JP2023037369A - Fluid bearing motor and rotary polygon mirror and image forming apparatus - Google Patents

Abstract

To provide a fluid bearing motor that can effectively prevent floating of a rotating body with a simple configuration and can effectively reduce noise caused by wind noise, a rotary polygon mirror using the same, and an image forming apparatus.SOLUTION: In a fluid bearing motor 32, a rotating body 33 having a shaft 40 and a flange 45 fixed integrally to the shaft 40 and having a large diameter part 45b and a small diameter part 45a, and a rotating body storage member 48 having a contour larger than the large diameter part 45b and having a circular through hole 48a with a diameter larger than the small diameter part 45a in a central part are provided in a sealed space 47; the rotating body 33 has the small diameter part 45a loosely fit into the through hole 48a so that a first gap 49 is formed between an outer peripheral surface of the rotating body and the through hole 48a, and is arranged rotatably in the sealed space 47 in a mode where a second gap 50 is formed between an undersurface of the large diameter part 45b and a top face of the rotating body storage member 48; during the rotation of the rotating body 33, an air current 53 is formed in which air inside the sealed space 47 flows in a circumferential direction from a lower part of the rotating body 33 toward an outer peripheral part of the large diameter part 45b through the first gap 49 and the second gap 50.SELECTED DRAWING: Figure 3

Description

The present invention relates to a fluid dynamic bearing motor, a rotating polygon mirror, and an image forming apparatus.

In optical scanners used in digital copiers, laser printers, etc., rotating polygon mirrors, which are generally used to deflect light beams at high speed, are required to rotate at high speed and have durability of several thousand hours or more. . For this reason, it is difficult to drive by a motor using a normal rolling bearing, and it is mainly driven by a fluid dynamic bearing motor.

As is conventionally known, the fluid dynamic bearing motor has a problem that the rotating body tends to float when the rotating body is rotated at high speed. That is, in order to reduce the drive energy as much as possible and increase the number of revolutions of the rotor, it is necessary to reduce the rotational efficiency of the rotor.
When such a rotating body is rotated at high speed in a closed space, the air in contact with the rotating body also rotates together with the rotating body. The atmospheric pressure on the outer peripheral side increases, forming a negative pressure above the shaft of the rotating body. If the rotor is light, the action of this negative pressure causes the rotor to float.

In the rotating polygon mirror described above, the outer peripheral surface of the rotating body is formed as a deflecting reflecting surface. and deterioration of vibration characteristics. As a technique for suppressing floating of a rotating body in such a fluid dynamic bearing motor, a technique described in "Patent Document 1" is known.
In the fluid dynamic bearing motor disclosed in "Patent Document 1", a flat plate member having a through hole is attached to the upper and lower surface of the upper case to form an air circulation passage. Then, after passing through the through hole of the flat plate member from the upper part of the shaft and heading toward the flange outer peripheral side between the flange upper surface and the flat plate member, from the flange outer peripheral side, the flat plate member and the surface portion (opposing the flange upper surface in the closed space An airflow (airflow of gas such as air enclosed in the closed space) is formed that circulates to the space above the shaft through the space between the shaft and the outer surface. With this configuration, the negative pressure in the vicinity of the upper portion of the shaft is effectively eliminated, and the levitation of the rotating body is effectively suppressed.

Further, in "Patent Document 2", there is disclosed an optical deflector in which a polygon mirror is fixed to a rotating body that is supported by a bearing and is rotationally driven by a motor. An optical deflector is disclosed that includes a ring-shaped permanent magnet fixed to a body, rotational position detection means for detecting the rotational position of the permanent magnet, and a stator assembly in which nine coils are fixed to a stator core. there is
According to the optical deflector described in "Patent Document 2", it is possible to provide an optical deflector that reduces the voltage drop due to the reactance (inductance) of the coil, increases the motor efficiency at high speed rotation, and reduces the power consumption.

However, in recent years, a high rotational speed exceeding 40,000 rpm is required for rotating polygon mirrors. There is a problem that the flat plate member is likely to generate noise and vibration due to the influence of the air current. In other words, it is considered that although the levitation of the rotating body is suppressed by the effect of the circulation passage and the airflow suppressing means, the rotating body rotates at high speed and noise is generated. In such a case, overall noise of 10 kHz or less is likely to increase together with high-frequency noise.
SUMMARY OF THE INVENTION The present invention solves the above-described problems, and provides a fluid dynamic bearing motor capable of effectively suppressing floating of a rotating body with a simple structure and effectively reducing noise due to wind noise, a rotating polygon mirror using the same, and an image forming apparatus. The purpose is to provide a device.

According to a first aspect of the invention, there is provided a fluid dynamic bearing motor for rotating a rotating body in a sealed space, wherein the rotating body has a shaft and a flange integrally fixed to the shaft and having a large diameter portion and a small diameter portion. and a rotating body accommodating member having an outer shape larger than that of the large-diameter portion and a circular through hole having a diameter larger than that of the small-diameter portion in the central portion is provided in the sealed space, and the rotating body The small-diameter portion is loosely fitted into the through-hole so that a first gap is formed between the outer peripheral surface and the through-hole, and between the lower surface of the large-diameter portion and the upper surface of the rotating body housing member. is rotatably disposed in the sealed space in such a manner that a second gap is formed between the two gaps, and when the rotating body rotates, air in the sealed space flows from the bottom of the rotating body into the first gap and the first gap. 2, an air current flowing in the circumferential direction toward the outer peripheral side of the large-diameter portion is formed.

According to the present invention, the negative pressure in the vicinity of the upper portion of the shaft is effectively eliminated, the floating of the rotor can be prevented, and stable rotation can be realized without the rotor swinging up and down in the axial direction. Moreover, since the rotating body accommodating member does not have grooves or protrusions that cause wind noise on the rotating body side, it is possible to effectively suppress the occurrence of wind noise. As a result, it is possible to realize quiet light beam deflection with little wind noise without deterioration of jitter characteristics and vibration characteristics due to floating of the rotating polygon mirror.

1 is a schematic front view of an image forming apparatus to which one embodiment of the invention can be applied; FIG. 1 is a schematic perspective view of an optical scanning device to which one embodiment of the invention can be applied; FIG. 1 is a schematic cross-sectional view illustrating a rotating polygon mirror as a fluid dynamic bearing motor according to one embodiment of the present invention; FIG. FIG. 4 is a schematic plan view showing a rotor 33 including a shaft 40 and a flange 45 and a rotating body accommodating member 48 by removing the upper portion of the case 35 of the rotating polygon mirror shown in FIG. FIG. 5 is a graph showing the results of examining the floating amount (mm) of the rotor by changing the rotational speed of the rotor in the range of 15000 to 55000 rpm in the configuration of one embodiment of the present invention and the conventional configuration having a flat plate member.

FIG. 1 shows an image forming apparatus to which one embodiment of the invention can be applied. In FIG. 1, an image forming apparatus 1 for forming a monochrome image includes a drum-shaped photoreceptor 2 as a latent image carrier, and supplies toner to an electrostatic latent image formed on the photoreceptor 2 to form a toner image. and a paper feeding unit 4 for supplying paper P as a recording medium.

The image forming apparatus 1 has an optical scanning device 6 as exposure means for forming an electrostatic latent image on the surface of the photoreceptor 2 based on image information from an externally connected host device 5 .
Further, the image forming apparatus 1 is a transfer unit that conveys the paper P and transfers the toner image formed on the photoreceptor 2 onto the paper P at a transfer position that is a nip portion between the photoreceptor 2 and the transfer roller 7 . It has a transfer/conveyance unit 8 .
Further, the image forming apparatus 1 has a cleaning device 9 for removing residual toner from the photosensitive member 2 after transfer.

The image forming apparatus 1 includes a pair of registration rollers 10 for feeding the paper P fed from the paper feeding unit 4 to a transfer position at a predetermined timing, and a toner image of the paper P transferred at the transfer position. and a fixing unit 11 for fixing.
Further, the image forming apparatus 1 includes a paper discharge unit 12 for discharging the paper P on which the toner image is fixed after passing through the fixing unit 11, and the above-described units including a CPU, a nonvolatile memory, and a volatile memory. and a control unit 13 as a control means for controlling the operation of.

The photoreceptor 2 is a cylindrical rotating body, and has a photosensitive layer 2a on its surface, which is a surface to be scanned by each scanning light emitted from the optical scanning device 6 . The photoreceptor 2 is rotatably supported by the apparatus main body 14, and is driven to rotate in the direction indicated by the arrow a in FIG. 1 by driving means (not shown).
The paper feed unit 4 has a manual paper feed unit 15 that feeds the paper P, and a paper feed roller 16 that feeds the paper P arranged in the manual paper feed unit 15 toward the registration roller pair 10 . .

The optical scanning device 6 forms an electrostatic latent image on the photosensitive layer 2a by emitted scanning light. In this embodiment, since the image forming apparatus 1 is an image forming apparatus that forms a monochrome image, only one optical scanning device 6 is provided in the apparatus main body 14 .
When a device capable of forming a color image is used as the image forming device, the image forming device forms electrostatic latent images corresponding to yellow, cyan, magenta, and black toners as optical scanning devices. A plurality of optical scanning devices are provided.

The developing unit 3 has a developing roller 17 which is a developer carrying member, and uses the developing roller 17 to adhere the toner accommodated inside to the electrostatic latent image formed on the photosensitive layer 2a, thereby statically developing the toner. A toner image is formed by visualizing the electrostatic latent image.
The transfer roller 7 is arranged to face the photosensitive member 2 at the transfer position, and transfers the toner image formed on the photosensitive layer 2a onto the paper P. As shown in FIG.

The fixing unit 11 has a heating roller 18 having a heat source inside, and a pressure roller 19 that presses against the heating roller 18 to form a fixing nip, which is a fixing position.
The fixing unit 11 fixes the transferred toner image on the surface of the paper P by passing the paper P with the toner image transferred through the fixing nip through the action of heat and pressure.
The heating roller 18 has an aluminum cylindrical roller, a silicone rubber layer formed on the outer circumference of the cylinder, and a halogen heater as a heat generator provided inside the cylinder.
The paper discharge unit 12 has a pair of paper discharge roller pairs 20 arranged facing each other, and a paper discharge tray 21 that holds the paper P discharged by the paper discharge roller pair 20 .

The control unit 13 has a CPU (Central Processing Unit), a main memory (MEM-P), a north bridge (NB), and a south bridge (SB).
Further, the control unit 13 has an AGP (Accelerated Graphics Port) bus, an ASIC (Application Specific Integrated Circuit), and a local memory (MEM-C).
Further, the control unit 13 has an HD (Hard Disk), an HDD (Hard Disk Drive), a PCI bus, and a network I/F.

The CPU processes and computes data according to programs stored in the main memory, and controls the operations of the above-described units. The main memory serves as a storage area for the control unit 13 and stores programs and data for realizing each function of the control unit 13 .
The local memory (MEM-C) is used as a copy image buffer and code buffer. The HD is a storage for accumulating image data, accumulating font data used for printing, and accumulating forms. The HDD controls reading or writing of data to the HD under the control of the CPU. The network I/F transmits and receives information to and from an external device such as an information processing device via a communication network.
The control unit 13 functions as communication control means for controlling two-way communication with a host device 5 such as a personal computer via a communication network or the like. Further, the control unit 13 also functions as image data processing means for sending image data sent from the host device 5 to the optical scanning device 6 .

As shown in FIG. 2, the optical scanning device 6 has a light source unit 22 composed of a surface emitting laser array as a light source of laser light composed of a light beam L which is scanning light, and a light beam L incident from the light source unit 22 to be parallel to each other. It has a coupling lens 23 that Further, the optical scanning device 6 has an aperture plate 24 arranged downstream of the coupling lens 23 in the traveling direction of the light flux L, and a cylindrical lens 25 .
The optical scanning device 6 includes a polygon mirror 26 as a rotating polygonal mirror which is a deflector that deflects the incident light beam L by rotation, and a uniform angular motion of the deflected scanning light in the main scanning direction into a uniform linear motion. and an f.theta. lens 27 as a scanning lens to be replaced.
The optical scanning device 6 has a toroidal lens 28 arranged on the optical path of the light beam L that has passed through the fθ lens 27, and two mirrors 29 and 30 for guiding the light beam L to a predetermined position by reflection. ing. Further, the optical scanning device 6 has a synchronization detecting means 31 for receiving part of the scanning light as scanning light for synchronization and determining the writing start position of the image.

The aperture plate 24 has an aperture and defines the beam diameter of the parallel light flux L transmitted through the coupling lens 23 . The cylindrical lens 25 converges the light flux L that has passed through the opening of the aperture plate 24 near the deflection reflecting surface of the polygon mirror 26 via the mirror 29 .
The polygon mirror 26 is made of a regular hexagonal columnar member having a low height, and has six deflecting reflecting surfaces formed on its side surfaces. The polygon mirror 26 is rotationally driven at a constant angular velocity in the direction indicated by the arrow b by driving means (not shown).

Next, a fluid dynamic bearing motor used in one embodiment of the present invention will be described. FIG. 3 is a view for explaining an embodiment in which the fluid dynamic bearing motor of the present invention is implemented as a rotating polygon mirror, showing a central cross-sectional view of the rotating polygon mirror.
In FIG. 3, a rotating polygon mirror 32, which is a fluid dynamic bearing motor, has a rotor 33 as a rotating body, a stator 34, and a case 35, and is configured as an outer rotating brushless motor that is airtight. there is

The stator 34 is constructed by fixing a base substrate 37 to a housing 36 made of aluminum, for example, with screws (not shown) for fixing the substrate, and caulking a bearing member 38 to the base substrate 37 . The upper portion of the bearing member 38 is formed in a hollow cylindrical shape, and a thrust plate 39 is arranged at the bottom of the bearing member 38 to rotatably support the lower end portion of the shaft 40 that is the axis of the rotor 33 .
The shaft 40 is rotatably supported by a sintered oil-impregnated bearing 41 provided inside the hollow cylindrical portion of the bearing member 38 . A seal member 42 is fixed to the upper end of the hollow cylindrical portion of the bearing member 38 to prevent lubricating oil from scattering from the inside of the bearing member 38 . A core 43 around which a driving coil 44 is wound is adhesively fixed to the outer peripheral portion of the hollow cylindrical portion of the bearing member 38 .
Instead of the support by the sintered oil-impregnated bearing 41, a bearing system using an air dynamic pressure bearing, a magnetic bearing, a fluid oil bearing, or the like may be adopted.

The rotor 33 is constructed by fixing a flange 45 to the shaft 40 and adhesively fixing a magnet 46 with multipolar magnetic attachment to the lower inner circumference of a cylindrical space in a small diameter portion 45a formed in the lower portion of the flange 45. ing. That is, the rotor 33, which is a rotating body, has a shaft 40 as an axis, a flange 45 integrally fixed to the shaft 40, and a magnet 46 integrated with the shaft 40 or the flange 45. there is The shaft 40 is made of martensitic stainless steel, and the flange 45 is made of an aluminum alloy. The stator 34 has a drive coil 44 that applies a drive magnetic field to the magnet 46, a bearing member 38 that supports the shaft 40, a base board 37 that holds the shaft 40 and the bearing member 38, and a housing 36 on which these are mounted. are doing.

Martensitic stainless steel (for example, SUS420J2) can be quenched and its surface hardness can be increased, so it is suitable as a material for the shaft 40 that requires wear resistance. The shaft 40 is fitted in a cylinder of a sintered oil-impregnated bearing 41 made of a sintered material and supported in the radial direction. The shaft 40 has a diameter of 15 μm or less (radius of 7.5 μm or less) in order to obtain the effect of efficiently circulating the impregnated oil and to obtain a suitable bearing rigidity. A dynamic pressure generating groove is provided.
As the dynamic pressure generating groove, a groove of a known suitable shape can be provided on the outer peripheral surface of the shaft 40 or the cylindrical inner peripheral surface of the sintered oil-impregnated bearing 41. It is more preferable to provide A lower end 40a of the shaft 40 has a spherical surface and functions as a pivot bearing by coming into contact with a thrust plate 39 made of wear-resistant resin.

The flange 45 forms a mirror portion of a rotating polygon mirror (polygon mirror), and six deflecting reflecting surfaces 45c are formed on the outer peripheral surface of the large diameter portion 45b. The rotor 33 is arranged in a closed space 47 formed by the housing 36 that constitutes the case 35 and the stator 34, and is cut off from the outside air. A fluid is enclosed in the sealed space 47, and examples of the fluid include gas, and examples of the gas include gases such as air, nitrogen, helium, and argon. Note that the fluid is not limited to these gases.
A protruding portion 45d is formed on the upper portion of the flange 45, and a recessed portion 35a is formed in a circular shape at a portion of the case 35 facing the protruding portion 45d to avoid interference with the shaft 40 and the protruding portion 45d. there is

A rotating body accommodating member 48 is arranged in the sealed space 47 at a portion located outside the small diameter portion 45 a of the flange 45 . The rotating body housing member 48 is made of stainless steel, other steel materials, aluminum alloys, plastics, or the like, and has a circular through hole 48a in its central portion. The rotating body accommodating member 48 has an outer shape formed so as to be able to be fitted into the inner peripheral surface of the case 35, and the diameter of the through hole 48a is formed to be slightly larger than the diameter of the small diameter portion 45a. The rotating body accommodating member 48 is adhesively fixed to the housing 36 in such a manner that the small-diameter portion 45a is loosely fitted in the through hole 48a and a gap is created between the lower surface and the upper surface of the large-diameter portion 45b, and is enclosed in the sealed space 47. fixed position.

That is, the rotating body housing member 48 is loosely fitted with the flange 45 constituting the rotor 33, which is the rotating body, and is brought close to the lower surface of the large-diameter portion 45b and its upper surface facing the lower surface with a gap therebetween. It is fixedly provided in the closed space 47 in a state.
The shape of the through-hole 48a is not limited to a circular shape, and may be a polygonal shape close to a circular shape. The polygonal shape that is close to a circular shape is, for example, a regular N-sided polygon such that N≧6.

The rotating body accommodating member 48 may be firmly fixed in the sealed space 47 to the extent that it does not vibrate due to the airflow generated in the sealed space 47. In addition to the adhesive fixing described above, the rotating body housing member 48 may be fixed by a method such as circumferential caulking or welding. You may When the rotor 33 and the rotating body accommodating member 48 are arranged at predetermined positions in the closed space 47, a first gap 49 is formed between the outer peripheral surface of the small diameter portion 45a and the through hole 48a, and the lower surface of the large diameter portion 45b is formed. and the upper surface of the rotating housing member 48, a second gap 50 is formed.
A side wall portion of the case 35 forming the sealed space 47 has a window for receiving the entrance and exit of the deflected light beam, that is, the light beam emitted from the light source side and for emitting the light beam deflected by the deflecting reflection surface 45c. 51 is formed, and a glass plate 52 is adhesively fixed to the side wall portion of the case 35 outside the window 51 .
Thus, the rotating polygon mirror 32 is unitized by the stator 34 , the case 35 and the rotor 33 . This configuration can improve workability during maintenance and replacement.

Methods for fixing the magnet 46 to the lower portion of the inner peripheral surface of the small-diameter portion 45a include adhesion and press-fitting. is preferred.
The core 43 is opposed to the inner surface of the magnet 46 with an appropriate gap therebetween. 33 is rotationally driven.
When the rotor 33 is driven to rotate at a high speed, a laser beam, which is a light beam from the light source side, enters the sealed space 47 through the window 25 and exits from the window 25 while being reflected and deflected by the deflection reflection surface 45c. be done.

4 is a plan view showing the rotor 33 including the shaft 40 and the flange 45 and the rotating body housing member 48, with the upper part of the case 35 removed in the rotating polygon mirror 32 shown in FIG.
When the rotor 33 rotates at high speed, as shown in FIG. 3, the gas in the second gap (0.3 to 3 mm in size) flows toward the outer periphery of the flange 45 due to centrifugal force, and near the deflecting reflecting surface 45c. And the upper part of the rotor 33 becomes a positive pressure. Further, the space between the lower surface of the large-diameter portion 45b and the upper surface of the rotating housing member 48 becomes negative pressure. This pressure relationship creates an airflow 53 within the enclosed space 47 .

That is, the airflow 53 flows from the bottom of the flange 45 through the first gap 49 and the second gap 50 to the large diameter portion 45b. formed by flowing in the circumferential direction to the outer peripheral side of the In other words, when the rotor 33 rotates, the rotary polygon mirror 32 moves from the lower part and the peripheral surface of the small-diameter part 45a of the flange 45 through between the lower surface of the large-diameter part 45b and the upper surface of the rotating body housing member 48, An air flow 53 for discharging the fluid is formed in the circumferential direction toward the outer peripheral portion of the large diameter portion 45b. The flow of this airflow 53 acts to eliminate uneven pressure in the sealed space 47, and this action effectively eliminates the negative pressure in the vicinity of the upper portion of the shaft 40, thereby preventing the rotor 33 from floating and allowing the rotor 33 to move in the axial direction. It was confirmed that stable rotation can be achieved without vertical rocking.
Further, since the rotating body housing member 48 does not have grooves or projections that cause wind noise on the rotor 33 side, it is possible to effectively suppress the generation of wind noise. As a result, it is possible to realize quiet light beam deflection with little wind noise without deterioration of jitter characteristics and vibration characteristics due to floating of the rotating polygon mirror.

Here, the size of the second gap 50 is preferably about 0.3 to 3 mm as described above. If the second gap 50 becomes larger or smaller than this range, it is not possible to effectively form the airflow 53 that flows in the circumferential direction toward the outer peripheral side of the large diameter portion 45b. Further, when the second gap 50 exceeds 3 mm, the height of the sealed space 47 that seals the rotor 33 increases, and the rotating polygon mirror 32 tends to increase in size.
In addition, it was confirmed that both the overall value noise of 10 kHz or less and the high frequency noise (in this embodiment, since the rotating polygon mirror is a hexahedral polygon, the frequency is six times as high as the rotation component) are both sufficiently small. was done.

A specific example of one embodiment of the present invention shown in FIGS. 3 and 4 will now be described.
The flange 45 was made of an aluminum alloy having six deflecting reflection surfaces 45c as described above, and was shrink-fitted to the cylindrical shaft 40 of martensitic stainless steel having a diameter of 3 mm. The weight of the rotor 33 is 19g.
A hydrodynamic groove was formed on the inner peripheral surface of the sintered oil-impregnated bearing 41 that supports the shaft 40, and the diameter of the bearing gap was set to 10 μm.

The flange 45 functioning as a polygon mirror has an inscribed circle radius of 36 mm for each deflecting reflection surface 45c. The case 35 is made of aluminum and has a thickness of 3-5 mm. A closed space 47 formed by the case 35 and the housing 36 has a cylindrical shape with a diameter of 60 mm and a height of 30 mm. The recess 35a has a diameter of 16 mm and a depth of 3 mm.
The rotating body accommodating member 48 is made of aluminum or resin material, and has a thickness of 10.3 mm, a diameter of 60 mm, and a diameter of the through hole 48a of 29 mm.
The gap between the lower surface of the large-diameter portion 45b and the upper surface of the rotating housing member 48, that is, the gap of the second gap 50 is 0.3 mm, and the thickness of the glass plate 52 is 2 mm. The diameter of the protrusion 45d is 12 mm, and the gap between the protrusion 45d and the recess 35a is 2 mm in radius.

In the apparatus of the embodiment described above, the floating amount (mm) of the rotor 33 was examined by changing the rotational speed of the rotor 33 in the range of 15000 to 55000 rpm, and the results shown in FIG. 5 were obtained. As shown in FIG. 5, by providing the rotating body accommodating member 48, it was possible to substantially prevent the rotor 33 from floating in the rotational speed range of 15,000 to 55,000 rpm. For comparison, the floating amount was examined when a flat plate member disclosed in "Patent Document 1" (Japanese Patent No. 4758076) was provided in place of the rotating body accommodating member 48 . As a result, as shown in FIG. 5, it was found that when the number of rotations exceeds 45000 rpm, a larger floating phenomenon occurs than when the rotating body accommodating member 48 is provided.

An acoustic sensor was installed at a position 500 mm away from the glass plate 52 in the apparatus of the above-described embodiment, and the overall noise of 10 kHz or less and the noise of the sixth harmonic (4596.4 Hz) were investigated. was 37.9 dB, and the sixth harmonic noise was 24.2 dB.
In the case of the rotating polygon mirror using the flat plate member as the comparative example, the overall noise was 39.9 dB, and the sixth harmonic noise was 27.5 dB.
From this, it was found that the use of the rotating body accommodating member 48 not only prevents the rotor 33 from floating, but also has the effect of reducing noise.

The rotating polygon mirror shown in the above-described embodiments and examples is a fluid dynamic bearing motor 32 that rotates a rotating body 33 within a closed space 47, and the rotating body 33 is integrally fixed to a shaft 40. It has a large-diameter portion 45b and a flange 45 having a small-diameter portion 45a, and has an outer shape larger than that of the large-diameter portion 45b. A body accommodating member 48 is provided in the closed space 47, and the small diameter portion 45a of the rotating body 33 is loosely fitted in the through hole 48a so that a first gap 49 is formed between the outer peripheral surface of the rotating body 33 and the through hole 48a. , is rotatably disposed in the closed space 47 in such a manner that a second gap 50 is formed between the lower surface of the large diameter portion 45b and the upper surface of the rotating body accommodating member 48, and when the rotating body 33 rotates, the closed space Fluid bearing motor 32 in which an air flow 53 is formed in which the air in 47 flows in the circumferential direction from the lower portion of the rotating body 33 to the outer peripheral side of the large diameter portion 45b via the first gap 49 and the second gap 50. (Claim 1).

The rotating body 33 has a stator 34 and a case 35 in which the rotating body 33 is enclosed, and the rotating body 33 has a magnet 46 integrated with the shaft 40 or the flange 45. a drive coil 44 that allows the motor to move, a bearing member 38 that supports the shaft 40, a base substrate 37 that holds the shaft 40 and the bearing member 38, and a housing 36 on which these are mounted. It is a fluid dynamic bearing motor 32 that forms a closed space 47 by forming a sealed space 47 (claim 2).
Further, the shaft 40 is the hydrodynamic bearing motor 32 rotatably supported by the sintered oil-impregnated bearing 41 of the bearing member 38 (claim 3).
The shaft 40 is made of martensitic stainless steel, the flange 45 is made of aluminum alloy, and the shaft 40 is fixed to the flange 45 by shrink fitting or press fitting (claim 4).

A plurality of deflecting reflection surfaces 45c are formed on the outer peripheral surface of the large-diameter portion 45b, and a window 51 through which light beams enter and exit is formed in the sealed space 47. The window 51 is covered with a glass plate 52. It is a mirror 32 (claim 5).
Also, the sealed space 47 is the rotating polygon mirror 32 formed by the stator 34 and the case 35 described in claim 2 (claim 6).
Also, the window 51 is the rotary polygon mirror 32 formed in the case 35 (claim 7).
Also, the rotating polygon mirror 32 is unitized by the stator 34, the case 35, and the rotating body 33 (claim 8).

Further, the image forming apparatus 1 is characterized by having a fluid dynamic bearing motor (Claim 9).
Further, the image forming apparatus 1 is characterized by having a rotating polygonal mirror (Claim 10).
The rotating polygon mirror 32, which is the fluid dynamic bearing motor shown in the above embodiment, can be applied as the polygon mirror 26 as the rotating polygon mirror in the image forming apparatus 1 shown in FIG. 1 and the optical scanning device 6 shown in FIG. is.
In the image forming apparatus 1 shown in FIG. 1, the housing 36 constituting the stator 34 shown in the above embodiment constitutes the optical scanning device 6 and accommodates therein an optical system comprising the polygon mirror 26 and various lenses. It may be the device main body of the optical scanning device 6 .

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise limited in the above description, the scope of the present invention set forth in the appended claims. Various modifications and changes are possible within the scope of the gist.
The effects described in the embodiments of the present invention merely exemplify the most suitable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. isn't it.

1 Image forming device 32 Fluid bearing motor (rotating polygon mirror)
33 rotating body (rotor)
34 Stator 35 Case 36 Housing 37 Base board 38 Bearing member 40 Shaft
41 Sintered Oil Impregnated Bearing 44 Drive Coil 45 Flange 45a Small Diameter Portion 45b Large Diameter Portion 45c Deflection Reflecting Surface 46 Magnet 47 Closed Space 48 Rotating Body Accommodating Member 48a Through Hole 49 First Gap 50 Second Gap 51 Window 52 Glass Plate 53 air flow

Japanese Patent No. 4758076 JP 2006-259446 A

Claims (10)

In a fluid dynamic bearing motor that rotates a rotating body in a closed space,
The rotating body has a shaft and a flange integrally fixed to the shaft and having a large diameter portion and a small diameter portion,
A rotating body accommodating member having an outer shape larger than that of the large diameter portion and having a circular through hole having a diameter larger than that of the small diameter portion in the central portion is provided in the sealed space,
The rotating body has the small diameter portion loosely fitted in the through hole so that a first gap is formed between the outer peripheral surface and the through hole, and the lower surface of the large diameter portion and the rotating body housing. rotatably arranged in the sealed space in such a manner that a second gap is formed between the upper surface of the member;
When the rotating body rotates, the air in the sealed space flows in the circumferential direction from the lower part of the rotating body to the outer peripheral side of the large diameter portion via the first gap and the second gap. A fluid dynamic bearing motor is formed. The fluid dynamic bearing motor according to claim 1,
Having a stator and a case in which the rotating body is enclosed,
The rotating body has a magnet integrated with the shaft or the flange,
The stator has a drive coil that applies a drive magnetic field to the magnet, a bearing member that supports the shaft, a base substrate that holds the shaft and the bearing member, and a housing on which these are mounted,
A fluid dynamic bearing motor, wherein the case cooperates with the stator to form the sealed space. 3. The fluid dynamic bearing motor according to claim 1,
A fluid dynamic bearing motor, wherein the shaft is rotatably supported by a sintered oil-impregnated bearing of the bearing member. The fluid dynamic bearing motor according to any one of claims 1 to 3,
A fluid dynamic bearing motor, wherein the shaft is made of martensitic stainless steel, the flange is made of an aluminum alloy, and the shaft is fixed to the flange by shrink fitting or press fitting. A rotating polygon mirror using the fluid dynamic bearing motor according to any one of claims 1 to 4,
A rotating multifaceted surface, wherein a plurality of deflecting reflecting surfaces are formed on an outer peripheral surface of the large diameter portion, a window for light beams entering and exiting is formed in the sealed space, and the window is covered with a glass plate. mirror. In the rotating polygon mirror according to claim 5,
3. A rotary polygon mirror, wherein said closed space is formed by the stator and the case according to claim 2. In the rotating polygon mirror according to claim 6,
A rotating polygon mirror, wherein the window is formed in the case. The rotating polygon mirror according to claim 6 or 7,
A rotating polygon mirror, wherein the stator, the case, and the rotating body are unitized. An image forming apparatus comprising the fluid dynamic bearing motor according to claim 1 . An image forming apparatus comprising the rotating polygon mirror according to claim 5 .

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