US20020021477A1 - Bearing device and deflecting-scanning apparatus using the same - Google Patents
Bearing device and deflecting-scanning apparatus using the same Download PDFInfo
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- US20020021477A1 US20020021477A1 US09/092,995 US9299598A US2002021477A1 US 20020021477 A1 US20020021477 A1 US 20020021477A1 US 9299598 A US9299598 A US 9299598A US 2002021477 A1 US2002021477 A1 US 2002021477A1
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- sleeve
- permanent magnet
- shaft
- deflecting
- rotatable
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/12—Scanning systems using multifaceted mirrors
- G02B26/121—Mechanical drive devices for polygonal mirrors
Definitions
- This invention relates to a bearing device having a sleeve fitted to a shaft and supporting it for rotation relative to the shaft, and a deflecting-scanning apparatus using the same.
- a deflecting-scanning apparatus of this kind has been used in an image forming apparatus such as a laser beam printer or a laser facsimile apparatus, and to make this deflecting-scanning apparatus highly accurate, a highly accurately rotatable bearing device has been required, and a dynamic pressure fluid bearing rotatable in non-contact is used in such a bearing device.
- FIG. 1 of the accompanying drawings is a cross-sectional view of a deflecting-scanning apparatus using a bearing device by a dynamic pressure fluid bearing which is disclosed in Japanese Laid-Open Patent Application No. 8-5951.
- a fixed shaft 22 formed of a ceramic material is fixed to the housing 21 of a drive motor, and a rotatable sleeve 24 formed of a ceramic material is rotatably fitted to the fixed shaft 22 .
- a flange 25 formed of aluminum or brass is fixed to the outer periphery of the rotatable sleeve 24 as by shrinkage fitting, and a driving magnet 26 is adhesively secured to the outer periphery of this flange 25 .
- a stator 28 is disposed on a base plate 27 fixed onto the housing 21 so as to be opposed to the driving magnet 26 , whereby a drive motor is constituted.
- a second permanent magnet 30 is mounted on the upper end of the fixed shaft 22 , and a first permanent magnet 29 is fixed to the rotatable sleeve 24 so that magnetic poles of different kinds may be vertically (axially of the fixed shaft) opposed to the second permanent magnet 30 .
- the rotatable sleeve 24 is floated up by a magnetic repulsive force and an air pool 31 is created between the fixed shaft 22 and the first permanent magnet 29 .
- a through-hole 23 a for communicating the air pool 31 with the outside is provided in the first permanent magnet 29 , and a plug 32 is removably mounted in this through-hole 23 a .
- a rotatable polygon mirror 34 is fixed onto the flange 25 by a leaf spring 33 fixed to the rotatable sleeve 24 .
- the fixed shaft 22 and the rotatable sleeve 24 are fitted together with the plug 32 being removed, they can be easily fitted together with the air in the rotatable sleeve 24 flowing out of the through-hole 23 a . Also, when the rotatable sleeve 24 is rotated, the rotatable sleeve 24 is supported in a radial direction by the air film between the rotatable sleeve 24 and the fixed shaft 22 , and is supported in a thrust direction by the repulsive forces of the permanent magnets 29 and 30 .
- the air in the air pool 31 enveloped by the plug 32 acts so as to attenuate the vertical movement of the rotatable sleeve 24 , and holds the rotatable sleeve 24 in its stable floated-up position.
- the two permanent magnets for thrust floating-up are provided so as to be opposed to each other axially of the fixed shaft.
- the rotatable sleeve 24 is very unstably vibrated vertically (axially) relative to a disturbance such as vibration to the apparatus.
- the vertical vibration of the rotatable sleeve is alleviated to some extent by the air pool 31 , but it alone is insufficient.
- Such vibration of the rotatable sleeve provides the vertical movement of the rotatable polygon mirror mounted thereon, and binders good deflection and scanning.
- a bearing device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
- a deflecting-scanning apparatus is structured to include a light source, a deflector for deflectively scanning a light beam from the light source, and a rotating device for rotatively driving the deflector.
- the bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
- the bearing device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device, and one of the first permanent magnet and the second permanent magnet is of such a shape as to surround the other of the first and second permanent magnets.
- the deflecting-scanning apparatus is structured to include a deflector for deflectively scanning a light beam, and a rotating device for rotatively driving the deflector.
- the bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device, and one of the first permanent magnet and the second permanent magnet is of such a shape as to surround the other of the first and second permanent magnet.
- the present invention has been made in view of the above-noted unsolved problem peculiar to the prior art, and an object thereof is to provide a bearing device which can prevent the bearing surface of a rotatable sleeve from being deformed by the pressure force of coupling means such as a spring for assembling a rotatable polygon mirror to the rotatable sleeve to thereby spoil the bearing characteristic and can greatly contribute to improvements in the higher speed and rotational performance of the rotatable polygon mirror, and a deflecting-scanning apparatus using the same.
- the bearing device of the present invention has a fixed shaft and a rotatable sleeve rotatably fitted to the fixed shaft, and is characterized in that the rotatable sleeve is provided with a level difference portion for locally changing the inner diameter of the rotatable sleeve.
- the deflecting-scanning apparatus of the present invention has a rotatable polygon mirror which is a deflector for reflecting a light beam, driving means for rotating it, dynamic pressure fluid bearing means provided with a rotatable sleeve rotatably fitted to a fixed shaft, and coupling means for coupling the rotatable polygon mirror integrally to the rotatable sleeve, and is characterized in that the rotatable sleeve is provided with an engagement portion for engaging the coupling means, and a level difference portion for locally changing the inner diameter of the rotatable sleeve in the engagement portion.
- design may preferably be made such that the inner diameter of the engagement portion of the rotatable sleeve is locally enlarged by the level difference portion.
- a magnet constituting a thrust bearing may preferably be assembled to the level difference.
- FIG. 1 shows the construction of a bearing device according to the prior art.
- FIG. 2 shows the construction of a first embodiment of the bearing device of the present invention.
- FIG. 3 shows the construction of a second embodiment of the bearing device of the present invention.
- FIG. 4 shows the construction of a deflecting-scanning apparatus using the bearing device of the present invention.
- FIG. 5 shows the construction of a third embodiment of the bearing device of the present invention.
- FIG. 6 shows the construction of a fourth embodiment of the bearing device of the present invention.
- FIG. 7 shows the construction of a fifth embodiment of the bearing device of the present invention.
- FIG. 8 shows the construction of a sixth embodiment of the bearing device of the present invention.
- FIG. 9 shows the construction of a seventh embodiment of the bearing device of the present invention.
- FIG. 2 is a cross-sectional view of a first embodiment of the bearing device of the present invention by a dynamic pressure fluid bearing.
- a fixed shaft 22 (a stator portion) formed of a ceramic material is fixed to the housing 21 of a drive motor, and a rotatable sleeve 24 (a rotor portion) formed of a ceramic material is rotatably fitted to the fixed shaft 22 .
- a flange 25 formed of aluminum or brass is fixed to the outer periphery of the rotatable sleeve 24 as by shrinkage fitting, and a driving magnet 26 is adhesively or otherwise secured to the outer periphery of this flange 25 .
- a stator 28 is disposed on a base plate 27 fixed onto the housing 21 , so as to be opposed to the driving magnet 26 , whereby a drive motor is constituted.
- a circular ring-shaped first permanent magnet 2 is mounted on the upper end portion of the rotatable sleeve 24
- a cylindrically shaped second permanent magnet 1 is mounted on the upper end portion of the fixed shaft 22 at a position opposed to the inner peripheral surface of the first permanent magnet 2 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction.
- the inner peripheral surface of the first permanent magnet 2 and the outer peripheral surface of the second permanent magnet 1 are designed such that magnetic poles opposed to each other in a circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the fixed shaft are different kinds of magnetic poles.
- the rotatable sleeve 24 is floated up relative to the fixed shaft 22 by a magnetic force working between the first permanent magnet 2 and the second permanent magnet 1 . Further, a rotatable polygon mirror 34 is fixed onto the flange 25 by a leaf spring 33 fixed to the rotatable sleeve 24 .
- the rotatable sleeve 24 when the rotatable sleeve 24 is rotated, the rotatable sleeve 24 is supported in a radial direction by the air film between the rotatable sleeve 24 and the fixed shaft 22 and is supported in a thrust direction by the magnetic force working between the first permanent magnet 2 and the second permanent magnet 1 .
- the first permanent magnet mounted on the rotor portion and the second permanent magnet mounted on the stator portion are provided in opposed relationship with each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction, whereby they are supported so as to be opposed to each other on the side of permanent magnets for thrust floating-up and therefore, as compared with the repulsive support in the vertical direction (axial direction) shown in FIG. 1, the positional restraining force in the thrust direction is very much strong, and against disturbance such as the vibration of the apparatus, the vertical vibration of the rotatable sleeve which is the rotor portion becomes very small.
- the vertical movement of the rotatable polygon mirror mounted on the rotatable sleeve can also be suppressed to a small level.
- the size in the height direction (axial direction) can be made small and therefore, the apparatus can be made compact.
- FIG. 3 shows a second embodiment of the bearing device of the present invention.
- a cover 23 is provided on the upper end portion of a circulating-shaped first permanent magnet 2 mounted on the upper end portion of a rotatable sleeve 24 .
- the same reference numerals as those in FIG. 2 designate the same members, and need not be described.
- an air pool 31 is created between the fixed shaft 22 and the cover 23 , and the air in this air pool 31 acts so as to attenuate the vertical movement of the rotatable sleeve 24 and therefore, it is possible to hold the rotatable sleeve 24 in a stabler floated-up position than in the first embodiment.
- FIG. 4 shows the construction of a deflecting-scanning apparatus using the bearing device according to the above-described first or second embodiment.
- a laser unit 36 is mounted on an optical box 35 , and on an optical path L from the laser unit 36 , a rotatable polygon mirror 34 and lenses 37 , 38 are disposed in the optical box 35 , and a photosensitive member 39 which is a recording medium is disposed outside the optical box 35 .
- the housing 21 of the drive motor is disposed in the optical box 35 .
- a laser beam emitted from the laser unit 36 is deflected and scanned by the rotatable polygon mirror 34 supported and rotated by the bearing device described above in the first or second embodiment, and is projected as a spotlight onto the photo-sensitive member 39 outside the optical box 35 via the lenses 37 and 38 , whereby main scanning is done.
- a point image formed on the photosensitive member 39 forms an electrostatic latent image with the main scanning by the rotation of the rotatable polygon mirror 34 and the sub-scanning by the photosensitive member 39 being rotated about the shaft of a rotatable drum.
- a corona discharger for uniformly charging the surface of the photosensitive member 39 , a developing device for visualizing the electrostatic latent image formed on the surface of the photosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and the recording information by the light beam emitted from the laser unit 36 is printed on the recording paper.
- a deflecting-scanning apparatus in which the vertical movement of the rotatable polygon mirror by disturbance such as the vibration of the apparatus can be suppressed and high-speed and highly accurate deflection and scanning are stably possible.
- the bearing device according to the present invention and the deflecting-scanning apparatus using the same are a bearing device comprising a sleeve fitted around a shaft for rotation relative to the latter, one of said shaft and said sleeve being a stator portion and the other being a rotor portion, a first permanent magnet mounted on said rotor portion, and a second permanent magnet mounted at a position opposed to said first permanent magnet, said rotor portion being floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet, and a deflecting-scanning apparatus using the same, wherein said first permanent magnet is mounted on the upper end portion of said rotor portion, said second permanent magnet is mounted on the upper end portion of said stator portion, and said first permanent magnet and said second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction.
- the permanent magnets for thrust floating-up are provided on the upper end portions of the rotor portion and the stator portion, respectively, so as to be opposed to each other in the circumferential direction perpendicular to the axial direction, whereby the vibration of the rotor portion (rotatable sleeve) can be prevented and high-speed and highly accurate rotation support and deflection and scanning can be made possible.
- FIG. 5 is a cross-sectional view of a third embodiment of the bearing device of the present invention by a dynamic pressure fluid bearing.
- a fixed shaft 22 (a portion of a stator portion) formed of a ceramic material is fixed to the housing 21 of a drive motor, and a rotatable sleeve 24 (a portion of a rotor portion) formed of a ceramic material is rotatably fitted to the fixed shaft 22 .
- a flange 25 formed of aluminum or brass is fixed to the outer periphery of the rotatable sleeve 24 as by shrinkage fitting, and a driving magnet 26 is adhesively or otherwise secured to the outer periphery of this flange 25 .
- a stator 28 comprised of a coil and a core is disposed on a base plate 27 fixed onto the housing 21 , so as to be opposed to the driving magnet 26 , whereby a drive motor is constituted.
- a circular ring-shaped first permanent magnet 2 is mounted on the upper end portion of the rotatable sleeve 24
- a cylindrically shaped second permanent magnet 1 is mounted on the upper end portion of the fixed shaft 22 at a position opposed to the inner peripheral surface of the first permanent magnet 2 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction.
- the inner peripheral surface of the first permanent magnet 2 and the outer peripheral surface of the second permanent magnet 1 are designed such that magnetic poles opposed to each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the fixed shaft are different kinds of magnetic poles.
- the disposition of the magnetic poles is not restricted thereto.
- the circular ring-shaped first permanent magnet 2 is made of plastic and is of such a shape as to cover the upper portion of the second permanent magnet 1 mounted on the upper end portion of the fixed shaft 22 . That is, the first permanent magnet 2 made of plastic has a circular ring-shaped portion and a lid-shaped portion magnetized so as to integrally have a thrust-supported magnet function. To form the circular ring-shaped portion and the lid-shaped portion integrally with each other as described above, a permanent magnet made of plastic composed of a magnetic material mixed with resin and injection molded is suitable.
- the rotatable sleeve 24 is floated up relative to the fixed shaft 22 by a magnetic force and an air pool 31 (an air damper chamber) is created among the fixed shaft 22 , the second permanent magnet 1 and the first permanent magnet 2 . Further, a rotatable polygon mirror 34 is fixed onto the flange 25 by a leaf spring 33 fixed to the rotatable sleeve 24 .
- the rotatable sleeve 24 when the rotatable sleeve 24 is rotated, the rotatable sleeve 24 is supported in a radial direction by the air film between the rotatable sleeve 24 and the fixed shaft 22 , and is supported in a thrust direction by a magnetic force working between the first permanent magnet 2 and the second permanent magnet 1 .
- the air in the air pool 31 enveloped by the first permanent magnet 2 acts so as to attenuate the vertical movement of the rotatable sleeve 24 , and can hold the rotatable sleeve 24 in a stable floated-up position.
- the first permanent magnet mounted on the rotor portion and the second permanent magnet mounted on the stator portion are provided in opposed relationship with each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction, whereby they are supported so as to be opposed to each other on the side of a permanent magnet for thrust floating-up and therefore, as compared with the vertical (axial) repulsive support shown in FIG. 1, the positional restraining force in the thrust direction is very much strong and against disturbance such as the vibration of the apparatus, the vertical vibration of the rotatable sleeve which is the rotor portion becomes very small. Therefore, the vertical movement of the rotatable polygon mirror mounted on the rotatable sleeve can also be suppressed to a small level.
- the size in the height direction (axial direction) can be made small and therefore, the apparatus can be made compact.
- a cover member for covering the upper portion of the permanent magnet mounted on the upper end portion of the fixed shaft by the use of the permanent magnet made of plastic is integrally molded and formed and therefore, the number of the assembling steps can be decreased and the number of parts can also be decreased, and this leads to a reduction in cost.
- FIG. 6 shows a fourth embodiment of the bearing device of the present invention.
- a through-hole 23 a for communicating the air pool 31 with the outside is formed in the first permanent magnet 2 , and a plug 32 is removably mounted in this through-hole 23 a .
- the same reference numerals as those in FIG. 5 designate the same members and need not be described.
- FIG. 7 shows a fifth embodiment of the bearing device of the present invention.
- This fifth embodiment is an embodiment of a deflecting-scanning apparatus using the bearing device by a dynamic pressure fluid bearing of the shaft rotation type, and use is made of a rotary shaft 3 formed of a ceramic material and a fixed sleeve 4 formed of a ceramic material.
- a groove portion for mounting a leaf spring 33 therein is provided in the upper portion of the rotary shaft 3 .
- a circular ring-shaped second permanent magnet 5 is mounted on the lower end portion of a fixed sleeve 4 which is a stator portion, and a cylindrically shaped first permanent magnet 6 is mounted on the lower end portion of the rotary shaft 3 at a position opposed to the inner peripheral surface of this second permanent magnet 5 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction.
- the inner peripheral surface of the second permanent magnet 5 and the outer peripheral surface of the first permanent magnet 6 are designed such that magnetic poles opposed to each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the rotary shaft are different kinds of magnetic poles.
- the circular ring-shaped second permanent magnet 5 is made of plastic and is of such a shape as to cover the lower portion of the first permanent magnet 6 mounted on the lower end portion of the rotary shaft 3 . That is, the second permanent magnet 5 made of plastic has a circular ring-shaped portion and a lid-shaped portion magnetized so as to integrally have a thrust-supported magnet function. To form the circular ring-shaped portion and the lid-shaped portion integrally with each other as described above, a permanent magnet made of plastic composed of a magnetic material mixed with resin and injection molded is suitable. Further, a through-hole 23 a for communicating an air pool 31 with the outside is formed in the second permanent magnet 5 , and a plug 32 is removably mounted in this through-hole 23 a .
- the same reference numerals as those in FIG. 6 designate the same members and need not be described.
- the shaft is of a rotary type and therefore a cylindrically shaped magnet small in inertia can be disposed on the rotary member side (the rotor portion side), and this leads to the effect that the inertia of the rotary member can be made small.
- the bearing devices according to the abovedescribed third, fourth and fifth embodiments are also used in the deflecting-scanning apparatus as shown in FIG. 4.
- a laser unit 36 is mounted on an optical box 35 , and on an optical path L from the laser unit 36 , a rotatable polygon mirror 34 and lenses 37 , 38 are disposed in the optical box 35 , and a photosensitive member 39 which is a recording medium is disposed outside the optical box 35 .
- the housing 21 of a drive motor is disposed in the optical box 35 .
- a laser beam emitted from the laser unit 36 is deflected and scanned by the rotatable polygon mirror 34 supported and rotated by the bearing device described above in the third, fourth and fifth embodiments, and is projected as a form of light spot onto the photosensitive member 39 outside the optical box 35 via the lenses 37 and 38 , whereby main scanning is done.
- a corona discharger for uniformly charging the surface of the photosensitive member 39 , a developing device for visualizing the electrostatic latent image formed on the surface of the photosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and recording information by the laser beam emitted from the laser unit 36 is printed on the recording paper or the like.
- a deflecting-scanning apparatus in which the vertical movement of the rotatable polygon mirror by disturbance such as the vibration of the apparatus can be suppressed and high-speed and highly accurate deflection and scanning become stably possible and of which the cost can be reduced.
- the bearing device according to the present invention and the deflecting-scanning apparatus using the same are a bearing device comprising a sleeve fitted around a shaft for rotation relative to the latter, one of said shaft and said sleeve being a stator portion and the other being a rotor portion, a first permanent magnet mounted on said rotor portion, and a second permanent magnet mounted at a position opposed to said first permanent magnet, said rotor portion being floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet, and a deflecting-scanning apparatus using the same, wherein said first permanent magnet and said second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction, and said first permanent magnet or said second permanent magnet is of such a shape as to cover said second permanent magnet or said first permanent magnet provided on the end portion of said shaft.
- the permanent magnets for thrust floating-up are provided on the end portions of the rotor portion and the stator portion so as to be opposed to each other in the circumferential direction perpendicular to the axial direction, whereby the vibration of the rotor portion (the rotatable sleeve or the rotary shaft) can be prevented and high-speed and highly accurate rotation support and deflection and scanning are made possible, and an air damper chamber can also be constructed by the use of the permanent magnets for thrust floating-up and therefore, the cost can be reduced.
- FIG. 8 shows the essential portions of a sixth embodiment of the bearing device of the present invention.
- a washer 44 which is a flange is made integral with a rotatable sleeve 43 fitted to a fixed shaft 42 and constituting dynamic pressure fluid bearing means and a rotor magnet 45 is secured to the washer 44 , and a rotatable polygon mirror 34 is urged against the washer 44 by a resilient urging mechanism 46 which is coupling means and integrally coupled thereto and a motor base plate 27 is supported by a motor housing 47 to which the fixed shaft 42 is fixed, and the rotor magnet 45 constitute a motor which is driving means with a stator coil 49 uprightly provided on the motor base plate 27 .
- This motor rotates the rotor magnet 45 and the rotatable polygon mirror 34 together with each other by the stator coil 49 being excited.
- the coupling means is designed to couple the rotatable polygon mirror 34 integrally to the rotatable sleeve 43 through the washer 44 .
- the rotatable sleeve 43 forms air film between it and the fixed shaft 42 by the rotation thereof and constitutes dynamic pressure fluid bearing means rotated in non-contact with the fixed shaft 42 .
- the dynamic pressure fluid bearing in the bearing portion of the rotatable polygon mirror 34 the higher speed of the deflecting-scanning apparatus can be expedited to thereby improve the rotational performance thereof.
- the resilient urging mechanism 46 for urging the rotatable polygon mirror 34 against the washer 44 has a fixed ring 46 a and an E-ring 46 c for urging the fixed ring 46 a against the rotatable polygon mirror 34 through a spring 46 b , and the E-ring 46 c is engaged with an annular groove portion 43 a provided in the rotatable sleeve 43 .
- the fixed shaft 42 and rotatable sleeve 43 constituting the dynamic pressure fluid bearing are made of a ceramic material such as high strength silicon nitride (Si 3 N 4 ) or a metallic material having its surface plated with a wear resisting material in order to reduce the friction between the two and prevent the galling or the like by the entry of dust or the like.
- the washer 44 is made of a metal such as aluminum or brass and is made integral with the rotatable sleeve 43 by shrinkage fitting, and the rotor magnet 45 is adhesively or otherwise secured to the washer 44 .
- the inner diameter thereof is locally changed to form a level difference 43 c to the bearing surface 43 b .
- This level difference 43 c serves to locally enlarge the inner diameter of the rotatable sleeve 43 to thereby prevent the deformation in the tip end portion of the rotatable sleeve 43 from spreading to the bearing surface 43 b of the rotatable sleeve 43 .
- a magnet 50 a is assembled to the level difference portion 43 c of the rotatable sleeve 43 .
- This magnet is opposed to a magnet 50 b secured to the upper end of the fixed shaft 42 , and the two magnets 50 a and 50 b together constitute a thrust bearing 50 for axially supporting the rotatable sleeve 43 and keeping the lower end of the rotatable sleeve 43 in non-contact with a motor housing 47 .
- the inside of the groove portion 43 a of the rotatable sleeve 43 is reinforced by the magnet 50 a assembled to the level difference portion 43 c , and this also leads to the advantage that the amount of deformation by the urging force of the resilient urging mechanism 46 can be reduced.
- the upper end opening of the rotatable sleeve 43 is closed by a lid member 51 , whereby an air pool is formed on the upper end of the fixed shaft 42 .
- This air pool with the thrust bearing 50 comprising the magnets 50 a and 50 b , serves to stabilize the axial position of the rotatable sleeve 43 .
- the resilient urging mechanism including the spring and the E-ring is used to couple the rotatable polygon mirror to the washer integral with the rotatable sleeve
- utilization can also be made of simple coupling means in which the inner end of a belleville spring or the like is directly engaged with the groove portion of the rotatable sleeve.
- FIG. 9 shows a seventh embodiment of the bearing device of the present invention.
- a flange portion 54 against which the underside of a rotatable polygon mirror 34 bears is integrally provided on a rotatable sleeve 53 made of a metal and the washer 44 of the device of FIG. 8 is omitted.
- the number of the assembled parts of the device can be curtailed and the manufacturing cost thereof can be reduced and moreover, there is the advantage that the working of the groove portion 53 a and the level difference 53 c is simple because the rotatable sleeve 53 is made of a metal.
- the bearing devices of the above-described sixth and seventh embodiments are both used in the deflecting-scanning apparatus as shown in FIG. 4.
- a laser unit 36 is mounted on an optical box 35 , and on an optical path L from the laser unit 36 , a rotatable polygon mirror 34 and lenses 37 , 38 are disposed in the optical box 35 , and a photosensitive member 39 which is a recording medium is disposed outside the optical box 35 .
- the housing 21 of a drive motor is disposed in the optical box 35 .
- a laser beam emitted from the laser unit 36 is deflected and scanned by the rotatable polygon mirror 34 supported and rotated by the bearing device described in the sixth or seventh embodiment, and is projected as a spotlight onto the photosensitive member 39 outside the optical box 35 via the lenses 37 and 38 , whereby main scanning is done.
- a corona discharger for uniformly charging the surface of the photosensitive member 39 , a developing device for visualizing an electrostatic latent image formed on the surface of the photosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and the recording information by the laser beam emitted from the laser unit 36 is printed on the recording paper or the like.
- the rotatable polygon mirror 34 abuts against the washer 44 integral with the rotatable sleeve 43 , and is integrally coupled to the rotatable sleeve 43 by the resilient urging mechanism 46 .
- the rotatable sleeve 43 has a groove portion 43 a for assembling the resilient urging mechanism 46 , and this portion is apt to be deformed by the reaction force of the urging force of the resilient urging mechanism 46 .
- a level difference 43 c is provided between the upper end portion of the rotatable sleeve 43 having the groove portion 43 a and the bearing surface 43 b to thereby prevent the deformation by the resilient urging mechanism 46 from spreading to the bearing surface 43 b.
- a dynamic pressure fluid bearing for rotatably supporting a rotatable polygon mirror or the like by air film formed between a fixed shaft and a rotatable sleeve. This is because if the rotatable polygon mirror is coupled to the rotatable sleeve by coupling means, a reaction force such as the pressing force of the coupling means may be applied to the engagement portion of the rotatable sleeve to thereby deform the bearing surface, whereby the bearing performance of the dynamic pressure fluid bearing may be spoiled.
- a level difference for locally changing the inner diameter of the engagement portion of the rotatable sleeve is provided so that even if the engagement portion of the rotatable sleeve is deformed by the above-mentioned coupling means, the deformation may be absorbed by the level difference and prevented from spreading to the bearing surface.
- the present invention can greatly contribute to an improvement in the rotational performance of the deflecting-scanning apparatus and the higher speed thereof.
Abstract
A bearing device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet. The rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet. The first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
Description
- 1. Field of the Invention
- This invention relates to a bearing device having a sleeve fitted to a shaft and supporting it for rotation relative to the shaft, and a deflecting-scanning apparatus using the same.
- 2. Related Background Art
- Heretofore, a deflecting-scanning apparatus of this kind has been used in an image forming apparatus such as a laser beam printer or a laser facsimile apparatus, and to make this deflecting-scanning apparatus highly accurate, a highly accurately rotatable bearing device has been required, and a dynamic pressure fluid bearing rotatable in non-contact is used in such a bearing device.
- FIG. 1 of the accompanying drawings is a cross-sectional view of a deflecting-scanning apparatus using a bearing device by a dynamic pressure fluid bearing which is disclosed in Japanese Laid-Open Patent Application No. 8-5951. A
fixed shaft 22 formed of a ceramic material is fixed to thehousing 21 of a drive motor, and arotatable sleeve 24 formed of a ceramic material is rotatably fitted to thefixed shaft 22. Also, aflange 25 formed of aluminum or brass is fixed to the outer periphery of therotatable sleeve 24 as by shrinkage fitting, and adriving magnet 26 is adhesively secured to the outer periphery of thisflange 25. Further, astator 28 is disposed on abase plate 27 fixed onto thehousing 21 so as to be opposed to thedriving magnet 26, whereby a drive motor is constituted. - On the other hand, a second
permanent magnet 30 is mounted on the upper end of thefixed shaft 22, and a first permanent magnet 29 is fixed to therotatable sleeve 24 so that magnetic poles of different kinds may be vertically (axially of the fixed shaft) opposed to the secondpermanent magnet 30. - Thus, the
rotatable sleeve 24 is floated up by a magnetic repulsive force and anair pool 31 is created between thefixed shaft 22 and the first permanent magnet 29. Also, a through-hole 23 a for communicating theair pool 31 with the outside is provided in the first permanent magnet 29, and aplug 32 is removably mounted in this through-hole 23 a. Further arotatable polygon mirror 34 is fixed onto theflange 25 by aleaf spring 33 fixed to therotatable sleeve 24. - When with such a construction, the
fixed shaft 22 and therotatable sleeve 24 are fitted together with theplug 32 being removed, they can be easily fitted together with the air in therotatable sleeve 24 flowing out of the through-hole 23 a. Also, when therotatable sleeve 24 is rotated, therotatable sleeve 24 is supported in a radial direction by the air film between therotatable sleeve 24 and thefixed shaft 22, and is supported in a thrust direction by the repulsive forces of thepermanent magnets 29 and 30. At this time, the air in theair pool 31 enveloped by theplug 32 acts so as to attenuate the vertical movement of therotatable sleeve 24, and holds therotatable sleeve 24 in its stable floated-up position. - As described above, in this example of the prior art, the two permanent magnets for thrust floating-up are provided so as to be opposed to each other axially of the fixed shaft.
- In such a construction, the
rotatable sleeve 24 is very unstably vibrated vertically (axially) relative to a disturbance such as vibration to the apparatus. The vertical vibration of the rotatable sleeve is alleviated to some extent by theair pool 31, but it alone is insufficient. - Such vibration of the rotatable sleeve provides the vertical movement of the rotatable polygon mirror mounted thereon, and binders good deflection and scanning.
- It is an object of the present invention to solve the above-noted problem and to provide a bearing device in which the disposition of permanent magnets for thrust floating-up is contrived to thereby prevent the vibration of a rotor portion (a rotatable sleeve or a rotary shaft), and a deflecting-scanning apparatus using the same.
- To achieve the above object, a bearing device according to the present invention is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
- Also, a deflecting-scanning apparatus according to the present invention is structured to include a light source, a deflector for deflectively scanning a light beam from the light source, and a rotating device for rotatively driving the deflector. The bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet is mounted on the upper end portion of the rotor portion, the second permanent magnet is mounted on the upper end portion of the stator portion, and the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device.
- Also, to achieve the above object, the bearing device according to the present invention is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device, and one of the first permanent magnet and the second permanent magnet is of such a shape as to surround the other of the first and second permanent magnets.
- Also, the deflecting-scanning apparatus according to the present invention is structured to include a deflector for deflectively scanning a light beam, and a rotating device for rotatively driving the deflector. The bearing device of the rotating device is structured to include a stator portion which includes one of a shaft and a sleeve, a rotor portion which includes the other of the shaft and the sleeve which are structured to be capable of relative rotation therebetween, a first permanent magnet mounted on the rotor portion, and a second permanent magnet mounted at a position opposed to the first permanent magnet, and wherein the rotor portion is floated up relative to the stator portion by a magnetic force working between the first permanent magnet and the second permanent magnet, and wherein the first permanent magnet and the second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction of the bearing device, and one of the first permanent magnet and the second permanent magnet is of such a shape as to surround the other of the first and second permanent magnets.
- Also, in the above-described example of the prior art, as previously described, a dynamic fluid bearing is used in the bearing portion of the rotatable polygon mirror to thereby cope with the higher speed or the like of the apparatus, but there is a problem still left to be solved that if the pressure force of the
leaf spring 33 for assembling therotatable polygon mirror 34 to theflange 25 is strong, the bearing surface of therotatable sleeve 24 will be deformed by the reaction force thereof and as the result, the dimension of the bearing gap will change and the performance of the dynamic pressure fluid bearing will be spoiled. - The present invention has been made in view of the above-noted unsolved problem peculiar to the prior art, and an object thereof is to provide a bearing device which can prevent the bearing surface of a rotatable sleeve from being deformed by the pressure force of coupling means such as a spring for assembling a rotatable polygon mirror to the rotatable sleeve to thereby spoil the bearing characteristic and can greatly contribute to improvements in the higher speed and rotational performance of the rotatable polygon mirror, and a deflecting-scanning apparatus using the same.
- To achieve the above object, the bearing device of the present invention has a fixed shaft and a rotatable sleeve rotatably fitted to the fixed shaft, and is characterized in that the rotatable sleeve is provided with a level difference portion for locally changing the inner diameter of the rotatable sleeve.
- Also, to achieve the above object, the deflecting-scanning apparatus of the present invention has a rotatable polygon mirror which is a deflector for reflecting a light beam, driving means for rotating it, dynamic pressure fluid bearing means provided with a rotatable sleeve rotatably fitted to a fixed shaft, and coupling means for coupling the rotatable polygon mirror integrally to the rotatable sleeve, and is characterized in that the rotatable sleeve is provided with an engagement portion for engaging the coupling means, and a level difference portion for locally changing the inner diameter of the rotatable sleeve in the engagement portion.
- Also, design may preferably be made such that the inner diameter of the engagement portion of the rotatable sleeve is locally enlarged by the level difference portion.
- Also, a magnet constituting a thrust bearing may preferably be assembled to the level difference.
- FIG. 1 shows the construction of a bearing device according to the prior art.
- FIG. 2 shows the construction of a first embodiment of the bearing device of the present invention.
- FIG. 3 shows the construction of a second embodiment of the bearing device of the present invention.
- FIG. 4 shows the construction of a deflecting-scanning apparatus using the bearing device of the present invention.
- FIG. 5 shows the construction of a third embodiment of the bearing device of the present invention.
- FIG. 6 shows the construction of a fourth embodiment of the bearing device of the present invention.
- FIG. 7 shows the construction of a fifth embodiment of the bearing device of the present invention.
- FIG. 8 shows the construction of a sixth embodiment of the bearing device of the present invention.
- FIG. 9 shows the construction of a seventh embodiment of the bearing device of the present invention.
- The bearing device of the present invention and a deflecting-scanning apparatus using the same will hereinafter be described in detail with respect to embodiments thereof shown in FIGS.2 to 4.
- FIG. 2 is a cross-sectional view of a first embodiment of the bearing device of the present invention by a dynamic pressure fluid bearing.
- Referring to FIG. 2, a fixed shaft22 (a stator portion) formed of a ceramic material is fixed to the
housing 21 of a drive motor, and a rotatable sleeve 24 (a rotor portion) formed of a ceramic material is rotatably fitted to thefixed shaft 22. Aflange 25 formed of aluminum or brass is fixed to the outer periphery of therotatable sleeve 24 as by shrinkage fitting, and adriving magnet 26 is adhesively or otherwise secured to the outer periphery of thisflange 25. Further, astator 28 is disposed on abase plate 27 fixed onto thehousing 21, so as to be opposed to thedriving magnet 26, whereby a drive motor is constituted. - On the other hand, a circular ring-shaped first
permanent magnet 2 is mounted on the upper end portion of therotatable sleeve 24, and a cylindrically shaped secondpermanent magnet 1 is mounted on the upper end portion of thefixed shaft 22 at a position opposed to the inner peripheral surface of the firstpermanent magnet 2 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction. The inner peripheral surface of the firstpermanent magnet 2 and the outer peripheral surface of the secondpermanent magnet 1 are designed such that magnetic poles opposed to each other in a circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the fixed shaft are different kinds of magnetic poles. - Thus, the
rotatable sleeve 24 is floated up relative to thefixed shaft 22 by a magnetic force working between the firstpermanent magnet 2 and the secondpermanent magnet 1. Further, arotatable polygon mirror 34 is fixed onto theflange 25 by aleaf spring 33 fixed to therotatable sleeve 24. - Also, when the
rotatable sleeve 24 is rotated, therotatable sleeve 24 is supported in a radial direction by the air film between therotatable sleeve 24 and thefixed shaft 22 and is supported in a thrust direction by the magnetic force working between the firstpermanent magnet 2 and the secondpermanent magnet 1. - As described above, the first permanent magnet mounted on the rotor portion and the second permanent magnet mounted on the stator portion are provided in opposed relationship with each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction, whereby they are supported so as to be opposed to each other on the side of permanent magnets for thrust floating-up and therefore, as compared with the repulsive support in the vertical direction (axial direction) shown in FIG. 1, the positional restraining force in the thrust direction is very much strong, and against disturbance such as the vibration of the apparatus, the vertical vibration of the rotatable sleeve which is the rotor portion becomes very small. The vertical movement of the rotatable polygon mirror mounted on the rotatable sleeve can also be suppressed to a small level.
- Also, as compared with the construction of the repulsive support in the vertical direction (axial direction) shown in FIG. 1, the size in the height direction (axial direction) can be made small and therefore, the apparatus can be made compact.
- FIG. 3 shows a second embodiment of the bearing device of the present invention. In this second embodiment, a
cover 23 is provided on the upper end portion of a circulating-shaped firstpermanent magnet 2 mounted on the upper end portion of arotatable sleeve 24. The same reference numerals as those in FIG. 2 designate the same members, and need not be described. - In this second embodiment, in addition to the effect of the first embodiment, an
air pool 31 is created between thefixed shaft 22 and thecover 23, and the air in thisair pool 31 acts so as to attenuate the vertical movement of therotatable sleeve 24 and therefore, it is possible to hold therotatable sleeve 24 in a stabler floated-up position than in the first embodiment. - FIG. 4 shows the construction of a deflecting-scanning apparatus using the bearing device according to the above-described first or second embodiment. A
laser unit 36 is mounted on anoptical box 35, and on an optical path L from thelaser unit 36, arotatable polygon mirror 34 andlenses optical box 35, and aphotosensitive member 39 which is a recording medium is disposed outside theoptical box 35. Thehousing 21 of the drive motor is disposed in theoptical box 35. - A laser beam emitted from the
laser unit 36 is deflected and scanned by therotatable polygon mirror 34 supported and rotated by the bearing device described above in the first or second embodiment, and is projected as a spotlight onto the photo-sensitive member 39 outside theoptical box 35 via thelenses - A point image formed on the
photosensitive member 39 forms an electrostatic latent image with the main scanning by the rotation of therotatable polygon mirror 34 and the sub-scanning by thephotosensitive member 39 being rotated about the shaft of a rotatable drum. - Around the
photosensitive member 39, there are disposed a corona discharger for uniformly charging the surface of thephotosensitive member 39, a developing device for visualizing the electrostatic latent image formed on the surface of thephotosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and the recording information by the light beam emitted from thelaser unit 36 is printed on the recording paper. - By using the bearing device according to the present embodiment, there can be provided a deflecting-scanning apparatus in which the vertical movement of the rotatable polygon mirror by disturbance such as the vibration of the apparatus can be suppressed and high-speed and highly accurate deflection and scanning are stably possible.
- As described above, the bearing device according to the present invention and the deflecting-scanning apparatus using the same are a bearing device comprising a sleeve fitted around a shaft for rotation relative to the latter, one of said shaft and said sleeve being a stator portion and the other being a rotor portion, a first permanent magnet mounted on said rotor portion, and a second permanent magnet mounted at a position opposed to said first permanent magnet, said rotor portion being floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet, and a deflecting-scanning apparatus using the same, wherein said first permanent magnet is mounted on the upper end portion of said rotor portion, said second permanent magnet is mounted on the upper end portion of said stator portion, and said first permanent magnet and said second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction.
- As described above, in the bearing device according to the present invention and the deflecting-scanning apparatus using the same, the permanent magnets for thrust floating-up are provided on the upper end portions of the rotor portion and the stator portion, respectively, so as to be opposed to each other in the circumferential direction perpendicular to the axial direction, whereby the vibration of the rotor portion (rotatable sleeve) can be prevented and high-speed and highly accurate rotation support and deflection and scanning can be made possible.
- The invention will be further described in detail with respect to embodiments thereof shown in FIGS.5 to 7.
- FIG. 5 is a cross-sectional view of a third embodiment of the bearing device of the present invention by a dynamic pressure fluid bearing.
- Referring to FIG. 5, a fixed shaft22 (a portion of a stator portion) formed of a ceramic material is fixed to the
housing 21 of a drive motor, and a rotatable sleeve 24 (a portion of a rotor portion) formed of a ceramic material is rotatably fitted to the fixedshaft 22. Aflange 25 formed of aluminum or brass is fixed to the outer periphery of therotatable sleeve 24 as by shrinkage fitting, and a drivingmagnet 26 is adhesively or otherwise secured to the outer periphery of thisflange 25. Further, astator 28 comprised of a coil and a core is disposed on abase plate 27 fixed onto thehousing 21, so as to be opposed to the drivingmagnet 26, whereby a drive motor is constituted. - On the other hand, a circular ring-shaped first
permanent magnet 2 is mounted on the upper end portion of therotatable sleeve 24, and a cylindrically shaped secondpermanent magnet 1 is mounted on the upper end portion of the fixedshaft 22 at a position opposed to the inner peripheral surface of the firstpermanent magnet 2 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction. The inner peripheral surface of the firstpermanent magnet 2 and the outer peripheral surface of the secondpermanent magnet 1 are designed such that magnetic poles opposed to each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the fixed shaft are different kinds of magnetic poles. The disposition of the magnetic poles is not restricted thereto. - The circular ring-shaped first
permanent magnet 2 is made of plastic and is of such a shape as to cover the upper portion of the secondpermanent magnet 1 mounted on the upper end portion of the fixedshaft 22. That is, the firstpermanent magnet 2 made of plastic has a circular ring-shaped portion and a lid-shaped portion magnetized so as to integrally have a thrust-supported magnet function. To form the circular ring-shaped portion and the lid-shaped portion integrally with each other as described above, a permanent magnet made of plastic composed of a magnetic material mixed with resin and injection molded is suitable. - Thus, the
rotatable sleeve 24 is floated up relative to the fixedshaft 22 by a magnetic force and an air pool 31 (an air damper chamber) is created among the fixedshaft 22, the secondpermanent magnet 1 and the firstpermanent magnet 2. Further, arotatable polygon mirror 34 is fixed onto theflange 25 by aleaf spring 33 fixed to therotatable sleeve 24. - Also, when the
rotatable sleeve 24 is rotated, therotatable sleeve 24 is supported in a radial direction by the air film between therotatable sleeve 24 and the fixedshaft 22, and is supported in a thrust direction by a magnetic force working between the firstpermanent magnet 2 and the secondpermanent magnet 1. At this time, the air in theair pool 31 enveloped by the firstpermanent magnet 2 acts so as to attenuate the vertical movement of therotatable sleeve 24, and can hold therotatable sleeve 24 in a stable floated-up position. - As described above, the first permanent magnet mounted on the rotor portion and the second permanent magnet mounted on the stator portion are provided in opposed relationship with each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction, whereby they are supported so as to be opposed to each other on the side of a permanent magnet for thrust floating-up and therefore, as compared with the vertical (axial) repulsive support shown in FIG. 1, the positional restraining force in the thrust direction is very much strong and against disturbance such as the vibration of the apparatus, the vertical vibration of the rotatable sleeve which is the rotor portion becomes very small. Therefore, the vertical movement of the rotatable polygon mirror mounted on the rotatable sleeve can also be suppressed to a small level.
- Also, as compared with the construction of the vertical (axial) repulsive support shown in FIG. 1, the size in the height direction (axial direction) can be made small and therefore, the apparatus can be made compact.
- Also, a cover member for covering the upper portion of the permanent magnet mounted on the upper end portion of the fixed shaft by the use of the permanent magnet made of plastic is integrally molded and formed and therefore, the number of the assembling steps can be decreased and the number of parts can also be decreased, and this leads to a reduction in cost.
- FIG. 6 shows a fourth embodiment of the bearing device of the present invention. In this fourth embodiment, a through-
hole 23 a for communicating theair pool 31 with the outside is formed in the firstpermanent magnet 2, and aplug 32 is removably mounted in this through-hole 23 a. The same reference numerals as those in FIG. 5 designate the same members and need not be described. - In this fourth embodiment, in addition to the effect of the third embodiment, when the fixed
shaft 22 and therotatable sleeve 24 are to be fitted together with theplug 32 being removed, the air in therotatable sleeve 24 flows out of the through-hole 23 a and they can be easily fitted together. - FIG. 7 shows a fifth embodiment of the bearing device of the present invention. This fifth embodiment is an embodiment of a deflecting-scanning apparatus using the bearing device by a dynamic pressure fluid bearing of the shaft rotation type, and use is made of a
rotary shaft 3 formed of a ceramic material and afixed sleeve 4 formed of a ceramic material. A groove portion for mounting aleaf spring 33 therein is provided in the upper portion of therotary shaft 3. - A circular ring-shaped second
permanent magnet 5 is mounted on the lower end portion of a fixedsleeve 4 which is a stator portion, and a cylindrically shaped firstpermanent magnet 6 is mounted on the lower end portion of therotary shaft 3 at a position opposed to the inner peripheral surface of this secondpermanent magnet 5 in a circumferential direction (the radial direction of the shaft) perpendicular to an axial direction. The inner peripheral surface of the secondpermanent magnet 5 and the outer peripheral surface of the firstpermanent magnet 6 are designed such that magnetic poles opposed to each other in the circumferential direction (the radial direction of the shaft) perpendicular to the axial direction of the rotary shaft are different kinds of magnetic poles. - The circular ring-shaped second
permanent magnet 5 is made of plastic and is of such a shape as to cover the lower portion of the firstpermanent magnet 6 mounted on the lower end portion of therotary shaft 3. That is, the secondpermanent magnet 5 made of plastic has a circular ring-shaped portion and a lid-shaped portion magnetized so as to integrally have a thrust-supported magnet function. To form the circular ring-shaped portion and the lid-shaped portion integrally with each other as described above, a permanent magnet made of plastic composed of a magnetic material mixed with resin and injection molded is suitable. Further, a through-hole 23 a for communicating anair pool 31 with the outside is formed in the secondpermanent magnet 5, and aplug 32 is removably mounted in this through-hole 23 a. The same reference numerals as those in FIG. 6 designate the same members and need not be described. - In this fifth embodiment, in addition to the effect of the fourth embodiment, the shaft is of a rotary type and therefore a cylindrically shaped magnet small in inertia can be disposed on the rotary member side (the rotor portion side), and this leads to the effect that the inertia of the rotary member can be made small.
- The bearing devices according to the abovedescribed third, fourth and fifth embodiments are also used in the deflecting-scanning apparatus as shown in FIG. 4. A
laser unit 36 is mounted on anoptical box 35, and on an optical path L from thelaser unit 36, arotatable polygon mirror 34 andlenses optical box 35, and aphotosensitive member 39 which is a recording medium is disposed outside theoptical box 35. Thehousing 21 of a drive motor is disposed in theoptical box 35. - A laser beam emitted from the
laser unit 36 is deflected and scanned by therotatable polygon mirror 34 supported and rotated by the bearing device described above in the third, fourth and fifth embodiments, and is projected as a form of light spot onto thephotosensitive member 39 outside theoptical box 35 via thelenses - Around the
photosensitive member 39, there are disposed a corona discharger for uniformly charging the surface of thephotosensitive member 39, a developing device for visualizing the electrostatic latent image formed on the surface of thephotosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and recording information by the laser beam emitted from thelaser unit 36 is printed on the recording paper or the like. - By using the bearing device according to the present embodiment, there can be provided a deflecting-scanning apparatus in which the vertical movement of the rotatable polygon mirror by disturbance such as the vibration of the apparatus can be suppressed and high-speed and highly accurate deflection and scanning become stably possible and of which the cost can be reduced.
- As described above, the bearing device according to the present invention and the deflecting-scanning apparatus using the same are a bearing device comprising a sleeve fitted around a shaft for rotation relative to the latter, one of said shaft and said sleeve being a stator portion and the other being a rotor portion, a first permanent magnet mounted on said rotor portion, and a second permanent magnet mounted at a position opposed to said first permanent magnet, said rotor portion being floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet, and a deflecting-scanning apparatus using the same, wherein said first permanent magnet and said second permanent magnet are provided in opposed relationship with each other in a circumferential direction perpendicular to an axial direction, and said first permanent magnet or said second permanent magnet is of such a shape as to cover said second permanent magnet or said first permanent magnet provided on the end portion of said shaft.
- As described above, in the bearing device according to the present invention and the deflecting-scanning apparatus using the same, the permanent magnets for thrust floating-up are provided on the end portions of the rotor portion and the stator portion so as to be opposed to each other in the circumferential direction perpendicular to the axial direction, whereby the vibration of the rotor portion (the rotatable sleeve or the rotary shaft) can be prevented and high-speed and highly accurate rotation support and deflection and scanning are made possible, and an air damper chamber can also be constructed by the use of the permanent magnets for thrust floating-up and therefore, the cost can be reduced.
- The invention will be further described in detail with respect to embodiments thereof shown in FIGS. 8 and 9.
- FIG. 8 shows the essential portions of a sixth embodiment of the bearing device of the present invention. In this embodiment, a
washer 44 which is a flange is made integral with arotatable sleeve 43 fitted to a fixedshaft 42 and constituting dynamic pressure fluid bearing means and arotor magnet 45 is secured to thewasher 44, and arotatable polygon mirror 34 is urged against thewasher 44 by aresilient urging mechanism 46 which is coupling means and integrally coupled thereto and amotor base plate 27 is supported by amotor housing 47 to which the fixedshaft 42 is fixed, and therotor magnet 45 constitute a motor which is driving means with astator coil 49 uprightly provided on themotor base plate 27. This motor rotates therotor magnet 45 and therotatable polygon mirror 34 together with each other by thestator coil 49 being excited. As described above, the coupling means is designed to couple therotatable polygon mirror 34 integrally to therotatable sleeve 43 through thewasher 44. - The
rotatable sleeve 43 forms air film between it and the fixedshaft 42 by the rotation thereof and constitutes dynamic pressure fluid bearing means rotated in non-contact with the fixedshaft 42. As described above, by using the dynamic pressure fluid bearing in the bearing portion of therotatable polygon mirror 34, the higher speed of the deflecting-scanning apparatus can be expedited to thereby improve the rotational performance thereof. - The
resilient urging mechanism 46 for urging therotatable polygon mirror 34 against thewasher 44 has a fixedring 46 a and an E-ring 46 c for urging the fixedring 46 a against therotatable polygon mirror 34 through aspring 46 b, and the E-ring 46 c is engaged with anannular groove portion 43 a provided in therotatable sleeve 43. - The fixed
shaft 42 androtatable sleeve 43 constituting the dynamic pressure fluid bearing are made of a ceramic material such as high strength silicon nitride (Si3N4) or a metallic material having its surface plated with a wear resisting material in order to reduce the friction between the two and prevent the galling or the like by the entry of dust or the like. Thewasher 44 is made of a metal such as aluminum or brass and is made integral with therotatable sleeve 43 by shrinkage fitting, and therotor magnet 45 is adhesively or otherwise secured to thewasher 44. - When the spring pressure (pressure force) by the
spring 46 b of theresilient urging mechanism 46 is strong, the inner peripheral surface of the upper portion of therotatable sleeve 43 is deformed by a reaction force created in thegroove portion 43 a of therotatable sleeve 43. When such deformation of the inner peripheral surface spreads to the bearingsurface 43 b of therotatable sleeve 43 which faces the dynamicpressure generating groove 42 a of the fixedshaft 42, the dimension of the bearing gap changes and the bearing characteristic as designed cannot be obtained. - For this reason, in the tip end portion (engagement portion) of the
rotatable sleeve 43 having thegroove portion 43 a, the inner diameter thereof is locally changed to form alevel difference 43 c to the bearingsurface 43 b. Thislevel difference 43 c serves to locally enlarge the inner diameter of therotatable sleeve 43 to thereby prevent the deformation in the tip end portion of therotatable sleeve 43 from spreading to the bearingsurface 43 b of therotatable sleeve 43. - Simply by providing the simple level difference on the inner peripheral surface of the
rotatable sleeve 43, the bearing characteristic of the dynamic pressure fluid bearing can be prevented from being degraded due to the spring pressure of theresilient urging mechanism 46. The bearing performance of therotatable polygon mirror 34 is improved in this manner, whereby the rotational performance of the deflecting-scanning apparatus can be stabilized and the higher speed thereof can be expedited. - A
magnet 50 a is assembled to thelevel difference portion 43 c of therotatable sleeve 43. This magnet is opposed to amagnet 50 b secured to the upper end of the fixedshaft 42, and the twomagnets thrust bearing 50 for axially supporting therotatable sleeve 43 and keeping the lower end of therotatable sleeve 43 in non-contact with amotor housing 47. The inside of thegroove portion 43 a of therotatable sleeve 43 is reinforced by themagnet 50 a assembled to thelevel difference portion 43 c, and this also leads to the advantage that the amount of deformation by the urging force of theresilient urging mechanism 46 can be reduced. - Also, the upper end opening of the
rotatable sleeve 43 is closed by alid member 51, whereby an air pool is formed on the upper end of the fixedshaft 42. This air pool, with the thrust bearing 50 comprising themagnets rotatable sleeve 43. - While in the present sixed embodiment, the resilient urging mechanism including the spring and the E-ring is used to couple the rotatable polygon mirror to the washer integral with the rotatable sleeve, utilization can also be made of simple coupling means in which the inner end of a belleville spring or the like is directly engaged with the groove portion of the rotatable sleeve.
- FIG. 9 shows a seventh embodiment of the bearing device of the present invention. In this embodiment, a
flange portion 54 against which the underside of arotatable polygon mirror 34 bears is integrally provided on arotatable sleeve 53 made of a metal and thewasher 44 of the device of FIG. 8 is omitted. The number of the assembled parts of the device can be curtailed and the manufacturing cost thereof can be reduced and moreover, there is the advantage that the working of thegroove portion 53 a and thelevel difference 53 c is simple because therotatable sleeve 53 is made of a metal. - The bearing devices of the above-described sixth and seventh embodiments are both used in the deflecting-scanning apparatus as shown in FIG. 4. A
laser unit 36 is mounted on anoptical box 35, and on an optical path L from thelaser unit 36, arotatable polygon mirror 34 andlenses optical box 35, and aphotosensitive member 39 which is a recording medium is disposed outside theoptical box 35. Thehousing 21 of a drive motor is disposed in theoptical box 35. - A laser beam emitted from the
laser unit 36 is deflected and scanned by therotatable polygon mirror 34 supported and rotated by the bearing device described in the sixth or seventh embodiment, and is projected as a spotlight onto thephotosensitive member 39 outside theoptical box 35 via thelenses - Around the
photosensitive member 39, there are disposed a corona discharger for uniformly charging the surface of thephotosensitive member 39, a developing device for visualizing an electrostatic latent image formed on the surface of thephotosensitive member 39 into a toner image, a transferring device for transferring the toner image to recording paper, etc., and the recording information by the laser beam emitted from thelaser unit 36 is printed on the recording paper or the like. - As described above, in the deflecting-scanning apparatus of the present invention, the
rotatable polygon mirror 34 abuts against thewasher 44 integral with therotatable sleeve 43, and is integrally coupled to therotatable sleeve 43 by theresilient urging mechanism 46. Therotatable sleeve 43 has agroove portion 43 a for assembling theresilient urging mechanism 46, and this portion is apt to be deformed by the reaction force of the urging force of theresilient urging mechanism 46. So, alevel difference 43 c is provided between the upper end portion of therotatable sleeve 43 having thegroove portion 43 a and the bearingsurface 43 b to thereby prevent the deformation by theresilient urging mechanism 46 from spreading to the bearingsurface 43 b. - According to the present invention, there is constructed a dynamic pressure fluid bearing for rotatably supporting a rotatable polygon mirror or the like by air film formed between a fixed shaft and a rotatable sleeve. This is because if the rotatable polygon mirror is coupled to the rotatable sleeve by coupling means, a reaction force such as the pressing force of the coupling means may be applied to the engagement portion of the rotatable sleeve to thereby deform the bearing surface, whereby the bearing performance of the dynamic pressure fluid bearing may be spoiled. So, a level difference for locally changing the inner diameter of the engagement portion of the rotatable sleeve is provided so that even if the engagement portion of the rotatable sleeve is deformed by the above-mentioned coupling means, the deformation may be absorbed by the level difference and prevented from spreading to the bearing surface.
- The present invention is constructed as described above and therefore achieves the following effects.
- It can be avoided that the rotatable sleeve is deformed by the resilient urging mechanism or the like for assembling the rotatable polygon mirror to the rotatable sleeve and the bearing performance of the dynamic pressure fluid bearing is spoiled. Thereby, the present invention can greatly contribute to an improvement in the rotational performance of the deflecting-scanning apparatus and the higher speed thereof.
- By using such a deflecting-scanning apparatus, there can be realized an image forming apparatus of high performance suited for a higher speed.
Claims (63)
1. A bearing device comprising:
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a first permanent magnet mounted on the upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction.
2. A bearing device according to claim 1 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet.
3. A bearing device according to claim 1 , wherein said rotor portion is a rotatable sleeve, and said stator portion is a fixed shaft.
4. A bearing device according to claim 1 , wherein said shaft and said sleeve are formed of a ceramic material.
5. A bearing device according to claim 1 , further comprising a cover provided on the upper end portion of said first permanent magnet.
6. A light deflecting apparatus comprising:
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam;
a first permanent magnet mounted on the upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction.
7. A light deflecting apparatus according to claim 6 , wherein said deflector is a rotatable polygon mirror.
8. A light deflecting apparatus according to claim 6 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet.
9. A light deflecting apparatus according to claim 6 , wherein said rotor portion is a rotatable sleeve, and said stator portion is a fixed shaft.
10. A light deflecting apparatus according to claim 6 , wherein said shaft and said sleeve are formed of a ceramic material.
11. A light deflecting apparatus according to claim 6 , further comprising a cover provided on the upper end portion of said first permanent magnet.
12. A deflecting-scanning apparatus comprising:
a light source;
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam from said light source;
a first permanent magnet mounted on said upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction.
13. A deflecting-scanning apparatus according to claim 12 , wherein said deflector is a rotatable polygon mirror.
14. A deflecting-scanning apparatus according to claim 12 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet.
15. A deflecting-scanning apparatus according to claim 12 , wherein said rotor portion is a rotatable sleeve, and said stator portion is a fixed shaft.
16. A deflecting-scanning apparatus according to claim 12 , wherein said shaft and said sleeve are formed of a ceramic material.
17. A deflecting-scanning apparatus according to claim 12 , further comprising a cover provided on the upper end portion of said first permanent magnet.
18. An image forming apparatus comprising:
a light source;
a recording medium;
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam from said light source;
a first permanent magnet mounted on said upper end portion of said rotor portion; and
a second permanent magnet mounted on the upper end portion of said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction.
19. An image forming apparatus according to claim 18 , wherein said deflector is a rotatable polygon mirror.
20. An image forming apparatus according to claim 18, wherein said rotor portion is floated up relative to said stator portion by a magnetic force working between said first permanent magnet and said second permanent magnet.
21. An image forming apparatus according to claim 18 , wherein said rotor portion is a rotatable sleeve, and said stator portion is a fixed shaft.
22. An image forming apparatus according to claim 18 , wherein said shaft and said sleeve are formed of a ceramic material.
23. An image forming apparatus according to claim 18 , further comprising a cover provided on the upper end portion of said first permanent magnet.
24. A bearing device comprising:
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a first permanent magnet mounted on said rotor portion; and
a second permanent magnet mounted on said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a shape as to surround the other of said first and second magnets.
25. A bearing device according to claim 24 , wherein said one of said first and second permanent magnets is a magnet made of plastic.
26. A bearing device according to claim 24 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force acting between said first permanent magnet and said second permanent magnet.
27. A bearing device according to claim 24 , wherein said shaft and said sleeve are formed of a ceramic material.
28. A light deflecting apparatus comprising:
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam;
a first permanent magnet mounted on said rotor portion; and
a second permanent magnet mounted on said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a shape as to surround the other of said first and second magnets.
29. A light deflecting apparatus according to claim 28 , wherein said deflector is a rotatable polygon mirror.
30. A light deflecting apparatus according to claim 28 , wherein said one of said first and second permanent magnets is a magnet made of plastic.
31. A light deflecting apparatus according to claim 28 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force acting between said first permanent magnet and said second permanent magnet.
32. A light deflecting apparatus according to claim 28 , wherein said shaft and said sleeve are formed of a ceramic material.
33. A deflecting-scanning apparatus comprising:
a light source;
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam from said light source;
a first permanent magnet mounted on said rotor portion; and
a second permanent magnet mounted on said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a shape as to surround the other of said first and second magnets.
34. A deflecting-scanning apparatus according to claim 33 , wherein said deflector is a rotatable polygon mirror.
35. A deflecting-scanning apparatus according to claim 33 , wherein said one of said first and second permanent magnets is a magnet made of plastic.
36. A deflecting-scanning apparatus according to claim 33 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force acting between said first permanent magnet and said second permanent magnet.
37. A deflecting-scanning apparatus according to claim 33 , wherein said shaft and said sleeve are formed of a ceramic material.
38. An image forming apparatus comprising:
a light source;
a recording medium;
a rotor portion comprising one of a shaft and a sleeve, said shaft being fitted into said sleeve so as to be capable of relative rotation between said shaft and said sleeve;
a stator portion comprising the other of said shaft and said sleeve;
a deflector mounted on said rotor portion for deflecting and scanning a light beam from said light source;
a first permanent magnet mounted on said rotor portion; and
a second permanent magnet mounted on said stator portion so as to be opposed to said first permanent magnet in a circumferential direction perpendicular to an axial direction;
wherein one of said first and second permanent magnets is of such a shape as to surround the other of said first and second magnets.
39. An image forming apparatus according to claim 38 , wherein said deflector is a rotatable polygon mirror.
40. An image forming apparatus according to claim 38 , wherein said one of said first and second permanent magnets is a magnet made of plastic.
41. An image forming apparatus according to claim 38 , wherein said rotor portion is floated up relative to said stator portion by a magnetic force acting between said first permanent magnet and said second permanent magnet.
42. An image forming apparatus according to claim 38 , wherein said shaft and said sleeve are formed of a ceramic material.
43. A bearing device comprising:
a fixed shaft; and
a rotatable sleeve rotatably fitted to said fixed shaft, said rotatable sleeve being provided with a level difference portion for locally changing the inner diameter of said rotatable sleeve.
44. A bearing device according to claim 43 , wherein the inner diameter of said rotatable sleeve is designed to be locally enlarged by said level difference portion.
45. A bearing device according to claim 43 , wherein a magnet constituting a thrust bearing is assembled to said level difference portion.
46. A light deflecting apparatus comprising:
a fixed shaft;
a rotatable sleeve rotatably fitted to said fixed shaft, said rotatable sleeve being provided with a level difference portion for locally changing the inner diameter of said rotatable sleeve;
a deflector for deflecting and scanning a light beam; and
coupling means for integrally coupling said deflector to said rotatable sleeve.
47. A light deflecting apparatus according to claim 46 , wherein said rotatable sleeve is provided with an engagement portion for engaging said coupling means, and said rotatable sleeve is provided with said level difference portion in said engagement portion.
48. A light deflecting apparatus according to claim 47 , wherein the inner diameter of said rotatable sleeve is designed to be locally enlarged in said engagement portion by said level difference portion.
49. A light deflecting apparatus according to claim 47 , wherein said coupling means is designed to integrally couple said deflector to said rotatable sleeve through a washer.
50. A light deflecting apparatus according to claim 46 , wherein said deflector is a rotatable polygon mirror.
51. A light deflecting apparatus according to claim 46 , wherein a magnet constituting a thrust bearing is assembled to said level difference portion.
52. A deflecting-scanning apparatus comprising:
a light source;
a fixed shaft;
a rotatable sleeve rotatably fitted to said fixed shaft, said rotatable sleeve being provided with a level difference portion for locally changing the inner diameter of said rotatable sleeve;
a deflector for deflecting and scanning a light beam from said light source; and
coupling means for integrally coupling said deflector to said rotatable sleeve.
53. A deflecting-scanning apparatus according to claim 52 , wherein said rotatable sleeve is further provided with an engagement portion for engaging said coupling means, and said level difference portion is provided in said engagement portion.
54. A deflecting-scanning apparatus according to claim 53 , wherein the inner diameter of said rotatable sleeve is designed to be locally enlarged in said engagement portion by said level difference portion.
55. A deflecting-scanning apparatus according to claim 53 , wherein said coupling means is designed to integrally couple said deflector to said rotatable sleeve through a washer.
56. A deflecting-scanning apparatus according to claim 52 , wherein said deflector is a rotatable polygon mirror.
57. A deflecting-scanning apparatus according to claim 52 , wherein a magnet constituting a thrust bearing is assembled to said level difference portion.
58. An image forming apparatus comprising:
a light source;
a recording medium;
a fixed shaft;
a rotatable sleeve rotatably fitted to said fixed shaft, said rotatable sleeve being provided with a level difference portion for locally changing the inner diameter of said rotatable sleeve;
a deflector for deflecting and scanning a light beam from said light source; and
coupling means for integrally coupling said deflector to said rotatable sleeve.
59. An image forming apparatus according to claim 58 , wherein said rotatable sleeve is further provided with an engagement portion for engaging said coupling means, and said level difference portion is provided in said engagement portion.
60. An image forming apparatus according to claim 59 , wherein the inner diameter of said rotatable sleeve is designed to be locally enlarged in said engagement portion by said level difference portion.
61. An image forming apparatus according to claim 59 , wherein said coupling means is designed to integrally couple said deflector to said rotatable sleeve through a washer.
62. An image forming apparatus according to claim 58 , wherein said deflector is a rotatable polygon mirror.
63. An image forming apparatus according to claim 58 , wherein a magnet constituting a thrust bearing is assembled to said level difference portion.
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9-168098 | 1997-06-10 | ||
JP16809897A JPH112776A (en) | 1997-06-10 | 1997-06-10 | Deflection scanner |
JP9-155068 | 1997-06-12 | ||
JP9155068A JPH112244A (en) | 1997-06-12 | 1997-06-12 | Bearing device and deflection scanner using it |
JP9161196A JPH116975A (en) | 1997-06-18 | 1997-06-18 | Bearing device and deflecting scanner using the same |
JP9-161196 | 1997-06-18 |
Publications (2)
Publication Number | Publication Date |
---|---|
US20020021477A1 true US20020021477A1 (en) | 2002-02-21 |
US6392771B1 US6392771B1 (en) | 2002-05-21 |
Family
ID=27320764
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/092,995 Expired - Lifetime US6392771B1 (en) | 1997-06-10 | 1998-06-08 | Bearing device and deflecting-scanning apparatus using the same |
Country Status (1)
Country | Link |
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US (1) | US6392771B1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6693733B2 (en) * | 2000-11-16 | 2004-02-17 | Sankyo Seiki Mfg. Co., Ltd. | Polygonal mirror fixing device |
US20060001939A1 (en) * | 2004-07-02 | 2006-01-05 | Samsung Electronics Co., Ltd. | Dynamic bearing and beam deflecting apparatus employing the same |
US20130135696A1 (en) * | 2011-11-30 | 2013-05-30 | Susumu Mikajiri | Optical scanner and image forming apparatus including same |
US20180284426A1 (en) * | 2017-03-31 | 2018-10-04 | Minebea Mitsumi Inc. | Polygon mirror scanner motor |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9783365B2 (en) | 2013-09-30 | 2017-10-10 | Canon Kabushiki Kaisha | Driving force transmission device and image-forming apparatus |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60244913A (en) * | 1984-05-21 | 1985-12-04 | Toshiba Corp | Supporting device for rotating body |
US5018880A (en) | 1988-06-28 | 1991-05-28 | Canon Kabushiki Kaisha | Dynamic pressure bearing device |
JPH0686503A (en) * | 1992-09-03 | 1994-03-25 | Hitachi Ltd | Motor, polygon mirror motor and disk driving motor |
JPH06160751A (en) * | 1992-11-19 | 1994-06-07 | Nippon Seiko Kk | Light deflection device |
JPH085951A (en) * | 1994-06-23 | 1996-01-12 | Canon Inc | Optical deflector |
JPH1114929A (en) * | 1997-06-27 | 1999-01-22 | Canon Inc | Deflection scanning device |
-
1998
- 1998-06-08 US US09/092,995 patent/US6392771B1/en not_active Expired - Lifetime
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6693733B2 (en) * | 2000-11-16 | 2004-02-17 | Sankyo Seiki Mfg. Co., Ltd. | Polygonal mirror fixing device |
US20060001939A1 (en) * | 2004-07-02 | 2006-01-05 | Samsung Electronics Co., Ltd. | Dynamic bearing and beam deflecting apparatus employing the same |
US20130135696A1 (en) * | 2011-11-30 | 2013-05-30 | Susumu Mikajiri | Optical scanner and image forming apparatus including same |
US8717640B2 (en) * | 2011-11-30 | 2014-05-06 | Ricoh Company, Ltd. | Optical scanner and image forming apparatus including same |
US20180284426A1 (en) * | 2017-03-31 | 2018-10-04 | Minebea Mitsumi Inc. | Polygon mirror scanner motor |
US10634905B2 (en) * | 2017-03-31 | 2020-04-28 | Minebea Mitsumi Inc. | Polygon mirror scanner motor |
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US6392771B1 (en) | 2002-05-21 |
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