Spur gears

Abstract

The present invention relates to a spur gear (10), which comprises a radially externally arranged, end-face meshing ring gear (30), a radially internally arranged hub (20), and a rotationally symmetrical radial connection structure (40) that integrally connects the ring gear (30) to the hub (20), wherein the radial connection structure (40) has mutually spaced pillars (44, 46) extending between the hub (20) and the ring gear (30) and axial through holes (48) arranged between the pillars (44, 46). The present invention is characterized in that the radial connection structure (40) has a disk-shaped base body (42) penetrated by the axial through hole (48), the base body having an axial front side and an axial rear side, and the pillars (44, 46) are arranged on the front side.

Description

Technical Field

[0001] The present invention relates to a spur gear, comprising

[0002] - a radially outer, rotationally symmetrical toothing ring gear,

[0003] - a radially inner hub, and

[0004] - a rotationally symmetrical radial connection which connects the ring gear to the hub (preferably in one piece),

[0005] The radial connection has struts which are spaced apart from one another and extend between the hub and the ring gear, and axial bores which are arranged between the struts. Background Art

[0006] Such a spur gear is known from DE 100 41 696 C1. Spur gears, in particular those used in the transmission of a motor vehicle drive unit, are subject to enormous mechanical loads. Their stability and in particular their fatigue strength are therefore essential quality features. On the other hand, the overall construction goal is to reduce the moving and heavy masses in the motor vehicle structure as much as possible. This leads to a conflict of objectives, in particular in the case of gears.

[0007] The aforementioned document discloses a stable spur gear in which a considerable material saving is achieved without a significant loss of stability due to a special design of the radial connection between the outer ring gear and the inner hub. The radial connection disclosed there consists of two groups of strip-shaped radial struts which are integrally formed on the hub on the one hand and on the ring gear on the other hand in two axially offset planes and are offset in the circumferential direction by half a period. Such a gear can be forged from steel.

[0008] A similarly shaped gear wheel but made of thermoplastic material is known from US Pat. No. 3,371,549. Here, all struts are located in the same radial plane at the hub and at the toothed ring, i.e., they are not axially offset from one another. However, the struts are designed to be arcuate in the axial direction, wherein two struts adjacent to one another in the circumferential direction are each bent in axially opposite directions.

[0009] DE 10 2017 201 383 A1 discloses a radial connection of spur gears injection-molded from a polymer material, which consists of a disk-shaped base body with arabesque-like webs placed thereon on both sides. Modern injection molding technology allows for almost any shape optimized in terms of rigidity and material saving for spur gears made of plastic, but the overall strength of such gears is extremely limited due to the material. In particular, plastic gears are not suitable for use in motor vehicle drive units that are subject to high mechanical fatigue.

[0010] In this case, production from metallic materials, in particular steel, is mandatory, wherein production by forming methods, in particular by forging, has proven to be particularly advantageous with regard to production speed and production costs. Summary of the invention

[0011] The object of the present invention is to further optimize such spur gears with regard to the conflict of objectives between stability on the one hand and material saving on the other hand, wherein production from metallic materials, in particular steel, preferably by forming methods, in particular by forging, should be possible.

[0012] The spur gear comprises

[0013] Radially externally arranged toothed ring gear with face engagement,

[0014] The radially inner hub, and

[0015] a rotationally symmetrical radial connection which integrally connects the ring gear to the hub,

[0016] The radial connection structure has pillars spaced apart from each other and extending from the hub to the ring gear, and axial through holes arranged between the pillars, which are realized in the following manner: the radial connection structure has a disk-shaped base body penetrated by the axial through holes, the base body has an axial front side and an axial rear side, and pillars are arranged on the front side thereof.

[0017] Preferred embodiments of the invention are the subject matter of the dependent patent claims.

[0018] The invention is based on the concept of a combination of a disk wheel and a spoke wheel, wherein the disk part and the spoke part are molded asymmetrically to one another. The rear side of the spur gear according to the invention essentially acts like a disk wheel pierced by relatively small axial through-holes. Conversely, its front side essentially acts like a spoke wheel with (except for the axial through-holes) closed spoke spacings. In other words, the disk-shaped base body is reinforced only on one side, namely on its axial front side, with the struts described, which serve as spokes. The invention thus breaks with the axisymmetric approach of through-gear technology.

[0019] The disk-shaped base body provides a certain basic stability, especially with regard to axial forces. However, in order to save material, it is designed so thin that it alone cannot absorb the high tensile and shearing forces that occur in the circumferential direction during operation without damage. The struts are used for this purpose, which can therefore be designed so fine that they alone, that is, without the disk-shaped base body, cannot absorb the axial forces without damage. The axial asymmetry selected according to the invention has proven to be harmless with regard to the stability of the resulting spur gear; however, with regard to production by metal forming methods, especially by forging, it has proven to be extremely advantageous to produce the complex shaping caused by the struts only on one side and to keep the rear side of the base body simply shaped and, in particular, without such struts.

[0020] Advantageously, the struts comprise a set of struts of a first type, wherein the struts of the first type are taller than they are wide in profile, and a set of struts of a second type, wherein the struts of the second type are wider than they are tall in profile. In this way, the different types of struts are optimized to absorb different types of acting forces, which results in a "task distribution" between the struts, each of which can therefore be designed more finely.

[0021] In a refinement of the "task distribution" method, it is provided that the struts extend straight and are inclined about the axial direction relative to a radial line intersecting their respective starting point, wherein struts of the first type are inclined in the opposite direction to struts of the second type. Such a design is particularly suitable for spur gears that rotate in a preferred main direction of rotation (i.e. not also in different directions) during operation. The struts of the first type, which are designed to be narrow and high, are primarily used here to absorb tensile forces, and the struts of the first type are preferably inclined at their hub starting point in the opposite direction of the intended direction of rotation. The struts of the second type, which are designed to be flat and wide, are particularly used to absorb shear forces, and the struts of the second type are preferably inclined at their hub starting point in the direction of the intended direction of rotation.

[0022] Particularly preferably, the struts of the first type are inclined by a greater angular amount than the struts of the second type. This stems from the inventors' insight into the force flow of the different types of forces to be supported.

[0023] As explained, the present invention, in particular in its described refinements, follows the concept of allocating different tasks to different structural elements of the radial connection. In order to embody this concept in the purest possible form, it is preferably provided that the individual pillars do not intersect one another. Instead, a preferred refinement of the present invention provides that the pillars of each pair of two adjacent pillars of different types contact one another at their radially outer starting point at the ring gear or at their radially inner starting point at the hub. In this embodiment, contact between adjacent pillars in their extension area between their respective two starting points is explicitly not provided. A person skilled in the art will of course understand here that the term "starting point" is of course to be understood as an expanded area that is generated by the finite width of a single structural element and is not point-shaped in the mathematical sense.

[0024] As explained at the outset, the rear side of the base body is essentially flat, i.e., in particular, it is designed without struts protruding from the disk plane. However, a preferred embodiment of the invention provides that reinforcement bodies are arranged on the rear side of the base body, transitioning radially inwards into the hub and extending radially outwards in a star-shaped manner. The star-shaped tips of the reinforcement bodies do not extend to the ring gear at all, which would make them struts in the sense of this description. On the contrary, it is preferably provided that the axial perforations are arranged in the radial extension of the star-shaped tips of the reinforcement bodies. The axial perforations mark the following positions in the radial connection structure, around which the forces occurring during operation are guided, i.e. via the struts. Therefore, the maximum material saving, i.e. the recesses, can be provided at these positions.

[0025] The shape of the axial perforation can be designed differently. In a first embodiment, they are circular. This shape is particularly advantageous in terms of manufacturing. In particular, such a circular perforation can be drilled afterwards.

[0026] However, it is more advantageous in terms of stability optimization to design the axial perforations in the form of rounded, preferably isosceles, flat triangles (angular dimension of the tip>90°) with radially inwardly directed tips. Such axial perforations must be introduced in the context of more complex forming methods. However, they allow more complete removal of material at locations that are not loaded during operation and thus lead to improved weight savings without sacrificing stability.

[0027] It has been found that the axial position of the radial connection designed according to the invention is largely unimportant for the functional properties of the resulting spur gear. The base body can therefore be arranged axially eccentrically, as is preferably provided. This is particularly advantageous in designs with limited installation space. This asymmetry allows the creation of a free space between the hub and the ring gear, which is arranged on one side of the radial connection and into which other gear components can engage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further details and advantages of the invention emerge from the following detailed description and the accompanying drawings.

[0029] in:

[0030] Figure 1 Two simplified views of a first embodiment of a spur gear according to the invention are shown,

[0031] Figure 2 Two simplified views of a second embodiment of a spur gear according to the invention are shown,

[0032] Figure 3 Shows the Figure 2 A top view of the front side of the spur gear,

[0033] Figure 4 Shows the Figure 2 A top view of the rear side of the spur gear,

[0034] Figure 5 Shown along Figure 3 The cross-section diagram of the section line VV in

[0035] Figure 6 Shown along Figure 3 The cross-section along section line VI-VI in FIG.

[0036] Figure 7 Shown along Figure 3 Sectional view along section line VII-VII. DETAILED DESCRIPTION

[0037] In the drawings, the same reference numerals denote the same or similar elements.

[0038] Figure 1 The front side of a first embodiment of a spur gear 10 according to the invention is shown (at Figure 1 center right) and rear (on Figure 1 The spur gear 10 includes a hub 20 radially inside and a gear ring 30 radially outside, but its end face meshing portion is Figure 1 The radial connection structure 40 extends between the wheel hub 20 and the gear ring 30, and the specific structure of the radial connection structure is the focus of the present invention.

[0039] The radial connection structure 40 includes a disc-shaped base 42, which is shown in the rear view of the spur gear 10 (in FIG. Figure 1 The matrix can be well identified in the left side of the figure. Figure 1On the front side of the radial connection structure shown on the right in the middle, a first type of support 44 and a second type of support 46 rise from the disk-shaped base body 42. The first type of support 44 is configured to be narrow and high, that is, in particular, higher than wide. The second type of support 46 is configured to be flat and wide, that is, in particular, wider than high. The support 44, 46 extends substantially straight, but does not extend radially. Instead, they are inclined relative to the radial lines that intersect them at their starting points (at the hub 20 or at the ring gear 30). The inclination of the first type of support 44 on the one hand and the second type of support 46 on the other hand is carried out in opposite directions here. In the embodiment shown, the first type of support 44 is inclined to the left at its starting point with the hub 20 relative to the radial line there. The second type of support 46 is inclined to the right at its starting point at the hub 20 relative to the radial line there. Here, the angle of inclination of the first type of support 44 is greater than the angle of inclination of the second type of support 46.

[0040] In the embodiment shown, the struts 44, 46 are arranged so that they do not intersect each other. Specifically, the second type of strut 46 extends from the hub start of the first type of strut 44 to the gear ring start of the adjacent first type of strut 44. The same applies to the first type of struts. Each first type of strut 44 extends from the hub start of the second type of strut 46 to the gear ring start of the adjacent second type of strut 46.

[0041] The areas of the base body 40 that are not reinforced with the struts 44, 46 are designed as axial perforations. Figure 1 In the embodiment of FIG. 4 , the axial aperture 48 has the shape of a rounded, flattened, isosceles triangle with a tip directed radially inwards.

[0042] On the rear side of the base body 42, its radial region adjacent to the hub 20 is reinforced with a star-shaped reinforcement 49. This reinforcement protrudes from the disk surface and transitions into the hub 20. Its star-shaped tips are each located on the same radial line as the center of the axial through-hole 48.

[0043] Figure 2 An alternative embodiment of a spur gear 10 according to the invention is shown. Figure 1 The embodiments differ only in the shape of the axial aperture 48 , which is designed in a circular shape here.

[0044] Figure 3 Shows the Figure 2 Detailed top view of the front side of the spur gear 10. Figure 3 In the illustration of FIG. 3 , the teeth of the toothed ring 30 can also be clearly seen. The wheel hub 20 is provided with a plug-in toothing on its inner circumference. Figure 4 The rear side of the same spur gear 10 is shown.

[0045] Figures 5 to 7 Shown along Figure 3 The section lines VV, VI-VI and VII-VII pass through Figure 3 and Figure 4 A cross section of a spur gear 10. Figures 3 to 7 The overview should convey to the skilled person a vivid picture of the design according to the invention of the radial connection structure 40 .

[0046] also, Figures 5 to 7 The sectional view of shows a preferred embodiment of the present invention, according to which the base body 42 is not arranged axially in the middle, but is arranged offset (to the left in the figure). An offset in the opposite direction and an offset of greater or lesser magnitude are also conceivable.

[0047] Of course, the embodiments discussed in the detailed description and shown in the drawings represent only illustrative embodiments of the invention. Based on the present disclosure, a wide range of variant possibilities are available to the skilled person. In particular, the mold according to the invention is suitable for the production of spur gears according to the invention made of metal materials, in particular steel, wherein the production can be achieved by a forming method, in particular by forging, such as it is also preferably provided for the creation of spur gears for use in drive units of motor vehicles, in particular in transmission mechanisms.

[0048] Reference numerals list

[0049] 10 Spur gears

[0050] 20 wheels

[0051] 30 Ring gear

[0052] 40 Radial connection structure

[0053] 42 Matrix

[0054] 44 Type 1 Pillar

[0055] 46 The Second Type of Pillar

[0056] 48 Axial perforation

[0057] 49 Strengthen the body.

Claims

1. A spur gear (10), comprising: a radially outer toothed ring gear (30), - a radially inner hub (20), and a rotationally symmetrical radial connection (40) which integrally connects the ring gear (30) to the hub (20), in, The radial connection structure (40) has pillars (44, 46) spaced apart from each other and extending from the hub (20) to the ring gear (30) and an axial through hole (48) arranged between the pillars (44, 46). It is characterized in that The radial connection structure (40) has a disc-shaped base (42) penetrated by the axial through hole (48), the base having an axial front side and an axial rear side, wherein the pillars (44, 46) are arranged only on the front side of the base, and the pillars (44, 46) include a group of first type pillars (44) and a group of second type pillars (46), wherein the first type of pillars (44) are taller than wide in profile, and the second type of pillars (46) are wider than high in profile.

2. The spur gear (10) according to claim 1, It is characterized in that The struts (44, 46) extend straight and are inclined about an axial direction relative to a radial line intersecting their starting point, wherein the struts (44) of the first type are inclined in an opposite direction to the struts (46) of the second type.

3. The spur gear (10) according to claim 2, It is characterized in that The first type of struts (44) are inclined at a greater angular amount than the second type of struts (46).

4. The spur gear (10) according to any one of claims 2 to 3, It is characterized in that The struts (44, 46) of each pair of two adjacent struts (44; 46) of different types contact each other at their radially outer starting points at the gear ring (30) or at their radially inner starting points at the hub (20).

5. The spur gear (10) according to any one of claims 1 to 3, It is characterized in that Arranged on the rear side of the base body (42) is a reinforcement body (49) which transitions radially inwardly into the hub (20) and extends radially outwardly in a star-shaped manner.

6. The spur gear (10) according to claim 5, It is characterized in that The axial through-hole (48) is arranged in the radial extension of the star-shaped tip of the reinforcement body (49).

7. The spur gear (10) according to any one of claims 1 to 3, It is characterized in that The axial aperture (48) is circular in shape.

8. The spur gear (10) according to any one of claims 1 to 3, It is characterized in that The axial aperture (48) is designed in the shape of a rounded, isosceles, flattened triangle with a tip pointing radially inwards.

9. The spur gear (10) according to any one of claims 1 to 3, It is characterized in that The base body (42) is arranged axially eccentrically.

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