# Three dimensional solid modeling of involute straight bevel gear

SolidWorks is a three-dimensional modeling software developed based on Windows system. It has the characteristics of powerful function, easy to learn and practical, and provides a variety of modeling methods. In addition, SolidWorks software provides a variety of 3D software data interface formats, including step, vdafs, IGES, UG, sat, STL, MDT, Parasolid, Pro / E, SolidEdge, inventor and other formats, which are input into parts and assemblies.

At present, some secondary plug-ins, such as Mindy tool set and geartrax, have added automatic generation tools for involute straight bevel gears, which can enable designers to quickly design products and complete assembly. However, this model is simplified, does not consider some details, is not accurate enough, and cannot be used for subsequent CAE analysis and production guidance.

Combined with the dimensional parameters of differential straight bevel gear pair for car, the accurate three-dimensional modeling of involute straight bevel gear is completed by using MATLAB and SolidWorks. The specific modeling process is as follows:

1) Generating spherical involute

According to equation (equation 2.1), it is solved by MATLAB software ϕ The corresponding spherical involute coordinate value in the interval [0,3 π]. In SolidWorks, the function of “curve passing through XYZ point” is used to generate the spherical involute of straight bevel gear tooth profile, as shown in Figure 1.

2) Create a gear tooth solid

Connect the endpoints of the large and small ends of the involute with the origin, and fill the surface to obtain a closed surface. Then, according to the relevant parameters of straight bevel gear, the tooth top cone and tooth root cone are obtained by rotation, and the ruled surface tangent to the two spherical involute surfaces is made to form a multi surface combination, as shown in Fig. 2. Using the surface deletion function to cut the redundant surface, the tooth entity can be obtained, as shown in Figure 3.

3) Complete Gear Solid Modeling

Array tooth entities, rotate the gear contour to obtain the gear matrix, and obtain the three-dimensional solid model of planetary gear and half shaft gear through combination and deletion, as shown in Fig. 4 and Fig. 5.

4) Assemble

In order to facilitate the subsequent dynamic simulation analysis of straight bevel gear system, the assembly of half shaft gear and planetary gear is completed according to the bevel gear assembly conditions:

① Create a new assembly. Insert planetary gear and halfshaft gear.

② Define the gear fit. The matching conditions of straight bevel gear pair mainly include: the axis of half shaft gear is perpendicular to the axis of planetary gear; The base cone apex of the planetary gear coincides with the base cone apex of the half shaft gear; The datum plane of the axis and the end face auxiliary line on the axle shaft gear coincides with the datum plane of the axis and the end face auxiliary line on the planetary gear.

③ Interference check. Use the interference inspection function to check whether the assembly model has interference, so as to ensure that the straight bevel gear assembly has no interference, and obtain the straight bevel gear transmission model that can be used for analysis, as shown in Fig. 6.

It can be seen from this that the three-dimensional modeling of straight bevel gear completed in SolidWorks software can be regarded as a parametric model, so the solid model of straight bevel gear with different relevant parameters can be generated only by modifying the model parameters, such as pressure angle, number of teeth, cone pitch, indexing circle diameter, etc.

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