JPH1031175A - Polygon scanner and handling method thereof - Google Patents

Abstract

(57) Abstract: When a rotating shaft is rotated while being in contact with a fixed shaft, when the thrust receiving member is worn by rotational contact, unstable rotation is caused by an increase in the contact area between the fixed shaft and the thrust receiving member. The object is to provide a polygon scanner that is easily replaceable when the thrust receiving member is worn because the reflection may not be accurately performed. The present invention relates to a rotating shaft provided with a field magnet, a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, and a resin material formed at the center of the rotating shaft. A fixed body having a fixed shaft that contacts the thrust receiving member, a fixed shaft provided with the fixed shaft, and a coil substrate on which a plurality of drive coils are fixed facing the field magnet. A polygon scanner,
This is achieved by providing a hole having a cylindrical inner peripheral diameter penetrating the upper portion of the rotary shaft, and fitting the thrust receiving member into the hole.

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 perfect circular dynamic bearing described above, the thrust bearing is formed by the contact between the fixed shaft 6 and the thrust receiving member 7a. There is a problem that the thrust receiving member 7a is worn.

When the rotating shaft 2 is rotated while being in contact with the fixed shaft 6, the thrust receiving member 7a is worn by the rotating contact. As the wear progresses, the contact surface of the thrust receiving member wears in a spherical shape at the distal end of the fixed shaft 6, so that the frictional force due to the contact with the rotating shaft 6 increases, and the load on the rotational drive of the rotating shaft 2 is Increase.

Further, as the bottom surface 24 of the thrust receiving member wears, the vertical position of the polygon mirror 1 attached to the rotating shaft 2 moves downward. Polygon mirror 1
Reflects the laser light on the mirror surface, but the effective area of the mirror surface moves downward, so that the laser light cannot be reflected or the fixed shaft 6 and the thrust receiving member 7a contact with each other due to wear. There is a possibility that the rotation becomes unstable due to the increase in the area, and the reflection cannot be performed accurately.

In order to suppress wear, there is a method of mixing metal powder or the like into the material of the thrust receiving member 7a. However, since the metal powder comes into contact with the fixed shaft 6, the tip shape of the fixed shaft 6 is changed. It may be deformed and may not be able to maintain stable rotation.

Accordingly, it is a first object of the present invention to provide a polygon scanner which is easily replaced when the thrust receiving member is worn and which is excellent in exchangeability.

Further, since the sleeve serving as the radial bearing is in contact with the fixed shaft at least during the initial rotation in which the rotating shaft is unstablely rotating, the radial bearing also wears. . It is a second object of the present invention to provide a polygon scanner capable of easily removing and replacing the sleeve while removing and replacing the thrust bearing member.

[0027]

To solve the above problems, the present invention employs the following means. That is, according to the first aspect of the present invention, a rotating shaft provided with a field magnet and a polygonal polygon mirror having a plurality of reflecting surfaces that reflect light while rotating the light, and a resin material at the center of the rotating shaft. A fixed body including the formed thrust receiving member, a fixed shaft that comes into contact with the thrust receiving member, and a coil substrate provided with the fixed shaft and having a plurality of drive coils fixed to face the field magnet. And a polygon scanner having
A hole having a cylindrical inner peripheral diameter penetrating the upper part of the rotating shaft is provided, and the thrust receiving member is fitted into the hole.

According to a second aspect of the present invention, in the first aspect of the present invention, the inner peripheral portion of the rotary shaft has a cylindrical shape with an inner diameter slightly larger than the outer diameter of the fixed shaft and is made of a resin material. A sleeve is provided.

According to a third aspect of the present invention, in the second aspect of the present invention, the inner diameter of the sleeve is smaller than the inner diameter of the hole, and the outer diameter is larger than the inner diameter of the hole. It is characterized by the following.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the outer peripheral shape of the sleeve is a conical shape having a C shape.

According to the fifth aspect of the present invention, the second to fourth aspects are described.
In the invention, the sleeve and the thrust receiving member have the same durability life.

According to a sixth aspect of the present invention, there is provided a rotating shaft provided with a field magnet and a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, and a resin material is provided at the center of the rotating shaft. A thrust bearing member formed of the above, a fixed shaft that comes into contact with the thrust bearing portion, and a coil substrate provided with the fixed shaft and having a plurality of drive coils fixed to face the field magnet. A thrust receiving member fitted into said hole, wherein said thrust receiving member is fitted in said hole. When the receiving member wears in contact with the rotating shaft, a new thrust receiving member is inserted from a hole on the side opposite to the contact position with the rotating shaft to a predetermined position while pushing out the worn thrust receiving member. You It is intended.

[0033]

According to the first and sixth aspects of the present invention, a new thrust bearing can be inserted from the side of the hole provided in the rotating body opposite to the fixed shaft. Since the thrust bearing portion is pushed out, it can be easily replaced.

According to the second aspect of the present invention, a sleeve serving as a radial bearing is further provided on the rotating shaft, and since the outer shape is conical, when an abrasion occurs due to contact with the fixed shaft, an external force is applied. It can be easily removed from the rotating shaft.

According to the third to fifth aspects of the present invention, when the thrust receiving member is removed, the thrust receiving member presses the sleeve, so that the thrust receiving member and the sleeve can be simultaneously removed.

[0036]

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, the sleeve 5, the thrust cover 7, and the thrust receiving member 7a will be described in detail. Note that the same members and components as those in FIG.

First, the first invention will be described in detail with reference to FIG. FIG. 2 is a schematic sectional view showing only the rotary shaft 2 and the sleeve 5, the thrust cover 7 and the thrust receiving member 7a used in FIG. The thrust cover 7 has a diameter d, and a hole 23 penetrating from the upper surface 21 of the thrust cover to the bottom surface 22 of the thrust cover is formed by cutting or the like.

The cylindrical thrust receiving member 7a having substantially the same shape as the hole 23 is press-fitted into the hole 23. When the thrust receiving member 7a is placed as shown in FIG. 1, the holding force of the hole portion with respect to the thrust receiving member 7a should be larger than the reaction force from the fixed shaft 6 when the thrust receiving member 7a is in contact with the fixed shaft 6. Thus, the thrust receiving member 7a can be prevented from moving toward the upper surface 21 side of the thrust cover due to the reaction force from the fixed shaft 6.

When the rotary shaft 2 is mounted on the polygon scanner unit shown in FIG. 1 and rotated while contacting the fixed shaft 6, the thrust receiving member 7a is worn by the rotational contact. As this wear progresses, the bottom surface 24 of the thrust receiving member is worn in a circular shape at the tip of the fixed shaft 6, so that
The frictional force due to the contact with the rotating shaft 6 increases, which causes an increase in the load on the rotation driving of the rotating shaft 2.

Further, as the bottom surface 24 of the thrust receiving member wears, the vertical position of the polygon mirror 1 attached to the rotating shaft 2 moves downward. Polygon mirror 1
Reflects the laser light on the mirror surface, but the effective area of the mirror surface moves downward, so that the laser light cannot be reflected or the fixed shaft 6 and the thrust receiving member 7a contact with each other due to wear. There is a possibility that the rotation becomes unstable due to the increase in the area, and the reflection cannot be performed accurately.

In such a state, the function as a polygon scanner cannot be performed, so that the worn thrust receiving member 7a must be replaced.

In the first embodiment of the present invention, when the thrust receiving member 7a is worn as described above, the thrust cover 7 is removed from the fixed shaft 2 and a new thrust receiving member 25 is inserted into the hole 23 from the upper surface of the thrust receiving member. With an external force F. By pushing the worn thrust receiving member 7a, the new thrust receiving member 25 is removed from the thrust cover 7, and the new thrust receiving member 25 can be pressed into a predetermined position.

In this replacement, the thrust cover 7 is detached from the rotary shaft 2, but this is because a new thrust receiving member 25 is used.
In particular, the thrust cover 7 is rotated to facilitate confirmation of installation at a predetermined position and to facilitate post-processing such as cutting for obtaining flatness with the bottom surface 22 of the thrust cover at the predetermined position. You may carry out in the state attached to the shaft 2.

The above-mentioned external force F is press-fitted with a force larger than the holding force between the thrust receiving member 7a fixed to the hole 23 and the hole 23.

Next, a second embodiment in which the sleeve 5 serving as a radial bearing is removed simultaneously with replacement of the thrust receiving member will be described in detail with reference to FIG.

FIG. 3 shows the rotary shaft 2 and the sleeve 5, the thrust cover 7 and the thrust receiving member 7a used in FIG.
It is the 2nd schematic sectional drawing which took out only. The thrust cover 7 has a diameter d and a hole 23 penetrating from the top surface 21 of the thrust cover to the bottom surface 22 of the thrust cover.
Is created by cutting or the like (the same as in the first embodiment).

The inner peripheral surface 31 of the rotary shaft has a cylindrical shape with a diameter (inner diameter) X, and the sleeve 5 having an inner diameter Y is press-fitted into the inner peripheral surface 31. This diameter X is equal to the thrust receiving member 7.
The diameter (outer diameter) d of a is smaller than the diameter (outer diameter) d of the thrust receiving member 7a.

As described above, the sleeve 5 usually has a fixed shaft 6.
However, during the initial rotation, the rotating shaft 2 is rotating in an unstable manner, so that the rotating shaft 2 partially contacts the rotating shaft 2, so that the sleeve is also worn by the contact with the fixed shaft 6. . As the wear progresses, the fixed shaft 6 and the sleeve 6
, And a stable dynamic pressure effect cannot be obtained, which causes unstable rotation of the rotating shaft 2.

Therefore, the thrust receiving member 7 is rotated with the rotation.
At the time of replacement due to abrasion of a, a new thrust receiving member 25 is pressed into the hole 23 with an external force W. As a result, the worn thrust receiving member 7a moves downward, and further moves downward with the bottom surface 26 of the worn thrust receiving member abutting on the upper surface 32 of the sleeve. And
When the new thrust receiving member 25 is installed at a predetermined position, the sleeve 5 protrudes from the bottom surface of the rotating shaft 2.

By pulling out the bottom surface 33 of the protruding sleeve, the sleeve 5 and the worn thrust receiving member 7 are removed.
a can be removed simultaneously.

Then, a new sleeve is press-fitted from the side opposite to the position of the thrust receiving member 7a. Then, an excess portion protruding from the rotating shaft is removed by cutting or cutting.

The outer peripheral surface 41 of the sleeve as shown in FIG.
However, since the bottom surface 33 of the sleeve is larger than the upper surface 32 of the sleeve and has a C-shaped conical shape, the sleeve 5 can be detached from the rotary shaft 2 only by an external force W from above. No special tool for pulling out from the rotating shaft 2 is required.

Further, the sleeve 5 and the thrust receiving member 7a
By making the durability life the same, the effect of simultaneously exchanging both is further increased. For example, the same resin is used if the contact time is almost the same, and if the contact time of the thrust receiving member 7a is longer, the life of the sleeve 5 is made equal by using a material having low durability. be able to.

[0054]

According to the first embodiment of the present invention, a new thrust bearing can be inserted from the side of the hole provided in the rotating body opposite to the fixed shaft. Since the worn thrust bearing portion is pushed out, it can be easily replaced.

In the second aspect, when the thrust receiving member is removed, the thrust receiving member presses the sleeve, so that the thrust receiving member and the sleeve can be simultaneously removed.

[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. 2 is a schematic sectional view of a thrust radial bearing according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of a thrust radial bearing according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a sleeve (radial bearing) according to a second embodiment of the present invention.

[Explanation of symbols]

2 rotating shaft, 5 sleeve, 7 thrust cover, 7a
Thrust receiving member 21 Top surface of thrust cover, 22 Bottom surface of thrust cover, 23 hole 24 Bottom surface of thrust receiving member 25 New thrust receiving member 31 Inner peripheral surface of rotating shaft 32 Top surface of sleeve, 33 Bottom surface of sleeve, 41
Outer peripheral surface of sleeve

Claims (6)

[Claims] 1. A rotating shaft provided with a field magnet and a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, and a thrust formed of a resin material at the center of the rotating shaft. A polygon comprising: a receiving member; a fixed shaft that comes into contact with the thrust receiving member; 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. A polygon scanner, comprising: a hole having a cylindrical inner peripheral diameter penetrating an upper part of the rotating shaft; and the thrust receiving member fitted into the hole. 2. A cylindrical sleeve having an inner diameter substantially equal to the outer diameter of the fixed shaft and made of a resin material is provided on an inner peripheral portion of the rotary shaft. 2. The polygon scanner according to claim 1, wherein: 3. The method according to claim 2, wherein the inner diameter of the sleeve is smaller than the inner diameter of the hole, and the outer diameter is larger than the inner diameter of the hole. Polygon scanner. 4. The sleeve according to claim 3, wherein the outer peripheral shape of the sleeve is a conical shape having a C shape.
Polygon scanner described in section. 5. The polygon scanner according to claim 2, wherein the sleeve and the thrust receiving member have the same durability life. 6. A rotating shaft provided with a field magnet and a polygonal polygon mirror having a plurality of reflecting surfaces for reflecting light while rotating, and a thrust formed of a resin material at the center of the rotating shaft. A fixed member having a receiving member, a fixed shaft that comes into contact with the thrust bearing portion, and a coil substrate on which the fixed shaft is provided and a plurality of drive coils are fixed facing the field magnet. A method of handling a polygon scanner in which a hole having a cylindrical inner diameter penetrating through an upper portion of the rotating body is provided, and the thrust receiving member is fitted in the hole, wherein the thrust receiving member is a rotating shaft. A polygonal scanner characterized in that when contact wear occurs, a new thrust receiving member is inserted into a predetermined position while pushing out the worn thrust receiving member from a hole opposite to the rotating shaft and the contact position. Handling method.