For car air conditioning, engine power requirements for a variable displacement compressor is less than a fixed displacement compressor as flow of the refrigerant can be varied as per cooling demands. Also, sudden clutching and declutching of a fixed displacement type compressor creates problem on smooth running of the engine.
The mechanism of this new variable displacement compressor is less complicated than other compressors of this category and so cheap as well and appropriate for car air conditioning.
On a circular base platform a number of compressor cylinders are arranged around the centre near the circumference of the platform. A central column stands just at the centre of the base platform. A driving disc mounted at the top end of the column through ball and socket joint at disc centre and the disc can oscillate up and down in every direction throughout 360 degree of horizontal plane about its centre. The piston rods are connected near the outer edge of the driving disc throughout its circumference through ball and socket joints. The lower end of the vertical driveshaft is forked end and placed just above the centre point of driving disc and this shaft is attached with drive unit. A driving arm fixed at its mid position with the fork end of driveshaft by a pin acts as fulcrum pin. Two rolls, one is pressure roll and the other one is guide roll, are attached with the driving arm and these rolls control the oscillatory motion of driving disc according to the inclination of driving arm. Rotation blocker and stopper rod prevent undesirable rotational movement of driving disc due to the pressure of rotating rolls. A control sleeve enclosed the driveshaft sleeve upside and linked with driving arm. The sleeve is further enclosed by the stroke control disc as such that the sleeve when rotates, the stroke control disc remains stationary. If the stroke control disc is pulled or pushed along the driveshaft axis through servo controlled pistons, the control sleeve also slides up and down along the shaft for the flanges of the sleeve and so through control link, the driving arm turns about its fulcrum and amount of inclination of driving disc is determined.
When the driving arm rotates with the driveshaft, the control sleeve also rotates as it is connected with the driving arm through a control link. The position of the sleeve is controlled by a stroke control disc as per requirement through servo control. When piston stroke is to be increased, control sleeve is brought to lower resulting the control link to press the pressure roll end of driving arm more downward, so inclination of driving disc is more and degree of oscillation of disc is also more, hence piston stroke is also increased. When control sleeve is pulled upwards by stroke control disc, the driving arm position changes to discharge refrigerant less as now guide roll presses the driving disc towards horizontal plane.