Flexible Printed Circuit for E-Bike Drive Unit Packaging
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Solution Overview
Problem
Existing electrically assisted bicycle drive units are constrained by the limited space available, restricting the positional arrangement of components and requiring a reduction in drive unit size to enhance flexibility and efficiency.
Innovation Solution
The use of flexible printed circuits to connect rigid boards and components within the drive unit, allowing for increased positional freedom and reduced space requirements, along with separate power and control circuit boards and a reinforcing plate for enhanced connectivity and noise suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional wiring methods (round wires) are used to connect components in the drive unit, then electrical connectivity is achieved, but the drive unit size increases and positional arrangement flexibility is reduced
Solution Approach 1:
The patent applies flexible printed circuits (thin film structures) instead of traditional round wires for electrical connections within the drive unit. The flexible printed circuit board includes conductive patterns on a flexible substrate that can be bent and shaped to accommodate different component positions, reducing the overall space required while maintaining electrical connectivity. This directly resolves the contradiction by enabling compact packaging without sacrificing adaptability.
2Volume of moving object
If components are arranged with high positional freedom to reduce drive unit size, then space efficiency improves, but connection reliability and signal integrity may deteriorate
Solution Approach 1:
The flexible printed circuit provides reliable electrical connections through controlled impedance traces and proper grounding schemes embedded in the flexible substrate. The rigid board with ground patterns works in conjunction with the flexible circuit to maintain signal integrity even when components are positioned with high flexibility. This combination ensures connection reliability while enabling compact design.
Solution Approach 2:
The patent replaces traditional mechanical wiring harnesses with printed circuit board technology, where electrical connections are formed through conductive patterns etched or deposited on the substrate. This substitution provides more stable and reliable connections compared to mechanical wire connections, while allowing greater design flexibility for component placement.
3Adaptability or versatility
If rigid board and predetermined component are connected with flexible printed circuit, then positional arrangement freedom increases, but manufacturing complexity may increase
Solution Approach 1:
The patent integrates the flexible printed circuit and rigid board with ground patterns into a unified circuit board assembly that serves multiple functions: electrical connection, grounding, and structural support. This merging reduces the overall number of separate components and simplifies the assembly process, offsetting the initial complexity of using flexible printed circuits.
Data Source
AI summary
A drive unit for an electrically assisted bicycle includes an electric motor, a housing accommodating a portion or an entirety of the electric motor, a pedal crank shaft extending through the housing and rotatably supported by the housing, a transmission to transmit a torque of the electric motor, a rigid board including an electric circuit to cause the electric motor to operate, and a flexible printed circuit to electrically connect the rigid board and another predetermined component in addition to the rigid board to each other.