Differential Reduction Brake Actuator Design
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Solution Overview
Problem
Current electric brake actuators for vehicles face challenges in achieving a balance between high reduction ratios, compactness, and low weight, particularly in disc brakes, which often result in complex and costly designs with increased maintenance requirements.
Innovation Solution
A linear actuator design incorporating a differential epicyclic gearbox with a screw-nut mechanism, featuring a combination of upstream and downstream epicyclic stages that share common kinematic elements, allowing for a significant reduction ratio while minimizing size and weight, and integrating the electric motor directly into the brake mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a high reduction ratio is achieved using conventional electric actuators, then the clamping force is sufficient, but the size and weight increase significantly
Solution Approach 1:
The patent implements nested epicyclic gear stages where the second epicyclic stage is positioned inside the first stage, with shared kinematic elements. The inner planet carrier of the first stage serves as the sun gear for the second stage, creating a compact nested configuration that achieves high reduction ratio without proportionally increasing size and weight
2Force
If a high reduction ratio is achieved using conventional electric actuators, then the clamping force is sufficient, but the complexity and cost increase
Solution Approach 1:
The patent merges two epicyclic gear stages into a single integrated mechanism by sharing kinematic elements. The inner planet carrier of the first epicyclic stage is combined with the sun gear of the second stage, and common satellites mesh with both fixed and mobile ring gears. This merging reduces the number of separate components and simplifies the overall structure while achieving the required high reduction ratio
3Volume of moving object
If the actuator is made compact, then the space requirement is reduced, but the reduction ratio may be insufficient
Solution Approach 1:
The patent achieves high reduction ratio in a compact volume by nesting the second epicyclic gear stage inside the first stage. The concentric arrangement of gear elements and shared kinematic components maximize the use of available space, allowing the mechanism to achieve a reduction ratio of approximately 1/100 or higher without a proportional increase in overall actuator volume
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 design provides a compact, lightweight, and reliable electric brake actuator that achieves high reduction ratios with reduced complexity and cost, enhancing manufacturing and maintenance simplicity while meeting the demands of both disc and drum brakes.
Implementation Method 1
a brake piston which is moved in translation by a screw-nut mechanism transforming a rotary drive into linear movement
Implementation Method 2
an upstream epicyclic stage, driven at the input by its planetary gear and which drives an input planet carrier with a first reduction
Implementation Method 3
a differential epicyclic gear reducer comprising a first and a second epicyclic stages which share between them a common element
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention proposes a linear actuator for activating a vehicle brake, notably for a disc-brake calliper. This actuator comprises a brake piston which is translationally moved by a screw-nut mechanism driven by a reduction gearbox of an electric motor. This actuator comprises an upstream reduction stage using an epicyclic geartrain (PR1) with fixed annulus (R1, 121), driven at input by its sun gear (S1). It drives the input of an epicyclic reduction gearbox referred to as "differential" comprising two epicylic geartrains sharing a common kinematic element. In a first family, these two geartrains comprise a planet carrier (140) in common, that meshes with a fixed annulus (R2) and a mobile annulus (R3), which bears an external screw thread which moves the piston. In the second family, the two geartrains are in series and drive an external screw thread which collaborates with the same toothset (201) as their planet wheels. This toothset is borne by the inside of the piston (16b) and has two crossed patterns performing the two functions. The invention also proposes a method for manufacturing such a piston, by stamping and then rolling a plate.