Pulsation phenomenon suppression mechanism of pump device

1. A pump device comprising:

a driving shaft;

a pump element having a rotor, a plurality of vanes and a cam ring, wherein

the rotor is driven and rotated by the driving shaft, and has a plurality of slits in a circumferential direction of a rotation axis of the driving shaft,

the plurality of vanes are movably set in the respective slits, and

the cam ring is formed into a ring shape, and forms a plurality of pump chambers by the rotor and the plurality of vanes; and

a pump housing having therein a pump element accommodating space, a suction passage, a discharge passage, a first fluid pressure chamber, a second fluid pressure chamber and a pressure plate on which a suction port, a discharge port and a first communication groove are formed, wherein

the pump element accommodating space accommodates therein the pump element,

the suction port faces and opens to a suction region where volumes of the plurality of pump chambers increase according to rotation of the driving shaft,

the suction passage is connected to the suction port, and supplies working fluid to the suction port according to the rotation of the driving shaft,

the discharge port faces and opens to a discharge region where the volumes of the plurality of pump chambers decrease according to the rotation of the driving shaft,

the discharge passage is connected to the discharge port, and discharges the working fluid from the discharge port according to the rotation of the driving shaft,

the first communication groove has, as a pair of end portions thereof in a rotation direction of the driving shaft, a first end portion connected to a start point of the discharge port and a second end portion at an opposite side to the first end portion,

the first communication groove is structured to communicate with the suction port by a configuration in which when a front-side vane of arbitrary adjacent two vanes of the plurality of vanes is positioned at the start point of the discharge port by the rotation of the driving shaft, the second end portion is positioned at a rear side in the rotation direction with respect to a rear-side vane of the adjacent two vanes which comes immediately after the front-side vane,

the first fluid pressure chamber and the second fluid pressure chamber are provided, as a pair of spaces, at an outer side, in a radial direction of the rotation axis of the driving shaft, of the cam ring in the pump element accommodating space, and serve to move the cam ring so that an eccentric amount of a center of an inner circumference of the cam ring with respect to the rotation axis of the driving shaft is changed by a pressure difference between the first fluid pressure chamber and the second fluid pressure chamber,

the first fluid pressure chamber is provided at a position where a volume of the first fluid pressure chamber decreases when the cam ring moves in a direction in which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft increases, and

the second fluid pressure chamber is provided at a position where a volume of the second fluid pressure chamber increases when the cam ring moves in the direction in which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft increases.

2. The pump device as claimed in claim 1 , wherein:

the cam ring has a cam profile by which when the cam ring is located at a position at which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft is a maximum and a rear-side vane of arbitrary adjacent two vanes of the plurality of vanes is positioned at an end point of the suction port, in a first closed region that is a region between a front-side vane of the adjacent two vanes and the end point of the suction port, a distance between an inner circumferential surface of the cam ring and the rotation axis of the driving shaft does not increase with the rotation of the driving shaft.

3. The pump device as claimed in claim 2 , wherein:

the cam ring has a cam profile by which when the cam ring is located at the position at which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft is the maximum, in the first closed region, the distance between the inner circumferential surface of the cam ring and the rotation axis of the driving shaft decreases with the rotation of the driving shaft.

4. The pump device as claimed in claim 3 , wherein:

the pump housing has a cam supporting surface that contacts an outer-side surface, in the radial direction of the rotation axis of the driving shaft, of the cam ring, and

the cam ring is provided so that when the cam ring is located at the position at which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft is the maximum, the center of the inner circumference of the cam ring is positioned at a suction region side with respect to the rotation axis of the driving shaft in a direction of a line connecting the cam supporting surface and the rotation axis of the driving shaft when viewing a cross section of the cam ring orthogonal to the rotation axis of the driving shaft.

5. The pump device as claimed in claim 4 , wherein:

the cam ring is provided so that, even in a state in which the working fluid is sucked from the suction port and discharged from the discharge port, when the cam ring is located at the position at which the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft is the maximum, the center of the inner circumference of the cam ring is positioned at the suction region side with respect to the rotation axis of the driving shaft in the direction of the line connecting the cam supporting surface and the rotation axis of the driving shaft when viewing the cross section of the cam ring orthogonal to the rotation axis of the driving shaft.

6. The pump device as claimed in claim 4 , wherein:

a distance from the center of the inner circumference of the cam ring to the inner circumference of the cam ring when viewing the cross section orthogonal to the rotation axis of the driving shaft is constant throughout an entire circumference in the circumferential direction of the rotation axis of the driving shaft.

7. The pump device as claimed in claim 3 , further comprising:

a rotation stopper pin, wherein

the rotation stopper pin is provided in the pump element accommodating space, and limits a relative rotation of the cam ring with respect to the pump housing in the circumferential direction of the rotation axis of the driving shaft.

8. The pump device as claimed in claim 3 , wherein:

a length of the first communication groove in the circumferential direction of the rotation axis of the driving shaft is set to be longer than the sum of a length of a pump chamber sandwiched between the front-side vane positioned at the start point of the discharge port and the adjacent rear-side vane and a thickness of either one of the arbitrary adjacent two vanes.

9. The pump device as claimed in claim 1 , wherein:

the pump housing has a second communication groove formed on the pressure plate, wherein

the second communication groove has a third end portion and a fourth end portion which are a pair of end portions in the rotation direction of the driving shaft,

the third end portion is connected to a start point of the suction port, and

when the rear-side vane is positioned at an end point of the discharge port, the fourth end portion is positioned at a rear side in the rotation direction with respect to the front-side vane.

10. The pump device as claimed in claim 9 , wherein:

the first communication groove and the second communication groove are formed so that when any one of the plurality of vanes is located at an overlap position with the second end portion of the first communication groove, none of the plurality of vanes overlap the fourth end portion of the second communication groove.

11. The pump device as claimed in claim 9 , wherein:

an entire length, in the circumferential direction of the rotation axis of the driving shaft, of the first communication groove is longer than that of the second communication groove.

12. The pump device as claimed in claim 11 , wherein:

the discharge port is formed so that as the eccentric amount of the center of the inner circumference of the cam ring with respect to the rotation axis of the driving shaft becomes smaller, a closing timing of the discharge port when communication of one pump chamber of the plurality of pump chambers with the discharge port is closed according to the rotation of the driving shaft becomes later.

13. The pump device as claimed in claim 1 , wherein:

a sectional area of the first communication groove in a rotation axis direction of the driving shaft is set to 0.8 mm 2 or less throughout an entire range in the circumferential direction from the first end portion to the second end portion of the first communication groove.

14. The pump device as claimed in claim 13 , wherein:

the sectional area of the first communication groove in the rotation axis direction of the driving shaft is constant throughout the entire range in the circumferential direction from the first end portion to the second end portion of the first communication groove in a rear-side region with respect to a front-side vane of arbitrary adjacent two vanes of the plurality of vanes when a rear-side vane of the adjacent two vanes overlaps the suction port.

15. The pump device as claimed in claim 13 , wherein:

the sectional area of the first communication groove in the rotation axis direction of the driving shaft in a front-side region with respect to a front-side vane of arbitrary adjacent two vanes of the plurality of vanes is greater than that in a rear-side region with respect to the front-side vane when a rear-side vane of the adjacent two vanes separates from an end point of the suction port.