Corrugated Cage Rivet Nitriding Through-Hole Design

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing methods for manufacturing corrugated cages for rolling bearings face challenges in cost-effective nitriding treatment, handling of intermediate assemblies, and durability, particularly due to issues with rivet press-fitting and nitriding coverage, leading to potential rivet falling out and reduced rigidity.

Innovation Solution

A method involving press-fitting rivets into through-holes with a smaller axial dimension than the holes, allowing nitriding treatment of intermediate assemblies, followed by single-body nitriding of cage elements, and forming caulking portions to prevent rivet protrusion and enhance fit, with a dimensional relationship of X=(0.50 to 0.90)Y for optimal results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If rivets are press-fitted into through-holes with the same axial dimension, then rivet falling out is prevented, but nitriding treatment coverage is reduced and durability is compromised

Engineering Contradiction:

Improverivet retentionVSAvoidnitriding coverage

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The through-hole is designed with different axial dimensions at different locations: the first axial dimension (press-fitting portion) matches the rivet for secure retention, while the second axial dimension (protrusion prevention portion) is smaller to prevent rivet protrusion and allow nitriding coverage. This local differentiation resolves the contradiction between rivet retention and nitriding coverage.

Inventive Principle:

Principle #3Local quality

2Strength

If rivet diameter is increased to improve strength, then durability is enhanced, but dimensional constraints are violated

Engineering Contradiction:

Improverivet strengthVSAvoidrivet diameter

Core Design Contradiction:

StrengthVSLength of moving object

Solution Approach 1:

Instead of changing the rivet diameter, the invention changes the axial dimension parameters of the through-hole to achieve both rivet retention and nitriding coverage. The press-fitting portion provides secure fitting while the protrusion prevention portion allows nitriding, eliminating the need to increase rivet diameter.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If nitriding treatment is performed on assembled rivets, then manufacturing cost is reduced, but rivet protrusion occurs reducing rigidity

Engineering Contradiction:

Improvemanufacturing costVSAvoidcage rigidity

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The through-hole is pre-designed with the protrusion prevention portion having a smaller axial dimension than the rivet. This preliminary structural preparation allows nitriding treatment to be performed on assembled rivets without causing protrusion, thus maintaining rigidity while reducing manufacturing cost.

Inventive Principle:

Principle #10Preliminary action

4Manufacturing precision

If press-fitting portion axial dimension equals through-hole axial dimension, then rivet fit is maximized, but nitriding treatment area is reduced

Engineering Contradiction:

Improverivet fit precisionVSAvoidnitriding treatment area

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

The through-hole is segmented into two distinct portions along the axial direction: the press-fitting portion for rivet insertion and the protrusion prevention portion for nitriding coverage. This segmentation allows the rivet to be securely fitted while preserving nitriding treatment area on the protrusion prevention portion.

Inventive Principle:

Principle #1Segmentation

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

This approach reduces the area without nitriding coverage, prevents rivet falling out, and enhances the durability and rigidity of the corrugated cage by ensuring proper fit and coverage during the manufacturing process.

Implementation Method 1

press-fitting the press-fitting portion (24) of each rivet (9b) into each through-hole (12a)

Methodology Applied

Scientific EffectPress-fitting: Mechanical Force

Implementation Method 2

performing, in a state where an intermediate assembly (17b) made by temporarily fixing each rivet (9b) to the cage element (8a) on one side is configured, nitriding treatment on the intermediate assembly (17b)

Methodology Applied

Scientific EffectNitriding: Nitriding

Implementation Method 3

forming a caulking portion (15b) by crushing a tip portion of each rod portion (13b)

Methodology Applied

Scientific EffectCrushing/Compression: Compression

Data Source

PatentEP3015726B1Method for manufacturing corrugated cage and corrugated cage

Publication Date: 2017.11.15 NSK LTD

Figure 1
Figure 2
Figure 3A~3B

AI summary

In the process of manufacturing a ribbon cage, an intermediate assembly (17a) is configured by press-fitting press-fit portions (24, 24) provided at base ends of pestle portions (13b, 13b) of respective rivets (9b, 9b) into respective through-holes (12a, 12a) of one cage element (8a), and the intermediate assembly (17a) is subjected to nitriding treatment. The axial dimension (X) of each of the press-fit portions (24, 24) is set smaller (X<Y) than the axial dimension (Y) of each of the through-holes (12a, 12a). Consequently, in a portion in the axial direction between the inner peripheral surface of each of the through-holes (12a, 12a) and the outer peripheral surface of each of the pestle portions (13b, 13b), portions that are not in close contact with each other are provided, and nitride layers are formed in the respective portions that are not in close contact with each other.