Pressure shifted valve timing

1. A hydraulic pump-motor comprising:

a cylinder block including a plurality of fluid chambers;

a piston in each of the fluid chambers;

a cam having a cam surface that engages the pistons and drives movement of the pistons relative to the fluid chambers in response to relative rotation between the cam and the fluid chambers;

a fixed valve area profile configured to control fluid flows between the fluid chambers and first and second ports during rotation of the fluid chambers relative to the cam and the fixed valve area profile; and

a timing adjustment actuator configured to adjust an angular orientation of the fixed valve area profile relative to an angular orientation of the cam based on a pressure differential between a pressure at the first port and a pressure at the second port, during rotation of the cam and the fixed valve area profile relative to the fluid chambers.

2. The hydraulic pump-motor of claim 1 , wherein the timing adjustment actuator drives the fixed valve area profile toward a first or second angular orientation relative to the angular orientation of the cam based on the direction of the pressure differential.

3. The hydraulic pump-motor of claim 2 , wherein:

the timing adjustment actuator comprises:

a housing connected to the fixed valve area profile; and

a vane actuator contained within an actuator chamber of the housing, the vane actuator having a fixed angular orientation relative to the cam, and dividing the actuator chamber into a first actuator chamber section connected to the first port and a second actuator chamber section connected to the second port; and

a non-zero pressure differential between the first and second ports creates a net pressure difference between the first and second actuator chambers and drives rotation of the fixed valve area profile and the housing toward the first angular orientation or the second angular orientation relative to the vane actuator and the cam based on the direction of the pressure differential.

4. The hydraulic pump-motor of claim 3 , wherein the timing adjustment actuator is configured to drive the fixed valve area profile toward the first angular orientation or the second angular orientation relative to the angular orientation of the cam based on the direction and magnitude of the pressure differential, and return the fixed valve area profile to a third angular orientation relative to the angular orientation of the cam when the pressure differential is zero.

5. The hydraulic pump-motor of claim 4 , wherein first and second angular orientations of the fixed valve area profile are each angularly offset in opposite directions from the third angular orientation.

6. The hydraulic pump-motor of claim 5 , wherein:

the timing adjustment actuator includes a biasing mechanism configured to bias the fixed valve area profile and the housing in the third angular orientation relative to the angular orientation of the cam; and

the non-zero pressure differential drives rotational movement of the fixed valve area profile relative to the cam from the third angular orientation toward the second or third angular orientation.

7. The hydraulic pump-motor of claim 1 , wherein:

the plurality of fluid chambers are in a radial configuration;

the cam comprises a radial cam having the cam surface that engages the pistons and drives radial movement of the pistons relative to the fluid chambers in response to relative rotation between the radial cam and the fluid chambers;

the fixed valve area profile comprises a disc valve configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the radial cam and the disc valve relative to the fluid chambers; and

the timing adjustment actuator is configured to adjust an angular orientation of the disc valve relative to an angular orientation of the radial cam based on the pressure differential during rotation of the radial cam and the disc valve relative to the fluid chambers.

8. The hydraulic pump-motor of claim 1 , wherein:

the plurality of fluid chambers are in a radial configuration;

the cam comprises a radial cam having the cam surface that engages the pistons and drives radial movement of the pistons relative to the fluid chambers in response to relative rotation between the fluid chambers and the radial cam;

the fixed valve area profile comprises a pintle configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the fluid chambers relative to the radial cam and the pintle; and

the timing adjustment actuator is configured to adjust an angular orientation of the pintle relative to an angular orientation of the radial cam based on the pressure differential during rotation of the fluid chambers relative to the radial cam and the pintle.

9. The hydraulic pump-motor of claim 1 , wherein:

the plurality of fluid chambers are in an axial configuration;

the cam surface drives axial movement of the pistons relative to the fluid chambers in response to relative rotation between the cam and the fluid chambers;

the fixed valve area profile comprises a port plate configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the fluid chambers relative to the cam and the port plate; and

the timing adjustment actuator is configured to adjust an angular orientation of the port plate relative to the cam based on the pressure differential during rotation of the fluid chambers relative to the cam and the port plate.

10. A hydraulic pump-motor comprising:

a cylinder block including a plurality of fluid chambers;

a piston in each of the fluid chambers;

a cam having a cam surface that engages the pistons and drives movement of the pistons relative to the fluid chambers in response to relative rotation between the cam and the fluid chambers;

a fixed valve area profile configured to control fluid flows between the fluid chambers and first and second ports during rotation of the fluid chambers relative to the cam and the fixed valve area profile; and

a timing adjustment actuator comprising:

a housing connected to the fixed valve area profile; and

a vane actuator contained within an actuator chamber of the housing, the vane actuator having a fixed angular orientation relative to the cam, and dividing the actuator chamber into a first actuator chamber section connected to the first port and a second actuator chamber section connected to the second port,

wherein a non-zero pressure differential between the first and second ports creates a net pressure difference between the first and second actuator chambers and adjusts an angular orientation of the fixed valve area profile relative to an angular orientation of the cam during rotation of the cam and the fixed valve area profile relative to the fluid chambers.

11. The hydraulic pump-motor of claim 10 , wherein the timing adjustment actuator drives the fixed valve area profile to a first or second angular orientation relative to the angular orientation of the cam based on the direction of the pressure differential.

12. The hydraulic pump-motor of claim 11 , wherein the timing adjustment actuator is configured to drive the fixed valve area profile toward the first angular orientation or the second angular orientation relative to the angular orientation of the cam based on the direction and magnitude of the pressure differential, and return the fixed valve area profile to a third angular orientation relative to the angular orientation of the cam when the pressure differential is zero.

13. The hydraulic pump-motor of claim 12 , wherein first and second angular orientations are each angularly offset from the first angular orientation in opposite directions.

14. The hydraulic pump-motor of claim 12 , wherein:

the timing adjustment actuator includes a biasing mechanism configured to bias the fixed valve area profile and the housing in the third angular orientation relative to the angular orientation of the cam; and

the non-zero pressure differential drives rotational movement of the fixed valve area profile relative to the cam from the third angular orientation toward the second or third angular orientation.

15. The hydraulic pump-motor of claim 10 , wherein:

the plurality of fluid chambers are in a radial configuration;

the cam comprises a radial cam having the cam surface that engages the pistons and drives radial movement of the pistons relative to the fluid chambers in response to relative rotation between the radial cam and the fluid chambers;

the fixed valve area profile comprises a disc valve configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the radial cam and the disc valve relative to the fluid chambers; and

the timing adjustment actuator is configured to adjust an angular orientation of the disc valve relative to an angular orientation of the radial cam based on the pressure differential during rotation of the radial cam and the disc valve relative to the fluid chambers.

16. The hydraulic pump-motor of claim 10 , wherein:

the plurality of fluid chambers are in a radial configuration;

the cam comprises a radial cam having the cam surface that engages the pistons and drives radial movement of the pistons relative to the fluid chambers in response to relative rotation between the fluid chambers and the radial cam;

the fixed valve area profile comprises a pintle configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the fluid chambers relative to the radial cam and the pintle; and

the timing adjustment actuator is configured to adjust an angular orientation of the pintle relative to an angular orientation of the radial cam based on the pressure differential during rotation of the fluid chambers relative to the radial cam and the pintle.

17. The hydraulic pump-motor of claim 10 , wherein:

the plurality of fluid chambers are in an axial configuration;

the cam surface drives axial movement of the pistons relative to the fluid chambers in response to relative rotation between the cam and the fluid chambers;

the fixed valve area profile comprises a port plate configured to control fluid flows between the fluid chambers and the first and second ports during rotation of the fluid chambers relative to the cam and the port plate; and

the timing adjustment actuator is configured to adjust an angular orientation of the port plate relative to the cam based on the pressure differential during rotation of the fluid chambers relative to the cam and the port plate.

18. A method of operating a hydraulic pump-motor, wherein:

the hydraulic pump motor comprises:

a cylinder block including a plurality of fluid chambers;

a piston in each of the fluid chambers;

a cam having a cam surface that engages the pistons;

a fixed valve area profile configured to control fluid flows between the fluid chambers and first and second ports; and

a timing adjustment actuator; and

the method comprises:

rotating the plurality of fluid chambers relative to the cam and the fixed valve area profile;

driving movement of the pistons relative to the fluid chambers in response to the rotating;

controlling fluid flows driven by the movement of the pistons between the fluid chambers and the first and second ports during the rotating using the fixed valve area profile; and

adjusting an angular orientation of the fixed valve area profile relative to an angular orientation of the cam during the rotating using the timing adjustment actuator based on a pressure differential between a pressure at the first port and a pressure at the second port.

19. The method of claim 18 , wherein adjusting the angular orientation of the fixed valve area profile relative to the angular position of the cam includes driving the fixed valve area profile to a first or second angular orientation relative to the angular orientation of the cam based on the direction of the pressure differential.

20. The method of claim 19 , wherein:

the timing adjustment actuator comprises:

a housing connected to the fixed valve area profile; and

a vane actuator contained within an actuator chamber of the housing, the vane actuator having a fixed angular orientation relative to the cam, and dividing the actuator chamber into a first actuator chamber section connected to the first port and a second actuator chamber section connected to the second port; and

a non-zero pressure differential between the first and second ports creates a net pressure difference between the first and second actuator chambers and drives rotation of the fixed valve area profile and the housing toward the first or second angular orientation relative to the vane actuator and the cam based on the direction of the pressure differential.