Internal Combustion Engine Starting Speed Limiter
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Solution Overview
Problem
Hand-held, portable tools with internal combustion engines often experience uncontrolled centrifugal clutch engagement during starting, leading to undesired operating states due to defects in mixture formation, resulting in excessive engine speed.
Innovation Solution
A method that activates a starting speed limitation when the engine speed exceeds an activation speed above the engagement speed, intervening in ignition to control the engine speed within a defined corridor, adjusting upper and lower engagement speeds over successive work cycles to prevent uncontrolled acceleration and ensure reliable starting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the centrifugal clutch is used to drive the tool when engine speed exceeds engagement speed, then the tool is automatically engaged at appropriate speed, but the clutch may close in an uncontrolled manner during starting, causing undesired operating states
Solution Approach 1:
The control unit activates a starting speed limitation mode before normal operation begins. During this preliminary phase, the control unit monitors engine speed and restricts ignition timing to prevent the engine speed from exceeding the clutch engagement speed, thereby preventing uncontrolled clutch closure during the starting process
Solution Approach 2:
The control unit continuously monitors the actual engine speed and compares it with the engagement speed of the centrifugal clutch. When the actual speed approaches or exceeds the engagement speed during starting, the control unit adjusts the ignition timing to limit the speed, creating a feedback control loop that prevents uncontrolled clutch engagement
2Productivity
If the engine speed is allowed to rise freely during starting, then the engine can start quickly, but excessive speed may occur due to defects in mixture formation, leading to undesired operating states
Solution Approach 1:
The control unit dynamically adjusts the ignition timing based on the current engine operating conditions and detected speed. During starting, the ignition timing is restricted to prevent excessive speed buildup. Once the engine reaches normal operating speed and stability, the control unit transitions to normal ignition timing control, allowing full power output
3Reliability
If the starting speed limitation intervenes in ignition when activation speed is exceeded, then the engine speed is controlled within a safe corridor, but the ignition timing is modified which may affect engine performance
Solution Approach 1:
The control unit applies periodic ignition timing restrictions during the starting phase to keep the engine speed within the safe corridor between lower and upper intervention speeds. This periodic intervention in ignition timing is temporary and only applies during starting, after which normal ignition timing is restored to maintain full engine power
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 method ensures a reliable start of the internal combustion engine while avoiding undesired operating states by controlling engine speed, maintaining a safe rotational speed difference below the clutch speed, and adjusting speed thresholds dynamically based on work cycles.
Implementation Method 1
The centrifugal clutch drives the tool when the speed of the combustion engine exceeds an engagement speed of the centrifugal clutch
Implementation Method 2
a control unit is provided which intervenes in the ignition depending on the determined speed of the internal combustion engine
Data Source
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AI summary
The invention relates to a method for safely starting an internal combustion engine (3) in a hand-held, portable work device (1). During starting, a starting speed limiter (12) is activated when the speed (n) of the internal combustion engine (3) exceeds an activation speed (ADZ) that is above the engagement speed (EKD) of a centrifugal clutch (7). After activation of the starting speed limiter (12), the ignition (11) is intervened for at least one operating cycle (ASP) of the internal combustion engine (3) such that the speed (n) of the internal combustion engine (3) decreases. After the speed (n) falls below a lower intervention speed (47), the ignition (11) is intervened such that the speed (n) increases. If the speed (n) exceeds an upper intervention speed (49), the ignition (11) is intervened again such that the speed (n) decreases.As the number of consecutive work cycles (WC) increases, the upper engagement speed (49) and/or the lower engagement speed (47) is changed.