Helical-Spline Clutch Roller Nitriding for Engine Starter Durability
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Solution Overview
Problem
The engine starter's clutch roller experiences deformation and failure due to excessive torque and frictional heat during abnormal engine rotation, leading to incomplete engagement and failed engine starts.
Innovation Solution
A compound film is formed on the clutch roller and contacting surfaces of the clutch inner and outer using nitriding or carbonitriding, enhancing durability and reducing friction, while the clutch roller is made of bearing steel with a surface extending axially to prevent local contact and ensure uniform force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch roller is made of conventional material without surface treatment, then the manufacturing cost is low, but the durability and resistance to frictional heat are insufficient under excessive torque
Solution Approach 1:
The clutch roller employs a composite structure combining bearing steel substrate with nitrided surface layer. The bearing steel provides mechanical strength and toughness, while the nitrided surface layer delivers high hardness and friction resistance. This composite material approach resolves the contradiction by achieving enhanced durability without fundamentally changing the manufacturing process, only adding a surface treatment step.
Solution Approach 2:
The invention applies nitriding treatment to change the physical and chemical parameters of the clutch roller surface. The nitriding process introduces nitrogen into the surface layer, transforming it into a hard, wear-resistant compound layer while maintaining the ductile core material properties. This parameter change enables the clutch roller to withstand excessive torque and frictional heat that would otherwise cause deformation and failure.
2Force
If the clutch roller surface area for contact is reduced, then the contact pressure increases improving engagement, but the frictional heat and stress concentration increase causing deformation
Solution Approach 1:
The clutch roller design applies local quality by extending the contact surface area specifically at the engagement region with the clutch inner. This extended contact surface distributes the engagement force over a larger area, reducing contact pressure and frictional heat concentration at any single point. The nitrided surface layer is applied uniformly to ensure consistent local properties across the entire contact surface.
3Stability of the object's composition
If the clutch roller contact surface is extended axially, then the force distribution becomes uniform preventing local deformation, but the manufacturing precision requirements increase
Solution Approach 1:
The axial extension of the clutch roller contact surface is achieved through controlled parameter changes in the rolling stock dimensions. By increasing the axial length of the roller within standard manufacturing tolerances, the design ensures uniform force distribution along the contact surface. The nitriding treatment further stabilizes the surface properties, reducing sensitivity to minor geometric variations and maintaining consistent performance.
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
The solution stabilizes sliding contacts, improves abrasion and fatigue resistance, and extends clutch life by reducing friction and thermal stress, allowing for reliable engine starting even under excessive loads.
Implementation Method 1
A compound film is formed on a surface of the clutch roller or surfaces of the clutch outer and the clutch inner
Implementation Method 2
A compound film is formed on a surface of the clutch roller or surfaces of the clutch outer and the clutch inner
Implementation Method 3
Reference numeral 14 denotes a spring that urges the clutch roller 13 toward a side of a clutch outer wall
Implementation Method 4
A high temperature state then occurs due to a frictional heat caused by the slipping
Implementation Method 5
A high temperature state then occurs due to a frictional heat caused by the slipping
Data Source
AI summary
An engine starter includes a motor that comprises a drive shaft; and a unidirectional rotation clutch system that is helical-splined to the drive shaft. The clutch system includes a clutch inner; a clutch outer; a clutch roller that is interposed between the clutch outer and the clutch inner; and a spring that urges the clutch roller, wherein a compound film is formed on a surface of the clutch roller or surfaces of the clutch outer and the clutch inner.