Capacitance Sensor Electrode Layout for Stable Pressure Detection

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Solution Overview

Problem

Variations in conductive rubber characteristics can lead to erroneous detection of pressure application, causing the system to incorrectly determine the presence or absence of a human body part, due to unreliable electric resistance value changes.

Innovation Solution

A capacitance detection sensor with a base material and pairs of electrodes, where one pair measures proximity and another pair measures pressure, using capacitance values to determine states independently of conductive characteristics, with an optional electrostatic shielding member to prevent measurement accuracy reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If electric resistance value is used to detect pressure application through conductive rubber, then pressure detection is enabled, but detection accuracy deteriorates due to variations in conductive characteristics of the conductive rubber

Engineering Contradiction:

Improvepressure detection accuracyVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the detection parameter from electric resistance value to capacitance value. By measuring capacitance between electrodes instead of resistance through conductive rubber, the system eliminates dependence on conductive rubber characteristics while maintaining pressure detection capability. The capacitance measurement is performed by applying an alternating voltage between a first electrode and a second electrode, and measuring the resulting current to calculate capacitance value.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the electrical resistance-based detection mechanism with a capacitance-based detection mechanism. Instead of measuring resistance through the conductive rubber material, the system uses electromagnetic field interaction to measure capacitance, thereby substituting a material-dependent electrical measurement with a field-based measurement that is independent of the conductive rubber's properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If conductive rubber is used for pressure detection, then pressure sensing is achieved, but detection stability worsens due to changes in conductive characteristics

Engineering Contradiction:

Improvepressure sensing capabilityVSAvoiddetection stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent changes the physical parameter used for detection from electrical resistance to capacitance. This parameter change allows pressure sensing to be maintained while eliminating the instability caused by variations in conductive rubber properties. The capacitance measurement reflects pressure-induced changes in electrode spacing and configuration without being affected by the conductive material's varying characteristics.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If capacitance measurement is performed between electrodes through base material, then proximity and contact detection is enabled, but measurement accuracy deteriorates due to electrostatic interaction with approaching objects

Engineering Contradiction:

Improveproximity detection accuracyVSAvoidelectrostatic interaction interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a third electrode as an intermediary element to measure capacitance that is affected by approaching objects. This third electrode, positioned to face the first electrode through the base material, serves as a sensing element that detects changes in capacitance caused by objects approaching from the outside, while the second electrode measures capacitance related to pressure applied to the contact surface. This separation of measurement functions eliminates interference between different detection purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 accurately determines the presence, proximity, contact, and pressure states with high accuracy, regardless of the conductive characteristics of the base material, improving detection reliability.

Implementation Method 1

capacitance C1 between the pair of first electrodes is measured, and capacitance C2 between the pair of second electrodes is measured

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a base material made of a dielectric

Methodology Applied

Scientific EffectDielectric: Dielectric

Data Source

PatentUS12117354B2Capacitance detection sensor, capacitance detection sensor module and state determination method using capacitance detection sensor

Publication Date: 2024.10.15 HONDA MOTOR CO LTD

AI summary

A pair of first electrodes 111, 112 is arranged in a state being separated in a direction parallel to a contact surface 102 of a base material 10 made of a dielectric and being at least partially in contact with the base material 10. A pair of second electrodes 121, 122 is arranged in a state of overlapping at least one of the pair of first electrodes and sandwiching the base material 10 at a position farther from the contact surface 102 of the base material 10 than the pair of first electrodes 111 and 112 in a direction perpendicular to the contact surface 102 of the base material 10. The proximity state of an object Q with respect to the contact surface 102 of the base material 10 is detected according to the measurement result of the capacitance C1 between the pair of first electrodes 111 and 112.