JPH04281160A - Refrigeration equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage refrigeration system having evaporators for refrigeration and refrigeration.

0002

[Prior Art] FIG. 2 shows, for example, US Pat. No. 3,150,498.
This is a refrigeration cycle diagram of a conventional refrigeration system as described in the above issue, in which 1 is two high-stage compressors connected in parallel, and the high-temperature and high-pressure gas refrigerant discharged from these compressors 1 is After being condensed in the condenser 2, some of the refrigerant passes through the first electromagnetic valve 3, is depressurized by the first expansion device 4, is evaporated in the first evaporator 5, and returns to the high-stage compressor 1. The first evaporator 5 is housed in, for example, a refrigerator showcase (not shown), and the evaporation temperature here is, for example, -10°C (internal temperature is 0°C).

6 is a second solenoid valve 7, a second throttle device 8,
A first bypass circuit is connected in this order to the second evaporator 9 and the low-stage compressor 10, and one end of the first bypass circuit 6 is connected between the condenser 2 and the first solenoid valve 3, The other end is connected between the first evaporator 5 and the high-stage compressor 1, and the remaining refrigerant out of the refrigerant condensed in the condenser 2 is passed through the second solenoid valve 7 to the second throttle. The pressure is reduced by the device 8 and the second evaporator 9
After being evaporated, it is sucked into the low-stage compressor 10. The temperature of the refrigerant discharged from the compressor 10 rises due to the compression action, but the mixture is mixed with the low-temperature gas refrigerant exiting the first evaporator 5 and sucked into the high-stage compressor 1. Reference numeral 11 denotes a second detour circuit equipped with a check valve 12 for preventing refrigerant from flowing backward from the discharge side to the suction side during operation of the low-stage compressor 10. When the refrigerant stops, this circuit 11 is bypassed and the refrigerant is allowed to flow.

The second evaporator 9 is housed in, for example, a refrigeration showcase (not shown), and the evaporation temperature here is, for example, -40°C. 13 is a detector for detecting the suction pressure of the high-stage compressor 1; 14 is an operation control device for controlling the number of operating high-stage compressors 1 for power saving; Taking advantage of the fact that the suction pressure of the high-stage compressor 1 changes depending on the cooling load at the A control signal for controlling the number of operating high-stage compressors 1 is output from the control device 14 . Reference numeral 15 is a protection device that detects the current of a motor (not shown) provided in the low-stage compressor 10, for example, and forcibly stops the low-stage compressor 10 when this current reaches an abnormal current value.

In the refrigeration system configured as described above, when the low stage compressor 10 abnormally stops, the refrigerant flows through the second detour circuit 11. However, since the number of high-stage compressors 1 in operation is controlled by the operation control device 14 that operates according to the cooling load state of the first evaporator 5, Operation is controlled regardless of the situation.

[0006]

[Problems to be Solved by the Invention] As described above, in the conventional refrigeration system, when the low-stage compressor 10 abnormally stops, the high-stage compressor 10 is stopped, regardless of the cooling load state of the second evaporator 9, which is used for refrigeration. Since the capacity of the compressor 1 is controlled, there is a problem in that frozen foods, ice cream, etc. stored in the freezer showcase may melt.

[0007] This invention was made in order to eliminate the above-mentioned problems, and even if the low-stage compressor stops abnormally, it is possible to minimize the melting of food stored in the freezer showcase. The object of the present invention is to obtain a refrigeration system that is backed up by a high-stage compressor.

[0008]

[Means for Solving the Problems] A refrigeration system according to the present invention includes a plurality of parallel-connected high-stage compressors or a capacity-controllable high-stage compressor, a condenser, a first throttle device, a first a refrigeration cycle in which the evaporators of a first detour circuit connected in this order to a throttling device, a second evaporator, and a low-stage compressor; and a check valve for blocking refrigerant flow from the discharge side to the suction side of the low-stage compressor. a second detour circuit that bypasses the low-stage compressor; a detector that detects the ambient air temperature of the first evaporator or the suction pressure of the high-stage compressor; An operation control device that compares the detected value with a preset value and outputs a signal for controlling the number of operating units or capacity of the high-stage compressor, and a protection device that operates when the low-stage compressor operates abnormally. and a set value changing device that lowers the set value of the operation control device by a predetermined value in accordance with the output signal of the protection device, and stops the low-stage compressor in response to the output signal of the protection device, and reduces the set value of the operation control device by a predetermined value. It is characterized by lowering the operation control value of the stage side compressor.

[0009]

[Operation] In this invention, since a set value changing device is provided to reduce the operation control value of the high stage compressor in response to the output of the protection device of the low stage compressor, the output of the set value changing device is As a result, the setting value for capacity control of the high stage compressor is shifted to a lower value by a predetermined value, and the capacity control of the high stage compressor accompanying the cooling load on the refrigeration side can be prevented.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a refrigeration cycle diagram of a refrigeration system according to the present invention, and since the symbols 1 to 15 are the same as those of the conventional refrigeration system shown in FIG. 2, their explanation will be omitted. 16 is protection device 1
a set value changing device which outputs a signal for shifting the set value of the operation control device 14 to a lower value by a predetermined value in response to the output signal of 5; 17 is the ambient air temperature of the first evaporator 5 or corresponds thereto; This is a detector such as a thermostat for detecting the temperature or pressure at a location, and closes the first electromagnetic valve 3 when the temperature or pressure falls below a predetermined value.

Next, the operation will be explained. For example, when using HCFC22 as a refrigerant, the setting value of the operation control device 14 is 2 kg/cm2 G (
The saturation temperature is set at −15° C.), and when the temperature drops below this value, one of the high-stage compressors 1 is stopped and the capacity is controlled. Next, when the protection device 15 of the low stage compressor 10 is activated,
At the same time as the low stage compressor 10 stops, a signal thereof is output to the set value changing device 16. As a result, for example, the setting value of the operation control device 14 is 0 kg/cm2 G (saturation temperature - 4
0°C). As a result, even if the cooling load on the first evaporator 5 decreases and the suction pressure of the high-stage compressor 1 decreases, the high-stage compressor 1 will continue to operate until the suction pressure becomes 0 kg/cm2 G or less. All units are in operation.

Furthermore, by providing a detector 17 for detecting the ambient air temperature of the first evaporator 5, the refrigerated food can be prevented from freezing by closing the first electromagnetic valve 3 when the temperature falls below a predetermined value. Nor.

[0013]

[Effects of the Invention] As explained above, according to the present invention,
A set value changing device is installed to reduce the operation control value of the high stage compressor based on the output of the protection device of the low stage compressor, so when the low stage compressor stops abnormally, the cooling load on the refrigeration side is reduced. Accordingly, it is possible to prevent the capacity control of the high-stage compressor in accordance with the present invention, thereby making it possible to prevent the frozen food from melting due to a temperature rise in the freezing showcase.

[Brief explanation of the drawing]

FIG. 1 is a refrigeration cycle diagram of a refrigeration system according to an embodiment of the present invention.

FIG. 2 is a refrigeration cycle diagram of a conventional refrigeration system.

[Explanation of symbols] 1　High stage side compressor 2 Condenser 3 First solenoid valve 4 First squeezing device 5 First evaporator 6 First detour circuit 7 Second solenoid valve 8 Second squeezing device 9 Second evaporator 10 Low stage compressor 11 Second detour circuit 12 Check valve 13 Detector 14 Operation control device 15 Protective device 16 Setting value changing device 17 Detector

Claims (1)

[Claims] Claim 1: A refrigeration cycle including a plurality of parallel-connected high-stage compressors or a capacity-controllable high-stage compressor, a condenser, a first throttling device, and a first evaporator, and one end of the refrigeration cycle. is connected between the condenser and the first throttle device, and the other end is connected between the high stage compressor and the first evaporator, and the second throttle device, the second evaporator, and the low stage A first detour circuit connected in order of the side compressors, and a check valve that blocks refrigerant flow from the discharge side to the suction side of the low stage compressor, bypassing the low stage compressor. a second detour circuit, a detector that detects the ambient air temperature of the first evaporator or the suction pressure of the high-stage compressor, and a detected value of this detector is compared with a preset value; an operation control device that outputs a signal for controlling the number of operating units or capacity of the high-stage compressor; a protection device that operates when the low-stage compressor operates abnormally; and a set value changing device that lowers the set value of the control device by a predetermined value, so that the output signal of the protection device stops the low stage compressor and lowers the operation control value of the high stage compressor. A refrigeration device characterized by: