Automobile Starter Front Bearing Force Distribution
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Solution Overview
Problem
Motor vehicle starters equipped with thermal engine stop-start systems experience premature wear due to increased usage, particularly in the armature shaft bearings, leading to reduced lifespan as they are subjected to higher stress and strain.
Innovation Solution
A motor vehicle starter design that incorporates a second front bearing with a larger diameter than the armature shaft, providing additional support and guidance, along with a flange and shoulder face to limit axial movement and distribute forces, while also forming a watertight partition and allowing for angular indexing to prevent pinching of planet gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guide ring is used to support the front end section of the armature shaft, then the starter can operate, but the guide ring wears prematurely due to high stress relative to its small diameter
Solution Approach 1:
The bearing support function is divided into two separate bearings: a rear bearing supporting the rear end of the armature shaft and a front bearing supporting the front end section. This segmentation allows each bearing to be optimized for its specific location and load conditions, with the front bearing having a larger diameter to handle the high stresses while the rear bearing handles the remaining loads.
Solution Approach 2:
The front bearing is designed with a larger diameter specifically at the location where high stresses occur during stop-start operation. This local quality enhancement concentrates the load-bearing capacity where it is most needed, rather than uniformly increasing the diameter of the entire armature shaft or guide ring.
2Strength
If the diameter of the front end guide section of the armature shaft is increased to improve bearing capacity, then the load bearing capacity increases, but the diameter is constrained by the output shaft bore dimensions
Solution Approach 1:
The front bearing is extracted as a separate component from the armature shaft structure. Instead of increasing the shaft diameter, the front bearing is positioned in the output shaft bore to provide the necessary support. This allows the armature shaft to maintain its original small diameter while the front bearing handles the high stresses independently.
Solution Approach 2:
The front bearing acts as an intermediary element between the armature shaft and the output shaft. It transfers the loads from the small-diameter armature shaft to the larger-diameter bearing structure, which is supported by the output shaft bore. This mediator allows the small shaft to benefit from the load-bearing capacity of the larger bearing without requiring the shaft itself to be larger.
3Reliability
If a second front bearing is added to support the front end of the armature shaft, then the load distribution improves and wear is reduced, but the device complexity increases
Solution Approach 1:
The front bearing performs multiple functions simultaneously: it supports the front end of the armature shaft, forms a watertight partition between the armature windings and the reducer, and provides angular indexing of the cylinder head with respect to the casing. By consolidating these functions into a single component, the overall device complexity is minimized while still achieving the reliability benefits of additional bearing support.
Solution Approach 2:
The front bearing combines several functional elements into one component: the bearing itself, the watertight partition seal, and the angular indexing mechanism. This merging reduces the total number of separate parts compared to having separate components for each function, thereby reducing assembly complexity while maintaining the load-bearing benefits.
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
The invention relates to an automobile starter (10) comprising: - an electric engine (16) comprising a rear armature shaft (18) supporting armature windings (22) and rotatably guided by a rear first bearing (32) and a front second bearing (68); - a front coaxial output shaft (20) supporting a starter drive assembly (64) and rotated by the armature shaft (18); and - an epicyclic gear train speed reducer (44) axially inserted between the rear armature shaft (18) and the front output shaft (20) for the coupling thereof, characterized in that the front second bearing (68) is axially inserted between the armature windings (22) and the speed reducer (44). (Refer to FIG. 1).