Planar Heating Element with Localized Resistance for Vehicle Window Defogging

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Solution Overview

Problem

Conventional methods for creating a planar heating element for vehicle windows using a resin base, such as polyacrylonitrile or polycarbonate, are ineffective as the transparent conductive thin film's specific resistance cannot be varied due to temperature limitations, preventing efficient defogging and defrosting.

Innovation Solution

A planar heating element with a conductive sheet of uniform specific resistance is applied to the resin base, featuring conductive current supply portions and a heat dissipation-preventing member to locally increase specific resistance when current is passed through, allowing for targeted heating and uniform surface heating without high-temperature laser processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If laser beam heating is used to vary specific resistance of transparent conductive thin film, then defogging efficiency is improved, but resin base is softened due to high temperature

Engineering Contradiction:

Improvedefogging efficiencyVSAvoidheating temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The heating element is designed with a non-uniform specific resistance distribution, where the intermediate portion has higher specific resistance than the upper and lower portions. This creates local heating zones that preferentially heat the intermediate portion first, improving defogging efficiency without requiring high-temperature laser processing that would soften the resin base.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the electrical parameter (specific resistance) of the heating element to achieve non-uniform heating. By varying the specific resistance along the heating element, different regions generate different amounts of heat when current flows through, enabling preferential heating of the intermediate portion without increasing overall temperature.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If transparent conductive thin film with varied specific resistance is used, then preferential heating of intermediate portion is achieved, but manufacturing complexity increases due to laser beam processing

Engineering Contradiction:

Improvepreferential heating capabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The invention replaces the complex laser beam processing system with a simpler approach of varying the specific resistance of the transparent conductive thin film during conventional sputtering deposition. This is achieved by controlling the deposition conditions (such as substrate temperature or deposition rate) in different regions, eliminating the need for post-deposition laser heating while achieving the same preferential heating effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If uniform specific resistance heating element is used, then manufacturing is simplified, but preferential heating of intermediate portion cannot be achieved

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoiddefogging efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The heating element incorporates a non-uniform specific resistance distribution where the intermediate portion has higher specific resistance than the upper and lower portions. This local variation in electrical property enables preferential heating of the intermediate region, improving defogging efficiency while maintaining a relatively simple manufacturing process through controlled sputtering deposition.

Inventive Principle:

Principle #3Local quality

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 enables preferential heating of desired areas and uniform heating of the window surface, improving visibility and reducing the need for high-temperature processing, making it suitable for vehicle windows with defogger functions.

Implementation Method 1

a heating element formed of a conductive sheet having a uniform specific resistance... when a current is passed through the heating element from the current supply portion, a locally increased specific resistance portion is generated

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a heat dissipation-preventing member provided on a surface of the heating element... to prevent heat generated from the heating element by passage of a current to the heating element from escaping outside

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS9769882B2Planar heating element for window and window for vehicle

Publication Date: 2017.09.19 TOYOTA INDUSTRIES CORP

AI summary

A planar heating element for a window includes a resin base having a flat or curved surface, a heating element formed of a conductive sheet having a uniform specific resistance and provided to spread in the form of a planar shape along the shape of the surface of the resin base, and conductive current supply portions provided to extend in the form of bands on opposite ends of the heating element, so as to allow a current to pass through the heating element. The heating element has a locally increased specific resistance portion whose specific resistance locally increases when a current is passed through the heating element from the current supply portions.