Differential Gear Friction Torque Limiter for Compact Drivetrains
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Solution Overview
Problem
Differential gear units in vehicles face challenges in withstanding excessive torque, leading to vibrations and the need for increased size and weight to enhance strength, which complicates integration into vehicles, especially in electric and hybrid vehicles where torque is significantly higher.
Innovation Solution
A differential gear unit design incorporating a ring gear mounted on a casing with a friction mechanism and an elastic member to establish frictional force, allowing the ring gear to reciprocate and transmit torque while using a friction mechanism as both a joint and torque limiter, eliminating the need for set bolts and reducing size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the size of the differential gear unit is increased to ensure sufficient strength to withstand maximum torque, then the strength increases, but the device complexity and difficulty of fitting into a vehicle increases
Solution Approach 1:
The patent changes the physical parameters of the contact surfaces by making them tapered instead of flat, and introduces an elastic member to dynamically adjust the contact pressure. This allows the system to withstand maximum torque without requiring an overall increase in the size of the differential gear unit, thereby resolving the contradiction between strength and device size.
Solution Approach 2:
The patent introduces an elastic member that allows the contact pressure between the ring gear and differential case to dynamically adjust based on the applied torque. This dynamic adjustment mechanism enables the system to handle peak torque loads without requiring excessive structural strength, thus avoiding size increase while maintaining sufficient strength.
2Strength
If the size of the differential gear unit is increased to ensure sufficient strength to withstand maximum torque, then the strength increases, but the weight increases
Solution Approach 1:
By changing the contact surface geometry to tapered surfaces and introducing an elastic member, the patent achieves sufficient strength to withstand maximum torque without increasing the overall size and weight of the differential gear unit. The localized reinforcement through tapered surfaces and elastic member provides the necessary strength while keeping the rest of the unit compact and lightweight.
3Reliability
If contact surfaces are tapered to prevent loosening of bolts, then the reliability increases, but the device complexity increases
Solution Approach 1:
The tapered contact surfaces serve multiple functions: they prevent bolt loosening through self-locking, provide structural reinforcement to withstand torque, and work in conjunction with the elastic member to dynamically adjust contact pressure. This multi-functionality increases reliability without proportionally increasing device 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 design effectively limits excessive torque transmission, prevents damage, and allows for downsizing without increasing strength, simplifying the structure and reducing weight, while maintaining durability.
Implementation Method 1
an elastic member that pushes the ring gear in a direction to increase the frictional force established by the friction mechanism
Implementation Method 2
a friction mechanism that is arranged between the ring gear and the casing to establish a frictional force for preventing relative rotation between the ring gear and the casing
Data Source
AI summary
A downsized differential gear unit designed to prevent transmission of an excessive torque. The differential gear unit comprises: a differential mechanism held in a casing; a ring gear mounted rotatably and reciprocatably on the casing; a friction mechanism that is arranged between the ring gear and the casing; and an elastic member that pushes the ring gear in an axial direction. A torque possible to be transmitted between the ring gear and the casing is set to a torque governed by a pushing force of the elastic member and the frictional force of the friction mechanism.