Engine Control Motoring for Catalyst Oxygen Occlusion

Solution Overview

Problem

The existing control systems for internal combustion engines with three-way catalysts face challenges in simultaneously removing hydrocarbon (HC) and carbon monoxide (CO) and nitrogen oxides (NOx) immediately after startup, due to oxygen occlusion in the catalysts, which impairs the NOx removal function and leads to NOx discharge.

Innovation Solution

A control system that includes a first and second three-way catalyst in series, with an electronic control unit managing motoring to limit oxygen occlusion in the first catalyst, preventing oxygen flow to the second catalyst, and adjusting fuel injection to optimize air-fuel ratios, ensuring effective removal of HC and CO by the first catalyst and NOx by the second catalyst upon engine restart.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If motoring is performed to supply oxygen to resolve HC poisoning or S poisoning in the three-way catalyst, then the removal of HC or CO is promoted, but the oxygen occlusion amount of the catalyst increases excessively

Engineering Contradiction:

Improveremoval of HC or COVSAvoidoxygen occlusion amount

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent controls the oxygen occlusion amount by adjusting motoring parameters (rotation speed, duration) to maintain oxygen storage within an optimal range that resolves poisoning without excessive accumulation. The ECU dynamically changes motoring conditions based on catalyst state to balance HC removal promotion with oxygen occlusion control.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If oxygen is supplied to the three-way catalyst by motoring, then HC poisoning or S poisoning is resolved, but the NOx removal function cannot be sufficiently exhibited after restart

Engineering Contradiction:

Improveresolution of HC poisoning or S poisoningVSAvoidNOx discharge

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent controls the oxygen occlusion amount by adjusting motoring parameters (rotation speed, duration) to maintain oxygen storage within an optimal range that resolves poisoning without excessive accumulation. The ECU dynamically changes motoring conditions based on catalyst state to balance HC removal promotion with oxygen occlusion control.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system uses feedback from oxygen sensors and catalyst temperature sensors to monitor catalyst state and adjust motoring duration and intensity accordingly. This closed-loop control ensures oxygen is supplied sufficiently to resolve poisoning but not excessive amounts that would impair NOx removal.

Inventive Principle:

Principle #23Feedback

3Quantity of substance

If fuel injection is stopped during motoring, then oxygen is supplied to the catalyst, but air mixes with exhaust gas causing lean air-fuel ratio that reduces NOx removal efficiency

Engineering Contradiction:

Improveoxygen supply to catalystVSAvoidNOx discharge

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent controls the oxygen occlusion amount by adjusting motoring parameters (rotation speed, duration) to maintain oxygen storage within an optimal range that resolves poisoning without excessive accumulation. The ECU dynamically changes motoring conditions based on catalyst state to balance HC removal promotion with oxygen occlusion control.

Inventive Principle:

Principle #35Parameter changes

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 approach enables simultaneous and efficient removal of HC, CO, and NOx immediately after engine startup, maintaining catalyst performance and reducing NOx emissions by controlling oxygen occlusion and air-fuel ratios.

Implementation Method 1

removal (oxidation) of HC or CO in the three-way catalyst

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

NOx removal function (NOx reduction function) of the three-way catalyst

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 3

an excess of oxygen that is not consumed to resolve the HC poisoning or S poisoning is occluded in the three-way catalyst

Methodology Applied

Scientific EffectOcclusion: Absorption (physical)

Data Source

PatentEP3450734B1Control system for internal combustion engine

Publication Date: 2020.12.16 TOYOTA JIDOSHA KK

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AI summary

In a control system for an internal combustion engine (1), the internal combustion engine (1) includes a first exhaust catalyst (40) that is a three-way catalyst disposed in an exhaust path (4) of the internal combustion engine (1), a second exhaust catalyst (41) that is a three-way catalyst disposed in the exhaust path (4) on a downstream side of the first exhaust catalyst (40), and a motor configured to drive the internal combustion engine (1). The control system includes an electronic control unit (5) configured to, when operation of the internal combustion engine (1) is stopped, stop fuel injection in the internal combustion engine (1) and then, execute motoring in which the internal combustion engine (1) is rotationally driven using drive power of the motor, and execute the motoring in a range in which an oxygen occlusion amount of the first exhaust catalyst (40) becomes an oxygen occlusion amount smaller than an upper limit oxygen occlusion amount of the first exhaust catalyst (40).