Capacitive Position Transducer Wear Resistance
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Solution Overview
Problem
Capacitive displacement sensors in power tools are susceptible to contamination and wear, leading to impaired or failed path-dependent control due to the use of sliding contacts, which are prone to damage from abrasive substances during operations like drilling, grinding, or sawing.
Innovation Solution
A capacitive displacement encoder design that eliminates sliding contacts by using a displaceable slide within a receptacle, where the slide is guided between a ground electrode and a reference electrode, and a measuring electrode, allowing for capacitance changes proportional to displacement without voltage between a wiper and resistance surface, and utilizing a microprocessor to generate a path-dependent signal through the CVD method, immune to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sliding contacts are used in the displacement sensor, then the device can measure displacement, but the sliding contacts are subject to wear due to contamination from abrasive substances
Solution Approach 1:
The patent replaces the mechanical sliding contact system with a capacitive sensing system. Instead of using physical sliding contacts that wear against each other, the invention uses capacitive electrodes that detect displacement through electrical fields, eliminating mechanical wear while maintaining measurement capability
Solution Approach 2:
The patent introduces a dielectric member as an intermediary between the capacitive electrodes and the environment. This dielectric member is displaced by the actuating element and modulates the capacitance between electrodes, allowing displacement measurement without direct contact between sensing elements
2Ease of operation
If sliding contacts are used to transmit movement from the actuating button, then speed control is possible, but the control is impaired or fails completely due to wear
Solution Approach 1:
The patent replaces the mechanical sliding contact-based speed control system with a capacitive sensing system connected to electronic control circuitry. The capacitive displacement sensor provides wear-free measurement of actuating element position, enabling stable and reliable electronic speed control without the degradation problems of mechanical contacts
3Reliability
If a capacitive displacement sensor without sliding contacts is used, then wear is eliminated, but the structure becomes more complex with multiple electrodes and a receptacle
Solution Approach 1:
The patent combines multiple functional elements into integrated components. The housing serves both as structural support and as part of the capacitive sensing structure. The dielectric member integrates the actuating element's movement with the capacitive sensing mechanism, reducing the need for separate transmission components
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 provides stable, travel-dependent control of electronic devices by minimizing wear and interference, ensuring precise speed control of electric motors despite environmental influences like humidity and temperature, with a simplified structure and reduced height.
Implementation Method 1
the capacitance of the capacitor changes
Data Source
AI summary
The invention relates to a capacitive travel sensor having a housing. A receptacle for a slide mounted such that it can be moved at least in a spatial direction is formed in the housing. The receptacle has a reference region in which the slide is guided, independently of the displacement path, between a plate-shaped earth electrode arranged on a first side of the slide and a plate-shaped reference electrode arranged on the second side of the slide opposite the first side. The receptacle also has a measuring region which adjoins the reference region and in which the slide is guided between a plate-shaped earth electrode arranged on the first side of the slide and a plate-shaped measuring electrode arranged on the second side of the slide, wherein the slide projects at least into a section of the measuring region on the basis of the displacement path. The invention also relates to a circuit arrangement having such a travel sensor and to an electronic apparatus having such a circuit arrangement.