Variable displacement vane pump and method of regulating the displacement thereof

Abstract

A variable displacement rotary vane pump for fluids is provided where displacement regulation is achieved thanks to the variation of the relative eccentricity between a regulation ring ( 11 ) in which a rotor ( 13 ) is arranged and the rotor itself. In a region of engagement between the external surface ( 11 A) of the regulation ring ( 11 ) and the internal surface ( 40 A) of a chamber ( 40 ) inside which the regulation ring ( 11 ) moves, a plurality of rolling elements ( 25 ), mounted in fixed position, is provided. The rolling elements ( 25 ) are provided only over a portion of such a region of engagement, including a zone (S) where a resultant of mechanical and fluidic forces generated in the pump during the regulation acts. A method of regulating the displacement of such a pump is also disclosed.

1 . A variable displacement rotary vane pump for fluids, comprising:
 a rotor ( 13 ) arranged to eccentrically rotate within a regulation ring ( 11 ) with a relative eccentricity which varies depending on operating conditions of the pump ( 1 );   means ( 17 ,  18 ) for moving the regulation ring ( 11 ) in a chamber ( 40 ) formed in a pump body ( 10 ) in order to vary said relative eccentricity, and hence the displacement of the pump, as said operating conditions vary; and   a plurality of rolling elements ( 25 ) interposed between an external surface ( 11 A) of the regulation ring ( 11 ) and an internal surface ( 40 A) of the chamber ( 40 );   characterised in that:   the rolling elements ( 25 ) are mounted in a supporting cage ( 26 ) and are provided only over a portion of a region of engagement between the external surface ( 11 A) of the regulation ring ( 11 ) and the internal surface ( 40 A) of the chamber ( 40 ), said portion including a zone (S) where a resultant (SV 1 , SV 2 ) of mechanical and fluidic forces generated in the pump during the regulation acts; and   the rolling elements ( 25 ) and said supporting cage ( 26 ) are arranged, in said portion of the region of engagement between said surfaces ( 11 A,  40 A), so as to move as an integral body along said surfaces ( 11 A,  40 A) during the movement of the regulation ring ( 11 ), the movement of the rolling elements ( 25 ) and of the supporting cage ( 26 ) having a smaller amplitude than a movement performed by the regulation ring ( 11 ) in order to make the pump pass from a maximum displacement to a minimum displacement.   
     
     
         2 . The pump as claimed in  claim 1 , wherein the regulation movement is a rotation of the regulation ring ( 11 ) and wherein:
 in said portion of the region of engagement, the external surface ( 11 A) of the regulation ring ( 11 ) and the internal surface ( 40 A) of the chamber ( 40 ) form, together with the rolling elements ( 25 ), a sector of a rolling bearing of which said surfaces form sectors of an inner race and an outer race, respectively; and   the rolling elements ( 25 ) are arranged within a seat ( 28 ) formed in the surface ( 11 A) of the regulation ring ( 11 ) and having a greater extension than the supporting cage ( 26 ) in which the rolling elements ( 25 ) are mounted.   
     
     
         3 . The pump as claimed in  claim 2 , wherein the supporting cage ( 26 ) is arranged to move in said seat, thereby moving the rolling elements ( 25 ), against the action of an opposing resilient member ( 30 ), which is arranged between one end of the cage ( 26 ) and one end ( 29 B) of the seat ( 28 ) and is capable of keeping or bringing again the cage ( 26 ) in contact with an opposite end ( 29 A) of the seat ( 28 ) in the maximum displacement condition of the pump. 
     
     
         4 . The pump as claimed in  claim 3 , wherein the rolling elements ( 25 ) are mounted in the supporting cage ( 26 ) so as to give it a labyrinth configuration arranged to maintain a fluidic support bearing generated in said zone (S) as a reaction to the action of the resultant (SV 1 , SV 2 ) of said forces. 
     
     
         5 . The pump as claimed in  claim 4 , wherein the rolling elements ( 25 ) are rollers or needles, and wherein the supporting cage ( 26 ) has an axial depth substantially corresponding to an axial depth of the regulation ring ( 11 ) and the rollers or needles ( 25 ) have a length shorter than the axial depth of the cage ( 26 ). 
     
     
         6 . The pump as claimed in  claim 1 , wherein the rotation of the regulation ring ( 11 ) is directly controlled by the pressure of the pumped fluid. 
     
     
         7 . The pump as claimed in  claim 1 , wherein the pump is a pump for the lubrication circuit of a motor vehicle engine. 
     
     
         8 . A method of regulating the displacement of a rotary variable displacement pump for fluids, of a kind comprising a rotor ( 13 ) arranged to eccentrically rotate within a regulation ring ( 11 ) with a relative eccentricity that is variable depending on operating conditions of the pump ( 1 ), the method comprising the steps of:
 providing, between an external surface ( 11 A) of the regulation ring ( 11 ) and an internal surface ( 40 A) of a chamber ( 40 ) housing the ring ( 11 ), a plurality of rolling elements ( 25 ) mounted in a fixed relative position; and   making the regulation ring ( 11 ) move in the chamber ( 40 ) in order to vary said relative eccentricity, and hence the displacement of the pump, as said operating conditions vary;   and being characterised in that the step of providing rolling elements ( 25 ) in the chamber ( 40 ) comprises the steps of:   providing the rolling elements ( 25 ) mounted in a supporting cage ( 26 ) only over a portion of a region of engagement between the external surface ( 11 A) of the regulation ring ( 11 ) and the internal surface ( 40 A) of the chamber ( 40 ), said portion including a zone (S) where a resultant (SV 1 , SV 2 ) of mechanical and fluidic forces generated in the pump during the regulation acts; and   during the regulation, making the rolling elements ( 25 ) and the supporting cage ( 26 ) move as an integral body in said portion of the region of engagement between said surfaces ( 11 A,  40 A), the movement of the rolling elements ( 25 ) and the supporting cage ( 26 ) having a smaller amplitude than a movement of the regulation ring ( 11 ) making the pump pass from a maximum displacement to a minimum displacement.   
     
     
         9 . The method as claimed in  claim 8 , wherein the regulation movement is a rotation of the regulation ring ( 11 ) and the step of providing the rolling elements ( 25 ) and the supporting cage ( 26 ) only over a portion of the region of engagement between said surfaces ( 11 A,  40 A) comprises the step of configuring the rolling elements ( 25 ) and the supporting cage ( 26 ), the external surface ( 11 A) of the regulation ring ( 11 ) and the internal surface ( 40 A) of the chamber ( 40 ) as a sector of a rolling bearing, of which said surfaces form circular sectors of an inner race and an outer race, respectively. 
     
     
         10 . The method as claimed in  claim 9 , wherein the step of making the rolling elements ( 25 ) and the supporting cage ( 26 ) move as an integral body comprises moving the rolling elements ( 25 ) and the supporting cage ( 26 ) in a seat ( 28 ) formed in the surface ( 11 A) of the regulation ring ( 11 ) and having a greater extension than an overall extension of said rolling elements ( 25 ) and said supporting cage ( 26 ). 
     
     
         11 . The method as claimed in  claim 8 , wherein the step of making the rolling elements ( 25 ) and the supporting cage ( 26 ) move as an integral body comprises moving the rolling elements ( 25 ) and the supporting cage ( 26 ) in a seat ( 28 ) formed in the surface ( 11 A) of the regulation ring ( 11 ) and having a greater extension than an overall extension of said rolling elements ( 25 ) and said supporting cage ( 26 ). 
     
     
         12 . The pump as claimed in  claim 2 , wherein the rolling elements ( 25 ) are mounted in the supporting cage ( 26 ) so as to give it a labyrinth configuration arranged to maintain a fluidic support bearing generated in said zone (S) as a reaction to the action of the resultant (SV 1 , SV 2 ) of said forces. 
     
     
         13 . The pump as claimed in  claim 12 , wherein the rolling elements ( 25 ) are rollers or needles, and wherein the supporting cage ( 26 ) has an axial depth substantially corresponding to an axial depth of the regulation ring ( 11 ) and the rollers or needles ( 25 ) have a length shorter than the axial depth of the cage ( 26 ). 
     
     
         14 . The pump as claimed in  claim 2 , wherein the rotation of the regulation ring ( 11 ) is directly controlled by the pressure of the pumped fluid. 
     
     
         15 . The pump as claimed in  claim 1 , wherein the supporting cage ( 26 ) is arranged to move in said seat, thereby moving the rolling elements ( 25 ), against the action of an opposing resilient member ( 30 ), which is arranged between one end of the cage ( 26 ) and one end ( 29 B) of the seat ( 28 ) and is capable of keeping or bringing again the cage ( 26 ) in contact with an opposite end ( 29 A) of the seat ( 28 ) in the maximum displacement condition of the pump. 
     
     
         16 . The pump as claimed in  claim 15 , wherein the rolling elements ( 25 ) are mounted in the supporting cage ( 26 ) so as to give it a labyrinth configuration arranged to maintain a fluidic support bearing generated in said zone (S) as a reaction to the action of the resultant (SV 1 , SV 2 ) of said forces. 
     
     
         17 . The pump as claimed in  claim 16 , wherein the rolling elements ( 25 ) are rollers or needles, and wherein the supporting cage ( 26 ) has an axial depth substantially corresponding to an axial depth of the regulation ring ( 11 ) and the rollers or needles ( 25 ) have a length shorter than the axial depth of the cage ( 26 ). 
     
     
         18 . The pump as claimed in  claim 15 , wherein the rotation of the regulation ring ( 11 ) is directly controlled by the pressure of the pumped fluid. 
     
     
         19 . The pump as claimed in  claim 1 , wherein the rolling elements ( 25 ) are mounted in the supporting cage ( 26 ) so as to give it a labyrinth configuration arranged to maintain a fluidic support bearing generated in said zone (S) as a reaction to the action of the resultant (SV 1 , SV 2 ) of said forces. 
     
     
         20 . The pump as claimed in  claim 19 , wherein the rolling elements ( 25 ) are rollers or needles, and wherein the supporting cage ( 26 ) has an axial depth substantially corresponding to an axial depth of the regulation ring ( 11 ) and the rollers or needles ( 25 ) have a length shorter than the axial depth of the cage ( 26 ).