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Control valve for variable displacement compressorRelated Patent Categories: Refrigeration, Automatic Control, Refrigeration Producer, Of Or By Evaporation ZoneControl valve for variable displacement compressor description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060053812, Control valve for variable displacement compressor. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCES TO RELATED APPLICATIONS, IF ANY [0001] This application claims priority of Japanese Application No. 2004-269661 filed on Sep. 16, 2004 and entitled "CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR" and No. 2005-161179 filed on Jun. 1, 2005, entitled "CONTROL VALVE FOR VARIABLE DISPLACEMENT COMPRESSOR". BACKGROUND OF THE INVENTION [0002] (1) Field of the Invention [0003] The present invention relates to a control valve for a variable displacement compressor, and more particularly to a control valve for a variable displacement compressor, which is mounted on a variable displacement compressor as a component of a refrigeration cycle of an automotive air conditioner, for controlling the flow of refrigerant discharged therefrom to a constant flow rate. [0004] (2) Description of the Related Art [0005] A compressor used in the refrigeration cycle of an automotive air conditioner, for compressing refrigerant, uses an engine as a drive source, and hence is incapable of performing rotational speed control. To eliminate the inconvenience, a variable displacement compressor capable of varying the compression capacity of refrigerant is employed so as to obtain an adequate cooling capacity without being constrained by the rotational speed of the engine. [0006] In such a variable displacement compressor, a wobble plate fitted on a shaft driven by the engine for rotation has compression pistons connected thereto, and by varying the inclination angle of the wobble plate, the stroke of the pistons is varied to vary the discharge amount of refrigerant. [0007] The inclination angle of the wobble plate is continuously changed by introducing part of compressed refrigerant into a hermetically closed crankcase, and causing a change in the pressure of the introduced refrigerant, thereby changing the balance of pressures acting on the opposite sides of each piston. [0008] The pressure in the crankcase is changed by a control valve for a variable displacement compressor, which is disposed between the discharge chamber of the compressor and the crankcase or between the crankcase and the suction chamber. This control valve provides control e.g. such that communication therethrough is allowed or blocked so as to maintain the differential pressure across a valve that controls the flow rate of refrigerant flowing from the discharge chamber into the crankcase, at a predetermined value, and more particularly, the differential pressure can be set to the predetermined value by externally changing a value of control current supplied to the control valve. With this configuration, when the rotational speed of the engine rises to increase the discharge pressure, the pressure introduced into the crankcase increases to reduce the capacity of refrigerant that can be compressed, whereas when the rotational speed of the engine lowers, the pressure introduced into the crankcase decreases to increase the capacity of refrigerant that can be compressed, whereby the amount of compression capacity of the compressor is maintained constant irrespective of the rotational speed of the engine. [0009] One known method of controlling the compression capacity of such a variable displacement compressor uses a control valve therefor, which provides control such that the flow rate of refrigerant discharged from the compressor becomes constant (see e.g. Japanese Unexamined Patent Publication (Kokai) No. 2001-107854 (Paragraph numbers [0034] to [0036], FIGS. 2 and 3)). [0010] According to this control valve for a variable displacement compressor, two pressure sensors are provided at locations spaced from each other in the direction of flow through the refrigerant passage toward the suction chamber; the differential pressure between the pressure monitoring points of the two sensors is detected to thereby indirectly grasp the flow rate of refrigerant drawn in; the control valve controls the flow rate of refrigerant introduced from the discharge chamber into the crankcase such that the suction flow rate of refrigerant becomes constant to thereby control the flow rate of refrigerant discharged from the compressor such that it becomes constant. [0011] However, the conventional control valve for a variable displacement compressor that controls the compressor such that the discharge flow rate of refrigerant becomes constant requires expensive pressure sensors and a control device for detecting the differential pressure across the refrigerant circulation passage and controlling the control valve for the compressor based thereon, which leads to an increase in the cost of the automotive air conditioner. SUMMARY OF THE INVENTION [0012] The present invention has been made in view of these problems, and an object thereof is to provide a control valve for use in a variable displacement compressor, for controlling the discharge flow rate of refrigerant to a constant flow rate, which can be constructed compact in size without necessitating pressure sensors for detecting a differential pressure. [0013] To solve the above problem, the present invention provides a control valve for a variable displacement compressor, for controlling a flow of refrigerant discharged from the compressor to a constant flow rate, comprising a first valve that has a passage area thereof set according to a flow rate of refrigerant introduced from a discharge chamber of the compressor and flowing out to an outlet port of the compressor, a second valve that controls pressure in a crankcase of the compressor in a manner interlocked with the first valve such that a differential pressure across the first valve is maintained at a predetermined differential pressure, and a solenoid that sets a differential pressure across the passage having the passage area set by the first valve to the predetermined differential pressure dependent on a flow rate of refrigerant to which the flow of refrigerant is to be controlled. [0014] The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a central longitudinal cross-sectional view showing details of the construction of a control valve for a variable displacement compressor, according to a first embodiment of the present invention. [0016] FIG. 2 is an enlarged cross-sectional view of essential parts of the control valve according to the first embodiment in a state immediately after energization thereof. [0017] FIG. 3 is an enlarged cross-sectional view of essential parts of the control valve according to the first embodiment in a transitional state after energization thereof. [0018] FIG. 4 is an enlarged cross-sectional view of essential parts of the control valve according to the first embodiment in a balanced state. [0019] FIG. 5 is an enlarged cross-sectional view of essential parts of the control valve according to the first embodiment in a transitional state at the time of a rapid increase in discharge pressure. [0020] FIG. 6 is a central longitudinal cross-sectional view showing details of the construction of a control valve for a variable displacement compressor, according to a second embodiment of the present invention. Continue reading about Control valve for variable displacement compressor... Full patent description for Control valve for variable displacement compressor Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Control valve for variable displacement compressor patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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