Gear

Abstract

Gearbox (1), in particular coaxial gearbox, comprising a toothed ring with internal teeth (3), a tooth carrier (5) with guides (7) oriented radially with respect to an axis of rotation of the gearbox, teeth (9) received in the guides (7) to engage with the internal teeth (3), wherein the teeth (9) are slidably mounted in the guides (7) in the direction of their longitudinal axis (11) with respect to the tooth carrier (5), and a cam disc (13) rotating about the axis of rotation in operative relation to the teeth (9), wherein each tooth (9) has a toothed head (15), wherein a toothed head width curve (53) extending along the toothed head (15) and over a tooth width (43) of the tooth (9) is produced at least partially curved in the direction of the longitudinal axis of the tooth.

Description

Field of invention

[0001] The invention relates to a gearbox, a tooth for a gearbox and a method for manufacturing a tooth for a gearbox. State of the art

[0002] Gearboxes are known from the prior art which include teeth mounted radially displaceable in a tooth carrier with respect to an axis of rotation of the gearbox. The teeth are operatively related to a cam disk which has a circumferential profile around the axis of rotation. The cam disk can be used, in particular, to drive the teeth in the radial direction. The teeth engage with a toothed section, resulting in a 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 cam disk with its profile. High gear ratios can be achieved in this way; an example of such a gearbox is published in EP 2 129 935 A2.

[0003] DE 10 2019 129667 A1 relates to a gear unit comprising a toothed section, a tooth carrier with guides, teeth which are received in the guides for meshing with the toothed section, wherein the teeth are mounted in the guides so as to be displaceable in the direction of their longitudinal axis relative to the tooth carrier, and a cam disk for driving the teeth along their respective longitudinal axis. A tooth comprises a tooth flank region with tooth flanks and a tooth tip. US 4 308 760 A relates to a heavy-duty gear. DE 10 2019 129662 A1 relates to a coaxial gearbox.

[0004] However, known gearboxes exhibit a distinct break-in period upon initial commissioning. Furthermore, known gearboxes may have limitations regarding load-bearing capacity. Disclosure of the invention

[0005] Aufgabe der Erfindung ist es, ein Getriebe oder einen Zahn anzugeben, welche gegenüber aus dem Stand der Technik bekannten Getrieben verbessert sind, wobei ein verringertes Einlaufverhalten, ein geringerer Verschleiß oder eine höhere Tragfähigkeit erreicht werden sollen. Weiterhin ist es Aufgabe der Erfindung, ein Verfahren zur Herstellung eines Zahns für ein Getriebe anzugeben.

[0006] The problem is solved by a gear according to claim 1 and by a tooth and a method according to the dependent claims. Advantageous further developments and embodiments are described in the dependent claims and in this description.

[0007] One aspect of the invention relates to a transmission according to independent claim 1, in particular a coaxial transmission. The transmission comprises a ring gear with internal teeth. The transmission comprises a gear carrier with guides oriented radially with respect to an axis of rotation of the transmission. The transmission comprises teeth which are received in the guides for engagement with the internal teeth, the teeth being slidably mounted in the guides in the direction of their longitudinal axis relative to the gear carrier. The transmission comprises a cam disk rotatable about the axis of rotation and operatively related to the teeth. Each tooth may have a tooth flank which is manufactured to be at least partially curved along a width curve extending over the width of the tooth flank.Each tooth has a tooth head, wherein a tooth head width curve running along the tooth head and over a tooth width is at least partially curved in the direction of the longitudinal axis of the tooth, the tooth head width curve running on the tooth head in a plane of the longitudinal axis and the tooth width.

[0008] Another aspect of the invention relates to a tooth according to claim 13. The tooth for a gear according to one of the typical embodiments described herein can have a tooth flank which is manufactured at least partially curved, in particular convexly curved, along a width curve extending over a width of the tooth flank. The tooth has a tooth head, wherein a tooth head width curve extending along the tooth head and over a tooth width is manufactured at least partially curved in the direction of the longitudinal axis of the tooth, in particular convexly curved, wherein the tooth head width curve lies on the tooth head in a plane of the longitudinal axis and the tooth width.

[0009] Another aspect of the invention relates to a method according to claim 14. The method for manufacturing a tooth according to claim 13 comprises providing a tooth blank. The method may include manufacturing a tooth flank of the tooth, wherein the tooth flank is manufactured at least partially curved along a width curve extending over a width of the tooth flank. The method includes manufacturing the tooth head of the tooth.

[0010] Typical embodiments of the invention relate to gearboxes, in particular coaxial gearboxes. Typically, gearboxes of the invention comprise a cam disk rotatable about an axis of rotation of the gearbox. The cam disk typically has a profile in the circumferential direction around the axis of rotation, for example, a profile with at least one projection in the radial direction, in particular with at least or exactly two projections or with at least or exactly three projections.

[0011] Typical gear units feature a tooth carrier with guides oriented radially to the axis of rotation. Typically, each guide receives a tooth according to the embodiments described herein. The teeth are typically mounted in a guide so as to be slidable relative to the tooth carrier in the direction of their longitudinal axis. Typically, the teeth are mounted in the tooth carrier so as to be slidable in exactly one direction, typically in the direction of the tooth's longitudinal axis. The guides of the tooth carrier can, for example, each be designed as a slot or opening, in particular as a slot or opening with a constant cross-section in the radial direction. The teeth are typically inserted in the tooth carrier with the tooth head running parallel to the axis of rotation.

[0012] In typical embodiments of the gears according to the invention, 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 gear. Rigid teeth include, in particular, teeth made of a metal alloy, especially steel or a titanium alloy, a nickel alloy, or other alloys.

[0013] Typical gearboxes feature a ring gear with internal teeth. Typically, the flanks of the internal teeth run parallel to the axis of rotation. The gear carrier is typically arranged radially between the ring gear and the cam. In particular, the cam may be arranged radially inwards, for example, around or on the axis of rotation of the gearbox. Unless otherwise specified, the terms "axial," "radial," and "circumferential" are typically understood to refer to the axis of rotation of the gearbox.

[0014] In typical embodiments, a pivot segment is arranged between the teeth and the profile of the cam disk. Typically, the pivot segments are mounted on a rolling bearing, which rests on the profile. The rolling bearing can, for example, be a needle roller bearing. The tooth is typically loosely connected to the pivot segment. "Loose connection" here means, in particular, that the tooth segment is merely placed on the pivot segment, or more specifically, placed directly on it. Pivot segments typically include a profile that prevents the tooth from slipping off the pivot segment or the pivot segment from slipping, at least in one direction. Such a profile can, for example, be a bead that engages in a recess at a radially inner end of the tooth. For a possible embodiment of a pivot segment, reference is made to DE 10 2015 105 523 A1.

[0015] In typical designs, the cam disc interacts with the teeth. In particular, the cam disc can be used as a drive element to drive the teeth radially. When the cam disc rotates around its axis, the teeth are typically moved radially by the profile, so that at any given time some of the teeth engage with the internal teeth of the ring gear, causing relative movement between the gear carrier and the ring gear. The gear output can be via the gear carrier or the ring gear.

[0016] 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.

[0017] 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.

[0018] These are particularly advantageous for applications with high requirements for torque and power density, large hollow shaft diameter, high stiffness, low or zero clearance, or compactness.

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

[0020] In typical embodiments, the teeth each comprise at least one tooth flank, in particular exactly two tooth flanks. Typically, the at least one tooth flank is arranged in a region radially outside the tooth body. In typical embodiments, the teeth each have a tooth tip. Typically, the tooth tip is located adjacent to the tooth flank and extends over one tooth width of the respective tooth. The tooth width corresponds to the width of the tooth in the direction parallel to the axis of rotation of the transmission. Typically, the tooth width corresponds to the width of the tooth tip. Typically, the tooth tip is located at one end of the tooth with respect to the longitudinal direction of the tooth, in particular at a radially outer end of the tooth with respect to the axis of rotation of the transmission. In typical embodiments, the tooth flank is inclined to the longitudinal axis of the tooth.For example, two tooth flanks of a tooth can converge, at least substantially, at an angle to the tooth head. Typically, the tooth head has a surface that extends from one tooth flank to the other. In particular, the surface of the tooth head can have a head radius between the two tooth flanks.

[0021] In typical designs, a tooth flank or tooth tip has a width. Typically, the width of a tooth flank or tooth tip is understood to be its extent parallel to the axis of rotation of the gear.

[0022] In typical embodiments, the tooth flank of a tooth is manufactured with a curve extending across the width of the tooth flank, at least partially curved. A curved curve is typically understood to be a non-straight curve, for example, an arc-shaped curve. In particular, the tooth flank may exhibit a flank correction or modification in the direction of the tooth flank's width compared to a straight flank. This flank correction or modification may, in particular, correspond to a reduction in the tooth flank's curvature compared to a straight flank along the tooth's width. A curved tooth flank following the curve of width may also be referred to as a correction, flank correction, or flank modification.

[0023] In known gear teeth, such as the gear according to EP 2 129 935 A2, the tooth flank profile is linear across the entire width in the direction of the gear's axis of rotation, i.e., it corresponds to a straight line. Known gears can exhibit a pronounced running-in behavior. Teeth with tooth flanks according to the embodiments described herein, featuring a curved width profile, can, in particular, avoid or reduce edge wear on the tooth flank edges. Edge wear in known gears arises, in particular, from the ring gear teeth, which are typically wider and therefore stiffer than the teeth, and from lubricant leakage from the contact area at the edge of the gear teeth.Tooth flanks with a curved width curve according to the embodiments described herein can in particular avoid or reduce wear on the edges of the tooth contact between tooth and ring gear, especially wear during a running-in phase of the gearbox.

[0024] In typical embodiments, the tooth flank has two edge regions along the width curve across the width of the tooth flank, and a central region between these two edge regions. In at least one of these two edge regions, the tooth flank is recessed inwards relative to the central region. "Inside" here refers to the interior of the tooth. The tooth flank may be at least partially convex along the width curve. Typically, the width curve curves inwards from the central region in both directions across the width of the tooth flank towards the edges of the tooth flank.

[0025] In typical embodiments, the at least one edge region is reduced in a direction perpendicular to the tooth flank by at most 1% of the maximum width of the tooth flank compared to the central region, in particular by at most 0.5% or at most 0.2%. In embodiments, the at least one edge region is reduced in a direction perpendicular to the tooth flank by at least 0.01% of the maximum width of the tooth flank compared to the central region, in particular by at least 0.02%. Typically, these reductions correspond to a maximum material removal on the flank compared to a central region or a straight flank profile; in particular, these reductions are located at the outer edge of the tooth flank. Typically, the maximum width of the tooth flank corresponds to the width of the tooth flank at a transition from the tooth flank to a tooth tip of the tooth.

[0026] In typical embodiments, the width curve is curved in at least one of the two edge regions, particularly in both edge regions. In typical embodiments, the width curve is straight in the central region of the tooth flank. For example, the two edge regions can each comprise at least 10%, particularly at least 20% or at least 25%, of the width of the tooth flank. In embodiments, the two edge regions each comprise a maximum of 40%, particularly at most 35%, of the width of the tooth flank. For example, the two edge regions can each comprise approximately 25% of the width of the tooth flank. Typically, the central region comprises the portion of the tooth flank from one edge region to the other edge region.Typically, the percentage specification of the edge areas refers to the division of edge areas and central area at the radially outer end of the tooth flank with respect to the axis of rotation of the gear, particularly at the transition of the tooth flank to the tooth tip. In particular, the percentage of edge areas in other regions of the tooth flank may differ from the percentage specifications. For example, in the case of a round tooth, the width of the edge areas may decrease from the radially outer end of the tooth flank to the radially inner end of the tooth flank and may, in particular, decrease to zero. In typical embodiments, the tooth flank has a width curve that is at least partially curved over at least 50% of its length, and in particular over at least 60% or at least 70%, as described herein. The length of the tooth flank is understood to be the longitudinal extent of the tooth flank perpendicular to its width.

[0027] In other typical embodiments, the central area can have a width of 0% of the tooth flank width. For example, the central area can be a line, in particular a central line, running along the tooth flank in a longitudinal direction. In particular, the tooth flank can be curved along the width curve over its entire width, and in particular, it can be convex over its entire width. In embodiments, the tooth flank can have a curved width curve over its entire length.

[0028] In typical embodiments, the width curve runs along the tooth flank and in a cross-sectional plane perpendicular to the tooth flank. Typically, the width curve runs in a region of the tooth flank intended for contact with the internal teeth of the ring gear.

[0029] In typical embodiments, the width curve is symmetrical with respect to the midpoint of the tooth flank width. In these embodiments, each tooth comprises a further tooth flank. The tooth flank and the further tooth flank of a tooth can also be referred to here as the first tooth flank and second tooth flank. Typically, the further tooth flank is manufactured in a mirror-symmetrical manner to the tooth flank, in particular in a mirror-symmetrical manner with respect to a plane that extends along the longitudinal axis of the tooth and parallel to the axis of rotation of the gear. Symmetrical teeth, in particular symmetrical round teeth, can, for example, be installed without special alignment of individual tooth flanks and can, in particular during operation, rotate about their respective longitudinal axis.

[0030] According to the invention, a tooth head adjacent to the tooth flank has a tooth head correction. A tooth head width curve extending along the tooth head and across the tooth width is manufactured with a curve at least partially curved in the direction of the tooth's longitudinal axis. The tooth head width curve runs on the tooth head in a plane defined by the longitudinal axis and the tooth width. In particular, the tooth head width curve can curve at least partially inwards from the center of the tooth head along the tooth width to the edge of the tooth, especially inwards in the direction of the tooth's longitudinal axis, towards the tooth body. This results in a changing tooth head height along the tooth flank or across the tooth width; in particular, the tooth head height decreases from the longitudinal axis towards the edge of the tooth, for example, in the form of a radius or a logarithmic function.In embodiments, the shape of the tooth tip width curve corresponds at least substantially to the shape of the tooth flank width curve. The tooth tip width curve can differ from a flank width curve by a linear factor, particularly depending on the angle of the tooth flank relative to the tooth's longitudinal axis. The tooth tip width curve can be at least partially curved, following a logarithmic function or a radius correction, on the tooth tip and across the tooth width. In particular, a curved portion of the tooth tip width curve can follow a logarithmic function or a radius. In embodiments, the tooth tip width curve is symmetrical with respect to the midpoint of the tooth width. Typically, the tooth tip is manufactured with mirror symmetry with respect to a plane of the longitudinal axis and the tooth width.

[0031] In typical embodiments, the tooth tip has two edge regions along the tooth tip width curve across the tooth width. Typically, the tooth tip has a central region between the two edge regions. Typically, the tooth tip is recessed inwards relative to the central region in at least one of the two edge regions. For example, the two edge regions of the tooth tip can each comprise at least 10%, in particular at least 20% or at least 25%, or a maximum of 40%, in particular a maximum of 35%, of the tooth width, for example, approximately 25% each. The central region can comprise the entire region between the two edge regions. In embodiments, the tooth tip width curve is curved in at least one edge region. The tooth tip width curve can be straight in a central region. In further typical embodiments, the central region of the tooth tip can have a width of 0% of the tooth width.In embodiments, the edge regions and the central region of the tooth head can correspond to the edge regions and the central region of the tooth flank.

[0032] Typically, the tooth head, in particular its height, is reduced in at least one marginal region of the tooth, and in particular in both marginal regions, relative to a maximum height of the tooth head in the direction of the tooth's longitudinal axis. The tooth head typically has its maximum height in the central region of the tooth, particularly in a central region around the longitudinal axis. Herein, the height of the tooth head is understood to mean its extension in the direction of the tooth's longitudinal axis. Typically, the tooth head is reduced in the at least one marginal region by at least 0.02% or at most 2% of the tooth width relative to a maximum height of the tooth head or relative to a straight line of the tooth head in the direction of the longitudinal axis. In typical embodiments, the tooth head is produced by grinding, in particular by grinding as described herein for the tooth flanks.

[0033] In typical designs, the reduction of the tooth flank or tooth tip towards the edge of the tooth flank can increase. For example, the correction amount at the edge of the tooth flank can be greater to prevent edge bearing. In particular, edge bearing can also be prevented under higher operating pressures or even with greater elastic deflection or flattening of the tooth flank in contact with the internal gearing.

[0034] According to a typical embodiment, a curved portion of the width curve corresponds to a logarithmic function or a radius correction. In particular, the logarithmic function or the radius correction can describe a reduction of the tooth flank along the width curve. For example, a curved portion of the width curve can correspond to a logarithmic function according to formula (1) below. In this and in other embodiments described herein, directions are specified with respect to an orthogonal x,y,z coordinate system for a given tooth. The x,y,z coordinate system can, in particular, correspond to a machine coordinate system for manufacturing the tooth. An x-axis is oriented in the direction of the width of the tooth flank or tooth tip, in particular parallel to the axis of rotation of the gear. A y-axis is oriented parallel to a longitudinal axis of the tooth, in particular in the radial direction of the gear.The z-axis is aligned 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 typical embodiments, the tooth flanks are produced by grinding, in particular by profile grinding, for example by discontinuous profile grinding. The grinding can be carried out according to the embodiments described herein, in particular as explained in connection with the typical methods for producing a typical tooth described herein. Formula (1) below specifies, in particular, a logarithmic function which indicates a correction amount dy(x) for a feed of a grinding wheel of a profile grinding machine in the y-direction. By changing the feed in the y-direction as a function of the x-position, the tooth flank and the tooth tip can, in particular, be produced with a curved width curve of the tooth flank and a curved tooth tip width curve of the tooth tip. dy x = b profil ⋅ ln 1 1 − x − x start x ende − x start 2

[0036] Formula (1) above describes the correction amount or a width curve or tooth head width curve starting from the center of the tooth flank or tooth head in one direction of width. The width curve can be symmetrical in the other direction of width with respect to the center of the tooth flank or tooth head. In Formula (1), b profile denotes a correction factor, in particular a constant. Furthermore, x denotes the x-position along the width of the tooth flank or tooth head, in particular with respect to the center of the tooth flank or tooth head as the zero point, where x is less than x end.

[0037] x start denotes the starting point of the correction in the x-direction, in particular the starting point of the logarithmically curved portion of the width curve. Typically, x start corresponds to the beginning of a boundary region where the width curve is curved. As described herein with regard to further embodiments, x start can also be zero in typical embodiments, so that the width curve is curved from the center outwards, in particular across the entire width of the tooth flank or tooth tip.

[0038] xend denotes the endpoint of the correction in the x-direction, specifically an x-position outside the margin of the tooth flank or the tooth head, for example, slightly outside the margin of the tooth flank or the tooth head. In particular, xend is typically chosen such that x-positions on the tooth flank are not equal to xend. Typically, xend is greater than x for all x-positions on the tooth flank, so that, in particular, the end of the correction curve lies outside the tooth flank.

[0039] In typical embodiments, a longitudinal curve running perpendicular to the tooth flank and its width is at least partially curved. The longitudinal curve can, for example, be in the form of a logarithmic spiral or with a radius. An embodiment of a tooth comprising a tooth flank with a longitudinal curve in the form of a logarithmic spiral is described, for example, in EP 2 129 935 A2. The inclination of the tooth flank to the longitudinal axis of the tooth can change along the at least partially curved longitudinal curve. In typical embodiments, a function describing the width curve depends on a position along the longitudinal axis (y-axis) of the tooth. In particular, a function that describes the course of the width curve on the tooth flank and in a section plane perpendicular to the tooth flank can depend on a local inclination of the tooth flank to the longitudinal axis of the tooth.

[0040] According to the invention, a method for manufacturing a tooth for a gear described herein is provided. The method comprises providing a tooth blank. The tooth blank can, for example, be a round tooth blank. In particular, the tooth blank can be cylindrical.

[0041] Typical methods include manufacturing a tooth flank, wherein the tooth flank is produced with at least partial curvature along a width curve extending over a width of the tooth flank. The tooth flank can be formed with a width curve according to embodiments described herein. The method includes manufacturing a tooth head with a tooth head width curve according to embodiments described herein. In embodiments, the tooth head is also manufactured along with the tooth flank.

[0042] In typical embodiments, the production of the tooth flank or tooth tip includes grinding the tooth blank. In particular, the tooth flank or tooth tip can be ground using a grinding wheel. Typically, the grinding of the tooth blank includes feeding the grinding wheel in the direction of a longitudinal axis of the tooth blank. In particular, the feeding in the y-direction can be performed according to an x,y,z coordinate system described herein. The grinding wheel typically rotates about an axis parallel to the z-axis. Typically, the grinding of the tooth blank includes changing the feeding of the grinding wheel in the direction of the longitudinal axis of the tooth blank (y-direction) depending on the position of the grinding wheel along the tooth width or the width of the tooth flank (x-direction). For example, the change in feeding by a correction amount dy(x) according to formula (1) can be performed.In some embodiments, the feed in the y-direction, performed by a grinding machine, can depend on the diameter D of a grinding wheel of the grinding machine, wherein the grinding wheel is configured for grinding the tooth flank or the tooth tip. In particular, the feed performed by the grinding machine can be a function f of the position of the grinding wheel in the x-direction and the diameter D: y = f(x, D). The function f can, for example, include the correction amount dy(x). Typically, the highest accuracies are achieved with a feed in the y-direction, for example, correction amounts in the lower micrometer range. In other typical embodiments, a feed in the z-direction, in particular in the direction of the axis of rotation of the grinding wheel, can be performed, or the tooth, in particular a round tooth, can be rotated about its longitudinal axis (about the y-axis) during the grinding operation.

[0043] In typical embodiments, the tooth flank and, in particular, the tooth tip are produced by profile grinding. Typically, the grinding wheel for grinding the tooth flank and, in particular, the tooth tip is designed as a profiled grinding wheel. In a profiled grinding wheel, the tooth profile is specifically dressed in negative. In embodiments, the method includes grinding a further tooth flank, in particular by discontinuous profile grinding. Specifically, the tooth flank, especially the tooth flank and the tooth tip, can be produced in a first grinding operation using the profiled grinding wheel. In a second grinding operation, the further tooth flank can be produced using the profiled grinding wheel, for example, after rotating the tooth relative to the grinding wheel by 180°.

[0044] Typically, the process of fabricating a tooth includes further steps to create additional features. For example, a tooth base can be prepared at the radially inner end of the tooth. These additional steps can be performed before or after fabricating the tooth flank or head.

[0045] According to an aspect not belonging to the invention, a method for manufacturing a transmission according to the embodiments described herein is specified, comprising manufacturing a plurality of teeth according to the typical methods described herein. The method further comprises providing additional components of a transmission described herein, such as a cam, a tooth carrier, or a ring gear. The method includes assembling the teeth and the additional components into a transmission according to the embodiments described herein.

[0046] Typical embodiments of the gearbox can offer the advantage over the prior art that edge bearing of the tooth flanks can be reduced or avoided. Typical gearboxes can exhibit reduced running-in behavior. Teeth with at least a partially curved width profile can, in particular, exhibit lower running-in wear during operation. In particular, a tooth flank manufactured according to the embodiments described herein can anticipate wear during operation. Furthermore, embodiments can exhibit higher load-bearing capacity, in particular a high hydrodynamic load-bearing capacity of the contact between the teeth and the internal gearing of the ring gear with low solid load-bearing content. Typical methods can, in particular, provide an advantageous method for manufacturing teeth with the tooth flanks described herein. Brief description of the drawings

[0047] The invention is explained in more detail below with reference to the accompanying drawings, the figures of which show: Fig. 1 shows a section of an embodiment of a typical gear in a schematic sectional view; Fig. 2 shows a tooth of a typical embodiment in a schematic view; Fig. 3 shows the tooth of the Fig. 2 in a side view; Fig. 4 a graph which represents the course of a correction amount dy(x) for a tooth flank in a boundary region of the tooth flank, wherein the zero point of the graph is at the middle of the width of the tooth flank; and Fig. 5 a flowchart of a method for manufacturing a tooth according to a typical embodiment. Description of exemplary implementations

[0048] Typical embodiments of the invention are described below with reference to the figures. The invention is not limited to these exemplary embodiments; rather, the scope of the invention is defined by the claims. In describing 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 respective features are always provided with a reference numeral, for example, the teeth (reference numeral 9 in the figure). Fig. 1 ).

[0049] In the Fig. 1 Figure 1 shows a section of a typical embodiment of a gearbox 1 in a schematic sectional view (radial section). Fig. 1 Figure 1 shows the gear unit 1 with teeth 9, which are slidably received in guides 7 of a gear carrier 5. The teeth 9 are typically designed according to the embodiments described herein. The gear carrier 5 is arranged between an internal toothing 3 of a ring gear 4 and a cam disk 13. In the Fig. 1 The guides 7 are radially aligned, and the teeth 9 are mounted in the guides 7 so as to be linearly radially displaceable. In particular, the teeth 9 are displaceable along their respective longitudinal axes 11. The teeth 9 can be displaced radially to engage with an internal tooth 3 of the ring gear 4.

[0050] The cam disc 13 serves in the gearbox 1 of the Fig. 1 as a drive element of the transmission 1. The cam disk 13 has a profile in the circumferential direction of the cam disk 13. The profile has in Fig. 1 The cam features a profile with two raised sections around its circumference, such that opposing teeth 9 engage furthest and to the same depth in the internal teeth 3. In further embodiments, the cam disc can have only one or more than two raised sections.

[0051] In the exemplary embodiment of the Fig. 1 The axis of rotation (not shown) of the cam disk 13 runs perpendicular to the plane of the image. Fig. 1 The cam disk 13 is arranged radially inside the teeth 9 with respect to the axis of rotation of the cam disk 13, and the internal teeth 3 of the ring gear 4 are arranged radially outside the teeth 9 with respect to the axis of rotation of the cam disk 13. In such a configuration, the output is taken from the ring gear 4 or from the gear carrier 5, with the other element being defined. In further embodiments, the drive of the transmission can be via the ring gear or via the gear carrier, and the output via the cam disk.

[0052] The gearbox 1 comprises a segmented bearing for the teeth 9. The segmented bearing includes pivot segments 25, each of which has a round tooth bearing surface 26 on the side facing the tooth 9. The tooth bearing surface 26 forms a bead on which a tooth base 33 of a tooth 9 is arranged, which is provided at a radially inner end of the tooth 9. The bead, together with a corresponding recess in the tooth base 33 of the respective tooth 9, prevents the tooth 9 from slipping relative to the pivot segment 25. The pivot segments 25 are connected via rolling elements 23, in Fig. 1 Needle rollers, mounted on the cam disc 13.

[0053] In the Fig. 1 Each tooth 9 comprises two tooth flanks, in particular a tooth flank 17 and a further tooth flank 18, which converge longitudinally on a tooth head 15 of the tooth 9. The tooth flanks and the tooth head 15 are provided at a radially outer end of the tooth 9 for engagement with the internal teeth 3. Between the tooth flanks and the tooth base 33 of the tooth 9, the tooth 9 has a tooth body 19, which is slidably mounted in a guide 7 of the tooth carrier 4.

[0054] Fig. 2 Figure 1 shows a schematic view of a tooth 9 according to a typical embodiment. The tooth 9 is designed as a single tooth, in particular as a round tooth. The tooth 9 comprises, in particular, a tooth flank 17, a further tooth flank 18, and a tooth head 15 provided between the tooth flanks. The tooth head 15 is formed with a head radius between the tooth flanks. The tooth flank 17 and the further tooth flank 18 are symmetrical with respect to a plane which encompasses the longitudinal axis 11 (y-direction) of the tooth 9 and runs parallel to a tooth width 43 (x-direction) of the tooth 9. In In a typical gearbox 1, the tooth width 43 of the tooth 9 is aligned parallel to the axis of rotation of the gearbox 1 and the longitudinal axis 11 is radial with respect to the axis of rotation.

[0055] The tooth flank 17 has two edge regions 49 in the direction of the width 41 of the tooth flank 17 and a central region 47 between the two edge regions 49. Fig. 3 Figure 9 shows tooth 9 in a side view. The tooth flank 17 is symmetrical with respect to a central longitudinal curve 55 of the tooth flank 17. The tooth flank 17 runs along a transverse curve 51 over the width 41 of the tooth flank 17, at least partially curved. Figuren 2 and 3 The tooth flank 17 is curved in the edge regions 49 in the direction of the width 41 of the tooth flank 17, for example as in connection with Fig. 4 Explained below. In particular, the tooth flank 17 exhibits a correction in the edge regions 49 in the form of an inward setback of the tooth flank 17 compared to the central region 47 of the tooth flank 17. In the central region 47, the width curve 51 is straight. In other typical embodiments, the width curve can be curved over the entire width of the tooth flank. Along the longitudinal curve 55, the tooth flank is Figuren 2 and 3curved shape, especially in the form of a logarithmic spiral.

[0056] The tooth head 15 also has a reduction in its edge regions 49 compared to the central region 47. This reduction in the edge regions 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 its height in the direction of the longitudinal axis 11, slopes down from the center of the tooth 9 towards the edge of the tooth head 15. The reduction at the tooth head 15 corresponds in form to the correction of the tooth flank 17. In particular, a tooth head width curve 53 extending in the direction of the tooth width 43 is curved in the edge regions 49, specifically in the form of a logarithmic function. In other typical embodiments, the tooth head width curve can be curved over the entire width of the tooth flank.

[0057] Fig. 4 Figure 400 shows a graph which specifies a logarithmic function according to formula (1) described herein. The logarithmic function, in particular, gives correction values ​​dy(x) for the feed of a grinding wheel in the y-direction for producing the tooth flank 17 of the [unclear text]. Figuren 2 and 3 Tooth 9 shown. In particular, the x and y directions of graph 400 correspond to that in Figuren 2 and 3 The orthogonal x,y,z coordinate system shown. Graph 400 shows the correction amounts for x-positions for only half a tooth width 45 (see Fig. 3 The zero point of graph 400 lies in the middle of the tooth width 43. Tooth 9, for example, has a tooth width 43 of 10.5 mm. As in Fig. 4 As shown, the tooth flank 17 exhibits the correction in a marginal region from x start = 2.7 mm to the edge of the tooth flank at x end = 5.25 mm. This marginal region comprises approximately 25% of the tooth width 43 of tooth 9. During the manufacturing of the tooth flank 17, a grinding wheel is moved closer to the tooth blank by the correction amount dy(x), depending on the x-position, to create a reduction of the tooth flank 17 and the tooth tip 15 in the form of a logarithmic function along the width 41 of the tooth flank 17. The resulting tooth tip width curve 53 also corresponds to the logarithmic function shown.

[0058] Fig. 5 Figure 1 shows a flowchart of a typical process 100 for manufacturing a tooth 9 for a gear 1. In block 110, the process 100 comprises providing a tooth blank, in particular a cylindrical tooth blank, for manufacturing a round tooth with two tooth flanks by discontinuous profile grinding.

[0059] In block 120, method 100 comprises producing a tooth flank 17 of the tooth 9, wherein the tooth flank 17 is produced at least partially curved along a width curve 51 extending over a width 41 of the tooth flank 17. A profiled grinding wheel is used to produce the tooth flank 17, which replicates the profile of the tooth flank 17 and the tooth tip 15. In block 120, the profiled grinding wheel is fed in the y-direction, the feed being changed by a correction amount depending on the position of the grinding wheel along the tooth width 43 (x-direction), for example by a correction amount dy(x) according to formula (1) or as in Fig. 4 As shown. With the correction of the tooth flank 17, the tooth head 15 is also produced with a corresponding reduction along a tooth head width curve 53 of the tooth head 15.

[0060] In block 130, process 100 comprises producing an additional tooth flank 18 of tooth 9. Specifically, the tooth blank and the grinding wheel are rotated 180° relative to each other about the longitudinal axis 11 (y-direction) of tooth 9. The additional tooth flank 18 is produced by profile grinding using the grinding wheel analogously to tooth flank 17. A tooth 9 produced in this manner can, when used in a gearbox 1, exhibit particularly lower wear during the gearbox's break-in phase.

Claims

1. Gear mechanism (1), in particular a coaxial gear mechanism, comprising - a ring gear with internal toothing (3), - a tooth carrier (5) with guides (7) radially aligned with respect to an axis of rotation of the gear mechanism, - teeth (9) which are received in the guides (7) for engagement with the internal toothing (3), wherein the teeth (9) are mounted in the guides (7) so as to be displaceable relative to the tooth carrier (5) in the direction of their longitudinal axis (11), and - a cam disc (13) rotatable about the axis of rotation in operative relationship with the teeth (9), - wherein the teeth (9) each have a tooth tip (15), wherein a tooth tip width curve (53) extending along the tooth tip (15) and over a tooth width (43) of the tooth (9) is produced at least partially curved in the direction of the longitudinal axis (11) of the tooth, wherein the tooth tip width curve (53) extends on the tooth tip (15) in a plane of the longitudinal axis (11) and the tooth width (43).

2. Gear mechanism (1) according to claim 1, wherein a curved part of the tooth tip width curve (53) is in the form of a logarithmic function or a radius.

3. Gear mechanism (1) according to claim 1 or 2, wherein the tooth tip (15) is recessed in an edge region of the tooth (9) by at least 0.02% and / or at most 2% of the tooth width relative to a maximum height of the tooth tip (15) in the direction of the longitudinal axis (11) of the tooth (9), wherein the tooth tip (15) has the maximum height in a region (47) of the tooth tip (15) central to the tooth width (43).

4. Gear mechanism (1) according to any of the preceding claims, wherein the teeth (9) each have a tooth flank (17) which is produced at least partially curved along a width curve (51) extending over a width (41) of the tooth flank (17).

5. Gear mechanism (1) according to claim 4, wherein the tooth flank (17) has two 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 edge regions (49), wherein the tooth flank (17) is recessed inwards in at least one edge region of the two edge regions (49) relative to the central region (47), with reference to the interior of the tooth (9), wherein in particular the at least one edge region is recessed in a direction perpendicular to the tooth flank by at most 1% of a maximum width of the tooth flank (17) relative to the central region (47).

6. Gear mechanism (1) according to claim 5, wherein the width curve (51) is curved in at least one edge region of the two edge regions (49) and is straight in the central region (47) of the tooth flank (17).

7. Gear mechanism (1) according to one of claims 5 or 6, wherein the two edge regions (49) each comprise at least 10% and / or a maximum of 40% of the width (41) of the tooth flank (17).

8. Gear mechanism (1) according to any of claims 4 to 7, wherein the width curve (51) is symmetrical with respect to a midpoint of the width (41) of the tooth flank (17), and / or wherein the teeth (9) each comprise a further tooth flank, wherein the further tooth flank is produced in a mirror-symmetrical manner to the tooth flank (17).

9. Gear mechanism (1) according to any of claims 4 to 8, wherein a curved part of the width curve (51) corresponds to a logarithmic function or a radius correction.

10. Gear mechanism (1) according to any of claims 4 to 9, wherein the width curve (51) extends on the tooth flank (17) and in a sectional plane perpendicular to the tooth flank.

11. Gear mechanism (1) according to any of claims 4 to 10, wherein the tooth flanks of the teeth (9) are produced by grinding.

12. Gear mechanism (1) according to any of claims 4 to 11, wherein a longitudinal curve (55) on the tooth flank (17) and extending perpendicular to the width (41) of the tooth flank (17) is at least partially curved.

13. Tooth (9) for a gear mechanism (1) according to any of the preceding claims, - wherein the tooth (9) has a tooth tip (15), wherein a tooth tip width curve (53) extending along the tooth tip (15) and over a tooth width (43) of the tooth (9) is at least partially curved in the direction of the longitudinal axis (11) of the tooth (9), in particular convexly curved, wherein the tooth tip width curve (53) extends on the tooth tip (15) in a plane of the longitudinal axis (11) and the tooth width (43).

14. Method (100) for producing a tooth (9) according to claim 13, comprising - providing a tooth blank of the tooth (9); and - producing the tooth tip (15) of the tooth (9).

15. Method (100) according to claim 14, wherein the production of the tooth tip (15) comprises grinding the tooth blank, comprising: - feeding a grinding wheel in the direction of a longitudinal axis of the tooth blank; - changing the feed of the grinding wheel in the direction of the longitudinal axis of the tooth blank depending on the position of the grinding wheel along the tooth width (43).

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