Ring Gear Differential Hardness Nitriding
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Solution Overview
Problem
Conventional ring gears with nitrocarburized internal and external teeth suffer from excessive wear of clutch discs, leading to gear noise and shift shock in automatic transmissions due to uneven hardness, where nitrocarburizing increases the surface hardness of both internal and external teeth.
Innovation Solution
A ring gear design with internal teeth formed using nitriding to achieve high hardness and accuracy, while external teeth have a lower hardness by removing the nitride layer, allowing for reduced wear and noise through differential nitrogen concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitrocarburizing is used to harden internal teeth, then wear resistance is improved, but processing temperature is high causing thermal distortion and reduced manufacturing accuracy
Solution Approach 1:
The patent changes the processing temperature parameter by using induction hardening (lower temperature) for external teeth instead of nitrocarburizing (higher temperature). This parameter change reduces thermal distortion and improves manufacturing accuracy while still achieving the required hardness through controlled induction heating and quenching.
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 solution effectively restrains wear of members meshing with external teeth and reduces gear noise by forming internal teeth with high hardness and accuracy without increasing the hardness of external teeth, thereby preventing clutch disc wear and shift shock.
Implementation Method 1
the internal teeth of the ring gear in the planetary gear unit of Japanese Patent Application Publication No. H04-285346 (JP H04-285346 A) have been subjected to nitrocarburizing in order to improve hardness of the internal teeth. Induction hardening may be used to increase hardness of the internal teeth. However, since the processing temperature of nitrocarburizing is lower than that of induction hardening, distortion due to nitrocarburizing is restrained and the internal teeth can be formed with high accuracy.
Implementation Method 2
Since the internal teeth of the ring gear are required to have predetermined hardness, the internal teeth of the ring gear in the planetary gear unit of Japanese Patent Application Publication No. H04-285346 (JP H04-285346 A) have been subjected to nitrocarburizing in order to improve hardness of the internal teeth.
Data Source
AI summary
A ring gear that, together with a sun gear and a pinion gear that is disposed radially outward of the sun gear and meshes with the sun gear, forms a planetary gear unit, the ring gear includes: a body, internal teeth that are configured to mesh with the pinion gear and that are formed in at least a part of an inner peripheral surface of the body, and external teeth that have a lower hardness than the internal teeth and that are formed in at least a part of an outer peripheral surface of the body, wherein a surface nitrogen concentration in the internal teeth is higher than that in at least tooth surfaces of the external teeth.