Steering Wheel Heater Capacitance Detection With Inductor
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Solution Overview
Problem
Conventional steering wheel heater devices cannot detect human hand contact when the heater is energized, leading to reduced sensitivity and poor detection performance due to parasitic capacitance and switching transients.
Innovation Solution
Incorporating a steering wheel heater with an electrical resistor, a first inductor connected in series, and a sensor circuit that determines contact based on capacitance, even when the heater is energized, using a high AC impedance configuration and a controller to manage valid detection periods and avoid transient noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the steering wheel heater is energized to provide heating function, then heating performance is improved, but detection sensitivity deteriorates due to parasitic capacitance and switching transients
Solution Approach 1:
The circuit is segmented into heating function path and detection function path. The sensor circuit is electrically connected to the first terminal of the steering wheel heater, while the switch is connected between the second terminal and power supply, creating separate functional paths that allow simultaneous operation without mutual interference.
Solution Approach 2:
The sensor circuit acts as an intermediary that can detect capacitance changes caused by hand contact while the heater is energized. The circuit configuration allows the sensor to measure capacitance through the first terminal without being affected by the switching transients and parasitic capacitance at the second terminal.
2Device complexity
If a conventional seating detection circuit is used with heater switches, then cost is reduced, but detection reliability deteriorates when the heater is energized
Solution Approach 1:
The steering wheel heater serves dual functions: heating when the switch is on, and capacitance detection when the switch is off. The same heater element acts as both the heating component and the detection electrode, eliminating the need for separate detection circuits and switches.
Solution Approach 2:
The system operates in periodic cycles where the heater is energized for heating, then switched off for detection periods. The controller manages these alternating states, allowing reliable detection during off-periods when parasitic capacitance effects are minimized.
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 accurate detection of human hand contact with the steering wheel even when the heater is energized, enhancing sensitivity and reducing the effects of parasitic capacitance and switching transients, thus improving detection reliability.
Implementation Method 1
a steering wheel heater configured of an electrical resistor which produces heat by electrical energy
Implementation Method 2
determines whether a detected subject is in contact with the steering wheel heater, based on a magnitude of capacitance of the steering wheel heater
Implementation Method 3
even when the supply of power to the steering wheel heater is turned on by the at least one switch all turning on, impedance on the side of the switch, when seen from the sensor circuit, is AC high impedance
Data Source
AI summary
A steering wheel heater device including: a steering wheel heater configured of an electrical resistor which produces heat by electrical energy; an inductor; at least one switch; and a sensor circuit, wherein the inductor is connected in series to a first terminal of the steering wheel heater, the at least one switch turns on and off the supply of power to the steering wheel heater, the sensor circuit is electrically connected to the first terminal and determines whether a detected subject is in contact with a steering wheel based on a magnitude of capacitance of the steering wheel heater, and the at least one switch is at least one of a switch connected in series to the first terminal of the steering wheel heater via the inductor and a switch connected in series to a second terminal of the steering wheel heater.