One-piece component with concealed circumferential gearing, as well as method and wobble tool for its manufacture

Abstract

Component (200), in particular gear or shaft, for power transmission in the drive train of a motor vehicle, with at least partially concealed circumferential teeth (230), characterized by the fact that this is a one-piece formed part made from a steel material (M), wherein the component (200) is rotationally symmetric, with: - a central pin (220) on which the circumferential teeth (230) are formed; - a plate-like flange (210) molded onto the pin (220); and - a ring (240) formed on the flange (210) and projecting in the axial direction (L), which concentrically surrounds the pin (220) and radially covers the circumferential teeth (230) over at least part of their axial length.

Description

[0001] The invention relates to a component for power transmission in the drive train of a motor vehicle, with at least partially concealed circumferential teeth. Preferably, it is a clutch and / or transmission component, and in particular a gear or a shaft.

[0002] The invention further relates to a method and a tool for manufacturing such a component.

[0003] The powertrain of a motor vehicle generally refers to all components that provide propulsion. These include, for example, the engine, the clutch, the transmission, the drive shafts, and any differential gears. Such components sometimes incorporate parts of the type mentioned above, which have at least one axially extending circumferential toothing (external circumferential toothing) that is concealed or covered in the radial direction over at least a portion of its axial length. Patent DE 10 2007 031 963 A1 of the same applicant shows a clutch input shaft designed in this way (see reference 2).

[0004] DE 197 44 639 B4 discloses a method for manufacturing a gear linkage, a device for carrying out the method and a gear linkage manufactured according to the method, and EP 1 382 407 B1 discloses a clutch gear with teeth and a method for manufacturing the same.

[0005] The invention is based on the objective of providing a component of this type that can be manufactured more cheaply while having the same or even better properties.

[0006] This problem is solved by a component according to the invention having the features of claim 1. With dependent claims, the invention also extends to a method according to the invention and to a wobbling tool according to the invention for manufacturing a component according to the invention. Preferred embodiments and configurations of the invention are described analogously for all subject matter of the invention in the dependent claims, the following description, and the figures.

[0007] The component according to the invention is characterized in that it is a one-piece formed part made of steel. The component according to the invention is therefore a steel formed part produced in one piece by forming processes (in particular orbital forming, as explained in more detail below). The forming process also includes, in particular, the forming of the circumferential gear teeth.

[0008] Up to now, the components in question have mostly been manufactured in multiple parts, usually in two parts (see DE 10 2007 031 963 A1). They are typically welded parts. Due to the required accessibility of the tools, the circumferential gear teeth are currently manufactured conventionally before joining, for example, by rolling, axial forming, or machining (e.g., broaching, reaming, and / or milling). The forming manufacturing process according to the invention, as explained in more detail below, enables significant cost, energy, and material savings, as well as a reduction in manufacturing time (shortening the entire process chain). Furthermore, the forming-manufactured, one-piece component according to the invention offers strength advantages.

[0009] The one-piece component according to the invention is rotationally symmetrical and has in particular the following features: - a central pin or dome on which the circumferential teeth are formed; - a plate-like flange molded onto the pin; and - a ring formed on the flange and projecting in the axial direction, which concentrically surrounds the pin and radially conceals or covers the circumferential teeth over at least part of their axial length.

[0010] The component according to the invention is in particular an input shaft for a dual-clutch transmission.

[0011] The circumferential gearing is preferably a pitch-centered splined gear (external splined gearing). As is known, splined gears, unlike running gears, do not mesh. "Pitch-centered" means that the mating component (e.g., the hub of a shift sleeve or the like) is centered via the pitch circle. Preferably, this circumferential or splined gearing is produced solely by forming (in particular by orbital forming), i.e., without subsequent machining. Traditionally, pitch-centered gearing can only be produced by grinding the pitch circle. Due to the purely forming manufacturing process, the splined gearing exhibits very good strength properties and is highly load-bearing. Furthermore, a relief groove or similar feature for the run-out of cutting tools can be omitted, which further improves the load-bearing capacity. The circumferentially or splined gearing produced by forming...Splined gearing is highly precise and can exhibit a high degree of fit (so-called splined gearing). Circumferential splined gearing can also be a flank-centered splined gear manufactured by forming, in particular by orbital forming.

[0012] The method according to the invention comprises at least the following steps: - Providing a blank made of steel material; - Forming this blank by orbital forming, whereby both the circumferential toothing and a radial cover, in particular the aforementioned ring, are produced essentially simultaneously, such that the circumferential toothing is produced by incremental transverse extrusion and the radial cover or ring is produced by incremental forward or backward extrusion.

[0013] Orbital forming (also known as orbital pressing) is an incremental forming process in which the forming takes place in many small, local forming steps. Orbital forming is performed using an orbital forming tool (orbital die), which is typically installed in an orbital press and consists of a first, upper tool part (upper die) and a second, lower tool part (lower die) that can perform a combined closing and orbiting motion relative to each other. This means that the forming force only acts partially or locally on a specific area of ​​the blank or workpiece being formed, thus successively deforming it. High degrees of deformation can be achieved with relatively low forming forces, and components with good dimensional accuracy and high surface quality can be produced.Reference is made to the patent specifications DE 10 2005 024 908 A1 (in particular .) regarding the technology of orbital forming, which is known in and of itself. Fig. 1) and DE 10 2012 017 525 A1 (in particular Fig. 5) the same applicant. Orbital forming is a bulk forming process.

[0014] According to the invention, orbital forming involves incremental or successive transverse extrusion, i.e., the steel material of the blank or workpiece flows in the orbital die perpendicular to the closing movement, thereby producing the circumferential gearing, preferably with an end contour (especially addendum-centered gearing, which, according to the current state of the art, requires machining, particularly grinding). The circumferential gearing, which functions particularly as a splined connection, can thus be produced by forming with high dimensional accuracy and surface finish. Preferably, it is a addendum-centered splined connection. The orbital die, especially the lower die part, has a negative contour that represents the circumferential gearing to be produced (ideally taking into account process-related elastic deformations of the die).

[0015] According to the invention, orbital forming involves incremental or successive forward or backward extrusion, i.e., the steel material of the blank or workpiece flows in the closing direction (forward extrusion) or against the closing direction or movement (backward extrusion), thereby producing the radial overlap of the teeth. The orbital tool, in particular the lower tool part, also has a negative contour that forms the overlap to be produced.

[0016] The combination of incremental transverse extrusion and incremental forward or reverse extrusion essentially produces the circumferential toothing and the radial overlap that at least partially covers this circumferential toothing simultaneously. "Simultaneously" can be understood to mean, at a minimum, that the complete orbital forming process occurs in a single stroke (forming stroke or closing stroke of the orbital press). Preferably, a stroke or closing stroke lasts only a few seconds, so that cycle times of less than 10 seconds are achievable.

[0017] Orbital forming is preferably a cold forming process. This means that the blank is at room temperature when placed in the orbital die. However, orbital forming can also be carried out in a lukewarm state (up to 300°C) or even a semi-warm state (up to 700°C), which can also be referred to as lukewarm or semi-warm forming.

[0018] After orbital forming, the component produced from the blank essentially has its final contour, which is particularly true for the circumferential gearing. However, it may be necessary to follow the orbital forming with a mechanical, i.e., machining, finishing process, which excludes the circumferential gearing that is difficult or impossible to access. In this process, areas requiring further machining can be brought to their final, ready-to-install contour by turning, deburring, milling, drilling, and similar operations.

[0019] The process design for the method according to the invention can include, among other things, the design of the blank or raw part geometry and the tool design of the wobble tool.

[0020] The blank should have a shape or geometry that is favorable for orbital forming, yet relatively simple. Preferably, the blank is first forged, particularly hot forging (at a temperature of approximately 850°C to 1200°C), into a preform suitable for orbital forming. This preform may, for example, already have a pre-contour of the cover or ring to be produced. Forging is preferably carried out on a horizontal high-speed forging press. The forging may be followed by heat treatment to achieve a desired microstructure and / or cleaning (e.g., by shot blasting), particularly to remove scale.

[0021] The preferred and also inventive tool design provides that the orbital forming tool used for orbital forming has a first (typically upper) tool part and a second (typically lower) tool part, which enclose or circumscribe a cavity defining the component shape. This cavity comprises an inner cavity section formed with a negative contour of the circumferential toothing to be produced on the component. This cavity further comprises an outer cavity section concentrically surrounding the inner cavity section, which is formed with a negative contour of the concentric cover or ring to be produced (for covering the circumferential toothing). Between these cavity sections is an annular collar, which is formed with a circumferential lead-in chamfer or lead-in rounding towards the outer cavity section.

[0022] The invention is explained in more detail below by way of example and in a non-limiting manner with reference to the figures. The features shown in the figures and / or explained below can, even independently of specific combinations of features, be general features of the invention and further develop the invention. Fig. Figure 1 shows a component according to the invention in a half section. Fig. Figure 2 shows a half-section of a blank for manufacturing the component. Fig. 1. Fig. Figure 3 shows a sectional view of a wobble tool according to the invention for manufacturing the component made of Fig. 1 with the blank made of Fig. 2. Fig. Figure 4 illustrates the process chain for manufacturing the component from Fig. 1.

[0023] Fig. Figure 1 shows a component 200 according to the invention, wherein it is an input shaft for a dual-clutch transmission, as shown in a similar embodiment in DE 10 2007 031 963 A1. The component 200, formed in one piece from case-hardening steel or special gear steel M, is rotationally symmetrical with respect to its longitudinal or rotational axis L and has a plate-like flange or flange disc 210 at one axial end, which projects in the radial direction R beyond a central, i.e., mid-mounted, pin 220. The pin or shaft section 220 is formed on the flange side with circumferential teeth 230 functioning as a splined connection. A circumferential toothing is understood to be an external toothing formed circumferentially on a cylindrical section of the pin 220. (The circumferential toothing 230 can, for example, also be conical.) The component orThe shaft 200 further features a ring 240 projecting axially L from the flange 210, concentrically surrounding the journal 220 and radially covering the circumferential teeth 230 over at least part of their axial length, thus making them difficult to access. The sealing lip of a shaft seal (RWDR) runs on the outer circumferential surface of the ring 240; the ring 240 could therefore also be described as a sealing ring. The teeth 230 are thus located in an area that is at least partially or sectionally covered by the ring 240 and is therefore difficult to access. Due to its radial overlap, the teeth 230 can also be described as embedded teeth, specifically as interlocking teeth.

[0024] According to the invention, component 200 is a one-piece formed part made of a steel material M, which is made from the in Fig. 2 reduced-size solid blank 100 by wobble forming in the in Fig. The workpiece is produced using the schematically shown wobble tool 300. The blank or raw part 100 is formed into the simple preform shown, particularly by forging. In principle, however, the blank 100 could also be a turned part or similar.

[0025] The orbital tool 300, installed in an orbital press (not shown), has a first punch-like upper tool part 310 and a second die-like lower tool part 320, which enclose a cavity 330 between them. As indicated by the arrow T, the upper tool part 310 can perform an orbital movement (the orbit angle is, for example, up to 2°), whereas the lower tool part 320 can perform a feed or closing movement in the direction of the upper tool part 310, as illustrated by the arrows F. The blank 100, previously inserted into the cavity 330, is thereby incrementally enlarged to the size in the Fig. The component shown in section 1 was reshaped by 200.

[0026] The cavity 330 of the orbital tool 300 has an inner cavity section 332, which is formed with a negative contour of the circumferential toothing 230 to be produced, and an outer cavity section 334, which is formed with a negative contour of the concentric ring 240 to be produced. During orbital forming, incremental transverse extrusion occurs in cavity section 332, whereby the steel material M of the blank 100 flows transversely to the closing movement F, thereby producing the circumferential toothing 230 in the inner area. Simultaneously, incremental reverse extrusion occurs in cavity section 334, whereby the steel material M of the blank 100 flows opposite to the closing movement F, thereby producing the ring 240 in the outer area.

[0027] The ring 240 forming the cover or cover and the circumferential toothing 230 thereby concealed and thus arranged in an undercut are thus produced simultaneously by orbital forming in the orbital tool 300. The toothing 230 extends to the flange 210 without a relief groove or the like (see Fig. 1), which has a positive effect on the mechanical strength of component 200. As a result, component 200 can be made smaller and lighter than previously possible. The finished component 200 can be ejected using the ejector 340 when the tool 300 is open. At least the toothing 230 has a final contour, meaning that no further mechanical machining of the toothing 230 is required. However, other areas of component 200, such as the flange 210 and especially the ring 240, particularly its outer circumferential surface, can be mechanically machined.

[0028] The two cavity sections 332 and 334 are located in the lower tool part 320, with the inner cavity section 332 being concentrically surrounded by the outer cavity section 334. During orbital forming, the collar or wall area 324 between the cavity sections 332 and 334 is supported and stabilized by the blank or workpiece material M located in the outer cavity section 334. The failure-critical collar 324 is further relieved of stress radially outwards by the circumferentially formed entry chamfer 325 (or alternatively, an entry slope) on the outer cavity section 334. This significant chamfer 325 results in a slight compressive stress state during orbital forming. During forming, compressive stresses are generated by the chamfer 325 and by the reinforcement (su) in the collar 324. The 325 inlet rounding therefore acts almost like an indirect reinforcement.Furthermore, by means of a targeted blank design (blank geometry), a favorable control of the material flow can be achieved during forming, thereby further relieving the collar 324, so that this tool area is subjected to as little stress as possible.

[0029] The non-wobbling lower tool part 320 is multi-part and comprises an outer part 321, an inner part 322, and a central part 323, each of which is ring-shaped. The parts 321, 322, and 323 form a composite. (Reinforcement is primarily provided by a machine-side reinforcement composite that surrounds and radially supports the lower tool part 320.) The particularly stressed and therefore replaceable central part 323 includes, among other things, the inner cavity section 332 and the collar 324, including the leading edge 325 formed thereon. The leading edge 325 can have a radius of curvature of at least 2.5 mm and preferably at least 5.0 mm. An alternative leading edge chamfer can have a preferred length of at least 2.5 mm and preferably at least 5.0 mm.

[0030] Based on the Fig. 4. The essential steps for producing the product will now be described. Fig.The steps of the shaft component 200 shown in Figure 1 are explained, although not all of these steps are the subject of the claimed method. Furthermore, additional, undescribed steps and intermediate steps may be provided.

[0031] First, the blank 100 is produced by forging, in particular by horizontal high-speed forging (10). The blank 100, which has a simple and suitable preform or initial shape, is heat-treated after forging to obtain a desired strength or a specific microstructure (20). After heat treatment, the blank 100 is cleaned, e.g., by shot blasting (30). The cleaned blank 100 is heated, if necessary, before orbital forming and coated with a lubricant (40). The lubricated blank 100 is then placed cold, lukewarm, or semi-warm into the cavity 330 of the orbital forming tool 300 and formed into the component 200 in a single forming stroke by orbital forming or orbital pressing (50). The component 200, which essentially has its final shape or at least is close to its final shape, is removed from the wobble tool 300 and optionally machined mechanically, i.e. by cutting, to obtain the final shape ready for installation (60).

[0032] This new manufacturing method involves significantly fewer steps in multi-part production, is faster, less complex, and more environmentally friendly (e.g., due to reduced material and machining costs). Furthermore, it achieves cost optimization (including in terms of equipment investment) and improved component quality, particularly gear quality. Reference symbol list 10 Process step 20 Process step 30 Process step 40 Process step 50 Process step 60 Process step 100 blanks 200 components (shaft) 210 flange 220 cones 230 circumferential gearing 240 rings 300 wobble tools 310 first tool part 320 second tool part 321 Outdoor part 322 Inner part 323 Middle section 324 Bund 325 Rounding, Bevel 330 Cavity 332 Cavity section 334 Cavity section 340 ejectors F Closing movement L Longitudinal axis M steel material O zero point of tumbling R radial direction T wobble motion

Claims

[1] Component (200), in particular gear or shaft, for power transmission in the drive train of a motor vehicle, with at least partially concealed circumferential teeth (230), characterized by , that this is a one-piece formed part made from a steel material (M), wherein the component (200) is rotationally symmetric, with: - a central pin (220) on which the circumferential teeth (230) are formed; - a plate-like flange (210) molded onto the pin (220); and - a ring (240) formed on the flange (210) and projecting in the axial direction (L), which concentrically surrounds the pin (220) and radially covers the circumferential teeth (230) over at least part of their axial length. [2] Component (200) according to claim 1, characterized by , that the circumferential toothing (230) is a pitch circle centered or flank centered splined toothing. [3] Method for manufacturing a component (200) according to any one of the preceding claims 1 to 2, comprising the steps: - Providing a blank made of steel material (M) (100); - Forming the blank (100) by orbital forming, wherein both the circumferential toothing (230) and a radial cover (240) are produced essentially simultaneously, such that the circumferential toothing (230) is produced by incremental transverse extrusion and the radial cover (240) is produced by incremental forward or backward extrusion. [4] Method according to claim 3, characterized by that the wobble forming takes place in one stroke. [5] Method according to claim 3 or 4, characterized by that wobble forming is a cold forming process. [6] Method according to claim 3 or 4, characterized by that wobble forming is a lukewarm or semi-warm forming process. [7] Method according to any one of claims 3 to 6, characterized by, that the orbital forming process is followed by a mechanical finishing process. [8] Method according to any one of claims 3 to 7, characterized by , that the blank (100) is first brought into a preliminary form by forging. [9] Wobble tool (300) for manufacturing a component (200) according to one of claims 1 to 2, in particular with a method according to one of claims 3 to 8, comprising a first tool part (310) and a second tool part (320) enclosing a cavity (330) between them, characterized by, that the cavity (330) has an inner cavity section (332) which is formed with a negative contour of the circumferential toothing (230) to be produced, and an outer cavity section (334) concentrically surrounding the inner cavity section (332) which is formed with a negative contour of a concentric ring (240) to be produced, wherein an annular collar (324) is arranged between these cavity sections (332, 334) which is formed with a circumferential lead-in chamfer or lead-in rounding (325) towards the outer cavity section (334).

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