Torque-Limiting Clutch Assembly for Planetary Ring Gear Overload Protection
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Solution Overview
Problem
Existing electric vehicle drive trains face excessive torque loads during abnormal driving conditions, leading to potential damage and the need for over-designed, costly, and heavy components due to complex hybrid drivetrains.
Innovation Solution
A torque limiting clutch assembly with alternating clutch plates and a preloading mechanism, integrated into the drive train, allows slippage under severe conditions to prevent excessive torque from damaging components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive train is designed to withstand excessive torque loads during abnormal driving conditions, then the reliability of the drive train is improved, but the weight and cost of the drive train components increase significantly due to over-design
Solution Approach 1:
A torque limiter device is introduced as an intermediary component between the motor and the drive train. This device includes a clutch assembly with friction plates and a spring mechanism that actively limits excessive torque during abnormal conditions (such as wheel slip). By placing this torque-limiting intermediary in the power transmission path, the drive train components can be designed for normal operating loads rather than being over-designed for rare abnormal conditions, thereby reducing weight while maintaining reliability.
2Strength
If the drive train components are made more robust to handle severe loading conditions, then the strength of the components is improved, but the manufacturing cost increases
Solution Approach 1:
The torque limiter acts as a protective intermediary that prevents excessive torque from reaching the drive train components during abnormal conditions. This allows components to be manufactured to standard specifications for normal operation rather than requiring expensive over-engineering to withstand rare severe loads, thereby maintaining strength while reducing manufacturing cost.
3Force
If a torque limiting device is added to the drive train, then the drive train load is reduced to a useful range, but the device complexity increases
Solution Approach 1:
The torque limiter is designed as a passive, self-regulating device. The spring mechanism automatically engages and disengages the clutch plates based on the torque load conditions without requiring external control systems, sensors, or active intervention. When torque exceeds the spring's preload force, the clutch plates slip to limit torque; when torque returns to normal, the spring re-engages the plates. This self-service mechanism limits drive train load while adding minimal complexity.
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 clutch assembly effectively limits torque loads during severe driving conditions, preventing damage to the drive train while maintaining efficiency and reducing complexity and weight.
Implementation Method 1
The spring member is configured to apply a preloading force on the clutch plate assembly. The preloading force prevents rotation of the ring gear relative to the electric motor housing under a first operating condition
Implementation Method 2
The first and second clutch plates may be fabricated from materials exhibiting a high coefficient of friction and which are suitable to handle excessive generated heat. Similarly, the first and second clutch plates may be coated with materials exhibiting a high coefficient of friction
Data Source
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Figure 5~6
AI summary
A torque limiting clutch assembly is provided that is mounted between the motor housing (221) and the ring gear (223) of a planetary gear assembly. During normal operation, the clutch assembly prevents rotation of the ring gear relative to the motor housing. In the event of a severe loading condition, the clutch assembly slips, thereby preventing excessive torque from being applied to the drive train and potentially damaging one or more drive train components.