Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-11-22
2001-05-22
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S061000
Reexamination Certificate
active
06234763
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement compressor used in a vehicle air conditioning system, and more specifically, to a variable displacement compressor that has a displacement control valve for controlling the displacement of the compressor.
A variable displacement compressor used in a vehicle air conditioning system is driven by a vehicle engine. The displacement, or cooling performance, of the variable displacement compressor is automatically controlled based on cooling load. A swash plate type variable displacement compressor has a swash plate located in a crank chamber. The inclination of the swash plate is altered by controlling the pressure in the crank chamber with a specially designed control valve. Altering the swash plate inclination changes the stroke of pistons, which varies the displacement of the compressor. The specially designed control valve can be an internally controlled valve or an externally controlled valve.
An internally controlled control valve includes a pressure sensing mechanism. The pressure sensing mechanism sets a target pressure and detects the gas pressure in a suction chamber of the compressor, or the suction pressure. The pressure sensing mechanism is displaced by the difference between the target pressure and the suction pressure, which automatically changes the opening amount of the control valve. The target pressure of the internally controlled control valve cannot be changed externally. It is sometimes desirable to change the displacement of a compressor in accordance with the running state of the engine regardless of the suction pressure, which represents the cooling load. However, if the compressor has an internally controlled control valve, the compressor displacement cannot be controlled based on the engine running state since the target pressure cannot be changed externally.
An externally controlled control valve includes a pressure sensing mechanism and an electromagnetic actuator coupled to the pressure sensing mechanism. The displacement of the compressor is determined by a controller based on the running state of the engine and the running state of the vehicle. The controller then electrically actuates the electromagnetic actuator, accordingly. In this manner, the target pressure of the externally controlled control valve is determined in accordance with external factors. Thus, the displacement of the compressor is optimized for the running state of the engine. Specifically, when the vehicle requires a relatively great amount of power, for example, when the vehicle is rapidly accelerated, the load of the compressor on the engine can be reduced.
The pressure sensing mechanism includes a pressure sensing member, which is a bellows, and a spring located in the bellows. The bellows is displaced along its axis, or expanded and contracted, in accordance with the suction pressure. The electromagnetic actuator includes a solenoid and associated parts. The solenoid is axially aligned with the bellows.
The pressure sensing mechanism must be axially aligned with the electromagnetic actuator such that the bellows is axially aligned with the solenoid. This complicates the structure of the control valve and increases the number of parts. Thus, the cost and the number of assembly steps are increased. Also, the size of the compressor is enlarged. The controller has an amplifier to actuate the solenoid. Since the pressure sensing mechanism is actuated by the electromagnetic actuator, a relatively great electrical load is applied to the amplifier.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a variable displacement compressor that varies the compressor displacement externally by changing the target pressure of an internally controlled control valve. The variable displacement compressor of the present invention is obtained by applying a simple change to a compressor having a prior art internally controlled control valve.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a variable displacement compressor that has a suction zone, a discharge zone, a crank chamber, a displacement control valve and a displacement control passage is provided. The displacement control passage is controlled by the displacement control valve to vary the pressure in the crank chamber. The compressor compresses gas drawn from the suction pressure zone and discharges the compressed gas to the discharge zone. The displacement of the compressor varies according to the pressure of the crank chamber. The displacement control valve includes a valve chamber, a valve body, a pressure sensing chamber, a pressure sensing mechanism and an electromagnetic valve. The valve chamber forms part of the displacement control passage. The valve body is located in the valve chamber to regulate an opening in the displacement control passage. The pressure sensing chamber is connected to the suction zone and the discharge zone. Gas flows into the pressure sensitive chamber from the discharge zone through an inlet passage and flows out of the pressure sensing chamber to the suction zone through an outlet passage. The pressure sensing mechanism is located in the pressure sensing chamber. The pressure sensing mechanism acts on the valve body to adjust the position of the valve body according to the pressure in the pressure sensing chamber. The electromagnetic valve regulates one of the inlet passage and the outlet passage to change the pressure of the pressure sensing chamber according to a determination based on external conditions.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 6010312 (2000-01-01), Suitou et al.
patent: 6036447 (2000-03-01), Kawaguchi et al.
patent: 6146106 (2000-11-01), Suitou et al.
patent: 8-338364 (1996-12-01), None
Adaniya Taku
Kurakake Hirotaka
Nishimura Kenta
Ota Masaki
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Pwu Jeffrey C
Walberg Teresa
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