Pump apparatus

Abstract

In a variable displacement vane pump, a cam profile of a cam ring includes a deviation region deviating from a perfect-circle cam profile outwardly in a radial direction regarding a rotational axis of a driving shaft in an intake region.

1 . A pump apparatus comprising:
 a pump housing, the pump housing including a pump element containing space, an intake passage, a discharge passage, an intake port, and a discharge port,   the intake passage being connected to the intake port,   the discharge passage being connected to the discharge port,   the pump apparatus further comprising:   a driving shaft rotatably provided in the pump housing;   a rotor provided on the driving shaft and including a plurality of slits;   a plurality of vanes provided movably in the plurality of slits, respectively, the plurality of vanes being made from a metallic material; and   a cam ring,   wherein the cam ring is annularly formed, and is provided in the pump element containing space,   wherein the cam ring forms a plurality of pump chambers together with the rotor and the plurality of vanes, and a first fluid pressure chamber and a second fluid pressure chamber are formed in the pump element containing space,   wherein the intake port is opened to a region where a volume of the pump chamber increases according to a rotation of the rotational shaft among the plurality of pump chambers,   wherein the discharge port is opened to a discharge region where the volume of the pump chamber reduces according to the rotation of the driving shaft among the plurality of pump chambers,   wherein, in a space formed on a radially outer side of the cam ring in a radial direction regarding a rotational axis of the driving shaft, the first fluid pressure chamber is provided in a portion in this space where the volume reduces as an eccentricity amount between the rotational axis of the driving shaft and a center of an inner peripheral edge of the cam ring increases,   wherein, in the space formed on the radially outer side of the cam ring in the radial direction regarding the rotational axis of the driving shaft, the second fluid pressure chamber is provided in a portion in this space where the volume increases as the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring increases,   wherein the cam ring is movable in the pump element containing space based on a pressure difference between the first fluid pressure chamber and the second fluid pressure chamber, and   wherein, assuming that a cam profile refers to a line extending along the inner peripheral edge of the cam ring,   an intake region corresponds to a range from a start end to a termination end of the intake port in a circumferential direction regarding the rotational axis of the driving shaft,   a first axis refers to an axis extending perpendicularly to the rotational axis of the driving shaft and passing through a point that divides in half a section between a termination end of the discharge port and the start end of the intake port in the circumferential direction regarding the rotational axis of the rotational shaft in cross section perpendicular to the rotational axis of the driving shaft,   a second axis refers to an axis extending perpendicularly to the first axis and passing through a point that divides in half a section between a pair of intersection points at which the cam profile and the first axis intersect with each other,   a cam profile central point refers to an intersection point between the first axis and the second axis,   a third axis refers to an axis passing through the cam profile central point and the termination end of the intake port,   a perfect-circle cam profile radius refers to a length between a point at which the third axis and the cam profile intersect with each other and the cam profile central point, and   a perfect-circle cam profile refers to a circular arc centered at the cam profile central point and having the perfect-circle cam profile radius,   the cam profile includes a deviation region deviating from the perfect-circle cam profile outwardly or inwardly in the radial direction regarding the rotational axis of the driving shaft in the intake region.   
     
     
         2 . The pump apparatus according to  claim 1 , wherein, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region, and the cam profile radius in the first state refers to a distance from the cam profile central point to the cam profile in the first state,
 the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft, and the cam profile radius in the second state refers to a distance from the cam profile central point to the cam profile in the second state,   a first cam profile deviation amount refers to a maximum value of an absolute value of a difference between the cam profile radius in the first state and the cam profile radius in the second state when comparing the cam profile in the first state and the cam profile in the second state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region, and   a second cam profile deviation amount refers to a maximum value of an absolute value of a difference between the perfect-circle cam profile radius and the cam profile radius in the first state when comparing the perfect-circle cam profile and the cam profile in the first state at the same position in the circumferential direction regarding the rotational axis of the driving shaft in the intake region,   the cam ring has such a shape that the cam profile in the first state satisfies the first cam profile deviation amount<the second cam profile deviation amount.   
     
     
         3 . The pump apparatus according to  claim 1 , wherein the deviation region deviates from the perfect-circle cam profile outwardly in the radial direction regarding the rotational axis of the driving shaft. 
     
     
         4 . The pump apparatus according to  claim 1 , wherein the deviation region is provided throughout the entire intake region. 
     
     
         5 . The pump apparatus according to  claim 1 , wherein the cam profile of the cam ring includes the deviation region when the eccentricity amount between the rotational axis of the driving shaft and the center of the inner peripheral edge of the cam ring is minimized. 
     
     
         6 . The pump apparatus according to  claim 1 , wherein each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft,
 wherein the vane distal end curved surface portion has a circular-arc shape convexed radially outwardly in cross section perpendicular to the rotational axis of the driving shaft, and   wherein the vane is in contact with the inner peripheral edge of the cam ring in a range exceeding 40% of a length of an outer peripheral edge of the vane distal end curved surface portion in the intake region.   
     
     
         7 . The pump apparatus according to  claim 1 , wherein each of the vanes includes a vane distal end curved surface portion provided at a distal end thereof on an outer side in the radial direction regarding the rotational axis of the driving shaft,
 wherein the vane distal end curved surface portion has a circular-arc shape convexed radially outwardly and having a curvature radius rv in cross section perpendicular to the rotational axis of the driving shaft, and   wherein, assuming that T represents a thickness of the vane in the circumferential direction regarding the rotational axis of the driving shaft,   the vane has a shape that satisfies 2×T<rv.   
     
     
         8 . The pump apparatus according to  claim 1 , wherein, assuming that the cam profile in a first state refers to the cam profile when the driving shaft is stopped and a discharge pressure is not applied to the discharge region, and
 the cam profile in a second state refers to the cam profile when the discharge pressure is applied to the discharge region according to the rotation of the driving shaft,   the cam ring is provided in the pump element containing space in such a manner that a center of the cam profile in the first state and a center of the camp profile in the second state deviate from the first axis toward the intake region side.