JP2008139342A - Light scanning optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a light scanning optical device capable of effectively preventing the deterioration in resist performance due to vibration of an exposure position adjusting motor without damaging print productivity and also preventing the interference of the exposure position adjusting motor with a deflector driving motor. <P>SOLUTION: The light scanning optical device is mounted on a color printer according to a tandem electrophotographic process. A polygon mirror 40 is fixed on a housing 27 with screws 44a via a plate 44. Skew-adjusting motors 51 are arranged in a line partially to the side opposite to the main scanning direction X with respect to fixed positions (screw 44a) of the polygon mirror 40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical scanning optical device, and more particularly, to an optical scanning optical device mounted as a print head in a tandem image forming apparatus using electrophotography.

  In an image forming apparatus such as an electrophotographic tandem printer or copier, three primary colors (Y, M, C) and black (K) are formed on four photoconductors arranged in parallel. Each image is primarily transferred onto the intermediate transfer belt and synthesized, and then further transferred onto the recording material. In this case, in order to prevent color misregistration, it is necessary to adjust the alignment with high accuracy so that the four images are accurately synthesized on the intermediate transfer belt.

  The items of color misregistration adjustment are as shown in FIG. 12 (the white circle indicates the design exposure position and the exposure position shifted from the black circle, respectively), the main scanning print start position, the overall magnification, the partial magnification, and the main scanning higher-order position. Deviation, sub-scan printing start position, skew (scan line inclination), bow (scan line curve), and sub-scan higher-order position deviation can be mentioned.

  Among these, regarding skew adjustment, a mechanism for correcting the tilt in the main scanning direction of a mirror that bends the optical path of each light beam deflected by a polygon mirror, as described in Patent Documents 1 and 2, is described. Yes. However, when skew correction is performed by driving a motor, the vibration of the motor propagates to various optical elements, and there is a risk that the resist performance deteriorates due to uneven pitch and jitter in each color image. In particular, when skew correction is performed between sheets that are continuously passed, this problem appears remarkably because the high-speed machine has a short sheet interval. If the next image forming operation is stopped until the vibration of the motor is attenuated, the print productivity (number of prints per unit time) is sacrificed, which is not preferable.

Further, the polygon mirror is provided with a motor which is a rotational drive source, and this polygon motor and the skew adjusting motor also have a problem that they influence each other.
JP-A-9-269455 JP 2002-283619 A

  Accordingly, an object of the present invention is to effectively prevent deterioration of resist performance due to vibration of an exposure position adjusting motor without impairing print productivity, and an exposure position adjusting motor, a deflector driving motor, It is an object of the present invention to provide an optical scanning optical device that can prevent the interference.

In order to achieve the above object, an optical scanning optical device according to the present invention includes:
A plurality of light sources, a deflector that deflects each light beam emitted from the light source on the same surface, an image forming element that forms an image on each photosensitive member deflected by the deflector, and the light beam respectively A mirror that leads to the corresponding photoconductor, a housing that holds each of these members, and a motor that adjusts the position at which the light beam is exposed on the photoconductor,
A plurality of the motors are arranged in the arrangement direction of the photoconductors,
The plurality of motors are arranged on a side facing the main scanning direction with respect to a fixed position of the deflector to the housing;
It is characterized by.

  In the optical scanning optical apparatus according to the present invention, the exposure position adjusting motor is disposed on the side facing the main scanning direction with respect to the fixed position of the deflector on the housing, and therefore the exposure position adjusting motor vibrates. When reaching the deflector, it is considerably weakened, and the pitch unevenness and jitter of each of the four color images can be suppressed to a predetermined allowable amount, and deterioration of resist performance can be suppressed. Furthermore, mutual interference between the drive motor for the deflector and the exposure position adjusting motor can be avoided.

  The exposure position adjusting motor is, for example, for adjusting the inclination (skew) of the scanning line for exposing the photosensitive member.

  In the optical scanning optical apparatus according to the present invention, it is preferable that the output shaft of the exposure position adjusting motor is provided in parallel to the mounting surface of the deflector. Since the vibration of the motor is generated in the axial direction of the output shaft, if the mounting surface is parallel to the output shaft, the rate at which the vibration is transmitted to the mounting surface is reduced, thereby effectively suppressing the vibration of the deflector. Can do.

  Further, the deflector may be attached to a plate having higher rigidity than the housing and fixed to the housing via the plate. Alternatively, the mounting surface of the housing deflector and the mounting surfaces of the plurality of motors may have a step. With these configurations, it is possible to effectively attenuate the vibration of the exposure position adjusting motor transmitted to the deflector, and to prevent mutual interference between the two motors as much as possible.

  Embodiments of an optical scanning optical device according to the present invention will be described below with reference to the accompanying drawings.

(Overall configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows a schematic configuration of a color printer 1 equipped with an optical scanning optical device according to the present invention. The color printer 1 is configured to synthesize four color images in a tandem manner. That is, the intermediate transfer belt 10 is disposed immediately above the four image forming stations 2 (2Y, 2M, 2C, 2K), and the optical scanning optical device 20 is disposed immediately below. Each image forming station 2 is provided with a photosensitive drum 3 (3Y, 3M, 3C, 3K), a developing device 4 (4Y, 4M, 4C, 4K), a charger (not shown), a residual toner cleaner, and the like. ing. Note that the image forming station 2K for forming a black image is configured in a large size so that a frequently used monochrome image can be formed at high speed.

  The optical scanning optical device 20 forms an image (electrostatic latent image) on each photosensitive drum 3 by the light beams By, Bm, Bc, and Bk emitted based on the Y, M, C, and K image data. This latent image is visualized with toner. Such an electrophotographic process is well known and will not be described.

  The intermediate transfer belt 10 is stretched endlessly around the driving roller 11 and the support roller 12, and the toner images of the respective colors formed on the respective photosensitive drums 3 are sequentially primary-transferred based on the rotation in the arrow Y direction. And synthesized. Further, in order to read an image (adjustment toner pattern) formed on the intermediate transfer belt 10, an optical sensor 71 is disposed immediately after the black image forming station 2K.

  The recording material is stored in the automatic paper feeding cassette 5 and is fed one by one at a predetermined timing, and a composite toner image is transferred from the intermediate transfer belt 10 to the secondary transfer position 13 via the paper passing path 6. After the secondary transfer, the toner is heated and fixed by the fixing device 15, and then discharged from the discharge roller 16 onto the paper discharge unit 9. On the other hand, during double-sided printing, the recording material is conveyed from the switchback roller 17 to the outside of the printer 1, switched back, and returned to the secondary transfer position 13 via the reverse path 7. Here, the recording material on which the toner image is secondarily transferred on the back surface is discharged from the discharge roller 16 onto the paper discharge unit 9.

(Schematic configuration of optical scanning optical device, see FIGS. 2 to 4)
2 is a cross-sectional view of the optical scanning optical device 20 according to an embodiment, FIG. 3 is a plan view, and FIG. 4 is a bottom view. This optical scanning optical device 20 includes a light source unit 21, a polygon mirror 40, first and second imaging lenses 31, 32, folding mirrors 34, 35, 36 provided for each optical path, and a third imaging lens 33. And a housing 27 for holding these members. The light source unit 21 includes a laser diode 22 (22Y, 22M, 22C, 22K), a composite mirror 23 (23Y, 23M, 23C), a folding mirror 24, and a cylindrical lens 25, and is mounted on a plate 26. Yes.

  The light beam emitted from the laser diode 22K is directly guided to the folding mirror 24. The light beams emitted from the laser diodes 22C, 22M, and 22Y are reflected by the combining mirrors 23C, 23M, and 23Y, respectively, and are guided to the folding mirror 24. Each light beam reflected by the folding mirror 24 is condensed by the cylindrical lens 25 substantially parallel to the sub-scanning direction Z (see FIG. 2), and has a predetermined angle in the sub-scanning direction Z on the same surface of the polygon mirror 40. Led.

  These light beams are deflected at a constant angular velocity in the main scanning direction X based on the rotation of the polygon mirror 40, and after passing through the first and second imaging lenses 31, 32, the light beam Bk passes through the third imaging lens 33K. Then, the light is reflected by the folding mirror 34K and exposed / scanned on the photosensitive drum 3K. The light beam Bc is reflected by the folding mirrors 34C and 35C, passes through the third imaging lens 33C, is further reflected by the folding mirror 36C, and exposes / scans the photosensitive drum 3C. The light beam Bm is reflected by the folding mirror 34M, passes through the third imaging lens 33M, is further reflected by the folding mirror 35M, and exposes / scans the photosensitive drum 3M. The light beam By is reflected by the folding mirror 34Y, is transmitted through the third imaging lens 33Y, is further reflected by the folding mirror 35Y, and exposes / scans the photosensitive drum 3Y.

  As shown in FIG. 2, the polygon mirror 40 is attached to a motor 42 fixed to the plate 44. A substrate 41 and a heat radiating plate 43 are further attached to the plate 44.

  Further, in order to detect the writing position of each scanning line on each photosensitive drum 3, that is, to obtain a main scanning synchronization signal, the upstream side beam in the main scanning direction of the beam Bk deflected by the polygon mirror 40 is As shown in FIG. 3, the light is reflected by the detection mirror 37, collected by the lens 38, and enters the sync signal detection light receiving sensor 39.

  Further, as shown in FIG. 3, a partial magnification adjustment mechanism 45 and a skew adjustment mechanism 50 are installed as color misregistration adjustment (registration adjustment). The skew adjustment mechanism 50 includes a stepping motor 51 fixed to the housing 27 via a bracket 59 as a drive source, and details thereof will be described later with reference to FIGS. The description of the partial magnification adjustment mechanism 45 is omitted.

(Color misregistration adjustment, see FIGS. 12 and 13)
For color misregistration (registration) adjustment, toner patterns Py, Pm, Pc, and Pk shown in FIG. 13 are formed at each image forming station 2 and primarily transferred onto the intermediate transfer belt 10, and the toner patterns Py to Pk are transferred. By detecting with the optical sensor 71, all or some of the adjustment items shown in FIG. 12 are adjusted.

(Polygon mirror placement and resist performance, see FIGS. 5-9)
As shown in FIGS. 5 and 6, the housing 27 is formed with a space portion 27a to which the polygon mirror 40 is attached and a space portion 27b to which the motor 51 as a vibration source is attached. A partition wall 27c that separates the portions 27a and 27b from each other is provided. The polygon mirror 40 has a plate 44 fixed to the mounting surface 27a 'of the space 27a by four screws 44a. The motor 51 is disposed in the arrangement direction of the photosensitive drums 3 (see arrow B in FIG. 5), and is disposed on the side facing the main scanning direction X with respect to the fixed position (screw 44a) of the plate 44. The housing 27 is fixed to a frame (not shown) of the color printer 1 by, for example, screwing at three fixing points Z1, Z2, and Z3.

  In the present optical scanning optical device 20, the color misregistration adjustment is performed, for example, when the leading end of the preceding recording material and the leading end of the subsequent recording material that are continuously conveyed are subjected to secondary transfer, including when the printer 1 is started up. This is also done while passing through position 13. If skew has occurred, the motor 51 is driven to displace the third lens 33 to adjust the skew. At this time, vibration generated when the motor 51 is driven propagates to the polygon mirror 40, and the polygon mirror 40 may vibrate, resulting in uneven pitch and jitter in the image, which may deteriorate the resist performance.

  In the present embodiment, the fixing position (screw 44a) of the polygon mirror 40 with respect to the housing 27 is arranged to be deviated to one side from the center line X ′ in the main scanning direction X, and the skew adjustment motor 51 is fixed to the fixing position (screw). 44a), the vibration of the motor 51 is considerably attenuated when reaching the polygon mirror 40, and the image pitch unevenness and jitter are reduced. It becomes below a predetermined allowable amount, and deterioration of resist performance can be suppressed.

  The polygon mirror 40 is disposed in the space 27a, the motor 51 is disposed in the space 27b, and the partition wall 27c is interposed between the spaces 27a and 27b. Is considerably attenuated when it reaches the polygon mirror 40.

  Here, vibration will be described. For example, the vibration of the motor 51 is a waveform A having an amplitude A1 shown in FIG. 7. When this vibration propagates through the housing 27 and is transmitted to the polygon mirror 40, a waveform B having an amplitude A2 is obtained. FIG. 8 shows the amplitude with respect to time, the curve D1 shows the conventional characteristics, and the curve D2 shows the characteristics of the present invention. Conventionally, at time T1, the amplitude A1 of the motor 51 is transmitted to the polygon mirror 40 almost as it is, but in the present invention, it is attenuated to the amplitude A2 (the amplitude is reduced).

  As shown in FIG. 9, when the polygon mirror 40 vibrates with an amplitude A1 as in the prior art, the pitch unevenness exceeds an allowable value, resulting in deterioration of resist performance. However, according to the present invention, since the amplitude of the polygon mirror 40 is attenuated to A2 which is less than or equal to the allowable value, deterioration of resist performance can be effectively suppressed.

  Further, a step E (see FIG. 5) may be formed between the attachment surface 27a 'for attaching the polygon mirror 40 of the housing 27 and the attachment surface 27b' of each motor 51. The vertical wall portion 27 c ′ provided at the step E effectively attenuates the vibration of the motor 51.

  In addition, the plate 44 that holds the polygon mirror 40 may be made of a material that is more rigid than the housing 27. For example, when the housing 27 is made of a resin material such as polycarbonate, the plate 44 is made of a metal material such as aluminum. Even in this case, the vibration of the motor 51 can be effectively attenuated.

  On the other hand, the rotation motor 42 of the polygon mirror 40 also generates vibration. The problem that the polygon motor 42 and the skew adjustment motor 51 affect each other also attenuates the vibration of the motor 51 as described above. It is solved by the configuration.

(Skew adjustment mechanism, see FIGS. 10 and 11)
The inclination (skew) of the scanning line is adjusted for the light beams Bc, Bm, and By using the light beam Bk as a reference. Therefore, the skew adjustment mechanism 50 shown in FIG. 10 is not installed for the third lens 33K arranged for the light beam Bk, but the third lenses 33C, 33c arranged for the light beams Bc, Bm, By. It is installed for 33M and 33Y. It goes without saying that skew adjustment may also be performed on the light beam Bk.

  Specifically, as shown in FIG. 11, the third lens 33 is held by a lens holder 52, and this lens holder 52 is supported by a pin 53 so that it can swing in the direction of arrow F at one end. Further, a receiving member 58 is fixed to the other end portion of the lens holder 52. As shown in FIG. 10, the receiving member 58 is pressed against the inclined surface 27g of the housing 27 by the leaf spring 54, and in the direction of arrow F. It is slidably attached to. The worm gear 55 fixed to the output shaft 51 a of the stepping motor 51 meshes with the worm wheel 56, and the outer peripheral surface of the eccentric cam 57 fixed coaxially with the worm wheel 56 is in contact with the bottom surface of the receiving member 58.

  The rotation of the stepping motor 51 is controlled in accordance with the state of skew detected from the toner patterns Py to Pk shown in FIG. 13, and the rotation of the worm gear 55 is transmitted from the worm wheel 56 to the eccentric cam 57 to be eccentric. The outer peripheral surface of the cam 57 pushes up the receiving member 58 to displace the third lens 33 together with the holder 52 to adjust the skew. The holder 52 is biased so as to be forcibly returned downward by a spring member (not shown).

  The output shaft 51a of the stepping motor 51 is provided in parallel to the mounting surface 27a 'of the polygon mirror 40. Since the worm gear 55 that meshes with the worm wheel 56 is attached to the output shaft 51a, the vibration of the motor 51 is generated in the axial direction of the output shaft 51a. Therefore, if the mounting surface 27a 'is parallel to the output shaft 51a, the rate at which vibration is transmitted to the mounting surface 27a' is reduced, and the vibration of the polygon mirror 40 can be effectively suppressed.

(Other examples)
The optical scanning optical device according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  In particular, the detailed configuration of the housing, the detailed configuration of the light source unit, and the configuration and arrangement of various optical elements forming the four optical paths are arbitrary. The skew adjustment may be performed by displacing a folding mirror or the like in addition to displacing the third lens.

1 is a schematic configuration diagram illustrating a color printer including an optical scanning optical device according to the present invention. It is sectional drawing which shows an optical scanning optical apparatus. It is a top view which shows an optical scanning optical apparatus. It is a bottom view which shows an optical scanning optical apparatus. It is sectional drawing which shows the arrangement | positioning relationship between a polygon mirror and a skew adjustment motor in an optical scanning optical apparatus. It is a top view which shows the arrangement | positioning relationship between a polygon mirror and a skew adjustment motor in an optical scanning optical apparatus. It is a chart figure which shows the vibration waveform of the motor for skew adjustment, and the vibration waveform of a polygon mirror. It is a graph which shows the relationship between the amplitude of a polygon mirror, and time. It is a graph which shows the relationship between the amplitude of a polygon mirror, and pitch nonuniformity. It is a perspective view which shows a skew adjustment mechanism. It is a perspective view which shows the holding | maintenance part of a 3rd lens. It is explanatory drawing which shows the kind of color shift. FIG. 6 is an explanatory diagram illustrating a toner pattern for color misregistration adjustment.

Explanation of symbols

3 (3Y, 3M, 3C, 3K) ... photosensitive drum 20 ... light scanning optical device 21 ... light source 27 ... housing 31,32,33 ... imaging lens 34,35,36 ... folding mirror 40 ... polygon mirror 44 ... Plate 44a ... Screw (fixed position)
51 ... Motor for skew adjustment 51a ... Output shaft E ... Step X ... Main scanning direction

Claims (5)

A plurality of light sources, a deflector that deflects each light beam emitted from the light source on the same surface, an image forming element that forms an image on each photosensitive member deflected by the deflector, and the light beam respectively A mirror that leads to the corresponding photoconductor, a housing that holds each of these members, and a motor that adjusts the position at which the light beam is exposed on the photoconductor,
A plurality of the motors are arranged in the arrangement direction of the photoconductors,
The plurality of motors are arranged on a side facing the main scanning direction with respect to a fixed position of the deflector to the housing;
An optical scanning optical device.   2. The optical scanning optical apparatus according to claim 1, wherein the motor is for adjusting the inclination of a scanning line for exposing the photosensitive member.   The optical scanning optical apparatus according to claim 1, wherein an output shaft of the motor is provided in parallel to a mounting surface of the deflector.   4. The optical scanning optical apparatus according to claim 1, wherein the deflector is attached to a plate having a higher rigidity than the housing, and is fixed to the housing through the plate.   5. The optical scanning optical device according to claim 1, wherein the mounting surface of the deflector of the housing and the mounting surface of the plurality of motors have a step.

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