JP2016208456A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of paper sheet detection parts each for detecting a feeding state of a paper sheet that passes a plurality of feeding paths.SOLUTION: In an image forming apparatus, a paper sheet before image formation and a document with an image formed thereon are passed through the predetermined feeding paths and the image of the document is formed on a surface of the paper sheet. The image forming apparatus comprises: a paper sheet detection part by which, after predetermined light is emitted to a space including the plurality of feeding paths through which the paper sheet and the document are passed, reflection light reflected by the paper sheet and the document passing any one of the plurality of feeding paths is detected; and a paper feed discrimination part which utilizes information acquired from the emitted light and the detected reflection light to discriminate the feeding path through which the paper sheet and the document are fed, from among the plurality of feeding paths. Based on a result of the discrimination, it is determined whether the paper sheet and the document normally pass the predetermined feeding paths.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus having a paper conveyance control function on which an image is formed and a paper jam detection function in a conveyance path.

In an image forming apparatus such as a copying machine, a sheet placed in a sheet feeding tray is automatically conveyed into the apparatus, a predetermined image is formed on the sheet, and then passed through a predetermined conveyance path to be placed on a paper discharge tray. Automatically conveys to
In addition, a sensor that detects the passage of the paper is provided in the transport path in order to detect the abnormal state in which the paper is jammed and the paper is not properly transported in the paper transport path. It has been.

  For example, Patent Document 1 discloses a sensor provided at an entrance for receiving a sheet discharged from an image forming apparatus, a staple discharge sensor that detects a trailing edge of a sheet conveyed to a staple processing tray, and a staple processing tray. A sensor that detects the presence or absence of the upper sheet, detects a jam occurring in the sheet conveyance path using detection information obtained from the sensor, sends an abnormal signal to the image forming apparatus, and causes the user to retain the sheet. A paper post-processing device for informing is provided.

Japanese Patent Laying-Open No. 2005-225672

However, in order to specify the position of a paper jam that has occurred on the transport path through which the paper passes, it is necessary to provide as many paper detection sensors as possible at major points on the transport path. As the number of sensors increases, it becomes necessary to secure the position and wiring path for mounting each sensor, the structure of the entire apparatus becomes complicated, and the manufacturing cost increases.
Further, when the size of the image forming apparatus is reduced, it may be difficult to secure a position where each sensor is attached, and the number of sensors may have to be reduced due to design requirements.

If the number of sensors is reduced, the user may not be able to find the position where the paper jam occurred. If the user restarts without removing the paper that caused the paper jam, the paper jam will occur again. It will be.
Therefore, it is desirable to have a configuration that can clearly identify the position at which a paper jam occurs even if the number of sensors is reduced.
The present invention has been made in consideration of the above circumstances, and even if the number of paper detection sensors provided in the paper or document transport path for forming an image is reduced, a conveyance abnormality is detected. It is an object to reduce the size and cost of an image forming apparatus.

  The present invention relates to an image forming apparatus for forming an image of the original on the surface of the paper by passing a paper before the image formation and the original on which the image is formed through a predetermined conveyance path, And a paper detection unit that detects reflected light reflected by the paper and the document passing through any of the plurality of transport paths, and the reflected light reflected by the document; A paper feed determination unit that determines which transport path of the plurality of transport paths the paper and the original are transported using information acquired from the emitted light and the detected reflected light, and the determination It is an object of the present invention to provide an image forming apparatus characterized in that it is determined whether or not the paper and the original have normally passed through the predetermined transport path based on the result.

  The paper detection unit includes a light emitting unit that emits light and a light receiving unit that receives light, and a light receiving confirmation unit that confirms that the reflected light is received by the light receiving unit; Using the time difference between the time when the light is emitted and the time when it is confirmed that the reflected light is received by the light receiving unit, between the light emitting unit and the sheet or document conveyed to the conveyance path. A light reception detection distance calculation unit that calculates a light reception detection distance that is a distance, and the paper feed determination unit determines a transport path along which the paper or the document is transported using the calculated light reception detection distance. When it is detected that a sheet or document has passed through the determined conveyance path during a predetermined time, it is determined that the sheet or document has normally passed through the conveyance path. And

  The light receiving unit further includes a storage unit, and the light reception detection is performed when the light emitted from the light emitting unit is reflected by a sheet or a document transported to a predetermined transport path and the reflected light is received by the light receiving unit. A reference distance serving as a reference for the light reception detection distance to be calculated by the distance calculation unit is stored in advance in the storage unit in association with each of the plurality of transport paths, and the paper feed determination unit calculates the light reception detection distance. The light reception detection distance calculated by the unit and the reference distance stored in the storage unit are compared, and when a light reception detection distance that can match any of the reference distances is calculated in a predetermined period, the light reception detection is performed. It is characterized in that it is determined that a sheet or document has been transported to a transport path corresponding to a reference distance that can match the distance.

  Further, an input unit is further provided, and after the instruction to start image formation on the paper is input by the input unit, the paper feed determination unit is configured so that the paper or the original is a predetermined time until a predetermined time elapses. After detecting that the paper or document has not been transported to the transport path S, a light reception detection distance that can be matched with a reference distance to be calculated when the paper or the document is transported to the transport path S is calculated for a certain time. Thus, when it is detected that the paper or document has been transported to the transport path S, and then it is detected that the paper or document has not been transported again to the predetermined transport path S, the paper or document is , It has been detected that it has passed through the transport path S.

The predetermined light emitted from the paper detection unit forms an image on the other surface of the paper and a conveyance path for single-sided printing for forming an image on one surface of the paper before the image formation. The sheet feeding determination unit uses the received light detection distance calculated by the received light detection distance calculation unit and the reference distance to convey the sheet. It is characterized in that it is determined whether the conveyance path is the one-side printing conveyance path or the two-sided printing conveyance path.
Further, the predetermined light emitted from the paper detection unit is a cassette paper feed conveyance path through which the paper taken out from the cassette paper feed unit in which the paper before the image formation is accommodated, and the user images The light reception detection distance calculated by the light reception detection distance calculation unit and the reference distance are emitted to the manual paper feed conveyance path through which the paper taken out from the manual paper supply unit where the paper before formation is arranged are conveyed. The paper feed determination unit determines whether the transport path from which the sheet is taken out is the transport path for the cassette paper feed or the transport path for the manual paper feed. And
The predetermined light emitted from the paper detection unit accumulates the original after the read original is read, and a conveyance path for feeding the original from the original reading unit on which the original is arranged. The paper feed determination unit uses the received light detection distance calculated by the received light detection distance calculation unit and the reference distance. It is characterized in that it is determined which of the transport path for transporting the original is the transport path for feeding the original and the transport path for discharging the original.

  Further, the apparatus further includes a display unit, and after the instruction to start image formation on the paper is input by the input unit, the paper feed determination unit is configured so that the paper or the original is If it is not detected that the paper or document has been transported to the transport path S, or if a certain period of time has elapsed with the paper or document being transported to the predetermined transport path S, A message indicating that there is an abnormality in paper or document feeding is displayed.

  According to the present invention, the paper is detected by detecting the reflected light that is reflected by the paper or the original and then returned to the space including the plurality of transport paths through which the paper or the original passes. It is not necessary to provide a means for detecting the conveyance of paper or the like in each of the plurality of conveyance paths, and one paper detection unit It is possible to detect which path of a plurality of conveyance paths has normally passed through a sheet or the like. Further, by reducing the number of sheet detection units, it is possible to reduce the size and cost of the image forming apparatus. Can be planned.

1 is a functional block diagram of an embodiment of an image forming apparatus according to the present invention. It is a schematic explanatory diagram of a paper detection method using a paper detection unit. FIG. 10 is an explanatory diagram of an embodiment of a paper feed determination process when a paper detection unit is provided in the conveyance path of image forming paper. FIG. 10 is an explanatory diagram of an embodiment of a paper feed determination process when a paper detection unit is provided in the conveyance path of image forming paper. FIG. 10 is an explanatory diagram of an example of a paper feed determination process when a paper detection unit is provided in a conveyance path for taking out paper from a paper feed tray. FIG. 10 is an explanatory diagram of an example of a paper feed determination process when a paper detection unit is provided in a conveyance path for taking out paper from a paper feed tray. FIG. 10 is an explanatory diagram of an embodiment of a paper feed determination process when a paper detection unit is provided in a document transport path. FIG. 10 is an explanatory diagram of an embodiment of a paper feed determination process when a paper detection unit is provided in a document transport path. 1 is a schematic explanatory diagram illustrating an overall configuration of an embodiment of an image forming apparatus according to the present invention. 1 is a schematic explanatory diagram of an embodiment of an automatic document reader according to the present invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, this does not limit the present invention.

<Schematic configuration of image forming apparatus>
FIG. 9 is a schematic explanatory diagram of the overall configuration of an embodiment of the image forming apparatus 100 of the present invention.
In FIG. 9, an image forming apparatus 100 forms multicolor and single color images on a predetermined sheet (hereinafter also referred to as a sheet or a recording sheet) in accordance with image data input from the outside. The image forming apparatus main body 110 and the automatic document reader 120 are configured.

  The image forming apparatus main body 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer unit 6, a fixing unit 7, a paper feed cassette 81, a paper discharge tray 91, and the like. Configured.

  A document placing table 92 made of transparent glass on which a document is placed is provided on the upper portion of the image forming apparatus main body 110, and an automatic document reading device 120 is attached to the upper side of the document placing table 92.

  The automatic document reading device 120 automatically conveys the document on the document placing table 92. Further, the automatic document reader 120 is configured to be rotatable in the direction of arrow A, and the document can be placed manually by opening the document table 92.

  The image data handled in the image forming apparatus 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, four developing devices 2, photosensitive drums 3, charging devices 5, and cleaner units 4 are provided so as to form four types of latent images corresponding to the respective colors, and black, cyan, magenta, and yellow are respectively provided. These are set to form four image stations.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to a charger type as shown in FIG. 9, a contact type roller type or brush type charger is used. Sometimes used.

  The exposure unit 1 is composed of a laser scanning unit (LSU) provided with a laser emitting portion, a reflection mirror, and the like. The exposure unit 1 includes a polygon mirror that scans a laser beam, and optical elements such as a lens and a mirror that guide laser light reflected by the polygon mirror to the photosensitive drum 3. In addition, as the exposure unit 1, for example, a technique using an EL or LED writing head in which light emitting elements are arranged in an array can be employed. Such an exposure unit 1 has a function of forming an electrostatic latent image corresponding to the image data on the surface thereof by exposing the charged photosensitive drum 3 according to the input image data.

The developing unit 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toners of four colors (Y, M, C, K).
The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  An intermediate transfer unit 6 is disposed above the photosensitive drum 3. The intermediate transfer unit 6 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. Four intermediate transfer rollers 64 are provided corresponding to the respective colors for Y, M, C, and K.

  The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 are driven to rotate while the intermediate transfer belt 61 is stretched. Each intermediate transfer roller 64 provides a transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 61.

  The intermediate transfer belt 61 is provided in contact with each photosensitive drum 3. A function of forming a color toner image (multicolor toner image) on the intermediate transfer belt 61 by sequentially superimposing and transferring the toner images of the respective colors formed on the photosensitive drum 3 onto the intermediate transfer belt 61. have. The intermediate transfer belt 61 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

  The toner image is transferred from the photosensitive drum 3 to the intermediate transfer belt 61 by an intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image.

  The intermediate transfer roller 64 is a roller based on a shaft made of a metal (for example, stainless steel) having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, etc.). is there. With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller shape is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic images visualized on the respective photosensitive drums 3 according to the respective hues are stacked on the intermediate transfer belt 61. In this way, the stacked image information is transferred to the sheet by rotation of the intermediate transfer belt 61 and a secondary transfer belt (not shown) of the secondary transfer unit 10 disposed at a contact position between the sheet and the intermediate transfer belt 61 described later. Transcribed above. At this time, the intermediate transfer belt 61 and the secondary transfer belt are pressed against each other at a predetermined nip.

  In addition, as described above, the toner adhered to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the paper by the secondary transfer belt, In order to cause color mixing of toner in the next process, the intermediate transfer belt cleaning unit 65 is configured to remove and collect the toner.

  The intermediate transfer belt cleaning unit 65 is provided with a cleaning blade that is in contact with the intermediate transfer belt 61, for example, as a cleaning member. The intermediate transfer belt 61 in contact with the cleaning blade is driven by an intermediate transfer belt driven roller 63 from the back side. It is supported.

  The paper feed cassette 81 is a tray for storing sheets (recording paper) used for image formation, and is provided below the exposure unit 1 of the image forming apparatus main body 110. A sheet used for image formation can also be placed in the manual sheet feeding cassette 82. Furthermore, a paper discharge tray 91 provided above the image forming apparatus main body 110 is a tray for collecting printed sheets face down.

  Further, the image forming apparatus main body 110 has a substantially vertical sheet for feeding the sheets of the paper feed cassette 81 and the manual paper feed cassette 82 to the paper discharge tray 91 via the secondary transfer unit 10 and the fixing unit 7. A conveyance path S is provided. In the vicinity of the paper transport path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, pickup rollers 11a and 11b, a plurality of transport rollers 12a, 12b, 12c and 12d, registration rollers 13, and secondary rollers. A transfer unit 10 and a fixing unit 7 are arranged.

The conveyance rollers 12 a to 12 d are small rollers for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 12 a to 12 d are provided along the sheet conveyance path S.
The pickup roller 11 a is provided near the end of the paper feed cassette 81, picks up sheets one by one from the paper feed cassette 81, and supplies them to the paper transport path S. Similarly, the pickup roller 11 b is provided in the vicinity of the end of the manual paper feed cassette 82, picks up sheets one by one from the manual paper feed cassette 82, and supplies them to the paper transport path S.

  The registration roller 13 temporarily holds the sheet being conveyed through the sheet conveyance path S. The sheet is transferred to the secondary transfer unit 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the sheet are aligned. It has a function to convey.

The fixing unit 7 includes a heat roller 71 and a pressure roller 72, and the heat roller 71 and the pressure roller 72 rotate with the sheet interposed therebetween.
The heat roller 71 is set to have a predetermined fixing temperature based on a signal from a temperature detector (not shown), and is transferred onto the sheet by thermocompression bonding of the toner to the sheet together with the pressure roller 72. It has the function of fusing, mixing, and pressing a multicolor toner image to thermally fix the sheet. An external heating belt 73 for heating the heat roller 71 from the outside is provided.

Next, the sheet conveyance path will be described in detail.
As described above, the image forming apparatus 100 is provided with the paper feed cassette 81 for storing sheets and the manual paper feed cassette 82 in advance. Pickup rollers 11a and 11b are arranged to feed sheets from these sheet feeding cassettes 81 and 82, and guide the sheets one by one to the conveyance path S.

  The sheet conveyed from each of the sheet feeding cassettes 81 and 82 is conveyed to the registration roller 13 by the conveying roller 12a in the sheet conveying path S, and the timing at which the leading edge of the sheet and the leading edge of the image information on the intermediate transfer belt 61 are aligned. It is conveyed to the secondary transfer unit 10 and image information is written on the sheet. Thereafter, the sheet passes through the fixing unit 7, whereby unfixed toner on the sheet is melted and fixed by heat, and then discharged onto the paper discharge tray 91 through the transport roller 12 b disposed thereafter.

  The above-described conveyance path is for a request for single-sided printing on a sheet. On the other hand, for a request for double-sided printing, as described above, after the sheet that has finished single-sided printing and has passed through the fixing unit 7. When the end is gripped by the final transport roller 12b, the transport roller 12b rotates in the reverse direction to guide the sheet to the transport rollers 12c and 12d. Thereafter, after printing is performed on the back surface of the sheet through the registration roller 13, the sheet is discharged to the discharge tray 91.

FIG. 10 is a schematic explanatory diagram of an embodiment of the automatic document reading device 120 and the reading unit 90.
The automatic document reading device 120 includes a document tray 80, a feeding roller 86, a transport roller pair 87, a transport roller pair 83, a paper discharge roller pair 84, and a paper discharge tray (sheet body storage device) 40. A discharge port 85 is provided immediately downstream of the discharge roller pair 84.

  The feeding roller 86 feeds the documents placed on the document tray 80 one by one. The document fed by the feed roller 86 passes through a position facing the document table 93 by the transport roller pair 87, passes through the transport roller pair 83, and the discharge roller pair 84 in this order, and then passes from the discharge port 85 to the discharge tray 40. Discharged.

The reading unit 90 includes a scanner head 94, a light receiving unit 95, an optical unit 96, and the like.
The scanner head 94 includes an irradiation lamp that irradiates light onto a reading area immediately above, a mirror that reflects reflected light from the reading area along a predetermined path, and the like. An optical unit 96 composed of a lens, a mirror, and the like is disposed in the vicinity of the scanner head 94, and reflected light from the reading area is guided from the scanner head 94 to the light receiving unit 95 via the optical unit 96.

  The paper discharge tray 40 is provided immediately below the document tray 80 and is positioned directly downstream of the paper discharge roller pair 84. The paper discharge tray 40 is a tray on which a document fed from the paper discharge roller pair 84 is placed. is there. On the upper surface of the paper discharge tray 40, a placement surface 41 is provided at the center along the discharge direction of the original discharged from the discharge roller pair 84. Since the placement surface 41 is provided only in the central portion, the document can be discharged while reducing the friction between the document and the placement surface 41 when the document is discharged.

The mounting surface 41 is formed with a step between the discharge port 85 and is an inclined surface that is inclined upward along the discharge direction, and is provided so that the downstream side in the discharge direction is slightly curved. Yes. As a result, the document discharge speed during document discharge can be reduced smoothly.
The paper discharge tray 40 is provided at a position adjacent to the discharge port 85, and a placement surface 41 on which a plurality of types of documents discharged from the discharge port 85 can be placed is formed on the upper surface.

  The arm member (biasing member) 45 is fixedly supported by a support portion 44 provided on the lower surface side of the document tray 80. The arm member 45 extends downward in the document discharge direction and urges the document so as to be sandwiched between the placement surface 41 located on the downstream side of the auxiliary tray 42. The arm member 45 is an urging member made of an elastic resin, and urges the document with an urging force that does not hinder movement of the document discharged along the placement surface 41 in the discharge direction. As a result, the sequentially discharged documents can be stacked in a state where they are arranged on the placement surface 41.

  The position where the arm member 45 abuts on the placement surface 41 is, for example, approximately the same length as the length in the ejection direction of an A4 size document at the end of the placement surface 41 on the discharge roller pair 84 side. It is set to be a position provided between. As a result, it is possible to align the discharge positions of the documents of the most frequently used document size among the documents discharged to the placement surface 41. Note that the arm member 45 may not be provided when it is not necessary to align the discharge positions of the discharged documents. The arm member 45 may be attached to the support portion 44 so as to be movable in the discharge direction. Thereby, the position of the arm member 45 can be changed according to the size of the document discharged from the discharge port 85.

<Functional Block of Image Forming Apparatus>
FIG. 1 shows a functional block diagram of an embodiment of the image forming apparatus of the present invention.
In FIG. 1, the image forming apparatus mainly includes a control unit 21, a paper detection unit 22, a light reception confirmation unit 23, a light reception detection distance calculation unit 24, a paper feed determination unit 25, an input unit 26, a display unit 27, and a conveyance control unit 28. A paper feed control unit 29, an image reading control unit 30, an image processing unit 31, and a storage unit 32.
In general, the image forming apparatus generates a still image by using various pieces of input information. Further, a sheet before image formation and a document on which an image is formed are shown in FIG. The image of the original is formed on the surface of the paper by passing through a predetermined transport path.
This image forming apparatus corresponds to, for example, a copying machine, a facsimile machine, or a multifunction machine.
In the following embodiment, a copying machine as shown in FIG. 9 will be described as an image forming apparatus.

In FIG. 1, a control unit 21 is a part for executing each function of the image forming apparatus according to the present invention, and mainly includes a CPU, a ROM, a RAM, an I / O controller, a timer, and the like.
In addition, the CPU organically operates hardware based on a program stored in a ROM or the like, thereby executing, for example, an image input process, an image forming process, a paper transport process, a paper feed process, and the like.

The sheet detection unit 22 is a part that detects the presence or absence of a sheet and a document using light. Specifically, after emitting predetermined light to a space including a plurality of conveyance paths through which the sheet and document pass, The reflected light reflected by the paper and the document passing through the plurality of transport paths is detected.
The paper detection unit 22 mainly includes a light emitting unit 22a that emits light and a light receiving unit 22b that receives light reflected by the paper.
As the emitted light, it is preferable to use infrared rays because of high detection sensitivity, but visible light, laser light, ultrasonic waves, or the like may also be used. In the following embodiments, infrared light is emitted from the light emitting unit 12a.

FIG. 2 is a schematic explanatory diagram of a paper detection method using the paper detection unit 22.
In FIG. 2, it is assumed that the paper 51 is transported in the transport direction H in the figure. When the sheet 51 being conveyed is conveyed on the optical path of the infrared ray 52 emitted from the light emitting unit 22a of the sheet detecting unit 22, the infrared ray 52 emitted rightward from the light emitting unit 22a is the sheet 51 on the optical path. In this case, it is reflected in the left direction, and a part of the infrared ray 52 returns to the paper detection unit 22.
That is, a part of the reflected infrared ray 52 is incident on the light receiving unit 22 b of the paper detection unit 22.
On the other hand, when the paper is not transported, the infrared light emitted from the light emitting unit 12a travels rightward without being reflected because there is no paper 51.

If the passage position of the path along which the paper 51 is transported is always substantially the same position, the distance L0 from the tip of the light emitting section 22a to the paper 51 being transported can be said to be substantially constant. The emitted infrared ray 52 travels a distance (2L) corresponding to twice the distance L0 and is received by the light receiving unit 22b. A distance L0 between the light emitting unit 22a and a sheet or document conveyed on a predetermined conveyance path is referred to as a light reception detection distance.
In this case, the time of emission and the time of light reception are shifted by a time T0 required for the infrared ray 40 to travel the distance (2L). That is, a time difference T0 occurs. The distance L0 (light reception detection distance) can be calculated by using the time difference T0 and the speed of light. Further, as will be described later, by comparing the calculated received light detection distance L0 with a pre-stored reference distance, it is possible to determine in which transport path the sheet is fed.

When the infrared ray 52 is incident on the light receiving unit 22b, an electrical signal corresponding to the received light intensity of the infrared ray is output.
Conventionally used infrared light emitting elements are used for the light emitting part 22a, and infrared light receiving elements for detecting infrared light are used for the light receiving part 22b. What is necessary is just to use what is called an infrared sensor which consists of a pair of infrared rays light emitting element and light receiving element as the paper detection part 22. FIG. A commercially available infrared sensor may be used.
As will be described later, it is possible to check the paper feed state of paper passing through different transport paths depending on the position where the paper detection unit 22 is provided.
For example, a check of paper fed on the transport path for image formation, a check of paper taken into the apparatus from the paper feed cassette, and a check of a document fed to the transport path for reading an image are performed. In order to do this, a paper detection unit 22 is provided at each predetermined position.

The light reception confirming unit 23 is a part for confirming that the reflected light is received by the light receiving unit 22b. Specifically, when the infrared light 52 is received by the light receiving unit 22b, the light output from the light receiving unit 22b. Check the signal.
For example, when an electrical signal having an intensity equal to or higher than a predetermined threshold is detected, it is determined that the infrared ray 52 has been received, and the control unit 21 is notified that the infrared ray has been received.

The light reception detection distance calculation unit 24 is a part that calculates the light reception detection distance L0 by using the time difference T0 between the emission time of the infrared rays and the light reception time when it is confirmed that the reflected light is received by the light reception unit 22b. .
For example, the control unit 21 obtains the current time using a timer, and the time when the infrared light is emitted from the light emitting unit 22a of the paper detection unit 22 and the light reception time confirmed by the light reception confirmation unit 33 calculate the light reception detection distance. When given to the unit 24, the light reception detection distance L0 is calculated using the time difference T0 between the two times and the infrared speed.

The paper feed determination unit 25 is a part that determines whether or not a paper is being fed into a predetermined transport path at a predetermined timing, and is acquired from the emitted light from the paper detection unit 22 and the detected reflected light. Using the information, it is determined which of the plurality of transport paths the paper and the original are transported.
Further, based on this determination result, it is determined whether or not the paper and the original have normally passed through a predetermined conveyance path.

The determination as to whether or not the sheet or the like has normally passed through the predetermined conveyance path is performed by determining the conveyance path along which the sheet or the like has been conveyed using the calculated light reception detection distance, This is performed by detecting that the determined conveyance path has been passed.
Here, the light reception detection distance L0 calculated by the light reception detection distance calculation unit 24 is compared with a reference distance Lh34 stored in advance in the storage unit 32 described later.
As a result of this comparison, when a light reception detection distance L0 that can match any of the reference distances Lh is calculated in a predetermined period, a sheet or the like is placed on the transport path corresponding to the reference distance Lh that can match the light reception detection distance L0. Is determined to have been conveyed.

For example, as will be described later, when the paper feed control unit 29 takes out the paper on which an image is to be formed from the cassette paper feed unit 37, the paper taken out from the cassette paper feed unit 37 is an infrared ray emitted from the paper detection unit 22. Since the timing of crossing the optical path 52 is almost determined, it is checked at that predetermined timing whether or not the light receiving detection distance L0 that can substantially coincide with the cassette sheet distance Lh3 is detected among the reference distance Lh34.
If the light receiving detection distance L0 corresponding to the cassette sheet distance Lh3 is detected for a certain period of time at a predetermined timing, it is determined that the sheet has been normally fed from the cassette sheet feeding unit 37.
On the other hand, if such a light receiving detection distance L0 is not detected at a predetermined timing, or if a distance corresponding to the cassette sheet distance Lh3 is detected for a certain time or longer, it is determined that there is an abnormality in paper feeding. The

  Further, generally, after an instruction to start image formation (for example, printing) on a sheet is input by the input unit 26, the paper feed determination unit 25 first performs the process until a predetermined time T elapses. Alternatively, after detecting that the document is not transported to the predetermined transport path S, the received light detection that can coincide with the distance to be calculated when the paper or the document is transported to the transport path S for a certain period of time. When the distance L0 is calculated, it is detected that the sheet or document has been transported to the transport path S, and then it is detected that the sheet or document has not been transported again to the transport path S. It is assumed that it has passed through the transport path S. That is, when a series of detections as described above are performed, it is determined that the sheet or the like has been normally fed.

  On the other hand, if it is not detected that the paper or the document has been transported to the predetermined transport path S until the predetermined time T elapses after the instruction to start image formation on the paper is input, or When a predetermined time has passed while detecting that the paper or document has been transported to the predetermined transport path S, it is determined that there has been an abnormality in paper feeding, for example, as described later. A message indicating that this has occurred is displayed.

  The light reception confirmation unit 23, the light reception detection distance calculation unit 24, and the paper feed determination unit 25 may be configured using hardware such as a logic circuit. The functions of these units are mainly performed by the CPU. It can be realized by performing arithmetic processing by software based on a program stored in a ROM or the like.

The input unit 26 is a part where the user performs an input operation for selecting predetermined information such as the number of prints and function selection such as printing start. For example, a keyboard or a touch panel is used.
The display unit 27 is a part for displaying information necessary for executing various functions, displaying an execution status and warning during function execution, displaying a message such as a paper feed abnormality, and the like. Used.
As will be described later, when it is confirmed that the paper feeding is not performed normally, a message indicating that there is a paper feeding abnormality or a position where the paper feeding abnormality has occurred is displayed on the display unit 27. .
Further, as a method of notifying the user of the message, not only the message display but also other methods may be used. For example, a speaker that outputs sound may be provided, and a message to be displayed may be output by sound.

The conveyance control unit 28 sequentially conveys the paper through a predetermined conveyance path (S1, S2) to the position of each functional unit such as exposure, development, transfer, and fixing in order to form an image. It is.
In order to check whether or not the sheet normally passes through the conveyance path (S1, S2) for performing the image forming process, as shown in FIGS. 3 and 4 to be described later, a sheet detection unit for conveyance detection. 22 is provided.
The paper feed control unit 29 takes out the paper from the cassette paper feed unit 37 and the manual paper feed unit 38 in which the paper is stored, and leads to the transport path (S1, S2) for performing the image forming process. This is the part that passes the transport path (S3, S4) and transports the paper.
In order to check whether or not the sheet normally passes through the transport path (S3, S4), a sheet detection unit 22 for detecting sheet feeding is provided as shown in FIGS.

The image reading control unit 30 is a part that conveys the original set on the original reading unit 35 shown in FIG. 3 one by one and conveys the original after the original reading process to the original discharge unit 39.
In order to check whether or not the document normally passes through the transport path (S5 and S6) through which the document is transported, as shown in FIGS. Is provided.
The image processing unit 31 is a part that performs a series of processes until an input image is printed on a sheet, such as image input, analysis, charging, exposure, development, transfer, fixing, and output.

The storage unit 32 stores information and programs necessary for executing each function of the image forming apparatus. The storage unit 32 includes a semiconductor storage element such as a ROM, a RAM, and a flash memory, a storage device such as an HDD and an SSD, and the like. A storage medium is used.
In the storage unit 32, for example, a light reception detection distance (L0) 33 and a reference distance (Lh) 34 are stored.
As described above, the light reception detection distance (L0) 33 is a distance calculated from the time difference between the time when the infrared light is emitted from the light emitting unit 22a and the time when the reflected light of the emitted infrared light is received by the light receiving unit 22b. is there.

  As described above, the reference distance (Lh) 34 is a distance corresponding to the light reception detection distance L0 calculated from the time difference between the emission time and the light reception time. Specifically, the light emitted from the light emitting unit 22a is a predetermined distance. This is a distance that serves as a reference for the light reception detection distance L0 to be calculated by the light reception detection distance calculation unit 24 when the reflected light is reflected on the light reception unit 22b after being reflected by the paper or document conveyed on the conveyance path. The reference distance (Lh) 34 is stored in advance in the storage unit 32 in association with each of a plurality of conveyance paths through which a sheet or document is conveyed.

  For example, the single-sided paper distance Lh1 indicates that when performing single-sided printing, infrared rays are emitted from the light emitting unit 22a of the paper detection unit 22 toward the conveyance path (conveyance path S1 of FIG. It means a distance that serves as a reference for the distance calculated from the time it takes for the infrared ray reflected by the paper that has passed through the conveyance path S1 to be received by the light receiving unit 22b.

Further, the double-sided paper distance Lh2 indicates that when performing double-sided printing, infrared rays are emitted from the light emitting unit 22a of the paper detection unit 22 toward a conveyance path (conveyance path S2 in FIG. 3 described later) through which a sheet to be printed on both sides passes. This means a distance that is a reference for a distance calculated from the time it takes for the infrared light reflected by the paper that has passed through the transport path S2 to be received by the light receiving unit 22b.
A sheet on which image formation is performed when the light reception detection distance L0 actually calculated by the light reception detection distance calculation unit 24 substantially coincides with the double-sided paper distance Lh2 at a predetermined timing after the instruction for duplex printing is input. Is normally determined to have passed through the duplex printing conveyance path.

The cassette paper distance Lh3 means a distance serving as a reference for the distance calculated from the time taken until the infrared light reflected by the paper conveyed from the cassette paper supply unit 37 is received by the light receiving unit 22b.
The manual sheet distance Lh4 means a distance that is a reference of a distance calculated from the time taken until the infrared ray reflected by the sheet conveyed from the manual sheet feeding unit 38 is received by the light receiving unit 22b.

The document feeding distance Lh5 is a reference for a distance calculated from the time taken for the infrared ray reflected by the document to be received by the light receiving unit 22b when the document set in the document reading unit 35 is taken in. Means distance.
The document discharge distance Lh6 is such that when the document set in the document reading unit 35 is taken in and read, and then conveyed to the document discharge unit 39, infrared light reflected by the document is received by the light receiving unit 22b. This means a distance that is a reference for the distance calculated from the time taken until the operation is performed.
After a document is set and a document reading instruction is input, at a predetermined timing, the light reception detection distance L0 actually calculated by the light reception detection distance calculation unit 24 first coincides substantially with the document feeding distance Lh5. Further, when the document discharge distance Lh6 substantially coincides with the document discharge distance Lh6 only after a fixed time has elapsed, it is determined that the document has normally passed through the conveyance path.

The reference distance Lh is stored in advance in the storage unit 32 for comparison with the calculated received light detection distance L0, but information stored in advance is not limited thereto.
For example, a reference time to be compared with the time difference T0 (light reception detection time) between the infrared emission time and the reflected light reception time for calculating the light reception detection distance L0 may be stored in advance.

<Embodiment 1>
FIG. 3 and FIG. 4 are explanatory diagrams of an embodiment of the paper feed determination process in the case where the paper detection unit 22 is provided in the paper conveyance path for image formation.
In FIG. 3, the document reading unit 35 corresponds to the document tray 80 described above, the paper discharge unit 36 corresponds to the paper discharge tray 91, the cassette paper feed unit 37 corresponds to the paper feed cassette 81, and the manual paper feed unit 38. Corresponds to the manual paper feed cassette 82, and the document discharge unit 39 corresponds to the discharge tray 40.

FIG. 3 shows the conveyance paths (S1, S2) through which the paper taken out from the cassette paper supply unit 37 passes for image formation.
A conveyance path S1 in FIG. 3 is a one-sided printing conveyance path for forming an image on one surface of a sheet before image formation. Further, the transport path S2 is a transport path for duplex printing for forming an image on the other surface of the paper. As shown in FIGS. 3 and 4, the infrared rays emitted from the light emitting unit 22a of the paper detection unit 22 are emitted toward the conveyance path S1 for single-sided printing and the conveyance path S2 for double-sided printing. That is, two transport paths (S1, S2) cross the infrared optical path.
Using the received light detection distance L0 calculated from the emitted light and reflected light and the reference distances (Lh1, Lh2) stored in advance, the transport path on which the sheet is transported is transported for single-sided printing. It is determined whether the route or the conveyance route for double-sided printing.

When performing single-sided printing, the transport path S1 is used. While the paper 51 is passing through the transport path S1, an image is formed on one side of the paper, and the paper on which the image has been formed is discharged to the paper discharge unit 36.
When carrying out duplex printing, two transport paths (S1, S2) are used. First, after the paper 51 passes through the transport path S1, after the image is formed on one side of the paper, the paper transported to the vicinity of the paper discharge unit 36 is sent out to the transport path S2, and again passes through the transport path S1. In the middle of passing, an image is formed on a surface different from the image forming surface and is discharged to the paper discharge unit 36.

Here, as shown in FIGS. 3 and 4, the sheet detection unit 22 is arranged so that infrared rays are emitted toward both the conveyance paths S <b> 1 and S <b> 2.
When the paper 51 is passing through the transport path S1, as shown in FIG. 4A, the infrared light emitted from the paper detection unit 22 is reflected by the paper 51 and received by the light receiving unit 22b. In this case, the infrared light is received by the light receiving unit 22b after reciprocating a distance corresponding to the above-described single-sided paper distance Lh1.
When the infrared light reception is confirmed, and it is detected that the light reception detection distance L0 calculated from the time difference between the infrared emission time and the light reception time is substantially equal to the single-sided paper distance Lh1, the paper passes through the transport path S1. It is determined that
Further, when the sheet is normally conveyed thereafter, the sheet is further conveyed upward and conveyed to the paper discharge unit 36. Therefore, the emitted infrared light is not reflected by the sheet and is not received by the light receiving unit 22b. .

Therefore, for example, when the user inputs an instruction to start printing on a sheet, infrared rays are emitted from the sheet detection unit 22 until a predetermined time Ta elapses after the instruction is input. When it is detected that there is no sheet on the conveyance path S1, and then a light reception detection distance L0 corresponding to the single-sided sheet distance Lh1 is detected for a certain period of time, and then it is detected that there is no sheet on the conveyance path S1, The paper feed determination unit 25 determines that the paper taken out from the cassette paper feed unit 37 has been normally transported through the transport path S1.
On the other hand, for example, when the light reception detection distance L0 corresponding to the single-sided paper distance Lh1 is not detected during the predetermined time Ta, or when the predetermined time has passed while the light reception detection distance L0 is detected, The paper feed determination unit 25 determines that there is an abnormality in paper transport.

For example, when the state in which the light reception detection distance L0 is detected continues for a certain time or more, it is determined that the sheet is stopped without being conveyed in the middle of the conveyance path S1.
When a paper transport error is detected, for example, a message indicating that a paper transport error has occurred such as "The paper is jammed in the paper print transport path and should be removed" is displayed. This is displayed on the unit 27. Alternatively, if a speaker is provided, the message may be output as a voice.

In the case of performing duplex printing, as shown in FIG. 4B, after printing on one side, the paper 51 passes through the transport path S2, so that the infrared rays emitted from the paper detection unit 22 are transmitted through the transport path. Reflected by the sheet passing through S2.
In this case, the infrared light is received by the light receiving unit 22b after reciprocating a distance corresponding to the double-sided paper distance Lh2.
When it is detected that the light reception detection distance L0 calculated from the time difference between the infrared emission time and the light reception time is substantially equal to the double-sided paper distance Lh2, it is determined that the paper passes through the transport path S2.

In the case of double-sided printing, after the single-sided printing is completed as shown in FIG. 4A, until the predetermined time Tb elapses, first, the sheet is transported along the conveyance path ( S1 and S2) are detected, and then a light reception detection distance L0 corresponding to the double-sided paper distance Lh2 is detected for a predetermined time, and thereafter it is detected that there is no paper in the transport path (S1, S2). In this case, the paper feed determination unit 25 determines that it has normally passed through the transport path S2.
After detecting the passage of the transport path S2, until the predetermined time Ta elapses, as shown in FIG. 4A, the detection of the distance L0 corresponding to the sheet non-detection and the one-sided sheet distance Lh1, If a series of detection processes for detecting no sheet is performed, it is determined that the sheet conveyance for double-sided printing has been performed normally.

On the other hand, in the case of FIG. 4B, if the double-sided paper distance Lh2 is not detected within the predetermined time Tb, or if the double-sided paper distance Lh2 remains detected for a certain time or longer, the paper is fed. The determination unit 25 determines that there is a paper conveyance abnormality in the conveyance path S2.
In this case, for example, a message indicating a paper transport abnormality such as “paper is jammed in the transport path for double-sided printing, please remove the paper” is displayed on the display unit 27, or a voice is output. To do.

  As described above, one sheet detection unit 22 is provided, and infrared rays are emitted into a space for monitoring the two conveyance paths (S1, S2) as shown in FIG. 3, and the two conveyance paths (S1, S2). Since the distance (light reception detection distance) from the light emitting unit 22a to the paper is calculated by receiving infrared reflected light from the paper passing through either of them, the paper conveyance in the case of single-sided printing and the case of double-sided printing It is possible to determine the conveyance abnormality for each sheet conveyance.

<Embodiment 2>
FIGS. 5 and 6 show an example of the paper feed determination process in the case where the paper detection unit 22 is provided in the transport path for taking out the paper in the paper feed unit (37, 38) in which the paper before image formation is accumulated. An explanatory view of an example is shown.
Here, the cassette paper supply unit 37 is a cassette tray that stores paper before image formation, and the manual paper supply unit 38 is a manual tray on which a user places paper before image formation.
FIG. 5 shows a conveyance process (S3, S4) until the paper taken out from the cassette paper supply unit 37 and the manual paper supply unit 38 is guided to the above-described conveyance path S1.
The conveyance path S <b> 3 is a path (conveyance path for cassette paper feeding) along which the paper taken out from the cassette paper feeding unit 37 is conveyed.
The conveyance path S4 is a path (conveyance path for manual sheet feeding) along which the sheet taken out from the manual sheet feeding unit 38 is conveyed.

Here, as shown in FIGS. 5 and 6, the paper detection unit 22 is arranged so that infrared rays are emitted toward both spaces of the transport paths S3 and S4.
Further, when the infrared ray is reflected by the paper, the paper is obtained by using the light reception detection distance L0 calculated by the light reception detection distance calculation unit 24 and the reference distances (Lh3, Lh4) stored in the storage unit 32 in advance. It is determined whether the transport path thus taken out is the transport path S3 for cassette paper feed or the transport path for manual paper feed.

When the paper 51 is passing through the transport path S3, as shown in FIG. 6A, the infrared light emitted from the paper detection unit 22 is reflected by the paper 51 and received by the light receiving unit 22b.
In this case, infrared rays are reciprocated by a distance corresponding to the cassette sheet distance Lh3 and received by the light receiving unit 22b.
When a light reception detection distance L0 that substantially matches the cassette sheet distance Lh3 is detected, the sheet feeding determination unit 25 determines that the sheet taken out from the cassette sheet feeding unit 37 is passing through the transport path S3.
After that, when the sheet is further conveyed normally and conveyed to the conveyance path S1, infrared rays are not reflected by the sheet and are not received by the light receiving unit 22b.

  When the user inputs an instruction to start printing on a sheet, infrared rays are emitted from the sheet detection unit 22 until a predetermined time Tc after the instruction is input, and is first transferred to the transport path S3. When it is detected that there is no sheet, and then a light reception detection distance L0 corresponding to the cassette sheet distance Lh3 is detected for a certain period of time, and then it is detected that there is no sheet in the transport path S3, a paper feed determination unit 25, it is determined that the sheet taken out from the cassette paper supply unit 37 has been normally transported along the transport path S3.

On the other hand, if the light reception detection distance L0 corresponding to the cassette paper distance Lh3 is not detected during the predetermined time Tc, or if the predetermined time has passed with the light reception detection distance L0 being detected, the paper is fed. The determination unit 25 determines that there is an abnormality in taking out the paper in the transport path S <b> 3 from the cassette paper supply unit 37.
If there is an abnormality in taking out the paper, for example, a message indicating that an abnormality such as “please remove the paper because the paper taken out from the cassette paper supply unit is jammed” is displayed on the display unit 27. Or output audio.

When the paper 51 is taken out from the manual paper feed unit 38, as shown in FIG. 6B, the paper 51 set in the manual paper feed unit 38 passes through the transport path S4. The emitted infrared light is reflected by the paper 51 passing through the transport path S4.
In this case, infrared rays are reciprocated by a distance corresponding to the manual sheet distance Lh4 and received by the light receiving unit 22b.
When it is detected that the light reception detection distance L0 calculated from the time difference between the infrared emission time and the light reception time is substantially equal to the manual paper feed distance Lh4, it is taken out from the manual paper feed unit 38 by the paper feed determination unit 25. It is determined that the sheet passes through the transport path S4.
Thereafter, when the sheet is further conveyed to the conveyance path S1, infrared light is not received.

When paper is fed from the manual paper feed unit 38, the paper is not detected and is equivalent to the manual paper distance Lh4 until a predetermined time Td elapses after a print instruction is input to the manually fed paper. When a series of detection processes such as detection of the distance L0 to be detected and detection of no sheet are performed, it is determined that the sheet has passed the conveyance path S4 and the sheet is normally fed from the manual sheet feeding unit 38. Is done.
On the other hand, if the manual paper distance Lh4 is not detected before the predetermined time Td elapses, or if the manual paper distance Lh4 remains detected for a certain time or longer, the paper feed determining unit 25 In the transport path S4, it is determined that there is a paper take-out abnormality.
In this case, for example, a message such as “Please remove the paper because the paper taken out from the manual paper feed unit is jammed” is displayed on the display unit 27 or outputted by voice.

  As described above, one sheet detection unit 22 is provided at a position from the cassette sheet feeding unit 37 and the manual sheet feeding unit 38 to the conveyance path S1, and two conveyance paths (S3, S4 as shown in FIG. 5) are provided. ) To the space for monitoring the distance between the light emitting unit 22a and the sheet (detection of received light) by receiving infrared reflected light from the sheet passing through one of the two transport paths (S3, S4). Distance) is calculated, it is possible to determine whether there is a paper conveyance abnormality from the cassette paper supply unit 37 and a paper conveyance abnormality from the manual paper supply unit 38, respectively.

<Embodiment 3>
FIGS. 7 and 8 are explanatory diagrams of an embodiment of the paper feed determination process when the paper detection unit 22 is provided in the transport path of the document on which the image is formed.
FIG. 7 shows a transport path (S 5, S 6) from when the document set in the document reading unit 35 is taken in, the document content is read, and transported to the document discharge unit 39.
The conveyance path S5 is a path for fetching a document from the document reading unit 35 on which the document is placed (a conveyance path for document feeding), and the conveyance path S6 stores the document after reading the fetched document. This is a path (a transport path for document discharge) sent to the document discharge unit 39 to be placed.

Here, as shown in FIGS. 7 and 8, the sheet detection unit 22 is arranged so that infrared rays are emitted toward both spaces of the transport paths S5 and S6.
Further, when infrared rays are reflected by the document, the document is obtained using the light reception detection distance L0 calculated by the light reception detection distance calculation unit 24 and the reference distances (Lh5, Lh6) stored in advance in the storage unit 32. It is determined whether the transport path being transported is a transport path S5 for feeding a document or a transport path S6 for discharging a document.

When the paper (original) 51 is passing through the transport path S5, as shown in FIG. 8A, the infrared light emitted from the paper detection unit 22 is reflected by the paper 51 and received by the light receiving unit 22b. The
In this case, the infrared rays are reciprocated by a distance corresponding to the document feeding distance Lh5 and received by the light receiving unit 22b.
That is, when a light reception detection distance L0 that substantially matches the document feed distance Lh5 is detected, the feed determination unit 25 determines that the document passes through the transport path S5.
Thereafter, when the paper 51 is conveyed to the left in the drawing and reaches a position where the paper 51 is turned to the right, the infrared rays are not reflected by the paper 51 and are not received.

When the user inputs an instruction to start printing on a sheet after setting the document, infrared rays are emitted from the sheet detection unit 22 until a predetermined time Te elapses after the instruction is input. First, when it is detected that there is no paper in the transport path S5, and then the light reception detection distance L0 corresponding to the document feed distance Lh5 is detected for a certain time, and then it is detected that there is no paper in the transport path S5. In addition, the paper feed determination unit 25 determines that the document has been normally transported along the transport path S5.
On the other hand, if the light reception detection distance L0 corresponding to the document feeding distance Lh5 is not detected during the predetermined time Te, or if the predetermined time elapses while the light reception detection distance L0 is detected, The paper determination unit 25 determines that there has been an abnormality in document capture in the transport path S5 for document capture.
If there is an abnormality in taking in the original, for example, a message indicating that an abnormality such as “the original is jammed, please remove the original and set it again” is displayed on the display unit 27. Or audio output.

Further, after the document normally passes through the transport path S5, it passes through the transport path S6 up to the document discharge section 39 as shown in FIG. 8B. At this time, the infrared light emitted from the paper detection unit 22 is reflected by the document passing through the transport path S6.
In FIG. 8B, the infrared rays reciprocate a distance corresponding to the document discharge distance Lh6 and are received by the light receiving unit 22b.
When it is detected that the light reception detection distance L0 calculated from the time difference between the infrared emission time and the light reception time is substantially equal to the document discharge distance Lh6, the document passes through the transport path S6 by the paper feed determination unit 25. It is determined that

  As described above, after detecting that the original has normally passed through the transport path S5, until the predetermined time Tf elapses, infrared light is emitted from the paper detection unit 22, and first there is no paper in the transport path S6. Then, when a light reception detection distance L0 corresponding to the document discharge distance Lh6 is detected for a predetermined time, and thereafter it is detected that there is no paper in the transport path S6, the paper feed determination unit 25 It is determined that the document has been normally conveyed on the conveyance path S6.

On the other hand, if the light reception detection distance L0 corresponding to the document discharge distance Lh6 is not detected during the predetermined time Tf, or if the predetermined time has passed with the light reception detection distance L0 being detected, The paper determination unit 25 determines that there is a document discharge abnormality in the transport path S6 for discharging the document.
When there is a document discharge error, for example, a message indicating that an error such as “The document could not be discharged, please remove the document and set it again” is displayed on the display unit 27. Or output audio.

  As described above, one paper feed detection unit 22 is provided in the vicinity of the conveyance path from the document reading unit 35 to the document discharge unit 39, and two conveyance paths (S5, S6) as shown in FIG. 7 are monitored. The distance from the light emitting portion 22a to the original is calculated by receiving infrared reflected light from the original that passes through one of the two transport paths (S5, S6). Thus, it is possible to determine whether there is a document taking-in abnormality and a document discharge abnormality.

As described above, in any of the three embodiments, one paper detection unit 22 is provided at a position where a space including two transport paths can be monitored. Each conveyance abnormality in the two conveyance paths can be detected.
That is, the number of the sheet detection units 22 can be reduced to half compared to the case where the sheet detection units 22 for monitoring the two conveyance paths are separately provided, so that the position where the sheet detection units 22 are provided is one place. Therefore, the size of the image forming apparatus can be reduced, and the number of the sheet detection units 22 can be reduced, so that the apparatus cost can be reduced.

DESCRIPTION OF SYMBOLS 1 Exposure unit, 2 Developer, 3 Photoconductor drum, 4 Cleaner unit, 5 Charger, 6 Intermediate transfer unit, 7 Fixing unit, 10 Secondary transfer unit, 11 Pickup roller, 12 Conveyance roller, 13 Registration roller, 21 Control Unit, 22 paper detection unit, 22a light emission unit, 22b light reception unit, 23 light reception confirmation unit, 24 light reception detection distance calculation unit, 25 paper feed determination unit, 26 input unit, 27 display unit, 28 transport control unit, 29 paper feed control 30, image reading control unit, 31 image processing unit, 32 storage unit, 33 light receiving detection distance L0, 34 reference distance Lh, 35 document reading unit, 36 paper discharge unit, 37 cassette paper feeding unit, 38 manual paper feeding unit, 39 Document discharge section, 40 Paper discharge tray, 41 Placement table, 44 Support section, 45 Arm member, 51 paper, 52 infrared, 61 intermediate transfer belt, 62 intermediate transfer belt driving roller, 63 intermediate transfer belt driven roller, 64 intermediate transfer roller, 65 intermediate transfer belt cleaning unit, 71 heat roller, 72 pressure roller, 80 Document tray, 81 paper feed cassette, 82 manual paper feed cassette, 83 transport roller pair, 84 paper discharge roller pair, 85 discharge port, 86 feed roller, 87 transport roller pair, 90 reading unit, 91 paper discharge tray, 92 Table, 93 Document table, 94 Scanner head, 95 Light receiving unit, 96 Optical unit, 100 Image forming apparatus, 110 Image forming apparatus main body, 120 Automatic document reading apparatus

Claims (8)

An image forming apparatus for forming an image of the original on the surface of the paper by passing a paper before image formation and the original on which the image is formed through a predetermined transport path,
A sheet detection unit that detects a reflected light reflected by a sheet and a sheet passing through one of the plurality of conveyance paths after emitting predetermined light to a space including a plurality of conveyance paths through which the sheet and the document pass. When,
A paper feed determination unit that determines which transport path of the plurality of transport paths the sheet and the document are transported using information acquired from the emitted light and the detected reflected light;
An image forming apparatus that determines whether or not the paper and the original have normally passed through the predetermined conveyance path based on the determination result. The paper detection unit includes a light emitting unit that emits light and a light receiving unit that receives light,
A light receiving confirmation unit for confirming that the reflected light is received by the light receiving unit;
A sheet or document conveyed to the light emitting unit and the conveyance path using a time difference between the time when the light is emitted from the light emitting unit and the time when the reflected light is confirmed to be received by the light receiving unit. A light reception detection distance calculation unit that calculates a light reception detection distance that is a distance between
The paper feed determination unit determines a transport path along which the paper or document is transported using the calculated light reception detection distance, and the transport path where the paper or document is determined during a predetermined time. The image forming apparatus according to claim 1, wherein when it is detected that the sheet has passed, the sheet or document is determined to have normally passed through the conveyance path. A storage unit;
When the light emitted from the light emitting unit is reflected by a sheet or original conveyed on a predetermined conveyance path and the reflected light is received by the light receiving unit, the light receiving detection distance calculating unit should calculate the light. A reference distance serving as a reference of the light reception detection distance is stored in advance in the storage unit in association with each of the plurality of transport paths,
The paper feed determination unit compares the light reception detection distance calculated by the light reception detection distance calculation unit with a reference distance stored in the storage unit,
When a light reception detection distance that can coincide with any of the reference distances is calculated in a predetermined period, it is determined that a sheet or document has been conveyed to a conveyance path corresponding to the reference distance that can coincide with the light reception detection distance. The image forming apparatus according to claim 2. An input unit,
After the instruction to start image formation on the paper is input by the input unit, the paper feed determination unit has not transported the paper or the document to the predetermined transport path S until a predetermined time elapses. After detecting that
The sheet or document is transported to the transport path S by calculating the received light detection distance that can be matched with the reference distance to be calculated when the sheet or document is transported to the transport path S for a certain time. Detected,
Thereafter, when it is detected that the sheet or document is not conveyed again to the predetermined conveyance path S, it is detected that the sheet or document has passed through the conveyance path S. The image forming apparatus according to claim 3. Predetermined light emitted from the paper detection unit is used to form an image on the other surface of the paper and a conveyance path for single-sided printing for forming an image on one surface of the paper before the image formation. Emitted to the transport path for duplex printing,
Using the received light detection distance calculated by the received light detection distance calculation unit and the reference distance,
5. The paper feed determination unit according to claim 4, wherein the transport path on which the paper is transported determines whether the transport path for single-sided printing or the transport path for double-sided printing. The image forming apparatus described. The predetermined light emitted from the paper detection unit is a cassette feeding path through which the paper taken out from the cassette paper feeding unit in which the paper before the image formation is accommodated, and the user before the image formation. The paper taken out from the manual paper feed unit where the paper is placed is output to the manual feed conveyance path to be conveyed,
Using the light reception detection distance calculated by the light reception detection distance calculation unit and the reference distance, the paper feed determination unit determines that the transport path from which the paper has been taken out is the transport path for the cassette paper feed and the cassette feed path. The image forming apparatus according to claim 4, wherein a determination is made as to which of the manual feed conveyance paths. The predetermined light emitted from the paper detection unit accumulates the original after the original has been read, and a conveyance path for feeding the original from the original reading unit on which the original is placed. Emitted to the document delivery path to be sent to the document delivery section,
Using the received light detection distance calculated by the received light detection distance calculation unit and the reference distance,
The paper feed determination unit determines whether a transport path along which the document is transported is the transport path for feeding the document or the transport path for discharging the document. 5. The image forming apparatus according to 4. A display unit;
After the instruction to start image formation on the paper is input by the input unit, the paper feed determination unit has transported the paper or the original to the predetermined transport path S until a predetermined time elapses. If it is not detected, or if a certain period of time has passed while detecting that the paper or document has been transported to a predetermined transport path S,
The image forming apparatus according to claim 4, wherein a message indicating that there is an abnormality in paper or document feeding is displayed on the display unit.