Patent ID: 12228200

DETAILED DESCRIPTION

Typical embodiments of the invention will be described hereunder by means of the figures, the invention not being limited to the exemplary embodiments, the scope of the invention rather being determined by the claims. In the description of the embodiment, in different figures and for different embodiments the same reference signs are at times used for identical or similar parts in order to improve the clarity of the description. However, this does not mean that corresponding parts of the invention are limited to the variants illustrated in the embodiments.

An exemplary embodiment is shown in a schematic sectional view inFIG.1.FIG.1schematically shows a section through a gearbox1which has a ring gear3having an internal encircling toothing5. Teeth7engage in the toothing5. For improved clarity, not each tooth7ofFIG.1is provided with the reference sign7. This also applies to other parts ofFIG.1which are present multiple times and are likewise not all provided with the respective reference sign. Two axially parallel gear rings are typically provided with individual teeth7.

The teeth7are mounted so as to be radially displaceable in a tooth carrier11. To this end, the tooth carrier11has radially aligned round openings in the manner of ducts, or openings in the manner of slots, which guarantee radial guiding of the teeth7in the tooth carrier11. By virtue of radial guiding in the openings, the teeth7are able to move only in the radial direction along their longitudinal axis. Twisting relative to the tooth carrier11about a longitudinal axis of the gearbox1is in particular precluded.

The longitudinal axis of the teeth typically describes the axis running from the tooth root to the tooth crest, while the longitudinal axis of the gearbox points in the direction of the rotation axis of the gearbox. This can be, for example, the rotation axis of the tooth carrier which can be used as the output, or else the rotation axis of a cam disk.

The teeth7are driven by a drive element in the form of a cam disk20which is embodied as a hollow cam disk20. The cam disk20has a profiled feature22for driving the teeth7in the radial direction. The profiled feature22has a profile having two peaks over the circumference such that respective opposite teeth7have entered the tooth gaps of the toothing5to the greatest extent (top and bottom inFIG.1).

The peaks of the profiled feature22of the cam disk20that have the largest radius about the rotation axis in the center are at the top and bottom inFIG.1, whereas the troughs having the smallest radius inFIG.1are in each case disposed on the right and the left of the cam disk, and so as to be rotated about 90° in relation to the peaks.

In gearbox1illustrated inFIG.1, the teeth7are disposed on the profiled feature22of the cam disk20by way of a mounting by plain bearing. The mounting by plain bearing comprises bearing segments24which slide on the profiled feature22by means of a lubricating film (not illustrated). A hydrodynamic mounting35by plain bearing is in each case typically configured between the respective running surfaces of the bearing segments and the cam disk during the operation of the gearbox.

In the exemplary embodiment ofFIG.1, the output is taken from the tooth carrier, wherein the ring gear is fixedly established by the toothing.

The bearing segments24on the side that faces the tooth7have in each case one round tooth-bearing face which in portions is in particular cylindrical (cf. alsoFIG.2) and forms a bead31on which the root of a tooth7, or in typical embodiments two, three or four teeth, can be disposed next to one another in the axial direction of the gearbox1. The bead31, conjointly with a corresponding clearance in the tooth root of the respective tooth7, prevents the tooth7from slipping on the bearing segment24.

Root articulations for the teeth7are in each case configured by the beads31, so that the teeth7can tilt relative to the bearing segments24in order to guarantee unconstrained guiding. The bead31on the radially outer side of the bearing segments24, the former engaging in each case in grooves of the teeth7, is disposed so as to be centric relative to the respective bearing segment24. In this way, a centric transmission of force by the bearing segment24is achieved.

The bearing segments24in the revolving direction have straight front33and rear34edges and are mutually displaceable in the revolving direction so that the spacings between the bearing segments24can be varied as a function of the position of the teeth. This enables largely unconstrained guiding and largely unconstrained radial driving of the bearing segments24by the profiled feature22of the cam disk20. In order for the frictional resistance between the profiled feature22and the bearing segments24to be minimized, or in order to ensure the lubricating film, respectively, those sides of the bearing segments24that face the cam disk have typical shapes which will be described by way of example hereunder.

The bead on the radially outer side of the bearing segments24, the former engaging in each case in grooves of the teeth7, is disposed so as be centric relative to the respective bearing segment24. A centric transmission of force by the bearing segment24is achieved in this way.

Three of the bearing segments24are illustrated in more detail inFIG.2. The shape of the running surface that faces the cam disk will be explained in more detail in particular by means of the central one of the three bearing segments24ofFIG.2, said shape of the running surface having the contact region26disposed so as to be centric in the running surface. The contact region26has a concave curvature, wherein the concave curvature is larger than the smallest convex cam curvature of the cam disk, and smaller than the largest convex cam curvature of the cam disk. The concave curvature is at least 50% larger than the smallest convex cam curvature of the cam disk, in particular of the cam curvature in the trough.

The cam curvature of the cam disk20describes in each case the cam curvature of the profiled feature22at a specific location.

Proceeding from the elevation illustrated above in the figure, two angles30which are utilized for specifying the curvature of the running surface26of the bearing segment in more detail are plotted inFIG.1. The concave curvature of the contact region26is constant over the region of the contact region26and is smaller than the smallest cam curvature within an angular range of 10° to 60° in both rotation directions, proceeding from the peak, typically at most 0.2% smaller than the smallest cam curvature within the angular range. More specifically, the concave curvature of the contact region is 99.8% of the smallest cam curvature between 10° and 60°. It is to be noted that the cam disk is typically of a symmetrical design.

The side of one of the bearing segments24that faces the cam disk is shown in more detail in a schematic view inFIG.3. One peripheral region27of the running surface adjoins in each case on either side of the centric contact region26, said peripheral region27being convexly configured. Adjoining thereto is in turn provided a flat sub-face28, which is then in each case adjoined by a convexly radiused edge29of the bearing segment24. This shaping can also be schematically derived fromFIG.2; however, the corresponding regions inFIG.2are not provided with reference signs for improved clarity.