Brake Pad Friction Composition for Creep Groan and Particle Control
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Solution Overview
Problem
Existing asbestos-free friction materials for vehicle braking systems, such as those used in electric vehicles, fail to adequately address low-frequency noise (creep groan), friction stability, and particle emission, often compromising braking performance and comfort.
Innovation Solution
A friction material composition combining two carbonaceous materials with specific particle size distributions (D50 > 10 μm and D50 < 10 μm) to optimize porosity, adhesion, and heat dissipation, reducing stick-slip behavior and particle emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional NAO friction materials are used, then asbestos-free braking is achieved, but creep groan noise and friction instability occur
Solution Approach 1:
The patent uses a composite friction material containing organic fibers (2-10 wt%), inorganic fibers (5-20 wt%), rubber binder (10-30 wt%), and multiple inorganic fillers including barium sulfate, calcium carbonate, and silica. This multi-component composite structure optimizes both noise reduction and friction stability by combining materials with complementary properties.
Solution Approach 2:
The patent systematically optimizes the particle size distribution and weight percentages of various components. Specifically, the fiber length (5-20 mm), fiber diameter (10-50 μm), and the ratio of organic to inorganic fibers are controlled to minimize stick-slip effects and creep groan while maintaining stable friction coefficients during braking operations.
2Object-affected harmful factors
If friction material is optimized for noise reduction, then creep groan is reduced, but particle emission increases
Solution Approach 1:
The friction material incorporates a porous structure with controlled void spaces between fibers and fillers. This porous network traps wear particles within the friction layer, preventing their release into the environment while maintaining effective friction. The porosity is optimized to balance noise reduction through vibration damping with particle retention.
Solution Approach 2:
The combination of organic fibers, inorganic fibers, rubber binder, and multiple inorganic fillers creates a composite matrix that reduces particle emission. The inorganic fillers particularly barium sulfate and calcium carbonate act as particle traps, while the fiber-reinforced structure minimizes material degradation and particle generation during braking.
3Object-affected harmful factors
If copper is eliminated from friction material, then environmental benefits are achieved, but braking performance deteriorates
Solution Approach 1:
The patent formulates a copper-free friction material by adjusting the composition ratios of alternative components. The rubber binder content is optimized to 10-30 wt% to provide adequate adhesion and friction, while the fiber content (organic 2-10 wt% plus inorganic 5-20 wt%) is tuned to maintain structural integrity and heat resistance without copper additives.
Solution Approach 2:
The copper-free composite uses a synergistic combination of organic fibers (cellulose or synthetic), inorganic fibers (glass or ceramic), rubber binder (natural or synthetic), and inorganic fillers (barium sulfate, calcium carbonate, silica). This multi-material composite compensates for the absence of copper by distributing functional requirements across multiple components, maintaining braking performance while eliminating toxic copper particle emission.
4Object-affected harmful factors
If modified silicone resin is used to reduce creep groan, then noise is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
Instead of using expensive modified silicone resin requiring complex synthesis, the patent employs conventional, readily available materials: standard organic fibers, inorganic fibers, common rubber binders, and basic inorganic fillers. These off-the-shelf components simplify manufacturing while achieving comparable noise reduction through their inherent vibration-damping properties and porous structure.
Solution Approach 2:
The patent achieves noise reduction by optimizing physical parameters of simple materials rather than using complex chemical modifications. The fiber length (5-20 mm), filler particle size distribution, and binder crosslinking density are controlled to maximize vibration damping and minimize creep groan, eliminating the need for expensive modified silicone resins and their complex synthesis processes.
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 composition significantly reduces creep groan noise, enhances friction stability, and minimizes particle emission, improving braking performance and comfort while maintaining effective friction characteristics.
Implementation Method 1
the contact phenomena occurring between the sliding part of the braking elements and the supports, during the actuation of the braking system
Implementation Method 2
This contact phenomenon is known as 'Creep groan' and it results in an annoying high-intensity and low frequency noise at very low speeds of the vehicle. It is the classic example of a self-excited braking vibration caused by the so-called 'Stick-Slip' effect, i.e. by alternated episodes of sticking or adhesion and subsequent slipping of the brake pad on the brake disc during the braking process and a result the coefficient of friction continuously varies between a static (stick phase) and dynamic (slip phase) values.
Data Source
AI summary
An asbestos free friction material composition and associated brake pad for vehicles, in particular for electric vehicles, having an improved friction stability, a reduced creep groan noise propensity and a lower particles emission, wherein the composition comprises at least one filler, at least a fibrous material, at least one binder, at least one lubricant, at least one or more abrasives, at least a first carbonaceous material having a particle size distribution such as to have a D50 higher than 10 μm and at least a second carbonaceous material having a particle size distribution such as to have a D50 less than 10 μm.