JPH0229948B2 - REITOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a refrigeration system, and more particularly to a refrigeration system that can prevent liquid compression by a compressor during defrosting operation.

[Conventional technology]

Conventional refrigeration systems are provided with a defrost circuit to remove frost adhering to the fins of the evaporator. In this defrosting circuit, the high temperature refrigerant discharged from the compressor flows directly into the evaporator.
The heat from the refrigerant was used to melt and defrost the frost adhering to the fins of the evaporator.

However, the compressor is driven at the same rotation speed during both freezing and defrosting operation, and during defrosting operation, the high temperature discharged from the compressor,
The high-pressure gas refrigerant is cooled and liquefied in the evaporator, and when this liquid refrigerant is sucked into the compressor, a phenomenon of liquid compression occurs, causing damage to the compressor. For this reason, during defrosting operation, it is possible to prevent damage to the compressor by driving the compressor at a limit rotation speed that does not cause liquid compression, but if the compressor is driven at this limit rotation speed during refrigeration operation, Refrigeration capacity will decrease.

As described above, there are contradictory drawbacks: if liquid compression is prevented, the refrigerating capacity decreases, and if the refrigerating capacity is improved, liquid compression occurs, and neither of these problems could be satisfied. For this reason, devices have been devised to reduce the capacity of the compressor during defrosting operation to eliminate the above-mentioned drawbacks, such as Utility Model Application No. 49-134768 and Utility Model Application No. 53-31855. .

[Problem to be solved by the invention]

However, all of these proposals attempt to control the rotation speed of the compressor by switching the polarity of the motor, and there is a problem in that the configuration becomes complicated.

In view of the above-mentioned circumstances, the present invention has been developed for a refrigeration system that is equipped with a speed change means for changing the rotation speed of the compressor during defrosting operation, and is capable of lowering the rotation speed of the compressor during defrosting operation to prevent liquid compression. It provides a control mechanism for the compressor.

[Means to solve the problem]

In order to achieve the above object, the refrigeration system of the present invention includes a compressor, a condenser, an expansion valve, and an evaporator to form a refrigeration cycle, in which the discharge side of the compressor and the suction side of the evaporator are connected. A first solenoid valve is disposed on the inlet side of the condenser, and a second solenoid valve is disposed on the bypass passage, and a compressor and a motor driving the compressor are connected to each other. The compressor and motor are of a shaft type, and one shaft side of the compressor and the motor are connected via a first transmission mechanism with a small reduction ratio and a first electromagnetic clutch, and the other shaft side is connected with a second transmission mechanism with a large reduction ratio,
Providing differential pressure detection means that are connected via a second electromagnetic clutch and detect a differential pressure between wind pressures on the air inflow side and the discharge side of the evaporator, and temperature detection means that detect the temperature on the refrigerant discharge side of the evaporator; During defrosting operation when the differential pressure detection means detects a differential pressure above a predetermined value and the temperature detection means detects a temperature below a predetermined value, the second electromagnetic valve is opened and the second electromagnetic clutch is opened. selectively energizing the first electromagnetic valve and the first electromagnetic clutch or the second electromagnetic valve and the second electromagnetic clutch based on the detection results of the differential pressure detection means and the temperature detection means so as to connect the It is characterized in that a switching means for switching is provided.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a refrigeration cycle diagram, in which a compressor 1, a first solenoid valve 2, a condenser 3, a liquid tank 4, an expansion valve 5, an evaporator 6, and an accumulator 7 are arranged in this order to form a cycle. . Further, the condenser 3 and the evaporator 6 are provided with fan motors 8 and 9, respectively, and a condenser fan 10 and an evaporator fan 11 are fixed to each of the fan motors 8 and 9.

Further, the discharge side of the compressor 1 and the suction side of the evaporator 6 are communicated by a bypass passage 12, and a second solenoid valve 13 is provided in the middle of the bypass passage 12. And evaporator 6
Sensors 14 and 15 for detecting wind pressure are provided on the air inflow side and air outflow side, respectively, and each sensor 1
The outputs of 4 and 15 are connected to a differential pressure switch 16, which is differential pressure detection means, and are also connected to a differential pressure switch 16, which is a differential pressure detection means.
A thermostat switch 17, which is a temperature detection means for defrosting release, is provided on the refrigerant discharge side of the refrigerant.

FIG. 2 shows the drive system of the compressor 1.
The motor 18 serving as a power source has a double-shaft output shaft 19, and a large pulley 20 and a small pulley 21 are fixed to each tip of the output shaft 19. A compressor 1 driven by this motor 18 is installed, and a driven shaft 22 of the compressor 1 is also of a double-shaft type, and a small pulley 2 is attached to each shaft end of this driven shaft 22.
The first electromagnetic clutch 25 with 3 and the large pulley 2
A second electromagnetic clutch 26 with a second electromagnetic clutch 26 is fixed thereto, and transmits rotational force from the output shaft 19 to the driven shaft 22 via the respective electromagnetic clutches 25 and 26.
A belt 27 is wound between the large pulley 20 and the small pulley 23 to constitute a first transmission mechanism with a small reduction ratio, and the small pulley 21 and the large pulley 2
4, a belt 28 is wound around the belt 28 to constitute a second transmission mechanism with a large reduction ratio.

FIG. 3 shows the control circuit of this embodiment. A relay 29, a differential pressure switch 16, and a thermostat switch 17 are connected in series between the power supply and the ground. Contacts 30 which are actuated and closed by a relay 29 are connected in parallel. This differential pressure switch 16 is turned on when the difference in wind pressure between the air inflow side and the air outflow side of the evaporator 6 exceeds a set value, and the thermostat switch 17 is turned off when the temperature exceeds the set temperature. .

Further, 31 is a changeover switch operated by the relay 29, a power supply is connected to the changeover terminal of this changeover switch 31, and a first contact 32 side that is turned on when the relay 29 is not activated is connected to the changeover terminal of the changeover switch 31. ,
The first solenoid valve 2 and the first solenoid clutch 25 are connected, and the second solenoid valve 13 and the second solenoid clutch 25 are connected to a second contact 33 that is turned on when the relay 29 is activated.
The relay 29 and the changeover switch 31 constitute a changeover means.

Next, the operation of this embodiment will be explained.

When the compressor 1 is driven by the motor 18, the refrigerant flows in the order of the first electromagnetic valve 2, the condenser 3, the liquid tank 4, the expansion valve 5, the evaporator 6, and the accumulator 7, and returns to the compressor 1, repeating the cycle. In this refrigeration operation cycle, relay 2
9 is not activated, and the changeover switch 31 is connected to the first contact 3.
2 side, and current flows through the first electromagnetic valve 2 and the first electromagnetic clutch 25. For this reason,
The first electromagnetic valve 2 is opened, the second electromagnetic valve 13 is closed, and the refrigerant does not flow into the bypass path 12, but instead flows in the direction of the solid arrow in FIG. Also, since current flows through the first electromagnetic clutch 25, this works,
The rotary shaft 22 of the compressor 1 is driven by the large pulley 20, the belt 27, and the first electromagnetic clutch 25 to perform refrigeration operation.

Next, when frost adheres to the fins of the evaporator 6, the flow path resistance on the ventilation side of the evaporator 6 increases, so that the difference in wind pressure between the air inflow side and the air outflow side of the evaporator 6 increases. These wind pressures are detected by two sensors 14 and 15, and the difference in wind pressure is determined by a differential pressure switch 16. When the wind pressure exceeds a predetermined value, the differential pressure switch 16 is turned on (at this time, the evaporator 6 has a predetermined thickness). frost is attached).

Therefore, current flows through the relay 29 (the thermostat switch 17 is on because the temperature is below the set temperature), turning on the contact 30 and causing the relay 29 to turn on.
is made to self-hold, and the changeover switch 31 is switched to bring it into contact with the second contact 33. As a result, the second electromagnetic valve 13 and the second electromagnetic clutch 26
A current flows through, the second solenoid valve 13 opens and the first solenoid valve 2 closes, and the refrigerant flows through the bypass path 12. The high-temperature gas refrigerant discharged from the compressor 1 flows directly into the evaporator 6 through the bypass passage 12, as shown by the dashed arrow in FIG. 1, and defrosts the adhering frost by heating the evaporator 6. perform an action.

At this time, since current flows through the second electromagnetic clutch 26, the large pulley 24 works, and the small pulley 2
1. Rotating shaft 2 via belt 28 and large pulley 24
2 is driven, the rotating shaft 22 is driven at a lower rotational speed than during refrigeration operation, the amount of refrigerant discharged is reduced, the amount of liquid refrigerant remaining in the evaporator 6 is reduced, and the amount of liquid refrigerant in the compressor 1 is reduced. There will be less inflow.

When the defrosting operation is performed and the frost on the evaporator 6 disappears, the thermostat switch 17 detects a temperature rise and turns off. As a result, the relay 29 is released and the contact 30 is also opened, the defrosting operation returns to the freezing operation, and the changeover switch 31 also switches to the first contact 3.
2 side and rotates the compressor 1 at high speed to perform the above-mentioned refrigeration cycle.

〔Effect of the invention〕

Since the present invention is configured as described above, the refrigeration operation and the defrosting operation are automatically switched, and the second electromagnetic clutch is connected during the defrosting operation, so that the double-shaft compressor can be operated on both sides. Since power is transmitted from the shaft-type motor through the second transmission mechanism with a large reduction ratio, the rotational speed is reduced and the amount of refrigerant discharged is reduced, so the compressor no longer compresses the liquid and the compression is reduced. During refrigeration operation, the first electromagnetic clutch is connected to the double-shaft compressor, and power is transmitted through the first transmission mechanism with a small reduction ratio. It rotates at high speed and can therefore fully demonstrate its refrigerating capacity.

[Brief explanation of drawings]

FIG. 1 is a refrigeration cycle diagram showing an embodiment of the present invention, FIG. 2 is a plan view showing a drive system of a motor and a compressor, and FIG. 3 is an electric circuit diagram showing a control system. 1... Compressor, 2... First solenoid valve, 13...
Second electromagnetic valve, 3... Capacitor, 5... Expansion valve, 6... Evaporator, 12... Bypass path,
16...Differential pressure switch (differential pressure detection means), 17...
...Thermostat (temperature detection means), 18 ... Motor, 20 ... Large pulley, 23 ... Small pulley, 2
7... Belt (first transmission mechanism), 21... Small pulley, 24... Large pulley, 28... Belt (second
transmission mechanism), 25...first electromagnetic clutch, 2
6...Second electromagnetic clutch, 29...Relay, 3
1... Selector switch, 32, 33... Contact (switching means).

Claims (1)

[Scope of Claims] 1. A refrigeration system comprising a compressor, a condenser, an expansion valve, and an evaporator to form a refrigeration cycle, wherein a bypass path is provided that communicates the discharge side of the compressor with the suction side of the evaporator, and the condenser A first solenoid valve is disposed on the inlet side of the compressor, and a second solenoid valve is disposed on the bypass passage, and the compressor and the motor that drives the compressor are of a double-shaft type, and the compressor and the motor are connected to each other. One shaft side is connected via a first transmission mechanism with a small reduction ratio and a first electromagnetic clutch, and the other shaft side is connected via a second transmission mechanism with a large reduction ratio and a second electromagnetic clutch. A differential pressure detecting means for detecting a differential pressure between wind pressures on an air inflow side and a discharge side of the evaporator, and a temperature detecting means for detecting a temperature on a refrigerant discharge side of the evaporator are provided, which are connected to each other. During defrosting operation when a differential pressure greater than a predetermined value is detected and a temperature less than a predetermined value is detected by the temperature detection means, the second electromagnetic valve is opened and the second electromagnetic clutch is connected. A switching means is provided for selectively switching energization to the first electromagnetic valve and the first electromagnetic clutch or the second electromagnetic valve and the second electromagnetic clutch based on the detection results of the pressure detection means and the temperature detection means. A refrigeration device featuring: