Method and tool for manufacturing a bevel gear

Abstract

Method comprising the following process steps: machining of a spur or helical bevel gear (4, 6) using a rotating tool (22), wherein teeth (8, 38) of the bevel gear (4, 6) are machined in a semi-completing process using the tool (22), in which the left flanks (32) and the right flanks (34) are each machined in a separate feed using the tool (22), wherein the teeth (8, 38) of the bevel gear (4, 6) are machined by rolling using the tool (22), wherein left flanks (32) of the teeth (8, 38) of the bevel gear (4, 6) are machined with a geometry-generating plane (24) of the rotating tool (22), wherein right flanks (34) of the teeth (8, 38) of the bevel gear (4, 6) are machined with the same geometry-generating plane (24) of the rotating (32) tool (22) is machined with which the left flanks are also machined,and wherein the geometry-generating plane (24) of the rotating tool (22) is oriented perpendicular to an axis of rotation (28) about which the tool (22) rotates.

Description

[0001] The present invention relates to a method and a tool for producing a straight-toothed bevel gear or a helical-toothed bevel gear.

[0002] Bevel gears or bevel gear pairs are used to transmit speeds and torques between mutually inclined shafts and, if necessary, convert them with an appropriate gear ratio or reduction. A bevel gear pair consisting of a ring gear and pinion is therefore considered an angular gear.

[0003] Bevel gears can be differentiated, among other things, by the type of their flank longitudinal line—namely, straight-toothed, helical-toothed, or spiral-toothed bevel gears. Spiral-toothed bevel gears include, for example, circular-arc bevel gears and, in particular, epicycloidal bevel gears. The present invention does not relate to spiral-toothed bevel gears, but rather to straight-toothed or helical-toothed bevel gears.

[0004] The present invention is based on the technical problem of providing an efficient method for producing a straight-toothed or helical bevel gear. Furthermore, a tool for producing a straight-toothed or helical bevel gear is to be provided.

[0005] The technical problem described above is solved according to the features of the independent claims. Further embodiments of the invention emerge from the dependent claims and the following description.

[0006] According to the invention, a method is specified with the method steps: machining a straight-toothed or helical-toothed bevel gear by means of a rotating tool, wherein teeth of the bevel gear are machined individually by means of the tool in a semi-completing process in which the left-hand flanks and the right-hand flanks are each machined in a separate infeed by means of the tool, wherein the teeth of the bevel gear are machined by means of the tool in a rolling manner, wherein left-hand flanks of the teeth of the bevel gear are machined with a geometry-generating plane of the rotating tool, wherein right-hand flanks of the teeth of the bevel gear are machined with the same geometry-generating plane of the rotating tool with which the left-hand flanks are machined, and wherein the geometry-generating plane of the rotating tool is oriented perpendicular to a rotation axis about which the tool rotates.

[0007] Investigations by the applicant have shown that a straight-toothed or a helical-toothed bevel gear, provided the above-mentioned conditions of semi-completing in the single-part process with rolling movement are met, can be produced with a comparatively simple tool geometry of a tool whose plane causing the chip removal, i.e. the plane generating the geometry, is a plane perpendicular to the tool rotation axis.

[0008] The present invention relates to straight-toothed bevel gears or helical-toothed bevel gears. Spiral-toothed bevel gears, which include in particular circular-toothed and cycloidal-toothed bevel gears, cannot be produced using the method and tool according to the invention. Conversely, the method according to the invention cannot be replicated using tools or methods for producing spiral-toothed bevel gears, since these methods and tools cannot produce straight-toothed or helical-toothed bevel gears within the meaning of this invention.

[0009] In the following, some definitions of terms for features of claim 1 are introduced, with the definitions of terms being explained in the order in which they appear in claim 1.

[0010] As mentioned at the beginning, the term "straight tooth" describes the shape of a particular tooth flank's longitudinal line, which in this case is a straight line. However, even spur gears can be modified to optimize the contact pattern of a particular gear. A classic example of such modifications is longitudinal crowning and vertical crowning, which serve to prevent edge wear.

[0011] The term "helical" also means that the shape of each flank's longitudinal line is straight. As is known from helical gear technology for helical gears, the teeth of helical bevel gears also exhibit a helix angle. Helical bevel gears can have modifications, such as the aforementioned crowning.

[0012] The term "bevel gear" as used in this text means that the bevel gear is part of a bevel gear pairing that, as an angular gear, is suitable for transmitting and converting torques and speeds between mutually inclined axes. A bevel gear pairing is not a face coupling.

[0013] The term "single-part" means that the teeth of the bevel gear are manufactured using a single-part process. The word "single-part process" is composed of the terms "single," "tooth pitch," and "process"—which suggests that the pitch of each gear tooth is individually machined into a given workpiece.

[0014] In the single-part process, the individual teeth or tooth gaps of the bevel gear are manufactured separately from one another in succession, each in at least one separate infeed of the tool. This means that to produce a tooth gap, the tool penetrates this tooth gap of the bevel gear workpiece in question one or more times and is infeeded to the intended tooth depth. The tool is then withdrawn from the tooth gap that has just been produced, the bevel gear workpiece is rotated by one tooth pitch (pitch rotation), and the process described above of infeeding to the intended tooth depth one or more times is repeated for the next tooth gap. Regardless of the number of infeeds per tooth gap, the single-part process is particularly characterized by the fact that only one tooth gap is machined per infeed, and no further tooth gap is machined during this time.

[0015] In contrast, the continuous indexing process is characterized by the fact that the bevel gear being machined performs a continuous indexing movement during machining. This continuous indexing movement is coupled with the rotation of a tool that removes the chips, so that the tool makes individual cuts at successive tooth gaps on the bevel gear being machined. The bevel gear being machined therefore rotates continuously and repeatedly around its own axis during continuous chip removal until the tool has created the full tooth depth on the bevel gear. The tool is therefore continuously in cutting contact with the bevel gear being machined.

[0016] The invention is limited to the single-part process. Continuous partial processes are not suitable for replicating the process according to the invention.

[0017] The term "semi-completing" means, as already stated in claim 1, that the left flanks and the right flanks are each finished by the tool in a separate infeed. In contrast, in the completing process, the left flanks and the right flanks of a respective tooth gap are finished simultaneously in a single infeed.

[0018] The invention is limited to semi-completion. Completion methods are not suitable for replicating the method according to the invention.

[0019] The term "rolling" means that the method according to the invention is a rolling process. In the rolling process, the tooth gaps of the pinion and ring gear of a bevel gear pair are each created in rolling processes.

[0020] In contrast, in the so-called forming or plunging process, the tooth gaps of the ring gear are produced only by plunging the rotating tool into the workpiece without a rolling movement, whereas the pinion gaps are produced in a special rolling process with the tool inclined to the rolling axis.

[0021] While in the plunge cutting process the profile shape of the tool is transferred to the tooth flanks, in the generating process, in which the tool and workpiece move relative to each other according to a certain law, the tooth flanks are created by enveloping cuts or as a result of the rolling relative kinematics - similar to the hobbing or generating grinding known from spur gear technology.

[0022] The invention is limited to rolling processes. Immersion processes are not suitable for replicating the process according to the invention.

[0023] The machining of the straight-toothed or helical-toothed bevel gear using the rotating tool includes both the machining of a pre-toothed bevel gear that already has tooth gaps that are further machined, and the machining of a non-pre-toothed blank in which tooth gaps are introduced for the first time or on which tooth gaps are created for the first time.

[0024] It can be provided that the machining comprises producing the teeth by milling, wherein the tool is a milling tool with a geometrically defined cutting edge. Such geometrically defined cutting edges can be mounted on the tool, for example, as replaceable bar blades or cutting plates.

[0025] According to one embodiment of the method, it is provided that the machining comprises a fine machining of the teeth by grinding, wherein the tool is a grinding tool with a geometrically undefined cutting edge.

[0026] The grinding tool can be a dressable grinding tool. When referring to a dressable grinding tool in this case, it refers, for example, to a vitrified bonded grinding tool. Alternatively, the dressable grinding tool can be a tool with a synthetic resin bond, for example. The dressable grinding tool can contain one or more of the following abrasive grain materials: quartz, corundum, emery, garnet, diamond, cubic boron nitride (CBN), or silicon carbide.

[0027] The grinding tool can be a non-dressable grinding tool.

[0028] When machining bevel gears using a non-dressable grinding tool, each bevel gear in a series to be produced is always machined with the same tool geometry and process kinematics. Compared to dressable tools, the diameter or overall geometry of the non-dressable grinding tool does not change during the machining of the series of bevel gears to be produced, as no dressing processes take place. Therefore, the straight-toothed bevel gears produced with such a non-dressable grinding tool always have the same final geometry.

[0029] The non-dressable grinding tool can be, for example, an electroplated CBN grinding tool or a diamond grinding tool. Non-dressable CBN grinding tools have, for example, a steel base coated with CBN crystals. The abbreviation CBN is derived from the English term "cubic boron nitrite."

[0030] A radius of the tool can be greater than or equal to three times the tooth width of the teeth of the bevel gear.

[0031] In particular, it can be provided that the tool does not perform any lifting movement in the tooth width direction during machining.

[0032] It can be provided that a radius of curvature of a tooth of the bevel gear is generated in the tooth root base, which corresponds to a radius of the tool.

[0033] The bevel gear can be a pinion or a ring gear of a bevel gear pair, wherein a relative kinematics for the pinion and the ring gear carried out between the tool and the tool during the machining has been calculated based on generating face gears with the same pitch cone length, in particular that for the calculation a respective virtual face gear for the pinion is set to an associated root cone of the pinion and a respective virtual face gear for the ring gear is set to an associated root cone of the ring gear.

[0034] The virtual face gears used to calculate the relative kinematics for the pinion and the ring gear are not the same.

[0035] The pairing of pinion and ring gear is not a conjugated toothing.

[0036] According to one embodiment of the method, it is provided that a tooth root of the respective teeth of the bevel gear has a curvature in the finished state. As already mentioned above, it can be provided, in particular, that a radius of curvature in the tooth root corresponds to a radius of the tool.

[0037] It can be provided that the teeth of the bevel gear do not have a constant tooth height in the finished state. In particular, the teeth have a tooth height that decreases from an outer diameter to an inner diameter of the bevel gear. Accordingly, the bevel gear has a root cone angle that differs from the tip cone angle.

[0038] The teeth of the bevel gear may have modifications in the finished machined state, such as twisting, longitudinal crowning, vertical crowning or the like.

[0039] It can be provided that the twist and / or longitudinal crowning are generated by setting a respective virtual face gear for the pinion to an associated root cone of the pinion for calculating the manufacturing kinematics, and setting a respective virtual face gear for the ring gear to an associated root cone of the ring gear, with the root cones having different root cone angles. The virtual face gears used to calculate the relative kinematics for the pinion and the ring gear are not the same.

[0040] According to the invention, a tool for machining a straight-toothed or helical-toothed bevel gear is specified, wherein the tool is designed for use in a method according to the invention, wherein the tool has a geometry-generating plane, wherein the geometry-generating plane is oriented perpendicular to a rotation axis of the tool.

[0041] The invention is explained in more detail below with reference to a drawing illustrating exemplary embodiments. The drawings schematically show: Fig. 1 a bevel gear pair in a sectional view; Fig. 2 a straight-toothed ring gear in a plan view; Fig. 3 a helical gear in a plan view; Fig. 4 Tool in a sectional view; Fig. 5 the tool Fig. 4 in a perspective view with a tooth of the ring gear from Fig. 2; Fig. 6 the tool Fig. 4 when producing a right flank of the tooth from Fig. 5; Fig. 7 the tool Fig. 4 when producing a left flank of the tooth from Fig. 5; Fig. 8 the tool Fig. 4 in a side view with the pinion of the bevel gear pair; Fig. 9 a flow chart of a method according to the invention.

[0042] Fig. Figure 1 shows a cross-sectional view of a bevel gear pair 2 forming an angular gear. The bevel gear pair 2 is designed to transmit speeds and torques between two rotating shafts that are inclined at a 90° angle to each other.

[0043] The bevel gear pair 2 has a pinion 4 and a crown gear 6. The pinion 4 has a head cone 1 and a root cone 3. The crown gear 6 has a head cone 5 and a root cone 7

[0044] In Fig. 1 shows a detail Z as an enlarged detail, in which it can be seen that teeth 8 of the bevel gear pair 2 do not have a constant tooth height. Thus, a tooth height H1 in the area of ​​an outer-diameter heel 10 of a respective tooth 8 of the ring gear 6 is greater than a tooth height H2 in the area of ​​an inner-diameter toe 12 of the respective tooth 8 of the ring gear 6.

[0045] The teeth 8 of the bevel gear pair 2, as they can be produced using the method according to the invention described in more detail below, can be designed as straight teeth.

[0046] Fig. 2 shows schematically and exemplarily the ring gear 6 in a plan view for the example of straight teeth 8. How Fig. 2, flank longitudinal lines 14 of the teeth 8 are according to Fig. 2 as a straight line, which points to a center point or a rotation axis 16 of the representation of the ring gear 6 according to Fig. 2 are directed.

[0047] Such a flank longitudinal line 14 is also shown schematically in Fig. 1 - namely in the enlarged detail Z of the Fig. 1. Next, a tooth width B is measured on the pitch cone 18 along this flank longitudinal line 14.

[0048] The teeth 8 of the bevel gear pair 2, as they can be produced using the method according to the invention described in more detail below, can be designed as helical gearing. Fig. 3 shows schematically and exemplarily the ring gear 6 in a plan view for the example of helical teeth 8. How Fig. 3, the flank longitudinal lines 14 of the teeth 8 are shown in Fig. 3 are formed as straight lines, which, however, in comparison to Fig. 2 have a helix angle of 20.

[0049] Fig. Figure 4 shows a tool 22 used in the method according to the invention, which will be described in more detail below. The tool 22 is a grinding tool with a geometrically undefined cutting edge. The tool 22 is a non-dressable grinding tool—in this case, a non-dressable CBN grinding tool.

[0050] The tool 22 has a geometry-generating plane 24 which is ring-shaped and covered with cutting grain 26.

[0051] The cutting grain 26 is represented by cross-hatching.

[0052] The geometry-generating plane 24 of the tool 22 is oriented perpendicular to a rotational axis 28 of the tool 22, around which the tool 22 rotates during grinding operation. The geometry-generating plane 24 is therefore an annular grinding surface perpendicular to the rotational axis 28.

[0053] The tool 22 has an inner cone 30 adjacent to the geometry-generating plane 24 and the cutting grain, which is oriented at an incline relative to the geometry-generating plane 24. According to alternative embodiments, the geometry-generating plane 24 can be circular, ie, the tool is designed without a recessed inner cone.

[0054] Fig. 5 shows the tool 22 and an example of a tooth 8 of the ring gear 6.

[0055] The straight-toothed ring gear 8 in the present example is machined by means of the rotating tool 22, wherein the teeth 8 of the ring gear 6 are machined individually by means of the tool 22 in a semi-completing process, in which in a process step (A) left flanks 32 ( Fig. 7) and in a process step (B) right flanks 34 ( Fig. 6) are each machined in a separate infeed by means of the tool 22, wherein the teeth 8 of the ring gear 6 are machined by rolling by means of the tool 22.

[0056] The left flanks 32 of the teeth 8 of the ring gear 6 are machined by rolling with the geometry-generating plane 24 of the rotating tool 22.

[0057] The right flanks 34 of the teeth 8 of the ring gear 6 are machined by rolling with the same geometry-generating plane 24 of the rotating tool with which the left flanks 32 were machined.

[0058] The geometry-generating plane 24 of the rotating tool 22 is oriented perpendicular to the rotation axis 28 around which the tool 22 rotates.

[0059] The order of machining the left flanks 32 and right flanks 34 can vary. Left and right flanks can also be machined alternately.

[0060] In Fig. Figure 8 shows an exemplary and schematic representation of the machining of the pinion 4 using the tool 22. As can be seen from the schematic representation, a radius R of the tool 22 corresponds to a multiple of the tooth width B. In the present example, the radius R is greater than three times the tooth width B.

[0061] According to the present method, no stroke movement of the tool 22 takes place in the tooth width direction, ie along the flank longitudinal lines. For this reason, the radius R of the tool 22 is reflected in the tooth root of the respective machined tooth 38 of the pinion 4. Although this is only shown here as an example for the pinion 4, this also applies equally to the teeth 8 of the ring gear 6. Such a curvature is for the ring gear in the detail Z of the Fig. 1 shown.

[0062] According to Fig.8 that the tooth root 36 of the respective teeth 38 has a curvature in the finished state, wherein a radius of curvature corresponds to the radius R of the tool 22. REFERENCE SYMBOL 1 pinion tip circle 2 bevel gear pairing 3 Root circle pinion 4 pinions 5 tip circle ring gear 6 ring gear 7 Root circle ring gear 8 tooth of the ring gear 10 Heel 12 toes 14 flank longitudinal line 16 Rotation axis 18 partial cones 20 helix angles 22 Tools / Grinding tools 24 geometry generating plane 26 abrasive grain 30 inner cones 32 Left flank 34 Right flank 36 Tooth root base 38 tooth of the pinion A process step B Process step B Tooth width H1 height / tooth height H2 height / tooth height R Radius Z Detail

Claims

[1] Procedure, with the following steps: - machining a straight-toothed or helical bevel gear (4, 6) by means of a rotating tool (22), - wherein teeth (8, 38) of the bevel gear (4, 6) are machined individually by means of the tool (22) in a semi-completing process, in which the left flanks (32) and the right flanks (34) are each machined in a separate infeed by means of the tool (22), - wherein the teeth (8, 38) of the bevel gear (4, 6) are machined by rolling by means of the tool (22), - wherein left flanks (32) of the teeth (8, 38) of the bevel gear (4, 6) are machined with a geometry-generating plane (24) of the rotating tool (22), - wherein right-hand flanks (34) of the teeth (8, 38) of the bevel gear (4, 6) are machined with the same geometry-generating plane (24) of the rotating (32) tool (22) with which the left-hand flanks are machined, and - wherein the geometry-generating plane (24) of the rotating tool (22) is oriented perpendicular to a rotation axis (28) about which the tool (22) rotates. [2] Method according to claim 1, characterized by that the machining comprises producing the teeth (8, 38) by milling, wherein the tool is a milling tool with a geometrically defined cutting edge. [3] Method according to claim 1, characterized by that the machining comprises a fine machining of the teeth (8, 38) by grinding, wherein the tool (22) is a grinding tool (22) with a geometrically indeterminate cutting edge. [4] Method according to claim 3, characterized bythat the grinding tool (22) is a non-dressable grinding tool (22), such as a galvanically coated CBN grinding tool (22) or the like. [5] Method according to one of the preceding claims, characterized by that a radius (R) of the tool (22) is greater than or equal to three times a tooth width (B) of the teeth (8, 38) of the bevel gear (4, 6). [6] Method according to one of the preceding claims, characterized byin that the bevel gear (4, 6) is a pinion (4) or a ring gear (6) of a bevel gear pair (2), wherein a relative kinematics for the pinion (4) and the ring gear (6) carried out between the tool and the bevel gear (4, 6) during the machining has been calculated in each case based on generating face gears with the same pitch cone length, in particular that for the calculation a respective virtual face gear for the pinion (4) is set to a root cone of the pinion (4) and a respective virtual face gear for the ring gear (6) is set to a root cone of the ring gear (6). [7] Method according to one of the preceding claims, characterized by that a tooth root base (36) of the respective teeth (8, 38) of the bevel gear (4, 6) has a curvature in the finished machined state. [8] Method according to one of the preceding claims, characterized bythat the teeth (8, 38) of the bevel gear do not have a constant tooth height (H1, H2) in the finished state. [9] Method according to one of the preceding claims, characterized by that the teeth (8, 38) of the bevel gear (4, 6) in the finished state have modifications such as twisting, longitudinal crowning, vertical crowning or the like. [10] Tool for machining a straight-toothed or helical-toothed bevel gear (4, 6), wherein the tool (22) is adapted for use in a method according to one of the preceding claims, wherein the tool (22) has a geometry-generating plane (24), wherein the geometry-generating plane (24) is oriented perpendicular to a rotation axis (R) of the tool (22).

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