Servo Screwdriver Kinetic Energy Accumulation for Low Reaction Torque
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Solution Overview
Problem
Existing servo-driven electric screwdrivers face challenges in achieving optimal ergonomics and productivity, particularly when dealing with assemblies of varying elasticity, as they require significant operator effort and have limitations in reducing the reaction force during the tightening process.
Innovation Solution
The design incorporates a low reduction ratio in the transmission system, allowing for kinetic energy accumulation and efficient energy transfer to achieve the target torque, reducing the duration of the torque build-up phase and minimizing operator effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional reduction ratio is used in the transmission system, then the maximum tightening torque is sufficient to achieve the objective torque, but the operator must develop significant reaction force to maintain the screwdriver during tightening
Solution Approach 1:
The motor is supplied with electric current during a pre-screwing phase to accumulate kinetic energy in the rotor before the actual tightening phase begins. This preliminary energy storage allows the motor to be disconnected during torque build-up, reducing the reaction torque transmitted to the operator's hand while still achieving the required tightening torque through the stored kinetic energy.
Solution Approach 2:
The motor supply is applied periodically rather than continuously - first during the pre-screwing phase to build kinetic energy, then disconnected during the tightening phase when torque build-up occurs. This periodic application of power separates the energy accumulation function from the torque application function, reducing operator effort during the critical tightening moment.
2Ease of operation
If the motor is braked early during the tightening phase, then the reaction force on the operator is reduced, but the tightening torque build-up is prolonged
Solution Approach 1:
Kinetic energy is accumulated in the motor rotor during the pre-screwing phase before the tightening phase begins. This preliminary energy storage ensures that when the motor is disconnected during torque build-up, the stored kinetic energy is available to drive the tightening process without requiring continuous motor supply or early braking, thus maintaining productivity while reducing reaction force.
3Reliability
If the pre-screwing speed is reduced to improve tightening control, then the productivity of the tool is decreased
Solution Approach 1:
The tightening operation is divided into two distinct phases: a pre-screwing phase with high speed for rapid approach, and a tightening phase with controlled torque build-up. This segmentation allows the tool to achieve both high productivity during the pre-screwing phase and reliable tightening control during the tightening phase, as each phase is optimized for its specific function.
Solution Approach 2:
The motor supply is applied periodically - first during the high-speed pre-screwing phase, then disconnected during the controlled tightening phase. This periodic action pattern enables the tool to maintain high pre-screwing speeds for productivity while ensuring controlled torque build-up during the disconnected phase, achieving both goals simultaneously.
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 approach significantly reduces the operator's holding force requirement, enhances ergonomics, and increases productivity by shortening the tightening time, while maintaining a high pre-screwing speed.
Implementation Method 1
transmission means able to allow an accumulation of a kinetic energy Ec when said motor means are supplied and then a return of said kinetic energy Ec to said terminal member
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an electric screwdriver with servo-controlled tightening comprising a housing (10), an end member (14) capable of being driven in rotation and intended to cooperate with an assembly to be tightened, motor means (13) having a maximum torque at constant speed Cmax, said motor means comprising a rotor, control means (16) of said motor means (13), transmission means (15) including a reduction (17) having ratio R and an efficiency µ coupled to said motor means (13) and said end member (14), at least one torque sensor (18) intended to measure information representative of the tightening torque of said assembly, a gripping member comprising a gripping zone distant from the axis of rotation of said end member by a distance B, said reduction (17) being configured such that R. µ. Cmax ≤ B. 100 and B.100 ≤ Cobj/2, Cobj being the target torque at which said assembly must be tightened.