JPH1031176A - Polygon scanner and handling method thereof - Google Patents

Abstract

(57) [Summary] (With correction) [Problem] The frictional force due to the contact between the fixed shaft and the rotating shaft increases, and it becomes impossible to appropriately reflect light due to unstable rotation. Provide a stable polygon scanner unit. A rotating shaft provided with a field magnet, a polygonal polygon mirror having a plurality of reflection surfaces for reflecting light while rotating, a thrust receiving portion, and a thrust receiving portion 7a
A polygonal scanner comprising: a fixed body provided with the fixed shaft; and a fixed body having the fixed shaft and a coil substrate on which a plurality of drive coils are fixed facing the field magnet. The thrust cover having a portion is detachably installed on the upper portion of the rotating shaft, and has a cylindrical shape with an inner diameter slightly larger than the outer diameter of the fixed shaft on the inner peripheral portion 31 of the rotating shaft, and has an outer peripheral surface. The end on the thrust cover side has a larger inverted C-shape, and a sleeve made of a resin material is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure of a polygon scanner used for reflecting a laser beam used in an image forming apparatus such as a laser beam printer and a digital copying machine.

[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]

In the above-described perfect circular dynamic bearing, the sleeve serving as the radial bearing makes contact with the fixed shaft at least during the initial rotation when the rotating shaft is unstablely rotating. Therefore, the radial bearing also wears.

As the wear progresses, the dynamic pressure effect formed in the gap between the fixed shaft 6 and the sleeve 5 is lost, and stable rotation cannot be performed.
May come into contact with the fixed shaft 6. Further, the contact between the two may cause abnormal noise.

Accordingly, it is an object of the present invention to provide an excellent polygon scanner capable of easily removing and replacing the sleeve while removing and replacing the thrust bearing member, and a method of handling the polygon scanner.

[0024]

To solve the above problems, the present invention employs the following means. That is, according to the first aspect of the invention, a field magnet, a polygonal polygon mirror having a plurality of reflecting surfaces that reflect light while rotating the light,
A rotating shaft provided with a thrust receiving portion, a fixed shaft in contact with the thrust receiving portion, and a coil substrate provided with the fixed shaft and having a plurality of drive coils fixed to face the field magnet. A polygonal scanner having a fixed body having the thrust receiving portion, the thrust cover having the thrust receiving portion is removably installed on the upper portion of the rotating shaft, and the inner peripheral portion of the rotating shaft is slightly smaller than the outer diameter of the fixed shaft. A cylindrical shape having a large inner peripheral diameter, and an outer peripheral surface having an inverted C-shape with a larger end at the thrust cover side, and a sleeve made of a resin material is further provided. Things.

According to a second aspect of the present invention, in the first aspect of the present invention, the upper end of the sleeve is in contact with the thrust cover.

According to a third aspect of the present invention, there is provided a rotating magnet having a field magnet, a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating the light, a rotating shaft provided with a thrust receiving portion, and the thrust receiving portion. A polygon scanner comprising: a fixed shaft that contacts a portion; and a fixed body having the fixed shaft and a coil substrate on which a plurality of drive coils are fixed facing the field magnet. The thrust cover having the thrust receiving portion is detachable on the upper portion of the rotating shaft, and the inner peripheral portion of the rotating shaft has a cylindrical shape having an inner diameter slightly larger than the outer diameter of the fixed shaft, In addition, the outer peripheral shape is a conical shape of an inverted V-shape having a larger end at the thrust cover side, and a sleeve made of a resin material is further removed. Ri said sleeve is characterized in carrying out the removal.

[0027]

According to the first to third aspects of the present invention, when the sleeve serving as the radial bearing is worn by contact with the fixed shaft,
By simply removing the thrust cover and then applying external force to the sleeve, the conical shape of the outer peripheral surface of the sleeve reduces the suppression force due to friction between the sleeve and the rotating shaft, making it easy to remove the sleeve It becomes possible.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
The overall structure is the same as that of FIG.
Here, mainly the structure relating to the rotating shaft 2 and the sleeve 5 will be described in detail. Note that the same members and components as those in FIG.

The sleeve 5 according to the present invention will be described in detail with reference to FIG. FIG. 2A is a schematic cross-sectional view showing the arrangement of the thrust cover 7 with the sleeve 5 according to the present invention mounted on the rotary shaft 2 and further having the thrust receiving member 7a fixed to the rotary shaft. FIG. 2B is a schematic sectional view showing the shape of the sleeve 5 according to the present invention.

The outer peripheral surface 21 of the sleeve is formed by injection molding, cutting or the like so that the diameter D of the upper surface 22 of the sleeve is larger than the diameter d of the lower surface 23 of the sleeve in an inverted C-shape.

The inner peripheral surface 31 of the rotating shaft has substantially the same shape as the outer peripheral surface 21 of the sleeve. The sleeve 5 is press-fitted into the inner peripheral surface 31 from above the rotating shaft, whereby the rotating shaft 2 is rotated. To be fixed. At this time, because of the conical shape, the reaction force due to friction on the contact surface is reduced, so that the press-fitting can be performed smoothly, and the parallelism with respect to the fixed shaft 6 can be further stabilized.

The sleeve 5 is fixed to the rotary shaft 2 by press-fitting, when there is a gap between the upper surface 23 of the sleeve and the thrust cover as shown in FIG. This is to ensure that it does not come off during use.
For this reason, the holding force (frictional force) between the rotating shaft 2 and the sleeve 5 due to the press-fitting is set to such a degree that the sleeve 5 does not shift during use.

When the thrust receiving member 7a is worn due to the contact with the fixed shaft 6, the thrust cover 7 is removed from the rotating shaft 2, and the lower surface 23 of the sleeve is pressed against the upper surface of the sleeve by an external force F. This external force F is applied to the rotating shaft 2 by press fitting.
The sleeve 5 can be removed from the rotary shaft 2 by pressing with a force greater than the holding force (frictional force) between the sleeve 5 and the sleeve 5. Then, the new sleeve is fixed to the rotary shaft 2 again by press-fitting, so that it can be used again.

[0034]

According to the present invention, the sleeve serving as the radial bearing can be removed and replaced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an overall structure of a polygon scanner proposed to solve a conventional problem.

FIG. 2A is a schematic cross-sectional view showing a positional relationship between a thrust cover and a rotation shaft according to the present invention. (B)
FIG. 3 is a schematic sectional view showing a shape of a sleeve 5 according to the present invention.

[Explanation of symbols]

21 outer peripheral surface of sleeve, 22 upper surface of sleeve, 23
Lower surface of sleeve 31 Inner peripheral surface of rotating shaft

Claims (3)

[Claims] 1. A rotating shaft having a field magnet, a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, a rotating shaft provided with a thrust receiving portion, and a fixed contact with the thrust receiving portion. A polygon scanner comprising: a shaft; and a fixed body including the fixed shaft and a coil substrate on which a plurality of drive coils are fixed facing the field magnet, wherein the thrust having the thrust receiving portion is provided. The cover is detachably installed on the upper part of the rotating shaft. The inner circumferential part of the rotating shaft has a cylindrical shape with an inner circumferential diameter slightly larger than the outer circumferential diameter of the fixed shaft, and the outer circumferential surface is on the thrust cover side. A polygon scanner having an inverted C-shape with a larger end, and a sleeve made of a resin material. 2. The polygon scanner according to claim 1, wherein an upper end of said sleeve is in contact with said thrust cover. 3. A rotating shaft provided with a field magnet, a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, a rotating shaft provided with a thrust receiving portion, and a fixed contact with the thrust receiving portion. A method of handling a polygon scanner, comprising: a shaft; and a fixed body having a fixed shaft, and a coil substrate on which a plurality of drive coils are fixed facing the field magnet. A thrust cover having a removable upper part of the rotating shaft, an inner circumferential portion of the rotating shaft, a cylindrical shape having an inner circumferential diameter slightly larger than the outer circumferential diameter of the fixed shaft, and the outer circumferential shape is The end on the thrust cover side has a larger inverted C-shape conical shape, and further a sleeve made of a resin material.The sleeve is removed from the thrust cover side by removing the thrust cover. A method for handling a polygon scanner, which is characterized in that it is detached.