1、 SURFACE VEHICLE INFORMATION REPORT Reduced Effort Brakes and Reduced Effort Vacuum Powered Brake Backup Systems SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary
2、, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your writte
3、n comments and suggestions. Copyright 2004 SAE International All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permissi
4、on of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS: http:/www.sae.org J2671 ISSUED AUG2004 Issued 2004-08 1. Scope, Classification, and Limitations 1.1 Scope This Information Report r
5、elates to a special class of automotive adaptive equipment which consists of modifications to the power brake booster systems provided as original equipment of motor vehicles. These modifications are generically called “Reduced Effort Power Brakes“ (REPB) The purpose of the modification is to lower
6、the amount of driver effort required to apply the brakes. Retention of reliability, ease of use and maintainability for disabled drivers, passengers, and the general public is of primary concern. Reduced Effort Power Brake modifications should be qualified by the tests referenced in the Recommended
7、Test Procedure. The tests set forth in that procedure should be applied, and failure of a Reduced Effort Power Brake modification to meet those tests should disqualify the modification from the claim of meeting the specifications of this Information Report. Because this is an Information Report, the
8、 numerical values for performance measurements presented in this report and in the accompanying Test Procedure, while based upon the best knowledge available at the time, have not been validated by a testing of the Test Procedure. 1.2 Classification Brake modifications discussed in this Information
9、Report can be classified as any modification to, or replacement of, the OEM power booster such that the reaction force to the driver is reduced. 1.3 Limitations These standards are limited to modifications which retain an OEM pedal and associated linkage, the OEM master cylinder and all plumbing dow
10、n to and including the brake wheel cylinders or actuators. They include adaptive equipment modifications for backup systems. Specifically excluded are hydrovac systems and modifications which use externally powered devices to reduce the braking effort. Rationale: “Joystick“ or servo type hand contro
11、lled systems which supplant the stock system or a major part of the stock system are out of scope. SAE J2671 Issued AUG2004 - 2 - 2. References 2.1 Applicable Documents The following publications form a part of the specification to the extent specified herein. Unless otherwise indicated, the latest
12、issue of SAE publications shall apply. 2.1.1 SAE PUBLICATIONS Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J656Automotive Brake Definitions and Nomenclature SAE J299In Service Brake Performance TestPassenger Car and Light Duty Trucks SAE J843dBrake System Road Test Code
13、Passenger Car and Light Duty Trucks SAE J937bService Brake System Performance RequirementsPassenger Car SAE J155Service Brake System Performance RequirementsLight Duty Trucks SAE J299Stopping Distance Test Procedures SAE J1808Vacuum Power Assist Brake Booster Test Procedure SAE J1211Recommended Envi
14、ronmental Practices for Electronic Equipment Design 2.1.2 MILITARY PUBLICATIONS Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094 MIL-STD-1472 (current revision)Department of Defence Design Control Criteria Standard: Human Engineering 2.1
15、.3 NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION Available from NHTSA, U.S. Department of Transportation, 400 7th Street SW., Washington, D.C. 20590. Federal Motor Vehicle Safety Standards (FMVSS), Part 49, CFR 571. web site: www.nhtsa.dot.gov. FMVSS No. 105Service, Emergency, and Power Brakes FMVS
16、S No. 106Brake Hoses FMVSS No. 135Passenger Car Brake Systems Part 595“Exemptions from the Make Inoperative Prohibition; Final Rule” 3. Definitions 3.1 Accumulator Tank See Vacuum Tank. 3.2 Actuator A transducer whose output is a force or torque and usually involves motion. SAE J2671 Issued AUG2004
17、- 3 - 3.3 Automotive Adaptive Equipment A piece of equipment designed to enable a person with a physical disability to operate a motor vehicle. 3.4 Anomaly Deviation from the common rule or type; irregularity. 3.5 Auxiliary See Backup. 3.6 Backup Any device which duplicates or otherwise fulfills the
18、 function of another if the latter fails or become inoperative. 3.7 Booster Any device for increasing power or output. 3.8 Diaphragm A flexible disc or membrane which deflects under pneumatic or hydraulic pressure and, in doing so, imparts linear motion to a centrally located rod or other form of me
19、chanical actuator, as in an air or brake carburetor. 3.9 Feedback The recycling of a portion of the output to the input of a system. Systems employing feedback are called closed-loop systems. 3.10 Logo A manufacturers name or trademark. 3.11 Original Equipment See OEM 3.12 OEM Original Equipment Man
20、ufacturer. This refers to the vehicle, and its systems, as they are designed and produced by the automobile manufacturer. SAE J2671 Issued AUG2004 - 4 - 3.13 Pedal Reserve The distance, measured from the under surface of the pedal to the floorboard along a line normal to the plane of the brake pedal
21、, when the brake pedal has been depressed to the point of brake lockup or activation of anti-lock brake system. 3.14 Primary Occurring first in time or sequence. Pertaining in the context of this document to the system which is intended to be in operation normally or routinely. 3.15 Power Brake Back
22、up System Refers to a system which provides backup to the modified or unmodified OEM brake boost system. 3.16 Reduced Effort Brakes A modification to the OEM power brake system which reduces pedal effort. 3.17 Shall The term to be used whenever the criteria for conformance with the specific recommen
23、dations requires that there be no deviation. (SAE J1159). (Note: Because this is an Information Report which makes recommendations, but is not standards, the use of the word shall has been replaced by should elsewhere in the report.) 3.18 Should The term to be used whenever non-compliance with the s
24、pecific recommendation is permissible. (SAE J1159) 3.19 Single-Point Failure Any failure of a component which directly causes the system, of which the failed component is a part, to cease to function. 3.20 Transducer A device which converts energy from one form or power level to another. 3.21 Vacuum
25、 Tank Usually a cylindrical container from which air has been partially exhausted, used to back-up a vacuum brake system, particularly in the event of failure of the engine operated system. SAE J2671 Issued AUG2004 - 5 - 4. Design Requirements 4.1 Maintenance of OEM Design Standards Modifications sh
26、ould not introduce new single-point failures of the brake system which do not exist in the OEM system and which compromise user safety, including compromise or elimination of crashworthiness provisions provided by the vehicle manufacturer in conformance with FMVSS 105, 135, 106, 116, 201, 203 and 20
27、4, or the general provisions of FMVSS 201. In any areas where the modification and reinstallation of OEM components or the installation of additional components has the potential to affect the vehicles conformance with the listed FMVSS standards, the manufacturer should submit documentation as to wh
28、y the modification does not affect performance or data showing that the performance of the modified system meets the standard. (APPENDIX RTP 3.1) Rationale: It is recognized that single-point failure modes exist in the OEM configuration of brake systems. The intent of this paragraph is to not compro
29、mise the inherent reliability of the original equipment configuration by introducing more single point failures. 4.2 Conventional Use of Motor Vehicle All power brake conversions to which this standard is applicable should be designed to permit the use of the brake pedal by able-bodied drivers. (APP
30、ENDIX RTP 3.2) Rationale: It is occasionally necessary for someone other than a disabled owner to operate a vehicle (family, maintenance personnel etc.) Although the level of effort is considerably less the conversion should not require operator inputs in directions of movement other than that found
31、 in the OEM system. Having these individuals operate a vehicle with controls with which they are not familiar and may not have had training is to be avoided. 4.3 Mandatory Backup for Reduced Effort Braking All reduced effort braking modifications should incorporate into the modification a backup cap
32、ability in case of primary power failure. The backup system should be activated automatically in case of engine failure. The backup source of braking energy should be isolated from the primary source through a check valve or other appropriate means of assuring that a primary system failure will not
33、cause a failure of the backup system. (APPENDIX RTP 3.3) Rationale: The purpose of this requirement is to provide the disabled driver some of the same protection from failure available to a non-disabled driver with the original brake system. The able-bodied driver can retain a measure of braking cap
34、ability in the event of loss of power boost. A disabled driver will not have this capability, since the modification covered herein is configured to adapt to his inability to use the original equipment powered system. 4.4 Energy for Reduced Effort Braking Backup Systems 4.4.1 The energy source for t
35、he Reduced Effort Braking Backup System should incorporate a vacuum tank. An auxiliary electric driven pump may be used in addition to, but not in place of, a vacuum tank. (APPENDIX RTP 3.4) SAE J2671 Issued AUG2004 - 6 - 4.4.2 The primary power for the backup brake system should be engine vacuum bu
36、t the system should operate when the engine is not running. (APPENDIX RTP 4.1.3) 4.5 Reduced Effort Braking Performance The force needed to apply the brakes should be measured according to the applicable procedures of SAE J299, “Inservice Brake Performance Test Procedure Passenger Car and Light Duty
37、 Truck“, and specifically paragraphs 1, 2, 3, 4, 5, 6.1, 7.1 (except 7.1.9), 7.2, 7.4, 7.5, and 7.6. 4.5.1 REDUCED PEDAL EFFORT Failure of the modified power brake system to attain the deceleration or stopping distances attainable with the (OEM) power brake with 30% less pedal force at both maximum
38、deceleration and at 0.3 g deceleration should be grounds for rejection of the modification. (APPENDIX RTP 4.1.1) Rationale: This performance test ascertains that, at a minimum, the modification in no way degrades the performance attainable with the unmodified power brake system. In fact, there shoul
39、d be a 20% reduction in force required to operate the brakes to specified levels of deceleration. 4.5.2 OPERATION AT HIGH ALTITUDE A label should be installed on the instrument panel of all vehicles modified with reduced effort brakes which states “THE REDUCED EFFORT BRAKES ON THIS VEHICLE WERE DESI
40、GNED FOR USE BELOW XX,000 FEET ALTITUDE”. The altitude should be determined by the manufacturer for his/her product and inserted in the space indicated. (APPENDIX RTP 3.9.2) Rationale: Modified boosters may suffer braking degradation at high altitudes where the pressure differential between engine v
41、acuum and atmospheric pressure is reduced. Some vehicles may require brake boosters which are larger than OEM boosters to retain adequate reduced effort braking. This will assure that the necessary changes in brake boosters have been made if needed or the user will know that the vehicle is not suita
42、ble for use at high altitudes. 4.6 Pedal Reserve The pedal reserve in the vehicle in which reduced effort braking and/or reduced effort braking backup system has been installed should be no less than in the vehicle with standard (OEM) power brakes. (APPENDIX RTP 4.1.2) Rationale: The modifications s
43、hould not compromise the braking system after normal wear on the brakes has occurred by causing the brake pedal to be any closer to the floor than in a vehicle with standard brakes 4.7 Operational Test The combined reduced effort braking and reduced effort braking backup system should withstand 70,0
44、00 cycles of bench test operation with no degradation in braking performance in stopping distance (as measured by brake line pressure), pedal pressure, pedal reserve or noticeable wear, fraying or other anomalous conditions not present at the commencement of testing. (APPENDIX RTP 4.2.6) SAE J2671 I
45、ssued AUG2004 - 7 - Rationale: Fifty thousand cycles should bring out any system design problems which arise in use but not necessarily due to wear. 4.8 Backup Vacuum Reserve The reduced effort braking backup system should provide sufficient backup for a minimum of ten stops using the backup system
46、alone. Braking performance should be equal to that provided with the normal vacuum source connected. Five of these stops should not require a force at the pedal in excess of that under primary power. Five more stops should be made at the end of which brake effort should not exceed twice the level of
47、 effort required for primary brake system actuation to achieve the same deceleration. (APPENDIX RTP 4.2.1) Rationale: A disabled driver may be totally dependent upon the backup system to get their vehicle off the road and bring it to a full stop. A vacuum sufficient for five full stops with no degra
48、dation of performance and five stops with maximal effort on the part of the operator is needed 4.9 Vacuum Maintenance Capability 4.9.1 The vacuum tank and lines of the reduced effort braking backup system should be sealed tightly enough such that when the system is not in use, the vacuum should not
49、drop below 50% of normal working level within 4 h. (APPENDIX RTP 4.2.2) 4.9.2 The vendor should certify that the vacuum tank wall thickness used meets ASTM standards for the vacuum and conditions encountered. (APPENDIX RTP 2.7) Rationale: This bench test establishes the tightness of the system. Experience has shown that even a vacuum control system for automotive heating and air conditioning controls can retain usable vacuum for 24 h when properly sealed. 4.10 Mandatory Automatic Actuation of Backup Systems 4.10.1 VACUUM TANKS If the vacuum tank is not dire
