Variable displacement pump with electric control of displacement regulation and method of regulating pump displacement

Abstract

A rotary positive displacement pump for fluids, in particular, for the lubrication of a motor vehicle engine ( 61 ), has a displacement that can be regulated through the rotation of a stator ring ( 42 ) having an eccentric cavity ( 43 ) in which the rotor ( 15 ) of the pump ( 1 ) rotates. The stator ring ( 42 ) is housed within an in eccentric cavity ( 13 ) of an external ring ( 12 ). A rotor actuator ( 50 ), controlled by the electronic control unit of the motor vehicle, causes a synchronous rotation by an equal amount in opposite directions of both rings. A method of regulating the displacement of the pump ( 1 ) and lubrication system for a motor vehicle engine in which the pump is used are also provided.

1 . A variable displacement rotary positive displacement pump for fluids, comprising a rotor ( 15 ;  115 ) arranged to rotate within an eccentric cavity ( 43 ;  143 ) of a stator ring ( 42 ;  142 ) in turn arranged to be rotated within a predetermined angular interval, as operating conditions of the pump ( 1 ;  101 ) vary and upon command of a system ( 62 ,  63 ) detecting such conditions, in order to vary a relative eccentricity between the eccentric cavity ( 43 ;  143 ) and the rotor ( 15 ;  115 ) and hence the pump displacement, the pump ( 1 ;  101 ) further including an electromagnetic actuator ( 50 ), integrated into or coupled with the pump, which is driven by said detecting system ( 62 ,  63 ) and is arranged to generate a rotary motion and to transmit it to said stator ring ( 42 ;  142 ) through a toothed wheel ( 53 ;  153 );
 the pump being characterised in that:
 said toothed wheel ( 53 ;  153 ) is located at least in part in a stator cavity ( 11   a ,  11   b ;  111 ) located in a peripheral position relative to said stator ring ( 42 ;  142 ); 
   and in that
 a toothed sector ( 52 ;  152 ) is located at the base of said peripheral stator cavity ( 11   a ,  11   b ;  111 ). 
   
     
     
         2 . The pump as claimed in  claim 1 , wherein said toothed sector ( 52 ;  152 ) located at the base of said peripheral stator cavity ( 11   a ,  11   b ;  111 ) meshes with said toothed wheel ( 53 ;  153 ) driven by the actuator ( 50 ) and develops according to a profile defined by an involute of the teeth of the wheel ( 53 ;  153 ). 
     
     
         3 . The pump as claimed in  claim 2 , wherein the stator ring ( 42 ) is housed within an eccentric cavity ( 13 ) of an external ring ( 12 ), and said actuator ( 50 ) is arranged to transmit the rotary motion to both rings ( 12 ;  42 ) in such a way as to cause a synchronous rotation thereof by an equal amount in opposite directions. 
     
     
         4 . The pump as claimed in  claim 3 , wherein the eccentric cavities ( 13 ,  43 ) have the same eccentricity and, in a minimum displacement condition, are arranged so that their eccentricities are offset by 180°. 
     
     
         5 . The pump as claimed in  claim 3 , wherein facing surfaces of the external ring ( 12 ) and the stator ring ( 42 ) have formed thereon respective toothed sectors ( 51 ,  52 ) with which a toothed wheel ( 53 ) driven by the actuator ( 50 ) meshes and which develop according to a profile defined by an involute of the teeth of the wheel ( 53 ), so that, during the rotation of the rings ( 12 ,  42 ), a centre (O′) of the cavity of the stator ring moves along a rectilinear path. 
     
     
         6 . The pump as claimed in  claim 2 , wherein the toothed wheel ( 53 ;  153 ) is arranged to cooperate with a member ( 34 ) opposing the rotation of the stator ring ( 42 ;  142 ), which member consists of a flat spiral spring secured at one end to a shaft ( 54 ) of the toothed wheel and at the other end to an element ( 33 ) rigidly connected to the pump body, the spring being associated with setting means ( 33 ,  55 ) arranged to set a desired steady state value for the displacement of the pump ( 1 ;  101 ), and wherein the flat spiral spring ( 34 ) is made of a bimetallic material and has a temperature-depending characteristic. 
     
     
         7 . The pump as claimed in  claim 2 , wherein the actuator ( 50 ) is a step-by-step micromotor or is a linearly moving actuator equipped with an escapement ratchet gear arranged to convert the actuator motion into a rotary motion. 
     
     
         8 . The pump as claimed in  claim 1 , wherein the pump ( 1 ;  101 ) is a pump for a lubrication circuit ( 60 ) of a motor vehicle engine ( 61 ). 
     
     
         9 . A method of regulating the displacement of a rotary positive displacement pump ( 1 ;  101 ) of a kind comprising a rotor ( 15 ;  115 ) arranged to rotate within an eccentric cavity ( 43 ;  143 ) of a stator ring ( 42 ;  142 ), the method comprising the step of making the stator ring ( 42 ;  142 ) rotate within a predetermined angular interval in order to vary the eccentricity between the cavity ( 43 ;  143 ) and the rotor ( 15 ;  115 ) as operating conditions of the pump ( 1 ;  101 ) vary, and being characterised in that it further comprises the steps of:
 providing an electromagnetic actuator ( 50 ) integrated into or coupled with the pump and arranged to transmit a rotary motion to the stator ring ( 42 ) through a toothed wheel ( 53 ;  153 ) located at least in part in a stator cavity ( 11   a ,  11   b ;  111 ) located in a peripheral position relative to said stator ring ( 42 ;  142 );   supplying the actuator ( 50 ) with commands corresponding to a desired rotation of the stator ring ( 42 ;  142 ).   
     
     
         10 . The method as claimed in  claim 9 , further comprising the steps of:
 providing an external ring ( 12 ) having an eccentric cavity ( 13 ) within which the stator ring ( 42 ) is housed; and   making the stator ring ( 42 ) and the external ring ( 12 ) rotate by a same angle at the same time and in opposite directions.   
     
     
         11 . The method as claimed in  claim 9  or  10 , arranged for regulating the displacement of a pump for the lubrication oil of a motor vehicle engine. 
     
     
         12 . A lubrication system for a motor vehicle engine ( 61 ), comprising a pump ( 1 ;  101 ) as claimed in  claim 1 . 
     
     
         13 . The pump as claimed in  claim 1 , wherein the stator ring ( 42 ) is housed within an eccentric cavity ( 13 ) of an external ring ( 12 ), and said actuator ( 50 ) is arranged to transmit the rotary motion to both rings ( 12 ;  42 ) in such a way as to cause a synchronous rotation thereof by an equal amount in opposite directions. 
     
     
         14 . The pump as claimed in  claim 13 , wherein the eccentric cavities ( 13 ,  43 ) have the same eccentricity and, in a minimum displacement condition, are arranged so that their eccentricities are offset by 180°. 
     
     
         15 . The pump as claimed in  claim 14 , wherein facing surfaces of the external ring ( 12 ) and the stator ring ( 42 ) have formed thereon respective toothed sectors ( 51 ,  52 ) with which a toothed wheel ( 53 ) driven by the actuator ( 50 ) meshes and which develop according to a profile defined by an involute of the teeth of the wheel ( 53 ), so that, during the rotation of the rings ( 12 ,  42 ), a centre (O′) of the cavity of the stator ring moves along a rectilinear path. 
     
     
         16 . The pump as claimed in  claim 13 , wherein facing surfaces of the external ring ( 12 ) and the stator ring ( 42 ) have formed thereon respective toothed sectors ( 51 ,  52 ) with which a toothed wheel ( 53 ) driven by the actuator ( 50 ) meshes and which develop according to a profile defined by an involute of the teeth of the wheel ( 53 ), so that, during the rotation of the rings ( 12 ,  42 ), a centre (O′) of the cavity of the stator ring moves along a rectilinear path. 
     
     
         17 . The pump as claimed in  claim 13 , wherein the toothed wheel ( 53 ;  153 ) is arranged to cooperate with a member ( 34 ) opposing the rotation of the stator ring ( 42 ;  142 ), which member consists of a flat spiral spring secured at one end to a shaft ( 54 ) of the toothed wheel and at the other end to an element ( 33 ) rigidly connected to the pump body, the spring being associated with setting means ( 33 ,  55 ) arranged to set a desired steady state value for the displacement of the pump ( 1 ;  101 ), and wherein the flat spiral spring ( 34 ) is made of a bimetallic material and has a temperature-depending characteristic. 
     
     
         18 . The pump as claimed in  claim 13 , wherein the actuator ( 50 ) is a step-by-step micromotor or is a linearly moving actuator equipped with an escapement ratchet gear arranged to convert the actuator motion into a rotary motion. 
     
     
         19 . The pump as claimed in  claim 1 , wherein the toothed wheel ( 53 ;  153 ) is arranged to cooperate with a member ( 34 ) opposing the rotation of the stator ring ( 42 ;  142 ), which member consists of a flat spiral spring secured at one end to a shaft ( 54 ) of the toothed wheel and at the other end to an element ( 33 ) rigidly connected to the pump body, the spring being associated with setting means ( 33 ,  55 ) arranged to set a desired steady state value for the displacement of the pump ( 1 ;  101 ), and wherein the flat spiral spring ( 34 ) is made of a bimetallic material and has a temperature-depending characteristic. 
     
     
         20 . The pump as claimed in  claim 1 , wherein the actuator ( 50 ) is a step-by-step micromotor or is a linearly moving actuator equipped with an escapement ratchet gear arranged to convert the actuator motion into a rotary motion.