Magnet Assembly Form-Fitting Connection for Steering Sensor
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Solution Overview
Problem
Magnet assemblies for detecting the rotation state of a steering shaft in motor vehicles face challenges in achieving a permanently rotationally fixed connection with minimal play, as the high magnetic particle filling in the plastic magnetic elements makes them brittle and prone to thermal stresses, leading to potential detachment and safety risks.
Innovation Solution
A magnet assembly with a form-fitting connection between the sleeve and the magnetic element, utilizing a stop flange and latching means that engage in recesses to secure the magnetic element axially and circumferentially, providing a secure and simple manufacturing solution independent of length tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnetic element is adhesively bonded to the sleeve, then the connection is simple to manufacture, but thermal stresses may cause adhesive layer damage or failure
Solution Approach 1:
The connection between sleeve and magnetic element is segmented into multiple independent form-fitting features: an outer diameter form-fitting connection and an inner diameter form-fitting connection. This segmentation distributes the thermal stress across multiple contact points rather than relying on a single adhesive layer, thereby maintaining manufacturing simplicity while improving reliability.
Solution Approach 2:
The adhesive bonding mechanism is replaced with a purely mechanical form-fitting connection system. The sleeve and magnetic element engage through precisely dimensioned outer and inner diameter interfaces that provide rotational and axial fixation without requiring adhesive materials, eliminating thermal stress concerns associated with adhesive layers.
2Strength
If the magnetic element is injection moulded directly onto the sleeve, then the connection is strong, but manufacturing complexity increases
Solution Approach 1:
The injection moulding process is segmented into two separate operations: first producing the sleeve with its form-fitting features, then separately producing the magnetic element with corresponding form-fitting features. These pre-formed components are subsequently assembled through mechanical engagement, reducing the complexity of the moulding process itself while maintaining connection strength.
Solution Approach 2:
The sleeve and magnetic element are preliminarily formed with their respective form-fitting features during separate manufacturing processes. The outer diameter of the magnetic element and the inner diameter of the sleeve are pre-configured with precise dimensional tolerances to enable direct mechanical assembly, eliminating the need for complex integrated moulding while ensuring strong connection.
3Stability of the object's composition
If a form-fitting connection is used between sleeve and magnetic element, then rotational fixation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The rotational fixation requirement is segmented into two independent form-fitting interfaces: an outer diameter interface between the magnetic element and sleeve, and an inner diameter interface providing additional mechanical engagement. This segmentation distributes the precision requirements across multiple features rather than requiring a single high-precision interface, making manufacturing more feasible while maintaining stable rotational fixation.
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 form-fitting connection ensures a secure, rotationally fixed attachment that is resistant to thermal stresses and manufacturing variations, maintaining signal quality and safety by preventing detachment and ensuring precise positioning of the magnetic element.
Implementation Method 1
the magnetic flux which occurs in the magnetic element, is dependent on the rotation state of the shaft and is intended for producing a sensor signal can be conducted from the magnetic element via a flux conductor to a magnetic sensor
Implementation Method 2
to a magnetic sensor, for example to a Hall sensor
Data Source
AI summary
The invention relates to a magnet assembly (10) for a sensor device for detecting a measurement variable characterizing a rotation state of a steering shaft of a motor vehicle, to a sensor device and to a motor vehicle, wherein the magnet assembly (10) has a sleeve (11) and a magnetic element (12), which is connected in a form-fitting manner to the sleeve (11), wherein the sleeve (11) is designed for connecting the magnet assembly (10) to a first part of the steering shaft and has at least one stop flange (11C), which extends outwards in the radial direction in a radial plane, for axially securing the magnetic element (12) in a first axial direction (A1), wherein the magnetic element (12) is arranged concentrically with respect to the sleeve (11) and, with its first end side (S1), is at least partially supported axially on the stop flange (11C) and is thereby secured in the first axial direction (A1). Furthermore, the magnetic element (12) is secured in the second axial direction (A2) and in the first circumferential direction (U1) and in the second circumferential direction (U2) by means of at least one latching means (11D) engaging in a recess (12B) which is open in the axial direction (A2) and has a plurality of inner surfaces (I1, I2, I3).