JP3322111B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device provided with a rotary polygon mirror for scanning a light beam on a photosensitive member.

[0002]

2. Description of the Related Art In a conventional optical scanning apparatus, a rotary polygon mirror held by a housing is covered with a rotary polygon mirror cover in order to prevent dust and foreign matter from entering. The optical scanning device shown in FIG. 6 shows one example, in which a rotating polygon mirror 5 driven by a motor 3 is held by a housing 2 and a rotating space occupied by the rotating polygon mirror 5 due to its rotation. 15 is covered with a rotating polygon mirror cover 14 and hermetically sealed.

In the technique described in Japanese Utility Model Laid-Open Publication No. 3-54913, in order to prevent the temperature of the optical scanning device from rising, an optical path for cooling a polygon mirror using a rotating polygon mirror cover and a housing cover is formed. A scanning device is disclosed. The optical scanning device shown in FIG. 7 shows one example, in which the rotary polygon mirror cover 14 is bent upward, and the ventilation cover 16 is formed in close contact with the housing cover 1, and the outside air is introduced into the ventilation passage 16. Rotating polygon mirror, rotating space 15
And the motor 3 is cooled.

[0004]

However, in the technique disclosed in the former conventional example, since the storage container is in a sealed state or a structure similar thereto, heat from the motor causes deformation of each part, thereby deteriorating image quality. At the same time, the heat of the motor and the drive circuit board may cause a reduction in the life of the bearings and the electric components of the motor.

In the technique disclosed in Japanese Utility Model Laid-Open No. 3-54913, a ventilation passage for cooling, a fan, and the like are required, so that the size of the apparatus is increased and the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an optical scanning device that reduces dust and foreign matter entering the device with a simple configuration and suppresses a rise in temperature due to sealing.

[0007]

According to a first aspect of the present invention, there is provided a driving device comprising a rotating polygon mirror and a driving circuit board for controlling the driving of the rotating polygon mirror. In the optical scanning device held in the outer diameter of the rotary polygon mirror is smaller than the rotor diameter of the driving means,
And the drive circuit board is attached to the outside of the housing in a separated state, and a space through which air flows is provided between the housing and the rotor of the drive means, and the housing is substantially sealed except for the space. It is characterized by being.

According to the first aspect of the present invention, in the optical scanning device, the rotating polygon mirror is rotated by the driving means having the driving circuit board. Due to the rotation of the rotary polygon mirror, air flows into a space between the housing and the rotor of the driving means. Since the outer diameter of the rotating polygon mirror is set smaller than the diameter of the rotor of the driving means, the direction of the flow of the air flows out from the inside of the housing to the outside. Due to this flow of air, the drive circuit board that is mounted separately from the outside of the housing is cooled. In addition, since the housing is substantially closed except for the above space, dust and foreign matter outside the housing can be prevented from entering the inside of the housing.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view of an optical scanning device according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.

As shown in FIGS. 1 and 2, the optical scanning device is covered by a housing 2 and a polygon mirror 5 serving as a light beam deflecting means is provided inside the housing 2.
(Rotating polygon mirror).

The polygon mirror 5 has the shape of a flat regular polygonal prism, and each deflecting surface forming the side surface is a plane mirror surface. In addition, polygon mirror 5
Is configured to be rotatable about a substantially vertical rotation axis O, and a motor 3 as a driving unit for rotating the polygon mirror 5 is disposed below the polygon mirror 5.

The motor 3 includes a rotor 9 for rotating the polygon mirror 5, a drive circuit board 6 for controlling the rotation of the rotor 9, and an attachment for attaching and fixing the drive circuit board 6 to the housing 2. And a unit 11.

Here, the polygon mirror 5 is directly attached to the rotor 9, but as shown in FIG. 2, the rotor diameter A, which is the diameter of the rotor 9, is set larger than the circumscribed diameter B of the polygon mirror 5. Have been.

By the way, the motor 3 and the polygon mirror 5 are mounted through a motor mounting hole 8A formed in the bottom of the housing 2 even when the housing 2 is sealed. Then, in a state where the motor 3 is mounted on the housing 2 via the mounting portion 11,
As shown in FIG. 1, the board surface 6A of the drive circuit board 6 is separated from the bottom of the housing 2 by a predetermined distance.

The motor mounting hole 8A of the housing 2
Is set to be larger than the rotor diameter A by a predetermined width. With this setting, when the motor 3 is mounted on the housing 2, the motor mounting hole 8
A space 8 is formed between A and the rotor 9 as a gap.

As shown in FIG. 2, on the side of the housing 2, a laser diode assembly 12 used as a light source is arranged. The laser diode assembly 12 includes a semiconductor laser that is turned on and off in accordance with an image signal by a modulator, a collimator lens for shaping a divergent light beam emitted from the semiconductor laser, an aperture stop for beam shaping, and the like. (Not shown).

Further, a photosensitive drum 13 is provided outside the housing 2 and at an end opposite to the polygon mirror 5.
Is arranged. The photosensitive drum 13 has a slender, substantially cylindrical shape having a photosensitive material that is exposed to a light beam applied to the surface thereof, and the scanning direction (main scanning direction) indicated by an arrow R is the photosensitive member. The drum 13 is disposed so as to substantially coincide with the longitudinal direction.

The photosensitive drum 13 has a rotating shaft W
Is rotated in a direction indicated by an arrow Q at a predetermined rotation speed by a driving unit (not shown) around the center of the scanning line, and this rotation moves a scanning line in a sub-scanning direction orthogonal to the main scanning direction.

Between the photosensitive drum 13 and the polygon mirror 5, the light beam reflected and deflected by the polygon mirror 5 is condensed as a light spot on the photosensitive drum 13 to form an image. Lens system 7 for moving the lens at the same speed on the surface of the photosensitive drum 13 is provided. The fθ lens system 7 is composed of, for example, two lenses as shown in the figure.

Further, a light transmitting member 1 for transmitting a light beam transmitted through the fθ lens system 7 is provided on a side portion of the housing 2 between the fθ lens system 7 and the photosensitive drum 13.
0 is attached. A cover 1 is attached to an upper portion of the housing 2.
Except for the space 8 described above, it is in a substantially sealed state.

Next, the optical scanning device according to the present embodiment
Dustproof and cooling operations will be described.

When the polygon mirror 5 of the optical scanning device according to the present embodiment rotates, air flows from the inside of the housing 2 to the outside as shown by an arrow C in FIG.
This can prevent dust and foreign matter outside the housing 2 from entering the inside of the housing 2.
Further, the rotor 9 and the drive circuit board can be efficiently cooled by the flowing air.

When the outer diameter of the polygon mirror 4 is larger than that of the rotor system, air flows from the outside of the housing 2 to the inside as shown by the arrow D in FIG. It is known from the following experiment (Tables 1, 2, and 3).

First, Table 1 shows the flow of air when the outer diameter of the rotating polygon mirror is changed when the rotor diameter is 42 mm and the motor mounting hole is 50 mm. As shown in Table 1, when the circumscribed diameters of the rotating polygon mirror are φ53 mm, φ39 mm, and φ26 mm, respectively, the flow of air passing through the space 8 is indicated by arrows D and C shown in FIGS. 3 and 4, respectively. The flow is as indicated by arrow C.

From the results shown in Table 1, it can be seen that there is a dustproof effect at φ39 mm and φ26 mm smaller than the rotor diameter of 42 mm. Note that the experimental results in Table 1 show that the air flow does not change even if the size of the housing 2 is changed, and that the size of the housing 2 is irrelevant in the size of the range tested.

Next, Table 2 shows the flow of air when the separation distance is changed within a predetermined range with a rotor diameter of 42 mm and a motor mounting hole of 50 mm. As shown in Table 2, the separation distance is 5 m
When m, 7 mm, and 9 mm are set, the direction of air flow is indicated by arrow C when the outer diameter of the rotating polygon mirror is φ39 mm and the rotor diameter is smaller than 42 mm.

On the other hand, the outer diameter of the rotating polygon mirror is φ53 m.
When m is larger than the rotor diameter φ42 mm, the air flows at the respective separation distances are all as indicated by the arrow D. From these results, it can be seen that within the range of the experimental separation distance, the air flow direction does not depend on the separation distance, and the magnitude relationship between the rotor diameter and the circumscribed diameter of the rotating polygon mirror is directly related. .

Next, the rotor diameter is 42 mm and the separation distance is 7 m.
Table 3 shows the air flow when the diameter of the motor mounting hole was changed by m. As shown in Table 3, when the diameters of the motor mounting holes are φ50 mm, φ55 mm, and φ60 mm, respectively, when the rotating polygon mirror circumscribed diameter is φ39 mm and the rotor diameter is smaller than 42 mm, all arrows C Become.

On the other hand, the outer diameter of the rotating polygon mirror is φ53 m.
When m is larger than the rotor diameter φ42 mm, the air flows at the respective separation distances are all as indicated by the arrow D. From these results, within the range of the motor mounting hole tested, the air flow direction does not depend on the diameter of the motor mounting hole, and the magnitude relationship between the rotor diameter and the circumscribed diameter of the rotating polygon mirror is directly related. You can see that there is.

The mounting portion 11 of the motor 3 and the drive circuit board 6 are not mounted separately from the housing 2, or a space 8 is provided between the motor mounting hole 8 A of the housing 2 and the rotor 9. Is not open, the air does not flow through the drive circuit board 6 and does not flow through the drive circuit board 6, so that the drive circuit board 6 cannot be cooled. Therefore, in the optical scanning device according to the present embodiment, it is necessary that the drive circuit board 6 be attached to the housing 2 while being separated from the housing 2 and that the space 8 be provided.

The optical scanning device according to the present embodiment has been described above, but is not limited to the above example. For example,
1 and 2, the fθ lens diameter 7, the laser diode assembly 12, and the motor 3 are housed in the same housing 2. However, as shown in FIG.
The laser diode assembly (not shown) may be housed in a separate housing.

[0033]

As described above, according to the first aspect of the present invention, the outer diameter of the rotary polygon mirror is smaller than the rotor diameter of the motor, and the drive circuit board is mounted outside the housing in a spaced state. In addition, a space through which air flows is provided between the housing and the rotor, and the housing is substantially sealed except for the above space, so that dust and foreign matter entering the apparatus can be reduced with a simple structure and the sealing is achieved. The effect that the temperature rise is suppressed can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a configuration of an optical scanning device according to an embodiment.

FIG. 2 is a plan view of a configuration of the optical scanning device according to the present embodiment.

FIG. 3 is a diagram showing a flow direction of air when a circumscribed diameter of a rotary polygon mirror is larger than a rotor diameter.

FIG. 4 is a diagram showing a flow direction of air when a circumscribed diameter of a rotary polygon mirror is smaller than a rotor diameter.

FIG. 5 is a sectional view of an optical scanning device in which the fθ lens is housed in a unit separate from the polygon mirror.

FIG. 6 is a configuration diagram of a conventional optical scanning device in which a rotating polygon mirror held by a housing is covered with a rotating polygon mirror cover in order to prevent dust and foreign matter from entering.

FIG. 7 is a configuration diagram of a conventional optical scanning device in which a ventilation path for cooling a polygon mirror is formed using a rotating polygon mirror cover and a housing cover in order to prevent a temperature rise of the optical scanning device.

[Explanation of symbols]

 2 Housing 3 Motor 5 Polygon mirror (rotating polygon mirror) 6 Drive circuit board

Claims (1)

(57) [Claims] 1. An optical scanning device in which a driving means including a rotary polygon mirror and a drive circuit board for driving and controlling the rotary polygon mirror is held in a housing, wherein the outer diameter of the rotary polygon mirror is controlled by the drive. A space smaller than the rotor diameter of the means, and the drive circuit board is attached to the outside of the housing in a separated state, and a space through which air flows is provided between the housing and the rotor of the drive means. An optical scanning device characterized by being substantially closed except for the space.