Torque-Limiting Friction Transmission With Cam Load Relief
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Solution Overview
Problem
Existing power transmission devices with torque limiting mechanisms are unable to stably prevent the transmission of torques above a certain magnitude due to unstable slip behavior in the friction plates.
Innovation Solution
A power transmission device incorporating an input rotary member, an intermediate rotary member, a friction engaging part, and a load adjusting mechanism that reduces the load on the friction engaging part when a predetermined torque is exceeded, using a cam mechanism and elastic members to control the friction force and prevent torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction plates are pressed against each other by a fixed urging force of a disc spring, then the torque limiting mechanism can engage by friction, but the torque causing slip is unstable and transmission of torque cannot be stably prevented
Solution Approach 1:
The patent applies the dynamics principle by making the urging force on the friction plates variable rather than fixed. The disc spring's urging force is dynamically adjusted based on the input torque magnitude: when input torque exceeds a predetermined threshold, the urging force is reduced to induce stable slip between friction plates, thereby stably preventing transmission of excessive torque. This dynamic adjustment resolves the contradiction by adapting the friction engagement characteristics to the actual operating conditions.
Solution Approach 2:
The patent implements parameter changes by varying the urging force parameter of the disc spring according to the input torque level. The system transitions between different operational states: at normal torque levels, high urging force maintains strong friction engagement for efficient power transmission; when torque exceeds the threshold, the urging force parameter is reduced to create controlled slip conditions, ensuring stable prevention of excessive torque transmission.
2Strength
If the urging force on friction plates is increased to improve torque transmission stability, then friction engagement is strengthened, but the torque required to cause slip increases and may not prevent excessive torque transmission
Solution Approach 1:
The system dynamically adjusts the urging force strength based on operating conditions. Rather than maintaining constantly high urging force, the disc spring provides high urging force during normal operation for strong friction engagement, but automatically reduces the urging force when excessive torque is detected, enabling the friction plates to slip and thereby limiting the transmitted torque to a safe level.
Solution Approach 2:
The disc spring mechanism is pre-configured to automatically reduce urging force when excessive torque is applied, creating a preliminary protective action. The spring's mechanical characteristics are designed so that under excessive torque conditions, the urging force naturally decreases before damage can occur, preventing the transmission of harmful torque levels through controlled slip.
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 device effectively prevents the transmission of torques above a predetermined magnitude by reducing the friction force, ensuring stable operation and preventing excessive torque from being transmitted to the output rotary member.
Implementation Method 1
The friction engaging part is engaged by friction with a friction force depending on a load applied thereto. Additionally, the friction engaging part transmits the torque between the intermediate rotary member and the output rotary member.
Implementation Method 2
a first elastic member elastically coupling the input rotary member and the intermediate rotary member in a circumferential direction
Implementation Method 3
The load adjusting mechanism adjusts the load applied to the friction engaging part in accordance with a torsion angle between the input rotary member and the intermediate rotary member.
Implementation Method 4
the load adjusting mechanism includes a cam mechanism. The cam mechanism reduces the load applied to the friction engaging part when the torsion angle becomes predetermined degrees or greater.
Data Source
AI summary
A power transmission device includes an input rotary member, an intermediate rotary member, an output rotary member, a friction engaging part and a load adjusting mechanism. A torque is inputted to the input rotary member. The torque is inputted from the input rotary member to the intermediate rotary member. The torque is outputted from the output rotary member. The friction engaging part is engaged by friction with a friction force depending on a load applied thereto. The friction engaging part is configured to transmit the torque between the intermediate rotary member and the output rotary member. The load adjusting mechanism is configured to adjust the load applied to the friction engaging part in accordance with the torque inputted to the input rotary member.