Engine EGR Control Synchronizing Intake Air to Prevent Torque Steps
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Solution Overview
Problem
Existing internal combustion engine control systems face challenges in managing torque steps caused by transient changes in intake air quantity during the start and stop of Exhaust Gas Recirculation (EGR), particularly in supercharging and non-supercharging regions, leading to deteriorated drivability due to response delays in EGR ratio changes.
Innovation Solution
A control device that predicts the change in EGR ratio in the cylinder and adjusts the intake control devices, such as the waste gate valve or throttle valve, based on this prediction to synchronize the intake air quantity with the EGR ratio change, thereby preventing torque steps without distinction between supercharging and non-supercharging regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening degree of the EGR control valve is changed to control EGR ratio, then exhaust performance and fuel economy are improved, but torque steps occur due to transient changes in intake air quantity
Solution Approach 1:
The system performs preliminary action by predicting the future EGR ratio at the cylinder based on current intake system conditions and airflow dynamics. This prediction allows the control system to prepare appropriate intake air quantity adjustments in advance, preventing torque steps before they occur during EGR valve transitions.
Solution Approach 2:
The control system implements feedback by continuously monitoring actual EGR ratio, intake air quantity, and engine operating conditions. This feedback loop enables real-time comparison between predicted and actual EGR ratios, allowing dynamic adjustment of intake control devices to maintain stable torque output during EGR operations.
2Reliability
If the EGR ratio is controlled based on cylinder EGR ratio, then exhaust performance is improved, but response delay occurs due to the time required for fresh air quantity to change in the cylinder
Solution Approach 1:
The system calculates the predicted EGR ratio at a predetermined position in the intake system in advance of when the cylinder EGR ratio actually changes. This preliminary calculation, based on airflow measurements and system dynamics models, provides early warning of upcoming EGR ratio changes, enabling the control system to respond before the cylinder experiences the full effect, thereby reducing perceived response delay.
Solution Approach 2:
The invention introduces a spatial dimension to EGR ratio monitoring by measuring and predicting EGR ratio at a predetermined position in the intake system rather than directly at the cylinder. This dimensional shift allows the control system to anticipate changes before they reach the cylinder, effectively compensating for transport delays in the EGR gas flow.
3Object-generated harmful factors
If the intake control device adjusts quantity of intake air quickly, then torque step is suppressed, but fresh air quantity in cylinder becomes unstable
Solution Approach 1:
The control system uses feedback from both the predicted EGR ratio and actual engine operating conditions to dynamically adjust intake air quantity. This closed-loop control ensures that fresh air quantity adjustments are made in precise proportion to EGR ratio changes, maintaining stability while preventing torque steps.
Solution Approach 2:
The system changes multiple parameters simultaneously - adjusting intake air quantity, monitoring EGR valve opening degree, and modifying predicted EGR ratio calculations - to achieve smooth torque transitions. By coordinating changes across these parameters, the system suppresses torque steps while maintaining fresh air quantity stability in the cylinder.
Data Source
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AI summary
In a case where EGR is started in a supercharging region, an opening degree of a waste gate valve (17) is changed at a timing T1 at which an EGR ratio in a first predetermined position changes by valve open of an EGR control valve (21). In a case where EGR is started in a non-supercharging region, a throttle valve (5) is changed at a timing T2 at which an EGR ratio in a second predetermined position changes by valve open of the EGR control valve (21). With these controls, it is possible to suppress an occurrence of torque step upon start of the EGR without distinction between the supercharging region and the non-supercharging region.