Cam Follower with Variable Curvature for Valve Drive
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing rocker arm designs for internal combustion engines with poppet lift valves experience abrupt changes in contact conditions and undesired vibrations due to constant curvature profiles, leading to high contact pressures and vibration excitations, especially with component tolerances and deactivated valve lifts.
Innovation Solution
A rocker arm with a contact surface featuring a continuously variable curvature, specifically a logarithmic profile, which eliminates the 'jerk' in profile change and maintains gentle kinematic transitions, reducing vibration excitations and contact pressures by adapting to both activated and deactivated valve lifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a contact surface with constant curvature areas is used, then the manufacturing is simplified, but abrupt profile changes cause vibration excitations and high contact pressures
Solution Approach 1:
The patent applies parameter changes by transitioning from constant curvature profiles to continuously variable curvature profiles. The contact surface is designed with a curvature function κ(s) that varies continuously along the profile, eliminating abrupt changes while maintaining manufacturability through defined mathematical relationships between curvature and position parameters.
Solution Approach 2:
The patent utilizes curvature principles by designing the contact surface with continuously variable curvature instead of constant curvature segments. The profile is constructed using circular arcs with carefully selected radii that ensure continuous curvature transition, reducing vibration excitations while maintaining the spherical contact geometry needed for proper valve train operation.
2Ease of manufacture
If a contact surface with constant curvature areas is used, then the manufacturing is simplified, but the profile point deviation from actual contact point causes high contact pressures
Solution Approach 1:
The patent changes the curvature parameter from constant to continuously variable along the contact surface profile. This is achieved by defining the profile through a curvature function κ(s) that varies smoothly with position, ensuring that the profile point coincides with the actual contact point throughout the valve lift cycle, thereby distributing contact pressures more evenly.
Solution Approach 2:
The patent introduces dynamic adaptation of the contact surface geometry to match the actual contact conditions during valve operation. The continuously variable curvature profile allows the contact point to migrate smoothly along the profile, maintaining optimal contact conditions regardless of component tolerances, thus preventing localized high contact pressures.
3Object-affected harmful factors
If a contact surface with continuously variable curvature is used, then vibration excitations are reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the continuously variable curvature profile into discrete circular arc segments. Each segment has a constant curvature that transitions smoothly to adjacent segments, combining the simplicity of constant curvature manufacturing with the benefits of continuous curvature variation. This segmented approach maintains geometric complexity while enabling practical manufacturing through standardized arc fabrication.
4Adaptability or versatility
If the profile point does not correspond to the actual contact point, then component tolerances are accommodated, but abrupt profile changes cause vibration excitations
Solution Approach 1:
The patent changes the curvature parameter from constant to continuously variable, allowing the profile to adapt smoothly to variations in the actual contact point position caused by component tolerances. The continuous curvature function ensures that regardless of where the actual contact occurs along the profile, the transition remains smooth without abrupt changes, thereby accommodating tolerances while preventing vibration excitations.
Data Source
Figure 1~3
AI summary
A cam follower (2) is proposed for a valve drive (1) of an internal combustion engine with a lifting disc valve (9), to the shaft end face (8) of which at least two different valve strokes can be applied via a contact face (7) of the cam follower (2). The contact face (7) has a profile which is curved convexly in the longitudinal direction of the cam follower (2) and has at least one profile point (P0) from which two contact areas (K1, Kx), having profiles which are different from one another and are respectively adapted to one of the valve strokes, proceed. In this context, at least one of the contact areas (K1, Kx) is intended to have a profile with a continuously changing curvature, wherein the curvatures of the contact areas (K1, Kx) at the profile point (P0) are essentially of the same size.