JPS6141384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting device that detects the temperature of an evaporator during a defrosting operation using hot gas from a compressor to terminate the defrosting operation.

Conventionally, in this type of equipment, as shown in Figure 1, near the end of defrosting operation, the high pressure side pressure and the coil temperature of the heat source side heat exchanger (evaporator) rise rapidly, but when the defrosting thermometer (outside air The thermostat, which detects the temperature and the coil temperature of the heat source side heat exchanger and sends a defrosting start/end signal based on the difference in temperature, cannot keep up with the sudden rise in the coil temperature of the heat source side heat exchanger (evaporator).
Even after the frost was completely removed, defrosting continued for about 10 seconds, which often caused the high-pressure side pressure switch of the safety device to operate and cause the unit to stop abnormally.

This invention was made in view of these circumstances, and is intended to prevent an abnormal increase in the high pressure side pressure by forcing air into the evaporator when the high pressure side pressure exceeds a predetermined level during defrosting. .

Hereinafter, one embodiment of the present invention will be described based on the drawings. Fig. 2 is a refrigeration cycle diagram. In the figure, 1 is a compressor, and the flow direction of the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 is determined by the four-way switching valve 2.
During heating, it is switched to the solid line arrow side, and after being condensed and liquefied in the user-side heat exchanger 3 (acts as a condenser during heating, and as an evaporator during cooling and defrosting),
The pressure is reduced by the throttle device 5 through the check valve 4a of the check valve group 4, and the pressure is reduced through the check valve 4b to the heat source side heat exchanger 6.
(It acts as an evaporator during heating, and as a condenser during cooling and defrosting.) It is evaporated in the air conditioner (acts as an evaporator during heating, and as a condenser during cooling and defrosting), and is sucked into the compressor 1 via the four-way switching valve 2 again. On the other hand, during cooling and defrosting, the four-way switching valve 2 is switched to the dotted line side,
The refrigerant flows in the direction of the dotted arrow, forming a well-known refrigeration cycle. 7 is a blower for forcing air into the heat source side heat exchanger 6. Reference numeral 8 denotes a defrosting thermometer, which has a coil temperature sensing element 8a for detecting the coil temperature of the heat source side heat exchanger 6 and an outside air temperature sensing element 8b for detecting the outside air temperature. When the difference between the coil temperature and the outside air temperature reaches a predetermined value, a defrosting start and end signal is issued. 9 is a high pressure side pressure switch which is one of the safety devices provided between the compressor 1 and the four-way switching valve 2; 10 is a high pressure side pressure switch provided similarly to the high pressure side pressure switch 9; This is a pressure switch for operating the blower 7 when the pressure rises above a predetermined value.

Next, the operation will be explained based on the electric circuit diagram shown in FIG. First, when the cooling/heating switch SW is turned on to the "warm" side, the coil 4 of the four-way switching valve 2
WV and _relay
A contact X ₂₁ of X ₂ is also closed. Next, turn on the start switch.
When PB- ₁ is turned on, relay X ₁ is energized, and a self-holding circuit is formed by closing its a contact X _11. At the same time, the other a contacts X ₁₂ and X ₁₃ are also closed, and the electromagnetic contact for compressor 1 is formed. The electromagnetic contactor 52C and the electromagnetic contactor 52F for the blower 7 are excited, and the respective contacts 52
C ₁ and 52F ₁ are closed, and the compressor 1 electric motor CM and the blower 7 electric motor FM are operated to start heating operation. Note that HPS is a contact point of the high pressure side pressure switch 9, SS is a group of other safety switches, and PB- ₂ is a stop switch. As the heating operation continues in this way, frost builds up on the heat source side heat exchanger 6, and the evaporation temperature, that is, the coil temperature of the heat source side heat exchanger 6 decreases. Now, if the outside temperature is A, then the third
In the figure, the coil temperature of the heat source side heat exchanger 6 under normal conditions is a, but as frosting progresses and the temperature drops to b, (the rate of change in the coil temperature of the heat source side heat exchanger 6 at this time) is small, so the coil temperature sensing element temperature of the defrosting thermometer 8 and the above-mentioned coil temperature are almost equal.) The contact point 23D of the defrosting thermostat 8 is opened. For this reason, the coil 4WV of the four-way switching valve 2,
Then, the coil of relay X ₂ is demagnetized, the refrigeration cycle is switched to the cooling cycle, and the blower 7 is stopped, and the refrigerant is circulated as shown by the dotted arrow in FIG. 2 to perform defrosting operation. During such defrosting, the high pressure side pressure and the coil temperature of the heat source side heat exchanger 6 change as shown in Fig. 1, and when the residual frost disappears,
rise rapidly. The coil temperature at this time is detected by the coil temperature sensing element 8a of the defrosting thermometer 8, and a defrosting end signal is issued. However, because the coil temperature changes rapidly, the temperature sensing by the coil temperature sensing element 8a is delayed. Even if the temperature value C shown in , Fig. 1, and Fig. 3 is reached (the same value is shown in Figs. 1 and 3), the contact 23D of the defrosting thermostat 8 does not close, and the end of the defrosting operation is delayed. , the high pressure side pressure continues to rise.
Then, the high-pressure side pressure switch 9 is activated and the entire system is stopped. However, in this invention, the high-pressure side pressure is set to the pressure value shown in FIG. When the pressure reaches a value slightly smaller than the pressure value (b), the pressure switch 10 is activated and its contact PS is closed. Therefore, relay X ₃ is energized, its a contact X ₃₁ is closed, and electromagnetic contactor 52
F is excited and the blower 7 is operated. As a result, the pressure on the high pressure side decreases as shown by the dashed line in FIG. On the other hand, the coil temperature of the heat source side heat exchanger 6 also decreases in rising speed, as shown by the dashed line. Therefore, when the temperature of the coil temperature sensing element 8a reaches the temperature value C shown in FIG.
Normal heating operation resumes without any activation.

As described above, according to the present invention, when the high-pressure side pressure in the defrosting cycle rises to a predetermined value before the end of defrosting, forced ventilation is forced into the evaporator during defrosting, so that the end of defrosting can be detected. Even if the temperature detection by the temperature detector cannot follow the change in the evaporator coil temperature and the defrosting ends a little late, the problem of the equipment stopping abnormally due to the high-pressure side pressure rising too much is eliminated, and stable defrosting can be achieved. It has the effect of frosting. Although the above embodiment describes reverse hot gas defrosting using a four-way switching valve, it is also applicable to hot gas bypass defrosting in which hot gas from the compressor is supplied to the evaporator by bypassing the condenser and throttling device. can do.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of the evaporator temperature and high pressure side pressure during defrosting, Fig. 2 is a refrigeration cycle diagram showing an embodiment of the present invention, and Fig. 3 is a characteristic diagram of the defrosting thermometer in this invention. , FIG. 4 is an electrical circuit diagram showing an embodiment of the present invention. In the figure, 1 is a compressor, 2 is a four-way switching valve, 3 is a user side heat exchanger, 6 is a heat source side heat exchanger, 7 is a blower,
8 is a defrosting thermostat, 9 is a high-pressure side pressure switch, and 10 is a pressure switch. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. Supplying high-temperature, high-pressure gas refrigerant from a compressor to a heat source-side heat exchanger having an air blower, stopping the air blower and performing defrosting operation, and detecting the temperature of the heat source-side heat exchanger. a high-pressure side pressure switch that operates when the high-pressure side pressure detected on the discharge side from the compressor rises to a predetermined value or more during the defrosting operation; A sequence circuit is provided in which when this high pressure side pressure switch operates, its auxiliary contact closes and excites the magnetic contactor for the normally open contact connected between the blower motor and the power supply for the blower. A defrosting device comprising: an electric circuit including an electric circuit, and forcibly operating the blower.