Steering Wheel Conductor Insertion for Heating and Sensing
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Solution Overview
Problem
Current methods for manufacturing vehicle steering wheels with integrated heating and hand contact sensing require complex multi-layer structures, leading to inefficiencies in heat transfer, increased manufacturing costs, and high tolerances, particularly in the rim area, due to the need for separate heating, guard, and sensor layers.
Innovation Solution
A method and tool for introducing two layers of electric conductors into the overmolding of a steering wheel frame, where one layer functions as both a heating and guard layer, and the other as a sensor layer, allowing for efficient heating and capacitive sensing without the need for additional layers, and enabling simultaneous introduction in a single process step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate heating layer, guard layer and sensor layer are used, then sensing accuracy and shielding are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the heating layer and guard layer into a single integrated layer structure. This merged layer performs both heating function and electromagnetic shielding function simultaneously, eliminating the need for separate guard layer while maintaining sensing accuracy. The combined layer reduces device complexity and manufacturing cost while preserving the essential functions of both heating and shielding.
Solution Approach 2:
The integrated layer is designed to perform multiple functions: it serves as both a heating element and an electromagnetic shield (guard layer). This multi-functional design allows a single layer to replace what would traditionally require two separate layers, thereby simplifying the overall structure while maintaining the necessary sensing accuracy and shielding performance.
2Ease of manufacture
If combined heating/guard mat is molded in first shot, then manufacturing steps are reduced, but heat transfer efficiency to outer wrapping decreases
Solution Approach 1:
The patent positions the integrated heating/guard layer at an optimized depth within the steering wheel structure, specifically 2-4mm from the outer surface. This dimensional positioning ensures sufficient proximity to the outer wrapping for efficient heat transfer, while maintaining the simplified single-shot molding process. The specific depth placement resolves the contradiction by optimizing the thermal conduction path without requiring additional manufacturing steps.
3Manufacturing precision
If electric conductors are introduced separately, then positioning precision is improved, but manufacturing time and productivity are reduced
Solution Approach 1:
The patent introduces both the heating conductor and sensor conductor simultaneously into pre-formed channels during the molding process itself. This preliminary action ensures precise positioning of both conductors before the overmolding material sets, while completing the operation in a single step. The pre-formed channels guide the conductors to their exact positions, maintaining precision without requiring separate introduction steps that would reduce productivity.
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 approach reduces manufacturing complexity and costs, enhances heat transfer efficiency by positioning the heating layer closer to the steering wheel surface, and improves sensing accuracy while maintaining reliability, with the ability to adapt heat output and sensing sensitivity through precise control of conductor placement.
Implementation Method 1
a first electric conductor layer (22a) which forms an inner first layer and functions as a heating layer
Implementation Method 2
the first electric conductor layer (22a) which forms an inner first layer and functions as a heating layer and as a guard layer
Implementation Method 3
a second electric conductor layer (22b) which forms an outer second layer and functions as a sensor layer
Implementation Method 4
the cut is closed due to the inherent elasticity of the overmolding and thus fixes the heating wire in position
Data Source
AI summary
A method for introducing electric conductors into an overmolding of a steering wheel frame is provided. The electric conductors are used for heating and shielding purposes and for sensing contact on a steering wheel. In a first step, at least one cut is introduced into the overmolding using a cutting tool. In a second step, both a first layer of an electric conductor and a second layer of an electric conductor are simultaneously introduced into the cut that has been created. The first layer forms both a heating layer for heating the steering wheel and a guard layer which, together with the second layer acting as a sensor layer, allows the capacitive sensing of hand contact.