JPS5919255B2 - Defrosting control method for air conditioners - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting control method for an air conditioner, and in particular, to appropriately control the start of defrosting operation of an air-cooled heat pump type air conditioner.

In conventional defrosting control, the force to start defrosting operation when the temperature difference between the evaporator temperature and its surrounding temperature exceeds a set value, or the rate of change of the slope of the evaporator temperature is set to a set value. The defrosting operation was controlled to start when the temperature was higher than that.

However, with the control method described above, the temperature of the evaporator changes due to sudden changes in the air temperature, humidity, wind speed, etc. around the evaporator, resulting in problems such as malfunctions when controlling the defrosting operation. .

This invention aims to eliminate the above-mentioned drawbacks, and aims to prevent malfunctions by temporarily suspending the flow of defrosting control when there is a large change in the ambient temperature of the evaporator.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 is a diagram showing the schematic configuration of an air-cooled heat pump type air conditioner (hereinafter simply referred to as an air conditioner), in which 1 is a compressor, 2 is a condenser, 3 is an expander, 4 is an evaporator, 5a and 5b are It is a four-way switching valve, and the above-mentioned parts are connected by refrigerant piping 6, and the inside is filled with refrigerant.

In the figure, solid line arrows indicate the flow of refrigerant during heating operation, and broken line arrows indicate the flow of refrigerant during cooling operation, and switching between the refrigerant for heating and cooling is performed by four-way switching valves 5a and 5b.

1 is a defrosting operation control device, 8 is an evaporator temperature detector, and 9 is an ambient temperature detector. Signals from these detectors are input to the defrosting operation control device 7, and from now on, four-way switching valves 5a and 5b are input.
It outputs an output signal to.

Next, its operation will be explained.

Now, if the air conditioner is in heating operation, the high temperature, high pressure gaseous refrigerant that exits the compressor 1 passes through the four-way switching valve 5a and enters the condenser 2, where it radiates heat (heats) and becomes liquid. become,
It reaches the expander 3 via the four-way switching valve 5b.

Here, the refrigerant expands, absorbs heat (cools) in the evaporator 4, becomes gaseous, and returns to the compressor 1 via the four-way switching valve 5a.

At this time, the evaporator 4 (ri) is usually installed outdoors, and as the heating operation continues, the temperature of the evaporator 4 gradually decreases, and depending on the outside air condition, when the temperature of the evaporator 4 drops below a certain temperature, the evaporator 4 Frost forms on the surface.

Here, as shown in Fig. 3, if we take the frosting rate c on the horizontal axis and the temperature ['C] of the evaporator 4 on the vertical axis, then at a certain frosting rate as shown in the figure,・It has been confirmed through experiments that the temperature of the evaporator 4 decreases rapidly.

From the above facts, find the slope 1 of the dθE temperature of the evaporator 4 (where θE is the evaporator temperature [℃] and t is the time [sec]), and when this value is larger than the set value, or A possible method is to start the defrosting operation t2 when the temperature gradient change d2θE conversion rate □- is larger than a set value.

However, with these methods, there is a risk of malfunction due to instantaneous fluctuations in the temperature of the evaporator 4 due to disturbances or the like.

Further, as shown in FIG. 2, the vertical axis shows the temperature θE of the evaporator 4,
If the horizontal axis represents the ambient temperature θO[tj'Y, then the temperature θE of the evaporator 4 is the ambient temperature θ as shown in the figure.

It has been confirmed through experiments that there is a high correlation with

Therefore, in this invention, the ambient air temperature θo'v of the evaporator 4 is
The ambient temperature is determined by the ambient temperature detector 9, the rate of change is determined by the defrosting operation control device 7, and when this value is negative, that is, in the direction of decreasing temperature, and is greater than the set value, the above-mentioned slope of the temperature of the evaporator 4 is determined. Even if the rate of change of d2θ is larger than the set value, the output of the switching signal from the defrosting operation control device 7 to the four-way switching valve 5at5b is suspended until the rate of change of the ambient water temperature detector 9 becomes positive. This is to prevent malfunctions.

Note that the defrosting operation ends when the temperature of the evaporator 4 becomes equal to or higher than the set temperature.

As explained above, according to the present invention, when the rate of change in the ambient air temperature of the evaporator is large, the command to start defrosting operation is temporarily postponed due to other factors, so that defrosting operation due to malfunction is prevented. This improves the reliability of the air conditioner.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an air conditioner implementing the method of the present invention, FIG. 2 is a characteristic diagram of evaporator temperature versus ambient air temperature, and FIG. 3 is a characteristic diagram of evaporator temperature versus frost formation rate. In the figure, 1 is a compressor, 2 is a condenser, 3 is an expander, 4 is an evaporator, 5ay5b is a four-way switching valve, 6 is a refrigerant pipe, 7 is a defrosting operation control device, and 8 and 9 are temperature detectors. be.

Claims (1)

[Claims] 1 The temperature of the evaporator of the air conditioner, which consists of a compressor, condenser, expander, evaporator 1, etc., is lower than the set temperature, and the blade
The defrosting operation is started when the rate of change of the temperature of the evaporator with respect to time is negative and the second derivative of the temperature with respect to time is greater than a set value. A defrosting control method for an air conditioner in which when the rate of change is negative and larger than a set value, the start sound of the defrosting operation is temporarily suspended even when the above-mentioned conditions for starting the defrosting operation are met.