Cable-Pulling Actuation System for Parking Brake
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Solution Overview
Problem
Existing cable-pulling systems for drum-in-hat parking brakes experience prolonged actuation times due to wear, increasing the distance between jaws and the bell, leading to slower locking and release operations, which is unacceptable for users seeking a more responsive parking system.
Innovation Solution
A cable-pulling actuation system incorporating a motor-driven tie rod with irreversible threaded screws and a transmission mechanism that includes an epicyclic gear train and a worm screw, optimizing the pitch and helix configuration to enhance actuation speed and ensure self-locking, thereby reducing the actuation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a cable-pulling system with conventional transmission means is used, then the structure is simple, but the actuation time increases due to jaw wear and increased stroke distance
Solution Approach 1:
The patent changes the pitch parameter of the screw threads to optimize actuation speed. By selecting specific pitch values between 1-5mm, the system achieves faster cable retraction while maintaining adequate braking force, directly addressing the actuation time issue without requiring complex additional mechanisms
Solution Approach 2:
The patent introduces a dynamic transmission system using planetary gears that can adapt the gear ratio during operation. This allows the system to optimize the balance between cable retraction speed and braking force application, enabling faster actuation while compensating for jaw wear effects
2Speed
If the pitch of the screw threads is increased to reduce actuation time, then the actuation speed improves, but the self-locking capability may be compromised
Solution Approach 1:
The patent optimizes the pitch parameter within a specific range (1-5mm) to achieve the best compromise between actuation speed and self-locking capability. This parameter optimization allows the screw mechanism to retract the cable quickly while maintaining sufficient friction to prevent back-driving and ensure reliable self-locking
Solution Approach 2:
The patent introduces planetary gears as an intermediary mechanism between the motor and the screw assembly. This gear train provides mechanical advantage and enhances the self-locking effect through high reduction ratios, allowing the use of larger pitch values for faster actuation while maintaining reliable braking force and self-locking capability
3Device complexity
If conventional screw mechanisms are used, then the structure is simple, but the actuation time is excessive due to wear-induced stroke increase
Solution Approach 1:
The patent employs a planetary gear system that provides dynamic gear ratio optimization. This allows the transmission mechanism to adapt to varying operational conditions and jaw wear levels, maintaining efficient actuation speeds without requiring excessive structural complexity. The modular design keeps the added complexity manageable while delivering significant performance improvements
Solution Approach 2:
The patent combines multiple functions into integrated components: the planetary gears serve both as speed reducers and as self-locking mechanisms, while the screw assembly simultaneously provides cable retraction and force multiplication. This functional merging reduces the need for separate components, keeping the overall system complexity reasonable while achieving faster actuation
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 system significantly reduces actuation time by doubling the speed of the cable-pulling mechanism, providing quicker locking and release operations, enhancing user experience by minimizing waiting times and ensuring the brake remains engaged after motor deactivation.
Implementation Method 1
the second end of the tie rod is integral in translation with a first screw, having a first thread with a first pitch, wherein said first screw is engaged, through the first thread, in a second screw
Implementation Method 2
said first and second thread are irreversible
Implementation Method 3
transmission means that operatively connect the motor means to a second end of the tie rod
Implementation Method 4
A cable-pulling actuation system incorporating a motor-driven tie rod with irreversible threaded screws and a transmission mechanism that includes an epicyclic gear train and a worm screw
Data Source
AI summary
A cable-pulling actuation system for a parking brake having a body that houses a motor, a tie rod, suitable to actuate along an actuation direction, in correspondence of a first end, an actuating member of a drum brake, and a transmission that operatively connects the motor to a second end of the tie rod. The second end of the tie rod is integral in translation with a first screw, having a first thread with a first pitch. The first screw is engaged, through the first thread, in a second screw. The second screw comprises a second thread with a second pitch, through which is in turn engaged in a nut screw integral with the body, the second thread being opposite to the first thread. The second screw being actuated in rotation by the transmission.