Steering Wheel Horn Actuation with Pre-stressed Load Cell
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Solution Overview
Problem
Steering wheel horn switches with load cells are susceptible to mechanical shock and wear due to the transmission of force, leading to potential breakage and rattling noises.
Innovation Solution
Incorporating an elastically deformable element, such as a compression spring, to pre-stress the load cell in a resting state, reducing mechanical stress when a pushing force is applied, and using a thick film strain gauge for precise electrical response without perceptible movement of the horn actuation element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load cell with rigid body is used to transmit force from the horn actuation element to the steering wheel body, then the horn actuation signal can be detected, but mechanical shock and high preload forces can cause breakage of the rigid body
Solution Approach 1:
The patent introduces a resilient element (such as a spring) between the load cell and the steering wheel body to absorb mechanical shocks and high preload forces before they reach the load cell. This beforehand cushioning protects the rigid load cell from breakage while maintaining its ability to detect horn actuation signals through strain gauge measurements.
2Ease of operation
If the horn actuation element moves relative to the steering wheel body during actuation, then the horn switch can be activated, but rattling noises and wearout occur
Solution Approach 1:
The patent replaces the traditional mechanical contact switch with a load cell-based strain gauge system. Instead of relying on mechanical contact between moving parts, the system detects horn actuation through electrical resistance changes in the strain gauge, eliminating mechanical wear and rattling noises while maintaining operational functionality.
3Reliability
If an elastically deformable element is added to protect the load cell, then mechanical shock resistance improves, but device complexity increases
Solution Approach 1:
The resilient element serves multiple functions simultaneously: it acts as a shock absorber to protect the load cell, provides a mounting structure for the load cell, and maintains preloading force on the strain gauge. This multi-functionality reduces overall device complexity despite adding the resilient element.
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 reduces the risk of mechanical failure, minimizes wear, and eliminates rattling noises by maintaining a 'travel-less' horn actuation mechanism while allowing for easy assembly and high preload forces without excessive mounting force.
Implementation Method 1
Load cells are resistors that change their electrical ohmic resistance in response to mechanical stress applied to them. A strain gauge is an example of a load cell.
Implementation Method 2
In order to avoid the above-mentioned disadvantage, an elastically deformable element, for example in form of a compression spring, is used.
Data Source
AI summary
A steering wheel having a steering wheel body (10) having a first force transmitting component, and a horn actuation element. The horn actuation element having a horn actuation surface (23) and having a second force transmitting component. A load cell (30) is provided having a sensitive element that changes at least one of its electrical properties in response to a compression force. The sensitive element placed between the first and second force transmitting components. At least one elastically deformable element is provided between the steering wheel body (10) and the horn actuation element. When a pushing force is applied to the horn actuation surface (23) the force applied to the sensitive element changes. In a resting state of the steering wheel a compression force is applied to the sensitive element by the first and second force transmitting components by a preload and in that the compression force applied to the sensitive element is reduced when a pushing force is applied to the horn actuation surface (23).