Capacitive Rotary Angle Sensor for Contactless Position Measurement

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Solution Overview

Problem

Conventional rotary selector switches in household appliances require a mechanical connection and a through-hole for the shaft to transmit rotational position to evaluation electronics, leading to increased manufacturing costs, potential entry of liquids and dirt, and complexity in injection-molded plastic panels.

Innovation Solution

A capacitive rotational angle sensor system using a signal-inducing unit with a center and rotary electrode, and a sensor unit with circularly arranged sensor electrodes, allowing for contactless and touchless measurement of angular position by calculating capacitance changes, eliminating the need for a through-hole and reducing manufacturing effort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a mechanical connection with a through-hole is used to transmit rotational position, then the rotational angle can be measured, but the manufacturing cost increases and the risk of liquid and dirt entry increases

Engineering Contradiction:

Improverotational angle measurementVSAvoidmanufacturing cost and complexity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical transmission system (shaft through hole) with an electromagnetic field-based capacitive sensing system. The rotary element with conductive coating creates capacitive coupling with sensor electrodes on the circuit board, allowing angular position detection without mechanical penetration through the housing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an electromagnetic field as an intermediary between the rotary element and the sensor. The capacitive coupling through the non-conductive housing material acts as the intermediary mechanism, eliminating the need for direct mechanical contact or through-holes while still transmitting rotational position information.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a mechanical connection with a through-hole is used to transmit rotational position, then the rotational angle can be measured, but the housing becomes more complex with weld lines

Engineering Contradiction:

Improverotational angle measurementVSAvoidhousing structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The mechanical shaft transmission system that requires complex housing modifications including weld lines and through-holes is replaced with a capacitive sensing system that works through the intact housing material, simplifying the housing structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If a mechanical connection is used to transmit rotational position, then the rotational angle can be measured, but the reliability decreases due to potential entry of liquids and dirt

Engineering Contradiction:

Improverotational angle measurementVSAvoidprotection against liquids and dirt

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces the mechanical open shaft system with a capacitive coupling system that operates through the housing material, sealing the interior and preventing liquid and dirt ingress while maintaining rotational position measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution reduces manufacturing costs, prevents liquid and dirt entry, and simplifies the manufacturing process by eliminating weld lines, while providing a reliable and cost-effective method for determining the angular position of rotary selector switches in household appliances.

Implementation Method 1

The ground electrode can influence a capacitance of the center electrode

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The rotary electrode can influence a capacitance of at least one of the sensor electrodes according to the angular position of the signal-inducing unit

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10113885B2Method and rotational angle sensor for measuring an angular position of a rotatable signal-inducing unit

Publication Date: 2018.10.30 MIELE & CO KG

AI summary

A method for measuring an angular position of a rotatable signal-inducing unit uses a sensor unit electrically isolated from the signal-inducing unit. The signal-inducing unit has a center electrode disposed in a signal-inducing unit plane and a rotary electrode disposed in the signal-inducing unit plane, the rotary electrode being conductively connected to the center electrode and laterally offset therefrom. The sensor unit has a first sensor electrode disposed in a sensor plane and at least one second sensor electrode disposed in the sensor plane, the sensor electrodes being arranged in a circle around a ground electrode disposed in the sensor plane, the signal-inducing unit plane and the sensor plane being oriented substantially parallel to one another. The signal-inducing unit is supported so as to be rotatable about the center electrode and the rotary electrode is movable along a circular path in the region of the sensor electrodes.