Variable displacement oil pump and method for producing variable displacement oil pump

Abstract

A variable displacement oil pump according to the present invention has a protrusion ( 46 ) that is partially formed on a spring contact surface ( 451 ) of an arm part ( 45 ) of a cam ring ( 4 ) so as to overlap with part of the outer circumference of a coil spring (SP). This protrusion ( 46 ) restricts tilting of the coil spring (SP) and makes it possible to suppress positional deviation of the coil spring (SP). Furthermore, because the protrusion ( 46 ) is provided partially on the spring contact surface ( 451 ) of the arm part ( 45 ) of the cam ring 4 , the coil spring (SP) need only be pushed inward of the protrusion ( 46 ) when installing the coil spring (SP), thus making it possible to ensure ease of installation of the coil spring (SP).

1 . A variable displacement oil pump comprising:
 a housing including a pump container;   a cam ring movably contained in the pump container;   a pump element that is rotatably contained in an inner circumferential side of the cam ring, and forms pump chambers in cooperation with the cam ring;   a coil spring that is disposed in the pump container, and biases the cam ring in a direction to increase an eccentricity of the cam ring with respect to a rotational axis of the pump element; and   a projection that is formed in the cam ring, extends in a longitudinal direction of the coil spring from a spring contact surface being in contact with the coil spring, and overlaps with a part of an outer periphery of the coil spring.   
     
     
         2 . The variable displacement oil pump as claimed in  claim 1 , wherein the housing includes a first restriction wall structured to restrict outward movement of the coil spring in a radial direction orthogonal to the rotational axis of the pump element. 
     
     
         3 . The variable displacement oil pump as claimed in  claim 1 , wherein the cam ring includes a second restriction wall structured to restrict inward movement of the coil spring in a radial direction orthogonal to the rotational axis of the pump element. 
     
     
         4 . The variable displacement oil pump as claimed in  claim 1 , wherein the projection is one in number. 
     
     
         5 . The variable displacement oil pump as claimed in  claim 1 , wherein the projection is positioned to overlap with a center of an outer diameter of the coil spring. 
     
     
         6 . The variable displacement oil pump as claimed in  claim 1 , wherein the housing includes a third restriction wall structured to restrict movement of the coil spring to a side opposite to the projection in a radial direction of the coil spring. 
     
     
         7 . The variable displacement oil pump as claimed in  claim 1 , wherein:
 the coil spring is disposed in an oil passage that is continuous from an oil suction inlet formed in the housing, to the pump chambers; and   the projection is positioned downstream with respect to the coil spring, in the oil passage.   
     
     
         8 . A method for producing the variable displacement oil pump as claimed in  claim 1 , the method comprising:
 a cam ring installation step for disposing the cam ring in the pump container; and   a coil spring installation step for disposing the coil spring in the pump container after the cam ring installation step, wherein the coil spring installation step includes:   retaining the coil spring in a compressed state with use of a jig including a first retainer and a second retainer, wherein the first retainer has a bifurcated shape with a cut-out part at a middle thereof and is structured to retain a first end of the coil spring, and the second retainer is structured to retain a second end of the coil spring; and   disposing the coil spring in the pump container by inserting the jig between the pump container and the cam ring in order to avoid the projection with use of the cut-out part of the first retainer.