Speed Reducer Torque Fluctuation Control
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Solution Overview
Problem
Existing power tools face sudden motor temperature increases when continuously used with load torque slightly below a predetermined value, leading to reduced workability due to inadequate speed reduction ratio switching.
Innovation Solution
A speed-changing device with a reduction gear train and a speed reduction ratio switching unit, including an actuator, controller, and drive state detector, which activates the actuator when the load torque index value exceeds or fluctuates between threshold values, forming an undulated pattern to adjust the speed reduction ratio and prevent motor overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the speed reduction ratio switching is activated only when the detected current value exceeds a predetermined threshold, then the motor temperature can be prevented from suddenly increasing under high load, but the motor temperature suddenly increases when the motor is continuously used with current value slightly lower than the threshold
Solution Approach 1:
The patent applies dynamics by making the speed reduction ratio switching responsive to dynamic fluctuations in current value. Instead of using a static threshold comparison, the system detects undulated patterns (fluctuations) in the current value between first and second thresholds. This dynamic approach allows the system to adapt to varying load conditions and switch speed reduction ratios proactively, preventing motor temperature increases while maintaining workability.
Solution Approach 2:
The patent implements feedback by continuously monitoring the current value and using this information to control the actuator that switches the speed reduction ratio. The controller receives feedback about current fluctuations and adjusts the speed reduction ratio accordingly. This closed-loop feedback mechanism enables the system to respond to load changes in real-time, preventing motor overheating while ensuring continuous operational capability.
2Device complexity
If the speed reduction ratio is not switched when the current value is slightly lower than the predetermined value, then the control system remains simple, but the motor temperature suddenly increases and heat the power tool thereby lowering workability
Solution Approach 1:
The patent applies dynamics by making the speed reduction ratio switching responsive to dynamic fluctuations in current value. Instead of using a static threshold comparison, the system detects undulated patterns (fluctuations) in the current value between first and second thresholds. This dynamic approach allows the system to adapt to varying load conditions and switch speed reduction ratios proactively, preventing motor temperature increases while maintaining workability.
Solution Approach 2:
The patent implements feedback by continuously monitoring the current value and using this information to control the actuator that switches the speed reduction ratio. The controller receives feedback about current fluctuations and adjusts the speed reduction ratio accordingly. This closed-loop feedback mechanism enables the system to respond to load changes in real-time, preventing motor overheating while ensuring continuous operational capability.
3Productivity
If the speed reduction ratio switching threshold is set lower to prevent motor heating, then workability is improved, but the motor rotation speed decreases and power output is reduced under normal operating conditions
Solution Approach 1:
The patent applies dynamics by making the speed reduction ratio switching responsive to dynamic fluctuations in current value. Instead of using a static threshold comparison, the system detects undulated patterns (fluctuations) in the current value between first and second thresholds. This dynamic approach allows the system to adapt to varying load conditions and switch speed reduction ratios proactively, preventing motor temperature increases while maintaining workability.
Solution Approach 2:
The patent applies parameter changes by using two different threshold values (first threshold and second threshold) to define the undulation detection range. The system monitors current fluctuations within this parameter range and triggers speed reduction ratio switching when undulated patterns are detected. This parameter-based approach allows flexible control of the switching decision, balancing motor temperature prevention with maintaining adequate rotation speed and power output.
Data Source
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AI summary
A speed-changing device includes a motor (1), a reduction gear train (2) that reduces a rotation speed of the motor (1) in accordance with a speed reduction ratio and transmits the rotation at the reduced speed, and a speed reduction ratio switching unit (20) that switches the speed reduction ratio. The speed reduction ratio switching unit (20) includes an actuator (6) that switches the speed reduction ratio, a controller (60) that controls the actuator (6), and a drive state detector (68) that detects an index value representing load torque applied to the motor (1). The controller (60) activates the actuator (6) when the index value exceeds a first threshold value (L1) and activates the actuator (6) when the index value fluctuates between the first threshold (L1) and a second threshold (L2) thereby forming an undulated pattern (L3) that satisfies a predetermined condition.