EP1462650A2

EP1462650A2 - Control valve for variable displacement compressor

Info

Publication number: EP1462650A2
Application number: EP04005114A
Authority: EP
Inventors: Ryosuke Yoshihiro; Morimitsu Kajiwara
Original assignee: TGK Co Ltd
Current assignee: TGK Co Ltd
Priority date: 2003-03-28
Filing date: 2004-03-04
Publication date: 2004-09-29
Also published as: EP1462650A3; US20040191078A1; JP2004293497A

Abstract

In a control valve for a variable displacement compressor, a valve section 10 for controlling the refrigerant flow rate at discharge pressure Pd to supply refrigerant at a control pressure Pc to a crankcase is implemented by a spool valve structure. A spool valve element 15 and a coaxial shaft 18 are configured such that the spool valve element 15 and the shaft 18 oppositely receive the discharge pressure Pd and the suction pressure Ps, respectively. The differential pressure between the discharge pressure Pd and suction pressure Ps, which is to be controlled, is set by a duty ratio controlled solenoid section 20. The spool valve element 15 performing micro vibrations due to duty ratio control is prevented from colliding against a valve seat 16 when it is close to the valve-closing position, so that it is possible to enhance the valve lift characteristics, and to improve durability of valve component parts.

Description

This invention relates to a control valve according to the preamble of claims 1 and 7, particularly for a refrigeration cycle of an automotive air conditioner.
In a variable displacement compressor in a refrigeration cycle of an automotive air conditioner, the control valve controls a communication between a discharge chamber and a crankcase to adjust a control pressure in the crankcase into which high-pressure refrigerant is introduced from the discharge chamber. The inclination angle of a swash plate is adjusted by the control pressure to control the displacement of compressed refrigerant. According to a known method the suction pressure is sensed and the control pressure is adjusted in response to a change in the suction pressure. According to a known method (JP-A-(Kokai) 2001-132650) the differential pressure between the discharge pressure and the suction pressure is sensed for controlling the control pressure in the crankcase such that the differential pressure becomes equal to a predetermined value.
Known control valves carry out the displacement control by supplying a current of a value corresponding to a set displacement to an electromagnetic coil of an electromagnetic solenoid. As known from JP-A-(Kokai) 2002-342946, a pulsed current is supplied with a frequency of approximately 400 Hz, and the duty ratio of the pulsed current is varied. The duty ratio controlled control valve has a set load based on an average current value which depends on the duty ratio.
In a known control valve sensing the differential pressure between the discharge pressure and the suction pressure of the compressor, either a ball valve is employed which has a ball-shaped valve element, or a needle valve, or a tapered valve which has a tapered valve element, or a flat valve which has a planar valve element, or the like. The flow rate between the discharge chamber and the crankcase is controlled by changing the lift of the respective valve element relative to a valve seat. When the compressor operates with minimum displacement, the valve lift is controlled to be maximum. When the compressor operates with maximum displacement, the valve lift is controlled to be minimum, i.e. in the valve-closed state.
However, in the known duty ratio controlled control valve the valve element and the shaft for actuating the valve element perform micro vibrations in the longitudinal direction of the control valve. When the valve element performs valve-closing operation, particularly when the valve element moves in valve-closing direction in response to an increase in the suction pressure occurring when the valve element already is close to the valve-closing position, the valve element again moves backwards in valve-opening direction after hitting against the valve seat. This results in non-linear lift characteristics of the control valve. Caused by the micro vibrations the valve element directly and repeatedly hits against the valve seat. This causes degradation of durability of both the valve element and the valve seat.
It is an object of the invention to provide a duty ratio controlled control valve for a variable displacement compressor which has improved valve performance.
This object is achieved by a control valve having the features of claims 1 and 7, respectively.
When the valve section is formed by a spool valve having a dive-in projection for co-action with the valve hole, even if the valve element of the spool valve performs micro vibrations in the valve opening/closing direction due to duty ratio control of the electromagnetic solenoid, the valve element even when actuated close to the valve-closing position is prevented from colliding against the valve seat. The control valve, furthermore, does not again open due to a collision with the valve seat immediately before the control valve is closed. This enhances the lift characteristics and valve performance of the control valve and also improves durability of the valve component parts.
Embodiments of the invention will be described with reference to the drawings. In the drawings is:

Fig. 1: a cross-section schematically showing a control valve (first embodiment),
Fig. 2: a cross-section of a second embodiment of the control valve,
Fig. 3: a cross-section of a third embodiment of the control valve,
Fig. 4: a cross-section of a fourth embodiment of the control valve,
Fig. 5: a cross-section of a fifth embodiment of the control valve, and
Fig. 6: a cross-section of a sixth embodiment of the control valve.

A control valve comprises a valve section 10 and a solenoid section 20, and forms a control valve of an external variable control type. When the control valve is incorporated in a variable displacement compressor, not shown, it is disposed such that it controls a communication between a discharge chamber and a crankcase, and at the same time communicates with a suction chamber of the compressor.
The valve section 10 has a discharge chamber port 12 in a longitudinal end of a body 11, for introducing refrigerant at discharge pressure Pd, a crankcase port 13 in a side of the body 11, for guiding out refrigerant at controlled control pressure Pc, and a suction chamber port 14 in the side of the body 11 at a location close to the solenoid section 20 for receiving the suction pressure Ps.
The valve section 10 comprises a spool valve provided in a passage between the ports 12, 13. More specifically, a spool valve element 15 is axially movably held by the body 11 opposed to a valve seat 16 such that the spool valve element 15 can be moved into and out from a valve hole 16b of the valve seat 16 from a downstream side thereof. The spool valve element is urged by a spring 17 in valve-opening direction. Further, the spool valve element 15 abuts a shaft 18 axially movably held by the body 11, on the side toward the solenoid section 20. The shaft 18 receives the suction pressure Ps at a free end face opposite to an end face in abutting at the spool valve element 15.
The spool valve element 15 is configured such that a free end or dive-in projection 15b when inserted into the valve hole has an outer diameter smaller than the inner diameter of the valve hole 16b by a predetermined value. The dive-in projection 15b may have a tapering neck portion 15c directly or indirectly merging into a substantially radially extending stepped portion 15a. As a result, when the end 15b of the spool valve element 15 is inserted into the valve hole 16b, a predetermined clearance is provided between the end and an inner wall surface of the valve hole 16b, and when the spool valve is open, the clearance functions as an orifice defining a fixed cross-sectional area of a refrigerant passage.
The solenoid section 20 has a sleeve 22 carrying an outer electromagnetic coil 21. A fixed core 23 is fixed to one end of the sleeve 22 on the side toward the valve section 10. A plunger 24 forming a movable core is axially movably disposed in the sleeve 22, in a state sandwiched between respective springs 25 and 26. The plunger 24 is rigidly fixed to an axial shaft 27. One end of the shaft 27 abuts the shaft 18, and the other end is supported by a closing part 28 in an end of the sleeve 22.
For energization, a pulsed current having a frequency of approximately 400 Hz is supplied to the electromagnetic coil 21. An attractive force is generated between the core 23 and the plunger 24 depending on a change in the average current value caused by varying the duty ratio of the pulsed current.
When pulsed current with a predetermined duty ratio is supplied to the electromagnetic coil 21, the plunger 24 inserts the spool valve element 15 into the valve hole 16b against the urging force of the spring 17. Refrigerant from the port 12 flows through the orifice formed by the clearance between the spool valve element 15 and the valve hole 16b and a controlled gap between the spool valve element 15 and the valve seat 16, (between the stepped portion 15a and a surface 16a surrounding the valve seat 16) and then from port 13 to the crankcase. The control valve now controls the control pressure Pc in the crankcase such that differential pressure between the discharge pressure Pd and the suction pressure Ps in the variable displacement compressor becomes equal to a constant differential pressure set by the duty ratio controlled solenoid section 20. More specifically, if the differential pressure between the discharge pressure Pd and the suction pressure Ps becomes larger than the set differential pressure, the spool valve is actuated in valve-opening direction to raise the control pressure Pc in the crankcase and to thereby reduce the displacement of the variable displacement compressor, whereby the differential pressure between the discharge pressure Pd and the suction pressure Ps is reduced. Inversely, if the differential pressure between the discharge pressure Pd and the suction pressure Ps becomes smaller than the set differential pressure, the spool valve is operated in the valve-closing direction to reduce the control pressure Pc in the crankcase and to thereby increase the displacement of the variable displacement compressor, whereby the differential pressure between the discharge pressure Pd and the suction pressure Ps is increased.
When a pulse current having a maximum duty ratio flows through the electromagnetic coil 21, the stepped portion 15a of the spool valve element 15 is brought into blunt abutment with the valve seat 16, i.e. the radially extending even surface 16a surrounding the valve seat 16, to place the valve section 10 in its valve-closed state, whereby the variable displacement compressor is operated with the maximum displacement.
It should be noted that when the spool valve element 15, i.e. the stepped portion 15a, is going to abut at the valve seat 16, i.e. the surface 16a, the restricted cross-section in the spool valve is a minimum and the refrigerant flow dampens movements of the spool valve element 15, and the duty ratio already is then close to a maximum value, so that axial strokes of micro vibrations of the spool valve element 15 are very small, whereby it is possible to prevent the lift characteristics and durability of the control valve from being degraded by hits of the spool valve element 15 against the valve seat 16. When the electromagnetic coil 21 is de-energized, the spring 17 moves the plunger 24 away from the core 23 to place the valve section 10 in its valve-open state, whereby the variable displacement compressor is operated with the minimum displacement.
The control valve in Fig. 2 is configured such that the spool valve element 15 and the shaft 18 receiving the suction pressure Ps are integrally formed with each other. The spring 17 of Fig. 1 is omitted, but the spring 25 of the solenoid section 20 plays the role of the spring 17 of Fig. 1 as well.
Since the spool valve element 15 and the shaft 18 are integrally formed with each other, and the spring 17 is omitted, it is possible to reduce the number of component parts of the control valve, thereby making it possible to manufacture the control valve at low costs.
The operation of the control valve of Fig. 2 with stabilized characteristics is the same as that of the control valve of Fig. 1.
The control valve in Fig. 3 is configured such that the spool valve element 15, the shaft 18 receiving the suction pressure Ps, and the shaft 27 of the solenoid section 20 are integrally formed with each other. The spring 17 of Fig. 1 is omitted, but the spring 25 of the solenoid section 20 plays the role of the spring 17 of Fig. 1 as well.
Since the spool valve element 15, the shaft 18, and the shaft 27 are integrally formed with each other, and the spring 17 is omitted, it is possible to reduce the number of component parts of the control valve, thereby making it possible to manufacture the control valve at low costs.
The operation of the control valve in Fig. 3 is the same as that of the control valve in Fig. 1.
The control valve in Fig. 4 is distinguished from the control valves of Figs 1-3 in that the valve section 10 includes two valve sections 10a, 10b and has two spool valves 15, 16, 19, 23a respectively disposed in a passage between the discharge chamber and the crankcase, and in a passage between the crankcase and the suction chamber.
The valve section 10 has the discharge chamber port 12 for introducing refrigerant at discharge pressure Pd, a first crankcase port 13a formed in the side of the body 11 for guiding out refrigerant at controlled control pressure Pc1, and a second crankcase port 13b formed in the side of the body 11 at a location closer toward the solenoid section 20 for introducing refrigerant at control pressure Pc2 (= Pc1) from the crankcase. Further, the core 23 of the solenoid section 20 having the body 11 fitted thereon is formed with the suction chamber port 14 for guiding out the controlled suction pressure Ps.
The first spool valve 15, 16 is provided in a passage between the ports 12,13a. More specifically, the spool valve element 15 is axially movably held by the body 11 opposed to the valve seat 16 such that the spool valve element 15 can be moved into and away from the valve hole of the valve seat 16 from the downstream side thereof. The spool valve element 15 is urged by the spring 17 in valve-opening direction. Further, the spool valve element 15 abuts at the shaft 18 axially movably held by the body 11, on the side facing toward the solenoid section 20.
The shaft 18 is part of second spool valve 19, 23a. A spool valve element 19 is formed at an end of the shaft 18 opposite to the end abutting at the spool valve element 15. The second spool valve 19, 23 serves for controlling the flow rate of refrigerant flowing from the crankcase to the suction chamber. More specifically, between the crankcase port 13b and the suction chamber port 14, a valve hole 23a is formed in the center of the core 23. The spool valve element 19 can be moved into and out of from the valve hole 23a. An end face of the spool valve element 19 receives the suction pressure Ps.
Each of the spool valve elements 15 and 19 is configured such that an end or diving projection which may be inserted into the associated valve hole has an outer diameter smaller than an inner diameter of the valve hole by a predetermined value. As a result, when the end is inserted into the valve hole, a predetermined clearance is formed between the end and an inner wall surface of the valve hole. This clearance functions as an orifice defining a fixed cross-sectional area of a refrigerant passage.
Now, when a pulsed current with a predetermined duty ratio is supplied to the electromagnetic coil 21, and the plunger 24 is attracted by the core 23, the shaft 27 pushes the spool valve element 19 in the valve-opening direction, and the shaft 18 in turn pushes the spool valve element 15 in the valve-closing direction. As a result, in the first spool valve 15, 16, the refrigerant flows from the port 12 through the orifice formed by the radial clearance between the spool valve element 15 and the valve hole of the valve seat 16 and through a controlled gap between the spool valve element 15 and the valve seat 16 (the stepped portion and the surface surrounding the valve seat 16), and then from the port 13a to the crankcase. Simultaneously, in the second spool valve 19, 23a, the spool valve element 19 is moved out of the valve hole 23a, and the refrigerant returned from the crankcase to the port 13b flows to the suction chamber through a controlled gap between the spool valve element 19 and the valve seat at the mouth of the valve hole 23a and through an orifice formed by a radial clearance between the spool valve element 19 and the valve hole 23.
The control valve is responsive to the differential pressure between the discharge pressure Pd and the suction pressure Ps, for controlling the pressures Pc1 and Pc2 in the crankcase such that the differential pressure becomes equal to the constant differential pressure set by the duty ratio controlled solenoid section 20.
More specifically, if the differential pressure between the discharge pressure Pd and the suction pressure Ps becomes larger than the set differential pressure, the first spool valve 15, 16 is operated in the valve-opening direction and the second spool valve 19, 23a is operated in the valve-closing direction to raise the pressures Pc1 and Pc2 in the crankcase to reduce the displacement of the variable displacement compressor, whereby the differential pressure between the discharge pressure Pd and the suction pressure Ps is reduced. Inversely, if the differential pressure between the discharge pressure Pd and the suction pressure Ps becomes smaller than the set differential pressure, the first spool valve 15, 16 is operated in the valve-closing direction and the second spool valve 19, 23a is operated in the valve-opening direction to reduce the pressures Pc1 and Pc2 in the crankcase to increase the displacement of the variable displacement compressor, whereby the differential pressure between the discharge pressure Pd and the suction pressure Ps is increased.
When a pulsed current with the maximum duty ratio flows through the electromagnetic coil 21, the stepped portion of the spool valve element 15 is brought into abutment with the valve seat 16, whereby the first spool valve is fully closed, and the spool valve element 19 is moved out of the valve hole 23a to fully open the second spool valve 19, 23a. This causes the variable displacement compressor to operate with maximum displacement.
When the electromagnetic coil 21 is de-energized, the first spool valve 15, 16 is fully opened and the second spool valve 19, 23a is fully closed, by the urging force of the spring 17, whereby the variable displacement compressor is operated with the minimum displacement.
The control valve in Fig. 5 is configured such that the spool valve element 15, the spool valve element 19, and the shaft 18 are integrally formed with each other, and the spring 17 of Fig. 4 is omitted, but the spring 25 of the solenoid section 20 plays the role of the spring 17 of Fig. 4 as well.
Since the spool valve elements 15 and 19 and the shaft 18 are integrally formed with each other to thereby omit the spring 17, it is possible to reduce the number of component parts of the control valve, thereby making it possible to manufacture the control valve at low costs.
The operation of the control valve of Fig. 5 is the same as that of the control valve of Fig. 4. The two spool valves 15, 16, 19, 23a eliminate hitting of the respective valve element 15, 19 against the valve seat 16, 23 to stabilize the characteristics of the valve.
The control valve in Fig. 6 is configured such that the spool valve element 15, the shaft 18, the spool valve element 19, and the shaft 27 of the solenoid section 20 are integrally formed with each other, and the spring 17 of Fig. 4 is omitted, but the spring 25 of the solenoid section 20 plays the role of the spring 17 of Fig. 4 as well. As a result, it is possible to reduce the number of component parts of the control valve, thereby making it possible to manufacture the control valve at low costs.
The operation of the control valve of Fig. 6 is also the same as that of the control valve of Fig. 4.
The invention is not limited to the embodiments of Figs 1-6. For instance, the control valves of Figs 1-3 instead may be used to control the flow rate of refrigerant drawn from the crankcase into the suction chamber. In this case, e.g. the spool valve element 15 would be situated at the upstream side of the valve seat 16 provided between the port 12 receiving the crankcase pressure Pc and the port 13 connected to the suction chamber (suction pressure Ps), while the discharge pressure Pd is introduced into the port 14. Alternatively, only one of the two spool valves of Figs 4-6 may be a spool valve.

Claims

A control valve for a variable displacement compressor, for controlling a difference between a compressor discharge pressure (Pd) and a compressor suction pressure (Ps) such that the pressure difference becomes equal to a constant differential pressure set by a duty ratio controlled electromagnetic solenoid section (20),
characterized in that a valve section (10) for controlling a communication passage between a first refrigerant inlet port (12) and a second refrigerant outlet port (13) comprises a spool valve (15, 16).
The control valve according to claim 1, characterized in that the valve section (10) includes a valve seat (16) formed in a passage between the ports (12, 13), a spool valve element (15) disposed in an upstream side space or a downstream side space adjacent to the valve seat (16) such that it can be moved into and out of a valve hole (16) of the valve seat (16b), a spring (17, 25) for urging the spool valve element (15) in valve-opening direction, and a pressure-sensing shaft (18) for transmitting the force of a pressure introduced into a third port (14) to the spool valve element (15).
The control valve according to claim 2, characterized in that the spool valve element (15) is disposed on the downstream side of the valve seat (16), that the compressor discharge pressure (Pd) is introduced into the first port (12), that a pressure (Pd) in a compressor crankcase is guided out from the second port (13), and that the compressor suction pressure (Ps) is introduced into the third port (14).
The control valve according to claim 2, characterized in that the spool valve element (15) is disposed on the upstream side of the valve seat (16), that pressure (Pc) in a compressor crankcase is introduced into the first port (12), that the compression suction pressure (Ps) is guided out from the second port (13), and that the compression discharge pressure (Pd) is introduced into the third port (14).
The control valve according to claim 2, characterized in that the spool valve element (15) and the pressure-sensing shaft (18) are integrally formed with each other.
The control valve according to claim 2, characterized in that the spool valve element (15), the pressure-sensing shaft (18), and a drive shaft (27) via which the electromagnetic solenoid actuates the spool valve element (15) are integrally formed with each other.
A control valve for a variable displacement compressor, for controlling a difference between a compressor discharge pressure (Pd) and a compressor suction pressure (Ps) such that the pressure difference becomes equal to a constant differential pressure set by a duty ratio controlled electromagnetic solenoid, characterized by
a first valve section (10a) for controlling a passage between a first discharge pressure port (12) and a second crankcase pressure port (13a) from which the refrigerant having a flow rate thereof controlled is guided to a crankcase; and
a second valve section (10b) for controlling a passage between a third crankcase pressure port (13b) and a fourth suction pressure port (14) from which the refrigerant having a flow rate thereof controlled is guided out to a suction chamber, the operation of the second valve section (10b) being interlocked with the operation of the first valve section (10a), and
at least one of the first and second valve sections (10a, 10b) comprising a spool valve (15, 16; 19, 23a) whose spool valve element (15, 19) can be moved into and out of a valve hole (16b, 23a) of an associated valve seat (16).
The control valve according to claim 8, characterized in that a valve element (15) of the first valve section (10a) and a valve element (19) of the second valve section (10b) are integrally formed with each other.
The control valve according to claim 8, characterized in that a valve element (15) of the first valve section (10a), a valve element (19) of the second valve section (10b), and a drive shaft (27) via which the electromagnetic solenoid actuates the valve elements (15, 19) are integrally formed with each other.
The control valve according to claim 2 or claim 8, characterized in that a predetermined clearance is provided between an end of the valve element (15, 19) of the spool valve (15, 16; 19, 23a) when inserted into valve hole (16b, 23a), and an inner wall surface of the valve hole (16b, 23a), so as to cause the clearance to function as an orifice.
The control valve as in at least one of claims 1 to 10, characterized in that said valve seat (16) surrounds an essentially cylindrical valve hole (16b), and that the spool valve element (15) has a free end or dive-in projection (15b) consisting of a substantially cylindrical part of smaller outer diameter than the inner diameter of said valve hole (16b), and of a tapering neck portion (15c) the larger end diameter of which substantially corresponds to the inner diameter of the valve hole (16b).
The control valve as in claim 11, characterized in that said valve seat (16) is surround by a substantially radial planar surface (16a), and that the spool valve element (15) has an essentially radially extending stepped portion (15a) merged with the tapering neck portion (15c) for creating a blunt abutment between the spool valve element (15) and said planar surface (16a) in the fully closed valve state.