Patent ID: 6503068
Filing Date: 2003-01-07
Classification: F04C

Abstract:
A variable capacity type pump comprising:a pump casing; a complete round rotor arranged in the pump casing so as to be rotated; a cam ring arranged in a periphery of the rotor, forming a pump chamber with respect to an outer peripheral portion of the rotor and capable of being eccentric with respect to the rotor; a suction port arranged in the pump casing and sucking a working fluid to the pump chamber; a discharge port arranged in the pump casing and discharging the working fluid from the pump chamber; a plurality of vanes received in a grooves of the rotor, protruding so as to freely move in a radial direction and being in contact with an inner periphery of the cam ring at front ends; the working fluid sucked from the suction port being held in a space between the adjacent vanes, the working fluid being transferred due to a rotation of the rotor so as to be discharged from the discharge port; and a discharge amount of the working fluid being increased by increasing an eccentric amount of the cam ring with respect to the rotor, wherein the inner periphery of the cam ring is constituted by a shape of a suction section sucking the working fluid from the suction port, a shape of a first closed section at a bottom dead center transferring the working fluid sucked from the suction port to the discharge port after previously compressing, a shape of a discharge section discharging the working fluid from the discharge port, and a shape of a second closed section transferring the working fluid held in the space between the adjacent vanes at a top dead to the suction port, wherein the inner periphery of the cam ring in the suction section and the discharge section is constituted by a complete round curve and a transient curve, and wherein the inner periphery of the cam ring in the first and second closed section is constituted by a negative slope curve in which a radius of curvature reduces along the rotational direction of the rotor so as to always reduce a dynamic radius of the vane with respect to an increase of the rotational angle of the rotor without relation to the eccentric amount of the cam ring.