Single-Cylinder Engine Starter Layout With Multi-Gear Reduction

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Solution Overview

Problem

In single-cylinder engines, large starter motors require significant rearward tilting of the cylinder, making it difficult to ensure space on the rear side for the motor's arrangement.

Innovation Solution

The engine is configured with a tilted cylinder towards the transmission, allowing the motor to be placed on the opposite side of the transmission and crankshaft, utilizing multiple gears for speed reduction to minimize the motor's size and reduce cylinder tilt, thereby optimizing space usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the motor has a large size, then the motor can provide sufficient output, but the cylinder is required to be tilted rearward largely, making it difficult to ensure space on the rear side of the cylinder

Engineering Contradiction:

Improvemotor outputVSAvoidspace on rear side of cylinder

Core Design Contradiction:

PowerVSArea of stationary object

Solution Approach 1:

The patent changes the spatial arrangement from placing the motor on the rear side of the cylinder to placing it on the front side. By tilting the cylinder forward and positioning the motor in the front space, the solution utilizes a different dimensional configuration to accommodate both the large motor and maintain rear space availability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Instead of the conventional arrangement where the motor is placed on the rear side of the cylinder, the patent inverts this arrangement by placing the motor on the front side of the cylinder. This inversion resolves the space conflict by utilizing the front space that is typically less constrained.

Inventive Principle:

Principle #13The other way round (Inversion)

2Volume of moving object

If multiple gears are used to reduce motor output, then the motor size can be reduced, but the device complexity increases

Engineering Contradiction:

Improvemotor sizeVSAvoidgear system complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent employs a planetary gear system where gears are nested within each other in a compact configuration. The planetary gears include a sun gear, planet gears, and a ring gear, with the planet gears rotating on carriers that are themselves part of the compact assembly. This nesting allows significant speed reduction in a small volume, reducing motor size while minimizing the space and complexity added by the gear system.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent changes the rotational speed parameter through the planetary gear reduction system. By using multiple stages of planetary gears with different gear ratios, the system achieves substantial speed reduction (e.g., 5:1 or 10:1 reduction) which allows a smaller motor to provide the required torque at the crankshaft, thereby reducing motor size while the compact gear design minimizes the complexity increase.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3663559B1Engine and vehicle

Publication Date: 2022.11.16 YAMAHA MOTOR CO LTD

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AI summary

The output of the starter motor 71 is reduced in speed by the multiple gears 81 to 86 and then transmitted to the crankshaft 61. Thus, output required for the starter motor 71 is small to allow size reduction of the starter motor 71. As a result, it becomes possible to ensure space for the arrangement of the starter motor 71 while the tilt of the cylinder 511 is suppressed.