JP2019137516A - Image formation apparatus, recording medium discrimination method and recording medium discrimination program - Google Patents

Abstract

To enhance the accuracy of detecting information on a recording medium without positioning the recording medium.SOLUTION: An MFP includes: a main conveyance path 41; a light projection part 59a which emits light to a detection area DA in the main conveyance path 41; a light reception part 59b which outputs a signal in accordance with the amount of the detected light by detecting the light from the detection area DA; a medium information decision part which decides the basis weight of the sheet on the basis of the signal output by the light reception part 59b while the sheet is moving in the detection area DA; and a position control mechanism 59c which changes the detection area DA so that the sheet passing through the main conveyance path 41 moves at a predetermined target position TP in the detection area DA.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an image forming apparatus, a recording medium determination method, and a recording medium determination program, and in particular, an image forming apparatus capable of forming an image on different types of recording media, a recording medium determination method and a recording executed by the image forming apparatus It relates to a medium determination program.

  In an image forming apparatus such as an MFP (Multi Function Peripheral), a plurality of types of sheets may be used. In this case, the quality of the formed image can be improved by appropriately setting the image forming conditions such as the toner transfer voltage and the fixing temperature during image formation according to the type of paper.

  As a technique for detecting the thickness of a sheet, Japanese Patent Laid-Open No. 2008-94600 (Patent Document 1) discloses a sheet guide plate arranged opposite to each other to convey and guide a sheet to a predetermined portion, and a sheet at the predetermined portion. Paper detecting means for detecting that the paper has been conveyed, pressing means for pressing the paper in the direction of the one paper guide plate, light is emitted in the thickness direction of the paper that has entered the predetermined position, and transmitted through the paper. In a paper transport device comprising a paper thickness detecting means for detecting a paper thickness based on light, the paper detecting means operates the pressing means to press the paper when the paper detecting means detects the paper. A paper transport device is described.

However, in the paper transport device described in Japanese Patent Application Laid-Open No. 2008-94600, in order to allow the paper to enter a predetermined position, the paper must be temporarily stopped and positioned during the transport. For this reason, there is a problem that the time required for image formation is prolonged and productivity is lowered.
JP 2008-94600 A

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide an image forming apparatus with improved accuracy for detecting information relating to a recording medium without positioning the recording medium. That is.

  Another object of the present invention is to provide a recording medium discriminating method with improved accuracy for detecting information relating to a recording medium without positioning the recording medium.

  Still another object of the present invention is to provide a recording medium discriminating program with improved accuracy for detecting information relating to a recording medium without positioning the recording medium.

  The present invention has been made to solve the above-described problems. According to one aspect of the present invention, an image forming apparatus injects an inspection medium into a main transport path and a detection area in the main transport path. And a collecting means for outputting a signal corresponding to the amount of the medium detected by detecting the inspection medium from the detection area, and a signal output by the collecting means while the recording medium moves in the detection area Medium information determining means for determining medium information relating to the recording medium, and position control means for changing the detection area so that the recording medium passing through the main transport path moves to a predetermined target position in the detection area And comprising.

  According to this aspect, the detection area is changed so that the recording medium passing through the main conveyance path moves to a predetermined target position in the detection area. An inspection medium can be detected from the detection region. Therefore, it is possible to detect the medium information of the recording medium with high accuracy. As a result, it is possible to provide an image forming apparatus with improved accuracy in detecting information related to the recording medium without positioning the recording medium.

  Preferably, the position control means changes the relative position of the detection area with respect to the main transport path.

  According to this aspect, since the relative position of the detection area with respect to the main transport path is changed, the target position can be matched with the position of the recording medium moving along the main transport path.

  Preferably, the position control unit changes the relative position of the ejection unit or the collection unit with respect to the main transport path in a state where the relative position between the ejection unit and the collection unit is fixed.

  According to this aspect, since the relative position of the ejection unit or the collection unit with respect to the main transport path is changed in a state where the relative position between the ejection unit and the collection unit is fixed, the relative position of the target position with respect to the detection region can be changed. The relative position of the detection area with respect to the main transport path can be changed.

  Preferably, the position control means moves the detection area in a direction parallel to the conveyance direction of the recording medium passing through the main conveyance path.

  According to this aspect, since the detection area is moved in a direction parallel to the recording medium conveyance direction, the target position can be adjusted to the position of the recording medium moving along the main conveyance path at an arbitrary position on the main conveyance path. it can.

  Preferably, the position control means moves the detection area in a direction intersecting with the recording medium moving along the main conveyance path.

  According to this aspect, since the detection area is moved in the direction intersecting with the recording medium moving along the main conveyance path, the target position can be matched with the position of the recording medium moving along the main conveyance path.

  Preferably, the position control means changes the detection area so that the recording medium passing through the main transport path moves the target position with a predetermined target posture with respect to the detection area.

  According to this aspect, the detection area is changed so that the recording medium passing through the main transport path moves in the target posture at the target position. It is possible to detect the inspection medium from Therefore, the accuracy of the signal output from the collecting means can be increased.

  Preferably, the position control means rotates the detection area around the target position.

  According to this aspect, the detection area is rotated around the target position, so that the target posture can be matched with the posture of the recording medium moving along the main transport path.

  Preferably, there are a plurality of injection means arranged with their relative positions fixed relative to the main conveyance path, and the collection means are arranged with their relative positions fixed with respect to the main conveyance path, and the position control means is The detection area is changed by selecting at least one of the plurality of injection means.

  According to this aspect, since at least one is selected from the plurality of injection means arranged with the relative position fixed relative to the main transport path, the detection area can be easily changed.

  Preferably, the injection means is arranged with a fixed relative position with respect to the main transport path, the collection means is arranged with a plurality of fixed positions with respect to the main transport path, and the position control means is The detection area is changed by selecting at least one of the plurality of collecting means.

  According to this aspect, at least one is selected from a plurality of light receiving surfaces arranged with their relative positions fixed relative to the main transport path, so that the detection area can be easily changed.

  Preferably, the apparatus further comprises a plurality of sub-transport paths connected upstream of the main transport path, and the position control means sets the detection area at a position corresponding to the sub-transport path through which the recording medium has passed among the plurality of sub-transport paths. change.

  According to this aspect, the detection area is changed to a position corresponding to the sub-transport path through which the recording medium passes among the plurality of sub-transport paths connected upstream of the main transport path. Even if the position of the recording medium in the path is different, the target position can be matched with the position of the recording medium in the main transport path.

  Preferably, a humidity sensor for detecting humidity is further provided, and the position control means changes the detection region to a position corresponding to the detected humidity.

  According to this aspect, since the detection area is changed to a position corresponding to the humidity, the target position of the recording medium in the main transport path is changed even when the deflection of the recording medium changes due to the humidity. Can be adjusted to the position.

  Preferably, the recording medium further includes size selection means for selecting the size of the recording medium, and the position control means changes the detection area to a position corresponding to the selected size.

  According to this aspect, since the detection area is changed to a position corresponding to the size of the recording medium, the target position in the main conveyance path can be changed even when the deflection amount of the recording medium varies depending on the size of the recording medium. It can be adjusted to the position of the recording medium.

  Preferably, the image forming apparatus further includes a paper grain selecting unit that selects a paper grain direction with respect to a conveyance direction of the recording medium passing through the main conveyance path, and the position control unit has a detection region at a position corresponding to the selected paper grain direction. To change.

  According to this aspect, since the detection area is changed to a position corresponding to the direction of the grain of the recording medium, the target position can be obtained even when the deflection amount of the recording medium changes due to the difference in the direction of the grain of the recording medium. Can be adjusted to the position of the recording medium in the main transport path.

  According to another aspect of the present invention, a recording medium determination method detects a main transport path, an ejection unit that ejects an inspection medium to a detection area in the main transport path, and an inspection medium from the detection area. And a collecting means for outputting a signal according to the amount of the detected medium, and a recording medium discrimination method executed by an image forming apparatus, wherein the collecting means moves while the recording medium is moving in the detection area. Based on the output signal, a medium information determining step for determining medium information regarding the recording medium, and changing the detection area so that the recording medium passing through the main transport path moves to a predetermined target position in the detection area. A position control step.

  According to this aspect, it is possible to provide a recording medium determination method with improved accuracy for detecting information about the recording medium without positioning the recording medium.

  According to still another aspect of the present invention, a recording medium discrimination program includes: a main transport path; an ejection unit that ejects an inspection medium to a detection area in the main transport path; and an inspection medium from the detection area. A recording medium discrimination program that is executed by a computer that controls an image forming apparatus including a collecting unit that outputs a signal according to the amount of the medium detected by the detection, and the recording medium moves the detection area A medium information determining step for determining medium information relating to the recording medium based on a signal output by the collecting means, and a recording medium passing through the main transport path to move a predetermined target position in the detection area, And a position control step for changing the detection area.

  According to this aspect, it is possible to provide a recording medium discriminating program with improved accuracy for detecting information relating to the recording medium without positioning the recording medium.

1 is a perspective view showing an external appearance of an MFP in the present embodiment. 2 is a block diagram illustrating an outline of a hardware configuration of an MFP. FIG. FIG. 3 is a schematic side view illustrating a part of the internal configuration of the image forming unit and the paper feeding unit. It is a figure which shows the position of the paper which approachs a detection area. It is a figure which shows the attitude | position of the paper which approachs a detection area. It is a figure which shows an example of the relationship between the position of a paper, and the light quantity which permeate | transmits a paper. FIG. 6 is a diagram illustrating an example of a relationship between a posture of a sheet and the amount of light transmitted through the sheet. It is a side view which shows the structure of the main conveyance path | route in this Embodiment, and a some sub conveyance path | route. It is a figure for demonstrating the parallel movement of a conveyance direction in a detection area | region. It is a figure for demonstrating the parallel movement of the direction where a detection area is extended in a detection area. It is a figure for demonstrating rotational movement in a detection area. FIG. 10 is a side view illustrating a state when a sheet enters the main transport path from the upper sheet feed tray through the sub transport path. FIG. 6 is a side view illustrating a state when a sheet enters a main transport path from a manual feed tray through a sub transport path. FIG. 10 is a side view illustrating a state when a sheet enters a main transport path through a sub transport path from the middle and lower sheet feed trays. It is a figure which shows an example of the function which CPU of MFP in this Embodiment has. It is a flowchart which shows an example of the flow of a recording medium discrimination | determination process. It is a figure which shows an example of the function which CPU of MFP in the 1st modification has. It is a side view which shows the structure of the main conveyance path | route in a 2nd modification, and a some sub conveyance path | route. It is the front view which looked at the detection apparatus of FIG. 18 along the direction of the arrow K. It is a figure for demonstrating the parallel movement of a conveyance direction in the detection area | region in a 2nd modification. It is a figure for demonstrating the parallel displacement of the direction which goes to the main conveyance path | route in the detection area | region in a 2nd modification. It is a figure for demonstrating rotational movement in the detection area | region in a 2nd modification. It is a side view which shows the structure of the main conveyance path | route and 2nd sub conveyance path | route in 2nd Embodiment. It is a figure which expands and shows the detection apparatus of FIG. FIG. 10 is a diagram illustrating an example of a function of a CPU of an MFP according to a second embodiment.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. In the following description, an MFP will be described as an example of an image forming apparatus. Furthermore, the MFP described below can form an image on any of a plurality of types of recording media having different medium information as a recording medium on which an image is to be formed. The medium information is information regarding the recording medium, and includes color, basis weight, or thickness. In the present embodiment, the case where the medium information is the basis weight will be described as an example. A plurality of types of recording media having different medium information include, for example, plain paper, high-quality paper, recycled paper, or photographic paper.

  FIG. 1 is a perspective view showing the appearance of the MFP according to the present embodiment. FIG. 2 is a block diagram showing an outline of the hardware configuration of the MFP. Referring to FIGS. 1 and 2, MFP 100 is an example of an image forming apparatus, and includes main circuit 110, document reading unit 130 for reading a document, and automatic document for conveying a document to document reading unit 130. A transport device 120, an image forming unit 140 for forming an image on a sheet based on image data, a sheet feeding unit 150 for supplying the image forming unit 140 with a sheet, and an operation panel 160 as a user interface. Including.

  The automatic document feeder 120 automatically conveys a plurality of documents set on the document tray 125 one by one to the document reading position of the document reading unit 130, and an image formed on the document by the document reading unit 130 The read original is discharged onto the original discharge tray 127. The automatic document feeder 120 includes a document detection sensor that detects a document placed on the document tray 125.

  The document reading unit 130 has a rectangular reading surface for reading a document. The reading surface is formed of platen glass, for example. The automatic document feeder 120 is connected to the main body of the MFP 100 so as to be rotatable about an axis parallel to one side of the reading surface, and can be opened and closed. A document reading unit 130 is disposed below the automatic document feeder 120, and the reading surface of the document reader 130 is exposed when the automatic document feeder 120 is rotated and opened. Therefore, the user can place a document on the reading surface of the document reading unit 130. The automatic document feeder 120 can change a state between an open state in which the reading surface of the document reading unit 130 is exposed and a closed state that covers the reading surface. The automatic document feeder 120 includes a state detection sensor that detects the open state of the automatic document feeder 120.

  The document reading unit 130 includes a light source that emits light and a photoelectric conversion element that receives light, and scans an image formed on a document placed on the reading surface. When a document is placed on the reading area, the light emitted from the light source is reflected by the document, and the reflected light is imaged by the photoelectric conversion element. When the photoelectric conversion element receives the light reflected from the document, the photoelectric conversion element generates image data obtained by converting the received light into an electric signal. The document reading unit 130 outputs the image data to the CPU 111 provided in the main circuit 110.

  The sheet feeding unit 150 conveys sheets stored in first to third sheet feeding trays and a manual feed tray described later to the image forming unit 140. The paper feed unit 150 detects information related to the paper conveyed to the image forming unit 140 as medium information. In the present embodiment, the medium information is the basis weight of the paper. Details of the configuration and operation for detecting medium information in the paper supply unit 150 will be described later.

  The image forming unit 140 is controlled by the CPU 111 and forms an image by a known electrophotographic method. In the present embodiment, the image forming unit 140 is conveyed by the paper feeding unit 150 based on image data input from the CPU 111 and a command signal from the CPU 111 based on medium information detected by the paper feeding unit 150. An image is formed on a sheet. The paper on which the image is formed is discharged to the paper discharge tray 159. The image data output from the CPU 111 to the image forming unit 140 includes image data such as print data received from the outside in addition to the image data input from the document reading unit 130.

  The main circuit 110 includes a CPU (Central Processing Unit) 111 that controls the entire MFP 100, a communication interface (I / F) unit 112, a ROM (Read Only Memory) 113, a RAM (Random Access Memory) 114, A hard disk drive (HDD) 115 as a mass storage device, a facsimile unit 116, and an external storage device 118 are included. CPU 111 is connected to automatic document feeder 120, document reading unit 130, image forming unit 140, sheet feeding unit 150, and operation panel 160, and controls the entire MFP 100.

  The ROM 113 stores a program executed by the CPU 111 or data necessary for executing the program. The RAM 114 is used as a work area when the CPU 111 executes a program. The RAM 114 temporarily stores image data continuously sent from the document reading unit 130.

  Operation panel 160 is provided on top of MFP 100. Operation panel 160 includes a display unit 161 and an operation unit 163. The display unit 161 is, for example, a liquid crystal display device (LCD), and displays an instruction menu for a user, information about acquired image data, and the like. For example, an organic EL (electroluminescence) display can be used in place of the LCD as long as it is an apparatus that displays an image.

  The operation unit 163 includes a touch panel 165 and a hard key unit 167. The touch panel 165 is a capacitive type. Note that the touch panel 165 is not limited to the capacitance method, and other methods such as a resistance film method, a surface acoustic wave method, an infrared method, and an electromagnetic induction method can be used.

  The touch panel 165 is provided with its detection surface superimposed on the display unit 161 on the upper or lower surface of the display unit 161. Here, the size of the detection surface of the touch panel 165 and the size of the display surface of the display unit 161 are the same. For this reason, the coordinate system of the display surface and the coordinate system of the detection surface are the same. The touch panel 165 detects the position where the user points the display surface of the display unit 161 on the detection surface, and outputs the coordinates of the detected position to the CPU 111. Since the coordinate system of the display surface and the coordinate system of the detection surface are the same, the coordinates output from the touch panel 165 can be replaced with the coordinates of the display surface.

  Hard key portion 167 includes a plurality of hard keys. The hard key is, for example, a contact switch. The touch panel 165 detects a position designated by the user on the display surface of the display unit 161. When the user operates the MFP 100, the user often takes an upright posture, and thus the display surface of the display unit 161, the operation surface of the touch panel 165, and the hard key unit 167 are arranged facing upward. This is because the user can easily visually recognize the display surface of the display unit 161 and the user can easily instruct the operation unit 163 with a finger.

  Communication I / F unit 112 is an interface for connecting MFP 100 to a network. The communication I / F unit 112 communicates with other computers or data processing devices connected to the network using a communication protocol such as TCP (Transmission Control Protocol) or FTP (File Transfer Protocol). The network to which the communication I / F unit 112 is connected is a local area network (LAN), and the connection form may be wired or wireless. The network is not limited to a LAN, and may be a wide area network (WAN), a public switched telephone network (PSTN), the Internet, or the like.

  The facsimile unit 116 is connected to the public switched telephone network (PSTN) and transmits facsimile data to the PSTN or receives facsimile data from the PSTN. The facsimile unit 116 stores the received facsimile data in the HDD 115, converts it into print data that can be printed by the image forming unit 140, and outputs the print data to the image forming unit 140. As a result, the image forming unit 140 forms an image of facsimile data received by the facsimile unit 116 on a sheet. Further, the facsimile unit 116 converts the data stored in the HDD 115 into facsimile data, and transmits the facsimile data to a facsimile machine connected to the PSTN.

  The external storage device 118 is controlled by the CPU 111, and a CD-ROM (Compact Disk Read Only Memory) 118A or a semiconductor memory is mounted. In this embodiment, an example in which the CPU 111 executes a program stored in the ROM 113 will be described. However, the CPU 111 controls the external storage device 118 to read a program to be executed by the CPU 111 from the CD-ROM 118A. The read program may be stored in the RAM 114 and executed.

  The recording medium for storing the program to be executed by the CPU 111 is not limited to the CD-ROM 118A, but is a flexible disk, cassette tape, optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc). )), A medium such as a semiconductor memory such as an IC card, an optical card, a mask ROM, and an EPROM (Erasable Programmable ROM). Further, the CPU 111 downloads a program from a computer connected to the network and stores it in the HDD 115, or loads the program stored in the HDD 115 into the RAM 114 so that the computer connected to the network writes the program to the HDD 115. Then, it may be executed by the CPU 111. The program here includes not only a program directly executable by the CPU 111 but also a source program, a compressed program, an encrypted program, and the like.

  FIG. 3 is a schematic side view illustrating a part of the internal configuration of the image forming unit and the paper feeding unit. Referring to FIG. 3, a main transport path 41 indicated by a thick dotted line is basically formed in MFP 100 so as to extend in the vertical direction. The main conveyance path 41 is a path for guiding the sheet conveyed from the sheet feeding unit 150 to the sheet discharge tray 159 through the image forming unit 140. In the main transport path 41 of this example, the lower end 30 on the opposite side of the upper end 13 located above the image forming unit 140 constitutes a carry-in entrance for receiving paper from the paper supply unit 150. Further, the upper end portion 13 of the main transport path 41 constitutes a discharge port for discharging the sheet after image formation to the discharge tray 159. A paper discharge roller 15 is provided at the upper end 13 of the main transport path 41. The lower end portion 30 of the main transport path 41 is connected to a plurality of sub transport paths SP1, SP2, SP3 of the paper feed section 150 described later. The sheet conveyance direction is a direction from the sheet feeding unit 150 toward the sheet discharge tray 159.

  The paper feed unit 150 includes three paper feed trays 151, 152, 153 and a manual feed tray 154. The three paper feed trays 151, 152, and 153 are stacked and arranged in this order from top to bottom. The manual feed tray 154 is provided on the side wall 101 of the MFP 100 and is positioned below the image forming unit 140. As shown by a thick dashed line in FIG. 3, in the paper feeding unit 150, the paper feeding tray 151, 152, 153 extends from the paper feeding tray 151 positioned at the upper stage to the lower end 30 of the main transport path 41. A sub-transport path SP1 is formed. Further, a sub transport path SP <b> 2 is formed so as to extend from the manual feed tray 154 to the lower end portion 30 of the main transport path 41. Further, two conveyance paths 152 a and 153 a extending from the respective sheet feeding trays 152 and 153 located in the middle and lower stages of the three sheet feeding trays 151, 152 and 153 to the lower end portion 30 of the main conveyance path 41 are formed. . A portion having a predetermined length from the lower end 30 of the main transport path 41 of each of the two transport paths 152a and 153a is a sub transport path SP3 shared by the two transport paths 152a and 153a.

  A paper feed roller 151r for supplying paper stored in the paper feed tray 151 to the main transport path 41 is provided in the sub transport path SP1. A paper feed roller 154r for supplying paper stored in the manual feed tray 154 to the main transport path 41 is provided in the sub transport path SP2. The transport path 152a is provided with a paper feed roller 152r for supplying the paper stored in the paper feed tray 152 to the main transport path 41 through the sub transport path SP3. Further, a paper feed roller 153r for supplying the paper stored in the paper feed tray 153 to the main transport path 41 through the sub transport path SP3 is provided in the transport path 153a.

  In MFP 100, when an image is formed on a sheet, a tray storing a sheet on which an image is to be formed is selected as a target tray from among three sheet feeding trays 151, 152, and 153 and manual feed tray 154. By operating the paper feed roller corresponding to the tray selected as the target tray among the three paper feed trays 151, 152, 153 and the manual feed tray 154, the sub transport paths SP1, SP2, SP2 from the tray selected as the target tray are operated. A sheet on which an image is to be formed is supplied to the main transport path 41 through one of SP3.

  The image forming unit 140 includes yellow, magenta, cyan, and black image forming units 51Y, 51M, 51C, and 51K. An image is formed by driving at least one of the image forming units 51Y, 51M, 51C, and 51K. When all of the image forming units 51Y, 51M, 51C, and 51K are driven, a full color image is formed. Printing data for yellow, magenta, cyan, and black are input to the image forming units 51Y, 51M, 51C, and 51K, respectively. Since the image forming units 51Y, 51M, 51C, and 51K differ only in the color of the toner to be handled, the image forming unit 51Y for forming a yellow image will be described here.

  The image forming unit 51Y includes an exposure head to which yellow printing data is input, a photosensitive drum (image carrier), a charging charger, a developing device, and a transfer roller 53Y. The exposure head emits laser light according to the received printing data (electrical signal). The emitted laser light is one-dimensionally scanned by a polygon mirror provided in the exposure head to expose the photosensitive drum. The direction in which the photosensitive drum is one-dimensionally scanned is the main scanning direction. The photosensitive drum is charged by a charging charger and then irradiated with laser light emitted from an exposure head. As a result, an electrostatic latent image is formed on the photosensitive drum. Subsequently, the developing device places toner on the electrostatic latent image to form a toner image. The toner image formed on the photosensitive drum is transferred onto the intermediate transfer belt 57 by the transfer roller 53Y.

  On the other hand, the intermediate transfer belt 57 is suspended by the driving roller 55 and the roller 55A so as not to be loosened. When the driving roller 55 rotates counterclockwise in the figure, the intermediate transfer belt 57 rotates counterclockwise in the figure at a predetermined speed. As the intermediate transfer belt 57 rotates, the roller 55A rotates counterclockwise.

  As a result, the image forming units 51Y, 51M, 51C, and 51K sequentially transfer the toner images onto the intermediate transfer belt 57. The timing at which each of the image forming units 51Y, 51M, 51C, 51K transfers the toner image onto the intermediate transfer belt 57 is adjusted by detecting a reference mark attached to the intermediate transfer belt 57. As a result, yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 57.

  In the main transport path 41, a timing roller 45, a transfer roller 47, and a fixing roller 49 are arranged at intervals in this order from the lower end 30 to the upper end 13. The paper supplied from the paper supply unit 150 to the main transport path 41 is sent to the timing roller 45.

  The timing roller 45 adjusts the conveyance state of the paper in the main conveyance path 41 so that the paper reaches the transfer roller 47 at the timing when the toner image formed on the intermediate transfer belt 57 reaches the transfer roller 47. The paper conveyed by the timing roller 45 is pressed against the intermediate transfer belt 57 by the transfer roller 47, and the transfer roller 47 is charged to superimpose the yellow, magenta, cyan, A black toner image is transferred to the paper. The voltage applied to the transfer roller 47 is controlled by the CPU 111 so that the charge amount of the transfer roller 47 becomes a value suitable for the basis weight of the paper.

  The sheet on which the toner image is transferred is conveyed to the fixing roller 49 and heated by the fixing roller 49. As a result, the toner is melted and fixed on the paper. Thereafter, the paper after the image formation is discharged from the upper end portion 13 of the main transport path 41 onto the paper discharge tray 159 by the paper discharge roller 15. The temperature of the fixing roller 49 is controlled by the CPU 111 so as to be a value suitable for the basis weight of the paper.

  MFP 100 according to the present embodiment is provided with detection device 59 having a detection area in main transport path 41. The detection device 59 includes a light projecting unit 59a and a light receiving unit 59b, and the light projecting unit 59a and the light receiving unit 59b sandwich the main transport path 41 at a position between the lower end 30 of the main transport path 41 and the timing roller 45. It arrange | positions so that it may mutually oppose. The light projecting unit 59a includes, for example, a light emitting element such as a light emitting diode, a drive circuit for the light emitting element, and an optical system, and emits light along the optical axis. A region in the main transport path 41 along the optical axis of the light projecting unit 59a is a detection region. The light receiving unit 59b includes a light receiving element such as a photodiode, and outputs a signal corresponding to the amount of light received by the light receiving element. The detection region of the detection device 59 is a region between the light projecting unit 59a and the light receiving unit 59b.

  In the detection device 59, a predetermined amount of light is emitted from the light projecting unit 59a to the detection area. In this state, when the sheet moves so as to cross the detection area, a part of the moving sheet is irradiated with light. At this time, a part of the light applied to the paper is transmitted through the paper, and the rest of the light is absorbed by the paper or reflected from the paper. The light receiving unit 59b receives light that has passed through the paper and outputs a signal corresponding to the amount of light received to the CPU 111.

  In the CPU 111, based on the output signal of the light receiving unit 59b, information regarding the sheet moving in the detection area is acquired as medium information. In the present embodiment, the medium information is information indicating the basis weight of the paper that moves in the detection area. The CPU 111 sets image forming conditions for the paper based on the acquired medium information. The image forming conditions for the paper include the voltage applied to the transfer roller 47 required to properly transfer the toner image formed on the intermediate transfer belt 57 to the paper, and the toner image transferred to the paper. The temperature of the fixing roller 49 required for proper fixing is included. For example, when the basis weight of the paper detected by the detection device 59 is large, the charge amount of the transfer roller 47 is set higher and the temperature of the fixing roller 49 is set higher. On the other hand, when the basis weight of the sheet detected by the detection device 59 is small, the charge amount of the transfer roller 47 is set lower and the temperature of the fixing roller 49 is set lower. Further, the paper image forming conditions may include a paper conveyance speed required for transferring and fixing the toner image onto the paper. For example, when the basis weight of the paper detected by the detection device 59 is large, the paper transport speed is set to be slower, and when the basis weight of the paper detected by the detection device 59 is small, the paper transport speed is set. Is set faster. Note that the sheet conveyance speed can be adjusted by controlling the rotation speed of the timing roller 45, the transfer roller 47, the fixing roller 49, and the paper discharge roller 15.

  In order to set image forming conditions more appropriately according to the type of paper, it is necessary to determine medium information with higher accuracy. However, as described above, when the medium information is determined based on the amount of light transmitted through the paper, when the position of the paper moving in the detection area changes, the output signal of the light receiving unit 59b also changes. Therefore, the detection results vary, and it is difficult to accurately determine the medium information. This variation occurs mainly due to which of the plurality of sub-conveyance paths the paper is conveyed in the paper supply unit 150. Specifically, the above-described variation is caused by, for example, the position and orientation of the sheet entering the detection area from one of the three sub-transport paths SP1, SP2, and SP3 of the paper feed section 150, and the paper feed section 150. This occurs because the position and posture of the sheet entering the detection area from the other sub-transport path among the plurality of sub-transport paths SP1, SP2, SP3 are different.

  FIG. 4 is a diagram illustrating the position of the sheet entering the detection area. With reference to FIG. 4, the position of the sheet is indicated by a distance from the reference point, with an intermediate point between the light projecting unit 59 a and the light receiving unit 59 b as a reference point. With respect to the position of the sheet, the light projecting portion 59a side is more positive than the reference point, and the opposite side to the light projecting portion 59a is negative. Thus, the position of the sheet entering the detection area is indicated by the distance from the light projecting unit 59a.

  FIG. 5 is a diagram illustrating the posture of the sheet entering the detection area. Referring to FIG. 5, a line connecting the center of light projecting unit 59a and the center of light receiving unit 59b is the optical axis of light emitted from light projecting unit 59a. The posture of the paper entering the detection area is an angle formed by the optical axis of the light emitted from the light projecting unit 59a and the normal of the paper. Here, in FIG. 5, the clockwise direction is positive.

  FIG. 6 is a diagram illustrating an example of the relationship between the sheet position and the amount of light transmitted through the sheet. Referring to FIG. 6, the horizontal axis indicates the paper position, and the vertical axis indicates the transmitted light amount. The amount of transmitted light is the amount of light transmitted through the paper. The relationship shown in FIG. 6 is that the amount of light received by the light receiving unit 59b is measured by changing the position of the paper in a state where the posture of the paper is 0 degree and the amount of light emitted from the light projecting unit 59a is constant. Results are shown. The amount of transmitted light is maximized at the reference point of the sheet, and the amount of transmitted light decreases as the position of the sheet moves away from the reference point on the plus side and the minus side.

  FIG. 7 is a diagram illustrating an example of the relationship between the posture of the paper and the amount of light transmitted through the paper. With reference to FIG. 7, the horizontal axis indicates the position of the paper, and the vertical axis indicates the amount of transmitted light. The relationship shown in FIG. 7 is that the position of the paper is used as a reference point, the amount of light emitted from the light projecting unit 59a is constant, and the amount of light received by the light receiving unit 59b is measured by changing the posture of the paper. Results are shown. The amount of transmitted light is maximized when the orientation of the sheet is 0 degrees, and the amount of transmitted light decreases as the angle of the orientation of the sheet increases. It can be seen that the transmittance is maximized when the paper posture is 0 degrees, and the transmittance decreases as the paper posture increases.

  FIG. 8 is a side view showing the configuration of the main transport path and the plurality of sub transport paths in the present embodiment. In FIG. 8, in order to facilitate understanding of the shapes of the main transport path 41 and the plurality of sub transport paths SP1, SP2, SP3 and their positional relationship, two different types of hatching are attached to the sub transport paths SP1, SP2. In addition, two different dot patterns are attached to the main transport path 41 and the sub transport path SP3.

  Referring to FIG. 8, as indicated by a dotted line in FIG. 8, detection device 59 is arranged to have detection area DA in main transport path 41. The detection area DA of the detection device 59 extends in the direction intersecting the paper pa moving in the main transport path 41 while intersecting the traveling direction of the paper pa. The detection area DA is an area between the light projecting unit 59a and the light receiving unit 59b. The direction in which the detection area DA extends is parallel to a line connecting the center of the light projecting unit 59a and the center of the light receiving unit 59b.

  The main transport path 41 has a predetermined curvature. In the vicinity of the connecting portion between the lower end portion 30 of the main transport path 41 and the plurality of sub transport paths SP1 to SP3, a path forming member B1 that partitions the sub transport path SP1 and the sub transport path SP3 is provided. Further, a path forming member B2 that partitions the sub transport path SP3 and the sub transport path SP2 is provided.

  When the paper pa is transported to the main transport path 41 through the sub transport path SP1, the paper pa entering the main transport path 41 from the sub transport path SP1 is guided to the detection area DA. When the paper pa is transported to the main transport path 41 through the sub transport path SP2, the paper pa entering the main transport path 41 from the sub transport path SP2 is guided to the detection area DA. When the paper pa is transported to the main transport path 41 through the sub transport path SP3, the paper pa entering the main transport path 41 from the sub transport path SP3 is guided to the detection area DA.

  The paper pa entering the main transport path 41 from the sub transport path SP1, the paper pa entering the main transport path 41 from the sub transport path SP2, and the paper pa entering the main transport path 41 from the sub transport path SP3 are detected. The position and orientation in the area DA may be different.

  The detection accuracy of the detection device 59 depends on the position and orientation of the paper that moves in the detection area DA. The position and orientation of the sheet moving in the detection area DA are determined by the relative position of the sheet with respect to the detection area DA. The distance between the paper pa moving in the detection area DA and the light projecting unit 59a is referred to as the paper position in the detection area DA. The angle formed by the normal line of the paper pa passing through the detection area DA and the direction in which the detection area DA extends is referred to as the posture of the paper in the detection area DA.

  The detection device 59 has the highest detection accuracy when the sheet moves in a target posture within the detection area DA. The target position TP is an ideal position where the paper pa moving on the main transport path 41 should pass in the detection area DA in order to detect the basis weight of the paper. The target position TP is a reference point. Here, the target position TP is set at a position that is a predetermined distance d1 away from the light projecting unit 59a along the optical axis of the light projecting unit 59a in the detection area DA. The target posture is an ideal posture in which the paper pa moving on the main transport path 41 is to be maintained in the detection area DA in order to detect the basis weight of the paper pa. Here, the target posture is set such that the angle formed by the normal line of the paper pa and the direction in which the detection area DA extends is 0 ° or almost 0 °.

  Detection device 59 further includes a position changing mechanism 59c. The position changing mechanism 59c moves the detection area DA relative to the main transport path 41. Specifically, the position changing mechanism 59c moves the light projecting unit 59a or the light receiving unit 59b relative to the main transport path 41 in a state where the relative position between the light projecting unit 59a and the light receiving unit 59b is fixed. Have a mechanism for. The position changing mechanism 59c moves the detection area DA in parallel to the conveyance direction of the paper pa with respect to the main conveyance path 41. In addition, the position changing mechanism 59c moves the detection area DA with respect to the main transport path 41 in the direction in which the detection area DA extends with respect to the main transport path 41. The direction in which the detection area DA extends is a direction that intersects the transport direction. Thus, since the position changing mechanism 59c moves the detection area DA relative to the main transport path 41, the target position TP can be aligned with the paper that moves in the detection area DA. Further, the position changing mechanism 59c rotates the detection area DA around the target position. The rotation surface of the detection area DA is a surface including the direction in which the detection area DA extends and the conveyance direction of the paper pa. As a result, it is possible to cause the sheet moving along the main transport path 41 to have the target posture in the detection area DA.

  In the detection device 59, a relative position determined as a default among the relative positions of the detection area DA to the main transport path 41 is referred to as a default position. Hereinafter, it is assumed that the detection area DA is set to the default position in the detection device 59 unless otherwise specified.

  FIG. 9 is a diagram for explaining the parallel movement in the transport direction in the detection region. Referring to FIG. 9, without changing the relative position between the light projecting unit 59a and the light receiving unit 59b from the default position, the light projecting unit 59a and the light receiving unit 59b move in a direction KA parallel to the transport direction. The detection area moves. As a result, the target position TP moves in parallel with the transport direction.

  FIG. 10 is a diagram for explaining the parallel movement of the detection region in the extending direction of the detection region. Referring to FIG. 10, without changing the relative position between light projecting unit 59a and light receiving unit 59b from the default position, light projecting unit 59a and light receiving unit 59b are connected to the center of light projecting unit 59a and the center of light receiving unit 59b. The detection area moves by moving in a direction KB parallel to the straight line connecting the two. As a result, the target position TP moves parallel to the direction in which the detection area DA extends.

  FIG. 11 is a diagram for explaining the rotational movement in the detection region. Referring to FIG. 11, without changing the relative position between light projecting unit 59a and light receiving unit 59b from the default position, light projecting unit 59a and light receiving unit 59b rotate around target position TP, thereby detecting region. DA moves. The rotation surface of the detection area DA is a surface including the direction in which the detection area DA extends and the conveyance direction of the paper pa. Thereby, the angle at which the direction in which the detection area DA extends intersects the transport direction is changed.

  FIG. 12 is a side view showing a state when the paper pa enters the main transport path 41 from the upper paper feed tray 151 through the sub transport path SP1. Referring to FIG. 12, when the paper pa is transported to the main transport path 41 through the sub transport path SP1, the paper pa is in contact with the path forming member B1 as shown by a thick solid arrow in FIG. It enters the main transport path 41 from the transport path SP1 and is guided to the detection area DA. Since the straight path passing through the sub transport path SP1 and the main transport path 41 cannot be secured, the shape of the path forming member B1 is set so that the paper pa is guided to the target position TP of the detection area DA in the target posture. Have difficulty. For this reason, the shape of the path forming member B1 is set to a first shape in which the paper pa is in a position as close as possible to the target position TP in the detection area DA and as close as possible to the target position. In this case, the paper pa moves in the detection area DA at a position that is closer to the light projecting unit 59a than the target position TP in a posture that is a positive angle than the target posture.

  On the other hand, the sheet moving along the sub-transport path SP1 is conveyed while being nipped by the sheet feeding roller 151r, and the downstream end of the sheet becomes a free end, but the position when the sheet pa moves in the detection area DA. And the posture should be within a predetermined range. Therefore, the position and orientation of the paper pa relative to the main transport path 41 when the paper pa enters the main transport path 41 through the sub transport path SP1 and moves in the detection area DA are determined by experiment or simulation. It can obtain | require as a position and a 1st attitude | position.

  FIG. 13 is a side view showing a state when the paper pa enters the main transport path 41 from the manual feed tray 154 through the sub transport path SP2. Referring to FIG. 13, when the paper pa is transported to the main transport path 41 through the sub transport path SP2, the paper pa is in contact with the path forming member B2 as shown by a thick solid line arrow in FIG. It enters the main transport path 41 from the transport path SP2 and is guided to the detection area DA. Since a straight path passing through the sub transport path SP2 and the main transport path 41 cannot be secured, the shape of the path forming member B2 is set so that the paper pa is guided to the target position TP of the detection area DA in a target posture. It is difficult. For this reason, the shape of the path forming member B2 is set to a second shape in which the paper pa is in a position as close as possible to the target position TP in the detection area DA as close as possible to the target position TP. In this case, the paper pa moves in the detection area DA at a position opposite to the light projecting unit 59a with respect to the target position TP in a posture that is a negative angle with respect to the target posture.

  On the other hand, the sheet moving along the sub-transport path SP2 is conveyed while being nipped by the sheet feeding roller 154r, and the downstream end of the sheet becomes a free end, but the position when the sheet pa moves in the detection area DA. And the posture should be within a predetermined range. Therefore, the position and orientation of the paper pa relative to the main transport path 41 when the paper pa enters the main transport path 41 through the sub transport path SP2 and moves in the detection area DA by experiment or simulation are determined. 2 position and the second posture.

  FIG. 14 is a side view showing a state when the sheet pa enters the main transport path 41 from the middle and lower sheet feed trays 152 and 153 through the sub transport path SP3. Referring to FIG. 14, as indicated by a thick solid arrow in FIG. 14, the paper pa enters the main transport path 41 from the sub transport path SP3 and is guided to the detection area DA. As shown in FIG. 14, a straight path passing through the sub transport path SP3 and the main transport path 41 can be selected. The shapes of the path forming member B1 and the path forming member B2 are set so that the paper pa is guided to the target position TP of the detection area DA in a target posture. For this reason, the sheet moving in the sub-conveying path SP3 is conveyed while being nipped by the sheet feeding roller 152r or the sheet feeding roller 153r, and the downstream end of the sheet becomes a free end, but the sheet pa is detected in the detection area DA. The probability of being guided to the target position TP in the target posture becomes high. Therefore, when the paper pa enters the main transport path 41 through the sub transport path SP3, the paper pa moves in the target posture at the target position TP set as the default position in the detection area DA.

  FIG. 15 is a diagram illustrating an example of functions of the CPU of the MFP according to the present embodiment. The functions illustrated in FIG. 15 are functions formed in the CPU 111 when the CPU 111 provided in the MFP 100 executes a recording medium determination program stored in the ROM 113, the HDD 115, or the CD-ROM 118A.

  Referring to FIG. 15, the CPU 111 includes a print data generation unit 61, an image formation control unit 63, a sensor control unit 65, a medium information determination unit 67, a path selection unit 71, a position control unit 81, including.

  The print data generation unit 61 executes a print job and generates print data used by the image forming unit 140 to form an image. For example, when the communication I / F unit 112 receives a print job from an external computer, the print data generation unit 61 executes the print job. The print job is described in, for example, PJL (Printer Job Language) or PCL (Printer Control Language), and includes print conditions and data to be subjected to image formation. Further, when the user operates the operation unit 163, the print data generation unit 61 generates print data based on data designated by the user. The data designated by the user includes image data that the document reading unit 130 reads and outputs a document, data stored in the HDD 115, and data stored in an external computer.

  The print data is, for example, bitmap format data. The printing data corresponds to the size of the paper that is the object of image formation, and defines an image to be formed on the paper with a plurality of pixel values. The print data includes four data corresponding to each of yellow, magenta, cyan, and black. Therefore, when the printing data is composed of a plurality of pages, the printing data includes four data corresponding to each of yellow, magenta, cyan, and black. The print data generation unit 61 outputs the print data to the image formation control unit 63.

  The path selection unit 71 selects one of the three sub-transport paths SP1, SP2, SP3 along which the sheet is transported. First, the path selection unit 71 selects a tray defined by print conditions from the three paper feed trays 151, 152, 153 and the manual feed tray 154. When the print job is received from the outside, the print condition is determined by the print job. The print conditions are determined by an operation input by the user when the user operates the operation panel 160. Here, the tray selected by the path selection unit 71 from the plurality of paper feed trays 151, 152, 153 and the manual feed tray 154 is the target tray. The route selection unit 71 gives tray information indicating the target tray to the medium information determination unit 67.

  When the document reading unit 130 reads the document, the path selection unit 71 detects the size of the document, and selects a paper having the same size as the document size from the three paper feed trays 151, 152, 153 and the manual feed tray 154. The tray to be stored may be selected as the target tray. When one of the three paper feed trays 151, 152, 153 and the manual feed tray 154 is determined by default, the path selection unit 71 sets the three paper feed trays 151, 152, 153 and the manual feed tray 154. Of these, a tray determined by default may be selected as the target tray.

  The route selection unit 71 selects a sub transport route corresponding to the target tray from the sub transport routes SP1, SP2, and SP3. Specifically, when the target tray is the paper feed tray 151, the sub transport path SP1 is selected, and when the target tray is the paper feed tray 152 or the paper feed tray 153, the sub transport path SP3 is selected, and the target tray is manually fed. In the case of the tray 154, the sub-transport path SP2 is selected. The route selection unit 71 gives information indicating the sub-transport route selected from the sub-transport routes SP1, SP2, and SP3 to the medium information determination unit 67.

  The image forming control unit 63 supplies paper to the image forming unit 140 from the target tray indicated by the tray information given from the path selecting unit 71 among the three paper feeding trays 151, 152, 153 and the manual feed tray 154. Control the paper roller. For example, the image formation control unit 63 rotates the paper feed roller 151r when tray information indicating the paper feed tray 151 is given. The image formation control unit 63 rotates the paper feed roller 152r when tray information indicating the paper feed tray 152 is given. By this control, the paper is transported from one of the paper feed trays 151, 152, 153 and the manual feed tray 154 to the main transport path 41.

  The sensor control unit 65 acquires the output signal of the light receiving unit 59b of the detection device 59 when the paper supplied from the paper supply unit 150 to the main transport path 41 moves in the detection area of the detection device 59, and the acquired output. The signal is output to the medium information determination unit 67.

  The position control unit 81 receives information indicating the sub-transport path on which the sheet moves from the sub-transport paths SP1, SP2, SP3 from the path selection unit 71, controls the detection device 59, and moves the detection area DA. MFP 100 stores a plurality of types of position control information in advance. A plurality of types of position control information are defined for each of the sub-transport routes SP1, SP2, SP3. Here, the first position control information is associated with the sub transport path SP1, the second position control information is associated with the sub transport path SP2, and the third position control information is associated with the sub transport path SP3. Are associated. The position control unit 81 selects position control information corresponding to the sub transport path along which the sheet moves from the sub transport paths SP1, SP2, and SP3 from among a plurality of types of position control information. Specifically, the position control unit 81 selects the first position control information when the sheet moves along the sub transport path SP1, and the second position control information when the sheet moves along the sub transport path SP2. The third position control information is selected when the sheet moves along the sub transport path SP3. The position control unit 81 controls the detection device 59 to move the detection area DA to a position determined by position control information selected from a plurality of types of position control information.

  As shown in FIG. 12, since the path forming member B1 is set in the first shape, the sheet pa entering the main transport path 41 through the sub transport path SP1 has a first position opposite to the main transport path 41. Move in the first posture. For this reason, by performing an experiment or simulation, the paper pa existing in the first position in the first position relative to the main transport path 41 is detected so as to be positioned in the target position in the target position of the detection area DA. The position of the area DA is obtained, and the obtained position of the detection area DA is set as first position control information.

  As shown in FIG. 13, since the path forming member B2 is set to the second shape, the sheet pa entering the main transport path 41 through the sub transport path SP1 has a second position opposite to the main transport path 41. Move in the second position. For this reason, by performing experiments or simulations, the sheet pa existing in the second position in the second position relative to the main transport path 41 is positioned in the target position in the target position of the detection area DA. The position of the detection area DA is obtained, and the obtained position of the detection area DA is set as second position control information.

  As shown in FIG. 14, when the paper pa enters the main transport path 41 through the sub transport path SP3 and moves in the detection area DA, the paper pa has the target position TP set at the default position in the target posture. Moving. For this reason, the third position control information may be set to the default position.

  Returning to FIG. 15, the medium information determination unit 67 determines the medium information associated with the output signal input from the sensor control unit 65 based on the conversion information. MFP 100 predefines conversion information. The conversion information is information that defines the relationship between the transmitted light amount indicated by the output signal of the detection device 59 and the basis weight of the paper, and is a table or a conversion formula. The medium information determination unit 67 outputs the determined medium information to the image formation control unit 63.

  Based on the printing data and the medium information, the image forming control unit 63 sets the transfer roller 47 to a potential suitable for transferring the toner image formed on the intermediate transfer belt 57 to the paper on which the image is to be formed. The image forming unit 140 is controlled to be charged. Further, the image formation control unit 63 adjusts the temperature of the fixing roller 49 based on the medium information so that the toner is fixed at a temperature suitable for the paper on which the image is to be formed. The image formation control unit 63 also includes a paper feed roller of the paper feed unit 150 corresponding to the target tray so that the paper is transported at a transport speed suitable for the paper on which image formation is performed based on the medium information. The operations of the timing roller 45, the transfer roller 47, the fixing roller 49, and the paper discharge roller 15 may be controlled.

  FIG. 16 is a flowchart illustrating an example of the flow of the recording medium determination process. The recording medium determination process is a process executed by CPU 111 when CPU 111 provided in MFP 100 executes a recording medium determination program stored in ROM 113, HDD 115, or CD-ROM 118A. Referring to FIG. 16, CPU 111 provided in MFP 100 determines whether an image formation instruction has been accepted. When the operation unit 163 is an operation input by the user and accepts an operation for instructing image formation, an image formation instruction is accepted. When the communication I / F unit 112 receives a print job from an external PC, it accepts an image formation instruction. Further, when the facsimile unit 116 receives facsimile data, it accepts an image formation instruction. The process waits until an image formation instruction is accepted (NO in step S11). If an image formation instruction is accepted (YES in step S11), the process proceeds to step S12.

  In step S12, the target tray is determined, and the process proceeds to step S13. Of the three paper feed trays 151, 152, 153 and the manual feed tray 154, the tray determined by the print conditions is selected as the target tray. When the print job is received from the outside, the print condition is determined by the print job. The print conditions are determined by an operation input by the user when the user operates the operation panel 160. The print conditions are determined by default when receiving facsimile data.

  In step S13, a sub-transport route is determined, and the process proceeds to step S14. A sub-transport path determined for the target tray determined in step S12 is determined from among the three sub-transport paths SP1, SP2, SP3. Specifically, when the target tray is the paper feed tray 151, the sub transport path SP1 is selected, and when the target tray is the paper feed tray 152 or the paper feed tray 153, the sub transport path SP3 is selected, and the target tray is manually fed. In the case of the tray 154, the sub-transport path SP2 is selected.

  In step S14, position control information corresponding to the determined sub-transport route is selected, and the process proceeds to step S15. Specifically, when the sub transport path SP1 is selected, the first position control information is selected, and when the sub transport path SP2 is selected, the second position control information is selected, and the sub transport path is selected. When SP3 is selected, the third position control information is selected.

  In step S15, the detection device 59 is controlled to move the detection area DA to the position determined by the position control information selected in step S14, and the process proceeds to step S16.

  In step S16, paper feeding is started and the process proceeds to step S17. From among the three paper feed trays 151, 152, 153 and the manual feed tray 154, the supply of the paper stored in the tray determined as the target tray in step S12 is started.

  In step S17, the amount of transmitted light is detected. The detection device 59 is controlled to irradiate the light projecting unit 59a with light, and the amount of transmitted light is determined based on the output signal output from the light receiving unit 59b. Then, medium information is determined (step S18), and the process proceeds to step S19. Using the predetermined conversion information, the basis weight corresponding to the transmitted light amount detected in step S17 is determined as the medium information.

  In step S19, a control variable is determined, and the process proceeds to step S20. The control variable is a setting value that is set to control the image forming unit 140 and is a value that varies depending on the basis weight. Control variables are predetermined for each of the plurality of basis weights, and a control variable corresponding to the basis weight determined in step S18 is determined. Here, the control variable includes a set value for determining the charge amount of the transfer roller 47 and a set value for determining the temperature of the fixing roller 49.

  In the next step S20, the image forming unit 140 is controlled according to the control variable determined in step S19, and image formation is started. Thereby, the transfer roller 47 is charged to a value suitable for the basis weight, and the fixing roller 49 is set to a temperature suitable for the basis weight, so that the quality of the image formed on the paper can be improved.

  In the next step S21, it is determined whether or not the image formation is completed. The process waits until image formation ends (NO in step S21). If image formation ends (YES in step S21), the process ends.

<First Modification>
In the first modification, a plurality of position control information is set for each of the three sub-transport routes SP1, SP2, SP3.

  FIG. 17 is a diagram illustrating an example of functions of the CPU of the MFP according to the first modification. The function shown in FIG. 17 is different from the function shown in FIG. 15 in that a size selection unit 73, a paper grain selection unit 75, and a humidity acquisition unit 77 are added, and a position control unit 81 is a position control unit. The point is changed to 81A. Other functions are the same as the functions shown in FIG. 15, and thus description thereof will not be repeated here.

  With reference to FIG. 17, the size selection unit 73 selects the size of the paper stored in the target tray, and outputs the selected size to the medium information determination unit 67. The size of the paper here is the length of the paper in the direction orthogonal to the transport direction. Each of the three paper feed trays 151, 152, 153 and the manual feed tray 154 has a size of the paper to be stored and a direction of the paper to be conveyed. A3 size paper is stored in the target tray in the vertical direction with its longitudinal direction parallel to the transport direction, and A4 size paper is stored in the target tray in the horizontal direction whose longitudinal direction is perpendicular to the transport direction. The size when stored in the direction is the same.

  The paper selection unit 75 selects the direction of the paper with respect to the conveyance direction of the paper stored in the target tray, and outputs the direction of the paper with respect to the selected conveyance direction to the medium information determination unit 67. The paper has a grain in the vertical direction or the horizontal direction. The paper grain is also referred to as a streak and is the direction of fibers constituting the paper. The paper grain is determined by the paper. For example, the line of the A4 sheet may be in the vertical direction parallel to the longitudinal direction, and the line of the A3 sheet may be in the horizontal direction perpendicular to the longitudinal direction. The paper selection unit 75 determines the line of the paper from the size and direction of the paper stored in the target tray, and selects the direction of the line with respect to the transport direction. The direction of the lines with respect to the transport direction includes a vertical direction perpendicular to the transport direction and a parallel direction parallel to the transport direction.

  Humidity acquisition unit 77 controls the humidity sensor provided in the main body case of MFP 100, acquires the humidity in the main body case of MFP 100, and outputs the acquired humidity to medium information determination unit 67. Paper has a different stiffness at different humidity levels. For this reason, if the humidity in a main body case is uniform, a humidity sensor will be set in the arbitrary places of a main body case. If the humidity in the main body case is not uniform, the humidity sensor is preferably disposed in the vicinity of each of the paper feed trays 151, 152, 153 and the manual feed tray 154.

  The position control unit 81A receives information indicating the sub-transport path in which the paper moves among the sub-transport paths SP1, SP2, and SP3 from the path selection unit 71, receives the paper size from the size selection unit 73, and selects the sheet size. The direction of the paper grain with respect to the conveyance direction is input from the unit 75, and the humidity is input from the humidity acquisition unit 77.

  Each of the first position control information, the second position control information, and the third position control information includes a plurality of position control information for each paper size, each paper direction, and each humidity. For example, a plurality of position control information included in the first position control information will be described. By performing experiments or simulations, the position and orientation relative to the main transport path 41 are determined as the first position and the second position for each sheet size, each sheet direction, and each humidity. Then, by performing an experiment or simulation for each paper size, each paper direction, and each humidity, the paper pa existing in the first position in the first position relative to the main transport path 41 is The position of the detection area DA is obtained so as to be positioned in the target posture at the target position of the detection area DA, and the obtained position of the detection area DA is set as position control information. In this way, position control information for each paper size, each paper direction, and each humidity is determined for the sub-transport path SP1. Accordingly, since position control information for each paper size, each paper direction, and each humidity is determined for the sub-transport path SP1, when the paper moves along the sub-transport path SP1, the paper size and the paper are determined. If the eye direction and the humidity are determined, one position control information is determined.

  The position control unit 81A selects position control information corresponding to the sub-transport path on which the sheet moves from the sub-transport paths SP1, SP2, and SP3 from among a plurality of types of position control information. Specifically, the position control unit 81A selects the first position control information when the sheet moves along the sub transport path SP1, and the second position control information when the sheet moves along the sub transport path SP2. The third position control information is selected when the sheet moves along the sub transport path SP3. Here, a case where the first position control information is selected will be described as an example.

  Further, the position control unit 81A is input from the paper size selection unit 75 and the paper size input from the size selection unit 73 among the plurality of position control information included in the selected first position control information. Position control information corresponding to the direction of the paper and the humidity input from the humidity acquisition unit 77 is selected.

  Each of the first position control information, the second position control information, and the third position control information includes a plurality of position control information for each paper size, each paper direction, and each humidity. However, a plurality of position control information may be included with respect to at least one combination of the paper size, the paper grain direction, and the humidity. Specifically, each of the first position control information, the second position control information, and the third position control information may include a plurality of position control information for each paper size, or for each humidity of each paper direction. A plurality of position control information may be included, or a plurality of position control information may be included for each humidity. Each of the first position control information, the second position control information, and the third position control information may include a plurality of position control information for each sheet size and each sheet direction, or for each sheet size. In addition, a plurality of position control information may be included for each humidity and a plurality of position control information may be included for each direction of paper and for each humidity.

<Second Modification>
In MFP 100 according to the present embodiment, a transmissive optical sensor is used as an example of detection device 59, but a reflective optical sensor may be used instead of detection device 59. A transmission type optical sensor detects the light transmittance, whereas a reflection type optical sensor detects the light reflectance. For this reason, the first to third position control information can be applied to the MFP 100 described above by corresponding to the reflective optical sensor.

  FIG. 18 is a side view showing the configuration of the main transport path and the plurality of sub transport paths in the second modification. Referring to FIG. 18, the difference from FIG. 8 is that the detection device 59 is changed to a detection device 91. Since other members are the same as those shown in FIG. 8, the description thereof will not be repeated here. The detection device 91 is a reflective optical sensor, includes a light projecting unit 91a and a light receiving unit 91b, and is located between the lower end 30 of the main transport path 41 and the timing roller 45, and the light projecting unit 91a and the light receiving unit. 91b is arranged on one surface of the main transport path 41 side by side in the direction crossing the transport direction. In other words, the light projecting unit 91a and the light receiving unit 91b are arranged side by side in a direction crossing the transport direction in a direction in which one surface of the sheet moving along the main transport path 41 is directed. Since the light projecting unit 91a and the light receiving unit 91b are disposed at a predetermined distance in the direction intersecting the transport direction, the light projecting unit 91a and the light receiving unit 91b are disposed at a predetermined distance parallel to the transport direction. Compared with the case where it does, the influence of the flutter of the paper which moves the main conveyance path | route 41 can be reduced.

  The light projecting unit 91a includes a light emitting element such as a light emitting diode, a drive circuit for the light emitting element, and an optical system, and emits light along the optical axis. The light receiving unit 91b includes a light receiving element such as a photodiode, and outputs a signal corresponding to the amount of light received by the light receiving element.

  FIG. 19 is a front view of the detection device of FIG. 18 as viewed in the direction of the arrow K. Referring to FIG. 19, a light projecting unit 91a and a light receiving unit 91b are arranged at a predetermined distance in a direction crossing the transport direction. In the main conveyance path 41, a space from the center of the emission surface that emits light of the light projecting unit 91a to the center of the light receiving surface that receives light of the light receiving unit 91b is the detection area DA. The light emitted from the light projecting unit 91a is reflected by the sheet moving along the main transport path 41 and received by the light receiving unit 91b. The target position TP is determined in advance as the paper position where the detection accuracy of the detection device 91 is most preferable. Here, the target position TP is determined with reference to the center of the exit surface from which the light projecting unit 91a emits light, and is only a distance d2 from the center of the exit surface in the optical axis direction of the light emitted from the light projecting unit 91a. It is in a remote position.

  The detection accuracy of the detection device 91 depends on the position and orientation of the paper that moves in the detection area DA. The position and orientation of the sheet moving in the detection area DA are determined by the relative position of the sheet with respect to the detection area DA. The distance between the point where the optical axis of the light projecting unit 91a intersects the paper pa moving in the detection area DA and the light projecting unit 91a is referred to as the paper position in the detection area DA. The angle at which the normal line of the paper pa passing through the detection area DA and the optical axis of the light projecting portion 91a intersect is called the paper posture.

  The detection device 91 has the highest detection accuracy when the sheet moves in a target posture at the target position TP in the detection area DA. The target posture is an ideal posture in which the paper pa moving on the main transport path 41 is to be maintained in the detection area DA in order to detect the basis weight of the paper pa. Here, a predetermined angle is determined as an angle formed between the normal of the paper pa and the optical axis of the light projecting unit 91a.

  Detection device 91 further includes a position changing mechanism 91c. The position changing mechanism 91c moves the detection area DA relative to the main transport path 41. Specifically, the position changing mechanism 91c moves the light projecting unit 91a or the light receiving unit 91b relative to the main transport path 41 in a state where the relative position between the light projecting unit 91a and the light receiving unit 91b is fixed. Have a mechanism for. The position changing mechanism 91c moves the detection area DA in parallel to the conveyance direction of the paper pa with respect to the main conveyance path 41. Further, the position changing mechanism 91c moves the detection area DA in a direction in which the light projecting unit 91a and the light receiving unit 91b are directed toward the main transport path. The direction in which the light projecting unit 91a and the light receiving unit 91b are directed to the main transport path is a direction that intersects the transport direction. Thus, since the position changing mechanism 91c moves the detection area DA relative to the main transport path 41, the target position TP can be aligned with the paper that moves in the detection area DA. Further, the position changing mechanism 91c rotates the detection area DA around the target position TP. The rotation surface of the detection area DA is a surface including a straight line parallel to the transport direction passing through the target position TP. As a result, it is possible to cause the sheet moving along the main transport path 41 to have the target posture in the detection area DA.

  In the detection device 91, a relative position determined as a default among the relative positions of the detection area DA to the main transport path 41 is referred to as a default position. Hereinafter, it is assumed that the detection area DA is set to the default position in the detection device 91 unless otherwise specified.

  FIG. 20 is a diagram for explaining the parallel movement in the transport direction in the detection region in the second modified example. Referring to FIG. 20, without changing the relative position between the light projecting unit 91a and the light receiving unit 91b from the default position, the light projecting unit 91a and the light receiving unit 91b move in the direction KA parallel to the transport direction. The detection area moves. As a result, the target position TP moves in parallel with the transport direction.

  FIG. 21 is a diagram for explaining the parallel movement in the direction toward the main transport path in the detection region in the second modified example. Referring to FIG. 21, without changing the relative position between the light projecting unit 91a and the light receiving unit 91b from the default position, the light projecting unit 91a and the light receiving unit 91b move in the direction KB toward the main transport path, The detection area moves. As a result, the target position TP moves in parallel with the direction in which the light projecting unit 91a and the light receiving unit 91b are directed to the main transport path. As a result, the target position TP moves in parallel with the direction in which the light projecting unit 91a and the light receiving unit 91b are directed to the main transport path.

  FIG. 22 is a diagram for explaining the rotational movement in the detection region in the second modification. Referring to FIG. 22, the detection region is detected by rotating light projecting unit 91 a and light receiving unit 91 b around target position TP without changing the relative positions of light projecting unit 91 a and light receiving unit 91 b from the default position. Move. The rotation surface of the detection area DA is a surface including a straight line parallel to the transport direction passing through the target position TP. Thereby, the angle at which the optical axis of the light emitted from the light projecting unit 91a intersects the normal line of the paper can be set to a predetermined angle.

  CPU 111 provided in MFP 100 in the second modification has the same function as CPU 111 provided in MFP 100 in the first embodiment illustrated in FIG. However, the position control information is different. MFP 100 according to the second modification stores a plurality of types of position control information corresponding to detection device 91 in advance. A plurality of types of position control information are defined for each of the sub-transport routes SP1, SP2, SP3. Here, the first position control information is associated with the sub transport path SP1, the second position control information is associated with the sub transport path SP2, and the third position control information is associated with the sub transport path SP3. Are associated.

  The first position control information for the detection device 91 includes the first position and the first position relative to the main transport path 41 of the paper pa that moves on the main transport path 41 through the sub transport path SP1 through experiments or simulations. 1 is obtained, the position of the detection area DA is obtained so that the sheet pa existing in the first position at the first position is located at the target position of the detection area DA, and the obtained detection is performed. The position of the area DA is set as the first position control information.

  Similarly, the second position control information for the detection device 91 is obtained by performing experiment or simulation or the like on the second position relative to the main transport path 41 of the paper pa that moves on the main transport path 41 through the sub transport path SP2. The position and the second attitude are obtained, and the position of the detection area DA is obtained and obtained such that the sheet pa existing in the second position in the second attitude is positioned at the target position of the detection area DA in the target attitude. The position of the detected area DA is set as second position control information.

  Similarly, the third position control information for the detection device 91 is obtained by performing third experiments or simulations, so that the third position control information relative to the main transport path 41 of the paper pa moving on the main transport path 41 through the sub transport path SP3. The position and the third posture are obtained, and the position of the detection area DA is obtained and obtained so that the paper pa existing in the third position in the third posture is positioned at the target position of the detection area DA in the target posture. The position of the detected area DA is set as second position control information.

<Third Modification>
As an example of the detection apparatus, the case where an optical sensor is used has been described as an example. However, an ultrasonic sensor that detects ultrasonic waves as a medium may be used. In this case, the first to third position control information can be applied to the MFP 100 described above by corresponding to the ultrasonic sensor.

<Fourth Modification>
The MFP 100 according to the fourth modified example includes a distance measuring sensor that measures a distance between the light projecting unit 59a and the paper pa, and an optical axis of the light projecting unit 59a upstream of the detection device 59 in the transport direction of the paper pa. A sensor for measuring the angle between the sheet and the normal and a sensor are arranged. The MFP 100 according to the fourth modification stores position control information for each distance and angle from the light projecting unit 59a, and changes the detection area DA using the position control information corresponding to the distance measured by the distance measuring sensor. To do.

<Second Embodiment>
The MFP 100 in the first embodiment changes the position of the detection device 59, but the MFP 100 in the second embodiment changes the detection device 59 to the detection device 93. In the following, MFP 100 according to the second embodiment will be described mainly with respect to differences from MFP 100 according to the first embodiment.

  FIG. 23 is a side view showing the configuration of the main transport path and the plurality of sub transport paths in the second embodiment. Referring to FIG. 23, the difference from the side view shown in FIG. 8 is that detection device 93 is added instead of detection device 59. The detection device 93 includes a plurality of light projecting units 95a, 95b, and 95c, and a light receiving unit 97.

  FIG. 24 is an enlarged view of the detection device of FIG. The light projecting units 95a, 95b, and 95c and the light receiving unit 97 are disposed to face each other across the main transport path 41. Light emitted from each of the light projecting units 95a, 95b, and 95c travels across the main transport path 41 and is received by the light receiving unit 97. A detection area DA1 is formed in the main transport path 41 between the light projecting part 95a and the light receiving part 97, and a detection area DA2 is formed in the main transport path 41 between the light projecting part 95b and the light receiving part 97, A detection area DA3 is formed in the main transport path 41 between the light projecting unit 95c and the light receiving unit 97. Each of the detection areas DA1, DA2, and DA3 intersects with the paper pa in the traveling direction and extends in a direction intersecting with the paper pa moving on the main transport path 41. The direction in which the detection area DA1 extends is parallel to the line connecting the center of the light projecting unit 95a and the center of the light receiving unit 97, and the direction in which the detection area DA2 extends is the center of the light projecting unit 95b and the center of the light receiving unit 97. The direction in which the detection area DA3 extends is parallel to the line connecting the center of the light projecting unit 95c and the center of the light receiving unit 97. The detection accuracy of the detection device 91 depends on the position and orientation of the paper that moves in the detection areas DA1, DA2, and DA3.

  The position and orientation of the sheet moving in the detection areas DA1, DA2, and DA3 are determined by the relative positions of the sheets with respect to the detection areas DA1, DA2, and DA3. In the detection area DA1, the length in the optical axis direction of the light projecting portion 95a up to the paper pa is referred to as the paper position in the detection area DA1, and the length in the optical axis direction up to the paper pa in the detection area DA2 is the paper in the detection area DA2. The length in the optical axis direction of the light projecting portion 95c up to the paper pa in the detection area DA3 is referred to as the paper position in the detection area DA3. The angle formed between the normal line of the paper pa and the direction in which the detection area DA1 extends in the detection area DA1 is referred to as the paper posture in the detection area DA1, and the normal line of the paper pa and the direction in which the detection area DA2 extends in the detection area DA2. The angle is referred to as the sheet orientation in the detection area DA2, and the angle formed by the normal line of the sheet pa and the direction in which the detection area DA3 extends in the detection area DA3 is referred to as the sheet orientation in the detection area DA3.

  In the detection device 93, target positions TP1, TP2, and TP3 are determined for the detection areas DA1, DA2, and DA3, respectively. The target position TP1 is an ideal position where the paper pa moving on the main transport path 41 in order to detect the paper basis weight should pass through the detection area DA1, and the target position TP2 detects the paper basis weight. Therefore, the sheet pa that moves along the main conveyance path 41 is an ideal position that should pass through the detection area DA2, and the target position TP3 is the sheet pa that moves along the main conveyance path 41 in order to detect the basis weight of the sheet. This is an ideal position to pass through in the detection area DA3. The target posture is an ideal posture in which the paper pa moving on the main transport path 41 in order to detect the basis weight of the paper pa should be maintained in each of the detection areas DA1, DA2, and DA3. Here, the target posture in the detection area DA1 is 0 ° or almost 0 ° between the normal line of the paper pa and the direction in which the detection area DA1 extends, and the target posture in the detection area DA2 is the normal line of the paper pa. And the direction in which the detection area DA2 extends is 0 ° or substantially 0 °, and the target posture in the detection area DA3 is 0 ° or substantially the angle between the normal of the paper pa and the direction in which the detection area DA3 extends. It is 0 °.

  In MFP 100 in the second embodiment, the light receiving unit 95a receives light so that the paper moving on the main transport path through the sub transport path SP3 moves at the target position TP1 of the detection area DA1 in the target posture of the detection area DA1. A relative position with respect to the portion 97 is determined. For this reason, the sub transport path SP3 corresponds to the light projecting unit 95a. Further, in the MFP 100 according to the second embodiment, the light projecting unit 95c is configured so that the sheet moving along the main transport path through the sub transport path SP1 moves in the target position TP3 of the detection area DA3 with the target posture of the detection area DA3. Relative position to the light receiving portion 97 is determined. For this reason, the sub-transport path SP1 corresponds to the light projecting unit 95c. Further, in MFP 100 according to the second embodiment, light projecting unit 95b is arranged so that the sheet moving on the main transport path through sub transport path SP2 moves at target position TP2 in detection area DA2 with the target posture in detection area DA2. Relative position to the light receiving portion 97 is determined. For this reason, the sub-transport path SP2 corresponds to the light projecting unit 95c.

  FIG. 25 is a diagram illustrating an example of the functions of the CPU of the MFP according to the second embodiment. A difference from the function shown in FIG. 15 is that the position control unit 81 is changed to a switching control unit 99. The other functions are the same as those shown in FIG. 15, and therefore description thereof will not be repeated here.

  The switching control unit 99 receives information indicating the sub-transport route in which the sheet moves among the sub-transport routes SP1, SP2, and SP3 from the route selection unit 71, controls the detection device 93, and controls a plurality of light projecting units 95a and 95b. , 95c. MFP 100 stores switching control information in advance. The switching control information is information that associates each of the sub-transport routes SP1, SP2, and SP3 with one of the light projecting units 95a, 95b, and 95c. Here, the switching control information associates the sub transport path SP1 with the light projecting unit 95c, associates the sub transport path SP2 with the light projecting unit 95b, and associates the sub transport path SP3 with the light projecting unit 95a.

  The switching control unit 99 selects a light projecting unit corresponding to the sub transport path along which the sheet moves from the sub transport paths SP1, SP2, and SP3 from the light projecting sections 95a, 95b, and 95c. Specifically, the switching control unit 99 selects the light projecting unit 95c when the paper moves along the sub transport path SP1, and selects the light projecting unit 95b when the paper moves along the sub transport path SP2. When the sheet moves along the transport path SP3, the light projecting unit 95a is selected. The switching control unit 99 controls the detection device 93 to drive one selected from the plurality of light projecting units 95a, 95b, and 95c to emit light.

<Fifth Modification>
In the second embodiment, the detection device 93 includes a plurality of light projecting units 95a, 95b, and 95c and one light receiving unit 97. However, the light receiving unit 97 includes a plurality of light projecting units 95a, 95a, Any one of 95b and 95c may be used.

<Sixth Modification>
Similar to the first modification, by increasing the number of light projecting units 95a, 95b, and 95c, one of the plurality of light projecting units is associated with each of the plurality of sub-transport routes SP1, SP2, and SP3. It may be.

<Seventh Modification>
As in the second modification, a reflective optical sensor may be used instead of the detection device 93.

<Eighth Modification>
Similarly to the third modification, an ultrasonic sensor that detects ultrasonic waves as a medium may be used instead of the detection device 93.

<Ninth Modification>
Similarly to the fourth modification, one of the light projecting units 95a, 95b, and 95c, for example, the distance between the light projecting unit 95a and the paper pa, is upstream of the detection device 93 in the transport direction of the paper pa. A distance measuring sensor that measures the angle and a sensor that measures the angle between the optical axis of the light projecting unit 95a, the paper, and the normal may be arranged. The MFP 100 according to the ninth modification drives one selected from the plurality of light projecting units 95a, 95b, and 95c based on the distance and angle from the light projecting unit 59a to emit light.

  As described above, the MFP 100 according to the first embodiment functions as an image forming apparatus, and the main transport path 41, the light projecting unit 59a that emits light to the detection area DA in the main transport path 41, and the detection. The light receiving unit 59b that outputs a signal corresponding to the amount of light received by receiving light from the area DA, and the basis weight of the paper pa based on the signal output by the light receiving unit 59b while the paper pa is moving in the detection area DA. The amount is determined, and the detection area DA is changed so that the paper pa passing through the main transport path 41 moves the target position TP in the detection area DA. For this reason, the light from the detection area DA can be received by the light receiving unit 59b in a state where the paper pa is located at the target position TP. Therefore, the basis weight of the paper pa can be detected with high accuracy.

  Further, since the relative position of the detection area DA with respect to the main transport path 41 is changed, the target position TP can be matched with the position of the paper pa that moves on the main transport path 41.

  In addition, since the relative position of the detection area DA with respect to the main transport path 41 is changed in a state where the relative position between the light projecting section 59a and the light receiving section 59b is fixed, the relative position of the target position TP with respect to the detection area DA is changed. The relative position of the detection area DA with respect to the main transport path 41 can be changed.

  Further, since the detection area DA is moved in a direction parallel to the transport direction of the paper pa passing through the main transport path 41, the target position TP is moved at an arbitrary position on the main transport path 41, and the paper is moved along the main transport path 41. It can be adjusted to the position of pa.

  Further, since the detection area DA is moved in a direction intersecting with the paper pa moving on the main transport path 41, for example, a direction perpendicular to the main sheet, the target position TP can be adjusted to the position of the paper pa moving on the main transport path 41. .

  Further, since the detection area DA is changed so that the paper pa passing through the main transport path 41 moves the target position TP with respect to the detection area DA with a predetermined target attitude, the paper pa is set to the target position TP. The light from the detection area DA can be received by the light receiving portion 59b in the state of For this reason, the precision of the signal which the light-receiving part 59b outputs can be improved.

  For example, since the detection area DA is rotated around the target position TP, the target posture can be matched with the posture of the paper pa moving along the main transport path 41.

  In addition, the detection device 93 provided in the MFP 100 according to the second embodiment includes a plurality of light projecting units 95 a, 95 b, and 95 c that are arranged with their relative positions fixed to the main transport path 41, and the main transport path 41. And a light receiving unit 97 disposed with a fixed relative position, and the detection area DA is changed by selecting at least one of the plurality of light projecting units 95a, 95b, and 95c. For this reason, the detection area DA can be easily changed.

  In addition, the detection device 93 provided in the MFP 100 according to the fourth modification has a light projecting unit arranged with a relative position fixed to the main transport path 41 and a relative position fixed to the main transport path 41. A plurality of light receiving units arranged, and the detection area DA is changed by selecting at least one of the plurality of light receiving units. For this reason, the detection area DA can be easily changed.

  In addition, each of MFPs 100 in the first and second embodiments corresponds to a sub-transport path through which paper pa has passed among a plurality of sub-transport paths SP1, SP2, SP3 connected upstream of main transport path 41. Therefore, even if the position of the paper pa in the main transport path 41 differs by the plurality of sub transport paths SP1, SP2, SP3, the target position TP is set as the paper pa in the main transport path 41. Can be adjusted to the position of

  In addition, each MFP 100 in the first and second embodiments changes the detection area DA to a position corresponding to the humidity detected by the humidity sensor that detects the humidity, so that the strain of the paper pa changes depending on the humidity. Even when the amount changes, the target position TP can be matched with the position of the paper pa in the main transport path 41.

  In addition, each MFP 100 in the first and second embodiments selects the size of the paper pa and changes the detection area DA to a position corresponding to the selected size, so that the paper pa is different depending on the size of the paper pa. Even when the amount of deflection differs, the target position TP can be adjusted to the position of the paper pa in the main transport path 41.

  In addition, each of MFPs 100 in the first and second embodiments selects the direction of the paper pa of the paper pa and changes the detection area DA to a position corresponding to the selected paper eye direction. Even when the deflection amount of the recording medium changes due to the difference in the direction of the paper, the target position can be adjusted to the position of the recording medium in the main transport path.

<Appendix>
(1) further provided with a distance detection means provided upstream of the detection area in the transport direction in which the recording medium is transported, and detecting a distance between the recording medium and the recording medium;
The image forming apparatus according to claim 5, wherein the position control unit moves the detection area in a direction intersecting with a recording medium that moves along the main conveyance path based on the detected distance.
(2) The image forming apparatus according to any one of claims 1 to 7, wherein the ejection unit and the collection unit are disposed to face each other across the main conveyance path. According to this aspect, since the ejection unit and the collection unit are arranged to face each other across the main transport path, the inspection medium ejected from the ejection unit passes through the recording medium and is received by the collection unit. . Therefore, the medium type can be determined based on the amount of the inspection medium that has passed through the recording medium.
(3) The ejecting unit and the collecting unit are arranged side by side in a direction in which one surface of the recording medium passing through the main transport path faces and in a direction intersecting with the transport direction of the recording medium passing through the main transport path. The image forming apparatus according to claim 1. According to this aspect, since the emitting means and the collecting means are arranged in the direction in which one surface of the recording medium faces, the inspection medium emitted from the emitting means is reflected by the recording medium and is collected by the collecting means. Accepted. Therefore, the medium type can be determined based on the amount of the inspection medium reflected by the recording medium. In addition, since the ejection unit and the collection unit are arranged side by side in a direction intersecting with the conveyance direction, it is possible to make the ejection unit and the collection unit less susceptible to the change in the posture of the recording medium passing through the main conveyance path.
(4) The image forming apparatus according to (8), wherein the plurality of ejection units are arranged in parallel with a conveyance direction of the recording medium. If this aspect is followed, it can be made hard to receive the influence of the difference in the attitude | position of the recording medium which passes a main conveyance path | route.
(5) The image forming apparatus according to (9), wherein the plurality of collecting units are arranged in parallel with a conveyance direction of the recording medium. If this aspect is followed, it can be made hard to receive the influence of the difference in the attitude | position of the recording medium which passes a main conveyance path | route.
(6) The image forming apparatus according to claim 12, wherein the size of the recording medium is a length in a direction perpendicular to a conveying direction of the recording medium passing through the main conveying path.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 MFP, 59, 91, 93 Detection device, 59a, 91a, 95a, 95b, 95c Emitting unit, 59b, 91b, 97 Light receiving unit, 59c, 91c Position change mechanism, 61 Printing data generation unit, 63 Image formation control Unit, 65 sensor control unit, 67, 67A medium information determination unit, 71 path selection unit, 73 size selection unit, 75 grain selection unit, 77 humidity acquisition unit, 81, 81A position control unit, 99 switching control unit, 13 upper end 15, 15 paper discharge roller, 30 lower end, 41 main transport path, 45 timing roller, 47, 53Y transfer roller, 49 fixing roller, 51Y, 51M, 51C, 51K image forming unit, 55 drive roller, 55A roller, 57 intermediate Transfer belt, 101 side wall, 110 main circuit, 111 CPU, 112 communication in Interface (I / F) section, 113 ROM, 114 RAM, 115 HDD, 116 facsimile section, 118 external storage device, 118A CD-ROM, 120 automatic document feeder, 125 document tray, 127 document discharge tray, 130 document reading , 140 Image forming unit, 150 Paper feed unit, 151, 152, 153 Paper feed tray, 151r to 154r Paper feed roller, 152a, 153a Transport path, 154 Manual feed tray, 159 Paper discharge tray, 160 Operation panel, 161 Display unit , 163 operation unit, 165 touch panel, 167 hard key unit, B1, B2 path forming member, DA, DA1, DA2, DA3 detection area, SP1, SP2, SP3 sub-transport path, TP, TP1, TP2, TP3 target position, d1 , D2 distance, pa paper.

Claims (15)

The main transport path;
Injection means for injecting a medium for inspection to a detection region in the main transport path;
A collecting means for outputting a signal corresponding to the amount of the medium detected by detecting the inspection medium from the detection area;
Medium information determining means for determining medium information relating to the recording medium based on a signal output by the collecting means while the recording medium is moving in the detection area;
An image forming apparatus comprising: a position control unit that changes the detection area so that a recording medium passing through the main conveyance path moves to a predetermined target position in the detection area.   The image forming apparatus according to claim 1, wherein the position control unit changes a relative position of the detection area with respect to the main transport path.   3. The image formation according to claim 2, wherein the position control unit changes a relative position of the ejection unit or the collection unit with respect to the main transport path in a state where a relative position between the ejection unit and the collection unit is fixed. apparatus.   The image forming apparatus according to claim 3, wherein the position control unit moves the detection area in a direction parallel to a conveyance direction of a recording medium passing through the main conveyance path.   5. The image forming apparatus according to claim 3, wherein the position control unit moves the detection area in a direction intersecting with a recording medium moving along the main conveyance path.   The said position control means changes the said detection area so that the recording medium which passes the said main conveyance path | route will move the said target position with the predetermined target attitude | position with respect to the said detection area. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 6, wherein the position control unit rotates the detection area around the target position. The injection means has a plurality of relative positions fixed to the main transport path,
The collecting means is arranged with a relative position fixed to the main transport path,
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area by selecting at least one of the plurality of ejection units. The injection means is disposed with a relative position fixed to the main transport path,
A plurality of the collecting means are arranged with their relative positions fixed with respect to the main transport path,
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area by selecting at least one of the plurality of collection units. A plurality of sub-transport paths connected upstream of the main transport path;
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area to a position corresponding to a sub conveyance path through which the recording medium has passed among the plurality of sub conveyance paths. A humidity sensor for detecting humidity is further provided,
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area to a position corresponding to the detected humidity. Size selection means for selecting the size of the recording medium,
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area to a position corresponding to the selected size. A paper grain selecting means for selecting a paper grain direction with respect to the conveyance direction of the recording medium passing through the main conveyance path,
The image forming apparatus according to claim 1, wherein the position control unit changes the detection area to a position corresponding to a direction of the selected sheet. The main transport path;
Injection means for injecting a medium for inspection to a detection region in the main transport path;
A collection unit that outputs a signal corresponding to the amount of medium detected by detecting a medium for inspection from the detection area, and a recording medium determination method that is executed in an image forming apparatus comprising:
A medium information determining step for determining medium information on the recording medium based on a signal output by the collecting means while the recording medium is moving in the detection area;
A position control step of changing the detection area so that the recording medium passing through the main transport path moves to a predetermined target position in the detection area. The main transport path;
Injection means for injecting a medium for inspection to a detection region in the main transport path;
A recording medium determination program executed by a computer that controls an image forming apparatus, and a collection unit that outputs a signal according to the amount of the medium detected by detecting the inspection medium from the detection area There,
A medium information determining step for determining medium information on the recording medium based on a signal output by the collecting means while the recording medium is moving in the detection area;
A recording medium determination program for causing the computer to execute a position control step of changing the detection area so that the recording medium passing through the main conveyance path moves to a predetermined target position in the detection area.

Images