Impact Screw Fastener Torque Control via Intermittent Motor Current
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Solution Overview
Problem
Conventional impact type screw fastening devices using electric motors face challenges in achieving high accuracy and reducing reaction force on the operator, particularly due to variations in torque transmission efficiency and the need for frequent adjustments in oil pressure systems.
Innovation Solution
A control method and unit that intermittently supplies current to the electric motor to generate pulse torque, with adjustable current increments and slopes to manage torque increments after reaching set values, reducing reaction force and improving torque accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If current is supplied intermittently to generate pulse torque, then reaction force on operator is reduced, but torque accuracy deteriorates due to transmission efficiency variations
Solution Approach 1:
The control unit measures the actual torque applied to the screw and compares it with the target torque, then adjusts the motor current in real-time to compensate for transmission efficiency variations. This closed-loop feedback mechanism ensures accurate torque control despite the intermittent pulse torque generation.
Solution Approach 2:
The system dynamically changes the motor current parameters (amplitude, pulse width, frequency) based on the measured torque feedback and transmission efficiency variations. By adjusting these electrical parameters, the system maintains accurate torque control while preserving the low reaction force benefit of intermittent current supply.
2Force
If conventional impact type mechanism is used, then reaction force is reduced through rotor inertia, but torque accuracy deteriorates due to impact energy generation mechanism variations
Solution Approach 1:
The patent replaces the mechanical impact energy generation mechanism (rotor inertia) with an electromagnetic system (motor with intermittent current supply). This substitution eliminates the mechanical wear and efficiency variations inherent in impact mechanisms while maintaining low reaction force through controlled pulse torque delivery.
Solution Approach 2:
The control unit acts as an intermediary between the motor and the screw fastening process. It precisely controls the timing and magnitude of current pulses to the motor, mediating the conversion of electrical energy to mechanical torque while ensuring accurate torque application despite the intermittent nature of the drive.
3Adaptability or versatility
If oil pulse wrench with bypass valve is used, then both impact generation and clutch mechanism are integrated, but device complexity increases due to frequent adjustment and replacement of components
Solution Approach 1:
The patent replaces the complex mechanical oil pulse system with an electric motor controlled by electronic circuits. This substitution eliminates the bypass valve, oil pressure adjustments, and mechanical wear components, significantly reducing device complexity while maintaining the integrated functions of impact generation and torque control.
Solution Approach 2:
The electronic control system automatically manages the motor operation without requiring manual adjustment of components. The control unit self-regulates the current pulses based on torque feedback, eliminating the need for operator intervention to adjust oil pressure or replace wear components, thus reducing operational complexity.
4Productivity
If continuous shaft rotation is used, then screw fastening speed is improved, but reaction force on operator increases due to direct transmission of tightening torque
Solution Approach 1:
Instead of continuous rotation, the system employs periodic current pulses to the motor, creating intermittent torque delivery. This periodic action allows the screw to be driven forward in discrete steps with impact-like force, maintaining fastening speed while reducing the continuous reaction force on the operator's hand.
Solution Approach 2:
The system dynamically switches between different operational states (current on/off, different pulse widths) to optimize the balance between fastening speed and reaction force. By making the drive dynamic rather than static continuous rotation, the system achieves high productivity with reduced operator load.
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
The solution effectively reduces reaction force on the operator, enhances torque accuracy, and shortens screw fastening time, while eliminating the need for complex oil pressure systems and consumable parts, leading to easier maintenance and energy efficiency.
Implementation Method 1
an electric motor as a rotation driving source... current is supplied to the motor intermittently so that the motor generates pulse torque
Implementation Method 2
an impact generating portion that generates an impact force utilizing a rotor inertia
Data Source
AI summary
An object is to improve accuracy of tightening torque and to shorten time necessary for fastening a screw in an impact type screw fastening device that uses an electric motor as a rotation driving source. A control method for the impact type screw fastening device that uses an electric motor as a rotation driving source includes the steps of driving the motor to rotate by supplying current to the motor intermittently so that torque exerted on a load by rotation of the motor becomes like pulses on the time axis, and controlling the current of every time of each pulse so that an increment of every time of each pulse of the torque after the torque reaches a target approach torque TQN that is a first set value becomes smaller than that before it reaches the target approach torque TQN.