JPH0232544B2 - KUKICHOWAKINOREIBAIRYURYOSEIGYOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a refrigerant flow rate control device for an air conditioner equipped with a pressure reducing device with a pressure reducing valve drive unit that can change the amount of pressure reduction by an electrical signal for pressure reduction control.

<Prior art> As shown in FIG. 1, a conventional air conditioner includes an electric refrigerant compressor 1, a refrigerant condenser 2, a refrigerant pressure reducing device 3, a refrigerant evaporator 4, and a refrigerant flow rate control device 5 of the pressure reducing device 3. I was prepared. As the pressure reducing device 3, it is possible to use an electric motor, a solenoid, or a device equipped with a pressure reducing valve driving section 3B that drives the pressure reducing valve 3A by combining a heater and a bimetal.
A control device so that the difference δH between the inlet temperature and the outlet temperature of the evaporator 4 detected by the first and second temperature detectors 5A and 5B provided at the inlet and outlet of the evaporator 4 is an appropriate value. 5 was outputting a control signal to the pressure reducing device 3 to change the amount of pressure reduction. FIG. 2 shows the relationship between the lift height h of the pressure reducing valve of the pressure reducing device 3 and the rotation angle θ of the stepping motor that drives the pressure reducing valve.

FIG. 3 shows an example of the control device 5, which includes temperature detectors 5A and 5B at the inlet and outlet of the evaporator 4,
An A/D converter 5C that converts the outputs of the temperature detectors 5A and 5B into digital quantities, and control that controls the pressure reducing device 3 to maintain the temperature difference δH at an appropriate value δHo from the output of the A/D converter 5C. It is composed of a circuit (microcomputer) 5D and an output converter 5E that outputs the calculation result from the control circuit 5D in accordance with the pressure reducing device 3.

The conventional control device 5 controls the pressure reducing device 3 by increasing the valve lift h of the pressure reducing device 3 when the temperature difference δH increases in response to changes in the temperature difference δH, and decreasing the temperature difference δH. When doing so, there is a so-called proportional control that outputs a control electric signal to reduce the valve head h, and a method that corrects the deviation between the temperature difference δH and the target value δHo, for example by calculating the deviation at regular intervals. This is a combination of integral control that outputs a control electric signal that changes the valve lift h in a direction that corrects the deviation if it is outside the allowable range. FIG. 4 shows an example of control results using such a method. In the figure, TH1 is the inlet temperature of the evaporator 4 obtained by the first temperature detector 5A, TH2 is the outlet temperature of the evaporator 4 obtained by the second temperature detector 5B, and h is the pressure reducing device 3. P is the refrigerant pressure at the inlet of the evaporator 4. In this example, the temperature at the inlet and outlet of the evaporator 4 is a continuous oscillation.
Therefore, it is clear that the temperature difference ΔH similarly oscillates, and it is difficult to say that the refrigeration cycle is maintained in an appropriate state. The reason why such a phenomenon (hunting phenomenon) occurs is that the response of the refrigeration cycle to a change in the valve lift h of the pressure reducing valve 3 is slow. In other words, even if the valve head h changes and the refrigerant flow rate changes, it takes time for the refrigerant in the evaporator 4 to stabilize to a new state, and as a result, the temperature response at the outlet of the evaporator 4 changes. This is because you will be late. Therefore, this response is detected by the first and second temperature detectors 5.
By the time the pressure reducing valve control device 5 outputs a new pressure reducing valve control signal based on signals A and 5B, it is already too late and the control is always excessive. To explain with Figure 4,
The outlet temperature TH2 of the evaporator 4 increases, and the temperature difference δH
When the difference between the current value and the target value δHo is large, that is, the degree of superheating of the refrigerant at the outlet of the evaporator 4 becomes large, and when an integral control electric signal is output to increase the pressure reducing valve head h, the proportional control immediately before is output. Therefore, the lift of the pressure reducing valve has already increased, and the refrigerant pressure P in the evaporator 4 has already increased. Despite this, when an integral control signal is output to further increase the pressure reducing valve head h, the pressure reducing valve head h becomes excessive, the refrigerant flow rate becomes excessive, and all of the refrigerant is not evaporated in the evaporator 4. The refrigerant will flow out directly to the outlet side. Therefore, the outlet side temperature of the evaporator 4
TH2 becomes low. On the other hand, when the outlet side temperature TH2 becomes low, the refrigerant flow rate on the inlet side is already controlled to be small, so the inlet side temperature TH1 becomes high. Therefore, in Figure 4, TH1>TH
2, and the hunting phenomenon becomes significant. Such excessive control results in oscillatory control results.

In order to stabilize control using conventional methods, it is possible to reduce the amount of valve lift operation by both integral control and proportional control. However, although this makes the control looser and improves stability, it becomes difficult to respond quickly to changes in load. As described above, with conventional methods, it has been difficult to achieve both quick response and stability of control.

<Purpose> The present invention has been made in order to eliminate such drawbacks, and provides control that can speed up the control phase and quickly and stably control the refrigeration cycle to an appropriate state by adding a simple configuration. It provides equipment.

That is, the present invention attempts to advance the phase of control by detecting the reversal of the slope of the temporal change in temperature difference and adjusting the head of the pressure reducing valve, thereby maintaining stability without impairing the responsiveness of control. It is something to do.

<Example> An example of the present invention will be described in detail below. In this example, components having the same functions as those of the conventional system are designated by the same reference numerals. The control device according to the present invention is an air conditioner equipped with an electric compressor 1, a refrigerant condenser 2, a refrigerant evaporator 4, and a refrigerant pressure reduction device 3 disposed between the condenser 2 and the evaporator 4. A first temperature detector 5A is provided on the inlet side of the refrigerant evaporator 4, and a second temperature detector 5B is provided on the outlet side of the evaporator 4, and the inlet temperature TH1 and the outlet temperature TH2 of the refrigerant evaporator 4 are A control circuit 5D is provided that outputs a pressure reduction control signal to the pressure reduction valve drive unit 3B of the pressure reduction device 3 so as to maintain the temperature difference δH at a temperature difference target value δHo that brings the optimum refrigeration cycle state.

As shown in FIG. 7, the control circuit 5D includes a temperature difference detection means 5a that detects the temperature difference δH, and sends a pressure reduction control signal to the pressure reduction valve drive unit 3B one by one based on the temperature difference δH detected by the temperature difference detection means 5a. The proportional control means 5b outputs the temperature difference δH and the temperature difference target value δHo from the temperature difference detection means 5a. an integral control means 5c that outputs a pressure reduction control signal to the pressure reducing valve drive section 3 when the deviation δH - δHo changes over time and its slope is reversed;
A deviation slope reversal control means 5d is provided for outputting a pressure reduction control signal to B. In addition, in Figure 7, 5e
is a timer for measuring a certain period of time during integral control.

As in the conventional case, this control device 5 includes the first and second temperature detectors 5A, 5B, and an A/C converter that converts the outputs of both temperature detectors 5A, 5B into digital quantities.
A control circuit (microcomputer) 5D that controls the pressure reducing device 3 to keep the temperature difference δH at an appropriate temperature difference target value δHo from the outputs of the D converter 5C and the A/D converter 5C; and an output converter 5E that outputs the calculated results according to the pressure reducing device 3.

Next, the method of controlling the pressure reducing valve will be explained mainly based on FIG. 5. FIG. 5 shows a flowchart of the control incorporated in the microcomputer 5D in the control device 5.
Note that the portion surrounded by dotted lines in FIG. 5 is the same control as the conventional one. To control the pressure reducing valve, first, the predetermined time ΔTi
It is determined whether or not the period has elapsed, and when it has elapsed, integral control is performed, and when it has not elapsed, proportional control is performed. In the integral control, the integral control means 5C calculates the temperature difference δH between the first and second temperature detectors 5A and 5B at fixed time intervals ΔTi (for example, every 30 seconds), and calculates the difference between the calculated value and the target temperature difference δHo. Depending on the magnitude of the deviation (hereinafter referred to as deviation), for example, as shown in FIG. 6, a control electrical signal is output to the pressure reducing device 3. As a simpler method, if the deviation is outside the allowable range, the pressure reducing device 3 may be driven by a fixed number of steps.

In addition, proportional control, for example, increases the temperature difference δH,
When the outlet temperature TH2 is large, the superheat of the refrigerant at the evaporator 4 outlet is increasing, so the proportional control means 5b reduces the amount of pressure reduction in the pressure reducing device 3 to increase the refrigerant flow rate and reduce the degree of superheating. Valve lift height h
Outputs a control signal that increases Furthermore, in addition to this proportional control, the inlet/outlet temperature TH obtained by the first temperature detector 5A and the second temperature detector 5B
The temperature difference between 1 and TH2 is calculated by the temperature difference detection means 5a, and the difference between this temperature difference δH and the temperature difference target value δHo, that is, the deviation changes over time and the slope is reversed, is determined as the deviation. Proportional control is performed by detecting the inclination inversion by the control means 5d.

Figure 6 shows the temperature deviation δH− over time.
An example of a change in δHo is shown. The control circuit (microcomputer) 5D monitors the temperature deviation δH-δHo at time intervals Δt that are sufficiently early in response to changes in the refrigeration cycle, and detects that the temporal change in the temperature deviation δH-δHo changes from upward to downward at point A1. When detected, it is determined that the amount of pressure reduction by the pressure reducing device 3 has already become too small and the flow rate of refrigerant to the evaporator 4 is becoming excessive, and a control signal is outputted to reduce the valve head h by Δh.

In addition, at point B1, when it is detected that the slope of the temperature deviation δH - δHo has changed from negative to positive, it is determined that the amount of pressure reduction is already excessive and the refrigerant flow rate to the evaporator is becoming too small, and the valve is closed. It works to increase the head h by Δh and reduce the amount of pressure reduction.

In this way, as the valve head h changes, the evaporator 4
Even if the response of the temperature at the outlet part of In combination with proportional control and integral control, rapid response is possible.

Therefore, by adding such control, the phase of the control can be advanced and the delay in response of the refrigeration cycle can be compensated for.

<Effects> As is clear from the above description, the present invention provides an air conditioner equipped with an electric compressor, a refrigerant condenser, a refrigerant evaporator, and a refrigerant pressure reduction device disposed between the condenser and the evaporator. A first temperature detector is provided on the inlet side of the refrigerant evaporator, a second temperature detector is provided on the outlet side of the evaporator, and the temperature difference between the inlet temperature and the outlet temperature of the refrigerant evaporator is detected. A control circuit is provided for outputting a pressure reduction control signal to the pressure reducing valve drive section of the pressure reducing device to maintain the temperature difference at a target value for achieving an optimum refrigeration cycle state, and the control circuit includes temperature difference detection means for detecting the temperature difference. , a proportional control means that outputs a pressure reduction control signal to the pressure reducing valve drive unit one by one based on the temperature difference detected by the temperature difference detection means; integral control means that outputs a pressure reduction control signal to the pressure reducing valve drive unit based on the magnitude of the deviation; and an integral control means that outputs a pressure reduction control signal to the pressure reducing valve drive unit when the deviation changes over time and its slope is reversed; and a deviation slope inversion control means for outputting a signal.

Therefore, according to the present invention, the deviation slope reversal control means outputs a pressure reduction control signal to the pressure reducing valve drive unit even when the deviation changes over time and its slope is reversed, so this method is more efficient than the conventional method. Changes in the refrigeration cycle can be detected more quickly and the pressure reducing device can be controlled, suppressing the instability of the refrigeration cycle (hunting phenomenon) caused by over-control, and not only achieving stable control, but also preventing sudden changes in load. It is now possible to quickly track disturbances such as
The practical effect is great.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional air conditioner, Figure 2 is a diagram showing the relationship between the rotation angle of the stepping motor for driving the pressure reducing valve and the lift of the pressure reducing valve, and Figure 3 is a diagram of the refrigerant flow rate control device. 4 is a diagram showing the relationship between the evaporator inlet and outlet temperature, pressure, and lift of the pressure reducing valve for the same time period; FIG. 5 is a control flowchart of the pressure reducing valve showing an embodiment of the present invention; The figure shows the change in the temperature difference between the inlet temperature and the outlet temperature of the evaporator and its relationship with the valve lift at that time, and FIG. 7 is a functional block diagram of the control circuit. 1: Compressor, 2: Condenser, 3: Pressure reducing device, 4:
Evaporator, 5A, 5B: Temperature detector, 5: Control device, 5D: Control circuit, 5a: Temperature difference detection means, 5
b: Proportional control means, 5c: Integral control means, 5d:
Deviation slope reversal control means, 5e: timer.

Claims (1)

[Claims] 1 In an air conditioner equipped with an electric compressor 1, a refrigerant condenser 2, a refrigerant evaporator 4, and a refrigerant pressure reducing device 3 disposed between the condenser 2 and the evaporator 4, the inlet of the refrigerant evaporator 4 A first temperature sensor 5A is provided on the side of the evaporator 4, and a second temperature sensor 5A is provided on the outlet side of the evaporator 4.
B is provided, and the inlet temperature TH of the refrigerant evaporator 4 is
A control circuit 5D is provided for outputting a pressure reduction control signal to the pressure reducing valve drive unit 3B of the pressure reducing device 3 so as to maintain the temperature difference δH between the temperature difference δH between the temperature difference δH between the temperature difference δH and the outlet temperature TH2 at the temperature difference target value δHo that brings the optimum refrigeration cycle state. The control circuit 5D includes a temperature difference detection means 5a that detects the temperature difference δH, and a proportional control means 5b that outputs a pressure reduction control signal to the pressure reduction valve drive unit 3B one by one based on the temperature difference δH detected by the temperature difference detection means 5a. , the detected temperature difference δH from the temperature difference detection means 5a, and the temperature difference target value δHo
an integral control means 5c which calculates the deviation (δH - δHo) from A refrigerant flow rate control device comprising: deviation slope inversion control means 5d for outputting a pressure reduction control signal to the pressure reduction valve drive unit 3B when the slope is reversed.