Engine Valve Overlap Control for NOx Purification
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Solution Overview
Problem
The rich spike control in internal combustion engines may not function effectively in high-torque ranges, leading to scavenging which reduces NOx purification efficiency by oxidizing reduction agents with high oxygen concentrations.
Innovation Solution
A control device that adjusts the overlap amount between the intake and exhaust valves during rich spike control, reducing scavenging by decreasing the overlap amount when intake pressure is higher than exhaust pressure, and maintaining or increasing the overlap when exhaust pressure is higher, to optimize air flow and reduce oxygen reaction with reduction agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If rich spike control is executed in high-torque range with advanced intake valve timing, then intake efficiency is enhanced, but scavenging occurs causing oxygen to oxidize reduction agents and deteriorate NOx purification efficiency
Solution Approach 1:
The patent applies dynamics by making the valve overlap amount adjustable based on operating conditions. The ECU dynamically changes the overlap amount between intake and exhaust valves depending on whether rich spike control is executed and the engine's torque range, allowing the system to adapt to different operational states and prevent scavenging during rich spike control while maintaining high intake efficiency during normal operation
Solution Approach 2:
The patent changes the parameter of valve overlap amount to resolve the contradiction. By reducing the overlap amount during rich spike control execution in high-torque range, the patent prevents excessive air flow from intake to exhaust ports, thereby preventing oxidation of reduction agents and maintaining NOx purification efficiency, while allowing larger overlap amounts during normal operation to maintain intake efficiency
2Power
If valve overlap amount is increased to enhance intake efficiency in high-torque range, then power output is improved, but scavenging causes oxygen to react with reduction agents reducing NOx purification
Solution Approach 1:
The system dynamically adjusts the valve overlap amount based on real-time operating conditions. During rich spike control execution in high-torque range, the overlap amount is reduced to prevent scavenging and protect NOx purification efficiency, while during normal high-torque operation, the overlap amount is maintained at higher levels to ensure adequate intake efficiency and power output
Solution Approach 2:
The patent changes the valve overlap parameter conditionally based on control mode and operating range. The ECU monitors whether rich spike control is executing and the current torque range, then adjusts the overlap amount accordingly - reducing it during rich spike control to prevent harmful oxidation reactions, while maintaining larger overlap for optimal power delivery during normal operation
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
The control device effectively maintains NOx purification efficiency by reducing oxygen reaction with reduction agents and promoting direct or indirect reactions between reduction agents and NOx, preventing NOx discharge into the atmosphere.
Implementation Method 1
The NO x storage-reduction catalyst can store NO x in exhaust gas under a lean atmosphere with excessive oxygen
Implementation Method 2
The selective catalytic reduction catalyst has a function for adsorbing ammonia (NH3)
Implementation Method 3
by supplying a reduction agent from an upstream side of the exhaust flow, NOx stored inside the apparatus can be purified by reducing NOx to N2
Data Source
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AI summary
A control device for an engine, the engine includes an exhaust gas control apparatus that is configured to store NOx and react NOx with a reduction agent. The control device includes an electronic control unit. The electronic control unit is configured to: (i) execute a rich spike control, the rich spike control is a control executed to temporarily change an in-cylinder air-fuel ratio from a leaner air-fuel ratio than the stoichiometric air- fuel ratio to the stoichiometric air- fuel ratio or a richer air-fuel ratio than the stoichiometric air-fuel ratio, and (ii) vary an overlap amount of an intake valve and an exhaust valve such that the overlap amount is less during non-execution of the rich spike control than during execution of the rich spike control, in an operation range where a pressure of the intake port becomes higher than a pressure of the exhaust port.