Brake Friction Material Composition for Rust Sticking and Creep Groan
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Solution Overview
Problem
Current friction materials fail to simultaneously prevent seizure due to corrosion and creep groan, especially after undergoing high temperature heat history, as they either do not address corrosion at elevated temperatures or do not account for moisture-induced noise issues.
Innovation Solution
A friction material comprising an alkali metal salt of phosphoric acid and a metal sulfide as friction modifiers, with a steel fiber content of 20-50 mass% and a binder selection among phenol resins, elastomer-modified phenol resins, melamine resin, epoxy resin, or polyimide resin, which includes a wax containing 50% or more of an ester of a higher fatty acid and higher alcohol, and limited copper content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional friction materials are used, then they can provide basic friction performance, but they fail to prevent seizure due to corrosion after high temperature exposure
Solution Approach 1:
The friction material uses a composite formulation combining organic binder (polyester resin) with inorganic friction modifiers (barium sulfate, calcium carbonate) and specific additives (sulfonated castor oil, zinc stearate). This composite structure provides both corrosion prevention through the alkali metal salt of phosphoric acid and metal sulfide, and maintains friction performance after high temperature exposure up to 400°C.
Solution Approach 2:
The invention specifies precise compositional parameters including alkali metal salt of phosphoric acid at 1-10 mass%, metal sulfide at 0.1-5 mass%, and barium sulfate at 10-50 mass%. These parameter optimizations ensure the material maintains both corrosion resistance and friction performance under high temperature conditions, resolving the contradiction between reliability and adaptability.
2Reliability
If friction materials are designed to prevent corrosion seizure, then they can protect against rust, but they fail to prevent creep groan noise
Solution Approach 1:
The friction material uses sulfonated castor oil and zinc stearate as intermediary substances that provide lubrication during brake release. These intermediaries reduce friction between the friction material and rotor when the brake is released, preventing the stick-slip phenomenon that causes creep groan noise, while not interfering with the corrosion prevention function.
Solution Approach 2:
The friction material formulation achieves multi-functionality by incorporating components that simultaneously prevent corrosion seizure and creep groan. The alkali metal salt of phosphoric acid and metal sulfide prevent corrosion, while sulfonated castor oil and zinc stearate prevent creep groan, allowing a single material to address both reliability issues.
3Force
If the friction material contains high copper content, then it can improve friction performance, but it increases the risk of corrosion and seizure
Solution Approach 1:
The invention replaces copper, which provides good friction but causes corrosion, with alternative materials including barium sulfate, calcium carbonate, and organic friction modifiers. These materials may require more frequent replacement but eliminate the corrosion problem associated with copper, trading initial performance for long-term reliability.
Solution Approach 2:
The invention optimizes the copper content parameter by limiting it to 0.5 mass% or less, and compensates for friction performance through increased barium sulfate (10-50 mass%) and calcium carbonate (10-30 mass%). This parameter change reduces corrosion susceptibility while maintaining adequate friction force through the combined action of multiple friction modifiers.
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 proposed friction material effectively prevents seizure due to corrosion and creep groan across various temperature conditions, maintaining stability and performance even after high temperature exposure.
Implementation Method 1
an alkali metal salt of phosphoric acid and a metal sulfide are contained as the friction modifier
Implementation Method 2
a steel fiber is contained as the fibrous material in a content of 20 mass% to 50 mass%
Implementation Method 3
the binder is selected among phenol resins, elastomer-modified phenol resins, a melamine resin, an epoxy resin and a polyimide resin
Implementation Method 4
a friction modifier may be a wax A containing 50 mass% or more of an ester of a higher fatty acid and a higher alcohol
Data Source
AI summary
The present invention addresses the problem of providing a friction material which is capable of suppressing the occurrence of rust sticking even in cases where the friction material is subjected to a high-temperature thermal history (for example, the temperature of a counterpart member is around 400°C), and which is also capable of suppressing the occurrence of creep groan. The present invention relates to a friction material which comprises a friction regulating material, a binder and a fiber base material, and which contains, as the friction regulating material, an alkali metal salt of phosphoric acid and a metal sulfide.