JPH1031188A - Polygon scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polygon scanner whose rotating body is rotated in stable contact with a fixed shaft to be a rotation center with respect to the polygon scanner using a non-contact radial bearing which is a thrust bearing by contact. SOLUTION: This polygon scanner is provided with the rotating body provided with a magnet for a magnetic field, a polygon mirror provided with plural reflection surfaces for reflecting light and a sleeve 101 and a fixed body provided with the fixed shaft to be the rotation center of the rotating body and a coil substrate to which plural driving coils are fixed facing the magnet for the magnetic field. A thrust bearing part 15 provided on the rotation center of the rotating body, the rotating body 15 rotated while being in contact with the tip part of the fixed shaft, an air pressure is raised in a clearance formed between the outer peripheral surface of the fixed shaft and the inner peripheral surface of the sleeve 101 and a non-contact state is attained. In this case, a groove 102 for making air flow out in a lower direction accompanying rotation is formed on the inner peripheral surface of the sleeve 101 or the outer peripheral surface of the fixed shaft.

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 rotating body 9 is freely rotatable by being inserted into the fixed shaft 6 without having a fixing force, but the rotating body 9 has a buoyancy caused by this rotation. There is a possibility that it will occur and float upward. Due to this floating, not only the polygon mirror 1 in the rotating body 9 cannot reflect light properly but also the rotating body 9 may come off from the fixed shaft 6. Accordingly, an object of the present invention is to provide a polygon scanner in which a rotating body stably rotates in contact with a fixed shaft serving as a rotation center in a polygon scanner using a thrust bearing by contact and a non-contact radial bearing. I do.

[0022]

To solve the above problems, the present invention employs the following means. That is, according to the first aspect of the invention, a rotating body having a sleeve and a polygonal mirror having a field magnet and having a plurality of reflecting surfaces reflecting light, a fixed shaft serving as a rotation center of the rotating body, And a fixed body having a coil substrate on which a plurality of drive coils are fixed in opposition to the field magnet.A thrust bearing is provided at the center of rotation of the rotating body, and the rotating body includes the thrust bearing. A polygon scanner that rotates while contacting the tip of a fixed shaft and increases air pressure in a gap formed between an outer peripheral surface of the fixed shaft and an inner peripheral surface of the sleeve to be in a non-contact state, A groove is formed on the inner peripheral surface of the sleeve or on the outer peripheral surface of the fixed shaft so as to allow air to flow downward with rotation.

According to a second aspect of the present invention, in the first aspect,
The groove is provided on an inner peripheral surface of the sleeve, and has a linear shape that is lower leftward along the rotation direction of the rotating body.

According to a third aspect of the present invention, in the first aspect,
The groove is provided on the outer peripheral surface of the fixed shaft, and has a linear shape that is downwardly to the right along the rotation direction of the rotating body.

According to the fourth aspect of the present invention, the second or third aspect is provided.
Wherein the groove is at least one continuous chord-winding spiral groove.

According to a fifth aspect of the present invention, in the first aspect,
The groove is provided at least in a range of a radial bearing formed by the sleeve and the fixed shaft.

According to the sixth aspect of the present invention, in the first aspect,
The fixed shaft projects from the sleeve of the rotating body in contact with the rotating body, and the outlet for air outflow of the groove has a boundary between the projected area and an area where the fixed shaft faces the sleeve of the rotating body. It is characterized by being provided in the vicinity.

[0028]

According to the present invention, since a rotating body having a polygon mirror in a polygon scanner is constantly applied with downward pressure during rotation, buoyancy due to rotation can be prevented and stable rotation can be performed. Further, a dynamic pressure effect is generated by the spiral groove that generates the downward direction, and the vibration in the radial direction can be stabilized.

[0029]

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 sleeve used in the first embodiment will be described with reference to FIG. The sleeve 101 has a single spiral groove 102 formed on the inner peripheral surface 101 a thereof in the shape of a string winding leftward and downward in the rotation direction X of the rotating body 9. An air start portion 102a of the spiral groove 102 is formed above the rotating body 9 as shown in FIG.
b is formed up to the bottom 101b of the sleeve. Thus, when the rotating body 9 is inserted into the fixed shaft 6, the spiral groove 102 allows air to flow out from the bottom 101b of the sleeve more easily.

Since the spiral groove 102 is formed on the entire inner peripheral surface 101a of the sleeve, when a radial bearing is formed by the fixed shaft 6 and the sleeve 101, the spiral groove is formed in the radial bearing region. Therefore, the air can be satisfactorily discharged downward (in the direction of arrow D in FIG. 2A), and a negative pressure can be generated.

Next, the operation when the sleeve 101 is mounted on the rotating body 9 and rotated will be described. FIG. 2 (b)
In the state where the distal end portion 6b of the fixed shaft 6 is in contact with the thrust receiving member 7a of the thrust cover 7 attached to the rotating body 9, the fixed shaft 6 moves the projecting region 103 projecting from the sleeve 5 of the rotating body. Has formed. Since the outlet 102b for the air outflow of the spiral groove is located at the bottom 101b of the sleeve, it is located near the boundary between the projecting region 103 of the fixed shaft 6 and the region where the fixed shaft 6 and the outer peripheral surface 101a of the sleeve face each other. Will be located. Therefore, this projecting region 1
Outflow of air can be easily performed from the open space 03. In this state, when the rotating body 9 is rotated while the tip 6b of the fixed shaft is in contact with the thrust receiving member 7a of the thrust cover 7, the rotation causes the air in the spiral groove 102 to flow downward.

The air flowing through the spiral groove 102 is discharged from the outlet 102b to the open space. The air to the outside becomes negative pressure in the gap formed between the sleeve 101 and the fixed shaft 6 by the transfer, so that the rotating body 9 is in a state of being pressed downward, and floating due to the rotation of the rotating body 9 is prevented. And stable rotation can be performed.

Although only one spiral groove 102 is formed on the inner peripheral surface 101a of the sleeve, a plurality of spiral grooves may be formed depending on the state of negative pressure. Also, the shape and depth of the spiral groove 102 are appropriately determined depending on the appropriate negative pressure state. Further, the length of the spiral groove 102 is
And the fixed shaft 6 may be formed so as to be formed at a position where the outlet 102b of the groove is formed so as to allow air to flow outside.

Next, a second embodiment according to the present invention will be described with reference to FIG. As shown in FIG. 3A, the second fixed shaft 201 has a second spiral groove 20 on its outer peripheral surface 201a.
2 is formed in the shape of a string winding downward to the right in the rotation direction X of the rotating body.

The air start portion 20 of the second spiral groove 202
3a is formed above the second rotating body 201 as shown in FIG. 3 (a), and the outlet 202b of the air outflow is formed up to the bottom 5b of the sleeve. Thus, when the rotating body 9 is inserted into the second fixed shaft 201, the second spiral groove 202 can easily cause air to flow out from the bottom 5b of the sleeve.

Since the second spiral groove 202 is formed over the entire outer peripheral surface 201a of the second fixed shaft, when a radial bearing is formed by the second fixed shaft 201 and the sleeve 5, this spiral groove is Since the air is formed in the radial bearing region, the air can be satisfactorily discharged downward (in the direction of arrow Y in FIG. 3A), and a negative pressure can be generated.

The operation when the rotating body 9 rotates while the rotating body 9 is inserted into the second fixed shaft 201 will be described. As shown in FIG. 3A, the vicinity of the bottom 5b of the sleeve (that is, the area where the second fixed shaft 201 and the rotating body 9 do not face each other) is in a released state, so that air can easily flow out. In this state, the rotating body 9 is moved to the tip 201 of the second fixed shaft.
b while being in contact with the thrust receiving member 7a of the thrust cover 7, this rotation causes the second spiral groove 2
The air in 02 flows downward (arrow Y direction).

Although only one second spiral groove 202 is formed on the outer peripheral surface 201a of the second fixed shaft, FIG.
As shown in (b), the outer peripheral surface 301 of the third fixed shaft 301
A plurality of third spiral grooves 302 may be formed in a.

The shapes and depths of the second and third spiral grooves 202 and 302 are also appropriately determined depending on the state of an appropriate negative pressure. Furthermore, their length is formed within the range of the radial bearing formed by the sleeve 5 and the second and third fixed shafts 201, 301, and the outlet of the groove is arranged at a position where air can flow out to the outside. What is necessary is just to determine.

[0041]

According to the present invention, a groove through which air flows downward is formed on a sleeve serving as a radial bearing of a rotating body or a radial bearing opposed to the sleeve and forming a radial bearing and serving as a rotation center. Since the rotating body is rotated, the rotating body is always pressed downward when the rotating body is rotated, so that the rotating body can be prevented from floating upward and stable rotation can be performed.

[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 perspective view showing a sleeve used in the first embodiment of the present invention. FIG. 2B is a schematic cross-sectional view illustrating a mounting structure of a rotating body and a fixed shaft to which a sleeve used in the first embodiment of the present invention is mounted.

FIG. 3A is a schematic cross-sectional view showing a mounting structure when a fixed shaft used in a second embodiment of the present invention is inserted into a rotating body. (B) It is a schematic sectional view showing the mounting structure when the fixed shaft used in the third embodiment of the present invention is inserted into the rotating body.

[Explanation of symbols]

101 sleeve, 102 spiral groove, 103 projecting area, 201 second fixed shaft 202 second spiral groove, 301 third fixed shaft, 302
Third spiral groove

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuichi Chihiki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A rotating body having a polygon and a sleeve having a field magnet and having a plurality of reflection surfaces for reflecting light, a fixed shaft serving as a rotation center of the rotating body, and a field magnet. And a fixed body having a coil substrate on which a plurality of drive coils are fixed, the thrust bearing being provided at the center of rotation of the rotating body, and the rotating body being provided at the tip of the fixed shaft. A polygon scanner that rotates while contacting a portion of the sleeve, and increases air pressure in a gap formed between an outer peripheral surface of the fixed shaft and an inner peripheral surface of the sleeve so as to be in a non-contact state. On the surface or the outer peripheral surface of the fixed shaft,
A polygon scanner having a groove for flowing air downward as it rotates. 2. The device according to claim 1, wherein said groove is provided on an inner peripheral surface of said sleeve, and has a linear shape which is lowered leftward along a rotation direction of said rotating body. Polygon scanner. 3. The device according to claim 1, wherein said groove is provided on an outer peripheral surface of said fixed shaft, and has a linear shape which is lower rightward along a rotation direction of said rotating body. Polygon scanner. 4. The polygon scanner according to claim 2, wherein said groove is at least one continuous chord-winding spiral groove. 5. The polygon scanner according to claim 1, wherein said groove is provided at least within a range of a radial bearing formed by said sleeve and said fixed shaft. 6. A fixed shaft projects from a sleeve of the rotating body in a state of contact with the rotating body, and an outlet portion of the groove for air outflow faces the projecting area and the fixed shaft and the sleeve of the rotating body. 2. The polygon scanner according to claim 1, wherein the polygon scanner is provided near a boundary with the set area.