Engine Speed Gradient Detection for Cold Start Fuel Control
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Solution Overview
Problem
Existing methods for determining start conditions in internal combustion engines, such as those in hand-held power tools, often inaccurately detect whether the engine is starting under cold or hot conditions, leading to incorrect fuel-air mixture supply and difficulties in restarting, especially when the engine has been idle for a short period.
Innovation Solution
The method involves determining the engine speed gradient during the slowdown phase after a pull stroke to differentiate between cold and hot start conditions, using the engine speed gradient and temperature measurements within the electronic control unit to adjust fuel supply accordingly, eliminating the need for external sensors and ensuring accurate start condition detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ambient temperature is used to determine start conditions, then the determination is simple, but the accuracy is poor when engine has been idle for short time
Solution Approach 1:
The patent introduces an intermediary parameter (engine speed gradient during slowdown phase) that indirectly reflects the true thermal state of the engine. This mediator allows accurate determination of start conditions without directly measuring engine temperature, resolving the contradiction between simple determination and accurate detection.
Solution Approach 2:
The patent performs preliminary measurement of engine speed during the slowdown phase before making the start condition determination. This preliminary action provides accurate data about the engine's actual thermal state, enabling correct fuel mixture preparation before ignition.
2Reliability
If cold start conditions are erroneously detected, then the fuel/air mixture becomes too rich, but engine starting becomes difficult
Solution Approach 1:
The patent uses feedback from engine speed measurements during the slowdown phase to continuously monitor and accurately determine actual start conditions. This feedback mechanism prevents erroneous detection and ensures the correct fuel/air mixture is supplied, maintaining both reliability and starting success.
3Device complexity
If temperature sensor is placed outside engine, then ambient temperature is measured, but engine temperature state is not accurately reflected
Solution Approach 1:
The patent replaces the mechanical/physical temperature sensing approach with a dynamic mechanical measurement approach. Instead of using temperature sensors that directly contact the engine, it substitutes the measurement of engine speed gradient during slowdown phase, which indirectly but accurately reflects engine thermal state without requiring internal sensor placement.
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 allows for reliable engine starting by accurately determining start conditions, preventing over-rich fuel mixtures and ensuring successful engine restarts under various ambient temperatures, improving engine behavior and reducing the need for additional hardware.
Implementation Method 1
a temperature sensor (17) arranged on a circuit board of the electronic control unit (12) is used for detecting a temperature (T)
Implementation Method 2
The rate at which the engine speed decreases during this slowdown phase depends on the friction of the internal combustion engine that, in turn, depends on the temperature of the lubricating oil
Data Source
AI summary
In a method for operating an internal combustion engine that has a starter device for starting the internal combustion engine and a device for supplying fuel controlled by a control device, it is determined whether cold start conditions or hot start conditions exist during starting of the internal combustion engine. In at least one operating range, during starting of the internal combustion engine, an engine speed gradient is determined during a slowdown phase of a pull stroke of a starter device and the engine speed gradient is used for determining whether cold start conditions or hot start conditions exist. The fuel quantity to be supplied to the internal combustion engine is controlled based on the determined cold start conditions or hot start conditions.