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 theref
2、rom, 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 and suggestions. Copyright 2011 SAE International All rights reserved. No part of this publication ma
3、y 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: +1 724-776-4970 (outside US
4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J880_201110SURFACEVEHICLESTANDARDJ880 OCT2011 Issued 1980-02 Revised 2011-10 Superseding J880 F
5、EB1997 Brake System Rating Test Code - Commercial Vehicles RATIONALEAll of the revisions, updates, and corrections to this RP, although many, are clearly editorial in nature, and do not generate any substantive changes to the methodology and procedures of this RP. Figure 2, which may exhibit a somew
6、hat different appearance, is identical to the previous Figure 2, except for the revisions and corrections required to address the various errors and omissions. The different appearance is due exclusively to the fact that the Figure had to be recreated from scratch, instead of just modifying the exis
7、ting Figure.1. SCOPE This code is intended for commercial vehicles over 4500 kg (10 000 lb) with brake systems having typical service pressure ranges 0 to 14.1 mPa (0 to 2050 psi) hydraulic or 0 to 830 kPa (0 to 130 psi) air and is not directly applicable to vehicles with other systems. Air over hyd
8、raulic systems are to be tested as air systems. 1.1 The code provides test procedures and instructions for: a. Instrumentation and equipment b. Vehicle preparation c. Determining brake system energy absorption capacity d. Calculation of brake rating 1.2 Purpose The purpose of this code is to provide
9、 a method for determining a brake system rating for new commercial highway vehicles, based on the energy absorption and dissipation capacity of the brake system as established by a repeated test procedure. For performance requirements, refer to SAE J257. 1.2.1 The code includes provision for those s
10、ingle unit, combination, and special vehicles which cannot be loaded to the manufacturers gross vehicle weight rating, or cannot be accelerated in the time interval required, or cannot attain the specified 80.5 km/h (50 mph) speed. 1.2.2 Methods for measuring energy absorption capacity, other than d
11、escribed herein, may be equally valid. SAE J880 Revised OCT2011 Page 2 of 13 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 Pub
12、lications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.SAE J257 Brake Rating Horsepower RequirementsCommercial Vehicles SAE J843 Brake System Road Test CodePassenger Car and L
13、ight-Duty Truck SAE J971 Brake Power Rating Test CodeCommercial Vehicle Inertia Dynamometer SAE J1505 Brake Force Distribution Test ProcedureTrucks and Buses SAE J2115 Air Brake Performance and Wear Test Code Commercial Vehicle Inertia Dynamometer 3. INSTRUMENTATION AND EQUIPMENT Each vehicle to be
14、checked must be equipped with: 3.1 A device for measuring deceleration that is accurate to the nearest 0.3 Gs (0.3 mpsps or 1.0 fpsps). 3.2 A fifth wheel speed indicator or calibrated speedometer or tachometer. 3.3 A device for measuring the stopping distance of the vehicle to an accuracy within 1 f
15、t from initial movement of the brake pedal until the vehicle has come to rest. 3.4 A calibrated line pressure gage. 3.5 A stop watch or timing device. 3.6 A means of monitoring the lining temperature to within 5 C (10 F) at each brake position either simultaneously or sequentially with a temperature
16、 range of 0 to 540 C (0 to 1000 F). Brake thermocouple installation is to conform to SAE J2115. 3.7 Provision for reservoir pressure control to limit service line pressure to maximum permitted. 3.8 Shutoff valve to permit cutoff of front and/or rear brakes if brake balance (Section 6) or individual
17、axle brake rating (see 8.3) tests are to be run. 4. VEHICLE INFORMATION AND DATA 4.1 Vehicle Information Sheet (Figure 1) to be filled in prior to starting test. 4.2 Brake Rating Test Data Sheet (Figure 2) for use during the tests. It should be noted that the maximum individual brake temperatures ar
18、e not to be used as criteria for brake rating. The measurement of brake temperatures as an index of brake condition during the test is necessary to provide test control and aid in analyzing test results. SAE J880 Revised OCT2011 Page 3 of 13 FIGURE 1 - VEHICLE INFORMATION SHEET SAE J880 Revised OCT2
19、011 Page 4 of 13 FIGURE 2 - BRAKE RAETING TEST DATA SHEET SAE J880 Revised OCT2011 Page 5 of 13 FIGURE 3 - WORK SHEET - CORRECTION FACTORS (FOR LOADS) OTHER THAN RATED CAPACITY OF AXLE(S) OR VEHICLE(S) SAE J880 Revised OCT2011 Page 6 of 13 4.3 Work Sheet Correction Factors (Figure 3) to be filled ou
20、t and used as required per 8.2. 5. VEHICLE CONDITION To rate the brake system properly, the vehicle should: 5.1 Be loaded to GVWR except as provided for in 8.3. The weight must be distributed as closely as possible to load each axle to its rated load GAWR. The center of gravity should be kept as low
21、 as possible. This can be accomplished by the proper selection of chassis, wheelbase, and type of weight used. 5.2 Be equipped with the largest production engine available for the chassis being tested. NOTE: If sufficient engine horsepower is not available to obtain some evidence of brake fade, then
22、 vehicle weight or deceleration rate correction must be made in accordance with 8.2. 5.3 Have new or relatively new tires inflated to the cold pressures specified for maximum tire load rating. 5.4 Have sufficient brake balance to obtain not less than 3.7 mpsps (12 fpsps) steady-state deceleration wi
23、thout locking any wheel or causing any wheel slip brake control system to cycle. (Brakes are to be adjusted to manufacturers specifications.)5.5 All vehicles are to be equipped with unmodified brake actuation systems (pressure proportioning valves, metering valves, and wheel slip brake control syste
24、ms are to be functional as installed in production vehicle) except for test equipment specified in 3.7 and 3.8. 5.6 Be equipped with new unburnished production linings which shall then be burnished as follows: Make 500 brake snubs from 64 to 32 km/h (40 to 20 mph) with a deceleration of 3 mpsps (10
25、fpsps) at 1.6 km (1 mile) intervals. Except where an adjustment is specified, after each application accelerate to and maintain 64 km/h until making the next brake application at a point 1.6 km (1 mile) from the initial point of the previous brake application. If the vehicle can not attain a speed o
26、f 64 km/h (40 mph) in 1.6 km (1 mile), continue to accelerate until the vehicle reaches 64 km/h (40 mph) or until the vehicle has traveled 2.4 km (1.5 miles) from the initial point of the previous application, whichever occurs first. The brakes may be adjusted up to three times (after 125, 250, and
27、375 snubs) in accordance with the manufacturers recommendations and shall be adjusted after completion of the burnish according to the manufacturers recommendations.Use velocity and deceleration corrections when required for axle-by-axle or vehicle-by-vehicle tests of combinations. Drive as nearly a
28、s possible at the uncorrected indicated velocity between snubs, drifting to the proper corrected velocity before each snub. 6. BRAKE BALANCE TEST This test is optional, and must be run prior to the start of the rating procedure when axle-by-axle or vehicle-by-vehicle ratings are to be combined in ac
29、cordance with 8.3. In addition, this procedure may be used optionally to provide useful information concerning the distribution of total braking effort among axles and/or vehicles. Such information can be of great use in adjusting brake inputs to achieve a desired proportioning of braking effectiven
30、ess among the axle and/or vehicle; but, no changes in the brakes or actuation system may be made at this point to improve brake balance unless new linings are installed and burnished before going to the rating procedure (Section 7). The Brake Force Distribution Test CodeCommercial VehiclesSAE J1505
31、is to be followed to determine brake balance. SAE J880 Revised OCT2011 Page 7 of 13 7. RATING PROCEDURE 7.1 General 7.1.1 It is recommended that brakes be re-adjusted to the manufacturers specifications after burnish. 7.1.2 A series of three rating tests must be run before a rating can be establishe
32、d. The first two tests are run at reduced energy input levels to condition the lining material and to familiarize the driver and observer with the test procedure prior to the qualifying test(s). 7.1.3 Starting temperature (hottest brake) must be 66 to 93 C (150 to 200 F); 1.02 mm 0.13 mm (0.040 in 0
33、.005 in) for conditioning prior to drift time, cold stop(s), rating tests, and cooled stop. It is recommended that the depth of the thermocouple recess be maintained at 1.02 mm 0.13 mm (0.040 in 0.005 in) prior to each test. 7.1.4 All brake applications in the following Test Sequence shall be made w
34、ith the transmission in neutral or the clutch disengaged.7.1.5 Record all data on Brake Rating Test Data Sheet (Figure 2). 7.2 Test Sequence 7.2.1 Temperature Conditioning Whenever temperature conditioning of the vehicle is required (for example; prior to the first test of the day), it shall consist
35、of a series of snubs from 80.5 to 24 km/h (50 to 15 mph) at 3.7 mpsps (12 fpsps) at 3.2 km (2 mile) intervals (using corrected velocities and decelerations where applicable) until the 66 to 93 C (150 to 200 F) temperature range for hottest brake is attained. 7.2.2 Drift Time The drift time shall be
36、determined immediately following temperature conditioning (at 66 to 93 C (150 to 200 F) hottest brake). The average drift time is determined by letting the vehicle coast (transmission in neutral) from 80.5 km/h (50 mph), or as corrected, to 24 km/h (15 mph). This value must be obtained in the same d
37、irection or directions with respect to the wind encountered during the test. 7.2.3 Cold Stop Make three stops from 32.2 km/h (20 mph) at sufficient deceleration to meet the cold stop distance requirement. The maximum service line pressure used shall not exceed 690 kPa (100 psi) for vehicles with air
38、 brakes or 12.0 mPa (1750 psi) for vehicles with hydraulic brakes. 7.2.4 Rating Tests For rating purposes, a test series of three to five rating test cycles are permitted on a specific set of linings. The objectiveis to determine the maximum number of snubs from 80.5 km/h (50 mph) to 24.1 km/h (15 m
39、ph) that can be performed in a 12 min time frame without departing from the specified deceleration and maximum pressure requirements. For the first rating test, begin by making 12 snubs. If the requirements are met, increase the number of snubs by one or two based on the performance margin of the pr
40、evious cycle. If it fails, reduce the number of snubs by one. Once the maximum number of snubs that can be completed within the required time without departing from the deceleration or pressure requirements has been established, the power rating can be calculated based on that test and the number of
41、 snubs completed using the equation in 7.4. Snubs should be made in accordance with the brake apply time shown in Table 1, thus continually compensating for fractions of seconds. Continue with the second and subsequent tests, each increasing in severity as required for proper rating.SAE J880 Revised
42、 OCT2011 Page 8 of 13 TABLE 1 - BRAKE APPLY TIME SCHEDULE FOR VARIOUS TOTAL NUMBER OF RATING TEST BRAKE SNUBS(1)TOTAL NUMBER OF BRAKE SNUBS (CYCLE TIME, S) SAE J880 Revised OCT2011 Page 9 of 13 To start the rating test, bring the vehicle to 24.1 km/h (15 mph). Start the stop watch and accelerate the
43、 vehicle to 80.5 km/h (50 mph) or to the corrected velocity as soon as possible. Make the predetermined number of snubs from 80.5 km/h (50 mph) to 24 km/h (15 mph) at the proper time cycle attempting to maintain a deceleration of 3.6 mpsps (12 fpsps) by varying the input pressure up to a maximum of
44、690 kPa (100 psi) service line air pressure or 12.0 mPa (1750 psi) hydraulic pressure on any snub. 7.2.5 Hot Stop Immediately following the final snub of the rating test, accelerate to 32.2 km/h (20 mph) and make a stop at sufficient deceleration to meet the hot stop distance requirement. The maximu
45、m service line pressure used shall not exceed 690 kPa (100 psi) for vehicles with air brakes or 12.0 MPa (1750 psi) for vehicles with hydraulic brakes. 7.2.6 Cooled Stop Cool the brakes to 93 C (200 F) maximum (hottest brake) and make a stop from 32.2 km/h (20 mph) without locking any wheel or cycli
46、ng any wheel slip brake control system at a deceleration of 2.7 to 3.7 mpsps (9 to 12 fpsps) to determine final brake stability. 7.2.7 Final Inspection Remove drums and visually inspect brakes for functional and structural integrity. 7.3 Rating Requirements In order to complete the rating test satis
47、factorily, the vehicle brake system must comply with the following: 7.3.1 Cold stop if no more than: a. 10.7 m (35 ft) if single-unit vehicle b. 12.2 m (40 ft) if combination vehicle 7.3.2 An initial deceleration of 3.7 mpsps (12 fpsps) with deceleration in subsequent snubs of not less than 2.7 mpsp
48、s (9 fpsps) during the rating test. 7.3.3 Hot stop of no more than: a. 12.8 m (42 ft) if single-unit vehicle b. 14.6 m (48 ft) if combination vehicle 7.3.4 Stability such as to remain in a 3.7 m (12 ft) lane during any brake application throughout all phases of the test procedure.7.3.5 Final inspect
49、ion showing no visual evidence of permanent deficiency in functional or structural integrity of the parts. 7.4 Power Rating Calculation The power rating of the brake system formula is shown in Equations 1 and 2: (Eq. 1) SAE J880 Revised OCT2011 Page 10 of 13 (Eq. 2) where:W = GVWR of the vehicle, kg (lb) V1= Standard velocity (initial), km/h (mph) V2= Standard velocity (final), km/h (mph) N = Number of snubs made
