Strain-wave gearing, and flexible spline for a strain-wave gearing, reference profile, gearing production tool, and method for producing a flexible spline for a strain-wave gearing

Abstract

The invention relates to a strain-wave gearing (8) comprising a circular spline (4), a wave generator (6) and a flexible spline (2) having an external toothing (14) comprising teeth, wherein each tooth conforms to a reference profile (16, 20, 24, 40, 48) which is parameterized in an xy plane as a reference-profile curve according to x = b ꞏ (ɸ - a ꞏ sin (ɸ)), y = 0.5 ꞏ h ꞏ cos(ɸ), where b is a width factor, ɸ is a functional parameter, a is a shape parameter, and h is a reference-profile height, and where -π <= ɸ <= π.

Description

[0001] Our reference: H003P117PCT December 13, 2024 Applicant: Harmonic Drive SE 1 Designation: Stress wave gear, as well as flexspline for a stress wave gear, reference profile, gear manufacturing tool and method for producing a flexspline for a stress wave gear Description The invention relates to a stress wave gear with a wave generator, a circular spline and a flexspline. It also relates to a flexspline, a reference profile for external teeth of a flexspline, a gear manufacturing tool and a method for producing a flexspline. Stress wave gears have a circular spline with internal teeth and a flexible flexspline with external teeth arranged within the circular spline as well as a wave generator arranged within the flexspline for deforming the flexspline in the radial direction.By deforming the flexspline, a positive, torque-transmitting connection is created between the circular spline and the flexspline at two opposite positions on the flexspline in two areas of the circular spline. Such stress wave gears therefore comprise three main components, namely the wave generator, the flexspline and the circular spline. When the wave gear is in reduction mode, i.e. when the speed is reduced, the elliptically shaped wave generator acts as the drive element. Via a rolling bearing, in particular a thin-ring rolling bearing, the wave generator (WG) deforms the flexspline (FS), which is in mesh with the internally toothed ring gear, the circular spline (CS). When the wave generator rotates, the major axis of the ellipse shifts and with it the tooth meshing area. As the flexspline has fewer teeth, in particular two teeth fewer, than the Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE Circular Spline, during one half revolution of the Wave Generator the Flexspline rotates relative to the Circular Spline, specifically by the angle of one tooth pitch, and during one full revolution by the angle of two tooth pitches. With a stationary Circular Spline, the Flexspline rotates in the opposite direction to the rotation of the Wave Generator. The Wave Generator usually consists of an elliptical steel disk with a thin-section rolling bearing mounted on it. This component is used as a drive element in reduction mode. The Circular Spline is an internally toothed ring gear whose teeth mesh with the external teeth of the Flexspline in the area of ​​the major ellipse axis of the Wave Generator. The Circular Spline usually has two more teeth than the Flexspline. The design of the Flexspline allows for large elastic deformations in the radial direction.It is given an elliptical shape by the wave generator. In the area of ​​the major axis of the ellipse, the external toothing of the flexspline engages with the internal toothing of the circular spline. A disadvantage of external toothing of flexsplines in known stress wave gears, in particular roller tension wave gears, is that the flexspline is subjected to heavy loads. The invention is based on the object of specifying a stress wave gear with a flexspline with improved external toothing. Furthermore, a flexspline, a reference profile, a gear manufacturing tool and a method for producing a flexspline are to be specified. With regard to the stress wave gear, this object is achieved according to the invention with the features of claim 1. The stress wave gear comprises a circular spline, a wave generator and a flexspline with external toothing with teeth, Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 3 where each tooth conforms to a reference profile which is parameterised in an xy plane as a reference profile curve according to x = b ^ (ɸ - a ^ sin (ɸ)), y = 0.5 ^ h ^ cos(ɸ), where b is a width factor, ɸ is a function parameter, a is a shape parameter and h is a reference profile height, and where -π <= ɸ <= π. In the context of the application, the term “reference profile” and the specified calculation rules or formulas always refer to a division of π of the standardised reference profile. A specific reference profile for a specific stress wave drive is obtained by multiplying the standardised reference profile by a scaling factor (module).In other words, the respective tooth satisfies a reference profile which is parameterised in an xy plane as a reference profile curve, whereby the x-value of the reference profile curve of the reference profile is the difference between a functional parameter and a product of a shape parameter with the sine of the functional parameter multiplied by a width factor, and whereby the y-value of the reference profile curve of the reference profile is the product of half a reference profile height and the cosine of the functional parameter, whereby the functional parameter lies in the interval between -Pi and +Pi. Advantageous embodiments of the invention are the subject of the dependent claims. The invention is based on the consideration that in order to reduce the stress on the flexspline, the contact surface between the toothing of the flexspline and the toothing of the circular spline orof rollers in the case of a roller tension shaft gear should be increased in order to reduce the load on the tooth flank and the wave generator bearing. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 4 As has now been recognized, this can be achieved by using a specific profile or reference profile for the production of the external teeth of the flexspline, the mathematical structure of which resembles the kinematics of the tooth mesh. The specific tooth profile, particularly through the use of parameters, can thus be adapted more easily and precisely to the kinematics of the tooth mesh of a roller HD gear. The reference profile is defined and explained below in connection with FIG. 3. The value of the reference profile height is preferably between 0.8 and 1.5. The reference profile height should be as large as possible. It is limited by the permissible deformation of the flexspline.The value of the shape parameter is preferably between 0.3 and 1.2, and particularly preferably between 0.4 and 0.8. The value of the shape parameter depends on the radial deformation of the flexspline. This factor allows the profile to be adapted to different deformations. The greater the relative deformation, the greater the value of the shape parameter. The value of the width factor is preferably less than or equal to 0.5. The value of 0.5 is the upper limit of the width factor. In this case, the width of the profile corresponds exactly to one tooth pitch. If smaller values ​​are selected, the reference profile must be supplemented with straight lines on both sides to achieve the tooth pitch. Smaller values ​​result in a narrower tooth, which can reduce bending loads. The choice of the width factor improves the options for adapting the profile to available roller diameters. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 5In a preferred embodiment, the parameterized curve is replaced by a geometric shape, in particular a circular segment, in a head region of the reference profile. This avoids excessively small radii at the head of the reference profile, since excessively small radii complicate production. Large values ​​(close to 1) for the shape parameter a lead to a peak or loop at the angle ɸ = 0. These impermissible areas can be eliminated by a defined radius. In a root region of the reference profile, it is preferably extended laterally with a geometric shape, in particular straight sections. In a preferred embodiment of the stress wave drive, the teeth of the circular spline are formed by rollers inserted in pockets.With regard to the flexspline, the above-mentioned object is achieved according to the invention by a flexspline for a stress wave transmission with an external toothing with teeth, wherein the respective tooth satisfies a reference profile which is parameterized in an xy plane as a reference profile curve according to x = b ^ (ɸ - a ^ sin (ɸ)), y = 0.5 ^ h ^ cos(ɸ), where b is a width factor, ɸ is a function parameter, a is a shape parameter and h is a reference profile height, and where -π <= ɸ <=. π .In other words, the flexspline for a stress wave gear has an external toothing with teeth, whereby the respective tooth satisfies a reference profile which is parameterized in an xy plane as a reference profile curve, whereby the x-value of the reference profile curve of the reference profile is the difference between a functional parameter and a product of a shape parameter with the sine of the functional parameter multiplied by a width factor, and whereby the y-value of the reference profile curve of the reference profile is the product of half the reference profile height and the cosine of the functional parameter, whereby the functional parameter lies in the interval between -Pi and +Pi.With regard to the reference profile, the above-mentioned object is achieved according to the invention by a reference profile for an external toothing of a flexspline for a stress wave transmission, which is parameterized in an xy plane as a reference profile curve according to x = b ^ (ɸ - a ^ sin(ɸ)), y = 0.5 ^ h ^ cos(ɸ), where b is a width factor, ɸ is a function parameter, a is a shape parameter and h is a reference profile height, where -π <= ɸ <= π. With regard to the gear manufacturing tool, the above-mentioned object is achieved according to the invention by a gear manufacturing tool with a reference profile described above. The gear manufacturing tool is advantageously designed as a grinding worm, grinding wheel, hob, cutting wheel, skiving wheel, planing comb or profile roller. With regard to the method, the above-mentioned object is achieved according to the invention by using a gear manufacturing tool described above to form the external toothing of the flexspline.The advantages of the invention lie in the fact that the proposed design of the flexspline's toothing, using a special reference profile, enables a torque increase of the corresponding gear by approximately 40-50%. By adapting the toothing to the specific tooth engagement, the reduced stress results in an increased service life of the gear. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 7 This enables improved use of the gear in continuous operation with optimized duty cycle and thermal limits. The invention enables the construction of more powerful stress wave gears with small reduction ratios (80 and smaller). These can be used, for example, in the fields of robotics or service robotics, packaging machines, wheel drives for automated guided vehicle systems (AGVs), and machine tools.Further aims, advantages, features and possible applications of the present invention will become apparent from the following description of an embodiment with reference to the drawing. All described and / or illustrated features, individually or in any meaningful combination, form the subject matter of the present invention, also regardless of their summary in the claims or their reference back to them. The following show, partly schematically: Figure 1A shows a stress wave gear in a preferred embodiment in an end view; Figure 1B shows the stress wave gear according to Figure 1A in a section along the component axis; Figure 2A shows a stress wave gear which is designed as a roller stress wave gear, in a preferred embodiment in an end view; Figure 2B shows the stress wave gear according to Figure 2A in a section along the component axis; Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 8 Figure 3 shows a representation of a spur gear and a rack; Figure 4 shows three unmodified reference profiles for an external toothing of a flexspline, which differ in the shape parameter; Figure 5 shows a reference profile modified in the tip area, and Figure 6 shows a profile B modified in the tip and root areas. ezugsprofi l .Identical or equivalent components are provided with reference numerals in the following figures of the drawing based on an embodiment to improve readability. A stress wave transmission 8 shown in Figures 1A and 1B comprises a flexspline 2 designed in silk-hat construction, a circular spline 4 arranged coaxially therewith, and a wave generator 6. The circular spline 4 is designed as an internally toothed, cylindrical ring gear. The flexspline 2 has, in some areas, the shape of a thin-walled hollow cylinder with external teeth 14. Located within the flexspline 2 is the wave generator 6, formed by a disk arranged in the center, the so-called plug 10, whose outer cross-section has an ellipse-like shape, and a rolling bearing 12 mounted on the outer surface of the plug 10.The cylindrical, thin-walled rings of the rolling bearing 12 and the flexspline 2 are elastically deformed by the plug 10 into an ellipse-like cross-section. Due to this deformation, the external toothing 14 of the flexspline 2 engages the internal toothing 26 of the circular spline 4 in two areas on both sides of the major ellipse axis. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 9 In the exemplary embodiment selected here, the external toothing 14 of the flexspline 2 has two fewer teeth than the internal toothing 26 of the circular spline 4. When the plug 10 rotates around the transmission axis, the tooth engagement areas shift in the circumferential direction following the major ellipse axis. Due to the different number of teeth of the Flexspline 2 and the Circular Spline 4, the components rotate relative to each other by the angle of two tooth pitches with one rotation of the Plug 10.Using the plug 10 as the input element and the circular spline 4 as the output, a gear with a high reduction ratio in one stage is obtained. A tension wave gear 8 shown in Figures 2A and 2B is designed as a roller tension wave gear. It comprises a flexspline 2 in a pot design, a circular spline 4 arranged coaxially thereto, and a wave generator 6. The flexspline 2 has, in some areas, the shape of a thin-walled hollow cylinder with external teeth 14. Within the flexspline 2 is the wave generator 6, formed by a disk arranged in the center, the so-called plug 10, whose outer cross-section has an ellipse-like shape, and a rolling bearing 12 mounted on the outer surface of the plug 10. The cylindrical, thin-walled rings of the rolling bearing 12 and the flexspline 2 are elastically deformed into an ellipse-like cross-section by the plug 10.A plurality of rollers 58 are arranged in pockets 60 formed in the circular spline 4 and are in contact with the external toothing 14 of the flexspline 2. The rollers 58 form the teeth or internal toothing of the circular spline 4. In the exemplary embodiment selected here, the external toothing 14 of the flexspline 2 has two fewer teeth than the number of rollers 58. When the plug 10 rotates about the gear axis, the tooth engagement areas shift in the circumferential direction following the major axis of the ellipse. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 10. Due to the different number of teeth of the Flexspline 2 and the rollers 58, the components rotate relative to each other by the angle of two tooth pitches with one revolution of the Plug 10. If the Plug 10 is used as the drive element and the Circular Spline 4 as the output, a gearbox with a high reduction in one stage is obtained.Figure 3 shows an example of a spur gear 62 and a rack 66. For spur gears 62, it is customary to define tooth profiles by specifying the rack profile. A rack profile, also called a reference profile, is created from the spur gear 62 at the boundary between the number of teeth and pitch circle in the direction of infinity. The rack 66 is a lateral arrangement of a geometric structure (tooth) that repeats cyclically and infinitely at a pitch p. The pitch is the width of the structure in the direction of lateral expansion. The geometric structure is the reference profile. The tooth profile of any spur gear 62 is generated from the reference profile by rolling in a rolling direction 82. During rolling, the spur gear 62 rolls with a pitch circle 70 without play on a pitch line 74. The pitch circle 70 is a virtual circle, concentric to the center axis of the spur gear 62 with the diameter pitch ^ number of teeth / π.The pitch line 74 is a virtual straight line that runs in the direction of the lateral extension of the rack 66. It is parallel to the extreme tip or root points of the rack 66. Its position in the reference profile can be freely selected within reasonable limits. Reasonable limits depend on the specific profile and cannot be specified in general terms. The tooth profile of the spur gear 62 is formed from the enveloping sections of the rack 66. During generating, 62 enveloping cuts 78 are created in the spur gear. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 11 The following figures explain preferred embodiments of reference profiles for the external toothing 14 of the Flexspline 2. All reference profiles 16, 20, 24, 40, 48 shown in Figures 4, 5 and 6 are standardized to a pitch of Pi. The coordinates are therefore dimensionless.Adaptation to a specific size (pitch) is achieved by multiplying by a scaling factor, which in gear technology is referred to as a module. The module has a dimension (unit of length, usually mm), which determines the size of the specific profile. Figure 4 shows three reference profiles 16, 20, 24 in a diagram. The respective reference profile 16, 20, 24 is parameterized as a reference profile curve, i.e., a pair of x-values ​​and y-values. The x-values ​​are plotted in Figure 2 on an x-axis 28, and the y-values ​​on a y-axis 32. The respective profile 16, 20, 34 is shown in Figure 4 and Figures 5, 6, 7 between the values ​​-π / 2 and π / 2. The three reference profiles 16, 20, 24 are parameterized as functions of a function parameter ɸ by the x-value according to x = b ^ (ɸ - a ^ sin(ɸ)) and the y-value according to y = 0.5 ^ h ^ cos(ɸ). Here, b is a width factor, a a shape parameter and h a reference profile height.The value of ɸ ranges from -π to +π. The three reference profiles 16, 20, and 24 differ in the choice of the shape parameter a. The value of the reference profile height hl preferably lies in a range between 0.8 and 1.5. The value of the shape parameter a1 preferably lies in a range between 0.3 and 1.2. The value of the width factor b is Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 12 preferably 0.5. If the profile is supplemented by a straight line segment 52, b is less than 0.5. As mentioned above, the three reference profiles 16, 20, and 24 shown in Figure 4 differ in the value of the shape parameter a. For the reference profile 16, this value is 0.3, for the reference profile 20, it is 0.5, and for the reference profile 20, it is 0.8. As can be seen in Figure 4, increasing the shape parameter a essentially leads to a constriction of the reference profiles 16, 20, 24 with more pointed flanks.All length dimensions are standardized to a pitch of π and are therefore dimensionless. Scaling to real sizes is achieved by multiplying the coordinates by a factor known in gearing technology as the module. The width of the reference profile is also called the pitch and is calculated using the relationship module ^ π. If all length dimensions are represented in relation to the module, the width of the reference profile is always equal to π. Using the reference profile height h and the shape parameter a, the profile is adapted to the design parameters of the gear unit, and the properties of the gear unit are optimized. The reference profile 16, 20, 24 can also be adapted in its head and / or foot area. Figure 5 shows an example of a reference profile 40, which represents a modification of the reference profile 20 according to Figure 4.In a head region 36 of the reference profile 40, an area that would result from the parameterization of the x-coordinate and the y-coordinate is replaced by a circular arc 44 with a constant radius R inserted tangentially into the reference profile 40. Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 13 Figure 6 shows an example of another reference profile 48, which is modified in the head region 36 and in its foot region 52 compared to the reference profile 40. The modification in the head region 36 corresponds to the modification by a circular arc shown in Figure 5. In the foot region 52 or in the area of ​​the foot, the profile can be supplemented by other geometric elements. As shown in Figure 6, the reference profile 40 was extended by a section of a straight line in each of the foot regions 52. The width factor b is then chosen to be b = 0.5-s / π, where s is the length of the straight line segment or segment of the straight line.

[0002] Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 14 List of reference symbols 2 Flexspline 4 Circular Spline 6 Wave Generator 8 Stress wave gear 10 Plug 12 Rolling bearing 14 External gearing 16 Reference profile l20 Reference profile l24 Reference profile l26 Internal gearing 28 x-axis 32 y-axis 36 Tip area 40 Reference profile l44 Circular arc 48 Reference profile l52 Root area 56 Profile section 58 Roller 60 Pocket 62 Spur gear 66 Rack 70 Pitch circle 74 Pitch line 78 Envelope sections 82 Rolling direction P Pitch Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 15 a Form parameter b, s Width factor h Reference profile lheight a Radius A, B point C, D point R radius

Claims

Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 1 Patent claims 1. Stress wave transmission (8), comprising a circular spline (4), a wave generator (6) and a flexspline (2) with an A ußenverzahnung (14) mit Zähnen, wobei der jeweil ige Zahn einem Bezugsprofi l (16, 20, 24, 40, 48) genügt, welches in einer xy-Ebene als Bezugsprofi lkurve parametrisiert ist gemäß x = b ^ (ɸ - a ^ sin (ɸ)), y = 0,5 ^ h ^ cos(ɸ), wobei b ein Breitenfaktor, ɸ ein function parameter, a a form parameter and h a B ezugsprofi lhöhe ist, und wobei -π <= ɸ <= π .

2. Stress wave transmission (8) according to claim 1, wherein the value of the B ezugsprofi lhöhe (h) zwischen 0,8 und 1,5 l iegt.

3. Stress wave transmission (8) according to claim 1 or 2, wherein the W ert des Formparameters (a) zwischen 0,3 und 1,2 l iegt.

4. Stress wave transmission (8) according to one of the preceding claims, wherein the value of the width factor (b) is less than or equal to 0.

5.

5. Stress wave transmission (8) according to one of the preceding claims, w obei in einem Kopfbereich (36) des Bezugsprofi ls (16, 20, 24, 40, 48) the parameterized curve is replaced by a geometric shape, in particular a circular segment (44). Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 2 6. Stress wave gear (8) according to one of the preceding claims, w obei in einem Fußbereich (52) des Bezugsprofi ls (16, 20, 24, 40, 48) dieses seit l ich mit einer geometrischen Formgebung,in particular straight sections.

7. Stress wave transmission (8) according to one of claims 1 to 6, wherein the teeth of the circular spline (4) are formed by rollers (58) inserted in pockets (60).

8. Flexspline (4) for a stress wave transmission (8) with an A ußenverzahnung (14) mit Zähnen, wobei der jeweil ige Zahn einem Bezugsprofi l (16, 20, 24, 40, 48) genügt, welches in einer xy-Ebene als Bezugsprofi lkurve parametrisiert ist gemäß x = b ^ (ɸ - a ^ sin (ɸ)), y = 0,5 ^ h ^ cos(ɸ), wobei b ein Breitenfaktor, ɸ ein function parameter, a a form parameter and h a B ezugsprofi lhöhe ist, und wobei -π <= ɸ <= π .

9. Bezugsprofi l (16, 20, 24, 40, 48) für eine Außenverzahnung (14) a flexspline (2) for a stress wave gear (8), which i n einer xy-Ebene als Bezugsprofi lkurve parametrisiert ist gemäß x = b ^ ( ɸ - a ^ sin (ɸ)), y = 0,5 ^ h ^ cos(ɸ), wobei b ein Breitenfaktor, ɸ a function parameter, a a shape parameter and h a B ezugsprofi lhöhe ist, wobei -π <= ɸ <= π . Our reference: H003P117PCT 13.12.2024 Applicant: Harmonic Drive SE 3 10. Getriebeherstellwerkzeug mit einem Bezugsprof i l (16, 20, 24, 40, 48) according to claim 9.

11. Gear manufacturing tool according to claim 10, which is designed as a grinding worm, grinding wheel, hob, cutting wheel, W älzschälrad, Hobelkamm, oder Profi lwalze ausgebildet ist.

12. A method for producing a flexspline (2) for a stress wave gear (8) with external teeth (14), wherein a gear manufacturing tool according to claim 10 or 11 is used to form the external teeth (14).

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