1、BRITISH STANDARDBS ISO 21995:2008Road vehicles Test of vehicle air braking systems with a permissible mass of over 3,5 t Acquisition and use of reference values using a roller brake testerICS 43.040.40g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g4
2、0g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS ISO 21995:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2008 BSI 2008ISBN 978 0 580 56208 2National forewordThis British St
3、andard is the UK implementation of ISO 21995:2008. The UK participation in its preparation was entrusted to Technical Committee AUE/11, Braking systems.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all t
4、he necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsReference numberISO 21995:2008(E)INTERNATIONAL STANDARD ISO21995First e
5、dition2008-03-15Road vehicles Test of vehicle air braking systems with a permissible mass of over 3,5 t Acquisition and use of reference values using a roller brake tester Vhicules routiers Essais des systmes de freinage air comprim des vhicules de masse admissible de plus de 3,5 t Acquisition et ut
6、ilisation des valeurs de rfrence en utilisant un banc de freinage rouleaux BS ISO 21995:2008ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms, definitions and symbols 1 3.1 Terms and definitions. 1 3.2 Symbols . 3 4 Acquisition method 3 5 Use of reference
7、values for testing on roller brake testers 7 6 Data acquisition and distribution by the vehicle manufacturers. 7 7 Documentation of results and evaluation 7 Annex A (informative) Examples 8 Bibliography . 13 BS ISO 21995:2008iv Foreword ISO (the International Organization for Standardization) is a w
8、orldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented
9、on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafte
10、d in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Stand
11、ard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21995 was prepared by
12、 Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 2, Braking systems and equipment. BS ISO 21995:2008vIntroduction UNECE Regulation No.13, paragraph 5.1.4.6 (on reference braking forces) requires, as part of the type approval process, that the manufacturer provides the Type 0 braking pe
13、rformance figures as reference values arranged in a tabular or graphical form. The purpose of reference values is to make adequate data available for conducting periodical vehicle tests, which are most easily performed on roller test benches. Within Council Directive 96/96/EC, testing in service is
14、required to achieve a heavy truck brake efficiency of at least 45 %, and this can be performed by road testing or, more conveniently, on roller brake test benches. The roller brake tests are based on the available reference values declared by the vehicle manufacturer at type approval. NOTE The minim
15、um requirements are: 50 % in the case of vehicles of categories M2, M3, N2, N3, O3 and O4, except semi-trailers; 45 % in the case of semi-trailers. This International Standard provides a procedure for testing both motor vehicles and trailers in service to the level of performance required for period
16、ical technical inspection (PTI). It is possible that the values will need adjustment to reflect national or international in-service requirements. BS ISO 21995:2008blank1Road vehicles Test of vehicle air braking systems with a permissible mass of over 3,5 t Acquisition and use of reference values us
17、ing a roller brake tester 1 Scope This International Standard provides a method for the acquisition of suitable braking reference values that the manufacturer is required to provide, and for the use of these reference values in periodical technical inspection (PTI) on air brake systems. 2 Normative
18、references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. UNECE Regulation No.13, Rev. 6, 2008,
19、Uniform provisions concerning the approval of vehicles of categories M, N and O with regard to braking 3 Terms, definitions and symbols 3.1 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1.1 braking system combination of parts which either progr
20、essively reduces the speed of the moving vehicle, or brings the vehicle to a halt and/or holds it stationary, or fulfils both functions 3.1.2 brake part of a braking system (3.1.1) in which the forces opposing the movement, or tendency to movement, of the vehicle are developed 3.1.3 braking force fo
21、rce at the contact surface between a wheel and the ground, produced by the effect of a braking system, which opposes the rotation of the wheel or the tendency for movement of the vehicle NOTE The force between the tyre and the rotating roller, produced at the circumference of the tyre during braking
22、, opposes the force generated at the interface by the roller brake tester attempting to cause continuing rotation of the wheel. 3.1.4 total braking force sum of the braking forces at all wheels of a vehicle BS ISO 21995:20082 3.1.5 reference braking force braking forces of each axle generated at the
23、 circumference of the tyre on a roller brake tester, relative to brake actuator pressure 3.1.6 braking force distribution ratio between the braking force of each axle and the total braking force 3.1.7 total normal force vertical force, corresponding to the total static mass on the axles of the vehic
24、le 3.1.8 braking rate z ratio between the instantaneous deceleration of the vehicle, a, and the acceleration due to gravity, g, where only braking forces can be measured azg= NOTE 1 This ratio is not applicable to semi-trailers. NOTE 2 Where a cannot be measured, the braking rate, z, is the ratio be
25、tween the total braking force, Ff, and the total normal force, Gs, corresponding to the maximum loading vehicle weight. 3.1.9 roller brake tester measuring machine consisting of two pairs of powered rollers used for the assessment of a vehicles braking performance 3.1.10 guaranteed maximum cylinder
26、pressure pressure of the actuating fluid in the brake cylinder, resulting from full actuation of the brake pedal with the supply at the cut-in pressure 3.1.11 brake threshold pressure brake chamber pressure at the intersection of brake force and pressure line (at force = 0 N) in the forcepressure di
27、agram BS ISO 21995:200833.2 Symbols Symbol Definition Unit a instantaneous deceleration of vehicle m/s2Fftotal braking force corresponding to maximum loading vehicle weightN Ff,mintotal braking force needed to achieve zminN FNibraking force of axle i at cylinder pressure pNneeded to achieve zminN FR
28、ibraking force of axle i at cylinder pressure pNaRiFsum of all FRion all axles N FRiPTIreference braking force of axle i suitable for PTI (i.e. at corresponding pAlevel) N g acceleration due to gravity m/s2 Gstotal normal force corresponding to maximum loading vehicle weight N pAbrake actuator/cylin
29、der pressurekPa bpNguaranteed maximum brake actuator/cylinder pressure kPa bpRibrake actuator/cylinder pressure of axle i for calculated PTI value kPa bp0ibrake threshold pressure of axle i kPa bz braking rate zminminimum demanded deceleration in relation to total normal force at PTI aAs declared by
30、 the manufacturer in accordance with UNECE Regulation No.13, paragraph 5.1.4.6. b100 kPa = 1 bar. 4 Acquisition method 4.1 At type approval it is impossible to test every version of a particular vehicle range. Consequently, the vehicle manufacturer chooses a “worst case” vehicle to be covered on the
31、 type approval certificate. This means that the certificate will then include many variants of the tested vehicle, provided that they all have the same braking system. In a Type 0 test, a modern heavy vehicle with an electronic braking system (EBS) and disc brakes normally achieves a deceleration of
32、 6,0 m/s2, whereas the minimum requirement is 5,0 m/s2. 4.2 The brake force distribution involves both the static and dynamic brake force distribution. The static distribution is the result of the different dimensioning of the brakes at the different axles (e.g. different brake and actuating cylinde
33、r diameters). The dynamic distribution is the result of the brake pressure distribution adjustments during braking. The static distribution is theoretically constant in all situations (excluding the variation of the friction coefficient of brake pads, which is one of the parameters under assessment)
34、. This can be seen as the different gradient of the “brake forcecylinder pressure line” of the axles. The pressure distribution varies as a function of many factors (e.g. levels of deceleration and of loading). This is shown by the upper limit of the “brake forcecylinder pressure line” of the axles
35、(see Figure 1). BS ISO 21995:20084 Key X cylinder pressure, in kPa Y brake force, in N NOTE Lines A and B illustrate how the gradient of the “brake forcecylinder pressure line” of the axles varies as a function of different factors. Figure 1 Static brake force distribution In contrast to the identic
36、al gradient of the “brake forcecylinder pressure lines”, the maximum cylinder pressures at the axles in a Type 0 test would be different in different vehicles with the same braking system. The manufacturer should therefore specify the reference braking forces described in UNECE Regulation No.13, par
37、agraph 5.1.4.6, in order to cover the whole pressure range as generated under Type 0 conditions. 4.3 The purpose of the brake performance test at PTI is to verify that the vehicle achieves a minimum deceleration in relation to maximum static mass. NOTE In the case of Council Directive 96/96/EC, this
38、 needs to be 4,5 m/s2. It is easy to calculate the total braking force Ff,minneeded to achieve this deceleration: the deceleration rate zmin(e.g. 0,45) needs to be multiplied by the force Gscorresponding to the total static mass on the axles of the vehicle (e.g. 180 kN for a vehicle with two axles a
39、nd a maximum static mass of 18 t), as shown in Equation (1): f,min min sF zG= (1) Because the roller brake test is a series of single axle tests, the minimum total brake force, Ff,min, as calculated in Equation (1), shall be achieved by summing the axle braking forces. It is reasonable to assume tha
40、t the installed static brake force distribution for the Type 0 test (see a and b in Figure 2) is distributed in a similar way to the brake force in the lower level characteristics needed to satisfy the PTI requirements. Therefore, the calculation of reference values for PTI shall include the same pr
41、oportion in the reduced brake performance from each axle (see c and d in Figure 2). BS ISO 21995:20085Key X cylinder pressure, in kPa Y brake force, in N NOTE Lines A and B represent the installed static brake force distribution for the Type 0 test. Lines C and D indicate the reduced brake performan
42、ce. Figure 2 Static brake force distribution showing reduced brake performance 4.4 It is therefore possible to calculate the braking force, FNi, of each axle needed to achieve the minimum demanded deceleration at PTI. This should be done using Equation (2): R f,minNRiiiFFFF=(2) where FRiis the braki
43、ng force of axle i at cylinder pressure pNshown by the manufacturer; Ff,minis the total braking force needed to achieve zmin; RiFis the sum of all FRion all axles. FNiis the lowest force that should be reached at the guaranteed maximum cylinder pressure. A linear equation that describes the PTI refe
44、rence braking forces needs a second point of reference, which is given by the pressure at the increasing point of braking force. The mathematical function given with the reference values of the manufacturer can be calculated for this point simply by using the mathematical equation for linear functio
45、ns. With these two points, it is possible to establish an equation that describes the reference braking forces for each axle of a vehicle corresponding to the minimum demanded deceleration level at PTI bases on the national regulation. BS ISO 21995:20086 4.5 The following formulae use given referenc
46、e values (FR1, pR1, FR2, pR2) which are points from one axle of the given values. FRiand pRiare points for the calculated PTI values. f,min minF zz= f,min R2f,min2R1 R2F FFFF=+R1 f,min R2F FF= R1 R2 R1 R2R PTI R PTI R1 R1R1 R2 R1 R2iiFF FFF pF ppp pp =+ (3) where Ff,min1is the minimum braking force
47、needed to achieve zminfor the vehicle on the front axle; Ff,min2is the minimum braking force needed to achieve zminfor the vehicle on the rear axle; FR1is the front axle minimum brake force for PTI to achieve zmin; FR2is the rear axle minimum brake force for PTI to achieve zmin; pRiPTIis the referen
48、ce break actuator/cylinder pressure of axle i suitable for PTI. For special conditions, the formula in Equation (3) can be simplified. For example, for the condition R1 R2 R1 R2;,FFp pif FR2= 0, then FRiPTIis derived from FR1, as follows: RPTI R1RPTI R1R1 R2 R1 R21iip pFFpp pp=+ If FR2= 0, then the
49、corresponding value of pR2is xRi, the pressure at the point of intersection with the brake force axle (for force = 0). 4.6 The general formula for calculating xRiis as shown in Equation (4): R1 R2R1 R1R1 R2RR1 R2R1 R2iFFF pppxFFpp=(4) which can be simplified into: R1 R2RR1R2R11ip pxpFF=For example, using Equation (4), if FR1= 13 000 N, pR1= 200 kPa, FR2= 5 400 N and pR2= 100 kPa, then xRiis calculated as follows: BS ISO 21995:20087R1 R2R1 R1R1 R2RR1 R2R1 R213 000 5 40013 000 200200 1
