Valve actuator assembly
A valve actuator assembly includes an axially moveable valve and a ramp roller thrust drive. The ramp roller thrust drive includes at least first and second opposed thrust plates, each plate including one or more ramps. A roller is positioned between corresponding opposed plate ramps and a rotation of one of the thrust plates relative to the other thrust plate causes the plates to move axially relative to one another such that axial motion is imparted to the valve.
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This application claims priority under 35 U.S.C. sec. 119 to provisional patent application No. 60/658,071, filed on Mar. 3, 2005, the entire contents of which is hereby incorporated by reference.
FIELD OF THE INVENTIONThe present invention relates to a valve actuator assembly for controlling axial motion of a valve.
BACKGROUND Typically valves in an internal combustion engine are opened and closed by the action of a camshaft lobe upon some type of valve lifter or rocker arm assembly.
In one embodiment, a valve actuator assembly includes an axially movable valve in an internal combustion engine and a ramp roller thrust drive. The ramp roller thrust drive includes at least first and second opposed thrust plates, each plate including one or more ramps. At least one roller is positioned between corresponding opposed plate ramps, and a rotation of one of the thrust plates relative to the other thrust plate causes the plates to move axially relative to one another such that axial motion is imparted to the valve. A plate actuating mechanism is configured to rotate one of the plates relative to the other plate.
A method for actuating an axially movable valve includes providing a ramp roller thrust drive including at least first and second opposed thrust plates, each plate including one or more ramps, and further including at least one roller positioned between corresponding opposed plate ramps. The method also includes rotating one of the thrust plates relative to the other thrust plate to impart axial motion to the valve.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting.
Referring to
In order to prevent the rollers 8 from moving out of position due to slipping on the ramps 7,
In cases where a greater increase in height for a given input movement is necessary, it is possible to stack ramp thrust drives in series to multiply the effect. For example,
Thus, the lower plate 15 acts directly on the valve 3 while the upper plate 14 reacts against a ground plane 17 connected to the primary structure of the engine. In the example shown, this ground plane 17 includes a hydraulic lash adjuster 18 which also helps insure proper seating of the valve 3 in the closed position. Input motion is applied to the center plate 16. In this example, rotation of the upper plate 14 is prevented by a pin 19 which is fixed to the ground plane 17. A slotted clip 20 is attached to the upper plate 14 and engages a pin 21 on the lower plate 15 to also prevent rotation of the lower plate 15. Pin 21 can move axially as necessary in the slot of clip 20. When plate 16 is rotated relative to the other plates 14, 15, the plates 15, 16 move axially relative to plate 14 and axial motion is imparted to the valve 3, thereby opening the valve 3.
In some cases, the timing of the valve opening can also be varied. As explained below, by altering the position of the clip 20 with respect to the plate 16 (and thus the ramps 7), the valve opening can occur at different times relative to a constant oscillating input motion.
Input motion, preferably oscillating input motion, can be provided to a plate in a variety of ways. As illustrated in
For example,
To improve the efficiency and performance of an internal combustion engine, it is often desirable to alter the valve opening cycle for specific operating conditions. There are various ways to accomplish this. For example, with reference to
Another manner in which the valve motion can be modified is by changing the hydraulic characteristics of the lash adjuster 18. Since the ramp thrust drive reacts against force of the lash adjuster 18 to open the valve 3, a reduction in stiffness of this member will allow some of the increase in ramp thrust drive height to be absorbed as “lost motion” by the lash adjuster 18. This can be accomplished by venting a portion of the fluid from a high pressure chamber of the lash adjuster 18 to a low pressure side for operating conditions that do not require full mechanical valve motion. An alternative to using the lash adjuster 18 to achieve modified valve motion would be to incorporate a position indicator and a feedback loop into the control system for the thrust drive 46. Therefore, the hydraulic lash adjuster 18 need not be used in the illustrated valve actuator assemblies.
Another embodiment of a valve actuator assembly 48B is shown in
Further, the valve 3B is modified by lengthening valve stem 38B so that it extends into the ramp thrust drive 46B, thereby eliminating the separate central pin 10 that is shown in
A distinct advantage of the arrangement illustrated in
In addition to directly coupling the ramp thrust drive 46 and the valve 3, various coupling mechanisms can be used instead. For example,
Claims
1. A valve actuator assembly comprising:
- an axially movable valve; and
- a ramp roller thrust drive including at least first and second opposed thrust plates, each plate including one or more ramps, and further including at least one roller positioned between corresponding opposed plate ramps, wherein a rotation of one of the thrust plates relative to the other thrust plate causes the plates to move axially relative to one another such that axial motion is imparted to the valve.
2. The valve actuator assembly of claim 1, wherein the valve is in an internal combustion engine.
3. The valve actuator assembly of claim 1, wherein the ramp roller thrust drive is a double roller thrust drive including a third stacked thrust plate.
4. The valve actuator assembly of claim 3, wherein the center thrust plate is caused to rotate and the other two of the thrust plates are prevented from rotating.
5. The valve actuator assembly of claim 4, wherein at least one of the stationary thrust plates is prevented from rotating using a slotted clip and a pin.
6. The valve actuator assembly of claim 1, further including a lash adjuster for biasing the valve in a closed position.
7. The valve actuator assembly of claim 1, further including a spring for biasing the valve in a closed position.
8. The valve actuator assembly of claim 7, further including a valve keeper for coupling the spring to the valve.
9. The valve actuator assembly of claim 7, wherein one of the thrust plates provides a seat for the spring.
10. The valve actuator assembly of claim 1, wherein a valve stem of the valve extends axially through at least one thrust plate and keeps the plates in a proper relationship to one another.
11. The valve actuator assembly of claim 1, further including at least one snap ring for coupling a movable plate to a valve stem of the valve.
12. The valve actuator assembly of claim 1, further including a plate actuating mechanism configured to rotate one of the thrust plates relative to the other thrust plate.
13. The valve actuator assembly of claim 12, wherein the plate actuating mechanism includes one of an electromagnetic actuator and an electromechanical actuator.
14. The valve actuator assembly of claim 12, wherein the plate actuating mechanism is configured to provide oscillating motion to one of the thrust plates.
15. The valve actuator assembly of claim 12, wherein the plate actuating mechanism includes a crankshaft and a connecting rod.
16. The valve actuator assembly of claim 1, further including a coupling mechanism linking the ramp thrust drive and the valve, wherein the coupling mechanism multiplies an amount of axial movement of the ramp thrust drive which is imparted to the valve.
17. The valve actuator assembly of claim 16, wherein the coupling mechanism includes one of a finger follower and a pivot rocker arm.
18. The valve actuator assembly of claim 1, wherein the roller and the ramps include gear teeth.
19. A valve actuator assembly comprising:
- a valve axially movable between a closed position for preventing a flow of gas to or from a combustion chamber of an internal combustion engine and an open position for allowing a flow of gas to or from the combustion chamber;
- a ramp roller thrust drive including at least first and second opposed thrust plates, each plate including one or more ramps and including a corresponding roller positioned between opposed plate ramps such that rotation of one of the thrust plates relative to the other thrust plate causes the plates to move axially relative to one another such that axial motion is imparted to the valve; and
- a plate actuating mechanism configured to provide oscillating rotative motion to one of the thrust plates relative to the other thrust plate.
20. A method for actuating an axially movable valve, the method comprising:
- providing a ramp roller thrust drive including at least first and second opposed thrust plates, each plate including one or more ramps, and further including at least one roller positioned between corresponding opposed plate ramps; and
- rotating one of the thrust plates relative to the other thrust plate to impart axial motion to the valve.
Type: Application
Filed: Mar 3, 2006
Publication Date: Sep 7, 2006
Applicant: Timken US Corporation (Torrington, CT)
Inventors: Charles Shattuck (West Goshen, CT), Richard Murphy (Torrington, CT), Carl Davenport (Greenville, SC)
Application Number: 11/367,968
International Classification: F01L 1/00 (20060101);