Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-07-07
2001-03-06
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06196808
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a displacement control valve system provided in a variable displacement compressor for use in automobile air conditioner or the like.
2. Description of the Related Art
Conventionally, a variable displacement compressor has been used in a refrigerating circuit of automobile air conditioner. A displacement control valve system is provided in a rear housing so as to change the volume of cooling refrigerant for compressing this variable displacement compressor. The displacement control valve system includes a valve casing and a solenoid. The valve casing has a pressure sensing space at an end thereof and a valve chamber at the other end. The pressure sensing space is connected to a suction chamber. Inside the sensing space, a bellows portion is disposed inside thereof. A valve chamber communicates with a crank chamber and discharge chamber of the compressor, and a path for communicating therebetween is opened or closed by a valve member accommodated in the valve chamber. An extension/contraction of the bellows portion is converted to a movement for opening/closing the valve via a transmission rod. Further, a solenoid adjusts the opening of this valve member.
In this displacement control valve system, if a cooling load of a compressor increases, an electromagnetic force increases so as to act for reducing a valve travel or valve lift, that is a opening degree of the valve. When the valve travel is decreased, the amount of refrigerant flowing into the crank chamber is decreased. As a result, a pressure of the crank chamber is reduced so that an inclination of the swash plate (angle relative to a plane perpendicular to a driving shaft) increases.
On the other hand, when the cooling load of the compressor is small, the electromagnetic force decreases so as to act for increasing the opening of the valve. As a result, the amount of refrigerant flowing into the crank chamber increases, so that a pressure of the crank chamber increases thereby the inclination of the swash plate being reduced.
This method is called external control method, which enables to change the displacement freely according to an external signal.
In the conventional external control method variable displacement compressor, it has been proposed to enforce the compressor to be maintained at its minimum displacement by detecting vehicle accelerations to reduce power consumption of the compressor, thereby improving the vehicle acceleration performance.
In the conventional displacement control valve system, even if power supply to the solenoid is turned OFF, a force which is a pressure difference acting to close the valve body is left. For example, if a suction chamber pressure exceeds an upper limit for control, the bellows is contracted so that the valve is closed. As a result, no discharge gas is supplied to the crank chamber. Therefore, the displacement cannot be maintained at its minimum level.
Further, such a problem also exists that when a constant current is supplied to the electromagnetic coil of the solenoid, the suction chamber pressure is changed by a discharge chamber pressure thereby a stabilized control being damaged.
Therefore, although a sealing area of the valve body has to be small to reduce an influence of the discharge chamber pressure, the amount of discharge gas introduced to the crank chamber becomes short, so that the displacement control becomes unstable.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a displacement control valve system for a variable displacement compressor in which a suction chamber pressure control accuracy is improved and the displacement thereof can be enforced to be maintained at its minimum one.
It is another object of the present invention to provide a variable displacement compressor employing the displacement control valve system.
To achieve the above object, according to an aspect of the invention, there is provided a variable displacement compressor having a discharge chamber, a suction chamber, a crank chamber, and a displacement control valve system for controlling a piston stroke by adjusting a pressure in the crank chamber. The displacement control valve system comprises: a pressure sensing means which is extended/contracted by sensing a pressure in the suction chamber or a pressure in the crank chamber; a transmission rod supported so as to be capable of passing through a valve casing with an end thereof being in contact with the pressure sensing means; a valve body for opening/closing a communication path between a discharge chamber and a crank chamber in correspondence to an extension/contraction of the pressure sensing means while the other end of the rod is in contact therewith; and a magnetic field applying means for applying a force based on an electromagnetic force to the valve body. In the displacement compressor, a valve shaft of the valve body is supported so as to be capable of passing through the stator which is the magnetic field applying means and the valve shaft is protruded into a plunger chamber of the magnetic field applying means so that the plunger chamber is made to communicate with the suction chamber.
Further, according to another aspect of the present invention, there is provided a displacement control valve system for a variable displacement compressor having a discharge chamber, a suction chamber, and a crank chamber for controlling a piston stroke by adjusting a pressure in the crank chamber. The displacement control valve system comprises: a pressure sensing means which is extended/contracted by sensing a pressure in the suction chamber or a pressure in the crank chamber; a transmission rod supported so as to be capable of passing through a valve casing with an end thereof being in contact with the pressure sensing means; a valve body for opening/closing a communication path between a discharge chamber and a crank chamber in correspondence to an extension/contraction of the pressure sensing means while the other end of the rod is in contact therewith; and a magnetic field applying means for applying a force based on an electromagnetic force to the valve body. In the displacement control valve system, a valve shaft of the valve body is supported so as to be capable of passing through the stator which is the magnetic field applying means and the valve shaft is protruded into a plunger chamber of the magnetic field applying means so that the plunger chamber is made to communicate with the suction chamber.
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Baker & Botts L.L.P.
Rodriguez William
Sanden Corporation
Thorpe Timothy S.
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