Electromotive Linear Actuator for Disk Brakes
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Solution Overview
Problem
Conventional electric linear motion actuators face issues with power increase limitations and wear due to lateral moments and uneven contact in electric disk brake systems, leading to inefficiencies and potential damage from excessive loads and torque loss.
Innovation Solution
An electric linear motion actuator design where the carrier is immovable along the center axis, with a non-rotatable outer ring member slidably fitted in the housing, and surface hardening treatments applied to key components to prevent wear and ensure smooth linear motion, along with optimized helical rib and groove designs to reduce contact pressure and torque loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the carrier is made short in axial dimension to compact the actuator, then the actuator size is reduced, but the carrier cannot smoothly handle lateral moments from braking forces
Solution Approach 1:
The patent inverts the traditional design by making the outer ring member the movable output member instead of the carrier. The carrier is fixed axially while the outer ring member slides axially within the housing, guided by the housing's radially inner surface. This inversion allows the output member to be properly guided against lateral moments while maintaining a compact carrier structure.
2Power
If conventional motion converters like ball screw mechanisms are used to increase power, then power multiplication is achieved, but the actuator becomes large in size due to additional speed reducers
Solution Approach 1:
The patent merges the motion conversion function and power multiplication function into a single integrated mechanism. The helical rib on the outer ring member engages with circumferential grooves on the planetary rollers, combining the screw mechanism's power multiplication with the planetary mechanism's motion conversion, eliminating the need for separate speed reducers.
Solution Approach 2:
The planetary rollers serve multiple functions simultaneously: they act as both the screw element (through circumferential grooves) and the planetary gear element (by revolving around the rotary shaft). This multi-functionality achieves power multiplication and motion conversion in one compact mechanism.
3Power
If the helical rib engages with circumferential grooves at different lead angles, then power multiplication is enhanced, but uneven contact causes excessive loads and torque loss
Solution Approach 1:
The patent optimizes the lead angle relationship between the helical rib and circumferential grooves. By carefully selecting the lead angle of the helical rib relative to the circumferential grooves, the design achieves effective power multiplication while maintaining uniform contact pressure distribution, thereby reducing torque loss and preventing excessive localized loads.
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 solution enables smooth linear motion under lateral moments, prevents wear on key components, and enhances the efficiency of rotary motion conversion to linear motion by minimizing contact resistance and wear, thus improving the performance and longevity of the electric disk brake system.
Implementation Method 1
the planetary rollers, which are in frictional contact with the rotary shaft, rotate about the center axes of the respective planetary rollers while revolving around the rotary shaft
Data Source
Figure 1
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AI summary
A linear motion actuator is provided of which the output member can be smoothly moved linearly even when lateral moment acts on the output member. A carrier (6) supporting planetary rollers (7) is axially immovable, while an outer ring member (5), as the output member, is axially slidably fitted in the radially inner surface of a cylindrical portion (1a) of a housing (1), and is rotationally fixed to a driven member through keys (22). Hard plating layers are formed on the radially outer surface of a rotary shaft (4), the radially outer surfaces of the planetary rollers (7), including helical grooves (7a), and the surface of a helical rib member (5b) which is fixed to the radially inner surface of the outer ring member (5) forming a helical rib.