Torque Limiter Mechanism for Planetary Speed Reducer Back Torque Protection
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Solution Overview
Problem
Existing motor power transmission devices for vehicles face excessive load on speed reduction gears due to direct transmission of back torque from wheels, which is not desired and can damage the gear mechanism.
Innovation Solution
A motor power transmission device incorporating a planetary speed reducer with a torque limiter mechanism between the planetary carrier and the output shaft, featuring a disengageable torque cam and urging member, which blocks excessive back torque from being transmitted to the speed reducer, thereby protecting it from excessive load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque limiter is positioned between the motor rotational shaft and the speed reduction gear input shaft, then excessive input torque can be blocked to protect the speed reduction gear, but excessive back torque from the output side cannot be blocked and directly loads the speed reduction gear
Solution Approach 1:
A torque limiter mechanism is introduced as an intermediary component between the planetary carrier and the output shaft. This torque limiter includes a torque cam and urging member that act as mediators to block excessive back torque from being transmitted to the planetary speed reducer, while allowing normal operation torque to pass through. The torque limiter serves as a protective intermediary that selectively transmits or blocks torque based on its magnitude.
2Reliability
If a torque limiter mechanism is added to block excessive back torque, then the planetary speed reducer is protected, but the device complexity increases
Solution Approach 1:
The torque limiter mechanism is designed with multi-functionality to minimize overall device complexity. The same torque limiter structure serves multiple purposes: it blocks excessive back torque, transmits normal operation torque, and integrates with the existing planetary carrier and output shaft configuration. The torque cam and urging member work together as a unified system that performs both protection and power transmission functions.
Solution Approach 2:
The torque limiter mechanism is nested within the existing planetary speed reducer structure. The torque cam is positioned between the planetary carrier and output shaft, utilizing the existing spatial arrangement of components. The urging member is integrated into the same assembly, allowing the torque limiter to be embedded within the compact planetary gear configuration without requiring separate external housing or additional space.
3Device complexity
If the torque limiter mechanism is designed with a disengageable torque cam and urging member, then the mechanism remains simple and compact, but the reliability of torque blocking must be ensured
Solution Approach 1:
The torque cam is designed with a curved cam surface that provides mechanical advantage for reliable torque blocking. The cam surface geometry is shaped to convert small axial movements of the planetary carrier into large radial forces that effectively block torque transmission when excessive back torque is detected. The curved surface ensures smooth engagement and disengagement while maintaining high blocking reliability with simple structural components.
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 effectively prevents excessive load on the planetary speed reducer by blocking excessive back torque, ensuring the device's protection and maintaining efficient operation while minimizing size and axial width.
Implementation Method 1
an urging member is provided to urge the planetary carrier to be pressed against the flange
Data Source
AI summary
In a motor power transmission device (30), wherein rotational power of an electric motor (40) is input to a sun gear (51) of a planetary speed reducer (50), and then the rotation of the sun gear (51) is converted to rotation of a planetary carrier (55), and wherein the planetary carrier (55) rotatably supports planetary gears (61, 62) and converts revolving motion of the planetary gears (61, 62) into rotating motion, and the rotation of the planetary carrier (55) is then output to an output shaft (15), a torque limiter mechanism (57) is interposed between the planetary carrier (55) and the output shaft (15). Thus, even if excessive back torque is input to the output shaft, transmission of the back torque to the speed reducer is blocked to protect the speed reducer.