Method for manufacturing a gearbox

Abstract

Method for manufacturing a gearbox (1) with a gear arrangement comprising at least a first gear (3) and a second gear (5) which are in mesh (ZE) with each other in an assembly position (ZSB) in the gearbox (1), wherein the method comprises gear machining (V) for pre-machining the gears (3, 5), finishing machining (F) and final assembly (EM) in which the two gears (3, 5) are installed in the gearbox (1) in an assembly position (ZSB), wherein the finishing machining (F) takes place prior to the final assembly (EM), wherein the gears (3, 5) are used as an identical gear pair in both final assembly (EM) and finishing (F) with identical tooth engagement (ZE) P , ZE) or identical assembly position (ZSB) P , ZSB) are ordered, and wherein in the finishing process (F) the two gears (3, 5) are wetted with an abrasive medium, and wherein the abrasive medium is added to a carrier fluid (G) as an additive, and wherein in the finishing process (F) the carrier fluid (G) with additive wets the gears (3, 5), and wherein by adding further additives to the carrier fluid (G) the abrasive particles of the abrasive medium chemically decompose after completion of the finishing process (F).

Description

[0001] The invention relates to a method for manufacturing a transmission with a gear arrangement according to claims 1 or 3.

[0002] An exemplary gear manufacturing process can be carried out in an automated process chain, in which a gear blank made of hardenable steel in its soft state is first provided. A tooth profile is milled into this blank, forming the gear. This is followed by hardening. The hardened gear then undergoes hard machining, in which, among other things, a flank allowance is removed from the tooth profile. This is done, for example, by gear grinding, where the material removal can range from 50 to 100 µm, or by gear honing, where the material removal can range up to 60 µm. The gear quality can be improved by a subsequent finishing process.

[0003] In finishing, the surface quality of the gear teeth is improved by mechanically removing roughness peaks in the surface microstructure. Finishing can be implemented as a fine grinding process, where material removal can be less than 5 µm. Finishing reduces minute geometric deviations and / or waviness in the gear teeth, which can cause noise during transmission operation and thus reduce comfort for vehicle occupants.

[0004] DE 481 762 A discloses a method for grinding gear flanks on gears. DE 10 2016 009 469 A1 discloses a method for hard-finishing internally toothed gears. DE 2 162 294 A discloses a gear lapping or testing machine. DE 42 11 515 A1 discloses a method for lapping gears. EP 3 139 228 A2 discloses a method for manufacturing a workpiece with teeth.

[0005] From DE 10 2016 223 058 A1, a gear pair with a gear having a surface structure, a transmission with a gear pair, and a method for manufacturing a gear are known. US 2003 / 0 040 264 A1 discloses a gear as well as a method and a device for finishing a tooth surface of a gear. From EP 2 682 327 A2, an electric power steering system is known. Reference is also made to NIEMANN, G.; WINTER, H.: Machine Elements. Volume 2: Transmissions in General, Gear Transmissions - Fundamentals, Spur Gear Transmissions. Second, completely revised edition. Heidelberg: Springer, 2003. Title page + Imprint + p. 241. ISBN 978-3-662-11874-0 and to KLINGELNBERG, Jan: Bevel Gears: Fundamentals, Applications. Heidelberg: Springer, 2008. Title page + imprint + pp. 329-336. ISBN 978-3-540-71859-8.

[0006] The object of the invention is to provide a method for manufacturing a transmission in which noise generation from meshing gears is reduced in a manufacturing-technically simple manner during driving operation.

[0007] The problem is solved by the features of claim 1 or 3. Preferred embodiments of the invention are disclosed in the dependent claims.

[0008] The invention relates to a process sequence by which a gear can be manufactured in which a gear pair consisting of a first gear and a second gear are meshed with each other in an assembled position. The two gears are pre-machined in a gear cutting process and then fine-machined in a finishing process.

[0009] According to a first embodiment of the invention, specifically according to claim 1, the gears are arranged as an identical gear pair in both final assembly and finishing, with identical tooth engagement or identical assembly position. According to this first embodiment, the finishing process takes place prior to final assembly. During finishing, the two gears are wetted with an abrasive medium, wherein the abrasive medium is added to a carrier fluid as an additive. During finishing, the carrier fluid with the additive wets the gears. Furthermore, by adding additional additives to the carrier fluid, the abrasive particles of the abrasive medium chemically decompose after finishing.

[0010] According to a second embodiment of the invention, namely according to claim 3, the final assembly of the gears in the transmission is carried out prior to the finishing process, so that the finishing process is performed with the gears already installed in the transmission in the assembled position. To conclude the finishing process, a washing operation is carried out in the transmission assembly line to remove an abrasive medium or the wear debris. In the finishing process, the two gears are wetted with an abrasive medium, and the abrasive medium is added to a carrier fluid as an additive. During the finishing process, the carrier fluid with the additive wets the gears, and by adding further additives to the carrier fluid, the abrasive particles of the abrasive medium chemically decompose after the finishing process.

[0011] In the finishing process according to the first and second embodiments of the invention, component and manufacturing tolerances that only become apparent in the assembled position or in the meshing position of the two gears are compensated for. The finishing process is carried out taking into account the interaction with the other gear in the assembled position. During the finishing process, the geometric conditions of the gear pair in meshing and / or in the assembled position are considered. Furthermore, the finishing process can be performed without an external finishing tool and can therefore be easily integrated into an automated process chain for manufacturing the gearbox.

[0012] According to the first and second embodiments of the invention, the finishing process following gear machining is no longer performed separately for each of the two gears. Instead, a joint finishing process is carried out for both gears. During this joint finishing process, the first and second gears are arranged in their assembled position and wetted with an abrasive medium containing abrasive particles. A running-in process then begins, during which the gears rotate and roll against each other in their assembled position. In this way, the abrasive medium creates wear on the tooth flanks, thereby improving the surface quality of the tooth flanks.

[0013] According to the first and second embodiments of the invention, the abrasive medium is added as an additive to a carrier fluid, in particular a gear oil. In this case, the carrier fluid with the added abrasive medium wets the gears during the finishing process. In a comparative embodiment not covered by the invention, the abrasive medium can be a component of a gear coating. In this case, a coating process step precedes the finishing process, in which the first and / or the second gear is coated with the gear coating. After the coating process step has been completed, the two gears are positioned in the assembled position and / or brought into meshing. The running-in process then begins.

[0014] In mass production, finishing can be carried out in a finishing station of a gearbox assembly line, while the final assembly of the gears in the gearbox takes place in a final assembly station.

[0015] In a first embodiment, the finishing station can include a test stand in which the two gears are mounted in their assembled position. The running-in process then begins, during which the gears, mounted in their assembled position, rotate and roll against each other, thereby improving the tooth flank surface quality and generating tooth flank abrasion. After completion of the finishing process, the gears are transferred to the final assembly station, where the two finished gears are finally assembled in the gearbox.

[0016] According to the second embodiment of the invention, the final assembly station in the gearbox assembly line is integrated upstream of the finishing station. In this case, the final assembly of the gears in the gearbox takes place before the finishing process. After final assembly, the gearbox with the gears installed is transferred to the finishing station. In the finishing station, the gears installed in the gearbox are lubricated with the carrier fluid to which the abrasive medium (i.e., abrasive particles) has been added. The running-in process then begins, during which the first and second gears in the gearbox rotate and roll against each other. The resulting tooth flank abrasion is carried away from the tooth engagement point via the gearbox oil.

[0017] According to the second embodiment according to the invention, after completion of the finishing process in the finishing station, the washing process takes place, for example with a gear oil change, in order to remove the gear oil containing abrasive medium or tooth flank abrasion from the gearbox.

[0018] To perform the running-in process, one of the gears can be driven by a power source. The other gear can be driven by a braking torque. The braking torque can be varied over the running-in period to control the finishing process.

[0019] Exemplary embodiments of the invention are described below with reference to the accompanying figures.

[0020] They show: Fig. 1 a roughly schematic block diagram illustrating a first process chain for the manufacture of a gearbox; Fig. 2 in a view according to the Fig. 1. a second process chain for the manufacture of a gearbox; and Fig. 3 a view according to the Fig. 1, a process chain known from the prior art for the manufacture of a gearbox.

[0021] For the sake of a simpler understanding of the invention, reference is first made to the Fig. Figure 3 illustrates a process chain for manufacturing a gearbox 1 that is known from the prior art. The figure in the Fig. Gearbox 1 shown in Figure 3 has a gear pair consisting of a first gear 3 and a second gear 5, which are in tooth mesh ZE in an assembly position ZSB.

[0022] The two gears 3 and 5 are manufactured from semi-finished gear products 7 and 9 made of hardenable steel in a gear machining operation V. The two semi-finished gear products 7 and 9 are milled to form the teeth. This is followed by hardening. The hardened gears 3 and 5 are then subjected to hard machining, in which, among other things, a flank allowance is removed from the respective teeth, for example by gear grinding or gear honing.

[0023] The pre-machined gears 3 and 5 are transferred to a finishing station F in the next stage of the process. In finishing station F, roughness peaks in the surface microstructure of the gear teeth are mechanically removed, thereby increasing the surface finish Rz of the gear teeth 3 and 5. After completion of finishing at station F, the gears 3 and 5 are transferred to a final assembly station EM, where they are installed in the gearbox 1 in the assembly position ZSB.

[0024] In the Fig. In the finishing station F, the two gears 3 and 5 are machined separately. In contrast, in the Fig. In the process chain shown in section 1, both gears 3 and 5 undergo a joint finishing operation F. Fig. 1. The gear machining V of gears 3, 5 can be carried out identically to the process chain known from the prior art ( Fig. 3) are carried out. For the joint finishing process, the finishing station F has a test stand 11 in which the first and second gears 3, 5 are in a test assembly position ZSB. P to be assembled, which is identical to the assembly status ZSB in gearbox 1.

[0025] In test stand 11 of the finishing station F, the gears 3, 5 are brought into tooth engagement ZE at rotary bearing points 13, 15 and in the assembly position ZSB P The two gears 3 and 5 are assembled. To prepare for finishing, they are lubricated with gear oil G containing an abrasive medium. A running-in process then begins, during which gear 3 is driven by a test bench electric motor 17, causing the two gears 3 and 5 to rotate and mesh against each other. During the running-in process, the abrasive medium in the gear oil G causes tooth flank abrasion, increasing the tooth flank surface quality Rz.

[0026] The two finished gears 3 and 5 are used in the Fig. 1 is transferred to the final assembly station EM in the further course of the process, where it is installed in gearbox 1.

[0027] In the Fig.Figure 2 shows an alternative process chain for the manufacture of the gearbox 1, in which the final assembly station EM is upstream of the finishing station F. Accordingly, immediately after gear machining V, the two gears 3 and 5 are installed in the gearbox 1 in their assembled position ZSB at the final assembly station EM. The gearbox 1, with gears 3 and 5 installed, is then transferred to the finishing station F. At the finishing station F, gearbox oil G containing an abrasive medium is supplied to the gearbox 1. The running-in process then begins, during which gear 3 is driven by the electric motor 17, causing the two gears 3 and 5 to roll against each other. The resulting tooth flank abrasion is carried away from the tooth engagement point ZE by the gearbox oil G.

[0028] At the end of the break-in process, a gear oil change is carried out in the finishing station F to remove the gear oil G, which contains abrasive medium and tooth flank abrasion, from the gearbox 1.

Claims

[1] Method for manufacturing a gearbox (1) with a gear arrangement comprising at least a first gear (3) and a second gear (5) which are in gear mesh (ZE) in the gearbox (1) in an assembly position (ZSB), wherein the method comprises gear machining (V) for pre-machining the gears (3, 5), finishing machining (F) and final assembly (EM) in which the two gears (3, 5) are installed in the gearbox (1) in an assembly position (ZSB), wherein the finishing machining (F) takes place prior to the final assembly (EM), wherein the gears (3, 5) are used as an identical gear pair in both final assembly (EM) and finishing (F) with identical tooth engagement (ZE) P , ZE) or identical assembly position (ZSB) P , ZSB) are ordered, and wherein in the finishing process (F) the two gears (3, 5) are wetted with an abrasive medium, and wherein the abrasive medium is added to a carrier fluid (G) as an additive, and wherein in the finishing process (F) the carrier fluid (G) with additive wets the gears (3, 5), and wherein by adding further additives to the carrier fluid (G) the abrasive particles of the abrasive medium chemically decompose after completion of the finishing process (F). [2] Method according to claim 1, characterized by , that the finishing machining is carried out in a finishing machining station (F) of a gearbox assembly line, and that in the finishing machining station (F) the two gears (3, 5) are in a test assembly position (ZSB) P ) as well as in the test tooth engagement (ZE) P ) are assembled and a running-in process is then started, and that after completion of the finishing process the final assembly (EM) takes place, in which the two gears (3, 5) are installed in the gearbox (1) with tooth engagement (ZE) and in the assembly position (ZSB). [3] A method for manufacturing a gearbox (1) with a gear arrangement comprising at least a first gear (3) and a second gear (5) which are in mesh (TE) with each other in an assembled position (ZSB) in the gearbox (1), wherein the method comprises gear machining (V) for pre-machining the gears (3, 5), finishing machining (F) and final assembly (EM) in which the two gears (3, 5) are installed in the gearbox (1) in an assembled position (ZSB), and wherein the final assembly (EM) of the gears (3, 5) in the gearbox (1) is carried out prior to the finishing machining (F), so that the finishing machining (F) is carried out with the gears (3, 5) already installed in the gearbox (1) in an assembled position (ZSB), wherein a washing process is carried out in the gearbox assembly line at the end of the finishing machining (F) to remove an abrasive medium or wear debris, wherein in the finishing machining (F) the two gears (3,5) be moistened with the abrasive medium, and, wherein the abrasive medium is added to a carrier fluid (G) as an additive, and wherein in the finishing process (F) the carrier fluid (G) with additive wets the gears (3, 5), and wherein by adding further additives to the carrier fluid (G) the abrasive particles of the abrasive medium chemically decompose after completion of the finishing process (F). [4] Method according to claim 3, characterized by that the washing process is a carrier fluid change or a transmission oil change. [5] Method according to any one of the preceding claims, characterized by , that in the finishing process (F) the surface quality (Rz) of the tooth flanks of the two gears (3, 5) is increased by mechanically removing roughness peaks in the surface microstructure of the tooth flanks. [6] Method according to any one of the preceding claims, characterized by, that in the finishing process (F) a running-in process takes place in which the two gears (3, 5) rotate and roll against each other, thereby generating abrasion and increasing the tooth flank surface quality (Rz). [7] Method according to claim 6, characterized by , that in the running-in process one of the gears (3, 5) is driven as a drive gear by a drive source (17), while the other gear is subjected to a braking torque as an output gear, and that the braking torque varies over a running-in period. [8] Method according to any one of the preceding claims, characterized by , that in the finishing process (F) a targeted influence on properties takes place, i.e. of pressure, temperature or solution properties.

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