Steering Wheel Grip Sensing Circuit for In-Grip Failure Diagnosis
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Solution Overview
Problem
Existing steering wheel units cannot diagnose failures in capacitance sensors when the steering wheel is gripped.
Innovation Solution
A hands-on detection device comprising a core metal, a shield electrode, and a sensor electrode, with a control unit that acquires capacitance values and determines failure based on short-circuiting the shield and core metal, using switches to short-circuit and apply voltage for precise failure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steering wheel is gripped during capacitance sensor diagnosis, then the hands-on detection function is activated, but the failure diagnosis capability is lost due to interference with the measurement circuit
Solution Approach 1:
The control unit performs failure diagnosis by measuring capacitance values before hands-on detection is activated. By conducting the measurement in advance when the steering wheel is not gripped, the system obtains baseline capacitance data that can be used for failure diagnosis without being affected by subsequent hands-on interference
Solution Approach 2:
The system dynamically switches between measurement mode and hands-on detection mode. The control unit determines based on the operational state whether to perform capacitance measurement for failure diagnosis or to perform hands-on detection, optimizing the function based on real-time conditions
2Reliability
If separate circuit configurations are used for hands-on detection and failure diagnosis, then each function can be optimized independently, but the device complexity and production costs increase
Solution Approach 1:
The same capacitance measurement circuit is used for both hands-on detection and failure diagnosis functions. The control unit configures the circuit differently based on the operational state - using it for hands-on detection when gripped and for failure diagnosis when not gripped, eliminating the need for separate dedicated circuits
Solution Approach 2:
The patent combines the hands-on detection circuit and the failure diagnosis circuit into a single integrated capacitance measurement system. By merging these functions into one circuit configuration, the system reduces component count, simplifies production, and lowers costs while maintaining both functional capabilities
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
Enables failure determination regardless of whether the steering wheel is gripped or not, reducing production costs and preventing erroneous determinations by using a single circuit configuration for both hands-on and failure detection.
Implementation Method 1
a shield electrode (22) provided outside the core metal (23) and separated by an insulator (In); a sensor electrode (21) further provided outside the shield electrode (22) and separated by an insulator (In)
Data Source
AI summary
A hands-on detection device of a steering wheel according to one embodiment of the present invention is a hands-on detection device of a steering wheel comprising: a core metal; a shield electrode provided outside the core metal and separated by an insulator (In); a sensor electrode further provided outside the shield electrode and separated by an insulator (In); and a control unit configured to acquire the capacitance value of the sensor electrode in a state in which the shield electrode and the core metal are short-circuited, and determine whether or not there is a failure based on the capacitance value.