Cycloidal Gear Relief Contours for Efficient E-Bike Torque Drive
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Solution Overview
Problem
Cycloidal gears used in electric bicycle drives lack optimization for high efficiency, low mass, small space requirements, reduced heat generation, and high power capacity, which are essential for bicycle applications, as they are primarily designed for robotics where exact positioning is prioritized over power transmission efficiency.
Innovation Solution
The cycloidal gear design features an eccentric arrangement of cycloid disk and counter-cycloid devices with free-cut contours that reduce radial forces and enhance torque transmission, along with a hermetically encapsulated structure for improved lubrication and maintainability, and the use of polymer materials for noise reduction and weight savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cycloidal gears are designed for high gear ratio and exact positioning (robotics application), then positioning precision is improved, but power transmission efficiency deteriorates
Solution Approach 1:
The cycloidal disk is designed with differentiated toothing zones: a first toothing zone with high gear ratio for positioning precision and a second toothing zone with lower gear ratio for power transmission efficiency. Each zone has optimized tooth geometry and engagement characteristics suited to its specific function, allowing the single component to excel at both positioning and power transmission without compromise.
2Strength
If cycloidal gears use traditional solid materials for strength, then structural integrity is improved, but mass and weight increase
Solution Approach 1:
The cycloidal disk employs composite construction combining aluminum alloy base material with polymer material inserts in the toothing zones. The aluminum alloy provides overall structural strength and rigidity, while the polymer material enhances tooth surface durability and reduces weight. This composite approach achieves both high strength and low weight requirements for bicycle drive applications.
3Power
If cycloidal gears operate with high radial forces for torque transmission, then power capacity is improved, but heat generation and wear increase
Solution Approach 1:
A lubricant is introduced as an intermediary substance between the cycloidal disk toothing surfaces and counter-toothing surfaces. The lubricant forms a protective film that reduces direct metal-to-metal contact, minimizing friction and heat generation during high-torque operation. This enables the gear to transmit high power while maintaining acceptable operating temperatures and reducing wear.
4Volume of moving object
If cycloidal gears are designed for compact size to meet space requirements, then installation space is reduced, but manufacturing complexity increases
Solution Approach 1:
The cycloidal disk is segmented into distinct functional zones with different toothing characteristics: a first toothing zone with cycloidal contours for high gear ratio and a second toothing zone with modified contours for power transmission. This segmentation allows each zone to be optimized independently for its specific function while maintaining a compact overall geometry suitable for bicycle drive applications.
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 achieves high efficiency, reduced noise, and extended service life while minimizing mass and weight, optimizing the cycloidal gear for electric bicycle drives by improving power transmission and structural integrity.
Implementation Method 1
a drive shaft device (1010, 1110) with an eccentric arrangement (1012, 1112) and an output shaft device (1020, 1120), wherein the drive shaft device (1010, 1110) and the output shaft device (1020, 1120) are arranged concentrically to one another and to an imaginary central axis (1002, 1102) of the cycloidal transmission
Implementation Method 2
at least one cycloidal disk device (1030, 1130) with a total of at least two at least approximately cycloidal or cylindrical cycloidal toothing arrangements (1032, 1132) and at least one counter-cycloidal device (1040, 1140) with a total of at least two at least approximately cycloidal or cylindrical counter-toothing arrangements (1042, 1142)
Data Source
Figure 1
Figure 2~2A
Figure 3~3A
AI summary
The present disclosure relates to a cycloidal gear (CG), an electric bicycle drive unit (DU) with a cycloidal gear (CG), an axial freewheel device (FA) for the drive unit (DU), and a speed sensor device (TMS) for the drive unit. The cycloidal gear (CG) comprises a drive shaft device (DSD), an eccentric arrangement (AE), and an output shaft device (SO), as well as at least one cycloidal disc device (DC1, DC2) with cycloidal gear arrangements (CT1, CT2) and at least one counter-cycloidal device (OC1, OC2) with counter-gear arrangements (OT1, OT2).In contact areas (CD1, CD2) of cycloidal disc device (DC1, DC2) and counter-cycloidal device (OC1, OC2), drive forces (FD1, FD2) in the circumferential direction of the cycloidal gear (CG) can be transmitted by means of drive contact between cycloidal disc contours (PC1, PC2) of the cycloidal gear arrangements and counter-cycloidal contours (PO1, PO2) of the at least one counter-cycloidal device (OC1, OC2) at least within a respective load flank sub-area (AL1, AL2). At least one of the cycloidal gear arrangements (CT1, CT2) and/or at least one of the counter-gear arrangements (OT1, OT2) has a relief contour (PR1, PR2) that is reduced in size along a relief area (AC1, AC2) arranged outside its load flank sub-area (AL1, AL2) of the respective contour (PC1, PC2, PO1, PO2) compared to the respective contour (PC1, PC2, PO1, PO2).This results in improvements to the cycloidal gear in terms of efficiency, heat and noise generation, wear and service life as well as manufacturing costs, while simultaneously reducing installation space and mass.