Brake Wear Measurement via Break-Free Torque and Spring Preload
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Solution Overview
Problem
Existing methods for monitoring brake wear in service and park brake assemblies, especially in electric motor-driven final drives, are inefficient due to the difficulty in accessing the brake disc pack for visual or mechanical inspection, requiring manual measurements and additional costly sensor arrangements, and often result in time-consuming processes and potential brake failure.
Innovation Solution
A system that determines brake wear by comparing the break-free torque required for a worn disc brake pack to that of a new one, using a command signal to rotate the output shaft of an electric motor, and calculates the corresponding spring preload loss and disc wear from the difference in spring length, with a load curve stored in an electric controller to derive the wear amount and alert the operator when it exceeds allowable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual measurement methods are used to check brake wear, then measurement can be performed, but the process is time-consuming and requires operator dismount from the cab
Solution Approach 1:
The brake monitoring system performs self-measurement by automatically detecting brake disc thickness and calculating wear using the formula (T1-T2)/2, eliminating the need for manual operator measurement and reducing time loss while maintaining measurement precision
Solution Approach 2:
The patent replaces manual mechanical measurement with an electronic detection system that uses sensors and a microprocessor to automatically measure brake disc thickness and calculate wear, substituting the mechanical measurement process with an electronic system that reduces time loss
2Volume of moving object
If the brake assembly is placed inboard of the final drive gears for compactness, then space is saved, but visual or mechanical inspection of the brake disc pack becomes difficult
Solution Approach 1:
The patent introduces a measurement tool or sensor as an intermediary that can reach the brake disc pack through the limited access space inboard of the final drive gears, enabling measurement without requiring disassembly while maintaining the compact space arrangement
Solution Approach 2:
The patent replaces the need for physical access and visual inspection with an electronic sensing system that can detect brake disc thickness through the constrained space, substituting mechanical inspection methods with electronic detection that overcomes the accessibility limitation
3Measurement precision
If additional sensor arrangements are installed to monitor brake wear, then measurement capability is improved, but the cost and device complexity increase
Solution Approach 1:
The patent designs the sensing system to serve multiple functions: measuring brake disc thickness, calculating wear amount, and providing maintenance alerts, allowing a single sensor arrangement to perform multiple measurement and monitoring tasks, thereby improving measurement precision without proportionally increasing device complexity
Solution Approach 2:
The patent combines the measurement function, calculation function, and alert function into a single integrated brake monitoring system, merging multiple functions into one device that reduces overall complexity while maintaining comprehensive measurement capability
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
This method allows for reliable and economical measurement of brake wear without additional measuring devices, enabling early prediction of brake failure and reducing downtime by providing alerts for maintenance before the brake disc pack reaches a worn-out condition.
Implementation Method 1
an input drive shaft driven by an electric motor
Implementation Method 2
the corresponding spring preload loss and disc wear from the difference in spring length
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A final drive assembly is driven by an electric motor 12, 14, 16, 18 and includes a park and service brake arrangement including a shared disc brake pack 84 that is compressed by a preload exerted by a compression spring arrangement 106 defined by a stack of Belleville springs for establishing an engaged park brake condition in the absence of pressurized brake actuating fluid being routed to a park brake piston 102. An electrical control is provided for computing disc brake pack wear based on a stored load curve of the stack of Belleville springs containing information correlating preload amounts to various compressed heights of the stack of Belleville springs, and on the magnitude of a drive signal sent to the electric motor 12, 14, 16, 18 for causing sufficient drive torque to be developed for causing the rotor discs 86 of the engaged disc brake pack 84 to slip relative to the stator discs 92.