1、 SURFACE VEHICLE INFORMATION REPORT Reduced Effort Power Steering and Power Steering 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, and its app
2、licability 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 written comments an
3、d 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 permission of SAE. TO
4、 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 J2672 ISSUED AUG2004 Issued 2004-08 1. Scope Classification, and Limitations 1.1 Scope This Information Report relates to a sp
5、ecial class of automotive adaptive equipment which consists of modifications to the hydraulic control mechanism of Original Equipment Manufacturer (OEM) power steering systems provided as original equipment on personally licensed vehicles. These modifications are generically called “reduced effort p
6、ower steering“. The purpose of the modification is to lower the amount of driver effort required to operate the steering system. Retention of reliability, ease of use for physically disabled drivers and maintainability are of primary concern. Because this is an Information Report, the numerical valu
7、es 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 Steering modifications are classified as any modification in whic
8、h the feedback torque is reduced. The reduction of feedback considered in this Information Report may be accomplished by: 1. changing the feedback torque device 2. changing the power steering control valve 3. completely replacing the power steering control valve with a fabricated item. 4. eliminatio
9、n of the feedback torque 1.3 Limitations and Inclusions These recommendations are limited to modifications which are designed to utilize an OEM steering wheel, steering column and mechanical/hydraulic steering system for steering control and an unchanged steering gearbox ratio. 1.3.1 This Informatio
10、n Report does include additional auxiliary power systems (henceforth referred to as power steering backup systems) which are installed to provide needed redundancy for backup/emergency operation. SAE J2672 Issued AUG2004 - 2 - 1.3.2 Although other types of auxiliary power systems are possible, this
11、Information Report will deal only with mechanical/hydraulic systems. 1.3.3 Although the recommendations are limited to changes to the power steering box (below the universal joint) and the power steering backup system, the modifications would be tested with an OEM steering column and steering wheel.
12、 1.3.4 Although it is possible to combine other steering wheel and/or steering column modifications with Reduced Effort Power Steering and Power Steering Backup Systems, those modifications will be not be considered as a part of this Information Report. Rationale: “Joystick“ and other type steering
13、systems which supplant the OEM system or a major part of the OEM system are out of scope by language of 1.1, 1.2, and 1.3. Although other type systems may be available in the future, at this time virtually all steering systems are of the mechanical/hydraulic type. 2. References 2.1 Applicable Docume
14、nts The following publications form a part of this specification to the extent specified herein. Unless otherwise specified, the latest issue of SAE publications shall apply. 2.1.1 SAE PUBLICATIONS Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J188Power Steering Pressure
15、 Hose High Volumetric Expansion Type, pp. 12.93. SAE J189Power Steering Return Hose Low Pressure, pp. 12.94. SAE J190Power Steering Pressure Hose Wire Braid, pp. 12.97. SAE J191Power Steering Pressure Hose Low Volumetric Expansion Type, pp. 12.96. 2.1.2 NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION
16、 Available from NHTSA, U. S. Department of Transportation, 400 7th Street SW. Washington, D.C. 20090. web site: www.nhtsa.dot.gov. Federal Motor Vehicle Safety Standards (FMVSS), Part 49, CFR 571. FMVSS No. 201Occupant Protection in Interior Impacts. FMVSS No. 203Steering Wheel Impact Protection. FM
17、VSS No. 204Steering Wheel Rearward Displacement Part 595, “Exemptions from the Make Inoperative Prohibition; Final Rule” 2.1.3 MILITARY PUBLICATIONS Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. MIL-STD-1472 (current revision) Depart
18、ment of Defense Design Control Criteria Standard: Human Engineering. SAE J2672 Issued AUG2004 - 3 - 3. Definitions 3.1 Able-bodied A person who does not require adaptive aids to operate a personally licensed vehicle. 3.2 Actuator A transducer whose output is a force or torque and usually involves mo
19、tion. 3.3 Backup Any device which duplicates or otherwise fulfills the function of another if the latter fails or becomes inoperative. 3.4 Booster Any device for increasing power or output. 3.5 Crashworthiness Degree to which the interior of a motor vehicle, devices installed in the passenger compar
20、tment, and the structure of the vehicle as a whole minimize injury to an occupant in the event of a crash. 3.6 dBA Decibels, referenced to the A scale of attenuation by frequency, which approximates the human ear: a measure of sound intensity. 3.7 Feedback The recycling of a portion of the output to
21、 the input of a system. Systems employing feedback are called closed loop systems. 3.8 Gear Ratio The ration of the angular velocity of meshed gears. 3.9 Joystick Any of a class of primary vehicle controls which substitutes a lever or tiller for the steering wheel. Some joysticks also incorporate co
22、ntrol of throttle and brake functions as well. 3.10 Lock-to-Lock Excursion of the front wheels of a motor vehicle from full left extent of travel to full right extent of travel. SAE J2672 Issued AUG2004 - 4 - 3.11 Logic Components in a system which have a decision-making function, or which perform s
23、witching activities based on certain conditions or events. 3.12 Logo A manufacturers name or trademark. 3.13 Major Assembly Functional unit of a system, such as a pump, steering wheel, steering gearbox or reservoir. Each major assembly is made up of a number of parts or components. 3.14 Nominal Norm
24、al or acceptable, within acceptable limits. 3.15 Original Equipment See OEM. 3.16 OEM Refers to the vehicle and its systems as they are designed and produced by the automobile manufacturer. 3.17 Power Steering Control Valve That part of the steering gearbox or connected to the steering gearbox which
25、 controls the admission of hydraulic fluid under pressure to the actuator which in turn moves the steering linkage of the motor vehicle. This valve is mechanically connected to the steering wheel through a feedback spring, and to the resultant output from the steering linkage. 3.18 Primary Pertainin
26、g to the system which is intended to be in operation normally or routinely. 3.19 Power Steering Backup System A hydraulic backup system for the engine driven power steering pump and peripheral components. 3.20 Protocol A set of procedures to be followed. SAE J2672 Issued AUG2004 - 5 - 3.21 Reduced E
27、ffort Power Steering A modification of a power steering system to lower the amount of effort required to steer the vehicle. This term includes both “Low Effort Power Steering System“ and a “Zero Effort Power Steering System“ 3.22 Shall The term to be used whenever the criteria for conformance with t
28、he specific recommendations requires that there be no deviation. (SAE J1159) (Note: Because this is an Information Report which makes recommendations, but is not a standard, the use of the word shall has been replaced by should elsewhere in the report.) 3.23 Should The term to be used whenever non-c
29、ompliance with the specific recommendation is permissible. (SAE J1159) 3.24 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. 3.25 Steering Gearbox That mechanism which translates the rotary input of the ste
30、ering wheel into the resultant movement which controls the angle of the front wheels of a vehicle. 3.26 Steering Wheel Any kind of hand wheel which controls steering by means of rotary motion. 4. Design Requirements 4.1 Conventional Use of Motor Vehicle All reduced effort power steering and power st
31、eering backup system modifications to which this Information Report applies should be designed to permit the conventional use of the steering wheel by able-bodied drivers. (APPENDIX RTP 3.1) Rationale: Although the wheel may be non-standard and the level of effort considerably less, the conversion d
32、oes not result in directions of movement opposite or dissimilar to (OEM) power assisted steering. SAE J2672 Issued AUG2004 - 6 - 4.2 Mandatory Power Steering Backup System All reduced effort power steering modifications should incorporate into the modification a power steering backup system for redu
33、ced effort power steering operation in case of primary power failure. The backup system should provide the disabled driver with a steering system as resistant to catastrophic failure as the original equipment steering system. The able-bodied driver can retain a measure of vehicle control in the even
34、t of loss of power boost. This use of physical strength is the able-bodied drivers “backup“ system. A disabled driver will not have this capability, since the purpose for the reduced effort steering is to adapt to his inability to use the original equipment powered steering system. Hence the modific
35、ation must include a powered backup system. The recommendations for the backup system are included with the recommendations for the reduced effort power steering because the backup system is mandatory with the reduced effort power steering. Within this document, however, some recommendations pertain
36、ing only to the backup system have been kept separate from the reduced effort power steering because there are occasions where it is appropriate to install only the backup system without the reduced effort power steering. (There are many individuals who do not need reduced effort power steering but
37、who could not steer if the primary system failed.) (APPENDIX RTP 3.3) Rationale: The rationale has been incorporated into the Information Report because it was felt that the reasons for a mandatory backup system were so important that they should not be lost if the Information Report is eventually p
38、rinted without the rationale sections. 4.3 Reduced Effort Power Steering 4.3.1 MAINTENANCE OF OEM DESIGN RECOMMENDATIONS Modifications should not introduce new single-point failures of the steering system which do not exist in the (OEM) system or compromise or eliminate crashworthiness provisions pr
39、ovided by the vehicle manufacturer in compliance with FMVSS 203 or 204, or the general provisions of FMVSS 201. (APPENDIX RTP 3.2) Rationale: It is recognized that single-point failure modes exist in the OEM configuration of steering systems. The intent of this paragraph is to not compromise the inh
40、erent reliability of the original equipment configuration by introducing additional single-point failure modes. 4.3.2 TORQUE REQUIRED FOR STEERING The torque required for steering control should be measured at the top of the steering shaft with vehicle engine running at the factory recommended curb
41、idle rpm with engine warm and air conditioning off. This torque should be within the range of 4.0 - 15.0 in-lb for steering designated as low effort steering and 1.5 to 4.0 in-lb for steering designated as “zero“ effort steering when tested with OEM wheels and tires on a dry smooth concrete surface.
42、 (APPENDIX RTP 5.1) Rationale: Two levels of reduced effort steering (with tolerance ranges for each) have been established. They correspond roughly to the results normally achieved by the two most common methods of steering modification. It was felt that even though it is possible to achieve virtua
43、lly any torque on some vans, it was better for those recommending modifications and those purchasing modifications to have ranges they could select rather than having to determine a specific value. The term “zero“ effort was chosen because of common usage already in practice for that modification ev
44、en though technically the steering effort is not zero (0) in-lb of torque. SAE J2672 Issued AUG2004 - 7 - 4.3.3 NUMBER OF TURNS REQUIRED FOR LOCK TO LOCK STEERING Turns lock to lock at the steering wheel should not exceed 8 full turns, nor should turns lock to lock be less than one full turn. (APPEN
45、DIX RTP 5.2) Rationale: Some versions of reduced effort power steering use a special reduction gear to lower the level of effort with a small diameter steering wheel. Test data of previous VA evaluations, plus literature suggest that up to 8 full turns lock to lock will provide acceptable steering p
46、erformance, and that less than one full turn makes a vehicle very sensitive to steering correction. Such changes require special evaluation and training. 4.4 Power Steering Backup Systems 4.4.1 AUTOMATIC ACTIVATION Automatic activation of the power steering backup system is mandatory in case of prim
47、ary power system failure as a result of at least the following causes: primary engine failure, broken power steering belt, power steering pump failure or a leak in the high pressure hose. 4.4.1.1 The power steering backup system should have automatic logic which can withstand a test of 2,500 cycles
48、of operation (APPENDIX RTP 5.3.1). 4.4.1.2 The power steering backup system should also have automatic logic such that the system comes on within one second when an appropriate sensor detects a reduction or cessation of flow below 0.75 gallons per minute in the high pressure line due to any or all o
49、f the following reason. 4.4.1.2.1 A decay in flow (from, for instance, a fluid leak). (APPENDIX RTP 5.3.2.1) 4.4.1.2.2 A sudden loss of flow (from, for instance, a broken belt or pump failure) (APPENDIX RTP 5.3.2.2.1). 4.4.1.2.3 A cessation of flow (from, for instance a blockage in the line) (APPENDIX RTP 5.3.2.2.2). Rationale: Automatic activation of the auxiliary power system is needed because primary power system failure may occur during a critical maneuver and the driver may not have time to manually activate the system and indeed may find both hands very busy at
