Steering Wheel Sensor Layer Using Conductive Ink

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Solution Overview

Problem

The existing steering wheel designs with sensor layers composed of conductive wires face complications in production due to the impairment of stretch properties, leading to difficulties in assembly and potential wrinkles or slacks, which complicates the mounting process.

Innovation Solution

A steering wheel design featuring a sensor layer with a sheet-shaped substrate and conductive ink applied to a grip area, covered by an insulation sheet, both with stretch properties, forming an annular band that can be easily mounted on the cladding layer without wrinkles or slacks, improving assembly ease and reducing uncomfortable sensations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a wire-based sensor is used in the sensor layer, then the sensor can detect driver grip, but the stretch properties of the sheet member are impaired, making assembly difficult and causing wrinkles or slacks

Engineering Contradiction:

Improvesensor detection capabilityVSAvoidassembly ease of sensor layer

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the wire-based mechanical sensor structure with a conductive ink pattern printed directly on the sheet member. This substitution eliminates the need for separate wire components that impede stretching, allowing the sensor layer to maintain full stretch properties while still detecting driver grip through changes in electrical conductivity when the driver touches the steering wheel.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state of the sensor material from solid wire to conductive ink deposited on a flexible substrate. This parameter change allows the sensor to conform to the stretching and deformation of the sheet member during assembly and use, preventing wrinkles and slacks while maintaining sensor functionality.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a wire-based sensor is used in the sensor layer, then the sensor can detect driver grip, but the production process becomes complicated due to special attention required for mounting

Engineering Contradiction:

Improvesensor detection capabilityVSAvoidproduction process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the sensor function directly into the sheet member by printing conductive ink patterns onto the substrate. This integration eliminates the need for separate wire components and their associated mounting procedures, simplifying the production process while maintaining sensor detection capability. The sensor layer becomes a unified structure rather than an assembly of multiple components.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If the sensor layer is mounted without proper stretching control, then assembly is faster, but wrinkles and slacks form on the sheet member

Engineering Contradiction:

Improveassembly speedVSAvoidsurface smoothness of sensor layer

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the material properties of the sensor layer by using conductive ink on a stretchable substrate instead of rigid wire structures. This allows the layer to be stretched uniformly during assembly without creating wrinkles or slacks, maintaining surface smoothness while enabling faster assembly compared to careful wire-by-wire mounting.

Inventive Principle:

Principle #35Parameter changes

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 enhances the assembly process of the sensor layer, prevents disconnection during mounting, and provides a thinner, more comfortable grip detection system with improved durability and uniform sensitivity.

Implementation Method 1

a sensor composed of a conductive ink having stretch properties that is applied to a grip area by the driver on a front surface of the substrate

Methodology Applied

Scientific EffectElectrical conductivity: Conduction (electrical)

Data Source

PatentUS11390312B2Steering wheel

Publication Date: 2022.07.19 TOYODA GOSEI CO LTD

AI summary

A steering wheel includes an annular rim portion, a boss section, one or more spokes interconnecting the rim portion and boss section, and a core member interconnecting these portions, the core member including a wheel portion disposed in the rim portion. The steering wheel further includes a cladding layer disposed around the wheel portion, a skin layer disposed on a front surface of the rim portion, and a sensor layer disposed between the cladding layer and the skin layer for detecting the driver's grip. The sensor layer includes a sheet-shaped substrate having stretch properties, a sensor composed of a conductive ink having stretch properties and applied to a front surface of the substrate, and an insulation sheet covering the sensor and having stretch properties. The sensor layer is generally formed into an annular band and mounted on an outer circumferential portion of the cladding layer by being stretched and expanded.