Capacitive Sensor Protection Against Water Infiltration
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Solution Overview
Problem
Capacitive sensors in vehicle door handles are not robust due to water infiltration, which causes electrical coupling and renders the locking or unlocking functionality unreliable, especially with saltwater, as drainage holes do not effectively address capillary action phenomena.
Innovation Solution
A watertight housing with a capacitive approach and/or contact detection sensor, including a detection electrode and a protective electrode separated from the detection electrode, and a method involving charging and discharging capacitors to maintain detection sensitivity despite water immersion, with the protective electrode connected to the same potential as the charging/discharging capacitor to prevent electrical coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If drainage holes are added to the handle to drain infiltrated water, then water drainage is improved, but capillary action causes water to stagnate and still create electrical coupling
Solution Approach 1:
A protective electrode is introduced as an intermediary element between the detection electrode and the water. This protective electrode acts as a mediator that prevents direct electrical coupling between the detection electrode and conductive water, thereby maintaining detection functionality even when water is present in the handle cavity.
Solution Approach 2:
The protective electrode is positioned and configured in advance to counteract the harmful effect of water infiltration before it can affect the detection electrode. By establishing this protective barrier beforehand, the system preemptively neutralizes the electrical coupling that would otherwise occur between the detection electrode and water.
2Reliability
If the handle is made watertight to prevent water infiltration, then detection reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of making the entire handle watertight, a protective electrode is introduced as a localized intermediary element within the handle cavity. This approach provides the necessary protection against water interference without requiring a complete redesign of the housing structure into a fully watertight configuration.
Solution Approach 2:
The solution applies protection locally rather than globally. The protective electrode is positioned specifically in the area where water infiltration occurs and where electrical coupling would affect detection, rather than requiring the entire handle to be sealed. This localized approach maintains simplicity while ensuring reliability.
3Ease of operation
If capacitive sensors are used for detection, then user intention detection is enabled, but water causes electrical coupling that renders sensors unreliable
Solution Approach 1:
The protective electrode serves as a mediator that shields the capacitive detection electrode from the distorting influence of water. This intermediary element prevents water from creating unwanted electrical coupling with the detection electrode, thereby maintaining the reliability and accuracy of contactless user intention detection.
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 ensures reliable detection of user intention to lock or unlock vehicle doors even when water stagnates in the handle, maintaining the sensitivity and operation of capacitive sensors by preventing electrical coupling and enhancing drainage.
Implementation Method 1
a capacitive approach and/or contact detection sensor (100), comprising a detection electrode (E2'), having a variable detection capacitance (Ce), representative of the approach of the hand of a user
Implementation Method 2
there is electrical coupling between the protective electrode (Ep) and the detection electrode (E2'), the protective electrode (Ep) being electrically connected to the first switching means (Sw1) at the same time as the first terminal of the charging/discharging capacitor
Data Source
AI summary
A device for detecting a user's intention to lock or to unlock a motor vehicle door. The device contained in a watertight housing, integrated into a non-watertight handle, the lower part of which includes drainage holes, a part of the housing being immersed in water. The device including: a capacitive approach and/or contact detection sensor, having at least one detection electrode, a variable detection capacitance representative of the approach of the user's hand, a charging/discharging capacitor Cs, and a protective electrode Ep situated in the part of the housing that is immersed in water, electrically coupled to the detection electrode and connected to a terminal of the charging/discharging capacitor Cs such that the protective electrode Ep is simultaneously at the same potential as the terminal of the charging/discharging capacitor during the various steps of charging/discharging the detection capacitor and the charging/discharging capacitor that are necessary to estimate the detection capacitance.