JP2007333503A - Lens surface shutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lens surface shutter capable of preventing not only the damage of a lens surface, but also the contamination of the lens surface due to cloud toner. <P>SOLUTION: When a shutter part 68 is moved to a lens surface exposing position from a lens surface protecting position, by shaking the shutter part 68 in an arcuate state centered about the base parts 64B and 66B of linking member 64 and 66 using a linking mechanism, felt 72 slides or the lens surface (surface) of a density sensor 60 to move away from the lens surface. Accordingly, the friction load on the lens surface can be reduced, as compared with the case where the felt 72 as moved in parallel to the lens surface and the lens surface can be made difficult to damage. Furthermore, since a load can be applied in a direction of closely bringing the felt 72 into contact with the lens surface, at the lens surface protecting position, contaminants are less likely to infiltrate, and contamination of the lens surface can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens surface shutter that opens and closes a lens surface of a density sensor that measures the density of an image formed on a detection surface.

  2. Description of the Related Art Conventionally, an image forming apparatus that forms an image by transferring and fixing a toner image formed on a photosensitive member (image carrier) or an intermediate transfer belt (belt member) onto a recording sheet (recording medium) is known. . In such an image forming apparatus, a test patch image is transferred and formed on a transfer conveyance belt or the like, and the density of the patch image is measured by a density sensor. The lens surface is covered, and the lens surface is exposed when detecting the density of the patch image.

  For example, in Patent Document 1, the shutter member is translated along the lens surface of the density sensor using a link mechanism. However, in the arrangement in which the lens surface of the density sensor and the shutter member are in close contact with each other, the lens is formed by the shutter member. The surface may be rubbed and the lens surface may be damaged. Further, when the lens surface and the shutter member are separated from each other, floating toner (so-called cloud toner) around the photoconductor moves into the shutter member, adheres to the lens surface, and the lens surface may be contaminated.

As another conventional technique, Patent Document 2 proposes a structure that opens and closes a shutter by rotating a cylindrical shutter member. However, the shutter member and the lens surface are structurally brought into close contact with each other. In other words, the shutter member and the lens surface must be spaced apart from each other, and the lens surface is contaminated by the cloud toner.
Japanese Patent Laid-Open No. 2001-100597 JP 2004-138976 A

  In view of the above circumstances, an object of the present invention is to obtain a lens surface shutter that can prevent lens surface damage and prevents contamination of the lens surface with cloud toner.

  In order to achieve the above object, according to the first aspect of the present invention, in the lens surface shutter, a density sensor that measures the density of the image formed on the detection surface, and the lens surface of the density sensor are opposed to each other. An opening for exposing the lens surface and a shielding surface covering the lens surface are provided, and the lens surface is opened and closed by moving in a circular arc, and the opening and the shielding surface are substantially parallel to the lens surface. And a shutter member for maintaining the above.

  According to the first aspect of the present invention, the shutter member facing the density sensor is provided with an opening that exposes the lens surface and a shielding surface that covers the lens surface, and the position of the lens surface of the density sensor matches the position of the opening. By doing so, the lens surface is exposed, and the toner density can be detected by the density sensor. On the other hand, when the positions of the lens surface and the shielding surface coincide with each other, the lens surface is covered with the shielding surface to prevent contamination of the lens surface with cloud toner.

  Here, when moving from a position where the lens surface is covered by the shielding surface (hereinafter referred to as “lens surface protection position”) to a position where the lens surface is exposed (hereinafter referred to as “lens surface exposure position”), On the other hand, when the shutter member is moved in parallel, the rubbing force of the shielding surface to the lens surface becomes substantially constant until the shielding surface is separated from the lens surface.

  However, as in the present invention, at the lens surface protection position and the lens surface exposure position, the opening and the shielding surface are maintained substantially parallel to the lens surface, and between the lens surface protection position and the lens surface exposure position. By moving the shutter member in an arc, the sliding force of the shielding surface to the lens surface can be changed while the shutter member is moved from the lens surface protection position to the lens surface exposure position. That is, the frictional load on the lens surface can be reduced, and the lens surface can be made difficult to be damaged.

  According to a second aspect of the present invention, in the lens surface shutter according to the first aspect, the shutter member is rotatable to the shutter portion provided with the opening and the shielding surface, and to both ends of the shutter portion. And a link member that is connected and tilts to move the shutter portion in an arc with respect to the lens surface.

  According to the second aspect of the present invention, the shutter member is tilted with respect to the lens surface by tilting the link member that is rotatably connected to both ends of the shutter unit provided with the opening and the shielding surface. Thus, the shutter portion moves while drawing an arc, and the shutter portion can be moved in an arc with respect to the lens surface.

  According to a third aspect of the present invention, in the lens surface shutter according to the second aspect, the pair of link members constitutes a parallel link mechanism having the same length, and the link member rotates along the width direction of the detected surface. It is characterized by moving.

  In the third aspect of the present invention, the shutter member moves along the width direction of the detected surface by rotating the link member along the width direction of the detected surface. In other words, since the drive mechanism for driving the shutter member can be disposed in the dead space on both ends of the density sensor along the width direction of the detection surface, the lens surface shutter can be made thin, and the image forming apparatus Downsizing can be realized.

  Further, by providing a driving mechanism for driving the shutter member in the dead space on both ends of the density sensor, a space around the density sensor can be secured, and a cooling effect of the density sensor can be expected. For this reason, the detection accuracy of the density sensor is improved.

  According to a fourth aspect of the present invention, in the lens surface shutter according to the second or third aspect, a plunger of a solenoid is connected to one of the link members, and the link member is swung by moving the plunger in and out. It is characterized by that.

  According to a fifth aspect of the present invention, in the lens surface shutter according to any one of the first to fourth aspects, a lens surface protection member that contacts the lens surface is provided on the shielding surface.

  In the invention according to claim 5, the lens surface protection member contacts the lens surface, but at the same time when the shutter portion moves, the lens surface of the density sensor rubs and moves away from the surface of the lens surface. As compared with the case where the lens surface protection member is moved in parallel, the rubbing force on the lens surface is reduced. In addition, at the lens surface protection position, by tilting the link member, a load can be applied in the direction in which the lens surface protection member is in close contact with the lens surface, so that dirt is difficult to enter and contamination of the lens surface is prevented. To do.

  Here, by changing the length of the link member that swings the shutter member, the balance between the close contact of the lens surface protection member with the lens surface and the rubbing can be adjusted. Specifically, by increasing the length of the link member and reducing the curvature due to the movement trajectory on the free end side of the link member, the lens surface protection member moves away from the surface of the lens surface with respect to the movement amount of the shutter portion. Therefore, the amount of sliding can be reduced, and the rubbing force of the lens surface by the lens surface protection member can be increased. Therefore, the shutter member can be used as a wiper mechanism for the lens surface.

  When the shutter member is a shutter mechanism that opens the lens surface, the length of the link member is shortened. As a result, the curvature due to the movement trajectory on the free end side of the link member can be increased. Therefore, the amount that the lens surface protection member moves away from the surface of the lens surface increases with respect to the movement amount of the shutter portion. The rubbing force on the lens surface by the protective member is reduced.

  According to a sixth aspect of the present invention, in the lens surface shutter according to the fifth aspect, the lens surface protection member is a felt, and the felt is moved along the moving direction of the shutter portion when the felt covers the lens surface. It is characterized by raising the brushed.

  In the invention according to claim 6, the lens surface when the raising comes into contact with the lens surface by tilting the felt raising along the moving direction of the shutter portion when the lens surface protection member covers the lens surface. The rubbing resistance to the lens can be reduced, and the lens surface can be made difficult to be damaged.

  The invention according to claim 7 is the lens surface shutter according to claim 5, characterized in that the napping of the felt is tilted in the direction opposite to the moving direction of the shutter portion when the felt covers the lens surface. To do.

  In the invention according to claim 7, the lens surface when the raising comes into contact with the lens surface by tilting the raising on the surface of the felt in a direction opposite to the moving direction of the shutter portion when the felt covers the lens surface. The sliding resistance to the lens is increased to improve the wiper function of the lens surface.

  Since the present invention has the above-described configuration, it is possible to provide an image forming apparatus capable of preventing the lens surface from being contaminated by the cloud toner and preventing the lens surface from being damaged.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below in detail based on the embodiments shown in the drawings. In each figure, for each color of yellow (Y), magenta (M), cyan (C), and black (K), “Y”, “M”, “ Some of them are marked with the letters “C” and “K”.

  First, an outline of the image forming apparatus 10 according to the present invention will be described. As shown in FIGS. 1 and 2, the image forming apparatus 10 opens a main body frame 12 that detachably houses an image carrier (photosensitive member) 20 and a development unit 16, and the image carrier 20 and the development unit 16. The cover unit 14 is closed, and the transport unit 18 including the transport belt 34 capable of sucking and transporting the recording paper P is detachably attached to the cover body 14.

  The developing unit 16 is configured to irradiate the image carrier 20 with image light based on the image data and uniformly charge the surface of the roll-shaped image carrier 20. The optical box 24 for forming the toner image, the developing roller 26 for selectively transferring the toner to the latent image for visualization, and the image carrier 20 after the toner image has been transferred are slidably contacted and remain on the image carrier 20. And a cleaning member 28 for cleaning the toner.

  The image carrier 20 has a photosensitive layer on the surface (peripheral surface), and the surface (peripheral surface) is uniformly charged by the charging roller 22 and then is irradiated with laser light (image) from the optical box 24. The surface (circumferential surface) is exposed to light, and the potential of the exposed portion is attenuated to form an electrostatic latent image (image). The charging roller 22 is in contact with the image carrier 20, and a voltage is applied between them to generate a discharge in a minute gap near the contact portion, thereby causing the surface (circumferential surface) of the image carrier 20 to be discharged. Charges almost uniformly.

  The optical box 24 scans the surface (circumferential surface) of the image carrier 20 with the blinking laser beam, and forms an electrostatic latent image based on the image data on the surface (circumferential surface) of the image carrier 20. In addition, as the optical box 24, what arrange | positions light emitting elements, such as LED, and blinks these based on image data etc. can be considered.

  The developing roller 26 is disposed so as to face the image carrier 20 in the vicinity thereof, and a developing bias voltage is applied between the developing roller 26 and the image carrier 20. As a result, a developing bias electric field is formed between the developing roller 26 and the image carrier 20, and the charged toner is transferred to the exposed portion on the image carrier 20 to form a visible image.

  On the other hand, the transport unit 18 includes a transport belt 34 stretched around at least the driving roller 30 and the driven roller 32, and is located at a predetermined position between the driving roller 30 and the driven roller 32 on the inner surface side of the transport belt 34. A plurality of transfer rollers 36 (four corresponding to each color to be described later) are arranged at a predetermined interval.

  When the cover body 14 is closed (when the cover body 14 is rotated toward the main body frame 12 to close the image carrier 20 and the like), the transfer roller 36 is connected to the image carrier 20 with the conveyance belt 34 interposed therebetween. By forming a transfer electric field between the image carrier 20 and the image carrier 20, the toner image (undecided) on the surface of the image carrier 20 is recorded on the recording paper P that is sucked and conveyed by the conveyance belt 34. Image) is transferred.

  Here, the developing unit 16 is arranged in the vertical direction in order of yellow (Y), magenta (M), cyan (C), and black (K), for example, from the bottom so that full-color printing is possible. A fixing device 38 is disposed downstream of the developing units 16Y to 16K in the conveyance direction of the recording paper P (upper part of the main body frame 12).

  The fixing device 38 includes a heating roller 40 and a pressure roller 42 that face each other and are pressed against each other with a predetermined pressure (nip), and the recording paper P is formed by the heating roller 40 and the pressure roller 42. The toner image is fixed to the recording paper P by heating and pressurizing the unfixed toner image transferred thereon.

  Note that the recording paper P on which the toner image is fixed by being heated and pressed by the fixing device 38 (the heating roller 40 and the pressure roller 42) is discharged onto the paper discharge tray 44. After the transfer of the toner image to the recording paper P, the surface (circumferential surface) of the image carrier 20 is cleaned by the cleaning member 28 to prepare for the next image forming process.

  A detachable paper feed cassette 46 is provided below the main body frame 12. The paper feed cassette 46 can be pulled out in the direction opposite to the direction in which the recording paper P is sent out, so that the recording paper P can be fed appropriately.

  In the vicinity of the leading end of the paper feed cassette 46, a paper feed roller pair 48 for feeding the recording paper P one by one from the paper feed cassette 46 is provided. The recording paper P sent from the paper feed roller pair 48 is provided. Is sent to the suction conveyance surface of the conveyance belt 34 at a predetermined timing by the registration roller pair 49 and conveyed to the transfer position of each color toner image.

  In the image forming apparatus 10 having the above configuration, the transport unit 18 that is detachably attached to the cover body 14 will be described next.

  As shown in FIG. 3, the transport unit 18 includes a frame 51 having a substantially U-shaped cross section, and a substantially flat casing 50 that holds the frame 51. A driving roller 30 is rotatably supported at the upper end of the shaft, and a driven roller 32 is rotatably supported at the lower end. A transport belt 34 capable of electrostatically attracting the recording paper P is wound and stretched around the driving roller 30 and the driven roller 32.

  On the inner surface side of the conveyor belt 34, between the driving roller 30 and the driven roller 32, transfer rollers 36Y to 36K are arranged at predetermined intervals for each color, and each of the transfer rollers 36Y to 36K is also a housing. 50 is rotatably supported by the shaft. On the other hand, a plurality (four in the drawing) of coil springs 58 are in contact with the outer surface side (the cover body 14 side) of the housing 50, and when the cover body 14 is closed, the transport unit 18 is moved to the main body. The frame 12 is pressed with a predetermined pressure. As a result, when the cover body 14 is closed, the transfer rollers 36Y to 36K are pressed against the image carriers 20Y to 20K with a predetermined pressure with the transport belt 34 interposed therebetween, and follow the travel of the transport belt 34. Then rotate.

  Further, a flange portion 50 </ b> A protrudes from the upper end portion of the housing 50, and can face the drive roller 30. At the center of the upper surface of the flange 50A, a density sensor 60 that faces the conveyor belt 34 and measures the density of the test toner image transferred and formed on the conveyor belt 34 is disposed.

  As shown in FIG. 4, the density sensor 60 is provided with an LED irradiation unit 60A so that light enters from the conveyance direction of the conveyance belt 34, and the toner image on the conveyance belt 34 is formed from the LED irradiation unit 60A. On the other hand, light is irradiated at a predetermined angle, and reflected light from the toner image is incident on the lens 60B at an angle of 90 ° with respect to the toner image. Then, the reflected light is imaged on the light receiving surface of the photodiode 60C through the lens 60B. Here, a mask 60D is provided immediately before the photodiode 60C to restrict the detection area of the toner image. Then, the electric signal converted by the reflected light imaged on the photodiode 60C is transmitted to a detection device (not shown), and the toner density is detected.

  Further, the density sensor 60 includes a shutter 62 that opens and closes an optical path for receiving reflected light from the toner image on the light receiving surface of the photodiode 60 </ b> C above the measurement position of the conveyance belt 34, and an opening formed in the shutter 62. The density of the toner image on the conveyor belt 34 can be measured in a state where 62A is disposed on the lower surface of the density sensor 60.

  Here, a transparent plastic 61 (hereinafter referred to as “lens surface 61”) is provided on the surface of the density sensor 60 to protect components in the density sensor 60 such as the lens 60B. A shutter member 62, which will be described later, is disposed on the front surface of the lens surface 61 so that the optical path from the LED irradiation unit 60A can be blocked.

  Here, the configuration of the shutter member 62 will be described.

  As shown in FIGS. 5 and 6, the shutter member 62 includes link members 64 and 66 and a shutter portion 68, and is a parallel link mechanism in which the link members 64 and 66 are arranged to face each other with the same length. is there. A hole 52 is formed in one end side 64 </ b> A (hereinafter referred to as “free end side 64 </ b> A”) of the link member 64, and a pin 53 fixed to one end side of the shutter portion 68 is inserted through the link member 64. The shutter portion 68 is rotatably connected.

  A hole (not shown) is formed on one end side of the link member 66 (hereinafter referred to as “free end side 66 </ b> A”), and a pair formed facing the other end side of the shutter portion 68. The pin 55 disposed between the shaft support plates 54 and fixed to the shaft support plate 54 is inserted therethrough, and the link member 66 and the shutter portion 68 are rotatably connected.

  On the other hand, through holes 56 and 57 are formed on the other end sides of the link members 64 and 66 (hereinafter referred to as “base portion 64B” and “base portion 66B”), respectively, from the case 55 to which the concentration sensor 60 is fixed. The bases 64B and 66B of the link members 64 and 66 are pivotally supported by the pins 58 and 59 that are erected.

  The free ends 64A and 66A of the link members 64 and 66 can swing in an arc shape around the base portion 64B and the base portion 66B, and the shutter portion 68 swings so as to draw an arc-shaped locus. Can be made.

  By the way, an opening 70 is formed in the shutter portion 68, and the opening 70 becomes the lens surface 61 of the density sensor 60 (see FIG. 4) as shown in FIG. The position of the opening 70 coincides with the position of the lens surface 61 (hereinafter referred to as “lens surface exposure position”).

  Further, a felt 72 as a lens surface protection member is attached to the inner surface of the shutter portion 68, and the position of the opening 70 and the position of the lens surface 61 of the density sensor 60 are shifted from each other in FIG. As shown in A), the position of the felt 72 and the lens surface 61 coincides with each other while the felt 72 is kept substantially parallel to the lens surface 61 of the density sensor 60 (hereinafter, “ Lens surface protection position ”).

  Incidentally, a solenoid 74 is disposed on the base 64B side of the link member 64 on the side opposite to the link member 66 so as to be parallel to the shutter portion 68, and on the base 64B side of the link member 64, the solenoid is provided. 74 plungers 74A are connected. Here, when the solenoid 74 is ON, the plunger 74A is pulled into the solenoid body 74B, and when the solenoid 74 is OFF, the plunger 74A is free (described later).

  On the other hand, a substantially L-shaped mounting piece 76 in a plan view extends on one end side of the shutter portion 68 in a direction perpendicular to the shutter portion 68, and one end portion of a coil spring 78 is provided on the mounting piece 76. Wearing. The other end of the coil spring 78 is attached to a pin 80 fixed between the link member 64 and the link member 66, so that the coil spring 78 is disposed substantially parallel to the shutter portion 68.

  For this reason, when the solenoid 74 is turned ON, as shown in FIG. 7C, the plunger 74A is drawn into the solenoid main body 74B, and the free end side 64A swings around the base portion 64B of the link member 64 ( In response to this, the shutter portion 68 swings in an arc shape, and the coil spring 78 expands to accumulate elastic force. At this time, the shutter member 62 is set to the lens surface exposure position.

  On the other hand, when the solenoid 74 is turned OFF, the plunger 74A becomes free, and the plunger 74A is pulled out from the solenoid body 74B by the restoring force of the coil spring 78 as shown in FIGS. The portion 68 swings in an arc shape.

  As shown in FIG. 7A, the shutter portion 68 is positioned in a state where the plunger 74A is completely pulled out, and this position is set as a lens surface protection position.

  Here, in the process of moving the shutter member 62 from the lens surface protection position to the lens surface exposure position, as shown in FIG. 7B, the shutter portion 68 and the link member 64, and the shutter portion 68 and the link member 66 are formed. Although the angle is 90 degrees, the lens surface 61 and the felt 72 are completely separated in this state.

  Here, the plunger 74A is free when the solenoid 74 is OFF. However, if the solenoid 74 is in the OFF state and the plunger 74A protrudes from the solenoid body 74B, the coil The spring 78 is not always necessary.

  Next, the operation of the image forming apparatus 10 having the above configuration will be described.

  First, as shown in FIG. 1, the recording paper P is taken out one by one from the paper cassette 46 by the paper feed roller pair 48, and is sent onto the transport belt 34 by the registration roller pair 49 at a predetermined timing. The recording paper P sent onto the conveying belt 34 is electrostatically attracted by the conveying belt 34 and is conveyed to the image carriers 20Y to 20K of the respective colors.

  On the other hand, in the developing unit 16, first, the surface (circumferential surface) of the image carrier 20 is uniformly charged by the charging roller 22. Then, laser light (image light) is scanned from the optical box 24 onto the surface (circumferential surface) of the image carrier 20, and an electrostatic latent image based on the image data is formed on the surface (circumferential surface) of the image carrier 20. Is done. Thereafter, the toner is transferred onto the image carrier 20 by the developing roller 26, and a visible image is formed on the surface (circumferential surface) of the image carrier 20.

  Thus, when a visible image is formed on the surface (circumferential surface) of the image carrier 20, the toner image (unfixed image) on the surface of the image carrier 20 is onto the recording paper P that is sucked and conveyed by the conveyance belt 34. Is transferred by the image carrier 20 and the transfer roller 36. This is performed in the order of yellow (Y), magenta (M), cyan (C), and black (K). When a full-color toner image (unfixed image) is transferred onto the recording paper P, the recording paper P is conveyed. It is conveyed to the fixing device 38 by the belt 34.

  The recording paper P conveyed to the fixing device 38 is fixed by heating and pressing the unfixed toner image transferred thereto by the heating roller 40 and the pressure roller 42. Then, the recording paper P on which the toner image is fixed by the fixing device 38 is discharged onto the paper discharge tray 44. After the transfer of the toner image onto the recording paper P, the surface (circumferential surface) of the image carrier 20 is cleaned by the cleaning member 28 to prepare for the next image forming process.

  Here, when a test toner image is transferred and formed on the conveyance belt 34 and the density of the toner image is measured, the solenoid 74 is turned on. As a result, the shutter member 62 becomes the lens surface exposed position (see FIG. 7C), and the toner density can be detected by the density sensor 60.

  When the solenoid 74 is turned off, the shutter member 62 is in the lens surface protection position (see FIG. 7A), the felt 72 contacts the lens surface 61, the lens surface 61 is covered with the felt 72, and the cloud toner. Contamination due to etc. is prevented.

  By the way, in the present invention, as shown in FIGS. 7A to 7C, a shutter mechanism is used to swing the shutter member 68 in a circular arc shape with the base portion 64B of the link members 64 and 66 as an axis. I try to let them. Thus, when the shutter unit 68 moves from the lens surface protection position (see FIG. 7A) to the lens surface exposure position (see FIG. 7C), the felt 72 draws an arc with respect to the lens surface 61. Will move.

  When the shutter unit 68 moves from the lens surface protection position to the lens surface exposure position, when the shutter unit 68 is translated with respect to the lens surface 61, the friction force of the felt 72 on the lens surface 61 is determined by the felt 72. It becomes substantially constant until it is separated from the lens surface 61.

  However, in the present invention, since the felt 72 slides on the lens surface 61 of the density sensor 60 and moves away from the surface of the lens surface 61 at the same time, the felt 72 is translated with respect to the lens surface 61. In comparison, the frictional load on the lens surface 61 can be reduced, and the lens surface 61 can be made difficult to be damaged.

  Further, by using the link mechanism to move the shutter portion 68 in an arc shape and tilting the link members 64 and 66, the lens surface 61 is felt with respect to the lens surface 61 at the lens surface protection position (see FIG. 7A). Since a load can be applied in the direction in which 72 is in close contact, dirt is less likely to enter and contamination of the lens surface 61 can be prevented.

  Further, link members 64 and 66 are disposed on both sides of the density sensor 60 in the width direction, and the shutter member 68 is formed on the lens surface 61 by rotating the link members 64 and 66 along the width direction of the density sensor 60. It will swing along the width direction of the density sensor 60 in the front.

  As a result, the solenoid 74 for driving the shutter member 62 can be disposed in the dead space on both sides of the density sensor 60 in the width direction, so that the shutter member 62 can be made thin and the image forming apparatus 10 can be made compact. Can be realized.

  Further, by arranging the solenoids 74 in the dead space on both sides in the width direction of the density sensor 60, a space around the density sensor 60 can be secured, and a cooling effect of the density sensor 60 can be expected. For this reason, the detection accuracy of the density sensor 60 is improved.

  By changing the lengths of the link members 64 and 66 that swing the shutter portion 68, the balance between the adhesion of the felt 72 to the lens surface 61 and the rubbing can be adjusted. For example, when the main object is to apply the shutter member 62 as a wiper mechanism, the felt 72 moves away from the lens surface 61 with respect to the movement amount of the shutter member 62 in order to increase the sliding operation of the lens surface 61. It is advantageous to set the amount small, and the length of the link members 64 and 66 is set to be long within the range allowed by the structure so that the curvature of the arc motion is small.

  That is, as shown in FIG. 8, the link is caused by the horizontal stroke S of the shutter unit 68 and the vertical drop H of the shutter unit 68 (the separation distance H between the felt 72 and the lens surface 61 shown in FIG. 7B). The swing angle θ of the members 64 and 66 is set, but by increasing the length of the link member (link member 82; L2), the curvature of the arc drawn by the free end side of the link member 82 is reduced.

  Here, when the drop H is substantially the same as that of the link members 64 and 66, the stroke S1 (> S) is increased by increasing the length of the link member (link member 82; L2). That is, since the amount of the felt 72 that moves away from the lens surface 61 can be reduced with respect to the amount of movement of the shutter member 62, the rubbing force of the lens surface 61 by the felt 72 can be increased. For this reason, the shutter member 62 can be used as a wiper mechanism for the lens surface 61.

  Although the drop H is not changed here, it is needless to say that the drop H may be changed to change the adhesion force of the felt 72 to the lens surface 61.

  On the other hand, when the main purpose is to apply the shutter member 62 as a shutter mechanism, the felt 72 moves away from the lens surface 61 with respect to the movement amount of the shutter member 62 in order to reduce the rubbing force of the lens surface 61. The amount may be set large, and the length of the link member is shortened.

  Further, for the felt 72, the direction of the raised 72A of the felt 72 may be changed between the shutter mechanism and the wiper mechanism described above. Specifically, in the case of the shutter mechanism, as shown in FIG. 9A, the moving direction of the shutter portion 68 when the felt 72 contacts the lens surface 61 (arrow direction; for convenience, only the horizontal component is shown. The tip of the raised 72A of the felt 72 is tilted along the lens surface 61 so that when the felt 72 comes into contact with the lens surface 61, it falls along the lens surface 61.

  On the other hand, in the case of the wiper function, as shown in FIG. 9B, the leading end side of the raised hair 72 </ b> A of the felt 72 toward the moving direction (arrow direction) of the shutter portion 68 when the felt 72 contacts the lens surface 61. When the felt 72 comes into contact with the lens surface 61, the direction is opposite to the lens surface 61.

  Here, the parallel crank mechanism is used to make the link members have the same length, but the link members need not necessarily have the same length. In addition, the free end side is moved in a circular arc around the base portion of the link member as an axis, but the shutter portion may be moved in parallel while being inclined with respect to the lens surface.

1 is a schematic side view illustrating a configuration of an image forming apparatus. FIG. 3 is a schematic perspective view showing a cover body and a main body frame to which a transport unit constituting the image forming apparatus is attached. It is a fragmentary broken view of the conveyance unit provided with the lens surface shutter which concerns on embodiment of this invention. It is explanatory drawing explaining the structure of a density sensor. It is a perspective view which shows the structure of the lens surface shutter which concerns on embodiment of this invention. It is a perspective view which shows the structure of the lens surface shutter which concerns on embodiment of this invention. (A)-(C) are partial sectional views which show operation | movement of the lens surface shutter which concerns on embodiment of this invention. It is explanatory drawing at the time of lengthening the link member of the lens surface shutter which concerns on embodiment of this invention. (A), (B) is sectional drawing which shows the direction of raising of the felt of the lens surface shutter which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 60 Density sensor 61 Lens surface 62 Shutter member 64 Link member (shutter member)
66 Link member (shutter member)
68 Shutter part (shutter member)
70 opening 72 felt (lens surface protection member)
74A Plunger 74 Solenoid 82 Link member (shutter member)

Claims (7)

A density sensor for measuring the density of the image formed on the detection surface;
An opening that is disposed opposite to the lens surface of the density sensor and that exposes the lens surface and a shielding surface that covers the lens surface are provided, and the lens surface is opened and closed by moving in an arc, and the opening and the shielding surface are A shutter member that maintains a state substantially parallel to the lens surface;
A lens surface shutter characterized by comprising:   The shutter member includes a shutter portion provided with the opening and the shielding surface, and a pair of links rotatably connected to both ends of the shutter portion, and tilted to move the shutter portion in an arc with respect to the lens surface. The lens surface shutter according to claim 1, comprising a member.   The lens surface shutter according to claim 2, wherein the pair of link members constitute a parallel link mechanism having the same length, and the link member rotates along the width direction of the detection surface.   4. The lens surface shutter according to claim 2, wherein a plunger of a solenoid is connected to one of the link members, and the plunger is rocked by moving the plunger in and out.   The lens surface shutter according to any one of claims 1 to 4, wherein a lens surface protection member that contacts the lens surface is provided on the shielding surface.   6. The lens surface shutter according to claim 5, wherein the lens surface protection member is a felt, and raising of the felt is tilted along a moving direction of the shutter portion when the felt covers the lens surface. .   6. The lens surface according to claim 5, wherein the lens surface protection member is felt, and raising of the felt is inclined in a direction opposite to a moving direction of the shutter portion when the felt covers the lens surface. Shutter.

Images