JP2009298538A - Paper conveying device and image forming device equipped with the same device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper conveying device capable of exactly measuring a paper conveying state in a wide measuring range, while reducing damage on paper without being restricted by arrangement. <P>SOLUTION: This paper conveying device has a paper conveying part 65 conveying the paper P and provided with an opening 65a, a distance detecting part 66 projecting light toward the paper P and receiving reflected light via the opening 65a to detect a distance up to the paper P, a light projecting region part 91 for transmitting projected light, a light receiving region part 92 for transmitting reflected light, and a shielding part 93 provided between the light projecting region part 91 and the light receiving region part 92 to shield flare light reflecting in the light projecting region part 91. The paper conveying device is provided with a cover member 90 disposed with a prescribed space in relation to a conveying passage surface 65b of the paper conveying part 65 on the distance detecting part 66 side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine using an electrophotographic method, and an image forming apparatus including the same, and in particular, a sheet for detecting a sheet conveying state. The present invention relates to a transport device and an image forming apparatus including the transport device.

  2. Description of the Related Art Conventionally, in an image forming apparatus, an image forming unit that forms a toner image, a transfer belt that transfers a toner image formed on the image forming unit, and a transfer unit that transfers a toner image transferred to the transfer belt to a sheet, The image forming apparatus includes a fixing unit that melts and fixes the sheet on which the toner image has been transferred. The sheet fed from the sheet feeding unit is conveyed to the transfer unit, and is further discharged to the fixing unit when the sheet is conveyed to the fixing unit.

  For example, in the transfer unit and the fixing unit, the paper conveyance speed is controlled to be the same. However, in recent years, the paper conveyance path between the transfer unit and the fixing unit has become shorter due to the downsizing of the apparatus, and the transfer is performed. If there is a variation in the sheet conveyance speed in the section and the sheet conveyance speed in the fixing section, the sheet is pulled or bent between the transfer section and the fixing section. When the conveyance speed of the fixing unit becomes faster than the conveyance speed of the transfer unit, the paper is pulled between them, causing a color shift in the image during transfer, while the conveyance speed of the fixing unit is higher than the conveyance speed of the transfer unit. However, the paper may bend between the two to cause jamming of the paper in the paper conveyance path.

  Therefore, in Patent Document 1, a detection sensor for detecting the deflection of the sheet is arranged in the sheet conveyance path between the transfer unit and the fixing unit, and the sheet being conveyed is bent, and the amount of the deflection exceeds a certain amount. In this case, the detection sensor detects this bending, and based on the detection result, the rotational speed of the motor that drives the fixing roller is increased to reduce the amount of bending of the paper. The detection sensor includes a photo interrupter and an actuator, and the actuator is displaced when it contacts the surface of the bent paper, and blocks the light of the photo interrupter. The detection sensor outputs an on / off signal according to the displacement of the actuator.

However, in the above-described conventional technology, the detection sensor detects the flexure of the paper by using the physical contact between the actuator and the paper, so that there is a risk of damaging the paper at the time of contact with the paper. In addition, since the surface of the paper on which the toner image is transferred is the surface that contacts the actuator, the toner image may be damaged. To avoid this, the end in the direction perpendicular to the paper conveyance The arrangement of the detection sensor, such as detecting a portion without printing, is restricted.
Japanese Patent Laid-Open No. 10-97154 (paragraphs [0013] to [0015], [0036], FIG. 1)

  The present invention has been made to solve the above-described problems, and is capable of accurately measuring the paper conveyance state in a wide measurement range without being restricted in arrangement and reducing damage to the paper. It is an object of the present invention to provide a paper transport device that can perform printing.

  In order to achieve the above object, the present invention conveys a sheet, and includes a sheet conveying unit having an opening, and projects light toward the sheet through the opening and receives reflected light from the sheet, to the sheet. A distance detection unit that detects the distance of the projection light, a light projecting region that transmits the projection light, a light receiving region that transmits the reflected light, and the light projecting region and the light receiving region. A shielding member that shields flare light reflected from the light projecting area, and a cover member that is disposed with a predetermined distance on the distance detection unit side with respect to the conveyance path surface of the paper conveyance unit. It is characterized by.

  According to this configuration, the projection light from the distance detection unit sequentially passes through the light projecting area of the cover member and the opening of the paper transport unit to reach the paper, and the reflected light reflected by the paper sequentially passes through the opening and the light receiving area. Then, the distance is received by the distance detection unit, and the distance to the sheet is detected based on the reflected light received by the distance detection unit. The shielding part of the cover member suppresses the flare light reflected by the light projection area part of the projection light from entering the distance detection part through the shielding part, and the cover member has a predetermined interval with respect to the conveyance path surface. Since it is provided on the detection unit side, the reflected light from the paper is received by the distance detection unit without being blocked by the shielding unit.

  According to a second aspect of the present invention, the sheet conveying section is formed so that the opposite surface of the conveying path surface is flat, and the cover member is attached to the opposite surface. According to this configuration, when the cover member is attached to the opposite surface of the conveyance path surface, the cover member is disposed with a predetermined interval with respect to the conveyance path surface.

  According to a third aspect of the present invention, the shielding portion is formed of a wall that is disposed perpendicularly to the transport path surface and that has been subjected to black processing. According to this configuration, the flare light reflected at the light projecting area is prevented from entering the distance detection section through the shielding section by the black-treated wall.

  According to a fourth aspect of the present invention, the distance detecting unit is disposed substantially below the sheet conveying unit. According to this configuration, foreign matter such as dust generated in the paper transport unit does not fall from the opening of the paper transport unit to the distance detection unit.

  According to a fifth aspect of the present invention, the sheet conveying unit and the distance detecting unit are arranged in an open / close frame that is openable and closable with respect to the apparatus main body. According to this configuration, foreign matter such as dust generated in the paper transport unit adheres to the cover member, but the foreign matter attached to the cover member can be removed by opening the opening / closing frame provided with the cover member from the apparatus main body. It is.

  According to a sixth aspect of the present invention, the paper transport unit is provided between a transfer unit that transfers the toner image formed on the photosensitive member to the paper and a fixing unit that melts and fixes the toner image of the transferred paper. The image forming apparatus includes a sheet conveying unit that conveys the sheet. According to this configuration, the distance detection unit detects the distance to the sheet based on the reflected light in the sheet conveyance unit between the transfer unit and the fixing unit.

  According to the first aspect of the present invention, the projection light from the distance detection unit sequentially passes through the light projecting area of the cover member and the opening of the paper transport unit to reach the paper, and the reflected light reflected by the paper is sequentially opened. The amount of deflection of the paper is measured without touching the paper by detecting the distance to the paper based on the reflected light received by the distance detector after passing through the light receiving area. In other words, the measurement target can be set anywhere in the center or the edge of the paper, and the placement of the distance detection unit or the like is not restricted, and the toner image on the paper or the paper is not damaged. Further, the shielding part of the cover member can prevent the flare light reflected by the light projection area part of the projection light from entering the distance detection part through the shielding part, so that the distance can be accurately measured. In addition, since the cover member is disposed on the distance detection unit side with a predetermined interval with respect to the conveyance path surface, the reflected light from the paper is received by the distance detection unit without being blocked by the shielding unit, and is wide. It is possible to detect a paper conveyance state such as bending in the measurement range.

  According to the second aspect of the present invention, when the cover member is attached to the opposite surface of the conveyance path surface, the cover member is disposed at a predetermined interval with respect to the conveyance path surface, so that the predetermined interval is easily set. be able to.

  Further, according to the invention described in claim 3, the flare light reflected at the light projecting area is prevented from entering the distance detecting section through the shielding section by the black-treated wall. There is no risk of erroneous measurement due to flare light, and the distance to the paper is accurately measured by the reflected light from the paper.

  According to the invention described in claim 4, foreign matter such as dust generated in the paper transport unit falls from the opening of the paper transport unit to the distance detection unit, and there is no risk of erroneous measurement due to foreign matter. The distance to the paper is accurately measured by the reflected light.

  According to the fifth aspect of the present invention, even if foreign matter such as dust generated in the paper transport unit adheres to the cover member, the opening / closing frame provided with the cover member is opened from the apparatus main body, and the cover member is opened. It is possible to easily remove the adhered foreign matter.

  According to the sixth aspect of the present invention, the distance detecting unit detects the distance to the sheet based on the reflected light in the sheet conveying unit between the transfer unit and the fixing unit, and the amount of bending of the sheet is determined. Accurate measurement is possible over a wide measurement range.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The embodiment of the present invention shows the most preferable form of the invention, and the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a cross-sectional plan view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is a tandem type color printer. As the photosensitive members 11a to 11d that are rotatable, an organic photosensitive member (OPC photosensitive member) is used as a photosensitive material for forming a photosensitive layer, and black (B), It is arranged corresponding to each color of yellow (Y), cyan (C) and magenta (M). The photosensitive layer may be amorphous silicon. Around each of the photoreceptors 11a to 11d, developing devices 2a to 2d, an exposure unit 12, chargers 13a to 13d, and static eliminators 14a to 14d are disposed.

  The developing devices 2a to 2d are arranged opposite to the lower right of the photoconductors 11a to 11d and supply toner to the photoconductors 11a to 11d. The chargers 13a to 13d are arranged on the upstream side of the developing device 2a to 2d in the rotation direction of the photosensitive member and opposed to the surfaces of the photosensitive members 11a to 11d, and uniformly charge the surfaces of the photosensitive members 11a to 11d. The static eliminators 14a to 14d are arranged on the downstream side of the photoconductor rotation direction of the developing devices 2a to 2d and to face the surfaces of the photoconductors 11a to 11d, and charge remaining on the surfaces of the photoconductors 11a to 11d after development. Remove static electricity.

  The exposure unit 12 scans and exposes each of the photoconductors 11a to 11d based on image data such as characters and patterns input from a personal computer or the like to an image input unit (not shown). The developing device 2a Is provided downstream of the chargers 13a to 13d in the rotation direction of the photosensitive member. The exposure unit 12 is provided with a laser light source and a polygon mirror, and a reflection mirror and a lens are provided corresponding to each of the photoreceptors 11a to 11d. Laser light emitted from the laser light source is applied to the surfaces of the photoconductors 11a to 11d via a polygon mirror, a reflection mirror, and a lens, and the surfaces of the photoconductors 11a to 11d are electrostatically applied to the surfaces of the photoconductors 11a to 11d. A latent image is formed, and the electrostatic latent image is developed into a toner image by each of the developing devices 2a to 2d.

  The intermediate transfer belt 17 is stretched around the tension roller 6, the driving roller 25, and the driven roller 27. The photoreceptors 11a to 11d are arranged below the intermediate transfer belt 17 so as to be in contact with the intermediate transfer belt 17 so as to be adjacent to each other from the upstream side in the transport direction (arrow direction in FIG. 1). . The primary transfer rollers 26a to 26d are arranged so as to face the photoreceptors 11a to 11d and contact the intermediate transfer belt 17 with the intermediate transfer belt 17 interposed therebetween, and are movable in the vertical direction in FIG. If necessary, a primary transfer nip portion is formed by being pressed against each of the photoreceptors 11a to 11d via the intermediate transfer belt 17, and is separated. In the primary transfer nip portion, the toner images formed by the photoconductors 11a to 11d are transferred to the surface of the intermediate transfer belt 17. The toner images on the photoconductors 11a to 11d are sequentially transferred to the intermediate transfer belt 17 at a predetermined timing along with the rotation of the intermediate transfer belt 17, whereby cyan, magenta, yellow, and black are transferred onto the surface of the intermediate transfer belt 17. A full color toner image is formed by superimposing the four color toner images. The belt cleaning 31 cleans the toner remaining on the intermediate transfer belt 17 after the transfer.

  The secondary transfer roller 34 is opposed to the driving roller 25 with the intermediate transfer belt 17 interposed therebetween, and presses against the intermediate transfer belt 17 to form a secondary transfer nip portion. In the secondary transfer nip portion, the intermediate transfer belt The toner image on the surface 17 is transferred to the paper P.

  A paper feed cassette 32 that stores paper P is disposed below the image forming apparatus 1, and a stack tray 35 that supplies manual paper is disposed in the middle of the image forming apparatus 1. On the left side of the image forming apparatus 1, a first conveyance path 33 that conveys the paper P fed from the paper feed cassette 32 to the secondary transfer nip portion formed by the intermediate transfer belt 17 is disposed. On the left side, a second transport path 36 for transporting the sheet fed from the stack tray 35 to the secondary transfer nip portion is provided. Further, in the upper left part of the image forming apparatus 1, a fixing unit 18 that performs a fixing process on the paper P on which an image has been formed, and a third transport path that transports the paper on which the fixing process has been performed to the paper discharge unit 37. 39 is disposed.

  The paper feed cassette 32 can be replenished by pulling it out of the apparatus (front side in FIG. 1), and the stored paper P is first fed one by one by the pick-up roller 33b and the separating roller 33a. It is fed out to the conveyance path 33 side.

  The first conveyance path 33 and the second conveyance path 36 are merged before the registration roller 33c, and the registration roller 33c takes the timing of the image forming operation and the paper feeding operation in the intermediate transfer belt 17 to form the sheet P. Is conveyed to the secondary transfer nip portion. The full-color toner image on the intermediate transfer belt 17 is secondarily transferred to the sheet P conveyed to the secondary transfer nip portion by the secondary transfer roller 34 to which a bias potential (a polarity opposite to the toner charging polarity) is applied. Then, it is conveyed to the fixing unit 18. The intermediate transfer belt 17 and the secondary transfer roller 34 constitute a transfer portion.

  The fixing unit 18 includes a fixing belt heated by a heater, a fixing roller, a pressure roller arranged in pressure contact with the fixing roller, and the like, and heats and presses the paper P on which the toner image is transferred. The fixing process is performed by the above. After being fixed by the fixing unit 18, the sheet P is reversed by the fourth conveyance path 40 as necessary, and the toner image is secondarily transferred to the back surface of the sheet by the secondary transfer roller 34 and fixed by the fixing unit 18. Then, it passes through the third conveyance path 39 and is discharged to the paper discharge portion 37 by the discharge roller 19a.

  Based on FIG. 2 and FIG. 3, an arrangement configuration of the sheet conveyance unit and the distance detection unit between the transfer unit and the fixing unit as the sheet conveyance device will be described. FIG. 2 is a cross-sectional plan view showing a paper conveyance unit and a distance detection unit according to the embodiment of the present invention, and FIG. 3 is a perspective view showing the paper conveyance unit and the distance detection unit. FIG. 3 shows a state in which the paper transport path is opened.

  As shown in FIG. 2, the transfer unit 41 includes an intermediate transfer belt 17 and a secondary transfer roller 34, and the fixing unit 18 includes a fixing belt 52, a fixing roller 53 heated by the fixing belt 52, and a pressure roller. 54. A fixing unit 18 is disposed on the upper left side of the transfer unit 41, and a paper transport unit 65 that guides the transport of the paper P that is transported in a broken line arrow in FIG. 2 between the transfer unit 41 and the fixing unit 18. It is arranged.

  The sheet conveyance unit 65 extends from the upper side of the transfer unit 41 to the upper left side below the fixing unit 18, and forms a conveyance path surface that guides conveyance of the sheet P on the surface side. A distance detection unit 66 is disposed at a position away from the sheet conveyance unit 65 on the opposite side of the conveyance path surface of the sheet conveyance unit 65. A surface of the distance detection unit 66 on which light is projected and received, which will be described later, faces the paper transport unit 65, and the distance detection unit 66 projects light in the direction of the solid line arrow in FIG.

  As shown in FIG. 3, the paper transport unit 65 is provided in the longitudinal direction of the secondary transfer roller 34, and includes a rectangular opening 65 a substantially at the center in the longitudinal direction. The opening 65 a is provided at a position that allows light to be projected and received by the distance detection unit 66 disposed on the back side of the paper transport unit 65.

  The paper transport unit 65 and the distance detection unit 66 are disposed on the open / close frame 85. The open / close frame 85 is a part constituting the side wall of the main body of the image forming apparatus 1, and can release the inside of the main body of the apparatus when performing jam processing of paper on the conveyance path. Therefore, the opening / closing frame 85 is rotatably supported by a shaft (not shown) and connected to the apparatus main body. When the swinging operation is performed around the support shaft, the opening / closing frame 85 is opened between the apparatus main body and the opening / closing frame 85. The state is switched between a state (the state shown in FIG. 3) and a closed state where image formation is possible.

  The distance detector 66 will be described in detail based on FIG. FIG. 4 is a side view showing a conceptual configuration of the distance detection unit according to the embodiment of the present invention.

  The distance detection unit 66 includes a light source 67 and a light projection lens 68 as a light projector, a PSD (Position Sensitive Detector) element 69 and a light reception lens 70 as a light receiver, and a driver circuit 72 that drives the light source 67, and a PSD. And an arithmetic circuit 73 for calculating the barycentric position of the amount of reflected light on the element 69. The driver circuit 72 and the arithmetic circuit 73 are controlled by the control unit 74.

  The projector and the light receiver are arranged in parallel with respect to the longitudinal direction of the secondary transfer roller 34 (see FIG. 3). In the projector, a light source 67 composed of an infrared light emitting diode is driven by a driver circuit 72, and the emitted light is collected by a projector lens 68 and projected toward the paper P. In the light receiver, the reflected light from the paper P is collected by the light receiving lens 70 and enters the PSD element 69.

  The PDS element 69 converts the reflected light from the paper P into a current proportional to the intensity of the light, and further splits the current into two current signals I1 and I2 at a rate depending on the incident position d. The output currents I1 and I2 are amplified and input to the arithmetic circuit 73. In the arithmetic circuit 73, the incident position corresponding to the barycentric position of the reflected light amount on the PDS element 69 based on the current ratio of the output currents I1 and I2. d is calculated.

The control unit 74 calculates the distance to the paper P based on the incident position d output from the arithmetic circuit 73 and the optical constants of the projector and the light receiver. That is, as shown in FIG. 4, when the distance from the light receiving lens 70 to the paper P is L, the focal length of the light receiving lens 70 is f, and the distance between the optical axes of the light receiving lens 70 and the light projecting lens 68 is B, the paper The relationship between the distance L to P and the incident position d is
L = B / fd (1)
It becomes. The controller 74 calculates the distance L of the paper P from the equation (1) according to the incident position d.

  Further, the control unit 74 determines whether or not the sheet P is bent from the calculated distance L, and if there is further bending, controls the rotation speed of each roller of the transfer unit 41 and the fixing unit 18 based on the amount of bending. Then, the paper transport unit 65 corrects the paper P so that it does not bend.

  Next, the cover member provided in the vicinity of the opening 65a of the paper transport unit 65 will be described with reference to FIG. FIG. 5 is a cross-sectional side view showing the cover member according to the embodiment of the present invention.

  The sheet conveying unit 65 includes a conveying path surface 65b that conveys the sheet P and an opposite surface 65c that faces the distance detecting unit 66 on the opposite side, and an opening 65a is formed between the conveying path surface 65b and the opposite surface 65c. Yes.

  The cover member 90 is made of a light-transmitting material such as acrylic resin, and is formed on a substantially rectangular flat plate having a size larger than the opening 65a. The cover member 90 has a surface (back surface) on the distance detection unit 66 side on the distance detection unit 66 side. A protruding shielding part 93 is provided, and is fixedly held by a cover holding member 86 on the opposite surface 65 c of the sheet conveying part 65. The cover holding member 86 is fixed to the paper transport unit 65 by bonding, screws, or the like by pressing the peripheral end of the cover member 90 against the opposite surface 65c with at least three pressing portions 86a.

  Further, the cover member 90 includes a light projecting area 91 on the left side of the shielding part 93 and a light receiving area 92 on the right side of the shielding part 93 on the back surface thereof. The light projecting area 91 transmits the light projected onto the paper P facing the light projector of the distance detecting section 66, and the light receiving area 92 transmits the reflected light of the paper P facing the light receiver of the distance detecting section 66. Make it transparent.

  Here, in the case where the range in which the distance detection is necessary to detect the amount of bending generated in the sheet is the section H from the point A to the point B on the conveyance path surface 65b, the distance detection unit 66 starts from the sheet P. It is only necessary to receive light in the range of the light rays L1 to L3 among the reflected light.

  Therefore, the shielding part 93 is formed as a standing wall perpendicular to the conveyance path surface 65b at a position where the light ray L1 is not blocked. Further, the shielding portion 93 is coated with a black paint on the surface of the standing wall on the side of the light projecting area 91, and the black processing is performed even if the light projected from the distance detecting unit 66 is reflected by the light projecting area 91. The light (flare light) reflected by the surface is shielded, and there is no possibility of entering the light receiver of the distance detecting unit 66 through the shielding unit 93. In addition, the shielding part 93 is configured by separately forming a black-painted member or a resin material in which a black pigment is dispersed, and attaching the member to a light-transmitting flat cover member 90 or the like. Also good. The cover member 90 is made of a translucent material, and a flat plate-like portion having a light projecting area 91 and a light receiving area 92, and a shielding part 93 are integrally provided, so that the surface of the shielding part 93 is made into minute irregularities. The flare light reflected by the light projecting area 91 may be scattered by the rough surface, and the flare light may be prevented from exiting the shielding portion 93 toward the light receiver. Moreover, the cross-sectional shape of the shielding part 93 may be a triangular shape or a trapezoidal shape instead of the rectangular configuration, and has a shape that suppresses flare light generated in the light projecting area 91 from coming out from the shielding part 93 to the light receiver side. If it is.

  Further, the pressing portion 86a of the cover holding member 86 extends to a position where the light beam L3 passes on the light receiving area portion 92 so that light other than the reflected light from the paper P does not enter the light receiver of the distance detecting portion 66. It may be. Thereby, since unnecessary light does not enter the light receiver of the distance detector 66, the accuracy of distance detection is further improved.

  In the above embodiment, the paper transport unit 65 is applied to the transport path for transporting the paper between the transfer unit 41 and the fixing unit 18, but the present invention is not limited to this, and the paper feed cassette 32 and You may apply to other conveyance paths, such as between the transfer parts 41.

  According to the embodiment, the paper transport device transports the paper P, projects the light toward the paper P through the paper transport unit 65 including the opening 65a, and the opening 65a, and reflects the reflected light from the paper P. A distance detector 66 that detects the distance to the paper P by receiving light, a light projecting area 91 that transmits projection light, a light receiving area 92 that transmits reflected light, a light projecting area 91 and a light receiving area And a shielding portion 93 that shields flare light reflected by the light projecting area 91, and has a predetermined distance (a distance between the conveyance path surface 65b and the opposite surface 65c) with respect to the conveyance path surface 65b of the sheet conveyance section 65. ) On the distance detection unit 66 side.

  According to this configuration, the projection light from the distance detection unit 66 sequentially passes through the light projection area 91 of the cover member 90 and the opening 65a of the paper transport unit 65 to reach the paper P, and the reflected light reflected by the paper P is sequentially opened. 65a and the light receiving area 92 are received by the distance detector 66, and the distance to the paper P is detected based on the reflected light received by the distance detector 66, so that the paper P is not contacted. The amount of deflection of the paper P is measured, and the measured part can be set anywhere in the center or end of the paper P. The measurement is not limited by the arrangement of the distance detection unit 66 and the like, and the paper P or the paper P The toner image is not damaged. In addition, the shielding part 93 of the cover member 90 is prevented from flare light reflected by the projection area 91 of the projection light entering the distance detection part 66 through the shielding part 93, so that the distance can be accurately determined. Further, since the cover member 90 is disposed on the distance detection unit 66 side with a predetermined interval with respect to the conveyance path surface 65b, the reflected light from the paper P is not blocked by the shielding unit 93. Since the light is received by the detection unit 66, it is possible to detect a paper conveyance state such as bending in a wide measurement range.

  Further, according to the above-described embodiment, the sheet conveying unit 65 is formed flat on the opposite surface 65c of the conveying path surface 65b, and the cover member 90 is attached to the opposite surface 65c, thereby having a predetermined interval with respect to the conveying path surface 65b. Therefore, the predetermined interval can be easily set.

  Moreover, according to the said embodiment, the shielding part 93 is distribute | arranged perpendicularly | vertically with respect to the conveyance road surface 65b, and is formed with the wall by which the black process was performed, By the wall by which the black process was performed, a light projection area | region Since the flare light reflected by the portion 91 is prevented from entering the distance detecting portion 66 through the shielding portion 93, there is no risk of erroneous measurement due to the flare light, and the reflected light from the paper P causes the light to reach the paper P. Distance is measured accurately.

  Further, according to the above embodiment, even if the distance detection unit 66 is disposed substantially below the paper transport unit 65, foreign matter such as dust generated in the paper transport unit 65 is detected from the opening 65 a of the paper transport unit 65. The distance to the paper P can be accurately measured by the reflected light from the paper P because there is no risk of falling into the section 66 and causing erroneous measurement due to foreign matter.

  Further, according to the above-described embodiment, the paper conveyance unit 65 and the distance detection unit 66 are disposed on the open / close frame 85 that is openable and closable with respect to the apparatus main body, so that foreign matter such as dust generated in the paper conveyance unit 65 is obtained. However, even if it adheres to the cover member 90, the open / close frame 85 provided with the cover member 90 can be opened from the apparatus main body, and the foreign matter attached to the cover member 90 can be easily removed.

  Further, according to the embodiment, the paper transport unit 65 includes the transfer unit 41 that transfers the toner image formed on the photosensitive member to the paper P, and the fixing unit 18 that melts and fixes the toner image of the transferred paper P. The distance detection unit 66 detects the distance to the sheet P based on the reflected light in the sheet conveyance unit 65 between the transfer unit 41 and the fixing unit 18 and conveys the sheet P. The amount can be accurately measured in a wide measuring range.

  INDUSTRIAL APPLICABILITY The present invention can be used for a sheet conveying apparatus used in an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method, and an image forming apparatus including the same. The present invention can be used in a sheet conveying device that detects a state and an image forming apparatus including the same.

1 is a cross-sectional plan view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional plan view showing a sheet conveyance path of a transfer unit and a fixing unit of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a perspective view illustrating a sheet conveyance path of a transfer unit and a fixing unit of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic side view showing a distance detection state to a sheet of a distance detection unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a cross-sectional side view illustrating a distance detection unit and a cover member in a sheet conveyance path of a transfer unit and a fixing unit of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 18 Fixing part 41 Transfer part 65 Paper conveyance part 65a Opening 65b Conveyance path surface 65c Opposite surface 66 Distance detection part 74 Control part 85 Opening / closing frame 86 Cover holding member 90 Cover member 91 Light projection area part 92 Light reception area part 93 Shielding Part P paper

Claims (6)

A paper transport unit that transports paper and includes an opening;
A distance detecting unit that projects light toward the paper through the opening and receives reflected light from the paper to detect the distance to the paper;
A light projecting area that transmits the projection light, a light receiving area that transmits the reflected light, and flare light that is provided between the light projecting area and the light receiving area and is reflected by the light projecting area. And a cover member disposed on the distance detection unit side with a predetermined interval with respect to a conveyance path surface of the sheet conveyance unit.   2. The sheet conveying apparatus according to claim 1, wherein the sheet conveying unit is formed flat on an opposite surface of the conveying path surface, and the cover member is attached to the opposite surface.   3. The sheet conveying device according to claim 1, wherein the shielding unit is formed of a wall that is disposed perpendicularly to the conveying path surface and is subjected to black processing. 4.   4. The paper transport apparatus according to claim 1, wherein the distance detection unit is disposed substantially below the paper transport unit.   5. The paper transport device according to claim 1, wherein the paper transport unit and the distance detection unit are disposed in an opening / closing frame that is openable and closable with respect to the apparatus main body.   The paper transport unit transports the paper between a transfer unit that transfers the toner image formed on the photosensitive member to the paper and a fixing unit that melts and fixes the toner image of the transferred paper. An image forming apparatus comprising the sheet conveying device according to claim 1.