Electric Parking Brake Actuator Self-Locking Mechanism
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Solution Overview
Problem
Traditional electric parking brake actuators using lead screws have low efficiency and lack self-locking mechanisms, leading to potential vehicle movement on slopes when brakes are applied, requiring continuous motor activation for safety reasons.
Innovation Solution
An actuator with a self-locking mechanism featuring a transmission device comprising a housing, a self-locking unit, and a transmission unit, where the self-locking unit includes a sleeve, a driving member, and a driven member with lock elements that engage to prevent reverse rotation, ensuring the brake remains engaged without continuous motor power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a lead screw is used in the actuator, then the structure is simple, but the efficiency is low
Solution Approach 1:
The patent replaces the traditional lead screw mechanical transmission system with a ball screw mechanism. The ball screw uses ball bearings to reduce friction between the screw and nut, substituting high-friction sliding contact with low-friction rolling contact. This mechanical substitution significantly improves transmission efficiency while maintaining structural simplicity.
2Productivity
If a ball screw is used to improve efficiency, then the actuator efficiency increases, but the self-locking capability is lost
Solution Approach 1:
The patent segments the transmission system into two independent functional components: a ball screw for efficient power transmission and a separate self-locking mechanism for maintaining brake engagement. The self-locking mechanism includes a lock nut with locking teeth that engage with the ball screw threads, creating a mechanical interlock that prevents reverse rotation. This segmentation allows each component to optimize its specific function without compromising the other.
Solution Approach 2:
The patent introduces a self-locking mechanism as an intermediary component between the ball screw and the brake assembly. This intermediary includes a lock nut with locking teeth that mesh with the ball screw threads, acting as a mechanical barrier that prevents the ball screw from rotating backward under load. The intermediary transfers the locking function separately from the power transmission function, resolving the contradiction between efficiency and self-locking.
3Reliability
If the motor remains active continuously to maintain brake engagement, then safety is ensured, but energy consumption increases
Solution Approach 1:
The patent implements preliminary action by engaging the self-locking mechanism during the brake application process. The locking teeth of the lock nut engage with the ball screw threads before the brake is released, pre-establishing a mechanical interlock that maintains brake engagement passively. This preliminary locking action eliminates the need for continuous motor activation, as the mechanical lock sustains the braking force without additional energy input.
Solution Approach 2:
The self-locking mechanism enables the actuator to maintain brake engagement through self-service, without requiring continuous external power. The locking teeth create a self-sustaining mechanical interlock that automatically holds the brake in the engaged position, using the brake load itself to maintain the locked state. This self-service capability significantly reduces energy consumption while ensuring safety.
Data Source
AI summary
An actuator of an electric parking brake system includes a motor, an output member, and a transmission device. The transmission device includes a housing, a self-locking unit and a transmission unit. The self-locking unit includes a fixed sleeve, and a driving member, a driven member and a lock holder that are rotatable with respect to the sleeve. The lock holder supports lock elements arranged to prevent the driven member from turning unless it is driven by the driving member. A planetary gear unit may be provided as part of the transmission device.