CS227656B2 - Multi-part hob - Google Patents

Description

The present invention relates to a multi-part hobbing machine for producing large gears up to a module of about 40.

When milling gear wheels in a separating manner, especially when roughing gear wheels with a large module, disc milling cutters are used. Also used are circular milling cutters provided with reversible carbide cutting inserts which are arranged with alternating teeth, and additional grinding of the tool is then unnecessary. Since all teeth are uniformly worn in circular milling cutters, it is therefore expedient to use expensive sintered carbide inserts, known from chip machining technology.

The production of gearing by means of a separating method is very time-consuming and therefore this method is suitable mainly for production on toothed racks, which leads to the fact that in the production of gearing on wheels is generally used hobbing cutters. In practice, these hobbing cutters are made either entirely of high-speed high-speed steel or are designed as milling cutters with a basic steel body and tooth teeth of high-performance high-speed steel. Such milling cutters allow multiple tooth cutting.

Further development of the hobbing cutters seems to have focused on the grinding problem in the past, especially when the use of hobbing cutters with staggered insert blades, which were designed especially for very large pitches and large dimensions of milling cutters, was adopted. Due to the alternating arrangement of the blades, such milling cutters were not ground as in the case of undercut milling cutters in front of the teeth, but on the external surfaces of the teeth. A separate machine was required for this type of grinding.

The problem of precision grinding has led to the creation of a multi-part hobbing cutter, which consists of a number of wheels provided with planar parallel faces and helical gear rims that correspond to the pitch of the milling cutter. More recently, the idea of a multi-piece cutter has also been watched again for more advantageous repairs, and it has been proposed to arrange alternate toothing with clamped insert blades made of sintered carbides.

However, the prior art solutions, both in terms of design and desirable economics, do not fully meet the increasing demands on the production of gears, especially in large-moon toothing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a large module gear hobbing machine with maximum economy.

It is an object of the invention that the multi-part hobbing cutter for the production of large gears consists of several circular discs provided with planar parallel faces. and helical gear rings corresponding to the pitch of the milling cutter, the gear rings being provided with replaceable sintered carbide inserts, with rotary teeth such as front and side cutting edges, being arranged in a radial radial manner such that the lateral cutting edges of the rotating inserts are rotated overlapping each other.

In the design of the hobbing cutter according to the invention, it is assumed that the expensive insertion of a circular milling cutter with rotary carbide inserts can be attributed to the cutting process, since all teeth are subject to a wear wall. Although the known arrangement of a multi-part hobbing milling cutter without the difficulty of transferring the rotary insert principle to low production, it has not yet been taken into account, for two reasons.

First of all, the manufacturing cost of such a hobbing cutter for a large number of teeth would be greatly increased. Furthermore, it was similarly assumed that all of the indexable inserts of such a hobbing cutter need to be turned from time to time.

The solution according to the invention has revealed that, at the same time, the surprising effect of the stressed combination is that, in fact, it is at the only one tooth travels over the center of the hob in one revolution, which cuts perpendicularly to the milling cutter axis, passing through the center of the gear, and thus has to perform the highest cutting performance. This tooth wears most and, in the case of the rolling milling machine according to the invention, therefore, it is not necessary to rotate all the indexable inserts from time to time, but only those individual or small number of indexable inserts. No specific passage is required since the immersion of such a front-cutting turntable remains unchanged upon rotation. The tool does not need to be changed when one or more rotary inserts are rotated, and no re-setting of the tool is required. ·

All of these advantages are evident even at high purchase costs of the hobbing cutter according to the invention for its otherwise inexpensive operating efficiency.

According to a further feature of the invention, the sintered carbide indexable inserts are mounted upright, with a narrow surface area as the front face. They are therefore not subjected to any bending stresses during milling and can therefore be milled with large ones. at high feed rates. It has been proven experimentally that, compared to a conventional one-part hobbing cutter, the machining time of a large gear could be reduced to at least one seventh. In addition, it has been found that the teeth are cleaned in one working passage and are therefore manufactured to the extent that they are large. Powerful gears are not required.

For large gears, the hobbing cutter may be formed with at least three set-up helical gears. For machining smaller diameter gears and a small module, a hob cutter made up of only one or two circular discs with helical gears may be sufficient.

The invention also solves the problem of rounding the tooth heel, the so-called protuberance, by means of which the allowance for grinding the tooth flank is determined. As is known, the gear ratios of the type of toothing used, for example involute toothing, are valid for rolling milling, since each tooth of the rolling milling cutter can be considered a counter-tooth in terms of the mesh ratios. As with the engagement of two gears, the engagement length extends, except for the entire length of the side of the head, to only a portion of the length of the heel side, and the hob can only form the tooth side length to the point on the heel which is given by the intersection of the milling head circle for involute gearing or with a rolling circle for cycloid gearing. The rest of the flank in the tooth base area becomes rounded into the tooth gap, and it is this transition that needs to be increased as a fillet or prominence in order to properly grind the effective flanks and only these. In the production of the protuberance, it is as if undercutting the effective tooth flanks to allow further processing of the tool, in this case the grinding wheel, to be free-run.

Until now, it was necessary to produce the protuberance by a special protuberance hobbing cutter in the second working process. The condition of the tools for each gear module had to include not only a separate undercut milling cutter, which is more expensive than a normal hobbing cutter, but even several undercut milling cutters with different rounding edges in order to influence the grinding allowance by grinding greater or lesser rounding of the heel.

It has been found that a special protuberance hobbing milling cutter and a second milling process to create a protuberance can be saved using a carbide-tipped milling cutter according to the invention by having at least a tooth running through the center effective on a perpendicular to the milling cutter axis The center of the gear is provided in the area of the tooth tip with a rotatable cemented carbide plate having a cutting edge in the form of a circular arc for rounding the tooth root, the radius being adapted to the desired tooth root radius.

In addition to a considerable reduction in costs, the solution according to the invention provides the possibility of selecting the amount of protuberance as desired by simply replacing the rounding or other diameter of the indexing insert. This need arises when it has been found, after the toothing of the gearwheel, that one or more teeth are particularly strongly drawn. It is then recommended to increase the grinding allowance on all tooth flanks so that the tooth flanks of the elongated teeth can also be reached by the grinding wheel. This selectable protuberance adjustability has so far been possible only by selecting a special protuberance cutter, but only at a graduation as predetermined by the respective protuberance cutters of the same gear module.

The rounded reversible plates can be formed by circular discs which are inserted into the tooth faces of the rolling milling cutter orbiting exactly or roughly over the center. Such circular indexable inserts have the advantage that they can be simply rotated 180 ° to engage a new circular arc-shaped cutting edge. However, the teeth provided with rounding plates have to be machined differently with respect to the seats on the uprightly inserted front and side cutting edges.

In order to be able to produce the teeth of the hobbing cutter with unchanged characteristics of successive rotary insert seats, the hobbing cutter according to the invention is provided with a successive sequence of at least two mirrored sintered carbide inserts mounted as right-hand and left-hand front and side cutting edges. The lateral machining is connected at a blunt tangential angle to the rounding edges in the form of a circular arc, which overlap when the milling cutter rotates. These mirrored rotating inserts need to be mounted in the tooth seats without rounding inserts for the front and side cutting edges, so that when machining the teeth of the hobbing cutter, it is not necessary to take into account which teeth are to be provided with rounding inserts.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail in the accompanying drawings, in which Fig. 1 is a hobbing cutter consisting of three circular discs, with a partial cross-sectional plane II of Fig. 2, Fig. 2 is a left side view of a hobbing cutter in Fig. 1; Fig. 3 is a partial sectional view of the hobbing cutter of Fig. 1 with rings as rounding plates; Fig. 4 is a left side view of half of the central circular disk of Fig. 3; Fig. 5 is another hobbing cutter similar to construction 3 and 4, with the same mirror image. Fig. 5a shows a pair of mirrored rounding plates in an enlarged view; and Figs. 6 is a left side view of the middle circular disk of FIG. 5.

The multi-part hobbing cutter according to the invention consists, in all exemplary embodiments, of three circular disks 1, 2, 3, provided with helical gear rings 1a, 2a, 3a, which are fitted with a through hole and onto the unmarked milling cutter, secured against rotation. clamping together. .

Single-loop · circular ·. of the disks 1, 2 lie on top of one another with their flame-parallel faces, of which only the outer face 5 of the circular disk 1 and the outer face 4 of the circular disk 2 are provided with reference numerals. The assembled set of toothed rims 1a, 2a, 3a clamped to the milling mandrel is limited by rings 7, 8, which are provided with a plurality of holes 9, as well as toothed rims 1a, 2a, 3a into which the pins are inserted to the helical gears' 1a, 2a, Да have been fixed in a continuous screw thread corresponding to the module-dependent pitch of the hobbing cutter.

The gear rings 2a, 2a, 3a of the hobbing cutter are provided with rotary inserts of sintered carbides with a shearing arrangement of teeth.

In an alternating arrangement of teeth, a distinction is made between side-cutting rotary inserts 10 and face-side rotating inserts 11, which are fixed by unmarked screws on milled seats in the toothed rims 1a, 2a, 3a ,. they are set upright, i.e. by a narrow limiting surface as the front face. In addition, the sintered carbide reversible plates 10, 11 are directed against rotation by adjacent inserts.

The turntables 10, 11 are arranged in successive order of teeth to cut right and in. For example, if the insert 22 ^{with the} front and side cutting edges is considered to be a left-hand revolving insert in the direction of rotation R of the milling cutter, then the following tooth is provided with a right-hand rotating shank 11. a tooth circumference other than the front and side edges of the plate 11 on the preceding tooth. These alternating radial distances cause the side edges of the rotary insert edges to overlap during the milling cycle.

Since in FIG. 1 the front and side cutting edges of the turntable 11 belong to the last tooth of the ring gear 1a of the circular disk 2, which is visible in the side view of FIG. 2; is then the successor of the tooth shown in FIG. 2, provided with the left-hand rotating plate 22, with the first tooth of the ring gear 2a of the circular disk of FIG. 1. In the side view of FIG. omitted.

In the case of large-module hobbing cutters, more than the left-hand or right-hand right-hand rotary insert 10 must be provided, but the radial radial spacing of the rotary inserts must always be set to overlap the successive edge of the rotary inserts.

In the exemplary embodiments, rotary plates 10, 11 having rectangular shape are inserted. It goes without saying that the indexable inserts could also be made square, the eight cutting edges of which can be reversed by comparison with the four cutting edges of the rectangular indexing inserts.

In the exemplary embodiment of FIGS. 3 and 4, the toothed rings 1a, 2a, 3a, as already described, are provided with rotary plates 20, 11 of sintered carbides, in the arrangement of alternating teeth.

The tooth of the ring gear 2a of the central circular disk 2 is according to the invention provided with a circular rotary plate 16 of cemented carbide, which is inserted in the tooth face in such a way that it can form a rounding at the base of the tooth as. right-handed and left-handed. It is the tooth of the hobbing cutter that runs. before milling, it adjusts the axial adjuster of the hobbing cutter. Also, one or more of the teeth adjacent to this tooth can be scattered with a rounded rounding plate to divide the cutting work.

It can be seen from FIG. 3 that the rotary indexing plate 16 pushes the generally designated front and side cutting edge 11 for this tooth, which becomes a mere lateral cutting edge na on the tooth provided with the circular indexing plate 16. Also, for a tooth provided with a circular rotary insert 16, the side cutting edges of the rotary inserts overlap each other as the milling cutter rotates. Since the circular indexing plate 16 cuts left and right, the gaps between the circular indexing plate 16 of the same tooth must be as small as possible so that they can be covered by the front and side edges 11, 10 of the following teeth.

Moonoot is used for rotating, cemented carbide inserts by turning and reversing several new cutting edges, although the circular rotating plate 16 is given, but this is not the main feature. More importantly, the sintered carbide rotary insert 16 can be arbitrarily scaled by a rotary insert of a different diameter to freely select the amount of rounding or protuberance at the base of the tooth and hence the grinding allowance.

The rotary cutter according to FIG. 5 corresponds to the exemplary embodiment of FIGS. 3 and 4 in its multi-part construction. As already described, the toothed gear rings 1a, 2a, 3a are provided with uprightly mounted sintered carbide index plates 10 forming side cutting edges. and sintered carbide indexing plates 11 forming the front and side cutting edges in the arrangement of alternating teeth, with the exception of two successive teeth -2 ^ 7 of the 2-side circular disc -2 ·

As can be seen from FIG. 5, one front and side cutting edge 11 is replaced on the first tooth 2a ' on the stationary rounding plate 17, which is provided with a side cutting edge 17a according to FIG. 5a passing into the cutting edge 17b in the form of a circular arc, with which the curvature can be partially machined to zsbovié.patn.

Then, the successor tooth 2 is provided with a rounding plate 1B having the shape of a mirror view of the rounding plate 17 and also having a laterally cutting edge 18a and a cutting edge 18b at the point where the front and side cutting edges would be inserted in the arrangement of the alternating teeth. circular arc shape for rounding the heel of the tooth.

As the milling cutter rotates, the two blades 17b, 18b overlap so that the tooth base is rounded in the same way as the circular rotary plate 16 of FIG. 3. The advantage of this arrangement is that the seats framed in the circular disc 2 for the front and side blades 11 without difficulty use - rounding inserts 17, -18.

Also, for the exemplary embodiment of Figs. 5 and 6, by replacing the rounding inserts 1T, 18, the amount of desired rounding at the base of the tooth can be reduced to obtain a greater or lesser grinding allowance. If the rounding inserts 18, 18 are to be rotated to engage new cutting edges, then they simply become confused so that the right-hand cutting edge becomes left-cutting and vice versa.

Claims (4)

SUBJECT OF THE INVENTION Multi-part hobbing cutter for producing large gears up to a module of about 40, characterized in that it consists of at least one circular disk (1, 2, 3) provided with pian-parallel faces and helical gear rims (1а, 2a, За) corresponding to the milling pitch wherein the gear rings (1a, 2a, За) are provided with interchangeable rotary inserts (10, 11, 17, 18) of cemented carbides and alternating teeth such as front and side blades, which in successive teeth are right-hand and left-hand, at an alternating radial distance such that the side cutting edges of the indexable inserts (10, 11, 17, 18) overlap each other when the milling cutter is rotated. 2. The multi-part hobbing cutter according to claim 1, characterized in that the sintered carbide inserts (10, 11, 17, 18) are mounted upright, with a narrow boundary surface as the end face. 3. The multi-part hobbing cutter according to claims 1 and 2, characterized in that at least a tooth running over the center, effective on a perpendicular to the milling cutter axis and passing through the center of the gear, is provided with a rotating plate (16, 17, cemented carbide having a cutting edge in the form of a circular arc for rounding the tooth root, the radius of which corresponds to the desired rounding of the tooth root. 4. The multi-part hobbing cutter according to claim 4, characterized in that it is provided with at least two sintered carbide reversible plates (17, 18) mounted as right-hand cutting and left-hand cutting front and side strips whose straight edges (17a, 18a) for the side The machining is followed by a rounded arc (17b, 18b) at the obtuse tangential angle (alpha) overlapping as the milling cutter rotates.