Calibration device, calibration method and machine tool

Abstract

To provide a calibration device and a calibration method that can perform stable calibration work through simple operation, and a machine tool that uses them.SOLUTION: A calibration device 10 comprises: an outer cylinder part 12 which is fixed to a machine tool 90; a rod-shaped shaft part 14 which is arranged inside the outer cylinder part 12 to have its axis in a Z-axial direction, the shaft part 14 having a male screw part 14a and guided by the outer cylinder part 12 to move forward / backward in the axial direction; an inner ring 26 which is formed along an outer periphery of the shaft part 14 and is configured to rotate on the axis of the shaft part 14 and restrict a Z-axial movement, and has a female screw part 26c engaging the male screw part 14a of the shaft part 14 and rotating relative to the shaft part 14 so that the shaft part 14 is moved forward / backward; and a Z-calibration part 18 which is formed as a reference surface at a tip of the shaft part 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a calibration device, a calibration method, and a machine tool. [Background technology]

[0002] Machine tools require position information, i.e., coordinates, of the workpiece to be machined in order to perform machining with high accuracy. This position information is obtained by manual measurement by the operator after the operator mounts the workpiece on the machine tool at the machining site, or by measurement using a measuring device equipped with a sensor that is attached to the machine tool. The measuring device referred to here is a measurement system equipped with a sensor, so it is necessary to recognize measurement errors using a reference gauge or the like and calibrate the measurement results. This calibration work is also called calibration work, and the accuracy of the measurement results is strongly dependent on the accuracy of the calibration work.

[0003] Patent Document 1 discloses a calibration device for a coordinate positioning machine, including a base, a calibration artifact, and a lockable mechanism for securing the calibration artifact to the base. The lockable mechanism of the calibration device can adopt an unlocked state in which the calibration artifact can be moved relative to the base by application of an external force, and a locked state in which the position of the calibration artifact is locked relative to the base. However, when a bar (a reference tool with a known length) held by the spindle of a machine tool is pressed into contact with a calibration artifact (a calibration sphere) for alignment, it is possible for the bar to be accidentally moved too far toward the calibration sphere. This not only damages the calibration device, but also potentially places a significant load on the spindle and machine tool via the bar. A similar problem can occur if the calibration process is initiated without first unlocking the calibration artifact. Furthermore, the psychological burden on the operator, who must pay attention to these issues while performing the calibration process, can be significant.

[0004] For example, Patent Document 2 discloses a calibration device for a touch probe used in a machine tool, which includes a rod-shaped shank that can be advanced along the axial direction, a planar Z calibration portion formed at the tip of the shank, a biasing portion that biases the shank in the advancing direction, and a fixing portion that can fix the shank to the outer tube. This calibration device allows the shank to be manually advanced from a retracted position to engage with a reference tool, significantly reducing the possibility of applying load to the machine tool. However, this calibration device requires the user to pull a lever to lock the shank after engaging it with the reference tool. During this locking operation, a lateral force may act on the calibration device, displacing the position of the calibration device. This may result in the Z calibration portion of the shank and the reference tool not being properly engaged. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2023-519290 [Patent Document 2] Patent No. 7316409 specification Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, an object of the present invention is to provide a calibration device and a calibration method that enable stable calibration work to be performed with simple operations, and a machine tool using these. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a calibration device for a machine tool equipped with a touch probe, comprising: a main body to be fixed to the machine tool; a rod-shaped shaft portion arranged inside the main body with its axis direction along the Z-axis direction, the shaft portion having a follower portion and guided by the main body so as to be able to move back and forth along the axial direction; a rotating ring provided on the main body along the outer periphery of the shaft portion, which is rotatable about the axis of the shaft portion and constrains movement in the Z-axis direction, the rotating ring having a driver portion formed to engage with the follower portion of the shaft portion and rotate relative to the shaft portion so as to move the shaft portion back and forth in response; and a Z calibration portion formed as a reference surface at the tip of the shaft portion.

[0008] Furthermore, according to one aspect of the present invention, there is provided a machine tool capable of mounting a calibration device according to one aspect of the present invention, characterized in that it comprises: a spindle for mounting a machining tool, the spindle being capable of mounting a reference tool or touch probe of a known length instead of the machining tool; a table for mounting an object to be machined and the calibration device; and a feed axis section for moving the spindle and the table relative to each other.

[0009] Furthermore, according to one aspect of the present invention, there is provided a method for calibrating a touch probe using a calibration device according to one aspect of the present invention, comprising: placing the calibration device on a machine tool; attaching a reference tool of a known length to a spindle of the machine tool; relatively moving the spindle to move the tip of the reference tool to a position axially above the Z calibration section of the shank; rotating a rotating ring relative to the shank to abut the Z calibration section against the reference tool; obtaining an axial reference coordinate of the abutted shank; attaching a touch probe to the spindle of the machine tool; and obtaining an axial calibration value based on the reference coordinate. [Effects of the Invention]

[0010] According to one aspect of the present invention, the calibration device includes a shaft portion guided by a main body, constrained in the rotational direction and configured to be able to advance and retreat along the axial direction, and a rotating ring formed along the outer periphery of the shaft portion, rotatable about the axis of the shaft portion, and constrained in the Z-axis direction. Therefore, by rotating the rotating ring relative to the shaft portion, the driver portion rotates, and the engaged follower portion of the shaft portion is driven, thereby advancing and retreating the shaft portion along the Z-axis. Thus, by simply rotating the rotating ring, the shaft portion formed with the Z calibration portion can be advanced and retreated to perform alignment for calibration work. Furthermore, because the configuration aligns the shaft portion and the Z calibration portion with respect to a reference tool, excessive load on the machine tool can be prevented or suppressed. Furthermore, when alignment is completed and the rotation of the rotating ring is stopped, the driver portion of the rotating ring and the follower portion of the shaft portion are engaged with each other, resulting in a self-locking effect and stabilizing the shaft portion relative to the main body. Therefore, the position of the calibration device relative to the machine tool can be stabilized without the need to actively lock the calibration device as described in Patent Documents 1 and 2. As a result, alignment can be performed easily and with good operability, regardless of the skill level of the operator, and calibration work can be performed with stable accuracy. By stabilizing the accuracy of the calibration work in this way, the machining accuracy of the machine tool and, ultimately, the quality of the machined product can be stabilized.

[0011] According to a machine tool according to one aspect of the present invention, the calibration device according to one aspect of the present invention can be attached, and a reference tool and a touch probe can be attached to the spindle. This allows for stable accuracy and allows calibration work to be performed easily and quickly. Furthermore, because the shaft portion and the Z calibration portion are aligned with the reference tool attached to the spindle of the machine tool, it is possible to prevent or suppress the tip of the reference tool from colliding with the shaft portion and applying a load to the machine tool, thereby ensuring the safety of the machine tool.

[0012] According to a calibration method according to one aspect of the present invention, alignment of the calibration device with respect to the machine tool and acquisition of the reference coordinates and calibration values ​​can be performed continuously and simply using a single calibration device. This allows calibration work to be performed simply and in a short time while stabilizing accuracy. Furthermore, because the configuration aligns the shaft portion and the Z calibration unit with respect to the reference tool attached to the spindle of the machine tool, it is possible to prevent or suppress the tip of the reference tool attached to the spindle of the machine tool from colliding with the shaft portion and applying a load to the machine tool, thereby ensuring the safety of the machine tool. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a perspective view of a calibration device according to the first embodiment. [Figure 2A-2B] FIG. 2A shows a side view of the calibration device according to the first embodiment, and FIG. 2B shows a cross-sectional view of the calibration device of FIG. 2A taken along line 2B-2B. [Figure 3] FIG. 3 shows a side view of the shaft. [Figure 4] FIG. 4 shows a side view of a shaft portion according to a modified example. [Figure 5] FIG. 5 shows a perspective view of a calibration device according to the second embodiment. [Figures 6A-6B] FIG. 6A shows a side view of the calibration device according to the second embodiment, and FIG. 6B shows a cross-sectional view of the calibration device of FIG. 6A taken along line 6B-6B. [Figure 6C] FIG. 6C shows a cross-sectional view of the calibration device of FIG. 6B taken along line 6C-6C. [Figure 7] FIG. 7 shows a side view of a machine tool with a reference tool and a calibration device attached. [Figure 8] Figure 8 shows a flowchart of the calibration process using a touch probe. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a calibration device, a machine tool, and a calibration method according to embodiments will be described with reference to the accompanying drawings. Similar or corresponding elements are designated by the same reference numerals, and duplicated explanations will be omitted. For ease of understanding, the scale of the drawings may be changed.

[0015] (First embodiment) A first embodiment of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 and 2A show a perspective view and a side view of a calibration device 10. As shown in FIG. 7, the calibration device 10 is used in a machine tool 90 to calibrate the position of a touch probe, for example, for the purpose of accurately measuring the position of a workpiece to be machined (both not shown). For this purpose, the calibration device 10 is attached to a table 92 of the machine tool 90 on which a workpiece is mounted. In the drawings, arrows indicate the front-to-rear, left-to-right, and up-to-down directions of the machine tool 90 when the machine tool 90 is placed on a horizontal plane such as the floor of a factory. In the drawings, X indicates the left-to-right direction (X-axis), and Z indicates the up-to-down direction (Z-axis). The front-to-back direction of the machine is referred to as the Y-axis.

[0016] 1 and 2A, the calibration device 10 includes an outer cylinder 12 as a main body, a metal shaft 14 disposed inside the outer cylinder 12, and a metal rotating unit cover 16 disposed above the outer cylinder 12. The calibration device 10 places the outer cylinder 12 on the upper surface of a table 92 (see FIG. 7) of a machine tool 90, and rotates the rotating unit cover 16, thereby advancing the rod-shaped metal shaft 14 toward the upper side of the outer cylinder 12 or retracting the advanced shaft 14 downward.

[0017] As shown in FIG. 2B , the outer tube 12 is made of metal and has a cylindrical outer periphery, with a central shaft extending through it along the axial direction. An inner ring 26, serving as a rotating ring, is disposed inside a rotating unit cover 16 located above the outer tube 12 and is configured to be rotatable relative to the outer tube 12. The inner ring 26 includes a cylindrical portion 26a formed so that its central axis coincides with the central axis of the outer tube 12, and an outer peripheral portion 26b integrally formed in an annular shape along the outer periphery above the cylindrical portion 26a. A female thread portion 26c serving as a driving link portion is formed on the inner periphery of the cylindrical portion 26a so that it can threadably engage with the shaft portion 14 inserted into the cylindrical portion 26a. Here, the female thread portion 26c is formed as a multiple-start thread, but a single-start thread may also be formed. Hemispherical or conical ball grooves 26d are formed at equal intervals along the circumferential direction on the upper surface of the outer peripheral portion 26b. Here, the ball grooves 26d are formed at four locations at 90-degree intervals along the circumferential direction of the outer edge portion 26b, but this is not limited to this, and a different number of ball grooves may be formed, for example, two locations at 180-degree intervals or six locations at 60-degree intervals.

[0018] Above the inner ring 26, an outer ring 28 is disposed as a rotating ring formed in an annular shape so that its central axis coincides with the central axes of the outer cylindrical portion 12 and the inner ring 26. The outer ring 28 has an outer edge portion extending downward, and its lower end is connected to the rotating unit cover 16 via a fall prevention pin 30. This allows the operator to rotate the outer ring 28 in conjunction with the rotation of the rotating unit cover 16. Furthermore, the outer ring 28 is restricted from moving in the Z-axis direction (up and down direction) relative to the rotating unit cover 16, i.e., the outer ring 28 can be prevented from falling off the rotating unit cover 16.

[0019] A ball plunger 32 is attached to the radially inner side of the outer ring 28, extending downward, i.e., toward the outer edge 26b of the inner ring 26. A ball portion 34 is biased by a biasing means (not shown) disposed inside the ball plunger 32 and is disposed at the tip (here, the lower end) of the ball plunger 32 so that it can move axially, i.e., in the up-and-down direction. Therefore, the outer ring 28 is disposed above the inner ring 26 so that only the ball portion 34 abuts against the outer edge 26b of the inner ring 26. Furthermore, when the ball plunger 32 is positioned so that the ball portion 34 is directly above the ball groove 26d of the outer edge 26b, the biased ball portion 34 enters the ball groove 26d and abuts against the ball groove 26d. This allows the outer ring 28 to engage with the inner ring 26, and when the rotating part cover 16 and the outer ring 28 are rotated, the inner ring 26 can also rotate in conjunction with them.

[0020] The shaft 14 is inserted into the center of the outer tube 12 through the outer ring 28 and the inner ring 26. As shown in FIG. 3, a Z calibration section 18 is formed at the tip of the shaft 14, having an XY plane that is perpendicular to the axial direction (here, the Z-axis direction) of the shaft 14, i.e., parallel to the mounting surface (see FIG. 7) of the table 92 on which the calibration device 10 is mounted. On the upper side of the shaft 14 that remains exposed from the outer tube 12 even after insertion, an XY calibration section 20 is formed on the outer peripheral surface of a cylindrical section that protrudes radially outward from the shaft 14. The cylindrical section on which the XY calibration section 20 is formed is formed so that its central axis coincides with the central axis of the shaft 14. Note that the XY calibration section may be formed directly on the outer peripheral surface of the shaft, rather than on the protruding cylindrical section. Here, regardless of the X-axis and Y-axis positions on the plane of the Z calibration unit 18 at which the reference tool 98 abuts, the relative difference between the Z-axis position at the X-axis and Y-axis positions where the reference tool 98 abuts and the Z-axis position at the central axis position of the XY calibration unit 20 is measured using a touch probe (not shown), thereby making it possible to obtain the accurate Z-axis position at the central axis position of the XY calibration unit 20 on the plane of the Z calibration unit 18. Therefore, positioning in the X-axis and Y-axis directions when the reference tool 98 abuts can be performed easily and in a short time. In this case, the tip of the reference tool 98 is preferably formed in a partial spherical shape. The Z calibration unit 18 formed at the tip of the shaft 14 as a reference surface that abuts against the reference tool 98 is not limited to a flat surface, and may be formed in a partial spherical surface. In this case, the tip of the reference tool 98 is preferably formed in a planar shape perpendicular to the axis.

[0021] The portion of the shaft 14 that is inserted into the outer cylindrical portion 12 is formed with a male thread 14a that is spirally threaded along its outer periphery. As shown in FIG. 2B , the male thread 14a can be threadedly engaged with a female thread 26c on the cylindrical portion 26a of the inner ring 26. The male thread 14a is formed with a multiple-start thread, which increases the stroke of the shaft 14 in relation to the rotation of the rotating unit cover 16. Note that, although the male thread 14a is formed as a multiple-start thread here, it is not limited thereto and may be formed with a single-start thread. The shaft 14 that is threadedly engaged with the female thread 26c is configured to rotate in conjunction with the rotation of the inner ring 26 by rotating the rotating unit cover 16 and the outer ring 28, advancing upward or retracting downward (direction Z1 in FIG. 2B ).

[0022] Additionally, an internal hole 14b is formed below the male threaded portion 14a of the shaft portion 14, extending upward along the central axis from the bottom of the shaft portion 14. A retraction spring 24 is disposed in the internal hole 14b along the central axis of the shaft portion 14, and its upper end is engaged with a spring engaging portion 14c formed on the upper end side of the internal hole 14b.

[0023] A disk-shaped magnet 22 is disposed on the bottom side of the central portion formed through the outer cylindrical portion 12 so as to cover it. This stabilizes the position of the calibration device 10 placed on a metal table 92 (see FIG. 7) so that it does not shift. Furthermore, a spring locking portion 22a for locking the lower end of the retraction spring 24 is formed on the upper end side of the magnet 22. This allows the retraction spring 24 to urge the shaft portion 14 downward. This eliminates backlash between the male thread portion 14a and the female thread portion 26c, and stabilizes the positioning of the shaft portion 14 relative to the outer cylindrical portion 12.

[0024] Furthermore, a rotation prevention groove 14d is formed along the axial direction of the shaft portion 14 at a radially outer portion of the inner bore 14b of the shaft portion 14. A rotation prevention pin 36 is disposed in a portion of the outer tube portion 12 facing the rotation prevention groove 14d, and its tip is inserted into the rotation prevention groove 14d. In this manner, the shaft portion 14 is restrained in the rotation direction relative to the outer tube portion 12. A ball plunger (not shown) is attached to the tip of the rotation prevention pin 36, and the rotation prevention pin 36 is inserted into the rotation prevention groove 14d so that the ball portion of the ball plunger abuts the inner surface of the rotation prevention groove 14d. Therefore, when the shaft portion 14 advances upward by rotating the rotating-unit cover 16, and the lower end of the rotation prevention groove 14d reaches the position of the rotation prevention pin 36, the shaft portion 14 is locked by the rotation prevention pin 36, preventing further upward advancement. Furthermore, the shaft portion 14 is pressed laterally by the ball plunger of the anti-rotation pin 36. This makes it possible to prevent or suppress the shaft portion 14 from rattling in the lateral direction.

[0025] As the shaft 14 is pulled downward by the retraction spring 24, the lower side of the threads of the male thread 14a formed on the shaft 14 and the upper side of the threads of the female thread 26c formed on the inner ring 26 come into contact due to the biasing force of the retraction spring 24. This generates appropriate friction between the male thread 14a and the female thread 26c, preventing rotation of the inner ring 26 due to vibrations of the machine tool. In addition, since the friction angle between the male thread 14a and the female thread 26c is shallow, a so-called self-locking effect occurs between the male thread 14a and the female thread 26c. The self-locking effect is a phenomenon in which, when the female threaded portion 26c (driver portion) is rotated, the shaft portion 14 moves back and forth via the male threaded portion 14a (follower portion), but conversely, even if a force that moves the shaft portion 14 back and forth is applied to the male threaded portion 14a (follower portion), the female threaded portion 26c (driver portion) does not rotate. Because of this self-locking effect, the shaft locking mechanism that was essential in Patent Documents 1 and 2 is not necessary in the present invention.

[0026] The self-locking effect is known as a phenomenon in a worm and worm wheel mechanism whereby when the worm (driver) is rotated, the worm wheel (follower) rotates, but conversely, when you try to rotate the worm wheel, the worm does not rotate.Similarly, a self-locking effect in which the driver cannot be moved from the follower is also present in the male screw-side advance / retract mechanism formed by the engagement between the female screw portion 26c (driver) and the male screw portion 14a (follower), the cam follower pin-side advance / retract mechanism formed by the engagement between the spiral cam groove (driver) and the cam follower pin 58 (follower) (see Figure 6B), and the spiral cam groove-side advance / retract mechanism formed by the engagement between the cam follower pin 26e (driver) and the spiral cylindrical cam groove 44a (follower) (see Figure 4). In the present invention, one rotation of the inner ring 26 moves the shaft 14 forward or backward by, for example, 7.5 mm, so the friction angle is shallow and a self-locking effect is sufficient. The cam follower pins 26e, 58 of the present invention are simply rod-shaped pins that slide in contact with the cam groove, without using rolling elements or the like to reduce friction in the part that engages with the cam groove. Therefore, a self-locking effect is produced.

[0027] The bottom surface of the outer cylindrical portion 12 is formed with an inclined surface 12a that is inclined toward the outer periphery of the outer cylindrical portion 12, i.e., toward the radially outer side, and toward the Z calibration unit 18, i.e., toward the upward side. Therefore, when mounting the calibration device 10 on the surface (mounting surface) of the table 92 (see FIG. 7), the calibration device 10 is tilted and first placed so that the inclined surface abuts against the mounting surface so that the magnet 22 does not contact the mounting surface. From this state, the calibration device 10 is tilted using the inclined surface as a fulcrum, so that the magnet 22 abuts against the mounting surface AS. Furthermore, when removing the calibration device 10 from the mounting surface, the calibration device 10 is tilted so that the inclined surface 12a abuts against the mounting surface of the table 92, separating the magnet 22 from the mounting surface. Then, with the magnet 22 not in direct contact with the mounting surface, the calibration device 10 can be lifted and removed from the table 92. Therefore, the magnetic force of the magnet 22 can be prevented or suppressed from forcefully abutting, i.e., colliding, the calibration device 10 with the mounting surface. Furthermore, since there is no need to pull up the calibration device 10 in the direction in which the magnetic force acts, i.e., in the vertical direction, the calibration device 10 can be easily and operably removed from the table 92. This makes it possible to prevent or suppress damage to the mounting surface of the table 92 when attaching and removing the calibration device 10. In this embodiment, the inclined surface 12a is formed on the entire outer periphery of the bottom surface of the outer cylindrical portion 12, but it may also be formed on only a portion of the outer periphery of the bottom surface. For example, it may be formed in one location, two locations 180 degrees apart, or four locations 90 degrees apart.

[0028] The effects of the calibration device 10, calibration method, and machine tool 90 according to this embodiment will be described below through an explanation of the calibration method following the flowchart shown in FIG.

[0029] First, proceed to step S10, and as shown in Fig. 7, install calibration device 10 on table 92 of machine tool 90 that will calibrate a touch probe for measuring a workpiece. At this time, shaft portion 14 is in the most retracted position. Here, calibration device 10 is installed so that the upper surface (plane) of Z calibration portion 18 is parallel to the lower end surface of main spindle 94, to which a tool of machine tool 90 is attached, i.e., so that the plane of Z calibration portion 18 is horizontal. In the case of a horizontal machine tool with a horizontal main spindle, calibration device 10 is installed so that the plane of Z calibration portion 18 is perpendicular to the Z axis.

[0030] Next, the process proceeds to step S20, where a reference tool 98 attached to a tool holder 96 whose length LT (see FIG. 7) is known is attached to the spindle 94. The process then proceeds to step S30, where the reference tool 98 is positioned. The reference tool 98 is positioned such that the tip of the reference tool 98, in this case the lower end, is positioned above the Z calibration unit 18 of the shank 14 at a predetermined distance (e.g., 4 mm) by a feed shaft device (not shown) disposed on the machine tool 90 and adapted to move the spindle 94 along the X-, Y-, and Z-axis directions. The predetermined distance may be within the range of the stroke (e.g., 10 mm) of the shank 14 advancing upward. According to the calibration device 10 of this embodiment, the shank 14 does not need to be pushed in by the reference tool 98, and therefore loads on the machine tool 90 can be prevented or minimized.

[0031] Once the reference tool 98 is positioned above the Z calibration unit 18, the process proceeds to step S40, where the operator rotates the rotating unit cover 16 to move the shaft 14 upward. This allows the Z calibration unit 18 to abut against the lower end of the reference tool 98, as shown in FIG. 7 . Once the Z calibration unit 18 has abutted, the process proceeds to step S50. In step S50, the operator does not stop the rotation of the rotating unit cover 16 and stop the shaft 14 in a state where the Z calibration unit 18 and the reference tool 98 are abutting against each other. Instead, the operator does not need to worry about the pressing force; instead, the operator simply stops the rotation of the rotating unit cover 16 after the torque limiter has acted, bringing the Z calibration unit 18 into abutment against the reference tool 98 with an appropriate pressing force. The elastic force of the biasing means of the ball plunger 32 is adjusted so that, when the Z calibration unit 18 abuts against the reference tool 98 with an appropriate pressing force, the ball 34 disengages from the ball groove 26d and spins freely. In other words, the ball plunger 32 acts as a torque limiter when the outer ring 28 is turned too far and the Z calibration portion 18 comes into contact with the reference tool 98 with excessive pressure, and also acts to always keep the contact with a constant pressure.

[0032] Next, the process proceeds to step S60, where the position where the tip of the reference tool 98 abuts on the plane of the Z calibration unit 18 is acquired as the reference Z coordinate in the Z axis direction. After the reference Z coordinate is set, the process proceeds to step S70, where a touch probe (not shown) is attached to the spindle 94 instead of the reference tool 98. Next, the process proceeds to step S80, where the measuring element disposed at the tip of the touch probe abuts on the XY calibration unit 20 from the positive and negative sides in the X axis direction and from the positive and negative sides in the Y axis direction. The coordinates of the center of the circle of the XY calibration unit 20 are calculated from the X and Y coordinate measurements at the time of abutment, and these are acquired as the reference X coordinate and reference Y coordinate. The process then proceeds to step 90, where calibration values ​​in the X, Y, and Z axis directions are acquired based on the reference X coordinate, reference Y coordinate, and reference Z coordinate thus obtained.

[0033] According to the calibration device 10, calibration method, and machine tool 90 of this embodiment, by rotating the inner ring 26 and the outer ring 28 relative to the shaft portion 14, the female thread portion 26c of the inner ring 26 serving as a driver rotates, and the male thread portion 14a of the shaft portion 14 serving as a driven member engaged therewith is driven. This allows the shaft portion 14, which is rotationally constrained relative to the outer cylindrical portion 12, to advance and retreat along the Z-axis. Thus, by simply rotating the rotating-unit cover 16, the shaft portion 14, on which the Z calibration portion 18 is formed, can be advanced and retreated, allowing for easy alignment for calibration work. Furthermore, because the shaft portion 14 and the Z calibration portion 18 are aligned relative to the reference tool 98, excessive load on the machine tool 90 can be prevented or suppressed. Furthermore, when alignment is completed and rotation of the rotating-unit cover 16 is stopped, the female thread portion 26c of the inner ring 26 and the male thread portion 14a of the shaft portion 14 are engaged with each other, allowing the shaft portion 14 to be stabilized relative to the outer cylindrical portion 12. Therefore, the position of calibration device 10 relative to machine tool 90 can be stabilized without any further operation of calibration device 10 or the need for a separate fixture. As a result, alignment can be performed easily and with good operability, regardless of the skill level of the operator, and calibration work can be performed with stable accuracy. By stabilizing the accuracy of the calibration work in this way, the machining accuracy of machine tool 90, and ultimately the quality of the machined product, can be stabilized.

[0034] According to the machine tool 90 according to one aspect of the present invention, the calibration device 10 can be easily attached, and the reference tool 98 and touch probe can be attached to the spindle 94. Therefore, the calibration work can be performed easily and in a short time while stabilizing accuracy. Furthermore, since the shaft 14 and the Z calibration unit 18 are configured to be aligned with the reference tool 98 attached to the spindle 94 of the machine tool 90, it is possible to prevent or suppress the tip of the reference tool 98 from colliding with the shaft 14 and applying a load to the machine tool 90, thereby ensuring the safety of the machine tool 90.

[0035] According to a calibration method according to one aspect of the present invention, alignment of the calibration device 10 with respect to the machine tool 90 and acquisition of the reference coordinates and calibration values ​​can be performed continuously and simply using one calibration device 10.

[0036] Furthermore, according to the calibration device 10, calibration method, and machine tool 90 of this embodiment, the calibration device 10 includes an XY calibration section 20 formed along the outer peripheral surface of the shaft section 14, and a Z calibration section 18 formed at the tip of the shaft section 14 and having a plane perpendicular to the Z-axis direction. Therefore, alignment in the X-axis direction, Y-axis direction, and Z-axis direction can be easily performed using a single shaft section 14, i.e., the calibration device 10. This allows calibration work to be performed regardless of the skill level of the operator. Furthermore, since such a simple calibration work can be performed periodically, the quality of the machined product, i.e., the machining accuracy, can be stabilized.

[0037] As described above, the calibration device 10, the calibration method, and the machine tool 90 according to this embodiment can perform stable calibration work with simple operations.

[0038] (Variation) A modified example of the calibration device 10 according to the first embodiment will be described below with reference to Fig. 4. Elements similar to or corresponding to those in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted.

[0039] FIG. 4 shows a side view of a shaft portion 44 according to this modification. Instead of a male thread, a cylindrical cam groove 44a is formed on the shaft portion 44 as a driven link. The cylindrical cam groove 44a is formed in a spiral shape along the outer periphery of the shaft portion 44. Furthermore, instead of the female thread portion 26c, a cam follower pin 26e is formed on the inner ring 26 as a driving link. Specifically, a columnar cam follower pin 26e is formed on the upper side of the inner periphery of the cylindrical portion 26a, extending horizontally radially inward. The outer diameter of the cam follower pin 26e is formed to be the same as the width of the cylindrical cam groove 44a, and the cam follower pin 26e is fitted across the entire width of the cylindrical cam groove 44a so as to engage with the cylindrical cam groove 44a. Furthermore, a retraction spring 24 engaged with a spring engaging portion 44c is disposed inside the shaft portion 44 and is retracted downward relative to the outer tube portion 12. In addition, an anti-rotation groove 44d is formed on the side of the shaft portion 44 along the axial direction of the shaft portion 44, and an anti-rotation pin 36 (see Figure 2B) is inserted into the anti-rotation groove 44d, so that the shaft portion 44 is restrained in the rotation direction relative to the outer tube portion 12.

[0040] In the calibration device 10 according to this modification, the retraction spring 24 uses its elastic biasing force to bring the upper side of the cylindrical cam groove 44a formed in the shaft portion 44 into contact with the upper side of the cam follower pin 26e formed in the inner ring 26, thereby eliminating so-called backlash between them. Because a self-locking effect operates between the cylindrical cam groove 44a and the cam follower pin 26e, when the rotation of the rotating unit cover 16 is stopped and the shaft portion 44 is stationary, the position of the shaft portion 44 in the up-down direction (Z-axis direction) can be stably maintained without a separate fixing device. As a result, even when a touch probe is attached to the spindle 94 and abuts against the XY calibration unit 20 and the Z calibration unit 18, the position of the shaft portion 14 can be maintained.

[0041] According to the calibration device 10, calibration method, and machine tool 90 of this modified example, by rotating the inner ring 26 and the outer ring 28 relative to the shaft portion 44, the cam follower pin 26e on the inner ring 26 serving as a driver rotates, and the cylindrical cam groove 44a of the shaft portion 44, into which the cam follower pin 26e is fitted, is driven. That is, the cam follower pin 26e slides with friction within the cylindrical cam groove 44a, allowing the shaft portion 44 to advance and retreat along the Z-axis direction. In this way, by simply rotating the rotating-unit cover 16, the shaft portion 44 on which the Z calibration unit 18 is formed can be advanced and retreated, allowing easy alignment for calibration work. Furthermore, because the shaft portion 44 and the Z calibration unit 18 are aligned relative to the reference tool 98, application of an excessive load to the machine tool 90 can be prevented or suppressed. Furthermore, when alignment is completed and rotation of the rotating unit cover 16 is stopped, the female thread portion 26c of the inner ring 26 and the male thread portion 14a of the shaft portion 44 are engaged with each other, thereby stabilizing the shaft portion 44 relative to the outer cylinder portion 12. Therefore, the position of the calibration device 10 relative to the machine tool 90 can be stabilized without any additional operation of the calibration device 10 or the need for a separate fixing device. As a result, alignment can be performed easily and with good operability, regardless of the skill level of the operator, and calibration work can be performed with stable accuracy. By stabilizing the accuracy of the calibration work in this way, the machining accuracy of the machine tool 90 and, ultimately, the quality of the machined product can be stabilized.

[0042] (Second embodiment) A calibration device 50 according to the second embodiment will be described below with reference to Figures 5 to 6C. Elements similar to or corresponding to those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted.

[0043] 5 and 6A, the calibration device 50 includes a main body 57 having a cylindrical shape with a generally inverted T-shaped cross section, a shaft 54 ​​arranged coaxially inside the main body 57, an inner ring 62 having a cylindrical shape with a generally inverted T-shaped cross section and arranged rotatably around the outer periphery of the small-diameter portion of the main body 57, an outer ring 56 loosely fitted around the outer side of the inner ring 62, and a cylindrical outer cover 52 arranged to surround the outer periphery of the main body 57 and restricting movement of the inner ring 62 and the outer ring 56 in the axial direction (Z-axis direction). The bottom of the main body 57 has a large diameter, incorporates a magnet 68, and is attached to a table 92 of a machine tool 90. By rotating the outer cover 52, the rod-shaped shaft 54 ​​can be advanced upward from the outer cover 52, or the advanced shaft 54 ​​can be retracted downward.

[0044] As shown in FIGS. 6B and 6C , an inner ring 62 serving as a rotating ring is disposed on the outer periphery of the main body 57 and is configured to be rotatable relative to the main body 57. The inner ring 62 includes a cylindrical portion 62a formed so that its central axis coincides with the central axes of the main body 57 and the shaft portion 54, and an outer edge portion 62b integrally formed in a circular ring shape along the outer periphery of the lower side of the cylindrical portion 62a. A female-threaded cam groove 62d serving as a driver is formed in the cylindrical portion 62a. A cam follower pin 58 serving as a follower is fixedly inserted through the lower side of the shaft portion 54 perpendicular to the axis, with both ends 58a of the cam follower pin 58 engaging with the cam groove 62d. A slit 57a is formed in the axial direction on the lower side of the main body 57, and the cam follower pin 58, which has an outer diameter the same width as the slit 57a, is inserted into the slit 57a so as to be movable forward and backward together with the shaft portion 54. In other words, slit 52b prevents rotation of shaft portion 54 and also functions as a mechanical stopper, with shaft portion 54 being positioned at its most retracted position when cam follower pin 58 abuts the lower end of slit 57a and at its most advanced position when cam follower pin 58 abuts the upper end of slit 57a. Hemispherical ball grooves 62c are formed on the upper surface of outer edge portion 62b at equal intervals along the circumferential direction. Here, ball grooves 62c are formed at four locations at 90-degree intervals along the circumferential direction of outer edge portion 62b, but the number of ball grooves is not limited to four, and may be formed in different numbers, such as two locations at 180-degree intervals or six locations at 60-degree intervals.

[0045] The outer ring 56 and the inner ring 62 are rotatably arranged coaxially with the main body 57, and are supported on their lower sides by the main body 57 and on their upper sides by the outer cover 52. Therefore, the outer ring 56 and the inner ring 62 are restricted from moving independently in the Z-axis direction (up and down direction) relative to the outer cover 52 and the main body 57.

[0046] A ball plunger 64 is attached to the radially inner side of the outer ring 56, extending downward, i.e., toward the outer edge 62b of the inner ring 62. A ball portion 66, biased by a biasing means (not shown) disposed inside the ball plunger 64, is disposed at the tip (here, the lower end) of the ball plunger 64 so as to be movable in the axial direction, i.e., in the up-and-down direction here. Therefore, the outer ring 56 is disposed above the inner ring 62 so that only the ball portion 66 abuts against the outer edge 62b of the inner ring 62. Furthermore, when the ball plunger 64 is positioned so that the ball portion 66 is directly above the ball groove 62c of the outer edge 62b, the biased ball portion 66 enters the ball groove 62c and abuts against the ball groove 62c. This allows the outer ring 56 to engage with the inner ring 62, and when the outer cover 52 and outer ring 56 are rotated, the inner ring 66 can also rotate in conjunction with them. The function of the ball plunger 64 is the same as in the first embodiment.

[0047] The shaft portion 54 is inserted into the center of the main body portion 57 through the outer ring 56 and the inner ring 62. A Z calibration portion 18 is formed at the tip of the shaft portion 54, having an XY plane that is perpendicular to the axial direction (here, the Z-axis direction) of the shaft portion 54, i.e., parallel to the mounting surface (see FIG. 7) of the table 92 on which the calibration device 50 is mounted. The upper side of the main body portion 57 has a cylindrical portion that protrudes radially outward from the shaft portion 54 and is configured to allow the shaft portion 54 to be housed (inserted) in its center, and an XY calibration portion 60 is formed on the outer peripheral surface of this cylindrical portion. The cylindrical portion on which the XY calibration portion 60 is formed is formed so that its central axis coincides with the central axes of the main body portion 57 and the shaft portion 54.

[0048] A hole is formed through the lower side of the shaft portion 54 in the radial direction of the shaft portion 54, and a rod-shaped cam follower pin 58 is inserted into this hole to connect the shaft portion 54 and the cam follower pin 58. Both ends 58a of the cam follower pin 58 are formed in a pin shape that engages with the cam groove 62d of the inner ring 62 so as to serve as a follower part for the cam groove 62d. The shaft portion 54, which engages with the cam groove 62d by both ends 58a, is configured to advance upward or retreat downward in a rotation-stopped state when the inner ring 62 rotates in conjunction with the rotation of the outer ring 56.

[0049] Further, the lower side of the central portion of the main body portion 57 is formed with an expanded-diameter portion 52a having a larger inner diameter than the upper side. Therefore, the inner diameter of the upper side of the central portion of the main body portion 57 is formed to be the same as the outer diameter of the shaft portion 54, and the inner diameter of the expanded-diameter portion 52a is formed to be larger than the outer diameter of the shaft portion 54. Therefore, in the expanded-diameter portion 52a, the outer peripheral surface of the shaft portion 54 is separated from the inner peripheral surface of the main body portion 57, forming a space. A push-down spring 70 is disposed in the space within the expanded-diameter portion 52a along the central axis of the shaft portion 54, and its upper end presses the outer cover 52 and its lower end presses the shaft portion 54. Therefore, the push-down spring 70 can urge the shaft portion 54 downward relative to the outer cover 52. This eliminates backlash between the cam groove 62d and both end portions 58a of the cam follower pin 58. The center of the main body 57 is formed with a through hole along the axial direction, and a disk-shaped magnet 68 is disposed to close this through hole.

[0050] Furthermore, a self-locking effect is exerted between the cam groove 62d, which is the driving link, and both end portions 58a of the cam follower pin 58, which is the driven link, so that the inner ring 62 cannot rotate even if the shaft portion 54 is moved back and forth. This self-locking effect makes it possible to stably hold the position of the shaft portion 54 in the up-and-down direction (Z-axis direction) without using a separate fixing device when the shaft portion 54 is stationary.

[0051] When the operator rotates the outer ring 56 while the shank 54 is in abutment with the reference tool 98 and stationary, the ball plunger causes the outer ring 56 to spin freely, weakening (dulling) the transmission of torque to the inner ring 62 and the shank 54. This torque limiting effect can prevent the shank 54 from advancing when the operator rotates the outer ring 56 more than necessary while the shank 54 is stationary.

[0052] As described above, the calibration device 50, calibration method, and machine tool 90 according to this embodiment can perform stable calibration work with simple operations.

[0053] Although the XY calibration unit 20 has been described as being formed radially outward of the shaft unit 14, this is not limiting and the XY calibration unit 20 may be formed on the outer peripheral surface of the main body unit. For example, when the XY calibration unit 60 is formed on the outer peripheral surface of the main body unit 57 as in the second embodiment, the positional relationship between the XY calibration unit 60 and the Z calibration unit 18 changes as the shaft unit advances, and this change amount needs to be corrected. However, as in the case where the XY calibration unit is formed on the outer peripheral surface of the shaft unit, alignment in the X-axis direction, Y-axis direction, and Z-axis direction can be easily performed by a single calibration device.

[0054] Furthermore, although the outer cylinder 12 has been described as being fixed to the metal table 92 by the magnet 22, this is not limiting and the outer cylinder 12 may be detachably disposed at any position on the machine tool by means of bolts or the like, or may be permanently fixed at a predetermined position on the machine tool. If the outer cylinder 12 is detachably disposed, it can be stored outside the machine tool when not in use, and is therefore not affected by chips or coolant. Furthermore, if it is detachable, it can be used on multiple machine tools.

[0055] Although the embodiments of the calibration device 10, 50, the calibration method, and the machine tool 90 have been described above, the present invention is not limited to the above embodiments. For example, instead of a vertical machine tool with a vertical spindle, a horizontal machine tool with a horizontal spindle may be used. In this case, the calibration device is attached to the vertical surface of the table so that the shaft is horizontal. In addition to the above, those skilled in the art will understand that various modifications of the above embodiments are possible. [Explanation of symbols]

[0056] 10 Calibration device 12 Outer cylinder (main body) 14 Shaft 14a Male thread portion (follower portion) 18 Z calibration section 20 XY calibration section 26 Inner ring (rotating ring) 26c Female thread part (driving joint part) 26e Cam follower pin (driving joint part) 28 Outer ring (rotating ring) 44 Shaft 44a Cylindrical cam groove (follower section) 50 Calibration device 52 outer cover 54 Shaft 56 Outer ring (rotating ring) 57 Main body 58 Cam follower pin (follower part) 60 XY calibration section 62 Inner ring (rotating ring) 62d Cam groove (driving joint part) 64 Ball Plunger 90 Machine tools 92 tables 94 Main axis 98 Reference tool

Claims

1. 1. A calibration device for a machine tool equipped with a touch probe, comprising: a main body portion fixed to the machine tool; a rod-shaped shaft portion disposed inside the main body portion with its axial direction along the Z-axis direction, the shaft portion having a follower portion, being guided by the main body portion, and configured to be able to advance and retreat along the axial direction; a rotating ring provided on the main body along the outer periphery of the shaft portion, rotatable around the axis of the shaft portion and constrained in movement in the Z-axis direction, the rotating ring having a driver section formed to engage with the follower section of the shaft portion and rotate relative to the shaft portion so that the shaft portion moves forward and backward in response; a Z calibration portion formed as a reference surface at the tip of the shaft portion; A calibration device comprising:

2. The calibration device according to claim 1 , further comprising an XY calibration section formed along an outer peripheral surface of the shaft section or an outer peripheral surface of an outer cylinder section formed on the main body section radially outside the shaft section.

3. the follower portion is a single-start male screw or a multiple-start male screw, or a cylindrical cam groove, formed in a spiral shape along the outer periphery of the shaft portion, 2. The calibration device according to claim 1, wherein the driving link portion includes a single-start female thread or a multiple-start female thread that is spirally formed along the inner circumference of the rotating ring and that can engage with the single-start male thread or the multiple-start male thread, respectively, or a cam follower pin that is formed on the inner circumference side of the rotating ring and that can engage with the cylindrical cam groove.

4. 2. The calibration device according to claim 1, wherein the driven link portion includes a cam follower pin formed on an outer circumferential side of the shaft portion and engageable with a cylindrical cam groove that is a driving link portion formed in the rotating ring.

5. 2. The calibration device according to claim 1, wherein the main body has a magnet at its bottom, and a sloped surface inclined toward the outer periphery of the main body and the Z calibration unit on a part or all of the periphery of the bottom.

6. The machine tool to which the calibration device according to claim 1 can be attached, a spindle for mounting a machining tool, the spindle being capable of mounting a reference tool having a known length or the touch probe in place of the machining tool; a table on which the workpiece and the calibration device are mounted; a feed shaft portion that moves the main shaft and the table relative to each other; A machine tool characterized by being equipped with:

7. A method for calibrating the touch probe using the calibration device according to claim 1, comprising: placing the calibration device on the machine tool; Attaching a reference tool having a known length to a spindle of the machine tool, and relatively moving the spindle to move a tip end of the reference tool to a position axially above the Z calibration portion of the shaft portion; rotating the rotating ring relative to the shaft portion to bring the Z calibration portion into contact with the reference tool; acquiring a reference coordinate in the axial direction of the abutted shaft portion; attaching the touch probe to the spindle of the machine tool; obtaining the axial calibration value based on the reference coordinate; A calibration method comprising:

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