Impact Wrench Torque Control Using Rotor Rebound Speed
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Solution Overview
Problem
Existing electric impact wrenches with rebounding impact mechanisms lack accurate torque control, often relying on impact count or torque measurement, which can be inefficient and costly, limiting their precision and robustness.
Innovation Solution
A method and device for controlling torque by determining the maximum rotational frequency of the rotor during rebounds and stopping the operation when a predetermined threshold is reached, using sensors or power supply control methods to ensure precise torque application without torque sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque measurement means are incorporated in impact wrenches, then torque control accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses the rebound phenomenon as an intermediary to indirectly measure torque. Instead of directly measuring torque with sensors, the system measures the rotor's rebound rotational frequency, which correlates with the torque applied to the fastener. This intermediary measurement approach achieves accurate torque control without requiring complex direct torque measurement devices.
Solution Approach 2:
The patent replaces mechanical torque measurement systems with an electrical/electronic measurement system. By using rotational frequency sensors and control electronics to monitor rebound characteristics, the system substitutes complex mechanical torque sensors with simpler electronic measurement and calculation methods.
2Measurement precision
If torque sensors are used to control tightening torque, then torque measurement accuracy is improved, but device size and cost increase
Solution Approach 1:
The patent extracts the essential measurement information (rebound rotational frequency) from the complex torque measurement process. By focusing only on measuring the rotor's rebound frequency rather than directly measuring torque force, the system eliminates the need for bulky torque sensors while retaining measurement accuracy.
Solution Approach 2:
The patent creates a correlation model between rebound rotational frequency and torque, using the frequency measurement as a copy or proxy for torque measurement. This allows the system to infer torque values from simpler frequency measurements, avoiding the need for physical torque sensors.
3Device complexity
If impact count method is used to control screw driving, then device complexity is reduced, but torque control accuracy deteriorates
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the rotor's rebound rotational frequency and uses this information to control the screw driving process. The control unit adjusts operation based on real-time feedback from the frequency measurements, ensuring accurate torque control while maintaining relatively simple device architecture.
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
Enables precise torque control in impact wrenches, enhancing accuracy and robustness, reducing costs by eliminating the need for bulky torque sensors, and allowing operation in a wide range of wrench capacities.
Implementation Method 1
driving said impact mechanism generating the occurrence of a plurality of successive impacts at the end of each of which said rotor rotates in a rebound in the opposite direction to the screwing/unscrewing operation
Data Source
AI summary
A method for controlling torque applied during a screw driving operation using a screw driving device. The device includes: an electric motor provided with a rotor; an output member capable of being rotated; and a rebounding impact mechanism rigidly connected to the rotor and to the output member. The method includes power supplying the motor inducing driving the impact mechanism by the rotor and periodically rotating the output member by the impact mechanism; driving the impact mechanism generating a plurality of successive impacts at the end of each of which the rotor rotates in a rebound in the opposite direction to the screw driving operation; determining a maximum rotational frequency reached by the rotor during the rebound following each of the impacts; and stopping the screw driving operation when the maximum rotational frequency reaches a predetermined threshold corresponding to a predetermined torque level.