Design of 25 pressure angle lobe grinding front gear hobs Qi Huaren, Zhang Shaowu, Wang Teng (Dalian Locomotive and Rolling Stock Factory, Liaoning Dalian introduced the structure, characteristics and design method of the front rake angle, 25 pressure angle lobe grinding front gear hob.
1 Overview Traction gears are important transmission components for diesel locomotives. The traction gear of the locomotive is subjected to huge traction torque and vibration load, and the working conditions are very bad. In recent years, in order to meet the requirements of high-speed and heavy-duty railway transportation, the traction gears of diesel locomotives have widely used 25-pressure angle gears with high root strength and strong anti-adhesive ability. However, it has been found in the application that the root crack and the tooth fracture occur frequently, and the DF4D passenger locomotive is particularly serious. An important reason for this phenomenon is that the 25-pressure angle gear tooth root is narrow, and the universal grinding front gear hob hobbing and grinding teeth are used, and the shape of the root transition curve is unreasonable, and the radius of curvature is small, as shown, The heat treatment at the root of the tooth brings difficulties, and it is easy to cause stress concentration at the root of the tooth. There are two ways to improve the shape of the tooth root transition curve after tooth root crack and early tooth fracture. One is to change the grinding process. With full-cogging grinding, the harmful bosses that cause stress concentration in the root can be eliminated. However, the side effect is that the grinding work is increased, the grinding efficiency is reduced, and because the contact area between the grinding wheel and the workpiece at the root is large, the heat dissipation condition is poor, and grinding vibration and other grinding defects are easily generated, and the tooth surface is reduced. Quality; full-cogging grinding not only does not improve the heat treatment conditions of the root, but destroys the quenching compressive stress of the root and reduces the root strength; the full-coil grinding wheel is difficult to trim, the consumption is large, and the other is improved. The toothed design allows the gear to obtain a reasonable root transition curve after hobbing, and the tooth surface can be smoothly connected with the tooth root formed by the hobbing after grinding, thereby improving the root strength. The design of the 25-pressure angle lobe grinding front gear hob will be described in detail.
2 Design principle 25 Pressure angle bulge Grinding front gear hob has a larger improvement on the tooth shape than the general grinding front gear hob, and its tooth shape is fully utilized by the knurling part and the standard part. The meshing movement of the tool and the workpiece, the lobe portion cuts the transition curve portion of the gear, and the standard portion cuts the involute portion of the gear. In this way, the root of the gear cut has a certain amount of undercut, which provides the necessary grinding wheel for the grinding. After the grinding of the grinding wheel, the involute formed by the grinding tooth and the root transition curve formed by the hobbing are smoothly connected. In order to eliminate the calculated hob index circle diameter d and the helix angle V tooth boss calculated in Grinding-88, the root quenching compressive stress is retained, the grinding accuracy is improved, and the gear is calculated according to the tooth top of the standard hob. For the purpose of designing the pre-grinding hob for the purpose of strength, the tooth shape of the gear grinding teeth before and after the hob machining is corrected.
Lobe grinding front gear hob hobbing without grinding tooth boss 25 pressure angle lobe grinding front gear hob design should meet the following conditions: (1) meet the basic requirements of gear meshing: the gear tooth profile of the cutting meets the standard The tooth profile of the open gear, the effective involute length necessary for the gear to mesh after grinding (2) meets the basic requirements of the hob cutting: the lobed portion should have sufficient side relief angle and corner fillet to Reduce the wear of the hob, the radius of curvature of the tooth root transition curve, improve the root strength and the service life of the hob. (3) Meet the requirements of standardization and serialization: the selection of parameters should adopt relevant national standards as much as possible to facilitate Manufacture and use.
25 pressure angle lobe grinding front gear hob is a kind of pre-grinding hobbing tool, its parameter design and modulus, pressure angle, number of teeth, displacement coefficient gear precision grade and grinding tooth of the gear and its conjugate gear The quantities are directly related, so you must understand the above parameters when designing. Taking the traction gear of DF4D diesel locomotive as an example, the original data necessary for the design and design of the 25-pressure angle lobe pre-grinding gear hob for machining main and driven gears is introduced. The hob design for DF locomotive traction gear processing shown in Table 1 is shown in Table 1. Straight groove Archimedes insert hob with single head, right handed, chip flute parallel to the axis of the hob. In order to improve the cutting performance, the hob is designed as a positive rake angle. The basic structural dimensions and related parameters are selected according to GB9205-88<Inlay gear hob, and the tooth top height of the hob is corrected. 3.3 The design of the axial tooth profile of the hob Since the tooth profile of the gear hob before the lobed grinding is complicated, it is very difficult to manufacture. In order to reduce the manufacturing error, the tooth profile of the hob should be designed in the axial section to facilitate the trimming of the grinding wheel. The axial tooth profile of the gear hob before grinding is shown. The main parameters are designed as follows.
Table 1 DF41 diesel locomotive traction gear parameter parameter name drive gear driven gear module m10m10 pressure angle T25 °T25 ° tooth number Z 0.512 tooth thickness upper deviation Ess-0.40Ess-0l40 tooth thickness deviation Ei-0.60Esi-Q60 grinding tooth allowance (tooth thickness direction, one side) 厶10.20厶2 Q303.2 Determination of basic parameters of hob (2) Maximum axial tooth thickness of standard hob Sxmax: Esi For the convenience of manufacture and use, the structure size, number of teeth and capacity of the hob The flute form should be as close as possible to the relevant national standards. The overall size of the high-speed steel hob can be selected according to GB8062.1-87 (the basic type and size of the pre-grinding gear hob). In order to save the tool material, the cutter can be made into a tooth structure. GB9205-88<Inlaying gear hob selection, but should pay attention to, GB9205(3) standard hob minimum axial tooth thickness SxmK(4) lobe grinding front hob actual axial tooth thickness Sx: (down to page 14) Two pieces of 310 B-shaped steel traction beams are assembled by special fixtures and moving trolleys, from one end of the beam to the other end, and the inner spacing of the two pieces of 310 B steel inner and outer butt welds are automatically welded by submerged arc. Use 3mm welding wire, welding wire grade H08A flux for high manganese high silicon low hydrogen soldering agent 431 MZ- 1-1000 flux with positive connection method and submerged arc automatic welding parameters of ZXG-1000R DC power supply. See Table 1 Welding internal sealing bottom weld When the middle of the traction beam is locked, the top of the traction beam is lifted by the air cylinder at the two ends. The welding table 1 is submerged arc automatic welding parameters welding current welding voltage welding speed wire length reverse deformation amount, so that the traction beam is basically after welding After the deflection welding, the 315t vertical Hydraulic Press is equipped with special mold and pad to level the traction beam, so that the flatness of the flange is not more than 1mm. The traction beam is pressed out of the traction beam of 4~2 position on the hydraulic straightening machine, and the group is set. Welding the impact seat. The deflection of the traction beam after welding is 1~ the amount of sag is 0~1mm. 2.6 The bottom frame is corrected by the C63A gondola undercarriage hydraulic correction device and the flame is used to correct the frame. After the correction, the deflection between the two bolster beams is 7~9mm, the upper wing or sag of the traction beam is not more than 5mm, the horizontal beam difference is not more than 6mm, and the disc spacing is not more than 0.5mm. Practice shows that the above process can effectively control The manufacturing quality of the all-steel tub type coal-powered special gondola chassis reduces the amount of correction and reduces the manufacturing cost, and is suitable for trial production and mass production.
(Continued from page 9) (7) Hob tooth radius radius R: (8) Hob maximum lob height hx: where p1p2 is the main, driven gear involute meshing start or end point The radius of curvature can be obtained according to the meshing angle and center distance of a pair of indexing gears. (9) The axial angle of the hob angle of the hob is 0: 3.4 The design of the front rake of the hob's rake face is designed. The tooth profile should be measured in the rake face. In order to facilitate the inspection during manufacturing, the tooth profile parameters of the rake face of the hob should be given in the design, such as the tooth profile angle of the main cutting edge and the lobed portion, and the tooth height of each part. , indexing round tooth thickness and so on. Since the cutting edge arc is elliptical in the rake face, it is not necessary to give the radius of the tooth tip arc in the rake face parameter.
The use of 25 pressure angle lobe grinding front gear hob has fundamentally improved the performance of the traction gear of the diesel locomotive, significantly increasing the radius of curvature of the root transition curve, effectively eliminating the grinding crown and achieving the heat treatment characteristics of the retained root. The purpose is to increase the root strength.
25 pressure angle lobe grinding front gear hob provides the necessary grinding wheel for the grinding process, which reduces the contact area between the grinding wheel and the workpiece during grinding, eliminates grinding vibration, improves tooth surface quality and grinding efficiency. Through the loading test of more than 1a, the application effect is good. At present, the processing of the traction gear of the DF4D locomotive has been carried out by using 25 pressure angle lobe grinding front gear hob hobbing. It should be noted that the 25-pressure angle lobe pre-grinding gear hob is a special pre-grinding hobbing tool, which has the modulus, pressure angle, number of teeth, displacement coefficient and grinding allowance of the gear to be processed. Close relationship, the actual application should be designed according to the specific processing conditions.
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