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Variable displacement compressor

Variable displacement compressor description/claims

This application claims priority to Japanese Patent application no. 2006-330899 filed Dec. 7, 2006.

The present invention relates to a variable displacement compressor that is operable to adjust the pressure in a pressure control chamber of the compressor thereby to change angle of inclination of a swash plate of the compressor, whereby the displacement of the compressor is controlled.

Japanese Patent Application Publication No. 2004-28090 discloses this type of variable displacement compressor (hereinafter referred to merely as “compressor”). Referring to FIG. 10 showing the compressor of the Publication, it has a housing in which a crank chamber 80 is formed and a shaft 81 rotatably supported by the housing and extending through the crank chamber 80. A rotor 92 is mounted on the shaft 81 in the crank chamber 80. A swash plate 82 is supported by the shaft 81 in the crank chamber 80 in such a way that the inclination angle of the swash plate 82 relative to the shaft 81 is variable. Plural pistons 83 engage with the swash plate 82 through plural pairs of shoes 84, respectively. The housing has formed therethrough plural cylinder bores 94 which receive therein the pistons 83 for reciprocation, respectively.

The housing has a discharge chamber 85 and a suction chamber 86. The discharge chamber 85 and the crank chamber 80 are in communication with each other through a first communication passage 87 and a second communication passage 88. The suction chamber 86 and the crank chamber 80 are in communication with each other through a bleed passage. The bleed passage includes an axial passage 89 formed axially in the shaft 81, a communication hole 90 formed in the shaft 81 so as to communicate with the crank chamber 80 and the axial passage 89 and a third passage 91 communicating with the axial passage 89 and the suction chamber 86. As shown in FIG. 10, the communication hole 90 is located between the swash plate 82 and the rotor 92.

In the above compressor, part of refrigerant gas in the discharge chamber 85 flows into the crank chamber 80 through the first communication passage 87 and the second communication passage 88. The refrigerant gas in the crank chamber 80 flows out thereof from the communication hole 90 to the suction chamber 86 through the axial passage 89 and the third passage 91. Thus, the compressor is operable to adjust the pressure in the crank chamber 80 thereby to change the angle of inclination of the swash plate 82, whereby the displacement of the compressor is controlled.

The refrigerant gas flowing from the discharge chamber 85 to the crank chamber 80 contains lubricating oil. The blow-by gas leaking into the crank chamber 80 through a clearance between the cylinder bore 94 and its corresponding piston 83 also contains lubricating oil. Before the refrigerant gas including the blow-by gas passing through the crank chamber 80 moves into the communication hole 90, the lubricating oil in the gas is supplied to various sliding parts (such as a sliding part between the swash plate 82 and the shoes 84) in the crank chamber 80. Specifically, the lubricating oil in the gas passing through the crank chamber 80 is separated therefrom by the centrifugal force of various rotating parts such as the swash plate 82 and the rotor 92 that are driven to rotate by the shaft 81 and dispersed around the shaft 81, the inner wall surface of the crank chamber 80 and the various sliding parts in the crank chamber 80. Thus, the sliding parts are lubricated by the lubricating oil.

On the other hand, because the lubricating oil in the refrigerant gas is dispersed around the shaft 81, the communication hole 90 and its vicinities are lack of lubricating oil, so that the lubricating oil in the crank chamber 80 does not sufficiently flow into the suction chamber 86 through the communication hole 90, the axial passage 89 and the third passage 91. Therefore, there exists an excessive amount of lubricating oil in the crank chamber 80. When such excessive amount of lubricating oil is stirred by the rotation of the swash plate 82 and the rotor 92, the lubricating oil is heated with the result that its viscosity and lubricity are reduced.

The inlet of the bleed passage through which the refrigerant gas in the crank chamber 80 flows out thereof to the suction chamber 86 may be formed, for example, in a stationary part of the compressor such as the end face of the housing or the cylinder block which forms the crank chamber 80 so that the lubricating oil is less subjected to the influence of the centrifugal force. In such structure, however, an excessive amount of the lubricating oil flows into the suction chamber 86, so that the amount of the lubricating oil in the crank chamber 80 is reduced and the sliding parts of the compressor will be poorly lubricated, accordingly.

The present invention, which has been made in light of the above problems, is directed to a variable displacement compressor which ensures an appropriate amount of lubricating oil in a pressure control chamber of the compressor.

In accordance with an aspect of the present invention, a variable displacement compressor includes a compressor housing, a rotary shaft, a lug plate, a swash plate, a hinge mechanism, a supply passage and a bleed passage. The compressor housing has a pressure control chamber, a discharge pressure region and a suction pressure region. The rotary shaft has a front end and a rear end. The rotary shaft is rotatably supported at the front end by a front portion of the compressor housing and at the rear end by a rear portion of the compressor housing, respectively. The lug plate is fixed on the rotary shaft in the pressure control chamber. The swash plate is accommodated in the pressure control chamber. The hinge mechanism is provided between the lug plate and the swash plate. The swash plate is directly supported by the rotary shaft and connected to the lug plate through the hinge mechanism so that the swash plate is rotatable in synchronization with the rotary shaft and the lug plate while inclination angle of the swash plate is variable. The supply passage communicates with the discharge pressure region and the pressure control chamber. The bleed passage communicates with the suction pressure region and the pressure control chamber. Pressure in the pressure control chamber is adjusted by supplying refrigerant gas in the discharge pressure region to the pressure control chamber through the supply passage and releasing the refrigerant gas in the pressure control chamber to the suction pressure region through the bleed passage, thereby to change the inclination angle of the swash plate, whereby displacement of the compressor is controlled. The pressure control chamber has a front region which extends between the swash plate and the lug plate, and a rear region on the opposite side of the swash plate as viewed from the lug plate. The rotary shaft has an axial bleed passage which forms part of the bleed passage and an inlet which is in communication with the axial bleed passage and opened to the front region of the pressure control chamber. At least one of the swash plate and the rotary shaft has a communication passage. The front region and the rear region of the pressure control chamber are in communication with each other through the communication passage.

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.

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal sectional view showing a variable displacement compressor according to an embodiment of the present invention;

FIG. 2 shows the front of a swash plate of the variable displacement compressor of FIG. 1;

FIG. 3 is side view showing the swash plate of FIG. 1;

FIG. 4 shows the rear of the swash plate of FIG. 1;

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