JPH0529830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a defrosting operation control method for a heat pump type air conditioner.

[Technical background of the invention and its problems]

In conventional heat pump air conditioners, low-temperature refrigerant flows through the outdoor heat exchanger during heating operation.
Because frost forms on the surface, a defrosting operation is sometimes performed to remove the frost by flowing high-temperature refrigerant through the outdoor heat exchanger.

In this defrosting operation, a method is generally used in which the refrigeration cycle is switched from a heating cycle to a cooling cycle.

However, this method has the disadvantage that low-temperature refrigerant flows into the indoor heat exchanger during defrosting operation, causing a significant drop in indoor temperature. For this reason, a method has recently been used in which a bypass circuit is provided in the refrigeration cycle and the high temperature refrigerant discharged from the compressor is guided directly to the outdoor heat exchanger. A heat pump type air conditioner that performs such a defrosting operation will be explained with reference to FIG. 1.

The refrigeration cycle of this air conditioner connects a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, a pressure reducer 4, and an indoor heat exchanger 5 in sequence through piping, and connects the Compressor discharge port piping 6
It is composed of a bypass circuit 8 that communicates with the main body and has a two-way valve 7 in the middle. Moreover, the outdoor fan 10 9 is an indoor fan.

In this air conditioner, for cooling operation, the four-way valve 2 is connected in the direction shown by the solid line in the figure, and the two-way valve 7 is closed to allow the refrigerant to flow in the direction of the dashed-dotted line in the figure to perform a predetermined room cooling. And, during heating operation, the four-way valve 2
is switched in the direction of the broken line arrow in the figure, the two-way valve 7 is closed, and the refrigerant is allowed to flow in the direction of the broken line in the figure, and the indoor heat exchanger 5
The high temperature refrigerant discharged from the compressor 1 is sent to the compressor 1, and the low temperature refrigerant after being depressurized by the pressure reducing device 4 is then sent to the outdoor heat exchanger 3, thereby heating the room.

When the frost on the outdoor heat exchanger 3 caused by this heating operation reaches a predetermined value or more, a defrosting operation is started. This defrosting operation is performed by opening the two-way valve 7 while maintaining the four-way valve 2 in the same direction as during the heating operation, and causing the high-temperature discharge refrigerant of the compressor 1 to flow through the bypass pipe 8. At this time, as shown by the solid arrow in the figure, the refrigerant branches into the bypass pipe 8 direction and the normal heating cycle direction at point A in the figure, but most of the circulating refrigerant flows through the bypass pipe 8 and passes through the outdoor heat exchanger. Perform step 3 of defrosting. Also, at this time, indoor fan 1
0 is stopped, and a small amount of refrigerant flowing into the indoor heat exchanger 5 prevents the temperature of the indoor heat exchanger 5 from decreasing.

Then, this defrosting operation is terminated depending on either the duration of the defrosting operation or the temperature of the outdoor heat exchanger 3.

However, the amount of heat for defrosting in this defrosting operation depends mostly on the amount of heat stored in the compressor 1 at the start of defrosting and the amount of heat held in the refrigerant, and the amount of heat input during the defrosting operation depends on the amount of heat stored in the compressor 1 at the start of defrosting. Since only input power is required, defrosting is hardly promoted even if defrosting operation is continued after the compressor 1 releases stored heat, and the defrosting time is unnecessarily prolonged, resulting in a drop in room temperature and wasted power. Ta.

[Purpose of the invention]

The present invention was made in consideration of the above circumstances, and
In a heat pump air conditioner that performs defrosting operation by guiding refrigerant discharged from a compressor directly to an outdoor heat exchanger through a bypass pipe, a defrosting system for a heat pump air conditioner that can appropriately terminate the defrosting operation is provided. The purpose is to provide a frost operation control method.

[Summary of the invention]

The present invention provides a heat pump type air conditioner that defrosts an outdoor heat exchanger by circulating compressor discharge refrigerant from a compressor discharge port to a bypass circuit communicating between a pressure reducing device and an outdoor heat exchanger. This is a defrosting operation control method for a heat pump air conditioner that detects the temperature of the air conditioner and ends the defrosting operation when the detected temperature drops to a predetermined value.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 2 to 6. Note that the same parts as in FIG. 1, which is a conventional example, are indicated by the same reference numerals.

The heat pump air conditioner according to this embodiment has the same heat pump refrigeration cycle as the conventional example,
As control circuits, an indoor control circuit 11 and an outdoor control circuit 12 are provided. This indoor control circuit 11
Both the outdoor control circuit 12 is a circuit consisting of a microcomputer, and the indoor control circuit 11 has an operation switch 13, a cooling/heating changeover switch 14, and a temperature setting device 1.
The indoor fan motor controller 17 receives control signals from the indoor temperature sensor 16 provided on the suction side of the indoor heat exchanger 5, and the outdoor control circuit 12, and the control signal from the outdoor control circuit 12. and sends a control signal to the outdoor control circuit 12.
The indoor fan motor controller 17 controls the speed of the indoor fan 10, and the control signal sent to the outdoor control circuit 12 includes information on operation stop and cooling/heating.

In addition to the indoor control circuit 11, the outdoor control circuit 12 inputs a compressor temperature sensor 18, an outdoor heat exchanger temperature sensor 19, and connects the entire equipment in the outdoor area, a compressor relay 20, a compressor heater relay 21, and a defrosting circuit. It controls a one-way valve relay 22, a four-way valve relay 23, an outdoor fan motor controller 24, and an expansion valve controller 25 that controls a motor 26 that changes the opening degree of the expansion valve 4.

Hereinafter, the control operation of this embodiment will be mainly explained according to the control flowcharts and control time charts shown in FIGS. 3 to 9.

First, the flowchart shown in Fig. 3 separates the operation of the air conditioner, and the states of the operation switch 13 and the cooling/heating switch 14 are determined by the indoor controller 11, and the operation is divided into cooling operation, heating operation, and heating operation stop. It is being

During the cooling operation and heating operation, the operation of each device is controlled by comparing the room temperature and the set temperature, and when the heating operation is stopped, the presser preheating control is performed by a compressor heater (not shown), which will be described later.

Next, protection against abnormal temperature rise of the compressor is shown in the flowchart of FIG. 4 and the graph of compressor temperature change and compressor operation diagram of FIG. 5. This control is performed by outdoor controller 1
It is processed and output in step 2, and the compressor temperature
Tc is detected by the compressor temperature sensor 18, and if the detected temperature Tc is below the temperature upper limit set value Tc ₁ , the state continues as it is, and if it exceeds this set value Tc ₁ (point A in Fig. 5), The compressor 1 is immediately stopped to protect the compressor 1. After this stop, the compressor temperature Tc continues to be detected, and when the temperature drops below the return temperature _TC2 (point B in FIG. 5), various controls are started. This abnormal temperature rise protection is constantly monitored during compressor operation.

6 and 7 show the compressor preheating control when the heating operation is stopped as described above. This preheating control aims to improve the startup characteristics of the air conditioner at the start of heating operation, so the compressor temperature is increased when the compressor is stopped during the heating season.
It is characterized by maintaining Tc between two set values Tc ₃ and Tc ₄ (Tc ₃ > Tc ₄ ). This control operation turns on the compressor heater (not shown) at point C in Figure 7 when the compressor temperature Tc becomes below the set value Tc ₄ , and then turns on the compressor heater (not shown) at point C when the compressor temperature Tc rises and becomes Tc = Tc ₃ . Turns OFF at point D in Figure 7. After that, repeat this operation,
Maintain Tc ₃ < Tc < Tc ₄ .

Finally, control during defrosting operation, which is the gist of the present invention, will be explained with reference to FIGS. 8 and 9. This defrosting operation is performed by the indoor control circuit 12 using the outdoor heat exchanger temperature sensor 1.
The process is started by determining the detected temperature drop in step 9. That is, the outdoor control circuit 12 starts the defrosting operation by comparing the outdoor heat exchanger temperature and the set value. At this time, the outdoor control circuit 12 is replaced by the indoor control circuit 11.
Upon receiving this signal, the indoor control circuit 11 switches the indoor fan 10 to low speed operation in order to prevent the temperature of the indoor heat exchanger 5 from decreasing.
Also, in the outdoor control circuit 12, START3 in FIG.
into control. In this defrosting operation control, first, the compressor relay 20 is turned off to stop the compressor and prevent sudden pressure changes in the refrigeration cycle.

Then, the defrosting two-way valve relay 22 is turned on, the two-way valve 7 is opened, and the bypass circuit 8 is opened.

Next, a motor 26 that changes the opening degree of the expansion valve 4
A signal is sent to the expansion valve controller 25 to fully open the valve. After this, the abnormal temperature rise protection control of the compressor is performed.
Perform steps from START2 to END2 to start compressor 1 operation. (Point E in Figure 9) This operation starts the defrosting operation of the refrigeration cycle, and the compressor 1
Most of the discharged high-temperature refrigerant is sent to the outdoor heat exchanger 3 through a bypass circuit 8 with low flow resistance. Then, a very small amount of discharged refrigeration is sent to the indoor heat exchanger 5. The outdoor heat exchanger 3 is rapidly defrosted by the heat of the high-temperature discharged refrigerant, and the low-temperature refrigerant returns from the outdoor heat exchanger 3 to the compressor 1. This low-temperature refrigerant is sucked into the compressor 1 and is turned into high-temperature discharge gas again by the heat of the compressor 1 body and the electric power input to the compressor 1, and the cycle is repeated. This cycle causes compressor 1
The temperature of the main body gradually decreases (between E and F in Figure 9).
The discharge refrigerant temperature also decreases. Then, the detected temperature Tc of the compressor temperature sensor 19 is the defrosting end setting value Tc ₅
When the following occurs (point F in Figure 9), outdoor control circuit 1
2 determines this and ends the defrosting operation, and compressor 1
to stop. Therefore, the temperature of the discharged refrigerant decreases, and the defrosting of the outdoor heat exchanger 3 is not promoted. This prevents wasteful defrosting operation, and also prevents the refrigerant blown into the compressor from turning into a large amount of liquid refrigerant, which may cause a malfunction of the compressor. Therefore, the defrosting operation can be completed in an appropriate state.
After the defrosting operation is completed, the two-way valve 7 is closed, the compressor 1 starts operating again, and the normal heating operation is resumed.

As described above, in the heat pump type air conditioner of this embodiment, the defrosting operation is ended at the compressor temperature, so the defrosting operation continues in vain. Problems such as inhaling large amounts of liquid refrigerant do not occur.

In addition, in this embodiment, three different types of control are performed by comparing the set values Tc ₁ to Tc ₅ and the compressor temperature Tc, ie, compressor preheating control to protect against abnormal compressor temperature rise, and defrosting operation termination control. This also has the effect that the number of sensors and peripheral circuits related to the sensors can be reduced, making circuit design easier.

In this example, the end of the defrosting operation was detected only by the compressor temperature, but the method of the present invention can be combined with conventional methods such as raising the temperature of the outdoor heat exchanger, combining the outdoor heat exchanger temperature and time, etc. The most optimal method is to terminate the defrosting operation at the first one of the respective termination detections in which the defrosting operation is detected.

〔Effect of the invention〕

Since the present invention controls the end of defrosting operation based on the compressor temperature, defrosting is not promoted and wasteful defrosting operation is continued after the discharge temperature decreases due to a decrease in compressor temperature. In addition, the suction refrigerant becomes a large amount of liquid refrigerant, and the defrosting operation can be completed in an appropriate state without causing a failure of the compressor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a heat pump refrigeration cycle of a conventional heat pump air conditioner, FIG. 2 is a diagram showing a heat pump refrigeration cycle and control block of a heat pump air conditioner according to an embodiment of the present invention, and FIG. is a control flowchart of the air conditioner, FIG. 4 is a flowchart of the abnormal temperature rise protection control of the air conditioner, and FIG. 5 is a time chart showing compressor temperature changes and compressor operations due to the same control.
Fig. 6 is a flowchart of the compressor preheating control of the air conditioner, Fig. 7 is a time chart showing the compressor temperature change and the operating state of the compressor heater due to the same control,
FIG. 8 is a flowchart of the defrosting operation control of the air conditioner, and FIG. 9 is a time chart showing changes in the compressor temperature and the operating state of the two-way valve under the same control. 1... Compressor, 2... Four-way valve, 3... Outdoor heat exchanger, 4... Expansion valve, 5... Indoor heat exchanger, 6...
... Compressor discharge port piping, 7 ... Two-way valve, 8 ... Bypass pipe, 9 ... Outdoor fan, 10 ... Indoor fan, 11 ... Indoor control circuit, 12 ... Outdoor control circuit, 18 ... Compression Machine temperature sensor, 20... Compressor relay, 21... Compressor heater relay, 22...
Two-way valve relay for defrosting.

Claims (1)

[Claims] 1. A heat pump refrigeration cycle in which a compressor, an indoor heat exchanger, a pressure reduction device, and an outdoor heat exchanger are connected in sequence, and a bypass circuit that communicates from the compressor discharge port between the pressure reduction device and the outdoor heat exchanger. A heat pump air conditioner that defrosts the outdoor heat exchanger by flowing refrigerant discharged from the compressor through the bypass circuit, further comprising a compressor temperature sensor that detects the temperature of the compressor. A defrosting operation control method for a heat pump type air conditioner, characterized in that the defrosting operation is terminated when the temperature detected by the temperature sensor falls to a predetermined value.