METHOD FOR PRODUCING AN ADJUSTABLE CAMSHAFT AND ADJUSTABLE CAMSHAFT

Abstract

An adjustable camshaft, which can be utilized in a motor vehicle, may include at least one fixed cam arranged rotationally fixed on at least one outer shaft segment and at least one adjusting cam arranged rotationally fixed to an inner shaft extending concentrically within the outer shaft segment. A method for producing such an adjustable camshaft may involve arranging an outer shaft segment on an inner shaft, generating a surface modification on a surface of the inner shaft to generate at least one arranging section, arranging a fixed cam on at least one section of the outer shaft segment, and arranging the adjusting cam on the arranging section of the inner shaft.

Claims

1.-10. (canceled)

11. A method for producing an adjustable camshaft of a motor vehicle, wherein the adjustable camshaft comprises a fixed cam disposed rotationally-fixed on an outer shaft segment and an adjusting cam disposed rotationally-fixed to an inner shaft extending concentrically within the outer shaft segment, the method comprising: positioning the outer shaft segment on the inner shaft; generating a surface modification on a surface of the inner shaft to generate an arranging section; positioning the fixed cam on a section of the outer shaft segment; and positioning the adjusting cam on the arranging section of the inner shaft.

12. The method of claim 11 wherein the generation of the surface modification occurs by way of a material elevation.

13. The method of claim 12 wherein the material elevation is generated by means of rolling.

14. The method of claim 11 wherein the fixed cam is a first fixed cam and the outer shaft segment is a first outer shaft segment, the method further comprising: positioning a second fixed cam adjacent to the adjusting cam; and positioning a second outer shaft segment on the inner shaft adjacent to the second fixed cam, wherein the second fixed cam is disposed on the second outer shaft segment.

15. The method of claim 11 further comprising connecting the fixed cam to the outer shaft segment in at least one of a force-fitted manner, a form-fitted manner, or a firmly bonded manner.

16. An adjustable camshaft of a motor vehicle, the adjustable camshaft comprising: a fixed cam disposed rotationally-fixed on an outer shaft segment; and an adjusting cam disposed rotationally-fixed to an inner shaft extending concentrically within the outer shaft segment, wherein the adjusting cam is at least force-fit connected to an arranging section of the inner shaft extending along a portion of the inner shaft, wherein the arranging section comprises a surface modification of a surface of the inner shaft.

17. The adjustable camshaft of claim 16 wherein the fixed cam is a first fixed cam, wherein the adjusting cam is disposed between the first fixed cam and a second fixed cam, wherein the first and second fixed cams are configured as single fixed cam elements or as a combined fixed cam element in a double-anvil design.

18. The adjustable camshaft of claim 16 wherein the outer shaft segment is a first outer shaft segment and the fixed cam is a first fixed cam, the adjustable camshaft further comprising a second outer shaft segment and a second fixed cam, wherein the second fixed cam is disposed rotationally-fixed on the second outer shaft segment.

19. The adjustable camshaft of claim 16 wherein the outer shaft segment comprises a distal shell surface region with an outer diameter that is smaller in dimension for at least a portion than an outer diameter of a remaining shell surface.

20. The adjustable camshaft of claim 16 wherein the adjusting cam and the fixed cam are disposed concentrically, wherein a through bore of the fixed cam is larger in dimension than a through bore of the adjusting cam.

21. An adjustable camshaft of a motor vehicle, the adjustable camshaft comprising: an inner shaft; an adjusting cam disposed on the inner shaft in a rotatably-fixed manner; a first outer shaft segment through which the inner shaft extends, wherein an end of the first outer shaft segment is adjacent to the adjusting cam; and a first fixed cam disposed on the first outer shaft segment in a rotatably-fixed manner, with the first fixed cam being adjacent to the adjusting cam.

22. The adjustable camshaft of claim 21 further comprising: a second outer shaft segment through which the inner shaft extends, wherein an end of the second outer shaft segment is adjacent to the adjusting cam such that the adjusting cam is disposed between the first and second outer shaft segments; and a second fixed cam disposed on the second outer shaft segment in a rotatably-fixed manner, with the second fixed cam being adjacent to the adjusting cam.

23. The adjustable camshaft of claim 22 wherein the first and second fixed cams are coupled together.

24. The adjustable camshaft of claim 23 wherein the adjusting cam is rotatably secured to the first and second fixed cams.

25. The adjustable camshaft of claim 21 wherein a diameter of a through bore of the first fixed cam is larger than a diameter of a through bore of the adjusting cam.

26. The adjustable camshaft of claim 21 wherein the adjusting cam is disposed on a material elevation of a surface of the inner shaft.

27. The adjustable camshaft of claim 21 wherein a thickness of the first outer shaft segment is reduced at a region of the first outer shaft segment that supports the first fixed cam.

28. The adjustable camshaft of claim 21 wherein a space exists between the first outer shaft segment and the adjusting cam.

29. The adjustable camshaft of claim 21 further comprising a limiting element disposed between the first outer shaft segment and the adjusting cam.

30. The adjustable camshaft of claim 22 wherein the adjusting cam and the first fixed cam are disposed concentrically.

Description

[0025] Embodiments of an adjustable camshaft according to the invention shall be explained more closely below by means of drawings. There are shown, each time schematically:

[0026] FIG. 1 in a perspective view, one embodiment of an adjustable camshaft,

[0027] FIG. 2 in a cross sectional side view, one embodiment of an adjustable camshaft according to the invention,

[0028] FIG. 3 in a cross sectional side view, an enlargement of cutout C, as shown in FIG. 2,

[0029] FIG. 4 in a perspective view, one embodiment of a cam pack of an adjustable camshaft according to the invention,

[0030] FIG. 5 in a cross sectional side view, one embodiment of a cam pack of a camshaft according to the invention,

[0031] FIG. 6 in a perspective view, a cutout from one embodiment of a camshaft according to the invention, showing a cam pack in a first arranging and

[0032] FIG. 7 in a perspective view the cutout shown in FIG. 7 for the camshaft according to the invention, in a second arranging of the cam pack.

[0033] Elements with the same function and mode of working are each time provided with the same reference numbers in FIGS. 1 to 7.

[0034] FIG. 1 shows in a perspective view one embodiment of an adjustable camshaft 1 according to the invention. The camshaft 1 comprises an inner shaft 2 as well as two outer shaft segments 3.1 and 3.2. Each outer shaft segment 3.1, 3.2 comprises at least one insertion region 10, being formed on a distal shell surface region 12. The fixed cams 7.1, 7.2, as shown in the exemplary embodiment of FIG. 1, are part of a cam pack 4.1, 4.2, it being conceivable for the camshaft 1 to have a plurality of such cam packs 4.1, 4.2. Each cam pack 4.1, 4.2 comprises a first fixed cam 7.1 and a second fixed cam 7.2, while between the two fixed cams, 7.1, 7.2 is arranged an adjusting cam. Advantageously, the inner shaft 2 extends through the through bore of the fixed cam B.sub.F, shown in FIG. 1, as well as through a through bore of the adjusting cam 8, not shown here, and through a corresponding through bore of the outer shaft segments 3.1 and 3.2, not shown here. The arrangement of the fixed cams 7.1, 7.2 and the adjusting cam 8 will be explained in particular in FIGS. 2 and 3.

[0035] FIGS. 2 and 3 show in a side view a cross sectional representation of one embodiment of the adjustable camshaft 1 according to the invention, FIG. 3 showing a magnified representation of the region C shown in FIG. 2. The section shown in FIG. 2 and of one embodiment of a camshaft 1 according to the invention comprises at least one cam pack 4, having a first fixed cam 7.1 and a second fixed cam 7.2 as well as an adjusting cam 8 arranged between the fixed cams 7.1 and 7.2. As can be seen from FIGS. 2 and 3, the through bore B.sub.F of the fixed cams 7.1 and 7.2 comprises a larger diameter than the through bore B.sub.V of the adjusting cam 8. In this way, it is advantageously possible to shove the cam pack 4 over the inner shaft 2 in a previously assembled condition during the assembly process for the adjustable camshaft 1, that is, a condition consisting of the two fixed cams 7.1 and 7.2 as well as the adjusting cam 8, while it would be conceivable for the inner shaft 2 to have already undergone a surface modification 20 and in particular a material elevation in the form of a rolling process. Based on the different diameters B.sub.V, B.sub.F of the bores of the fixed cams 7.1, 7.2 and adjusting cam 8, it is consequently assured that, especially when shoving the cam pack 4 onto the inner shaft 2, the first fixed cam 7.1 in particular is moved across the surface modification 20 and especially the material elevation 20 of the inner shaft 2, while during further movement of the cam pack 4 along the inner shaft 2 especially in the represented arrow direction P a contacting occurs between the surface of the through bore B.sub.V of the adjusting cam 8 and the material elevation 20 or the surface modification 20 of the inner shaft 2. This advantageously makes possible a frictional connection between the adjusting cam 8 and the inner shaft 2. It is conceivable that, after the mounting of the cam pack 4 on the inner shaft 2 and an arranging of the adjusting cam 8 at the arranging section 21 of the inner shaft 2, having the surface modification 20, advantageously a first outer shaft segment 3.1 and a second outer shaft segment 3.2 is shoved onto the inner shaft 2. It would also be conceivable for the first outer shaft segment 3.1 or 3.2, depending on the mounting direction, to have already been shoved onto the inner shaft 2 even before the placement of the cam pack 4.

[0036] As shown in FIGS. 2 and 3, the two outer shaft segments 3.1 and 3.2 advantageously have an insertion region 10 at both distal ends 12 and especially at the distal shell surface regions 12. This insertion region can be designed, for example, in the form of a shoulder, an insert bevel, a recess or slot, or a comparable form geometrically changing the shell surface. Advantageously, the outer diameter and especially the circumferential diameter of the outer shaft segments 3.1 and 3.2 comprises a smaller diameter in the region of the insertion regions 10, as indicated by the reference Da, than in the remaining region of the outer shaft segment, as indicated by the reference Db. The shape and size or geometrical configuration of the insertion regions 10 will not be limited to a particular geometrical shape in the context of the invention. Instead, it should be noted that the insertion regions 10 are designed such as to advantageously ensure a frictional connection between the fixed cams 7.1 and 7.2 and the respective outer shaft segments 3.1 and 3.2. Advantageously, the insertion region 10 of the respective outer shaft segment 3.1 or 3.2 also serves to prevent too far a placement or shoving of the cam pack 4 or the fixed cam 7.1 or 7.2 of the cam pack 4 onto the outer shaft segment 3.1 or 3.2.

[0037] In the context of the invention, it would also be conceivable to first shove or mount the outer shaft segment 3.1 or 3.2 onto the inner shaft 2, before a rolling of the inner shaft 2 and especially a surface treatment of the inner shaft 2 to generate a surface modification 20 takes place. Accordingly, it would be conceivable in the method for creating the camshaft according to the invention to first shove a first outer shaft segment 3.1 onto an inner shaft 2, which is accommodated for example in a chuck on an automatic cam placing machine. After this, the rolling of the inner shaft 2 could occur, in order to create a material elevation 20 on the surface of the inner shaft 2. In a further step, it would be conceivable to mount the cam pack 4, preferably with adjusting cam 8 threaded or arranged between the fixed cam 7.1, on the inner shaft 2, so that a frictional connection is produced between the first fixed cam 7.1 and the first outer shaft segment 3.1 as well as the adjusting cam 8 and the surface modification 20 or the material elevation 20 of the inner shaft 2. In a further, following step, it would be conceivable for a second outer shaft segment 3.2 to be shoved onto the inner shaft 2 and this far enough into the region of the cam pack 4 onto the inner shaft 2 so that in particular the insertion region 10 is force-fitted connected to the second fixed cam 7.2 of the cam pack 4. It is conceivable for a spacing to be present between the outer shaft segments 3.1 and 3.2 and the adjusting cam 8 in order to prevent a contacting of the outer shaft segments 3.1 or 3.2 with the adjusting cam 8. Advantageously, this will prevent friction during movement between outer shaft or outer shaft segments 3.1, 3.2 and inner shaft 2 and especially between fixed cams 7.1 and 7.2 and adjusting cam 8. Too far a shoving of the fixed cam 7.1, 7.2 onto the outer shaft segments 3.1, 3.2 is advantageously prevented by a limiting element 9, such as is shown for example in FIG. 3. This limiting element 9 is advantageously part of the insertion region 10 and comprises a wall which extends substantially—at least for a portion—in the radial direction.

[0038] FIG. 4 shows in perspective view an embodiment of a cam pack 4, being an element of the adjustable camshaft 1 according to the invention. The cam pack 4 comprises a first fixed cam 7.1 and a second fixed cam 7.2, enclosing the adjusting cam 8. The adjusting cam 8 advantageously comprises an identical cam contour to the fixed cams 7.1 and 7.2 and is mounted concentrically to the fixed cams 7.1 and 7.2, so that upon movement of the adjusting cam 8 relative to the fixed cams 7.1 and 7.2 a rotation of the cams 7.1, 7.2, 8 about a common axis of rotation D, as shown in particular in FIG. 4, can occur. Advantageously, the adjusting cam 8 is designed to be movable relative to the fixed cams 7.1 and 7.2. As shown in FIG. 4, the through bore B.sub.F of the fixed cam 7.1 or 7.2 as well as the through bore B.sub.V of the adjusting cam 8 each comprises—at least for a portion—a structured surface 30 or 31, which can be designed identical to each other or also different from each other. Based on this structured surface 30, 31, a frictional connection is optimized between the fixed cams 7.1, 7.2 and the surfaces of the outer shaft segments 3.1 and 3.2 as well as between the adjusting cam 8 and the surface of the inner shaft 2, as shown for example in FIGS. 1 to 3. The fixed cams 7.1 and 7.2 are advantageously joined together in their base region 7.3 and consequently form a fixed cam consisting of two cam profiles. Such an arrangement of fixed cams with respect to each other is also called a double anvil in the context of the invention. Consequently, a recess is formed between the cam contours of the individual fixed cams 7.1 and 7.2, which are spaced apart from each other, in which the adjusting cam 8 is encompassed. However, it would also be conceivable to arrange only one adjusting cam 8 and one fixed cam 7.1 or 7.2. Advantageously, in this case, at least the fixed cam 7.1 or 7.2 and/or the adjusting cam 8 could be press-fitted on a sleeve (not shown here), and this sleeve is or can be operatively connected at least to one outer shaft segment 3.1 or 3.2 or to the inner shaft 2, advantageously making use of a frictional connection.

[0039] FIG. 5 shows schematically in a side view a cross sectional representation of one embodiment of a cam pack 4. The cam pack 4 shown in FIG. 5 advantageously comprises a first fixed cam 7.1 and a second fixed cam 7.2, not shown here, between which is arranged an adjusting cam 8. As is also shown in particular in FIG. 5, the adjusting cam 8 comprises a through bore B.sub.V, which is smaller in dimension than the through bore B.sub.F of the fixed cam 7.1 or 7.2. The fixed cam 7.1 or 7.2 or the fixed cam element designed as a double anvil can be moved about an axis of rotation D identical to the adjusting cam 8, so that consequently the fixed cams 7.1, 7.2 and the adjusting cam 8 are arranged concentrically or coaxially to each other with respect to their axis of rotation D. Furthermore, the adjusting cam 8 comprises a clearance 11, inside which runs the transition region 7.4 of the base region 7.3 of the double-anvil fixed cam. Based on the clearance 11 of the adjusting cam 8, a rotation of the adjusting cam 8 relative to the fixed cam 7.1 or 7.2 is possible. Advantageously, this clearance 11 also serves for mounting the inner shaft 2 in at least one of the outer shaft segments 3.1, 3.2.

[0040] The movement or rotary movement of the adjusting cam 8 relative to the fixed cams 7.1 and 7.2 and especially the movement of the cam pack 4 is shown advantageously in FIGS. 6 and 7. Thus, FIG. 6 shows schematically in a perspective view a cutout of an embodiment of a camshaft 1 according to the invention with a cam pack 4 in a first arranging, in which the adjusting cam 8 comprises undergone no rotary movement relative to the fixed cam 7.1 or 7.2. Consequently, the cam pack 4 comprises a flat cam contour. Upon rotary movement of the inner shaft 2 relative to the outer shaft or the outer shaft segments 3.1 or 3.2, a rotary movement of the adjusting cam 8 relative to the fixed cam 7.1 or 7.2 consequently occurs. In this way, the cam pack 4 experiences a spreading of the adjusting cam 8 relative to the fixed cams 7.1 and 7.2, as shown especially in FIG. 7. Based on the spreading, the cam profile of the entire cam pack 4 is consequently changed, by which a tapping element controls the setting or adjusting of intake and/or exhaust valves.

[0041] Advantageously, the method according to the invention for the production of an adjustable camshaft as well as an adjustable camshaft of a motor vehicle according to the invention advantageously produced with the method of the invention will enable a production or fabrication and assembly of an adjustable camshaft in an easier and more economical manner. Thus, advantageously, it is no longer required to arrange a connection element, such as a pin, for connecting the inner shaft to the adjusting cam. Furthermore, it should be mentioned advantageously that the method according to the invention makes possible a production or assembly of the adjustable camshaft in a single layout, the individual elements, namely the inner shaft as well as the outer shaft segments, the cam pack with the fixed cams and the adjusting cam being able to be mounted in a common layout. This advantageously prevents the time-consuming and costly transport of intermediate workpieces and avoids damage to semi-assembled or preassembled camshafts. Furthermore, it is advantageous that ground cams and especially ground fixed cams and ground adjusting cams can be installed by means of the method according to the invention.

LIST OF REFERENCE NUMBERS

[0042] 1 Camshaft [0043] 2 Inner shaft [0044] 3.1 First outer shaft segment [0045] 3.2 Second outer shaft segment [0046] 4.1 First cam pack [0047] 4.2 Second cam pack [0048] 4 Cam pack [0049] 7.1 First fixed cam [0050] 7.2 Second fixed cam [0051] 7.3 Base region [0052] 7.4 Transition region [0053] 8 Adjusting cam [0054] 9 Limiting element [0055] 10 Insertion region [0056] 11 Clearance [0057] 12 Distal end/distal shell surface region [0058] 20 Surface modification/material elevation [0059] 21 Arranging section [0060] 30 Structured surface of the fixed cam [0061] 31 Structured surface of the adjusting cam [0062] B.sub.F Through bore of the fixed cam [0063] B.sub.V Through bore of the adjusting cam [0064] D Axis of rotation [0065] Da Outer diameter of distal shell surface region [0066] Db Outer diameter of the remaining shell surface [0067] P Arrow direction