JP2006072038A - Optical deflector, optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical deflector in which a turbulence is suppressed by straightening the airflow in the vicinity of a motor, a power consumption is reduced and an uneven rotation is reduced. <P>SOLUTION: The optical deflector comprises: a rotating body on which a mirror is formed; a bearing which supports the rotating body; a motor which drives the rotating body; and a case member arranged around the rotating body which is housed in a substantially sealed space. A partition wall is provided between the rotating part and the non-rotating part of the motor, and the substantially sealed space is formed between the case member and the partition wall. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical deflector used in an optical scanning device of an electrophotographic copying machine, a printer, a facsimile machine, or a combination of these.

An electrophotographic recording apparatus using a laser writing apparatus such as a digital copying machine or a laser printer is an optical deflector that rotates at a high speed of 20000 revolutions / minute or more as the printing speed increases and the pixel density increases. Has been put to practical use.
With regard to such a technique, the present applicant has applied for an optical deflector as described below in Patent Document 1, for example. That is, in a brushless motor having a magnetic gap in the radial direction, the rotor magnet 5 is an open magnetic path in the state of a rotating body, and a single magnetic flux is linked so that the axial leakage flux in the axial direction and the radial leakage flux are interlinked. A brushless motor having a magnetic body 14 disposed therein and a sealed polygon scanner using the brushless motor include a motor housing made of a single metal member, and a fixed shaft fixed to a holding portion provided at a central portion thereof. It is structured and connected to the circuit board 24 with a harness by cutting out a portion corresponding to the harness portion 23.
As a problem of this conventional example, since the outer peripheral surface of the stator core facing the rotor magnet has irregularities, the airflow around the stator core is disturbed by the rotation of the rotating body, and turbulence is generated, resulting in an increase in power consumption. At the same time, there is a problem that the rotation unevenness also increases.
Further, by cutting out a portion corresponding to the harness portion 23, the harness is connected to the circuit board 24 by a harness, and the cut-out portion through the harness is sealed with a resin. It was difficult to ensure sex.
On the other hand, as the speed of rotation of the optical deflector increases, the windage loss, which is a loss due to friction between the mirror and the air, increases, and as a result, the power consumption and heat generation of the motor increase, which hinders high-speed rotation. And the influence of the temperature rise of the optical deflector mounted on the optical scanning device affects the optical parts such as lenses arranged in the periphery, and the deformation due to the temperature rise of the optical parts deteriorates the optical characteristics and degrades the image quality. There are things to do. Therefore, it is necessary to reduce the heat generation as much as possible in the optical deflector that is a heating element.
By the way, since the windage loss of the mirror of the optical deflector is large at atmospheric pressure, the following method is known as a conventional technique for reducing the air pressure around the mirror in order to reduce the windage loss.
1) A method in which the product is used under a reduced pressure in the production stage (for example, see Patent Document 2).
2) A method in which an optical deflector and a pump are connected, and the periphery of the mirror of the optical deflector is decompressed by the pump and used (for example, see Patent Document 3).
3) A method in which the dynamic pressure air bearing is provided with a pump function, and the pressure around the mirror is reduced as the mirror rotates (for example, see Patent Document 4).
JP 2002-272077 A Japanese Patent Laid-Open No. 09-19100 Japanese Patent Laid-Open No. 08-121471 Japanese Patent No. 2645773

However, in any of the above methods, in order to maintain a constant reduced pressure state, it is necessary to ensure the airtightness of the space in which the rotating body is accommodated. It was difficult to secure the product for a long time, and there was a problem that sufficient reliability could not be obtained.
An object of the present invention is to regulate airflow around a motor to suppress turbulence, reduce power consumption, and reduce rotation unevenness.
In addition, the airtightness of the sealed space where the rotating body is stored is sufficiently secured, and the air pressure around the mirror is reduced to reduce the windage of the mirror, and the motor power consumption and heat generation are reduced to increase the speed. It is to provide an optical deflector.
It is another object of the present invention to provide an optical scanning device with low power consumption and high accuracy by using the optical deflector of the present invention, and to provide a high-quality image forming apparatus.
Specifically, in claim 1, a partition wall is provided between the rotating portion and the non-rotating portion of the motor, and a substantially sealed space is formed between the case member and the partition wall, whereby a substantially sealed space in which the rotating body is accommodated. By improving the airtightness of the motor and reducing the turbulent flow generated at the rotating part and the non-rotating part of the motor, it is possible to reduce the power consumption and reduce the rotation unevenness, thereby providing a high-speed optical deflector.
According to a second aspect of the present invention, there is provided an optical deflector that reduces the air loss around the rotating body, reduces power consumption and heat generation, and increases the speed by reducing the pressure of the substantially enclosed space to the atmospheric pressure of 98 kPa.
According to the third aspect of the present invention, the pressure of the substantially sealed space is set to 30 kPa to 90 kPa, so that the bearing rigidity of the dynamic pressure gas bearing is ensured even when the pressure is reduced, and an optical deflector with stable rotation is provided.
According to a fourth aspect of the present invention, there is provided an optical deflector that can easily reduce the pressure of the sealed space after assembling the case and the partition wall by providing a pressure reducing gate.

According to a fifth aspect of the present invention, there is provided an optical deflector that fills a substantially sealed space with a gas having a specific gravity smaller than that of air, thereby reducing windage loss around the rotating body, reducing power consumption and heat generation, and increasing the speed.
According to a sixth aspect of the present invention, there is provided an optical deflector in which deterioration of optical characteristics (reflectance, etc.) is small, such as mirror contamination, by using an inert helium gas as the gas filling the substantially sealed space.
According to a seventh aspect of the present invention, there is provided an optical deflector in which the partition wall is made of a nonmagnetic material, thereby increasing the use efficiency of the magnetic flux of the motor.
According to an eighth aspect of the present invention, there is provided an optical deflector that is made of stainless steel and has a sufficient partition wall strength and a reduced partition wall thickness to increase the use efficiency of the magnetic flux of the motor.
According to a ninth aspect of the present invention, there is provided an optical deflector that performs optical scanning of a plurality of light sources by forming a plurality of mirrors in the axial direction.
According to a tenth aspect of the present invention, there is provided an optical deflector in which a partition is easily provided between a rotating portion and a fixed portion of a motor by using an axial gap type motor.
According to the eleventh aspect of the present invention, there is provided an optical scanning device in which the scanning speed is increased by increasing the speed of the optical deflector. Further, the present invention provides an optical scanning device in which the power consumption and heat generation of the optical deflector are reduced, the temperature change of optical components such as lenses due to the heat generated by the optical deflector is small, and the scanning beam shape is constant and stable.
According to a twelfth aspect of the present invention, there is provided a multi-beam optical scanning device in which the scanning speed is increased by increasing the speed of the optical deflector. Further, the present invention provides a multi-beam optical scanning device in which the power consumption and heat generation of the optical deflector are reduced, the temperature change of optical components such as lenses due to the heat generated by the optical deflector is small, and the scanning beam shape is constant and stable.
According to a thirteenth aspect of the present invention, there is provided an image forming apparatus in which image formation is speeded up by increasing the scanning speed of the optical scanning device. In addition, a temperature change of an optical component such as a lens due to heat generated by the optical deflector is small, and a scanning beam of the optical scanning device is constant and stable, and an image forming apparatus with high image quality is provided.

In order to solve the above-mentioned problem, the invention according to claim 1 is a rotating body on which a mirror is formed, a bearing that supports the rotating body, a motor that drives the rotating body, and the periphery of the rotating body. In the optical deflector in which the rotating body is housed in a sealed space, a partition is provided between the rotating portion and the non-rotating portion of the motor, and the sealed space is connected to the case member. The most important feature is that it is formed between the partition walls.
The invention according to claim 2 is characterized in that, in the optical deflector according to claim 1, the air pressure in the sealed space is reduced with respect to the atmospheric pressure.
The invention according to claim 3 is characterized in that, in the optical deflector according to claim 2, the bearing is a dynamic pressure gas bearing, and the pressure in the sealed space is reduced to 30 kPa to 90 kPa.
The invention according to claim 4 is characterized in that, in the optical deflector according to claim 2, the case is provided with a gate for reducing the pressure of the sealed space.
The invention according to claim 5 is characterized in that, in the optical deflector according to claim 1, the sealed space is filled with a gas having a specific gravity smaller than that of air.
According to a sixth aspect of the present invention, in the optical deflector according to the fifth aspect, the gas filled in the sealed space is helium gas.
According to a seventh aspect of the invention, in the optical deflector of the first aspect, the partition is made of a nonmagnetic material.

The invention according to claim 8 is characterized in that, in the optical deflector according to claim 7, the nonmagnetic material is austenitic stainless steel.
The invention according to claim 9 is characterized in that, in the optical deflector according to claim 1, a plurality of the mirrors are formed in the axial direction.
The invention according to claim 10 is characterized in that, in the optical deflector according to claim 1, the motor is an axial gap type motor.
According to the eleventh aspect of the present invention, a beam from a semiconductor laser is guided to a scanned surface through an optical system including an optical deflector to form a light spot and deflected by the optical deflector. An optical scanning device that scans a scanning surface with a scanning line is characterized in that the optical deflector is the optical deflector according to any one of claims 1 to 10.
According to a twelfth aspect of the present invention, there are a plurality of beams from the semiconductor laser, and a plurality of light spots are formed by being guided to a scanned surface via an optical system including the optical deflector. In an optical scanning device that performs adjacent scanning of a plurality of scanning lines on the surface to be scanned by deflecting, the optical deflector is the optical deflector according to any one of claims 1 to 10. Features.
A thirteenth aspect of the present invention is an image forming apparatus for forming a latent image by performing optical scanning with a light scanning device on a photosensitive surface of a photosensitive medium, and visualizing the latent image to obtain an image. The most important feature is that the optical scanning device according to claim 11 or 12 is used as an optical scanning device for optically scanning the photosensitive surface.

According to claim 1, by providing a partition between the rotating part and the non-rotating part of the motor, and forming a substantially sealed space between the case member and the partition, the airtightness of the substantially sealed space in which the rotating body is accommodated. By reducing the turbulence generated at the rotating part and the non-rotating part of the motor, it is possible to provide an optical deflector that reduces the power consumption and the rotational unevenness and increases the speed.
According to the second aspect of the present invention, there is provided an optical deflector which reduces the windage loss around the rotating body, reduces power consumption and heat generation, and increases the speed by reducing the pressure in the substantially sealed space with respect to the atmospheric pressure of 98 kPa. can do.
According to the third aspect, by setting the atmospheric pressure of the substantially sealed space to 30 kPa to 90 kPa, it is possible to provide an optical deflector that secures the bearing rigidity of the dynamic pressure gas bearing even when the pressure is reduced and the rotation is stable.
According to the fourth aspect of the present invention, it is possible to provide an optical deflector that can easily reduce the pressure of the substantially sealed space after assembling the case and the partition wall by providing the pressure reducing gate.
According to the fifth aspect of the present invention, an optical deflector is provided that fills a substantially sealed space with a gas having a specific gravity smaller than that of air, thereby reducing windage loss around the rotating body, reducing power consumption and heat generation, and increasing the speed. can do.
According to the sixth aspect of the present invention, it is possible to provide an optical deflector in which deterioration of optical characteristics (reflectance, etc.), such as mirror contamination, is small by using an inert helium gas as the gas filling the substantially sealed space. it can.

According to the seventh aspect of the present invention, it is possible to provide an optical deflector in which the use efficiency of the magnetic flux of the motor is increased by configuring the partition wall with a nonmagnetic material.
According to the eighth aspect, by using stainless steel, it is possible to provide an optical deflector in which the partition wall thickness is reduced and the use efficiency of the magnetic flux of the motor is increased while sufficiently securing the partition wall strength. .
According to the ninth aspect, it is possible to provide an optical deflector that performs optical scanning of a plurality of light sources by forming a plurality of mirrors in the axial direction.
According to the tenth aspect, it is possible to provide an optical deflector in which a partition is easily provided between the rotating part and the fixed part of the motor by making the motor an axial gap type.
According to the eleventh aspect, it is possible to provide an optical scanning device in which the scanning speed is increased by increasing the speed of the optical deflector. Further, it is possible to provide an optical scanning device in which the power consumption and heat generation of the optical deflector are reduced, the temperature change of optical components such as lenses due to the heat generated by the optical deflector is small, and the scanning beam shape is constant and stable.
According to the twelfth aspect, it is possible to provide a multi-beam optical scanning device in which the scanning speed is increased by increasing the speed of the optical deflector. Further, it is possible to provide a multi-beam optical scanning device in which the power consumption and heat generation of the optical deflector are reduced, the temperature change of optical components such as lenses due to the heat generated by the optical deflector is small, and the scanning beam shape is constant and stable.
According to the thirteenth aspect, it is possible to provide an image forming apparatus in which image formation is speeded up by increasing the scanning speed of the optical scanning device. In addition, a temperature change of an optical component such as a lens due to heat generated by the optical deflector is small, and the scanning beam of the optical scanning device is constant and stable, and an image forming apparatus with high image quality can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The configuration and operation of the optical deflector according to the first embodiment will be described with reference to FIGS. The bearing shown here is an embodiment using a dynamic pressure air bearing for high speed rotation. The bearing may be a hydrodynamic fluid bearing, a ball bearing, a magnetic bearing, or the like.
An attachment reference surface 1 a to the optical housing is formed on the lower surface of the case 1. A bearing mounting portion 1b is formed at the center of the case 1, and a fixed shaft 2 constituting a dynamic pressure air bearing is fixed. An opening for light to enter and exit is formed on the outer periphery of the case 1, and a plate-like glass 4 is fixed to the opening in a highly airtight state. Here, as a material of the case 1, an aluminum alloy is used.
On the cylindrical surface of the fixed shaft 2, a groove 2a for forming a dynamic pressure bearing is formed. When the rotating body 3 starts to rotate, the air pressure in the bearing clearance formed between the sleeve 16 and the fixed shaft 2 increases, and the rotating body 3 is supported in the radial direction (radial direction) without contact.
A fixed portion 5 of an attraction type magnetic bearing is fixed inside the fixed shaft 2. The fixed portion 5 of the attraction type magnetic bearing is fixed by being sandwiched in the axial direction by press-fitting and fixing the cap 6 and the stopper 7 to the inner cylinder portion of the fixed shaft 2. A fine hole having a diameter of about 0.2 to 0.5 is formed in the center of the cap 6 to attenuate the vertical vibration by using the viscous resistance when the gas passes. Both the cap 6 and the stopper 7 are made of a non-magnetic material such as a stainless steel plate.
The fixed portion 5 of the attraction type magnetic bearing is made of a ferromagnetic material in which a ring-shaped permanent magnet 8 magnetized in two poles in the rotation axis direction and a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8 are formed. 1 fixed yoke plate 9, and similarly, a second fixed yoke plate 10 made of a ferromagnetic material having a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8. The first fixed yoke plate 9 and the second fixed yoke plate 10 sandwich the ring-shaped permanent magnet 8 in the axial direction, and the central circle of the first fixed yoke plate 9 and the central circle of the second fixed yoke plate 10. Is arranged and fixed so as to be coaxial with the rotation center axis. As a material of the ring-shaped permanent magnet 8, a rare earth permanent magnet is mainly used. Steel plates are used for the fixed yoke plates 9 and 10.

The rotating body 3 includes a sleeve 16, an outer peripheral member 18 fixed to the outside of the sleeve 16 and formed with mirrors 18 a and 18 b, a closing member 17 press-fitted and fixed to one end of the outer peripheral member 18, and a magnetic bearing fixed to the closing member 17. The rotating part 19 and the rotor magnet 14 fixed to the outer peripheral member 18 are configured.
The material of the sleeve 16 is ceramic, the outer peripheral member 18 is made of an aluminum alloy, and the sleeve 16 and the outer peripheral member 18 are fixed by shrink fitting.
The motor rotor magnet 14 fixed to the lower side of the outer peripheral member 18 is fixed by adhesion or press-fitting. The rotor magnet 14 is formed in a ring shape so that adhesion or press-fitting can be easily performed. The rotor magnet 14 may be a permanent magnet divided in the circumferential direction. By holding the outer periphery of the rotor magnet 14 with the outer peripheral member 18, the rotor magnet 14 is prevented from being broken by centrifugal force due to high-speed rotation.
If a plastic magnet having a linear expansion coefficient substantially the same as that of the outer peripheral member 18 is used for the rotor magnet 14 and is fixed by press-fitting, it is possible to suppress a change in unbalanced vibration of the rotating body due to a temperature change, and thus a motor for higher speed rotation. It is suitable as.
The outer peripheral member 18 is integrally formed with two-stage mirrors 18a and 18b in the axial direction. An outer cylindrical surface that forms a magnetic gap is formed between the central circle of the first fixed yoke plate 9 and the central circle of the second fixed yoke plate 10 on the rotating portion 19 of the attractive magnetic bearing. It arrange | positions so that a cylinder surface may become coaxial with a rotation center axis | shaft. A permanent magnet or a steel-based ferromagnetic material is used for the rotating portion 19 of the attractive magnetic bearing.

In order to rotate the rotator 3 at a high speed, balance correction is performed on the correction surfaces 18 d and 14 a at two upper and lower portions of the rotator 3. Since the center of gravity of the rotating body is arranged in the vicinity of the middle of the hydrodynamic bearing, the balance of the rotating body can be corrected with high accuracy, and unbalanced vibration can be reduced to a very small level.
The motor unit includes a rotor magnet 14 attached to the rotating body 3, a stator core 12 around which a motor winding 12a is wound, a printed circuit board 11 to which the motor winding 12a is connected, and a hall element 13 mounted on the printed circuit board 11. The The motor system is a radial gap type brushless motor in which a magnetic gap is formed in a radial direction with respect to a rotating shaft. The stator core 12 is a laminate of electromagnetic steel plates such as silicon steel plates so that eddy currents do not flow and iron loss increases.
A partition wall 21 is provided between the rotor magnet 14 which is a rotating part of the motor and the stator core 12 which is a fixed part of the motor, the printed board 11 and the like. The partition wall 21 is joined and fixed to the case 1 by a highly airtight adhesive or welding. The rotating body 3 is accommodated in a substantially sealed space formed between the case 1 and the partition wall.
The partition wall 21 is made of a nonmagnetic material such as an aluminum alloy or austenitic stainless steel so that the magnetic flux of the motor portion can be transmitted. In order to reduce the thickness of the partition wall, an austenitic stainless steel plate having high mechanical strength is used.
The case 1 and the partition wall 21 are joined in a highly airtight state, and the air pressure in the substantially sealed space that is a complete airtight chamber is assembled in a state where the pressure is reduced to 30 kPa to 90 kPa with respect to the atmospheric pressure of 98 kPa.

The printed circuit board 11 is mounted with a hall element 13 which is a position detection element for switching energization to the motor winding, and is wired with the motor winding 12 a and the hall element 13. The printed circuit board 11 is fixed to the spacer 22 and the drive circuit, and is connected to the drive circuit 20 by the harness 23. In accordance with the position detection signal of the Hall element 13, the drive circuit 20 sequentially switches energization to the motor winding 12a to rotate the rotating body 3 and perform constant speed control.
In the first embodiment, the partition wall 21 is provided between the rotating part and the non-rotating part of the motor, and a substantially sealed space is formed between the case 1 and the partition wall 21, so that the sealed body is accommodated. While improving the airtightness of space, the turbulent flow which generate | occur | produces in the rotation part and non-rotation part of a motor can be reduced. As a result, it is possible to provide an optical deflector that reduces the power consumption and the rotation unevenness and increases the speed.
Conventionally, the non-rotating part of the motor is also housed in a substantially sealed space, and the notch part through which the harness for supplying driving power to the motor passes is sealed with resin. In the conventional structure for sealing the harness portion, it was difficult to ensure sufficient airtightness, but in the optical deflector of Example 1, by increasing the airtightness of the joint between the case 1 and the partition wall 21, The airtightness of the substantially sealed space can be easily increased.
In the optical deflector of Example 1 in which the airtightness of the substantially enclosed space is increased, the air loss in the vicinity of the rotating body is reduced by reducing the atmospheric pressure in the substantially enclosed space with respect to the atmospheric pressure of 98 kPa, thereby reducing power consumption and heat generation. It is possible to provide an optical deflector with reduced and increased speed.
By setting the atmospheric pressure in the substantially sealed space to 30 kPa to 90 kPa, it is possible to provide an optical deflector that secures the bearing rigidity of the dynamic pressure gas bearing even in a reduced pressure state and is stable in rotation. If the pressure is reduced from 30 kPa, the bearing rigidity of the dynamic pressure gas bearing cannot be sufficiently secured, and rotational instability such as 1/2 whirl may occur.
When a bearing other than a dynamic pressure gas bearing such as a dynamic pressure fluid bearing, a ball bearing, or a magnetic bearing is used as the bearing, the pressure may be reduced to 0 kPa, that is, a state close to a vacuum.

Although not shown in FIG. 1, a gate may be provided in the case so that the substantially sealed space is decompressed after assembly. By providing the pressure reducing gate, it is possible to provide an optical deflector that can easily reduce the pressure in the substantially sealed space after joining the case and the partition.
Further, instead of air, a gas having a specific gravity smaller than that of air may be filled in a substantially sealed space. By filling a gas having a specific gravity smaller than that of air in a substantially sealed space, it is possible to provide an optical deflector that reduces windage loss around the rotating body, reduces power consumption and heat generation, and increases the speed.
Instead of air, an inert gas helium gas can be used as the gas filling the substantially sealed space. Since helium gas has a small specific gravity with respect to air of about 0.14, the windage loss can be made smaller than that of air. In addition, since it is difficult for an inert gas to react with other substances, it is possible to provide an optical deflector in which deterioration of optical characteristics (reflectance, etc.) such as mirror contamination is small.
In addition, since the partition wall 21 is made of a nonmagnetic material, an optical deflector with improved use efficiency of the magnetic flux of the motor can be provided.
Furthermore, since the partition wall 21 is made of stainless steel, it is possible to provide an optical deflector in which the partition wall 21 is sufficiently thin and the thickness of the partition wall 21 is reduced to increase the use efficiency of the magnetic flux of the motor.
In addition, since the mirrors 18a and 18b are formed in a plurality of stages in the axial direction, an optical deflector that performs optical scanning of a plurality of light sources can be provided.

The configuration and operation of the optical deflector according to the second embodiment will be described with reference to FIG. The configuration of the motor is different from that of the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
The rotating body 30 includes a sleeve 16, an outer peripheral member 18 that is fixed to the outside of the sleeve 16 and formed with mirrors 18 a and 18 b, a flange 31 that is press-fitted and fixed to one end of the outer peripheral member 18, and a magnetic bearing that is fixed to the flange 31. The unit 19 and the rotor magnet 32 are included.
The motor rotor magnet 32 fixed to the flange 31 is fixed by adhesion or press fitting. The rotor magnet 32 is formed in a ring shape so that it can be easily bonded or press-fitted. The rotor magnet 32 may be a permanent magnet divided in the circumferential direction. By holding the outer periphery of the rotor magnet 32 with the outer peripheral member 18, the rotor magnet 32 is prevented from being broken by centrifugal force due to high-speed rotation. If a plastic magnet having a linear expansion coefficient substantially the same as that of the outer peripheral member 18 is used for the rotor magnet 32 and is fixed by press-fitting, a change in unbalanced vibration of the rotating body due to a temperature change can be suppressed to a small level. It is suitable as. The outer peripheral member 18 is integrally formed with two-stage mirrors 18a and 18b in the axial direction.
In order to rotate the rotating body 30 at a high speed, balance correction is performed on the correction surfaces 18d and 31a at two upper and lower portions of the rotating body 30. Since the center of gravity of the rotating body is arranged in the vicinity of the middle of the hydrodynamic bearing, the balance of the rotating body can be corrected with high accuracy, and unbalanced vibration can be reduced to a very small level.

The motor unit includes a rotor magnet 32 attached to the rotating body 30, a winding coil 33, a Hall element (not shown), and a printed circuit board 34 on which the winding coil 33 and the Hall element are mounted. The motor system is an axial gap type brushless motor in which a magnetic gap is formed in the axial direction.
A partition wall 35 is provided between a rotor magnet 32 that is a rotating part of the motor, a winding coil 33 that is a fixed part of the motor, and a printed board 34. The partition wall 35 is fixed to the case 1 by a highly airtight adhesive or welding. The rotating body 30 is accommodated in a substantially sealed space formed between the case 1 and the partition wall 35.
The partition wall 35 is made of a nonmagnetic material such as an aluminum alloy or austenitic stainless steel. In order to reduce the thickness of the partition wall, an austenitic stainless steel plate having high mechanical strength is used.
The case 1 and the partition wall 35 are joined in a highly airtight state, and the air pressure in the sealed space that is a complete airtight chamber is assembled in a state where the pressure is reduced to 30 kPa to 90 kPa with respect to the atmospheric pressure 98 kPa.
The printed circuit board 34 is mounted with a hall element (not shown) that is a position detection element for switching energization to the winding coil 33, and is wired in a pattern with the winding coil 33 and the hall element. The printed circuit board 34 is fixed to the spacer 36 and is connected to the drive circuit 20 by the harness 23. The drive circuit 20 performs constant speed control by sequentially switching energization to the winding coil 33 and rotating the rotating body 30 in accordance with the Hall element position detection signal.
In the second embodiment, the same effect as in the first embodiment can be obtained, and the motor is an axial gap type in which a magnetic gap is formed in the axial direction. Therefore, a partition wall is provided between the rotating portion and the fixed portion of the motor. An optical deflector that can be easily provided can be provided.

FIG. 4 shows a configuration of a main part of an optical scanning device provided with the optical deflector according to the present invention. This optical scanning device is a single beam type device. The optical scanning device according to the present embodiment includes a light source 101, a coupling lens 102, an aperture 103, a cylindrical lens 104, a polygon mirror 105, lenses 106 and 107, a mirror 108, a photoconductor 109, a mirror 110, a lens 111, and a light receiving element 112. Have.
The light source 101 is a semiconductor laser element that emits light for optical scanning. The coupling lens 102 is a lens for adapting the light emitted from the light source 101 to the optical system. The aperture 103 makes the beam light for optical scanning a predetermined shape. The cylindrical lens 104 condenses incident beam light in the sub-scanning direction. The polygon mirror 105 is an optical deflector, and reflects incident light on the deflection reflection surface. The lenses 106 and 107 are lenses for forming an image of the beam light on the photoconductor 109. The mirror 108 bends the optical path of the beam light and guides it to the photoconductor 109. The photoconductor 109 forms an electrostatic latent image in accordance with the irradiated beam light. The mirror 110 and the lens 111 collect the beam light on the light receiving element 112. The light receiving element 112 is a light detection element such as a photodiode.

A beam emitted from the light source 101 which is a semiconductor laser element is a divergent light beam and is coupled to a subsequent optical system by a coupling lens 102. The form of the coupled beam depends on the optical characteristics of the subsequent optical system, and may be a weak divergent light beam, a weak converging light beam, or a parallel light beam. When the beam that has passed through the coupling lens 102 passes through the opening portion 2 of the aperture 103, a portion having a low light intensity around the light beam is blocked and “beam-shaped”, and a cylindrical that is a “linear imaging optical system” The light enters the lens 104. The cylindrical lens 104 has an approximately semi-cylindrical shape, and a direction without power (a direction in which light is not refracted) is directed to the main scanning direction, and a positive power (power for focusing light) is incident in the sub-scanning direction. The incoming beam is converged in the sub-scanning direction and condensed near the deflection reflection surface of the polygon mirror 105 which is an “optical deflector”.
The beam reflected by the deflecting and reflecting surface of the polygon mirror 105 passes through the two lenses 106 and 107 forming the “scanning optical system” while being deflected at a constant angular velocity as the polygon mirror 105 rotates at a constant speed. The optical path is bent by the bending mirror 8 and condensed as a light spot on the photoconductive photoconductor 109 forming the substance of the “scanned surface”, and the scanned surface is scanned. Prior to scanning, the beam enters the mirror 110 and is focused on the light receiving element 112 by the lens 111. The timing of writing to the photoconductor 109 is determined by a control unit (not shown) based on the output of the light receiving element 112.
Thus, the optical deflector according to the present invention is applicable to a single beam type optical scanning device. In the single beam type optical scanning apparatus to which the optical deflector according to the present invention is applied, the polygon mirror 105 which is an optical deflector is rotated at high speed, and optical scanning can be performed at high speed. In addition, the power consumption and heat generation of the optical deflector are reduced, the temperature change of the optical components such as the lens due to the heat generated by the optical deflector is small, and a stable optical scanning with a constant scanning beam shape can be performed.

FIG. 5 shows a configuration of a main part of an optical scanning device provided with the optical deflector according to the present invention. This optical scanning device is a multi-beam type device. In addition, about the same member as FIG. 4, the same code | symbol is attached | subjected and shown.
The light source 101A is a semiconductor laser array in which four light emitting sources ch1 to ch4 are arranged in a line at equal intervals. In the present embodiment, the light sources ch1 to ch4 are arranged in the sub-scanning direction, but the semiconductor laser array 101A may be tilted so that the arrangement direction of the light sources is tilted with respect to the main scanning direction.
The four beams emitted from the four light emission sources ch1 to ch4 are divergent light beams in which the major axis direction of the “elliptical far field pattern” is directed to the main scanning direction as shown in FIG. It is coupled to the subsequent optical system by a coupling lens 102 common to the two beams. The form of each coupled beam depends on the optical characteristics of the subsequent optical system, and may be a weak divergent light beam, a weak convergent light beam, or a parallel light beam.
The four beams transmitted through the coupling lens are “beam shaped” by the aperture 3 and converged in the sub-scanning direction by the action of the cylindrical lens 104 which is a “common line imaging optical system”. The four beams converged in the sub-scanning direction are separated from each other in the sub-scanning direction as line images that are long in the main scanning direction in the vicinity of the deflection reflection surface of the polygon mirror 105 that is an “optical deflector”. To do.

The four beams deflected at a constant angular velocity by the deflecting reflecting surface of the polygon mirror 105 are transmitted through the two lenses 106 and 107 forming the “scanning optical system”, and the optical path is bent by the bending mirror 108. The four beams whose optical paths are bent are condensed as four light spots separated in the sub-scanning direction on the photoconductor 109 forming the substance of the “scanned surface”, and four scanning lines on the scanned surface are obtained. Are simultaneously scanned.
Prior to optical scanning, one of the beams enters the mirror 110 and is focused on the light receiving element 112 by the lens 111. The timing of writing to the photoconductor 109 by the four beams is determined by a control unit (not shown) based on the output of the light receiving element 112.
The “scanning optical system” in the present embodiment is an optical system that condenses the four beams simultaneously deflected by the optical deflector (polygon mirror 105) as four light spots on the surface to be scanned of the photoconductor 109. This system is composed of two lenses 106 and 107.
As described above, the optical deflector according to the present invention can be applied to a multi-beam optical scanning device. In the multi-beam type optical scanning apparatus to which the optical deflector according to the present invention is applied, the polygon mirror 105 as the optical deflector is rotated at high speed, and optical scanning can be performed at high speed. In addition, the power consumption and heat generation of the optical deflector are reduced, the temperature change of the optical components such as the lens due to the heat generated by the optical deflector is small, and a stable optical scanning with a constant scanning beam shape can be performed.

FIG. 6 shows the configuration of a tandem type full-color laser printer provided with the light deflecting device according to the present invention. A conveyor belt 202 is provided on the lower side of the apparatus so as to convey a transfer sheet (not shown) that is disposed in the horizontal direction and is fed from the sheet feeding cassette 201. On the conveyance belt 202, a yellow (Y) photosensitive member 203Y, a magenta (M) photosensitive member 203M, a cyan (C) photosensitive member 203C, and a black (K) photosensitive member 203K are provided from the upstream side. They are arranged at regular intervals in order. Hereinafter, subscripts Y, M, C, and K are appropriately added to the reference numerals to distinguish each color.
These photoreceptors 203Y, 203M, 203C, and 203K are all formed to have the same diameter, and process members are sequentially arranged around the photoreceptors in accordance with an electrophotographic process.
Taking the photoconductor 203Y as an example, a charging charger 204Y, an optical scanning device 205Y, a developing device 206Y, a transfer charger 207Y, a cleaning device 208Y, and the like are sequentially arranged. The same applies to the other photoconductors 203M, 203C, and 203K. That is, in the present embodiment, the photosensitive members 203Y, 203M, 203C, and 203K are irradiated surfaces set for each color, and a pair of optical scanning devices 205Y, 205M, 205C, and 205K is provided for each. 1 correspondence relationship.
In addition, a registration roller 209 and a belt charging charger 210 are provided around the transport belt 202 at the upstream side of the photosensitive member 205Y, and a belt separation charger 211, at a downstream side of the photosensitive member 205K. A static elimination charger 212, a cleaning device 213, and the like are sequentially provided. A fixing device 214 is provided downstream of the belt separation charger 211 in the transport direction, and is connected to a paper discharge tray 215 via a paper discharge roller 216.

In the above configuration, for example, in the full color mode (multiple color mode), each of the photoconductors 203Y, 203M, 203C, and 203K is based on an image signal of each color for Y, M, C, and K. An electrostatic latent image is formed by optical scanning of a light beam by the optical scanning devices 205Y, 205M, 205C, and 205K. These electrostatic latent images are developed with the corresponding color toners to become toner images, and are superimposed on each other by being sequentially transferred onto transfer paper that is electrostatically attracted onto the transport belt 202 and transported. The transfer paper on which the toner images of the respective colors are superimposed is fixed on the transfer paper as a full color image by the fixing device 214, and the transfer paper on which the image is fixed is discharged to the paper discharge tray 215 by the paper discharge roller 216.
In the black mode (monochrome mode), the photoconductors 203Y, 203M, and 203C and these process members are deactivated, and only the photoconductor 203K is lighted based on the black image signal. An electrostatic latent image is formed by optical scanning of a light beam by a scanning device (one optical scanning device) 205K.
This electrostatic latent image is developed with black toner to become a toner image, and is electrostatically attracted onto the transport belt 2 and transferred onto the transfer paper transported. The toner image transferred onto the transfer paper is fixed on the transfer paper as a monochrome image by the fixing device 214, and the transfer paper on which the image has been fixed is discharged onto a paper discharge tray 215 by a paper discharge roller 216.
Thus, the optical deflector according to the present invention is applicable to a tandem type full color laser printer. In the optical deflector according to the present invention, in the optical scanning devices 205Y, 205M, 205C, and 205K of the tandem type full-color laser printer, one optical deflector 300 in which two-stage mirrors are formed in the axial direction is shared. By increasing the scanning speed, it is possible to provide an image forming apparatus in which image formation is accelerated. Further, the temperature change of the optical components such as the lens due to the heat generated by the optical deflector 300 is small, the scanning beam shape is constant, and stable optical scanning can be performed.
Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications are possible.

Sectional drawing of the optical deflector of Example 1 of this invention. Sectional drawing of the optical deflector of Example 2 of this invention. 1 is an exploded perspective view of an optical deflector according to a first embodiment of the present invention. FIG. 3 is an explanatory diagram of a main part of an optical scanning device including an optical deflector according to the present invention. FIG. 3 is an explanatory diagram of a main part of an optical scanning device including an optical deflector according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a tandem type full color laser printer provided with an optical deflecting device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case, 1a Mounting reference plane, 1b Bearing mounting part, 2 Fixed shaft, 2a Groove, 3 Rotating body, 5 Fixed part, 6 Cap, 7 Stopper, 8 Ring-shaped permanent magnet, 9 1st fixed yoke board, 10 1st 2 fixed yoke plates, 11 printed circuit board, 12 stator core, 12a motor winding, 13 Hall element, 14 rotor magnet, 14a correction surface, 16 sleeve, 17 closing member, 18 outer peripheral member, 18a, 18b mirror, 18d correction surface, 19 Rotating part of magnetic bearing, 20 drive circuit, 21 partition, 22 spacer, 23 harness, 30 rotating body, 31 flange, 31a correction surface, 32 rotor magnet, 33 winding coil, 34 printed circuit board, 35 partition, 36 spacer, 101 light source, 102 coupling lens, 103 aperture, 104 cylindrical lens, 105 poly Mirror, 106, 107 lens, 108 mirror, 109 photoconductor, 110 mirror, 111 lens, 112 light receiving element, 101A light source, 201 paper feed cassette, 202 transport belt, 203Y, 203M, 203C, 203K photoconductor, 204Y charging charger, 205Y optical scanning device, 206Y developing device, 207Y transfer charger, 208Y cleaning device, 209 registration roller, 210 belt charging charger, 211 belt separation charger, 212 discharger, 213 cleaning device, 214 fixing device, 215 discharge tray, 216 discharge Paper roller, 300 optical deflector

Claims (13)

A rotating body in which a mirror is formed, a bearing that supports the rotating body, a motor that drives the rotating body, and a case member that is disposed around the rotating body, and the rotating body is housed in a sealed space In the optical deflector
An optical deflector, wherein a partition wall is provided between a rotating part and a non-rotating part of the motor, and the sealed space is formed between the case member and the partition wall.   2. The optical deflector according to claim 1, wherein an air pressure in the sealed space is reduced with respect to an atmospheric pressure.   3. The optical deflector according to claim 2, wherein the bearing is a dynamic pressure gas bearing, and the air pressure in the sealed space is reduced to 30 kPa to 90 kPa.   3. The optical deflector according to claim 2, wherein the case is provided with a gate for reducing the pressure of the sealed space.   2. The optical deflector according to claim 1, wherein the sealed space is filled with a gas having a specific gravity smaller than that of air.   6. The optical deflector according to claim 5, wherein the gas filled in the sealed space is helium gas.   2. The optical deflector according to claim 1, wherein the partition wall is made of a nonmagnetic material.   8. The optical deflector according to claim 7, wherein the nonmagnetic material is austenitic stainless steel.   2. The optical deflector according to claim 1, wherein the mirror is formed in a plurality of stages in the axial direction.   2. The optical deflector according to claim 1, wherein the motor is an axial gap type motor.   A beam from the semiconductor laser is guided to the surface to be scanned through an optical system including an optical deflector to form a light spot and deflected by the optical deflector, thereby scanning the scanning surface with the scanning line. The optical scanning device according to claim 1, wherein the optical deflector is the optical deflector according to claim 1.   A plurality of beams from the semiconductor laser are guided to the surface to be scanned through an optical system including the optical deflector to form a plurality of light spots, and deflected by the optical deflector. 11. An optical scanning device for scanning a plurality of scanning lines adjacent to each other, wherein the optical deflector is the optical deflector according to any one of claims 1 to 10. An image forming apparatus for forming a latent image on a photosensitive surface of a photosensitive medium by an optical scanning device and visualizing the latent image to obtain an image, the light performing optical scanning of the photosensitive surface of the photosensitive medium An image forming apparatus using the optical scanning device according to claim 11 or 12 as a scanning device.

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