Automatic Gearshift Device for Power Tools
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Solution Overview
Problem
Existing automatic gearshift devices for power tools require time and effort to ensure proper positioning of components, leading to potential misalignment and inefficient switching of speed reduction ratios due to the need for manual verification of the relative positional relationship between the displacement sensor and the switching member.
Innovation Solution
An automatic gearshift device that includes a gearshift motor, cam member, rotation body with a positioning mark, and position detector, which automatically aligns and positions the switching member to engage with the gear member, allowing for easy and accurate switching of speed reduction ratios by detecting the rotation angle and generating corresponding values to control the gearshift motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a displacement sensor is used to detect the position of the switching member, then the speed reduction ratio can be automatically switched, but the component positioning becomes complex and time-consuming
Solution Approach 1:
The patent introduces a rotation body with positioning marks as an intermediary element between the displacement sensor and the switching member. The rotation body rotates in synchronization with the cam member, and its positioning marks provide reference signals to the displacement sensor, enabling automatic detection without requiring direct positioning of the sensor relative to the switching member.
Solution Approach 2:
The rotation body serves itself by providing positioning marks that automatically reference the displacement sensor. As the rotation body rotates with the cam member, its marks self-generate the necessary positional information for the sensor, eliminating the need for manual alignment and positioning adjustments.
2Ease of manufacture
If the displacement sensor is positioned without establishing relative position relationship, then assembly is simpler, but the switching member may fail to reach target position
Solution Approach 1:
The rotation body acts as a mediator that decouples the positioning requirement. The displacement sensor only needs to detect the rotation body's marks, not directly track the switching member's position. This intermediary layer ensures reliable detection even when the sensor and switching member have no fixed relative position relationship.
Solution Approach 2:
The rotation body is pre-configured with positioning marks at specific angular positions corresponding to different speed reduction ratios. These marks are prepared in advance to guide the displacement sensor, ensuring the switching member reaches the correct target position without requiring real-time positioning adjustments.
3Manufacturing precision
If manual checking and correction of positional relationship is performed, then positioning accuracy is improved, but time and effort are increased
Solution Approach 1:
The rotation body with its positioning marks performs the positioning function automatically. As it rotates with the cam member, the marks self-align with the displacement sensor's detection field, providing continuous positional reference without requiring manual intervention for checking or correction.
Solution Approach 2:
The displacement sensor continuously monitors the positioning marks on the rotation body, providing real-time feedback about the cam member's angular position. This feedback mechanism automatically maintains positioning accuracy throughout operation, eliminating the need for periodic manual verification and adjustment.
Data Source
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AI summary
An automatic gearshift device for a power tool (11) includes a speed reduction mechanism (18) that decelerates and transmits a rotary power of a motor (16), a ring gear (24) that slides and moves to switch a speed reduction ratio, a cam member (45) that moves the ring gear (24), a rotation body (44) rotated in cooperation with the cam member (45), a position detector (43) that detects the position of the ring gear (24), and a controller (46) that controls the driving of the gearshift motor (27) based on the value generated by the position detector (43). An adjustment gear (42) forming the rotation body (44) includes a slot (42a) used as a positioning mark at a predetermined location in the rotating direction. When the slot (42a) of the adjustment gear (42) is aligned with a predetermined device side positioning reference, the rotation body (44) is positioned in an initial position in a relative positional relationship with the ring gear (24).