EGR Valve and Intake Throttle Coordination for Torque Stability
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Solution Overview
Problem
Existing engine systems with exhaust gas recirculation (EGR) face delays and transient torque changes due to slow EGR valve adjustments, leading to degraded engine performance and emissions, as the distributed position of EGR valves and throttles cause inefficiencies in EGR flow control.
Innovation Solution
A method involving an EGR passage with an oxygen sensor to adjust both the EGR valve and first intake throttle in concert, using a model to compensate for delays in dilution propagation, allowing for simultaneous or sequential adjustments to achieve precise and rapid EGR flow control, while coordinating with a second main intake throttle to maintain desired torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EGR valve adjustments are made in response to oxygen sensor output, then EGR emissions control is improved, but response delay occurs due to distributed position of EGR valves and throttles
Solution Approach 1:
The system performs preliminary action by adjusting the first intake throttle in advance to facilitate faster EGR flow changes. By pre-positioning the first intake throttle based on predicted EGR requirements and oxygen sensor trends, the system reduces the time lag between detecting EGR dilution needs and achieving the desired EGR flow, thus resolving the contradiction between reliable emissions control and response speed.
2Reliability
If EGR valve adjustments are made to control EGR flow, then EGR emissions control is improved, but transient torque changes occur
Solution Approach 1:
The system applies preliminary anti-action by using the second intake throttle to preemptively counteract transient torque changes. When EGR valve adjustments are made to improve emissions control, the second intake throttle is simultaneously adjusted in the opposite direction to compensate for torque disturbances, thus eliminating the harmful transient torque changes while maintaining effective EGR emissions control.
3Measurement precision
If multiple sensors are used to accurately estimate EGR flow, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system applies universality by making the oxygen sensor perform multiple functions: it not only measures oxygen content for traditional combustion control but also serves as the primary sensor for EGR flow estimation. By processing oxygen sensor output in conjunction with intake throttle positions and engine operating parameters, the system achieves accurate EGR flow measurement without adding dedicated EGR sensors, thus maintaining measurement precision while reducing device complexity.
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 faster and more precise EGR flow control, reducing transient torque disturbances and improving engine performance by coordinating EGR valve and throttle adjustments, even when one actuator is limited or in a non-linear region, using a single oxygen sensor to infer dilution and reduce the need for multiple sensors.
Implementation Method 1
an oxygen sensor positioned in the engine intake gas stream, downstream of the mixing point of the EGR valve and the first intake throttle, and upstream of a second main intake throttle
Implementation Method 2
fresh air may be mixed with exhaust gas from the EGR passage at a mixing point in the intake passage, upstream of the compressor, to provide a desired EGR dilution and desired EGR flow
Data Source
AI summary
Methods and systems are provided for adjusting an EGR valve and one or more intake throttles responsive to the output of an intake oxygen sensor to provide a desired amount of EGR flow while maintaining engine torque. The adjustments are coordinated to improve distributed control of the EGR valves and intake throttles, and enable EGR flow even when one actuator is limited.