Wave Gear Device Anti-Ratcheting Friction Coupling
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Solution Overview
Problem
Wave gear devices in robot arms and similar applications experience ratcheting (gear jumping) due to torque overload, leading to plastic deformation, increased vibrations, and reduced durability, making it difficult to readjust and reuse the device, especially during speed reducing, speed increasing, and stopping states.
Innovation Solution
A wave gear device with a friction member sandwiched between the wave generator and the rotating input shaft, utilizing a frictional coupling force to prevent slippage when the transmission torque reaches 60 to 75% of the ratcheting torque, thereby preventing ratcheting and plastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wave gear device operates under excessive load or collision conditions, then torque transmission is maintained, but ratcheting occurs causing plastic deformation and reduced durability
Solution Approach 1:
The friction member is pre-installed between the wave generator and input shaft to create a frictional coupling that proactively prevents ratcheting before it occurs. The friction force is designed to engage at 60-75% of the ratcheting torque threshold, creating a preventive barrier against excessive load damage during speed reducing, speed increasing, and stopping states.
Solution Approach 2:
The friction member acts as an intermediary element between the wave generator and input shaft. It transmits torque through frictional coupling while preventing direct rigid connection that would allow ratcheting. This intermediary friction interface absorbs and dissipates excessive torque through controlled slippage, protecting the gear teeth from plastic deformation.
2Productivity
If the wave gear device allows torque transmission during speed reducing state, then power transmission efficiency is maintained, but ratcheting torque is highest causing gear jumping
Solution Approach 1:
The frictional coupling parameter is designed to change its effective engagement based on torque conditions. During normal operation, the friction member maintains sufficient grip for power transmission. When torque approaches the ratcheting threshold (60-75% threshold), the friction interface allows controlled slippage, effectively changing from a rigid torque transmitter to a protective coupling that prevents gear jumping while maintaining overall system productivity.
3Reliability
If a friction member is added to prevent ratcheting, then durability is improved, but device complexity increases
Solution Approach 1:
The friction member serves multiple functions simultaneously: it transmits torque during normal operation, prevents ratcheting during excessive load conditions, and protects against plastic deformation of gear teeth. This multi-functional design achieves reliable anti-ratcheting protection without adding significant structural complexity, as the friction member integrates into the existing wave generator-input shaft connection.
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 implementation of a friction member between the wave generator and the rotating input shaft ensures consistent torque transmission, preventing ratcheting and plastic deformation across different operating modes, enhancing the durability and reusability of the wave gear device.
Implementation Method 1
a friction member disposed between the wave generator and the rotating input shaft so as to be sandwiched from the radial direction or the axial direction thereof; the wave generator and the rotating input shaft integrally rotate due to a frictional coupling force of the friction member
Data Source
AI summary
A wave gear device is proposed having an anti-ratcheting mechanism having a simple configuration, wherein a center through-hole is formed in a cylinder hub of a wave generator, a small-diameter shaft end portion of a rotating input shaft is concentrically inserted in the center through-hole, and the two members are fastened by a fastening bolt, and a friction ring is concentrically sandwiched between the small-diameter shaft end portion and the cylinder hub and pressed in the radial direction with a prescribed force, whereby when transmission torque from the rotating input shaft to the wave generator 4 becomes excessive, slippage occurs in the rotational direction between the two members, transmission torque is limited, ratcheting generated between the two gears can be prevented.