Electronic Clutch Torque Control in Impact Tools
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Solution Overview
Problem
Power tools with impact mechanisms often produce excessive torque during low-torque applications, leading to overdriving of fasteners before the user can react, as they lack precise control to stop the fastening process once the desired torque is reached.
Innovation Solution
Incorporating an electronic clutch with a user-selectable threshold that is set lower than the trip torque value of the impact mechanism, allowing the controller to activate the clutch when the motor current exceeds this threshold, thereby controlling the torque application and preventing overdriving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If an impact mechanism is used to provide high torque, then fastening capability is improved, but torque control precision deteriorates causing overdriving of fasteners
Solution Approach 1:
The patent segments the torque control function into two distinct mechanisms: an electronic clutch that operates at lower torque thresholds for precise control, and an impact mechanism that activates at higher torque thresholds for high-force applications. This segmentation allows each mechanism to operate in its optimal range, preventing overdriving while maintaining fastening capability.
Solution Approach 2:
The electronic clutch acts as an intermediary between the motor and the impact mechanism. It monitors motor current and interrupts power delivery when the clutch threshold is reached, serving as a mediator that prevents excessive torque from reaching the fastener while allowing the impact mechanism to function when needed.
2Measurement precision
If the clutch threshold is set below the trip torque value, then torque control precision is improved, but the impact mechanism cannot be activated in clutch mode
Solution Approach 1:
The patent implements dynamic mode selection where the controller can switch between clutch mode and impact mode based on operational requirements. In clutch mode, the electronic clutch threshold operates below the trip torque value for precise control. In impact mode, the system allows the impact mechanism to activate when needed. This dynamic adaptability resolves the contradiction by allowing each mode to have optimized parameters.
3Ease of operation
If a mechanical clutch is used, then torque control is simplified, but response time and control precision deteriorate
Solution Approach 1:
The patent replaces the traditional mechanical clutch with an electronic clutch system that uses a current sensor and controller to monitor motor current and interrupt power delivery electronically. This substitution eliminates mechanical wear and lag, providing faster response time and more precise control while maintaining the simplicity of clutch-based torque control.
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 enables precise control during low-torque fastening operations, ensuring that fasteners are driven accurately and stopped when flush with the workpiece surface, preventing overdriving and allowing for efficient operation across various torque applications.
Implementation Method 1
a spring within the impact mechanism. The spring has a stiffness related to a trip torque value of the impact mechanism, and the spring is configured to axially bias the hammer to engage the anvil
Implementation Method 2
a current sensor electrically connected to the motor. The current sensor is configured to detect a current of the motor
Data Source
AI summary
A power tool including a hammer, an anvil, and a spring having a stiffness indicating a trip torque value. A mode selection mechanism is configured to select between an electronic clutch mode and an impact mode. The electronic clutch mode includes an electronic clutch threshold that is less than a trip torque value. A load sensor is connected to the motor. The load sensor is configured to detect a load of the motor. A controller is connected to the mode selection mechanism, the current sensor, and the motor. The controller is configured to receive a mode selection signal from the mode selection mechanism, drive the motor in response to the mode selection signal, receive a load signal from the load sensor related to the load of the motor, and activate the electronic clutch when the load of the motor is greater than the electronic clutch threshold.