U.S. patent application number 15/945052 was filed with the patent office on 2019-10-10 for cam follower assembly.
The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Maqsood Rizwan Ali Khan, Kenneth J. Veenstra.
Application Number | 20190309658 15/945052 |
Document ID | / |
Family ID | 67991937 |
Filed Date | 2019-10-10 |
United States Patent
Application |
20190309658 |
Kind Code |
A1 |
Ali Khan; Maqsood Rizwan ;
et al. |
October 10, 2019 |
CAM FOLLOWER ASSEMBLY
Abstract
An improved cam follower includes a lifter body, a spring seat,
a tower, a spring and an anti-rotation member defining at least one
interference rib. The lifter body may engage with a cam via a
rolling member. The lifter body defines a longitudinal axis, a
first open end, and a second end. The spring seat which defines a
spring seat opening may be disposed at the first open end of the
lifter body. The tower which includes an upper flange may be
couples a pushrod to the lifter body. The spring may be disposed
between the spring seat and the upper flange of the tower. The
anti-rotation member may be disposed proximate to the first open
end of the lifter body and includes an outer surface and an inner
surface with an interference rib integral to the inner surface
which engages with an upper region of the lifter body.
Inventors: |
Ali Khan; Maqsood Rizwan;
(Rochester Hills, MI) ; Veenstra; Kenneth J.;
(Jenison, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
Detroit |
MI |
US |
|
|
Family ID: |
67991937 |
Appl. No.: |
15/945052 |
Filed: |
April 4, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/14 20130101; F01L
1/2422 20130101; F01L 2305/00 20200501; F01L 1/146 20130101; F01L
2307/00 20200501; F01L 2001/467 20130101; F01L 2301/00 20200501;
F01L 2305/02 20200501; F01L 13/0005 20130101 |
International
Class: |
F01L 1/14 20060101
F01L001/14 |
Claims
1. An improved cam follower for a vehicle engine comprising: a
lifter body operatively configured to engage with a cam via a
rolling member, the lifter body defining a longitudinal axis, a
lifter body diameter, a first open end, and a second end; a spring
seat disposed at the first open end of the lifter body, the spring
seat defining a spring seat opening; a tower operatively configured
to couple a pushrod to the lifter body, the tower being disposed in
a pin housing through the spring seat opening at the first open end
of the lifter body, the tower having an upper flange; a spring
disposed between the spring seat and the upper flange of the tower;
and an anti-rotation member disposed proximate to the first open
end of the lifter body, the anti-rotation member having an outer
surface and an inner surface with an interference rib integral to
the inner surface which engages with an upper region of the lifter
body.
2. The improved cam follower as defined in claim 1 wherein the
interference rib is substantially parallel to the longitudinal axis
of the lifter body.
3. The improved cam follower as defined in claim 1 wherein the
interference rib is substantially perpendicular to the longitudinal
axis of the lifter body.
4. The improved cam follower as defined in claim 2 wherein the
rolling member is affixed to the lifter body at the second end.
5. The improved cam follower as defined in claim 3 wherein the
rolling member is affixed to the lifter body at the second end.
6. The improved cam follower as defined in claim 4 wherein a planar
surface is defined on the interior surface of the anti-rotation
member proximate to a lower end of the anti-rotation member.
7. The improved cam follower as defined in claim 5 wherein a planar
surface is defined on the interior surface of the anti-rotation
member proximate to a lower end of the anti-rotation member.
8. The improved cam follower as defined in claim 6 wherein the
interference rib is over-molded onto the planar surface.
9. The improved cam follower as defined in claim 7 wherein the
interference rib is over-molded onto planar surface.
10. The improved cam follower as defined in claim 6 wherein the
lifter body defines a compatible planar surface being configured to
engage with the planar surface of the anti-rotation member.
11. The improved cam follower as defined in claim 7 wherein the
lifter body defines a compatible planar surface being configured to
engage with the planar surface of the anti-rotation member.
12. The improved cam follower as defined in claim 10 wherein the
interference rib deforms upon actuation of lifter body and roller
onto the cam during an initial operation of the vehicle engine.
13. The improved cam follower as defined in claim 11 wherein the
interference rib deforms upon actuation of lifter body and roller
onto the cam during an initial operation of the vehicle engine.
14. An anti-rotation member for guiding a cam follower in a vehicle
engine, the anti-rotation member comprising: an outer surface; an
inner surface; and an interference rib integral to the inner
surface, the interference rib being configured to deform and retain
a first open end of a lifter body when the first open end of the
lifter body engages with the interference rib.
15. The anti-rotation member as defined in claim 14 wherein the
interference rib is over-molded onto the inner surface.
16. The anti-rotation member as defined in claim 14 wherein the
interference rib is injection molded simultaneously with the inner
surface and the outer surface.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to cam followers and more
particularly directed to a cam follower assembly for maintaining
the position of lifter body relative to a camshaft.
BACKGROUND
[0002] Hydraulic valve lifters and solid valve lifters, for use in
internal combustion engines, are well known in the engine art. A
valve lifter of this type, engaging a camshaft lobe at one end and
a push-rod or valve stern at the other end, slides reciprocally in
a bore of the engine block. The lifter, typically assembled from
the top side of the engine block, engages a camshaft lobe via a
camshaft follower end which preferably includes a roller. Unless
suitably constrained by an anti-rotation guide, a roller follower
lifter may rotate radially in its bore during reciprocation,
thereby undesirably misaligning its roller follower from the
associated cam lobe.
[0003] Lifter anti-rotation guides in the prior art are positioned
on and secured to the top side surface of the engine block adjacent
the lifter bore. When fastened to the engine block above the
lifter, a closely-fitting aperture in the anti-rotation guide
snuggly surrounds an end of the lifter exposed above the engine
block opposite the roller follower end. Within the anti-rotation
guide aperture, a flat ("plastic shear") is generally defined on
the inner surface of the guide aperture which mates with a similar
feature on the lifter body of lifter to hold the lifter inside of
the anti-rotation guide during the assembly process and to also
prevent the lifter from rotating about its longitudinal axis during
reciprocation engine operation. Typically, a lifter is installed
into the anti-rotation guide as a sub-assembly, and then this
subassembly is then installed onto the top side of the engine.
[0004] During the assembly and engine operation processes, the
lifter must be positioned properly within the anti-rotation guide
so that the roller of the lifter is properly aligned with the cam
once this subassembly is attached to the engine. In the event the
roller of the lifter is misaligned relative to the cam, it is
understood that undesirable, premature degradation at the
roller-cam interface may occur. As noted above, plastic guide
shears are generally defined within the anti-rotation guide
aperture in the form of a flat surface on the inner wall of the
anti-rotation guide. However, such guide shears do not always
maintain the lifter in position and when a lifter inadvertently
falls out of the traditional anti-rotation guide, the risk of
improperly orienting the lifter is heightened when the lifter is
re-inserted into the guide later in the assembly process.
[0005] Accordingly, there is a need to improve the anti-rotation
guides for lifters so that a lifter is maintained within the
anti-rotation guide throughout the assembly process and properly
aligned with the cam associated with the lifter when the lifter and
anti-rotation guide is installed on an engine.
SUMMARY
[0006] The present disclosure provides an improved cam follower for
a vehicle engine which maintains the position of the lifter within
the guide throughout the assembly process so that the lifter
guide's roller is properly aligned with the cam thereby reducing
the risk of cam spalling or premature failure at the interface
between the cam and the roller.
[0007] In one embodiment, the improved cam follower includes a
lifter body, a spring seat, a tower, a spring and an anti-rotation
member having one or more interference ribs. The anti-rotation of
member of the present disclosure includes an upper end and a lower
end, and may further include an outer surface and an inner surface
with one or more interference ribs integral to the inner surface.
The one or more interference ribs may be defined on an inner
surface of the anti-rotation member proximate to the lower end. The
interference rib is configured to abut the lifter body when the
lifter body is inserted inside of the anti-rotation member. It is
also understood that the interference rib(s) may deform upon
insertion of the lifter body within the anti-rotation member, or
the interference rib(s) may deform when the engine is operating and
the lifter body reciprocates relative to the camshaft. In yet
another embodiment, the interference rib(s) may simply disintegrate
such that at least a portion of the interference rib falls off when
the lifter body is inserted or when the engine is operating and the
lifter body reciprocates relative to the camshaft. Under this
circumstance, a small amount of the interference rib may go into
the engine oil without disrupting the engine's operation.
[0008] The interference rib(s) or dimple may protrude from the
inner surface of the anti-rotation member by a depth which falls in
the range of 1 mm to 5 mm wherein the interference rib may be
integral to the anti-rotation member via an injection molding
process, or in yet another non-limiting, optional arrangement, the
interference rib is integral to the anti-rotation member via an
over-molding process. It is also understood that each interference
rib may have a width which may fall in a range of about 1 mm to 5
mm. It is understood that the interference rib or dimple may come
in various shapes. Regardless, the interference rib or dimple may
be any raised feature which may deform or disintegrate as
described.
[0009] While each anti-rotation member may include as few as one
interference rib, an anti-rotation member of the present disclosure
may, but not necessarily include a plurality of interference ribs
in various regions of the inner surface. The inner surface of the
anti-rotation member may vary such that the inner surface includes
at least one flat region and at least one curved region 39.
Regardless, the interference rib of the present disclosure may be
integral to either a flat region or a curved region 39 of the inner
surface.
[0010] The lifter body may be disposed along the longitudinal axis
wherein the lifter body includes a first open end, and a second
end. The lifter body may engage with a cam via a rolling member
affixed to the second end. A spring seat may be disposed at the
first open end of the lifter body wherein the spring seat defines a
spring seat opening which supports the tower. An example,
non-limiting tower may be implemented to couple a pushrod to the
lifter body. The tower may also include an upper flange such that a
spring may be disposed between the spring seat and the upper flange
of the tower. As shown in FIGS. 2C-2D, the tower may, but not
necessarily, be disposed in a pin housing through the spring seat
opening at the first open end of the lifter body. The pin housing
is disposed within the lifter body such that the pin housing, the
tower, the lifter body and the aperture of the anti-rotation member
are aligned with the longitudinal axis.
[0011] A lifter body of the present disclosure may be inserted into
the lower end of the anti-rotation member such that the first open
end of the lifter body engages with the lower end of the
anti-rotation member with the interference ribs abutting the lifter
body. wherein. As shown, the interference rib(s) are configured to
engage with an upper region of the lifter body so as to prevent the
lifter body from falling out of the anti-rotation member during the
assembly process. Moreover, the interference ribs are configured to
prevent the lifter body from rotating out of position within the
anti-rotation member. As indicated earlier, the roller (rolling
member) of the lifter body needs to be aligned with the roller's
associated cam in order to prevent premature damage/failure at the
cam. It is understood that "proper alignment" between the rolling
member and the cam should be construed to mean that the each of the
rolling member and the cam are centered and aligned with the
longitudinal axis of the lifter body.
[0012] The cam follower assembly of the present disclosure may
include one or more interference ribs which are substantially
parallel to the longitudinal axis. In yet another example,
non-limiting improved cam follower of the present disclosure, the
assembly of the present disclosure may include one or more
interference ribs which are substantially perpendicular to the
longitudinal axis, or the interference rib(s) may also be disposed
at an angle relative to the longitudinal axis of each lifter
body/guide aperture.
[0013] An example, non-limiting cam follower assembly of the
present disclosure may include a planar surface (or flat region)
which is defined on the interior surface of the anti-rotation
member proximate to a lower end of the anti-rotation member. As
shown, the interference rib may be defined on the planar surface
such that the interference rib may be over-molded onto the planar
surface or the interference rib may injection molded as the planar
surface and the remainder of the anti-rotation member is injection
molded. The interference rib or dimple may be formed from the same
polymeric material as the anti-rotation member or it may be formed
from a different polymeric material or a wax.
[0014] When the interference rib(s) is/are formed on a planar
surface (or flat region) of the anti-rotation member, it is
understood that the lifter body may define a compatible planar
surface which is configured to engage with and mate with the planar
surface of the anti-rotation member. Alternatively, the
interference rib(s) may be formed on a curved surface 39 (or curved
region 39) of the anti-rotation member. Regardless of whether the
interference rib(s) is/are formed on a flat region or a curved
region 39, the interference rib(s) are configured to prevent the
lifter body from falling out of the anti-rotation member's opening
during the assembly process and also to prevent the lifter body
from rotating out of position within the anti-rotation member's
opening--so that the roller member is properly aligned with the
roller' member's associated cam. Accordingly, the interference
rib(s) may deform upon initial insertion of the lifter body into
the anti-rotation member's opening at a pre-determined insertion
force, or the interference rib(s) may deform upon actuation of
lifter body and roller onto the cam during an initial operation of
the vehicle engine.
[0015] In yet another embodiment of the present disclosure, an
anti-rotation member is provided such that the anti-rotation member
includes an outer surface, an inner surface and an interference rib
integral to the inner surface. The interference rib may be
configured to deform and retain a first open end of a lifter body
when the first open end of the lifter body engages with the
interference rib. In one non-limiting example arrangement, the
interference rib(s) may be over-molded onto the inner surface. In
yet another non-limiting example arrangement, the interference
rib(s) may be injection molded simultaneously with the inner
surface and the outer surface.
[0016] The present disclosure and its particular features and
advantages will become more apparent from the following detailed
description considered with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other features and advantages of the present
disclosure will be apparent from the following detailed
description, best mode, claims, and accompanying drawings in
which:
[0018] FIG. 1 is a cross sectional view of the cam follower
assembly according to the present disclosure wherein the cam
follower assembly is disposed within an engine block and operable
to enable the valve to open and close.
[0019] FIG. 2A is a front view of an example, non-limiting cam
follower assembly according to the present disclosure.
[0020] FIG. 2B is a rear view of an example, non-limiting cam
follower assembly according to the present disclosure.
[0021] FIG. 2C is a front cross-sectional view of an example,
non-limiting cam follower assembly according to the present
disclosure.
[0022] FIG. 2D is a rear cross-sectional view of an example,
non-limiting cam follower assembly according to the present
disclosure.
[0023] FIG. 3A is a bottom view of an example, non-limiting
anti-rotation member according to the present disclosure
[0024] FIG. 3B is a bottom view of another example, non-limiting
anti-rotation member according to the present disclosure
[0025] FIG. 4 is a perspective view of an example, non-limiting cam
follower assembly according to various embodiments of the present
disclosure.
[0026] Like reference numerals refer to like parts throughout the
description of several views of the drawings.
DETAILED DESCRIPTION
[0027] Reference will now be made in detail to presently preferred
compositions, embodiments and methods of the present disclosure,
which constitute the best modes of practicing the present
disclosure presently known to the inventors. The figures are not
necessarily to scale. However, it is to be understood that the
disclosed embodiments are merely exemplary of the present
disclosure that may be embodied in various and alternative forms.
Therefore, specific details disclosed herein are not to be
interpreted as limiting, but merely as a representative basis for
any aspect of the present disclosure and/or as a representative
basis for teaching one skilled in the art to variously employ the
present disclosure.
[0028] Except in the examples, or where otherwise expressly
indicated, all numerical quantities in this description indicating
amounts of material or conditions of reaction and/or use are to be
understood as modified by the word "about" in describing the
broadest scope of the present disclosure. Practice within the
numerical limits stated is generally preferred. Also, unless
expressly stated to the contrary: percent, "parts of," and ratio
values are by weight; the description of a group or class of
materials as suitable or preferred for a given purpose in
connection with the present disclosure implies that mixtures of any
two or more of the members of the group or class are equally
suitable or preferred; the first definition of an acronym or other
abbreviation applies to all subsequent uses herein of the same
abbreviation and applies mutatis mutandis to normal grammatical
variations of the initially defined abbreviation; and, unless
expressly stated to the contrary, measurement of a property is
determined by the same technique as previously or later referenced
for the same property.
[0029] It s also to be understood that this present disclosure is
not limited to the specific embodiments and methods described
below, as specific components and/or conditions may, of course,
vary. Furthermore, the terminology used herein is used only for the
purpose of describing particular embodiments of the present
disclosure and is not intended to be limiting in any way.
[0030] It must also be noted that, as used in the specification and
the appended claims, the singular form "a," "an," and "the"
comprise plural referents unless the context clearly indicates
otherwise. For example, reference to a component in the singular is
intended to comprise a plurality of components.
[0031] The term "comprising" is synonymous with "including,"
"having," "containing," or "characterized by." These terms are
inclusive and open-ended and do not exclude additional, un-recited
elements or method steps.
[0032] The phrase "consisting of" excludes any element, step, or
ingredient not specified in the claim. When this phrase appears in
a clause of the lifter body 14 of a claim, rather than immediately
following the preamble, it limits only the element set forth in
that clause; other elements are not excluded from the claim as a
whole.
[0033] The phrase "consisting essentially of" limits the scope of a
claim to the specified materials or steps, plus those that do not
materially affect the basic and novel characteristic(s) of the
claimed subject matter.
[0034] The terms "comprising", "consisting of", and "consisting
essentially of" can be alternatively used. Where one of these three
terms is used, the presently disclosed and claimed subject matter
can include the use of either of the other two terms.
[0035] Throughout this application, where publications are
referenced, the disclosures of these publications in their
entireties are hereby incorporated by reference into this
application to more fully describe the state of the art to which
this present disclosure pertains.
[0036] The following detailed description is merely exemplary in
nature and is not intended to limit the present disclosure or the
application and uses of the present disclosure. Furthermore, there
is no intention to be bound by any theory presented in the
preceding background or the following detailed description.
[0037] The present disclosure provides an improved cam follower
assembly 10 for a vehicle engine 54 which enables increased lost
motion range of the roller thereby reducing the risk of cam
spalling. With reference to FIG. 1, a cross sectional view of the
cam follower assembly 10 of the present invention is shown. The cam
follower assembly 10 is disposed within an engine block 12 and
operable to enable the valve 48 to open and close against a
combustion chamber 50 via the rocker arm 28 and push-rods 22.
[0038] Referring again to FIG. 1, the cam follower assembly 10 is
part of a cam 60 in head 56 arrangement in an internal combustion
engine 54. A cam 60 of a camshaft is rotatably mounted within the
head 56 of the engine 54 as is commonly known in the art. A valve
48 having a valve stem 52 extends from cylinder head 56 toward the
rocker arm 28 as is also commonly known in the art. A coiled spring
(not shown) biases the valve 48 stem 52 upward in the closed
position. The rocker arm 28 is pivotally mounted within the head 56
of the engine as is also commonly known in the art. A first end 30
of the rocker arm 28 engages a top portion of the valve 48 stem 52.
A lash adjuster is also provided to adjust valve 48 clearance. In
the embodiment shown in FIG. 1, cam follower assembly 10 is mounted
within a bore of the head 56 of the engine 54 between the cam 60
and a second end 20 of the rocker arm 28. As the cam 60 rotates the
cam follower assembly 10 is forced upwards to engage the second end
20 of the rocker arm 28 causing the rocker arm 28 to pivot and
displace the first end 30 of the rocker arm 28 downward to open the
valve 48. The hydraulic cam follower assembly 10 may be disposed
between the cam 60 and rocker arm 28 to provide zero lash
adjustment. The basic arrangement for the position of the valve 48,
combustion chamber 50 and cam shaft 124 is generally known in the
art. The present invention is directed to the improved structure of
the cam follower assembly 10 to support reduced cam spalling while
meeting packaging requirements in such a layout.
[0039] Pitting is generally known as a surface fatigue phenomenon
which occurs in the concentrated rolling and sliding contact area
on the cam lobe 60 in the region where the roller 64 makes contact.
Due to the high stresses between the two members as the contact
area for the cam lobe 60 surface geometry changes against the
roller 64, particles may break out of affected areas, leaving cam
lobe 60 surfaces pockmarked with scattered holes. As the pitting
progresses to a macro level, a cam lobe spalling condition may
occur where the pits on the cam lobe 60 surface coalesce and form
irregular craters, cavities and cracks. Cam lobe spalling may occur
at 60 degrees from the top of the nose whereas sliding wear may be
concentrated at the top of the nose of the cam lobe 60. The large
particles that pits produce may be caught in the oil filter or
settle at the bottom of the sump. Moreover, when cam lobe spalling
occurs, this condition may present operational issues for the
combustion chamber 50. Therefore, in order to significantly reduce
the cam lobe spalling issue, a cam lobe follower assembly 10 is
provided in the present disclosure which allows for an increased
range of motion thereby, when combined with a rocker arm with
reduced "cam lift to valve lift" ratio, relieving the excessively
high concentration of stresses between the roller 64 and the cam
lobe 60.
[0040] With reference again to FIG. 1, FIG. 2A thru 2D the cam
follower assembly 10 of the present invention includes a lifter
body 14 and a tower 26 positioned within a first open end of the
lifter body bore 92. Preferably the lifter body 14 and the tower 26
associated with the lifter body 14 are seated in a portion of the
head 56 of the engine 54 conventionally suited for hydraulic cam
followers. The upper or first open end 18 of the cam follower
assembly 10 is adapted to engage the second end 20 of the rocker
arm 28 via a pushrod 22. As shown, the pushrod 22 is disposed
within a bore 24 of the tower 26 such that the tower 26 and lifter
body 14 engage the second end 20 of the rocker arm 28. A primary
spring 32 is disposed in spring recess 34 defined by an upper
flange 36 of the tower 26, the tower side wall 40, and the spring
seat 38. It is further understood that an anti-rotation member 80
may surround this the primary spring 32 and the first open end 18
of the cam follower assembly 10. The primary spring 32 is
operatively configured to bias the pushrod 22 and its associated
combustion chamber 50 valve 48 into an extended position. A locking
member 46 may be further provided to lock the pushrod 22 in the
extended position (FIG. 2C) for normal activated operation of the
cam follower assembly 10. During normal operation, where the valve
48 (FIG. 1) and locking member 46 (FIG. 3A) is activated as shown
in FIG. 3A, the cam 60 causes the cam follower assembly 10 together
with the pushrod 22 to move up and down in a reciprocating manner
to engage the rocker arm 28 and reciprocatingly operate the valve
48. FIG. 1 shows the cam follower assembly 10 and valve 48 in a
closed position.
[0041] However, when the valve 48 (FIG. 1) and locking member 46
(FIGS. 2C and 2D) are not activated, the locking member 46 is
stowed in a retracted position (as shown in FIG. 2D) enabling
roller 64 and the lifter body 14 to slide up the longitudinal axis
90 toward the tower 26, pin housing 62 and the lifter body 14 as
the cam lobe 60 geometry changes as the camshaft rotates. That is,
the force exerted by the cam lobe 60 against the roller 64
overcomes the biasing force provided by the primary spring 32 when
the locking member 46 is deactivated as shown in FIG. 2D such that
the roller 64 and lifter body housing 14 may slide upward relative
to the pin housing 62 and tower 26. Accordingly, the position of
the pushrod 22 is not affected, and therefore, the combustion
chamber valve 48 is not actuated despite the cam lobe 60 engaging
the roller 64.
[0042] With further reference to the roller 64 in FIGS. 2A-2D, a
roller 64 may be rotatably mounted to a second end 88 of the lifter
body 14 of the cam follower assembly 10 and engages a portion of
the cam lobe 60 to provide a rolling interface there between.
However, as indicated, as the cam 60 rotates the cam follower
assembly 10 and pushrod 22 are forced upward and the rocker arm 28
pivots and the valve 48 opens when the locking member 46 is
actuated given that the cam follower does not "absorb" the
movement/force applied by the cam lobe 60. Therefore, when the
locking member 46 is actuated, the entire cam follower assembly 10
together with the pushrod 22 is urged in the upward most position
as the roller 64 engages the highest portion of the cam 60.
Consequently, the rocker arm 28 pivots clockwise and the valve stem
52 is forced downward to open the valve 48. As the cam lobe 60
continues to rotate, the valve 48 is then allowed to close by
virtue of the biasing force of the spring (not shown) in the
cylinder head.
[0043] However, when the valve 48 is to be deactivated, the locking
member 46 disengages with the inner surface of the lifter body 14,
as shown in FIG. 2D, to allow the pushrod 22 to recede within the
bore 24 of the tower 26 and lifter body 14 to take up the cam 60
lift so that the valve 48 is not opened. As can be seen in FIG. 2D,
the roller 64 may engage the cam 60 (not shown) at its highest
point which causes upward movement of the roller 64 in comparison
to FIG. 3C. However, the rocker arm 28 and valve 48 of FIG. 1 shall
remain in the closed position when the locking member 46 of the
lifter body 14 is deactivated. It is understood that, in this
example, pressurized oil may be selectively supplied to the locking
member 46 to disengage the locking member 46 from the lifter body
14 thereby releasing the pushrod 22/pin housing 62/tower subsystem
52 relative to the lifter body 14 and thus permitting the pushrod
22 to move deeper within the bore of the lifter body 14. As the cam
60 urges the lifter body 14 upward, the pushrod 22 remains
substantially stationary relative to the cylinder head 56.
Accordingly, when the locking member 46 is disengaged (or
deactivated), the lifter body 14 and roller 64 rides upward
relative to the tower 26 and pin housing 62 such that the pushrod
22 recesses further within the bore 24 when the highest point of
the cam lobe 60 engages with the roller or rolling member 64. The
spring biases the pushrod 22 upward relative to the lifter body 14
to engage the second end 20 of the rocker arm 28. Similarly, a
primary spring 32 urges the lifter body 14 and roller 64 downward
to maintain constant contact with the cam 60.
[0044] Due to issues with respect to cam spalling at the roller 64
interface, the cam follower assembly 10 must be properly aligned at
the roller 64-cam 60 interface. FIG. 2A is a front view of a prior
art cam follower. FIG. 2B is a rear view of a prior art cam
follower 10 where the anti-rotation member 80 is shown in phantom.
It is understood that the upon assembly and in operation, the
anti-rotation member 80 engages only with the platform 47 (FIG. 2B)
defined on the rear side of the lifter body 14 when assembled as
part of a traditional cam follower assembly 10. It is desirable to
require a certain insertion force to install the cam follower into
the anti-rotation member 80 so that the cam follower stays in its
proper position (rotationally and linearly) when the sub-assembly
of the anti-rotation member 80 and lifter body 14 are put together
and when the sub-assembly is mated to the engine.
[0045] As previously noted, plastic guide shears in a traditional
anti-rotation member (not shown) are defined on the inner surface
of a traditional anti-rotation member which engage with a platform
defined on the lifter body (not shown) of a traditional cam
follower assembly (not shown). However, despite this interface, cam
followers have been known to fall out of the anti-rotation members
during the subassembly process and the assembly process of mating
the subassembly to the engine. As a result, there is a risk for the
roller of the cam follower to be misaligned with the cam when the
cam follower is re-inserted into a traditional anti-rotation
member.
[0046] With reference to FIGS. 3A-3B and 4, an improved cam
follower assembly 10 is provided. The improved cam follower
includes a lifter body 14, a spring seat 38, a tower 26, a spring
32 and an anti-rotation member 80 having one or more interference
ribs 35. It is understood that the interference rib(s) 35 or
dimple(s) 35 may come in various shapes. Regardless, the
interference rib 35 or dimple 35 may be any raised feature which
may deform or disintegrate as described. The anti-rotation member
80 of the present disclosure may further include an upper end 45
and a lower end 43, and my further includes an outer surface 31 and
an inner surface 33 with one or more interference ribs integral to
the inner surface 33. The one or more interference ribs may be
defined on an inner surface 33 of the anti-rotation member 80
proximate to the lower end 43. The interference rib 35 is
configured to abut an upper region 51 (FIGS. 2A-2B) of a lifter
body 14 when the lifter body 14 is inserted inside of the
anti-rotation member 80. It is also understood that the
interference rib(s) 35 may deform upon insertion of the lifter body
14 within the anti-rotation member 80, or the interference rib(s)
35 may deform when the engine is operating and the lifter body 14
reciprocates relative to the camshaft.
[0047] Referring again to FIGS. 3A-3B, the interference rib(s) 35
may protrude from the inner surface 33 of the anti-rotation member
80 by a distance/depth 39 (FIGS. 3A-3B) which falls in the range of
about 1 mm to about 5 mm (and/or a width 37 shown in FIGS. 2A and
2B which falls in the range of about 1 mm to about 5 mm) wherein
the interference rib 35 may be integral to the anti-rotation member
80 via an injection molding process, or in yet another
non-limiting, optional arrangement, the interference rib 35 is
integral to the anti-rotation member 80 via an over-molding
process. While each anti-rotation member 80 may include as few as
one interference rib 35. an anti-rotation member 80 of the present
disclosure may, but not necessarily include a plurality of
interference ribs 35 in various regions of the inner surface 33.
The inner surface 33 of the anti-rotation member 80 may vary such
that the inner surface 33 includes at least one flat region and at
least one curved region 39. Regardless, the interference rib 35 of
the present disclosure may be integral to either a flat region or a
curved region 39 of the inner surface 33.
[0048] With reference now to 2C and 2D, an example, non-limiting
lifter body 14 is shown which may be implemented as part of the cam
follower assembly 10 of the present disclosure. The lifter body 14
may be disposed along the longitudinal axis 90 wherein the lifter
body 14 includes a first open end 44, and a second end 88. The
lifter body 14 may engage with a cam via a rolling member 64
affixed to the second end 88. A spring seat 38 may be disposed at
the first open end of the lifter body 14 wherein the spring seat 38
defines a spring seat opening 84 which supports the tower 26. As
shown in the non-limiting example of FIGS. 2C and 2D, an example,
non-limiting tower 26 may be implemented to couple a pushrod to the
lifter body 14. The tower 26 may also include an upper flange 36
such that a spring may be disposed between the spring seat 38 and
the upper flange 36 of the tower 26. As shown in FIGS. 2C-2D, the
tower 26 may, but not necessarily, be disposed in a pin housing 62
through the spring seat opening 84 at the first open end of the
lifter body 14. The pin housing 62 is disposed within the lifter
body 14 such that the pin housing 62, the tower 26, the lifter body
14 and the aperture of the anti-rotation member 80 are aligned with
the longitudinal axis 90.
[0049] As shown in FIG. 4, lifter body 14 may be inserted into the
lower end 43 of the anti-rotation member 80 such that the first
open end of the lifter body 14 engages with the lower end 43 of the
anti-rotation member 80 with the interference ribs abutting the
lifter body 14. wherein. As shown, the interference rib(s) 35 are
configured to engage with an upper region of the lifter body 14 so
as to prevent the lifter body 14 from falling out of the
anti-rotation member 80 during the assembly process. Moreover, the
interference ribs are configured to prevent the lifter body 14 from
rotating out of position within the anti-rotation member 80. As
indicated earlier, the roller (rolling member 64) of the lifter
body 14 needs to be properly aligned with the roller's associated
cam in order to prevent premature damage/failure at the cam. Again,
it is understood that "proper alignment" between the rolling member
64 and the cam 60 should be construed to mean that the each of the
rolling member 64 and the cam 60 are centered and aligned with
longitudinal axis 90. See FIG. 2A.
[0050] Referring now to FIGS. 3A and 4, an example, non-limiting
improved cam follower assembly 10 of the present disclosure may
include one or more interference ribs which are substantially
parallel to the longitudinal axis 90. Alternatively, with reference
to FIG. 3B, another example, non-limiting improved cam follower of
the present disclosure may include one or more interference ribs
which are substantially perpendicular to the longitudinal axis 90.
While not shown, the interference rib of the present disclosure may
also be disposed at an angle relative to the longitudinal axis 90
of each lifter/guide aperture.
[0051] Referring now to FIGS. 3A and 3B, an example, non-limiting
cam follower may include a planar surface 41 (or flat region 41)
which is defined on the interior surface of the anti-rotation
member 80 proximate to a lower end 43 of the anti-rotation member
80. As shown, the interference rib 35 may be defined on the planar
surface 41 such that the interference rib 35 may be over-molded
onto the planar surface 41 or the interference rib 35 may injection
molded as the planar surface 41 and the remainder of the
anti-rotation member 80 is injection molded. The anti-rotation
member 80 and the interference rib(s) 35 may, but not necessarily,
be formed from material such as Nylon 66 with 32% glass, or other
like material. In the event the interference rib 35 is overmolded
onto the anti-rotation member 80, the interference rib 35 may be
formed from another polymeric material which may or may not have a
higher modulus of elasticity. In yet another non-limiting option,
the interference rib 35 may be formed from a wax like material
which is molded onto the inner surface 33.
[0052] When the interference rib(s) 35 is/are formed on a planar
surface 41 (or flat region 41) of the anti-rotation member 80, it
is understood that the lifter body 14 may define a compatible
planar surface 47 (as shown in FIG. 2B) which is configured to
engage with and mate with the planar surface 41 of the
anti-rotation member 80. Alternatively, the interference rib(s) 35
may be formed on a curved surface 39 (or curved region 39) of the
anti-rotation member 80 as shown in FIG. 2B. Regardless of whether
the interference rib(s) 35 is/are formed on a flat region 41 or a
curved region 39, the interference rib(s) 35 are configured to
prevent the lifter body 14 from falling out of the anti-rotation
member's opening 97 during the assembly process and also to prevent
the lifter body 14 from rotating out of position within the
anti-rotation member's opening 97--so that the roller member is
properly aligned with the roller member's associated cam 60.
Regardless of whether the interference rib(s) 35 are defined on a
curved region or on a flat region 41 of the anti-rotation member
80, the interference rib(s) 35 may deform upon initial insertion of
the lifter body 14 into the anti-rotation member's opening 97.
Alternatively, the interference rib(s) 35 may deform upon actuation
of lifter body 14 and roller onto the cam 60 during an initial
operation of the vehicle engine.
[0053] In yet another embodiment of the present disclosure, an
anti-rotation member 80 may include an outer surface 31, an inner
surface 33 and an interference rib 35 integral to the inner surface
33. The interference rib 35 may be configured to deform and retain
a first open end 44 of a lifter body 14 when the first open end 44
of the lifter body 14 engages with the interference rib 35. In one
non-limiting example arrangement, the interference rib(s) 35 may be
over-molded onto the inner surface 33. In yet another non-limiting
example arrangement, the interference rib(s) 35 may be injection
molded simultaneously with the inner surface 33 and the outer
surface 31.
[0054] With reference to FIGS. 3A-3D, the improved cam follower 10
includes a lifter body 14. The lifter body 14 may come in various
forms. However, in the example of FIGS. 2C-2D, the lifter body 14
may include a spring seat 38 and a primary spring 32 made from
steel. The example primary spring 32 of FIGS. 2A-2D may have a
specified spring constant.
[0055] FIG. 3A is a front view of an example, non-limiting cam
follower assembly 10 of the present disclosure where the
anti-rotation member 80 shown in phantom while FIG. 3B is a rear
view of the cam follower assembly 10 in FIG. 3A. As shown, the
lifter body 14 defines a first open end 44, and a second end 88.
The spring seat 38 may define a spring seat opening 84. The spring
seat 38 may be affixed to the first open end 44 of the lifter body
14. The tower 26 may be disposed in a pin housing 62 through the
spring seat opening 84 at the first open end 44 of the lifter body
14. The tower 26 further includes an upper flange 36 and a spring
which abuts the upper flange 36 at a first spring end 78. The
second spring end 76 abuts the spring seat 38. The anti-rotation
member 80 accordingly may be coupled to the lifter body 14 via the
spring seat 38.
[0056] With reference to the non-limiting example lifter body 14 of
FIGS. 2C-2D, the pin housing 62 may support the push rod seat 63
within the lifter body 14, and the lifter body 14 be fixed relative
to the tower 26. However, as shown in FIGS. 2C-2D, the lifter body
14 moves relative to the pin housing 62 and tower 26. As shown, the
pin housing 62 may be affixed to a second end 86 of the tower 26.
The pin housing 62 may also be disposed entirely within the lifter
body 14 such that the pin housing 62 may slide relative to the
lifter body 14 depending on whether the locking member 46 is
engaged (as shown in FIG. 2C) or disengaged (as shown in FIG. 2D).
When the locking member 46 is engaged into the locking recesses 47
defined in the interior wall of the lifter body 14, the first open
end 61 of the pin housing 62 may be disposed proximate to or
adjacent to the first open end 44 of the lifter body 14 as shown in
FIG. 2C. However, when the locking member 46 is disengaged from the
lifter body 14, the lifter body 14 and roller 64 of the cam
follower 10 may slide relative to the pushrod 22 and pin housing 62
which remain stationary.
[0057] With further reference to the non-limiting example lifter
body 14 shown in FIGS. 2A-2D, the example primary spring 32 may
include a first spring end 78 and a second spring end 76. The first
spring end 78 abuts an upper flange 36 of the tower 26 at a first
spring end 78 and abuts the spring seat 38 at a second spring end
76 upon assembly. The spring recess 34 is therefore defined by the
tower side wall 40, the upper flange 36, and the spring seat 38,
and the spring recess 34 is configured to retain the primary spring
32 as described above for the improved cam follower assembly 10.
Therefore, the second spring end 76 (shown in FIG. 2A) is supported
by the spring seat 38.
[0058] While at least one exemplary embodiment has been presented
in the foregoing detailed description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or exemplary embodiments
are only examples, and are not intended to limit the scope,
applicability, or configuration of the disclosure in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing the
exemplary embodiment or exemplary embodiments. It should be
understood that various changes can be made in the function and
arrangement of elements without departing from the scope of the
disclosure as set forth in the appended claims and the legal
equivalents thereof.
* * * * *