Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-04-20
2001-04-17
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
Reexamination Certificate
active
06217291
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compressors for compressing and discharging gas, and more particularly, to a compressor that varies displacement in accordance with the difference between the pressure of a discharge chamber and the pressure of a crank chamber, a control valve for controlling the pressure difference, and a method for varying the displacement of the compressor.
FIG. 20
shows a prior art compressor
200
. An inclinable swash plate
201
is accommodated in a crank chamber
203
. The displacement of the compressor
200
varies in accordance with the inclination of the swash plate
201
. A control valve
202
controls the pressure of the crank chamber
203
to alter the inclination of the swash plate
201
. The inclination of the swash plate
201
changes the stroke of pistons
204
, which are retained in the compressor
200
. There are two types of control valves
202
, a self-controlled type and an externally controlled type.
A self-controlled type control valve detects the suction pressure of the compressor
200
. The control valve automatically controls its position in accordance with the difference between the detected suction pressure value and a threshold pressure value. The threshold value is determined by the characteristics of a pressure sensing member (bellows), which is retained in the control valve. Accordingly, in a self-controlled type control valve, the threshold value cannot be changed when the compressor is operating.
In a externally controlled control valve, the threshold value can be changed when the compressor is operating. Typically, the externally controlled valve has an electromagnetic actuator and a controller
207
. The electromagnetic actuator includes a solenoid
206
and other relevant parts (e.g., steel core). In the control valve, the solenoid
206
is arranged coaxially with a pressure sensing member. The controller
207
controls the electromagnetic actuator in accordance with data sent from various types of sensors (e.g., ambient temperature). The electromagnetic actuator is actuated to change the threshold value. The threshold value is changed to vary and optimize the displacement of the compressor under different conditions.
Since the prior art self-controlled control valve cannot change the threshold value, the displacement of a compressor using such a valve cannot be flexibly varied. Although the externally controlled control valve can change the threshold value in accordance with the conditions surrounding the compressor, the electromagnetic actuator, which includes the solenoid and other relevant parts, increases the size of the compressor and complicates the structure of the compressor. This increases the product costs of the compressor. Furthermore, an amplifier having a large electric capacity must be used to actuate the electromagnetic actuator, which is controlled by the controller. However, the employment of a compressor using a high-capacity amplifier in an automotive air conditioning system significantly increases the load applied to the vehicle.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a control valve that easily varies the displacement of a compressor, a compressor using such a control valve, and a method for varying the displacement of a compressor.
To achieve the above objective, the present invention provides a control valve installed in a variable displacement compressor for compressing gas. The compressor includes a discharge pressure region, a suction pressure region, and a crank chamber. The pressure in the discharge pressure region is higher than that of the suction pressure region. The crank chamber accommodates a crank mechanism for compressing the gas. The control valve changes the displacement of the compressor by controlling a difference between the pressure in the crank chamber and the pressure in the discharge pressure region or the suction pressure region. The control valve has the following structure. A pressure sensitive chamber is connected to a control region, which is one of the discharge pressure region or the suction pressure region. A first passage connects the crank chamber to the control region. A valve chamber is located in the first passage. A valve body is accommodated in the valve chamber for selectively closing and opening the first passage. A displaceable pressure sensitive mechanism is connected to the valve body and accommodated in the pressure sensitive chamber. The displacement of the pressure sensitive mechanism causes the valve body to move between an open position and a closed position. The pressure sensitive mechanism produces a force for determining an initial threshold pressure value at which the valve body is switched between the open position and the closed position. A controller controls the pressure in the pressure sensitive chamber by supplying gas from the discharge pressure region to the pressure sensitive chamber or by discharging gas from the pressure sensitive chamber to the suction pressure region to change the threshold value from the initial value to a second threshold value. The pressure sensitive mechanism functions in accordance with the pressure of the pressure sensitive chamber. The valve body behaves in accordance with the threshold value selected by the controller.
The present invention further provides a variable displacement compressor for compressing gas. The compressor includes a discharge pressure region and a suction pressure region. The pressure in the discharge pressure region is higher than that of the suction pressure region. The compressor has the following structure. A crank chamber accommodates a crank mechanism for compressing the gas. A control valve changes the displacement of the compressor by controlling a difference between the pressure in the crank chamber and the pressure in a control region, which is one of the discharge pressure region or the suction pressure region. The control valve has the following structure. A pressure sensitive chamber is connected to the control region. A first passage connects the crank chamber to the control region. A valve chamber is located in the first passage. A valve body is accommodated in the valve chamber for selectively closing and opening the first passage. A displaceable pressure sensitive mechanism is connected to the valve body and accommodated in the pressure sensitive chamber. The displacement of the pressure sensitive mechanism causes the valve body to move between an open position and a closed position. The pressure sensitive mechanism produces a force for determining an initial threshold pressure value at which the valve body is switched between the open position and the closed position. The compressor further includes a controller that controls the pressure in the pressure sensitive chamber by supplying gas from the discharge pressure region to the pressure sensitive chamber or by discharging gas from the pressure sensitive chamber to the suction pressure region to change the threshold value from the initial value to a second value. The pressure sensitive mechanism functions in accordance with the pressure of the pressure sensitive chamber. The valve body behaves in accordance with the threshold value selected by the controller.
The present invention further provides a method for controlling a displacement of a variable displacement compressor installed in a vehicle. The compressor has a discharge pressure region, a suction pressure region, a crank chamber, which accommodates a crank mechanism for compressing gas, and a control valve. The pressure in the discharge pressure region is higher than that of the suction pressure region. The control valve has the following structure. A valve body selectively closes and opens a passage that connects the crank chamber to the discharge pressure region or the suction pressure region. A pressure sensitive chamber is connected to the discharge pressure region or the suction pressure region. The control valve changes the displacement of the compressor by regulating the dif
Adaniya Taku
Kurakake Hirotaka
Nishimura Kenta
Ota Masaki
Freay Charles G.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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