Swivel unit for a machine tool

Abstract

The invention relates to a swivel unit for a machine tool for holding at least one workpiece, wherein the swivel unit has a swivel beam and the swivel beam is pivotable about a horizontally oriented pivot axis (S), wherein a drive unit for pivoting the swivel beam about the horizontal axis (S) is provided at an end section of the swivel unit, wherein the drive unit is connected to the swivel beam by means of a bevel gear drive, wherein the drive unit has a first drive motor with a first bevel pinion and a second drive motor with a second bevel pinion, wherein the first and second bevel pinions are engaged with a ring gear connected to the swivel beam for transmitting the swiveling movement from the drive unit to the swivel beam.

Description

[0001] The invention relates to a swiveling unit for a machine tool according to the preamble of the first claim.

[0002] For machining workpieces in a single setup on a machine tool, a fifth NC axis of a machining center is preferably used. For this purpose, a rotary table (axis 4) can be arranged on a swiveling beam in the form of a swivel bridge (axis 5). The force required to move the swivel bridge, also referred to as a swiveling support or swiveling workpiece carrier, is generated, in particular, via an intermediate gearbox between the motor and the swivel bridge.

[0003] The requirement for a drive for such a swivel unit is, on the one hand, precise backlash-free positioning of the swivel unit and, on the other hand, the transmission of high machining forces and feed forces, whereby the beam should not deform elastically due to its drive, since deformations lead to faulty machining of workpieces.

[0004] Not only the static stiffness of the swivel unit is important, but also the stiffness of the drive train. This is crucial for controlling and precisely setting positions accurate to the micrometer.

[0005] Depending on the requirements, the swivel unit must exhibit high rigidity and enable high positioning speeds. However, conventional drive concepts according to the state of the art do not possess the necessary power density and / or rigidity.

[0006] Known arrangements according to the prior art are based primarily on two principles. The first principle is a direct drive, in which the motor or rotor is directly connected to the pivoting beam of the swivel unit. This motor can be mounted on one or both sides of the swivel unit. A direct drive on both sides prevents twisting of the swivel beam. This drive principle represents the optimum for a rigid, backlash-free drive. However, the high costs of such a design are a disadvantage. Additionally, there are limits to its economic viability and performance with regard to workpiece size and mass.

[0007] The indirect drive is the second principle used. Here, a gearbox is positioned between the drive motor and the pivoting beam. Gearboxes have backlash and, depending on the type, significantly lower stiffness. However, gearboxes allow for the economical generation of high forces to move large masses.

[0008] It is known that with this principle, a drive can also be located on both sides of the pivotally mounted beam. By tensioning these drives, backlash can be eliminated from the gearbox. A disadvantage of this design is that the beam of the pivot axis is elastically deformed by the torques applied on both sides.

[0009] From German patent application DE 19622060 C 1, 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 high torsional rigidity in 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.

[0010] The object of the invention is to develop a swivel unit for a machine tool which drives a beam of the swivel unit without backlash, but does not elastically deform the swivel beam and additionally has a high power density in relation to the installation space.

[0011] This problem is solved using the features of the first patent claim.

[0012] Advantageous embodiments result from the dependent claims.

[0013] The swivel unit according to the invention for a machine tool for holding at least one workpiece has a swivel beam, wherein the swivel beam is pivotable about a horizontally oriented pivot axis. For this purpose, a drive unit for pivoting the swivel beam about the horizontal axis is provided at an end section of the swivel unit. According to the invention, the drive unit is connected to the swivel beam by means of a bevel gear transmission, wherein the drive unit has a first drive motor with a first bevel pinion and a second drive motor with a second bevel pinion such that the first and second bevel pinions are engaged with a ring gear connected to the swivel beam for transmitting the swiveling movement from the drive unit to the swivel beam. The simultaneous engagement of the bevel pinions with the ring gear counteracts backlash in the bevel gear transmission.

[0014] Preferably, and to increase accuracy, the first drive motor and the second drive motor are pre-tensioned against each other. This pre-tensioning is achieved by means of an electrical control system.

[0015] The bevel gear drive is particularly preferred in the form of a spiral bevel gear drive with two spirally toothed bevel pinions.

[0016] In an advantageous embodiment, the drive motors of the drive unit are arranged in a V-shape relative to each other, although other positions such as opposite each other or in an L-shape relative to each other are also conceivable.

[0017] The bevel gear is preferably arranged on one side of the pivot beam to transmit the pivoting motion. Particularly preferably, the pivot beam is supported in a first and second leg, with the bevel gear, connected to the pivot beam, being arranged in one of the legs. With a one-sided arrangement and force application, twisting of the pivot beam, as occurs with drives on both sides using gearboxes, is prevented. The drive unit is therefore also arranged on the leg of the pivot beam that accommodates the bevel gear.

[0018] In an advantageous embodiment, to reduce the required motor power, the first and / or second drive motor is equipped with a gearbox.

[0019] The use of a planetary gearbox as a secondary gearbox is particularly advantageous. By using a planetary gearbox, the required installation space of the drive motor can be reduced.

[0020] A rotary table for holding a pallet for clamping at least one workpiece directly on this pallet or within a fixture is particularly preferred on the swivel beam. A swivel unit designed in this way enables 5-axis machining of at least one clamped workpiece.

[0021] In an advantageous embodiment of the swivel unit, it is arranged on a Z-slide of a machine tool and can be moved in the Z direction.

[0022] The direct connection of the motor via the various gear stages ensures that safety clamping is achieved through the motor brake. An additional safety clamp is therefore unnecessary.

[0023] The present invention achieves backlash-free operation in the drive without creating tension in the pivot beam. The pivot unit, and in particular the bevel gear drive, exhibits high overall rigidity and can be designed in a space-saving manner with high power density and excellent cost-effectiveness.

[0024] The invention is explained in more detail below with reference to an exemplary embodiment and the accompanying drawings. These show: Fig. 1 a swivel unit according to the invention with rotary unit and drive unit, Fig. 2 a swivel unit from the viewpoint of a milling spindle in a machining center, Fig. 3 a drive unit with a first drive motor and a second drive motor on a bevel gear, Fig. 4 a sectional view of the swivel unit, Fig. 5 the force flow in a swivel unit according to Fig. 4.

[0025] A swivel unit 1 in a front view is in Fig. 1 shown. A representation of the swivel unit according to Fig. 1 from the direction of a milling spindle (not shown) of a machine tool or machining center is in Fig. 2 shown.

[0026] The swivel unit 1 has a swivel beam 2 which is mounted between a first leg 1.1 and a second leg 1.2 and is pivotable about a horizontally oriented pivot axis S. A drive unit 3 for the swivel movement about the pivot axis S of the swivel beam 2 is provided in the first leg 1.1 by means of a helical bevel gear stage with two bevel pinions.

[0027] The drive unit 3 has at least two drive motors in the form of a first drive motor 3.1 and a second drive motor 3.2, which are arranged in the area of ​​the first leg 1.1. A rotary table 4 with a pallet 5 mounted on it for clamping at least one workpiece is arranged on the swivel beam. The swivel unit 1 is designed as a rotary-swivel unit for the 5-axis movement of a workpiece.

[0028] Furthermore, the swivel unit 1 is arranged on a Z-slide 6 of a machine tool (not shown) and can be moved along the Z-axis of the machine tool.

[0029] The Fig. Figure 3 shows a drive unit 3 with a first drive motor 3.1 and a second drive motor 3.2, which are arranged in a v-shape at an acute angle α to each other.

[0030] However, the drive motors 3.1, 3.2 can also be positioned at any other angle to each other, e.g. 90°, 180° or other angles.

[0031] The smallest angle a is determined by the outer contours of the gearbox housings.

[0032] The first drive motor 3.1 has a first bevel pinion 3.1.1 and the second drive motor 3.2 has a second bevel pinion 3.2.1, which mesh with a common ring gear 7 connected to the pivot beam (not shown). The bevel pinions 3.2.1, 3.2.2 are designed as spiral bevel pinions.

[0033] The drive motors 3.1 and 3.2 are preferably identical in design and each has a gear unit 3.1.2 and 3.2.2, respectively, which enables high power density and reduced motor power. The rotary motion is transmitted from the drive unit 3, consisting of the first drive motor 3.1 and the second drive motor 3.2, to the swivel beam (not shown) via the bevel gear 7. The drive motors 3.1 and 3.2 of the drive unit 3 are electronically controlled such that they are pre-tensioned against each other, thereby eliminating backlash in the bevel gear unit. A position encoder is integrated into each of the drive motors 3.1 and 3.2. These are necessary for the internal control loop.

[0034] A sectional view through the first leg 1.1 of the swivel unit is shown in the Fig. Figure 4 shows a corresponding representation of the force flow F within the swivel unit 1. Fig.5 is marked.

[0035] The first drive motor 3.1 and the second drive motor 3.2, located below it and not visible in this illustration, each have a reduction gear 3.1.2, preferably a planetary gear, to reduce the motor power. The first bevel pinion 3.1.1 transmits the driving force F of the drive motor 3.1 to the ring gear 7 via the upstream reduction gear 3.1.2. The ring gear 7 is arranged in the first leg 1.1 and connected to a drive shaft 2.1 of the pivot beam 2, whereby the pivoting movement about the pivot axis S is transmitted to the pivot beam 2.

[0036] The drive unit 3 in conjunction with the ring gear 7 is sealed against the drive shaft 2.1 of the swivel beam 2 by means of a seal 8.

[0037] Furthermore, a measuring system 9 with an associated holder 10 for the measuring system is arranged in the first leg 1.1. The measuring system 9 is connected via a drive shaft 11 to the drive axis 2.1 of the swivel beam 2 for detecting the swivel movement of the swivel beam 2 about the swivel axis S.

[0038] The present invention generates a very high drive torque in a relatively compact installation space. It combines the specific advantages of the respective drive types and mitigates their disadvantages through the arrangement of the elements. With the present invention, the pivot beam can be driven backlash-free and without elastic deformation by arranging the drive unit on only one leg of the pivot unit.

[0039] Combining this with a planetary gearbox as a front-end gearbox offers further advantages. For example, the higher drive stiffness of spur gear drives, compared to cycloidal gear drives, ensures backlash-free dynamic drive, even in simultaneous operation.

[0040] Since gear drives are significantly "softer" than direct drives, the mechanics dampen disturbances and resonance frequencies to a certain extent. Consequently, considerably fewer filters are required in the machine's control system.

[0041] One disadvantage of planetary gears is, for example, their overload capacity (depending on size) due to the constant line contact between the gears. This disadvantage is minimized by generating the high forces only at the bevel gear with its rolling surfaces.

[0042] The smooth running of spiral bevel gear drives also ensures that vibrations originating from the planetary gear set, specifically from the gears, are dampened. These vibrations are visible as shadows on high-precision reflective surfaces. Reference symbol list 1 swivel unit 1.1 first leg 1.2 second leg 2 swivel beams 2.1 Drive axle 3 Drive unit 3.1 First drive motor 3.1.1 Conical pinion 3.1.2 Front gearbox / planetary gearbox 3.2 Second drive motor 3.2.1 Conical pinion 3.2.2 Front gearbox / Planetary gearbox 4 Turntable 5 pallets 6 Z-carriages 7 ring gear 8 Seal 9 Measuring system 10 holders 11 Drive shaft S swivel axis

Claims

[1] Swivel unit for a machine tool for receiving at least one workpiece, wherein the swivel unit (1) has a swivel beam (2) and the swivel beam (2) is pivotable about a horizontally oriented swivel axis (S) and for this purpose a drive unit (3) for pivoting the swivel beam (2) about the horizontal axis (S) is provided at an end section of the swivel unit (1), characterized by , that the drive unit (2) is connected to the pivot beam (2) by means of a bevel gear drive, wherein the drive unit (3) has at least one first drive motor (3.1) with a first bevel pinion (3.1.1) and at least one second drive motor (3.2) with a second bevel pinion (3.2.1) such that the first and second bevel pinions (3.1.1, 3.2.1) engage with a ring gear (7) connected to the pivot beam (2) for transmitting the pivoting motion from the drive unit (3) to the pivot beam (2). [2] Swivel unit according to claim 1, characterized by , that the first drive motor (3.1) and the second drive motor (3.2) are preloaded against each other. [3] Swivel unit according to claim 1 or 2, characterized by , that the bevel gear drive is designed in the form of a spiral bevel gear drive with two spirally toothed bevel pinions (3.1.1, 3.2.1). [4] Swivel unit according to one of the preceding claims, characterized by , that the drive motors (3.1, 3.2) of the drive unit (3) are arranged in a v-shape relative to each other. [5] Swivel unit according to one of the preceding claims, characterized by , that the ring gear (7) is arranged on one side of the pivot beam (2) to transmit the pivoting movement about the pivot axis (S). [6] Swivel unit according to one of the preceding claims, characterized by , that the first and / or second drive motor (3.1, 3.2) has a pre-gearbox (3.1.2, 3.2.2). [7] Swivel unit according to claim 6, characterized by , that the pre-assembly gear (3.1.2, 3.2.2) is designed in the form of a planetary gear (3.1.2, 3.2.2). [8] Swivel unit according to one of the preceding claims, characterized by that the drive unit (3) is mounted on one side of the swivel beam (2). [9] Swivel unit according to one of the preceding claims, characterized by , that a rotary table (4) for receiving a pallet (5) for clamping at least one workpiece is arranged on the swivel beam (2). [10] Swivel unit according to one of the preceding claims, characterized by , that the swivel unit (1) is arranged on a Z-slide (6) of a machine tool.

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