Control valve for variable displacement compressor

Abstract

In a control valve for a variable displacement compressor, for controlling the discharge flow rate of refrigerant to be constant, to dispense with a check valve in a refrigerant outlet port of the compressor. The control valve includes a first control valve that controls the passage cross-sectional area of a refrigerant passage through which refrigerant passes from a discharge chamber of the compressor to a refrigerant outlet port thereof, and a second control valve that controls the flow rate of refrigerant allowed to flow from the discharge chamber to a crankcase such that a differential pressure (Pdh−Pdl) across the first control valve generated by the refrigerant passing therethrough becomes constant. The control valve is configured such that when a solenoid section is not energized, a first valve element is engaged with a piston to forcibly fully open the second control valve. The piston has an outer diameter equal to the inner diameter of a second valve seat, so that the discharge pressure Pdl on a refrigerant outlet port side is inhibited from adversely affecting the fully-opening operation of the second control valve, to thereby maintain the fully-closed state of the first control valve. This makes it possible to dispense with a check valve conventionally provided in the refrigerant outlet port.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central longitudinal cross-sectional view of the whole construction of a control valve for a variable displacement compressor, according to a first embodiment.

FIG. 2 is a partial enlarged cross-sectional view of the construction of a valve section of the control valve according to the first embodiment.

FIG. 3 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a second embodiment.

FIG. 4 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a third embodiment.

FIG. 5 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a fourth embodiment.

FIG. 6 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a fifth embodiment.

FIG. 7 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a sixth embodiment.

FIG. 8 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to a seventh embodiment.

FIG. 9 is a central longitudinal cross-sectional view of the construction of a control valve for a variable displacement compressor, according to an eighth embodiment.

FIGS. 10A to 10C are views for explaining characteristics of a diaphragm, in which FIG. 10A shows a state in which no differential pressure is applied to the diaphragm, FIG. 10B shows a state in which the diaphragm is displaced by a differential pressure, and FIG. 10C shows a state in which the differential pressure is applied to the displaced diaphragm in a direction opposite to the direction of the displacement.

FIGS. 11A to 11C are explanatory views showing the construction of a differential pressure-sensing section of the control valve according to the eighth embodiment, in which FIG. 11A shows a case where pressure in a discharge chamber of the compressor is higher than pressure in a refrigerant outlet port of the compressor, and FIG. 11B shows a case where the pressure in the discharge chamber is lower than the pressure in the refrigerant outlet port.

Claims

1. A control valve for a variable displacement compressor, including a first control valve that controls a flow rate of refrigerant which said first control valve allows to flow from a discharge chamber of the compressor to a refrigerant outlet port of the compressor, a second control valve that controls a flow rate of refrigerant which said second control valve allows to flow from the discharge chamber into a crankcase of the compressor based on a differential pressure across said first control valve, to change a displacement of the compressor, to thereby control the flow rate of the refrigerant allowed to flow by said first control valve to be constant, and a solenoid section that sets the flow rate of refrigerant which said first control valve is to allow to flow, wherein the control valve is made insensitive to pressure on a downstream side of said first control valve, and when said solenoid section is in a non-energized state, said first control valve is in a fully closed state, and said second control valve is in a fully open state, said second control valve is forcibly held in the fully open state even when the pressure on the downstream side of said first control valve is equal to or higher than pressure on an upstream side of said first control valve.

2. The control valve according to claim 1, wherein: said first control valve has a first valve element that has a lift position thereof set according to an urging force of said solenoid section and is urged in a valve-closing direction against the urging force of said solenoid section;said second control valve has a differential pressure-sensing section that has a same pressure-receiving area as a pressure-receiving area of part of said first valve element, which receives the pressure on the downstream side of said first control valve when said first valve element is in a closed position, and senses a differential pressure between the pressure on the upstream side of said first control valve and the pressure on the downstream side of said first control valve, which are generated across said first control valve, and a second valve element that is held by said differential pressure-sensing section; andupon transition of said solenoid section from a control state in which said solenoid section sets said first control valve to a non-energized state, said first valve element being shifted to a fully closed position by the urging force engages with said differential pressure-sensing section which has been away from said first valve element during the control state, to cause said second valve element to shift to a fully open position.

3. The control valve according to claim 2, wherein said second control valve, said first control valve, and said solenoid section are arranged along a same axis in order, wherein said first control valve has a first port formed on a side toward said solenoid section, for introducing refrigerant from the discharge chamber, a second port formed on a side toward said second control valve, for discharging refrigerant into the refrigerant outlet port, a first valve seat provided between said first port and said second port, and said first valve element disposed on a downstream side of said first valve seat in a manner movable to and away from said first valve seat, andsaid second control valve has a third port separated from said second port by said differential pressure-sensing section, for introducing refrigerant from the discharge chamber, a fourth port formed on a side opposite from said first control valve and along an axis thereof, for discharging refrigerant into the crankcase, said differential pressure-sensing section urged in a valve-closing direction, a second valve seat disposed in said fourth port, and said second valve element disposed on an upstream side of said second valve seat and held by said differential pressure-sensing section in a manner movable to and away from said second valve seat.

4. The control valve according to claim 3, wherein said first control valve has a guide slidably disposed along an axis of said first valve element within a space communicating with said first port and connected to said first valve element via a valve hole, for guiding an axial motion of said first valve element, and a spring disposed between said guide and said first valve seat, for urging said first valve element in the valve-closing direction.

5. The control valve according to claim 4, wherein said guide has a same pressure-receiving area as a pressure-receiving area of part of said first valve element, which receives the pressure on the upstream side of said first control valve when said first valve element is in the closed position, and receives the pressure on the upstream side of said first control valve in a valve-closing direction of said first control valve.

6. The control valve according to claim 5, wherein said first valve element is slidably disposed along an axis of said first control valve within a space communicating with said second port.

7. The control valve according to claim 5, wherein said first valve element and said guide connected thereto have a refrigerant passage axially formed therethrough, and a check valve for closing said refrigerant passage when pressure in said refrigerant passage on a side toward said second port has become higher than pressure in said refrigerant passage on a side toward said solenoid section.

8. The control valve according to claim 6, wherein said first valve element and said guide connected thereto have a refrigerant passage axially formed therethrough, and a valve that engages with said differential pressure-sensing section to thereby close said refrigerant passage when said first valve element forcibly shifts said second valve element to a fully open position.

9. The control valve according to claim 4, wherein said guide is provided with an intercommunicating hole for making pressure in said solenoid section equal to the pressure on the upstream side of said first control valve.

10. The control valve according to claim 3, wherein said second control valve has a piston as said differential pressure-sensing section for receiving pressure from said second port and pressure from said third port at axially opposite ends thereof to operate according to a differential pressure between the pressures, and a spring urging said piston in the valve closing direction.

11. The control valve according to claim 10, wherein said spring is disposed between said piston and said first valve element.

12. The control valve according to claim 10, wherein said second control valve has a film-like seal ring which is disposed on at least one of open ends of a clearance where the clearance formed between said piston and a body that axially movably holds said piston opens toward said second port and said third port, for sealing the clearance by the pressure from said second port or said third port.

13. The control valve according to claim 12, wherein said second control valve has a valve element base portion-accommodating portion formed in an end face of said piston, opposed to said second valve seat, and a base portion of said second valve element is accommodated in said valve element base portion-accommodating portion in a state urged in the valve-closing direction and in a manner prevented from coming off.

14. The control valve according to claim 3, wherein said second control valve has a bellows that has axially opposite ends thereof tightly connected to said differential pressure-sensing section holding said second valve element, and a body that axially movably accommodates said differential pressure-sensing section, said bellows being capable of axially extending and contracting while sealing said third port from said second port.

15. The control valve according to claim 3, wherein said second control valve has a diaphragm as said differential pressure-sensing section, which is disposed between said second port and said third port in a manner sealing said second port from said third port, for receiving pressure from said second port and pressure from said third port at axially opposite surfaces thereof to cause said second valve element to operate by a differential pressure between the pressures.

16. The control valve according to claim 15, wherein said diaphragm is tightly connected to a body in a state in which an outer periphery thereof is sandwiched between a first ring and a second ring, a central portion thereof being sandwiched between a center disk and a flange portion integrally formed with said second valve element having a hollow cylindrical shape, said diaphragm being fixed to a shaft fitted thereon in a manner axially extending therethrough, together with said center disk and said flange portion.

17. The control valve according to claim 16, wherein said diaphragm is configured such that a pressure-receiving area thereof for receiving pressure when the pressure in said third port is higher than the pressure in said second port is equal to a pressure-receiving area of said first valve element for receiving the pressure from said second port when said first control valve is in a closed state.

18. The control valve according to claim 17, wherein said diaphragm is configured such that an inner diameter of said second ring is made smaller than an inner diameter of said first ring, and an outer diameter of said flange portion is made smaller than an outer diameter of said center disk, whereby a pressure-receiving area of said diaphragm for receiving pressure when the pressure in said second port is higher than the pressure in said third port is made smaller than the pressure-receiving area for receiving pressure when the pressure from said third port is higher than the pressure from said second port.

19. The control valve according to claim 2, wherein said second control valve, said first control valve, and said solenoid section are arranged along a same axis in order, and wherein said first control valve has a first port formed on a side toward said solenoid section, for discharging refrigerant into the refrigerant outlet port, a second port formed on a side toward said second control valve, for introducing refrigerant from the discharge chamber, a first valve seat disposed between said first port and said second port, and said first valve element disposed on an upstream side of said first valve seat in a manner movable to and away from said first valve seat, and wherein said second control valve has a third port formed on a side opposite from said first control valve and along an axis thereof, for discharging refrigerant introduced into said second port into the crankcase, a hollow cylindrical body that has said first valve seat fixed to an inside thereof and is axially movably disposed in a state urged in the valve-closing direction, forming said differential pressure-sensing section, and a second valve element integrally formed with said hollow cylindrical body, for opening and closing said third port.

20. The control valve according to claim 19, wherein said first control valve includes a piston slidably disposed along an axis of said first valve element within a space communicating with said first port, and connected to said first valve element via a valve hole, for guiding an axial motion of said first valve element, and a spring disposed between said piston and a body accommodating said piston, for urging said first valve element in a valve-closing direction.

21. The control valve according to claim 20, wherein said piston is configured to have a same outer diameter as that of said hollow cylindrical body of said second control valve, to thereby inhibit said piston from sensing the pressure on the downstream side of said first control valve when said first valve element is in the closed position.

22. The control valve according to claim 20, wherein said first valve element and said piston connected thereto have a refrigerant passage axially formed therethrough for causing pressure of the refrigerant introduced into said second port to be received by an end face toward said solenoid section via said refrigerant passage.

23. The control valve according to claim 22, wherein when a shaft of said solenoid section urges said first valve element, said refrigerant passage is closed by said shaft.

24. The control valve according to claim 2, wherein said second control valve, said first control valve, and said solenoid section are arranged along a same axis in order, and wherein said first control valve has a first port formed on a side toward said solenoid section, for discharging refrigerant into the refrigerant outlet port, a second port formed on a side toward said second control valve, for introducing refrigerant from the discharge chamber, a first valve seat disposed between said first port and said second port, and said first valve element disposed on an upstream side of said first valve seat in a manner movable to and away from said first valve seat, and wherein said second control valve has a third port for discharging refrigerant into the crankcase, a fourth port formed on a side opposite from said first control valve and along an axis thereof, for introducing refrigerant from the discharge chamber, a hollow cylindrical body disposed within a space communicating with said second port and having said first valve seat rigidly fixed to an inside thereof in a state urged in the valve-closing direction, forming said differential pressure-sensing section, a second valve seat provided in said fourth port, and a second valve element that is disposed such that one end thereof is opposed to said second valve seat, and the other end thereof is urged in the valve closing direction with respect to said first valve element, for thereby being engaged with said hollow cylindrical body, and is movable to and away from said second valve seat.

25. The control valve according to claim 24, wherein said first control valve includes a piston slidably disposed along an axis of said first valve element within a space communicating with said first port, and connected to said first valve element via a valve hole, for guiding an axial motion of said first valve element, and a spring disposed between said piston and a body accommodating said piston, for urging said first valve element in the valve-closing direction, and wherein said first valve element has a refrigerant passage axially formed therethrough which is closed by a shaft of said solenoid section when said shaft urges said first valve element.

26. The control valve according to claim 25, wherein said piston is configured such that a portion thereof receiving the pressure at said first port in the valve-closing direction has a same outer diameter as that of said hollow cylindrical body of said second control valve, to thereby inhibit said piston from sensing the pressure on the downstream side of said first control valve when said first valve element is in the closed position.