Engine Limp-Home Fuel Injection Control for Stable Self-Travel
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Solution Overview
Problem
In engine devices with electronic throttle mechanisms, when a problem occurs, the engine enters a limp home mode where self-traveling is enabled, but the throttle valve cannot be electronically controlled, leading to unstable self-traveling due to variations in the default opening within the tolerance of the valve rotation mechanism unit.
Innovation Solution
An engine control device that includes a revolution speed detection unit and an arithmetic unit to calculate the throttle valve opening and fuel injection amount. In limp home mode, if the engine revolution speed exceeds a predetermined limiting value, the arithmetic unit suppresses fuel injection to maintain stable self-traveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the throttle valve opening is mechanically maintained at a default opening in limp home mode, then self-traveling is enabled, but the engine revolution speed becomes unstable due to variation within the tolerance of the valve rotation mechanism unit
Solution Approach 1:
The control device changes the fuel injection amount parameter based on the detected engine revolution speed. When the revolution speed exceeds the predetermined limiting value, the control device reduces the fuel injection amount to lower the engine output, thereby stabilizing the revolution speed. This dynamic parameter adjustment resolves the contradiction by allowing self-traveling while preventing excessive speed variation.
Solution Approach 2:
The control device implements a feedback mechanism where the revolution speed detection unit continuously monitors the engine revolution speed, and the arithmetic unit compares the detected speed with the predetermined limiting value. Based on this feedback, the control device adjusts the fuel injection amount to maintain stable self-traveling conditions, resolving the speed instability issue.
2Reliability
If the electronic throttle mechanism is deactivated in limp home mode, then the throttle valve can be mechanically maintained, but the precision of throttle valve opening control is lost
Solution Approach 1:
The control device acts as an intermediary by using fuel injection control to indirectly manage engine output and revolution speed. Instead of directly controlling the throttle valve opening (which would require the electronic mechanism), the system mediates through fuel injection amount adjustment to achieve the desired engine performance while maintaining the mechanically held throttle position.
Data Source
AI summary
Provided is an engine control device and an engine device that enable stable self-travelling of the engine in a limp home mode. The engine control device includes a revolution speed detection unit that detects revolution speed of the engine, and an arithmetic unit that calculates an opening of a throttle valve opened by an electronic throttle mechanism, and an injection amount of fuel injected by injectors. In an operation of the engine in the limp home mode, in a case where the revolution speed of the engine detected by the revolution speed detection unit exceeds a predetermined limiting value, the arithmetic unit performs an operation to suppress injection of the fuel to be injected by the injectors.