JP2001166241A - Deflecting and scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce vibration of a return mirror. SOLUTION: The scanning line of a rotary polygon mirror 2 is guided out of a window 11 of an optical box 10 through an imaging lens system 3 and the return mirror 4 and imaged on a photosensitive body on a rotary drum. The return mirror 4 is made to abut against a couple of mirror support members 12 and 13 united with the optical box 10 and fixed to the optical box 10 by being pressed by an elastic member 14 on the back side. The mirror support members 12 and 13 are long-sized members which extend along the length of the return mirror 4, i.e., in a horizontal scanning direction (Y-axial direction) and both the breadthwise end parts of the return mirror 4 are tightly supported to reduce the vibration of the return mirror 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device used for an image forming apparatus such as a laser beam printer and a laser facsimile.

[0002]

2. Description of the Related Art A deflection scanning device used in an image forming apparatus such as a laser beam printer (LBP) or a laser facsimile reflects a light beam such as a laser beam by a rotating polygon mirror rotating at a high speed, and converts the obtained scanning beam. An electrostatic latent image is formed by forming an image on a photoconductor on a rotating drum. Next, the electrostatic latent image on the photoconductor is visualized into a toner image by a developing device,
This is transferred to a recording medium such as recording paper and sent to a fixing device,
Printing is performed by heating and fixing the toner on the recording medium.

[0003] Figure 6 shows a deflector of a conventional example, which includes a light source unit 101 that the unit of the semiconductor laser and the collimator lens, for deflecting and scanning the laser beam L ₀ of the parallel light beam generated therefrom Rotating polygon mirror 1
02, a lens 103 for forming an image of the laser beam deflected and scanned on the photosensitive member on the surface of the rotating drum D ₀ (shown in FIG. 7);
It has a folding mirror 104 and the like, the rotating polygon mirror 102 and the lens 103 are accommodated in an optical box 110, and the light source unit 101 is assembled on the side wall of the optical box 110.

[0004] As shown in FIG. 7, the upper opening of the optical box 110 is closed by a lid member 120 after all necessary components are incorporated in the optical box 110. Note that a window 111 for taking out toward deflection scanning laser beam by rotary polygon mirror 102 (scanning light) to the outside of the rotary drum D ₀ is provided in the bottom wall of the optical box 110.

[0005] Laser light L ₀ generated from the semiconductor laser of the light source unit 101 is collimated by a collimator lens inside the laser light L ₀ , condensed linearly on a reflecting surface of a rotary polygon mirror 102 by a cylindrical lens 101 a, and It is taken out toward the rotary drum D ₀ through the window 111 of the optical box 110 via a folding mirror 104.
Such a laser beam focused on the photosensitive member on the rotary drum D ₀ and, the now accompanied in the sub scanning by rotation of the rotary drum D ₀ and the main scanning by the rotating polygon mirror 102 to form an electrostatic latent image.

A motor 1 for rotatingly driving a polygon mirror 102
Numeral 02a includes a rotor integrated with the rotary polygon mirror 102 and a stator mounted on a motor board. The stator is excited by a drive current supplied from a drive circuit on the motor board to rotate the rotor.

[0007] A part of the scanning light from the rotary polygon mirror 102 is supplied to the BD mirror 105 at one end in the main scanning direction (Y-axis direction).
And is introduced into the BD sensor 106 and converted into a scanning start signal by a controller (not shown). The semiconductor laser of the light source unit 101 receives this scanning start signal and starts modulation for writing an image.

[0008] The bottom wall of the optical box 110 is fastened to the main body frame of the image forming apparatus by a known method such as a screw via support members provided at four corners. The optical box 110 is integrally formed of a generally known resin material.

Folding mirror 10 for optical box 110
As shown in FIG. 8, the assembling method of No. 4 is such that both ends in the longitudinal direction of the folding mirror 104, which is a long rod, are brought into contact with a mirror support 112 integrated with the side wall of the optical box 110. It is common to fix with a spring that does not.

[0010]

However, in recent years, the performance of laser beam printers, laser facsimile machines and the like has been improved, and accordingly, the speed of the deflection scanning device has been required. To increase the speed of the deflection scanning device, it is necessary to rotate the rotating polygon mirror at a high speed.However, the vibration caused by the high-speed rotation of the rotating polygon mirror propagates through the optical box to the folding mirror, which causes the folding mirror to vibrate. Therefore, there is an unsolved problem that the image forming position of the scanning light fluctuates and image deterioration such as uneven pitch occurs.

More specifically, the folding mirror is a long object arranged along the scanning line in the main scanning direction, that is, the Y-axis direction, and is itself in a state of being easily vibrated. In recent years, with the increase in speed of the deflection scanning device, the motor of the rotary polygon mirror generates large vibration, and the vibration that propagates to the return mirror tends to increase. Further, the return mirror may vibrate due to vibration transmitted from a driving system external to the deflection scanning device via the main body frame of the image forming apparatus.

Further, when the fundamental frequency of the motor approaches the natural frequency of the return mirror, the return mirror itself vibrates due to resonance. In particular, in a model in which the number of rotations of the rotating polygon mirror is set to a plurality, the difference between the fundamental frequency of the motor and the natural frequency of the folding mirror is reduced to several tens of Hz to avoid a design that easily causes a resonance state. Difficult to do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and can effectively reduce the vibration of a folding mirror to greatly contribute to improvement of image quality and speeding up of printing. It is an object of the present invention to provide a deflection scanning device.

[0014]

In order to achieve the above object, a deflection scanning apparatus according to the present invention comprises: a deflection scanning means for deflecting and scanning a light beam to convert the light beam into scanning light; Mirroring means comprising: an imaging optical system including an image forming means for forming an image on a mirror and a folding mirror; and a pair of supporting portions for supporting both ends of the folding mirror in the short direction across a scanning line of the scanning light. It is characterized by having.

It is preferable that the pair of support portions have a pair of mirror support members configured to abut both ends in the short direction of the folding mirror.

At least one of the support portions may be constituted by a plurality of members for respectively supporting a plurality of portions in the longitudinal direction of the folding mirror.

It is preferable that at least one of the supporting portions is integrally formed with an optical box for housing the deflection scanning means and the imaging optical system.

At least one of the support portions may be a component manufactured separately from the optical box that houses the deflection scanning means and the imaging optical system.

It is preferable that at least one of the support portions is a mirror support member longer than the length of the folding mirror.

[0020]

Instead of supporting the return mirror at both ends in the longitudinal direction, a pair of long mirror support members and the like for supporting the return mirror at both ends in the short direction across the scanning line are provided. By supporting both ends in the short direction of the folding mirror in this way, the natural frequency of the folding mirror can be reduced by the fundamental frequency of the motor such as the rotating polygon mirror and the frequency of the gears, etc., as compared with the case where the mirror is supported by both ends in the longitudinal direction. From the high frequency side.

It is possible to prevent the return mirror from resonating due to vibration of a motor or the like, and to improve image quality and speed up printing.

[0022]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a deflection scanning apparatus according to a first embodiment. The deflection scanning apparatus converts a laser beam, which is a light beam generated from a light source unit in which a semiconductor laser and a collimator lens are unitized, into a rotary polygon mirror. And a scanning lens deflected and scanned by the rotary polygon mirror 2 serving as a deflecting and scanning means, for forming an image on a photosensitive member which is an imaging surface on a rotating drum. It has an image forming optical system including an image forming lens system 3 and a folding mirror 4 as means, and the rotating polygon mirror 2, the cylindrical lens, the image forming lens system 3, the folding mirror 4, and the like are provided in an optical box 10 as a housing. Is housed. The upper opening of the optical box 10 is closed by a lid member (not shown) after assembling the components to the optical box 10.

The rotating drum is disposed outside the optical box 10, and the scanning light is reflected by the folding mirror 4 and is extracted from the window 11 provided on the bottom wall of the optical box 10 toward the rotating drum.

A motor 2a for driving the rotary polygon mirror 2 to rotate.
Has a rotor integral with the rotating polygon mirror 2 and a stator integral with the motor substrate, and excites the stator with a drive current supplied from a drive circuit on the motor substrate to rotate the rotor.

The scanning light which forms an image on the photosensitive member of the rotating drum is
An electrostatic latent image is formed on the photoconductor along with main scanning by the rotation of the rotary polygon mirror 2 and sub-scanning by the rotation of the rotating drum.

The imaging lens system 3 includes a lens 3a having an fθ function for correcting a point image caused by the scanning light focused on the photosensitive member.
3b.

A part of the scanning light of the rotary polygon mirror 2 is reflected by a BD mirror at one end in the main scanning direction (Y-axis direction), introduced into a BD sensor, and converted into a scanning start signal by a controller (not shown). The semiconductor laser of the light source unit receives this scanning start signal and starts modulation for writing an image.

The folding mirror 4 has a mirror supporting member (supporting portion) 1 as a mirror supporting means integrally formed with the optical box 10 at both ends in the transverse direction (Z-axis direction) which is the sub-scanning direction.
2 and 13 respectively, and are supported by the elastic member 14.
By pressing, it is accurately fixed to the optical box 10.

As shown in FIG. 2, the mirror support members 12,
Reference numeral 13 denotes a rod-shaped member that is disposed in parallel with the main scanning direction with the scanning line R of the scanning light interposed therebetween and has a length equal to or longer than the length of the folding mirror 4 in the side wall of the optical box 10. Is provided. The mirror support member 1
The components 2 and 13 must be designed in consideration of contact with the opposite end portions in the sub-scanning direction excluding the return mirror effective portion so as not to block the reflected laser beam.

As shown in FIG. 3, the elastic member 14 for fixing the return mirror 4 is a spring having a contact portion 14a which comes into contact with the center of the return mirror 4 in the lateral direction.

By using the mirror supporting member abutting on the two portions in the short direction and the elastic member pressing the space therebetween, the folding mirror is supported at both ends in the short direction, as in the conventional example. As compared with the case where both ends are supported in the longitudinal direction, the natural frequency of the folding mirror is significantly increased. This can be said from the basic formula of the natural frequency.

That is, assuming that the distance between both ends in the short direction is b and the distance between both ends in the longitudinal direction is d, the natural frequency of the folding mirror is expressed by the following equation.

[0034]

(Equation 1) Here, f ₁ : natural frequency in the case of supporting both ends in the longitudinal direction f ₂ : natural frequency in the case of supporting both ends in the transverse direction A, B, h: constants b << d, f ₁ <<F ₂

As a result, the natural frequency of the return mirror can be brought to a higher frequency band than the high frequency generated by the high-speed LBP.

In this way, it is possible to greatly reduce the vibration of the return mirror which affects the image deterioration and the like.

FIGS. 4 and 5 show a main part of the deflection scanning apparatus according to the second embodiment. One of the support portions for supporting both end portions in the short direction of the folding mirror 4 is a mirror support member 32 having a columnar shape, which is manufactured as a separate component from the optical box 10 and is parallel to the main scanning direction. Installed. The columnar mirror support member 32 is in contact with the entire area in the longitudinal direction of the return mirror 4, and the mirror support member 33, which is the other support portion, is embossed and spaced apart in the longitudinal direction of the return mirror 4 by a plurality. It is a member provided integrally with 10. The lower mirror support member 32
The optical box 10 may be formed separately from the optical box 10 without being integrally formed with the optical box 10.

Elastic member 34 for fixing folding mirror 4
Presses the center in the short direction from the back side of the folding mirror 4. Note that the folding mirror 4 and the optical box 10 are the same as those in the first embodiment, so they are denoted by the same reference numerals, and description thereof is omitted.

The point that the natural frequency of the return mirror can be brought to a higher frequency band than the high frequency generated by the LBP which is accelerated, and the vibration of the return mirror which affects image deterioration and the like can be reduced. This is the same as the first embodiment.

The present embodiment has an additional advantage that the mirror supporting member to be brought into contact with the folding mirror can be made of a material having higher rigidity than the optical box by using a separate member. As a result, vibration of the return mirror that causes image deterioration can be further reduced.

[0041]

Since the present invention is configured as described above, the following effects can be obtained.

The vibration characteristics of the folding mirror can be greatly improved, and the frequency can be largely shifted to the high frequency side from the frequency of the motor portion of the rotating polygon mirror rotating at high speed or the frequency of gears or the like that cause vibration. Thereby, the vibration of the folding mirror can be reduced, and the improvement of the image quality and the speeding up of printing can be greatly promoted.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a deflection scanning device according to a first embodiment.

FIG. 2 is an enlarged partial perspective view showing a part of the apparatus of FIG. 1 in an enlarged manner.

FIG. 3 is a sectional view showing the apparatus of FIG. 2;

FIG. 4 is an enlarged partial perspective view showing a main part of a deflection scanning device according to a second embodiment.

FIG. 5 is a sectional view showing the device of FIG. 4;

FIG. 6 is a schematic plan view showing one conventional example.

FIG. 7 is a sectional view showing the device of FIG. 6;

8 is a partially enlarged perspective view showing a part of the apparatus of FIG. 6 in an enlarged manner.

[Explanation of symbols]

 2 rotating polygon mirror 3 imaging lens system 4 folding mirror 10 optical box 11 window 12, 13, 32, 33 mirror support member 14, 34 elastic member

Claims (6)

[Claims] 1. An image forming optical system comprising: a deflection scanning means for deflecting and scanning a light beam to convert it into scanning light; an imaging means for forming the scanning light on an imaging surface; and a folding mirror; A deflection scanning device having mirror support means provided with a pair of support portions for supporting both ends of the folding mirror in the short direction with the scanning line interposed therebetween. 2. The deflection scanning device according to claim 1, wherein the pair of support portions have a pair of mirror support members configured to abut both ends in the short direction of the folding mirror. 3. The deflection scanning device according to claim 1, wherein at least one of the support portions is constituted by a plurality of members respectively supporting a plurality of portions in the longitudinal direction of the folding mirror. 4. The deflection scanning device according to claim 1, wherein at least one of the support portions is formed integrally with an optical box that houses the deflection scanning means and the imaging optical system. . 5. The apparatus according to claim 1, wherein at least one of the support portions is a component manufactured separately from the optical box that houses the deflection scanning means and the imaging optical system.
13. The deflection scanning device according to claim 1. 6. The deflection scanning device according to claim 1, wherein at least one of the support portions is a mirror support member that is longer than the length of the folding mirror.