EP1165272A1

EP1165272A1 - Method of producing homokinetic joints

Info

Publication number: EP1165272A1
Application number: EP00912491A
Authority: EP
Inventors: Manfred Hirschvogel; Karl Schuster; Peter Kettner; Walter Pischel; Michael Dahme; Hubert Nägele
Original assignee: Hirschvogel Umformtechnik GmbH
Current assignee: Hirschvogel Umformtechnik GmbH
Priority date: 1999-04-08
Filing date: 2000-02-21
Publication date: 2002-01-02
Anticipated expiration: 2020-02-21
Also published as: EP1165272B1; DE50006499D1; DE19915879A1; WO2000061317A1; US6516647B1; JP2003527244A; ATE267063T1

Abstract

The invention relates to a method of manufacturing the outer part of a constant velocity joint, the outer part having in the finished condition a hollow chamber with a cylinder-shaped inner wall, in which there are provided ball raceways (1c) which run obliquely of the cylinder axis and are inclined with respect to one another. First, a wobble press die (4) is axially introduced into a goblet-shaped preliminary workpiece (1a) for the outer part having a conically developing inner and outer wall and pre-formed ball raceways (1c) in the inner wall. The preliminary workpiece (1a) is pressed (drawing process) by means of the wobble press die (4), sitting on the floor of the hollow chamber, through an opening in an outer die (2), so that a drawing process is carried out in which the preliminary workpiece (1a) is so cold formed that the inner wall of the hollow chamber is given a cylindrical shape. Thereafter the outer die (2) and the wobble press die (4), having a truncated cone-shaped outer contour, and having elevations (4a) on its outer side corresponding to the ball raceways (1c) and having a lesser diameter than the cylindrical hollow chamber of the drawn preliminary workpiece (1a), are set into a wobbling circular movement relative to one another such that the elevations (4a) of the wobble press die (4) move over the pre-formed ball raceways (1c) on the inner wall of the hollow chamber in a pressing and material shaping manner. Thereafter the wobble press die (4) is axially drawn out of the preliminary workpiece (1a) and finally, the finished joint outer part is ejected from the outer die (2).

Description

Method of manufacturing constant velocity joints

The present invention relates to a method for producing outer parts of cross groove constant velocity joints according to the preamble of claim 1.

With constant velocity joints of this type, e.g. in the publication “Universal Joint and Driveshaft Design Manual, Advances in Engineering Series No. 7 "of the Society of Automotive Engineers, Inc., the outer part has a cylindrical inner contour, elongated recesses being made in it. They form ball raceways for the balls arranged in a cage of the inner part. The cylindrical inner contour of the outer joint part naturally has no undercut However, a separation of the outer part and the inner part of the constant velocity joint is not easily possible since the ball raceways are not axially parallel and also inclined to one another.

A method for producing outer joint parts of the type just described is described in the patent EP 0 270 538. A pre-workpiece has the shape of a goblet diverging towards the open end, the inside of which the ball races are already preformed. By pressing the pre-workpiece into a cylindrical opening of an external tool, the pre-workpiece is deformed so that it finally has a cylindrical inner contour. The required force is exerted via a press ram which is formed from several segments which are movable relative to one another. These have elevations that are inclined towards one another. Before the pre-workpiece is pressed, an expansion body is axially inserted into a cavity located in the press ram and holds the segments in their operating position. When the pre-workpiece is drawn in and deformed, the elevations of the segments exert pressure on the inside of the pre-workpiece and have a cold-deforming effect on the inclined ball raceways.

To remove the press ram from the joint outer part machined in this way, the expansion body is first removed from the press ram. As a result, the segments pivot in the direction of the central axis of the entire arrangement and thus disengage from the ball raceways. In a second step, the segments can then be removed from the finished workpiece. Another method for the production of outer parts of constant velocity joints is known from German patent DE 196 37 839, which is however limited to the production of so-called Rzeppa constant velocity joints. In contrast to the Cross Groove outer joint parts, the ball raceways in this type of joint run in the axial direction. An axial separation of the outer and inner part of the constant velocity joint is prevented here in that either the ball raceways and / or the cage guide surface have an axial undercut. In this known method, the pre-workpiece is also subjected to an operation by cold working. This is done by a wobble press die which is curved in different convex segments, which is first immersed in the cavity of the pre-workpiece which is mounted and fixed in an external tool. Due to the different curvatures of the segments, the wobble stamp has on its surface rib-shaped contours that are used to machine the ball raceways.

The wobble press punch is then set in a wobble movement, whereby it is rolled over the surfaces of the pre-workpiece to be deformed in several circular rotations. The wobble point of this movement is just below the underside of the pre-workpiece. Only a small area of the ball raceways to be deformed is deformed during the wobble pressing. Once the desired deformations have been achieved in the pre-workpiece, the wobble process is ended and the wobble die is removed again. It is advantageous in this known method that a one-part wobble stamp can be used, which is cheaper to produce than a multi-part segment stamp and ensures greater precision in the production of outer joint parts.

The invention has for its object to use the wobble method known for the production of Rzeppa constant velocity joints with a one-part wobble press ram also for the production of cross groove constant velocity joints.

The object is achieved with the method specified in claim 1, namely using a wobble press die with the features according to claim 8. The wobble press die according to the invention has - in a projection directed perpendicular to its axis - straight projection edges and is particularly simple and inexpensive to produce.

The invention is explained in more detail below with reference to the figures in the accompanying drawing. Show it: Figure 1 shows the arrangements of the pre-workpiece, the outer tool and the wobble press stempeis at the beginning of a method for manufacturing the outer part of a cross groove joint.

2a the drawing of the pre-workpiece into the external tool;

Figure 2b shows in section the arrangement of the wobble press stempeis in the pre-workpiece during the drawing.

3a shows the shaping of the pre-workpiece by the wobble die;

3b shows in section the arrangement of the wobble press stempeis in the pre-workpiece during the wobble pressing.

Fig. 4 is a finished cross groove outer joint part in supervision.

An embodiment of the method is first explained in more detail with reference to FIGS. 1 to 3b.

The preliminary workpiece 1, the upper part 1 a of which initially has the shape of a cup diverging towards the open end, is centered in a first step, which is shown in FIG. 1, in a downwardly narrowing, funnel-shaped opening 2a of the outer tool 2 of a wobble press Machine axis arranged. The ball raceways lc are already preformed on the inner wall of the upper part la. In the lower area, the preliminary workpiece 1 has in one piece a pin 1b running in the axial direction. For stabilization, this pin 1b is enclosed by a jacket 3 which can be displaced in the axial direction and on the upper edge of which the goblet-shaped upper part la of the preliminary workpiece 1 also rests. In order to avoid twisting of the pre-workpiece 1 during the subsequent wobble process, the pin 1b can have on its surface a toothing, not shown, which engages in a corresponding toothing of the jacket 3. It would also be conceivable that the pin 1b has a non-round shape when viewed in cross section.

A wobble press punch 4 is then placed centrally on the machine axis on the bottom of the upper part 1 a. This wobble press punch 4 is frustoconical in its lower region, with line-like elevations 4a corresponding to the ball raceways lc being arranged in one piece on its outside, which are inclined in the longitudinal direction with respect to the truncated axis of the wobble press stem 4. The funnel-shaped section 2a of the outer tool 2 is continued by a cylindrical second section 2b, the shape of which corresponds to the outer contour of the finished upper part la of the outer joint part. By exerting an axial pressure on the wobble punch 4, the preliminary workpiece 1 is pressed downward, the cup-shaped upper part 1 a being drawn into the cylindrical section 2 b of the external tool 2 by the funnel-shaped section 2 a and the pin 1 b and the jacket 3 surrounding it being pushed further down become. The side walls of the upper part la so that they run parallel to the machine axis at the end of the retraction and the inner wall of the cavity of the upper part la thus becomes cylindrical, as can be seen in Fig. 2a. The shape of the wobble press stempeis 4 including its elevations 4a is chosen so that it does not touch the side walls of the upper part la. Its arrangement in the pre-workpiece 1 during drawing is shown in section in Fig. 2b.

Then the wobble press punch 4 and the pre-workpiece 1 are set in a wobbling circular movement relative to one another, the wobble angle α, i.e. the angle between the machine axis and the axis of the wobble punch 4 is adjustable. If the wobble angle α is greater than 0 °, the two axes intersect at the wobble point 5, which is located above the outer tool 2 in the example shown. The wobble stamp 4 rolls with its outer contour on the cylindrical inner wall of the cavity. It is designed in such a way that the outer part machining the upper part la of the preliminary workpiece 1 and also the corresponding elevation 4a run parallel to the machine axis and to the side walls of the upper part la which have already been erected. This is achieved by the selected truncated cone shape, taking into account the parameters of the wobble movement. The relative arrangement between the side walls of the upper part la, the wobble press punch 4 and the elevations 4a is shown in a side view in Fig. 3a and in section in Fig. 3b.

With the embodiment just described, it is achieved that the wobble punch 4 always processes the preliminary workpiece 1 over the entire height of the side wall of the upper part 1 a during the exchange. This allows both an extremely precise and a very effective processing, so that with this method, a close-to-contour shape can be achieved on the inside of the cup-shaped upper part la, which would not be accessible by pulling in and pressing alone. In particular, there is no machining post-processing of the preliminary workpiece 1, which means that the time required the production and also the manufacturing costs of an outer joint part can be significantly reduced.

After the wobble machining process has ended, the wobble press punch 4 is pulled out of the finished workpiece 1. As with the drawing in of the pre-workpiece 1, the wobble punch 4 is aligned parallel to the machine axis, i.e. α is equal to 0 °. Accordingly, when designing the wobble punch 4, it must be taken into account that its outer contour, including the line-like elevations 4a located on the surface of the frustoconical section, must not have a larger diameter than the cavity of the finished joint outer part.

Finally, the jacket 3 is pushed up again, so that the finished workpiece 1 can be easily removed or ejected from the funnel-shaped opening 2a of the outer tool 2. The outer part of a cross groove joint produced in this way is shown in a top view in FIG. 4.

The shape of the wobble die proposed here is characterized in particular by the fact that the greatest possible contact between the wobble die and the workpiece is achieved, which enables a very effective machining of the workpiece. Furthermore, a wobble press stamp of this shape is not only cheaper and easier to manufacture, but also with lower error tolerances than the segment or expansion stamp known from the manufacturing process for external parts of a Rzeppa constant velocity joint.

It should also be noted that various types of wobble presses can be used in the method described above. The most common wobble presses are classified into several types according to their tool movements.

In the type 1 wobble press, the outer tool 2 with the workpiece 1 inserted therein executes a driven rotational movement about the machine axis. The wobble press die 4 rotates synchronously with the rotational movement of the outer tool 2 about the wobble axis inclined by the wobble angle α. A translatory movement, which corresponds to a lifting movement during the forming process, is likewise initiated hydraulically by the wobble punch 4. This translational movement is carried out in order to keep the wobble punch 4 at a suitable height with respect to the workpiece 1 at all times. If the rotary movement of the wobble punch 4 is not driven, ie it rotates freely with the workpiece 1 around the wobble axis, this is called the wobble press type 1A. If, on the other hand, the rotational movement of the wobble punch 4 is additionally driven, this wobble press is called type 1B.

The type 2 wobble press has a fixed outer tool 2 which cannot carry out any translational or rotational movements. The workpiece 1 is stationary during the entire machining process. For this purpose, the wobble ram 4 performs a total of three movements, a rotation about the wobble axis, a wobble movement about the machine axis, and a hydraulically driven lifting movement in the axial direction.

Type 3 wobble presses, on the other hand, are the most common type of wobble press. Here the hydraulically driven lifting movement takes place through a cylinder in the lower part of the machine. The translational movement is therefore carried out by the external tool. The wobble movement is initiated by the wobble press punch 4, outer tool 2 and workpiece 1 remain stationary with respect to the rotational movement.

In general, the wobble point 5 can also be mathematically infinitely far away in all of the above types, which leads to a rolling movement (wobble angle α = 0 °). This rolling movement thus represents an extreme case of a wobble movement.

Regardless of the type of wobble press used, it is only important for the method according to the invention that the outer tool 2 performs a wobbling circular movement relative to the wobble press die 4. How the individual movement components of the wobble movement are divided among the different tool parts of the wobble press used is basically irrelevant.

Claims

Expectations

1. A process for producing the outer part of a constant velocity joint, the finished part having a cavity with a cylindrical inner wall in which ball raceways (lc) which are inclined to the cylinder axis and are inclined with respect to one another are provided, with the following method steps: a) into a goblet-shaped pre-workpiece (la) for the outer part with a tapered inner and outer wall and preformed ball raceways (lc) in the inner wall, a wobble press ram (4) is inserted axially, b) the pre-workpiece (la) is stamped by means of the wobble press seated on the bottom of the cavity (4) pressed through an opening in an outer tool (2) so that a pulling-in process is carried out in which the front tool (la) is cold-deformed such that the inner wall of the cavity takes on a cylindrical shape, c) then the outer tool (2 ) and the wobble press having a frustoconical outer contour temple (4), the outside of the

Ball raceways (lc) have corresponding elevations (4a) and a smaller diameter than the cylindrical cavity of the inserted pre-workpiece (la), in a wobbling circular movement relative to one another, such that the elevations (4a) of the wobble press die (4) press and Moving the material over the preformed ball raceways (lc) on the inner wall of the cavity, d) then the wobble punch (4) is pulled axially out of the pre-workpiece (la) and e) finally the finished outer joint part is ejected from the outer tool (2).

2. The method according to claim 1, characterized in that in step c) the outer tool (2) with the workpiece inserted therein (1) executes a driven rotational movement about a machine axis and the wobble die (4) synchronously with the rotational movement of the outer tool (2) rotates about the wobble axis inclined by a wobble angle α.

3. The method according to claim 2, characterized in that that the rotary movement of the wobble press stempeis (4) is additionally driven.

4. The method according to claim 2 or 3, characterized in that α = 0 ° applies to the wobble angle.

5. The method according to claim 1, characterized in that in step c) the outer tool (2) is stationary and the wobble press punch (4) simultaneously performs a rotation about the wobble axis, a wobble movement about the machine axis and a lifting movement in the axial direction.

6. The method according to claim 1, characterized in that in step c) the outer tool (2) a lifting movement in the axial direction and the wobble press punch (4) simultaneously a rotation about the wobble axis and a wobble movement around the machine axis.

7. The method according to any one of claims 1 to 6, characterized in that the wobble point (5) of the wobble movement lies above the bottom of the cavity.

8. wobble press ram (4) for producing the outer part for a constant velocity joint, which has a cavity with a cylindrical inner wall in which inclined to the cylinder axis inclined ball raceways (lc) are provided, characterized in that it has a truncated cone-shaped outer contour arranged thereon has line-like elevations (4a) which run obliquely to the truncated cone axis and are inclined towards one another.