Variable displacement pump

Abstract

A variable displacement oil pump for an automotive engine. The oil pump includes a cam ring accommodating thereinside a pump element having a rotor. The cam ring is swingingly movably accommodated in a housing and biased in a direction to increase an eccentricity amount of the cam ring relative to the axis of the rotor by a biasing member. First and second pressure chambers are defined inside the housing by the outer peripheral section of the cam ring. The first pressure chamber is supplied with a discharge pressure to be applied to the cam ring to oppose to a biasing force of the biasing member. The second pressure chamber is supplied with the discharge pressure to be applied to the cam ring to assist the biasing force of the biasing member. Additionally, a control device is provided for controlling supply of the discharge pressure to the second pressure chamber.

What is claimed is: 
     
       1. A variable displacement oil pump for supplying oil at least to sliding sections of an internal combustion engine, comprising:
 a pump element including a rotor configured to be rotationally driven by the internal combustion engine, and a plurality of vanes disposed at an outer peripheral section of the rotor; 
 a cam ring having an inner peripheral section for accommodating the pump element thereinside, and an outer peripheral section having a swinging movement fulcrum, the cam ring being swingingly movable around the swinging movement fulcrum to change an eccentricity amount of the cam ring relative to an axis of the rotor;
 a housing for accommodating the cam ring thereinside and including side walls disposed respectively on axially opposite sides of the cam ring to define a plurality of hydraulic fluid chambers each of which is defined by the rotor and adjacent ones of the vanes, the housing further including: a discharge section in which volumes of the hydraulic fluid chambers decrease along the discharge section in a rotational direction of the rotor to realize pumped oil, a first pressure chamber bounded by the outer peripheral section of the cam ring and an inner surface of the housing, a discharge hole opened through at least one of the side walls to discharge the pumped oil from the variable displacement oil pump, with the first pressure chamber opening to the discharge hole, and a suction hole opened through at least one of the side walls to supply oil to a suction section in which volumes of the hydraulic chambers increase along the rotational direction of the rotor; 
 
 a biasing member for biasing the cam ring in a direction to increase the eccentricity amount of the cam ring relative to the axis of the rotor; 
 the first pressure chamber having a first pressure receiving surface on the outer peripheral section of the cam ring, and directly connected to the discharge section via an open valve-less path, to constantly receive a discharge pressure of the pumped oil fed into the first pressure chamber from the discharge section, to allow the discharge pressure to be applied through the first pressure receiving surface to the cam ring to oppose to a biasing force of the biasing member so as to provide the cam ring with a swinging force in a direction to decrease the eccentricity amount of the cam ring; 
 a second pressure chamber defined by the outer peripheral section of the cam ring and the housing, and having a second pressure receiving surface on the outer peripheral section of the cam ring, where introduction of the same discharge pressure that is introduced into the first pressure chamber causes the discharge pressure to be applied through the second pressure receiving surface to the cam ring to assist the biasing force of the biasing member so as to provide the cam ring with a swinging force in a direction to increase the eccentricity amount of the cam ring, the second pressure receiving surface being set smaller in pressure receiving area than the first pressure receiving surface; and 
 a hydraulic switch for changeover controlling supply of the discharge pressure to the second pressure chamber, based on an energizing current. 
 
     
     
       2. A variable displacement oil pump as claimed in  claim 1 , where the hydraulic switch is selectable between a first state where the second pressure chamber is connected via a first hydraulic path to receive the discharge pressure, and a second state where the second pressure chamber is connected via a second hydraulic path to release pressurization to achieve a pressure lower than the discharge pressure. 
     
     
       3. A variable displacement oil pump as claimed in  claim 2 , wherein the hydraulic switch has a configuration to establish the first state in a current supply condition, and to establish the second state in a non-current supply condition. 
     
     
       4. A variable displacement oil pump as claimed in  claim 2 , wherein the hydraulic switch has a configuration to establish the second state in a current supply condition, and to establish the first state in a non-current supply condition. 
     
     
       5. A variable displacement oil pump as claimed in  claim 3 , wherein the hydraulic switch is a solenoid valve. 
     
     
       6. A variable displacement oil pump as claimed in  claim 1 , further comprising a control device configured to control the hydraulic switch in accordance with an engine speed of the engine. 
     
     
       7. A variable displacement oil pump as claimed in  claim 1 , further comprising a control device configured to control the hydraulic switch in accordance with an engine load of the engine. 
     
     
       8. A variable displacement oil pump as claimed in  claim 1 , further comprising a control device configured to control the hydraulic switch in accordance with an oil temperature of the engine. 
     
     
       9. A variable displacement oil pump as claimed in  claim 1 , wherein each of the first and second pressure chamber is defined by an outer peripheral surface of the cam ring, an inner peripheral surface of the housing and the swinging movement fulcrum of the cam ring. 
     
     
       10. A variable displacement oil pump as claimed in  claim 9 , wherein a region within the housing and outside the cam ring, except for the first and second pressure chambers, is set at atmospheric pressure or a suction pressure. 
     
     
       11. A variable displacement oil pump as claimed in  claim 10 , wherein the biasing member is disposed at a site where the atmospheric pressure or the suction pressure is set, in the region outside the cam ring. 
     
     
       12. A variable displacement oil pump for supplying oil at least to sliding sections of an internal combustion engine, comprising:
 a pump element including a rotor configured to be rotationally driven by the internal combustion engine, and a plurality of vanes disposed at an outer peripheral section of the rotor; a cam ring having an inner peripheral section for accommodating the pump element thereinside, and an outer peripheral section having a swinging movement fulcrum, the cam ring being swingingly movable around the swinging movement fulcrum to change an eccentricity amount of the cam ring relative to an axis of the rotor; 
 a housing for accommodating the cam ring thereinside and including side walls disposed respectively on axially opposite sides of the cam ring to define a plurality of hydraulic fluid chambers each of which is defined by the rotor and adjacent ones of the vanes, the housing further including: a discharge section in which volumes of the hydraulic fluid chambers decrease along the discharge section in a rotational direction of the rotor to realize pumped oil, a first pressure chamber bounded by the outer peripheral section of the cam ring and an inner surface of the housing, a discharge hole opened through at least one of the side walls to discharge the pumped oil from the variable displacement oil pump, with the first pressure chamber opening to the discharge hole, and a suction hole opened through at least one of the side walls to supply oil to a suction section in which volumes of the hydraulic chambers increase along the rotational direction of the rotor;
 a biasing member for biasing the cam ring in a direction to increase the eccentricity amount of the cam ring relative to the axis of the rotor; 
 the first pressure chamber having a first pressure receiving surface on the outer peripheral section of the cam ring, and directly connected to the discharge section via an open valve-less path, to constantly receive a discharge pressure of the pumped oil fed into the first pressure chamber from the discharge section, before the pumped oil is discharged out of the discharge hole of the oil pump, to allow the discharge pressure to be applied through the first pressure receiving surface to the cam ring to oppose to a biasing force of the biasing member, so as to provide the cam ring with a swinging force in a direction to decrease the eccentricity amount of the cam ring; 
 a second pressure chamber defined by the outer peripheral section of the cam ring and the housing, and having a second pressure receiving surface on the outer peripheral section of the cam ring, where introduction of the same discharge pressure that is introduced into the first pressure chamber, causes the discharge pressure to be applied through the second pressure receiving surface to the cam ring to assist the biasing force of the biasing member so as to provide the cam ring with a swinging force in a direction to increase the eccentricity amount of the cam ring, the second pressure receiving surface being set smaller in pressure receiving area than the first pressure receiving surface; and 
 
 a hydraulic switch for changeover controlling supply of the discharge pressure to the second pressure chamber, based on an energizing current; 
 wherein a part of the first pressure chamber is disposed overlapping with the discharge section in a radial direction of the rotor. 
 
     
     
       13. A variable displacement oil pump as claimed in  claim 12 , wherein whole of each of the first and second pressure chambers is disposed overlapping with a range of the discharge section, in the radial direction of the rotor. 
     
     
       14. A variable displacement oil pump as claimed in  claim 12 , wherein a whole of each of the first and second pressure chambers is disposed overlapping with a peripheral direction range in which the discharge section is formed. 
     
     
       15. A variable displacement oil pump for supplying oil at least to sliding sections of an internal combustion engine, comprising:
 a pump element including a rotor configured to be rotationally driven by the internal combustion engine, and a plurality of vanes disposed at an outer peripheral section of the rotor; 
 a cam ring having an inner peripheral section for accommodating the pump element thereinside, and an outer peripheral section having a swinging movement fulcrum, the cam ring being swingingly movable around the swinging movement fulcrum to change an eccentricity amount of the cam ring relative to an axis of the rotor; 
 a housing for accommodating the cam ring thereinside and including side walls disposed respectively on axially opposite sides of the cam ring to define a plurality of hydraulic fluid chambers each of which is defined by the rotor and adjacent ones of the vanes, the housing further including: a discharge section in which volumes of the hydraulic fluid chambers decrease along the discharge section in a rotational direction of the rotor to realize pumped oil, a first pressure chamber bounded by the outer peripheral section of the cam ring and an inner surface of the housing, a discharge hole opened through at least one of the side walls to discharge the pumped oil from the variable displacement oil pump, with the first pressure chamber opening to the discharge hole of the oil pump, and a suction hole opened through at least one of the side walls to supply oil to a suction section in which volumes of the hydraulic chambers increase along the rotational direction of the rotor;
 a biasing member for biasing the cam ring in a direction to increase the eccentricity amount of the cam ring relative to the axis of the rotor; 
 the first pressure chamber having a first pressure receiving surface on the outer peripheral section of the cam ring, and directly connected to the discharge section via an open valve-less path, to constantly receive a discharge pressure of the oil pump fed into the first pressure chamber from the discharge section, before the pumped oil is discharged out of the discharge hole of the oil pump, to allow the discharge pressure to be applied through the first pressure receiving surface to the cam ring to oppose to a biasing force of the biasing member so as to provide the cam ring with a swinging force in a direction to decrease the eccentricity amount of the cam ring; and 
 a second pressure chamber defined by the outer peripheral section of the cam ring and the housing, and having a second pressure receiving surface on the outer peripheral section of the cam ring, where introduction of the same discharge pressure that is introduced into the first pressure chamber causes the discharge pressure to be applied through the second pressure receiving surface to the cam ring to assist the biasing force of the biasing member so as to provide the cam ring with a swinging force in a direction to increase the eccentricity amount of the cam ring, the second pressure receiving surface being set smaller in pressure receiving area than the first pressure receiving surface; 
 a hydraulic switch for changeover controlling supply of the discharge pressure to the second pressure chamber, based on an energizing current; 
 wherein the first and second pressure chambers are disposed nearer to the swinging movement fulcrum than to the axis of the rotor. 
 
 
     
     
       16. A variable displacement oil pump as claimed in  claim 15 , wherein the singing movement fulcrum is a pivot formed integral with the outer peripheral section of the cam ring. 
     
     
       17. A variable displacement oil pump as claimed in  claim 16 , wherein each of the first and second pressure chambers is defined by an outer peripheral surface of the cam ring, and an inner peripheral surface of the housing, and are separated from each other by the fulcrum. 
     
     
       18. A variable displacement oil pump as claimed in  claim 16 , wherein the pivot is swingably movably disposed supported in a depression formed in the inner peripheral section of the housing. 
     
     
       19. A variable displacement oil pump as claimed in  claim 15 , wherein a region outside the cam ring, except for the first and second pressure chambers, is set at atmospheric pressure or a suction pressure. 
     
     
       20. A variable displacement oil pump for supplying oil at least to sliding sections of an internal combustion engine, comprising:
 a pump element including a rotor configured to be rotationally driven by the internal combustion engine, and a plurality of vanes disposed at an outer peripheral section of the rotor;   a ring having an inner peripheral section for accommodating the pump element thereinside, and an outer peripheral section, the ring being movable to change a position of the ring relative to an axis of the rotor;   a housing for accommodating the ring thereinside and including side walls disposed respectively on axially opposite sides of the ring to define a plurality of hydraulic fluid chambers each of which is defined by the rotor and adjacent ones of the vanes, the housing further including:   a discharge section in which volumes of the hydraulic fluid chambers decrease along a rotational direction of the rotor to realize pumped oil,   a first pressure chamber bounded by the outer peripheral section of the ring and an inner surface of the housing,   a discharge hole opened through at least one of the side walls to discharge the pumped oil from the variable displacement oil pump, and   a suction hole opened through at least one of the side walls to supply oil to a suction section in which volumes of the hydraulic chambers increase along the rotational direction of the rotor;   a biasing member for biasing the ring in a direction to increase differentiation in volume of the hydraulic fluid chambers;   the first pressure chamber having a first pressure receiving surface on the outer peripheral section of the ring, and the first pressure chamber being connected to the discharge section via an open valve-less path, to receive a discharge pressure of the pumped oil fed into the first pressure chamber from the discharge section, to allow the discharge pressure to be applied through the first pressure receiving surface to the ring to provide the ring with a force against the biasing force of the biasing member in a direction to decrease differentiation in volume of the hydraulic fluid chambers;   a second pressure chamber defined by the outer peripheral section of the ring and the housing, and having a second pressure receiving surface on the outer peripheral section of the ring, where introduction of the pumped oil from the same discharge section that is introduced into the first pressure chamber causes a discharge pressure to be applied through the second pressure receiving surface to the ring to assist the biasing force of the biasing member so as to provide the ring with a force in a direction to increase a moving amount of the ring, the second pressure receiving surface being set different in pressure receiving area from the first pressure receiving surface; and   a controller configured to be electrically driven for changeover controlling supply of the hydraulic fluid to the second pressure chamber, based on an energizing current, and allowing the second pressure chamber to be opened to an atmospheric environment.   
     
     
       21. A variable displacement oil pump as claimed in claim 20, wherein the ring comprises a cam ring, and the outer peripheral section of the ring has a swinging movement fulcrum. 
     
     
       22. A variable displacement oil pump as claimed in claim 20, wherein the first pressure chamber is directly connected to the discharge section. 
     
     
       23. A variable displacement pump, comprising:
 a housing;   a pump element movably contained in the housing to suck and discharge hydraulic fluid, volumes of the hydraulic fluid discharged by the pump element being changed according to the position of the pump element;   a biasing element that biases the pump element in a direction for increasing the discharged volumes of the hydraulic fluid;   a first control fluid chamber defined between the pump element and the housing, the hydraulic fluid discharged from the pump element being introduced into the first chamber, the pump element being moved in a direction for decreasing the discharged volumes of the hydraulic fluid by the hydraulic fluid being introduced into the first chamber;   a second control fluid chamber defined between the pump element and the housing, the second chamber being separately formed from the first chamber, the hydraulic fluid discharged from the pump element being introduced into the second chamber, the pump element being moved in a direction for increasing the discharged volumes of the hydraulic fluid by the hydraulic fluid being introduced into the second chamber; and   an electrically controlled valve that is provided in a fluid passage that guides the hydraulic fluid discharged from the pump element to the second chamber,   the valve including a first condition for allowing the hydraulic fluid discharged from the pump element to be therethrough introduced into the second chamber and a second condition for allowing the second chamber to be opened to atmospheric environment,   the valve being maintained in the second condition when the valve is deenergized.   
     
     
       24. A variable displacement pump as claimed in claim 23, wherein the valve comprises:
 a body,   a valve member that moves between the first condition and the second condition,   an elastic member that biases the valve in a direction such that the valve member is placed in the second condition, and   an actuator that is electrically driven to bias the valve member in a direction such that the valve member is placed in the first condition.   
     
     
       25. A variable displacement pump as claimed in claim 24, wherein
 the valve member is controlled between the first condition and the second condition.   
     
     
       26. A variable displacement pump as claimed in claim 23, wherein
 the valve includes an inlet port connected to a discharged port of the pump element, an outlet port connected to the second chamber, and a drain port connected to the atmosphere.