WO2009098005A2 - Shaft and method for producing a shaft, in particular for the engine of a motor vehicle - Google Patents

Abstract

The invention relates to a shaft, in particular for the engine of a motor vehicle, comprising at least one cylindrical bearing region (10) that extends along a rotational axis (A) of the shaft and comprises at least one cut-out section (14) in relation to a cylindrical encasement surface (12), said section running axially relative to the rotational axis (A). In addition, the bearing region (10) comprises at least one cut-out section (18) in relation to the cylindrical casement surface (12), said section running radially relative to the rotational axis (A). The invention also relates to a method for producing a shaft of this type, according to which at least part of the shaft is produced by a forming method.

Description

 Shaft and method for producing a shaft, in particular for a motor of a

motor vehicle

The invention relates to a shaft, in particular for an engine of a motor vehicle specified in the preamble of patent claim 1 and a method for producing a shaft specified in the preamble of claim 7 Art.

Such a wave and such a method are, for example, already in the Motor Technology Journal, Issue 06/2007, Volume 68, p. 460 to be taken as known. The shaft is formed as a cast balancing shaft of an engine of a motor vehicle and comprises two cylindrical bearing portions which extend along an axis of rotation of the shaft and relative to a circular cylindrical envelope surface each having an axial recess relative to the axis of rotation, whereby the shaft compared to conventional round profile shafts a lesser Owns weight.

The object of the present invention is to provide a shaft and a method for producing a shaft, which enable a further weight saving.

The object is achieved by a shaft with the features of claim 1 and by a method having the features of claim 7. Advantageous embodiments with expedient and non-trivial developments are specified in the respective subclaims, wherein advantageous embodiments of the shaft - where applicable - are to be regarded as advantageous embodiments of the method and vice versa.

A shaft which allows a further weight saving, according to the invention created by the fact that the storage area at least one against the Enveloping surface with respect to the axis of rotation radial recess comprises. In other words, at least one recess in the bearing area is provided on the circumference of the shaft, which leads to a reduction of the cylindrical portion. This allows, in addition to the weight savings achieved by this, an additional reduction of the friction power and accordingly lower storage temperatures during operation of the shaft. In addition, since a self-priming effect of lubricant-for example engine oil-is made possible due to the radial recess, a higher lubricant film thickness reserve results, as a result of which the shaft has less wear and thus an increased service life.

Another aspect of the invention relates to a method for producing a shaft according to one of the preceding embodiments, wherein according to the invention at least a part of the shaft is produced by means of a forming process. In addition to the resulting additional weight savings of the shaft is achieved by the use of a forming process in addition, a significant reduction in unit costs. In addition, such waves are mass parts, so that there are additional cost advantages with correspondingly reduced unit costs. It has proven to be advantageous that a deep-drawing process and / or a hydroforming process is used as the forming process. This allows automated and rapid production even of complex shaft geometries, whereby waves with a reduced total weight and improved running properties can be produced quickly and inexpensively.

Further advantages, features and details of the invention will become apparent from the following descriptions of exemplary embodiments and with reference to the drawings, in which the same or functionally identical elements are provided with identical reference numerals. Showing:

Fig. 1 is a perspective view of a formed as a balance shaft shaft according to the prior art;

FIG. 2 shows a schematic sectional view of a bearing region of the shaft according to the sectional plane H-II shown in FIG. 1; FIG. Fig. 3 is a schematic and partial side view of a

Storage area of a shaft according to the invention according to a first embodiment;

Fig. 4 is a schematic and partial side view of a

Storage area of a shaft according to the invention according to a second embodiment;

Fig. 5 is a schematic and partial side view of a

Storage area of a shaft according to the invention according to a third embodiment; and

Fig. 6 is a schematic and frontal sectional view of a storage area of a shaft according to the invention according to a fourth embodiment.

1 shows a perspective view of a shaft designed as a balance shaft for an engine of a motor vehicle according to the prior art. The shaft in this case comprises two cylindrical bearing regions 10a _1, 10b which both extend along an axis of rotation A of the shaft and in each case comprise a recess 14a, 14b, which is axial with respect to the axis of rotation A, relative to a circular cylindrical enveloping surface 12 (see FIG. The bearing areas 10a, 10b, which serve to mount the shaft in a motor housing, not shown, thus have, despite a certain weight reduction with respect to a shaft with solid profile bearing areas a constant außenumfängliche bearing width 16th

FIG. 2 shows a schematic sectional view of the storage area 10a according to the sectional plane H-II shown in FIG. It can be seen in particular that the storage area 10a has a wrap angle of over 180 ° relative to the wrapping surface 12 in order to ensure reliable guidance and to make it impossible for the shaft to "drop" within its associated storage housing.

3 shows a schematic and partial side view of the bearing area 10 of a shaft according to the invention in accordance with a first exemplary embodiment. The shaft can optionally be designed as a balance shaft, camshaft or crankshaft. In contrast to the previously described shaft according to FIG. 1 and FIG. 2, the bearing region 10 in this case comprises two opposite the cladding surface 12 in relation to FIG on the rotation axis A radial recesses 18a, 18b, whereby an additional weight saving is achieved. In contrast to the prior art, the storage area 10 thus has a variable storage width 16 over the circumference of the storage area 10. The storage width 16 can vary by 60% and more over the circumference of the storage area 10. It can also be provided that the bearing region 10 has an open cross-sectional contour-as shown in FIG. 2 -or a closed cross-sectional contour-as shown in FIG. The radial recesses 18a, 18b are advantageously formed in a region of the bearing region 10, which is mechanically less loaded during operation of the shaft and extend in the present embodiment, along a lying outside the storage area 10 length range 20a, 20b of the shaft. The radial recesses 18a, 18b are furthermore designed such that at least the bearing region 10 is mirror-symmetrical and has a mirror symmetry plane IH-III. This prevents tilting of the bearing area 10 within the motor housing due to undesired acceleration forces and ensures a correspondingly reliable and uniform operation of the shaft. Due to the reduced friction surface of the bearing area 10, the shaft thus consumes a correspondingly lower friction power, which additionally results in lower storage temperatures during operation. This reduces wear and increases the life of the shaft according to the invention. The radial recesses 18a, 18b also allow the formation of a Selbstansaugeffektes lubricant, whereby a higher lubricant film thickness reserve is ensured during the operation of the shaft and the lubrication is improved overall. In this case, it may additionally be provided that the shaft comprises a cavity 24 (see Fig. 6) which can be filled with the lubricant, for example engine oil, so that, on the one hand, a further reduction in weight is provided and, on the other hand, a further improvement in heat dissipation is achieved.

The shaft shown, which is a mass part, is produced here by means of a hydroforming process at a pressure between about 2000 bar and 2500 bar from a steel sheet. As steel, a hardenable alloy is preferably used here, at least in the bearing area 10, in order to ensure a correspondingly high longevity and operational reliability of the shaft. In this way, in contrast to the usual primary molding process - in particular casting process - achieved significant reductions in manufacturing costs. In addition, this represents a quick, simple and cost-effective way to additionally form the fillable with the lubricant cavity 24 in one step. Alternatively, you can be provided that the shaft is made by welding at least two, formed as deep-drawn parts Teilwelien.

4 shows a schematic and partial side view of the bearing area 10 of the shaft according to the invention in accordance with a second exemplary embodiment. In contrast to the preceding, first embodiment, the bearing area 10 in addition to the radial recesses 18a, 18b additionally comprises three groove-shaped radial recesses 18c-e, which provide an additional volume for receiving the lubricant. As a result, in addition to the further weight saving, an additional reduction of the thermal bearing load during operation of the shaft is ensured.

5 shows a schematic and partial side view of the bearing area 10 of the shaft according to the invention in accordance with a third exemplary embodiment. In contrast to the previous exemplary embodiments, the bearing region 10 is not mirror-symmetrical in this case and, in addition to the radial recesses 18a, 18b, comprises five cross-shaped radial recesses 18c-g. The recesses 18c-g each have a width and a depth of 1 mm and can be introduced, for example, inexpensively and fully automatically on a lathe by means of a thread turning process into the storage area 10. The pairwise distance of the recesses 18c-g can then be easily determined via the thread pitch 22. The recesses 18c-g shown also provide for improved ventilation and increased delivery volume of the lubricant, which reduces the frictional losses of the shaft and increases the service life of the shaft.

6 shows a schematic and frontal sectional view of the bearing area 10 of the shaft according to the invention in accordance with a fourth exemplary embodiment. In contrast to the preceding exemplary embodiments, the bearing region 10 has a closed contour, which comprises two radial recesses 18a, 18b in relation to the circumferential surface 12, which is circular in cross-section. The bearing area 10 is thus similar to a cam of a known camshaft, but does not extend beyond the envelope surface 12 of the shaft. The two recesses 18a, 18b also improve the lubricating film structure and "push" during operation of the shaft lubricant before him, so that there is also an additional lubricant delivery volume and improved lubrication. However, the storage area 10 shown can alternatively be used as a cam, wherein by adaptation of the recesses 18a and 18b influence on a Ansteuerweg or a Angular acceleration of a component to be actuated - for example, a gas exchange valve - can be taken. The embodiment shown can also be combined with the preceding embodiments. Likewise, an embodiment of the shaft can be provided as duo or triple camshaft to allow, for example, different lifting curves of the component to be actuated.

Claims

claims 1. shaft, in particular for an engine of a motor vehicle, having at least one cylindrical bearing area (10) which extends along an axis of rotation (A) of the shaft and with respect to a circular cylindrical envelope surface (12) at least one with respect to the axis of rotation (A) axial recess (14), characterized in that the storage area (10) at least one opposite the wrapping surface (12) in With respect to the axis of rotation (A) comprises radial recess (18). 2. Shaft according to claim 1, characterized in that the at least one radial recess (18) is formed in a mechanically less loaded during operation of the shaft region of the bearing region (10). 3. Shaft according to claim 1 or 2, characterized in that the at least one radial recess (18) is formed such that at least the bearing region (10) is formed mirror-symmetrically. 4. Shaft according to one of claims 1 to 3, characterized in that the at least one radial recess (18) is groove-shaped. 5. Shaft according to one of claims 1 to 4, characterized in that the shaft is designed as a balance shaft, camshaft or crankshaft. 6. Shaft according to one of claims 1 to 5, characterized in that the shaft comprises a with a lubricant, in particular a motor oil, fillable cavity (24). 7. A method for producing a shaft according to any one of claims 1 to 6, characterized in that at least a part of the shaft is produced by means of a forming process. 8. The method according to claim 7, characterized in that a thermoforming process and / or a hydroforming process is used as the forming process. 9. The method according to claim 7 or 8, characterized in that the shaft is produced by welding at least two partial waves. 10. The method according to any one of claims 7 to 9, characterized in that at least in the storage area (10) a hardenable steel is used as a shaft material.