JPH11245442A - Scanning optical device - Google Patents

Abstract

(57) [Problem] To prevent the adhesion of dust to the reflection surface of a rotary polygon mirror and to suppress the problem of heat generation due to high-speed rotation of a drive motor. SOLUTION: A drive motor 20 in which a rotating polygon mirror 16 is fixed to a rotating shaft 22 is attached to an optical frame 11 which forms an optical box with a lid member 12. Rotating polygon mirror 16
Is disposed in the optical box and has a housing 21 for the drive motor 20 and a circuit board 2 for driving the drive motor 20.
6 is located outside the optical box. In the optical box, a cylindrical cover member 19 made of a member that transmits a laser beam is provided around the rotary polygon mirror 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a latent image on a charged photosensitive member while blinking a laser beam in accordance with image information, and attaching toner on the latent image to form a latent image on a recording medium. The present invention relates to a scanning optical device that is used in an electrophotographic image forming apparatus that forms an image by transferring and scans a photosensitive member with a laser beam.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus uniformly charges the surface of a photoreceptor, and irradiates the charged photoreceptor with a laser beam in accordance with image information to thereby form an electrostatic latent image on the surface of the photoreceptor. After the image is formed, toner is adhered to the surface of the photoreceptor on which the electrostatic latent image is formed, and the toner is transferred and fixed on recording paper to perform recording. Here, for forming an electrostatic latent image on the surface of the photoconductor, a scanning optical device that irradiates the photoconductor with a laser beam while scanning is used.

FIG. 3 is a plan view of a conventional scanning optical device. In FIG. 3, the light source device 114 is a single point light source.
Is transmitted through a cylindrical lens 115 having a refractive index in only one direction, and is condensed linearly on a reflection surface of a rotary polygon mirror 116. Rotating polygon mirror 1
16 is fixed to the rotation shaft of the drive motor 120,
By rotating the drive motor 120 according to a control command from a drive circuit that drives the drive motor 120, the drive motor 120 is rotated at a high speed in the direction of arrow a in the figure. The drive circuit of the drive motor 120 includes:
The circuit board 126 is provided as an electric circuit. The laser beam L reflected by the reflecting surface of the rotating polygon mirror 116 is
High-speed deflection scanning is performed in the direction of arrow b in the figure as the drive motor 120 rotates. The laser beam L deflected and scanned is
After passing through the imaging lens 117 having the fθ characteristic and being reflected by the reflection mirror 118, an image is formed on the surface of the photosensitive drum 140 in a minute spot.

The optical members such as the light source device 114, the cylindrical lens 115, the rotating polygon mirror 116, the image forming lens 117 and the reflection mirror 118 are precisely arranged in the optical frame 111. Further, the drive motor 120 and the circuit board 126 are also arranged in the optical frame 111.

In recent years, image forming apparatuses such as a laser beam printer having such a scanning optical apparatus have been developed to increase the speed of forming an image and to increase the definition thereof. It is required that the beam L be scanned on the photosensitive drum 140 at a higher speed.

[0006]

However, in the above-described conventional scanning optical apparatus, when the rotating polygon mirror is rotated at a high speed in order to achieve high-speed and high-definition image formation, the reflection of the rotating polygon mirror is reduced. Dust easily adheres to the surface. If dust adheres to the reflecting surface of the rotary polygon mirror, the amount of the laser beam applied to the photosensitive drum decreases, and a desired image cannot be obtained.

To solve this problem, it is conceivable to prevent dust from adhering to the reflecting surface of the rotary polygon mirror by surrounding the rotary polygon mirror with a transparent cover. However, when the drive motor is rotated at high speed, the amount of heat generated by the windings of the drive motor and the electric elements on the drive circuit increases, and when the periphery of the rotating polygon mirror is surrounded by a cover, the temperature inside the cover also increases. I will. As a result, there arise problems such as distortion of the reflection surface of the rotary polygon mirror and shortening of the life of the drive motor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning optical apparatus which prevents dust from adhering to a reflecting surface of a rotary polygon mirror and suppresses a problem caused by heat generated by a high speed rotation of a driving motor.

[0009]

In order to achieve the above object, a scanning optical device according to the present invention is a scanning optical device for deflecting and scanning by reflecting a light beam by a rotating polygon mirror rotated by a drive motor. It has a transparent cover member surrounding the periphery of the mirror, and a portion generating heat by driving the drive motor is arranged outside a space surrounded by the cover member.

In the scanning optical device of the present invention configured as described above, since the periphery of the rotary polygon mirror is surrounded by the cover member, dust adheres to the reflection surface of the rotary polygon mirror even when the drive motor is rotated at high speed. Never. Moreover, since the portion that generates heat by driving the drive motor is disposed outside the space surrounded by the cover member, heat generated by high-speed rotation of the drive motor does not stay in the space surrounded by the cover member. .

The arrangement of such a portion generating heat by driving the drive motor is such that the rotary polygon mirror is housed in an optical box composed of a frame member and a lid member, and the drive motor is mounted on the frame member from outside the optical box. This can be achieved by fixing.

Further, in order to reduce the loss during rotation of the rotary polygon mirror and to further suppress heat generation of the drive motor, it is preferable that the cover member has a cylindrical shape.

Further, by providing a fan outside the optical box, the temperature rise of the heat generating portion due to the driving of the driving motor can be more efficiently suppressed. Even when the fan is provided in this manner, since the periphery of the rotary polygon mirror is surrounded by the cover member, dust does not adhere to the reflection surface of the rotary polygon mirror due to the wind sent by the fan. When the fan is provided, the drive motor is fixed to the frame member via the seal member, thereby preventing dust from entering the space inside the cover member. In addition, the cover member may be configured to be held between the frame member and the cover member. In this case, by forming the cover member from metal, the temperature rise around the rotary polygon mirror is more efficiently increased. Is suppressed.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of an embodiment of the scanning optical device of the present invention. The scanning optical apparatus shown in FIG. 1 uses a laser beam printer to scan a photosensitive drum 40 whose surface is uniformly charged while blinking a laser beam L in accordance with image information.
To form an electrostatic latent image on the surface.

In FIG. 1, a laser beam L emitted from a light source device 14, which is a single point light source, passes through a cylindrical lens 15 having a refractive index in only one direction, and is reflected on a reflection surface 16a of a rotary polygon mirror 16. Light is condensed linearly. The rotary polygon mirror 16 is fixed to a rotary shaft 22 of a drive motor 20 and rotates at a high speed in a direction indicated by an arrow a.

The laser beam L reflected by the reflecting surface 16a of the rotary polygon mirror 20 is deflected and scanned at a high speed in the direction of the arrow b shown in the figure with the rotation of the drive motor 20, and transmitted through the imaging lens 17 having fθ characteristics. Thereafter, the light is reflected by the reflection mirror 18 and formed into an image on the surface of the photosensitive drum 40 in a minute spot. Thereby, the photosensitive drum 4
0, an electrostatic latent image is formed on the surface of the photosensitive drum 40 on which the electrostatic latent image is formed, and the toner is transferred and fixed on the recording paper to form an image on the recording paper. Is formed.

The optical members such as the light source device 14, the cylindrical lens 15, the image forming lens 17, and the reflection mirror 18 are precisely arranged in the optical frame 11. The drive motor 20 is attached to the optical frame 11, whereby the rotary polygon mirror 16 is also arranged in the optical frame 11. The optical frame 11 is covered with a lid member 12 (see FIG. 2), and the above-mentioned optical member is housed in an optical box composed of the optical frame 11 and the lid member 12.

Here, the mounting structure of the drive motor 20 and the structure around the rotary polygon mirror 16 are shown in FIGS.
This will be described with reference to FIG. FIG. 2 is a sectional view of a portion around the drive motor and the rotary polygon mirror of the scanning optical device shown in FIG.

An opening is formed in the bottom surface of the optical frame 11, and a housing 21 of the drive motor 20 is formed in the opening.
Is fitted from below the optical frame 11, and the drive motor 20 is positioned and fixed to the optical frame 11 by screws 30 at the flange portion 21 a of the housing 21.

The rotary shaft 22 of the drive motor 20 is located inside the optical box, and the rotary polygon mirror 16 is fixed to the rotary shaft 22 by a spring 31 and a fixture 32. The drive motor 20 has a rotor unit 23 integrated with a rotating shaft 22 in a housing 21, and a magnet 24 is attached to the rotor unit 23. Further, a winding 25 is arranged at a position directly opposite to the magnet 24, and the drive motor 20 is rotated by energizing the winding 25.

By positioning the drive motor 20 on the optical frame 11 as described above, most of the housing 21 of the drive motor 20 is mounted on the optical frame 1.
The magnet 24 and the winding 25 provided inside the housing 21 are also located outside the optical box.

A drive circuit for rotating the drive motor 20 is provided on a circuit board 26 provided below the optical frame 11, that is, outside the optical box. Various electric circuits constituting the drive circuit are provided on the circuit board 26. An element 27 is mounted.

The drive motor 2 inside the optical frame 11
An annular projection 11a surrounding the opening is integrally provided around the opening where 0 is fixed. Protrusion 11
A transparent cylindrical cover member 19 made of a resin such as acrylic is fitted into a of the rotary polygon mirror 1.
6 is surrounded by a cover member 19.

The cover member 19 is in close contact with the upper end surface of the cover member 19, and the cover member 19 is held by the optical frame 11 and the cover member 12. Thereby, the rotating polygon mirror 1
6 is arranged in a space isolated from the surroundings. A seal member 33 made of rubber sponge is interposed between the flange portion 21a of the drive motor 20 and the optical frame 11, thereby improving the tightness of the space inside the cover member 19.

As described above, the rotating polygon mirror 16 is
Since it is hermetically closed by the cover member 19, even when the drive polygon mirror 16 is rotated at high speed by rotating the drive motor 20 at high speed, dust does not adhere to the reflection surface 16a of the polygon mirror 16. As a result, a desired image can be obtained without reducing the light amount of the laser beam L applied to the photosensitive drum 40.

When the drive motor 20 is rotated at a high speed, the windings 25 of the drive motor 20 and the electric elements 27 mounted on the circuit board 26 generate heat. Since most of the housing 21 and the circuit board 26 are located outside the optical box, even if they generate heat, the heat does not stay in the space closed by the cover member 19. As a result, the rotating polygon mirror 16
The reflection position of the laser beam L reflected by the rotary polygon mirror 16 is stabilized since distortion due to heat does not occur on the reflection surface 16a. With respect to heat around the rotary polygon mirror 16, if a metal plate having good heat dissipation is used for the lid member 12, a rise in temperature around the rotary polygon mirror 16 can be more efficiently prevented.

Further, as described above, by separating the space in which the rotary polygon mirror 16 is arranged and the space in which the heat generating portion is provided due to the high speed rotation of the drive motor 20, the wind for cooling the heat generating portion is separated. Is sent to the circuit board 2
6, etc., can also be installed outside the optical box. Thus, the temperature rise of the heat generating portion is suppressed, and the life of the drive motor 20 and the electric element 27 is not adversely affected. In addition, the surrounding dust may fly up due to the driving of the fan 35, but since the mounting portion between the drive motor 20 and the optical case 11 is sealed by the seal member 33, such dust enters the inside of the cover member 11. Thus, it does not adhere to the reflection surface 16a of the rotary polygon mirror 16.

The suppression of the temperature rise of the heat generating portion also contributes to the fact that the cover member 11 has a cylindrical shape. That is, by making the cover member 11 cylindrical, loss such as windage loss that occurs when the rotary polygon mirror 16 rotates is reduced, and the winding 25 of the drive motor 20 is reduced.
This is because the amount of heat generated from the above is reduced.

The sealing member 33 is provided with
Has a function of preventing the optical frame 11 from entering into the inside of the optical frame 11, since the rubber sponge is used as the sealing member 33 in the present embodiment. The drive motor 20 rotating at high speed is likely to generate large vibration. for that reason,
When this vibration causes the light source device 14, the imaging lens 17, and the reflection mirror 18 to vibrate via the optical frame 11, the irradiation position of the laser beam L varies, and a desired image cannot be obtained. Therefore, as in the present embodiment, it is preferable to interpose a member that absorbs vibration, such as a rubber sponge, in the attachment portion between the drive motor 20 and the optical frame 11.

In this embodiment, an example in which a transparent resin is used as the cover member 19 has been described. However, the cover member 19 may be made of glass as long as it is a member that transmits the laser beam L. Is obtained. Also, the cover member 1
In the present embodiment, the cylindrical shape 9 is also used, but the shape is not limited to this.

[0032]

As described above, according to the present invention, the periphery of the rotary polygon mirror is surrounded by a transparent cover member, and a portion which generates heat by driving the drive motor is arranged outside the space surrounded by the cover member. Even when the drive motor is rotated at a high speed, it is possible to prevent dust from adhering to the reflecting surface of the rotary polygon mirror and suppress a rise in temperature around the rotary polygon mirror.

Further, by making the cover member cylindrical, loss during rotation of the rotary polygon mirror is reduced, and heat generation of the drive motor can be further suppressed.

Further, in the configuration in which the rotating polygon mirror is housed in the optical box, a fan is provided outside the optical box to prevent dust from adhering to the reflecting surface of the rotating polygon mirror and to drive the motor. The part which generates heat by the drive can be efficiently cooled.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of a scanning optical device of the present invention.

FIG. 2 is a cross-sectional view of a portion around a driving motor and a rotary polygon mirror of the scanning optical device shown in FIG.

FIG. 3 is a plan view of a conventional scanning optical device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Optical frame 12 Cover member 14 Light source device 15 Cylindrical lens 16 Rotating polygon mirror 16a Reflection surface 17 Imaging lens 18 Reflection mirror 19 Cover member 20 Drive motor 21 Housing 22 Rotation axis 23 Rotor part 24 Magnet 25 Winding 26 Circuit board 27 Electricity Element 30 Screw 33 Seal member 35 Fan 40 Photoconductor drum

Claims (8)

[Claims] 1. A scanning optical device for deflecting and scanning by reflecting a light beam by a rotating polygon mirror rotated by a driving motor, comprising: a transparent cover member surrounding a periphery of the rotating polygon mirror; A scanning optical device, wherein a portion generating heat is disposed outside a space surrounded by the cover member. 2. The scanning optical device according to claim 1, wherein the cover member has a cylindrical shape. 3. The portion that generates heat by driving the drive motor includes a winding provided in a housing of the drive motor, and an electric element forming a drive circuit for driving the drive motor. Or the scanning optical device according to 2. 4. The rotary polygon mirror is housed in an optical box composed of a frame member and a lid member, and the drive motor is fixed to the frame member from outside the optical box. Or the scanning optical device according to 3. 5. The scanning optical device according to claim 4, wherein a fan for sending cooling air to a portion generating heat by driving the drive motor is provided outside the optical box. 6. The scanning optical device according to claim 5, wherein the drive motor is fixed to the frame member via a seal member. 7. The cover member is held between the frame member and the cover member.
3. The scanning optical device according to claim 1. 8. The scanning optical device according to claim 7, wherein said lid member is made of metal.