Oil pump

Abstract

A guide slot having an elongated-hole shape is formed in a capacity adjustment member, so that displacement of the capacity adjustment member is regulated, by a guide pin inserted into the guide slot, to a longitudinal direction of the guide slot. Two spaces separated by the guide pin into one side and the other side in the longitudinal direction of the guide slot are formed inside the guide slot, and a communicating passage is provided so as to communicate the spaces with each other.

What is claimed is: 
     
         1 . An oil pump comprising:
 an input shaft;   an inlet port;   a discharge port;   a capacity-variable mechanism configured to change a discharge amount per one rotation of the input shaft, the capacity-variable mechanism including a capacity adjustment member, the capacity adjustment member having a guide slot having an elongated-hole shape, the guide slot including a guided surface provided on an inner periphery of the guide slot; and   a housing including a guide pin, the guide pin being inserted into the guide slot, the guide pin including a guide surface provided on an outer periphery of the guide pin,   the guide pin being configured to regulate displacement of the capacity adjustment member to a longitudinal direction of the guide slot, the guide pin being configured to separate the guide slot into a first space and a second space in the longitudinal direction, the guide surface of the guide pin making sliding contact with the guided surface of the guide slot, oil flowing between the first space and the second space via a gap between the guide surface and the guided surface, and   at least one of the guide pin and the capacity adjustment member being provided with a communicating passage, the communicating passage being configured to communicate the first space with the second space.   
     
     
         2 . The oil pump according  claim 1 , wherein
 a sectional area of the communicating passage is larger than a sectional area of the gap between the guide surface and the guided surface.   
     
     
         3 . The oil pump according to  claim 1 , wherein
 the guide pin includes a first sectional area part and a second sectional area part along an axial direction of the guide pin, the first sectional area part having a sectional area smaller than a sectional area of the second sectional area part, and   the guide pin includes a recess provided on an outer peripheral surface of the guide pin in the first sectional area part, the recess constituting the communicating passage.   
     
     
         4 . The oil pump according to  claim 3 , wherein
 the first sectional area part is provided at an axially intermediate part of the guide pin.   
     
     
         5 . The oil pump according to  claim 3 , wherein
 the first sectional area part of the guide pin includes a tapered part having a sectional area that gradually increases toward the second sectional area part.   
     
     
         6 . The oil pump according to  claim 1 , wherein
 the communicating passage penetrates through the guide pin, and   the communicating passage is configured to communicate the first space with the second space.   
     
     
         7 . The oil pump according to  claim 1 , wherein
 an inner peripheral surface of the guide slot has a groove extending in the longitudinal direction of the guide slot, and   the groove constitutes the communicating passage.   
     
     
         8 . The oil pump according to  claim 1 , wherein
 the communicating passage is provided inside the capacity adjustment member, and   both ends of the communicating passage are opened on an inner peripheral surface of the guide slot.   
     
     
         9 . The oil pump according to  claim 1 , wherein
 the housing includes a low hydraulic chamber, and   the guide slot communicates with the inlet port via the low hydraulic chamber.   
     
     
         10 . The oil pump according to  claim 1 , further comprising:
 a drive rotor as an external gear rotated by the input shaft; and   a driven rotor as an internal gear meshing with the drive rotor so as to be rotated accordingly, wherein   the housing includes a control hydraulic chamber,   the capacity adjustment member has an annular holding portion configured to rotatably hold the driven rotor from an outer periphery of the driven rotor, the capacity adjustment member is configured to be displaced by a hydraulic pressure of the control hydraulic chamber, and   the capacity-variable mechanism is configured to change relative positions of the drive rotor and the driven rotor to the inlet port and the discharge port, along with the displacement of the capacity adjustment member, such that a discharge amount of the oil pump is changed.