Power Tool Speed Reduction Ratio Control via Feedback
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Solution Overview
Problem
Existing power tools experience unexpected changes in speed reduction ratios due to gear displacement caused by operational vibration or wear of mechanical components, leading to deviations from predetermined values.
Innovation Solution
A power tool with a motor and power transmission unit that includes a shifting member and a gear shift actuator, where a position detector and torque detector work with a control unit to adjust the speed reduction ratio based on load torque and ensure the shifting member is at the target position, using a gear shift actuator that moves the shifting member while decreasing operational speed if it's not aligned, and stops after a predetermined time if still misaligned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the gear shift actuator stops operating after shifting the speed reduction ratio, then the actuator returns to idle state, but the speed reduction ratio deviates from predetermined value due to gear displacement from vibration or wear
Solution Approach 1:
The control unit continuously monitors the position of the shifting member using a position detector and compares it with the target position. After the gear shift actuator stops operating, the control unit determines whether the shifting member is located at the target position corresponding to the shifted speed reduction ratio. If deviation is detected, the control unit activates the actuator again to correct the position, forming a closed-loop feedback system that maintains accuracy despite vibration or wear.
Solution Approach 2:
The control unit performs preliminary verification of the shifting member's position immediately after the gear shift actuator completes its operation. By checking the position before the actuator fully returns to idle state and during the deceleration phase, the control unit can detect and correct potential deviations caused by inertial rotation or vibration before they affect the speed reduction ratio accuracy.
2Productivity
If the gear shift actuator operates to shift the speed reduction ratio, then the shifting member moves to target position, but inertial rotation causes displacement from target position
Solution Approach 1:
The control unit initiates a position verification check during the deceleration phase of the gear shift actuator, before the shifting member comes to complete rest. This preliminary action allows the system to detect inertial displacement early and make corrective adjustments while the actuator is still under control, rather than waiting until after the actuator has fully stopped.
Solution Approach 2:
The position detector continuously provides feedback on the shifting member's position during the entire gear shifting process, including the deceleration and stopping phases. The control unit uses this real-time feedback to determine when the shifting member has reached the target position and to make fine adjustments if inertial rotation causes deviation, ensuring precise positioning despite the dynamics of motor deceleration.
Data Source
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AI summary
A power tool that suppresses unexpected changes in the speed reduction ratio. A control unit (23) controls a gear shift actuator (27) to shift a speed reduction ratio of a power transmission unit (22) in accordance with the detected load torque. After shifting the speed reduction ratio, when a ring gear (RG) is not located at a target position corresponding to the shifted speed reduction ratio, that is, when a cam (30) is not located at a first engagement position or a second engagement position, the control unit (23) uses the gear shift actuator (27) to pivot the cam (30) again and move the ring gear (RG).