Expansible chamber devices – Displacement control of plural cylinders arranged in... – Parallel cylinders
Reexamination Certificate
1999-04-09
2001-06-12
Look, Edward K. (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Parallel cylinders
C417S222200
Reexamination Certificate
active
06244159
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a variable displacement type swash plate compressor, and, more particularly, to a variable displacement type swash plate compressor capable of reducing power consumption of a compressor when an air-conditioning system is off and a displacement control valve for use in the compressor.
Typically, a compressor for compressing refrigerant gas is incorporated in a cooling circuit for a vehicle air-conditioning system. Such compressors are generally driven by the vehicle's engine and are often coupled to the engine by an electromagnetic clutch mechanism. The electromagnetic clutch connects the compressor to the engine only when a cooling load exists. Providing a compressor with the electromagnetic clutch mechanism however increases the total weight and the manufacturing cost, and the clutch draws power from the engine.
As a solution to those problems, a clutchless compressor has been proposed that directly connects the compressor to the engine and transmits power to the compressor whenever the engine is running. Recently, variable displacement type swash plate compressors have been considered suitable for such clutchless systems. Variable displacement type swash plate compressors are good at variably controlling the compression performance (discharge displacement) according to a variation in cooling load, either automatically or by means of an external control unit. However, they continuously apply a load to the engine.
As long as the cooling load is high and continuous, a clutchless, variable displacement type swash plate compressor works well. However, there is a need to reduce the load applied to the engine by the compressor when the cooling function is stopped in response to an external command, such as when a person in the vehicle turns off the air-conditioning switch.
In general, the discharge displacement of a variable displacement type swash plate compressor is controlled by adjustment of the piston stroke, which is accomplished by controlling the angle (inclination angle) of a swash plate with respect to the drive shaft by means of a displacement control valve. The inclination angle of the swash plate is controlled by controlling the internal pressure (Pc) of a crank chamber defined in the housing. Specifically, the internal pressure Pc of the crank chamber is increased to decrease the inclination angle, which reduces the discharge displacement. To tilt the swash plate in a direction that increases the inclination angle with such a structure, the swash plate must move toward the maximum inclination angle when the internal pressure Pc of the crank chamber falls. To return the swash plate to its maximum inclination angle, the minimum inclination angle should not be in the vicinity of 0° (as measured with respect to a plane perpendicular to the drive shaft). That is, with the minimum inclination angle of the swash plate set near 0°, little or no compression takes place, and no compression reactive force large enough to regain the maximum inclination angle is produced. This makes it very difficult or impossible to return the swash plate back to the maximum inclination angle. It is therefore necessary to set the minimum inclination angle of the swash plate to about a range of +30° to +50°, for example, so that there is some discharge from the compressor, even at the minimum inclination angle, which produces a small but significant compression reactive force. The compression reaction force contributes to increasing the inclination angle of the swash plate at the appropriate time. This permits the swash plate angle to increase in response to a reduction in the internal pressure Pc of the crank chamber, which is caused by the displacement control valve.
If a conventional variable displacement type swash plate compressor is designed as a clutchless type and is installed in a vehicle air-conditioning system, even when the start switch for the air-conditioner is turned off to set the inclination angle of the swash plate to the minimum inclination angle, the compressor continues operation with a minimum discharge displacement to continuously apply a compression reactive force to the swash plate. Thus, a small load is always applied to the vehicle engine. To reduce the load when the air-conditioning system is off, it is necessary to make the compression reactive force as low as possible by reducing the inclination angle of the swash plate as much as possible. If the compression reactive force is set too low, the swash plate cannot be inclined when there a need to increase the displacement. Since there is a compromise between reducing the power consumption under the minimum discharge displacement and using the compression reactive force to incline the swash plate to the maximum inclination angle, it is necessary to precisely adjust the minimum discharge displacement (or the minimum inclination angle) to satisfy both requirements. This is difficult to achieve in conventional variable displacement type swash plate compressors, which leads to increased manufacturing costs.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a variable displacement type swash plate compressor which can reduce its power consumption with an air-conditioning system in an OFF state as much as possible without sacrificing the ability to return from the minimum discharge displacement (minimum inclination angle), and which is easy to manufacture. It is another objective of this invention to provide a displacement control valve for use in such a compressor.
To achieve the above objective, the present invention provides a variable displacement compressor including a housing, which defines a cylinder bore, a crank chamber, a suction chamber and a discharge chamber. A piston is accommodated in the cylinder bore. A drive shaft is rotatably supported in the crank chamber by the housing. A drive plate is coupled to the piston for converting rotation of the drive shaft to reciprocation of the piston. The drive plate is supported on the drive shaft to incline with respect to a plane perpendicular to the axis of the drive shaft and to rotate integrally with the drive shaft. The drive plate moves in a range between a maximum inclination angle position and a minimum inclination angle position in accordance with a moment applied to the drive plate. The moment includes a moment based on the pressure in the crank chamber and a moment based on the pressure in the cylinder bore as components. The drive plate varies the stroke of the piston in accordance with its inclination angle to change displacement of the compressor. A pressure control mechanism controls pressure in the crank chamber to change the inclination of the drive plate. The minimum inclination angle is smaller than a limit angle. The limit angle is determined by the lower limit of a range of inclination within which the drive plate can be moved to increase its angle by a reaction force of pressure applied to the piston. An urging member urges the drive plate to increase its inclination angle when the inclination of the drive plate is less than the limit angle.
The present invention also provides a displacement control valve for controlling the displacement of a variable displacement compressor by adjusting inclination angle of a drive plate located in a crank chamber. The compressor includes a supply passage for connecting a discharge chamber to the crank chamber and a bleed passage for connecting the crank chamber to a suction chamber. The displacement control valve includes a first valve located in the supply passage. The first valve includes a first valve body for adjusting an opening size of the supply passage and a first spring for urging the first valve body to open. A second valve is located in the bleed passage. The second valve includes a second valve body for adjusting an opening size of the bleed passage, a pressure sensitive member for urging the second valve body to close with a force related to the pressure in the suction chamber, and a se
Kaneshige Yuji
Kimura Kazuya
Mizutani Hideki
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Lazo Thomas E.
Look Edward K.
Morgan & Finnegan , LLP
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