Steering Torque Sensor Sleeve Ultrasonic Forming Without Cracking
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Solution Overview
Problem
Existing electromechanical power steering systems face challenges in manufacturing due to the weakness and high cost of ultrasound welding seams and the difficulty in achieving precise serrations, which can lead to component stress and cracking.
Innovation Solution
The use of thermoplastic materials for the ring magnet sleeve and stator holder, molded by ultrasound forming, with a knurling structure for secure form-fitting onto the steering shaft, eliminating the need for press fitting and injection molding, and allowing for a reliable, low-stress connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultrasound welding is used to connect the ring magnet sleeve to the steering shaft, then the manufacturing process is simplified and costs are reduced, but the strength of the welded seam is insufficient
Solution Approach 1:
The patent employs a composite connection approach combining ultrasound welding with a thermoplastic material layer. The ring magnet sleeve includes a thermoplastic material layer that is ultrasonically welded to the steering shaft, creating a hybrid joint that leverages both the simplicity of ultrasound welding and the bonding strength of thermoplastic materials, thereby resolving the contradiction between ease of manufacture and connection strength
Solution Approach 2:
The patent utilizes parameter changes in the thermoplastic material during the ultrasound welding process. The thermoplastic material undergoes phase change from solid to molten state under ultrasonic vibration and heat, then solidifies to form a strong bond. This parameter change allows the material to flow into the knurling structure during welding and create a mechanically interlocked, high-strength connection
2Reliability
If press fitting and injection molding with serration are used to fasten the ring magnet, then a secure connection is achieved, but the required low tolerances are hard to achieve and the design is prone to cracks
Solution Approach 1:
The patent replaces the traditional mechanical press fitting and injection molding process with ultrasound forming. Instead of using mechanical forces to create serrations and achieve connection, the patent uses ultrasonic vibration to directly form the connection between the thermoplastic material layer and the steering shaft, eliminating the need for precise mechanical tolerances and serration features while maintaining connection reliability
Solution Approach 2:
The patent employs mechanical vibration in the form of ultrasonic waves to perform the forming and welding operation. The ultrasonic vibration generates localized heat and mechanical agitation that allows the thermoplastic material to flow and bond with the steering shaft, replacing the static mechanical pressing and molding processes that previously required tight tolerances
3Reliability
If press fitting and injection molding processes are used to manufacture the sleeve and fasten the magnet, then a connection is achieved, but high costs are involved
Solution Approach 1:
The patent merges multiple traditional manufacturing steps (sleeve production, magnet insertion, and fastening) into a single ultrasound forming operation. The ring magnet sleeve is produced with an integrated thermoplastic material layer that is simultaneously formed and welded to the steering shaft in one step, eliminating the need for separate injection molding and press fitting operations, thereby reducing manufacturing costs while maintaining connection reliability
Solution Approach 2:
The thermoplastic material layer serves multiple functions simultaneously: it provides the structural sleeve, acts as the bonding agent, and forms the welded connection. The material's own properties (thermoplasticity) enable it to be formed and bonded during the ultrasound process without requiring additional materials or complex multi-step manufacturing, thereby reducing overall manufacturing cost
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 method simplifies the manufacturing process, reduces costs, and ensures a strong, crack-resistant connection between the ring magnet and the steering shaft, enhancing the durability and reliability of the torque sensor system.
Implementation Method 1
the ring magnet sleeve and/or the stator holder is made from a thermoplastic material and is molded by means of ultrasound forming in the steering shaft in one region for mounting on the steering shaft
Data Source
AI summary
An electromechanical power steering unit for a motor vehicle includes an integral component having a torque sensor unit, which detects the rotation of the upper steering shaft relative to the lower steering shaft. The torque sensor unit includes a ring magnet rotationally fixed to the upper steering shaft and a magnetic flux guide connected to the lower steering shaft. A magnet sensor detects the rotation of the shaft connected to the ring magnet with respect to the lower shaft connected to the magnetic flux guide and the ring magnet is carried by a ring magnet sleeve, which sits on the upper steering shaft and is made from a thermoplastic material and is molded by way of ultrasound forming in the upper steering shaft in one region for mounting on the upper steering shaft.