Conveying device and image forming system

Abstract

The present invention provides a transport device and an image forming system that prevent malfunctions in the image forming section caused by unsuitable recording materials, while also keeping the size of the device down. [Solution] A transport device comprising: a transport path for transporting recording material supplied from a recording material supply unit to an image forming unit; a double-feed detection unit for detecting double-feeding of the recording material supplied from the recording material supply unit; a media sensor for detecting characteristic information corresponding to the characteristics of the recording material; and a branch path provided branching off from the transport path at a branching point on the transport path, which purges the recording material for which the characteristic information has been detected by the media sensor without passing through the image forming unit, wherein the recording material for which double-feeding has been detected by the double-feed detection unit is purged via the branch path.

Description

Technical Field

[0001] The present invention relates to a conveying device and an image forming system.

Background Art

[0002] In image formation on a recording material such as paper, the recording material is supplied one by one to the image forming unit. If the recording materials overlap, that is, double feeding occurs, proper image formation becomes impossible. For this reason, for example, as disclosed in Patent Document 1, a technique for detecting double feeding of a recording material has been proposed.

[0003] In recent years, images have been formed on various types of recording materials. By adjusting the image forming conditions according to the characteristics of the recording material used, it is possible to improve the quality of the image. For example, in electrophotographic image formation, conditions such as the transfer voltage of toner and the fixing temperature are adjusted according to the characteristics of the recording material. For example, Patent Document 2 discloses a technique of providing a sensor for detecting the characteristics of a recording material on the conveyance path.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a recording material in which double feeding is detected is carried into the image forming unit, there is a risk of malfunction in the image forming unit. Further, after the characteristics are detected by the sensor, the recording material may be charged or folded. If this recording material is carried into the image forming unit as it is, there is a risk of malfunction in the image forming unit.

[0006] It is desirable that recording material in which double feeding has been detected, and recording material after characteristic detection by the sensor, can be discharged without passing through the image forming section. On the other hand, it is also desirable to minimize the increase in size of the device caused by this discharge mechanism.

[0007] The present invention has been made in view of the above circumstances, and provides a transport device and an image forming system that can prevent malfunctions in the image forming section caused by unsuitable recording materials, while also suppressing the increase in size of the device. [Means for solving the problem]

[0008] The above objectives of the present invention are achieved by the following means.

[0009] (1) A transport device comprising: a transport path for transporting recording material supplied from a recording material supply unit to an image forming unit; a double-feed detection unit for detecting double-feeding of the recording material supplied from the recording material supply unit; a media sensor for detecting characteristic information corresponding to the characteristics of the recording material; and a branch path provided branching off from the transport path at a branching point on the transport path, which purges the recording material for which the characteristic information has been detected by the media sensor without passing through the image forming unit, wherein the recording material for which double-feeding has been detected by the double-feed detection unit is purged via the branch path.

[0010] (2) The transport device described in (1) above, wherein the branching section is located upstream of the image forming section in the transport direction of the recording material.

[0011] (3) The branching path is the transport device described in (1) above, which is located between the recording material supply unit and the image forming unit.

[0012] (4) The transport device according to (1) above, further comprising a tray on which the recording material purged via the branching path can be placed.

[0013] (5) The media sensor is the transport device described in (1) above, which is located on the branch path.

[0014] (6) The transport device according to (5) above, wherein the media sensor includes a contact-type sensor that contacts the recording material to detect the characteristic information.

[0015] (7) The transport device according to (5) above, wherein the media sensor includes at least one of a sensor that detects characteristic information by applying a voltage to the recording material and a sensor that detects characteristic information by pressing the recording material.

[0016] (8) The transport device according to (5) above, wherein the media sensor includes at least one of the following: a sensor for detecting characteristic information corresponding to the resistance of the recording material, a sensor for detecting characteristic information corresponding to the rigidity of the recording material, and a sensor for detecting characteristic information corresponding to the smoothness of the recording material.

[0017] (9) The transport device described in (1) above, wherein the media sensor is located upstream of the branching section in the transport direction of the recording material.

[0018] (10) The transport device according to (9) above, wherein the media sensor includes a non-contact sensor that detects the characteristic information without contacting the recording material.

[0019] (11) The transport device according to (9) above, wherein the media sensor includes at least one of the following: a sensor for detecting characteristic information corresponding to the basis weight of the recording material, a sensor for detecting characteristic information corresponding to the thickness of the recording material, and a sensor for detecting characteristic information corresponding to the moisture content of the recording material.

[0020] (12) The transport device according to (1) above, wherein the double-feed detection unit is located upstream of the media sensor in the transport direction of the recording material.

[0021] (13) The double-feed detection unit is located upstream of the branching unit in the transport direction of the recording material, as described in (12) above.

[0022] (14) Further, the conveying device according to (1) above, which has a control unit that controls the media sensor based on the detection result of the double-feed detection unit.

[0023] (15) The conveying device according to (14) above, wherein the control unit acquires the characteristic information of the recording material for which double-feed has not been detected, and controls the image forming unit based on the acquired characteristic information.

[0024] (16) The conveying device according to (14) above, wherein for the recording material for which double-feed has been detected, the control unit does not execute the detection of the characteristic information by the media sensor or does not acquire the characteristic information.

[0025] (17) The conveying device according to (14) above, wherein the control unit controls the conveyance of the recording material, and when the media sensor detects the characteristic information of the recording material, the control unit stops the conveyance of the recording material for which the characteristic information has been detected.

[0026] (18) The conveying device according to (17) above, wherein the control unit conveys the recording material for which double-feed has been detected without stopping it at the position corresponding to the media sensor on the branch path.

[0027] (19) The conveying device according to (14) above, wherein the control unit controls the conveyance of the recording material, and when the media sensor detects the characteristic information of the recording material, the control unit continues the conveyance of the recording material for which the characteristic information has been detected.

[0028] (20) An image forming system including the conveying device according to (1) above, the recording material supply unit, and the image forming unit.

Advantages of the Invention

[0029] The transport device and image forming system according to the present invention have a control unit, so that recording material for which double feeding has been detected and recording material for which characteristic information has been detected by a media sensor are purged via a shared branch path. This branch path is configured not to pass through the image forming unit. Therefore, it is possible to discharge recording material for which double feeding has been detected and recording material after characteristic detection by the sensor without passing through the image forming unit, while also suppressing the increase in size of the device. [Brief explanation of the drawing]

[0030] The advantages and features provided by one or more embodiments of the present invention will be better understood from the following detailed description and accompanying drawings, which are for illustrative purposes only and are not intended to define any limitations of the present invention. [Figure 1] This figure shows an example of a schematic configuration of an image forming system according to one embodiment. [Figure 2] Figure 1 is a block diagram showing an example of the configuration of an image forming apparatus. [Figure 3] An example of the configuration of the paper characteristic detection mechanism shown in Figure 2 (block). [Figure 4] This figure shows an example of a specific configuration of the paper characteristic detection mechanism shown in Figure 1. [Figure 5] Figure 4 shows an example of the configuration of the basis weight sensor and moisture content sensor. [Figure 6] This figure shows an example of the configuration of the size sensor shown in Figure 4. [Figure 7] This figure shows an example of the configuration of the paper thickness sensor shown in Figure 4. [Figure 8] Figure 4 shows an example of the configuration of a basis weight sensor. [Figure 9] This figure shows an example of the configuration of the moisture content sensor shown in Figure 4. [Figure 10] This figure shows an example of the configuration of the stiffness sensor shown in Figure 4. [Figure 11] This figure shows an example of the configuration of the surface sensor shown in Figure 4. [Figure 12] Figure 4 shows an example of the configuration of the resistance sensor. [Figure 13] Figure 2 is a flowchart showing an example of the processing performed by the control unit. [Figure 14] A flowchart showing an example of the process following the steps in the flowchart shown in Figure 13. [Modes for carrying out the invention]

[0031] Embodiments of the present invention will be described below with reference to the attached drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios. In the drawings, the vertical direction is the Z direction, the front and back directions of the image forming system or transport device are the Y direction, and the direction perpendicular to these Y and Z directions is the X direction. The X direction is also called the paper transport direction. The Y direction is also called the width direction.

[0032] [Embodiment] <Overall configuration of the image forming system 1000> Figure 1 is a diagram showing the schematic configuration of an image forming system 1000 according to one embodiment. Figure 2 is a block diagram showing the hardware configuration of the image forming system 1000. In the image forming system 1000, an image is formed on a recording material. Here, the image forming system 1000 forms an image on paper 90. Paper 90 includes printing paper and various films. Paper 90 is manufactured, for example, using plant-derived mechanical pulp and / or chemical pulp. Paper 90 includes, for example, coated paper and uncoated paper. Coated paper includes, for example, gloss paper and matte paper. Uncoated paper includes, for example, plain paper and fine paper. The recording material may be made of resin or metal, etc.

[0033] The image forming system 1000 includes, for example, an image forming apparatus 10, a post-processing device 40, and a transport device 50. The paper 90 is transported in the order of transport device 50, image forming apparatus 10, and post-processing device 40. In other words, in the transport direction of the paper 90, the transport device 50, image forming apparatus 10, and post-processing device 40 are arranged from upstream to downstream. The image forming apparatus 10, post-processing device 40, and transport device 50 are mechanically and electrically connected to each other. The transport device 50 includes, for example, a paper feeding mechanism 20 and a paper characteristic detection mechanism 30.

[0034] The image forming apparatus 10 forms an image on paper 90 transported from the transport device 50. The image forming apparatus 10 includes a control unit 11, a storage unit 12, an image forming unit 13, a paper feed and transport unit 14, an operation panel 15, a printer controller 17, and a communication unit 19, etc. Each component of the image forming apparatus 10 is interconnected via signal lines, such as a bus.

[0035] The control unit 11 is composed of, for example, a CPU, ROM, and RAM. CPU is an abbreviation for Central Processing Unit. ROM is an abbreviation for Read Only Memory. RAM is an abbreviation for Random Access Memory. The control unit 11 executes various processes by running programs stored in the ROM or memory unit 12, and controls each part of the device and performs various calculations. The control unit 11 includes, for example, an overall control unit 111, an engine control unit 112, a paper characteristic detection mechanism control unit 113, a post-processing device control unit 114, a paper feeding mechanism control unit 115, and a transport / image forming control unit 116.

[0036] The memory unit 12 is composed of, for example, ROM, RAM, and auxiliary memory. Various programs and data are pre-stored in the ROM. RAM temporarily stores programs and data as a working area. The auxiliary memory unit is, for example, a hard disk and stores various programs and data.

[0037] The memory unit 12 stores, for example, paper information related to the paper 90. The paper information includes, for example, information about the brand of paper 90, the size of paper 90, the basis weight of paper 90, and the type of paper 90. The size of paper 90 is, for example, the width and length of paper 90. The type of paper 90 is, for example, gloss coated paper, matte coated paper, plain paper, fine paper, and rough paper. The memory unit 12 may also store the brand of paper 90. The memory unit 12 may also store algorithms used to determine control parameters. The memory unit 12 may also store paper profiles.

[0038] The image forming unit 13 forms an image on the paper 90, for example, by an electrophotographic method. The image forming unit 13 includes, for example, a writing unit, a photosensitive drum, and a developer. The developer contains, for example, a two-component developer including toner and a carrier. The writing unit, photosensitive drum, and developer have configurations corresponding to basic colors such as Y (yellow), M (magenta), C (cyan), and K (black). The image forming unit 13 further includes, for example, an intermediate transfer belt, a secondary transfer unit, and a fixing unit. In the image forming unit 13, a toner image is formed on the photosensitive drum by the developer. This toner image is superimposed on the intermediate transfer belt and transferred to the paper 90 in the secondary transfer unit. The toner image transferred to the paper 90 is heated and pressurized in the fixing unit. This fixes the toner image to the paper 90.

[0039] The paper feeding and transport unit 14 includes, for example, transport paths 141 and 142 and a plurality of paper trays 145. The transport paths 141 and 142 include, for example, a transport path, a plurality of transport roller pairs provided along the transport path, and a drive motor that drives these transport roller pairs. The paper feeding and transport unit 14 also includes, for example, a discharge roller. This discharge roller sends the uppermost sheet of paper from the plurality of sheets of paper 90 placed in the paper tray 145 to the transport path 141. The transport path 141 is connected to the transport path 341 of the transport device 50.

[0040] The transport path 141 transports the paper 90 from the paper feed tray 145 to the image forming unit 13. The transport path 141 then transports the paper 90, on which an image has been formed in the image forming unit 13, to the post-processing device 40. In the post-processing device 40, the paper 90 is discharged onto the output tray 41. When an image is formed on both the front and back surfaces of the paper 90, that is, when double-sided printing is performed, the transport path 142 is used. The paper 90 with an image formed on one side is transported to the transport path 142. The transport path 142 is located, for example, at the bottom of the main body of the device. In this transport path 142, the front and back surfaces of the paper 90 are reversed in a switchback path. After this, the paper 90 is transported to the transport path 141.

[0041] The control panel 15 includes, for example, a touch panel, a numeric keypad, a start button, and a stop button. The control panel 15 displays the status of the image forming apparatus 10 or the image forming system 1000. The control panel 15 may also be used for inputting instructions from the user. For example, the user may input the type of paper 90 into the control panel 15.

[0042] The printer controller 17 acquires a print job. For example, a print job is sent to the image forming system 1000 from a terminal device such as a PC. The print job may also be input to the operation panel 15. PC is an abbreviation for Personal Computer. The print job includes print data written in, for example, PDL format or PDF format. PDL is an abbreviation for Page Description Language. This print data is rasterized by the printer controller 17 and converted into image data for each page. This image data for each page is temporarily stored, for example, in page memory. The image data stored in page memory is read out at a predetermined timing and stored in a buffer. The image data stored in this buffer is output as an exposure signal to the writing unit for each main scan line, synchronized with the writing timing.

[0043] The communication unit 19 is an interface for communicating with other devices.

[0044] When the overall control unit 111 receives a print job from the printer controller 17, it instructs the engine control unit 112 to execute the print job based on the print job's configuration information.

[0045] The engine control unit 112 executes image formation processing by controlling the post-processing unit control unit 114, the paper feeding mechanism control unit 115, and the transport / image formation control unit 116. The post-processing unit control unit 114 controls the post-processing unit 40. Specifically, the post-processing unit control unit 114 transmits to the post-processing unit 40 the timing for transporting the paper 90 and setting information for post-processing of the transported paper 90. The paper feeding mechanism control unit 115 controls the paper feeding mechanism 20. Specifically, the paper feeding mechanism control unit 115 transmits instructions to the paper feeding mechanism 20 regarding the paper tray 245 to be used and instructions regarding the timing for transporting the paper 90. The paper feeding mechanism control unit 115 may also receive information from the paper feeding mechanism 20.

[0046] The transport and image formation control unit 116 controls the image formation unit 13 and the paper feed transport unit 14. Specifically, the transport and image formation control unit 116 controls the image formation conditions, the timing of image formation, and the paper feed transport of the paper 90.

[0047] The paper characteristic detection mechanism control unit 113 controls the paper characteristic detection mechanism 30 in response to instructions from the engine control unit 112. Specifically, the paper characteristic detection mechanism control unit 113 controls the sensors included in the paper characteristic detection mechanism 30.

[0048] The post-processing device 40 performs post-processing on the paper 90 transported from the image forming apparatus 10 according to the settings of the print job. The post-processing device 40 includes, for example, output trays 41, 42, a post-processing unit 43, and a transport path 441. The post-processing device 40 may further include a control unit, a storage unit, a transport unit, a communication unit, etc. Each component of the post-processing device 40 is interconnected via signal lines, such as a bus.

[0049] The paper 90 transported along the transport path 441 is discharged into the output trays 41 and 42. The output trays 41 and 42 are configured to be selectable according to, for example, the settings of a print job. The transport path 441 is connected to the transport path 141 of the image forming apparatus 10. In the post-processing unit 43, post-processing is performed on the paper 90 transported from the transport path 141. Post-processing may include, for example, stapling, punching, cutting, folding, or binding. The post-processing unit 40 may also discharge the paper 90 into the output trays 41 and 42 without performing any post-processing on the paper 90.

[0050] The transport device 50, which includes the paper feeding mechanism 20 and the paper characteristics detection mechanism 30, supplies the paper 90 to the image forming apparatus 10 and causes the paper characteristics detection mechanism 30 to detect the characteristics of the paper 90.

[0051] The paper feeding mechanism 20 includes, for example, a paper feeding and transport unit 24 and a double-feed detection unit 26. The paper feeding mechanism 20 further includes, for example, a control unit, a storage unit, and a communication unit. Each component of the paper feeding mechanism 20 is interconnected via, for example, signal lines such as a bus. The paper feeding and transport unit 24 includes, for example, a plurality of paper feeding trays 245 and a transport path 241. The transport path 241 is the transport path for paper 90 from the paper feeding trays 245 to the paper characteristics detection mechanism 30. In the paper feeding mechanism 20, paper 90 is supplied from each paper feeding tray 245 to the transport path 241. The paper 90 supplied to the transport path 241 is transported to the paper characteristics detection mechanism 30. Here, the paper feeding trays 245 correspond to one specific example of the recording material supply unit of the present invention.

[0052] For example, a double-feed detection unit 26 is positioned along the transport path 341. The control unit of the paper feeding mechanism 20 causes the double-feed detection unit 26 to detect a double feed of paper 90. A double feed is when multiple sheets of paper 90 are fed from the paper tray 245 while overlapping each other.

[0053] The double-feed detection unit 26, for example, transmits ultrasonic waves to the paper 90 and detects a double feed of the paper 90 based on the intensity of the ultrasonic waves that have passed through the paper. The double-feed detection unit 26 has, for example, an ultrasonic wave transmitting element and a receiving element. The transmitting element and the receiving element are, for example, positioned opposite each other across the transport path 241. When the double-feed detection unit 26 detects a double feed of the paper 90, the control unit of the paper feeding mechanism 20 continues to transport the paper 90 to be detected and causes the double-feed detection unit 26 to detect the double feed of the paper 90.

[0054] Figure 3 is a block diagram showing the configuration of the paper characteristics detection mechanism 30. The paper characteristics detection mechanism 30 includes, for example, a control unit 31, a storage unit 32, a transport unit 34, a first detection unit 35, a second detection unit 37, an environmental sensor 38, and a communication unit 39. The environmental sensor 38 detects at least one of the temperature and humidity inside the device body. The communication unit 39 is an interface for communicating with other devices.

[0055] The control unit 31 is composed of, for example, a CPU, ROM, and RAM. The control unit 31 controls the operation of the transport unit 34, the first detection unit 35, the second detection unit 37, the environmental sensor 38, and the communication unit 39. The control unit 31 causes the first detection unit 35 and the second detection unit 37 to detect characteristic information corresponding to the characteristics of the paper 90. The control unit 31 transmits the characteristic information detected by the first detection unit 35 and the second detection unit 37 to, for example, the control unit 11. The control unit 31 obtains information from the control unit of the paper feeding mechanism 20 regarding whether or not a double feed has been detected by the double feed detection unit 26. Based on this information, the control unit 31 controls, for example, the transport unit 34, the first detection unit 35, and the second detection unit 27.

[0056] The storage unit 32 includes, for example, a ROM, RAM, and an auxiliary storage unit. The storage unit 32 stores, for example, an environmental correction table that associates the detected values ​​of the environmental sensor 38 with correction values. The control unit 31 may correct the detection results of the first detection unit 35 and the second detection unit 37 according to the detected values ​​of the environmental sensor 38 and the environmental correction table.

[0057] The transport unit 34 includes, for example, a transport path 341, a branching path 342, and a purge tray 349. The transport path 341 and the branching path 342 each include a transport path, a plurality of transport roller pairs provided along the transport path, and a drive motor for driving the transport roller pairs.

[0058] Figure 4 is a schematic diagram showing an example of the configuration near the transport path 341 and the branch path 342. The transport path 341 is the main transport path. The transport path 341 connects the transport path 241 of the paper feeding mechanism 20 and the transport path 141 of the image forming apparatus 10. In other words, in the transport direction of the paper 90, the transport paths are arranged in the order of transport path 241, transport path 341, and transport path 141 from the upstream side. For example, the first detection unit 35 is located along the transport path 341. In the transport direction of the paper 90, for example, the double-feed detection unit 26 is located upstream of the first detection unit 35. The transport path 341 extends in a substantially horizontal direction.

[0059] The branching path 342 is provided by branching off from the transport path 341 at a branching point s1 on the transport path 341. The branching point s1 is located, for example, downstream of the first detection unit 35 in the transport direction of the paper 90. The branching path 342 is located between the paper feed tray 245 and the image forming unit 13, or more specifically, between the first detection unit 35 and the image forming apparatus 10. The branching path 342 connects the branching section s1 and the purge tray 349. Paper 90 transported along the branching path 342 is purged into the purge tray 349 without passing through the image forming section 13. For example, a second detection section 37 is positioned along the branching path 342. At least a portion of the branching path 342 extends in a substantially vertical direction. A portion of the branching path 342 may be curved. The branching path 342 may have a curved shape such as an S-shape.

[0060] The first detection unit 35 detects, for example, the paper characteristics of the paper 90 being transported along the transport path 341. The first detection unit 35 includes, for example, a plurality of media sensors. The first detection unit 35 includes, for example, a size sensor 351, a paper thickness sensor 352, a basis weight sensor 353, and a moisture content sensor 354. The characteristic information detected by the first detection unit 35 includes, for example, information regarding characteristic values ​​or physical properties of the paper 90. The characteristic information may be index values ​​such as current values ​​and voltage values ​​indicated by the media sensors of the first detection unit 35.

[0061] In the first detection unit 35, for example, in the transport direction of the paper 90, the size sensor 351 and the paper thickness sensor 352 are arranged in this order from the upstream side. The basis weight sensor 353 and the moisture content sensor 354 are arranged downstream of the paper thickness sensor 352.

[0062] In the size sensor 351, the size of the paper 90 is determined when the paper 90 passes through the detection position. For this reason, it is preferable that the size sensor 351 be positioned at least by the length of the longest paper that the image forming system 1000 can handle, upstream of the image forming position of the image forming unit 13. In the first detection unit 35, by positioning the size sensor 351 upstream of the other sensors, it becomes possible to increase the distance between the size sensor 351 and the image forming unit 13.

[0063] It is preferable that the paper thickness sensor 352 is positioned upstream of the basis weight sensor 353 and the moisture content sensor 354 in the paper transport direction of the paper 90. This allows the thickness of the paper 90 to be detected when the basis weight sensor 353 and the moisture content sensor 354 are detected, making it possible to set the measurement range and measurement conditions of the basis weight sensor 353 and the moisture content sensor 354 more appropriately.

[0064] Figure 5 shows an example of the configuration of the vicinity of the basis weight sensor 353 and the moisture content sensor 354. The basis weight sensor 353 and the moisture content sensor 354 are arranged, for example, at the same position in the paper transport direction, but at different positions in the width direction. This allows the overall length of the first detection unit 35 in the transport direction to be reduced, thereby saving space.

[0065] When the first detection unit 35 detects characteristic information of the paper 90, the control unit 31 continues to transport the paper 90 to be detected and causes the first detection unit 35 to detect the characteristic information. This makes it possible to detect the characteristic information of the transported paper 90 without reducing productivity. The control unit 31 may also cause the first detection unit 35 to detect the characteristic information of each of the continuously transported paper 90.

[0066] For example, characteristic information regarding the size, thickness, and basis weight of the paper 90 corresponds to the paper type, and characteristic information regarding the moisture content of the paper 90 corresponds to changes in the state of the paper 90. This makes it possible to detect abnormalities in the characteristics of the paper 90 when the type of paper 90 loaded into the paper tray 245 differs from the print job settings, or when the state of the paper 90 changes significantly during continuous printing.

[0067] The second detection unit 37 detects, for example, the paper characteristics of the paper 90 being transported along the branch path 342. The second detection unit 37 includes, for example, a plurality of media sensors. The second detection unit 37 includes, for example, a stiffness sensor 371, a surface quality sensor 372, and a resistance sensor 373. The characteristic information detected by the second detection unit 37 includes, for example, information regarding the characteristic values ​​or physical properties of the paper 90. The characteristic information may be index values ​​such as current values ​​and voltage values ​​indicated by the media sensors of the second detection unit 37.

[0068] In the second detection unit 37 arranged along the branching path 342, for example, a stiffness sensor 371, a surface quality sensor 372, and a resistance sensor 373 are arranged in this order, starting from a position close to the branching section s1. The stiffness sensor 371 and the surface quality sensor 372 may be arranged in reverse. In the region where the stiffness sensor 371 is located, it is preferable that the branching path 342 extends in a substantially vertical direction. Here, substantially vertical means within a range of 90 ± 1°.

[0069] It is preferable that the resistance sensor 373 is positioned downstream of the stiffness sensor 371 in the paper transport direction of the paper 90. After characteristic information is detected by the resistance sensor 373, charge accumulates on the paper 90, and the paper 90 may become electrostatically charged. With electrostatically charged paper 90, accurate stiffness detection may not be possible. By positioning the resistance sensor 373 downstream of the stiffness sensor 371, it becomes possible to detect the stiffness of the paper 90 more accurately.

[0070] When the second detection unit 37 detects characteristic information of the paper 90, the control unit 31 stops the transport of the paper 90 at the respective detection positions of the stiffness sensor 371, surface quality sensor 372, and resistance sensor 373. When the length of the paper 90 in the transport direction is sufficient, the control unit 31 may simultaneously perform the detection of characteristic information by the stiffness sensor 371, surface quality sensor 372, and resistance sensor 373. By stopping the transport of the paper 90 and detecting the characteristic information, it is possible to reduce damage to the paper 90 caused by the second detection unit 37.

[0071] The control unit 31 may cause the second detection unit 37 to detect characteristic information for all of the paper 90 being transported to the second detection unit 37, or it may cause the control unit 31 to detect characteristic information for only a portion of the paper 90 being transported to the second detection unit 37.

[0072] <Configuration of the first detection unit 35> Figures 6 to 9 show an example of the specific configuration of the first detection unit 35.

[0073] Figure 6 shows a schematic configuration of the size sensor 351. The size sensor 351 is a non-contact media sensor that detects the size of the paper 90 without contacting the paper 90. The size sensor 351 detects the size of the paper 90 using, for example, an optical method. The size sensor 351 includes, for example, an image sensor.

[0074] The size sensor 351 includes, for example, line sensors 511 and 512. The line sensors 511 and 512 include, for example, a plurality of photoelectric conversion elements arranged in a line. The photoelectric conversion elements are composed of, for example, CIS. CIS is an abbreviation for Contact Image Sensor. The line sensors 511 and 512 read, for example, a one-dimensional image.

[0075] The line sensors 511 and 512 further include, for example, optical elements such as light-emitting elements and lens arrays. Light is emitted from these light-emitting elements toward the paper 90 on the transport path 341. The length of the line sensors 511 and 512 is, for example, 200 mm to 300 mm. The line sensors 511 and 512 are arranged to overlap each other in the Y direction, for example. The line sensors 511 and 512 are arranged adjacent to each other in the X direction. This makes it easier to read the total width of the transported paper 90.

[0076] The size sensor 351 generates read image data by reading the paper 90, which is transported at a predetermined transport speed, using line sensors 511 and 512. The size sensor 351 detects the edges of the paper 90 by processing the generated read image data. This allows characteristic information regarding the size of the paper 90 to be detected. The size sensor 351 may have one line sensor or three or more line sensors.

[0077] Figure 7 shows a schematic configuration of the paper thickness sensor 352. The paper thickness sensor 352 is a contact-type media sensor that detects the paper thickness of the paper 90 by contacting the paper 90, for example. The paper thickness sensor 352 detects the thickness of the paper 90 mechanically, for example. The paper thickness sensor 352 includes, for example, a transport roller pair 521 and a displacement sensor. When the paper 90 is transported to the nip of the transport roller pair 521, the axial position of one of the rollers of the transport roller pair 521 is displaced according to the thickness of the paper 90. The thickness of the paper 90 is measured by measuring the height of this displaced axis.

[0078] The conveyor roller pair 521 is composed of, for example, an upper roller and a lower roller. For example, the axis of the lower roller is fixed, and the lower roller is the drive roller. The upper roller is biased to move toward and away from the lower roller, and the upper roller is the driven roller.

[0079] The displacement sensor detects the height of the upper roller. The displacement sensor includes, for example, an actuator that contacts the upper roller shaft and an encoder that measures the amount of rotation of this actuator. The paper thickness sensor 352 detects characteristic information regarding the thickness of the paper 90 based on the detection result of the displacement sensor.

[0080] Figure 8 shows a schematic configuration of the basis weight sensor 353. The basis weight sensor 353 is a non-contact media sensor that detects the basis weight of the paper 90 without contacting the paper 90. The basis weight sensor 353 detects the basis weight of the paper 90 optically, for example. The basis weight sensor 353 has, for example, a light-emitting part and a light-receiving part. The basis weight sensor 353 measures, for example, the amount of attenuation of light transmitted through the paper 90 and the amount of reflected light at the paper 90.

[0081] The basis weight sensor 353 has, for example, a plurality of light-emitting units 531 and one light-receiving unit 532. The light-emitting units 531 include, for example, a first light-emitting unit 531a, a second light-emitting unit 531b, and a third light-emitting unit 531c. The first light-emitting unit 531a emits a first irradiation light, the second light-emitting unit 531b emits a second irradiation light, and the third light-emitting unit 531c emits a third irradiation light. The first light-emitting units 531a and 2 light-emitting units 531b and the light-receiving unit 532 are arranged to face each other with a transport path 341 in between. The third light-emitting unit 531c is arranged, for example, in the vicinity of the light-receiving unit 532.

[0082] The light-emitting section 531 and the light-receiving section 532 are located near the upper guide plate 3411 and the lower guide plate 3412. The upper guide plate 3411 and the lower guide plate 3412 face each other in the Z direction with the transport path 341 in between. The upper guide plate 3411 is provided with an opening a12, and the lower guide plate 3412 is provided with an opening a22. The opening a22 is located opposite the opening a12. The openings a12 and a22 have, for example, the same planar shape. The openings a12 and a22 have, for example, a rectangular planar shape. For example, a transparent sheet 534a is attached to the opening a12, and a transparent sheet 534b is attached to the opening a22. By attaching sheets 534a and 354b to the openings a12 and a22, it is possible to suppress the adhesion of foreign matter such as paper dust from the paper 90 passing through the transport path 341 to the light-emitting section 531 and the light-receiving section 532. The sheets 534a and 354b are made of, for example, PET. The sheets 534a and 354b are configured to allow the first, second, and third irradiation lights to pass through. PET is an abbreviation for Poly Ethylene Terephthalate.

[0083] The first irradiation light emitted from the first light-emitting unit 531a contains light of a first wavelength. The first wavelength is, for example, a wavelength longer than the wavelength of the visible light band, for example, a wavelength in the near-infrared band. More specifically, the first wavelength is, for example, 750 nm to 900 nm. The first irradiation light is irradiated onto the transport path 341 through apertures a12 and a22. The first irradiation light that has passed through the transport path 341 is received by the light-receiving unit 532.

[0084] The second irradiation light emitted from the second light-emitting unit 531b contains light of a second wavelength. The second wavelength is, for example, a wavelength in the blue band included in the visible light band. More specifically, the second wavelength is, for example, 400 nm to 470 nm. The second irradiation light is irradiated onto the transport path 341 through apertures a12 and a22. The second irradiation light that has passed through the transport path 341 is received by the light-receiving unit 532.

[0085] The third illumination light emitted from the third light-emitting unit 531c contains light of a third wavelength. The third wavelength is, for example, a wavelength in the green band included in the visible light band. More specifically, the third wavelength is, for example, 495 nm to 570 nm. The third wavelength is different from the first and second wavelengths. The third illumination light is reflected by the reflecting unit 533 and received by the light-receiving unit 532. The reflecting unit 533 is, for example, provided near the aperture a22 of the lower guide plate 3412. The reflecting unit 533 is, for example, painted green, the same color as the third illumination light, and reflects the third illumination light.

[0086] In the basis weight sensor 353, for example, the first light-emitting unit 531a and the second light-emitting unit 531b emit first and second light at different timings. The light-receiving unit 532 detects the amount of light from the received first and second light.

[0087] The basis weight sensor 353 detects characteristic information regarding the basis weight of the paper 90, for example, based on the transmittance of the first and second irradiated light passing through the paper 90 and the reflectance of the third irradiated light reflected by the paper 90. The basis weight sensor 353 may also determine the type of paper 90 from this characteristic information and the determination criteria stored in the storage unit 12.

[0088] Figure 9 shows a schematic configuration of the moisture content sensor 354. The moisture content sensor 354 is a non-contact media sensor that detects the moisture content of the paper 90 without contacting the paper 90. The moisture content sensor 354 detects the moisture content of the paper 90 optically, for example. The first detection unit 35 may have a moisture content sensor instead of the moisture content sensor 354.

[0089] The moisture content sensor 354 includes, for example, a first light-emitting unit 541, a second light-emitting unit 542, a light-receiving unit 543, a temperature detection sensor 544, and lenses 545, 546, etc. The first light-emitting unit 541 and the second light-emitting unit 542 irradiate light toward the paper 90 being transported along the transport path 341.

[0090] The first light-emitting unit 541 emits light with a wavelength in the near-infrared band, for example. The wavelength of the light emitted by the first light-emitting unit 541 is selected to be in a band where the light absorption rate by the paper 90 does not change easily depending on the moisture content of the paper 90. The first light-emitting unit 541 is, for example, an LED. LED is an abbreviation for Light Emitting Diode. The first light-emitting unit 541 emits light onto the paper 90 through the lens 545. This light is reflected by the paper 90 and received by the light-receiving unit 543 through the lens 546.

[0091] The second light-emitting unit 542 emits light with a wavelength in the near-infrared band, for example. The wavelength of the light emitted by the second light-emitting unit 542 is selected to be in a band where the light absorption rate by the paper 90 is easily affected by the moisture content of the paper 90. The second light-emitting unit 542 is, for example, an LED. The second light-emitting unit 542 emits light onto the paper 90 through the lens 545. This light is reflected by the paper 90 and received by the light-receiving unit 543 through the lens 546.

[0092] The light-receiving unit 543 includes, for example, a CCD or CMOS image sensor. CCD is an abbreviation for Charge-Coupled Device. CMOS is an abbreviation for Complementary metal-oxide-semiconductor. The moisture content sensor 354 detects characteristic information regarding the moisture content of the paper 90 based, for example, on the absorption rate of the paper 90 to light irradiated from the first light-emitting unit 541 and the absorption rate of the paper 90 to light irradiated from the second light-emitting unit 542.

[0093] <Configuration of the second detection unit 37> Figures 10 to 12 show an example of the specific configuration of the second detection unit 37.

[0094] Figure 10 shows a schematic configuration of the stiffness sensor 371. The stiffness sensor 371 is a contact-type media sensor that detects the stiffness of the paper 90 by contacting it, for example. The stiffness sensor 371 detects the stiffness of the paper 90 mechanically, for example.

[0095] The rigidity sensor 371 is positioned, for example, vertically below a pair of rollers 347 that hold the stopped paper 90. The rollers 347 are controlled to rotate by a motor M2.

[0096] The stiffness sensor 371 includes, for example, a paper detection sensor 710, a pressing part 711, a pressing force detection part 712, a support mechanism 715, and a motor M1. The motor M1 moves the support mechanism 715 horizontally. As a result, when the stiffness sensor 371 detects the stiffness of the paper 90, the tip of the pressing part 711 connected to the support mechanism 715 is positioned at a predetermined position in the X direction. The paper detection sensor 710 detects the presence or absence of paper 90 at the detection position.

[0097] The pressing section 711 presses the lower end of the paper 90 from the side. The pressing section 711 has, for example, a blade 711a and a base 711b that is continuous with one end of the blade 711a in the horizontal direction.

[0098] The pressing force detection unit 712 detects the pressing force when the paper 90 is pressed and bent by the pressing unit 711. The pressing force detection unit 712 includes, for example, a load cell. Based on the pressing force detected by this pressing force detection unit 712, the stiffness sensor 371 detects characteristic information regarding the stiffness of the paper 90.

[0099] Figure 11 shows a schematic configuration of the surface quality sensor 372. The surface quality sensor 372, also called a smoothness sensor, detects characteristic information regarding the smoothness of the paper 90. The surface quality sensor 372 is a non-contact type media sensor that detects the surface quality of the paper 90 without contacting it. The surface quality sensor 372 detects the surface quality of the paper 90 optically, for example. The surface quality sensor 372 detects characteristic information regarding the smoothness of the paper 90 based on specular reflection and scattered reflection on the paper 90, for example. The surface quality sensor 372 is positioned near the upper guide plate 3411 and the lower guide plate 3412, for example. The upper guide plate 3421 and the lower guide plate 3422 are provided facing each other on the left and right sides with a branch path 342 in between.

[0100] For example, the upper guide plate 3421 is provided with an opening a11, and the lower guide plate 3422 is provided with an opening a21. The opening a11 is roughly rectangular in shape. The opening a21 is positioned in a position corresponding to the opening a11 and is larger than the opening a11. The pressing plate 729 of the pressing mechanism is positioned in the opening a21. As this pressing plate 729 moves from the left to the right in Figure 10, the paper 90 is pressed against the upper guide plate 3421, and the paper 90 is fixed in place.

[0101] The surface quality sensor 372 detects surface quality based on specular and scattered light from the surface of the paper 90 placed on the reference surface of the aperture a11. The reference surface corresponds to the inner surface of the upper guide plate 3421.

[0102] The surface sensor 372 includes, for example, a housing 721, a light-emitting unit 722, a collimating lens 723, and light-receiving units 724a, 724b, etc. Light emitted from the light-emitting unit 722 is specularly reflected off the surface of the paper 90 and received by the light-receiving unit 724a. Light emitted from the light-emitting unit 722 is scattered and reflected off the surface of the paper 90 and received by the light-receiving unit 724b.

[0103] The light-emitting unit 722 is positioned such that the angle of incidence of the light emitted from the light-emitting unit 722 with respect to the reference plane is 75°. This angle of incidence of 75° is set in accordance with JIS standards. The reference plane is a virtual plane that includes the lower surface of the upper guide plate 3421. The light-emitting unit 722 is positioned on the substrate b1. The light-emitting unit 722 includes a light source such as an LED that emits light of a predetermined wavelength. The light emitted from the light-emitting unit 722 becomes substantially parallel light through the collimating lens 723. The wavelength of the light emitted from the light-emitting unit 722 is preferably in the range of greater than 405 nm and less than 525 nm, more preferably in the range of 445 nm to 500 nm, and the most preferred wavelength is around 465 nm. The light-emitting unit 722 and the light-receiving unit 724 are positioned, for example, along the width direction. The light-emitting unit 722 and the light-receiving unit 724 are positioned, for example, on the same XY plane.

[0104] The light-receiving sections 724a and 724b include, for example, light-receiving elements such as photodiodes or phototransistors. The light-receiving section 724a is positioned at a reflection angle of 75°, corresponding to the incident angle of 75° of the light-emitting section 722, and receives specularly reflected light. The light-receiving section 724b is positioned at any reflection angle other than 75°, within the range of reflection angles of 0° or more and less than 90°, and receives diffusely reflected light. Preferably, the light-receiving section 724b is positioned at reflection angles of 60°, 30°, and 0°, more preferably at two locations, 60° and 30°, or at one location, 60°. The light-receiving section 724a is positioned on, for example, substrate b2, and the light-receiving section 724b is positioned on, for example, substrate b3. In the light-receiving paths of the light-receiving sections 724a and 724b, the housing 721 is provided with apertures a3 and a4. The apertures a3 and a4 have, for example, the same planar shape.

[0105] Figure 12 shows a schematic configuration of the resistance sensor 373. The resistance sensor 373 is a contact-type media sensor that, for example, contacts the paper 90 to detect the resistance of the paper 90. The resistance sensor 373 applies a high voltage between the front and back surfaces of the paper 90 and detects the current value flowing through it. Based on this current value, the resistance sensor 373 detects characteristic information regarding the electrical resistance of the paper 90.

[0106] The resistance sensor 373 includes, for example, a detection roller 732, an opposing roller 731, and a high-voltage power supply unit 733.

[0107] The detection roller 732 is positioned to be in contact with one side of the paper 90. The detection roller 732 is made of an elastic material, such as conductive rubber.

[0108] The opposing roller 731 is positioned opposite the detection roller 732 with the paper 90 in between. The opposing roller 731 is positioned so as to be able to contact the other side of the paper 90. The opposing roller 731 is made of, for example, a metal material. The opposing roller 731 is grounded.

[0109] The high-voltage power supply unit 733 is a unit for applying a high voltage to the paper 90. The high-voltage power supply unit 733 is electrically connected to the detection roller 732 and the opposing roller 731. This constitutes an electrical circuit in the detection roller 732, the opposing roller 731, and the high-voltage power supply unit 733. The high-voltage power supply unit 733 has an ammeter and a high-voltage power supply circuit. The ammeter is electrically connected to the detection roller 732. The ammeter detects the current flowing due to the voltage applied in the high-voltage power supply circuit.

[0110] The high-voltage power supply circuit is electrically connected to the detection roller 732 via an ammeter. The high-voltage power supply circuit is configured to be able to apply a high voltage. A voltage is applied from the high-voltage power supply circuit to the detection roller 732 via the ammeter. The high-voltage power supply circuit is configured to be able to apply a high voltage of, for example, 1kV to 5kV.

[0111] <Processing by Control Unit 11> Figures 13 and 14 are flowcharts illustrating an example of a process performed by the control unit 11. The processes shown in these flowcharts may be executed, for example, according to a program stored in the control unit 11. The processes shown in these flowcharts may also be executed by other control units. The process shown in Figure 13 is the process of preparing for printing, and the process shown in Figure 14 is the process of performing printing.

[0112] (Step S11) When a print job is input, the control unit 11 feeds and transports the paper 90 to be used in the print job based on the print job setting information of the input print job. Print jobs are input based on instructions sent from an external terminal such as a PC. For example, the control unit 11 feeds the paper 90 from the paper tray 245 of the paper feeding mechanism 20 and transports the paper 90 to the transport path 241. This paper 90 is the first sheet on the paper tray 245.

[0113] (Step S12) The control unit 11 determines whether or not a double feed of paper 90 has been detected by the double feed detection unit 26. For example, when the double feed detection unit 26 detects paper 90, the control unit 11 continues to transport the detected paper 90. The control unit 11 controls, for example, the paper feed transport unit 24 and the double feed detection unit 26 to determine whether or not a double feed of paper 90 has been detected.

[0114] (Step S13) If no double feed is detected in step S12 (step S12: NO), the control unit 11 causes the first detection unit 35 to detect the characteristic information of the paper 90. For example, when the first detection unit 35 detects the characteristic information of the paper 90, the control unit 11 continues to transport the paper 90 to be detected. The control unit 11, for example, controls the transport unit 34 and the first detection unit 35 to detect the characteristic information of the paper 90.

[0115] (Step S14) After the first detection unit 35 detects the characteristic information of the paper 90 in step S13, the control unit 11 transports the paper 90 from the transport path 341 to the branch path 342 via the branching unit s1. The control unit 11 then has the second detection unit 37 detect the characteristic information of the paper 90 transported to the branch path 342. For example, when the second detection unit 37 detects the characteristic information of the paper 90, the control unit 31 stops the transport of the paper 90 to be detected. The control unit 11 may stop the transport of the paper 90 multiple times. After the second detection unit 37 detects the characteristic information of the paper 90, the control unit 11 executes the process in step S15.

[0116] (Steps S15, S16) The control unit 11 discharges the paper 90 transported along the branch path 342 into the purge tray 349. After this, the control unit 11 uses the characteristic information obtained from steps S13 and S14 to determine the parameters of each process, such as the image forming unit 13, and proceeds to step S21. Specifically, the control unit 11 determines the control parameters for each process: fixing, transfer, transport, paper feeding, and post-processing.

[0117] (Steps S17, S18) When a double feed is detected in step S12 (step S12: YES), the control unit 11 causes the paper 90 to be transported from the transport path 341 to the branch path 342 via the branch s1. At this time, the control unit 11, for example, continues transporting the paper 90 in which a double feed was detected, and executes the processing of the next step S19 without causing the first detection unit 35 and the second detection unit 37 to detect characteristic information of the paper 90.

[0118] (Step S19) The control unit 11 discharges the paper 90 that has been transported along the branch path 342 into the purge tray 349. After this, for example, the control unit 11 returns to the process of step S11.

[0119] (Step S21) The control unit 11 determines whether or not to start executing the print job. If it determines to start executing the print job (step S21: YES), the control unit 11 proceeds to step S22. If it determines not to start executing the print job (step S21: NO), the process of step S21 is repeated. The print job is started, for example, when the user presses the start execution button. The control unit 11 may also determine to start executing the print job at the end of the process in step S16.

[0120] (Step S22) The control unit 11 first feeds and transports the paper 90 to be used for the print job. The control unit 31, for example, feeds the paper 90 from the paper tray 245 to the transport path 341 and transports the paper 90 downstream along the transport path 341. The control unit 11 may also control the paper feeding mechanism 20 to continuously feed and transport the paper 90 from the paper tray 245.

[0121] (Step S23) The control unit 11 determines whether or not a double feed of paper 90 has been detected by the double feed detection unit 26. For example, when the double feed detection unit 26 detects paper 90, the control unit 11 continues to transport the detected paper 90. The control unit 11 controls, for example, the paper feed transport unit 24 and the double feed detection unit 26 to determine whether or not a double feed of paper 90 has been detected.

[0122] (Step S24) If no double feed is detected in step S23 (step S23: NO), the control unit 11 causes the first detection unit 35 to detect the characteristic information of the paper 90. For example, when the first detection unit 35 detects the characteristic information of the paper 90, the control unit 11 continues to transport the paper 90 to be detected. The control unit 11, for example, controls the transport unit 34 and the first detection unit 35 to detect the characteristic information of the paper 90.

[0123] (Step S25) After the first detection unit 35 detects the characteristic information of the paper 90 in step S24, the control unit 31 determines whether or not the paper 90 is inappropriate based on the detected characteristic information of the paper 90. For example, if the difference between the characteristic information of the paper 90 set in the print job currently running and the detected characteristic information of the paper 90 is within a predetermined range, the control unit 11 determines that it is not inappropriate paper. If the difference between the characteristic information of the paper 90 set in the print job currently running and the detected characteristic information of the paper 90 is outside the predetermined range, the control unit 11 determines that it is inappropriate paper.

[0124] For example, if a sheet of paper different in size and type from the paper 90 set in the print job settings is mixed in with the stack of paper, the control unit 11 will determine that the paper 90 is inappropriate. For example, if the moisture content of the paper 90 is significantly different from the moisture content of the previous sheets of paper 90, the control unit 11 will determine that the paper 90 is inappropriate. For example, if a sheet of paper of a different size is mixed in with the stack of paper loaded into the paper tray 245, the control unit 11 will determine that the paper 90 is inappropriate. For example, if a sheet of paper 90 of a different size or type is supplied to the paper tray 245 due to a user's mistake, the control unit 11 will determine that the paper 90 is inappropriate.

[0125] (Step S26) If it is determined in step S25 that the paper 90 is not an inappropriate paper (step S25: NO), the control unit 11 transports the paper 90 from the transport path 341 to the image forming unit 13 via the transport path 141. As a result, an image is formed on the paper 90. The image-formed paper 90 is then discharged into the output tray 41 of the post-processing device 40.

[0126] (Step S27) The control unit 11 determines whether the print job has finished. If it determines that the print job has not finished (step S27: NO), the control unit 11 returns to the process in step S22. If it determines that the print job has finished (step S27: YES), the control unit 11 terminates the process.

[0127] (Step S41) If it is determined in step S25 that paper 90 is unsuitable (step S25: YES), the control unit 11 stops the execution of the print job and terminates the process. Specifically, it ejects the paper 90 that has been determined to be unsuitable into the output tray 42 without performing image formation. It then stops the transport of subsequent sheets of paper 90.

[0128] (Steps S31, S32) When a double feed is detected in step S23 (step S23: YES), the control unit 11 causes the paper 90 to be transported from the transport path 341 to the branch path 342 via the branch s1. At this time, the control unit 11, for example, continues transporting the paper 90 in which a double feed was detected, and executes the process of step S33 without causing the first detection unit 35 and the second detection unit 37 to detect characteristic information of the paper 90.

[0129] (Step S33) The control unit 11 discharges the paper 90 that has been transported along the branch path 342 into the purge tray 349. After this, the control unit 31 proceeds to the process in step S27.

[0130] Furthermore, if it is determined in step S25 that the paper 90 is an inappropriate paper, the control unit 11 may transport the paper 90 to the branch path 342 and purge it.

[0131] <Effects of the transport device 50 and the image forming system 1> The transport device 50 and image forming system 1000 according to this embodiment have a control unit 31, so that the paper 90 for which double feeding has been detected and the paper 90 for which characteristic information has been detected by the first detection unit 35 and the second detection unit 37 are purged via a shared branch path 342. This branch path 342 is configured not to pass through the image forming unit 13. Therefore, it is possible to prevent malfunctions in the image forming unit 13 caused by unsuitable paper 90 and to suppress the increase in size of the device. Specifically, since there are no discharge paths provided for detection by the first detection unit 35 and the second detection unit 37, the increase in size of the device is suppressed. The effects of this will be explained below.

[0132] When paper is fed from the paper tray into the transport path, double feeding can occur. In a double-feed state, that is, when multiple sheets of paper are stacked on top of each other, it is not possible to form a proper image. Furthermore, if double-feed paper is transported to the image forming unit, problems such as jams may occur. By switching the transport path of paper that has been detected as double-feeded and ejecting it before it is transported to the image forming unit, the occurrence of such problems can be suppressed.

[0133] Furthermore, by using a media sensor to detect characteristic information about the paper's properties, it becomes possible to appropriately set image formation conditions according to the paper's characteristics. After the detection of characteristic information by the media sensor, the paper may change or deform. For example, with a resistance sensor, the paper may become charged, and with a stiffness sensor, the paper may fold or bend. If such changed or deformed paper is transported to the image formation unit, it may result in a decrease in the quality of the formed image and problems such as jams. By ejecting paper whose characteristic information has been detected by the media sensor without transporting it to the image formation unit, the occurrence of such problems can be suppressed.

[0134] In this case, when combining the conventional paper output paths with the above-mentioned paper output, one possible configuration is to provide separate output paths for paper where double feeding is detected and for paper whose characteristic information is detected by the media sensor. However, this configuration requires space to install multiple paper output paths within the device, which tends to make the device larger.

[0135] In contrast, in this embodiment, in the transport device 50 and the image forming system 1000, both the paper 90 for which a double feed has been detected by the double feed detection unit 26 and the paper 90 for which characteristic information has been detected by the first detection unit 35 and the second detection unit 37 are discharged to the purge tray 349 via a common branching path 342. That is, the discharge path for the paper 90 for which a double feed has been detected and the discharge path for the paper 90 for which characteristic information has been detected are shared. Therefore, it is possible to realize a compact transport device 50 and image forming system 1000 with fewer problems.

[0136] Furthermore, when a double feed is detected by the double feed detection unit 26, the paper 90 is ejected to the purge tray 349 without its characteristic information being detected by the first detection unit 35 and the second detection unit 37. This is because it is difficult to accurately detect the characteristic information of the paper 90 when it is in a double feed state. In addition, when a double feed is detected by the double feed detection unit 26, the transport of the paper 90 can be continued, allowing for high-speed purging.

[0137] The configuration of the transport device 50 and the image forming system 1000 equipped therewith described above is merely a description of the main configuration in order to explain the features of the above embodiment, and is not limited to the above configuration, and can be modified in various ways within the scope of the claims. Furthermore, it does not exclude the configurations that are generally found in image forming apparatuses.

[0138] For example, the first detection unit 35 and the second detection unit 37 each only need to have at least one media sensor. The first detection unit 35 may have media sensors other than a size sensor, paper thickness sensor, basis weight sensor, and moisture content sensor. The second detection unit 37 may have media sensors other than a stiffness sensor, surface quality sensor, and resistance sensor.

[0139] Furthermore, although the above embodiment describes an example in which the double-feed detection unit 26 detects double feeding of paper 90 using ultrasound, the double-feed detection unit 26 may have other configurations. The double-feed detection unit 26 may, for example, detect double feeding of paper 90 based on the length of paper 90 being transported along the transport path 341. In this case, the double-feed detection unit 26 may include, for example, a line sensor.

[0140] Furthermore, although the above embodiment describes an example in which the conveying device 50 has a first detection unit 35 and a second detection unit 37, the conveying device 50 may have only one of the first detection unit 35 and the second detection unit 37. The conveying device 50 may also have other detection units.

[0141] Furthermore, in the first embodiment described above, an example was described in which paper 90 for which characteristic information has been detected by the first detection unit 35 and the second detection unit 37 is discharged to the purge tray 349 via the branching path 342. However, paper 90 for which characteristic information has been detected by the first detection unit 35 but not by the second detection unit 37 may be discharged to the purge tray 349 via the branching path 342. Alternatively, paper 90 for which characteristic information has not been detected by the first detection unit 35 but has been detected by the second detection unit 37 may be discharged to the purge tray 349 via the branching path 342.

[0142] Furthermore, the means and methods for performing various processing in the transport device 50 and image forming system 1000 according to the above embodiment can be implemented by either a dedicated hardware circuit or a programmed computer. The program may be provided, for example, on a computer-readable recording medium such as a USB memory or DVD-ROM, or it may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. The program may also be provided as a standalone application software, or it may be incorporated into the software of the device as a function of the device.

[0143] While embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for illustrative purposes only and are not limiting. The scope of the present invention should be interpreted in accordance with the language of the appended claims. [Explanation of Symbols]

[0144] 1000 Image Forming Systems 10 Image forming apparatus 11 Control Unit 13 Image forming unit 20 Paper feeding mechanism 26 Double feed detection unit 30. Paper characteristics detection mechanism 31 Control Unit 32 Storage section 34 Conveying section 341 Transport Route 342 Branch Routes 349 Purge Tray s1 Branch section 35 First detection unit 351 Size Sensor 352 Paper Thickness Sensor 353 basis weight sensor 354 Moisture content sensor 37 Second detection unit 371 Stiffness Sensor 372 Surface Sensor 373 Resistance Sensor 38 Environmental Sensors 39 Communications Department 50 Conveying device

Claims

1. A transport path for transporting recording material supplied from the recording material supply unit to the image forming unit, A double-feed detection unit that detects double feeding of the recording material supplied from the recording material supply unit, A media sensor that detects characteristic information corresponding to the characteristics of the recording material, The transport path includes a branch path that branches off from the transport path at a branching point on the transport path and purges the recording material whose characteristic information has been detected by the media sensor without passing through the image forming unit. A transport device in which, when a double feed is detected by the double feed detection unit, the recording material is purged via the branched path.

2. The transport device according to claim 1, wherein the branching section is located upstream of the image forming section in the transport direction of the recording material.

3. The transport device according to claim 1, wherein the branching path is arranged between the recording material supply unit and the image forming unit.

4. The transport device according to claim 1, further comprising a tray on which the recording material purged via the branching path can be placed.

5. The transport device according to claim 1, wherein the media sensor is arranged on the branch path.

6. The transport device according to claim 5, wherein the media sensor includes a contact-type sensor that contacts the recording material to detect the characteristic information.

7. The transport device according to claim 5, wherein the media sensor includes at least one of a sensor that detects characteristic information by applying a voltage to the recording material and a sensor that detects characteristic information by pressing the recording material.

8. The transport device according to claim 5, wherein the media sensor includes at least one of a sensor that detects characteristic information corresponding to the resistance of the recording material, a sensor that detects characteristic information corresponding to the rigidity of the recording material, and a sensor that detects characteristic information corresponding to the smoothness of the recording material.

9. The transport device according to claim 1, wherein the media sensor is positioned upstream of the branching portion in the transport direction of the recording material.

10. The transport device according to claim 9, wherein the media sensor includes a non-contact sensor that detects the characteristic information without contacting the recording material.

11. The conveying device according to claim 9, wherein the media sensor includes at least one of a sensor that detects characteristic information corresponding to the basis weight of the recording material, a sensor that detects characteristic information corresponding to the thickness of the recording material, and a sensor that detects characteristic information corresponding to the moisture content of the recording material.

12. The transport device according to claim 1, wherein the double-feed detection unit is positioned upstream of the media sensor in the transport direction of the recording material.

13. The conveying device according to claim 12, wherein the double-feed detection unit is located upstream of the branching unit in the conveying direction of the recording material.

14. Furthermore, the transport device according to claim 1, further comprising a control unit that controls the media sensor based on the detection result of the double-feed detection unit.

15. The transport device according to claim 14, wherein the control unit acquires the characteristic information of the recording material for which double feeding was not detected, and controls the image forming unit based on the acquired characteristic information.

16. The transport device according to claim 14, wherein the control unit does not perform detection of the characteristic information by the media sensor or does not acquire the characteristic information for the recording material in which double feeding has been detected.

17. The control unit controls the transport of the recording material, The transport device according to claim 14, wherein when the media sensor detects the characteristic information of the recording material, the control unit stops transporting the recording material for which the characteristic information has been detected.

18. The transport device according to claim 17, wherein the control unit transports the recording material for which double feeding has been detected without stopping it at a position corresponding to the media sensor on the branch path.

19. The control unit controls the transport of the recording material, The transport device according to claim 14, wherein when the media sensor detects the characteristic information of the recording material, the control unit continues transporting the recording material for which the characteristic information has been detected.

20. The conveying device according to claim 1, The recording material supply unit, The image forming unit and An image forming system comprising the following features.

Images