Power Tool Gear Shift Mechanism Using Thrust Bearing Mediator
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Solution Overview
Problem
Existing power tools face poor operability and inefficient meshing of transmission gears due to strong contact between teeth crests, leading to difficulties in smoothly switching transmission ratios.
Innovation Solution
A power tool design incorporating a gear train with a transmission ratio switching operation unit, a holding spring, and a biasing mechanism that uses a turning biasing mechanism to engage the gear operation mechanism in the thrust shaft direction, ensuring smooth meshing of transmission and meshed gears by converting turning motion into movement in the thrust shaft direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission paddle is turned to change the transmission ratio, then the transmission ratio switching is achieved, but the operability of the transmission paddle deteriorates due to strong contact between the crests of teeth
Solution Approach 1:
A thrust bearing is introduced as an intermediary component between the ring gear and the meshed gear. This thrust bearing absorbs the contact force between the crests of teeth when the transmission paddle is operated, preventing direct transmission of this force to the gears. The thrust bearing acts as a mediator that allows the transmission ratio switching to occur smoothly without the harmful contact forces affecting the operability of the transmission paddle.
2Reliability
If the inclined cam presses the pushpin to move the ring gear in the thrust shaft direction, then the transmission ratio changes, but the crests of the teeth abut strongly against each other causing poor meshing
Solution Approach 1:
The thrust bearing serves as a mediator that separates the ring gear and the meshed gear, preventing direct contact between their crests of teeth. When the inclined cam presses the pushpin to move the ring gear in the thrust shaft direction, the thrust bearing absorbs the contact forces, allowing the gears to be positioned accurately without the harmful abutment forces that would degrade meshing quality.
Solution Approach 2:
The thrust bearing provides beforehand cushioning by being pre-installed between the ring gear and the meshed gear. This cushioning effect is active before the transmission ratio switching occurs, preventing the strong abutment of tooth crests from degrading the gear meshing quality. The thrust bearing is in place to absorb any contact forces that may occur during the switching operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances operability and ensures smooth switching of transmission ratios without deteriorating the operation unit's performance, allowing for effective gear meshing and efficient speed changes.
Implementation Method 1
When the pushpin pushes a coil spring, a biasing force of the coil spring is applied to a ring gear (transmission gear) in the thrust shaft direction. As a result, the ring gear moves in the thrust shaft direction
Implementation Method 2
an inclined cam formed on the transmission ratio switching ring moves a pushpin in a thrust shaft direction
Data Source
Figure 1
Figure 2~3D
Figure 4
AI summary
A power tool (11) includes a transmission mechanism (17) capable of selecting one of a plurality of transmission gear ratios by changing a combination of gears of a gear train (30) to be meshed with each other, a transmission ratio switching operation unit (25; 26) capable of turning around the thrust shaft and operating to change the combination of the gears, a gear operation mechanism (63, 29a, 42c, 46b) to move a transmission gear (42; 46) of the gear train in a thrust shaft direction in accordance with turning motion of the transmission ratio switching operation unit, and a biasing mechanism (32, 65) to bias the gear operation mechanism in accordance with the turning motion of the transmission ratio switching operation unit such that the transmission gear moves in the thrust shaft direction and meshes with a meshed gear corresponding to the selected transmission gear ratio.