Planetary Transmission Lubrication Barrier in Portable Power Tools
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Solution Overview
Problem
The centrifugal forces generated by the rotating ring gear in planetary transmissions of portable power tools make it difficult to reliably lubricate and meter lubricant to the planet gears, leading to increased friction and wear.
Innovation Solution
A cylindrical cutout in the planet gear and a circular arc collar on the planet carrier form a barrier that counteracts centrifugal forces, allowing lubricant to enter and preventing its ejection, ensuring effective lubrication of the planet gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the planetary transmission operates at high speed, then productivity is improved, but centrifugal forces increase making lubricant delivery unreliable
Solution Approach 1:
The collar is divided into multiple segments that can move independently relative to each other. This segmentation allows the collar to flex and adapt to centrifugal forces while maintaining the barrier function, ensuring reliable lubricant delivery even at high operating speeds
Solution Approach 2:
The collar transitions from a static structure to a dynamic one with segments that can move relative to each other. This dynamic structure allows the collar to respond to varying centrifugal forces during operation, maintaining effective lubricant barrier function across different speed conditions
2Speed
If centrifugal forces are high, then speed is improved, but lubricant ejection increases reducing lubrication effectiveness
Solution Approach 1:
The collar is segmented into multiple movable parts that can adjust to centrifugal forces. This segmentation prevents the collar from acting as a rigid barrier that would be completely overwhelmed by high-speed centrifugal forces, thereby reducing lubricant ejection
Solution Approach 2:
The movable collar segments act as an intermediary between the high-speed rotating components and the lubricant. They dynamically adjust to centrifugal forces, mediating the interaction between speed and lubricant retention to prevent excessive ejection
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
This configuration ensures consistent lubrication of the planet gears, reducing friction and wear, thereby enhancing the performance and longevity of the planetary transmission in portable power tools.
Implementation Method 1
Centrifugal forces brought about by the rotating ring gear make it harder to reliably feed and meter the lubricant in the region of the planet gears
Implementation Method 2
The individual moved components of the planetary transmission are wetted with a lubricant in order to reduce friction and wear
Data Source
AI summary
A portable power tool 1 has a tool holder 2 for retaining a tool 3, a handle 7, an electric motor 4, and a drive train 10. The drive train couples the electric motor 4 to the tool holder 2. The drive train 10 contains a planetary transmission 11 with a planet carrier 13 and a plurality of planet gears 14. At least one of the planet gears 14 has a cylindrical cutout 30 and the planet carrier 13 has a collar 24 in the form of a circular arc that protrudes into the cutout 30.