gearbox

Abstract

a cam disc (20) rotatable about the rotation axis (5) and having a cam curvature that is variable over its circumference to drive the teeth (7) radially, wherein a bearing segment (24) slidably mounted on the cam disc (20) is arranged between the teeth (7) and the cam disc (20), the bearing segment (24) having a contact area with a concave curvature and arranged so as to be centered on a running surface facing the cam disc (20), the concave curvature being greater than the minimum cam curvature of the cam disc and less than the maximum cam curvature of the cam disc.

Description

Technical Field

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[0001] The present invention relates to a gearbox and a method of operating the gearbox.

Background Art

[0002] Gearboxes with teeth mounted displaceably in the radial direction within a tooth carrier are known from the prior art. To drive the teeth, a drive element having a contour shape, such as a cam disk, for example, is used. The teeth engage with the internal teeth of the tooth part such that relative movement occurs between the tooth carrier with teeth and the tooth part. Here, the relative movement between the tooth part and the teeth is at least 1 magnitude smaller than the movement of the drive element having the contour shape. In this way, a high gear ratio can be achieved.

[0003] In these gearboxes, the attachment of the teeth to the cam disk is an important problem. For this purpose, solutions from the prior art to date use a so-called segment attachment having bearing segments (see, for example, DE 10 2015 105525 A1). However, the structure using a rolling bearing under the bearing segment is complex.

Summary of the Invention

[0004] The object of the present invention is to identify a gearbox improved compared to gearboxes known from the prior art, the intention being to achieve less friction in relation to a simple structure. Furthermore, the object of the present invention is to identify a method for operating such a gearbox.

[0005] This object is achieved by the gearbox according to claim 1 and a method of operating the gearbox according to the corresponding claims. Advantageous improvements and embodiments result from the dependent claims and the present description.

[0006] One aspect of the present invention relates to a gearbox, more particularly a coaxial gearbox, which comprises a tooth carrier for receiving teeth of a gearing arranged around the rotation axis of the gearbox, the tooth carrier having teeth arranged on the tooth carrier such that the teeth are radially displaceable and guided, and a cam disc that is rotatable around the rotation axis and has a cam curvature that is variable over the circumference for driving the teeth radially, wherein a bearing segment slidably mounted on the cam disc is positioned between the teeth and the cam disc, and the bearing segment has a concave curvature. Then On the running surface facing the cam disc central part They are arranged in such a way. It has a contact area, and is recessed. The curvature is greater than the minimum cam curvature of the cam disc and less than the maximum cam curvature of the cam disc.

[0007] Further aspects of the present invention relate to a method for operating a gearbox in one of the typical embodiments described herein.

[0008] When comparing curvatures, the absolute values ​​of the curvatures are generally compared, as described herein for various ranges. The cam curvature of a cam disc is typically convex around its entire circumference and, in any case, not concave around its entire circumference, at least in typical embodiments.

[0009] The bearing segment is typically mounted to slide on the cam disc. In particular, the bearing segment is directly mounted to the cam disc, separated only by a lubricating film. In a typical embodiment, the bearing segment is non-magnetic or made of a non-magnetic material. The bearing segment and the cam disc are typically made of a material that does not accumulate any magnetic force, or at least substantially any magnetic force, between the cam disc and the bearing segment. In each case, the hydrodynamic mounting by the sliding bearing is typically configured between the corresponding running surface of the bearing segment and the cam disc during the operation of the gearbox.

[0010] In a typical embodiment, the concave curvature of the contact area of ​​the bearing segment is constant, at least partially, or at least in the central region of each contact area. It should be noted that, with respect to the term curvature, this should be understood as the degree of curvature of the corresponding surface at the observation point. Curvature is typically defined by kappa:dphi / ds, and therefore by the angular change over the arc length, i.e., 1 / r. A consideration here is that, for example, a cam disk may have a certain axial width and, within that range, the same cross-section but with different curvatures along the circumferential direction.

[0011] Embodiments of the present invention relate particularly to coaxial gearbox devices. The axial direction typically refers to the longitudinal axis of the gearbox. The tooth engagement in the teeth of the ring gear typically refers to the tooth engagement in the internal teeth of the teeth, the latter of which, in a typical embodiment, lies on a constant pitch circle diameter.

[0012] The term "cam disc" is typically understood to mean that the corresponding component does not necessarily have to be disc-shaped. Rather, the cam disc may be part of the drive shaft, have an extended range, or in particular may be composed of multiple parts. One or more such parts may have varying radii so as to fulfill the function of the cam disc. Yet another part may have other functions, for example, being cylindrical or having a rim, for example, for torque transmission. The term cam disc is typically used primarily in relation to the function of this component, in particular in relation to its function of providing a contour shape that rotates to drive the teeth radially in accordance with the angular position of the drive shaft, and thereby, for example, the cam disc allows the teeth to slide back within the guide.

[0013] The teeth are typically encircling teeth. The internal teeth of the teeth engage with the teeth, and the teeth are typically mounted so that they are radially linearly displaceable relative to the tooth carrier. Here, "radially linear" usually means that there is a guide in the radial direction that allows the teeth to move only in the radial direction. Typically, as a result of being guided, the teeth are linearly displaceable in exactly one direction, which can be achieved, for example, by having a constant cross section over a certain distance in the direction of displacement, where the tooth carrier has an opening for the teeth that also has a constant cross section. The teeth are usually mounted to the tooth carrier so that they are displaceable in exactly one direction, typically in the direction of the longitudinal axis of the teeth. In a typical embodiment, the degree of freedom of rotation of the teeth relative to the tooth carrier about the longitudinal axis of the gearbox is further blocked. This can be achieved, for example, by a linear guide of the teeth radially within the tooth carrier. In this way, the teeth rotate around the longitudinal axis of the gearbox in cooperation with the tooth carrier, but not relative to the tooth carrier.

[0014] In a typical embodiment of the gearbox according to the present invention, at least a portion of the teeth are embodied to have bending rigidity. Here, the term “bending rigidity” should typically be understood in a technical sense, meaning that the rigidity of the tooth material results in very little tooth deflection, and that deflection is at least substantially irrelevant in terms of the gearbox's kinematics. Bending rigidity teeth particularly include teeth made from metallic alloys, especially steel, or titanium alloys, nickel alloys, or other alloys. Furthermore, bending rigidity teeth made from plastic materials can be provided, in particular, in the case of a gearbox in which at least one of the following components is also made from plastic material: teeth on a ring gear or gear wheel, tooth carriers, and drive elements. In a typical embodiment of the present invention, the tooth carriers and teeth, or further teeth, or further drive elements, are made from metallic alloys. Such gearboxes offer the advantage of very high torsional rigidity and high load-bearing capacity. Gearboxes, or gearboxes having components made from plastic material, at least a portion of which are made from plastic material, offer the advantage of being lightweight. The term “bending rigidity” refers in particular to bending rigidity about the transverse axis of the teeth.

[0015] In a typical embodiment, a bearing segment is positioned between the teeth and the cam disc, and the bearing segment is supported on the cam disc by a lubricating film during rotational operation. An advantageous embodiment includes a bearing segment positioned between the cam disc and at least one tooth in each. The bearing segment allows the teeth to tilt relative to the running surface of the cam disc or relative to the bearing segment. At least two teeth are typically mounted on one bearing segment. In a further embodiment, just one tooth, e.g., a round tooth or a flat tooth, is mounted on one of the bearing segments in each case. A flat tooth can be fixed in a tooth guide so as not to twist around its axis, and a round tooth can typically be fixed by form-fitting with the bearing segment. Multiple teeth mounted on one bearing segment are typically arranged adjacent to each other in a single row in the axial direction. Smooth running of the bearing segment can be enhanced using such an arrangement of multiple teeth or by using a flat tooth.

[0016] A typical embodiment of the present invention comprises a cam disc as a drive element. The cam disc preferably has a non-circular or non-elliptic arc shape or curve. The non-circular or non-elliptic arc shape offers the advantage that different curves can be used, for example, to set different gear ratios. In the context of this application, an eccentric shape is typically included in circular or elliptic shapes, since in the case of an eccentric shape only the axis of rotation does not coincide with the central axis of the circle, but a circle exists nonetheless. A typical cam disc has at least or just two peaks or ridges, which are typically uniformly distributed over the circumference. The peaks are sometimes called the highest points. If there are multiple peaks, more teeth engage with the teeth. A typical cam disc usable in the present invention can be obtained, for example, from Galaxie G135 (registered trademark) by WITTENSTEIN galaxie GmbH (limited liability company) located at 97999 Igersheim, Germany.

[0017] In a typical embodiment, the tooth carrier or teeth are configured as circular in shape. This offers the advantage of a simple geometric shape for both the tooth carrier and teeth. Force transmission typically occurs between the teeth and tooth carrier on the low-speed side of the gearbox. This offers the advantage of an extremely short force transmission distance, thus achieving extremely high rigidity.

[0018] The internal teeth and teeth of the tooth structure typically have curved sides. In a typical embodiment, the internal teeth and teeth each have a tooth apex, and their cross-sections correspond to the cross-sections of a truncated pyramid or pyramid with curved sides in each case. For potential embodiments of curvature in the form of a logarithmic spiral, see publication DE 10 2007 011 175 A1. The curved surface offers the advantage that the engaging sides make planar contact rather than merely linear or point contact. In this way, the load can be actively distributed to many teeth, and force transmission between teeth can be performed with an extremely high level of rigidity.

[0019] In a typical embodiment, the concave curvature of the contact area of ​​the bearing segment is greater than the convex cam curvature of the cam disc at at least one trough of the cam disc. At least one trough of the cam disc is distinguished by the minimum distance of the running planes from the longitudinal axis. At this location, the cam disc typically has minimum cam curvature, and the term “minimum cam curvature” of the cam disc in a typical embodiment may be understood as the cam curvature at this location or in the region around the trough being equal to 0. The concave curvature of the bearing segment is typically smaller than the convex cam curvature of the cam disc at at least one apex of the cam disc, and therefore the distance of the running planes from the longitudinal axis is typically maximum. The cam curvature of the cam disc is typically maximum in the region of at least one apex. However, in further embodiments, the maximum cam curvature may be different from at least one apex.

[0020] Cam discs typically have a maximum radius from the axis of rotation. distance Having just one top and the minimum radius from the axis of rotation. distance One that has Tanibe The bearing segment has a concave curvature, which is typically within an angular range of 5% to 35% of the entire angular range of the cam disc progressing from the top in both rotational directions. The best in Smaller than the curvature of a small convex cam. In a typical embodiment having a cam disk with just one apex, the concave curvature is typically in an angular range of 20° to 120° from the apex in both rotational directions. The most within Smaller than the curvature of a small cam.

[0021] A typical embodiment is the maximum radius from the axis of rotation. distance It has two vertices, each located between the vertices and having the minimum radius from the axis of rotation. distance The cam disc has two valleys, and the concave curvature of the bearing segment is within an angular range of 5% to 35% of the total angular range progressing from the first apex to the second apex. The most in Smaller than the small cam curvature. In a typical embodiment having a cam disk with two peaks, the concave curvature is typically within an angular range of 10° to 60° from the peaks in both rotational directions. The most in Smaller than the small cam curvature. In a further typical embodiment having three vertices, the concave curvature is typically within an angular range of 6° to 40° from the vertices, progressing in both rotational directions. The most in Smaller than the curvature of a small cam.

[0022] The so-called engagement region of the teeth, that is, the region in which the teeth engage with the internal teeth on one side and with the bearing segment on the other in the manner of force transmission, is located at least substantially typically within a predetermined angular range. A typical cam disc, in any case, has a symmetrical curved contour around the apex and the valleys.

[0023] The concave curvature is typically less than the minimum cam curvature by a maximum of 0.2%, a maximum of 0.5%, or a maximum of 1% within the angular ranges described above, for example, 5% to 35%, 20° to 120°, 10° to 60°, or 6° to 40°.

[0024] In a typical embodiment, the running surfaces of the bearing segments in the peripheral region of the running surface are all convexly curved in the circumferential direction. The circumferential peripheral regions are each located before and after the contact region having a concave curvature, and can be either directly adjacent to the concave curvature or separated from the contact region by a flat surface. Also, in each of the embodiments, one flat sub-surface can be arranged adjacent to the convex peripheral region. Thus, in a typical embodiment, proceeding circumferentially from the central part running surface results in the following order: the concave curvature of the contact region, the convex curvature of the peripheral region, the flat sub-surface, and optionally further the convex curvature of the edge of the bearing segment. This geometry aids in the formation of the lubricating film. In a further typical embodiment, the peripheral region is fully embodied with a very small convex curvature.

[0025] The running surfaces of the bearing segments typically include a sliding bearing material, such as bronze, brass, or white metal, and the wording "or" also includes in each case a combination of "and / or". Alternatively or additionally, a coating of the running surface of the cam disk may be provided. In this way, pitting can be largely eliminated, so that local damage to the lubricating film and contact with individual particles do not directly cause damage to the bearing characteristics.

[0026] In a typical embodiment, a bead having a bearing surface is configured on the surface of the bearing segment facing away from the cam disk, and the bearing surface has a partial cylindrical shape such that its axis is at least substantially located in the region of the running surface. In this way, the pivot axis of the teeth on the running surface is displaced, thereby avoiding any movement of the pressure point or any movement of the pressure point from the center of the bearing segment. "Substantially in the region of the running surface" typically refers to a region that is at most 20% or at most 10% of the radial thickness of the bearing segment above or below the running surface.

[0027] Bearing segments typically have one straight leading edge and one straight trailing edge in the direction of rotation. This simplifies the structure.

[0028] The advantages of a typical embodiment may be, in particular, high durability, increased damping, or high load-bearing capacity, especially in the output range with a consistently high rotational speed. [Brief explanation of the drawing]

[0029] The present invention will be described in more detail below with reference to the accompanying drawings. [Figure 1] Figure 1 schematically shows a first embodiment of the present invention in a cross-sectional view. [Figure 2] Figure 2 schematically shows the details of the embodiment shown in Figure 1. [Figure 3] Figure 3 schematically shows the bearing segment of the embodiment in Figure 1 in a top view. [Modes for carrying out the invention]

[0030] Typical embodiments of the present invention are described below with reference to the drawings, but the present invention is not limited to these exemplary embodiments, and the scope of the present invention is determined by the claims. In the description of embodiments, the same reference numerals may be used for identical or similar parts in different drawings or different embodiments in order to improve clarity of explanation. However, this does not mean that corresponding parts of the present invention are limited to the modifications shown in the embodiments.

[0031] An exemplary embodiment is shown in the schematic cross-sectional view of Figure 1. Figure 1 schematically shows a cross-section of a gearbox 1 having a ring gear 3 with an internal surrounding tooth portion 5. The teeth 7 engage with the tooth portion 5. For clarity, each of the teeth 7 in Figure 1 is not denoted by a reference numeral 7. This also applies to the other parts of Figure 1, of which there are multiple, and similarly not all of them are denoted by their respective reference numerals. Two gear rings parallel in the axial direction are typically provided with individual teeth 7.

[0032] The teeth 7 are mounted within the tooth carrier 11 so as to be radially displaceable. For this purpose, the tooth carrier 11 has radially arranged duct-shaped circular openings or slot-shaped openings, which ensure radial guidance of the teeth 7 within the tooth carrier 11. By being radially guided within the openings, the teeth 7 are made movable only radially along their longitudinal axis. Torsion of the tooth carrier 11 around the longitudinal axis of the gearbox 1 is particularly eliminated.

[0033] The longitudinal axis of a tooth typically represents the axis extending from the root to the tip of the tooth, while the longitudinal axis of a gearbox refers to the direction of the gearbox's axis of rotation. This could be, for example, the axis of rotation of the tooth carrier usable as an output, or the axis of rotation of the cam disk.

[0034] The teeth 7 are driven by a drive element in the form of a cam disc 20, which is embodied as a hollow cam disc 20. The cam disc 20 has a contour shape 22 for driving the teeth 7 radially. The contour shape 22 has a contour with two peaks on its circumference, so that each opposing tooth 7 can enter the intertooth gap of the tooth portion 5 to its maximum extent (top and bottom in Figure 1).

[0035] The two peaks of the contour shape 22 of the cam disc 20, which has the largest radius around the central axis of rotation, are shown on the upper and lower sides in Figure 1, while the valleys, which have the smallest radius in Figure 1, are located on the right and left sides of the cam disc, respectively, and are rotated approximately 90° relative to the peaks.

[0036] In the gearbox 1 shown in Figure 1, the teeth 7 are positioned on the contour shape 22 of the cam disc 20 by mounting using sliding bearings. The mounting using sliding bearings involves bearing segments that slide on the contour shape 22 by a lubricating film (not shown). 24 Includes.

[0037] In the exemplary embodiment shown in Figure 1, the output is obtained from the tooth carrier, and the ring gear is fixedly established by the teeth.

[0038] Each bearing segment 24 facing the tooth 7 has a circular tooth contact surface, which is partially and particularly cylindrical (see also Figure 2) and forms a bead on which the roots of one tooth 7, or in a typical embodiment two, three, or four teeth, may be positioned adjacent to each other in the axial direction of the gearbox 1. The bead works in cooperation with the corresponding clearance at the root of each tooth 7 to prevent the tooth 7 from slipping on the bearing segment 24.

[0039] The root joints of each tooth 7 are formed by a bead, thereby allowing the tooth 7 to tilt relative to the bearing segment 24 and ensuring unconstrained guidance. The radially outer beads of the bearing segment 24 engage with the grooves of the teeth 7 in each and are positioned to be centered relative to each bearing segment 24. In this way, central force transmission by the bearing segment 24 is achieved.

[0040] The rotational bearing segments 24 have linear leading and trailing edges and are displaceable relative to each other in the rotational direction, thereby allowing the spacing between the bearing segments 24 to change depending on the position of the teeth. This allows the contour shape 22 of the cam disc 20 to provide largely unconstrained guidance and largely unconstrained radial drive of the bearing segments 24. To minimize frictional resistance between the contour shape 22 and the bearing segments 24, or to ensure a reliable lubrication film, the side surfaces of the bearing segments 24 facing the cam disc have the typical shapes illustrated below.

[0041] The radially outer beads of each bearing segment 24 engage with the grooves of the teeth 7 and are positioned to be centered relative to each bearing segment 24. Central force transmission by the bearing segments 24 is thus achieved.

[0042] Figure 2 shows the three bearing segments 24 in more detail. The shape of the running surface facing the cam disc is explained in more detail using the central of the three bearing segments 24 in Figure 2, and the shape of its running surface is as follows: central part It has a contact region 26 arranged such that the following occurs. The contact region 26 has a concave curvature, which is greater than the minimum convex cam curvature of the cam disk and less than the maximum convex cam curvature of the cam disk. The concave curvature is at least 50% greater than the minimum convex cam curvature of the cam disk, especially the cam curvature in the valleys.

[0043] The cam curvature of the cam disc 20 indicates the cam curvature of the contour shape 22 at a specific position in each case.

[0044] Proceeding from the projection shown on the upper side of the figure, two angles 30 are plotted in Figure 1 for use in more detail in identifying the curvature of the running surface 26 of the bearing segment. The concave curvature of the contact region 26 is constant across the region of the contact region 26 and within an angular range of 10° to 60° progressing from the apex in both rotational directions. The best in Smaller than the curvature of a small cam, and typically within that angular range The best in It is up to 0.2% smaller than the small cam curvature. More specifically, the concave curvature of the contact area is 99.8% of the minimum cam curvature between 10° and 60°. Note that the cam disk is typically symmetrically designed.

[0045] One side of the bearing segment 24 facing the cam disc is shown in more detail in the schematic diagram of Figure 3. Each peripheral region 27 of the running surface is adjacent to either side of the central contact region 26, and the peripheral region 27 is convex. Adjacent to this, a flat sub-surface 28 is provided, which is adjacent to each of the convex bearing segments 24 by R-shaped edges 29. This shape can also be schematically derived from Figure 2, but for clarity, the corresponding regions in Figure 2 are not denoted by reference numerals.

Claims

1. It is a gearbox, A tooth carrier for receiving the teeth of a gearing arranged around the rotation axis of a gearbox, wherein the tooth carrier is arranged such that the teeth are radially displaceable and guided within the tooth carrier, It comprises a cam disc that is rotatable around a rotation axis and has a cam curvature that is variable over the circumference in order to drive teeth in the radial direction, A bearing segment, which is slidably mounted on the cam disk, is positioned between the teeth and the cam disk. The bearing segment has a concave curvature and a contact region positioned to be central on the running surface facing the cam disc, wherein the concave curvature is greater than the minimum cam curvature of the cam disc and less than the maximum cam curvature of the cam disc.

2. The cam disc has exactly one peak having the maximum radial distance from the axis of rotation and exactly one valley having the minimum radial distance from the axis of rotation. The gearbox according to claim 1, wherein the concave curvature is smaller than the minimum cam curvature within an angular range of 5% to 35% of the entire angular range of the cam disk progressing from the top.

3. The cam disc has at least two peaks having the maximum radial distance from the axis of rotation, and at least two valleys, each located between the peaks and having the minimum radial distance from the axis of rotation. The gearbox according to claim 1, wherein the concave curvature is smaller than the minimum cam curvature in an angular range from 5% to 35% of the entire angular range of the cam disk progressing from the first of the apexes to the second.

4. The gearbox according to claim 2, wherein the concave curvature is at most 1% smaller than the minimum cam curvature within an angular range of 5% to 35%.

5. The gearbox according to claim 1, wherein the running surfaces of the bearing segments are all curved in a convex shape in the circumferential direction in their peripheral regions.

6. The gearbox according to claim 5, wherein the peripheral region is located between the contact region and the flat subsurface.

7. The gearbox according to claim 1, wherein the running surface of the bearing segment includes a sliding bearing material.

8. The gearbox according to claim 1, wherein each bead having a tooth contact surface is located on the surface of a bearing segment facing away from the cam disc.

9. The gearbox according to claim 1, wherein the bearing segment has, when viewed from the direction of rotation, one straight leading edge and one straight trailing edge.

10. The gearbox according to claim 1, wherein, during the operation of the gearbox, mounting by sliding bearings is configured between the running surface of the bearing segment and the cam disc.

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