JP2013234059A - Sheet conveying device, and image forming device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveying device that hardly receive an influence of the paper powder or dust of a sheet such as a document or a recording sheet and does not cause the erroneous detection of the sheet.SOLUTION: When many documents are conveyed through a document conveyance passage 43, the paper powder or dust of a document drops down through a lower rectangular opening 43c. Then, the paper powder or dust drops to a projection region E where the lower rectangular opening 43c is projected to the gravity direction, and in inside a recessed part 61c of a vessel 61. Furthermore, the optical axis J of a light emitting element 62a passes an outer region F so that the emitted light of a light emitting element 62a does not enter the paper powder or dust accumulated in the projection region E. Therefore, the emitted light of the light emitting element 62a is not reflected by the paper powder or dust accumulated in the projection region E and does not enter the light receiving surface of the light receiving element 62b, and the paper powder or dust accumulated in the recessed part 61c does not cause the erroneous detection of the document by a reflective optical sensor 62.

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet such as a document or a recording sheet, and an image forming apparatus including the sheet conveying apparatus.

  As this type of image forming apparatus, there is an apparatus in which a document is read while being conveyed along a conveyance path, an image of the read document is printed on a sheet, and the document is copied. Document conveyance is performed by a document conveyance device. This document transport device includes a transport path for transporting and guiding a document, and an optical sensor for detecting the leading edge of the document being transported. The leading edge of the document being conveyed is detected by the optical sensor upstream of the reading position in the document conveyance direction.

  For example, an optical sensor (a light emitting element and a light receiving element) is provided on the upper side of the document conveyance path upstream of the document image reading position in the document conveyance direction, and a black member is provided at a lower portion of the conveyance path facing the optical sensor. The leading edge of the document is detected by the optical sensor when the document passes between the optical sensor and the black member. Specifically, when the light emitting surface of the light emitting element and the light receiving surface of the light receiving element are directed to the black member and the document does not pass through, the light emitted from the light emitting element is absorbed by the black member, and the light receiving element receives almost no light. If there is no document and the document is passing, the light emitted from the light emitting element is reflected by the document and enters the light receiving element so that the amount of light received by the light receiving element is increased. , That is, the timing when the leading edge of the document passes.

  In Patent Document 1, a photo sensor (light emitting element and light receiving element) is provided below the document conveyance path, and a recess (inside the rib) is provided at an upper portion of the conveyance path facing the photo sensor. The bottom surface is roughened to roughen the bottom surface, and when the document is not passing, the light emitted from the light emitting element is diffusely reflected by the bottom surface of the recess, so that the light receiving element receives little light and the document When the light is passing, the light emitted from the light emitting element is reflected by the original and enters the light receiving element so that the amount of light received by the light receiving element is increased, and the original is detected based on the light receiving output of the light receiving element.

JP 2009-263126 A

  However, in the configuration in which the optical sensor (light emitting element and light receiving element) is provided on the upper side of the document conveyance path and the black member is provided on the lower portion of the conveyance path, the document passes over the black member. The paper dust and dust of the original adhere to the. If the amount of paper dust or dust attached to the black member increases, the light emitted from the light emitting element is not absorbed by the black member but reflected by the paper dust or dust, and the amount of light received by the light receiving element increases, resulting in an error in the document. Detection occurred. For this reason, it is necessary to frequently clean the black member.

  Further, as in Patent Document 1, a concave portion is provided on the upper portion of the conveyance path, the bottom surface of the concave portion is subjected to texturing, and a photo sensor (light emitting element and light receiving element) is provided on the lower side of the original conveyance path. However, it is difficult for paper dust and dust to adhere to the inside or bottom of the recess, but paper dust and dust from the document adhere to the light emitting surface of the light emitting element and the light receiving surface of the light receiving element. occured. For this reason, it is necessary to frequently clean the light emitting surface of the light emitting element and the light receiving surface of the light receiving element.

  Therefore, the present invention has been made in view of the above-described conventional problems, and a paper transport device that is not easily affected by paper dust or dust of a paper such as an original or a recording paper and does not cause erroneous paper detection, and An object is to provide an image forming apparatus provided.

  In order to solve the above problems, a paper transport apparatus according to the present invention includes a transport path that transports and guides a sheet, and an optical sensor that detects an end of the sheet that is transported along the transport path. An apparatus, wherein an opening is formed in the transport path, the optical sensor is provided above the opening, a recess is provided below the opening, and an optical axis of a light emitting element of the optical sensor Passes through the inside of the recess and the outside of the projection area in which the opening is projected in the direction of gravity.

  In such an invention, since the optical sensor is provided above the opening of the conveyance path and the recess is provided below the opening, the paper dust and dust of the paper fall and accumulate in the lower recess. Paper dust and dust do not adhere to the upper optical sensor, and erroneous detection of paper by the optical sensor does not occur. Further, since a large amount of paper dust and dust can be stored in the recess, it is not necessary to clean the recess frequently.

  Further, the optical axis of the light emitting element passes inside the concave portion and outside the projection area where the opening is projected in the direction of gravity. This is because most of the paper dust and dust falls and accumulates in such a projection area, so that the light axis of the light emitting element passes through the inside of the recess and the outside of the projection area, and the emitted light of the light emitting element passes through the projection area. This is to prevent light from being incident on paper dust and dust, and to suppress the amount of light reflected by the paper dust and dust in the projection area and received by the light receiving element of the optical sensor. As a result, it is possible to prevent erroneous detection of the optical sensor due to paper dust or dust accumulated in the recess.

  In the paper transport device of the present invention, the inner surface of the recess has a lower reflectance than the paper.

  In this case, when the light emitted from the light emitting element is incident on the recess when the paper is not passing through, the light received by the light receiving element is clearly reduced because the emitted light is almost absorbed by the inner surface of the recess. The difference between the amount of light received at this time and the amount of light received by the light receiving element when receiving reflected light from the passing paper is increased, and the detection accuracy of the paper based on the light received output of the light receiving element is increased. . In order to make the inner surface of the recess have a low reflectance, the inner surface may be colored black, matte, or roughened.

  Furthermore, in the paper transport device of the present invention, the light emitting element includes a reading unit that reads the paper transported through the transport path, downstream of the opening in the transport path in the transport direction of the paper. The outer position through which the optical axis passes is further away from the paper reading position of the reading unit than the projection area.

  When disturbance light enters the paper reading position of the reading unit, the reading accuracy of the paper by the reading unit decreases. For this reason, the outer position through which the optical axis of the light emitting element passes is separated from the paper reading position relative to the projection area, so that the light emitted from the light emitting element does not enter the paper reading position.

  In the paper transport device of the present invention, the concave portion is a container having a bottom surface and a side wall surface provided along a peripheral edge of the bottom surface.

  In this case, when the light emitted from the light emitting element once enters the concave portion when the paper is not passing, the emitted light does not leak into both the bottom direction and the lateral direction of the concave portion, and the emitted light becomes disturbance light. Therefore, the amount of light received by the light receiving element of the optical sensor is clearly reduced, and the amount of light received at this time and the reflected light from the passing paper are received. The difference from the amount of light received by the light receiving element is increased, and the detection accuracy of the paper based on the light receiving output of the light receiving element is increased.

  Furthermore, in the paper transport device of the present invention, a partition portion that divides the projection region with respect to the outer position through which the optical axis of the light emitting element passes is provided on the bottom surface of the concave portion.

  In this case, since the paper dust and dust are prevented from diffusing outward from the projection area by the partition, the paper dust and dust do not move to an outer position through which the optical axis of the light emitting element passes, and the light emitted from the light emitting element Is not reflected by paper dust or dust, and light reflected from the paper dust or dust is not received by the light receiving element, so that erroneous detection of paper due to such reflected light does not occur.

  In the paper transport device of the present invention, the paper transport device includes a paper reading glass through which the paper transported through the transport path passes, and a support member that supports the paper reading glass, and the concave portion is formed on the support member. Installed.

  In order to set the timing for starting the reading of the sheet image, the front end of the sheet being conveyed is detected by the optical sensor upstream of the sheet image reading position in the sheet conveying direction. In order to improve the accuracy of the reading start timing of the paper image, it is preferable to arrange the optical sensor in the vicinity of the paper reading glass, and therefore, the concave portion is also arranged in the vicinity of the paper reading glass. Therefore, the recess is attached to the supporting member of the paper reading glass. Further, since the concave portion is not provided integrally with the supporting member of the sheet reading glass, but the concave portion is a separate member that can be attached to the supporting member, the degree of freedom in designing the concave portion and the supporting member is increased. For example, the entire concave portion can be formed of a low reflectance black synthetic resin, and the support member can be formed of another color synthetic resin.

  Furthermore, in the paper transport device of the present invention, the recess is detachably attached to the support member.

  This facilitates the removal of paper dust, dust and the like accumulated in the projection area of the recess.

  In the paper transport device of the present invention, the paper transport device further includes a reading unit that reads the paper transported along the transport path, and the light emitting element and the light receiving element of the optical sensor are arranged in the transport direction of the paper, and the light emitting element Is arranged farther from the paper reading position of the reading unit than the light receiving element.

  When disturbance light enters the paper reading position of the reading unit, the reading accuracy of the paper by the reading unit decreases. For this reason, the light emitting element is further away from the paper reading position than the light receiving element, so that the light emitted from the light emitting element does not enter the paper reading position.

  In the paper transport device of the present invention, the center of the paper transported in the transport path is aligned with the central reference of the transport path, and the optical sensor is moved from the central reference of the transport path to the transport direction of the paper. They are arranged apart in the orthogonal direction.

  When a plurality of punch holes are formed at the edge of the paper, one of the punch holes is often located at the center of the paper edge. If the optical sensor is arranged at the center reference (paper center) of the transport path, the optical sensor detects the part of the punch hole of the paper, and the detection accuracy of the edge of the paper by the optical sensor is lowered. In view of this, the optical sensor is arranged away from the center reference of the transport path in a direction orthogonal to the transport direction of the paper so that the punch hole portion of the paper is not detected by the optical sensor.

  On the other hand, an image forming apparatus according to the present invention includes the above-described paper conveyance device according to the present invention, a reading unit that reads the paper conveyed by the paper conveyance device, and a printing unit that prints an image read by the reading unit on the paper. It has.

  Such an image forming apparatus of the present invention also has the same operational effects as the paper conveying apparatus of the present invention.

  In the present invention, since the optical sensor is provided above the opening of the transport path and the recess is provided below the opening, the paper dust or dust of the paper drops and accumulates in the lower recess. Paper dust and dust do not adhere to the optical sensor, and erroneous detection of the paper by the optical sensor does not occur. Further, since a large amount of paper dust and dust can be stored in the recess, it is not necessary to clean the recess frequently.

  Further, the optical axis of the light emitting element passes inside the concave portion and outside the projection area where the opening is projected in the direction of gravity. This is because most of the paper dust and dust falls and accumulates in such a projection area, so that the light axis of the light emitting element passes through the inside of the recess and the outside of the projection area, and the emitted light of the light emitting element passes through the projection area. This is to prevent light from being incident on paper dust and dust, and to suppress the amount of light reflected by the paper dust and dust in the projection area and received by the light receiving element of the optical sensor. As a result, it is possible to prevent erroneous detection of the optical sensor due to paper dust or dust accumulated in the recess.

1 is a cross-sectional view illustrating an image forming apparatus including a document conveying device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing the periphery of a reflective optical sensor, an opening, and a recess of a document conveying device when viewed from the side. FIG. 3 is a cross-sectional view showing the periphery of a reflective optical sensor, an opening, and a recess of a document conveying device as viewed from the front. It is a top view which shows an image reading apparatus. It is a top view which shows roughly the positional relationship of the light emitting element and light receiving element of a reflection type optical sensor. It is a top view which shows roughly the other positional relationship of the light emitting element and light receiving element of a reflection type optical sensor.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an image forming apparatus provided with a document conveying device according to an embodiment of the present invention. The image forming apparatus 1 has a copying function for reading a document and printing it on a recording sheet. An image reading device 2 and a document conveying device (ADF) 3 according to the present embodiment are arranged at the top of the image forming device 1, and the image forming device 1 is the top. A paper feeding cassette 5 is arranged at the bottom, a printing unit 4 is arranged above the paper feeding cassette 5, the image reading device 2 and the printing unit 4 are separated from each other, and a paper discharge tray 6 is arranged therebetween. doing.

  In such an image forming apparatus 1, a document is conveyed by the document conveying device 3, an image (color or monochrome image) of the document is read by the image reading device 2, and the image is printed on a recording sheet by the printing unit 4. Here, the printing unit 4 records a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black). In order to perform printing, four each of the developing device 12, the photosensitive drum 13, the drum cleaning device 14, and the charger 15 are provided, and four image stations are associated with each of black, cyan, magenta, and yellow. Pa, Pb, Pc, and Pd are configured.

  In each of the image stations Pa, Pb, Pc, and Pd, after the residual toner on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is set to a predetermined potential by the charger 15. It is charged uniformly, the surface of the photosensitive drum 13 is exposed by the optical scanning device 11, an electrostatic latent image is formed on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12, A toner image is formed on the surface of the photosensitive drum 13. As a result, a toner image of each color is formed on the surface of each photosensitive drum 13.

  Subsequently, while the intermediate transfer belt 21 is moved in the direction of the arrow C, the residual toner on the intermediate transfer belt 21 is removed and collected by the belt cleaning device 22, and then each color toner image on the surface of each photoconductive drum 13 is intermediate transferred. The toner images are sequentially transferred onto the belt 21 and overlapped to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 23a of the secondary transfer device 23. The intermediate transfer is performed while the recording paper conveyed through the paper conveyance path S is sandwiched and conveyed in the nip area. The color toner image on the surface of the belt 21 is transferred onto the recording paper. The fixing device 17 heats and pressurizes the recording paper to fix the color toner image on the recording paper.

  Further, the recording paper is pulled out from the paper feeding cassette 5 by the pickup roller 24, transported through the paper transport path S, passes through the secondary transfer device 23 and the fixing device 17, and is discharged through the paper discharge roller 25. It is carried out to 6. In this paper conveyance path S, after the recording paper is temporarily stopped and the leading edges of the recording paper are aligned, recording is performed in accordance with the transfer timing of the color toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 23a. A registration roller 27 for starting the conveyance of the paper, each conveyance roller 28 for urging the conveyance of the recording paper, a paper discharge roller 25, and the like are arranged.

  Next, a schematic configuration of the image reading device 2 and the document conveying device 3 mounted on the upper body of the image forming apparatus 1 will be described. The document conveying device 3 is pivotally supported by the back side of the image reading device 2 and is opened and closed by moving the front portion up and down. When the document conveying device 3 is opened, the document reading glass 31 and the document placing glass 32 of the image reading device 2 are opened, and the document can be placed on the document placing glass 32.

  In the image reading apparatus 2, the first and second scanning units 33 and 34 are moved while maintaining a predetermined speed relationship with each other, and the surface of the document on the document placement glass 32 is illuminated by the light source 33 a of the first scanning unit 33. Then, the reflected light from the document surface is guided to the imaging lens 36 by the mirrors 33b and 34b of the first and second scanning units 33 and 34, and the image on the document surface is CCD (Charge Coupled Device) by the imaging lens 36. The image is formed on 37. The CCD 37 repeatedly reads an image on the document surface in the main scanning direction and outputs image data indicating the image on the document surface.

  Further, the image reading device 2 can read not only a stationary document but also an image on the surface of the document conveyed by the document conveying device 3. In this case, as shown in FIG. 1, the first scanning unit 33 is moved to a reading position below the original reading glass 31, and the second scanning unit 34 is positioned in accordance with the position of the first scanning unit 33. Then, the document conveying device 3 starts conveying the document.

  In the document transport device 3, the pickup roller 41 is pressed against the document on the document tray 42 and rotated to pull out the document and transport the document through the document transport path 43. A registration roller 44 that transports the document after aligning the leading end thereof and a transport roller 45 that transports the document are disposed along the document transport path 43. The original passes between the original reading glass 31 and the reading guide plate 46 and is further conveyed from the paper discharge roller 47 to the paper discharge tray 48.

  When the document is conveyed, the surface of the document is illuminated by the light source 33a of the first scanning unit 33 via the document reading glass 31, and the reflected light from the document is reflected on the mirrors 33b and 34b of the first and second scanning units 33 and 34. The image is reflected and guided to the imaging lens 36, and the image on the document surface is formed on the CCD 37 by the imaging lens 36, and the image on the document surface is read by the CCD 37.

  Further, when such a document is conveyed, an image on the back side of the document can be read by the back surface reading unit 51 built in the document conveying device 3. The back surface reading unit 51 includes a light source 52, a document guide glass 53 disposed along the document transport path 43, a plurality of mirrors 54, an imaging lens 55, a CCD 56, and the like.

  In the back surface reading unit 51, the light source 52 illuminates the back surface of the document through the document guide glass 53, reflects the reflected light from the document by each mirror 54, and guides it to the imaging lens 55. Is imaged on the CCD 56, and the image on the back side of the document is read by the CCD 56.

  The original images read by the CCDs 37 and 56 are output as analog image signals from the CCDs 37 and 56, and the analog image signals are A / D converted into digital image signals. The digital image signal (image data) is subjected to various image processing and then input to the optical scanning device 11 of the printing unit 4, and an image indicated by the image data is recorded on the recording paper by the printing unit 4. .

  By the way, in the document conveying device 3, when a document read by the image reading device 2 is conveyed, it is conveyed by a reflective optical sensor upstream of the document reading glass 31 (document image reading position) in the document conveying direction. The leading edge of the document inside is detected. This is because the reading start timing of the document image is set based on the detection timing of the leading edge of the document by the reflective optical sensor.

  However, since paper dust or dust enters from the document being conveyed, it is desirable to prevent erroneous detection of the reflective optical sensor due to these paper dust and dust. Therefore, in the document conveying device 3 of the present embodiment, an opening is formed in the document conveying path 43 upstream of the document reading glass 31 in the document conveying direction, and a reflective optical sensor is provided above the opening. A concave portion is provided below the opening, and paper dust and dust are dropped and collected in the lower concave portion so that the paper dust and dust of the original do not adhere to the upper reflective optical sensor.

  Next, such a reflective optical sensor, an opening, and a recess will be described in detail. FIG. 2 is a cross-sectional view showing the periphery of the reflective optical sensor, the opening, and the recess of the document conveying device 3 as viewed from the side. FIG. 3 is a cross-sectional view showing the periphery of the reflective optical sensor, the opening, and the recess when viewed from the front. Further, FIG. 4 is a plan view showing the image reading device 2.

  As shown in FIG. 2, the document reading glass 31 and the reading guide plate 46 are arranged to face each other with a slight gap Q, and the document conveying path is located upstream and downstream in the conveying direction A with respect to the document reading glass 31. 43 is provided to transport the document in the transport direction A through the document transport path 43 and the gap Q.

  The document conveyance path 43 is formed between the outer peripheral guide wall 43a and the inner peripheral guide wall 43b. A part of the outer periphery of the registration roller 44 contacts the document on the document transport path 43 through each cutout window 43e (shown in FIG. 3) of the inner peripheral guide wall 43b and transports the document. Further, the conveyance auxiliary roller 49 contacts the document on the document reading glass 31 through the notch window portion (not shown) of the reading guide plate 46 and conveys the document.

  Further, a lower rectangular opening 43c is formed in the outer peripheral guide wall 43a, an upper rectangular opening 43d is formed in the inner peripheral guide wall 43b, and the lower rectangular opening 43c and the upper rectangular opening 43d are formed. Are facing each other. A container 61 is provided below the lower rectangular opening 43c, a reflective optical sensor 62 is provided above the upper rectangular opening 43d, and the container 61 and the reflective optical sensor 62 are placed on the lower and upper sides. They are arranged.

  Here, the container 61 is attached in the vicinity of the document reading glass 31 of the image reading device 2. As shown in FIGS. 2 and 4, the document reading glass 31 is supported by being framed by a frame-shaped support member 63, and both ends 63 a of the frame-shaped support member 63 are arranged outside the document reading glass 31. A guide inclined surface 63 c is formed at the front end portion 63 b of the frame-shaped support member 63, and a scooping surface 63 e is formed at the rear end portion 63 d of the frame-shaped support member 63. The guide inclined surface 63 c guides the conveyed document from the upstream document transport path 43 to the gap Q between the document reading glass 31 and the reading guide plate 46. The scooping surface 63e scoops up the document from the document reading glass 31 and guides it to the document transport path 43 on the downstream side.

  In addition, a rectangular notch 63f is formed at the tip 63b of the frame-shaped support member 63, and the container 61 is detachably fitted to the rectangular notch 63f from below. Both the frame-shaped support member 63 and the container 61 are molded products of synthetic resin, the frame-shaped support member 63 is colored in an appropriate single color, and the container 61 is black with a lower reflectance than the document surface (white). It is colored.

  Further, the inside of the container 61 is a concave portion 61c composed of a bottom surface 61a and a side wall surface 61b provided along the periphery (four sides) of the bottom surface 61a. The inner surface (the bottom surface 61 a and the side wall surface 61 b) of the recess 61 c is not only black like the container 61, but is also subjected to a frosting process, and the light reflectance thereof is further reduced. Further, the recess 61c has a rectangular shape in plan view, and has a size of about 18 mm × 18 mm, for example.

  In addition, a partition 61d that partitions the two regions is formed on the bottom surface 61a. The partition 61d is provided at the boundary between the projection area E obtained by projecting the lower rectangular opening 43c of the outer peripheral guide wall 43a in the direction of gravity and the outer area F outside the projection area E inside the recess 61c. Yes. The outer area F is further away from the document reading glass 31 (document image reading position) than the projection area E is.

  Next, the reflective optical sensor 62 includes a light emitting element 62a and a light receiving element 62b, and the light emitting surface of the light emitting element 62a and the light receiving surface of the light receiving element 62b are the lower rectangular opening 43c and the upper rectangular opening. It faces the inside of the recess 61c of the container 61 through the portion 43d. Specifically, as shown in FIG. 3, the light emitting element 62a and the light receiving element 62b are arranged side by side along a direction (main scanning direction) orthogonal to the document transport direction A, and as shown in FIG. 2, the light emitting element 62a. The optical axis J is passed through the outer region F inside the recess 61 c of the container 61.

  FIG. 5 is a diagram schematically showing the light emitting element 62a, the light receiving element 62b, the document conveyance path 43, the recess 61c, and the like in plan view. As shown in FIG. 5, the light receiving surface of the light receiving element 62b is directed in the direction in which the light emitted from the light emitting surface of the light emitting element 62a and reflected by the document P in the document transport path 43 enters.

  3 and 4, when the center position of the document transport path 43 (the center position of the document reading glass 31 and the reading guide plate 46) is the center reference G in the document transport apparatus 3, the center reference G Thus, the lower rectangular opening 43c of the outer peripheral guide wall 43a and the upper rectangular opening 43d of the inner peripheral guide wall 43b are positioned away from each other in the direction (main scanning direction) perpendicular to the document conveying direction A. . Accordingly, the container 61 and the reflective optical sensor 62 are also positioned away from the central reference G in the direction orthogonal to the document transport direction A.

  In the document conveying device 3, the document is read with the center of the document aligned with the central reference G of the document conveying path 43 regardless of the size of the document. For example, after the center of the document is aligned with the central reference G on the document tray 42, the document is transported to the document reading glass 31 through the document transport path 43, and the document is read or the document is placed on the document placement glass 32. The document is read after the center of the image is aligned with the central reference G. Accordingly, the container 61 and the reflection type optical sensor 62 are arranged at positions away from the direction of the document in the direction orthogonal to the document transport direction A.

  The container 61 (recess 61 c) is provided on the image reading device 2 side. However, in order to detect the leading edge of the document being conveyed on the document conveyance path 43 of the document conveyance device 3, the container 61 (recess 61 c) Since it is used in combination with the provided reflective optical sensor 62, it is a component of the document feeder 3.

  In the document conveying device 3 having such a configuration, since the optical axis J of the light emitting element 62a of the reflective optical sensor 62 passes through the outer region F inside the recess 61c of the container 61, the lower rectangular opening 43c and the upper side are arranged. When the document does not pass between the rectangular opening 43d, the light emitted from the light emitting element 62a enters the recess 61c. Once the light emitted from the light emitting element 62a is incident on the concave portion 61c, it does not come out of the concave portion 61c unless it is reflected once or a plurality of times by the bottom surface 61a and the side wall surface 61b of the concave portion 61c. Since it is absorbed by the low-reflectance bottom surface 61a and the side wall surface 61b that have been subjected to the erasing process while being colored in black, it hardly leaks out from the recess 61c. Further, even if light leaks from the recess 61c, the direction of the leaked light is not determined, and the leaked light is directed to a light receiving surface of the light receiving element 62b directed in a certain direction as shown in FIG. Is hardly incident. Accordingly, the light emitted from the light emitting element 62a does not enter or hardly enters the light receiving surface of the light receiving element 62b.

  Further, when the leading edge of the original reaches between the lower rectangular opening 43c and the upper rectangular opening 43d, as shown in FIG. 5, the light emitted from the light emitting element 62a is white and has high reflectivity. Since the light is reflected at the tip of the light and enters the light receiving surface of the light receiving element 62b, the amount of light received by the light receiving element 62b significantly increases.

  Therefore, the difference between the amount of light received by the light receiving element 62b when the document is not passing and the amount of light received by the light receiving element 62b when receiving the reflected light from the leading edge of the passing document is increased. The leading edge of the document can be easily detected from the change in the received light output of 62b, and the detection accuracy is increased.

  When a plurality of punch holes are formed at the leading edge of the document, one of the punch holes is often located at the center of the leading edge of the document. If the reflective optical sensor 62 is disposed at the center reference G (original center) of the document transport path 43, the reflective optical sensor 62 detects the portion of the punch hole in the document, and the reflective optical sensor. The detection accuracy of the leading edge of the document by 62 is lowered. However, in the present embodiment, the reflection type optical sensor 62 is arranged away from the center reference G of the document conveyance path 43 in the direction orthogonal to the document conveyance direction A. The punch hole part is not detected, and the detection accuracy of the leading edge of the document is not lowered.

  Further, since the outer area F is farther from the original reading glass 31 (original image reading position) than the projection area E, the optical axis J of the light emitting element 62a passing through the outer area F is separated from the original image reading position. The light of the light emitting element 62a does not enter the reading position of the original image as disturbance light, and the reading accuracy of the original of the image reading apparatus 2 does not decrease due to the light of the light emitting element 62a.

  On the other hand, when a large number of documents are conveyed through the document conveyance path 43, the paper dust and dust of the documents fall downward through the lower rectangular opening 43c. Then, the paper dust and dust fall into the projection area E where the lower rectangular opening 43c is projected in the direction of gravity, and accumulate inside the recess 61c of the container 61. Further, since the projection area E is partitioned from the outer area F by the partition portion 61d of the bottom surface 61a of the recess 61c, paper dust and dust accumulate only inside the recess 61c and only in the projection area E, and the accumulated paper dust. The dust does not diffuse from the projection area E to the outer area F.

  Further, since the optical axis J of the light emitting element 62a passes through the outer region F, the light emitted from the light emitting element 62a does not enter the paper dust or dust accumulated in the projection region E. For this reason, the light emitted from the light emitting element 62a is not reflected by the paper dust or dust in the projection area E and enters the light receiving surface of the light receiving element 62b, but is caused by paper dust or dust accumulated in the recess 61c. In addition, erroneous detection of the document by the reflective optical sensor 62 does not occur.

  Furthermore, since a large amount of paper dust and dust can be stored in the projection area E partitioned by the partition 61d, it is not necessary to frequently perform an operation for removing the paper dust and dust collected in the recess 61c. . In addition, since the container 61 is attached to the rectangular cutout portion 63f of the frame-like support member 63 that supports the document reading glass 31 so as to be detachable from below, it can be removed to remove paper dust and dust. Can be easily performed. Further, since the recess 61c is about 18 mm × 18 mm in size, if the document feeder 3 is opened and the container 61 is exposed, a waste cloth or a brush can be used without removing the container 61. It is possible to remove paper dust and dust accumulated in the recess 61c.

  In the present embodiment, the inner surface (the bottom surface 61a and the side wall surface 61b) of the recess 61c is made black and the inner surface of the recess 61c is matted, but the inner surface of the recess 61c is a gray color close to black. However, the inner surface of the recess 61c may be roughened instead of the matting process. Further, a hole may be formed in the outer region F inside the recess 61c so that the emitted light of the light emitting element 62a passes through the hole, and the emitted light of the light emitting element 62a does not return to the light receiving element 62b. . Furthermore, although the side wall surfaces 61b are provided on the four sides of the bottom surface 61a of the recess 61c, the two side wall surfaces 61b facing each other in the direction orthogonal to the document conveying direction A may be omitted.

  Further, as shown in FIG. 6, the light emitting element 62a and the light receiving element 62b of the reflective optical sensor 62 may be arranged side by side along the document conveying direction A. In this case, if the light emitting element 62a is further away from the original reading glass 31 (original image reading position) than the light receiving element 62b, the light emitted from the light emitting element 62a is less likely to enter the original image reading position. The reading accuracy of the original by the image reading device 2 does not decrease due to the emitted light.

  Furthermore, the present invention can be applied not only to the document conveying device 3 but also to a paper conveying device that conveys other types of paper. For example, in the image forming apparatus 1 of FIG. 1, the recording paper is pulled out from the paper feed cassette 5 and transported along the paper transport path S, and an optical sensor (not shown) is disposed upstream of the registration rollers 27 in the transport direction of the recording paper. 3), and the optical sensor detects the leading edge position of the recording paper. Therefore, by applying the present invention, it is possible to obtain the same effect as that of the document conveying device 3.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

1 Image forming device 2 Image reading device (reading unit)
3 Document transport device 4 Printing section 5 Paper feed cassette 6 Paper discharge tray 11 Optical scanning device 12 Developing device 13 Photosensitive drum 14 Drum cleaning device 15 Charger 17 Fixing device 21 Intermediate transfer belt 31 Document reading glass 32 Document placement glass 43 Document transport path (transport path)
43c Lower rectangular opening (opening)
43d Upper rectangular opening 61 Container 61a Bottom surface 61b Side wall surface 61c Recess 61d Partition 62 Reflective optical sensor (optical sensor)
62a Light emitting element 62b Light receiving element E Projection area F Outside area

Claims (10)

A paper transport device comprising a transport path for transporting and guiding a paper, and an optical sensor for detecting an end of the paper transported in the transport path;
Forming an opening in the transport path, providing the optical sensor above the opening, and providing a recess below the opening;
An optical axis of a light emitting element of the optical sensor passes through the outside of a projection area that is inside the recess and projects the opening in the direction of gravity. The sheet conveying device according to claim 1,
The sheet conveying apparatus according to claim 1, wherein the inner surface of the recess has a lower reflectance than the sheet. The paper conveying device according to claim 1 or 2,
A reading unit that reads the paper transported in the transport path on the downstream side in the transport direction of the paper from the opening in the transport path;
The paper conveying apparatus characterized in that the outer position through which the optical axis of the light emitting element passes is further away from the paper reading position of the reading unit than the projection area. A paper conveying device according to any one of claims 1 to 3,
The paper conveyance device, wherein the concave portion is a container having a bottom surface and a side wall surface provided along a peripheral edge of the bottom surface. The sheet conveying device according to any one of claims 1 to 4,
A paper conveying apparatus, comprising: a partition portion that divides the projection region with respect to the outer position through which an optical axis of the light emitting element passes on a bottom surface of the concave portion. The paper conveying device according to claim 1 or 2,
A paper reading glass through which the paper transported in the transport path passes;
A support member for supporting the paper reading glass,
The paper conveyance device, wherein the concave portion is attached to the support member. It is a paper conveying apparatus of Claim 6, Comprising:
The paper conveyance device, wherein the concave portion is detachably attached to the support member. A paper conveying apparatus according to any one of claims 4 to 7,
A reading unit that reads the sheet being conveyed along the conveyance path;
A paper transporting device, wherein the light emitting element and the light receiving element of the optical sensor are arranged in the transport direction of the paper, and the light emitting element is arranged farther from the paper reading position of the reading unit than the light receiving element. A paper conveying device according to any one of claims 1 to 8,
The center of the sheet transported along the transport path is aligned with the center reference of the transport path, and the optical sensor is disposed away from the center reference of the transport path in a direction perpendicular to the transport direction of the sheet. Paper transport device.   10. The sheet conveying device according to claim 1, a reading unit that reads a sheet conveyed by the sheet conveying device, and a printing unit that prints an image read by the reading unit on a sheet. An image forming apparatus provided.

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