Three-Stage Planetary Gear Electric Brake Actuator
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Solution Overview
Problem
Conventional electric parking brake systems for vehicles, particularly sedans and small trucks, are inadequate for large vehicles as they require higher actuator output and a higher gearbox ratio to achieve sufficient parking forces, which is not met by existing deceleration transmission mechanisms.
Innovation Solution
An electric brake actuator with a three-stage planetary gear mechanism, where each stage has at least one planet gear supported by a planet carrier, and the planet gears of different stages are made of distinct materials, such as plastic and metal, to achieve a high gear reduction ratio and output torque suitable for large vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-stage planetary gear mechanism is used, then the device complexity is low, but the gear reduction ratio is insufficient for large vehicles
Solution Approach 1:
The patent divides the gear mechanism into three separate planetary gear stages, each with its own planet gears and planet carriers. This segmentation allows each stage to contribute to the overall reduction ratio while maintaining manageable complexity in each individual stage, achieving a cumulative reduction ratio of 250:1 to 300:1 suitable for large vehicle applications.
2Power
If the gear reduction ratio is increased to provide higher torque, then the output torque increases, but the weight of the actuator increases
Solution Approach 1:
The patent employs composite material construction where planet gears are made from material different than planet carriers. Specifically, planet gears can be made from steel or cast iron while planet carriers use aluminum or aluminum alloy, combining the high strength requirements of gear teeth with the weight reduction benefits of aluminum for supporting structures, thereby achieving high torque output with minimized actuator weight.
3Strength
If high-strength materials are used for all planet gears to handle high torque, then the strength is sufficient, but the noise and weight increase
Solution Approach 1:
The patent applies local quality by using different materials for planet gears versus planet carriers. The planet gears use high-strength materials (steel or cast iron) where strength is critical for torque transmission, while the planet carriers use lighter aluminum materials where full structural strength is not required. This localized material selection optimizes the strength-to-noise ratio and strength-to-weight ratio for each component's specific functional requirements.
Data Source
AI summary
An electric brake actuator includes a housing, a three-stage planetary gear mechanism provided in the housing, the planetary gear mechanism having a first stage, a second stage, and a third stage that are sequentially meshed from one end to the other end of the planetary gear mechanism, and each stage of planetary gear mechanism comprising at least one planet gear, and a planet carrier supporting the planet gear; a motor provided in the housing; and at least one gear connected between the planetary gear mechanism and the motor, the at least one gear being arranged the motor to drive the planetary gear mechanism. The at least one planet gear of the first stage is made of a first material that is different from a second material of which the planet gear of the second stage or the planet gear of the third stage is made.