Strain Wave Gear Grease Return Path for Bearing Seal Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In unit-type strain wave gearing devices, grease lubrication in the meshing section between internally and externally toothed gears leads to leakage through the oil seal of the bearing due to the pump effect caused by radial deflection of the external gear, resulting in grease flowing into the raceway groove and potentially leaking outside.
Innovation Solution
Incorporating a grease-flowing hole in the externally toothed gear that communicates between the gap between the bearing and the gear, allowing pushed-out grease to flow back into the gear's inner space, reducing the amount of grease entering the raceway groove and minimizing leakage through the oil seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease is coated on or filled in the meshing section for lubrication, then the meshing section is properly lubricated, but grease leaks out through the oil seal due to the pump effect caused by radial deflection of the external gear
Solution Approach 1:
The invention divides the internal space of the externally toothed gear into two separate regions: a meshing section and an inner space, separated by a partition wall. This segmentation prevents grease pushed out by the pump effect from directly entering the raceway groove and leaking through the oil seal, while still maintaining lubrication in the meshing section.
Solution Approach 2:
The partition wall acts as an intermediary structure between the meshing section and the inner space. It allows the system to accommodate the pump effect-induced grease flow while preventing harmful leakage, by providing a controlled interface that directs grease flow away from the raceway groove.
2Ease of operation
If a gap is formed between the cylindrical barrel part and the inner ring of the cross roller bearing to allow relative movement, then the bearing can support the gears in a relative rotatable state, but grease flows into the gap and enters the raceway groove
Solution Approach 1:
The partition wall segments the internal space to create a controlled barrier between the meshing section and the inner space. This allows the gap to remain open for necessary relative movement while preventing uncontrolled grease flow into the raceway groove, as the partition wall restricts grease movement to specific pathways.
3Productivity
If the cylindrical barrel part is repeatedly flexed in the radial direction to enable strain wave gearing operation, then the wave generator functions properly, but grease is pushed out from the meshing section due to the pump effect
Solution Approach 1:
The invention converts the harmful pump effect-induced grease displacement into a beneficial controlled flow path. The partition wall guides the grease pushed out by the wave generator's operation to flow into the inner space through a designated opening, rather than allowing it to enter the raceway groove and cause leakage. This transforms a problematic side effect into a manageable flow pattern.
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
The solution effectively reduces grease leakage by redirecting it back into the gear's inner space, thereby preventing external leakage and maintaining the integrity of the lubrication within the device.
Implementation Method 1
a cylindrical barrel part (12a) capable of flexing in a radial direction... the wave generator (11) repeatedly flexing the cylindrical barrel part (12a) in the radial direction
Implementation Method 2
strain wave gearing device... a flexible externally toothed gear... in which a meshing section between the internally toothed gear and the externally toothed gear is lubricated by grease
Implementation Method 3
Due to the pump effect caused by deflection of the external gear in the radial direction, grease is pushed from the meshing section which is lubricated by the grease
Implementation Method 4
a grease-flowing hole formed in the externally toothed gear, wherein the externally toothed gear is provided with: a cylindrical barrel part capable of flexing in a radial direction... the grease-flowing hole penetrates at least one of the cylindrical barrel part and the diaphragm to communicate between the gap and an inner space of the cylindrical barrel part
Data Source
AI summary
A unit-type strain wave gearing device provided with a cross roller bearing that supports an internally toothed gear and an externally toothed gear in a state in which both gears can rotate relative to each other, and a meshing section of both gears is lubricated with grease. A gap by which the meshing section and the cross roller bearing raceway groove communicate is formed between the inner ring of the cross roller bearing and the external gear. Due to the pump effect caused by deflection of the external gear, grease is pushed from the meshing section to the gap. Some grease is returned to the inner space of the externally toothed gear via a grease-flowing hole that penetrates the diaphragm of the external gear. Thus, leakage of grease from an oil seal of the cross roller bearing to the unit side can be controlled.