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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 therefr
2、om, 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 2002 Society of Automotive Engineers, Inc. All rights reserved. No part of
3、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 PLACE A DOCUMENT ORDER:Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4
4、970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS:http:/www.sae.org SURFACE VEHICLE RECOMMENDED PRACTICE J1247 REV. AUG2002 Issued1980-04 Revised2002-08 Superseding J1247 SEP1993 Simulated Mountain-Brake Performance Test Procedure ForewordThis procedure was developed in respo
5、nse to requests for a flat-road test procedure that would simulate the power- and energy-duty cycles occurring during mountain driving. A number of different mountain roads were investigated. In general, the mountain roads in the Eastern United States tend to have steeper grades, sharper curves, and
6、 shorter descent distances as compared to many mountain roads in the Western United States. This procedure simulates the longer descents found in the Western United States and complements the fade schedules in SAE J843 which requires a higher average power input to the brakes, but for a shorter time
7、. A general correlation with actual mountain descents has been established by analysis of actual power, energy, and temperature measurements. This procedure is intended as a development test. Line pressure usage rather than pedal force is recommended to provide a more precise measure of the input to
8、 the brakes. 1.ScopeThis SAE Recommended Practice establishes a uniform procedure for a flat-road simulation of a mountain-fade test of the brake systems of light-duty trucks and multipurpose passenger vehicles up to and including 4500 kg (10 000 lb) GVW and all classes of passenger cars. 1.1Purpose
9、The purpose of this test code is to establish brake system characteristics while simulating a mountain descent. This procedure is intended to be used to evaluate the following characteristics of a brake system: a.Brake temperature relative to fluid boil b.Fade resistance and reserve pedal travel c.O
10、verall structural durability d.Subjective stability 2.References 2.1Applicable PublicationsThe following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE publications shall apply. 2.1.1SAE PUBLICATIONSAvailable from SA
11、E, 400 Commonwealth Drive, Warrendale, PA 15096-0001. SAE J79Brake Disc and Drum Thermocouple Installation SAE J291Determination of Brake Fluid Temperature SAE J843Brake System Road Test CodePassenger Car and Light-Duty Truck SAE J1247 Revised AUG2002 -2- 3.Instrumentation 3.1Line pressure or pedal
12、force gauge. 3.2Decelerometer. 3.3Speedometer (calibrated vehicle unit or fifth-wheel type). 3.4Stop watch or cycle timer. 3.5Thermometer or ambient sensitive thermocouple. 3.6Odometer (calibrated). 3.7Direct-reading temperature instrument. 3.8Brake lining and brake-fluid thermocouples. 3.9Optional
13、instrumentation: a.Pedal travel gauge b.Solenoid stop counter c.Brake-torque transducers d.Brake-drum (or rotor) thermocouples e.Slip rings (for brake drum or rotor temperatures) 4.Installation Details 4.1Thermocouples 4.1.1LININGInstall plug-type thermocouples in each brake per current SAE J843. 4.
14、1.2BRAKE FLUIDInstall fluid thermocouples in each brake per current SAE J291. 4.1.3BRAKE DRUM (OR ROTOR) (OPTIONAL)Install disc/drum thermocouples in each brake per current SAE J79. 4.2Friction Material PreparationAttach and finish friction material per vehicle manufacturers specification. 4.3Brake
15、Drum (or Rotor) and Hub AssemblyNew drums or rotors are recommended. Surface finish and dimensional characteristics, with special emphasis on runout of rubbing surface, shall be in accordance with vehicle manufacturers specifications. 4.4Brake AssemblyBrakes shall be prepared in accordance with vehi
16、cle manufacturers specifications. New linings and springs are recommended on all brakes. Adjust brakes to manufacturers specifications. 4.5Uniformity of Brake Components (Optional)The objectives for each test shall determine the selection of uniformity requirements. Since braking-system balance duri
17、ng the high-temperature portion of this test may be affected by uniformity of components, care should be exercised in selecting components such that unbalance is controlled (that is, if lining stability is to be evaluated, other components such as drums or rotors should be matched or mismatched left
18、 to right with respect to surface finish, mass, runout, etc.). NOTESpecifications for the brake components and the installation may not be available for experimental development tests. In such cases, the selection will have to be made by the testing agency. SAE J1247 Revised AUG2002 -3- 4.6Vehicle T
19、est WeightConduct the test at GVW, unless otherwise indicated by the test requester, then it should be noted as such. 4.7Vehicle PowertrainThe powertrain should be selected by the user based on the test objectives. Normal practice in evaluating production vehicles is to select a powertrain providing
20、 the least engine braking. NOTE The variation in engine braking among powertrains will normally have only a small effect on test results but may have a significant effect on brake performance obtained during actual mountain descents. The reason is that drag affects the power absorbed by the powertra
21、in only when the vehicle is coasting or when the brakes are applied. This is a small part of the total time for the test but may be a large part of the total time for actual mountain descents. Caution should be exercised in interpreting comparative results between vehicles having widely differing dr
22、ag characteristics. Since vehicle drag affects braking severity during actual descents, drag should be measured and recorded with the data. The final speed for the snub may be adjusted as a function of vehicle drag. At this date, there is insufficient information to define the adjustment to the snub
23、 final speed as a function of vehicle drag, or if such a correction will simulate braking duty as a function of vehicle drag. The snub final speed of 27 km/h (17 mph) stated in 5.5 is based on best simulation of mountain descents for full-size domestic vehicles equipped with automatic transmissions
24、and standard-axle ratios. 5.Test Procedure 5.1Test Notes 5.1.1With the exception of the burnish portion of this test, all test stops and snubs shall be conducted on a substantially level (not to exceed 1% grade), dry, smooth, hard-surfaced roadway of Portland cement concrete (or other surface with e
25、quivalent coefficient of surface friction) that is free from loose materials. 5.1.2During all phases of this procedure, any unusual performance such as wrap-up or noise characteristics are to be noted and recorded. Note any uncontrollable braking action causing the vehicle to pull or swerve out of a
26、 3.66 m (12 ft) wide roadway lane. 5.1.3Initial Brake Temperature will be recorded at apply. Apply is the point in time when the pedal force reached 20 N (4.5 lb) or a pressure equivalent to that pedal force assuming no pedal force gauge is used in the test. 5.1.4Because variations in ambient temper
27、ature have a significant effect on test results, this test should be conducted within a range of ambient temperature of 4 to 32 C (40 to 90 F). Record ambient temperature as indicated on data sheets. Wind velocity should be less than 16 km/h (10 mph) and should be recorded. 5.1.5Decelerations used i
28、n test stops and snubs refer to values at which the decelerometer is held approximately constant during the stop or snub by varying the input pressure. 5.1.6Deceleration and line pressure readings shall not be taken below 8 km/h (5 mph). 5.1.7All stops and snubs should normally be made with vehicle
29、in normal driving gear. 5.1.8Paragraphs 5.3 to 5.10 of this procedure shall be run continuously without interruption; 102 min, 30 s are required to complete these paragraphs. 5.1.9To permit a check of consistency in performing the test, each segment of the test (except 5.2 and 5.11) should be timed,
30、 and vehicle mileage covered should be recorded. The average speed provides the parameter for measuring consistency. SAE J1247 Revised AUG2002 -4- 5.1.10The test should be terminated if the pedal force reaches 900 N (200 lb) (or a line pressure equivalent to 900 N (200 lb) pedal force) and/or, if th
31、e pedal travel becomes excessive, or at any time the vehicle is considered to be unsafe. 5.2BurnishCondition the braking system as follows: a.Stop speed64 to 0 km/h (40 to 0 mph) b.Stop deceleration3.66 m/s2 (12 ft/s2) c.Stop intervalAs required to achieve 120 C (250 F) initial-brake temperature or
32、a maximum of 1.6 km (1 mile) NOTEThe 1.6 km (1 mile) maximum must be observed even though the initial temperature exceeds 120 C (250 F). d.Cooling speed64 km/h (40 mph) (moderate acceleration to cooling speed) e.Stops required200 (first 10 stops shall be used as a general check of instrumentation, b
33、rakes, and vehicle function) f.OptionalInspect and adjust brakes after burnish cycle. Record if either operation is performed. g.Record odometer and time at end of first stop, maximum line pressure, stop interval, and initial-brake temperature for the first and every twentieth stop, and odometer and
34、 time at end of last stop. 5.3Initial-Brake TemperatureWarm the brakes to 65 to 95 C (150 to 200 F) initial-brake temperature using the burnish procedure and shorten the interval if necessary. Record odometer at the last stop used to warm the brakes. Proceed immediately to 5.4. NOTE If only a limite
35、d range of ambient temperature exists, the brakes can be warmed by making 10 stops from 64 km/h (40 mph) at a 60 s interval. This procedure specifies the braking duty and would result in lower initial-brake temperatures for systems that have good heat dissipation and, therefore, more nearly reflects
36、 real-world conditions. The disadvantage is that the initial-brake temperature becomes dependent upon the ambient temperature. This procedure is, therefore, only recommended for a test series in which small changes in ambient temperature are expected. 5.4First (Cold) Effectiveness CheckImmediately a
37、fter the previous stop, moderately accelerate to 97 km/h (60 mph) and drive at 97 km/h (60 mph) for 200 s including acceleration time. Make check stops as follows: a.Stop speed97 to 0 km/h (60 to 0 mph) b.Stop deceleration4.6 m/s2 (15 ft/s2) c.Stops required3 d.Cooling speed97 km/h (60 mph) (moderat
38、e acceleration at cooling speed) e.Stop intervalBegin stop every 200 s f.RecordMaximum line pressure for each stop, brake lining, and fluid temperatures immediately before each stop, and odometer at the end of the third stop 5.5First Simulated Mountain DescentImmediately after effectiveness check st
39、op 3, moderately accelerate to 56 km/h (35 mph) and drive at 56 km/h (35 mph) for 15 s including acceleration time. Begin the simulated descent as follows: a.Snub speeds56 to 27 km/h (35 to 17 mph) b.Snub deceleration2.4 m/s2 (8 ft/s2) c.Snubs required80 d.Snub intervalBegin snub every 15 s e.Speed
40、between snubs56 km/h (35 mph) with moderate acceleration f.RecordMaximum line pressure every fourth snub, brake lining, and fluid temperatures immediately before every eighth snub, and odometer at the end of the last snub SAE J1247 Revised AUG2002 -5- 5.6Second (Hot) Effectiveness CheckImmediately a
41、fter the last snub in the simulated descent, moderately accelerate to 97 km/h (60 mph) and drive at 97 km/h (60 mph) for 50 s including the acceleration time. Make check stops as follows: a.Stop speeds97 to 0 km/h (60 to 0 mph) b.Stop deceleration4.6 m/s2 (15 ft/s2) c.Stops required3 d.Cooling speed
42、97 km/h (60 mph) (moderate acceleration to cooling speed) e.Stop intervalBegin stop every 50 s f.RecordMaximum line pressure for each stop, brake lining, and fluid temperatures immediately before each stop, and odometer at the end of the third stop 5.7RecoveryImmediately after the third stop in the
43、second effectiveness check, moderately accelerate to 64 km/h (40 mph) and drive at 64 km/h (40 mph) for 120 s including the acceleration time. Make recovery stops as follows: a.Stop speed64 to 0 km/h (40 to 0 mph) b.Stop deceleration3.7 m/s2 (12 ft/s2) c.Stops required10 d.Cooling speed64 km/h (40 m
44、ph) (moderate acceleration to cooling speed) e.Stop intervalBegin stop every 120 s f.RecordMaximum line pressure for each stop, brake lining, and fluid temperatures immediately before each stop, and odometer at the end of the last stop 5.8Second Simulated Mountain DescentImmediately after the tenth
45、stop in the first recovery, moderately accelerate to 56 km/h (35 mph) and drive at 56 km/h (35 mph) for 15 s including acceleration time. Repeat the simulated descent as stated in 5.5. 5.9SoakImmediately after the final snub in the second mountain descent, drive the vehicle the minimum distance poss
46、ible to allow the vehicle to be parked in a windless area with the engine running at idle, and soak for 20 min. At 1 min intervals during the soak, apply the brakes to the average line pressure measured in 5.4 and hold for approximately 5 s before releasing. Note if pedal is spongy or goes to floor
47、and if brake-warning indicator illuminates during the applications. Record brake lining and fluid temperatures immediately before each fourth application. Do not proceed to 5.10 if the pedal travel is excessive during the final check at the end of the soak. 5.10 Third (Cold) Effectiveness CheckImmed
48、iately after the soak, repeat 5.4. 5.11 ReburnishRepeat 5.2 except 35 stops required. Record odometer and time at end of the first stop, maximum line pressure, stop interval, and initial-brake temperature for the first and every fifth stop, and odometer and time at the end of the stop. 5.12 Fourth (
49、Cold) Effectiveness CheckImmediately after the last burnish stop, repeat 5.4. 5.13 Final InspectionDisassemble all brakes, inspect, and record all pertinent observations. 6.Vehicle-Drag Measurement (Optional)Make 10 closed-throttle coast-downs with the transmission in the gear being simulated (usually top gear, but could be a lower gear). Ambient wind velocity should be less than 8 km/h (5 mph). The direction should be alternated to reduce the effects of ambient wind. The coast-downs should be started at 64 km/h