JP2002303815A - Dynamic pressure air bearing type polygon scanner, and processing method for dynamic pressure air bearing type polygon scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive, high-precision dynamic pressure air bearing type polygon scanner which uses a radial dynamic pressure air bearing and a suction type axial magnetic bearing, and to provide a processing method for the dynamic pressure air bearing type polygon scanner. SOLUTION: A hollow rotary shaft 11 of the dynamic pressure air bearing type polygon scanner 1 has at least its dynamic pressure air bearing part 11a and polygon mirror part 11c formed integrally of a metal material consisting principally of aluminum; and the hollow rotary shaft 11 has a polygon mirror processing reference surface formed orthgonally to the dynamic pressure air bearing part 11a and the surface of the dynamic air bearing surface is processed. Thus, the dynamic air bearing part 11a and polygon mirror part 11c of the hollow rotary shaft 11 are formed integrally of the metal material consisting essentially of aluminum without being processed by providing shrink p arts respectively, so the hollow rotary shaft 11 can be formed at a low cost with high precision by decreasing its constitution component and a polygon surface is prevented from being strained to have worse flatness, thereby maintaining a high-precision mirror surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure air bearing type polygon scanner and a method of processing the dynamic pressure air bearing type polygon scanner. About the method.

[0002]

2. Description of the Related Art An electrophotographic recording apparatus using a laser writing system, such as a digital copying machine or a laser printer, has features such as good printing quality, high printing speed, and low noise. Recently, it has been rapidly spreading because of the lower price.

A polygon scanner used in a laser writing system of the electrophotographic recording apparatus is required to rotate a polygon mirror at a rotation speed corresponding to a printing speed and a pixel density of the recording apparatus. In recent years, with the increase in print speed and pixel density,
The polygon scanner is required to rotate at a very high speed of 20,000 rpm or more.

In such a polygon scanner that requires ultra-high speed rotation, a conventional ball bearing type bearing device cannot satisfy the required image quality in terms of bearing life and bearing noise.

[0005] Therefore, conventionally, a polygonal scanner requiring ultra-high-speed rotation has used a dynamic pressure air bearing utilizing dynamic pressure air.

An apparatus using such a dynamic pressure air bearing is, for example, a high-speed rotating body outside a ceramic fixed shaft and constituting a gas dynamic pressure bearing together with the ceramic fixed shaft in a radial direction. A high-speed rotating body composed of a ceramic sleeve having a constant thickness and a metal outer peripheral member which is shrink-fitted and fixed to the outer periphery thereof and has a larger coefficient of thermal expansion than the ceramic sleeve, wherein the ceramic sleeve is formed of A high-speed rotating body has been proposed in which the inside diameter is worked into a predetermined conical shape after shrink-fitting and fixing (see JP-A-7-190047).

A conventional rotary polygon mirror for deflecting and scanning illumination light applied to an outer peripheral surface toward a photoreceptor, comprising a polygonal column-shaped main body having an outer peripheral surface covered with a reflective film, and rotating the main body. There has been proposed a rotary polygon mirror having a driving unit for driving the main body made of fine ceramic (Japanese Patent Application Laid-Open No. H07-1995).
-306374).

That is, this rotary polygon mirror is specifically attached to a regular polygonal column-shaped main body made of fine ceramic having a large Young's modulus and a small linear expansion coefficient as compared with aluminum or the like and its outer peripheral surface. It has a reflective film, the main body has a sleeve integrally formed of the same fine ceramic, and the sleeve is loosely fitted on a fixed shaft integral with the base, and is thereby rotatably supported. The motor for rotating the rotary polygon mirror is composed of a rotor magnet integrated with the sleeve and a stator coil on a circuit board supported by the base.

[0009]

However, such a conventional bearing device has room for improvement as a high-speed rotating bearing such as a polygon scanner.

That is, in the high-speed rotating body described in Japanese Patent Application Laid-Open No. 7-190047, when a mirror-finished polygon mirror is shrink-fitted, the compressive stress at the time of shrink-fitting distorts the polygon mirror surface and flatness. It deteriorates and cannot maintain a highly accurate mirror surface. As a result, there is a problem that a good image output cannot be obtained. Further, even when the mirror surface of the polygon mirror is processed after shrink fitting, when the temperature of the rotating body increases due to high speed rotation, the linear expansion coefficient of the ceramic rotary sleeve is smaller than the linear expansion coefficient of the metal outer peripheral member. Therefore, as a result of removing the compressive stress caused by shrink fitting, the polygon mirror surface is distorted, the flatness is deteriorated, and a highly accurate mirror surface cannot be maintained. As a result, there is a problem that a good image output cannot be obtained.

In the rotating polygon mirror described in Japanese Patent Application Laid-Open No. 7-306374, if the rotating polygon mirror and the sleeve are integrally formed of fine ceramics, the hardness of the fine ceramics is extremely high. However, there is a problem that the cost of the grinding is very high, and the cost of the polygon scanner is high.

[0012] In view of the above, according to the first aspect of the present invention, a fixed shaft is inserted into a hollow portion of a hollow rotary shaft that forms a rotary body by fixing a polygon mirror to a hollow rotary shaft having a hollow portion in the axial direction. The rotating body is rotated by a motor having a printed circuit board or the like, and the dynamic pressure of air generated by the rotation of the rotating body is received by a dynamic pressure air bearing surface including an inner peripheral surface of a hollow rotating shaft and an outer peripheral surface of a fixed shaft. The hollow rotating shaft of a dynamic pressure air bearing type polygon scanner that supports a rotating body rotatably in the radial and axial directions by a dynamic pressure air bearing and a predetermined axial bearing, at least the radial dynamic pressure air bearing portion and the polygon mirror portion are made of aluminum. Is formed integrally with a metal material whose main component is a polygon mirror machining reference surface orthogonal to the radial dynamic pressure air bearing is formed on the hollow rotary shaft, and the surface is displayed on the dynamic pressure air bearing surface. It is assumed that the processing has been applied, so that the dynamic pressure air bearing of the hollow rotary shaft and the polygon mirror do not have to be provided with shrink-fitting parts, and are processed by a metal material mainly composed of aluminum. And the polygon mirror are integrally formed to reduce the number of components of the rotator and to be formed inexpensively and with high precision, and the polygon mirror is formed at a fixed angle with respect to the hollow rotating shaft, and optical scanning is performed. The variation of the scanning position of each mirror surface at the time is reduced, and at the high speed rotation or the change of the ambient temperature,
Even if the temperature of the rotating body changes, the polygon mirror surface is prevented from being distorted and the flatness is not deteriorated, the highly accurate mirror surface is maintained, and the dynamic pressure air bearing type polygon scanner that can improve the image quality It is intended to provide.

According to a second aspect of the present invention, a dynamic pressure air bearing surface of a hollow rotary shaft is formed on an inner cylindrical portion of the hollow rotary shaft, and a closing portion for substantially closing one end of the dynamic pressure air bearing is provided with a dynamic pressure air bearing. By integrally forming the same metal material as aluminum as the main component with the air bearing portion and the polygon mirror portion, a closing member for closing one end of the dynamic pressure air bearing is not required, and the number of components of the hollow rotary shaft is reduced. An object of the present invention is to provide a dynamic pressure air bearing type polygon scanner which is more inexpensive and can improve image quality.

According to a third aspect of the present invention, as a surface treatment for a hydrodynamic air bearing surface, a surface reforming treatment by collision of fine particles is performed, thereby improving the recyclability of the hollow rotary shaft, making it even more inexpensive and environmentally friendly. It is an object of the present invention to provide a dynamic pressure air bearing type polygon scanner having good image quality.

According to a fourth aspect of the present invention, a surface modification treatment is performed only on both ends of the bearing surface of the dynamic pressure air bearing,
It is an object of the present invention to provide a dynamic pressure air bearing type polygon scanner with reduced surface treatment cost, lower cost, and good image quality.

According to a fifth aspect of the present invention, there is provided a cutting process for forming at least a hydrodynamic air bearing surface and a mirror processing reference surface of a polygon mirror on a hollow rotary shaft, and a surface on a bearing surface of a hydrodynamic air bearing portion. A shrink-fit portion is provided on each of the hydrodynamic air bearing of the hollow rotary shaft and the polygon mirror by performing a surface treatment processing process for forming a processing film and a mirror surface cutting process for forming a mirror surface of the polygon mirror. In addition, the hydrodynamic bearing and polygon mirror are integrally formed of a metal material containing aluminum as the main component to reduce the number of components of the rotating body and to be formed inexpensively and with high precision. A polygon mirror is formed at a fixed angle to reduce variations in the scanning position of each mirror surface when performing optical scanning, and the temperature of the rotating body is increased due to high-speed rotation or changes in the ambient temperature. Even if the polygon mirror is distorted, the polygon mirror surface is prevented from being distorted and the flatness is not deteriorated, and the high-precision mirror surface can be maintained and the image quality can be improved. It is an object of the present invention to provide a processing method of a dynamic pressure air bearing type polygon scanner which can be processed into a shape.

[0017]

According to a first aspect of the present invention, there is provided a dynamic pressure air bearing type polygon scanner, wherein a polygon mirror is fixed to a hollow rotating shaft having a hollow portion in an axial direction to form a rotating body. A fixed shaft is inserted into the hollow portion of the shaft, the rotating body is rotated by a motor having a printed circuit board or the like as a fixed portion, and a dynamic pressure of air generated by rotation of the rotating body is applied to an inner peripheral surface of the hollow rotating shaft. A dynamic pressure air bearing type polygon scanner that supports the rotating body rotatably in a radial direction and an axial direction by a radial dynamic pressure air bearing received on a dynamic pressure air bearing surface formed of an outer peripheral surface of the fixed shaft and a predetermined axial bearing. In the hollow rotary shaft, at least the radial dynamic pressure air bearing portion and the polygon mirror portion are integrally formed of a metal material containing aluminum as a main component, and the hollow rotary shaft is Polygon mirror working reference plane that is perpendicular to the radial dynamic pressure air bearing is formed by a surface treatment to the dynamic pressure air bearing surface is applied, it has achieved the above objects to.

According to the above construction, the polygon mirror is fixed to the hollow rotary shaft having the hollow portion in the axial direction, and the fixed shaft is inserted into the hollow portion of the hollow rotary shaft forming the rotary body. A radial dynamic pressure air bearing in which a rotating body is rotated by a motor having a dynamic pressure air bearing surface formed by an inner peripheral surface of a hollow rotating shaft and an outer peripheral surface of a fixed shaft. The hollow rotary shaft of the dynamic pressure air bearing type polygon scanner that supports the rotating body rotatably in the radial direction and the axial direction by a predetermined axial bearing, at least the radial dynamic pressure air bearing portion and the polygon mirror portion are mainly made of aluminum. The hollow rotary shaft is integrally formed with a polygon mirror processing reference surface orthogonal to the radial dynamic pressure air bearing, and the dynamic pressure air bearing surface is surface-treated. Therefore, the dynamic pressure bearing and polygon mirror are integrated with a metal material containing aluminum as the main component, without the need to provide shrink-fit parts on the hydrodynamic air bearing of the hollow rotary shaft and the polygon mirror. When it is possible to reduce the number of components of the rotating body and form it inexpensively and with high precision, and to perform optical scanning by forming a polygon mirror at a fixed angle with respect to the hollow rotating shaft Of the scanning position of each mirror surface
Also, even if the temperature of the rotating body changes due to high-speed rotation or a change in the ambient temperature, it is possible to prevent the polygon mirror surface from being distorted and the flatness from being deteriorated, and to maintain a highly accurate mirror surface, Image quality can be improved.

In this case, for example, the hollow rotary shaft has a dynamic pressure air bearing surface formed on an inner cylindrical portion of the hollow rotary shaft, and one end of the dynamic pressure air bearing. May be integrally formed of the same metal material mainly composed of aluminum as the hydrodynamic air bearing portion and the polygon mirror portion.

According to the above construction, the dynamic pressure air bearing surface of the hollow rotary shaft is formed in the inner cylindrical portion of the hollow rotary shaft, and the closing portion for substantially closing one end of the dynamic pressure air bearing is provided with the dynamic pressure air bearing. Since the unit and the polygon mirror unit are integrally formed of the same metal material mainly composed of aluminum, a closing member for closing one end of the hydrodynamic air bearing is not required, and the number of components of the hollow rotary shaft can be reduced. In addition, the cost can be further reduced, and the image quality can be improved.

Further, for example, as set forth in claim 3, the dynamic pressure air bearing surface may be subjected to a surface modification treatment by particle collision as the surface treatment.

According to the above structure, the surface treatment of the dynamic pressure air bearing surface is performed by the particle reforming treatment by the collision of fine particles. Therefore, the recyclability of the hollow rotary shaft can be improved, and the cost can be further reduced. And image quality can be improved.

Further, for example, as described in claim 4, the dynamic pressure air bearing is provided only at both ends of the bearing surface.
The surface modification treatment may be applied.

According to the above configuration, since the surface modification is performed only on both ends of the bearing surface of the dynamic pressure air bearing, the cost of the surface treatment can be reduced, and the cost can be further reduced. And the image quality can be improved.

According to a fifth aspect of the present invention, there is provided the working method of the polygon scanner of the present invention, wherein the polygonal mirror is fixed to a hollow rotary shaft having a hollow portion in the axial direction to form a rotary body. A fixed shaft is inserted into the hollow part,
The rotating body is rotated by a motor having a printed circuit board or the like as a fixed part, and the dynamic pressure of air generated by the rotation of the rotating body is changed to the dynamic pressure air comprising the inner peripheral surface of the hollow rotating shaft and the outer peripheral surface of the fixed shaft. A method for processing a dynamic pressure air bearing type polygon scanner that supports the rotating body rotatably in a radial direction and an axial direction by a radial dynamic pressure air bearing and a predetermined axial bearing received on a bearing surface, wherein the hollow rotating shaft includes: At least, a cutting process for forming the dynamic pressure air bearing surface and a mirror processing reference surface of the polygon mirror, and a surface processing process for forming a surface treatment film on the bearing surface of the dynamic pressure air bearing portion, The above object is achieved by performing a mirror surface cutting process for forming a mirror surface of the polygon mirror.

According to the above construction, at least a cutting process for forming a dynamic pressure air bearing surface and a mirror processing reference surface of a polygon mirror on the hollow rotary shaft, and a surface treatment film on the bearing surface of the dynamic pressure air bearing portion. Since the surface treatment processing process for forming the mirror and the mirror surface cutting process for forming the mirror surface of the polygon mirror are performed, the shrink-fit portions are provided on each of the dynamic pressure air bearing of the hollow rotary shaft and the polygon mirror. In addition, the hydrodynamic bearing and the polygon mirror are integrally formed of a metal material mainly composed of aluminum, so that the components of the rotating body can be reduced and formed at low cost and with high accuracy. A polygon mirror is formed at a fixed angle to reduce the variation in the scanning position of each mirror surface when optical scanning is performed. Even if the temperature changes, the polygon mirror surface is prevented from being distorted and the flatness is not deteriorated, and a high-precision dynamic-pressure air-bearing polygon scanner that can maintain high-precision mirror surface and improve image quality is inexpensive And can be easily processed.

[0027]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.

FIGS. 1 to 4 are views showing an embodiment of a dynamic pressure air bearing type polygon scanner and a working method of a dynamic pressure air bearing type polygon scanner according to the present invention. FIG. 1 is a front sectional view of a hydrodynamic air bearing polygon scanner 1 to which an embodiment of a processing method of a hydrodynamic air bearing polygon scanner and a hydrodynamic air bearing polygon scanner is applied, and FIG. 2 is a hydrodynamic air bearing type of FIG. FIG. 2 is an exploded perspective view of the polygon scanner 1.

In FIG. 1, the appearance of a polygon scanner 1 of a dynamic pressure air bearing type is formed by a housing 2 and an upper cover (casing) 3 fixed on the housing 2 by screws. A reference surface 2a for attachment to the optical housing is formed.

As shown in FIG. 2, the housing 2 is formed in a substantially disk-like hollow shape, and a cylindrical bearing reference portion 2b is formed in the center of the housing 2. The bearing reference portion 2b has a fixed shaft. 4 is fixed. The fixed shaft 4 has a bearing reference portion 2b.
It is fixed by press-fitting, shrink fitting, or adhesive fixing.

The fixed shaft 4 has a herringbone groove 4a formed at an appropriate position on a peripheral wall portion thereof, and a ring-shaped member having a predetermined length in an axial direction (axial direction) is formed in a cylinder of the fixed shaft 4. Of the attraction type magnetic bearing fixing part 5 is the bearing reference part 2b.
It is buried with reference to the upper end surface. The attraction type magnetic bearing fixing portion 5 is fixed by being sandwiched in the axial direction by the cap member 6 and the stopper 7 being press-fitted and fixed to the inner cylindrical portion of the fixed shaft 4. At the center of the cap member 6, a vertical vibration is attenuated by utilizing viscous resistance when air passes.
Fine holes of about 0.2 to 0.5 are formed. Both the cap member 6 and the stopper 7 are made of a non-magnetic material such as a stainless steel plate.

As shown in FIG. 2, a center circle of a predetermined size is formed at the center of the attraction type magnetic bearing fixing portion 5, and the magnetic portion is magnetized to two poles in the axial direction and the magnetic poles are oriented in the axial direction. A ring-shaped permanent magnet 8 and a ferromagnetic material fixed at both axial ends (both axial ends) of the permanent magnet 8 and having a central circle smaller than the central circle (inner diameter) of the permanent magnet 8 are formed at the center thereof. A pair of the first fixed yoke plate 9 and the second fixed yoke plate 10 are formed. The attraction-type magnetic bearing fixing portion 5 has a state in which the permanent magnet 8 is sandwiched between the first fixed yoke plate 9 and the second fixed yoke plate 10, and the center circle of the first fixed yoke plate 9 and the second fixed yoke plate. In a state where the center circle of 10 coincides with the axis center of the fixed shaft 4 (becomes coaxial),
It is embedded in the cylinder of the fixed shaft 4. The first fixed yoke plate 9 and the second fixed yoke plate 10 are formed of a steel-based plate material, and the permanent magnet 8 is, for example, mainly a rare-earth permanent magnet. The fixed shaft 4 is made of a non-magnetic material such as an aluminum alloy, and has a wear-resistant or lubricated surface treatment film.

As shown in FIG. 1, the fixed shaft 4 is inserted into the hollow of the hollow rotary shaft 11, and the hollow rotary shaft 11 is
As shown in FIG. 2 to FIG. 4, the metal member mainly composed of aluminum is formed in a cap shape to form the dynamic pressure air bearing portion 11 a, and outward (in a radial direction).
A flange portion 11b protruding in a flange shape is fixed to the flange portion 11b.
A suction-type magnetic bearing rotation unit 12 is press-fitted and fixed to the center of the upper surface of the cap shape of the hollow rotation shaft 11. The suction-type magnetic bearing rotation unit 12 is formed by a center circle portion of the first fixed yoke plate 9 and a second circle. An outer cylindrical surface which forms a magnetic gap is formed between the fixed yoke plate 10 and the center circle. The outer cylinder surface is arranged so as to be coaxial with the rotation center axis of the suction type magnetic bearing rotating unit 12.

A polygon mirror portion 1 is provided on the upper outer peripheral surface of a flange-shaped portion of the flange portion 11b of the hollow rotary shaft 11.
1c is formed integrally with the polygon mirror 1
A magnet holding portion 11d is formed below 1c. The magnet holding portion 11d has a rotor magnet 13 for a motor adhered or press-fitted and fixed. The rotor magnet 13 is formed of, for example, an aluminum-manganese metal magnet having a light weight and high mechanical strength (tensile strength). ing. Dynamic pressure air bearing 11a of hollow rotary shaft 11
The inner peripheral surface is a dynamic pressure bearing surface, and a wear-resistant surface treatment film is formed to suppress contact wear at the time of starting and stopping.

An air reservoir 14 is formed in a hollow portion closed by the upper end of the fixed shaft 4 and the upper surface of the hollow rotary shaft 11, and a fine hole (φ0.2 to 0.5) formed on the upper surface of the hollow rotary shaft 11 is formed. A vertical vibration damping effect is obtained by viscous resistance of air when entering and exiting (not shown). The closing portion on the upper surface of the hollow rotary shaft 11 can be formed by press-fitting another component, but the number of components is small by integrally forming the polygon mirror portion 11c and the dynamic pressure air bearing portion 11a. Lower cost. In addition, the integration reduces the number of components, and the balance of the rotating body is lost due to temperature changes.
In order not to increase the vibration, the hollow rotary shaft 11 is
The two correction surfaces 11 above and below the hollow rotary shaft 11 so that the unbalanced vibration is at a very small level.
e and the correction surface 13a are subjected to balance correction.

The rotating portion 12 of the attraction type magnetic bearing is made of a material such as a permanent magnet or a ferromagnetic material of iron or steel. Further, the fixed shaft 4 and the hollow rotary shaft 11 are formed of a nonmagnetic material such as a ceramic or an aluminum alloy, and prevent the magnetic flux of the attraction type magnetic bearing from leaking, so that the attraction to the axial bearing described later can be efficiently performed. Generate force.

The hollow rotary shaft 11, the attraction type magnetic bearing rotating portion 12, the polygon mirror portion 11c and the rotor magnet 13 constitute a rotating body 15 integrally.

Magnet holding portion 11d of hollow rotary shaft 11
A stator core 16 is disposed on a surface of the bearing reference portion 2b of the housing 2 facing the rotor magnet 13 described above, and a motor winding 16a is wound around the stator core 16. Rotor magnet 13 and motor winding 16
A printed circuit board 17 is provided on the housing 2 below the stator core 16 wound with the letter a. As shown in FIG. 2, the printed circuit board 17 has a hole formed at a substantially central portion, and an inner peripheral portion of the hole is formed in the bearing reference portion 2 of the housing 2.
b and is attached to the housing 2 while being in close contact with b.

The spacer 18 and the starter core 16 around which the motor winding 16a is wound are fitted in order on the outer peripheral portion of the bearing reference portion 2b of the housing 2 while being in contact with the upper surface of the printed circuit board 17. The tip of 2b is caulked (plastically deformed), and these parts are fixed.

The printed circuit board 17 has a Hall element 19, a driving element 20, other circuit elements 21, a connector 22 and the like mounted on a surface formed of the metal substrate.
The back surface made of the Al alloy is fixed in close contact with the housing 2. Therefore, the heat capacity of the circuit element against the heat generated by the circuit element such as the drive element 20 can be increased, the heat radiation efficiency can be improved, and a small and inexpensive circuit element can be used.

The printed circuit board 17 is provided with a region where no circuit element is mounted, and the elastic seal member 23 is disposed and compressed on the non-circuit element mounted portion, and the upper cover 3 is attached. 15 and printed circuit board 17
The part where the above circuit elements are arranged and the outside are cut off,
Sealed.

By arranging the rotator 15 in the closed space in this manner, the amount of air agitated by the polygon mirror 11c is reduced, the windage loss is reduced, and the current flowing through the drive element 20 is reduced. The required power consumption is reduced.
In addition, the wind noise of the polygon mirror 11c is reduced by the upper cover 3.
To reduce the noise level.

A radial gap outer rotor type brushless motor 24 is constituted by the rotor magnet 13, the printed board 17, the motor winding 16a, the Hall element 19, the drive element 20, and the like. 17, the Hall element 19, the driving element 20 and the like function as a fixing part of the brushless motor 24. The brushless motor 24 is mounted on the printed circuit board 17.
The drive element 20 controls the energization of the motor winding 16a sequentially based on the position detection signal of the Hall element 19, and switches the excitation, thereby rotating the rotating body 15,
Control at constant speed.

Since the herringbone groove 4a is formed on the outer peripheral surface of the fixed shaft 4 as described above, when the rotating body 15 is rotated by driving the brushless motor 24, the hollow rotating shaft 11 and the fixed shaft 4 are rotated. The air pressure in the bearing clearance in the gap increases, and the inner peripheral surface of the hollow rotary shaft 11 and the outer peripheral surface of the fixed shaft 4 function as a dynamic pressure air bearing surface to function as a radial bearing (dynamic pressure bearing) using dynamic pressure air. The rotor 15 is supported in a radial direction (radial direction) without contact.

Further, the suction type magnetic bearing rotating part 12 fixed to the flange part 11b is embedded in the cylinder of the fixed shaft 4.
The attraction type magnetic bearing fixing portion 5 including the fixed permanent magnet 8, the first fixed yoke plate 9, and the second fixed yoke plate 10 is an attraction type magnetic bearing rotating portion 12 and the attraction type magnetic bearing embedded and fixed to the fixed shaft 4. Attraction force is generated in the magnetic bearing fixing portion 5, and the rotating body 15
Functions as an axial bearing (magnetic bearing) for floating the rotor 15 and supports the rotating body 15 in a non-contact manner in the axial direction. That is, the axial bearing is formed radially inward of the dynamic pressure air bearing surface of the radial bearing.

In the upper cover 3, a glass window 26 is fixed to an opening 25 for inputting and outputting laser light from a semiconductor laser (not shown) with a double-sided tape or an adhesive, and the inside is closed.

The dynamic pressure air bearing type polygon scanner 1
Is a case in which the upper cover 3 having the opening 25 for inputting and outputting laser light is attached to the housing 2, but the rotating body 15 is arranged in a closed space when attached to the optical housing (casing). , The upper cover 3 may be removed.

The hollow rotary shaft 11 has the following 3
One processing step, namely, the first step: a cutting step of the inner diameter of the dynamic pressure air bearing portion 11a and the mirror processing reference surface of the polygon mirror section 11c, the second step: a bearing surface surface treatment step, and the third step: a polygon mirror It is formed by performing each processing in the mirror cutting process of the portion 11c.

First, in the first step, as shown in FIG.
Inner diameter of dynamic pressure air bearing 11a and its dynamic pressure air bearing 11
A mirror-finish reference surface 11f of the polygon mirror portion 11c orthogonal to the inner diameter of a is formed by cutting. At this time, as shown in FIG. 5, since the inner diameter of the dynamic pressure air bearing 11a and the reference surface 11f for mirror finishing can be formed by one chuck, the inner diameter of the dynamic pressure air bearing 11a is processed. Compared to the case where the mirror processing reference surface 11f is formed based on the inner diameter of the dynamic pressure air bearing portion 11a, the mirror processing reference surface 11f with respect to the inner diameter of the dynamic pressure air bearing portion 11a is provided.
Can have an extremely high orthogonality. In FIG. 5, reference numeral 30 denotes a cutting blade for processing. The mirror processing reference surface may be provided at 11g, 11h, or the like in the cross section of the hollow rotary shaft 11 in FIG.

In the second step, the dynamic pressure air bearing 11a
A surface treatment film to be a dynamic pressure bearing surface is formed on the inner diameter. In the surface treatment of the dynamic pressure air bearing portion 11a, a surface reforming treatment by collision of fine particles is performed. As a surface modification treatment by the collision of fine particles, for example, there is a WPC treatment (refer to Japanese Patent No. 1594395) by Fuji Seisakusho. This surface modification treatment is achieved by colliding ceramic fine particles at high speed.
An abrasion-resistant surface treatment film of several μm is formed. In the surface modification treatment by the collision of fine particles, since the dimensional change before and after the treatment is small, it is possible to form a surface treatment film having improved abrasion resistance while maintaining the dimensions before the treatment. Therefore, the bearing can be finished to a desired bearing size by precision cutting before the treatment, and can be used as the bearing surface as it is after the surface modification treatment, so that the bearing surface can be formed more easily than in the past.

In the ordinary surface treatment, the shape and dimensions change before and after the treatment, and the amount of the change varies. Therefore, after the treatment, machining for forming the bearing surface by grinding such as honing or cylindrical grinding is required. Become.

In this surface modification treatment, the treatment time can be shortened and the cost can be reduced by performing the surface modification treatment only on both ends of the dynamic pressure air bearing portion 11a, which is likely to be in contact wear as a bearing surface. The surface treatment may be any as long as it has a small dimensional change between before and after the treatment and has abrasion resistance or lubricity. Therefore, as compared with the case where a dissimilar material is formed as a surface treatment film, the recyclability as an aluminum material is excellent.

In the third step, the hollow rotary shaft 11 is fixed on the mirror-finish reference surface 11f, and the polygon mirror 1
Form a 1c plane. Here, in the first step, since the orthogonal accuracy of the mirror-finished reference surface 11f is formed with extremely high precision with respect to the inner diameter of the dynamic pressure air bearing portion 11a, it is constant with respect to the inner diameter of the dynamic pressure air bearing portion 11a. The mirror surface of the polygon mirror portion 11c can be formed with high precision at the angle of. As a result, when performing optical scanning as a polygon scanner,
Variations in position for each surface can be reduced, and image quality is improved.

A portion of the printed circuit board 17 is exposed from between the housing 2 and the upper cover 3, and a connector 22 for input / output signals and a drive power supply is mounted on the exposed portion. By arranging the connector 22 for input / output signals and driving power above the mounting reference plane of the housing 2, the harness can be mounted even after the polygon scanner has been mounted, and the workability is good due to the insertion from above.

As described above, the dynamic pressure air bearing type polygon scanner 1 of the present embodiment is configured including the upper cover 3, so that it is small, compact, and has uneven rotation at high speed rotation and noise. It is easy to assure characteristics and to inspect.

Also, a dynamic pressure air bearing type polygon scanner 1
Is mounted on an optical housing made of aluminum die-cast provided with a surface that is in close contact with the mounting reference surface 2a of the housing 2. Further, it is possible to secure a heat radiation path transmitted to the optical housing. As a result, the temperature rise of the drive element 20 and the like of the dynamic pressure air bearing type polygon scanner 1 can be suppressed to be low, and the polygon scanner 1 can be used in a state where reliability is secured.

Although the invention made by the inventor has been specifically described based on the preferred embodiments, the invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the invention. It goes without saying that it is possible.

[0058]

According to the first aspect of the present invention, a polygonal mirror is fixed to a hollow rotary shaft having a hollow portion in the axial direction to form a rotary body. The rotating shaft is rotated by a motor having a printed board or the like as a fixed portion, and the dynamic pressure of air generated by the rotation of the rotating body is changed to the inner circumferential surface of the hollow rotating shaft and the outer circumferential surface of the fixed shaft. The hollow rotating shaft of a dynamic pressure air bearing type polygon scanner that supports a rotating body rotatably in a radial direction and an axial direction by a radial dynamic pressure air bearing received on a dynamic pressure air bearing surface and a predetermined axial bearing,
At least the radial dynamic pressure air bearing portion and the polygon mirror portion are integrally formed of a metal material containing aluminum as a main component. Since the surface is surface-treated, the dynamic pressure air bearing of the hollow rotary shaft and the polygon mirror do not have to be provided with shrink-fitting parts and work with metal material mainly composed of aluminum. By forming the pressure bearing and the polygon mirror integrally, the components of the rotating body can be reduced and it can be formed inexpensively and with high accuracy, and the polygon mirror is formed at a fixed angle with respect to the hollow rotating shaft. When the optical scanning is performed, the variation in the scanning position for each mirror surface is reduced, and even if the temperature of the rotating body changes due to high-speed rotation or a change in the ambient temperature, Thereby preventing the flatness is deteriorated distorted Rigonmira surface, it is possible to maintain a highly accurate mirror surface, it is possible to improve the image quality.

According to the second aspect of the present invention, the dynamic pressure air bearing surface of the hollow rotary shaft is formed on the inner cylindrical portion of the hollow rotary shaft, and one end of the dynamic pressure air bearing is formed. Since the closing portion that substantially closes is integrally formed of the same metal material mainly composed of aluminum as the dynamic pressure air bearing portion and the polygon mirror portion, a closing member for closing one end of the dynamic pressure air bearing is unnecessary, The number of components of the hollow rotary shaft can be reduced, the cost can be further reduced, and the image quality can be improved.

According to the dynamic pressure air bearing type polygon scanner of the third aspect of the present invention, since the surface treatment of the dynamic pressure air bearing surface is performed by the surface reforming process by the collision of fine particles,
The recyclability of the hollow rotary shaft can be improved, and the hollow rotary shaft can be made even more inexpensive and environmentally friendly, and the image quality can be improved.

According to the dynamic pressure air bearing type polygon scanner of the fourth aspect of the present invention, since only the both ends of the bearing surface of the dynamic pressure air bearing are subjected to the surface modification treatment, the surface treatment cost is reduced. The cost can be further reduced, and the image quality can be improved.

According to the fifth aspect of the present invention, there is provided a cutting method for forming at least a dynamic pressure air bearing surface and a mirror processing reference surface of a polygon mirror on a hollow rotary shaft. Processing, a surface treatment processing step of forming a surface treatment film on the bearing surface of the dynamic pressure air bearing portion,
Mirror surface cutting process processing for forming the mirror surface of the polygon mirror,
Because the dynamic pressure air bearing of the hollow rotary shaft and the polygon mirror are not provided with shrink fit portions, the dynamic pressure bearing and the polygon mirror are integrally formed of a metal material mainly composed of aluminum, The components of the rotating body can be reduced and it can be formed at low cost and with high accuracy.
A polygon mirror is formed at a fixed angle with respect to the hollow rotating shaft to reduce variations in the scanning position of each mirror surface when performing optical scanning, and to rotate the rotating body at high speeds or changes in ambient temperature. Even if the temperature changes, the polygon mirror surface is prevented from being distorted and the flatness is not deteriorated, and the high-precision mirror surface can be maintained and the image bearing quality can be improved. And can be easily processed.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a dynamic pressure air bearing type polygon scanner to which an embodiment of a dynamic pressure air bearing type polygon scanner and a working method of the dynamic pressure air bearing type polygon scanner of the present invention is applied.

FIG. 2 is an exploded perspective view of the polygon scanner of FIG. 1;

FIG. 3 is an enlarged exploded perspective view of the hollow rotary shaft of FIG. 1;

FIG. 4 is an enlarged front sectional view of the hollow rotary shaft of FIG. 1;

FIG. 5 is an explanatory view of a processing step of the hollow rotary shaft of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dynamic pressure air bearing type polygon scanner 2 Housing 2b Bearing reference part 3 Upper cover 4 Fixed shaft 5 Attraction type magnetic bearing fixing part 6 Cap member 7 Stopper 8 Permanent magnet 9 First fixed yoke plate 10 Second fixed yoke plate 11 Hollow rotation Shaft 11a Dynamic pressure air bearing portion 11b Flange portion 11c Polygon mirror portion 11d Magnet holding portion 11e Correction surface 11f, 11g, 11h Mirror surface reference surface 12 Suction type magnetic bearing rotating portion 13 Rotor magnet 13a Correction surface 14 Air pocket 15 Rotating body Reference Signs List 16 Stator core 16a Motor winding 17 Printed circuit board 18 Spacer 19 Hall element 20 Drive element 21 Circuit element 22 Connector 23 Elastic seal member 24 Brushless motor 25 Opening 26 Glass window

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/036 B41J 3/00 D 5C072 1/113 H04N 1/04 104A F-term (Reference) 2C362 BA06 BA09 BA10 2H045 AA07 AA14 AA24 AA62 3J011 AA20 BA02 CA02 CA05 DA01 DA02 KA02 KA05 MA02 SB04 3J102 AA01 AA08 BA03 BA04 BA17 BA18 CA02 CA16 CA18 CA22 DA03 DA07 DA10 DA16 FA03 FA16 FA22 GA02 5C051 AA04 CA07 DB02 X

Claims (5)

[Claims] A polygon mirror is fixed to a hollow rotary shaft having a hollow portion in the axial direction, and a fixed shaft is inserted into the hollow portion of the hollow rotary shaft forming a rotary body, and has a printed board or the like as a fixed portion. The rotating body is rotated by a motor, and the dynamic pressure of air generated by the rotation of the rotating body is received by a dynamic pressure air bearing surface including an inner peripheral surface of the hollow rotating shaft and an outer peripheral surface of the fixed shaft. A dynamic pressure air bearing type polygon scanner that rotatably supports the rotating body in a radial direction and an axial direction by a bearing and a predetermined axial bearing, wherein the hollow rotating shaft includes at least the radial dynamic pressure air bearing portion and the polygon. The mirror portion is integrally formed of a metal material containing aluminum as a main component, and a polygon mirror processing reference surface orthogonal to the radial dynamic pressure air bearing is formed on the hollow rotary shaft. , Dynamic pressure air bearing type polygon scanner, wherein a surface treatment is applied to the dynamic pressure air bearing surface. 2. The dynamic pressure air bearing surface of the hollow rotary shaft is formed on an inner cylindrical portion of the hollow rotary shaft, and a closing portion for substantially closing one end of the dynamic pressure air bearing is provided with the dynamic pressure air bearing. 2. The dynamic pressure air bearing type polygon scanner according to claim 1, wherein the bearing portion and the polygon mirror portion are integrally formed of the same metal material containing aluminum as a main component. 3. The dynamic pressure air bearing type polygon according to claim 1, wherein said dynamic pressure air bearing surface is subjected to a surface modification treatment by particle collision as said surface treatment. Scanner. 4. The polygon scanner according to claim 3, wherein the surface modification is performed only on both ends of the bearing surface of the dynamic pressure air bearing. 5. A polygonal mirror is fixed to a hollow rotary shaft having a hollow portion in the axial direction, and a fixed shaft is inserted into the hollow portion of the hollow rotary shaft forming a rotary body, and has a printed board or the like as a fixed portion. The rotating body is rotated by a motor, and the dynamic pressure of air generated by the rotation of the rotating body is received by a dynamic pressure air bearing surface including an inner peripheral surface of the hollow rotating shaft and an outer peripheral surface of the fixed shaft. A processing method of a hydrodynamic air bearing type polygon scanner that rotatably supports the rotating body in a radial direction and an axial direction by a bearing and a predetermined axial bearing, wherein the hollow rotating shaft has at least the hydrodynamic air bearing surface. And a cutting process for forming a mirror processing reference surface of the polygon mirror; a surface processing process for forming a surface treatment film on a bearing surface of the hydrodynamic air bearing portion; Method for processing a dynamic pressure air bearing type polygon scanner and mirror cutting step process for forming a mirror surface of Ra, characterized in that the subjecting.