WO2022214355A1

WO2022214355A1 - Method for machining a ball hub for a constant-velocity ball joint and device for machining a ball hub

Info

Publication number: WO2022214355A1
Application number: PCT/EP2022/058262
Authority: WO
Inventors: René FEUERSTEIN; Thomas Keppler-Ott
Original assignee: Thyssenkrupp Presta Ag; Thyssenkrupp Ag
Priority date: 2021-04-07
Filing date: 2022-03-29
Publication date: 2022-10-13
Also published as: DE102021203430B4; DE102021203430A1

Abstract

The present invention relates to a method for machining a ball hub (1) for a constant-velocity ball joint, which ball hub has on its outer circumference pairs (12a/b, 13a/b, 14a/b) of ball tracks (12a, 12b, 13a, 13b, 14a, 14b) which are located radially opposite one another relative to a centre axis (M), have a ball track profile, and which for each pair of tracks (12a/b, 13a/b, 14a/b) run parallel to a track plane parallel to the centre axis (M) with a ball track radius (Kr) about a ball track axis (12K, 13K, 14K), the ball tracks (12a, 12b, 13a, 13b, 14a, 14b) being machined by means of a tool assembly (2) of a machining device (2) having at least one tool (41, 42). In order to allow a reduced manufacturing expenditure, the following steps may be carried out according to the invention: - rotating the ball hub (1) about an axis of rotation (R) relative to the tool assembly (4), the centre axis (M) being oriented perpendicular to the axis of rotation (R), and a ball track axis (12K, 13K, 14K) is oriented along the axis of rotation (R), - advancing the tool (41, 42), which is stationary relative to the rotation of the ball (1) radially in the direction towards the axis of rotation (R), and machining the ball tracks (12a, 12b, 13a, 13b, 14a, 14b) until a predetermined ball track radius (Kr) is achieved.

Description

Process for machining a ball boss for a ball constant velocity joint and apparatus for machining a ball boss

State of the art

The invention relates to a method for machining a ball hub for a ball constant velocity joint, which has on its outer circumference pairs of tracks of ball tracks which are radially opposite one another with respect to a central axis and have a ball track profile, which for each pair of tracks is parallel to a track plane which is parallel to the central axis and has a ball track radius run around a ball track axis, the ball tracks being machined mechanically by means of a tool arrangement of a machining device having at least one tool. A device for carrying out the method is also subject matter of the invention.

Rzeppa type constant velocity joints have an inner joint part in the form of a ball boss located in an outer joint part. Torque-transmitting balls are arranged between ball tracks arranged on the outside of the ball hub and distributed over the circumference and corresponding ball tracks arranged radially opposite on the inside in the outer joint part.

In each case two ball tracks forming a track pair are formed radially in pairs opposite one another on the outside of the ball hub with respect to the central axis, which is identical to the axis of a shaft part connected to the ball hub. In the generic design, several, for example three, track pairs are arranged distributed evenly over the circumference. The ball tracks of each pair of tracks extend in an arc around a ball track axis parallel to a track plane oriented along the central axis.

The axis of the ball track of each pair of tracks is thus perpendicular to the associated track level and intersects the central axis perpendicularly at a center point.

The ball tracks are designed in the form of grooves with a concave groove cross section formed radially from the outside into the ball hub, which forms the open ball track cross section, which is equivalently referred to as a positive ball track profile. The profile of the ball track is adapted to the rolling of the ball, for example as a circular or gothic profile. The cross section of the ball track thus extends in sections toroidally around the ball track axis. For the dimensionally accurate formation of the ball tracks, machining of the ball hub by machining is known in the prior art, as is described, for example, in DE 11 2004001 175 B1 or WO 2018/072835 A1. The ball hub is spatially oriented and fixed in a receptacle, and the ball tracks are machined using a tool assembly. In order to produce the ball tracks or to machine them to size, the tool, for example a rotating grinding head, is moved along the arcuate course of the respective ball track relative to the ball hub. In WO 2018/072835 A1, for example, it is proposed to fix the ball hub in terms of rotation about the central axis by means of a first tool, and by means of a second tool that is guided in space in an arcuate manner relative thereto and has a rotating milling or grinding head, one ball track in each case to edit.

Although the tools that follow the spatial trajectory of the ball tracks in the known methods allow in principle a sufficiently precise machining of the ball tracks, the effort required to guide the tool and the relative orientation of the ball hub with the required narrow dimensional tolerances is relatively high.

In view of the problems explained above, it is an object of the present invention to specify a method which enables reduced production costs.

Presentation of the invention

According to the invention, this object is achieved by the steering system having the features of claim 1. Advantageous developments result from the dependent claims.

In a method for machining a ball hub for a constant velocity ball joint, which has on its outer circumference pairs of tracks of ball tracks which are radially opposite one another with respect to a central axis and have a ball track profile, which for each pair of tracks run parallel to a track plane which is parallel to the central axis and have a ball track radius about a ball track axis, wherein the ball tracks are mechanically processed by means of a tool arrangement of a processing device having at least one tool, the following steps are provided according to the invention: rotating the ball hub about an axis of rotation relative to the tool assembly, with the central axis being oriented perpendicular to the axis of rotation, and a ball track axis being oriented along the axis of rotation,

- Advancing the rotation of the holder fixed tool radially in the direction of the axis of rotation, and editing the ball tracks until a predetermined ball track radius is reached.

The method according to the invention starts with a prefabricated ball hub. This is a partially machined pre-product, for example a soft calibrated formed part, for example an extruded part preferably made of steel, or a pre-machined milled part or the like. The ball tracks are oversized, i.e. the dimensions are outside the permissible tolerance ranges, and the surface of the track cannot be used as a rolling track for the balls. If necessary, the prefabricated ball hub can also be hardened by thermal processes, at least in the area of the ball tracks, for example by case hardening. Dimensional deviations and impairments of the surfaces can also occur during hardening, which necessitate post-processing or fine-tuning.

By means of the method according to the invention, the ball tracks can be reworked or finely machined in order to produce the required dimensional accuracy and surface properties.

The machining by the method according to the invention provides that the prefabricated ball hub is rotated in each case about a ball track axis which is correlated with a pair of tracks and which is therefore identical to a rotation axis of the machining. As a result, the two ball tracks of the pair of tracks revolve on an orbit in the ball track radius around the ball track axis, with the ball track profile running along a toroidal surface enclosing the ball track axis, the surfaces of the two ball tracks of the track pair being formed by peripheral sections of this toroidal surface. If a tool with regard to the rotation of the ball hub is approached radially from the outside of the axis of rotation by radial feed, it comes into mechanical contact with the two ball tracks of the track pair one after the other with each complete revolution of the ball hub. In this case, the speed of the ball track surfaces can be achieved by the circumferential speed of the ball track surfaces by means of the tool which is stationary relative thereto, a mechanical, preferably machining, machining of the concave ball track surfaces in the circumferential direction. The tool can be fed with a feed movement, preferably with a linear movement radially in the direction of the axis of rotation, ie it can be advanced, with the mechanical processing in the area of both ball tracks of the track pair removing material mechanically, preferably by cutting, until the two ball tracks at the finished machined ball hub have reached the final dimension specified for the radius of the ball track.

One advantage of processing in pairs according to the method according to the invention is that both ball tracks can be processed to size in one operation. The ball hub only has to be clamped once and only one tool is required, which has to be positioned relative to the ball hub for machining. This quasi-simultaneous or parallel machining of both ball tracks of a pair of ball tracks reduces the manufacturing effort compared to the prior art, in which only a single ball track is ever engaged in machining. Another important advantage is that the tool in the machining operation is aligned practically identically to the two ball tracks circling around it due to its alignment with the axis of rotation. As a result, the two ball tracks in the pair of ball tracks have the identical final dimension within the tightest of tolerances. In the prior art, compliance with such narrow tolerance specifications could only be achieved with significantly greater effort in the individual machining.

To implement the method, it can be provided that the ball hub is received in a holder that can be driven in rotation about the axis of rotation, with the central axis being aligned perpendicularly to the axis of rotation, and a ball track axis being aligned along the axis of rotation, and the holder for rotating the ball hub around the Rotation axis is rotated. The holder has a receiving or clamping device in which the ball hub can be releasably fixed relative to the tool for machining. The ball hub can be adjusted relative to the holder for processing all pairs of tracks, so that the axes of the ball tracks of each pair of tracks can be aligned with the axis of rotation in subsequent processing steps. The holder is preferably connected to a motor drive device of a rotary drive and can be driven by it to rotate about the axis of rotation. For efficient machining, it is advantageous that the ball hub can be accommodated on the holder in a simple, precise and secure manner, which can in principle be implemented with clamping devices of simple design. All that is required for the mechanical processing is a rotating drive of the holder, which can be implemented with high concentricity and with little outlay on machinery, so that the required accuracy of the track pairs can be guaranteed without any problems. The rotary drive preferably has a controllable electric drive that enables the rotational speed to be adjusted in order to adapt the peripheral speed of the circling ball track surfaces optimally to the mechanical processing, for example to the grinding or cutting speed of the tool used.

For mechanical processing, the holder can be positioned in a tool arrangement which surrounds the axis of rotation and has at least one tool which is directed radially towards the axis of rotation. In the tool arrangement, which is preferably rotationally symmetrical to the axis of rotation, the tool can be brought into mechanical processing contact with the rotating ball tracks. At least radially in NEN aligned against the axis of rotation tool is directed with its processing side radially from the outside against the ball tracks of the track pair whose ball track axis is aligned identically to the axis of rotation.

The tool can preferably have a negative ball track profile on its machining side directed against the ball tracks. The negative ball track profile is designed as a tool profile which has a machining contour which is transverse to the circumferential direction and which is adapted to the ball track cross-section, ie the positive ball track profile. Corresponding to the circumferential concave groove shape of this positive ball track profile, the tool profile has a convex negative ball track profile projecting radially against the axis of rotation, ie a convex machining contour. This can have a convex cutting arrangement, which can preferably be realized by a grinding wheel which is convex in shape accordingly to the negative ball track profile. A tool with a tool profile that is preferably adapted to the entire ball track profile enables machining of the entire ball track surfaces of a pair of tracks in one operation, with the tool only having to be guided in the radial direction relative to the ball hub. As a result, greater accuracy can advantageously be achieved with less effort than with the tools that are moved along trajectories in the prior art.

The tool can preferably be designed in the shape of a circle or a segment of a circle, adapted to the predetermined ball track profile, or have a Gothic or other shaped tool profile. Such different tool profiles can be made available with relatively little effort and enable flexible and efficient production.

A high level of accuracy and low surface roughness can be achieved with relatively little manufacturing effort, in particular by means of a grinding wheel. After positioning relative to the tool arrangement, the ball tracks of the pair of tracks are preferably aligned relative to the tool. The path plane perpendicular to the axis of rotation of the pair of paths intended for machining is positioned relative to the tool in such a way that the convex tool profile can be adjusted congruently with the specified concave ball track cross-section simply by radial feed. According to the invention, this can be achieved by positioning the ball hub and the tool in the same track plane.

For mechanical purposes, the tool can be moved radially inwards—preferably after alignment—preferably with a linear feed with its convex tool profile ahead in a feed direction until it comes into machining engagement with the ball tracks. The feed in the feed direction is continued until the required final dimension is reached.

The tool is preferably displaced by means of a motorized feed device, also referred to as an infeed device, which has a feed drive designed for displacing the tool. The feed device can preferably be controlled automatically, so that the tool is automatically advanced in the feed direction until it reaches the specified final dimension.

It is advantageous that the rotation speed is adapted to the feed speed of the feed. This ensures optimal processing. For this purpose, the rotary drive and the feed device can preferably be connected to a control device, which enables automated control in order to comply with specified processing parameters.

After the specified final dimension has been reached, the processing of a pair of tracks is complete. The rotation of the holder is then stopped and the tool is retracted radially in the direction away from the axis of rotation, ie counter to the feed direction, in order to release the ball hub.

If not all ball tracks of the ball hub have been processed using the tool after the completed processing of a track pair, the ball hub is rotated about its central axis relative to the holder until the ball track axis is still one unprocessed track pair is aligned in the manner described above relative to the tool. The mechanical processing then takes place in the manner described above.

If all of the ball tracks of the ball hub have been processed using the tool, the processing of the ball hub is terminated using the method according to the invention. The holder is removed from the tool and the finished ball hub is removed from the holder.

Provision is preferably made for the tool to extend over a circumferential section. The tool has a tool segment which extends around the axis of rotation over an angular section corresponding to the circumferential section. This ensures that during machining, when the tool is advanced radially into the machining engagement with the ball tracks, the machining engagement takes place over an enlarged peripheral section over which the ball track moves relative to the tool during mechanical machining. The tool can preferably have a segment-shaped toroidal grinding body which, with its negative, convex tool contour, extends in segments over a defined circumferential or angular section. Due to the fact that the mechanical processing, for example by the sliding contact with the grinding body, can take place over a relatively long path according to the path length of the tool segment, relatively fast material removal and high processing accuracy can advantageously be achieved.

In order to enable more effective machining, it can preferably be provided that the tool arrangement extends over a predominant portion of the circumference, i.e. includes more than 50% of the circumference.

In a particularly preferred development, it can be provided that the tool is designed to essentially completely enclose the axis of rotation, ie it is designed in the form of a closed ring and extends over 100% of the circumference, or over at least 85% of the circumference. As used herein, the term substantially complete is intended to encompass the range from 85% to 100%. For this purpose, the tool can preferably comprise a rotating toroidal grinding body. The advantages of a tool that is completely closed in the form of a ring are a high machining speed, high accuracy of the end dimension of the ball tracks and a long service life of the tool due to the relatively large machining contact area with the ball tracks. A preferred embodiment of the invention can provide that the tool arrangement has at least two tools distributed over the circumference. These tools, which are also referred to as sub-tools, tool elements or tool segments, together form the tool and comprise, for example, two or more segment-shaped, toroidal grinding wheels, which in their entirety extend over a circumferential section of the axis of rotation, preferably over a predominant one Circumferential section of > 50%, and particularly preferably can be closed in a ring shape to enclose 100% of the full circumference, at least 85%.

The tools are preferably distributed symmetrically around the axis of rotation. For example, two tools can be provided, which are arranged radially opposite each other with respect to the axis of rotation, and each preferably extend over about 50% of the circumference, so that they form tool halves that are arranged practically mirror-symmetrically to the axis of rotation, each of which is continuous over 50% of the circumference have toroidal convex tool contour. The tool halves can be designed essentially identically. Alternatively, three or more toroidal tool segments arranged symmetrically to the axis of rotation can also be provided.

Because the tool halves or segments are moved toward one another, a tool arrangement that is closed in the form of a ring can be formed. The negative, convex tool contours engage radially in the ball tracks in such a way that the ball hub is optimally aligned relative to the tool without further measures. To remove the ball hub, the tool segments are moved radially outwards against the direction of feed.

In the method according to the invention, the tools are moved toward one another when the tool is advanced with respect to the axis of rotation, preferably advanced symmetrically radially toward the axis of rotation in the direction of advance. As a result, the individual tool parts come into machining contact symmetrically and essentially simultaneously with the ball tracks of a pair of tracks. The forces that occur during processing can be safely absorbed by the symmetrical arrangement, which means that the processing accuracy can be increased even further without additional effort.

The tool or tools are preferably advanced in the direction of advance by a motorized feed device and pulled back to release the finished ball hub. Provision can preferably be made for the tools to have corresponding stop surfaces which can be contacted with one another. These are arranged in such a way that they come into contact with one another when the two or more tools reach the end position of the feed corresponding to the final dimension. The method according to the invention can then provide for the advancement to take place until corresponding stop surfaces on the tools come into contact with one another in the advancement direction. The stop surfaces can preferably be arranged parallel to the axis of rotation, so that they provide a stop in the feed direction. Machining using the method according to the invention can be massively simplified by simply advancing the tools towards one another until they hit one another. Then the final dimensions of the ball tracks can be reliably generated without complex control or monitoring, and the reproduction accuracy is particularly high for a large number of ball tracks.

Provision is preferably made for the machining to be carried out by grinding. Alternatively, however, a milling operation or a combination of grinding and milling can also be carried out. Several steps are also conceivable, with different processing methods being used.

In the method according to the invention, it can be provided that the machining is carried out at least twice with different tools. For this purpose, the ball hub, which is preferably rotating in a holder as described above, can be successively brought into machining contact with two differently designed tools, which can differ, for example, with regard to the achievable accuracy and surface quality. For example, abrasives with different grit sizes can be used in order to first produce the specified dimensional accuracy with a coarser grit in fine machining, and then with a finer grit for finishing or superfinishing to produce the highest surface qualities.

In a device for machining a ball hub for a constant velocity ball joint, which has on its outer circumference pairs of tracks of ball tracks that are radially opposite one another with respect to a central axis, which for each pair of tracks run parallel to a track plane parallel to the central axis with a ball track radius around a ball track axis, comprising a holder for the ball hub and a tool arrangement with at least one tool that can be moved relative to the holder, the invention provides that the holder can be driven in rotation about an axis of rotation by a rotary drive, the ball hub in the holder with its central axis perpendicular to the axis of rotation and can be received with a ball track axis aligned along the axis of rotation, and the tool arrangement has a tool that is stationary at least with respect to the rotation of the holder.

In the device, the method according to the invention can be carried out as described above. All of the features explained in connection with the method can be implemented structurally with the device.

The holder is preferably connected to an electric motor rotary drive, which is an integral part of the device according to the invention, for rotating the drive about the axis of rotation.

The tool is preferably connected to an electromotive feed device. By means of the feed device, which is part of the device according to the invention, the tool can be controlled for processing in the feed direction radially inwardly ge conditions the ball tracks are advanced, and in the opposite direction to release the ball hub.

The rotary drive and/or the feed device can preferably be connected to an electrical control device. As a result, the rotational speed, the feed path and/or the feed speed can be specified and, if necessary, automatically matched to one another.

Provision can preferably be made for the tool arrangement to extend over a circumferential section with respect to the axis of rotation. The peripheral section is preferably more than 50%, particularly preferably 90-100%, in which case the tool arrangement can preferably be designed in the form of a closed ring around the axis of rotation.

The tool arrangement can be toroidal as described above. The tool profile can have a machining cross section that is circular at least in sections, for example a semicircular cross section that protrudes convexly inward. Alternatively, a cross-section deviating from a circular shape can be realized, for example a Gothic-ogival, parabolic or other cross-section. The cross section can be symmetrical with respect to a mirror plane perpendicular to the axis of the ball track, or asymmetrical. Provision can preferably be made for the tool arrangement to have at least two tools distributed over the circumference. As described above, the sub-segments can be designed as tool elements or segments, which are preferably arranged symmetrically with respect to the axis of rotation.

In principle, it is also conceivable and possible to provide a tool made up of several sub-segments, which are correspondingly pushed towards the center from several directions for machining.

It can be advantageous for the tools, or the sub-segments of the tool, to have corresponding stop surfaces that can be contacted with one another.

Provision can preferably be made for a ball hub in the holder to be adjustable in rotation about the central axis. By rotating around the central axis, a ball track axis corresponding to a pair of tracks can be aligned identically on the axis of rotation. The ball hub can preferably be releasably fixed to the holder in the aligned orientation, for example by means of a locking or clamping device.

Preferably, the holder can have a clamping spigot which extends transversely to the axis of rotation and on which the ball hub can be clamped.

The ball hub preferably has a central fastening opening which is coaxial with the central axis. This fastening opening is designed for non-rotatably attaching the ball hub to a cardan shaft, specifically a part of a steering shaft connected to the ball hub. To carry out the method according to the invention, the ball hub can preferably be clamped with the fastening opening on the holder for machining. For example, the holder can have a clamping pin that can be releasably braced in the fastening opening.

The holder can preferably have an adjusting device which is designed to rotate a ball hub that is held there about its central axis. The adjustment device enables a rotary adjustment of the ball hub, so that one ball track axis can be aligned with the rotation axis of the holder in order to process the associated ball tracks. The adjusting device can be motor-driven in order to adjust the ball hub after the finished processing of one track pair for the processing of the next track pair that is still to be processed. Description of the drawings

Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. Show in detail:

Figure 1 shows a ball hub according to the invention in a schematic perspective

Depiction,

Figure 2 shows a raw part or starting part of a ball hub according to the invention in a schematic perspective view,

3 shows a holder of a device according to the invention in a schematic perspective view, FIG. 4 shows the holder according to FIG. 3 with a raw part of a ball hub according to FIG. 2 accommodated therein,

FIG. 5 shows a tool arrangement of a device according to the invention in a schematic perspective representation,

6 shows a device according to the invention comprising the tool arrangement according to FIG. 4 together with the holder and a blank of a ball hub accommodated therein according to FIG. 4 in a first step of the method according to the invention,

FIG. 7 shows the device according to the invention according to FIG. 6 in a second step of the method according to the invention,

FIG. 8 shows the device according to the invention according to FIG. 7 in a third step of the method according to the invention,

9 shows the device according to the invention according to FIG. 8 in a fourth step of the method according to the invention, FIG. 10 shows the device according to the invention according to FIG. 9 in a fifth step of the method according to the invention, FIG. 11 shows the device according to the invention according to FIG. 10 in a sixth step of the method according to the invention,

FIG. 12 shows the device according to the invention according to FIG. 11 in a seventh step of the method according to the invention,

13 shows the device according to the invention according to FIG. 12 in an eighth step of the method according to the invention, FIG. 14 shows the device according to the invention according to FIG. 11 in a ninth step of the method according to the invention,

FIG. 15 shows a ball hub machined according to the method according to the steps in FIGS. 6 to 14 in a schematic perspective representation,

FIG. 16 shows a longitudinal section through the device including the ball hub according to FIG. 7 in a first rotational state of the holder,

FIG. 17 shows a longitudinal section through the device as in FIG. 16 in a second rotational state of the holder,

FIG. 18 shows a cross section through the device according to FIG. 16,

19 shows a longitudinal section through a tool according to one of FIGS. 5 to 14 in a longitudinal sectional view as in FIG. 16,

FIG. 20 shows a longitudinal section through a tool in a further embodiment.

Embodiments of the invention

In the various figures, the same parts are always ver see with the same reference numerals and are therefore usually named or mentioned only once.

1 shows a ball hub 1 according to the invention. This has a coaxial to its central axis M continuous opening 11, which forms a fastening opening for non-rotatable attachment to a shaft part, not shown. Spherical tracks 12a, 12b, 13a, 13b, 14a, 14b, which have a ball track profile that is concavely introduced radially from the outside and is rounded in an arc shape. Two ball tracks 12a and 12b, as well as 13a and 13b, as well as 14a and 14b are located radially opposite each other in pairs with respect to the central axis M, and each form the track pair 12a/b, formed from ball tracks 12a and 12b, as well as the track pair 13a/b, formed from ball tracks 13a and 13b, and the pair of tracks 14a/b, formed from ball tracks 14a and 14b. Adjacent ball tracks 12a, 12b, 13a, 13b, 14a, 14b on the circumference are each offset by an angle a with respect to the central axis M, ie by 60° in each case for the three pairs of tracks in the embodiment shown.

Each of the track pairs 12a/b, 13a/b, 14a/b has a ball track axis 12K, 13K, 14K.

The ball tracks 12a, 12b, 13a, 13b, 14a, 14b run in a defined, predetermined ball track radius Kr in toroidal pairs for each track pair 12a/b, 13a/b, 14a/b around the assigned ball track axis 12K, 13K, 14K, the respective stand perpendicular to the central axis M. The ball track radius Kr designates the radial distance from the central axis M, for example measured at the lowest point of the concave ball track profile.

In the figures 6 to 14 a device 2 according to the invention is shown in different views. This has a holder 3 and a tool arrangement 4 with two tools 41, 42 (partial tools).

FIG. 2 shows an initial part 100 or blank of a ball hub 1 prior to machining according to the present invention. Such blanks can be cold forged or hot forged. The opening 11 can already be finished, for example already in the forging process.

The holder 3 is shown separately in FIG. It has an axis of rotation R about which it can be driven in rotation by a motorized rotary drive (not shown).

The holder 3 has a fork-shaped receptacle 31, in which a ball hub 1 or the output part 100 can be accommodated, so that the central axis M is perpendicular to the axis of rotation R and one of the ball track axes 12K, 13K, or 14K is identical and coaxial with the axis of rotation R are aligned, as is shown in FIG. 4 as an example for the ball track axis 12K of the pair of tracks 12a/b. In the respectively aligned position, the ball hub 1 can be releasably clamped to the holder 3 in the receptacle 31 . The tool arrangement 4 shown in FIG. 5 has two tools 41 and 42, which are also referred to as partial tools and are arranged symmetrically to the axis of rotation R. Each of the tools 41, 42 has a toroidal, convex in cross-section, radially inwardly projecting tool contour 43, which is also referred to as the machining contour 43 be. The tool contour 43 can have a convex cutting edge arrangement, which can preferably be implemented by a grinding wheel which is convex in shape in accordance with the negative ball track profile and can be designed in the same way for both tools 41 and 42 .

In the example shown, the tools 41, 42 each form tool halves, each of which has a convex tool contour 43 that extends over essentially 50%, i.e. half of the circumference. Substantially means here an angular range of 165 angular degrees to 180 angular degrees of the circumference. The tools 41, 42 have corresponding stop surfaces 44 lying opposite one another with respect to a parting plane parallel to the axis of rotation R. While Figure 4 shows the open state of the tool arrangement 4, in which the stop surfaces 44 are at a distance from one another, the tools 41, 42 can be moved toward one another to adjust the machining position by means of a feed device, not shown, preferably a motor, as shown in Figure 7 indicated by the arrows until the partial tools 41, 42 are brought to a distance from one another which feeds the tool contours 43 to the desired diameter for the respective pairs of paths 12a/b, 13a/b, 14a/b. For example, the stop surfaces 44 can serve for this purpose, which are brought into contact with one another. In this closed processing position, which is assumed in the following FIGS. 7, 10 and 13 as well as in FIGS. 16 and 18, the two processing contours 43 essentially completely enclose the axis of rotation R, i.e. extend over its, preferably entire, circumference .

The machining contours 43 are arranged symmetrically with respect to a central point C lying on the axis of rotation R. By definition, this central point C is at the height of the vertex of the convex tool profile 43.

In a first step of the method according to the invention, the holder 3 with an initial part 100 of the ball hub received therein as shown in FIG. 4 is inserted between the tools 41, 42 located in the open state according to FIG. 4, as shown in FIG. The ball track axis 12K assigned to the pair of tracks 12,a/b is aligned identically to the axis of rotation R, and the central axis M runs perpendicularly through the Central point C. As a result, the machining contours 43 are aligned with the ball tracks 12a and 12b of the pair of tracks 12a/b for machining.

In the next step, as indicated by the curved arrow in Figure 7, the holder 3 is set in rotation about the axis of rotation R, and the two tools 41 and 42 are moved towards one another in a feed direction perpendicular to the axis of rotation R, as in Fi gur 6 indicated by the straight arrows, moved together to a defined infeed position that corresponds to the desired diameter for the ball tracks. A travel distance, at most until the tools 41 and 42 come into contact with the stop surfaces 44 against one another, i.e. strike against one another. As a result, the tool 4 is closed and the ball tracks 12a and 12b are moved circumferentially along the tool contours 43 during the rotation of the ball hub 1 generated by the holder 3 in the circumferential direction in machining contact over the circumference.

In the area of the tool profile 43, the tools 41 and 42 preferably have grinding bodies by 45. Alternatively, it would be conceivable and possible to attach teeth for a milling operation, such as milling teeth or such cutting tools. In a first step, rough machining could be carried out with a tool with milling teeth, and in a second step, the finish machining could be carried out with a tool with grinding bodies.

Both ball tracks 12a and 12b of the pair of tracks 12a/b are machined over the entire circumference, and when the stop surfaces 44 come into contact, both ball tracks 12a and 12b have the identical ball track radius Kr, which is predetermined by the inner diameter of the negative toroidal shape of the tool profile 43, within the smallest of tolerances .

In the next step, as shown in FIG. 8, the rotation of the holder 3 is stopped and the tools 41 and 42 are moved apart against the feed direction, as indicated by the two arrows, so that the tool 4 is open.

The partially machined output part 100 of the ball hub is then rotated by means of an adjusting device 5 about its central axis M relative to the holder 3, namely by an angle a, corresponding to the angular offset between the adjacent ball tracks 12a and 13a or 12b and 13b. As a result, the finished ball tracks 12a and 12b are pivoted out of the machining engagement of the tool profile 43, and the ball tracks 13a and 13b are aligned such that the ball track axis 13K assigned to them is aligned identically to the axis of rotation R. This is now that Pair of ball tracks 13a/b aligned relative to the tool profile 43, as previously in FIGS. 6 and 7, the pair of ball tracks 12a/b.

After alignment has taken place, as indicated in FIG. 9, the adjustment device 5 can be withdrawn in the opposite direction to the adjustment direction of FIG. 8, as indicated by the arrow.

In the next step, which is illustrated in FIG. 10, the holder 3 is rotated about the axis of rotation R analogously to the procedure described for FIG. 7, and the two tools 41 and 42 are moved towards one another in the feed direction until the predetermined position is reached is, in order to represent the desired diameter, at most until the stop surfaces 44 strike against one another. The ball tracks 13a and 13b are machined to size like the ball tracks 12a and 12b above.

As shown in FIGS. 11, 12 and 13, the steps shown in FIGS. 8, 9 and 10 are then repeated again in order to further rotate the output part 100 of the ball hub relative to the holder 3 in order to rotate the remaining ball tracks 14a and 14b to machine the ball tracks 12a, 12b, 13a, 13b as before.

After the final processing of the ball tracks 14a and 14b, the tools 41 and

41 is moved apart as shown in FIG. 14 and the tool 4 is thereby opened. The holder 3 is removed from the tool 4 and the ball hub 1 shown in FIG.

FIG. 16 shows a longitudinal section along the axis of rotation R during machining according to FIG

42 are in machining engagement with the ball tracks 12a and 12b of the pair of tracks 12a/b.

The tool profiles 43 are formed on the cross-hatched grinding wheels 45 from. These can have a circular or semi-circular cross-section, as in the embodiment shown in FIG. Alternatively--as in the embodiment shown in FIG. 20--a cross-section deviating from the circular shape can also be realized, for example in the shape of a parabolic or Gothic pointed arch. FIG. 16 clearly shows that the tool profiles 43 are spaced radially in the ball track radius Kr from the axis of rotation R in their apex pointing radially inwards, and thus from the set ball track axis 12K of the set pair of tracks 12a/b. In the same view as in FIG. 16, FIG. 17 shows the holder 3 in a rotational position rotated further by 90°.

FIG. 18 shows a cross section through the device 2 at the height of the central point C. The tool profiles 43 enclosing the ball hub 1 over the entire circumference with respect to the axis of rotation R can be seen.

Reference List

1 ball hub

11 hole (mounting hole)

12a, 12b, 13a, 13b, 14a, 14b ball track 12a/b, 13a/b, 14a/b pair of tracks

12K, 13K, 14K ball track axis 100 blank ball hub in different production stages 2 fixture

3 holder 31 recording

4 tool arrangement

41, 42 tool (part tool)

43 tool profile

44 Stop surface 45 Grinding wheel

5 adjustment device

M central axis

R axis of rotation

C central point (centre)

Kr ball track radius

Claims

PATENT CLAIMS

1. Method for machining a ball hub (1) for a constant velocity ball joint, which has on its outer circumference pairs of tracks (12a/b, 13a/b, 14a/b) of ball tracks (12a, 12b, 13a , 13b, 14a, 14b) with a ball track profile, which for each track pair (12a/b, 13a/b, 14a/b) parallel to a track plane parallel to the central axis (M) with a ball track radius (Kr) about a ball track axis ( 12K, 13K 14K), the ball tracks (12a, 12b, 13a, 13b, 14a, 14b) being mechanically machined by means of a tool arrangement (2) of a machining device (2) having at least one tool (41, 42), characterized by the Steps:

Rotating the ball hub (1) about an axis of rotation (R) relative to the tool arrangement (4), the center axis (M) being perpendicular to the axis of rotation (R) and a ball track axis (12K, 13K, 14K) along the axis of rotation ( R ) is aligned,

- Advancing the relation to the rotation of the ball hub (1) stationary tool (41, 42) radially in the direction of the axis of rotation (R), and machining the ball tracks (12a, 12b, 13a, 13b, 14a, 14b) until a predetermined ball track radius (Kr) is reached.

2. The method according to claim 1, characterized in that the ball hub (1) is received in a holder (3) that can be driven in rotation about the axis of rotation (R), the central axis (M) being aligned perpendicularly to the axis of rotation (R), and a ball track axis (12K, 13K, 14K) is aligned along the axis of rotation (R ), and the holder (3) is rotated about the axis of rotation (R ) to rotate the ball hub (1).

3. The method according to any one of the preceding claims, characterized in that the holder (3) is positioned in a tool arrangement (4) surrounding the axis of rotation (R) and having at least one tool (41, 42) which is positioned radially against the axis of rotation (R ) is directed.

4. The method according to claim 1, characterized in that the tool arrangement (4) extends over a peripheral section.

5. The method according to any one of the preceding claims, characterized in that the tool arrangement (4) has at least two tools (41, 42) distributed over the circumference with respect to the axis of rotation (R).

6. The method according to any one of the preceding claims 4 or 5, characterized in that the tools (41 42) are moved towards one another when being advanced with respect to the axis of rotation (R).

7. The method according to any one of the preceding claims 4 to 6, characterized in that the advancement takes place until corresponding stop surfaces (44) on the tools (41, 42) come into contact with one another in the feed direction.

8. The method according to any one of the preceding claims, characterized in that the processing is carried out by grinding.

9. The method according to any one of the preceding claims, characterized in that the machining is carried out at least twice with different tools (4) in order to produce a defined surface structure of the ball tracks.

10. Device for machining a ball hub (1) for a constant velocity ball joint, which has on its outer circumference pairs of tracks (12a/b, 13a/b, 14a/b) of ball tracks (12a, 12b, 13a , 13b, 14a, 14b), which for each track pair (12a/b, 13a/b, 14a/b) are parallel to a track plane parallel to the central axis (M) and have a ball track radius (Kr) about a ball track axis (12K, 13K , 14K), comprising a holder (3) for the ball hub (1) and a tool arrangement (4) with at least one tool (41, 42) that can be moved relative to the holder (3), characterized in that the holder (3) can be driven to rotate about an axis of rotation (R) by a rotary drive, the ball hub (1) in the holder (3) with its central axis (M) perpendicular to the axis of rotation (R) and with a ball track axis (12K, 13K, 14K) along the axis of rotation (R) is aligned receivable, and the tool assembly (4) at least with respect to Rotation of the holder (3) has a stationary tool (41, 42) which can be pushed radially in the direction of the axis of rotation (R).

11. The device according to claim 10, characterized in that the tool (41,

42) is connected to a feed device.

12. Device according to claim 10 or 11, characterized in that the tool arrangement (4) extends over a peripheral section.

13. Device according to one of claims 10 to 12, characterized in that the tool arrangement (4) is toroidal.

14. Device according to one of claims 10 to 13, characterized in that the tool arrangement (4) has at least two tools (41, 42) distributed over the circumference.

15. Device according to claim 13 and 14, characterized in that the tools (41, 42) have corresponding stop faces (44) which can be contacted against one another.

16. Device according to one of claims 10 to 15, characterized in that a ball hub (1) in the holder (3) is rotatably adjustable about the central axis (M).

17. Device according to one of claims 10 to 16, characterized in that the rotary drive and/or the feed device are connected to a control device.