Spherical Splined Coupling for Final Drive Wear Reduction
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Solution Overview
Problem
The final drive of agricultural vehicles experiences excessive wear due to misalignment between the wheel shaft and the bull gear, caused by the wheel load-induced bending moment, which is not constant and affects the alignment between the input and wheel shafts, leading to uneven wear patterns.
Innovation Solution
A spherical splined coupling is introduced between the bull gear and the wheel shaft, with curved splines that allow the wheel shaft to rotate without misaligning the bull gear's axis with the input shaft, reducing stress on the meshing teeth and preventing increased wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the wheel shaft is supported by two support bearings spaced from one another along the length of the wheel shaft, then the wheel shaft can be stably supported, but the wheel load induced bending moment causes misalignment between the wheel shaft and bull gear, leading to increased wear at the meshing teeth
Solution Approach 1:
The splined coupling is designed with a spherical shape, featuring a spherical outer surface that fits into a spherical inner surface. This spherical geometry allows the wheel shaft to rotate about any diameter of the sphere, accommodating misalignment caused by bending moments while preventing increased wear at the meshing teeth between the bull gear and input shaft
2Reliability
If curved teeth are provided to the coupling to take up misalignment of the bull gear, then wear is reduced, but the contact surface between meshing teeth becomes too small to adequately transfer drive from the input shaft to the bull gear
Solution Approach 1:
The spherical splined coupling provides a curved surface that accommodates angular misalignment while maintaining adequate contact area. The spherical geometry allows rotation about any diameter while preserving sufficient meshing surface area between the bull gear and input shaft teeth, thus maintaining both wear resistance and torque transmission capability
3Force
If the axis of the wheel shaft moves out of parallel alignment with the input shaft due to wheel load, then the final drive can support the weight, but the misalignment accelerates wear of the gearing coupling the two shafts
Solution Approach 1:
The spherical splined coupling enables the wheel shaft axis to move out of parallel alignment with the input shaft to support wheel loads, while the spherical geometry simultaneously prevents accelerated wear of the gearing. The spherical outer surface of the coupling fits into the spherical inner surface, allowing rotation about any diameter and accommodating misalignment without increasing stress on the meshing teeth
Data Source
Figure 1
Figure 2
AI summary
A final drive for an agricultural vehicle has a casing (10), a wheel shaft (12) supported in the casing by means of two support bearings (16,18) spaced from one another along the length of the wheel shaft (12), an input shaft (20) rotatably supported in the casing (10) with its axis parallel to but laterally offset from that of the wheel shaft (12), and a bull gear (26) connected to the wheel shaft (12) by means of a splined coupling (30') disposed between the support bearings (16,18) of the wheel shaft and having external teeth (32) meshing with teeth on the input shaft (20) to transmit torque to the wheel shaft (12) from the input shaft (20). In order to reduce wear on the gearing of the final drive, the splined coupling (30') between the bull gear and the wheel shaft is spherical.