Positive-Displacement Pump, Method for Operating a Positive-Displacement Pump, and Steering System

Abstract

A positive-displacement pump, in particular a vane-type pump for the delivery of a fluid for a consumer of a steering system includes a rotor, a cam ring, a housing-side control plate, and a cover-side control plate that form, in an assembled state, a rotor assembly. The housing-side control plate is arranged adjacent to a housing face surface in an axial direction and the cover-side control plate is arranged adjacent to a cover face surface in the axial direction. The rotor assembly is movable in the axial direction between the housing face surface and the cover face surface.

1 . A positive displacement pump for delivering a fluid for a consumer of a steering system, comprising:
 a pump housing;   a cam ring arranged in the pump housing;   a rotor mounted rotatably in the cam ring, the rotor having slots in which vanes are guided in a radially displaceable manner, the vanes configured to be acted upon with a fluid pressure by way of a channel located behind the vanes, wherein the channel is formed in the rotor and is configured to connect the slots to a pressure side of the positive displacement pump, and wherein outer vane ends are configured to be positioned against an inner wall of the cam ring; and   a working chamber formed by the cam ring and the rotor, the working chamber is bounded in an axial direction by an end side of a housing side control plate and by an end side of a cover side control plate,   wherein the rotor, the cam ring the housing side control plate, and the cover side control plate in the assembled state form a rotor assembly,   wherein the housing side control plate is arranged in the axial direction adjacent to a housing end surface and the cover side control plate is arranged in the axial direction adjacent to a cover end surface, and   wherein the rotor assembly is movable in the axial direction between the housing end surface and the cover end surface.   
     
     
         2 . The positive displacement pump as claimed in  claim 1 , wherein:
 a direction of rotation of the rotor is reversible,   the fluid can be delivered in a first direction of rotation of the rotor or in a second direction of rotation of the rotor, and   during operation, a respective pressure side of the positive displacement pump positions the rotor assembly against the housing end surface or the cover end surface lying opposite the pressure side of the positive displacement pump.   
     
     
         3 . The positive displacement pump as claimed in  claim 2 , wherein a channel system, which is formed in the rotor, of a pressure supply behind the vanes is closable in a sealing manner on a side of the rotor assembly bearing against the housing end surface or the cover end surface. 
     
     
         4 . The positive displacement pump as claimed in  claim 1 , wherein:
 in an inoperative position, the rotor assembly is spaced apart from the housing end surface and the cover end surface, and   a gap formed between the rotor assembly and in each case the housing end surface and the cover end surface is at least 0.2 mm.   
     
     
         5 . The positive displacement pump as claimed in  claim 1 , wherein:
 a first end side of the rotor assembly and a second end side of the rotor assembly each have an annular groove into which an O ring formed from an elastic material or a spring element is fitted,   in order to space the rotor assembly from the housing end surface and the cover end surface, a thickness of the O ring and of the spring element are configured to be greater than a depth of the groove, and   a spring constant of the O ring and of the spring element is at least 200 N/mm.   
     
     
         6 . The positive displacement pump as claimed in  claim 1 , wherein a respective pressure side and suction side of the positive displacement pump depending on the direction of rotation of the rotor are separated from each other by a sealing ring arranged on an outer side of the cam ring. 
     
     
         7 . The positive displacement pump as claimed in  claim 1 , wherein:
 the rotor has, on a first end surface or on a second end surface, an annular groove, into which a spring element is inserted, and   the spring element engages under the inner vane ends of the vanes and positions the vanes against the inner wall of the cam ring.   
     
     
         8 . The positive displacement pump as claimed in  claim 1 , wherein:
 the rotor has, on a first end surface or on a second end surface, an annular groove, into which a tubular body, which is inserted into the housing side control plate or into the cover side control plate, projects with an equidistant sliding curve with respect to the cam ring, and   when the rotor is started up, the vanes, by contact with the tubular body, are extendable in the radial direction of the rotor in the respective slots for positioning the outer vane ends against the inner wall of the cam ring.   
     
     
         9 . The positive displacement pump as claimed in  claim 8 , wherein:
 the tubular body projects at least 3 mm into the groove formed on the first end surface or on the second end surface of the rotor, and   the tubular body is in the form of a metal sheet and is secured at an annular groove formed in the housing side control plate or in the cover side control plate.   
     
     
         10 . The positive displacement pump as claimed in  claim 8 , wherein a pressure against the vanes from behind the vanes is controllable by a size difference between an end side of the tubular body, which end side is adjacent to the rotor, and a depth of the annular groove formed in the first end surface or in the second end surface of the rotor. 
     
     
         11 . A method for operating a positive displacement pump for delivering a fluid for a consumer of a steering system, comprising:
 providing a pump housing, a cam ring arranged in the pump housing, and a rotor mounted rotatably in the cam ring, wherein slots in which vanes are guided in a radially displaceable manner are formed in the rotor;   acting upon the vanes with a fluid pressure through a channel behind the vanes, which is formed in the rotor and connects the slots to a pressure side of the positive displacement pump;   positioning outer ends of the vanes against an inner wall of the cam ring,   providing a working chamber which is formed by the cam ring and the rotor and is bounded in an axial direction by an end side of a housing side control plate and by an end side of a cover side control plate; and   providing a rotor assembly consisting of at least the rotor, the cam ring, the housing side control plate and the cover side control plate which in the assembled state form the rotor assembly,   wherein the housing side control plate is arranged in the axial direction adjacent to a housing end surface and the cover side control plate is arranged in the axial direction adjacent to a cover end surface, and   wherein the rotor assembly is movable in the axial direction between the housing end surface and the cover end surface.   
     
     
         12 . The method as claimed in  claim 11 , wherein:
 a direction of rotation of the rotor is reversible,   the fluid is delivered in a first direction of rotation of the rotor or in a second direction of rotation of the rotor, and   during operation, a respective pressure side of the positive displacement pump positions the rotor assembly against a housing end surface or cover end surface lying opposite the pressure side of the positive displacement pump.   
     
     
         13 . A steering system, comprising:
 at least one consumer; and   a positive displacement pump configured to deliver a fluid for the at least one consumer of the steering system, the positive displacement pump comprising
 a pump housing, 
 a cam ring arranged in the pump housing, 
 a rotor mounted rotatably in the cam ring, the rotor having slots in which vanes are guided in a radially displaceable manner, the vanes configured to be acted upon with a fluid pressure by way of a channel located behind the vanes, wherein the channel is formed in the rotor and is configured to connect the slots to a pressure side of the positive displacement pump, and wherein outer vane ends are configured to be positioned against an inner wall of the cam ring, and 
 a working chamber formed by the cam ring and the rotor, the working chamber bounded in an axial direction by an end side of a housing side control plate and by an end side of a cover side control plate, 
   wherein the rotor, the cam ring, the housing side control plate, and the cover side control plate in the assembled state form a rotor assembly,   wherein the housing side control plate is arranged in the axial direction adjacent to a housing end surface and the cover side control plate is arranged in the axial direction adjacent to a cover end surface, and   wherein the rotor assembly is movable in the axial direction between the housing end surface and the cover end surface.   
     
     
         14 . The steering system as claimed in  claim 13 , wherein the positive displacement pump is formed by a vane pump.