Track Bearing Bushing Hardening Layout for Sprocket Wear
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Solution Overview
Problem
Conventional bearing bushings for tracks in work machines, such as hydraulic excavators and bulldozers, do not adequately extend the life of the track due to wear caused by sliding contact with the sprocket wheel, despite the use of rotatable bushings.
Innovation Solution
A bearing bushing made of steel with an annular shape, featuring inner and outer peripheral surface-hardened layers and a first end face-hardened layer, each with a hardness of 63 HRC or more, and an unhardened region, is designed to provide enhanced wear resistance by quench-hardening and tempering specific regions to achieve a thickness of 3 mm or more from the first end face.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotatable bushing is disposed in the track link to extend track life, then wear resistance is improved, but the track life is not extended sufficiently due to wear from sliding contact with the sprocket wheel
Solution Approach 1:
The bushing is designed with differentiated hardness zones: a hardened layer (63 HRC or more) at the outer peripheral surface and first end face that contact the sprocket wheel, and a softer inner peripheral surface. This local quality differentiation allows the contact surfaces to resist wear from the sprocket wheel while the inner surface maintains rotational flexibility relative to the track pin, thereby sufficiently extending track life
2Reliability
If the entire bushing is hardened to improve wear resistance, then surface hardness is increased, but toughness and impact resistance deteriorate
Solution Approach 1:
Instead of hardening the entire bushing, only the outer peripheral surface and first end face are hardened to 63 HRC or more, while the inner peripheral surface remains softer. This localized hardening provides wear resistance at contact surfaces while preserving toughness in the bulk material and inner regions, preventing brittleness and maintaining impact resistance
3Reliability
If the hardened layer thickness is increased to improve wear resistance, then wear protection is enhanced, but manufacturing complexity and cost increase
Solution Approach 1:
The invention specifies a minimum hardened layer thickness of 3 mm at the contact surfaces (outer peripheral surface and first end face) to ensure adequate wear protection. This parameter-based approach provides a clear manufacturing target that balances wear resistance with manufacturing feasibility, avoiding excessive complexity while ensuring sufficient protection against sprocket wheel wear
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 steel bearing bushing significantly extends the life of the track by improving wear resistance, preventing wear grooves and lubricant leakage, thus reducing the need for frequent replacements.
Implementation Method 1
the heated region that is heated to a temperature of not lower than the A1 transformation point of the steel is formed
Implementation Method 2
a part of the material ring is quench-hardened by cooling the heated region from the temperature of not lower than the A1 transformation point to a temperature range of not higher than the Ms point
Implementation Method 3
the partially quench-hardened material ring is heated to a temperature of lower than the A1 transformation point, to temper the material ring
Data Source
AI summary
A bearing bushing for a track has an annular shape including an inner peripheral surface, an outer peripheral surface, a first end face, and a second end face located axially opposite the first end face. The bearing bushing for a track includes an inner peripheral surface-side hardened layer formed to include the inner peripheral surface, an outer peripheral surface-side hardened layer formed to include the outer peripheral surface, a first end face-side hardened layer formed to include the first end face and having a region with a hardness of 63 HRC or more that has a thickness of 3 mm or more from the first end face, and an unhardened region lower in hardness than the inner peripheral surface-side hardened layer, the outer peripheral surface-side hardened layer, and the first end face-side hardened layer, and including at least the second end face. The bearing bushing is made of steel.