Differential Gear Pinion Retaining Friction Asymmetry
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Solution Overview
Problem
Existing differential gear units fail to generate differential-limiting force suitable for various driving states of a vehicle, as they cannot differentiate frictional forces during acceleration and deceleration effectively.
Innovation Solution
A differential gear unit design that incorporates a pinion gear capable of spinning and revolving, with a pinion retaining portion that varies frictional forces based on contact area and shape during different driving states, allowing for differential-limiting force adjustment according to the vehicle's state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pinion retaining portion uses a uniform frictional force design, then the structure is simple, but the differential-limiting force cannot be adjusted for different driving states
Solution Approach 1:
The pinion retaining portion is designed with different friction coefficients at different locations. Specifically, the first contact surface has a different friction coefficient than the second contact surface, allowing the differential gear unit to generate different differential-limiting forces during acceleration and deceleration. This local variation in friction properties enables adaptability to different driving states without requiring a completely separate mechanism for each state.
Solution Approach 2:
The pinion retaining portion employs an asymmetric design where the frictional characteristics differ between the acceleration side and deceleration side. The first frictional force generated during acceleration is intentionally made different from the second frictional force during deceleration. This asymmetric friction design allows the same pinion retaining portion to provide optimized differential-limiting force for both driving states, resolving the contradiction between adaptability and structural simplicity.
2Force
If the contact area between pinion retaining portion and pinion gear is increased, then the frictional force increases, but the differential-limiting force becomes excessive for certain driving states
Solution Approach 1:
Instead of uniformly increasing the contact area, the invention applies local quality by creating different contact surface areas with different friction coefficients. The first contact surface and second contact surface are designed with distinct friction properties, allowing the system to generate appropriate frictional forces for different driving states. This approach enables force adjustment without simply scaling the contact area, maintaining adaptability while achieving the required differential-limiting force.
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
Enables the generation of differential-limiting force appropriate for acceleration and deceleration by varying frictional forces, enhancing torque transfer and driving efficiency by adjusting contact areas and shapes of the pinion retaining portion.
Implementation Method 1
frictional force during acceleration which is generated between the pinion gear and the case during acceleration is different from the frictional force during deceleration which is generated between the pinion gear and the case during deceleration
Data Source
AI summary
A differential gear unit has a pinion gear that can spin as well as revolve, a differential case that has a pinion retaining portion that supports the pinion gear, and a pair of side gears that mesh with the pinion gear. Frictional force generated at a portion where the pinion gear contacts the pinion retaining portion when the rotation speed of one side gear is faster than the rotation speed of the other side gear is different from the frictional force generated between the pinion gear and the pinion retaining portion when the rotation speed of the one side gear is slower than the rotation speed of the other side gear.