Engine Speed Limiting via Throttle Position Control
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Solution Overview
Problem
Internal combustion engine devices, such as chain saws and grass trimmers, pose a safety risk due to accidental activation of working assemblies when the engine speed exceeds the clutch-in speed during start-up, as operators may not engage safety brakes promptly.
Innovation Solution
Implementing an electronic control unit that limits engine speed by controlling fuel supply and ignition timing based on throttle valve position, ensuring the engine speed remains below the clutch-in speed until the throttle is intentionally moved, thereby preventing inadvertent activation of the working assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the throttle valve is positioned in a starting position to ensure efficient start-up, then the engine rotational speed increases above the clutch-in speed, but the working assembly may be inadvertently activated causing safety risks
Solution Approach 1:
The electronic control unit performs preliminary action by detecting the throttle valve position before engine start-up and pre-configuring the ignition system to skip sparks or limit fuel supply during the start-up phase. This prevents the engine speed from immediately exceeding the clutch-in speed, thereby avoiding inadvertent working assembly activation while maintaining efficient start-up capability.
Solution Approach 2:
The electronic control unit continuously monitors the throttle valve position and engine speed, using feedback signals from sensors to dynamically adjust ignition timing and fuel supply. When the throttle valve is detected in the starting position, the control unit automatically implements speed limitation by reducing ignition frequency, creating a closed-loop safety mechanism that prevents harmful effects.
2Speed
If the engine speed quickly rises upon starting, then the clutch-in speed is achieved before the operator is ready for the working assembly to begin operation, but this creates a safety hazard
Solution Approach 1:
The electronic control unit detects the throttle valve position in advance during the starting phase and pre-configures the ignition system to skip sparks or limit fuel supply. This preliminary action controls the rate of engine speed increase, ensuring it does not quickly exceed the clutch-in speed before the operator is ready, thereby preventing safety hazards.
Solution Approach 2:
The electronic control unit dynamically changes the ignition parameter (spark frequency) and fuel supply parameters based on the detected throttle valve position. During start-up with the throttle in the starting position, the control unit reduces ignition frequency and limits fuel supply, effectively controlling the engine speed increase rate to remain below the clutch-in speed threshold.
3Reliability
If the operator does not engage the mechanical brake or security arrangements, then the safety protection is compromised, but the engine speed limitation system provides an additional layer of protection
Solution Approach 1:
The electronic control unit provides self-service safety protection by automatically detecting the throttle valve position and engine operating conditions, then autonomously adjusting ignition timing and fuel supply to maintain engine speed below the clutch-in speed. This self-regulating mechanism ensures safety protection without requiring additional manual intervention from the operator, thereby enhancing reliability while using existing control components.
Solution Approach 2:
The electronic control unit, which already manages normal engine operation, is extended to perform the additional function of speed limitation during start-up. By utilizing the existing electronic control system for both normal operation and safety protection, the patent avoids adding separate complex safety mechanisms, thereby enhancing reliability without proportionally increasing device complexity.
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 solution effectively prevents accidental activation of the working assembly by maintaining engine speed below the clutch-in speed until the operator intentionally engages the throttle, enhancing safety without requiring additional complex clutch assemblies or components.
Implementation Method 1
a spark plug disposed proximate to the combustion chamber to ignite the mixture by generating a spark
Implementation Method 2
a centrifugal clutch that engages the working assembly when the engine exceeds a certain rotational speed
Data Source
Figure 1A
Figure 1B~1D
Figure 2
AI summary
An internal combustion engine for driving a working assembly with a clutch, including a combustion chamber into which a mixture of fuel and air is supplied, a spark plug to ignite the mixture, ignition of the mixture driving a piston operably coupled to a crank portion of the engine, a fuel supply system including a fuel valve and a throttle valve, a throttle position sensor configured to determine a position of the throttle valve, a speed sensor configured to determine engine speed, and an electronic control unit configured to control operation of the fuel valve and the spark plug, the electronic control unit being configured to initiate a speed limitation operation in response to a first position of the throttle valve at engine start-up, wherein the speed limitation operation continues until the throttle valve is moved from its first position.