Motor-gear unit for driving a bevel pinion

Abstract

Motor-gear unit (1) with a motor (3) to which a gearbox (4) is connected, with which a bevel pinion (2) can be driven, characterized in that the gearbox (4) has a main bearing in the form of an axial-radial bearing (9) on the output side.

Description

[0001] The invention relates to a motor-gear unit for driving a bevel pinion according to the preamble of the first claim.

[0002] Depending on the application, gearbox bearings are available in a wide variety of designs. For example, in planetary gearbox bearings, deep groove ball bearings or preloaded angular contact ball bearings can be used for low loads.

[0003] However, cylindrical roller bearings or tapered roller bearings have become the standard in mechanical engineering.

[0004] Depending on the pressure angle of the main bearing, the force absorption at the gearbox flange varies more in the direction of axial and less in the radial force absorption, or vice versa.

[0005] For example, gearboxes for rack and pinion drives are designed more for high radial forces and less for axial loads.

[0006] Gearboxes used to drive bevel gears must absorb both radial and axial forces. Spiral bevel gears are a special case. The helix angle of the teeth generates additional high axial forces.

[0007] Often, additional supports for the bevel pinion are not possible, and the bearing is subjected to high stress due to the "floating" mounting.

[0008] A disadvantage is that the high forces involved usually necessitate selecting a gearbox one or two sizes larger to avoid overloading the bearings. With larger gearboxes, not only do the bearings often need to be larger, but the gears themselves must also be designed for higher loads. The overall package can thus exceed the available installation space. The main bearing of the gearbox output, for example, tapered roller bearings, must be preloaded to optimally absorb the forces. This preload is usually achieved by precise adjustment using shims or similar devices. This process must be carried out carefully, as excessive preload can lead to increased heat generation and wear, while insufficient preload can result in inaccuracies in the pinion and poor power transmission.

[0009] Typical gearboxes use angular contact ball bearings, tapered roller bearings, or similar bearings. Depending on the design, however, these units are either very large or fail to meet the requirements for force absorption and rigidity.

[0010] From German patent application DE 196 22 060 C1, for example, a drive unit, particularly for worktables of machine tools, is known, with which the worktable can be pivoted about a horizontal pivot axis. The drive unit consists of a drive motor and a gearbox assembly with two gear trains that can be pre-tensioned against each other, the output pinions of which mesh with a toothed gear on the component to be driven. High positioning accuracy and torsional stiffness with a small installation space are achieved by each gear train containing a high-ratio compact gearbox in the form of a cycloidal gear, by the fact that the drive shafts of the two compact gearboxes are driven by the drive motor via a common toothed belt, and by each compact gearbox containing at least one actuating element for pre-tensioning the two gear trains. However, the cycloidal gear used here is not suitable for transmitting higher axial forces.

[0011] Cycloidal gears of this type are also unsuitable for driving a bevel pinion. Particularly when driving a spiral bevel pinion, high axial forces occur that cannot be absorbed by conventional gear solutions, especially when installation space is limited.

[0012] For example, in the precision machining of components, compliances and defects in the drive train ultimately affect positioning accuracy just as much as defects in the axle assembly itself. High compliances due to low stiffness also lead to increased wear, for example on gears.

[0013] To minimize errors caused by compliance, i.e., deformations due to machining forces, for example, the drive train must exhibit the highest possible stiffness. Therefore, it is essential that the auxiliary gearbox also has high bearing stiffness and can absorb the high forces from both axial and radial directions.

[0014] At the same time, however, the installation space for such gearboxes is limited. A large space requirement negatively impacts the overall design, for example of a machining center, because it reduces the overall space requirement of the machining center or leads to a restriction of the travel distances.

[0015] The object of the invention is to develop a motor-gear unit for driving a bevel pinion, in particular a spiral-toothed bevel pinion, which requires a small installation space for transmitting high torques and is suitable for high axial and radial forces.

[0016] This problem is solved by the features of the first claim. Advantageous embodiments are described in the dependent claims.

[0017] According to the invention, the motor-gearbox unit comprises a motor to which a gearbox is connected, with which a bevel pinion can be driven, the gearbox having a main bearing in the form of an axial-radial bearing. The bevel pinion is in particular a spiral-toothed bevel pinion.

[0018] Preferably, the transmission comprises a planetary gear set with a sun gear and one or more planet gears meshing in a ring gear, each with an axis, as well as an output-side planet carrier with an output flange, wherein the sun gear is operatively connected to a drive shaft of the motor and the output flange of the planetary gear set is radially and axially supported by the axial-radial bearing. The axial-radial bearing is axially attached by an outer ring to a mounting flange of the transmission attached to the housing and has two axial roller assemblies and a radial roller set.

[0019] The ring gear of the planetary gearbox is fixedly arranged between the gearbox housing and the mounting flange of the housing.

[0020] It is possible to drive a spiral-toothed bevel gear using two motor-gearbox units pre-tensioned against each other on the drive side and their output-side spiral-toothed bevel pinions. The bevel gear can then be used to pivot a swivel beam of a swivel unit in a machine tool around a horizontal swivel axis.

[0021] With the development of the motor-gearbox unit according to the invention, it was advantageously possible to use a gear set for the planetary gearbox of a smaller gearbox size through the use of the axial-radial bearing.

[0022] The invention is explained in more detail below with reference to drawings.

[0023] They show: Fig. 1 A three-dimensional view of a motor-gearbox unit for driving a gear, here a bevel pinion, Fig. 2 a front view according to Fig. 1, Fig. 3. Side view of a motor-gearbox unit without bevel pinion, Fig. 4 a longitudinal section according to Fig. 3 through the motor-gearbox unit without bevel pinion, Fig. 5 two motor-gear units with bevel pinions, which engage with a toothed ring gear of a swivel gear to drive, for example, a swivel bridge of a machine tool, Fig. 6 a variant of a drive for a swing bridge.

[0024] In Fig. 1 is the three-dimensional view, in Fig. Figure 2 shows the front view of a motor-gear unit 1, which has a helical gear on the output side, here a spiral bevel gear 2. Fig. Figure 3 shows the side view of the motor-gearbox unit 1 without bevel pinion 2.

[0025] The motor-gearbox unit 1 comprises a motor 3, to which a gear assembly 4 is connected. The bevel pinion 2, which in this case is a spiral-toothed bevel pinion 2, is driven via the motor 3 and the gear assembly 4.

[0026] From the side view according to Fig. Figure 3 shows the motor 3 and the gearbox unit 4. The gearbox unit 4 has a housing 4.1 and a mounting flange 4.2. The ring gear 6.5 of a planetary gear set 5 is fixedly mounted between these, and the planetary gear set has an output flange 6.4 on its output side (see also Figure 3). Fig. 4)

[0027] The longitudinal section of the motor-gearbox unit 1 without gear (bevel pinion) is shown in Fig. 4 shown.

[0028] The gearbox assembly 4 is surrounded by a gearbox housing 4.1.

[0029] The motor 3 drives a planetary gear set 5 via its motor shaft 3.1. For this purpose, the sun gear 6 (drive gear) of the planetary gear set 5 is operatively connected to the motor shaft 3.1 by a clamp. A planet gear 6.1 (preferably three planet gears and one gear stage) meshes with the sun gear 6 around an axis 6.2 in the housing-mounted ring gear 6.5. The planet carrier 6.3 (output gear) of the planetary gear set 5 has an output flange 6.4. The rotating planet carrier 6.3 is supported on the gear housing 4.1 by a support bearing 7 in the form of a deep groove ball bearing.

[0030] A first shaft seal 8.1 is provided between a mounting flange 4.2 of the gearbox 4 and the output flange 6.4, and a second shaft seal 8.2 is provided between the housing 4.1 and the sun gear 6.

[0031] The bevel pinion (not shown here) is attached to the output flange 6.4.

[0032] The main bearing is an axial-radial bearing 9, which is supported radially on the output flange 6.4 of the planetary gear 5 and axially on the mounting flange 4.2 on the housing 4.1 of the gear assembly 4.

[0033] The axial-radial bearing 9 has cylindrical rollers 9.1 supporting themselves radially towards the output flange 6.4 and cylindrical rollers 9.2 and 9.3 supporting themselves axially on both sides and radially outside the cylindrical rollers 9.1.

[0034] In Fig. The power flow from the motor shaft 3.1 via the sun gear 6, the planet gears 6.1 to the planet carrier 6.3 (output gear) with the output flange 6.4 is shown in dashed line 4.

[0035] The axial-radial bearing 9 used here as the main bearing is normally used for rotary table applications, but here it is being used for the first time in a motor-gearbox unit 1 to drive a gear, specifically a helical bevel pinion / bevel gear 2. These axial-radial bearings 9 are highly load-bearing and exhibit very high axial and radial stiffness values. The possible tilting moment is also very high.

[0036] In this way, a very compact gearbox with a heavy-duty bearing for driving the spiral bevel pinion 2 could be developed for the first time. This axial-radial bearing 9 can be used as a single bearing in the gearbox. In conjunction with an inexpensive deep groove ball bearing as a support bearing 7 for the planet carrier 6.3, the stiffness at the output flange 6.4 could be significantly increased again. The main bearing, in the form of the axial-radial bearing 9, is lubricated by lifetime lubrication with grease, not oil, and can therefore be separated from the oil chamber of the gears of the planetary gearbox 5.

[0037] The gearbox assembly 4 of the motor-gearbox unit 1 is preferably used as a front gearbox for driving axis assemblies of a machining center in order to provide a high torque for positioning tasks in the drive train.

[0038] The high axial and radial forces occurring through the use of the motor-gearbox unit 1 to drive a swivel bridge of a machining center can be absorbed by the main bearing in the form of the axial-radial bearing 9.

[0039] Fig. Figure 5 shows two motor-gear units 1 with spiral-toothed bevel pinions 2, which engage with a spiral-toothed ring gear 10 of a swiveling gear unit (not shown), for example for realizing a swiveling movement of a swivel beam of a swiveling table of a machine tool about a horizontal swivel axis.

[0040] The drive is thus provided via the at least two motor-gear units 1 and the two output-side bevel pinions 2, both of which engage with the same ring gear 10.

[0041] The motor-gearbox units 1 are arranged here at an acute angle α to each other with respect to their unlabelled longitudinal axes, whereby any other arbitrary angle α is also possible, e.g. 90°, 180° or other.

[0042] The smallest angle α is defined by the outer diameters of the gearbox housings.

[0043] These motor-gear units 1 are electronically controlled in such a way that the drives are pre-tensioned against each other and the beam of the swivel table (not shown) can thus be driven without play and without elastic deformation by the drive – here by means of the motor-gear units via the ring gear 10 – and fixed in a desired position.

[0044] Fig.Figure 6 shows a swivel bridge or swivel beam 11 on which a rotary table 12 is arranged. A pallet 13 for clamping a workpiece (not shown) to be machined is mounted on the rotary table 12. The two motor-gear units 1 engage with the bevel gears (not shown) in the ring gear (also not shown), which is rotatable about the pivot axis A, which corresponds to the drive axis of the swivel beam 11. When the ring gear 10 pivots, the swivel beam 11 and thus the rotary table 12 also pivot about the pivot axis A.

[0045] The swivel beam 11 is thereby driven without backlash, but is not elastically deformed, resulting in a high power density in relation to the installation space. Reference symbol list 1 motor-gearbox unit 2 bevel gear 3 Engine 4 gearboxes 4.1 4.2 Gearbox housing Mounting flange 5 planetary gears 6 sun wheel 6.1 Planetary gear 6.2 Axis 6.3 Planetary Carrier 6.4 Output flange 6.5 Ring gear 7 support bearings 8 Shaft seal 8.1 First shaft seal 8.2 Second shaft seal 9 axial-radial bearings 10 Ring gear 11 swivel beams 12 Turntable 13 pallets A swivel axis QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 196 22 060 C1

[0010]

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