Silent Chain Guide Plate Profile and Hardness Design

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Silent chains experience frictional losses and noise due to premature contact between guide plates and sprocket teeth, and bending of connecting pins under tension, leading to reduced power-transmitting efficiency and performance.

Innovation Solution

The silent chain design features guide plates with a high inner profile to prevent premature contact with sprocket teeth, low tensile hardness relative to connecting pins to avoid warping, and concave or arcuate back surfaces to minimize contact with chain guides, ensuring proper engagement and reducing frictional losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the guide plate inner profile is increased to prevent premature contact with sprocket teeth, then noise and frictional loss are reduced, but the guide plate becomes more complex and harder to manufacture

Engineering Contradiction:

Improvenoise and frictional loss from premature contactVSAvoidguide plate manufacturing complexity

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The guide plate inner profile is designed in advance to have a height that prevents premature contact between the guide plate and sprocket teeth. This preliminary geometric configuration ensures that during operation, the link plate engages the sprocket tooth before the guide plate can contact it, even when lateral swing occurs. The profile is calculated and formed during manufacturing to achieve the desired engagement sequence.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The guide plate is designed with a localized high inner profile only in the specific region where it interacts with the sprocket tooth during engagement. This localized geometric modification prevents premature contact without requiring the entire guide plate to be more complex or heavier. The high inner profile is concentrated where it is most effective.

Inventive Principle:

Principle #3Local quality

2Reliability

If the tensile hardness of the guide plate is reduced to prevent connecting pin bending, then connecting pin reliability is improved, but the guide plate strength may be compromised

Engineering Contradiction:

Improveconnecting pin bending resistanceVSAvoidguide plate strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The tensile hardness parameter of the guide plate is specifically adjusted to be lower than that of the connecting pin. This parameter change ensures that under tensile load, the guide plate deforms before the connecting pin, preventing pin bending and failure. The hardness values are selected within specific ranges to achieve this protective effect while maintaining sufficient guide plate strength for its structural function.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The guide plate acts as an intermediary protective element between the connecting pin and the external loads. By having lower tensile hardness, the guide plate serves as a sacrificial component that deforms first, absorbing energy and preventing the more critical connecting pin from bending or failing. This mediates the stress distribution in favor of pin reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If the back surface of the guide plate is modified to minimize contact with chain guides, then frictional loss is reduced, but the guide plate design becomes more complex

Engineering Contradiction:

Improvefrictional loss at chain guide contactVSAvoidguide plate back surface geometry

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The back surface of the guide plate is given a concave or arcuate curvature instead of a flat surface. This curved geometry reduces the contact area between the guide plate back surface and the chain guide sliding-contact surface. The curvature is designed to minimize line or area contact, thereby reducing frictional loss during chain operation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Productivity

If the guide plate inner profile is increased to prevent lateral swing contact, then power-transmitting efficiency is improved, but the guide plate height and complexity increase

Engineering Contradiction:

Improvepower-transmitting efficiencyVSAvoidguide plate height

Core Design Contradiction:

ProductivityVSLength of stationary object

Solution Approach 1:

The guide plate is designed with a high inner profile only in the specific local region where it interfaces with the sprocket tooth during engagement. This localized geometric enhancement prevents premature contact and improves power-transmitting efficiency without requiring the entire guide plate height to be increased. The high profile is concentrated where it provides the most benefit.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8974335B2Silent chain

Publication Date: 2015.03.10 TSUBAKIMOTO CHAIN CO

AI summary

In a silent chain, frictional losses and noise are reduced, and power transmitting efficiency is improved, by making the inner profile of each guide plate sufficiently high in relation to a link plate tooth of a link plate overlapped by each said guide plate that engagement between a sprocket tooth and said link plate tooth takes place before engagement of the last mentioned sprocket tooth with said guide plate, even when the chain moves laterally. The tensile hardness of the guide plates is sufficiently low in relation to the bending rigidity of the connecting pins of the chain to prevent substantial warping of the guide plates as a result of tension acting on the chain. The back surfaces of the guide plates are configured to avoid contact with a sliding contact surface of a chain guide on which a back surfaces of the link plates of said chain can slide.