Electromechanical variable valve actuator with a spring controller

Abstract

Actuators, and corresponding methods and systems for controlling such actuators, provide independent lift and timing control with minimum energy consumption. In an exemplary embodiment, an electromechanical actuator comprises a housing, first and second electromagnets rigidly disposed in the housing and separated from each other by an armature chamber, an armature disposed in the armature chamber and movable between the first and second electromagnets, an armature rod rigidly connected with the armature and operably connected with a load, at least one first actuation spring biasing the armature in a first direction, at least one second actuation spring biasing the armature in a second direction, and one fluid-operated spring controller capable of controlling the position of the first-direction end of the at least one second actuation spring. The spring controller allows the actuation springs at their least compressed state and the engine valve closed when engine power is off. The spring controller may also be adjusted, with a low or moderate control fluid pressure, to allow the engine valve to operate with a partial lift.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of one preferred embodiment of the electromechanical actuator, at its zero-lift state;

FIG. 2 is a schematic illustration of the embodiment of FIG. 1 at the end of the start-up process, when the second actuation spring is greatly compressed.

FIG. 3 is a schematic illustration of the embodiment of FIG. 1 when the actuation springs are substantially equally compressed, the net spring force is zero, the armature is at the middle point between the electromagnets, and the engine valve is half open.

FIG. 4 is a schematic illustration of the embodiment of FIG. 1 with the spring controller experiencing a small displacement when the fluid supply pressure is adjusted to a low or moderate value.

FIG. 5A is a schematic illustration of another preferred embodiment including an intentional, substantial gap between the spring-controller cylinder and the spring-controller piston outer dimension to pressurize both spring-controller first and second chambers.

FIG. 5B is a schematic illustration of yet another preferred embodiment including at least one spring-controller orifice that is to equalize steady-state pressures in the spring-controller first and second chambers and provide damping effect to reduce oscillation the spring controller may experience.

FIG. 5C is a schematic illustration of another preferred embodiment including a housing extension.

FIG. 6 is a schematic illustration of another preferred embodiment with the second actuation spring and the spring controller relocated to the first-direction end of the actuator.

FIG. 7 is a schematic illustration of another preferred embodiment, in which the steady-state or power-off armature first air gap and the engine valve opening are equal to a small value, instead of zero, when the spring-controller first surface is up against the spring-controller cylinder first surface.

Claims

1. An electromechanical actuator, comprising: first and second electromagnets separated from each other by an armature chamber,an armature disposed in the armature chamber and movable between the first and second electromagnets,an armature rod operably connected with the armature,an engine valve operably connected with the armature rod,at least one first actuation spring biasing the armature in a first direction,at least one second actuation spring biasing the armature in a second direction, andone spring controller, controlling the position of one end of the at least one second actuation spring and thus the neutral position of the armature and engine valve, and having a predetermined maximum spring-controller displacement and a default or power-off position such that the engine valve is closed at power-off.

2. The electromechanical actuator of claim 1, further including means for the spring controller to stay in between zero displacement and the predetermined maximum spring-controller displacement, whereby the engine valve to operate at partial as well as full strokes.

3. The electromechanical actuator of claim 1, wherein the spring controller is situated between the second electromagnet and the at least one second actuation spring, andthe first and second actuation springs are distal in the second direction to the second electromagnet.

4. The electromechanical actuator of claim 1, wherein the spring controller is driven with a fluid medium.

5. The electromechanical actuator of claim 4, wherein the spring controller is slideably disposed within a spring-controller cylinder and around the armature rod.

6. The electromechanical actuator of claim 1, further including at least one damping mechanism, whereby reducing oscillation in the position of the spring controller.

7. The electromechanical actuator of claim 4, further including first and second chambers, andspring controller first and second surfaces of differential surface areas.

8. The electromechanical actuator of claim 7, further including at least one flow restriction between the first and second chambers, whereby reducing oscillation in the position of the spring controller.

9. The electromechanical actuator of claim 4, further includes a switchable fluid source.

10. The electromechanical actuator of claim 4, further includes a switch valve that supplies a fluid medium under at least two alternative levels of pressure.

11. A method of controlling an actuator comprising: (a) providing an actuator including the following components: first and second electromagnets separated from each other by an armature chamber,an armature disposed in the armature chamber and movable between the first and second electromagnets,an armature rod operably connected with the armature,an engine valve operably connected with the armature rod,at least one first actuation spring biasing the armature in a first direction,at least one second actuation spring biasing the armature in a second direction, andone spring controller controlling the position of one end of the at least one second actuation spring and thus the neutral position of the armature and engine valve; and(b) closing the engine valve at power-off by subjecting the spring controller primarily to the spring force and allowing sufficient axial extension of the actuation springs.

12. The method of claim 11, wherein further including means for the spring controller to stay in between zero displacement and a predetermined maximum spring-controller displacement, whereby the engine valve operates at partial stroke as well as full stroke.

13. The method of claim 11, wherein the spring controller is driven with a fluid medium.

14. The method of claim 13, wherein the fluid medium is de-pressurized automatically when the engine is off.

15. The method of claim 13, wherein the engine valve operates at a small stroke by adjusting the fluid supply pressure to a low or moderate value, and operates at a full stroke by adjusting the fluid supply pressure to a high value.

16. The method of claim 11, wherein the axial position of the spring controller is stabilized by a damping mechanism.

17. The method of claim 12, wherein the damping mechanism is in the form of a flow restriction.

18. The method of claim 13, further including a switch valve with a predetermined default or power-off position, whereby de-pressurizing the fluid medium at power-off.

19. The method of claim 11, wherein the spring controller is slideably disposed around the armature rod and within a spring-controller cylinder having an inner dimension, and has a flange feature possessing an outer dimension and dividing the spring-controller cylinder into first and second chambers, with a predetermined substantial clearance between the cylinder inner dimension and the flange outer dimension, whereby providing flow restriction between the first and second chambers to reduce position oscillation for the spring controller, eliminating one pair of tightly sliding surfaces, and reducing the associated manufacturing cost.