Machine tool having a cooling device

Abstract

The invention relates to a machine tool (1) having a turntable (2) with a table plane (T), wherein the turntable (2) can be rotated about an axis of rotation (X – X). The machine tool (1) also comprises a bearing (3), which supports the turntable (2) on a housing (4), and a cooling device (5) having a cooling channel (51), designed for a coolant to flow therethrough. Between the cooling device (5) and the turntable (2) there is a gap (6), which ensures that the turntable (2) can be rotated. The machine tool is characterized in that the cooling device (5) is located between the table plane (T) and a bearing plane (L) running through a center of the bearing (3).

Description

[0001] Applicant:

[0002] P&L GmbH & Co. KG

[0003] Scheibenstraße 6

[0004] 29614 Soltau

[0005] Machine tool with cooling device

[0006] Description

[0007] The invention relates to a machine tool with a cooling device.

[0008] In the machine tool industry, there has long been a trend toward shortening machining times. This has resulted in high-speed machining and ever-faster machining steps. At the same time, efforts are being made to improve the machining accuracy of workpieces. However, these high machining speeds lead to increased heating of the workpiece and the machine components. The resulting thermal heating of the components leads to uncontrolled linear expansion and distortion, which negatively impacts machining quality.

[0009] Rotary tables allow a workpiece to be mounted and machined from different sides. During workpiece machining, the rotary table bearings, in particular, but also their drive unit, are exposed to heat, partly due to friction. Due to direct contact with the workpiece, the heat can be transferred via the table to the workpiece. The heat generated by the rotary table negatively impacts the machining accuracy of the machine tool.

[0010] The object of the invention is to develop a machine tool with a rotary table and a cooling device that controls the temperature of the rotary table and keeps it as constant as possible. Furthermore, the machine tool with the cooling device should be as simple and cost-effective to manufacture as possible.

[0011] This problem is solved by a machine tool having the features of claim 1.

[0012] The machine tool according to the invention with the features of claim 1 has the advantage that the cooling device is cleverly arranged between a bearing of the machine tool, which rotatably supports the rotary table in a housing, and a table plane T of the rotary table. Furthermore, the cooling device is arranged directly adjacent to the rotary table and separated from the rotary table only by a thin gap. Thus, the cooling device can optimally dissipate heat both from the area of ​​the table plane of the rotary table and from the bearing, ensuring a defined temperature of the rotary table and increased machining inaccuracy due to lower thermal expansion and less distortion. The cooling device is a component with an integrated cooling channel through which a coolant flows. Due to the modular design of the cooling device, it can be easily manufactured and integrated into the machine tool.This eliminates the need for complex cooling channels in the turntable or the housing that houses it. Maintenance-prone seals between the turntable and the housing are also eliminated.

[0013] The subclaims show preferred developments of the invention.

[0014] The gap preferably comprises a first gap region on a first side of the cooling device and a second gap region on a second side of the cooling device. The first side of the cooling device is arranged in the direction of the turntable, parallel to the table plane, and the second side is preferably oriented radially inward from the cooling device in the direction of a rotation axis X-X. Thus, at least two of the four sides of the cooling device contribute to cooling the turntable, allowing the cooling device to efficiently dissipate heat from the turntable despite the gap.

[0015] Further preferably, the cooling device is configured to cool the housing on a third side. The third side is preferably arranged parallel to the table plane between the cooling device and the housing. Furthermore, the housing and the cooling device lie directly against one another on the third side. The housing absorbs heat from the bearing and the drive unit. Because the cooling device and housing lie directly against one another via the third side, there is good heat conduction between the housing and the cooling device, whereby heat is efficiently dissipated from the housing and preferably fewer sides of the cooling device run along the housing than along the turntable.

[0016] According to a further preferred embodiment of the invention, the cooling device comprises a base body and a cover, wherein a cooling channel is formed in the base body. The cover preferably closes off the cooling channel to the outside. The two-part construction allows for simple manufacture of the cooling device. The cooling channel is preferably open in the base body, so that it can be easily manufactured. The two-part construction of base body and cover also facilitates maintenance of the cooling device. The cover and the base body are preferably made of a material with high thermal conductivity properties.

[0017] Preferably, the second gap between the heat sink and the rotary table is stepped. This stepped shape increases the heat exchange surface between the two components and thus enables better heat dissipation from the rotary table. The respective steps in the rotary table and the cooling device are easy to manufacture, for example, by machining on a lathe.

[0018] It is also advantageous for the gap to have a contact seal. During machining, cooling lubricant is introduced into the working area of ​​the machine tool, creating a large number of chips and other particles that are carried away by the cooling lubricant. It is essential to prevent cooling lubricant and other particles from entering the gap between the housing and the rotary table, as they can damage the bearing or other components. A contact seal can reliably prevent cooling lubricant and particles from penetrating the gap between the rotary table and the frame. Since the friction of the contact seal generates additional heat, it is preferably located in the gap area between the rotary table and the cooling device. This allows the cooling device to directly dissipate the frictional heat of the contact seal. The contact seal can, for example, be a lip seal.

[0019] Particularly advantageously, the contact seal is located in the first gap area between the cooling device and the rotary table. Thus, the contact seal is positioned particularly close to the opening of the gap towards the work area, so that the gap area that is not sealed is as small as possible.

[0020] According to a further preferred embodiment of the invention, a labyrinth seal is arranged in the first gap region between the cooling device and the rotary table. The labyrinth seal also prevents the penetration of cooling lubricant or other particles into the gap between the rotary axis and the housing. There is no direct contact between the cooling device and the rotary table. Due to the large specific surface area, heat can be efficiently dissipated from the rotary table to the cooling device via the labyrinth seal. Due to the narrow tolerances in the gap region, labyrinth seals are difficult to use with fluctuating temperature gradients between the sealing partners. Installing the labyrinth seal in the first gap region between the rotary table and the cooling device allows for efficient sealing of the gap at controlled temperatures.

[0021] Preferably, the labyrinth seal is formed exclusively by a protruding annular flange of the cooling device and a groove in the rotary table. The labyrinth seal's design, consisting of the groove in the rotary table and the annular flange of the cooling device, enables simple manufacturing. The increased surface area of ​​the cooling device and the rotary table in the first gap area due to the labyrinth seal improves heat transfer from the rotary table to the cooling device.

[0022] The cooling device further preferably has a dirt trap groove on its exterior. The dirt trap groove is designed to keep the cooling lubricant away from the gap opening. This is achieved by a groove in the cooling device, the radially inner surface of which is preferably closer to the rotational axis X-X than the gap opening toward the working space. This creates a shoulder that prevents the cooling lubricant or particles from being directed into the gap. The gap opening is preferably oriented perpendicular to the table plane T, so that the cooling lubricant or particles must overcome the force of gravity to reach the gap.

[0023] Preferably, the dirt trap groove is the only area of ​​the cooling device that is in direct contact with the working area of ​​the machine tool. Thus, the remaining areas are in contact with the housing or, via the gap, with the rotary table, and contribute to heat dissipation.

[0024] The cooling device is preferably attached to the housing via a screw connection. The screw connection secures the cover to the base body and the base body to the housing. Screw connections can be easily and cost-effectively integrated into the housing. Furthermore, a screw connection allows for easy assembly and disassembly of the cooling device. A screw made of a material with good thermal conductivity can improve heat transfer between the housing and the cooling device.

[0025] Another advantage is that the gap is 1 mm narrower, especially 0.3 mm narrower. This narrow gap improves heat transfer between the turntable and the cooling device. Heat transfer is facilitated by temperature regulation with the cooling device, which allows for tighter tolerances due to reduced thermal expansion.

[0026] According to a further preferred embodiment of the invention, the cooling device borders an inner ring of the bearing, at least partially overlapping it in the direction of the rotation axis X-X. The cooling device is separated from the inner ring by the second gap region. Due to the overlapping arrangement, the cooling device can still dissipate heat from the inner ring of the bearing. Thus, the arrangement according to the invention allows heat to be dissipated directly from the source, so that less heat is transferred to the turntable. Further details, advantages, and features of the present invention will become apparent from the following description of an exemplary embodiment with reference to the drawing. It shows:

[0027] Fig. 1 is a schematic sectional view of a section of the machine tool in the area of ​​the rotary table, according to a preferred embodiment, and

[0028] Fig. 2 is a schematic detailed view of the machine tool in the area of ​​the cooling device, according to the preferred embodiment.

[0029] A machine tool 1 according to a preferred embodiment of the invention is described in detail below with reference to Figure 1 and Figure 2.

[0030] The machine tool 1 comprises a rotary table 2, which is a rotationally symmetrical component configured to rotate about a rotation axis X-X. The rotary table is connected to a housing 4 via a bearing 3. The housing 4 is designed as the C-axis of the machine tool 1.

[0031] At a first end along the rotation axis X-X of the rotary table 2, a table top 22 with a flat table plane T is attached via a screw connection. The table top 22 is configured to accommodate a workpiece for machining with the machine tool 1. Alternatively, the rotary table 2 can also be designed as a single piece with an integrated table top 22.

[0032] The rotary table 2 is connected to the housing 4 via the bearing 3. Furthermore, a cooling device 5 is arranged between a bearing plane L, which runs through a center of the bearing 3, and the table plane T. The cooling device 5 extends in a ring around the rotation axis X - X of the rotary table 2. A gap 6 is provided between the rotary table 2 and the cooling device 5, ensuring the rotatability of the rotary table 2.

[0033] The bearing 3 consists of an inner ring 31, an outer ring 32, and cylindrical rollers 33. In the exemplary embodiment, the bearing 3 is designed as an axial-radial cylindrical roller bearing. Due to the axial and radial alignment of the cylindrical rollers 33, the bearing 3 is characterized by very high strength and tilting rigidity and achieves high precision in axial and radial concentricity. The inner ring 31 connected to the turntable 2 is constructed in two parts and has a C-shaped cross-section which axially encloses the outer ring 32. The outer ring 32 is fastened to the housing 4 via a screw connection. Depending on the requirements profile, the bearing 3 can also be designed in a different manner.

[0034] The rotary table 2 is directly electrically driven. For this purpose, a rotor 23 is mounted on the rotary table 2 below the bearing 3 in the direction of a second end of the rotation axis X-X, opposite the table plane. A stator 41 is mounted on the housing 4, enclosing the rotor 23 with a gap 6, and drives the rotor 23 electromechanically. Alternatively, a direct mechanical drive of the rotary table 2 is also conceivable, for example, via a gear. In particular, the stator 41 of the electric drive preferably has an independent cooling device.

[0035] The cooling device 5 from Figure 1 is shown in detail in Figure 2. It is arranged on the housing 4, adjacent to the table top 22. The cooling device 5 has a first side 5a, which is aligned parallel to the table plane T in the direction of a first gap region 6a, and a second side 5b, which runs parallel to the rotation axis X-X and is aligned in the direction of the second gap region 6b. A third side 5c runs parallel to the table plane T and is aligned in the direction of the housing 4. A final fourth side 5d runs parallel to the rotation axis X-X and is directed radially outwards.

[0036] On the second side 5b, the cooling device 5 has two steps that increase the heat exchange surface. A corresponding step structure in the rotary table 2 forms a stepped second gap region 6b. The step structure can also have more than two steps. The surface-enlarging structure in the second gap region 6b can also have other shapes, such as a wave shape. To further increase heat exchange, the cooling device 5 and the rotary table 2 can also have a surface-enlarging structure in the first gap region 6a.

[0037] The cooling device 5 consists of a base body 52 and a cover 53. The cover 53 is connected to the base body 52 via a screw connection 9. The screw connection 9 further fixes the base body 52 via the third side 5c to the housing 4 in a threaded hole. The base body 52 rests flush against the housing 4.

[0038] The screw head is recessed into the cover 53, so that the screw connection 9 has no influence on the first gap area 6a. Alternatively, the cooling device 5 can also be welded, soldered, pressed, or glued to the housing 4, for example. The cooling device 5 can also be designed without the cover 53 as a component with an integrated cooling channel 51 and, for example, be cast or additively manufactured.

[0039] A first cooling channel 51a and a second cooling channel 51b are integrated into the base body 52. ​​The first cooling channel is arranged closer to the rotation axis X-X than the second cooling channel 51b. In this case, the first cooling channel 51a is preferably a supply line and the second cooling channel 51b is a return line. The cooling channel 51 can also consist of just a single channel or a plurality of channels in the cooling device 5. In Figures 1 and 2, the cooling channel 51 is rectangular, which results in easy manufacturing. Alternatively, the cooling channel 51 can also have any other shape. A fluid flows through the cooling channel 51, which can be water or a special cooling liquid, for example. The cooling channel 51 should, on the one hand, have the largest possible contact area with the base body 52 of the cooling device 5 in order to enable high heat exchange, and, on the other hand, have the lowest possible pressure loss along the cooling channel 51.A turbulent flow through the cooling channel 51 enables a rapid absorption of the heat energy into the fluid flowing through the cooling channel 51.

[0040] Two contact seals 7, designed as lip seals, are integrated into grooves in the cover 53 to the left and right of the screw connection. The contact seals 7 rest against the tabletop 22 of the rotary table 2 and seal the first gap area 6a from the working chamber 10. The contact seal 7 could also be mounted in a groove in the rotary table 2 or the tabletop 22 and rest against the cooling device 5. Depending on the sealing requirements, only one or more than two lip seals could be integrated into the gap 6.

[0041] In the exemplary embodiment according to the invention, the base body has a dirt trap groove 54 on the fourth side 5d, which borders the working space 10. The purpose of the dirt trap groove 54 is to keep the particles released in the working space during machining and the cooling lubricant from the opening of the gap 61. This is achieved by the indentation, which creates a step at the opening of the gap 61 so that particles or cooling lubricant are not directed directly into the opening of the gap 61. The opening of the gap 61 opens into the dirt trap groove 54 perpendicular to the table plane T. Furthermore, a groove 21 is provided in the table top 22, which results in a U-shaped gap section. Analogous to the groove 21, the cooling device 5 has an annular flange 55.

[0042] In the first gap area 6a, a labyrinth seal 8 is formed directly after the opening of the gap 61 through the groove 21 and the annular flange 55, which further prevents the penetration of dirt.

[0043] This results in a machine tool 1 with a rotary table 2 and a cooling device 5 that controls the temperature of the rotary table 2 and keeps it as constant as possible. Furthermore, the machine tool 1 with the cooling device 5 is simple and cost-effective to manufacture. In addition to the above written description of the invention, reference is hereby explicitly made to the drawings of the invention in Figs. 1 to 2 for its supplementary disclosure.

[0044] List of reference symbols

[0045] 1 machine tool

[0046] 2 turntables

[0047] 3 camps

[0048] 4 housings

[0049] 5 Cooling device

[0050] 5a First page

[0051] 5b Second page

[0052] 5c Third page

[0053] 5d Fourth page

[0054] 6 gap

[0055] 6a First gap area

[0056] 6b Second gap area

[0057] 7 Contact seal

[0058] 8 Labyrinth seal

[0059] 9 Screw connection

[0060] 10 work space

[0061] 21 grooves

[0062] 22 Table top

[0063] 23 Rotor

[0064] 31 inner ring

[0065] 32 outer ring

[0066] 33 cylindrical rollers

[0067] 41 Stator

[0068] 51 Cooling channel

[0069] 51a First cooling channel

[0070] 51b Second cooling channel

[0071] 52 basic bodies

[0072] 53 lids

[0073] 54 Dirt trap groove

[0074] 55 Ring flange

[0075] 61 Opening the gap

[0076] L Storage level

[0077] T Table level

[0078] X - X rotation axis

Claims

Claims 1. Machine tool (1) comprising • a rotary table (2) with a table plane (T), wherein the rotary table (2) is rotatable about a rotation axis (X - X), • a bearing (3) which supports the rotary table (2) on a housing (4) and • a cooling device (5) with a cooling channel (51) arranged for a flow of a coolant, • wherein a gap (6) is present between the cooling device (5) and the turntable (2), which ensures the rotatability of the turntable (2), and • wherein the cooling device (5) is arranged between the table plane (T) and a storage plane (L) which runs through a center of the storage (3).

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

3. Machine tool (1) according to claim 2, wherein the cooling device (5) is arranged on a third side (5c) to cool the housing (4).

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

5. Machine tool (1) according to one of claims 2 to 4, wherein the second gap region (6b) is step-shaped.

6. Machine tool (1) according to one of the preceding claims, wherein a contact seal (7) is arranged in the gap (6) 7. Machine tool (1) according to claim 6, wherein the contact seal (7) is arranged in the first gap region (6a).

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

9. Machine tool (1) according to claim 8, wherein the labyrinth seal (8) is formed by a projecting annular flange (55) of the cooling device (5) and a groove (21) in the rotary table (2).

10. Machine tool (1) according to one of the preceding claims, wherein the cooling device (5) has a dirt trap groove (54) on an outer side.

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

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

13. Machine tool (1) according to one of the preceding claims, wherein the gap (6) is narrower than or equal to 1 mm.

14. Machine tool according to one of the preceding claims, wherein the cooling device (5) adjoins an inner ring (31) of the bearing (3), at least partially in the direction of the rotation axis (X - X), overlapping it.

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