Oil Pump

Abstract

An oil pump includes: a valve receiving hole including; a first port connected with the suction port, a second port connected with the switching port, a third port connected with the discharge port, and a discharge pressure introduction port arranged to receive the discharge pressure, a valve element arranged to switch a first state in which the second port and the third port are connected, and a second state in which the first port and the second port are connected; and an urging member arranged to urge the valve element toward the first end side, the pressure receiving area of the valve element and the urging force of the urging member being set so that the oil pump is switched from the first state to the second state when the pressure within the hydraulic fluid chambers to which the switching port is opened is a negative pressure.

1 . An oil pump comprising:
 a pump constituting section arranged to continuously increase or decrease volumes of a plurality of hydraulic fluid chambers by being driven by an internal combustion engine;   a port block including;
 a suction port opened in a region in which volumes of the hydraulic fluid chambers are increased, 
 a switching port opened on an upstream side of a region in which the volumes of the hydraulic fluid chambers are decreased, and 
 a discharge port opened on a downstream side of the region in which the volumes of the hydraulic fluid chambers are decreased, 
   a valve receiving hole including;
 a first port formed in an inner circumference surface of the valve receiving hole, and connected with the suction port, 
 a second port formed in the inner circumference surface of the valve receiving hole, and connected with the switching port, 
 a third port formed in the inner circumference surface of the valve receiving hole, and connected with the discharge port, and 
 a discharge pressure introduction port formed at a first end portion of the valve receiving hole, and arranged to receive the discharge pressure which is the hydraulic pressure within the discharge port, 
   a valve element slidably received within the valve receiving hole, and arranged to switch a first state in which the second port and the third port are connected and a connection between the first port and the second port is restricted, and a second state in which the first port and the second port are connected and the connection between the second port and the third port is restricted; and   an urging member provided on a second end side of the valve receiving hole, and arranged to urge the valve element toward the first end side of the valve receiving hole,   the valve element having a pressure receiving area which is on the first end side of the valve element, and to which the discharge pressure is acted, the pressure receiving area of the valve element and the urging force of the urging member being set so that the oil pump is switched from the first state to the second state when the pressure within the hydraulic fluid chambers to which the switching port is opened is a negative pressure.   
     
     
         2 . The oil pump as claimed in  claim 1 , wherein the pump constituting section is arranged to vary the discharge amount in accordance with the discharge pressure; and the discharge pressure by which the valve element switches from the first state to the second state is set to a value smaller than a discharge pressure at which the discharge amount per one rotation of the oil pump is minimized. 
     
     
         3 . The oil pump as claimed in  claim 2 , wherein the pump constituting section includes a rotor which is driven and rotated by the internal combustion engine, and which has a plurality of grooves that are formed on an outer circumference side, and that extend in the radial directions, a cam ring which is disposed radially outside the rotor, and which is moved so that a center of an inner circumference surface of the cam ring is eccentric from a center of the rotation of the rotor, and vanes each of which is received within one of the plurality of the grooves, each of which is moved in a radially inward direction and in a radially outward direction, and each of which has one end portion abutted and slid on the inner circumference surface of the cam ring; and the port block is disposed on both sides of the cam ring in the axial direction so that each of the hydraulic fluid chambers is separated by the port block, the rotor, the cam ring, and the vanes. 
     
     
         4 . The oil pump as claimed in  claim 3 , wherein an eccentric amount between the center of the rotation of the rotor and the center of the inner circumference surface of the cam ring is decreased when the discharge pressure reaches a first pressure; the eccentric amount between the center of the rotation of the rotor and the center of the inner circumference surface of the cam ring is further decreased when the discharge pressure reaches a second pressure higher than the first pressure; and the discharge pressure at which the valve element switches from the first state to the second state is set greater than the first pressure, and lower than the second pressure. 
     
     
         5 . The oil pump as claimed in  claim 4 , wherein the oil pump further comprises two springs which have different spring loads, and which act urging forces on the cam ring; the cam ring is moved against the urging force of one of the springs having a relatively small spring load, in a direction to decrease the eccentric amount between the center of the rotation of the rotor and the center of the inner circumference surface of the cam ring, when the discharge pressure reaches the first pressure; and the cam ring is moved against the urging force of one of the springs having the relatively large spring load, in a direction to further decrease the eccentric amount between the center of the rotor and the center of the inner circumference surface of the cam ring, when the discharge pressure reaches the second pressure. 
     
     
         6 . The oil pump as claimed in  claim 4 , wherein a side surface of the cam ring covers a part of the suction port when the eccentric amount between the center of the rotation of the rotor and the center of the inner circumference surface of the cam ring is decreased. 
     
     
         7 . The oil pump as claimed in  claim 4 , wherein the pump constituting section is driven by a rotational speed larger than a rotational speed of a crank shaft of the internal combustion engine. 
     
     
         8 . The oil pump as claimed in  claim 7 , wherein the pump constituting section is driven by twice the rotational speed of the crank shaft. 
     
     
         9 . The oil pump as claimed in  claim 8 , wherein the pump constituting section is driven by a balancer apparatus arranged to decrease a secondary oscillation of the internal combustion engine. 
     
     
         10 . The oil pump as claimed in  claim 1 , wherein the pump constituting section is assembled in a balancer apparatus. 
     
     
         11 . An oil pump comprising:
 a pump constituting section arranged to continuously increase or decrease volumes of a plurality of hydraulic fluid chambers by being driven by an internal combustion engine;   a port block including;
 a suction port opened in a region in which volumes of the hydraulic fluid chambers are increased, 
 a switching port opened on an upstream side of a region in which the volumes of the hydraulic fluid chambers are decreased, and 
 a discharge port opened on a downstream side of the region in which the volumes of the hydraulic fluid chambers are decreased, and 
   a control section configured
 to control so that the switching port discharges the hydraulic fluid to an outside with the discharge port at a low rotational speed at which the pressure within the hydraulic fluid chamber to which the switching port is opened is a positive pressure, and 
 to control so that the hydraulic fluid is supplied from a low pressure portion connected with the suction port, to the switching port at a high rotational speed at which the pressure within the hydraulic fluid chambers to which the switching port is opened is a negative pressure. 
   
     
     
         12 . The oil pump as claimed in  claim 11 , wherein the control section is electrically controlled. 
     
     
         13 . The oil pump as claimed in  claim 12 , wherein the control section is controlled in accordance with a sensed engine speed of the internal combustion engine. 
     
     
         14 . The oil pump as claimed in  claim 13 , wherein the control section is controlled in accordance with a sensed temperature of the internal combustion engine. 
     
     
         15 . The oil pump as claimed in  claim 12 , wherein the control section is controlled in accordance with a sensed pressure of the switching port. 
     
     
         16 . An oil pump comprising:
 a pump constituting section arranged to continuously increase or decrease volumes of a plurality of hydraulic fluid chambers by being driven by an internal combustion engine;   a port block including;
 a suction port opened to at least a region in which volumes of the hydraulic fluid chambers are increased, and 
 a discharge port opened to a region in which volumes of the hydraulic fluid chambers are decreased; and 
   a control section configured to control so that, at a rotational speed at which the pressure within the hydraulic fluid chambers on an upstream side of the region in which the volumes of the hydraulic fluid chambers are decreased becomes a negative pressure, the hydraulic fluid is supplied from a low pressure portion to the hydraulic fluid chambers which are the negative pressure.   
     
     
         17 . The oil pump as claimed in  claim 16 , wherein a region in which the hydraulic fluid is sucked is enlarged and a region in which the hydraulic fluid is discharged is decreased at a rotational speed at which the hydraulic chambers on the upstream side of the region in which the volumes are decreased becomes the negative pressure. 
     
     
         18 . The oil pump as claimed in  claim 17 , wherein the region in which the hydraulic fluid is sucked is continuously enlarged in accordance with the rotational speed. 
     
     
         19 . The oil pump as claimed in  claim 18 , wherein the port block is provided with a partition member partitioning the suction port and the discharge port; and a suction region of the hydraulic fluid is enlarged by moving the partition member in accordance with the rotational speed.