve (22). Through the high-stage compressor (21),
It is compressed in two stages and supplied to a predetermined heat exchanger (31). In this case, the predetermined heat exchanger (31) is, for example, an indoor heat exchanger that becomes a condenser during a heating operation in an air conditioner. Then, after the refrigerant is condensed in this heat exchanger, the remaining steps of the refrigeration cycle, that is, the expansion step by the expansion mechanism and the evaporation step by the evaporator (in this case, the outdoor heat exchanger) are performed, and the low-stage It is sucked into the side compressor (11).

On the other hand, in the second communication state, the low-stage compressor (11) communicates with the predetermined heat exchanger (31), and the high-stage compressor
(21) is a state where the suction side and the discharge side communicate with each other. At this time, the high-stage compressor (21) stops, and a single-stage compression operation in which the discharge side or the suction side of the low-stage compressor (11) communicates with the predetermined heat exchanger (31) is established. Therefore, for a given heat exchanger (3
When 1) is the indoor heat exchanger of the above air conditioner,
The indoor heat exchanger as a condenser, heating operation with the outdoor heat exchanger as an evaporator, and conversely, the outdoor heat exchanger as a condenser,
A cooling operation using the indoor heat exchanger as an evaporator can be performed.

Also, during single-stage compression operation, the high-stage compressor (2
1) is not used and the discharge side and the suction side of the high-stage compressor (21) are in communication with each other, but by providing the overpressure release passage (44), the high-stage compressor When the liquid refrigerant accumulated in (21) evaporates due to an increase in ambient temperature or the like, the refrigerant can escape from the high-stage compressor (21) to the gas line (40G). Further, when the liquid refrigerant is accumulated in the high-stage compressor (21), the refrigerant can be sent out into the circuit by heating as necessary with a crankcase heater or the like.

[0013]

As described above, according to the above-described solution, a single-stage compression operation and a two-stage compression operation are switched by using one four-way switching valve (22) instead of a plurality of solenoid valves. I have. Therefore, the cost can be reduced and the circuit can be simplified. Further, since only one four-way switching valve (22) is used, all the passages connected to the four-way switching valve (22) are not simultaneously closed. In other words, operation switching can be performed with high reliability without performing difficult control.

When the overpressure release passage (44) is provided, the refrigerant accumulated in the high-stage compressor (21) can escape into the circuit, so that the liquid refrigerant is heated and (21) It is possible to prevent the inside from becoming high pressure, and it is possible to prevent the circulation amount of the refrigerant in the circuit from being reduced by heating occasionally as necessary with a crankcase heater or the like.

[0015]

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

According to the embodiment of the present invention, the single-stage compression operation and the two-stage compression can be switched during the heating operation, and the single-stage compression operation and the two-stage compression are performed in the air conditioner (1) in which the single-stage compression is performed during the cooling operation. A four-way switching valve is used as a switching mechanism for switching between the stage compression operation.

The specific circuit configuration of the air conditioner (1) is as follows.

That is, as shown in FIG. 1, this air conditioner comprises an outdoor unit (10), an intermediate unit (20),
And a plurality of indoor units (30) connected in parallel. The intermediate unit (20) enables the two-stage compression operation in the existing air conditioner (1) of the single-stage compression system, and the existing air conditioner having the outdoor unit (10) and the indoor unit (30) It is configured so that it can be expanded.

The outdoor unit (10) includes a low-stage compressor (11) having a variable capacity, a first four-way switching valve (12) for switching between a cooling operation and a heating operation, and an outdoor heat exchanger (13). , Outdoor expansion valve (14)
And The intermediate unit (20) is connected to the high-stage compressor (2
1), a second four-way switching valve (22) as a switching mechanism for switching between the two-stage compression operation and the single-stage compression operation during the heating operation, an intermediate expansion valve (23), and a gas-liquid separator (24). It has. Also,
Each indoor unit (30) consists of an indoor heat exchanger (31) and an indoor expansion valve.
(32). These devices are connected in order by a refrigerant pipe (40) and configured to perform a vapor compression refrigeration cycle, and include a low-stage compressor (11) and a high-stage compressor (12). A two-stage compression mechanism (11, 21) is constituted. The refrigerant pipe (40) is connected between the units (10, 20, 30) by a pipe joint (41).

Specifically, the low-stage compressor (11) and the high-stage compressor (21) have a first four-way switching valve (12) and a second four-way switching valve on the suction side and the discharge side, respectively. It is connected to two ports of (22). First four-way switching valve (12) and second four-way switching valve (22)
Are connected to each other, one port of the first four-way switching valve (12) is connected to the outdoor heat exchanger (13), and the other port of the second four-way switching valve (22) is connected to the other port. It is connected to the indoor heat exchanger (31). By switching the four-way switching valves (12, 22) to the state shown by the solid line in FIG. 1, the low-stage compressor (11)
Is discharged into the high-stage compressor (21) through the two-way switching valve (12, 22). As described above, the gas line (40G) is formed between the outdoor heat exchanger (13) and the indoor heat exchanger (31).

As described above, the second four-way switching valve (22), which is a switching mechanism for switching between two-stage compression and single-stage compression, includes the low-stage compressor (11) and the high-stage compressor (21). It is connected to the indoor heat exchanger (31). The second four-way switching valve (22) has a first communication state in which the low-stage compressor (11), the high-stage compressor (21), and the indoor heat exchanger (31) sequentially communicate with each other; The low-stage compressor (11) and the indoor heat exchanger (31) are configured to be able to be set to a second communication state in which they communicate with each other.

More specifically, when the second four-way switching valve (22) is set to the first communication state, the discharge side of the low-stage compressor (11) and the suction side of the high-stage compressor (21) And the high-stage compressor (2
The discharge side of 1) communicates with the indoor heat exchanger (31). When the second four-way switching valve (22) is set to the second communication state, the discharge side or the suction side of the low-stage compressor (11) and the indoor heat exchanger (31)
And the suction side and the discharge side of the high-stage compressor (21) communicate with each other.

On the other hand, the indoor heat exchanger (31) and the outdoor heat exchanger (1)
3), the indoor expansion valve (32), the intermediate expansion valve (23), and the gas-liquid separator in order from the indoor heat exchanger (31) side.
(24) and an outdoor expansion valve (14). The gas outlet of the gas-liquid separator (24) is connected to the suction pipe to the high-stage compressor (21) between the two four-way switching valves (12, 22) to form an injection passage (42). are doing. An opening / closing valve (43) such as a solenoid valve is provided in the injection passage (42).

Further, the gas line (40G) between the two four-way switching valves (12, 22), the second four-way switching valve (22) and the high-stage compressor (2
An overpressure release passage (44) that bypasses the four-way switching valve (22) is connected to the suction pipe during 1). The over-pressure release passage (44) is provided with an over-pressure release valve (45) formed of a check valve, so that only refrigerant flows from the high-stage compressor (21) to the gas line (40G). Is allowed. Then, when the high-stage compressor (21) is stopped during single-stage compression, the high-stage compressor (21) is cooled in order to prevent the liquid refrigerant from accumulating due to cooling. (21) is heated by heating means (25) such as a crankcase heater so that the gas refrigerant is discharged from the overpressure release passage (44).

As the second four-way switching valve (22), for example, a rotary four-way switching valve can be used. The rotary four-way switching valve may be configured to switch the flow path by employing an electromagnetic driving method, a motor driving method, or the like.

-Operation- Next, the operation of the air conditioner (1) will be described.

First, the operation when the heating operation is performed by the two-stage compression will be described with reference to FIG. 2 showing the flow direction of the refrigerant. At this time, each of the four-way switching valves (12, 22) is set to the state shown by the solid line in FIG. The indoor expansion valve (3
2) is set to fully open, the opening degree of the intermediate expansion valve (23) is set to reduce the high pressure refrigerant to a predetermined intermediate pressure, and the outdoor expansion valve (13) sets the intermediate pressure refrigerant to a predetermined low pressure. The opening is set to reduce the pressure. The above settings are for gas injection, and at this time, the injection passage (42)
Open / close valve (43) is open.

The low-pressure compressor (11) compresses the low-pressure refrigerant in one stage and discharges it, and discharges the discharged gas to the high-stage compressor.
In (21), two-stage compression is performed. The gas refrigerant discharged from the high-stage compressor (21) flows into the indoor heat exchanger (31) via the second four-way switching valve (22) and exchanges heat with the indoor air to heat the indoor air. .
The heated indoor air is blown into the room by an indoor fan (not shown), and warm air is supplied to the room.

The refrigerant condensed by the heat exchange in the indoor heat exchanger (31) passes through the indoor expansion valve (32) and then passes through the intermediate expansion valve (2).
A part expands in 3) and becomes a two-phase refrigerant and flows into the gas-liquid separator (24). Then, the liquid refrigerant and the gas refrigerant are separated by the gas-liquid separator (24), and the liquid refrigerant flows out of the gas-liquid separator (24), is decompressed by the outdoor expansion valve (14), and is discharged from the outdoor heat exchanger (13). ).
Then, in the outdoor heat exchanger (13), the refrigerant exchanges heat with outdoor air and is heated, and changes into a gaseous refrigerant and changes into a first four-way switching valve.
After passing through (12), it is sucked into the low-stage compressor (11).

On the other hand, the gas refrigerant in the gas-liquid separator (24) flows out of the gas outlet and merges with the discharge gas refrigerant of the low-stage compressor (11) through the injection passage (42) to form a high-stage gas refrigerant. It is sucked into the side compressor (21). Therefore, since the amount of the refrigerant flowing through the indoor heat exchanger (31) increases, the heating capacity can be increased. When gas injection is not performed, the intermediate expansion valve (23) is set fully open, and the on-off valve (43) of the injection passage (42) is set to "closed".

Next, a single-stage compression heating operation will be described with reference to FIG. 3 showing the flow direction of the refrigerant. At this time, the low-stage compressor (11) is operated to stop the high-stage compressor (21), and the two-way switching valves (12, 22) are set to the state shown by the solid line in FIG. At this time, the first four-way switching valve (12)
2, but the second four-way switching valve (22) is switched to the second communication state while being in the first communication state in FIG. Then, the indoor expansion valve (32) and the intermediate expansion valve (23) are fully opened, and the electromagnetic valve (43) in the injection passage (42) is closed.

With this arrangement, the gas discharged from the low-stage compressor (11) is supplied to the indoor heat exchanger (31) via the first four-way switching valve (12) and the second four-way switching valve (22). ) And flows into the indoor heat exchanger (31)
In the room air. The refrigerant condensed at that time passes through the indoor expansion valve (32), the intermediate expansion valve (23), and the gas-liquid separator (24), and is decompressed to a predetermined low pressure by the outdoor expansion valve (14). It flows into the heat exchanger (13). This outdoor heat exchanger (1
In 3), the refrigerant is heated and changes to the gas phase, and the low-stage compressor
Inhaled to (11). The single-stage compression heating operation is performed by repeating the above cycle.

When frost is formed on the outdoor heat exchanger (13) by performing the heating operation in the two-stage compression or the single-stage compression, a defrost operation showing the flow of the refrigerant in FIG. 4 is performed. During defrost operation,
Both compressors (11, 21) are operated in a state where the capacity of the low-stage compressor (11) is larger than the capacity of the high-stage compressor (21), and the first four-way switching valve (12) is shown in FIG. The second four-way switching valve (22)
Is set to the state indicated by the solid line. Further, the indoor expansion valve (32) is set to fully open, the opening degree of the intermediate expansion valve (23) and the outdoor expansion valve (14) is controlled so as to reduce the high-pressure liquid refrigerant to a predetermined low pressure, and the injection passage ( The solenoid valve (43) of 42) is set to "open".

With the above settings, as shown in FIG.
The discharge gas of the low-stage compressor (11) flows into the outdoor heat exchanger (13) via the first four-way switching valve (12), and the outdoor heat exchanger (13)
Heat to defrost. At this time, the outdoor fan (not shown) is stopped, the refrigerant is cooled somewhat, flows out of the outdoor heat exchanger (13), is decompressed by the outdoor expansion valve (14), and is almost in a gas phase. (24).

On the other hand, the gas discharged from the high-stage compressor (21) flows into the indoor heat exchanger (31) via the second four-way switching valve (22). At this time, the indoor fan (not shown) is rotating, and heat exchange between the refrigerant and the indoor air is performed. Therefore, the blowing of the warm air into the room is continued, and the refrigerant is condensed and flows out of the indoor heat exchanger (31). The refrigerant is then supplied to the intermediate expansion valve (23)
The pressure is reduced to a gas-liquid two-phase state, flows into the gas-liquid separator (24), and mixes with the low-stage refrigerant.

This refrigerant is heated by the residual heat of the low-stage refrigerant in the gas-liquid separator (24). And gas-liquid separator (24)
The gas refrigerant flows out of the compressor and splits into the lower stage and the higher stage, and is sucked into the compressors (11, 21). The refrigerant drawn into each of the compressors (11, 21) is compressed again and discharged, and the above cycle is repeated on the outside and the inside of the room. Thus, in the present embodiment, the heating operation can be continued while the outdoor heat exchanger (13) is being defrosted.

Next, the cooling operation is performed by operating only the low-stage compressor (11) and switching the two-way switching valves (12, 22) to the state shown by the broken line in FIG. At this time, the outdoor expansion valve (14) and the intermediate expansion valve (23) are set to fully open, and the opening of the indoor expansion valve (32) is controlled so as to reduce the high-pressure refrigerant to a predetermined low pressure. Further, the solenoid valve (43) of the injection passage (42) is closed. With the above settings, the refrigerant flows in the low-stage compressor (11) and the first four-way switching valve as shown in FIG.
(12), outdoor heat exchanger (13), outdoor expansion valve (14), gas-liquid separator
(24), intermediate expansion valve (23), indoor expansion valve (32), indoor heat exchanger
(31), the second four-way switching valve (22) flows in this order, and cool air is blown into the room when heat is exchanged in the indoor heat exchanger (31).

When the high-stage compressor (21) is stopped, such as during a heating operation or a cooling operation by single-stage compression,
The high-stage compressor (21) is heated by a heating means (25) such as a crankcase heater and the gas refrigerant is drawn from the overpressure release passage (44) to the gas line (40G). The liquid refrigerant is prevented from accumulating in 21). The high-stage compressor (2
Even if the liquid refrigerant accumulated in 1) evaporates due to an increase in ambient temperature, the refrigerant can escape to the gas line (40G), preventing the pressure of the high-stage compressor (21) from rising abnormally. it can.

-Effects of Embodiment- As described above, in this embodiment, the single-stage compression operation and 2
As a mechanism for switching between the two-stage compression operation, a single second four-way switching valve (22) is used as a switching mechanism instead of a plurality of solenoid valves, so that the cost is reduced as compared with the case of using a plurality of solenoid valves. And the circuit can be simplified. In addition, even when the electromagnetic drive system is employed for the second four-way switching valve (22), which is a switching mechanism, the number can be reduced as compared with the case where a plurality of electromagnetic valves are used, so that cost reduction can be achieved even with the same electromagnetic system. It is possible to plan.

In the above embodiment, since the four-way switching valve (22) is used as the switching mechanism, all the paths connected to the four-way switching valve (22) are not closed at the same time. Therefore, the switching between the single-stage compression operation and the two-stage compression operation can be performed with high reliability without performing difficult control.

Further, an overpressure release passage (44) is provided to allow the refrigerant accumulated in the high-stage compressor (21) to escape to the gas line (40G). It is possible to prevent the inside of the high-stage compressor (21) from becoming abnormally high pressure, and to heat the refrigerant of the high-stage compressor (21) occasionally as necessary with a crankcase heater (25) or the like. Can be sent out into the circuit, so that the amount of circulating refrigerant in the circuit can be prevented from being reduced.

[0042]

Other Embodiments of the Invention The present invention may be configured as follows with respect to the above embodiment.

For example, in the above embodiment, the air-conditioning apparatus (1) capable of cooling and heating is configured to be able to switch between the single-stage compression operation and the two-stage compression operation during heating. The present invention can also be applied to an air conditioner capable of performing the above-described method, a refrigeration device other than the air conditioner, and the like. Also,
The circuit configuration of the above-described embodiment is merely an example. For example, the intermediate unit (20) may not be used, and the outdoor unit (10) may include a two-stage compression mechanism (11, 21). Thus, in the present invention, the specific configuration may be arbitrarily determined as long as the single-stage compression operation and the two-stage compression operation can be switched using the four-way switching valve.

Furthermore, as the second four-way switching valve (22), a rotary four-way switching valve of an electromagnetic drive type or a motor drive type has been exemplified, but the drive type and the switching structure are not limited to these. Instead, an arbitrary method or structure may be appropriately selected.

[Brief description of the drawings]

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

FIG. 2 is an operation state diagram showing an operation when performing a heating operation by two-stage compression in the air-conditioning apparatus of FIG.

FIG. 3 is an operation state diagram showing an operation when performing a heating operation by single-stage compression in the air-conditioning apparatus of FIG. 1;

FIG. 4 is an operation state diagram showing an operation when performing a defrost operation in the air-conditioning apparatus of FIG. 1;

FIG. 5 is an operation state diagram showing an operation when performing a cooling operation in the air-conditioning apparatus of FIG. 1;

[Explanation of symbols]

 (1) Air conditioner (refrigerator) (10) Outdoor unit (11) Low stage compressor (12) First four-way switching valve (13) Outdoor heat exchanger (14) Outdoor expansion valve (20) Intermediate unit (21) High-stage compressor (22) Second four-way switching valve (switching mechanism) (23) Intermediate expansion valve (24) Gas-liquid separator (25) Heating means (30) Indoor unit (31) Indoor heat exchange (32) Indoor expansion valve (40) Refrigerant piping (40G) Gas line (40L) Liquid line (41) Piping joint (42) Injection passage (43) Open / close valve (44) Overpressure release passage (45) Overpressure release valve

Claims (3)

[Claims] 1. A two-stage compression mechanism (11, 21) comprising a low-stage compressor (11) and a high-stage compressor (21), and a switching mechanism for switching between a two-stage compression operation and a single-stage compression operation. (22), and configured to perform a refrigeration cycle, the switching mechanism (22), the low-stage compressor (11) and the high-stage compressor (21)
And a predetermined heat exchanger (31).
1), a first communication state in which the high-stage compressor (21) and the predetermined heat exchanger (31) communicate sequentially, and a low-stage compressor (11) and the predetermined heat exchanger (31). A refrigeration apparatus including a four-way switching valve that can be set to a second communication state in which communication is performed. 2. The four-way switching valve (22) communicates with the discharge side of the low-stage compressor (11) and the suction side of the high-stage compressor (21) in the first communication state, While the discharge side of the compressor (21) communicates with the predetermined heat exchanger (31), in the second communication state, the discharge side or suction side of the low-stage compressor (11) communicates with the predetermined heat exchanger (3).
The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is configured so that the suction side and the discharge side of the high-stage compressor (21) communicate with each other. 3. An over-pressure release passage connected to a gas line (40G) connected to the low-stage compressor (11) from the high-stage compressor (21) by bypassing the four-way switching valve (22). (44), and the overpressure release passage (44) is connected to the gas line from the high-stage compressor (21).
The refrigeration apparatus according to claim 2, further comprising a check valve (45) that allows only the flow of the refrigerant to the (40G).