Fastening Tool Motor Stop Control for Consistent Screw Depth
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Solution Overview
Problem
Existing fastening tools experience variations in screw engagement due to the contact between the driver bit and screw recess, leading to inconsistent fastening depth and unstable finishes, such as the screw head being embedded in the fastening target.
Innovation Solution
A fastening tool with a bit holding portion that rotates and moves axially, controlled by a motor and detector, determines disengagement between the driver bit and screw, stopping rotation when the screw is fully fastened to ensure consistent depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the driver bit and screw recess are in contact at an inclined surface during rotation, then the screw can be fastened to the target, but the amount of engagement varies causing inconsistent fastening depth
Solution Approach 1:
The system uses a detector to monitor the engagement state between the driver bit and screw recess, providing feedback to the controller. When disengagement is detected (indicating the screw head is flush with the target surface), the controller stops rotation, ensuring consistent fastening depth regardless of initial engagement variations.
Solution Approach 2:
The system allows the fastening process to proceed naturally with variable engagement, then uses automatic detection of the completion state (disengagement event) to stop the process. The system serves itself by using the natural disengagement event as the stopping criterion rather than requiring precise pre-calculated rotation counts.
2Device complexity
If a fixed rotation count is used to stop the motor, then the control is simple, but the fastening depth varies when engagement amount varies
Solution Approach 1:
Instead of using a fixed rotation count, the system continuously monitors the engagement state through the detector and adjusts the rotation stop timing based on real-time feedback. When the detector signals disengagement (screw head flush with target), the controller stops the motor, ensuring precise and consistent fastening depth.
3Reliability
If the motor rotation is not stopped at the correct timing, then the screw may not be fully fastened, but continued rotation causes the driver bit to disengage and creates unstable fastening
Solution Approach 1:
The detector provides real-time feedback on the engagement state between driver bit and screw recess. When disengagement is detected (indicating the screw head has become flush with the target surface), the controller immediately stops rotation, preventing both incomplete fastening and over-rotation that would cause instability.
Solution Approach 2:
The system converts the potentially harmful disengagement event into a useful signal. Instead of treating disengagement as a failure condition, the system uses it as the precise indicator that the screw has been properly fastened and rotation should stop, thereby ensuring both completion and stability.
Data Source
AI summary
A fastening tool includes a bit holding portion configured to hold a driver bit engageable with a screw and that is rotatable in a circumferential direction and movable in an axial direction of the driver bit, a motor configured to rotate the bit holding portion, a controller configured to control the motor, and a detector configured to detect a state of the motor. In a state where the screw engaged with the driver bit is fastened to a fastening target, the controller determines whether the driver bit and the screw are disengaged based on the state of the motor detected by the detector and stops the rotation of the motor in a case where the controller determines that the driver bit and the screw are disengaged.