Derailleur Motor Unit Torque Limiter for External Force Protection
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Solution Overview
Problem
Existing motor units for human-powered vehicles lack effective protection against external forces, which can damage the motor device and linkage components during physical contact with obstacles.
Innovation Solution
A motor unit incorporating a torque limiter and a transmitting structure that reduces or blocks external forces by allowing relative movement between components and controlling torque transmission, ensuring the electric motor is protected from external forces while allowing necessary force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor unit uses a fixed rigid connection between components, then the structure is simple and strong, but external forces can damage the motor device and linkage components
Solution Approach 1:
The patent applies dynamics by making the connection between components movable rather than fixed. The torque limiter allows the first and second members to move relative to each other when torque exceeds a threshold, enabling the system to adapt dynamically to external forces while maintaining structural integrity.
Solution Approach 2:
The torque limiter serves as an intermediary element between the motor device and linkage components. It mediates the transmission of torque by allowing relative movement when torque exceeds the threshold, thereby protecting the motor device from external forces while still enabling necessary force transmission.
2Reliability
If the torque limiter allows relative movement between first member and second member, then external forces are reduced, but torque transmission efficiency decreases
Solution Approach 1:
The system dynamically adjusts its behavior based on torque levels. During normal operation below the torque threshold, the first and second members move together maintaining efficient torque transmission. When external forces exceed the threshold, the members move relative to each other to protect the motor device, minimizing energy loss only when necessary.
Solution Approach 2:
The torque limiter changes the operational parameters of the system by switching between two states: a coupled state for normal torque transmission and a decoupled state for protection against excessive torque. This parameter change allows the system to optimize between efficiency and protection based on operating conditions.
3Reliability
If the transmitting structure restricts torque transmission from second race to second intermediate element, then the motor is protected, but the ability to transmit necessary force is reduced
Solution Approach 1:
The transmitting structure dynamically controls torque transmission based on the direction and magnitude of applied loads. The first intermediate element can move toward or away from the first race depending on whether the second race or second intermediate element is pushing, allowing the system to protect the motor from excessive reverse torque while maintaining forward force transmission capability.
Solution Approach 2:
The transmitting structure is segmented into multiple independent elements (first race, second race, first intermediate element, second intermediate element) that can move relative to each other. This segmentation allows selective restriction of torque transmission in specific directions while maintaining transmission capability in other directions, balancing protection with productivity.
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 motor unit effectively protects the electric motor from external forces while maintaining the ability to transmit necessary forces, enhancing the durability and reliability of the motor unit.
Implementation Method 1
The first intermediate element is configured to move toward the first race in response to the first intermediate element pushed by the second race in a first circumferential direction with respect to the transmitting-structure rotational axis
Implementation Method 2
The first intermediate element is configured to move away from the first race in response to the first intermediate element pushed by the second intermediate element in the first circumferential direction
Data Source
AI summary
A motor unit comprises a torque limiter and a transmitting structure. The torque limiter includes a first member and a second member. The first member and the second member are movable relative to each other in a state where a torque applied to the torque limiter is equal to or higher than a torque threshold. The first member and the second member are movable together with each other in a state where the torque is lower than the torque threshold. The transmitting structure includes a first race, a second race, a first intermediate element at least partially provided between the first race and the second race, and a second intermediate element at least partially provided between the first race and the second race.