JP2007034167A - Scanning optical apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning optical apparatus case in which a variety of resonance frequencies are prevented with one and the same case structure. <P>SOLUTION: The scanning optical apparatus 51 has deflection scanning means 19 and 20 which deflect and scan a luminous flux generated from a light source 11 with rotating polygon mirrors 12 and 18, an optical box 21 for fixing the deflection scanning means 19 and 20. A plurality of fixing parts 16 for fixing the optical box 21 on an optical base 100 of an image forming apparatus 60 are disposed on the optical box 21, and the optical box 21 is selectively fixed on the optical base 100 at a part or all of the plurality of fixing parts 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning optical device and a color image forming apparatus such as a color laser beam printer or a color digital copying machine using the scanning optical device.

  2. Description of the Related Art Conventionally, there is a scanning optical device that simultaneously forms four electrostatic latent images on an image carrier by simultaneously scanning four light beams on four image carriers arranged in a color image forming apparatus. (For example, refer to Patent Document 1). In this scanning optical device, two light sources are arranged inside the casing, and two light beams emitted from the light sources are scanned symmetrically by a rotating polygon mirror disposed inside the casing. As a result, the light beam is simultaneously scanned symmetrically to prevent positional displacement of the electrostatic latent image formed on the image carrier and provide a good image.

  However, when the rotary polygon mirror rotates, vibration is generated in the housing of the scanning optical device. For this reason, in a scanning optical device having a plurality of deflection scanning means such as a rotating polygon mirror in the casing, the vibration increases as the number increases. Due to this vibration, the performance of the optical element is not sufficiently exhibited, and image deterioration may occur.

  In order to prevent this problem, some devices have been devised so that the natural frequency of the scanning optical device does not coincide with the rotational speed of the deflection scanning means. Specifically, the scanning optical device is configured by combining the structure of the optical box, the selection of materials, the screwing position of the optical box with respect to the optical bench, etc., and avoids the natural frequency (for example, see Patent Document 1). .

JP2004-109806

  However, when there are multiple rotation speeds of the deflection scanning means for driving the scanning optical device, or by using the scanning optical device in common with different models, an attempt to reduce the manufacturing cost by reducing the investment of the mold and production equipment It is disadvantageous to carry out. This is because the resonance frequency that must be avoided differs depending on the configuration of the scanning optical device, and as the number of types of device configuration increases, the resonance frequency that must be avoided also increases.

  An object of the present invention is to provide a scanning optical device casing capable of avoiding many resonance frequencies even in the same casing configuration.

  In order to achieve the above object, a typical configuration according to the present invention includes a deflection scanning unit that deflects and scans a light beam generated from a light source using a rotary polygon mirror, and an apparatus housing for assembling the deflection scanning unit. In the scanning optical device, the apparatus housing includes a plurality of fixing portions for assembling the apparatus housing to the optical bench of the image forming apparatus, and the device housing is provided in a part or all of the plurality of fixing portions. A body is selectively fixed to the optical bench.

  As described above, even in the same casing configuration, the resonance frequency of the apparatus casing can be changed by having a plurality of fixing portions and selecting and fixing a part or all of them. For this reason, the scanning optical apparatus housing | casing which can avoid many resonance frequencies can be provided.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings. In the description, first, the outline of the image forming apparatus and the scanning optical apparatus will be described, and then the detailed configuration of the casing of the scanning optical apparatus will be described.

(Image forming device 60)
FIG. 1 is a schematic cross-sectional view of the image forming apparatus 60. As shown in FIG. 1, an image forming apparatus 60 includes a scanning optical device 51 fixed to an optical bench 100, and photosensitive drums 1Y, 1M, 1C, and 1Bk as image carriers arranged at an equal pitch. A transfer belt 8 and the like are included. The subscripts Y, M, C, and Bk indicate Y (yellow), M (magenta), C (cyan), and Bk (black), respectively. Hereinafter, an image forming operation by the image forming apparatus 60 will be described while explaining the configuration of the image forming apparatus 60 with reference to FIG.

  First, a light beam (laser beam L) light-modulated based on image information is emitted from the scanning optical device 51. The laser beams LY, LM, LC, and LBk irradiate the corresponding photosensitive drums 1Y, 1M, 1C, and 1Bk, respectively, to form an electrostatic latent image on the photosensitive drum 1. The electrostatic latent images are formed on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1Bk that are uniformly charged by the primary chargers 2Y, 2M, 2C, and 2Bk, respectively.

  Then, yellow, magenta, cyan, and black toners are supplied to the electrostatic latent image by the developing devices 4Y, 4M, 4C, and 4Bk, respectively. As a result, the electrostatic latent image on the photosensitive drum 1 is visualized as a toner image.

  The toner images of the respective colors formed on the photosensitive drum 1 are electrostatically transferred by being drawn toward the transfer belt 8 by the transfer rollers 5Y, 5M, 5C, and 5Bk to which a voltage is applied. Then, the toner images of the respective colors are superimposed on the transfer belt 8.

  On the other hand, the transfer material P is stacked on the feeding tray 23 in order to transfer the toner image. Then, the sheets are sequentially fed one by one by the feeding roller 22 and are fed out onto the conveyor belt 7.

  While being transported on the transport belt 7, a color toner image is formed on the surface of the transfer belt 8 as described above. Then, the color toner image is transferred onto the transfer material P of the conveyor belt 7. As a result, a color toner image is transferred and formed on the transfer material P.

  The color toner image formed on the transfer material P is pressurized or overheated by the fixing device 25 and thermally fixed. Finally, by the action of the discharge roller 26 and the like, it is transported outside the apparatus and output outside the apparatus.

  The residual toner remaining on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1Bk is removed by the cleaners 6Y, 6M, 6C, and 6Bk, and the primary charger 2Y, It is charged uniformly by 2M, 2C and 2Bk.

(Schematic configuration of the scanning optical device 51)
FIG. 2 is a perspective view of the scanning optical device 51 of the first embodiment, and FIG. 3 is a top view of the scanning optical device 51 of the first embodiment. As shown in FIG. 2, the scanning optical device 51 is configured by assembling various optical elements to an optical box 21 as a device housing. The optical box 21 is formed of a resin such as plastic. The optical element includes a first scanning lens 13, a second scanning lens 15, and a folding mirror 14 as described below.

  Two light sources 11a, 11b, 11c, and 11d for generating and emitting light beams are arranged in parallel on one side of the side surface of the optical box 21 of the present embodiment. Laser beams (light beams) emitted from the light sources 11a and 11b are incident on different reflecting surfaces of the rotary polygon mirror 12 of the deflection scanning means 19 and scanned. On the other hand, the light beams emitted from the light sources 11 c and 11 d are scanned by the rotary polygon mirror 18 of the deflection scanning means 20.

  The light beams scanned by the rotary polygon mirrors 12 and 18 are transmitted through the first scanning lenses 13a, 13b, 13c, and 13d and the second scanning lenses 15a, 15b, 15c, and 15d, respectively. Images are formed on the drums 1Bk, 1C, 1M, and 1Y.

  As shown in FIGS. 1 to 3, folding mirrors 14a, 14b, 14c, and 14d disposed at the same pitch as the photosensitive drum 1 are disposed between the scanning lens 13 and the scanning lens 15. (The folding mirrors 14b and 14d are not shown in FIG. 2). The folding mirror 14 is arranged at an angle of approximately 45 ° with respect to the incident light beam. As a result, the light beam transmitted through the scanning lens 13 can be reflected at an angle of 90 ° and guided to the scanning lens 15.

(Configuration of the fixing portion 16 of the optical box 21 of the scanning optical device 51)
The optical box 21 of the present embodiment is provided with convex fixing portions 16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, and 16i on the surface thereof. The fixing unit 16 is assembled to the optical table 100 of the image forming apparatus with screws (not shown) or the like. As a result, the scanning optical device 51 is fixedly arranged with respect to the image forming device 60.

  In the present embodiment, nine fixing portions 16 are disposed, but the present invention is not limited to this. That is, a plurality of fixing parts 16 are necessary to maintain high rigidity when the scanning optical device 51 is assembled to the optical bench 100, but the specific number of the fixing parts 16 is not limited. However, when the optical box 21 is fixed to the optical stage 100 at multiple points, the rigidity of the scanning optical device 51 is increased, and the influence on the optical element due to the vibration of the optical box 21 can be suppressed. For this reason, it is preferable to fix and arrange at about nine points as in this embodiment.

  Further, all of the fixing portions 16 may not be fixed to the optical bench 100. By selectively fixing to the optical stage 100, the natural frequency of the optical box 21 can be changed. Also in the present embodiment, since the plurality of fixing portions 16 are provided, the natural frequency can be easily changed by changing the number of fixing portions 16 to be fixed.

  In addition, as described above, some of the fixing portions 16 may not be fixedly disposed to the optical bench 100. At this time, as shown in FIG. 4, the fixing portion 16 that is not fixedly disposed on the optical bench 100 is formed so as not to be in direct contact with the optical bench 100. In this way, the fixing unit 16 that is not fixed and the optical bench 100 do not directly contact each other, so that even if vibration occurs in the optical box 21, the optical bench 100 and the optical box 21 do not collide with each other. For this reason, the noise by the vibration at the time of apparatus operation can be prevented.

  As shown in FIG. 4, the fixed portion 16 is not in contact with the optical bench 100. The diameter of the fixing hole 101 formed in the optical bench 100 is made smaller than the diameter of the convex portion 17 of the fixed bracket 16, as shown in FIG. A gap s is formed between the part 16 and the optical bench 100. The shape that does not come into contact with 100 is not limited to the shape as shown in FIG. 4, and it is sufficient that the optical bench 100 and the fixing portion 16 do not contact each other.

  With the above configuration, when the fixing unit 16 of the scanning optical device 51 is fixedly disposed with respect to the optical table 100, the relationship between the number of the fixing units 16 fixed to the optical table 100 and the natural frequency of the scanning optical device 51 is as follows. explain. Of the fixing portions 16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, and 16i, the natural frequency when the position and number of the actual fixing with respect to the optical bench 100 are selectively changed is shown in FIG. Shown in The horizontal axis represents the natural frequency mode, and the vertical axis represents the frequency.

  The number and location of fixed points in the figure were set as follows. In the case of 3 points, it is fixed at 3 points of the fixed part 16a, the fixed part 16f, and the fixed part 16g. In the case of 4 points, it is fixed at 4 points of the fixed part 16a, the fixed part 16c, the fixed part 16g and the fixed part 16i. In the case of five points, fixing is performed at five points: a fixing portion 16a, a fixing portion 16c, a fixing portion 16e, a fixing portion 16g, and a fixing portion 16i. In the case of 6 points, the fixing part 16a, the fixing part 16c, the fixing part 16d, the fixing part 16f, the fixing part 16g, and the fixing part 16i are fixed.

  As a result, as shown in FIG. 5, it can be seen that the frequency increases as the number of fixed points increases in any natural frequency mode. In this way, by increasing the number of fixing points, the natural frequency of the optical box 21 can be easily changed, and resonance with the rotary polygon mirrors 12 and 18 can be easily avoided. Further, while maintaining the same shape of the optical box 21 at the time of manufacture, a desired natural frequency can be obtained by changing the fixed point for each model. For this reason, the optical box 21 having the same shape can be used for a plurality of models.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a top view of the scanning optical device 51 of the second embodiment. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. In the configuration of this embodiment, a plurality of fixing portions 31 between the deflection scanning means 19 and 20 and the optical box 21 are provided, and all or part of them are fixedly arranged, and the resonance frequency of the scanning optical device 51 is adjusted. is there.

  As shown in FIG. 6, in the optical box 21 of the present embodiment, five fixing portions 31 (31a, 31b, 31c, 31d, 31e) are provided to fix the deflection scanning means 19, 20 and the optical box 21. It has been. In the present embodiment, four of them (31a, 31b, 31c, 31e) are selectively fixed.

  When the deflection scanning means 19 and 20 and the optical box 21 are selectively fixed, the rigidity around the deflection scanning means 19 and 20 changes according to the number and position of the fixed points. When the rigidity around the deflection scanning means 19 and 20 is changed, the natural frequency of the scanning optical device 51 also changes. Thus, by changing the number and position of the fixed points between the deflection scanning means 19 and 20 and the optical box 21, the natural frequency of the scanning optical device 51 can be easily changed to a desired value. .

  With this configuration, the natural frequency of the scanning optical device 51 is changed to a desired value as follows. First, while measuring the vibration of the scanning optical device 51, the number and position of fixed points by screws between the deflection scanning means 19 and 20 and the optical box 21 are changed. Next, it is determined which fixing part 31 should be screw-fixed so that the vibration of the scanning optical device 51 can be suppressed. Finally, in the determined fixing portion 31, the deflection scanning means 19 and 20 and the optical box 21 are fixed with screws.

  In this embodiment, screws are used for fixing, but other fixing methods may be used. Moreover, although this embodiment has five fixing | fixed parts 31 and has fixed four places, it is not restricted to this.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a top view of the scanning optical device 51 of the third embodiment. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. In the configuration of the present embodiment, the cover member 35 that covers the optical box 21 is provided with a plurality of fixing portions 41 for fixing to the optical box 21, and all or a part thereof is fixedly arranged. It is intended to adjust. The lid member 35 is formed with slits 36 (36a, 36b, 36c, 36d) from which light flux is emitted.

  The fixing portion 41 of the lid member 35 is formed at eight locations (41a, 41b, 41c, 41d, 41e, 41f, 41g, 41h) in this embodiment. The optical box 21 and the lid member 35 are screw-fixed at a part or all of the fixing portions 41 provided at the eight locations. In the present embodiment, three portions (41b, 41c, 41f) of the fixing portion 41 are fixed. Here, the natural frequency of the scanning optical device 51 can be easily changed by selectively performing the screw fixing.

  As a result of the examination, if it is fixed in the vicinity of the deflection scanning means 19, 20, the rigidity around the deflection scanning means 19, 20 can be increased, and vibrations generated from the deflection scanning means 19, 20 during driving can be suppressed. I know it. For this reason, if the optical box 21 and the lid member 35 are fixed by the fixing portions 41g and 41h in the vicinity of the deflection scanning means 19 and 20, vibration can be suppressed.

  As described above, by providing a plurality of fixing portions 41 for fixing the optical box 21 and the lid member 35 and selectively fixing a part or all of the fixing portion 41, the natural frequency of the scanning optical device 51 is changed. be able to. Accordingly, when the scanning optical device 51 is manufactured, the number and position of the fixing portion 41 fixed to the screw are changed while measuring the vibration of the scanning optical device 51, and the vibration is suppressed most. The vibration at the time of driving 51 can be suppressed.

  In the present embodiment, three of the eight fixed portions 41 (41b, 41c, 41f) are screw-fixed, but the number and positions of screw fixing are not limited thereto.

[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to the drawings. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 8 is a view showing a state in which the optical box 21 is assembled to the optical bench 100 with a normal screw 222, and FIG. is there.

  In the present embodiment, the fixing of the fixing portion 16 (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, 16i) of the first embodiment is changed. Specifically, fixing several points of the fixing part 16 with normal screws 222 (see FIG. 8) is the same, but the other fixing parts 16 are fixed with stepped screws 223 (see FIG. 9). That is different. The stepped screw 223 fixes the fixing portion 16 and the optical table 100 via, for example, a flat seat spring 224 as an elastic member. Here, the flat spring 224 is pressed against the optical bench 100 by the stepped screw 223, and maintains a certain degree of bending.

  Fig. 3 shows the natural frequency when the position and number of fixing parts 16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, 16i are selectively changed with respect to the optical bench 100 with screws 222. 10 shows. The horizontal axis represents the natural frequency mode, and the vertical axis represents the frequency.

  The number and location of fixed points in the figure were set as follows. When fixing with the screw 222 was performed at three points, the fixing point 16a, the fixing unit 16f, and the fixing unit 16g were fixed, and the other points were fixed with the stepped screw 223. When the fixing with the screws 222 was four points, the four points of the fixing portion 16a, the fixing portion 16c, the fixing portion 16g, and the fixing portion 16i were fixed, and the other points were fixed with the stepped screws 223. When the fixing with the screw 222 was five points, five points of the fixing portion 16a, the fixing portion 16c, the fixing portion 16e, the fixing portion 16g, and the fixing portion 16i were fixed, and the other points were fixed with the stepped screw 223. When fixing with screws 222 is 6 points, fix 6 points of fixing part 16a, fixing part 16c, fixing part 16d, fixing part 16f, fixing part 16g and fixing part 16i, and fix the other with stepped screw 223 did.

  As a result, as shown in FIG. 10, it can be seen that the frequency increases as the number of fixed points increases in any natural frequency mode. In addition, since the stepped screw 223 is used, the natural frequency is significantly higher than when the stepped screw 223 is not used (see FIG. 5). In this way, by using the stepped screw 223 in combination, the width of the natural frequency of the scanning optical device 51 that can be set can be increased, and the degree of freedom in design can be increased.

  In this way, the natural frequency can be changed by changing the number of portions fixed by the screws 222 in the fixing portion 16. Also, by using the stepped screw 223 in combination, it is possible to set a higher natural frequency, and the natural frequency of the scanning optical device 51 is changed in various ways while using the same optical box 21. be able to. For this reason, it is possible to easily avoid resonance with the rotary polygon mirrors 12, 18 and the like and to emit more stable scanning light, so that it is possible to form a stable and high-quality image.

  The natural frequency can also be changed by changing the position of the fixing portion 16 that is fixed by the screw 222. This will be described next. FIG. 11 shows the natural frequency when the fixing method (fixed position) is selectively changed without changing the fixed points as four points.

  The fixing method in the figure was set as follows. In the fixing method 1, the fixing portions 16 a, 16 c, 16 g, and 16 i are fixed with screws 222, and the other fixing portions 16 are fixed with stepped screws 223. In the fixing method 2, the fixing parts 16 a, 16 c, 16 f and 16 g were fixed with screws 222, and the other fixing parts 16 were fixed with stepped screws 223. In the fixing method 3, the fixing portions 16b, 16d, 16f, and 16h are fixed with screws 222, and the other fixing portions 16 are fixed with stepped screws 223.

  As a result, as shown in FIG. 11, the natural frequency varies depending on the fixing method. Thus, the natural frequency of the optical box 21 or the scanning optical device 51 can be easily changed by changing the location to be fixed with the screw.

  Accordingly, if the natural frequency of the optical box 21 and the scanning optical device 51 is set to be different from the natural frequency of the rotary polygon mirrors 12 and 18, the scanning optical device 51 and the rotary polygon mirrors 12 and 18 resonate. This can be easily prevented. Further, although the present embodiment describes the engagement between the optical box 21 and the optical bench 100, the present invention is not limited to this.

FIG. 1 is a schematic cross-sectional view of the image forming apparatus 60. 1 is a perspective view of a scanning optical device 51 according to a first embodiment. FIG. 3 is a top view of the scanning optical device 51 of the first embodiment. Sectional drawing showing the relationship between the fixing | fixed part 16 and optical stand 100 of 1st Embodiment. The figure which shows the experimental result of 1st Embodiment. The top view of the scanning optical apparatus 51 of 2nd Embodiment. The top view of the scanning optical apparatus 51 of 3rd Embodiment. The state figure assembled | attached with the normal screw | thread 222 of 3rd Embodiment. The state figure assembled | attached with the stepped screw 223 of 3rd Embodiment. The figure which shows the experimental result of 3rd Embodiment (changes the number of fixed points). The figure which shows the experimental result of 3rd Embodiment (changes a fixing method).

Explanation of symbols

L ... Laser beam, P ... Transfer material, s ... Gap, 1 ... Photosensitive drum (image carrier), 12 ... Rotating polygon mirror, 13 ... Scanning lens, 16 ... Fixed portion, 18 ... Rotating polygon mirror, 19 ... Deflection Scanning means, 20 ... deflection scanning means, 21 ... optical box (device casing), 31 ... fixed portion, 35 ... lid member, 41 ... fixed portion, 51 ... scanning optical device, 60 ... image forming device, 100 ... optical bench , 222 ... Screws, 223 ... Stepped screws, 224 ... Flat seat spring (elastic member)

Claims (6)

In a scanning optical device having a deflection scanning means for deflecting and scanning a light beam generated from a light source by a rotary polygon mirror, and an apparatus housing for assembling the deflection scanning means,
The apparatus casing is provided with a plurality of fixing portions for assembling the apparatus casing to the optical bench of the image forming apparatus,
A scanning optical apparatus characterized in that the apparatus housing is selectively fixed to the optical bench in a part or all of the plurality of fixing portions. The deflection scanning means is provided with a plurality of fixing portions for assembling the deflection scanning means to the apparatus housing,
The scanning optical apparatus according to claim 1, wherein the deflection scanning unit is selectively fixed to the apparatus housing in a part or all of the plurality of fixing portions. A lid member for protecting the device housing, the lid member being provided with a plurality of fixing portions for assembling the lid member to the device housing;
3. The scanning optical apparatus according to claim 1, wherein the lid member is selectively fixed to the apparatus housing in a part or all of the plurality of fixing portions.   4. The scanning optical apparatus according to claim 3, wherein at least one of the fixing portions for assembling the lid member and the apparatus housing is provided in the vicinity of the deflection scanning unit.   5. The scanning optical device according to claim 1, wherein a fixed portion that is not selected among the fixed portions is assembled via an elastic body. 6. In an image forming apparatus comprising: an image carrier; and a scanning optical device that exposes the image carrier to form an electrostatic latent image.
The image forming apparatus according to claim 1, wherein the scanning optical apparatus is the scanning optical apparatus according to claim 1.

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