Central Motor Layout for Electric Grass Cutting Machine

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Solution Overview

Problem

Existing electric grass cutting machines with electric motors for each wheel require high frequency usage and occupy large space, limiting the layout for a conveying duct and increasing costs.

Innovation Solution

The electric motor and gear transmission are positioned between the rear wheels in the front/rear direction, allowing for reduced motor usage and compact design, with the motor supported by a transmission case and oil cooling system, and the battery placed at the front to maintain balance and protect it from elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If an electric motor is provided for each one of a pair of left and right wheels, then the driving performance is improved, but the frequency of use of the electric motor increases and the disposing space increases

Engineering Contradiction:
Improvedriving performanceVSAvoidfrequency of use of electric motor
Core Design Contradiction:
PowerVSDevice complexity

Solution Approach 1:

The patent merges the driving function from individual wheel motors into a single central electric motor located in the hollow shaft of the rear wheel. This single motor drives both left and right rear wheels through a differential mechanism, reducing the number of motors from two to one, thereby decreasing the frequency of motor usage and simplifying the overall system structure while maintaining driving performance.

Inventive Principle:
Principle #5Merging (Combining)

2Power

If an electric motor is provided for each one of a pair of left and right wheels, then the driving performance is improved, but the disposing space between left and right wheels increases

Engineering Contradiction:
Improvedriving performanceVSAvoiddisposing space between wheels
Core Design Contradiction:
PowerVSArea of stationary object

Solution Approach 1:

The patent consolidates the motor positioning into the hollow shaft of the rear wheel, merging what would have been two separate motor locations into a single centralized position. This eliminates the need for large spaces between left and right wheels that would be required to accommodate two separate motors, thereby reducing the disposing space while maintaining the driving function.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The electric motor is nested within the hollow shaft structure of the rear wheel, utilizing the existing hollow space. This nesting approach allows the motor to be positioned compactly within the wheel assembly itself, rather than requiring additional space between the wheels, thus optimizing the use of available space.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Productivity

If a conveying duct is laid out between left and right rear wheels, then the grass collection function is achieved, but the space for the electric motor is reduced

Engineering Contradiction:
Improvegrass collection functionVSAvoidspace for electric motor
Core Design Contradiction:
ProductivityVSArea of stationary object

Solution Approach 1:

The electric motor is nested within the hollow shaft of the rear wheel, utilizing the internal hollow space of the wheel structure. This nesting allows the motor to be positioned without occupying the space between the wheels that is required for the conveying duct, thereby resolving the spatial conflict between motor placement and grass collection duct layout.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The motor positioning is moved from the horizontal space between wheels to the vertical dimension within the hollow shaft. This dimensional shift allows the conveying duct to occupy the horizontal space between wheels for effective grass collection, while the motor is positioned vertically within the wheel's hollow structure, eliminating spatial conflict.

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 reduces the frequency of motor usage, optimizes space usage, and allows for a more compact machine design while maintaining effective cooling and balance, thus lowering costs and improving operational efficiency.

Implementation Method 1

a gear transmission configured to speed-change an output from the electric motor and to transmit the speed-changed output to the traveling device

Methodology Applied
Scientific EffectGear transmission: Gear

Implementation Method 2

an oil circulation circuit configured to supply oil in circulation to the cooling jacket

Methodology Applied
Scientific EffectConvection cooling: Convection

Implementation Method 3

a battery disposed in the front hood and configured to supply power to the electric motor

Methodology Applied
Scientific EffectBattery: Battery (electricity)

Data Source

PatentEP3673723B1Electric grass cutting machine
Publication Date: 2024.05.08 KUBOTA CORP
  • EP3673723B1 patent drawingFigure 1
  • EP3673723B1 patent drawingFigure 2
  • EP3673723B1 patent drawingFigure 3

AI summary

In an electric grass cutting machine relating to the present invention, an electric motor (2) for driving a travelling device having a pair of left and right front wheels (1F) and a pair of left and right rear wheels (1R) and a gear transmission for speed-changing output from the electric motor (2) and transmitting the resultant power to the travelling device are disposed between the left and right rear wheels (1R) and arranged one after the other in the front/rear direction at positions laterally of a conveying duct (44) for guiding cut grass pieces from a rear discharge type mower device to a grass collecting container (50) supported to a rear portion of a machine body frame (10).