EP0073985A2 - Method of forging - Google Patents

Abstract

Coupling members with a negative relief of their load-bearing contact surfaces, are produced by a rough-forging process followed by a cold gauging process. First of all contact surfaces (5) parallel to the direction of the forging stroke are produced with an admeasurement k at the top faces (2) in the marginal region adjoining edges (3). Subsequently, the top faces are cold forged with exact measurements so that every finished contact surface extends obliquely towards the top face enlarged by the gauging. <IMAGE>

Description

The invention relates to a method for the precision forging of forgings with at least one coupling surface serving for power transmission in cooperation with a counterpart, in particular claws or pockets having coupling parts or synchronizing parts with short teeth for manual transmissions, in which the parts are first forged and then cold calibrated .

Furthermore, the invention relates to workpieces produced by the above method, namely coupling bodies for dog clutches, synchronous coupling bodies for manual transmissions or the like, coupling parts having short teeth or claws or pockets, and also ratchet bodies, gear; lenkwellenkör he ^p etc.

Since there is a risk of coupling parts of the type mentioned that they detach themselves from their respective counterparts during operation, which under certain circumstances can lead to considerable gear damage, or at least to undesirable operational uncertainty, the coupling claws or teeth have been adopted Form short gears with trailing flanks. This is to be understood to mean that the surfaces which effect the coupling and which transmit the load or the torque, which are referred to below as coupling surfaces and correspond to the tooth flanks in the case of toothings, are set behind by approximately 1 to 3 degrees in the direction of the coupling movement, i. H. with respect to a claw or tooth on a coupling part, that the claw or tooth narrows from the head towards the foot. If the counterpart of the coupling part has the same rear position, this results in a clutch engagement in which loosening under load is avoided.

In addition, such a clutch engagement requires that the bearing portion of the backed area is more than 50%. In this way, a sufficiently long service life of the coupling parts is to be ensured.

The forging of coupling parts with rear clutch surfaces is practically not possible, since a division of the forging die that tolerates the backing can neither be realized economically nor technically. In a known forging method (British Patent 10 39 905) for producing a bevel gear, after the forging of the gear by cold calibration in a calibration die, a correction of the flank shape of the teeth to change the contact pattern is generated. This results in a material transport limited to a thin surface layer from the edges to the center of the tooth flanks without causing undercuts.

Another known method (US-PS 28 43 927) relates to the production of racks, with a negative backing of the tooth flanks between 14.5 and 20 degrees. The toothing is formed by the webs remaining between a row of punch holes in a base body. The punching process here causes the flanks of these webs to be set at an angle, which are then calibrated from the rear to give them their finished surface.

Finally, the manufacture of forgings is known (US Pat. No. 3,739,664) which has a series of projections, the gaps between the projections on the one hand showing a negative and on the other hand a positive position of the flanks. Since all flanks of such a workpiece are aligned, the workpiece can be removed from the die after forging.

In contrast, the present invention is based on the object of designing a method of the type mentioned at the outset in such a way that workpieces, in particular coupling parts, can be produced with a negative backing of the load-transmitting coupling surface.

This object is achieved in that, during the forging, parallel to the impact direction coupling surfaces with the adjacent head surfaces increasing allowance at least in the respective common edge of this Surfaces adjoining the edge area are produced and that during the cold calibration the head surfaces are forged precisely, in such a way that each finished coupling surface runs obliquely towards the head surface widened by the calibration.

According to this method, it is possible to create the backing of the clutch surfaces up to about 5 degrees. With correct dimensioning and distribution of the allowance, any bulging of the coupling surfaces into a spherical shape is avoided, the calibration stroke with free, i.e. H. without any support from the die shape, deformation of the coupling surfaces until reaching an inclined position in the sense of the desired undercut. During the calibration stroke, the material flow is first triggered by the measurement in the edge area before the pressure is distributed over the entire head surface. In this way, any convex shape of the coupling surfaces can be reliably avoided.

In the case of toothings on coupling parts, whether claws or pockets or short toothing, the opposing tooth flanks of a tooth or claw forming the coupling surfaces are each negatively positioned in such a way that the tooth gaps widen towards the tooth base. Of course, it is also possible within the scope of the method according to the invention to produce individual coupling surfaces with provision, the im Back area opposite surface can be formed straight or even with a positive position.

To achieve a controlled provision of the coupling surfaces, it is advantageous that the forged parts are only supported by the die during cold calibration between two die surfaces that are parallel to the direction of impact and run transversely to the coupling surfaces.

In order to keep the symmetry error in gearings small and at the same time to achieve that at least 75% of the teeth of a toothed ring are worn, it can be advantageous that the widening of the tooth tip surfaces is limited by supporting surfaces of the die arranged at a corresponding distance from the preform. It is sufficient if the support surfaces are only available within the radius described by the head surfaces.

The dimensioning of the allowance is decisive for the angle reached by the positioning, as well as the flat shape of the coupling surface. For this purpose, it is proposed according to the invention that the oversize volume per coupling surface is dimensioned according to its selected rear position or inclined position with respect to the head surface.

At the same time, it is essential that the distribution of the allowance has a maximum in or near the coupling surface along a section running transversely to the coupling surface.

In order to control the edge pressure during cold calibration and at the same time the deformation pressure over the entire coupling surface, it is expedient that the distribution of the allowance describes a course which decreases in a straight line or concave fashion in the edge region of the head surface adjoining the coupling surface.

The preferred application of the method according to the invention relates to claw couplings, the load-transmitting flanks of the claws or pockets of the two interacting coupling parts corresponding to the coupling surfaces, with every or every second flank being placed behind. In the same way, the method according to the invention can be applied to the short teeth known per se with pointed teeth, the undercuts previously produced by subsequent rolling or eroding being produced by the method according to the invention. This is not only suitable for producing undercuts on claws or pockets, but also on involute gears, both external and internal gears.

• Figur 1 einen in Umfangsrichtung geführten Schnitt durch eine Klaue nach dem Vdnschmieden
• Figur 2 einen in Umfangsrichtung geführten Schnitt durch die Klaue gemäß Figur 1 nach dem Kalibrieren,
• Figur 3 eine perspektivische Ansicht der Klaue gemäß Figur 1.
• Figur 4 einen in Umfangsrichtung geführten Schnitt durch eine Klaue mit Schlupffasetim Bereich der zwischen Kopffläche und Kupplungsfläche gebildeten Kanten.
• Figur 5 eine Draufsicht auf ein Kupplungsstirnrad mit vier Taschen und
• Figur 6 die Abwicklung eines in Umfangsrichtung geführten Teilschnitts gemäß VI - VI der Figur 5.

• Gemäß Figur 1 besitzt eine Klaue 1 nach dem Vorschmiedegine konvexe Kopffläche 2, die radialen Flanken 3 der Klaue 1 stehen senkrecht auf der Klauengrundfläche 4. Eine gestrichelte Linie k, welche parallel zur Klauengrundfläche 4 verläuft, verdeutlicht das Aufmaß der Kopffläche 2 vor dem Kaltkalibrieren.
• Figur 2 zeigt die in Figur 1 dargestellte Klaue nach dem Kaltkalibrieren. Die.Kopffläche 2 verläuft parallel zur Klauengrundfläche 4. In radialer Richtung ist die Klaue 1 beidseitig durch hinterstellte Kupplungsflächen 5 begrenzt, wobei der die Hinterstellung definierende Winkel mit d bezeichnet ist.
• Figur 3 zeigt einen Ausschnitt aus einem Kupplungskörper mit Klauen 1, die axial gegenüber einem Ringteil 6 vorspringen. Die Formgebung des Kupplungskörper entspricht seiner Zwischenform nach dem Vorschmieden, wobei das Aufmaß der Kopffläche mit strichlierten Linien angegeben ist.
• Figur 4 zeigt einen in Umfangsrichtung geführten schnitt durch eine Klaue 7, mit seitlichen Schlupffasen 8 zwischen Kopffläche 2 und Kupplungsfläche 5, die durch das Vorschmieden erzeugte Vorform ist mit strichlierten Linien angedeutet.
• Figur 5 zeigt die Draufsicht eines-Kupplungskörpers für eine Schaltkupplung einss Motorradgetriebes, etwa in natürlicher Größe. Der Kupplungskörper 9 besitzt etwa die Form einer Scheibe, welche vier in Umfangsrichtung erstreckte kreisbogenförmige Taschen 10 aufweist, in welche die Klauen eines Gegenstücks beim Herstellen einer Antriebsverbindung eingreifen. Die seitlichen Kupplungsflächen 5 der Taschen sind in gleicher Weise hinterschnitten, wie die Kupplungsflächen der (nicht dargestellten) Klauen.

Several exemplary embodiments of the invention are described below with reference to the drawing. It shows

• 1 shows a circumferential section through a claw after the forging
• FIG. 2 shows a section in the circumferential direction through the claw according to FIG. 1 after calibration,
• FIG. 3 shows a perspective view of the claw according to FIG. 1.
• FIG. 4 shows a section in the circumferential direction through a claw with slip fiber in the region of the edges formed between the head surface and the coupling surface.
• Figure 5 is a plan view of a clutch spur gear with four pockets and
• 6 shows the development of a partial section in the circumferential direction according to VI-VI of FIG. 5.

• According to FIG. 1, a claw 1 has a convex head surface 2 after the forging process, the radial flanks 3 of the claw 1 are perpendicular to the claw base surface 4. A dashed line k, which runs parallel to the claw base surface 4, illustrates the dimensions of the head surface 2 before the cold calibration.
• Figure 2 shows the claw shown in Figure 1 after cold calibration. The head surface 2 runs parallel to the claw base surface 4. In the radial direction, the claw 1 is delimited on both sides by coupling surfaces 5, the angle defining the positioning being designated by d.
• FIG. 3 shows a section of a coupling body with claws 1 which project axially relative to a ring part 6. The shape of the coupling body corresponds to its intermediate shape after pre-forging, the dimensions of the head surface being indicated by dashed lines.
• Figure 4 shows a circumferential section through a claw 7, with side slip chamfers 8 between the head surface 2 and coupling surface 5, the preform produced by the forging is indicated by dashed lines.
• FIG. 5 shows the top view of a clutch body for a clutch of a motorcycle transmission, approximately in natural size. The coupling body 9 has approximately the shape of a disk which has four circular-arc-shaped pockets 10, in which the claws of a counterpart engage when a drive connection is made. The lateral coupling surfaces 5 of the pockets are undercut in the same way as the coupling surfaces of the claws (not shown).

Claims (7)

1. A method for the forging of forgings with at least one coupling surface serving to transmit the force in cooperation with a counterpart, in particular claws or pockets having coupling parts or synchronizing parts with short teeth for manual transmissions, in which the parts are first forged and then cold calibrated, thereby featured,
that during pre-forging, coupling faces (5) parallel to the direction of impact with oversize that adjoins the adjoining head faces (2) are produced at least in the edge area adjacent to the respective common edge (3) of these faces, and that the head faces (2) are forged accurately during cold calibration, in such a way that each finished coupling surface (5) runs obliquely towards the head surface (2) widened by the calibration. 2. The method according to claim 1,
.characterized,
that the forgings during cold calibration are supported by the die only between two die surfaces which are parallel to the direction of impact and run transversely to the coupling surfaces (2). 3. The method according to claim 1 or 2,
characterized,
that the widening of the head surfaces (2) is limited by supporting surfaces of the die arranged at a corresponding distance from the preform. 4. The method according to any one of claims 1-3,
characterized,
that the measurement volume per coupling surface (5) is dimensioned according to its selected rear position (d) or inclined position relative to the head surface (2). 5. The method according to any one of claims 1-4,
characterized,
that the distribution of the allowance along a section running transversely to the coupling surface has a maximum in or near the coupling surface. 6. The method according to claim 5,
characterized,
that the distribution of the oversize describes a linear or concave decreasing course in the edge region of the head surface (2) adjoining the coupling surface (5). 7. claw coupling, produced by a method according to one or more of claims 1-6,
characterized,
that the flanks of the claws or pockets (9) of the two interacting coupling parts correspond to the coupling surfaces (5), with each or every second flank being placed behind.

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