JPH04240355A - Controlling method for electronic expansion valve of air conditioner - Google Patents

Abstract

PURPOSE:To suppress the rise of discharge temperature of a compressor during a superheat control by detecting superheat amount and discharge temperature of suction gas, and switching the opening regulation of an electronic expansion valve between the superheat control and the discharge temperature control. CONSTITUTION:When an electronic expansion valve 4 is controlled based on signals from a suction temperature sensor 10, a saturated temperature sensor 11 and a discharge temperature sensor 12 by a controller 8, a superheat control is conducted at the time of starting an operation. That is, the valve 4 is so controlled that the superheat amount to be obtained by a temperature difference between the suction temperature and the saturated temperature becomes a predetermined value. When the discharge temperature becomes a set temperature (allowable limit temperature) or higher during the superheat control, the discharge temperature control is executed. That is, the valve 4 is so controlled that the discharge temperature becomes constant, and when the superheat amount exceeds a set value during the discharge temperature control, it is again returned to the superheat control.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electronic expansion valve in an air conditioner, and more particularly to a method for controlling superheat and discharge temperature.

0002

[Prior Art] Conventionally, an air conditioner has a variable capacity compressor 1, a four-way valve 2, an indoor heat exchanger 3, as shown in FIG.
, electronic expansion valve (PMV) 4, and outdoor heat exchanger 5 are sequentially connected with refrigerant piping to configure a refrigeration cycle, and a controller 8
The number of revolutions of the compressor 1 is controlled by an inverter device 9 according to a frequency command from the inverter device 9. In order to cause the compressor 1 to compress gas, there is also a suction temperature sensor 10 that detects the temperature of the compressor suction, a saturation temperature sensor 11 that detects the saturation temperature of the suction portion of the compressor, and a discharge temperature sensor 12 that detects the discharge temperature of the compressor. The signals from these temperature sensors are input to the controller 8 to control the electronic expansion valve 4 so that the amount of superheat in which the suction temperature exceeds the saturation temperature is constant. When the discharge temperature increases, the operating frequency of the compressor 1 is lowered to suppress the increase in discharge temperature.

0003

[Problem to be Solved by the Invention] However, when the discharge temperature of the compressor increases, the above method of reducing the operating frequency of the compressor to suppress the increase in discharge temperature has the problem that the rotational speed of the compressor decreases. There has been a problem in that the cooling capacity or heating capacity of the air conditioner is reduced.

[0004] An object of the present invention is to provide a method of controlling an electronic expansion valve that can suppress an increase in the discharge temperature of a compressor in superheat control without reducing the cooling capacity or heating capacity of an air conditioner. be.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a refrigeration cycle using an electronic expansion valve, and a temperature sensor for detecting the suction temperature of the compressor, the saturation temperature of this part, and the compressor discharge temperature. In an air conditioner equipped with a controller that controls the electronic expansion valve using signals from these temperature sensors, at the start of operation,
Based on the temperature difference detected between the suction temperature sensor and the saturation temperature sensor, superheat control is performed by adjusting the opening of the electronic expansion valve to maintain the superheat amount of the suction gas of the compressor at a constant value. When the detected temperature exceeds the set value set as the allowable limit temperature,
Discharge temperature control is performed by adjusting the opening of the electronic expansion valve to maintain the compressor discharge temperature at a constant value within the above-mentioned allowable limit temperature, and during discharge temperature control, the superheat amount is set as a limit value exceeding the above-mentioned constant value. When the temperature exceeds the set value, the system returns to superheat control again.

[0006]

[Operation] The amount of superheat and discharge temperature are detected and the opening degree adjustment of the electronic expansion valve is switched between superheat control and discharge temperature control. Controlled. Therefore, there is no need to lower the operating frequency of the compressor.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

In FIG. 1, the air conditioner of this embodiment has the following features:
It has a refrigeration cycle configured similarly to that shown in FIG. That is,
Compressor 1, four-way valve 2, indoor heat exchanger 3 on the indoor unit side
, an electronic expansion valve 4, and an outdoor heat exchanger 5 are provided on the outdoor unit side, and these are connected in order by piping to constitute a heat pump cycle. Further, a saturation temperature detection circuit 6 is provided before and after the electronic expansion valve 4 and reaches the suction side of the compressor 1 via a capillary 7.

Reference numeral 8 denotes a controller that comprehensively includes an indoor controller and an outdoor controller, and is mainly composed of a microcomputer. The former indoor controller controls the compressor 1 based on inputs such as ON/OFF commands and operation mode commands from a remote controller (not shown), inputs from a room temperature sensor, and inputs from an indoor heat exchanger temperature sensor (not shown). It has the function of controlling the operating frequency of the air conditioner and the operation of the entire air conditioner. The latter outdoor controller decodes the serial operation signal sent from the indoor controller, and uses the contents of this command and temperature data from a current sensor and an outdoor heat exchanger temperature sensor (not shown) to control the compressor 1. The output frequency of the inverter device 9 is controlled, and the rotation speed of the compressor 1 is operated at a variable speed of 30 to 120 Hz.

The control circuit for the electronic expansion valve includes the controller 8, a suction temperature sensor 10, a saturation temperature sensor 11, a discharge temperature sensor 12, and the electronic expansion valve 4. The controller 8 receives signals from the suction temperature sensor 10, the saturation temperature sensor 11, and the discharge temperature sensor 12, and controls the electronic expansion valve 4.

A basic control flow of the electronic expansion valve 4 by the controller 8 is shown in FIG. Control of the electronic expansion valve 4 is as follows:
Broadly speaking, it is divided into superheat control A and discharge temperature control B. In the superheat control A, the electronic expansion valve 4 ( PMV)
control. This is because if the refrigerant gas is superheated by about 5° C., all of the fine particles of the liquefied refrigerant in the refrigerant gas will evaporate and become a somewhat superheated gas, allowing gas compression. On the other hand, in discharge temperature control B, the discharge temperature Td detected by the discharge temperature sensor 12 is a constant value (in this embodiment, the target value is 95°C).
The electronic expansion valve 4 is controlled so that This means that the opening degree of electronic expansion valve 4 is slightly back to liquid level (super heat amount is 0).
℃) to suppress the rise in discharge temperature without lowering the operating frequency of the compressor 1.

As shown in FIG. 2, after startup, superheat control A is first performed to control the electronic expansion valve 4 (PMV) so that the amount of superheat is 5°C. At this time, the discharge temperature Td is set at the allowable limit temperature (in this example, 10
5℃) or higher. Since the temperature is less than 105° C. under normal conditions, superheat control A is performed as is.

However, if heat radiation from the condenser is small and heat input from the evaporator is large, the discharge temperature Td may reach 105° C., which is the limit value of the compressor. Therefore, when the discharge temperature Td becomes 105 degrees Celsius or more, the discharge temperature control B is entered and the electronic expansion valve 4 is slightly opened so that the discharge temperature Td reaches the target value of 95 degrees Celsius (superheat amount 0 degrees Celsius).
control.

During this discharge temperature control B, if the heat input in the evaporator is small and the heat radiation in the condenser is large,
When trying to maintain the discharge temperature Td at 95°C, the superheat amount SH becomes the target value of 5°C in superheat control A.
becomes much larger. Therefore, we monitor whether the superheat amount SH has increased to the set value (10°C in this example) determined as this limit value, and if it is less than the set value of 10°C, discharge temperature control B is performed as is. If the superheat amount SH becomes 10°C or higher, the process returns to the superheat control A and maintains the target value of the superheat control A at 5°C.

[0015] In this way, since the superheat amount SH and the discharge temperature Td are detected and the opening degree adjustment of the electronic expansion valve 4 is switched between the superheat control A and the discharge temperature control B, the opening degree adjustment of the electronic expansion valve 4 is enough. Both superheating and discharge temperature control can be performed, and the discharge temperature Td can be kept constant without reducing the operating frequency of the compressor 1. This effect can be obtained in both heating operation and cooling operation.

Next, the action during heating operation will be specifically explained.

At startup, the refrigerant leaving the compressor 1 returns to the compressor 1 through the indoor heat exchanger 3, electronic expansion valve 4, and outdoor heat exchanger 5. At this time, the controller 8 calculates the superheat amount SH from the difference in temperature detected by the suction temperature sensor 10 and the saturation temperature sensor 11, and controls the electronic expansion valve 4 so that the superheat amount SH becomes a constant value of 5°C. . At this time, the discharge temperature Td is monitored based on the signal from the discharge temperature sensor 12, and depending on whether the discharge temperature Td is less than the set value of 105°C, the superheat control A is continued or the discharge temperature control B is switched. We are determining whether At startup or under normal conditions, the discharge temperature Td is less than 105° C., so superheat control A is normally performed.

However, when the indoor temperature is high or the operating frequency is high, the high pressure increases and the discharge temperature Td decreases to 10
Temperatures may exceed 5℃. In this case, the controller 8 detects the discharge temperature Td from the suction temperature sensor 10 at a set value of 10
It is determined that the temperature exceeds 5°C, and the discharge temperature control is switched to B. In this discharge temperature control B, the discharge temperature Td is controlled at 95°C, so the electronic expansion valve 4 is slightly opened, and the cycle is slightly back-fluid (the amount of superheat is 0°C).
As a result, the discharge temperature Td decreases.

From discharge temperature control B to super heat control A
When returning to , check the superheat amount SH. That is, during discharge temperature control, the heating capacity decreases due to a decrease in outside air temperature, a decrease in operating frequency, etc., and when the high pressure decreases, the discharge temperature decreases below 95°C. For this reason, controller 8
The electronic expansion valve is throttled to increase superheat and maintain the discharge temperature at the set value of 95°C. Then, by keeping the discharge temperature at 95° C., the amount of superheat becomes too large. In this case, if the superheat amount SH becomes equal to or higher than the set value of 10° C. during the discharge temperature control, the discharge temperature control B returns to the superheat control A.

[0020]

[Effects of the Invention] In summary, according to the present invention, the frequency of the compressor is lowered in order to detect the superheat amount and discharge temperature and switch the electronic expansion valve opening adjustment between superheat control and discharge temperature control. Therefore, the discharge temperature can be kept constant. Therefore, an increase in the discharge temperature of the compressor can be suppressed without reducing the cooling capacity or heating capacity of the air conditioner.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a refrigeration cycle of an air conditioner to which the control method of the present invention is applied.

FIG. 2 is a diagram showing an embodiment of the control method of the present invention.

FIG. 3 is a diagram showing a refrigeration cycle and a controller of a conventional air conditioner.

[Explanation of symbols]

1 Compressor 2 Four-way valve 3 Indoor heat exchanger 4　Pressure reduction device 5 Outdoor heat exchanger 6 Saturation temperature detection circuit 7 Capillary 8 Controller 9 Inverter device 10 Suction temperature sensor 11 Saturation temperature sensor 12 Discharge temperature sensor

Claims (1)

[Claims] [Claim 1] A refrigeration cycle using an electronic expansion valve,
In an air conditioner that has a temperature sensor that detects the suction temperature of the compressor, the saturation temperature of this part, and the compressor discharge temperature, and a controller that controls the electronic expansion valve based on the signals from these temperature sensors, when starting operation, , performs superheat control that adjusts the opening of the electronic expansion valve to maintain the amount of superheat of the suction gas of the compressor at a constant value based on the temperature difference detected by the suction temperature sensor and the saturation temperature sensor, and during superheat control, the discharge temperature sensor When the detected temperature exceeds the set value set as the allowable limit temperature, discharge temperature control is performed by adjusting the opening of the electronic expansion valve to maintain the compressor discharge temperature at a constant value within the above allowable limit temperature. A method for controlling an electronic expansion valve in an air conditioner, characterized in that during control, when the amount of superheat exceeds a set value determined as a limit value exceeding the above-mentioned certain value, the control returns to superheat control again.