Honeycomb Heating Device with Intermediate Members for Thermal Stress Management

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Solution Overview

Problem

Existing honeycomb heating devices for catalysts in exhaust gas purification systems face challenges in efficiently heating the catalyst to active temperature, especially in low-engine-start-frequency vehicles, due to durability issues and thermal stress, leading to inadequate exhaust gas purification immediately after engine start.

Innovation Solution

A honeycomb type heating device with pillar-shaped substrate, resistance heating type heaters, and intermediate members with high thermal conductivity and Young's modulus, covering 20-100% of the heater area, to efficiently transmit heat and withstand thermal stress, ensuring the catalyst reaches active temperature before engine start.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a tubular resistance heating type heater is arranged to surround the circumferential wall of the honeycomb structure, then the honeycomb structure can be heated externally, but the heater is easily damaged due to thermal stress

Engineering Contradiction:

Improvehoneycomb structure temperatureVSAvoidheater durability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The single tubular heater is divided into multiple resistance heating elements arranged adjacently on the circumferential face. Each heater is independent, so if one is damaged, others continue functioning. This segmentation reduces thermal stress on individual heaters while maintaining heating capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Heaters are arranged at specific locations on the circumferential face rather than surrounding the entire structure. The local heating approach allows targeted heat application while reducing overall thermal stress on the heater system.

Inventive Principle:

Principle #3Local quality

2Temperature

If a monolithic resistance heating type heater is used, then heating can be provided, but thermal resistance between the heater and honeycomb structure surface is large due to gaps and surface unevenness

Engineering Contradiction:

Improvehoneycomb structure temperatureVSAvoidheat transmission efficiency

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

Heaters are arranged adjacently to cover the circumferential face, with intermediate members filling gaps between heaters and the honeycomb structure surface. This local contact approach ensures efficient heat transmission at each heating point while accommodating surface unevenness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Intermediate members are introduced between the heaters and the honeycomb structure circumferential face. These intermediaries improve thermal contact by filling gaps and adapting to surface unevenness, thereby reducing thermal resistance and enhancing heat transmission efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Temperature

If the honeycomb structure itself generates heat by energization, then heating can be achieved, but a slight crack causes current path variation and temperature distribution problems

Engineering Contradiction:

Improvehoneycomb structure temperatureVSAvoidtemperature distribution stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The heating function is segmented from the honeycomb structure itself and placed in separate adjacent heaters. This external heating approach eliminates the problem of current path variation through cracks in the honeycomb structure, as the heaters are independent of the structure's integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate members serve as thermal mediators between the external heaters and the honeycomb structure, enabling efficient heat transfer without requiring electrical contact through the structure, thus avoiding current path issues.

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 ensures efficient heat transfer to the honeycomb substrate, maintaining temperature stability even with slight cracks and damaged heaters, effectively purifying exhaust gas immediately after engine start by ensuring the catalyst is at active temperature.

Implementation Method 1

resistance heating type heaters... by causing each of a plurality of heaters to generate heat

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

intermediate members having high thermal conductivity... to efficiently transmit heat

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9976466B2Honeycomb type heating device, method of using the same, and method of manufacturing the same

Publication Date: 2018.05.22 NGK INSULATORS LTD

AI summary

There is provided a honeycomb type heating device including: a pillar-shaped honeycomb substrate having a partition wall defining a plurality of cells extending from one end face to the other end face and a circumferential wall surrounding the partition wall; a plurality of heaters adjacently arranged on a circumferential face that is an outside surface of the circumferential wall in a circumferential direction of the circumferential face; and intermediate members interposed between the circumferential face of the honeycomb substrate and the plurality of heaters. The sum of areas of portions of the circumferential face covered with the intermediate members between the circumferential face of the honeycomb substrate and the plurality of heaters is 20 to 100% of the sum of areas of portions of the circumferential face covered with the plurality of heaters.