JPH06288654A - Device for controlling motor-operated expansion valve in air conditioner - Google Patents

Abstract

PURPOSE:To provide a device mentioned above which, during the heating when the outdoor air temperature is low, can control the degree of superheat without excessively lowering the suction pressure of the compressor so as not to decrease the heating capacity of the indoor apparatus and which can at the same time ensure the reliability of the compressor. CONSTITUTION:During the heating operation when the outdoor air temperature, detected by an outdoor air temperature sensor 110, is low, control of the degree of superheat based on the difference in temperature between a suction temperature sensor 116 and a saturation temperature sensor 115 is not carried out. Instead, there is provided a controller 3 for controlling the discharge temperature detected by a discharge temperature sensor 2 and the saturation temperature detected by a saturation temperature sensor 115.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superheat control device in a refrigeration cycle of an air conditioner.

[0002]

2. Description of the Related Art In recent years, the separation type air conditioner has a tendency that the amount of refrigerant circulation greatly changes due to the use of an inverter or the like. Therefore, a fine refrigerant flow rate control is required for the efficiency and safety of products.

Conventionally, the configuration of an electric expansion valve control device for a separation type air conditioner of this type will be described with reference to FIG.

As shown in the figure, an outdoor unit 101 is provided with a compressor 102 controlled by an inverter, a four-way valve 103 for switching a refrigerant flow path, an outdoor heat exchanger 104, and an electric expansion valve 105 of a refrigerant throttling mechanism. There is. The compressor 102 is driven by an operation command from the indoor unit 106, and the refrigerant discharged from the compressor 102 passes through the four-way valve 103, is condensed by the outdoor heat exchanger 104 during cooling, and is condensed by the indoor unit 106 during heating. The electric expansion valve 105
Is reduced in pressure by the indoor unit 106 during cooling, and heat is exchanged as evaporating action in the outdoor heat exchanger 104 during heating,
A refrigeration cycle of returning to the compressor 102 was formed.

In the above structure, the operation command from the indoor unit 106 is sent through the signal line 107 to the inverter section 108.
Is transmitted to the superheat control device 109, and the inverter unit 10
Reference numeral 8 determines the drive frequency of the compressor 102 by the signal from the indoor unit 106 and the outside air temperature sensor 110, and the superheat degree control device 109 causes the liquid receiver 111 to pass through the saturation temperature capillary tube 112 at regular intervals. The saturation temperature sensor 115 attached to the bypass pipe 114 connected to the suction pipe 113 led out to the compressor 102 and the suction temperature sensor 116 attached to the suction pipe 113 detect the saturation temperature sensor 115 and the suction temperature. The superheat degree of the entire refrigeration cycle is detected by the temperature difference of the sensor 116, and an opening / closing command is transmitted to the electric expansion valve 105 by the signal line 117 to adjust the superheat degree to an appropriate degree.

[0006]

In such a conventional electric expansion valve control device for an air conditioner, the pressure of the refrigerant sucked into the compressor 102 is low during heating operation when the outside air temperature is low, and the degree of superheat is reduced. If the opening degree of the electric expansion valve 105 is reduced to obtain the superheat degree, the superheat degree can be obtained, but the refrigerant suction pressure decreases, so that the evaporation pressure of the refrigerant in the outdoor heat exchanger 104 also decreases,
At the same time, since the evaporation temperature in the outdoor heat exchanger 104 is lowered, the surface of the outdoor heat exchanger 104 becomes frosted,
The heat exchange is hindered and the suction pressure of the compressor 102 is reduced, and the circulation is repeated, resulting in the indoor unit 106.
There was a problem that the heating capacity of the car would be reduced. Further, under the condition that the indoor unit 106 maximizes the heating capacity, the degree of superheat becomes almost zero, and even if the opening degree of the electric expansion valve 105 is changed, the degree of superheat hardly changes. Therefore, the indoor unit 106 exhibits the maximum heating capacity. There is a problem that the conditions to be applied cannot be judged from the degree of superheat.

The present invention solves the above problems, and an object thereof is to provide an electric expansion valve control device for an air conditioner that can maximize the heating capacity of an indoor unit even during heating operation at low outside air temperature. And

[0008]

In order to achieve the above object, an electric expansion valve control device for an air conditioner according to the present invention has an inverter-controlled compressor in an outdoor unit, a four-way valve, an outdoor heat exchanger, and a refrigerant. An electric expansion valve for decompression, a refrigeration cycle provided with a liquid receiver, an outside air temperature sensor for detecting an outside air temperature, a discharge pipe temperature sensor for detecting a temperature of a discharge pipe of the compressor, and the liquid receiver. A bypass pipe having a saturation temperature capillary tube provided between the suction pipe and the suction pipe, and a suction temperature sensor and a saturation temperature sensor respectively provided in the suction pipe and the bypass pipe, respectively, in the cooling operation and high outside air conditions During heating operation, the degree of superheat is detected by the temperature difference between the suction temperature and the saturation temperature, and during the heating operation under low outside air temperature conditions where the temperature detected by the outside air temperature sensor is low, The temperature sensor and the saturated temperature sensor and structure provided with a control device for controlling the opening degree of the electric expansion valve.

[0009]

With the above-described structure, the present invention detects the discharge temperature and the saturation temperature of the compressor and sets the proper refrigeration cycle condition in the heating operation at the low outside air temperature, so that the superheat degree cannot be obtained. Also, the heating capacity of the indoor unit can be maximized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The same parts as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in the figure, a discharge temperature sensor 2 for detecting a discharge temperature in a discharge pipe 1 led out from a compressor 102 controlled by an inverter, and an outside air temperature sensor 11 are provided.
0 and suction temperature sensor 116 and saturation temperature sensor 1
A control device 3 for controlling the opening degree of the electric expansion valve 105 by selecting the superheat degree control by the detection of 15 and the superheat degree control by the discharge temperature sensor 2 and the saturation temperature sensor 115 is provided.

In the above structure, the outside air temperature sensor 110 detects the outside air temperature, and the controller 3 receives the suction temperature sensor 11 in the heating operation when the outside air temperature is low.
6 and the saturation temperature sensor 115 do not perform superheat control due to the temperature difference between the discharge temperature sensor 2 and the saturation temperature sensor 1.
By controlling the control device 3 so that the discharge temperature falls within the range of the constant temperature condition and the saturation temperature becomes equal to or higher than the constant temperature by the detected temperature of 15, the overheat is performed even under the condition that the degree of superheat cannot be accurately detected. If the degree is high, the characteristic that the discharge temperature rises can be used to make it possible to set the discharge temperature above a certain level, and the electric expansion valve 105 reduces the opening too much, so that the suction pressure of the compressor 102 decreases. Too much can be prevented by controlling the saturation temperature above a certain level.

As described above, according to the electric expansion valve control device for the air conditioner of the embodiment of the present invention, the compressor 10 is operated even during the heating operation at the low outside air temperature where the degree of superheat cannot be accurately grasped.
It is possible to secure the reliability of the compressor 102 without excessively lowering the suction pressure of 2 and taking a superheat degree.

[0014]

As is apparent from the above embodiments, according to the present invention, the outside air temperature detected by the outside air temperature sensor
By selecting the superheat control by detecting the suction temperature sensor and the saturation temperature sensor of the compressor and the superheat control by the discharge temperature sensor and the saturation temperature sensor, it is difficult to grasp the superheat degree. Also, it is possible to provide an electric expansion valve control device for an air conditioner that can ensure the reliability of the compressor and maximize the heating capacity of the indoor unit.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram of an electric expansion valve control device for an air conditioner according to an embodiment of the present invention.

FIG. 2 is a refrigeration cycle diagram of a conventional electric expansion valve control device for the same air conditioner.

[Explanation of symbols]

 1 Discharge pipe 2 Discharge temperature sensor 3 Control device 101 Outdoor unit 102 Compressor 103 Four-way valve 104 Outdoor heat exchanger 105 Electric expansion valve 110 Outside air temperature sensor 111 Liquid receiver 112 Saturation temperature capillary tube 113 Suction pipe 114 Bypass pipe 115 Saturation Temperature sensor 116 Suction temperature sensor

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor controlled by an inverter, a four-way valve, an outdoor heat exchanger, an electric expansion valve for decompressing a refrigerant, and a liquid receiver are provided in an outdoor unit, and an outside air temperature for detecting an outside air temperature. A sensor, a discharge pipe temperature sensor for detecting the temperature of the discharge pipe of the compressor, a bypass pipe having a saturation temperature capillary tube provided between the liquid receiver and the suction pipe, the suction pipe and the bypass. A suction temperature sensor and a saturation temperature sensor respectively provided in the pipe are provided, and the superheat degree is detected by the temperature difference between the suction temperature and the saturation temperature during the cooling operation and the heating operation when the outside air temperature is high. A control device for controlling the opening degree of the electric expansion valve by the discharge temperature sensor and the saturation temperature sensor during the heating operation under the low outside air temperature condition where the detected temperature is low. An electric expansion valve control device for the air conditioner provided.