Gerotor-type oil pump

Abstract

An oil pump includes a housing defining a pump cavity having an inner circumferential wall with a first segment located in a low-pressure side of the pump cavity. The first segment defines a recessed cutout. A gerotor pump set is disposed in the cavity and includes an inner drive rotor and an outer driven annulus. An outer circumferential wall of the outer annulus and the cutout cooperate to form an increased radial clearance to reduce friction losses between the outer annulus and the housing.

What is claimed is: 
     
         1 . An oil pump comprising:
 a housing defining a pump cavity having an inner circumferential wall with a first segment located in a low-pressure side of the pump cavity, the first segment defining a recessed cutout; and   a gerotor pump set disposed in the cavity and including an inner drive rotor and an outer driven annulus, wherein an outer circumferential wall of the outer annulus and the cutout cooperate to form an increased radial clearance to reduce friction losses between the outer annulus and the housing.   
     
     
         2 . The oil pump of  claim 1 , wherein the first segment further defines a second recessed cutout circumferentially spaced from the cutout. 
     
     
         3 . The oil pump of  claim 2 , wherein the first segment defines a bumper between the cutout and the second cutout. 
     
     
         4 . The oil pump of  claim 1 , wherein the recessed cutout has a depth of at least 0.2 millimeters. 
     
     
         5 . The oil pump of  claim 1 , wherein the inner circumferential wall defines an inner surface, and recessed cutout has a first surface extending radially outboard from the inner surface, a back surface extending circumferentially from the first surface, and a second surface extending radially inboard from the back surface to the inner surface. 
     
     
         6 . The oil pump of  claim 1 , wherein the pump cavity further has a face defining a recessed outlet shadow port having a first portion radially inboard of a root circle of the inner drive rotor. 
     
     
         7 . The oil pump of  claim 6 , wherein the outlet shadow port further has a second portion radially outboard of the root circle. 
     
     
         8 . The oil pump of  claim 7 , wherein the first portion is recessed shallower than the second portion. 
     
     
         9 . The oil pump of  claim 1  further comprising a cover attached to the housing to seal the pump cavity, the cover defining a recessed port located radially inboard of a root circle of the inner drive rotor. 
     
     
         10 . An oil pump comprising:
 a housing defining a face and an inner circumferential wall cooperating with the face to define a pump cavity having a high-pressure side and a low-pressure side, wherein the circumferential wall defines a recessed cutout extending arcuately along a portion of the circumferential wall in the low-pressure side;   a gerotor pump set disposed in the cavity and including:
 an outer driven annulus defining internal lobes and an outer circumferential wall circumscribed by the inner circumferential wall, and 
 an inner drive rotor eccentrically received within the outer annulus and defining external lobes cooperating with the internal lobes to define a plurality of fluid chambers; and 
   a driveshaft extending through the face and coupled to the inner drive rotor, the driveshaft being configured to rotate the gerotor pump set within the cavity such that the outer annulus rotates relative to the inner circumferential wall, wherein the cutout forms an increased radial clearance between the inner and outer circumferential walls to reduce friction losses when the outer annulus rotates relative to the housing.   
     
     
         11 . The oil pump of  claim 10 , wherein the circumferential wall further defines a second recessed cutout extending arcuately along another portion of the circumferential wall that is circumferentially spaced from the cutout and is in the low-pressure side. 
     
     
         12 . The oil pump of  claim 11 , wherein the circumferential wall between the cutout and the second cutout forms a bumper. 
     
     
         13 . The oil pump of  claim 10  further comprising a cover defining an inlet port and an outlet port, wherein a portion of the inlet port or the outlet port is disposed radially inboard of a root circle of the inner drive rotor. 
     
     
         14 . The oil pump of  claim 10  further comprising a cover defining an outlet port, wherein a portion of the outlet port is disposed radially inboard of a root circle of the inner drive rotor. 
     
     
         15 . The oil pump of  claim 10  further comprising a cover having a face disposed over the pump cavity and defining a recessed portion at least partially disposed radially inboard of a root circle of the inner drive rotor. 
     
     
         16 . The oil pump of  claim 10  further comprising an electric machine operably coupled to the driveshaft. 
     
     
         17 . An oil pump comprising:
 a housing defining a pump cavity;   a gerotor pump set disposed in the cavity and including an inner drive rotor and an outer driven annulus; and   a cover including a front face disposed over the pump cavity, the front face defining an inlet port and an outlet port, wherein a portion of the outlet port is radially inboard of a root circle of the inner drive rotor.   
     
     
         18 . The oil pump of  claim 17 , wherein the portion is a shallow portion of the outlet port, and the outlet port further has a main portion, and wherein the main portion has an axially extending wall and the shallow portion has a bottom wall extending radially from the axially extending wall. 
     
     
         19 . The oil pump of  claim 18 , wherein housing defines a back face of the pump cavity, the back face defining inlet and outlet shadow ports that are opposite the inlet and outlet ports, respectively, wherein a portion of the outlet shadow port is radially inboard of the root circle of the inner drive rotor. 
     
     
         20 . The oil pump of  claim 19 , wherein the portion of the outlet shadow port is a shallow portion, and the outlet shadow port further has a deeper portion that is radially outboard of the root circle of the inner drive rotor.