Speed Control Circuit for Combustion Engine Handheld Tools
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Solution Overview
Problem
Existing methods for deactivating speed blocking circuits in internal combustion engines of hand-held tools require additional sensors or complex technical efforts, making them inefficient and cumbersome.
Innovation Solution
A method that generates a deactivation signal for the speed blocking circuit based on the frequency of control interventions by the speed control device, monitoring the number of control interventions over time to determine when the user has given full throttle, allowing the circuit to be switched off without additional sensors, ensuring the engine reaches a stable state before releasing the entire speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a speed blocking circuit is used to keep engine speed below the engagement speed during starting phase, then the clutch engagement is protected from damage, but the engine speed range is restricted after starting
Solution Approach 1:
The speed blocking circuit is designed to dynamically change its behavior based on operating conditions. During the starting phase, it actively limits speed below the clutch engagement speed. After starting, it automatically deactivates when detecting full throttle operation, allowing the engine to reach its full speed range. This dynamic adaptation resolves the contradiction by providing speed protection when needed and full performance when the user demands it.
2Measurement precision
If additional sensors are added to detect operating state changes for deactivating the speed blocking circuit, then the deactivation can be more precise, but the device complexity increases
Solution Approach 1:
The system uses existing components to detect operating state changes rather than adding dedicated sensors. The speed control device's own control intervention frequency serves as the detection mechanism - when the user applies full throttle, the control device must work harder to maintain speed limits, and this increased control activity automatically triggers deactivation of the speed blocking circuit. This self-service approach eliminates the need for additional sensors while maintaining precise operating state detection.
Solution Approach 2:
The speed control device performs multiple functions: it not only controls engine speed during the starting phase but also detects operating state changes to trigger deactivation of the speed blocking circuit. By making the speed control device multi-functional, the patent avoids adding separate detection components, thus reducing device complexity while maintaining measurement precision.
3Reliability
If the speed blocking circuit remains active after starting, then speed protection is continuous, but the user cannot access the full speed range for work applications
Solution Approach 1:
The speed blocking circuit transitions from an always-active state to a conditionally-active state. It provides continuous protection during the starting phase and idle operation, but automatically deactivates when the user applies full throttle, allowing access to the complete engine speed range for work applications. This dynamic behavior ensures both continuous protection when needed and full productivity when the user demands it.
Solution Approach 2:
The system periodically monitors control intervention frequency to detect when the user applies full throttle. When the control device needs to intervene frequently to maintain speed limits, this periodic detection triggers deactivation of the speed blocking circuit, allowing the engine to operate at full speed for work applications while maintaining protection during normal operation.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for controlling the speed limitation of an internal combustion engine (8) in a handheld power tool (1), such as a chainsaw. A cylinder (9) of the internal combustion engine (8) has a combustion chamber (22) delimited by a piston (10), the piston (10) driving a crankshaft via a connecting rod (11). The crankshaft drives a power tool via a clutch (33) that engages depending on the engine speed (n), wherein above a clutch engagement speed (33), a drive connection with the crankshaft (13) is established, and below this engagement speed, the drive connection is interrupted. A spark plug (23) is arranged in the combustion chamber (22) and is controlled by an ignition device (30).A speed control device (50) monitors the speed (n) of the internal combustion engine (8) and includes a speed limiter circuit (51) that limits the speed (n) of the internal combustion engine to a limit speed (nG) below the engagement speed. The speed limiter circuit (51) is switched on when the internal combustion engine (8) is started; it is switched off after the internal combustion engine (8) has been started when a deactivation signal is present, the deactivation signal being generated when an operating change signal of the internal combustion engine (8) is detected.