BALANCE SHAFT

Abstract

A balance shaft for balancing forces of inertia and/or moments of inertia of a reciprocating-piston internal combustion engine, including: at least one elongate main body; at least one bearing seat disposed on the elongate main body, for the mounting of a radial bearing, wherein in the center point of the bearing seat is provided the rotational axis of the balance shaft. On the elongate main body is provided at least one unbalance portion the center of mass of which lies outside the rotational axis of the balance shaft. On the at least one unbalance portion substantially no material is provided in the region of the rotational axis of the balance shaft. A method for producing such a balance shaft is also provided.

Claims

1. A balance shaft for balancing forces of inertia and/or moments of inertia of a reciprocating-piston internal combustion engine, the balance shaft comprising: at least one elongate main body; at least one bearing seat disposed on the elongate main body for mounting a radial bearing, wherein in a center point of the bearing seat a rotational axis of the balance shaft is provided; and at least one unbalance portion provided on the elongate main body, the at least one unbalance portion having a center of mass that lies outside the rotational axis of the balance shaft, wherein on the at least one unbalance portion substantially no material is provided in a region of the rotational axis of the balance shaft.

2. The balance shaft according to claim 1, wherein, on the at least one bearing seat, substantially no material is provided in the region of the rotational axis of the balance shaft.

3. The balance shaft according to claim 1, wherein the elongate main body comprises at least two adjacent unbalance portions between which a connecting portion is provided that runs through the rotational axis of the balance shaft.

4. The balance shaft according to claim 3, wherein the centers of mass of the at least two adjacent unbalance portions are provided on opposite sides of the rotational axis.

5. The balance shaft according to claim 1, wherein the balance shaft is of substantially point-symmetrical configuration.

6. The balance shaft according to claim 1, wherein the balance shaft is of substantially mirror-symmetrical configuration and the axis of symmetry runs substantially perpendicular or perpendicular to the rotational axis.

7. The balance shaft according to claim 1, wherein at least one bearing seat is provided laterally on the at least one unbalance portion and/or within the unbalance portion.

8. The balance shaft according to claim 1, wherein the connecting body is configured such that this is twistable to establish a reduced noise development upon the start-up of the balance shaft.

9. The balance shaft according to claim 1, wherein the at least one unbalance portion at least partially corresponds to a partial shape of a hollow body which comprises at least side walls running parallel to the rotational axis of the balance shaft.

10. The balance shaft according to claim 9, wherein the unbalance portion is at least partially of shell-shaped, tub-shaped and/or notch-shaped configuration.

11. The balance shaft according to claim 1, wherein the at least one unbalance portion has different wall thicknesses.

12. The balance shaft according to claim 1, wherein the unbalance portions is arranged offset from the rotational axis of the balance shaft.

13. The balance shaft according to claim 1, wherein the balance shaft has on at least one end portion an engagement element, which is configured such that the balance shaft is connectable to a drive or a chain wheel drive.

14. The balance shaft according to claim 1, wherein a center of symmetry of the balance shaft is provided in a connecting portion connecting two adjacent unbalance portions.

15. A method for producing a balance shaft according to claim 1, the method comprising: providing at least one elongate main body; and performing at least one forming operation, which is performed substantially perpendicular to the rotational axis of the balance shaft such that on the elongate main body at least one unbalance portion is formed, wherein the center of mass of the unbalance portion lies outside the rotational axis of the balance shaft, and wherein on the at least one unbalance portion substantially no material remains in the region of the rotational axis of the balance shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0026] FIG. 1 shows a schematic view of a first embodiment of a balance shaft according to the invention;

[0027] FIG. 2 shows a further schematic view of the balance shaft from FIG. 1;

[0028] FIG. 3 shows a schematic view of a second embodiment of a balance shaft according to the invention; and

[0029] FIG. 4 shows a schematic view of a third embodiment of a balance shaft according to the invention.

DETAILED DESCRIPTION

[0030] FIGS. 1 and 2 show a first embodiment of a balance shaft 10 according to the invention. The balance shaft 10 comprises on opposite end portions two engagement elements 11, 12, with which the balance shaft 10 is connectable to a drive, in particular a chain drive.

[0031] In addition, in this preferred embodiment the balance shaft 10 comprises four bearing seats 13, 14, 15, 16 for the mounting of a radial bearing. In the center point of the bearing seats 13, 14, 15, 16 lies the rotational axis of the balance shaft 10.

[0032] The bearing seats 13, 16 can here respectively have a bearing inner ring, on which a bearing, for example, a roller bearing, can respectively be arranged. In this context, it is preferred to provide a bearing seat 13, 16 by way of a bearing inner ring which is formed onto the main body and onto which the bearings can subsequently be slipped or clipped. Such a bearing inner ring can be provided, for instance, by virtue of the fact that two appropriately shaped shoulder regions (not shown), which, joined together, respectively form a bearing inner ring, are formed onto the main body. In other words, a bearing inner ring, onto which the bearing can subsequently be slipped or clipped, can respectively be formed by the two shoulder regions. Alternatively, the possibility also exists of providing the bearings already complete with a bearing inner ring and of respectively slipping this composite laterally onto the bearing seat 14, 15. In this case, it is preferred that, prior to the slip-on operation, an appropriate contact surface, for example, in the form of a shoulder, for the bearing (more precisely for the bearing inner ring) is respectively provided on the main body. The composite of bearing and bearing inner ring can then respectively be slipped onto the main body and brought into engagement with the contact surface. Subsequently a second shoulder is formed on the main body by forming, in particular by a calibration (i.e. through a so-called calibration stroke), so that the bearing inner rings, and thus the bearings, can be held or received by the two shoulders.

[0033] As can clearly be seen in FIGS. 1 and 2, the balance shaft 10 comprises two unbalance portions 17, 18, which are connected to each other by a connecting portion 19. The unbalance portions 17, 18 are here of tub-shaped configuration with lateral walls, so that substantially no material is arranged in the region of the rotational axis. Alternatively to the shown tub shape, the unbalance portions 17, 18 can also be of shell-shaped or notch-shaped configuration.

[0034] By means of the represented tub shape, non effectively used material in the region of the rotational axis can thus be avoided or considerably reduced, so that the component can be correspondingly reduced in weight. Preferably, stiffening measures on the component can thereby also be avoided.

[0035] A further advantage of the material saving is that the connecting body (i.e. the tub shape) between the two connecting bodies is more easily twistable, which has a positive effect on the anticipated noise development upon the start-up of the balance shaft, in that the noise development (a rattling) between the two drive wheels, on the balance shaft and crankshaft sides is reduced. The necessary or maximal stiffness of the tub shape can here be controlled via stiffening ribs (framework) introduced by forging.

[0036] By virtue of a forging-based production, restrictions in terms of length and employed wall thicknesses barely exist.

[0037] Through the proposed geometry of the unbalance portions 17, 18, i.e. through the reduction of that mass of the unbalance portions 17, 18 which is not necessary for the balancing forces, the possibility exists of reducing the mass of a balance shaft 10 according to the invention to the bare essential. The possibility also exists of providing the bearing seats 14, 15 at least partially or fully in the region of the tub-shaped unbalance portions 17, 18, so that the unbalance portions 17, 18 are in no way interrupted by the bearing seats 14, 15, but rather mass can be provided also at the bearing seats 14, 15 in order to provide balancing forces.

[0038] In the exemplary embodiments shown in FIGS. 1 to 3, the centers of gravity of the unbalance portions 17, 18, 17, 18 are here arranged on opposite sides of the rotational axes of the balance shafts 10, 10. This arrangement is provided, for instance, for 3-cylinder engines. As can likewise clearly be seen in FIGS. 1 to 3, the unbalance portions 17, 18, 17, 18 are arranged in a point-symmetrical manner, wherein the centers of symmetry 20, 20 are respectively arranged in the region of the connecting portions 20, 20.

[0039] FIG. 3 shows an embodiment of a balance shaft 10 according to the invention. The embodiment shown in FIG. 3 substantially corresponds to that embodiment of the balance shaft 10 which is shown in FIGS. 1 and 2. Same parts are therefore provided with same apostrophized reference symbols. Unlike the embodiment shown in FIGS. 1 and 2, the balance shaft 10 shown in FIG. 3 comprises no bearing seats within the unbalance portions 17, 18, but just two bearing seats 13, 16 arranged laterally on the unbalance portions 17, 18.

[0040] FIG. 4 shows an embodiment of a balance shaft 100 according to the invention. Here, the balance shaft 100 comprises an unbalance portion which runs on one side of the rotational axis and which extends substantially over the entire longitudinal extent of the balance shaft 100. The unbalance portion here comprises at least one tub-shaped region 101. As can also clearly be seen in FIG. 4, the unbalance portion can comprise various sections having different widths. The balance shaft 100 likewise comprises two bearing seats 102, 103, on which appropriate bearings, for example, roller bearings, can be arranged. The balance shaft 100 shown in FIG. 4 is here of substantially mirror-symmetrical configuration, wherein the axis of symmetry is provided in the tub-shaped region 101 of the balance shaft 100.

[0041] The present invention is not limited to the preceding illustrative embodiments, as long as it is embraced by the subject of the following claims. Furthermore, the preceding illustrative embodiments are mutually combinable and intercombinable in any chosen manner. In particular, besides the shown tub-shaped unbalance portions, other geometries, for instance shell-shaped or notch-shaped geometries, can alternatively or additionally be provided. The centers of mass of the unbalance portions can also be still further altered relative to the rotational axis of the balance shaft by a displacement of the mass of the main body and/or by an offset arrangement of the main body from the rotational axis of the balance shaft. Various additional (separately or integrally configured) balancing weights can also be provided in the main body (preferably in the region of the unbalance portions). Finally, it should be pointed out that the respective masses or the bearing seats of the balance shaft can be adapted, with respect to their arrangement along the rotational axis, to the respectively specific installation environment.

[0042] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.