Note: Descriptions are shown in the official language in which they were submitted.
2~ 3
G-11176 C-4375 , ~ .
LOW MA5S DIRECT ACTING HYDRAULIC VALVE LIFTER
Technical Field `
This invention relates to hydraulic valve
lifters (HVL's) for engines and, in more particular
embodiments, to direct acting I~VL'~ of light weight
for use in relatively high speed overhead cam (OHC)
automotive engines and the like. HVL's may al~o be
referred to as hydraulic tappet~ and sometime~ are
called hydraulic lash adjusters, and direct acting
hydraulic valve lifters (D~HVL's) are sometimes called ;
bucket tappets, however these various names are not
nece~sarily of equivalent scope.
Back~round
It is known in the art relating to overhead cam
(OHC) internal combuction engines to provide a direct
acting hydraulic valve lifter (DAHVL) that is
contacted by a cam and directly actuates one or more
valve~ of the engine. One ~uch arrangement which has
been used in production engines is shown in United
State~ patent 4,745,888 issued May 24, 1988 to the `
assignee of the present invention.
In that patent disclosur~, a camshaft 18 ~;
supported in an aluminum cam~haft carrier 11 has ~ams
22, each of which directly engage~ a DAHVL ~tappet 23)
that in turn engages the ~tem 34 of a poppet valv~
con~entionally ~arried in a cylinder head, not ~hown,
to actuate the valve. Each lifter 23 includes a
cup-like follower having a cam engaging alloy ca~t
30~ iron upper end 24 diffusion bonded to a cold formed
ste~l baffle ~hell including an annular outer wall
(~kirt 26) and an inwardly supported central wall 27.
The central wall include~ a radial supporting baffle
and an axial annular cylinder portion in whlch a
~ '';';
'
',`
2~9~993
hydraulic element assembly (HEA) (hydraulic lash
ad~uster 28) i9 reciprocably supported. The HEA i9
supplied with hydraulic fluid (engine oil) through an
annular oil feed chamber 30 which is fed at it5 lower
edge through an opening 32 via an external groo~e 31.
The follower construction is thin-walled to
maintain a low reciprocating wei~ht for the lifter 23
as is desirable for operation at higher eng'ne speeds.
However, the chamber 30 is filled with a significant
volume of oil which increases the reciprocating mass
of the lifter in operation. Also, the oil in the ~ .
chamber 30 may drain from thP lifter whan the engine
i9 gtopped SO that, upon starting, the oil supply must
again fill the chamber 30 before a dependable feed of
oil is again provided to the HEA 28. During this ~
period, the HEA must rely upon an internal oil ..
reservoir for its oil supply. In addition, air may :. .
enter the system such.as through draining of the
chamber 30 when the engine is stopped or foaming of
the oil supply during engine operation. This air may
enter the HEA through an i~let from the chamber 30,
resulting in unwanted tappet noise and/or improper
:. ~ valve actua~ion for an extended period until the air
: is removed ~rom the lifter by escape through the
:25 clearances apart from or along with the escaping oil.
: Copending commonly assigned U.S. 5,119,774
issued ~une 9, 1992, disclo~ee DAHVL's in which oil i5
displaced from the chamber 30 by oil resistant foam
which reduces the operating reciprocating mas~ o~ the
~lifter and supports or a~9i8t~ in supporting the axial ~ .
cyIinder portion of the central wall that in turn
.:
~ 2 :
.
.
~4~3 ~:
supports the HEA. Reference to that patent
application, which is incorporated herein by
reference, as well as to corresponding applications
elsewhere will further explain the background of the
additional features included i.n the present invention.
Summary of the In~ention :-.
The present invention involves direct acting .
hydraulic valve lifters (DAHVL' 8) which utilize the
foam filler and other features of the aforementioned
U.S. patent 5,119,774 while providing improvements in ,
the cam follower construction that can reduce mass and
complexity wikh potentially lower manufacturing co~t.
Among the improved features of the invention are:
A follower having an optional ~ingle piece ~hell
combined with a light pla~tic baffle retained by the .~
foam filler for low mass and C08t; : .;.
Suitable for use with conventional hydraulic :~
element assemblies (HEA' 8) or other piston
arrangement~
A preferred polymer material for the baffle . .,:
; ~ having low ~asQ and good stability characteristics; ~.
A rlser chamber that provides a fluid inlet path
and sufficient volume for maintaining pre~ure under
; cold flow. This can be formed as part of the plastic
~25 baffle and/or within the:~upporting foam;
Sealing and as~embly mea~Q and methods ~or ~
reliability and efficiency of manufacture. ;;
These and other features and advantages of the
invention will be more fully underetood from the
following description of certain specific embodiments
,
, .
~ 3
: ~ ~: ,: ;;
9 3
of the invention taken togethe:r with the accompanying
drawings.
Brlef Dra_inq Description
In the drawings:
Figure 1 is a cross-sectional view of an enyine
valve ~rain incorporating a direct acting hydraulic
valve lifter tDAHVL) having a riser chamber and other
feature~ according to the invention;
Figure 2 is a top view of the plastic baffle
member of Figure 1;
Figure 3 i~ a pictorial view of the plastic
baffle member of Figure 1;
Figure 4 is an enlarged ~iew of the cixcled :
portion of Figure 1 showing an optional "cru~h edge" ; ;
~ealing feature;
Figure 5 is a cross-sectional view of an
alternative embodiment having other option~l features; :
Figure 6 i9 a cro s-~ectional view of another .
~embodiment of follower formed with a lost core shown
20 ~ prior to removal; ~ ~.
: Figure 7 is a top end view o~ the baffle for the
embodiment of Figure 6 showing the lo~t core in place :
: ~ ~prior to a~embly into the:~hell; and
Figure 8~ i9 a pictorial view of the ba~fle of ';
25:~ Figures 6 and~7 with the lost:core in po~ition for
a~em~ly. :
~Petailed~De~a~iE~1Qa
Referring~now to Figures 1-4 of the drawing~ in
: : : detail, numeral 10 generally indicatee a preferred
:30 embodiment of dlrect acting h~draulic valve lifter
D~HVL~ according to the invention. Lifter 10 is ~. .
:
.
- :,.
,
,:
2~9~993
somewhat similar in its general construction to the
tappets or lifters described in the previously cited
patents 4,745,888 and 5,119,774 and i~ adapted to be
reciprocably mounted between a cam 11 and the stem 12
of a cylinder poppet valve in an engine 14 in a
conventional manner as shown, for example, in the
cited patent.
The lifter 10 comprises a cam follower 15 and a
hydraulic element assembly (H~A) 16. The follower 15
10includes a cup-like outer shell 18, an inner baffle 19 '!
and a foam filler 20.
The shell 18 has an annular skirt or outer wall
22 with an open bottom end 23 and a cam-engaging head ~,
24 closing the upper end. (The head 24 is often
referred to as a foot for consistency with other valve
lifters, including historical direct acting types, in ~-
which the lifter rides on top of the cam). For ~ome
applications, the head 24 may be formed o~ steel
integral with the outer wall 22. However, where an
~alloy cast iron or other head material is preferred,
the head 24 may be separately formed~and attached to
the wall 22 in any suitable manner such a~, for
example, by diffusion bonding or laser welding. The
she11 outer wall, as shown in Figure 2, is of circular
~ cross section centered on an axis 26, however it may
be~oval, rectangular or another uitable shape if
desired. Between itB ends, an inwardly extending
annular groove 27 is formed, as~by rolling or
machining. An oil inlet opening 28 pa~se3 through the ;
shell on the upper side of the groove 27.
.
~ 5 ~
2~993
The baffle 19 is formed æeparately from the
shell of a suitable lightweight material and
construction and i9 retained in the upper portion of
the shell 18. Baffle 19 includes an upstanding inner .
5 wall 30 that preferably.extend~3 to the head 24 of the .
shell 18. The upper portion of the wall 30 foxms an
annular recess 31 similar to a counterbore in
appearance. Below the recess, the wall 30 defines an
inner cylinder 32 which is preferably of circular
cross section to receive a conventional HEA. A flange
34 extend~ outward from the cylinder, preferably at
the bottom of the wall 30. In the illu~trated ~i.
embodiment, the flange extends radially for part of
it~ diameter and then slopes downward to engage the
shell outer wall 22 inward of the oil groo~a 27. The
raised central portion of the flange provides
clearance for a~sociated valve train component~. The
flange may include a ~ill hole 35 and a ~maller vent
hole 36 to be later discussed. :;
Along one side of the inner wall 30 and aliyned
with the inlet opening 28 are auxiliary wall mean~
defining a riser chamber 38 extending axially along
: the inner wall 30 from the flange 34 to the head 24 of .:
the shell. In the Figure 1-4 embodiment, the wall ~ :
means include spaced lateral walls 39 and 40 that :.
:~ extPnd radially outwardly from the inner wall 30 and a
boundary wall ~2 that connect~ outer edges of the
lateral walls between the inner and outer walls 30, 22 ;.
to define the outer extent of the riser chamber.
Walls 39, 40, 42 also engage the inner side of the .:
head 24 and extend to the flange 34 below. An inlet
' :
: .
: : .
2~94~93
hole 43 through the boundary wall 42 near the flange
is aligned with the opening 28 in the wall 22.
When assembled, the shell 18 and the baffle 19
define an annular first space 44 between the inner and
outer walls. This space is filled with the foam
filler 20 except for the riser chamber 38 which is
open to the passage of oil. A passage 46 formed :
through the foam between the inlet opening 28 and the
inlet hole 43 allows oil flow from the oil groove 27
into the riser chamber 38. A slot 47 through the .
upper portion of the inner wall 30 connects the riser .i
chamber 38 with a second space 48 within the inner
wall and a shallow recess 50 in the head 24 permits
oil to flow from the chamber 38 through the slot 47
and recess 50 to an inner re~ervoir 51 in the HEA.
The feature3 of the HEA form no part of the
present invention since they are of known conventional
: form or are di clo ed in the prior copending U.S.
: patent 5,119,774. Detailed di3cu~sion of the HEA is
not therefore required. In general, however, the HEA ;`
comprises a closed end pi~ton 52 internally carrying a
plunger 54 enga~able with the head 24 and having a
: check valve con~rolled orifice 55 that allows one way
oil flow ~rom the re~ervoir 5} to a pre~ure chamber
56 between the pi8ton and plunger. The recirculation
: holeY 58 in the plunger and cIearance means formed as ..
a flat on the piston or as a groove 60 acros~ the
cylinder 32 surface provide optional xecirculation and
vent means a~ de~cribed and claimed in the afore~aid
30: u.S. patent 5,119,774.
' ;"'
:: 7
.
,.
~9~993
Another optional feature shown in Figure 4, an
enlarged view of the circled area 4 of Figure 1, is a
crush edge 62 at the lower outer edge of the baffle
flange 34. Formed as a sharp edge 62 (shown in da~hed
lines) in the plastic material prior to assembly, the
edge 62 is deformed by interference fitting within the
smaller inner diameter of the outer wall 22 adjacent
the oil groove 27. This tight fitting crushed edge 62
forms a seal against the escape of the foam filler . .
during its installation in the follower first space
44.
Figure 5 ~hows a DAHVL 63 similar to that of
Figure 1 wherein like numerals designate like parts.
Several optional features are included in a modified
follower 64. A two-piece shell 66 is provided having
a thin steel outer wall 67 attached, such as by
diffusion bonding, to an alloy cast iron head 68. The
two-piece construction i~ optio~al :and similar to
: ~prior commercial ~alve lifters ~uch as that shown in
the aforementioned~patent 4,745,888~
A;baffle 70~similar to:that of~ Figures 1-4 is
also provided having two other~modifications. The
inner wall 71~has at its upper ènd a lip 72 extending
outward and~engaging an inner side of the head 6R.
The l~p can aasi~t in preventing~leakage o~ foam into : :
the second space 48 containing the HEA 16. A modi~ied
riser chamber 7~ is also formed by providing an :
outward extens1on 75 ~rom the lower portion~ of the .:
:- : auxiliary wall:s 76 to form an enlarged inlet portion
~: 30 78. Thi~ extends the riser chamber outward and
8 ; : ~
: :: . .
2~ 93
''.i
,.
further reduces resistance to Eluid flow from the
inlet opening 28 to the second ~pace 48.
In this Figuxe 5 embodiment, the joint 79
between the baffle 70 and the outer wall 67, at the
S location of the riser chamber :inlet portion 78, is
sealed a~ainst oil leakage by the close fitting of the
parts and, optionally, by a crushed edge 62 forming ~i
seal means as shown in Figure 4. However, it does not
have the additional sealing effect of the foam filler
at this location as does the Figure 1-4 embodiment.
If desired, other types of 8eal5 could be provided as
seal means to control leakage at this joint. Also,
such seals as resilient rings or gaskets could be u~ed
around the baffle edges to control foam leakage during
filling.
~ Figure 6 illustrates another embodiment o~
follower 80 for a DAHVL according to the invention.
The shell 18 is optionally like that of Figure 1 but
the baffle 82 is modified to eliminate auxiliary ~
walls. Instead, a lost core 83 is applied during -~-
manufacture as shown in Figures 6-8. The core 83 fits
within the annular recess 31 of the inner wall 30 of
baffle ~2 closing the upper part of the ~econd space
48. A small radial segment 84 o~ the core extends
through the 910t 47 in the wall 30 out to the outer
wall 22 and down to the flange 34 of the baffle at the
~inlet opening 28 to prevent the inflow of foam fillex
~20 to the cored volume during the filling proces~.
The core i~ ~ub8equently remoYed, as will be discussed
later, forming a ri~er chamber 86 in the first ~pace
i ,
g , :
' ': '
`:
, .
~ ~ :. ,.
2~9~9g3
that is bordered by the foam filler 20 and connects
the inlet opening 28 with the ~econd Rpace 48.
In operation of the described embodiments, oil
admitted throltgh the opening 28 passes through the
riser chamber 38, 74, 86, slot 47 and rece~s 50 to the
reservoir 51. From there, it i8 allowed to pas~
through the check valved orifice 55 and xefill the
pressure chamber 56 at each cycle as the HEA 16
operates to adjust the valve lash in known mannar,
urging the follower head 24, 68 lightly against the
cam 11 and the HEA piston 52 against the valve stem
12. Then as the rotating cam 11 force~ the follower
15, 64, 80 downward, the HEA piston 52 opens the valve
by forcing down the stem 12 and spring ~eat 87 against ..
the force of the spring 88, ~urther cam rotation again
allowing the valve to close and the replacement of oil
which has leaked from the pressure chamber 56.
: ~nder warmed-up engine operation, oil~flows
freely into the inlet passages. However, the ri~er ; .
chamber 38, 74, 86 i~ made with sufficient cross
: sestion transverse to the direction of oil flow to
avoid substantial resistance to cold oil flow and
encourage normal filling of the pr0ssure cha~ber even .j~ ;
under cold starting condition~ when the oil is more
: 25 viæcous. The recirculation holes 5~ and vent groove
60, if provided, operate to minimize the entry of oil
entrained air into the reservoir 51. .
In manufacture of a li~ter follower as in
Figures 1-4, the ~hell may be cold formed from a
conventional hardenable steel with the oil groove 27 ;~
: ~ being roll formed or machi~ned a~ desired.
,., "
'.
.
2~993
The baffle is preferably molded of a low mass
polymer plastic having good dimensional control,
thermal expansion stability and chemical resistance.
A presently preferred example is Fortron~ 6165, a
highly glass reinforced and mineral filled
polyphenylene sulfide (PPS) molding material available
from Hoechst Celanese, Engineering Plastics Divisioni,
Summit, New Jersey. The groove 60, if used, may be
molded into the cylinder 32 or the cylinder and groove
60 may be machined for clearance control if desired.
Alternatively, the baffle may be made from any
suitable material which may he selected, for example,
from among the thermoplastic and thermosetting
reinforced and filled engineering pla~tics. Among the
needed or desired characteristics of such baffle
materials are durability in a lubricating oil
environment at temperature6 from -400 to 1500C., a
coefficient of linear thermal expansion closely
matched to the mating metallic components, re~istance
to lubricating oil contaminants and an ability to be
molded with close tolerance and low warp.
After assembly of the baffle into the 3hell, the
foam filler i~ installQd a~ a liquid into the first
~space 44 through a nozzle insarted into the fill hole
35 in the flange 34. The filler foams and hardens in
place, with air escaping from the space 44 through the
vent hole 36. ~eakage of foam into the second ~pace
; 48 and the ri.ser chamber 38 may be prevented if
nece~sary by pressurizin~ the~e apaces through the
inlet hole 43, the bottom of the cylinder 32 being
~ealed off duri~g the process. However, the joints
.
11 '
. ;: . i; - .: . . . .:
2~9~993
may be adequately sealed by engagement of the baffle
and shell members, possible with the aid of crush
edges such as 62 acting as seal means.
After hardening, the foam filler has sufficient
strength and adhesion to retain the plastic baffle in
position within the shell under engine operating
conditions. A preferred selection of foam filler
material ie a modified polyurethane foam provided ~y
System-Chardonol Division of Cook Composites and
Polymers Co. (formerly the Freeman Chemical Company)
of Port Washington, Wisconsin and having a mix ration
of 100 parts by weight Chempol~ 030-A944-70 resin to
200 parts by weight Chempol0 030-2416 Isocyanate.
At present, a prefexred proce~s for assembling
the lifter follower includes the following steps~
1. Provide a follower shell and plasti~ baffle
as described abo~e, both of which should be clean and
dry.
2. Heat the shell to 1500F. This heIps to
assure proper expansion and correct physical and
mechanical propertie~ of the cured foam.
3. Assemble the baffle into the shell,
orienting the baffle rieer chamber with the shell
inlet opening.
4. In a fixture, clamp the baffle in the ~hell
and seal the baffle at the ~hell inner diameter.
5. Mix the two part foam and injec~ through the
baffle foam ~i}l hole.
~. When foam expan~ion begin~, apply air
pressure to baffle interior volume to prevent foam
seepage thereinto.
12
. .
2~4993
7. Heat the follower asse~bly with the clamped
baffle at 1500F until the foam is cured and set.
8. When complete, remov~e the baffle from the
cl~mping fixture.
Manufacture of the Figure 5 embodiment can be
essentially as above while the embodiment of Figures
6-8 differs in the previously de~cribed use of the
lost core 8i3. Any suitable core material can be used
which can be removed after assembly of the lifter
follower. Possible examples are oil or water soluble -~
foam materials, ice, etc.
While the invention has been described by
reference to certain preferred embodiments, it should
be understood that numerous changes could be made
within the spirit and scope of the invéntive concepts
described. Accordingly it is intended that ~he
invention not be limited to the disclosed embodiments,
but that it have the full ~cope permitted by the
language o~ the following claims.
.
.
: ,
:: :
,.
:
13
.
" ~ . ..... " .~, ... . , . , . ,". ;. . , . . , ., . ~: . .
