Compact E-Bike Drive Unit With Intersecting Motor-Crank Axes
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Solution Overview
Problem
In bicycle drive units, it is challenging to reduce the size of the propulsion assist motor component in a direction parallel to the crankshaft's rotational axis without compromising the motor's output torque or increasing the overall dimensions of the unit.
Innovation Solution
The bicycle drive unit design incorporates a housing with a propulsion assist motor whose rotational axis intersects the crankshaft's axis, allowing for a compact configuration where the motor's output torque ranges from 10 Nm to 80 Nm, and the housing is partially accommodated within the bicycle frame to minimize size while maintaining effective propulsion assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rotational axis of the propulsion assist motor is made parallel to the rotational axis of the crankshaft, then the motor can be positioned conveniently, but the size of the bicycle drive unit in the direction parallel to the crankshaft cannot be reduced
Solution Approach 1:
The patent changes the spatial relationship between the motor and crankshaft from a parallel arrangement to an intersecting arrangement. Specifically, the rotational axis of the propulsion assist motor intersects with the rotational axis of the crankshaft, allowing the motor to be positioned in a different dimensional orientation that reduces the overall length of the drive unit in the direction parallel to the crankshaft while maintaining operational effectiveness
2Length of moving object
If the propulsion assist motor is made compact to reduce size, then the overall dimensions are reduced, but the output torque may be compromised
Solution Approach 1:
The patent specifies precise parameter ranges for the propulsion assist motor to achieve the optimal balance between compact size and sufficient torque output. The maximum output torque is set within the range of 10 Nm to 80 Nm, and the dimension of the first portion in the direction in which the crankshaft extends is limited to 100 mm or less. These parameter changes enable the motor to maintain adequate torque while achieving a compact form factor that reduces overall drive unit dimensions
3Ease of operation
If the housing is made larger to accommodate the motor, then the motor can be properly positioned, but the unified appearance with the frame is compromised
Solution Approach 1:
The patent applies the nesting principle by having the housing at least partially accommodated within the frame of the bicycle. This nested arrangement allows the motor to be properly positioned and accommodated while maintaining a streamlined, unified appearance between the drive unit and the bicycle frame, eliminating the need for external mounting that would compromise aesthetics
Data Source
AI summary
A bicycle drive unit includes a housing, a crankshaft and a propulsion assist motor. The housing is configured to be coupled to a frame of a bicycle. The housing includes first and second portions. The crankshaft is provided to the first portion of the housing. The propulsion assist motor is provided to the second portion of the housing. The propulsion assist has a rotational axis extending in a direction intersecting with a direction in which the crankshaft extends. A maximum dimension of the first portion in the direction in which the crankshaft extends is less than or equal to 100 mm. A maximum output torque of the propulsion assist motor is greater than or equal to 10 Nm and less than or equal to 80 Nm.