Starter Ring Gear Damping Pads With Rounded Corners for Durability
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Solution Overview
Problem
The existing starters for heat engines in motor vehicles experience rapid tearing of damping studs due to high local pressures, particularly in 'stop and start' type starters that undergo a high number of operating cycles, leading to reduced durability.
Innovation Solution
The design includes damping studs with an axial length less than the tabs, positioned set back to avoid contact with projecting edges, and a square shape with rounded corners to prevent contact with lugs, along with a radial play in the ring gear for self-centering and a plastic layer to support the bearing, reducing stress and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If damping pads with conventional shape are used, then torque limitation is achieved, but rapid tearing of the stud occurs due to strong local pressures
Solution Approach 1:
The damping pad is designed with rounded corners instead of sharp edges. The corner radius is specifically optimized to distribute contact pressure more evenly across the stud surface, preventing stress concentration that leads to tearing. This curvature modification maintains the torque limitation function while significantly improving stud durability by eliminating the stress concentration points caused by sharp edges.
Solution Approach 2:
The damping pad features non-uniform geometry with specifically designed corner radii that differ from the central region. This local quality variation allows the pad to provide enhanced pressure distribution at the corners where stress concentration occurs, while maintaining effective torque limitation in the central area. The localized geometric modification targets the specific problem area without compromising overall functionality.
2Ease of operation
If the launcher is positioned in active position, then engagement with ring gear is achieved, but significant internal stresses occur due to overhang of the drive shaft
Solution Approach 1:
The drive shaft is designed with a pre-bent configuration that anticipates the loading conditions during operation. The bend is pre-formed to position the drive shaft optimally during engagement, reducing the dynamic stress peaks that would otherwise occur. This preliminary geometric adjustment allows the launcher to engage the ring gear effectively while minimizing the internal stresses and fatigue risks associated with shaft overhang.
3Manufacturing precision
If the ring gear is mounted without radial play, then positioning precision is improved, but noise increases due to lack of self-centering capability
Solution Approach 1:
The ring gear is designed with controlled radial play that enables self-centering through the action of the satellites during operation. The clearance is sufficient to allow the ring gear to automatically adjust its position and center itself under operational forces, eliminating misalignment-induced noise. This self-service mechanism maintains positioning precision while providing the noise-reducing self-centering capability.
Data Source
Figure 1
Figure 2a~2b
Figure 2c~3a
AI summary
The invention relates mainly to a heat engine starter for a motor vehicle, comprising: a planetary-type speed reduction gear mounted between the rotor shaft and the drive shaft; and a base plate (106) having a plastic-material portion comprising abutment portions (120), wherein the ring gear (102) has tabs (121) at its outer periphery and damping pads (122) are mounted between said tabs (121) and said abutment portions (120), characterised in that each damping pad (122) has at least one rounded corner (145) on the side of a projecting edge (146) of a corresponding tab (121) of said ring gear (102), which rounded corner is rounded along a radius of curvature located in a plane containing all the corners of said damping pad (122) such that a space is provided between said rounded corner (145) and a right-angled corner defined by the intersection of planes passing through side faces joined by this rounded corner (145).