Cylinder-Specific Post-Injection Control for NOx Catalyst Regeneration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing air-fuel ratio control methods for internal combustion engines, particularly in lean combustion states, often result in excess post-injection amounts leading to undesired combustion such as excess HC and soot production due to the reliance on a single lambda sensor for determining post-injection amounts across all cylinders.
Innovation Solution
The method involves using exhaust temperature sensors for each cylinder to estimate air-fuel ratios and adjust post-injection amounts accordingly, eliminating the need for a lambda sensor per cylinder and enabling more precise and efficient post-injection control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one unit of lambda sensor is used to control post-injection amount for all cylinders, then device complexity and cost are reduced, but manufacturing precision and reliability of post-injection control deteriorate due to air-fuel ratio differences among cylinders
Solution Approach 1:
The patent introduces exhaust gas temperature as an intermediary parameter to indirectly estimate air-fuel ratio for each cylinder. Instead of directly measuring air-fuel ratio with lambda sensors, the system uses temperature sensors to detect exhaust gas temperature, which serves as a mediator reflecting the combustion state and air-fuel ratio conditions in each cylinder, enabling precise control without additional lambda sensors
Solution Approach 2:
The patent replaces the chemical sensing system (lambda sensors) with a thermal sensing system (exhaust gas temperature sensors). By substituting the direct electrochemical measurement of air-fuel ratio with indirect thermal measurement of exhaust gas temperature, the system achieves similar control functionality while avoiding the cost and complexity of multiple lambda sensors
2Device complexity
If post-injection amount is controlled based on representative value from one lambda sensor, then device complexity is reduced, but injection efficiency deteriorates due to excess post-injection amount in some cylinders
Solution Approach 1:
The patent segments the post-injection control from a unified cylinder-agnostic approach to an individual cylinder-specific approach. By dividing the control strategy into cylinder-level units, each cylinder receives customized post-injection amounts based on its own exhaust gas temperature characteristics, eliminating the inefficiencies caused by using a single representative value for all cylinders
Solution Approach 2:
The patent applies local quality by making post-injection control parameters specific to each cylinder's local conditions. Instead of applying a uniform post-injection strategy across all cylinders, the system adjusts post-injection amounts according to the specific exhaust gas temperature and combustion characteristics of each individual cylinder, optimizing injection efficiency locally
3Ease of operation
If excess post-injection amount is supplied to achieve target air-fuel ratio, then air-fuel ratio control is simplified, but harmful factors increase due to excess HC and soot production
Solution Approach 1:
The patent implements feedback control by continuously monitoring exhaust gas temperature and using this information to adjust post-injection amounts. The system measures the actual combustion state through temperature sensors and dynamically modifies post-injection strategy to maintain optimal air-fuel ratios, preventing both excess and insufficient post-injection conditions that would respectively cause harmful emissions or fail to regenerate the catalyst
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 appropriate post-injection amounts to be set for each cylinder, enhancing injection efficiency and stability, thereby reducing undesired combustion and improving the reliability of exhaust gas purification devices.
Implementation Method 1
an exhaust temperature sensor on the upstream side of a NOx catalyst is used for detecting an information reflecting a post-injection amount
Implementation Method 2
a nitrogen oxide occlusion catalyst that occludes nitrogen oxides reaches a saturated state
Implementation Method 3
the engine is brought into an over-rich combustion (rich combustion) state before the nitrogen oxide occlusion catalyst
Data Source
Figure 1
Figure 2
Figure 3
AI summary
To improve injection efficiency and stability of post injection required for regeneration of a nitrogen oxide occlusion catalyst. An average post-injection amount as a post-injection amount that is unambiguously determined for each cylinder on the basis of PID control, an-air fuel ratio detected by a lambda sensor, and a target average air-fuel ratio as a target air-fuel ratio is computed (S100). Next, a post-injection deviation by cylinder that corresponds to an excess/shortage amount in a post-injection amount for each of the cylinders with respect to the average post-injection amount is computed on the basis of a characteristic deviation by cylinder that corresponds to a variation in the air-fuel ratio of each of the cylinders (S200 and S300). Post injection is performed by setting an addition result of the average post-injection amount and the post-injection deviation by cylinder as a post-injection amount by cylinder that is the post-injection amount required for each of the cylinders to realize the target average air-fuel ratio.