Rotary positive displacement pump and method of regulating its displacement

Abstract

A rotary positive displacement pump for fluids for the lubrication oil of a motor vehicle engine, has a displacement that can be regulated by the translation of a stator ring surrounding the rotor of the pump with an eccentricity depending on the position taken by the same ring due to the translation. The translation is guided by guiding fins sliding in contact with a surface of a guiding chamber, communicating with the delivery side of the pump, thanks to the fluid under pressure introduced into the same chamber and acting on the fins. The contact zone is such that a homogeneous contact pressure distribution is ensured as the operating conditions of the pump and, consequently, the position of the stator ring, vary. A method is disclosed of regulating the displacement of the pump and a lubrication system for a motor vehicle engine, in which system the pump is used.

1 - 11 . (canceled) 
     
     
         12 . A rotary positive displacement pump for fluids, comprising a rotor arranged to eccentrically rotate in a chamber defined within a stator ring, which is located in a seat formed in a pump body and is connected to means for translating such a ring relative to the rotor, as the operating conditions of the pump vary, in order to change the pump displacement, wherein the stator ring includes guiding means arranged to slide in a guiding chamber formed in the pump body and communicating with a pressure zone of the pump or with utilisation devices of a pumped fluid, in order to receive fluid under pressure therefrom, characterised in that the guiding means, during the translation of the stator ring, are arranged to be pushed by the fluid under pressure into sealing contact with a surface of the guiding chamber and, in a zone of contact with such a surface, they have a curvature with such a radius of curvature that a homogeneous contact pressure distribution is ensured as the operating conditions of the pump and, consequently, the position of the stator ring, vary. 
     
     
         13 . The pump as claimed in  claim 12 , wherein the guiding means comprise a pair of oppositely directed fins extending substantially tangentially to the stator ring from an outer surface of the stator ring and defining a common push surface that is acted upon by the fluid under pressure and a pair of contact areas each having said curvature with such a radius of curvature that the homogeneous contact pressure distribution is ensured. 
     
     
         14 . The pump as claimed in  claim 13 , wherein the fins have rounded free ends. 
     
     
         15 . The pump as claimed in  claim 12 , wherein the translation of the stator ring is controlled by a first and a second push head, which act on diametrically opposite areas of the ring and are arranged to slide in a first and a second push chamber, respectively, which chambers are distinct from the guiding chamber and communicate with the pressure zone of the pump or, preferably, with the utilisation devices of the pumped fluid, through a regulation valve or directly, respectively. 
     
     
         16 . The pump as claimed in  claim 13 , wherein the translation of the stator ring is controlled by a first and a second push head, which act on diametrically opposite areas of the ring and are arranged to slide in a first and a second push chamber, respectively, which chambers are distinct from the guiding chamber and communicate with the pressure zone of the pump or, preferably, with the utilisation devices of the pumped fluid, through a regulation valve or directly, respectively. 
     
     
         17 . The pump as claimed in  claim 15 , wherein the regulation valve is integrated in the pump. 
     
     
         18 . The pump as claimed in  claim 16 , wherein the regulation valve is integrated in the pump. 
     
     
         19 . The pump as claimed in  claim 15 , wherein the push heads are arranged to separate a suction environment of the pump from a high pressure environment where the guiding means slide. 
     
     
         20 . The pump as claimed in  claim 16 , wherein the push heads are arranged to separate a suction environment of the pump from a high pressure environment where the guiding means slide. 
     
     
         21 . The pump as claimed in  claim 17 , wherein the push heads are arranged to separate a suction environment of the pump from a high pressure environment where the guiding means slide. 
     
     
         22 . The pump as claimed in  claim 12 , wherein the translation of the stator ring is controlled by an electric motor. 
     
     
         23 . The pump as claimed in  claim 13 , wherein the translation of the stator ring is controlled by an electric motor. 
     
     
         24 . The pump as claimed in  claim 12 , wherein the pump is a pump for the lubrication circuit of an engine of a motor vehicle. 
     
     
         25 . A method of regulating the displacement of a rotary positive displacement pump, comprising the steps of:
 translating, relative to a rotor of the pump, a stator ring inside which the rotor eccentrically rotates;   guiding the translation of the stator ring through guiding means arranged to slide in a guiding chamber formed in a pump body and communicating with a pressure zone of the pump or with utilisation devices of the pumped fluid;   
       the method being characterised in that it further comprises the steps of:
 making the pumped fluid act upon the guiding means in order to keep them in sealing contact with a surface of the guiding chamber during the translation of the stator ring; and 
 making the guiding means contact the surface of the guiding chamber at a zone of the surface of the guiding means having a curvature with such a radius of curvature that a homogeneous contact pressure distribution is ensured as the operating conditions of the pump and, consequently, the position of the stator ring, vary. 
 
     
     
         26 . The method as claimed in  claim 25 , for regulating the displacement of a pump for the lubrication oil for the engine of a motor vehicle. 
     
     
         27 . A lubrication system for an engine of a motor vehicle, comprising a pump according to  claim 12 .