Variable-Width Rocker Arm Reduces Inertia
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing rocker arms for variable-stroke valve trains in internal combustion engines have a high mass moment of inertia due to their design, leading to unfavorable speed limitations and potential loss of contact between the cam contact surface and the cam, which cannot be adequately addressed by reducing mass through lightweight materials or sheet metal construction without significant additional costs.
Innovation Solution
The rocker arm features a variable-width stroke transmission surface along the direction of oscillation, with a maximum width greater than or equal to the maximum width of the idle stroke area, and a barrel-like bulging shape to reduce mass moment of inertia while maintaining permissible contact pressures, and is constructed from a one-piece sheet metal lever with parallel side walls to minimize material usage and mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rocker arm is designed with conventional constant-width stroke transmission surface, then the contact pressure is maintained, but the mass moment of inertia is high leading to speed limitations
Solution Approach 1:
The stroke transmission surface is designed with variable width along the direction of oscillation, creating different local geometries in different zones. The width is reduced in regions where full width is not needed for contact pressure maintenance, thereby reducing mass moment of inertia while preserving contact pressure where critical.
Solution Approach 2:
The geometric parameter of the stroke transmission surface (width) is changed along the direction of oscillation. By varying the width parameter spatially, the patent achieves reduction in mass moment of inertia while maintaining contact pressure within permissible limits through optimized distribution.
2Speed
If lightweight materials are used to reduce mass moment of inertia, then the speed limitation is improved, but the production costs increase significantly
Solution Approach 1:
Instead of changing material parameters, the patent changes the geometric parameters of the existing material. The variable width design of the stroke transmission surface reduces mass moment of inertia using conventional materials, avoiding the need for expensive lightweight materials while achieving the same dynamic performance improvement.
3Weight of moving object
If sheet metal construction is used to reduce mass, then the mass moment of inertia is reduced, but the mass reduction is limited by forming process constraints
Solution Approach 1:
The sheet metal rocker arm features localized geometric variation in the stroke transmission surface width. This local quality change allows mass reduction in specific regions without requiring complex overall restructuring, making the design compatible with conventional sheet metal forming processes while achieving reduced mass moment of inertia.
4Speed
If the stroke transmission surface width is reduced to lower mass moment of inertia, then the speed performance improves, but the contact pressure may exceed permissible limits
Solution Approach 1:
The stroke transmission surface is designed with spatially varying width, providing full width where contact pressure requirements are critical and reduced width where mass reduction is prioritized. This local differentiation maintains contact pressure within permissible limits while achieving overall mass moment of inertia reduction.
Solution Approach 2:
The width parameter of the stroke transmission surface is optimized along the direction of oscillation to balance contact pressure requirements and mass moment of inertia. By changing the width parameter strategically, the patent maintains acceptable contact pressure while achieving speed performance improvement.
Data Source
Figure 1~4
AI summary
The arm has supporting, tappet starting and stroke transmission surfaces on end section, center section and another end section, respectively. An outer shell surface of a roller supported in a valve lever is subjected with contact force changeable in a swinging direction. The transmission surface (16) has a width, which is changeable along the direction, during contact pressing between the transmission and shell surfaces. The maximum width of a stroke area (19) is formed larger or equal to the maximum width of an idle-stroke area (18) and larger than the minimum width of the idle-stroke area.