Electric Bicycle Drive Unit Mounting with Resilient Spring Bars

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Solution Overview

Problem

Existing electric bicycle drive unit fastening arrangements face challenges in providing a stable and noise-reducing attachment, as they often rely on rigid connections that fail to compensate for manufacturing tolerances and transmit structure-borne noise.

Innovation Solution

A resilient fastening arrangement using vertically standing spring bars that connect the drive unit to the bicycle frame, allowing elastic mobility in the transverse axis, with adapters that compensate for tolerance differences and reduce noise transmission through a combination of metallic materials with optimized spring properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a rigid fastening arrangement is used to ensure stable connection, then structural stability is improved, but structure-borne noise is transmitted without dampening and manufacturing tolerances cannot be compensated

Engineering Contradiction:
Improvestructural stabilityVSAvoidstructure-borne noise
Core Design Contradiction:
Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the mechanical parameter of the fastening arrangement from rigid to resilient by introducing spring bars. These spring bars provide elastic compliance that allows the drive unit to be resiliently mounted to the frame, absorbing vibrations and reducing structure-borne noise while maintaining stable connection. The spring bars enable controlled movement and damping without compromising overall structural integrity.

Inventive Principle:
Principle #35Parameter changes

2Stability of the object's composition

If a rigid fastening arrangement is used, then connection stability is improved, but gaps from manufacturing tolerances cannot be compensated during assembly

Engineering Contradiction:
Improveconnection stabilityVSAvoidtolerance compensation
Core Design Contradiction:
Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The spring bars change the connection from rigid to resilient, providing elastic compliance that absorbs dimensional variations from manufacturing tolerances. This allows the drive unit to be securely mounted even when minor gaps or misalignments exist between frame and drive unit mounting surfaces, while maintaining stable connection during operation.

Inventive Principle:
Principle #35Parameter changes

3Object-affected harmful factors

If resilient mounting is implemented to reduce noise, then structure-borne noise is dampened, but device complexity increases due to additional components

Engineering Contradiction:
Improvestructure-borne noiseVSAvoidfastening arrangement complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent uses spring bars as flexible mounting elements that resiliently connect the drive unit to the frame. These spring bars provide noise dampening through their elastic properties while maintaining a relatively simple structural form. The flexible connection absorbs vibrations and reduces structure-borne noise without requiring complex active damping systems or multiple separate components.

Inventive Principle:
Principle #30Flexible shells and thin films

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

The solution achieves a stable and noise-reduced attachment, allowing for weight savings and reduced mechanical stress by cushioning force peaks, while maintaining structural integrity and aesthetics.

Implementation Method 1

The mounting arrangement comprises at least two spring bars positioned essentially vertically in the longitudinal plane of the electric bicycle, each of which elastically connects the frame flange directly or indirectly to the drive unit

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

The two spring bars are dimensioned and arranged with regard to their base areas in such a way that the drive unit is almost immobile in the longitudinal direction of the electric bicycle and in the vertical axis of the electric bicycle with respect to the drive mount or the bicycle frame

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3988437B1Electric bicycle drive unit attachment assembly
Publication Date: 2024.07.24 SRAM LLC
  • EP3988437B1 patent drawingFigure 1
  • EP3988437B1 patent drawingFigure 2~3

AI summary

The invention relates to an electric bicycle drive unit mounting arrangement (100) by which an electric mid-drive motor drive unit (30) is resiliently mounted in the transverse direction to a drive mount (21) of a bicycle frame (20), wherein the drive mount (21) has two mutually parallel, frame-fixed, rigid, and vertical frame flanges (211, 212) that are oriented in a longitudinal plane (V) of the electric bicycle. The mounting arrangement (100) has at least two spring bars (41, 42) that are oriented substantially vertically in a longitudinal plane of the electric bicycle, with each spring bar (41, 42) directly and elastically connecting a frame flange (211, 212) to the drive unit (30) in a transverse direction.