The present invention relates to a swash plate type variable displacement compressor.
Japanese Patent Application Publication No. 6-117365 discloses a swash plate type variable displacement compressor (hereinafter referred to merely as “compressor”). The compressor has front and rear housings, a cylinder block, a drive shaft, a swash plate, an inclination angle change mechanism, six pistons, a displacement control valve, and a collection and supply mechanism.
The cylinder block has therein six cylinder bores around the axis of the drive shaft. The front housing has therein a crank chamber. The rear housing has therein a suction chamber and a discharge chamber that are communicable with each cylinder bore. The drive shaft extends through and is rotatably supported by the front housing and the cylinder block. The swash plate is mounted on the drive shaft and in the crank chamber. The swash plate is rotatable in the crank chamber with the rotation of the drive shaft.
The inclination angle change mechanism includes a link mechanism and a wobbling motion conversion mechanism. The link mechanism is comprised of a lug member, a support arm, and a pin. The lug member is mounted on the drive shaft for rotation therewith and located on the front side of the swash plate in the crank chamber. The support arm is formed behind the lug member and connects the lug member and the swash plate. Each piston is received in its corresponding cylinder bore and a compression chamber is thus formed in the cylinder block. The wobbling motion conversion mechanism is comprised of a thrust bearing, a wobbling plate and a connecting rod. Each piston is connected to the swash plate through the wobbling motion conversion mechanism so that the piston reciprocates in the corresponding cylinder bore with rotation of the swash plate. The displacement control valve controls the pressure of the crank chamber.
The collection and supply mechanism is comprised of a communication passage for each cylinder bore and a bypass groove. The six communication passages are formed in the cylinder block and the number of the communication passages is the same as that of the cylinder bores. Each communication passage is formed in the cylinder block extending radially between the drive shaft hole and its corresponding cylinder bore. The bypass groove is formed circumferentially in part of the outer periphery of a rotary valve mounted on the drive shaft. Any two adjacent communication passages are communicable by the bypass groove of the rotary valve that is rotatable synchronously with the drive shaft.
In operation of the compressor, the rotation of the swash plate on the drive shaft causes each piston to reciprocate in the cylinder bore. As the piston is moved from the top dead center toward the bottom dead center, or during the phase of backward stroke of the piston, refrigerant gas is drawn into the cylinder bore. As the piston is moved from the bottom dead center toward the top dead center in the cylinder bore, or during the phase of the forward stroke of the piston, refrigerant gas in the cylinder bore is compressed and discharged out of the cylinder bore. During the phase of the forward stroke, re-expansion of residual refrigerant gas remaining in the cylinder bore even after the discharge phase occurs, before suctioning of refrigerant gas from the suction chamber. A compression chamber that is formed in a cylinder bore from the end of discharge phase after the end of re-expansion phase will be defined as the compression chamber of collection phase or the collection-phase compression chamber. A compression chamber that is formed in a cylinder bore during the compression of refrigerant gas will be defined as the compression chamber of supply phase or the supply-phase compression chamber. The cylinder bore having therein a collection-phase compression chamber will be defined as the cylinder bore of collection phase or the collection-phase cylinder bore. The cylinder bore having therein a supply-phase compression chamber will be defined as the cylinder bore of supply phase or the supply-phase cylinder bore.
In this compressor, the pressure in the crank chamber is changed by the displacement control valve, so that the inclination angle change mechanism changes the inclination angle of the swash plate with respect to a plane extending perpendicularly to the axis of rotation of the drive shaft. Thus, the stroke length of each piston reciprocated can be changed. Thus, the displacement of refrigerant gas per rotation of the drive shaft can be changed.
In the compressor, the collection-phase cylinder bore is communicable with the supply-phase cylinder bore through the communication passage and the residual refrigerant gas bypass groove, so that the residual refrigerant gas in the collection-phase compression chamber is collected and the refrigerant gas thus collected is supplied to the supply-phase compression chamber. Thus, re-expansion of the residual refrigerant gas is prevented and the volumetric efficiency is improved.
In the above-described conventional compressor, however, noise development tends to occur when the inclination angle is less than the maximum angle, as compared when the swash plate is at the maximum inclination angle position.
Additionally, the collection and supply of residual refrigerant gas causes the temperature of refrigerant gas in the compression chamber to be increased due to the residual refrigerant gas of high temperature and therefore, the power required for the compression is increased. As a result, COP (Coefficient Of Performance) is deteriorated.
The present invention is directed to providing a swash plate type variable displacement compressor that achieves silence in operation and improved COP.