《BS-235-1987.pdf》由会员分享,可在线阅读,更多相关《BS-235-1987.pdf(16页珍藏版)》请在三一文库上搜索。
1、BRITISH STANDARD BS 235:1987 Specification for Gears for electric traction UDC 621.833:621.33 + 629.03-83 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 235:1987 This British Standard, having been prepared under the direction of the Mach
2、inery and Components Standards Committee, was published under the authority of the Board of BSI and comes into effect on 23 December 1987 BSI 04-2000 First published February 1927 First revision January 1951 Second revision February 1972 Third revision December 1987 The following BSI references rela
3、te to the work on this standard: Committee reference MCE/5 Draft for comment 86/71474 DC ISBN 0 580 15833 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Machinery and Components Standards Committee (MCE/-) to Technical Committee MCE/5
4、, upon which the following bodies were represented: Advanced Manufacturing Technology Research Institute Association of Consulting Engineers British Clock and Watch Manufacturers Association British Coal British Gear Association British Horological Institute British Railways Board Engineering Equipm
5、ent and Materials Users Association Federation of Manufacturers of Construction Equipment and Cranes Gauge and Tool Makers Association Institution of Mechanical Engineers Institution of Production Engineers Lloyds Register of Shipping Milling Cutter Association Ministry of Defence Power Generation A
6、ssociation (BEAMA Ltd.) Society of Motor Manufacturers and Traders Limited The following bodies were also represented in the drafting of the standard through subcommittees and panels: Brush Electrical Machines Ltd. London Regional Transport Railway Industry Association of Great Britain Amendments is
7、sued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 235:1987 BSI 04-2000i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Gear tooth accuracy grades
8、1 4Symbols1 5Normal modules1 6Form of gear tooth1 7Gear tooth accuracy3 8Hardness and case depth of finished, surface hardened gears5 9Gear load capacity7 10Features of the wheels and pinions7 11Marking7 Appendix A Ordering instructions8 Appendix B Guidance on materials for the manufacture of tracti
9、on gears8 Appendix C Recommended method for determining bedding area of taper bores8 Appendix D Guidance on the selection of the gear tooth accuracy grade8 Figure 1 Basic rack tooth profile for unit normal metric module3 Figure 2 Typical tooth profile modification4 Figure 3 Typical tooth profile tol
10、erance chart5 Figure 4 Example of a typical tooth profile tolerance chart6 Table 1 Nominal tooth dimensions of wheels and pinions2 Table 2 Tolerance on pitch3 Table 3 Limits of tolerance on tooth profile3 Table 4 Limits of tolerance on total composite error4 Table 5 Limits of tolerance on tooth alig
11、nment5 Table 6 Case depth of finished, surface hardened gears7 Table 7 Materials for traction gears complying with BS 970-18 Table 8 Gear tooth accuracy grades9 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy
12、, (c) BSI BS 235:1987 ii BSI 04-2000 Foreword This revision of this British Standard has been prepared under the direction of the Machinery and Components Standards Committee. The main changes incorporated are the inclusion of metric module gears and the deletion of diametral pitch gears, the relati
13、ng of gear accuracy grades to pitch surface velocity, reference to a method of calculating gear loading and the addition of a list of ordering instructions. This revision of BS 235 supersedes BS 235:1972, which is withdrawn. A British Standard does not purport to include all the necessary provisions
14、 of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, an ins
15、ide back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (
16、c) BSI BS 235:1987 BSI 04-20001 1 Scope This British Standard specifies requirements for spur and helical gears in accuracy grades 5, 6, 7 and 8 of BS 436-2, for the drive between the electric motors and the axles of vehicles running on rails. It also specifies requirements for the permissible devia
17、tions and tolerances of tooth form and dimensions, hardness and the fitting surfaces, keys and keyways of wheels and pinions. NOTE 1Appendix A lists the instructions that should be supplied by the customer to the gear designer. Guidance is given in Appendix B on the materials for the manufacture of
18、gears. Appendix C recommends a method for determining the bedding surface of taper bored pinions. Appendix D gives guidance on the choice of gear tooth accuracy grades. NOTE 2The titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purpos
19、es of this British Standard the definitions given in BS 2519-1 apply, together with the following. case depth of a surface hardened gear the depth measured normal to the surface of the gear at which the hardness is 550 HV 1 for carburized and hardened gears and 80 % of surface hardness HV 1 for all
20、other surface hardened gears 3 Gear tooth accuracy grades Gears for electric traction shall belong to accuracy grades 5, 6, 7 or 8 of BS 436-2. 4 Symbols For the purposes of this British Standard the symbols shown in BS 2519-2 apply. For convenience the list of symbols used in this standard is as fo
21、llows: 5 Normal modules Normal modules, mn, for traction gears shall be within the following range: 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 14 mm. NOTEPreferred values are given in bold type face. 6 Form of gear tooth 6.1 Basic rack profile Any modifications to the basic rack tooth profile as specif
22、ied in BS 436-2 and shown in Figure 1 shall be within the following limits: a) variation of the total depth within the limits 2.25 to 2.40, permitting an increase in root clearance within the limits 0.25 to 0.40 to allow for different manufacturing processes; b) variation of the root radius within t
23、he limits 0.25 to 0.39; c) variation of the pressure angle. NOTE 1The basic rack tooth profile has a pressure angle of 20. NOTE 2Protuberance cutters should be used to ensure that root fillets are free from grinding or other mechanical damage post-heat treatment operations. 6.2 Tooth dimensions The
24、teeth of wheels and pinions shall have the dimensions calculated from the formulae given in Table 1. NOTEUnless precluded by design considerations, pinion helix angles should be right hand. aCentre distance bFace width b1Face width, pinion b2Face width, wheel dReference circle diameter d1Reference d
25、iameter, pinion d2Reference diameter, wheel daTip diameter da1Tip diameter, pinion da2Tip diameter, wheel dbBase diameter haAddendum KAApplication factor kNumber of teeth over which base tangent span is measured lLength of arc mnNormal module sArc tooth thickness WkBase tangent span xAddendum modifi
26、cation coefficient x1Addendum modification coefficient, pinion x2Addendum modification coefficient, wheel yCentre distance modification coefficient zNumber of teeth z1Number of teeth, pinion z2Number of teeth, wheel nNormal pressure angle at reference cylinder tTransverse pressure angle at reference
27、 cylinder twTransverse pressure angle, working Helix angle at reference cylinder bBase helix angle fTolerance factor for tooth profile deviation pTolerance factor for total composite deviation Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
28、BS 235:1987 2 BSI 04-2000 Table 1 Nominal tooth dimensions of wheels and pinionsa DimensionsSymbolFormula Reference circle diameterd Centre distanceba Addendumchamn (1 + x) Total tooth depth (addendum and dedendum)d 2.25 mn Arc tooth thickness on reference circle s Tip diameterda Transverse pressure
29、 anglettan1 (tan nsec ) Base diameterdbd cos t Base helix anglebsin b= sin cos n Number of teeth over which base tangent span is measuredef k Base tangent spanWkmncos n (k 0.5) + 2x tan n+ z inv t a Numbers appropriate for pinion dimensions and wheel dimensions to be entered, i.e. z 1 and x1, and z2
30、 and x2 respectively. b Gears designed for (1) will engage with minimum backlash, gears designed to (2) may have additional backlash to any envisaged by cutting details. c Guidance is given on the addendum modification coefficient x in PD 6457. d This may have any value from 2.25 m n to 2.40 mn see
31、6.1 a). e The value of k should be rounded to the nearest integer. The term x/8 is an empirical value which ensures that the rounding is to the most practical value. f A check should be made to ensure that the face width of helical gears enables the measurement to be made over the base tangent span.
32、 mnz cos - Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 235:1987 BSI 04-20003 7 Gear tooth accuracy NOTEThe data in clause 7 are taken from BS 436-2 and are included in this standard for convenience. 7.1 Limits of tolerance on pitch Li
33、mits of tolerance on gearwheel and pinion tooth profiles shall comply with Table 2 as appropriate. Measurement of the transverse pitch deviation shall be made on a circle which is concentric with the axis of rotation. Table 2 Tolerance on pitch 7.2 Limits of tolerance of tooth profile deviation Limi
34、ts of tolerance of tooth profile deviation shall comply with Table 3, as appropriate. Where gear teeth are profile ground the surface roughness on the tooth flank, measured in accordance with BS 1134-1, shall not exceed 0.8 4m Ra. NOTE 1The tolerance values are based on a tolerance factor f, given b
35、y the following equation: f= mn+ 0.1 d where Table 3 Limits of tolerance on tooth profile NOTE 2The limits of tolerance apply to the unmodified (true involute) section of the tooth profile. In most applications part of the gear tooth profile will be modified from true involute form. This will normal
36、ly take the form of “tip” or “root” relief, as shown in Figure 2, and known as profile modification. Such profile modifications are designed to accommodate the effects of tooth deflection under load and small pitch variations. They are specified by the gear designer when required and may be applied
37、to the pinion, the wheel or both. NOTE 3Checking of gear tooth profiles is normally performed using a generative involute profile measuring machine, which measures variation from true involute, It is usual for such machines to show a true involute as a straight line on the record sheet, with departu
38、res from true involute being shown as a deviation from a straight line. For this reason, profile tolerances are shown in the form of a profile diagram. An illustration of this type of diagram is shown in Figure 3, and Figure 4 shows a sample profile diagram with typical dimensions. Figure 1 Basic ra
39、ck tooth profile for unit normal metric module Accuracy gradeLimits of tolerance 4m 5 6 7 8 1.6 l + 4.0 2.5 l + 6.3 3.55 l + 9.0 5.0 l + 12.5 NOTEl is any selected length of an arc less than d/2 (in mm). mnis the normal module (in mm); dis the reference circle diameter (in mm). Accuracy grade Profil
40、e tolerance 4m 5 6 7 8 0.40 f+ 5.0 0.63 f+ 6.5 1.00 f+ 8.0 1.60 f+ 10.0 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 235:1987 4 BSI 04-2000 7.3 Limits of tolerance of total composite deviation Limits of tolerance of total composite dev
41、iation shall comply with Table 4, as appropriate. NOTEThe tolerance values are based on the factor p, given by the following equation: p= mn0.25 d where Table 4 Limits of tolerance on total composite error 7.4 Backlash Backlash shall be not less than (20 mn+ 40) 4m or greater than (50 mn+ 100) 4m i.
42、e. maximum backlash = 2.5 minimum backlash. NOTE 1Tooth thicknesses of wheels and pinions should be adjusted as necessary to provide this specified range of backlash. It is essential that adjustments to tooth thickness are compatible with tooth strength requirements. NOTE 2Backlash should be measure
43、d at nominal (minimum) centre distances (i.e. the centre distances given in Table 1). 7.5 Tolerance of tooth alignment The limits of tolerance of tooth alignment deviation shall be in accordance with the formulae given in Table 5. NOTE 1Tolerances are related to a proportion or to the whole of the f
44、ace width b (in mm) of the gear and apply up to a maximum value of 150 mm. NOTE 2In specifying the accuracy of gear helices and gear mounting arrangements, tolerances should be chosen which will enable mesh misalignment to be kept within the required limits. NOTEThis figure is for guidance only and
45、does not form part of this standard. Figure 2 Typical tooth profile modification mnis the normal module (in mm); dis the reference circle diameter (in mm). Accuracy grade Total composite tolerance 4m 5 6 7 8 2.00 p+ 25.0 3.15 p+ 40.0 4.50 p+ 56.0 5.60 p+ 71.0 Licensed Copy: sheffieldun sheffieldun,
46、na, Tue Nov 28 13:50:17 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 235:1987 BSI 04-20005 Table 5 Limits of tolerance on tooth alignment 7.6 Crowning or taper relief When the gear teeth have been modified by crowning or by taper relief so as to mitigate the effects of mesh misalignment resulting f
47、rom shaft deflection bearing clearances etc., backlash shall be determined at the unmodified part of the teeth. NOTESome guidance of this subject is given in Appendix C of BS 436-3:1986. 8 Hardness and case depth of finished, surface hardened gears 8.1 Hardness tests Hardness tests, appropriate to t
48、he gear being tested, shall be carried out on finished, surface hardened gears in accordance with BS 240, BS 427-1, BS 891-1, BS 6479 or BS 6481. In cases where it is necessary to convert hardness numbers, such conversions shall be in accordance with BS 860. 8.2 Position and number of hardness tests
49、 When measurements on a sufficient number of gears show the relationship between hardness at the chosen position and tooth flank hardness to be consistent, hardness tests shall be carried out on both flanks of two teeth approximately 180 apart or on crests, roots or ends of teeth. 8.3 Carburized and hardened gears The surface hardness of carburized and hardened gears shall be not less than 650 HV 30 (58.0 HRC). Maximum hardness, appropriate to the materials being used, s
链接地址:https://www.31doc.com/p-3730802.html