JPH0260941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a defrosting device for an evaporator during heating operation of a heat pump type air conditioner.

[Prior art] Generally, during heating operation of a heat pump type air conditioner, there are cases where the surface temperature of the outdoor heat exchanger, which is an evaporator, is below the freezing point, and as a result, frost may form on the surface of the outdoor heat exchanger. Impedes heat exchange. In order to remove this frost, a method has been adopted in which the refrigerant cycle is temporarily switched to cooling, the outdoor heat exchanger is used as a condenser, and the frost is melted away by the heat of condensation.
During defrosting, the blower on the outdoor side is naturally stopped so that the heat can effectively defrost. This control has been similarly performed for frost formation that occurs during heating overload when the indoor temperature is high.

Figure 1 shows how this defrosting method is applied.
For example, this is a configuration diagram of a general heat pump type air conditioner shown in Japanese Patent Publication No. 59-1936. In the figure, 1 is a compressor, 2 is a motor for driving this compressor, and 3 is a four-way valve that operates a refrigerant cycle. Used to determine switching, refrigerant cycle operation, or heating cycle operation.

In this example, the case where the refrigerant flows in the direction of the solid line arrow is a heating cycle, and the case where the refrigerant flows in the direction of the broken line arrow is a refrigerant cycle. 4 is an indoor heat exchanger that serves as a condenser in the heating cycle and an evaporator in the cooling cycle; 5 is an evaporator in the heating cycle;
An outdoor heat exchanger that serves as a condenser in the cooling cycle; 6 is an expansion valve or a capillary; 7 is a connection between the compressor 1, the four-way valve 3, the indoor and outdoor heat exchangers 4 and 5, and the expansion valve or capillary 6; This is a refrigerant pipe through which a refrigerant passes and constitutes a refrigerant cycle 8. 9 is an indoor side blower, 10 is an outdoor side blower, 11 is an indoor heat exchanger temperature sensor that detects the temperature of the indoor heat exchanger 4, and 12 is an outdoor heat exchanger temperature sensor that detects the temperature of the outdoor heat exchanger 5. be.

In the above configuration, when the four-way valve 3 is switched to the heating operation cycle and the compressor 1 and the blowers 9 and 10 are driven to start the heating operation, the high temperature and high pressure refrigerant discharged from the compressor 1 passes through the four-way valve 3. It is guided to a pipe 7 via an indoor heat exchanger (condenser) 4, where it releases heat and is condensed and liquefied. This liquefied high-pressure refrigerant expands adiabatically in the expansion valve 6 and becomes low-temperature, low-pressure vapor. However, by passing through the outdoor heat exchanger (evaporator) 5, heat is absorbed from the outside air and the refrigerant is heated. It passes through the four-way valve 3, is adiabatically compressed by the compressor 1, and is discharged again as a high-temperature, high-pressure medium. In this cycle, the amount of heat released and removed by the indoor heat exchanger 4, which is a condenser, becomes a heating heat source, and the amount of heat is absorbed from the outside air by the outdoor heat exchanger 5, which is an evaporator. If such operation continues, the temperature of the outdoor heat exchanger 5 becomes below the freezing point, and frost builds up on its surface. Since heat exchange is reduced due to frost formation on the outdoor heat exchanger 5, the refrigerant is not sufficiently heated in the outdoor heat exchanger 5, and the refrigerant sucked into the compressor 1 contains a large amount of wet steam. Therefore, the temperature of the refrigerant discharged from the compressor 1 also decreases, and the heating effect deteriorates. To remove this frost, the temperature sensor 12 detects a defrosting condition in which the evaporation temperature of the outdoor heat exchanger 5 is below a predetermined temperature, switches the four-way valve 3, and stops the outdoor fan 10. The refrigerant cycle 8 is temporarily switched to the cooling cycle. As a result, the outdoor heat exchanger 5 is operated as a condenser, the frost is melted away by heating with the refrigerant, and after a certain period of time, the four-way valve 3 is switched again and the blower 10
starts operation and enters heating operation.

However, in heating operation, if the room temperature becomes too high and an overload condition occurs, overload protection operation control is generally performed to stop the outdoor fan 10 in order to protect the refrigerant from increasing in pressure. Even in such a state, the evaporation temperature of the outdoor heat exchanger 5 decreases,
Sometimes there are defrosting conditions. However, in this case, the amount of frost formed on the outdoor heat exchanger 5 is small, and even if a defrosting operation is performed, the amount of frost formed is such that the defrosting is completed in an instant. Therefore, if normal defrost control is performed during such overload protection operation, it will not only result in unnecessary excessive defrost operation and energy loss, but also cause the room temperature to drop due to switching to an unnecessary cooling cycle. The refrigerant refrigerant noise decreases, impairing comfort, and unnecessary switching of the four-way valve produces unpleasant refrigerant noise.

[Summary of the Invention] This invention has been made to eliminate the above-mentioned drawbacks. During overload protection operation, even if defrosting conditions are reached, the outdoor fan does not immediately enter defrosting operation, but instead operates the outdoor fan at a constant level. A heat pump type air conditioner that prevents wasteful defrosting operation during overload protection operation by operating for a certain period of time and then starting defrosting operation only when the defrosting conditions are met. The purpose is to provide a defrosting device.

[Embodiment of the Invention] Fig. 2 is a system configuration diagram showing an embodiment of the present invention.
15 and 16 are A/D converters that convert the temperature signals from these temperature detection means 13 and 14 into digital signals, and 17 is a micro Central processing unit (hereinafter referred to as CPU) such as processor, 18
1 is an overload state detection means for detecting that the condensation temperature Tc from the A/D converter 15 is equal to or higher than a set temperature T1 which is a high pressure protection temperature in the event of a high room temperature overload;
9 is a defrosting condition detecting means for detecting that the evaporation temperature Te from the A/D converter 16 is lower than the set temperature T2 which is the defrosting condition temperature; 20 is an overload state detecting means 18; a defrosting condition detecting means The signal from the means 19 is processed to generate an overload protection operation signal when there is only an overload state signal from the overload state detection means 18, and to remove the overload protection operation signal when there is only a defrost condition signal from the defrost condition detection means 19. a processing circuit that outputs a frost operation signal and an outdoor blower operation signal when the signals from both means 18 and 19 are input; 21 is a control relay drive circuit controlled by a signal from the processing circuit 20; 22 is an outdoor side blower relay, 23 is a four-way valve relay, and the control relay drive circuit 21 drives the outdoor side blower relay 22 to the stop side according to the overload protection operation signal from the processing circuit 20, and the outdoor side blower relay 22 is driven to the stop side by the defrosting operation signal. The blower relay 22 is stopped, the four-way valve relay 23 is driven to the cooling cycle side, and the outdoor blower operation signal is activated.
The outdoor blower relay 22 is driven to the operating side.

Next, its operation will be explained. Now indoor heat exchanger 4
During normal heating operation when the condensation temperature Tc is below T1,
Assuming that frost forms on the outdoor heat exchanger 5, the evaporation temperature detection means 14 passes through the A/D converter 16.
The temperature signal Te taken into the CPU 17 decreases,
A defrosting condition detection means 19 in the CPU 17 detects a defrosting condition of Te≦T2 and outputs a detection signal to the processing circuit 20. On the other hand, since the overload state detection means 18 has not detected an overload state, there is no output, and the processing circuit 2
A defrosting operation signal is output from 0. This signal controls the control relay drive circuit 21 to drive the outdoor blower relay 22 to the stop side and the four-way valve relay 23 to the cooling operation side for a certain period of time.

Next, the operation when an overload condition occurs during heating operation will be explained with reference to FIG. FIG. 3a is a time chart showing changes in the condensing temperature Tc and evaporation temperature Te, and FIG. 3b is a time chart showing the operating states of the outdoor fan relay 22 and the four-way valve relay 23. During heating operation, the compressor 1 becomes overloaded, and the condensing temperature detecting means 13 passes through the A/D converter 15.
The condensing temperature signal Tc taken into the CPU 17 rises and exceeds the set temperature T1, and at time t1,
Detection means 18 detects an overload condition. An overload protection operation signal is output from the processing circuit 20 based on the detection signal. In response, the control relay drive circuit 21 drives the outdoor fan relay 22 to the stop side, thereby stopping the outdoor fan 10. As a result, the heat exchange function of the outdoor heat exchanger 5 decreases, its evaporation temperature Te decreases, and the condensation temperature Tc of the indoor heat exchanger 4 stops increasing and gradually decreases, preventing the refrigerant from increasing in pressure. Ru. However, if the operation continues in this state, the evaporation temperature Te of the outdoor heat exchanger 5 continues to decrease, and finally at time t2, the defrosting condition detection means 1
9 detects the defrosting condition Te≦T2. At this point, since the overload state detection signal is also output from the overload state detection means 18, the processing circuit 20 outputs the outdoor side blower operation signal for a certain period of time TM. Thereby, the control relay drive circuit 21 drives the outdoor fan relay 22 to the operating side for a certain period of time TM. By operating the outdoor fan 10, heat exchange by the outdoor heat exchanger 5, that is, heat absorption from the outside air is promoted, and the temperature of the outdoor heat exchanger 5 increases. In this operating state, the temperature of the refrigerant on the indoor heat exchanger 4 side is originally high, so normally, when the outdoor fan 10 resumes operation, the temperature of the outdoor heat exchanger 5 rises and the frost is immediately removed. Thereafter, the intermittent operation of the blower 10 is repeated until the overload is eliminated. However, even if the specified time TM has elapsed at time t3 after the blower 10 resumes operation, only when the defrosting condition detection means 19 is still detecting the defrosting condition.
The outdoor blower relay 22 is switched to the stop side and the four-way valve relay 23 is switched to the cooling cycle side, and defrosting operation is performed for a certain period of time until time t4. As a result of this defrosting operation, the temperature of the indoor heat exchanger 4 decreases, the temperature of the outdoor heat exchanger 5 increases, and both the overload condition and the defrosting condition are resolved, and after time t4, the heating operation is resumed. be exposed.

In the above embodiment, an increase in the condensing temperature of the indoor heat exchanger 4 is detected to detect an overload state, but the energizing current of the compressor drive motor 2, that is, the compressor drive current becomes equal to or higher than a predetermined set value. It may also be possible to detect this.

FIG. 4 is a system configuration diagram showing an embodiment in this case. In the figure, 14, 16, 17, 19 to 23 are the same as in FIG. 2, and 24 is a compressor drive current detection means, which detects the drive current. Take out the proportional current Ic. 25 is an A/D converter, and 26 is an overload state detection means that outputs a signal when Ic exceeds a set value Io corresponding to the compressor drive current at the permissible limit of the internal pressure of the indoor heat exchanger 4. be. In this embodiment, the voltage proportional to the compressor drive current is converted into digital data and the set value is compared in the CPU 17. Ic≧
A signal generated when Io is reached may be input to the CPU 17.

[Effects of the Invention] As described above, in response to detection of defrosting conditions during overload protection operation of the compressor, the outdoor blower is operated for a certain period of time without immediately entering defrosting operation. Therefore, it has the effect of reducing energy loss due to unnecessary defrosting operation, discomfort caused by a drop in room temperature, and frequent occurrence of four-way valve switching noise.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a general heat pump type air conditioner to which the method of the present invention is applied, Fig. 2 is a system block diagram showing an embodiment of the present invention, and Fig. 3 is an explanatory diagram of its operation. FIG. 4 is a system configuration diagram showing another embodiment of the present invention. In the figure, 1 is a compressor, 3 is a four-way valve, 4 is an indoor heat exchanger, 5 is an outdoor heat exchanger, 6 is an expansion valve or capillary tube, 7 is a refrigerant pipe, 8 is a refrigerant cycle, 9
10 is an indoor blower, 10 is an outdoor blower, 19 is a defrosting condition detection means, 18 and 26 are compressor overload state detection means, 20 is a processing circuit, 21 is a control relay drive circuit, 22 is an outdoor blower relay, 23 is a four-way valve relay. Identical or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Scope of Claims] 1. A compressor, a four-way valve for refrigerant cycle switching, an indoor heat exchanger that serves as a condenser in a heating cycle and an evaporator in a cooling cycle, an evaporator in a heating cycle, and a condenser in a cooling cycle. a refrigerant cycle consisting of an outdoor heat exchanger, an expansion valve or a capillary tube, an indoor blower, an outdoor blower, a defrosting condition detection means for detecting defrosting conditions of the outdoor heat exchanger, and heating of the compressor. An overload state detection means for detecting an overload state is provided, and when the heating overload state is detected by this means, the above-mentioned outdoor blower is stopped and overload protection operation is performed, and the defrosting condition is determined by the above-mentioned defrosting condition detection means. In the defrosting device of the heat pump type air conditioner, the outdoor blower is stopped and the four-way valve is switched to perform the defrosting operation for a predetermined period of time upon detection of the overload state signal from the overload state detection means. When only input, the overload operation signal to perform the above overload protection operation is
When only the defrost condition signal from the defrost condition detection means is input, the defrost operation signal is sent to perform the defrost operation, and when both the overload condition signal and the defrost condition signal are input, the outdoor blower is 1. A defrosting device for a heat pump type air conditioner, characterized in that the defrosting device is equipped with a processing circuit that outputs an outdoor blower operation signal to drive the air conditioner for a certain period of time. 2. The defrosting device for a heat pump air conditioner according to claim 1, wherein the defrosting condition detection means is means for detecting that the evaporation temperature of the outdoor heat exchanger is equal to or lower than a predetermined set temperature. 3. The heat pump air conditioner according to claim 1 or 2, wherein the compressor overload state detection means is a means for detecting that the condensing temperature of the indoor heat exchanger is equal to or higher than a predetermined set temperature. Defrost equipment. 4. The heat pump type according to claim 1 or 2, wherein the compressor overload state detection means is a means for detecting that the drive motor current of the compressor has exceeded a predetermined set current value. Defrosting device for air conditioners.