Roller Speed Reducer Layout for Lower Axial Bearing Load
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Solution Overview
Problem
Existing power transmission devices, such as speed reducers, require larger bearings to support both radial and axial loads, leading to increased size and torque loss due to the use of balls that contact at inclined angles, which are less tolerant in the axial direction.
Innovation Solution
The use of cylindrical rollers as rolling elements that primarily transmit torque in the radial direction, with symmetrically arranged fixed members to cancel out moments and reduce axial loads, allowing for miniaturization of bearings and improved torque transmission efficiency by using friction reducing members at contact points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If balls are used as rolling elements that contact at inclined angles, then torque transmission is achieved, but axial loads are generated requiring larger bearings
Solution Approach 1:
The patent changes the rolling element shape from spherical (balls) to cylindrical (rollers), which fundamentally alters the contact mechanics. Cylindrical rollers contact the corrugated groove at angles closer to the radial direction, significantly reducing the axial load component while maintaining effective torque transmission capability
Solution Approach 2:
The patent introduces fixed members with rolling element engaging grooves at specific locations to create localized contact points. By positioning these grooves symmetrically above and below the rotation center, the design ensures that axial load components from different contact points cancel each other out, while radial components effectively transmit torque
2Force
If larger bearings are used to support both radial and axial loads, then load capacity is improved, but device size increases
Solution Approach 1:
By changing from balls to cylindrical rollers, the patent fundamentally alters the load distribution characteristics. The roller geometry naturally directs contact forces closer to the radial direction, eliminating the need for bearings to support significant axial loads, thus allowing smaller bearing selection
Solution Approach 2:
The patent employs symmetric arrangement of fixed members and rolling element engaging grooves above and below the rotation center. This symmetry creates counterbalancing axial load components that cancel each other out, effectively neutralizing the axial load that would otherwise require larger bearings
3Power
If balls are used as rolling elements, then torque transmission occurs, but torque loss increases due to axial load components
Solution Approach 1:
The patent changes the rolling element from spherical to cylindrical shape, which modifies the contact angle characteristics. Cylindrical rollers maintain more favorable contact angles with the corrugated groove, reducing the axial load component and thereby minimizing torque loss in the bearing
Solution Approach 2:
By introducing fixed members with specifically positioned rolling element engaging grooves, the patent creates optimized local contact zones. These localized contact points are arranged to maximize radial torque transmission while minimizing axial load generation, reducing energy loss
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 solution miniaturizes the power transmission device, reduces torque loss, and enhances efficiency by limiting bearing loads to radial directions and preventing roller collapse through symmetric contact force distribution.
Implementation Method 1
a plurality of rollers 4 having cylindrical outer peripheral surfaces as rolling elements that transmit a rotation input to an input rotating part 2 to an output rotating part 3 coaxially disposed at a predetermined gear ratio
Implementation Method 2
the pair of fixed members 5 and the pair of output members 31 and 32 are disposed symmetrically in the axial direction around the input member 10, the rollers 4 are inserted into the first pockets 13 of the input member 10 and the second pockets 17 of the pair of output members 31 and 32, and both ends of each roller 4 in the axial direction engage with the rolling element engaging grooves 16 of both fixed members 5
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A speed reducer 1 includes a plurality of rollers 4, an input member 10 (first member) having a plurality of first pockets 13 into which the plurality of rollers 4 is inserted, a pair of fixed members 5 (second members) provided on both sides of the input member 10 in an axial direction and each having a rolling element engaging groove 16 engaging with the plurality of rollers 4, and a pair of output members 31 and 32 (third members) provided between the input member 10 and the pair of fixed members 5 in the axial direction and having a plurality of second pockets 17 into which the plurality of rollers 4 is inserted. The plurality of first pockets 13 is formed along a circle having a curvature center eccentric from a rotation center X. The rolling element engaging groove 16 is formed along a corrugated curve alternately intersecting a pitch circle having a curvature center on the rotation center X.