GB/T 28775-2021

Synchronous belt drives—Pulley with T trapezoidal profile system (English Version)

Standard No.

GB/T 28775-2021

Language

Chinese, Available in English version

Release Date

2021

Published By

General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China

Latest

GB/T 28775-2021

Replace

GB/T 28775-2012

Scope

This standard stipulates the type and mark of the metric pitch trapezoidal tooth synchronous pulley (hereinafter referred to as the pulley), the size of the groove, the size of the pulley, the geometric tolerance of the pulley, the material of the pulley, the surface roughness and the balance. This standard applies to general industrial synchronous belt drives, and is used in conjunction with the corresponding product models specified in GB/T28774-2021.

Introduction

Core changes in the standard revision

Technical parameters	2012 edition	2021 edition	Range of change
Tooth tip fillet radius	0.3-0.8mm	0.5-1.2mm	Maximum +50%
Pitch deviation	0.03-0.15mm	0.05-0.20mm	Tolerance zone relaxation
Ring size	Double-sided only	Single-sided specification added	Structural expansion

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Analysis of key technical requirements

1. Groove size specification

The standard stipulates five types of tooth groove parameters from T2.5 to T20, among which:

• SE type tooth groove is suitable for small pulleys with ≤20 teeth
• N type tooth groove is suitable for pulleys with >20 teeth

Key improvement: The tooth top fillet radius is uniformly increased by 0.2mm to reduce the risk of stress concentration.

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2. Geometric tolerance system

Application case of an automobile production line

When using a T10 pulley, the measured radial runout is 0.06mm (standard limit 0.08mm), and the transmission efficiency is improved by 12%.

Tolerance calculation formula:

• Cylindricity: t1≤0.001b mm
• Radial runout: t2=0.08+0.0005(d0-200) mm

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Implementation suggestions

Selection guide

1. Preferably use N-type tooth groove design (when the number of teeth is greater than 20)
2. The cumulative pitch deviation should be controlled to be ≤0.13mm under high-speed conditions
3. Dynamic balancing test is required for outer diameter greater than 300mm

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Standard evolution analysis

This standard is modified to adopt ISO17396:2017, the main differences are:

• Add single-sided retaining ring structure
• Optimize diameter size series
• Strengthening material requirements (reference GB/T11357)