JP2001091064A - Refrigeration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable refrigeration system, in which liquid compression caused by refrigerant flowing from a liquid injection circuit into a compressor and failure of compressor due to frequent start/stop can be prevented. SOLUTION: A liquid injection circuit 9 in then vicinity of a scroll compressor 1 is provided with a first solenoid valve 15 which openes during operation of the scroll compressor 1 and closes upon stoppage thereof. The liquid injection circuit 9 is further provided, on the upstream side of the first solenoid valve 15 in the direction of refrigerant flow, with flow regulation resistors 17, 18, and a second solenoid valve 16 which opens/closes, depending on the temperature of refrigerant delivered from the scroll compressor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus used for, for example, a supermarket showcase, a refrigerator, a freezer, and the like, and more particularly to an improvement in reliability thereof.

[0002]

2. Description of the Related Art A conventional refrigeration apparatus of this type is disclosed in Japanese Patent Application Laid-Open No. Hei 5-172408. FIG. 4 is a refrigerant piping system diagram showing the refrigeration apparatus, in which 1 is a compressor, 2 is a condenser, 3 is a decompression device (expansion valve), 4 is an evaporator, and 5 is a first-stage electromagnetic device. A valve, 6 is a second-stage solenoid valve, 7 is a first-stage capillary tube, and 8 is a second-stage capillary tube. The compressor 1 is of a volume type such as a scroll or a screw. Also, the high-pressure liquid pipe coming out of the condenser 2 and the middle of the compression process of the compressor 1 are connected to the first-stage solenoid valve 5 and the first-stage capillary tube 7 or the second-stage solenoid valve 6 and the second-stage capillary tube. A liquid injection circuit (bypass circuit) that communicates with the circulating fluid through an inlet 8 is formed.

Next, the operation will be described. The high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 1 is liquefied by the condenser 2. When the temperature of the discharged gas from the compressor 1 becomes equal to or higher than a predetermined temperature, the first-stage solenoid valve 5 is opened, and a part of the refrigerant from the condenser 2 is branched to a liquid injection circuit, and the first-stage capillary tube 7 is used. The pressure is reduced and injected during the compression process, whereby the temperature of the gas refrigerant discharged from the compressor 1 is reduced. Further, when the bypass amount of the first-stage capillary tube 7 is insufficient and the discharge gas temperature becomes equal to or higher than the next predetermined temperature, the second-stage solenoid valve 6 is also opened.
The refrigerant that has passed through the stage capillary tube 8 is similarly injected during the compression process to cool the discharged gas. The detection of the temperature of the discharge gas refrigerant from the compressor 1 is performed by a thermostat, a thermistor, or the like attached to the discharge gas pipe (detailed description is omitted). By setting the discharge gas temperature in two stages and forming a two-stage bypass circuit in this way, the injection flow rate by the liquid injection circuit is optimized.

As described above, in the conventional refrigeration system, by providing the liquid injection circuit, a part of the liquid refrigerant is bypassed and injected into the middle part (intermediate pressure part) of the compression process of the compressor 1 and recompressed. The theoretical Mollier diagram in that case is shown in FIG. In the figure, G is a refrigerant circulation amount that actually contributes to cooling on the load side, and g is a refrigerant flow rate (injection flow rate) flowing through the liquid injection circuit. Further, a solid line indicates a refrigeration cycle when the liquid injection circuit is provided, and a broken line indicates a refrigeration cycle when the liquid injection circuit is not provided. The above-described liquid injection contributes to a decrease in the discharge gas temperature of the compressor 1 as shown in FIG.

[0005]

In the conventional refrigeration system, the state of the refrigerant in the liquid injection circuit can be understood from the fact that the refrigerant is located inside the saturated vapor line and the saturated liquid line in FIG. In a gas-liquid two-phase state.
Therefore, when the compressor 1 is stopped, the gas-liquid two-phase refrigerant present in the liquid injection circuit downstream of the first-stage solenoid valve 5 and the second-stage solenoid valve 6 flows into the compressor 1,
Liquid compression may occur at the next startup. When the refrigerant in the liquid injection circuit flows during the stop, the suction pressure of the compressor 1 increases. Therefore, when the suction pressure of the compressor 1 is detected and the operation / stop of the compressor 1 is controlled based on the detected suction pressure, the suction pressure of the compressor 1 is reduced to a predetermined value by the inflow of the refrigerant. In some cases, the start / stop operation is repeated, for example, when the pressure reaches the pressure and the compressor 1 starts and stops. As described above, conventionally, in order to cause liquid compression or frequently start and stop, the compressor 1
However, there is a problem that the mechanical life is shortened and the possibility of failure at an early stage is increased. In particular, in the refrigerating apparatus having a large volume in the liquid injection circuit and a small compression chamber volume (displacement amount) in the compressor 1, the above-described problem is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is caused by liquid compression or frequent start and stop caused by refrigerant in a liquid injection circuit flowing into a compressor. An object of the present invention is to provide a highly reliable refrigeration apparatus that prevents a compressor from malfunctioning.

[0007]

To achieve the above object, the present invention provides a refrigerant circuit in which a scroll compressor, a condenser, a decompression device, and an evaporator are sequentially connected to a pipe, from a condenser to a decompression device. Refrigeration apparatus provided with a liquid injection circuit that communicates a refrigerant circuit between the compressor and the intermediate pressure section of the scroll compressor, the liquid injection circuit near the scroll compressor opens when the scroll compressor is operating and closes when the scroll compressor is stopped. A first solenoid valve for providing a valve is provided,
The liquid injection circuit upstream of the first solenoid valve in the refrigerant flow direction is provided with a flow rate adjusting resistor and a second solenoid valve that opens and closes according to the temperature of the refrigerant discharged from the scroll compressor.

[0008] Further, a refrigerant circuit in which a scroll compressor, a condenser, a decompression device, and an evaporator are sequentially connected to a pipe, a refrigerant circuit from the condenser to the decompression device, and an intermediate pressure portion of the scroll compressor are provided. A liquid injection circuit that communicates via a flow rate adjusting resistor and an electromagnetic valve, a pressure detection device that detects a suction pressure of the scroll compressor, and a control that starts and stops the scroll compressor according to the pressure detected by the pressure detection device. And a control device for performing the operation of the compressor, the control device, for a predetermined time after the pressure detected by the pressure detection device reaches a predetermined compressor start pressure, compressor start delay means for delaying the start of the scroll compressor It is provided.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. Embodiment 1 of the Invention FIG. 1 shows a refrigeration apparatus (condensing unit) according to Embodiment 1 of the present invention. In the figure, 1 is a scroll compressor, 2 is a condenser, 3 is a decompression device, and 4 is an evaporator, and these are sequentially connected to form a refrigerant circuit A. Also, 9
Is a refrigerant circuit A between the condenser 2 and the pressure reducing device 3.
And a liquid injection circuit provided so as to communicate with the intermediate pressure section (middle part of the compression process) of the scroll compressor 1.

Reference numeral 15 denotes a first solenoid valve provided in the liquid injection circuit 9 near the scroll compressor 1.
The first solenoid valve 15 is configured to always open while the scroll compressor 1 is operating, and to always close while the scroll compressor 1 is stopped. Reference numeral 16 denotes a second electromagnetic valve provided in the liquid injection circuit 9 on the upstream side of the first electromagnetic valve 15 in the refrigerant flow direction. The second electromagnetic valve 16 controls the temperature of the gas refrigerant discharged from the scroll compressor 1. It is configured to open and close accordingly. More specifically, if the temperature of the refrigerant discharged from the scroll compressor 1 is equal to or lower than a predetermined temperature, the second
When the solenoid valve 16 is closed and the temperature of the discharged refrigerant is equal to or higher than the predetermined temperature, the second solenoid valve 16 is opened.
The temperature of the discharged refrigerant is detected by a thermostat or thermistor attached to the discharge gas pipe of the scroll compressor 1 (illustration and detailed description are omitted).

Reference numeral 17 denotes a first capillary tube (a flow regulating resistor) connected in parallel with the second solenoid valve 16;
Reference numeral 8 denotes a second capillary tube (a flow regulating resistor) provided between the second solenoid valve 16 and the first solenoid valve 15, each of which is configured by a capillary tube or the like.
The temperature of the refrigerant discharged from the scroll compressor 1 does not rise abnormally,
Also, an appropriate flow rate of the liquid refrigerant flows so as not to drop abnormally.

Next, the operation of the refrigeration system will be described.
The high-temperature and high-pressure gas refrigerant compressed and discharged by the scroll compressor 1 is liquefied by the condenser 2. Here, since the first solenoid valve 15 is always open during the operation of the scroll compressor 1, a part of the high-pressure refrigerant flowing out of the condenser 2 branches off from the refrigerant circuit A to the liquid injection circuit 9 side, and usually, While the flow rate is controlled by the flow path resistance of both the first capillary tube 17 and the second capillary tube 18, the liquid is injected from the liquid injection circuit 9 to the intermediate pressure portion of the scroll compressor 1, and the discharged refrigerant temperature of the scroll compressor 1 Lower. And in the above, the injection flow rate is insufficient,
When the temperature of the refrigerant discharged from the scroll compressor 1 rises above the predetermined temperature, the second solenoid valve 16 in addition to the first solenoid valve 15 is opened, and the first capillary tube 17 is bypassed. Refrigerant whose flow rate is controlled by the resistance of only the tube 18 is injected into the intermediate pressure portion of the scroll compressor 1, and cools the discharged gas during the compression process.
That is, by opening the second solenoid valve 16, the injection flow rate increases, and the effect of lowering the discharge temperature increases.

As described above, by setting two stages, that is, the case where the discharge gas refrigerant temperature is equal to or lower than the predetermined temperature and the case where the discharge gas refrigerant temperature is equal to or higher than the predetermined temperature, a two-stage bypass circuit is formed. Liquid injection can be performed at a flow rate.

On the other hand, the cooling load on the evaporator 4 side decreases,
When the scroll compressor 1 stops, the first solenoid valve 15 and the second solenoid valve 16 also close in conjunction. At this time, a gas-liquid two-phase refrigerant is present in the liquid injection circuit 9, and the refrigerant flows into the compression chamber of the scroll compressor 1 due to a pressure difference between the high-pressure side liquid pipe and the intermediate pressure portion of the scroll compressor 1. Easy to flow. However, in this embodiment, the first solenoid valve 15 is provided at a position near the scroll compressor 1 downstream of the second solenoid valve 16, the first capillary tube 17, and the second capillary tube 18. In the liquid injection circuit 9, the internal volume of the pipe 9a connecting the first solenoid valve 15 and the scroll compressor 1 is small, and the amount of the gas-liquid two-phase refrigerant present here is also small. Also, after the first solenoid valve 15 is closed in conjunction with the scroll compressor 1, the refrigerant in the liquid injection circuit 9 upstream of the first solenoid valve 15 does not flow to the scroll compressor 1 side. . Therefore, only a small amount of refrigerant existing in the pipe 9a downstream of the first solenoid valve 15 flows into the compression chamber when the scroll compressor 1 is stopped.
The load on the scroll compressor 1 due to liquid compression when the is started is small. Therefore, with the above-described configuration, it is possible to prevent the failure of the scroll compressor 1 due to the liquid compression.

Further, since the amount of refrigerant flowing from the liquid injection circuit 9 is small, an increase in the suction pressure of the stopped scroll compressor 1 is suppressed. Therefore, even when the suction pressure of the scroll compressor 1 is detected and the operation / stop of the scroll compressor 1 is controlled based on the detected suction pressure, the suction pressure of the scroll compressor 1 is reduced to a predetermined compressor starting pressure by the inflow of the refrigerant. , And a compressor operation command is issued even though the load on the evaporator 4 side is small. Therefore, the failure of the scroll compressor 1 due to the frequent start / stop operation can be prevented. If the first solenoid valve 15 is provided at the most downstream side of the liquid injection circuit 9, the other solenoid valves and the capillary tube (flow rate adjusting resistor) may be arranged differently from the above.

Embodiment 2 of the Invention In the second embodiment of the present invention, the reliability of the refrigeration system is ensured with a configuration different from that of the first embodiment. In FIG. 2, reference characters A,
1-4, 9 and 15-18 are the same components as in the first embodiment. However, in this embodiment, the first solenoid valve 15 is provided on the most upstream side of the liquid injection circuit 9, then the second solenoid valve 16 and the first capillary tube 17 are provided in parallel, and the second capillary is provided on the most downstream side. A tube 18 is provided.

A pressure detecting device 10 detects the suction pressure of the scroll compressor 1 (a refrigerant pressure on the suction side).
Is a control device for controlling the operation of the scroll compressor 1 in accordance with the pressure detected by the pressure detection device 10.
Although not shown, the pressure detecting device 11 includes:
Compressor start delay means for delaying the start of the scroll compressor 1 for a predetermined time after the pressure detected by the pressure detection device 10 reaches a predetermined compressor start pressure is also provided.

The basic operation of the refrigerating apparatus according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted. Here, the operation of the pressure detecting device 10 and the control device 11 will be described. Normally, the refrigerating apparatus is set at a compressor stop pressure slightly lower than the saturation pressure for the evaporation temperature on the evaporator 4 side (for example, a supermarket showcase). For example, when the evaporating temperature is −40 ° C., the compressor stop pressure is −
It is set to about 0.02 MPa (gauge pressure).
Then, when the suction pressure of the scroll compressor 1 decreases to the compressor stop pressure, the control device 11 stops the operation of the scroll compressor 1.

After the scroll compressor 1 is stopped, the load on the evaporator 4 increases again as time passes. That is, the temperature in the refrigerator rises, and cooling becomes necessary. At this time, the suction pressure that rises with the temperature in the refrigerator is changed to a predetermined compressor starting pressure (for example, 0.05 MPa).
, The pressure detection device 10 sends the signal to the control device 1
1 and the control device 11 starts the scroll compressor 1 again. Normally, the refrigerating apparatus keeps the temperature on the evaporator 4 side substantially constant by repeating the above operation.

As described above, the control device 11 controls the scroll compressor 1 based on the suction pressure detected by the pressure detection device 10.
In order to control the operation / stop of the scroll compressor, the suction pressure increases due to the inflow of the refrigerant from the liquid injection circuit 9 when the scroll compressor 1 is stopped, and although the load on the evaporator 4 is not actually increased, the scroll compression is not performed. Conventionally, the machine 1 was operated. On the other hand, in this embodiment, the control device 11 is provided with a compressor start delay means, and as shown in FIG. 3, even after the suction pressure reaches the compressor start pressure, a predetermined time (for example, 60 seconds). ) Suspends the activation of the scroll compressor 1 and activates the scroll compressor 1 after the lapse of the predetermined time. By delaying the start-up of the scroll compressor 1 in this way, it is possible to prevent the scroll compressor 1 from frequently starting and stopping due to the inflow of the refrigerant, and to thereby reduce the life and the occurrence of failures,
The reliability of the refrigeration system can be improved.

[0021]

The present invention is configured as described above, and has the following effects. That is,
The first that opens and closes in conjunction with the operation of the scroll compressor
By providing the solenoid valve as close as possible to the scroll compressor in the liquid injection circuit, the volume of the liquid injection circuit between the first solenoid valve and the scroll compressor can be reduced. Therefore, it is possible to prevent the liquid compression at the time of startup caused by the gas-liquid two-phase refrigerant in the liquid injection circuit flowing into the stopped scroll compressor, to extend the life of the scroll compressor, and to improve the reliability of the refrigeration system. Performance can be improved.

Further, even if the suction pressure of the scroll compressor reaches a predetermined compressor starting pressure, the starting of the scroll compressor is delayed until a predetermined time has elapsed. Therefore, while the scroll compressor is stopped, it is possible to prevent frequent start and stop of the scroll compressor due to the gas-liquid two-phase refrigerant flowing in the liquid injection circuit flowing and the suction pressure rising,
The life of the scroll compressor can be extended, and the reliability of the refrigerating device can be improved.

[Brief description of the drawings]

FIG. 1 is a refrigerant piping system diagram of a refrigeration apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a refrigerant piping system diagram of a refrigeration apparatus according to Embodiment 2 of the present invention.

FIG. 3 is an explanatory diagram illustrating operation stop control of a scroll compressor according to Embodiment 2 of the present invention.

FIG. 4 is a refrigerant piping system diagram of a conventional refrigeration apparatus.

FIG. 5 is a theoretical Mollier diagram.

[Explanation of symbols]

1 scroll compressor, 2 condenser, 3 decompression device, 4
Evaporator, 9-liquid injection circuit, 10 pressure detector, 11 controller, 15 first solenoid valve, 16 second solenoid valve, 17 first capillary tube (flow control resistor), 18 second capillary tube (flow control) Resistor), A refrigerant circuit.

Claims (2)

[Claims] A scroll compressor, a condenser, a decompression device,
And a refrigerant circuit formed by sequentially connecting a pipe and an evaporator, and a liquid injection circuit that communicates the refrigerant circuit between the condenser and the pressure reducing device with an intermediate pressure section of the scroll compressor. In the liquid injection circuit in the vicinity of the scroll compressor, a first solenoid valve that opens during operation of the scroll compressor and closes when the scroll compressor is stopped is provided, and a first solenoid valve is disposed upstream of the first solenoid valve in the refrigerant flow direction. A refrigerating apparatus, wherein the liquid injection circuit is provided with a flow rate adjusting resistor and a second solenoid valve that opens and closes according to the temperature of refrigerant discharged from the scroll compressor. 2. A scroll compressor, a condenser, a decompression device,
And a refrigerant circuit in which an evaporator is sequentially connected to a pipe, and the refrigerant circuit between the condenser and the pressure reducing device and an intermediate pressure portion of the scroll compressor through a flow rate adjusting resistor and an electromagnetic valve. A liquid injection circuit communicating therewith, a pressure detection device for detecting a suction pressure of the scroll compressor, and a control device for controlling the operation and stop of the scroll compressor according to the pressure detected by the pressure detection device. In the refrigeration apparatus, the control device is provided with compressor activation delay means for delaying activation of the scroll compressor for a predetermined time after the pressure detected by the pressure detection device reaches a predetermined compressor activation pressure. And refrigeration equipment.