Starter Motor Pinion Assembly Axial Separation Prevention
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Solution Overview
Problem
The direct contact between the connection shell and the drive collar and output gear in starter motors leads to heat and wear, causing axial separation and rapid failure due to relative rotation, resulting in the output gear remaining engaged with the flywheel after engine startup.
Innovation Solution
A pinion gear assembly design that includes a drive collar with a tubular engaging part and an annular plate, an elastic member sandwiched between the drive collar and output gear, and a connection shell with clamping parts that prevent direct contact between the connection shell and the drive collar or output gear, allowing relative rotational movement while restricting axial separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the connection shell directly contacts the drive collar and output gear, then the structure is simple and easy to manufacture, but heat and wear occur due to relative rotation causing rubbing, leading to damage and axial separation
Solution Approach 1:
The patent introduces an intermediate structure (connection shell with restricted contact surfaces) between the drive collar/output gear and the external environment. The connection shell is designed with specific geometric features that limit contact to non-rotating surfaces, thereby mediating the interaction to eliminate harmful friction while maintaining structural integrity and reliability
Solution Approach 2:
The connection shell is segmented into distinct functional zones: a first clamping part for axial positioning and a second clamping part for radial constraint. This segmentation allows each part to perform its specific function without causing harmful relative rotation, thereby reducing wear while maintaining manufacturing simplicity
2Reliability
If the connection shell allows relative rotational movement between drive collar and output gear, then wear is reduced, but axial separation may occur compromising the engagement
Solution Approach 1:
The connection shell employs a dynamic constraint mechanism where the first clamping part allows controlled relative rotation between the drive collar and output gear through a designed interface, while the second clamping part dynamically maintains axial positioning. This dynamic design permits necessary motion while preventing harmful separation
Solution Approach 2:
The patent separates the constraint functions into different spatial dimensions: the first clamping part operates in the rotational dimension allowing relative movement, while the second clamping part operates in the axial dimension preventing separation. This dimensional separation resolves the contradiction by enabling rotation freedom while maintaining axial stability
3Object-affected harmful factors
If the elastic member is sandwiched between drive collar and output gear, then shock is reduced during engagement, but the connection shell must prevent axial separation of all three components
Solution Approach 1:
The patent merges the functions of the connection shell with the elastic member by integrating the clamping parts directly onto the elastic member structure. The first clamping part is formed as an extension of the elastic member, combining the shock-absorbing function with the axial positioning function in a single integrated component, thereby reducing overall assembly complexity
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 design prevents axial separation and wear on the connection shell, ensuring the output gear disengages from the flywheel after engine startup, thereby extending the starter motor's lifespan by avoiding direct contact and reducing friction-related damage.
Implementation Method 1
an elastic member sandwiched between the drive collar and the pinion. The drive collar moves along the output shaft when the output shaft begins to rotate, which causes the pinion to move along the output shaft to engage the flywheel. The elastic member reduces the shock between the drive collar and the pinion as the pinion engages the flywheel.
Data Source
AI summary
A starter motor for an internal combustion engine has an electric motor, a shaft driven by the motor, and a pinion assembly arranged to engage a flywheel of the engine. The pinion assembly has a drive collar mounted to a helical spline of the shaft, an output gear and an elastic member disposed between the drive collar and the output gear. A connection shell prevents axial separation between the drive collar and the output gear. The elastic member prevents direct contact between the connection shell and at least one and possibly both of the drive collar and the output gear.