Grass Cutter Planetary Gear Guide Mechanism Backlash Control
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Solution Overview
Problem
The two-blade grass cutter with a planetary gear train suffers from durability issues due to backlash and gear misalignment caused by wear, leading to tooth skipping and hindered rotation when used in heavy load states for business purposes.
Innovation Solution
Incorporating a sun gear-side guide and a ring gear-side guide that engage directly or through another member to prevent radial movement, along with a thickened small gear that can be reversed for extended use, and seal packing to support radial and thrust loads, maintaining the positional relationship between the sun gear and ring gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the planetary gear train is used to decelerate the motor for rotating blade plates at low speed, then safety is improved by preventing broken blade pieces from flying away, but durability deteriorates due to backlash and gear misalignment caused by wear in heavy load states
Solution Approach 1:
The patent applies beforehand cushioning by providing guide members (sun gear guide and ring gear guide) that preemptively prevent radial movement and misalignment of gears before wear can cause backlash. The guide members create a constrained pathway that compensates for and prevents the harmful effects of wear, maintaining proper gear engagement even after extended use in heavy load states.
Solution Approach 2:
The guide members act as intermediary elements between the sun gear and ring gear, mediating their relative positions and preventing direct harmful interactions. The guide members transmit and distribute the loads while maintaining the correct spatial relationship between gears, preventing backlash and misalignment that would otherwise occur due to wear in the planetary gear train.
2Duration of action of moving object
If the small gears are worn out due to long use in heavy load state, then gaps between gears are enlarged, but the patent thickens the small gear and allows periodic reversal to extend its life
Solution Approach 1:
The patent applies discarding and recovering by allowing the small gear to be periodically reversed and reused. Instead of discarding the worn small gear, the design enables it to be flipped and continued in service, effectively doubling its potential service life while maintaining reliable gear engagement through the guide members that prevent misalignment during this extended usage.
Solution Approach 2:
The patent changes the parameter of the small gear by thickening it (increasing its dimensional size) to allow for wear while maintaining functional clearance. The increased thickness provides a buffer against wear, and when wear does occur, the gear can be reversed to use the opposite face, effectively extending the service life while maintaining reliable engagement parameters.
3Reliability
If thrust load is applied only to the sun gear or ring gear during grass cutting operation, then eccentric force is generated that makes the gear eccentric, but the guide members prevent radial movement to maintain concentric alignment
Solution Approach 1:
The guide members function as counterbalancing elements that oppose and neutralize the eccentric forces generated during operation. When thrust loads create eccentric forces that would normally cause radial movement and misalignment, the guide members provide counteracting constraints that prevent this movement, maintaining the concentric alignment of the sun gear and ring gear despite the applied forces.
Solution Approach 2:
The guide members provide beforehand cushioning by pre-establishing constrained pathways that prevent radial movement before eccentric forces can cause harmful misalignment. The guides create a protective framework that anticipates and prevents the damaging effects of eccentric loading, maintaining proper gear alignment even under heavy thrust loads during grass cutting operations.
Data Source
AI summary
A body unit of a grass cutter incorporates a deceleration mechanism unit. The deceleration mechanism unit has a ring gear-side member, a sun gear-side member, a retainer board member, and a small gear. Eleven rollers mounted on the retainer board member are each provided in a gap between a ring gear-side guide and a sun gear-side guide, and engagement portions of the rollers are in contact with both the ring gear-side guide and the sun gear-side guide. The small gear engages with both a ring gear and a sun gear.