Vehicle Starter Base Plate Plastic Overmolded Bearing
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Solution Overview
Problem
The existing starter configurations for motor vehicle thermal engines face issues with flexibility and stress on bearings due to angle changes in the drive shaft, leading to reduced wear life and increased internal stresses.
Innovation Solution
A starter configuration that integrates a metal base plate with a plastic overmolded bearing, where a plastic layer between the metal plate and the bearing supports angle changes and reduces edge pressure, combined with damping pads and a shoulder on the metal plate to minimize stress, and a front bearing with helical splines to manage launcher position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal plate with a press-fitted bushing is used to support the drive shaft, then the drive shaft is rigidly supported, but the bushing experiences high stress and edge overpressures due to drive shaft bending angles
Solution Approach 1:
The base plate combines a metal plate with a plastic portion overmolded on it, creating a composite structure. The metal plate provides rigid support for the drive shaft, while the plastic portion absorbs bending angles and reduces edge overpressures on the bushing, thereby extending bushing wear life without sacrificing support rigidity.
Solution Approach 2:
The invention changes the material parameters of the base plate by introducing a plastic component with specific mechanical properties (flexibility, damping characteristics) that complement the metal plate's rigidity. This allows the system to accommodate drive shaft bending angles while maintaining adequate support.
2Stability of the object's composition
If the drive shaft is made rigid to support the launcher, then structural stability is improved, but internal stresses increase due to overhang and launcher activation
Solution Approach 1:
The base plate's axial length is optimized to reduce the drive shaft overhang, thereby minimizing bending moments and internal stresses during launcher activation. The plastic portion's damping characteristics also help reduce stress peaks.
Solution Approach 2:
The plastic portion acts as a cushioning element that absorbs and dampens shocks and vibrations occurring during launcher activation, protecting the rigid metal plate and drive shaft from high internal stresses.
3Stability of the object's composition
If the crown is securely mounted in the yoke, then radial positioning is improved, but shock loads are transmitted to the structure
Solution Approach 1:
Shock-absorbing pads are positioned between the crown and the yoke to cushion shock loads before they are transmitted to the structure. This maintains radial positioning while protecting against impact forces.
Solution Approach 2:
The crown is designed with specific geometric parameters (tooth profile, mounting position) that optimize the distribution of radial forces while minimizing shock transmission to the yoke structure.
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
This configuration enhances the wear life and fatigue resistance of the system by distributing pressure and reducing internal stresses, particularly in configurations with significant overhang and 'stop on groove' launcher setups.
Implementation Method 1
The plastic layer between the metal of the pad and the bearing thus makes it possible to support the angle taken by the bearing generated by the bending of the drive shaft in order to limit edge overpressures.
Implementation Method 2
a plastic portion overmolded on the pad and the bearing to make them integral with each other
Data Source
Figure 1
Figure 2a~2b
Figure 2c~3
AI summary
The invention relates mainly to a starter for a motor vehicle heat engine, comprising: an electric motor comprising a yoke and a rotor mounted on a shaft, a drive shaft capable of being rotated by said rotor, and an epicyclic reduction gear mounted between said rotor shaft and said drive shaft, characterised in that said starter also includes a base plate (106) supporting said toothed ring gear, said base plate (106) being rigidly connected to said yoke of said electric motor and comprising: a metal plate (107), a bushing (108) mounted on said drive shaft in order to guide the rotation of said drive shaft, and a plastic portion (109) overmoulded on said plate (107) and said bushing (108) in order to secure them to one another, said plastic portion (109) comprising a layer of plastic (112) between an outer periphery of said bushing (108) and an inner periphery of said metal plate (107).