Brushless DC Motor Module with Planetary Gearbox for Garden Tools
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Solution Overview
Problem
Conventional electric gardening tools, particularly electric lawn mowers, face challenges with high power consumption and limited design flexibility due to the use of large brushed or brushless DC motors, which are unsuitable for tools requiring high torque and efficient energy use.
Innovation Solution
A modular motor module comprising a brushless DC motor with a gearbox having a gear reduction ratio of at least 5:1, a planetary gearbox, and a controller for interfacing with various electric gardening tools, allowing for reduced rpm and lower power consumption while maintaining cutting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If large brushed or brushless DC motors are used in electric gardening tools, then high torque is achieved, but power consumption increases and design flexibility decreases
Solution Approach 1:
The motor system is segmented into two functional components: a high-speed brushless DC motor for efficient energy conversion and a gearbox for torque multiplication. This segmentation allows each component to operate in its optimal performance range, resolving the contradiction between torque output and power consumption.
Solution Approach 2:
A gearbox is introduced as an intermediary mechanism between the motor and the rotary element. The gearbox with gear reduction ratio of at least 2:1 acts as a mediator that transforms the motor's high-speed low-torque output into low-speed high-torque output, enabling the system to achieve high torque without requiring a large motor that consumes excessive power.
2Force
If large brushed or brushless DC motors are used in electric gardening tools, then high torque is achieved, but design flexibility and adaptability decrease
Solution Approach 1:
The motor module design with standardized gearbox and coupling mechanisms creates a universal interface that can be adapted to multiple different gardening tool applications. The gearbox serves as a multi-functional component that can accommodate various rotary elements (blades, trimmer lines, hedge trimmer blades) while maintaining consistent torque delivery, thereby enhancing design flexibility and adaptability across different tool types.
Solution Approach 2:
By separating the motor module from the tool-specific components, the system allows independent optimization of each part. The standardized motor module can be reused across different tool designs, while only the rotary elements and housing need to be modified for different applications, significantly improving design flexibility.
3Productivity
If high rpm motors are used in electric gardening tools, then cutting efficiency is maintained, but power consumption increases
Solution Approach 1:
The system changes the operational parameters by using a gear reduction mechanism to transform the motor's high rpm output into lower rpm with higher torque. The gearbox with reduction ratio of at least 2:1 allows the motor to operate at optimal high speed for efficiency while the output shaft delivers appropriate speed and torque for cutting applications, effectively decoupling motor operating parameters from tool operating parameters.
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 provides a compact, energy-efficient motor module that extends battery life and simplifies design and production by enabling use across multiple gardening tools, while maintaining effective cutting performance.
Implementation Method 1
a brushless DC motor having a motor drive shaft
Implementation Method 2
a planetary gearbox comprising a sun gear driven by the motor drive shaft and two planet gears to drive the rotary element, the sun gear and the two planet gears retained within a stationary ring gear
Data Source
AI summary
A motor module (100) for an electrically driven garden tool comprises: a brushless DC motor (102) having a motor drive shaft (104); and a gearbox having an output shaft (108), the gearbox configured to receive the motor drive shaft (104) from the brushless DC motor (102) and drive a rotary element of the electrically driven garden tool with the output shaft (108), wherein the gearbox having a gear reduction ratio of at least 2:1. An electrically driven garden tool comprises: a housing (602) comprising a receptacle for receiving a motor module (100); and a rotary element drivable with an electric motor, the rotary element comprises a receiving element having a keyed interface corresponding to the keyed surface (122) or structure on the output shaft (108) of the motor module (100). A grass compactor (900) comprises: mounting structure to attach the grass compactor (900) to a lawn mower (1000); an inlet (1104) for receiving cut grass from an underside of the lawn mower (1000); a channel (1206) for transporting cut grass from the inlet (1104) to a feed hopper (1400); and a compaction conveyor (1404) configured to receive cut grass from the feed hopper (1400), and to compact and convey cut grass along a length thereof and discharge compacted cut grass from the outlet (1210).