CN101066568A - Elliptical internal gear hob - Google Patents

Abstract

The present invention discloses one kind of ellipsoidal ring gear hob for machining large ring gear, and features that the hob blade has tooth form distributing in circumference normal direction to constitute one part of one virtual gear not coaxial with the hob axis. The ellipsoidal ring gear hob has toothed blades with all the cutting edges on one ellipsoidal helicoidal surface. The technological scheme of the present invention makes the ellipsoidal ring gear hob, which is superior to a spherical hob, possess high machining precision, long service life, good versatility and other advantages.

Description

Elliptical internal gear hob

technical field

The invention relates to an internal gear processing tool, in particular to an elliptical internal gear hob.

technical background

Gear shaping is currently the most commonly used method for machining internal gears based on the generating principle. At present, the maximum modulus of the gear shaper cutter that domestic tool factories can manufacture is 15, while the diameter of the internal gear processed by the largest gear shaper machine in domestic heavy machinery factories is 1.5m ~ 2m. Large internal gears that exceed the above range cannot be processed domestically and can only be imported. The gear hobbing machine is much larger and can process large gears with a length of 5 meters. As long as there is a high-precision, easy-to-manufacture internal gear hob, the processing of high-precision and larger modulus internal gears can be realized. The research on internal gear hobs at home and abroad has a history of several decades, but the hobs studied have a common disadvantage of being difficult to manufacture, inconvenient to use, and low in precision. In 1989, the first inventor of the company cooperated with Dalian Heavy Machinery Factory to complete the research and development of the spherical hob. The developed spherical hob solved the problem of processing the internal gear of the planetary reducer of the factory. The processing module is 12mm and the number of teeth is 97. Internal gear, the precision reaches 8-7-7 grade. The design of the spherical hob is based on the principle of machining the internal gear by the gear shaping cutter. After the structure is reground, the tooth shape of the processed workpiece remains unchanged, and it has the advantages of high machining accuracy, long service life and good versatility. The spherical hob is currently the most ideal tool among hobbing tools for large internal gears. However, the diameter of the spherical hob is proportional to the modulus of the hob and the number of teeth of the pinion in the axial section. Therefore, the larger the modulus, the larger the diameter of the hob, and the number of teeth in the pinion in the axial section cannot be too small, because the more teeth The less, the lower the accuracy of the spherical hob, which is the shortcoming of the spherical hob also limits the application of the spherical hob in the processing of larger modulus internal gears.

Contents of the invention

In order to overcome the shortcoming that the diameter of the spherical hob is proportional to the hob modulus and the number of imaginary teeth, and the larger the hob modulus, the larger the diameter, the invention provides a new type of ellipsoidal internal gear hob, which can effectively solve the problem of Machining problems of large diameter gears.

An ellipsoidal internal gear hob, comprising a wedge screw, a hoop, a clamping wedge, a toothed blade, a cutter body, and a hoop screw, and the toothed blade is closely mounted in the groove of the cutter body, It is clamped by the clamping wedge and fixed on the cutter body through the hoop. The clamping wedge and the hoop are fixed by the wedge screw and the hoop screw. The tooth shape of the toothed blade is according to The distribution of the normal direction of the circumference is a part of an imaginary gear. The center of the imaginary gear is not on the axis line of the ellipsoidal internal gear hob. The ellipsoidal internal gear hob is ellipsoidal. The cutting edges of the serrated blades are all on an ellipsoidal helical surface.

By adopting this scheme, the ellipsoidal hob not only retains the advantages of high machining accuracy, long service life, and good versatility, but also solves the problem that the larger the modulus of the spherical hob, the larger the diameter of the hob, so that it cannot be manufactured. At the same time, due to the use of CNC relief grinding, the normal tooth pitch error of the hob can be corrected, and the manufacturing accuracy of the hob can be improved.

As an improvement of the present invention, in the ellipsoidal internal gear hob, the outer diameter of the ellipsoidal internal gear hob has nothing to do with the outer diameter of the imaginary gear in the axial section of the ellipsoidal internal gear hob.

As another improvement of the present invention, in the ellipsoidal internal gear hob, the normal and axial section tooth profiles of the hob are both involute, which are processed by CNC relief grinding.

In this way, the ellipsoidal internal tooth hob has high processing precision, long service life, reasonable structure size and stronger versatility.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 is the front view of ellipsoid internal gear hob;

Fig. 2 is a left view of the ellipsoidal internal gear hob.

In Fig. 1 and Fig. 2, 1. Wedge screw, 2. Round hoop, 3. Clamping wedge, 4. Toothed blade, 5. Cutter body, 6. Round hoop screw, R is the imaginary gear indexing circle Radius, L is the distance between the center of the imaginary gear index circle and the center line of the hob, D is the outer diameter of the hob, B is the width of the hob, _B0 is the width of the threaded part of the hob, and K is the shovel back.

Detailed ways

The ellipsoidal hob shown in Fig. 1 and Fig. 2 is an inlay structure, which consists of a wedge screw 1, a hoop 2, a clamping wedge 3, a toothed blade 4, a cutter body 5, and a hoop screw 6. , the three cutter teeth in each row are made into one body, the axial profile of the elliptical internal gear hob is distributed on a circle with a pitch circle radius R according to the normal direction, it is a part of a gear, and this gear is also It is called an imaginary gear of the ellipsoidal internal gear hob, and the center of the imaginary gear is not on the axis line of the ellipsoidal internal gear hob. It is a gear with a larger radius and more teeth than the imaginary gear of the spherical hob, or when the radii R of the imaginary gears of the ellipsoidal hob and the spherical hob are the same, the outer radius of the ellipsoidal hob is larger than that of the spherical hob. The radius of the outer circle of the hob should be smaller by an L value.

When the ellipsoidal hob rotates around its own axis, although the center of the imaginary gear is not on the axis of the hob, it is still the pinion that rotates one tooth around its center in the axial section, so when using this When this kind of hob processes the internal gear, it is still equivalent to a small gear and a large internal gear for meshing generating motion. If the processed gear is an involute gear, the tooth profile of the hob is also involute. If the tooth profile of the processed gear is other curves, the corresponding tooth profile of the hob can also be obtained according to the conjugate theory. Since the center of the imaginary gear does not coincide with the axis of the hob, the outer diameter of the imaginary gear of the hob has nothing to do with the outer diameter of the hob. Both the number of teeth of the imaginary gear of the hob and the diameter of the hob can select the most reasonable values respectively. If the modulus of the hob is larger, it can also be made with a single tooth. The hob can also be made into a welded structure, and the choice of its structural form is no different from that of ordinary hobs. Inserts can be pre-machined before mounting on the cutter body, leaving sufficient finishing allowance. The cutter body can be turned into a spherical worm on a four-axis CNC spherical surface processing machine tool, or it can be segmentally milled into an approximate spherical worm on a milling machine with an end milling head that can turn the angle, which can also meet the use requirements.

When the hob is working, the tooth pattern of the hob should follow the tooth groove of the processed internal gear, so the axis of the hob must be inclined at an angle, and the normal modulus of the hob is equal to the normal modulus of the processed internal gear. The normal tooth shape determines the tooth shape of the processed internal gear. When the hob is made into a spherical shape, both the axial section and the normal section are perfect circles. When the hob is made into an ellipsoid, the axial section is still a perfect circle within the working range of the cutter teeth, but the normal section is not a perfect circle. A circle is theoretically an ellipse, so the shape error of the hob is generated. There is no doubt that the larger the helix angle of the hob is, the greater the shape error of the hob is.

For the ellipsoidal hob, when the outer diameter decreases, the helix angle λ _n at any point has: $\mathrm{the\; tan}{\mathrm{\λ}}_{\mathrm{no}}=\frac{1}{(\cos \mathrm{\φ}-\frac{L}{R})\&Center\; Dot;Z_0}$ In the formula: L, R are shown in Figure 1. The greater the distance between the center of the imaginary gear and the axis of the hob, the smaller the number of teeth of the imaginary gear of the hob, and the wider the hob is made (the larger the φ angle at the edge), all of which will increase the helix angle of the hob. That is to say, the normal pitch error of the hob increases and the roundness error of the normal section of the hob increases. However, the calculation shows that when the hob modulus m _n =30mm, the number of imaginary gear teeth Z _n ≥ 24, and the distance between the center of the imaginary gear and the axis of the hob L≤80mm, the normal pitch error is less than 0.03mm, which meets the requirements of a class A hob. As shown in Figure 1, when the hob is made of three rows of teeth, the roundness error of the normal section is 0.024mm, while the radial runout error of the A-level ordinary hob teeth is required to be 0.09mm. A large number of calculations show that if the number of imaginary teeth of the hob is too small or L is too large, the normal tooth pitch error may exceed the requirements of the A-class hob. The pitch is equal to the normal pitch, so as to improve the manufacturing accuracy of the hob. Since the internal gear hob usually only has three rows of teeth, the roundness error of the normal section can meet the requirements of a class A hob in many possible situations in the actual application of the hob.

The manufacturing method of the ellipsoidal hob is basically the same as that of the spherical hob except that the relief grinding process is different.

Claims (3)

1. An ellipsoidal internal gear hob, including a wedge screw (1), a hoop (2), a clamping wedge (3), a toothed blade (4), a cutter body (5) and a hoop screw ( 6), the toothed blade (4) is closely installed in the knife groove of the cutter body (5), clamped by the clamping wedge (3), and fixed on the cutter body by the hoop (2), The clamping wedge (3) and the hoop (2) are fixed by the wedge screw (1) and the hoop screw (6), and it is characterized in that: the tooth shape of the toothed blade (4) is Distributed according to the normal direction of the circumference, it is a part of an imaginary gear. The center of the index circle of the imaginary gear is not on the axis of the ellipsoidal internal gear hob. The ellipsoidal internal gear hob is ellipsoidal. The cutting edges of all toothed blades (4) on the circumference are all on an ellipsoid helicoid. 2. The ellipsoidal internal gear hob according to claim 1, wherein the outer diameter of the ellipsoidal internal gear hob has nothing to do with the outer diameter of the imaginary gear in the axial section of the ellipsoidal internal gear hob . 3. The ellipsoidal internal gear hob according to claim 1 or 2, characterized in that: the hob's normal and axial cross-section tooth shapes are involute, and are processed by numerical control relief grinding.

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