Hand-held Power Tool Control System for Engine Start Safety
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Solution Overview
Problem
Existing control systems for hand-held power tools with internal combustion engines lack effective differentiation between sensors, leading to inadequate start safety functions and inefficient speed control, particularly during the starting procedure of the engine.
Innovation Solution
A control system utilizing two sensors with distinct electrical properties connected to an electronic control logic, allowing for differentiation between their states and enabling adaptive speed limitation control, which is deactivated based on specific sensor states to prevent unintentional engagement of the working tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor is used to detect engine speed and throttle position, then the device complexity is reduced, but the measurement precision and reliability of sensor states deteriorate
Solution Approach 1:
The patent divides the sensing function into two separate sensors: a first sensor for detecting engine speed and a second sensor for detecting throttle valve position. This segmentation allows each sensor to specialize in its specific measurement task, improving measurement precision and reliability while enabling the control system to accurately determine when to activate or deactivate the rotational speed limitation based on the combined information from both sensors.
2Reliability
If rotational speed limitation is always active to prevent unintentional tool rotation, then safety is improved, but the ease of operation deteriorates due to unnecessary restrictions during normal operation
Solution Approach 1:
The control system dynamically adjusts the rotational speed limitation based on real-time sensor inputs. The system activates the speed limitation when the first sensor detects low engine speed and the second sensor detects the throttle valve in the starting position. When the throttle valve is moved to a position other than the starting position, the control system automatically deactivates the speed limitation, allowing the engine to operate without restrictions during normal operation.
Solution Approach 2:
The control system continuously monitors the states of both sensors and uses this feedback to determine when to activate or deactivate the rotational speed limitation. This feedback mechanism ensures that the safety function is only active when actually needed (during starting procedure with throttle in starting position), while automatically disengaging during normal operation to maintain ease of use.
3Productivity
If throttle valve is positioned in starting position with more air flow to ensure efficient engine start-up, then the productivity is improved, but the harmful factors increase due to risk of unintentional tool rotation
Solution Approach 1:
The control system implements a preliminary protective measure by detecting when the throttle valve is in the starting position (which allows more air flow for efficient engine start-up) and automatically activating the rotational speed limitation at that moment. This preliminary action prevents the harmful effect of unintentional tool rotation before it can occur, allowing the operator to safely use the throttle in the starting position for efficient engine starting without risking accidental tool engagement.
Data Source
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AI summary
Herein a control system (10) for controlling an internal combustion engine of a hand-held power tool (2) is disclosed. The control system (10) comprises an electronic control logic (24), a first and a second sensor (26, 28). A first conductive path (36) comprises the first sensor (26). A second conductive path (38) comprises the second sensor (28). The first and second conductive paths are connected to an input (40) of the electronic control logic (24). The first and second conductive paths are connected to a fixed voltage potential. The first conductive path (36) has a first electrical property and the second conductive path (38) has a second electrical property. The first electrical property and the second electrical property together are different from at least one of the first electrical property and the second electrical property, such that the electronic control logic (24) is able to detect different states.