Compact Electric Vehicle Drive Unit With Nested Axial Gear Transmission
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Solution Overview
Problem
Existing drive units for electric vehicles face challenges in reducing their size while maintaining sufficient output characteristics.
Innovation Solution
The drive unit incorporates a motor with a rotor having an opening at its center, a housing, a crankshaft, a sprocket, and a power transmission mechanism with gears disposed to overlap in the axial direction of the crankshaft, allowing for compact design and efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the motor and board are placed close together to reduce size, then the drive unit size is reduced, but the output characteristics are compromised
Solution Approach 1:
The patent applies dimensional change by positioning the gear mechanism in the axial direction of the crankshaft, utilizing the opening portion of the rotor to arrange components along the rotation axis rather than only in the radial direction. This allows the power transmission mechanism to be integrated within the motor's axial space, reducing overall drive unit volume while preserving power transmission capability through the concentric arrangement of the motor shaft and crankshaft.
Solution Approach 2:
The patent implements nesting by placing the gear mechanism inside the opening portion of the rotor, effectively utilizing the internal space of the motor structure. The gear is positioned such that its tooth portions overlap axially with the rotor, allowing the power transmission mechanism to be nested within the motor housing without increasing the external dimensions of the drive unit.
2Volume of moving object
If the gear is disposed inside the opening portion with tooth portions overlapping the rotor, then the drive unit size is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The motor shaft is designed to serve multiple functions: it acts as both the rotational output shaft of the motor and as the alignment reference for the crankshaft and gear mechanism. The concentric arrangement of the motor shaft and crankshaft provides a universal positioning reference that simplifies the manufacturing and assembly of the gear mechanism, reducing the precision requirements for individual component positioning.
Solution Approach 2:
The opening portion of the rotor serves a dual purpose: it is both a structural feature of the motor and a positioning feature for the gear mechanism. The axial overlap between the rotor and gear tooth portions allows the rotor itself to provide the positioning reference for the gear, eliminating the need for separate precision positioning features and simplifying manufacturing.
Data Source
AI summary
A drive unit used for an electric vehicle includes: a motor; a crankshaft; a sprocket that outputs a rotational power of the motor; and a power transmission mechanism that decelerates or accelerates the rotational power of the motor to transmit the power to the sprocket, wherein the power transmission mechanism includes at least one gear provided with tooth portions on a surface, the rotor and the tooth portions are disposed at positions overlapping in an axial direction of the crankshaft, and at least part of the gear is disposed inside the opening portion.