JP2005300848A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent smudge on the detection face of a detecting part for detecting information, regarding toner on an image carrier. <P>SOLUTION: The covering area of a shutter 110, when closed, is larger than the moving range of a cleaning member 114, which moves accompanying the opening or closing operation of the shutter 110. Therefore, sticking of toner T1 will not occur in the moving range of the cleaning member 114, when the shutter 110 is closed. This prevents the cleaning member 114 from becoming smudged, as it moves, and accordingly, a detection face 1206A is prevented from becoming smudged by the cleaning member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus.

  In an image forming apparatus that forms an image of an electrostatic latent image formed on a photoreceptor by a known electrophotographic process, a toner density detection pattern is formed on the image carrier in order to form a stable image over a long period of time. A toner density detecting device that detects the density of the toner density detecting pattern and controls the image forming conditions is known.

Further, paper dust generated from the recording paper onto which the toner image is transferred may cause the detection surface of the toner density detection device to become dirty and cause false detection. Therefore, there has been proposed an image forming apparatus provided with a paper dust preventing member for preventing paper dust from adhering to the detection surface of the toner concentration detecting device. (For example, refer to Patent Document 1).
JP 2002-31919 A

  However, in the configuration described in Japanese Patent Application Laid-Open No. 2002-31919, the gap between the detection surface of the toner concentration detection device and the paper dust prevention member is spaced, so that floating toner or the like floating in the device is present on the detection surface. Adhering to it could cause contamination and false detection.

  Further, since the distance between the image carrier and the detection surface is large, the apparatus becomes large. Also, the detection accuracy is not good.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent contamination on a detection surface of a detection unit that detects toner information of an image carrier.

  The image forming apparatus according to claim 1, an image carrier on which a toner image is formed, a detection unit that receives reflected light reflected by the image carrier and detects information on the toner image, and the detection And a cleaning member attached to the shutter and cleaning the detection surface in accordance with the opening / closing operation of the shutter, wherein the shutter is provided with the opening / closing operation of the shutter. It covers the periphery of the detection surface that is wider than the range of movement of the.

  The image forming apparatus according to claim 1 detects information on the toner image of the image carrier in order to form a stable image over a long period of time.

  For this reason, a detection unit that receives reflected light reflected by the image carrier and detects information of the toner image is provided. The detection surface of the detection unit is opened and closed with a shutter. A cleaning member for cleaning the detection surface accompanying the opening / closing operation is attached to the shutter.

  And the shutter has covered the circumference | surroundings of the detection surface wider than the movement range to which a cleaning member moves with opening / closing operation | movement of a shutter. Therefore, for example, toner or paper dust does not adhere to the periphery of the detection surface in the moving range in which the cleaning member moves in accordance with the opening / closing operation of the shutter.

  Therefore, even if the cleaning member moves, toner, paper dust, and the like adhere to the cleaning member and become dirty, and the detection surface is not soiled by the dirty cleaning member. Therefore, the information on the toner image on the image carrier can be detected stably.

  Further, since the detection surface is not soiled, the distance between the image carrier and the detection surface can be shortened. Therefore, it is possible to stably detect and contribute to downsizing of the image forming apparatus. In addition, the detection accuracy is improved by shortening the distance between the image carrier and the detection surface.

  The image forming apparatus according to a second aspect is characterized in that, in the configuration according to the first aspect, the cleaning member is in contact with the entire surface of the detection surface when the shutter is closed.

  In the image forming apparatus according to the second aspect, when the shutter is closed, since the cleaning member is in contact with the entire detection surface, the detection surface is not exposed. Therefore, for example, toner or paper dust does not adhere to the detection surface when the shutter is closed.

  According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the detection surface is the highest surface in a movement range in which the cleaning member moves in accordance with the opening / closing operation of the shutter. It is characterized by becoming.

  In the image forming apparatus according to the third aspect, the detection surface is the highest surface in the movement range in which the cleaning member moves in accordance with the opening / closing operation of the shutter. For this reason, the shutter covers the detection surface wider than the moving range in which the cleaning member moves in accordance with the opening and closing operation of the shutter. However, for example, toner or paper dust is in the moving range in which the cleaning member moves for some reason. Even if it adheres, the cleaning member does not come in contact, or even if it comes in contact, the contact force is weak, so that the toner adheres to the cleaning member and does not get dirty. For this reason, the detection surface is not soiled.

  The image forming apparatus according to claim 4 is the configuration according to any one of claims 1 to 3, wherein the detection surface conveys a recording medium onto which the toner image of the image carrier is transferred. It is characterized by facing the road.

  In the image forming apparatus according to the fourth aspect, the detection surface of the detection unit faces the conveyance path of the recording medium onto which the toner image of the image carrier is transferred. For this reason, the detection surface and the periphery of the detection surface are charged by friction due to the conveyance of the recording medium.

  When the detection surface and the periphery of the detection surface are charged, for example, a large amount of toner or paper dust adheres due to electrostatic force. However, since the shutter covers the periphery of the detection surface wider than the moving range in which the cleaning member moves in accordance with the opening / closing operation of the shutter, toner, paper dust or the like does not adhere to the moving range in which the cleaning member moves. Therefore, the detection surface is not soiled. Therefore, even if the detection surface of the detection unit faces the conveyance path of the recording medium onto which the toner image on the image carrier is transferred, the information on the toner image on the image carrier can be detected stably.

  As described above, according to the present invention, for example, toner or paper dust does not adhere to the moving range in which the cleaning member moves in accordance with the opening / closing operation of the shutter. Etc. will adhere and will not contaminate the detection surface. Therefore, the information on the toner image on the image carrier can be detected stably.

  Hereinafter, as an example to which the image forming apparatus according to the present invention is applied, a color printer to which a known electrophotographic process is applied will be described with reference to the drawings. The image forming apparatus to which the present invention is applied is not limited to a color printer described below, and may be an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine.

  FIG. 1 shows an outline of a color printer 10 according to an embodiment of the present invention. The color printer 10 includes a color printer main body 12, and an open / close cover 16 that is rotatable about a rotation fulcrum 14 is provided on the upper portion of the color printer main body 12. In addition, a paper feeding unit 18 is disposed below the color printer main body 12.

  The paper supply unit 18 includes a paper supply unit main body 20 and a paper supply cassette 22 in which the recording paper P is stored. A feed roll 24 that feeds recording paper P from the paper feed cassette 22 and a retard roll 26 that scoops the supplied recording paper P one by one are arranged in the upper part near the rear end of the paper feed cassette 22.

  The conveyance path 28 is a path for the recording paper P from the feed roll 24 to the discharge port 30 through the guide member 29. The conveyance path 28 is in the vicinity of the back side (the right side surface in FIG. 1) of the color printer main body 12 and is formed substantially vertically from the paper feeding unit 18 to the fixing device 90. A secondary transfer roll 80 and a secondary transfer backup roll 72 are arranged on the upstream side of the fixing device 90 in the conveyance path 28, and a resist roll 32 is arranged on the upstream side of the secondary transfer roll 80 and the secondary transfer backup roll 72. Has been. In addition, a discharge roll 34 is disposed in the vicinity of the discharge port 30 of the conveyance path 28.

  Accordingly, the recording paper P sent out from the paper feed cassette 22 of the paper feeding unit 18 by the feed roll 24 is rolled by the retard roll 26 and only the uppermost recording paper P is guided to the transport path 28 and temporarily sent by the registration roll 32. The toner image is transferred between the secondary transfer roll 80 and the secondary transfer backup roll 72 at the timing, and the transferred toner image is fixed by the fixing device 90 and discharged by the discharge roll 34. The gas is discharged from the outlet 30 to a discharge portion 36 provided at the top of the opening / closing cover 16. The discharge portion 36 has a low discharge port portion and is inclined so as to gradually increase toward the front direction (left direction in FIG. 1).

  In the color printer main body 12, a rotary developing device 38 is disposed at a substantially central portion. On the front side (left side in FIG. 1) of the rotary developing device 38, a control unit 39 that controls each part constituting the color printer 10 is provided. Has been placed.

  The rotary developing device 38 includes developing units 42a to 42d that respectively form toner images of four colors of yellow, yellow, magenta, cyan, and black in the developing unit main body 40. It rotates counterclockwise (counterclockwise in FIG. 1) about the rotary developing device center 44. Each of the developing units 42a to 42d has developing rolls 46a to 46d, and is pressed in the normal direction of the developing unit main body 40 by elastic bodies 48a to 48d such as coil springs.

  The rotary developing device 38 is arranged so that the photosensitive drum 50 comes into contact therewith, and the developing rolls 46a to 46d are not in contact with the photosensitive drum 50, and a part of the outer periphery of each of the developing rollers 46a to 46d About 2 mm protrudes from the outer periphery of 40 in the radial direction. Further, a tracking roll (not shown) having a diameter slightly larger than the diameter of the developing rolls 46a to 46d is provided at both ends of each of the developing rolls 46a to 46d so as to rotate coaxially with the developing rolls 46a to 46d. Yes. That is, the developing rolls 46a to 46d of the developing units 42a to 42d are arranged on the outer periphery of the developing unit main body 40 with an interval of 90 ° around the rotary developing device center 44, and the tracking rolls of the developing rolls 46a to 46d are photosensitive. The latent image on the photosensitive drum 50 is abutted against flanges (not shown) provided at both ends of the photosensitive drum 50, and a predetermined gap is formed between the developing rolls 46a to 46d and the photosensitive drum 50. Develop with each color toner.

  A charging roll 52 is provided below the photosensitive drum 50, and a charging bias is applied to the charging roll 52 to uniformly charge the photosensitive drum 50. Further, a photosensitive drum cleaner 54 is in contact with the photosensitive drum 50 on the upstream side of the charging roll 52 in the rotation direction of the photosensitive drum 50. The photoreceptor drum cleaner 54 includes a cleaning blade 56 that scrapes off toner remaining on the photoreceptor drum 50 after primary transfer, and a toner collection case 58 that collects toner scraped off by the cleaning blade 56. Note that a rib or the like is formed on the back side (right side in FIG. 1) of the toner collection case 58 and forms a part of the conveyance path 28 together with the guide member 29.

  Below the rotary developing device 38, an exposure device 60 for writing a latent image on the photosensitive drum 50 charged by the charging roll 52 with a light beam such as a laser beam is disposed. Further, an intermediate transfer device 62 that conveys the toner image visualized by the rotary developing device 38 from the primary transfer portion to the secondary transfer position A is provided above the rotary developing device 38.

  The intermediate transfer device 62 includes an intermediate transfer belt 64, a primary transfer roll 66, a wrap-in roll 68, a wrap-out roll 70, a secondary transfer backup roll 72, a scraper backup roll 74, and a brush backup roll 76. The intermediate transfer belt 64 has elasticity and is stretched substantially flat so as to have a long side and a short side above the rotary developing device 38. The long side on the upper surface side of the intermediate transfer belt 64 is stretched so as to be substantially parallel to the discharge portion 36 provided on the upper portion of the color printer main body 12. Further, the intermediate transfer belt 64 is arranged between a wrap-in roll 68 disposed on the upstream side of the primary transfer roll 66 below the long side and a lap-out roll 70 disposed on the downstream side of the primary transfer roll 66. 1 has a primary transfer portion (photosensitive drum wrap region) that abuts in a wrap shape, is wound around the photosensitive drum 50 by a predetermined range, and is driven by the rotation of the photosensitive drum 50. As described above, the intermediate transfer belt 64 primarily transfers the toner image on the photosensitive drum 50 by the primary transfer roll 66 in the order of yellow, magenta, cyan, and black, and the primary transferred toner image is secondarily transferred. It is conveyed toward the roll 80. Note that the wrap-in roll 68 and the wrap-out roll 70 are separated from the photosensitive drum 50.

  Further, a flat surface portion (short side) is formed on the back side (right side surface in FIG. 1) of the intermediate transfer belt 64 by a wrap-out roll 70 and a secondary transfer backup roll 72, and this flat surface portion is subjected to secondary transfer. It faces the transport path 28 as a surface.

  Note that the wrap-out roll 70 is disposed on the secondary transfer surface so that the intermediate transfer belt 64 and the conveyance path 28 have an angle of about 12 °.

  The scraper backup roll 74 assists the scraper 84 scraping off the toner remaining on the intermediate transfer belt 64 after the secondary transfer, and the brush backup roll 76 removes the toner remaining on the intermediate transfer belt 64 after the secondary transfer. Help 86 to scrape.

  A secondary transfer roll 80 is opposed to the secondary transfer backup roll 72 of the intermediate transfer device 62 with the conveyance path 28 interposed therebetween. That is, the secondary transfer position A on the secondary transfer surface is between the secondary transfer roll 80 and the secondary transfer backup roll 72, and the secondary transfer roll 80 is supported by the secondary transfer backup roll 72. The toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the recording paper P at the secondary transfer position A. Here, the secondary transfer roll 80 is rotated while the intermediate transfer belt 64 rotates three times, that is, while the toner images of three colors of yellow, magenta, and cyan are primarily transferred and conveyed on the intermediate transfer belt. It is separated from the intermediate transfer belt 64, and comes into contact with the intermediate transfer belt 64 when a black toner image is transferred.

  A transfer bias is applied to the secondary transfer roll 80 so that a predetermined transfer bias voltage is generated between the secondary transfer roll 80 and the secondary transfer backup roll 72. Connected to ground (GND).

  As shown also in FIG. 2, a detection device 81 is disposed between the secondary transfer roll 80 and the guide member 29.

  The detection device 81 includes a detection unit 120. The detection unit 120 irradiates the sensor light S1 from the detection surface 120A toward the intermediate transfer belt 64. The density of the reference toner image formed on the intermediate transfer belt 64 is detected by receiving the reflected light S2 that changes according to the reference toner image for toner density detection formed on the intermediate transfer belt 64. When the density of the reference toner image is detected, this detection information is sent to the control unit 39 (see FIG. 1).

  The control unit 39 controls the charging bias voltage of the charging roll 52, the exposure light amount of the exposure device 60, the developing bias voltage of the developing devices 42a to 42d, and the like according to the detected toner concentration, thereby adjusting the toner concentration on the intermediate transfer belt 64. adjust. (See FIG. 1).

  The detection surface 120A of the detection unit 120 faces the conveyance path 28 of the recording paper P, and is exposed on the side (front side) facing the intermediate transfer belt 64 (the detection surface 120A of the detection unit 120 and the intermediate transfer belt 64). Between the secondary transfer surface is a conveyance path 28 of the recording paper P).

  As shown in FIG. 1, an intermediate transfer belt cleaner 82 is provided in contact with the end of the intermediate transfer belt 64 on the side opposite to the photosensitive drum 50. The intermediate transfer belt cleaner 82 scrapes off and removes the toner remaining on the intermediate transfer belt 64 after the secondary transfer, and the brush roll 86, scraper 84, and brush roll for further scraping off the toner remaining after cleaning by the scraper 84. The toner collecting case 88 collects the toner scraped off by the nozzle 86. The scraper 84 is made of a thin stainless steel plate, and a voltage having a polarity opposite to that of the toner is applied. The brush roll 86 is made of a brush such as acrylic that has been subjected to a conductive treatment. Further, while the intermediate transfer belt 64 conveys the toner image, the scraper 84 and the brush roll 86 are separated from the intermediate transfer belt 64 and come into contact with the intermediate transfer belt 64 at a predetermined timing. Has been.

  A fixing device 90 is disposed above the secondary transfer position A. The fixing device 90 includes a heating roll 92 and a pressure roll 94, and fixes the toner image secondarily transferred to the recording paper P by the secondary transfer roll 80 and the secondary transfer backup roll 72 to the recording paper P. It is conveyed toward the discharge roll 34. The discharge roll 34 discharges the recording paper P from the discharge port 30 to a discharge unit 36 provided at the upper part of the opening / closing cover 16.

  The intermediate transfer device 62, the photosensitive drum 50, the charging roll 52, the photosensitive drum cleaner 54, and the intermediate transfer belt cleaner 82 are integrated to constitute an image forming unit 96. The image forming unit 96 is disposed immediately below the discharge portion 36 of the opening / closing cover 16 and is detachable from the color printer main body 12. The image forming unit 96 is attached / detached by opening the opening / closing cover 16.

  Next, the detection device 81 will be described in detail.

  FIG. 3 shows the detection device 81.

  The detection device 81 responds to a light source (not shown) that irradiates the sensor light S1 (see FIG. 2) toward the reference toner image for density detection formed on the intermediate transfer belt 64 (see FIG. 2), and the reference toner image. A detection unit 120 including a sensor (not shown) that receives the reflected light S2 (see FIG. 2) of the sensor light S1 that changes is fixed inside the detection device casing 100. The surface through which the sensor light S1 and the reflected light S2 of the sensor light S1 are transmitted is the detection surface 120A.

  A plate-shaped shutter 110 is attached to the detection device casing 100 so as to be rotatable about a rotation shaft 112. And it rotates by the drive mechanism which is not shown in figure, and as shown also in FIG. 4, 120 A of detection parts 120 (surface facing the intermediate transfer belt 64) is opened and closed.

  On the lower surface of the shutter 110, a cleaning member 114 made of felt or the like is attached to a portion corresponding to the detection surface 120A of the detection unit 120. Further, the cleaning member 114 is in contact with the entire surface of the detection surface 120A. Therefore, as shown in FIGS. 3 and 4A and 4A, when the shutter 110 is closed, the entire detection surface 120A is covered with the cleaning member 114 and is not exposed. In addition, a protruding portion 110A is formed on the left side (relative to the shutter opening direction) to which the cleaning member 114 of the shutter 110 is attached.

  When the detection device 81 detects the density of the reference toner image formed on the intermediate transfer belt 64 (see FIG. 1) under the control of the control unit 39 (see FIG. 1), FIGS. As shown in FIG. 2, the shutter 110 is opened, and the detection surface 120A of the detection unit 120 is exposed toward the intermediate transfer belt 64 (see FIG. 2). When the detection is completed, the shutter 110 is closed as shown in FIGS.

  As shown in FIGS. 4A and 4B, as the shutter 110 is opened and closed, the cleaning member 114 is brought into sliding contact with the detection surface 120A for cleaning. Since the shutter 110 has an overhang portion 110A, the area covered by the entire shutter 110 when the shutter 110 is closed is the movement of the cleaning member 114 that moves as the shutter 110 is opened and closed. It is wider than the range. Further, in the moving range of the cleaning member 114, the upper surface 100A of the detection device housing 100 is lower than the detection surface 120A.

  Next, the operation of the above embodiment will be described.

  As shown in FIG. 1, when an image forming signal is sent, the photosensitive drum 50 is uniformly charged by the charging roll 52, and the charged photosensitive drum 50 receives light from the exposure device 60 based on the image signal. Is emitted. The light beam from the exposure device 60 exposes the surface of the photosensitive drum 50 to form a latent image. The latent image on the photosensitive drum 50 formed by the exposure device 60 is developed with yellow, magenta, cyan, and black toner images by the rotary developing device 38, and is primarily transferred onto the intermediate transfer belt 64. In the primary transfer, waste toner remaining on the photosensitive drum 50 is scraped off and collected by the photosensitive drum cleaner 54.

  On the other hand, the recording paper P stored in the paper feed cassette 22 by a paper feed signal or the like is sent out by the feed roll 24, turned by the retard roll 26, guided to the transport path 28, and temporarily stopped by the registration roll 32, It is conveyed toward the guide member 29 with timing. The guide member 29 guides the recording paper P to the detection device 81. When an image is formed on the recording paper P under the control of the control unit 39, the detection device 81 closes the shutter 120 and covers the detection surface 120A of the detection unit 120 with respect to the intermediate transfer belt 64 (FIG. 3, FIG. The recording paper P conveyed between the secondary transfer surface of the intermediate transfer belt 64 and the shutter 110 by the guide member 29 is fed to the secondary transfer position A as shown in FIGS.

  When the recording sheet P is guided to the secondary transfer position A, the toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the recording sheet P by the secondary transfer roll 80 and the secondary transfer backup roll 72. The Waste toner remaining on the intermediate transfer belt 64 after the secondary transfer is scraped off and collected by the intermediate transfer belt cleaner 82.

  The recording paper P to which the toner image has been transferred is guided to the fixing device 90, and the toner image is fixed by the thermal pressure of the heating roll 92 and the pressure roll 94. The recording paper P on which the toner image is fixed is discharged from the discharge port 30 to the discharge unit 36 by the discharge roll 34.

  The color printer 10 also supplies a reference toner image for toner density detection to the intermediate transfer belt 64 so that the image transferred to the intermediate transfer belt 64 is not affected when the power is turned on and after a predetermined number of images are formed. Form on top. When the reference toner image is formed on the intermediate transfer belt 64 and the reference toner image moves to a position facing the detection device 81, the shutter 110 of the detection device 81 is opened, and the detection surface 120 </ b> A of the detection unit 120 is placed on the intermediate transfer belt 64. To expose. (See FIGS. 4B and 4B).

  The detection unit 120 irradiates the reference toner image formed on the intermediate transfer belt 64 with the sensor light S1 (see FIG. 2) from the detection surface 120A, and the reflected light S2 (see FIG. 2) that changes according to the reference toner image. ) Is detected, the density of the toner image formed on the intermediate transfer belt 64 is detected. When the toner density is detected by the detection device 81, this detection information is sent to the control unit 39. The control unit 39 controls the charging bias voltage of the charging roll 52, the exposure light amount of the exposure device 60, the developing bias voltage of the developing devices 42a to 42d, and the like according to the detected toner density, and the toner on the intermediate transfer belt 64. Adjust the density. Therefore, the color printer 10 can stably form an image with a predetermined toner density.

  As described above, when detecting the density of the reference toner image, the detection device 81 opens the shutter 110 and exposes the detection surface 120A of the detection unit 120 to the intermediate transfer belt 64 and the conveyance path 28, thereby performing intermediate transfer. The density of the reference toner image formed on the belt 64 is detected. The shutter 110 is closed except when detecting the density.

  Further, the cleaning member 114 attached to the shutter 110 is in contact with and covers the entire detection surface 120 of the detection unit 120. That is, the detection surface 120A is not exposed. Therefore, the detection surface 120A of the detection unit 120 is not soiled by paper dust or floating toner generated from the recording paper P. Therefore, the detection unit 120 does not cause a detection failure and stably detects the density of the reference toner image.

  Further, when the shutter 110 rotates, the cleaning member 114 is in sliding contact with the detection surface 120A of the detection unit 120. Therefore, even if the detection surface 120A becomes dirty for some reason, the detection surface 120A is cleaned, so that the detection is performed. The contamination of the surface 120A can be further prevented.

  For example, in the detection device 500 shown in FIG. 5, the area covered by the shutter 502 is narrower than the moving range of the cleaning member 504 that moves in accordance with the opening / closing operation of the shutter 502. Therefore, when the shutter 502 is closed, the cleaning member 502A becomes dirty with the opening / closing operation of the shutter 502 with the toner T3 attached to the upper surface 510 of the detection device casing 510 around the detection surface 506A of the detection unit 506. (See FIG. 5 (b)). And this detection stains the detection surface 506A. (See FIG. 5 (c)).

  However, in the present embodiment, as shown in FIGS. 4A and 4B, the area covered by the shutter 110 when the shutter 110 is closed is the cleaning member 114 that moves in accordance with the opening / closing operation of the shutter 110. It is wider than the moving range. Therefore, when the shutter 110 is closed, the toner T1 does not adhere to the range in which the cleaning member 114 moves. Therefore, the cleaning member 114 is contaminated by the movement, and this detection prevents the detection surface 1206A from becoming dirty. Has been.

  Furthermore, the upper surface 100A of the detection device casing 100 around the detection surface 120A is lower than the detection surface 120A. Therefore, even if the toner T2 slightly adheres to the moving range of the cleaning member 114 for some reason when the shutter 110 is closed, it does not contact the cleaning member 114 or the contact pressure is maintained even if it contacts. Since it is small, the cleaning member 114 is not soiled.

  Therefore, since the cleaning member 114 is not soiled, the detection surface 1220 is not soiled.

  Since the detection surface 120A is not contaminated in this way, the distance between the intermediate transfer belt 64 and the detection surface 120A of the detection unit 120 can be shortened as shown in FIG. Therefore, the density of the reference toner image on the intermediate transfer belt 64 can be stably detected, and it contributes to the size reduction of the color printer 10 in the front-rear direction (left-right direction in FIG. 1). Further, the detection accuracy is improved by shortening the distance between the intermediate transfer belt 64 and the detection surface 120A.

  Further, in the present embodiment, as shown in FIG. 2, the detection device 81 is disposed between the secondary transfer roll 80 and the guide member 29, and the detection surface 120 </ b> A of the detection unit 120 is the conveyance path 28 of the recording paper P. Facing the intermediate transfer belt 64 and exposed on the side (front side) facing the intermediate transfer belt 64 (between the detection surface 120A of the detection unit 120 and the secondary transfer surface of the intermediate transfer belt 64). ).

  For this reason, the detection device 81 is easily charged by friction with the recording paper P or the like. Therefore, a large amount of paper powder or floating toner tends to adhere to the detection surface 120A and the detection surface 120A due to electrostatic force. However, as described above, the detection device 81 does not cause the stain detection failure even if the detection unit 120 is disposed at the position as in the present embodiment, and the density of the reference toner image is reduced. Stable detection.

  The present invention is not limited to the above embodiment.

  For example, the detection device 81 (detection unit 120) is disposed between the secondary transfer roll 80 and the guide member 29, but is not limited thereto. For example, the intermediate transfer belt 64 may be disposed above or below the long side, or may be disposed at other positions.

  Further, for example, in the above embodiment, the detection device detects the density of the reference toner image formed on the intermediate transfer belt. However, the present invention is not limited to this, and for example, an image is formed using only black toner. In the case of a monochrome printer, the density of the reference toner image formed on the photosensitive drum may be detected.

  Further, for example, the detection device is not limited to the detection of the density of the reference toner image formed on the intermediate transfer belt or the photoconductive drum, but may be the position of the toner image formed on the intermediate transfer belt or the photoconductive drum, for example. Information may be detected.

  Further, a recording medium other than the recording paper P may be used. For example, an OHP sheet may be used, or another recording medium may be used.

1 is a cross-sectional view schematically showing the inside of a color printer according to an embodiment of the present invention. It is a figure which shows a detection apparatus and its periphery typically. (A) is the figure which looked at the detection apparatus from the upper surface, (B) is a figure of the AA cross section of (A). (A) is the figure seen from the upper surface in the state which the shutter of the detection apparatus closed, (a) is a figure of the AA cross section of (A). (B) is the figure seen from the upper surface in the state which the shutter of the detection apparatus opened, (b) is a figure of the BB cross section of (B). (A)-(b) is a figure which shows the opening / closing operation | movement of the shutter of the conventional detection apparatus.

Explanation of symbols

10 Color printer (image forming device)
28 Conveyance path 64 Intermediate transfer belt (image carrier)
110 Shutter 114 Cleaning member 120 Detection unit 120A Detection surface
P Recording paper (recording medium)

Claims (4)

An image carrier on which a toner image is formed;
A detector that receives reflected light reflected by the image carrier and detects information of the toner image;
A shutter that opens and closes the detection surface of the detection unit;
A cleaning member attached to the shutter and cleaning the detection surface in accordance with the opening and closing operation of the shutter;
With
The image forming apparatus, wherein the shutter covers a periphery of the detection surface wider than a moving range in which the cleaning member moves in accordance with the opening / closing operation of the shutter.   The image forming apparatus according to claim 1, wherein the cleaning member is in contact with the entire surface of the detection surface when the shutter is closed.   3. The image forming apparatus according to claim 1, wherein the detection surface is the highest surface in a movement range in which the cleaning member moves in accordance with the opening / closing operation of the shutter.   The image forming apparatus according to claim 1, wherein the detection surface faces a conveyance path of a recording medium to which the toner image of the image carrier is transferred. .

Images