Power Tool Startup Torque Control Through Backlash Pre-Rotation
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Solution Overview
Problem
Power tools face challenges in achieving high torque impulses near zero speed due to backlash in gear systems, which can lead to stuck accessories and reduced performance, especially in applications like drilling where the accessory becomes stuck in the workpiece.
Innovation Solution
A system that includes a controller with a processor and memory to manage the motor's operation by reversing its direction by a predetermined amount to increase backlash in the gear train, allowing for higher torque output at startup, and utilizing a torque sensor to ensure the motor continues to rotate until a threshold torque value is met, thereby enhancing the tool's ability to break free from stuck conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If backlash is increased in the gear train, then startup torque is improved, but manufacturing precision deteriorates
Solution Approach 1:
The system performs a preliminary reverse rotation of the motor before normal operation to intentionally open the backlash gap in the gear train. This preliminary action prepares the mechanical system by separating the driving member from the load, allowing subsequent torque to be applied without the constraint of gear tooth contact, thereby achieving higher startup torque without requiring lower manufacturing precision
2Force
If reverse rotation is applied to increase backlash, then startup torque is improved, but device complexity increases
Solution Approach 1:
The system uses a torque sensor to monitor the actual torque being applied to the load and provides feedback to the controller. The controller processes this feedback information and adjusts the motor's reverse rotation duration and magnitude accordingly, dynamically optimizing the backlash opening process. This feedback mechanism enables the system to achieve high startup torque while maintaining controlled complexity through intelligent adaptation rather than mechanical complexity
3Force
If reverse rotation duration is extended, then torque impulse is improved, but loss of time increases
Solution Approach 1:
The torque sensor continuously monitors the torque level during reverse rotation and provides real-time feedback to the controller. When the measured torque reaches the desired threshold, the controller immediately terminates the reverse rotation, regardless of the elapsed time. This feedback-based termination ensures optimal torque impulse is achieved while minimizing unnecessary time extension, dynamically balancing torque generation with time efficiency
Data Source
AI summary
A power tool including a housing, an input, a gear train, a motor at least partially supported by the housing and coupled to the gear train, and a controller including a processor and a memory. The controller is coupled to the input and the motor and is configured to receive an input signal from the input, determine an operating direction and an operating speed based on the input signal, cause the motor to rotate the gear train in a direction opposite the operating direction for a predetermined amount of rotation, and cause the motor to rotate in the operating direction at the operating speed.