U.S. patent application number 11/367968 was filed with the patent office on 2006-09-07 for valve actuator assembly.
This patent application is currently assigned to Timken US Corporation. Invention is credited to Carl W. Davenport, Richard F. Murphy, Charles W. Shattuck.
Application Number | 20060196457 11/367968 |
Document ID | / |
Family ID | 36617220 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060196457 |
Kind Code |
A1 |
Shattuck; Charles W. ; et
al. |
September 7, 2006 |
Valve actuator assembly
Abstract
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.
Inventors: |
Shattuck; Charles W.; (West
Goshen, CT) ; Murphy; Richard F.; (Torrington,
CT) ; Davenport; Carl W.; (Greenville, SC) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
Timken US Corporation
Torrington
CT
|
Family ID: |
36617220 |
Appl. No.: |
11/367968 |
Filed: |
March 3, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60658071 |
Mar 3, 2005 |
|
|
|
Current U.S.
Class: |
123/90.2 |
Current CPC
Class: |
F01L 1/185 20130101;
F01L 2820/032 20130101; F01L 1/3442 20130101; F01L 13/0031
20130101; F01L 1/182 20130101; F01L 1/042 20130101; F01L 31/12
20130101; F01L 1/2405 20130101; F01L 1/04 20130101; F01L 1/14
20130101; F01L 1/356 20130101; F16H 25/186 20130101 |
Class at
Publication: |
123/090.2 |
International
Class: |
F01L 1/00 20060101
F01L001/00 |
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.
Description
CROSS REFERENCE TO OTHER APPLICATIONS
[0001] 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 INVENTION
[0002] The present invention relates to a valve actuator assembly
for controlling axial motion of a valve.
BACKGROUND
[0003] 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. FIG. 1 shows a typical type of prior
art valve actuator with a cam lobe 1 acting directly upon a bucket
lifter 2 which then transmits this motion to the valve 3. Another
type of prior art valve actuator is shown in FIG. 2, where the cam
lobe 1 acts upon a roller finger follower 2A which pivots on a
hydraulic lash adjuster 4 to open and close the valve 3. It is
often desirable to vary the timing of when the valve opens and the
duration it remains open. These typical valve actuators make it
difficult to control the timing and duration of the opening of the
valve.
SUMMARY
[0004] 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.
[0005] 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
[0006] FIGS. 1 and 2 are side elevation schematic views of prior
art valve actuators;
[0007] FIGS. 3 and 3A are perspective, exploded views of roller
ramp thrust drives of the present invention;
[0008] FIGS. 4 and 5 are side elevation views of roller ramp thrust
drives of the present invention;
[0009] FIG. 6 is a side elevation view of a first embodiment of a
valve ramp actuator assembly;
[0010] FIG. 6A is a side elevation view of a second embodiment of a
valve ramp actuator assembly;
[0011] FIG. 7 is a side elevation view of a valve ramp actuator
assembly along with an illustrative plate actuating mechanism;
[0012] FIG. 8 is a side elevation view of a valve ramp actuator
assembly along with an alternative plate actuating mechanism;
[0013] FIGS. 9A-9C are a top plan view, a side cross sectional view
and a graph, respectively, illustrating the valve lift in
conjunction with a moderate oscillation angle;
[0014] FIGS. 10A-10C are a top plan view, a side cross sectional
view and a graph, respectively, illustrating the valve lift in
conjunction with a maximum oscillation angle;
[0015] FIGS. 11A-11C are a top plan view, a side cross sectional
view and a graph, respectively, illustrating the valve lift in
conjunction with a minimum oscillation angle;
[0016] FIG. 12 is a side elevation view of a third embodiment of a
valve ramp actuator assembly;
[0017] FIG. 13 is a side elevation view of a fourth embodiment of a
valve ramp actuator assembly; and
[0018] FIG. 14 is a side elevation view of a fifth embodiment of a
valve ramp actuator assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] 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.
[0020] Referring to FIG. 3, a valve ramp actuator such as roller
ramp thrust drive 45 is operable to convert rotary input motion
into axial motion that is transmitted to a valve 3 (shown in FIGS.
6-8 and 12-14) in an internal combustion engine. Ramp thrust drive
45 includes a first plate 5 and a second plate 6, each of which
have one or more specially shaped, radially oriented recesses or
ramps 7 which act as cam surfaces. Rollers 8, which can be
cylindrical or tapered in shape, are placed in corresponding
recesses and may be held in correct relative positions by a
separator 9. A central pin 10 is used to keep the plates 5, 6 and
separator 9 in the proper relationship to one another.
[0021] In order to prevent the rollers 8 from moving out of
position due to slipping on the ramps 7, FIG. 3A shows the use of a
plurality of rollers 8A with gear teeth 49 formed on the ends,
which mesh with gear teeth 49 formed in the ramps 7A, for example
on the outer periphery of plates 5A, 6A. The gear teeth could also
be formed elsewhere on the rollers and plates.
[0022] FIG. 4 shows the operation of the roller ramp thrust drive
45 of FIG. 3. A plate actuating mechanism 53 (such as that shown in
FIGS. 7 and 8) provides relative rotative motion between the plates
5, 6. For example, as depicted in FIG. 4 the plate 6 is stationary
while plate 5 is rotated in the direction of the arrow. This action
causes the rollers 8 to ride up the ramps 7 to cause an increase in
the height H of the roller ramp thrust drive 45. The ramps 7 can be
shaped in such a way that a desired change in height is achieved
for a given movement of a plate (or relative movement between
plates). In general, the distance D the plate 5 is moved is greater
than the increase in height .DELTA.H of thrust drive 45. The result
is a multiplication of the input force which is useful to overcome
the forces holding a valve closed.
[0023] 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, FIG. 5 shows
such a double ramp thrust drive 46 wherein an upper plate 14 and a
lower plate 15 are stationary and a center plate 16 rotates
relative to the upper and lower plates 14, 15. One benefit of the
double ramp thrust drive 46 is that for a given amount of input
movement and needed valve lift, the ramp angles can be made
shallower to reduce contact stresses and improve the mechanical
efficiency of the unit.
[0024] FIG. 6 illustrates an embodiment of a valve ramp actuator
assembly 48 including a double ramp thrust drive 46 that is used to
actuate a valve 3 in an internal combustion engine. Valve 3 is
axially movable between a closed position and an open position and
can be an intake valve for allowing air to be drawn into a
combustion chamber or an exhaust valve for allowing products of
combustion to be removed from the combustion chamber. Valve 3 can
be normally biased in a closed position by spring 51 having a
spring retainer 37. Guide 40 provides proper guidance for the
axially movable valve 3.
[0025] FIG. 6 illustrates details of the spring retainer 37 and
valve keeper 39 which is composed of two halves. In FIG. 6, the
spring retainer 37 has been pushed downward, compressing the valve
spring 51. Although not shown in the exploded view of FIG. 6, the
upper end of valve stem 38 is meant to be positioned within a bore
42 in the plate 15. A tapered inner diameter of retainer 37 engages
the tapered outer diameters of the valve keeper 39, forcing them
inward to engage a groove 47 on the valve stem 38. When this
occurs, the valve 3, retainer 37 and valve keeper 39 will be locked
together and move as one unit if a force is applied to the upper
end of the valve stem 38 via the movement of plate 15. Note that
for simplification, central pin 10 of FIG. 5 is not shown in FIG.
6.
[0026] 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.
[0027] 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.
[0028] FIG. 6A illustrates an embodiment of a valve ramp actuator
assembly 48A including a double ramp thrust drive 46A that is used
to actuate valve 3 in an internal combustion engine. In this
embodiment, double roller ramp thrust drive 46A includes
anti-slipping gear teeth 49 on rollers 8A and plates 14A, 15A, 16A.
FIG. 6A also illustrates valve 3 in a closed position.
[0029] Input motion, preferably oscillating input motion, can be
provided to a plate in a variety of ways. As illustrated in FIG. 7,
input motion is provided to center plate 16 of double roller ramp
thrust drive 46 by a plate actuating mechanism 53. In this case,
plate actuating mechanism includes an auxiliary rotating crankshaft
22 and connecting rod 23 which oscillates the center plate 16
through an oscillation angle 25 of the double roller ramp thrust
drive 46. Input motion can also be provided by a variety of other
mechanical, hydraulic, electromechanical, electromagnetic, or
similar devices.
[0030] For example, FIG. 8 shows the same ramp thrust drive 46 as
in FIG. 7, wherein plate actuating mechanism 53 provides
oscillating input motion and includes a linear electromechanical
actuator 27. Actuators of this type can accurately control
position, but are limited in their ability to control velocity. The
double roller ramp thrust drive 46 provides the proper valve lift,
velocity and acceleration for a given input displacement. The
mechanical advantage provided by the double roller ramp thrust
drive 46 means that a relatively low-power plate actuating
mechanism 53 can be used to provide input motion to achieve a
desired amount of valve lift.
[0031] 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 FIG. 7, altering
the throw T of the crankshaft 22 will increase or decrease the
oscillation angle 25 of the center plate 16 about a midpoint. This
alters the amount of cam surface of the ramps 7 available to
provide valve lift. In this same example, altering the length L of
the connecting rod 23 will change the midpoint of the input
oscillation towards one end of the cam surface or the other. An
advantage of the thrust drive 46 is that the amount of valve lift
for a given position of plate 16 is a direct function of the height
of the cam surface or ramp 7 and an indirect function of the plate
position. Having these two functions related, but separate, offers
significant advantages in controlling valve motion.
[0032] FIGS. 9A-9C, 10A-10C, and 11A-11C show how alterations in
the oscillation angle and/or center point of rotation can use
different parts of the cam surface for different operating
conditions. For example, FIGS. 9A-9C demonstrate a moderate
oscillation angle 28 which results in roller movement over range 29
of the cam surface. The resulting valve lift 30 is sufficient to
produce moderate engine power for normal operation. In FIGS.
10A-10C, the oscillation angle 31 has been increased, resulting in
roller movement over range 32 of the cam surface. The resulting
valve lift 33 is both higher and broader, which can be used to
allow an engine to develop maximum power. The oscillation angle 34
in FIGS. 11A-11C has been reduced and its midpoint shifted toward
the flatter area of the cam surface. This results in roller
movement over range 35 of the cam surface and minimal valve lift
36, allowing an engine to operate with great efficiency under low
load conditions such as idling.
[0033] 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.
[0034] Another embodiment of a valve actuator assembly 48B is shown
in FIG. 12, which shows a cross section of a double roller ramp
thrust drive 46B not including the rollers 8 and ramps 7. In this
embodiment, the lower plate 15B of the drive 46B is modified to
include a valve spring seat 50 so that lower plate 15B can function
as the upper seat for valve spring 51B. This eliminates separate
valve spring retainer 37, such as is shown in FIG. 6, and
significantly reduces the reciprocating mass that must be
accelerated as a function of opening the valve. This improves the
performance and efficiency of the valve actuator assembly 48B.
[0035] 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 FIGS. 3,
3A, and 5. Two snap rings 44 engage grooves in the valve stem 38B
above and below plate 15B. Elements 3B, 15B, and 44 then move as
one unit against the valve spring 51B, with the motion being
provided by the axial movement of the ramp thrust drive 46B. A
central bore 54 in the middle plate 16B allows for a slip fit on
the valve stem 38B, and relative movement between the middle plate
16B and valve stem 38B equal to half the valve lift. A central
recess 55 in the upper plate 14B provides a slip fit with the stem
38B like the middle plate, however in this case the relative motion
between the two is equal to the full extent of the valve lift. For
this reason, it may be necessary to increase the thickness of the
upper plate 14B to have sufficient piloting length for the valve
stem 38B. Because the upper plate 14B is stationary, this
additional material is not detrimental to the performance of the
valve assembly.
[0036] A distinct advantage of the arrangement illustrated in FIG.
12 concerns the guidance of the valve 3B. In current internal
combustion engines this function is accomplished entirely by the
valve guide 40. In this embodiment, the valve stem 38B is also
guided in the upper plate 14B which is biased, in this example, by
the lash adjuster 18. The fact that the valve is now guided in two
places, and that these are widely separated, means that the
alignment of the valve 3B relative to its seat is significantly
improved. This also means that the valve guide 40 can be made
shorter or otherwise modified to reduce its size or improve the
performance of the engine.
[0037] In addition to directly coupling the ramp thrust drive 46
and the valve 3, various coupling mechanisms can be used instead.
For example, FIG. 13 shows how the ramp thrust drive 46 can be used
to replace the conventional cam lobe in the arrangement shown in
FIG. 2. The axial movement of the ramp thrust drive 46 causes a
roller finger follower 52, which pivots on hydraulic lash adjuster
18A, to open and close the valve 3. In this case, all of the
advantages of the ramp thrust drive 46 still apply, however in this
case the roller finger follower 52 can be used to multiply the
amount of lift created by the ramp thrust drive 46.
[0038] FIG. 14 shows another coupling mechanism that can multiply
the lift generated by the ramp thrust drive 46. In this case a
center pivot rocker arm 43 is used to perform this function. A lash
adjuster 18B can be used to compensate for excess clearance in the
system.
* * * * *