Exhaust Purification System Electrostatic PM Detection

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Solution Overview

Problem

Existing exhaust purification systems, such as diesel particulate filters (DPFs), face challenges in accurately estimating the amount of accumulated particulate matter due to decreased sensitivity at low exhaust gas flow rates and require individual electrode configuration, making them inflexible with varying DPF specifications.

Innovation Solution

An exhaust purification system that includes an oxidation catalyst, a filter downstream to collect particulate matter, an electrostatic capacity detecting unit to measure the electrostatic capacity of the oxidation catalyst, and a filter regenerating unit that performs forced regeneration by injecting fuel when the accumulated particulate matter exceeds a predetermined amount, using an electronic control unit to estimate and manage the regeneration process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the pressure difference method is used to estimate accumulated PM, then the estimation can be performed, but the sensitivity drops significantly at low exhaust gas flow rates making accurate estimation difficult

Engineering Contradiction:

ImprovePM accumulation estimation accuracyVSAvoidexhaust gas flow rate

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces the mechanical pressure difference measurement method with an electrostatic capacity measurement method. The electrostatic capacity between electrodes in the oxidation catalyst changes in response to PM accumulation, providing a measurement mechanism that is not dependent on exhaust gas flow rate, thus resolving the sensitivity drop issue at low flow rates.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If individual electrode configuration is used to match specific DPF specifications, then measurement accuracy can be optimized, but the system becomes inflexible and complex to adapt to varying DPF specifications

Engineering Contradiction:

ImprovePM accumulation estimation accuracyVSAvoidflexibility with DPF specifications

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal measurement system where the electrostatic capacity detection method can be applied to different DPF specifications without requiring individual electrode configuration. The oxidation catalyst's inherent electrostatic capacity serves as a universal sensor for PM accumulation across various DPF designs, eliminating the need for custom electrode arrangements for each specification.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If additional sensors are added to improve detection accuracy, then measurement precision improves, but the apparatus size and cost increase

Engineering Contradiction:

ImprovePM accumulation detection accuracyVSAvoidapparatus size and sensor quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the oxidation catalyst itself serve as the detection sensor by utilizing its inherent electrostatic capacity. Instead of adding separate sensors to measure PM accumulation, the system uses the oxidation catalyst's own electrical properties (electrostatic capacity between its electrodes) as the detection mechanism, thereby avoiding additional sensors and reducing apparatus complexity.

Inventive Principle:

Principle #25Self-service

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 system accurately detects and manages the accumulation of particulate matter in DPFs, maintaining high sensitivity even at low exhaust gas flow rates and varying conditions, optimizing regeneration efficiency without the need for additional sensors, thus reducing costs and apparatus size.

Implementation Method 1

an electrostatic capacity detecting unit that detects an electrostatic capacity (capacitance) of the oxidation catalyst

Methodology Applied

Scientific EffectElectrostatic capacity (capacitance): Capacitance

Implementation Method 2

a filter provided in the exhaust passage at a position downstream of the oxidation catalyst to collect particulate matter contained in exhaust gas

Methodology Applied

Scientific EffectPhysical filtration: Filter (physical)

Implementation Method 3

a filter regenerating unit that executes a forced regeneration to burn and remove the particulate matter that has accumulated at least in the filter

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 4

by injecting fuel to the oxidation catalyst when the amount of the accumulated particulate matter entered from the accumulation amount estimating unit exceeds a predetermined amount

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS9784200B2Exhaust purification system

Publication Date: 2017.10.10 ISUZU MOTORS LTD

AI summary

An exhaust purification system includes: a diesel oxidation catalyst (DOC) provided on an exhaust passage of an engine; a diesel particulate filter (DPF) provided on the exhaust passage at a position downstream of the DOC to collect particulate matter contained in exhaust gas; electrodes that detect a capacitance of the DOC; a particulate matter accumulation estimating unit that estimates an amount of particulate matter accumulated in the DPF on the basis of the detected capacitance; and a forced regeneration control unit that injects fuel into the DOC and performs forced regeneration that burns and removes at least the particulate matter accumulated in the DPF when the estimated accumulated particulate matter amount surpasses a predetermined amount.