1、Brake Design and Safely Third Edition Rudolf Limpert SAE International Brake Design and Safety Third EditionOther related resources from SAE International: Brake Technology Handbook By Bert J. Breuer and Karlheinz Bill (Product Code: R-375) Electric and Hybrid-Electric Vehicles - Braking Systems and
2、 NVH Considerations By Ronald K. Jurgen (Product Code: PT-143/4) Disc Brake Squeal By Frank Chen, Chin An Tan, and Ronald L. Quaglia (Product Code: R-353) Advanced Brake Technology By Bert J. Breuer and Uwe Dausend (Product Code: R-352) For more information or to order a book, contact SAE Internatio
3、nal at 400 Commonwealth Drive, Warrendale, PA 15096-0001 E-mail: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada)724-776-4970 (outside USA) Fax: 724-776-0790 http:/books.sae.orgBy Rudolf Limpert Brake Design and Safety Third Edition Warrendale, PA USA Copyright 2011 SAE Internation
4、al eISBN: 978-0-7680-5789-8400 Commonwealth Drive Warrendale, PA 15096-0001 USA E-mail: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada)724-776-4970 (outside USA) Fax: 724-776-0790Copyright 2011 SAE International. All rights reserved. No part of this publication may be reproduced,
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6、x: 724-772-9765. ISBN 978-0-7680-3438-7 SAE Order No. R-398 DOI 10.4271/R-398 Information contained in this work has been obtained by SAE International from sources believed to be reliable. However, neither SAE International nor its authors guarantee the accuracy or completeness of any information p
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8、ender engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. To purchase bulk quantities, please contact: SAE Customer Service E-mail: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada)724-776-4970 (o
9、utside USA) Fax: 724-776-0790 Visit the SAE Bookstore at http:/books.sae.org Limpert, Rudolf. Brake design and safety / Rudolf Limpert. 3rd ed. p. cm. Includes index. ISBN 978-0-7680-3438-7 1. AutomobilesBrakesDesign and construction. I. Title. TL269.L56 2011 629.246dc222011011904 Library of Congres
10、s Cataloging-in-Publication Datav Dedication To Dr. Hans Strien, at Alfred Teves, Co. in Frankfurt, Germany, who took into his brake department a young engineering trainee. 16. April 1963.vii Table of Contents Chapter 1 Fundamentals of Braking Performance, Design, and Safety 11.1 The Functions of a
11、Brake System 11.2 Vehicle Deceleration and Stopping Distance .21.3 Elements of Automotive Brake System Design 101.4 Pedal Force and Pedal Travel 171.5 Design Solution Selection Process . 181.6 Braking System Involvement in Accidents . 20 Chapter 2 Design and Analysis of Friction Brakes . 272.1 Brake
12、 Torque 272.2 Brake Factor 272.3 Brake Factor of Drum Brakes 292.4 Disc Brakes . 48 Chapter 3 Thermal Analysis of Automotive Brakes . 653.1 Temperature Analysis 653.2 Thermal Stress Analysis 1073.3 Thermal Design Measures 112 Chapter 4 Analysis of Mechanical Brake Systems 1194.1 General Observations
13、 1194.2 Wheel Brakes 1204.3 Driveshaft-Mounted Brakes . 122 Chapter 5 Analysis of Hydraulic Brake Systems 1255.1 Manual Hydraulic Brakes . 1255.2 Boost System Analysis . 1275.3 Brake Line Pressure Control Devices 1415.4 Brake Fluid Volume Analysis . 1505.5 Dynamic Response of Hydraulic Brake Systems
14、 . 175Brake Design and Safety viii Chapter 6 Analysis of Air Brake Systems 1836.1 Basic Concepts . 1836.2 Foundation Brakes . 1846.3 Brake Torque 1906.4 Vehicle Deceleration 1946.5 ABS Modulating Valves 1966.6 PC-BRAKE AIR Multi-Axle Software Application 1996.7 Response Time of Air Brake Systems 200
15、6.8 Electronic Brake Control (Braking by Wire) . 209 Chapter 7 Single Vehicle Braking Dynamics . 2137.1 Static Axle Loads 2137.2 Dynamic Axle Loads . 2147.3 Optimum Braking Forces . 2167.4 Actual Braking Forces Developed by Brakes 2247.5 Comparison of Optimum and Actual Braking Forces .2257.6 Tire-R
16、oad Friction Utilization . 2287.7 Braking Efficiency 2307.8 Fixed Brake Force Distribution Analysis 2327.9 Variable Brake Force Distribution Analysis . 2387.10 Braking Dynamics of Two-Axle Truck Equipped with Air Brakes . 2497.11 Three-Axle Straight Truck Air Brakes 2537.12 Vehicle Stability Analysi
17、s 2587.13 Braking Dynamics While Turning 267 Chapter 8 Braking Dynamics of Combination Vehicles 2758.1 Tow Vehicle-Trailer Combination . 2758.2 Electronic Stability Control and Trailer Swing 2788.3 Braking of Tractor-Trailer Combinations . 2798.4 Braking of 2-S1 Combination . 2818.5 2-S1 Tractor-Tra
18、iler Combination PC-BRAKE AIR Software . 3028.6 Braking of 3-S2 Tractor-Semitrailer Combination 3128.7 2-S12 Combination: Two-Axle Tractor, Single-Axle Semitrailer, and Double-Axle Trailer 3188.8 2-S2 Tractor-Semitrailer 3208.9 2-S3 Tractor-Semitrailer Triple-Axle Trailer with Leaf Springs . 3218.10
19、 Test Results . 325Table of Contents ix Chapter 9 Automatic Brake Control 3279.1 Basic Considerations 3279.2 Wheel-Lockup Analysis . 3289.3 Basic Performance Requirements of ABS Systems 3439.4 Hydraulic ABS Systems . 3539.5 ABS System Components . 3609.6 Drivetrain Influence on ABS 3649.7 ABS System
20、s for Air Brakes 364 Chapter 10 Analysis of Brake Failure . 37310.1 Basic Considerations . 37310.2 Development of Brake Failure 37410.3 Analysis of Partial Brake Failure 37610.4 Comparison of Dual Brake Systems 38910.5 Vacuum Assist Failure . 39110.6 Full Power Brake Failure . 39210.7 Degraded Braki
21、ng Due to Air Inclusion . 39310.8 Brake Fluid Considerations in Design and Failure Analysis 39410.9 Seal and Rubber Materials 39610.10 Data Collection in Brake System Failures. 39610.11 Failure of Air Brake Systems. 403 Index .405 About the Author . 415xi While writing the third edition, I have care
22、fully considered the comments received from readers all over the world. One engineer remarked that whenever he has new trainees in his brake department, they must read Limperts brake book. Following that mandate I have added explanations and examples to the theoretical analysis of braking and brake
23、temperature while retaining the practical aspects of brake system design. Electronic system controls have significantly increased the potential of braking systems. Notwithstanding the advances made in applying brakes by mechanical, hydraulic, or electrical means, vehicles are slowed and stopped by f
24、riction between pad and rotor. Only when the underlying brake system is properly engineered will automatic controls perform effectively and vehicles brake safely under all foreseeable operating conditions. The third edition provides the fundamental tools necessary to design efficient braking systems
25、 that will comply with safety standards, minimize consumer complaints, and perform safely and efficiently long before and while electronic brake controls become active. New to the readers is the brake design software, developed by the author as an effective companion tool to this edition. The effici
26、ent design of automotive brake systems, including trucks and trailers, with PC-BRAKE software is demonstrated with detailed examples. Automotive engineering students, brake engineers, and forensic experts will benefit greatly from the third edition in conjunction with the computer programs and brake
27、 design workshop available from the authors website www. . Rudy Limpert Preface to the Third Editionxiii The Second Edition continues to provide a systems approach to designing safer brakes. Consulting experts will find it a single reference in determining the involvement of brakes in accident causa
28、tion. Brake system technology has attained a high standard of quality over the last two decades. Nearly all automobiles are now equipped with antilock brakes. Federal braking standards require commercial vehicles to use antilock brakes. Revolutionary innovative brake designs are not expected. Improv
29、ements in brake systems will only be achieved through basic research, the application of sound engineering concepts, and testing, resulting in small, yet important, design changes. The objective of the Second Edition is to assist the brake engineer in accomplishing his task to design safer brakes th
30、at can be operated and maintained safely. The brake expert will find all the analytical tools to study and determine the potential causes of brake failures. The Second Edition is expanded to cover all essential subjects, including the mechanical and thermal analysis of disk brakes. Mistakes found in
31、 the First Edition were corrected. I thank all those who have made valuable suggestions and comments and helped me to understand brakes better, in particular the many individuals who attended my Brake Design and Safety seminars. Preface to the Second Editionxv The purpose of this book is to provide
32、a systems approach to designing safer brakes. Much of the material presented was developed during my work as a brake design engineer, conducting automotive research, consulting as a brake expert, and teaching brake design. The book is written for automotive engineers, technical consultants, accident
33、 reconstruction experts, and lawyers involved with the design of brake systems, the analysis of braking performance, and product liability issues. Junior engineers will benefit from the book by finding in one single source all essential concepts, guidelines, and design checks required for designing
34、safer brakes. Chapter 1 reviews basic stopping distance performance, design rules, and product liability factors. In Chapter 2, drum and disc brakes are discussed. Brake torque computations are shown for different drum and disc brake designs. Temperature and thermal stresses are analyzed in Chapter
35、3. Practical temperature equations are shown whenever possible. Chapter 4 briefly reviews basic concepts involved in analyzing mechanical brake systems. The operation and design of hydraulic brakes are discussed in Chapter 5. Air brake systems and their components are discussed and analyzed in Chapt
36、er 6. Brake force distribution, braking efficiency, optimum brake force distribution, and vehicle stability during braking for the single vehicle are analyzed in Chapter 7. Car-trailer and commercial truck-trailer braking is discussed in Chapter 8. Important elements of antilock braking performance
37、and design are introduced in Chapter 9. Brake failures are discussed in Chapter 10. Preface to the First Edition1 Fundamentals of Braking Performance, Design, and Safety Chapter 1 Fundamentals of Braking Performance, Design, and Safety 1.1 The Functions of a Brake System A vehicle is connected to th
38、e roadway by the normal and traction forces produced by the tires. Braking, steering, or accelerating forces must be generated by the small tire tread area contacting the ground. Only forces equal to or less than the product of tire normal force and tire-road coefficient of friction can be transmitt
39、ed between vehicle and ground. Even the ideal braking and stability control system cannot utilize more traction than provided by the tires and road. The safe operation of a motor vehicle requires continuous adjustment of its speed to changing traffic conditions. The brakes and tires along with the s
40、teering system are the most safety-critical accident avoidance components of a motor vehicle. Brakes must perform safely under all reasonably foreseeable operating conditions, including slippery, wet, and dry roads; with a lightly or fully laden vehicle; when braking straight or while turning; with
41、new or worn brakes; when applied by the novice or experienced driver; on smooth or rough roads; or when pulling a trailer. The basic functions of a brake system must be provided under foreseeable circumstances, at reasonable cost and brake wear life, while providing directional stability and accepta
42、ble tire-road friction utilization. The braking system must comply will all applicable safety standards. Under most conditions, safety standards are considered minimum performance requirements. 1.1.1 Slowing and/or Stopping Decelerating a vehicle to a lower speed or to a complete stop is the functio
43、n most often performed by the service brakes of a vehicle. Safety standards and industry practices place stringent requirements on effectiveness of stops including repeated braking under a variety of operating conditions. Critical design parameters include proper brake balance front-to-rear to ensur
44、e directional stability while braking at, or near, the limit of tire-road friction, 2 Brake Design and Safety and optimum brake rotor geometry to minimize brake temperature rise and thermal stresses. Statistically speaking, most domestic drivers rarely exceed 0.1 to 0.2 g braking severity, and may a
45、pproach dry-road brake lockup or antilock braking system (ABS) modulation only twice a year. Consequently, optimizing brake designs with respect to maximum-effectiveness braking may not yield optimum braking performance in terms of brake wear life for low-level braking effectiveness or continued bra
46、king. Large values of thermal conductivity, specific heat, and density for brake rotors yield lower swept surface temperatures. 1.1.2 Maintaining Speed on a Downgrade In most downgrade driving situations, service brake systems perform adequately when properly used by the driver. During constant-spee
47、d downgrade operation, the potential energy is converted into thermal energy by the brakes, resulting in increased brake temperature. As long as the operating conditions in terms of the potential energy rate (weight, slope, and speed) are such that the steady-state brake temperature reached is less
48、than a brake-specific critical temperature, the vehicle will be able to safely descend the downgrade. Important design parameters are that each brake produces an optimum share of the overall low-level braking force over an extended time, which is often different from the share required for maximum-e
49、ffectiveness braking; that the convective cooling is optimized through effective ambient airflow and large cooling areas; and that, in the case of interstate buses and similar vehicles, cooling airflow obstructions are eliminated or minimized. 1.1.3 Holding Stationary on a Downgrade Holding a vehicle stationary is primarily a function of the force transmission or mechanical gain between the application lever and braked tires. Safety standards generally require a specified hill-holding capacity. However, because a parking brake may be used in an emerge
