1 Parametric modeling of spline gears Take the spline gears used in a certain type of pumping stroke shifter as an example. The gears and splines are involute straight teeth, and the parameters are shown in Table 1. Parametric modeling of gears and splines with Pro/E.
1.1 Modeling steps of the involute gear (1) Establish the basic parameters of the gear. Use the parameter list provided by Pro/E to set the parameter table of 1 and input the following equation: 111dmz=, gear index circle diameter 1 (2) admzh= , gear tip diameter 1 (22) fadmzhc
Gear tooth root diameter 1 spline gear basic parameters involute gear parameter involute spline parameter tooth number Z125 tooth number z218 modulus m14 modulus m22.5 index circle pressure angle Α 120o index circle pressure angle α230 tooth top height Coefficient ha1 large diameter da277.4 headspace coefficient C
0.25 small diameter df269.28 tooth width B140 tooth width B265 (2) establish the gear base gear base is a cylinder, a new cylindrical tensile body in Pro / E, diameter 1ad, length B.
(3) Establishing a new coordinate system If the spline curve is directly established in the existing coordinate system by the usual method, there is no guarantee that the relative positions of A and B will not change when the parameters are changed. To this end, the following assumption is made: that each time the model is generated, if the center line of the gear tooth profile A and the spline tooth profile B are located on the x-axis of the current coordinate system CSYS, the position alignment requirement can be satisfied. Based on the above ideas, a new coordinate system CS1 is created, which is the current coordinate system CSYS rotates counterclockwise around the z-axis o145/zλ=; then a new plane passing through the z-axis and having an angle with the TOP plane of o167.5/zψ= DTM1.
(4) Establishing the spline curve Set the coordinate system CS1 to the Cartesian coordinate system and establish the involute spline curve CURVE1. The equation is:
r=d_1/2ang=t90s=(pirt)/2xc=rcos(ang)yc=rsin(ang)x=xc (ssin(ang))y=yc-(scos(ang))z=0rotate copy CURVE1, The rotation angle is o1225/zχ, and a new spline curve CURVE2 is obtained. The spline curve CURVE1 is mirrored by DTM1 as a symmetry plane to generate a spline curve CURVE3, as shown in 2. CURVE2 and CURVE3 are a cogging shape curve of the gears built.
2 Spline curve generation (5) Generating gears Using the spline curves CURVE2, CURVE3, the tip circle 1ad and the root circle 1fd, a complete gear tooth groove can be drawn, stretched, and the gear base is used as the axis. The array has an array number of 1z and an array angle of 1360/z. A complete and accurate involute gear is available.
It can be seen from the calculation that the angle between the center line of the tooth groove and the x-axis of the coordinate system CSYS is 1180/z° due to the correct setting of the λψχ and the three angles, which is exactly equal to the central angle corresponding to one tooth thickness.
Therefore, the center line of one tooth shape (A) can be guaranteed to be on the x-axis of the coordinate system CSYS.
1.2 Parametric modeling of internal splines The modeling steps of the internal splines are the same as the gears, and will not be described here.
1.3 The establishment of other features The rotation, stretching, thread modification, mirroring, chamfering and other tools to establish other features of the spline gear are parameterized. It should be pointed out that after the model of the gears and splines is established, the reference faces of the threaded holes C and D have been determined, and it is convenient to establish the parameterized modeling of the threaded holes C and D without re-establishing the reference. surface. The spline gear end view created by the parameters is its three-dimensional shape. If the modulus and the number of teeth of the splines and gears are changed to 139z=, 13m=, 224z=, 2m=, the generated model is as shown in 5.
3 Conclusions (1) For the three-dimensional modeling of spline gears that require changing parameters, parameters such as Pro/E should be used for parametric modeling to avoid repetitive design, automate the design process, and improve design efficiency.
In this paper, a new parametric coordinate system is established, and a spline curve is established on this basis. The parameterization modeling of spline based on Pro/E is realized, which not only ensures the accuracy of the model and high design efficiency, but also satisfies the specific Location requirements.
(2) Pro/E can be used to realize parametric design within a certain parameter range. However, if the parameters of the part change too much, the topology of the part will change, and the regeneration of the part will be wrong. Therefore, in this design, the number of teeth and the modulus of the spline gear must be within a certain range.
(3) In this paper, the method of setting the position of spline curve generation can increase the position of the constant item according to the use requirement, and it has certain reference significance for the parametric modeling of other disk parts.
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