Hand-held Power Tool Pneumatic Impact Control
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Solution Overview
Problem
Hand-held power tools with pneumatic impact mechanisms experience repetitive switching on and off due to insufficient pressing force, leading to user control difficulties and potential damage.
Innovation Solution
The control method senses acceleration and phase of the pneumatic impact mechanism to estimate pressing force, regulating the electric motor's rotational speed and maintaining the impact mechanism's activation by adjusting the power output based on sensed conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the pressing force threshold for impact mechanism activation is set low, then the tool can be easily activated, but the impact mechanism switches off repeatedly when pressing force momentarily becomes insufficient
Solution Approach 1:
The patent applies dynamics by making the activation threshold variable rather than fixed. The control unit dynamically adjusts the pressing force threshold based on the operational state: during startup it uses a lower first threshold for easy activation, and during continuous operation it uses a higher second threshold to prevent repetitive switching. This dynamic threshold adjustment resolves the contradiction between ease of activation and operational reliability.
Solution Approach 2:
The patent implements preliminary action by detecting pressing force before the impact mechanism activates and using this information to control motor power output in advance. The control unit monitors the pressing force sensor signal and adjusts the motor's rotational speed proactively, ensuring the impact mechanism receives sufficient power to maintain activation and prevent repetitive switching off.
2Reliability
If the pressing force threshold is set high to prevent repetitive switching, then operational stability improves, but the tool becomes difficult to activate
Solution Approach 1:
The control unit dynamically switches between two threshold values based on operational phase. During startup, the lower first threshold enables easy activation. Once activated, the system transitions to using the higher second threshold for stable continuous operation. This dynamic threshold management resolves the contradiction between ease of activation and operational stability.
Solution Approach 2:
The patent uses periodic action by implementing distinct operational phases with different threshold requirements. The system alternates between a startup phase (low threshold) and a continuous operation phase (high threshold), ensuring both easy initial activation and stable sustained operation without repetitive switching.
3Reliability
If the motor power output is increased to maintain impact mechanism activation, then repetitive switching is prevented, but power consumption increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the motor's rotational speed based on pressing force conditions. When pressing force is sufficient, the motor operates at optimal speed for efficient power delivery. When pressing force decreases, the control unit proactively adjusts motor power output to maintain activation, preventing repetitive switching while optimizing energy consumption through adaptive speed control.
Solution Approach 2:
The system implements feedback by continuously monitoring the pressing force sensor signal and using this information to regulate motor power output. The control unit receives feedback about pressing force conditions and adjusts the motor's rotational speed accordingly, ensuring the impact mechanism maintains activation while optimizing energy consumption based on actual operational needs.
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 stabilizes the operation of the hand-held power tool by ensuring consistent power delivery, preventing repetitive switching and enhancing user control over the tool, while preventing damage from insufficient pressing force.
Implementation Method 1
An acceleration sensor serves to sense an acceleration along a working axis of the machine housing
Implementation Method 2
an impact piston of the impact mechanism is coupled to the exciter piston via a pneumatic chamber
Data Source
AI summary
In a control method for a hand-held power tool, a striking mechanism is driven with an electric motor, wherein an exciter piston of the pneumatic striking mechanism is driven periodically by the electric motor and a striking piston of the striking mechanism is coupled to the exciter piston via a pneumatic chamber. The method includes detecting the acceleration of a machine housing along a striking direction of the striking piston in different phases of the movement of the exciter piston; and controlling a rotational speed of an electric motor according to the detected acceleration in the different phases.