Displacement control valve of a variable displacement swash plate

Description

BACKGROUND OF THE INVENTION

The present invention relates to a displacement control valve of a variable displacement swash plate compressor.

Japanese Patent Laid-Open Publication No. 9-268973 discloses a displacement control valve of a variable displacement swash plate compressor comprising a valve body provided with a valve shaft, a driver for applying driving force to the valve body, a tube-shaped valve chest accommodating the valve body to be capable of reciprocal movement and provided with a valve shaft inserting hole through which the valve shaft of the valve body is passed slidably at one end wall, an inlet hole at a circumferential wall and a valve hole which is opened and closed by the valve body at the other end wall, wherein the inlet hole communicates with an outlet chamber of the compressor and the valve hole communicates with a crank chamber of the compressor.

In the aforementioned displacement control valve, the valve body opens and closes the valve hole to control the introduction of the refrigerant gas in the outlet chamber into the crank chamber, thereby controlling the internal pressure in the crank chamber and the displacement of the compressor. As a result, refrigerant gas pressure in the inlet chamber is controlled at a desired level.

The aforementioned displacement control valve has a problem in that small particles of foreign matter or abraded matter in the compressor, or small particles of foreign matter in an external refrigeration circuit flow through the inlet hole into the valve chest entrained by the refrigerant gas to invade into a space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body, thereby preventing smooth movement of the valve shaft and the operation of the displacement control valve.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a displacement control valve of a variable displacement swash plate compressor comprising a valve body provided with a valve shaft, a driver for applying driving force to the valve body, a tube-shaped valve chest accommodating the valve body to be capable of reciprocal movement and provided with a valve shaft inserting hole through which the valve shaft of the valve body is passed slidably at one end wall, an inlet hole at a circumferential wall and a valve hole which is opened and closed by the valve body at the other end wall, wherein the inlet hole communicates with an outlet chamber of the compressor and the valve hole communicates with a crank chamber of the compressor, and wherein invasion of small particles of foreign matter into a space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is prevented.

In accordance with the present invention, there is provided a displacement control valve of a variable displacement swash plate compressor comprising a valve body provided with a valve shaft, a driver for applying driving force to the valve body, a tube-shaped valve chest accommodating the valve body to be capable of reciprocal movement and provided with a valve shaft inserting hole through which the valve shaft of the valve body is passed slidably at one end wall, an inlet hole at a circumferential wall and a valve hole which is opened and closed by the valve body at the other end wall, wherein the inlet hole communicates with an outlet chamber of the compressor and the valve hole communicates with a crank chamber of the compressor, and wherein the inlet hole is directed at right angle to and located radially offset from the central axis of the valve chest.

In the displacement control valve of the present invention, refrigerant gas passed into the valve chest through the inlet hole whirls in the valve chest to apply centrifugal force to small particles of foreign matter dispersed in the refrigerant gas, thereby making them move toward the circumferential wall of the valve chest because the inlet hole is directed at right angle to and located radially offset from the central axis of the valve chest. As a result, the small particles of foreign matter dispersed in the refrigerant gas are kept away from the vicinity of the valve shaft inserting hole located at the center of the one end wall of the valve chest. Therefore, invasion of small particles of foreign matter into a space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is prevented.

In a preferred embodiment of the present invention, the valve chest is provided with a plurality of inlet holes circumferentially distanced from each other.

When the valve chest is provided with a plurality of inlet holes circumferentially distanced from each other, generation of the whirl movement of the refrigerant gas in the valve chest is promoted and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is promoted.

In another preferred embodiment of the present invention, the inlet hole is directed tangentially to the circumferential wall of the valve chest.

When the inlet hole is directed tangentially to the circumferential wall of the valve chest, generation of the whirl movement of the refrigerant gas in the valve chest is promoted and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is promoted.

In another preferred embodiment of the present invention, the valve chest has a cylindrical shape.

When the valve chest has a cylindrical shape, generation of the whirl movement of the refrigerant gas in the valve chest is promoted and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is promoted.

In another preferred embodiment of the present invention, the valve chest has a truncated-cone-shape convex toward the other end wall.

When the valve chest has a truncated-cone-shape convex toward the other end wall, the flow of the refrigerant gas from the inlet hole to the valve hole at the time when the valve hole is opened becomes smooth. Therefore, the small particles of foreign matter are discharged from the valve chest more easily.

In another preferred embodiment of the present invention, a tube member surrounding the valve shaft inserting hole extends from the one end wall of the valve chest toward the other end wall of the valve chest beyond the inlet hole.

When a tube member surrounding the valve shaft inserting hole extends from the one end wall of the valve chest toward the other end wall of the valve chest beyond the inlet hole, the refrigerant gas entering in the valve chest through the inlet hole flows in an annular space between the circumferential wall of the valve chest and the tube member. Therefore, generation of the whirl movement of the refrigerant gas is promoted, the whirl flow of the refrigerant gas is prevented from directly contacting the valve shaft inserting hole, and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole and the valve shaft of the valve body is promoted.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional view of a variable displacement swash plate compressor provided with a displacement control valve in accordance with a preferred embodiment of the present invention.

FIG. 2 is a sectional view of a displacement control valve in accordance with a preferred embodiment of the present invention.

FIG. 3 is a view in the direction of arrows III-III in FIG. 2.

FIG. 4 is a fragmentary sectional view of a displacement control valve in accordance with another preferred embodiment of the present invention.

FIG. 5 is a fragmentary sectional view of a displacement control valve in accordance with another preferred embodiment of the present invention.

FIG. 6 is a view in the direction of arrows VI-VI in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A displacement control valve of a variable displacement swash plate compressor in accordance with a preferred embodiment of the present invention will be described.

As shown in FIG. 1, a variable displacement swash plate compressor A is provided with a rotating shaft 10, a rotor 11 fixed to the rotating shaft 10, a swash plate 12 fitted on the rotating shaft 10 to engage the rotating shaft 10 sidably and to be variable in inclination relative to the rotating shaft 10. The swash plate 12 is connected to the rotor 11 through a linkage 13 to be variable in inclination relative to the driving shaft 10, thereby rotating synchronously with the rotating shaft 10.

A plurality of pistons 15 engage the swash plate 12 through a plurality of pairs of shoes 14 that slidably engage the outer peripheral portion of the swash plate 12. The pistons 15 are inserted into cylinder bores 16a formed in a cylinder block 16.

The plurality of pairs of shoes 14, the pistons 15 and the cylinder bores 16a are distanced from each other in the circumferential direction.

A dish-shaped front housing 18 cooperates with the cylinder block 16 to form a crank chamber 17 for accommodating the rotating shaft 10, the rotor 11 and the swash plate 12.

One end portion of the rotating shaft 10 passes through the front housing 18 to extend out of the front housing 18. A seal member 19 is disposed in the annular space between the front housing 18 and the rotating shaft 10.

A pulley 20 fixed to the one end portion of the rotating shaft 10 is connected to a car engine not shown in the drawings through an endless belt not shown in the drawings.

A cylinder head 23 is installed to form an inlet chamber 21 and an outlet chamber 22. The inlet chamber 21 communicates with the radiator of a car air conditioner through an inlet port not shown in the drawings. The outlet chamber 22 communicates with the condenser of the car air conditioner through an outlet port not shown in the drawings.

A valve plate 24 is disposed between the cylinder block 16 and the cylinder head 23. The valve plate is provided with inlet holes and outlet holes communicating with the cylinder bores 16a. Inlet valves and outlet valves are fitted to the valve plate 24.

The crank chamber 17 communicates with the inlet chamber 21 through an orifice hole 24a formed in the valve plate 24.

The front housing 18, the cylinder block 16, the valve plate 24 and the cylinder head 23 are assembled as a unitary body by a plurality of through bolts 25 circumferentially distanced from each other.

A displacement control valve B for controlling the displacement of the variable displacement swash plate compressor A is fitted in and fixed to a concave 26 formed in the cylinder head 23 adjacent to the outlet chamber 22 and communicating with the inlet chamber 21.

As shown in FIG. 2, the displacement control valve B comprises a pressure sensitive chamber 201 and a bellows 202 disposed in the pressure sensitive chamber 201. The pressure sensitive chamber 201 communicates with the inlet chamber 21 through a communicating hole 201a formed in the circumferential wall. The bellows 202 is provided with a vacuum inner space and a spring disposed in the inner space. The bellows 202 operates as a pressure sensitive member for receiving internal pressure of the inlet chamber 21 (hereinafter called inlet pressure). A pressure sensitive rod 204 is slidably supported by a valve casing 203 and abuts the bellows 202 at one end. A valve body 206 is formed integrally with the pressure sensitive rod 204. The valve body 206 opens and closes a valve hole 203a depending on the telescopic motion of the bellows 202 to open and close a communication passage between the outlet chamber 22 and the crank chamber 17 extending from the outlet chamber 22 through a communication passage 27, inlet holes 203b, a tube-shaped valve chest 205, the valve hole 203a, outlet holes 203c and a communication passage 28 to the crank chamber 17. The valve body 206 is provided with a valve shaft 206a sidably supported by a fixed iron core 207. A solenoid rod 209 abuts one end of the valve shaft 206a at one end. The solenoid rod 209 is passed through a through hole 207a formed in the fixed iron core 207 without contacting the circumferential wall of the through hole 207a at the longitudinal middle and fixed to a plunger 208 at the other end. The plunger 208 is forced in the closing direction of the valve body 206 by a spring 210. The plunger 208 is slidably supported at the outer circumference by a tube 212 made of non-magnetic material and fixed to a solenoid housing 211. An electromagnetic coil 213 fixed to the solenoid housing 211 surrounds the tube 212.

As shown in FIGS. 2 and 3(a), the valve chest 205 is made cylindrical. The valve chest 205 is provided with a valve shaft inserting hole 207b through which the valve shaft 206a is passed slidably at the center of one end wall formed by the fixed iron core 207. The valve chest 205 is provided with the inlet holes 203b at a circumferential wall and the valve hole 203a at the other end wall. The inlet holes 203b communicate with the outlet chamber 22 through the communication passage 27. The valve hole 203a communicates with the crank chamber 17 through the outlet holes 203c and the communication passage 28. The valve shaft inserting hole 207b and the valve hole 203a extend coaxially with the central axis X of the valve chest 205. The valve body 206 moves reciprocally in the valve chest 205 along the central axis X to open and close the valve hole 203a.

As shown in FIGS. 2 and 3(a), the inlet holes 203b are directed at right angle to and located radially offset from the central axis X of the valve chest 205.

The bellows 202 is supported by a bellows guide 214 at the lower end. The bellows guide 214 is sidably supported by a pressure setting member 215 forming the bottom wall of the pressure sensitive chamber 201. A spring 216 is disposed between the pressure setting member 215 and the bellows guide 214 to force the bellows 202 in the opening direction of the valve body 206. The control characteristics of the displacement control valve B is adjusted by adjusting the depth to which the pressure setting member 215 is press fitted into the circumferential wall of the pressure sensitive chamber 201.

The pressure sensitive chamber 201 communicates with the through hole 207a of the fixed iron core 207 through a pressure introducing passage 203d. Therefore, the one end of the valve shaft 206a opposing the through hole 207a of the fixed iron core 207, the fixed iron core 207, the plunger 208 and the spring 210 receive the inlet pressure.

The sectional area of the valve shaft 206a is made slightly larger than that of the valve hole 203a to prevent the internal pressure of the outlet chamber 22 (hereinafter called outlet pressure) from forcing the valve body 206 in the closing direction thereof.

Refrigerant gas leaks from the valve chest 205 to the through hole 207a of the fixed iron core 207 through an annular space between the valve shaft 206a and the circumferential wall of the valve shaft inserting hole 207b. However, the leakage of the refrigerant gas does not affect the internal pressure of the through hole 207a of the fixed iron core 207 because the flow rate of the leaking refrigerant gas is very low and the refrigerant gas leaked from the valve chest 205 into the through hole 207a is discharged to the inlet chamber 21 through the pressure introducing passage 203d and the pressure sensitive chamber 201.

The electromagnetic force generated by the electromagnetic coil 213 acts upon the one end of the valve shaft 206a through the plunger 208 and the solenoid rod 209 to force the valve body 206 in the closing direction thereof.

The operation of the displacement control valve B will be described.

In the displacement control valve B, the bellows 202 expands when the inlet pressure is lower than a predetermined level to push the valve body 206 in the opening direction thereof against the electromagnetic force generated by the electromagnetic coil 213, thereby opening the valve hole 203a. The outlet pressure is introduced to the crank chamber 17 to increase the internal pressure of the crank chamber 17 (hereinafter called crank chamber pressure), thereby decreasing the inclination of the swash plate 12 and decreasing the displacement of the compressor A. As a result, the flow rate of the refrigerant gas circulating through the external refrigeration circuit decreases to increase the inlet pressure. When the inlet pressure exceeds the predetermined level, the bellows 202 contracts. The electromagnetic force generated by the electromagnetic coil 213 pushes the valve body 206 in the closing direction thereof to close the valve hole 203a. As a result, introduction of the refrigerant gas to the crank chamber 17 is stopped. The crank chamber pressure decreases as the refrigerant gas in the crank chamber 17 discharges to the inlet chamber 21 through the orifice hole 24a to increase the inclination of the swash plate 12, thereby increasing the displacement of the compressor A. As a result, the flow rate of the refrigerant gas circulating through the external refrigeration circuit increases to decrease the inlet pressure. The opening and closing of the valve hole 203a is repeated to maintain the inlet pressure at the predetermined level, thereby maintaining comfortable car air conditioning.

The amount of electric current supply to the electromagnetic coil 213 uniquely determines the operation point of the internal displacement control valve constituted by the bellows 202, the pressure sensitive rod 204 and the valve body 206.

In the displacement control valve B, refrigerant gas passed into the valve chest 205 through the inlet holes 203b whirls in the valve chest 205 as indicated by arrows in FIG. 3(a) because the inlet holes 203b are directed at right angle to and located radially offset from the central axis X of the valve chest 205. Small particles of foreign matter or abraded matter in the compressor, or small particles of foreign matter in the external refrigeration circuit, which are dispersed in the refrigerant gas, receive centrifugal force to move toward the circumferential wall of the valve chest 205. As a result, the small particles of foreign matter dispersed in the refrigerant gas are kept away from the vicinity of the valve shaft inserting hole 207b located at the center of the one end wall of the valve chest 205. Therefore, invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole 207b and the valve shaft 206a of the valve body 206 is prevented.

The valve chest 205 is cylindrically shaped. Therefore, generation of the whirl movement of the refrigerant gas in the valve chest 205 is promoted and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole 207b and the valve shaft 206a of the valve body 206 is promoted.

It is possible to direct the inlet holes 203b tangentially to the circumferential wall of the valve chest 205 as shown in FIG. 3(b). When the inlet holes 203b are directed tangentially to the circumferential wall of the valve chest 205, generation of the whirl movement of the refrigerant gas in the valve chest 205 is promoted and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole 207b and the valve shaft 206a of the valve body 206 is promoted.

It is possible to dispose a single inlet hole 203b as shown in FIG. 3(c) or more than three inlet holes 203b instead of disposing a pair of inlet holes 203b as shown in FIG. 3(a).

When the valve chest 205 is provided with a plurality of inlet holes 203b circumferentially distanced from each other, generation of the whirl movement of the refrigerant gas in the valve chest 205 is promoted and the prevention of the invasion of small particles of foreign matter into a space between the circumferential wall of the valve shaft inserting hole 207b and the valve shaft 206a of the valve body 206 is promoted.

It is possible to make the valve chest 205 truncated-cone-shaped convex toward the other end wall provided with the valve hole 203a as shown in FIG. 4. When the valve chest 205 is given a truncated-cone-shape convex toward the other end wall provided with the valve hole 203a, the flow of the refrigerant gas from the inlet holes 203b to the valve hole 203a at the time when the valve hole 203a is opened becomes smooth. Therefore, the small particles of foreign matter are discharged from the valve chest 205 more easily.

It is possible to extend a tube member 207c surrounding the valve shaft inserting hole 207b from the fixed iron core 207 forming the one end wall of the valve chest 205 toward the other end wall of the valve chest 205 provided with the valve hole 203a beyond the inlet holes 203b as shown in FIGS. 5 and 6.

When the tube member 207c surrounding the valve shaft inserting hole 207b extends from the fixed iron core 207 forming the one end wall of the valve chest 205 toward the other end wall of the valve chest 205 provided with the valve hole 203a beyond the inlet holes 203b, the refrigerant gas entering in the valve chest 205 through the inlet holes 203b flows in the annular space between the circumferential wall of the valve chest 205 and the tube member 207c. Therefore, generation of the whirl movement of the refrigerant gas is promoted, the whirl flow of the refrigerant gas is prevented from directly contacting the valve shaft inserting hole 207b, and the prevention of the invasion of small particles of foreign matter into the space between the circumferential wall of the valve shaft inserting hole 207b and the valve shaft 206a of the valve body 206 is promoted.

The present invention can be widely used for displacement control valves of variable displacement swash plate compressors.

While the present invention has been described with reference to preferred embodiments, one of ordinary skill in the art will recognize that modifications and improvements may be made while remaining within the spirit and scope of the present invention. The scope of the invention is determined solely by the attached claims.