Logarithmic Spring Clutch-Brake Assembly for High-Torque EMAs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional clutch/brake assemblies for electromechanical actuators (EMAs) are bulky, heavy, and generate excessive heat due to high current requirements, making them unsuitable for high-torque regions, and they fail to effectively disconnect the motor from the gear reducer in case of damage, posing safety risks.
Innovation Solution
A clutch/brake assembly utilizing a logarithmic spring mechanism that amplifies torque transmission with reduced solenoid force, allowing operation in high-torque regions with a smaller, lighter design and minimal heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional clutch/brake assembly is located downstream of the reducer in a high torque region, then safety requirements are met, but the solenoid becomes large and heavy requiring high power and heat dissipation
Solution Approach 1:
The patent changes the physical state and parameters of the spring from a conventional linear spring to a logarithmic spring, fundamentally altering its mechanical properties. This parameter change allows the spring to provide progressively increasing force with displacement, enabling high torque transmission with a smaller solenoid force input, thus resolving the contradiction between safety and weight
Solution Approach 2:
The logarithmic spring acts as an intermediary mechanical element between the solenoid and the clutch plates. It amplifies the solenoid's force through its unique logarithmic geometry, allowing a small solenoid to control a large torque transmission system, thereby reducing solenoid weight while maintaining safety
2Reliability
If a conventional clutch/brake assembly is located downstream of the reducer in a high torque region, then safety requirements are met, but the solenoid becomes large and heavy requiring high power
Solution Approach 1:
By changing the spring parameter from linear to logarithmic geometry, the force-displacement relationship is fundamentally altered. The logarithmic spring generates exponentially increasing force with displacement, allowing the solenoid to operate at lower power levels while still achieving the necessary clutch engagement force for high torque regions
Solution Approach 2:
The logarithmic spring intermediary provides mechanical advantage through its geometric progression, amplifying the solenoid's power output. This allows the system to meet safety requirements in high torque regions without requiring a high-power solenoid, as the spring converts small input power into large output force
3Reliability
If a conventional clutch/brake assembly is located downstream of the reducer in a high torque region, then safety requirements are met, but heat dissipation requirements increase due to high current
Solution Approach 1:
The logarithmic spring parameter change creates a non-linear force-displacement curve that allows efficient engagement with lower current requirements. By operating at lower current, the electromagnetic coil generates less heat, reducing the thermal management burden while still achieving reliable clutch engagement for safety-critical applications
Solution Approach 2:
The logarithmic spring intermediary reduces the current requirement by providing mechanical force amplification. This lower current operation directly reduces heat generation in the electromagnetic coil, simplifying the thermal management system while maintaining the safety function in high torque regions
4Weight of moving object
If a clutch/brake assembly is located upstream of the reducer, then the region has minimum torque, but the clutch cannot disconnect the output in case of gear reducer damage
Solution Approach 1:
The logarithmic spring's unique force-displacement characteristics enable it to function effectively in high torque environments, allowing the clutch to be relocated downstream of the reducer where it can provide safety disconnection while the spring's parameter properties handle the increased torque loads
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 logarithmic spring design reduces solenoid force requirements by approximately 5 times, resulting in a compact, lightweight assembly with reduced heat dissipation needs, enhancing safety and efficiency in EMAs.
Implementation Method 1
a clutch/brake assembly utilizing a logarithmic spring mechanism that amplifies torque transmission with reduced solenoid force
Implementation Method 2
These require a compressive force to be applied proportional to the torque to be transmitted. In the case of high torques, there is therefore a need for high power and heavy solenoids.
Implementation Method 3
Conventional friction base clutch/brake assemblies comprise a number of plates or cones that are forced into frictional engagement
Data Source
Figure 1~2
Figure 3
AI summary
A clutch/brake assembly comprising: an input shaft (42) arranged to be rotated, in use, by a motor; an output shaft (44) configured to be rotated by the input shaft when brought into engagement therewith; rotating clutch plate elements (47) configured to transmit torque from the input shaft to the output shaft when engaged; a logarithmic spring (45) mounted around the input shaft; a translating shaft (46) around the spring; an output sleeve (48) between the output shaft and the clutch plate elements; and a solenoid (50) connected to the translating shaft; whereby the solenoid, in a first state of energization, causes movement of the translating shaft to compress the spring in a first direction to bring the clutch plate elements and the input shaft and the output sleeve into engagement such that torque is transmitted from the input shaft to the output shaft via the spring, the clutch plate elements and the output sleeve, or, in a second state of energization, to compress the spring in a second direction such that the clutch plate elements are disengaged from the output sleeve such that torque is not transmitted between the clutch plate elements and the output shaft.