Torque Limiting Mechanism Using Ball Ramp Section
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Solution Overview
Problem
Existing torque limiting mechanisms, such as slip clutches, face challenges in reliably limiting output torque to a prescribed value due to instability in friction coefficients and the occurrence of surge or overshoot phenomena, leading to increased frictional torque and wear during slip events.
Innovation Solution
A torque limiting mechanism incorporating a ball ramp section with cam elements having recesses with specific internal side surface shapes, allowing for controlled axial thrust to reduce frictional torque by shifting the ball contact from a first to a second contact position, thereby managing the increase in input torque and axial thrust to prevent excessive output torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If friction plates are elastically biased to be pressed against each other to transmit torque, then torque transmission capability is improved, but frictional torque increases causing heat generation and wear
Solution Approach 1:
The invention changes the pressure parameter between friction plates dynamically. During normal operation, friction plates are pressed together with sufficient force for torque transmission. When excessive torque is detected, the ball ramp mechanism reduces the pressure between friction plates, thereby reducing frictional torque and heat generation while maintaining torque transmission capability during normal operation
2Reliability
If slip clutch is used to limit excessive torque, then torque limiting function is achieved, but surge or overshoot phenomenon occurs causing output torque to exceed prescribed value
Solution Approach 1:
The ball ramp mechanism performs preliminary action by detecting excessive input torque before slip occurs and proactively reducing the frictional torque between friction plates. This preliminary reduction prevents the surge and overshoot phenomena by ensuring that the frictional torque decreases in advance, allowing output torque to be limited precisely to the prescribed value without exceeding it
3Reliability
If frictional torque is increased to prevent slip, then torque transmission reliability is improved, but heat generation and wear increase
Solution Approach 1:
The invention makes the frictional torque dynamic rather than static. The ball ramp mechanism continuously adjusts the pressure between friction plates based on the input torque conditions. During normal operation, sufficient frictional torque maintains reliable torque transmission. When excessive torque is detected, the mechanism dynamically reduces frictional torque to minimize heat generation and wear, achieving both reliability and thermal management
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 approach enables high-precision torque limiting while minimizing frictional torque during slips, reducing heat generation and wear by precisely controlling the axial thrust and frictional torque, ensuring output torque remains within the prescribed value.
Implementation Method 1
friction between friction plates forming the slip clutch section
Implementation Method 2
ball ramp section...transmitting an input torque at least partially to one cam element...utilizing an axial thrust produced
Data Source
AI summary
A high-precision torque limiting mechanism capable of limiting an output torque to a magnitude of not more than a prescribed value, as well as to reduce a frictional torque produced upon occurrence of a slip. To accomplish this object, a ball ramp section (13) is attached to a slip clutch section (3) for reducing friction between friction plates (31) and (32) forming the slip clutch section (3) and limiting a torque to be transmitted by utilizing an axial thrust produced at the ball ramp section (13) in accordance with the magnitude of an input torque. The precision with which the torque to be transmitted is limited is enhanced by making improvements to the shape of an internal side surface of a recess (G) formed in each of cam elements (131) and (132) of the ball ramp section (13).