Magnet Unit Cohesive Connection for Steering Sensor
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Solution Overview
Problem
Existing magnet units for torque and steering angle sensors in motor vehicles face challenges in providing a reliable connection between the magnet element and the carrier sleeve due to shrinkage stresses and structural space constraints, particularly in injection molding processes which are cumbersome and expensive.
Innovation Solution
A method involving a cohesive connection between the magnet element and the carrier sleeve using a plastics element, where the connection is achieved through adhesive bonding or welding, such as laser or ultrasound welding, eliminating the need for positive locking and reducing production outlay while ensuring a robust and reliable connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnet element is directly injection-moulded onto the carrier sleeve, then the connection is simple and direct, but shrinkage stresses arise during cooling which can lead to cracks in the magnet element
Solution Approach 1:
The patent introduces an intermediate element made of elastomeric material between the magnet element and the carrier sleeve. This intermediary absorbs the shrinkage stresses during cooling through its elastic properties, preventing crack formation in the brittle magnet element while maintaining a reliable connection. The intermediate element acts as a stress buffer that accommodates the different thermal expansion coefficients of the magnet material and the metal sleeve.
2Reliability
If an elastic intermediate element is used to connect the magnet element to the carrier sleeve, then crack formation is prevented, but the connection becomes cumbersome and expensive due to positive locking requirements and sealing surfaces
Solution Approach 1:
The patent segments the connection system into three distinct components: the carrier sleeve, the intermediate elastomeric element, and the magnet element. This segmentation allows each component to be optimized independently - the elastomeric intermediate element is designed with specific geometric features that enable simple attachment methods without complex positive locking mechanisms or sealing surfaces, thereby reducing overall connection complexity while maintaining reliability.
Solution Approach 2:
The patent changes the material parameter of the intermediate element to elastomeric material with specific viscoelastic properties. This material parameter change allows the intermediate element to dissipate shrinkage stresses through viscous flow and elastic deformation, preventing crack formation without requiring complex mechanical interlocking or sealing arrangements. The elastomeric material's ability to undergo reversible deformation provides a simple yet effective stress management mechanism.
3Volume of stationary object
If the magnet element is directly connected to the carrier sleeve, then structural space is minimized, but the connection reliability deteriorates due to thermal expansion differences and shrinkage stresses
Solution Approach 1:
The patent employs a composite connection structure consisting of the metal carrier sleeve, the elastomeric intermediate element, and the plastics-bonded magnet element. This composite arrangement allows each material to contribute its advantageous properties - the metal sleeve provides mechanical strength and mounting capability, the elastomeric intermediate layer provides stress absorption and thermal expansion accommodation, and the magnet element provides the magnetic field. The composite structure achieves reliable connection without significantly increasing the overall volume, as the intermediate element is designed with minimal thickness sufficient to provide stress buffering.
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 approach simplifies the production process, reduces thermal distortion, and provides a reliable and robust connection between the magnet element and the carrier sleeve, addressing the issues of shrinkage stresses and structural space constraints while maintaining the desired structural integrity.
Implementation Method 1
the connection is achieved through adhesive bonding or welding, such as laser or ultrasound welding
Implementation Method 2
the connection is achieved through adhesive bonding or welding, such as laser or ultrasound welding
Implementation Method 3
the connection is achieved through adhesive bonding or welding, such as laser or ultrasound welding
Implementation Method 4
Via the stator—which is normally composed of two separate stator parts—the magnetic flux of the magnet is conducted to a first and to a second flux conductor
Data Source
AI summary
A method for producing a magnet unit for a sensor device for detecting a measurement variable which is characteristic of a state of rotation of a steering shaft of a motor vehicle provides a ring-shaped magnet element composed of a plastics-bonded magnet material and a carrier sleeve for the connection of the magnet unit to a shaft part of the steering shaft and connects the magnet element to the carrier sleeve, in particular axially adjacent to one another by way of respective axial face sides. A plastics element is provided on the carrier sleeve, and the connecting includes the plastics element and the magnet element being cohesively connected to one another.