Internal-combustion engines – Poppet valve operating mechanism – Rocker
Patent
1999-02-18
2000-03-21
Lo, Wellun
Internal-combustion engines
Poppet valve operating mechanism
Rocker
123 9019, 123 9036, 123 9055, F01L 124
Patent
active
060390174
ABSTRACT:
A hydraulic lash adjuster having a piston capable of forming a pivot for a member of an engine valve train connecting a cam and a valve includes a hydraulic lash adjusting element of varying length for acting in the valve train, an expansion spring for extending the length of the lash adjuster to take up lash in the valve train between valve opening events and a lash spring which biases the adjuster element away from the piston a small amount to maintain a sufficient amount of lash in the valve train between valve opening events to prevent holding open of the valve during cold engine operation. Various embodiments of lash adjusters and lash springs are disclosed. During steady state operation, the lash spring introduces a fixed amount of mechanical lash into the valve train. In nonsteady state transient operations, such as during cold engine start up, the amount of mechanical lash may be reduced when growth of the valve train components exceeds the leak down rate of the hydraulic lash adjusting element. However, as long as the amount of mechanical lash is adequate to offset the excessive growth of the valve train components, opening of the valve due to thermal pump up is prevented. As the engine warms up and a normal leakdown rate of the hydraulic lash adjusting element is reached, operation with a fixed amount of mechanical lash returns.
REFERENCES:
patent: 2937632 (1960-05-01), Voorhies
patent: 3542001 (1970-11-01), Line
Cichosz Vincent A.
General Motors Corporation
Lo Wellun
LandOfFree
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