Coaxial gearbox

Abstract

Coaxial gear (1), comprising a toothing (5) axially aligned with respect to an axis of rotation (3) of the coaxial gear (1), a tooth carrier (7) with axially aligned guides (9), teeth (11) which are received in the guides (9) for engagement with the toothing (5), wherein the teeth (11) are axially aligned in the guides (9) with their respective longitudinal axes (13) and are axially displaceable in the guides (9), and a cam disk (15) rotatable about the axis of rotation (3) for axially driving the teeth (11), wherein the toothing (5) comprises tooth flanks (41), wherein the tooth flanks each extend along a profile curve (47), wherein the profile curve (47) corresponds to a winding of a first curved curve (59) onto a cylinder (91).

Description

Field of invention

[0001] The invention relates to a coaxial gearbox and a use of a coaxial gearbox. State of the art

[0002] Gearboxes are known in the art which include teeth mounted axially displaceably in a tooth carrier. Drive elements with a profile, such as cam discs, are used to drive the teeth in an axial direction. The teeth are moved axially and engage with a toothed section, resulting in relative movement between the tooth carrier with the teeth and the toothed section. The relative movement between the toothed section and the teeth is typically at least one order of magnitude smaller than the movement of the drive element with the profile. High gear ratios can be achieved in this way. An example of such a gearbox is published in DE 10 2019 129 662 A1, in which the gearbox, in particular, has toothed sections and teeth with flanks that each follow a helical path.

[0003] However, existing state-of-the-art solutions have limitations, particularly with regard to the load-bearing capacity of the gearbox, the efficiency of the gearbox, or the service life of the gearbox. Disclosure of the invention

[0004] The object of the invention is to provide a coaxial drive which is improved compared to coaxial drives known from the prior art, in particular by achieving a higher load-bearing capacity, a higher efficiency, or a longer service life. Furthermore, it is an object of the invention to provide a use for such a coaxial drive.

[0005] The problem is solved by a coaxial gearbox according to claim 1 and a use according to the dependent claim. Advantageous further developments and embodiments are described in the dependent claims and in this description.

[0006] One aspect of the invention relates to a coaxial drive. The coaxial drive comprises a toothed section axially aligned with respect to an axis of rotation of the coaxial drive. The coaxial drive comprises a tooth carrier with axially aligned guides. The coaxial drive comprises teeth which are received in the guides for engagement with the toothed section, wherein the teeth are axially aligned with their respective longitudinal axes in the guides and are axially displaceable within the guides. The coaxial drive comprises a cam disk rotatable about the axis of rotation for axially driving the teeth. The toothed section comprises tooth flanks, wherein the tooth flanks each extend along a profile curve, the profile curve corresponding to a winding of a first curved curve onto a cylinder.

[0007] Another aspect of the invention relates to the use of a coaxial transmission according to one of the embodiments described herein.

[0008] Typically, terms such as "axial", "radial" or "circumferential direction" are to be understood in relation to the axis of rotation of the coaxial drive, for example, the axis of rotation of the cam disk of the coaxial drive or the tooth carrier of the coaxial drive.

[0009] In typical embodiments, the guides of the gear carrier are axially aligned with respect to the axis of rotation of the coaxial drive. Typically, the teeth are mounted in the guides of the gear carrier so as to be axially displaceable. Typically, each tooth in the gear carrier is mounted so as to be displaceable in exactly one direction, typically along the longitudinal axis of the tooth. This can be achieved, for example, by ensuring that the tooth has a constant cross-section in the direction of displacement over a certain length, particularly along the longitudinal axis of the tooth. Typically, the guide for the tooth in the gear carrier is designed as a bore or opening with a constant cross-section in the axial direction. Typically, the bores are designed with chamfers at the edges to prevent edge bearing.

[0010] Typical tooth carriers comprise guides with a tooth base opening on one tooth base side of the tooth carrier and a tooth head opening on one tooth head side. Typically, the tooth base opening is oriented towards the cam disk, and the tooth head opening towards the toothing. This allows the teeth to be received so that they are axially displaceable along their respective longitudinal axes within the guide relative to the axis of rotation of the coaxial drive. The longitudinal axis of a tooth typically runs from the tooth base to the tooth head. Typically, each tooth is supported at its tooth base on a bearing segment, with the bearing segments in turn being supported on the cam disk. In typical embodiments, the tooth carrier is circular or annular. Typical guides for the teeth within the tooth carrier are designed as through-holes or through-bores.Other typical tooth carriers include rectangular milled recesses, elongated holes, or slots as guides.

[0011] In typical embodiments, the coaxial drive comprises a cam disk with a profiled section as a drive element for the axial drive of the teeth, in particular by axial stroke of the teeth. Typically, the profiled section along the circumferential direction of the cam disk has at least one axial projection, and in particular at least two or at least three projections. By driving the cam disk with the profiled section, a force can be exerted on the teeth via the bearing segments in the direction of their respective longitudinal axes, so that the teeth are pushed out of the guides on the tooth tip side of the tooth carrier. The bearing segments are typically configured to support the teeth on the profiled section of the cam disk. In particular, the bearing segments can be mounted on the cam disk via a rolling bearing arrangement.Typically, rolling bearing elements, in particular needle rollers, are provided between the bearing surface of the bearing segments and the profile of the cam disc. In further embodiments, the bearing segments can be slidably mounted on the cam disc via a sliding bearing surface of the bearing segments.

[0012] Typical coaxial gearboxes have an input shaft and an output shaft. Typically, the input shaft and the output shaft are rotatably mounted about the axis of rotation of the coaxial gearbox. Typically, the input shaft or the output shaft, or both, are designed as hollow shafts. Typically, the cam disc is provided on the input shaft. In typical embodiments, the gear carrier is provided on the output shaft, wherein, in particular, the gear teeth or a face gear with the gear teeth are rotationally fixed to a housing of the coaxial gearbox or are not rotatable relative to the housing. In further typical embodiments, gear teeth or a face gear with the gear teeth are provided on the output shaft, wherein, in particular, a gear carrier is rotationally fixed to a housing of the coaxial gearbox or is not rotatable relative to the housing.

[0013] Typical designs can also be used in the reverse direction of transmission, with the cam disc acting as the output element and the toothed carrier as the input element. In this way, for example, a generator can be driven via the cam disc, utilizing a torque that drives the toothed carrier at a low speed. Drive or output via the housing or the teeth of the ring gear is also possible.

[0014] Typical gearboxes according to the invention are used, for example, in robotics, machine tools, packaging machines, lathes or milling machines, medical technology, logistics, automotive engineering, construction, and other industrial drive trains. In generator mode, they can be used in wind turbines or other energy generation plants.

[0015] These components are particularly advantageous for applications with high demands on torque and power density, large hollow shaft diameter, high stiffness, low or zero backlash, or compactness. Their compact size and low weight, combined with maximum precision and safety, are especially beneficial for use in medical robotics.

[0016] In typical embodiments of the coaxial gears according to the invention, at least a portion of the teeth are designed to be rigid. The term "rigid" is typically to be understood in a technical sense, meaning that bending of the teeth due to the stiffness of the tooth material is so small that it is at least essentially insignificant for the kinematics of the coaxial gear.

[0017] In typical embodiments, a tooth has a tooth head with tooth flanks in a first end region facing the gear teeth. Typically, the tooth comprises a tooth base in a second end region facing the cam. The tooth base typically has a hemispherical recess, with the bearing segments having a raised section, at least partially shaped like a spherical cap, for supporting the respective tooth. In other embodiments, the tooth base typically has a tooth base bulge. The tooth base bulge is typically configured to support the tooth in a tooth recess of a bearing segment.

[0018] In typical designs, the tooth comprises a tooth body between the tooth tip and the tooth base. The tooth body extends along the longitudinal axis of the tooth over a body length. Typically, apart from lubrication channels or similar features, the tooth body has at least a substantially uniform cross-section along its body length.

[0019] In typical embodiments, the tooth is designed as a round tooth. For example, the tooth body has a circular cross-section that is at least substantially constant. Typically, the tooth body is at least substantially cylindrical.

[0020] In other typical embodiments, one tooth is designed as a flat tooth. Flat teeth are typically guided in guides with a non-circular cross-section within the tooth carrier. In typical embodiments, two or more flat teeth are arranged side by side, or the tooth has a width at least twice as great, for example in the axial direction of the coaxial drive, as its thickness, for example in the circumferential direction of the coaxial drive. Further embodiments include round or circular teeth, or circular teeth with flattened sections.

[0021] Typical coaxial gears comprise axially oriented gear teeth. In particular, the gear teeth can be designed as the teeth of a face gear. Typically, the gear teeth are circumferential around the axis of rotation. The gear teeth typically comprise a plurality of teeth and teeth, with a tooth flank extending between each tooth and tooth head.

[0022] Typically, the tooth flanks of the gear teeth each extend along a profile curve. This profile curve typically runs along the tooth flank and along a cylindrical surface around the axis of rotation. The cylindrical surface can, for example, correspond to the surface area of ​​the cylinder at the inner diameter of the gear teeth, at the outer diameter of the gear teeth, or at a diameter between the inner and outer diameters.

[0023] In typical embodiments, the profile curve corresponds to the winding of a first curved curve onto a cylinder. Typically, the first curved curve lies in a plane before the winding. Here, a "curved" curve or a curve "with curvature" is typically understood to mean a curve with a non-zero curvature. The reference to a cylinder or a cylindrical surface serves only to describe the shape or the graphical construction of the profile curve of a gear flank or the tooth profile curve of a tooth. In particular, the cylinder is not to be understood as a component of the transmission. In embodiments, which can be combined with other embodiments described herein, a gear profile curve can additionally or alternatively be a curve that has a curvature about a straight line perpendicular to the axis of rotation.According to embodiments that can be combined with further embodiments described herein, a gear profile curve can additionally or alternatively be a curve in which a component of the profile curve extending in the axial and circumferential directions has a curvature. According to embodiments that can be combined with further embodiments described herein, a gear profile curve can additionally or alternatively be a helix that is not constantly compressed or stretched in the axial direction. According to embodiments that can be combined with further embodiments described herein, a gear profile curve can additionally or alternatively be a profile curve that is curved in the gear height direction. The gear height direction is oriented in the axial direction.

[0024] In typical embodiments, the curvature of the profile curve changes along its length. Specifically, the curvature of the profile curve typically changes across the tooth height of the tooth flank. The profile curve is typically different from a curve with constant curvature, and in particular, different from a helix. In typical embodiments, the profile curve exhibits a curvature about the axis of rotation.

[0025] For example, a profile curve can be described as a curve x→ can be represented according to formula (1). x→=(r⋅cos(x / r)r⋅sin(x / r)h(x))

[0026] In formula (1) x→ the Cartesian coordinates of the profile curve. h(x) corresponds to the first curved curve for winding onto a cylinder with radius r. Furthermore, x corresponds to an x-coordinate of the first curved curve h(x).

[0027] In typical embodiments, the first curved curve in its unwound form, for example the first curved curve h(x) in formula (1), comprises a logarithmic spiral, a circular arc, a logarithmic function, a polynomial, a piecewise trigonometric function, an exponential function, an involute, or a combination thereof. Typically, a derivative of the first curved curve in Cartesian coordinates is non-zero. The first curved curve is typically not a straight line.

[0028] In typical designs, the gear teeth are each concave. Typically, the profile curve of a gear tooth is designed such that the gear tooth curves inwards along the axial path of the profile curve.

[0029] In certain embodiments, a gear flank can extend along the profile curve at at least one radius relative to the axis of rotation, for example, at an inner radius or at an outer radius of the gear with respect to the axis of rotation. The profile of the gear flank at the other radii of the gear can result from a radial projection of the profile curve with respect to the axis of rotation.

[0030] Typically, gear flanks extend radially along flank lines. Typically, the gear flanks extend at least substantially along straight flank lines that intersect the axis of rotation at least substantially perpendicularly. "At least substantially along straight flank lines" means, in particular, that the gear flanks may exhibit a flank line correction in the form of a radial crown. In typical embodiments, a gear flank with a flank line correction may have a parabolic, logarithmic, or arcuate crown. A crown of a gear flank may, at the edges of the gear tooth, involve a reduction of the gear flank relative to a flank line, where the flank line, for example, passes through a vertex of the gear flank.The crowning can, in particular, exhibit a reduction of up to 10% of the width of the tooth. "At least substantially perpendicular" means, in particular, that the flank lines intersect the axis of rotation perpendicularly or perpendicularly with a deviation of no more than 2°, especially with a deviation of no more than 1°. The profile curves or flank lines are to be understood here in a geometric sense.

[0031] In certain embodiments, the gear flanks can exhibit one or more deviations from the profile curve. In particular, these deviations can include recesses or bulges with respect to the profile curve or the flank lines. A deviation can, for example, take the form of an arc-shaped recess at the tip or root of the gear. In other typical embodiments, the gear flank can exhibit a deviation from the profile curve in the form of profile crowning. Corrections to the gear flanks, the tips of the gear, or the roots of the gear can, for example, compensate for misalignments caused by manufacturing imperfections. Typically, the gear flank follows the profile curve over at least 70% of the axial height of the gear flank, and in particular over at least 80% or at least 90% of the axial height.

[0032] In typical embodiments, the teeth each comprise tooth flanks for meshing with the tooth flanks of the gearing. In typical embodiments, the tooth flanks of the teeth each extend along a tooth profile curve, wherein the tooth profile curve corresponds to the winding of a second curved curve onto a cylinder. Typically, the second curved curve lies in a plane before the winding. According to embodiments, which can be combined with other embodiments described herein, a tooth profile curve of a tooth can additionally or alternatively be a curve that has a curvature about a straight line perpendicular to the axis of rotation.According to embodiments that can be combined with further embodiments described herein, a tooth profile curve can additionally or alternatively be a curve wherein a component of the tooth profile curve extending in the axial and circumferential directions has a curvature. According to embodiments that can be combined with further embodiments described herein, a tooth profile curve can additionally or alternatively be a helix that is not constantly compressed or stretched in the axial direction. According to embodiments that can be combined with further embodiments described herein, a tooth profile curve can additionally or alternatively be a tooth profile curve that is curved in the tooth height direction. The tooth height direction is oriented in the axial direction.

[0033] In certain embodiments, the curvature of the tooth profile curve changes along its length. Specifically, the curvature of the tooth profile curve typically changes across the tooth height of the tooth flank. The tooth profile curve is typically a curve with a constant curvature, and in particular, it is not a helix. In typical embodiments, the tooth profile curve exhibits a curvature about the axis of rotation. Typically, the tooth profile curve runs along a tooth flank and along a cylindrical surface about the axis of rotation.

[0034] Typically, the curvature of the tooth profile curve differs from the curvature of the gear teeth. Similarly, the curvature of the first curved section differs from the curvature of the second. At least partial surface contact between a gear tooth flank and a tooth flank with different curvatures can develop during operation due to deformation of the gear teeth and lubrication of the transmission. According to typical embodiments, the tooth flanks are convex. Typically, the tooth profile curve of a tooth flank is designed such that the tooth flank curves outwards along the axial path of the tooth profile curve.

[0035] According to typical embodiments, when the teeth engage with the gear teeth, they form a convex-concave contact between a tooth flank and a tooth flank of the gear teeth. In particular, the convex-concave contact can be formed between a convex tooth flank and a concave tooth flank of the gear teeth. In contrast to a planar contact between tooth flank and tooth flank, a convex-concave contact can provide improved load-bearing capacity, especially improved hydrodynamic load-bearing capacity. For example, in a convex-concave contact according to embodiments, in addition to a drag flow (Couette flow), a hydrodynamic load-bearing effect can be generated due to the displacement of a lubricant by a rolling motion of the convex tooth flank on the concave tooth flank (see also Fig. 9 and Fig. 10) In particular, a higher hydrodynamically effective contact velocity can be achieved through a convex-concave contact than through a planar contact or a convex-convex contact.

[0036] According to typical embodiments, the second curved curve in unwound form comprises a logarithmic spiral, a circular arc, a logarithmic function, a polynomial, a piecewise trigonometric function, an exponential function, an involute, or a combination thereof.

[0037] In certain embodiments, a tooth flank can extend along the tooth profile curve at at least one radius relative to the axis of rotation, for example, at an inner or outer radius of the tooth flank with respect to the axis of rotation. The profile of the tooth flank at the other radii of the tooth flank can result from a radial projection of the tooth profile curve with respect to the axis of rotation.

[0038] Typically, tooth flanks extend radially along tooth flank lines. Typically, the tooth flanks extend at least substantially along straight tooth flank lines that intersect the axis of rotation at least substantially perpendicularly. Typically, the plane of symmetry of two adjacent tooth flanks intersects the axis of rotation of the coaxial gear at every point of engagement. The tooth flanks may have corrections, particularly width or profile corrections. These corrections may be designed as described for gear teeth.

[0039] In typical embodiments, the teeth each have a tooth head region with more than two tooth flanks. In particular, the tooth head region can, for example, have two or more tooth heads, each bordered by two tooth flanks. The tooth head region can include a base on which the tooth flanks are arranged in the direction of the toothing, and between the tooth flanks, in particular, the tooth heads or tooth roots are arranged. In other typical embodiments, the teeth are each designed as individual teeth with two tooth flanks.

[0040] In typical embodiments, the toothing between circumferentially adjacent tooth flanks alternately comprises a head and a root of the toothing in the circumferential direction. In these embodiments, a tooth head line running on a tooth head is straight and perpendicular to the axis of rotation. In these embodiments, a tooth root line running on a tooth root is straight and perpendicular to the axis of rotation.

[0041] The tip of a tooth typically has no edge at the transition to a tooth flank. For example, a tooth tip line coincides with a flank line of the tooth flank at the boundary. Typically, the root of a tooth is continuously rounded circumferentially between two tooth flanks, in particular with a root radius or a polynomial, especially a polynomial of degree 4 to 8, for example, a polynomial of degree 6. The root of the tooth typically has no edge at the transition to a tooth flank. In particular, a tooth root line coincides with a flank line of the tooth flank at the boundary. In typical embodiments, a smooth transition of the root through the tooth can be achieved by a continuous rounding of the tooth root.

[0042] Typically, the teeth of the coaxial gear each comprise a tooth tip, with a tip line running along the tooth tip being straight and perpendicular to the axis of rotation. The tooth tip extends, in particular, between two tooth flanks of a tooth. Typically, the tooth tip is circumferentially rounded between two tooth flanks, especially with a tooth tip radius. The tooth tip typically has no edge at the transition to a tooth flank. In particular, a tooth tip line coincides with a tooth flank line of the tooth flank at the boundary with a tooth flank.

[0043] Typically, the tip of a tooth is narrower around the axis of rotation than the root of the tooth. Specifically, the tip radius is smaller than the root radius. This allows for a smooth transition of a tooth from one tooth flank to an adjacent tooth flank, or prevents a tooth from simultaneously contacting two tooth flanks.

[0044] In typical embodiments, the coaxial gear's toothing is designed as a running gear. Typically, the toothing is designed to be traversed by the teeth. Typically, relative movement occurs between the toothing and the teeth during operation. Typically, the toothing has tooth flanks, particularly finely machined tooth flanks, which are designed for the tooth flanks of the teeth to slide along the tooth flanks of the toothing. In particular, the coaxial gear's toothing is not designed as a splined connection.

[0045] Typically, the components of the coaxial drive, in particular the gearing, the teeth, the gear carrier, the bearing segments, or the cam disc, are made of plastic, metal, or a plastic-metal composite. In exemplary embodiments, the teeth are made of metal and the gearing of plastic. In further exemplary embodiments, the gearing and the teeth are made of metal, in particular steel.

[0046] In typical embodiments, the gear teeth, in particular a face gear with the gear teeth, or the teeth themselves, are manufactured by injection molding, especially plastic injection molding or metal powder injection molding. Other typical gear teeth are manufactured by rapid prototyping, sintering, or electrical discharge machining (EDM), typically die-sinking EDM. In typical embodiments, the gear teeth are manufactured by a rolling process. Typically, the gear teeth are manufactured by cold forming, in particular gear rolling, or by machining processes, in particular gear hobbing, or by grinding processes, in particular gear grinding.

[0047] Typical embodiments of coaxial gears offer advantages over the prior art in that, for axially toothed components, particularly the gear teeth, the curvature of the gear flanks or tooth flanks can be specifically selected. This allows, for example, improved hydrodynamics in the contact between the gear teeth and the tooth flanks. For instance, higher hydrodynamic load-carrying capacity can be achieved in the contact between the gear teeth and the teeth. In particular, the transmission of greater forces or higher torques can be accomplished. These embodiments can also feature improved lubrication film formation between the teeth and the gear teeth. Typical coaxial gears can exhibit reduced wear, lower heat generation, lower thermal stress, higher performance, or a longer service life.Furthermore, the embodiments described herein can exhibit a higher efficiency. During operation of a typical gearbox according to the embodiments described herein, continuous surface meshing can develop between the toothed components, particularly due to the lubrication of the gearbox and the deformation of the components during operation. Further advantages over known gearboxes may include higher resource efficiency or a smaller installation space requirement. Brief description of the drawings

[0048] The invention is explained in more detail below with reference to the accompanying drawings, the figures of which show: Fig. Figure 1 shows a section of a schematic sectional view of a typical embodiment of the coaxial gearbox; Fig. Figure 2A shows a schematic isometric view of a plane gear with the teeth of a typical coaxial gear; Fig. Figure 2B shows a schematic detail view of the plan wheel of the Fig. 2A; Fig. Figure 3A shows a section of a schematic side view of a gear from radially outside in the direction of the axis of rotation; Fig. Figure 3B shows a section of another schematic side view of a gear toothing from radially outside in the direction of the axis of rotation; Fig. Figure 4 shows a schematic representation of winding a first curved curve onto a cylinder; Fig. Figure 5 shows a section of a schematic top view of a gear along the axis of rotation; Fig. Figure 6 shows a schematic representation of a tooth in engagement with a toothing according to embodiments; Fig. Figure 7 shows a section of a schematic side view of a tooth from radial inside; Fig. Figure 8 shows a schematic view of a tooth with more than two tooth flanks; Fig. Figure 9 shows a schematic representation of the hydrodynamically effective velocity of a contact between a convex tooth flank and a flat gear flank; and Fig. Figure 10 shows a schematic representation of the hydrodynamically effective velocity of a contact between a convex tooth flank and a concave gear flank according to typical embodiments described herein. Description of exemplary implementations

[0049] Typical embodiments of the invention are described below with reference to the figures. The invention is not limited to these embodiments; rather, the scope of the invention is defined by the claims. In the description of the embodiments, the same reference numerals may be used for identical or similar parts in different figures and for different embodiments. For the sake of clarity, some features already described in connection with other figures are not described again. For clarity, not all features are always provided with a reference numeral, for example, the gear teeth (reference numeral 41).

[0050] In the Fig. Figure 1 shows a section of a typical embodiment of the invention in a schematic sectional view. Fig. Figure 1 shows a coaxial gearbox 1 with a toothing 5 axially aligned with respect to a rotational axis 3 of the coaxial gearbox 1. The toothing 5 is designed as the toothing of a face gear 29 rotating around the rotational axis 3. The face gear 29 is rotationally fixed to a housing 31 of the coaxial gearbox 1.

[0051] The coaxial gearbox 1 comprises a tooth carrier 7, which is provided on an output shaft 34. The output shaft 34 is rotatably mounted on the housing 31 about the axis of rotation 3 via a first bearing 33. The tooth carrier 7 has axially aligned guides 9, in each of which teeth 11 are received. The teeth 11 are axially displaceable along their respective longitudinal axes 13 in the guides 9 with respect to the axis of rotation 3.

[0052] Each tooth 11 comprises tooth flanks oriented for engagement with the toothing 5 and a tooth base projecting from the guide 9 of the respective tooth 11 and supported on a bearing segment 17. A tooth 11 further comprises a tooth body between the tooth base and the tooth flanks, the tooth body being at least partially received in the guide 9. The tooth base of the tooth 11 rests with a recess 21 on a partially spherical-cap-shaped elevation 19 of the bearing segment 17.

[0053] The bearing segments 17 are each supported by a running surface 23 on their side facing away from the tooth on a rolling bearing with rolling elements 27, which in turn is supported on a profile 25 of a cam disk 15 of the coaxial drive 1. The rolling bearing is located in the Fig. Figure 1 shows a section of a cage 26 for the rolling elements 27 (partially obscured). The rolling elements 27 are designed as needle rollers. In further embodiments, the rolling elements can be designed as cylindrical rollers. In still further embodiments, the bearing segments 17 are each mounted on the profile 25 of the cam disk 15 of the coaxial drive 1 via a sliding bearing surface. The coaxial drive 1 of the Fig. 1 further comprises an anti-rotation ring 28 arranged between the teeth 11 and the bearing segments 17, which in particular prevents the teeth 11 from rotating about their respective longitudinal axis 13.

[0054] The cam disc 15 is mounted on a drive shaft 36. The drive shaft 36 is rotatably mounted on the toothed carrier 7, and thus indirectly also on the housing 31, via a second bearing 35 about the axis of rotation 3. The cam disc 15 is mounted relative to the housing 31 via a thrust bearing 32 with needle rollers. The profile 25 extends around the axis of rotation 3 and has in the Fig. 1 two axial elevations in the direction of teeth 11.

[0055] The Fig. 2A and Fig. Figure 2B shows schematic views of a plane gear 29 with a toothing 5 arranged circumferentially around the axis of rotation 3. The toothing 5 has tooth flanks 41 which extend along profile curves and flank lines according to the embodiments described herein. The toothing 5 has, between circumferentially adjacent tooth flanks 41, an alternating head 43 and a root 45 of the toothing 5 in the circumferential direction. In the Fig. Figures 2B, 3A, and 3B clearly show the gear flanks 41 with a pronounced curvature. Typical embodiments may also exhibit a less pronounced curvature.

[0056] The Fig. 3A and Fig. Figures 3B each show a section of a schematic side view of a gear 5 from radially outside in the direction of the axis of rotation 3, wherein Fig. 3A onto a head 43 of the gearing 5 and Fig. 3B is centered on a foot 45 of the toothing 5. The tooth flanks 41 extend in particular along profile curves. In Fig. 3B shows, for example, an inner profile curve 48 at an inner radius of the gear 5 for each of two gear flanks 41, as well as an outer profile curve 49 at an outer radius of the gear 5. In the Fig. 3B the inner profile curve 48 and the profile curves at the further radii between the outer radius and the inner radius result from a radial projection of the outer profile curve 49 with respect to the axis of rotation 3.

[0057] In typical embodiments, the profile curve 47 corresponds to a winding of a first curved curve 59 onto a cylinder 91, as shown schematically in, for example, Fig. The first curved curve 59 lies in a plane 93. In particular, the first curved curve 59 already exhibits a non-zero curvature in the plane 93. The curved curve 59 can be described, for example, by the function h(x) in the formula (1) described above. In particular, the first curved curve 59 is not a straight line. The first curved curve 59 is wound onto a cylinder 91 (indicated by arrows 97). The cylinder 91 extends around the axis of rotation 3 with a radius 95, which corresponds, for example, to the inner radius of the gear 4. By winding the first curved curve 59, the profile curve 47 is obtained, as shown in Fig. 4 by a dashed line. In typical embodiments, a tooth profile curve of a tooth flank of a tooth can be constructed analogously using a second curved curve, wherein the second curved curve is in particular different from the first curved curve 59.

[0058] The Fig. Figure 5 shows one half of a schematic top view along the axis of rotation 3 of a gear tooth 5. The gear tooth 5 comprises gear flanks 41, each extending from an inner radius 67 of the gear tooth 5 to an outer radius 68 of the gear tooth 5. The gear flanks 41 each extend from a root 45 of the gear tooth 5 to a tip 43 of the gear tooth 5. The gear flanks 41 run in Fig. 5 each along a profile curve according to the embodiments described herein and along straight flank lines 51 which intersect the axis of rotation 3 perpendicularly. A root 43 and a head 45 of the gear 5 are each continuously and edge-free rounded at the transition to a tooth flank 41. The head 43 extends along tooth tip lines 63, which are straight and intersect the axis of rotation 3 perpendicularly. The root 45 extends along tooth root lines 65, which are straight and intersect the axis of rotation 3 perpendicularly. In the Fig. Figure 5 shows exemplary gear tip lines 63, each located at a boundary between a tip 43 and the gear flanks 41, or in the center of a tip 43. The exemplary gear root lines 65 each run along a boundary between a root 45 and the gear flanks 41.

[0059] The Fig. Figure 6 shows a tooth 11 engaging with a gear 5 in a schematic side view from the radial outside in the direction of the axis of rotation 3 of a typical coaxial drive. The tooth 11 is slidably mounted in a tooth carrier in the direction of its longitudinal axis 13, which is shown in the schematic representation of the Fig. Figure 6 is not shown for clarity. The tooth 11 is designed as a single tooth with two tooth flanks 71 converging on a tooth head 72. The tooth flanks 71 each extend along tooth profile curves according to the embodiments described herein and along straight tooth flank lines that intersect the axis of rotation 3 perpendicularly. In particular, the tooth flanks 71 are convex. The gear teeth 41 are concave, so that when the tooth 11 engages the gear teeth 5, a convex-concave contact 69 is formed between a tooth flank 71 of the tooth 11 and a gear tooth flank 41 of the gear teeth 5.

[0060] The Fig. Figure 7 shows a section of a tooth 11 according to a further embodiment in a view from radially inside to radially outside. In particular, the Fig. Figure 7 shows a section of a round tooth. The tooth 11 is designed as a single tooth with two tooth flanks 71, which extend from a tooth body 73 of the tooth 11 to a tooth tip 72 of the tooth 11. The tooth flanks 71 each extend, in particular, along an inner tooth profile curve 53 at an inner radius of the gear 5 and along an outer tooth profile curve 55 at an outer radius of the gear 5. The inner tooth profile curve 53 and the outer tooth profile curve 55 each correspond to the winding of a curved curve onto a cylinder.

[0061] The Fig. Figure 8 shows a view of a tooth 11 according to another typical embodiment. The tooth 11 comprises a tooth body 73, which is provided for receiving in a guide of a tooth carrier. The tooth body 73 has a diameter in cross-section that is at least substantially constant with respect to the longitudinal axis 13 of the tooth 11. The tooth 11 comprises a tooth base 75 for receiving in a bearing segment of a coaxial drive. In other typical embodiments, the tooth base 75 may have a recess, in particular for supporting the tooth base 75 on a bearing segment, as in the Fig. Figure 1 shows the tooth 11 having a tooth head region 70, which includes a base 81. More than two tooth flanks 71 are provided on the base 81 for engagement in the toothing, in which Fig. 8 for example ten tooth flanks 71. The tooth flanks 71 each extend along a profile curve according to the embodiments described herein.

[0062] As in the Fig. 9 and Fig. As schematically illustrated in Figure 10, in certain embodiments the curvature profile of the gear teeth or tooth flanks can be specifically selected, particularly to provide improved hydrodynamics in the contact between the gear teeth and the tooth flanks. In particular, in certain embodiments the lubrication of the flanks can be improved by increasing the hydrodynamically effective velocity in the contact between the gear teeth and tooth flanks.

[0063] The Fig. Figure 9 schematically depicts a tooth 100 in engagement with a planar tooth flank 104 of a tooth 103 at a first time t, wherein the tooth is not designed according to the typical embodiments described herein, in particular not with a profile curve according to typical embodiments. At time t, there is contact between the tooth flank 102 of the tooth 100 and the planar tooth flank 104 at a first contact position 105. The tooth flank 102 of the tooth 100 is convex. The tooth 100 is also shown as tooth 101 at a second time t+Δt of the engagement, wherein the tooth 101 has moved by a feed distance Δl in the time interval Δt. The contact between the tooth flank 102 and the planar tooth flank 104 exists at the second time in a second contact position 106. In particular, the contact moves in Fig. 9 in the time interval Δt along the planar gear flank 104 from the first contact position 105 to the second contact position 106 by the distance Δs, where the feed path Δl is equal to the distance Δs, i.e.: Δl=Δs. In Fig. 9 is therefore the hydrodynamically effective velocity u that is primarily responsible for the formation of a lubricating film. hydr equal to the feed rate u Flanke of the tooth engaging in the planar tooth flank 104: uhydr=ΔsΔt=uFlanke

[0064] The Fig. Figure 10 schematically depicts the engagement of a convex tooth flank 102 of a tooth 100 with a concave tooth flank 114 of a gear 113 at a first time t, wherein the tooth flank 102 and the concave tooth flank 114 are each formed along a profile curve or tooth profile curve according to the embodiments described herein. In particular, the profile curve and the tooth profile curve have different curvatures, especially to avoid the tooth flank and the tooth flank being identical. Similar to in Fig. Figure 9 shows tooth 100 as tooth 101 at a second time point t+Δt, where tooth 101 has covered the feed distance Δl in the time interval Δt. However, the convex-concave contact between the convex tooth flank 102 and the concave gear flank 114 in the Fig.10. The distance Δs between the first contact position 115 and the second contact position 116 has been covered, where the distance Δs is greater than the feed path Δl, i.e.: Δs>Δl. Therefore: uhydr=ΔsΔt>uFlank=ΔlΔt

[0065] Typical designs can therefore achieve an increased hydrodynamically effective speed u hydr provide. In particular, a convergent lubrication gap, i.e., one that changes across the tooth engagement, can be formed to provide improved hydrodynamic load-bearing capacity. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 129 662 A1

[0002]

Claims

[1] Coaxial gearbox (1), with - a toothing (5) axially aligned with respect to an axis of rotation (3) of the coaxial drive (1), - a tooth carrier (7) with axially aligned guides (9), - teeth (11) which are received in the guides (9) for engagement with the toothing (5), wherein the teeth (11) are axially aligned in the guides (9) with their respective longitudinal axes (13) and are axially displaceable in the guides (9), and - a cam disk (15) rotatable about the axis of rotation (3) for axially driving the teeth (11), wherein the toothing (5) comprises tooth flanks (41), wherein the tooth flanks each extend along a profile curve (47), wherein the profile curve (47) corresponds to a winding of a first curved curve (59) onto a cylinder (91). [2] Coaxial gear unit (1) according to claim 1, wherein the profile curve (47) has a curvature about the axis of rotation (3). [3] Coaxial gear unit (1) according to one of the preceding claims, wherein the curvature of the profile curve (47) changes along the profile curve (47). [4] Coaxial gear (1) according to one of the preceding claims, wherein the profile curve (47) runs on the gear flank (41) and along a cylindrical surface around the axis of rotation (3). [5] Coaxial gear (1) according to one of the preceding claims, wherein the gear flanks extend at least substantially along straight flank lines (51); wherein the flank lines (51) intersect the axis of rotation (3) at least substantially perpendicularly. [6] Coaxial gear (1) according to one of the preceding claims, wherein the gear flanks (41) are each concave. [7] Coaxial gear (1) according to one of the preceding claims, wherein the teeth (11) each comprise tooth flanks (71) for engagement with the tooth flanks (41) of the gearing (5), wherein the tooth flanks (71) are each convex. [8] Coaxial gear (1) according to claim 7, wherein the tooth flanks (71) of the teeth (11) each extend along a tooth profile curve, the tooth profile curve corresponding to a winding of a second curved curve onto a cylinder. [9] Coaxial gear (1) according to claim 8, wherein a curvature of the tooth profile curve is different from a curvature of the profile curve (47) of the gearing. [10] Coaxial gear (1) according to one of the preceding claims, wherein the teeth (11) when engaging the teeth (11) in the gearing (5) each form a convex-concave contact (69) between a tooth flank (71) and a gear flank (41) of the gearing (5). [11] Coaxial gear (1) according to one of the preceding claims, wherein the teeth (11) each have a tooth head region (70) with more than two tooth flanks (71). [12] Coaxial gear (1) according to one of the preceding claims, wherein the first curved curve (59) in unwound form comprises a logarithmic spiral, a circular arc, a logarithmic function, a polynomial, a piecewise trigonometric function, an exponential function, an involute, or a combination thereof. [13] Coaxial gear (1) according to one of the preceding claims, wherein a gear head line (63) extending on a head (43) of the gearing (5) extends straight and perpendicular to the axis of rotation (3), and / or wherein a gear foot line (65) extending in a foot (45) of the gearing (5) extends straight and perpendicular to the axis of rotation (3). [14] Use of a coaxial drive (1) according to any one of claims 1 to 13.

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