Capacitive Sensor Steering Wheel Horn Module

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Solution Overview

Problem

Conventional floating horn modules in vehicle steering wheels require multiple contacts and compression springs for horn actuation, leading to large gap dimensions and unwanted vibrations, as well as costly electrical connections with multiple cables and printed circuit boards.

Innovation Solution

A contactless sensor system measures the axial stroke of a movable airbag module, eliminating the need for mechanical contacts and compression springs, allowing for parallel guidance and small gap dimensions, and integrating horn triggering logic in a microcontroller or simpler threshold-based systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple contacts and compression springs are used for horn actuation, then the airbag module can be reliably actuated, but the gap dimensions increase and unwanted vibrations occur

Engineering Contradiction:

Improvehorn actuation reliabilityVSAvoidvibrations and gap dimensions

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical contact-based horn actuation system with a capacitive sensor system. The capacitive sensor detects the approach of the airbag module without physical contact, eliminating the need for compression springs and multiple contacts. This substitution removes the source of vibrations and allows for smaller gap dimensions while maintaining reliable horn actuation detection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a capacitive sensor as an intermediary between the airbag module and the horn actuation system. This sensor mediates the detection process by measuring capacitance changes caused by the airbag module's approach, eliminating the need for direct mechanical contact and associated harmful vibrations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If multiple contacts and cables are used for horn contacts, then the horn can be actuated, but the electrical connection cost increases

Engineering Contradiction:

Improvehorn contact functionVSAvoidelectrical connection components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the horn detection function into the existing airbag control unit by implementing a capacitive sensor within the airbag module. This integration eliminates the need for separate contacts, cables, and printed circuit boards dedicated to horn actuation, reducing electrical connection complexity and cost while maintaining the horn's functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The capacitive sensor serves multiple functions: it detects both airbag deployment conditions and horn actuation intent. By making the sensor system universal, the patent eliminates the need for dedicated horn contacts and cables, reducing the overall number of electrical connection components required in the steering wheel system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If the airbag module is allowed to tilt laterally for decentral pressure, then horn triggering is ensured, but the distance to lateral guide increases

Engineering Contradiction:

Improvedecentral pressure responseVSAvoiddistance to lateral guide

Core Design Contradiction:

Ease of operationVSLength of moving object

Solution Approach 1:

The patent replaces the mechanical tilting mechanism with a capacitive sensing system that detects lateral pressure applications regardless of their position. The capacitive sensor measures changes in capacitance caused by any pressure on the airbag module, eliminating the need for the module to physically tilt or maintain specific distances from lateral guides.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If mechanical contacts are used for stroke detection, then the horn can be triggered, but wear and ageing of contacts occurs

Engineering Contradiction:

Improvehorn triggeringVSAvoidcontact lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent replaces mechanical contacts with a capacitive sensor system for stroke detection. The capacitive sensor detects the airbag module's movement and compression without physical contact, eliminating wear and ageing issues associated with mechanical contacts while ensuring reliable horn triggering throughout the component's service life.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Ensures reliable horn triggering with fewer components, reduces wear and vibration, and achieves smaller gap dimensions while simplifying electrical connections and eliminating the need for multiple cables and printed circuit boards.

Implementation Method 1

the sensor system comprises a capacitive sensor for contactless measurement of the stroke of the airbag module

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS7481450B2Vehicle steering wheel with an airbag module

Publication Date: 2009.01.27 ZF AUTOMOTIVE SAFETY GERMANY GMBH

AI summary

A vehicle steering wheel (20) includes a movable airbag module (24) which can be depressed by a limited axial stroke for generating a horn signal. The vehicle steering wheel (20) further includes a sensor system (22a, 22b) operating in a contactless manner for determining the stroke.