JPH0691717B2 - Electric machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electric machine, and more particularly to a flat structure in which a rotor and a stator are arranged with a magnetic gap in the direction of the rotation axis of the rotor, Moreover, the present invention relates to an electric machine that does not require a drive shaft that transmits a rotational force.

[Prior Art] FIG. 11 is a vertical cross-sectional view of a brushless flat motor which is an example of a conventional electric machine. The base 21 and the stator coil mounting substrate 22 are connected together by a stator bolt 23 to form a frame. Bearings 24 and 2 fixed to the base 21 and the substrate 22, respectively.
A rotor 27 having a rotor magnet fixed thereto is fixed to a motor shaft 26 pivotally attached to the motor 5. Substrate 22 to rotor 27
The stator coil 28 is fixed to the substrate 22 with the
A tachogenerator 33 electromotive force generated by a rotor 27 and a hall element 29 for controlling the rotation speed are fixed to the rotor 22. The structure is the same for the sheet coil motor in which the motor coil is manufactured by photo etching in which the stator coil is extremely thin.

This electric machine can be used as a laser canner by fixing a polygon mirror to the motor shaft 26, as an optical disk drive device by directly fixing an optical disk directly to the rotor 27, or as a fan blade on the rotor 27. There are various things, such as fixing and making it a blower.

[Problems to be Solved by the Invention] In the electric machine as described above, the radial clearances of the bearings 24 and 25 may be large and the rotor 27 may vibrate. In particular, there are places where ball bearings are used for the bearings 24 and 25, which may cause vibrations, which is a problem in tape recorders and VTRs that resist vibration.

Further, the radial bearing cannot be used in water without the excellent corrosion resistance without the shaft sealing means. Further, the durability was insufficient even in an environment where dew condensation was repeated.

In addition, rotation unevenness is a problem particularly in motors used in electronic products, but there are cases in which rotation unevenness occurs due to large fluctuations in frictional resistance in the radial bearing portion.

In such an electric machine, a thin type having a short axial length is often suitable, but the motor cannot be made thin unless the interval between the radial bearings 24 and 25 is shortened. If the radial bearing spacing is shortened, the bearing load with respect to the radial load increases,
The inclination of the motor shaft due to the bearing clearance also increases.

Further, in this type of electric machine, the thrust load by the rotor magnet always acts, and if it is stopped for a long time, the metal balls of the ball bearing and the retainer may be permanently deformed and may not start. . Further, when used as a high-speed laser scanner for reproducing high-definition images, the machining accuracy of the motor shaft 26 and the bearings 24, 25 is extremely high in order to reduce the swing width of the surface of the polygon mirror, and at the same time, The assembly accuracy with the polygon mirror must also be high.

[Object] The present invention provides an electric machine having a magnetic gap in the rotational axis direction of the rotor and having a rotor and a stator arranged therein, which has a simple structure and is highly durable. It also provides an electric machine that minimizes vibration and surface vibration of the rotor. Furthermore, it has excellent durability and wear resistance, and can be used in a wide range of operating environments such as in gas and liquid. An electric machine that can be used is provided.

[Means for Solving the Problems] The present invention relates to an electric machine in which a stator is arranged so as to face an end surface of a rotor in the rotation axis direction, and a rotation-side sliding surface is formed on the end surface of the rotor that faces the stator. The surface of the stator facing the sliding surface of the rotating side is a fixed bearing surface, and the sliding surface of the rotating side and the bearing surface of the fixed side are each made of a hard ceramic material. One of the fixed-side bearing surfaces is a smooth flat surface, and the other surface is a flat surface in which a groove for generating dynamic pressure is formed. The hard ceramic materials that make up the rotating-side sliding surface and the stationary-side bearing surface are β-SiC, Si ₃ N ₄ , or Be.
It is one of O-containing α-SiC.

Further, according to the second aspect of the present invention, rotating side sliding surfaces are respectively formed on both end surfaces of the rotor in the rotation axis direction, the stator is arranged so as to face one rotating side sliding surface, and the other rotating side sliding surface is arranged. In the electric machine having a swingable bearing surface facing the side sliding surface, the surface of the stator facing the rotating side sliding surface is the fixed side bearing surface, and the two rotating side sliding surfaces and The two bearing surfaces facing each other are made of hard ceramic materials, and
This is an electric machine in which a groove for generating a dynamic pressure is provided on one of two surfaces forming a sliding portion formed on both end surfaces of the rotor in the rotation axis direction and the other surface is a smooth flat surface.

Furthermore, in the third aspect of the present invention, rotating side sliding surfaces are respectively formed on both end surfaces of the rotor in the rotational axis direction, and the stator is arranged so as to face one rotating side sliding surface, and the other is arranged. An electric machine having a swingable bearing surface facing the rotation side sliding surface of the rotor, the fixed shaft extending on the rotation axis of the rotor is fixed to the stator, and the fixed shaft corresponding to the fixed shaft is fixed to the stator. A through hole is formed in the center of the rotor, and the outer peripheral surface of the fixed shaft and the inner peripheral surface of the through hole are slidingly engaged with each other to form a radial bearing, and the outer peripheral surface of the fixed shaft is a groove for generating dynamic pressure. A surface of the stator facing the rotation-side sliding surface is a fixed-side bearing surface, and the two rotation-side sliding surfaces and 2 facing the rotation-side sliding surface.
Each of the two bearing surfaces is made of a hard ceramic material, and a groove for generating a dynamic pressure is provided on either one of the two surfaces that form the sliding portion formed by both end surfaces of the rotor in the rotation axis direction. , The other surface is a smooth electric machine.

[Operation] In the electric machine of the present invention, since the sliding portions between the rotor and the stator are each made of a hard ceramic material, and a groove for generating a dynamic pressure is formed on either one of the surfaces, Due to the rotation of the rotor, a fluid dynamic pressure is generated in the sliding portion, and the rotor floats and rotates, and the sliding resistance at this time is extremely small.

Further, the vibration of the rotor is suppressed by the damping action of the fluid film formed on the sliding portion.

In the second aspect, since both end surfaces of the rotor in the direction of the rotation axis are supported by the sliding portions each having a damping action, the vibration of the rotor becomes smaller.

Further, in the third aspect, a sliding portion for supporting a radial load is formed between the through hole formed in the center of the rotor and the fixed shaft, but since a fluid film is similarly formed. Its sliding resistance is small.

EXAMPLES Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a general-purpose brushless flat motor in which a rotation-side sliding surface is formed on one of the end surfaces of the rotor 10 in the rotation axis direction. With a yoke 1 made of a dish-shaped iron having a circular plane, an annular permanent magnet 2 fitted and fixed to the yoke 1, and a ceramic plate 100 fixed to the yoke 1 and the permanent magnet 2 on the inner circumference of the permanent magnet 2. The rotor 10 is configured.
A plurality of magnetic poles are annularly magnetized in the permanent magnet 2 at equal intervals. The ceramic plate 100 is a hard ceramic material,
For example, dense ceramics such as β-SiC, α-SiC, and Si ₃ N ₄ are used, and the surface 8 on the stator side has a smooth flat surface on which grooves for generating dynamic pressure are formed. That is, the rotation-side sliding surface 9 facing the stator has a waviness of 1 μm or less on the entire surface, and a spiral groove having a depth of 3 to 50 μm is processed as a groove for generating a dynamic pressure. A hemispherical recess 12 is formed at a position on the axis.

On the other hand, on the stator side, a stator coil 4 is fixed to a fixed plate 6 which is fixed to a fixed member (not shown) with screws, and a fixed bearing 3 made of a hard ceramic material is fixed on the stator coil 4.

The stator coil 4 is formed by adhering and fixing a plurality of sheet-shaped coils, and includes a Hall element 29 for detecting the magnetic pole of the permanent magnet 2 of the rotor 10 and a tachogenerator 33 for detecting the rotation speed of the rotor 10. It is fixed together.
Further, the surface 8 of the fixed-side bearing 3 fixed to the stator coil 4 corresponding to the rotation-side sliding surface 9 of the rotor 10 is processed into a flat surface with less waviness, like the rotation-side sliding surface 9. A hemispherical recess 11 is also formed at a position corresponding to the rotation axis of the rotor. The space formed by the two recesses 11 and 12 is made of plastic,
A small ball 7 made of metal or ceramics is accommodated,
It is designed to support small radial loads. FIG. 2 is an enlarged cross-sectional view of the central portion of the rotation side sliding surface 9 and the fixed side bearing surface 8 of FIG.

Hemispherical recesses 11 and 1 formed on the rotary shaft 13 of the rotor, respectively.
The space formed by 2 has a substantially spherical shape, and a small ball 7 smaller than the space is accommodated therein. Further, the rotating-side sliding surface 9 of the ceramic plate 100 and the fixed-side bearing surface 8 of the fixed-side bearing 3 are in contact with each other with substantially no clearance when the rotor 10 is stationary. , Rotor 10
When is rotated, dynamic pressure of the fluid 14 is generated in this sliding portion, and the rotor 10 floats. The floating amount of the rotor 10 is determined by various factors such as the viscosity of the fluid interposed in the sliding portion, the rotation speed of the rotor 10, the thrust load in the sliding portion and the shape of the groove for generating dynamic pressure. The viscosity of the upper fluid has a particularly large effect.

FIG. 3 is a front view of the rotary side sliding surface 9, in which a circular ceramic plate 100 is formed with a spiral groove 15 in one direction, and the center 16 of the ceramic plate is processed to the same depth as the groove 15. Has been done. Of course, the center 16 may have the same height as the flat surface, which is the same as the land portion 17 adjacent to the spiral groove 15, or may be deeper than the spiral groove 15. However, since the starting torque is large in this type of electric machine, it is desirable to reduce the area of the land portion 17 which is the convex portion on the rotation-side sliding surface 9.

In FIG. 3, the arrow A indicates the direction in which the rotor 10 rotates, and since the rotation side sliding surface 9 also rotates integrally with the rotor 10, the spiral groove 15 causes the fluid 14 to flow from the outer peripheral side toward the center 16 to form a spiral. A large dynamic pressure is generated in the groove portion 15 from the outer peripheral edge toward the inner peripheral edge, and the center 16 has a uniform pressure distribution. It should be noted that the magnitude of the dynamic pressure generated here is proportional to the magnitude of the force with which the rotor 10 is pressed against the stator 101.
The 10 and the stator 101 can rotate with extremely small sliding resistance via the fluid film.

The most protruding portion of the rotation side sliding surface 9 is the land portion 17, the waviness on the entire surface is within 1 μm, and the protruding portion on the bearing surface 8 side is this smooth bearing surface. The swell on the entire surface is also 1
It is within μm.

Further, the fluid present in this sliding portion is the sliding surface 9 on the rotation side.
Since the gap between the fixed bearing surface 8 and the fixed bearing 8 is small, it also has a damping effect and suppresses a sudden change in the gap of the sliding portion. Therefore, when the rotor 10 rotates, The vibration is extremely small. As described above, the gap between the sliding portions is small and stable, so that the gap between the permanent magnet 2 and the stator coil 4 of the rotor 10 is narrowed, and the magnetic field generated by the coil 4 is also effective.
Transmitted to the side. The fixed plate 6 on the back surface of the coil 4 may be made of silicon steel to prevent leakage of magnetic flux.

Here, since the hard ceramic material used as the fixed-side bearing 3 interposed between the stator coil 4 and the permanent magnet 2 is inserted into the rotating magnetic field, in order to reduce the eddy current loss, the electric A material having a high resistance is preferable, and among the ceramic materials, it is desirable to use α-SiC added with Si ₃ N ₄ or BeO.

In FIG. 1, the fixed-side bearing surface 8 may be used as the surface for forming the groove for generating the dynamic pressure, and in this case, the rotating-side sliding surface 9 facing the fixed-side bearing surface 8 is a smooth flat surface. Use the one left as it is.

FIG. 4 is a longitudinal sectional view of an embodiment in which both ends can output.

A coil 4 formed by stacking sheet coils is fixed from both sides by two ceramic fixed-side bearings 3,3. The fixed-side bearings 3,3 have a central bearing surface 8,8 that is a smooth flat surface. The reference numeral 33 is concave relative to the bearing surface 8 in the central portion so that there is no solid contact with the facing surface of the rotor 10.

In FIG. 4, the position of the permanent magnet 2 attached to the rotor 10 on the lower side is detected by a hall element 29, and a predetermined coil 4 is energized by a control device (not shown) to lower the rotor.
10 will rotate. Since the magnetic flux generated by the coil 4 at this time also appears on the upper surface side of the coil 4, the upper rotor 10 also rotates.

However, the opposite poles of the upper and lower rotors 10 are completely opposite to each other, and as a result, the rotors 10 and 10 attract each other, so that the two rotors 10 and 1 can be attracted without providing special fixing means.
0 is held by the stator.

The small balls 7 correspond to a kind of radial bearing. The small balls 7 have an effect of preventing the rotors 10, 10 and the stator 101 from moving in the radial direction, that is, the radial direction, and also serve as a guide for positioning. As described above, as the small spheres, in addition to iron spheres, stainless spheres, and ceramic spheres, various shapes such as a cylinder and both cones can be used.

In the present invention, the main reason for using a hard ceramic material as a member that constitutes the sliding portion is that a groove for generating a dynamic pressure can be processed with high accuracy, and a slide suitable for generating the dynamic pressure is used. This is because the shape of the portion is maintained even in the state where the dynamic pressure is generated, and furthermore, it has durability against a solid rubbing generated at the time of starting and stopping as long as a certain load is applied.

Also, as a method of processing a groove for dynamic pressure generation on the surface of a hard ceramic material, a resin mask corresponding to the land is attached to the surface of the ceramic material finished to a smooth flat surface, or After applying a resin by screen printing to the area to be cured and hardening it, Al ₂ O ₃ particles, SiC particles, etc. are blown to the exposed ceramic area with high pressure air. After the tossing step, the resin layer on the surface of the ceramic may be removed. As a result, the land becomes the surface as it is when it is finished to be a smooth flat surface, and the groove becomes a processed surface of satin finish.
Incidentally, also in the case of manufacturing a radial bearing utilizing the dynamic pressure effect described later, the groove processing by the shot blast can be similarly performed.

Furthermore, when the electric machine of the present invention is used in various applications, polygonal mirrors are formed on the outer peripheral edge of the rotor to form polygon mirrors, blades are directly fixed to the rotor to form pumps, There is a case where a device for detachably fixing the disk is provided on the upper surface of the disk to be a drive device for the magnetic disk or the optical disk.

FIG. 5 is a vertical cross-sectional view when the electric machine according to the second aspect of the present invention is used as a polygon mirror driving device.

In FIG. 5, reference numeral 50 denotes a support base fastened to a fixing member (not shown), and a cap 51 is arranged on the support base 50 so as to be screwed. The cap 51 separates an inner rotating part from the outside, and a glass window 53 is provided at a position corresponding to the inner polygon mirror 52.

A stator coil 54 is fixed to the support base 50, and a fixed-side bearing 55 made of a hard ceramic disc whose surface is finished to have a smooth surface is fixed to the upper surface of the stator coil 54, and the smooth flat surface 56. Is the fixed bearing surface. A hemispherical recess 57 is formed at a position of the fixed bearing surface 56 corresponding to the rotation axis of the polygon mirror 52, and a groove for generating dynamic pressure is formed outside the recess 57. A polygon mirror 52 is rotatably installed above the fixed-side bearing 55.
A pressing plate 58 is provided above the 52.

The polygon mirror 52 includes a lower rotation side sliding plate 59 made of a hard ceramic material on a surface facing the stator coil 54 and an upper rotation side sliding plate 60 made of a hard ceramic material on a surface facing the pressing plate 58. Permanent magnet 61 and mirror section 62
Is fixed. Lower and upper rotating side sliding plates 59,6
The surface of 0 is similarly polished to a flat surface with less waviness, and hemispherical recesses 63 and 64 are formed at positions on the rotation axis of the polygon mirror 52, respectively. The pressing plate 58 is
A back plate 65 made of iron, a rubber plate 66, and a bearing plate 67 made of a hard ceramic material are laminated and adhered,
The bearing plate 67 faces the polygon mirror 52.

Further, the back plate 65 and the cap 51 are elastically coupled by the spring 68, and press the pressing plate 58 against the polygon mirror 52. A solenoid 69 is provided inside the spring 68, and when the solenoid 69 is powered on, the back plate 58 is attracted to the solenoid 69 and the pressing force on the polygon mirror 52 is reduced or eliminated.

The surface (the lower surface in the figure) of the bearing plate 67 has a flat surface with less undulations and a groove for dynamic pressure generation having a depth of 3 to 50 μm is formed, and a hemispherical recess 70 at a position on the rotation axis of the polygon mirror 52. Are formed.

The recesses 57, 63 and 64, 70 face each other, and small balls 71, 72 made of a hard material (ceramic or metal) are housed in the substantially spherical space formed by the recesses.

FIG. 6 is a horizontal sectional view taken along the line AA in FIG. 5, in which the permanent magnet 61 has a disk shape, eight magnetic poles are magnetized in an annular shape, and the outer circumference thereof forms a mirror portion 62. The part that reflects the laser beam is the part 73 of the regular polygonal side of the mirror part 62, and each side is finished as a mirror surface with high reflectance.
5 and 6, when rotating the polygon mirror 52, the solenoid 69 is energized to slightly lift the pressing plate 58, and then the stator coil 54 is powered on. Since a circuit for speed detection and an element for magnetic pole detection are provided on the upper surface of the stator coil 54 as in the above-described embodiment, the optimum coil is energized by a drive control device (not shown) that receives output signals from these circuits. Then, the polygon mirror 52 rotates at a desired rotation speed. Here, the energization of the solenoid 69 is cut off before the rotation speed of the polygon mirror 52 reaches the rated rotation speed. Therefore, the polygon mirror 52 is in a state in which the pressing plate 58 is pressed by the elasticity of the spring 68. In addition, the polygon mirror 52 rotates with the fluid film formed in the sliding portion between both ends in the rotation axis direction of the polygon mirror 52.

In this embodiment, the vibration of the polygon mirror 52, which is the rotor, in the direction of the rotation axis is suppressed by the damping action of the fluid film formed on both sides of the polygon mirror 52. Further, since the mirror portion 62 of the polygon mirror 52 is a regular polygon that is almost inscribed in the outer peripheral edges of the upper and lower rotary side sliding plates 59, 60,
When handling the polygon mirror 52, the mirror portion 62 is not contaminated.

7 and 8 show an embodiment related to the third aspect of the present application, FIG. 7 is a vertical cross-sectional view of a driving device for a polygon mirror, and FIG. 8 is a horizontal cross-sectional view taken along the line BB in FIG. Is. In FIG. 7, parts common to those in FIG. 5 are designated by the same reference numerals, and similar parts are designated by adding “100”.

Referring to FIG. 7, the cap 51 is screwed to the support base 50, and the end portion 76 of the fixed shaft 74 made of a hard ceramic material is fitted and fixed to the through hole 75 in the center. A stator coil 54 is annularly arranged outside the fixed shaft 74, and this stator coil 54 is also fixed to the support base 50 by an adhesive or a known fastening means. A fixed bearing 155 made of an annular disk made of a hard ceramic material is fixed to the upper surface of the stator coil 54, that is, the surface facing the polygon mirror 152, and the surface of the fixed bearing facing the polygon mirror 152 has less waviness. The surface is finished to have a smooth flat surface and a groove for dynamic pressure generation having a depth of 3 to 50 μm is formed. Further, the surface of the fixed-side bearing and the axis of the fixed shaft 74 are fixed at a right angle.

The polygon mirror 152 has rotation-side sliding surfaces formed on both end surfaces in the rotation axis direction, and the upper rotation-side sliding plate 160 and the lower rotation-side sliding plate 159 are each made of a hard ceramic material. In particular, the lower rotary side sliding plate 159 is integrated with the rotary sleeve 79 of the polygon mirror 152. The inner peripheral surface 78 of the rotary sleeve 79 is a smooth cylindrical surface and maintains a good squareness with the surface of the rotary sliding plate 159 facing the stator coil 54. Further, a groove 80 for generating dynamic pressure is formed in a portion of the fixed shaft 74 corresponding to the rotary sleeve 79 of the polygon mirror 152. This herringbone groove 80
The groove depth of 3 to 15 μm is suitable, and the fixed shaft 74
The clearance between the rotary sleeve 79 and the rotary sleeve 79 is preferably in the range of 2 to 3 μm on each side. The fluid film for supporting the radial load formed by the relative rotational movement between the fixed shaft 74 and the rotary sleeve 79 is preferably such that the parallelism of the sliding surface between the fixed shaft 74 and the rotary sleeve 79 is maintained well. However, in this embodiment, since the length of the rotary sleeve 79 of the polygon mirror 152 (substantially equal to the thickness of the polygon mirror 152) is short, the outer peripheral surface of the fixed shaft 74 and the rotary shaft are rotated. Processing of the inner peripheral surface of the sleeve 79 is easier than that of the conventional example, and high processing accuracy can be achieved.

It should be noted that the mirror section 62, the upper rotary side sliding plate 160, the permanent magnet 161, and the lower rotary side sliding plate 15 which form the polygon mirror 152.
9 (including the rotating sleeve 79) is bonded together, and then the surface of the upper rotating side sliding plate 160 is polished to improve the parallelism of the upper and lower rotating side sliding plates, and the balance is further improved. It has been adjusted.

FIG. 8 is a cross section taken along the line BB in FIG. 7. The permanent magnet 161 has eight poles magnetized in an annular shape, and the outer peripheral edge of the mirror portion 62 has a regular octagonal shape.

FIG. 9 shows the pattern of the sliding surface of the stationary bearing 155 fixed to the upper surface of the stator coil 54.

An arrow 81 indicates the rotation direction of the polygon mirror 152, and a reference numeral 82 indicates a through hole through which the fixed shaft 74 penetrates. Spiral-shaped dynamic pressure generating grooves 83 shown in black and spiral lands 84 are alternately formed all over the surface of the fixed-side bearing 155, and the inner peripheral end of the groove 83 is even. The pressure grooves 85 communicate with each other. Further, a land 86 is formed on the inner peripheral side of the pressure equalizing groove 85. The lands 84 and 86 are located on the same plane.

Therefore, when the polygon mirror rotates in the direction of arrow 81,
The surrounding fluid (air) receives a force from the outer peripheral side of the spiral groove 83 toward the inner peripheral side, and a dynamic pressure of the fluid is generated in the sliding portion.

FIG. 10 shows an example of a groove for generating a dynamic pressure suitable for a polygon mirror for high speed rotation, which is formed on the rotation side sliding surface. An arrow 87 indicates the rotation direction of the polygon mirror, and a through hole 89 for the fixed shaft to pass through is provided in the center of the rotation side sliding plate 88.
Is formed, and the inner peripheral surface 90 of the through hole 89 serves as a rotating sleeve. Spiral-shaped dynamic pressure generating grooves 91 (black-painted portions) are formed on the surface of the rotation-side sliding plate 88, and the adjacent lands 92 are finished into a smooth flat surface. In addition, the outer peripheral edge 93 of the rotation side sliding plate 88 is also a continuous land over the entire circumference, and when the polygon mirror rotates in the direction of the arrow 87, the fluid is generated by the centrifugal force of the spiral groove 91. The fluid flows from the inner peripheral side toward the outer peripheral side, and the fluid pressure is contained by the lands 93 surrounding the outer peripheral side. Therefore, a larger dynamic pressure is generated on the outer peripheral side of the spiral groove 91.

When the groove pattern for dynamic pressure generation of the type shown in FIG. 10 is used, the fluid as a whole flows from the central portion to the outer periphery, and therefore, the central portion of the pressing plate 58 and / or the central portion of the stator coil 54. It is necessary to form a pressure-equalizing passage in the portion that communicates with the atmosphere on the outer peripheral side so that the fluid can be replenished.

[Effects] In the present invention, in the electric machine in which the stator is arranged so as to face the end surface of the rotor in the rotation axis direction, the flat dynamic bearing made of a hard ceramic material is arranged at the sliding portion between the rotor and the stator. Therefore, 1. a small, lightweight, long-life electric machine can be constructed.

2.Thrust bearing has improved wear resistance and corrosion resistance, so maintenance is easy.

3. It can be used in both liquid and gas environments, and even in slurry.

4. The sliding friction resistance of the thrust bearing is 0.001 or less, and the power loss in the bearing is extremely small.

5. A flat motor can be created.

6. Various electric machines can be constructed with a simple structure by fixing functional members such as blades and reflecting mirrors to the rotor or by constructing them integrally with the rotor.

In addition, in the second mode, in addition, 7. Since both ends of the rotor in the direction of the rotation axis are provided with dynamic pressure bearings made of a hard ceramic material, the rotor is As the rotor rotates due to the damping action of the sliding surface, the vibration of the rotor becomes extremely small.

In the third aspect, in addition to the effects of 1 to 7, there are the following effects: 8. A through hole formed in the central portion of the rotor, and a fixed shaft that extends through the through hole. Since the radial bearing thus constructed has a short length in the direction of the rotation axis, it has good machining accuracy and a large dynamic pressure effect.

9. Also, radial bearings are easy to process.

10. If the thrust bearings formed on both end surfaces of the rotor in the direction of the rotation axis are so-called pump-in type dynamic pressure bearings that push the fluid from the outer circumference toward the inner circumference, The pressure rises and the dynamic pressure effect in the radial bearing becomes greater.

11. If one of the thrust bearings formed on both end surfaces of the rotor in the direction of the rotation axis is the pump-in type and the other is the pump-out type, the fluid intervening in the sliding portion will flow in one direction, and The sliding part can be cooled.

12. By adopting the method of 10 above, it is possible to reduce the air resistance of the polygon mirror by incorporating the rotor in a decompressed airtight container.

[Brief description of drawings]

1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a partially enlarged view of FIG. 1, and FIG. 4 is another embodiment of the present invention. FIG. 5 is a vertical cross-sectional view of another embodiment of the present invention, FIG. 6 is a vertical cross-sectional view of another embodiment of the present invention, and FIG. 7 is a vertical cross-sectional view of another embodiment of the present invention. Fig. 8 shows B- in Fig. 7.
B sectional view, FIGS. 9 and 10 show another embodiment of the portion shown in FIG.
The figure is a conventional example. In the drawings, 3 ... Fixed plate, 4 ... Coil 6 ... Fixed plate, 7 ... Small ball 8 ... Bearing surface, 9 ... Rotating side sliding surface 10 ... Rotor, 15 ... Spiral groove 100 ... Ceramic plate

Continuation of front page (72) Inventor Victory Chiba 4720 Fujisawa, Fujisawa-shi, Kanagawa Ebara Research Institute Co., Ltd. (56) Bibliography 57-89357 (JP, U) JP-B 31-10720 (JP, JP, B1)

Claims (8)

[Claims] 1. A rotor (10) rotatably arranged with respect to a stator, the stator having a stator end surface and a stator coil (4) opposed to the rotor end surface in the rotation axis direction, and the rotor being a stator coil. In an electric machine having a permanent magnet (2) having a plurality of magnetic poles facing each other with a gap, the rotor end surface has a rotating side sliding surface made of a hard ceramic material, and the stator end surface facing the rotating side sliding surface. Has a stator bearing surface made of a hard ceramic material that slide-engages with the rotation-side sliding surface, one of the rotation-side sliding surface and the stator bearing surface is a smooth flat surface, and the other is dynamic pressure. It is composed of a flat surface with a groove (15) for generation, a rotation-side recess is formed at a position on the rotation axis of the rotation-side sliding surface, and a fixed-side recess rotates at a position of the stator bearing surface facing the rotation-side recess. In the side recess Facing each other and allowing relative rotational movement between the rotating sliding surface and the stator bearing surface while preventing relative radial movement in the space defined by the rotating and fixed recesses. The hard ceramic material that houses the hard member (7) and that constitutes the stator-side receiving surface is either β-SiC, Si ₃ N ₄ , or BeO-containing α-SiC. 2. Rotor-side sliding surfaces are formed on both end surfaces of the rotor in the rotation axis direction, a stator is arranged facing one rotating-side sliding surface, and the other rotating-side sliding surface is opposed. In an electric machine having a swingable bearing surface, the stator has a stator end surface and a stator coil (54) that face one rotation side sliding surface of the rotor, and the rotor faces the stator coil with a gap. Has a permanent magnet (61) having a plurality of magnetic poles, the stator end surface has a stator bearing surface in a part thereof, and two rotation side sliding surfaces of the rotor,
The stator bearing surface and the swingable bearing surface are each made of hard ceramic material. And a flat surface having a groove for dynamic pressure generation, and
Opposing recesses (57, 63) are provided at positions on the rotation axis of the stator bearing surface and one rotating side sliding surface that are slidingly engaged with each other, and the stator is provided in a space formed by the opposed recesses. A hard member (71) is housed that allows relative rotational movement between the bearing surface and one of the rotary sliding surfaces while blocking relative radial movement, and the other of the swingable bearing surface and rotor The rotation-side sliding surfaces of the two are slidably engaged with each other, and one of them is formed by a smooth flat surface and the other is formed by a flat surface provided with a groove for dynamic pressure generation, and another facing concave portion ( 70, 64) are provided at positions on the rotation axis of the swingable bearing surface and the other rotation-side sliding surface of the rotor, which are slidably engaged with each other, and within the space formed by the other opposed recesses. The relative rotational movement between the swingable bearing surface and the other rotating side sliding surface of the rotor. Rigid member to prevent relative radial movement while in (72)
Is contained and the hard ceramic material forming the stator bearing surface is either β-SiC, Si ₃ N ₄ , or BeO-containing α-SiC. 3. The electric machine according to claim 2, wherein a polygonal mirror is provided on the outer peripheral surface of the rotor. 4. A rotor-side sliding surface is formed on each end surface of the rotor in the rotational axis direction, a stator is disposed facing one rotor-side sliding surface, and a stator is disposed on the other rotor-side sliding surface. In an electric machine having a swingable bearing surface, the stator has a stator end surface and a stator coil (54) that face one rotation side sliding surface of the rotor, and the rotor faces the stator coil with a gap. Has a permanent magnet (161) having a plurality of magnetic poles, the stator end surface has a stator bearing surface in a part thereof, and the two rotation side sliding surfaces of the rotor, the stator bearing surface and the swingable bearing surface are respectively Composed of a hard ceramic material, the stator bearing surface and one of the rotation-side sliding surfaces are in sliding engagement with each other, one of which is a smooth flat surface and the other is a groove for dynamic pressure generation. It is composed of a plane The oscillating bearing surface and the other rotation-side sliding surface of the rotor are in sliding engagement with each other, one of which is a smooth flat surface and the other is a flat surface having a groove for dynamic pressure generation. The fixed shaft (74) is fixed to the stator so as to extend on the rotary shaft of the rotor, and a through hole is formed in the center of the rotor corresponding to the fixed shaft. The inner peripheral surface (78) of the through hole is slidably engaged with each other to form a radial bearing, and the outer peripheral surface of the fixed shaft is provided with a groove (80) for generating dynamic pressure. The outer peripheral surface of the shaft and the inner peripheral surface (78) of the through hole are made of a hard ceramic material, and the hard ceramic material forming the stator bearing surface and the outer peripheral surface of the fixed shaft and the inner peripheral surface (78) of the through hole are formed. The hard ceramic material is characterized by being either β-SiC, Si ₃ N ₄ , or BeO-containing α-SiC. Electric machine to do. 5. The electric machine according to claim 4, wherein the fixed shaft (74) penetrates through both ends of the through hole of the rotor. 6. The electric machine according to claim 5, wherein a polygonal mirror is provided on the outer peripheral surface of the rotor. 7. The electric machine according to any one of claims 4 to 6, wherein a rotor position detecting element is fixed to the stator bearing surface. . 8. The electric machine according to claim 7, wherein a magnetic body is fixed to a position corresponding to the position detecting element on the rotation side sliding surface corresponding to the stator bearing surface, and a large number of magnetic poles are provided. An electric machine characterized by being magnetized.