Spindle device for machine tool, and machine tool

Abstract

This spindle device for a machine tool is equipped with: a rotating body having a posterior end section and a distal end section that supports a tool; a bearing comprising an inner ring and an outer ring; a housing for supporting the rotating body via the bearing so as to be rotatable about a first axis; a supply flow passage for supplying a mixed fluid containing oil and air to the bearing; and a recovery flow passage for recovering oil that has passed through the bearing. The rotating body comprises: a first portion that supports the inner ring and has a first outer peripheral surface; a second portion that has a second outer peripheral surface of a smaller diameter than that of the first outer peripheral surface and that is arranged further to a first direction side than the first portion; and a stepped surface connecting the first outer peripheral surface and the second outer peripheral surface. The housing comprises: a third portion supporting the outer ring; and a fourth portion defining an annular accommodation space which receives oil from a first gap between the first portion and the third portion. The fourth portion has: an opening through which oil is guided from the annular accommodation space to the recovery flow passage; and an annular protrusion that faces both the stepped surface and the annular accommodation space and protrudes out in a direction away from the first axis.

Description

Spindle device of machine tool, and machine tool

[0001] The present invention relates to a spindle device of a machine tool and a machine tool.

[0002] A lubrication device for a spindle of a machine tool is known.

[0003] As a related technique, Patent Document 1 discloses a lubrication device for a vertical spindle of a machine tool. The lubrication device described in Patent Document 1 includes a vertical spindle rotatably supported within a spindle housing via a rolling bearing, a nozzle device that injects lubricating oil onto the rolling bearing, and an oil recovery passage that recovers the lubricating oil supplied to the rolling bearing via an oil discharge passage formed in the spindle housing. The lubrication device described in Patent Document 1 also includes a labyrinth device provided below the rolling bearing to form a lubricating oil receiving chamber, an air seal device provided below the labyrinth device to supply pressurized air to prevent oil leakage through a gap between the spindle housing and the vertical spindle, and a mechanical seal device interposed between the labyrinth device and the air seal device to prevent oil leakage when the supply of pressurized air is stopped.

[0004] Japanese Unexamined Patent Publication No. 63-062638

[0005] An object of the present invention is to provide a spindle device of a machine tool that suppresses oil from leaking outside the spindle device through a gap between a rotating body and a housing, and a machine tool.

[0006] A spindle unit of a machine tool in some embodiments includes a rotating body having a rear end and a front end for holding a tool, a bearing having an inner ring and an outer ring, a housing rotatably supporting the rotating body via the bearing about a first axis, a supply passage for supplying a mixed fluid containing oil and air to the bearing, and a recovery passage for recovering the oil that has passed through the bearing. The rotating body includes a first portion supporting the inner ring and having a first outer peripheral surface, a second portion having a second outer peripheral surface with a diameter smaller than that of the first outer peripheral surface and disposed closer to the first direction than the first portion when a direction from the rear end to the front end is defined as a first direction, and a stepped surface connecting the first outer peripheral surface and the second outer peripheral surface. The housing includes a third portion supporting the outer ring and a fourth portion defining an annular receiving space that receives the oil from a first gap between the first portion and the third portion. The fourth portion has an opening that guides the oil from the annular receiving space to the recovery passage, and an annular protrusion that faces both the step surface and the annular receiving space and protrudes in a direction away from the first axis.

[0007] In some embodiments, a machine tool includes a machining head having a rotating body, a plurality of bearings including a first bearing, a housing rotatably supporting the rotating body via the plurality of bearings, a first rotation drive device rotating the rotating body about a first axis, a lubrication device supplying a mixed fluid containing oil and air to the first bearing through a supply passage, a recovery device recovering at least a portion of the oil that has passed through the first bearing through a recovery passage, a workpiece support device supporting a workpiece, a moving device moving the machining head relative to the workpiece support device, and a control device controlling at least the first rotation drive device and the moving device. The rotating body has a rear end, a front end for holding a tool, a first portion supporting an inner ring of the first bearing and having a first outer peripheral surface, a second outer peripheral surface having a diameter smaller than the first outer peripheral surface, and a step surface connecting the first outer peripheral surface and the second outer peripheral surface, where the second portion is positioned closer to the first direction when a direction from the rear end to the front end is defined as a first direction. The housing has a third part that supports the outer ring of the first bearing, and a fourth part that defines an annular receiving space that receives the oil from the first gap between the first part and the third part. The fourth part has an opening that guides the oil from the annular receiving space to the recovery passage, and an annular protrusion that faces both the stepped surface and the annular receiving space and protrudes in a direction away from the first shaft.

[0008] The present invention can provide a spindle device of a machine tool that prevents oil from leaking outside the spindle device through the gap between the rotating body and the housing, and a machine tool.

[0009] FIG. 1 is a schematic cross-sectional view showing a spindle unit of a machine tool according to a first embodiment. FIG. 2 is an enlarged view of a portion surrounded by a dashed-dotted rectangle A in FIG. 1. FIG. 3 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. FIG. 4 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. FIG. 5 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. FIG. 6 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to a modified example of the first embodiment. FIG. 8 is an enlarged view of a portion shown by a dashed-dotted circle B in FIG. 6. FIG. 9 is a cross-sectional view taken along the arrows CC in FIG. 6. FIG. 10 is a view showing a portion of a spindle unit of a machine tool according to the first embodiment. FIG. 11 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. Fig. 12 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to a second modified example of the first embodiment. Fig. 13 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the first embodiment. Fig. 14 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to a second embodiment. Fig. 15 is an enlarged view of a portion surrounded by a dash-dot rectangle D in Fig. 14. Fig. 16 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the second embodiment. Fig. 17 is a cross-sectional view taken along the arrows E-E in Fig. 16. Fig. 18 is an enlarged view of a portion indicated by a dash-dot circle F in Fig. 16. Fig. 19 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the second embodiment. Fig. 20 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to the second embodiment. Fig. 21 is a schematic cross-sectional view showing a portion of a spindle unit of a machine tool according to a modified example of the second embodiment. Fig. 22 is a schematic cross-sectional view showing a spindle device of a machine tool according to a second embodiment. Fig. 23 is a schematic cross-sectional view showing a part of a spindle device of a machine tool according to a second embodiment. Fig. 24 is a schematic cross-sectional view showing a part of a spindle device of a machine tool according to a second embodiment.Fig. 25 is a schematic perspective view showing an example of a machine tool according to the third embodiment. Fig. 26 is a schematic perspective view showing another example of a machine tool according to the third embodiment. Fig. 27 is a diagram showing a state in which a control device can control a plurality of control target devices. Fig. 28 is a schematic cross-sectional view showing a modified example of the first and second parts of the rotating body. Fig. 29 is a schematic cross-sectional view showing a first modified example of the first gap. Fig. 30 is a schematic cross-sectional view showing a second modified example of the first gap.

[0010] Hereinafter, a spindle unit 1 of a machine tool and a machine tool 100 according to an embodiment will be described with reference to the drawings. In the following description of the embodiment, parts and members having the same functions are denoted by the same reference numerals, and repeated description of parts and members denoted by the same reference numerals will be omitted.

[0011] (Definition of direction) In this specification, the direction from the rear end 22 of the rotating body 2 toward the front end 24 of the rotating body 2 is defined as the "first direction DR1," and the direction opposite to the first direction DR1 is defined as the "second direction DR2."

[0012] In this specification, the direction approaching the first axis AX1, which is the rotation axis of the rotor 2, is defined as the "radially inward direction DR3" or "inward." Furthermore, the direction away from the first axis AX1, which is the rotation axis of the rotor 2, is defined as the "radially outward direction DR4" or "outward."

[0013] The direction from the rear end 22 of the rotating body 2 toward the front end 24 of the rotating body 2 is, for example, downward or sideways. If the attitude of the spindle unit 1 is changeable, the direction from the rear end 22 of the rotating body 2 toward the front end 24 of the rotating body 2 changes in accordance with the change in attitude of the spindle unit 1. In this specification, regardless of the actual attitude of the spindle unit 1, the direction from the rear end 22 of the rotating body 2 toward the front end 24 of the rotating body is referred to as the "downward direction," and the direction from the front end 24 of the rotating body 2 toward the rear end 22 of the rotating body is referred to as the "upward direction." Furthermore, in this specification, regardless of the actual attitude of the spindle unit 1, the surface on the first direction DR1 side is referred to as the "lower surface," and the surface on the second direction DR2 side is referred to as the "upper surface."

[0014] First Embodiment A spindle unit 1A of a machine tool according to a first embodiment will be described with reference to FIGS. 1 to 13. FIG. 1 is a schematic cross-sectional view showing the spindle unit 1A of a machine tool according to the first embodiment. FIG. 2 is an enlarged view of a portion surrounded by a dashed-dotted rectangle A in FIG. 1. FIG. 3 is a schematic cross-sectional view showing a portion of the spindle unit 1A of a machine tool according to the first embodiment. FIGS. 4 and 5 are schematic cross-sectional views showing a portion of the spindle unit 1A of a machine tool according to the first embodiment. Note that FIG. 5 shows half of the portion shown in FIG. 4. FIG. 6 is a schematic cross-sectional view showing a portion of the spindle unit 1A of a machine tool according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a portion of a spindle unit 1A of a machine tool according to a modified example of the first embodiment. FIG. 8 is an enlarged view of a portion indicated by a dashed-dotted circle B in FIG. 6. FIG. 9 is a cross-sectional view taken along the line C-C in FIG. 6. Fig. 10 is a diagram schematically showing a portion of a spindle unit 1A of a machine tool in the first embodiment. Fig. 11 is a schematic cross-sectional view schematically showing a portion of a spindle unit 1A of a machine tool in the first embodiment. Fig. 12 is a schematic cross-sectional view schematically showing a portion of a spindle unit 1A of a machine tool in a second modified example of the first embodiment. Fig. 13 is a schematic cross-sectional view schematically showing a portion of a spindle unit 1A of a machine tool in the first embodiment.

[0015] As illustrated in FIG. 1 , a spindle device 1A of a machine tool in the first embodiment includes a rotating body 2, a bearing 3, a housing 4, a supply flow path 66, and a recovery flow path 71.

[0016] In the example shown in FIG. 1 , the rotating body 2 is a rotating shaft 20. The rotating body 2 is rotatable around a first axis AX1. The rotating body 2 (more specifically, the rotating shaft 20) has a rear end 22 and a tip end portion 24 that holds a tool T. Note that a tool holder HD that holds the tool T may be attached to the tip end portion 24. In this case, the tool T is held by the tip end portion 24 via the tool holder HD. Therefore, in this specification, the "tip end portion 24 that holds a tool" includes both a tip end portion 24 that directly holds the tool T and a tip end portion 24 that holds the tool T via the tool holder HD. In other words, in this specification, the tip end portion 24 may be configured to directly hold the tool T, or may be configured to hold the tool T via the tool holder HD.

[0017] The housing 4 supports the rotor 2 rotatably about the first axis AX1 via the bearing 3. In the example shown in Fig. 1, the housing 4 is formed by assembling a plurality of parts.

[0018] In the example shown in Fig. 1, the spindle unit 1A includes a bearing 3 (for example, a first bearing 3a). As illustrated in Fig. 2, the bearing 3 (for example, the first bearing 3a) has an inner ring 31 and an outer ring 32. The bearing 3 (for example, the first bearing 3a) also has rolling elements 33 arranged between the inner ring 31 and the outer ring 32.

[0019] The supply flow path 66 supplies a mixed fluid containing oil and air to the bearing 3 (for example, the first bearing 3a). This mixed fluid is sometimes called oil-air. In oil-air, the oil is carried by the air. In other words, in oil-air, the air functions as a carrier fluid that carries the oil. More specifically, by supplying oil-air to the bearing 3 (for example, the first bearing 3a), a small amount of oil is continuously supplied to the bearing 3 (for example, the first bearing 3a) using the flow of compressed air.

[0020] The recovery passage 71 recovers at least a portion of the oil E that has passed through the bearing 3 (e.g., the first bearing 3 a). The recovery passage 71 may recover substantially all of the oil E that has passed through the first bearing 3 a. Additionally, the recovery passage 71 may recover at least a portion of the air that has passed through the bearing 3.

[0021] As illustrated in FIG. 2, the rotating body 2 (more specifically, the rotating shaft 20) has a first portion 25, a second portion 26, and a step surface 25a.

[0022] The first portion 25 supports an inner ring 31a of a bearing 3 (for example, the first bearing 3a). The first portion 25 has a first outer circumferential surface 25u.

[0023] The second portion 26 has a second outer peripheral surface 26u that has a smaller diameter than the first outer peripheral surface 25u. In other words, the diameter of the second outer peripheral surface 26u of the second portion 26 is smaller than the diameter of the first outer peripheral surface 25u of the first portion 25. The second portion 26 is disposed closer to the first direction DR1 than the first portion 25.

[0024] The step surface 25 a connects the first outer peripheral surface 25 u of the first portion 25 and the second outer peripheral surface 26 u of the second portion 26 .

[0025] As illustrated in FIG. 2 , the housing 4 has a third portion 41 and a fourth portion 42 .

[0026] The third portion 41 supports the outer ring 32a of the bearing 3 (e.g., the first bearing 3a). A first gap G1 is formed between the first portion 25 of the rotating body 2 and the third portion 41. In the example shown in Fig. 2, oil E that has passed through the bearing 3 (e.g., the first bearing 3a) is present in the first gap G1. In the first gap G1, the oil E may be present in the form of oil air, oil mist, or liquid oil.

[0027] The fourth portion 42 defines an annular receiving space SP that receives the oil E from the first gap G1. In the annular receiving space SP, the oil E may be present in the form of oil-air, oil mist, or liquid oil.

[0028] In the example shown in FIG. 2 , the fourth portion 42 has an opening 45 that guides the oil E from the annular receiving space SP to the recovery passage 71 , and an annular protrusion 441 .

[0029] The annular protrusion 441 faces both the step surface 25a and the annular receiving space SP. In the example shown in Fig. 2, the surface of the annular protrusion 441 facing the second direction DR2 (hereinafter referred to as the "upper surface 441a") faces the step surface 25a. Also, the surface of the annular protrusion 441 facing the first direction DR1 (hereinafter referred to as the "lower surface 441d") faces the annular receiving space SP.

[0030] The annular protrusion 441 protrudes in a direction away from the first axis AX1. Therefore, the annular protrusion 441 can be said to be an outward annular protrusion.

[0031] In the machine tool spindle unit 1A of the first embodiment, the housing 4 has an annular receiving space SP. Therefore, the oil E that has passed through the bearing 3 can be temporarily received in the annular receiving space SP. The oil E in the annular receiving space SP is recovered by the recovery passage 71. In this way, oil is prevented from leaking out of the machine tool spindle unit 1A from the gap between the rotating body 2 and the housing 4.

[0032] Furthermore, in the first embodiment, the annular protrusion 441 prevents or inhibits the oil E that has entered the annular receiving space SP from flowing back in the second direction DR2 beyond the annular protrusion 441. Therefore, in the first embodiment, oil is more effectively inhibited from leaking out of the spindle unit 1A of the machine tool from the gap between the rotating body 2 and the housing 4.

[0033] For example, assume that it is undesirable for oil to adhere to a workpiece being machined by the tool T. More specifically, assume that a workpiece made of a carbon material, to which oil adhesion would cause problems, is machined. In such a case, the first embodiment is useful.

[0034] Furthermore, dry machining may be used when machining a resin material or the like using the tool T. In the first embodiment, oil is prevented from leaking out of the spindle device 1A of the machine tool, and oil is effectively prevented from adhering to the workpiece (e.g., a resin material, etc.). Therefore, the first embodiment is also useful when dry machining is used.

[0035] In the first embodiment, oil leakage around the spindle unit 1A of the machine tool is suppressed, and contamination of the work environment by oil is prevented or suppressed. This improves the work environment and reduces the burden on the environment. Furthermore, even when coolant is used during workpiece machining (in other words, even when dry machining is not performed), the first embodiment suppresses oil leakage and prevents oil from mixing with the coolant. Therefore, in this case as well, the burden on the environment is reduced.

[0036] (Optional Additional Configuration) Next, optional additional configurations that can be employed in the spindle unit 1A of the machine tool in the first embodiment will be described with reference to FIGS. 1 to 13.

[0037] (Annular Receiving Space SP) In Fig. 3, the annular receiving space SP is hatched with dots to make the shape of the annular receiving space SP easier to understand. In the example shown in Fig. 3, in a longitudinal cross section passing through the first axis AX1, the annular receiving space SP has a shape that combines a first rectangular shape SH1 and a second rectangular shape SH2 that is larger than the first rectangular shape. Alternatively, in a longitudinal cross section passing through the first axis AX1, the annular receiving space SP may have a triangular shape, a trapezoidal shape, a pentagonal shape, or other shape.

[0038] 3, the first gap G1 and the annular receiving space SP are arranged on a straight line LN parallel to the first axis AX1. In this case, the oil E present in the first gap G1 is smoothly guided into the annular receiving space SP.

[0039] 4 to 6 , the fourth portion 42 has an annular protrusion 44 that protrudes inward toward the first axis AX1. Note that in FIGS. 5 and 6 , the annular protrusion 44 is hatched with dots to make the shape of the annular protrusion 44 easier to understand.

[0040] In the example shown in Figure 6, the annular protrusion 44 has the above-mentioned annular protrusion 441 that protrudes outward, a first surface 44a facing the step surface 25a, and a second surface 44b facing the outer peripheral surface of the second part 26 of the rotating body 2 (in other words, the second outer peripheral surface 26u).

[0041] The first surface 44a is the surface of the annular protrusion 44 on the second direction DR2 side. The first surface 44a is, for example, an annular surface perpendicular to the first axis AX1. Alternatively, the first surface 44a may be a surface inclined with respect to the first axis AX1 or may be a stepped surface (see FIG. 7).

[0042] 8 , at least a portion of the first surface 44 a is the surface of the outwardly protruding annular protrusion 441. More specifically, at least a portion of the first surface 44 a is formed by the surface of the annular protrusion 441 on the second direction DR2 side (in other words, the upper surface 441 a of the annular protrusion 441).

[0043] In the example shown in Fig. 8, a second gap G2 fluidly communicating with the first gap G1 is formed between the first surface 44a and the step surface 25a. In the example shown in Fig. 8, the second gap G2 is located on the second direction DR2 side of the annular protrusion 441. In addition, in the example shown in Fig. 8, a third gap G3 fluidly communicating with the second gap G2 is formed between the second surface 44b and the second outer peripheral surface 26u of the rotating body 2.

[0044] A path from the first gap G1 to the outside of the spindle unit 1A of the machine tool is assumed. This path can be a source of oil leakage. In the example shown in FIG. 8 , the path from the first gap G1 to the outside of the spindle unit 1A of the machine tool includes a second gap G2 between the first surface 44a and the step surface 25a. Therefore, the presence of the second gap G2 prevents oil from leaking out of the spindle unit 1A of the machine tool via the above-described path.

[0045] In the example shown in Fig. 8, the extension direction of the first gap G1 and the extension direction of the second gap G2 are different. Therefore, oil in the first gap G1 is prevented from moving toward the second gap G2. For example, oil moving downward from the first gap G1 is prevented from entering the second gap G2. In the example shown in Fig. 8, the extension direction of the first gap G1 is the first direction DR1, and the extension direction of the second gap G2 is the radially inward direction DR3 (more specifically, a direction perpendicular to the first axis AX1 and toward the first axis AX1).

[0046] As illustrated in Figure 9, the difference between the radius RD1 of the outer peripheral edge e1 of the first surface 44a and the radius RD2 of the inner peripheral edge e2 of the first surface 44a is defined as the first width W1. The first width W1 is, for example, 5 mm or greater. By making the first width W1 sufficiently large, oil that has entered the second gap G2 is prevented or inhibited from reaching the third gap G3 (see Figure 8). This further effectively inhibits oil from leaking outside the spindle unit 1A of the machine tool.

[0047] 8, the entire annular receiving space SP is disposed closer to the second gap G2 in the first direction DR1, which further effectively reduces the possibility that the oil received in the annular receiving space SP will flow back into the second gap G2.

[0048] In the example shown in Figure 8, the spindle unit 1A of the machine tool has an area SE where the first gap G1, the second gap G2, and the annular receiving space SP intersect, and the second gap G2 is connected to the first gap G1 via the area SE.

[0049] In the example shown in Fig. 8, the third gap G3 is connected to the second gap G2 via a corner CN. The extending direction of the third gap G3 is different from the extending direction of the second gap G2. In the example shown in Fig. 8, the extending direction of the third gap G3 is the first direction DR1, and the extending direction of the second gap G2 is the radially inward direction DR3 (more specifically, a direction perpendicular to the first axis AX1 and toward the first axis AX1).

[0050] The second surface 44b is a cylindrical surface with the first axis AX1 as its central axis. As illustrated in Fig. 8 , the length of the second surface 44b in the direction along the first axis AX1 is defined as a first length L1. The first length L1 may be greater than, less than, or equal to the first width W1. The first length L1 may be 0.5 to 5 times the first width W1.

[0051] 10 , the annular protrusion 44 has a first annular groove V1 that faces the annular receiving space SP and is recessed in the radially inward direction DR3. In FIG. 10 , to make it easier to understand the shape of the first annular groove V1, portions other than the first annular groove V1 are indicated by dashed lines, and the first annular groove V1 is indicated by solid lines. The first annular groove V1 prevents or suppresses oil in the annular receiving space SP from flowing back toward the first gap G1 or the second gap G2.

[0052] In the example shown in Fig. 10 , the first annular groove V1 is defined by three surfaces (more specifically, two surfaces 443d and 444d perpendicular to the first axis AX1, and a surface 445d connecting the two surfaces). In the example shown in Fig. 10 , the first annular groove V1 has a substantially C-shape in a vertical cross section passing through the first axis AX1. Alternatively, the first annular groove V1 may be defined by two surfaces. In this case, the first annular groove V1 may have a substantially V-shape in a vertical cross section passing through the first axis AX1.

[0053] 10 , part of the surface of the first annular groove V1 is the surface of the annular protrusion 441. More specifically, part of the surface of the first annular groove V1 is formed by the surface of the annular protrusion 441 on the first direction DR1 side (more specifically, the lower surface 441 d of the annular protrusion 441).

[0054] 10 , the annular protrusion 44 has a third surface 44 f that forms a part of the end surface 4 f on the first direction DR1 side of the housing 4. The third surface 44 f may be a surface that is perpendicular to the first axis AX1, or may be a surface that is slightly inclined with respect to the first axis AX1.

[0055] (Annular Protrusion 441) In the example shown in FIG. 11, the annular protrusion 441 functions as a barb that prevents the oil that has entered the annular receiving space SP from returning to the first gap G1 or the second gap G2.

[0056] 11 , the distance between the outermost edge e3 of the stepped surface 25a of the rotating body 2 and the first axis AX1 is defined as a first distance LT1, and the distance between the outermost edge 441e of the annular protrusion 441 and the first axis AX1 is defined as a second distance LT2. In the example shown in FIG. 11 , the second distance LT2 is equal to the first distance LT1. Alternatively, as shown in FIG. 12 , the second distance LT2 may be smaller than the first distance LT1.

[0057] When the second distance LT2 is equal to or less than the first distance LT1, the oil E flowing from the first gap G1 in the first direction DR1 is prevented or suppressed from hitting the annular protrusion 441. Therefore, the oil E flowing from the first gap G1 in the first direction DR1 is less likely to enter the gap between the stepped surface 25 a and the annular protrusion 441 (or the second gap G2 between the stepped surface 25 a and the first surface 44 a).

[0058] In the example shown in FIG. 13, the annular protrusion 441 has an upper surface 441a, an outer side surface 441c, and a lower surface 441d.

[0059] The upper surface 441a is an annular surface facing the stepped surface 25a of the rotating body 2. The upper surface 441a may be perpendicular to the first axis AX1, or may be inclined with respect to a plane perpendicular to the first axis AX1.

[0060] 13, the outer side surface 441c faces the annular receiving space SP. In a longitudinal cross section passing through the first axis AX1, the outer side surface 441c is parallel to the first axis AX1. Alternatively, in a longitudinal cross section passing through the first axis AX1, the outer side surface 441c may be inclined with respect to the first axis AX1.

[0061] 13, the lower surface 441d is an annular surface facing the annular receiving space SP. The lower surface 441d may be perpendicular to the first axis AX1, or may be inclined with respect to a plane perpendicular to the first axis AX1.

[0062] Second Embodiment A spindle unit 1B of a machine tool according to a second embodiment will be described with reference to Figs. 14 to 24. Fig. 14 is a schematic cross-sectional view showing a spindle unit 1B of a machine tool according to the second embodiment. Fig. 15 is an enlarged view of a portion surrounded by a dashed-dotted rectangle D in Fig. 14. Fig. 16 is a schematic cross-sectional view showing a portion of a spindle unit 1B of a machine tool according to the second embodiment. Fig. 17 is a cross-sectional view taken along the line E-E in Fig. 16. Fig. 18 is an enlarged view of a portion indicated by a dashed-dotted circle F in Fig. 16. Figs. 19 and 20 are schematic cross-sectional views showing a portion of a spindle unit 1B of a machine tool according to the second embodiment. Fig. 21 is a schematic cross-sectional view showing a portion of a spindle unit 1B of a machine tool according to a modified example of the second embodiment. Fig. 22 is a schematic cross-sectional view showing a spindle unit 1B of a machine tool according to the second embodiment. 23 and 24 are schematic cross-sectional views showing a part of a spindle unit 1B of a machine tool according to the second embodiment.

[0063] In the second embodiment, differences from the first embodiment will be mainly described. On the other hand, in the second embodiment, repeated descriptions of matters already described in the first embodiment will be omitted. Therefore, it goes without saying that matters already described in the first embodiment can be applied to the second embodiment even if they are not explicitly described in the second embodiment. Conversely, all matters described in the second embodiment can be applied to the first embodiment.

[0064] As illustrated in FIGS. 14 and 15 , a spindle unit 1B of a machine tool in the second embodiment includes: (1) a rotating body 2 (more specifically, a rotating shaft 20) having a rear end portion 22 and a front end portion 24 that holds a tool; (2) a bearing 3 (more specifically, a first bearing 3 a) having an inner ring 31 a and an outer ring 32 a; (3) a housing 4 that rotatably supports the rotating body 2 about a first axis AX1 via the bearing 3 (more specifically, via a plurality of bearings including the first bearing 3 a); (4) a supply flow path 66 that supplies a mixed fluid containing oil and air to the bearing 3 (more specifically, the first bearing 3 a); and (5) a recovery flow path 71 that recovers oil that has passed through the bearing 3 (more specifically, the first bearing 3 a).

[0065] 15 , the rotating body 2 (more specifically, the rotating shaft 20) includes a first portion 25 that supports the inner ring 31a and has a first outer peripheral surface 25u. The rotating body 2 (more specifically, the rotating shaft 20) also includes a second portion 26 that has a second outer peripheral surface 26u that has a smaller diameter than the first outer peripheral surface 25u and is positioned closer to the first direction DR1 than the first portion 25. Furthermore, the rotating body 2 (more specifically, the rotating shaft 20) has a step surface 25a that connects the first outer peripheral surface 25u and the second outer peripheral surface 26u.

[0066] 15 , the housing 4 has a third part 41 that supports the outer ring 32a, and a fourth part 42 that defines an annular receiving space SP that receives the oil E from the first gap G1 between the first part 25 and the third part 41. The fourth part 42 also has an opening 45 that guides the oil E from the annular receiving space SP to the recovery passage 71, and an annular protrusion 441 that faces both the stepped surface 25a and the annular receiving space SP and protrudes in a direction away from the first axis AX1.

[0067] Therefore, the spindle unit 1B of the machine tool in the second embodiment has the same effects as the spindle unit 1A of the machine tool in the first embodiment.

[0068] (Optional Additional Configuration) Next, with reference to Figs. 14 to 24, an optional additional configuration that can be employed in the spindle device 1B of the machine tool in the second embodiment (or the spindle device 1A of the machine tool in the above-described first embodiment) will be described.

[0069] 15, the annular receiving space SP is hatched with dots to make the shape of the annular receiving space SP easier to understand. As illustrated in Fig. 15, the annular receiving space SP may have a shape in which the cross-sectional area perpendicular to the first axis AX1 increases continuously or stepwise along the first direction DR1.

[0070] 16 and 17 , the fourth portion 42 has an annular protrusion 44 that protrudes inward toward the first axis AX1. Note that in Fig. 16 , the annular protrusion 44 is hatched with dots to make the shape of the annular protrusion 44 easier to understand.

[0071] In the example shown in Figure 18, the annular protrusion 44 has the above-mentioned annular protrusion 441 that protrudes outward, a first surface 44a facing the step surface 25a of the rotating body 2, and a second surface 44b facing the second outer peripheral surface 26u of the rotating body 2.

[0072] 18 , at least a portion of the first surface 44a is the surface of an outwardly protruding annular protrusion 441. More specifically, at least a portion of the first surface 44a is formed by an upper surface 441a of the annular protrusion 441.

[0073] 18 , a second gap G2 fluidly communicating with the first gap G1 is formed between the first surface 44a and the step surface 25a. In the example shown in FIG. 18 , the second gap G2 is fluidly communicating with the first gap G1 via the annular receiving space SP. The second gap G2 is located closer to the second direction DR2 than the annular protrusion 441. In the example shown in FIG. 18 , a third gap G3 fluidly communicating with the second gap G2 is formed between the second surface 44b and the second outer peripheral surface 26u of the rotating body 2.

[0074] 18 , the first gap G1 and the second gap G2 extend in different directions. This prevents oil in the first gap G1 from moving toward the second gap G2. In the example shown in FIG. 18 , the first gap G1 extends in the first direction DR1, and the second gap G2 extends in the radially inward direction DR3 (more specifically, in a direction perpendicular to the first axis AX1 and toward the first axis AX1).

[0075] 18 , the annular protrusion 44 has a first annular groove V1 that faces the annular receiving space SP and is recessed in the radially inward direction DR3. The first annular groove V1 prevents or suppresses the oil in the annular receiving space SP from flowing back toward the second gap G2.

[0076] 18 , part of the surface of the first annular groove V1 is the surface of the annular protrusion 441. More specifically, part of the surface of the first annular groove V1 is formed by the lower surface 441d of the annular protrusion 441.

[0077] 18, the end e4 of the annular receiving space SP on the first direction DR1 side is disposed closer to the first direction DR1 than the second gap G2, and the end e5 of the annular receiving space SP on the second direction DR2 side is disposed closer to the second direction DR2 than the second gap G2. In this case, the size of the area including the annular receiving space SP and the second gap G2 can be made more compact than when the entire annular receiving space SP is disposed closer to the first direction DR1 than the second gap G2.

[0078] As illustrated in Figure 19, the distance between the outermost edge e6 of the first gap G1 and the first axis AX1 is defined as the third distance LT3, and the distance between the outermost edge e7 of the annular receiving space SP and the first axis AX1 is defined as the fourth distance LT4.

[0079] 19, the fourth distance LT4 is greater than the third distance LT3. In this case, a portion of the annular receiving space SP can be secured radially outward in the radial direction DR4 from the first gap G1, thereby increasing the overall volume of the annular receiving space SP.

[0080] 20 , the fourth portion 42 of the housing 4 has a first annular groove V1 recessed in a radially inward direction DR3 (i.e., a direction toward the first axis AX1) and a second annular groove V2 recessed in a radially outward direction DR4 (i.e., a direction away from the first axis AX1). In the example shown in Fig. 20 , the second annular groove V2 faces the annular receiving space SP and is disposed opposite the first annular groove V1.

[0081] 20, both the first annular groove V1 and the second annular groove V2 can receive oil. In this case, the annular receiving space SP includes a space defined by the first annular groove V1 and a space defined by the second annular groove V2, which increases the overall volume of the annular receiving space SP.

[0082] (Arrangement of opening 45) As illustrated in Figures 8 and 19, the spindle device 1 of the machine tool has an opening 45 that guides oil from the annular receiving space SP to the recovery passage 71. At least a portion of the opening 45 is arranged closer to the first direction DR1 than the second gap G2. It is preferable that at least a portion of the opening 45 is arranged closer to the first direction DR1 than the outermost edge 441e of the annular protrusion 441. It is also preferable that the entire opening 45 is arranged closer to the first direction DR1 than the first surface 44a.

[0083] The distance between the end e4 of the annular receiving space SP on the first direction DR1 side and the opening 45 is defined as a fifth distance LT5, and the distance between the end e5 of the annular receiving space SP on the second direction DR2 side and the opening 45 is defined as a sixth distance LT6. In the example shown in FIG. 19 , the fifth distance LT5 is smaller than the sixth distance LT6. In this case, the opening 45 is positioned relatively close to the bottom of the annular receiving space SP. Therefore, the amount of oil remaining at the bottom of the annular receiving space SP without being recovered by the recovery passage 71 is reduced. Furthermore, oil is less likely to flow back from the annular receiving space SP into the first gap G1.

[0084] In the example shown in Fig. 20, the entire opening 45 faces the outer side surface S1 of the annular receiving space SP. Alternatively, as illustrated in Fig. 21, at least a part of the opening 45 may face the end surface S2 of the annular receiving space SP in the first direction DR1. In the example shown in Fig. 21, a part of the opening 45 faces the outer side surface S1 of the annular receiving space SP, and another part of the opening 45 faces the end surface S2 of the annular receiving space SP in the first direction DR1.

[0085] (Annular Protrusion 441) In the example shown in FIG. 18, the annular protrusion 441 functions as a barb that prevents the oil E that has entered the annular receiving space SP from entering the second gap G2.

[0086] 19 , the distance between the outermost edge 441 e of the annular protrusion 441 and the first axis AX1 (in other words, the “second distance LT2”) is shorter than the distance between the first axis AX1 and the outermost edge e3 of the stepped surface 25 a of the rotating body 2 (in other words, the “first distance LT1”). Alternatively, the second distance LT2 may be equal to the first distance LT1.

[0087] When the second distance LT2 is equal to or less than the first distance LT1, the oil E flowing from the first gap G1 in the first direction DR1 is prevented or suppressed from hitting the annular protrusion 441. Therefore, the oil E flowing from the first gap G1 in the first direction DR1 is less likely to enter the gap between the stepped surface 25a and the annular protrusion 441 (or the second gap G2 between the stepped surface 25a and the first surface 44a).

[0088] In the example shown in FIG. 20, the annular protrusion 441 has an upper surface 441a, an outer side surface 441c, and a lower surface 441d.

[0089] The upper surface 441a is an annular surface facing the stepped surface 25a of the rotating body 2. The upper surface 441a may be perpendicular to the first axis AX1, or may be inclined with respect to a plane perpendicular to the first axis AX1.

[0090] 20, the outer side surface 441c faces the annular receiving space SP. In a longitudinal cross section passing through the first axis AX1, the outer side surface 441c is parallel to the first axis AX1. Alternatively, in a longitudinal cross section passing through the first axis AX1, the outer side surface 441c may be slightly inclined with respect to the first axis AX1.

[0091] In the example shown in Figure 20, the lower surface 441d is an annular surface facing the annular receiving space SP. The lower surface 441d may include an inclined surface CS that approaches the first axis AX1 as it moves in the first direction DR1. As shown by the dashed arrow in Figure 20, the inclined surface CS guides oil moving upward within the annular receiving space SP in a direction away from the second gap G2 (more specifically, a direction away from the first axis AX1). This effectively prevents oil in the annular receiving space SP from moving toward the second gap G2.

[0092] 20, the lower surface 441d includes a surface HS perpendicular to the first axis AX1 in addition to the inclined surface CS. The outer edge of the surface HS is connected to the inner edge of the inclined surface CS. Note that either the inclined surface CS or the surface HS may be omitted.

[0093] 16 , the housing 4 has a first part CP1 (more specifically, the annular first part CP1) including the above-described annular protrusion 441, and a second part CP2 (more specifically, the annular second part CP2) that supports the first part CP1. When the first part CP1 including the annular protrusion 441 is a part different from the second part CP2, the degree of freedom in designing the internal shape of the housing 4 (for example, the degree of freedom in the shape of the annular receiving space SP) increases.

[0094] 16 , the first part CP1 and the second part CP2 each have a portion facing the annular receiving space SP. The first part CP1 and the second part CP2 may each constitute a part of a surface defining the first annular groove V1. Furthermore, the first part CP1 may have a substantially L-shape in a vertical cross section passing through the first axis AX1. The second part CP2 may be an end plate disposed at the end of the housing 4 on the first direction DR1 side.

[0095] 16, the annular protrusion 44 is made up of a plurality of parts (CP1, CP2). Alternatively, the annular protrusion 44 may be made up of a single part.

[0096] (Air injection port OP1 and discharge port 49) In the example shown in FIG. 18, an air injection port OP1 communicating with the third gap G3 is formed between the tip end 46 of the housing 4 and the rotating body 2.

[0097] The housing 4 also has an air flow path 93 formed therein through which air supplied from an air source (hereinafter referred to as "second air" to distinguish it from the air in the mixed fluid supplied by the lubrication device) flows.

[0098] Furthermore, an outlet 49 for discharging the second air is formed in the housing 4. The outlet 49 discharges the second air received from the air flow path 93 into the third gap G3 so that a first air flow from the third gap G3 toward the second gap G2 and a second air flow from the third gap G3 toward the air ejection port OP1 are formed.

[0099] The second air injected from the air injection port OP1 prevents foreign matter such as chips from entering the spindle device 1 of the machine tool through the third gap G3, etc. More specifically, in the example shown in Fig. 14, the second air injected from the air injection port OP1 forms an air curtain AC around the tool T or the tool holder HD. This air curtain prevents foreign matter such as chips from entering the spindle device 1 of the machine tool through the third gap G3, etc.

[0100] 18 , the second air flowing from the third gap G3 to the second gap G2 prevents the oil E from entering the second gap G2 from the first gap G1 or the annular receiving space SP. In addition, the second air flowing from the third gap G3 to the second gap G2 pushes back the oil that has entered the second gap G2 toward the annular receiving space SP.

[0101] At least a portion of the second air flowing from the third gap G3 toward the second gap G2 reaches the annular receiving space SP. The air that reaches the annular receiving space SP is recovered via the recovery passage 71.

[0102] (Rotating Body 2) In the example shown in FIG. 22 , the rotating body 2 (more specifically, the rotating shaft 20) has a rotating shaft main body 21, an attachment portion 28 to which a tool T is attached, and a rod-shaped member 291 connected to the attachment portion 28. The rod-shaped member 291 is disposed inside the rotating shaft main body 21. In the example shown in FIG. 22 , when the attachment portion driving device 11 of the machining head 10 presses the rod-shaped member 291 in the first direction DR1, the rod-shaped member 291 and the attachment portion 28 move relative to the rotating shaft main body 21 in the first direction DR1. In this state, the tool T attached to the attachment portion 28 can be replaced with another tool. After the tool is replaced, a biasing member 293 (e.g., a disc spring) disposed on the rotating shaft 20 presses the rod-shaped member 291 in the second direction DR2. In this manner, the rod-shaped member 291 and the attachment portion 28 move relative to the rotating shaft main body 21 in the second direction DR2.

[0103] In Fig. 23 , the first portion 25 of the rotating body 2 is hatched with dots to make the shape of the first portion 25 easier to understand. In the example shown in Fig. 23 , the first portion 25 and the second portion 26 each constitute a part of the rotating shaft main body 21. In other words, the rotating shaft main body 21 includes the first portion 25 and the second portion 26. The first portion 25 and the second portion 26 may be formed by a single component, or may be formed by an assembly of multiple components. Furthermore, the first portion 25 and the second portion 26 may each be formed by a single component, or may be formed by an assembly of multiple components.

[0104] In the example shown in Figure 23, the first portion 25 has the above-mentioned step surface 25a and the above-mentioned first outer peripheral surface 25u. Additionally, the first portion 25 may have a second step surface 25b and / or a third outer peripheral surface 25w. In the example shown in Figure 23, the step surface 25a, the first outer peripheral surface 25u, and the second step surface 25b define an annular protrusion 250 that protrudes outward. In other words, the first portion 25 of the rotating body 2 has the annular protrusion 250, which has the step surface 25a, the first outer peripheral surface 25u, and the second step surface 25b.

[0105] 23 , the stepped surface 25a is the surface on the first direction DR1 side of the first portion 25. The first outer peripheral surface 25u is a surface that is disposed opposite at least a part of the third portion 41 of the housing 4. The second stepped surface 25b is a surface that contacts the end face of the inner ring 31a of the first bearing 3a on the first direction DR1 side. The third outer peripheral surface 25w is a surface that contacts the inner peripheral surface of the inner ring 31a of the first bearing 3a.

[0106] The first portion 25 of the rotating body 2 may have a first inner circumferential surface 25 n that contacts the tool holder HD. In the example shown in Fig. 23, the first inner circumferential surface 25 n is a tapered surface whose diameter increases in the first direction DR1.

[0107] 23, the maximum outer diameter of the second portion 26 of the rotating body 2 is smaller than the outer diameter of the stepped surface 25a. In other words, the entire second portion 26 has a smaller diameter than the outer peripheral edge of the stepped surface 25a.

[0108] 23, the second portion 26 has a second outer circumferential surface 26u and an end surface 26f. The end surface 26f is disposed at the end of the second portion 26 on the first direction DR1 side.

[0109] The end face 26 f of the second portion 26 is located further in the first direction DR1 than the end face of the fourth portion 42 of the housing 4 on the first direction DR1 side (more specifically, the third surface 44 f of the annular protrusion 44). A tool holder HD may be arranged in contact with the end face 26 f of the second portion 26.

[0110] The second portion 26 of the rotating body 2 may have a second inner circumferential surface 26n that contacts the tool holder HD. In the example shown in Fig. 23 , the second inner circumferential surface 26n is a tapered surface whose diameter increases in the first direction DR1. In the example shown in Fig. 23 , the inner circumferential surfaces (25n, 26n) that contact the tool holder HD are disposed across the first portion 25 of the rotating body 2 and the second portion 26 of the rotating body 2.

[0111] (Housing 4) In the example shown in FIG. 22, the housing 4 has a front end portion 4a, a rear end portion 4b, and an intermediate portion 4c between the front end portion 4a and the rear end portion 4b.

[0112] The front end portion 4a of the housing 4 supports the outer rings of the front bearings. In the example shown in Fig. 24, the front end portion 4a of the housing 4 supports the outer ring 32a of the first bearing 3a and the outer ring 32c of the third bearing 3c.

[0113] The tip portion 4a of the housing 4 includes the above-described third portion 41 and fourth portion 42. In the example shown in Fig. 24, the fourth portion 42 includes the entire surface of the housing 4 that defines the annular receiving space SP and the entire annular protrusion 44. The fourth portion 42 is also disposed closer to the first direction DR1 than the third portion 41.

[0114] 2 or 15 , the fourth portion 42 has a base 43 continuing to the third portion 41 and an annular protrusion 44 protruding in a direction toward the first axis AX1 from the base 43. In the example shown in Fig. 8 or 18 , the annular protrusion 44 has a first wall 440a that defines the bottom surface of the annular receiving space SP (in other words, the end surface on the first direction DR1 side of the annular receiving space SP), a second wall 440b that defines a second surface 44b facing the second outer peripheral surface 26u of the rotating body 2, and an annular protrusion 441 that protrudes from the second wall 440b in a direction away from the first axis AX1.

[0115] 18 , the first wall 440a is an annular wall that is continuous with the base 43 of the fourth portion 42 and extends from the base 43 in the radially inward direction DR3. The second wall 440b is an annular wall that is continuous with the inner edge of the first wall 440a and extends from the inner edge in the second direction DR2. The annular protrusion 441 is continuous with the end of the second wall 440b on the second direction DR2 side and protrudes from that end in the radially outward direction DR4.

[0116] The housing 4 may have an outwardly protruding flange 47. In the example shown in Fig. 24, the flange 47 is disposed on the tip portion 4a of the housing 4. An outlet port 71p of the recovery passage 71 may be provided on the flange 47.

[0117] The rear end portion 4b of the housing 4 supports the outer ring of the rear bearing. In the example shown in Fig. 22, the rear end portion 4b of the housing 4 supports the outer ring of the second bearing 3b. The rear end portion 4b may have an end plate 40b arranged at the end of the housing 4 on the second direction DR2 side.

[0118] 22, the intermediate portion 4c of the housing 4 has a cylindrical side wall 40c. The intermediate portion 4c of the housing 4 (more specifically, the cylindrical side wall 40c) may support a stator 51, which will be described later.

[0119] 22 , the plurality of bearings 3 that support the rotating body 2 rotatably about the first axis AX1 include a first bearing 3a and a second bearing 3b. Additionally, the plurality of bearings 3 may include a third bearing 3c. The third bearing 3c is disposed between the first bearing 3a and the second bearing 3b in the direction along the first axis AX1. The third bearing 3c is, for example, a ball bearing.

[0120] The first bearing 3a constitutes at least a part of a front bearing that supports the tip end 24 of the rotating body 2. In the example shown in FIG. 22 , the first bearing 3a is the bearing that is arranged closest to the first direction DR1 (in other words, closest to the tip end) among the multiple bearings 3 that support the rotating body 2. The first bearing 3a is, for example, a ball bearing. The front bearing that supports the tip end 24 of the rotating body 2 may include multiple bearings. In the example shown in FIG. 22 , the front bearing includes the first bearing 3a and a third bearing 3c.

[0121] The second bearing 3b constitutes at least a part of a rear bearing that supports the rear end portion 22 of the rotating body 2. The second bearing 3b is, for example, a roller bearing. The second bearing 3b has an inner ring supported by the rotating body 2 and an outer ring supported by the housing 4. The rear bearing may include multiple bearings.

[0122] (First rotation drive device 5) In the example shown in Fig. 22 , the spindle device 1 of the machine tool includes a first rotation drive device 5 that rotates the rotating body 2 (more specifically, the rotating shaft 20) about the first axis AX1. The first rotation drive device 5 may be a first motor. In the example shown in Fig. 22 , the first rotation drive device 5 (more specifically, the first motor) has a stator 51 and a rotor 53. In this case, when a current is supplied to the stator 51, the rotor 53 rotates about the first axis AX1 due to electromagnetic action. In the example shown in Fig. 22 , the stator 51 is fixed to the housing 4, and the rotor 53 is fixed to the rotating body 2 (more specifically, the rotating shaft 20).

[0123] 22, the rotor 53 is disposed in the intermediate portion 23 of the rotating shaft 20. In the example shown in Fig. 22, the rotor 53 is disposed closer to the second direction DR2 than the first bearing 3a, and closer to the first direction DR1 than the second bearing 3b.

[0124] 22 , the first rotation drive device 5 is disposed inside the housing 4. Alternatively, the first rotation drive device 5 may be disposed outside the housing 4. For example, the first rotation drive device 5 disposed outside the housing 4 may be configured to rotate the rotating body 2 via any power transmission mechanism (e.g., gears, transmission belts, etc.).

[0125] (Supply flow path 66) The spindle unit 1 of the machine tool includes a supply flow path 66 that supplies a mixed fluid containing oil and air to the bearing 3 (for example, the first bearing 3a). At least a portion of the supply flow path 66 is arranged in the housing 4. At least a portion of the supply flow path 66 may be configured by a through-hole formed in the housing 4.

[0126] The supply passage 66 may supply a mixed fluid containing oil and air to a plurality of bearings including the first bearing 3 a. In the example shown in Fig. 22, the supply passage 66 supplies the mixed fluid containing oil and air to the first bearing 3 a and the third bearing 3 c. Additionally, the supply passage 66 may supply the mixed fluid containing oil and air to the second bearing 3 b.

[0127] (Recovery Channel 71) The spindle unit 1 of the machine tool has a recovery channel 71 that recovers oil E that has passed through the bearing 3 (more specifically, the first bearing 3a). The recovery channel 71 may recover at least a portion of the air supplied from the supply channel 66 to the bearing 3 (more specifically, the first bearing 3a). The recovery channel 71 may also recover at least a portion of the second air supplied from the air channel 93 to the third gap G3 (see FIG. 18 if necessary). At least a portion of the recovery channel 71 is arranged in the housing 4. At least a portion of the recovery channel 71 may be formed by a through-hole formed in the housing 4.

[0128] (Second recovery passage 72) The spindle unit 1 of the machine tool may be provided with a second recovery passage 72 that recovers an oil-containing fluid, including oil and air, from the bearing 3 (more specifically, the first bearing 3a). In the example shown in Fig. 22 , the second recovery passage 72 is a passage separate from the recovery passage 71. In the example shown in Fig. 22 , the second recovery passage 72 recovers oil directly from the bearing 3 (more specifically, the first bearing 3a). Oil E that has passed through the bearing 3 (more specifically, the first bearing 3a) without being recovered by the second recovery passage 72 is recovered by the recovery passage 71.

[0129] At least a portion of the second recovery passage 72 is disposed in the housing 4. At least a portion of the second recovery passage 72 may be configured by a through-hole formed in the housing 4.

[0130] The second recovery passage 72 may recover an oil-containing fluid containing oil and air from a plurality of bearings including the first bearing 3 a. In the example shown in Fig. 22, the second recovery passage 72 recovers an oil-containing fluid from the first bearing 3 a that constitutes a part of the front bearing and the third bearing 3 c that constitutes a part of the front bearing.

[0131] (Third recovery passage 73) The spindle unit 1 of the machine tool may be provided with a third recovery passage 73 that recovers an oil-containing fluid, including oil and air, from the second bearing 3b. In the example shown in Fig. 22, the third recovery passage 73 is a passage separate from the recovery passage 71 and the second recovery passage 72. In the example shown in Fig. 22, the third recovery passage 73 recovers oil directly from the second bearing 3b.

[0132] At least a portion of the third recovery passage 73 is disposed in the housing 4. At least a portion of the third recovery passage 73 may be constituted by a through-hole formed in the housing 4.

[0133] The third recovery passage 73 may recover the oil-containing fluid from a plurality of bearings including the second bearing 3 b. For example, the third recovery passage 73 may recover the oil-containing fluid from a plurality of bearings that constitute the rear bearing.

[0134] Air (or oil) that is not recovered by the recovery flow path 71, the second recovery flow path 72, the third recovery flow path 73, etc. is discharged outside the spindle device 1 of the machine tool through gaps in the spindle device (see the dashed arrow in Figure 22).

[0135] (Third embodiment) A machine tool 100 according to a third embodiment will be described with reference to Figures 1 to 27. Figure 25 is a schematic perspective view showing an example of machine tool 100 according to the third embodiment. Figure 26 is a schematic perspective view showing another example of machine tool 100 according to the third embodiment. Figure 27 is a diagram showing a state in which control device 140 can control a plurality of control target devices.

[0136] In the third embodiment, differences from the first and second embodiments will be mainly described. On the other hand, in the third embodiment, repeated descriptions of matters already described in the first or second embodiment will be omitted. Therefore, it goes without saying that matters already described in the first or second embodiment can be applied to the third embodiment, even if they are not explicitly described in the third embodiment.

[0137] As illustrated in Figures 25 and 27, the machine tool 100 in the third embodiment includes a machining head 10, a lubrication device 6, a recovery device 7, a work support device 110 that supports the workpiece W, a moving device 120 that moves the machining head 10 relative to the work support device 110, and a control device 140 that controls at least the first rotation drive device 5 and the moving device 120.

[0138] As illustrated in Figure 14, the machining head 10 includes: (1) a rotating body 2 (more specifically, a rotating shaft 20) having a rear end 22 and a front end 24 that holds a tool T; (2) a plurality of bearings 3 including a first bearing 3a; (3) a housing 4 that supports the rotating body 2 rotatably around a first axis AX1 via the plurality of bearings 3; and (4) a first rotation drive device 5 that rotates the rotating body 2 around the first axis AX1.

[0139] 15 , the rotating body 2 (more specifically, the rotating shaft 20) has a first portion 25, a second portion 26, and a stepped surface 25a. The first portion 25 supports the inner ring 31a of the first bearing 3a and has a first outer peripheral surface 25u. The second portion 26 is disposed closer to the first direction DR1 than the first portion 25 and has a second outer peripheral surface 26u that has a smaller diameter than the first outer peripheral surface 25u. The stepped surface 25a connects the first outer peripheral surface 25u and the second outer peripheral surface 26u.

[0140] The rotating body 2 has already been described in the first or second embodiment, so a repeated description of the rotating body 2 will be omitted.

[0141] As illustrated in Figure 15, the housing 4 has a third part 41 that supports the outer ring 32a of the first bearing 3a, and a fourth part 42 that defines an annular receiving space SP that receives oil E from the first gap G1 between the first part 25 of the rotating body 2 and the third part 41.

[0142] The fourth part 42 has an opening 45 that guides oil E from the annular receiving space SP to the recovery flow path 71, and an annular protrusion 441 that faces both the step surface 25a of the rotating body 2 and the annular receiving space SP and protrudes in a direction away from the first axis AX1.

[0143] The housing 4 has already been described in the first or second embodiment, so a repeated description of the housing 4 will be omitted.

[0144] In the example shown in FIG. 22, the lubrication device 6 supplies a mixed fluid containing oil and air to the first bearing 3 a via a supply passage 66 .

[0145] The recovery device 7 recovers at least a portion of the oil E that has passed through the first bearing 3 a via a recovery passage 71 .

[0146] The third embodiment provides the same effects as the first embodiment (or the second embodiment).

[0147] (Optional additional configuration) Next, with reference to FIGS. 1 to 27, optional additional configurations that can be employed in machine tool 100 in the third embodiment (or spindle device 1A of the machine tool in the first embodiment, or spindle device 1B of the machine tool in the second embodiment) will be described.

[0148] (Lubrication device 6) In the example shown in FIG. 22, the lubrication device 6 has an air source AS1 (e.g., an air compressor), an oil tank 62, a pump 63, a mixer 64, a supply flow path 66, and a supply pipe 68 connecting the mixer 64 and the supply flow path 66.

[0149] The air source AS1 supplies air to the mixer 64. The pump 63 supplies oil from the oil tank 62 to the mixer 64. The mixer 64 mixes the air received from the air source AS1 with the oil received from the oil tank 62 to form a mixed fluid containing oil and air (more specifically, oil-air). The mixer 64 also sends the mixed fluid to the supply flow path 66 via a supply pipe 68.

[0150] 22 , the supply pipe 68 is arranged outside the housing 4, and the supply passage 66 is arranged inside the housing 4. The supply passage 66 supplies a mixed fluid containing oil and air to at least the first bearing 3 a. Additionally, the supply passage 66 may supply a mixed fluid containing oil and air to the second bearing 3 b and / or the third bearing 3 c.

[0151] 22 , the recovery device 7 includes a recovery passage 71, a first ejector 75a, a first pipe 74a connecting the recovery passage 71 and the first ejector 75a, a first exhaust pipe 76a, an exhaust cleaner 77, a recovery container 78, and an air source AS2 (e.g., an air compressor). The air source AS2 of the recovery device 7 may be the same as the air source AS1 of the lubrication device 6, or may be different from the air source AS1 of the lubrication device 6.

[0152] The recovery device 7 may include a second recovery passage 72, a second ejector 75b, a second pipe 74b connecting the second recovery passage 72 and the second ejector 75b, and a second exhaust pipe 76b. The recovery device 7 may also include a third recovery passage 73, a third ejector 75c, a third pipe 74c connecting the third recovery passage 73 and the third ejector 75c, and a third exhaust pipe 76c.

[0153] 22, the recovery passageway 71 is disposed inside the housing 4, and the first conduit 74a is disposed outside the housing 4. In the example shown in Fig. 24, the recovery passageway 71 and the first conduit 74a are fluidly connected via an outlet port 71p provided in the housing 4 (more specifically, the flange 47).

[0154] 24 , the recovery passage 71 receives oil from the annular receiving space SP through the opening 45. More specifically, the recovery passage 71 receives, from the annular receiving space SP, an oil-containing fluid (hereinafter referred to as the “first oil-containing fluid”) that contains at least a portion of the oil that has passed through the first bearing 3a.

[0155] 22, the first ejector 75a generates negative pressure in the first pipe 74a using air (hereinafter referred to as "third air") supplied to the first ejector 75a from the air source AS2. The first ejector 75a also sends the third air received from the air source AS2 and the first oil-containing fluid received from the recovery passage 71 via the first pipe 74a to the exhaust cleaner 77 via the first exhaust pipe 76a.

[0156] 22, the second recovery passage 72 is disposed inside the housing 4, and the second conduit 74b is disposed outside the housing 4. In the example shown in Fig. 22, the second recovery passage 72 and the second conduit 74b are fluidly connected via a second outlet port 72p provided in the housing 4 (more specifically, the flange 47).

[0157] 22 , the second recovery passage 72 receives the oil-containing fluid (hereinafter referred to as the “second oil-containing fluid”) from at least the first bearing 3 a. The second recovery passage 72 may receive the second oil-containing fluid from a plurality of front bearings including the first bearing 3 a (e.g., the first bearing 3 a and the third bearing 3 c).

[0158] 22, the second ejector 75b generates negative pressure in the second pipe 74b using air (hereinafter referred to as "fourth air") supplied to the second ejector 75b from the air source AS2. The second ejector 75b also sends the fourth air received from the air source AS2 and the second oil-containing fluid received from the second recovery passage 72 via the second pipe 74b to the exhaust cleaner 77 via the second exhaust pipe 76b.

[0159] 22 , the third recovery passage 73 is disposed inside the housing 4, and the third conduit 74c is disposed outside the housing 4. In the example shown in FIG. 22 , the third recovery passage 73 and the third conduit 74c are fluidly connected via a third outlet port 73p provided in the housing 4.

[0160] The third recovery passage 73 receives the oil-containing fluid (hereinafter referred to as the "third oil-containing fluid") from at least the second bearing 3 b. The third recovery passage 73 may receive the third oil-containing fluid from multiple rear bearings including the second bearing 3 b.

[0161] 22, the third ejector 75c generates negative pressure in the third pipe 74c using air (hereinafter referred to as "fifth air") supplied to the third ejector 75c from the air source AS2. The third ejector 75c also sends the fifth air received from the air source AS2 and the third oil-containing fluid received from the third recovery passage 73 via the third pipe 74c to the exhaust cleaner 77 via the third exhaust pipe 76c.

[0162] The exhaust cleaner 77 receives the oil-containing fluid from a plurality of ejectors (e.g., the first ejector 75a, the second ejector 75b, and the third ejector 75c) including the first ejector 75a via a plurality of exhaust pipes (e.g., the first exhaust pipe 76a, the second exhaust pipe 76b, and the third exhaust pipe 76c) including the first exhaust pipe 76a. The exhaust cleaner 77 also separates the oil-containing fluid received from the plurality of exhaust pipes including the first exhaust pipe 76a into liquid oil and air. The liquid oil separated from the oil-containing fluid by the exhaust cleaner 77 is stored in a collection container 78.

[0163] (Air Supply Device 9) The machine tool 100 in the third embodiment may include an air supply device 9. The air supply device 9 supplies air to a discharge port 49 formed in the housing 4.

[0164] 22 , the air supply device 9 has an air source AS3 (e.g., an air compressor), an air flow path 93, and an air supply pipe 91 connecting the air source AS3 and the air flow path 93. The air source AS3 of the air supply device 9 may be the same as the air source AS1 of the lubricating device 6, or may be different from the air source AS1 of the lubricating device 6. Furthermore, the air source AS3 of the air supply device 9 may be the same as the air source AS2 of the collecting device 7, or may be different from the air source AS2 of the collecting device 7. The air source AS3 supplies second air to the air flow path 93 via the air supply pipe 91.

[0165] 22, the air supply pipe 91 is disposed outside the housing 4, and the air flow path 93 is disposed inside the housing 4. In the example shown in Fig. 22, the air supply pipe 91 and the air flow path 93 are fluidly connected via a supply port 93p provided in the housing 4 (more specifically, the flange 47).

[0166] The air flow path 93 supplies the second air received from the air supply pipe 91 to the discharge port 49. In the example shown in Fig. 18, the discharge port 49 discharges the second air received from the air flow path 93 into the third gap G3. The second air discharged into the third gap G3 forms a first air flow from the third gap G3 toward the second gap G2 and a second air flow from the third gap G3 toward the air ejection port OP1.

[0167] 25 , the workpiece support device 110 has a support 111 (more specifically, a table 111a) that supports the workpiece W, and a second rotation drive device 112 that rotates the support 111 (more specifically, the table 111a) about a second axis AX2. The workpiece support device 110 may also have a tilting device 113 that tilts the table 111a about an axis AX3 that is perpendicular to the second axis AX2.

[0168] Alternatively, as illustrated in FIG. 26, the work support device 110 may have a chuck 111b that holds the work W and a second rotation drive device 112 that rotates the chuck 111b around the second axis AX2.

[0169] (Moving device 120) The moving device 120 moves the machining head 10 relative to the workpiece support device 110. The moving device 120 may be a device capable of moving the machining head 10 three-dimensionally. The moving device 120 may be capable of moving the machining head 10 along a Z-axis parallel to the vertical direction. The moving device 120 may be capable of moving the machining head 10 along an X-axis parallel to the horizontal direction. The moving device 120 may also be capable of moving the machining head 10 along a Y-axis perpendicular to both the X-axis and the Z-axis. In the example shown in FIGS. 25 and 26 , the machining head 10 is supported by the base 130 via the moving device 120.

[0170] (Control Device 140 ) The control device 140 controls at least the first rotation drive device 5 and the movement device 120 .

[0171] 27 , when the control device 140 transmits a first movement command J1 to the movement device 120, the movement device 120 that receives the first movement command J1 moves the machining head 10 relative to the workpiece support device 110. In this way, the tool T held by the rotating body 2 can be moved toward the workpiece W.

[0172] Furthermore, when the control device 140 transmits a first rotation command R1 to the first rotation drive device 5, the first rotation drive device 5 that receives the first rotation command R1 rotates the rotating body 2 about the first axis AX1. In this way, the workpiece W can be machined by the tool T held by the rotating body 2.

[0173] The control device 140 may be capable of controlling the lubrication device 6 and / or the recovery device 7 .

[0174] For example, when the control device 140 transmits a first control command C1 to the lubrication device 6 (e.g., the air source AS1, the pump 63, the on-off valve, the flow control valve, etc.), the lubrication device 6 that receives the first control command C1 supplies a mixed fluid containing oil and air to at least one bearing, including the first bearing 3a. Furthermore, when the control device 140 transmits a second control command C2 to the recovery device 7 (e.g., the air source AS2, the on-off valve, the flow control valve, etc.), the recovery device 7 that receives the second control command C2 recovers at least a portion of the oil that has passed through the first bearing 3a. Furthermore, the recovery device 7 that receives the second control command C2 recovers the oil-containing fluid from the first bearing 3a, the second bearing 3b, and the third bearing 3c.

[0175] The control device 140 may be capable of controlling the air supply device 9. For example, when the control device 140 transmits a third control command C3 to the air supply device 9 (e.g., the air source AS3, an on-off valve, a flow control valve, etc.), the air supply device 9 that receives the third control command C3 supplies the second air to the discharge port 49. The discharge port 49 discharges the second air received from the air flow path 93 into the third gap G3. The second air discharged into the third gap G3 forms a first air flow from the third gap G3 toward the second gap G2 and a second air flow from the third gap G3 toward the air ejection port OP1.

[0176] The control device 140 may be capable of controlling the second rotation drive device 112. For example, when the control device 140 transmits a second rotation command R2 to the second rotation drive device 112, the second rotation drive device 112 that receives the second rotation command R2 rotates the support tool 111 that supports the workpiece W around the second axis AX2.

[0177] 27 , the control device 140 includes a hardware processor 141 (hereinafter simply referred to as the “processor 141”), a memory 142, a communication circuit 144, and an input device 146 (for example, a touch panel display 146a). The processor 141, the memory 142, the communication circuit 144, and the input device 146 are connected to one another via a bus 148.

[0178] Memory 142 stores data 142a necessary for machining a workpiece and programs 142b for operating each component of machine tool 100. Memory 142 is a storage medium readable by processor 141 of control device 140. Memory 142 may be, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, or flash memory, a magnetic disk, or any other type of memory.

[0179] The input device 146 is not limited to the touch panel display 146a. For example, the control device 140 may include an input device 146 such as a button, a switch, a lever, a pointing device, or a keyboard, and a display that displays data input to the input device 146 or other information. Furthermore, multiple computers may work together to function as the control device 140. Furthermore, the memory 142 may be distributed across multiple locations. For example, part of the memory 142 may be included in cloud storage.

[0180] The processor 141 of the control device 140 executes the program 142b stored in the memory 142, causing the control device 140 to generate a control command. The communication circuit 144 also transmits the control command to the devices to be controlled (more specifically, the first rotation drive device 5, the moving device 120, the lubricating device 6, the collecting device 7, the air supply device 9, the second rotation drive device 112, etc.). In this way, the processor 141 executes the program 142b, allowing the control device 140 to control the first rotation drive device 5, the moving device 120, the lubricating device 6, the collecting device 7, the air supply device 9, the second rotation drive device 112, etc.

[0181] The present invention is not limited to the above-described embodiments or modifications, and it is clear that each embodiment or modification can be appropriately modified or changed within the scope of the technical concept of the present invention. Furthermore, various techniques used in each embodiment or modification can be applied to other embodiments or modifications as long as no technical contradiction occurs. Furthermore, optional additional configurations in each embodiment or modification can be omitted as appropriate.

[0182] 25, the machine tool 100 is a vertical machining center. Alternatively, the machine tool 100 in the embodiment may be a horizontal machining center. Furthermore, the machine tool 100 may be a multi-tasking machine capable of performing machining other than cutting.

[0183] 2, 7, 12, 15, and 21 show examples in which the first portion 25 of the rotating body 2 and the second portion 26 of the rotating body 2 are each formed of a part of the rotating shaft main body 21. Alternatively, as shown in Fig. 28, at least a part of the first portion 25 of the rotating body 2 and the second portion 26 of the rotating body 2 may be formed of a member other than the rotating shaft main body 21.

[0184] 28 , the first portion 25 of the rotating body 2 is composed of a part of the rotating shaft main body 21 and a base end portion BL1 of the inner race holder BL. The inner race holder BL constitutes a part of the rotating body 2 and has a first outer peripheral surface 25u. The inner race holder BL is fixed to the rotating shaft main body 21 via a fixing member such as a bolt.

[0185] 28 , the inner ring 31 is supported by the rotating shaft main body 21 and the inner ring holder BL. A first gap G1 is formed between the first portion 25 of the rotating body 2 (more specifically, the base end portion BL1 of the inner ring holder BL) and the third portion 41 of the housing 4.

[0186] 28 , the second portion 26 of the rotating body 2 is configured by a tip portion BL2 of the inner race holder BL. The second portion 26 of the rotating body 2 (more specifically, the tip portion BL2 of the inner race holder BL) has a second outer peripheral surface 26u that has a smaller diameter than the first outer peripheral surface 25u, and is disposed closer to the first direction DR1 than the first portion 25 of the rotating body 2 (more specifically, the base end portion BL1 of the inner race holder BL).

[0187] 28 , the rotating body 2 (more specifically, the inner ring holder BL) has a stepped surface 25a connecting the first outer peripheral surface 25u and the second outer peripheral surface 26u. A second gap G2 that fluidly communicates with the first gap G1 is formed between the first surface 44a of the annular protrusion 44 and the stepped surface 25a. Furthermore, a third gap G3 that fluidly communicates with the second gap G2 is formed between the second surface 44b of the annular protrusion 44 and the second outer peripheral surface 26u.

[0188] 2, 7, 12, 15, and 21, the first gap G1 is linear in a vertical cross section including the first axis AX1. Alternatively, as illustrated in FIG. 29, the first gap G1 may have a labyrinth shape in a vertical cross section including the first axis AX1. Alternatively, or additionally, as illustrated in FIG. 30, a notch CT may be formed in a part of the surface defining the first gap G1. The notch CT may be formed in the first outer peripheral surface 25u of the rotating body 2, or may be formed in the surface of the third portion 41 of the housing 4.

[0189] DESCRIPTION OF SYMBOLS 1, 1A, 1B... spindle device of machine tool, 2... rotating body, 3... bearing, 3a... first bearing, 3b... second bearing, 3c... third bearing, 4... housing, 4a... front end portion of housing, 4b... rear end portion of housing, 4c... intermediate portion of housing, 4f... end surface of housing, 5... first rotation drive device, 6... lubrication device, 7... recovery device, 9... air supply device, 10... machining head, 11... mounting portion drive device, 20... rotating shaft, 21... rotating shaft main body, 22... rear end portion of rotating body, 23... intermediate portion of rotating shaft, 24... front end portion of rotating body, 25... first portion, 25a... step surface, 25b... Second step surface, 25n...first inner peripheral surface, 25u...first outer peripheral surface, 25w...third outer peripheral surface, 26...second portion, 26f...end surface of second portion, 26n...second inner peripheral surface, 26u...second outer peripheral surface, 28...mounting portion, 31, 31a...inner ring, 32, 32a, 32c...outer ring, 33...rolling element, 40b...end plate, 40c...housing side wall, 41...third portion, 42...fourth portion, 43...base, 44...annular protrusion, 44a...first surface, 44b...second surface, 44f...third surface, 45...opening, 46...tip portion, 47...housing flange, 49...discharge port, 51...stator, 53...rotor, 62...oil Tank, 63... pump, 64... mixer, 66... ​​supply flow path, 68... supply pipe, 71... recovery flow path, 71p... outlet port, 72... second recovery flow path, 72p... second outlet port, 73... third recovery flow path, 73p... third outlet port, 74a... first pipe, 74b... second pipe, 74c... third pipe, 75a... first ejector, 75b... second ejector, 75c... third ejector, 76a... first exhaust pipe, 76b... second exhaust pipe, 76c... third exhaust pipe, 77... exhaust cleaner, 78... recovery container, 91... air supply pipe, 93... air flow path, 93p... supply port, 100... machine tool, 110...workpiece support device, 111...support tool, 111a...table, 111b...chuck, 112...second rotation drive device, 113...tilting device, 120...movement device, 130...base, 140...control device, 141...hardware processor, 142...memory, 142a...data, 142b...program, 144...communication circuit, 146...input device, 146a...touch panel display, 148...bus, 250...annular protrusion, 291...rod-shaped member, 293...urging member, 440a...first wall, 440b...second wall, 441...annular protrusion, 441a...upper surface, 441c...outer side surface,441d...lower surface, 441e...outermost edge, 443d, 444d, 445d...surfaces constituting first annular groove, AC...air curtain, AS1, AS2, AS3...air source, BL...inner ring holder, BL1...base end portion of inner ring holder, BL2...tip end portion of inner ring holder, C1...first control command, C2...second control command, C3...third control command, CN...corner portion, CP1...first part, CP2...second part, CS...inclined surface, CT...notch, E...oil, G1...first gap, G2...second gap, G3...third gap , HD...tool holder, HS...surface perpendicular to the first axis, J1...first movement command, OP1...air injection port, R1...first rotation command, R2...second rotation command, S1...outer side surface, S2...end surface, SP...annular receiving space, T...tool, V1...first annular groove, V2...second annular groove, W...workpiece, e1...outer peripheral edge of the first surface, e2...inner peripheral edge of the first surface, e3...outermost edge of the stepped surface, e4...end of the annular receiving space on the first direction side, e5...end of the annular receiving space on the first direction side, e6...outermost edge of the first gap, e7...outermost edge of the annular receiving space,

Claims

a rotor having a rear end and a front end for holding a tool; a bearing having an inner ring and an outer ring; a housing supporting the rotor via the bearing for rotation about a first axis; a supply passage for supplying a mixed fluid containing oil and air to the bearing; and a recovery passage for recovering the oil that has passed through the bearing, wherein the rotor has: a first portion supporting the inner ring and having a first outer peripheral surface; a second portion having a second outer peripheral surface with a diameter smaller than that of the first outer peripheral surface, the second portion being positioned on the first direction side of the first portion when a direction from the rear end to the front end is defined as a first direction; and a step surface connecting the first outer peripheral surface and the second outer peripheral surface; and the housing has: a third portion supporting the outer ring; and a fourth portion defining an annular receiving space that receives the oil from a first gap between the first portion and the third portion, the fourth portion having an opening for guiding the oil from the annular receiving space to the recovery passage; a ring-shaped protrusion facing both the step surface and the annular receiving space and protruding in a direction away from the first axis.

2. A spindle device of a machine tool as described in claim 1, wherein the fourth portion has an annular protruding portion protruding toward the first axis, the annular protruding portion having the annular protrusion, a first surface facing the step surface, and a second surface facing the second outer peripheral surface.

3. A spindle unit of a machine tool as described in claim 2, wherein a second gap fluidically communicating with the first gap is formed between the first surface and the step surface, and a third gap fluidically communicating with the second gap is formed between the second surface and the second outer peripheral surface.

4. A spindle unit of a machine tool as described in claim 3, wherein an air injection port communicating with the third gap is formed between the tip of the housing and the rotating body, an air flow path is formed in the housing through which second air supplied from an air source flows, and a discharge port is formed in the housing for discharging the second air received from the air flow path into the third gap so that a first air flow is formed from the third gap toward the second gap, and a second air flow is formed from the third gap toward the air injection port.

5. A spindle unit for a machine tool as described in claim 3 or 4, wherein the entire annular receiving space is positioned on the first direction side of the second gap.

6. A spindle unit of a machine tool as described in claim 3 or 4, wherein the second gap is connected to the first gap via the annular receiving space, and when a direction opposite to the first direction is defined as a second direction, the end of the annular receiving space on the first direction side is positioned on the first direction side of the second gap, and the end of the annular receiving space on the second direction side is positioned on the second direction side of the second gap.

7. A spindle device for a machine tool according to any one of claims 2 to 6, wherein the annular protrusion has a first annular groove recessed in a direction toward the first axis, and the first annular groove faces the annular receiving space.

8. The spindle unit of a machine tool according to claim 7, wherein the fourth portion of the housing has a second annular groove recessed in a direction away from the first axis, the second annular groove facing the annular receiving space.

9. A spindle device for a machine tool according to any one of claims 1 to 8, wherein the annular projection has a lower surface, and the lower surface includes an inclined surface that approaches the first axis as it extends in the first direction.

10. A spindle device of a machine tool according to any one of claims 1 to 9, wherein the housing has a first part including the annular projection, and a second part supporting the first part.

11. A spindle device for a machine tool according to any one of claims 1 to 10, wherein the first gap and the annular receiving space are arranged on a straight line parallel to the first axis.

12. A spindle unit of a machine tool according to any one of claims 1 to 11, wherein when a distance between the outermost edge of the step surface and the first axis is defined as a first distance, and a distance between the outermost edge of the annular protrusion and the first axis is defined as a second distance, the second distance is equal to or less than the first distance.

13. A machining head having a rotor, a plurality of bearings including a first bearing, a housing rotatably supporting the rotor via the plurality of bearings, and a first rotary drive device rotating the rotor around a first axis; a lubrication device supplying a mixed fluid containing oil and air to the first bearing via a supply passage; a recovery device recovering at least a portion of the oil that has passed through the first bearing via a recovery passage; a work support device supporting a work; a moving device moving the machining head relative to the work support device; and a control device controlling at least the first rotary drive device and the moving device, wherein the rotor has: a rear end; a front end for holding a tool; a first portion supporting an inner ring of the first bearing and having a first outer circumferential surface; a second portion having a second outer circumferential surface smaller in diameter than the first outer circumferential surface, and being disposed on the first direction side of the first portion when the direction from the rear end toward the front end is defined as a first direction; and a step surface connecting the first outer circumferential surface and the second outer circumferential surface, and the housing A machine tool comprising: a third part supporting an outer ring of the first bearing; and a fourth part defining an annular receiving space that receives the oil from a first gap between the first part and the third part, the fourth part having an opening that guides the oil from the annular receiving space to the recovery passage, and an annular protrusion that faces both the step surface and the annular receiving space and protrudes in a direction away from the first shaft.

14. A machine tool as described in claim 13, wherein the fourth portion has an annular protruding portion protruding toward the first axis, the annular protruding portion having the annular protrusion, a first surface facing the step surface, and a second surface facing the second outer peripheral surface.

15. A machine tool as described in claim 14, wherein a second gap fluidically communicating with the first gap is formed between the first surface and the step surface, and a third gap fluidically communicating with the second gap is formed between the second surface and the second outer peripheral surface.

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