Motor Control Unit Placement Using Airflow Cooling in Straddled Vehicles

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Solution Overview

Problem

In straddled vehicles, the motor control unit is often placed far from the engine and transmission to avoid thermal influences, leading to long electric cables that increase cost and weight, while also limiting space under the seat for other components.

Innovation Solution

The motor control unit is positioned closer to the engine and transmission by utilizing airflow for cooling, and its placement is optimized relative to the main harness and actuator motors to shorten the electric cables and maximize space utilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the motor control unit is disposed far from the engine to avoid thermal influence, then the motor control unit is protected from heat, but the electric cable becomes longer increasing cost and weight

Engineering Contradiction:
Improvethermal protection of motor control unitVSAvoidweight of electric cable
Core Design Contradiction:
TemperatureVSWeight of moving object

Solution Approach 1:

The invention utilizes the harmful hot airflow from the engine as a cooling resource for the motor control unit. By positioning the motor control unit in the engine's exhaust airflow path, the previously harmful thermal environment is converted into a beneficial cooling mechanism, allowing the unit to be placed closer to the engine without overheating concerns.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

2Temperature

If the motor control unit is disposed far from the engine to avoid thermal influence, then the motor control unit is protected from heat, but the electric cable becomes longer increasing cost

Engineering Contradiction:
Improvethermal protection of motor control unitVSAvoidcost of electric cable
Core Design Contradiction:
TemperatureVSEase of manufacture

Solution Approach 1:

The invention utilizes the harmful hot airflow from the engine as a cooling resource for the motor control unit. By positioning the motor control unit in the engine's exhaust airflow path, the previously harmful thermal environment is converted into a beneficial cooling mechanism, allowing the unit to be placed closer to the engine without overheating concerns.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Temperature

If the motor control unit is disposed far from the engine to avoid thermal influence, then the motor control unit is protected from heat, but the space under the seat is reduced

Engineering Contradiction:
Improvethermal protection of motor control unitVSAvoidspace under the seat
Core Design Contradiction:
TemperatureVSVolume of moving object

Solution Approach 1:

The invention changes the spatial arrangement by positioning the motor control unit in the longitudinal dimension (front portion of the vehicle body) rather than in the vertical dimension (under the seat). This dimensional shift allows the under-seat space to be fully utilized while still achieving thermal protection through strategic placement in the airflow 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 effectively protects the motor control unit from heat, reduces the length and weight of electric cables, and enhances the use of space under the seat, improving overall vehicle efficiency and design.

Implementation Method 1

The motor control unit needs to be disposed in a front portion of a straddled vehicle... if the motor control unit can receive a running airflow... Use of a running airflow is one conceivable means for cooling the motor control unit.

Methodology Applied
Scientific EffectConvection cooling: Convection

Data Source

PatentEP4349700B1Straddled vehicle
Publication Date: 2025.04.30 YAMAHA MOTOR CO LTD
  • EP4349700B1 patent drawingFigure 1(A)~1(B)
  • EP4349700B1 patent drawingFigure 2
  • EP4349700B1 patent drawingFigure 3

AI summary

A straddled vehicle 1 can have a motor control unit with precautions against heat, the straddled vehicle being capable of shortening an electric cable connected to the motor control unit while achieving effective use of a space. The straddled vehicle 1 includes an actuator mechanism 14 including a clutch motor and/or a shift motor, a motor control unit 15, an electric cable, and a main harness. The motor control unit 15 is attached to a frame holding the main harness, such that a distance from a left-right center line to the motor control unit 15 is longer than a distance from the left-right center line to a motor control unit branch portion, and such that at least a part of the motor control unit is positioned further in a backward direction than a front fork 12 and further in a forward direction than the clutch motor and/or the shift motor.