JPS62158952A - Controller for refrigeration cycle - 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 Industrial Application] The present invention relates to a refrigeration cycle control device that increases the efficiency of the refrigeration cycle, particularly in an air conditioner.

[Conventional technology]

Fig. 7 is a block diagram showing a conventional refrigeration cycle control device as disclosed in, for example, Japanese Patent Application Laid-Open No. 56-44566. 02 is a condenser whose capacity can be changed by changing the capacity, 8 is an electrically operated expansion valve whose opening can be adjusted, and 4II'i is an evaporator.The parts that make up each of these refrigeration cycles are connected in a ring by refrigerant piping. o
5atl'i is a first temperature sensor attached to the inlet of the evaporator 4; 5b is a second temperature sensor attached to the suction of the compressor 1;
5C is a third temperature sensor attached to the middle part of the condenser 2, 6 is each of these temperature sensors 5a, 5
This is a control circuit that controls the opening degree of the expansion valve 3 according to the detected values from b and 5c.

Next, the operation will be explained. When the compressor 1 is driven, refrigerant flows through the refrigerant piping, and the refrigeration cycle is operated.

Here, the temperature difference Δ5H between the refrigerant temperature Ta at the inlet of the evaporator 40 detected by the first temperature sensor 5a and the refrigerant temperature Tb at the suction part of the compressor 1 detected by the second temperature sensor 5b =Tb-Ta is M5H= within the range where the pressure loss in the evaporator 4 and the refrigerant piping around it can be considered constant with respect to the actual superheat degree of 8H of the refrigeration cycle.
It can be considered that there is a relationship of SH + △T (△T is a constant) 0. Then, during normal operation, the opening degree of the expansion valve 3 is controlled by the control circuit 6 so that the temperature difference △SH becomes the set value 8Ho. Also, when the compressor 1 is started, the expansion valve is activated when the refrigerant temperature Tc of the condenser 2, which has been detected by the third temperature sensor 5C from the control circuit 6, reaches a predetermined temperature TCO. When a control signal is output to fully open the refrigerant temperature TC and the refrigerant temperature TC satisfies Tc≧TCO, the refrigeration cycle is then controlled in accordance with the temperature difference Δ8H.

[Problem that the invention seeks to solve]

The conventional refrigeration cycle control device is configured as described above, and the difference ΔSH between the temperature of the artificial part of the evaporator 4 and the temperature of the suction part of the compressor 1 is calculated as ΔSH28H10△1゛. Therefore, if the refrigerant pipe is long from the inlet of the evaporator 4 to the suction of the compressor 1, the pressure loss will increase and the constant ΔT will be very large. In addition, there was a point where the refrigeration cycle could not be efficiently controlled due to variations in the value that could not be regarded as a constant due to load fluctuations. In air conditioners and the like, where each unit is installed in a separate unit, it is necessary to send and receive detected temperature data between the units, which poses a problem in that the circuitry required to do so becomes complex.

This invention was made to solve these problems, and an object of the present invention is to provide a refrigeration cycle control device that can perform highly efficient operation control of a refrigeration cycle with a simple configuration. Means for Solving the Problems] The refrigeration cycle control device of the present invention is equipped with a control circuit that adjusts the opening degree of the expansion valve based on the operating capacity of the compressor and the outside temperature or the amount of change thereof. .

[Effect]

The control circuit adjusts the opening degree of the expansion valve based not only on the operating capacity of the compressor but also on the outside air temperature. Therefore, efficient operation of the refrigeration cycle can be performed with a simple configuration.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, 1Fi is a variable capacity compressor, 2 is a condenser, 3#i is an electric expansion valve with adjustable opening, and 4Fi is an evaporator. These are connected in a ring by refrigerant piping, and constitute a refrigeration cycle. 01 is a capacity control circuit that variably controls the operating capacity of the compressor l, 8 is a temperature sensor that detects the outside air temperature, and 9ij
: A control circuit that adjusts the opening degree of the expansion valve 3 based on the operating capacity of the compressor and the outside air temperature or the amount of change thereof. The opening degree of the expansion valve 30, which is determined based on the predicted operating capacity of the compressor l and the outside air temperature, is kept fixed. Normally, when trying to operate the refrigeration cycle of an air conditioner with high efficiency, It is known that it is sufficient to perform control to maintain an appropriate degree of superheating during each operation and heating operation. Figure 2 shows the optimum table for the valve opening of the expansion valve 3 that provides the degree of superheating during heating. , which shows an example of the results when measurements were taken while changing the operating capacity of the compressor 1 and the outside air temperature. As shown in the figure, for the optimum valve opening L#i of the expansion valve 3 and the operating capacity f of the compressor 1, L=a11f+b (a and b are constants)
It can be expressed as Furthermore, the value of this constant S depends on the outside air temperature Tout t, b = O・T out (Ofi
Since it can be expressed as a constant), L = a m f + c a
Using the function represented by Tout, it is possible to predict the optimum valve opening degree from the capacity f and the outside air temperature Tout.

The constants a and c are eigenvalues of the air conditioner (0) Therefore, the control circuit 9 detects the operating capacity f from the capacity control circuit 7 of the compressor l, and also uses the temperature sensor 8 to determine the outside air temperature Tout. Detected at regular intervals or according to operating conditions
Either adjust the absolute opening of the expansion valve 3 to the valve opening determined by the above two values each time there is a change in the outside air temperature Tout, or adjust the valve opening ji calculated at each detection.
Relative difference between L o and the valve opening degree calculated this time △L = L
- Outputs any command to the expansion valve 3 to change the valve opening by an amount of 0. This relationship also holds true when the compressor 1 is started.

That is, if the operating capacity f of the compressor 1 is known before the engine is started, the optimal valve opening degree of the expansion valve 3 can be set in advance from both equations by detecting the outside air temperature Tout. FIG. 3 shows the change over time in the degree of superheating of the refrigeration cycle due to differences in the initial setting opening degree of the expansion valve 3. Generally, in a refrigeration cycle equipped with a variable capacity compressor 1, control is performed to gradually increase the operating capacity from the stable operation capacity set at startup.On the other hand, immediately after startup, most of the refrigerant is in the compressor 1. Since the amount of refrigerant passing through the expansion valve 3 is extremely small, there is a margin in the heat exchange capacity of the evaporator 4, and the degree of superheating is likely to increase. Therefore, if the opening degree of the expansion valve 3 that is set at the time of startup is too small, the peak value of the degree of superheat that occurs will become large, and the degree of superheat when the engine is stable will also become large because the throttle is too narrow. , the amount of refrigerant circulating seems to be insufficient, and the capacity is not fully demonstrated. On the other hand, if the set valve opening degree is too large, liquid return to the compressor 1 becomes a problem. In the end, in both cases, the correction control to search for the optimal valve position is forced.In the case of zero operation, the valve opening is fixed for a certain period of time at the valve opening determined from the above relationship using the set value or predicted value of the operating capacity during stable operation. If this is done, the degree of superheat will peak to some extent, but then it will stabilize at the optimum value, and correction control will not take much effort.

FIG. 4 is a block diagram showing another embodiment of the present invention. In the figure, 10 is a temperature sensor attached to the discharge part of the compressor 1, and the detected value can be inputted to the control circuit 9. In addition, FIG. This shows an example of the results when the value of the refrigerant discharge temperature at the time of obtaining the temperature is measured by changing the operating capacity of the compressor l and the outside air temperature.
α is for the operating capacity i1f of compressor 1 Td=α・f+
It can be expressed as e, and it can be seen that the value of the second term e in this equation is a function value that changes depending on the outside temperature.Also, in Figure 6, the operating capacity is fixed during cooling and changes with the outside temperature. As shown in the figure, the function value e for the outside air temperature Tout is -6=g
It can be considered as aTout, and the functional formula Tα=dsf+
The optimum discharge temperature is determined from the operating capacity f and the outside air temperature Tout using geTout, and the actual discharge temperature is controlled so as to be stabilized within a certain temperature range centered around this temperature.In other words, if the discharge temperature rises, an appropriate valve is activated. Control is performed such that it opens at the opening level and closes when the opening level decreases.

In this way, not only the operating capacity of the compressor 1 but also the outside air temperature is detected, and the appropriate opening degree of the expansion valve 3 is adjusted based on the detected data using a functional formula, so that the refrigeration cycle can be operated efficiently. It becomes possible. Further, even immediately after the compressor 1 is started, by detecting the temperature of the refrigerant discharged from the compressor 1, the opening degree of the expansion valve 3 can be set to an appropriate value, and moreover, it is possible to adjust the opening degree of the expansion valve 3 to an appropriate value even when the compressor 1 is started. It becomes possible to easily control the refrigerant cycle with high efficiency regardless of the situation.

〔Effect of the invention〕

As explained above, according to the present invention, since the opening degree of the expansion valve is adjusted based on the operating capacity of the compressor and the outside temperature or the amount of change thereof, pressure loss and load fluctuations in the refrigerant piping can be prevented. The refrigeration cycle can be controlled with high efficiency regardless of the temperature, and even if the refrigeration cycle is configured by unit, the circuit for transmitting and receiving the refrigerant temperature detection signal is not complicated and can be easily operated with high efficiency. It has the effect of being able to do the following.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing an embodiment of the present invention, Figure 2 is a diagram showing the optimum opening degree of the expansion valve determined by the compressor operating capacity and outside temperature, and Figure 3 is a diagram showing the compressor. FIG. 4 is a diagram showing the relationship between the operating capacity of the compressor and the degree of superheat, FIG. 4 is a configuration diagram showing another embodiment of the present invention, FIG. FIG. 6 is a diagram showing changes in temperature of discharged refrigerant with respect to outside air temperature, and FIG. 7 is a configuration diagram showing a conventional refrigeration cycle control device. 1...Compressor 3...Electric expansion valve 8...Temperature sensor 9...Control circuit Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (3)

[Claims] (1) In a control device for a refrigeration cycle having a variable capacity compressor and an expansion valve whose opening degree can be adjusted, the opening degree of the expansion valve is controlled based on the operating capacity of the compressor and the outside temperature or the amount of change thereof. A refrigeration cycle control device comprising a control circuit for adjustment. (2) The control circuit is characterized in that the opening degree of the expansion valve is maintained for a predetermined period of time after the start of the compressor, the degree of opening of the expansion valve being determined based on a preset predicted value of operating capacity and outside temperature. A refrigeration cycle control device according to claim 1. (3) The control circuit controls the opening degree of the expansion valve so that the temperature of the refrigerant discharged from the compressor falls within a predetermined range determined based on the operating capacity of the compressor and the outside air temperature. A refrigeration cycle control device according to claim 1 or 2, characterized in that: