Floating Sun Gear Planetary System with Helical Gearing
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Solution Overview
Problem
In planetary gear systems with flexpins, the use of spur gears leads to unequal torque transfer through each array due to different torsional spring rates, resulting in inefficient power distribution and potential misalignment of planet pinions under thrust loads, which are exacerbated by helical gearing that experiences radial deflection.
Innovation Solution
The implementation of a planetary gear system with helical gearing and planet pinions arranged in two arrays on flexpins, where the sun and ring gears have opposite helix angles, and the planet pinions have single angle helixes, along with a floating sun gear that compensates for deflection by adjusting its position to maintain equal axial forces and thus equal torque transfer through both torque paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If spur gears are used in a planetary gear system with flexpins, then the system can transfer torque, but unequal torque transfer occurs through each array due to different torsional spring rates
Solution Approach 1:
The patent changes the gear type from spur gears to helical gears, fundamentally altering the engagement characteristics and force distribution. Helical gears provide gradual tooth engagement and better load distribution, which helps equalize torque transfer through both arrays despite differences in torsional spring rates of the flexpins.
Solution Approach 2:
The patent introduces asymmetry by giving the sun gear and ring gear opposite hand helices, while planet pinions in different arrays have different helix angles. This asymmetric configuration compensates for the asymmetric torsional spring rates of the flexpins, enabling equal torque distribution through both torque paths.
2Object-affected harmful factors
If helical gearing is used to operate smoothly with less noise, then thrust loads are generated that tilt the planet pinions and disturb the mesh
Solution Approach 1:
The patent uses asymmetric helix angle configuration where the sun gear and ring gear have opposite hand helices, and planet pinions in different arrays have different helix angles. This asymmetry creates balancing thrust loads that counteract each other, preventing planet pinion tilting and maintaining stable mesh despite the inherent thrust loads from helical gearing.
Solution Approach 2:
The patent employs the concept of counterbalancing by arranging planet pinions in two arrays with opposite hand helices. The thrust loads generated by one array counteract the thrust loads from the other array, eliminating the net tilting moment that would otherwise disturb the mesh and causing noise.
3Volume of moving object
If planet pinions are arranged on flexpins to achieve maximum downsizing, then torque transfer paths have different stiffness leading to unequal power distribution
Solution Approach 1:
The patent changes from spur gears to helical gears with specifically designed helix angles for planet pinions in different arrays. This parameter change enables the system to maintain compact flexpin architecture while achieving equal power distribution through both torque paths by compensating for the inherent stiffness differences.
Solution Approach 2:
The patent applies different helix angles to planet pinions in different arrays, creating local quality differences that compensate for the different torsional spring rates of the flexpins. This localized parameter optimization ensures equal torque transfer through each array while maintaining the compact downsized structure.
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 equal torque transfer through both torque paths, minimizing deflection and maintaining a stable mesh between planet pinions and gears, thereby achieving balanced power distribution and reducing noise and misalignment issues.
Implementation Method 1
a floating sun gear that compensates for deflection by adjusting its position to maintain equal axial forces
Implementation Method 2
The sun and ring gears have opposite helix angles, and the planet pinions have single angle helixes
Data Source
AI summary
A planetary gear system (P) includes a sun gear (2), a ring gear (4) a carrier (6) located between the sun and ring gears (2, 4), and planet pinions (8, 10) organized in two arrays and supported on flexpin assemblies (32, 34) in the carrier (6). All of the gearing is helical, with the sun and ring gears (2, 4) having their teeth arranged in at double helix angles (herringbone) and the planet gears (8, 10) at single helix angles. The pinions (8) of the one array engage the teeth of one angle on the sun and ring gears (2, 4) and the pinions (10) of the other array engage the teeth of the other angle on the sun and ring gears (2, 4). Torque transfers through the carrier (6) through two torque paths (a, b) - one to the flexpin assemblies (32) for one array and the other to the flexpin assemblies (34) of the other array - and the paths (a) is stiffer than the path (b). Owing to the helical cut of the teeth the planet pinions (8, 10) of the two arrays exert oppositely directed axial forces (A) on the sun gear (2). The sun gear (2) is free to shift axially or float with respect to the planet pinions (8, 10) of the two arrays, so the axial forces (A) imparted to the sun gear, while opposite, are equal. Hence, the tangential forces (T), which transfer the torque, are likewise equal, notwithstanding the difference in flexibility of the two torque paths (a, b). Even though the carrier (6) may undergo different deflections at the flexpin assemblies (32, 34) for the two arrays of planet pinions (8, 10), the planet pinions (8, 10) of the two arrays transfer torques of equal magnitude.