Continuously variable displacement vane pump and system

1. A vane pump with continuously variable output pressure, comprising:

a variable displacement vane pump having a pump control ring which is moveable to alter the displacement of the pump and spring biased to a position of maximum displacement;

a first control chamber operable to create a force on the pump control ring to urge the pump control ring towards a position of minimum displacement, the force resulting from pressurized working fluid in the first control chamber;

a second control chamber operable to create a force on the pump control ring to urge the pump control ring towards the position of maximum displacement, the force resulting from pressurized working fluid in the second control chamber;

a control means operable to vary supply of pressurized working fluid to at least one of the first and second control chambers to vary the displacement of the control ring during operation of the pump to achieve an output pressure selected from a continuously variable range of output pressures from the pump which are independent from an operating speed of the pump.

2. The vane pump of claim 1 wherein the control means comprises a switching modulator operable to selectively supply, isolate or relieve pressurized working fluid from the first and second control chambers.

3. The vane pump of claim 1 wherein the pump control ring pivots between the maximum displacement position and the minimum displacement position.

4. The vane pump of claim 1 wherein the pump control ring slides between the maximum displacement position and the minimum displacement position.

5. The vane pump of claim 1 further comprising the biasing spring to urge the pump control ring towards the maximum displacement position.

6. The vane pump of claim 1 wherein the first control chamber is continuously supplied with pressurized working fluid when the pump is operating and wherein the control means comprises a valve to selectively supply or relieve pressurized working fluid to the second control chamber.

7. The vane pump of claim 1 further comprising a third control chamber positioned to urge the pump control ring against the force of the biasing spring, the third control chamber and the biasing spring providing a failsafe function should a failure occur in any of the control means, first control chamber or second control chamber.

8. A vane pump to supply pressurized working fluid to a mechanical system, the output pressure being selected from a continuously variable range of output pressures from the pump which are independent of the operating speed of the pump, comprising:

a variable displacement vane pump having a pump control ring which is moveable to alter the displacement of the pump;

a first control chamber operable to receive working fluid pressurized by the pump to create a force to urge the pump control ring towards a position of minimum displacement;

a biasing spring to urge the pump control ring towards a maximum displacement position;

a second control chamber operable to receive working fluid pressurized by the pump to create a force to urge the pump control ring towards the position of maximum displacement;

a control means operable to vary the supply of pressurized working fluid to at least one of the first and second control chambers to vary the displacement of the pump during operation of the pump to achieve an output pressure selected from a continuously variable range of output pressures from the pump which are independent from an operating speed of the pump; and

a third control chamber operable to continuously receive working fluid pressurized by the operation of the pump to create a force on the pump control ring to oppose the force of the biasing spring, the third control chamber and the biasing spring providing a failsafe function should a failure occur in the control means, the first control chamber or the second control chamber.

9. The vane pump of claim 8 wherein the control means is responsive to a predefined set of parameters to alter the displacement of the pump to correspond to the operating conditions of the mechanical system supplied with pressurized fluid from the pump.

10. The vane pump of claim 9 wherein the set of parameters comprises a set of operating speed and corresponding working fluid pressure requirements for the mechanical system.

11. The vane pump of claim 10 wherein the mechanical system is an internal combustion engine and the working fluid comprises lubricating oil.

12. The vane pump of claim 8 wherein the control means comprises a switching modulator operable to selectively supply or relieve pressurized working fluid from the first and second control chambers.

13. The vane pump of claim 12 wherein the switching modulator is controlled by a microcontroller.

14. The vane pump of claim 8 wherein the control means comprises a switching modulator operable to selectively supply, isolate or relieve pressurized working fluid from the first and second control chambers.

15. The vane pump of claim 8 wherein the pump control ring pivots between the maximum displacement position and the minimum displacement position.

16. The vane pump of claim 8 wherein the pump control ring slides between the maximum displacement position and the minimum displacement position.