Hand-Held Power Tool Motor Control for Screw Connection Integrity
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Solution Overview
Problem
Existing hand-held power tools, such as rotary impact wrenches, face challenges in ensuring proper screw connections due to user error, over-tightening, and the inability to detect work progress accurately, leading to potential screw connection failures.
Innovation Solution
A method for operating hand-held power tools that involves monitoring the operating variables of the electric motor during screw connections, evaluating these signals to determine if the screw connection was properly executed, and using intelligent tool functions to assist the user in achieving high-quality screw connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the user continues the rotational screwing operation with a screw already tightened in the impact operation, then the screw connection can be completed, but the grooved or cut thread in the material, or the screw itself, can be destroyed
Solution Approach 1:
The control unit continuously monitors operating variables (motor speed, impact frequency) and provides feedback to detect when the screw is already tightened. When the screw head contacts the material surface, the impact frequency changes, which the control unit detects and uses to determine when to stop or reduce motor speed, preventing thread destruction while ensuring complete screw connection
2Productivity
If the user does not notice the defect and leaves the screw connection in this condition, then the work progress can be maintained, but this can lead to failure of the screw connection at a later time
Solution Approach 1:
The control unit monitors operating variables throughout the screwing process and automatically detects when the screw is properly tightened or when thread damage occurs. This automated feedback eliminates the need for user inspection, ensuring that defective screw connections are identified and flagged immediately, preventing later failures while maintaining work progress
Solution Approach 2:
The tool performs self-diagnosis by monitoring its own operating variables to detect screw connection status. The control unit automatically determines when the screw is properly tightened or when damage has occurred, eliminating the need for user intervention to assess connection quality
3Reliability
If a fixed limit value and/or threshold value is set for impact detection, then the automatic shutdown can be reliable for one application, but as soon as the application case changes, the impact detection based on the set limit value no longer functions
Solution Approach 1:
The control unit dynamically adjusts the threshold values for impact detection based on the detected application case. When different screw types, materials, or operating conditions are detected, the control unit automatically modifies the threshold parameters to maintain reliable impact detection and automatic shutdown across diverse applications
Solution Approach 2:
The system changes the detection parameters (threshold values, monitoring criteria) based on the identified application case. By adapting these parameters to match the specific screwing conditions, the system maintains high reliability for automatic shutdown while becoming versatile enough to handle multiple application scenarios
4Manufacturing precision
If the user requires high concentration on work progress to ensure proper reaction to machine characteristics, then the screw connection quality can be controlled, but it is often not possible for the user to react quickly enough or appropriately
Solution Approach 1:
The control unit continuously monitors operating variables and automatically reacts to machine characteristics such as impact frequency changes, motor current variations, and speed fluctuations. This automated feedback system eliminates the need for user concentration and quick manual reactions, while maintaining precise control over screw connection quality through programmatic response
Data Source
AI summary
A method for operating a hand-held power tool is disclosed, wherein the hand-held power tool includes an electric motor. The method includes carrying out a screw connection of a connecting device in a support, providing at least one signal of an operating variable of the electric motor during the screwing, evaluating the received signal of the operating variable of the electric motor, and deciding whether the screw connection has been properly carried out, the decision being at least partially based on the evaluation of the received signal of the operating variable of the electric motor. A hand-held power tool is also disclosed.