JPH0643378A - Rotary structure - Google Patents

Abstract

PURPOSE:To reduce aberration and vibration due to thermal expansion by increasing an effective contact area by providing a rotor in which plural members are fixed by a frictional force by surface contact, and specifying the surface toughness of the contact plane. CONSTITUTION:A polygonal scanner 11 is fixed in a hole at the lover part of a case 12, and it is equipped with the rotor 16 provided with a hollow rotary shaft 15 fitted in the outer periphery of a fixed shaft 13, and a polygonal mirror 18 is placed on the upper plane of a flange 15a at the upper part of the hollow rotary shaft 15. In such a case, the surface roughness of the mounting reference plane of the polygonal mirror 18 is set at around Rmax1s, and that of the polygonal mirror mounting plane of the hollow rotary shaft 15 with surface contact with the mounting reference plane is set at around Rmax1s. Therefore, since both the surface roughness of the contact planes with surface contact mutually are smaller than Rmax2s, the effective contact area can be increased, and also, the dispersion of the contact plane can be reduced, and a contact frictional force can be increased. Therefore, the rotor 16 can be rotated at high speed, and the aberration of the polygonal mirror 18 for the shaft center of the hollow rotary shaft 15 can be held at a low level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to rotating structures such as
The present invention relates to a rotating structure that rotates at high speed, such as a polygon scanner used in a laser printer, a digital copier, or the like.

[0002]

2. Description of the Related Art As a conventional rotary structure, there is, for example, one shown in FIG. 4 (a) described in Japanese Patent Laid-Open No. 1-300216. In this dynamic pressure air bearing type polygon scanner 1, the polygon mirror 2 is provided with a flange portion 4a at the axial center of the hollow rotary shaft 4 of the rotating body 3 and is locked to this flange portion 4a. However, such a structure has a problem that the processing cost of the hollow rotary shaft 4 becomes high.

Therefore, an improved polygon scanner 6 shown in FIG. 4B has been proposed. In FIG. 4B, the same components as those in FIG. In the polygon scanner 6 shown in FIG. 4B, a flange portion 4c is provided on the upper end portion 4b of the hollow rotary shaft 4, and a mirror holder 7 for positioning that fits into the inner diameter portion of the upper end portion 4b of the hollow rotary shaft 4 is provided. , The polygon mirror 2 is arranged on the flange portion 4c, the mounting surface 2A of the polygon mirror 2 is aligned and brought into surface contact with the mounting reference surface 4A of the flange portion 4c, and both of these friction surfaces are pressure-contacted by the mirror retainer 7. The flange portion 4c is pressed to increase the frictional force and fix the same. Here, the mounting surface 2A of the polygon mirror 2 is a processing reference surface of the mirror surface 2a, and is subjected to flat lapping of several μm or less,
The surface roughness is about Rmax 1s. Further, the mounting reference surface 4A of the flange portion 4c is perpendicular to the axis of rotation, and is ground by using the inner cylindrical surface of the hollow rotating shaft 4 as a reference, and the surface roughness is about Rmax 5 to 6 s.

[0004]

However, in such a conventional polygon scanner 6, the temperature of the polygon scanner 6 rises with the operation of the polygon scanner 6, and the polygon mirror 2 and the hollow rotary shaft 4 are caused. Heats up. There is a problem in that the polygon mirror 2 is largely displaced in a certain direction with respect to the hollow rotation shaft 4, the unbalance amount of the rotating body 3 increases, and finally the vibration of the rotating body 3 increases.

As a result of various researches on the cause of this vibration, the inventors have found that the surface roughness of the mounting surface 2A of the polygon mirror 2 is about Rmax 1s, while the mounting reference of the hollow rotating shaft 4 is the standard. The surface roughness of the surface 4A is about Rmax 5 to 6 s. Therefore, as shown in the model in FIG. 2C, the effective contact area between the polygon mirror 2 and the hollow rotary shaft 4 is small. As a result, it has been found that the contact friction force becomes small and the variation on the contact surface becomes large, so that the polygon mirror 2 is displaced with respect to the hollow rotating shaft 4 in a certain direction in which the contact friction force is small.

[0006]

SUMMARY OF THE INVENTION The present invention has been made on the basis of such a conventional technique, and the surface roughness Rmax of the contact surfaces of the members to be in surface contact with each other is set to 2 s or less so that the effective contact area in the contact surfaces is increased. It is an object of the present invention to provide a rotating structure capable of increasing the contact frictional force, reducing the displacement due to thermal expansion, and significantly reducing the vibration, and further reducing the cost.

[0007]

In order to achieve the above object, the present invention comprises, in claim 1, at least one member comprising a plurality of members.
The point is that in a rotary structure having a rotating body in which members are assembled and fixed by frictional force due to surface contact with each other, the surface roughness Rmax of the contact surface of the surface contacting members is 2 s or less, respectively. According to another aspect of the present invention, the surface-contacting member is the rotary shaft of the rotary body in the polygon scanner and the polygon mirror, and the surface roughness Rmax of the mounting surface of the rotary shaft for mounting the polygon mirror is 2 s or less. According to a third aspect of the present invention, in the rotary structure according to the second aspect, the mounting surface of the rotary shaft is lapped.

[0008]

According to the first aspect of the present invention, since the surface roughness Rmax of the contact surfaces of the surface-contacting members are both 2 s or less, the effective contact area when the contact surfaces of the members contact each other is significantly increased. At the same time, the variation becomes smaller, and the mutual contact frictional force is significantly increased.

In the second aspect, the surface roughness Rmax of the mounting surface of the rotary shaft on which the polygon mirror is mounted is 2 s or less, while the surface roughness Rmax of the mounting surface of the polygon mirror is approximately 1 s. Has a surface roughness Rmax of 2 s or less, and the contact friction force is significantly increased. According to the third aspect, the surface processing of the contact surface is lapping, which can be inexpensive.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of the rotary structure according to claims 1 to 3 of the present invention. First, the configuration will be described. In FIG. 1, reference numeral 11 denotes a polygon scanner which is a rotating structure, and the polygon scanner 11 is fixed to a hole in the lower portion of the case 12 by press fitting or shrink fitting, and has a columnar shape having two pairs of herringbone grooves 13a on the outer circumference. Fixed shaft of 13
And a rotating body 16 having a hollow rotating shaft 15 fitted on the outer periphery of the fixed shaft 13. A tubular rotor magnet 17 and a balance ring 17A are provided on the outer periphery of the lower portion of the hollow rotary shaft 15.
Is attached to the outside of the rotor magnet 17, a coil,
It is a so-called inner rotor type motor composed of a slot iron core, a Hall element and the like, and is adapted to rotate the rotor magnet 17 or the rotating body 16 at high speed by switching the excitation. The high speed rotation of the rotating body 16 increases the pressure in the gap between the rotating body 16 and the fixed shaft 13 to form a dynamic pressure bearing, and supports the rotating body in the radial direction without contact. A flange portion 15a is provided on the upper part of the hollow rotary shaft 15, and a polygon mirror 18, which is a rotary polygon mirror, is placed on the upper surface of the flange portion 15a. Above the polygon mirror 18 is a hollow rotary shaft.
A disk-shaped mirror retainer 20 fitted and positioned on the inner peripheral portion of 15 is provided, and the polygon retainer 20 is provided by the polygon retainer 20.
Is positioned coaxially with the axis of the hollow rotary shaft 15, is pressed from above the polygon mirror 18 toward the flange portion 15a of the hollow rotary shaft 15, and is locked to the flange portion 15a by a plurality of screws 21. Polygon mirror 18, mirror retainer 20, hollow rotary shaft 1
5, the rotor magnet 17 and the balance ring 17A constitute the rotating body 16.

An annular magnet 22b is provided at the center of the mirror retainer 20.
Is attached, and a fine shaft hole 23 that communicates the inside and outside of the rotating body 16 is provided in the center portion. A balance correction groove 20A is provided on the outer peripheral portion of the mirror presser 20. Rotating body 16
Is a few mg in the upper and lower balance correction grooves 20A and balance ring 17A in order to reduce vibration due to imbalance during rotation.
It is possible to correct the unbalanced amount (about 8 mg) or less. A magnet 22c is attached above and below the fixed shaft 13 in the axial direction facing the magnet 22b, and a magnet 22a is attached to the upper lid of the polygon scanner 11. Magnet 22a, magnet 22
b, the magnetic poles of the magnet 22c have mutually facing surfaces having the same pole, the magnet 22b is repelled from above and below and floats, and the rotor 16 is supported in a non-contact manner.

In FIG. 2, the polygon mirror 18 has a shaft hole formed therein, and the inner circumference 18a serves as a radial positioning reference when the polygon mirror 18 is attached to the hollow rotary shaft 15. The polygon mirror 18 is made of high-purity aluminum and has a mirror surface 18
b is formed by ultra-precision cutting. A taper portion 18e toward the mirror surface 18b is formed on the outer peripheral portion of the attachment reference surface (also the processing reference surface) 18c of the polygon mirror 18 and the back surface 18d thereof to prevent the occurrence of flaws due to chips during stacking processing. At the same time, wind loss during rotation is reduced.

This polygon scanner 11 is designed to prevent uneven scanning pitch between mirror surfaces during laser light scanning.
All the mirror surfaces 18b are assembled at a constant angle with respect to the center of the rotation axis, and the angle variation between the mirror surfaces is several 1 in terms of angle.
It is extremely small, 0 seconds or less. For this reason, the mirror surface 18b is a mounting reference surface even in the case of a single polygon mirror.
It is formed at a constant angle with respect to 18c, and the angle variation between the mirror surfaces is extremely small. Further, the polygon mirror mounting surface 15b of the hollow rotary shaft 15 is formed at a right angle to the rotary shaft center, and the perpendicularity to the rotary shaft center, that is, the vertical deflection of the outer peripheral line of the flange portion 15a is several μm or less.

Since the mirror surface 18b of the polygon mirror 18 is formed at a constant angle with respect to the mounting reference surface 18c, the mounting reference surface is formed.
18c also serves as a processing reference surface, and is flat-lapped to a flatness of several μm or less, and its surface roughness is about Rmax 1s. Also, the polygon mirror mounting surface of the rotating shaft 15
Since 15b is formed at right angles to the rotation axis, cylindricity of several μm or less is required to form a dynamic pressure air bearing, that is, the radial deflection of the peripheral surface with respect to the axis is less than several μm. It is finished so that it is ground and lapped with the inner surface of the rotating shaft as the processing reference, and its surface roughness is Rmax.
It is finished in about 1s.

Next, the operation will be described. In the present invention, the surface roughness R ₁₈ of the mounting reference surface 18c of the polygon mirror 18 is
Is about Rmax 1 s, and the surface roughness R ₁₅ of the polygon mirror mounting surface 15b of the hollow rotary shaft 15 that makes surface contact with the mounting reference surface 18c.
Is about Rmax 1s, and the surface roughness of the contact surfaces that are in surface contact with each other is smaller than Rmax 2s, so the effective contact area increases and the variation of the contact surface also decreases, and the polygon mirror 18 and the hollow rotary shaft 15 The contact friction force becomes large. For this reason, the rotating body 16 rotates at high speed, the polygon mirror 18 and the hollow rotating shaft 15 become high in temperature, and both of them become high in temperature, and they try to expand thermally, but they are pressed against each other by a large contact frictional force, and the hollow rotating shaft 15 The deviation of the polygon mirror 18 from the axis is extremely small
The unbalanced amount of 16 was about 2.5 mg on average. This was an extremely excellent result at an allowable unbalance amount of 8.0 mg or less.

Next, the mounting reference surface 18c of the polygon mirror 18
Maximum with respect to the surface roughness R ₁₈ is Rmax1.0S, per case of changing the polygon mirror mounting surface 15b surface roughness R ₁₅ of the hollow rotary shaft 15 in four levels, amount of imbalance of the rotating body 16 at the time of temperature rise of The values, the minimum value and the average value were compared and tested. The surface roughness R ₁₅ of the polygon mirror mounting surface 15b has four levels, that is, the surface roughness R ₁₅ is about 6.5 s (only after grinding), about 1.0 s (after grinding and lapping), Approximately 0.5 s (ground and lapped) and 0.1 s (ground and fully lapped) were made into 5 prototypes each, and each of them was rotated by a normal method to raise the temperature of the rotating body 16
The unbalanced amount (balance change) was measured. The measurement result is
As shown in FIGS. 3 (a) and 3 (b), the unbalanced amounts of the rotating body 16 with respect to the surface roughness R ₁₅ of the polygon mirror mounting surface 15b are 7.5 mg, 2.5 mg, 1.6 mg and 1.1 mg on average, respectively. , And the maximum value is 12.9mg, 5.1mg, 2.5mg, 1.9mg
Becomes When the surface roughness R ₁₅ is about 2.0 s or less, the maximum unbalance amount is 8.0 mg or less. That is, by setting the surface roughness Rs of the polygon mirror mounting surface 15b of the hollow rotating shaft 15 to 2.0 s or less, the unbalance amount of the rotating body 16 can be significantly reduced.

[0017] This is by improving the polygonal mirror mounting surface 15b surface roughness R ₁₅ of the hollow rotary shaft 15 by lapping, the effective contact of the polygon mirror 18 and the rotary shaft 15 as a model shown in FIG. 2 (b) Since the area is large, the resulting contact friction force is large and the variation on the contact surface is small,
It is considered that this is because the polygon mirror 18 does not shift in a certain direction with respect to the hollow rotation shaft 15.

In this experiment, the member of the polygon mirror is made of high-purity aluminum, and the member of the hollow rotary shaft is made of stainless steel, and the linear expansion coefficients are different.

[0019]

As described above, according to the present invention,
The surface roughness Rmax of the contact surface of the surface-contacting member is 2
When it is s or less, the effective contact area in the contact surface can be increased to increase the contact frictional force, the deviation due to thermal expansion can be reduced, the vibration can be significantly reduced, and these can be made inexpensive.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment in which a rotary structure according to claims 1, 2, and 3 of the present invention is applied to a polygon scanner,
(A) is the whole sectional view, (b) is a perspective view of the polygon mirror.

2A and 2B are views showing the main part of FIG. 1, in which FIG. 2A is an exploded cross-sectional view thereof, FIG. 2B is a model explanatory view showing the contact state thereof, and FIG. 2C is a conventional contact corresponding to FIG. It is a model explanatory view showing a state.

3 is a diagram showing the relationship between the surface roughness of the polygon mirror mounting surface 15b in FIG. 2 and the amount of unbalance at high temperature. FIG. 3 (a) shows the relationship between the amount of unbalance at the time of changing the surface roughness to four levels and the allowable amount of unbalance. And (b) is a table showing the specific numerical values.

4A and 4B are diagrams showing a polygon scanner to which a conventional rotary structure is applied, in which FIG. 4A is an overall sectional view thereof, and FIG. 4B is another overall sectional view.

[Explanation of symbols]

11 Polygon scanner (rotating structure) 15 Hollow rotating shaft 15b Polygon mirror mounting surface (mounting surface) 16 Rotating body 18 Polygon mirror 18c Mounting reference surface R ₁₅ Surface roughness (surface roughness Rmax) R ₁₈ Surface roughness

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Company (72) Inventor Yoshio Hashimoto 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Inside Ricoh Company (72) Inventor Takao Abe 3-1 Shinmeidou, Nakameisei, Shibata-cho, Shibata-gun, Miyagi Tohoku Ricoh Co., Ltd.

Claims (3)

[Claims] 1. A rotary structure having a rotating body comprising a plurality of members, at least one portion of which is assembled and fixed to each other by a frictional force caused by surface contact with each other. The rotating structure is characterized in that each Rmax is 2 s or less. 2. The surface contacting member is a rotary shaft of the rotating body in a polygon scanner and a polygon mirror,
2. The surface roughness Rmax of the mounting surface of the rotary shaft on which the polygon mirror is mounted is 2 s or less.
The rotating structure described. 3. The rotary structure according to claim 2, wherein a mounting surface of the rotary shaft is lapped.