JP5294016B2 - Rotary table runout control apparatus, machine tool equipped with the same, and rotary table runout control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a highly accurate processing by suppressing the deflection of a bearing at the original point of a turn table. <P>SOLUTION: The turn table 3 is rotatably supported through the bearing 10 with respect to a base 2. The driving force of a drive motor is transmitted from an output gear to a worm shaft input gear of a worm shaft, and a disc gear 17 is rotated integrally with the turn table through a worm shaft output gear. The original point of every one rotation of the output gear is detected by a rotational position detector, and the original point of every one rotation of the turn table is detected by a turn table position detector. The gear ratio of the output gear to the worm shaft input gear is made to be 1:N.5 (N is a positive integer), and the gear ratio of the worm shaft output gear to the disc gear is made to be 1:Na (Na is an odd number). A contact angle &alpha; in a second and third rollers 14, 15 is 90&deg;, and a movement angle &beta; by the revolution is 1/2 of a rotational angle &xi; of the turn table 3. When the turn table 3 is rotated even-numbered times, the second and third rollers of the bearing 10 are returned to the original point and thereby the fluctuation of deflection can be suppressed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention includes a rotary table runout control apparatus that rotates the rotary table to suppress runout of the upper surface of the rotary table by rotating while rotating the rolling element of the bearing with respect to the base, and the same. The present invention relates to a machine tool and a method for controlling a swing of a rotary table.

In recent years, due to demands for high-precision machining and high-speed machining in machine tools, the support means of a rotary table to which a workpiece is attached for machining is shifting from a sliding bearing having a large sliding resistance to a rolling bearing.
As a mechanism for rotating a rotary table or adjusting an angle by a rolling bearing, for example, there are mechanisms described in Patent Documents 1 and 2 below.
The rotary table device of the machine tool described in Patent Document 1 includes a cross roller bearing between the rotary table and a support base that rotatably supports the rotary table. In this cross roller bearing, a rolling element whose central axis is inclined at a predetermined angle is rotatably accommodated between the first V-shaped groove and the second V-shaped groove and rolls in contact therewith. Adjacent rolling elements are arranged with their rolling axes orthogonal.
Moreover, the angle adjustment table apparatus described in patent document 2 supports the rotary table rotatably with a cross roller bearing, and makes the arm contact the rotary table. Then, the rotary table is rotationally driven by a minute angle by moving the arm in the orthogonal direction by the linear motion guide units orthogonal to each other.

Japanese Patent Laid-Open No. 2003-311565 Japanese Patent Laid-Open No. 2002-341076

By the way, since the rolling bearing including the cross roller bearing described above has a structure in which the rolling element is sandwiched between the inner and outer rings, a positional deviation occurs between the rotation angle of the rotary table and the revolution angle of the rolling element. Even when the rotary table rotates once and the indexing angle returns to the origin (0 °), the position of the rolling element inside the bearing does not return to the original position that is the original position. Although the rolling element is formed in a spherical or cylindrical shape, an extremely fine dimensional error remains in the radial direction.
In this case, if the rolling element does not return to the original position which is the original position, a deviation corresponding to an error in the diameter of the rolling element that contacts the inner and outer rings occurs on the upper surface of the rotary table. This swing of the rotary table causes an error in the axial direction (rotational axis direction) of the rotary table at the mounting position of the work supported on the rotary table. Therefore, even if the indexing position of the rotary table is the same, A processing error is caused and processing accuracy is not stable.
FIG. 6 is a diagram showing axial deflection of the rotary table that holds the scale to which the workpiece is fixed.

The rotation angle of the rotary table and the rolling bearing and the movement angle (revolution angle from the origin) of the rolling element in the plane of rotation have the relationship of the following equation (1).
Rolling body movement angle β = {1- (Da · cos α / dpc} / 2 · ξ (1)
Where Da: outer diameter of the rolling element α: contact angle of the rolling element with respect to the center axis of the rotary table dpc: rolling element pitch circle diameter.
ξ: Rotation angle of inner ring of bearing By the way, the bearing used for supporting the rotary table is generally a precision grade with a runout accuracy Max: 5 μm, and an ultraprecision grade with Max: 3 μm, and no runout is possible.

  The present invention has been made in view of such circumstances, and a shake control device for a rotary table capable of realizing high-precision machining by suppressing the shake of the rolling bearing at the origin position of the rotary table, and the same. It is an object to provide a machine tool equipped with a rotary table and a method for controlling a swing of a rotary table.

  A shake control device for a rotary table according to the present invention includes a rotary table that is rotatably supported with respect to a base, a worm shaft that transmits a driving force from a drive motor, a rotary table that rotates integrally with the rotary table, and A disc gear that meshes with the output gear to transmit the driving force, a bearing that is disposed between the base and the rotary table, and that includes a rolling element that rotates and revolves according to the rotation of the rotary table, and is connected to the drive motor. A rotation position detector for detecting the origin position for each rotation of the output gear, and a rotation table position detector for detecting the origin position for each rotation of the rotation table, which are detected by the rotation table position detector. The revolution position of the rolling element of the bearing returns to the origin at the position where the origin position of the rotary table and the origin position of the output gear of the drive motor detected by the rotation position detector are detected in synchronization. Characterized in that the so that.

  The rotation of the drive motor is transmitted from the output gear to the disk gear via the worm shaft, and the rotating table rotates together with the disk gear while revolving the rolling element of the bearing, and is detected by the rotating table position detector. The revolution position of the rolling element in the bearing can be returned to the origin at a position where the origin position and the origin position of the output gear of the drive motor detected by the rotational position detector are detected in synchronization. If this origin position is repeatedly detected as an index position, and machining a workpiece fixed to the rotary table, for example, at that position is repeated, fluctuations in error can be suppressed for these workpieces and stable machining accuracy can be obtained. .

The gear ratio between the output gear of the drive motor and the worm shaft input gear provided on the worm shaft meshing with the output gear is 1: N. 5 (where N is a positive integer) and the gear ratio between the worm shaft output gear provided on the worm shaft and the disc gear meshing with the worm shaft output gear is 1: Na (where Na is an odd number) Preferably there is.
According to the present invention, for the origin position of the rotary table detected by the rotary table position detector at every even number of rotations of the disc gear, the origin position of the output gear connected to the drive motor detected by the rotary position detector and Can be detected synchronously.
In addition, the bearing is configured such that the rolling element is sandwiched between an outer ring portion that is fixed and held and an inner ring portion that rotates integrally with the rotary table, and the rolling element revolves while revolving in conjunction with the inner ring portion. Is preferred.
Thereby, the rolling element revolves while rotating by the inner ring portion in conjunction with the rotation of the rotary table.

Further, the contact angle α of the rolling element provided in the bearing with respect to the center axis of the rotary table is set to 90 °. In this case, if the rotation angle from the origin position of the rotary table is ξ, the origin of the rolling element is It is preferable to make the movement angle β revolved from the position β = ξ / 2.
In this case, since the rotation angle ξ of the rotary table and the inner ring portion and the revolution angle of the rolling element, that is, the movement angle β, are 2: 1, the gear ratio between the output gear of the drive motor and the worm shaft input gear, the worm It becomes easy to set the gear ratio between the shaft output gear and the disk gear.

In addition, when the contact angle α, which is the angle of the rolling element provided on the bearing with respect to the center axis of the rotary table, is set to less than 90 °, and the rotation angle from the origin position of the rotary table is ξ, from the origin position of the rolling element The revolved movement angle β may be expressed by the following equation (1).
β = {1- (Da · cos α / dpc} / 2 · ξ (1)
Where Da: outer diameter of the rolling element α: contact angle of the rolling element with respect to the center axis of the rotary table dpc: rolling element pitch circle diameter.
In this case, the movement angle β of the rolling element is calculated by the equation (1), and the position where the rotation table and the output gear obtained by integrating the movement angle β are the origin positions is stored in memory. The rolling element of the bearing can be revolved at the position to return to the origin.

In a machine tool equipped with a turntable deflection control device according to the present invention, the turntable is provided in a machine tool for machining a work with a tool, and the work is fixed to a reference surface of a holder fixed to the turntable. The workpiece fixed to the reference surface may be processed at the position where the rolling element of the bearing returns to the origin.
In this case, at the time of each processing, the rolling element of the bearing is at the position where it has returned to the origin, and the deflection error due to the difference in the diameter of the rolling element can be eliminated from the processing accuracy of the work, so that the processing accuracy is stabilized for a plurality of works.

  According to the rotation table swing control method of the present invention, the driving force from the drive motor is transmitted to the disk gear via the worm shaft output gear provided on the worm shaft, and the rotation table that rotates integrally with the disk gear is used as a base. On the other hand, it is a method of controlling the runout of the rotary table that is supported rotatably via a bearing and revolves while rotating the rolling elements of the bearing according to the rotation of the rotary table. The gear ratio of the meshing worm shaft to the worm shaft input gear is 1: N. 5 (where N is a positive integer) and the gear ratio between the worm shaft output gear and the disc gear meshing with it is set to 1: Na (where Na is an odd number) The rolling element returns to the origin position together with the rotary table at a position where the timing for detecting the origin position for each rotation of the output gear of the motor and the timing for detecting the origin position for each revolution of the rotary table are detected in synchronization. It was made to do.

  According to the present invention, when the output gear of the drive motor rotates an even number of times, the output gear that returns to the origin is detected by the rotational position detector, and the worm shaft input gear of the worm shaft that meshes with the output gear is also located at the origin. To do. Since the worm shaft output gear also rotates integrally, the disk gear with an odd number of teeth Na meshing with the worm shaft output gear also returns to the origin, and the rotary table is also located at the origin. The rolling elements of the bearing revolve while rotating in synchronization with an even number of rotations of the rotary table based on the formula (1), so that the processing error, etc. is the same at the start before rotation and at the return to origin after rotation. Can be controlled.

Further, the contact angle α that is the angle of the rolling element with respect to the central axis of the rotary table may be set to 90 °.
When the contact angle α of the rolling element is 90 °, the rolling element rotates 1/2 times the even number of rotations of the rotating table and returns to the origin, and the swinging of the rotating table in the central axis direction occurs. It will be the same. In this case, since the rotation angle ξ of the rotary table and the inner ring portion and the revolution angle of the rolling element, that is, the movement angle β are 2: 1 by the above formula (1), the output gear of the drive motor and the worm shaft input It becomes easy to set the gear ratio between the gear and the gear ratio between the worm shaft output gear and the disk gear.

  According to the present invention, there is provided a rotary table shake control device, a machine tool equipped with the same, and a rotary table shake control method that restores the rolling element shake, which is a characteristic of a rolling bearing, to its original state at the origin position of an index angle of 0 °. By returning and maintaining the rotary table in the same posture, the swing of the rotary table can be suppressed and high-precision machining can be realized.

It is a center longitudinal cross-sectional view of the shake control apparatus of the rotary table of the machine tool by embodiment of this invention. It is a principal part longitudinal cross-sectional view of the bearing provided between the rotary table and the base in FIG. It is an AA line horizontal sectional view in FIG. It is a schematic diagram for demonstrating the rotation angle of an inner ring | wheel part and a rolling element with respect to the outer ring | wheel part of the bearing shown in FIG. FIG. 6 is a plan view showing a shake measurement location of the rotary table in the rotary table shake control apparatus according to the embodiment. It is explanatory drawing which shows the state which a shake of an axial direction generate | occur | produces, when a rolling bearing is provided in the conventional rotary table.

Hereinafter, a swing table swing control device in a machine tool according to an embodiment of the present invention will be described with reference to FIGS.
1 to 4 show an embodiment of the present invention. The machine tool in this embodiment is, for example, a machining center, and is provided with a turntable deflection control device 1 shown in FIG. 1 facing a column having a main shaft provided on a base (not shown). The rotary table deflection control device 1 that holds the workpiece W and the main shaft to which the tool is fixed are relatively movable in the directions of three axes (X axis, Y axis, Z axis) orthogonal to each other.

In the shake control device 1 for the turntable 3 shown in FIG. 1, the turntable 3 is rotatably supported on a base 2. The rotary table 3 holds a workpiece W on an scale 7 as a holder (jig) fixed to the upper surface 4 a of the pallet 4 connected to the rotary table 3, and can rotate around a central axis O perpendicular to the upper surface 4 a of the pallet 4. . The base 2 is configured such that the swing control device 1 of the rotary table 3 can slide in the Z-axis direction, for example, by the slide block 6 being slidably fitted to the slide rail 5. In this case, for example, a column (not shown) can move in the X-axis direction, and a main shaft provided on the column can move up and down in the Y-axis direction.
Then, the shake control device 1 of the rotary table 3 fixes the scale 7 made of, for example, a quadrangular prism to the top surface 4a of the pallet 4, adjusts the processing or posture with one side surface of the scale 7 as the reference surface 7a, and adjusts the reference surface 7a. The workpiece W is attached to the workpiece and used for processing. In addition, the workpiece | work W may be attached to the side surface 7b facing the reference surface 7a of the scale 7 or two adjacent side surfaces, and the workpiece W can be attached to any one or a plurality of side surfaces for processing.

In FIG. 2, a substantially cylindrical turret 9 having a central axis O as a rotational axis is fixed to the lower surface of the rotary table 3, and a compound rolling bearing 10, for example, serves as a bearing between the turret 9 and the base 2. It is provided over the entire circumference around O. In the composite rolling bearing 10, three first rollers 13, second rollers 14, and third rollers 15 are arranged in the circumferential direction at predetermined intervals between an outer ring portion 11 and an inner ring portion 12 in a longitudinal sectional view.
As shown in FIG. 2, the outer ring portion 11 has a ring plate shape with a predetermined thickness having an inner peripheral surface 11 a, an upper surface 11 b, and a lower surface 11 c, and is fixedly disposed on the base 2. The inner ring portion 12 is formed in a recessed section in the outer peripheral surface side of the turret 9 and can rotate integrally with the turret 9. The outer ring portion 11 is inserted into the concave portion of the inner ring portion 12, and an outer peripheral surface 12a, an upper surface 12b, and a lower surface 12c are formed to face the respective surfaces 11a, 11b, and 11c.
The first roller 13, the second roller 14, and the third roller 15 are supported so as to be able to rotate and revolve between the outer and inner peripheral surfaces 12a, 11a, the upper surfaces 12b, 11b, the lower surfaces 12c, 11c of the inner and outer ring portions 11, 12 facing each other. Has been. These rollers 13, 14, 15 are made of, for example, a cylindrical needle roller, and constitute rolling elements.
The composite rolling bearing 10 supports a composite load of an axial direction (center axis O direction) load, a radial load, and a moment load of the rotary table 3.

In FIG. 1, a ring-shaped disk gear 17 is coaxially connected to the lower part of the turret 9 in the rotary table 3.
FIG. 3 is a horizontal sectional view showing a transmission mechanism for transmitting the rotational force to the disk gear 17 in FIG. In FIG. 3, a drive motor 18 is attached to one side surface of the base 2, and an output gear 19 is connected to an output shaft thereof.
The output gear 19 sets the rotation start position from the stop state of the drive motor 18 as the index position (0 °), that is, the origin. A detection dog (marker) 20 is attached to one tooth portion at the origin, and a rotational position detector 21 that detects the detection dog 20 is provided opposite to the detection dog 20 at the origin. The rotation position detector 21 detects the detection dog 20 that returns to the origin position every rotation of the drive motor 18 and outputs an ON signal. When the output gear 19 is at another angle, the detection dog 20 is not detected. , OFF signal is output.

The output gear 19 meshes with a worm shaft input gear 24 provided at one end of a worm shaft 23 that is rotatably attached to the base 2, and the rotation of the drive motor 18 directly or through a reduction mechanism (not shown). And transmitted to the worm shaft 23 through the rotation. A worm shaft output gear 25 that meshes with the disk gear 17 of the rotary table 3 is integrally fixed to the worm shaft 23. In place of the worm shaft input gear 24, a screw gear, a hypoid gear, or the like may be used for meshing with the output gear 19.
The rotary table 3 is provided with a rotary table position detector 27. The rotary table position detector 27 sets the rotation start position of the rotary table 3 as the index position (0 °), that is, the origin. The rotary table position detector 27 detects the rotation angle of the rotary table 3.

Further, it is assumed that the gear ratio between the output gear 19 of the drive motor 18 and the worm shaft input gear 24 is set to 1: N + 0.5. N is a positive integer. It is assumed that the gear ratio between the worm shaft output gear 25 of the worm shaft 23 and the disk gear 17 is set to 1: Na (where Na is an odd number).
When the turntable 3 (and the pallet 4) rotates an odd number of times, the gear ratio with the worm shaft output gear 25 is an odd number: 1, so the worm shaft 23 rotates an odd number of times. In this case, since the gear ratio of the worm shaft input gear 24 is N + 0.5: 1 with respect to the output gear 19, the output gear 19 rotates (integer + 0.5) times. In this case, the rotary table position detector 27 detects and outputs the origin (0 ° position), but the rotary position detector 21 outputs an OFF signal.
On the other hand, when the rotary table 3 (and the pallet 4) rotates an even number of times, the worm shaft 23 rotates an even number of times even if the gear ratio with the worm shaft output shaft 25 is an odd number. In this case, since the gear ratio of the worm shaft input gear 24 is N + 0.5 with respect to the output gear 19, the output gear 19 rotates an integer number of times. In this case, the rotary table position detector 27 outputs the origin (0 ° position), and the rotary position detector 21 outputs an ON signal.
These relationships are as shown in Table 1.

The above-described composite rolling bearing 10 has a typical deflection accuracy in the thrust direction of a maximum of 5 μm in the precision class and a maximum of 3 μm in the ultra-precision class.
Here, in the shake control device 1 for the turntable 3 according to the present embodiment, the first roller 13 is arranged in a vertical direction parallel to the central axis O of the turntable 3 in the composite rolling bearing 10 shown in FIGS. Thus, even if there is a shake due to a dimensional error of the diameter, the shake of the upper surface 4a of the pallet 4 is not affected.
On the other hand, the second roller 14 and the third roller 15 are in contact with the upper and lower surfaces 12b and 12c of the concave inner ring portion 12 at an angle inclined by 90 ° with respect to the central axis O (referred to as a contact angle α). The upper and lower surfaces 12b and 12c form a plane that forms 90 ° with respect to the central axis O. Therefore, each shake due to the difference in diameter between the second and third rollers 14 and 15 causes a position error on the upper surface 4a of the rotary table 3 and the pallet 4, and the workpiece W attached to the reference surface 7a of the scale 7 or other side surface. Cause machining errors.
The wobbling generated on the reference surface 7a of the scale 7 is due to wobbling due to dimensional errors of the second and third rollers 14 and 15, which are rolling elements, and the upper surfaces 12b and 11b of the inner and outer ring portions 11 and 12 in contact with the wobbling. This is due to the flatness, flatness, and shake due to the parallelism of the lower surfaces 12c and 11c. Further, the diameters of the rollers 13, 14, and 15 are very small as compared with the pitch circle diameter dpc by revolution shown below, and the accuracy of the dimensions and roundness is the same as the accuracy of the contact surfaces of the inner and outer ring portions 11 and 12. Since it is far superior in comparison, a minute error in the circumferential direction due to the rotation position of each roller can be ignored.

FIG. 4 is a schematic diagram showing a positional relationship by rolling between the second roller 14 (and the third roller 15 and the first roller 13) and the inner and outer ring portions 11 and 12. As shown in FIG. When the disk gear 17 and the pallet 4 rotate around the central axis O, the inner ring portion 12 of the composite rolling bearing 10 rotates around the central axis O, and the second roller 14 (and the third roller 15) also rolls and revolves. . Therefore, for example, when the turntable 3 and the inner ring portion 12 rotate by an angle ξ, the second roller 14 (third roller 15) that revolves while rotating in contact with the upper surface 12b (lower surface 12c) of the inner ring portion 12 is expressed by the following equation. By (1), the angle β (this is called the movement angle β) is revolved with the index position as a reference.
Traveling angle β = {1- (Da · cos α / dpc} / 2 · ξ (1)
Where Da: outer diameter of second roller 14 (third roller 15) α: contact angle of second roller 14 (third roller 15) dpc: pitch circle diameter of second roller 14 (third roller 15) ξ: The rotation angle of the inner ring portion 12.
The pitch circle diameter dpc of the second roller 14 (third roller 15, first roller 13) is the diameter of the circle of the central axis due to the revolution of the second roller 14 (third roller 15, first roller 13). Show.

Therefore, when the contact angle α = 90 °, the movement angle β of the second roller 14 and the third roller 15 is 0.5ξ according to the equation (1). That is, the second roller 14 (third roller 15) makes one revolution and returns to the original position by two rotations (even rotations) from the original position of the turntable 3. When the workpiece W fixed with the scale 7 fixed to the rotary table 3 is cut, the origin of the second roller 14 (and the third roller 15) always contacts the upper surface 12b (and the lower surface 12c) of the inner ring portion 12. If it is the reference position, no fluctuations appear on the upper surface 4a of the rotary table 3 and the pallet 4, so that cutting can be performed with the same accuracy.
In the shake table control device 1 of the rotary table 3, an ON signal from the rotary position detector 21 and an origin (0 °) signal from the rotary table position detector 27 are input to the control device 30. The control device 30 determines whether or not these input ON signals and the origin signal are synchronized. If they are synchronized, the rotary table 3, the second roller 14 and the third roller 15 are located at the origin (0). It can be recognized that the state has been returned to (°).

The shake control device 1 for the rotary table 3 of the machine tool according to the present embodiment has the above-described configuration, and a shake control method will be described next.
First, the shake control device 1 of the rotary table 3 is installed at the initial position. At this position, it is assumed that the output gear 19 and the rotary table 3 provided on the drive motor 18 of the shake control device 1 are both at the origin position. At this time, the rotational position detector 21 is in the ON state, and the rotary table position detector 27 indicates the origin (0 ° position).
At this position, the side surface of the scale 7 fixed to the rotary table 3 that faces the main shaft (not shown) is set as a reference surface 7a by machining or positioning adjustment, and the workpiece W is fixed to the reference surface 7a and the other side surface 7b, respectively. . In the cutting of the workpiece W on the reference surface 7a, the positional relationship between the tool fixed to the main shaft and the workpiece W is determined in advance, and each of the bearings 10 provided between the outer ring portion 11 and the inner ring portion 12 is provided. The second and third rollers 14 and 15 in the horizontal direction are set at an inclination angle of 90 °, for example. In this state, the workpiece W fixed to the reference surface 7a is cut.

Then, the drive motor 18 is driven to rotate the rotary table 3 and the pallet 4 by a predetermined angle, for example, to process another workpiece W fixed to the other side surface 7b, etc., and then the processed workpiece W is removed and a new workpiece W is removed. An unprocessed workpiece W is attached to the reference surface 7a of the scale 7 or the like. In order to machine a new workpiece W fixed to the reference surface 7 a, the drive motor 18 is rotationally driven to rotate the disk gear 17 and the rotary table 3 via the worm shaft 23.
When the output gear 19 is rotated by the rotation of the drive motor 18, the detection dog 20 of the output gear 19 is detected by the rotation position detector 21 for each rotation, and an ON signal is output to the control device 30. In conjunction with the rotation of the output gear 19, the worm shaft 23 is rotated via the worm shaft input gear 24 that meshes therewith. The worm shaft output gear 25 fixed to the worm shaft 23 rotates the disk gear 17 meshing with the worm shaft output gear 25 to rotate the rotary table 3 and the pallet 4 together. The rotation table 3 detects the origin (0 ° position) by the rotation table position detector 27 for each rotation and outputs it to the control device 30.

  As the rotary table 3 and the pallet 4 rotate, the inner ring portion 12 of the bearing 10 also rotates integrally, and as shown in FIG. 4, the second roller 14 and the third roller 14 are in contact with the upper surface 12b and the lower surface 12c of the concave inner ring portion 12. The roller 15 revolves while rotating. In this embodiment, since the contact angle α between the second roller 14 and the third roller 15 is 90 °, the movement angle of the second roller 14 and the third roller 15 with respect to the rotation angle ξ of the inner ring portion 12 and the rotary table 3. β is 1 / 2ξ from the above equation (1). Therefore, when the inner ring portion 12 and the rotary table 3 rotate twice (2ξ = 720 °), the second roller 14 and the third roller 15 revolve once (β = 360 °) and return to the origin (0 °).

Therefore, according to Table 1, when the rotary table 3 rotates an odd number of times (for example, one rotation), the rotary table detector 27 outputs an origin (0 ° position) signal to the control device 30 every rotation. Due to the odd number of rotations of the turntable 3, the gear ratio of the disc gear 17 to the worm shaft output gear 25 is odd: 1, so the worm shaft 23 also rotates odd. Then, the worm shaft input gear 24 has a gear ratio N. 5: 1, so odd number × N. The output gear 19 rotates by (integer + 0.5). Therefore, the rotation position detector 21 cannot detect the detection dog 20 and is turned OFF.
When the turntable 3 rotates an even number of times (for example, two turns), the turntable detector 27 outputs the same origin (0 ° position) signal to the control device 30 every turn. As the rotary table 3 rotates even times, the worm shaft 23 also rotates even times, and the worm shaft input gear 24 is an even number × N. The output gear 19 rotates an integer number of times. Therefore, the rotational position detector 21 detects the detection dog 20 and outputs an ON signal. When the rotary table 3 rotates an even number of times, the second and third rollers 14 and 15 of the bearing 10 rotate 1/2 of the rotary table 3 and thus return to the origin. Therefore, the shake of the second and third rollers 14 and 15 returns to the original state, and the shake of the upper surface 3a of the turntable 3 can be adjusted to the same state.

  In addition, this position can be identified by outputting an ON signal from the rotational position detector 21 and the rotary table position detector 27 in synchronization with the control device 30. Therefore, by synchronously outputting these ON signals, the stop position of the rotary table 3 can be repeatedly detected, and the workpiece W exchanged and fixed on the reference surface 7a is sequentially processed, so that the workpiece is first processed on the reference surface 7a. Since the workpiece W is in the same state, the same machining accuracy can be obtained.

  As described above, according to the deflection control device 1 of the rotary table 3 according to the present embodiment, the rotary table 3 and the pallet 4 that hold and hold the workpiece W by the composite rolling bearing 10 having a small sliding resistance are rotatably supported. The revolution positions (angles) of the second and third rollers 14 and 15 are controlled so as to return the deflection, which is a characteristic of the rolling bearing 10, to the original state at the origin of the index position (0 °). Accordingly, the workpiece W on the upper surface 3a of the rotary table 3 is held in the same posture via the scale 7 without changing the deflection caused by the difference in diameter due to the revolution accompanying the rotation of the second and third rollers 14 and 15. Work W can be processed sequentially. Therefore, highly accurate processing can be performed.

  In addition, when cutting the workpiece W provided on the other side of the scale 7 other than the reference surface 7a, for example, the opposing side surface 7b (see FIG. 1), the rotation is performed in the same manner as the swing control method of the turntable 3 according to the above-described embodiment. The reference surface 7a of the scale 7 is indexed at the rotational position of the rotary table 3 and the pallet 4 output in synchronization with the origin (0 ° position) signal from the position detector 21 and the rotary table position detector 27, and further the rotary table. If the workpiece W is machined by rotating 3 and the pallet 4 by 180 °, the same runout can be obtained and the same machining accuracy can be obtained. Further, even when the workpiece W is fixed to both side surfaces of the reference surface 7a of the scale 7, the workpiece W can be processed with the same processing accuracy in the same manner.

Next, as an example of the shake control device 1 for the turntable 3 according to the above-described embodiment, the shake on the upper surface 4a of the pallet 4 fixed to the turntable 3 was measured by a measuring tool such as a dial gauge and verified.
The deflection accuracy in the axial direction (center axis O direction) of the bearing 10 in the deflection control device 1 of the rotary table 3 described above was measured 4 μm. As shown in FIG. 5, the pallet 4 fixed to the turntable 3 was made into a substantially square of 800 mm × 800 mm, and the bearing 10 having an outer diameter of φ560 mm was used. The distance between the corner portion P1 of the pallet 4 and the central axis O is set to 500 mm, and each time the rotary table 3 and the pallet 4 are rotated once, the dial gauge runs between the two adjacent corner portions P1 and P2 of the upper surface 4a. The axial runout of 4a was measured. The results are shown in Table 2.
In Table 2, the axial deflection of the upper surface 4a of the pallet 4 was 0 when the rotary table 3 was rotated an even number of times, and a shake of 7 to 8 μm occurred when the rotary table 3 was rotated an odd number.

In the above-described embodiment, the contact angle α that is the inclination angle of the second and third rollers 14 and 15 provided on the bearing 10 with respect to the central axis O is set to 90 °, but instead, the contact angle of the rolling elements is set to 90 °. You may set to less than 90 degrees.
Even when the contact angle α is less than 90 °, the rotation angle β from the origin position (0 °) of the second and third rollers 14 and 15 with respect to the rotation angle ξ from the origin position of the turntable 3 is 1) It is represented by the formula.
β = {1- (Da · cos α / dpc} / 2 · ξ (1)
Where Da: outer diameter of the rolling element α: contact angle with the perpendicular of the rolling element dpc: rolling element pitch circle diameter.
In this case, the rotation table 3 and the output gear 19 obtained by calculating the movement angle β of the second and third rollers 14 and 15 and integrating the calculated movement angle β by the equation (1) Stores data of a specific position (angle) from the start position of the drive motor 18 to the origin position. Then, control may be performed so as to determine the origin position from these specific positions.

1. Swing control device for rotary table
2 Base 3 Rotary table 4 Pallet 10 Bearing 11 Outer ring part 12 Inner ring part 13 First roller (rolling element)
14 Second roller (rolling element)
15 Third roller (rolling element)
18 drive motor 19 output gear 20 detection dog 21 rotational position detector 23 worm shaft 24 worm shaft input gear 25 worm shaft output gear 27 rotary table position detector 30 controller W work

Claims (7)

A turntable supported rotatably with respect to the base;
A worm shaft for transmitting driving force from the driving motor;
A disk gear that rotates the rotary table integrally and meshes with an output gear of the worm shaft to transmit a driving force;
A bearing provided with a rolling element disposed between the base and the rotary table and revolving while rotating according to the rotation of the rotary table;
A rotational position detector for detecting an origin position for each rotation of an output gear coupled to the drive motor;
A rotary table position detector for detecting an origin position for each rotation of the rotary table;
The revolution position of the rolling element of the bearing is a position where the origin position of the rotation table detected by the rotation table position detector and the origin position of the output gear detected by the rotation position detector are detected in synchronization. A swing control device for a rotary table, characterized in that it returns to the origin.   The gear ratio between the output gear of the drive motor and the worm shaft input gear provided on the worm shaft meshing with the output gear is 1: N. 5 (where N is a positive integer), and the gear ratio between the worm shaft output gear provided on the worm shaft and the disk gear meshing with the worm shaft output gear is 1: Na (where Na is an odd number) 2. The swing control device for a rotary table according to claim 1.   The bearing is configured such that the rolling element is sandwiched between an outer ring portion that is fixedly held and an inner ring portion that rotates integrally with the rotary table, and the rolling element revolves while rotating in conjunction with the inner ring portion. The shake control device for a rotary table according to claim 1 or 2. The contact angle α, which is the angle of the rolling element provided in the bearing with respect to the central axis of the rotary table, is set to 90 °,
The rotary table according to any one of claims 1 to 3, wherein when the rotation angle from the origin position of the rotary table is ξ, the movement angle β revolved from the origin position of the rolling element is equal to ξ / 2. Run-out control device.   The rotary table is provided in a machine tool for processing a workpiece, the workpiece is fixed to a reference surface of a holder fixed to the rotary table, and the rolling element of the bearing returns to the origin, A machine tool comprising the turntable deflection control device according to any one of claims 1 to 4, wherein a workpiece fixed to a reference surface is machined. The driving force from the drive motor is transmitted to the disk gear via the worm shaft output gear provided on the worm shaft, and the rotary table that rotates integrally with the disk gear is supported rotatably on the base via the bearing. And a swing control method for the rotary table that revolves while rotating the rolling elements of the bearing according to the rotation of the rotary table,
The gear ratio between the output gear of the drive motor and the worm shaft input gear of the worm shaft meshing therewith is 1: N. 5 (where N is a positive integer), and the gear ratio between the worm shaft output gear and the disk gear meshing therewith is set to 1: Na (where Na is an odd number) ,
At the position where the timing for detecting the origin position for each rotation of the output gear of the drive motor and the timing for detecting the origin position for each rotation of the rotary table are detected synchronously, the rolling element is the rotary table. And a swing control method for the rotary table, wherein the return to the home position is performed.   7. The method of controlling a shake of the rotary table according to claim 6, wherein a contact angle α, which is an angle of the rolling element with respect to a central axis of the rotary table, is set to 90 °.

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