Electric Vehicle Power Unit Compact Layout via Nested Shaft

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Solution Overview

Problem

Existing electric three-wheeled vehicles face challenges in reducing the size of the power unit, as the motor output shaft and speed change gears or continuously variable transmission components require larger housing dimensions, either transversely or longitudinally, due to their axial arrangements.

Innovation Solution

The power unit is designed with a centrifugal clutch coaxially located at the motor output shaft, a counter shaft positioned inside the motor, and a differential mechanism that overlaps with the counter gear, allowing for a compact arrangement that reduces the overall size and increases torque without additional transmissions, while maintaining efficient power transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a stepped variable transmission with gear pairs is provided between motor output shaft and rear wheel axle, then speed change function is achieved, but the housing dimension in vehicle transverse direction must be larger

Engineering Contradiction:

Improvespeed change functionVSAvoidhousing dimension in vehicle transverse direction

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The counter shaft is arranged inside the outer periphery of the motor in a side view, and the motor output shaft, counter shaft, and axles are arranged in sequence from the vehicle forward side, creating a nested compact layout that reduces housing dimension while maintaining speed change function through the differential mechanism

Inventive Principle:

Principle #7Nested doll (Nesting)

2Adaptability or versatility

If a belt converter type continuously variable transmission is provided between motor output shaft and rear wheel axle, then continuous speed variation is achieved, but the housing dimension in vehicle longitudinal direction must be larger

Engineering Contradiction:

Improvecontinuous speed variation functionVSAvoidhousing dimension in vehicle longitudinal direction

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The counter shaft is positioned inside the motor's outer periphery, and components are arranged in a compact sequence from front to rear (motor output shaft → counter shaft → axles), reducing the longitudinal footprint while maintaining transmission functionality

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The axis center of the counter shaft is positioned below the line connecting the axis centers of the motor output shaft and axle in the side view, utilizing vertical space to reduce horizontal dimension requirements

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If the motor output shaft, counter shaft, and axle are arranged linearly in a row in side view, then power transmission is simplified, but the center of gravity is higher and longitudinal dimension is larger

Engineering Contradiction:

Improvepower transmission arrangementVSAvoidcenter of gravity position

Core Design Contradiction:

Device complexityVSWeight of moving object

Solution Approach 1:

The axis center of the counter shaft is located below the line connecting the axis centers of the motor output shaft and axle in the side view, utilizing the vertical dimension to lower the center of gravity and reduce the longitudinal footprint while maintaining the power transmission path

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This configuration results in a more compact power unit with reduced dimensions in both the longitudinal and transverse directions, enabling increased motor diameter without interference, improved torque delivery, and a lower center of gravity, enhancing the vehicle's design efficiency and performance.

Implementation Method 1

A centrifugal clutch which transmits the rotary driving power to the counter shaft when a revolution speed of the motor exceeds a prescribed value is coaxially located at one end of the motor output shaft

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS8839898B2Electric vehicle

Publication Date: 2014.09.23 HONDA MOTOR CO LTD

AI summary

In an electric three-wheeled vehicle, a centrifugal clutch transmits rotary driving power to a counter shaft when the revolution speed of a motor exceeds a prescribed value. The clutch is coaxially located at one end of a motor output shaft. A counter shaft is located inside the outside diameter of the motor in a side view of the vehicle. The motor output shaft, counter shaft, and axles are arranged from a vehicle forward side in the order of mention. The axis center of the counter shaft is located below a line connecting the axis center of the motor output shaft and the axis center of the axle in a side view of the vehicle.