Machine tool with cooling device

Abstract

The invention relates to a machine tool (1) comprising a rotary table (2) having a table plane (T), the rotary table (2) being rotatable about an axis of rotation (X-X). Furthermore, the machine tool (1) comprises a bearing (3) which supports the turntable (2) on the housing (4); and a cooling device (5) having a cooling channel (51) through which a coolant flows. In this case, there is a gap (6) between the cooling device (5) and the turntable (2), which gap ensures the turnability of the turntable (2). The machine tool is characterized in that the cooling device (5) is arranged between a bearing plane (L) extending through the center of the bearing (3) and a table plane (T).

Description

Technical Field

[0001] The present invention relates to a machine tool having a cooling device. Background Art

[0002] In the machine tool industry, there has long been a trend to shorten the machining time. In this context, high-speed cutting and increasingly fast machining steps have been achieved. On the other hand, efforts have been made to improve the machining accuracy of workpieces. However, high machining speeds lead to significant heating of the workpiece and machine components. The resulting thermal expansion of the components causes uncontrolled linear expansion and deformation, which has a negative impact on the machining quality.

[0003] The turntable enables the workpiece to be received and machined from different sides. Here, during workpiece machining, mainly the bearings of the turntable, but also its drive unit, are subject to heating, mainly due to friction. Due to direct contact with the workpiece, the heating can be transferred to the workpiece through the table. The heating of the turntable has a negative impact on the machining accuracy of the machine tool. Summary of the Invention

[0004] The object of the present invention is to develop a machine tool having a turntable and a cooling device, which controls the temperature of the turntable and keeps it as constant as possible. In addition, the machine tool with a cooling device should be as simple and cost-effective as possible in terms of manufacturing.

[0005] This object is achieved by a machine tool having the features of claim 1.

[0006] The machine tool according to the invention having the features of claim 1 has the advantage that the cooling device is cleverly arranged between the bearing of the machine tool and the table plane T of the turntable, which rotatably supports the turntable in the housing. In addition, the cooling device is arranged directly adjacent to the turntable and is separated from the turntable only by a thin gap. Therefore, the cooling device can dissipate heat as well as possible from the area of the table plane of the turntable and from the bearing, and ensures a defined temperature of the turntable and improved machining accuracy due to lower thermal expansion and smaller deformation. The cooling device is here a component having integrated cooling channels, which are configured to be flowed through by a coolant. The modular construction of the cooling device enables it to be manufactured and integrated into the machine tool in a simple manner. Therefore, the cooling channels do not have to be laboriously integrated into the turntable or the housing receiving the turntable. Seals that often require maintenance can also be omitted between the turntable and the housing.

[0007] The dependent claims show preferred refinements of the invention.

[0008] The gap preferably includes a first gap region at a first side of the cooling device and a second gap region at a second side of the cooling device. Here, the first side of the cooling device is arranged parallel to the table plane in the direction of the turntable, and the second side preferably extends radially inwards from the cooling device in the direction of the rotation axis X-X. Thus, at least two of the four sides of the cooling device contribute to cooling the turntable, whereby the cooling device can effectively dissipate heat from the turntable despite the gap.

[0009] The cooling device is also preferably configured to cool the housing at a third side. The third side is preferably arranged parallel to the table plane between the cooling device and the housing. In addition, the housing and the cooling device are in direct contact with each other at the third side. The housing absorbs heat from the bearing and the drive unit. Since the cooling device and the housing are in direct contact with each other at the third side, good heat conduction exists between the housing and the cooling device, whereby heat is effectively dissipated from the housing, and preferably the side of the cooling device extending along the housing is less than the side extending along the turntable.

[0010] According to another preferred design of the present invention, the cooling device has a base body and a cover, wherein cooling channels are formed in the base body. The cover preferably closes the cooling channels towards the outside. The cooling device can be easily manufactured due to the two-piece structure. Here, the cooling channels are preferably implemented to be open in the base body, so that the cooling channels can be easily manufactured. The two-piece structure composed of the base body and the cover also makes the maintenance of the cooling device easy. The cover and the base body are preferably made of materials with high thermal conductivity characteristics.

[0011] Preferably, the second gap region between the cooling body and the turntable is configured in a stepped shape. The stepped shape increases the heat exchange surface between the two components and can therefore better conduct heat away from the turntable. The corresponding steps in the turntable and the cooling device are easy to manufacture, for example, by machining on a lathe.

[0012] The gap further advantageously has a contact seal. During machining, cooling lubricant is introduced into the working space of the machine tool and a large amount of chips and other particles are generated, and these chips and other particles are carried away by the cooling lubricant. It is necessary to prevent the cooling lubricant and other particles from entering the gap between the housing and the turntable, because they will damage the bearing or other components. The contact seal can reliably prevent the cooling lubricant and particles from invading the gap between the turntable and the frame. Since additional heat is generated by the friction of the contact seal, it is preferably arranged in the gap region between the turntable and the cooling device. Thus, the cooling device can directly dissipate the frictional heat of the contact seal. The contact seal can be, for example, a lip seal.

[0013] Particularly advantageously, the contact seal is arranged in the first gap region between the cooling device and the turntable. Thus, the contact seal is arranged particularly close to the opening of the gap facing the working space, such that the unsealed gap region is as small as possible.

[0014] According to another preferred design of the present invention, the labyrinth seal is arranged in the first gap region between the cooling device and the turntable. The labyrinth seal also prevents coolant lubricant or other particles from entering the gap between the rotational axis and the housing. Here, there is no direct contact between the cooling device and the turntable. Due to the high special surface, heat can be effectively dissipated from the turntable to the cooling device via the labyrinth seal. Due to the narrow tolerances in the gap region, it is difficult to use the labyrinth seal in the case of temperature gradient fluctuations between the sealing mating parts. Mounting the labyrinth seal in the first gap region between the turntable and the cooling device enables effective sealing of the gap at a controlled temperature.

[0015] Preferably, the labyrinth seal is here constituted only by the protruding annular flange of the cooling device and the groove in the turntable. Implementing the labyrinth seal by means of the groove in the turntable and the annular flange of the cooling device enables simple manufacturability. The heat transfer from the turntable to the cooling device is improved by the increased surface in the first gap region due to the labyrinth seal of the cooling device and the turntable.

[0016] The cooling device further preferably has a dirt collecting groove on the outer side. The dirt collecting groove is configured to keep the coolant lubricant away from the opening of the gap. This is achieved by means of a groove in the cooling device, the radially inner surface of which is preferably closer to the rotational axis X-X than the opening of the gap in the direction of the working space. Thus, a shoulder is obtained, which prevents the coolant lubricant or particles from being directly introduced into the gap. The opening of the gap is here preferably oriented perpendicular to the table plane T, such that the coolant lubricant or particles have to overcome gravity to enter the gap.

[0017] Preferably, the dirt collecting groove is the only region of the cooling device that is in direct contact with the working space of the machine tool. Thus, the remaining regions are in contact with the housing, or in contact with the turntable via the gap, and contribute to heat dissipation.

[0018] The cooling device is preferably fixed to the housing via screwed connectors. Here, the screwed connectors fix the cover to the base and the base to the housing. The screwed connectors can be simply and inexpensively integrated into the housing. In addition, the screwed connectors make the cooling device easy to assemble and disassemble. Screwed connectors made of a material with good heat conduction characteristics can improve the heat transfer between the housing and the cooling device.

[0019] The gap is further advantageously less than or equal to 1 mm, in particular less than or equal to 0.3 mm. The small gap improves the heat transfer between the turntable and the cooling device. The heat transfer can be achieved by temperature control by means of the cooling device, which enables a narrower tolerance due to the reduced thermal expansion.

[0020] According to another preferred design of the invention, the cooling device is adjacent to the inner ring of the bearing in such a way that at least part of it overlaps in the direction of the rotational axis X-X. Here, the cooling device is separated from the inner ring by a second gap region. By the overlapping arrangement, the cooling device can still dissipate heat from the inner ring of the bearing. Therefore, by the arrangement according to the invention, heat can be dissipated directly from the source, so that less heat is transferred to the turntable. Description of the Drawings

[0021] Other details, advantages and features of the invention result from the following description of embodiments with reference to the drawings. In the drawings:

[0022] Figure 1 A schematic cross-sectional view of a section in the region of the turntable of a machine tool according to a preferred embodiment is shown, and

[0023] Figure 2 A schematic detailed view in the region of the cooling device of a machine tool according to a preferred embodiment is shown. Detailed Description of the Invention

[0024] The following refers to Figure 1 and Figure 2 The machine tool 1 according to a preferred embodiment of the invention is described in detail.

[0025] The machine tool 1 includes a turntable 2, which is a rotationally symmetric member, and the rotationally symmetric member is configured to rotate about the rotational axis X-X. The turntable is connected to the housing 4 via a bearing 3. The housing 4 is implemented as the C-axis (C-Achse) of the machine tool 1.

[0026] At a first end along the rotational axis X-X of the turntable 2, a flat table plane T is mounted via a screwed connection on a table plate 22. The table plate 22 is configured to receive a workpiece to be machined using the machine tool 1. Alternatively, the turntable 2 can also be implemented as one-piece with an integrated table plate 22.

[0027] The turntable 2 is connected to the housing 4 via a bearing 3. In addition, a cooling device 5 is arranged between a bearing plane L extending through the center of the bearing 3 and the table plane T. The cooling device 5 extends annularly around the rotational axis X-X of the turntable 2. Here, there is a gap 6 between the turntable 2 and the cooling device 5, which ensures the rotatability of the turntable 2.

[0028] The bearing 3 consists of an inner ring 31, an outer ring 32 and rollers 33. In the embodiment, the bearing 3 is implemented as an axial-radial roller bearing. Due to the axial and radial orientation of the rollers 33, the bearing 3 is characterized by very high strength and tilting stiffness, and high precision in axial and radial rotation is achieved. The inner ring 31 connected to the turntable 2 is constructed as a two-piece and has a C-shaped cross-section that axially surrounds the outer ring 32. The outer ring 32 is fastened to the housing 4 via screw connectors. Depending on the required outer shape, the bearing 3 can also be implemented in different structural ways.

[0029] The turntable 2 is directly driven by electricity. For this purpose, the rotor 23 is mounted on the turntable 2 at the second end of the bearing 3 in the direction of the rotational axis X-X opposite to the table plane. The stator 41 is mounted in the housing 4 in such a way as to surround the rotor 23 with a clearance 6, and the stator drives the rotor 23 electromechanically. Alternatively, a direct mechanical drive of the turntable 2 can also be envisaged, for example via a transmission mechanism. In particular, the stator 41 of the electric drive preferably has an independent cooling device.

[0030] In Figure 2 is depicted in detail Figure 1 the cooling device 5. The cooling device is arranged at the housing 4 adjacent to the table plate 22. The cooling device 5 has a first side 5a oriented parallel to the table plane T in the direction of the first clearance region 6a and a second side 5b extending parallel to the rotational axis X-X and oriented in the direction of the second clearance region 6b. The third side 5c extends parallel to the table plane T and is oriented in the direction of the housing 4. The last fourth side 5d extends parallel to the rotational axis X-X and points radially outwards.

[0031] At the second side 5b, the cooling device 5 has two steps that increase the heat exchange surface. A stepped second clearance region 6b is formed in the turntable 2 by an associated stepped structure. The stepped structure can also have more than two steps. The surface-increasing structure in the second clearance region 6b can also have other shapes, such as a wavy shape. To further improve heat exchange, the cooling device 5 and the turntable 2 can also have a surface-increasing structure in the first clearance region 6a.

[0032] The cooling device 5 consists of a base 52 and a cover 53. Here, the cover 53 is connected to the base 52 via screw connectors 9. The screw connectors 9 also fix the base 52 at the housing 4 via the third side 5c in threaded holes. Here, the base 52 lies flush against the housing 4.

[0033] The screw connection head is inserted into the cover 53, so that the screw connection 9 has no influence on the first gap region 6a. Alternatively, the cooling device 5 can also be welded, brazed, crimped or glued to the housing 4, for example. The cooling device 5 can also be embodied as a component with an integrated cooling channel 51 without the cover 53 and can be cast or additively manufactured, for example.

[0034] The first cooling channel 51a and the second cooling channel 51b are integrated in the base body 52. The first cooling channel is arranged closer to the rotational axis X-X than the second cooling channel 51b. Preferably, the first cooling channel 51a is a supply passage here, and the second cooling channel 51b is a return passage.

[0035] The cooling channel 51 can also consist of only a single channel or multiple channels in the cooling device 5. Figure 1 and Figure 2 In, the cooling channel 51 is embodied as rectangular, which enables simple manufacturability. Alternatively, the cooling channel 51 can also have any other shape. A fluid flows through the cooling channel 51, and this fluid can be water or a special cooling liquid, for example. Here, on the one hand, the cooling channel 51 should have the largest possible contact surface with the base body 52 of the cooling device 5 in order to enable high heat exchange, while on the other hand, it should have the smallest possible pressure loss along the cooling channel 51. The turbulent flow guidance through the cooling channel 51 enables the heat energy to be quickly absorbed into the fluid flowing through the cooling channel 51.

[0036] Two contact seals 7 embodied as lip seals are integrated into the grooves in the cover 53 on the left and right sides of the screw connection. The contact seals 7 abut against the platen 22 of the turntable 2 and seal the first gap region 6a against the working space 10. The contact seals 7 can also be installed in the grooves in the turntable 2 or the platen 22 and abut against the cooling device 5. Depending on the sealing requirements, only one or more than two lip seals can also be integrated into the gap 6.

[0037] In an embodiment according to the invention, the base body has a dirt collecting groove 54 at the fourth side 5d, and this dirt collecting groove is adjacent to the working space 10. The purpose of the dirt collecting groove 54 is to prevent the particles and cooling lubricant released in the working space during processing from entering the opening of the gap 61. This is achieved by means of a recess, whereby a shoulder facing the opening of the gap 61 is obtained, so that the particles or cooling lubricant are not directly guided into the opening of the gap 61. Here, the opening of the gap 61 leads into the dirt collecting groove 54 perpendicular to the table plane T. In addition, a groove 21 is provided in the platen 22, which results in a U-shaped gap section. Similar to the groove 21, the cooling device 5 has an annular flange 55.

[0038] Thus, in the first gap region 6a, a labyrinth seal 8 is formed by the groove 21 and the annular flange 55 immediately after the opening of the gap 61, which further prevents the intrusion of dirt.

[0039] Thus, a machine tool 1 with a turntable 2 and a cooling device 5 is obtained. The cooling device controls the temperature of the turntable 2 and keeps it as constant as possible. In addition, the machine tool 1 with the cooling device 5 is simple and low-cost in manufacturing.

[0040] In addition to the above-written description of the present invention, a graphical representation of the present invention in Figures 1 to 2 is hereby expressly referred to for its supplementary disclosure.

[0041] List of reference numerals

[0042] 1 Machine tool

[0043] 2 Turntable

[0044] 3 Bearing

[0045] 4 Housing

[0046] 5 Cooling device

[0047] 5a First side

[0048] 5b Second side

[0049] 5c Third side

[0050] 5d Fourth side

[0051] 6 Gap

[0052] 6a First gap region

[0053] 6b Second gap region

[0054] 7 Contact seal

[0055] 8 Labyrinth seal

[0056] 9 Screwed connection

[0057] 10 Working space

[0058] 21 Groove

[0059] 22 Platen

[0060] 23 Rotor

[0061] 31 Inner ring

[0062] 32 Outer ring

[0063] 33 Roller

[0064] 41 Stator

[0065] 51 Cooling channel

[0066] 51a First cooling channel

[0067] 51b Second cooling channel

[0068] 52 Substrate

[0069] 53 Cover

[0070] 54 Dirt collecting trough

[0071] 55 Annular flange

[0072] 61 Opening of the gap

[0073] L-bearing plane

[0074] T-stage plane

[0075] X-X rotation axis

Claims

1. A machine tool (1), comprising · a turntable (2) having a table plane (T), wherein the turntable (2) is rotatable about a rotation axis (X-X), · a bearing (3) which supports the turntable (2) at a housing (4), and · a cooling device (5) having a cooling channel (51) configured to be flowed through by a coolant, · wherein a gap (6) exists between the cooling device (5) and the turntable (2), the gap ensuring the rotatability of the turntable (2), and · wherein the cooling device (5) is arranged between a bearing plane (L) extending through the center of the bearing (3) and the table plane (T).

2. The machine tool (1) according to claim 1, wherein the gap (6) comprises a first gap region (6a) at a first side (5a) of the cooling device (5) and a second gap region (6b) at a second side (5b) of the cooling device (5).

3. The machine tool (1) according to claim 2, wherein the cooling device (5) is configured to cool the housing (4) at a third side (5c).

4. The machine tool (1) according to any one of the preceding claims, wherein the cooling device (5) has a base body (52) and a cover (53), and the cooling channel (51) is formed in the base body.

5. The machine tool (1) according to any one of claims 2 to 4, wherein the second gap region (6b) is configured to be stepped.

6. The machine tool (1) according to any one of the preceding claims, wherein a contact seal (7) is arranged in the gap (6).

7. The machine tool (1) according to claim 6, wherein the contact seal (7) is arranged in the first gap region (6a).

8. The machine tool (1) according to any one of claims 2 to 7, wherein a labyrinth seal (8) is arranged in the first gap region (6a).

9. The machine tool (1) according to claim 8, wherein the labyrinth seal (8) is constituted by a protruding annular flange (55) of the cooling device (5) and a groove (21) in the turntable (2).

10. The machine tool (1) according to any one of the preceding claims, wherein the cooling device (5) has a dirt collecting groove (54) at the outer side.

11. The machine tool (1) according to claim 10, wherein the cooling device (5) is in direct contact with the working space (10) of the machine tool (1) only at the dirt collecting groove (54).

12. The machine tool (1) according to any one of claims 4 to 11, wherein the cover (53) is fixed to the base body (52) by means of a screw connection (9), and the screw connection (9) also fixes the base body (52) in the housing (4).

13. The machine tool (1) according to any one of the preceding claims, wherein the gap (6) is less than or equal to 1 mm.

14. A machine tool according to any one of the preceding claims, wherein the cooling device (5) is adjacent to the inner ring (31) of the bearing (3) in such a way that they at least partially overlap in the direction of the rotation axis (X-X).

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