ZA200604293B

ZA200604293B - Cold forming method for producing ball journals

Info

Publication number: ZA200604293B
Application number: ZA200604293A
Authority: ZA
Inventors: Kruse Jochen; Rosenberger Klaus
Original assignee: Zahnradfabrik Friedrichshafen
Priority date: 2003-11-27
Filing date: 2004-11-25
Publication date: 2007-11-28
Also published as: US20090038157A1; RU2006122631A; DE502004003316D1; SI1689556T1; ES2281845T3; CN1886229A; WO2005051594A2; WO2005051594A3; PL1689556T3; JP2007512961A; BRPI0416946A; KR20060123162A; EP1689556B1; ATE357307T1; EP1689556A2; DE10356111B4; DE10356111A1; RU2353498C2

Abstract

A cold forming process for manufacturing ball pivots with a ball area, a cone area and a thread area for installation in ball and socket joints by cold forming is presented, in which a ball pivot blank (1) with a shaped cone area (3) and cylindrical areas for the thread (2) and the ball (5) is manufactured at first from a bar-shaped semifinished bar stock by extrusion. The extrusion operation is followed by the forming of the ball area as another manufacturing step by means of a rolling processes. At the same time, the thread area can be formed in its final shape. Thus, the ball pivot is manufactured as a whole by cold forming only and it makes it possible to significantly increase the production output per unit of time compared to the processes known from the state of the art. At the same time, it is possible to use less expensive grades of steel, because sufficient fatigue strength of the ball pivot can be guaranteed by the cold forming.

Description

. 1566 PCT . 1 -

Cold forming method for producing ball journals a

Description

The invention relates to a cold forming method for producing ball journals com prising a ball region, a conical region and a threaded reg ion for installation in ball-and-socket joints.

For producing ball journals which are intended for installation in ball-and-socket joints, in principle cutting as well as non-cutting production methods are used.

Duri ng the forming by cutting large quantities of waste material occur, which must be disposed of. This furthermore has the disadvantage tha t the waste material first of all had to be acquired as a semi-finished product. A further disadvantage is that on present-day machine tools no cycle times are possible that lie consider- ably above a quantity of 10 units per minute. With the forming by cutting it is moreover necessary to process at least the threaded region by a rolling operation in order to provide the required thread in this region. The cycle times of such rollimg operations also lie in the abovementioned range of approximately 10 units per minute.

Altesrnatively to the cutting method it is known in the state of the art to produce ball journals by cold- or hot-pressing. The pressing operati on can take place in the direction of the longitudinal axis of the ball journal, in which case normally burr

1566 PCT occurs at one end of the ball journal blank, or horizontally in a two-part pressing die, in which case burr occurs around the entire die-formed blank. Acco rding to the prior art the pressing burrs are removed by a cutting finishing operation.

Accordingly, also with a non-cutting forming of the bail journal cost- ard time- intensive operatio ns are required for finishing the ball journal.

Also known from the state of the art are ball journals that consist of several parts, but no further details of their manufacture will be given here as the method according to the invention relates to the producing of one-piece ball jourmals.

The object of the present invention is to disclose a method for producing ball journals comprising a ball region, a conical region and a threaded region, with which the quantity per time unit for the production of individual ball jourreals can be increased considerably, so that the necessary production costs can be reduced significartly.

This object is addressed by the technical teachings disclosed in claim 1.

Essential according to the invention is that first of all, from a rod-shaped semi- finished bar material, a ball journal blank is produced by extrusion comprising a formed conical region and cylindrical regions for the thread and ball, wherein the extrusion rim is arranged at the free end of the region provided for forming the ball, and subsequently in a further production step by means of a triggered synchronised rollimg method the ball region is formed by rolling shaped parts.

By the novel combination of the described production steps it is possible to dispense with any shaping by cutting. The cycle times for the extrusion operation as well as for the subsequent rolling are for the extrusion approx. 100 units per minute and for the rolling approximately 50 units per minute.

AMENDED SHEET DATED 26 NOVEMBER 2007

N 1566 PCT - 3 . .

The rolling method may be a so-called flat cheek rolling method or a round cheek rolling method.

By the combination of the aforementioned production steps it is possible, therefore, to produce a considerably greater quantity of ball journals than is known from the state of thes art. This is, among others, the result of the fact that with the flat-cheek rolling or with the round-cheek rolling several function regions, e.g. the ball region, the conical region and the threaded region, can be produced simultaneously by one tool . In addition the disposing of any waste material, as required with the cutting preoduction method, falls away of course.

Since the investment costs for a rolling machine are about the same as for the acquisition of a lathe, also with respect to the initial investment costs for producing ball journals, cost advantages are obtained by the new solution according to the invention as a result of the higher output of work-pieces.

With the method according to the invention it has furthermore proved advantageous when during the flat-cheek or round-cheek rolling first a neck region is formed between the conical region and the cylindrical region provided for forming the ball. Strength measurements on ball journals produced by the new method carried out by way of example have shown that by forming a neck region by rolling, the fatigue strength of the ball journals can be increased by up to 50%.

By increasing the fatigue strength by the neck rolling, it becomes possible to use steels with micro-alloying e lements, the purchase costs of which are considerably lower than those of the annealing steels required for heat treatments. The cold forming of C-Mn steels provided with micro-alloying elements suffices especially in the neck region for obtaining an adequate strength. The increase in the

] 1566 PCT 4 ) . strength values can be utilised to reduce the sizes of such ball journals at identical external stresses.

In addition, as a further special embodiment of the method according to the invention it has proved expedient when prior to the rolling operation a pocket-hole shaped recess is formed into the free end of the ball journal blank provided for forming the ball region. The pocket-hole recess can be formed by the top die used for the extrusion. T he recess facilitates the forming of the cylindrical portion of the ball journal provided for forming the ball region to its final spherical shape.

Furthermore the recess constitutes, of course, a saving of material. If after producing the ball regio n of the ball journal the pocket-hole recess, the so-called pole hole, is still present, then the recess can be used, for example, for accom- modating sensors or as a grease reservoir. In this connection also the closing of the pole hole by, for example, a plastic cover is of course possible.

In the following the ope rations during the flat-cheek rolling as well as the round- cheek rolling will be explained in more detail with reference to the attached drawings, wherein:

Figure 1 shows the side view of a ball journal blank prior to forming the ball region by means of the triggered synchronised rolling method,

Figure 2 is a diagrammatic top view onto a flat-cheek rolling device with a ball journal arranged therein during the rolling operation,

Figure 3A is a sectional view through the flat-cheek rolling device at the start of the rolling operation along the sectional line A-A of Figure 2,

. 1566 PCT . 5 ) : . [

Figure 3B is a sectional view through the flat-cheek rolling device at the start of the rolling operation along the sect ional line B-B of Figure 2,

Figure 3C is a sectional view through the flat-eheek rolling device at the start of the rolling operation along the sectional line C-C of Figure 2,

Figure 4 is a diagrammatic sectional view through a round-cheek rolling device with a ball journal blank arranged t herein,

Figure 5 is a top view onto the round-cheek rolling device of Figure 4,

Figure 6 is a perspective view of another variant of a round-cheek rolling device with a ball journal blank arranged therein,

Figure 7 is a diagrammatic view through a round-cheek rolling device with ball journal blank arranged therein, and

Figure 8 is atop view onto the round-cheel< rolling device of Fig. 7.

The ball journal blank illustrated in Figure 1 is produced by means of an extrusion process and essentially comprises several part regions of different spatial shapes arranged behind one another in the longitudinal direction of the ball journal. After the extrusion the various regions are to be formed to their final shape by means of the combination of method characteristics according to the invention, wherein on completion of the cold forming method according to the invention a ball journal shape as illustrated in Figure 3C is obtained.

} 1566 P CT . 6

The b all journal blank with the overall reference numeral 1 comprises, therefore, according to the illustration of Figure 1, a cylindrical region 2 arrarmged at one free end o f the ball journal blank 1, where on completion of the ball journal a thread will be located for fastening the ball journal to a machine or motorcar component.

Imme diately adjoining the cylindrical region 2 is a conical region 3. After the extrusion operation this conical region in principle already has its Finished dimen- sions, wherein in a subsequent operation a smoothing of the coni cal surface can be carried out. The conical region 3 is in turn followed by a further cylindrical region 4, which comprises the so-called neck section of the finished ball journal and into which, as shown in Figure 3C, an indentation is formed as transition to the adjoining region. As the final region of the ball journal blank 1 another cylindrical region 5 is arranged at its second free end, which in the transition to the cylindrical region 4 may comprise a semi-circular section 6. Alternatively to the semi-circular shape of section 6, also a conical transition to the cylindrical region 4 is possible here. Within the framework of the method according to the invention the last cylindrical region 5 is to be given a spherical shaape so that the ball h ead 18 illustrated in Figure 3C is obtained at the top free end of the ball journal. To facilitate the forming process, at the top free end an essentially cylindrically shaped recess 7 in the form of a pocket hole can be provided in the cylindrical region 5. This can take place within the framework o f the preceding : extruding operation and is ensured by means of the top die of the extrusion machine. The two extrusion die halves are shaped here in sucha a way that the separating line between the two halves lies in the region of the separating line 8, so thatthe die separating plane and any burr accumulations asso ciated therewith lie ou tside the cylindrical region 5 that has to be given a spheric al shape.

For the final forming of the ball journal blank 1 by means of a triggered syn- chronised rolling method by rolling down formed bodies, in principle three

. 1566 PCT . 7 possible rolling method variants are available. These three different methods will be explained in the following with reference to the illustrations.

One rolling method variant is the so-called flat-cheek rolling method. With this rolling method the rolling device in question comprises two flat cheeks 9 and 10, one of the flat cheeks, in the present illustration of Figure 2 indicated by 9, being a stationary flat cheek, while the opposite flat cheek 10 executes a translatory movement in the direction of the arrow P. Between the flat cheeks 9 and 10 is the roll nip 11 with an inlet region 12 and an outlet region 13. At the beginning of the flat-cheek rolling method the ball journal blank 1 is introduced into the roll nip 11 in the area of the sectional lime A-A, at which time the movable rolling cheek 10 assumes a position indicated by the dot-dash lines. By moving the movable flat cheek 10 and the resultant ro ling-down movement of the ball journal blank 2 the latter is transported through the roll nip 11. The forming of the ball journal as well as of the adjoining neck region takes place during the moving of the ball journal blank inside the roll nip 11. F or the purpose of the forming the flat cheeks 9 and have at the beginning of the actual rolling operation an outline according to

Figure 3A, which essentially corresponds to that of the ball journal blank 1. To this end Figure 3A shows the bal | journal blank 1 together with the flat cheek 9. The outline profile of the other flak cheek 10, not illustrated in Figures 3A, 3B and 3C, corresponds in principle to th at of the flat cheek 9 illustrated in said Figures. The profile of the flat cheeks 9 and 10 on the side surfaces 14 and 15 facing one another changes continuously up to the finished outline contour in he outlet region 13 corresponding to Figure 3C of the finished ball journal. Due to the translatory movement of the movable flat cheek 10, the starting profile of the flat cheek 9 illustrated in Figure 3A is of course in the case of the flat cheek 10 in the illustration of Figure 2 positioned in the bottom region in the area of point C, whereas the end profile of the flat cheek 9 illustrated in Figure 3C is in the case of the flat cheek 10 positioned at point A. The flat cheeks 9 and 10 are, therefore, symmetrical in the area of the sectional line B-B in Figure 2. From the changing of

‘ : 1566 PCT 8 I “ . the outline contours of the side surfaces 14 and 15 respectively of the flat cheeks 9 and 10 it can be noted that the operation of forming the spherical head as well as the neck region takes place in successive phases. Afte r introducing the ball journal blank 1 into the roll nip 11, first of all the neck part 16 is formed, during which at the same time a forming-in takes place in the head area 17 of the cylindrical region 5, which is facilitated by the recess 7 at th e free end of the ball journal blank 1 explained with reference to Figure 1. The forming of the neck section 16 by means of the rolling method leads to a considerable increase in strength in this region, seeing that in contrast to producing the neck section by cutting, no removal of material takes place, but in said region the material of the ball journal blank is just reshaped. in the further course of the rolling operation between the area of the sectional lines B-B and C-C the final forming of the ball head 18 to its final shape takes place, wherein on completion of the rolling operation the movable flat cheek 10 assumes the dotted position lll in Figure 2. At the same ti me, during the entire rolling operation a smoothing of the surface of the conical region 3 of the ball journal blank 1 can take place by means of a suitable shaping of the contour of the side surfaces 14 and 15 respectively of the flat cheeks 9 and 10. In addition, also the required thread in the cylindrical region 2 at thes free end of the ball journal blank 1 can, of course, be provided. Accordingly by a suitable shaping of the flat cheeks, during a translatory movement of the mowable fiat cheek 10, a correct shaping of the entire ball journal possibly takes place without any cutting away of material as required during a forming by cutting and without any disposal of material being required. In addition the rolling operation on the whole leads to an increase in strength of the surface, so that subsequent hardening measures can be dispensed with.

The described course of the rolling operation for producing the finished ball journal can, alternatively to the flat-cheek rolling method, also be carried out by devices the rolling cheeks of which have a curved shape. In the following a first

. 1566 PCT : 9 a form of the round-cheek rolling will be explained with reference to Figures 4 and 5. The round-cheek rolling device according to the illustration of Figures 4 and 5 comprises two roller cylinders 21 and 22 arranged next to one another on parallel axes of rotation 19 and 20. Between the two roller cylinders, the same as with the flat-cheek rolling, there is a roll nip 11, into which the ball journal blank 1 is introduced. Both roller cylinders 21 and 22 have on their outer surface the negative shape of the outline of the ball journal blank 1 and in another angle region, which can be arranged on the periphery offset by approx. 270° the outlines of the finished ball journal. The rolling operation takes place by the roller cylinders 21 and 22 turning in opposite directions, during which the ball journal itself remains stationary in the roll nip 11.

The illustration of Figures 4 and 5 shows a position of the roller cylinders immediately after introduc ing the ball journal blank 1 into the roll nip 11. In the sectional view of Figure 4 it can also be noted that on the periphery of the roller cylinders 21 and 22, offset by 180° in the area of points P1 and P2, a profile is formed, which essentially corresponds to that of Figure 3B of the flat cheek 9 illustrated there. In the area of points P3 and P4 respectively, on the periphery of the roller cylinders 21 and 22, an outline contour is formed in the peripheral surface corresponding to tihat of Figure 3C with the flat cheek 9 illustrated there.

The rolling operation of the ball journal blank to its final shape takes place, therefore, during a 270° revolution of the roller cylinders 21 and 22. Also with the so-called round-cheek roll ing method a simultaneous smoothing of the conical region 3 of the ball jourreal blank 1 can of course take place, and also the providing of the required thread in the cylindrical region 2.

As further variant of a so-called round-cheek rolling method, devices can be used with which one rolling chee=k is formed by a roller cylinder 23, similar to that of the first variant described abowe, while the second rolling cheek is formed by a hollow

L

1566 PCT 10 - roller cylinder 24 which concentrically encloses the roll er cylinder 23. Analogously to the alternative rolling methods described above, between the roller cylinder 23 and the hollow roller cylinder 24 surrounding it a roll nip 11 is formed, as shown in

Figure 6, into which the ball journal blank 1 to be processed is introduced. On the inside surface of the hollow roller cylinder 24 as well a's on the outside surface of the roller cylinder 23 the changeable shape of the outline structure of the to be rolled ball journal blank 1 is provided. The actual rolling operation takes place by the roller cylinder 23 and hollow roller cylinder 24 turning in opposite directions, wherein the relative movement of the roller cylinder 23 and the hollow roller cylinder 24 are decisive for the shaping. Itis, therefores also possible that only one of the cylinders 23 or 24 turns while the other is stationary. Also with this method the ball head as well as the neck section and possibly in addition the conical region as well as the threaded region of the finished ball journal can be formed.

Accordingly also this other round-cheek rolling variant offers the corresponding advantages with respect to high production quantities as well as an increase in strength compared to the methods known from the state of the art.

The forming of the ball journal can also take place with a known round-cheek rolling device, as illustrated by way of example in Figures 7 and 8. Here the processing of the ball journal blank 1 takes place by a rolling btween the symmetrical roller cylinders 25 and 26 rotating around their axes of rotation. The ball journal blank 1 is arranged between the roller cylinders 25, 26 in the roll nip 11. The ball journal blank 1 receives its spherical shape from the correspondingly shaped peripheral geometry of the roller cylinders 25, 26. In the surface 27 and 28 respectively of the roller cylinders 25, 26 a negativ e contour is formed, which can also form the cylindrically shaped region 5 of the ball journal blank 1. In this case the rotating roller cylinders 25, 26 are first moved towards the ball journal 1.

This movement can take place, for example, by means of a hydraulic cylinder.

* . 1566 PCT 11 -

List of reference numerals 1. Ball journal blank 2. Cylindrical region 3. Conical region 4. Cylindrical region 5. Cylindrical region 6. Semi-circular partial region 7. Recess 8. Separating line 9. Flat cheek 10. Flat cheek 11. Roll nip 12. Inlet region 13. Outlet region 14. Side surface 15. Side surface 16. Neck section 17. Head region 18. Ball head 19. Axis of rotation 20. Axis of rotation 21. Roller cylinder 22. Roller cylinder 24. Hollow roller cylinder 25. Roller cylinder 26. Roller cylinder 27. Inside/outside surface

Claims

1566 PCT Cold forrming method for producing ball joumals Claims

1. Cold forming method for producing ball journals comprising a ball region, a conical region and a threaded region for installation in ball-and-socket joints, with which first of all from a rod-shaped semi-finished bar material a ball journal blank is produced by extrusion comprising a formed conical region and cylindrical regions for the thread and ball, wherein the extrusion rim is arranged at the free end of the region provided for forming the ball, and with which subsequently in at least one further production step by means of a rolling method the ball region is formed by rolling shaped parts.

2. Method according to claim 1, characterised in that the rolling method is a triggered synchronised rolling method.

3. Method according to claim 1 or 2, characterised in that simultaneously with the forming of the ball region to its final shape the threaded region is formed. AMEND ED SHEET DATED 26 NOVEMBER 2007

1666 PCT

4. Method according to any one of the claims 1 to 3, characterised in that simultaneously with the forming of the ball region te its final shape the conical region formed during the prior extrusion proce ss is smoothed.

5. Method according to any one of the claims 1 to 4, characterised in that prior to the rolling operation a pocket-hole shaped recess open at the end is formed into the free end of the ball journa | blank provided for forming the ball region.

6. Method according to claim 5, characterised in that the recess is formed by the top die used during the extrusion.

7. Method according to any one of the claims 1 to 6, characterised in that during the rolling first a cylindrical neck region is formed between the conical region and the cylindrical region provided for foeming the ball.

8. Method according to any one of the claims 1 to 7, characterised in that as rolling method a flat-cheek rolling method is used.

9. Method according to any one of the claims 1 to 7, characterised in that as rolling method a round-cheek rolling method is usead. AMENDED SHEET DATED 26 NOVEMBER 20 07

1566 PCT

10. Method according to claim 9, characterised in that the round-cheek rollers are formed by roller cylinders arranged on parallel axes of rotation, the outside contour of which in each instance comprises half a negative form of the outline of the ball jousmal to be rolled, wherein the ball journal during the rolling process is aranged in a roll nip between the roller cylinders.

11. Method according to claim 9 or 10, characterised in that the round-cheek rollers are formed on the one harad by a roller cylinder and on the other by a hollow cylinder which concentrically encloses the roller cylinder, wherein the outside contour of the rolle=r cylinder and the inside contour of the hollow cylinder each form half a ne gative form, changeable over the outer and inner periphery respectively, of the outline form of the ball journal to be roiled and wherein the ball journal during the rolling process is arranged in the roll nip between the outside and inside contour of the roller cylinder and hollow rolier cyli nder. AMENDED SHEET DATED 26 NOVEMBER 2007