Graphite Cover-Layer Commutator for Starter Wear Resistance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional starters for idling stop systems face challenges with brush wear resistance and commutator durability due to thin hard cover layers, which are costly and have low productivity, leading to reduced service life and increased maintenance costs.

Innovation Solution

A starter with a commutator coated in a graphite cover-layer containing graphite as the main component and metal sulfide solid lubricants, which enhances hardness and lubrication properties, forming a hard carbide compound through reaction with heat and sparks, eliminating the need for costly sputtering or ion plating methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a thin hard cover layer (1-2 μm) of Ti or Ta nitride/carbide is formed on the commutator surface using sputtering or ion plating, then the surface hardness is improved, but the durability and service life of the commutator decreases

Engineering Contradiction:

Improvesurface hardnessVSAvoidcommutator service life

Core Design Contradiction:

StrengthVSDuration of action of stationary object

Solution Approach 1:

The patent changes the thickness parameter of the hard cover layer from the conventional thin layer (1-2 μm) to a thick layer (5-20 μm). This parameter change resolves the contradiction by providing sufficient material depth to maintain durability and service life while still achieving the desired surface hardness and wear resistance properties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material structure consisting of a thick hard cover layer (Ti or Ta nitride/carbide) on the commutator surface. The thick layer composition provides both the hardness needed for wear resistance and sufficient thickness for long-term durability, resolving the contradiction between surface strength and service life.

Inventive Principle:

Principle #40Composite materials

2Strength

If sputtering or ion plating methods are used to form a hard cover layer on the commutator surface, then the surface hardness is improved, but the productivity decreases and material cost increases

Engineering Contradiction:

Improvesurface hardnessVSAvoidmanufacturing efficiency

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The patent replaces expensive sputtering and ion plating processes with a more economical coating method that uses readily available coating materials and simpler application processes. This substitution maintains the required surface hardness while significantly improving productivity and reducing material costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the manufacturing process parameters by adopting a thick layer coating approach (5-20 μm) that can be achieved through more productive and cost-effective methods compared to thin layer deposition techniques, thereby resolving the contradiction between surface hardness and manufacturing efficiency.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a thin hard cover layer is formed on the commutator, then the abrasion resistance is improved, but the cost increases and productivity decreases

Engineering Contradiction:

Improveabrasion resistanceVSAvoidmanufacturing cost and complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the cover layer thickness parameter to 5-20 μm, which provides sufficient abrasion resistance while being compatible with simpler, more cost-effective manufacturing processes. This parameter change resolves the contradiction by achieving the required reliability without the high costs and low productivity associated with thin layer deposition methods.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs cost-effective coating materials and simplified coating processes to achieve the required abrasion resistance, replacing expensive sputtering/ion plating methods with more economical alternatives that maintain performance while improving ease of manufacture.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 graphite cover-layer significantly increases the commutator's wear resistance and service life, maintaining shape precision and reducing spark-induced deterioration, while being cost-effective and maintaining high productivity.

Implementation Method 1

The graphite cover-layer contains a hard compound that has a Vickers hardness of more than 10 Gpa

Methodology Applied

Scientific EffectHard compound reinforcement:

Implementation Method 2

a metal sulfide solid lubricant

Methodology Applied

Scientific EffectSolid lubrication: Lubrication

Implementation Method 3

forming a hard carbide compound through reaction with heat and sparks

Methodology Applied

Scientific EffectThermal chemical reaction: Exothermic Reaction

Data Source

PatentUS10855149B2Starter, and formation of graphite cover layer for commutator surface

Publication Date: 2020.12.01 DENSO CORP

AI summary

A starter includes a motor configured with a direct current motor. The direct current motor has a brush and a commutator. The brush is a sintered material formed of graphite and a copper powder. The commutator is formed of either copper or a copper alloy that has a copper content of 99% or more. A surface of is a sliding portion of the commutator which has sliding movement with the brush is provided with a graphite cover-layer that contains graphite as a main component. The graphite cover-layer contains a hard compound which has a Vickers hardness higher than 10 GPa and a metal sulfide solid lubricant.