Motor

Abstract

Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) which has the following features: a stationary section (2A; 2) comprising a stator (23A; 23); and a rotating section (3A; 3; 3C; 3E) which is supported in such a way as to be rotatable about a central axis (9A; 9) which extends in a vertical direction with respect to the stationary section (2A; 2) and which includes a shaft (31A; 31; 31D) which is arranged to extend along the central axis (9A; 9); wherein the stationary section (2A; 2) includes the following features: a bearing (24A; 24; 24D) arranged to rotatably support the shaft (31A; 31; 31D); and a base section (20A; 20) arranged to hold the stator (23A; 23); The rotating section (3A; 3; 3C; 3E) includes the following features: a rotor hub section (32A; 32; 32B; 32C; 32D; 32F) which is arranged to extend in an annular shape around the shaft (31A; 31; 31D); a magnet (34A; 34) which is attached directly or indirectly to the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) and is arranged opposite the stator (23A; 23); a flywheel (35A; 35; 35B; 35C; 35E) arranged axially above the rotor hub section (32A; 32; 32B; 32C; 32D; 32F); and a sealing section (60A; 60; 60B; 60C) arranged to have a lesser thickness than the magnet (34A; 34); at least part of an outer circumferential surface of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) is a metal surface (340A; 340; 340B); The metal surface (340A; 340; 340B) has a higher reflectivity than an outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E) and a surface of the sealing section (60A; 60; 60B; 60C); and the metal surface (340A; 340; 340B) is covered with the sealing section (60A; 60; 60B; 60C).

Description

[0001] The present invention relates to a motor.

[0002] A motor for use in a DLP single-chip projector (DLP = Digital Light Processing) is described in JP 2005-278309A. In this projector, light emitted from a light source passes through a color wheel that rotates with the motor. The light passing through the color wheel is converted into light in one of the RGB bands. This light strikes a digital micromirror element, and the light reflected from the digital micromirror element is then directed onto a predetermined screen to display an image. Further motors for use in digital cameras are known from JP 2006-129607A and US 2013 / 0214621A1.

[0003] In addition, a motor with a stator and a rotor with magnets is known from JP 2000 - 132 906 A, wherein a flywheel is mounted axially above the rotor.

[0004] The object of the present invention is to create a motor with improved characteristics.

[0005] This problem is solved by a motor according to claim 1.

[0006] In the case of a motor used in a device that manipulates light, such as the motor described in JP 2005-278309A, reflection of light emitted from a light source by an outer surface of the motor can cause scattering. Such scattering causes noise in the output light intended to be emitted from the device. In particular, in the motor described in JP 2005-278309A, a rotor hub surface is made of a metallic material. Therefore, light emitted from the light source and reflected by the metallic surface of the rotor hub tends to cause slight scattering.

[0007] The present invention was designed to reduce the reflection of light through an outer circumferential surface of a rotating section of a motor.

[0008] A motor according to a preferred embodiment of the present invention comprises a stationary section, which includes a stator; and a rotating section, which is supported to be rotatable about a central axis extending in a vertical direction with respect to the stationary section and which includes a shaft arranged to extend along the central axis. The stationary section includes a bearing arranged to rotatably support the shaft and a base section arranged to hold the stator.The rotating section comprises a rotor hub section arranged to extend around the shaft in an annular shape; a magnet attached directly or indirectly to the rotor hub section and positioned opposite the stator; a flywheel arranged axially above the rotor hub section; and a sealing section arranged to have a thinner profile than the magnet. At least a portion of an outer circumferential surface of the rotor hub section is a metallic surface. The metallic surface has a higher reflectivity than an outer circumferential surface of the flywheel and a surface of the sealing section. The metallic surface is covered by the sealing section.

[0009] The preferred embodiment of the present invention described above is capable of reducing the reflection of light by an outer circumferential surface of the rotating section. Furthermore, since the sealing section has a small thickness, the center of gravity of the rotating section can be maintained radially inwards, thus enabling stable rotation.

[0010] The above and further elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings. These show: Fig. 1 a vertical sectional view of a motor according to a first preferred embodiment of the present invention; Fig. 2 a vertical sectional view of a motor according to a second preferred embodiment of the present invention; Fig. 3 a vertical partial sectional view of the motor according to the second preferred embodiment; Fig. 4 a vertical partial sectional view of the motor according to the second preferred embodiment; Fig. 5 a vertical sectional view of a bearing according to the second preferred embodiment; Fig. 6 a bottom view of a bushing according to the second preferred embodiment; Fig. 7 a vertical sectional view of a motor according to a modification of the second preferred embodiment; Fig. 8 a vertical partial sectional view of a motor according to a modification of the second preferred embodiment; Fig. 9 a vertical partial sectional view of a motor according to a modification of the second preferred embodiment; Fig. 10 a vertical sectional view of a motor according to a modification of the second preferred embodiment; and Fig. 11 a vertical sectional view of a motor according to a modification of the second preferred embodiment.

[0011] Motors according to preferred embodiments of the present invention are described below. It is assumed here that a direction parallel to a central axis of a motor is designated as the "axial direction" or "axial," that directions perpendicular to the central axis of the motor are each designated as the "radial direction" or "radial," and that a direction extending along a circular arc centered on the central axis of the motor is designated as the "circumferential direction" or "circumferential...". It is further assumed here that an axial direction is a vertical direction, that a side on which a flywheel is arranged with respect to a rotor hub section is a top side, and that the shape of each component or section and the relative positions of various components or sections are described based on the above assumptions.However, it should be noted that the above definitions of the vertical direction and the top and bottom are not intended to restrict in any way the orientation of a motor according to any preferred embodiment of the present invention at the time of manufacture or in use.

[0012] Fig. Figure 1 is a vertical sectional view of a motor 1A according to a first preferred embodiment of the present invention. With reference to Fig. In section 1, the motor 1A comprises a rotating section 3A and a stationary section 2A, which includes a stator 23A. The rotating section 3A is supported in such a way that it is rotatable about a central axis 9A, which extends in the vertical direction, relative to the stationary section 2A.

[0013] The stationary section 2A comprises a bearing 24A arranged to support a shaft 31A, which is described below, and a base section 20A arranged to rotatably support the stator 23A.

[0014] The rotating section 3A comprises a rotor hub section 32A, a magnet 34A, a flywheel 35A, and a sealing section 60A. The rotating section 3A includes the shaft 31A, which is columnar and arranged to extend along the central axis 9A. Note that the shaft 31A may be integrally defined with the rotor hub section 32A. The rotor hub section 32A is arranged to extend in an annular form around the shaft 31A. The magnet 34A is attached to the rotor hub section 32A and comprises a pole face arranged radially opposite the stator 23A. Note that the magnet 34A may be attached directly to the rotor hub section 32A or indirectly, with another component located between them. The flywheel 35A is arranged axially above the rotor hub section 32A.The sealing section 60A is arranged to have a smaller thickness than the magnet 34A.

[0015] At least part of the outer circumferential surface of the rotor hub section 32A is a metal surface 340A. The metal surface 340A is covered by the sealing section 60A. Note that the metal surface 340A has a higher reflectivity than an outer circumferential surface of the flywheel 35A and than a surface of the sealing section 60A. That is, the metal surface 340A, which has a relatively high reflectivity, is covered by the sealing section 60A, which has a lower reflectivity than the metal surface 340A. This contributes to a reduction in the reflection of light by an outer circumferential surface of the rotating section 3A. Furthermore, since the sealing section 60A has a small thickness, the center of gravity of the rotating section 3A can be maintained radially inward, which allows for stable rotation. Engine structure

[0016] Fig. Figure 2 is a vertical sectional view of a motor 1 according to a second preferred embodiment of the present invention. With reference to Fig. The motor 1 comprises a rotating section 3 and a stationary section 2, which includes a stator 23. The rotating section 3 is mounted such that it is rotatable about a central axis 9, which extends in the vertical direction, relative to the stationary section 2.

[0017] The stationary section 2 comprises a bearing 24 arranged to rotatably support a shaft 31, which is described below, and a base section 20 arranged to hold the stator 23. The base section 20 comprises a mounting plate 21 and a stator holder 22.

[0018] The mounting plate 21 is a plate-shaped component designed to support the stator holder 22. A metal, such as stainless steel, is used as the material for the mounting plate 21. The mounting plate 21 is arranged to be perpendicular or substantially perpendicular to the central axis 9. Furthermore, the mounting plate 21 includes a circular through-hole 210 into which a lower end section of the stator holder 22 is fitted. When the motor 1 is used, the mounting plate 21 is attached, for example, by screwing it to a frame of a device. Note that a printed circuit board may be arranged on a surface of the mounting plate 21 to provide electrical control currents to the coils 42 of the stator 23.

[0019] The stator holder 22 is a cylindrical component arranged to extend in the axial direction. The lower end section of the stator holder 22 is inserted into the through-hole 210 of the mounting plate 21 and is crimped to the mounting plate 21. Note, however, that the stator holder 22 can alternatively be attached to the mounting plate 21 by another method, such as welding. It should also be noted that the mounting plate 21 and the stator holder 22 can alternatively be defined by a single, continuous monolithic component.

[0020] The stator 23 comprises a stator core (a stator lamination stack) 41 and the coils 42. The stator core 41 is defined, for example, by laminated steel sheets, each of which is a magnetic body. The stator core 41 includes a core back face 411 in the form of a circular ring and a plurality of teeth 412. The core back face 411 is attached to an outer circumferential surface of the stator holder 22. The teeth 412 are arranged to project radially outward from the core back face 411. One surface of each of the teeth 412 is coated with an insulating layer. In addition, a conductor wire is wound around each of the teeth 412 to define the coils 42. Note that an insulator made of a resin may be arranged between each of the teeth 412 and a corresponding coil 42.

[0021] The bearing 24 is a component arranged to rotatably support the shaft 31, as described below. The bearing 24 comprises a bushing 25, which is arranged to extend axially to assume a cylindrical shape around the shaft 31, and a disk-shaped cover 26, which is arranged to close an opening at a lower end section of the bushing 25. A lower section of the bushing 25 is inserted into a space radially within the stator holder 22 and is attached to the stator holder 22, for example, by means of an adhesive. An upper end section of the bushing 25 is arranged axially above an upper end section of the stator holder 22 and an upper end section of the stator 23.

[0022] The rotating section 3 comprises a rotor hub section 32, a bracket 33, a magnet 34, a flywheel 35, and a sealing section 60, which are described below. The rotating section 3 includes the shaft 31, which is columnar and arranged to extend along the central axis 9. The shaft 31 may be integral with the rotor hub section 32 or may be defined by a component separate from the rotor hub section 32. The rotor hub section 32 comprises a hub 320 and an inertial section 36. Note that the rotor hub section 32 may alternatively be defined by only the hub 320. A detailed description of this is provided below.

[0023] A metal such as stainless steel is used as the material for the shaft 31. A lower section of the shaft 31 is arranged radially inside the bushing 25. Meanwhile, an upper end section 311 of the shaft 31 is arranged axially above the upper end section of the bushing 25. An outer circumferential surface of the shaft 31 and an inner circumferential surface of the bushing 25 are arranged radially opposite each other, with a small gap between them.

[0024] Furthermore, a disk-shaped ring section 37 is attached to a lower end section of the shaft 31. The ring section 37 is arranged to extend radially outward from a lower end of the shaft 31. An upper surface of the ring section 37 and a lower surface of the bushing 25 are arranged axially opposite each other, with a small gap between them. Additionally, a lower surface of the ring section 37 and an upper surface of the cover 26 are arranged axially opposite each other, with a small gap between them. Note that the shaft 31 and the ring section 37 can alternatively be defined by a single monolithic component.

[0025] The rotor hub section 32 is arranged to extend in a ring shape around the shaft 31. The rotor hub section 32 comprises the inertial section 36, which is ring-shaped, made of a metal, and arranged to have a greater relative density than the flywheel 35, as described below, and the hub 320 to which the inertial section 36 is attached. A metal such as stainless steel, an aluminum alloy, or the like is used as the material for the hub 320. With reference to Fig. 2 The hub 320 comprises a connecting section 321, a cylindrical section 322, and a flanged section 323. The connecting section 321 is arranged most radially inward within the rotor hub section 32 and is attached to the outer circumferential surface of the shaft 31. That is, the connecting section 321 is arranged to extend in an annular shape from an upper section of the shaft 31. A through-hole 330, extending axially through the rotor hub section 32, is defined radially within the connecting section 321. The upper end section 311 of the shaft 31 is press-fitted into the through-hole 330 of the rotor hub section 32.

[0026] Furthermore, an adhesive (not shown) is arranged between an outer circumferential surface of the upper end section 311 of the shaft 31 and an inner circumferential surface of the connecting section 321. Thus, in this motor 1, the shaft 31 and the rotor hub section 32 are joined to one another by means of an interference fit and the adhesive. Note, however, that the shaft 31 and the rotor hub section 32 can alternatively be joined to one another solely by means of an interference fit or solely by means of the adhesive. Note further that the shaft 31 and the rotor hub section 32 can alternatively be joined to one another by means of another method, such as shrink-fitting.

[0027] The cylindrical section 322 of the rotor hub section 32 is arranged to extend axially, assuming a cylindrical shape radially outside the connecting section 321 and radially inside the inertia section 36. The flange section 323 is arranged to extend radially outward from a lower section of the cylindrical section 322. The flange section 323 is located axially below the inertia section 36.

[0028] The inertial section 36 is an annular component arranged radially outside the cylindrical section 322, axially above the flange section 323, and axially below the flywheel 35, as described below. A lower surface of the inertial section 36 is arranged to be in contact with an upper surface of the flange section 323. Furthermore, the inertial section 36 is attached to the cylindrical section 322 or the flange section 323, for example, by means of an adhesive. Accordingly, the inertial section 36 rotates together with the hub 320 and the flywheel 35 while the engine 1 is running.

[0029] A metal such as stainless steel is used as the material for at least part of the rotor hub section 32, including the inertial section 36. The inertial section 36 is arranged to have a higher relative density than the flywheel 35, as described below. Accordingly, the presence of the inertial section 36 increases the inertial force of the rotating section 3 while the motor 1 is running. This contributes to stabilizing the position of the rotating section 3. In particular, in this motor 1, the rotor hub section 32 is arranged to have a total mass greater than the mass of the flywheel 35. This lowers the center of gravity of the rotating section 3, resulting in a more stable position of the rotating section 3. Note that the inertial section 36 need not necessarily be arranged to have a greater mass than the flywheel 35.This means that the inertial section 36 can be arranged to have a lower mass than the flywheel 35.

[0030] As described above, in this motor 1, the lower surface of the inertial section 36 is arranged to be in contact with the upper surface of the flange section 323. This stabilizes the axial position of the inertial section 36. Furthermore, in this motor 1, the inertial section 36 is located above the flange section 323 and below the flywheel 35. That is, the inertial section 36 is held between the rotor hub section 32 and the flywheel 35. This further stabilizes the axial position of the inertial section 36. The stabilized axial position of the inertial section 36 helps to prevent it from tilting. This contributes to further stabilizing the position of the rotating section 3 while the motor 1 is running.

[0031] The bracket 33 is cylindrical, attached to a radially outer side of the magnet 34, as described below, and is arranged to hold the magnet 34. At least one outer circumferential surface of the bracket 33 is, for example, black, gray, or green. An outer circumferential surface of the magnet 34 is attached to an inner circumferential surface of the bracket 33. The bracket 33 is arranged to be substantially coaxial with the central axis 9. An upper end section of the bracket 33 is attached, for example, by means of an adhesive or by crimping, to a lower surface of the flange section 323 of the rotor hub section 32. A magnetic material, such as iron or the like, is used as the material of the bracket 33.Accordingly, the bracket 33 has a higher relative density than the rotor hub section 32 if the rotor hub section 32 is made of a metal such as aluminum or the like. Thus, the mass of the bracket 33 contributes to increasing the inertial force of the rotating section 3. This results in a more stable position of the rotating section 3 while the motor 1 is running.

[0032] The magnet 34 is attached, for example, to the inner circumferential surface of the bracket 33 by means of an adhesive. In this motor 1, a permanent magnet in the form of a circular ring is used as magnet 34. The magnet 34 has a cylindrical or substantially cylindrical shape and is arranged radially outside the stator 23. An inner circumferential surface of the magnet 34 comprises a north and a south pole, which are arranged to alternate in a circumferential direction. Furthermore, the inner circumferential surface of the magnet 34 is arranged radially opposite a radially outer end surface of each of the teeth 412 of the stator 23, with a small gap between them. That is to say, the magnet 34 comprises a pole surface that is arranged radially opposite the stator 23.

[0033] Note that instead of the single magnet 34, which has the form of a circular ring, a plurality of magnets can be used. In the case where multiple magnets are used, the plurality of magnets 34 are arranged on the inner circumferential surface of the bracket 33 such that the north and south poles alternate in the circumferential direction. In the present preferred embodiment, the magnet 34 is indirectly attached to the rotor hub section 32, with the bracket 33 located between them. Note that, alternatively, the magnet 34 can be attached directly to the rotor hub section 32 without the bracket 33 being located between them.

[0034] After electrical control currents are supplied to the coils 42 of the stator 23, a rotating magnetic field is generated around the teeth 412 of the stator core 41. Subsequently, an interaction between the magnetic flux of the teeth 412 and the magnetic flux of the magnet 34 causes a circumferential torque. Consequently, the rotating section 3, which includes the magnet 34, is caused to rotate about the central axis 9.

[0035] The flywheel 35 is arranged axially above the rotor hub section 32. The flywheel 35 is attached to the rotor hub section 32, for example, by means of an adhesive. Accordingly, the flywheel 35 rotates together with the rotor hub section 32. An ABS resin, which is, for example, a thermoplastic resin, is used as the material for the flywheel 35. Note that instead of ABS resin, another material, such as a thermosetting resin or a metal, can alternatively be used as the material for the flywheel 35. If the flywheel 35 is made of a resin, it can be lighter than if it were made of a metal. Using a resin for the flywheel 35 thus reduces the load during the rotation of the motor 1.Note that the flywheel 35 can be arranged to have an axial dimension greater than the axial distance from a lower end surface of the stationary section 2 to an upper end surface of the rotor hub section 32. The position of the rotating section 3 while the motor 1 is running can be stabilized by arranging the inertial section 36, which has a higher relative density than the flywheel 35, below the flywheel 35, as described above.

[0036] Furthermore, the flywheel 35 in this motor 1 is arranged to have a circular outer shape, with the central axis 9 forming a center when viewed in the axial direction. This circular outer shape of the flywheel 35 contributes to a reduction in the oscillation of the rotating section 3 while the motor 1 is running. Detailed structure of the outer circumferential surface of the rotating section

[0037] Next, the detailed structure of an outer circumferential surface of the rotating section 3 of the motor 1 is described below.

[0038] Fig. Figure 3 is a vertical partial sectional view of the motor 1 according to the second preferred embodiment. With reference to Fig. 3 is at least a part of an outer circumferential surface of the flange section 323 of the rotor hub section 32 a metal surface 340. Note that an outer circumferential surface of the rotor hub section 32 refers to any surface of the rotor hub section 32 that is exposed with respect to a space outside the motor 1 when the rotor hub section 32 is not covered by the sealing section 60, and may include a side surface, a top surface, a bottom surface, or an inclined surface. In the present preferred embodiment, the metal surface 340 is located in a radially outer side surface of the flange section 323.

[0039] The metal surface 340 is preferably a cut surface on which no surface treatment process has been performed. The metal surface 340 has a higher reflectivity than an outer circumferential surface of the flywheel 35 and than a surface of the sealing section 60, as described below. For example, the flywheel 35 is made of a resin and the metal surface 340 is made of a metal such as stainless steel or aluminum, in which case the outer circumferential surface of the flywheel 35 has a lower reflectivity than the metal surface 340. Note that a coating having a lower reflectivity than the metal surface 340 can be applied to the outer circumferential surface of the flywheel 35 instead of, or in addition to, the resin-made flywheel 35.Note further that a tape made of a material with low reflectivity can be glued to the outer circumferential surface of the flywheel 35.

[0040] Furthermore, the rotor hub section 32 is preferably arranged to have an outer diameter that is equal to or substantially equal to the outer diameter of the flywheel 35. Specifically, it is desirable that at least a portion of the metal surface 340 of the rotor hub section 32 and at least a portion of the outer circumferential surface of the flywheel 35 are arranged to axially overlap each other. Increasing the outer diameter of the rotor hub section 32 leads to an increase in the mass of the rotating section 3, which comprises the rotor hub section 32 and has a high relative density. This, in turn, leads to an increase in the inertial force of the rotating section 3, thereby stabilizing its rotation. Since, moreover, the rotor hub section 32 and the flywheel 35 have the same or substantially the same outer diameter, the sealing section 60, which is described below, can be readily attached.Note that the outer diameter of the rotor hub section 32 and the outer diameter of the flywheel 35 may differ slightly.

[0041] This motor 1 is placed in an enclosure, and a mirror (not shown) is used to reflect light emitted by a light source. If the metal surface 340, which has a high reflectivity, were exposed, some of the light emitted by the light source would be reflected by the metal surface 340. The reflected light would then cause diffuse reflection within the enclosure. Thus, the light reflected by the mirror and the light reflected by the metal surface 340 could mix, hindering a desired function that the reflected light is intended to perform.

[0042] With reference to Fig. In the present preferred embodiment, the metal surface 340 is covered by the sealing section 60, which has a smaller thickness than the magnet 34. Accordingly, the light emitted by the light source is blocked by the sealing section 60 and does not reach the metal surface 340. Furthermore, the sealing section 60 is arranged to have a lower reflectivity than the metal surface 340. Thus, some of the incident light is absorbed by the surface of the sealing section 60, which reduces the occurrence of diffuse reflection in the casing. Since the sealing section 60 is also arranged to have a small thickness, the center of gravity of the rotating section 3 can be maintained radially inwards. This contributes to further stabilizing its rotation.

[0043] Here, it is desirable that the surface of the sealing section 60 has a color that does not readily allow reflection, for example, black, dark green, gray, or the like, and that the sealing section 60 is defined by a band made of a resin or an opaque material and is arranged to have a thickness of 30 µm or more and sufficient strength. Furthermore, it is sufficient that the metal surface 340 is covered by the sealing section 60 over its entire circumferential extent, and both circumferential end sections of the sealing section 60 may overlap or be slightly offset from one another. Note that the metal surface 340 may be covered with several layers of the sealing section 60 over its entire circumferential extent.

[0044] In the present preferred embodiment, an upper end of the sealing section 60 is attached to the outer circumferential surface of the flywheel 35, for example by means of an adhesive, and at least a portion of the outer circumferential surface of the flywheel 35, including a lower end thereof, is covered by the sealing section 60. Furthermore, a lower end of the sealing section 60 is attached to the outer circumferential surface of the bracket 33, for example by means of an adhesive, and at least a portion of the outer circumferential surface of the bracket 33, including a lower end thereof, is covered by the sealing section 60. Consequently, the metal surface 340 of the rotor hub section 32, which has a high reflectivity, and the inertial section 36 are reliably covered by the sealing section 60.Furthermore, the probability of light reaching a gap between the flange section 323 and the inertial section 36, or a gap between the flange section 323 and the bracket 33, to cause diffuse reflection is reduced. Note, however, that the upper and lower ends of the sealing section 60 need not necessarily be attached to the outer circumferential surface of the flywheel 35 or the outer circumferential surface of the bracket 33, respectively, as long as the sealing section 60 covers the metal surface 340. For example, the upper end of the sealing section 60 can alternatively be attached to an outer circumferential surface of the inertial section 36, near its upper end.

[0045] Note that, in order to reduce the probability that incident light strikes the surface of the sealing section 60, the outer circumferential surface of the flywheel 35, or the outer circumferential surface of the yoke 33 and is diffusely reflected to the surroundings, it is desirable that at least the surface of the sealing section 60 and the outer circumferential surfaces of the flywheel 35 and the yoke 33 have low light reflectivity. Accordingly, it is desirable that the outer circumferential surface of the yoke 33 be roughened.Examples of roughening processes include a method for forming machining marks on the outer circumferential surface using a cutting process or press machining; a method for performing jet cleaning by blowing an abrasive such as sand onto the outer circumferential surface; a method of applying a resin in which minute particles are finely dispersed onto the outer circumferential surface and solidifying the resin; a method of applying a chemical solvent to the outer circumferential surface to dissolve the surface; and a method of spraying a chemical solvent onto the outer circumferential surface using a sprayer.

[0046] Note that, instead of roughening the outer circumferential surface of the bracket 33, a plating process and an oxidation treatment can be carried out to reduce the reflectivity. Note further that a component made of a metal or resin that has a lower reflectivity than the metal surface 340 of the rotor hub section 32 can be attached to the outer circumferential surface of the bracket 33, that a coating that has a lower reflectivity than the metal surface 340 can be applied to the outer circumferential surface of the bracket 33, or that a tape made of such a material can be bonded to the outer circumferential surface of the bracket 33. Fluid dynamic bearing

[0047] Next, a fluid dynamic bearing 5, which is included in the motor 1, will be described below. Fig. Figure 4 is a vertical partial sectional view of engine 1. With reference to Fig. 4 A lubricating oil 50 is arranged between the bearing 24, which includes the bushing 25 and the cover 26, and a combination of the shaft 31 and the ring section 37. For example, a polyolester oil or a diester oil is used as the lubricating oil 50.

[0048] Fig. Figure 5 is a vertical sectional view of bearing 24. With reference to Fig. The bushing 25 comprises an upper radial groove array 511 and a lower radial groove array 512 on its inner circumferential surface. The lower radial groove array 512 is arranged axially beneath the upper radial groove array 511. Both the upper and lower radial groove arrays 511 and 512 form a groove array arranged in a so-called "herringbone" pattern. While the motor 1 is running, the upper and lower radial groove arrays 511 and 512 exert a dynamic pressure on a portion of the lubricating oil 50 present between the inner circumferential surface of the bushing 25 and the outer circumferential surface of the shaft 31. This generates a radial load-bearing force between the bushing 25 and the shaft 31.

[0049] That is, in this motor 1, the inner circumferential surface of the bushing 25 and the outer circumferential surface of the shaft 31 are arranged radially opposite each other, with the lubricating oil 50 located between them to define a radial bearing section 51. Furthermore, the radial bearing section 51 comprises an upper radial bearing section 501, which is arranged to generate a dynamic pressure through the upper radial groove array 511, and a lower radial bearing section 502, which is arranged to generate a dynamic pressure through the lower radial groove array 512. The lower radial bearing section 502 is arranged axially below the upper radial bearing section 501. Note that it may be sufficient for both the upper and the lower radial groove arrays 511 and 512 to be defined in at least either the inner circumferential surface of the bushing 25 and / or the outer circumferential surface of the shaft 31.It should also be noted that the number of radial dust shroud arrays can alternatively be one or more than two.

[0050] Furthermore, with reference to Fig. In this motor 1, the axial dimension h1 of the upper radial groove array 511 is larger than the axial dimension h2 of the lower radial groove array 512. Therefore, the axial dimension of the upper radial bearing section 501 is larger than the axial dimension of the lower radial bearing section 502. This causes the lubricating oil 50 to generate a higher dynamic pressure at a position closer to the center of gravity of the rotating section 3. This results in a more stable position of the rotating section 3 during its rotation. This, in turn, reduces the probability that vibration of the rotating section 3 will cause damage to the connecting section 321.

[0051] Furthermore, in this motor 1, at least a part of the inertial section 36 and at least a part of the radial bearing section 51 are arranged to radially overlap each other. In detail, with reference to Fig. 4 A lower section of an axial region A1, in which the inertial section 36 extends, is arranged to overlap with an upper section of an axial region A2, in which the upper radial bearing section 501 extends. Accordingly, the upper radial bearing section 501 is able to generate a strong dynamic pressure in the lubricating oil 50 at a level equivalent to that of the inertial section 36, which has a high relative density, in order to support the rotating section 3. This results in a more stable position of the rotating section 3 during its rotation. A stabilized position of the rotating section 3 further reduces the probability that vibration of the rotating section 3 will cause damage to the connecting section 321.

[0052] Fig. Figure 6 is a bottom view of socket 25. With reference to Fig. 6. The bushing 25 comprises a shear ring array 521 on its lower surface. The shear ring array 521 comprises a plurality of shear grooves arranged circumferentially. The shear grooves are arranged to extend radially in a spiral shape. Note that the shear ring array 521 can alternatively be arranged in a herringbone pattern. While the motor 1 is running, the shear ring array 521 contains a fluid back pressure in a portion of the lubricating oil 50 located between the lower surface of the bushing 25 and the upper surface of the annular section 37. This generates an axial load-bearing force that supports the annular section 37 relative to the bushing 35, thereby stabilizing the rotation of the rotating section 3.

[0053] This means that in this motor 1, the lower surface of the bushing 25 of the stationary section 2 and the upper surface of the annular section 37 of the rotating section 3 are arranged axially opposite each other, with a space between them containing the lubricating oil 50 to define a thrust bearing section 52. Note that it may be sufficient for the thrust bearing array 521 to be defined in at least either the lower surface of the bushing 25 and / or the upper surface of the annular section 37. Furthermore, note that the number of thrust bearing sections 52 can be two or more. Also note that the thrust bearing section 52 can alternatively be defined between the upper surface of the cover 26 and the lower surface of the annular section 37.

[0054] As described above, a space in the form of a bubble, encompassing the radial bearing section 51 and the thrust bearing section 52, is defined between a combination of the bushing 25 and the cover 26 and the combination of the shaft 31 and the annular section 37. This space comprises a thrust gap defined between the upper or lower surface of the annular section 37 and a surface of the bushing 25 or the cover 26 axially opposite the annular section 37, and a radial gap defined between the outer circumferential surface of the shaft 31 and a surface of the bushing 25 radially opposite the shaft 31. The radial bearing section 51 is defined within the radial gap, while the thrust bearing section 52 is defined within the thrust gap. The lubricating oil 50 is continuously present in the space encompassing the thrust gap and the radial gap.The shaft 31 is supported by the lubricating oil 50 to allow rotation relative to the bushing 25 and the cover 26. When the lubricating oil 50 is completely contained within the space, a fluid surface of the lubricating oil 50 is defined only near the upper end of the bushing 25, between the outer circumferential surface of the shaft 31 and the inner circumferential surface of the bushing 25; that is, only at or near the upper end of the radial space. Thus, the fluid dynamic bearing 5 of this motor 1 is configured to have a so-called "full-fill structure," in which the fluid surface of the lubricating oil 50 is defined at only one location.The use of the full-fill structure, in which the lubricating oil 50 is arranged between the stationary section 2 and the rotating section 3, contributes to a reduction of the vibration of the rotating section 3 due to the orientation in which the motor 1 is placed and / or a shock, and further contributes to preventing contact between the stationary section 2 and the rotating section 3 when a shock acts on the motor 1 during its rotation.

[0055] The fluid dynamic bearing 5 is defined by the combination of the bushing 25 and the cover 26 of the stationary section 2, the combination of the shaft 31 and the annular section 37 of the rotating section 3, and the lubricating oil 50 located between them. The rotating section 3 is supported by the fluid dynamic bearing 5 and rotates about the central axis 9. Note that, alternatively, the rotating section 3 can be supported by another bearing, such as a ball bearing or a plain bearing, instead of the fluid dynamic bearing 5, in such a way that it is rotatable with respect to the stationary section 2.

[0056] Although preferred embodiments of the present invention have been described above, it is understood that the present invention is not limited to the preferred embodiments described above.

[0057] Fig. Figure 7 is a vertical sectional view of a motor 1B according to a modification of the second preferred embodiment. In the Fig. In the illustrated modification 7, a sealing section 60B is arranged to cover an area extending from at least part of an outer circumferential surface of a flywheel 35B to a lower end of an outer circumferential surface of a cylindrical bracket 33B attached to a rotor hub section 32B. Consequently, a metal surface 340B of the rotor hub section 32B, which has a high reflectivity, is more reliably covered by the sealing section 60B. Accordingly, the probability of light reaching a gap between the rotor hub section 32B and the bracket 33B to cause diffuse reflection can be further reduced.Note that in the case where the sealing section 60B is arranged to provide a cover up to the lower end of the outer circumferential surface of the bracket 33B, a process such as a roughening process, a plating process, an oxidation treatment or the like may not be carried out on the outer circumferential surface of the bracket 33B.

[0058] Fig. Figure 8 is a vertical partial sectional view of a motor 1C according to a further modification of the second preferred embodiment. In the Fig. In the modification illustrated in Figure 8, a rotor hub section 32C comprises a groove section 324C, which is radially recessed inwards in at least a portion of an outer circumferential surface of a flange section 323C or an inertial section 36C. The motor 1C may further comprise at least one balancing correction element 325C, which has sufficient mass to perform the function of correcting the balance of a rotating section 3C at one or more circumferential positions in the groove section 324C. The balance of the motor 1C, which comprises the rotating section 3C, can thus be corrected after a flywheel 35C has been attached to the rotor hub section 32C, and thus the rotation of the motor 1C with the attached flywheel 35C can be further stabilized. In particular, the rotor hub section 32C is, according to the arrangement of the balancing correction element,The balance correction element 325C is covered with the sealing section 60C, resulting in a more reliable fastening of the balance correction element(s) 325C.

[0059] It is desirable that, on the outer circumferential surface of the rotor hub section 32C, the groove section 324C is arranged to extend circumferentially over the entire circumference of the rotor hub section 32C. This allows the number of balance correction elements 325C and the position(s) of the balance correction element(s) 325C to be chosen arbitrarily, leading to improved operational efficiency. Note, however, that the groove section 324C can alternatively be defined by a cut or cuts located at only one or more circumferential positions on the outer circumferential surface of the rotor hub section 32C.

[0060] Fig. Figure 9 is a vertical partial sectional view of a motor 1D according to yet another modification of the second preferred embodiment. In the Fig. In the modification illustrated in Figure 9, a rotor hub section 32D is attached to a circumference of an upper end section of a shaft 31D. Furthermore, a lower surface of a connecting section 321D and an upper surface of a bushing 25D are arranged axially opposite each other, with a small gap (i.e., a second shear gap) between them. In the modification shown in Fig. In the modification illustrated in Figure 9, a lubricating oil 50D is also arranged in this second shear gap. Furthermore, a second shear ring array (not shown) is defined in either the lower surface of the connecting section 321D or the upper surface of the bushing 25D. While the motor 1D is running, the second shear ring array includes a back pressure in a portion of the lubricating oil 50D that is present between the lower surface of the connecting section 321D and the upper surface of the bushing 25D. This generates an axial load-bearing force that supports the rotor hub section 32D with respect to the bushing 25D.

[0061] In a situation where the lubricating oil 50D is completely contained within a space, a fluid surface of the lubricating oil 50D is defined near an upper end section of the bushing 25D between an outer circumferential surface of the bushing 25D and an inner circumferential surface of a cylindrical section 322D of the rotor hub section 32D. That is, a fluid dynamic bearing 5D of this motor 1D is arranged to have a so-called full-fill structure, in which the fluid surface of the lubricating oil 50D is defined at only one position.

[0062] That is, in the case of the Fig. In the illustrated motor 1D, the second thrust gap, the lower surface of the connecting section 321D, and the upper surface of the bushing 25D are arranged axially opposite each other, with the lubricating oil 50D located between them to define a second thrust bearing section 52D. Furthermore, the lubricating oil 50D is continuously present in a gap that includes a radial bearing section 51D and the second thrust bearing section 52D. This results in more stable rotation of the motor 1D.

[0063] Note that a plain bearing (e.g., a sintered bearing) (not shown) impregnated with a lubricating oil can alternatively be used as bearing 24D. In this case, it is desirable for a housing (not shown) to be additionally arranged radially outside the bushing 25D to prevent oil leakage. In this case, when the lubricating oil 50D is completely located within the space, a fluid surface of the lubricating oil 50D is defined near an upper end section of the housing between an outer circumferential surface of the housing and the inner circumferential surface of the cylindrical section 322D of the rotor hub section 32D. Likewise, in the second thrust space, the lower surface of the connecting section 321D and the upper surface of the bushing 25D are axially opposed to each other, with the lubricating oil 50D present between them to define the second thrust bearing section 52D.

[0064] Fig. Figure 10 is a vertical sectional view of a motor 1E according to yet another modification of the second preferred embodiment. In the Fig. In the illustrated modification 10, a rotating section 3E includes a mirror 40E. The mirror 40E is supported by a flywheel 35E. After the motor 1E is driven, the mirror 40E is caused to rotate together with the flywheel 35E. This allows light approaching the flywheel 35E to be reflected, while the light is deflected at a fixed rate.

[0065] Fig. Figure 11 is a vertical sectional view of a motor 1F according to yet another modification of the second preferred embodiment. As in Fig. As illustrated in Figure 11, a rotor hub section 32F of the motor 1F may not include an inertial section and may consist only of a hub 320F.

[0066] Note that the flywheel is a resin injection-molded part produced with the inertial segment as an insert. In this process, molten resin is poured into a cavity of a mold, with the inertial segment positioned within the mold, and the resin is then cured to complete the flywheel manufacturing process. This achieves the simultaneous forming of the flywheel and its attachment to the inertial segment, thus reducing the number of processes required to manufacture the engine. Furthermore, the flywheel and inertial segment can be joined together with increased strength.

[0067] Note that details of the structure and shape of an engine according to a preferred embodiment of the present invention may differ from details of the structure and shape of each engine as illustrated in the accompanying drawings of the present application. Furthermore, note that features of the preferred embodiments and modifications thereof described above may be combined appropriately, provided no conflict arises.

[0068] Preferred embodiments of the present invention are applicable to motors.

[0069] Although preferred embodiments of the present invention have been described above, it is understood that variations and modifications will be obvious to those skilled in the art without deviating from the scope of protection and the essence of the present invention. The scope of protection of the present invention shall therefore be determined exclusively by the following patent claims.

Claims

[1] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) having the following features: a stationary section (2A; 2) comprising a stator (23A; 23); and a rotating section (3A; 3; 3C; 3E) which is supported in such a way as to be rotatable about a central axis (9A; 9) which extends in a vertical direction with respect to the stationary section (2A; 2) and which includes a shaft (31A; 31; 31D) which is arranged to extend along the central axis (9A; 9); wherein the stationary section (2A; 2) includes the following features: a bearing (24A; 24; 24D) arranged to rotatably support the shaft (31A; 31; 31D); and a base section (20A; 20) arranged to hold the stator (23A; 23); The rotating section (3A; 3; 3C; 3E) includes the following features: a rotor hub section (32A; 32; 32B; 32C; 32D; 32F) which is arranged to extend in an annular shape around the shaft (31A; 31; 31D); a magnet (34A; 34) which is attached directly or indirectly to the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) and is arranged opposite the stator (23A; 23); a flywheel (35A; 35; 35B; 35C; 35E) arranged axially above the rotor hub section (32A; 32; 32B; 32C; 32D; 32F); and a sealing section (60A; 60; 60B; 60C) arranged to have a lesser thickness than the magnet (34A; 34); at least part of an outer circumferential surface of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) is a metal surface (340A; 340; 340B); The metal surface (340A; 340; 340B) has a higher reflectivity than an outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E) and a surface of the sealing section (60A; 60; 60B; 60C); and the metal surface (340A; 340; 340B) is covered with the sealing section (60A; 60; 60B; 60C). [2] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to claim 1, wherein at least a part of the metal surface (340A; 340; 340B) of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) and at least a part of the outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E) are arranged to overlap axially. [3] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to one of claims 1 and 2, wherein the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) comprises the following features: an inertial section (36; 36C) which is annular, made of a metal and arranged to have a higher specific density than the flywheel (35A; 35; 35B; 35C; 35E); and a hub (320; 320F); the hub (320; 320F) includes the following features: a connecting section (321; 321D) which is arranged to extend in an annular shape from an upper part of the shaft (31A; 31; 31D); a cylindrical section (322; 322D) arranged to extend in an axial direction from an outer circumferential section of the connecting section (321; 321D); and a flanged section (323; 323C) arranged to extend radially outward from a lower section of the cylindrical section (322; 322D); and the inertial section (36; 36C) is attached to the cylindrical section (322; 322D) or the flanged section (323; 323C). [4] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 3, wherein the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) is arranged to have a greater mass than the flywheel (35A; 35; 35B; 35C; 35E). [5] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 4, wherein the flywheel (35A; 35; 35B; 35C; 35E) is made of a resin and at least part of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) is made of a stainless metal. [6] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 5, wherein the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) comprises a groove section (324C) which is radially recessed inwards in at least part of its outer circumferential surface; and the motor (1A; 1; 1B; 1C; 1D; 1E; 1F) further comprises a balance correction element (325C) which is arranged in the groove section (324C). [7] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to claim 6, wherein the groove section (324C) is arranged in the outer circumferential surface of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F) to extend in a circumferential direction over an entire circumferential extent of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F). [8] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 7, wherein at least a part of the outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E) is covered with the sealing section (60A; 60; 60B; 60C). [9] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 8, wherein the magnet (34A; 34) is arranged radially outside the stator (23A; 23); the rotating section (3A; 3; 3C; 3E) further comprises a cylindrical bracket (33; 33B) which is attached to a radially outer side of the magnet (34A; 34); the bracket (33; 33B) is attached to the rotor hub section (32A; 32; 32B; 32C; 32D; 32F); an upper end of the sealing section (60A; 60; 60B; 60C) is attached to the outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E); and a lower end of the sealing section (60A; 60; 60B; 60C) is attached to an outer circumferential surface of the bracket (33; 33B). [10] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 9, wherein the magnet (34A; 34) is arranged radially outside the stator (23A; 23); the rotating section (3A; 3; 3C; 3E) further comprises a cylindrical bracket (33; 33B) which is attached to a radially outer side of the magnet (34A; 34); the bracket (33; 33B) is attached to the rotor hub section (32A; 32; 32B; 32C; 32D; 32F); and the sealing section (60A; 60; 60B; 60C) is arranged to cover an area extending from at least a part of the outer circumferential surface of the flywheel (35A; 35; 35B; 35C; 35E) to a lower end of an outer circumferential surface of the bracket (33; 33B). [11] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 10, which further comprises a thrust bearing section (52; 52D) in which a part of the stationary section (2A; 2) and a part of the rotating section (3A; 3; 3C; 3E) are arranged axially opposite each other, wherein there is a space between them, wherein lubricating oil (50; 50D) is arranged in the space, and wherein a fluid back pressure is caused in the lubricating oil (50; 50D). [12] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to claim 11, wherein the bearing (24A; 24; 24D) comprises a bushing (25; 25D) and a disc-shaped cover (26) arranged to close a lower end section of the bushing (25; 25D); the rotating section (3A; 3; 3C; 3E) further comprises a disk-shaped ring section (37) which is arranged to extend radially outwards from a lower end of the shaft (31A; 31; 31D) and which is arranged axially opposite the cover (26); the space includes the following features: a shear gap defined between an upper surface or a lower surface of the ring section (37) and a surface of the bushing (25; 25D) or the cover (26) axially opposite the ring section (37); and a radial gap defined between an outer circumferential surface of the shaft (31A; 31; 31D) and a surface of the bushing (25; 25D) that is radially opposite the shaft (31A; 31; 31D); the shear pressure bearing section is defined in the shear space; the lubricating oil (50; 50D) is continuously present in the space comprising the shear gap and the radial gap; and in a situation where the lubricating oil (50; 50D) has been completely arranged in the space, a fluid surface of the lubricating oil (50; 50D) is defined only at an upper end of the radial space. [13] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to claim 12, wherein the gap further comprises a second shear gap defined between an upper surface of the bushing (25; 25D) and a lower surface of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F); and the second shear gap has a second shear bearing section (52; 52D) defined in the same way. [14] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 13, wherein the rotating section (3A; 3; 3C; 3E) comprises a mirror (40E) which is carried by the flywheel (35A; 35; 35B; 35C; 35E) and is arranged to reflect light approaching the flywheel (35A; 35; 35B; 35C; 35E). [15] Motor according to any one of claims 1 to 14, wherein the flywheel (35A; 35; 35B; 35C; 35E) is arranged to have an outer diameter equal to an outer diameter of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F). [16] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 15, wherein the flywheel (35A; 35; 35B; 35C; 35E) is arranged to have an axial dimension greater than an axial distance between a lower end surface of the stationary section (2A; 2) and an upper end surface of the rotor hub section (32A; 32; 32B; 32C; 32D; 32F). [17] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 16, wherein the metal surface (340A; 340; 340B) is covered over its entire circumference by the sealing section (60A; 60; 60B; 60C); and Both circumferential end sections of the sealing section (60A; 60; 60B; 60C) are arranged to overlap each other. [18] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 1 to 17, wherein the sealing section (60A; 60; 60B; 60C) is made of a resin and the surface of the sealing section (60A; 60; 60B; 60C) has a black color. [19] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 9 to 18, wherein at least the outer circumferential surface of the bracket (33; 33B) is roughened. [20] Motor (1A; 1; 1B; 1C; 1D; 1E; 1F) according to any one of claims 9 to 19, wherein at least the outer circumferential surface of the bracket (33; 33B) has a black color.

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