Spark Ignition Catalyst Diagnosis via Deceleration Oxygen Storage
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Solution Overview
Problem
Existing methods for diagnosing post-treatment systems in spark-ignition engines, particularly those involving three-way catalysts and oxygen sensors, are intrusive and disrupt normal engine operation, leading to increased emissions and decreased driving pleasure, and are limited by requiring stable engine conditions, which are not always feasible, especially for large volume catalysts.
Innovation Solution
A method that opportunistically calculates the oxygen storage capacity of the catalyst during phases when the accelerator pedal is lifted, cutting off fuel injection and opening the throttle body to quickly saturate the catalyst with oxygen, allowing for non-intrusive diagnosis by detecting when the catalyst is empty and calculating the oxygen storage capacity during these phases, using a proportional upstream oxygen sensor and a binary downstream oxygen sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intrusive diagnostic methods are used to calculate oxygen storage capacity, then diagnosis accuracy is improved, but engine emissions increase and driving pleasure decreases
Solution Approach 1:
The system prepares the catalyst for diagnosis by creating favorable conditions in advance - specifically, it waits for and identifies deceleration phases where the catalyst is naturally empty of oxygen, then initiates the diagnostic calculation during this pre-prepared state, avoiding the need to forcibly empty the catalyst through intrusive rich mixture injections
Solution Approach 2:
The invention converts normally wasted deceleration phases (where fuel injection is already cut off and the catalyst naturally empties of oxygen) into beneficial diagnostic opportunities. These phases that would otherwise be idle time are transformed into effective diagnostic windows, turning a passive state into an active diagnostic resource
2Measurement precision
If intrusive diagnostic methods are used to calculate oxygen storage capacity, then diagnosis accuracy is improved, but driving pleasure decreases
Solution Approach 1:
The system prepares the catalyst for diagnosis by creating favorable conditions in advance - specifically, it waits for and identifies deceleration phases where the catalyst is naturally empty of oxygen, then initiates the diagnostic calculation during this pre-prepared state, avoiding the need to forcibly empty the catalyst through intrusive rich mixture injections
Solution Approach 2:
The invention converts normally wasted deceleration phases (where fuel injection is already cut off and the catalyst naturally empties of oxygen) into beneficial diagnostic opportunities. These phases that would otherwise be idle time are transformed into effective diagnostic windows, turning a passive state into an active diagnostic resource
3Reliability
If diagnostic methods requiring stable engine conditions are used, then measurement reliability is improved, but diagnostic frequency is reduced
Solution Approach 1:
The invention transitions from static diagnostic requirements (stable engine conditions) to dynamic opportunistic diagnosis. The system adapts to changing engine conditions by identifying and utilizing deceleration phases that naturally occur during normal driving, allowing diagnosis to proceed under varying rather than fixed conditions
Solution Approach 2:
The system uses the engine's own operational characteristics (deceleration phases with fuel injection cutoff) to create diagnostic conditions, rather than requiring external intervention or stable conditions. The normal driving cycle itself provides the diagnostic opportunity
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 allows for more frequent and accurate diagnosis of the catalyst and downstream oxygen sensor without disrupting normal engine operation, reducing emissions and improving driving experience, and can be performed under various engine conditions, including transient ones.
Implementation Method 1
an upstream oxygen sensor (9) proportional type to regulate the richness of the air/fuel mixture to be introduced into the engine (2)
Implementation Method 2
a downstream oxygen sensor (10) of binary type mounted on the exhaust line downstream of the catalyst (8)
Implementation Method 3
the management of the quantity of oxygen (or: OS, for "Oxygen Storage") which is present in the catalyst
Implementation Method 4
The post-treatment of polluting emissions from spark-ignition engines with oxidation-reduction catalysis
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for diagnosing an after-treatment system of a spark ignition engine of a motor vehicle, comprising a three-way catalytic converter associated with a proportional upstream oxygen probe and a binary downstream probe. In order to diagnose the catalytic converter, its oxygen storage capacity (OSC) is calculated. According to the invention, said calculation is carried out during the phases of lifting the foot from the vehicle accelerator pedal, at the start of which it is observed that the catalytic converter is charged to less than 10% of its oxygen storage capacity. At this stage, the fuel injection is cut off and the engine throttle body is opened. The oxygen storage capacity (OSC) is calculated until the downstream probe switches to lean burn. Prior to the catalytic converter diagnosis, the upstream and downstream probes are diagnosed as being in good condition so as to avoid false readings.