JPH0228034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric expansion valve used in a heat pump type air conditioner for both cooling and heating in a refrigeration cycle.

Figure 1 is a diagram of the refrigeration cycle of an air conditioner using a conventional electric expansion valve. In the figure, 1 is a compressor, 2 is a four-way valve, 3 is an outdoor heat exchanger, and 4 is an electric expansion valve. , 5 is an indoor heat exchanger. The destination of the high temperature and high pressure refrigerant gas compressed by the compressor is
Depending on the cooling or heating operation, the four-way valve 2 switches to the outdoor heat exchanger 3 side or the indoor heat exchanger 5 side. Figure 1 shows an example of cooling operation.
The high-temperature, high-pressure refrigerant gas that passes through the four-way valve 2 is condensed in the outdoor heat exchanger 3 and reaches the electric expansion valve 4. Here, the refrigerant expands adiabatically and becomes a low-pressure gas-liquid two-phase evaporated gas in the indoor heat exchanger 5, passes through the four-way valve 2 again, reaches the accumulator 6, and from there passes through the suction pipe 12. Then, it returns to the compressor 1 again. In the refrigeration cycle operated according to the above cycle, the opening degree of the electric expansion valve 4 is controlled by using a temperature sensor 7 provided in the middle of the suction pipe 12.
and the signal from the pressure sensor 8, which is also provided in the middle of the suction pipe 12, are sent to the controller 11, and the controller 11 calculates the amount of superheat from these two signals. I was getting used to it.

Another method is to detect the evaporator saturation temperature with a temperature sensor 9 installed in the piping of the evaporator (the indoor heat exchanger 5 in the case of Figure 1) instead of the pressure sensor 8, and use this signal and the The amount of superheat was calculated and controlled based on the signal from the temperature sensor 7 of the pipe 12. In this case, when the operation of the refrigeration cycle is reversed and heating is started, the temperature sensor 10 attached to the outdoor heat exchanger 3 and the temperature sensor 7 of the suction pipe 12 are used.

However, in the former case, the pressure sensor for detecting the suction pressure to the compressor 1 is expensive and unreliable, making it unsuitable for practical use. In the latter case, temperature sensors must be provided in both the outdoor heat exchanger and the indoor heat exchanger in order to detect the evaporator saturation temperature. Furthermore, during excessive operation or startup, the area detected by the temperature sensor is not necessarily in a steady saturated state, making it difficult to use as a temperature control.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide an electric reversible expansion valve that has an additional function of accurately detecting the saturation temperature of the compressor suction pressure even during excessive operation or startup. The high pressure side of the refrigerant flow path of the expansion valve so that the refrigerant is always bypassed from the low pressure side of the expansion valve to the refrigerant suction side of the accumulator.
A bypass path is formed from each opening on the low pressure side to a refrigerant outlet connected to the refrigerant suction side of the accumulator, and opening/closing means for opening the low pressure side and closing the high pressure side of the two openings is provided. It is prepared.

The following will be described in detail with reference to illustrated embodiments.

FIG. 2 is a sectional view of the electric reversible expansion valve 24 of the present invention, where 13 is the main body, 14 is the refrigerant inlet connected to the pipe from the outdoor heat exchanger 3, and 15 is the indoor heat exchanger. A refrigerant flow path is formed between the refrigerant inlet 14 and the refrigerant outlet 15 at the refrigerant outlet connected to the piping from the container 5 . Note that although the case of cooling operation is shown here, during heating operation, 1
4 is a refrigerant outlet, and 15 is a refrigerant inlet. 16
Reference numeral 17 indicates a valve port as a throttle valve portion forming a valve port 16a provided between the inlet 14 and the outlet 15, and 17 indicates a valve pin made of a magnetic material to adjust the opening degree of the valve port 16a. 18 is body 13
The lid and valve pin stopper is also made of magnetic material. A spring 19 is provided between the stopper 18 and the valve pin 17 and always urges the valve pin 17 to close the valve port 16a. 20 is an electromagnetic coil, and 21 is its lead wire. 22 is a bypass path provided in the valve port 16, which connects the refrigerant inlet 14 and the refrigerant outlet 1.
5, and has a bypass refrigerant outlet 22a. 23 are two valve balls serving as opening/closing means for opening and closing the two openings of this bypass passage 22;
They are connected to each other, and the opening on the high-pressure side of the refrigerant inlet 14 is closed by the inflow pressure of the refrigerant, and the opening on the low-pressure side of the refrigerant outlet 15 is opened. Therefore, since the refrigerant inflow side and the refrigerant outflow side are switched during cooling operation and heating operation, opening and closing by the valve ball are also reversed.

The electric reversible expansion valve having such a configuration operates the valve pin 17 in response to an electric signal from the lead wire 21.
moves against the biasing force of the spring 19 to adjust the opening degree of the valve port 16a. Therefore, the opening degree can be adjusted by electrical signals. Since the refrigerant inflow side of the bypass passage 22 is closed by the valve ball 23 and the outflow side thereof is open, the refrigerant after adiabatic expansion, that is, the refrigerant on the low pressure side always flows into the bypass passage 22.

A refrigeration cycle device using the electric reversible expansion valve as described above will be explained based on FIG. 3. In Fig. 3, 1 is a compressor, 2 is a four-way valve, 3 is an outdoor heat exchanger, 5 is an indoor heat exchanger, 6 is an accumulator, and 7 is an intake temperature sensor, which are shown in Fig. 1. It is the same as the conventional device. 2
5 is an electric reversible expansion valve 24 whose one end is shown in FIG.
The other end of the refrigerant pipe is connected to the bypass refrigerant outlet 22a of the bypass passage 22, and the other end thereof is connected to the refrigerant suction pipe of the accumulator 6. 26 is a temperature sensor installed near the intake side of the accumulator of this pipe 25, and 11 is a controller whose configuration is similar to the fourth one.
As shown in the figure, a microcomputer manufactured by Mitsubishi Electric
It is mainly composed of M8748. That is, suction pipe 1
The second temperature sensor 7 is connected to an input port of a microcomputer 28 via an A/D converter 27. Similarly, the temperature sensor 26 is also A/D.
It is connected to a microcomputer 28 via a converter 27. Current flows from the DC power source 30 to the electromagnetic coil 20 of the electric reversible expansion valve 24 through the light receiving portion of the photocoupler 29 . The control signal from the output port of the microcomputer 28 is sent to the inverter 31.
A current corresponding to the control signal is passed through the light emitting section of the photocoupler 29, the light emitting section emits light according to the current, and a current corresponding to the control signal is passed through the electromagnetic coil 20 via the light receiving section.

In a refrigeration cycle device having such a configuration, the refrigerant is adiabatically expanded by the electric reversible expansion valve 24, and then a part of the refrigerant is bypassed to the refrigerant suction pipe of the accumulator 6 through the bypass path 22. forms the same refrigerant circuit as the conventional device shown in FIG.

FIG. 5 shows the movement of the refrigeration cycle according to the embodiment of FIG. 3 on a Mollier diagram, where the horizontal axis shows enthalpy H and the vertical axis shows pressure P. In the figure, A indicates the suction refrigerant state of the compressor 1, B the discharge refrigerant state, C the refrigerant state at the expansion valve inlet, and D the expansion valve outlet refrigerant state. Further, E indicates the state of the refrigerant at the outlet of the refrigerant pipe 25 from the bypass path 22, and the broken line indicates an isobaric/isothermal line on the Mollier diagram of the refrigerant (Freon R-22).

FIG. 6 is a model diagram of the flow pattern of the refrigerant in the evaporator, for example, the indoor heat exchanger 5 during cooling operation,
The flow direction of the refrigerant is indicated by an arrow, where a indicates a wavy flow, b indicates an annular flow, c indicates a spray flow, and d indicates a gas flow.

Figures 7 and 8 are characteristic diagrams based on experimental results of changes in the physical properties of the refrigerant in the evaporator when the refrigeration cycle is started. Figure 7 shows the heat transfer tubes numbered in order from the refrigerant inlet to the outlet of the evaporator. Figure 8 is a characteristic diagram of the temperature of the pipe wall measured at each location during the time, and shows the change in temperature from startup to steady state. Figure 8 is a characteristic diagram of pressure drop △P against refrigerant permeability x. It is.

As in the conventional refrigeration cycle shown in FIG. 1, a temperature sensor 9 or 10 is used to detect the amount of superheat.
Therefore, when attempting to ascertain the tube wall temperature of the evaporator shown in FIG. 7, an accurate amount of superheat cannot be detected. In other words, the exact amount of superheat is determined by the difference between the saturation temperature of the refrigerant corresponding to the compressor suction pressure and the actual compressor suction temperature. As the temperature changes, a pressure drop distribution as shown in Figure 8 occurs in the evaporator, and the pressure is lower at the evaporator outlet than at the inlet. The saturation temperature detected by An accurate amount of superheat cannot be detected from the compressor suction refrigerant temperature (point A) measured by sensor 7. However, according to the embodiment shown in FIG. 3, saturated refrigerant flows out from the bypass passage 22 of the electric reversible expansion valve 24, and this refrigerant reaches a pressure near point E in FIG. The temperature is generated near point E. Therefore, by detecting the temperature near this point E with the temperature sensor 26, the saturation temperature for the compressor suction pressure can be accurately detected, and by calculating the difference between the temperature detected by the temperature sensor 7, the temperature to the compressor can be determined. The amount of superheat of the refrigerant gas can be calculated accurately, and since the opening degree of the electric reversible expansion valve is controlled based on this, the amount of superheat can be kept constant and operation with the maximum coefficient of performance possible.

Next, one embodiment of the calculation and judgment functions within the control device 11 will be described with reference to the flowchart of FIG. In FIG. 9, T ₁ is the refrigerant suction temperature into the compressor 1 detected by the temperature sensor 7, T _S is the saturation temperature corresponding to the compressor suction pressure detected by the temperature sensor 26, SH is the amount of superheat,
SH ₁ and SH ₂ are set values, E is the opening degree of the electric reversible expansion valve at the time of detection, ΔE is the opening width, and K is a constant.

In this FIG. 9, at every fixed time Δt in step A, the saturation temperature T _S measured by the temperature sensor 26 shown in FIG.
Load.

Next, in step B, the above suction temperature Ti
The difference between and the saturation temperature T _S is calculated as the superheat amount SH.

Therefore, the process moves to step C, and if the calculated superheat amount SH is larger than the set value SH1 but smaller than SH2, the process returns from step C to step A, leaving the opening degree E* of the electric reversible expansion valve 24 as it is again. t
Take measurements after hours.

Further, in step C, when the calculated super heat amount is larger than the set value SH2, the process moves from step C to step F, and the electric reversible expansion valve 2
Opening degree E* of 4 outputs a signal △E in the opening direction.

Conversely, when the computed superheat amount SH is less than the set value SH1 (step D), the opening degree E* of the electric reversible expansion valve 24 outputs a signal -K.ΔE in the closing direction at step E.

What is special about this case is that the signal for opening the electric reversible expansion valve 24 is △E, while the signal for closing the electric reversible expansion valve 24 is -K・△E.
(K>1), which means that the closing width is large.

This is because the closing speed or closing amount is increased in order to avoid liquid compression as much as possible in order to protect the compressor 1.

FIG. 10 shows another embodiment of the electric reversible expansion valve 24. Whereas the one shown in FIG. 2 is an electromagnetic type, this uses a pulse motor, When control signal pulses from the control device 11 are input to the stator coil 20, the rotor 32 integrated with the valve pin 17 rotates in accordance with the number of pulses to adjust the opening degree of the valve port. 3
4 is a pressure equalizing hole, and the other parts are substantially the same as those shown in FIG.

As described above, according to the present invention, of the two openings provided in the refrigerant flow path in the expansion valve, the opening/closing means always opens the opening on the low pressure side and closes the opening on the high pressure side. Since a bypass path is provided to bypass the refrigerant from this opening, the low-pressure refrigerant after adiabatic expansion can bypass the refrigeration cycle accumulator, which corresponds to the compressor suction pressure of the refrigerant in the refrigeration cycle. It is now possible to create a refrigeration cycle that can accurately measure the saturation temperature, accurately calculate the amount of superheat based on the saturation temperature of the refrigerant and the intake temperature to the compressor, and ensure control using this amount of superheat. This has the effect of making it easier to perform.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional refrigeration cycle, Fig. 2 is a longitudinal sectional view of an electric reversible expansion valve according to an embodiment of the present invention, and Fig. 3 is an embodiment using the electric reversible expansion valve of Fig. 2. A refrigeration cycle configuration diagram showing an example, Fig. 4 is a circuit diagram of the control unit shown in Fig. 3, Fig. 5 is a Mollier diagram of the device shown in Fig. 3, and Fig. 6 is a model of the refrigerant flow pattern in the evaporator tube. Figure 7 is a characteristic diagram showing the temperature distribution on the evaporator tube wall, Figure 8 is a characteristic diagram showing the pressure loss distribution in the evaporator tube, Figure 9 is a flow chart showing an example of the program of the control device, and Figure 10 is FIG. 2 is a longitudinal cross-sectional view of an electric reversible expansion valve showing another embodiment of the present invention. The same symbols in the figures indicate the same or corresponding parts, 1
is a compressor, 2 is a four-way valve, 3 is an outdoor heat exchanger, 5
1 is an indoor heat exchanger, 6 is an accumulator, 7 is a suction temperature sensor, 11 is a control device, 13 is a body, 14 is a refrigerant inlet, 15 is a refrigerant outlet, 1
6 is a valve port, 16a is a valve port, 17 is a valve pin, 20 is an electromagnetic coil, 22 is a bypass path, 2
2a is a bypass refrigerant outlet, 23 is a valve ball, 24 is an electric reversible expansion valve, 26 is a saturation temperature sensor, 28
is a microcomputer, 29 is a photocoupler,
32 is a rotor.

Claims (1)

[Claims] 1. In an electric reversible expansion valve provided in a refrigeration cycle, a refrigerant flow path formed within the expansion valve body, a throttle valve section provided in this refrigerant flow path, and the above-mentioned refrigerant divided by this throttle valve section. A bypass path is formed from two openings that open in the middle of both flow paths to a refrigerant outlet that is connected via piping to the refrigerant suction side of the accumulator in the refrigeration cycle, and a An electric reversible expansion valve characterized by comprising an opening/closing means for opening a side opening and closing a high pressure side opening.