JPH0226145B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to control of an electric expansion valve provided in a refrigeration cycle device when starting a compressor.

Conventionally, there has been a device of this type as shown in FIG. In the figure, 1 is a compressor, 2 is a condenser, 3 is a temperature-sensitive expansion valve, 4 is a temperature-sensitive tube, 5 is an evaporator, and 6 is an accumulator.

Next, the operation will be explained. When the compressor 1 starts, the refrigerant compressed to high temperature and high pressure by the compressor 1 is
It flows into the condenser 2 and exchanges heat, but since the pressure is not yet high enough, it is not sufficiently liquefied, and flows into the expansion valve 3 as a two-phase mixture of liquid and gas.
Therefore, since the refrigerant is in a two-phase state and this type of expansion valve has a small valve lift of about 0.2 mm to 0.3 mm, the amount of refrigerant passing through the expansion valve is extremely reduced, and the pressure on the low pressure side is reduced. As a result, the specific volume of the refrigerant at the inlet of the compressor 1 increases and the amount of refrigerant displaced decreases, so it takes a considerable amount of time to reach a stable state, and if the temperature condition on the high pressure side is low, the low pressure cut works and operation is interrupted. There was a flaw that made it impossible to do it.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and when the compressor is started, the amount of superheat is detected and the electric expansion valve is opened until the amount of superheat exceeds the peak value. By keeping the valve opening fully open and controlling the valve opening during steady operation based on the detected amount of superheat, it is possible to quickly reach a steady state without lowering the low pressure side pressure at startup. I can,
Another object of the present invention is to provide a refrigeration cycle device that can suppress the amount of superheat at startup.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, 7 is an electric expansion valve, and 8 is an accumulator 6 from both sides of the electric expansion valve 7.
A capillary tube is provided as a pressure reducing mechanism 9 in the middle of the bypass path that bypasses the inlet of the pump. 10 is a first temperature sensor provided at the exit of the bypass path 8; 11 is a second temperature sensor provided on the inlet side of the accumulator 6 (on the evaporator side from the bypass connection); 12 is a first and second temperature sensor provided Temperature sensor 1
0 and 11 are connected to a relay (not shown) for detecting start/stop of the compressor 1, and a controller for controlling the electric expansion valve 7; 13 is a lead wire. The rest of the configuration is similar to that of the conventional device shown in FIG. FIG. 3 shows the structure of the electric expansion valve 7, which includes an electromagnetic coil 31, a plunger 32, a cylinder 33, and a slit 34. 35 is a piston,
36 and 37 are springs, 38 and 39 are refrigerant pipes, and when a current is input from the controller 12 to the lead wire 13,
A force that pulls the plunger 32 in the direction of the arrow is generated in the electromagnetic coil 31 in proportion to the current flowing, and the spring 36,
It stops at a balanced position due to the force relationship with 37. Therefore, as the applied current increases, the stopping positions of the plunger 32 and the piston 35 also move in the direction of the arrow, and the opening area of the slit 34 provided in the cylinder 33 increases. FIG. 6 is a characteristic diagram showing the change in the amount of superheat Sh with respect to the elapsed time t when the valve opening degree of the electric expansion valve 7 is kept fully open from the start of the compressor.
rises from the start of the compressor, reaches a peak value, and then decreases to a steady state. Furthermore, FIG. 4 shows that the peak value of the superheat amount Sh that changes as shown in FIG. 6 when the electric expansion valve 7 is kept fully open from the start of the compressor is This is a characteristic diagram showing how the refrigerant flow rate G during steady operation, which is determined by the frequency, changes depending on the refrigerant flow rate. show. Furthermore, FIG. 5 shows the correlation between the refrigerant flow rate G during steady state and the optimum valve opening X during steady operation of the electric expansion valve 7.

First, the operation during steady operation will be explained. Refrigerant vapor that has become high temperature and high pressure in the compressor 1 undergoes heat exchange in the condenser 2, becomes liquid, and flows into the expansion valve 7. Then, it is depressurized by the expansion valve 7, becomes low temperature and low pressure, undergoes heat exchange in the evaporator 5, becomes superheated steam, and returns to the compressor 1 through the accumulator 6, forming a circulation cycle. On the other hand, the refrigerant passing through the bypass passage 8 that bypasses the inlet of the accumulator 6 from both sides of the electric expansion valve 7 has a higher pressure when connected to the condenser 2 side. (Evaporator 5
A part of the vapor is depressurized through the capillary tube 9 to the inlet pressure of the accumulator 6, becomes a two-phase state, mixes with the heated steam exiting the evaporator 5, and returns to the compressor 1 through the accumulator 6. Therefore, since the pressure in the bypass passage 8 is equal to the refrigerant pressure at the inlet of the accumulator 6, the temperature in this portion becomes the saturation temperature of the inlet pressure of the accumulator 6. Therefore, the first temperature sensor 10 is provided near the exit of the bypass path through which the refrigerant at the saturated temperature flows, and the second temperature sensor 11 is provided near the inlet of the accumulator 6 where superheated steam is sent from the evaporator 5. Therefore, the accurate superheat amount of the refrigerant at the inlet of the accumulator 6 can be calculated by the controller 12 from the difference between the detected values of both temperature sensors 10 and 11. Then, from this amount of superheat, a current is outputted to adjust the electric expansion valve 7 to the optimum valve opening degree, thereby controlling the amount of superheat to a predetermined amount.

Next, the startup of the compressor 1 will be explained. When the electric expansion valve 7 is kept fully open during startup, as shown in FIG. 4, when the stable refrigerant flow rate is large, the superheat sh at startup becomes large.
Furthermore, as shown in FIG. 5, the valve opening degree x in a stable state must be increased as the flow rate G becomes larger. Therefore, the peak of superheat sh
It can be seen that when the value is large, the valve opening degree when stable is also increased. When the compressor 1 is started, a relay that detects whether the compressor 1 starts or stops operates, and the controller 12 applies a large current to the electric expansion valve 7 to fully open the valve.
The superheat on the inlet side of the accumulator 6 detected by the temperature sensors 10 and 11 is reduced to zero because the refrigerant accumulated in the evaporator 5 returns to the compressor 1 side when the evaporator 5 is stopped. This is the detected value. On the other hand, the refrigerant that exits the compressor 1 undergoes heat exchange in the condenser 2, but because the temperature is not high enough, it does not completely liquefy and enters the electric expansion valve 7 in a two-phase state, but the valve opening is fully opened. Therefore, the flow rate will not decrease drastically. Therefore, there is little pressure drop on the low pressure side, and stable operation can be achieved quickly. In addition, the superheat value increases as the pressure decreases on the low pressure side, but as the pressure drop on the low pressure side is suppressed as mentioned above, the peak value of superheat is also smaller than with conventional temperature-sensitive expansion valves. can do. Even when the amount of superheat increases from the time of startup and reaches the amount of superheat during steady operation, the opening degree of the electric expansion valve 7 is not controlled and is kept fully open until it reaches its peak.
The peak value of this superheat is determined by determining the amount of superheat from the difference in temperature detected by the temperature sensors 10 and 11, for example, and determining the point at which the amount of superheat changes from an upward trend to a downward trend based on a change in the amount of superheat as shown in FIG. can be easily obtained by detecting it by calculation in the controller 12. temperature sensor 10,
When the superheat detected in step 11 reaches its peak, the controller 12 calculates the valve opening at a stable time based on this peak value using the relationships shown in Figures 4 and 5. Since the electric current value corresponding to the current value is outputted to the electric expansion valve 7, stable operation can be achieved quickly, and the start-up is quick and highly efficient operation can be achieved.

In the above embodiment, the current value that corresponds to the valve opening at a stable state is output to the electric expansion valve 7 as soon as the superheat reaches its peak at startup. It is also possible to output a current value to the electric expansion valve 7 that gradually becomes a stable valve opening after a period of time equivalent to that of . Furthermore, the temperature sensor 11 may be located at a position that detects the temperature of the piping near the compressor suction.

As described above, according to the present invention, when the compressor is started, the valve opening of the expansion valve is kept fully open until the peak of superheat, and the controller calculates and sets the valve opening when stable from this peak value. As a result, the drop in low pressure at startup can be kept small, the peak value of superheat can also be reduced, and the valve opening can be quickly reached during stable steady-state operation, resulting in faster start-up and highly efficient operation. .

[Brief explanation of drawings]

Fig. 1 is a refrigerant circuit diagram of a conventional refrigeration cycle device, Fig. 2 is a refrigerant circuit diagram of a refrigeration cycle device showing an embodiment of the present invention, Fig. 3 is a structural sectional view of an electric expansion valve, and Fig. 4 Figure 5 is a characteristic diagram showing the relationship between the peak value of superheat sh when the electric expansion valve is fully opened when starting the compressor and the refrigerant flow rate G at a stable time, and Figure 5 shows the relationship between the refrigerant flow rate G and the electric expansion at a stable time. FIG. 6 is a characteristic diagram showing the relationship with the valve opening x of the valve. FIG. 6 is a characteristic diagram showing the change in the amount of superheat over time when the electric expansion valve is fully opened at the time of starting the compressor. The same reference numerals in the figures indicate the same or corresponding parts.1
is a compressor, 2 is a condenser, 3 is a temperature-sensitive expansion valve, 5 is an evaporator, 6 is an accumulator, 7 is an electric expansion valve, 8 is a bypass path, 9 is a capillary tube, 10 and 11 are temperature sensors, 12 is the controller.

Claims (1)

[Claims] 1. In a refrigeration cycle device in which a compressor, a condenser, an electric expansion valve, an evaporator, and an accumulator are connected in sequence, the electric expansion valve is connected to the inlet of the accumulator from both sides, and a pressure reducing mechanism is provided in the middle. a bypass path, a first temperature sensor that detects the exit temperature of the bypass path, a second temperature sensor that detects the temperature at the inlet of the accumulator, and a temperature difference between the detected values of the first and second temperature sensors at the inlet of the accumulator. The amount of superheat is calculated, and the opening degree of the electric expansion valve is kept fully open from the time the compressor is started until the amount of superheat exceeds the peak value, and steady operation is performed based on the amount of superheat calculated above. A refrigeration cycle device comprising: a controller that controls the opening degree of the electric expansion valve when the electric expansion valve is opened.