JPH1031178A - Optical writing unit - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an optical writing unit that can easily attach a fixed shaft to a housing with high accuracy. A rotating body having a field magnet and having a polygonal mirror provided with a plurality of reflecting surfaces for reflecting light, a fixed shaft serving as a rotation center of the rotating body, and a field magnet. A fixed body having a coil substrate to which a plurality of drive coils are fixed facing each other, and at least the rotating body, a housing 42 in which the fixed shaft and the fixed body are arranged, and a thrust bearing portion at a rotation center of the rotating body. In the optical writing unit that rotates while the thrust bearing portion is in contact with the tip of the fixed shaft, the fixed shaft is fixed to the bottom by integral molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polygon motor scanner used in an image forming apparatus, and more particularly, to a polygon motor having a thrust bearing including a slide bearing.

[0002]

2. Description of the Related Art Small rotors are generally supported by rolling bearings. However, when the rotation speed exceeds 10,000 rpm, vibration, noise, and the life of lubricating oil in the bearing portion become problems. For this reason, gas bearings are often used as high-speed, high-precision bearings of 10,000 rpm or more.

[0003] As a conventional dynamic pressure gas bearing that generates pressure for supporting its own weight by rotation of a rotor, a perfect circular bearing and a tilting pad bearing are used.

Among them, the perfect circular bearing is easy to machine,
When supporting a vertical rotor, an eccentric force acts due to its own weight, so if the bearing interval is small, 15000 rpm
VTRs for broadcasting in the past
Has been used for supporting the rotor, but when the vertical rotor was supported, it could not be used because unstable whirl occurred from low speed.

[0005] Further, the tilting pad bearing has a bearing surface divided into three or four partial arc pads, and the high speed stability of the rotor is increased by softly supporting the pads. It is used for bearings. However, there is a drawback that the tilting pad bearing has low bearing accuracy and complicated processing,
It is not suitable for a gas bearing when it is used as a vertical rotor of an image forming apparatus that requires precise rotation and requires low cost.

Incidentally, there is a grooved bearing as a bearing which solves the above-mentioned problems of the bearing. In this bearing, a spiral groove is formed on the bearing surface for swepting gas from the outside by rotation. The spiral groove generates a radial bearing reaction force even if the bearing is not eccentric, and concentrically. The bearing has a radial bearing strength at the position, so that even a vertical rotor can support a high speed of tens of thousands of revolutions (rpm). In forming the grooves, methods such as etching, rolling, and laser processing are used.

[0007] Also, multi-arc bearings have been used in turbo machines as liquid lubricating bearings that have not been used as gas bearings but are stable up to relatively high speeds. The multi-arc bearing is one in which two or three circular bearings are divided, and each arc is fixed closer to the initial circular state. Thus, the shaft and the bearing are equivalently given a large eccentricity, so that the whirl stability can be improved. However, since the bearings are divided, high-precision machining of μm or less is not easy, and the gas pressure generation area is also reduced, so that it has not been used for gas bearings requiring a smiling bearing interval of several μm.

For these reasons, grooved bearings are frequently used as dynamic pressure gas bearings in laser scanner gas bearings, which are often used as vertical rotors.

However, in such a conventional grooved bearing, since grooves are formed by etching, rolling, laser processing, etc., the number of steps required for processing the bearing increases, and the manufacturing cost is reduced. There were problems such as an increase. In addition, grooved bearings have good stability during rotation,
There is also a problem that the dynamic rigidity is reduced with respect to the imbalance of the rotor as compared with a perfect circular bearing.

Therefore, in order to realize this, a perfect circular dynamic pressure bearing has been proposed as a low-cost non-contact type bearing as shown in FIG. First, the configuration of this perfect circular dynamic pressure bearing will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing the entire structure of the polygon scanner motor.

In FIG. 1, reference numeral 1 denotes a polygonal polygonal mirror (polygonal mirror) made of an aluminum alloy or the like whose peripheral surface is mirror-finished, and the polygonal mirror 1 is formed of a flange 2a of a cylindrical rotary shaft 2. It is attached to the upper surface and is configured to rotate integrally with the rotating shaft 2.

Further, a rotor yoke 3 and a rotor magnet 4 are attached to the lower surface of the flange portion 2a of the rotary shaft 2, and a cylindrical sleeve 5 is fitted to the cylindrical inner peripheral surface of the rotary shaft 2. It is fixed. The rotating shaft 2 to which the sleeve 5 is fitted and fixed is rotatably and loosely fitted to the fixed shaft 6, and constitutes a rotating body (rotor) 9 as a whole.

A small interval of several μm to several tens μm is provided between the inner peripheral surface 5 a of the sleeve 5 and the outer peripheral surface 6 a of the fixed shaft 6. Constitutes a dynamic pressure bearing which is a non-contact type radial bearing for supporting a load in a radial direction of a rotating shaft.

The upper end surface of the fixed shaft 6 is a spherical surface 8 having the rotation center O as a vertex. On the lower surface of the thrust cover 7 of the rotating shaft 2 disposed opposite to the spherical surface 8, a flat plate-shaped thrust receiving member 7a which is in rolling contact with the spherical surface 8 is fixedly provided. Member 7
The a and the spherical surface 8 constitute a thrust bearing as a point contact type axial bearing for supporting a load in the axial direction of the rotating shaft.

The sleeve 5 and the thrust receiving member 7a are made of a member having excellent wear resistance and lubricity, for example, a resin material such as a polyimide resin. The fixed shaft 6 is made of a metal material such as carbon steel or stainless steel.

An annular groove 2b is formed on the upper surface of the rotary shaft 2, and an outer peripheral edge of the rotor yoke 3 is bent upward to form an annular edge 3a. The annular groove 2b and the annular edge 3a are for attaching a weight for balance adjustment. As shown in the figure, by attaching the weights 2c and 3b at predetermined positions, the imbalance of the rotating body 9 is corrected. Is what you do.

The fixed shaft is vertically attached to a base member 12 by a base collar 11. A printed circuit board 13 is disposed on the upper surface of the base member 12, on which the winding coil 14, the Hall element 15, the control IC 16, and the connector 17 are mounted.

The winding coil 14 is fixed on the printed circuit board 13 with a slight gap from the rotor magnet 4 attached to the rotating body 9. Control IC 1 based on phase
By controlling the switching of the exciting current of the winding coil 14 by means of 6, the rotating body 9 is rotated as a motor.

When the rotating body 9 rotates as described above,
The air pressure in the gap formed between the inner peripheral surface 5a of the sleeve 5 and the outer peripheral surface 6a of the fixed shaft 6 increases, and the rotating body 9
, And rotate in a non-contact state with the outer peripheral surface of. For this reason, the rotational friction of the bearing peripheral surface is extremely small, and the bearing can be smoothly rotated up to a high rotational speed without noise.

A groove for the pressure pump for efficiently increasing the air pressure in the gap formed between the inner peripheral surface 5a of the sleeve 5 and the outer peripheral surface 6a of the fixed shaft 6 is formed on the outer peripheral surface of the fixed shaft 6. Has not been formed at all, and its cross section is a perfect circle. Such a dynamic pressure bearing having a perfect circular shaft which is not cut with a pressure pumping groove is called a perfect circular dynamic pressure bearing. Further, a fluid utilizing air as a fluid for generating dynamic pressure as shown in the figure is called a perfect circular dynamic pressure air bearing.

[0021]

The polygon motor unit 18 shown in FIG. 1 is mounted on a housing (not shown). At that time, since it is necessary to make the parallelism of the laser beam highly accurate, the fixed shaft 6 must be attached to the printed circuit board 13 with high accuracy, and the printed circuit board 13 must be attached to the housing with high accuracy. .

Accordingly, an object of the present invention is to provide an optical writing unit capable of easily mounting a fixed shaft to a housing with high accuracy.

[0023]

To solve the above problems, the present invention employs the following means. That is, a rotating body having a field magnet and having a polygonal mirror provided with a plurality of reflecting surfaces for reflecting light, a fixed shaft serving as a rotation center of the rotating body, and a plurality of rotating bodies facing the field magnet. A fixed body having a coil substrate to which the drive coil is fixed, and at least the rotating body, a housing for arranging the fixed shaft and the fixed body, and a thrust bearing portion provided at a rotation center of the rotating body; The rotating body is an optical writing unit that rotates while contacting the thrust bearing portion with the tip portion of the fixed shaft, wherein the fixed shaft is fixedly integrated with the bottom portion by integral molding. .

[0024]

According to the first aspect of the present invention, since the fixed shaft is fixed to the housing, it is possible to manufacture and design in consideration of only the mounting accuracy between the fixed shaft and the housing.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
1 are the same as those described above, and different portions will be described here.

First, the image forming apparatus of the present invention will be described with reference to FIG. The image forming apparatus shown in FIG. 3 is a digital copying machine. The digital copying machine shown in FIG. 2 includes an image reading device 22 that reads image information from a document placed on a contact glass 21, and a laser recording device 25 including an image forming device 23 and a laser scanning device 24. I have.

In FIG. 1, an image of a document placed on a contact glass 21 is read by an image reading device 22 through optical scanning by a scanner 26,
The image data is converted into multi-tone image data by the image processing unit 7 and further converted into binary image data, and stored in an image memory (not shown). Next, the image data is read and output to the laser recording device 25.

In the laser recording device 25, an image recording signal of binary image data is input to a laser driving unit (not shown), and a laser driver modulated and controlled according to the image recording signal drives the semiconductor laser to blink or weakly emit light. . In this way, the semiconductor laser emits laser light that has been modulated.

The laser beam passes through a collimator lens and a cylindrical lens, enters a polarizer, is rotated at a constant speed by the polarizer, passes through an fθ lens, a mirror, and dust-proof glass, is guided onto a photosensitive drum 28, and Scanning is performed on the drum 28 in parallel with the fixed axis of the photosensitive drum 28.

The photosensitive drum 28, which is uniformly charged by a charger around the photosensitive drum 28, forms a latent image of a recorded image by exposure to laser light, and the formed latent image is developed by a developing device. Then, it becomes a visible image. The transfer paper taken out from the paper feed unit 29 is supplied to the photosensitive drum 28.
Is sent to the transfer section in synchronization with the timing of the visual image formed on the transfer section. Then, the visible image is transferred onto the transfer paper by the transfer charger. Thereafter, the transfer sheet is subjected to a visible image fixing process by a fixing unit, and is discharged.

Next, a laser scanning device according to the present invention will be described with reference to FIG. When the laser scanning device 24 is disposed in the housing 42, the fixed shaft 43 of the polygon motor unit is used as an insert and the bottom surface 4
The housing 42 is formed by injection molding so as to be inserted at a position located at the position 4 to form an integral structure.

At this time, by providing the disk portion 45 near the bottom of the fixed shaft 43, the fixed shaft 4
Stability by vibration of 3 can be secured, and verticality (perpendicularity)
Can also be secured.

Then, the base member 51 and the printed board 5
2, holes 53, 54 into which the fixed shaft 43 is inserted, respectively.
Are formed. The base member 51 to which the printed circuit board 52 is attached is fixed to a predetermined position on the bottom surface 61 of the housing by screws or the like while inserting a fixed shaft into the holes 53 and 54.

By inserting the rotating body 9 into the fixed shaft 43, an optical writing unit is obtained. Needless to say, the housing 42 further includes a laser driving unit, a collimator lens, a cylindrical lens, an fθ lens, a mirror, and dustproof glass. The upper part of the housing 42 is closed by a cover (not shown).

[0035]

According to the present invention, the fixed shaft of the polygon scanner motor can be attached to the housing with high accuracy, and the perpendicularity of the polygon motor unit can be ensured, so that stable laser light reflection is possible.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the entire structure of a conventional polygon scanner.

FIG. 2 is a schematic view showing an image forming apparatus according to the present invention.

FIG. 3 is a schematic sectional view showing one embodiment of an optical writing unit according to the present invention.

[Explanation of symbols]

42 housing, 43 fixed shaft, 44 bottom of housing, 45 disk

Claims (1)

[Claims] 1. A rotating body having a field magnet and a polygon mirror having a plurality of reflecting surfaces for reflecting light, a fixed shaft serving as a rotation center of the rotating body, and a rotating shaft facing the field magnet. And a housing for disposing at least the rotating body, the fixed shaft and the fixed body, and a thrust bearing at the center of rotation of the rotating body. Wherein the rotating body is an optical writing unit that rotates while contacting the thrust bearing portion with the tip end of the fixed shaft, wherein the fixed shaft is fixedly formed integrally with the bottom portion. Optical writing unit.