Machine tool and control method for machine tool

Abstract

To provide a machine tool capable of removing foreign matter mixed into bearings. [Solution] The machine tool comprises a spindle, a bearing that rotatably holds the spindle, a detection means for periodically detecting foreign matter contamination in the bearing, a supply means for supplying lubricating oil to the bearing, and a control means for controlling the supply of lubricating oil by the supply means. When foreign matter contamination is detected, the control means increases the amount of lubricating oil supplied by the supply means per unit time compared to when no foreign matter contamination is detected.

Description

Technical Field

[0001] The present disclosure relates to a machine tool and a method for controlling a machine tool.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2020-171986 (Patent Document 1) discloses a spindle device including a spindle, a housing, and a bearing that supports the spindle within the housing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] If foreign matter such as dust enters the bearing, the bearing may seize. Therefore, it is necessary to remove foreign matter within the bearing.

[0005] The present disclosure provides a machine tool and a method for controlling a machine tool capable of removing foreign matter mixed into a bearing.

Means for Solving the Problems

[0006] According to an aspect of the present disclosure, a machine tool includes a spindle, a bearing that rotatably holds the spindle, a detection unit that periodically detects foreign matter intrusion into the bearing, a supply unit that supplies lubricating oil to the bearing, and a control unit that controls the supply of lubricating oil by the supply unit. When foreign matter intrusion is detected, the control unit increases the amount of lubricating oil supplied to the supply unit per unit time compared to when foreign matter intrusion is not detected.

[0007] According to other aspects of this disclosure, a method for controlling a machine tool includes the steps of periodically detecting foreign matter in a bearing that rotatably holds a spindle, and, when foreign matter is detected, increasing the amount of lubricating oil supplied to the bearing per unit time compared to when no foreign matter is detected. [Effects of the Invention]

[0008] According to the above configuration, it becomes possible to remove foreign matter that has entered the bearing. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a machine tool equipped with a spindle. [Figure 2] This is a perspective view showing the inside of a machine tool. [Figure 3] This is a perspective view showing the spindle assembly. [Figure 4] This is a cross-sectional view showing the spindle assembly in Figure 3. [Figure 5] This is a cross-sectional view showing the spindle apparatus within the area enclosed by the dashed line V in Figure 4. [Figure 6] This is a perspective view showing the first bearing group in Figure 5. [Figure 7] This is a front view showing the first bearing group in Figure 5. [Figure 8] This figure partially shows the outer circumferential surface of the outer ring in the first bearing group in Figure 6. [Figure 9] This is a diagram showing the system configuration inside a machine tool. [Figure 10] This diagram shows the flow of processing performed by the bearing condition detection unit. [Figure 11] This is a diagram illustrating the further configuration of the machine tool. [Figure 12] This diagram shows the discharge route for lubricating oil. [Figure 13] This is a diagram illustrating the processing flow in a machine tool. [Modes for carrying out the invention]

[0010] Hereinafter, each embodiment according to the present invention will be described while referring to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0011] [A. Overall Structure of Machine Tool] FIG. 1 is a perspective view showing a machine tool provided with a spindle device. FIG. 2 is a perspective view showing the inside of the machine tool of FIG. 1.

[0012] Referring to FIG. 1, the machine tool 100 includes an operation panel 150. The operation panel 150 is a general-purpose computer. The operation panel 150 has an upper panel 151 and a lower panel 152. The upper panel 151 includes a touch screen for displaying a manual or various application screens, etc., and for being operated when using an application. The lower panel 152 includes a touch screen for displaying the operating state of the machine tool 100 or the processing status of the workpiece, and for being operated when operating the machine tool 100, and an operation unit such as buttons or switches for operating the machine tool 100.

[0013] Referring to FIGS. 1 and 2, the machine tool 100 includes a spindle device 10 in a machining chamber 190. Note that the machining chamber 190 is a space where the workpiece W is machined.

[0014] Referring to FIG. 2, the machine tool 100 is a machining center that performs workpiece machining by bringing a rotating tool T into contact with the workpiece W. The machine tool 100 is a horizontal machining center in which the rotation center axis of the tool T extends in the horizontal direction. The machine tool 100 is a numerically controlled (NC) machine tool in which various operations for workpiece machining are automated by computer numerical control.

[0015] In FIG. 2, a "Z-axis" parallel to the horizontal direction and parallel to the rotation center axis of the tool T, an "X-axis" parallel to the horizontal direction and orthogonal to the Z-axis, and a "Y-axis" parallel to the vertical direction are shown.

[0016] The machine tool 100 has a bed 12, a column 14, a spindle device 10, and a table 16.

[0017] The bed 12 is a base member for supporting the column 14, the spindle device 10, the table 16, etc., and is fixed to the floor surface of a factory or the like. The bed 12 is made of metal such as cast iron.

[0018] The column 14 is supported by the bed 12. As a whole, the column 14 has a portal shape rising upward from the bed 12. The column 14 is disposed at the end of the bed 12 in the Z-axis direction. The column 14 is movable in the X-axis direction by various feed mechanisms, guide mechanisms, servo motors, etc.

[0019] The spindle device 10 is supported by the column 14. As a whole, the spindle device 10 has a cylindrical shape protruding in the Z-axis direction from the column 14. The spindle device 10 is movable in the Y-axis direction by various feed mechanisms, guide mechanisms, servo motors, etc.

[0020] The spindle device 10 has a spindle 21. The spindle 21 has a cylindrical shape centered on a predetermined axis 101 parallel to the Z-axis. The spindle 21 is rotatable about the predetermined axis 101 by a motor. A clamp mechanism for holding the tool T for workpiece machining in the machine tool 100 is built into the spindle 21. As the spindle 21 rotates, the tool T held by the spindle 21 rotates about the predetermined axis 101.

[0021] The maximum rotational speed of the spindle 21 may be, for example, 15000 (min

[0022] , ) or more, or 30000 (min -1 ) or more.

[0022] The predetermined axis 101 corresponds to the rotational axis of the main spindle 21. The radial direction of the main spindle 21 is the radial direction of the cylindrical main spindle 21 and is perpendicular to the predetermined axis 101. The axial direction of the main spindle 21 is the axial direction of the cylindrical main spindle 21 (Z-axis direction) and is the axial direction of the predetermined axis 101. The circumferential direction of the main spindle 21 is the circumferential direction of the cylindrical main spindle 21 and is the circumferential direction centered on the predetermined axis 101.

[0023] Table 16 is supported by bed 12. Table 16 is mounted on bed 12. Table 16 is positioned away from column 14 in the Z-axis direction. Table 16 is a device for holding workpiece W. Table 16 holds workpiece W in a position opposite the spindle 21 in the Z-axis direction. Table 16 is movable in the Z-axis direction by various feed mechanisms, guide mechanisms and servo motors. Table 16 has a built-in swivel mechanism for swiveling a pallet mounted on table 16 around a pivot axis extending in the Y-axis direction (vertical direction).

[0024] In this configuration, the machining position of the workpiece W by the tool T is moved in three dimensions by a combination of the movement of the column 14 in the X-axis direction, the movement of the spindle device 10 (spindle 21) in the Y-axis direction, and the movement of the table 16 in the Z-axis direction.

[0025] Furthermore, the machine tool equipped with the spindle device in the present invention is not limited to the horizontal machining center described above, but may also be a vertical machining center, or a multi-tasking machine having both a turning function using a fixed tool and a milling function using a rotary tool. The machine tool equipped with the spindle device in the present invention may also be an AM / SM hybrid machine capable of additive manufacturing and subtractive manufacturing of a workpiece.

[0026] [B. Structure of the spindle unit] Figure 3 is a perspective view showing the spindle assembly. Figure 4 is a cross-sectional view showing the spindle assembly in Figure 3. In Figures 3 and 4, and in subsequent drawings, "spindle front side" corresponds to the side of the spindle assembly 10 where the tool T held by the spindle assembly 10 is positioned, and "spindle rear side" corresponds to the opposite side of the spindle 21 in the axial direction of the spindle assembly 10 from the "spindle front side".

[0027] Referring to Figures 3 and 4, the spindle unit 10 has a clamping mechanism for holding the tool T, which includes a collet 23 capable of gripping the tool T, a drawbar 24 that opens and closes the collet 23 by moving along the axial direction of the spindle 21, and a disc spring 25 fitted on the outer circumference of the drawbar 24. The collet 23, the drawbar 24, and the disc spring 25 are housed in the spindle 21.

[0028] The spindle unit 10 further includes an unclamping cylinder 26 for hydraulically unclamping the clamped tool T. The unclamping cylinder 26 is located at the rear end (rear end) of the spindle unit 10 on the rear side of the spindle.

[0029] In the clamped state, when the tool T is held, the drawbar 24 is pulled towards the rear of the spindle by the spring force of the disc spring 25. This causes the collet 23 to close, and the tool T is gripped by the closed collet 23. When transitioning from the clamped state to the unclamped state, when the tool T is released, the unclamping cylinder 26 is supplied with hydraulic pressure, pushing the drawbar 24 towards the front of the spindle against the spring force of the disc spring 25. This causes the collet 23 to open, and the tool T is released from the open collet 23.

[0030] The spindle unit 10 further comprises a housing 50, a motor housing 33, and a rear housing 45.

[0031] The motor housing 33 is positioned between the housing 50 and the rear housing 45 in the axial direction of the spindle 21. The housing 50 is connected to the front end of the motor housing 33 on the front side of the spindle. The rear housing 45 is connected to the rear end of the motor housing 33 on the rear side of the spindle. The housing 50, motor housing 33, and rear housing 45 extend cylindrically along a predetermined axis 101. As shown in Figure 2, the spindle base 11 is connected to the column 14 so as to be slidable in the Y-axis direction. The motor housing 33 is fitted inside the cylindrical portion of the spindle base 11.

[0032] The spindle unit 10 further comprises a rotor 31 and a stator 32. The rotor 31 has a cylindrical shape centered on a predetermined axis 101. The rotor 31 is fitted onto the outer circumferential surface of the spindle 21. The stator 32 has a cylindrical shape centered on the predetermined axis 101. The stator 32 is fitted onto the inner circumferential surface of the motor housing 33. A small gap is provided between the rotor 31 and the stator 32 in the radial direction of the spindle 21. The rotor 31 and the stator 32, together, constitute a motor for rotating the spindle 21 around the predetermined axis 101.

[0033] The spindle device 10 further includes a first bearing group 71, a second bearing group 72, and a third bearing group 73. The first bearing group 71, the second bearing group 72, and the third bearing group 73 support the spindle 21 so that it can rotate around a predetermined axis 101.

[0034] The first bearing group 71 is positioned between the spindle 21 and the housing 50 in the radial direction of the spindle 21. The first bearing group 71 is positioned between the spindle 21 and the housing body 51, which will be described later, in the radial direction of the spindle 21. In the assembly process of the spindle device 10, the first bearing group 71 is inserted into the housing 50 from the front side of the spindle.

[0035] The second bearing group 72 is positioned between the spindle 21 and the housing 50 in the radial direction of the spindle 21. The second bearing group 72 is positioned between the spindle 21 and the sleeve 61, which will be described later, in the radial direction of the spindle 21. The second bearing group 72 is provided at a distance from the first bearing group 71 in the axial direction of the spindle 21. The second bearing group 72 is positioned further rearward on the spindle than the first bearing group 71. In the assembly process of the spindle device 10, the second bearing group 72 is inserted into the housing 50 from the rear side of the spindle.

[0036] The third bearing group 73 is positioned radially between the spindle 21 and the rear housing 45. The third bearing group 73 is positioned further rearward than the second bearing group 72.

[0037] Figure 5 is a cross-sectional view showing the spindle assembly within the area enclosed by the dashed line V in Figure 4. Referring to Figures 3 to 5, the housing 50 has a housing body 51 and a sleeve 61. The housing body 51 constitutes the main part of the housing 50. The sleeve 61 is located inside the housing body 51. The sleeve 61, together with a plurality of elastic members 66 which will be described later, constitutes a preload application mechanism for applying preload to the second bearing group 72.

[0038] The housing body 51 has a cylindrical shape centered on a predetermined axis 101. The housing body 51 includes a front portion 53, an intermediate portion 54, a rear portion 55, and a flange portion 56 as its constituent parts.

[0039] The front section 53, the intermediate section 54, and the rear section 55 are aligned in the axial direction of the spindle 21. The front section 53 is located on the front side of the spindle in the housing body 51. The rear section 55 is located on the rear side of the spindle in the housing body 51. The intermediate section 54 is located between the front section 53 and the rear section 55 in the axial direction of the spindle 21. The inner diameter (diameter of the inner circumferential surface) of the rear section 55 centered on the predetermined shaft 101 is larger than the inner diameter of the front section 53 centered on the predetermined shaft 101.

[0040] The inner diameter of the intermediate portion 54 centered on the predetermined shaft 101 is smaller than the inner diameter of the rear portion 55 centered on the predetermined shaft 101, and also smaller than the inner diameter of the front portion 53 centered on the predetermined shaft 101. The intermediate portion 54 has a convex shape that protrudes radially inward from the main shaft 21 on the inner circumferential surface of the housing 50. The flange portion 56 protrudes radially outward from the rear portion 55 from the main shaft 21 and has a flange shape that circumfers around the main shaft 21 in the circumferential direction.

[0041] The housing 50 (housing body 51) has a first end face 50a and a second end face 50b. The first end face 50a is located at the front end of the housing 50. The first end face 50a is a plane perpendicular to the predetermined axis 101. The first end face 50a faces the front side of the spindle 21 in the axial direction of the spindle 21. The front portion 53 of the housing body 51 has the first end face 50a. The second end face 50b is located on the opposite side of the first end face 50a in the axial direction of the spindle 21. The second end face 50b is located at the rear end of the housing 50. The second end face 50b is a plane perpendicular to the predetermined axis 101. The second end face 50b faces the rear side of the spindle 21 in the axial direction of the spindle 21. The rear portion 55 of the housing body 51 has the second end face 50b.

[0042] The spindle unit 10 further includes a cover 43. The cover 43 is attached to the housing 50 (housing body 51). The cover 43 has a cylindrical shape that forms the appearance of a frustoconical shape centered on a predetermined axis 101. The cover 43 is positioned to cover the outer circumferential surface 50c of the housing 50 (housing body 51) while facing the end face 56a of the flange portion 56 in the axial direction of the spindle 21. An internal space 120 is partitioned inside the cover 43.

[0043] The spindle unit 10 further includes a cover 327. The cover 327 is attached to the housing 50 (housing body 51). The cover 327 is attached to the outer circumferential surface 50c of the housing 50.

[0044] Figure 6 is a perspective view showing the first bearing group in Figure 5. Figure 7 is a front view showing the first bearing group in Figure 5.

[0045] Referring to Figures 5 to 7, the first bearing group 71 includes a first bearing 71A and a second bearing 71B. Each of the bearings in the first bearing 71A and the second bearing 71B is an angular contact bearing.

[0046] The first bearing 71A has an outer ring 76, an inner ring 77, a plurality of rolling elements 78, and a cage 79. The outer ring 76 is fitted to the inner circumferential surface of the housing 50. The outer ring 76 is fitted to the housing 50 in a clearance fit relationship. The outer ring 76 has an inner circumferential surface 76b on the rolling element 78 side and an outer circumferential surface 76a located on the opposite side of the inner circumferential surface 76b and in contact with the housing 50. The inner circumferential surface 76b is in contact with the rolling element 78.

[0047] The inner ring 77 is fitted onto the outer surface of the main shaft 21. The inner ring 77 is fitted to the main shaft 21 in an interlocking fit.

[0048] The rolling elements 78 consist of balls. Multiple rolling elements 78 are arranged between the inner ring 77 and the outer ring 76 in the radial direction of the main shaft 21. A cage 79 holds the multiple rolling elements 78 between the inner ring 77 and the outer ring 76. The multiple rolling elements 78 are held by the cage 79 at intervals from each other in the circumferential direction around a predetermined shaft 101.

[0049] The second bearing 71B has the same shape as the first bearing 71A. The second bearing 71B is aligned with the first bearing 71A in the axial direction of the main shaft 21.

[0050] The first bearing 71A and the second bearing 71B are combined in a parallel configuration. The first bearing 71A and the second bearing 71B are positioned to be able to receive axial loads in the axial direction of the spindle 21, from the rear side of the spindle to the front side of the spindle.

[0051] The first bearing 71A is positioned further forward of the spindle than the second bearing 71B. The second bearing 71B is positioned further rearward of the spindle than the first bearing 71A. The distance between the first end face 50a and the first bearing 71A in the axial direction of the spindle 21 is smaller than the distance between the first end face 50a and the second bearing 71B in the axial direction of the spindle 21. The outer ring 76 of the second bearing 71B is in contact with the intermediate portion 54 of the housing body 51 in the axial direction of the spindle 21.

[0052] The spindle unit 10 further includes a front cover 41 and a nut 42. The front cover 41 has a ring shape centered on a predetermined axis 101. The front cover 41 is attached to the housing 50. The front cover 41 is attached to the housing body 51 (front portion 53). The front cover 41 faces the first end face 50a in the axial direction of the spindle 21. The front cover 41 is in contact with the outer ring 76 of the first bearing 71A in the axial direction of the spindle 21. The outer ring 76 of the first bearing 71A and the outer ring 76 of the second bearing 71B are sandwiched between the front cover 41 and the intermediate portion 54 in the axial direction of the spindle 21.

[0053] The spindle 21 has a threaded portion 28. The threaded portion 28 is provided on the outer circumferential surface of the spindle 21. The threaded portion 28 is provided on the forward side of the spindle 21 in the axial direction of the spindle 21, ahead of the first bearing group 71. The nut 42 is screwed onto the threaded portion 28. The nut 42 is in contact with the inner ring 77 of the first bearing 71A in the axial direction of the spindle 21. The inner rings 77 of the first bearing 71A and the inner rings 77 of the second bearing 71B are sandwiched between the nut 42 and a ring 46, which will be described later, in the axial direction of the spindle 21. The nut 42, together with the front cover 41, forms a labyrinth structure to prevent foreign matter from entering the inside of the housing 50.

[0054] As shown in Figure 5, the second bearing group 72 includes a third bearing 72C and a fourth bearing 72D. Each of the third bearing 72C and the fourth bearing 72D is an angular contact bearing.

[0055] Each of the third bearing 72C and the fourth bearing 72D has an outer ring 76, an inner ring 77, a plurality of rolling elements 78, and a cage 79. Each of the third bearing 72C and the fourth bearing 72D has the same shape as the first bearing 71A.

[0056] The third bearing 72C and the fourth bearing 72D are combined in a parallel configuration. The third bearing 72C and the fourth bearing 72D are positioned to be able to withstand axial loads in the axial direction of the spindle 21, from the front of the spindle to the rear of the spindle.

[0057] The direction of the axial load that the first bearing group 71 (first bearing 71A, second bearing 71B) can withstand and the direction of the axial load that the second bearing group 72 (third bearing 72C, fourth bearing 72D) can withstand are opposite directions along the axial direction of the main shaft 21.

[0058] The third bearing 72C is positioned further forward of the spindle than the fourth bearing 72D. The fourth bearing 72D is positioned further rearward of the spindle than the third bearing 72C. The distance between the second end face 50b and the fourth bearing 72D in the axial direction of the spindle 21 is smaller than the distance between the second end face 50b and the third bearing 72C in the axial direction of the spindle 21.

[0059] Assuming that the first bearing 71A and the second bearing 71B are reversed front to back along the axial direction of the main shaft 21, the third bearing 72C corresponds to the second bearing 71B in that case, and the fourth bearing 72D corresponds to the first bearing 71A in that case.

[0060] The spindle device 10 further includes a ring 46. The ring 46 has a ring shape centered on a predetermined shaft 101. The ring 46 is positioned on the outer circumference of the spindle 21. In the axial direction of the spindle 21, the ring 46 is positioned between the first bearing group 71 and the second bearing group 72. The spindle 21 has an enlarged diameter portion 27. The outer diameter (diameter of the outer circumference) of the enlarged diameter portion 27 centered on the predetermined shaft 101 is larger than the inner diameter (diameter of the inner circumference) of the inner ring 77 centered on the predetermined shaft 101.

[0061] The inner ring 77 of the third bearing 72C is in contact with the intermediate portion 54 of the housing 50 in the axial direction of the main spindle 21. The inner ring 77 of the fourth bearing 72D is in contact with the enlarged diameter portion 27 in the axial direction of the main spindle 21. The inner rings 77 of the third bearing 72C and the fourth bearing 72D are sandwiched between the intermediate portion 54 and the enlarged diameter portion 27 in the axial direction of the main spindle 21.

[0062] The sleeve 61 extends cylindrically around a predetermined shaft 101. The sleeve 61 is positioned inside the housing body 51 so as to be slidable in the axial direction of the main shaft 21. The sleeve 61 is interposed between the housing body 51 and the outer ring 76 of the third bearing 72C and the outer ring 76 of the fourth bearing 72D. The sleeve 61 is prevented from rotating relative to the housing body 51 by an anti-rotation mechanism (not shown).

[0063] The sleeve 61 has a cylindrical portion 62 and a flange portion 63 as its constituent parts. The cylindrical portion 62 has a cylindrical shape centered on a predetermined axis 101. The flange portion 63 protrudes radially inward from the front end of the cylindrical portion 62 toward the main shaft 21 and has a flange shape that circumfers around the predetermined axis 101. In the radial direction of the main shaft 21, the cylindrical portion 62 is interposed between the housing body 51 (rear portion 55) and the outer ring 76 of the third bearing 72C and the outer ring 76 of the fourth bearing 72D. In the axial direction of the main shaft 21, the flange portion 63 is interposed between the housing body 51 (intermediate portion 54) and the outer ring 76 of the third bearing 72C.

[0064] The spindle device 10 further comprises a plurality of elastic members 66. Each elastic member 66 consists of a coil spring extending spirally along the axial direction of the spindle 21. The plurality of elastic members 66 are attached to the housing body 51. The plurality of elastic members 66 are spaced apart from each other in the circumferential direction of the spindle 21. The plurality of elastic members 66 are in contact with the sleeve 61 in the axial direction of the spindle 21. The plurality of elastic members 66 impart an elastic force to the sleeve 61 in the axial direction of the spindle 21, from the front side of the spindle to the rear side of the spindle.

[0065] As the spindle 21 expands due to its rotation, it stretches from the front to the rear. In this case, if the inner ring 77 of the second bearing group 72 slides with the spindle 21 from the front to the rear, the multiple rolling elements 78 will not be fixed between the inner ring 77 and the outer ring 76. In contrast, the sleeve 61 receives elastic force from the multiple elastic members 66 and slides from the front to the rear of the spindle. By pushing the outer ring 76 from the front to the rear of the spindle, the sleeve 61 can hold the multiple rolling elements 78 at a constant pressure between the inner ring 77 and the outer ring 76.

[0066] Furthermore, instead of the elastic force provided by the multiple elastic members 66 described above, hydraulic pressure may be used in the preload application mechanism for applying preload to the second bearing group 72.

[0067] The wiring routes in the spindle device 10 will now be described. Figure 8 is a diagram that partially shows the outer circumferential surface of the outer ring in the first bearing group in Figure 6. In Figure 8, the outer circumferential surface 76a of the outer ring 76 in the first bearing group 71 is shown in a planar unfolded view.

[0068] Referring to Figure 8, the spindle device 10 further has first wiring 210 (210A, 210B). The first wiring 210 is for sensing the state of the first bearing group 71.

[0069] More specifically, the first wiring 210 is an optical fiber for sensing the strain of the outer ring 76 in the first bearing group 71. The optical fiber is wound around the outer circumferential surface 76a of the outer ring 76. Optical grooves are provided at equal pitches on the inner circumferential surface of the optical fiber. When the outer ring 76 expands due to thermal expansion, the pitch of the optical grooves changes. At this time, the frequency and intensity of the reflected light from the grooves within the optical fiber change, and the strain of the outer ring 76 is sensed by detecting this change.

[0070] As shown in Figures 6 to 8, the outer rings 76 of the first bearing 71A and the second bearing 71B are provided with a first wiring groove 81, a second wiring groove 82, and a third wiring groove 83.

[0071] The first wiring groove 81 is recessed from the outer circumferential surface 76a of the outer ring 76 and has a groove shape that circumfers around the predetermined shaft 101. The first wiring groove 81 is located in the axial direction of the predetermined shaft 101, closer to the end face of the outer ring 76 on the rear side of the main spindle than to the end face of the outer ring 76 on the front side of the main spindle. The groove depth of the first wiring groove 81 is greater than the groove depths of the second wiring groove 82 and the third wiring groove 83.

[0072] The second wiring groove 82 is recessed from the outer circumferential surface 76a of the outer ring 76 and has a groove shape that extends in the axial direction of the predetermined shaft 101. The second wiring groove 82 extends between the end face of the outer ring 76 on the front side of the main spindle and the end face of the outer ring 76 on the rear side of the main spindle in the axial direction of the predetermined shaft 101. The second wiring groove 82 penetrates the outer ring 76 in the axial direction of the predetermined shaft 101. The second wiring groove 82 is provided at a single angular position in the circumferential direction centered on the predetermined shaft 101. The second wiring groove 82 intersects the first wiring groove 81 at a right angle. The second wiring groove 82 straddles the space between the first bearing 71A and the second bearing 71B and extends in the axial direction of the predetermined shaft 101. The second wiring groove 82 extends in a straight line between the first bearing 71A and the second bearing 71B.

[0073] The third wiring groove 83 is recessed from the outer circumferential surface 76a of the outer ring 76 and has a groove shape that extends between the first wiring groove 81 and the second wiring groove 82. The third wiring groove 83 is connected to the first wiring groove 81 at a position circumferentially separated from the second wiring groove 82 around the predetermined shaft 101. The third wiring groove 83 is connected to the second wiring groove 82 at a position adjacent to the end face of the outer ring 76 on the front side of the main shaft in the axial direction of the predetermined shaft 101. The third wiring groove 83 extends in an arc shape between the first wiring groove 81 and the second wiring groove 82.

[0074] The connecting groove 88 is provided at a single angular position in the circumferential direction centered on the predetermined axis 101. The connecting groove 88 is provided at an angular position offset from the second wiring groove 82 in the circumferential direction centered on the predetermined axis 101. The connecting groove 88 is provided at an angular position offset from the anti-rotation groove 86 in the circumferential direction centered on the predetermined axis 101.

[0075] As shown in Figure 7, the outer rings 76 of the first bearing 71A and the second bearing 71B are further provided with oil holes 92 (92A, 92B).

[0076] The oil hole 92 opens on the outer circumferential surface 76a of the outer ring 76. The oil hole 92 has a circular opening shape on the outer circumferential surface 76a of the outer ring 76. The oil hole 92 extends between the outer circumferential surface 76a and the inner circumferential surface of the outer ring 76. The oil hole 92 is a through hole that penetrates the outer ring 76 in the radial direction of the circumference centered on a predetermined axis 101.

[0077] The oil holes 92 are located at an angular position offset from the second wiring groove 82 in the circumferential direction centered on the predetermined axis 101. The oil holes 92 are located at an angular position offset from the anti-rotation groove 86 in the circumferential direction centered on the predetermined axis 101. The oil holes 92 are located at an angular position offset from the connecting groove 88 in the circumferential direction centered on the predetermined axis 101. The oil holes 92A and 92B are located at angular positions offset from each other in the circumferential direction centered on the predetermined axis 101.

[0078] As shown in Figure 8, the first wiring 210A is an optical fiber for sensing the strain of the outer ring 76 of the first bearing 71A. The first wiring 210B is an optical fiber for sensing the strain of the outer ring 76 of the second bearing 71B.

[0079] The first wiring 210A is routed on the outer circumferential surface 76a of the outer ring 76 of the first bearing 71A. The first wiring 210A passes through the second wiring groove 82, the first wiring groove 81, and the third wiring groove 83 of the first bearing 71A in that order. The first wiring 210B passes through the outer circumferential surface 76a of the outer ring 76 of the first bearing 71A and is routed on the outer circumferential surface 76a of the outer ring 76 of the second bearing 71B. The first wiring 210B passes through the second wiring groove 82 of the first bearing 71A and enters the outer circumferential surface 76a of the outer ring 76 of the second bearing 71B. The first wiring 210B passes through the second wiring groove 82, the first wiring groove 81, and the third wiring groove 83 of the second bearing 71B in that order. The first wiring 210B passes through the second wiring groove 82 in the first bearing 71A again and exits from the outer circumferential surface 76a of the outer ring 76 of the second bearing 71B.

[0080] With the above configuration, the first wiring 210 (210A, 210B) is drawn out from the first bearing group 71 to the front side of the spindle 21 in the axial direction through the second wiring groove 82.

[0081] The spindle device 10 further includes a second wiring 220 (see Figure 9). The second wiring 220 is for sensing the state of the second bearing group 72. More specifically, the second wiring 220 is an optical fiber for sensing the strain of the outer ring 76 in the second bearing group 72 (third bearing 72C, fourth bearing 72D).

[0082] Each outer ring 76 of the third bearing 72C and the fourth bearing 72D is provided with a first wiring groove 81, a second wiring groove 82, and a third wiring groove 83, in the same manner as those provided with the outer rings 76 of the first bearing 71A and the second bearing 71B.

[0083] As already explained, assuming that the first bearing 71A and the second bearing 71B are reversed front to back along the axial direction of the main shaft 21, the third bearing 72C corresponds to the second bearing 71B in that case, and the fourth bearing 72D corresponds to the first bearing 71A in that case. Furthermore, the second wiring groove 82 provided on the outer ring 76 of the first bearing group 71 and the second wiring groove 82 provided on the outer ring 76 of the second bearing group 72 are positioned at offset angular positions relative to each other in the circumferential direction of the main shaft 21.

[0084] In this configuration, the second wiring 220 is drawn out from the second bearing group 72 to the rear side of the spindle 21 in the axial direction through the second wiring groove 82.

[0085] The second wiring 220 extends from the second bearing group 72 to a position facing the second end face 50b in the axial direction of the spindle 21. The second wiring 220 extends from a position where the outer ring 76 of the second bearing group 72 is projected radially onto the spindle 21 to a position facing the second end face 50b in the axial direction of the spindle 21. At the position facing the second end face 50b in the axial direction of the spindle 21, the second wiring 220 extends in the circumferential direction of the spindle 21.

[0086] For the sake of explanation, the following description will focus on the first bearing group 71 and the second bearing group 72, out of the three bearing groups 71 and 72. The third bearing group 73 also undergoes the same lubrication oil supply control (see Figure 13) as the first and second bearing groups 71 and 72.

[0087] [C. Processes executed by machine tools] Figure 9 shows the system configuration inside the machine tool 100. As shown in Figure 9, in addition to the control panel 150, the machine tool 100 includes a control device 500, an amplifier 610, a motor 620, a sensor 630, a sensor 640, a junction box 710, and an interrogator 720. Sensor 630 detects the current value of the motor 620. Sensor 640 detects the rotational speed of the spindle 21. Note that in Figure 9, for convenience, only one of each of the amplifier 610, motor 620, sensor 630, and sensor 640 is shown, but the machine tool 100 has multiple amplifiers 610, motors 620, and sensors 630. One of the multiple motors 620 rotates the spindle 21.

[0088] As described above, the control panel 150 comprises an upper panel 151, a lower panel 152, a processor (not shown), and memory (not shown). The processor controls the screen display of the upper panel 151 and the screen display of the lower panel 152 by executing a program stored in the memory.

[0089] More specifically, the upper panel 151 includes a touchscreen 1510. The touchscreen 1510 has a display 1511 and a touch panel (not shown). Similarly, the lower panel 152 includes a touchscreen 1520. The touchscreen 1520 has a display 1521 and a touch panel (not shown).

[0090] The control device 500 comprises a numerical control device 501, a communication function unit 502, a bearing state detection unit 503, a data holding unit 504, a PLC (Programmable Logic Controller) 505, and a servo control unit 506. The data holding unit 504 stores the machining program. The numerical control device 501, the communication function unit 502, the bearing state detection unit 503, the data holding unit 504, the PLC 505, and the servo control unit 506 are connected to each other via a bus or the like so that they can communicate with one another.

[0091] Junction box 710 is connected to the first wiring 210 (210A, 210B) and the second wiring 220 (220A, 220B). More specifically, the input and output ends of the first wiring 210A, the input and output ends of the first wiring 210B, the input and output ends of the second wiring 220A, and the input and output ends of the second wiring 220B are connected to junction box 710.

[0092] Interrogator 720 is connected to junction box 710 and control device 500. Interrogator 720 transmits optical signals to the input ends of each first wiring 210A and 210B via junction box 710. Interrogator 720 receives optical signals output from the output ends of each first wiring 210A and 210B via junction box 710.

[0093] Similarly, the interrogator 720 transmits optical signals to the input ends of each second wiring 220A and 220B via the junction box 710. The interrogator 720 receives optical signals output from the output ends of each second wiring 220A and 220B via the junction box 710.

[0094] The interrogator 720 converts the optical signal into an electrical signal. The interrogator 720 associates time information with the electrical signal and transmits it to the control device 500.

[0095] The numerical control device 501 of the control device 500 calculates the tool's movement path, tool movement speed, etc., based on the machining program stored in the data holding unit 504. The servo control unit 506 receives the command value generated by this calculation and operates the motor 620. More specifically, the servo control unit 506 drives the motor 620 by sending a command to the amplifier (drive device). Based on the detection result from the detector (sensor) 630 that detects the rotational speed of the motor 620, the servo control unit 506 controls the rotation of the motor 620 so that its rotation becomes the command value.

[0096] The PLC 505 is connected to various devices such as sensors and operation buttons, and receives input signals from each device and issues operation commands to each device. The communication function unit 502 exchanges data with the control panel 150 and an external information processing device (not shown).

[0097] The bearing state detection unit 503 detects the states of the first bearing 71A, the second bearing 71B, the third bearing 72C, and the fourth bearing 72D. The bearing state detection unit 503 is a functional block that is realized by a processor (not shown) executing a program.

[0098] Figure 10 shows the flow of processing performed by the bearing state detection unit 503. In Figure 10, we will focus on the first bearing 71A, one of the first to fourth bearings 71A, 71B, 72C, and 72D described above. In this example, the processing shown in Figure 10 is performed for all bearings.

[0099] As shown in Figure 10, in step S1, the bearing condition detection unit 503 calculates the circumferential strain (specifically, the amount of strain) of the first bearing 71A based on the output from the first wiring 210A. Specifically, it senses the strain of the outer ring 76 of the first bearing 71A. Next, in step S2, the bearing condition detection unit 503 calculates the temperature of the outer ring 76 of the first bearing 71A, the radial load (specifically, magnitude and direction) of the first bearing 71A, and the axial load (specifically, magnitude and direction) of the first bearing 71A based on the calculated strain.

[0100] Furthermore, in step S3, the bearing condition detection unit 503 calculates the surface pressure of the first bearing 71A based on the temperature of the outer ring 76 of the first bearing 71A, the radial load on the first bearing 71A, and the axial load on the first bearing 71A. Specifically, the bearing condition detection unit 503 calculates the load (pressure) that each of the multiple rolling elements 78 applies to the outer ring 76. Note that each calculation from step S1 to step S3 is performed periodically.

[0101] Furthermore, the bearing condition detection unit 503 periodically detects whether or not foreign matter has entered the first bearing 71A based on fluctuations in the amount of strain of the first bearing 71A (more specifically, frequency fluctuations). This process may be performed in parallel with steps S2 and S3, or before or after steps S2 and S3. The timing of the process is not particularly limited as long as it is after step S1.

[0102] Figure 11 is a diagram illustrating the further configuration of the machine tool 100. As shown in Figure 11, the machine tool 100 further comprises a control device 500 and, in addition to the first to fourth bearings 71A, 71B, 72C, and 72D, a lubrication device 810 and a suction device 820.

[0103] The lubrication device 810 discharges lubricating oil. The discharged lubricating oil is supplied to the first to fourth bearings 71A, 71B, 72C, and 72D. The lubrication device 810 supplies lubricating oil to the first to fourth bearings 71A, 71B, 72C, and 72D from above via a predetermined oil passage (not shown). The lubricating oil is supplied to the rolling elements 78 and the like via the oil holes 92.

[0104] More specifically, the lubrication device 810 includes a tank 811 that stores lubricating oil and a mixing valve 812. The mixing valve 812 is connected to the tank 811. Lubricating oil is supplied to the mixing valve 812 from the tank 811. The mixing valve 812 is also called an oil-air metering valve. The mixing valve 812 includes an air adjustment valve (not shown) and a metering valve (not shown), each connected to a pipe (not shown), and a nozzle (not shown) attached to the end of the pipe.

[0105] The mixing valve 812 periodically discharges a predetermined amount of lubricating oil in accordance with instructions from the control device 500 (specifically, the PLC 505). During normal operation, in this example, the mixing valve 812 discharges 0.03 cc of lubricating oil once per cycle T1. This lubricating oil is supplied to the first to fourth bearings 71A, 71B, 72C, and 72D, as described above.

[0106] The lubrication device 810 may also be equipped with a mixing valve 812 for each of the first to fourth bearings 71A, 71B, 72C, and 72D. Alternatively, the lubrication device 810 may be equipped with a mixing valve 812 for each of the first and second bearing groups 71 and 72.

[0107] The suction machine 820 operates according to commands from the control device 500 (specifically, the PLC 505). The suction machine 820 is connected to the first to fourth bearings 71A, 71B, 72C, and 72D by oil passages. The suction machine 820 sucks the lubricating oil from the first to fourth bearings 71A, 71B, 72C, and 72D through these oil passages. As a result, the suction machine 820 discharges the lubricating oil from the first to fourth bearings 71A, 71B, 72C, and 72D.

[0108] Figure 12 shows the lubricating oil discharge path. The suction unit 820 is connected to the piping 901 on the intake side. The suction unit 820 is connected to the piping 902 on the discharge side. The piping 901 is connected to a drain hole 951 formed in the housing 50 of the machine tool 100. The drain hole 951 discharges lubricating oil from the oil passage 950 inside the housing 50 to the outside of the housing 50. The oil passage 950 is connected to the first to fourth bearings 71A, 71B, 72C, and 72D.

[0109] Therefore, by operating the suction device 820, the lubricating oil held in the first to fourth bearings 71A, 71B, 72C, and 72D can be sucked out. The operating and stopping timings of the suction device 820 will be described later.

[0110] Figure 13 is a diagram illustrating the processing flow in the machine tool 100. As shown in Figure 13, in step S11, the control device 500 starts the rotation of the spindle 21. In step S12, the control device 500 causes the lubrication device 810 to supply a predetermined amount of lubricating oil to the first to fourth bearings 71A, 71B, 72C, and 72D at a cycle T1.

[0111] In step S13, the control device 500 determines, based on the detection result from the bearing condition detection unit 503, whether or not foreign matter is present in at least one of the first to fourth bearings 71A, 71B, 72C, and 72D. If the control device 500 determines that foreign matter is present (YES in step S13), it stops the rotation of the spindle 21 in step S14. On the other hand, if the control device 500 determines that no foreign matter is present (NO in step S13), it proceeds to step S21.

[0112] In step S15, the control device 500 causes the lubrication device 810 to supply a predetermined amount of lubricating oil to the first to fourth bearings 71A, 71B, 72C, and 72D at a period T2 shorter than the period T1. In step S16, the suction operation is started by operating the suction machine 820. Initially, the suction force of the suction machine 820 is set to suck up more lubricating oil than the amount supplied from the mixing valve 812.

[0113] As mentioned above, the amount of bearing distortion can fluctuate due to foreign matter such as dirt. In machine tool 100, as described above, a large amount of lubricating oil is supplied to the first to fourth bearings 71A, 71B, 72C, and 72D. This lubricating oil is discharged to the outside of housing 50. Therefore, with machine tool 100, foreign matter can be removed from the first to fourth bearings 71A, 71B, 72C, and 72D. In particular, the lubricating oil supplied to the first to fourth bearings 71A, 71B, 72C, and 72D is discharged while being sucked up by a suction device 820. Therefore, compared to a configuration in machine tool 100 where the lubricating oil is not sucked up, foreign matter can be removed more quickly.

[0114] In step S17, the control device 500 determines whether or not foreign matter is present in the first to fourth bearings 71A, 71B, 72C, and 72D. If the control device 500 determines that no foreign matter is present (YES in step S17), it stops the suction device 820 in step S18. This stops the suction of lubricating oil. On the other hand, if the control device 500 determines that foreign matter is present (NO in step S17), it proceeds to step S15.

[0115] In step S19, the control device 500 restarts the rotation of the spindle 21. In step S20, the control device 500 returns the lubrication oil supply cycle from the lubrication device 810 from cycle T2 to cycle T1. In step S21, the rotation of the spindle 21 is stopped, and the series of processes is completed.

[0116] The order of steps S14, S15, and S16 is not particularly limited. The order of steps S18, S19, and S20 is not particularly limited.

[0117] [D. Summary] The machine tool 100 can be summarized as follows:

[0118] (1) The machine tool 100 includes a spindle 21, first to fourth bearings 71A, 71B, 72C, and 72D that rotatably hold the spindle 21, a detection unit (in this example, a first wiring harness 210, a second wiring harness 220, a junction box 710, an interrogator 720, and a bearing condition detection unit 503) that periodically detects foreign matter contamination in the first to fourth bearings 71A, 71B, 72C, and 72D, a lubrication device 810 that supplies lubricating oil to the first to fourth bearings 71A, 71B, 72C, and 72D, and a control device 500 that controls the supply of lubricating oil by the lubrication device 810. When foreign matter contamination is detected, the control device 500 increases the amount of lubricating oil supplied per unit time to the lubrication device 810 compared to when foreign matter contamination is not detected.

[0119] According to the machine tool 100, when foreign matter is detected in the first to fourth bearings 71A, 71B, 72C, and 72D, the amount of lubricating oil supplied to the first to fourth bearings 71A, 71B, 72C, and 72D per unit time can be increased compared to when no foreign matter is detected. Therefore, according to the machine tool 100, the foreign matter can be removed from the first to fourth bearings 71A, 71B, 72C, and 72D by the lubricating oil. Furthermore, by removing the foreign matter, seizure of the first to fourth bearings 71A, 71B, 72C, and 72D can be prevented.

[0120] (2) When no foreign matter is detected, the control device 500 causes the lubrication device 810 to supply a predetermined amount of lubricating oil at a cycle T1. When foreign matter is detected, the control device 500 causes the lubrication device 810 to supply a predetermined amount of lubricating oil at a cycle T2 that is shorter than cycle T1. With this configuration, when foreign matter is detected, the amount of lubricating oil supplied per unit time to the first to fourth bearings 71A, 71B, 72C, and 72D can be increased compared to when no foreign matter is detected.

[0121] (3) The control device 500 further controls the rotation of the spindle 21. When the control device 500 supplies a predetermined amount of lubricating oil to the lubrication device 810 at a cycle T2, it stops the rotation of the spindle 21. With this configuration, it is easier to remove foreign matter than when the predetermined amount of lubricating oil is supplied to the lubrication device 810 while the spindle 21 is rotating.

[0122] (4) The machine tool 100 further comprises a housing 50 that houses the spindle 21 and the first to fourth bearings 71A, 71B, 72C, and 72D. The housing 50 has a drain hole 951 for discharging lubricating oil. The machine tool 100 further comprises a suction device 820 that sucks the lubricating oil supplied to the first to fourth bearings 71A, 71B, 72C, and 72D from the drain hole 951. With this configuration, foreign matter mixed in with the first to fourth bearings 71A, 71B, 72C, and 72D can be removed quickly and with high accuracy compared to a configuration without the suction device 820.

[0123] (5) The detection unit described above detects foreign matter contamination based on the variation in the amount of strain of the first to fourth bearings 71A, 71B, 72C, and 72D. With this configuration, foreign matter contamination of the first to fourth bearings 71A, 71B, 72C, and 72D can be detected.

[0124] (6) The first to fourth bearings 71A, 71B, 72C, and 72D each include an inner ring 77, an outer ring 76, and rolling elements 78 positioned between the inner ring 77 and the outer ring 76. The outer ring 76 has an inner circumferential surface 76b on the rolling element 78 side and an outer circumferential surface 76a located on the opposite side of the inner circumferential surface 76b and in contact with the housing 50. The outer ring 76 has first to third grooves 81 to 83 recessed from the outer circumferential surface 76a, formed at least in the circumferential direction of the outer ring 76. The detection unit described above includes optical fibers (first wiring 210, second wiring 220) arranged along the first to third grooves 81 to 83 and for detecting the amount of strain of the first to fourth bearings 71A, 71B, 72C, and 72D. The detection unit detects the amount of circumferential strain in the first to fourth bearings 71A, 71B, 72C, and 72D based on the state of the light output from the optical fiber. With this configuration, the strain in the first to fourth bearings 71A, 71B, 72C, and 72D can be detected. Furthermore, the detection unit further detects fluctuations in the amount of strain based on the detected strain (amount of strain).

[0125] [E. Variant] (1) In the above, the inclusion of foreign matter in the first to fourth bearings 71A, 71B, 72C, and 72D was detected based on the variation in the amount of strain of the first to fourth bearings 71A, 71B, 72C, and 72D, but this is not the only method.

[0126] If foreign matter enters the first to fourth bearings 71A, 71B, 72C, and 72D, the current value of the motor 620 will change. Specifically, if foreign matter enters, the current value of the motor 620 will increase. Therefore, the control device 500 may detect the presence of foreign matter in the first to fourth bearings 71A, 71B, 72C, and 72D based on the fluctuation in the current value detected by the sensor 630.

[0127] Alternatively, a vibration meter may be used as the sensor 640, and the control device 500 may detect foreign matter contamination in the first to fourth bearings 71A, 71B, 72C, and 72D based on the fluctuation in vibration frequency detected by the sensor 640.

[0128] (2) In the above, when foreign matter contamination is detected, the control device 500 causes the lubrication device 810 to supply a predetermined amount (0.03 cc in this example) of lubricating oil at a cycle T2 shorter than the cycle T1, thereby increasing the amount of lubricating oil supplied to the lubrication device 810 per unit time compared to when no foreign matter contamination is detected.

[0129] However, the method for increasing the amount of lubricating oil supplied per unit time is not limited to this. The machine tool 100 may be configured so that the amount of lubricating oil supplied per instance can be changed without changing the lubricating oil supply cycle.

[0130] (3) In the above description, an example was given of a configuration in which optical fibers are laid in each of the first to fourth bearings 71A, 71B, 72C, and 72D, but the explanation is not limited to this. It is sufficient that optical fibers are laid in at least one of the first to fourth bearings 71A, 71B, 72C, and 72D.

[0131] (4) The machine tool 100 does not necessarily have to be equipped with a suction device 820. It may be configured so that foreign matter is naturally discharged to the outside along with the lubricating oil, rather than being forcibly discharged.

[0132] [F. Addendum] The housing further comprises the main shaft and the bearing, The bearing includes an inner ring, an outer ring, and rolling elements disposed between the inner ring and the outer ring. The outer ring has a first surface on the rolling element side and a second surface located on the opposite side of the first surface and in contact with the housing. The outer ring has a groove formed in the circumferential direction of the outer ring, recessed from the second surface. The detection means is It includes an optical fiber disposed along the groove and for detecting the amount of strain on the bearing, A machine tool that detects the amount of circumferential strain of the bearing based on the state of light output from the optical fiber.

[0133] The embodiments disclosed herein are illustrative and not limited to those described above. The scope of the present invention is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0134] 10 Spindle unit, 11 Spindle base, 12 Bed, 14 Column, 16 Table, 21 Spindle, 23 Collet, 24 Drawbar, 25 Disc spring, 26 Unclamp cylinder, 27 Enlarged diameter section, 28 Threaded section, 31 Rotor, 32 Stator, 33 Motor housing, 41 Front cover, 42 Nut, 43 Cover, 45 Rear housing, 46 Ring, 50 Housing, 50a First end face, 50b Second end face, 50c, 76a Outer circumference, 51 Housing body, 53 Front section, 54 Middle section, 55 Rear section, 56, 63 Flange section, 56a End face, 61 Sleeve, 62 Cylindrical section, 66 Elastic member, 71 First bearing group, 71A First bearing, 71B Second bearing, 72 Second bearing group, 72C Third bearing, 72D 4th bearing, 73 3rd bearing group, 76 Outer ring, 76b Inner surface, 77 Inner ring, 78 Rolling element, 79 Cage, 81 1st groove, 82 2nd groove, 83 3rd groove, 86 Anti-rotation groove, 88 Connecting groove, 92 Oil hole, 100 Machine tool, 101 Designated shaft, 120 Internal space, 150 Control panel, 151 Upper panel, 152 Panel, 190 Machining chamber, 210, 210A, 210B 1st wiring, 220, 220A, 220B 2nd wiring, 327 Cover, 500 Control device, 501 Numerical control device, 502 Communication function unit, 503 Bearing state detection unit, 504 Data holding unit, 505 PLC, 506 Servo control unit, 610 Amplifier, 620 Motor, 630, 640 Sensor, 710 Junction box, 720 Interrogator, 810 Fueling device, 811 Tank, 812 Mixing valve, 820 Suction device, 901, 902 Piping, 950 Oil passage, 951 Drain hole, T Tool, W Workpiece.

Claims

1. The main shaft, A bearing that rotatably holds the main shaft, A detection means for periodically detecting the presence of foreign matter in the bearing, A supply means for supplying lubricating oil to the bearing, The system comprises a control means for controlling the supply of the lubricating oil by the supply means and the rotation of the main shaft, The control means is If no foreign matter contamination is detected, a predetermined amount of the lubricating oil is supplied to the supply means in the first cycle. When the presence of foreign matter is detected, the amount of lubricating oil supplied to the supply means per unit time is increased compared to when the presence of foreign matter is not detected, by supplying a predetermined amount of lubricating oil to the supply means in a second cycle that is shorter than the first cycle. A machine tool that stops the rotation of the spindle when supplying the predetermined amount of lubricating oil to the supply means in the second cycle.

2. The main shaft, A bearing that rotatably holds the main shaft, A detection means for periodically detecting the presence of foreign matter in the bearing based on fluctuations in the amount of strain of the bearing, A supply means for supplying lubricating oil to the bearing, The system comprises control means for controlling the supply of lubricating oil by the supply means, A machine tool wherein, when the presence of foreign matter is detected, the control means increases the amount of lubricating oil supplied to the supply means per unit time compared to when no foreign matter is detected.

3. The housing further comprises the main shaft and the bearing, The housing is provided with a drain hole for discharging the lubricating oil. The machine tool according to claim 1, further comprising a suction device for sucking the lubricating oil supplied to the bearing from the drain hole.

4. A motor that rotates the main shaft, The system further comprises a sensor for detecting the current value of the motor, The machine tool according to claim 1, wherein the detection means detects the presence of foreign matter based on fluctuations in the current value.

5. The system further includes a sensor for detecting the vibration frequency of the main shaft, The machine tool according to claim 1, wherein the detection means detects the presence of foreign matter based on the fluctuation of the vibration frequency.

6. A step of periodically detecting the presence of foreign matter in the bearing that rotatably holds the main shaft, If no foreign matter contamination is detected, the procedure involves supplying a predetermined amount of lubricating oil to the bearing in a first cycle. When the presence of foreign matter is detected, the process involves supplying a predetermined amount of lubricating oil to the bearing in a second cycle shorter than the first cycle, thereby increasing the amount of lubricating oil supplied to the bearing per unit time compared to when no foreign matter is detected. A method for controlling a machine tool, comprising the step of stopping the rotation of the spindle when supplying a predetermined amount of lubricating oil to the bearing in the second cycle.

7. A step of periodically detecting the presence of foreign matter in a bearing that rotatably holds the main shaft based on fluctuations in the amount of strain of the bearing, A method for controlling a machine tool, comprising the step of increasing the amount of lubricating oil supplied to the bearing per unit time compared to when no foreign matter is detected, when the presence of foreign matter is detected.

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