1、 _ 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 applicability and suitability for any particular use, including any patent infringement arising ther
2、efrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2016 SAE International All rights reserved. No part of this
3、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 PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-49
4、70 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J2923_201605 SURFACE VEHICLE RECOMMENDED PRACTICE J2923 MAY2016 Issued 2016-05 I
5、nertia-dynamometer Disc Brake Drag Measurement Test Procedure for Vehicles Less Than 4540 kg GVWR RATIONALE This Recommended Practice is the result of an industry effort to develop inertia-dynamometer test procedures to assess brake drag under a series of speed, pressure, and temperature conditions.
6、 The test allows the project or application engineer to determine or compare the amount of brake drag for a given design level or configuration. The test provides a standard method to better quantify and better understand the parasitic (drag) torque generated by the brake corner during the off-brake
7、 condition under repeatable laboratory conditions. This inertia-dynamometer test procedure provides a method to quantify brake drag measurements combining light, moderate, and severe braking with a brake drag matrix. This matrix combines increasing static preconditioning pressure applications before
8、 measuring brake drag at increasing braking speeds. Data from this test is useful to assess the influence of certain design features, determine brake sensitivity to braking conditions, and support a comprehensive brake performance evaluation in conjunction with other measurements for pedal feel, noi
9、se, performance, and durability. Elements from this recommended practice are also applicable or useful for other laboratory test procedures to assess brake drag following standard fuel economy cycles. To better characterize the brake drag behavior of a given brake corner, include other brake drag pr
10、ocedures which rely more on vehicle-level evaluations. These inertia dynamometer evaluations use speed profiles and test sequences to replicate coast-down testing from proving ground testing. Due to the novelty of this Recommended Practice, the Task Force encourages users of this document to contact
11、 the SAE Staff Representative for Ground Vehicle; Motor Vehicle Council; Chassis Systems Group; Foundation Brake Steering Committee, or the Chairman of the Brake Dynamometer Standards Committee with questions and comments. This feedback will prove valuable for future revisions and updates to the Rec
12、ommended Practice. The Task Force is working on developing an example of the test output to present the recommended report layout. This SAE Recommended Practice is intended as a guide towards standard practices and is subject to change to keep pace with experience and technical advances. TABLE OF CO
13、NTENTS 1. SCOPE 2 2. REFERENCES 2 3. DEFINITIONS . 3 4. TEST CYCLES 4 5. TEST EQUIPMENT . 6 6. TEST CONDITIONS AND SAMPLE PREPARATION 7 7. DYNAMOMETER TEST INERTIA 8 8. TEST PROCEDURES . 8 9. TEST REPORT . 14 10. NOTES 15 SAE INTERNATIONAL J2923 MAY2016 Page 2 of 16 1. SCOPE This Recommended Practic
14、e applies to on-road vehicles with a GVWR below 4540 kg equipped with disc brakes. 1.1 Purpose Quantify brake drag using a laboratory-based procedure under various conditions and friction couple braking history. The test sequence includes performance-type of braking events along with optional sectio
15、ns for hot drag evaluation and brake drag measurement for parking brake systems. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE publications shall apply. 2.1.1 SAE
16、 International Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. SAE J2789 Inertia Calculation Method for Single-Ended Inertia-Dynamometer Testing SAE J2522 Dynamometer Global
17、Brake Effectiveness (AK Master) SAE J2986 Wear Measurements during Inertia Dynamometer Testing (draft) 2.1.2 ISO Publications Copies of these documents are available online at http:/webstore.ansi.org/ ISO/PAS 12158 Road vehicle - Braking systems - Temperature measuring methods ISO 16610-31 Geometric
18、 product specifications (GPS) - Filtration - Robust profiles filters: Gaussian regression filters ISO 16610-32 Geometric product specifications (GPS) - Filtration - Robust profiles filters: Spline filters 2.2 Related Publications The following publications are provided for information purposes only
19、and are not a required part of this SAE Technical Report. ASTM E4-10 Standard Practices for Force Verification of Testing Machines ASTM E2624-09 Standard Practice for Torque Calibration of Testing Machines and Devices DIN 51309: 2002-12 Materials Testing Machines Calibration of Torque Measuring Devi
20、ces for Static Torque. German language only DKD-R 3-5: 1998-12 Calibration of Torque Measuring Devices for Static Alternating Torques. German language only EURAMET/cg-10/v.01: 2007-07 Guidelines on the Calibration of Static Torque Measuring Devices VDA/VDE 2646: 2006-02 Torque Measuring Devices Mini
21、mum Requirements in Calibrations. German/English SAE INTERNATIONAL J2923 MAY2016 Page 3 of 16 3. DEFINITIONS 3.1 Apparent Friction for Disc Brakes Ratio of brake output torque to total input torque. Also referenced as brake effectiveness. Per Equation 1: KP effPThresholdrAppT2105(Eq. 1)where: P = ap
22、parent friction for disc brakes. unitless T = output torque. Nm p = brake pressure. kPa Thresholdp= minimum pressure required to start developing braking torque. Unless otherwise specified by the test requestor, use threshold pressure of 50 kPa PA = total piston area acting on one side of the calipe
23、r for disc brakes where the hydraulic pressure is exerted by the brake actuation system. mm2 effr = radial distance from centerline of the piston to the axis of rotation for disc brakes, unless other dimensions are provided by the requestor. mm K= caliper brake efficiency; ratio of input hydraulic f
24、orce to effective force acting on the brake pad unitless 3.2 Brake Drag Measurable torque generated by the brake with no active or intentional input from the brake actuation system. Nm 3.3 Breakaway Torque Torque required to initiate brake rotation after cable tension, input force, or enabling comma
25、nd is applied (or sent) to the parking brake mechanism. Nm 3.4 Deceleration-Controlled Brake Application Inertia-dynamometer control algorithm that adjusts the real time brake pressure to maintain a constant torque output calculated from the instantaneous deceleration specified in the test procedure
26、. 3.5 Initial Brake Temperature IBT Rotor temperature at the start of the brake application. C 3.6 Pressure-Controlled Brake Application Inertia-dynamometer control algorithm that maintains a constant input pressure to the brake irrespective of the torque output. 3.7 Gross Vehicle Weight GVWR Maximu
27、m vehicle weight indicated by the manufacturer. kgf 3.8 Lightly Loaded Vehicle Weight LLVW Unloaded vehicle curb weight plus 180 kg for driver and test instrumentation. kgf SAE INTERNATIONAL J2923 MAY2016 Page 4 of 16 3.9 Maximum Vehicle Speed Vmax Highest speed attainable by accelerating at a maxim
28、um rate from a standstill to a distance of 3.2 km on a level surface, with the vehicle at LLVW for vehicles per FMVSS 135 or at GVWR for vehicles per FMVSS 105. For electric vehicles, the speed attainable is determined with the propulsion batteries at a state of charge of not less than 95% at the be
29、ginning of the run. km/h 3.10 Tire Dynamic Rolling Radius null Rdyn Tire radius that equates to the Revolutions Per Mile (RevsPerMile) published by the tire manufacturer for the specific tire size. If unknown, the rolling radius can be calculated from the RevsPerMile value using Equation 1. Use the
30、tire dynamic rolling radius to calculate test inertia and the dynamometer rotational speed in revolutions per minute (r/min) for a given linear vehicle speed. nullnullnullnull=1 609 3442nullnullnullnullnullnullnullnullnullnullnullnullnullnull(Eq. 1) Where: nullnullnullnull= tire dynamic rolling radi
31、us mm nullnullnullnullnullnullnullnullnullnullnull = tire manufacturer specification for revolutions per mile. Typically shown for the tire size on the manufacturers website 3.11 Maximum park brake input force Measured or calculated force applied at the brake equivalent to 400 N input force at the c
32、abin for hand-operated (or 500 N for foot-operated) parking brake systems. For calculated values use the pedal (or hand lever) ratio, the cable efficiency, and the multiplying factor of the parking brake mechanism to determine the effective force acting on the brake pads. For electric park brake sys
33、tems, unless otherwise specified by the test requestor, the maximum force is the nominal value at full nominal current and nominal voltage of the system. For all park brake systems, unless otherwise specified by the test requestor, use a maximum park brake input force of 1500 N. 4. TEST CYCLES 4.1 D
34、ynamic Brake Application Figure 1 illustrates the main time-stamps used to characterize the brake application. SAE INTERNATIONAL J2923 MAY2016 Page 5 of 16 Figure 1 - Typical brake application time stamps 4.1.1 Time t0 Brake application initiation. At this time, the pressure starts to rise. 4.1.2 Ti
35、me t1 Time at level reached. At this time, the brake reaches its target level for torque or pressure control. At time t1, the calculation of average by time and the average by distance begins. 4.1.3 Time t2 Time at the end of averages. At time t2 the inertia-dynamometer data acquisition system termi
36、nates the calculation of average by time and average by distance. Time t2 is the end of the stable portion of the brake application. t2 is defined as the time at which speed is 0.5 km/h above the release speed (t3). 4.1.4 Time t3 Time at release speed. At time t3, the inertia-dynamometer servo contr
37、oller releases the brake (specified in 8.1.3). 4.1.5 Time t4 Time at brake pressure and torque lost. At time t4, pressure and torque are below the minimum thresholds. The inertia-dynamometer considers the braking event complete. SAE INTERNATIONAL J2923 MAY2016 Page 6 of 16 5. TEST EQUIPMENT 5.1 Sing
38、le-ended brake inertia-dynamometer capable of performing deceleration- and pressure-controlled brake applications. Coordinate with the test requestor the option to conduct the brake drag matrix on a special-purpose test system. 5.2 Automatic data collection system capable of recording digitally the
39、following channels at 200 Hz minimum: 5.2.1 Brake equivalent linear speed. km/h 5.2.2 Brake input pressure. kPa 5.2.3 Brake output torque. Nm 5.2.4 Brake drag torque. Nm 5.2.5 Brake fluid displacement. mm3 5.2.6 Parking brake cable tension (rear brakes testing only). N 5.2.7 Parking brake cable trav
40、el (rear brakes testing only). mm 5.3 Automatic data collection system capable of recording digitally the following channels at 30 Hz minimum: 5.3.1 Brake rotor temperature. C 5.3.2 Brake pad or brake shoe temperature. C 5.3.3 Hub bearing temperature measured at the hub bearing. C 5.3.4 Cooling air
41、temperature, relative humidity, and speed. 5.4 Brake drag measurement. Use a torque measuring device with an accuracy of 0.1 Nm from zero to 10 Nm in both directions. Report the uncertainty of measurement and the accuracy class. Reference the different standards from item 2.2 for the proper calibrat
42、ion process, torque steps (especially when calibrating below 20% of the full-scale for the torque measuring device), calibration report, and the associated uncertainty of measurement budget; unless the specific method used for the test is agreed upon between the test requestor and the test facility.
43、 Indicate the torque measuring method in the final test report. Verify the hysteresis of the drag torque measuring system (including the influence of overhanging masses from the brake fixture) in the forward and reverse directions. When the test system (instrumentation, control, and data collection)
44、 allows, measure brake drag 4 s before and 4 s after completing the dynamic brake applications. This will allow the evaluation of brake drag at multiple speed and temperature combinations during the test. 5.5 Test fixture can use the hub and bearing assembly or a hubless fixture. Unless otherwise sp
45、ecified by the test requestor, ensure rotor-to-caliper mounting surface parallelism and rotor-to-fixture concentricity is within 0.050 mm. Document the fixture setup with pictures as part of the test report. 5.5.1 When using a hub and bearing configuration, remove the seals from the bearing and subt
46、ract the bearing losses from the total brake drag torque (see 8.2.3.) 5.5.2 When using a hubless fixture with the rotor mounted on the dynamometer shaft with no physical connection to the tailstock, ensure stiffness and alignment are equivalent to the knuckle or axle assembly. Estimate the stiffness
47、 of the fixture by measuring a knuckle assembly of similar material, size, and geometry. See Figure 2. SAE INTERNATIONAL J2923 MAY2016 Page 7 of 16 Figure 2 - Alignment specification for hubless test fixture 5.6 Control brake cooling air temperature to 25 5 C, and humidity to 9.92 g/kg (11.57 g/m3)
48、at sea level. Use a psychrometric chart to find acceptable relative humidity conditions to meet absolute humidity requirements. If no environmental conditioning is available, record and report cooling air temperature and humidity during the test. 5.7 Park brake testing capabilities (for rear brakes)
49、. 5.7.1 Ability to apply torque from zero shaft rotational speed sufficient to cause breakaway. 5.7.2 Mechanism to apply and control input park brake force or to energize the electric parking brake system as applicable. 5.7.3 Mechanism to lock the parking brake cable in position during parking brake output evaluation. 6. TEST CONDITIONS AND
