Cordless Circular Saw Gravity Center Balancing
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Solution Overview
Problem
The transition to a brushless motor in cordless circular saws results in a shorter motor length, allowing for reduced product width, but leads to a heavier gear cover side, causing the gravity center to shift closer, thereby deteriorating operability.
Innovation Solution
The cordless circular saw design positions the battery pack on the left side relative to the handle portion and places the control circuit board between the battery pack and the saw cover, balancing the gravity center and maintaining a compact layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a brushless motor is used as the driving source, then the motor length is shortened and the full width of the product is reduced, but the gear cover side becomes heavier and the gravity center shifts closer to the gear cover side, deteriorating operability
Solution Approach 1:
The patent redistributes components along the longitudinal axis (front-rear direction) rather than only laterally. By positioning the battery pack at the rear and the control circuit board in the intermediate region, the design balances the gravity center along the longitudinal dimension, compensating for the weight shift caused by the brushless motor while maintaining compact width.
Solution Approach 2:
The patent employs asymmetric component layout where the battery pack is positioned at the rear and the control circuit board is placed in the intermediate region between the battery pack and the circular saw blade. This asymmetric arrangement strategically balances the gravity center to offset the weight concentration on the gear cover side, thereby maintaining operability despite using a lighter brushless motor.
2Weight of moving object
If the motor weight is reduced by using a brushless motor, then the full width is reduced, but the gravity center position shifts closer to the gear cover side
Solution Approach 1:
The patent uses the battery pack and control circuit board as counterweights to balance the gravity center. By strategically positioning these components, they create a counterbalancing effect that offsets the weight reduction on the motor side and the weight concentration on the gear cover side, thereby maintaining an optimal gravity center position for operability.
3Ease of operation
If the control circuit board is positioned to balance the gravity center, then operability is improved, but the layout complexity increases
Solution Approach 1:
The patent merges the control circuit board placement with the gravity center balancing requirement. By positioning the control circuit board in the intermediate region between the battery pack and the circular saw blade, the design simultaneously achieves functional requirements (control circuit placement) and ergonomic requirements (gravity center balancing) in a single integrated layout decision, reducing overall system complexity.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A cordless circular saw includes a handle portion (4) a rechargeable battery (20) which is removably attached to a battery attaching portion (4a) provided at the handle portion (4), a brushless motor (9) which operates by electric power from the rechargeable battery (20), a control circuit board (21) which has a controller for the brushless motor (9), a circular saw blade (8) which is rotated by the brushless motor (9), and a gear cover (5) which accommodates a mechanism for transmitting rotation between the brushless motor (9) and the circular saw blade (8). The brushless motor (9) is provided on one side of a left side and a right side of the handle portion (4). The gear cover (5) and the circular saw blade (8) are provided on the other side of the handle portion (4). The rechargeable battery (20) extends from the handle portion (4) toward the one side of the handle portion (4). The control circuit board (21) is provided between the rechargeable battery (20) and the circular saw blade (8).