Engine Valve Gear Slant Portion Prevents Reverse Rotation Damage
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Solution Overview
Problem
Existing valve gear designs are prone to unexpected cam element portion switching and operational member breakdown due to reverse engine rotation, which can cause improper valve operation and damage.
Innovation Solution
Incorporating a camshaft with a cam element portion featuring a slant portion on the rotary-delay side of the end-face cam, which allows the operational member to slide and retreat to a safe position when the engine rotates reversely, preventing unexpected switching and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the end-face cam has a descent portion that decreases projection amount gradually, then the operational member can smoothly return to retreat position during normal rotation, but the operational member contacts the descent portion during reverse rotation causing unexpected cam element portion switching
Solution Approach 1:
The end-face cam surface is segmented into distinct functional zones: a lift portion for normal operation, a slant portion positioned on the rotary-delay side that prevents reverse rotation engagement, and a descent portion for smooth return. This segmentation allows each zone to perform its specific function independently, preventing unintended cam switching during reverse rotation while maintaining smooth operational member return during normal operation.
2Productivity
If the end-face cam has a step portion that decreases projection amount suddenly, then the operational member can quickly return to retreat position, but the operational member hits against the step portion during reverse rotation causing breakdown
Solution Approach 1:
The slant portion is positioned on the rotary-delay side of the maximum-lift portion to preemptively prevent reverse rotation engagement. During reverse rotation, the operational member encounters the slant portion first, which guides it to slide and retreat before it can reach the step portion. This preliminary protective action eliminates the risk of operational member breakdown while maintaining the quick return capability provided by the step portion.
3Reliability
If the slant portion is positioned on the rotary-delay side from the maximum-lift portion, then the operational member slides and retreats during reverse rotation preventing damage, but the structure becomes more complex
Solution Approach 1:
The slant portion is merged with the end-face cam structure, forming an integrated protective feature rather than a separate component. The slant portion shares the same structural base as the lift and descent portions, combining multiple functions (normal operation, reverse rotation protection, and smooth return) into a single unified cam element. This merging approach provides reliable protection while minimizing structural complexity.
Data Source
AI summary
A cam element portion comprises a slant portion (reverse-rotation return slope portion), which is positioned on a rotary-delay side from a maximum-lift portion (lift ending point) of an end-face cam and slants inward toward the rotary-delay side from an outer peripheral face of the end-face cam. Accordingly, in a valve gear of an engine in which cams operative to control opening/closing of a valve are switchable, it can be properly prevented that the cam element portion is switched unexpectedly and improperly or an operational member breaks down which are possibly caused by an engine's reverse rotation.