A method and apparatus for manufacturing a gear wheel with stub toothing, wherein a gear-wheel body is drop-forged in a first forming step and the stub toothing is finish-swaged in at least one further forming step by cold die-grooving by means of a swaging tool having swaging parts disposed in a fan-like pattern, wherein the swaging ends plunge into the inter-tooth spaces.
According to a known method (DE 2040413) for manufacturing a stub toothing on a gear wheel of a gearbox, it is provided that a partial toothed gear with stub toothing is manufactured separately then is welded together with the part of the gear wheel supporting the drive toothing. During the manufacture of the stub toothing of the partial toothed gear, the teeth of the stub toothing are first manufactured with tooth flanks oriented in parallel by die-pressing. This is followed by numerous forming steps by cold grooving up to finishing of the exact tooth shape of the stub toothing. This involves the formation of a roof-like shape in the region of the tooth tip as well as an undercut in the region of the tooth flanks, for which a special beveling apparatus is provided with swaging parts plunging in a fan-like pattern into the interstices of the stub toothing. The individual swaging parts are mounted pivotally and with their inwardly pivoted ends bring about grooving of the inter-tooth spaces.
As a consequence of the numerous machining operations, the known method leads to high manufacturing costs. During machining of the stub toothing by the pivoting swaging parts, overlaps are produced during material forming, potentially leading to malfunctions during subsequent operation.
In contrast, the object underlying the present invention is to avoid the disadvantages of the known manufacturing method in an apparatus and in a method of the type mentioned in the introduction, and in particular to enable the manufacture of a stub toothing on gear wheels that is characterized by improved accuracy of the stub toothing and ensures long-lasting use without malfunctions. An objective for the manufacturing method as such is to permit a high production rate with long service lives of the die components.
This object is achieved according to the invention with a method of the type mentioned in the introduction, wherein the swaging parts of the swaging tool are guided together between an upper and a lower holding plate and are moved radially inward in a direction such that precise formation of the teeth of the stub toothing is achieved by cold grooving, in which material flows from the region of the tooth flanks into the regions of the tooth roots. In the process, a stub toothing with high accuracy of shape of both the actual tooth shape and of the inter-tooth spaces is produced by material forming.
As a consequence of the material forming achieved with the inventive method, the hollow profile of the die becomes completely filled in the region of the tooth tips. Because of the sharp-edged structure of the lower edges of the roof-like faces achieved thereby in the region of the tooth tips—in connection with the undercut of the tooth flanks—gearing errors caused by axial separation of the shifted drive connection and known as gear jumpers are reliably avoided.
A particularly advantageous configuration is one in which the direction of plunging of the swaging parts of the swaging tool is selected to be oblique relative to the root space of the teeth, so that excess material after complete filling of the hollow profile of the die flows into a cavity of the die adjoining the root space.
In this way, it is possible to avoid the overlapping of the material that occurs as a consequence of cold forming with only superficial displacement of material and that is recognized as disadvantageous.
In order to guarantee precise operation of the swaging parts, it is proposed according to the invention that the gear-wheel body be pressed under a spring-loaded hydraulic force against the upper holding plate during cold grooving, while the swaging parts are pushed inward against a stop between the upper and lower holding plates. These two holding plates are axially fixed by the spring-loaded pressing action.
The kinematics of the displacement of the swaging parts has a definitive influence on the accuracy of tooth formation. Advantageously they are displaced simultaneously and uniformly by means of a vertically movable actuating ring via mutually engaging conical pressure faces on swaging parts and actuating ring, so that the swaging ends of the swaging parts are always forced inward into the inter-tooth spaces under constant conditions. In this regard, close-tolerance guidance of the swaging parts between upper and lower holding plate is particularly advantageous.
In a method variant that is particularly suitable with respect to service life of the die on the one hand and precision of the manufactured stub toothing on the other hand, the stub toothing is produced in two grooving steps, wherein the teeth of the stub toothing are swaged with axially parallel tooth flanks in a first grooving step and are finish-grooved in a second grooving step, in which the swaging parts of the swaging tool produce an undercut of the tooth flanks followed by root rounding.
These two grooving steps are preceded by drop-forging of the stub toothing as the first forming step. In this process, the stub toothing can be extensively manufactured in finished condition in terms of the roof-like form of the teeth in the tip region, and so the later forming work by the subsequent grooving steps can be limited to a minimum in the interests of increasing the accuracy of shape and the service life of the dies.
The tooth flanks of the stub toothing, having been forged to be axially parallel at first, are advantageously given their undercut only by the grooving step using the fan-shaped swaging tool.
In an apparatus for implementing the inventive method, it is provided that the swaging parts of the swaging tool are individual flat pushing parts, which are disposed circumferentially in axial planes relative to the axis of the die at angular intervals corresponding to the circumferential pitch of the stub toothing.
According to a further proposal of the invention, a displacement of the pushing parts with high accuracy can be achieved by guiding the pushing parts between an upper and a lower holding plate of the die and displacing them radially inward in a direction from a starting position to an end position corresponding to the finished tooth shape.
In this regard it is advantageously provided that the gear-wheel body is mounted in such a way in the die that the stub toothing together with the tooth tips points downward. In a further configuration of the inventive apparatus, it is provided that the displacement of the pushing parts is directed obliquely relative to the axis of the die, approximately toward the root region of the stub toothing. A suitable obliqueness of the pushing direction ranges between 5° and 20°, preferably between 10° and 15° and particularly preferably is approximately 12°. For this purpose, the pushing parts are moved both radially and axially until they reach a radially inner stop position.
With the objective of a process workflow that is as free of vibrations as possible and largely uninfluenced by bending forces, it is further proposed according to the invention that the upper and lower holding plates be securely connected to one another and that they define guides for holding the pushing parts, and that—in a further configuration—the lower holding plate end at its radially inner side with a collar part, which points toward the gear-wheel body and the radially outer circumferential face of which acts as a stop in the end position of the pushing parts.
The collar part offers the additional advantage that its upper side can be used as a seat to support a ring-shaped projection of the gear-wheel body, in other words as the static part of the die.
In this way it is possible to create a die structure with which the objective of the present invention can be optimally achieved in view of the special cross-sectional shape of the respective gear wheel.
Particularly advantageously, the pushing parts can be actuated by an actuating ring encircling the swaging parts externally such that, when it is moved vertically, the pushing parts can be displaced via mutually engaging conical pressure faces on pushing parts and actuating ring into their end position in contact with the circumference of the collar part.
An exemplary embodiment of the invention will be explained hereinafter on the basis of the drawing, wherein
In this forming step, which is followed by a second grooving step as illustrated in
From top to bottom, the die structure according to
Hold-down member 2 and female part 3 are each fitted inside cylindrical housing parts. In this way, hold-down member 2 is guided inside a guide ring 7 and female part 3 is fixed inside a first die ring 8, which in turn is seated inside an outer die ring 9 and is connected by means of bolts 12 with a base plate 10. A die plate 11 mounted on base plate 10 engages in inner die ring 8, on which female part 3 is mounted.
Gear-wheel body 1 has a hub part 13 encircling its middle bore 5 and ending downward with a conical part 14. During shifting of the gear wheel, the outer cone of conical part 14 functions to adapt the speed of rotation of a clutch sleeve to that of the gear wheel by means of a synchronizing ring, the inner cone of which climbs on outer cone 41 of conical part 14. Outer cone 41 of conical part 14 is clearly illustrated in
A toothing body 17, on the outer circumference of which stub toothing 15 is formed as illustrated in
Between a pressure plate 25 of the upper die and an outer bracing ring 26 of the lower die, the grooving die according to
It is particularly advantageous to guide pushing parts 31 in such a way that they are angled obliquely relative to the axis of the die during their shape-imparting radial movement toward it, so that the material flow in the region of the inter-tooth spaces takes place upward toward the tooth-root region, where the excess material from the tooth flanks can flow into the tooth-root region and possibly into an adjacent unoccupied cavity of the die thereabove, located underneath spacer ring 16 (
The obliqueness of the pushing direction of pushing parts 31 advantageously ranges between 5° and 20°, or is approximately 12° in the example of the grooving die illustrated in
Besides its function as the inner end stop for pushing parts 31, collar 37 of lower holding plate 30 together with its upper end face functions as the support for toothing body 17 of gear-wheel body 1, so that disturbing vibrations in the engaging region of swaging ends 36 of pushing parts 31 are avoided.
The schematic detail of
The fixation of upper holding plate 29 on lower holding plate 30 is not illustrated in more detail in the drawing. Upper holding plate 29 is designed as a continuous annular plate, which with its underside limits the upward guidance of pushing parts 31 in such a way that pushing parts 31 are guided on all sides.
After the die has been opened, and therefore when the pushing parts are retracted to their starting position PA and pressure plate 25, on the underside of which actuating ring 35 is fixed, has been raised, the gear wheel together with finish-swaged stub toothing can be removed upward from the lower die, as illustrated in
Number | Date | Country | Kind |
---|---|---|---|
10 2011 114 504.8 | Sep 2011 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2012/003968 | 9/22/2012 | WO | 00 | 4/23/2014 |