Steering Wheel Grip Sensing With Segmented Capacitive Electrodes
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Solution Overview
Problem
The existing steering wheel designs, such as those described in Japanese Patent Laid-Open Publication No. 2016-165940, suffer from variability in detection accuracy due to non-uniform configuration of the conductive layer, leading to inconsistent gripping detection based on differences in gripped portions by the occupant.
Innovation Solution
A steering device with a core metal part symmetrical across a rotation part, featuring independently arranged first and second conductive parts on opposite sides of a symmetrical plane, connected by a harness, and a detector to accurately detect gripping conditions based on capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single conductive layer is arranged on the entire periphery of the rim part, then the outer cover functions as an electrode, but the potential may differ at different portions and detection accuracy varies depending on gripped portions
Solution Approach 1:
The conductive layer is divided into multiple independent conductive portions (first conductive portion, second conductive portion, third conductive portion) arranged at different locations on the rim part. Each portion independently detects capacitance changes, and the detection result is determined based on whether any of the portions detects gripping, thereby improving detection consistency regardless of which portion is gripped.
Solution Approach 2:
Different conductive portions are strategically positioned at specific locations (e.g., upper, lower, left, right sides of the rim part) to ensure that at least one portion is always close to the occupant's hand regardless of grip position. This local distribution of conductive elements ensures consistent detection accuracy across different gripping scenarios.
2Area of stationary object
If the conductive layer is configured to cover the entire rim part, then it provides comprehensive coverage, but potential differences and non-uniform configuration reduce detection reliability
Solution Approach 1:
Instead of using a single continuous conductive layer, the patent segments the conductive coverage into multiple discrete conductive portions. Each portion is independently configured and connected to the detection circuit, allowing localized detection without the potential issues of large-area potential variations.
Solution Approach 2:
The conductive portions are arranged in multiple spatial dimensions around the rim part (different angular positions and radial locations) rather than forming a single planar layer. This three-dimensional distribution ensures that at least one conductive portion is optimally positioned relative to the occupant's hand regardless of grip position or orientation.
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 provides consistent and accurate detection of gripping conditions, minimizing variability and maintaining high production efficiency by ensuring each conductive part has a smaller area and is less affected by differences in gripped portions.
Implementation Method 1
a detector electrically connected to the first conductive part and the second conductive part via the harness, configured to detect gripping condition of the gripping part based on change in capacitance generated in at least one of the first conductive part and the second conductive part
Data Source
AI summary
A steering device includes a rotation part and a gripping part. The gripping part includes a core metal part symmetrical across the rotation part, and a covering part that covers the core metal part. The covering part has a first conductive part on one side with respect to a symmetrical plane of the core metal part, formed of a material having conductivity, and a second conductive part on the other side with respect to the symmetrical plane of the core metal part, formed of a material having conductivity. The first and the second conductive parts are arranged independently from each other. The steering device further includes a harness electrically connecting the first and the second conductive parts, and a detector that detect gripping condition of the gripping part based on change in capacitance generated in the first conductive part and the second conductive part.