JP7415584B2 - rotary table device - Google Patents

Description

The present invention relates to a rotary table device for rotating a rotating object placed on a rotary table.

Conventionally, some machine tools such as machining centers perform machining while rotating a workpiece using a rotary table device. As such a rotary table device, those described in Patent Documents 1 and 2 are known.

The rotary table device described in Patent Document 1 includes a base having a shaft member extending upward, and a rotary table rotatable around the axis of the shaft member. The rotary table is supported so as to be smoothly rotatable on the base by a hydrostatic bearing structure in which oil is supplied from an oil supply source to a fluid pressure chamber defined by a side wall provided on the base.

In the rotary table device described in Patent Document 2, a sliding member made of oil-impregnated resin is disposed on the upper surface of a support base serving as a base, and a steel sliding member is attached to the lower surface of the rotary table. The rotary table is rotated relative to the base by a rotary power source such as an electric motor, and the sliding member slides on the upper surface of the sliding member.

Japanese Patent Application Publication No. 2016-129921 JP 2017-159394 Publication

In order to improve the machining accuracy of the workpiece, in order to prevent the rotary table from lifting or shifting from the base due to the machining load, the rotary table should be lubricated with solid lubrication to the base, as in the rotary table device described in Patent Document 2. It is desirable to support it rotatably. However, in this case, when the rotary table rotates with a workpiece placed on the rotary table, and when the rotary table rotates with no workpiece placed on the rotary table, the rotary table The problem is that it is difficult to adjust the control gains (proportional speed control gain and integral control gain) in the feedback control of the electric motor to ensure that the rotary table rotates smoothly relative to the base in any state because the sliding resistance of the rotary table varies greatly. There is.

Specifically, if the control gain of the electric motor is adjusted under a light load condition with no workpiece placed on the rotary table, the control gain will be adjusted under a heavy load condition with a heavy workpiece placed on the rotary table. Responsiveness of position control of the rotary table becomes low. Furthermore, if the control gain of the electric motor is adjusted under a heavy load, vibrations are likely to occur when the rotary table is rotated under a light load. For this reason, for example, there have been cases where the control gain has to be set to a value that keeps the responsiveness low under heavy loads.

Therefore, the present invention reduces the difference between the sliding resistance when the rotary table rotates under a light load and the sliding resistance when the rotary table rotates under a heavy load, thereby suppressing vibration during light loads. It is an object of the present invention to provide a rotary table device that can achieve both responsiveness under heavy loads.

In order to achieve the above object, the present invention includes a rotating shaft member that rotates around a vertical axis of rotation, a rotating table that rotates integrally with the rotating shaft member, and a sliding member on which the lower surface of the rotating table slides. a base having a sliding surface and receiving a vertical load from the rotary table by the sliding surface; and a base disposed below the rotary table between the rotary shaft member and the base and having a plurality of rolling elements. and a thrust bearing sandwiched between a pair of bearing rings in the vertical direction , and the rotary table rotates with respect to the base by solid-to-solid sliding between the lower surface and the sliding surface. The upper bearing ring of the pair of bearing rings is pressed vertically downward, so that a preload is applied to the rotating shaft member, and the lower bearing ring of the pair of bearing rings is applied to the rotating shaft member. A rotary table device is provided with a receiving portion for receiving a bearing ring, and in which a preload applied to the thrust bearing decreases when a load acting on the sliding surface received from the rotary table increases .

According to the rotary table device according to the present invention, it is possible to reduce the difference between the sliding resistance when the rotary table rotates under a light load and the sliding resistance when the rotary table rotates under a heavy load. This makes it possible to achieve both vibration suppression during heavy loads and responsiveness during heavy loads.

1 is an external perspective view showing a horizontal machining center using a rotary table device according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of the rotary table device. FIG. 3 is a partially enlarged view of the main part of FIG. 2; FIG. 3 is a configuration diagram of the rotary table device viewed from above along the Y-axis direction. (a) thru|or (c) are explanatory drawings which show the state of the rotary table apparatus at the time of light load, the time of medium load, and the time of heavy load. FIG. 7 is a cross-sectional view showing main parts of a rotary table device according to a second embodiment. (a) and (b) are explanatory diagrams showing the states of the rotary table device in the second embodiment when the load is light and when the load is heavy.

[First embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some portions specifically illustrate various technical matters that are technically preferable. However, the technical scope of the present invention is not limited to this specific embodiment.

FIG. 1 is an external perspective view showing a horizontal machining center 1, which is a type of machine tool, in which a rotary table device 2 according to a first embodiment of the present invention is used. In FIG. 1, three linear drive axes that are perpendicular to each other are shown as an X-axis, a Y-axis, and a Z-axis, of which the X-axis and Z-axis are horizontal, and the Y-axis is vertical. Further, in FIG. 1, a workpiece to be machined is indicated by the reference numeral 10. In the following description, "upper" and "lower" refer to the vertical direction along the Y-axis.

This horizontal machining center 1 includes a machine side bed 11 on which a pair of rails 111 are provided parallel to each other on the upper surface, and a Z machine bed 11 that is movable forward and backward in the Z-axis direction along the pair of rails 111 on the machine side bed 11. An axis moving column 12, a Y-axis moving body 13 arranged to be movable forward and backward in the Y-axis direction along a pair of rails 121 provided parallel to each other on the Z-axis moving column 12, and a Y-axis moving body 13 fixed to the Y-axis moving body 13. It has a spindle head 14 and a tool 15 that rotates with respect to the spindle head 14. The tool 15 rotates around the Z-axis direction and processes the workpiece 10.

The workpiece 10 is fixed by an unillustrated jig onto a pallet 20 held by a rotary table device 2 that moves forward and backward on a conveyance bed 16 in the X-axis direction. A pair of rails 161 are provided on the transport bed 16 in parallel with each other along the X-axis direction. Furthermore, a ball screw shaft 162 for moving the rotary table device 2 along a pair of rails 161 is arranged on the conveyance bed 16 . The ball screw shaft 162 is rotationally driven by a drive device (not shown).

FIG. 2 is a sectional view of the rotary table device 2. As shown in FIG. FIG. 3 is a partially enlarged view of the main part of FIG. 2. FIG. 4 is a configuration diagram of the rotary table device 2 viewed from above along the Y-axis direction. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 4, and shows a state in which the workpiece 10 is not placed on the pallet 20. In FIG. 4, the pallet 20 is shown by a virtual line (two-dot chain line).

The rotary table device 2 includes a movable table 3 (hereinafter referred to as the base) that moves forward and backward in the X-axis direction guided by a pair of rails 161 provided parallel to each other on the transfer side bed 16, and a movable table 3 (hereinafter referred to as the base) that moves forward and backward in the On the other hand, there is a cylindrical rotating shaft member 4 that rotates around a rotational axis O in the Y-axis direction, a disc-shaped rotating table 5 that rotates integrally with the rotating shaft member 4, and a rotating shaft member 4 that rotates with respect to the base 3. a bearing mechanism 6 that supports the rotary table 5, a drive mechanism 7 that rotationally drives the rotary table 5, a clamp mechanism 8 that fixes the pallet 20 to the rotary table 5, and a rotary joint 9 that has an inner distributor 91 and an outer distributor 92. It is equipped with

The rotary shaft member 4 and the rotary table 5 are made of metal, and rotate together with the pallet 20 with respect to the base 3 about a vertical axis of rotation O. A load receiving member 50 is disposed on the upper surface 5a of the rotary table 5 and is in contact with the pallet 20 to receive the load from the pallet 20. Hereinafter, the direction parallel to the rotational axis O will be referred to as the axial direction.

The base 3 includes a movable base main body 31 (hereinafter referred to as the base main body) having a recess 30 formed in the center center around the rotation axis O so as to be depressed vertically downward; A preload applying member 33 and a cylinder block 34 are fastened by a plurality of preload bolts 32 as fastening members, a brake piston 35 is arranged to be movable in the vertical direction with respect to the cylinder block 34, and a brake piston 35 is fixed to the base body 31. A rail receiving member 361 that slides on the rail 161, a ball screw nut 362 that is screwed onto the ball screw shaft 162, and a holding member 363 that holds the ball screw nut 362.

The rail receiving member 361, the ball screw nut 362, and the holding member 363 are attached to the lower side of the base body 31. The rotational force of the ball screw shaft 162 is converted into a moving force in the X-axis direction by the ball screw nut 362, and the base 3 moves along the pair of rails 161 by this moving force.

The preload bolt 32 has a head 321 and a shaft portion 322, and a male thread 323 is provided at the tip of the shaft portion 322. The head 321 is housed in a housing hole 341 formed in the cylinder block 34. The shaft portion 322 is inserted into bolt holes 340, 330, and 310 formed in the cylinder block 34, the preload applying member 33, and the base body 31, respectively. The male thread 323 is screwed into a female thread 311 formed at the lower end of the bolt hole 310 of the base body 31.

The bearing mechanism 6 includes a radial bearing 61 that restricts the movement of the rotating shaft member 4 in the radial direction with respect to the base 3, and a thrust bearing 62 that restricts the movement of the rotating shaft member 4 in the axial direction with respect to the base 3. There is. The radial bearing 61 includes an outer bearing ring 611, an inner bearing ring 612, and a plurality of rolling elements 613 arranged between the outer bearing ring 611 and the inner bearing ring 612. In this embodiment, the radial bearing 61 is a double-row cylindrical roller bearing, and cylindrical rolling elements 613 are arranged in double rows between the outer raceway 611 and the inner raceway 612.

The thrust bearing 62 is disposed below the rotary table 5 and the radial bearing 61 between the rotating shaft member 4 and the base 3, and includes a pair of bearing rings, an upper bearing ring 621 and a lower bearing ring 622. It has a plurality of rolling elements 623 arranged between an upper bearing ring 621 and a lower bearing ring 622. The upper bearing ring 621 and the lower bearing ring 622 are arranged in the vertical direction and sandwich the plurality of rolling elements 623 in the vertical direction. In this embodiment, the thrust bearing 62 is a ball bearing, and the spherical rolling elements 623 have a raceway surface 621a formed on the upper bearing ring 621 with an arcuate cross section and a raceway surface 621a with an arcuate cross section formed on the lower bearing ring 622. It rolls on the raceway surface 622a.

The rotating shaft member 4 is rotatably supported by a radial bearing 61 and a thrust bearing 62 with respect to the base 3 . Further, the rotating shaft member 4 includes a cylindrical body 41 fixed to the rotary table 5 with bolts 431 and a receiving member 42 fixed to the lower end of the cylindrical body 41 with bolts 432. The radial bearing 61 is arranged between the rotating table 5 and the thrust bearing 62 in the axial direction of the rotating shaft member 4, and the outer raceway ring 611 is arranged between the preload applying member 33 of the base 3 and the cylinder block 34. The inner raceway ring 612 is sandwiched between the rotary table 5 and the receiving member 42 .

The receiving member 42 is provided with a receiving portion 421 that receives the lower bearing ring 622 of the thrust bearing 62 from below. The thrust bearing 62 is sandwiched between the preload applying member 33 and the receiving portion 421 of the receiving member 42, and receives preload directed downward in the vertical direction from the preload applying member 33. In this embodiment, since the preload applying member 33 is tightened to the base main body 31 by the preload bolt 32 and is in contact with the upper bearing ring 621, the thrust bearing 62 is pushed downward by the axial force of the preload bolt 32. Preload is applied. That is, by fastening the preload applying member 33 to the base main body 31 by the preload bolt 32, a downward preload is applied to the upper raceway ring 621 of the thrust bearing 62. The receiving member 42 is pressed downward by a preload transmitted from the lower bearing ring 622 to the receiving portion 421 .

The thrust bearing 62 and one end portion of the rotating shaft member 4 including the receiving portion 421 are housed in the recessed portion 30 of the base body 31 . The recess 30 is formed with a large-diameter inner circumferential surface 30a and a small-diameter inner circumferential surface 30b having different inner diameters, and the small-diameter inner circumferential surface 30b is formed below the large-diameter inner circumferential surface 30a. The thrust bearing 62 is arranged between the large-diameter inner circumferential surface 30a of the recess 30 and the receiving member 42 of the rotating shaft member 4. An annular stepped surface 30c pointing upward is formed between the large-diameter inner circumferential surface 30a and the small-diameter inner circumferential surface 30b, and a portion of the outer circumferential side of the lower surface 622b of the lower bearing ring 622 is a stepped surface. 30c in the axial direction.

As shown in FIG. 2, a disk-shaped flange portion 911 of the inner distributor 91 is attached to the bottom surface 30d at the lower end of the recess 30. Further, the inner distributor 91 has a shaft-shaped joint portion 912 having an outer diameter smaller than that of the flange portion 911, and this joint portion 912 is connected to a first joint portion 921 of the outer distributor 92 formed in a cylindrical shape. It is accommodated. Further, the outer distributor 92 has a second joint portion 922 having a larger outer diameter than the first joint portion 921 above the first joint portion 921 . The second joint portion 922 is fitted into a fitting hole 500 formed in the center of the rotary table 5.

The drive mechanism 7 connects an electric motor 71 as a drive source, a worm gear shaft 72 rotated by the torque of the electric motor 71, a worm wheel 73 meshed with the worm gear shaft 72, and the worm wheel 73 and the rotary table 5. The connecting member 74 has an annular shape. The worm wheel 73 is fixed to a connecting member 74 with bolts 751, and the connecting member 74 is fixed to the rotary table 5 with bolts 752. The electric motor 71 is controlled by the control device 100, and generates a torque that rotates the worm gear shaft 72 using a current supplied from the control device 100. Note that a deceleration mechanism that decelerates the rotation of the electric motor 71 may be further provided between the electric motor 71 and the worm gear shaft 72.

The connecting member 74 is formed with a friction surface 74a with which the contact surface 35a of the brake piston 35 comes into contact. The brake piston 35 is restricted from rotating relative to the cylinder block 34 and is movable in the vertical direction with respect to the cylinder block 34. When the brake piston 35 moves downward, the contact surface 35a contacts the friction surface 74a. contacts and generates frictional force. Between the brake piston 35, the cylinder block 34, and the preload applying member 33, there is an upper oil chamber 301 to which hydraulic oil is supplied when the brake piston 35 is moved downward, and an upper oil chamber 301 that is supplied with hydraulic oil when the brake piston 35 is moved upward. A lower oil chamber 302 to which hydraulic oil is supplied is formed. Leakage of hydraulic oil from the upper oil chamber 301 and the lower oil chamber 302 is suppressed by O-rings 351, 352, and 353 attached to the brake piston 35.

When the electric motor 71 is rotated, the control device 100 controls an electromagnetic hydraulic valve (not shown) to supply hydraulic oil to the lower oil chamber 302 to reduce the friction between the contact surface 35a of the brake piston 35 and the coupling member 74. It is separated from the surface 74a. Further, the control device 100 controls the electric motor 71 to rotate the rotary table 5 to the target position, and then controls the electromagnetic hydraulic valve to supply hydraulic oil to the upper oil chamber 301 so that the brake piston 35 is in contact with the brake piston 35. The contact surface 35a is brought into contact with the friction surface 74a of the connection member 74 to brake the connection member 74 and the rotary table 5.

The clamping mechanism 8 includes a rectangular plate-shaped pallet clamper 81, a plurality of guide pins 82 that guide the pallet clamper 81 with respect to the rotary table 5 in the Y-axis direction, and the pressure of hydraulic oil supplied through the rotary joint 9. The pallet clamper 81 is configured to have a plurality of clamp pins 83 that move the pallet clamper 81 in the Y-axis direction. The guide pin 82 is fixed to the pallet clamper 81 with a nut 821, and supported by the sleeve 51 attached to the rotary table 5 so as to be movable in the axial direction.

The clamp pin 83 has a disk-shaped piston portion 831 and a shaft portion 832, and the piston portion 831 is housed in a cylinder 52 provided on the rotary table 5. The shaft portion 832 is inserted through the cap 53 fixed on the rotary table 5, and the end portion protruding upward from the cap 53 is fixed to the pallet clamper 81 with a nut 84. The upper end of the cylinder 52 is closed by a cap 53. The rotary table 5 is formed with an unillustrated oil passage that guides hydraulic oil supplied via the rotary joint 9 to the upper and lower sides of the piston portion 831 in the cylinder 52. When hydraulic oil is supplied to the upper side of the piston part 831, the pallet clamper 81 is lowered, and when hydraulic oil is supplied to the lower side of the piston part 831, the pallet clamper 81 is raised.

The pallet 20 is formed with a cavity 200 that accommodates the pallet clamper 81, and a contact part 201 that abuts the pallet clamper 81 when the pallet clamper 81 accommodated in the cavity 200 is lowered. The pallet 20 moves relative to the rotary table device 2 along the longitudinal direction of the pallet clamper 81 with the pallet clamper 81 at the rising end, and the pallet clamper 81 is inserted into the cavity 200. The pallet 20 is fixed to the rotary table 5 by the pallet clamper 81 descending and abutting against the abutting portion 201 . Furthermore, the pallet 20 is provided with a plurality of T-slots 202 that are open on the upper surface 20a and are used to attach jigs for fixing the workpiece 10.

The base body 31 is made of cast iron, and has a sliding surface 31a on an upper end 312 on the outer diameter side of the connecting member 74 of the drive mechanism 7, on which the lower surface 5b of the rotary table 5 slides. The sliding surface 31a is an annular flat surface perpendicular to the Y-axis direction. The rotary table 5 is driven by the drive mechanism 7 and rotates by sliding the lower surface 5b on the sliding surface 31a. That is, the rotary table 5 rotates due to the solid sliding movement between the sliding surface 31a of the base body 31 and the lower surface 5b of the rotary table 5. Note that lubricating oil may be supplied between the sliding surface 31a of the base body 31 and the lower surface 5b of the rotary table 5, and at least any of the sliding surface 31a of the base body 31 and the lower surface 5b of the rotary table 5 may be A lubricant made of resin or the like having solid lubricating properties may be disposed.

The base body 31 receives a vertical load along the axial direction from the rotary table 5 through the sliding surface 31a. The sliding surface 31a is formed near the outer peripheral end of the base main body 31, and the radial bearing 61 and the thrust bearing 62 are located close to the sliding surface 31a when viewed in the axial direction of the base 3, as shown in FIG. placed inside.

Here, a light load state in which the pallet 20 is not held on the rotary table 5, and a heavy load state in which a heavy workpiece 10 is placed on the pallet 20 held on the rotary table 5. If the vertical load that the main body 31 receives from the rotary table 5 differs greatly, the sliding resistance when rotating the rotary table 5 will vary greatly between light loads and heavy loads. In either state, it becomes difficult to adjust the control gain (proportional speed control gain or integral control gain) in feedback control of the electric motor 71 for smoothly rotating the rotary table 5.

In this embodiment, by applying a vertically downward preload to the thrust bearing 62, fluctuations in the sliding resistance of the rotary table 5 due to the weight of the workpiece 10 are reduced. Next, with reference to FIG. 5, vertical loads during light loads, medium loads, and heavy loads will be specifically explained.

FIG. 5A shows a light load state in which the pallet 20 is not held on the rotary table 5. In this state, a vertical load consisting of a load F1 due to the weight of the rotary table 5 and a load F2 due to the preload applied to the thrust bearing 62 acts on the sliding surface 31a of the base body 31. In addition, in FIG. 5(a) and FIGS. 5(b) and (c) described later, the magnitude of the load is represented by the length of the arrow.

FIG. 5(b) shows a medium-load state in which a pallet 20 is held on the rotary table 5 and a relatively light workpiece 10A is placed on the pallet 20. In this state, a vertical load is applied to the base body 31 by combining the load F1 due to the weight of the rotary table 5, the load F2 due to the preload applied to the thrust bearing 62, and the load F3 due to the weight of the pallet 20 and the workpiece 10A. It acts on the sliding surface 31a of.

In this medium load state, the load F2 due to the preload applied to the thrust bearing 62 is smaller than in the light load state shown in FIG. 5(a). This change in load F2 is caused by the weight of the pallet 20 and the workpiece 10A causing the central part of the rotary table 5 to elastically deform so as to sink downward, and the rotary shaft member 4 to move downward relative to the base 3. This is because the preload that the thrust bearing 62 receives from the preload applying member 33 becomes smaller. That is, as the load that the rotary table 5 receives from the pallet 20 increases, the preload that the thrust bearing 62 receives from the preload applying member 33 decreases, and this change in preload causes the load F2 to decrease. Then, this decrease in load F2 is offset by a part of load F3, and the increase in vertical load, which is the sum of loads F1, F2, and F3, is alleviated when compared to the light load shown in Fig. 5(a). .

FIG. 5C shows a heavily loaded state in which a pallet 20 is held on the rotary table 5 and a relatively heavy workpiece 10B is placed on the pallet 20. In this state, the load F3 increases compared to when the load is medium, and the lower surface 622b of the lower bearing ring 622 of the thrust bearing 62 comes into contact with the step surface 30c of the recess 30, and the load F2 due to the preload applied to the thrust bearing 62 becomes zero. In this way, the load F2 becomes zero, so that the increase in the vertical load acting on the sliding surface 31a of the base body 31 is greater than the increase in the load F3 due to the weight difference between the workpiece 10A and the workpiece 10B. This also reduces the variation in sliding resistance when rotating the rotary table 5.

As described above, according to the present embodiment, as the load weight, which is the total weight of objects placed on the rotary table 5, increases, the load F2 due to the preload applied to the thrust bearing 62 decreases. The rate of change in the sliding resistance of the rotary table 5 with respect to the rate of change in the load weight becomes small, and even if the control gain is adjusted appropriately for medium loads or heavy loads, the occurrence of vibrations can be suppressed under light loads. This makes it possible to achieve both vibration suppression during light loads and responsiveness during medium and heavy loads.

Further, according to the present embodiment, the thrust bearing 62 that restricts the axial movement of the rotary table 5 with respect to the base 3 is disposed in the recess 30 of the base 3, so that the tool 15 can be attached to the workpiece 10. It becomes possible to suppress lifting of the rotary table 5 with respect to the base 3 due to being pressed. Furthermore, in this embodiment, since a preload directed downward in the vertical direction is applied to the thrust bearing 62, lifting of the rotary table 5 can be suppressed more reliably.

Further, according to the present embodiment, since the thrust bearing 62 is arranged below the radial bearing 61, the distance between the thrust bearing 62 and the sliding surface 31a is wider than when this arrangement is reversed. , it becomes possible to more reliably suppress lifting of the rotary table 5.

[Second embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the first embodiment, a case has been described in which a preload is applied to the thrust bearing 62 by fastening the preload applying member 33 to the base body 31 with the preload bolt 32. However, in this embodiment, the rotary table 5 The thrust bearing 62 is provided with a pressing device 300 that presses the thrust bearing 62 downward with a pressing force corresponding to the loaded weight, and the pressing device 300 applies a preload to the thrust bearing 62.

FIG. 6 is a sectional view showing the main parts of the rotary table device 2A in this embodiment. The rotary table device 2A according to the present embodiment includes an oil guiding member 37 and a cylinder 370 using the oil guiding member 37 instead of the preload bolt 32 and the preload applying member 33 of the rotary table device 2 according to the first embodiment. The piston 38 presses the thrust bearing 62 downward by the hydraulic pressure of the introduced hydraulic oil. The other configuration of the rotary table device 2A is the same as that of the rotary table device 2 according to the first embodiment, so the rotary table device 2 according to the first embodiment will be explained with reference to FIG. 6 and FIG. 7 described later. Components common to those described above are given the same reference numerals as those used in the first embodiment, and redundant explanation will be omitted.

The piston 38 is an annular member having an L-shaped cross section and is disposed between the oil guiding member 37 and the thrust bearing 62. Press. An oil passage 371 is formed in the oil guide member 37 to guide hydraulic oil supplied from the hydraulic unit 900 to the cylinder 370. The openings of the oil passage 371 other than those on the cylinder 370 side are closed by a plug body 372 . Further, an oil passage 313 communicating with the oil guide member 37 is formed in the base body 31 . Leakage of hydraulic oil from the cylinder 370 is suppressed by O-rings 381 and 382 attached to the piston 38 and an O-ring 314 attached to the base body 31.

The hydraulic unit 900 includes a hydraulic pump 901, an electric motor 902 that drives the hydraulic pump 901, and an electromagnetic hydraulic valve 903 disposed in a flow path from the hydraulic pump 901 to the cylinder 370. The control device 100 includes a motor control section 101 that controls the electric motor 71 of the drive mechanism 7 , as well as a hydraulic control section 102 that controls the electromagnetic hydraulic valve 903 . In the electromagnetic hydraulic valve 903, the valve opening degree of the forward and return paths of hydraulic oil changes depending on the current supplied from the hydraulic control unit 102.

The control device 100 can acquire information on the weight of the pallet 20 and the workpiece 10, that is, the loaded weight of the rotary table 5, from the control device of the horizontal machining center 1 or the control device that oversees the entire production line, for example. The electromagnetic hydraulic valve 903 is controlled so that the thrust bearing 62 is pressed with a pressing force corresponding to the loaded weight. The oil guiding member 37, the piston 38, the hydraulic unit 900, and the hydraulic control section 102 constitute a pressing device 300.

Here, the "pressing force according to the loaded weight of the rotary table 5" means that even if the loaded weight of the rotary table 5 changes, the amount of change in the vertical load acting on the sliding surface 31a of the base body 31 becomes small. The pressing force is adjusted as follows, and the larger the loaded weight of the rotary table 5, the smaller the pressing force with which the piston 38 presses the upper bearing ring 621.

FIG. 7A shows a light load state in which the pallet 20 is not held on the rotary table 5 in this embodiment. FIG. 7(b) shows a heavily loaded state in which the workpiece 10 is placed on the pallet 20 held on the rotary table 5. In FIGS. 7(a) and 7(b), arrows indicate the magnitudes of the load F1 due to the weight of the rotary table 5, the load F2 due to the preload applied to the thrust bearing 62, and the load F3 due to the weight of the pallet 20 and the workpiece 10. It is expressed as the length.

In this embodiment, the thrust bearing 62 is pressed downward with a pressing force that corresponds to the loaded weight of the rotary table 5. Therefore, as shown in FIGS. 7(a) and 7(b), the In either case, the vertical load acting on the sliding surface 31a of the base body 31 can be kept substantially constant. As a result, the control gain can be adjusted more appropriately, vibrations can be suppressed under light loads, and responsiveness under heavy loads can be improved. Further, as in the first embodiment, it is possible to suppress the rotation table 5 from floating up.

(Additional note)
Although the present invention has been described above based on the first and second embodiments, these embodiments do not limit the invention according to the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are essential for solving the problems of the invention.

In addition, the present invention can be implemented with appropriate modifications by omitting some configurations, or adding or replacing configurations, without departing from the spirit thereof. For example, the present invention can be implemented with appropriate modifications. It is also possible to use it for applications other than machine tools.

1... Horizontal machining center 100... Control device 101... Hydraulic control section (control section) 2, 2A... Rotary table device 20... Pallet 3... Base (moving table)
30... Concavity 300... Pressing device 31... Base main body (moving table main body) 31a... Sliding surface 32... Preload bolt (fastening member) 33... Preload imparting member 37... Oil guide member 370... Cylinder 38... Piston 4... Rotating shaft Member 421...Reception part 5...Rotary table 61...Radial bearing 62...Thrust bearing 621...Upper bearing ring 622...Lower bearing ring 623...Rolling element 900...Hydraulic unit

Claims (4)

a rotating shaft member that rotates around a vertical rotational axis;
a rotary table that rotates together with the rotary shaft member;
a base having a sliding surface on which a lower surface of the rotary table slides, and receiving a vertical load from the rotary table by the sliding surface;
a thrust bearing disposed below the rotary table between the rotary shaft member and the base, and comprising a plurality of rolling elements vertically sandwiched between a pair of bearing rings;
The rotary table rotates with respect to the base due to solid sliding between the lower surface and the sliding surface,
A preload is applied to the thrust bearing by pressing an upper one of the pair of bearing rings vertically downward;
The rotating shaft member is provided with a receiving portion for receiving a lower bearing ring of the pair of bearing rings,
When the load acting on the sliding surface received from the rotary table increases, the preload applied to the thrust bearing decreases;
Rotary table device. The base includes a preload applying member that sandwiches the thrust bearing between the base and the receiving portion, and a base main body to which the preload applying member is fastened by a fastening member,
The preload is applied to the thrust bearing by the preload applying member being fastened to the base main body by the fastening member,
When the load acting on the sliding surface received from the rotating table increases, the rotating shaft member moves downward with respect to the base, and the preload applied to the thrust bearing decreases;
The rotary table device according to claim 1. comprising a pressing device that presses the thrust bearing with a pressing force corresponding to the loaded weight of the rotary table,
the preload is applied by the pressing device;
The rotary table device according to claim 1. The pressing device includes a piston that receives hydraulic pressure of hydraulic oil supplied to the cylinder and presses the upper bearing ring of the pair of bearing rings, a hydraulic unit that supplies the hydraulic oil to the cylinder, and the hydraulic unit. and a control unit that controls the
The rotary table device according to claim 3.

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