Spindle device

Abstract

A spindle device according to the present invention comprises: a spindle shaft; a spindle column through which the spindle shaft passes, and which rotatably supports the spindle shaft; and a sensor installed in the spindle column, and has the advantage that overheating or malfunctioning can be determined using a signal from the sensor.

Description

spindle device

[0001] The present invention relates to a spindle device, and more specifically, to a spindle device comprising a spindle shaft and a spindle column that rotatably supports the spindle shaft.

[0002] Generally, a spindle device is a device for rotating a workpiece or a tool in a machine tool, and is composed of a rotatable spindle shaft on which the tool is mounted and a spindle column that rotatably supports the spindle shaft.

[0003] The spindle shaft is connected to a drive unit, such as an electric motor, and rotates relative to the spindle column by the driving force of the drive unit, thereby rotating the tool.

[0004] Korean Patent Publication No. 10-2720535 (October 22, 2024) (hereinafter referred to as the "prior art") discloses a "fluid pressure bearing spindle."

[0005] The above prior art relates to a fluid pressure bearing spindle comprising a shaft and a housing, wherein a cylindrical bearing bushing is press-fitted into the hollow portion of the housing, and the shaft is inserted into the inner side of the bearing bushing; the housing is formed with an oil intake hole for drawing oil from an oil tank outside the fluid pressure bearing spindle and an oil passage communicating with the oil intake hole; the housing further comprises an end cover covering the motor-side end of the housing and an eccentric ring received inside the end cover while being fastened to the eccentric ring fastening portion of the shaft; a gap is formed between the outer surface of the eccentric ring and the inner surface of the end cover so that oil flows in through the oil intake hole and the oil passage, and oil from the oil tank is drawn in through the oil intake hole and the oil passage by negative pressure generated by the rotation of the eccentric ring which is fastened to the shaft and rotates; a shaft taper portion is formed on the outer surface of the shaft, and a bushing taper portion corresponding to the shaft taper portion is also formed on the inner surface of the bearing bushing. The shaft taper section and the bushing taper section are characterized by acting as a radial bearing for the vertical component of force and a thrust bearing for the horizontal component of force.

[0006] In a spindle device such as the above-mentioned prior art, a large amount of heat is generated due to friction as the shaft rotates, and in this case, the rotation of the shaft must be stopped until the generated heat cools down in order to prevent damage to the spindle.

[0007] However, the aforementioned conventional technology had a problem in that it was difficult to determine whether the heat was generated because a means for detecting the heat was not installed.

[0008] To solve the aforementioned problems, a spindle device according to the present invention is proposed as part of the development of a sensor-embedded mechanical component for predictive maintenance of mechanical equipment.

[0009] The problem that the present invention aims to solve is to provide a spindle device including a sensor for determining overheating or operational abnormalities.

[0010] The problems of the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0011] To achieve the above objective, a spindle device according to the present invention comprises a spindle shaft, a spindle column, and a sensor. The spindle shaft passes through the spindle column. The spindle column rotatably supports the spindle shaft. The sensor is installed on the spindle column.

[0012] The spindle column may be composed of a first spindle column, a second spindle column, and a sensoring. The second spindle column may be spaced axially apart from the first spindle column. The sensoring may be positioned between the first spindle column and the second spindle column. The sensor may be installed in the sensoring.

[0013] A flat surface may be formed on the outer surface of the above-mentioned sensor. The sensor may be installed on the flat surface.

[0014] An outwardly convex curved surface may be further formed on the outer surface of the sensor ring. The flat surface and the curved surface may be formed alternately in the circumferential direction. The flat surface may be formed of a plurality of flat surfaces. The curved surface may be formed of a plurality of curved surfaces. The sensor may be provided with a plurality of sensors each disposed on the plurality of flat surfaces.

[0015] In the above sensoring, axial holes that communicate with each other in the axial direction may be formed on both sides of the axial direction of the portion where the planar portion is formed.

[0016] The above axial hole can penetrate at least a portion spaced radially inward from the sensor.

[0017] In the above sensoring, axial grooves may be formed on each side in the axial direction of the portion where the planar portion is formed.

[0018] The above axial groove may extend to a portion spaced radially inward from the sensor at least.

[0019] The ratio of the sum of the depths of the axial grooves formed on each side of the axial direction of the portion where the above-mentioned planar portion is formed to the axial length of the sensor ring may be 0.8 or less.

[0020] The axial grooves formed on each side in the axial direction of the portion where the planar portion is formed may be formed as a plurality of axial grooves spaced apart from each other in a direction parallel to the planar portion.

[0021] The sensor installed on the above-mentioned planar portion may be provided as a plurality of sensors.

[0022] A radial groove may be formed in the curved portion of the sensoring above.

[0023] The radial inner surface of the above radial groove can be formed in a concave round shape.

[0024] The ratio of the depth of the radial groove to the thickness of the portion where the curved surface is formed in the sensoring may be 0.8 or less.

[0025] Specific details of other embodiments are included in the detailed description and drawings.

[0026] The spindle device according to the present invention has the effect of detecting overheating or operational abnormalities by using the signal of the sensor, since a sensor is installed in the spindle column.

[0027] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0028] FIG. 1 is a perspective view showing a spindle device according to a first embodiment of the present invention,

[0029] FIG. 2 is a rear perspective view of FIG. 1 viewed from the opposite side,

[0030] FIG. 3 is an exploded perspective view of FIG. 1,

[0031] FIG. 4 is a perspective view showing the sensing illustrated in FIG. 3,

[0032] FIG. 5 is a bottom perspective view of FIG. 4 viewed from the opposite side.

[0033] Fig. 6 is a cutaway perspective view of Fig. 4,

[0034] FIG. 7 is a perspective view showing a second embodiment of the sensing,

[0035] FIG. 8 is a rear perspective view of FIG. 7,

[0036] FIG. 9 is a cross-sectional view showing a cutaway perspective view of FIG. 7 and a part thereof,

[0037] FIG. 10 is a perspective view showing a third embodiment of the sensing,

[0038] FIG. 11 is a rear perspective view of FIG. 10,

[0039] FIG. 12 is a cutaway perspective view of FIG. 10,

[0040] FIG. 13 is a perspective view showing a fourth embodiment of the sensing,

[0041] FIG. 14 is a rear perspective view of FIG. 13,

[0042] FIG. 15 is a cross-sectional view showing the cutaway perspective view of FIG. 13 and a part thereof.

[0043] Hereinafter, a spindle device according to embodiments of the present invention will be described with reference to the drawings.

[0044] It should be noted that when assigning reference numerals to the components of each drawing, the same components are assigned the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0045] In describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc., may be used. These terms are intended merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by such terms. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0046] FIG. 1 is a perspective view showing a spindle device according to a first embodiment of the present invention, FIG. 2 is a rear perspective view of FIG. 1 viewed from the opposite side, and FIG. 3 is an exploded perspective view of FIG. 1.

[0047] In the following description, the axial direction may be the same direction as the longitudinal direction of the spindle shaft (100), and the radial direction may be the same direction as the radial direction of the spindle shaft (100).

[0048] Referring to FIGS. 1 to 3, a spindle device (1) according to one embodiment of the present invention may include a spindle shaft (100) and a spindle column (200).

[0049] The spindle shaft (100) may be formed in a straight shape having a predetermined length and may have a circular cross-section. The spindle shaft (100) may be formed as a hollow. The spindle shaft (100) may be rotatable in the circumferential direction. For example, the spindle shaft (100) may be connected to an electric motor and rotated in the circumferential direction by the driving force of the electric motor.

[0050] A tool that processes a workpiece while rotating can be coupled to the spindle shaft (100). That is, when the spindle shaft (100) rotates in a circumferential direction, the tool can process the workpiece while rotating in a circumferential direction together with the spindle shaft (100).

[0051] A spindle shaft (100) can pass through the spindle column (200). That is, the spindle shaft (100) can pass through the spindle column (200) in the longitudinal direction. The spindle column (200) can be formed in a cylindrical shape through which the spindle shaft (100) passes in the longitudinal direction.

[0052] The spindle column (200) can rotatably support the spindle shaft (100). For example, the spindle shaft (100) can be rotatably positioned relative to the spindle column (200) through bearings (310, 320).

[0053] The bearing (310, 320) may be formed as a ball bearing having a plurality of balls between the inner ring and the outer ring. The inner ring may be rotatable relative to the outer ring through the plurality of balls. The inner ring is installed on the outer surface of the spindle shaft (100) so that the spindle shaft (100) passes through it, thereby allowing the spindle shaft (100) to be rotatable relative to the spindle column (200).

[0054] The bearings (310, 320) may include a first bearing (310) disposed at one end in the longitudinal direction of the spindle column (200) and a second bearing (320) disposed at the other end in the longitudinal direction of the spindle column (200).

[0055] The first bearing (310) may be provided with a pair of first bearings (310) arranged axially with each other, and the second bearing (320) may also be provided with a pair of second bearings (320) arranged axially with each other.

[0056] A sensor (235) may be installed on the spindle column (200). The sensor (235) may be installed on the outer surface of the spindle column (200). The sensor (235) may be provided as a plurality of sensors (235) formed spaced apart from each other in the circumferential direction of the spindle column (200). However, the sensor (235) does not necessarily have to be provided as a plurality of sensors (235), and may be provided as at least one sensor (235).

[0057] Here, the sensor (235) may be a temperature sensor that detects temperature. However, the sensor (235) does not necessarily have to be a temperature sensor and may be another sensor for detecting the operation of the spindle shaft (100). That is, the sensor (235) may be a strain sensor that detects deformation, a vibration sensor that detects vibration, or a noise sensor that detects noise.

[0058] Additionally, when the sensor (235) is provided with a plurality of sensors, it may be composed of a combination of the temperature sensor, the strain sensor, the vibration sensor, and the noise sensor. That is, the sensor (235) may be provided with at least one of the temperature sensor, the strain sensor, the vibration sensor, and the noise sensor.

[0059] The detection value detected by the sensor (235) can be input to the control unit. The control unit can determine overheating using the detection value detected by the temperature sensor, determine deformation using the detection value detected by the strain sensor, and determine operational abnormalities using the detection value detected by the vibration sensor or the noise sensor.

[0060] The spindle column (200) may include a first spindle column (210), a second spindle column (220), and a sensor (230).

[0061] The first spindle column (210) and the second spindle column (220) may be spaced apart from each other in the axial direction. That is, the first spindle column (210) may be spaced apart from the second spindle column (220) in the axial direction, and the second spindle column (220) may be spaced apart from the first spindle column (210) in the axial direction.

[0062] The sensor ring (230) may be positioned between the first spindle column (210) and the second spindle column (220). A sensor (235) may be installed in the sensor ring (230). The sensor (235) may be installed on the outer surface of the sensor ring (230).

[0063] The sensoring (230) can connect between the first spindle column (210) and the second spindle column (220). The sensoring (230) can be positioned between the first spindle column (210) and the second spindle column (220) and combined with the first spindle column (210) and the second spindle column (220).

[0064] For example, the sensor ring (230) can be pressed between the first spindle column (210) and the second spindle column (220). One axial side of the sensor ring (230) can be pressed into the first spindle column (210), and the other axial side of the sensor ring (230) can be pressed into the second spindle column (220). For the press-fit, a press-fit projection and a press-fit groove may be formed on the mutually contacting surfaces of the first spindle column (210) and the sensor ring (230), and a press-fit projection and a press-fit groove may also be formed on the mutually contacting surfaces of the second spindle column (220) and the sensor ring (230). The press-fit projection may be pressed into the press-fit groove.

[0065] Below, the specific structure of the sensoring (230) will be described in detail.

[0066] FIG. 4 is a perspective view showing the sensoring illustrated in FIG. 3, FIG. 5 is a bottom perspective view of FIG. 4 viewed from the opposite side, and FIG. 6 is a cutaway perspective view of FIG. 4.

[0067] Referring to FIGS. 4 to 6, the sensor ring (230) according to the first embodiment of the present invention may be formed in a ring shape. However, a flat portion (231) may be formed on the outer surface of the sensor ring (230). The flat portion (231) may be formed as a rectangular plane.

[0068] The portion of the outer surface of the sensor ring (230) excluding the flat portion (231) may be formed as an outwardly convex curved portion (232). The curved portion (232) may be formed as a square curved surface. The curved portion (232) may be formed convexly outwardly in the radial direction of the sensor ring (230).

[0069] The entire inner surface of the sensor ring (230) can be formed as a curved surface that is concave outward in the radial direction.

[0070] The sensor (235) may be installed on the planar portion (231). The planar portion (231) may be formed with a plurality of planar portions (231). In this embodiment, the plurality of planar portions (231) is formed with four planar portions (231). However, the number of planar portions (231) may be formed with the same number as the number of sensors (235), and since the sensor (235) may be provided as at least one sensor (235), the planar portion (231) may be formed with at least one planar portion (231).

[0071] The curved portion (232) may be formed with a plurality of curved portions (232). The curved portion (232) may be formed with the same number as the flat portion (231). In this embodiment, since the flat portion (231) is formed with four flat portions (231), the curved portion (232) may be formed with four curved portions (232).

[0072] The flat portion (231) and the curved portion (232) may be formed alternately in the circumferential direction. That is, one curved portion (232) may be formed between a pair of flat portions (231) that are spaced apart from each other in the circumferential direction, and one flat portion (231) may be formed between a pair of curved portions (232) that are spaced apart from each other in the circumferential direction.

[0073] The sensor (235) may be provided as a plurality of sensors (235) each disposed on a plurality of planar portions (231). In this embodiment, since the plurality of planar portions (231) are formed as four planar portions (231), the plurality of sensors (235) may be provided as four sensors (235) each installed on one of the four planar portions (231).

[0074] Meanwhile, in order to reduce the weight of the sensor ring (230) and improve the detection capability of the sensor (235), a hole (231A, see FIGS. 4 to 6) or a groove (231B, 231C, see FIGS. 7 to 12) (232A, see FIGS. 13 to 15) may be formed in the sensor ring (230). Hereinafter, the hole (231A) or groove (231B, 231C) (232A) formed in the sensor ring (230) will be described.

[0075] In the sensoring (230), axial holes (231A) that communicate with each other in the axial direction may be formed on both sides of the axial direction of the portion where the flat portion (231) is formed. In this embodiment, since the plurality of flat portions (231) are formed as four flat portions (231), axial holes (231A) may be formed in each of the portions where the four flat portions (231) are formed in the sensoring (230), thereby forming four axial holes (231A).

[0076] The sensor ring (230) can have its weight reduced by the space of the axial hole (231A). Additionally, the sensor ring (230) can have elasticity due to the axial hole (231A), so that noise generation of the sensor (235) due to vibration or external pressure can be reduced, thereby improving the detection capability of the sensor (235).

[0077] Additionally, the axial hole (231A) can penetrate a portion spaced radially inward from the sensor (235). Therefore, since heat, vibration, and noise introduced through the axial hole (231A) pass through a portion adjacent to the sensor (235), the detection capability of the sensor (235) for the heat, vibration, and noise can be improved.

[0078] However, if an axial hole (231A) is formed in the sensor ring (230), the weight of the sensor ring (230) can be reduced and the detection capability of the sensor (235) can be improved, but the problem of the rigidity of the sensor ring (230) being somewhat reduced may occur. Therefore, if it is implemented in the form of a groove instead of an axial hole (231A), the weight of the sensor ring (230) can be reduced, the detection capability of the sensor (235) can be improved, and the rigidity of the sensor ring (230) can also be secured. Hereinafter, an embodiment implemented in the form of a groove instead of an axial hole (231A) will be described with reference to FIGS. 7 to 15.

[0079] FIG. 7 is a perspective view showing a second embodiment of the sensoring, FIG. 8 is a rear perspective view of FIG. 7, and FIG. 9 is a cutaway perspective view of FIG. 7 and a longitudinal section showing a part thereof. Here, the same reference numerals are assigned to components identical to the sensoring (230) according to the first embodiment of the present invention described above, so a detailed description thereof is omitted, and only the differences are described.

[0080] Referring to FIGS. 7 to 9, it can be seen that the sensoring (230-2) according to the second embodiment of the present invention is different from the sensoring (230) according to the first embodiment of the present invention described above.

[0081] That is, in the sensor ring (230) according to the first embodiment of the present invention described above, axial holes (231A) that communicate with each other in the axial direction are formed on both sides of the axial direction of the part where the flat portion (231) is formed, but in the sensor ring (230-2) according to the second embodiment of the present invention, axial grooves (231B, 231C) may be formed on each side of the axial direction of the part where the flat portion (231) is formed.

[0082] The axial grooves (231B, 231C) can be formed to be relatively long in a direction parallel to the planar portion (231) and relatively short in the radial direction of the sensoring (230-2), which is perpendicular to the planar portion (231).

[0083] The axial grooves (231B, 231C) may include a first axial groove (231B) formed on one axial side of the portion where the flat portion (231) of the sensor ring (230-2) is formed, and a second axial groove (231C) formed on the other axial side of the portion where the flat portion (231) of the sensor ring (230-2) is formed.

[0084] The first axial groove (231B) and the second axial groove (231C) can be separated from each other by a partition plate (236) formed at a position spaced radially inward from the center of the sensor (235). That is, the axial grooves (231B, 231C) can extend to at least a portion spaced radially inward from the sensor (235). Accordingly, heat, vibration, and noise, etc. introduced through the axial grooves (231B, 231C) can be introduced to a portion adjacent to the sensor (235), thereby improving the detection capability of the sensor (235) for the heat, vibration, and noise, etc.

[0085] As described above, it is preferable that the minimum depth of the axial groove (231B, 231C) extends to a portion spaced radially inward from the sensor (235).

[0086] The ratio ((H1+H2) / L) of the sum of the depths (H1+H2) of the axial grooves (231B, 231C) formed on each side of the axial direction of the part where the flat portion (231) of the sensor ring (230-2) is formed, and the axial length (L) of the sensor ring (230-2) may be 0.8 or less.

[0087] If the above ratio ((H1+H2) / L) is greater than 0.8, the rigidity of the sensor ring (230-2) may be reduced, so it is preferable that the above ratio ((H1+H2) / L) be 0.8 or less.

[0088] As described above, the maximum depth of the axial grooves (231B, 231C) is preferably such that the ratio ((H1+H2) / L) is 0.8.

[0089] FIG. 10 is a perspective view showing a third embodiment of the sensoring, FIG. 11 is a rear perspective view of FIG. 10, and FIG. 12 is a cutaway perspective view of FIG. 10. Here, the same reference numerals are assigned to components identical to the sensoring (230-2) according to the second embodiment of the present invention described above, so a detailed description thereof is omitted, and only the differences are described.

[0090] Referring to FIGS. 10 to 12, it can be seen that the sensoring (230-3) according to the third embodiment of the present invention is different from the sensoring (230-2) according to the second embodiment of the present invention described above.

[0091] That is, in the sensor ring (230-2) according to the second embodiment of the present invention described above, one axial groove (231B, 231C) is formed on each side of the portion where the flat portion (231) is formed, but in the sensor ring (230-3) according to the third embodiment of the present invention, three axial grooves (231B, 231C) can be formed on each side of the portion where the flat portion (231) is formed.

[0092] That is, the axial grooves (231B, 231C) formed on each side in the axial direction of the portion where the planar portion (231) is formed in the sensoring (230-3) according to the third embodiment of the present invention may be formed as a plurality of axial grooves (231B, 231C).

[0093] A plurality of axial grooves (231B, 231C) of the sensor ring (230-3) according to the third embodiment of the present invention may be formed such that their length in the direction parallel to the planar portion (231) is shorter than that of the axial grooves (231B, 231C) of the sensor ring (230-3) according to the second embodiment of the present invention described above. A plurality of axial grooves (231B, 231C) of the sensor ring (230-3) according to the third embodiment of the present invention may be formed spaced apart from each other in the direction parallel to the planar portion (231).

[0094] FIG. 13 is a perspective view showing a fourth embodiment of the sensoring, FIG. 14 is a rear perspective view of FIG. 13, and FIG. 15 is a cutaway perspective view of FIG. 13 and a longitudinal section showing a part thereof. Here, the same reference numerals are assigned to components identical to the sensoring (230) according to the first embodiment of the present invention described above, so a detailed description thereof is omitted, and only the differences are described.

[0095] Referring to FIGS. 13 to 15, it can be seen that the sensoring (230-4) according to the fourth embodiment of the present invention is different from the sensoring (230) according to the first embodiment described above.

[0096] That is, in the first embodiment of the sensoring (230) described above, one sensor (235) is installed in one planar section (231), so a total of four sensors (235) are installed in four planar sections (231), but in the fourth embodiment of the sensoring (230-4) according to the present invention, a plurality of sensors (235) may be installed in one planar section (231). Specifically, in the fourth embodiment of the sensoring (230-4) according to the present invention, two sensors (235) are installed in one planar section (231), so a total of eight sensors (235) may be installed in four planar sections (231).

[0097] Additionally, the sensoring (230) according to the first embodiment described above has axial holes (231A) formed on both sides of the axial direction of the portion where the flat portion (231) is formed, which are axially interconnected, whereas the sensoring (230-4) according to the fourth embodiment of the present invention may have radial grooves (232A) formed on the curved portion (232).

[0098] Since the curved portion (232) is formed with four curved portions (232), one radial groove (232A) is formed on each of the four curved portions (232), so a total of four radial grooves (232A) can be formed in the sensoring (230-4) according to the fourth embodiment of the present invention.

[0099] The sensoring (230-4) according to the fourth embodiment of the present invention can reduce weight by the volume of the radial groove (232A), and since the radial groove (232A) has elasticity, noise generation of the sensor (235) due to vibration or external pressure can be reduced, thereby improving the detection capability of the sensor (235).

[0100] The radial inner surface of the radial groove (232A) can be formed in a concave round shape.

[0101] The ratio (H3 / T) of the depth (H3) of the radial groove (232A) and the thickness (T) of the portion (232) of the sensor ring (230-4) where the curved portion (232) is formed may be 0.8 or less. Of course, since the radial groove (232A) must be formed in the curved portion (232) so that the sensor ring (230-4) has elastic force, the ratio (H3 / T) must be greater than 0. If the ratio (H3 / T) is greater than 0.8, there may be a problem where the sensor ring (230-4) is elastically deformed by vibration or external pressure transmitted to the sensor ring (230-4) and then fails to recover and breaks; therefore, it is preferable that the ratio (H3 / T) be 0.8 or less.

[0102] As described above, the spindle device according to the embodiments of the present invention can detect overheating or operational abnormalities by using the signal from the sensor (235) because the sensor (235) is installed in the spindle column (200).

[0103] A person skilled in the art to which the present invention pertains will understand that the present invention may be implemented in other specific forms without altering its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included within the scope of the present invention.

[0104] <Explanation of Symbols>

[0105] 1 : Spindle device 100 : Spindle shaft

[0106] 200: Spindle column 210: First spindle column

[0107] 220: 2nd spindle column 230, 230-2, 230-3, 230-4: Sensoring

[0108] 231 : Planar section 231A : Axial hole

[0109] 231B, 231C: Axial grooves 232: Curved surface

[0110] 232A: Radial groove 235: Sensor

Claims

1. Spindle shaft; A spindle column through which the spindle shaft passes and which rotatably supports the spindle shaft; and A spindle device comprising a sensor installed on the spindle column.

2. In Claim 1, The above spindle column is, The first spindle column and, A second spindle column spaced axially from the first spindle column, and It includes a sensoring disposed between the first spindle column and the second spindle column, and The above sensor is a spindle device installed in the above sensing ring.

3. In Claim 1, A flat portion is formed on the outer surface of the above-mentioned sensoring, and The above sensor is a spindle device installed on the above-described plane.

4. In Claim 3, An outwardly convex curved surface is further formed on the outer surface of the sensoring above, and The above planar portion and the above curved portion are formed alternately in the circumferential direction, the planar portion is formed of a plurality of planar portions, and the above curved portion is formed of a plurality of curved portions. The above sensor is a spindle device comprising a plurality of sensors each disposed in the plurality of planar portions.

5. In Claim 3, The above-described sensoring is a spindle device in which axial holes are formed on both sides of the axial direction of the portion in which the planar portion is formed, and which communicate with each other in the axial direction.

6. In Claim 5, The above-mentioned axial hole is a spindle device that penetrates a portion spaced radially inward from the sensor.

7. In Claim 3, The above-described sensoring includes a spindle device in which axial grooves are formed on each side in the axial direction of the portion in which the planar portion is formed.

8. In Claim 7, The above-mentioned axial groove is a spindle device that extends to a portion spaced radially inward from the sensor.

9. In Claim 8, A spindle device in which the ratio of the sum of the depths of the axial grooves formed on each side in the axial direction of the portion in which the above-mentioned planar portion is formed to the axial length of the sensor ring is 0.8 or less.

10. In Claim 7, A spindle device in which the axial grooves formed on each side of the axial direction of the portion in which the planar portion is formed are formed as a plurality of axial grooves spaced apart from each other in a direction parallel to the planar portion.

11. In Claim 3, The sensor installed on the above-mentioned planar portion is a spindle device equipped with a plurality of sensors.

12. In Claim 3, The above-described sensoring includes a spindle device in which a radial groove is formed on the curved surface.

13. In Claim 12, A spindle device in which the radial inner surface of the above radial groove is formed in a concave round shape.

14. In Claim 12, A spindle device in which the ratio of the depth of the radial groove to the thickness of the portion in which the curved surface is formed during the sensing is 0.8 or less.

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