Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-07-20
2001-12-25
Jeffery, John A. (Department: 3742)
Refrigeration
Automatic control
Refrigeration producer
C062S196300, C062S115000
Reexamination Certificate
active
06332329
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a variable swash plate displacement compressor assembled in a refrigeration cycle of an air conditioning system for a vehicle and the like and adapted to compress refrigerant gas.
BACKGROUND ART
In swash plate variable displacement compressors, there is a known compressor as disclosed in Japanese Patent Publication No. 6-89741. This discloses, for example, that exciting current of a solenoid controls an opening degree of a pilot valve. High-pressure side refrigerant in a refrigerant discharge chamber is caused to act on a back portion of a piston valve. The piston valve controls a flow-rate of refrigerant flowing into a refrigerant suction chamber.
DISCLOSURE OF INVENTION
In the above art, a swash plate variable displacement compressor has a basic structure of so-called clutch-attached type, which has an electromagnetic clutch incorporated into a compressor driving pulley. Therefore, not only complication of the structure but also weight increase is caused. Moreover, the number of parts increases, and it is disadvantageous in terms of cost.
In a drive state of the compressor connected with the clutch, when a flow-rate of refrigerant is reduced to a zero for preventing an evaporator from freezing, the refrigerant flowing into the refrigerant suction chamber of the compressor, it is necessary to maximize the exciting current of the solenoid that operates the pilot valve and to bring the piston valve to a full stroke on a valve-opening side, thus to increase power consumption.
It is an object of the present invention to provide a variable displacement swash plate compressor in which operation of the compressor can be turned on and off without attaching the clutch, thereby obtaining a structure without the clutch. It is another object of the present invention to provide a variable displacement swash plate compressor in which a solenoid is demagnetized for operating a pilot valve that controls a flow-rate of the refrigerant and a flow-rate of refrigerant is reduced to a zero, the refrigerant flowing into a refrigerant suction chamber of the compressor, thereby preventing an evaporator from freezing.
To achieve the objects, a first aspect of the invention is provided with a variable displacement swash plate compressor which has a flow-rate control valve installed in a low-pressure side refrigerant path upstream refrigerant suction chamber, and having a spool valve, a spring for biasing the spool valve in a valve closing direction, and a pressure chamber for accumulating pressure for the spool valve to be worked in the valve opening direction; and a flow-rate control valve drive mechanism installed in a path for communication between a refrigerant discharge chamber and the pressure chamber, and having a pilot valve to be normally closed by a spring and to be controlled of a valve opening degree by an exciting current of a solenoid for a high-pressure side refrigerant of the refrigerant discharge chamber to be introduced and controlled as working pressure to the pressure chamber. A flow-rate of a refrigerant to flow in the refrigerant suction chamber is controlled for pressures of the refrigerant suction chamber and a crank chamber to be regulated.
Preferably, the spool valve has a spool groove having opposite side faces having pressure receiving areas equal to each other.
Preferably, the flow-rate control valve drive mechanism detects an evaporator-side pressure upstream the flow-rate control valve, for the pilot valve to be operated in the valve opening direction or a valve closing direction when the evaporator-side pressure varies from a certain pressure with the pilot valve being in a predetermined opening degree, for an opening degree of the flow-rate control valve to be regulated, and for the evaporator-side pressure to be kept at a constant value.
Preferably, the flow-rate control valve drive mechanism has a pressure regulating path for communication between the crank chamber and the evaporator-side of the low-pressure side refrigerant path upstream the flow-rate control valve.
Preferably, the flow-rate control valve drive mechanism has a pressure regulating path for communication between the pressure chamber of the flow-rate control valve and the refrigerant suction chamber.
Preferably, a variable displacement swash plate compressor further has: a temperature detector for detecting a temperature of an evaporator; and a controller for controlling a valve opening degree of the pilot valve in accordance with the temperature of the evaporator detected by the temperature detector.
Preferably, the controller demagnetizes the solenoid for the pilot valve to be closed when the temperature detector detects the temperature of the evaporator less than a freezing temperature.
A second aspect of the invention is provided with a control method for a variable displacement swash plate compressor which has: demagnetizing a solenoid for a pilot valve to be closed when an evaporator is at a temperature less than a freezing temperature; closing a spool valve for a pressure of a refrigerant suction chamber to be fallen lower than that of a crank chamber; and raising an inclined swash plate for a compressing work of the compressor to be reduced to substantially a zero.
According to the above-described inventions, when an electric current which is supplied to a solenoid of a flowrate control valve drive mechanism is reduced to a zero for the solenoid to be demagnetized, a pilot valve is closed. In order to stop supplying working pressure to a pressure chamber by the flow-rate control valve, a spool valve is closed for a flow-rate of the refrigerant flowing in a refrigerant suction chamber to be reduced to a zero. Falling pressure of an evaporator-side upstream the flow-rate control valve of a low-pressure side refrigerant path is stopped, thus preventing the evaporator from freezing.
Therefore, when operating an evaporator for preventing freezing, supplying an exciting current to a solenoid is stopped. Power consumption is reduced and totally closing a spool valve makes a load of the compressor substantially a zero, thus to improve output of a drive source.
Supplying an exciting current to a solenoid is stopped for a spool valve of a flow-rate control valve to be operated to close. Pressure of a refrigerant suction chamber is fallen for differential pressure between the crank chamber and the refrigerant suction chamber to be a maximum value. Inclined swash plate is raised for a piston stroke to be a minimum value and for compressing work to be reduced to substantially a zero, and thus exciting and demagnetizing the solenoid allows operation of a compressor to be turned off and on without a clutch.
Therefore, a structure of the compressor is simplified, a size and a weight of the structure are reduced, and the structure is obtained at advantage cost.
Pressure receiving areas of the opposite side faces of a spool groove installed to a spool valve of a flow-rate control valve are equal to each other. Only controlling a spring force of a spring for biasing the spool valve in a valve closing direction and working pressure that acts on a pressure chamber makes opening and closing strokes of the spool valve establish accuracy, thereby carrying out control of the flow-rate with accuracy.
If a vehicle is suddenly accelerated or decelerated with a pilot valve being at a predetermined opening degree by a predetermined exciting current, an evaporator-side pressure upstream a flow-rate control valve of a low-pressure side refrigerator path varies. Since the evaporator-side pressure is maintained at constant pressure, and variation of a control temperature of the evaporator due to sudden acceleration or deceleration of a vehicle is prevented.
Further a crank chamber communicates with an evaporator side upstream a flow-rate control valve of a low-pressure side refrigerant path through a pressure regulating path such that a pressure of the crank chamber is constantly maintained at the identical value, and variation of the pressure due to blowby gas is prevented, the
Higashihara Shinichiro
Kawachi Masaki
Makishima Hiroyuki
Ogawa Masanori
Takehana Kouetsu
Calsonic Kansei Corporation
Fastovsky Leonid M
Jeffery John A.
McDermott & Will & Emery
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