Brake Assembly Wrap Spring for Bidirectional Wear Adjustment

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Solution Overview

Problem

Existing brake assemblies face challenges in efficiently adjusting for brake pad wear and maintaining optimal braking performance due to complex and costly wear adjuster mechanisms.

Innovation Solution

A brake assembly with a bidirectional wrap spring mechanism that allows for torque transmission in both rotational directions, utilizing a single wrap spring to adjust for brake pad wear by varying slip torques based on rotational direction, simplifying the design and reducing parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional wear adjuster mechanism is used, then brake pad wear adjustment is achieved, but the device complexity and cost increase

Engineering Contradiction:
Improvebrake pad wear adjustmentVSAvoidwear adjuster mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the wear adjustment function with the existing piston and shaft rotation mechanism. The wrap spring mechanism integrates wear compensation into the rotational movement of the piston, eliminating the need for separate complex wear adjuster components while maintaining reliable brake pad wear adjustment

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The piston rotation mechanism serves dual purposes: it provides the primary braking actuation function and simultaneously drives the wrap spring mechanism to compensate for brake pad wear. This multi-functionality reduces overall device complexity by using existing components for multiple purposes

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Measurement precision

If a bidirectional wrap spring mechanism is used, then torque transmission accuracy improves, but the spring design complexity increases

Engineering Contradiction:
Improvetorque transmission accuracyVSAvoidwrap spring design
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The wrap spring is designed with asymmetric engagement characteristics: it engages with different surfaces (piston outer surface vs. shaft surface) depending on rotational direction. This asymmetric design enables bidirectional torque transmission with varying slip torques, achieving accurate torque control while maintaining a relatively simple spring structure

Inventive Principle:
Principle #4Asymmetry

Solution Approach 2:

The wrap spring exhibits different engagement properties at different locations and rotational directions. One end engages the piston with higher friction for tight torque transmission, while the other end engages the shaft with lower friction allowing controlled slip. This local differentiation of engagement quality achieves precise torque transmission without requiring a complex overall spring design

Inventive Principle:
Principle #3Local quality

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 bidirectional wrap spring mechanism provides a simpler, cost-effective, and efficient wear adjuster system with accurate torque transmission, lower power consumption, and improved bearing life, while maintaining optimal brake pad alignment.

Implementation Method 1

The wrap spring is configured to slip with respect to the piston but not slip with respect to the shaft when the wrap spring is rotated in a first rotational direction. The wrap spring is configured to slip with respect to the shaft but not slip with respect to the piston when the wrap spring is rotated in a second rotational direction.

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4343167B1Brake assembly and method of control
Publication Date: 2025.08.13 ARVINMERITOR TECHNOLOGY LLC
  • EP4343167B1 patent drawingFigure 1
  • EP4343167B1 patent drawingFigure 2
  • EP4343167B1 patent drawingFigure 3

AI summary

A brake assembly and a method of control. The brake assembly includes a wrap spring that is configured to slip with respect to a piston but not slip with respect to a shaft when the wrap spring is rotated in a first rotational direction. The wrap spring is configured to slip with respect to a shaft but not slip with respect to the piston when the wrap spring is rotated in a second rotational direction.