Steering Wheel Sensor Shielding for Parasitic Capacitance
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Solution Overview
Problem
Existing steering wheel sensors face issues with parasitic capacitance due to capacitive coupling between the sensor electrode and internal conductive members, which affects detection accuracy and robustness.
Innovation Solution
Incorporating a shielding member between the sensor electrode and the internal conductive member, which extends beyond the sensor electrode, to suppress capacitive coupling and reduce parasitic capacitance, while also considering the placement of a decorative member to further minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electrically conductive member is provided at the inner peripheral side of the metal core to enable capacitive coupling, then the sensor can detect steering operations, but parasitic capacitance is generated at the external electrode due to capacitive coupling between the external electrode and the electrically conductive member
Solution Approach 1:
The patent introduces a shielding member as an intermediary component positioned between the sensor electrode and the electrically conductive member. This shielding member acts as a mediator that blocks the direct capacitive coupling path, thereby reducing parasitic capacitance while allowing the sensor to maintain its detection function. The shielding member is connected to ground potential, creating an electromagnetic shield that prevents harmful capacitive coupling between the sensor electrode and internal conductive structures.
2Object-generated harmful factors
If a shielding member is added between the sensor electrode and the electrically conductive member to suppress capacitive coupling, then parasitic capacitance is reduced, but the device complexity increases
Solution Approach 1:
The shielding member is designed to serve multiple functions simultaneously: it acts as an electromagnetic shield to reduce parasitic capacitance, provides structural support within the steering wheel assembly, and can be integrated with existing decorative or functional components. By making the shielding member multi-functional, the patent reduces the need for additional separate components, thereby minimizing the increase in device complexity while achieving the desired reduction in parasitic capacitance.
3Object-generated harmful factors
If the shielding member extends out with respect to the sensor electrode to properly suppress capacitive coupling, then parasitic capacitance is reduced, but the area occupied by the sensor assembly increases
Solution Approach 1:
The shielding member is configured to extend primarily in the radial direction (perpendicular to the sensor electrode surface) rather than expanding the lateral footprint of the sensor assembly. By utilizing the radial dimension for shielding effectiveness, the patent achieves proper capacitive coupling suppression without significantly increasing the lateral area occupied by the sensor assembly, thus maintaining a compact overall structure.
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 configuration effectively reduces parasitic capacitance, enhancing the detection accuracy and robustness of the sensor by minimizing capacitive coupling between the sensor electrode and internal conductive members, even when the sensor electrode is not directly positioned within the decorative member.
Implementation Method 1
capacitive coupling is generated between the external electrode and the electrically conductive member, parasitic capacitance would be generated at the external electrode
Implementation Method 2
parasitic capacitance would be generated at the external electrode
Data Source
AI summary
At a rim portion of a steering wheel, a shielding layer is disposed between a sensor electrode and a rim metal core portion. The shielding layer extends with respect to the sensor electrode. Therefore, generation of capacitive coupling between the sensor electrode and the rim metal core portion can be suppressed properly by the shielding layer, and parasitic capacitance that is generated at the sensor electrode can be reduced.