Planetary Gear Shaft Skew Compensation Under Carrier Twist
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Solution Overview
Problem
The twisting deformation of a planet carrier in planetary gears causes skewed geometric axes of rotation, impairing meshing between planet wheels and sun/gear rings, leading to reduced torque transfer capacity and shorter gear life, necessitating costly materials and design compensation.
Innovation Solution
Planet wheel shafts with end-portions and a middle-portion that are skewed relative to each other, allowing for twisting deformation compensation in the planet carrier, which reduces material tensions and maintains geometric axis alignment under load, using a planet carrier with shifted holes for ends of the shafts to manage torque distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planet wheel shafts are made more flexible to compensate for twisting deformation, then the skewedness of geometric axes is reduced and load sharing is equalized, but material tensions increase and torque transfer capacity decreases
Solution Approach 1:
The planet wheel shaft is designed with non-uniform flexibility: the first end-section has lower flexibility (higher rigidity) while the second end-section has higher flexibility (lower rigidity). This local differentiation allows the shaft to compensate for twisting deformation at the loaded end while maintaining sufficient stiffness at the other end to transmit torque effectively, thus resolving the contradiction between meshing quality and torque transfer capacity.
2Strength
If rigid planet wheel shafts are used, then torque transfer capacity is improved, but twisting deformation compensation is insufficient and skewedness increases
Solution Approach 1:
The planet wheel shaft is designed with non-uniform flexibility: the first end-section has lower flexibility (higher rigidity) while the second end-section has higher flexibility (lower rigidity). This local differentiation allows the shaft to compensate for twisting deformation at the loaded end while maintaining sufficient stiffness at the other end to transmit torque effectively, thus resolving the contradiction between meshing quality and torque transfer capacity.
3Duration of action of stationary object
If flexible planet wheel shafts are used to eliminate skewedness, then bearing life is extended, but material tensions increase requiring expensive materials
Solution Approach 1:
The planet wheel shaft is designed with non-uniform flexibility: the first end-section has lower flexibility (higher rigidity) while the second end-section has higher flexibility (lower rigidity). This local differentiation allows the shaft to compensate for twisting deformation at the loaded end while maintaining sufficient stiffness at the other end to transmit torque effectively, thus resolving the contradiction between meshing quality and torque transfer capacity.
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 design extends the life of planetary gear bearings, reduces material tensions, and enhances torque transfer capacity without the need for expensive materials, while minimizing skewedness compensation in planet wheel design.
Implementation Method 1
the planet carrier is twisted with respect to each other. The twisting deformation of the planet carrier leads to a situation where geometric axes of rotation of the planet wheels are skewed
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3b
AI summary
A planetary gear comprises a planet carrier (104), a sun wheel, a gear ring (103), and planet wheels (105-107) meshing with the sun wheel and with the gear ring. Each planet wheel shaft (109) of the planetary gear is arranged to rotatably support a respective planet wheel so that, in an unloaded situation, a geometric axis of rotation (113) of the planet wheel is skewed (α) with respect to the axial direction (z) of the planetary gear. In a loaded situation, torque directed to the planet carrier causes twisting deformation in the planet carrier and thereby the skewedness of the geometric axis of rotation is at least partly eliminated by the twisting deformation. Thus, in the loaded situation, the direction of the geometric axis of rotation can be closer to the axial direction than in a planetary gear where there is no skewedness in an unloaded situation.