Compact Motor-Gear Drive Unit with Cycloidal Reduction
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Solution Overview
Problem
Conventional motor-gear drive units face challenges in achieving a compact and robust design with high reduction ratios, low component count, and single-side mounting, particularly in applications like indoor patient lift vehicles where maneuverability and user friendliness are crucial, as they often result in large size, high friction, and increased manufacturing costs.
Innovation Solution
An integrated motor-gear drive unit with a cycloidal reduction mechanism, where the motor output shaft transmits rotational force to an outer rotatable body through a combined carrier body and cycloidal gear discs, utilizing carrier pin devices that protrude through holes in the discs to prevent rotation and distribute forces, allowing for a compact, high-torque output with reduced axial width and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reduction mechanisms (worm gears, multi-stage planetary gears) are used to achieve large reduction ratios, then the reduction ratio is improved, but the size and device complexity increase
Solution Approach 1:
The patent merges the carrier body and mounting structure into a single integrated component. The carrier body serves dual functions: supporting the cycloidal gear disc and providing the mounting interface for the entire drive unit. This integration eliminates the need for separate mounting brackets or additional carrier components, achieving compactness while maintaining the required reduction ratio.
Solution Approach 2:
The patent employs a nested structure where the cycloidal gear disc is positioned within the carrier body, and the outer rotatable body encompasses the entire gear mechanism. The carrier pin devices are inserted through holes in the cycloidal gear disc, creating a compact nested arrangement that maximizes space utilization and minimizes overall size.
2Productivity
If conventional reduction mechanisms are used to achieve large reduction ratios, then the reduction ratio is improved, but the device complexity and component count increase
Solution Approach 1:
The patent combines multiple functions into fewer components. The carrier body integrates structural support, mounting, and positioning functions. The carrier pin devices simultaneously serve as structural connectors and as the mechanism for preventing rotation of the cycloidal gear disc. This merging reduces component count while achieving the required reduction ratio.
Solution Approach 2:
The carrier pin devices perform multiple functions: they structurally connect the carrier body to the cycloidal gear disc, position the gear disc eccentrically, and prevent rotation of the gear disc through the holes. This multi-functionality reduces the need for separate components and simplifies the overall device structure.
3Ease of operation
If the drive unit is designed for single-side mounting to improve maneuverability, then ease of operation is improved, but the structural stability may be compromised
Solution Approach 1:
The patent employs asymmetric mounting where all mounting interfaces are concentrated on one side of the drive unit. The carrier body is designed with an asymmetric structure that provides robust single-side mounting capability. The mounting carrier body includes integrated mounting features that distribute loads effectively, maintaining structural stability despite the asymmetric configuration.
Solution Approach 2:
The outer rotatable body is designed as a ring-shaped structure that can be suspended from one side, creating a balanced asymmetric configuration. The curved geometry of the ring structure distributes mechanical loads effectively, maintaining structural integrity and stability during single-side mounting while enabling improved maneuverability.
4Measurement precision
If cycloidal gear discs with tight tolerances are used to prevent rotation, then the reduction precision is improved, but the manufacturing difficulty increases
Solution Approach 1:
The patent divides the rotation prevention function into discrete segments through the use of multiple carrier pin devices (at least two) that protrude through holes in the cycloidal gear disc. Each carrier pin device independently prevents rotation at its location, and the combination of multiple pins provides robust rotation prevention. This segmentation allows for more practical manufacturing tolerances compared to a single tight-tolerance feature.
Solution Approach 2:
The holes in the cycloidal gear disc serve as intermediary features that facilitate the connection between the carrier pin devices and the gear disc. The holes provide a practical interface that accommodates reasonable manufacturing tolerances while still effectively preventing rotation when the carrier pin devices are inserted. This intermediary structure mediates between the need for precision and the realities of manufacturing.
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 design achieves a compact and robust motor-gear drive unit with high reduction ratios, minimal component count, and the ability to be mounted on one side, supporting large axial and radial forces while minimizing vibration and noise, suitable for applications requiring high torque and maneuverability.
Implementation Method 1
Each cycloidal gear disc is rotatably supported, for example by means of a plain bearing or a separate gear disc bearing, on an eccentric body which is connected to the motor output shaft. The rotation of the eccentric body within the gear disc forces each cycloidal gear disc to move.
Data Source
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Figure 3a
AI summary
The present invention pertains to an integrated motor-gear drive unit, for example an in-wheel motor, for transmitting rotational movement from a motor output shaft with cycloidal reduction to an outer rotatable body; the integrated motor-gear drive unit comprising; a mounting carrier body (3) and a secondary carrier body (2), wherein the mounting carrier body (3) and the secondary carrier body (2) are structurally connected by at least two carrier pin devices (4,11) forming a combined carrier body (2,3,4,11); an outer rotatable body (1) rotatably supported on the mounting carrier body (3) and on the secondary carrier body (2); a motor (5) and a rotatable motor output shaft (6m), at least one cycloidal gear disc (10) and an eccentric body (8), wherein the eccentric body (8) is rotatably supporting the cycloidal gear disc (10) and wherein the motor output shaft (6m) is arranged for rotating the eccentric body (8) within the cycloidal gear disc (10). The invention also pertains to a device to which such a unit is connected.