JPH09222578A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce dust, a foreign matter entering a device with simple constitution and to suppress a temp. rise due to sealing. SOLUTION: In an optical scanner holding a drive means 3 provided with a rotary polygon mirror 5 and a drive circuit board 6 for drive controlling the rotary polygon mirror 5 in a housing 2, the outside diameter of the rotary polygon mirror 5 is set smaller than the rotor size of the drive means 3. Then, the drive circuit board 6 is attached apart from the outside of the housing. Further, the space through which air flows is provided between the housing 2 and the drive means 3, and the housing 2 is made a nearly harmetically sealed state excepting the space. By setting respective components in such a manner, when the rotary polygon mirror 5 is rotated, the air flows out from the inside to the outside through the space. Thus, the dust, the foreign matter entering the device are reduced with simple constitution, and the temp. rise due to the sealing is suppressed.

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 having a rotary polygon mirror for scanning a light beam on a photosensitive member.

[0002]

2. Description of the Related Art Some conventional optical scanning devices cover a rotary polygon mirror held by a housing 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 an example thereof, in which the rotary polygon mirror 5 driven by the motor 3 is held by the housing 2, and the rotary space occupied by the rotary polygon mirror 5 due to the rotation thereof. The periphery of 15 is covered with a rotary polygon mirror cover 14 and hermetically sealed.

Further, in the technique disclosed in Japanese Utility Model Laid-Open No. 3-54913, in order to prevent the temperature rise of the optical scanning device, an optical path for cooling a polygon mirror is formed by using a rotary polygon mirror cover and a housing cover. A scanning device is disclosed. The optical scanning device shown in FIG. 7 shows an example thereof, in which the rotary polygon mirror cover 14 is bent upward and brought into close contact with the housing cover 1 to form an air passage 16, and outside air is supplied to the air passage 16. Circulating polygon mirror, rotating space 15
And cooling the motor 3.

[0004]

However, in the technique disclosed in the former conventional example, the heat from the motor causes the deformation of each component and the deterioration of the image quality because the container is in a sealed state or a structure close to the sealed state. In addition, the heat of the motor and the drive circuit board may shorten the life of the bearings and electric parts of the motor.

Further, the technique disclosed in Japanese Utility Model Laid-Open No. 3-54913 requires a ventilation passage for cooling, a fan, etc., which results in an increase in size and cost of the apparatus.

In view of the above problems, it is an object of the present invention to provide an optical scanning device in which dust and foreign matter that enter the device are reduced with a simple structure and the temperature rise due to sealing is suppressed.

[0007]

In order to achieve the above-mentioned object, the invention of claim 1 is such that the drive means provided with a rotary polygon mirror and a drive circuit board for driving and controlling the rotary polygon mirror has a housing. In the optical scanning device held by, the outer diameter of the rotary polygon mirror is smaller than the rotor diameter of the drive means,
Further, the drive circuit board is attached to the outside of the housing in a state of being separated from each other, 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 rotary polygon mirror is rotated by the drive means having the drive circuit board. The rotation of the rotary polygon mirror causes air to flow into the space between the housing and the rotor of the drive means. Since the outer diameter of the rotating rotary polygon mirror is set to be smaller than the rotor diameter of the driving means, the direction of the air flow is from the inside of the housing to the outside. This flow of air cools the drive circuit board mounted outside the housing in a separated state. Moreover, since the housing is substantially sealed except for the above space, it is possible to prevent dust and foreign matter outside the housing from entering the inside of the housing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

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

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

The polygon mirror 5 has the shape of a flat regular polygonal prism, and each deflecting surface forming the side surface thereof is a flat mirror surface. Also, the polygon mirror 5
Is configured to be rotatable about a rotation axis O in a substantially vertical direction, and a motor 3 as a drive unit for rotating the polygon mirror 5 is arranged 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 fixing the drive circuit board 6 to the housing 2. It is composed of a section 11 and.

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 to be larger than the circumscribed diameter B of the polygon mirror 5. Has been done.

By the way, the motor 3 and the polygon mirror 5 can be mounted through a motor mounting hole 8A formed in the bottom of the housing 2 even when the housing 2 is sealed. When the motor 3 is attached to the housing 2 via the attachment portion 11,
As shown in FIG. 1, the substrate surface 6A of the drive circuit substrate 6 is in a state of being separated from the bottom of the housing 2 by a predetermined distance.

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

Further, as shown in FIG. 2, a laser diode assembly 12 used as a light source is arranged on a side portion of the housing 2. The laser diode assembly 12 includes a semiconductor laser that is on / off controlled by a modulator according to an image signal, a collimator lens for shaping a divergent light beam emitted from the semiconductor laser, an aperture stop for beam shaping, and the like. And (not shown).

Further, at the outer end of the housing 2 opposite to the polygon mirror 5, the photosensitive drum 13 is provided.
Is arranged. The photosensitive drum 13 has a shape of an elongated cylinder having a surface coated with a photosensitive material that is sensitive to a light beam, and the scanning direction (main scanning direction) indicated by an arrow R is the photosensitive member. The drum 13 is arranged so as to substantially coincide with the longitudinal direction of the drum 13.

The photosensitive drum 13 has a rotary shaft W.
Is configured so as to rotate in the direction of arrow Q at a predetermined constant rotation speed by a driving unit (not shown) as a center, and this rotation moves the scanning line in the sub-scanning direction orthogonal to the main scanning direction.

Further, between the photosensitive drum 13 and the polygon mirror 5, the light beam reflected and deflected by the polygon mirror 5 is focused on the photosensitive drum 13 as a light spot to form an image, and the light spot is also formed. An fθ lens system 7 is arranged for moving the surface of the photosensitive drum 13 at a constant speed. 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 the 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. Further, the cover 1 is attached to the upper part of the housing 2, and the present optical scanning device is
Except for the space 8 described above, it is in a substantially sealed state.

Next, the optical scanning device according to the present embodiment is
The 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.

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

First, Table 1 shows the air flow 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 rotating polygon mirror circumscribed diameters are φ53 mm, φ39 mm, and φ26 mm, respectively, the air flow passing through the space 8 is the arrow D, the arrow C shown in FIGS. It becomes the flow of arrow C.

From the results shown in Table 1, it can be seen that there is a dustproof effect when the rotor diameter is φ39 mm and φ26 mm which are smaller than 42 mm. In the experimental results of Table 1, it was found that the air flow did not change even when the size of the housing 2 was changed, and the size of the housing 2 was irrelevant in the size of the range tested.

Next, Table 2 shows the air flow when the separation distance is changed within a predetermined range with the rotor diameter φ42 mm and the motor mounting hole φ50 mm. As shown in Table 2, the separation distance is 5 m
When the rotating polygonal mirror circumscribed diameter is φ39 mm and the rotor diameter is smaller than 42 mm, the flow directions of air when m, 7 mm, and 9 mm are all indicated by arrow C.

On the other hand, the circumscribed diameter of the rotary polygon mirror is 53 m.
When m is larger than the rotor diameter φ42 mm, the air flow at each separation distance is the flow of arrow D. From these results, it can be seen that, within the range of the separated distance, the air flow direction does not depend on the separated distance, and the size 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 is 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, the air flow direction is indicated by arrow C when the rotating polygon mirror circumscribed diameter is φ39 mm and smaller than the rotor diameter 42 mm. Become.

On the other hand, the circumscribed diameter of the rotating polygon mirror is 53 m.
When m is larger than the rotor diameter φ42 mm, the air flow at each separation distance is the flow of arrow D. From these results, within the range of the experimental motor mounting hole, the air flow direction does not depend on the diameter of the motor mounting hole, and the size relationship between the rotor diameter and the rotating polygon mirror circumscribed diameter is directly related. You can see that

It should be noted that the mounting portion 11 of the motor 3 and the drive circuit board 6 are not mounted in a state of being separated from the housing 2, or a space 8 is provided between the motor mounting hole 8A of the housing 2 and the rotor 9. If is not opened, the air does not flow through the drive circuit board 6 and thus 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 is attached to the housing 2 in a separated state and the space 8 exists.

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

[0033]

As described above, according to the invention of claim 1, 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, since a space through which air flows is provided between the housing and the rotor, and the housing is configured to be substantially sealed except for the above space, dust and foreign matter that enter the device can be reduced with a simple structure and sealed. The effect of suppressing the temperature rise is obtained.

[Brief description of drawings]

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

FIG. 2 is a plan view of the 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 rotating 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 rotating polygon mirror is smaller than a rotor diameter.

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

FIG. 6 is a configuration diagram of a conventional optical scanning device in which 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.

FIG. 7 is a configuration diagram of a conventional optical scanning device in which a ventilation path for cooling a polygon mirror is formed by using a rotary 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)

[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 an outer diameter of the rotary polygon mirror is the drive. Means is smaller than the rotor diameter, the drive circuit board is attached to the outside of the housing in a state of being separated, and a space through which air flows is provided between the housing and the rotor of the drive means. An optical scanning device, which is substantially sealed except for the space.