Hydraulic Lash Adjuster with Mechanical Compensation
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Solution Overview
Problem
Hydraulic lash adjusters (HLAs) often permit unintended valve reopening, especially at low temperatures or during engine start-up, due to their inability to effectively compensate for tolerance variations and thermal deformations, and prior attempts to combine mechanical and hydraulic lash features have resulted in complex manufacturing and installation issues.
Innovation Solution
A lash adjuster comprising a hydraulic lash assembly, a mechanical lash assembly, and a check assembly, where the mechanical lash assembly includes a shim, a spacer, and a spring to form a gap between the top and leak-down plungers, allowing for adjustable lash compensation and preventing valve reopening through a combination of mechanical and hydraulic mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a hydraulic lash adjuster is used to maintain valve clearance, then thermal deformation compensation is improved, but valve reopening occurs at low temperatures
Solution Approach 1:
The patent combines a mechanical lash adjuster and a hydraulic lash adjuster into a single integrated device. The mechanical portion handles low-temperature conditions where hydraulic fluid is viscous, while the hydraulic portion handles normal operating temperatures, preventing valve reopening across the full temperature range.
Solution Approach 2:
The patent creates a dynamic system where the mechanical and hydraulic components work together with different characteristics depending on operating conditions. The mechanical spring provides immediate response at low temperatures, while the hydraulic system provides precise compensation at normal temperatures.
2Reliability
If a mechanical lash feature is combined within a hydraulic lash adjuster, then valve clearance maintenance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the mechanical lash adjuster and hydraulic lash adjuster into a single integrated device with shared components such as the body, plunger, and check valve, reducing the number of separate parts while maintaining the benefits of both systems.
Solution Approach 2:
The integrated lash adjuster performs multiple functions: mechanical lash adjustment for low-temperature operation, hydraulic lash adjustment for normal-temperature operation, and valve clearance maintenance across all conditions, all within a single device structure.
3Reliability
If a mechanical lash feature is combined within a hydraulic lash adjuster, then valve clearance maintenance is improved, but installation adjustability is reduced
Solution Approach 1:
The integrated system provides dynamic adaptability where the mechanical and hydraulic components work together to automatically adjust to different valve clearance requirements, eliminating the need for manual selection and fitting during installation.
Solution Approach 2:
The combined mechanical-hydraulic lash adjuster performs self-adjustment during installation and operation, automatically compensating for tolerance variations and thermal deformations without requiring manual intervention or selection of different parts.
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 solution improves assembly efficiency, reduces scrap, and enhances part re-use by enabling easy select-fitting, effectively preventing valve reopening across varying temperature conditions by leveraging both mechanical and hydraulic lash adjustments.
Implementation Method 1
a spring pressing against the spacer and the shim to form a gap between the top plunger and the leak down plunger
Implementation Method 2
A hydraulic lash adjuster (HLA) is a device that can be used for maintaining a specified valve clearance in an internal combustion engine. The HLA can compensate some tolerance variation and thermal deformation
Implementation Method 3
The hydraulic lash assembly can comprise a body, a top plunger, a leak down plunger, and the check assembly between the body and the leak down plunger
Data Source
AI summary
A lash adjuster can include a hydraulic lash assembly, a mechanical lash assembly, and a check assembly. The hydraulic lash assembly can include a body, a top plunger, a leak down plunger, and the check assembly between the body and the leak down plunger. The mechanical lash assembly can be between the top plunger and the leak down plunger. The mechanical lash assembly can include a shim abutting the top plunger, a spacer, and a spring pressing against the spacer and the shim to form a gap between the top plunger and the leak down plunger. The lash adjuster can include the spring pressing directly against the spacer and directly or indirectly against the shim.