Stepper motor driven proportional actuator
AssigneeWoodward Governor Company
InventorMark A. Spickard
Life of this patent
Estimating the term…
Abstract
A low energy stepper motor driven actuator that eliminates the need for a position sensor is provided. The stepper motor rotates a cam in a control piston valve. The cam rotation increases the gap between the cam and nozzle on one side of the cam and decreases the gap between the cam and nozzle on the other side. The gap differences affect the pressures on the control piston ends, which forces the piston in the direction that will re-equalize the cam-nozzle gaps. As a result, piston moves to a position such that the head or rod of the actuator piston receives high pressure flow, thereby moving the actuator. Movement of the actuator rod provides mechanical feedback to the cam, causing the cam to move back to its mechanical null position.
Claims20
A stepper motor driven actuator comprising:
- a stepper motor;
- a cam operatively connected to the stepper motor, the cam rotating position in response to stepping of the stepper motor, the cam positioned within a valve body having an inlet port, a rod port, a head port and at least one drain port;
- a control piston positioned within the valve body and having a plurality of nozzles positioned on opposite sides of the cam in close proximity to a surface of the cam and movable between a null position and flow positions, each of the plurality of nozzles having a flow path, the control piston moving as a result of a pressure imbalance at the ends of the control piston occurring in response to a change in position of the cam such that a difference between a first gap between the surface of the cam and one of the plurality of nozzles and a second gap between the surface of the cam and an other of the plurality of nozzles is minimized;
- and
- an actuator having a piston integral to a rack that is operably coupled to the cam, the piston having a first side and a second side, the first side being in fluid communication with the head port and the second side being in fluid communication with the rod port, the cam moving in response to the rack moving.
A stepper motor driven actuator system comprising:
- a stepper motor;
- a gearbox operatively connected to the stepper motor;
- a cam operatively connected to the gearbox, the cam rotating position in response to stepping of the stepper motor, the cam positioned within a valve body having an inlet port, a rod port, a head port and at least one drain port;
- a control piston positioned within the valve body and having a pair of nozzles positioned on opposite sides of the cam in close proximity to a surface of the cam so as to each define a gap therebetween, each of the pair of nozzles having a flow path, the control piston moving as a result of a pressure imbalance at the ends of the control piston occurring in response to a change in the gap between the surface of the cam and each of the nozzles due to a change in position of the cam;
- and
- an actuator having a piston integral to a rack, the piston having a first side and a second side, the first side in fluid communication with the head port and the second side in fluid communication with the rod port, the rack in mesh relationship to the gearbox, the cam moving in response to the rack moving.
Dependencies are inferred from the claim text.