Hat-shaped flexspline for a stress wave transmission

Abstract

Hat-shaped flexspline for a stress wave transmission comprising: a. a cylinder section with external teeth, b. a rim having a connecting portion, a diaphragm portion, and a first transition portion having at least one curved outer surface and connecting the connecting portion to the diaphragm portion, c. a second transition section having at least one curved outer surface and connecting the cylinder section to the rim, characterized in that d. the diaphragm section has a first diaphragm end section which is directly adjacent to the first transition section and a second diaphragm end section which is directly adjacent to the second transition section, wherein a diaphragm middle section is arranged between the first diaphragma end section and the second diaphragma end section, which middle section has a smaller axial thickness than the first diaphragma end section and / or the second diaphragma end section.

Description

The invention relates to a hat-shaped flexspline for a strain wave transmission, comprising: a. a cylinder section having an external toothing, b. a brim having a connection section, a diaphragm section and a first transition section, which has at least one curved outer surface and which connects the connection section to the diaphragm section, c. a second transition section, which has at least one curved outer surface and which connects the cylinder section to the brim.CN 218408404 U discloses a hat-shaped flexspline which has a plurality of relief grooves in the rim and in the cylinder section.U.S. Pat. No. 11 668 384 B2 discloses a strain wave transmission with a hat-shaped flexspline. In the hat-shaped flexspline, the ratio of the axial length of the cylinder portion to the radial width of the diaphragm portion is in the range of 1 to 5, and the ratio of the axial thicknesses of the radially inner end of the diaphragm portion to the axial thicknesses of the radially outer end of the diaphragm portion is in the range of 0.83 to 0.98.EP 3 550 178 B1 discloses a strain wave transmission with a hat-shaped flexspline. In the hat-shaped flexspline, the axial thickness of the radially inner end of the diaphragm portion is greater than the axial thickness of the radially outer end of the diaphragm portion. In addition, the axial thickness of the radially outer end of the diaphragm portion is greater than the axial thickness of the diaphragm portion at its center. In addition, the radial thickness of the cylinder portion is thinner than the axial thickness of the diaphragm portion at its center.It is therefore the object of the present invention to specify a hat-shaped flexspline which is particularly resilient and enables precise production.The object is achieved by a hat-shaped flexspline, which is characterized in that the diaphragm section has a first diaphragm end section which directly adjoins the first transition section and a second diaphragm end section which directly adjoins the second transition section, wherein a diaphragm central section which has a smaller axial thickness than the first diaphragm end section and / or the second diaphragm end section is arranged between the first diaphragm end section and the second diaphragm end section.The invention achieves an improved elastic deformability of the flexspline during operation. In particular, the reduced wall thickness of the diaphragm middle section enables a defined flexibility and flexibility, which leads to an advantageous stress distribution in the component and reduces stress peaks in the transition sections. At the same time, the end sections ensure structural integrity in the regions which adjoin the transition sections. This contributes to a longer lifetime of the flexspline and reduces the risk of material fatigue. The invention provides a functionally reliable and durable design of the flexspline that is simple to produce and is suitable in particular for dynamically stressed transmission applications.The connection section can advantageously be designed, for example, as a fastening flange.An embodiment is particularly advantageous in which the first diaphragm end section and / or the second diaphragm end section has outer surfaces running parallel to one another. In particular, it can advantageously be provided that the first diaphragm end section and / or the second diaphragm end section have planar outer surfaces running parallel to one another. This measure results in an accumulation of material in these sections compared to the embodiments known from the prior art. In contrast to the embodiments known from the prior art, this achieves an advantageous stress distribution in the flexspline material which is not constant along the course of the diaphragm end portions. In the regions of the material accumulations it is thus possible to absorb further stresses, in particular due to torsion, which can occur during operation of a stress wave transmission. By the design of the flexspline according to the invention and due to the described material accumulations, the stresses occurring during operation in the transition regions can be reduced in a targeted manner and absorbed by the diaphragm section.A further advantage of parallel outer surfaces of the first diaphragm end section and / or of the second diaphragm end section is that a reliable and process-safe measurement of the axial thickness is made possible. Process-safe is understood to mean that tolerances can be restricted and the desired axial thickness can be achieved more precisely. This increase in the process stability can ensure to an increased extent that the manufactured flexsplines correspond to the desired geometry within limited tolerances and, along with this, the stress distribution in the material of the flexspline takes place as desired. A precise measurement of the axial thickness is reliably possible during production because of the parallel outer surfaces, so that if necessary, the material can be worked again in a targeted manner until the desired measurement is reached.Preferably, at least the cylinder section together with its external toothing, the diaphragm section and the transition sections and at least a part of the connection section are jointly produced in one piece from the same piece of raw material. The transition sections each end at the location at which the curvature of the at least one outer surface thereof ends. If both outer surfaces have a curvature, the transition section ends in each case at the point at which the curvature extending further in the direction of the respectively adjoining section ends.In an advantageous embodiment, it is advantageously provided that the second transition section has a radial width ÜB2and an axial length UL2, and that the cylinder section has an axial length ZL, and that the diaphragm section has a radial width DB, wherein the following applies: 1.25<(ÜB2+DB) / (UL2+ZL)<3. By limiting the ratio to a range between 1.25 and 3, a balanced ratio between radial extent and axial overall length is achieved. This contributes to an improved mechanical load capacity and to a more favorable distribution of stress during operation of the strain wave transmission. Too low a ratio could result in excessive axial expansion, which would adversely affect the flexibility and durability of the flexspline. Conversely, too high a ratio could result in insufficient stiffness.Alternatively or additionally, it can advantageously be provided that the second transition section has an axial length UL2and that the cylinder section has an axial length ZLand that the external toothing has a tip circle diameter KD, wherein the following applies: 0.25<(UL2+ZL) / KD<0.7. Furthermore, alternatively or additionally, it can advantageously be provided that the second transition section has a radial width ÜB2and that the diaphragm section has a radial width DBand that the external toothing has a tip circle diameter KD, wherein the following applies: 0.1<(ÜB2+DB) / KD<0.25.These geometric boundary conditions ensure that the flexspline remains both sufficiently elastically deformable to fulfil the desired function in the strain wave gearing and is sufficiently stiff and resistant to the loads occurring during operation.An embodiment is particularly advantageous in which the diaphragm middle section has at least one convexly curved outer surface. Alternatively or additionally, it can advantageously be provided that the diaphragm middle section has at least one concavely curved outer surface. It is also possible in particular for the diaphragm middle section to have a curved profile overall. By such a shaping, the elastic deformability of the diaphragm middle section is further improved and at the same time a more uniform stress distribution is achieved. The curved outer surfaces or curved diaphragm center portion assist in the absorption and transmission of forces during operation of the strain wave gearing, which reduces local stress spikes and increases component life. Depending on the application, the respective curvature can be adapted to the prevailing load and deformation conditions. Overall, the curved configuration of the diaphragm center portion thus contributes to improved functionality, higher durability, and optimized mechanical performance of the flexspline.In an advantageous embodiment, the diaphragm middle section has outer surfaces which are mirror-symmetrical to one another with respect to a plane perpendicular to the axial center axis of the hat-shaped flexspline.This symmetrical configuration leads to uniform deformation of the diaphragm central portion under axial and radial loading, whereby asymmetrical stress distributions are avoided and undesired bending loads are reduced. The symmetry also promotes advantageous elastic behavior of the component during operation, whereby the functional reliability and precision of the strain wave gearing is improved.An embodiment of the hat-shaped flexspline is very particularly advantageous in which the diaphragm central portion extends partially outside a plane perpendicular to the axial central axis of the hat-shaped flexspline, which plane intersects the first transition portion and / or the second transition portion and / or the first diaphragm end portion and / or the second diaphragm end portion. This asymmetrical arrangement of the diaphragm middle section achieves a differentiated elastic characteristic which allows the deformation properties of the flexspline to be influenced in a targeted manner in specific regions, which allows optimized kinematics during operation.In a particular embodiment, it is provided that the diaphragm central portion has a radial width which is in the range of 0.6 times to 0.9 times the radial width of the entire diaphragm portion. This configuration of the central portion contributes to an optimum balance between flexibility and stability. As a result, a uniform stress distribution can be achieved throughout the diaphragm portion while local overloads are avoided. Overall, this feature results in improved mechanical performance, increased durability, and increased functional reliability of the flexspline.In an advantageous embodiment, the diaphragm middle section has its smallest axial thickness in the middle between the first diaphragm end section and the second diaphragm end section. This targeted thinning in the central region of the diaphragm central section leads to a particularly uniform and defined elastic deformation under operating load. The smallest wall thickness in the center produces a preferred region for elastic deformation there. At the same time, the thicker end sections adjoining on both sides ensure structural stability and have a stress concentration-reducing effect. This design results in improved durability by reducing fatigue of the material.In an advantageous embodiment, the diaphragm section has only a single thickness reduction. This advantageously leads to a clearly defined, targeted weakening of the component in a specific region, whereby a precisely controllable elastic deformation is made possible. The restriction to a single thickness reduction simplifies the component geometry and reduces the complexity of the load conditions, which facilitates both the design and the computational simulation. In addition, the simple geometry reduces the risk of unwanted stress peaks, as could occur in the case of multiple thickness changes.In particular, it can be advantageous that the diaphragm section does not have any corrugated outer surfaces. By avoiding wavy structures, a more uniform stress distribution is achieved and the risk of local material fatigue or crack initiation at wave peaks and valleys is reduced. At the same time, a uniformly running outer contour facilitates production and improves reproducibility of the component properties.In a manner according to the invention, however, it is not excluded that the diaphragm section has a plurality of thickness tapers or that the diaphragm section has at least one corrugated outer surface.In an advantageous embodiment, the first diaphragm end section has a radial width which is in the range of 0.05 to 0.2 times the radial width of the entire diaphragm section (DB). Alternatively or additionally, it can advantageously be provided that the second diaphragm end section also has a radial width in this region. This radial width of the end portions prevents excessive stiffness in the transition zones, which contributes to more uniform deformation of the entire diaphragm portion and reduces local stress spikes. At the same time, this allows precise control of the bending characteristic of the flexspline, which has a positive effect on the functional stability and service life of the component.In a very particularly advantageous embodiment, it is provided that the outer surfaces of the first transition section continuously merge into the outer surfaces of the first diaphragm end section. Such a continuous transition, i.e. without abrupt changes in the curvature or thickness, leads to a harmonic stress distribution in the region of the geometric transitions, whereby stress concentrations and associated risks for material fatigue or crack formation are effectively reduced. This not only improves the flexspline life, but also contributes to softer, uniform elastic deformation, which positively affects the performance of the strain wave transmission.Analogously, alternatively or additionally, it can advantageously be provided that the outer surfaces of the first diaphragm end section continuously merge into the outer surfaces of the diaphragm middle section. Here too, the advantage of a continuous stress and strain distribution along the diaphragm section is obtained. The smooth transition between the functional regions prevents abrupt changes in shape, which could act as weak points. This results in an overall more robust, durable and reliable component.Analogously to the same advantages, it can advantageously be provided that the outer surfaces of the second transition section continuously merge into the outer surfaces of the second diaphragm end section and / or that the outer surfaces of the second diaphragm end section continuously merge into the outer surfaces of the diaphragm middle section.The hat-shaped flexspline according to the invention is preferably made of steel. Other materials are, however, quite possible.A strain wave transmission which includes a hat-shaped flexspline according to the invention is particularly advantageous. Such a strain wave transmission has a high torque load capacity.An actuator which has a drive motor and a strain wave transmission according to the invention, which is connected downstream of the drive motor in terms of drive technology, is very particularly advantageous.A robot, in particular an industrial robot, which includes at least one tension shaft gear according to the invention or an actuator according to the invention is very particularly advantageous. In particular, the transmission according to the invention can be used in a robot joint. A very particular advantage here is that the strain wave gearing can be loaded particularly, which increases the performance of the robot.A chassis, in particular an active chassis, for a motor vehicle, which has at least one strain wave transmission according to the invention or an actuator according to the invention is very particularly advantageous. A very particular advantage here is that the strain wave gearing can be loaded particularly, which increases driving safety. A steering system, in particular a passenger car steering system or truck steering system, which has at least one transmission according to the invention is very particularly advantageous. The steering system can be, in particular, a power steering system and / or a superposition steering system.The subject matter of the invention is illustrated by way of example and schematically in the drawing and is described below with reference to the figures, wherein identical or identically acting elements are also usually provided with the same reference numerals in different exemplary embodiments. The following are shown: FIG. 1 shows a first exemplary embodiment of a hat-shaped flexspline according to the invention, FIG. 2 shows a detailed view of the first exemplary embodiment of a hat-shaped flexspline according to the invention, FIG. 3 shows a detailed view of a second exemplary embodiment of a hat-shaped flexspline according to the invention, FIG. 4 shows a detailed view of a third exemplary embodiment of a hat-shaped flexspline according to the invention, FIG. 5 shows a detailed view of a fourth exemplary embodiment of a hat-shaped flexspline according to the invention, FIG. 6 shows a detailed view of a fifth exemplary embodiment of a hat-shaped flexspline according to the invention.FIG. 1 shows a first exemplary embodiment of a hat-shaped flexspline according to the invention for a strain wave transmission. The hat-shaped flexspline has a cylinder section 1 with an external toothing 2 and a brim 3. The rim 3 has a connecting section 4, for example designed as a fastening flange. The hat-shaped flexspline is designed rotationally symmetrically with respect to its axial center axis 5, wherein only the upper half of the sectional plane is shown in each of the figures.FIG. 2 shows a detailed view of the first exemplary embodiment of a hat-shaped flexspline according to the invention. In addition to the connection section 5, the rim 3 has a diaphragm section 6 and a first transition section 7, which has at least one curved outer surface and which connects the connection section 5 to the diaphragm section 6. The hat-shaped flexspline also has a second transition section 8, which has at least one curved outer surface and which connects the cylinder section 1 to the brim 3.The diaphragm section 6 has a first diaphragm end section 9 which directly adjoins the first transition section 7 and a second diaphragm end section 10 which directly adjoins the second transition section 8, wherein a diaphragm central section 11 which has a smaller axial thickness than the first diaphragm end section 9 and the second diaphragm end section 10 is arranged between the first diaphragm end section 9 and the second diaphragm end section 10.In this embodiment, both outer surfaces of the diaphragm central portion 11 are curved.The first diaphragm end section 9 and the second diaphragm end section 10 each have planar outer surfaces running parallel to one another.FIG. 3 shows a detailed view of the second exemplary embodiment of a hat-shaped flexspline according to the invention. In addition to the connection section 5, the rim 3 has a diaphragm section 6 and a first transition section 7, which has at least one curved outer surface and which connects the connection section 5 to the diaphragm section 6. The hat-shaped flexspline also has a second transition section 8, which has at least one curved outer surface and which connects the cylinder section 1 to the brim 3.The diaphragm section 6 has a first diaphragm end section 9 which directly adjoins the first transition section 7 and a second diaphragm end section 10 which directly adjoins the second transition section 8, wherein a diaphragm central section 11 which has a smaller axial thickness than the first diaphragm end section 9 and the second diaphragm end section 10 is arranged between the first diaphragm end section 9 and the second diaphragm end section 10.In this embodiment, the outer side of the diaphragm middle section 11 facing away from the external toothing 2 is curved.The first diaphragm end section 9 and the second diaphragm end section 10 each have planar outer surfaces running parallel to one another.FIG. 4 shows a detailed view of the third exemplary embodiment of a hat-shaped flexspline according to the invention. In addition to the connection section 5, the rim 3 has a diaphragm section 6 and a first transition section 7, which has at least one curved outer surface and which connects the connection section 5 to the diaphragm section 6. The hat-shaped flexspline also has a second transition section 8, which has at least one curved outer surface and which connects the cylinder section 1 to the brim 3.The diaphragm section 6 has a first diaphragm end section 9 which directly adjoins the first transition section 7 and a second diaphragm end section 10 which directly adjoins the second transition section 8, wherein a diaphragm central section 11 which has a smaller axial thickness than the first diaphragm end section 9 and the second diaphragm end section 10 is arranged between the first diaphragm end section 9 and the second diaphragm end section 10.In this embodiment, both outer surfaces of the diaphragm center portion 11 are curved away from the external teeth 2. In this embodiment, the diaphragm central portion extends partially outside a plane 12 perpendicular to the axial central axis of the hat-shaped flexspline, intersecting the first transition portion 7 and the second transition portion 8, and the first diaphragm end portion 9 and the second diaphragm end portion 10.The first diaphragm end section 9 and the second diaphragm end section 10 each have planar outer surfaces running parallel to one another.FIG. 5 shows a detailed view of the third exemplary embodiment of a hat-shaped flexspline according to the invention. In addition to the connection section 5, the rim 3 has a diaphragm section 6 and a first transition section 7, which has at least one curved outer surface and which connects the connection section 5 to the diaphragm section 6. The hat-shaped flexspline also has a second transition section 8, which has at least one curved outer surface and which connects the cylinder section 1 to the brim 3.The diaphragm section 6 has a first diaphragm end section 9 which directly adjoins the first transition section 7 and a second diaphragm end section 10 which directly adjoins the second transition section 8, wherein a diaphragm central section 11 which has a smaller axial thickness than the first diaphragm end section 9 and the second diaphragm end section 10 is arranged between the first diaphragm end section 9 and the second diaphragm end section 10.In this embodiment, both outer surfaces of the diaphragm center portion 11 are curved toward the external teeth 2.The first diaphragm end section 9 and the second diaphragm end section 10 each have planar outer surfaces running parallel to one another.FIG. 6 shows a detailed view of a fifth exemplary embodiment of a hat-shaped flexspline according to the invention, wherein the forces occurring during operation of the tension wave transmission are schematically depicted in the form of arrows. The second diaphragm end section 10 has a kind of additional advantageous material accumulation 13 compared to the flexsplines known from the prior art.List of reference numbers:1 Cylinder section 2 external toothing 3 rim 4 connection section 5 connection section 6 diaphragm section 7 first transition section 8 second transition section 9 first diaphragm end section 10 second diaphragm end section 11 diaphragm middle section 12 plane 13 material accumulationReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedCN 218408404 U

[0002] U.S. Pat. No. 11 668 384 B2

[0003] EP 3 550 178 B1

[0004]

Claims

Hat-shaped flexspline for a strain wave transmission, comprising: a. a cylinder section having an external toothing, b. a brim having a connection section, a diaphragm section and a first transition section, which has at least one curved outer surface and which connects the connection section to the diaphragm section, c. a second transition section, which has at least one curved outer surface and which connects the cylinder section to the brim, characterized in that d. the diaphragm section has a first diaphragm end section which directly adjoins the first transition section and a second diaphragm end section which directly adjoins the second transition section, wherein a diaphragm middle section which has a smaller axial thickness is arranged between the first diaphragm end section and the second diaphragm end section, as the first diaphragm end portion and / or the second diaphragm end portion.Hat-shaped flexspline according to Claim 1, characterized in that the connection section is designed as a fastening flange.Hat-shaped flexspline according to Claim 1 or 2, characterized in that the first diaphragm end section has outer surfaces running parallel to one another.Hat-shaped flexspline according to Claim 1 or 2, characterized in that the first diaphragm end section has planar outer surfaces running parallel to one another.Hat-shaped flexspline according to one of Claims 1 to 4, characterized in that the second diaphragm end section has outer surfaces running parallel to one another.Hat-shaped flexspline according to one of Claims 1 to 5, characterized in that the second diaphragm end section has planar outer surfaces running parallel to one another.Hat-shaped flexspline according to one of Claims 1 to 6, characterized in that the second transition section has a radial width ÜB2 and an axial length UL2, and in that the cylinder section has an axial length ZL, and in that the diaphragm section has a radial width DB, where the following applies: 1.25 < (U%0020̈ B + DB) / (U%0020̈ L 2 + ZL) < 3. Hat-shaped flexspline according to one of Claims 1 to 7, characterized in that the second transition section has an axial length UL2 and in that the cylinder section has an axial length ZL and in that the external toothing has a tip diameter KD, where the following applies: 0.25 < ( U%0020̈ L 2 + ZL ) / KD < 0.

7. Hat-shaped flexspline according to one of Claims 1 to 8, characterized in that the second transition section has a radial width ÜB2 and in that the diaphragm section has a radial width DB and in that the external toothing has a tip diameter KD, where the following applies: 0.1 < ( U%0020̈ B 2 + DB ) / KD < 0.

25. Hat-shaped flexspline according to one of Claims 1 to 9, characterized in that the diaphragm central section has at least one convexly curved outer surface.Hat-shaped flexspline according to one of Claims 1 to 10, characterized in that the diaphragm central section has at least one concavely curved outer surface.Hat-shaped flexspline according to one of Claims 1 to 11, characterized in that the diaphragm central section has outer surfaces which are mirror-symmetrical to one another with respect to a plane perpendicular to the axial central axis of the hat-shaped flexspline.Hat-shaped flexspline according to one of Claims 1 to 12, characterized in that the diaphragm central section has a curved profile.Hat-shaped flexspline according to one of Claims 1 to 13, characterized in that the diaphragm central section extends partially outside a plane which is perpendicular to the axial central axis of the hat-shaped flexspline and intersects the first transition section and / or the second transition section and / or the first diaphragm end section and / or the second diaphragm end section.Hat-shaped flexspline according to one of Claims 1 to 14, characterized in that the diaphragm central section has a radial width which is in the range from 0.6 times to 0.9 times the radial width DB of the diaphragm section.Hat-shaped flexspline according to one of Claims 1 to 15, characterized in that the diaphragm central section has its smallest axial thickness in the middle between the first diaphragm end section and the second diaphragm end section.Hat-shaped flexspline according to one of Claims 1 to 16, characterized in that the diaphragm section has only a single reduction in thickness.Hat-shaped flexspline according to one of Claims 1 to 17, characterized in that the diaphragm section has no corrugated outer surfaces.Hat-shaped flexspline according to one of Claims 1 to 18, characterized in that the diaphragm section has a plurality of thickness reductions.Hat-shaped flexspline according to one of Claims 1 to 19, characterized in that the diaphragm section has at least one corrugated outer surface.Hat-shaped flexspline according to one of Claims 1 to 20, characterized in that the first diaphragm end section has a radial width which is in the range from 0.05 times to 0.2 times the radial width DB of the diaphragm section.Hat-shaped flexspline according to one of Claims 1 to 21, characterized in that the second diaphragm end section has a radial width which is in the range from 0.05 times to 0.2 times the radial width DB of the diaphragm section.Hat-shaped flexspline according to one of Claims 1 to 22, characterized in that the outer surfaces of the first transition section merge steadily into the outer surfaces of the first diaphragm end section.Hat-shaped flexspline according to one of Claims 1 to 23, characterized in that the outer surfaces of the first diaphragm end section merge steadily into the outer surfaces of the diaphragm central section.Hat-shaped flexspline according to one of Claims 1 to 24, characterized in that the outer surfaces of the second transition section merge steadily into the outer surfaces of the second diaphragm end section.Hat-shaped flexspline according to one of Claims 1 to 25, characterized in that the outer surfaces of the second diaphragm end section merge steadily into the outer surfaces of the diaphragm central section.A strain wave transmission comprising a hat-shaped flexspline according to any one of claims 1 to 26.Actuator comprising a drive motor and a power shaft transmission according to claim 27 which is drivingly connected downstream of the drive motor.Robot joint, which has at least one gear mechanism according to Claim 27 or an actuator according to Claim 28.A robot comprising at least one gear according to claim 27 or an actuator according to claim 28.Chassis, in particular active chassis for a motor vehicle, which has at least one transmission according to Claim 27 or an actuator according to Claim 28.Steering system, in particular car steering system or truck steering system, which has at least one transmission according to Claim 27 or an actuator according to Claim 28.Steering system according to Claim 32, characterized in that the steering system is a power steering system and / or a superposition steering system.

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