Hydraulic Lash Compensation Device Mechanical Lift Loss Adjustment
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Solution Overview
Problem
Conventional hydraulic lash adjusters experience mechanical lift loss and require significant modifications and precise machining for adjusting lift loss, leading to inefficiencies and potential valve train issues under varying operating conditions.
Innovation Solution
A hydraulic lash compensation device with a mechanical lift loss feature, incorporating an annular lift stop member and adjustment mechanism, allowing for precise adjustment of the lash offset through an Allen screw and lash spring configuration, which enables controlled oil flow and pressure management within the high and low pressure chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional leakdown lash adjusters are used, then fluid escapes the pressure chamber between the plunger and the wall of the lash adjuster body, but this results in mechanical lift loss and requires significant modification and precise machining for adjustment
Solution Approach 1:
The invention divides the adjustment mechanism into discrete, pre-configured components (shim stock of specific thicknesses) that can be selectively installed. This segments the adjustment process into discrete steps rather than requiring continuous precise machining, thereby reducing manufacturing complexity while maintaining adjustment precision.
Solution Approach 2:
The desired lash offset adjustment is pre-calculated and pre-configured by selecting the appropriate shim stock thickness before assembly. This preliminary action eliminates the need for complex post-assembly adjustments and precise machining operations, reducing both manufacturing complexity and potential errors.
2Manufacturing precision
If precise machining is used to adjust lift loss, then adjustment precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The adjustment range is segmented into discrete increments corresponding to different shim stock thicknesses. This allows precise lash offset adjustment through simple component selection rather than complex machining operations, maintaining manufacturing precision while significantly improving ease of manufacture.
Solution Approach 2:
The invention uses inexpensive shim stock components that can be easily manufactured and replaced. These simple, cheap components achieve the same adjustment function as complex precision machining would provide, making the manufacturing process much easier and more cost-effective.
3Reliability
If lift loss is accommodated by lost motion of the lash adjuster, then negative lash is quickly accommodated and valve closure is ensured, but device complexity increases due to spring mechanisms
Solution Approach 1:
The invention extracts the lift loss accommodation function from complex spring mechanisms and implements it through a simpler geometric solution using the shim stock thickness. This removes unnecessary mechanical complexity while maintaining the reliability of valve closure by ensuring proper lash offset adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device effectively manages mechanical lift loss and valve train alignment, ensuring efficient operation and reduced noise and wear by allowing for adjustable lash offset, accommodating thermal growth and maintaining proper valve operation across varying conditions.
Implementation Method 1
Hydraulic lash adjusters operate on the principle of transmitting the energy of the valve actuating cam through hydraulic fluid, which is trapped in a pressure chamber under a plunger
Implementation Method 2
The valve actuation event is characterized by a varying radius between the cam center of rotation and the cam follower, which effectively transmits cam energy to open and close an engine valve
Implementation Method 3
The load increases the pressure of the hydraulic fluid within the lash adjuster pressure chamber, in proportion to the plunger area
Data Source
Figure 1~2
Figure 3
AI summary
A hydraulic lash compensation device for an engine includes a plunger assembly slidingly received within a body bore to define a high pressure chamber. The plunger assembly includes a lower pressure chamber, an upper plunger element, and a lower plunger element. A mechanical lift loss feature includes a generally annular lift stop member retained to the upper plunger element by an adjustment member that extends through the lift stop member and is adjustably received in upper plunger element. The lift stop member is biased away from upper plunger element by a spring. When the upper plunger element is received into the body, the upper plunger element is offset a predetermined distance from the lower plunger element by virtue of the lift stop member's engagement with the lower plunger element. The offset is adjustable based on the position of the lift stop member relative to the upper plunger element.