Friction Material Composition for Drum Brake Noise Reduction
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Solution Overview
Problem
Friction materials used in drum brake shoes for passenger cars fail to effectively reduce low frequency noise and maintain wear resistance due to the ineffectiveness of cleavable substances like graphite and mica, which are effective in disc brake pads but not in drum brake shoes, primarily due to differences in operating environments.
Innovation Solution
A friction material composition for drum brake shoes that omits cleavable substances and includes specific amounts of phenolic thermosetting resin as a binder, cashew dust and rubber particles as organic friction modifiers, and aluminum particles as an inorganic friction modifier, providing improved braking effectiveness and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cleavable substances such as graphite, mica, and vermiculite are added to the friction material composition for drum brake shoes, then low frequency noise is reduced initially, but the effectiveness diminishes over time and low frequency noise occurs
Solution Approach 1:
The patent removes cleavable substances (graphite, mica, vermiculite) from the friction material composition for drum brake shoes, despite their initial effectiveness in reducing low frequency noise. This extraction eliminates the problem of diminishing effectiveness over time, as these substances deplete from the friction surface during drum brake operation, unlike disc brake conditions where they remain effective
Solution Approach 2:
The patent changes the compositional parameters by specifying exact weight percentages of alternative friction modifiers (cashew dust: 5-15%, rubber particles: 3-10%, aluminum particles: 2-8%) to replace cleavable substances. This parameter change creates a composition that maintains continuous noise inhibition effectiveness specific to drum brake operating conditions
2Duration of action of stationary object
If the friction material wear does not progress easily in drum brake, then the friction surface remains in a relatively new condition, but low frequency noise occurs when cleavable substance disappears from the friction surface
Solution Approach 1:
The patent takes preliminary action by formulating the friction material with alternative friction modifiers (cashew dust, rubber particles, aluminum particles) that are designed to maintain continuous effectiveness throughout the entire service life of the brake shoe. This preliminary composition design ensures that noise inhibition effectiveness does not diminish over time, addressing the long-duration operation characteristic of drum brakes
Solution Approach 2:
The patent ensures continuity of useful action by creating a friction material composition where the friction modifiers continuously provide noise inhibition effectiveness throughout the service life. Unlike cleavable substances that deplete over time, the selected materials (cashew dust, rubber particles, aluminum particles) maintain their effectiveness continuously, matching the long service life and repeated braking cycles of drum brake applications
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 friction material composition continuously reduces low frequency noise and enhances braking effectiveness and wear resistance by minimizing stick slip and maintaining effective noise inhibition throughout the life of the brake shoe.
Implementation Method 1
containing 8-12 weight % of phenolic thermosetting resin as the binder
Implementation Method 2
9-18 weight %, relative to the total amount of the friction material composition, of cashew dust as the organic friction modifier and 6-12 weight %, relative to the total friction material composition, of the rubber particle as the organic friction modifier
Implementation Method 3
4-10 weight %, relative to the total amount of the friction material composition, metallic aluminum particle as the inorganic friction modifier
Implementation Method 4
heat press forming the mixed friction material composition
Implementation Method 5
baking the heat press formed friction material composition
Data Source
AI summary
To provide a friction material used for a brake shoe of a drum brake for a passenger car, which continuously reduces generation of low frequency noise and provides excellent braking effectiveness and wear resistance and is manufactured by forming a friction material composition which contains no cleavage substance, 8-12 weight % of a phenolic thermosetting resin as the binder, 9-18 weight % of cashew dust as the organic friction modifier, 6-12 weight % of a rubber particle, where the total amount of the cashew dust and rubber particle is 18-25 weight %, and 4-10 weight % of the aluminum particle as the inorganic friction modifier, all relative to the total amount of the friction material composition. The friction material contains the phenolic thermosetting resin consists of a straight novolak phenolic resin and the unvulcanized nitrile rubber (NBR) particle.