JPH0325412A - High speed rotary polygon mirror in image forming device - Google Patents

Abstract

PURPOSE:To prolong the life of the rotary polygon mirror and to reduce the size, weight, and power consumption of a driving motor by providing the rotary polygon mirror consisting of a support which is made of a light-transmissive member and has a polygonal hollow part and reflecting surfaces formed in contact with the polygonal hollow part, and a driving device which rotates the rotary polygon mirror fast. CONSTITUTION:An optical device 10 has a light emitting device 12, the rotary polygon mirror 17 which is rotated fast by the driving motor 16 as a driving device to put a laser beam 13 in deflecting and scanning operation in a main scanning direction or the lengthwise direction of a photosensitive drum 14, and an image forming lens unit 18 which images the laser beam 13 reflected by the rotary polygon mirror 17 on the photosensitive drum 14. Then the rotary polygon mirror 17 consists of the glass-made support 21 which is a columnar light-transmissive support and have a polygonal hollow part or an octagonal columnar hollow part 21a recessed inside, and the reflecting surfaces 22a - 22h formed by vapor-depositing aluminum on the surface of the hollow part 21a. Consequently, the life of the rotary polygon mirror 17 is prolonged, the load, size, and weight of the driving motor 16 are reducible.

Description

Detailed Description of the Invention Object of the Invention (Industrial Application Field) The present invention is an image forming apparatus that forms images using a laser beam, such as a laser printer or a copying machine, by deflecting and scanning a laser beam at high speed. This invention relates to improvements in high-speed rotating polygon mirrors in image forming apparatuses.

(Prior Art) Image forming apparatuses such as copying machines and printers often use a laser beam as a means for forming an electrostatic latent image on a photoreceptor which is an image carrier. In other words, in such a device, a laser beam emitted from a laser emitting device such as a semiconductor laser is transmitted to a rotating polygon mirror that is housed in a housing together with a drive motor and rotates at a high speed of several thousand to tens of thousands [rpal]. Accordingly, the photoreceptor drum is deflected and scanned in the longitudinal direction to form an electrostatic latent image on the photoreceptor drum.

However, in such a device, the rotating polygon mirror is
Although it is housed together with the drive motor in a housing that has shielding properties and prevents the intrusion of external dust, the reflective surface is exposed inside the housing. For this reason, the reflective surface deteriorates due to oxidation, etc., or is susceptible to tM (M), and small floating objects inside the housing adhere to it, so it must be cleaned. Since the reflective surface is directly wiped during cleaning, there is a risk of deterioration and damage to the reflective surface, which significantly impedes its longevity.Furthermore, there is a problem in that the surrounding polygonal vertices A rotating polygon mirror whose surface is exposed requires a power of 3 usually p-cMρRLω when rotating at high speed.

[However, CM-4.17/N (N is the number of surfaces), ρ: density of surrounding fluid, R: radius of circumscribed circle of rotating polygon mirror, L: thickness of rotating polygon mirror, ω: angular velocity] and others. If the conditions are the same, the power P becomes smaller as the number of surfaces N of the rotating polygon mirror increases. This is affected by air resistance, and when the number of surfaces N is small,
This is because when the air resistance is large and the number of surfaces N is large and it is close to a circle, the air resistance becomes small. Moreover, under the same conditions, the air resistance generated in the rotating polygon mirror increases rapidly as the rotation speed increases. Therefore, in the drive motor, it is necessary to increase the power consumed by the air resistance, which increases the load on the drive motor and shortens its life. On the other hand, if we try to meet the increase in power, the drive motor will become larger and the power consumption will increase, resulting in higher costs and hindering the miniaturization and weight reduction of the device. There is also the problem that it hinders

(Problems to be Solved by the Invention) As mentioned above, in the past, the reflective surface of the rotating polygon mirror was exposed to the outside inside the housing, so it was easily damaged or deteriorated due to oxidation, etc. Cleaning is required to remove the deposits, which hinders the extension of its lifespan. Furthermore, due to the shape of the rotating polygon mirror, when rotating at high speed,
Since the air resistance is large, the load on the drive motor increases and the life of the drive motor is shortened. For this reason, if an attempt is made to increase the power, a large drive motor is required, which increases power consumption, prevents the device from being made smaller and lighter, and further impedes the ability to further increase the speed of the rotating polygon mirror. This problem has also arisen.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks, it is an object of the present invention to provide a high-speed rotating polygon mirror for use in an image forming apparatus, which prevents damage and deterioration of the reflecting surface and extends the life of the rotating polygon mirror. Furthermore, the air resistance of the rotating polygon mirror that rotates at high speed is reduced, reducing the load on the drive motor, extending the life of the drive motor, making the drive motor smaller and lighter, and saving power consumption. It is an object of the present invention to provide a polygon mirror and, moreover, a high-speed rotating polygon mirror in an image forming apparatus that can increase the speed of ghost image formation.

[Aside from the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides a support body made of a translucent member and having a multifaceted hollow part, and a support body formed in close contact with the multifaceted hollow part. A rotating polygon mirror consisting of a reflecting surface and a drive device for rotating the rotating polygon mirror at high speed are provided.

(Function) According to the above-mentioned means, the reflective surface of the rotating polygon mirror is in close contact with the transparent support, so that the scanning of the laser beam is not obstructed, and moreover, the anti-9.1 surface is protected. The purpose is to easily prevent oxidation, ijt scratches, and adhesion of floating substances, thereby extending the life of the rotating polygon mirror.

(Example) Next, a first example of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows an optical device 1O in a laser beam printer (not shown), which irradiates a photosensitive drum 14, which is an image carrier, with a laser beam 13 emitted from a light emitting device 12 made of a semiconductor laser. be. That is, the optical device 10 has a power output of about 10,000 [rp@l] by the light emitting device 12 and the drive motor l6 which is the drive device.
a rotating polygon mirror l7 which deflects and scans the laser beam 13 in the main scanning direction, which is the longitudinal direction of the photoreceptor drum l4;
, and the laser beam t reflected from the rotating polygon mirror l7
The image forming apparatus includes an imaging lens unit l8 that forms an image of 3 on a photoreceptor drum l4. And for the rotating polygon mirror l7,
The support 21 is made of glass and has a cylindrical support that is translucent, and has an octahedral columnar hollow part 21a that is a polyhedral hollow part formed in the shape of a depression, and the surface of the hollow part 21a is made of aluminum. It consists of reflective surfaces 22a to 22h that are steamy and intimidating.

Next, FIG. 3 shows how the rotary polygon mirror 17 is attached to the drive motor 16. It is fixed at the portion 2l with a nut 27 via an elastic seat 24 and a pressure disk 2B. The rotating spindle 23 is connected to the motor housing 3 via a dynamic pressure bearing 30 that supports the lower end of the fixed shaft 28.
It is fixed at l. Further, 32a and 32b are magnetic rings and form thrust bearings. Furthermore, the motor section 33 includes a motor rotor 34 attached to the rotating spindle 23, and a drive coil 37 attached to a motor stator 36 supported by the motor housing 3l.
It consists of a circuit board 38. The upper G of the motor housing 3l is a translucent motor cover 40.
is attached via a shield member (not shown) to provide a shield to protect the rotating polygon mirror 17 and the drive motor 16 from external dust and the like.

Next, we will discuss the effect. When printing starts, the laser beam 13 is emitted from the light emitting device 12 in response to a printing signal from the main body (not shown), and the rotating polygon mirror 17 is moved in the direction of the arrow y by the drive motor 1B at 10000 [r4]. be rotated. The laser beam 13 emitted from the light emitting device l2 is guided to the rotating polygon mirror l7 rotated by the drive motor 1B, passes through the support 2l, and is reflected 1j2.
Irradiated from 2a to 22h. Next, the laser beam 13 is reflected by the reflecting surfaces 22a to 22h while changing its reflection direction according to the rotation of the rotating polygon mirror 17, and is again reflected on the support 2.
It is transmitted through the imaging lens unit 18, deflected and scanned in the longitudinal direction of the photoreceptor drum l4, and the photoreceptor drum l4
This results in the formation of an electrostatic latent image thereon. In addition, rotating polygon mirror l
7 is subjected to air resistance around it when rotated by the drive motor l6, but since II has a cylindrical outer periphery, the power generated by air resistance is lower than that of a conventional rotating polygon mirror in which the apex of the polygon is exposed. Less loss.

With this configuration, the reflective surfaces 22a to 22h are connected to the support body 2.
The skewer is not damaged or deteriorated by oxidation because it is in close contact with the support 2l, protected by the support 2l, and isolated from the outside air. Further, even if t[ or deterioration occurs, it will be from the back side of the reflective surfaces 22a to 22h, so if it is only a small amount, it will not directly affect the image quality as it is in the conventional case. Further, the image quality is not deteriorated due to adhesion of floating objects, and cleaning is not necessary.

Furthermore, since the outer periphery of the support body 2l is cylindrical, the air resistance that the rotating polygon mirror 17 receives is reduced compared to conventional devices. Therefore, the loss of power for rotating the rotating polygon mirror is reduced compared to the conventional method, reducing the burden on the drive motor, extending the life of the drive motor, and making it possible to downsize the drive motor. Therefore, it is possible to save power consumption, reduce driving noise, and reduce heat generation. Furthermore, with the same power, it is possible to rotate the rotating polygon mirror at an even higher speed.

Next, a second embodiment of the present invention will be described with reference to FIG. Note that the same parts as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted. The rotating polygon mirror 4l of this embodiment consists of a glass support 42 through which an octahedral columnar hollow part 42a is penetrated, and reflective surfaces 43a to 43h formed by depositing aluminum on the surface of the hollow part 42a. . The rotating polygon m41 attached to the rotating spindle 23 has its hollow portion 42a closed by an elastic sheet 44 and a pressure disk 4B having a larger diameter than the hollow portion 42a.
It is fixed by 7.

When printing starts, the rotating polygon mirror 4l is driven in exactly the same manner as in the first embodiment, and scans the laser beam 13 emitted from the light emitting device l2 in the longitudinal direction of the photoreceptor drum l4. Become.

With this configuration, the reflecting surfaces 43a to 43h are protected by the support 42, and there are no skewers that are damaged or deteriorated by oxidation as in the first embodiment, and there are no floating objects, etc. There is no risk of adhesion. Moreover, the elastic sheet 44 and the pressure disk 46 allow the reflective surfaces 43a to 43h to
Since it is completely shielded from the outside, the reflective surfaces 43a~
43h also eliminates the fear of being damaged from the back side. Further, the outer periphery of the rotating polygon mirror 4l is cylindrical, and power loss due to air resistance during rotation is reduced compared to the conventional one, as in the first embodiment.
Since the hollow part 42a is completely cut off from the outside, the hollow part 42a
Surrounding air flows into the second embodiment, and there is no generation of extra airflow that causes a loss of power, and the loss of power can be further reduced compared to the first embodiment.

Therefore, the life of the drive motor can be further extended or the drive motor can be made smaller.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the number of reflective surfaces provided in the hollow part of the rotating polygon mirror or the number of rotations can be changed as desired, and the material of the support body can also be changed. , resin or the like may be used as long as it has translucency. Further, the shape of the outer periphery of the support is not limited as long as it closely protects the surface of the reflective surface, for example, a lens that forms an image of a laser beam emitted from the reflective surface and irradiated onto the photoreceptor drum. It may have a functional shape, but if the outer periphery is cylindrical as shown in the example, air resistance during high-speed rotation can be more effectively reduced, and the load on the drive motor can be further reduced. I can do it.

[Effects of the Invention] As detailed above, according to the present invention, the reflecting surface of the rotating polygon mirror is closely protected by the transparent support, so that the reflecting surface is not damaged or deteriorated. There are no skewers to be removed, and the cleaning required in the past is also no longer necessary, making it possible to extend the life of the rotating polygon mirror. Furthermore, if the outer periphery of the rotating polygon mirror is made into a cylindrical shape as in the example, air resistance during high-speed rotation can be reduced, and the load on the drive motor can be reduced. It becomes possible.

[Brief explanation of drawings]

1 to 4 show a first embodiment of the present invention, FIG. 1 is a schematic explanatory diagram showing an optical device, FIG. 2 is a top view of a rotating polygon mirror, and FIG. 3 is a top view of a rotating polygon mirror and FIG. 4 is a sectional view showing the drive motor, FIG. 4 is a perspective view showing a rotating polygon mirror attached to a rotating spindle, and FIG. 5 is a partial sectional view showing a second embodiment. 10... Optical device, l2... Light emitting device, 1
3... Laser beam, 14... Photosensitive drum,
1B... Drive motor, 17... Rotating polygon mirror,
2l... Support body, 22a to 22h... Reflective surface, 21a... Hollow part,

Claims (1)

[Claims] In a high-speed rotating polygon mirror that deflects and scans a laser beam and irradiates it onto an image carrier to form an electrostatic latent image, a support body made of a translucent member and having a multifaceted hollow part and closely formed in the multifaceted hollow part are used. 1. A high-speed rotating polygon mirror for use in an image forming apparatus, comprising: a rotating polygon mirror having a reflective surface that is shaped like a mirror; and a drive device that rotates the rotating polygon mirror at high speed.