JP2002221377A - Pressure control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure control valve, in which cycle stability in particular at a low load is improved, miniaturization and weight reduction can be attained without problem, and the degree of freedom in the valve shape is improved. SOLUTION: The pressure control valve includes a compressor, a radiator, and an evaporator. The compressor can change the capacity of compression and discharge of the refrigerant, the radiator radiates the heat of the refrigerant discharged from the compressor, and the evaporator evaporates the refrigerant. The control valve is employed in the refrigeration cycle, in which the refrigerant is brought into a supercritical state, and is placed between the radiator and evaporator. In the control valve, the pressure of the refrigerant cooled by the radiator is reduced, and the refrigerant is supplied to the evaporator. The control valve is formed of a valve element 6, a throttling path 7, and a control means. The valve element 6 is displaced in accordance with the pressure and temperature of the refrigerant on the inlet side of the control valve. In the path 7, the opening area is changed in response to the position of the valve element 6. The control means controls the position of the valve element 6 so as to secure a specified opening area S, when the opening area of the path 7 has become smallest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control valve which is used in a vehicle air conditioner or the like and which constitutes a part of a refrigeration cycle for circulating a refrigerant such as carbon dioxide in a supercritical state.

[0002]

2. Description of the Related Art Conventionally, in a refrigeration cycle used for an air conditioner or the like, a refrigerant in a high pressure line (a line from a compressor to a pressure control valve) is made to have a pressure higher than a critical pressure by using carbon dioxide or the like as a refrigerant. It has been known. In addition, as a compressor for pumping the refrigerant, there is a variable displacement type compressor which can change the compression and discharge amount of the refrigerant, and among them, according to the pressure of a low pressure line (line from the pressure control valve to the compressor). In order to change the amount of refrigerant discharged to a high-pressure line, many types are used. As a control method of the variable displacement type compressor, in many cases, the discharge amount of the refrigerant is increased as the low pressure becomes higher, and the discharge amount is decreased as the low pressure becomes lower. Further, the pressure control valve has a function of reducing the pressure of the refrigerant cooled by the radiator and flowing the refrigerant to the evaporator side. As a control method, at the inlet side of the pressure control valve, the temperature of the refrigerant at each time is controlled. Some of the valves open and close so as to obtain an optimal pressure according to the pressure. Generally, the target high pressure is set to increase as the refrigerant temperature in the high pressure line increases.

In a refrigeration cycle having the above-described variable displacement compressor and pressure control valve, when the load is low, the pressure in the low pressure line decreases, so that the refrigerant discharge amount of the compressor decreases. As a result, the pressure in the high pressure line rises slowly, so the pressure control valve remains closed for a long time,
Once opened, it may close immediately. This phenomenon impairs cycle stability at low load.

In Japanese Patent Application Laid-Open No. 2000-74513, a bypass passage for bypassing a pressure control valve is provided,
There is disclosed a refrigeration cycle in which the flow of refrigerant from a high pressure line to a low pressure line is not interrupted.

[0005]

However, in the refrigeration cycle disclosed in Japanese Patent Application Laid-Open No. 2000-74513, since a pipe for a bypass passage must be provided separately from a normal pipe, the size is reduced. However, there is a problem in reducing the weight. Also, if the flow rate of the refrigerant in the bypass passage is too small, the effect of improving the stability of the cycle is diminished, while if the flow rate is too large, the supply amount of the refrigerant to the evaporator at a low load becomes too large. The frost phenomenon that the evaporator freezes may occur.

As shown in FIG. 9, many of the pressure control valves have a structure in which a valve element 40 is attached to and detached from a valve seat 42 formed on the peripheral edge of a throttle passage 41.
If the angle of inclination (clipping angle) θ formed at the fitting portion of 0 is too large, a phenomenon (biting) in which the valve body 40 fitted to the valve seat 42 may not come off may occur, and in particular, carbon dioxide, etc. In a supercritical cycle using, the bite is likely to occur because the pressure in the high pressure line increases. Therefore, it is necessary to reduce the included angle θ, and the valve body 40
And the degree of freedom in the shape of the valve seat 42 was small.

Accordingly, the present invention can improve the stability of a cycle, especially at a low load, and
It is an object of the present invention to provide a pressure control valve which is not disadvantageous in reducing the size and weight and has a high degree of freedom in the shape of the valve.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a compressor capable of changing a capacity of compressing and discharging a refrigerant, and a radiator for radiating the refrigerant discharged from the compressor. And used in a refrigeration cycle configured to include a evaporator for evaporating the refrigerant and in which the refrigerant can be in a supercritical state, and disposed between the radiator and the evaporator and cooled by the radiator. In a pressure control valve for reducing the pressure of the refrigerant and sending it to the evaporator side,
The pressure control valve includes a valve body that is displaced according to the pressure and temperature of the refrigerant on the inlet side of the pressure control valve, and a throttle passage whose opening area changes according to the position of the valve body, and the opening area of the throttle passage is the smallest. In such a case, a means for regulating the position of the valve element is provided so that a predetermined opening area is secured when it comes to the above (claim 1).

Thus, the flow of the refrigerant from the high-pressure line to the low-pressure line can be prevented from being interrupted without providing a separate bypass pipe or the like, which is disadvantageous in reducing the size and weight. Without this, the stability of the cycle, especially at a low load, can be favorably maintained.
In addition, since the valve body does not contact the valve seat (the end of the throttle passage), there is no need to worry about biting, so that the degree of freedom of the shape of the valve body and the valve seat is improved.

The predetermined opening area is 0.07 to 0.07.
It is good to be within the range of 0.20 mm ² (claim 2).

If the opening area is too small, the effect of improving the stability of the cycle is weakened. If the opening area is too large, the refrigerant flows excessively into the evaporator, so that the frost that the evaporator freezes at a low load. A phenomenon may occur. As a result of the experiment, the inventor has found that the best opening area for improving the cycle stability is 0.07 mm ² to 0.1 mm.
It was found to be 20 mm ² . For this reason, by setting the opening area within the above range, a pressure control valve having good performance can be provided.

[0012]

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

A pressure control valve 1 according to an embodiment of the present invention shown in FIG. 1 has a refrigeration cycle R as shown in FIG.
C, which constitutes a part of the refrigeration cycle RC.
Is a variable capacity compressor A capable of changing the compression and discharge capacity of the refrigerant in accordance with the operating conditions; a radiator B for releasing the refrigerant compressed by the compressor A by heat exchange with the outside air; An internal heat exchanger C for exchanging heat between the refrigerant in the line H and the refrigerant in the low-pressure line L; a pressure control valve 1 as an expansion device for decompressing the refrigerant in the high-pressure line H and sending it to the low-pressure line L; Evaporator D that evaporates by exchanging the refrigerant depressurized by the air with the air that is blown into the room, and an accumulator E that separates the refrigerant flowing out of the evaporator D into gas and liquid and flows only the gas phase to the compressor A. Is configured. In addition, this refrigeration cycle RC
Uses carbon dioxide as a refrigerant, and compresses carbon dioxide to a supercritical pressure by the compressor A.

The pressure control valve 1 opens and closes in accordance with the pressure and temperature of the refrigerant in the high-pressure line H, so that the pressure control valve 1 is optimized according to the temperature at that time, that is, so that the coefficient of performance is maximized. The pressure of H is adjusted. The pressure control valve 1 includes an upper shell 2, a lower shell 3, a bellows 4, a slide member 5, a valve element 6, a throttle path 7, a high-pressure communication path 8, a low-pressure communication path 9, and a valve element movement restricting section 10. ing. The upper shell 2 and the lower shell 3 are screwed to each other, and are hermetically connected by a sealing ring 12 disposed on a screwing portion 11. A space 15 is defined. A high-pressure communication passage 8 communicating with the high-pressure line H is connected to the upper shell 2 so as to communicate with the internal space 15, and a low-pressure communication passage 9 communicating with the low-pressure line L is connected to the lower shell 3. It is connected so that it may communicate with.

The internal space 15 includes a bellows 4, a slide member 5, a valve body 6, a throttle passage 7, and a valve body movement restricting section 10.
Is provided. The bellows 4 is formed in a bellows shape by a metal foil or the like and is made to be able to expand and contract, and a gas such as carbon dioxide as a refrigerant circulating through the refrigeration cycle RC is sealed in the hollow inside. The slide member 5 is slidable up and down along the inner wall of the upper shell 2. The valve element 6 is displaced up and down with the expansion and contraction of the bellows 4, and has a shape such that the lower end portion can be fitted into the throttle passage 7. The throttle passage 7 is formed so as to have a predetermined inner diameter by a protrusion 16 formed integrally with the lower shell 3 so as to protrude substantially toward the center of the internal space 15, and from the high-pressure line H to the low-pressure line L. It has a function of reducing the volume of the flowing refrigerant, and its opening area changes depending on the positional relationship with the valve body 6, and becomes smaller as the valve body 6 approaches the throttle passage 7.

The bellows 4 has an upper end fixed to a fixing member 17 fixed to the upper surface of the upper shell 2.
A slide member 5 is fixed to a lower end thereof, and an upper end of a valve body 6 is fixed to a lower surface side of the slide member 5. The bellows 4 expands and contracts according to the pressure and temperature of the refrigerant in the high-pressure line H flowing into the internal space 15, and moves the valve 6 up and down. That is, when the pressure of the refrigerant increases, a force for contracting the bellows 4 acts, and when the temperature of the refrigerant increases, a force for expanding the bellows 4 acts because the volume of the gas sealed in the bellows 4 expands. In this way, the bellows 4 expands and contracts, the valve element 6 is displaced up and down, and the opening area of the throttle passage 7 changes according to the balance between the pressure and the temperature of the refrigerant in the high-pressure line H.

Further, as shown in FIGS. 3 (a) and 3 (b), the slide member 5 in this embodiment has a substantially disk shape and has six through holes 20 penetrating from the upper surface to the lower surface. The edge 2 has a flange 2 protruding downward.
1 is formed.

As shown in FIG. 1, the valve body movement restricting portion 10 includes a flange 21 formed on the slide member 5.
And a base 22 formed integrally with the upper shell 2 at the lower end of the upper shell 2. When the lower end of the flange 21 abuts on the upper surface of the base 22, the slide member 5 is prevented from moving below a predetermined position. As a result, the valve element 6 does not completely block the throttle passage 7.

The movement restricting section 10 allows the valve 6 to be
The positional relationship with the throttle passage 7 is shown in FIGS.
Become like As described above, the flange 21 and the platform
The sliding member 5 is restricted from descending.
As a result, the valve element 6 completely closes the throttle passage 7.
The position P1 above the position P0 by the distance d to the lowermost position
When the valve body 6 comes to this lowermost position P1, FIG.
As shown in (b), an opening area S is secured in the throttle passage 7.
Thus, the throttle passage 7 is not completely closed. Soshi
In this embodiment, the opening area S is
0.07-0.20mm ^TwoSet to be within the range of
Have been.

Here, the relationship between the amount of refrigerant bypassing the pressure control valve and the stability of the refrigeration cycle under a predetermined low load condition will be verified with reference to the experimental data shown in FIGS. The refrigeration cycle in this experiment was provided with a bypass pipe for the refrigerant to bypass the pressure control valve. Each data shown in FIGS. 5 to 8 shows the inner diameters of four types of bypass pipes (with no bypass pipe). ), The relationship between the elapsed time during the start-up of the compressor and the temperature and pressure of the refrigerant in each part of the cycle.
30 is the temperature at the pressure control valve inlet, 31 is the temperature at the compressor inlet, 32 is the pressure at the pressure control valve inlet, 33 is the pressure at the evaporator outlet, 34 is the pressure at the compressor inlet, 35 is the evaporator Indicates the temperature at the vessel outlet.

First, the graph shown in FIG. 5 shows a refrigeration cycle in which the refrigerant is not supplied from the high pressure line to the low pressure line when no bypass pipe is provided, that is, when the pressure control valve is fully closed. In this case, the temperature and the pressure in each part are unstable for a while after the start of the compressor, and the temperature 30 at the pressure control valve inlet and the temperature 35 at the evaporator outlet fluctuate greatly. The temperature at the pressure control valve inlet 30
The fluctuation of the temperature 35 at the outlet of the evaporator indicates that it takes a long time for the pressure control valve, which has been closed, to open again, which indicates that the cycle is unstable.

Next, the graph shown in FIG. 6 is for the case where the inner diameter of the bypass pipe is 0.3 mm (cross-sectional area of about 0.07065 mm ² ). It can be seen that the fluctuation in the temperature at the time of the absence is small, but the fluctuation of the temperature 30 at the inlet of the pressure control valve and the temperature 35 at the outlet of the evaporator are still large.

Next, the graph shown in FIG. 7 is for the case where the inner diameter of the bypass pipe is 0.4 mm (the cross-sectional area is about 0.1256 mm ² ). Since the pressure and the pressure are stable and the temperature 35 at the outlet of the evaporator does not become 0 ° C. or less, it is understood that the cycle is stable and the possibility that frost of the evaporator occurs is negligible.

Next, the graph shown in FIG. 8 is for the case where the inner diameter of the bypass pipe is 0.5 mm (the cross-sectional area is about 0.19625 mm ² ). And the pressure is stable, but since the temperature 35 at the outlet of the evaporator is 0 ° C. or less, it is understood that the possibility of frost is high.

From the above, it is possible to obtain cycle stability.
The minimum diameter of the bypass pipe is 0.3 mm
About 0.07mm^Two) About required, and raw frost
In order to prevent interference, the inner diameter of the bypass
mm (cross-sectional area about 0.20mm ^Two)
As will be discussed, as described above,
Should be secured in the throttle passage 7 of the pressure control valve 1 according to the embodiment.
The opening area S is 0.07 to 0.20 mm^TwoRange
It is good to be inside.

[0026]

As described above, according to the present invention, the flow of the refrigerant from the high pressure line to the low pressure line can be prevented from being interrupted without providing a separate bypass pipe or the like. The cycle stability can be improved, especially at low load, without being disadvantageous in reducing the weight and weight. Further, since the valve body does not contact the valve seat (the end of the throttle passage), there is no need to worry about biting, so that the degree of freedom of the shape of the valve body and the valve seat can be improved. Further, good performance can be ensured by setting the opening area secured in the throttle passage in the range of 0.07 to 0.20 mm ² .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pressure control valve according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a refrigeration cycle in which the pressure control valve according to the embodiment is used.

FIG. 3A is a top perspective view showing a structure of a slide member of the pressure control valve, and FIG. 3B is a bottom perspective view showing a structure of a slide member of the pressure control valve.

FIG. 4A is an enlarged sectional view showing a lowermost position of a valve body of the pressure control valve according to the embodiment;
FIG. 4B is a cross-sectional view of AA ′ in FIG.

FIG. 5 is experimental data showing the relationship between the elapsed time from the start of the compressor and the temperature and pressure of the refrigerant in each part of the cycle when the compressor is not used, when the bypass pipe is not used.

FIG. 6 is experimental data showing the relationship between the elapsed time from the start of the compressor and the temperature and pressure of the refrigerant in each part of the cycle when a bypass pipe having an inner diameter of 0.3 mm is used. is there.

FIG. 7 is experimental data showing the relationship between the elapsed time from the start of the compressor and the temperature and pressure of the refrigerant at each part of the cycle when a bypass pipe having an inner diameter of 0.4 mm is used. is there.

FIG. 8 is experimental data showing the relationship between the elapsed time from the start of the compressor and the temperature and pressure of the refrigerant in each part of the cycle when a bypass pipe having an inner diameter of 0.5 mm is used. is there.

FIG. 9 is a view showing a structure of a valve body in a conventional pressure control valve.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure control valve 2 upper shell 3 lower shell 4 bellows 5 slide member 6 valve element 7 throttle path 8 high-pressure communication path 9 low-pressure communication path 10 valve element movement restricting section 16 protruding section 20 through hole 21 flange 22 base section A compressor B radiator C Internal heat exchanger D Evaporator E Accumulator RC Refrigeration cycle

Claims (2)

[Claims] 1. A compressor capable of changing a capacity of compressing and discharging a refrigerant, a radiator for dissipating heat of the refrigerant discharged from the compressor, and an evaporator for evaporating the refrigerant. In a pressure control valve that is used in a refrigeration cycle in which the refrigerant can be in a supercritical state, and that is disposed between the radiator and the evaporator and that depressurizes the refrigerant cooled by the radiator and sends it to the evaporator side, A valve body that is displaced in accordance with the pressure and temperature of the refrigerant on the inlet side of the pressure control valve, and a throttle passage whose opening area changes in accordance with the position of the valve body, wherein the opening area of the throttle passage is the smallest. A pressure control valve, comprising: means for restricting the position of the valve element so that a predetermined opening area is secured when the pressure is changed. 2. The method according to claim 1, wherein the predetermined opening area is 0.07 to 0.1.
^2. The pressure control valve according to claim 1, wherein the pressure is within a range of 20 mm ² .