U.S. patent application number 14/661847 was filed with the patent office on 2016-09-22 for valve actuation system having grooved adjusting screw.
This patent application is currently assigned to CATERPILLAR INC.. The applicant listed for this patent is CATERPILLAR INC.. Invention is credited to Gopinath BASKARAN, Indrajith KIZHAKKETHARA, Bhavin N. MEHTA, John S. PIPIS, JR., Sathishkumar RAMAN, Paul D. RUDOLPH.
Application Number | 20160273415 14/661847 |
Document ID | / |
Family ID | 56519197 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273415 |
Kind Code |
A1 |
KIZHAKKETHARA; Indrajith ;
et al. |
September 22, 2016 |
VALVE ACTUATION SYSTEM HAVING GROOVED ADJUSTING SCREW
Abstract
A valve actuation system is disclosed for an internal combustion
engine. The system may have a gas exchange valve, a rocker arm
pivotally connected to a shaft, a pushrod, a lash adjuster disposed
in the pushrod. The system may also have an adjusting screw
disposed in the rocker arm and configured to engage and fluidly
supply the lash adjuster. The adjusting screw may include a shaft
having a threaded outer annular surface, and a head connected to
the shaft and having a rounded outer surface and a flat end face.
The adjusting screw may also include an axial passage passing
through the flat end face, a radial passage formed in the shaft and
extending from the threaded bore of the rocker arm to the axial
passage, and at least one radial groove formed in the rounded outer
surface of the head and passing through the axial passage.
Inventors: |
KIZHAKKETHARA; Indrajith;
(West Lafayette, IN) ; RAMAN; Sathishkumar;
(Tamilnadu, IN) ; MEHTA; Bhavin N.; (Gujarat,
IN) ; PIPIS, JR.; John S.; (Washington, IL) ;
BASKARAN; Gopinath; (Timailnadu, IN) ; RUDOLPH; Paul
D.; (Lafayette, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CATERPILLAR INC. |
Peoria |
IL |
US |
|
|
Assignee: |
CATERPILLAR INC.
Peoria
IL
|
Family ID: |
56519197 |
Appl. No.: |
14/661847 |
Filed: |
March 18, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01L 1/24 20130101; F01L
1/2422 20130101; F01L 2001/2444 20130101; F01L 1/20 20130101; F01L
1/146 20130101 |
International
Class: |
F01L 1/20 20060101
F01L001/20; F01L 3/20 20060101 F01L003/20 |
Claims
1. An adjusting screw for a valve actuation system, the adjusting
screw comprising: an elongated cylindrical shaft having a first
end, a second end, and a threaded outer annular surface extending
between the first and second ends; a head connected to the
elongated cylindrical shaft at the first end and having a rounded
outer surface; an axial passage formed in the elongated cylindrical
shaft and passing through the head; and at least one radial groove
formed in the rounded outer surface of the head and connected with
the axial passage.
2. The adjusting screw of claim 1, wherein the axial passage is a
blind passage.
3. The adjusting screw of claim 2, further including a radial
passage formed in the elongated cylindrical shaft and extending
from the axial passage through the rounded outer surface.
4. The adjusting screw of claim 3, further including a restrictive
orifice formed in the radial passage.
5. The adjusting screw of claim 3, wherein the at least one radial
groove is oriented generally orthogonal to an axis of the radial
passage.
6. The adjusting screw of claim 1, wherein the at least one radial
groove passes through the axial passage.
7. The adjusting screw of claim 1, wherein: the head includes a
planar shoulder located opposite the rounded outer surface and
oriented generally orthogonal to the axial passage; and the at
least one radial groove terminates short of the planar
shoulder.
8. The adjusting screw of claim 1, wherein the at least one radial
groove has a consistent width and depth along its length.
9. The adjusting screw of claim 1, further including a tool
engagement head located at the second end.
10. The adjusting screw of claim 9, wherein an outer diameter of
the tool engagement head has an outer diameter that is the same as
or less than an outer diameter of the elongated cylindrical
shaft.
11. The adjusting screw of claim 1, wherein a radius of the at
least one radial groove is about 0.4-0.6 times a radius of the
axial passage.
12. The adjusting screw of claim 11, wherein the head includes a
flat end face formed at a center of the rounded outer surface
around the axial passage.
13. The adjusting screw of claim 12, wherein the flat end face has
an outer diameter of 45-55% of outer diameter of the rounded outer
surface.
14. An adjusting screw for a valve actuation system, the adjusting
screw comprising: an elongated cylindrical shaft having a first
end, a second end, and a threaded outer annular surface extending
between the first and second ends; a head connected to the
elongated cylindrical shaft at the first end and having a rounded
outer surface; an axial passage formed in the elongated cylindrical
shaft and passing through the head; a flat end face formed at a
center of the rounded outer surface around the axial passage; and
at least one radial groove formed in the rounded outer surface of
the head.
15. The adjusting screw of claim 14, wherein the at least one
radial groove is also formed in the flat end face.
16. The adjusting screw of claim 14, further including: a radial
passage formed in the elongated cylindrical shaft and extending
from the axial passage through the rounded outer surface; and a
restrictive orifice formed in the radial passage.
17. The adjusting screw of claim 14, wherein: the head includes a
planar shoulder located opposite the rounded outer surface and
oriented generally orthogonal to the axial passage; and the at
least one radial groove terminates short of the planar
shoulder.
18. The adjusting screw of claim 14, wherein the at least one
radial groove has a consistent width and depth along its
length.
19. The adjusting screw of claim 14, further including a tool
engagement head located at the second end, wherein an outer
diameter of the tool engagement head has an outer diameter that is
the same as or less than an outer diameter of the elongated
cylindrical shaft.
20. A valve assembly, comprising: at least one gas exchange valve;
a shaft; a rocker arm pivotally connected to the shaft and having a
first end operatively engaged with the at least one gas exchange
valve, a second end with a threaded bore, and a passage extending
from the shaft to the threaded bore; a pushrod having a cam end and
a rocker arm end; a lash adjuster disposed in the rocker arm end of
the pushrod; and an adjusting screw disposed in the second end of
the rocker arm and configured to engage and fluidly supply the lash
adjuster in the pushrod, the adjusting screw including: an
elongated cylindrical shaft having a first end, a second end, and a
threaded outer annular surface extending between the first and
second ends; a head connected to the elongated cylindrical shaft at
the first end and having a rounded outer surface and a flat end
face formed at a center of the rounded outer surface; an axial
passage formed in the elongated cylindrical shaft and passing
through the flat end face of the head; radial passage formed in the
elongated cylindrical shaft and extending from the threaded bore of
the rocker arm to the axial passage; and at least one radial groove
formed in the rounded outer surface of the head and passing through
the axial passage.
Description
TECHNICAL FIELD
[0001] The present disclosure is directed to a valve actuation
system and, more particularly, to a valve actuation system having
an adjusting screw with oil distribution grooves.
BACKGROUND
[0002] Each cylinder of an internal combustion engine is equipped
with one or more gas exchange valves (e.g., intake and exhaust
valves) that are cyclically opened during normal operation to allow
fuel and air into the engine and to discharge exhaust from the
engine. In a conventional engine, the valves are opened by way of a
camshaft/rocker arm arrangement. The camshaft includes one or more
lobes oriented at particular angles corresponding to desired lift
timings and amounts of the associated valves. The cam lobes are
connected to stem ends of the associated valves by way of the
rocker arm and associated pushrod linkage. As the camshaft rotates,
the cam lobes come into contact with a first pivoting end of the
rocker arm, thereby forcing a second pivoting end of the rocker arm
against the stem ends of the valves. This pivoting motion causes
the valves to lift or open against a spring bias. As the cam lobes
rotate away from the rocker arm, the valves are released and
allowed to return to their closed positions.
[0003] Over time, components of the engine (e.g., the valves,
associated seats, rocker arm, pushrod linkage, etc.) wear, creating
clearances or spaces between the components. These clearances can
cause the valves to not open or close properly. When this happens,
the engine can become noisy, lose performance, and wear at an
accelerated rate. Accordingly, the clearances should be
periodically checked and adjusted.
[0004] One way to adjust these clearances is through the use of an
adjusting screw. A typical adjusting screw is located at a cam-end
of the rocker arm, and has a spherical head that extends from the
rocker arm into a rounded socket of an associated pushrod. The
adjusting screw is selectively turned to extend a greater distance
from the rocker arm toward the pushrod as the engine wears, thereby
taking up any clearance that has developed due to the wear.
[0005] An exemplary adjusting screw is disclosed in WO Patent No.
2012153102 of Wotherspoon that published on Nov. 15, 2012 ("the
'102 patent"). In particular, the '102 patent discloses a
connection member having a shank inserted into a bore of a rocker
arm. The shank is cylindrical and provided with an outer thread
that engages an inner thread of the bore. An outer head is provided
at a top end of the shank to allow the connection member to be
adjusted relative to the rocker arm, thereby eliminating slack in
an associated valve train. The connection member also includes a
spherical pivot head at an opposite end that is configured to be
inserted into a spherical socket of an associated pushrod, thereby
permitting relative articulation of the connection member. A
lubricant channel is formed in the connection member, and extends
from an exit hole in the spherical pivot head to an annular recess
located just below the outer head. One or more radial grooves are
machined into the spherical pivot head to promote the dispersion of
lubricant from the lubricant channel within an area between the
spherical outer surface of the pivot head and the socket of the
pushrod. The grooves extend from an annular periphery of a contact
area centered at the pivot head towards a peripheral edge. A width
and depth of the grooves increases away from the exit hole. Due to
little clearance between the pivot head and the socket inside the
contact area, the pressure of the lubricant flowing therethrough
creates a film bearing for loads transmitted between the connecting
member and the pushrod.
[0006] Although the connection member of the '102 patent may
function well as an adjusting screw in many applications, it may be
less than optimal in other applications. For example, in some
applications, it may require too much pressure to adequately
separate the connecting member from the pushrod socket and create
the film bearing, and the high-pressure flow through the
constricted contact area may not properly cool the interface. In
addition, the variable width and depth of the grooves, along with
the method of fabricating the grooves, may increase a cost of the
connection member.
[0007] The valve actuation system of the present disclosure is
directed towards overcoming one or more of the problems set forth
above and/or other problems of the prior art.
SUMMARY
[0008] One aspect of the present disclosure is directed to an
adjusting screw for a valve actuation system. The adjusting screw
may include an elongated cylindrical shaft having a first end, a
second end, and a threaded outer annular surface extending between
the first and second ends. The adjusting screw may also include a
head connected to the elongated cylindrical shaft at the first end
and having a rounded outer surface, an axial passage formed in the
elongated cylindrical shaft and passing through the head, and at
least one radial groove formed in the rounded outer surface of the
head and connected with the axial passage.
[0009] Another aspect of the present disclosure is directed to
another adjusting screw for a valve actuation system. This
adjusting screw may include an elongated cylindrical shaft having a
first end, a second end, and a threaded outer annular surface
extending between the first and second ends. The adjusting screw
may also include a head connected to the elongated cylindrical
shaft at the first end and having a rounded outer surface, and an
axial passage formed in the elongated cylindrical shaft and passing
through the head. The adjusting screw may further include a flat
end face formed at a center of the rounded outer surface around the
axial passage, and at least one radial groove formed in the rounded
outer surface of the head.
[0010] Yet another aspect of the present disclosure is directed to
a valve actuation system. The valve actuation system may include at
least one gas exchange valve, a shaft, and a rocker arm pivotally
connected to the shaft. The rocker arm may have a first end
operatively engaged with the at least one gas exchange valve, a
second end with a threaded bore, and a passage extending from the
shaft to the threaded bore. The valve actuation system may also
include a pushrod with a cam end and a rocker arm end, a lash
adjuster disposed in the rocker arm end of the pushrod, and an
adjusting screw disposed in the second end of the rocker arm and
configured to engage and fluidly supply the lash adjuster in the
pushrod. The adjusting screw may have an elongated cylindrical
shaft with a first end, a second end, and a threaded outer annular
surface extending between the first and second ends, and a head
connected to the elongated cylindrical shaft at the first end and
having a rounded outer surface and a flat end face formed at a
center of the rounded outer surface. The adjusting screw may also
have an axial passage formed in the elongated cylindrical shaft and
passing through the flat end face of the head, a radial passage
formed in the elongated cylindrical shaft and extending from the
threaded bore of the rocker arm to the axial passage, and at least
one radial groove formed in the rounded outer surface of the head
and passing through the axial passage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagrammatic illustration of an exemplary
disclosed engine;
[0012] FIG. 2 is a cross-sectional illustration of an exemplary
disclosed valve actuation system that may be used with the engine
of FIG. 1; and
[0013] FIGS. 3 and 4 are isometric and cross-sectional
illustrations, respectively, of an exemplary disclosed adjusting
screw that may be included in the valve actuation system of FIG.
2.
DETAILED DESCRIPTION
[0014] FIG. 1 illustrates an engine 10 equipped with an exemplary
disclosed valve actuation system 12. For the purposes of this
disclosure, engine 10 is depicted and described as a four-stroke
diesel engine. One skilled in the art will recognize, however, that
engine 10 may embody any type of combustion engine such as, for
example, a two- or four-stroke, gasoline or gaseous fuel-powered
engine. As will be described in more detail below, valve actuation
system 12 may help regulate fluid flows through engine 10.
[0015] Engine 10 may include an engine block 14 that at least
partially defines one or more cylinders 16. A piston 18 and a
cylinder head 20 may be associated with each cylinder 16 to form a
combustion chamber 22. Specifically, piston 18 may be slidably
disposed within each cylinder 16 to reciprocate between a
top-dead-center (TDC) position and a bottom-dead-center (BDC)
position, and cylinder head 20 may be positioned to cap off an end
of cylinder 16, thereby forming combustion chamber 22. Engine 10
may include any number of combustion chambers 22 and combustion
chambers 22 may be disposed in an "in-line" configuration, in a "V"
configuration, in an opposing-piston configuration, or in any other
suitable configuration.
[0016] Engine 10 may also include a crankshaft 24 rotatably
disposed within engine block 14. A connecting rod 26 may connect
each piston 18 to crankshaft 24 so that a sliding motion of piston
18 between the TDC and BDC positions within each respective
cylinder 16 results in a rotation of crankshaft 24. Similarly, a
rotation of crankshaft 24 may result in a sliding motion of piston
18 between the TDC and BDC positions. In a four-stroke engine,
piston 18 may reciprocate between the TDC and BDC positions through
an intake stroke, a compression stroke, a power stroke, and an
exhaust stroke. In a two-stroke engine, piston 18 may reciprocate
between the TDC and BDC positions through a power/exhaust/intake
stroke and an intake/compression stroke.
[0017] Cylinder head 20 may define one or more fluid passages 28
associated with each combustion chamber 22 that are configured to
direct gas (e.g., air and/or exhaust) or a mixture of gas and fluid
(e.g., fuel) into or out of the associated chamber 22. In the
disclosed embodiment, cylinder head 20 is shown as defining a
single passage 28. Passage 28 may represent either an intake
passage or an exhaust passage in this embodiment. It should be
noted that, while only a single fluid passage 28 is shown, as many
intake and/or exhaust passages may be provided within cylinder head
20 as desired. As an intake passage, passage 28 would be configured
to deliver compressed air and/or an air and fuel mixture into a top
end of combustion chamber 22. As an exhaust passage, passage 28
would be configured to direct exhaust and residual gases from the
top end of combustion chamber 22 to the atmosphere. It is
contemplated that, in some embodiments, only an exhaust passage may
be formed within cylinder head 20 and the corresponding intake
passage may instead be formed within engine block 14. In these
configurations, the intake passage would be configured to direct
air or the mixture of air and fuel radially inward to combustion
chamber 22 through a side wall of cylinder 16.
[0018] A plurality of gas exchange valves 30 may be disposed within
openings of passageway 28 and movable to selectively engage
corresponding seats 32. Specifically, each valve 30 may be movable
between a first position at which valve 30 is engaged with seat 32
to inhibit a flow of fluid through the opening, and a second
position at which valve 30 is moved away from seat 32 (i.e.,
lifted) to allow a flow of fluid through the opening. The timing at
which valve 30 is moved away from seat 32 (relative to a position
of piston 18 between the TDC and BDC positions), as well as a lift
height of valve 30 at the particular timing, may have an effect on
the operation of engine 10. For example, the timing and lift height
may affect production of emissions, production of power, fuel
consumption, efficiency, temperature, pressure, etc. A spring 36
may be associated with each valve 30 and configured to bias valve
30 toward the first position and against seat 32. A spring
retainer, not shown, may connect spring 36 to a stem end of each
valve 30.
[0019] Valve actuation system 12 may be operatively engaged with
cylinder head 20 and configured to simultaneously move valves 30
against the biases of springs 36 from their first positions toward
their second positions at desired timings. It should be noted that,
when each cylinder head 20 is provided within both intake and
exhaust passages and corresponding intake and exhaust valves,
engine 10 may include a separate valve actuation assembly for each
set of intake and exhaust valves. Each valve actuation system 12
may include, among other things, a common camshaft 38, one or more
pushrods 40, and a dedicated rocker arm 42.
[0020] Camshaft 38 may operatively engage crankshaft 24 in any
manner readily apparent to one skilled in the art, where a rotation
of crankshaft 24 results in a corresponding rotation of camshaft
38. For example, camshaft 38 may connect to crankshaft 24 through a
gear train (not shown) that decreases the rotational speed of
camshaft 38 to approximately one half of the rotational speed of
crankshaft 24 (in the exemplary 4-stroke arrangement).
Alternatively, camshaft 38 may connect to crankshaft 24 through a
chain, a belt, or in any other appropriate manner. At least one cam
lobe 44 may be connected to camshaft 38 and associated with each
pairing of valves 30. An outer profile of cam lobe 44 may
determine, at least in part, the actuation timing and lift profile
of valves 30 during operation of engine 10.
[0021] Each pushrod 40 may reside in a cam follower that rides on
and moves in accordance with the profile of cam lobe 44 as camshaft
38 rotates, and transfers a corresponding reciprocating motion to a
first pivoting end of rocker arm 42. This reciprocating motion
imparted to rocker arm 42 may cause rocker arm 42 to pivot about a
shaft 46, thereby creating a corresponding reciprocating motion at
an opposing second end of rocker arm 42 that lifts and releases
valves 30. Thus, the rotation of camshaft 38 may cause valves 30 to
move from the first position to the second position to create a
specific lift pattern corresponding to the profile of cam lobe
44.
[0022] Rocker arm 42 may be connected to valves 30 by way of a
valve bridge 48. Specifically, rocker arm 42 may include a pin 50
that is received within a second end of rocker arm 42, and a button
52 configured to receive an exposed end of pin 50. Button 52 may be
able to swivel somewhat relative to pin 50, and includes a
generally flat bottom surface that is configured to slide along a
corresponding upper surface of valve bridge 48. The ability of
button 52 to swivel and slide along the upper surface of valve
bridge 48 may allow rocker arm 42 to transmit primarily vertical
(i.e., axial) forces into valve bridge 48. The only horizontal
(i.e., transverse) forces transmitted between rocker arm 42 and
valve bridge 48 may be relatively low and due only to friction at
the sliding interface between button 52 and bridge 48. This
interface may be lubricated and/or polished to reduce the
associated friction.
[0023] As can be seen in FIG. 2, valve actuation system 12 may
include, among other things, one or more lash adjusters 54 disposed
with an upper end of pushrod 40, and an adjusting screw 56 located
within the first end of rocker arm 42. As will be described in more
detail below, lash adjuster 54 may be configured to automatically
adjust a clearance between a corresponding valve 30 and its
associated seat 32 (and/or between other valve train components)
when cam lobe 44 is rotated away from pushrod 40, while adjusting
screw 56 may be configured to connect rocker arm 42 with pushrod 40
in a manually adjustable manner.
[0024] Lash adjuster 54 may embody any conventional type of
adjuster that is configured to fill with oil as camshaft 38 rotates
away from rocker arm 42, and then to internally trap the oil and
function as a hydraulic link between pushrod 40 and rocker arm 42
as camshaft 38 rotates back toward rocker arm 42. In the disclosed
embodiment, lash adjuster 54 is a check-valve type of adjuster
having a valve element 58 that is spring biased against a seat 60.
Valve element 58 may be pushed away from seat 60 during the
retracting cam movement to fill an associated hydraulic chamber 62
with oil, and re-engage seat 60 during the extending cam movement
to lock the oil inside hydraulic chamber 62. It is contemplated
that lash adjuster 54 may have another form, if desired.
[0025] The oil directed to lash adjuster 54 may be provided via
rocker shaft 46, rocker arm 42, and adjusting screw 56.
Specifically, the oil may be pressurized by an engine-driven pump
(not shown) and directed into a centralized axial passage 64 of
shaft 46. The oil may then be directed outward via one or more
radial passages 66 to an annular groove 68 that surrounds shaft 46.
From annular groove 68, the oil may be directed to the opposing
ends of rocker arm 42 via corresponding passages 70 and 72. The oil
in passage 70 may lubricate pin 50, button 52, and valve bridge 48,
while the oil in passage 72 may be directed through adjusting screw
56 to lash adjuster 54.
[0026] Adjusting screw 56 may disposed within a bore 74 of rocker
arm 42 at the first end. In particular, as shown in FIGS. 3-4,
adjusting screw 56 may include an elongated cylindrical shaft 76
having a first end 78, a second end 80, and an outer annular
surface 82 that extends between first and second ends 78, 80.
Threads 84 may be formed in outer annular surface 82 and configured
to engage corresponding threads in bore 74 of rocker arm 42
(referring to FIG. 2). A tool engagement head 86 may be formed at
first end 78 of shaft 76 and used to manually turn adjusting screw
56 and thereby selectively adjust an axial position of shaft 76
relative to rocker arm 42 (i.e., as adjusting screw 56 translates
into and out of bore 74). In the disclosed embodiment, tool
engagement head 86 may have an outer diameter that is the same as
or less than an outer diameter of shaft 76. A lock nut 88 (shown
only in FIGS. 1 and 2) may be provided to engage threads 84
adjacent tool engagement head 86 and to abut an upper surface of
rocker arm 42, thereby inhibiting undesired axial movement of
adjusting screw 56.
[0027] A pivot head 90 may be located at an end of shaft 76
opposite tool engagement head 86 and configured to engage lash
adjuster 54 (e.g., to engage a spherical socket 91 formed in an
upper end of lash adjuster 54--see FIG. 2). Pivot head 90 may have
a rounded outer surface 92, and a planar shoulder 94 located
opposite outer surface 92. Planar shoulder 94 may be generally
orthogonal to an axis 96 of shaft 76. In the disclosed example,
outer surface 92, together with shoulder 94, forms a hemispherical
shape (e.g., surface 92 may arc through about 180.degree.). An
outer diameter of pivot head 90 may be larger than the outer
diameter of shaft 76, for example about 40-50% larger. Outer
surface 92 may be truncated at its vertex or center, such that
pivot head 90 has a flat end face 98 that is generally orthogonal
to axis 96. In one embodiment, end face 98 may have an outer
diameter d that is about 45-55% of an outer diameter D of outer
surface 92. When pivot head 90 is received within socket 91 of lash
adjuster 54, the flattened nature of end face 98 may, together with
socket 91, create a hemispherical void that functions to collect
debris, which can subsequently be washed out of valve actuation
system 12.
[0028] As described above, adjusting screw 56 may function to
transport pressurized oil from rocker arm 42 (e.g., from passage
72) to lash adjuster 54. In particular, an axial passage 100 may be
formed within shaft 76. Axial passage 100 may be a blind passage,
extending from outer surface 92 to a location inside shaft 76
generally aligned with an outlet of passage 72 in rocker arm 42. A
radial passage 102 may communicate passage 72 with axial passage
100. In some embodiments, an annular collection recess 104 (see
FIG. 2) may be formed in bore 74 of rocker arm 42 at an opening of
radial passage 102, such that oil from passage 72 may collect in
this region before entering radial passage 102. This may facilitate
oil flow into radial passage 102, regardless of the orientation of
adjusting screw 56. A restrictive orifice 106 (shown only in FIG.
4) may be located inside radial passage 102 in order to provide a
desired flow rate and/or pressure of fluid throughout (e.g., up
stream of) valve actuation system 12.
[0029] One or more radial grooves 108 may be formed in pivot head
90 (e.g., within outer surface 92 and/or flat end face 98) that
fluidly connect with axial passage 100. In the disclosed
embodiment, radial groove 108 passes completely through an outlet
of axial passage 100 (i.e., such that there are either two ends of
one continuous groove or two separate grooves that meet at axial
passage 100), and terminates short of shoulder 94. By terminating
short of shoulder 94, a peripheral edge strength of pivot head 90
may be improved and sharp features (e.g., groove corners) that
could cause damage to socket 91 of lash adjuster 54 may be avoided.
It should be noted that, although radial groove 108 may terminate
short of shoulder 94 at its outer ends, radial groove 108 may
extend far enough to provide a relatively unrestricted flow of oil
from passage 100 over a lip 109 of socket 91. That is, as adjusting
screw 56 pivots within socket 91 of lash adjuster 54, the
terminuses of radial groove 108 should extend out of socket 91 and
clear lip 109 of socket 91 at least once per engine cycle, thereby
ensuring an unrestricted flow of oil out of radial groove 108. In
the disclosed embodiment, radial groove 108 may arc through an
angle of about 155-160.degree..
[0030] Radial groove 108 is oriented generally orthogonal relative
to an axis 110 of radial passage 102, in the disclosed example, and
may have a curved or square bottom. It should be noted that other
orientations of radial groove 108 may be possible, and allowing a
variable orientation may improve manufacturability of adjusting
screw 56. A width and a depth of radial groove 108 within outer
surface 92 may be generally consistent (e.g., within manufacturing
tolerances) along its length, and radial grooves 108 may be
fabricated via a cold forming process. The shape and orientation or
radial groove 108, along with the method of fabrication, may help
to simplify manufacturing efforts and cost associated with
adjusting screw 56.
[0031] A radius r of radial groove 108 may be about 0.4-0.6 times a
radius R of axial passage 100, such that the flow from axial
passage 100 may be divided into three streams of oil (i.e., a main
stream available to lash adjuster 54, and two equal and smaller
streams of oil flowing in opposite directions away from axial
passage 100). These flows of oil may supply lash adjuster 54 with
the oil necessary to set the clearance of valves 30 and, just as
importantly, also function to draw heat away from the interface
between pin 50 and lash adjuster 54 (e.g., between head 90 and
socket 91).
INDUSTRIAL APPLICABILITY
[0032] The disclosed valve actuation system may have applicability
with internal combustion engines. In particular, the disclosed
valve actuation system may be used to lift one or more gas exchange
valves of an engine, while maintaining a desired valve clearance
during operation of the engine. In addition, the disclosed valve
actuation system may have a unique adjusting screw that provides
for cooling flows of oil to an interface with a lash adjuster
disposed inside an associated pushrod. The cooling flows may be
generated via radial grooves formed in a pivot head of the
disclosed adjusting screw.
[0033] Several advantages may be associated with the disclosed
adjusting screw. In particular, because radial grooves 108 may
extend completely to axial passage 100 (i.e., without significant
restriction at outer surface 92), a relatively low-pressure flow of
oil may be used to cool and lubricate the interface between pivot
head 90 and lash adjuster 54. In addition, this low-pressure oil
may have a velocity that allows it to absorb a desired amount of
heat from the interface. Further, the geometry of adjusting screw
56 may be relatively simple, robust, and inexpensive to
fabricate.
[0034] It will be apparent to those skilled in the art that various
modifications and variations can be made to the valve actuation
system of the present disclosure without departing from the scope
of the disclosure. Other embodiments will be apparent to those
skilled in the art from consideration of the specification and
practice of the embodiments disclosed herein. It is intended that
the specification and examples be considered as exemplary only,
with a true scope of the disclosure being indicated by the
following claims.
* * * * *