Gearbox

Abstract

To specify an improved gearbox or tooth, whereby achieving reduction of running-in behavior, and less wear or higher load-bearing capability, and to furthermore specify a method for producing a tooth for a gearbox.SOLUTION: A gearbox, in particular coaxial gearbox, comprises: a ring gear having an internal toothing; a tooth carrier having guides that are aligned radially with respect to a rotation axis of the gearbox; teeth 9 that, for engaging with the internal toothing, are received in the guides, wherein the teeth 9 are mounted in the guide displaceably in a direction of their longitudinal axis 11 relative to the tooth carrier; and a cam disk that is rotatable about the rotation axis and is operatively connected to the teeth 9; wherein the teeth 9 have in each case a tooth flank 17 that is formed to be at least partially curved along a width curve extending over a width 41 of the tooth flank 17.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gearbox, teeth for a gearbox, and a method for manufacturing teeth for a gearbox. [Background technology]

[0002] Gearboxes with teeth mounted on a tooth carrier so as to be radially displaceable relative to the rotation axis of the gearbox are known in the prior art. The teeth are operatively connected to a cam disk having a circumferential profile about the rotation axis. The cam disk can be used, in particular, to drive the teeth radially. The teeth engage with the toothing so that relative movement occurs between the tooth carrier and the toothing. Here, the relative movement between the toothing and the toothing is typically at least an order of magnitude smaller than the movement of the cam disk with its profiling. In this way, high gear ratios can be achieved; an example of such a gearbox is disclosed in EP 2 129 935 A2.

[0003] However, known gearboxes exhibit a particular running-in behavior when first used. Additionally, known gearboxes may have limitations with respect to their load-bearing capabilities. Summary of the Invention

[0004] It is an object of the present invention to define an improved gearbox or teeth compared to gearboxes known in the prior art, thereby achieving reduced running-in behavior, less wear or higher load-bearing capacity.A further object of the present invention is to define a method for manufacturing teeth for gearboxes.

[0005] This object is achieved by a gearbox according to claim 1 and by a tooth and method according to the associated claims. Advantageous refinements and embodiments can be obtained from the dependent claims and the present description.

[0006] One aspect of the invention relates to a gearbox, in particular a coaxial gearbox. The gearbox comprises a ring gear with internal toothing. The gearbox comprises a tooth carrier with a guide arranged radially relative to the rotation axis of the gearbox. The gearbox comprises teeth received in the guide for engagement with the internal toothing, the teeth being mounted in the guide so as to be displaceable in the direction of the longitudinal axis relative to the tooth carrier. The gearbox comprises a cam disk rotatable about the rotation axis and operably connected to the teeth. The teeth in each case have tooth flanks, which are formed so as to be at least partially curved along a width curve extending over the width of the tooth flank.

[0007] A further aspect of the invention relates to a gearbox, in particular a coaxial gearbox. The gearbox comprises a ring gear with internal toothing. The gearbox comprises a tooth carrier with a guide arranged radially relative to the rotation axis of the gearbox. The gearbox comprises teeth received in the guide for engagement with the internal toothing, the teeth being mounted in the guide so as to be displaceable in the direction of the longitudinal axis relative to the tooth carrier. The gearbox comprises a cam disk rotatable about the rotation axis and operably connected to the teeth. The teeth have in each case tooth heads, and a tooth head width curve extending along the tooth heads over the tooth width is formed so as to be at least partially curved in the direction of the longitudinal axis of the tooth.

[0008] Yet another aspect of the present invention relates to a tooth for a gearbox according to one of the exemplary embodiments described herein. The tooth has a tooth flank, which is formed so as to be at least partially curved, in particular convexly curved, along a width curve extending across the width of the tooth flank. Additionally or alternatively, the tooth has a tooth head, which is formed so as to be at least partially curved, in particular convexly curved, along the tooth head across the tooth width.

[0009] A further aspect of the present invention relates to a method for manufacturing teeth for a gearbox according to one of the exemplary embodiments described herein. The method includes providing a tooth blank for the tooth. The method includes forming a tooth flank of the tooth, the tooth flank being formed to be at least partially curved along a width curve extending across the width of the tooth flank. Additionally or alternatively, the method includes forming a tooth head of the tooth, the tooth head being formed so that a tooth head width curve extending across the tooth width along the tooth head is at least partially curved in the direction of a longitudinal axis of the tooth.

[0010] An exemplary embodiment of the present invention relates to a gearbox, in particular a coaxial gearbox, which typically comprises a cam disc rotatable about the rotation axis of the gearbox, the cam disc typically having a circumferential profiling about the rotation axis, for example having at least one ridge in the radial direction, in particular having at least or exactly two ridges, or at least or exactly three ridges.

[0011] A typical gearbox has a tooth carrier with a guide arranged radially relative to the rotation axis. Typically, one tooth according to the embodiments described herein is received in each guide. The tooth is typically mounted in the guide so that it can be displaced in the direction of the longitudinal axis relative to the tooth carrier. Typically, each tooth can be mounted in the tooth carrier so that it can be displaced in exactly one direction, typically in the direction of the tooth's longitudinal axis. The guide in the tooth carrier can in each case be configured as a slot or opening, in particular as a slot or opening with a constant cross section in the radial direction. The tooth is typically inserted into the tooth carrier with its head extending parallel to the rotation axis.

[0012] In a typical embodiment of the gearbox according to the invention, the teeth are configured to be flexurally rigid. The term "flexurally rigid" is typically to be understood in its technical sense, i.e. meaning that the rigidity of the tooth material makes the tooth deflection so small that it is at least substantially irrelevant with regard to the kinematics of the gearbox. Flexurally rigid teeth include in particular teeth made from metal alloys, in particular steel or titanium alloys, nickel alloys or other alloys.

[0013] A typical gearbox has a ring gear with internal toothing. Typically, the flanks of the internal toothing herein extend parallel to the axis of rotation. The tooth carrier is typically arranged radially between the ring gear and the cam disc. In particular, the cam disc may be arranged radially inward, for example around or on the axis of rotation of the gearbox. Unless otherwise specified, the terms "axial", "radial" and "circumferential" herein should typically be understood with respect to the axis of rotation of the gearbox.

[0014] In typical embodiments, the pivot segment is in each case arranged between the tooth and the profiling of the cam disc. The pivot segment is typically arranged on a rolling bearing that rests on the profiling. For example, the rolling bearing can be formed as a needle roller bearing. Typically, the tooth is loosely connected to the pivot segment. "Loosely connected" in this context particularly means that the tooth segment is simply arranged on the pivot segment, in particular directly on it. The pivot segment typically has a profile that prevents the tooth from shifting from the pivot segment or that prevents the pivot segment from shifting out of position in at least one direction. Such a profile can be, for example, a clearance-engaging bead on the radially inner end of the tooth. For potential embodiments of the pivot segment, see DE 10 2015 105 523 A1.

[0015] In a typical embodiment, a cam disc is operatively connected to the teeth. In particular, the cam disc can be used as a drive element for driving the teeth radially. Upon rotation of the cam disc about the rotation axis, the teeth typically move radially by profiling, so that a portion of the teeth constantly engages with the internal toothing of the ring gear, resulting in relative motion between the tooth carrier and the ring gear. The output of the gearbox can be output by the tooth carrier or the ring gear.

[0016] In a typical embodiment, the opposite transmission direction can also be used, in which the cam disc is used as the output element and the tooth carrier is used as the drive element. In this way, for example, a generator can be driven via the cam disc, thereby utilizing the torque that drives the tooth carrier at low rotational speeds. Drive input or output via the teeth of the housing or ring gear is also possible.

[0017] Typical gearboxes according to the invention are used, for example, in robotics, machine tools, packaging machines, turning or milling machines, medical technology, logistics, automotive engineering, the construction sector and other industrial drive trains. When operating in conjunction with a generator, the gearbox can be used in wind power plants or other plants for generating energy.

[0018] Said gearbox is particularly advantageous in applications with high requirements regarding torque and power density, large diameter hollow shaft, high stiffness, low or zero backlash, or compactness.

[0019] In typical embodiments, the tooth in each case comprises a tooth body. The tooth body typically has a sliding surface for mounting the tooth in a friction bearing of the tooth in the guide of the tooth carrier. In typical embodiments, the tooth is formed in each case as a single tooth, in particular as a round tooth. The round tooth typically has a round tooth body. In particular, the tooth body can be designed to be round, for example circular, in the circumferential direction about the longitudinal axis of the tooth. In embodiments, the tooth body is formed to be at least substantially cylindrical, at least in the region along the longitudinal axis of the tooth. Typically, the guide of the tooth carrier has an opening in the radial direction corresponding to the cross section of the tooth, for example a rounded, in particular circular, opening for a round tooth.

[0020] In a typical embodiment, each tooth has at least one tooth flank, in particular exactly two tooth flanks. The at least one tooth flank is typically arranged in a radially outer region of the tooth body. In a typical embodiment, each tooth has one tooth head. The tooth head is typically arranged adjacent to the tooth flank and extends over the tooth width of the respective tooth. The tooth width of the tooth corresponds to the tooth width parallel to the rotation axis of the gearbox. Typically, the tooth width of the tooth corresponds to the width of the tooth head. The tooth head is typically arranged at one end of the tooth relative to the longitudinal axis of the tooth, in particular at the radially outer end of the tooth relative to the rotation axis of the gearbox. In a typical embodiment, the tooth flanks are inclined with respect to the longitudinal axis of the tooth. For example, the two tooth flanks of one tooth may at least substantially converge obliquely toward the tooth head of the tooth. The tooth head typically has a surface extending from the first tooth flank to the second tooth flank of the tooth. In particular, the surface of the tooth head may be designed to have a head radius between the two tooth flanks.

[0021] In a typical embodiment, the tooth flank or head has a width, which is typically understood to be the extent of the tooth flank or head parallel to the axis of rotation of the gearbox.

[0022] According to an exemplary embodiment, the tooth flanks of the teeth are formed to be at least partially curved along a width curve extending across the width of the tooth flank. A curved width curve is understood to mean a width curve that is typically not linear, for example, an arcuate width curve. In particular, the tooth flanks can have a tooth flank correction or tooth flank modification in the width direction of the tooth flank with respect to a linear tooth flank profile in the width direction. The tooth flank correction or tooth flank modification can in particular correspond to a recess of the tooth flank with respect to the linear tooth flank profile along the width of the tooth flank. In this specification, the curved profile of the tooth flank according to the width curve can also be referred to as a correction, tooth flank correction, or tooth flank modification.

[0023] For teeth of known gearboxes, such as those of the gearbox according to EP 2 129 935 A2, the tooth flank profile is linear (i.e., corresponds to a straight line) across its entire width relative to the direction of the rotation axis of the gearbox. Known gearboxes may have a particular running-in behavior. Teeth with tooth flanks according to the embodiments described herein, i.e., with a curved width curve, can particularly avoid or reduce edge stresses on the edges of the tooth flanks. In known gearboxes, edge stresses are caused in particular by the ring gear teeth of the ring gear, which are wider and therefore stiffer than normal teeth, and by the loss of lubricant from the contact area on the outer edges of the toothing. Tooth flanks with a curved width curve according to the embodiments described herein can particularly avoid or reduce wear on the periphery of the meshing contact between the tooth and the ring gear, especially during the running-in phase of the gearbox.

[0024] According to a typical embodiment, the tooth flank has two outer edge regions along a width curve across the width of the tooth flank, and a central region between the two outer edge regions. In this embodiment, the tooth flank in at least one of the two outer edge regions is concave inward relative to the central region, and in particular curved inward relative to the central region. "Inward" in this context refers to the interior of the tooth. The tooth flank can be designed to be at least partially convex along the width curve. Typically, the width curve curves inward from the central region in both directions of the width of the tooth flank to the periphery of the tooth flank.

[0025] In a typical embodiment, at least one peripheral region is recessed in a direction perpendicular to the tooth surface by at most 1%, particularly at most 0.5%, or at most 0.2% of the maximum width of the tooth surface relative to the central region. In an embodiment, at least one peripheral region is recessed in a direction perpendicular to the tooth surface by at least 0.01%, particularly at least 0.02%, of the maximum width of the tooth surface relative to the central region. Typically, these recesses correspond to the maximum reduction on the tooth surface relative to the central region or linear profile of the tooth surface; these recesses are particularly present on the outer edge of the tooth surface. Typically, the maximum width of the tooth surface corresponds to the width of the tooth surface at the transition from the tooth surface to the tooth crest.

[0026] In a typical embodiment, the width curve extends in a curved manner in at least one of the two outer edge regions, particularly in both outer edge regions. In a typical embodiment, the width curve extends in a linear manner in the central region of the tooth flank. For example, the two outer edge regions may each comprise at least 10%, particularly at least 20%, or at least 25% of the width of the tooth flank. In an embodiment, the two outer edge regions each comprise at most 40%, particularly at most 35% of the width of the tooth flank. For example, the two outer edge regions each comprise approximately 25% of the width of the tooth flank. Typically, the central region includes the portion of the tooth flank from one outer edge region to the other outer edge region. Typically, the specified percentage proportion of the outer edge region relates to the distribution of the outer edge region and the central region on the radially outer end of the tooth flank relative to the rotation axis of the gearbox, particularly at the transition from the tooth flank to the tooth head. In particular, the percentage proportion of the outer edge region in other regions of the tooth flank may deviate from the specified percentage proportion. For example, in the case of rounded teeth, the width of the outer edge region may decrease in profile from the radially outer end of the tooth flank to the radially inner end of the tooth flank, in particular decrease to zero. In typical embodiments, the tooth flank has an at least partially curved width curve according to the embodiments described herein over at least 50%, in particular over at least 60% or at least 70% of the length of the tooth flank in each case. The length of the tooth flank is understood to be the longitudinal extent of the tooth flank perpendicular to the width of the tooth flank.

[0027] In a further exemplary embodiment, the central region may have a width of 0% of the width of the tooth flank. For example, the central region may be a line extending on the tooth flank in the longitudinal direction of the tooth flank, in particular a center line. In particular, the tooth flank may be designed to be curved along a width curve over its entire width, in particular to be spherical over its entire width. In an embodiment, the tooth flank may in particular have a width curve that is curved over the entire length of the tooth flank in each case.

[0028] According to an exemplary embodiment, the width curve extends on the tooth flank and in a cross section perpendicular to the tooth flank. Typically, the width curve extends in a region of the tooth flank that is provided to contact the internal toothing of the ring gear.

[0029] In a typical embodiment, the width curve extends symmetrically with respect to the center of the width of the tooth flank. In an embodiment, the tooth is in each case provided with an additional tooth flank. In this specification, the tooth flank and the additional tooth flank may also be referred to as a first tooth flank and a second tooth flank. Typically, the additional tooth flank is manufactured to be mirror-symmetric with respect to the tooth flank, in particular with respect to a plane extending along the longitudinal axis of the tooth and parallel to the rotation axis of the gearbox. Symmetrical teeth, in particular symmetrical rounded teeth, can be mounted, for example, without special adjustment of the individual tooth flanks, and can be twisted, in particular around their respective longitudinal axes, during operation.

[0030] Typically, the tooth head adjacent to the tooth surface has a tooth head correction. In an embodiment, the tooth head width curve extending along the tooth head across the tooth width is at least partially curved, particularly curved in the direction of the longitudinal axis of the tooth. For example, the tooth head width curve may extend on the tooth head in the plane of the longitudinal axis and the tooth width. In particular, the tooth head width curve may at least partially curve inward toward the tooth body, particularly in the direction of the longitudinal axis of the tooth, in a profile from the center of the tooth head along the tooth width to the outer edge of the tooth. This results in a variable height of the tooth head along the tooth surface or across the tooth width; in particular, the height of the tooth head decreases, for example, radially or logarithmically, from the longitudinal axis toward the outer edge of the tooth. In an embodiment, the shape of the tooth head width curve at least substantially corresponds to the shape of the width curve of the tooth surface. The tooth head width curve may differ from the width curve on the tooth surface by a linear factor, particularly as a function of the inclination of the tooth surface relative to the longitudinal axis of the tooth. The head width curve may extend at least partially curvedly over the head and across the head width in a logarithmic or radius-corrected manner. In particular, the curved portion of the head width curve may extend in a logarithmic or radius-corrected manner. In an embodiment, the head width curve extends symmetrically about the center of the tooth width. Typically, the head is manufactured to be mirror-symmetrical about the plane of the longitudinal axis and the tooth width.

[0031] In a typical embodiment, the tooth head has two outer edge regions along a tooth head width curve across the tooth width. Typically, the tooth head has a central region between the two outer edge regions. Typically, the tooth head in at least one of the two outer edge regions is concave inward relative to the central region, and particularly curved inward relative to the central region. For example, the two outer edge regions of the tooth head may in each case comprise at least 10%, particularly at least 20%, or at least 25%, or at most 40%, particularly at most 35%, e.g., about 25% in each case, of the tooth width. The central region may comprise the entire region between the two outer edge regions. In an embodiment, the tooth head width curve extends in a curved manner in at least one outer edge region. The tooth head width curve may extend in a linear manner in the central region. In a further typical embodiment, the central region of the tooth head may have a width of 0% of the tooth width. In an embodiment, the outer edge region and the central region of the tooth head may correspond to the outer edge region and the central region of the tooth surface.

[0032] Typically, the tooth head, in particular the height of the tooth head, is recessed in at least one outer edge region of the tooth, in particular both outer edge regions, relative to the maximum height of the tooth head in the direction of the longitudinal axis of the tooth. The tooth head typically has a maximum height in the central region of the tooth, in particular in the central region centered on the longitudinal axis. The tooth head height in this specification is understood to be the extent of the tooth head in the direction of the longitudinal axis of the tooth. Typically, the tooth head in at least one outer edge region is recessed by at least 0.02% or at most 2% of the tooth width relative to the maximum height of the tooth head or relative to the linear profile of the tooth head in the direction of the longitudinal axis. In a typical embodiment, the tooth head is formed by grinding, in particular by grinding as described herein, relative to the tooth face.

[0033] In typical embodiments, the recesses of the tooth flanks or tooth heads can widen toward the outer edges of the tooth flanks. For example, the correction can be greater at the outer edges of the tooth flanks to prevent edge stresses. In particular, edge stresses can be prevented at higher compressions during operation or when the tooth flanks are subjected to stronger elastic compression or flattening when in contact with the internal toothing.

[0034] According to typical embodiments, the curved portion of the width curve corresponds to a logarithmic function or a radius correction. In particular, the logarithmic function of the radius correction can represent the recession of the tooth flank along the width curve. For example, the curved portion of the width curve can correspond to a logarithmic function according to the following equation (1): In the latter, and in further embodiments described herein, for each tooth, directions are defined with reference to an orthogonal x, y, z coordinate system. The x, y, z coordinate system can correspond in particular to a machine coordinate system for manufacturing the tooth. The x-axis is arranged in the direction of the width of the tooth flank or tooth head, in particular parallel to the rotation axis of the gearbox. The y-axis is arranged parallel to the longitudinal axis of the tooth, in particular in the radial direction of the gearbox. The z-axis is arranged perpendicular to the x-axis and perpendicular to the y-axis, in particular perpendicular to the width of the tooth flank or tooth head and perpendicular to the longitudinal axis of the tooth.

[0035] In an exemplary embodiment, the tooth flanks of the teeth are formed by grinding, particularly by profile grinding, for example by discontinuous profile grinding. Grinding may be performed according to the embodiments described herein, particularly as described in the context of the exemplary method for manufacturing the exemplary teeth described herein. The following equation (1) describes, in particular, a logarithmic function representing a correction value dy(x) for the y-direction movement of the grinding disk of the profile grinding machine. By varying the y-direction movement as a function of the x position, the tooth flanks and tooth heads can be formed, in particular, with a curved width curve of the tooth flanks and a curved tooth head width curve of the tooth heads.

[0036] <Formula (1)> JPEG2025165894000002.jpg42167

[0037] The above formula (1) describes a correction value, or a width curve or tooth head width curve, that progresses from the center of the tooth flank or tooth head in the width direction. In particular, the width curve can be formed so as to be symmetrical in the other width direction with the center of the tooth flank or tooth head as the reference. In formula (1), bprofil represents a correction coefficient, in particular a constant. Furthermore, x represents the x position along the width of the tooth flank or tooth head, in particular with the center of the tooth flank or tooth head as the origin, and x is smaller than xende.

[0038] xstart represents the start point of the correction in the x-direction, in particular the start point of the logarithmic curve portion of the width curve. Typically, xstart corresponds to the start position of the outer edge region where the width curve is designed to curve. As described herein with respect to additional embodiments, xstart in exemplary embodiments may also be 0, in which case the width curve is designed to curve from the center, in particular across the entire width of the tooth flank or head.

[0039] Xende represents the end point of the correction in the x direction, and in particular represents an x ​​position outside the outer edge of the tooth surface or tooth head, for example, slightly outside the outer edge of the tooth surface or tooth head. In particular, Xende is typically selected so that no x position on the tooth surface coincides with Xende. Typically, Xende is greater than x at all x positions on the tooth surface, and therefore, in particular, the end of the correction curve is located outside the tooth surface.

[0040] In a typical embodiment, the longitudinal curve extending on the tooth surface and perpendicular to the width of the tooth surface is at least partially curved. For example, the longitudinal curve may be configured in the shape of a logarithmic spiral or with a radius. Tooth designs with tooth surfaces having a longitudinal curve in the shape of a logarithmic spiral are described, for example, in EP 2 129 935 A2. The inclination of the tooth surface relative to the longitudinal axis of the tooth may vary along the longitudinal curve extending in an at least partially curved manner. In a typical embodiment, the function describing the width curve depends on the position along the longitudinal axis (y-axis) of the tooth. In particular, the function describing the profile of the width curve on the tooth surface in a cross section perpendicular to the tooth surface may depend on the local inclination of the tooth surface relative to the longitudinal axis of the tooth.

[0041] According to an exemplary embodiment, a method for manufacturing a tooth for a gearbox as described herein is specified. The method includes providing a tooth blank for the tooth. The tooth blank can have, for example, a rounded tooth surface. In particular, the tooth blank can be designed to be cylindrical.

[0042] An exemplary method includes forming a tooth flank, the tooth flank formed to be at least partially curved along a width curve extending across the width of the tooth flank. The tooth flank may be formed to have a width curve according to embodiments described herein. Additionally or alternatively, the exemplary method includes forming a tooth head having a tooth head width curve according to embodiments described herein. In an embodiment, the tooth head is also formed in conjunction with the tooth flank.

[0043] According to an exemplary embodiment, forming the tooth flank or tooth head includes grinding the tooth blank. In particular, the tooth flank or tooth head may be ground using a grinding disk. Typically, grinding the tooth blank includes moving the grinding disk in the direction of the tooth blank's longitudinal axis. In particular, this movement can be performed in the y direction in the x, y, z coordinate system described herein. The grinding disk typically rotates around an axis parallel to the z axis. Typically, grinding the tooth blank includes varying the movement of the grinding disk in the direction of the tooth blank's longitudinal axis (y direction) as a function of the position of the grinding disk along the tooth width or tooth flank width (x direction). For example, the variation in movement can be performed by a correction value dy(x) according to Equation (1). In an embodiment, the movement in the y direction performed by the grinding machine can be a function of the diameter D of the grinding disk of the grinding machine, and the grinding disk is specified to grind the tooth flank or tooth head. In particular, the movement performed by the grinding machine can be a function f of the position of the grinding disk in the x-direction and the diameter D: y = f(x, D). For example, the function f can include a correction value dy(x). The highest precision, e.g., correction values ​​in the low μm range, is typically achieved for movements in the y-direction. In additional exemplary embodiments, movements can be performed in the z-direction, in particular in the direction of the rotation axis of the grinding disk, or a rotation of the tooth, in particular a round tooth, around its longitudinal axis (around the y-axis) during grinding can be performed.

[0044] According to a typical embodiment, the tooth flanks, in particular the tooth heads, are formed by profile grinding. A grinding disk for grinding the tooth flanks, in particular the tooth heads, is typically designed as a profile grinding disk. The negative shape of the tooth profile is particularly present in the profile grinding disk. In an embodiment, the method includes grinding the additional tooth flanks, in particular by discontinuous profile grinding. In particular, the tooth flanks, in particular the tooth flanks and tooth heads, can be formed in a first grinding pass using a profile grinding disk. In a second grinding pass, the additional tooth flanks can be formed using a profile grinding disk, for example, after rotating the tooth 180° relative to the grinding disk.

[0045] The method for manufacturing the tooth typically includes additional steps to form further features of the tooth. For example, a root on the radially inner end of the tooth can be machined. The additional steps can be performed before or after forming the tooth face or tooth head.

[0046] According to a further aspect, a method of manufacturing a gearbox according to embodiments described herein is identified, which includes manufacturing a plurality of teeth according to the exemplary methods described herein. The method further includes providing an additional component of the gearbox described herein, such as a cam disc, a tooth carrier, or a ring gear. The method includes assembling the teeth and the additional component to form a gearbox according to embodiments described herein.

[0047] Compared to the prior art, exemplary embodiments of the gearbox may provide the advantage of reducing or avoiding edge stresses on the tooth flanks. The exemplary gearbox may exhibit reduced running-in behavior. Teeth having at least a partially curved width curve may exhibit less running-in wear, particularly during operation. In particular, tooth flanks manufactured in accordance with the embodiments described herein may eliminate any wear during operation. Furthermore, the embodiments may have higher load-bearing capacity, particularly high hydrodynamic load-bearing capacity for contact between the teeth and the internal toothing of the ring gear, with a small solid contact area percentage. The exemplary method may provide advantageous manufacturing of teeth having the tooth flanks described herein, among others. [Brief explanation of the drawings]

[0048] The invention is explained in more detail below with the aid of the accompanying drawings. [Figure 1] FIG. 1 shows a schematic cross-sectional view of part of a typical gearbox embodiment. [Figure 2] FIG. 2 shows a schematic diagram of a tooth according to an exemplary embodiment. [Figure 3] FIG. 3 shows the tooth of FIG. 2 in side view. [Figure 4] FIG. 4 is a graph showing the profile of the correction value dy(x) of the tooth flank in the outer edge region of the tooth flank, with the origin of the graph being at the center of the width of the tooth flank. [Figure 5] FIG. 5 shows a flow chart of a method for manufacturing a tooth according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0049] In the following text, exemplary embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the exemplary embodiments, and the scope of the present invention is defined by the claims. In describing the embodiments, the same reference numerals are used in some cases for the same or similar parts in different drawings and different embodiments. For clarity, some parts that have already been described with reference to other drawings will not be described again. For clarity, in some cases, not all of the individual components will be labeled with reference numerals, such as the teeth (reference numeral 9 in FIG. 1).

[0050] A portion of an exemplary embodiment of a gearbox 1 is shown in a schematic cross-section (radial cross-section) in Figure 1. Figure 1 shows a gearbox 1 having teeth 9 displaceably received in guides 7 of a tooth carrier 5. The teeth 9 are typically designed according to an embodiment described herein. The tooth carrier 5 is arranged between the internal toothing 3 of the ring gear 4 and a cam disc 13. In Figure 1, the guides 7 are arranged radially, and the teeth 9 are mounted radially displaceably within the guides 7. In particular, the teeth 9 are displaceable along their respective longitudinal axes 11. The teeth 9 are radially displaceable to engage with the internal toothing 3 of the ring gear 4.

[0051] The cam disc 13 of the gearbox 1 of Figure 1 functions as a driving element of the gearbox 1. The cam disc 13 has profiling in the circumferential direction of the cam disc 13. In Figure 1, the profiling has a profile with two circumferential ridges, so that the opposing teeth 9 engage to a maximum and equal depth within the internal toothing 3. In additional embodiments, the cam disc may have only one ridge or more than two ridges.

[0052] In the exemplary embodiment of Fig. 1, the rotation axis (not shown) of the cam disc 13 extends perpendicular to the image plane (paper plane) of Fig. 1. The cam disc 13 is arranged radially inside the teeth 9 relative to the rotation axis of the cam disc 13, and the internal toothing 3 of the ring gear 4 is arranged radially outside the teeth 9 relative to the rotation axis of the cam disc 13. In such a configuration, the drive output is obtained on the ring gear 4 or on the tooth carrier 5, with each other element being fixedly established. In additional embodiments, the drive of the gearbox can be via the ring gear or via the tooth carrier, and the drive output can be via the cam disc.

[0053] The gearbox 1 comprises a segmented mounting for the teeth 9. The segmented mounting comprises in each case pivot segments 25 which have rounded tooth bearing surfaces 26 on the side facing the teeth 9. The tooth bearing surfaces 26 form beads in which the roots 33 of the teeth 9 are located, said roots 33 being provided on the radially inner ends of the teeth 9. In conjunction with a corresponding clearance at the roots 33 of each tooth 9, the beads prevent the teeth 9 from shifting out of position relative to the pivot segments 25. The pivot segments 25 are attached to the cam disc 13 by means of rolling elements 23, which in FIG. 1 are needle bearings.

[0054] In Figure 1, the tooth 9 comprises in each case two tooth flanks, in particular a tooth flank 17 and an additional tooth flank 18, which converge in the longitudinal direction of the tooth 9 towards the head 15 of the tooth 9. The tooth flank and the head 15 are provided on the radially outer end of the tooth 9 so as to engage with the internal tooth 3. Between the tooth flank and the tooth root 33 of the tooth 9, the tooth 9 has a tooth body 19 which is displaceably mounted in the guide 7 of the tooth carrier 4.

[0055] 2 shows a schematic diagram of a tooth 9 according to a typical embodiment. The tooth 9 is configured as a single tooth, in particular as a rounded tooth. The tooth 9 in particular comprises a tooth flank 17, an additional tooth flank 18, and a tooth head 15 provided between the tooth flanks. The tooth head 15 is designed to have a head radius between the tooth flanks. The tooth flank 17 and the additional tooth flank 18 are formed symmetrically with respect to a plane that includes the longitudinal axis 11 of the tooth 9 (y-direction) and extends parallel to the tooth width 43 of the tooth 9 (x-direction). In a typical gearbox 1, the tooth width 43 of the tooth 9 is arranged parallel to the rotation axis of the gearbox 1, and the longitudinal axis 11 is arranged radially with respect to the rotation axis.

[0056] The tooth flank 17 has two outer edge regions 49 in the width 41 direction of the tooth flank 17 and a central region 47 between the two outer edge regions 49. FIG. 3 shows the tooth 9 in a side view. The tooth flank 17 is particularly designed to be symmetrical with respect to a central longitudinal curve 55 of the tooth flank 17. The tooth flank 17 extends at least partially curved along a width curve 51 across the width 41 of the tooth flank 17. In FIGS. 2 and 3, the tooth flank 17 in the outer edge region 49 extends curvedly in the width 41 direction of the tooth flank 17, as will be explained below, for example, in the context of FIG. 4. In particular, the tooth flank 17 has a correction in the shape of the recess of the tooth flank 17 in the outer edge region 49 that faces inward relative to the central region 47 of the tooth flank 17. The width curve 51 extends linearly in the central region 47. In additional exemplary embodiments, the width curve may be configured to curve across the entire width of the tooth flank. The tooth flanks in Figures 2 and 3 are designed to be curved along a longitudinal curve 55, in particular in the form of a logarithmic spiral.

[0057] The tooth head 15 likewise has a recess in the outer edge region 49 relative to the central region 47. Here, the recess in the outer edge region 49 is formed in the direction of the longitudinal axis 11 of the tooth 9, so that the profile of the tooth head 15, in particular the height of the tooth head 15 in the direction of the longitudinal axis 11, decreases from the center of the tooth 9 towards the outer edge of the tooth head 15. The recess on the tooth head 15 corresponds in its shape to a correction of the tooth flank 17. In particular, the tooth head width curve 53 extending in the direction of the tooth width 43 extends in the outer edge region 49 so as to be curved, in particular in the shape of a logarithmic function. In further exemplary embodiments, the tooth head width curve may be configured to be curved over the entire width of the tooth flank.

[0058] FIG. 4 shows a graph 400 representing a logarithmic function according to equation (1) described herein. The logarithmic function specifically shows the correction value dy(x) for the grinding disk's motion in the y direction to form the tooth flank 17 of tooth 9 shown in FIGS. 2 and 3. In particular, the x and y directions of graph 400 correspond to the x, y, z Cartesian coordinate system shown in FIGS. 2 and 3. Here, graph 400 shows the correction value for the x position only for half the tooth width 45 (see FIG. 3). The origin of graph 400 is at the center of the tooth width 43. The tooth width 43 of tooth 9 is, for example, 10.5 mm. As shown in FIG. 4, tooth flank 17 has a correction in the outer edge region from xstart=2.7 mm to xende=5.25 mm at the outer edge of the tooth flank. The outer edge region constitutes approximately 25% of the tooth width 43 of tooth 9. In forming the tooth flank 17, the grinding disk is operated to approximate the tooth blank as a function of x position by a correction value dy(x) so as to form a recess in the tooth flank 17 and tooth head 15 in the form of a logarithmic function along the width 41 of the tooth flank 17. The resulting tooth head width curve 53 also corresponds to the logarithmic function shown.

[0059] 5 shows a flow chart of an exemplary method 100 for manufacturing teeth 9 for a gearbox 1. In block 110, the method 100 includes providing a tooth blank, in particular a cylindrical tooth blank, for forming a round tooth having two tooth flanks by discontinuous profile grinding.

[0060] In block 120, the method 100 includes forming the tooth flank 17 of the tooth 9, where the tooth flank 17 is formed to be at least partially curved along a width curve 51 extending across the width 41 of the tooth flank 17. A profile grinding disk representing the profile of the tooth flank 17 and the tooth head 15 is used to form the tooth flank 17. In block 120, the profile grinding disk is moved in the y direction, and its movement is modified, for example, by a correction value dy(x) according to equation (1) or as a function of the position of the grinding disk along the tooth width 43 (x direction), as shown in FIG. 4. In conjunction with the correction of the tooth flank 17, the tooth head 15 is also formed to have a corresponding recess along the tooth head width curve 53 of the tooth head 15.

[0061] In block 130, the method 100 includes forming the additional tooth flank 18 of the tooth 9. In particular, the tooth blank and the grinding disk are rotated 180° relative to each other about the longitudinal axis 11 (y-direction) of the tooth 9. The additional tooth flank 18 is formed by profile grinding with a grinding disk in a similar manner to the tooth flank 17. When used in the gearbox 1, the tooth 9 produced in this way may exhibit particularly low wear during the running-in process of the gearbox.

Claims

1. A gearbox (1), in particular a coaxial gearbox, a ring gear having internal teeth (3); a tooth carrier (5) having a guide (7) arranged radially relative to the rotation axis of the gearbox; teeth (9) received in the guide (7) for engagement with the internal toothing (3), wherein the teeth (9) are mounted in the guide (7) displaceable in the direction of their longitudinal axis (11) relative to the tooth carrier (5); and a cam disc (13) rotatable about said axis of rotation and operatively connected to said teeth (9); A gearbox (1) in which the teeth (9) have tooth flanks (17) that are formed so as to be at least partially curved along a width curve (51) that extends across the width (41) of the tooth flank (17) in each case.

2. 2. The gearbox (1) according to claim 1, wherein the tooth flank (17) has two outer edge regions (49) along the width curve (51) over the width (41) of the tooth flank (17) and a central region (47) between the two outer edge regions (49), and the tooth flank (17) in at least one of the two outer edge regions (49) is recessed inward with respect to the central region (47).

3. 3. A gearbox (1) according to claim 2, wherein the at least one outer edge region is recessed relative to the central region (47) by a maximum of 1% of the maximum width of the tooth flank (17) in a direction perpendicular to the tooth flank.

4. 4. A gearbox (1) according to claim 2 or 3, wherein the width curve (51) extends so as to be curved in at least one of the two outer edge regions (49) and extends so as to be straight in the central region (47) of the tooth flank (17).

5. 5. A gearbox (1) according to any one of claims 2 to 4, wherein the two outer edge regions (49) comprise in each case at least 10% and / or at most 40% of the width (41) of the tooth flank (17).

6. 10. A gearbox (1) according to any one of the preceding claims, wherein the width curve (51) extends symmetrically about the centre of the width (41) of the tooth flank (17).

7. 10. A gearbox (1) according to any one of the preceding claims, wherein the teeth (9) in each case comprise one additional tooth flank, said additional tooth flank being formed in mirror symmetry with respect to said tooth flank (17).

8. 10. A gearbox (1) according to any one of the preceding claims, wherein the curved portion of the width curve (51) corresponds to a logarithmic function or a radius correction.

9. 10. A gearbox (1) according to any one of the preceding claims, wherein the curved portion (51) extends on the tooth flank (17) and in a cross section perpendicular to said tooth flank.

10. 10. A gearbox (1) according to any one of the preceding claims, wherein the tooth flanks of the teeth (9) are formed by grinding.

11. 10. A gearbox (1) according to any one of the preceding claims, wherein the longitudinal curve (55) extending on the tooth flank (17) and perpendicular to the width (41) of the tooth flank (17) is at least partially curved.

12. A gearbox (1), in particular a coaxial gearbox, a ring gear having internal teeth (3); a tooth carrier (5) having a guide (7) arranged radially relative to the rotation axis of the gearbox; teeth (9) received in the guide (7) for engagement with the internal toothing (3), wherein the teeth (9) are mounted in the guide (7) displaceable in the direction of their longitudinal axis (11) relative to the tooth carrier (5); and a cam disc (13) rotatable about said axis of rotation and operatively connected to said teeth (9); A gearbox (1) in which the teeth (9) have in each case tooth heads (15), and a tooth head width curve (53) extending along the tooth heads (15) across the tooth width (43) of the teeth (9) is formed so as to be at least partially curved in the direction of the longitudinal axis of the tooth.

13. 13. A gearbox (1) according to claim 12, wherein the curved portion of the tooth head width curve (51) extends logarithmically or radially.

14. the tooth heads (15) in the outer edge region of the teeth (9) are recessed by at least 0.02% and / or at most 2% of the tooth width relative to the maximum height of the tooth heads (15) in the direction of the longitudinal axis (11) of the teeth (9); 14. A gearbox (1) according to claim 12 or claim 13, wherein the tooth head (15) has a maximum height in a central region (47) of the tooth head (15) in relation to the face width (43).

15. A tooth (9) for a gearbox (1) according to any one of the preceding claims, comprising: the teeth (9) have tooth flanks (17) that are formed so as to be at least partially curved, in particular convexly curved, along a width curve (51) that extends over the width (41) of the tooth flanks (17); and / or The tooth (9) has a tooth head (15), wherein a tooth head width curve (53) extending along the tooth head (15) across the tooth width (43) of the tooth (9) is formed so as to be at least partially curved in the direction of the longitudinal axis of the tooth (9), in particular so as to be convexly curved.

16. A method (100) for manufacturing teeth (9) for a gearbox (1) according to any one of the preceding claims, comprising the following steps: Providing a tooth blank for said tooth (9); and forming the tooth flanks (17) of the teeth (9), wherein the tooth flanks (17) are formed to be at least partially curved along a width curve (51) extending across the width (41) of the tooth flanks (17); and / or A step of forming the tooth head (15) of the tooth (9), wherein a tooth head width curve (53) extending across the tooth width (43) is formed to be at least partially curved in the direction of the longitudinal axis of the tooth (9).

17. 17. The method (100) of claim 16, wherein forming the tooth flank (17) comprises grinding the tooth blank, and comprises the following steps: moving a grinding disk along the longitudinal axis of the tooth blank; and Varying the motion of the grinding disk along the longitudinal axis of the tooth blank as a function of the position of the grinding disk along the width of the tooth flank (17).

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