JP7279326B2 - Machine Tools - Google Patents

Description

The present invention relates to a machine tool having a position correction function.

Conventionally, in machine tools, a feed screw and a spindle are driven by a motor. As a result, the heat generated by the motor, the frictional heat generated by the rotation of the bearings, the frictional heat generated by the engagement between the ball screw and the ball nut of the feed screw, etc. cause thermal expansion of the main shaft, feed screw, bed, etc., and the mechanical position of each part of the machine tool changes. displaced. That is, there is a possibility that the relative positional relationship between the work to be positioned and the tool may be deviated. This variation in mechanical position due to heat poses a problem in high-precision machining.

Conventionally, as a method of correcting the displacement of the machine position due to heat, displacement sensors and temperature sensors are provided as shown in Patent Documents 1 and 2, and the amount of displacement of each part of the machine tool is calculated based on the detected displacement and temperature. There is a method of calculating and correcting the command position during machining based on the calculated displacement amount.

JP-A-10-225843 JP-A-10-138091 Japanese Patent No. 2915147 JP-A-53-35972 JP-A-63-76225 Japanese Patent No. 4544566

However, with the method of correcting the thermal displacement of the machine position of the machine tool by providing a temperature sensor, it is difficult to accurately derive the displacement of each part due to the structure of the machine tool. Further, in the method of correcting thermal displacement by providing a displacement sensor, highly reliable and expensive sensors are required to accurately detect the displacement of each part in an environment where coolant and chips are floating. In addition, the displacement sensor takes a long time to measure, which in turn lengthens the processing time, leading to an increase in cost. On the other hand, the inventors have proposed sensors used for correcting thermal displacement, such as those shown in Patent Documents 3 to 6, which are inexpensive and highly durable against environments in which coolant and cutting chips float. We focused on the photoelectric sensor.

The present invention has been made in view of the above problems, and uses a photoelectric sensor to detect the thermal displacement of each part with low cost and accuracy even in an environment where coolant and chips are floating. It is an object of the present invention to provide a machine tool having a position correction function capable of performing position correction with high accuracy.

One aspect of the present invention is a support base that supports a workpiece;
a tool table that supports a tool for machining the workpiece and is relatively movable in a first axial direction with respect to the support table;
a first moving device that relatively moves the support table and the tool table in the first axial direction;
Based on the control amount of the first moving device, the relative position of the support table and the tool table relatively moved in the first axial direction by the first moving device is derived as a first relative position under normal temperature conditions. a first relative position derivation unit;
a first position correcting device for correcting the first relative position by the amount of thermal displacement when the relative position of the support table and the tool table is thermally displaced;
a second moving device that relatively moves the support table and the tool table in a second axial direction orthogonal to the first axial direction on a horizontal plane;
Based on the control amount of the second moving device, the relative position of the support table and the tool table relatively moved in the second axial direction by the second moving device is derived as a second relative position under normal temperature conditions. a second relative position derivation unit;
a second position correcting device for correcting the second relative position by the amount of thermal displacement when the relative position of the support table and the tool table is thermally displaced ;
A machine tool having a position correction function comprising
The first position correction device is
a light projecting element that is fixed to one of the support table and the tool table and projects light from a light projecting surface;
When the support base and the tool base are fixed to the other of the support base and the tool base, and the relative positions of the support base and the tool base in the first axial direction are positioned within a preset first light receiving range, the light a light-receiving element for receiving on the light-receiving surface,
A straight line fixed to one of the light projecting element and the light receiving element and formed on a plane including the first axial direction so that the light projected from the light projecting surface is perpendicular to the first axial direction. A first slit plate that passes through a shaped first slit,
The first moving device relatively moves the support base and the tool base in the first axial direction, causes the light receiving surface of the light receiving element to receive the light through the first slit, and the first light receiving range a first end position detector that detects the position of the first end in
the first relative position derivation unit calculating the predetermined first relative position based on the predetermined control amount of the first moving device at the time of detecting the first end;
a first position changing unit that changes the predetermined first relative position based on a first reference relative position that is positioned within the preset first light receiving range and prepared in advance;
The second position correction device is
the light projecting element;
the light-receiving element that receives the light on the light-receiving surface when the relative positions of the support table and the tool table in the second axial direction are within a preset second light-receiving range;
The other of the light projecting element and the light receiving element is fixed so as to be parallel to the first slit plate, and the light projected from the light projecting surface is applied to the first slit of the first slit plate, a second slit plate that allows passage in a rectangular shape through a linear second slit formed parallel to the first axial direction;
The second moving device relatively moves the support base and the tool base in the second axial direction, causes the rectangular light receiving surface to receive the light, and positions the second end of the second light receiving range. a second end position detector that detects
a second relative position deriving unit that calculates the predetermined second relative position based on the predetermined control amount of the second moving device at the time of detecting the second end;
a second position changing unit positioned within the preset second light receiving range and changing the predetermined second relative position based on a second reference relative position prepared in advance. .

As described above, in the machine tool according to the present invention, after thermal displacement, the relative positions of the support table and the tool table are positioned at the first reference relative position using the photoelectric sensor composed of a pair of light emitting element and light receiving element. Let Also, a predetermined first relative position, which is a calculated relative position of the support base and the tool base when positioned at the first reference relative position, is obtained. Then, the first position changer changes and corrects the predetermined first relative position based on the first reference relative position. As a result, even if the predetermined first relative position is thermally displaced, it can be accurately corrected despite the inexpensive configuration.

At this time, the machine tool processes the workpiece using the tool. Therefore, in the environment around the machining position, a large amount of coolant and chips are usually floating, and visibility is poor. However, even in such a poor environment, the photoelectric sensor, even if it is inexpensive, can detect the light projected from the light projecting element at the light receiving element in a short time and with relatively high accuracy. . Therefore, the predetermined first relative position after the thermal displacement can be grasped with high accuracy by a further inexpensive structure, and the predetermined first relative position can be corrected with high accuracy. Further, since the photoelectric sensor has high durability in an environment where coolant and chips are floating as described above, the first position correcting device having high durability can be obtained.

It is the outline of the front view of the screw grinder concerning an embodiment. 2 is a plan view of the thread grinder of FIG. 1; FIG. 3 is a detailed explanatory diagram of an X-axis drive circuit and a Z-axis drive circuit shown in FIGS. 1 and 2; FIG. FIG. 3 is a sectional view taken along line IV-IV of FIG. 2; 5 is a view taken along line V-V in FIG. 4; FIG. 5 is a view taken along line VI-VI of FIG. 4; FIG. 5 is a graph illustrating an outline of changes in the relative positions of the movable table (support table) and the column (tool table) when the first moving device is operated at room temperature and at elevated temperature. 7 is a graph illustrating an overview of changes in the relative positions of the movable table (support table) and the column (tool table) when the second moving device is operated at room temperature and at elevated temperature. It is a figure explaining an example of the arrangement|positioning state of the light-projection part and light-receiving part of a photoelectric sensor after a thermal displacement. FIG. 4 is a diagram for explaining the arrangement state of the grinding wheel, the workpiece, and the photoelectric sensor at the processing position at the start of processing by the position correcting device; 4 is a flowchart 1 for explaining processing of the first position correction device; 2 is a flowchart 2 for explaining processing of a second position correction device; FIG. 5 is a diagram for explaining the operation of the light projecting part and the light receiving part when detecting the relative position of the movable table and the column after thermal displacement by the photoelectric sensor in the first position correcting device; It is a figure explaining the relative movement of a light projection part and a light-receiving part after FIG. 12A. 12C is a diagram illustrating relative movement of the light projecting unit and the light receiving unit after FIG. 12B; FIG. FIG. 12C is a diagram for explaining the relative movement of the light projecting part and the light receiving part after FIG. 12C in the operation of the second position correcting device; 12D is a diagram illustrating relative movement of the light projecting unit and the light receiving unit after FIG. 12D; FIG. 12E is a diagram illustrating relative movement of the light projecting unit and the light receiving unit after FIG. 12E; FIG. FIG. 11 is a diagram for explaining Modification 2;

<1. First Embodiment>
(1-1. Configuration of Thread Grinding Machine 10)
An example of a thread grinder 10 (corresponding to a machine tool) having a position correction function (displacement correction function) according to the first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the thread grinding machine 10 includes a bed 11, a movable table 12 (corresponding to a support table), a first moving device 13, a second moving device 14, and a A headstock 16 and a tailstock 17, a column 23 (corresponding to a tool table), a wheelhead 19, a first position correction device 50, a second position correction device 70, a control device 60, and Prepare.

As shown in the front view of FIG. 1, the movable table 12 (supporting table) is placed on the bed 11 so as to be horizontally movable relative to the bed 11 in the Z-axis direction (corresponding to the second axis direction). placed. At this time, as shown in FIGS. 1 and 2, the direction perpendicular to the Z-axis direction (corresponding to the second axis direction) on the horizontal plane is defined as the X-axis direction (corresponding to the first axis direction).

The movable table 12 is controlled to reciprocate in the Z-axis direction by the operation of the second moving device 14 . The second moving device 14 includes a ball shaft 14a, a ball nut 14b, a motor 14c, and a Z-axis drive circuit 14d. As shown in FIG. 1, the ball nut 14b is fixed to the lower surface of the movable table 12 and screwed onto the ball shaft 14a inserted through the bed 11 via a ball (not shown).

The motor 14c, which is a servomotor, has an encoder 14c1. As shown in FIG. 2, the motor 14c and the encoder 14c1 are connected to the control device 60 via the Z-axis drive circuit 14d. As a result, the rotation of the motor 14c is controlled by the controller 60 via the Z-axis drive circuit 14d. When the controller 60 controls the motor 14c to rotate the ball shaft 14a, the encoder 14c1 detects the rotational phase Raz (rad) of the ball shaft 14a controlled by the motor 14c. The detected rotational phase Raz is converted into a second relative position Zm1 by the Z-axis drive circuit 14d and transmitted to the control device 60. FIG.

The control device 60 controls the rotation of the motor 14c attached to one end of the bed 11 via the Z-axis drive circuit 14d as described above to rotate the ball shaft 14a forward and backward. As a result, the movable table 12 moves back and forth along with the ball nut 14b on the bed 11 in the left-right direction (Z-axis direction) in FIG. That is, the second moving device 14 relatively moves the movable table 12 (support table) and the column 23 (tool table) in the Z-axis direction (second axis direction). Note that hereinafter, when only the term “relative movement” is described without special explanation, it means the relative movement between the movable table 12 and the column 23 .

A headstock 16 and a tailstock 17 are placed facing each other on the movable table 12 so that both ends of the workpiece 30 can be supported. Thereby, the movable table 12 rotatably supports the workpiece 30 around the rotation axis through the headstock 16 and the tailstock 17 . In addition, in this embodiment, the workpiece 30 is a long-axis ball screw. The axis of the workpiece 30 is parallel to the Z-axis direction (second axis direction).

The headstock 16 includes a spindle 16a, a motor 16b, which is a servomotor whose rotating shaft is connected to the spindle 16a, and a spindle drive circuit 16d. The spindle 16 a supports the workpiece 30 with the tailstock 17 . The motor 16b also includes an encoder 16b1. As shown in FIG. 2, the motor 16b and the encoder 16b1 are connected to the controller 60 via the spindle drive circuit 16d. As a result, the rotation of the motor 16b is controlled by the controller 60 via the spindle drive circuit 16d.

When the control device 60 controls the motor 16b to rotate the main shaft 16a, the encoder 16b1 changes the rotation phase of the main shaft 16a controlled by the motor 16b, that is, the rotation phase Raw (rad) of the workpiece 30 around the axis. It is detected and transmitted to the spindle drive circuit 16d. The spindle drive circuit 16d transmits the detected rotation phase Raw to the control device 60 and causes the storage unit 62 to store it.

As shown in FIG. 2, a column 23 (tool table) is fixed to the movable table 15 behind the movable table 12 (upper side in the drawing). A turntable 18 is supported by a horizontal shaft 44 on the front surface of the column 23 and is rotatable around the axis of the horizontal shaft 44 . Further, a grinding wheel 19 is fixed to the front surface of the turntable 18, and the grinding wheel 19 rotates a screw grinding wheel 27 (corresponding to a tool, hereinafter referred to only as the grinding wheel 27) around the rotation axis. To support. That is, the column 23 supports a grinding wheel 27 for processing the workpiece 30 via the turntable 18 and the grinding wheel head 19 . The column 23 is relatively movable in the X-axis direction (first axis direction) with respect to the movable table 12 (support base).

A shaft 20 that is rotated about its axis by a motor 45 fixed to a column 23 is provided on the rear side of the turntable 18 so as to extend vertically in FIG. A worm (not shown) that rotates integrally with the shaft 20 is fixed to the shaft 20 . The worm meshes with a worm wheel 22 provided on the outer circumference of a horizontal shaft 44 (see FIG. 2). As a result, when the control device 60 operates the motor 45 to rotate the worm forward and backward, the turntable 18 rotates about the axis of the horizontal shaft 44 , and the grinding wheel 19 and grinding wheel 27 rotate on the horizontal shaft 44 . rotate about the axis of

Further, as shown in FIG. 2, a first moving device 13 is provided below the moving table 15 in the gravity direction (Y-axis direction). The first moving device 13 includes a ball shaft 13a, a ball nut (not shown), a motor 13c that is a servomotor, and an X-axis driving circuit 13d. The ball shaft 13a is rotated by the control device 60 controlling the motor 13c fixed to the bed 11. As shown in FIG. The ball nut is fixed to the moving table 15 and screwed with the ball shaft 13a via a ball (not shown).

The motor 13c has an encoder 13c1. As shown in FIG. 2, the motor 13c and the encoder 13c1 are connected to the controller 60 via the X-axis drive circuit 13d. As a result, the rotation of the motor 13c is controlled by the controller 60 via the X-axis drive circuit 13d. When the controller 60 controls the motor 13c to rotate the ball shaft 13a, the encoder 13c1 detects the rotational phase Rax (rad) of the ball shaft 13a controlled by the motor 13c. The detected rotation phase Rax is sent to the X-axis drive circuit 13d.

The control device 60 controls the rotation of the motor 13c via the X-axis drive circuit 13d to rotate the ball shaft 13a forward and backward. As a result, the moving table 15 (column 23) advances and retreats in the X-axis direction (first axis direction, vertical direction in FIG. 2) parallel to the horizontal axis 44. As shown in FIG. The grinding wheel 27 of the grinding wheel head 19 approaches or separates from the workpiece 30 (ball screw) by advancing and retreating in the X-axis direction. That is, the first moving device 13 (moving device) relatively moves the movable table 12 (support table) and the column 23 (tool table) in the X-axis direction (first axis direction).

The wheel head 19 is equipped with a motor 19a, a rotating shaft 19b (output shaft) of the motor 19a rotatably supported by the wheel head 19, and the grinding wheel 27 described above. The grinding wheel 27 is fixed to the end of the rotating shaft 19b of the motor 19a. When the motor 19a is actuated under the control of the control device 60, the rotating shaft 19b and the grinding wheel 27 are integrally rotated relative to the grinding wheel head 19 around the axis.

When the tooth flank of the workpiece 30 is ground by the thread grinding machine 10 having the above configuration, first, as shown in FIG. A workpiece 30 (ball screw) is supported so that Then, the control device 60 controls the motor 14c of the second moving device 14, the motor 13c of the first moving device 13, and the motor 16b to rotate the spindle 16a while relatively moving the grinding wheel 27 and the workpiece 30. Then, the grinding wheel 27 mounted on the grinding wheel head 19 is used to grind the tooth surface of the workpiece 30 .

When the workpiece 30 is a ball screw as in this embodiment, the axis 19c of the rotating shaft 19b connected to the grinding wheel 27 is aligned with the axis C1 of the workpiece 30 (ball screw). is inclined by an amount corresponding to the angle of the tooth flank of the thread groove. For example, the controller 60 activates the motor 45 in order to set the tilt to the desired tilt angle α° (see FIG. 1). As a result, the worm is rotated to rotate the turntable 18 about the axis of the horizontal shaft 44, so that the axis 19c is adjusted to the desired inclination angle α°.

Thereafter, by operating the first moving device 13, the grinding wheel 27 is moved in the X-axis direction and pressed against the tooth flank of the thread groove of the workpiece 30 to grind the tooth flank. The control of the control device 60 when grinding the tooth flank of the thread groove is as described above. Although not described in detail, the thread grinder 10 adjusts the height of the workpiece 30 and the slanted grinding wheel 27 in the Y-axis direction perpendicular to the X-axis and the Z-axis. 30 and the grinding wheel 27 are provided with a Y-axis relative movement mechanism (not shown).

The control device 60 includes a central processing unit 61 (CPU), the storage unit 62 described above, and a display unit 63, as shown in FIGS. The central processing unit 61 (CPU) is a known CPU. The storage unit 62 stores a third relative position Xn (not shown in the storage unit 62), a fourth relative position Zn (not shown in the storage unit 62), and an X-axis correction program that controls the operation of the first position correction device 50. 64, and a Z-axis correction program 65 for controlling the operation of the second position correction device 70, etc. are stored.

The X-axis correction program 64 and the Z-axis correction program 65 describe the first reference relative position Xp and the second reference relative position Zp at the "predetermined machining standby position P", respectively. The X-axis correction program 64 and Z-axis correction program 65 will be described later in detail when describing the operation of the first position correction device 50 and the second position correction device 70 . In addition, the display unit 63 displays a third relative position Xn and a fourth relative position Zn, which are the current positions, on a liquid crystal panel or the like.

The predetermined machining standby position P is a position where the grinding wheel 27 is separated from the workpiece 30 in the X-axis direction to such an extent that the workpiece 30 can be carried in and out. Moreover, this is the position where the operating table 12 is positioned in the Z-axis direction so that the grinding wheel 27 can start machining the workpiece 30 simply by moving it in the X-axis direction. That is, if the machining is started from the predetermined machining standby position P, the moving distance of the grinding wheel 27 with respect to the workpiece 30 is shortened, and the machining time can be shortened.

(1-2. First Position Correction Device 50 and Second Position Correction Device 70)
Next, the first position correction device 50 and the second position correction device 70 will be described. The first position correction device 50 and the second position correction device 70 have similar configurations and functions. Therefore, when describing the first position correction device 50 and the second position correction device 70, mainly in the description of the first position correction device 50, the configuration of the second position correction device 70 corresponding to each configuration is shown in parentheses. Do it while writing it together.

The first position correction device 50 (second position correction device 70) will be described with reference to FIGS. 1 to 12F. The first position correcting device 50 (second position correcting device 70) is adjusted in the first axial direction (second axial direction), and the contact position (processing position) between the workpiece 30 supported by the movable table 12 (support base) and the grinding wheel 27 (tool) supported by the column 23 (tool base), that is, the first This device detects and corrects a deviation corresponding to thermal displacement when thermal displacement occurs in the relative position in the axial direction (second axial direction).

As shown in FIGS. 1 to 6, the first position correction device 50 (second position correction device 70) includes the photoelectric sensor 51, the first slit plate 51a, the second slit plate 51b, and the X-axis correction device. The program 64 includes a first end position detection unit 64a (second end position detection unit 65a), a first relative position derivation unit 13d1 (second relative position derivation unit 14d1), and a first position change unit 13d2 (second and a two-position changer 14d2).

Note that, as shown in FIG. 3, the first relative position deriving section 13d1 and the first position changing section 13d2 are included in the above-described X-axis driving circuit 13d. Also, the second relative position deriving section 14d1 and the second position changing section 14d2 are provided in the Z-axis drive circuit 14d described above. The first position correction device 50 (second position correction device 70 ) is controlled by an X-axis correction program 64 (Z-axis correction program 65 ) provided in the control device 60 .

The photoelectric sensor 51 projects "light" such as visible light and infrared rays from a light projecting surface 53a (see FIG. 4) of a light projecting element 53 (light projecting section 52), which will be described later. Then, the projected “light” is detected by a light receiving surface 57 a of a light receiving element 57 (light receiving portion 55 ), which will be described later, and an ON signal indicating the detection is output to the control device 60 . Since the photoelectric sensor 51 is publicly known, further detailed description of its functions will be omitted.

As shown in FIGS. 1 and 2 , the photoelectric sensor 51 is shared by the first position correction device 50 and the second position correction device 70 . As shown in FIG. 4, the photoelectric sensor 51 includes the light projecting section 52 and the light receiving section 55 described above. The light projecting unit 52 includes a light projecting element 53 and a light projecting main body 54 that is a housing that holds the light projecting element 53 . The light projecting main body 54 is formed in a rectangular parallelepiped shape, and a through-hole 54c is formed in the center of predetermined back-facing surfaces 54a and 54b so as to penetrate between the back-facing surfaces 54a and 54b. A columnar light projecting element 53 is arranged in the through hole 54c.

One end surface of the cylindrical light projecting element 53 is provided with a light projecting surface 53a. A wiring to the control device 60 is connected to the other end face of the light projecting element 53 . In this embodiment, the shape of the light Li projected from the light projecting surface 53a is a circle with a radius R1 (see FIG. 5). When the light projecting part 52 is attached to the thread grinding machine 10, the light projecting surface 53a is arranged parallel to the horizontal plane and facing downward in the direction of gravity (Y-axis direction) as shown in FIG. Further, as shown in FIG. 4, in the light projecting section 52, the above-described first slit plate 51a is arranged on the back surface 54a of the light projecting main body 54 on the side of the light projecting surface 53a.

As shown in FIG. 5, the first slit plate 51a is composed of two split slit plates 51a1 and 51a2 formed in the same shape. The divided slit plates 51a1 and 51a2 form a linear gap (first slit 51a3) having a uniform interval between them while being fixed to the back surface 54a. The split slit plates 51a1 and 51a2 are fixed to the back surface 54a by bolts or the like (not shown) so that the width W1 of the first slit 51a3 is, for example, about 5 μm.

At this time, the center O1 of the circular light projected by the light projecting surface 53a having the radius R1 is positioned substantially at the center of the width W1 of the first slit 51a3 in the width direction. The split slit plates 51a1 and 51a2 are fixed to the back surface 54a so that the width W1 of the first slit 51a3 can be freely changed (adjusted). As a result, even when measurement with a different width W1 of the first slit 51a3 is required, the photoelectric sensor 51 does not need to be replaced. Since it can respond, it can respond to low cost and is very efficient.

The width W1 is adjusted by fixing the divided slit plates 51a1 and 51a2 to the back surface 54a in a state in which known gap gauges having the same thickness are sandwiched between both ends of the first slit 51a3. It can be removed from one slit 51a3. At this time, the fixing positions of the divided slit plates 51a1 and 51a2 on the back surface 54a are gradually displaced relative to the back surface 54a according to the thickness of the gap gauge. This misalignment can be dealt with by making the diameter of the bolt through holes provided in the split slit plates 51a1 and 51a2 slightly larger than the outer diameter of the shaft of the bolt to allow relative movement of the split slit plates 51a1 and 51a2 with respect to the bolt. do it. However, this correspondence example is merely an example, and any correspondence may be made.

The extending direction of the first slit 51 a 3 is the Z-axis direction when the light projecting section 52 is attached to the thread grinder 10 . That is, the first slit 51a3 is arranged on a horizontal plane including the first axial direction so as to be orthogonal to the X-axis direction (first axial direction) (see FIG. 5). 1 and 2, the light projecting part 52 is fixed in a cantilevered state to the column 23 (corresponding to one of the support base and the tool base), which is a tool base, via a first support member 68. be done.

That is, one end of the first support member 68 is fixed to the side surface of the column 23 and the other end of the first support member 68 is fixed to the light projecting section 52 . Further, in other words, it can be said that the light projecting part 52 is attached to the bed 11 of the thread grinding machine 10 via the column 23 and the like. Then, the light projecting unit 52 allows the light Li projected in a circular shape from the light projecting surface 53a to pass through the first slit 51a3 in a straight line toward the light receiving unit 55 opposite to the light projecting surface 53a. .

At this time, the light projecting section 52 is arranged such that the light projecting surface 53a is positioned relatively close to the grinding wheel 27 . Further, the light projecting section 52 is moved integrally with the grinding wheel 27 in the X-axis direction (first axis direction). Also, the first support member 68 is preferably made of a material with a low coefficient of thermal expansion. As an example, if it is a metal material, invar (or umber) is preferable. Also, the first support member 68 may be made of fine ceramics or the like without being limited to metal materials.

However, a metal material having a higher coefficient of thermal expansion than invar, fine ceramics, or the like may be used. A corresponding effect can also be expected from this. As a result, when the temperature of, for example, the bed 11 of the screw grinder 10 rises and thermally expands, the position of the light projecting surface 53a is affected by the thermal displacement of the bed 11, similar to the grinding wheel 27 supported by the bed 11. Follow and displace.

As shown in FIG. 4, the light receiving portion 55 includes the light receiving element 57 described above and a light receiving body portion 58 that holds the light receiving element 57 . The light-receiving main body 58 is formed in a rectangular parallelepiped shape like the light-projecting main body 54, and a through hole 58c is formed in the center of predetermined back-facing surfaces 58a and 58b so as to penetrate between the back-facing surfaces 58a and 58b. A cylindrical light receiving element 57 is arranged in the through hole 58c.

One end face of the cylindrical light receiving element 57 is provided with a light receiving surface 57a. The other end surface of the light receiving element 57 is connected to a control device 60, and a wiring is connected to transmit a light receiving signal to the control device 60 when the light receiving surface 57a receives light projected from the light projecting surface 53a. be. As shown in FIG. 6, the light-receiving surface 57a is formed of a circle having a radius R2 that is the same as (the same diameter as) or slightly larger than the shape (circular shape) of the light projected from the light-projecting surface 53a (R2≧R1 ).

As shown in FIG. 4, when the light-receiving part 55 is attached to the thread grinding machine 10, the light-receiving surface 57a is arranged parallel to the horizontal plane and facing upward in the direction of gravity (Y-axis direction). Further, as shown in FIG. 4, the light receiving portion 55 includes a second slit plate 51b on the back surface 58a of the light receiving body portion 58 on the side of the light receiving surface 57a.

The extension direction of the second slit 51b3 is the X-axis direction (first axis direction) when the light receiving portion 55 is attached to the thread grinder 10 . That is, the second slit 51b3 is arranged so as to be orthogonal to the extending direction of the first slit 51a3 (see FIG. 6). In other words, when the light receiving unit 55 is attached to the screw grinder 10, the second slit 51b3 is arranged on the horizontal plane so as to be perpendicular to the Z-axis direction (second axis direction).

As shown in FIG. 6, the second slit plate 51b is composed of two divided slit plates 51b1 and 51b2 formed in the same shape. The divided slit plates 51b1 and 51b2 form a linear gap (second slit 51b3) having a uniform interval therebetween while being fixed to the back surface 58a. The split slit plates 51b1 and 51b2 are fixed to the back surface 58a by bolts or the like (not shown) so that the width W2 of the second slit 51b3 is, for example, about 5 μm.

At this time, the center O2 of the circular light-receiving surface 57a having the radius R2 is positioned substantially at the center in the width direction of the width W2 of the second slit 51b3. Similar to the split slit plates 51a1 and 51a2 provided in the light projecting section 52, the split slit plates 51b1 and 51b2 are oriented so that the width W2 of the second slit 51b3 can be freely changed (adjusted). It is fixed to the surface 58a. As a result, even when measurement with a different width W2 of the second slit 51b3 is required, the photoelectric sensor 51 does not need to be replaced. Since it can respond, it can respond to low cost and is very efficient. The method for adjusting the width W2 is the same as the method for adjusting the width W1 of the first slit 51a3.

In addition, the widths W1 and W2 of the first slit 51a3 and the second slit 51b3, which can be changed in the above description, are such that the smaller the value, the more thermal displacement occurs in the relative position between the workpiece 30 and the grinding wheel 27 (tool). The detection accuracy of the amount of displacement in the case is improved. Therefore, in the above description, the case where it is necessary to measure the width W1 of the first slit 51a3 and the width W2 of the second slit 51b3 which are different is, for example, the case where it is desired to detect the amount of displacement with higher accuracy. In this case, the width W1 of the first slit 51a3 and the width W2 of the second slit 51b3 should be reduced.

However, when the widths W1 and W2 are reduced, the amount of light passing through the first slit 51a3 and the second slit 51b3 is reduced. Therefore, the amount of light received by the light receiving element 57 also decreases. In order to deal with this, the threshold value for determining whether the light is ON is changed to a lower value for an amplifier (not shown) provided between the light receiving element 57 and the control device 60 . A sufficient effect can be obtained by reducing only one of the widths W1 and W2, rather than reducing both of the widths W1 and W2.

Specifically, considering the case where the first position correction device 50 (the second position correction device 70) is applied to the thread grinder 10 as in the present embodiment, the thread grinder 10 normally has the workpiece 30 Positioning accuracy in the axial direction is important. Therefore, in the slit on the side that moves in the axial direction of the workpiece 30 (corresponding to the second slit 51b3 of the second slit plate 51b in this embodiment), the direction of the width (W2) is aligned with the axis of the workpiece 30. Arrange to match the direction. When it is desired to improve the positioning accuracy of the workpiece 30 in the axial direction, the width (W2) of the slit (second slit 51b3) in the axial direction of the workpiece 30 is reduced.

Moreover, when the first position correcting device 50 (the second position correcting device 70) is applied to, for example, a cylindrical grinder, the positioning accuracy of the workpiece 30 in the radial direction is usually important. For this reason, in the slit on the side that moves in the radial direction of the workpiece 30 (corresponding to the first slit 51a3 of the first slit plate 51a in this embodiment), the direction of the width W1 is aligned with the radial direction of the workpiece 30. Arrange to match. When it is desired to increase the radial positioning accuracy of the workpiece 30, the width of the first slit 51a3 in the radial direction of the workpiece 30 is reduced.

The light receiving unit 55 is fixed to the movable table 12 (corresponding to the other of the support base and the tool base) as a support base in a cantilevered state via a second support member 69 . That is, one end of the second support member 69 is fixed to the side surface of the movable table 12 , and the light receiving section 55 is fixed to the other end of the second support member 69 . Further, in other words, it can be said that the light receiving unit 55 is attached to the bed 11 of the thread grinding machine 10 via the movable table 12 and the like. Also, the second support member 69 is preferably made of a material having a low coefficient of thermal expansion, like the first support member 68 .

As a result, when the temperature of, for example, the bed 11 of the thread grinder 10 rises and thermally expands, the position of the light receiving surface 57a will change as the screw workpiece 30 supported by the bed 11 heats up. Displaced following the displacement.

At this time, when the relative positions of the movable table 12 (support table) and the column 23 (tool table) are positioned at a preset "predetermined machining standby position P" as shown in FIG. 2, and machining is started from there. , the distance Xγ in the X-axis (first axis) direction between one end of the first support member 68 fixed to the side surface of the column 23 and the side surface of the movable table 12 to which one end of the second support member 69 is fixed is kept constant. Also, a distance Zγ in the Z-axis (second axis) direction between one end of the second support member 69 fixed to the side surface of the movable table 12 and the side surface of the column 23 to which one end of the first support member 68 is fixed is kept constant.

The light-receiving surface 57a of the light-receiving unit 55 is such that the relative positions of the column 23 (tool table) on which the grinding wheel 27 is supported and the movable table 12 (support table) are "predetermined processing standby position P" at room temperature. (that is, the first reference relative position Xp and the second reference relative position Zp), the center O2 of the light receiving surface 57a is vertically aligned with the center O1 of the light projecting surface 53a of the light projecting element 53. Set to match and oppose. 1 and 2 show a state in which the column 23 and the movable table 12 are positioned at the "predetermined processing standby position P".

Also, as shown in FIG. 2, the actual relative position in the X-axis direction from the axis C1 of the workpiece 30 to the tip of the grinding wheel 27 is the third relative position Xn, and the tip of the grinding wheel 27 from the end face 16a1 of the main spindle 16a. Assuming that the actual relative position in the Z-axis direction is a fourth relative position Zn, the third relative position Xn and the fourth relative position Zn are always displayed on the display unit 63 of the control device 60 . In addition, the control device 60 controls the relative positions of the column 23 (tool table) on which the grinding wheel 27 is supported and the movable table 12 (support table) when they are positioned at the "predetermined machining standby position P". The X-axis correction program 64 and the Z-axis correction program 65 of the storage unit 62 describe the position Xn as the "first reference relative position Xp" and the fourth relative position Zn as the "second reference relative position Zp".

The relative movement of the movable table 12 and the grinding wheel 27 to the "predetermined machining standby position P", which is the relative position, is performed by the control device 60, the X-axis drive circuit 13d, the Z-axis drive circuit 14d, etc. so that the third relative position Xn is set to " The fourth relative position Zn is controlled to be the "second reference relative position Zp" at the "first reference relative position Xp". That is, as shown in the graphs of FIGS. 7A and 7B, at room temperature, the control device 60 sets the motors 13c and 14c of the first moving device 13 and the second moving device 14 to the "first reference relative position Xp". , and the rotational phases Raxt and Razt (predetermined control amounts) corresponding to the "second reference relative position Zp", respectively, so that the movable table 12 and the grinding wheel 27 move in the X-axis direction and the Z-axis direction, respectively. , the relative position is relatively moved to a predetermined machining standby position P (Xp, Zp).

However, for example, when the temperature of the bed 11 rises and the bed 11 thermally expands (thermally displaces), as shown by straight lines L3 and L4 in FIGS. When 14c is rotationally controlled at preset predetermined rotational phases Raxt and Razt, it moves to relative position P1 (third relative position Xn, fourth relative position Zn) that intersects straight lines L3 and L4, respectively.

At this time, at the relative position P1, as shown in FIG. (For example, β1, β2). Therefore, in the present invention, after the thermal displacement, the displacement amounts (β1, β2) corresponding to the thermal displacement of the relative positions of the movable table 12 and the grinding wheel 27 are corrected.

In the above, the straight lines L3 and L4 are, for example, the rotation phases Rax and Raz (control amounts) when the temperature is increased by a predetermined temperature (for example, 1 degree) from the temperature at the time of detection of the straight lines L1 and L2, and the movable table 12 (support table) and a correlation graph with a third relative position Xn and a fourth relative position Zn, which are actual relative positions of a column 23 (tool table). Since FIG. 7A (FIG. 7B) is an enlarged view of the area around Raxt (Razt), the straight lines L2 and L4 and the straight lines L1 and L3 are nearly parallel to each other.

When the ball shaft 13a (ball shaft 14a) thermally expands, the horizontal axis in FIG. 7A (FIG. 7B) extends. Further, when the bed 11 thermally expands, the vertical axis in FIG. 7A (FIG. 7B) extends. Depending on the thermal expansion of each of the ball shaft 13a (ball shaft 14a) and the bed 11, the positions of Raxt and Xn (Razt and Zn) may change along the straight line L1 (L2), or the inclination of the straight line L1 (L2) may change. It may be a straight line L3 (L4) that is gentle, or a straight line L3 (L4) that is steeper than the straight line L1 (L2).

As shown in FIGS. 1 and 2, the first end position detection section 64a (second end position detection section 65a) is provided in the X-axis correction program 64 (Z-axis correction program 65) provided in the control device 60. FIG. Since the first end position detection unit 64a and the second end position detection unit 65a have the same configuration and functions, the corresponding configurations will be described in parentheses as much as possible. .

The first end position detector 64a (second end position detector 65a) controls the first moving device 13 and the second moving device 14 to move the column 23 (tool table) and the movable table 12 (support table). It is relatively moved in the direction of the first axis and the direction of the second axis. As a result, the light is received by the light receiving surface 57a of the light receiving element 57 via the first slit plate 51a and the second slit plate 51b, and the first end portion of the first light receiving range Ar1 (second light receiving range Ar2) to be described later. The positions of E1 and E2 (second ends E3 and E4) are detected. Details will be provided later in the description of operation.

As shown in FIG. 3, the first relative position derivation section 13d1 (second relative position derivation section 14d1) is included in the X-axis drive circuit 13d (Z-axis drive circuit 14d) as described above. The first relative position derivation unit 13d1 (second relative position derivation unit 14d1) is connected to the encoder 13c1 (14c1), and determines the predetermined rotational phase (control amount) Rax1 of the motor 13c (14c) detected by the encoder 13c1 (14c1). (Raz1) is input.

Then, the first relative position derivation unit 13d1 (second relative position derivation unit 14d1) is based on the predetermined control amount Rax1 (Raz1) input from the encoder 13c1 (14c1). 14) is a predetermined first relative position Xm1, which is a calculated relative position at room temperature between the movable table 12 (support table) and the column 23 (tool table) relatively moved in the first axial direction (second axial direction). (Predetermined second relative position Zm1) is calculated and derived. Note that such calculations by the first relative position derivation unit 13d1 (the second relative position derivation unit 14d1) are well known, and detailed description thereof will be omitted.

Specifically, the first relative position derivation unit 13d1 (second relative position derivation unit 14d1) detects the first end E1, E2 (second end E3, E4) at the time when the first moving device 13 ( A predetermined first relative position Xm1 (predetermined second relative position Zm1) is calculated based on a predetermined control amount Rax1 (predetermined control amount Raz1) of the second moving device 14). The derived first predetermined relative position Xm1 (second predetermined relative position Zm1) is transmitted to the first position changing section 13d2 (second position changing section 14d2).

The first position changer 13d2 (second position changer 14d2) is included in the X-axis drive circuit 13d (Z-axis drive circuit 14d) as described above (see FIG. 3). The first position changer 13d2 (second position changer 14d2) includes two calculators A and B (E and F). The calculation unit A(E) is connected to the first relative position derivation unit 13d1 (second relative position derivation unit 14d1), and obtains a predetermined first relative position from the first relative position derivation unit 13d1 (second relative position derivation unit 14d1). A position Xm1 (predetermined second relative position Zm1) is input. Further, the calculation unit A (E) is connected to the control device 60, and the first reference relative position Xp (the second reference relative position Zp ) is entered.

Based on the following formulas (1) and (2), the calculation unit A(E) calculates the first reference relative position Xp (second reference relative position Zp) and the predetermined first relative position Xm1 (predetermined second relative position A position error .DELTA.X1 (.DELTA.Z1) which is the difference between the position Zm1) is calculated. The first reference relative position Xp is the tip position of the grinding wheel 27 in the X-axis (first axis) direction with the axis C1 of the workpiece 30 as a reference, as shown in FIG. As shown in FIG. 2, the second reference relative position Zp is the tip position of the grinding wheel 27 in the Z-axis (second axis) direction when the end face of the spindle 16a on the workpiece 30 side is used as a reference. The position error .DELTA.X1 (.DELTA.Z1) is stored and held in the calculation section A (E) until the X-axis correction program 64 (Z-axis correction program 65) is next operated. When the X-axis correction program 64 (Z-axis correction program 65) is activated, the position error .DELTA.X1 (.DELTA.Z1) of the calculation section A (E) is reset to zero.
ΔX1=Xp-Xm1 (1)
ΔZ1=Zp−Zm1 (2)

In the above description, the rotation phase Rax (Raz) (control amount) from the predetermined reference position S (T) of the motor 13c (14c) at room temperature and the first relative position Xm (second As an example, the relationship with the relative position Zm) can be represented by a straight line L1 (L2) in the graph of FIG. 7A (FIG. 7A). Also, the relative position between the rotational phase (controlled amount) Rax (rotational phase (controlled amount) Raz) from the predetermined reference position S(T) of the motor 13c (14c) after thermal displacement and the movable table 12 and the column 23 The relationship with the fourth relative position Zn is represented by straight line L3 (L4) in the graph of FIG. 7A (FIG. 7B) as an example.

Calculation unit B (F) includes calculation unit A (B), first relative position derivation unit 13d1 (second relative position derivation unit 14d1), first machining control unit 13d3 (second machining control unit 14d3), and control device 60 connected to The position error ΔX1 (ΔZ1) is input from the calculation unit A(E) to the calculation unit B(F). Further, the predetermined first relative position Xm1 (predetermined second relative position Zm1) is input to the calculation unit B(F) from the first relative position deriving unit 13d1 (second relative position deriving unit 14d1). Then, the calculation unit B(F) calculates and derives the third relative position Xn (fourth relative position Zn), which is the actual relative position, based on the following equations (3) and (4).
Xn=Xm1+ΔX1 (3)
Zn=Zm1+ΔZ1 (4)

Then, the calculation unit B(F) transmits the derived third relative position Xn (fourth relative position Zn) to the first machining control unit 13d3 (second machining control unit 14d3) and the control device 60. At this time, if the bed 11 or the like is thermally displaced, the predetermined second relative position Zm1 becomes a value different from the fourth relative position Zn indicating the position after the thermal displacement by ΔZ1, and the bed 11 or the like is changed. In the normal temperature state where there is no thermal displacement, the predetermined second relative position Zm1 has a value equal to the fourth relative position Zn.

In this way, the first position changer 13d2 (second position changer 14d2) is the first reference relative position Xp (second reference relative position Zp), the position error ΔX1 (ΔZ1) is calculated and stored, and the first relative position Xm1 (second relative position Zm1) is changed to the third relative position Xn (fourth relative position Zn). As a result, the thermal displacement is canceled and corrected. A detailed change method will be described later.

In addition, in the above, the first processing control unit 13d3 (second processing control unit 14d3) connected to the first position changing unit 13d2 (second position changing unit 14d2) is connected to the first position changing unit 13d2 (second position changing unit 14d2). It is a control unit that generates a machining command value for the workpiece 30 using the third relative position Xn (fourth relative position Zn) that is the actual relative position after thermal displacement derived by the unit 14d2).

The first processing control section 13d3 (second processing control section 14d3) will be briefly described. As shown in FIG. 3, the first machining controller 13d3 (second machining controller 14d3) includes a comparator C (G) and a phase converter D (H). Comparator C (G) is connected to control device 60, calculator B (F) and phase converter D (H). The comparator C (G) receives the third relative position Xn (fourth relative position Zn) from the computing section B (F). A target relative position Xt (Zt) during machining is input from the control device 60 to the comparator C (G). As a result, the comparator C (G) obtains the position difference ΔX2 (ΔZ2) between the third relative position Xn (fourth relative position Zn) and the target relative position Xt (Zt). Send.

Phase converter D (H) is connected to motor 13c (14c). Phase converter D (H) converts position difference ΔX2 (ΔZ2) into rotational phase Rax2 (Raz2), which is a phase signal, and transmits rotational phase Rax2 (Raz2) to motor 13c (14c). Rotate (14c). As a result, the workpiece 30 can be machined in a state in which the thermal displacement ΔX1 (ΔZ1) is corrected, so that a highly accurate machining state can be obtained.

Moreover, in the above description, the first position correction device 50 (the second position correction device 70) can be operated (processed) at various timings. As an example, the first position correcting device 50 (the second position correcting device 70) may perform correction processing at the timing when a predetermined machining program stored in the control device 60 ends. As another example, the thread grinder 10 (machine tool) may include a temperature sensor 80 (see FIG. 2) that measures the temperature at a predetermined position, and a correction opportunity detection program 66 provided in the storage unit 62. good.

At this time, the correction opportunity detection program 66 acquires the temperature Tn detected by the temperature sensor 80 (see FIGS. 1 to 3). Then, the acquired measurement result of the current temperature Tn is compared with the allowable temperature Ta preliminarily held in the storage unit 62, and at a predetermined timing when the current temperature Tn exceeds the allowable temperature Ta (not shown), the first A correction command signal may be transmitted to the position correction device 50 (second position correction device 70) to cause correction processing.

Furthermore, as another example of the timing for operating the first position correcting device 50 (second position correcting device 70), at the timing when a predetermined machining program is completed, the thread grinder 10 starts operating (turns on the power). If the elapsed time has passed the set time, it may be operated and corrected. Further, as another example of timing, the operation and correction may be performed based on the increase in room temperature instead of the temperature of each part of the thread grinder 10 (machine tool).

(1-3. Operation)
Next, operations of the first position correction device 50 and the second position correction device 70 will be described mainly based on flowcharts 1 and 2 of FIGS. 10 and 11. FIG. In this embodiment, as an example, it is assumed that the correction process is performed by the second position correction device 70 after the correction processing is performed by the first position correction device 50 .

In the correction processing by the first position correcting device 50, the search for the first reference relative position Xp between the movable table 12 and the grinding wheel 27 after thermal displacement is performed as follows. That is, the search for the first reference relative position Xp is started from the machining position Pw (see FIG. 9) where the grinding wheel 27 (tool) contacts and grinds the workpiece 30, and is spaced apart in the X-axis direction. This is performed when relatively moving toward a position in the vicinity of the predetermined machining standby position P shown. These processes are controlled by the X-axis correction program 64. FIG.

Further, the processing by the first position correcting device 50 will be described as being performed at the timing of moving to the predetermined machining standby position P just before the predetermined machining program stored in the control device 60 is finished. The processing by the first position correction device 50 includes steps S10 to S32, as shown in flowchart 1 of FIG. Further, the processing by the second position correcting device 70 includes steps S40 to S62, as shown in flowchart 2 of FIG.

As shown in FIG. 10, in step S10 (first end position detection unit 64a), the control device 60 moves to a predetermined machining standby position P just before the end of a predetermined machining program stored in the control device 60. is operated, the first end position detection unit 64a operates the motor 13c of the first moving device 13 via the X-axis drive circuit 13d, and at the same time ΔX1 of the calculation unit A is reset to 0. do. As a result, the column 23 supporting the grinding wheel 27 starts moving away from the machining position Pw shown in FIG. 9 in the X-axis direction (first axis direction).

In other words, the light projecting section 52 and the light receiving section 55 start moving relatively close to each other on the horizontal plane. At this time, it is assumed that the light projected from the light projecting surface 53a is not received by the light receiving surface 57a immediately after the start of movement in the direction away from the processing position Pw.

In step S12 (first end position detector 64a), the first moving device 13 relatively moves the grinding wheel 27 with respect to the movable table 12 in a direction away from the processing position Pw. While relatively moving, as shown in FIG. 12A, the light-receiving surface 57a emits light from the light-projecting surface 53a, and emits point-like (rectangular) light passing through the first slit 51a3 and the second slit 51b3 that are orthogonal to each other. The first end E1 that receives and turns on the light is detected. At this time, the first end E1 is a point on the outer peripheral edge of the circle of radius R2 that forms the light receiving surface 57a.

In step S14 (first end position detection unit 64a), the grinding wheel 27 (column 23) detects the relative position X1 in the X-axis direction where the first end E1 is detected, and stores it in the storage unit 62. In addition, step S14 may be processed after the end of step S12, or may be processed simultaneously with step S12.

In step S16 (first end position detection unit 64a), while the grinding wheel 27 is relatively moved further away from the processing position Pw, the light receiving surface 57a detects a point-like light projected from the light projecting surface 53a. is detected as an OFF point (see FIG. 12B) at which no light is received. Then, the position before the OFF point in the movement in the X-axis direction is calculated from the movement speed in the X-axis direction and stored as the second first end E2 (see FIG. 12C).

At this time, the first end E2 is also a point on the outer peripheral edge of the circle of radius R2 that forms the light receiving surface 57a, like the first end E1. In this manner, the first position correction device 50 detects both ends in contact with the outer peripheral edge of the circle forming the light receiving surface 57a in the X-axis direction. Here, the range between the first end E1 and the first end E2 in the X-axis direction (first axis direction) is defined as a first light receiving range Ar1. That is, when the relative positions of the movable table 12 and the grinding wheel 27 in the X-axis direction are within the width of the preset first light receiving range Ar1, the photoelectric sensor 51 detects that the light receiving surface 57a extends from the light projecting surface 53a. It is possible to receive projected point-like light.

In step S18 (first end position detection unit 64a), the position before the OFF point in the movement in the X-axis direction is defined as the first end E2 (see FIG. 12C), and the OFF point is detected from the machining position Pw. The position, that is, the relative position X2 in the X-axis direction that can be regarded as the first end E2 is calculated from the moving speed in the X-axis direction and stored in the storage unit 62 .

Then, in step S20 (first end position detection unit 64a), the relative position X1 obtained in step S30 is added to the calculated relative position X2, and then equally divided to obtain the middle point of the relative position X1 and the relative position X2. A relative position X3 in the X-axis direction is calculated and stored in the storage unit 62 . At this time, the relative position X3 is the actual relative position and corresponds to the first reference relative position Xp.

In step S22 (first end position detection section 64a), the grinding wheel 27 is moved in the X-axis direction (first-axis direction) to align the center O1 and the center O2 in the X-axis direction. That is, the X-axis correction program 64 rotates the motor 13c of the first moving device 13 in the direction opposite to that in step S10 from the state of FIG. 12C. As a result, the grinding wheel 27 is relatively moved in the X-axis direction in a direction approaching the processing position Pw, and as shown in FIG. , coincide with the center O2 of the light receiving surface 57a.

In step S24, a predetermined control amount Rax1 (first end portion The encoder 13c1 detects a predetermined control amount at the time when E1 and E2 are detected, and transmits it to the first relative position deriving section 13d1.

In step S26 (first relative position deriving unit 13d1), as shown in FIG. 3, a predetermined first relative position Xm1 is calculated based on the transmitted predetermined control amount Rax1, and the first position changing unit 13d2 calculates sent to Part A. At the same time, the "first reference relative position Xp" written in the X-axis correction program 64 is sent to the calculation unit A.

In step S28 (first position changing unit 13d2), as shown in FIG. ΔX1 is calculated (see formula (1) above), and the position error ΔX1 is transmitted to the calculation section B of the first position change section 13d2. Further, at this time, the predetermined first relative position Xm1 is transmitted to the calculation unit B from the first relative position deriving unit 13d1. At this time, the position error ΔX1 is an error caused by thermal displacement due to temperature rise. The position error ΔX1 is stored and held until the next X-axis correction program 64 is operated.

In step S30 (first position changer 13d2), the calculator B calculates the third relative position Xn based on the above equation (3). Here, the third relative position Xn is obtained by correcting the predetermined first relative position Xm1 by the position error ΔX1. That is, the third relative position Xn is the actual relative position corrected for the thermal displacement.
Then, the third relative position Xn is transmitted to the control device 60 and displayed on the display section 63 by step S32 (first position changing section 13d2). As a result, the actual relative position corrected for the thermal displacement is displayed on the display section 63 .

In addition, in this embodiment, as described above, the X-axis drive circuit 13d includes the first machining control section 13d3. The first machining control unit 13d3 is a processing unit that allows the control device 60 to control the rotation of the motor 13c in a state in which the thermal displacement is corrected when the workpiece 30 is machined. Specifically, the third relative position Xn corrected by the first position correction device 50 is used.

That is, in step S30, the third relative position Xn is sent not only to the control device 60 but also to the comparator C of the first machining control section 13d3. At this time, a target relative position Xt, which is originally a target value for machining the workpiece 30, is input to the comparator C from the control device 60. As shown in FIG. Then, the comparator C obtains the position difference ΔX2 between the third relative position Xn and the target relative position Xt, and transmits it to the phase converter D.

Next, the phase converter D converts the position difference ΔX2 into a rotational phase Rax2, which is a phase signal, and transmits it to the motor 13c to control the rotation of the motor 13c. Thus, the X-axis correction program 64 ends. As a result, the rotation of the motor 13c is controlled in a state in which the amount of thermal displacement is corrected, so that machining accuracy is improved.

Next, processing by the second position correction device 70 which is performed subsequently after the processing by the first position correction device 50 will be described based on the flowchart 2 of FIG. In step S40, the Z-axis correction program 65 of the control device 60 is activated, and the second end position detection section 65a operates the motor 14c of the second moving device 14 via the Z-axis drive circuit 14d. Reset ΔZ1 of E to zero. As a result, as shown in FIG. 12D, in the Z-axis direction (second axis direction), the movable table 12 (workpiece 30) moves toward the left (Z-axis direction) in FIG. Start relative movement.

In step S42 (second end position detection unit 65a), the second moving device 14 moves the movable table 12 relative to the grinding wheel 27 in the Z-axis direction, as shown in FIG. 12E. The light-receiving surface 57a detects the position of the second end E3 that receives the point-like (rectangular) light projected from the light-projecting surface 53a. At this time, the second end E3 is a point on the outer peripheral edge of the circle of radius R1 that forms the light projecting surface 53a.

Therefore, in order to detect the second end E3, as in the detection of the first end E2, first, while moving the movable table 12 relative to the grinding wheel 27 in the Z-axis direction, the light receiving surface An OFF point position (not shown) is detected at which point-like light projected from the light projection surface 53a is no longer received by the light projection surface 53a. After that, the movable table 12 is moved in the opposite direction relative to the grinding wheel 27, and the second end E3 is detected again as shown in FIG. 10E in the ON state.

In step S<b>44 (second end position detector 65 a ), the relative position Z<b>1 in the Z-axis direction where the second end E<b>3 is detected is detected and stored in the memory 62 .
Further, in step S46 (the second end position detection unit 65a), the motor 14c is rotated in the same direction as the rotation direction when it is turned on from the OFF point in step S42. Then, by relatively moving the movable table 12 in the Z-axis direction, the OFF point position (not shown) is detected, the position before the OFF point is calculated from the moving speed in the Z-axis direction, and the second end E4 is calculated. (See FIG. 12F).

In step S<b>48 (second end position detector 65 a ), the relative position Z<b>2 of the second end E<b>4 in the Z-axis direction is calculated from the moving speed in the Z-axis direction, and stored in the storage unit 62 . In the above, the second end E4 is also a point on the outer peripheral edge of the circle of radius R1 that forms the light projecting surface 53a, similarly to the second end E3. In this way, both ends in contact with the outer peripheral edge of the circle forming the light projecting surface 53a are detected in the Z-axis direction. A virtual line connecting the second end E3 and the second end E4 passes through the center O1 of the light projecting surface 53a.

At this time, the range between the second end E3 and the second end E4 in the Z-axis direction is defined as a second light receiving range Ar2. That is, when the relative position of the movable table 12 and the grinding wheel 27 in the Z-axis direction (second axis direction) is within the width of the preset second light-receiving range Ar2, the photoelectric sensor 51 detects the light-receiving surface 57a. can receive point-like light projected from the light projection surface 53a.

In step S50 (second end position detection unit 65a), after adding the relative position Z1 to the calculated relative position Z2, the relative position Z3 in the Z-axis direction, which is the middle point between the relative positions Z1 and Z2, is calculated. is obtained and stored in the storage unit 62 . At this time, the relative position Z3 is the actual relative position and corresponds to the second reference relative position Zp.

In step S52 (second end position detection unit 65a), the grinding wheel 27 is moved in the Z-axis direction (second axis direction) to completely match the center O1 and the center O2 (not shown). In this way, the process of moving to the predetermined machining standby position P is completed, the machining program is completed, and preparations for the next machining program are made.

In step S54, a predetermined control amount Raz1 (second end portion The encoder 14c1 detects a predetermined control amount at the time when E3 and E4 are detected, and transmits it to the second relative position deriving section 14d1.

In step S56 (second relative position derivation unit 14d1), as shown in FIG. 3, a predetermined second relative position Zm1 is calculated based on the transmitted predetermined control amount Raz1, and the predetermined second relative position Zm1 is calculated as It is transmitted to the calculation unit E of the second position change unit 14d2. At the same time, the "second reference relative position Zp" written in the Z-axis correction program 65 is sent to the calculation unit E.

In step S58 (second position changing unit 14d2), as shown in FIG. ΔZ1 is calculated (see formula (2) above), and the position error ΔZ1 is sent to the calculation unit F of the second position change unit 14d2. Also, at this time, the second predetermined relative position Zm1 is transmitted to the calculation unit F from the second relative position deriving unit 14d1. At this time, the position error ΔZ1 is an error caused by thermal displacement due to temperature rise. The position error ΔZ1 is stored until the Z-axis correction program 65 is activated next time.

In step S60 (second position changer 14d2), the calculator F calculates the fourth relative position Zn based on the above equation (4). Here, the fourth relative position Zn is obtained by correcting the predetermined second relative position Zm1 by the position error ΔZ1. That is, the fourth relative position Zn is an actual relative position corrected for thermal displacement.
Then, in step S62 (second position changing unit 14d2), the fourth relative position Zn is transmitted to the control device 60 and displayed on the display unit 63. As a result, the display unit 63 displays an accurate relative position corrected for the thermal displacement.

In this embodiment, as described above, the Z-axis drive circuit 14d includes the second machining control section 14d3. The second machining control unit 14d3 is a processing unit that allows the control device 60 to control the rotation of the motor 14c in a state in which the thermal displacement is corrected when the workpiece 30 is machined. Specifically, the fourth relative position Zn corrected by the second position correction device 70 is used.

That is, in step S60, the fourth relative position Zn is sent not only to the display section 63 (control device 60) but also to the comparator G of the second machining control section 14d3. At this time, a target relative position Zt, which is originally a target value for machining the workpiece 30 , is input to the comparator G from the control device 60 . The comparator G obtains the position difference ΔZ2 between the fourth relative position Zn and the target relative position Zt, and transmits it to the phase converter H.

The phase converter D converts the position difference ΔZ2 into a rotational phase Raz2, which is a phase signal, and transmits the rotational phase Raz2 to the motor 14c to control the rotation of the motor 14c. Thus, the Z-axis correction program 65 ends. As a result, the rotation of the motor 14c is controlled in a state in which the amount of thermal displacement is corrected, so that machining accuracy is improved. A machining program is started from a predetermined machining standby position P, and after returning to the predetermined machining standby position P, the machining program ends. Since the third relative position Xn corrected by the position error ΔX1 and the fourth relative position Zn corrected by the position error ΔZ1 are used when moving from the predetermined machining standby position P to the machining position, the machining accuracy is improved. .

Further, after that, for example, when the process of moving to a predetermined machining standby position P just before one machining program ends, it is confirmed that the temperature rises by a predetermined temperature (for example, 1 ° C.). In this case, steps S10 to S32 and steps S40 to S62 are repeated. Note that these controls are automatically performed by the control device 60 . However, the present invention is not limited to this mode, and the operator manually moves the workpiece 30 side in the X-axis direction while confirming the temperature rise in a state where the machining program of one cycle is completed and the predetermined machining standby position P is reached. , and the X-axis correction program 64 and the Z-axis correction program 65 may be executed sequentially. Furthermore, as another embodiment, before a new ball screw is attached and the machining start button is pressed, the temperature rise is confirmed, and if the temperature rises, the ball is manually moved to the workpiece 30 side in the X-axis direction. It may be moved, the X-axis correction program 64 and the Z-axis correction program 65 may be sequentially executed, and steps S10 to S32 and steps S40 to S62 may be performed.

(1-4. Effects of First Embodiment)
According to the thread grinder 10 (machine tool) of the first embodiment, the first position correcting device 50 (and the second position correcting device 70) is configured such that the first moving device 13 (second moving device 14) is a movable table. 12 and the column 23 are relatively moved in the first axial direction (second axial direction), and rectangular light is received by the light receiving surface 57a of the light receiving element 57 via the first slit plate 51a and the second slit plate 51b. First end position detector 64a (second end position detector 65a) for detecting the positions of first ends E1 and E2 (second ends E3 and E4) in one light receiving range Ar1 (second light receiving range Ar2) ) and a predetermined control amount Rax1 (predetermined control amount Raz1) of the first moving device 13 (second moving device 14) at the time when the first ends E1 and E2 (second ends E3 and E4) are detected. A first relative position derivation unit 13d1 (second relative position derivation unit 14d1) that calculates a predetermined first relative position Xm1 (predetermined second relative position Zm1) based on a predetermined first light receiving range Ar1 (second Predetermined first relative position Xm1 (predetermined second relative position Zm1) based on the first reference relative position Xp (second reference relative position Zp) which is positioned within the light receiving range Ar2) and is prepared in advance, is changed to a position error ΔX1 ( a first position changer 13d2 (second position changer 14d2) that corrects only the position error ΔZ1) and changes to the third relative position Xn (fourth relative position Zn).

As described above, in the thread grinding machine 10 (machine tool) according to the present invention, the relative positions of the movable table 12 (support table) and the column 23 (tool table) are determined by the pair of light emitting elements 53 and the light receiving elements 53 after thermal displacement. It is positioned at the first reference relative position Xp (second reference relative position Zp) using the photoelectric sensor 51 including the element 57 . Further, a predetermined first relative position Xm1 which is a calculated relative position between the movable table 12 (support table) and the column 23 (tool table) when positioned at the first reference relative position Xp (second reference relative position Zp) (Predetermined second relative position Zm1) is obtained. Then, the predetermined first relative position Xm1 (predetermined second relative position Zm1) is changed to the first reference relative position Xp (second reference relative position Zp) by the first position changing section 13d2 (second position changing section 14d2). Based on this, only the position error ΔX1 (position error ΔZ1) is corrected. As a result, even if the predetermined first relative position Xm1 (predetermined second relative position Zm1) is thermally displaced, it can be accurately corrected despite the inexpensive configuration.

Further, at this time, the thread grinder 10 (machine tool) processes the workpiece 30 with the grinding wheel 27 (tool). Therefore, in the environment around the machining position, a large amount of coolant and chips are usually floating, and visibility is poor. However, even in such a poor environment, the photoelectric sensor 51 detects the light projected from the light projecting element 53 at the light receiving element 57 relatively accurately in a short time, even if it is inexpensive. It is possible. Therefore, the predetermined first relative position Xm1 (predetermined second relative position Zm1) after thermal displacement can be accurately grasped with a more inexpensive structure, and the predetermined first relative position Xm1 (predetermined second relative position Zm1) can be accurately grasped. The relative position Zm1) can be corrected with high accuracy. Moreover, since the photoelectric sensor 51 has high durability in an environment in which coolant and chips are floating as described above, the first position correcting device 50 having high durability can be obtained.

Further, at this time, the light projected from the light projecting surface 53a and received by the light receiving surface 57a passes through the first slit 51a3 of the first slit plate 51a, and then crosses the first slit 51a3 perpendicularly in the X-axis direction. By passing through the linear second slit 51b3 of the second slit plate 51b formed parallel to (the first axial direction), the light becomes a rectangular point and is received. As a result, the positions of the ends E1 to E4 can be detected with high accuracy, and the predetermined first relative position Xm1 and the predetermined second relative position Xm1, which are the relative positions after thermal displacement corresponding to the positions of the ends E1 to E4, can be detected. Relative position Zm1 can be accurately detected.

Further, in the above-described first embodiment, the first and second ends of the first light receiving range Ar1 and the second light receiving range Ar2 detected by the first position correction device 50 are the first and second ends in the X-axis direction (first axis direction). First end portions E1, E2 and second end portions E3, E4 on both sides of one light receiving range Ar1 and second light receiving range Ar2 in the Z-axis direction (second axial direction). Then, in the first light receiving range Ar1 and the second light receiving range Ar2, the first ends E1, E2 and the second ends E3, E4 are detected, and the detected first ends E1, E2 and the second ends E3, A predetermined first relative position Xm1 and a predetermined second relative position Zm1 after thermal displacement are calculated based on E4.

After that, based on the predetermined first relative position Xm1 and the predetermined second relative position Zm1, the third relative position Xn and the fourth relative position Zn, in which the amount of thermal displacement is corrected, are obtained. Although this is a simple method, both ends of the first light receiving range Ar1 and the second light receiving range Ar2 are obtained, and based on the obtained both ends, the actual third relative position Xn and the fourth relative position after thermal displacement are calculated. Since the position Zn is derived, the accuracy is good.

In the first embodiment described above, in the first position correcting device 50, the first axis direction is the direction (X axis direction). In the second position correcting device 70, the second axial direction is the direction (Z-axis direction) in which the column 23 (tool table) moves in parallel relative to the movable table 12 (support table).

When the first position correction device 50 detects the first ends E1 and E2 of the first light receiving range Ar1, the grinding wheel 27 is positioned at the processing position Pw where the workpiece 30 is processed. The column 23 (tool table) is moved relative to the movable table 12 (support table) in the first axis direction for detection. As a result, the first position correction device 50 can efficiently and accurately detect the amount of thermal displacement. In other words, the column 23 (tool table) having the grinding wheel 27 positioned at the machining position Pw is relatively moved in the first axial direction toward the machining standby position P, and the first column 23 in the X-axis direction is moved. The first ends E1 and E2 of the light receiving range Ar1 can be quickly detected.

After that, the second position correcting device 70 relatively moves the movable table 12 (support table) with respect to the column 23 (tool table) in the second axial direction (Z-axis direction) to obtain the second position in the second light receiving range Ar2. The positions of the ends E3 and E4 can be detected quickly. Thus, the first ends E1, E2 and the second ends E3, E4 can be easily detected with only a small relative movement, which is efficient. Moreover, since both the light projecting part 52 and the light receiving part 55 can be arranged in the vicinity of the workpiece 30 and the grinding wheel 27, it is easy to grasp the amount of displacement of the workpiece 30 and the grinding wheel 27 due to heat.

Further, in the first position correction device 50 and the second position correction device 70 of the first embodiment, the widths W1 and W2 of at least one of the first slit 51a3 and the second slit 51b3 are adjustable. As a result, even if the widths W1 and W2 of the slits need to be changed depending on the measurement conditions or the like, it is not necessary to replace each photoelectric sensor 51, so the cost can be reduced.

Further, according to the first position correction device 50 and the second position correction device 70 of the first embodiment, the shape of the light projected from the light projecting surface 53a of the light projecting element 53 is circular. As a result, the photoelectric sensor 51 can be inexpensive. In addition, in the X-axis direction and the Z-axis direction, the shape is always symmetrical regardless of how it is arranged.

(1-5. Modified example of the first embodiment)
(1-5-1. Modification 1)
In the first embodiment, when the relative positions of the movable table 12 and the grinding wheel 27 after thermal displacement are detected by the operation of the first position correcting device 50 and the second position correcting device 70, Both the predetermined first relative position Xm1 and the predetermined second relative position Zm1 in the Z-axis direction are corrected. However, the present invention is not limited to this aspect, and as Modification 1 (not shown), only one of the predetermined first relative position Xm1 and the predetermined second relative position Zm1 in the Z-axis direction may be corrected. As a result, the cost can be reduced accordingly, and the grinding accuracy of the workpiece 30 can be improved accordingly.

(1-5-2. Modification 2)
In the first embodiment, the first position correction device 50 and the second position correction device 70 have the first slit 51a3 parallel to the Z-axis direction and the second slit 51b3 parallel to the X-axis direction. The first slit plate 51a and the second slit plate 51b are arranged between the photoelectric sensors 51 so that However, it is not limited to this aspect, and as a modification 2, only one of the first slit 51a3 and the second slit 51b3 may be provided between the photoelectric sensors 51 .

However, when only the first slit 51a3 is provided, as shown in FIG. 13, the light-receiving range of the light-receiving surface 57a becomes wider than in the case of the first embodiment. As a result, although the detection accuracy of the relative position is lower than that of the first embodiment, both the first ends E1 and E2 in the X-axis direction can be detected on the light receiving surface 57a. Similarly, when only the second slit 51b3 is provided (not shown), although the detection accuracy of the relative position is similarly lowered compared to the first embodiment, both slits 51b3 in the Z-axis direction are detected on the light-receiving surface 57a. Two ends E3, E4 can be detected. This also increases the grinding accuracy of the workpiece 30 accordingly.

(1-5-3. Modification 3)
Further, in the above-described first embodiment, the shape of the light projected from the light projecting surface 53a is a "circle". However, it is not limited to this aspect. As Modified Example 3 (not shown), the shape of the light may be any shape as long as it is line-symmetrical in the X-axis direction and the Z-axis direction. For example, any shape such as an ellipse, rectangle, or daruma shape may be used. This also provides the same effects as the first embodiment. If the shape of the light is rectangular and the length of each side is known, it is sufficient to detect either one of the ends of the light without detecting both ends of the light. That is, by detecting the edge on one side, each center position in the X-axis direction and the Z-axis direction can be derived by calculation. This also has a corresponding effect.

(1-5-4. Modification 4)
Further, in the first embodiment, the first position correction device 50 and the second position correction device 70 adjust the first end portions E1, E2 and the second end portion E3 of the first light receiving range Ar1 and the second light receiving range Ar2. , E4, first, the grinding wheel 27 (column 23 (tool table)) is relatively moved in the first axial direction to detect the positions of the first ends E1 and E2 in the first light receiving range Ar1. After that, the movable table 12 (support table) was moved relative to the grinding wheel 27 in the second axial direction to detect the positions of the second ends E3 and E4 in the second light receiving range Ar2. As described above, the amount of thermal displacement can be detected efficiently and accurately.

However, it is not limited to this aspect. As Modified Example 4 (not shown), first, the movable table 12 (support table) is moved relative to the grinding wheel 27 in the second axial direction to determine the positions of the second ends E3 and E4 in the second light receiving range Ar2. is detected, and then the grinding wheel 27 is relatively moved in the first axial direction to detect the positions of the first ends E1 and E2 in the first light receiving range Ar1. This also has a corresponding effect.

(1-5-5. Modification 5)
Further, in the first embodiment described above, the width W1 of the first slit 51a3 and the width W2 of the second slit 51b3 are adjustable. As such, one or both of widths W1 and W2 may be non-adjustable. A corresponding effect can also be obtained by this.

(1-5-6. Modification 6)
Further, in the first embodiment described above, the timing of processing by the first position correction device 50 and the second position correction device 70 was explained as being based on the temperature rise of each part after the end of each machining program. It is not limited to this aspect. As Modified Example 6 (not shown), the first position correction device 50 and the second position correction device 70 count the number of machined workpieces 30, and the counted number of machined workpieces reaches a preset number (for example, 10 The correction process may be performed at the timing of reaching the number of books). This also provides the same effects as the first embodiment.

(1-5-7. Modification 7)
Further, in the first embodiment described above, in the thermal displacement correction processing by the first position correction device 50 and the second position correction device 70, the grinding wheel 27 (tool) processes the workpiece 30 at the processing position Pw (Fig. 7 ) in the X-axis direction and is relatively moved toward the machining standby position P shown in FIG. However, the present invention is not limited to this mode, and thermal displacement may be corrected in any situation as Modified Example 7 (not shown).

(1-5-8. Modification 8)
In the first embodiment, the first relative position derivation unit 13d1 (second relative position derivation unit 14d1) and the first position change unit 13d2 (second position correction device 70) of the first position correction device 50 (second position correction device 70) The two-position changer 14d2) is provided in the X-axis drive circuit 13d (Z-axis drive circuit 14d). However, the present invention is not limited to this aspect, and as Modified Example 8 (not shown), the first relative position deriving section 13d1 (second relative position deriving section 14d1) and the first position changing section 13d2 (second position changing section 14d2) The control device 60 may be provided and all may be processed by calculation. This also provides the same effects as the first embodiment.

<2. Others>
In addition, in the above embodiment, the machine tool is described as being the thread grinder 10 . However, the machine tool is not limited to this aspect, and may be, for example, a normal grinding machine. The machine tool may also be a centerless grinder. The same effects as those of the first embodiment can be expected from these as well.

10; Thread grinding machine (machine tool) 12; Movable table (support base) 13; First moving device 13c; Motor 13c1; Encoder 13d1; 2nd moving device 14c; motor 14c1; encoder 14d1; second relative position deriving unit 14d2; second position changing unit 23; First position correction device 51 Photoelectric sensor 51a First slit plate 51b Second slit plate 53 Light projecting element 57 Light receiving element 60 Control device 64a First end position detection Second end position detector 70; Second position correction device E1, E2; First end E3, E4; Second end Rax1; Predetermined control amount Raz1; Predetermined control First predetermined relative position Xn; Third relative position Xp; First reference relative position Zm1; Second predetermined relative position Zn; Fourth relative position Zp; Second reference relative position.

Claims (8)

a support base for supporting the workpiece;
a tool table that supports a tool for machining the workpiece and is relatively movable in a first axial direction with respect to the support table;
a first moving device that relatively moves the support table and the tool table in the first axial direction;
Based on the control amount of the first moving device, the relative position of the support table and the tool table relatively moved in the first axial direction by the first moving device is derived as a first relative position under normal temperature conditions. a first relative position derivation unit;
a first position correcting device for correcting the first relative position by the amount of thermal displacement when the relative position of the support table and the tool table is thermally displaced;
a second moving device that relatively moves the support table and the tool table in a second axial direction orthogonal to the first axial direction on a horizontal plane;
Based on the control amount of the second moving device, the relative position of the support table and the tool table relatively moved in the second axial direction by the second moving device is derived as a second relative position under normal temperature conditions. a second relative position derivation unit;
a second position correcting device for correcting the second relative position by the amount of thermal displacement when the relative position of the support table and the tool table is thermally displaced ;
A machine tool having a position correction function comprising
The first position correction device is
a light projecting element that is fixed to one of the support table and the tool table and projects light from a light projecting surface;
When the support base and the tool base are fixed to the other of the support base and the tool base, and the relative positions of the support base and the tool base in the first axial direction are positioned within a preset first light receiving range, the light a light-receiving element for receiving on the light-receiving surface,
A straight line fixed to one of the light projecting element and the light receiving element and formed on a plane including the first axial direction so that the light projected from the light projecting surface is perpendicular to the first axial direction. A first slit plate that passes through a shaped first slit,
The first moving device relatively moves the support base and the tool base in the first axial direction, causes the light receiving surface of the light receiving element to receive the light through the first slit, and the first light receiving range a first end position detector that detects the position of the first end in
the first relative position derivation unit calculating the predetermined first relative position based on the predetermined control amount of the first moving device at the time of detecting the first end;
a first position changing unit that changes the predetermined first relative position based on a first reference relative position that is positioned within the preset first light receiving range and prepared in advance;
The second position correction device is
the light projecting element;
the light-receiving element that receives the light on the light-receiving surface when the relative positions of the support table and the tool table in the second axial direction are within a preset second light-receiving range;
The other of the light projecting element and the light receiving element is fixed so as to be parallel to the first slit plate, and the light projected from the light projecting surface is applied to the first slit of the first slit plate, a second slit plate that allows passage in a rectangular shape through a linear second slit formed parallel to the first axial direction;
The second moving device relatively moves the support base and the tool base in the second axial direction, causes the rectangular light receiving surface to receive the light, and positions the second end of the second light receiving range. a second end position detector that detects
a second relative position deriving unit that calculates the predetermined second relative position based on the predetermined control amount of the second moving device at the time of detecting the second end;
a second position changer that changes the predetermined second relative position based on a second reference relative position that is positioned within the preset second light receiving range and prepared in advance. 2. The machine tool according to claim 1, wherein said first end position detection section detects respective positions of said first ends on both sides in said first axial direction in said first light receiving range. The first relative position derivation unit calculates the predetermined control amount of the first moving device at the time of detecting each of the first ends on both sides in the first axial direction, and the control amount on both sides in the first axial direction. 3. The machine tool according to claim 2 , wherein said predetermined first relative position is calculated based on the relative position of the midpoint of said first end of. The support table rotatably supports the workpiece,
The first axial direction is a direction in which the tool base relatively approaches the support base,
the second axial direction is a direction in which the tool table is parallel to the rotation axis of the workpiece with respect to the support table;
The first position correction device and the second position correction device are
When detecting the first end and the second end of the first light receiving range and the second light receiving range,
First, from a state in which the support base and the tool base are positioned at a machining position where the tool machines the workpiece, the support base and the tool base are moved relative to each other in the first axial direction to obtain the first light receiving range. detecting the position of the first end in the second light receiving range, and then detecting the position of the second end in the second light receiving range by relatively moving the support base and the tool base in the second axial direction. Item 1. The machine tool according to item 1. 3. The machine tool according to claim 1, wherein the width of at least one of said first slit and said second slit is adjustable. The machine tool includes a temperature sensor that measures a temperature at a predetermined position on the machine tool,
The first position correction device and the second position correction device are
The predetermined first relative position and the predetermined second relative position derived by the first relative position deriving unit and the second relative position deriving unit at predetermined timings set based on the measurement result of the temperature sensor. 3. A machine tool according to claim 1 or 2, wherein at least one of the positions is corrected. The first position correction device and the second position correction device are
counting the number of processed workpieces,
The predetermined first relative position and the predetermined second relative position derived by the first relative position deriving unit and the second relative position deriving unit at the timing when the counted number of processed lines reaches a preset number 3. A machine tool according to claim 1 or 2, wherein at least one of the positions is corrected. The machine tool according to any one of claims 1 to 7 , wherein the light projected from the light projecting surface of the light projecting element has a circular shape.

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