Capacitive Sensor Light Guide for Vehicle Control Panels
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Solution Overview
Problem
Existing motor vehicle control panels with capacitive buttons face complex assembly challenges and backlighting constraints due to the use of multiple components and light propagation properties of capacitive films.
Innovation Solution
A motor vehicle control panel design featuring a capacitive detection element with a rigid tubular part and an elastic part that compensates for assembly clearances and light leakage, using electrically conductive materials for efficient light guidance and contact, allowing for a single-component front face and improved backlighting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a capacitive film is used for backlighting control zones, then the control zones can be illuminated, but light leakage occurs and complex assembly is required
Solution Approach 1:
The patent combines multiple functions into the capacitive detection element: it serves as both the capacitive sensor and the light guide structure. The rigid tubular part forms a light guide that channels light from the LED through the capacitive element to illuminate control zones, eliminating the need for separate backlighting components and reducing assembly complexity
Solution Approach 2:
The elastic part acts as an intermediary element that compensates for clearances and ensures proper positioning between the rigid tubular part and both the front face and printed circuit board. This intermediary component facilitates reliable electrical contact and mechanical alignment without requiring complex assembly procedures
2Adaptability or versatility
If a capacitive film is used for control zones, then capacitive control buttons can be formed, but light propagation constraints limit backlighting efficiency
Solution Approach 1:
The rigid tubular part of the capacitive detection element has specific local optical properties that enable it to guide light efficiently. The tubular structure acts as a light guide that directs light from the LED through the capacitive element to the control zones, ensuring effective illumination while maintaining capacitive functionality
Solution Approach 2:
The capacitive detection element uses composite construction with a rigid tubular part (providing structural support and light guiding) and an elastic part (providing compliance and electrical contact). This composite structure combines mechanical strength with optical and electrical properties needed for efficient backlighting and capacitive sensing
3Ease of manufacture
If clearances are present between components, then assembly tolerance is accommodated, but electrical contact reliability deteriorates
Solution Approach 1:
The elastic part provides dynamic compliance to accommodate assembly clearances and tolerances. It can deform elastically to ensure continuous electrical contact between the capacitive detection element and the printed circuit board, maintaining reliable electrical connection despite manufacturing variations
Solution Approach 2:
The elastic part acts as a cushioning element that anticipates and compensates for clearance issues before they affect electrical contact reliability. By incorporating this compliant element in advance, the design ensures reliable electrical connection even when assembly tolerances result in gaps or misalignments
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
Simplifies assembly, ensures reliable electrical contact, and enhances backlighting by using a capacitive detection element with a rigid tubular part and elastic parts to guide light effectively, addressing assembly and backlighting constraints.
Implementation Method 1
at least one rigid tubular part forming a light guide for the light beam
Implementation Method 2
at least one elastic part made in one piece with the rigid tubular part so as to compensate the clearances between the rear surface and the detection element and between the printed circuit board and the detection element
Data Source
AI summary
A motor vehicle control panel includes a front face including a control zone; a printed circuit board; at least one electrically conductive capacitive detection element extending along a vertical axis from the rear surface of the front face to an electrical contact zone of the printed circuit board; a light source mounted on the printed circuit board and able to produce a back lighting light beam toward the control zone through the capacitive detection element; the capacitive detection element also comprises at least one rigid tubular part forming a light guide for the light beam and at least one elastic part made in one piece with the rigid tubular part so as to compensate the clearances between the rear surface and the detection element and between the printed circuit board and the detection element.