ISC Valve Timing Control for Torque Reduction and Combustion Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In internal combustion engines with superchargers, reducing output torque while preventing ignition timing delays that can lead to unstable combustion and emissions, especially when the actual intake air amount exceeds the target, is challenging due to limited ignition timing margin and potential fuel backflow through the ISC valve.
Innovation Solution
A control device that fully opens the ISC valve when the predicted generation torque exceeds the request torque and the downstream intake pressure is higher than the upstream pressure, causing intake air to flow back and reducing torque, while prohibiting lean combustion operations to stabilize combustion and prevent fuel backflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the ISC valve is opened to reduce torque when actual intake air exceeds target, then torque can be reduced, but fuel may backflow through the ISC passage causing unstable combustion and worsening emissions
Solution Approach 1:
The patent introduces an intermediary control mechanism that monitors the opening/closing timing of the ISC valve relative to the intake valve. By coordinating these two valve operations, the system ensures that the ISC valve closes before the intake valve opens, preventing fuel backflow while maintaining the torque reduction benefit. This intermediary timing control resolves the contradiction between torque reduction and combustion stability.
Solution Approach 2:
The control device uses feedback from sensors monitoring intake air amount, torque output, and valve positions to dynamically adjust ISC valve timing. When fuel backflow is detected or predicted (based on pressure differential and valve timing data), the system adjusts the ISC valve closing timing to prevent backflow while maintaining torque control. This feedback mechanism resolves the contradiction by continuously optimizing valve timing based on actual operating conditions.
2Power
If ignition timing is delayed to reduce torque when actual intake air exceeds target, then torque reduction is achieved, but the margin to delay limit is small and torque cannot be sufficiently reduced
Solution Approach 1:
The patent segments the torque control function into two independent control mechanisms: ignition timing control and ISC valve control. Ignition timing provides fine-grained torque adjustment within its limited range, while the ISC valve provides additional torque reduction capability by controlling intake air amount. This segmentation allows the system to achieve broader torque control range without compromising the precision of ignition timing control.
Solution Approach 2:
The control device merges two torque control methods (ignition timing control and ISC valve control) into a unified control strategy. When torque reduction is needed beyond what ignition timing delay can provide, the system activates the ISC valve control as a complementary mechanism. This merging expands the overall torque control range while maintaining the advantages of both control methods.
3Quantity of substance
If the ISC valve is opened to cause intake air to flow back, then the amount of intake air flowing into the cylinder is reduced, but the intake air flowing back in the ISC passage causes fuel backflow and unstable combustion
Solution Approach 1:
The control device performs preliminary action by setting the ISC valve closing timing to occur before the intake valve opening timing. This preliminary closing of the ISC valve prevents the pressure differential that would cause fuel backflow, while still allowing the ISC valve to open during operation to reduce intake air amount and control torque. This preliminary timing arrangement eliminates fuel backflow while preserving the beneficial intake air control function.
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 effectively reduces torque variation by controlling the ISC valve to prevent fuel backflow, ensuring stable combustion and improved emissions by switching to stoichiometric combustion during ISC valve full opening control.
Implementation Method 1
when the downstream intake pressure is higher than the upstream pressure... causing intake air to flow back
Implementation Method 2
switching to stoichiometric combustion during ISC valve full opening control
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An internal combustion engine of the present invention is an internal combustion engine equipped with port injectors. Further, the internal combustion engine has an ISC passage that connects an upstream side and a downstream side of a throttle valve in an intake passage, and an ISC valve that regulates an amount of air flowing in the ISC passage. A control device of the present invention performs valve opening control that makes an opening degree of the ISC valve an opening degree larger than a reference opening degree when request torque required by the internal combustion engine is smaller than estimated torque that can be generated in the internal combustion engine, and sets a timing for fuel injection from the port injector at an opening timing of an intake valve of a cylinder in which the port injector is installed during the valve opening control.