Machine tool with automatic tool exchanger and eddy current sensor used for the same
Patent Information
- Application Number
- JP2023047701
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-03-24
- Publication Date
- 2026-02-03
AI Technical Summary
Conventional eddy current sensors in automatic tool changers face challenges in maintaining detection accuracy when the tool change operation is sped up, as they are prone to collisions and damage due to increased gaps, leading to reduced detection precision.
The eddy current sensor is designed with a spiral-shaped coil and a core made of soft magnetic material, where the core length is either equal to or slightly longer than the coil length, allowing for increased detection accuracy and distance from the tool, thus preventing collisions and maintaining sensitivity.
This configuration maintains detection accuracy and prevents sensor damage by allowing for a larger operational gap between the sensor and the tool, enhancing reliability and sensitivity without increasing the sensor's size.
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Abstract
Description
[Technical field]
[0001] The present invention relates to an automatically controlled machine tool, such as an NC (numerically controlled) processing machine or machining center, which performs automatic control of machining of a workpiece (object to be machined, object to be measured), and is particularly suitable for a machine tool with an automatic tool changer (ATC) that appropriately selects and attaches and detaches machining tools, and that automatically measures the shape, etc. of a workpiece during machining of the object to be machined or at the time when a certain machining process is completed, and an eddy current sensor used therein. [Background technology]
[0002] NC machines and machining centers are devices that automatically select various tools according to the machining process and automatically attach them to the spindle to perform various types of machining. They are equipped with a machining table on which a workpiece is placed and fixed, a spindle head that drives the attached tools for machining attached to the tool spindle at a position that passes through the tool spindle where the tools are attached, and an automatic tool changer (ATC device) that appropriately selects and attaches / detaches the attached tools attached to the spindle head.
[0003] Tools are changed by an automatic tool change (ATC: auto tool holder change) device. The ATC device automatically removes the tool holder with the tool attached from the tool magazine and automatically attaches it to the spindle (tool change operation). The tool is attached to the tool holder, whose size, shape, etc. are determined by a given standard so that it can be attached and detached by the ATC device.
[0004] In automatic tool changers, it is desirable to speed up tool change operations in order to reduce the cost of processed products and shorten cycle times (the time required for one process). Normally, during a tool change operation, the tool swings left and right when it is attached to or detached from the spindle of the machining center and placed in the tool magazine. Conventionally, the ATC runout detection system has been configured to measure tool runout by using an eddy current sensor to measure the gap between the metal tool and the eddy current sensor when the tool is rotating.
[0005] It is known that in an ATC runout detection system, an eddy current sensor is attached to the spindle head via a bracket and detects the distance to the outer peripheral surface of the flange portion of the tool holder attached to the spindle head as an electrical displacement signal, and this is described in Patent Document 1. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] JP 2018-89738 A Summary of the Invention [Problem to be solved by the invention]
[0007] In the above-mentioned conventional technology, the eddy current sensor had to be placed as close as possible to the outer peripheral surface of the flange of the tool holder in order to improve detection accuracy. Also, the runout of the tool increases when the tool change operation is performed at high speed, and the gap (distance) between the tool and the eddy current sensor had to be increased in order to prevent the eddy current sensor from colliding with the tool.
[0008] If an eddy current sensor collides with a tool, the eddy current sensor will be destroyed and fail, resulting in cracks in the outer casing of the eddy current sensor and breakage of the internal wiring. Conventional eddy current sensors have a short detection distance, and it was difficult to improve detection accuracy when the gap (distance) between the tool and the eddy current sensor was expanded.
[0009] The object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a machine tool with an automatic tool changer and an eddy current sensor used therein that can speed up tool change operations without compromising detection accuracy in an ATC runout detection system using an eddy current sensor. Another object is to improve the reliability of the ATC runout detection system using an eddy current sensor. [Means for solving the problem]
[0010] In order to achieve the above-mentioned object, the present invention provides a machine tool with an automatic tool changer in which a tool holder with a tool attached is attached to a spindle head and the spindle head is rotated to machine a workpiece, the machine tool having an eddy current sensor installed so that its measurement end face faces the outer peripheral surface of a flange portion of the tool holder, and a data processing device that detects runout of the tool attached to the spindle head based on data measured by the eddy current sensor, the eddy current sensor comprising a coil held in a bobbin which is a cylindrical container and formed in a spiral shape, and a core which is a soft magnetic material and arranged on the measurement end face side of the coil at the axial center.
[0011] In the above-mentioned machine tool with an automatic tool changer, it is preferable that a core length, which is the axial length of the core, is substantially equal to a coil length, which is the axial length of the coil.
[0012] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that a core length, which is the axial length of the core, is extended on the side opposite to the measurement end face further than a coil length, which is the axial length of the coil.
[0013] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that the diameter of the coil is smaller than the thickness H of the flange portion.
[0014] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that the material of the core is any one of a nickel-based ferrite core, a manganese-based ferrite core, and a permalloy.
[0015] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil, (core length / coil length) is 1.35 to 1.65.
[0016] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil, (core length / coil length) is 1.40 to 1.60.
[0017] Furthermore, in the above-mentioned machine tool with an automatic tool changer, it is preferable that the ratio (core length / coil length) of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil, is 1.70 or less.
[0018] In addition, in order to achieve the above-mentioned object, the present invention provides an eddy current sensor used to detect runout of a tool attached to a spindle head of a machine tool equipped with an automatic tool changer, the sensor comprising: a coil held in a bobbin which is a cylindrical container and formed into a spiral shape; and a core which is a soft magnetic material and arranged on the measurement end face side of the coil at the axial center, wherein the ratio (core length / coil length) of the core length which is the axial length of the core to the coil length which is the axial length of the coil is 1.35 to 1.65. Effect of the Invention
[0019] According to the present invention, in a machine tool with an automatic tool changer, an eddy current sensor installed with its measurement end face facing the outer circumferential surface of a flange portion of a tool holder includes a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape, and a core, which is a soft magnetic material, arranged on the measurement end face side at the axial center of the coil, so that the detection accuracy is not impaired even if the gap (distance) between the eddy current sensor and the tool is enlarged. Therefore, by enlarging the gap (distance) between the eddy current sensor and the tool, it is possible to avoid a collision between the eddy current sensor and the tool that occurs when the tool change operation is accelerated. [Brief description of the drawings]
[0020] [Figure 1] 1 is a cross-sectional view of a conventional eddy current sensor and an eddy current sensor according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a front view showing a machining center (machine tool equipped with an automatic tool changer) according to an embodiment of the present invention; [Diagram 3] FIG. 1 is a side view showing a machining center (machine tool equipped with an automatic tool changer) according to an embodiment of the present invention; [Figure 4] Cross-sectional view showing the tool holder installed [Diagram 5] Block diagram showing the ATC runout detection system [Figure 6] Cross-sectional view showing the tool holder being attached and detached [Figure 7] A diagram showing how high-frequency magnetic flux is generated by an eddy current sensor [Figure 8] High-frequency magnetic flux generated by an eddy current sensor visualized by computer simulation [Figure 9] Graph showing distance vs. output voltage of an eddy current sensor [Figure 10] Graph showing the results of analyzing the ratio of core length to coil length vs. sensitivity DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 shows a cross-sectional view of an eddy current sensor 1, where (a) is a conventional eddy current sensor 1, (b) is an example of the arrangement of a core 1-1, and (c) is an eddy current sensor 1 according to an embodiment of the present invention. The eddy current sensor 1 generates a high-frequency magnetic flux by passing a high-frequency current through an internal coil 1-2.
[0022] When the object to be measured (metal) is placed in a high-frequency magnetic flux, eddy currents flow on the surface of the object in a direction perpendicular to the passage of the magnetic flux due to electromagnetic induction. A change in the distance between the eddy current sensor 1 and the object to be measured (metal) results in a change in the amount of magnetic flux passing through the coil, which changes the impedance of the coil 1-2. The distance is then measured as a change in DC voltage by rectifying the oscillation amplitude that accompanies this change.
[0023] The eddy current sensor 1 is installed so that its measurement end face 1-4 faces the outer peripheral surface of a flange portion 11B (see FIG. 5) of a tool holder 11, which is the object to be measured. A disk-shaped coil 1-2 formed into a spiral shape is held in shape by a plastic such as epoxy, and then held in a bobbin 1-3, which is a cylindrical container made of resin and has a cap shape. The bobbin 1-3 is housed in a cylindrical outer case 1-5. In a typical eddy current sensor 1, the outer diameter of the outer case 1-5 is φ5 mm, and the axial length is approximately 16 mm. The coil length, which is the axial length of the coil 1-2, is approximately 2 mm.
[0024] FIG. 1(b) shows an example in which a core 1-1, which is a soft magnetic material made of ferrite or the like whose magnetic permeability does not decrease in the high frequency range, is arranged on the measurement end face 1-4 side at the axial center of the coil 1-2 in the eddy current sensor 1. The axial length of the core 1-1 shown in FIG. 1(b) is substantially equal to the axial length of the coil 1-2 which is the coil length. This increases the magnetic flux density penetrating the core 1-1 and improves the directivity, improving the sensitivity compared to the conventional eddy current sensor 1 in FIG. 1(a). At this time, the core 1-1 is arranged so as not to protrude from the end of the coil 1-2 on the measurement end face 1-4 side. In other words, the core 1-1 and the coil 1-2 are arranged so as to be flat and without steps on the measurement end face 1-4 side (flush).
[0025] Fig. 1(c) shows an eddy current sensor 1 according to one embodiment, in which the core 1-1 extends backward, opposite the measurement end face 1-4, i.e., the core length, which is the axial length of the core 1-1, extends further toward the opposite side of the measurement end face 1-4 than the coil length, which is the axial length of the coil 1-2. In Fig. 1(c), the ratio of the core length to the coil length (core length / coil length) is set to approximately 1.50 (150%). This increases the magnetic flux density penetrating the core 1-1 and improves the directivity, resulting in improved sensitivity compared to the eddy current sensor 1 in Fig. 1(b).
[0026] Therefore, when obtaining the same sensitivity, the distance between the eddy current sensor 1 and the object to be measured (metal), i.e., the distance d (see Figure 5) between the eddy current sensor 1 and the outer peripheral surface of the flange portion 11B of the tool holder 11, can be increased, so that it is possible to avoid collision between the eddy current sensor 1 and the tool holder 11 by increasing the distance d (see Figure 5).
[0027] Before describing the details of the eddy current sensor 1 according to an embodiment, a machining center 20 equipped with an automatic tool changer (ATC device) will be described. Fig. 2 is a front view showing the machining center 20 according to the embodiment of the present invention, and Fig. 3 is a side view.
[0028] 2 and 3, a workpiece 24 (which serves as a machining target during machining and as a measurement target during measurement) is placed on the upper surface of a movable table 21 of a machining center 20 and fixed by a fixture 23. A spindle head 26 to which a mounting tool 25-1 is attached is disposed above the workpiece 24.
[0029] The machining center 20 is a numerically controlled machine tool that performs various machining operations such as milling, drilling, boring, and tapping without changing the attachment of the workpiece 24. A large number of tools 25 are stored in a tool magazine 28. Then, machining is performed by automatically changing the tools 25 according to commands from a computer numerical control. Therefore, since machining is the main purpose, the environment in which the machining center 20 is installed contains fine particles such as oil mist and dust, and furthermore, there is dirt and cutting chips around the workpiece and spindle.
[0030] The spindle head 26 is equipped with a mechanism for feeding the tool 25 vertically and a mechanism for rotating the tool 25 in a horizontal plane, and the tool spindle 29 serves as the axis of rotation about which the attached tool 25-1 rotates. The tools 25 are individually attached to the tool holders 11 by an automatic tool changer (ATC device) 27, and the tool holders 11 are automatically attached to and detached from the spindle head 26.
[0031] Further, the automatic tool changer (ATC device) 27 uses the arm 17 under the control of the control device 22 to take out the attached tool 25-1 from a tool magazine 28 that stores the tool 25 via the tool holder 11. The automatic tool changer (ATC device) 27 is provided with a mechanism for mounting and dismounting the attached tool 25-1 to and from the spindle head 26 and storing it in the tool magazine 28.
[0032] A series of controls related to the movement of the movable table 21 in the X-axis and Y-axis directions, the movement of the spindle head 26 in the Z-axis direction, the replacement of the attached tool 25-1, machining such as cutting, and measurement of the shape and machining error of the workpiece 24 are performed by the control device 22 executing machining and measurement programs stored therein.
[0033] 4 is a cross-sectional view showing the attachment state of the tool holder, illustrating the state in which the tool holder 11 is attached to the spindle head 26. The tool holder 11 has a conical fitting portion 11A, and is attached by fitting the fitting portion 11A into a conical fitted portion 26A formed on the spindle head 26. To attach the tool holder 11, first, the shaft rod 33 is pulled upward, causing the ball holder 34 and balls 35 to move.
[0034] Next, the movement of the ball 35 pulls the pull stud (draw bolt) 36, and the conical fitting portion 11A of the tool holder 11 is pressed against the conical fitted portion 26A of the spindle head 26. As a result, the fitting portion 11A comes into close contact with the fitted portion 26A, and attachment (chucking) is performed.
[0035] 5 is a block diagram showing the ATC runout detection system, and shows a shape measuring unit 50 for the flange portion 11B of the tool holder 11 that holds the attached tool 25-1. The shape measuring unit 50 is a device that automatically detects the mounting state of the tool holder 11 mounted on the spindle head 26 by the ATC device, and is mainly composed of an eddy current sensor 1 and a data processing device 3. The eddy current sensor 1 is attached to the spindle head 26 via a bracket 10. The eddy current sensor 1 detects the distance d to the outer peripheral surface of the flange portion 11B of the tool holder 11 mounted on the spindle head 26 as a signal voltage.
[0036] The shape of the tool holder 11 is standardized and unified not only for the fitting portion 11A but also for the outer peripheral shape of the flange portion 11B. Therefore, the mounting state of the mounting tool 25-1 can be determined by measuring the outer peripheral shape of the flange portion 11B. The outer peripheral shape can be obtained by rotating the tool holder 11 once and measuring the distance d.
[0037] The data processing device 3 detects runout indicating the mounting state of the tool 25-1 mounted on the tool holder 11 based on the data measured by the eddy current sensor 1, and includes an A / D converter 4, a CPU 6, a memory 5, an input / output circuit 7, etc. The A / D converter 4 converts the signal voltage output from the eddy current sensor 1 into a digital signal and outputs it to the CPU 6.
[0038] The data processing device 3 detects runout indicating the mounting state of the tool 25-1 mounted on the spindle head 26 based on the data converted into a digital signal. The calculation process of the distance d by the CPU 6 is performed upon receiving a command to start measurement from the control device 22 via the input / output circuit 7. Then, the data of the distance d outputted from the eddy current sensor 1 is stored in the memory 5.
[0039] Fig. 6 is a cross-sectional view showing the attachment and detachment state of the tool holder 11, and shows the state when the tool holder 11 with the attached tool 25-1 attached is attached to and detached from the spindle head 26. Normally, as shown in Fig. 6(a), the tool holder 11 does not swing and is attached and detached from the spindle head 26 as shown by the arrow. However, as shown in Fig. 6(b), if the tool holder 11 is attached and detached while tilting and swinging, the flange portion 11B of the tool holder 11 and the eddy current sensor 1 collide.
[0040] If the eddy current sensor 1 and tool holder 11 collide, the eddy current sensor will be destroyed and malfunction, resulting in cracks in the outer case of the eddy current sensor and breakage of the internal wiring. Compared to Fig. 6(b), by increasing the distance d to the outer peripheral surface of the flange portion 11B of the tool holder 11 as shown in Fig. 6(c), it is possible to avoid collision between the eddy current sensor 1 and tool holder 11.
[0041] Furthermore, increasing the distance d to the outer peripheral surface of the flange portion 11B of the tool holder 11 not only enables detection of the mounting condition of the mounting tool 25-1 during rotation, such as a condition in which dirt or chips have become mixed in between the fitting portion 11A and the fitted portion 26A causing increased vibration, but also makes it possible to determine whether the tool holder 11 moves violently when attaching or detaching the tool holder 11.
[0042] 7A and 7B are diagrams showing the generation of high-frequency magnetic flux by the eddy current sensor 1. As shown in Fig. 7A, when a high-frequency current is passed through the coil 1-2, the high-frequency magnetic flux is generated radially toward the flange portion 11B, which is the target metal. Also, as shown in Fig. 7B, the coil 1-2 can be made larger in diameter to increase sensitivity and increase the distance d.
[0043] In this case, however, in addition to the installation restrictions, the range of the high-frequency magnetic flux becomes larger than the thickness H of the flange portion 11B to be measured, and is therefore affected by the surrounding metal. For this reason, it is preferable that the diameter of the coil 1-2 is smaller than the thickness H of the flange portion 11B. Although it is better for the diameter of the core 1-1 to be larger, it is determined in conjunction with the diameter of the coil 1-2 and is set within the inner diameter of the coil 1-2.
[0044] Figure 8 is a diagram visualizing the high-frequency magnetic flux generated by eddy current sensor 1 using a computer simulation, with Figure 8(a) being the case of Figure 1(a), i.e., when there is no core 1-1, Figure 8(b) being the case of Figure 1(b), i.e., when there is a core 1-1 of a length substantially equal to the coil length, and Figure 8(c) being the case of Figure 1(c), visualizing the magnetic flux distribution when high-frequency current is passed through an eddy current sensor 1 having a core 1-1 longer than the coil length.
[0045] In the conventional eddy current sensor 1 in Fig. 8(a), the high-frequency magnetic flux spreads radially from the tip (measurement end surface 1-4) of the coil 1-2, and the magnetic flux in the center facing the flange portion 11B is sparse and the magnetic flux density is low. In Fig. 8(b), the magnetic flux in the center is denser than in Fig. 8(a) (the magnetic flux is concentrated and appears darker in the figure), and it can be seen that the magnetic flux density is higher.
[0046] In Fig. 8(c), it can be seen that the magnetic flux in the center is denser than in Fig. 8(b), resulting in a higher magnetic flux density. The magnetic flux distribution is more concentrated in the center, increasing directivity and improving the sensitivity of the eddy current sensor 1. It is preferable to use a nickel-based ferrite core, manganese-based ferrite core, permalloy, etc. as the material for the core 1-1 in order to avoid the effects of temperature changes.
[0047] Moreover, the sensitivity of the eddy current sensor 1 can be adjusted by changing the material of the core 1-1, and the detection distance of the eddy current sensor 1 can be controlled. The sensitivity adjustment is required so as not to exceed the allowable input voltage range of the data processing device 3 (see FIG. 5). In other words, by providing the core 1-1, the sensitivity and detection distance can be appropriately adjusted according to the purpose without increasing the size of the eddy current sensor 1.
[0048] Fig. 9 is a graph showing distance d versus output voltage of eddy current sensor 1. The vertical axis shows the output voltage (V) of eddy current sensor 1, and the horizontal axis shows distance d from eddy current sensor 1 to the outer peripheral surface of flange portion 11B. Fig. 9(a) shows the results of measurement using eddy current sensor 1 shown in Fig. 1(a), Fig. 9(b) shows the results of measurement using eddy current sensor 1 shown in Fig. 1(b), and Fig. 9(c) shows the results of measurement using eddy current sensor 1 shown in Fig. 1(c). The slope of each graph represents the sensitivity of eddy current sensor 1. In order to increase sensitivity, it is preferable to install eddy current sensor 1 at a point where the slope is greatest.
[0049] Figure 9(a) shows an eddy current sensor 1 without a core 1-1; when the eddy current sensor 1 was placed at point A so that the distance d was 1 mm, the sensitivity was 7 V / mm. Similarly, Figure 9(b) shows an eddy current sensor 1 with a core 1-1 placed as in Figure 1(b); when the eddy current sensor 1 was placed at point B so that the distance d was 2 mm, the sensitivity was 7 V / mm. As a result, the eddy current sensor 1 with the core 1-1 placed can increase the distance d without reducing sensitivity compared to when the core 1-1 is not placed.
[0050] Figure 9(c) shows that the core 1-1 is extended backward as in Figure 1(c), and when the eddy current sensor 1 is installed at point B so that the distance d is 2 mm, the sensitivity is 14 V / mm. This shows that the eddy current sensor 1 with the extended core 1-1 not only increases the distance d compared to when the core 1-1 is not present, but also improves the sensitivity. Therefore, the eddy current sensor 1 with the extended core 1-1 not only avoids collision between the eddy current sensor 1 and the tool holder 11, but also increases the directivity and improves the sensitivity without increasing the diameter of the coil 1-2.
[0051] Fig. 10 is a graph showing the results of an analysis of sensitivity versus the ratio of core length to coil length. The horizontal axis shows the ratio of core length to coil length (core length / coil length, in %), and the vertical axis shows the sensitivity ratio, shown as a multiple based on the sensitivity of the conventional eddy current sensor 1. Fig. 10 shows the results when the distance d is constant.
[0052] 10, the ratio of the core length, which is the axial length of the core 1-1, to the coil length, which is the axial length of the coil 1-2 (core length / coil length) should be 135 to 165% (1.35 to 1.65) (range M in the figure) and more preferably 140 to 160% (1.40 to 1.60) in order to improve sensitivity at a position where the distance d is doubled as shown in Fig. 9. Also, from the viewpoint of further improving sensitivity, the ratio of the core length (core length / coil length) is preferably 170% (1.70) or less. [Explanation of symbols]
[0053] 1...Eddy current sensor 1-1…Core 1-2…Coil 1-3…Bobbin 1-4…Measurement end face 1-5…Outer case 3. Data processing device 4...A / D converter 5. Memory 6…CPU 7... Input / Output circuit 10…Bracket 11...Tool holder 11A...Mating part 11B…Flange section 17…Arm 20...Machining center 21... Movable table 22...Control device 23...Fixing tool 24…Work 25...Tools 25-1…Installation tool 26...Spindle head 26A…Mated part 28…Tool magazine 29…Tool spindle 33...Axle rod 34…Ball holder 35…Ball 50...Shape measurement section
Claims
1. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.35 to 1.
65.
2. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.40 to 1.
60.
3. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length), is 1.70 or less.
4. An eddy current sensor used to detect runout of a tool attached to a spindle head of a machine tool with an automatic tool changer, a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; wherein the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.35 to 1.
65.
5. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with a core length, which is the axial length of the core, extending further toward the opposite side of the measurement end face than a coil length, which is the axial length of the coil; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.35 to 1.
65.
6. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with The diameter of the coil is smaller than the thickness H of the flange portion, A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.35 to 1.
65.
7. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with the core is made of a material selected from the group consisting of nickel-based ferrite core, manganese-based ferrite core, and permalloy; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.35 to 1.
65.
8. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with a core length, which is the axial length of the core, extending further toward the opposite side of the measurement end face than a coil length, which is the axial length of the coil; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.40 to 1.
60.
9. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with The diameter of the coil is smaller than the thickness H of the flange portion, A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.40 to 1.
60.
10. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with the core is made of a material selected from the group consisting of nickel-based ferrite core, manganese-based ferrite core, and permalloy; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length) is 1.40 to 1.
60.
11. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with a core length, which is the axial length of the core, extending further toward the opposite side of the measurement end face than a coil length, which is the axial length of the coil; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length), is 1.70 or less.
12. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with The diameter of the coil is smaller than the thickness H of the flange portion, A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length), is 1.70 or less.
13. A machine tool with an automatic tool changer in which a tool holder having a tool attached thereto is attached to a spindle head and the spindle head is rotationally driven to machine a workpiece, an eddy current sensor installed so that a measurement end surface faces an outer peripheral surface of a flange portion of the tool holder; a data processing device that detects runout of a tool attached to the spindle head based on data measured by the eddy current sensor, The eddy current sensor a coil held in a bobbin, which is a cylindrical container, and formed into a spiral shape; a core made of a soft magnetic material arranged on the measurement end face side at the axial center of the coil; Equipped with the core is made of a material selected from the group consisting of nickel-based ferrite core, manganese-based ferrite core, and permalloy; A machine tool with an automatic tool changer, characterized in that the ratio of the core length, which is the axial length of the core, to the coil length, which is the axial length of the coil (core length / coil length), is 1.70 or less.