Worm gear for auxiliary drive, in particular steering mechanism of motor vehicle

Abstract

The invention relates to a worm gear drive (10) for an auxiliary drive, in particular a steering mechanism of a motor vehicle, comprising the following features: a worm (100) having a helical toothing which is designed as a spherical toothing or an approximately spherical toothing; a worm gear (200) engaged with the worm (100) in a meshing manner; the toothing of the worm (100) has a tooth (130) in at least one of the two axial edge regions (112, 114) thereof, the tooth height (H2) of which is smaller than the tooth height (H1) of the other teeth of the worm (100). The invention further relates to a worm for such a worm gear, and to a method for producing such a worm.

Description

Technical Field

[0001] This invention relates to a worm gear transmission device for auxiliary drive devices, particularly steering mechanisms of motor vehicles, as well as the worm in such a worm gear transmission device and a method for manufacturing the same. Background Technology

[0002] For example, patent document WO 2019 / 057377 A1 discloses a worm gear transmission device for a motor vehicle steering system. This worm gear transmission device includes a worm and a worm wheel. The worm is either globoidisch or globooid. The difference between a spherical worm and a globoidisch worm is that a spherical worm maintains a constant distance from the worm wheel over its entire length, while the globoidisch worm in this document does not possess this characteristic. Instead, the globoidisch worm has a region along its length that engages with the worm wheel, and two regions located before and after this engagement region that do not engage with the worm wheel.

[0003] DE 19630567 A1 describes another worm gear drive for use in motor vehicle auxiliary drive systems. This worm gear drive is applied to adjustment devices for motor vehicle seats, such as seat longitudinal adjustment, seat back adjustment, or seat height adjustment. This drive also includes a spherical worm and a worm wheel meshing with it.

[0004] Compared to cylindrical worm gear drives (where the worm is designed as a cylinder), spherical or near-spherical worm gears, due to the arched side surface of the worm, increase the engagement area between the worm teeth and the matching teeth of the worm wheel. More load-bearing teeth participate in the engagement, therefore, under the same safety conditions, a smaller tooth module can be selected.

[0005] Worm gear drives employing spherical worms exhibit higher load-carrying capacity and longer service life compared to drives using cylindrical worms or spherical worm gears, given the same installation space and material spacing. Due to the special tooth geometry on the spherical worm, multiple tooth pairs advantageously engage simultaneously at all times, thus creating a larger meshing surface. This reduces the root stress and flank pressure of the worm gear under the same torque. On the other hand, under the same root stress and flank pressure, a worm gear drive with a spherical worm can transmit a greater torque than a worm gear drive with a cylindrical worm. Summary of the Invention

[0006] The purpose of this invention is to improve known worm gear drives that employ spherical worms or spherical worms in terms of their installation space and torque, thereby eliminating or greatly avoiding damage to the matching worm gear during operation.

[0007] The above objective is achieved by a worm gear transmission device according to one aspect of this application.

[0008] The unique feature of the solution according to the invention is that the spherical or near-spherical toothed portion of the worm has teeth in at least one of its two axial edge regions, the tooth height of which is less than the tooth height of the remaining teeth of the worm.

[0009] It should be noted here that the terms "spherical worm" or "spherical teeth" used below refer not only to the teeth of a worm that have a pure spherical surface from one end of the worm to the other, but also to teeth that are similar to a sphere, approximately spherical, or only partially spherical.

[0010] According to the present invention, the reduced tooth height of the spherical worm enables the spherical worm to avoid damage to the teeth of the worm wheel in its edge region.

[0011] Ideally, the tooth height of at least one or more teeth in the two axial edge regions of the worm is designed to be less than the tooth height of the teeth arranged in the middle of the worm.

[0012] In one improved embodiment of the invention, the worm gear has a central region or an edge region, said central region or said edge region having a cylindrical envelope surface. In the remaining regions, the teeth are designed to be spherical.

[0013] In another embodiment of the invention, the worm teeth are specified to have a root circle and an addendum circle, the root circle having a first radius RF and the addendum circle having a second radius RK. RK is chosen to be greater than RF, and the imaginary center of the root circle is closer to the worm's central axis than the imaginary center of the addendum circle. This ensures that the teeth at the outer edge of the worm are designed to be shorter than the teeth in the middle of the worm.

[0014] In one improved embodiment of the invention, the teeth of the worm are designed at least partially as a concave spherical structure (hohlballig) between the root circle and the tip circle. This results in a more tighter meshing of the teeth when the worm and worm wheel are rolling. Furthermore, the tooth flank pressure is increased, thereby enhancing the tooth flank load-bearing capacity of the gear pair.

[0015] In another embodiment of the invention, the sharp teeth of the worm, particularly the tooth tips, are designed to be rounded. This rounding design blunts the sharp teeth, effectively preventing damage to the matching worm gear during operation of the worm gear drive.

[0016] In another embodiment of the invention, the meshing angle of the worm gear transmission is specified to be between about 13° and 17°, preferably between 14° and 16°.

[0017] In the turbine drive according to the invention, the worm is made of metal, particularly free-cutting steel, while the worm wheel is preferably made entirely or at least partially of plastic.

[0018] The width of the worm gear's gear ring can be approximately 10mm to 30mm, preferably 16mm to 20mm.

[0019] According to the present invention, the worm gear is designed to be symmetrical or asymmetrical.

[0020] In an improved embodiment of the invention, the ratio of the tooth thickness of the worm to the tooth thickness of the worm wheel is in the range of approximately 20:80 to 50:50.

[0021] Another subject of the present invention is a worm for use in the worm gear transmission device according to the present invention described above.

[0022] A preferred method for manufacturing the worm gear of the present invention may include the following steps:

[0023] - A worm gear blank, preferably cylindrical and made of metal, is provided;

[0024] - Machining an annular groove with radius R, the center of which is chosen such that the teeth in the middle of the resulting worm have a full tooth height H1, while the teeth at the edge of the worm have a truncated tooth height H2;

[0025] - Machining spherical teeth or spherical tooth sections with a root circle radius RF smaller than the radius R.

[0026] Preferably, at least the teeth arranged in the edge region of the worm are then rounded in their tooth tip region.

[0027] Although the preferred manufacturing method requires machining the annular groove into the worm blank made of metal, the invention is not limited thereto. In fact, if the profile and shape of the teeth according to the invention are machined into the worm blank by any removal process (such as scraping, honing, whirl milling, grinding, and cutting), the annular groove can be omitted. It should be noted that the tooth height of the teeth in at least one edge region of the spherical worm is less than the tooth height in the middle of the worm. If, during this manufacturing process, it is found, for example, that very sharp or pointed teeth are formed on the spherical teeth of the worm by cutting, it is preferably stipulated that the teeth are rounded at their tooth tips, at least in the edge region of the spherical teeth, preferably over the entire spherical teeth. In an improvement of the invention, all teeth of the worm are rounded at their tooth tips. Attached Figure Description

[0028] The worm gear transmission device, the corresponding worm, and the manufacturing method thereof according to the present invention are described in detail in the following figures by way of embodiments.

[0029] The attached diagram shows:

[0030] Figure 1 The spherical worm is a known worm gear transmission device in the prior art.

[0031] Figure 2 To provide a worm gear transmission device employing the worm gear and spherical worm according to the present invention,

[0032] Figure 3 for Figure 1 A detailed view of the engagement area between the worm and the worm wheel.

[0033] Figures 4a to 4d Multiple views are provided to illustrate the manufacturing process of the spherical worm according to the invention, which has shortened teeth in the edge region of the spherical worm.

[0034] Figures 5a to 5d Multiple views of a tooth profile with a modified tooth tip.

[0035] Figures 6a to 6d Different views of a spherical worm with a modified tooth tip.

[0036] Figures 7a to 7k A detailed view of the modified tooth geometry in the edge region of the spherical worm gear.

[0037] Figures 8a to 8b These are two views of the engagement area between the spherical worm and the worm wheel at different tooth thickness ratios.

[0038] Figures 9a to 9b Two views of the teeth of a worm gear with straight, concave spherical, and convex tooth flank orientations, and...

[0039] Figures 10a to 10b Schematic diagrams show two examples of worm gear drives employing asymmetric spherical worms. Detailed Implementation

[0040] In the following figures and descriptions, unless otherwise specified, the same reference numerals denote the same parts having the same function.

[0041] Figure 1 A known worm 100 is shown, which meshes with a worm wheel, for example, in a known worm gear drive, and is designed as a spherical worm. The worm 100 is symmetrically designed and has a central axis 110. The worm 100 has a first edge 112 and... Figure 1The second edge 114 on the right side of the view, opposite the first edge. The spherical worm 100 has symmetrical spherical teeth arranged around a central axis 110, including a central tooth 120 and outer teeth 130 arranged near the first edge 112 and the second edge 114. All teeth 120 and 130 of the spherical tooth portion of this known worm 100 have the same tooth height. The tooth height of the central tooth 120 is H1, and the tooth height of the outer teeth is H2. The tooth heights H1 and H2 are derived from the distance from the root circle FK to the tip circle KK of the spherical tooth portion. Figure 1 As shown, the root circle FK and the addendum circle KK of the known spherical worm 100 extend at the same distance from each other along the entire length of the worm 100, so all the teeth of the spherical tooth section have the same tooth height. The root circle FK has a radius RF, and the addendum circle KK has a slightly smaller radius RK, but both share a common center MF.

[0042] Figure 2 A worm gear drive 10 according to the invention is schematically shown. The worm gear drive 10 includes a worm 100 made of metal, preferably free-cutting steel, designed as a spherical worm with quasi-spherical teeth, and meshing with a worm wheel 200. According to the invention, the worm wheel 200 is made of plastic, or at least partially made of plastic. The worm wheel 200 may also be composed of multiple parts, i.e., a so-called multi-part gear. The engagement area between the worm 100 and the worm wheel 200 is the area where the teeth of the worm 100 mesh with the worm wheel 200. In the illustrated example, a tooth thickness ratio of approximately 80:20 is chosen. Therefore, the thickness of the teeth of the worm wheel 200 is approximately four times the thickness of the teeth of the worm.

[0043] The teeth of the spherical worm 100 are specially designed in their edge region, that is, shorter than in other regions. This can be seen from... Figure 3 It is clearly visible in the text.

[0044] Figure 3 Show Figure 1 An enlarged view of the worm gear transmission 10 in the engagement area. The worm 100 has a central axis 110, a left edge region 112, and a right edge region 114. The worm 100 has spherical teeth on its outer circumference. These teeth of the worm 100 have teeth 120 in the central region of the worm 100 and teeth 130 arranged near the left edge region 112 and the right edge region 114. Figure 2 It is clearly visible that the tooth height H1 of the tooth 120 in the central region of the worm 100 is significantly higher than the tooth height H2 of the tooth 130 in the two edge regions 112 and 114 of the worm 100. By reducing the tooth height H2 and preferably rounding the tooth 130 (which will be detailed in the following description of the figures), it is ensured that the fragile and relatively soft worm wheel 200, made of plastic, is not damaged when the worm 100 meshes with the worm wheel 200.

[0045] like Figure 3 As further shown, the teeth 210 of the worm gear 200 are designed to be significantly thicker than the teeth 120 and 130 of the worm 100. The ratio of the tooth thickness of the worm gear 200's teeth 210 to the tooth thickness of the worm 100's teeth 120 and 130 is preferably in the range of approximately 80:20 to approximately 50:50. Since the load-bearing capacity of plastic gears is significantly lower than that of metal gears, in a metal-plastic gear pair, the plastic gear, i.e., the worm gear in this case, is configured to have a larger tooth thickness, i.e., in the range of approximately up to 80:20. This tooth thickness ratio is... Figure 3 It is clearly visible in the middle.

[0046] also, Figure 3 The root circle of the worm gear teeth is marked with FK. It rotates about the center MF with radius RF. The tip circle GK of the teeth is designed to be flatter than the root circle FK, and its radius RK, or approximate radius trajectory RK, is greater than RF. Furthermore, the center MK of the radius RK is far from the central axis 110 of the worm 100. Preferably, an imaginary straight line between the centers MF and MK is perpendicular to the central axis 110 of the worm 100.

[0047] In principle, the teeth 130 located in the edge regions 112, 114 of the worm 100 can be shortened relative to the teeth 120 in the middle of the worm 100 in any manner, and preferably also rounded. For this purpose, for example, a complete spherical tooth portion can be provided, which first provides teeth of equal height in the edge regions 112, 114 and the middle region 114 of the worm 100. Then, in subsequent machining steps, the teeth in the two edge regions 112, 114 are shortened accordingly and rounded. However, this method of manufacturing the worm 100 according to the invention is very costly.

[0048] exist Figure 4a A first embodiment of the spherical worm 100 according to the invention is shown in Figure 114. The teeth 120 in the middle of the worm 100 have a tooth height H1, and the teeth 130 in the edge region have a tooth height H2, where H2 is less than H1. The radius and thus curvature of the root circle FK are less than the radius and thus curvature of the addendum circle GK. The root circle FK and the addendum circle GK are close to each other in a direction toward the edge regions 112, 114 of the worm 100.

[0049] This worm 100 can be manufactured by any method. It is only necessary to note that the tooth height H2 of the teeth 130 in the edge regions 112, 114 of the worm 100 is less than the tooth height of the teeth 120 in the middle region of the worm 100. An exemplary method of manufacturing such a worm 100 made of metal includes first cutting a quasi-spherical tooth profile in a metal blank, having, for example, a tooth ratio of 50:50. Therefore, the dimensions of the tooth groove and the tooth tip are approximately equal. Subsequently, the tooth portion is machined by a tooth thickness reduction process, resulting in a significantly narrower tooth tip and a wider tooth root. During this tooth tip reduction process of the spherical tooth portion, the teeth 130 in the edge regions 112, 114 of the worm 100 are quasi-automatically shortened, so that their tooth height H2 is lower than the tooth height H1 of the teeth 120 in the middle region of the worm 100. During this tooth thickness reduction process, the teeth 130 in the edge regions 112, 114 of the worm 100 become relatively sharp and pointed due to the cutting process. In subsequent processing steps, it is preferable to round at least the teeth 130 in the edge region, more preferably to round the teeth 120 in the middle of the worm 100, and particularly preferably to round all the teeth of the worm 100.

[0050] Another preferred method for manufacturing the worm gear of the present invention is as follows: Figure 4b )to Figure 4d As shown in [reference needed]. To manufacture the worm 100, a metal worm blank 300 is first provided, whose wall around the central axis 110 already has a radius R (see [reference needed]). Figure 4b The radius R is chosen such that, in subsequent steps, when machining the spherical teeth in the blank 300, the teeth 130 located in the edge regions 112, 114 cannot form tips 130, because there is no material at this location in the blank 300 for cutting spherical teeth in the blank 300. This principle is... Figure 4c As shown in the figure.

[0051] The process of cutting the spherical structure into blank 300 is coordinated in such a way that the teeth 120 in the middle of the worm gear 100 to be produced can be formed with their full height H1. However, as the teeth are arranged closer to the two edge regions 112, 114, the reduction in tooth height H2 due to the material loss in the blank 300 at this point gradually increases due to the selected radius R in the blank 300. The missing tooth area is located in... Figure 4c The tooth region, schematically indicated by reference numeral 133 in the figure, is shown above radius R, but it is actually omitted during the cutting of the spherical tooth and does not actually exist. The non-existent tooth region 133 is... Figure 4c The instructions in this document are for illustrative purposes only.

[0052] like Figure 4cAs further shown, the worm 100 has teeth with a root circle FK corresponding to... Figure 4a The root circle FK of the spherical worm 100 shown in the figure.

[0053] The tooth tip circle of worm gear 100 is at Figure 4c The worm 100 is also designated by the reference numeral GK in the accompanying drawings. The radius of the addendum circle GK of the worm 100 is the same as or approximately the radius R of the blank 300. Clearly, the addendum circle GK or R of the spherical worm according to the invention has a radius greater than... Figure 4a The tooth tip circle GK (i.e., a conventional spherical worm where all the teeth of the worm are of equal height).

[0054] Figure 4d ) shows by Figure 4b The worm gear 100 is made from a blank with radius R.

[0055] Figure 5 illustrates the basic principles of tooth profile modifications without tooth tips and those with tooth tips through multiple sub-figures. Figure 5a The diagram shows a typical tooth profile, such as that of a worm gear. This tooth is indicated by reference numeral 400. Tooth 400 has a tooth crest 401 and a tooth root 402, which are interconnected by opposing tooth flanks 403. Figure 5a In the embodiment shown, the tooth tip 401 is horizontal, and its two ends have angular transitions with the tooth side 403.

[0056] Figure 5b In the diagram, tooth 400 has a tooth tip radius (Kopfradius) at the aforementioned corner. The tooth tip radius is indicated by reference numeral 405 on both the left and right sides. The tooth tip radius 405 makes... Figure 5a The edges of the teeth 400 are rounded.

[0057] Figure 5c This shows another modification to the tooth tip of tooth 400. Here, from... Figure 5a The material removed from the 400mm tooth edges is significantly more than the material produced. Figure 5b The material with a tooth tip radius of 405.

[0058] like Figure 5c As shown, during the tooth tip retraction (Kopfrücknahme), small edges are still retained on the upper tooth side 403 of tooth 400 and on both sides of the tooth tip 401.

[0059] Figure 5d The image shows tooth 400, which undergoes both tooth tip radius adjustment and tooth tip retraction 407. Clearly, its tooth tip 401 is not only rounded but also significantly larger than... Figure 5a )and Figure 5b The tooth tip is thinner.

[0060] This tooth tip modification scheme, particularly the tooth 130 in the edge region of the spherical worm 100 according to the invention, is schematically shown in FIG6.

[0061] Figure 6a The tooth profile of the spherical worm 100 without tooth tip modification is shown.

[0062] Figure 6b The diagram shows the outline of the teeth of the spherical worm 100 during tooth tip retraction in the edge region of the spherical worm 100.

[0063] Figure 6c This shows a tooth profile modified using the tooth tip radius. Figure 6d The diagram shows the tooth profile of a spherical worm that simultaneously has tooth tip retraction and tooth tip radius.

[0064] Since the cross-section of the tooth 130 in the edge region of the spherical worm 100 in Figure 6 is difficult to identify, Figure 7 shows the principle of tooth profile machining (Zahnprofilierung) by tooth tip rounding and tooth tip retraction in an enlarged view.

[0065] Figure 7a The diagram shows a spherical worm 100, wherein the teeth on the left and right edges of the worm 100 are designed to be shorter than the teeth in the middle of the worm 100.

[0066] Figure 7b ) shows Figure 7a An enlarged view shows, for example, how teeth are formed in the middle of a spherical worm 100.

[0067] Figure 7c (Enlarged display) Figure 7a The tooth is located on the left edge of the spherical worm gear 100. The tooth flank length is unequal and the tooth is asymmetrical. It can be clearly seen that the tooth is formed in a sharp manner, and if the tooth is designed to be too long, it will cause the aforementioned problems when meshing with the plastic worm gear.

[0068] Figure 7d The image shows a spherical worm 100 with all teeth having rounded tips.

[0069] Figure 7e The image shows the teeth in the middle of the spherical worm 100, with a noticeable rounding at the tooth tips. Figure 7f The diagram shows the tooth tip rounding performed on the corresponding teeth in the edge region of the spherical worm 100.

[0070] Figure 7g The same spherical worm 100 is shown, but here the tooth tip retraction is performed, that is, significant material removal is performed in the area of ​​the tooth tip (i.e., on the upper left and upper right tooth sides of the tooth).

[0071] Figure 7h The image shows the teeth in the middle of the spherical worm 100. Figure 7i The corresponding teeth in the edge region of the spherical worm 100 are shown.

[0072] Figure 7j This illustrates a spherical worm 100 that simultaneously performs tooth tip rounding and tooth tip retraction. The corresponding teeth in the middle of this spherical worm 100... Figure 7k As shown in the diagram, the teeth in the edge region of the spherical worm 100 are... Figure 7l As shown in ). From Figure 7l The outline of the teeth in the diagram clearly shows that they no longer have a tip in the sense of this invention.

[0073] Figure 8a The diagram shows a gear pair according to the invention with a tooth thickness ratio of approximately 80:20, i.e., the thickness of the tooth 210 of the worm gear 200 is approximately four times the thickness of the tooth of the metal worm 100. Figure 8b A similar gear pair is shown, but with a tooth thickness ratio of approximately 50:50, and the teeth in the edge region of the worm 100 are truncated. Both gear pairs are within the scope of this invention. The teeth of the worm 100 located in the edge region have a significantly lower height than the teeth in the middle of the worm 100. Furthermore, these teeth are preferably rounded.

[0074] Figure 9 schematically illustrates another variant of the design and modification scheme of the teeth of the spherical worm 100. Figure 9a The diagram shows a tooth 400 having a tooth flank 403, a tooth crest 401, and a tooth root 402. The tooth flank 403 extends in a straight line. The spherical design of the tooth flank 403 is indicated by 410, and the orientation of the concave or concave spherical tooth flank 403 is indicated by reference numeral 409. When implementing the spherical worm gear 100 according to the invention, it has proven advantageous to provide a concave spherical or slightly concave spherical shape for the tooth flank 403, as this contributes to better tooth flank load-bearing capacity. Figure 9b Such an embodiment is shown in (). Although in Figure 9a The concave or convex design of the tooth flank 403 is shown in an extremely exaggerated manner, but Figure 9b The diagram roughly shows the true proportions of the spherical worm 100 according to the invention, and it can be clearly seen that the concave sphere is basically provided in the area of ​​the tooth root or in the area near the tooth root 402.

[0075] Although the symmetrically designed spherical worm 100 has been described above, the present invention also covers worm gear transmission devices 10 employing an asymmetrically designed spherical worm, wherein only a portion or part of the teeth is spherical.

[0076] exist Figure 10aIn this configuration, the spherical worm 100 is designed as a hemispherical shape (Halbgloboid). Essentially, this corresponds to the worm 100, as discussed in the previous example, where the worm 100 is split at half the length of its central axis 110, and only half of the spherical worm 100 is used in the worm gear drive 10. Figure 10b This also shows a hemispherical worm. However, the hemispherical connecting cylindrical portion 150 of the worm 100, i.e., the cylindrical envelope, can preferably also be provided with teeth. This cylindrical portion... Figure 10b The figure is marked with 150 in the attached diagram.

[0077] List of reference numerals

[0078] 10. Worm Gear Transmission Device

[0079] 100 spherical worm

[0080] 110 Central Axis

[0081] 112 First Edge

[0082] 114 Second Edge

[0083] 120 teeth in the middle

[0084] 130 Outer teeth

[0085] 133 Missing tooth area

[0086] 150 cylindrical area

[0087] 200 worm gear

[0088] 210 teeth

[0089] 300 worm gear blank

[0090] 400 teeth without a tooth tip modification plan

[0091] 401 Tooth Tip

[0092] 402 Tooth Root

[0093] 403 Tooth flank

[0094] 405 Tooth tip radius

[0095] 407 Tooth tip retraction

[0096] 409 Concave spherical tooth flank (concave tooth flank)

[0097] 410 convex tooth side

[0098] R radius

[0099] H1 First Tooth Height

[0100] H2 Second Tooth Height

[0101] FK tooth root circle

[0102] GK spherical worm gear tooth tip circle

[0103] RF tooth root circle radius

[0104] RK tooth tip circle radius

[0105] MF tooth root center

[0106] MK tooth tip circle center.

Claims

1. A worm gear transmission device (10) for auxiliary drive devices, particularly for steering mechanisms of motor vehicles, comprising: - Worm (100) having helical teeth, said helical teeth being designed as spherical teeth or near-spherical teeth; - Worm gear (200), which engages with the worm (100) in a meshing manner; Its features are: The worm (100) has teeth (130) in at least one of its two axial edge regions (112, 114) whose tooth height (H2) is less than the tooth height (H1) of the other teeth of the worm (100).

2. The worm gear transmission device (10) according to claim 1, Its features are, The worm (100) has one or more teeth (130) in its two axial edge regions (112, 114) whose tooth height (H2) is less than the tooth height of the tooth (120) arranged in the middle of the worm.

3. The worm gear transmission device (10) according to claim 1 or 2, Its features are, The worm (100) has a central region or an edge region, and the central region or edge region has a cylindrical envelope or a cylindrical region (150).

4. The worm gear transmission device (10) according to claim 1, 2 or 3, Its features are, The worm (100) has a toothed portion having a root circle (FK) and an addendum circle (GK), the root circle having a first radius or at least an approximate radius (RF), and the addendum circle having a second radius (RK), wherein the imaginary center of the root circle (FK) is closer to the central axis (110) of the worm (100) than the imaginary center (MK) of the addendum circle (GK).

5. The worm gear transmission device (10) according to claim 4, Its features are, The teeth of the worm (100) between the root circle (FK) and the tip circle (GK) are designed to have at least a portion of concave spherical tooth flanks (409).

6. The worm gear transmission device (10) according to any one of claims 1 to 5, Its features are, The tooth tip (401) of the worm (100) is designed to be rounded.

7. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The meshing angle of the worm gear transmission device (10) is between 13° and 17°, preferably between 14° and 16°.

8. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The worm (100) is made of metal, preferably of free-cutting steel.

9. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The worm gear (200) is at least partially, preferably entirely, made of plastic.

10. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The tooth ring width of the worm gear (200) is about 10 mm to 30 mm, preferably 16 mm to 20 mm.

11. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The worm (100) is designed to be asymmetrical.

12. The worm gear transmission device (10) according to any one of the preceding claims, Its features are, The ratio of the tooth thickness of the worm (100) to the tooth thickness of the worm wheel (200) is in the range of approximately 20:80 to 50:

50.

13. A worm gear (100) for use in a worm gear transmission device (10) according to any one of claims 1 to 12.

14. A method for manufacturing the worm gear (100) according to claim 13, comprising the following steps: - Provides a rod-shaped worm gear blank (300) made of metal. - A ring-shaped groove with radius R is machined, wherein the center of the groove is selected such that the teeth (120) in the middle of the resulting worm (100) have a full tooth height (H1), while the teeth (130) at the edge of the worm (100) have a reduced tooth height (H2). - Spherical teeth are machined in the groove, with the root circle radius (RF) being smaller than the radius R. -At least the teeth (130) arranged in the edge region of the worm (100) will be rounded in the tooth tip (401) region.

15. The method according to claim 14, Its features are, All teeth (120, 130) of the worm (100) are rounded at their tooth tips (401).

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