Voltage wave gears in pot or hat design

Abstract

Stress wave gear in pot or hat design with a. a circular spline (1) whose circular spline toothing (2) has a number of teeth Cz of 100 < Cz < 104, in particular Cz = 102 teeth, b. a flexspline (3) whose flexspline toothing (4) has a number of teeth Fz of Fz = Cz-2 and a pitch circle diameter TDFS and engages in the circular spline toothing (2) at two opposite points and whose wall (5) in its basic form is circular in cross-section and has a flexspline inner diameter IDFS, and with c. a shaft generator (6) having a radially flexible rolling bearing (7) by means of which an oval shaft generator insert (8) is rotatably mounted, characterized in that d. for the pitch circle diameter TDFS: 34.4 mm < TDFS < 35.4 mm, in particular 34.9 mm, and / or that for the flex spline inner diameter IDFS: 33.4 mm < IDFS < 34.4 mm, in particular IDFS = 33.9 mm, and that e. for the axial length LFS of the wall (5) of the flexspline (3) the following applies: LFS < IDFS / 2.05, in particular LFS < IDFS / 2.16 or LFS < IDFS / 3.35, and that i. the oval shape of the wave generator insert (8) in polar coordinates (φ, R(φ)) satisfies the following conditions: - For all φ ∈ {kπ | k ∈ ℤ}, Hmin < | R(φ) | < Hmax, where Hmin = 12.830 mm and Hmax = 12.838 mm, and - For all φ ∈ {π / 4 + kπ / 2 | k ∈ ℤ}, the following holds: | R(φ) | > c, where c = 12.549 mm, and - For all φ ∈ {π / 2 + k·π | k ∈ ℤ}, the following holds: | R(φ) | < d, where d = 12.22 mm, and / or ii. that the radially flexible rolling bearing (7) has a cross-sectional height Sh in the direction φ=0 and a cross-sectional height Sn in the direction φ=π / 2 and that the oval shape of the radially flexible rolling bearing (7) in polar coordinates (φ, R(φ)) satisfies the following conditions: - For all φ ∈ {kπ | k ∈ ℤ}, Hmin + Sh < | R(φ) | < Hmax + Sh, where Hmin = 12.830 mm and Hmax = 12.838 mm, and - For all φ ∈ {π / 4 + kπ / 2 | k E ℤ}, | R(φ) | > c+(Sh+Sn) / 3, in particular | R(φ) | > c+(Sh+Sn) / 2.6 or | R(φ) | > c+(Sh+Sn) / 2.3, where c = 12.549 mm, and - For all φ ∈ {π / 2 + k·π | k ∈ ℤ}, the following holds: | R(φ) | < d+Sn, where d = 12.22 mm.

Description

[0001] The invention relates to a tension wave transmission in a pot or hat design with a. a circular spline whose circular spline toothing has a number of teeth Cz of 100 < Cz < 104, in particular Cz = 102 teeth, b. a flexspline whose flexspline toothing has a number of teeth Fz of Fz = Cz-2 and a pitch circle diameter TDFS and engages in the circular spline toothing at two opposite points and whose wall in its basic form is circular in cross-section and has a flexspline inner diameter IDFS, and with c. a shaft generator which has a radially flexible rolling bearing by means of which an oval shaft generator insert is rotatably mounted.

[0002] A wave gear, also called a wave gear, typically has a rigid, ring-shaped, internally toothed gear called the circular spline, and a flexible, externally toothed gear located inside the rigid internally toothed gear, called the flex spline. The circular spline and the flex spline have a different number of teeth. When not installed, the flex spline wall has a circular cross-section and, in the area where the wave generator is mounted, an inner diameter of IDFS. Within the flex spline, in the area of ​​the external teeth, is the oval, and usually elliptical, wave generator, which has a wave generator insert mounted on a radially flexible rolling bearing for rotation.The wave generator deforms the flexspline into an oval shape, thus engaging the external teeth of the flexspline with the internal teeth of the circularspline at each end of the wave generator's vertical axis. At the other axial end of the flexspline's wall, a cup-shaped base and a cap-shaped rim are arranged. A shaft, such as an output shaft, is often fixed to the cup base or rim in a rotationally fixed manner. In the region of the wave generator's vertical axis, the flexspline is pushed radially outward, while along the low axis, the opposing wall sections approach each other. The flexspline's wall tapers conically from the end with the external teeth toward the cup base or rim. This effect is known as "coning."

[0003] Tension shaft gearboxes are high-precision reduction gearboxes that, due to their design, operate without backlash, enable large gear ratios in a compact form, and are used in numerous technical applications. The achievable service life is the primary factor determining the operating limits of these gearboxes. In contrast to conventional gear drives, where tooth flank strength is typically the determining factor for service life, the service life of tension shaft gearboxes is primarily determined by the cyclic elastic stress on the thin-walled flexspline and by the fatigue of the shaft generator bearing. These components are subjected to high load cycles with every revolution and therefore represent the weak points in the overall system.

[0004] To describe load-bearing capacity, parameters such as rated torque and rated speed have become established in practice. However, these are not fixed physical quantities, but rather values ​​derived from assumptions about a desired nominal service life. For example, a tension shaft gearbox with a specific rated torque and a defined rated speed can complete a total number of revolutions corresponding to a nominal service life of several thousand operating hours. If the desired service life is set higher, this inevitably results in a lower rated torque, and vice versa.

[0005] Since different manufacturers, and even different product lines from the same manufacturer, use different specifications for nominal service life and rated speed, the rated torque is largely arbitrary. While some manufacturers use a nominal service life of L10 = 6,000 hours, others use L10 = 10,000 hours or different rated speeds. This means that gearboxes of the same size can have very different rated torques depending on the manufacturer or product line, even though the gearboxes are not technically very different. In practice, the rated torque specifications are therefore often determined more by marketing considerations than by technical differences.

[0006] Against this background, there is a particular interest in providing stress wave gearboxes that actually have a particularly long service life, regardless of the nominal conditions applied.

[0007] It is therefore the object of the present invention to provide a tension wave gear which has a particularly long service life.

[0008] The problem is solved by a stress wave transmission of the type mentioned above, which is characterized by the fact that d. for the pitch circle diameter TDFS: 34.4 mm < TDFS < 35.4 mm, in particular 34.9 mm, and / or that for the flex spline inner diameter IDFS: 33.4 mm < IDFS < 34.4 mm, in particular IDFS = 33.9 mm, and that e. for the axial length LFS of the wall (5) of the flexspline (3) the following applies: LFS < IDFS / 2.05, in particular LFS < IDFS / 2.16 or LFS < IDFS / 3.35, and that i. the oval shape of the wave generator insert (8) in polar coordinates (φ, R(φ)) satisfies the following conditions: - For all φ ∈ {kπ | k ∈ ℤ}, Hmin < | R(φ) | < Hmax, where Hmin = 12.830 mm and Hmax = 12.838 mm, and - For all φ ∈ {π / 4 + kπ / 2 | k ∈ ℤ}, the following holds: | R(φ) | > c, where c = 12.549 mm, and - For all φ ∈ {π / 2 + k·π | k ∈ ℤ}, the following holds: | R(φ) | < d, where d = 12.22 mm, and / or ii. that the radially flexible rolling bearing (7) has a cross-sectional height Sh in the direction φ=0 and a cross-sectional height Sn in the direction φ=π / 2 and that the oval shape of the radially flexible rolling bearing (7) in polar coordinates (φ, R(cp)) satisfies the following conditions: - For all φ ∈ {kπ | k ∈ ℤ}, Hmin + Sh < | R(φ) | < Hmax + Sh, where Hmin = 12.830 mm and Hmax = 12.838 mm, and - For all φ ∈ {π / 4 + kπ / 2 | k ∈ ℤ}, | R(φ) | > c+(Sh+Sn) / 3, in particular | R(φ) | > c+(Sh+Sn) / 2.6 or | R(φ) | > c+(Sh+Sn) / 2.3, where c = 12.549 mm, and - For all φ ∈ {π / 2 + k·π | k ∈ ℤ}, the following holds: | R(φ) | < d+Sn, where d = 12.22 mm.

[0009] It has been shown, quite surprisingly, that the stress wave drive according to the invention exhibits a particularly long service life, which is up to 30% longer than that of conventional stress wave drives of the same radial size. A particular advantage arises especially from the combination of the short axial design of the flex spline with the special shape of the shaft generator insert. It has been shown that this combination contributes significantly to achieving a very uniform and controlled cyclic deformation of the flex spline, despite its short axial length. In particular, local stress peaks are avoided or at least reduced, which contributes considerably to the exceptionally long service life.In addition to extending service life, the short axial design is also very advantageous in terms of space utilization, as it allows for the realization of compact gearboxes that are particularly suitable for installation in space-critical applications.

[0010] Insofar as the present application refers to the pitch circle diameter TDFS, this refers to the pitch circle diameter of the flexspline gearing in the circular basic form of the flexspline, i.e., in the unloaded state before installation in the stress wave gear. The value TDFS thus denotes a design property of the flexspline and is independent of the elastic deformation caused by the shaft generator in the installed state.

[0011] The characteristic that the flexspline wall has a circular cross-section in its basic form and a flexspline inner diameter IDFS means that the flexspline, in its unloaded state before installation in the stress wave gear, possesses a circular inner contour. The flexspline inner diameter IDFS refers to the diameter of this inner contour in the aforementioned circular basic form. In designs where the inner contour is not cylindrical, the flexspline inner diameter IDFS refers to the inner diameter in a plane perpendicular to the axial direction, in which the external teeth of the flexspline are also arranged. This clarifies that the flexspline inner diameter IDFS is a design-related component property that is independent of the elastic deformation caused by the shaft generator in the installed state.

[0012] Features i and ii mentioned in claim 1 can advantageously be realized simultaneously. However, according to the invention, it is also possible for the built-in radially flexible rolling bearing to have the shape defined in feature ii of claim 1 if the shaft generator insert is designed differently, in particular larger or smaller, than the shaft generator insert defined in feature i of claim 1. Likewise, it is possible for the shaft generator insert to be designed according to feature i of claim 1, while the built-in radially flexible rolling bearing has a shape other than that defined in feature ii of claim 1.

[0013] In a particularly advantageous embodiment, the following applies to the circumference UW of the oval contour of the shaft generator insert: UWmin < UW < UWmax, where UWmin = 78.72 mm and UWmax = 78.92 mm. Alternatively or additionally, the following applies advantageously to the circumference UR of the radially flexible rolling bearing: URmin < UR < URmax, where URmin = 106.38 mm and URmax = 106.58 mm. It has been found that, of the shaft generator insert shapes and radially flexible rolling bearing shapes defined in claim 1, those embodiments whose contour has a circumference within the aforementioned narrow range are particularly advantageous with regard to a long service life. In these shaft generator inserts, the deformation of the flexspline is particularly uniform, thereby further avoiding local stress peaks.At the same time, an optimal number of teeth in engagement is achieved, resulting in a more even load distribution and reducing both wear on the teeth and fatigue stress on the flexspline.

[0014] In an advantageous embodiment, the cross-sectional height Sh of the radially flexible rolling bearing in the direction of φ = 0 and the cross-sectional height Sn in the direction of φ = π / 2 are matched such that Sh ≤ Sn ≤ Sh / 0.95. It has been shown that this ratio of cross-sectional heights leads to a particularly uniform elastic deformation of the rolling bearing, which avoids local stress and pressure peaks. For this purpose, Sn is preferably slightly larger than Sh due to a bearing clearance present in the direction of φ = π / 2 and in the direction of φ = π³ / 2. Preferably, the radially flexible rolling bearing has no bearing clearance in the direction of φ = 0 and φ = π.

[0015] If the stress wave gear is designed as a hat gear, the following preferably applies to the axial length LFS of the wall of the flexspline: LFS < IDFS / 2.05, especially LFS < IDFS / 2.16.

[0016] If the stress wave gear is designed as a pot gear, the following preferably applies to the axial length LFS of the wall of the flexspline: LFS < IDFS / 3.35.

[0017] In an advantageous embodiment, the axial length of the flexspline wall is in the range of 8.9 mm to 9.3 mm, or 9.1 mm, particularly if the flexspline is cup-shaped. Alternatively, the axial length of the flexspline wall can be in the range of 14.7 mm to 15.1 mm, or 14.9 mm, particularly if the flexspline is hat-shaped. It has been shown that these specific dimensional ranges are particularly advantageous depending on the design of the flexspline. Adherence to these dimensional ranges ensures, on the one hand, sufficient and largely uniform deformation during operation, and on the other hand, stable and uniform force transmission via the splines.

[0018] Insofar as the axial length of the wall of the flexspline is mentioned, this refers to the axial distance that extends from the end face of the end of the flexspline where the external teeth are located, to the plane perpendicular to the axial direction in which the inside of the cup bottom or the outside of the rim of the flexspline facing the external teeth is located.

[0019] In an advantageous embodiment, the low-axis length E = 2R(π / 2) lies in the range of 95.0% to 95.2% of the high-axis length D = 2R(0) or is 95.1% of the high-axis length D = 2R(0). Alternatively or additionally, it can be advantageously provided that the low-axis length E = 2R(π / 2) lies in the range of 69.8% to 70.0% of the pitch circle diameter TDFS or is 69.9% of the pitch circle diameter TDFS. It has been shown that these geometric relationships result in a particularly favorable design of the oval shape of the shaft generator insert with regard to the service life of the stress wave gear.

[0020] In an advantageous embodiment, the oval shape of the shaft generator insert exhibits a deflection d = R(0) - R(π / 2), where: 0.61 mm < d < 0.65 mm. Such a deflection is particularly advantageous because it achieves a very favorable compromise between reliable tooth engagement and moderate deformation of the flexspline, tolerable over many load cycles, in the tension shaft drive according to the invention. This significantly extends both the service life of the flexspline and that of the entire tension shaft drive.

[0021] In an advantageous embodiment, the tension wave gear has at least one of the following features: a. the numerical value of the deflection d lies in the range of 2.3% to 2.5% of the vertical axis length D = 2R(0) or is 2.4% of the vertical axis length D = 2R(0), b. the numerical value of the deflection d lies in the range of 2.5% to 2.7% of the low-axis length E = 2R(π / 2) or is 2.6% of the low-axis length E = 2R(π / 2), c. the numerical value of the deflection d is in the range of 1.7% to 1.9% of the pitch circle diameter TDFS or is 1.8% of the pitch circle diameter TDFS, d. the module of the flexspline toothing (4) is in the range of 55.5% to 55.7% of the deflection or is 55.6% of the deflection.

[0022] It has been shown that by adhering to at least one of these specific relations, preferably all of these specific relations, between the deflection, the main dimensions of the shaft generator insert and the module of the gearing, a particularly advantageous tuning of the gear geometry is achieved with regard to improving the service life of the stress shaft drive.

[0023] In a particularly advantageous embodiment, the radially flexible rolling bearing has a cross-sectional height Sh in the direction φ=0 of 4.0 mm to 4.8 mm, 4.2 mm to 4.6 mm, or 4.4 mm. The cross-sectional height is defined as the radial distance between the surfaces of the bearing rings of the radially flexible rolling bearing facing away from the rolling elements, i.e., the inner and outer rings.

[0024] It has been shown that the cross-sectional height has a significant influence on the service life of the stress wave drive according to the invention, with the aforementioned range representing an advantageous compromise between elasticity and load-bearing capacity. If the cross-sectional height is above this range, the radial stiffness of the bearing increases, thereby reducing the elastic compliance required for the function of the stress wave drive. Conversely, if the cross-sectional height is below this range, the load-bearing capacity of the bearing decreases, which can lead to premature fatigue and a significantly shortened service life of the bearing.

[0025] In an advantageous embodiment, the rolling elements of the radially flexible rolling bearing, particularly balls, have a rolling element diameter in the range of 3.0 mm to 3.4 mm, 3.1 mm to 3.3 mm, or 3.2 mm. Maintaining this diameter range achieves an advantageous compromise between the number of load-bearing rolling elements and their individual load-bearing capacity. With smaller rolling elements, the number of load-bearing elements would increase, but the load-bearing capacity of each individual rolling element would decrease, potentially leading to higher contact pressures and accelerated fatigue. With larger rolling elements, the number of load-bearing elements is excessively reduced, distributing the load over too few rolling elements and potentially resulting in localized overloads.Adhering to the aforementioned narrow diameter range thus achieves an optimal compromise between the number of load-bearing rolling elements and their individual load-bearing capacity. This not only contributes to a significantly increased service life of the bearing itself, but also improves the service life of the entire tension shaft drive.

[0026] In an advantageous embodiment, the teeth of the circular spline gearing have a profile angle in the range of 22.0 degrees to 30.0 degrees, or in the range of 24.0 degrees to 28.0 degrees, or 26.7 degrees, and / or the teeth of the flex spline gearing have a profile angle in the range of 24.0 degrees to 32.0 degrees, or in the range of 26.0 degrees to 30.0 degrees, or 28.1 degrees. The profile angle is the angle of the tooth flank relative to the plane of the tooth center on the reference profile. The reference profile is a universally valid, module-independent reference profile used to define a gear tooth. It corresponds to a gear with an infinite number of teeth, which increases the pitch circle diameter to infinity, resulting in a rack as the reference geometry. Adherence to the aforementioned narrow angular ranges of the profile angle ensures an optimal compromise between load-bearing capacity, sliding coefficient, and surface pressure.

[0027] It is particularly advantageous if the difference between the profile angle of the circular spline gearing and the profile angle of the flex spline gearing lies in the range of -2.0 degrees to +2.0 degrees, especially in the range of -1.5 degrees to +1.5 degrees. This ensures that the profile angles of the circular spline and flex spline gearing are optimally matched, resulting in a very uniform load distribution across the meshing teeth. This reduces tooth flank pressure and stabilizes the contact conditions, significantly extending the service life of the gearing.

[0028] A particularly advantageous feature is a transmission device comprising a tension wave transmission according to the invention and an output bearing by means of which an output shaft connected to the flex spline is rotatably mounted relative to the circular spline or relative to a transmission base rigidly connected to the circular spline, in particular a transmission chassis or a transmission housing. Mounting the output shaft relative to the circular spline or to a transmission base connected to it is particularly advantageous because this results in a highly rigid overall structure.

[0029] The output bearing can advantageously be designed as a multi-row rolling bearing, a crossed roller bearing, or a wire rod bearing. These specific bearing designs have proven particularly beneficial for reliably absorbing the forces generated by the stress wave drive. A multi-row rolling bearing offers high load-carrying capacity while maintaining a compact design, making it especially suitable for applications with high radial and axial loads. A crossed roller bearing, with its rollers arranged at a 90° angle, allows for the simultaneous absorption of radial and axial forces as well as tilting moments, ensuring highly precise and rigid guidance of the output shaft. A wire rod bearing, in turn, is characterized by its very low weight and space-saving design, which is particularly advantageous in applications with limited installation space.Using one of these bearing designs significantly increases the operational reliability and service life of the gearbox.

[0030] A particularly advantageous actuator comprises a drive motor and a tension wave drive according to the invention, or the aforementioned transmission device according to the invention, wherein the tension wave drive is connected downstream of the drive motor. A significant advantage is that the long service life of the tension wave drive according to the invention directly benefits the entire actuator, enabling it to operate reliably even under continuous operation and high load fluctuations. Furthermore, the tension wave drive allows for a very compact actuator design and thus space-saving integration into systems with limited installation space. The actuator is advantageously suited, for example, for precise motion control, which is particularly beneficial in robotics, automation technology, automotive engineering, and medical technology applications.

[0031] A robot joint is particularly advantageous if it incorporates a tension wave drive and / or a gear unit and / or an actuator according to the invention. The tension wave drive enables the realization of compact, high-precision, and especially durable robot joints. A particular advantage is that the compact design of the tension wave drive allows the robot joints to be made especially slim and space-saving.

[0032] A robot is particularly advantageous if it incorporates a tension wave drive and / or a gear unit and / or an actuator according to the invention. The long service life of the tension wave drive contributes to the robot's reliable continuous operation, even in high-cycle and high-stress applications. Furthermore, the compact design of the tension wave drive enables space-saving robot arm construction, thereby reducing weight and inertia and allowing for faster and more precise movements. This makes the robot particularly suitable for applications in industrial automation, medical technology, and sensitive fields where maximum reliability and accuracy are required.

[0033] A vehicle component comprising a tension wave drive and / or a transmission device and / or an actuator according to the invention is particularly advantageous. The use of the tension wave drive enables a particularly compact, high-precision, and durable design of vehicle components, especially in the chassis and steering systems. A particular advantage is that the long service life and robustness of the tension wave drive are ensured even under the typically harsh operating conditions found in vehicle applications, such as alternating loads, vibrations, and temperature fluctuations. Furthermore, the compact design saves installation space and weight, facilitating integration into modern, space-constrained vehicle architectures.

[0034] An exoskeleton is particularly advantageous if it incorporates a tension wave drive and / or a transmission device and / or an actuator according to the invention. A particular advantage is that the tension wave drives according to the invention, due to their long service life and robustness, operate reliably even under the high load cycles and continuous loads that typically occur when using an exoskeleton. At the same time, the compact design of the tension wave drive according to the invention allows for a slim construction, which reduces the weight of the exoskeleton and improves the wearer's freedom of movement.

[0035] A seat drive comprising a tension wave drive and / or a transmission device and / or an actuator according to the invention is particularly advantageous. Modern seat drives, for example in vehicles or agricultural machinery, not only serve to adjust the seat position and tilt, but can also be integrated into active vibration or shock compensation systems. In this case, the seat drive is controlled in a targeted manner to actively compensate for vibrations and shocks that occur when driving over uneven terrain. The tension wave drive according to the invention results in an exceptionally long service life for the seat drive. It has been shown that, especially in seat drives where many small adjustment movements with frequent load changes occur, the features according to the invention lead to a significant reduction in wear on the flex spline, gearing, and bearings.Furthermore, the compact design of the tension wave drive according to the invention allows for discreet and space-saving integration into the seat. This provides a space-saving and durable solution for a seat drive.

[0036] The invention is shown in the drawing in an exemplary and schematic manner and is described below with reference to the figures, whereby identical or similarly functioning elements are usually provided with the same reference numerals even in different embodiments. The figures show: Fig. 1 a schematic top view of a first embodiment of a tension wave gear according to the invention in a pot design, wherein the plane of the drawing is arranged perpendicular to the central axis of the tension wave gear, Fig. 2 a schematic cross-sectional representation of the first embodiment of the tension wave drive according to the invention, wherein the central axis of the tension wave drive is arranged in the plane of the drawing, Fig. 3 a schematic cross-sectional representation of the flexspline of the first embodiment in its basic form before installation in the stress wave gear, Fig. 4 a schematic cross-sectional representation of the second embodiment of the tension wave drive according to the invention, wherein the central axis of the tension wave drive is arranged in the plane of the drawing, Fig. 5 a schematic cross-sectional representation of the flexspline of the second embodiment, Fig. 6 a schematic cross-sectional representation of the oval shape of the wave generator insert, Fig. 7 a schematic representation of the polar coordinate system used, Fig. 8 an illustration regarding the profile angle.

[0037] The Fig. Figure 1 shows a schematic top view of a first embodiment of a tension wave gear according to the invention in a pot design, wherein the plane of the drawing is arranged perpendicular to the central axis 9 of the tension wave gear.

[0038] The stress wave gear includes a circular spline 1, whose circular spline toothing 2 is designed as internal teeth and has a number of teeth of 100 < Cz < 104, which does not exactly match the number of teeth in the schematic drawing.

[0039] The tension wave gear also includes a flexspline 3, whose externally designed flexspline toothing 4 has a number of teeth of Fz = Cz - 2 (which does not exactly match the number of teeth in the schematic drawing) and a pitch circle diameter TDFS (in Fig. 3 shown) and engages in the circular spline toothing 2 at two opposite points.

[0040] The stress wave drive also includes a shaft generator 6, which has a radially flexible rolling bearing 7 by means of which an oval shaft generator insert 8 is rotatably mounted within the flexspline 3. The shaft generator insert 8 is formed by an oval disk and has a bearing seat on its outer circumference for an inner ring 10 of the radially flexible rolling bearing 7. The outer ring 11 of the radially flexible rolling bearing 7 is in direct contact with the flexspline 3 when installed. The radially flexible rolling bearing 7 has rolling bearing balls 12 arranged between the inner ring 10 and the outer ring 11.

[0041] The oval shape of the wave generator insert 8 is entirely schematic and greatly exaggerated in Fig. Figure 6 is shown. Alternatively or additionally, the radially flexible rolling bearing 7 can have the outer contour defined in claim 1.

[0042] The wave generator insert 8 has a vertical axis length D and a low axis length E.

[0043] The radially flexible rolling bearing 7 exhibits (with reference to the one in Fig. 7 described polar coordinate system) in the direction φ=0 a cross-sectional height Sh and in the direction φ=π / 2 a cross-sectional height Sn.

[0044] As the Fig. 2 and Fig. As shown in Figure 3, the flexspline 3 has a cup base 13. A flange 14, for example for coupling a shaft, is arranged on the cup base 13 of the flexspline 3. In the Fig. Figure 2 shows the rotational position of the shaft generator insert 8, in which the vertical axis length D lies in the plane of the drawing and the (not shown) low axis length E runs perpendicular to the plane of the drawing. In the region of the vertical axis, the flexspline 3 is pushed radially outwards, so that the circular spline teeth 2 and the flexspline teeth 4 are engaged at two opposite points in the plane of the vertical axis, while the opposing wall sections of the low axis are brought closer together, causing the circular spline teeth 2 and the flexspline teeth 4 to be disengaged in the plane of the low axis.

[0045] The Fig. Figure 3 shows a schematic cross-sectional view of the flexspline 3 of the first embodiment in its basic form before installation in the tension wave gear. The wall 5 of the flexspline 3, in its basic form before installation in the tension wave gear, has a circular cross-section and a flexspline inner diameter IDFS. The flexspline inner diameter IDFS denotes the diameter of the circular inner contour of the flexspline 3 in the aforementioned circular basic form.

[0046] The wall 5 of the flexspline 3 has an axial length LFS. In the case of a cup gear, the axial length LFS of the wall 5 of the flexspline 3 refers to the axial distance extending from the plane 16 of the end face of the end of the flexspline 3, where the external toothing 4 is located, to the plane 17 perpendicular to the axial direction, in which the inner surface 18 of the cup base 13 of the flexspline 3 is located.

[0047] The Fig. Figure 4 shows a schematic cross-sectional representation of a second embodiment of a tension wave drive according to the invention in a hat design, wherein the central axis 9 of the tension wave drive is arranged in the plane of the drawing.

[0048] The stress wave gear includes a circular spline 1, whose circular spline toothing 2 is designed as internal toothing and has a number of teeth of 100 < Cz < 104.

[0049] The tension wave gear also includes a flexspline 3, whose flexspline toothing 4, designed as external teeth, has a number of teeth of Fz = Cz - 2 and a pitch circle diameter TDFS (in Fig. 5 shown) and engages in the circular spline toothing 2 at two opposite points.

[0050] The stress wave drive also includes a shaft generator 6, which has a radially flexible rolling bearing 7 by means of which an oval shaft generator insert 8 is rotatably mounted within the flexspline 3. The shaft generator insert 8 is formed by an oval disk and has a bearing seat on its outer circumference for an inner ring 10 of the radially flexible rolling bearing 7. The outer ring 11 of the radially flexible rolling bearing 7 is in direct contact with the flexspline 3 when installed. The radially flexible rolling bearing 7 has rolling bearing balls 12 arranged between the inner ring 10 and the outer ring 11.

[0051] The oval shape of the wave generator insert 8 is entirely schematic and greatly exaggerated in Fig. Figure 6 is shown. Alternatively or additionally, the radially flexible rolling bearing 7 can have the outer contour defined in claim 1.

[0052] The wave generator insert 8 has a vertical axis length D and a low axis length E.

[0053] The radially flexible rolling bearing 7 exhibits (with reference to the one in Fig. 7 described polar coordinate system) in the direction φ=0 a cross-sectional height Sh and in the direction φ=π / 2 a cross-sectional height Sn.

[0054] As the Fig. 4 and Fig. As shown in Figure 5, the flexspline 3 has a flange 15. A flange 14, for example for coupling a shaft, is arranged on the flange 15 of the flexspline 3. In the Fig. Figure 4 shows the rotational position of the shaft generator insert 8, in which the vertical axis length D lies in the plane of the drawing and the (not shown) low axis length E runs perpendicular to the plane of the drawing. In the region of the vertical axis, the flexspline 3 is pushed radially outwards, so that the circular spline teeth 2 and the flexspline teeth 4 are engaged at two opposite points in the plane of the vertical axis, while the opposing wall sections of the low axis are brought closer together, causing the circular spline teeth 2 and the flexspline teeth 4 to be disengaged in the plane of the low axis.

[0055] The Fig. Figure 5 shows a schematic cross-sectional view of the flexspline 3 of the second embodiment in its basic form before installation in the tension wave gear. The wall 5 of the flexspline 3, in its basic form before installation in the tension wave gear, has a circular cross-section and a flexspline inner diameter IDFS. The flexspline inner diameter IDFS denotes the diameter of the circular inner contour of the flexspline 3 in the aforementioned circular basic form.

[0056] The wall 5 of the flexspline 3 has an axial length LFS. In the case of a hat gear, the axial length LFS of the wall 5 of the flexspline 3 refers to the axial distance extending from the plane 16 of the end face of the end of the flexspline 3, where the external toothing 4 is located, to the plane 17 perpendicular to the axial direction, in which the outer surface 19 of the flange 15 of the flexspline 3, facing the external toothing 4, is located.

[0057] The Fig. Figure 6 shows a schematic cross-sectional view of the oval shape of the wave generator insert 8. The oval shape of the wave generator insert 8 satisfies the following conditions in polar coordinates (φ, R(φ)): - For all φ ∈ {kπ | k ∈ ℤ}, Hmin < | R(φ) | < Hmax, where Hmin = 12.830 mm and Hmax = 12.838 mm, and - For all φ ∈ {π / 4 + kπ / 2 | k ∈ ℤ}, the following holds: | R(φ) | > c, where c = 12.549 mm, and - For all φ ∈ {π / 2 + k·π | k ∈ ℤ}, the following holds: | R(φ) | < d, where d = 12.22 mm.

[0058] Thus, the oval shape of the wave generator insert 8 deviates significantly from the shape of an ellipse.

[0059] In the present description and in the claims, a polar coordinate system (φ: R(φ)) is used to define the contour of the shaft generator insert and the contour of the radially flexible rolling bearing, as described in the Fig. Figure 7 illustrates this. Here, the angle φ denotes the azimuth angle measured in a plane perpendicular to the axis of rotation of the gearbox, and R(φ) denotes the radial distance of a point on the contour of the shaft generator insert from a coordinate origin located at the center of this plane. The coordinate origin corresponds to the intersection of the gearbox's axis of rotation with this plane. The angle φ is measured counterclockwise from a defined zero direction (φ = 0) along the vertical axis and is expressed in radians, where values ​​of φ in the formulas are expressed as multiples of π or as multiples of fractions of π, for example, π / 4 or k·π / 2. The function R(φ) thus describes the radial profile of the contour of the shaft generator insert or the contour of the radially flexible rolling bearing as a function of the angle φ.

[0060] The profile angle 27 is, as Fig.Figure 8 illustrates the angle between a tangent 24 placed at the midpoint 26 between the tip circle 20 and the root circle 21 on the tooth flank 22 of a tooth 23 and the tooth midline 25 with respect to the reference profile of the gearing. Reference symbol list: 1 Circular spline 2 Circular spline interlocking 3 Flexspline 4 Flexspline toothing 5 wall 6-wave generator 7 radially flexible rolling bearing 8 shaft generator insert 9 Central axis of the tension wave gear 10 inner ring 11 Outer ring 12 rolling bearing balls 13 Pot bottom 14 flange 15 rim Level 16 Level 17 18 Inside of the pot bottom 19 Outside of the brim 20 Head Circle 21 foot circle 22 Tooth flank 23 teeth 24 Tangent 25 Tooth midline 26 Middle 27 profile angles D vertical axis length E Low axle length Sh cross-sectional height in the direction of φ=0 Sn cross-sectional height in the direction φ=π / 2 LFS axial length of the wall of the flexspline IDFS Flexspline inner diameter TDFS pitch circle diameter of the flexspline gearing

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