Motor built-in type spindle device

Abstract

To provide a motor built-in type spindle device which can suppress temperature rise of a rear bearing regardless of use conditions.SOLUTION: A motor built-in type spindle device includes: a rotary shaft 11; a front bearing 50 and a rear bearing 60 rotationally supporting the rotary shaft 11; and a motor 30 disposed between the front bearing 50 and the rear bearing 60. Between a motor side inner ring spacer 66 disposed at the motor side relative to the rear bearing 60 and a sleeve 18, a clearance C in which a negative pressure is generated is formed in the middle of a first communication passage 81 allowing communication between a bearing space 70 of the rear bearing 60 and a motor chamber 34.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spindle unit with a built-in motor, and more particularly to a spindle unit with a built-in motor used in machine tools, high-speed motors, or rotating machines that rotate at high speeds, such as centrifuges and turbo refrigerators. [Background technology]

[0002] The general structure of a grease-lubricated spindle unit with a built-in motor is that the rotor of the built-in motor is mounted between the front bearing (the side where the tool is attached) and the rear bearing (the side opposite the side where the tool is attached). The rotor is fitted onto the shaft with an interference fit, but in order to pass the rotor onto the shaft from the rear, the inner diameter of the rear bearing must be the same as or smaller than the inner diameter of the rotor. Also, since the front bearing bears the machining load, a larger bearing is selected than the rear bearing. For this reason, the rear bearing is generally smaller than the front bearing.

[0003] In spindle units with built-in motors, the outer periphery of the stator is cooled with water or oil to ensure that the motor performs to its full potential. Also, since the front bearing is large in size (high dmn), it is prone to heat generation, and some models employ a structure that cools the front bearing housing to prevent thermal deterioration of the lubricant and to mitigate the thermal impact around the machine tool by suppressing thermal displacement.

[0004] On the other hand, rear bearings are often not provided with a housing cooling structure because they are smaller in size (lower dmn) than front bearings and therefore generate less heat. Also, rear bearings often have a structure in the housing to absorb the thermal expansion of the shaft, making it difficult to provide a housing cooling structure.

[0005] Patent Document 1 discloses a spindle device with a built-in motor that lowers the temperature inside the spindle device by introducing external air, which has a lower temperature than the inside of the spindle device, from the outside of the spindle device through a rear space behind the rear bearing, and forming an air flow path that discharges the air from a labyrinth seal between a flinger and a housing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7070340 Summary of the Invention [Problem to be solved by the invention]

[0007] However, depending on the temperatures of the cooling water and oil, a higher temperature may transfer from the front bearing to the rear bearing due to heat conduction, resulting in a higher temperature at the rear bearing. Furthermore, in a vertical position where the rear bearing is positioned at the top, high-temperature air may move toward the top of the spindle unit, causing the rear bearing to become hotter. Therefore, even if the rear bearing generates little heat (low dmn), the rear bearing's temperature may rise depending on the cooling and mounting conditions, making it susceptible to thermal degradation in grease lubrication and potentially shortening its lifespan. The spindle unit with a built-in motor described in Patent Document 1 does not incorporate any measures for the rear bearing, leaving room for further improvement.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a spindle device with a built-in motor that has a long life and can suppress temperature rise in the rear bearing regardless of the conditions of use. [Means for solving the problem]

[0009] Therefore, the above object of the present invention is achieved by the following configuration [1] relating to a motor built-in type spindle device. [1] A rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; A motor built-in type spindle device comprising: a motor-side inner ring spacer that abuts against an axial end face of the inner ring or inner ring spacer of the rear-side bearing is disposed closer to the motor than the rear-side bearing; Between the motor-side inner ring spacer and a component with which the outer ring of the rear bearing is fitted, a gap in which negative pressure is generated is formed in the middle of a first communication passage that communicates a bearing space of the rear bearing with a motor chamber in which the motor is disposed. Spindle unit with built-in motor. [Effects of the Invention]

[0010] According to the spindle device with a built-in motor of the present invention, the temperature rise of the rear bearing can be suppressed regardless of the conditions of use, and the life of the spindle device with a built-in motor can be extended. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a spindle device with a built-in motor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a main part of FIG. [Figure 3] FIG. 3 is an enlarged view of a first modified example of the first embodiment. [Figure 4] FIG. 4 is an enlarged view of a second modified example of the first embodiment. [Figure 5] FIG. 5 is an enlarged view of a third modified example of the first embodiment. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a main part of a spindle device of a motor built-in type according to a second embodiment of the present invention. [Figure 7] FIG. 7 is an enlarged cross-sectional view of a main part of a spindle device of a built-in motor type according to a third embodiment of the present invention. [Figure 8]FIG. 8 is an enlarged cross-sectional view of a main part of a spindle device of a built-in motor type according to a fourth embodiment of the present invention. [Figure 9] FIG. 9 is an enlarged cross-sectional view of a main part of a spindle device of a motor built-in type according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of a motor built-in type spindle device according to the present invention will be described in detail with reference to the drawings.

[0013] (First embodiment) 1 and 2, in a motor-built-in type spindle unit 10 for a machine tool spindle (hereinafter also simply referred to as "spindle unit 10"), a rotating shaft 11 is rotatably supported in a housing H by four rows of front bearings 50 arranged on the tool side (left side in FIG. 1) and two rows of rear bearings 60 arranged on the side opposite to the tool (right side in FIG. 1). The housing H is mainly composed of, in order from the tool side, a front housing 12, an outer cylinder 13, a rear housing 14, and a rear cover 15, which are all fastened together with bolts (not shown).

[0014] Each front bearing 50 is an angular contact ball bearing having an outer ring 51, an inner ring 52, balls 53 as rolling elements arranged at a contact angle, and a cage (not shown), while each rear bearing 60 is an angular contact ball bearing having an outer ring 61, an inner ring 62, balls 63 as rolling elements arranged at a contact angle, and a cage (not shown). The four rows of front bearings 50 are arranged as a duplex bearing, with two rows of front bearings paired back to back with two other rows of front bearings. The two rows of rear bearings 60 are also arranged as a duplex bearing, with each other paired back to back with one another.

[0015] The outer ring 51 of the front bearing 50 is fitted into the front housing 12 and is axially positioned and fixed relative to the front housing 12 via multiple outer ring spacers 54 by a front outer ring holder 16 fixed to the front of the front housing 12.

[0016] The front housing 12 has a substantially annular cooling groove 41 between it and the cylindrical member 35 fitted thereto, through which a cooling medium (oil, water, etc. at room temperature ±0°C to +2°C) is supplied to cool the front bearing 50.

[0017] In addition, the inner ring 52 of the front bearing 50 is fitted onto the rotating shaft 11 and is axially positioned and fixed to the rotating shaft 11 via a plurality of inner ring spacers 55 by a nut 17 fastened to the rotating shaft 11.

[0018] 2, the outer ring 61 of the rear bearing 60 is fitted into the sleeve 18 which is fitted into the rear housing 14 so as to be slidable in the axial direction, and is axially positioned and fixed to the sleeve 18 via a plurality of outer ring spacers 64 by an outer ring holder 19 which is fixed integrally to the sleeve 18 with bolts (not shown). The sleeve 18 has an annular portion 18b which protrudes radially inward at the end on the motor side.

[0019] The inner ring 62 of the rear bearing 60 is fitted onto the rotating shaft 11, and is axially positioned and fixed to the rotating shaft 11 by a nut 21 fastened to the rotating shaft 11 via a plurality of inner ring spacers 65, a motor side inner ring spacer 66, and a ring member 67 to be detected of the speed sensor.

[0020] The motor side inner ring spacer 66 has a boss portion 66a that abuts against a step portion 11a of the rotating shaft 11 when fitted onto the rotating shaft 11, an outward flange portion 66b that extends radially outward from one axial end of the boss portion 66a, and a cylindrical portion 66c that extends from the outer diameter side end of the outward flange portion 66b in the same direction as the boss portion 66a, and is formed with a substantially U-shaped cross section.

[0021] The sleeve 18 is provided with an annular recess 18a that accommodates the cylindrical portion 66c of the motor-side inner ring spacer 66 and faces the outer peripheral surface, tip side surface, and inner peripheral surface of the cylindrical portion 66c with a small gap between them. A gap C of approximately 0.2 to 0.5 mm exists between the outer peripheral surface of the cylindrical portion 66c of the motor-side inner ring spacer 66 and the inner peripheral surface of the annular recess 18a of the sleeve 18.

[0022] Therefore, a first communication passage 81 is formed between the motor side inner ring spacer 66 and the sleeve 18. The first communication passage 81 passes through a U-shaped gap between the outer peripheral surface of the boss portion 66a of the motor side inner ring spacer 66 and the inner peripheral surface of the annular portion 18b of the sleeve 18, between the side surfaces of the outward flange portion 66b of the motor side inner ring spacer 66 and the annular portion 18b, and between the cylindrical portion 66c and the annular recess 18a. The first communication passage 81 connects the bearing space of the pair of rear bearings 60, 60, i.e., a bearing space 70 including the internal space of the pair of rolling bearings 60, 60 and the internal space between the outer ring spacer 64 and the inner ring spacer 65, with the motor chamber 34, which will be described later.

[0023] Furthermore, a second communication passage 82 is formed between both side surfaces of the detectable ring member 67 and the outer ring holder 19, passing through a U-shaped gap between the annular uneven portion 19a of the outer ring holder 19 and the annular uneven portion 67a of the detectable ring member 67. The second communication passage 82 connects the bearing space 70 of the pair of rear bearings 60, 60 with the rear space 45. As a result, a bearing space 70 for the pair of rear bearings 60, 60 is formed between the rotary shaft 11 and the sleeve 18, and communicates with the first communication passage 81 and the second communication passage .

[0024] The tool side of the rotating shaft 11 is provided with a tool mounting hole and internal thread (not shown) that pass through the center of the shaft and are formed in the axial direction. The tool mounting hole and internal thread are used to mount a tool (not shown) such as a cutting tool to the rotating shaft 11. Instead of the tool mounting hole and internal thread, a conventionally known draw bar (not shown) may be slidably inserted into the axial core of the rotating shaft 11. Each draw bar has a collet portion that secures a tool holder (not shown), and is biased in the direction away from the tool by the force of a disc spring.

[0025] A motor 30 is disposed approximately in the axial center between the front bearing 50 and the rear bearing 60 of the rotating shaft 11 so as to be rotatable together with the rotating shaft 11. The motor 30 includes a rotor 31 having a permanent magnet attached to its outer periphery, and a stator 32 disposed around the rotor 31. The stator 32 is fixed to the outer cylinder 13 that constitutes the housing H by fitting a cooling jacket 33, which is shrink-fitted to the stator 32, into the outer cylinder 13.

[0026] The motor 30 supplies power to the stator 32 via an electric wire to generate a rotational force in the rotor 31, thereby rotating the rotary shaft 11. The motor 30 is housed in a motor chamber 34, which is a space surrounded by the front housing 12, the outer cylinder 13, the rear housing 14, and the sleeve 18 around the rotary shaft 11.

[0027] The rear cover 15 is disposed behind the rotary shaft 11 and defines a rear space 45 together with the rear housing 14 and the sleeve 18 .

[0028] Next, the operation of the spindle unit 10 of this embodiment will be described. When the motor-side inner ring spacer 66, which has a gap C of about 0.2 to 0.5 mm between it and the annular recess 18a of the sleeve 18, rotates, the air in the vicinity is drawn along, generating negative pressure. As a result, the hot air in the bearing space 70 of the pair of rear bearings 60, 60 passes through the first communication passage 81 between the motor-side inner ring spacer 66 and the sleeve 18 and is discharged into the motor chamber 34 as shown by arrow A.

[0029] This prevents heat from building up inside the bearing space 70, mitigating the effects of thermal degradation on the grease and extending its lifespan. Furthermore, hot air generated around the rotor 31 does not enter the bearing space 70, reducing grease degradation due to hot air and extending the lifespan of the motor-built-in type spindle unit 10.

[0030] 3 to 5 show three modifications of this embodiment. 3, the motor-side inner ring spacer 66 has a cylindrical portion 66c whose outer diameter is the same as the outer diameter of the sleeve 18, and is disposed so that the inner peripheral surface of the cylindrical portion 66c overlaps in the radial direction with the outer peripheral surface of the corner cutout portion 18c of the sleeve 18. A gap C set to about 0.2 to 0.5 mm is formed between the inner peripheral surface of the cylindrical portion 66c and the outer peripheral surface of the corner cutout portion 18c.

[0031] In the modified example of Fig. 4, the motor-side inner ring spacer 66 does not have a cylindrical portion 66c, and the outer diameter of the outward flange portion 66b is the same as the outer diameter of the sleeve 18. A gap C set to about 0.2 to 0.5 mm is formed between both side surfaces of the sleeve 18 and the outward flange portion 66b.

[0032] 5, sleeve 18 does not have annular recess 18a or corner notch 18c, and the inner diameter of cylindrical portion 66c of motor-side inner ring spacer 66 is larger than the outer diameter of sleeve 18, and cylindrical portion 66c is disposed so as to overlap radially with the outer peripheral surface of sleeve 18. A gap C set to about 0.2 to 0.5 mm is formed between the inner peripheral surface of cylindrical portion 66c and the outer peripheral surface of sleeve 18.

[0033] Therefore, in either modified example, a first communication passage 81 having a gap C set to about 0.2 to 0.5 mm is formed between the motor side inner ring spacer 66 and the sleeve 18. As a result, when the motor side inner ring spacer 66 rotates, negative pressure is generated in the gap C, and the high-temperature air in the bearing space 70 is discharged through the first communication passage 81 to the motor chamber 34 in the direction of arrow A, thereby suppressing deterioration of the grease due to the hot air.

[0034] (Second embodiment) 6, in the spindle unit 10 of the present embodiment, the outer diameters of the motor-side inner ring spacer 66 of the rear bearing 60 and the inner ring spacers 65a, 65b are set to gradually increase toward the motor chamber 34. That is, the outer diameter of the boss portion 66a of the motor-side inner ring spacer 66 is larger than the outer diameter of the inner ring spacer 65a by a dimension σ, and the outer diameter of the inner ring spacer 65a between the rear bearings 60 is larger than the outer diameter of the inner ring spacer 65b on the anti-motor side by a dimension δ. As a result, the difference in centrifugal effect caused by the difference in the outer diameter of each inner ring spacer promotes the flow of air through the first communication passage 81 that connects the bearing space 70 and the motor chamber 34, effectively suppressing grease deterioration due to hot air.

[0035] (Third embodiment) As shown in FIG. 7, in the spindle unit 10 of this embodiment, the outer peripheral surfaces of the boss portions 66a of the inner ring spacers 65 of the rear bearing 60 and the motor side inner ring spacer 66 are formed in a tapered shape with a larger diameter toward the motor chamber 34 side. As a result, the difference in centrifugal effect caused by the difference in outer diameter of each inner ring spacer promotes the flow of air through the first communication passage 81 that connects the bearing space 70 and the motor chamber 34, further suppressing the deterioration of grease due to hot air.

[0036] (Fourth embodiment) 8, in the spindle unit 10 of this embodiment, the outer ring holder 19 has an annular uneven portion 19a that faces the annular uneven portion 67a of the detectable ring member 67, provided on the axial side of the sleeve 18, thereby shortening the axial length of the outer ring holder 19 and contributing to a reduction in the overall size of the spindle unit 10. Also in the second communication passage 82, there is a gap C of about 0.2 to 0.5 mm between the outer peripheral surface of the annular uneven portion 67a of the detectable ring member 67 and the inner peripheral surface of the annular uneven portion 19a of the outer ring holder 19.

[0037] In addition, the rear cover 15, rear housing 14, sleeve 18, and outer ring spacer 64 are provided with an axial flow path 84 and a radial flow path 85, which are air supply paths that extend axially and radially from an opening provided on the axial end face of the rear cover 15 and are connected to the bearing space 70.

[0038] When the rotating shaft 11, i.e., the motor side inner ring spacer 66 and the detectable ring member 67, are rotated together with the rotating shaft 11, air is supplied from the outside of the spindle device 10 to the bearing space 70 via the axial flow path 84 and the radial flow path 85, and the air is discharged by negative pressure through the first communication passage 81 in the direction of arrow A to the motor chamber 34, and also through the second communication passage 82 in the direction of arrow B to the rear space 45, thereby further suppressing deterioration of the grease due to hot air.

[0039] (Fifth embodiment) 9, in the spindle unit 10 of this embodiment, a cylindrical roller bearing 60A is applied to the rear bearing. That is, the cylindrical roller bearing 60A has an outer ring 61 fitted inside a fixed housing 14A fixed to the rear housing 14, and the cylindrical rollers 63a are allowed to move slightly in the axial direction relative to the outer ring 61. Furthermore, a counter-motor side inner ring spacer 68 is provided between the inner ring 62 of the cylindrical roller bearing 60A and the detection target ring member 67. The counter-motor side inner ring spacer 68 has a boss portion 68a, an outward flange portion 68b extending radially outward from the other axial end of the boss portion 66a, and a cylindrical portion 68c extending from the outer diameter side end of the outward flange portion 68b in the same direction as the boss portion 68a, and is formed into a generally U-shaped cross section. The cylindrical portion 68c is accommodated in the annular uneven portion 19a of the outer ring holder 19 fixed to the fixed housing 14A, forming a second communication passage 82 between the anti-motor side inner ring spacer 68 and the outer ring holder 19, and forming a gap C of approximately 0.2 to 0.5 mm between the inner surface of the annular uneven portion 19a of the outer ring holder 19 and the outer surface of the cylindrical portion 68c.

[0040] Therefore, in the spindle unit 10 of this embodiment, the first communication passage 81 is formed mainly between the motor side inner ring spacer 66 and the sleeve 18, connecting the bearing space 70 to the motor chamber 34, and the second communication passage 82 is formed mainly between the outer ring holder 19 and the anti-motor side inner ring spacer 68, connecting the bearing space 70 to the rear space 45.

[0041] Furthermore, there is a gap C of about 0.2 to 0.5 mm between the outer peripheral surface of the cylindrical portion 66c of the motor side inner ring spacer 66 and the inner peripheral surface of the annular recess 18a of the sleeve 18, and between the inner peripheral surface of the annular uneven portion 19a of the outer ring holder 19 and the outer peripheral surface of the cylindrical portion 68c, which is capable of generating negative pressure.

[0042] When the motor side inner ring spacer 66 and the anti-motor side inner ring spacer 68 rotate together with the rotating shaft 11, negative pressure is generated in the gap C, and the hot air in the bearing space 70 is discharged in the directions of arrows A and B through the first communication passage 81 and the second communication passage 82 to the motor chamber 34 and the rear space 45, thereby suppressing deterioration of the lubricant due to the hot air.

[0043] The present invention is not limited to the above-described embodiment, and can be appropriately modified, improved, etc. For example, the embodiments of the present invention can be combined within the scope of feasibility. For example, in the above embodiment, the ring portion to be detected of the speed sensor is used, but the ring member of the present invention is not limited to this and may be any other part as long as it abuts against the axial end face of the inner ring or inner ring spacer of the rear bearing and forms another gap where negative pressure is generated between it and the outer ring retainer.

[0044] As described above, the present specification discloses the following: (1) a rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; A motor built-in type spindle device comprising: a motor-side inner ring spacer that abuts against an axial end face of the inner ring or inner ring spacer of the rear-side bearing is disposed closer to the motor than the rear-side bearing; Between the motor-side inner ring spacer and a component with which the outer ring of the rear bearing is fitted, a gap in which negative pressure is generated is formed in the middle of a first communication passage that communicates a bearing space of the rear bearing with a motor chamber in which the motor is disposed. Spindle unit with built-in motor. According to this configuration, regardless of the conditions of use of the spindle device, the temperature rise of the rear bearing can be suppressed, and the effect of heat on the grease can be suppressed, thereby extending the life of the sealed grease.

[0045] (2) The motor-side inner ring spacer has a boss portion that abuts against the axial end face of the inner ring of the rear bearing or the inner ring spacer, an outward flange portion that extends radially outward from the boss portion, and a cylindrical portion that extends from an outer diameter side end of the outward flange portion in the same direction as the boss portion, a gap in which the negative pressure is generated is formed between the cylindrical portion and a component with which the outer ring of the rear bearing is fitted; A spindle device with a built-in motor as described in (1). According to this configuration, a gap in which negative pressure is generated can be easily formed between the motor-side inner ring spacer and the part in which the outer ring of the rear bearing is fitted.

[0046] (3) An outer ring holder that abuts against an axial end face of the outer ring of the rear bearing and a ring member that abuts against an axial end face of the inner ring or inner ring spacer of the rear bearing are provided on the opposite side of the motor with respect to the rear bearing, Between the outer ring holder and the ring member, another gap in which negative pressure is generated is formed in the middle of a second communication passage that communicates between the bearing space of the rear bearing and a rear space formed by the rear cover. A motor built-in type spindle device according to (1) or (2). With this configuration, it is possible to further suppress the temperature rise of the rear bearing, suppress the influence of heat on the grease, and extend the life of the sealed grease.

[0047] (4) The rear bearing includes a pair of angular contact ball bearings, a component into which the outer ring of the rear bearing is fitted is a sleeve that is fitted inside the housing and is movable in the axial direction of the rotation shaft; The motor built-in type spindle device according to any one of (1) to (3). According to this configuration, expansion and contraction of the rotary shaft due to heat can be absorbed while suppressing a temperature rise in the rear bearing.

[0048] (5) The rear bearing is a cylindrical roller bearing, The component into which the outer ring of the rear bearing is fitted is the housing. The motor built-in type spindle device according to any one of (1) to (3). According to this configuration, it is possible to suppress a temperature rise in the spindle device in which the rear bearing is a cylindrical roller bearing.

[0049] (6) An air supply path is further provided for supplying air to the bearing space from the outside of the motor built-in type spindle device. The motor built-in type spindle device according to any one of (1) to (5). According to this configuration, by supplying air from the air supply path, the temperature rise of the spindle device can be further suppressed.

[0050] (7) The rear bearing is lubricated with grease or oil. The motor built-in type spindle device according to any one of (1) to (6). This configuration can suppress the temperature rise of the grease or oil, thereby extending the lubrication life.

[0051] (8) The rotating shaft is a machine tool spindle. The motor built-in type spindle device according to any one of (1) to (7). According to this configuration, the temperature rise of the rear bearing of the machine tool spindle unit can be suppressed, the effects of heat can be suppressed, and the life of the sealed grease can be extended. can.

[0052] (9) The rotating shaft is a main shaft for a high-speed motor. A high-speed rotation device including a motor-built-in type spindle device according to any one of (1) to (7). According to this configuration, the temperature rise of the rear bearing of the high-speed motor main shaft can be suppressed, the influence of heat can be suppressed, and the life of the sealed grease can be extended. [Explanation of symbols]

[0053] 10. Spindle unit with built-in motor 11 Rotation axis 15 Rear lid 18 Sleeve (the part that the outer ring of the rear bearing fits into) 19 Outer ring holder 30 motor 31 Rotor 32 Stator 34 Motor Room 45 Rear space 50 Front bearing 60 Rear bearing 61 Outer ring 62 Inner circle 66 Motor side inner ring spacer 67 Detectable ring member (ring member) 70 Bearing space 81 1st communication passage 82 2nd communication passage C gap, other gaps H Housing

Claims

1. A rotation axis; a front bearing and a rear bearing that respectively support the rotary shaft rotatably relative to a housing; a motor including a rotor disposed between the front bearing and the rear bearing so as to be rotatable integrally with the rotary shaft, and a stator disposed around the rotor; A motor built-in type spindle device comprising: a motor-side inner ring spacer that abuts against an axial end face of the inner ring or inner ring spacer of the rear-side bearing is disposed closer to the motor than the rear-side bearing; a gap in which negative pressure is generated is formed in the middle of a first communication passage that communicates a bearing space of the rear bearing with a motor chamber in which the motor is disposed, between the motor-side inner ring spacer and a component with which the outer ring of the rear bearing is fitted; Spindle unit with built-in motor.

2. the motor-side inner ring spacer has a boss portion that abuts against an axial end face of the inner ring of the rear-side bearing or the inner ring spacer, an outward flange portion that extends radially outward from the boss portion, and a cylindrical portion that extends from an outer diameter side end of the outward flange portion in the same direction as the boss portion, a gap in which the negative pressure is generated is formed between the cylindrical portion and a component with which the outer ring of the rear bearing is fitted; 2. The motor built-in type spindle device according to claim 1.

3. an outer ring holder that abuts against an axial end face of the outer ring of the rear bearing, and a ring member that abuts against an axial end face of the inner ring or inner ring spacer of the rear bearing are provided on an anti-motor side opposite the motor with respect to the rear bearing, Between the outer ring holder and the ring member, another gap in which negative pressure is generated is formed in the middle of a second communication passage that communicates between the bearing space of the rear bearing and a rear space formed by the rear cover.

2. The motor built-in type spindle device according to claim 1.

4. the rear bearing includes a pair of angular contact ball bearings; a component into which the outer ring of the rear bearing is fitted is a sleeve that is fitted inside the housing and is movable in the axial direction of the rotation shaft; 2. The motor built-in type spindle device according to claim 1.

5. the rear bearing is a cylindrical roller bearing, The component into which the outer ring of the rear bearing is fitted is the housing.

2. The motor built-in type spindle device according to claim 1.

6. An air supply path is further provided for supplying air to the bearing space from the outside of the motor built-in type spindle device.

2. The motor built-in type spindle device according to claim 1.

7. The rear bearing is lubricated with grease or oil.

2. The motor built-in type spindle device according to claim 1.

8. The rotating shaft is a machine tool spindle. The motor built-in type spindle device according to any one of claims 1 to 7.

9. The rotating shaft is a main shaft for a high-speed motor. The motor built-in type spindle device according to any one of claims 1 to 7.

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