JP2003140073A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce resonance of an optical box and a folding mirror due to vibration of a rotary polygon mirror and vibration generated when driving an image forming apparatus by a holding position and a shape of the optical box. And a high-performance optical scanning device capable of responding to improvements in image quality and high-speed printing. SOLUTION: A light source that emits a laser beam, a polygon mirror 4 that reflects the laser beam from the light source, a polygon mirror motor 5 that rotationally drives the polygon mirror 4, and a waveform shaping of the laser beam reflected by the polygon mirror 4 A lens block 6 and a reflecting mirror 7 that reflects the laser light waveform-shaped by the lens block 6 are housed therein, and an emission light opening 8a that emits the laser light, and a holding unit 8b that holds the laser light in the main body 1 of the image forming apparatus. , 8c in the optical scanning device 3 having the optical box 8 having three or more positions, the height h from the center of gravity of the reflecting mirror 4 to the holding portions 8b and 8c of the optical box 8 is the height H1 of the optical box 8, A minimum height H2 from the center of gravity of the reflecting mirror 7 to the bottom of the optical box 8, a width a and a height b in a cross section of the reflecting mirror 7,
^{H2 <h <H1- (a 2} + b 2) has a ^0.5 relationship, and holding portion 8c of the holding portion 8b and the other end of the optical box 8 arranged in the sub-scanning direction has a height different.

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, and more particularly to an optical scanning device mounted on an image forming apparatus such as a digital copying machine or a printer.

[0002]

2. Description of the Related Art An optical scanning device in an electrophotographic image forming apparatus generates a vibration generated by a driving unit such as a polygon mirror motor of the optical scanning device itself and a driving unit of a main body of the image forming apparatus such as a photoconductor. The vibration causes the optical box, the various lenses, the reflecting mirror, and the like that form the optical scanning device to resonate.

As a result, there is a problem in that the laser light fluctuates, a line is deviated in the main scanning direction on the image, and uneven density occurs in the sub-scanning direction to deteriorate the image quality. In particular, since the lens block and the reflecting mirror arranged on the rearmost side of the optical path are long in the main scanning direction, the central portion is easily bent and the structure is easily affected by vibration.

For this reason, various proposals have been made so far so that the optical scanning device can cope with higher speed and higher image quality. In particular, various proposals have been made to prevent deterioration of image quality due to vibrations generated from a polygon mirror motor that rotationally drives a rotary polygon mirror, a motor of a drive unit of an image forming apparatus, and the like.

JP-A-9-120039, 9-26946
In Japanese Patent No. 0, the resonance frequency of the folding mirror is attached to the folding mirror to separate it from the frequency of vibration caused by the rotation of the rotary polygon mirror. In this proposal, since the weight of the weight and the mounting position of the weight can be freely changed, it is possible to avoid the resonance frequency of the rotary polygon mirror and the folding mirror. Therefore, the vibration of the folding mirror is suppressed,
A good image without pitch irregularity can be formed.

However, since the folding mirror is mounted on the optical box, and the optical box is mounted on the main body frame of the image forming apparatus, the attenuation properties of the main body frame and the optical box itself are lowered, and the resonance frequency of the folding mirror is reduced. It may not be specified, or there may be no clear anti-resonance peak between resonance frequencies. Therefore, even if the resonance state between the vibration frequency of the rotary polygon mirror and the folding mirror is avoided, the vibration of the folding mirror cannot be suppressed.

Further, since the weight is attached to the folding mirror,
The resonance frequency of the folding mirror is lower than that when the weight is not attached. The frequency component of the vibration generated when the image forming apparatus is driven is most often 300 Hz or less. Therefore, even if the resonance frequency between the vibration of the rotary polygon mirror and the folding mirror is avoided, there is a problem that the frequency of the vibration generated when driving the image forming apparatus and the possibility of resonance between the folding mirror increase. .

In Japanese Laid-Open Patent Publication No. 11-38347, a mirror holder made of resin or sheet metal is added to the folding mirror to separate it from the frequency of vibration caused by rotation of the rotary polygon mirror.

In this proposal, since the rigidity of the folding mirror is strengthened by integrating the folding mirror and the mirror holder, the resonance frequency of the folding mirror changes, and the vibration frequency of the rotary polygon mirror and the folding mirror are changed. The resonance state can be avoided, and the vibration propagating through the optical box from the motor that rotates the rotary polygon mirror can be reduced. Therefore, the vibration of the folding mirror is suppressed, and a good image without pitch unevenness can be formed.

However, when the folding mirror and the mirror holder made of resin are integrated, the primary resonance frequency thereof becomes lower than the primary resonance frequency of the folding mirror alone. The longitudinal elastic modulus of the resin, which is the material of the mirror holder, is smaller than the longitudinal elastic modulus of the glass, which is the material of the folding mirror. As a result, the mirror holder is equivalent to adding a weight to the folding mirror.

Further, if a resin having a longitudinal elastic modulus similar to that of glass, which is the material of the folding mirror, is used, for example, a resin containing glass fiber or the like, the cost is increased and the weight is increased. Further, in order to enhance the rigidity by the shape of the mirror holder, its wall thickness must be increased. Also in this case, the weight of the mirror holder increases and the cost also increases.

Further, although the problems can be avoided by using the sheet metal-made mirror holder, when the sheet metal-made mirror holder is used, it becomes difficult to maintain the surface accuracy of the folding mirror. In order to maintain the shape and dimensional accuracy of the mirror holder, sheet metal is more costly than resin.

The frequency component of the vibration generated when driving the image forming apparatus is most often 300 Hz or less. Therefore, even if a resin or sheet metal mirror holder is added to the folding mirror to avoid the vibration frequency of the rotary polygon mirror and the resonance state with the folding mirror, the vibration frequency generated when the image forming apparatus is driven is reduced. Resonance with the folding mirror may not be avoided.

In Japanese Patent Laid-Open No. 10-90627, the rigidity of the optical box is enhanced by partially providing a hollow wall having a double wall structure on the side wall of the optical box. In this proposal, the side wall near the folding mirror is prevented from being largely deformed due to the vibration caused by the rotation of the rotary polygon mirror. Therefore, the vibration of the folding mirror is suppressed, and a good image without pitch unevenness can be formed.

However, although the rigidity of the side wall side peripheral portion of the window for taking out the scanning light on the bottom wall of the optical box can be solved,
It is not effective in strengthening the lens side peripheral portion of the window for extracting the scanning light. This is because the vibrations on the side wall side and the lens side peripheral portion of the window for taking out the scanning light on the bottom wall of the optical box occur at different frequencies, and the points of insufficient rigidity that cause these vibrations are different. .

The support of the folding mirror is formed along the widthwise direction of the window for taking out the scanning light and longer than the lengthwise direction of the window for taking out the scanning light. As a result, when the lens side peripheral portion of the window for taking out the scanning light on the bottom wall of the optical box vibrates, the support of the folding mirror is also affected. For this reason,
Even if the double wall structure is partially provided on the side wall of the optical box, the vibration of the folding mirror cannot be suppressed.

In Japanese Patent Laid-Open No. 10-319339, the supporting members at the four corners of the optical box are fixed to the body frame with screws, and the projecting portions projecting downward from the bottom wall of the optical box are held by the elastic body on the body frame side. I am letting you. In this proposal,
Since the central part of the optical box is elastically restrained to the main body frame, the primary resonance frequency of the optical box is moved to the high frequency side,
Vibration of the optical box can be reduced. Therefore, the vibration of the optical box is suppressed, and a good image without pitch unevenness can be formed.

However, since the central portion of the optical box is elastically restrained by the main body frame, the vibration from the drive of the main body is easily transmitted to the central portion of the optical box, that is, the lens and the folding mirror. Therefore, even if the central portion of the optical box is elastically restrained by the main body frame, the vibration of the folding mirror cannot be suppressed.

In Japanese Patent Laid-Open No. 11-218706, the folding mirror cover portion for covering the folding mirror is formed by a part of an optical box which is formed with an opening for emitting scanning light. In this proposal, it is possible to reduce the vibration of the folding mirror cover portion and the folding mirror support body by changing the vibration mode by devising the shape of the folding mirror cover portion. Therefore, the vibration of the folding mirror is suppressed, and a good image without pitch unevenness can be formed.

However, the support of the folding mirror is formed along the widthwise direction of the window for taking out the scanning light and longer than the lengthwise direction of the window for taking out the scanning light. As a result, when the peripheral portion of the window for taking out the scanning light on the side of the folding mirror cover portion vibrates, the support body of the folding mirror is also affected. For this reason, even if the vibration mode is changed by devising the shape of the folding mirror cover part, there arises a problem that the vibration of the folding mirror cannot be suppressed. Further, if the folding mirror cover part is divided, there arises a problem that the hermeticity of the optical box cannot be ensured.

[0021]

However, in these proposals, a weight or a mirror holder is attached to the folding mirror, or the holding position of the optical box is added to the holding position of the conventional optical box. It is possible to avoid the vibration state of the rotary polygon mirror and the resonance state of the folding mirror by increasing the number or devising the side wall shape of the optical box, but to avoid the vibration that occurs when the image forming apparatus is driven. ,
It is not possible to avoid resonance of the folding mirror or to sufficiently reduce vibration.

The present invention has been made in view of the above-mentioned problems in the optical scanning device used in the electrophotographic image forming apparatus, and its purpose is to vibrate the rotary polygon mirror and drive the image forming apparatus. To provide a high-performance optical scanning device capable of effectively reducing resonance of an optical box, a folding mirror, etc. due to generated vibration depending on a holding position and a shape of the optical box and improving image quality and speeding up printing. It is in.

[0023]

[Means for Solving the Problems] To achieve the above object
The invention according to claim 1 provides a light source for emitting a laser beam, and a light source.
The polygon mirror that reflects the laser light from the source and the polygon mirror are rotated.
Moving polygon mirror motor and laser reflected by the polygon mirror
In the lens block and the lens block that shapes the waveform of light
Accommodates a reflection mirror that reflects laser light whose waveform is shaped better
And an emission light opening for emitting laser light, and an image forming apparatus
Equipped with an optical box that has three or more holding parts to hold the main body of
In the optical scanning device, the optical box is kept from the center of gravity of the reflecting mirror.
The height h to the holding part depends on the height H1 of the optical box and the weight of the reflecting mirror.
The minimum height H2 from the core to the bottom of the optical box and the disconnection of the reflector
Width a and height b on the surface, and H2 <h <H1- (a²+
b ²)^0.5And are arranged in the sub-scanning direction.
The holding part at one end and the holding part at the other end of the optical box have different heights.
The most important feature is the optical scanning device.

According to a second aspect of the present invention, the optical box is provided with ribs along the line connecting the holding portion at one end and the holding portion at the other end, and ribs along the center line perpendicular to the main scanning direction on the back surface. 1
The described optical scanning device is a main feature.

A third aspect of the present invention is characterized mainly in the optical scanning device according to the first aspect, wherein the optical box has a rib on the back surface which is connected to a step formed on the bottom wall.

The invention according to claim 4 is characterized mainly in the optical scanning device according to claim 2 or 3 in which the rib has a thickness equivalent to the average thickness of the optical box.

According to a fifth aspect of the present invention, the optical box has an exit light opening at a position facing the laser light reflecting surface of the reflecting mirror, a bottom having a projection at the upper end and a rib at the lower end. The optical scanning device according to claim 1 provided with a wall is a main feature.

A sixth aspect of the present invention is mainly characterized in that the projection and the rib are connected to both side walls of the optical box in the main scanning direction.

The invention according to claim 7 is characterized mainly in the optical scanning device according to claim 5, wherein the projections and the ribs have a thickness equivalent to the average thickness of the optical box.

The eighth aspect of the present invention is characterized mainly in the optical scanning device according to the third or fifth aspect, in which the rib has the same height as the side walls of the intersecting optical boxes.

A ninth aspect of the present invention is characterized mainly in the optical scanning device according to the fifth aspect, wherein the shape of the protrusion is a triangle.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a digital copying machine equipped with an optical scanning device according to an embodiment of the present invention. FIG. 2 is a detailed view of the main parts of the optical scanning device of FIG. The structure and operation of the digital copying machine will be described below with reference to FIGS.

Main body 1 of digital copying machine (image forming apparatus)
A document reading device 2 is provided on the upper part of. The document reading device 2 illuminates a document set on a contact glass with a light source, reflects a reflected image from the document with a plurality of reflecting mirrors, and forms an image on a CCD image sensor (solid-state image sensor) with an imaging lens. Has become. The CCD image sensor converts an image of a document into an electric signal corresponding to the amount of light reflected from the image. The image data converted into an electric signal is converted by an image processing unit (not shown) and then output to the optical scanning device 3.

As shown in FIG. 2, the optical scanning device 3 includes a semiconductor laser (not shown) that emits a laser beam, a polygon mirror 4 that reflects the laser beam, and a polygon mirror motor that drives the polygon mirror 4 to rotate. 5 and a lens block 6 such as an fθ lens or a toroidal lens for shaping the laser beam from the polygon mirror 4
And a component such as a reflecting mirror 7 for reflecting the laser beam that has been acted on by the lens block 6 is housed in the optical box 8 and an emission light opening 8a through which the laser light is emitted as writing light toward the photoconductor 9. It is sealed with dust-proof glass and has a substantially sealed structure.

Below the original reading device 2, a charger, an optical scanning device 3, a developing device, a transfer device, a separator, and
A cleaning device is arranged, and an electrostatic latent image is formed by the optical scanning device 3 on the charged portion of the photoconductor 9 that is uniformly charged by the charger. Then, the electrostatic latent image is visualized as a toner image by a developing device, the toner image is transferred onto a sheet by a transfer device, and the residual toner is collected by a cleaning device.

Further, the paper carrying section has a paper feeding roller, a paper feeding guide plate, a registration roller, a carrying belt, a fixing roller and a paper discharging roller, and by driving the paper feeding roller, a paper feeding cassette Each of the sheets is taken out one by one and guided to a transfer device to transfer a toner image, and the toner image is heated and fixed by a fixing roller, and then discharged onto a receiving table.

(Structure / Operation for Claim 1) FIG. 3 shows a sectional view of an optical box of an optical scanning device according to claim 1 of the present invention. In the present invention, the holding height h (h1, h2) of the holding portions 8b and 8c of the optical box 8 held by the main body 1 of the image forming apparatus from the center of gravity of the reflecting mirror 7 is the height H1 of the optical box 8.
When, the minimum height H2 from the center of gravity of the reflector 7 to the bottom of the optical box 8, the width a of the cross section of the reflector 7, the height b, H2 <h <H1- ( a 2 + b 2) 0.5 Relationship Are set and arranged to have.

Further, the holding portion 8b at one end and the holding portion 8c at the other end of the optical box 8 arranged in the sub scanning direction from the center of gravity of the reflecting mirror 7 are arranged so as to have different heights h1 and h2.

The optical box 8 is fastened to the frame of the main body 1 of the image forming apparatus by a known method such as screwing via the holding portions 8b and 8c. Similarly, the reflecting mirror 7 is also supported by the optical box 8 by a known method such as being pressed by an elastic support.

A cross-sectional view of a general conventional optical scanning device is shown in FIG. 4 for comparison with FIG. As shown in FIG. 4, the heights h1 and h2 of the holding portions 8b and 8c of the optical box 8 held by the main body 1 of the image forming apparatus are the minimum heights from the center of gravity of the reflecting mirror 7 to the bottom of the optical box 8. It is located at H2.

FIG. 5 shows a plan view of the optical box of the optical scanning device according to the first aspect. In the present invention, in order to be held by the main body 1 of the image forming apparatus, the maximum holding interval D 2 of the two holding portions 8b provided on the side wall of the optical box 8 arranged in the main scanning direction on the side of the reflecting mirror 7 is Length W1 of the reflecting mirror 7 in the main scanning direction
And a support interval W2 for supporting the reflecting mirror 7 in the main scanning direction,
The relationship of W2 <D <W1 is established, and the center of gravity of the reflecting mirror 7 is set on the center line of the maximum holding distance D.

Further, at least one holding portion 8c provided on the side wall opposite to the side wall having the holding portion 8b is arranged within the maximum holding distance D.

Further, for comparison with FIG. 5, a plan view of a general conventional optical scanning device is shown in FIG. As shown in FIG. 6, the holding portion 8b of the optical box 8 held by the main body 1 of the image forming apparatus is arranged at a position sandwiching the reflecting mirror 7 in the main scanning direction.

Hereinafter, prevention of resonance or reduction of vibration in the optical scanning device according to the embodiment of the present invention will be described.

In the optical scanning device 3 of the present invention shown in FIG. 3, the holding portion 8 of the optical box 8 on the side of the reflecting mirror 7 from the center of gravity of the reflecting mirror 7.
The height h1 of b is 16.77 mm, and the height h2 of the holding portion 8c on the polygonal mirror 4 side is 33.77 mm. The height H1 of the optical box 8 is 45 mm, the minimum height H2 from the center of gravity of the reflecting mirror 7 to the bottom of the optical box 8 is 10.77 mm, and the width a in the cross section of the reflecting mirror 7 is 10 mm and the height b is 12
mm. The basic thickness of the optical box 8 is 3 mm.

In the conventional optical scanning device 3 shown in FIG. 4, the heights h1 and h2 of the holding portions 8b and 8c of the optical box 8 from the center of gravity of the reflecting mirror 7 and from the center of gravity of the reflecting mirror 7 to the bottom of the optical box 8. Has a minimum height H2 of 10.77 mm. The basic thickness of the optical box 8 is 3 mm.

In the optical scanning device 3 according to the present invention shown in FIG. 5, the maximum holding distance D of the optical box 8 is 250 mm, the length W1 of the reflecting mirror 7 in the main scanning direction is 252 mm, and the reflecting mirror 7 is supported in the main scanning direction. The supporting interval W2 is 245 mm.

Further, one holding portion 8c is arranged on the side wall facing these so as to hold the maximum holding distance D. The holding portion 8c is arranged at a position symmetrical with respect to a line segment that passes through the center of gravity of the reflecting mirror 7 with respect to the rotation axis center of the polygon mirror motor 5 that drives the polygon mirror 4 to rotate. This holding portion 8c is
It is at a position displaced by 7.5 mm from the center of gravity of the reflecting mirror 7.

In the conventional optical scanning device 3 shown in FIG. 6, the maximum holding distance D of the optical box 8 is 348 mm, the length W1 of the reflecting mirror 7 in the main scanning direction is 252 mm, and the reflecting mirror 7 is supported in the main scanning direction. The support interval W2 is 245 mm.

The vibration mode of the primary resonance frequency of the optical box 8 is a vibration mode in which the bottom of the central part of the optical box 8 is bent and deformed vertically. This primary resonance frequency contributes most to the vibration amount of the optical box 8. When the bottom portion of the central portion of the optical box 8 is bent and deformed, the optical component or the like that is adhered to the bottom portion of the optical box 8 or is pressed by the supporting portion of the optical box 8 is bent and deformed according to the optical box 8.

In particular, the optical scanning device 3 according to the first aspect has the effect of moving the resonance frequency of the vibration mode in which the bottom portion of the central portion of the optical box 8 is vertically bent and deformed to the high frequency side. .

The resonance frequency of the vibration mode in which the bottom of the central portion of the optical box 8 of the optical scanning device 3 according to the embodiment of the present invention shown in FIG. 3 bends vertically is 214 Hz. The resonance frequency of this vibration mode in the conventional example shown in FIG. 4 is 154 Hz. In the embodiment of the present invention, the resonance frequency of the vibration mode in which the bottom of the central portion of the optical box 8 is bent and deformed vertically is improved by 60 Hz as compared with the conventional example, so the vibration amount in this vibration mode can be reduced. .

In the embodiment of the present invention, the primary resonance frequency of the optical box 8 is moved to the high frequency side as compared with the conventional example. Therefore, the vibration frequency of the rotary polygon mirror 4 and the image forming apparatus are driven. It is possible to reduce the vibration amount of the vibration that occurs when performing, and to prevent resonance.

(Structure / Operation for Claim 2) FIG. 7 shows a rear view of the optical box of the optical scanning device according to claim 2 of the present invention. In order to maximize the rigidity of the optical box 8, it is preferable to determine the holding portions 8b and 8c so as to minimize the area of the polygon formed by connecting the holding portions 8b and 8c. Holding part 8
The position on the line connecting b and 8c is the position where the rigidity of the optical box 8 is highest, and it is most desirable that the side wall of the optical box 8 is originally located at that position.

However, since the long lens block 6 and the reflecting mirror 7 are housed in the optical box 8, the polygonal area formed by connecting the holding portions 8b and 8c is minimized and the holding portion 8b is formed. , 8c, it is difficult to dispose the side wall of the optical box 8 on the line connecting them.

Therefore, in the present invention, the optical box 8 has the holding portion 8
A rib 8d along a line segment connecting b and 8c, and a rib 8d perpendicular to the main scanning direction at the center thereof are arranged on the back surface. The rib 8d is arranged on the back surface of the optical box 8 in order to secure a sufficient height of the rib 8d and increase the rigidity of the optical box 8. When the rib 8d is arranged on the surface of the optical box 8, the height of the rib 8d is considerably limited in order to avoid blocking the scanning laser light, and the rigidity of the optical box 8 cannot be sufficiently increased.

Particularly, in the optical scanning device 3 according to the second aspect, the resonance frequency of the vibration mode in which the central portion of the outgoing light opening 8a of the optical box 8 on the B side undergoes bending deformation and vibrates is shifted to the high frequency side. Have an effect.

The resonance frequency of the vibration mode in which the central portion on the B side of the outgoing light opening 8a of the optical box 8 of the optical scanning device 3 according to the embodiment of the present invention shown in FIG. 5 causes bending deformation and vibrates is 345 Hz. is there. The resonance frequency of this vibration mode in the conventional example shown in FIG. 6 is 301 (Hz). In the embodiment of the present invention, the resonance frequency of the vibration mode in which the B side central portion of the outgoing light opening 8a of the optical box 8 causes bending deformation and vibrates is improved by 44 Hz compared to the conventional example.
The amount of vibration in this vibration mode can be reduced.

(Structure / Operation for Claim 3) FIG. 8 is a sectional view of an optical box of an optical scanning device according to claim 3 of the present invention. In the present invention, the rib 8d is connected to the step formed on the bottom wall of the optical box 8 provided to keep the height of the laser light at the light source, the polygon mirror 4, the lens block 6 and the reflecting mirror 7 constant. It was arranged so as to have it on the back surface.

Particularly, in the optical scanning device 3 according to the third aspect, the resonance frequency of the vibration mode in which the central portion of the exit light opening 8a of the optical box 8 on the B side causes bending deformation and vibrates is shifted to the high frequency side. Have an effect.

The resonance frequency of the vibration mode in which the central portion on the B side of the outgoing light opening 8a of the optical box 8 of the optical scanning device 3 according to the embodiment of the present invention shown in FIG. is there. The resonance frequency of this vibration mode in the conventional example shown in FIG. 6 is 301 Hz. In the embodiment of the present invention, as compared with the conventional example, the outgoing light opening 8 of the optical box 8 is
Since the resonance frequency of the vibration mode in which the central portion on the B side of a causes bending deformation and vibrates is improved by 40 Hz, the vibration amount in this vibration mode can be reduced.

(Structure / Operation for Claim 4) In the optical box 8 of the optical scanning device 3 according to claims 2 and 3 of the present invention, the rib 8d has a thickness equal to the average thickness of the optical box 8. I had it.

Conventionally, generally, the ribs 8d arranged on the optical box 8 are often in the form of a lattice. Lattice rib 8
In order to sufficiently secure the rigidity of the optical box 8 by d, it is necessary to narrow the interval between the grid-shaped ribs 8d and increase the number thereof. Therefore, the thickness of the grid-shaped ribs 8d is about 1/2 of the average thickness of the optical box 8. However, the lattice-shaped ribs 8d are less effective in increasing the rigidity of the optical box 8 as the number of ribs 8 is arranged, and further increase the weight of the optical box 8. Also,
It also increases the cost of mold production.

Therefore, in the present invention, the ribs 8d for improving the rigidity of the optical box 8 are properly arranged in the optical box 8 of the optical scanning device 3 according to the second and third aspects. Along with this, the thickness of the rib 8d is made equal to the average thickness of the optical box 8 so that the effect of the rib 8d is further enhanced. Accordingly, when the optical box 8 is made of resin, it is possible to perform molding with stable accuracy and shorten the molding time.

(Structure / Operation for Claim 5) FIG. 9 shows an enlarged cross-sectional view of an optical box of an optical scanning device according to claim 5 of the present invention. In the present invention, the outgoing light opening 8 of the optical box 8 is
A bottom wall 8e having a is formed to face the laser light reflecting surface of the reflecting mirror 7, and a projection 8f is provided at the upper end of the bottom wall 8e and a rib 8d is provided at the lower end.

In particular, in the optical scanning device 3 according to the fifth aspect, the resonance frequency of the vibration mode in which the central portion of the exit light aperture 8a of the optical box 8 on the A and B sides undergoes bending deformation and vibrates to the high frequency side. It has the effect of shifting.

The resonance frequency of the vibration mode in which the central portion on the A side of the outgoing light opening 8a of the optical box 8 of the optical scanning device 3 according to the embodiment of the present invention shown in FIG. is there. The resonance frequency of this vibration mode in the conventional example shown in FIG. 6 is 301 Hz. In the embodiment of the present invention, as compared with the conventional example, the outgoing light opening 8 of the optical box 8 is
Since the resonance frequency of the vibration mode in which the central portion on the A side of a causes bending deformation and vibrates is improved by 334 Hz, the vibration amount in this vibration mode can be reduced.

Similarly, B of the outgoing light opening 8a of the optical box 8 of the optical scanning device 3 according to the embodiment of the present invention shown in FIG.
The resonance frequency of the vibration mode in which the central portion on the side causes bending deformation and vibrates is 385 Hz. The resonance frequency of this vibration mode in the conventional example shown in FIG. 6 is 301 Hz. Since the embodiment of the present invention improves the resonance frequency of the vibration mode in which the central portion on the A side of the outgoing light opening 8a of the optical box 8 causes bending deformation to vibrate, it is 84 Hz higher than that of the conventional example. The amount of vibration in the vibration mode can be reduced.

(Structure / Operation for Claim 6) In the optical box 8 of the optical scanning device 3 according to claim 5 of the present invention, the projection 8f and the rib 8d are formed so as to be connected to the side wall of the optical box 8. . Most of the rigidity of the optical box 8 is carried by the side wall of the optical box 8. Therefore, the protrusion 8f and the rib 8d can be connected to the side wall of the optical box 8, the effect of the protrusion 8f and the rib 8d can be further enhanced, and the rigidity of the optical box 8 can be improved.

(Structure / Operation for Claim 7) In the optical box 8 of the optical scanning device 3 according to claim 5 of the present invention, the projection 8f and the rib 8d have a wall thickness equivalent to the average wall thickness of the optical box 8. To have. Accordingly, when the optical box 8 is made of resin, it is possible to perform molding with stable accuracy and shorten the molding time.

(Structure / Operation for Claim 8) In the optical box 8 of the optical scanning device 3 according to claim 5 of the present invention, the rib 8d has the same height as the side walls of the intersecting optical boxes 8. I chose Most of the rigidity of the optical box 8 is carried by the side wall of the optical box 8. Therefore, by making the height of the rib 8d equal to the side wall of the optical box 8 and connecting the rib 8d and the side wall of the optical box 8, the effect of the rib 8d can be further enhanced and the rigidity of the optical box 8 can be increased. Can also be improved.

(Structure / Operation for Claim 9) In the optical box 8 of the optical scanning device 3 according to claim 5 of the present invention, the projection 8f is formed in a triangular shape. If the rib 8d is arranged to increase the rigidity of the outgoing light opening 8a, the rigidity of the outgoing light opening 8a is improved, but this effect may be reduced due to the weight of the rib 8d. However, if the projection 8f has a triangular shape, the outgoing light aperture 8a
The rigidity can be improved without increasing the weight in the vicinity.

Further, the bottom wall 8e having the exit light opening 8a is formed.
Is formed so as to face the laser light reflecting surface of the reflecting mirror 7,
The compatibility with the bottom wall on which the lens block 6 is mounted is improved, and when the optical box 8 is made of resin, stable molding can be performed and the molding time can be shortened.

[0074]

According to the apparatus of the first aspect, the height h from the center of gravity of the reflecting mirror to the holding portion of the optical box is the height H1 of the optical box and from the center of gravity of the reflecting mirror to the bottom of the optical box. Minimum height H2, width a and height b in the cross section of the reflecting mirror, and H2 <
Since the holding part at one end and the holding part at the other end of the optical box arranged in the sub-scanning direction have different heights, there is a relationship of h <H1− (a ² + b ² ) ^0.5 . It is possible to shift the primary resonance frequency at which the bottom of the optical system bends and the resonance frequency at which the outgoing light aperture of the optical box bends to the high frequency range side. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the apparatus of the second aspect, the optical box is provided on the back surface with ribs along a line connecting the holding portion at one end and the holding portion at the other end and a rib along a center line perpendicular to the main scanning direction. Therefore, the resonance frequency at which the outgoing light aperture of the optical box bends can be shifted to the high frequency range side. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the apparatus of claim 3, since the optical box is provided with the rib connected to the step formed on the bottom wall on the back surface, the resonance frequency at which the exit light opening of the optical box bends is at the high frequency range side. Can be shifted to. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the fourth aspect of the present invention, since the rib has a thickness equal to the average thickness of the optical box, the rib shifts the resonance frequency at which the opening of the outgoing light of the optical box bends to the high frequency range side. Can be made. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to. Further, when the optical box is made of resin, the wall thickness of the optical box can be made uniform and molding can be facilitated, and the die manufacturing cost and the production cost can be reduced.

According to the fifth aspect of the present invention, the optical box has an outgoing light opening at a position facing the laser light reflecting surface of the reflecting mirror, and a protrusion is formed at the upper end and a rib is formed at the lower end. Since the bottom wall is provided, the resonance frequency at which the outgoing light opening of the optical box bends can be shifted to the high frequency range side. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the invention described in claim 6, since the projection and the rib are connected to both side walls of the optical box in the main scanning direction,
It is possible to shift the resonance frequency at which the emitted light aperture of the optical box bends to the high frequency range side. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the seventh aspect of the present invention, since the projections and ribs have the same thickness as the average thickness of the optical box, the resonance frequency at which the outgoing light aperture of the optical box bends is shifted to the high frequency range side. Can be made. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to. Further, when the optical box is made of resin, the wall thickness of the optical box can be made uniform and molding can be facilitated, and the die manufacturing cost and the production cost can be reduced.

According to the apparatus of claim 8, since the rib has the same height as the side wall of the optical box which intersects, the resonance frequency at which the exit light opening of the optical box bends is shifted to the high frequency range side. You can In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror.
For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to.

According to the apparatus of the ninth aspect, since the shape of the protrusion is a triangle, it is possible to shift the resonance frequency at which the exit light aperture of the optical box bends to the high frequency range side. In addition, it is possible to suppress local vibration near the lens block of the optical box and the supporting portion of the reflecting mirror. For this reason, line deviation in the main scanning direction and uneven density in the sub scanning direction due to vibrations generated from the polygon mirror motor that rotationally drives the rotary polygon mirror and the motor of the drive unit of the image forming apparatus can be reduced, and the deterioration of image quality can be prevented. be able to. Also, when the optical box is made of resin, the thickness of the optical box can be made uniform, making it easier to mold,
Die production cost and production cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a digital copying machine equipped with an optical scanning device according to an embodiment of the present invention.

FIG. 2 is a detailed view of a main part of the optical scanning device of FIG.

FIG. 3 is a sectional view of an optical box of the optical scanning device according to claim 1 of the present invention.

FIG. 4 is a cross-sectional view of a general conventional optical scanning device for comparison with FIG.

FIG. 5 is a plan view of an optical box of the optical scanning device according to claim 1 of the present invention.

FIG. 6 is a plan view of a general conventional optical scanning device for the purpose of comparison with FIG.

FIG. 7 is a rear view of the optical box of the optical scanning device according to the second aspect of the present invention.

FIG. 8 is a cross-sectional view of an optical box of the optical scanning device according to claim 3 of the present invention.

FIG. 9 is an enlarged cross-sectional view of an optical box of the optical scanning device according to claim 5 of the present invention.

[Explanation of symbols]

1 Image forming device body 2 Document reader 3 Optical scanning device 4 polygon mirror 5 polygon mirror motor 6 lens block 7 Reflector 8 optical box 8a Output light aperture 8b holding part 8c holding part 8d rib 8e Bottom wall 8f protrusion 9 photoconductor

Claims (9)

[Claims] 1. A light source that emits laser light, a polygonal mirror that reflects the laser light from the light source, a polygonal mirror motor that drives the polygonal mirror to rotate, and a lens block that waveform-shapes the laser light reflected by the polygonal mirror. An optical box that houses a reflection mirror that reflects the laser light whose waveform has been shaped by the lens block and that emits the laser light, and has three or more holding portions that hold the main body of the image forming apparatus. In the optical scanning device, the height h from the center of gravity of the reflecting mirror to the holding portion of the optical box is the height H1 of the optical box, the minimum height H2 from the center of gravity of the reflecting mirror to the bottom of the optical box, and the reflecting mirror. the width of the cross-section a, the height b, H2 <h <H1- ( a 2 + b 2) has a ^0.5 relationship, and, holding the holding portion of the one end and the other end of the optical box which is arranged in the sub-scanning direction Optical scanning device characterized in that the parts have different heights Place 2. The optical box has, on its back surface, ribs along a line connecting a holding portion at one end and a holding portion at the other end, and a rib along a center line perpendicular to the main scanning direction. Optical scanning device. 3. The optical scanning device according to claim 1, wherein the optical box has a rib on the back surface which is connected to a step formed on the bottom wall. 4. The optical scanning device according to claim 2, wherein the rib has a thickness equal to the average thickness of the optical box. 5. The optical box has an outgoing light opening at a position facing the laser light reflecting surface of the reflecting mirror, and a projection at an upper end,
2. The optical scanning device according to claim 1, further comprising a bottom wall having a rib formed at a lower end thereof. 6. The optical scanning device according to claim 5, wherein the projection and the rib are connected to both side walls of the optical box in the main scanning direction. 7. The optical scanning device according to claim 5, wherein the projections and the ribs have a thickness equal to the average thickness of the optical box. 8. The optical scanning device according to claim 3, wherein the rib has the same height as the side walls of the intersecting optical boxes. 9. The optical scanning device according to claim 5, wherein the shape of the protrusion is a triangle.