Variable Displacement Compressor

Abstract

Disclosed is a variable displacement compressor having improved compressor performance such as reduced pulsation and improved durability and resistance to pressure and allowing smooth and high-precision control of a swash plate tilt angle at a target tilt angle by using an axial movement member. The variable displacement compressor is provided with a cylinder head in which a suction chamber and a discharge chamber are formed, a cylinder block having a cylinder bore into which a piston is inserted at a condition capable of being reciprocated, a crank chamber formed by the cylinder block and a front housing, a swash plate which is disposed in the crank chamber and which is rotated with a main shaft and is supported so that the tilt angle thereof can be changed relative to the main shaft, and a movement conversion mechanism for converting the rotational movement of the swash plate to the reciprocating movement of the piston, wherein: a suction path for intake of a suction gas into the compressor is formed so as to open into the crank chamber; a communication path for communicating the crank chamber and the suction chamber is provided in the cylinder block; around the main shaft, an axial movement member is provided that can move in a direction along the axis of the main shaft in an essentially one to one correspondence with the tilt angle of the swash plate; the axial movement member is disposed such that one end is applied with the pressure in the crank chamber, and the other end is applied with an intermediate pressure between the pressure in the discharge chamber and the pressure in the suction chamber; and an intermediate pressure control mechanism which can control the intermediate pressure is also provided.

1 . A variable displacement compressor provided with a cylinder head in which a suction chamber and a discharge chamber are formed, a cylinder block having a cylinder bore into which a piston is inserted at a condition capable of being reciprocated, a crank chamber formed by said cylinder block and a front housing, a swash plate which is disposed in said crank chamber and which is rotated with a main shaft and is supported so that a tilt angle thereof can be changed relative to said main shaft, and a movement conversion mechanism for converting rotational movement of said swash plate to reciprocating movement of said piston, characterized in that a suction path for intake of a suction gas into said compressor is formed so as to open into said crank chamber, a communication path for communicating said crank chamber and said suction chamber is provided in said cylinder block, an axial movement member, which can move in a direction along an axis of said main shaft in an essentially one to one correspondence with said tilt angle of said swash plate, is provided around said main shaft, said axial movement member is disposed such that one end is applied with a pressure in said crank chamber and the other end is applied with an intermediate pressure between a pressure in said discharge chamber and a pressure in said suction chamber, and an intermediate pressure control mechanism which can control said intermediate pressure is also provided. 
     
     
         2 . The variable displacement compressor according to  claim 1 , wherein said suction path is formed in said front housing. 
     
     
         3 . The variable displacement compressor according to  claim 1 , wherein said suction path is formed from said cylinder block to said front housing. 
     
     
         4 . The variable displacement compressor according to  claim 1 , wherein said suction path is formed from said cylinder head to said front housing through said cylinder block. 
     
     
         5 . The variable displacement compressor according to  claim 1 , wherein an intermediate pressure chamber controlled at said intermediate pressure is formed on said other end of said axial movement member, and said intermediate pressure chamber is sealed against said crank chamber. 
     
     
         6 . The variable displacement compressor according to  claim 5 , wherein said intermediate pressure control mechanism has a communication path (A) between said discharge chamber and said intermediate pressure chamber, a control valve provided in said communication path (A) and capable of controlling pressure reduction from a pressure in said discharge chamber to a predetermined intermediate pressure, a communication path (B) between said intermediate pressure chamber and said suction chamber, and a throttle provided in said communication path (B). 
     
     
         7 . The variable displacement compressor according to  claim 5 , wherein said intermediate pressure control mechanism has a communication path between said discharge chamber and said intermediate pressure chamber, a communication path between said intermediate pressure chamber and said suction chamber, and a control valve which is provided in both said communication paths and which can control pressure reduction from a pressure in said discharge chamber to a predetermined intermediate pressure and can control a degree of throttling for a gas flow from said intermediate pressure chamber to said suction chamber. 
     
     
         8 . The variable displacement compressor according to  claim 5 , wherein said intermediate pressure control mechanism has a communication path (A) between said discharge chamber and said intermediate pressure chamber, a throttle provided in said communication path (A), a communication path (B) between said intermediate pressure chamber and said suction chamber, and a control valve provided in said communication path (B) and capable of controlling pressure reduction to a predetermined intermediate pressure in said intermediate pressure chamber. 
     
     
         9 . The variable displacement compressor according to  claim 1 , wherein said movement conversion mechanism has a wabble plate in which said rotational movement of said swash plate is converted into a wabble movement of said wabble plate and which transmits said wabble movement to said piston via a connecting rod and makes said piston reciprocate, and a rotation preventing mechanism of said wabble plate. 
     
     
         10 . The variable displacement compressor according to  claim 9 , wherein said rotation preventing mechanism of said wabble plate comprises (a) an inner ring provided in a housing movably in an axial direction although rotation is prevented, and having a plurality of guide grooves for guiding a plurality of balls provided for power transmission, (b) an outer ring having a plurality of guide grooves for guiding said balls at positions opposing respective guide grooves of said inner ring, connected with said wabble plate at an outer circumference and supported at a condition capable of wabbling together with said wabble plate, and (c) a plurality of balls held by said guide grooves formed in said inner ring and said outer ring at a condition of opposing each other and performing power transmission by being compressed between said guide grooves, and said inner ring is formed as said axial movement member. 
     
     
         11 . The variable displacement compressor according to  claim 10 , wherein said rotation preventing mechanism of said wabble plate further comprises (d) a sleeve functioning as a wabble central member of said wabble movement of said wabble plate, provided on said main shaft to rotate relatively to said main shaft and to move in an axial direction, and engaged with said inner ring movably in an axial direction together with said inner ring, and said outer ring is supported on said sleeve wabblingly 
     
     
         12 . The variable displacement compressor according to  claim 1 , wherein said movement conversion mechanism is formed as a mechanism for conversion into reciprocal movement of said piston via a pair of shoes slid on both surfaces of an outer circumference of said swash plate. 
     
     
         13 . The variable displacement compressor according to  claim 1 , wherein said tilt angle of said swash plate can be changed through a cam mechanism interposed between said main shaft and said swash plate, and a cam profile of said cam mechanism is set so that a momentary rotation center of said swash plate is given at a position at which a load due to a compression reactive force of at least one piston among a plurality of pistons present in a compression stroke operates as a couple moment acting in a direction for decreasing displacement relatively to said swash plate. 
     
     
         14 . The variable displacement compressor according to  claim 13 , wherein said cam mechanism comprises a sliding engagement mechanism formed by a slot formed on one of an arm extending from main shaft side and an arm extending from swash plate side and a pin provided on the other, and said cam profile is set by forming a shape of said slot as an S-shape. 
     
     
         15 . The variable displacement compressor according to  claim 1 , wherein respective parts are set so that a total balance of a couple moment generated in a tilt angle changing plane of said swash plate by at least rotational and reciprocal movement of said respective parts becomes one in a direction for decreasing tilt angle in every tilt angle of said swash plate. 
     
     
         16 . The variable displacement compressor according to  claim 15 , wherein a spring for urging at least said swash plate in a direction for decreasing tilt angle is further provided, and a total balance of a couple moment generated in a tilt angle changing plane of said swash plate by said rotational and reciprocal movement including by an urging force of said spring is set so as to become one in a direction for decreasing tilt angle in every tilt angle of said swash plate.