Calibration device, calibration method, and machine tool

Abstract

Provided are a calibration device and a calibration method capable of performing stable calibration work by a simple operation, and a machine tool using the calibration device and the calibration method.　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 disposed inside the outer cylinder part (12) with an axial direction thereof aligned along the Z-axis direction, the shaft part (14) having a male screw part (14a), being guided by the outer cylinder part (12), and being configured to be able to advance and retreat along the axial direction; an inner ring (26) which is formed along the outer periphery of the shaft part (14), is configured so as to be rotatable around the axis of the shaft part (14) and restrict the movement in the Z-axis direction, and has a female screw part (26c) that engages with the male screw part (14a) of the shaft part (14) and is formed such that, by rotating relative to the shaft part (14), the shaft part (14) is driven to advance and retreat; and a Z calibration part (18) which is formed as a reference surface at the tip end of the shaft part (14).

Description

Calibration device, calibration method and machine tool

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

[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 Literature 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 a machine tool spindle is pressed into contact with a calibration artifact (calibration sphere) for alignment, it can accidentally move too far toward the calibration sphere. This can not only damage the calibration device, but also place 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] Therefore, 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 pushed-in position to engage with a reference tool, significantly reducing the possibility of applying load to the machine tool as described above. 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, shifting its position. This may result in an inability to maintain proper engagement between the Z calibration portion of the shank and the reference tool.

[0005] Special Publication No. 2023-519290 Publication Patent No. 7316409 Specification

[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.

[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 shank arranged inside the main body with its axis along the Z-axis direction, the shank having a follower section 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 shank, rotatable about the axis of the shank and configured to restrict movement in the Z-axis direction, the rotating ring having a driver section formed to engage with the follower section of the shank and rotate relative to the shank so that the shank moves back and forth in response; and a Z calibration section formed as a reference surface at the tip of the shank.

[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] 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, the calibration method 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.

[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 movable forward and backward 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 against movement 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 moving the shaft portion forward and backward 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 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 calibration work to be performed easily and quickly while stabilizing accuracy. 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 a calibration device with respect to a machine tool and acquisition of 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 shank and Z calibration unit are aligned with a 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 shank and applying a load to the machine tool, thereby ensuring the safety of the machine tool.

[0013] FIG. 1 shows a perspective view of a calibration device according to a first embodiment. 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. FIG. 3 shows a side view of a shaft. FIG. 4 shows a side view of a shaft according to a modified example. FIG. 5 shows a perspective view of a calibration device according to a second embodiment. 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. FIG. 6C shows a cross-sectional view of the calibration device of FIG. 6B taken along line 6C-6C. FIG. 7 shows a side view of a machine tool to which a reference tool and a calibration device are attached. FIG. 8 shows a flowchart of a calibration operation using a touch probe.

[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 now be described 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 is disposed inside the rotating unit cover 16, which is 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 whose 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 26c is formed on the inner periphery of the cylindrical portion 26a as a driving link portion so that it can threadably engage with the shaft portion 14 inserted into the cylindrical portion 26a. Here, the female thread 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] An outer ring 28 is disposed above the inner ring 26 and serves 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 edge of the outer ring 28 extends downward, and its lower end is connected to the rotating unit cover 16 via a fall prevention pin 30. This allows an 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) 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 unit cover 16 and the outer ring 28 are rotated, the inner ring 26 can also rotate in conjunction with them.

[0020] The shaft portion 14 is inserted into the center of the outer tube portion 12 through the outer ring 28 and the inner ring 26. As shown in FIG. 3 , a Z calibration portion 18 is formed at the tip of the shaft portion 14, having an XY plane perpendicular to the axial direction (here, the Z-axis direction) of the shaft portion 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 portion 14 that remains exposed from the outer tube portion 12 even after insertion, an XY calibration portion 20 is formed on the outer peripheral surface of a cylindrical portion that protrudes radially outward from the shaft portion 14. The cylindrical portion on which the XY calibration portion 20 is formed is formed so that its central axis coincides with the central axis of the shaft portion 14. The XY calibration portion may be formed directly on the outer peripheral surface of the shaft portion, rather than on the protruding cylindrical portion. Here, regardless of the X-axis and Y-axis positions in which the reference tool 98 abuts on the plane of the Z calibration unit 18, 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 obtaining 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 portion 14 as a reference surface that abuts on 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 threaded 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, thereby increasing 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 also be formed with a single-start thread. The shaft 14 that is threaded 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 (in the Z1 direction in FIG. 2B ).

[0022] 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 through-hole formed in the outer tube 12 to cover it. This stabilizes the position of the calibration device 10 placed on a metal table 92 (see FIG. 7 ). A spring locking portion 22a is formed on the upper end of the magnet 22 to lock the lower end of the retraction spring 24. This allows the retraction spring 24 to bias the shaft 14 downward. This eliminates backlash between the male thread portion 14a and the female thread portion 26c, stably maintaining the position of the shaft 14 relative to the outer tube 12.

[0024] Furthermore, a detent groove 14d is formed along the axial direction of the shaft portion 14 at the radially outer portion of the internal bore 14b of the shaft portion 14. A detent pin 36 is disposed in the outer tube portion 12 at a portion facing the detent groove 14d, and its tip is inserted into the detent groove 14d. In this manner, the shaft portion 14 is restrained in the rotational direction relative to the outer tube portion 12. A ball plunger (not shown) is attached to the tip of the detent pin 36, and the detent pin 36 is inserted into the detent groove 14d so that the ball portion of the ball plunger abuts the inner surface of the detent groove 14d. Therefore, when the shaft portion 14 advances upward by rotating the rotating unit cover 16, and the lower end of the detent groove 14d reaches the position of the detent pin 36, the shaft portion 14 is locked by the detent 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 (driving link portion) is rotated, the shaft portion 14 moves back and forth via the male threaded portion 14a (follower link 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 link portion), the female threaded portion 26c (driving link 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 an attempt is made 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 FIG. 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 FIG. 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 occurs.

[0027] The bottom surface of the outer cylindrical portion 12 has an inclined surface 12a that is inclined toward the outer periphery of the outer cylindrical portion 12, i.e., radially outward, and toward the Z calibration unit 18, i.e., upward. 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 positioned 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 to bring the magnet 22 into abutment with 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 cylinder portion 12, but it may also be formed on only a part 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 Figure 7, install the calibration device 10 on the table 92 of the machine tool 90 that will calibrate a touch probe for measuring a workpiece. At this time, the shaft portion 14 is in the most retracted position. Here, the calibration device 10 is installed so that the upper surface (plane) of the Z calibration portion 18 is parallel to the lower end surface of the main spindle 94 to which the tool of the machine tool 90 is attached, that is, so that the plane of the Z calibration portion 18 is horizontal. In the case of a horizontal machine tool with a horizontal main spindle, install the calibration device 10 so that the plane of the 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 (here, the lower end) of the reference tool 98 is positioned above the Z calibration portion 18 of the shank 14 at a predetermined distance (e.g., 4 mm) by a feed axis 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 reference tool 98 does not need to be pushed into the shank 14, 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, in which the operator rotates the rotating unit cover 16 to advance 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 in which the Z calibration unit 18 and the reference tool 98 are abutting. 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 bring the Z calibration portion 18 into contact with the reference tool 98 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 + and - sides in the X axis direction, and from the + and - 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 measurement values ​​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 causes 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 the calibration device 10 relative to the machine tool 90 can be stabilized without any further 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.

[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 portion 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 portion 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 a single 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] (Modification) A modification 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 will be given the same reference numerals, and duplicated descriptions 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 vertical (Z-axis) position of the shaft portion 44 can be stably maintained without a separate fastener. As a result, the position of the shaft portion 14 can be maintained even when a touch probe is attached to the main shaft 94 and abuts against the XY calibration unit 20 and the Z calibration unit 18.

[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 portion 18 is formed can be advanced and retreated, allowing easy alignment for calibration work. Furthermore, because the shaft portion 44 and the Z calibration portion 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 tube 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 a 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 designated by the same reference numerals, and redundant description 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 Figures 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 an annular 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, having 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 not only prevents rotation of shaft portion 54, but also serves as a mechanical stopper, with the position where cam follower pin 58 abuts against the lower end of slit 57a being the most retracted position of shaft portion 54 and the position where cam follower pin 58 abuts against the upper end of slit 57a being the most advanced position of shaft portion 54. Hemispherical ball grooves 62c are formed on the upper surface of outer edge portion 62b at equal intervals around the periphery thereof. Note that, here, four ball grooves 62c are formed at 90-degree intervals around the periphery of outer edge portion 62b, but the number of ball grooves is not limited to four, and a different number of ball grooves may be formed, for example, two at 180-degree intervals or six 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 is biased by a biasing means (not shown) disposed inside the ball plunger 64 and is disposed at the tip (here, the lower end) of the ball plunger 64 so that it can move axially, i.e., in the up-and-down direction. 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 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 accommodate (insert) the shaft portion 54 into 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. 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] Furthermore, an expanded-diameter portion 52a is formed on the lower side of the central portion of the main body portion 57, with an inner diameter larger than that of the upper side. Therefore, the inner diameter of the upper side of the central portion of the main body portion 57 is the same as the outer diameter of the shaft portion 54, and the inner diameter of the expanded-diameter portion 52a is 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, while 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 ends 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, if 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 must 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 using 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.

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

Claims

1. A calibration device for a machine tool equipped with a touch probe, comprising: a main body fixed to the machine tool; a rod-shaped shaft arranged inside the main body with its axis along the Z-axis direction, the shaft having a follower section and guided by the main body so that it can move back and forth along the axial direction; a rotating ring provided on the main body along the outer periphery of the shaft, rotatable around the axis of the shaft and configured to restrict movement in the Z-axis direction, the rotating ring having a driver section formed to engage with the follower section of the shaft and rotate relative to the shaft so that the shaft moves back and forth in response; and a Z calibration section formed as a reference surface at the tip of the shaft.

2. A calibration device as described in claim 1, having an XY calibration section formed along the outer peripheral surface of the shaft section or the outer peripheral surface of an outer cylinder section formed on the main body section radially outside the shaft section.

3. A calibration device as described in claim 1, wherein the driven link portion is a single-start or multiple-start male thread, or a cylindrical cam groove, formed in a spiral shape along the outer periphery of the shaft portion, and the driving link portion is a single-start or multiple-start female thread, formed in a spiral shape along the inner periphery of the rotating ring, which is engageable with the single-start or multiple-start male thread, respectively, or includes a cam follower pin formed on the inner periphery of the rotating ring and engageable with the cylindrical cam groove.

4. A calibration device as described in claim 1, wherein the driven link portion includes a cam follower pin formed on the outer periphery of the shaft portion and capable of engaging with a cylindrical cam groove, which is a driving link portion, formed in the rotating ring.

5. A calibration device as described in claim 1, wherein the main body has a magnet at the bottom, and a sloped surface on part or all of the outer periphery of the bottom that slopes toward the outer periphery of the main body and the Z calibration unit.

6. A machine tool capable of mounting the calibration device according to claim 1, characterized in that it comprises: a spindle for mounting a machining tool, wherein a reference tool of known length or the touch probe can be mounted in place of the machining tool; a table for mounting the workpiece and the calibration device; and a feed axis section for moving the spindle and the table relative to each other.

7. A method for calibrating a touch probe using the calibration device of claim 1, comprising: placing the calibration device on the machine tool; attaching a reference tool of known length to the spindle of the machine tool, and 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 the rotating ring relative to the shank to abut the Z calibration section against the reference tool; obtaining a reference coordinate in the axial direction of the abutted shank; attaching the touch probe to the spindle of the machine tool; and obtaining a calibration value in the axial direction based on the reference coordinate.

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