JP2000337735A - Pressure reducer for air cooling cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the fuel consumption of a vehicle and the degree of freedom in the layout thereof while reducing the size and weight by providing a back pressure line communicating with a refrigerant inlet and a cylinder chamber on the axis of a power element and a back pressure control valve on a control pressure release pipe. SOLUTION: A pressure reducing hole 1 is made in a refrigerant passage between a refrigerant inlet 9 and a refrigerant outlet 10 and a cylinder chamber 2 communicating with the refrigerant passage and the refrigerant outlet 10 are interconnected through a control pressure release pipe 11. A piston 3 in the cylinder chamber 2 is coupled with a valve 4 for opening/closing the pressure reducing hole 1 through a stem 5 thus constituting a power element 6. A back pressure line 7 communicating with the refrigerant inlet 9 and the cylinder chamber 2 is provided on the axis of the power element 6 and a back pressure control valve 8 is provided on the control pressure release pipe 11. Carbon dioxide is employed as refrigerant and the opening of the pressure reducing hole 1 is controlled by means of the valve 4 based on the difference between the fluid pressure acting on one end face of the piston 3 and the refrigerant pressure acting on the other end face thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for obtaining an arbitrary pressure reduction of a refrigerant for use in a cooling cycle of an air conditioner for a vehicle, and more particularly to a pilot-type pressure reducing apparatus having a piston for a cooling cycle.

2. Description of the Related Art In a cooling cycle of an air conditioner for vehicles, H
Although chlorofluorocarbon refrigerants such as FC12 and HFC134a are used, if these are released into the atmosphere, there is a concern about environmental problems such as global warming due to destruction of the ozone layer. For this reason, a cooling cycle using carbon dioxide, ethylene, ethane, nitric oxide, or the like has been proposed as one of the measures against chlorofluorocarbon (see, for example, Japanese Patent Publication No. Hei 7-18602). The cooling cycle using carbon dioxide or the like as a refrigerant is in principle the same as a conventional cooling cycle using chlorofluorocarbon, but for example, the critical temperature of carbon dioxide is about 31 ° C.
And the critical temperature of conventional fluorocarbon (for example, R-12 is 112
℃), the temperature of carbon dioxide on the radiator (gas cooler) side becomes higher than the critical temperature of carbon dioxide in summer when the outside air temperature rises, and the carbon dioxide does not condense at the outlet of the radiator. Are different. The state of the outlet of the radiator is determined by the discharge pressure of the compressor and the temperature of the carbon dioxide at the outlet of the radiator, and the temperature and pressure of the carbon dioxide at the outlet of the radiator are determined by the radiator's heat radiation capacity and the outside air temperature. And is determined by However, since the outside air temperature cannot be controlled, the temperature and pressure of carbon dioxide at the outlet of the radiator cannot be substantially controlled. However, since the state at the outlet of the radiator can be controlled by controlling the discharge pressure of the compressor (the refrigerant pressure at the outlet of the radiator), sufficient cooling capacity (enthalpy difference) can be obtained in summer when the outside air temperature is high. In order to secure (1), the refrigerant pressure at the outlet of the radiator is increased.
Among such pressure reducing devices that control the refrigerant pressure at the outlet of the radiator, a pilot type pressure reducing device having a piston structure has been proposed. (See, for example, JP-A-9-264449). According to this type of pilot pressure reducing device, an electric signal (ON / OFF) corresponding to a target outlet pressure of the radiator is provided.
By transmitting the duty ratio signal), the opening degree of the pressure reducing valve is controlled via the piston, so that fine control according to the heat load can be performed. In the cooling cycle using a CFC refrigerant, a so-called temperature-sensitive expansion valve that controls the opening of the pressure reducing valve by sensing the outlet temperature of the evaporator is used. In the cooling cycle using the refrigerant, the refrigerant pressure in the cycle is 3.5 to 15MP.
a, which is significantly higher than that of the conventional Freon system (0.2 to 3.0 MPa), there is a problem with the pressure resistance of the diaphragm constituting the conventional temperature-sensitive expansion valve. For these reasons, pilot-type pressure reducing devices are mainly used in cooling cycles using carbon dioxide or the like as a refrigerant.

However, in such a conventional technique, a long piston back pressure tube is required as shown in FIG. 7, so that the decompression device becomes large and the weight increases. there were. Also, in a pilot pressure reducing device using a refrigerant such as carbon dioxide,
Since a very large pressure is applied to the joint of the piston back pressure tube, there is a problem that it is difficult to guarantee the refrigerant leakage. The present invention has been made in view of the above-described problems, and in a pilot-type pressure reducing device, while reducing the size and weight of the pressure reducing device and reducing the number of joints such as pipes in order to minimize refrigerant leakage. The purpose is to do.

According to the present invention, a pressure reducing hole formed in a refrigerant flow path between a refrigerant inlet and a refrigerant outlet, a cylinder chamber communicating with the refrigerant flow path, A control pressure release pipe communicating the cylinder chamber with the refrigerant outlet, a piston provided in the cylinder chamber, a valve connected to the piston to open and close the pressure reducing hole, the piston and the valve, A power element composed of a connecting stem and carbon dioxide as a refrigerant, wherein the valve element is driven by a differential pressure between a fluid pressure acting on one end face of the piston and a refrigerant pressure acting on the other end face of the piston. In the pressure reducing device for controlling the degree of opening of the pressure reducing hole, a back pressure line communicating between the refrigerant inlet and the cylinder chamber is provided in the axis of the power element, and a back pressure control valve is provided in the control pressure release pipe. Characterized in that was. According to the second aspect of the present invention, in the pressure reducing apparatus for a cooling cycle according to the first aspect, the dynamic pressure acting on the valve body is eliminated while ensuring the circulation of the refrigerant to the back pressure line at the refrigerant inlet. A protective wall is provided.

According to the first aspect of the present invention, since the back pressure line is provided in the power element, it is not necessary to provide a piston back pressure pipe outside the high pressure control valve as in the prior art. As a result, the configuration can be reduced in size and the weight can be reduced, so that the fuel efficiency of the vehicle can be improved and the layout flexibility can be improved. In addition, it is possible to reduce the number of joints in the pipe, thereby preventing refrigerant leakage. According to the second aspect of the present invention, in the pressure reducing apparatus for a cooling cycle according to the first aspect, by providing a protection wall below the valve body, unstable operation of the power element due to dynamic pressure of the refrigerant is eliminated. It is possible to perform stable valve operation.

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 2 is an overall circuit diagram showing an example of a cooling cycle to which the pressure reducing device of the present invention is applied. First,
Explaining from the configuration of the cooling cycle shown in FIG. 2, in the cooling cycle according to the first embodiment, the compressor 1, the radiator 2, the pressure reducing device 3, the evaporator 4, and the accumulator 5 are connected by the refrigerant pipe 8 in this order. Connected to form a closed circuit. The compressor 1 obtains a driving force from an engine or the like (not shown) to compress the gaseous carbon dioxide refrigerant,
Discharge toward. The radiator 2 cools the carbon dioxide refrigerant compressed by the compressor 1 by exchanging heat with the outside air or the like. In order to promote the heat exchange or to allow the heat exchange even when the vehicle is stopped, the radiator 2 is cooled. Fan 6 is loaded. The radiator 2 is disposed, for example, on the front of a vehicle in order to maximize the difference between the temperature of the carbon dioxide refrigerant in the radiator 2 and the outside air temperature. The pressure reducing device 3 reduces the pressure of the high-pressure (about 10 MPa) carbon dioxide refrigerant flowing out of the radiator 2 by passing it through the pressure reducing holes 13, which will be described later. In addition, the pressure reducing device 3 reduces the pressure of the carbon dioxide refrigerant and
The carbon dioxide refrigerant decompressed by the decompression device 3 flows into the evaporator (heat absorber) 4 in a gas-liquid two-phase state. Evaporator 4
Is for cooling the air blown into the passenger compartment, for example, built in the casing of the air conditioning unit mounted on the vehicle,
When the outside air or the inside air taken in by the fan 7 passes through the evaporator 4, the taken air is cooled, and is blown out to a desired position in the vehicle room through an outlet (not shown). That is, the carbon dioxide refrigerant in the gas-liquid two-phase state flowing down from the decompression device 3 is cooled by removing latent heat of evaporation from the intake air when evaporating (vaporizing) in the evaporator 4. The accumulator 5 separates the carbon dioxide refrigerant having passed through the evaporator 4 into a gas phase refrigerant and a liquid phase refrigerant, sends only the gas phase refrigerant to the compressor 1, and temporarily converts the liquid phase refrigerant. It is something to store. next,
The pressure reducing device 3 will be described in detail with reference to FIG. The pressure reducing device 3 according to the first embodiment includes housings 301 and 302 and an end socket 303, and the end socket 3
A refrigerant inlet 15 through which the high-pressure refrigerant from the radiator 2 flows is formed in 03, and a refrigerant outlet 22 through which the depressurized refrigerant flows out toward the evaporator 4 is formed in the housing 302. A ring seal 25 for preventing refrigerant leakage is provided at a contact portion between the housing 301 and the end socket 303. The refrigerant inlet 15 and the refrigerant outlet 2
Between them, a pressure reducing hole 13 and a power element 23 are provided. This power element 23 is a piston 1
2, a stem 14 and a valve body 19, which operate integrally with the movement of the piston 12. Above the piston 12, a coil spring 23 is provided,
The valve body 19 is spring-biased in the opening direction of the pressure reducing hole 13.
A back pressure line 2 is provided at the axis of the power element 23.
The back pressure line 20 communicates the refrigerant inlet 15 with the cylinder chamber 11 provided in the housing 302. Thereby, the back pressure is applied to the piston 12 by sending the high-pressure refrigerant to the space above the piston of the cylinder chamber 11 from the refrigerant inlet 15, and the valve is opened by overcoming the high pressure applied to the valve 19 and pushing down the valve 19. It is configured to assist the operation. The cylinder chamber 11 is provided with a control pressure release pipe 16 that communicates the refrigerant outlet 22 with the cylinder chamber 11, and a back pressure control valve 17 is provided on the control pressure release pipe 16.
Is provided. Cylinder chamber 1 by back pressure line 20
The back pressure applied to the piston 12 is adjusted by leaking to the refrigerant outlet 22 while adjusting the pressure of the high-pressure refrigerant sent to the space above the first piston by the back pressure control valve 17, and the opening degree of the valve is adjusted. I have. The housing 301 is provided with a protective wall 21 for eliminating the influence of the fluid pressure of the high-pressure refrigerant. The protective wall 21 is provided with a hole through which the refrigerant flows, and is configured to supply the refrigerant pressure to the cylinder chamber 11 without the refrigerant fluid directly hitting the valve body 19. A coil spring 18 is provided between the protection wall 21 and the valve element 19, and the valve element 19 is
Is biased in the closing direction. Next, the operation of the cooling cycle in the first embodiment will be described with reference to the Mollier diagram of FIG. First, the gas-phase carbon dioxide refrigerant is compressed by the compressor 1 (A-B), and the high-temperature and high-pressure gas-phase carbon dioxide refrigerant is cooled by the radiator 2 (B-B).
C). After the pressure is reduced by the pressure reducing device 3 (C-
D) The carbon dioxide refrigerant in the gas-liquid two-phase state is
(DA) to take in the latent heat of evaporation from the air and cool it. Thereby, the intake air introduced into the unit of the air conditioner is cooled, and is blown out into the passenger compartment, thereby cooling the passenger compartment. The carbon dioxide refrigerant that has passed through the evaporator 4 is gas-liquid separated by the accumulator 5, and only the refrigerant in a gaseous state is sucked into the compressor 1 again. In the pressure reduction process of CD in the Mollier diagram, the following control is executed according to the heat load on the evaporator 4. That is, when the heat load is high (when a large amount of cooling is required), such as in summer, it is necessary to supply a large amount of refrigerant from the pressure reducing device 3 to the evaporator 4. Is reduced, the duty ratio of the back pressure control valve 17 is reduced (the open time ratio is reduced). As a result, the high-pressure refrigerant is introduced into the space on the top surface side of the piston 12 through the back pressure line 20 and the differential pressure increases.
Is pressed downward, as a result, the valve body 19 also moves downward via the stem 14, and the pressure reducing hole 13 is opened. On the other hand, when the heat load is not so large, the back pressure control valve 1
By increasing the duty ratio of 7 and increasing the pressure of the refrigerant outlet 22, the piston 12 moves upward, and accordingly, the valve element 19 also moves upward, and the opening degree of the pressure reducing hole 13 decreases. . When the piston 12 moves upward from the lower position, the refrigerant introduced into the space above the piston 12 is released to the refrigerant outlet 22 via the control pressure release pipe 16, so that the operation of the piston 12 can be performed smoothly. Done. In addition, as shown in FIG. 5, a conventional refrigerant inlet (point A),
The piston 12 was moved up and down by adjusting the pressure difference gradient with the space above the piston (point C).
In the present invention, by providing the back pressure control valve 17 on the control pressure release pipe 16, the space above the piston 12 (point C)
The piston 12 is moved up and down by valve-adjusting a pressure difference gradient between a space below the piston 12 (point E) connected to the refrigerant outlet and the refrigerant outlet. At this time, when the valve element 19 opens the pressure reducing hole 13, high-pressure refrigerant flows from the radiator 2 into the refrigerant inlet 15 of the pressure reducing device, and the dynamic pressure accompanying the flow velocity of the refrigerant collides with the valve element 19, Since the movement of the piston may be unstable, in the first embodiment, an unstable element due to the dynamic pressure of the refrigerant is eliminated by installing the protection wall 21. As described above, the first embodiment employs a structure in which the piston back pressure pipe does not need to be provided outside the control valve as in the related art, so that the pressure reducing device can be downsized. An air-conditioning system using carbon dioxide refrigerant can be directly installed in the system mounting space. (Embodiment 2) In Embodiment 1, the protective wall 2
Although a pipe for sending the refrigerant to the back pressure line 20 was provided at the center of 1, the configuration is not limited to this.
As shown in FIG. 4 (a), a ball valve 28 is used as a valve body, and a protective wall 27 (see FIG. 4 (b)) having a disk corresponding to the projected area of the ball valve 28 at the center is provided. This may be configured to collide with the ball portion and disperse the force due to the dynamic pressure of the refrigerant pushed up from below. Thereby, stable valve operation can be performed with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing a pressure reducing device for a cooling cycle according to the present invention.

FIG. 2 is an overall circuit diagram illustrating an example of a refrigeration cycle to which the pressure reducing devices of Embodiments 1 and 2 are applied.

FIG. 3 is an end view showing the cooling cycle decompression device of the first embodiment.

FIG. 4 is an end view showing a pressure reducing device for a cooling cycle according to a second embodiment.

FIG. 5 is a diagram showing pressures at various parts of the pilot pressure reducing device.

FIG. 6 is a Mollier diagram for explaining a cooling cycle using carbon dioxide as a refrigerant.

FIG. 7 is an end view showing a conventional pilot pressure reducing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Decompression device 4 Evaporator 5 Accumulator 6 Cooling fan 7 Fan 8 Refrigerant piping 11 Cylinder chamber 12 Piston 13 Decompression hole 14 Stem 15 Refrigerant inlet 16 Control pressure release pipe 17 Back pressure control valve 18 Coil spring 19 Valve Body 20 Back pressure line 21 Protective wall 22 Refrigerant outlet 23 Powertrain 23a Powertrain 24 Coil spring 25 Ring seal 26 Oil seal 27 Protective wall 28 Ball valve

Claims (2)

[Claims] 1. A pressure reducing hole (1) formed in a refrigerant channel between a refrigerant inlet (9) and a refrigerant outlet (10); a cylinder chamber (2) communicating with the refrigerant channel; A control pressure release pipe (11) communicating between the chamber (2) and the refrigerant outlet (10); and a piston (3) provided in the cylinder chamber (2).
A valve element (4) connected to the piston (3) for opening and closing the pressure reducing hole (1); and a stem (5) connecting the piston (3), the valve element (4), and these elements. And a power element (6), which uses carbon dioxide as a refrigerant, and has a differential pressure between a fluid pressure acting on one end of the piston (3) and a refrigerant pressure acting on the other end of the piston (3). In a pressure reducing device for a cooling cycle, which controls an opening degree of a pressure reducing hole (1) by a valve body (4), between a refrigerant inlet (9) and a cylinder chamber (2) at an axis of the power element (6). And a back pressure control valve (8) provided in the control pressure release pipe (11). 2. The pressure reducing device for a cooling cycle according to claim 1, wherein the refrigerant acts on the valve element (4) while ensuring the flow of the refrigerant to the back pressure line (7) at the refrigerant inlet (9). A pressure reducing device for a cooling cycle, comprising a protective wall for eliminating dynamic pressure.