Dual Spur Gear E-Bike Drive Assembly for Seamless Power Shifting
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Solution Overview
Problem
Existing drive arrangements with manual transmissions on the bottom bracket suffer from increased size, inefficiency, lack of power shifting capability, interruptions in tractive force, and idle travel, particularly in friction ring gears and hollow shaft motor systems.
Innovation Solution
A drive arrangement with a rotationally adjustable spur gear system that includes a first and second spur gear shift transmission, coupled via independent coupling devices to achieve a variable transmission ratio without interruption of traction, utilizing planetary gears and friction clutches for efficient torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If friction ring gearboxes or hollow shaft motors are integrated into the bottom bracket drive, then the drive system can transmit torque, but the size increases and efficiency decreases with increased losses
Solution Approach 1:
The drive system is segmented into two separate spur gear transmissions (first and second) that can operate independently. Each transmission handles specific torque ranges, allowing optimization of each segment rather than using a single complex transmission system. This segmentation reduces overall losses while maintaining compact size.
Solution Approach 2:
The system dynamically switches between the first and second spur gear transmissions based on torque requirements. The variable transmission ratio is achieved by selectively engaging different gear stages, allowing the system to adapt to varying load conditions and maintain high efficiency across different operating points.
2Adaptability or versatility
If manual transmission systems are used in the bottom bracket, then the structure can be simplified, but power shifting capability is lost and tractive force interruptions occur
Solution Approach 1:
The system performs preliminary gear selection in the unloaded state before torque application. The variable transmission ratio can be changed by selecting different gear combinations in advance, and only after the new ratio is prepared does the system engage the selected gear stage, ensuring seamless power transfer without traction interruptions.
Solution Approach 2:
The dual spur gear transmission design ensures continuous torque transmission by having one transmission ready to take over as the other disengages. The overlapping capability and rapid switching mechanism maintain uninterrupted power flow to the output, eliminating free play and ensuring continuous tractive force.
3Adaptability or versatility
If a single-stage transmission is used, then the structure can be simplified, but the ability to provide variable transmission ratios under load is limited
Solution Approach 1:
The transmission system is divided into two separate spur gear transmissions, each with specific gear ratios. This segmentation allows the system to offer multiple variable transmission ratios by selectively engaging different gear stages from the two transmissions, providing adaptability without requiring a single complex multi-stage transmission.
Solution Approach 2:
Both the first and second spur gear transmissions share a common output and can function interchangeably depending on torque requirements. This multi-functionality allows the system to achieve variable transmission ratios using two relatively simple transmission units rather than one complex transmission, reducing overall structural complexity while maintaining versatility.
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
Enables efficient torque transmission with reduced losses and negligible idle travel, allowing for seamless power shifting and compact design suitable for electric bicycles and pedelecs.
Implementation Method 1
a first coupling device (21) is assigned to the first spur gear transmission (51) and a second coupling device (22) is assigned to the second spur gear transmission (52)
Data Source
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AI summary
The invention relates to a drive assembly (80) for a vehicle (1), an electric bicycle, ebike, or pedelec, which can be driven by muscle force and/or motor force, in particular which can additionally be driven by motor force, and which comprises a crankshaft (15) that can be rotated about a rotational axis (Y) for receiving a first torque generated by muscle force in particular and a transmission device (20), said transmission device being designed to transmit the first torque from the crankshaft (15) to an output element (4) which can be coupled to a drive wheel (9-2) of the vehicle (1) and for a variable transmission by means of a multistage shiftable spur gear transmission (50), in particular an automatically shiftable spur gear transmission, wherein the spur gear transmission (50) has a first spur gear shift transmission (51) and a second spur gear shift transmission (52) which is separate from the first spur gear shift transmission for the variable transmission. The first spur gear shift transmission (51) and the second spur gear shift transmission (52) have a common transmission output for the output element (4) which can be coupled thereto, and the first spur gear shift transmission (51) and the second spur gear shift transmission (52) can be coupled reciprocally and alternatively into the power flow and torque flow of the transmission device (20).