Electromechanical Actuator Tapered Shaft Locking
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Solution Overview
Problem
Existing electromechanical actuators for hydraulic braking systems face challenges in achieving fast response times and generating large pressure increases while maintaining a compact and robust design, particularly in ensuring secure locking and torque transmission across the actuator interface.
Innovation Solution
The design incorporates a cylindrical rotor with a tapered bore and shaft, a four-point contact bearing assembly, and a drive nut system with a locking mechanism, allowing for efficient axial load distribution and torque transmission, and enabling the actuator to be assembled independently before integration into the motor housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a traditional electromagnetic actuator with hollow rotor and ball screw drive is used, then the actuator can generate large pressure increases, but the response time is slow and the structure is complex
Solution Approach 1:
The patent replaces the traditional ball screw mechanical drive with a direct-drive permanent magnet synchronous motor. The motor's rotor directly connects to the piston rod without intermediate mechanical transmission components. This substitution eliminates mechanical backlash and friction, significantly improving response time while maintaining the ability to generate large pressure increases through direct electromagnetic force conversion.
Solution Approach 2:
The patent removes the hollow rotor structure and ball screw mechanism from the actuator design. By extracting these complex mechanical transmission components, the design achieves a simpler structure with fewer moving parts, reducing inertia and improving response time while the motor directly provides the necessary force for pressure generation.
2Volume of moving object
If the actuator components are integrated into a single housing, then the structure is compact, but manufacturing and assembly become more difficult
Solution Approach 1:
The patent divides the actuator into modular components: a motor assembly containing the permanent magnet synchronous motor, a piston assembly with the piston rod and seal, and a housing that integrates the cylinder bore. These segmented modules can be manufactured separately with optimized processes and then assembled together, reducing manufacturing complexity while achieving a compact integrated structure.
Solution Approach 2:
The patent merges the motor housing and cylinder housing into a single integrated housing structure. The motor assembly and piston assembly are positioned within this unified housing, eliminating the need for separate housings and reducing the overall actuator volume. The integration is achieved through precise positioning features and sealing arrangements that allow modular assembly within the compact unified structure.
3Reliability
If additional locking features are added to secure the shaft, then the actuator becomes more reliable, but the device complexity increases
Solution Approach 1:
The patent employs a self-locking mechanism where the permanent magnet synchronous motor's rotor structure inherently prevents reverse rotation through magnetic detent effects. The rotor magnets interact with the stator magnetic fields to create natural holding positions, eliminating the need for additional mechanical locking features such as keys, splines, or detent springs. This self-service locking approach maintains reliability while keeping the structure simple.
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 configuration enables a compact, robust, and efficient electromechanical actuator capable of high axial loads and pressure increases, ensuring reliable operation in hydraulic braking systems by securely locking the shaft and transmitting torque without additional locking features.
Implementation Method 1
a permanent magnet synchronous motor having a stator and a rotor
Implementation Method 2
The drive comprises an elongate screw having an external helical groove that complements that of the rotor. The two grooves are filled with metal balls and the balls act on the screw to create a linear movement of the screw relative to the stator.
Implementation Method 3
hydraulic braking system for a vehicle... generates an increased hydraulic pressure in a hydraulic fluid connected to a brake caliper or drum
Data Source
AI summary
An electromechanical actuator for use in a hydraulic braking circuit of a vehicle comprises an electric motor having a stator and a rotor, and a linear actuator that is located within the motor. The linear actuator comprises an elongate shaft having a screw part at one end carrying an external thread that extends along a portion of the shaft, and a fixing part at the other end shaft, the linear actuator further comprising a drive nut that surrounds the screw part of the shaft and is located at least in a retracted position inside an enlarged bore of the first portion of the rotor body, the drive nut being connected to the screw part through a set of balls that engage the threads of the drive nut and screw part, and the fixing part of the shaft includes a tapering portion that engages a complimentary tapering portion of the bore in the second portion of the rotor body.