Rotor component, axis of rotation, rotor, motor and machine tool

Abstract

Rotor element (300, 300A) fitted on a rotary axis (200) which rotates about an axial center of the rotary axis, wherein the rotor element (300, 300A) comprises the following: a sleeve (301) comprising an inner circumferential surface (304) which is pressed in with respect to an outer circumferential surface (202) of the axis of rotation (200); and a rotor component that is mounted on an outer circumferential surface (305) of the sleeve (301), wherein the inner circumferential surface (304) of the sleeve (301) comprises a tapered surface (306) having a diameter whose taper varies along the axial center, and the tapered surface (306) has a corrugated surface structure that retains a lubricant and is configured to wear down by pressing in the rotor component (300, 300A) with respect to the axis of rotation (200); characterized by the fact that the surface structure is formed by subjecting the tapered surface (306) to an oxidation treatment.

Description

Background of the invention; Field of the invention

[0001] The present invention relates to a rotor component, a rotary axis and a rotor for a motor which uses a wedge sleeve, and a motor which includes the rotor, and a machine tool which includes the motor. General state of the art

[0002] In a rotor for a motor comprising a rotating shaft and a sleeve mounted on an outer circumferential surface of the rotating shaft, the sleeve must be firmly attached to the rotating shaft so that the position of the sleeve relative to the rotating shaft is not deflected during rotation of the rotor. In this respect, a rotor is known in which an inner circumferential surface of the sleeve is press-fitted to the outer circumferential surface of the rotating shaft, so that the rotating shaft and the sleeve are integrated together (see, for example, JP 2013-9528A and JP H11-89142A).

[0003] In JP 2013-9528A, the outer circumferential surface of the pivot shaft and the inner circumferential surface of the sleeve each have a tapered shape. When the sleeve is mounted on the pivot shaft, a lubricant is applied to the outer circumferential surface of the pivot shaft, and the pivot shaft is pressed in along the inner circumferential surface of the sleeve. In JP H11-89142A, on the other hand, an oil channel is formed in the sleeve, and high-pressure oil is introduced through the oil channel into a section facing the inner circumferential surface of the sleeve. The hydraulic pressure caused by the high-pressure oil temporarily increases the inner diameter of the sleeve, thus fitting the sleeve onto the pivot shaft.

[0004] In the rotor disclosed in JP 2013-9528A, as previously described, the lubricant is located on the mating surfaces of the axis of rotation and the sleeve. This reduces the frictional force between the axis of rotation and the sleeve, and allows the sleeve to be deflected relative to the axis of rotation during rapid rotation. Furthermore, in the rotor disclosed in JP H11-89142A, as previously described, a separate hydraulic device must be provided to apply hydraulic pressure to the inner circumferential surface of the sleeve, increasing manufacturing costs. Additionally, the formation of the oil channel in the sleeve reduces the sleeve's strength.

[0005] A generic teaching is disclosed in DE 10 2012 011 913 A1. Further prior art is disclosed in US 2003 / 0 201 683 A1 and JP 2000 - 245 086 A. Brief description of the invention

[0006] One embodiment of the present invention relates to a rotor element with the features of claim 1, which is fitted to a rotational axis rotating about an axial center of the rotational axis, wherein the rotor element comprises: a sleeve comprising an inner circumferential surface that is pressed in with respect to an outer circumferential surface of the rotational axis; and a rotor component that is mounted on an outer circumferential surface of the sleeve. The inner circumferential surface of the sleeve comprises a tapered surface having a diameter whose taper varies along the axial center, and the tapered surface has a corrugated surface structure that retains a lubricant and is configured to wear down by pressing in the rotor element with respect to the rotational axis.

[0007] Another embodiment of the present invention relates to a rotary axis with the features of claim 3, which rotates about an axial center of the rotary axis and comprises the following: an outer circumferential surface which is pressed in with respect to an inner circumferential surface of a cylindrical rotor element, wherein the outer circumferential surface comprises a tapered surface having a diameter the taper of which varies along the axial center, and the tapered surface has a corrugated surface structure which retains a lubricant and is configured to wear down by pressing in the rotary axis with respect to the rotor element.

[0008] Yet another embodiment of the present invention relates to a rotor with the features of claim 5, comprising: an axis of rotation which rotates about an axial center of the axis of rotation; and a rotor element comprising an inner circumferential surface onto which an outer circumferential surface of the axis of rotation fits.The outer circumferential surface of the rotary axis and the inner circumferential surface of the rotor element comprise corresponding tapered surfaces, each having a diameter whose taper varies along the axial center, the tapered surfaces being in full contact with each other while the outer circumferential surface of the rotary axis is pressed in with respect to the inner circumferential surface of the rotor element, and at least one of the tapered surfaces of the rotary axis and the tapered surface of the rotor element having a corrugated surface structure that retains a lubricant before the rotary axis is pressed in with respect to the rotor element, being configured to wear down as the rotary axis is pressed in with respect to the rotor element in order to release the lubricant.

[0009] Yet another embodiment of the present invention relates to a motor according to claim 11, comprising the above rotor.

[0010] Yet another embodiment of the present invention relates to a machine tool according to claim 12, which includes the above motor. Brief description of the drawings

[0011] They show: Fig. 1 a cross-sectional view of a motor according to an embodiment of the present invention. Fig. 2 a cross-sectional view of a rotation axis, as in Fig. 1 shown. Fig. 3 a cross-sectional view of a rotor component, as in Fig. 1 shown. Fig. 4 an external view of the rotor component, as shown in Fig. Figure 1 shows a view from an axial direction. Fig. 5 a cross-sectional view of a sleeve, as in Fig. 3 shown. Fig. 6. A perspective view of a magnet, as in Fig. 3 shown. Fig. 7 a perspective view of a holding element, as in Fig. 3 shown. Fig. 8 A cross-sectional view to describe a press-in step for pressing the rotor component into the axis of rotation. Fig. 9 a cross-sectional view showing the rotor after the pressing step. Fig. 10 a cross-sectional view in which the rotor is schematically shown in its completed state. Fig. 11 a diagram showing a change in Fig. 1 depicts. Fig. 12 A cross-sectional view of a rotor used for a motor in Fig. 11 is used. Fig. 13 a diagram illustrating a schematic configuration of a machine tool to which the motor is applied according to the embodiments of the present invention. Detailed description

[0012] The embodiments of the present invention are described below with reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12 to Fig. 13 described. First, a configuration of a motor according to the embodiments of the present invention is described. Fig. Figure 1 is a cross-sectional view of a motor 100 according to an embodiment of the present invention. A direction along an axial center O1 of a rotation axis of the motor 100 is defined as the axial direction, a direction along a circumferential surface of a circle around the axial center O1 is defined as the circumferential direction, and a direction extending radially from the axial center O1 is defined as the radial direction. Furthermore, as shown in the drawings, one side and the other side of the motor 100 are defined as axially front and axially rear, respectively. It should be noted that axially front and axially rear are defined accordingly for ease of understanding and not to restrictively specify a particular direction, such as in front of or behind the motor.

[0013] Fig. Figure 13 is a diagram illustrating an example of a machine tool to which the motor 100 is applied according to the embodiments of the present invention. As shown in Fig. Figure 13 shows, for example, the machine tool 500 is a horizontal machining center and comprises a base 501, a column 502 standing on the base 501, a main shaft 503 provided on the column 502, and a table 504 on which a workpiece 510 is placed, in which a tool 505 is mounted on the main shaft 503. It should be noted that in Fig. 13 a horizontal direction parallel to an axis of rotation of the main shaft 503 is defined as the Z-axis, a perpendicular direction of the axis of rotation is defined as the Y-axis, and a horizontal direction orthogonal to both the Z-axis and the Y-axis is defined as the X-axis, and an X-axis direction, a Y-axis direction and a Z-axis direction are each indicated by an arrow.

[0014] The main shaft 503 is moved in the Y-axis direction by a drive via a feed spindle and the column 502 in the Z-axis direction by a drive via a feed spindle. The table 504 is moved in the X-axis direction by a drive via an X-axis motor and a feed spindle. The motor 100 according to this embodiment is an integrated motor used to drive the main shaft 503 of the machine tool 500. One function of the integrated motor is to be mounted directly in a rotating object, namely the main shaft 503, and to drive the main shaft 503 directly. The motor for driving the main shaft of the machine tool 500 is configured as an integrated motor, as described above, so that the machining accuracy of the main shaft 503 can be improved.

[0015] As in Fig. As shown in Figure 1, the motor 100 comprises a housing 102 that defines an interior 101, a stator 110 that is statically arranged in the interior 101 of the housing 102, and a rotor 400 that is rotatably provided on a radially inner side of the stator 110. A plurality of magnets 311 (see Figure 1) are also provided. Fig. 6) is mounted on a surface of the rotor 400, and the motor 100 is a surface magnet motor (surface permanent magnet (SPM) motor). The stator 110 comprises a stator lamination stack 103 and a coil 104 wound around the stator lamination stack 103. For example, thin plates, which are electromagnetic steel sheets, are stacked on top of each other to form the stator lamination stack 103.

[0016] A power line (not shown), electrically connected to the coil 104, is drawn from the stator 110 and connected to a power source (not shown) located outside the motor 100 through a through-hole provided in the housing 102. During operation of the motor 100, for example, three-phase current is supplied to the coil 104, and a rotating magnetic field forms around the rotor 400.

[0017] The rotor 400 comprises a rotary axis 200 extending axially into the interior 101, and a rotor element 300 attached to a radially outer side of the rotary axis 200. The motor 100 generates rotational power through magnetic interaction between the rotor 400 and the stator 110, and the rotary axis 200 and the rotor element 300 rotate together around the axial center O1.

[0018] The rotor element 300 is attached to an outer circumferential surface of the axis of rotation 200 by pressing it in. This pressing is accomplished by axially moving the rotor element 300 relative to the axis of rotation 200. In other words, while the axis of rotation 200 is stationary, the rotor element 300 is moved axially; or while the rotor element 300 is stationary, the axis of rotation 200 is moved axially; or both the axis of rotation 200 and the rotor element 300 are moved axially, each performing the pressing action. Hereinafter, the pressing-in process, as described above, will be referred to uniformly as "pressing the axis of rotation 200 into the rotor element 300".

[0019] Next, the axis of rotation is defined according to the embodiments of the present invention with reference to Fig. 2 described. Fig. Figure 2 is a cross-sectional view of the axis of rotation 200 according to this embodiment. As in Fig. As shown in Figure 2, the axis of rotation 200 is a cylindrical element formed around the axial center O1 and comprising an inner circumferential surface 201 and an outer circumferential surface 202. Since, according to this embodiment, the motor 100 is configured as a built-in motor used for the main shaft 503 of the machine tool 500, the axis of rotation 200 is cylindrical, which is not a limiting factor. In other words, the axis of rotation 200 can be formed as a solid element.

[0020] The rotary shaft 200 is made of an iron-based metal, such as an iron-based material including S45C, STKM, SS, SCM, and SNCM. The axial center O1 of the rotary shaft 200 is an axial center of a rotary shaft of the motor 100. An axially front side section of the rotary shaft 200 is rotatably supported by the housing 102 via a bearing (not shown) mounted on a wall section on a front side of the housing 102. Similarly, an axially rear side section of the rotary shaft 200 is rotatably supported by the housing 102 via a bearing (not shown) mounted on a wall section on a rear side of the housing 102.

[0021] The outer circumferential surface 202 of the axis of rotation 200 includes a tapered surface 203 formed around the axial center O1. The tapered surface 203 has a diameter that gradually increases from an axially rearward side toward an axially frontward side. An axially frontal side section 205 of the outer circumferential surface 202 and a stepped section 204 are examples of a contact section provided for practical reasons during manufacturing. The tapered surface 203 extends continuously over a predetermined axial length from a taper initiation section 206 to the stepped section 204. A cylindrical surface 207, extending linearly along the axial direction, is formed on the outer circumferential surface 202 behind the taper initiation section 206.

[0022] It should be noted that the tapered surface 203 is preferably a linearly tapered surface, i.e., a conical surface. In this case, the radius of the tapered surface 203 increases linearly from the initial taper section 206 towards the offset section 204. The tapered surface 203 is preferably a linearly tapered surface having a taper ratio of, for example, 1 / 200 to 1 / 30.

[0023] The contact section 205 and the recessed section 204 are examples of a design to facilitate assembly during manufacturing. The contact section 205 has a cylindrical outer circumferential surface extending along the axial direction and is shaped such that it projects radially outwards from the tapered surface 203, thereby forming the recessed section 204 between the contact section 205 and the tapered surface 203.

[0024] Next, the rotor component according to the embodiments of the present invention is described with reference to Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 described. Fig. Figure 3 is a cross-sectional view of the rotor component 300 according to this embodiment, and Fig. 4 is an external view (view in the direction of arrow IV in Fig. 3 seen) of the rotor element 300, viewed from the axial direction. As in Fig. 3 and Fig. As shown in Figure 4, the rotor element 300 comprises a cylindrical sleeve 301, a plurality of magnets 311 arranged such that they are circumferentially aligned, and a retaining element 321 that radially covers the entire plurality of magnets 311 from the outside.

[0025] The magnets 311 are permanent magnets, each having an inner diameter side that forms a circular arc along an outer circumferential surface 305 of the sleeve 301, i.e., the magnets each have a partially cylindrical shape. In an example from Fig. In Figure 4, four of the magnets 311 are arranged circumferentially at regular intervals along the outer circumferential surface 305 of the sleeve 301. It should be noted that a different number of magnets 311 than that of the magnets 311 in the example from Fig. 4 can be arranged circumferentially. In other words, the number of magnets 311 can be other than four, as long as the plurality of magnets 311 is arranged circumferentially symmetrically.

[0026] Given the manufacturing and magnet formation conditions, the magnets 311 can be axially divided into several parts, and in an example from Fig. 3. The magnets 311 are axially divided into two parts. It should be noted that the division into three or more parts can occur in the axial direction. Furthermore, the magnets 311, which are positioned on the axially rear side, are arranged in corresponding positions axially aligned by providing the sleeve 301 with a structure, such as a projecting section 307. For example, neodymium magnets with high magnetic energy can be used as magnets 311. This allows for a compact and powerful motor, and its use for the main shaft 503 of the machine tool 500 is suitable. The magnets 311 are preferably held firmly on the outer circumferential surface 305 of the sleeve 301 such that they do not slide, at least in the circumferential direction, and can be attached, for example, using an adhesive.

[0027] Fig. Figure 5 is a cross-sectional view of sleeve 301. As in Fig. Figure 5 shows that the sleeve 301 is a cylindrical element formed around the axial center O2 and comprises a first end section 302 on the axially rear side, a second end section 303 on the axially front side, and an inner circumferential surface 304 and an outer circumferential surface 305 extending along the axial direction. The projecting section 307 at an axially rear end of the sleeve 301, which extends radially outward from the outer circumferential surface 305, is an example of a design to facilitate the alignment of the positions of the magnets 311 in the axial direction during manufacturing.

[0028] The sleeve 301 is made of an iron-based metal, such as an iron-based material including S45C, STKM, SS, SCM, and SNCM. The inner circumferential surface 304 of the sleeve 301 includes a tapered surface 306 formed around the axial center O2. The tapered surface 306 has a diameter that gradually increases from the axially rearward side toward the axially forward side. From the first end section 302 to the second end section 303, the tapered surface 306 extends continuously over at least one axial portion (magnet mounting portion) in which the magnets 311 are mounted on the outer circumference. In other words, the tapered surface 306 is a tapered surface formed in the magnet mounting portion of the inner circumferential surface of the sleeve 301 and has a continuous and constant taper ratio and a radius that increases axially forward.

[0029] The tapered surface 306 is a linearly tapered surface with a constant taper ratio. The radius of the tapered surface 306 increases linearly from the first end section 302 towards the second end section 303, increasing from a radius R1 of the tapered surface 306 at the first end section 302 to a radius R2 (>R 1 ) of the tapered surface 306 at the second end section 303. The tapering ratio of the tapered surface 306 is preferably set in a range of, for example, 1 / 200 to 1 / 30.

[0030] The taper of the tapered surface 306 is adjusted such that it corresponds to the taper of the tapered surface 203 of the axis of rotation 200. More precisely, if the tapered surface 203 of the axis of rotation 200 and the tapered surface 306 of the sleeve 301 are each linearly tapered surfaces, the tapered surface 203 and the tapered surface 306 are adjusted such that they have an identical or substantially identical taper ratio (e.g., 1 / 100).

[0031] If the engine is 100, as in Fig. As shown in Figure 1, when assembled, the sleeve 301 is press-fitted onto the tapered surface 203 of the axis of rotation 200, such that the axial center O1 of the axis of rotation 200 and the axial center O2 of the sleeve 301 coincide. In this state, the second end section 303 of the sleeve 301 and the stepped section 204 come into contact with each other, and the radius R2 of the tapered surface 306 at the second end section 303 and the radius of the tapered surface 203 at a front end are equal or substantially equal.

[0032] Furthermore, in this state, the tapered surface 306 of the sleeve 301 and the tapered surface 203 of the axis of rotation 200 are in full contact with each other under high surface pressure, and the sleeve 301 is pressed by the axis of rotation 200 towards a radially outer side. It should be noted that a mounting structure for the sleeve 301 on the axis of rotation 200 will be described later.

[0033] Fig. Figure 6 is a perspective view of one of the magnets 311. As in Fig. As shown in Figure 6, each magnet 311 is a circular arc-shaped magnetic segment having an inner diameter of a predetermined radius of curvature. Specifically, each magnet 311 comprises an end surface 312 on the axially front side, an end surface 313 on the axially rear side, an end surface 314 at one end in the circumferential direction, an end surface 315 at the other end in the circumferential direction, an inner circumferential surface 316 on the radially inner side, and an outer circumferential surface 317 on the radially outer side. The inner circumferential surface 316 of each magnet 311 has a circular arc shape (constant curvature), whereas the outer circumferential surface 317 consists of an optionally curved surface having a circular arc shape or a shape other than a circular arc shape, a plane, or a combination of a curved surface and a plane.

[0034] In an example from Fig. Figure 6 shows end surfaces 312, 313, 314, and 315 as examples of embodiments. However, depending on the circumstances, such as the magnetic circuit design and the motor specifications, the end surfaces may be curved surfaces or minimal surfaces in contact with a tapered or curved surface. Therefore, in practice, the end surfaces are not always clearly defined. Additionally, the sides forming each surface are often chamfered or gently inclined towards a curved surface and are thus not always bounded by clear lines.

[0035] Fig. Figure 7 is a perspective view of the retaining element 321. As in Fig. Figure 7 shows that the retaining element 321 is a cylindrical element extending axially and has the function of surrounding the plurality of magnets 311 in order to hold the magnets 311. In particular, the retaining element 321 comprises an end surface 322 on the axially front side, an end surface 323 on the axially rear side, a cylindrical inner circumferential surface 324, and an outer circumferential surface 325. In an example from Fig. Figure 7 clearly shows the end surfaces 322 and 323 as examples of the embodiments; however, the end surfaces are not always clearly visible depending on the material, structure, and manufacturing process of the retaining element. Furthermore, the cross-sectional shape of the inner circumferential surface 324 and the outer circumferential surface 325 is not limited to a circle.

[0036] The retaining element 321 exhibits high resistance to deformation, such as expansion in the radially outer direction. In other words, the retaining element 321 has a radius (diameter) that is difficult to vary. Additionally, to prevent heat generation due to magnetic flux and power reduction due to magnetic flux leakage, the retaining element 321 is preferably made of a non-magnetic material. Furthermore, the retaining element 321 preferably has a low density to reduce centrifugal force generated by rotation. The retaining element 321 consists, for example, of a cylindrical body. It should be noted that the material forming the retaining element 321 can be wound around the outer circumferential surface 317 of each of the plurality of magnets 311, thereby forming the retaining element 321.For example, a thread-like, belt-like or arc-like material can be wound several times around the outer circumferential surface 317 of each magnet 311, surrounding it in a direction of rotation, before a predetermined thickness is achieved by which it is formed.

[0037] Suitable materials for the retaining element 321 include those with excellent specific strength (tensile strength per unit density), such as carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, boron fiber, titanium alloy fiber, extremely high molecular weight polyethylene fiber, or polybutylene terephthalate fiber. Furthermore, suitable materials for the retaining element 321 include a resin-reinforced fiber (FRP) that utilizes carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, boron fiber, titanium alloy fiber, extremely high molecular weight polyethylene fiber, or polybutylene terephthalate fiber, or composite materials combining several of these materials. Finally, a non-magnetic metal, such as austenitic stainless steel, titanium, or a titanium alloy, can be used as the material for the retaining element 321.

[0038] The retaining element 321 is attached to the radially outer side of the plurality of magnets 311 such that it surrounds each magnet 311 from the radially outer side, and when the motor 100 is assembled as shown in Fig. As shown in Figure 1, the sleeve 301 is pressed towards the radially outer side by the axis of rotation 200. This pressing forces the sleeve 301 to deform towards the radially outer side, which in turn forces each magnet 311 towards the radially outer side. On the other hand, as previously described, the retaining element 321 exhibits high resistance to deformation, such as expansion towards the radially outer side. Consequently, the pressure exerted by the magnets 311 is received, and as a counterforce, the magnets 311 are pressed back towards the radially inner side.

[0039] This configuration allows the magnets 311 to be firmly inserted between the sleeve 301 and the retaining element 321. Therefore, when the rotor element 300 rotates at high speed while the motor 100 is driven, this prevents the magnets 311 from moving (so-called slippage) circumferentially with respect to the sleeve 301 and the retaining element 321.

[0040] An oversize of the retaining element 321 is set such that the clamping torque between the sleeve 301 and the axis of rotation 200 and the clamping torque between the magnets 311 and the sleeve 301 exceed the maximum torque of the motor 100 across the entire speed range that the motor 100 can achieve. This ensures that the clamping torque between the axis of rotation 200 and the sleeve 301 and the clamping torque between the sleeve 301 and the magnets 311 exceeds the maximum torque of the motor 100 regardless of the motor 100's speed. Consequently, the occurrence of positional displacement between the axis of rotation 200 and the sleeve 301 and between the sleeve 301 and the magnets 311 can be prevented while the motor 100 is driven.

[0041] Furthermore, to prevent positional displacement of the rotor element 300 (sleeve 301) with respect to the axis of rotation 200 during the rotation of the motor 100, a sufficient interference fit must be provided between the axis of rotation 200 and the sleeve 301. In this respect, fitting the axis of rotation 200 and the sleeve 301 together via the tapered surfaces 203 and 306, as in the present embodiment, provides a sufficient interference fit compared to insertion by expansion. However, if press-fitting via the tapered surfaces 203 and 306 is used, the interference fit increases as the press-fit amount increases, and the contact area of ​​the tapered surfaces 203 and 306 increases such that the press-fit load increases during the insertion of the axis of rotation 200 into the rotor element 300.Consequently, deformation of an axial end surface of the rotary axis 200 and an axial end surface of the sleeve 301, upon which a pressing load is exerted by a pressing device, can occur, as can twisting and bending of the rotary axis 200, and the like. Furthermore, in order to generate a large pressing load, a large-format pressing device must be provided, and therefore the manufacturing costs increase.

[0042] To reduce the applied pressing load, a method is considered in which a lubricant is applied to the mating surfaces of the rotary axis 200 and the sleeve 301 (the outer circumferential surface 202 of the rotary axis 200 and the inner circumferential surface 304 of the sleeve 301) to reduce the frictional force on the mating surfaces during the press fit. When a lubricant is applied to the mating surfaces, the frictional force on the mating surfaces during rotation of the motor 100 is reduced such that rotation of the rotor element 300 with respect to the rotary axis 200 can occur.

[0043] On the other hand, another method for reducing the pressing load is considered, in which an oil channel is formed from the first end section 302 towards the inner circumferential surface 304 in the preceding section 307 of the sleeve 301, high-pressure oil is introduced through the oil channel onto the inner circumferential surface 304 during pressing, and the inner diameter of the sleeve 301 is temporarily increased by the hydraulic pressure. However, in order to apply hydraulic pressure to the inner circumferential surface of the sleeve 301 according to this method, a hydraulic device must be provided, and therefore the manufacturing costs increase. Furthermore, the formation of the oil channel in the sleeve 301 leads to a reduction in the strength of the sleeve.

[0044] In order to reduce the pressing load during the pressing of the rotary axis 200 into the rotor element 300 in this embodiment, and thereby increase a fastening torque of the rotor element 300 with respect to the rotary axis 200, and to prevent a positional displacement of the rotor element 300 with respect to the rotary axis 200 during the rotation of the motor 100, the rotor 400 is configured as follows.

[0045] The tapered surface 203 of the rotary axis 200 and the tapered surface 306 of the sleeve 301 each have a corrugated surface structure that retains a lubricant. This surface structure is achieved, for example, by subjecting the tapered surfaces 203 and 306 to a chemical oxidation treatment. The chemical oxidation treatment is based on phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid, and the like. Since, in this embodiment, the rotary axis 200 and the sleeve 301 are both made of an iron-based metal, an oxidation coating treatment based on phosphoric acid, sulfuric acid, or hydrochloric acid is preferably carried out, and, more specifically, an oxidation coating treatment based on manganese phosphate is particularly preferred.

[0046] When the manganese phosphate-based phosphate coating treatment is applied to the tapered surfaces 203 and 306, fine phosphate crystals, ranging in size from several micrometers to several dozen micrometers, are deposited onto these surfaces. This results in a fine unevenness on the tapered surfaces 203 and 306, increasing the surface area of ​​each. When a lubricant is applied to each of the tapered surfaces 203 and 306 while the axis of rotation 200 and the rotor element 300 are separated, the lubricant can be advantageously retained due to the surface unevenness. This formation of the corrugated surface structure on each of the tapered surfaces 203 and 306 allows for an increase in the amount of lubricant per unit area.Consequently, the coefficient of friction decreases when the axis of rotation 200 is pressed into the rotor component 300, thus reducing the pressing load.

[0047] When the rotary axis 200 is pressed into the rotor component 300 (sleeve 301), the tapered surfaces 203 and 306 slide against each other, causing wear on each surface structure. It should be noted that each surface structure can not only wear but also deform. Surface pressure between the tapered surfaces 203 and 306 then causes the lubricant, which has a certain degree of fluidity, to be gradually forced axially outwards. After the pressing process is complete, the lubricant is drained, the tapered surfaces 203 and 306 are in full contact with each other, and the coefficient of friction between them increases.This increases the frictional force between the tapered surfaces 203 and 306 such that the fastening torque between the sleeve 301 and the axis of rotation 200 increases, which prevents a displacement of the position of the rotor element 300 with respect to the axis of rotation 200 during the rotation of the motor 100.

[0048] When the tapered surface 306 of the sleeve 301 is subjected to phosphate treatment, the entire sleeve is preferably immersed in a treatment solution, and the entire surface of the sleeve 301 is preferably exposed to the phosphate treatment. In other words, if the area of ​​surface treatment is limited, masking and the like are necessary, whereas if the surface treatment is carried out on the entire sleeve, the work for masking and the like is eliminated, and the surface treatment can be performed effortlessly. Furthermore, not only the tapered surface 305 of the sleeve 301 but also the outer circumferential surface 305 is subjected to phosphate treatment, so that the adhesive force during the attachment of the magnets 311 to the outer circumferential surface 305 of the sleeve 301 can also be improved by an adhesive agent.

[0049] The corrugated surface structure can be configured to include a multitude of depressions that store a lubricant and wall sections surrounding each depression. The depth and diameter of each depression are preferably several µm to 100 µm or less, more preferably 60 µm or less. In this case, since the tapered surfaces 203 and 306 slide during the pressing in of the rotary axis 200, the wall sections of the surface structure gradually wear down, and the lubricant gradually flows out of the depressions. This provides a lubricating effect during the pressing-in process and reduces the pressing load. After the pressing-in process is complete, the wall sections wear down, increasing the contact area, while surface pressure between the tapered surfaces 203 and 306 causes the lubricant to be forced out of them.As a result, the tapered surfaces 203 and 306 are in full contact with each other, while the coefficient of friction between the tapered surfaces 203 and 306 increases, so that the fastening torque between the sleeve 301 and the axis of rotation 200 increases.

[0050] Each depression can be formed, for example, similarly to the dimples of golf balls. It should be noted that, unlike golf balls, the shape and size of each depression need not be uniform. In other words, each depression can have a shape other than a sphere and a curved surface, and can consist of a bottom surface with a flat or curved top and a wall surface. Furthermore, the top view of each depression need not be circular. The depressions can be formed in such a way that a surface of a honeycomb structure is covered by a plane. It should be noted that hexagonal depressions need not be precisely aligned but can be configured arbitrarily, as long as they contain spaces, each deep enough to retain a lubricant, and wall sections to divide each space.The surface structure exhibiting such depressions and wall sections can be achieved by performing a chemical surface treatment or a blasting treatment on the tapered surfaces 203 and 306. The blasting treatment includes, for example, sandblasting and matting.

[0051] It should be noted that the corrugated surface structure can be provided on either the tapered surface 203 of the rotary axis 200 or the tapered surface 306 of the sleeve 301. For example, the corrugated surface structure can be provided only for the tapered surface 203 or only for the tapered surface 306. If at least one of the tapered surface 203 of the rotary axis 200 and the tapered surface 306 of the sleeve 301 has the corrugated surface structure, which retains a lubricant, the coefficient of friction between the tapered surfaces 203 and 306 can be reduced during press-fitting and increased after press-fitting.

[0052] Furthermore, in this embodiment, the tapered surface 203 of the rotary axis 200 is subjected to heat treatment or surface treatment, such that the tapered surface 203 of the rotary axis 200 is harder than the tapered surface 306 of the sleeve 301. The heat treatment or surface treatment is preferably carried out when only the tapered surface 306 of the sleeve 301 has the corrugated surface structure. If the tapered surfaces slide against each other when the surface hardness is low and the surface pressure is high, grooving, cracking, or deposition of the tapered surfaces, or the like, can occur. Increasing the surface hardness of the rotary axis 200 makes it possible to prevent this. It should be noted that, since the diameter of the sleeve 301 increases during the pressing in of the rotary axis 200, increasing the hardness causes a crack in the sleeve 301.Therefore, increasing the surface hardness of the rotary axis 200, rather than the sleeve 301, is preferred through heat treatment or surface treatment.

[0053] Heat treatment includes local heat treatment, such as induction hardening, carburizing, vacuum carburizing, and laser hardening. Carburizing is particularly suitable for press-fitting because increasing the carbon content improves sliding properties. Surface treatment includes electroplating or nitriding. For example, hard chrome plating is particularly suitable because it smooths the surface while increasing surface hardness. Similarly, nitriding is particularly suitable because it increases surface hardness while improving surface sliding properties. It should be noted that materials with different hardnesses can be used for the corresponding rotary axis 200 and sleeve 301, so the tapered surface 203 of the rotary axis 200 is harder than the tapered surface 306 of the sleeve 301.For example, the sleeve 301 can be made of SS400, and the rotary axis 200 can be made of SCM435 or SNCM630, and in this case the heat treatment and surface treatment on the tapered surface 203 can be omitted.

[0054] Next, a manufacturing process for the rotor 400 according to the embodiments of the present invention is described. First, the sleeve 301 is prepared. The sleeve 301 is obtained as follows. For example, an inner circumferential surface and an outer circumferential surface of a cylindrical element made of an iron-based metal are subjected to a cutting process, forming the tapered surface 306 and the outer circumferential surface 305, forming the aforementioned section 307. Subsequently, the tapered surface 306 is subjected to oxidation treatment, blasting treatment, or the like, providing the entire tapered surface with the corrugated surface structure having a height of approximately several dozen µm. The entire sleeve is immersed in a phosphoric acid-based treatment solution, and the tapered surface 306 and the outer circumferential surface 305 of the sleeve 301 are subjected to phosphate treatment (e.g., phosphating).B. a manganese phosphate treatment) so that the surface structure is achieved.

[0055] Furthermore, the magnets 311 and the retaining element 321 are prepared. Each magnet 311 is produced by configuring a permanent magnet in which the inner circumferential surface 316 has a substantially circular arc shape with a predetermined radius of curvature. The retaining element 321 is produced, for example, by a carbon fiber-reinforced resin formed into a cylindrical shape.

[0056] Next, the plurality of magnets 311 are arranged at equal intervals along the outer circumferential surface 305 of the sleeve 301. In this case, the magnets 311 are arranged such that the magnets 311 that lie next to each other circumferentially each have different inner circumferential magnetic poles and different outer circumferential magnetic poles. For example, if four of the magnets 311A ​​to 311D are arranged circumferentially, the magnets 311A ​​and 311B, 311B and 311C, 311C and 311D, and 311D and 311A ​​are arranged next to each other. Now, the magnets 311A ​​to 311D are arranged such that an inner circumferential side of the magnets 311A ​​and 311C is an S-pole and an outer circumferential side of the same is an N-pole, while an inner circumferential side of the magnets 311B and 311D is an N-pole and an outer circumferential side of the same is an S-pole.In other words, the magnets 311A ​​to 311D are arranged circumferentially to face the outer circumferential surface 305 of the sleeve 301, so that the corresponding magnetic poles alternate in the circumferential direction.

[0057] Next, an adhesive is impregnated between the sleeve 301 and the multiple opposing magnets 311 before the retaining element 321 is mounted such that it covers the multiple magnets 311 on its radially outer side. In other words, the retaining element 321 is fitted to the radially outer side of each magnet 311 such that the inner circumferential surface 324 of the retaining element 321 faces the outer circumferential surface 317 of each magnet 311. Both can now be fitted by a loose fit or an interference fit to a certain degree. If an interference fit is used, a slight interference is sufficient to prevent the retaining element 321 from falling off.

[0058] The adhesive is impregnated over the entire area between the outer circumferential surface 305 of the sleeve 301 and the inner circumferential surface of each magnet 311, or at least over a portion of this area. The adhesive cannot be impregnated before the magnets 311 are surrounded by the retaining element 321, but only after the magnets 311 are surrounded by the retaining element 321. If the magnets 311 are arranged along the outer circumferential surface 305 of the sleeve 301, the adhesive can be applied to at least one area between the outer circumferential surface 305 of the sleeve 301 and the inner circumferential surface 316 of each magnet 311.

[0059] Next, the rotary axis 200 will be prepared, as shown in Fig. Figure 2 shows the rotation axis 200 being achieved as follows. For example, an outer circumferential surface of a cylindrical rod element undergoes a cutting process to form the tapered surface 203. The cylindrical outer circumferential surface 207 and the contact section 205 can be provided at the front and rear of the tapered surface 203, respectively, as required. Subsequently, the tapered surface 203 undergoes oxidation or blasting treatment, which imparts the corrugated surface structure to the entire tapered surface, which has a height of approximately several dozen µm.Instead of providing the tapered surface 203 with the corrugated surface structure, or while providing the surface structure, the tapered surface 203 can be subjected to a heat treatment, such as hardening, or a surface treatment, such as electroplating and nitriding, so that the tapered surface 203 of the rotary axis 200 is harder than the tapered surface 306 of the sleeve 301. For example, if the sleeve 301 is made of SS400 and the rotary axis 200 is made of SCM435 or SNCM630, the rotary axis 200 is harder than the sleeve 301. In this case, the heat treatment and surface treatment of the tapered surface 203 can be omitted.

[0060] Next, the rotor component 300 is fitted into the axially rear side of the rotary axis 200 before the adhesive cures. In other words, the rotary axis 200 and the rotor component 300 are pressed together. The pressing-in step will be described in more detail later. Fig. 8 and Fig. Figure 9 contains diagrams describing the pressing-in step. As shown in Fig. As shown in Figure 8, the sleeve 301 of the rotor component 300 is first fitted to an axially rear end of the axis of rotation 200 from one side of the second end section 303.

[0061] In this case, for example, at the axis of rotation 200, an end surface (not shown) on an axially second side (front side) of the axis of rotation 200 is held in the direction of an axially first side (rear side), while the end section 302 (protruding section 307) of the sleeve 301 of the rotor element 300 is pushed. In other words, the rotor element 300 is pushed axially forward, as indicated by arrow E in Fig. Figure 8 shows that this brings an axially forward end of the tapered surface 306 of the sleeve 301 and the tapered surface 203 of the axis of rotation 200 into contact at a contact section P.

[0062] From this state, the rotor element 300 is pushed further towards the axially forward side with respect to the axis of rotation 200. In particular, a pressing load is exerted on an end surface of the protruding section 307 of the sleeve by the pressing device to push the rotor element 300 towards the axially forward side until the second end section 303 of the sleeve 301 reaches a predetermined position, e.g., comes into contact with the offset section 204 of the contact section 203, as illustrated in an example in the drawing. This presses the axis of rotation 200 into the rotor element 300. Since the protruding section 307 has a radial thickness, a pressing load is exerted on the end surface of the protruding section 307, thereby allowing a release of surface pressure with respect to the pressing load.

[0063] When the rotary axis 200 is pressed into the sleeve 301, the tapered surfaces 203 and 306 slide against each other, causing each surface structure to wear down. It should be noted that each surface structure can not only wear down but also deform. When the surface structures are worn, the tapered surfaces 203 and 306 are in full contact with each other, and a frictional force between them increases. Meanwhile, surface pressure between the tapered surfaces 203 and 306 causes the lubricant, which has a certain degree of fluidity, to be gradually forced out axially.

[0064] During the pressing in of the rotary axis 200, the sleeve 301 moves axially forward along the tapered surface 306 from the contact section P to the offset section 204 and expands radially outward. In other words, the rotor element 300 is press-fitted to the rotary axis 200 in this state. It should be noted that the sleeve 301 can deform beyond its elastic deformation range in this state. While pressed into a predetermined position, the sleeve 301 is forced radially outward, and the magnets 311 also move radially outward accordingly. Consequently, a radially outward pressing force acts on the retaining element 321, and the retaining element 321 also expands radially outward.

[0065] This creates an elastic compressive force in the retaining element 3121, and this elastic compressive force pushes the magnets 311 and the sleeve 301 between the tapered surface 203 of the rotary axis 200 and the retaining element 321. In this case, the magnets 311 are attached to the outer circumferential surface 305 of the sleeve 301 by pressure (surface pressure) exerted between each of the contact surfaces, while the tapered surface 306 of the sleeve 301 is attached to the tapered surface 203 of the rotary axis 200.

[0066] In the manner described above, the rotor 400 is used, as shown in Fig. 9 shown, manufactured. Fig. Figure 10 is a cross-sectional view showing the rotor 400 schematically completed. When the rotor 400 is completed, there is no lubricant between the tapered surfaces 203 and 306, and the tapered surfaces 203 and 306 are in full contact with each other, resulting in a large frictional force between them. Consequently, the clamping torque between the sleeve 301 and the axis of rotation 200 increases, preventing displacement of the rotor element 300 relative to the axis of rotation 200 during rotation of the motor 100.

[0067] According to the present embodiment, the following effects can be achieved. (1) The rotor assembly 300 comprises: the sleeve 301, which includes the inner circumferential surface 304 pressed in with respect to the outer circumferential surface 202 of the axis of rotation 200; and the magnets 311, which are mounted on the outer circumferential surface 305 of the sleeve 301. The inner circumferential surface 304 of the sleeve 301 includes the tapered surface 306, which has a diameter whose taper varies along the axial center O2, and the tapered surface 306 has a corrugated surface structure that retains a lubricant and is configured to wear down by the pressing in of the rotor assembly 300 with respect to the axis of rotation 200.Furthermore, the rotary axis 200 includes the outer circumferential surface 202, which is pressed in with respect to the inner circumferential surface 304 of the rotor element 300 (sleeve 301), the outer circumferential surface 202 includes the tapered surface 203, which has a diameter whose taper varies along the axial center O1, and the tapered surface 203 has a corrugated surface structure that stores a lubricant and is configured to wear down by pressing in the rotary axis 200 with respect to the rotor element 300.

[0068] This reduces the frictional force between the rotor element 300 and the rotary axis 200 during the pressing-in of the rotary axis 200 with respect to the rotor element 300, and reduces the pressing load, so that the rotary axis 200 can be pressed into the rotor element 300 without difficulty. Furthermore, the reduced pressing load allows a universal pressing device to be used during the pressing-in process, and a large interference fit can be achieved without special equipment. Additionally, deformation in sections (end surface of the aforementioned section 307 and the like) that are points of application of force in the rotary axis 200 and the sleeve 301 can be avoided, as can twisting and bending of the rotary axis 200.

[0069] Furthermore, after the rotary axis 200 is pressed into the rotor element 300, the surface structures of the corresponding tapered surfaces 203 and 306 wear down to such an extent that a frictional force between the rotor element 300 and the rotary axis 200 increases. Consequently, a displacement of the rotor element 300 relative to the rotary axis 200 during rapid rotation of the rotor 400 can be prevented. In other words, if, for example, a lubricant with high viscosity or a solid lubricant, such as molybdenum dioxide, is used for the tapered surfaces 203 and 306, its lubricating effect is maintained even after pressing. Thus, the rotor element 300 slides relative to the rotary axis 200, so that no torque suitable for the motor 100 can be generated.In contrast, with this embodiment, a lubricating effect does not remain after pressing in, so that the rotor element 300 does not slide with respect to the axis of rotation 200 and a torque suitable for the motor 100 can be generated.

[0070] (2) Such finely corrugated surface structures for releasing the lubricant by wear can be easily formed by subjecting the tapered surfaces 203 and 306 to an oxidation treatment or a shot blasting treatment.

[0071] (3) If the sleeve 301 and the pivot axis 200 are made of an iron-based metal, the use of a phosphate coating treatment as an oxidation treatment coating is particularly effective in reducing the coefficient of friction between the tapered surfaces 203 and 306 during the pressing process and increasing the coefficient of friction after the pressing process is completed.

[0072] (4) The rotor 400 comprises: the axis of rotation 200, which rotates about the axial center O1; and the rotor element 300, which comprises the inner circumferential surface 304, onto which the outer circumferential surface 202 of the axis of rotation 200 fits.The outer circumferential surface 202 of the rotary axis 200 and the inner circumferential surface 304 of the rotor element 300 comprise corresponding tapered surfaces 203 and 306, each having a diameter whose taper varies along the axial center O1, wherein the tapered surfaces 203 and 306 are in full contact with each other while the outer circumferential surface 202 of the rotary axis 200 is pressed in with respect to the inner circumferential surface 304 of the rotor element 300, and at least one of the tapered surfaces 203 and 306 has a corrugated surface structure that retains a lubricant before the rotary axis 200 is pressed in with respect to the rotor element 300, being configured to wear down by the pressing in of the rotary axis 200 with respect to the rotor element 300 in order to release the lubricant.This prevents an increase in the pressing load during the pressing in of the rotary axis 200, and ensures a desired fastening torque between the rotary axis 200 and the rotor element 300 after completion of the pressing, thus preventing the rotor element 300 from rotating with respect to the rotary axis 200.

[0073] (5) If the rotary shaft 200 is made of an iron-based metal, and the tapered surface 203 of the rotary shaft 200 is subjected to heat treatment or surface treatment such that the tapered surface 203 is harder than the tapered surface 306 of the rotor element 300, the surface hardness of the rotary shaft 200 is increased, and grooving, cracking, deposition, and the like of surface defects during the pressing in of the rotary shaft 200 can be prevented. In this case, the hardness of the sleeve 301 is no greater than necessary, and cracking and the like of the sleeve 301 can be prevented when the sleeve 301 is stretched due to the pressing in of the rotary shaft 200.

[0074] (6) The fact that the tapered surface 203 of the axis of rotation 200 is subjected to electroplating or nitriding as a surface treatment is advantageous because the surface is smoothed, while the surface hardness can be increased. If the tapered surface 203 of the axis of rotation 200 is subjected to hardening as a heat treatment, the surface is similarly smoothed, while the surface hardness can be increased.

[0075] (7) The rotor element 300 further comprises: the plurality of magnets 311 arranged along the outer circumferential surface 305 of the sleeve 301; and the cylindrical retaining element 321 surrounding the plurality of magnets 311, wherein the sleeve 301 and the plurality of magnets 311 are inserted between the axis of rotation 200 and the retaining element 321 by an elastic restoring force in the direction of a radially inner side, which is generated in the retaining element 321 by pressing the axis of rotation 200 into it with respect to the rotor element 300. When the rotor element 300 rotates at a high speed, circumferential movement of the magnets 311 with respect to the sleeve 301 and the retaining element 321 can be prevented.

[0076] (8) When the magnets 311 are mounted on the outer circumferential surface 305 of the sleeve 301, the fact that the outer circumferential surface 305 is subjected to a phosphate coating treatment makes it possible to increase the adhesive force during the attachment of the magnets 311 to the outer circumferential surface 305 by means of an adhesive. If the outer circumferential surface 305 and the tapered surface 306 of the sleeve 301 are both subjected to a phosphate coating treatment, this can readily be done by immersing the entire sleeve in a treatment solution.

[0077] (9) In this embodiment, the rotor 400 has a sufficient oversize of the rotor element 300 so that the rotor element 300 does not slip with respect to the axis of rotation 200, and the rotor 400 can rotate at a high speed. Thus, the maximum number of rotations of the motor 100, which includes the rotor 400, can be increased, and the power output of the motor 100 can be increased.

[0078] (10) The use of the motor 100 for the machine tool 500 enables an improvement in the processing and production performance of the machine tool 500. If the motor 100 is a built-in motor to drive the main shaft of the machine tool 500, the operation of pressing in the rotary axis 200 with respect to the rotor element 300 is performed by a user who is a purchaser of the motor, and thus the efficiency of the operating processes is particularly important. In this respect, the rotor 400, in this embodiment, can prevent an increase in the pressing load and thus has excellent operational efficiency.

[0079] It should be noted that in the above embodiments, the magnets 311 and the sleeve 301 are attached to one another by an adhesive, but this adhesive can be omitted. In the above embodiments, the plurality of magnets 311 is surrounded by the retaining element 321, but the other cylindrical element can be arranged around the retaining element 321. This protects joint sections at the end sections of the retaining element 321 from flaking off due to wind pressure during the rotation of the rotor 400, and extends the service life of the rotor 400.

[0080] In the above embodiments, the magnets 311 are mounted on the outer circumferential surface of the sleeve 301, but the magnets 311 can be replaced by a rotor component. Thus, the motor to which the rotor is applied need not be a surface magnet motor (SPM motor) but a different type of motor. Fig. Figure 11 is a cross-sectional view (view seen parallel to the axial center O1) of a motor, illustrating an example where a 400A rotor is applied to a 100A induction motor, and Fig. Figure 12 is a cross-sectional view (view perpendicular to the axial center O1) of the rotor 400A, which is in the motor 100A in Fig. 11 is included. In Fig. 11 and Fig. 12 are parts similar to those in Fig. 1 and Fig. 10 with similar reference symbols.

[0081] The 100A motor in Fig. 11 and Fig. The 12 differs from the 100 engine in Fig. 1 and Fig. 10 in the rotor 400A, in particular through a configuration of the rotor component 300A. In other words, as in Fig. 11 and Fig. As shown in Figure 12, the 100A motor comprises a rotor lamination stack 331, a plurality of feed rails 332 and a pair of end rings 333 in place of the magnets 331 and the retaining element 321.

[0082] The rotor lamination stack 331 consists of a layered body in which a plurality of electromagnetic steel sheets are stacked one above the other along the axial center O1. The feed rails 332 are arranged circumferentially at regular intervals and adjacent to an outer circumferential surface of the rotor lamination stack 331 along the axial center O1. The end rings 333 are arranged adjacent to both the front and rear end surfaces of the rotor lamination stack 331, which are connected to the end sections of each feed rail 332, and enable the two ends of each feed rail 332 to be electrically short-circuited.

[0083] In the above embodiments, the motor 100 is applied to the machining center in a horizontal manner ( Fig.13), however, it can be similarly applied to a vertical machining center and other machine tools, and the configuration of the machine tool is not limited to the above description. Furthermore, examples are described in the above embodiments in which the rotor element 300 and the rotor 400 are applied to the motor to drive the main shaft of the machine tool, but the rotor element and the rotor according to the present invention can similarly be applied not only to the motor for the machine tool but also to other motors. Furthermore, the rotor element and the rotor according to the present invention can similarly be applied to other rotating electrical machines besides the motor. Effects of the invention

[0084] According to the present invention, at least one of the tapered surfaces of the corresponding rotor component and the axis of rotation has a corrugated surface structure that retains a lubricant. This reduces the frictional force between the rotor component and the axis of rotation during the pressing of the axis of rotation into the rotor component, allowing the axis of rotation to be pressed into the rotor component without difficulty. Furthermore, after the axis of rotation has been pressed into the rotor component, the surface structures of the corresponding tapered surfaces wear down, increasing the frictional force between the rotor component and the axis of rotation and preventing displacement of the rotor component relative to the axis of rotation during rapid rotor rotation.

Claims

Rotor element (300, 300A) fitted on a rotary axis (200) which rotates about an axial center of the rotary axis, wherein the rotor element (300, 300A) comprises: a sleeve (301) comprising an inner circumferential surface (304) which is pressed in with respect to an outer circumferential surface (202) of the rotary axis (200); and a rotor component mounted on an outer circumferential surface (305) of the sleeve (301), wherein the inner circumferential surface (304) of the sleeve (301) comprises a tapered surface (306) having a diameter whose taper varies along the axial center, and the tapered surface (306) has a corrugated surface structure which retains a lubricant and is configured to wear down by pressing in the rotor component (300, 300A) with respect to the axis of rotation (200); characterized in that the surface structure is formed by subjecting the tapered surface (306) to an oxidation treatment. Rotor element (300, 300A) according to claim 1, wherein the sleeve (301) is made of an iron-based metal, and the oxidation treatment is a phosphate coating treatment. A rotary axis (200) rotating about an axial center of the rotary axis, comprising: an outer circumferential surface (202) pressed in with respect to an inner circumferential surface (304) of a cylindrical rotor element (300, 300A), wherein the outer circumferential surface (202) comprises a tapered surface (203) having a diameter whose taper varies along the axial center, and the tapered surface (203) has a corrugated surface structure which retains a lubricant and is configured to wear down by the pressing in of the rotary axis (200) with respect to the rotor element (300); characterized in that the surface structure is formed by subjecting the tapered surface (306) to an oxidation treatment. axis of rotation according to claim 3, wherein the axis of rotation (200) is made of an iron-based metal, and the oxidation treatment is a phosphate coating treatment. Rotor (400, 400A), comprising: a rotational axis (200) which rotates about an axial center of the rotational axis; and a rotor element (300, 300A) comprising an inner circumferential surface (304) onto which an outer circumferential surface (202) of the axis of rotation (200) fits, wherein the outer circumferential surface (202) of the axis of rotation (200) and the inner circumferential surface (304) of the rotor element (300, 300A) comprise corresponding tapered surfaces (203, 306) each having a diameter whose taper varies along the axial center, wherein the tapered surfaces (203, 306) are in full contact with each other, while the outer circumferential surface (202) of the axis of rotation (200) is pressed in with respect to the inner circumferential surface (304) of the rotor element (300, 300A), and at least one of the tapered surface (203) of the axis of rotation (200) and the tapered surface (306) of the rotor element (300, 300A) has a corrugated surface structure which stores a lubricant,before the rotary axis (200) is pressed in with respect to the rotor element (300, 300A), wherein it is configured to wear down by pressing in the rotary axis (200) with respect to the rotor element (300, 300A) in order to release the lubricant; characterized in that the surface structure is formed by subjecting the tapered surface (306) to an oxidation treatment. Rotor (400, 400A) according to claim 5, wherein the axis of rotation (200) is made of an iron-based metal, and the tapered surface (203) of the axis of rotation (200) is harder than the tapered surface (306) of the rotor element (300, 300A). Rotor (400, 400A) according to claim 6, wherein the tapered surface (203) of the axis of rotation (200) is subjected to electroplating or nitriding treatment. Rotor (400, 400A) according to claim 6, wherein the tapered surface (203) of the axis of rotation (200) is subjected to heat treatment. Rotor (400, 400A) according to one of claims 5 to 8, wherein the rotor element (300, 300A) further comprises: a sleeve (301); a plurality of magnets (311) arranged along an outer circumferential surface (305) of the sleeve (301); and a cylindrical retaining element (321) surrounding the plurality of magnets (311), wherein the sleeve (301) and the plurality of magnets (311) are inserted between the axis of rotation (200) and the retaining element (321) by an elastic restoring force in the direction of a radially inner side, which is generated in the retaining element (321) by pressing the axis of rotation (200) in with respect to the rotor element (300, 300A). Rotor (400, 400A) according to claim 9, wherein the outer circumferential surface (305) of the sleeve (301) is subjected to a phosphate coating treatment. Motor comprising the rotor (400, 400A) according to one of claims 5 to 10 . Machine tool (100, 100A) comprising the motor according to claim 11.

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