Actuating gear and method for determining an inner contour of a tooth element of an actuator

Abstract

Actuating gear (2), comprising: - a concentric axis to a transmission axis (A A ) arranged essentially rigid ring gear (6) with internal teeth (8); - a wave generator (10) with an eccentric axis (A B ), which are offset parallel to the transmission central axis (A A ) around the same area; - Tooth elements (14, 16, 18, 20, 22), each - are arranged radially between the ring gear (6) and the shaft generator (10), - have an external toothing (32) that engages with the internal toothing (8), and - have a device (34) that rests against a running surface (36) of the wave generator (10); and - a drive gear (24) opposite which the tooth elements (14, 16, 18, 20, 22) - limited mobility and - are circumferentially supported, with the transmission central axis (A A) and the eccentric axis (A↓B) span a wave generator symmetry plane (54) that is perpendicular to the gearbox central axis (A A ) lying reference plane in a wave generator symmetry line (55) intersects, characterized by the fact that The tooth flanks of the internal gearing (8) and the external gearing (32) fit together in such a way that two instantaneous poles (M) exist in the reference plane. E , M D ) of the tooth elements (16, 14) which transmit power in operation of the actuating gear (2) always remain on the wave generator symmetry line (55).

Description

[0001] The invention relates to an actuating gear and a method for determining an inner contour of a tooth element of an actuating gear.

[0002] From DE 10 2022 000 408 A1 an actuating gear according to the preamble of claim 1 is already known. The actuating gear has, among other things, - a substantially rigid ring gear with internal teeth arranged concentrically to a central transmission axis; - a wave generator with an eccentric axis that rotates parallel to the central axis of the gearbox; - Tooth elements, each - are arranged radially between the ring gear and the wave generator, - have an external toothing that engages with the internal toothing, and - have a system that rests against a running surface of the wave generator; and - a driving wheel, opposite which the toothed elements - limited mobility and - can be supported circumferentially. The gearbox's central axis and the eccentric axis span a wave generator's symmetry plane, which intersects a reference plane perpendicular to the gearbox's central axis in a wave generator's symmetry line. With such a control gear, a high speed can be converted into a low speed with high torque.

[0003] Further actuating gears are known from DE 10 2020 002 965 A1 and EP 3 779 239 B1, which are discussed in more detail in the following statement of advantages.

[0004] The object of the invention is to further improve the noise development and also the efficiency of such an actuating gear.

[0005] The object is achieved according to the invention with the features of patent claim 1 and the independent patent claim 3. Furthermore, the object is achieved by a method according to claim 7.

[0006] According to claim 1, it is provided that tooth flanks of the internal toothing and the external toothing fit together in such a way that in the reference plane two instantaneous poles of the tooth elements, which transmit force during operation of the actuating gear, always remain on the wave generator symmetry line.

[0007] Put simply, the instantaneous poles of the toothed elements are always located on the wave generator's symmetry line, which rotates around a central gear axis. This makes the actuator gear quiet, smooth, and highly efficient. Furthermore, it is possible to manufacture such an actuator gear cost-effectively.

[0008] The actuator gear according to the invention can be used, for example, in a robot or a vehicle seat adjustment system. In robots, such an actuator gear is required for precise positioning and for high forces or torques. Advantageously, the actuator gear is particularly torsionally rigid and low-backlash. This allows the robot to be moved quickly and precisely.

[0009] When components move relative to one another during operation of the actuator, this movement can be described by a sequence of rotations around the instantaneous pole. The instantaneous pole is defined as the pivot point of two components at a given instant. This instant is an infinitesimally small time interval, so that practically no time passes in such an instant. Time is only slightly greater than zero at this instant so that the time interval can be defined. Since the instantaneous poles change, instantaneous pole trajectories are obtained over time, along which the instantaneous poles move.

[0010] Because the instantaneous poles of all toothed elements lie on a common wave generator symmetry line, the actuator gear always has the same gear ratio i, even in the event of manufacturing inaccuracies. This ensures smooth gear operation, which also results in consistent noise levels.

[0011] The toothed elements have a large number of teeth and thus multiple tooth contacts with the internal teeth of the ring gear. Due to manufacturing inaccuracies, it is not possible to accurately predict which tooth contact of the toothed element will transmit a force and which will not. Each of these forces forms a force vector. All of these force vectors of a toothed element converge at the instantaneous center of rotation.

[0012] If, according to the state of the art, the instantaneous pole of the tooth element is not located on the wave generator symmetry line, the force vector, ie the contact normal of each tooth, has a different intersection point with the wave generator symmetry line, ie depending on the manufacturing inaccuracy, different force vectors are in function.

[0013] In any case, all of the teeth of the toothed element are never in a force-transmitting state to the same extent. This results in the intersection of the lines of force with the wave generator's symmetry line constantly changing slightly. This also causes the gear ratio to constantly change. It is also possible that the toothed element tends to rotate around an impossible instantaneous center. This creates a constant noise, and the operating behavior of the actuator gear becomes jerky.

[0014] In conventional spur gears, the gear ratio is determined by the ratio of the number of teeth. Another method for determining the gear ratio is based on the distances between the instantaneous poles. This requires that all instantaneous poles involved be aligned, as is the case with spur gears.

[0015] For actuators of the type described here, the design and layout of the tooth contours and gear ratio can also be based on the tooth count ratio. This design has the disadvantages described above in the case of manufacturing inaccuracies.

[0016] The wave generator in actuators of the type described here consists of an arrangement of rotationally symmetrical rolling bearings. For this reason, the wave generator's symmetry line is a particularly advantageous choice. There is the instantaneous pole between the toothed element and the ring gear, the instantaneous pole between the toothed element and the drive gear, the instantaneous pole between the wave generator and the drive gear, the instantaneous pole between the ring gear and the drive gear, and the instantaneous pole between the rolling bearing on the wave generator and the wave generator. These instantaneous poles are all located on the wave generator's symmetry line, which is particularly advantageous.

[0017] The ratio of the actuating gear is then determined by the distances between the instantaneous poles located on the wave generator symmetry line.

[0018] If the instantaneous pole between the toothed element and the drive gear is fixed, the instantaneous pole between the toothed element and the ring gear must also lie on the rotating wave generator's symmetry line. This is inevitable if all other instantaneous poles (i.e., of the wave generator) already lie on the wave generator's symmetry line.

[0019] In this way, an actuating gear is created with independent tooth elements, which are indirectly connected to each other by the geometric-constructive wave generator symmetry line and the transmission ratio i of the actuating gear.

[0020] In contrast, in actuators according to DE 10 2020 002 965 A1 and EP 3 779 239 B1, all tooth elements are connected to one another by elastic spring regions, so that the tooth elements form an elastic spur gear. These elastically connected tooth elements also have instantaneous poles. However, the positions of these instantaneous poles cannot be easily determined by design. Instead, the instantaneous poles result from the condition that all tooth elements are connected to one another by elastic spring regions and that all tooth elements are always the same distance from one another.

[0021] In contrast, according to the independent patent claim 3, during operation of the adjusting gear, an angle spanned in the reference plane between the two toothed element symmetry lines, whose vertex lies on the eccentric axis, constantly changes. This angle can, in particular, be approximately one degree. Known adjusting gears always assume that the circumferential distance between the toothed elements remains constant. This is the basis for the calculation of known adjusting gears.

[0022] In the actuators mentioned in DE 10 2020 002 965 A1 and EP 3 779 239 B1, the inner contour of the toothed element, which is in contact with the driver body, results solely from the fact that it is an elastic spur gear. This is due to the requirement that all toothed elements must always be the same distance from each other. Otherwise, the spring areas between the toothed elements would bend elastically to different degrees.

[0023] If the tooth elements are interdependent, this inevitably results in instantaneous poles that are not located on the wave generator's symmetry line. This results in noise caused by a changing instantaneous pole in the event of manufacturing inaccuracies.

[0024] But the mere fact that the instantaneous poles are not located on the wave generator's symmetry line means that the gear ratio does not match the instantaneous pole ratio. This leads to the gear elements not rotating in a defined manner around their corresponding instantaneous poles during operation of the actuator gear. In other words, the gear elements don't "know" which instantaneous pole they should rotate around, or they can't rotate around the instantaneous pole they "want" to rotate around. The result is jerky and noisy gear operation.

[0025] To ensure smooth gear operation, it is necessary that all instantaneous poles of the actuator always lie on a common position line. Only in this way does the gear ratio remain constant throughout one revolution of the wave generator. Designing the actuator based solely on the tooth count ratio leads to poorly operating gears. While the wave generator symmetry line is not the only possible position line for the instantaneous poles of the actuator, it is an advantageous position line because it creates an actuator that runs equally or similarly in both opposite directions of rotation.

[0026] If the envelope contour of the wave generator is not represented by an ellipse, but by two offset circular paths, then the instantaneous pole between the wave generator and the tooth element lies on the wave generator symmetry line.

[0027] The actuator gear according to the invention is a coaxial gear, meaning the input shaft and the output element rotate around the same central gear axis. This means that the input and output shafts have the same instantaneous pole. This requirement results in the wave generator symmetry line being the necessary position line for the instantaneous poles of the actuator gear.

[0028] The instantaneous pole between the toothed element and the drive gear can then be a fixed point on the wave generator's symmetry line, making the instantaneous pole path a circular path around the actuator's central axis. However, the instantaneous pole path can also be another contour intersected by the wave generator's symmetry line.

[0029] The benchmark for the design of the actuating gear is the inner contour of the toothed element on which the driver body is supported. In this respect, claim 7 relates to a method for determining the inner contour of the toothed element of the actuating gear according to a combination of claims 5 and 2.

[0030] If the inner contour is determined in this way (drawn or calculated), then not only does the instantaneous center of the toothed element relative to the ring gear lie on the wave generator's symmetry line, but the instantaneous center of the toothed element opposite the drive gear also lies on the wave generator's symmetry line. No further measures are required for this. Only the correct gear ratio must be maintained.

[0031] The method according to the invention also makes it possible to produce an inner contour for a toothed element which is in contact with a driver body, so that the instantaneous poles of the toothed element always lie on a wave generator symmetry line rotating around the gear central axis, wherein the toothed element is mirror-symmetrical so that opposite directions of rotation can be realized.

[0032] In principle, a solvable differential equation can be formulated to determine the inner contour, which has a unique result. This means that only a single solution results from the requirements described.

[0033] The internal toothing of the ring gear can only consist of a large number of identical teeth, whereas the shape of the tooth flanks of each tooth element is different for each tooth. These different tooth shapes of the tooth element result from the different distances of the teeth from the instantaneous pole of the tooth element relative to the ring gear.

[0034] The shape of the tooth flanks of the internal gearing of the ring gear can, for example, be described by a radius. This results in identical tooth flanks with the same curvature and a fixed center of curvature. If a connecting line is then drawn between the instantaneous center of the tooth element relative to the ring gear and a center of curvature of the tooth flank of a tooth of the internal gearing of the ring gear, the shape of the tooth flank of a tooth of the external gearing of the tooth element is determined when the wave generator is rotating. The prerequisite for this is that all parts move within the desired gear ratio, so that the intersection points of the connecting line with the shape of the tooth flank of the tooth of the ring gear lie on the desired shape of the tooth flank of the tooth element.

[0035] The shape of the tooth flanks of the internal toothing of the ring gear can also be described by a shape with changing centers of curvature, such as the well-known involute shape.

[0036] It is important that the relationship between the instantaneous pole distances on the wave generator symmetry line must always remain constant and that these instantaneous pole distances determine the gear ratio.

[0037] Further advantageous developments and embodiments emerge from the subclaims and from this description.

[0038] The invention is explained in more detail using an embodiment shown in the drawings.

[0039] They show: Fig. 1 a view of a first embodiment of an actuating gear in the direction of a gear central axis, wherein the actuating gear has a wave generator and tooth elements with inner contours; Fig. 2 a detail of Fig. 1, wherein the wave generator is rotated by an angle relative to the Fig. 1 is further rotated; Fig. 3 shows a flow chart of a method for determining geometries of the actuating gear and in particular the inner contour of one of the tooth elements according to Fig. 1; Fig. 4 as a single part a toothed element of the actuating gear of Fig. 1; Fig. 5 a second embodiment of an actuating gear in a view analogous to the view Fig. 1; Fig. 6 a third embodiment of an actuating gear in a view analogous to the view of Fig. 1; and Fig. 7 schematically shows one of the tooth elements from Fig. 1 and corresponding straight lines for determining the inner contour of the tooth element.

[0040] Fig. 1 shows an actuating gear 2 in a view in the direction of a gear central axis A A, which is perpendicular to the plane of the sheet, which is also referred to as the reference plane. The actuator 2 comprises: - a concentric to the gearbox central axis A A arranged, essentially rigid ring gear 6 with an internal toothing 8; - a wave generator 10 with two eccentric axes A B , A C , the intersect the reference plane at points B and C, which is offset parallel to the transmission central axis A A are arranged and during operation of the actuating gear 2 around the gear central axis A A circulate; - five tooth elements 14, 16, 18, 20, 22 and - a drive wheel 24.

[0041] The ring gear 6 is rotatably mounted in or on the drive gear 24 by means of a bearing (not shown in detail). The drive gear 24 is, for example, disc-shaped. To save weight, however, the drive gear 24 can also have recesses, contrary to the illustration. Bolt-shaped drive bodies 26 are firmly inserted into the drive gear 24 and are offset parallel to the transmission's central axis A. A arranged and distributed circumferentially uniformly around the same. One end of the bolt-shaped driver bodies 26 is pressed or screwed into the driver wheel 24. In addition, the bolt-shaped driver bodies 26 can also be fastened with their other end to another part of the driver wheel 24 or at least supported on it in the circumferential direction. This other part of the driver wheel 24 would then lie above the plane of the drawing of Fig. 1. The drive elements 26 protrude through openings 28 of the toothed elements 14, 16, 18, 20, 22. The openings 28 are delimited by an inner contour 30 of the toothed elements 14, 16, 18, 20, 22. The openings 28 are larger than the drive elements 26 such that the toothed elements 14, 16, 18, 20, 22 are movable to a limited extent in both the radial and circumferential directions relative to the drive wheel 24. The toothed elements 14, 16, 18, 20, 22 thus have both a circumferential functional distance 27 and a radial functional distance 29 relative to the drive wheel 24 or the drive elements 26. The radial functional distance 27 is provided so that the respective toothed element can move relative to the driver body, as is necessary for the function of the actuating gear 2. Therefore, the radial functional distance 27 is approximately one tooth height of the internal toothing 8 or of an external toothing 32, which will be explained below.This allows the external toothing 32 to engage the internal toothing 8 and then disengage from the meshing. In alternative designs, however, the radial functional distance can also be greater than the tooth height. The functional distance can even be a multiple of the tooth height.

[0042] To limit their mobility, the carrier bodies 26 can be supported circumferentially and radially on the inner contour 30. Furthermore, the toothed elements 14, 16, 18, 20, 22 are fixed, depending on the angle of rotation, by the ring gear 6 on the one hand and the wave generator 10 on the other.

[0043] The tooth elements 14, 16, 18, 20, 22 and their inner contour 30 are each mirror-symmetrical to a corresponding tooth element symmetry plane, which intersects the reference plane in a tooth element symmetry line 31. This mirror symmetry is required so that the actuating gear 2 can operate equally smoothly in the two opposite directions of rotation.

[0044] The toothed elements 14, 16, 18, 20, 22 are identically designed. The toothed elements 14, 16, 18, 20, 22 are arranged radially between the ring gear 6 and the wave generator 10, which is rotatably mounted in the drive gear 24. The toothed elements 14, 16, 18, 20, 22 are held on the drive gear 24 for limited movement in the manner explained above. To this extent, the toothed elements 14, 16, 18, 20, 22 are distributed evenly around the circumference of the drive gear 24 only to the extent that their mobility relative to the drive bodies 26 allows. The tooth elements 14, 16, 18, 20, 22 each have external teeth 32, which can engage with the internal teeth 8 of the ring gear 6 to varying depths depending on the radial position of the tooth element 14, 16, 18, 20, or 22. In order to radially shift the position of the tooth elements 14, 16, 18, 20, 22, the tooth elements 14, 16, 18, 20, 22 bear against a running surface 36 of the wave generator 10.For this purpose, the tooth elements 14, 16, 18, 20, 22 have two abutments 34 which project radially inwards, wherein at least one of the two abutments 34 of the respective tooth element is in contact with the running surface 36.

[0045] The wave generator 10 has two rolling bearings 38, 40 which are arranged in the direction of the transmission central axis A A one behind the other. The first rolling bearing 38 has the eccentric axis A C as the central axis, whereas the second rolling bearing 40 has the parallel offset eccentric axis A B as its central axis. The rolling bearings 38, 40 are parallel to the transmission central axis A A offset so that the transmission central axis A A centrally between the eccentric axes A B , A C or the same distance to the two eccentric axes A B , A CThe rolling bearings 38, 40 have circular inner parts 42 connected to one another in a rotationally fixed manner, which form the input or drive shaft of the actuating gear 2. During operation of the actuating gear 2, rolling elements 44 rotate on these circular inner parts 42. These rolling elements are inserted into outer rings 45, 46 of the rolling bearings 38, 40 and are held at a distance from one another by a bearing cage. The outer rings 45, 46 together form the running surface 36 for the toothed elements 14, 16, 18, 20, 22. In this respect, the bearings 34 extend parallel to the central axis A of the gear. A over a length which is greater than a width of each of the two rolling bearings 38, 40, which are identically designed, wherein this width of the rolling bearing 38 or 40 in the direction of the respective associated eccentric axis A B or A CPreferably, the length of the raceway 36 is almost equal to the width of the two combined rolling bearings. Some tooth elements 18, 20 bear against one outer ring 45, whereas other tooth elements 14, 16, 22 bear against the other outer ring 46.

[0046] In a radially inner area of ​​the driving wheel 24, bolt-shaped guide bodies 48 are inserted, which are parallel to the transmission central axis A A are aligned. Each of the toothed elements 14, 16, 18, 20, 22 is assigned two of the guide bodies 48. The two guide bodies 48 assigned to a toothed element serve to align the respective toothed element in a radial direction or to guide it into a necessary central position between the two guide bodies 48 when the external toothing 32 of the toothed element in question is no longer in engagement with the internal toothing 8. In this case, the toothed element is located as a result of a force of a further below Fig. 4 explained compression spring 72 simultaneously on both outer rings 44, 46 of the wave generator. In Fig. In Figure 1, none of the toothed elements 14, 16, 18, 20, 22 is shown in its central position. However, the guide bodies 48 can be omitted without replacement in this and all alternative embodiments of the actuating gear 2.

[0047] Since the outer toothing 32 of the toothed element in question is not in engagement with the inner toothing 8 of the ring gear 6 in the central position, no power is transmitted via the toothed element in question. Instead, power is transmitted via other toothed elements, namely the toothed elements that are circumferentially closer to a wave generator symmetry plane 54, which will be explained below.

[0048] The wave generator 10 has the wave generator symmetry plane 54, in which the transmission central axis A A and the two eccentric axes A B , A CThis wave generator symmetry plane 54 rotates around the central gear axis A during operation of the actuating gear 2 A . In a Fig. 1 graphically illustrated vertical rotation angle position of the wave generator symmetry plane 54, the same intersects the reference plane in a wave generator symmetry line 55, which in this respect in Fig. 1 is congruent with a vertical reference line 56.

[0049] When the input shaft of the wave generator 10 rotates once around the central axis A of the gear during operation of the actuating gear 2 A rotates, then the ring gear 6 rotates by exactly two teeth of the internal toothing 8.

[0050] Fig. 2 shows the actuator 2 from Fig. 1, wherein the wave generator symmetry line 55 is tilted clockwise by an angle of rotation α relative to the reference line 56. In this respect, the inner parts 42 of the input shaft of the wave generator 10 are Fig. 1 around the transmission central axis AA further rotated at the angle of rotation α. ​​For the sake of clarity, two tooth elements 16, 14 are shown with almost the same circumferential distance from the vertical reference line 56. The tooth element 16 located to the left of the reference line 56 is hereinafter referred to as the left-hand tooth element 16, and the tooth element 14 located to the right of the reference line 56 is hereinafter referred to as the right-hand tooth element 14. "Right-hand" means clockwise, and "left-hand" means counterclockwise.

[0051] Circumferentially between the two tooth elements 16, 14, there is a point E in the reference plane, which lies on the wave generator symmetry line 55 and is congruent with an instantaneous pole M E is, around which the two tooth elements 16, 14 pivot relative to the ring gear 6 at the moment in question.

[0052] The external toothings of the tooth elements 16, 14 each have a plurality of teeth and thus also a plurality of tooth contacts with the internal toothing 8 of the ring gear 6. In the present embodiment, each tooth element has seven teeth and thus up to seven tooth contacts. However, these tooth contacts—more precisely, the internal toothing 8 and the external toothings—have unavoidable manufacturing inaccuracies, which is why tolerances are incorporated in the design. Due to these manufacturing inaccuracies, it is not possible to precisely predict how much force each individual tooth contact transmits at any given moment.

[0053] The tooth flanks 58, 60 of the external toothing 32 and the internal toothing 8 are matched to one another in such a way that the common instantaneous pole M E the tooth elements 16, 14 always remains on the wave generator symmetry line 55 when the eccentric axes A B , A Cduring operation of the actuating gear 2 around the gear central axis A A rotate and the tooth elements 16, 14 transmit a force to operate the actuating gear 2.

[0054] At the seven tooth contacts K 1.1 ...K 1.7 of the right-hand tooth element 14 and the six tooth contacts K 2.1 ...K 2.6 of the left-hand tooth element 15, contact normals N1 and N2 are drawn, which are perpendicular to tangents (not shown in the drawing) that are on the curved tooth flanks of the tooth contacts K 1.1 ...K 1.7 , K 2.1 ...K 2.6 All of these contact normals N1, N2 meet at the instantaneous pole M E . On the left-hand tooth element 16, only six instead of seven contact normals are shown because there is no longer any contact on the circumferentially outermost tooth of the external toothing 32.

[0055] Even if individual or groups of teeth do not transmit forces due to manufacturing inaccuracies, the force-transmitting teeth always act on the instantaneous pole M E .

[0056] The transmission central axis A A is by definition an instantaneous pole M A of the ring gear 6, the drive gear 24 and the wave generator 10, since the wave generator 10 in the drive gear 24 around the transmission central axis A A is rotatably mounted.

[0057] The left-hand tooth element 16 rests with its inner contour 30 on the left side against its associated driver body 26, whereas the right-hand tooth element 16 rests with its inner contour 30 on the right side against its associated driver body 26. These tooth elements 16, 14 are supported with their inner contours at linear contact points X1, X2 on driver bodies 26, so that tangential planes can be formed at the contact points X1, X2, on which contact normals can be set up perpendicularly in the reference plane, which are referred to below as straight lines N3, N4. These straight lines N3, N4 intersect at a point D, which lies on the wave generator symmetry line 55 and has an instantaneous pole M D between the respective tooth element and the associated driver body.

[0058] This instantaneous pole M DThis does not arise by chance because it is the intersection point of the wave generator symmetry line 55 with the straight lines N3 and N4, respectively, but because the inner contours 30 of the tooth elements 14, 16, 18, 20, 22 have a correspondingly shaped geometry, which can be calculated or - as is the case here - determined graphically.

[0059] The calculation or graphic creation of the inner contour 30 is described below with reference to a summary of Fig. 2, Fig. 3 and Fig. 7 is initially explained in overview and then in detail. Fig. 7 is not drawn to scale, but exaggerated to illustrate the very small angles of rotation α, α', α''. Moreover, the inner contour 30 is not yet fixed during the determination process. However, for the sake of clarity, Fig. 7 already shows the finished inner contour, the finished tooth element and the corresponding external toothing, although these geometries of the tooth element are not yet fixed at this point in time.

[0060] In simple terms, in the method for determining the inner contour 30 of the toothed element 14 of the actuating gear 2, the shape of the inner contour 30 is determined via its contact points X2, X2', X2'' with the associated driver body 26 by the wave generator symmetry line 55 being mathematically or graphically rotated incrementally by an angle of rotation α, α' α''. In this case, for each of the angles of rotation α, α' α'', a straight line N3 is determined, which - runs in the reference plane, - the second instantaneous pole M D cuts, - intersects a center of curvature or a center point 92 of the driver body 26, and - intersects the respective contact point X2, X2', X2'', whereby each of the contact points X2, X2', X2'' is assigned to only one of the rotation angles α, α' α''.

[0061] Both in the graphical and mathematical creation of the inner contour 30, i.e. the wave generator symmetry line 55 increment by increment around the gearbox central axis A A rotated relative to the reference line 56, so that the gear elements of the adjusting gear 2 assume a sequence of different positions. The sum of the combined rotation angles α + α' + α'' + ... becomes increasingly larger. Therefore, both in the graphical and mathematical creation of the inner contour 30, the wave generator symmetry line 55 is rotated incrementally around the gear central axis A. A rotated relative to the reference line 56, so that the gear elements of the actuating gear 2 assume a sequence of different positions.

[0062] The instantaneous pole of the considered tooth element 16 with the wave generator 10 is the intersection point of the eccentric axis A B with the reference plane (sheet plane). The instantaneous center M D of the considered tooth element 16 with the driving wheel 24 is point D.

[0063] To be precise, when calculating or drawing the inner contour 30 in a Fig. 3, the first method step 78 starts from the point D defined on the wave generator symmetry line 55. The defined point D lies on an instantaneous pole path 66 ( Fig. 3), which is a circle around the point A or the transmission central axis A AIn a second method step 80, starting from point D, the straight line N3 is drawn, passing through the center 92 of the driver body 26, which has a circular cross-section. If the cross-section is not circular, a center of curvature of the driver body would have to be selected to determine the straight line N3.

[0064] The intersection point of the straight line N3 with the surface of the driver body 26 forms the first contact point X2 and is thus also congruent with a part of the inner contour 30 to be created. In the next process step 80, the wave generator symmetry line 55 with its point B is rotated further by a small angle of rotation α - for example 0.1° -, for example clockwise. The next contact point X2' ( Fig. 7) of the inner contour 30 is created in a subsequent process step 82. In this process step 82, in order to determine the next contact point X2' along the inner contour 30, the question is asked mathematically or graphically by which angle δ the first contact point X2 must be rotated about the point D so that the point B assumes the position of a point B' that was created by the rotation of the wave generator symmetry line 55 at the angle of rotation α' about the point A. The absolute value of the angle of rotation α' is equal to the angle of rotation α. ​​The angle δ is thus the angle at which the toothed element 16 rotates about the point D. The angle of rotation α and the angle δ thus represent the relative movement of the gear components of the actuating gear 2. From this rotation at the angle δ around the point D, the next contact point X2' results from the contact point X2 rotated further at the angle δ.In a subsequent process step 84, the instantaneous pole D is further rotated on the circular instantaneous pole path 66 at the angle of rotation α'.

[0065] Subsequently, after a branch 86, method steps 78 to 84 are carried out again to determine the next contact point X2'' or the next point on the inner contour. However, method step 78 now begins with the instantaneous pole D' rotated further around point A at the angle of rotation α'. These method steps 78 to 84 are repeated until the wave generator symmetry line 55 has passed through a rotation angle of, for example, approximately 50°. The inner contour 30, which is composed of the contact points X2, X2', X2'', ..., is then uniquely determined. Intermediate points are interpolated between these contact points for a continuous inner contour line. The remainder of the inner contour 30 is to be mirrored symmetrically accordingly. In further alternatives, rotation angles smaller than or greater than 0.1° are used for each repetition of the method steps.In particular, in a computer-implemented method, very small rotation angles α can be used for each loop iteration.

[0066] The determination of the inner contour 30 described above already ensures that points D and E lie on the wave generator's symmetry line 55. The geometry of the tooth pairing of the ring gear and tooth elements can then be determined. For this purpose, the internal toothing of the ring gear can be specified appropriately, for example, as involute or circular toothing. The appropriate counter-contour of the tooth flanks of the external toothing of the tooth elements is then determined using CAD software.

[0067] As already explained, the following central question arises for the creation of the next contact point X2', X2'', ... of the inner contour 30: Into which position must the tooth element 16 in question rotate about the point D so that the point B, with the position of the point D and the wave generator symmetry line 55 unchanged, again assumes the point B' of the wave generator symmetry line 55 which is then further rotated at the angle of rotation α'.

[0068] The said angles of rotation α and δ correspond to the distances between the points A, B and D. The answer to the above question is therefore also given by the ratio of the absolute distances AB and BD, i.e. the ratio of the absolute distance between the points A and B and the absolute distance between the points B and D.

[0069] The virtual "stopping" of point D and the wave generator symmetry line 55 results in a very small error, which is very small because the selected increment is very small and can therefore be neglected. At the beginning of the process for determining the inner contour, the tooth element 16 in question consists only of the point at the first contact point X2. As the sequence progresses, more and more points are created, which then form the inner contour 30 of the tooth element 16.

[0070] The correct tooth count ratio has already been explained in previously published patent applications by the same applicant, which is why reference is made to these applications, which are also cited in this present application. The number of carrier bodies and the number of teeth of the internal gearing on the ring gear are important for the tooth count ratio.

[0071] Since the instantaneous pole M Ealways lies on the wave generator symmetry line 55, the transmission ratio i of the actuating gear 2 also remains the same. In practice, this means that the ring gear 6 also rotates very uniformly at a very uniform input speed of the input shaft.

[0072] For the following calculation of the gear ratio i of the actuator 2, the aforementioned points D, E, A, and B are considered. The gear ratio i of the actuator 2 is determined by the following formula: i=AE¯ED¯⋅BD¯AB¯

[0073] Here, AE is the absolute distance between points A and E. ED is the absolute distance between points E and D. BD is the absolute distance between points B and D. AB is the absolute distance between points A and B.

[0074] This formula is only valid if all four points A, B, D, E or the instantaneous poles M A , M B , M Dand M E lie on the wave generator symmetry line.

[0075] The calculation of the gear ratio i according to the above formula must be possible using an integer number of teeth.

[0076] Knowing the formula i=AE¯ED¯⋅BD¯AB¯ The geometry of the tooth pairing can be determined. A straight line is drawn from point E to the center of curvature of the respective ring gear tooth. At the intersection of this straight line with the ring gear tooth, a first contact point Y is created. The wave generator is then rotated at an angle of rotation α and the ring gear at an angle i × α. For each angle of rotation α, a further contact point Y', Y'', ... is created, which is stationary with the tooth element. As a result, the further contact points Y', Y'', ... are created, each of which is stationary with the tooth element 16. The contact points Y, Y', ... thus form the tooth contour of the tooth element 16 with the teeth of the internal toothing 8 located near the tooth element.

[0077] Fig. 4 shows a tooth element as a single part with its inner contour 30 and the compression spring 72. The geometry of the inner contour 30 is the same for all tooth elements.

[0078] The teeth of the external toothing 32 are symmetrical to the tooth element symmetry line 31. The number of teeth in the tooth element is odd, so that there is a central tooth and outer teeth. Only the central tooth, the tip of which lies on the tooth element symmetry line 31, has tooth flanks on both sides of the tooth element symmetry line 31 that are identical or mirror-symmetrical to one another. For each of the outer teeth, the left-hand tooth flank has a different contour than the right-hand tooth flank of the outer tooth in question. This means that the two tooth flanks of each outer tooth are not mirror-symmetrical. However, the left-hand outer teeth are mirror-symmetrical to the right-hand outer teeth with respect to the tooth element symmetry line. Of course, an even number of teeth per tooth element is also possible, in which case the teeth are also symmetrical to the tooth element symmetry line.

[0079] Each of the toothed elements 14 or 16 or 18 or 20 or 22 has a blind hole 70 in which a compression spring 72 is accommodated. The compression spring 72 ensures that the external toothing 32 of the toothed element is safely disengaged from the internal toothing 8. If a driver body symmetry plane 74 (see Fig. 1) of a considered tooth element is located in an angular range of 40° to 60° relative to the wave generator symmetry plane 54 or wave generator symmetry line 55, no significant forces act on the tooth element of the considered driver body 26. In this angular range of 40° to 60°, the compression spring relaxes at least partially. Due to the preload force of the compression spring, the tooth element is moved in the direction of the transmission's central axis A. A displaced because the driver body 26 is pressed against the radially outermost area of ​​the inner contour 30.

[0080] The operation of actuator 2 is explained below: Tooth elements 14 or 16 or 18 or 20 or 22 only transmit torque during operation when the teeth of the respective tooth element are in tooth contact with the internal gearing. However, the tooth element only has such torque-transmitting tooth contact over a limited force transmission angle. This force transmission angle can be, for example, 50°. However, the force transmission angle can also be somewhat larger or smaller than 50°. For example, a first leg of this force transmission angle can be between 5° and 15°, whereas the second leg of this force transmission angle is between 35° and 60°, with the said 5° being seen starting from the wave generator symmetry plane 55, which is shown in Fig. 1 is shown in the twelve o'clock or 0° position, with the affected tooth element 14 also being shown in this 0° position. This means that the affected tooth element 14 transmits in the 0° position of Fig. 1, there is no torque yet. Torque transmission occurs, for example, at approximately 5° at the earliest and at 15° at the latest.

[0081] One of the toothed elements 14, 16, 18, 20, 22 begins to transmit force or torque at the tooth contacts from the drive gear 24 to the ring gear 6 as soon as the wave generator symmetry plane 54 is at a rotation angle of 10° from the associated drive body 26. The end of the power transmission is reached when the wave generator symmetry line 55 has exceeded a rotation angle of 50° from the drive body 26. The start of the power transmission does not need to be at a rotation angle of exactly 10°, but can be in a range of 5° - 15°. The end of the power transmission does not need to be at a rotation angle of exactly 50°, but can be in a range of 40° - 60°. Outside of this force-transmitting rotation angle range of 5° to 60°, there is no power transmission and no clearly defined instantaneous poles M E , M D of the respective tooth element under consideration.

[0082] Since the aforementioned actuating gear 2 has five toothed elements 14, 16, 18, 20, 22 evenly distributed around the circumference, at least one of these five toothed elements 14, 16, 18, 20, 22 can always transmit force to the internal toothing 8 of the ring gear 6 via its tooth flanks. This one toothed element is also referred to below as the main force-transmitting toothed element. The main force-transmitting toothed element switches to one of the opposing toothed elements each time the input shaft is rotated by 36°.

[0083] However, a different number of tooth elements can also be provided. The number of tooth elements does not have to be odd, but can also be even.

[0084] Fig. 5 shows a second embodiment of an actuating gear 102, which is analogous to Fig. 1 and Fig. 2, but has twice the number of toothed elements. Unless components are discussed in more detail, these components are identical to the first exemplary embodiment. In the second exemplary embodiment, the wave generator 110 is not directly mounted in the drive gear 124. Instead, the drive shaft 90 is a separate component from the wave generator 110. The drive shaft 110 is mounted in the drive gear 124. The drive shaft 110 is connected to an inner part 142 of the wave generator 110 via a shaft-hub connection in a torque-transmitting manner. The shaft-hub connection compensates for an axial offset between the drive shaft 90 and the inner part 142 during operation of the actuating gear 102. The shaft-hub connection enables the inner body to be displaced relative to the drive shaft 90 in the direction of a wave generator plane of symmetry 154 or a wave generator line of symmetry 155.

[0085] For this purpose, the inner part 142 has a double-edged recess into which a double-edged pin of the drive shaft is inserted. Lateral flattened areas of the double-edged recess and the double-edged pin extend parallel to the wave generator's plane of symmetry 154. Due to the relatively high number of tooth elements compared to the first exemplary embodiment and the even number of tooth elements, there are always two diametrically opposed tooth elements that are in a main force-transmitting state. Due to the special design of the shaft-hub connection, which allows mobility of the inner body 142 relative to the drive shaft 90 exclusively in the direction of the wave generator's plane of symmetry 154, the position of the wave generator 110 can always be compensated in such a way that equal forces always act on the two main force-transmitting tooth elements.

[0086] Fig. Figure 6 shows a third embodiment of an actuating gear 202, which, analogous to the first embodiment, has five toothed elements 214, 216, 218, 220, 222. Unless components are described in detail, these components are identical to the first embodiment.

[0087] Compared to the first embodiment, a different wave generator 210 is provided. Instead of multiple rolling bearings, the wave generator 210 has a single rolling bearing 238 with a running surface 236 composed of two circular arcs and is therefore oval. This oval shape is found in an outer ring 245 with the running surface 236, a hardened inner ring 291, and an inner part 242. The rolling elements 242 are arranged between the outer ring 245 and the inner ring 291. During operation of the actuating gear 202, the outer ring 245 is elastically deformed, for which purpose the outer ring 245 is relatively thin, in particular thinner than a diameter of the rolling elements 242. Instead of a bearing cage, the rolling elements 242 are held together by the outer ring 245. The two circular arcs have centers that are located on eccentric axes A B , A C lay.

[0088] In the reference plane, the tooth element symmetry lines 31 form two legs that span an angle β. The eccentric axis A B forms the apex of this angle β. The tooth elements 214, 216, 218, 220, 222 have both a circumferential functional distance 227 and a radial functional distance 229 with respect to the driver bodies and thus with respect to the driver wheel 24. As a result, the angle β changes constantly during operation of the actuating gear 202. This relationship also applies to the actuating gears 2, 102 according to the first and second embodiments. However, the relationship was only shown graphically for the third embodiment, in order to illustrate in particular the Fig. 1 and Fig. 2 not to overload the drawings.

[0089] The elastically deformable relatively thin outer ring 245 of the wave generator 210 according to Fig. 6 can also be used with a wave generator according to Fig. 1 or Fig. 5. In this case, such an elastically deformable outer ring is radially between - the axially and parallel offset circular rolling bearings on the one hand and - the tooth elements on the other hand.

[0090] In alternative embodiments, the toothed elements can be elastically supported against one another. Guide pins can be omitted in these and other alternative embodiments.

[0091] The individual features of the embodiments can also be combined with each other in any way.

[0092] If the driver body 26 is arranged in a movement-proof manner on the driver wheel 24 as shown in the drawing, it can be a component manufactured separately from the associated tooth element 14, 16, 18, 20, 22.

[0093] Alternatively, all actuators can also be configured with a kinematic reversal of the driver body and inner contour. In this case, the driver body would be located on the toothed element, and the inner contour would be located on the driver wheel. The driver body would then be fixed to the toothed elements and have limited movement relative to the driver wheel. In this case, the driver bodies or even the toothed element itself could engage in recesses in the driver wheel and have contact points with an inner contour of the driver wheel.

[0094] If the driver body 26 is arranged on the toothed element in a movement-proof manner, it can be a component manufactured separately from the toothed element or can be formed in one piece with the toothed element.

[0095] In alternative embodiments, the number of teeth of the tooth element is even, so that there is no circumferentially central tooth.

[0096] In an alternative embodiment, at least one spring element extends circumferentially. The spring element can be designed as a spring ring similar to the spring ring known from DE 10 2020 002 965 A1. The spring ring can also be designed as a single piece with the toothed elements, as is known from EP 3 779 239 B1. This spring ring known from EP 3 779 239 B1 consists of a plurality of webs, each of which is arranged circumferentially between two toothed elements and is thereby integral with the toothed elements. These webs can have at least one wave. Due to the waviness of the webs, they are relatively soft, which facilitates the mobility of the toothed elements in relation to one another. As an alternative to being arranged as a single piece with the toothed elements, a plurality of individual spring elements can also be provided, each of which is arranged between two toothed elements. In this respect, the spring elements or the spring element can be one-piece or segmented.However, one or more spring elements do not necessarily have to be present.

[0097] The openings for receiving the driver bodies in the tooth elements can also be arranged radially far outwards on the tooth elements so that the tooth elements are open radially on the outside, as is known from WO 2016 / 165684 A2. In this case, no material of the respective tooth element is provided between the associated driver body and the internal toothing of the ring gear. Alternatively, the openings for receiving the driver bodies in the tooth elements can also be arranged radially far inwards on the tooth elements so that the tooth elements are open radially on the inside. In this case, no material of the respective tooth element is provided between the associated driver body and the wave generator.

[0098] Regardless of whether the opening is arranged radially outwards or radially inwards, the respective opening is then arranged circumferentially centrally on the associated tooth element.

[0099] The carrier bodies can also have a cross-section that is not round. In particular, the cross-section can be flattened where the carrier body does not come into contact with the toothed element. However, with the appropriate inner contour of the toothed element, the carrier body can also have other shapes, for example, a square.

[0100] Instead of the circular instantaneous pole path 66, another instantaneous pole path can be chosen for determining the inner contour, such as the one from Fig. 2 visible straight line 67.

[0101] The blind holes and in particular the compression springs in the tooth elements can be omitted without replacement in all embodiments. List of reference symbols 2 actuator gears 6 ring gear 8 Internal gearing 10, 210 wave generator 14 tooth element 16 tooth element 18 tooth element 20 tooth element 22 tooth element 24 Drive wheel 26 driver bodies 27 circumferential functional distance 28 openings 29 radial functional distance 30 inner contour 31 Tooth element symmetry line 32 external gearing 34 systems 36 tread 38, 40, 230 rolling bearings 42 interior parts 44 rolling elements 45, 46 outer rings 48 guide bodies 54 wave generator symmetry plane 55 wave generator symmetry line 56 Reference line 66 Instantaneous pole orbit 67 straight 70 blind hole 72 compression spring 74 Driver body symmetry plane 76 radially outermost area of ​​the inner contour 78, 80, 82, 84, 88 Procedural steps 86 branching 90 drive shaft 92 Center / Center of curvature 102 Actuator 110 wave generator 124 Drive wheel 154 wave generator symmetry plane 155 wave generator symmetry line 202 Actuator 214 to 222 tooth elements 227 circumferential functional distance 229 radial functional distance 238 rolling bearings 236 tread 242 Inside 244 rolling elements 245 outer ring 291 inner ring A A Transmission central axis A B , A C Eccentric axes M A , M B M E , M D Instantaneous poles A, B, E, D points X1, X2 contact points N1, N2 contact standards N3, N4 straights F1, F2 centroids S1, S2 limb

Claims

[1] Actuating gear (2), comprising: - a concentric to a transmission central axis (A A ) arranged substantially rigid ring gear (6) with an internal toothing (8); - a wave generator (10) with an eccentric axis (A B ), which is offset parallel to the transmission central axis (A A ) orbits around it; - toothed elements (14, 16, 18, 20, 22), each - are arranged radially between the ring gear (6) and the wave generator (10), - have an external toothing (32) which engages with the internal toothing (8), and - have a bearing (34) which bears against a running surface (36) of the wave generator (10); and - a driving wheel (24), opposite which the toothed elements (14, 16, 18, 20, 22) - limited mobility and - can be supported circumferentially, whereby the transmission central axis (A A) and the eccentric axis (A↓B) span a wave generator symmetry plane (54) which is perpendicular to the transmission central axis (A A ) lying reference plane in a wave generator symmetry line (55), characterized by , that Tooth flanks of the internal toothing (8) and the external toothing (32) fit together in such a way that two instantaneous poles (M E , M D ) of the tooth elements (16, 14), which transmit force during operation of the actuating gear (2), always remain on the wave generator symmetry line (55). [2] Actuating gear according to claim 1, characterized by , that - the first of the instantaneous poles (M E ) of the tooth element (16 or 14) the instantaneous pole (M E ) of the toothed element (16 or 14) relative to the ring gear (6) and that - the second of the instantaneous poles (M D ) of the tooth element (16 or 14) the instantaneous pole (M D) of the toothed element (16 or 14) relative to the driving wheel (24). [3] Actuating gear according to the preamble of claim 1, characterized by , during operation of the actuating gear (202) an angle (β) constantly changes, which angle is spanned in the reference plane between the two tooth element symmetry lines (31), the apex of which lies on the eccentric axis (A B ) lies. [4] Actuating gear according to one of claims 1 to 3, characterized by that the wave generator (10) has two eccentric axes (A B , A C ) which, with respect to the transmission central axis (A A ) are diametrically opposed to each other and are the same distance from the gearbox central axis (A A ) have. [5] Actuating gear according to one of the preceding claims, characterized by that the driving wheel (24) has driving bodies (26) which are connected to it in a movement-proof manner and which extend in a direction parallel to the central transmission axis (A A) extend within openings (28) of the tooth elements (14, 16, 18, 20, 22), such that the openings (28) are delimited by inner contours (30) which have a radial functional distance (29) from the respective driver body (26). [6] Actuating gear according to claim 2, characterized by that the external toothing (32) has at least three teeth, two of which are arranged as circumferentially outer teeth on both sides of a tooth element symmetry plane (31) and mirror-symmetrically to one another, wherein each of the two outer teeth has two tooth flanks facing away from one another, which have a different shape and are shaped such that contact normals (N1 and N2) at tooth contacts of the outer teeth with the internal toothing (8) in the first instantaneous pole (M E ) cut. [7] Method for determining the inner contour (30) of the toothed element (14) of the actuating gear (2) of a combination of claims 5 and 2, characterized bythat the shape of the inner contour (30) is determined via its contact points (X2, X2', X2'') with the associated driver body (26) by the wave generator symmetry line (55) being rotated mathematically or graphically incrementally by an angle (α, α' α'') and in the process a straight line N3 is determined for each of the angles (α, α' α''), which - runs in the reference plane, - the second instantaneous pole (M D ) cuts, - intersects a center of curvature, in particular a center point (92) of the driver body (26), and - intersects the respective contact point (X2, X2', X2''), whereby each of the contact points (X2, X2', X2'') is assigned to only one of the angles (α, α' α'').

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