Vehicle Engine Cranking Torque Control for Coasting Restart
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Solution Overview
Problem
Engines may not properly restart during coasting if the throttle position is small, leading to misfire due to excessive fuel injection relative to intake air, and increasing intake air to avoid misfire results in abrupt driving force increases.
Innovation Solution
A vehicle with an engine and a motor that generates cranking torque, controlled by a device adjusting the target torque based on engine rotation speed to maintain a region where misfire is avoided without increasing intake air, during engine starting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of fuel injected from the injector is reduced to avoid misfire, then misfire can be avoided, but the engine may still not restart properly if the fuel amount remains excessively large relative to intake air
Solution Approach 1:
The control device changes the target torque parameter based on engine rotation speed during coasting. When rotation speed is high (above threshold), the target torque is set lower to reduce cranking torque, which prevents excessive fuel injection relative to intake air and avoids misfire. When rotation speed is low (below threshold), the target torque is set higher to ensure sufficient fuel injection for proper engine restart.
2Reliability
If the amount of intake air is increased to avoid misfire, then misfire can be avoided, but an abrupt increase in driving force occurs at the time of engine restarting
Solution Approach 1:
Instead of changing intake air amount, the control device changes the target torque parameter based on engine rotation speed. During coasting with high rotation speed, the target torque is reduced to maintain stable driving force. This avoids the problem of abrupt driving force increase that would occur if intake air amount were increased, while still preventing misfire through controlled fuel injection.
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 engine rotation speed is maintained in a region that avoids misfire without increasing intake air, allowing for successful engine restart during coasting.
Implementation Method 1
a motor that can generate cranking torque applied to a rotation shaft of the engine
Data Source
AI summary
An ECU is mounted on a vehicle including an engine and a motor that can generate cranking torque applied to a rotation shaft of the engine. Where a request for starting the engine is not issued, the ECU determines whether the engine is during coasting or not. The ECU changes cranking target torque in accordance with engine rotation speed. In this way, engine rotation speed during cranking can be reduced to and remain in the optimum region where misfire and resonance can be avoided.