Brake Disc Wear Indicator Recess for Tool-Free Wear Assessment

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Solution Overview

Problem

Conventional brake discs with high hardness coatings for friction surfaces are difficult to measure wear levels without specialized tools, making it impossible to determine when they need replacement, and they release harmful fine particles into the atmosphere.

Innovation Solution

A brake disc design with a wear indicator featuring a visible recess on the friction zones and friction-free zones, utilizing a two-layer coating with a hard outer layer and an intermediate layer, where the recess depth indicates wear levels visibly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a high hardness coating is applied to the friction surface of the brake disc, then the wear resistance is improved, but the measurability of wear level deteriorates

Engineering Contradiction:
Improvewear resistanceVSAvoidwear level measurability
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The brake disc friction surface is segmented into multiple friction zones separated by friction-free zones. The wear indicator recess is positioned in a friction-free zone, allowing it to remain visible and measurable even as the friction zones wear down. This segmentation enables the wear indicator to function independently from the wear-prone friction surfaces.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The wear indicator recess acts as an intermediary element between the friction zones and the measurement process. By placing the recess in a friction-free zone, it serves as a reference feature that does not wear away with the friction zones, enabling accurate wear assessment through visual or measurement tool inspection of the recess depth relative to the worn friction zones.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Duration of action of stationary object

If a high hardness coating is applied to the friction surface, then the service life is extended, but the ease of wear assessment deteriorates

Engineering Contradiction:
Improvebrake disc service lifeVSAvoidwear assessment simplicity
Core Design Contradiction:
Duration of action of stationary objectVSEase of operation

Solution Approach 1:

The brake disc is divided into friction zones that experience wear and friction-free zones that do not. The wear indicator recess is located in a friction-free zone, creating a permanent reference feature that allows easy visual assessment of wear by comparing the recess visibility against the worn friction zones, eliminating the need for complex measurement procedures.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The wear indicator utilizes visual appearance changes - specifically the visibility or partial visibility of the recess - to indicate wear level. As the friction zones wear away, the recess transitions from being completely visible to partially visible or invisible, providing an intuitive visual cue for wear assessment without requiring specialized tools or procedures.

Inventive Principle:
Principle #32Color changes

3Object-generated harmful factors

If the friction surface hardness is increased to reduce particle emissions, then the environmental harm is reduced, but the wear measurability deteriorates

Engineering Contradiction:
Improvefine particle emissionsVSAvoidwear level measurement
Core Design Contradiction:
Object-generated harmful factorsVSMeasurement precision

Solution Approach 1:

By segmenting the brake disc surface into friction zones and friction-free zones, the wear indicator recess in the friction-free zone serves as a stable reference feature. This allows wear measurement of the high-hardness friction zones without requiring the recess itself to be measurable with the same tools, as wear assessment is done by visual inspection of recess visibility rather than direct measurement.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The wear indicator recess serves as an intermediary reference feature that enables wear assessment of the high-hardness friction surface. Since the recess is located in a friction-free zone with different wear characteristics, it provides a stable reference that facilitates wear measurement of the friction zones through visual comparison rather than direct measurement of the worn surface.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Enables visual assessment of wear without tools, ensuring timely replacement and reducing particle emissions by providing a clear indication of wear state through a simple, rapid, and economical manufacturing process.

Implementation Method 1

the coating being obtained according to a very high speed laser material deposition technique called EHLA

Methodology Applied
Scientific EffectLaser material deposition: Laser Ablation

Implementation Method 2

at least one wear indicator comprising a recess visible to the naked eye and comprising a first portion extending over the friction zone and a second portion extending the first portion and extending over the friction-free zone

Methodology Applied
Scientific EffectGeometric wear indication: Geometry

Data Source

PatentEP4621258A1Brake disc with wear indicator
Publication Date: 2025.09.24 RENAULT SA
  • EP4621258A1 patent drawingFigure 1
  • EP4621258A1 patent drawingFigure 2~4
  • EP4621258A1 patent drawingFigure 5

AI summary

Brake disc comprising a first face (2) and a second face (3) opposite the first face (2), each of the first and second faces (2, 3) comprising a substrate and an external surface (2a, 3a) of the substrate (2a, 3a), at least one of the external surfaces (2a, 3a) comprising a friction zone (4) of a brake pad and at least one friction-free zone (5, 6) of the brake pad. In addition, the brake disc (1) comprises at least one wear indicator (10) comprising a recess visible to the naked eye and comprising a first portion (12) extending over the friction zone (4) of said at least one external surface (2a, 3a) and a second portion (13) extending the first portion (12) and extending over the friction-free zone (5, 6).