Catalyst Deterioration Detection via Air-Fuel Ratio Switching Control
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Solution Overview
Problem
Conventional catalyst deterioration determination systems may erroneously determine deterioration of a three-way catalyst due to fuel injection timing retardation or divided injection during the warm-up state of an internal combustion engine, leading to inaccurate assessments.
Innovation Solution
A catalyst deterioration determination system that includes a first oxygen concentration sensor upstream of the catalyst, a second oxygen concentration sensor downstream, and an electronic control unit (ECU) performing air-fuel ratio switching control and prohibiting fuel injection timing retardation and divided injection during deterioration determination, ensuring accurate oxygen inflow calculation and air-fuel ratio management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fuel injection timing is retarded or fuel is injected in a divided manner during warm-up state, then combustion stability is improved, but catalyst deterioration determination accuracy deteriorates due to erroneous detection
Solution Approach 1:
The system applies preliminary anti-action by detecting the fuel injection mode beforehand and prohibiting retard control and divided injection control when catalyst deterioration determination is being performed. This prevents the harmful effects of retarded injection timing and divided injection on the determination accuracy before they can occur.
Solution Approach 2:
The system dynamically adjusts the fuel injection control strategy based on the operational state. When catalyst deterioration determination is required, the control mode is switched to prohibit retarded timing and divided injection, while allowing these modes during normal operation for combustion stability.
2Reliability
If air-fuel ratio switching control is performed during warm-up state with retarded injection timing, then oxygen storage capacity testing is enabled, but false deterioration signals are generated
Solution Approach 1:
The ECU detects whether retard control or divided injection control is being performed before conducting catalyst deterioration determination. When these control modes are detected, the system prohibits the deterioration determination process, thereby preventing false deterioration signals from being generated while still allowing oxygen storage capacity testing under appropriate conditions.
3Productivity
If divided injection control is used during warm-up, then fuel combustion efficiency is improved, but local fuel richness causes erroneous catalyst status detection
Solution Approach 1:
The system performs preliminary detection of the fuel injection mode and prohibits catalyst deterioration determination when divided injection control is active. This prevents local fuel richness caused by divided injection from creating erroneous deterioration signals, while maintaining the benefits of divided injection for combustion efficiency during warm-up.
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
Prevents erroneous determination of catalyst deterioration by suppressing local fuel richness and accurately performing air-fuel ratio switching control, thereby improving the accuracy of catalyst deterioration assessment.
Implementation Method 1
a first oxygen concentration sensor (LAF sensor 27) that is provided on the upstream side of the catalyst
Implementation Method 2
a second oxygen concentration sensor (O2 sensor 28) that is provided on the downstream side of the catalyst
Implementation Method 3
a catalyst (three-way catalyst 14a) provided in an exhaust system (exhaust passage 12 in the embodiment (the same applies hereinafter in the paragraph)) of an internal combustion engine 1, having an oxygen storing capacity
Data Source
AI summary
A catalyst deterioration determination system effectively prevents erroneous determination caused by increase of the H2 component in exhaust gas and improves accuracy of determination. A LAF sensor and an O2 sensor are provided on the upstream side and downstream side of a three-way catalyst. Deterioration of the three-way catalyst is determined on the basis of an output of the O2 sensor, which is detected during air-fuel ratio switching control in which an air-fuel ratio is alternately switched to the rich side and lean side of the stoichiometric air-fuel ratio according to a detected equivalent ratio detected by the LAF sensor, on the basis of a result of comparison between an oxygen inflow into the three-way catalyst and a lean side-limiting value and a rich side-limiting value which are target values of the oxygen inflow. Fuel injection timing retardation control and/or divided fuel injection control are prohibited during the deterioration determination.