JPH0231299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a defrosting control device for a heat pump type air conditioner.

Configuration of conventional example and its problems Conventionally, in this type of control device, as shown in the conventional example in FIG. Outdoor blower 5
It is connected in parallel with a series circuit consisting of a normally closed pressure switch 8 and a power supply 11 via a thermostat 9 of the indoor unit 7 and a cooling/heating changeover switch 10.
It is connected to the. Further, the electromagnetic four-way valve 6 connected in series with the normally closed contact 4 of the frost detector 3 is connected to the power supply 1 via the cooling/heating changeover switch 10 in parallel with the frost detector 3.
1 is connected. Further, the indoor blower 12 is connected to the normally closed contact 4 of the frost detector 3 and the power source 11.

In other words, during cooling operation, the cooling/heating selector switch 10
Since the cooling side contact circuit 13 is ON, the compressor 2 and the outdoor blower 5 are controlled to be turned on and off by the thermostat 9. This state is shown in area a of the time chart in FIG.

During the heating operation, the heating side contact circuit 14 of the cooling/heating changeover switch 10 is turned ON, so the electromagnetic four-way valve 6 is turned ON, and the refrigeration cycle is switched to the heating side to perform the heating operation. If the room temperature rises in this state, the thermostat 9 is turned off, the compressor 2 is stopped, and the room temperature is controlled.

When the outside temperature is high and the heating capacity is high, the pressure switch 8 is turned OFF to stop the outdoor fan 5, and the thermostat 9 is turned ON and OFF with the heating capacity reduced. This state is shown in area b of FIG.

If frost forms on the outdoor heat exchanger, the frost detector 3
operates and opens the normally closed contact 4,
The outdoor blower 5 is stopped, and the energization to the electromagnetic four-way valve 6 is stopped. This switches the refrigeration cycle and melts and removes the frost. At the same time, the indoor blower 12 is stopped to prevent cold air from blowing out. This defrosting operation state is shown in area c of FIG.

In the conventional defrosting control circuit described above, the detection temperature of the frost detector 3 is fixed at one point and is set to a low temperature (about -6°C), so the outside air temperature is low and the heating capacity is low. In a low condition range, the frost formation temperature is sufficiently low (-10℃ or less) to accurately detect frost formation.

On the other hand, in a condition where the outside air temperature is high and the heating capacity is high, the pressure switch 8 described above operates frequently, and the pressure switch 8 turns OFF.
When the outdoor blower 5 stops, the temperature of the outdoor heat exchanger decreases. However, because the outside air temperature is high, the frost formation temperature cannot reach the above-mentioned detection temperature (approximately -6℃), making detection impossible, and the amount of frost formation increases over time, making it impossible to operate. was.

Furthermore, if the detected temperature is set high (approximately 0° C.), unnecessary defrosting operations will be performed frequently when the outside air temperature is low, resulting in discomfort and shortening the life of the device.

OBJECTS OF THE INVENTION The present invention provides a defrosting control device that solves the various drawbacks found in the above-mentioned conventional examples and is compatible with a wide range of heating conditions.

Composition of the Invention In order to achieve this object, the present invention detects the pressure of the refrigeration cycle and changes the detected temperature of the frost detector by operating a pressure switch that controls the operation of the outdoor blower. The configuration is such that the optimal detection temperature is set according to the temperature.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. Here, the general operation of the refrigeration cycle will be omitted because it is well known. Components that are the same as those in the conventional example will be described using the same reference numerals.

Here, the only difference between the present invention and the conventional example is the configuration of the pressure switch 8 provided in the outdoor unit 1 and the temperature detection circuit of the frost detector 3, but the other configurations and operations are completely the same. Therefore, the following description will focus on the pressure switch 8 and the frost detector 3.

In FIG. 1, a normally closed pressure switch 8 that controls an outdoor blower 5 is provided with a normally open contact 8a, and a normally open contact 8a of the pressure switch 8 is connected to a frost detector 3.
connected to the temperature detection circuit. The voltage generated by the thermistor 15 and input resistor 16 in the frost detector 3 shown in FIG.
The normally open contact 8 is connected to the input voltage (V-) side of the temperature detection circuit composed of a comparator 19 etc.
A and a series circuit of resistor 20 are connected.

In addition, in FIG. 3, a resistor 21 is used to set the defrosting end temperature. Also, the IC control circuit (hereinafter
(referred to as an IC circuit) 22 includes a timer means for generating a defrosting prohibition time t, and a determining means for determining the output of the comparator 19 and transmitting a defrosting signal,
This defrosting signal turns on the relay coil 24 via the transistor 23, opens the normally closed contact 4, and performs defrosting control. 25 and 26 are diodes, and 27 is a DC power supply.

In the refrigeration cycle diagram of FIG. 4, 28 and 29 are an outdoor heat exchanger and an indoor heat exchanger, respectively, and 30 and 31 are a cooling capillary tube and a heating capillary tube, respectively.

In the above configuration, the cooling operation is completely the same as that of the conventional example as shown in area A of the time chart in FIG. 2, so a description thereof will be omitted.

On the other hand, during heating operation, the electromagnetic four-way valve 6 is turned ON via the cooling/heating changeover switch 10, and the refrigeration cycle is switched to the heating cycle to perform the heating operation. In this state, when operating in a condition where the outside air temperature is low and the heating capacity is low, the high pressure of the refrigeration cycle does not reach the set pressure of the pressure switch 8, so the pressure switch 8 is in the ON operation state, and the pressure switch 8 is in the ON operation state. The normally open contact 8a remains in the OFF operation. Then, thermostat 9 turns ON and OFF depending on the change in room temperature.
The compressor 2 and outdoor fan 5 are both turned on.
OFF control.

Therefore, in this state, defrosting control is performed even if the detected temperature of the frost detector 3 is set to a low value. This state is shown in area C as well as area B of the heating operation in the time chart of FIG.

When the outside temperature rises and the heating capacity increases, the pressure in the refrigeration cycle increases, and pressure switch 8
operates OFF to stop the outdoor fan 5, reduce the amount of heat absorbed by the outdoor heat exchanger 28, and reduce the heating capacity, and the normally open contact 8a of the pressure switch 8
is turned ON, and the correction resistor 20 is connected in parallel with the input resistor 16. Therefore, the temperature detected by the thermistor 15 becomes high. Therefore, even if the outside temperature is high and the frosting temperature is high, the frosting detection temperature is set high in conjunction with the pressure switch 8, so the frosting detector 3 can reliably detect the frosting state. Defrost control is performed using This state is shown in area D in FIG.

Effects of the Invention As described above, the defrosting control device of the present invention changes the detected temperature of the frost detector in conjunction with the pressure switch that controls the heating capacity according to the pressure of the refrigeration cycle. By prohibiting unnecessary defrosting operations under conditions where the temperature is low, unpleasant noises caused by defrosting operations can be prevented as much as possible, and the life of the equipment can be extended. Furthermore, it has many advantages, such as being able to perform reliable defrosting control even when the outside air temperature is high, providing a comfortable feeling of heating under a wide range of heating load conditions, and improving operational efficiency.

[Brief explanation of drawings]

FIG. 1 shows a schematic control circuit of a separate air conditioner equipped with a defrosting control device showing one embodiment of the present invention;
Fig. 2 is a time chart explaining the operation of the defrosting control device, Fig. 3 is an electronic circuit diagram of the frost detector in the defrosting control device, Fig. 4 is a refrigeration cycle diagram of the air conditioner, FIG. 5 is a defrosting control circuit of a conventional separation type air conditioner, and FIG. 6 is a time chart illustrating the operation of the defrosting control device. 2...Compressor, 3...Frost formation detector, 5...Outdoor blower, 6...Solenoid four-way valve, 8...Pressure switch, 8a...Normally open contact, 15...Thermistor, 1
6...Input resistance, 17,18...Reference input resistance,
20... Correction resistor, 22... IC control circuit, 28
...Outdoor heat exchanger, 29...Indoor heat exchanger.

Claims (1)

[Claims] 1. Air conditioner that includes a compressor, an electromagnetic four-way valve for switching between cooling and heating modes, a heat pump refrigerant circuit in which an outdoor heat exchanger, a pressure reducing device, and an indoor heat exchanger are connected in a ring, an indoor blower, and an outdoor blower. The machine is provided with a frost detector that is activated by detecting the state of frost on the outdoor heat exchanger, and a pressure switch provided on the high pressure side of the refrigerant circuit and connected in series with the outdoor blower, The frost detector includes a comparison means for comparing a set temperature and a detected temperature, and a determination means for determining the output of the comparison means and outputting a defrosting signal, and the A defrosting control device for air conditioners that connects a pressure switch contact and a series circuit of a correction resistor.