TRANSMISSION

Description

Field of the invention

[0001] The invention relates to a transmission and a use of a transmission and a tooth for a transmission. State of the art

[0002] Gearboxes are known from the prior art which comprise teeth mounted radially displaceably in a tooth carrier. Drive elements with a profile, such as cam disks, are used to drive the teeth. The teeth engage with a toothing, resulting in a relative movement between the tooth carrier with the teeth and the toothing. The relative movement between the toothing and the teeth is at least an order of magnitude smaller than the movement of the drive element with the profile. In this way, high gear ratios can be achieved; an example of such a gearbox is published in DE 10 2007 011 175 A1. DE 10 2015 105 524 A1, which shows the features of the preamble of claim 1, and DE 10 2006 042 786 A1 each relate to a gearbox. DE 10 2012 104 083 A1 relates to a bearing for a gearbox.

[0003] A critical aspect of these gears is the positioning of the teeth in the tooth carrier. When power is transmitted from a tooth to the tooth carrier, which may represent the output, contact forces occur between the tooth and the tooth carrier. This leads to heat generation and, under certain circumstances, material removal due to the movement of the teeth. Both can be undesirable during operation. Disclosure of the invention

[0004] The object of the invention is to provide a gear or a tooth that is improved over prior art gears, while achieving reduced heat generation or wear in the area of ​​the tooth guide. Furthermore, the object of the invention is to provide a use for such a gear.

[0005] This object is achieved with a gear according to claim 1, a corresponding tooth according to claim 11, and a use according to the independent claim. Advantageous further developments and embodiments are set forth in the dependent claims.

[0006] One aspect of the invention relates to a transmission according to independent claim 1. A transmission, in particular a coaxial transmission, comprises a toothing, a tooth carrier with guides, teeth which are received in the guides for engagement with the toothing, wherein the teeth are mounted in the guides so as to be displaceable relative to the tooth carrier in the direction of their longitudinal axis, a cam disk for driving the teeth along the respective longitudinal axis of the teeth, wherein at least one of the teeth has a tooth flank region with tooth flanks and a tooth body, wherein between the tooth body and the tooth flanks a shoulder is provided which recesses inwards from the tooth body to the tooth flank. The transmission is characterized in that, in a sectional plane which runs along the longitudinal axis of the tooth and perpendicular to the tooth flanks, a tangent to one of the tooth flanks intersects a volume of the tooth body.

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

[0008] A further aspect of the invention relates to a tooth according to the independent claim 11 for a gear in one of the typical embodiments described herein. A tooth has a tooth flank region with tooth flanks and a tooth body, wherein between the tooth body and the

[0009] Each tooth flank has a shoulder that recedes inward from the tooth body to the tooth flank. The tooth is characterized in that, in a cutting plane that runs along the longitudinal axis of the tooth and perpendicular to the tooth flanks, a tangent to one of the tooth flanks intersects a volume of the tooth body.

[0010] Typically, the shoulder of a tooth is located in a shoulder region of the tooth. Typically, the shoulder region is located between the tooth flank region of the tooth and the tooth body. Typically, the shoulder region and the tooth flank region together form a tooth tip of the tooth. In particular, the tooth flank region herein comprises that region of the tooth along the longitudinal axis of the tooth in which the tooth flanks of the tooth and a tooth tip of the tooth are located.

[0011] Embodiments of the invention particularly relate to coaxial gears. Gears of the invention typically comprise an internal cam with a profile as the drive element and a ring gear with internal toothing, or an external drive element with internal profiling and an internal gear or an internal rack, which, in the case of the external drive element, provides the toothing. Configurations of embodiments relate to linear gears for converting rotation into linear movement. The toothing is typically a circumferential toothing. The teeth or the tooth tips of the teeth engage in the toothing, whereby the teeth are typically mounted radially or axially displaceably relative to the tooth carrier.

[0012] In typical embodiments, the guides of the tooth carrier are aligned radially with respect to the cam's rotational axis. Typically, the teeth are mounted in the guides of the tooth carrier so that they can be moved radially with respect to the cam's rotational axis. Typically, the teeth are mounted linearly radially relative to the tooth carrier. "Linear radial" usually means that the guide is radial, allowing only radial movement of the tooth and, in particular, tilting of the tooth within the guide clearance.

[0013] In other typical embodiments, the guides of the tooth carrier are axially aligned with respect to the rotational axis of the cam disc. Typically, the teeth are mounted in the guides of the tooth carrier so that they can be axially displaced relative to the rotational axis of the cam disc. Typically, the teeth are mounted in a linear axial manner relative to the tooth carrier. "Linear axial" usually means that there is a guide in the axial direction, which only allows movement of the tooth in the axial direction.

[0014] Typically, the teeth are each mounted in the tooth carrier so they can move in exactly one direction, typically along the longitudinal axis of the tooth. This can be achieved, for example, by the tooth having a constant cross-section in the direction of displacement over a certain length, in particular over a certain length along the longitudinal axis of the tooth, with the guide for the tooth in the tooth carrier being designed as a slot or opening with a constant cross-section.

[0015] In typical embodiments of the gears according to the invention, at least some of the teeth are designed to be rigid. The term "rigid" is typically understood in a technical sense, meaning that bending of the teeth, due to the rigidity 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, in particular steel or a titanium alloy, a nickel alloy, or other alloys. Furthermore, rigid teeth made of plastic can also be provided, particularly in gears in which at least one of the following parts is also made of plastic: toothing on a ring gear or a gearwheel, tooth carrier, and drive element.In typical embodiments of the invention, the tooth carrier and the teeth are made of a metal alloy, or the gearing or, furthermore, the drive element is made of a metal alloy. Such gears offer the advantage of being extremely torsionally rigid and capable of withstanding high loads. Plastic gears offer the advantage of being lightweight. The term "flexurally rigid" refers in particular to a flexural rigidity about a transverse axis of the tooth. This means, in particular, that when the tooth is viewed as a beam extending from a tooth base to a tooth flank region, a flexural rigidity is present that at least substantially eliminates bending deformations between the tooth flank region and the tooth base.

[0016] The bending stiffness ensures that the gearbox has an extremely high load capacity and torsional stiffness.

[0017] In typical embodiments, a pivoting segment is arranged between the tooth and the profile. This pivoting segment is mounted on a roller bearing, which in turn rests on the profile. Typically, the tooth is loosely connected to the pivoting segment. "Loose connection" preferably means that the tooth segment is merely placed on the pivoting segment, usually directly. Preferred pivoting segments comprise a profile that prevents the tooth from slipping off the pivoting segment or the pivoting segment from slipping in at least one direction. Such a profile can, for example, be a bead that engages a recess at the base of the tooth. For a possible embodiment of a pivoting segment, reference is made to DE 10 2015 105 523 A1.

[0018] Typical tooth carriers comprise guides, each with a tooth base opening and a tooth tip opening. Typically, the tooth base opening is oriented towards the cam disk and the tooth tip opening in the direction of the toothing. This allows the teeth to be accommodated so that they can move along their respective longitudinal axes in the guide. The longitudinal axis of a tooth typically runs from a tooth base to the tooth flank area. The teeth are each mounted with their respective tooth base on pivot segments, which in turn are mounted on the cam disk via rolling elements. In typical designs, the tooth carrier is circular or ring-shaped. Typical guides for the teeth in the tooth carrier are designed as through openings or through bores. Other typical tooth carriers comprise rectangular milled recesses or elongated holes or slots as guides.The teeth are typically housed in the tooth carrier so that the tooth tip protrudes from the tooth tip opening or can be pushed out of the tooth tip opening, and the tooth base protrudes from the tooth base opening. By driving the cam disc with the profile, a force can be exerted on the teeth via the rolling elements and the pivoting segments in the direction of the respective longitudinal axis of the teeth, forcing them out of the guides on the tooth tip side.

[0019] The gearing and the teeth typically have curved flanks. Examples of flank curvatures include a cylindrical curvature, a curvature of the flanks along a helix or helical surface around the rotational axis of the coaxial gear, or a curvature in the form of a logarithmic spiral. For a possible embodiment of a curvature in the form of a logarithmic spiral, reference is made to DE 10 2007 011 175 A1. The curved surface offers the advantage that the meshing flanks contact one another over a large area and not merely in lines or points. This achieves extreme rigidity in the force transmission between the gearing and the teeth. "Flanks" here refers in particular to the tooth flanks of the teeth or flanks of the gearing.

[0020] In typical embodiments, a tooth crest of a tooth has a tooth flank region with tooth flanks along the longitudinal axis of the tooth. Typically, the tooth includes a tooth base in an end region of the tooth opposite the crest. The tooth base typically has a recess for supporting the tooth on a profile of a pivot segment.

[0021] In typical embodiments, the tooth comprises a shoulder region and a tooth body between the tooth flank region and the tooth base. The tooth body extends along the longitudinal axis of the tooth over a body length. Typically, the tooth body has at least a substantially constant cross-section over the body length, apart from lubrication channels or the like. Typically, the tooth body is at least substantially cylindrical in shape.

[0022] For example, forces can be transmitted between a tooth and a tooth carrier via a tooth guiding contact, in particular via a tooth guiding contact between the tooth body and the guide of the tooth. In particular, the body length of a typical tooth with a shoulder can be longer than the body length of a tooth without a shoulder known from the prior art. For example, the tooth flank region along the longitudinal axis of the tooth can be shortened compared to a tooth known from the prior art, in particular without changing the overall length of the tooth compared to the tooth known from the prior art. By extending the body length, for example, the outer tooth guiding contact can be shifted further in the direction of the toothing. This can result in an improved leverage effect with lower contact forces at the tooth guiding contact or in the support of forces between the tooth and the tooth carrier.

[0023] In typical embodiments, the tooth is designed as a flat tooth or a round tooth. Flat teeth are typically guided in guides with a non-circular cross-section in the tooth carrier. In typical embodiments, the tooth has a width (e.g., in the axial direction of the gear) at least twice as large as its thickness (e.g., in the circumferential direction of the gear). Other embodiments include circular or oval teeth, or circular teeth with flats.

[0024] In typical embodiments, a tooth comprises a shoulder between the tooth flanks of the tooth flank region and the tooth body, which shoulder projects inwards from the tooth body towards the tooth flank, in particular inwards towards the longitudinal axis of the tooth. In particular, the shoulder is provided in a shoulder region between the tooth flanks and the tooth body. The shoulder is, for example, rounded inwards, in particular inwards towards the longitudinal axis of the tooth, or is formed with a radius. In other typical embodiments, the shoulder is designed as a shoulder or a step. In particular, the shoulder can be designed with an edge extending inwards in the direction of the longitudinal axis.

[0025] Typically, in the shoulder region of the tooth, an outer tooth surface of the tooth is at least partially formed by the shoulder. In particular, the shape of the outer tooth surface between two tooth flanks and the tooth body of the tooth is predetermined by a respective shoulder. The outer tooth surface of the tooth can comprise surfaces in the shoulder region or in the tooth flank region that have a shape other than a shoulder or a tooth flank, for example, partial surfaces of a conical base body or a cylindrical base body. In embodiments, the outer contour of the tooth tip runs along a conical or cylindrical base body in a region in which no tooth flanks or shoulder are formed.

[0026] In typical embodiments, the tooth flanks each enclose a flank angle with the longitudinal axis. The flank angle is typically at least 15°, in particular at least 20° or at least 25°, or a maximum of 45°, in particular a maximum of 40° or a maximum of 35°. In this context, a tooth flank is understood to mean in particular a surface of the tooth flank region which can come into contact with the toothing or which can bear a load, for example a surface load, from the contact of the tooth with the toothing. The flank angle is understood to mean in particular an angle which a flank line of the tooth flank encloses in a sectional plane of the tooth with the longitudinal axis of the tooth, wherein the sectional plane of the tooth runs along the longitudinal axis and perpendicular to the tooth flank.For example, the flank line in the section plane can correspond to a mean tangent to the tooth flank or a tangent to the tooth flank in the middle of the tooth flank or a secant through the end points of the tooth flank in the section plane.

[0027] Typically, a shoulder is concavely rounded. Typically, the shoulder has a recess relative to the tooth flank. In typical embodiments, the shoulder, in particular the recess of the shoulder, is concavely rounded at the transition to a tooth flank. In particular, the recess of the shoulder is rounded inwards with respect to a tooth flank trace. In particular, the tooth at the recess of the shoulder does not come into contact with the toothing during gear engagement. In particular, the tooth at the recess of the shoulder does not bear any load from the toothing. One advantage of the recess of the shoulder compared to the tooth flank can be that churning losses in the contact between the tooth and the toothing can be reduced. In particular, the tooth flank can be reduced in size due to the recess, meaning that lubricating oil has to be displaced from a smaller area.

[0028] Typically, in a sectional plane of the tooth along the longitudinal axis and perpendicular to the tooth flank, the shoulder at a first location, in particular at a first location at the transition to the tooth body, is more inclined to the longitudinal axis of the tooth than the tooth flank. For example, the inclination of the shoulder to the longitudinal axis at the first location is greater than the flank angle of the tooth flank, in particular by at least 5° or at least 10°.

[0029] In typical embodiments, in a sectional plane of the tooth along the longitudinal axis and perpendicular to the tooth flank, the shoulder is inclined less sharply to the longitudinal axis of the tooth than the tooth flank at a second location, in particular at a second location at the transition to the tooth flank. For example, the inclination of the shoulder to the longitudinal axis at the second location is smaller than the flank angle, in particular by at least 3° or at least 5°. In particular, the shoulder can have a first location and a second location.

[0030] In typical embodiments, a tangent to one of the tooth flanks intersects a volume of the tooth body in a cutting plane that runs along the longitudinal axis of the tooth and perpendicular to the tooth flanks. In particular, the tangent intersects the volume of the tooth body and a volume of the shoulder region of the tooth. Typically, the volume of the tooth body is cut by a flank surface into at least two sub-volumes, with the flank surface extending along the flank line and perpendicular to the cutting plane.

[0031] In typical embodiments, a tooth tip of the tooth, in particular the tooth flank region and the shoulder together, has an axial length that is greater than the depth of a tooth gap of the toothing. The "axial length" of the tooth tip is understood to mean, in particular, the combined length of the tooth flank region and the shoulder relative to the longitudinal axis of the tooth. In a gear with radially aligned guides, the depth of the tooth gap is understood to mean, in particular, the difference between a radial maximum and a radial minimum of the toothing. In a gear with axially aligned guides, the depth of the tooth gap is understood to mean, in particular, the difference between an axial maximum and an axial minimum of the toothing.In exemplary embodiments, the axial length of the tooth flank region and shoulder can be less than 1.2 times the depth of the tooth gap, in particular less than 1.1 times or 1.05 times the depth of the tooth gap. In further exemplary embodiments, with a complete engagement of the tooth flank region in the toothing, an outer edge of the shoulder at the boundary between the tooth body and shoulder can have a distance in the axial direction of the tooth from a tooth crest of the toothing of a maximum of 0.1 times, for example 0.05 times, the depth of a tooth gap of the toothing.

[0032] In typical embodiments, the tooth body has a cone in a lead-in region, particularly adjacent to the shoulder, wherein a tangent to the outer circumference of the cone encloses a cone angle of a maximum of 2°, particularly a maximum of 1° or a maximum of 0.5°, with the longitudinal axis of the tooth. Typical cone angles of the tooth cone are at least 0.05°, at least 0.1°, or at least 0.2°. The cone can extend partially from the tooth body into the shoulder region or into the tooth flank region, particularly up to a tooth tip of the tooth, for example, on outer tooth surfaces that are not designed as a shoulder or tooth flank. The term "cone" in the lead-in region also includes chamfers, particularly chamfers attached to flat teeth. Typical lead-in regions can be flat and have a chamfer. Typically, a transition between the cone of the tooth and the tooth body is crowned.This allows the tooth to slide smoothly along the guide. Typically, the tooth is accommodated in the guide of the tooth carrier in such a way that, at maximum radial or axial stroke of a tooth in the direction of the toothing, the cone of the tooth protrudes from the guide. In other embodiments, the cone remains at least partially within the guide.

[0033] Typically, the surface of the tooth at the shoulder is machined differently than the tooth flanks. In particular, the surface of the tooth at the shoulder is less finely machined than the tooth flanks. For example, the shoulder may be machined less finely during tooth manufacture. In particular, the larger the shoulder or the shoulder area in which the shoulder is intended, the fewer surfaces need to be machined.

[0034] Typical embodiments of the gear can offer the advantage over the prior art that the gear has an improved leverage effect in supporting tooth forces between teeth and tooth carrier. In particular, the gear can have a higher load-bearing capacity or less wear or a longer service life. A further advantage of typical gears can be that the manufacturing of the teeth or the gear is simplified. For example, the shoulder of the tooth can be machined less finely or with significantly less precision than the tooth flanks. In particular, a tooth can be manufactured more quickly or more cost-effectively. Typical gears can offer the further advantage that churning losses in the tooth contact can be reduced. For example, typical gears have smaller tooth flanks, meaning that lubricating oil has to be displaced from a smaller area. Short description of the drawings

[0035] The invention is explained in more detail below with reference to the accompanying drawings, in which the figures show: Fig. 1 shows a section of a typical embodiment of the invention 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 tooth of another typical embodiment in a schematic view; and Fig. 5 the tooth of the Fig. 4 in a side view; Description of implementation examples

[0036] In the following, typical embodiments of the invention are described with reference to the figures, wherein the invention is not limited to the embodiments, but rather the scope of the invention is determined by the claims. In the description of the embodiments, the same reference numerals may be used for the same or similar parts in different figures and for different embodiments. In some cases, features that have already been described in connection with other figures are not described again for the sake of clarity. For the sake of clarity, not all respective features are provided with a reference numeral, for example the teeth (reference numeral 9 in the Fig. 1 ).

[0037] In the Fig. 1 A section of a typical embodiment of the invention is shown in a schematic sectional view. Fig. 1 shows a gear 1 with teeth 9, which are slidably received in guides 7 of a tooth carrier 5. The tooth carrier 5 is arranged between a 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 for linear radial displacement. In particular, the teeth 9 are displaceable along their respective longitudinal axes 11. The teeth 9 can be displaced radially to engage with a toothing 3 of the ring gear 4.

[0038] The cam disc 13 serves in the gear 1 of the Fig. 1 as a drive element of the transmission 1. The cam disc 13 has a profile in the circumferential direction of the cam disc 13. The profile has a course with two elevations over the circumference, so that opposite teeth 9 engage the furthest and with the same depth into tooth gaps 29 of the toothing 3. In further embodiments, the cam disc has three elevations, and in still further embodiments, the cam disc has only one elevation, or in further embodiments, more than three elevations.

[0039] In the exemplary embodiment of the Fig. 1 the axis of rotation of the cam disc 13 is perpendicular to the imaging plane of the 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 toothing 3 of the ring gear 4 is arranged radially outside the teeth 9 with respect to the axis of rotation of the cam disk 13. With such a configuration, the output is tapped at the ring gear 4 with the toothing 3 or at the tooth carrier 5, with the other element being fixed in each case. In further embodiments, the drive element is arranged on the outside, i.e. outside the tooth carrier, and the toothing is arranged on the inside. Again, it is possible to tap the output at the inner toothing or at the tooth carrier. The tooth carrier can also be referred to as a tooth cage with its openings, in which teeth are accommodated so as to be displaceable in a radially linear manner.

[0040] The gear 1 comprises a segmented bearing for the teeth 9. The segmented bearing comprises pivot segments 25, each of which has a round tooth bearing surface 26 on the side facing the tooth 9. This tooth bearing surface forms a bead on which a tooth base 33 of a tooth 9, or in typical embodiments, two, three, or four teeth, can be arranged next to one another in the axial direction of the gear 1. The bead, together with a corresponding recess 35 in the tooth base 33 of the respective tooth 9, prevents the tooth 9 from slipping on the pivot segment 25.

[0041] The beads form tooth base joints for the teeth 9, allowing the pivot segments 25 to tilt relative to the teeth 9 to ensure friction-free guidance. The pivot segments 25 are radially movable relative to one another, allowing the spacing between the pivot segments 25 to be varied. This enables largely friction-free guidance and a largely friction-free radial drive of the pivot segments 25 through the profiling of the cam disk 13. To minimize frictional resistance between the profiling and the pivot segments 25, the rolling elements 23 are provided as needle rollers. In further embodiments, balls or other rolling bearings are provided for supporting the pivot segments.

[0042] In the Fig. 1 A tooth 9 comprises a tooth flank region 15 with tooth flanks 17 and a tooth tip of the tooth 9, wherein the tooth flank region 15 is arranged in a tooth tip of the tooth 9 facing the toothing 3 of the ring gear 4. The tooth 9 comprises a tooth base 33 in an end region of the tooth 9 facing the cam disk 13, a tooth body 19 adjacent to the tooth base 33, and a shoulder 21 arranged between the tooth body 19 and the tooth flank region 15, in particular a shoulder region of the tooth 9 with the shoulder 21 arranged in the shoulder region. The shoulder 21, in particular the shoulder region, and the tooth flank region 15 together form the tooth tip of the tooth 9.

[0043] The tooth body 19 has at least a substantially constant cross-section over a body length along the longitudinal axis 11 of the tooth 9. The tooth body 19 is in contact with a guide 7 of the tooth carrier 5. Forces can be transmitted between the tooth 9 and the tooth carrier 5 via the contact surfaces, contact lines, or contact points, for example, through leverage.

[0044] The tooth flank area 15 includes tooth flanks 17, which can come into contact with the toothing 3. Forces can be transmitted between the toothing 3 and the tooth 9 via the tooth flanks 17.

[0045] Between the tooth body 19 and the tooth flanks 17 of the tooth flank region 15, a shoulder 21 projects inward from the tooth body 19 toward the tooth flanks 17. The shoulder 21 and the tooth flank region 15 together have an axial length that is greater than the depth of a tooth gap 29 of the toothing 3. The shoulder 21 can serve, in particular, to extend the body length of the tooth body 19 up to an edge 31 at the boundary between the tooth body 19 and the shoulder 21. In particular, leverage effects during the transmission of forces between a tooth 9 and the tooth carrier 5 can be improved, for example, by a tooth guide contact between the tooth body 19 and the guide 7 that is shifted far in the direction of the toothing 3.

[0046] Fig. 2 shows a schematic view of a tooth 9 of a typical embodiment, wherein the viewing plane runs perpendicular to tooth flanks 17 of a tooth flank region 15 of the tooth 9. The tooth flank region 15 is the axial region along the longitudinal axis 11 of the tooth 9, in which the tooth flanks 17 and a tooth tip of the tooth 9 are arranged. Between the tooth flank region 15 and a tooth body 19 of the tooth 9, the tooth 9 comprises a shoulder 21 which recesses from the tooth body 19 to the tooth flanks 15. The shoulder 21 is arranged in a shoulder region 20 of the tooth 9. The tooth body 19 comprises a cone 45 in an inlet region, which extends in an axial direction with respect to the longitudinal axis 11 of the tooth 9 from the tooth body, in particular from an edge 52, towards the tooth tip and borders on the shoulder 21. The cone 45 has an angle of 2° relative to the longitudinal axis 11 of the tooth 9.The transition between the cone 45 of tooth 9 and the cylindrical part of the tooth body 19 is crowned. As shown in . Fig. 3 As shown, conical surfaces of the cone 45 extend partially into the shoulder region 20 and into the tooth flank region 15 of the tooth 9, in particular into parts of the tooth 9 in which no shoulder 21 or no tooth flank 17 is provided.

[0047] In the Fig. 2 a flank line 41 is drawn for a tooth flank 17, which in the Fig. 2 for example, a mean tangent to the tooth flank 17 in a sectional plane of the tooth 9. The flank line 41 intersects a volume of the tooth body 19. The flank line 41 encloses a flank angle 42 with the longitudinal axis 11. The shoulder 21 is inclined at a first location 49, for example at or near the edge 31, more strongly to the longitudinal axis 11 than the tooth flank 17. In particular, the inclination of the shoulder 21 to the longitudinal axis at the first location 49 is greater than the flank angle 42. In the Fig. 2 The shoulder 21 is rounded with a radius. The shoulder 21 is less finely machined than the tooth flank 17.

[0048] Fig. 3 shows schematically a side view of the tooth 9, wherein the view plane of the side view is perpendicular to the view plane of the Fig. 2 stands. The Fig. 3 shows the shoulder 21 and the tooth flank region 15 with tooth flanks 17, wherein a tooth tip 43 of the tooth, which comprises the shoulder 21 and the tooth flank region 15, has an axial length greater than the depth of a tooth gap of a gearing in a typical transmission. In particular, the tooth 9 with the tooth flank region 15 can be fully engaged in the gearing without the shoulder 21 coming into contact with the gearing.

[0049] Fig. 4 shows schematically a view of a tooth 9 of a further typical embodiment, wherein the viewing plane is perpendicular to tooth flanks 17 of a tooth flank region 15 of the tooth 9. In the Fig. 4 a shoulder 21 is concavely rounded towards the tooth flank 17, for example, concave inwards towards the longitudinal axis 11. The shoulder 21 has an inward recess 47 relative to a tooth flank 17 or a flank line 41. In particular, the recess of the shoulder 21 is inclined more sharply to the longitudinal axis 11 than the tooth flank 17 at a first location 49 near the transition to a tooth body 19 of the tooth 9, in particular with an inclination that is greater than the flank angle 42. The recess 47 of the shoulder 21 is inclined less sharply to the longitudinal axis 11 than the tooth flank 17 at a second location 51 near the transition to a tooth flank 17 of the tooth flank region 15 of the tooth 9, in particular with an inclination that is smaller than the flank angle 42.

[0050] The Fig. 5 shows schematically a side view of the tooth 9, wherein the view plane of the side view is perpendicular to the view plane of the Fig. 4 stands. In the Figuren 4 und 5the shoulder 21, in particular the recess 47, is less finely machined than the tooth flank 17. By means of the recess 47 of the shoulder 21, the tooth flanks 17 can be reduced, for example, to those surfaces which are required for the transmission of forces between a toothing of a ring gear and the tooth flank region 15 of the tooth 9. By means of the recess 47 and the reduction of the flank surfaces, churning losses can be reduced, which can occur due to the displacement of lubricating oil between a tooth and a toothing.

[0051] The invention is not limited to the embodiment described above, but the scope of the invention is determined by the appended claims.

Claims

1. Gear mechanism (1), in particular a coaxial gear mechanism, comprising - gear toothing (3), - a tooth carrier (5) having guides (7), - teeth (9) which are accommodated in the guides (7) for engagement with the gear toothing (3), the teeth (9) being mounted in the guides (7) so as to be displaceable in the direction of their longitudinal axis (11) relative to the tooth carrier (5), and - a cam disc (13) for driving the teeth (9) along each longitudinal axis (11) of the teeth (9), - at least one of the teeth (9) comprising a tooth flank region (15) that has tooth flanks (17) and a tooth body (19), - a shoulder (21) being provided between each tooth body (19) and the tooth flanks (17) which is inwardly set back from the tooth body (19) with respect to the tooth flank (17), characterised in that, - in a cutting plane which runs along the longitudinal axis (11) of the tooth (9) and perpendicularly to the tooth flanks (17), a tangent to one of the tooth flanks (17) intersects a volume of the tooth body (19).

2. Gear mechanism (1) according to claim 1, wherein the tooth body (19) is cylindrical.

3. Gear mechanism (1) according to either of the preceding claims, wherein the tooth flanks (17) include a flank angle (42) with the longitudinal axis (11), and wherein the flank angle (42) is at least 15° and / or a maximum of 45°.

4. Gear mechanism (1) according to any of the preceding claims, wherein, at the transition to the tooth flanks (17), the shoulder (21) is rounded inwards, in particular is concave.

5. Gear mechanism (1) according to any of the preceding claims, wherein the tooth flank region (15) and the shoulder (21) have a combined axial length which is greater than a depth of a tooth gap (29) of the gear toothing (3).

6. Gear mechanism (1) according to any of the preceding claims, wherein the tooth body (19) has a bevel (45) in an entry region, in particular in an entry region adjacent to the shoulder (21), and wherein a tangent to the outer circumference of the bevel (45) includes a bevel angle of a maximum of 2° with the longitudinal axis (11) of the tooth (9).

7. Gear mechanism (1) according to any of the preceding claims, wherein the surface of the tooth (9) on the shoulder (21) is machined differently from the tooth flanks (17).

8. Gear mechanism (1) according to any of the preceding claims, wherein the guides (7) of the tooth carrier (5) are radially aligned with respect to the axis of rotation of the cam disc (13); and wherein the teeth (9) are mounted in the guides (7) of the tooth carrier (5) so as to be radially displaceable with respect to the axis of rotation of the cam disc (13).

9. Gear mechanism (1) according to any of claims 1 to 7, wherein the guides (7) of the tooth carrier (5) are axially aligned with respect to the axis of rotation of the cam disc (13); and wherein the teeth (9) are mounted in the guides (7) of the tooth carrier (5) so as to be axially displaceable with respect to the axis of rotation of the cam disk (13).

10. Use of a gear mechanism (1) according to any of the preceding claims.

11. Tooth (9) for a gear mechanism (1) according to any of claims 1 to 9, the tooth (9) comprising a tooth flank region (15) that has tooth flanks (17) and a tooth body (19), a shoulder (21) being provided between the tooth body (19) and the tooth flanks (17) which is inwardly set back from the tooth body (19) with respect to the tooth flank (17), characterised in that, in a cutting plane which runs along the longitudinal axis (11) of the tooth (9) and perpendicularly to the tooth flanks (17), a tangent to one of the tooth flanks (17) intersects a volume of the tooth body (19).