JP5111026B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device suitable for a so-called tandem type image forming apparatus that scans a plurality of laser beams to simultaneously expose a plurality of photosensitive members.

  Conventionally, an optical scanning device used in a tandem color image forming apparatus that forms cyan, magenta, yellow, and black images on four photoconductors and forms a full color image by superimposing them on an intermediate transfer member or recording paper. There is. This optical scanning apparatus can obtain a high-quality color image by accurately exposing a laser beam to a desired position on the photosensitive member. Here, for example, the following configurations have been proposed for the purpose of reducing color misregistration and pitch unevenness.

  In Patent Document 1, it is proposed to suppress changes in the posture and position of the optical element by pulling the cover against the optical box.

  In Patent Document 2, it is proposed to reduce vibration of the optical scanning device by fastening a cover to the optical box at a plurality of locations.

  In Patent Document 3, it is proposed that a reinforcing member made of a material having a smaller linear expansion coefficient than that of the optical box is provided along the light source and the optical path to suppress fluctuations in the optical axis height at the time of temperature rise.

JP 2006-150687 JP2000-258712 JP2006-259545

  However, there has been a demand for both reducing vibration of the optical scanning device, suppressing distortion of the optical box of the optical scanning device due to fastening of the cover, and suppressing displacement of the optical element.

  An object of the present invention is to achieve both the reduction of the vibration of the optical scanning device and the suppression of the displacement of the optical element due to the distortion of the optical box, thereby improving the image quality.

In order to achieve the above object, a typical configuration according to the present invention includes a deflector for deflecting laser light emitted from a light source, and a box in which an opening is formed and the deflector is held inside the opening . and optical box shape, said having a cover which is fastened to the optical box in a state where the opening was Tsu covering the optical box, wherein the optical box arranged in the main scanning direction, which is supported by the image forming unit more In the optical scanning device that performs deflection scanning with the laser light on the photosensitive member of the image forming unit in a state where the optical box is supported by the image forming unit , the cover includes the optical box. includes a cover body covering the opening portion, and two cover fastening part that will be fastened to the optical box is arranged in the main scanning direction so as to sandwich the cover main body, the optical box, the two covers Fastened with each of the fastening parts Two equipped with optical box fastening portion that, the two optical box fastening portion is disposed in the vicinity of each of the support portions, each of said two cover fastening portion, the width in the direction orthogonal to the main scanning direction It is a plate-shaped protrusion part which protruded from the said cover main-body part smaller than the width | variety of the said cover main-body part, It is characterized by the above-mentioned.

  Since the present invention has the configuration as described above, when the cover is fastened to the optical box, it is avoided that the optical box is distorted by the rigidity of the cover and the posture of the imaging lens and the reflection mirror is changed. This contributes to providing a color image with little color misregistration. At the same time, the natural frequency is increased by increasing the rigidity of the optical box. As a result, there is no need to use means for increasing the cost, such as increasing the thickness of the optical box or changing the material of the optical box to a material with higher strength. Further, it is possible to prevent image unevenness due to a shift of the scanning position on the surface of the photosensitive member while reducing vibration of the optical box, and to improve image quality.

  The cover has a plate-like portion protruding from the outer periphery of the cover, and the plate-like portion straddles the opening of the optical scanning device and in the vicinity of any two points fixed to the image forming apparatus. To form a portion that bends independently in the fastening direction. As a result, the same effect as described above can be realized without adding any parts.

  In addition, the plate-like member or cover has the same linear expansion coefficient as that of the optical box, so that the above effect is maintained and the optical box is distorted due to the difference in the linear expansion coefficient when the ambient temperature changes. It avoids changing the posture of the image lens and the reflecting mirror.

[First Embodiment]
A first embodiment of the present invention will be described with reference to the drawings.

(Image forming device)
A schematic configuration of the image forming apparatus 15 will be described with reference to FIG. 1A and 1B are cross-sectional views illustrating the configuration of the image forming apparatus 15, where FIG. 1A is an overall cross-sectional view of the image forming apparatus, and FIG.

  As shown in FIG. 1, the image forming apparatus 15 includes an optical scanning device 16 (16a, 16b). In the present embodiment, each light beam (laser light) 3C, 3Y, 3M, and 3K that is optically modulated based on image information is emitted from the optical scanning devices 16a and 16b. Each light beam 3 irradiates the corresponding photoreceptors 1C, 1Y, 1M, and 1K as image carriers to form a latent image on the photoreceptor 1. The latent images are visualized as cyan C, yellow Y, magenta M, and black K toner images by the developing devices 4C, 4Y, 4M, and 4K, respectively. A color image is obtained by superimposing these images. The color image is transferred to a recording material such as plain paper and fixed by a fixing device, whereby the color image formed on the photoreceptor 1 is fixed to the recording material.

(Optical scanning device)
A schematic configuration of the optical scanning device 16 will be described with reference to FIG. FIG. 2 is a diagram illustrating the internal configuration of the optical scanning device 16. The light beam 3 emitted from the light source 10 disposed above and below in the Z direction is condensed on the light beam reflecting surface 22 of the rotary polygon mirror (deflector) 21. The rotary polygon mirror 21 is rotationally driven by a drive motor constituting the deflector 23 and deflects and scans the incident light beam 3. The deflected first light beam 3C passes through the first fθ lens 20, is reflected by the reflection mirror 24, passes through the second fθ lens 25, and is condensed and scanned on the photosensitive member 1C, thereby forming an electrostatic latent image. Are formed on a predetermined imaging plane. The deflected second light beam 3Y passes through the first fθ lens 20, is reflected by the reflection mirror 26 and the reflection mirror 27, then passes through the second fθ lens 28, and is condensed and scanned on the photoreceptor 1Y. Then, an electrostatic latent image is formed. Optical parts such as the deflector, reflecting mirror, and fθ lens (imaging lens) described above are held in an optical box 29 made of resin. The upper opening of the optical box 29 is closed by a cover 19 (see FIGS. 1 and 3).

(Fixing of optical scanning device to image forming device)
A method for fixing the optical scanning device 16 to the image forming apparatus 15 will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a diagram illustrating a state in which the optical scanning device of the present embodiment is mounted on the image forming apparatus 15. FIG. 4 is an enlarged view of the opening holes 34 and 35 formed in the image forming apparatus 15. FIG. 5 is an enlarged view of the long hole 36 formed in the image forming apparatus 15.

  As shown in FIG. 3, the frame (frame body) of the image forming apparatus 15 includes a left side plate 30, a right side plate 31, a scanner stay 32, and an intermediate plate 33. The left side plate 30 and the right side plate 31 are provided with opening holes 34 and 35 for fixing and supporting the optical scanning device 16, respectively.

  In this embodiment, the optical scanning device is fixed at three points with respect to the image forming apparatus. Specifically, it is fixed in two opening holes and one scanner stay. By fixing at three points in this way, the optical scanning device is prevented from being distorted when the optical scanning device is mounted on the image forming apparatus.

  As shown in FIG. 4, in the opening holes 34 and 35, reference surfaces 34x and 35x serving as attachment references in the X direction are formed. Similarly, in the opening holes 34 and 35, reference surfaces 34z and 35z serving as attachment references in the Z direction are formed. The scanner stay 32 has a reference surface 32z (see FIG. 1B) serving as a reference for attachment in the Z direction. The optical scanning device 16 projects the reference surfaces 50x, 50z, 51x, 51z, and 52z of the support portions 50, 51, and 52 provided in the optical box 29 against the reference surfaces 34x, 34z, 35x, 35z, and 32z of the frame. Hit it. Specifically, as shown in FIG. 4, the reference plane 50x is abutted against the reference plane 34x and the reference plane 35x of the frame, and the reference plane 50z is abutted against the reference plane 34z and the reference plane 35z of the left side plate 30 of the frame. Hit it. Further, 51x and 51z (not shown) are abutted against the reference surfaces 34x, 35x, 34x and 34z of the right side plate 31 of the frame. Then, as shown in FIG. 1B, the reference surface 52z is abutted against the reference surface 32z of the scanner stay 32 of the frame. As a result, positioning is performed in the X and Z directions. That is, the optical scanning device 16 is supported by the body frame at two points in the X direction and at three points in the Z direction.

  As shown in FIG. 5, a long hole 36 is provided in the lower middle plate 33 of the optical scanning device 16. The optical scanning device 16 is positioned in the Y direction by fitting a reference boss 57 formed on the bottom of the optical box 29 into the elongated hole 36.

  In this way, the optical scanning device 16 positioned on the main body frame is fixed by the fixing means at the three points of the opening holes 34 and 35 and the reference surface 32z. In this way, by arranging two optical scanning devices 16 that emit two scanning lines, four scanning lines are emitted, and scanning lines corresponding to the photoreceptors 1C, 1Y, 1M, and 1K are obtained.

(Structure of beam)
A plate-like beam (beam) 100, which is a feature of this embodiment, will be described with reference to FIG. FIG. 6 is a view showing a state in which the beam 100 is attached to the optical scanning device 16.

  As shown in FIG. 6, the plate-like beam 100 is disposed on the opening side (the side with the opening U) on the optical box 29. The beam 100 straddles the opening U of the optical box 29 and is fastened by screws at two fastening portions 100a and 100b near the support portion 50 and near the support portion 51 of the optical scanning device 16. Since the plate-like beam 100 is weak in the bending direction B, there is an effect of suppressing deformation of the optical box 29 when the plate-like beam 100 is fastened. For example, when the flatness of the fastening portions 100a and 100b of the plate-like beam 100 and the flatness of the fastening portions 29c and 29d of the optical box 29 do not match, the flatness does not match because the plate-like beam 100 is bent (or twisted). To absorb. As a result, deformation of the optical box 29 is suppressed. As a result, the posture of the optical element in the optical box 29 is hardly changed, and the change in the position of the scanning line on the photosensitive member can be suppressed, and a color image with little color shift can be provided. Further, the flexural strength in the longitudinal direction is 1.5 times or more the flexural strength in the fastening direction. For this reason, the plate-like beam has a shape that suppresses bending in the longitudinal direction and is easily bent in the fastening direction.

(Vibration in optical box)
The vibration in the optical box will be described with reference to FIG. FIG. 7 is a diagram schematically illustrating a deformation when the vibration of the lowest frequency natural frequency (first mode) in the optical box 29 is generated.

  The primary mode vibration of the optical box 29 vibrates in the direction in which the opening U (see FIG. 2) opens or closes as illustrated. That is, the deformation | transformation which the support parts 50 and 51 of the optical scanning device 16 approach or leave is produced.

  As shown in FIG. 7, the plate-like beam 100 is weak in the arrow B direction (bending direction, fastening direction) and strong in the arrow T direction (tensile direction, longitudinal direction). Since the deflection strength in the tension direction T of the beam 100 is stronger than the deflection strength in the B direction, when the plate-like beam 100 is fastened with screws near the support portions 50 and 51 of the optical scanning device 16, the optical scanning device 16 is supported. The deformation | transformation which the parts 50 and 51 approach or move away can be suppressed. Thereby, the vibration frequency of the primary mode of the optical box 29 can be increased by about 10 to 30 Hz. The cause of the vibration of the optical box 29 is a vibration generated mainly by meshing of a gear used for transporting a recording material such as paper or driving an image carrier. Changing the frequency of 10 to 30 Hz is effective to avoid the frequency that causes vibration.

  Further, by moving the fixed interval of the plate-like beam 100, the amount of change in the resonance frequency can be controlled. This will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the fixed interval of the plate-like beam 100 and the amount of change in frequency. In FIG. 8, the horizontal axis represents the amount of change in the resonance frequency, and the vertical axis represents the fixed interval of the plate-like beam 100.

  As shown in FIG. 8, it can be seen that when the fixed interval of the beam 100 is shortened, the amount of change in the resonance frequency increases. As described above, the fixing portions 29 a and 29 b of the optical box 29 are widely formed so that a plurality of intervals for fastening the plate-like beam 100 to the optical box 29 can be selected. Moreover, it was set as the structure which can change the space | interval of the part fastened by the fastening part 100a of the beam 100, and the part fastened by the fastening part 100b. As a result, a more optimal frequency can be selected.

  The linear expansion coefficient of the beam in the present embodiment is preferably the same linear expansion coefficient as that of the optical box 29. Even if the optical box expands and contracts depending on the environment, the beam expands and contracts accordingly. Therefore, the distortion of the optical box is suppressed and the change in the attitude of the optical element is avoided while maintaining the effect of the beam.

[Second Embodiment]
A second 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. 9 is a diagram illustrating the configuration of the optical scanning device 16 according to the second embodiment.

  As shown in FIG. 9, protruding plate-like fastening portions 19 a and 19 b are provided on the outer peripheral portion of the cover 19 that covers the optical box 29. The fastening portions 19a and 19b are fastened to the fastening portions 29a and 29b of the optical box 29 in the same manner as in the first embodiment. In other words, the cover 19 is fastened in the vicinity of two arbitrary points that cross the opening U of the optical scanning device 16 and are fixed to the image forming device 15. Thus, the site | part which bends in a fastening direction independently is formed.

  The protruding plate-like fastening portions 19a and 19b are weak in the arrow B direction (bending direction, fastening direction) and in the arrow T direction (tensile direction, longitudinal direction), like the plate-like beam 100 of the first embodiment. Is strong. Therefore, the same effects as those of the first embodiment can also be obtained by providing the plate-like fastening portions 19 a and 19 b protruding from the cover 19. The fastening portions 19a and 19b of the cover 19 are less likely to deform the optical box 29 as the protruding amount increases.

  Note that the linear expansion coefficient of the cover 19 in this embodiment is preferably the same linear expansion coefficient as that of the optical box 29. Even if the optical box expands and contracts depending on the environment, the cover 19 also expands and contracts accordingly. Therefore, the distortion of the optical box is suppressed and the change in the posture of the optical element is avoided while maintaining the function and effect of the cover 19. .

FIG. 3 is a cross-sectional view illustrating the configuration of the image forming apparatus 15. The figure explaining the internal structure of the optical scanning device 16. FIG. 3 is a diagram showing a state in which the optical scanning device is mounted on the image forming apparatus 15. FIG. 3 is an enlarged view of opening holes 34 and 35 formed in the image forming apparatus 15. FIG. 3 is an enlarged view of a long hole 36 formed in the image forming apparatus 15. The figure which showed the state which attached the beam 100 to the optical scanning device 16. FIG. The figure which modeled the deformation | transformation at the time of producing the vibration of the natural frequency (primary mode) of the lowest frequency in the optical box 29. FIG. The graph which shows the relationship between the fixed space | interval of plate-shaped beam 100, and the variation | change_quantity of a frequency. The figure explaining the structure of the optical scanning device 16 which concerns on 2nd Embodiment.

Explanation of symbols

  U ... opening, 1 ... photoconductor, 3 ... light beam, 10 ... light source, 16 ... optical scanning device, 19 ... cover, 19a ... fastening part, 19b ... fastening part, 20 ... fθ lens, 21 ... rotating polygon mirror, 22 DESCRIPTION OF SYMBOLS ... Light beam reflective surface, 23 ... Deflector, 25 ... f (theta) lens, 26 ... Reflection mirror, 27 ... Reflection mirror, 28 ... f (theta) lens, 29 ... Optical box, 50 ... Support part, 51 ... Support part, 100 ... Beam, 100a ... Fastening part, 100b ... Fastening part

Claims (5)

A deflector for deflecting the laser light emitted from the light source;
A box-shaped optical box having an opening formed therein and holding the deflector inside the opening ;
A cover that is fastened to the optical box in a state where Tsu covering an opening of the optical box,
The optical box includes a plurality of support portions arranged in the main scanning direction supported by the image forming unit, and the optical box is supported by the image forming unit on the photosensitive member of the image forming unit. In an optical scanning device that performs deflection scanning with the laser beam ,
The cover includes a cover body for covering an opening of the optical box, and a two cover fastening part that will be fastened to the optical box is arranged in the main scanning direction so as to sandwich the cover main body,
The optical box includes two optical box fastening parts fastened to the two cover fastening parts, respectively, and the two optical box fastening parts are arranged in the vicinity of the support part,
Each of the two cover fastening portions is a plate-like protruding portion protruding from the cover main body portion having a width in a direction orthogonal to the main scanning direction smaller than the width of the cover main body portion. Optical scanning device. The optical scanning device according to claim 1 , wherein the cover has the same linear expansion coefficient as the optical box. An image forming apparatus comprising the optical scanning device according to claim 1 and the image forming unit and forming an image on a recording material . The image forming unit includes a first side plate and a second side plate provided to face each other,
The image forming apparatus according to claim 3, wherein the plurality of support portions of the optical box are respectively supported by the first side plate and the second side plate . The image forming unit includes a stay provided between the first side plate and the second side plate,
The optical box includes another support portion provided between the plurality of support portions in the main scanning direction, and the another support portion is supported by the stay. The image forming apparatus described .