JP4175311B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus, and more particularly, to an optical scanning apparatus and an image forming apparatus that can form a high-quality image with a small size and high accuracy.

  2. Description of the Related Art Conventionally, an optical scanning device of an image forming apparatus adopting an electrophotographic method is a method in which a light beam is reflected by a rotating polygon mirror (rotating polygon mirror) to move the light beam and scan it on a photoconductor to form a latent image. There is. In this case, the position of the polygon mirror in the scanning plane direction can be adjusted by controlling the oscillation of the laser diode as a light source, but the inclination of the reflecting plane in the direction perpendicular to the scanning plane of the polygon mirror is controlled in this way. Some corrections cannot be made, and so-called surface tilt correction is required. This surface tilt correction requires an optical system for forming an image of the light beam once converged on the reflection surface of the polygon mirror on the photosensitive drum or the like to be scanned again. Since this surface tilt correction optical system is required, the optical path after being reflected by the polygon mirror needs to have a certain length.

In recent years, downsizing of an image forming apparatus has been required, and an optical scanning apparatus that has been downsized in accordance with this demand has been proposed. For example, Patent Document 1 proposes a laser writing system unit that is an optical scanning device of an image forming apparatus. Here, FIG. 5 is a diagram showing a laser writing system unit which is an example of the conventional optical scanning device. As shown in this example, the conventional optical scanning device uses a fixed mirror for the optical path described above. The size is reduced by bending the light beam. With such an optical scanning device, the length of the optical scanning device can be reduced compared to the case where the light beam is configured linearly without being bent by the fixed mirrors 132, 133, and 135, and image formation is performed. This can contribute to downsizing of the apparatus. In addition, on the upper side, the thickness is such that the reflection surface of the polygon mirror 123 (hereinafter collectively referred to as a polygon mirror unit) with the motor 124, the fθ lens 131, the support frame that supports the lens, and the first fixed mirror 132. And the distance between the second support lens 134, the second fixed mirror 133, and the third fixed mirror 135 on the lower surface. Note that the lid 122 must have a predetermined gap between the lid 122 and the polygon mirror 123 so as not to interfere with the air flow generated by the polygon mirror 123 rotating at high speed. Furthermore, if the laser beam is too close to the support member and surrounding members, even if there is no disturbance in the light beam of the highly concentrated laser beam, light that is a wave is diffracted and leaks to the surroundings, causing stray light. Therefore, it is necessary to leave a predetermined interval from this point as well.
JP-A-6-34901

  However, in the above-described conventional optical scanning device, the length of the optical scanning device is surely shortened by bending the light beam. However, since the thickness is increased by that amount, the requirement for miniaturization is met in view of the occupied volume. There was a problem that it was not. Even if the thickness of the optical scanning device is reduced as it is, the thickness of the optical scanning device is determined by the position and thickness of the polygon mirror unit and each optical element arranged on the flat support member as described above. However, there is a problem that the thickness of the optical scanning device cannot be made thinner than the thickness determined by these.

  In addition, if the optical element itself is made thin, there is a problem in that it is easy to be affected by molding distortion and the accuracy is lowered, and grinding and thinning are troublesome and increase the production cost. It was. Further, if the optical element is formed thin, it is easily affected by humidity, and an expensive moisture-proof material has to be used, resulting in a high production cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device and an image forming apparatus which are small in size, thin in thickness, high in accuracy and low in stray light.

To achieve this object, in the optical scanning device according to the first aspect of the present invention, a polygon mirror unit comprising a polygon mirror that rotates and reflects a light beam from a light source and a motor that drives the polygon mirror; An optical element for forming an image of a light beam reflected by the polygon mirror on a photosensitive member, a plurality of mirrors for reflecting light that has passed through the optical element, and a support member for supporting the polygon mirror unit and the optical element; The support member is composed of a plurality of plane parts, and includes at least a polygon mirror unit support plane part that supports the polygon mirror unit, and the polygon mirror among the optical elements. a first lens support plane section for supporting the first lens reflected light beam is first passed, as the plurality of mirrors, A first fixed mirror that bends a light flux passing through the first lens is provided in the vicinity of an end of the serial support member on the back side direction and the mounting surface side of the first lens which is a surface opposite to the supporting member The light beam provided in the vicinity of the first fixed mirror and bent by the first fixed mirror is bent so that the light beam that has passed through the first lens on the back surface side of the support member is substantially parallel and travels in the opposite direction. comprising at least a second fixed mirror, further as it said optical element, said first lens passes through, a second lens, wherein the light beam is bent by the second fixed mirror passes, said support member further the second lens comprises a second lens support surface section for supporting the, the way the second lens supporting plane portion approaches the light beam passed through the first lens, the first lens support with the second lens support surface portion Plane part and Characterized in that a flat portion for connection for connecting with a step between.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the light beam bent by the second fixed mirror is further directed toward the photosensitive member as the plurality of mirrors. A third fixed mirror that deflects and reflects, the support member is bent to form a recess on the back side of the support member, and the third fixed mirror is fixed to the recess formed in the support member; It is characterized by.

According to a third aspect of the present invention, there is provided an optical scanning device comprising: a polygon mirror unit comprising a polygon mirror for rotating and reflecting a light beam from a light source; and a motor for driving the polygon mirror; and a light beam reflected by the polygon mirror. An optical scanning device comprising: an optical element for forming an image on a photosensitive member; a plurality of mirrors that reflect a light beam that has passed through the optical element; and a support member that supports the polygon mirror unit and the optical element. The support member includes a plurality of plane portions, and includes at least a polygon mirror unit support plane portion that supports the polygon mirror unit, and the plurality of mirrors are provided near end portions of the support member. A first fixed mirror that bends the light beam reflected by the polygon mirror unit in the direction of the back surface of the support member; and the first fixed mirror. The second fixed light beam is bent near the first bent mirror so that the light beam is bent on the back side of the support member so as to travel in a direction substantially parallel to and opposite to the light beam reflected by the polygon mirror unit. A mirror, and a third fixed mirror that deflects and reflects the light beam bent by the second fixed mirror toward the photoreceptor, and the polygon is formed on the back surface side of the support member by bending the support member. A recess is formed so as to bite into a space between the mirror and the first lens, and the third fixed mirror is fixed to the recess formed in the support member.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect of the invention, the support member supports a first lens through which the light beam reflected by the polygon mirror first passes. characterized by comprising a lens supporting plane portion.

In the image forming apparatus of the invention according to claim 5, a charger for charging the photosensitive member and the photosensitive member, an optical scanning device for scanning a light beam modulated based on image data with respect to the photosensitive member, the photosensitive member characterized in that an image forming apparatus and a developing unit for developing a latent image formed on said optical scanning device, an optical scanning apparatus according to any one of claims 1 to 4 And

According to the optical scanning device of the first aspect of the present invention, the light beam reflected by the polygon mirror passes through the first lens supported by the first lens support plane part, and is reflected by the first fixed mirror. The second fixed mirror provided in the vicinity of the first fixed mirror is bent in the rear surface direction that is the surface opposite to the mounting surface side of the first lens of the support member, and the rear surface side of the support member Thus, the light beam is bent so as to be substantially parallel to the light beam that has passed through the first lens and to travel in the opposite direction. At this time, the second lens support surface portion is closer to the light flux passing through the first lens, the connection for connecting with a step between the second lens support surface portion and the first lens support plane portion Since the flat portion is provided, each optical element can be arranged in a space-efficient manner by supporting each optical element with a support member provided with a step instead of a flat surface. Therefore, the thickness can be reduced by bringing the light beams on both sides of the support member closer.

  According to the optical scanning device of the invention of claim 2, in addition to the effect of the invention of claim 1, the light beam is bent by the first fixed mirror and the second fixed mirror to shorten the length of the optical scanning device. In addition, the support member is bent to form a recess on the back side of the support member, and the third fixed mirror is fixed to the recess, so that the third fixed mirror does not protrude and the optical scanning device Thinning can be achieved.

According to the optical scanning device of the third aspect of the invention, not only the light beam is bent by the first fixed mirror and the second fixed mirror to shorten the length of the optical scanning device, but also the support member is bent and the support is made. Since a recess is formed on the back side of the member so as to bite into the space between the polygon mirror and the first lens, and the third fixed mirror is fixed in the recess, the third fixed mirror does not protrude, Thinning of the optical scanning device can be achieved.

According to the optical scanning device of the invention of claim 4 , in addition to the effect of the invention of claim 3 , the first lens through which the light beam reflected by the polygon mirror by the first lens support plane part first passes is provided. Can be supported.

In the image forming apparatus according to the fifth aspect of the present invention, since the thinned optical scanning device having the configuration according to any one of the first to fourth aspects is used, the image forming apparatus can be reduced in size. .

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of an optical scanning device and an image forming apparatus including the optical scanning device according to the invention will be described. First, the outline of the configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the image forming apparatus 1 as viewed from the side in a direction orthogonal to the paper conveyance direction. The overall shape of the image forming apparatus 1 is formed in a substantially rectangular parallelepiped shape by the main body frame 11. In FIG. 1, the right side is the front surface of the image forming apparatus 1 and the near side is the left surface of the image forming apparatus 1. A paper feed unit 19 including a paper feed cassette for storing and feeding paper P is provided below the main body frame 11, and the paper P stored in the paper feed unit 19 is conveyed from the front of the image forming apparatus 1 by the transport unit 18. Be transported. A developing unit 17 configured integrally as a process unit is disposed above the transport unit 18, and an optical scanning device 12 configured as a laser scanner is disposed above the developing unit 17. In the developing unit 17, a laser beam LB modulated by an image signal is scanned by the optical scanning device 12 on the photosensitive drum 77 uniformly charged by a charger 78 made of a scorotron to form a latent image. The latent image is developed by the developer T conveyed by the developing roller 75 to be visualized to form an image. This actualized image is transferred onto the paper P by the transfer roller 87. The sheet P to which the image has been transferred is conveyed by the conveying unit 18 to the fixing unit 15 on the left side of the developing unit 17. In the fixing unit 15 integrally configured as a fixing unit, the developer T is fixed by heating and pressing the paper P on which the image is formed. After fixing, the paper discharge unit 16 whose paper discharge direction can be switched is discharged to the printed paper placement unit 69 at the back of the apparatus 1 or at the top of the apparatus. The schematic configuration of the image forming apparatus 1 is as described above. Hereinafter, the configuration of each unit will be described in detail.

  As shown in FIG. 1, the paper feeding unit 19 is formed in a substantially rectangular parallelepiped shape by a frame 91 and has a drawer-like configuration in which a handle 97 is arranged on the front surface. And a storage portion 92 that can be stored. In the vicinity of the center of the bottom of the storage portion 92, there is provided a swingable paper press 93 pivotally attached to the base, and a coil spring (not shown) is disposed below the paper press 93. 93 is urged upward. Accordingly, even when a large number of sheets P are stacked and stored, or even when the number of sheets P decreases and the stacked thickness decreases, the uppermost sheet P of the stored sheets P is always fed. 81 can be contacted with an appropriate magnitude of force. A separation pad 94 made of a material having a large friction coefficient with respect to the paper P is disposed in front of the paper presser 93 (on the right side in FIG. 1). The separation pad 94 puts the paper P in the direction of the paper feed roller 81. It is urged by a separation pad spring 95 comprising a coil spring disposed below the pressure contact. The separation pad 94 holds the sheet P other than the sheet conveyed by the sheet feeding roller 81 by its frictional force and feeds only one sheet to the conveying unit 18.

  The paper feeding unit 19 is configured to be pulled forward by pulling the handle 97 forward, so that the paper P can be easily replenished and a paper jam can be easily processed. In that case, the separation pad 94 and the driven roller 96 are separated from the paper feed roller 81 together with the drawer of the paper feed unit 19 and can be processed without the paper P being pinched.

  Next, the transport unit 18 will be described. The sheet P drawn from the sheet feeding unit 19 obliquely forward (upper right in FIG. 1) by the sheet feeding roller 81 and the driven roller 96 is guided upward by the guide 82 and further back along the guide 82 Be guided to. Further, when the paper P is transported by the paper feed roller 81 and the driven roller 96, the front end of the paper P pushes down the first paper feed sensor 83 and enters. Then, the leading end of the sheet P comes into contact with the contact portion between the registration roller 84 and the driven roller 85 that rotates with the registration roller 84.

  The registration roller 84 and the driven roller 85 correct the skew of the paper P. That is, the registration roller 84 is stopped for a predetermined time after the first paper feed sensor 83 detects the leading edge of the paper P. Since the paper P continues to be conveyed by the paper feed roller 81 and the driven roller 96, the leading edge of the paper P is prevented from coming into contact with the contact portion between the registration roller 84 and the driven roller 85 without being caught. However, since the entire paper P is conveyed by the paper feed roller 81 and the driven roller 96, the intermediate portion of the paper P whose leading end is already in contact with the registration roller 84 and the driven roller 85 is bent in the space of the guide 82. It is. In the meantime, the paper P is conveyed by the paper feed roller 81 and the driven roller 85, and all the leading edges of the paper P come into contact with the contact portions of the registration roller 84 and the driven roller 85. At the time of such contact, the leading edge of the paper P is completely parallel to the rotation axis of the registration roller 84, that is, the skew is corrected. If the control unit 20 rotates the registration roller 84 in the paper conveyance direction at this stage, the skew of the paper P is corrected and conveyed in a correct posture.

  When the skew correction is completed by the registration roller 84, the paper P is further conveyed, the second paper feed sensor 86 is pushed down at the front end portion, and the front end is further sandwiched between the photosensitive drum 77 and the transfer roller 87. The position of the leading end portion of the paper P is recognized by the control unit 20 by the second paper feed sensor 86, and the control unit 20 conveys the paper P including a margin up to a predetermined printing start portion of the paper P. In this way, printing is performed from the printing start portion of the predetermined paper P. Here, the description of the optical scanning device 12 will be simplified first.

  FIG. 4 is a plan view of the optical scanning device 12 as viewed from above (Z direction in FIG. 1) with the lid 22 removed. As shown in FIG. 4, the upper surface side (see FIG. 2) of the optical scanning device 12 includes a laser diode 41, a laser diode holder 42 that supports the laser diode 41, and a substrate 43 to which the lead wire of the laser diode 41 is connected. A lens cell including a light emitting unit 47 configured, a collimating lens 45 that converts the diffused light of the laser beam LB emitted from the light emitting unit 47 into parallel light, and a slit (not shown) that restricts the parallel light to a predetermined width. 44 (hereinafter, the light emitting unit 47 and the lens cell 44 are collectively referred to as a parallel light unit), a first cylindrical lens 46 for converging the parallel laser beam LB on the mirror surface of the polygon mirror 23, and the converged light at high speed. A polygon mirror 23 that sequentially reflects and deflects the light beam by six plane mirrors arranged on the side surface of the hexagonal column shape rotating at The fθ lens 31 that scans the surface of the photosensitive drum 77 (see FIG. 3) to be scanned at a constant speed with the laser beam LB deflected at a constant angular velocity by the mirror 23, and the light beam that has passed through the fθ lens 31 is moved downward. An optical element of the first fixed mirror 32 to be bent is disposed.

  FIG. 2 is a cross-sectional view taken along a line AA in FIG. As shown in FIG. 2, the optical scanning device 12 has a support member 21 as a partition wall and is separated from the upper surface side and the lower surface side, and optical elements are arranged on both surfaces thereof. The light beam reflected by the polygon mirror 23 and transmitted through the fθ lens 31 while being diffused in the vertical direction and bent downward by the first fixed mirror 32 is further deflected by the second fixed mirror 33 and substantially the same as the light beam on the upper surface side. Go parallel and in the opposite direction. The lower side surface includes a second cylindrical lens 34 for converging the light beam in the vertical direction so that the diffused light beam reflected by the second fixed mirror 33 is imaged on the photosensitive drum 77 to be scanned, and the converged light beam. The optical elements of the third fixed mirror 35 are arranged so as to be deflected toward the photosensitive drum 77 and reflected. With this configuration, the optical scanning device 12 scans the photosensitive drum 77 disposed in the developing unit 17 with the laser beam LB modulated based on the image data to form a latent image.

  3 is an enlarged view of a part of the optical scanning device 12, the developing unit 17, and the main body frame 11 of the image forming apparatus 1 shown in FIG. As shown in FIG. 3, the developing unit 17 is disposed on a frame 70 in which each component is housed and supported as a process unit. The frame 70 is roughly divided into a developer chamber 71 and a developing chamber 73. The developer chamber 71 contains a non-magnetic one-component developer T, and a blade-like stirring member 72 called an agitator is supported on a rotating shaft driven by a motor (not shown). Therefore, the developer T is always replenished from the developer chamber 71 to the developing chamber 73 by the rotation of the stirring member 72.

  In the developing chamber 73, a photosensitive drum 77, a developing roller 75 that is disposed in front of the photosensitive drum 77 (on the right side in FIG. 3) and rotates in the opposite direction to the photosensitive drum 77, and further forward of the developing roller 75 are provided. And a supply roller 74 that is rotated in the same direction as the developing roller 75, a paper dust removing unit 79 that is disposed behind the photosensitive drum 77, a charger 78 that is disposed above the photosensitive drum 77, and the like. .

  The supply roller 74 rotates and attaches fine granular developer T to the developing roller 75 on the sponge surface. The layer thickness regulating blade 76 is urged and contacted with a predetermined pressure to equalize the amount of the developer T adhered to the developing roller 75 by the supply roller 74 to an appropriate level. The adhesion amount of the developer T is adjusted so as to scrape off the toner.

  The photosensitive drum 77 is driven by a motor (not shown) so as to rotate in the paper transport direction (clockwise in FIG. 3), and can transport the paper P in cooperation with the transfer roller 87. First, the paper dust adhered to the photosensitive drum 77 is removed from the photosensitive drum 77 by the paper dust removing unit 79. The paper dust removing unit 79 of the present embodiment is configured to use a brush, a nonwoven fabric, or the like, although details are not shown, pass the residual developer on the surface of the photosensitive drum 77 and capture the paper dust. Yes. The portion of the photosensitive drum 77 that has passed through the paper dust removing unit 79 moves to a position facing the charger 78 by the rotation of the photosensitive drum 77.

  In the charger 78, a charging wire 78a made of a tungsten wire called a corona wire having a diameter of 50 to 100 μm is arranged in parallel with a distance of about 10 mm from the photosensitive drum 77, and the periphery is covered with a shield electrode 78d made of aluminum, A groove-shaped opening along the photosensitive drum 77 is provided at a portion facing the photosensitive drum 77, and a grid electrode 78b made of several wires or meshes is disposed in the opening to be insulated from the shield electrode 78d. Configured as a scorotron. A cleaning hole 78c, which is a hole for slidably guiding a cleaning member that slidably sandwiches the charged charging wire 78a, is exposed on the opposite side of the surface of the shield electrode 78d that faces the photosensitive drum 77. Along the longitudinal direction of the body drum 77, a groove-like opening is formed facing the optical scanning device support portion 11a.

  The charging line 78a is connected to a positive pole of a power supply device (not shown), and a high voltage of 5 to 10 kv is applied, and positive ions generated thereby move to the surface of the photosensitive drum 77 to be charged. The charging potential is regulated by applying a bias voltage to the grid electrode 78b, and charging can be controlled by changing the voltage. The surface of the photosensitive drum 77 is positively charged by the charger 78. The charger 78 may be a corotron that does not have the grid electrode 78b instead of the scorotron shown in the embodiment, and may be of another type as long as it can generate corona discharge such as brush charging.

  The portion of the photosensitive drum 77 whose surface is positively charged by the charger 78 moves by rotation, and the laser beam LB is irradiated by the optical scanning device described above. Since the photosensitive drum 77 is replaced as a process unit as a unit with the replacement of the developer T, the photosensitive drum 77 is composed of an organic OPC (Organic PhotoConductor) photosensitive body that is relatively low in durability but is lightweight and relatively inexpensive. Yes. When the laser beam LB is irradiated, the conductivity of the surface of the photosensitive drum 77 irradiated with the laser beam LB is increased, so that the charging potential is lowered and a latent image is formed due to the potential difference. Note that the photosensitive drum 77 may be composed of aSi (amorphous silicon), a selenium photosensitive material made of Se or an Se-based alloy, CdS (cadmium sulfide), or the like that can be exposed at high speed and has a long-life photoconductivity. Good.

  The portion of the photosensitive drum 77 on which the latent image is formed by the laser beam LB comes into contact with the developing roller 75 having the developer T attached to the surface thereof by the rotation of the photosensitive drum 77. The developing roller 75 is a rubber roller made of a base material in which carbon black is dispersed in silicon rubber or urethane rubber on a metal roller shaft such as stainless steel, and the roller surface is coated with a fluororesin. The developer T adhering to the developing roller 75 is frictionally charged by the supply roller 74 and the layer thickness regulating blade 76 and is positively charged.

  When the developing roller 75 comes into contact with the photosensitive drum 77, the developer T adheres to the portion where the laser beam LB is irradiated and the charging potential is lowered. Therefore, the latent image is visualized and visualized by the developer T, and the development is completed. At this time, the developer T remaining on the photosensitive drum 77 is collected by the developing roller 75. The developed image is further conveyed to a position facing the paper P in the nip portion with the transfer roller 87 by the rotation of the photosensitive drum 77.

  The transfer roller 87 is configured as a conductive roller whose surface is covered with a base material in which carbon black is dispersed in silicon rubber or urethane rubber to provide conductivity, and is connected to a negative pole of a power supply unit (not shown) and applied with a voltage. Therefore, the developer T formed on the photosensitive drum 77 is formed by applying a voltage to the paper P and bringing the paper P and the photosensitive drum 77 into contact with each other by the transfer roller 87 biased in the direction of the photosensitive drum 77. The image is transferred to the paper P.

  As shown in FIG. 1, an image is formed on the paper P by the developing unit 17 configured as described above, and the paper P is further transported by the transport unit 18 and enters the fixing unit 15.

  As shown in FIG. 1, the fixing unit 15 is provided with a heat roller 52 having a halogen heater 53 in the frame 51, a pressure roller 54 for urging the paper P to the heat roller 52, and a downstream side in the paper transport direction. A first discharge roller 55 and a driven roller 56 that is driven by the first discharge roller 55 are configured as a fixing unit.

  The heat roller 52 is disposed so as to be approximately the width of the sheet and perpendicular to the sheet conveyance direction, and is configured to be in close contact with the image formed by the developing unit 17 on the conveyed sheet P. The heat roller 52 is formed in an aluminum hollow cylindrical shape, is rotatably supported at both ends, and is rotated by transmission of power through a gear train (not shown). The surface is coated with a fluororesin so that developer T or the like does not adhere even when heated.

  The halogen heater 53 is disposed at the center of the heat roller 52. The halogen heater 53 is a heater in which a halogen gas is sealed in a quartz tube, and the internal temperature can be increased from 700 ° C. to a high temperature of 800 ° C. in a short time. When the halogen heater 53 is turned on to generate heat, the surface temperature is raised from about 400 ° C. to 450 ° C., the heat roller 52 is heated from the inside, and the surface temperature is raised to about 200 ° C.

  A pressure roller 54 is arranged so as to press-contact the paper P conveyed to the heat roller 52. The pressure roller 54 is formed of a heat-resistant rubber material so that the surface thereof can be in close contact with the heat roller 52, and is further coated with a fluororesin to prevent adhesion of the developer T and the like. The pressure roller 54 is configured to rotate with the rotation of the heat roller 52, and at this time, a rotation shaft (not shown) disposed at both ends so as to press the paper P against the heat roller 52 is biased by a coil spring (not shown). Is configured to do.

  When the sheet P enters the fixing unit 15 configured as described above, an image formed by the developer T formed on the sheet P is pressed against the surface of the heat roller 52 by the pressure roller 54. At this time, the surface of the heat roller 52 is at a high temperature, and the developer T melts and penetrates into the fibers of the paper P. At this stage, since the developer T is not completely solidified, the image formed on the sheet P is completely fixed when the sheet P is cooled by the outside air.

  Further, the sheet P is discharged from the fixing unit 15 by a first discharge roller 55 that is disposed downstream of the heat roller 52 in the sheet conveyance direction and is driven by a driving unit (not shown) and a driven roller 56 that is driven by the first discharge roller 55. .

  Next, as shown in FIG. 1, the sheet P on which the image is fixed by the fixing unit 15 is discharged by a first discharge roller 55 and a driven roller 56 provided in the fixing unit 15. A paper discharge direction switching device 62 is disposed downstream in the direction (leftward in FIG. 1). The paper discharge direction switching device 62 guides the front end of the paper P upward from the rear of the device so as to guide the paper P to the printed paper placement unit 69, and further changes the direction forward (right in FIG. 1). Thus, the guide part 62a which formed the path | route of the curved paper P is provided, and the guide part 62a is pivotally supported by the shaft support part 62b in the upper part. The shaft support portion 62b is regulated by a restricting portion 62d that restricts the shaft support portion 62b to be movable only in the vertical direction, and is urged downward by a biasing portion 62e formed of a wire spring that biases the shaft support portion 62b downward. Yes. Further, a torsion coil spring formed integrally with the urging portion 62e is disposed on the shaft support portion 62b, and urges the guide portion 62a to jump up rearward (upper left in FIG. 1). . The main body frame 11 in the vicinity of the lower end of the guide portion 62a in a state where the guide portion 62a is closed is provided with a hook portion 63 for hooking the guide portion 62a to hook the lower end of the guide portion 62a.

  According to the paper discharge direction switching device 62 configured in this way, if the lower end of the guide portion 62a is hooked to the hook portion 63, the guide portion 62a is moved downward by the biasing portion 62e via the shaft support portion 62b. Since it is energized, the latch is not released and the coil spring (not shown) does not spring up upward. Therefore, the leading end of the paper P discharged from the fixing unit 15 is guided by the first paper discharge roller 55 and the driven roller 56 into the guide unit 62a to be guided to the printed paper placement unit 69 and guided. Is further conveyed by the second paper discharge roller 65 and the driven roller 66 and is discharged to the printed paper stacking portion 69. A paper discharge extension tray 68 is pivotally attached to the front portion of the printed paper placement portion 69 so that it can be unfolded forward.

  On the other hand, when the finger is hooked on the finger hooking portion 62f of the guide portion 62a and shifted upward, the shaft support portion 62b is shifted upward along the restricting portion 62d against the biasing force of the biasing portion 62e, and the hooking portion 63 is moved. The latch by is released. For this reason, the guide portion 62a is displaced by a torsion coil spring (not shown) to a state in which the guide portion 62a is flipped up rearward about the shaft support portion 62b. In this state, the paper P discharged from the fixing unit 15 by the first paper discharge roller 55 and the driven roller 56 does not enter the guide unit 62a and is discharged to the rear of the apparatus (left side in FIG. 1) as it is. Paper. A sheet discharge tray (not shown) is attached to the rear of the apparatus, and the discharged sheets P can be stacked and placed.

  As shown in FIG. 1, a control unit 20 including a CPU, a ROM, and a RAM (not shown) that controls the apparatus is provided at the rear of the main body frame 11. The control unit 20 is a device for image data input, processing, modulation control of the oscillation of the laser diode 41, control of the polygon mirror drive motor 24, control of the transport unit 18, control of the halogen heater 53, control of the power supply, etc. It also performs general control.

Further, here, the optical scanning device 12 according to the present invention will be described in detail.
First, the light emitting unit 47 will be described in detail. The laser diode 41 oscillates when a voltage is applied from a laser diode driving circuit provided on the substrate 43 by a control signal based on image data from a CPU (not shown) of the control unit 20.

  As shown in FIG. 4, the laser diode 41 formed in a substantially columnar shape is formed on a rectangular thick plate with aluminum having a high heat dissipation effect, and a hole for fitting the laser diode 41 is formed in a substantially central portion thereof. It is supported by the laser diode holder 42 with its central axis facing the polygon mirror 23. The laser diode holder 42 and the substrate 43 are provided with screw holes for screwing to the support member 21, and the substrate 43 is laminated on the outside of the optical scanning device 12 with the laser diode holder 42. Two screws that pass through the substrate 43 and the laser diode holder 42 are arranged substantially parallel to the optical axis of the laser diode 41 at a position sandwiching the left and right 41, and these screws are screwed into the support member 21. The substrate 43 and the laser diode holder 42 are locked to the support member 21. The lead wire of the laser diode 41 is soldered and connected to the substrate 43, and is driven in response to the drive signal described above.

  On the light emitting side of the light emitting unit 47, a lens cell 44 having a collimating lens 45 and a slit (not shown) is disposed on the optical path. The laser beam LB emitted when the laser diode 41 oscillates is diffused light. The collimating lens 45 made of a convex lens converts the diffusing laser beam LB into parallel light. Since the laser beam LB made into a parallel light beam by the collimator lens 45 has a large light beam width, a hole is provided only in a portion through which the light beam passes, and a slit for restricting the light beam width is disposed on the optical path. The light emitting unit 47 and the lens cell 44 constitute a parallel light unit, and the laser beam LB emitted by the parallel light unit and made parallel and the width of the light beam is regulated is directed to the polygon mirror 23.

  The polygon mirror 23 has a flat regular hexagonal prism shape, and the side surface portion is composed of six plane mirrors. As shown in FIG. 2, a polygon mirror drive motor 24 is disposed below the polygon mirror 23, and supports the polygon mirror 23 by a rotating shaft 24a to drive the polygon mirror 23. The polygon mirror drive motor 24 is supported by the support member 21 via the vibration isolation leg 25. The anti-vibration leg 25 absorbs the vibration of the polygon mirror drive motor 24 and prevents the vibration of the polygon mirror drive motor 24 from being transmitted to the support member 21. The polygon mirror 23, the polygon mirror drive motor 24, and the vibration isolation leg 25 constitute a polygon mirror unit.

  As shown in FIG. 4, the light beam of the laser beam LB emitted from the light emitting unit 47 is arranged so as to hit the rotating polygon mirror 23, and the laser beam hitting the polygon mirror 23 rotating clockwise (clockwise) in FIG. LB is reflected on the same plane as the rotating surface of the polygon mirror 23 and is continuously deflected and displaced from the LBL position shown in FIG. 4 to the LBR position. When the laser beam LB reaches the LBR position, the laser beam LB emitted from the light emitting unit 47 is reflected on a new plane of the rotating polygon mirror 23, and the reflected laser beam LB returns to the LBL position again. It is continuously deflected and displaced to the position of LBR. In this way, scanning is performed by repeatedly displacing the laser beam LB. In the present application, a surface on which the laser beam LB is displaced is referred to as a scanning surface.

  In this scanning range, if the modulation timing of the laser beam LB is not synchronized with the rotation of the polygon mirror 23, the position where the image is formed is shifted along the scanning plane, so the scanning is performed in a range larger than the range for forming the actual image. And has a predetermined margin. Therefore, in order to match the actual print start position with the modulation start position of the laser beam LB, a start beam detector 49a is provided on the LBL line in FIG. 4, and the light of the laser beam LB is incident on the start beam detector 49a. A signal is transmitted from the start beam detector 49 a to the control unit 20. Receiving this signal, the control unit 20 controls the oscillation timing of the laser diode 41 so as to modulate the unmodulated laser beam LB from the position where an actual image is to be formed based on the image data. In this manner, the positional deviation along the scanning plane is adjusted.

  Furthermore, an end beam detector 49b is provided on the LBR line, and the control unit 20 uses a signal from the end beam detector 49b so that the laser diode LB ends scanning of the laser beam LB at a position where the actual image formation is to end. 41 is controlled.

  The first cylindrical lens 46 is a well-known cylindrical lens obtained by cutting a part of a cylinder in the height direction. The first cylindrical lens 46 is disposed at an intermediate position between the parallel light unit and the polygon mirror 23, and perpendicularly emits the parallel light emitted from the parallel light unit. It is focused on the mirror surface of the polygon mirror 23 by converging in the direction. Therefore, it is arranged so that the thickness changes in a direction perpendicular to the scanning plane with a constant thickness in the scanning plane direction. The first cylindrical lens 46 is formed of an acrylic resin on a rectangular tube having a substantially square cross section and is integrally formed with a frame body that supports the cylindrical lens.

  The fθ lens 31 is provided on the optical path of the laser boom LB reflected by the polygon mirror 23. When the laser beam LB rotated and moved at a constant angular velocity by the polygon mirror 23 is scanned as it is, the scanning speed of the left and right ends of the photosensitive drum 77 to be scanned becomes higher than the scanning speed of the central portion, and the image is distorted. It will occur. Therefore, it is a lens that corrects the laser beam LB rotated at a constant angular velocity by the polygon mirror 23 so as to scan on the photosensitive drum 77 at a constant velocity.

  As shown in FIGS. 4 and 2, the first fixed mirror 32 corresponds to the laser beam LB that has passed through the fθ lens 31, and covers one surface of the elongated rectangular parallelepiped glass body whose longitudinal direction is provided along the scanning plane. It has an aluminum coating as a reflective surface. The laser beam LB corrected by the fθ lens 31 is reflected and arranged so as to deflect the light beam on the upper surface side substantially perpendicularly to the lower surface side.

  As shown in FIG. 2, the second fixed mirror 33 has the same configuration as the first fixed mirror. The second fixed mirror 33 further vertically deflects the light beam deflected downward in FIG. It is arranged at the guiding angle.

  The second cylindrical lens 34 is configured in substantially the same manner as the first cylindrical lens. However, since the laser beam LB moves, the second cylindrical lens 34 is formed wide along the scanning plane so as to correspond to the moving range. The second cylindrical lens 34 diffuses the diffused light again in the vertical direction after the laser beam LB converged on the polygon mirror 23 by the first cylindrical lens 46 is reflected by the polygon mirror 23. 77 used to converge again.

  The third fixed mirror 35 has the same configuration as the first fixed mirror 32 and is configured to correspond to the scanning width of the laser beam LB, and is arranged so as to deflect the laser beam LB in the direction of the photosensitive drum 77 and reflect it. Is configured.

  Here, so-called “surface tilt correction” performed by an optical system including such an optical element will be described. If the laser beam LB is projected onto the polygon mirror 23 that rotates with the same light beam without the first cylindrical lens 46 and the second cylindrical lens 34, the laser beam LB reflected by the polygon mirror 23 passes through the fθ lens 31. The photosensitive drum 77 is scanned by being reflected by the first fixed mirror 32, the second fixed mirror 33, and the third fixed mirror 35. At this time, the six plane mirrors provided in the polygon mirror 23 must reflect the laser beam LB so as to accurately scan a predetermined position of the photosensitive drum 77. However, the angle of the vertical tilt of the six plane mirrors is not limited. It is difficult to completely adjust the angle, and if there is an error in the angle of inclination, the polygon mirror 23 rotates and the scanning direction changes every time it is reflected by the next plane mirror having a different angle.

  Therefore, the light beam of the laser beam LB is first converged in the vertical direction by the first cylindrical lens 46 and focused on the polygon mirror 23. Then, the laser beam LB is reflected by the polygon mirror 23 in a state where it is most converged in the vertical direction. The laser beam LB reflected by the polygon mirror 23 is reflected while being diffused in various directions by swinging in the vertical direction according to the angle of the polygon mirror 23. The laser beam LB is converged by the second cylindrical lens 34 so as to be focused again on the surface of the photosensitive drum 77. One of the properties of a cylindrical lens is that light emitted from the focal point or the vicinity of the focal point always passes through the opposite focal point or a predetermined point regardless of which part of the lens hits. Therefore, if one focal point of the second cylindrical lens is aligned with the polygon mirror 23 and the other focal point is aligned with a predetermined scanning position of the photosensitive drum 77, the light converged on the polygon mirror 23 is reflected on each plane mirror of the polygon mirror 23. Even if each of them is tilted, it always hits a predetermined position to be scanned. The above is the principle of correcting the tilting. In accordance with this principle, the optical elements of the optical scanning device 12 of the present embodiment are arranged.

  The support member 21 includes the parallel light unit, the first cylindrical lens 46, the polygon mirror unit 26, the fθ lens 31, the first fixed mirror 32, the second fixed mirror 33, the second cylindrical lens 34, and the third fixed lens as described above. It is a member that supports optical elements such as the mirror 35. The support member 21 is made of amorphous engineering plastic in which glass fiber is mixed with polyphenylene ether (modified PPE). Therefore, it has excellent electrical characteristics, flame retardancy, heat resistance, dimensional stability, and moldability and high strength, but it can also be composed of other materials such as, for example, a glass fiber mixed with glass fiber.

  As shown in FIG. 2, when the plane perpendicular to the Z direction is the horizontal direction, the support member 21 has a side wall portion 220 formed around the horizontal direction, and supports each optical element so as to be surrounded by the side wall portion 220. The first flat surface portion 211 to the ninth flat surface portion 219 are provided. The first plane portion 211 horizontally supports the polygon mirror 23 and the polygon mirror drive motor 24 for driving the polygon mirror 23 on the surface disposed in the horizontal direction via the anti-vibration legs 25.

  Behind the first plane portion 211 (on the left side in FIG. 2), a second plane portion 212 is provided that is a plane that is bent vertically upward with respect to the first plane portion 211 and is continuous. The reason why the second plane portion 212 is provided vertically is to obtain a step by obtaining a large vertical distance with the shortest horizontal distance. By doing so, it becomes possible to provide a sufficient space for the polygon mirror unit 26, and the anti-vibration legs 25 that can stably support the polygon mirror drive motor 24 and can sufficiently absorb vibration are provided. The mirror drive motor 24 is configured to increase stability and not transmit vibration to other parts.

  Continuing from the second plane portion 212, a third plane portion 213 is provided 45 degrees upward from the horizontal direction. Here, the third flat surface portion 213 is provided 45 degrees upward from the horizontal direction in this way so that this surface is close to the optical path of the diffusing laser beam LB reflected by the polygon mirror 23. Therefore, it is scattered by light derived from the light beam of the laser beam LB, for example, light when the traveling direction of the light beam fluctuates, such as when the reflection surface of the polygon mirror 23 is not exactly vertical, or dust in the space. And light derived from the laser beam LB (hereinafter referred to as harmful light), such as diffracted light generated because the laser beam LB is a wave that oscillates, may hit the third plane portion 213. If the surface is configured to be vertical or at an angle close to it as if the second plane portion 212 was extended as it was, the harmful light reflected here would go back and directly hit the polygon mirror 23 again. Ri likely to be the cause of stray light. Also, if this surface is configured at an angle that is horizontal or close to it, the harmful light reflected here is reflected in a direction close to the traveling direction of the original luminous flux, directly hits the fθ lens 31 and also causes stray light. Cheap. In particular, if the light enters the inside of the fθ lens 31, it is totally reflected inside and unnecessary light easily enters in the rear, so that the harmful light hit here is reflected substantially perpendicularly to other optical elements. This is to prevent direct hit. That is, in this way, unnecessary harmful light is vertically reflected so that the quality of the latent image formed on the photosensitive drum 77 is not affected.

  Here, as described above, the support member 21 is manufactured, for example, by mixing glass fiber into modified PPE. However, in normal injection molding, it is advantageous to have a smooth mold surface, so that the support member 21 is smoothed. For this reason, even if the material is colored black, it reflects several percent or more of light rays. In addition, it is troublesome and expensive to carry out fine unevenness and flocking treatment so that the surface is difficult to reflect. Therefore, if stray light can be prevented by adjusting the reflection angle of harmful light, it is advantageous in terms of cost.

  The angle of the third plane portion 213 is most effective for preventing stray light by deflecting harmful light approximately perpendicularly to the horizontal plane at 45 degrees. Various angles can be adopted as long as the harmful light reflected here does not directly reflect on each optical element. In addition, when the support member 21 is injection-molded, it is better to form the angle gently from this point, because it is easier to form the one having a gentle angle. On the other hand, in order to make a large step at a short horizontal distance, it is better to be close to the vertical as in the second flat portion 212, but it is a precondition that reflected light is not reflected on each optical element. Therefore, in principle, an inclination of approximately 30 ° to 60 ° from the horizontal plane is effective, and 45 ° is particularly desirable. Of course, it does not preclude the most appropriate configuration from exceeding this range in consideration of the optical characteristics such as the size of each optical element, the focal length of the optical element, and various characteristics.

  The fourth plane portion 214 is provided horizontally behind the third plane portion 213. Since this portion is close to the light flux of the diffusing laser beam LB, harmful light that did not hit the third plane portion 213 may hit the horizontal plane of the fourth plane portion 214, and in the traveling direction of the laser beam LB. If harmful light in a near direction is incident, the reflected light is directly incident on the fθ lens 31 and causes stray light. However, since the third fixed mirror 35 is supported on the lower surface side of the fifth flat portion 215, it is better to make it horizontal in terms of space. Therefore, the first light shielding portion 29 is provided as follows.

  The first light shielding portion 29 is overhanging on the fourth plane portion 214 side so as to form a surface extending from the surface of the third plane portion 213 at the boundary portion between the third plane portion 213 and the fourth plane portion 214. It is configured as a wall-shaped part. The first light shielding portion 29 is configured to have a height that blocks harmful light from directly hitting the horizontal surface of the fourth flat portion 214, and even if this harmful light hits the first light shielding portion 29, the harmful light is converted into a laser beam. It is reflected substantially perpendicular to the LB light beam.

  A fifth plane portion 215 is provided obliquely downward and rearward of the fourth plane portion 214. Since the fifth fixed portion 35 directly fixes the third fixed mirror 35 to the lower surface side, the fifth fixed portion 215 is connected to the fourth flat portion 214 in accordance with the angle at which the third fixed mirror 35 reflects the laser beam LB, as will be described later. It is formed at an angle of about 30 ° obliquely downward from the part.

  A sixth plane part 216 is provided on the horizontal rear side in continuation with the fifth plane part 215. An fθ lens 31 is provided on the upper surface side of the sixth plane portion 216. For example, if the thickness of the fθ lens 31 is about 12 mm, the fθ lens 31 is actually used at a fraction of about 3 mm to 4 mm including the central portion at most. This is because distortion is likely to occur if a thin lens is made during lens molding as described above, so it is not only in terms of accuracy and production cost that a thick lens is molded and a center-free portion is used. Furthermore, it is advantageous in that it is less susceptible to the influence of humidity, and problems such as those when using a thin lens are less likely to occur. Therefore, the laser beam LB reflected by the polygon mirror 23 only needs to have a space of about 3 to 4 mm at the center of the fθ lens 31, and the other part is a support member between the polygon mirror 23 and the fθ lens 31. There may be 21 obstacles.

  For this reason, the second flat surface 212 to the fifth flat surface between the first flat surface portion 211 and the sixth flat surface portion 216 in which the polygon mirror 23 and the fθ lens 31 are arranged among the portions constituting the support member 21. The portion 215 is disposed so as to bite into the space between the polygon mirror 23 and the fθ lens 31, and the third fixed mirror 35 is disposed on the lower surface using this space. By doing so, it is possible to reduce the vertical size without degrading the optical performance.

  In particular, the portion of the polygon mirror drive motor 24 disposed below the polygon mirror 23 has a large space. Therefore, in the conventional configuration shown in FIG. 5, since the polygon mirror 123, the motor 124 for driving the polygon mirror 123, and the fθ lens 131 are supported by the support frame 121 on the same plane, the optical axes of the polygon mirror 123 and the fθ lens 131 are changed. In order to align them, it is necessary to provide a spacer 136 below the fθ lens 131. The space below the laser beam LB between the polygon mirror 123 and the fθ lens 131 becomes a dead space, which hinders miniaturization of the optical scanning device. It was. In the optical scanning device 12 according to the present embodiment, the space efficiency can be remarkably increased by adopting a lean configuration as described above.

  Continuing from the sixth plane part 216, a seventh plane part 217 is provided in a 45 ° direction obliquely upward rearward. In addition, an eighth plane portion 218 is provided horizontally behind the seventh plane portion 217. And the surface of the 7th plane part 217 is extended, and the 2nd light shielding part 30 is comprised as an overhang-like wall-shaped part at the 8th plane part 218 side. The second light shielding unit 30 is configured to have a height that blocks harmful light from directly striking the horizontal plane of the eighth plane unit 218, and reflects this harmful light substantially perpendicularly to the light beam of the laser beam LB. In particular, since the laser beam LB is greatly diffused in this portion and easily shakes up and down, and the eighth plane portion 218 is disposed long in the front-rear direction (left-right direction in FIG. 2), harmful light strikes the eighth plane portion 218. Cheap. For this reason, this 2nd light-shielding part 30 plays an important role for stray light generation prevention.

  A second cylindrical lens 34 is disposed on the lower surface side of the eighth plane portion 218. Since the position of the light beam on the lower surface side is determined by the second cylindrical lens 34, bringing the second cylindrical lens 34 closer to the light beam on the upper surface side means reducing the thickness of the optical scanning device 12. By the way, also in the second cylindrical lens 34, as in the case of the fθ lens 31 described above, the portion that is actually used by passing the laser beam LB is limited to the vicinity of the central portion in the vertical direction. In addition, when the sixth plane portion 216 that supports the fθ lens 31 and the eighth plane portion 218 that supports the second cylindrical lens 34 are arranged on the same plane, the fθ lens 31 and the second cylindrical lens 34 are disposed on the support member 21 side. A dead space will be created. For this reason, in the present embodiment, the seventh plane portion 217 is provided as a connecting portion for connecting the portions supporting these two optical elements with a step. The seventh plane portion 217 provides a step in the sixth plane portion 216 and the eighth plane portion 218, eliminates the dead space, and reduces the vertical distance between the fθ lens 31 and the second cylindrical lens 34. The distance between the laser beam LB on the lower surface side and the optical scanning device 12 can be reduced.

  A ninth plane portion 219 is provided horizontally at substantially the same height as the eighth plane portion 218 with a gap therebetween, and this end portion is connected to the side wall portion 220. The reflection surface is approximately perpendicular from FIG. 2 so that the laser beam LB transmitted through the fθ lens 31 by the first fixed mirror 32 on the upper surface side of the ninth plane portion 219 is deflected from the gap with the eighth plane portion 218 to the lower surface side. It is disposed at a position rotated 57 ° clockwise (clockwise).

  Further, on the lower surface side of the ninth plane portion 219, the laser beam LB deflected from the upper surface side to the lower surface side by the first fixed mirror 32 is deflected again in a direction substantially parallel to the laser beam LB on the upper surface side, and second. In order to align with the optical axis of the cylindrical lens 34, the second fixed mirror 33 is disposed at a position where the reflecting surface is rotated about 22 ° counterclockwise (counterclockwise) in FIG. Therefore, in the present embodiment, the light beam on the lower surface side is lowered by 2 ° in FIG. 2 with respect to the light beam on the upper surface side. This is for adjusting the distance to the photosensitive drum 77 (see FIG. 3) in the present embodiment. Accordingly, each optical element can be configured so that the optical scanning device 12 can be configured most compactly, such as by arranging the first fixed mirror 32 and the second fixed mirror 33 so that the angles of the first fixed mirror 32 and the second fixed mirror 33 are inclined by 45 ° from the vertical (Z direction). Needless to say, it can be appropriately changed in accordance with the characteristics.

  As described above, since each optical element does not create a dead space in each of the flat portions 211 to 219 of the support member 21, the entire structure is made compact.

  A lid 22 is provided that fits outside so as to cover the entire upper surface side of the support member 21 configured as described above. The lid body 22 is formed by bending an iron thin plate, and the lid body 22 is a member that is sealed so that dust or the like does not enter inside. The distance between the lid 22 and each optical element is arranged close to each other as long as it does not interfere with the laser beam LB. However, since the polygon mirror 23 rotates at a high speed, the air around the polygon mirror 23 is caused to flow. If the space near the polygon mirror 23 is narrow, the pressure increases in part due to the flow, and exchange with the outside air occurs. Will be encouraged. Thus, when alternating with the outside air, the developer T and dust enter the optical scanning device 12. Therefore, it is desirable that there is a certain space in the vicinity of the polygon mirror 23.

  As shown in FIG. 3, the entire image forming apparatus 1 includes a main body frame 11 made of amorphous engineering plastic in which glass fibers are mixed into a modified PPE, like the support member 21 of the optical scanning device 12. As shown in FIG. 3, a box-shaped optical scanning device support portion 11a having an open upper portion is provided so as to be suspended from an upper plastic portion of the main body frame 11 in order to support the optical scanning device 12. The optical scanning device support portion 11a is formed of an iron thin plate that has a high strength per volume and can ensure a certain strength with respect to its thickness.

  As shown in FIG. 2, the lower surface side of the support member 21 of the optical scanning device 12 is open, but the optical scanning device 12 is fixed to the bottom of the box-shaped optical scanning device support portion 11a to The lower part is configured to be closed. In addition, a groove-shaped opening for allowing the laser beam LB to irradiate the photosensitive drum 77 with the laser beam LB reflected by the third fixed mirror 35 of the optical scanning device 12 is provided in the optical scanning device support portion 11a. The cover glass 27 is formed of a flat glass plate that is isolated so that the air inside and outside the optical scanning device 12 is exchanged so that the developer T from the developing unit 17 does not enter the opening. Is provided. This cover glass 27 is closely fixed to the iron plate of the optical scanning device support portion 11 a by a resin cover glass presser 28 and a resin portion 37.

  As shown in FIG. 3, the resin portion 37 is a resin member that is inserted into a groove-shaped opening formed at a position facing the charger 78 of the optical scanning device support portion 11a, and reflects stray light. It is a lid-shaped member formed from polypropylene (PP) colored black to prevent it. As described above, in the charger 78, a high voltage is applied to the charging wire 78a to perform corona discharge, and positive ions generated by the corona discharge are applied to the surface of the photosensitive drum 77 connected to the negative electrode. Move and become charged. At this time, positive ions generated by corona discharge positively charge not only the surface of the photosensitive drum 77 but also the developer T and dust floating around. Here, the charger 78 needs to clean the charging line 78a because the developer T or the like adheres to the charging line 78a. For this purpose, a groove-like hole 78c for slidably guiding a cleaning member (not shown) to be cleaned by sandwiching and sliding the charging wire 78a on the surface of the charger 78 facing the optical scanning device 12 is provided. Yes. For this reason, the floating developer T or dust charged positively inside the charger 78 flows out toward the optical scanning device 12 through the hole 78c.

  Here, if the resin portion 37 is not provided on the optical scanning device support portion 11a, the optical scanning device support portion 11a is formed of an iron plate, and this iron plate is considered to be a ground potential. The mirror image force acts on a certain iron plate, and the positively charged floating developer T or dust adheres. For this reason, if the optical scanning device 12 at the upper part of the main body frame 11 is opened upward together with the optical scanning device support 11a for the dirt maintenance of the optical scanning device support 11a, the user's hand may be soiled. Further, when the charged developer T or the like adheres here and the potential drops with time, it reattaches to the nearby cover glass 27, lowering the illuminance of scanning with the laser beam LB and adversely affecting image formation. become.

  On the other hand, in the present embodiment, since the resin portion 37 formed of PP having low conductivity is provided in the portion facing the charger 78 of the optical scanning device support portion 11a, it floats positively charged. Even if the developer T or the like flows out from the cleaning hole 78 c of the charger 78, the mirror image force does not act on the resin portion 37 and does not adhere to the resin portion 37. For this reason, the optical scanning device support 11a can be disposed close to the charger 78, and together with the thinning of the optical scanning device 12, it can contribute to the miniaturization of the image forming apparatus 1 itself. .

  Here, a case where a scorotron is used as an example of the charger of the present embodiment has been described as an example, but the same applies to the case where a corotron is used. The same applies to a negatively charged system. Further, a contact-type charger using brush charging or the like also performs the same operation since microscopic corona discharge is performed.

  Since the image forming apparatus of the present embodiment is configured as described above, it has the following operations and effects. That is, as shown in FIG. 2, the length of the apparatus is shortened by providing three fixed mirrors and bending the light beam, and the polygon mirror unit 26, the fθ lens 31, the first fixed mirror 32 constituting the optical scanning device 12, Since the second fixed mirror 33, the second cylindrical lens 34, the third fixed mirror 35, and the like are disposed on the support member 21 provided with a step so as not to create a dead space, the thickness of the optical scanning device 12 is reduced. Since the thickness can be reduced and the volume can be reduced as compared with the prior art, the apparatus optical scanning device 12 can be downsized, and the entire image forming apparatus 1 can be downsized.

  Further, the shape of the support member 21 reflects the harmful light from the traveling direction so that the harmful light becomes stray light and does not interfere with the original light beam of the laser beam LB. In particular, the light shielding portions 29 and 30 are provided in close proximity so as to actively block harmful light, so that the generation of stray light is reduced, and the quality of the latent image formed by scanning on the photosensitive drum 77 is improved. There is an effect that a quality image can be formed. In addition, even if the optical scanning device support portion 11a is disposed close to the charger 78, the resin portion 37 is disposed, so that the charged developer T or the like is hardly adhered, and the optical scanning device 12 is disposed. Combined with the reduction in thickness, the image forming apparatus 1 can be further downsized.

  Further, since the resin portion 37 that is an insulator is provided on the optical scanning device support portion 11a, the charged dust and the developer T do not adhere to the optical scanning device support portion 11a due to mirror image force. Further, the resin part 37 is used as the same member as the cover glass holder, and the resin part 37 can also serve as a holder for the cover glass 27, thereby reducing the number of parts.

  Although the present invention has been described based on one embodiment, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention. Can be easily guessed.

  For example, the number of fixed mirrors may be one, two, or four or more, and it goes without saying that the design can be appropriately changed according to the configuration of the image forming apparatus or the like. The arrangement of the polygon mirror drive motor 24 may be arranged on the opposite side of the support member 21 of the polygon mirror 23. Furthermore, each optical element can also have an optical configuration in which, for example, the first cylindrical lens is omitted. The type of the light source is not limited to the laser diode, and various light sources can be used.

FIG. 3 is a cross-sectional view of the image forming apparatus 1 viewed from the side in a direction orthogonal to the paper conveyance direction. It is sectional drawing in the AA part of FIG. FIG. 2 is an enlarged view of a part of an optical scanning device 12, a developing unit 17, and a main body frame 11 of the image forming apparatus 1 shown in FIG. FIG. 3 is a plan view of the optical scanning device 12 as viewed from above (Z direction in FIG. 1) with the lid body 22 removed. It is a figure which shows an example of the conventional optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Main body frame 11a Optical scanning device support part 12 Optical scanning device 17 Development part 21 Support member 211 1st plane part 212 2nd plane part 213 3rd plane part 214 4th plane part 215 5th plane part 216 1st 6 plane part 217 7th plane part 218 8th plane part 219 9th plane part 220 side wall part 22 lid body 23 polygon mirror 24 polygon mirror drive motor 25 anti-vibration leg 26 polygon mirror unit 27 cover glass 28 cover glass holder 29 first Light shielding portion 30 Second light shielding portion 31 fθ lens 32 First fixed mirror 33 Second fixed mirror 34 Second cylindrical lens 35 Third fixed mirror 37 Resin portion (resin member)
41 laser diode 42 laser diode holder 43 substrate 44 lens cell 45 collimating lens 46 first cylindrical lens 47 light emitting unit 70 frame 77 photosensitive drum 78 charger 78a charging line 78b grid electrode 78c cleaning hole 78d shield electrode LB laser beam P paper T Developer

Claims (5)

A polygon mirror unit comprising a polygon mirror for rotating and reflecting a light beam from a light source and a motor for driving the polygon mirror; and an optical element for imaging the light beam reflected by the polygon mirror on a photosensitive member; An optical scanning device comprising a plurality of mirrors that reflect light that has passed through the optical element, and a support member that supports the polygon mirror unit and the optical element,
The support member is composed of a plurality of plane parts, and at least a polygon mirror unit support plane part that supports the polygon mirror unit, and a light beam reflected by the polygon mirror among the optical elements first passes. A first lens support plane part for supporting one lens ,
As the plurality of mirrors, bending the light beam passed through the first lens provided in the vicinity of an end of the support member on the back side direction and the mounting surface side of the first lens which is a surface opposite to the supporting member A first fixed mirror that
A light beam that is provided in the vicinity of the first fixed mirror and bent by the first fixed mirror is bent so as to travel in a direction substantially parallel to and opposite to the light beam that has passed through the first lens on the back surface side of the support member. At least two fixed mirrors,
Further, as the optical element, passes through the first lens, a second lens which the light flux is bent by the second fixed mirror passes,
It said support member further includes a second lens support surface section for supporting the second lens,
As the second lens supporting plane portion approaches the light beam passed through the first lens, the connection for connecting with a step between the first lens support plane portion and the second lens support surface portion An optical scanning device comprising a flat portion . The plurality of mirrors further includes a third fixed mirror that deflects and reflects the light beam bent by the second fixed mirror toward the photoconductor,
2. The optical scanning according to claim 1, wherein the support member is bent to form a recess on a back surface side of the support member, and the third fixed mirror is fixed to the recess formed in the support member. apparatus. A polygon mirror unit comprising a polygon mirror for rotating and reflecting a light beam from a light source and a motor for driving the polygon mirror; and an optical element for imaging the light beam reflected by the polygon mirror on a photosensitive member; An optical scanning device comprising a plurality of mirrors that reflect the light beam that has passed through the optical element, and a support member that supports the polygon mirror unit and the optical element,
The support member includes a plurality of plane portions, and includes at least a polygon mirror unit support plane portion that supports the polygon mirror unit.
The plurality of mirrors are provided in the vicinity of the end of the support member, and a first fixed mirror that bends the light beam reflected by the polygon mirror unit in the direction of the back surface of the support member;
A light beam bent in the vicinity of the first fixed mirror and bent by the first fixed mirror is bent on the back side of the support member so as to travel in a direction substantially parallel to and opposite to the light beam reflected by the polygon mirror unit. A second fixed mirror that
A third fixed mirror that reflects and reflects the light beam bent by the second fixed mirror toward the photoconductor;
The support member is bent so that a recess is formed on the back side of the support member so as to bite into the space between the polygon mirror and the first lens, and the third fixing is performed in the recess formed in the support member. An optical scanning device characterized in that a mirror is fixed. The support member includes an optical scanning apparatus according to claim 3, characterized in that the light flux reflected by the polygon mirror having a first lens support plane section for supporting the first lens to first pass. A photoconductor, a charger that charges the photoconductor, an optical scanning device that scans the photoconductor with a light beam modulated based on image data, and a developing unit that develops a latent image formed on the photoconductor An image forming apparatus comprising:
An image forming apparatus comprising said optical scanning device, an optical scanning apparatus according to any one of claims 1 to 4.

Images