Integral formed oil column extender for hydraulic lash adjuster

A hydraulic lash adjuster for an internal combustion engine, and a method of its construction is disclosed. The lash adjuster has a cylindrical follower body in which a tubular plunger is slidingly disposed. The plunger cooperates with the follower body to define a high pressure chamber therebetween which is supplied with fluid through a valved port. A low pressure chamber which operates to supply fluid to the high pressure chamber through the valved opening, is defined by an axial passage through the plunger. Fluid flows into and out of the low pressure chamber through a port in the wall of the plunger. Intermediate of the port and the valved opening is a radially inwardly extending annular shelf which is integral formed with the axial passage of the plunger using a mechanical shaving step to plow a portion of the plunger material from the wall of the axially extending passage. The annular shelf operates as a baffle to prevent loss of fluid from the low pressure chamber when the hydraulic lash adjuster is installed at an angle from vertical.

TECHNICAL FIELD 
The invention relates to hydraulic lash adjusters for use in internal 
combustion engines. 
BACKGROUND 
When a hydraulic lash adjuster is used, for example, in an overhead cam 
engine to serve as the fulcrum for a rocker arm in the poppet valve 
operating train of the engine, the lifters are typically dependent on an 
internal oil reservoir for proper function on initial engine start-up. 
During inoperative periods, pressure chamber oil will typically escape 
therefrom between the sliding surfaces of the lash adjuster plunger and 
follower body. Oil stored within the follower body is used by the lash 
adjuster to refill the pressure chamber during the time interval that the 
engine lubricating system requires to refill the lifter. The performance 
of these lifters is adversely affected by angles of installation which 
effectively reduce the height of the stored oil column in the follower 
body. 
The problem created by large installation angles has been addressed 
previously by installation of a separate baffle member into the lash 
adjuster body. The baffle member is configured to increase the height of 
the stored oil column. The addition of the baffle increases the cost of 
the lifter substantially as processing is impacted by the additional 
operation required to install the baffle and by the cost of the component 
which is typically a precision stamped piece. 
SUMMARY OF THE INVENTION 
The present invention relates to a hydraulic lash adjuster for use in an 
internal combustion engine where large angles of installation are 
required. The adjuster includes a closed-end follower body having a 
tubular plunger slideable therein. A check valve assembly is disposed 
between the plunger and the follower body to define a high pressure 
chamber below the valve and a low pressure oil chamber above the valve and 
within the plunger. The plunger is constructed by extruding an axially 
extending tubular passage which extends substantially the length of the 
plunger. An integral baffle feature is defined by an annular shelf 
disposed intermediate of the plunger ends. The shelf extends radially 
inwardly from the walls of the plunger and includes a central opening. The 
baffle is formed by shaving material from the inner wall of the plunger 
following initial extrusion of the cylindrical passage. The integral 
baffle operates to increase the volume of retained-oil, stored in the low 
pressure oil chamber of the plunger, when the plunger is angularly 
installed within the engine by relocating the exit opening through which 
the oil must pass to exit the plunger. The integral design of the baffle 
simplifies construction of the hydraulic lash adjuster by eliminating a 
separate baffle component and its installation. 
The details, as well as other features and advantages of the preferred 
embodiment of the invention are set forth in the following detailed 
description and drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1 and 2 there is shown a valve lash adjuster, designated generally 
as 10, which includes a generally cup-shaped cylindrical body 12 configured 
to be received in an engine cylinder head 14, or other suitable 
installation location. The cup-shaped cylindrical body 12 forms a dash pot 
for a tubular plunger 16 configured for sliding disposition within the bore 
18 of the body 12. In the embodiment shown, the tubular plunger 16 includes 
a semispherically shaped, upper thrust end 20 which extends out from the 
body 12 for engagement with a corresponding, concave portion 22 of a 
rocker arm 24 in cylinder head 14. 
A plunger return spring 26 is interposed between the bottom 28 of the 
cup-shaped body 12 and the lower end 30 of the plunger 16 and acts to bias 
the plunger 16 such that contact is maintained with the spherically concave 
portion 22 of the rocket arm 24. Fluid for the dash pot of the lash 
adjuster 10 is in the form of oil supplied from the engine lubricating 
system to a gallery 32. An external annular groove 34 in the body 12 
communicates through port 36 to deliver oil to annular space 38 defined by 
the inner wall 40 of the body 12 and an annular groove 42 in the outer 
surface of the tubular plunger 16. A second port 46 extends through the 
plunger wall and provides a means for fluid communication between annular 
space 38 and the interior, low pressure reservoir 48 of the plunger 16. 
The lower end of the plunger 16 is provided with an outlet port 50 through 
which oil, stored within the low pressure reservoir 48, may flow into the 
high pressure chamber 52 defined between the lower end 30 of the plunger 
16 and the bottom, closed end 28 of the cup-shaped body 12. Flow through 
the outlet port 50 is controlled by a one-way valve in the form of a ball 
54 which closes against a seat 56 encircling the lower end of the outlet 
port 50. A suitable valve cage 58 and valve return spring 60 limits open 
travel of the valve ball 54 to the amount necessary to accomplish 
replenishment of the pressure chamber 52 with oil which normally escapes 
therefrom between the sliding surfaces of the tubular plunger 16 and the 
cup-shaped follower body 12 as "leak-down". As shown, the valve cage 58 is 
held against the plunger 16 by the plunger spring 26 or, alternatively, the 
valve cage could be fixed to the plunger 16 using an interference fit. 
The interior, low-pressure chamber 48 of the plunger 16 extends 
substantially the length of the plunger, from adjacent the outlet port 50 
to the semi-spherical thrust end 20. An opening 62 extends through the 
thrust end 20 of the plunger 16 to enable oil within the reservoir 48 to 
lubricate the end 22 of the rocker arm 24. An integral baffle 64 is 
disposed within the low-pressure chamber 48 intermediate the ends of the 
chamber. The baffle 64 is configured as an annular shelf which extends 
radially inwardly from the inner wall 66 of the low-pressure chamber 48 to 
define a central opening 68 for the passage of oil from the oil supply port 
46 to the outlet port 50. 
As illustrated in the sequential illustration of FIGS. 3A-3C, the integral 
baffle 64 functions to increase the quantity of retained oil in the low 
pressure chamber 48 of the plunger 16 through the damming action of the 
radially inwardly extending shelf. The shelf establishes an increase in 
the volume of retained oil which must fill the low pressure chamber prior 
to spilling through the opening 68 in the baffle 64 and out of the plunger 
16 through the inlet port 46. The volume of retained oil is a function of 
lash adjuster installation angle 70. 
Construction of the plunger 16 is illustrated in the sequential 
illustration of FIGS. 4A-4F. The process begins with a slug 72, FIG. 4A, 
which is inserted into a die for subsequent extrusion, FIGS. 4B and 4C, of 
the axial passage 78 which will eventually form the low-pressure chamber 48 
of the plunger 16. The extrusion is preferably a multiple step process 
which results in a stepped internal plunger diameter with a ledge 76 
separating the larger and smaller diameter portions 78 and 80, 
respectively. A first extrude results in a partially drawn piece, FIG. 4B, 
having a reduced diameter lead-in 78 for the second extrude, FIG. 4C, which 
matches the smaller diameter of the lead-in 78 to establish the stepped 
inner diameter 80. Subsequent to complete extrusion of the stepped 
diameter, axial passage 78, FIG. 4C, the lower web 81 is pierced to form 
the outlet passage 50 through which oil may flow to the high pressure 
chamber 52 of the assembled lash adjuster 10. The integral baffle 64 is 
formed utilizing excess wall material from the smaller diameter portion 80 
of the plunger wall. A shave punch, or other suitable tooling, is inserted 
into the plunger 16 and moved axially inwardly to engage and "plow back" 
the ledge 76 to form the annular shelf of the integral baffle 64, FIG. 4E. 
The opening 68 defined by the radially inwardly extending baffle 64 is 
formed by a properly sized nose on the punch. Following formation of the 
integral baffle 64 within the axial passage 78 of the plunger 16, the 
thrust end 20 of the plunger 16 is coined and formed so as to properly 
mate with the concave end 22 of the rocker arm 24. Forming the baffle 64 
integrally with the plunger body 16 during the formation of the body, 
requires minimal additional forming steps and eliminates handling, 
installation and cost issues associated with a separately installed 
baffle. 
While the present invention has been disclosed with respect to a particular 
embodiment of hydraulic lash adjuster, it is contemplated that the integral 
baffle has application in many configurations of lash adjuster having a 
similarly constructed plunger in which the quantity of oil retained in the 
low-pressure chamber for supply to the high-pressure chamber is desired to 
be increased as a result of extreme installation angles of the lash 
adjuster. 
The foregoing description of the preferred embodiment of the invention has 
been presented for the purpose of illustration and description. It is not 
intended to be exhaustive nor is it intended to limit the invention to the 
precise form disclosed. It will be apparent to those skilled in the art 
that the disclosed embodiment may be modified in light of the above 
teachings. The embodiment described was chosen to provide an illustration 
of the principles of the invention and of its practical application to 
thereby enable one of ordinary skill in the art to utilize the invention 
in various embodiments and with various modifications as are suited to the 
particular use contemplated. Therefore, the foregoing description is to be 
considered exemplary, rather than limiting, and the true scope of the 
invention is that described in the following claims.