Power Tool Spindle Positioning for Balanced Center of Gravity
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Solution Overview
Problem
The existing screwdriver design with a clutch detecting mechanism radially outward of the clutch and in front of the motor results in an unbalanced center of gravity, making the tool less user-friendly for performing operations.
Innovation Solution
A power tool with a rotary shaft that can move between two positions, featuring a brushless motor and a detecting mechanism positioned opposite the rotation transmitting mechanism, allowing for controlled rotation speed based on the shaft's position, which balances the center of gravity and enhances operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch detecting mechanism is provided radially outward of the clutch and in front of the motor, then the clutch engagement can be detected, but the center of gravity shifts to the front end region making the tool less user-friendly
Solution Approach 1:
The detecting mechanism is inverted from its conventional position (radially outward and in front of the motor) to a position on the rear side of the motor, opposite to the rotation transmitting mechanism. This inversion relocates the center of gravity to the rear region, improving balance and user-friendliness while maintaining detection functionality through the rear-side positioning of the detector relative to the rotating shaft.
2Strength
If the rotary shaft is held fixed in the front end region, then the tool accessory can be securely held, but the center of gravity is located in the front region reducing operability
Solution Approach 1:
The rotary shaft is made movable between a front end region position and a rear region position along the axial direction. This dynamic positioning allows the shaft to be located at the front for secure tool accessory holding, and enables the detecting mechanism to be positioned at the rear, thereby balancing the center of gravity and improving overall operability.
3Device complexity
If a conventional motor with brush is used, then the structure is simpler, but the rotation speed control is less accurate and power consumption is higher
Solution Approach 1:
The conventional motor with mechanical brush contact is replaced with a brushless motor that uses electromagnetic fields for commutation. This substitution eliminates mechanical wear, improves rotation speed control accuracy through electronic control, and reduces power consumption, while the added complexity is offset by the rear-side positioning of the detecting mechanism that maintains overall tool balance.
Data Source
AI summary
It is an object of the invention to provide a technique for enhancing the operability of a power tool.A representative screwdriver 100 is provided which has a motor 110 and a driving mechanism 120. The driving mechanism 120 has a rotation transmitting mechanism including a driving cam 137 and a driven cam 157, and a cam engagement state is switched by movement of the spindle 150 in a longitudinal direction of the spindle. The position of the spindle 150 in the longitudinal direction is detected by a detecting mechanism 162 that is disposed on the opposite side of the rotation transmitting mechanism from a front end region in the longitudinal direction of the spindle 150. A controller 180 controls the rotation speed of the motor 110 based on the detection result of the detecting mechanism 162 and drives the motor 110.