JPS6162770A - Method of controlling refrigerating air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to refrigerators, package air conditioners, chiller units,
The present invention relates to a method of controlling a refrigeration air conditioner applied to a room air conditioner or the like.

[Background of the invention]

BACKGROUND ART Conventionally, in a refrigeration and air conditioner equipped with an electronically controlled expansion valve that changes the degree of valve opening in response to an electrical signal, the expansion valve is controlled so that the degree of superheating of the refrigerant at the outlet of the evaporator remains constant. However, in such a refrigeration and air conditioning system, when the load increases (1) For example, when the indoor and outdoor air temperature increases,
Since the discharge temperature of the compressor also rose significantly, there was a risk that the compressor motor windings would burn out.

Therefore, when the above-mentioned discharge temperature rises above the allowable value Td1, this is memorized, and the opening degree of the electronically controlled expansion valve is increased until the discharge temperature becomes below the set value Td2, and the discharge temperature becomes below the set value. A control method has been proposed in which the degree of superheat is controlled again when the degree of superheat has decreased (Utility Model Application No. 56-16).
Publication No. 3257).

However, in this control method, the allowable value Td1 and the set value Td
Due to the differential of Also fluctuates. This may lead to a decrease in the refrigeration and air conditioning capacity and a decrease in the reliability of the electronically controlled expansion valve.

In view of the above, the present invention stably controls the discharge temperature of the compressor even when the discharge temperature rises.

Another object of the present invention is to minimize changes in the opening degree of the electronically controlled expansion valve, thereby increasing the refrigeration and air conditioning capacity and improving the reliability of the expansion valve.

[Summary of the invention]

In order to achieve the above object, the present invention provides a refrigeration and air conditioner equipped with an electronically controlled expansion valve, in which temperature sensors and electronically controlled expansion valves are normally provided on the suction sides of a compressor and an evaporator, respectively, to determine the degree of superheating of suction refrigerant. When the discharge temperature of the compressor rises above the set value, the discharge temperature is controlled by both temperature sensors, the electronically controlled expansion valve, and the temperature sensor installed on the discharge side of the compressor. At the time of control, if the discharge temperature is below the set value and the degree of superheat is above the set value, the superheat degree control is performed again.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a refrigeration cycle of a refrigeration and air conditioner to which this embodiment is applied, and this refrigeration cycle consists of a compressor 1. Condenser 2
．． An electronically controlled expansion valve 3 and an evaporator 4 are sequentially connected in an operative manner. On the suction side and discharge side of the compressor 1,
A first temperature sensor 5 that detects the suction temperature of the refrigerant and a third temperature sensor 6 that detects the discharge temperature are provided, and a second temperature sensor 6 that detects the evaporation temperature is provided on the inlet side of the evaporator 4. ing. These temperature sensors 5 to 7 and the electronically controlled expansion valve 3 are connected to a controller 8, and depending on the temperature detected by the temperature sensors 5 to 7,
A controller 8 controls the valve opening degree of the electronically controlled expansion valve 3.

The gas refrigerant discharged from the compressor 1 flows into the condenser 2 and is condensed and liquefied. The liquid refrigerant discharged from the condenser 2 flows into the electronically controlled expansion valve 3 and is depressurized.
It flows into the evaporator 4 and is evaporated and gasified. This gas refrigerant is sucked into the compressor 1 again.

Next, a method of controlling the electronically controlled expansion valve 3 will be explained.

In normal operation, the electronically controlled expansion valve 3 is connected to the first temperature sensor 5.
The valve opening degree is controlled so that the difference between the temperatures detected by the second temperature sensor 6 and the second temperature sensor 6, that is, the degree of superheating of the suction refrigerant, becomes equal to the first set value SR. The indoor and outdoor air temperature increases, and the temperature detected by the third temperature sensor 7, that is, the discharge temperature, is equal to or higher than the second set value Td□, and is detected by the first temperature sensor 5 and the second temperature sensor 6, respectively. temperature difference.

That is, when the degree of superheat is equal to or lower than the third H constant value SH2, the valve opening degree of the electronically controlled expansion valve 3 is set to the discharge temperature of the compressor 1 (the third H constant value SH2).
The temperature detected by the temperature sensor 7) is controlled to be equal to the second set value Td.

Discharge temperature control is performed. Furthermore, when controlling the discharge temperature,
When the indoor and outdoor air temperature decreases, the degree of superheat increases because the discharge temperature is controlled to the second set value Td□.

Then, the degree of superheating, that is, the difference between the detection degrees of the first temperature sensor 5 and the second temperature sensor 6 is greater than or equal to the fifth set value SH, and the detected temperature (discharge temperature) of the third temperature sensor 6 is the fifth set value SH. 4
If it is less than the set value Td2, superheat degree control is performed again.

FIG. 2 is a control characteristic diagram showing the relationship between the superheat degree SH of the suction refrigerant and the discharge temperature Td, and shows each set value and each control range described above.

When the load is small, superheat control is performed at point A within superheat control range Y. When the load increases and reaches point B within the discharge temperature control range X, the process shifts to discharge temperature control. Further, when the load increases and reaches the 0 point within the discharge temperature control range X, the suction refrigerant becomes wet. Conversely, the load changes from 0 point to B
, when the temperature drops to point D, when the point D is reached, the superheat control is performed again and the temperature returns to around point A.

The set values SH,,SH,,SH,and Td,.

Even if the Td2 values are very similar to each other, stable control without hunting can be performed because the discharge temperature is constantly detected during overheated skin control, and the degree of superheat is constantly detected during discharge temperature control.

Therefore, since the opening degree change of the electronically controlled expansion valve is small and the degree of superheat is controlled to be smaller than a certain set value, optimum control can be performed in terms of performance.

FIG. 3 is a control characteristic diagram of another embodiment, and this control characteristic is the set value SR in the control characteristic diagram of the previous embodiment (FIG. 2),
and SH3 are set equal.

This figure shows the respective control ranges x' and y' when the set values Td1 and Td are set equal.1 In this embodiment, since the set values of the discharge temperature in each control switching are the same, the discharge temperature is Although it is not possible to completely match the set value Td1, it is possible to make the range of variation very small. Furthermore, since the control is significantly simplified, it is very advantageous in terms of cost.

In the above embodiments, the control algorithm for each control method is not particularly limited, but the simplest control algorithm is the difference e between the detected value and the set value, as expressed by equation (1),
There is a method of determining the correction amount ΔV (expansion valve opening degree) according to the deviation.

AV=K-a,...
(1) K: constant Although such a simple control method is low cost, it is difficult to accurately match the degree of superheating to the set value. Stable control can be achieved by using a speed type PI control algorithm that combines motion and integral motion.

JV=to, (e, -e, -t)+Kse, ·τ, -(2
) In equation (2), eavem is the time tel
It is the difference (deviation) between the detected value and the set value at t, -1, and τ8 is the sampling interval. Therefore, in this control method, a correction amount is given that is proportional to the temporal change in the deviation and the product of the sampling time and the deviation, and accurate and stable control can be performed.

〔Effect of the invention〕

As explained above, according to the present invention, superheat degree control and discharge temperature control can be performed stably, and switching between the two controls can be performed smoothly, thereby increasing the refrigeration and air conditioning capacity and increasing the electronically controlled expansion valve. , the reliability of other equipment can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a refrigeration cycle of a refrigeration and air conditioner to which the control method of the present invention is applied, and FIGS. 2 and 3 are control characteristic diagrams of each embodiment of the control method of the present invention. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 3... Electronically controlled expansion valve, 4... Evaporator, 5-7... Temperature sensor, 8...
··controller.

Claims (3)

[Claims] 1. A refrigeration cycle is constructed by operatively connecting a compressor, a condenser, an electronically controlled expansion valve, and an evaporator, and a first temperature sensor and a third temperature sensor are provided on the suction side and discharge side of the compressor, respectively, and In a refrigeration and air conditioner in which a second temperature sensor is provided on the suction side of the device, and the electronically controlled expansion valve and the first to third temperature sensors are connected to a controller, the first temperature sensor and the second temperature sensor are usually connected to the controller. The degree of superheat control is performed by controlling the opening and closing of the electronically controlled expansion valve so that the difference between the respective detected temperatures becomes equal to the first set value, and the temperature detected by the third temperature sensor is equal to or higher than the second set value, and If the difference between the temperatures detected by the first temperature sensor and the second temperature sensor is less than or equal to a third set value, the electronically controlled expansion valve is controlled so that the temperature detected by the third temperature sensor becomes equal to the second set value. Discharge temperature control is performed, and when the discharge temperature is controlled, the detected temperature of the third temperature sensor is equal to or higher than the fourth set value, and the difference between the detected temperatures of the first temperature sensor and the second temperature sensor is equal to or higher than the fifth set value. A method for controlling a refrigerating and air conditioning apparatus, characterized in that the degree of superheating is controlled. 2. While making the third setting value and the fifth setting value equal to each other,
2. The method of controlling a refrigerating and air conditioning system according to claim 1, wherein the second set value and the fourth set value are made equal. 3. 3. The method of controlling a refrigerating and air conditioner according to claim 1, wherein the superheat degree control and the discharge temperature control are controlled by a PI control algorithm.