JP2007241086A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner equipped with a correcting mechanism for position and posture, and an image forming apparatus. <P>SOLUTION: The optical scanner deflects luminous flux from a light source by a deflecting means and converges the deflected luminous flux into a light spot on a scanned surface by an imaging optical system to make an optical scan. The optical scanner includes a holding means of holding at least one or more optical elements constituting the imaging optical system from a vertical scanning direction and two or more driving means having operation points in the vertical scanning direction substantially on the same planes of the optical elements in a horizontal scanning direction, and suitably corrects the tilt and scanning position of a scanning line by the holding means and driving means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus provided with a position and orientation correction mechanism.

  The light beam from the light source is deflected by the light deflecting means of the rotary polygon mirror, and the deflected light beam is condensed toward the scanned surface using a scanning imaging optical system such as an fθ lens. 2. Description of the Related Art An optical scanning device that forms a light spot and scans a surface to be scanned with the light spot is widely known as being mounted on an image forming apparatus such as an optical printer, an optical plotter, or a digital copying machine.

  In an image forming apparatus using an optical scanning device, an image writing step of writing an image by optical scanning is adopted as one step in the image forming process. The quality of an image formed by the image process is light. It is influenced by the quality of scanning. The quality of optical scanning depends on the scanning characteristics of the optical scanning device in the main scanning direction and the sub-scanning direction.

  One of the scanning characteristics in the main scanning direction of the optical scanning device is the constant speed of optical scanning. For example, when a rotating polygon mirror is used as the light deflecting means, the light beam is deflected at a constant angular velocity. Therefore, in order to realize the constant speed of the optical scanning, a scanning imaging optical system having an fθ characteristic is used. Used.

  However, it is not easy to realize perfect fθ characteristics due to the relationship with other performance required for the scanning imaging optical system. For this reason, in the actual optical scanning, the optical scanning is not performed at a completely constant speed, and the constant speed as the scanning characteristic is accompanied by a deviation from the ideal constant speed scanning.

  Further, scanning characteristics in the sub-scanning direction in the optical scanning device include scanning line bending and scanning line inclination. A scanning line is a movement locus of a light spot on a surface to be scanned such as a belt-shaped or drum-shaped photoconductor, and is ideally a straight line, and the optical scanning device is designed so that the scanning line is a straight line. Done. However, in practice, the scanning line is usually bent due to processing errors or assembly errors of the optical elements or mechanical parts.

  In principle, when an imaging mirror is used as the scanning imaging optical system and an angle is formed in the sub-scanning direction of the deflected light beam between the incident direction and the reflected direction of the deflected light beam, Even when the scanning line is bent and the scanning imaging optical system is configured as a lens system, the scanning line is bent in the multi-beam scanning method in which the scanning surface is optically scanned with a plurality of light spots separated in the sub-scanning direction. Inevitable.

  On the other hand, the inclination of the scanning line is a phenomenon in which the scanning line is not correctly orthogonal to the sub-scanning direction, and is a kind of bending. Therefore, in the following description, unless otherwise specified, the inclination of the scanning line is included in the expression “bending of the scanning line”.

  If the constant speed of optical scanning is not perfect, distortion in the main scanning direction occurs in the formed image, and scanning line bending causes distortion in the sub-scanning direction in the formed image. When an image is so-called monochrome and written by a single optical scanning device, scanning line bending or imperfection of isokineticity that deviates from the ideal isokinetic scanning can be suppressed to some extent. The formed image is not distorted so as to be visually recognized. However, such image distortion is as small as possible.

  In addition to the monochrome image, three colors of magenta (M), cyan (C), yellow (Y), or four colors with black (B) added thereto are formed as color component images. Conventionally, a color image is formed synthetically by superimposing component images on a color copying machine or the like.

  As one of the methods for forming such a color image, an image for each color component is formed on a photoconductor capable of forming an image for each color component by using an optical scanning device provided for each color component. There is a so-called tandem type image forming method. In the case of such an image forming method, if the scanning line curvature or inclination differs between the optical scanning devices, even if the scanning line bending for each optical scanning device is corrected, An abnormal image called “deviation (positional deviation)” appears, and the image quality of the color image deteriorates.

  Further, as a cause of color misregistration, there is also a cause due to speed fluctuation of not only an optical system but also a driving system such as a photoreceptor and an intermediate transfer belt. Furthermore, if the thickness of the intermediate transfer belt varies, the linear velocity fluctuates, and if this is transferred in an overlapping manner, further color misregistration occurs.

  Further, as a way of causing the color misregistration phenomenon, there is a phenomenon that the color tone in the color image does not become a desired one. As a prior art for preventing the occurrence of such problems as color misregistration, the invention disclosed in Patent Document 1 is known. In Patent Document 1, an adjustment unit using an adjustment screw that is movable in the optical axis direction of the long lens is provided on one side of the support unit that sandwiches the optical axis of the long lens that forms the imaging optical system in the sub-scanning direction. In addition, a configuration is disclosed in which scanning line bending is corrected by rotating and adjusting a long lens within a cross section perpendicular to the deflection scanning direction by tightening the adjustment screw.

As a prior art related to the scanning line inclination correction mechanism, the invention disclosed in Patent Document 2 is known. Patent Document 2 includes a holding unit that holds the imaging lens, and the holding unit is swingably attached to the housing with the position of the holding unit corresponding to the center in the longitudinal direction of the imaging lens as a rotation center. The configuration is disclosed.
JP 2002-131694 A JP 2003-262816 A

  However, in the configuration shown in Patent Document 1 described above, there is a case where the scanning line bending cannot still be corrected with respect to environmental fluctuations in which the material of the lens used in the imaging optical system to be adjusted is affected. is there. The reason is as follows.

  In recent years, in order to improve scanning characteristics, it has become common to adopt special surfaces typified by aspherical surfaces in the imaging optical system of optical scanning devices, and such special surfaces can be easily formed. An imaging optical system made of a resin material that can be manufactured at a low cost is often used. An imaging optical system made of a resin material is susceptible to changes in temperature and humidity due to changes in temperature and humidity, and such changes in optical characteristics change the degree of scanning line bending and the constant velocity. For this reason, for example, when several tens of color images are continuously formed, the temperature in the apparatus rises due to continuous operation of the image forming apparatus, and the optical characteristics of the imaging optical system change. The bending and constant speed of the scanning line written by the writing device change gradually, and due to the phenomenon of color misregistration, the color image obtained in the initial stage and the color image obtained in the final stage will be completely different. There is.

  A scanning imaging lens such as an fθ lens, which is a typical scanning optical system, is generally formed as a strip-shaped lens that is long in the main scanning direction by cutting a lens unnecessary portion (portion where no deflected light beam is incident) in the sub-scanning direction. When the scanning imaging lens is composed of a plurality of lenses, the lens length in the main scanning direction increases as the arrangement position moves away from the light deflecting unit, and the length of the tens of centimeters to 20 centimeters or more is increased. A long lens is required. Such a long lens is generally formed by resin molding using a resin material. However, if the temperature distribution in the lens becomes non-uniform due to a change in the external temperature, the lens will warp and the lens will not bow in the sub-scanning direction. It becomes a shape. Such warping of the long lens causes the above-described scanning line bending, but when the warping is significant, the scanning line bending is extremely generated.

  Such a phenomenon occurs even when the initial adjustment is performed using the configuration shown in Patent Document 1. In addition, in the configuration of Patent Document 1, no countermeasure is taken against the inclination of the scanning line that causes problems such as color misregistration other than scanning line bending. Further, the configuration disclosed in Patent Document 1 has a problem in that it is difficult to ensure positioning accuracy because positioning in the optical axis direction changes depending on how the screws are fastened.

  In addition, it is possible to correct the scanning line tilt by swinging the imaging lens about the optical axis using the configuration disclosed in Patent Document 2, but in the case where an in-machine temperature fluctuation occurs. Is not configured to suppress fluctuations in scanning line bending, and therefore, the imaging lens is warped, and scanning line bending fluctuations occur.

  In view of such a problem, the present invention provides a holding unit that holds an optical element from the sub-scanning direction, and at least two or more driving units that have an action point with respect to the sub-scanning direction on substantially the same plane in the main scanning direction. It is an object to provide an optical scanning device and an image forming apparatus having the above.

  In order to achieve the above object, according to the first aspect of the present invention, the light beam from the light source is deflected by the light deflecting means, and the deflected light beam is condensed as a light spot on the surface to be scanned by the imaging optical system. An optical scanning device that performs optical scanning, the holding means for holding at least one or more optical elements constituting the imaging optical system from the sub-scanning direction, and substantially the same plane in the main scanning direction of the optical elements, And at least two drive means having an action point with respect to the sub-scanning direction.

  According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the holding unit has a holding member that holds the optical element by pressing in the sub-scanning direction, and the optical element is sub-scanned by the holding member. The holding member and the driving means are integrated by sandwiching and pressing from two directions.

  According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the driving means is constituted by a differential gear mechanism having a stepping motor, a screw, and a gear.

  According to a fourth aspect of the present invention, in the optical scanning device according to any one of the first to third aspects, the optical scanning device includes a scanning line bending correcting unit that corrects a scanning line bending of the optical element, At least two of the driving means include a pressing member that is disposed outside both ends of the optical element in the main scanning direction and that presses the scanning line bending correction means in the sub-scanning direction, and includes a plurality of driving means. It is selectively operated to correct the inclination and position of the scanning line.

  According to a fifth aspect of the present invention, in the optical scanning device according to the fourth aspect, the pressing member is a leaf spring, and one of the end portions of the leaf spring is fastened to the scanning line bending correction means, and the end portion The other of the two is fastened to a fixed portion that forms a part of the outline of the optical scanning device, and an axis that connects a plurality of action points of a plurality of driving means is substantially coaxial with an axis that connects a plurality of action points of a leaf spring. Alternatively, the leaf spring is provided so as to be in a plane connecting a plurality of action points of the leaf spring.

  According to a sixth aspect of the present invention, in the optical scanning device according to any one of the first to fifth aspects, a color misregistration detecting means for detecting a color misregistration of an image formed in the vicinity of the intermediate transfer member, and an intermediate It has a thickness fluctuation detecting means for detecting the fluctuation of the thickness of the transfer body, and controls the driving means based on the detection results of the color misregistration detecting means and the thickness fluctuation detecting means.

  According to a seventh aspect of the present invention, in the optical scanning device according to the sixth aspect, the thickness fluctuation detecting means controls the driving means based on the period of the thickness fluctuation of the intermediate transfer member.

  According to an eighth aspect of the present invention, in the optical scanning device according to any one of the first to seventh aspects, a plurality of scanned surfaces on which the light spots are collected by the imaging optical system are provided. .

  A ninth aspect of the invention is an image forming apparatus including the optical scanning device according to any one of the first to eighth aspects.

  Thus, according to the present invention, the holding unit that holds the optical element from the sub-scanning direction, and at least two or more drive units that have an action point with respect to the sub-scanning direction on substantially the same plane in the main scanning direction. An optical scanning device and an image forming apparatus can be provided.

  In this embodiment, the scanning line bending is always stable and highly accurate without depending on the waviness pitch and direction of waviness of the scanning line bending generated by accumulating the shape accuracy and position accuracy of the optical elements constituting the optical scanning device. An object of the present invention is to enable correction and scanning line inclination correction, and to correct a color shift caused by a thickness variation of the intermediate transfer member with high accuracy.

  Hereinafter, an optical scanning device and an image forming apparatus of the present embodiment will be described with reference to the drawings. In addition, this embodiment is not limited to what is described below, A various change is possible in the range which does not deviate from the meaning.

First, before describing the scanning line bending correction mechanism, the scanning line inclination correction mechanism, and the correction method of the optical scanning apparatus according to the present embodiment, the configuration and operation of the image forming apparatus to which the optical scanning apparatus is applied will be described. This will be described with reference to FIG.
FIG. 10 is a cross-sectional view showing a configuration of an image forming apparatus using the optical scanning device of the present embodiment.

  Examples of the image forming apparatus 1 in FIG. 10 include a copying machine and a printer capable of forming a full-color image, or a facsimile apparatus capable of performing an image forming process similar to that of a copying machine or a printer based on a received image signal. . Needless to say, the image forming apparatus 1 of the present embodiment includes not only the above-described color image but also an image forming apparatus that targets a single color image.

  The image forming apparatus 1 is color-separated into four colors of yellow, cyan, magenta, and black, and can form an image corresponding to each color. In this embodiment, the image forming apparatus 1 is a photosensitive as a plurality of image carriers to be scanned surfaces. A tandem structure in which the body drums 11A, 12A, 13A, and 14A are juxtaposed in the horizontal direction is used. In the image forming apparatus 11, the visible images formed on the photosensitive drums 11A, 12A, 13A, and 14A are conveyed by a transfer belt 15 as an intermediate transfer medium that can move while facing the photosensitive drums. It is configured to be superimposed and transferred onto transfer paper (paper) S that is a recording medium.

  The configuration relating to the image forming process of the present embodiment will be described on behalf of one photosensitive drum 11A. Since the other photosensitive drums 12A to 14A have the same configuration and processing, the parts related to the photosensitive drums 12A to 14A are indicated by the numbers attached to the members related to the photosensitive drum 11A for convenience. Only the reference numerals are given, and detailed description is omitted.

  Around the photosensitive drum 11A, a charging device 11B using a configuration such as corotron or scoroton is used in order to execute an image forming process along the rotation direction indicated by the arrow in FIG. The optical scanning device 30, the developing device 11D, and the cleaning device 11E that form a latent image on the photosensitive drum 11A using the laser light from the laser light source are respectively disposed.

  In the image forming apparatus 11, a document reading unit 16 is disposed above an image forming unit in which various apparatuses that perform these image forming processes are disposed. Then, the reading device 17 reads a document (not shown) placed on the document placing table 16A of the document reading unit 16, outputs image information to an image processing control unit (not shown), and writes information to the optical scanning device 30 described above. Can be obtained.

  In FIG. 10, the charging device 11B employs a contact type using a roller, but the present embodiment is not limited to this, and a corona discharge type using a discharge wire can also be used. In this embodiment, as an example of the arrangement of the developing devices 11D to 14D, the developing devices 11D to 14D are arranged in the order in which yellow, cyan, magenta, and black toner can be supplied from the right side of the extended portion of the transfer belt 15. Of course, the order of arrangement of the developing devices 11D to 14D is not limited to this.

  The reading device 17 includes a light source 17A, a CCD 17B, a reflecting mirror 17C, and an imaging lens 17D. The light source 17A scans a document (not shown) placed on the document placement table 16A. The CCD 17B is provided with the reflected light from the original corresponding to the color for each color separation, and image information corresponding to the light intensity for each color separation is output from each CCD 17B to an image processing control unit (not shown). The reflecting mirror 17C and the imaging lens 17D form an image of the original scanned by the light source 17A on the CCD 17B.

  The transfer belt 15 is composed of a member made of a dielectric material such as a polyester film wound around a plurality of rollers. Further, the transfer belt 15 has one of the extended portions facing each of the photosensitive drums 11A to 14A, and the transfer devices 18A, 18B, 18C, and 18D are disposed inside the positions facing the respective photosensitive drums. Yes. The transfer devices 18 </ b> A to 18 </ b> D have a characteristic of electrostatically attracting images carried on the photosensitive drums 11 </ b> A to 14 </ b> A toward the transfer paper S using positive corona discharge.

  To the transfer belt 15, a transfer sheet S as a recording medium fed out from the sheet feeding cassette 20 </ b> A of the sheet feeding device 20 is fed to the transfer belt 15 via the registration roller 19. Then, it is electrostatically attracted and conveyed by corona discharge from the transfer device 18A. Further, the cleaning device 23 in FIG. 10 removes the toner remaining on the transfer belt 15.

  A separation device 21 that separates the transfer sheet S from the transfer belt 15 is disposed at a position where the transfer sheet S after image transfer from the photosensitive drums 11A to 14A moves. In addition, a static eliminating device 22 that is opposed to the belt with a belt interposed therebetween is disposed in the other portion of the stretched portion.

  The separation device 21 performs negative AC corona discharge from the upper surface of the transfer paper S, thereby neutralizing the charge accumulated on the transfer paper S and releasing the electrostatic adsorption state. As a result, separation using the curvature of the transfer belt 15 is made possible, and toner dust due to peeling discharge during separation is prevented.

  The static eliminator 22 performs negative AC corona discharge having a polarity opposite to the charging characteristics of the transfer devices 18 </ b> A to 18 </ b> D from both the front and back surfaces of the transfer belt 15. As a result, the electric charges are neutralized and the electrical initialization is performed.

In the photosensitive drums 11A to 14A, the surfaces of the photosensitive drums 11A to 14A are uniformly charged by the charging devices 11B to 14B. Then, based on the image information for each color separation color read by the reading device 17 in the document reading unit 16, an electrostatic latent image is formed on the photosensitive drum using the exposures 11C to 14C from the writing device. Furthermore, the electrostatic latent image is subjected to visible image processing with toner of a color having a complementary color relationship corresponding to the color separation color supplied from the developing devices 11D to 14D. At the same time, the transfer paper S is carried on the transfer belt 5 and conveyed, and electrostatic latent images are transferred to the transfer paper S via the transfer devices 18A to 18D. The transfer sheet S on which the image for each color separation carried on each of the photosensitive drums 11A to 14A is transferred is neutralized by the neutralization device 21, and then is separated by curvature using the curvature of the transfer belt 15, and then fixed. Moving to the device 24, the toner in the unfixed image is fixed and discharged.
In this way, the image forming apparatus of the present embodiment forms an image on the transfer paper.

Next, the configuration and operation of the optical scanning device according to the present embodiment will be described with reference to FIG.
FIG. 1 is an exploded perspective view showing the configuration of the optical scanning device according to the present embodiment.

  The optical scanning apparatus according to the present embodiment includes semiconductor laser units 101 and 102, folding mirrors 103, 111-113, 116, and 117, cylinder (cylindrical) lenses 104 and 105, polygon mirrors 106 and 107, and a first mirror. Scanning lenses 108 and 109, second scanning lenses 110 and 115, and photoconductors 114 and 118 are provided.

  As shown in FIG. 1, the optical scanning device (optical scanning device 30: FIG. 10) of this embodiment is a tandem writing optical system. Although the scanning lens system is adopted as the optical scanning device in the present embodiment, the scanning lens system or the scanning mirror system can be used. In FIG. 1, for convenience of illustration, two stations are shown and will be described below. However, the present embodiment is not limited to this. For example, the polygon mirrors 106 and 107 shown in FIG. By configuring symmetrically, it is possible to have four stations, which can be used in the image forming apparatus 1 shown in FIG.

  The semiconductor laser units 101 and 102 as light sources are arranged at a predetermined distance in the sub-scanning direction (vertical direction in FIG. 1). The beam emitted from the upper semiconductor laser unit 101 is bent in the same direction as the beam emitted from the lower semiconductor laser unit 102 by the folding mirror 103 on the way, and is incident on the cylinder lenses 104 and 105, respectively. Then, the light is condensed linearly in the vicinity of the reflection surfaces of the upper and lower polygon mirrors 106 and 107 separated by a predetermined distance in the sub-scanning direction.

  The beams deflected by the polygon mirrors 106 and 107 are shaped by the first scanning lenses 108 and 109 separated by a predetermined distance in the sub-scanning direction, respectively, and further, the fθ characteristics are obtained by the second scanning lenses 110 and 115. The beam is shaped to have a predetermined beam spot diameter and scanned on the photoreceptor surfaces of the photoreceptors 114 and 118, respectively. The beams deflected by the polygon mirrors 106 and 107 pass through different paths after passing through the first scanning lenses 108 and 109, respectively, and are guided onto two different photoconductors 114 and 118.

  The upper beam, that is, the beam transmitted through the first scanning lens 108 is first directed upward by 90 ° by the folding mirror 111. Next, after being further bent by 90 ° by the folding mirror 112, the light enters the second scanning lens 110. In this embodiment, a long plastic lens is used as the second scanning lens. Further, the photosensitive member 114 is scanned by being bent in the vertical direction by the folding mirror 113.

  On the other hand, the lower beam, that is, the beam transmitted through the first scanning lens 109 is incident on the second scanning lens 115 (long plastic lens) without entering the folding mirror halfway unlike the upper beam. Is done. Then, the optical path is bent by the two folding mirrors 116 and 117, and the photosensitive member 118 having a predetermined pitch between the drums is scanned.

  Here, in general, a scanning optical system is required to adopt a plastic lens because of a demand for cost reduction. In particular, in the tandem type writing unit, one set of optical elements is required for each station. Therefore, the number of parts is quadrupled, and the cost reduction effect due to plasticization becomes very large.

  However, a long plastic optical element is likely to warp in the longitudinal direction, particularly in the direction orthogonal to the scanning plane, due to molding conditions, residual stress, and the like. The amount of warpage is several tens of microns, and the amount and direction may vary depending on the type. The scanning line curve occurs in the entire scanning optical system, and the shape of the scanning line curve becomes wavy. For this reason, it is very difficult to bend the scanning line between the stations or to incline the scanning line with high accuracy.

  Further, when the temperature in the apparatus rises, even if the initial adjustment is performed with high accuracy, a temperature distribution difference between the main scanning direction and the sub-scanning direction of the plastic optical element occurs, and the warpage changes. As a result, there arises a problem that the bending of the scanning line or the inclination of the scanning line changes.

Therefore, an optical scanning device for correcting the bending of the scanning line or the inclination of the scanning line in this embodiment will be described with reference to the drawings.
2 and 3 are diagrams showing a scanning line bending correction mechanism, a scanning line inclination correction mechanism, and a shape holding unit in which these two correction mechanisms are integrated in the optical scanning apparatus according to the present embodiment.

FIG. 2 is a perspective view showing a scanning line correction mechanism, a scanning line inclination correction mechanism, and a scanning line correction mechanism which is a shape holding means in which these correction mechanisms are integrated.
As shown in FIG. 2, the scanning line correction mechanism 100 of the present embodiment includes a scanning lens 1, an emboss 2, a lower sheet metal 3, an upper sheet metal 4, a spacing member 5, an optical housing 6, and a leaf spring. 7, a bending correction mechanism 8, and an operating gear mechanism 9.

  The scanning lens 1 refers to the second scanning lenses 110 and 115 in FIG. 1, and in this embodiment, a resin lens is used. The emboss 2 is a protrusion provided in the longitudinal direction of the lower sheet metal 2 in two half-cut shapes, and fixes the scanning lens 1, and is composed of, for example, a pin and is further fixed to the lower sheet metal 3. Yes.

  The lower sheet metal 3 mounts and fixes the scanning lens 1, and the scanning lens 1 is sandwiched between the emboss 2, the upper sheet metal 4, and the interval holding member 5. Space holding members 5 are provided on both ends of the lower metal plate 3 and on the outer side in the longitudinal direction of the scanning lens 1. The interval holding member 5 is formed with a thickness equal to or less than the thickness of the scanning lens 1 in the sub-scanning direction, and is clamped with the lower metal plate 3 and the upper metal plate 4 with screws or the like to sandwich the scanning lens 1. Hold.

  The upper sheet metal 4 is provided on the upper portion of the scanning lens 1, and the bending correction mechanism 8 and the stepping motor of the differential gear mechanism 9 are provided on the upper portion of the upper sheet metal 4. Further, one end of the leaf spring 7 is fixed to both ends in the longitudinal direction of the upper metal plate 4, and the other end of the leaf spring 7 is fixed to the optical housing 6. The plane of the upper metal plate 4 to which the plate spring 7 is fixed is substantially parallel to the plane of the optical housing 6. Detailed configurations of the bending correction mechanism 8 and the differential gear mechanism 9 will be described later.

  The lower sheet metal 3 and the upper sheet metal 4 are subjected to a channel bending process, thereby increasing the bending rigidity. A differential gear mechanism 9 is provided outside the fixed holding member 5 that holds the scanning lens together with the lower sheet metal 3 and the upper sheet metal 4 so that the lower sheet metal 3 and the upper sheet metal 4 communicate with each other.

  That is, the scanning line correction mechanism 100 according to the present embodiment has the differential gear mechanism 9 disposed at both ends of the frame structure surrounded by the upper sheet metal 3, the lower sheet metal 4, and the interval holding member 5. The nut portion integrated with the gear in the mechanism 9 abuts the optical housing 6 and the left and right nuts are selectively moved up and down while being pressed in the sub-scanning direction by the leaf springs 7 provided at both ends of the upper metal plate 3. By doing so, the inclination of the scanning line and the scanning line position adjustment are performed.

Next, in the scanning line correction mechanism 100 of the present embodiment, a bending correction mechanism and a bending correction method related to scanning line bending correction will be described with reference to FIG.
FIG. 4 is an enlarged cross-sectional view showing the configuration of the scanning line bending correction mechanism of the present embodiment.

  As shown in FIG. 4, the bending correction mechanism 8 for correcting the scanning line bending according to the present embodiment is for pressing the scanning lens 1, and includes a bracket 81, a taper pin 82, and a roller 38. In the present embodiment, the bending correction mechanism 8 is provided at a total of three locations in the longitudinal direction of the upper sheet metal 4 as shown in FIG.

  The bracket 81 fixes the taper pin 82 and the roller 83 together with the upper sheet metal 4. Further, the taper pin 82 contacts the roller 83 at the taper portion (the inclined surface portion of the taper pin 82), and presses the roller 83 against the scanning lens 1. By adjusting the contact surface at the taper portion, the pressure between the roller 83 and the scanning lens 1 is adjusted. The roller 83 presses the scanning lens 1 via the taper pin 82 and is arranged so that its axial direction is parallel to the optical axis direction of the scanning lens 1.

  As shown in FIG. 4, the bottom surface of the bracket 81 is bent into a U shape, and a square hole having the same shape is provided on the contact surface with the upper metal plate 4. The roller 83 is fitted into the square hole, and the taper pin 82 is tightened by the square hole of the bracket 81 and the taper pin 82 supported by the screw portion from a direction orthogonal to the axial direction of the roller 83. In this way, the bending of the scanning line can be corrected by bringing the tapered portion of the taper pin 82 into contact with the roller 83 and pressing and bending the scanning lens 1 in the sub-scanning direction.

  In addition, as shown in FIG. 7, a pressing leaf spring 71 that holds the scanning lens 1 together with the roller 83 may be installed at a position facing the scanning lens 1. In this case, the lower sheet metal 3 is provided with a storage portion 31 for positioning and storing the pressing plate spring 71, and the semicircular protruding portion of the pressing plate spring 71 is disposed at a position facing or offset from the roller 83. .

  By providing the pressing leaf spring 71 in this way, the scanning lens 1 can be pressed from the lower side, and the scanning lens 1 is held after the bending adjustment related to the scanning line bending correction is performed with high accuracy. , Can hold the shape. Furthermore, the shape of the scanning lens 1 can be maintained even when temperature fluctuations in the apparatus occur.

Next, in the scanning line correction mechanism 100 of this embodiment, an inclination correction mechanism and an inclination correction method related to the scanning line inclination correction will be described with reference to FIG.
FIG. 5 is an enlarged cross-sectional view showing the configuration of the scanning line tilt correction mechanism of the present embodiment.

  The tilt correction mechanism of the present embodiment refers to the differential gear mechanism 9 shown in FIG. 2, and acts as an actuator that performs scanning line tilt correction and scanning line position correction. The differential gear mechanism 9 includes a stepping motor 91, a screw part 92, a nut part 93, a first stage gear 94, and a two-stage gear 95.

  In the present embodiment, a male thread is cut at a predetermined pitch at the tip of the motor shaft of the stepping motor 91 to form a threaded portion 92. A first gear 94 is provided on the base side of the motor shaft. The first stage gear 94 is attached as a spur gear with a predetermined number of teeth integrally with the motor shaft.

  A nut portion 93 is provided around the screw portion 92. As shown in FIG. 5, the nut portion 93 is provided so as to cover the periphery of the motor shaft described above, and a spur gear having a predetermined number of teeth is formed on the outer side, like the first stage gear 94. Further, a nut with a female thread cut is formed at the center (inner side) of the nut portion 93 and is screwed with a screw section 92 with a male screw cut. The two-stage gear 95 is provided as a two-stage upper and lower gear so as to be parallel to the position of the spur gear outside the nut portion 93 and the position of the spur gear of the first-stage gear 94.

  In the differential gear mechanism 9 of the present embodiment, when the motor shaft of the stepping motor 91 rotates, the two-stage gear 95 rotates in the reverse direction. Then, the gear of the nut portion 93 that meshes with the lower gear of the two-stage gear 95 rotates in the same direction as the motor shaft of the stepping motor 91.

  That is, if the number of teeth of the four gears in the outer gear of the nut portion 93, the gear of the first gear 94, and the gear of the second gear 95 are all the same, the motor shaft and the nut portion of the stepping motor 91 are the same. No rotational phase difference with respect to 93 occurs. Therefore, no change occurs in the positional relationship between the motor shaft and the nut portion 93 in the sub-scanning direction.

  However, the rotational phase difference between the nut and the stepping motor shaft is generated by changing the number of teeth of the gear train so that the final stage nut is slightly decelerated or accelerated. Movement occurs. For example, referring to FIG. 5, when the number of teeth of the upper gear of the first gear 94 and the second gear 95 is the same and the number of teeth of the lower gear of the second gear 95 is reduced by one, The number of teeth of the gear outside the nut portion 93 is increased by one. Thus, according to this embodiment, when the resolution per one step angle is compared with the resolution between the conventional nut and the motor shaft, the accuracy can be improved by one digit or more.

  Further, in the present embodiment, the upper sheet metal 4 and the lower sheet metal 3 are configured and integrated as bearings of the differential gear mechanism 9 and are arranged at both outer ends of the scanning lens 1. The nut portion 93 is supported in a state where the tip of the nut portion 93 is in contact with the optical housing 6, and the nut portion 93 is selectively moved up and down. As a result, the posture and position of the scanning lens 1 can be adjusted, and scanning line inclination correction and scanning line position correction can be performed.

FIG. 6 is a diagram schematically showing the positional relationship between the operating point of the nut portion 93 and the operating point of the leaf spring 7.
As shown in FIG. 6, in this embodiment, the action points of the leaf springs 7 are equally distributed in the optical axis direction with respect to the center line connecting the action points of the nut portion 93. By arranging in this positional relationship, the scanning lens 1 can be held in a stable state without causing a tilt in the β tilt direction. As shown in FIGS. 2 and 3, both ends of the leaf spring 7 are fixed to the fixed-side optical housing 6 and the swing-side upper metal plate 4 by screw fastening to improve vibration resistance. Yes.

Next, correction of color misregistration due to variation in the thickness of the intermediate transfer body using the optical scanning device of the present embodiment will be described with reference to the drawings.
FIG. 8 and FIG. 9 are diagrams illustrating a case where color misregistration correction caused by the thickness variation of the intermediate transfer member is performed using the optical scanning device of the present embodiment. 8 and 9, description will be made using a quadruple tandem image forming apparatus.

  In general, in a four-tandem image forming apparatus, in order to obtain a resist so that there is no color misregistration of four colors, simply increasing the component accuracy and assembly accuracy leads to higher cost and color misregistration correction. Is difficult. Therefore, in the present embodiment, self-printing is performed in the image forming apparatus, and after the color misregistration amount in the sub-scanning direction is recognized therefrom, the scanning line correction mechanism 100 is used for each photoconductor according to the color misregistration amount. An accurate color resist is realized by slightly changing the beam scanning position.

  In practice, a patch pattern for recognizing color misregistration is created on the transfer belt 15 (which will be described as an intermediate transfer medium here), and this is detected by the P sensor 1001. The P sensor 1001 is controlled by the CPU 1002, and the CPU 1002 activates the scanning line correction mechanism 100 via the driver 1003 based on the detection result of the P sensor 1001 to perform control.

  After forming a line-shaped four-color pattern on the transfer belt 15 and recognizing how much other Y, M, and C colors have shifted in the forward or backward direction with respect to the black (K) line as a reference, at time timing Then, color misregistration correction is performed for writing each color.

  This color misregistration detection and correction is performed, for example, when the entire process control is performed when the power is turned on, when the temperature difference in the apparatus becomes 5 ° C., when several hundred jobs are in progress, For example, when the photosensitive member, the developing unit and the belt unit are replaced. When this color misregistration correction process is completed, these patterns are cleaned by a cleaning bias roller (not shown) and removed from the transfer belt 15.

  In this embodiment, the beam scanning position is slightly changed according to the color misregistration correction data with respect to the belt speed unevenness caused by the belt thickness unevenness. As a result, it is possible to obtain a highly accurate print image in which writing is performed at a desired position and a constant image writing without fluctuation can be performed.

  As a factor that causes unevenness in the thickness of the endless belt, for example, there is variation in manufacturing the endless belt. When this endless belt is manufactured using a mold, a variation occurs because the center of the inner mold that forms the inner wall of the belt and the outer mold that forms the outer wall of the belt are misaligned. Further, the belt thickness unevenness occurs in a substantially sinusoidal shape with respect to the belt circumference. Actually, if a belt is stretched over various rollers and left to be tensioned, a partial recess corresponding to the portion may be generated. Here, the description will be made on the premise of a substantially sine wave.

  In this embodiment, an endless transfer belt 15 for a direct transfer belt or an intermediate transfer belt is provided, and a thickness detection unit for detecting the thickness of the endless transfer belt 15 is detected by the thickness detection unit. Based on the result, the scanning line correction mechanism 100 (differential gear mechanism 9) is driven in real time to correct the scanning line position.

  In normal color misregistration correction control, the speed fluctuation or position based on the detected belt thickness is fed back to the belt drive motor to perform operation control. However, in this embodiment, control is performed by returning to the scanning line correction mechanism 100 (differential gear mechanism 9).

  In the present embodiment, as a means for knowing the thickness deviation of the transfer belt 15, a method of measuring the thickness of the belt offline in advance before mounting it in the image forming apparatus and storing the deviation profile in a memory; It is conceivable to measure the deviation while driving in an actual machine mounted state.

  Specific methods of the latter include (1) a method of knowing by setting a direct thickness meter on the belt surface, (2) a method of predicting from the rotational speed of a roller that rolls following the belt surface, ( 3) A method of predicting from fluctuations in the rotational speed of the driven roller that rotates on the inner surface of the belt loop as the belt moves can be considered.

  In the present embodiment, in the following description, after knowing the thickness deviation for one round of the belt by the method (1) above, the cycle of the variation in the thickness of the intermediate transfer medium (explained here as the intermediate transfer medium) In response to the above, the attitude of the resin imaging element is controlled by the scanning line position correcting means and / or the scanning line inclination correcting means.

  One point of HP mark 1101 for knowing the reference position is formed on the intermediate transfer belt 15A, and this reference position is recognized by the HP sensor 1102 which is a transmission type or reflection type photosensor. With this position as a reference, data from the belt thickness detection sensor 1103 using a stylus type or laser light is taken in via the CPU 1104 as digital data by sampling at a constant period. The belt thickness detection sensor 1103 is installed in front of the first photoconductors arranged in the order of image formation. The front side of the first photoconductor is a position where the writing-transfer distance is more than a distance, and is a straight portion. At this position, the intermediate transfer belt 15A is rotated n times, the data is taken in and averaged, and the profile of the thickness deviation of one round is determined. This data is stored in a memory 1105 such as a RAM.

  Based on the thickness deviation data of the belt around the home position as a reference, the beam scanning position to each of the photoconductors 11A to 14A is slightly changed by the scanning line correction mechanism 100 via the driver 1106 and recorded. Control. In order to increase the productivity of printing, a plurality of HP sensors 1102 for detecting the HP mark 1101 are provided, and the beam scanning position based on the deviation data from the position corresponding to the HP sensor 1102 detected at the highest speed. It is effective to perform correction. In the present embodiment, the case where two HP sensors 1102 are used is shown, but the number of HP sensors 1102 arranged is not limited.

  As described above, according to the optical scanning device and the image forming apparatus of the present embodiment, the scanning line bending correction, the inclination correction, and the position correction can be performed independently, so that the scanning line inclination correction and the scanning line position correction are the same. This makes it possible to efficiently perform feedback control with this actuator. In addition, the optical element can be held and held from two surfaces in the sub-scanning direction, and the posture of the optical element can be held in a stable state, so that the scanning line bend and the scanning line inclination due to the environmental temperature change in the apparatus Can be prevented.

  Further, according to the present embodiment, the adjustment resolution per pulse of the stepping motor can be improved by one digit or more as compared with the prior art, so that further high accuracy can be achieved. Further, it is possible to simultaneously perform the inclination correction of the scanning line and the scanning position correction by using the same mechanism. In addition, by appropriately disposing the position of the actuator action point with respect to the position of the action point of the leaf spring, stable holding strong against disturbance can be achieved.

  Further, according to the present embodiment, it is possible to efficiently correct the color shift caused by the thickness variation of the intermediate transfer member using the same actuator. Also, when used as an optical scanning device of a tandem multicolor image forming apparatus using an electrophotographic process, the scanning line bending, the scanning line inclination and the scanning line position on each photoconductor are corrected and stably held. Therefore, it is possible to increase the density and speed of monochromatic and multicolor output images and to improve the image quality with little color shift. Therefore, the downtime required for color misregistration control is greatly reduced. Furthermore, it leads to a reduction in power consumption, vibration noise, and heat generation, and an environmental load can be reduced.

It is a disassembled perspective view which shows the structure of the optical scanning device concerning this embodiment. It is a perspective view which shows the scanning line bending correction | amendment mechanism, scanning line inclination correction | amendment mechanism, and shape holding | maintenance means of the optical scanning device of this embodiment. It is sectional drawing which shows the scanning line bending correction | amendment mechanism, scanning line inclination correction | amendment mechanism, and shape holding | maintenance means of the optical scanning device of this embodiment. It is sectional drawing which shows the scanning line bending correction | amendment mechanism of the optical scanning device of this embodiment. It is sectional drawing which shows the scanning line inclination correction | amendment mechanism of the optical scanning device of this embodiment. It is a figure which shows a nut action point and a leaf | plate spring action point typically. It is a figure which shows another example of the press means of the optical scanning device of this embodiment. 1 is a diagram illustrating an example of a scanning line correction mechanism and an image forming apparatus according to an embodiment. It is a figure which shows another example of the scanning line correction | amendment mechanism and image forming apparatus of this embodiment. 1 is a diagram illustrating an image forming apparatus according to an exemplary embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scan lens 2 Embossing 3 Lower sheet metal 4 Upper sheet metal 5 Space | interval holding member 6 Optical housing 7 Plate spring 71 Pressing plate spring 8 Bending correction mechanism 81 Bracket 82 Taper pin 83 Roll 9 Differential gear mechanism 91 Stepping motor 92 Screw part 93 Nut part 94 First stage gear 95 Second stage gear 100 Scan line correction mechanism 1001 P sensor 1002 CPU
1003 Driver

Claims (9)

An optical scanning device that performs light scanning by deflecting a light beam from a light source by a light deflecting unit and condensing the deflected light beam as a light spot on a scanned surface by an imaging optical system,
Holding means for holding at least one or more optical elements constituting the imaging optical system from the sub-scanning direction;
An optical scanning device comprising: at least two or more driving units having an action point with respect to the sub-scanning direction on substantially the same plane in the main scanning direction of the optical element. The holding means includes a holding member that presses and holds the optical element in the sub-scanning direction,
2. The optical scanning device according to claim 1, wherein the holding member and the driving unit are integrated by sandwiching and pressing the optical element from two directions in the sub-scanning direction.   3. The optical scanning device according to claim 1, wherein the driving means is constituted by a differential gear mechanism having a stepping motor, a screw, and a gear. The optical scanning device has scanning line bending correction means for correcting scanning line bending of the optical element,
At least two of the plurality of driving units include a pressing member that is disposed outside both ends of the optical element in the main scanning direction and presses the scanning line bending correction unit in the sub-scanning direction,
4. The optical scanning device according to claim 1, wherein the plurality of driving units are selectively operated to correct the inclination and position of the scanning line. 5. The pressing member is a leaf spring;
One of the end portions of the leaf spring is fastened to the scanning line bending correction means, and the other end of the leaf spring is fastened to a fixing portion that forms a part of the outer shape of the optical scanning device,
An axis connecting a plurality of action points of the plurality of driving means is substantially coaxial with an axis connecting a plurality of action points of the leaf spring, or in a plane connecting the plurality of action points of the leaf spring. So that
The optical scanning device according to claim 4, wherein the plate spring is provided. In the vicinity of the intermediate transfer member, there is a color shift detection unit that detects a color shift of the formed image, and a thickness variation detection unit that detects a variation in the thickness of the intermediate transfer member,
6. The optical scanning device according to claim 1, wherein the driving unit is controlled based on detection results by the color misregistration detection unit and the thickness variation detection unit.   The optical scanning apparatus according to claim 6, wherein the thickness variation detecting unit controls the driving unit based on a cycle of the thickness variation of the intermediate transfer member.   8. The optical scanning device according to claim 1, comprising a plurality of scanning surfaces on which light spots are condensed by the imaging optical system.   An image forming apparatus comprising the optical scanning device according to claim 1.

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