Friction Element Salt Bath Hardening for Clutch Thermal Stability

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Solution Overview

Problem

Counter-plates in multi-plate clutches, especially those made of aluminum alloys, face overheating issues due to inadequate lubrication and cooling, leading to reduced strength and efficiency, as they lack grooves for oil distribution and cooling in wet-running applications.

Innovation Solution

A friction element with a metallic base body is salt bath-hardened, creating crater-shaped areas with discrete oxides that act as an oil reservoir, enhancing lubrication and adhesive connection of oil additives, and reducing wear by forming a structured surface that stores lubricating oil and improves tribological properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If counter-plates are made of aluminum alloys to reduce weight, then weight is reduced, but thermal stability and strength are reduced due to overheating

Engineering Contradiction:
Improveweight of counter-plateVSAvoidthermal stability
Core Design Contradiction:
Weight of moving objectVSTemperature

Solution Approach 1:

The salt bath hardening process creates a porous oxide layer on the aluminum alloy surface with crater-shaped areas that serve as micro-reservoirs for lubricating oil. This porous structure enables the lightweight aluminum alloy to retain lubrication and resist overheating, resolving the contradiction between weight reduction and thermal stability.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The invention changes the surface parameters of the aluminum alloy through salt bath hardening, creating a hardened layer with specific oxide composition and crater structure. This surface modification allows the material to maintain its lightweight properties while gaining improved thermal stability and wear resistance.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If grooves are added to counter-plates for oil distribution, then lubrication is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:
Improvelubrication efficiencyVSAvoidstructural complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

Instead of adding grooves across the entire surface, the invention creates localized crater-shaped oxide areas through salt bath hardening. These localized porous regions are sufficient to retain and distribute lubricating oil, improving lubrication without adding overall structural complexity.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The salt bath hardening process itself creates the oil-retaining structure as a byproduct of the hardening treatment. The oxide layer formation naturally produces crater-shaped areas that serve as oil reservoirs, eliminating the need for separate groove machining operations.

Inventive Principle:
Principle #25Self-service

3Strength

If salt bath hardening is applied to create oxide layer, then wear resistance is improved, but surface roughness increases requiring additional processing

Engineering Contradiction:
Improvewear resistanceVSAvoidsurface finish
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The invention converts the harmful surface roughness created by salt bath hardening into a beneficial porous oxide structure. The crater-shaped areas that would normally be considered defects are actually the desired oil-retaining features, eliminating the need for corrective polishing or washing operations.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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 provides improved thermal stability, reduced wear, and enhanced lubrication, leading to better frictional performance, noise reduction, and cost-effective production by eliminating the need for subsequent processing steps like washing and polishing.

Implementation Method 1

the salt bath-hardened surface being at least partially oxidized, with a number of different Oxides being formed on the surface in discrete, at least partially crater-shaped areas

Methodology Applied
Scientific EffectOxidation: Oxidation

Implementation Method 2

the crater-shaped areas act as an oil reservoir, enhancing lubrication and adhesive connection of oil additives, and reducing wear by forming a structured surface that stores lubricating oil

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Data Source

PatentEP2460896B1Method for producing a friction element
Publication Date: 2018.01.24 MIBA FRICTEC
  • EP2460896B1 patent drawingFigure 1~2
  • EP2460896B1 patent drawingFigure 3~4
  • EP2460896B1 patent drawingFigure 5~6

AI summary

Manufacture of friction element (2) involves providing a metallic base component (10), and curing the base component in portion(s) of its surfaces (11,12) in a salt bath.