Titanium Alloy Connecting Rod Chromium Nitride Coating Anti-Seizing

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Solution Overview

Problem

Conventional titanium-alloy connecting rods face high production costs and potential seizing issues due to the use of bushings, which can lead to increased wear and strain from high-temperature oxidation treatments.

Innovation Solution

A split-type titanium-alloy connecting rod with a chromium nitride layer formed on the inner peripheral surfaces of the small and big ends, providing improved anti-seizing and anti-fretting properties without the need for bushings, and using a Ti-5Al-1Fe alloy to reduce costs while maintaining strength and processibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bushing is provided between the inner peripheral surface of the small end and the piston pin to prevent seizing, then the anti-seizing property is improved, but the production cost increases

Engineering Contradiction:

Improveanti-seizing propertyVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts and removes the bushing component from the connecting rod structure. Instead of using a separate bushing to prevent seizing, the patent applies a chromium nitride coating directly to the inner peripheral surface of the small end, thereby eliminating the need for a bushing while maintaining anti-seizing functionality. This reduces production cost by removing an additional manufacturing step and component assembly requirement.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the surface property parameter of the small end by applying a chromium nitride coating. This coating provides the necessary anti-seizing properties that would otherwise require a bushing, while being more cost-effective to produce. The coating process modifies the surface characteristics directly on the connecting rod material without adding a separate component layer.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If an oxidation treatment is performed by heating to high temperature to improve anti-seizing property, then the anti-seizing property is improved, but strain is induced causing seizing or wear

Engineering Contradiction:

Improveanti-seizing propertyVSAvoidstructural integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention changes the surface treatment approach from thermal oxidation (high temperature heating) to physical vapor deposition of chromium nitride coating. This alternative parameter change achieves anti-seizing properties without subjecting the titanium alloy connecting rod to high temperatures that would induce harmful strain and compromise structural integrity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the thermal field-based oxidation treatment with a coating deposition process. Instead of using heat to create an oxide layer, the patent uses physical vapor deposition to apply a chromium nitride coating, thereby avoiding the thermal strain issues while achieving the same anti-seizing functional outcome.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a solid bushing is used for titanium-alloy connecting rod, then the anti-seizing property is improved, but the production cost increases significantly

Engineering Contradiction:

Improveanti-seizing propertyVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts and eliminates the solid bushing component entirely. By applying a chromium nitride coating directly to the small end's inner peripheral surface, the patent removes the need for a separate bushing component, thereby significantly reducing production cost while maintaining the anti-seizing function.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention uses a composite structure where a chromium nitride coating is applied to the titanium alloy surface of the small end. This composite approach provides the anti-seizing properties of a bushing material while being integrated directly into the connecting rod, eliminating the need for a separate solid bushing component and reducing overall production cost.

Inventive Principle:

Principle #40Composite materials

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 chromium nitride layer enhances the anti-seizing properties of the small end and anti-fretting properties of the big end, reducing production costs and preventing seizing and wear, while allowing for easier lubricant introduction and improved mechanical performance.

Implementation Method 1

a chromium nitride layer, which is formed on at least all of an inner peripheral surface of the small end

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Data Source

PatentEP3015723B1Connecting rod, internal combustion engine, automotive vehicle, and production method for connecting rod

Publication Date: 2018.10.10 YAMAHA MOTOR CO LTD

Figure 1A~1B
Figure 2A~2C
Figure 3~4

AI summary

The anti-seizing property of a small end (20) of a titanium-alloy connecting rod (1) is suitably improved. A connecting rod (1) made of a titanium alloy includes a rod main body (10), a small end (20) provided at one end of the rod main body, and a big end (30) provided at another end of the rod main body. The connecting rod further includes a chromium nitride layer (50) formed at least on an inner peripheral surface (20i) of the small end.