Steering Wheel Sensor Unit Ring Magnet Sealing
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Solution Overview
Problem
Existing steering wheel sensor units for steer-by-wire systems lack protection against water and moisture penetration, and they do not efficiently combine sensing and friction generation for providing resistance to steering wheel rotation, which affects driver feedback and system reliability.
Innovation Solution
A steering wheel sensor unit design featuring a ring magnet attached to the shaft within a housing, with sensing elements encapsulated outside, and a magnetic hysteresis loss plate providing both sensing and friction, while being environmentally sealed to prevent water intrusion, allowing for low-profile and robust installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing elements are placed inside the shaft housing, then they can sense rotation directly, but they become vulnerable to water and moisture penetration
Solution Approach 1:
The sensing elements are moved from the interior dimension (inside the shaft housing) to the exterior dimension (outside the shaft housing), allowing them to sense rotation through the housing wall while being positioned in an environmentally protected location. This spatial relocation resolves the contradiction by separating the sensing function from the vulnerable interior environment.
Solution Approach 2:
The shaft housing acts as an intermediary medium that transmits the rotational position information from the magnet to the sensing elements while simultaneously providing environmental protection. The housing wall allows magnetic field penetration for sensing purposes while blocking water and moisture, thus mediating between the need for accurate sensing and protection from harmful factors.
2Ease of operation
If a magnetic friction device is added to provide resistance, then driver feedback is improved, but the device complexity increases
Solution Approach 1:
The magnetic friction device is integrated with the existing shaft and ring magnet assembly, combining the sensing function and the friction feedback function into a unified magnetic interaction system. The same ring magnet that provides positional information to the sensor also interacts with the magnetic friction plate to provide resistance, merging two functions into one compact arrangement rather than adding separate mechanical friction components.
Solution Approach 2:
A magnetic friction system replaces traditional mechanical friction devices (such as slide bearings, bushings, or spring-based mechanisms). The magnetic interaction between the ring magnet and magnetic friction plate provides the necessary resistance without requiring complex mechanical assemblies, thereby reducing overall device complexity while maintaining ease of operation through smooth, wear-free friction.
3Reliability
If the sensing elements are encapsulated outside the housing, then they are protected from environment, but the total height of the device increases
Solution Approach 1:
The sensing elements are positioned in a different spatial dimension (radially outside the shaft housing) rather than extending axially, allowing environmental protection without significantly increasing the overall height of the device. The encapsulation leverages the existing housing structure as a protective barrier while placing sensors in an adjacent radial zone.
Solution Approach 2:
The shaft housing serves multiple functions simultaneously: it provides mechanical support for the shaft, contains the magnet, and acts as an environmental barrier for the sensing elements. This multi-functionality eliminates the need for additional protective housings or extended encapsulation structures that would increase device height, as the existing housing is utilized for dual purposes.
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 effectively protects electronics from moisture, provides consistent friction for improved driver feedback, and maintains a low profile, enhancing the reliability and usability of steer-by-wire systems by integrating sensing and friction generation within a compact, environmentally sealed package.
Implementation Method 1
a ring magnet (6) is provided on the periphery of the widened part (1a) of the shaft (1), thus circumferentially surrounding the shaft (1) and rotatable with the shaft inside the interior of the shaft housing (2)
Implementation Method 2
In that case the ring magnet (6) inside the shaft housing (2) is surrounded, at least partially, by a magnetic hysteresis loss plate (11), being arranged as part of a circular ring and surrounding at least that part of the ring magnet (6) that not is on the side of the shaft housing where the sensors and electronics (7) are located
Data Source
AI summary
Disclosed is a steering wheel sensor unit, wherein the steering wheel is mounted on a shaft, which is journaled in a housing. The unit includes a ring magnet attached to the shaft within a shaft housing for rotation with the shaft, and sensing elements being arranged radially outside the shaft housing in an encapsulated compartment sensing rotation of the magnet and the shaft through the shaft housing.