Electric Parking Brake Torque Limiting Mechanism
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Solution Overview
Problem
The complexity of coordinating control for electric parking brakes with twin brake pistons in disc brake assemblies, requiring separate motors for each piston, increases the complexity of the system.
Innovation Solution
A single electric motor is used to actuate both brake pistons through torque limiting devices that adjust torque transmission based on clamp force thresholds, allowing for coordinated control without the need for separate motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate motors are provided for each of the twin brake pistons, then the brake force and parking brake function are improved, but the device complexity increases due to coordinated control of two separate motors
Solution Approach 1:
The patent merges two separate motor control systems into a single motor system. The single electric motor drives a common spindle that rotates to actuate both brake pistons simultaneously through a unified mechanical linkage, eliminating the need for coordinated control of two separate motors while maintaining the parking brake function for twin piston assemblies
Solution Approach 2:
The single electric motor is designed to perform the function of multiple motors by driving a common spindle that distributes rotational motion to both brake pistons. This multi-functional approach allows one motor to replace two while maintaining independent control capability over each piston through the mechanical gearing system
2Device complexity
If a single motor is used to actuate both brake pistons, then the device complexity is reduced, but the torque control precision for each piston may be compromised
Solution Approach 1:
The patent introduces torque limiting devices as intermediary mechanisms between the single motor and the two brake pistons. These devices include friction elements and clutch mechanisms that precisely control torque transmission to each piston, ensuring that the single motor can accurately regulate the clamping force applied to each brake piston independently despite the simplified motor configuration
Solution Approach 2:
The torque limiting devices utilize adjustable friction coefficients and spring forces to dynamically control torque transmission parameters. By varying the normal force on friction surfaces and the spring preload, the system can precisely regulate the torque delivered to each brake piston, maintaining manufacturing precision while using a single motor
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 solution simplifies the control system by using a single motor to manage the torque for both brake pistons, reducing complexity and enhancing the efficiency of the electric parking brake function.
Implementation Method 1
The friction surface of the torque limiting device may include a friction disc and a friction pad. The friction pad may be pressed against the friction disc by a spring force to transmit a portion of the torque from the sun gear to the planet gears
Data Source
AI summary
An electrically actuated parking brake has a single electric motor producing a torque, a first torque limiting device with a first spring force, and a second torque limiting device with a second spring force. The first torque limiting device fully transmits a first portion of the torque to a first spindle until a first clamp force overcomes the first spring force and the second torque limiting device fully transmits a second portion of the torque to a second spindle until a second clamp force overcomes the second spring force. When the first clamp force overcomes the first spring force and the second spring force overcomes the second clamp force, the first portion of the torque that exceeds the first spring force is transmitted to the second spindle by the second torque limiting device.