Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
2000-12-06
2001-12-04
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090360, C123S090460
Reexamination Certificate
active
06325034
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE DISCLOSURE
The present invention relates generally to hydraulic lash adjusters for internal combustion engines, and more particularly, to a hydraulic lash adjuster (HLA) which is very compact in size, especially in overall length.
Although the present invention may be utilized in conjunction with hydraulic lash adjusters for use with a number of different types of engine valve gear train, the invention is especially advantageous when used in a valve gear train of the end-pivot rocker arm type, and will be described in connection therewith. When an HLA is used in an end-pivot rocker arm type of valve gear train, the HLA is stationary and is disposed in a bore formed in the engine cylinder head.
A conventional HLA of the type to which the invention relates includes an output plunger assembly engaging the rocker arm (in the case of an overhead cam engine) with the output plunger assembly typically being of either a one piece or a two piece construction. The plunger assembly includes a ball plunger element which engages a socket formed in the rocker arm, and a leakdown plunger element which defines a check valve seat and further defines a leakdown land, the leakdown plunger element being precisely fit within a bore of the body to provide a closely controlled fluid leakdown path during normal operation.
The above-described plunger assembly results in an overall HLA structure which is relatively long, such that it can be difficult to allocate sufficient space within the cylinder head to locate the HLA. The above-described problem is particularly acute in some of the new, compact, multi-valve engines. The length of conventional, prior art hydraulic lash adjusters can also cause constraints on other aspects of the design of the engine, such as valve location, valve angle, the location and orientation of the spark plug, and the location of oil galleries, coolant passages and valve ports.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a hydraulic lash adjuster which is very compact, particularly in terms of its overall length.
It is a more specific object of the present invention to provide a hydraulic lash adjuster which effectively eliminates the traditional lash adjuster body, by providing a ball plunger which reciprocates directly within the bore formed in the cylinder head.
The above and other objects of the invention are accomplished by the provision of an improved hydraulic lash adjuster adapted to be disposed within a bore defined by an internal combustion engine, the hydraulic lash adjuster comprising a ball plunger including a body portion. The body portion is reciprocable in the bore as the ball plunger reciprocates between a relatively retracted position and a relatively extended position. The hydraulic lash adjuster firther comprises a leakdown plunger assembly disposed within the body portion and adapted to be disposed downward in response to downward movement of the ball plunger and the body portion. The leakdown plunger assembly has a bottom portion disposed toward a bottom of the bore, the plunger assembly and one of the bottom portion and the bottom of the bore cooperating to define a high pressure chamber.
The improved hydraulic lash adjuster is characterized by the ball plunger and the body portion comprising a single, integral formed member. The body portion defines an axial length equal to a major portion of the entire axial length of the bore and further defines an outside diameter wherein the axial length is from about 1.0 to about 1.4 times the outside diameter.
REFERENCES:
patent: 5655487 (1997-08-01), Maas et al.
patent: 5875748 (1999-03-01), Haas et al.
patent: 5983848 (1999-11-01), Calka
Eaton Corporation
Kasper L. J.
Lo Weilun
LandOfFree
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