Paper characteristic detection device and image forming system

Abstract

To suppress deterioration in reliability in image forming.SOLUTION: A sheet characteristic detection device 30 includes: a first conveyance passage 341 where a sheet is conveyed; a second conveyance passage 342 which branches from the first conveyance passage 341 and in which the sheet that is purged is conveyed, without going through an image forming part 13; and a first detection part 35 which is arranged in the first conveyance passage 341, and which can detect sheet characteristic information corresponding to at least one out of a sheet size, sheet thickness, basis weight and a water content amount.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a paper characteristic detection device and an image forming system. [Background technology]

[0002] In recent years, image forming devices such as electrophotographic printers have come to be widely used in the color printing industry. In the field of PP (production print) corresponding to the color printing industry, there is a demand for adaptability to a wider variety of papers than those used in offices. In order to perform high-quality printing on these various papers, there are image forming devices that set multiple items of paper characteristics stored in a paper feed tray and print under image formation conditions according to the set items.

[0003] In order to set up such a wide variety of paper types, a configuration has been proposed in which a detection unit is placed in the paper transport path to detect characteristics such as the type of paper and physical properties (hereinafter referred to as paper characteristics) (see, for example, Patent Document 1).Furthermore, a configuration has been proposed in which, if the paper characteristics detected by the detection unit differ from the settings, the paper is discharged from the image forming device without forming an image on it (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-128269 A [Patent Document 2] JP 2020-008621 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned image forming apparatus, the paper whose characteristics have been detected is discharged after passing through the image forming unit. ,exampleFor example, when measuring electrical resistance as a paper characteristic in the detection unit, the paper may be charged. For example, if the paper is an insulator, the surface electrical resistance is 10 10 ~10 12 In this case, the residual potential of the paper is not discharged in a short time, the paper sticks in the image forming section, and the transfer of the charge, which is important in the electrophotographic process, is not performed correctly. This may cause a decrease in the reliability of the image forming operation in the image forming section.

[0006] The present invention has been made in consideration of the above circumstances, and provides a paper transport device and an image forming system that are capable of suppressing a decrease in reliability during image formation. [Means for solving the problem]

[0007] The above object of the present invention can be achieved by the following means.

[0008] (1) a first transport path along which paper is transported; a second conveying path that branches off from the first conveying path and conveys the paper to be purged without passing through an image forming unit; a first detection unit disposed on the first transport path and capable of detecting paper characteristic information corresponding to at least one of a size, a thickness, a basis weight, and a moisture content of the paper; A paper characteristic detection device comprising: (2) a first transport path along which paper is transported; a second conveying path that branches off from the first conveying path and conveys the paper to be purged without passing through an image forming unit; a first detection unit that is disposed on the first transport path and is capable of detecting paper characteristic information corresponding to paper characteristics of the paper while transporting the paper; A paper characteristic detection device comprising:

[0009] ( 3 2. The paper characteristic detection device according to claim 1, wherein the first detection unit detects the paper characteristic information while conveying the paper.

[0010] ( 4 2. The paper characteristic detection device according to claim 1, wherein the first detection unit detects paper characteristic information of each of a plurality of sheets of paper that are continuously conveyed.

[0011] ( 5 2. The paper characteristic detection device according to claim 1, wherein the first detection unit detects paper characteristic information corresponding to at least one of the type of paper or a change in the state of the paper.

[0012] ( 6 ) The paper characteristic detection device described in (1) or (2) above, wherein the first detection unit is equipped with at least one of a size sensor, a paper thickness sensor, a basis weight sensor, and a moisture content sensor capable of detecting paper characteristic information corresponding to size, paper thickness, basis weight, and moisture content, respectively.

[0013] ( 7 ) The first detection unit includes the moisture sensor. 6 ) A paper characteristic detection device as described above.

[0014] ( 8 ) The first detection unit includes at least one of the basis weight sensor, the paper thickness sensor, and the basis weight sensor. 6 ) A paper characteristic detection device as described above.

[0015] ( 9 ) the first detection unit includes the paper thickness sensor, the basis weight sensor, and the moisture sensor, In the first conveying path, the basis weight sensor and the moisture sensor are disposed downstream of the paper thickness sensor. 6 ) A paper characteristic detection device as described above.

[0016] ( 10 the first detection unit includes the moisture sensor and the basis weight sensor, In the first conveying path, the moisture sensor and the basis weight sensor are disposed at different positions in a width direction perpendicular to the conveying direction at the same position in the conveying direction. 6 ) A paper characteristic detection device as described above.

[0017] ( 11) the first detection unit includes the size sensor and another sensor corresponding to other paper characteristic information different from the size, In the first transport path, the size sensor is disposed upstream of the other sensors. 6 ) A paper characteristic detection device as described above.

[0018] ( 12 ) The size sensor is an image sensor, and is capable of detecting the size of the paper in the conveying direction and the width direction based on the read image data obtained by reading the paper being conveyed. 6 ) A paper characteristic detection device as described above. (13) The paper characteristic detection device according to (1) or (2), wherein the first detection unit is disposed upstream of a branch point of the first transport path and the second transport path.

[0019] ( 14 ) The paper characteristic detection device described in (1) or (2) above, further comprising a second detection unit arranged on the second transport path and capable of detecting paper characteristic information corresponding to at least one of the stiffness, surface properties, and resistance of the paper.

[0020] ( 15 ) Located on the second transport path, The paper characteristic information is detected by stopping the paper being transported on the second transport path, or the paper characteristic information is detected while the paper is being transported at a transport speed slower than the transport speed on the first transport path. The above (1) or (2) further comprising a second detection unit. The paper characteristic detection device according to claim 1 .

[0021] ( 16 the second detection unit includes at least one of a stiffness sensor, a surface property sensor, and a resistance sensor capable of detecting sheet characteristic information corresponding to stiffness, surface property, and resistance of the sheet, respectively; The sensor of the second detection unit detects the paper characteristic information by stopping the paper conveyed on the second conveying path. 14 ) A paper characteristic detection device as described above.

[0022] ( 17 the second detection unit includes at least one of the rigidity sensor and the surface property sensor, and the resistance sensor; In the second transport path, at least one of the stiffness sensor and the surface property sensor is disposed upstream of the resistance sensor. 16 ) A paper characteristic detection device as described above.

[0023] ( 18 the second detection unit includes the stiffness sensor and the surface property sensor, In the second transport path, the stiffness sensor is disposed upstream of the surface property sensor. 16 ) A paper characteristic detection device as described above.

[0024] ( 19 ) a moisture sensor that detects paper characteristic information corresponding to the moisture amount of the paper and a resistance sensor that detects paper characteristic information corresponding to the resistance of the paper are disposed in at least one of the first transport path and the second transport path, and the moisture sensor is disposed upstream of the resistance sensor; 14 ) A paper characteristic detection device as described above.

[0025] ( 20 ) An environmental sensor for measuring the surrounding environment; The detection result of the paper characteristic information is corrected according to the detection value of the environment sensor. 14 ) A paper characteristic detection device as described above.

[0026] ( 21 The first transport path is a transport path connected to the image forming unit, as described above in (1). Or (2) above The paper characteristic detection device according to claim 1 .

[0027] ( 22 The second detection unit includes the stiffness sensor, The stiffness sensor is disposed on the second transport path which faces upward in the vertical direction, and includes a pressing section which presses the rear end portion, which is now a free end, of the stopped paper from a side direction, and a pressure detection section which detects the pressing force of the pressing section on the paper. the above( 16 ) A paper characteristic detection device as described above.

[0028] ( 23 ) the second detection unit includes the resistance sensor, The resistance sensor includes a pair of rollers that contact the front and back sides of the paper, respectively, and measures the resistance of the paper by applying a voltage between the pair of rollers and measuring the current that flows. 16 ) A paper characteristic detection device as described above.

[0029] ( 24 ) the first detection unit includes the moisture sensor, The moisture sensor includes a first light emitting unit and a second light emitting unit that irradiate the surface of the paper with light of a predetermined wavelength, and a light receiving unit that receives light reflected from the surface of the paper in response to the light of each wavelength. 6 ) A paper characteristic detection device as described above.

[0030] ( 25 )(1) above Or (2) above and an image forming apparatus including the image forming unit, the image forming device is disposed downstream of the first transport path; Image forming system.

[0031] ( 26 ) A paper feeder having a paper feed unit that supplies paper and a conveying unit, The above-mentioned ( 25 ) An image forming system according to the present invention. Effect of the Invention

[0032] The paper characteristic detection device according to the present invention includes a first transport path along which paper is transported, a second transport path that branches off from the first transport path and transports paper to be purged without passing through an image forming unit, and a first detection unit that is disposed on the first transport path and is capable of detecting paper characteristic information corresponding to at least one of the paper size, paper thickness, basis weight, and moisture content. In this way, it is possible to suppress a decrease in reliability during image formation. [Brief description of the drawings]

[0033] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming apparatus including a paper characteristic detection device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a block diagram of an image forming apparatus. [Diagram 3] FIG. 2 is a block diagram of a paper characteristic detection device. [Figure 4] FIG. 2 is a diagram illustrating a schematic configuration of a paper characteristic detection device. [Diagram 5] FIG. 4 is a diagram showing the positions of a basis weight sensor and a moisture percentage sensor. [Figure 6] FIG. 2 is a diagram showing a schematic configuration of a size sensor. [Figure 7] FIG. 2 is a diagram showing a schematic configuration of a paper thickness sensor. [Figure 8] FIG. 2 is a diagram showing a schematic configuration of a basis weight sensor. [Figure 9] FIG. 2 is a diagram showing a schematic configuration of a moisture percentage sensor. [Figure 10] FIG. 2 is a diagram showing a schematic configuration of a stiffness sensor. [Figure 11] FIG. 1 is a diagram showing a schematic configuration of a surface sensor. [Figure 12] FIG. 1 is a diagram showing a schematic configuration of a resistance sensor. [Figure 13] FIG. 13 is a schematic diagram showing a control parameter determination method. [Figure 14] 3 is a diagram for explaining quality items in each process of the image forming processing and paper characteristics related to each quality item. FIG. [Figure 15] 10 is a flowchart showing a paper characteristic detection process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. However, the scope of the present invention is not limited to the disclosed embodiment. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted. In addition, the dimensional ratios of the drawings are exaggerated for convenience of description, and may differ from the actual ratios. In the drawings, the up-down direction (vertical direction) is the Z direction, the front and back directions of the image forming system or the paper characteristic detection 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 conveying direction. The Y direction is also called the width direction. In this embodiment, the paper includes printing paper (hereinafter simply called paper) and various films. In particular, the paper includes those manufactured using mechanical pulp and / or chemical pulp derived from plants. In addition, the types of paper include coated gloss paper and matte paper, and uncoated plain paper and fine paper.

[0035] Fig. 1 is a diagram showing a schematic configuration of an image forming system 1000 including a paper characteristic detection device 30 according to this embodiment. Fig. 2 is a block diagram showing a hardware configuration of the image forming system 1000. As shown in Fig. 1, the image forming system 1000 includes an image forming device 10, a paper feeder 20, a paper characteristic detection device 30, and a post-processing device 40, which are mechanically and electrically connected to each other.

[0036] (Image forming apparatus 10) The image forming apparatus 10 forms an image on paper 90 sent from the upstream paper characteristic detection device 30. The image forming apparatus 10 includes a control unit 11, a storage unit 12, an image forming unit 13, a paper feed conveyance unit 14, an operation panel 15, a printer controller 17, a communication unit 19, etc. These are connected to each other via signal lines such as a bus for exchanging signals.

[0037] (Control unit 11) The control unit 11 is composed of a CPU, ROM, RAM, etc., and executes various processes by executing programs stored in the ROM or in the storage unit 12 described below, and controls each unit of the device and performs various calculation processes according to the programs. The control unit 11 functions as an overall control unit 111, an engine control unit 112, a paper characteristic detection device control unit 113, a post-processing device control unit 114, a paper feeder control unit 115, and a conveyance / image formation control unit 116. The functions of these sub-control units 111 to 116 will be described later.

[0038] (Storage unit 12) The storage unit 12 is made up of auxiliary storage units such as a ROM for storing various programs and data in advance, a RAM for temporarily storing programs and data as a working area, and a hard disk for storing various programs and data. The storage unit 12 also stores information on the paper stored in each paper feed tray. The paper information includes information on the paper brand, size (paper width, paper length), basis weight, and paper type (gloss coated paper, matte coated paper, plain paper, fine paper, rough paper, etc.). The storage unit 12 may also store paper brands, a determination model (determination model algorithm) used to determine control parameters, and a paper profile.

[0039] (Image forming unit 13) The image forming unit 13 forms an image, for example, by an electrophotographic method. The image forming unit 13 includes writing units corresponding to the basic colors of Y (yellow), M (magenta), C (cyan), and K (black), a photosensitive drum, and a developing unit that contains a two-component developer consisting of toner and carrier of each color. The image forming unit 13 further includes an intermediate transfer belt, a secondary transfer unit, and a fixing unit. The toner images formed on the photosensitive drum by the developing units of each color are superimposed on the intermediate transfer belt, and are transferred to the paper 90 conveyed in the secondary transfer unit. The toner image on the paper 90 is fixed onto the paper 90 by being heated and pressed in the fixing unit downstream.

[0040] (Paper feed conveying section 14) The paper feed conveying section 14 includes conveying paths 141 and 142, a plurality of paper feed trays 145, etc. The conveying path 141 includes a plurality of conveying roller pairs provided along the conveying path, and a drive motor (not shown) that drives these conveying roller pairs. The paper feed conveying section 14 includes a feed roller that feeds the uppermost sheet of paper 90 stacked and placed in the paper feed tray 145, and sends the sheets 90 in the paper feed tray one by one to the conveying path on the downstream side. A first conveying path 341 of the paper characteristic detection device 30 is connected to the upstream side of the conveying path 141.

[0041] The paper feed conveying section 14 conveys the paper 90 fed from the paper feed tray 145 or the like. The paper 90 conveyed along the conveying path 141 has an image formed on it by the image forming section 13, and is then discharged onto the paper output tray 41 via the subsequent post-processing device 40. When performing double-sided printing in which an image is also formed on the back side of the paper 90, the paper 90 with an image formed on one side is conveyed to a conveying path 142 for double-sided image formation located at the bottom of the device main body. The paper 90 conveyed to this conveying path 142 is turned over on a switchback path, and then merges with the conveying path 141 for one side, where an image is again formed on the other side of the paper 90 by the image forming section 13.

[0042] (Operation panel 15, etc.) The operation panel 15 is equipped with a touch panel, a numeric keypad, a start button, a stop button, etc., and is used to display the status of the image forming apparatus 10 or the image forming system 1000, and to allow the user to set the type of paper placed in the paper feed tray 145, etc., and to input instructions.

[0043] The printer controller 17 acquires a print job sent from a terminal device such as a PC (personal computer). The print data (image data) described in PDL (Page Description Language) or PDF format included in the print job is rasterized by the printer controller 17 and converted into image data for each page in raster format, which is then temporarily stored in a page memory. The image data from the page memory is read out at a predetermined timing and stored in a buffer, and is output as an exposure signal to the writing unit for each main scanning line in synchronization with the writing timing.

[0044] The communication unit 19 is an interface for communicating with other devices.

[0045] (Sub-control units 111 to 116) When a print job is input, the overall control unit 111 causes the engine control unit 112 to execute the print job based on the print job setting information of the input print job. The print job is input based on instructions sent from the operation panel 15 or an external terminal such as a network-connected PC operated by a user.

[0046] The engine control unit 112 performs processing related to image formation by controlling the post-processing device control unit 114, the paper feeder control unit 115, and the transport / image formation control unit 116. The post-processing device control unit 114 controls the post-processing device 40. Specifically, the post-processing device control unit 114 transmits, to the post-processing device 40, paper transport timing, setting information for post-processing of the transported paper, etc. The paper feeder control unit 115 controls the paper feeder 20. Specifically, the paper feeder control unit 115 communicates with the paper feeder 20 to transmit and receive information on the paper feed tray to be used, the paper transport timing, etc.

[0047] The conveyance / image formation control unit 116 controls the paper feed / conveyance unit 14 (including drive motors for the conveyance paths 141, 142, the fixing unit, etc.) to control the feeding and conveyance of the paper 90. The conveyance / image formation control unit 116 also controls the image forming unit 13, and controls the image formation conditions and the image formation timing according to the paper position.

[0048] The paper characteristic detection device control unit 113 controls the paper characteristic detection device 30 in response to an execution instruction request from the engine control unit 112, and causes various sensors included in the paper characteristic detection device 30 to measure the paper characteristics.

[0049] (Paper feeder 20) As shown in FIG. 1, the paper feeder 20 includes a paper feed conveying section 24. The paper feed conveying section 24 functions as a paper feed section. In addition to the paper feed conveying section 24, the paper feeder 20 also includes a control section, a storage section, and a communication section (none of which are shown), which are connected to each other via signal lines such as a bus for exchanging signals. The paper feed conveying section 24 includes a plurality of paper feed trays 245 and a conveying path 241. The conveying path 241 is connected to a conveying path 341. The paper 90 fed from each paper feed tray 245 and conveyed along the conveying path 241 is conveyed to the paper characteristic detection device 30 on the downstream side, where the paper characteristics are measured, and an image is formed on the paper by the image forming device 10 on the downstream side.

[0050] (Post-processing device 40) The post-processing device 40 performs post-processing on the paper 90 sent from the image forming device 10 and discharges the paper 90 according to the settings of the print job. The post-processing device 40 includes paper output trays 41 and 42, a post-processing unit 43, and a conveying path 441. The post-processing device 40 also includes a control unit, a storage unit, a conveying unit, and a communication unit (none of which are shown), which are connected to each other via signal lines such as a bus for exchanging signals. The paper output trays 41 and 42 are selected according to the settings of the print job. The conveying path 441 is connected to the conveying path 141 on the upstream side. The post-processing unit 43 performs at least one of post-processing, including stapling, punching, cutting, folding, and bookbinding, on the paper 90 on which an image has been formed.

[0051] (Paper characteristic detection device 30) Next, the paper characteristic detection device 30 will be described with reference to Figs. 3 to 12. Fig. 3 is a block diagram of the paper characteristic detection device 30, and Fig. 4 is a diagram showing a schematic configuration of the paper characteristic detection device. The paper characteristic detection device 30 includes 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.

[0052] The control unit 31 has a CPU and a memory, similar to the above-mentioned control unit 11. The control unit 31 controls the operations of the first and second detection units 35 and 37 to detect paper characteristic information corresponding to the paper characteristics of the paper 90.

[0053] The storage unit 32 is made up of auxiliary storage units such as a ROM for storing various programs and data in advance, a RAM for temporarily storing programs and data as a working area, and a hard disk for storing various programs and data. The storage unit 32 also stores an environmental correction table that associates the detection value of the environmental sensor 38 with a correction value. The control unit 31 corrects the detection results of the first and second detection units 35 and 37 according to the detection value of the environmental sensor 38 and the environmental correction table.

[0054] The conveying section 34 includes a first conveying path 341, a second conveying path 342, a purge tray 349 for discharging the paper 90 to be purged, and the like. The first and second conveying paths 341 and 342 include a plurality of pairs of conveying rollers provided along the conveying paths, and a drive motor (not shown) for driving these pairs of conveying rollers. The first conveying path 341 is a main conveying path, and the upstream side is connected to the conveying path 241 of the paper feeder 20, and the downstream side is connected to the conveying path 141 of the image forming device 10. The second conveying path 342 branches off from the first conveying path 341 at a branching point s1. The second conveying path 342 conveys the paper 90 to be purged to the purge tray 349 without passing through the image forming section 13 (arranged in the conveying path 141). The first conveying path 341 extends in a substantially horizontal direction. At least a part of the second conveying path 342 extends in a substantially vertical direction. In particular, in the region where the stiffness sensor 371 described below is disposed, the second transport path 342 extends in a substantially vertical direction, and the transport direction of the paper is upward. Here, substantially vertical indicates that it is in the range of 90±1°. Note that the entire second transport path 342 does not have to be a straight line. As long as at least the measurement region of the stiffness sensor 371 of the second transport path 342 is straight, the other paths may be partially curved. For example, the second transport path 342 may be a curved transport path that is S-shaped overall.

[0055] 1 and 4, the first detection unit 35 is disposed on the first transport path 341 and detects the paper characteristics of the paper 90 transported on the first transport path 341, with the first transport path 341 as a detection area. In particular, the first detection unit 35 is disposed on the first transport path 341, upstream of the branching portion s1. The second detection unit 37 is disposed on the second transport path 342, downstream of the branching portion s1.

[0056] As shown in FIG. 3 and FIG. 4, the first detection unit 35 includes a size sensor 351, a paper thickness sensor 352, a basis weight sensor 353, and a moisture percentage sensor 354. These sensors may provide paper characteristic information such as a characteristic value or physical property value of the paper itself or a value that indicates the characteristic, such as a current or voltage of a sensor corresponding to the characteristic value or physical property value. As shown in FIG. 4, the basis weight sensor 353 and the moisture percentage sensor 354 are disposed downstream of the paper thickness sensor 352 in the first conveying path 341. FIG. 5 is a diagram showing the arrangement positions of the basis weight sensor 353 and the moisture percentage sensor 354. As shown in FIG. 5, the basis weight sensor 353 and the moisture percentage sensor 354 are disposed side by side at different positions in the width direction (Y direction) at the same position in the conveying direction (X direction) in the first conveying path 341. In this way, the length of the first detection unit 35 in the conveying direction as a whole can be shortened, and space can be reduced. Furthermore, in the first conveying path 341, the size sensor 351 is disposed upstream of the other sensors. That is, the size sensor 351 is disposed upstream of the other sensors, namely, the paper thickness sensor 352, the basis weight sensor 353, and the moisture percentage sensor 354. Normally, before the image is transferred onto the paper 90 by the image forming unit 13, the leading edge of the paper is stopped and the paper is made to wait temporarily, but by disposing the size sensor 351 upstream of the other sensors, the distance between the size sensor 351 and the image forming unit 13 can be made wider, and the paper 90 can be prevented from being stopped in the middle of detection by the size sensor 351.

[0057] (Positional Arrangement of Sensors in First Detection Unit 35) The size sensor 351, the paper thickness sensor 352, the basis weight sensor 353, and the moisture percentage sensor 354 of the first detection unit 35 detect paper characteristic information corresponding to the size, paper thickness, basis weight, and moisture percentage while conveying the paper 90 conveyed on the first conveying path 341 without stopping it. In this way, when executing a print job in which continuous printing is performed, the first detection unit 35 can detect the paper characteristic information of each of the multiple sheets of paper 90 conveyed continuously. In other words, the first detection unit 35 can detect the paper characteristic information of all the sheets. Among them, the paper characteristic information of the size, paper thickness, and basis weight is paper characteristic information corresponding to the paper type (paper type), and the paper characteristic information of the moisture percentage is paper characteristic information corresponding to a change in the state of the paper 90.

[0058] In this way, the first detection unit 35 detects the paper type of the paper 90 or the paper characteristic information corresponding to the change in the paper condition every time. This allows appropriate detection of cases where the type of paper 90 loaded in the paper feed tray is different from the print job settings, where incorrect paper is mixed in the paper stack (mainly related to basis weight, thickness, and size), where the paper condition changes during continuous printing, or where the paper stack contains paper whose paper condition is not uniform (mainly related to moisture content) (hereinafter, referred to as inappropriate paper). Then, as described later, in the paper characteristic detection device 30, when the first detection unit 35 detects an inappropriate paper 90, the paper 90 is switched to a purge path (second conveying path 342) and conveyed to a purge tray 349. In this way, the inappropriate paper is not sent to the subsequent stage, and jams and image defects can be prevented in the image forming device 10, the post-processing device 40, etc.

[0059] Also, the size sensor 351 is disposed on the most upstream side. In principle, the size sensor 351 cannot determine the size of the paper 90 until it passes the detection position (photographing position). Therefore, the size sensor 351 needs to be disposed upstream of the image forming position of the image forming unit 13 (more specifically, the stopping position of the registration rollers) by the length of the longest paper that the image forming system 1000 can handle (e.g., long paper of about 900 mm). Therefore, the size sensor 351 is disposed on the most upstream side of the first conveying path 341.

[0060] Moreover, the paper thickness sensor 352 is disposed second from the upstream side. By detecting the thickness of the paper 90 first, the paper characteristic detection device 30 can appropriately set the measurement range (latitude), measurement conditions, etc., when the subsequent basis weight sensor 353 and moisture percentage sensor 354 detect the thickness.

[0061] (Positional Arrangement of Sensors in Second Detection Unit 37) As shown in FIG. 3 and FIG. 4, the second detection unit 37 includes a stiffness sensor 371, a surface property sensor 372, and a resistance sensor 373. These sensors may provide, as the paper characteristic information, a characteristic value or physical property value of the paper itself, or a value that indicates the characteristic, such as a current or voltage of a sensor corresponding to the characteristic value or physical property value. As shown in FIG. 4, the stiffness sensor 371 and the surface property sensor 372 are disposed upstream (below) of the resistance sensor 373 in the second conveying path 342. Note that, in the example shown in FIG. 4, the stiffness sensor 371 and the surface property sensor 372 are disposed in this order in the conveying direction (Z direction), but this order may be reversed. In addition, for reasons to be described below, the size sensor 351 is disposed upstream of the moisture content sensor 354 in the path from the first conveying path 341 to the second conveying path 342.

[0062] During detection, the resistance sensor 373 applies a high voltage to the paper 90 and causes a current to flow through the paper 90. Therefore, after the resistance is detected, the surface of the paper 90 may accumulate electric charge and become statically charged (particularly in a low humidity environment). Since there is a risk that the stiffness detection cannot be performed accurately with a statically charged paper 90, the stiffness sensor 371 is disposed upstream (below) of the resistance sensor 373. In addition, there is a risk that the moisture content of the paper 90 may change due to the slight heating caused by passing a current through the paper 90 during detection by the resistance sensor 373. To eliminate this effect, the moisture content sensor 354 is disposed upstream of the resistance sensor 373 (first transport path 341).

[0063] The second detection unit 37 stops the paper at each sensor position, performs detection, and sends the paper 90 to the next sensor downstream. The next sensor performs measurement when the rear end of the paper is not clamped by the components (rollers, etc.) of the previous sensor (leaving the end open makes it easier for the components of the sensor to press the paper to fix the surface). If the length (length in the conveying direction) of the paper 90 is sufficient, for example, if it is longer than A4 size, the paper 90 can be positioned across the detection positions of the three sensors. Therefore, the second detection unit 37 can simultaneously perform resistance detection by the resistance sensor 373, surface property detection by the surface property sensor 372, and stiffness detection by the stiffness sensor 371 with a single stop, minimizing the decrease in productivity.

[0064] (First detection unit 35) Hereinafter, with reference to Figs. 6 to 9, configuration examples of the size sensor 351, paper thickness sensor 352, basis weight sensor 353, and moisture percentage sensor 354 will be described. As described above, these sensors 351 to 354 detect paper characteristic information corresponding to the size, paper thickness, basis weight, and moisture percentage while conveying the paper 90 conveyed along the first conveying path 341 without stopping it. In particular, these sensors 351 to 354 detect the paper characteristic information while conveying the paper 90 at the conveying speed during image formation (hereinafter also referred to as the normal conveying speed). In this way, the paper characteristic information for all sheets of paper 90 is detected without reducing productivity.

[0065] (Size Sensor 351) The size sensor 351 optically detects the size (shape) of the paper 90. The size sensor 351 is, for example, one or two image sensors. FIG. 6 is a diagram showing a schematic configuration of the size sensor 351. In the example shown in FIG. 6, the size sensor 351 is two line sensors 511 and 512, and each of the line sensors 511 and 512 is an image sensor in which photoelectric conversion elements composed of CIS (Contact Image Sensor) or the like are arranged in one or more lines, and reads a one-dimensional image. The line sensor 171 also has optical elements such as light-emitting elements and lens arrays arranged along the line of the photoelectric conversion elements. The light-emitting elements irradiate uniform light in the extension direction of the line toward the paper 90 on the first transport path 341. In the example shown in FIG. 6, each of the line sensors 511 and 512 has a length in the longitudinal direction of 200 to 300 mm. These line sensors 511 are arranged adjacent to each other in the transport direction (X direction) so as to overlap in the width direction (Y direction). As a result, the entire width of the conveyed paper 90 is read, even when the paper 90 has a width such as A3+ size. The paper 90 conveyed at a predetermined conveying speed is read by both line sensors 511 and 512 to generate read image data. The control unit 31 detects the edges (positions of the four sides or the outer shape) of the paper 90 by image processing the obtained read image data for one sheet of paper 90, and detects the size (shape). The control unit 31 may detect the shape and size of the paper 90 by processing each of the two read image data obtained from the two sensors 511 and 512. Alternatively, the control unit 31 may detect the shape and size of the paper 90 by synthesizing the two read image data into one and processing it. In addition, in the example shown in FIG. 6, the two sensors 511 and 512 are arranged to overlap each other in the width direction, but one large-sized sensor may be used to correspond to the size of the paper such as A3+ size.

[0066] (Paper thickness sensor 352) FIG. 7 is a diagram showing a schematic configuration of the paper thickness sensor 352. The paper thickness sensor 352 detects the thickness of the paper 90 by mechanically measuring the amount of displacement. As the paper 90 is transported to the nip of the transport roller pair 521, the axial position of one of the driven 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. The transport roller pair 521 is made up of two rollers, the lower one of which is a fixed (axial center is fixed) drive roller, and the upper one is a driven roller that is biased toward the drive roller so as to be able to move toward and away from the drive roller. The height of the upper roller is detected by a displacement sensor. The displacement sensor is composed of an actuator (detection lever) that contacts the upper roller shaft and an encoder that measures the amount of rotation of this actuator. For example, the paper thickness (microns) is output from the paper thickness sensor 352 as the measurement result of the paper thickness.

[0067] (Basis weight sensor 353) 8 is a diagram showing a schematic configuration of the basis weight sensor 353. The basis weight sensor 353 is a transmission and reflection type optical sensor that detects the basis weight of the paper, and includes a light emitting section and a light receiving section, and detects the basis weight of the paper 90 by measuring the amount of attenuation (transmittance) of light that passes through the paper 90 and the amount of reflected light.

[0068] As shown in FIG. 8, the basis weight sensor 353 includes a plurality of light-emitting units 531 and a single light-receiving unit 532. The light-emitting unit 531 includes a first light-emitting unit 531a, a second light-emitting unit 531b, and a third light-emitting unit 531c. The first, second, and third light-emitting units respectively irradiate the irradiation area with first, second, and third irradiation light. This irradiation area (second irradiation area) is an inner area of ​​the opening a12 when viewed from the Z direction. The opening a12 is provided in the upper guide plate 3411. The lower guide plate 3412 also has an opening a22 at a position opposite the opening a12. The openings a12 and a22 have the same shape, for example, a rectangle. In order to prevent foreign matter such as paper dust from the paper 90 passing through the first transport path 341 from adhering to the openings a12 and a22, transparent sheets 534a and 534b made of PET or the like that transmit the wavelengths of each irradiation light are attached.

[0069] The first light-emitting unit 531a emits a first irradiation light having a first wavelength. The first wavelength is, for example, a near-infrared wavelength longer than the wavelength of visible light. More specifically, the first wavelength includes, for example, a wavelength between 750 nm and 900 nm. The second light-emitting unit 531b emits a second irradiation light having a second wavelength. The second wavelength is, for example, a wavelength of blue light included in visible light. More specifically, the second wavelength includes, for example, a wavelength between 400 nm and 470 nm. The first light-emitting unit 531a and the second light-emitting unit 531b are both disposed on the opposite side of the first transport path 341 from the light-receiving unit 532, and the third light-emitting unit 531c is disposed on the same side as the light-receiving unit 532 and in the vicinity of the light-receiving unit 532. The third light-emitting unit 531c emits a third irradiation light having a third wavelength toward the irradiation area (opening a12). The third wavelength is, for example, a wavelength of green light among visible light. More specifically, the third wavelength includes, for example, a wavelength between 495 nm and 570 nm. The third wavelength is a wavelength different from the first wavelength (for example, a wavelength between 750 nm and 900 nm) and the second wavelength (for example, 400 nm to 470 nm).

[0070] The third irradiation light is irradiated toward the first transport path 341 inside the upper and lower guide plates 3411 and 3412. A reflecting portion 533 is provided on the inside of the lower guide plate 3412 provided near the first light emitting portion 531a and the second light emitting portion 531b. The reflecting portion 533 is painted, for example, in green, the same color as the third irradiation light, and reflects the third irradiation light. Note that the reflecting portion 533 does not reflect the first irradiation light (near-infrared rays) and the second irradiation light (blue light rays), which are not the same color.

[0071] In this embodiment, the control unit 31 controls the first light emitting unit 531a and the second light emitting unit 531b during measurement to irradiate the first irradiation light and the second irradiation light at different timings. The light receiving unit 532 receives the first irradiation light and the second irradiation light, detects the amount of light of each irradiation light, and outputs the detected amount of light of the first irradiation light and the second irradiation light to the control unit 31. Similarly, the control unit 31 irradiates the paper 90 transported to the position of the opening a12 with the first irradiation light and the second irradiation light. The light receiving unit 532 receives the transmitted light (first transmitted light, second transmitted light) of the first irradiation light and the second irradiation light, detects the amount of light of each irradiation light, and outputs the detected amount of light of the first transmitted light and the second transmitted light to the control unit 31. That is, the light receiving section 532 detects the first irradiated light and the second irradiated light when the paper 90 is not present, and the first transmitted light and the second transmitted light when the paper 90 is present in the opening a12.

[0072] Similarly, with respect to the third light-emitting element 531c, the light-receiving element 532 detects a first reflected light reflected by the reflecting element 533 when no paper 90 is present, and a second reflected light reflected by the surface of the paper 90 when the paper 90 is in the opening a12.

[0073] The control unit 31 calculates a first transmittance by dividing the amount of the first transmitted light by the amount of the first irradiated light. Similarly, the control unit 31 calculates a second transmittance by dividing the amount of the second transmitted light by the amount of the second irradiated light. Then, the type of the paper 90 is determined based on the first and second transmittances and the determination criteria stored in the memory unit 12.

[0074] Furthermore, in addition to the first and second transmittances, the control unit 31 may divide the amount of light of the second reflected light by the amount of light of the first reflected light to calculate the reflectance, and may take this reflectance into consideration when determining the type of paper 90. Although the third light-emitting unit 531c and the reflecting unit 533 are provided in this embodiment, they may be omitted.

[0075] (Moisture Sensor 354) 9 is a diagram showing a schematic configuration of the moisture sensor 354. The moisture sensor 354 measures the moisture content of the paper 90. Note that in this embodiment, a moisture sensor that measures the moisture content of the paper is described as an example of paper characteristic information, but a moisture amount sensor that measures the amount of moisture contained in the paper as paper characteristic information may also be applied.

[0076] 9, the moisture percentage sensor 354 includes 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 and 546. The first light-emitting unit 541 and the second light-emitting unit 542 are light-emitting units that irradiate light toward the paper.

[0077] The first light emitter 541 emits first near-infrared light (reference light) in a specific wavelength band toward the paper P. A specific example of the first light emitter 541 is an LED (Light Emitting Diode) or the like. The first near-infrared light is light whose absorption rate in the paper P when reflected by the paper P is not dependent on the moisture content of the paper P. The light receiver 543 receives the first near-infrared light emitted from the first light emitter 541 and reflected by the paper P via a lens 545 via a lens 546. The light receiver 543 outputs information on the first amount of received light, which is the amount of the reflected first near-infrared light received, to the control unit 31. A specific example of the light receiver 543 is a CCD (Charge-Coupled Device) or a CMOS image sensor (Complementary metal-oxide-semiconductor), or the like.

[0078] The second light emitter 542 emits second near-infrared light in a specific wavelength band toward the paper P. A specific example of the second light emitter 542 is an LED or the like. The second near-infrared light is light whose absorptivity in the paper P when reflected by the paper P varies depending on the moisture content of the paper P. The light receiver 543 receives, via a lens 546, the second near-infrared light emitted from the second light emitter 542 and reflected by the paper P via a lens 545. The light receiver 543 then outputs information on a second amount of received light, which is the amount of the reflected second near-infrared light received, to the control unit 31.

[0079] That is, the first light-emitting unit 541 and the second light-emitting unit 542 emit light of wavelengths that are absorbed by moisture in the paper at different rates. The second near-infrared light emitted by the second light-emitting unit 542 has a wavelength that is absorbed by moisture in the paper at a higher rate than the first near-infrared light (reference light) emitted by the first light-emitting unit 541.

[0080] The control unit 31 determines the moisture percentage of the paper based on the ratio between the first amount of received light and the second amount of received light (the ratio between the output of the light receiving unit 543 for the first near-infrared light and the second near-infrared light). The higher the moisture percentage of the paper, the greater the amount of absorbed second near-infrared light, and therefore the smaller the amount of second received light. Therefore, the control unit 31 can correspond the ratio between the first amount of received light and the second amount of received light to the moisture percentage of the paper based on a relational expression or table that indicates the relationship between the moisture percentage of the paper and the ratio between the first amount of received light and the second amount of received light, and calculate the moisture percentage of the paper from the ratio between the first amount of received light and the second amount of received light.

[0081] (Second detection unit 37) 10 to 12, configuration examples of the stiffness sensor 371, the surface property sensor 372, and the resistance sensor 373 will be described below. These sensors 371 to 373 detect sheet characteristic information corresponding to stiffness, surface property, and electrical resistance while stopping the sheet 90 transported on the second transport path 342 or transporting the sheet at a speed slower than the normal transport speed.

[0082] (Rigidity Sensor 371) 10 is a diagram showing a schematic configuration of the stiffness sensor 371. The stiffness sensor 371 detects the stiffness of the paper 90 by mechanically measuring the amount of displacement.

[0083] The stiffness sensor 371 is disposed vertically below a pair of rollers 347 that hold the stopped paper 90. The rollers 347 are controlled to rotate by a motor M2. The rollers 347 function as a conveying section for conveying the paper 90 in the second conveying path 342, and also function as a holding section when measuring stiffness. The stiffness sensor 371 includes a paper detection sensor 710, a pressing section 711, a pressing force detection section 712, a support mechanism 715, and a motor M1. The motor M1 moves the support mechanism 715 in the horizontal direction (X direction). As a result, the tip of the pressing section 711 connected to the support mechanism 715 is positioned at a predetermined position in the X direction when measuring stiffness. The paper detection sensor 710 is a non-contact optical sensor that detects the presence or absence of paper at a detection position (indicated by an arrow in FIG. 10), i.e., the rear end of the paper.

[0084] When measuring stiffness, the paper 90 being transported along the second transport path 342 is stopped so that its rear end is located at the detection position of the paper detection sensor 710 (or at a position a predetermined distance beyond the detection position). In the stopped state, the rear end of the paper 90 becomes a free end, as shown in Fig. 10. The pressing portion 711 of the stiffness sensor 371 presses the bottom end of the paper 90 from the lateral direction. More specifically, the stiffness sensor 371 presses the bottom end of the paper 90 from the horizontal direction at a position a specific distance above the detection position.

[0085] The pressing unit 711 has a blade 711a and a base 711b continuous with one end of the blade 711a in the horizontal direction Y. The blade 711a is formed in a long plate shape that is long in the width direction (Y direction) so that it can contact the entire width of the paper 90 transported in the vertical direction (Z direction). The blade 711a comes into contact with a position (measurement point) that is a specific distance above the bottom end of the paper 90 in the vertical direction. In other words, the measurement point is located vertically below the portion of the paper 90 that is held by the roller 347.

[0086] The pressing force detection unit 712 is connected to a surface of the base 711b of the pressing unit 711 opposite to the surface continuing to the blade 711a. The pressing force detection unit 712 detects the pressing force when the pressing unit 711 is pressed horizontally by the repulsive force (rigidity) of the paper 90 when the blade 711a of the pressing unit 711 arranged at a predetermined position in the X direction presses the paper 90 by the motor M1 and the support mechanism 715. In other words, the pressing force detection unit 712 detects the pressing force when the pressing unit 711 bends the paper 90. For example, a load cell (pressure sensor) can be used as the pressing force detection unit 712.

[0087] (Surface Sensor 372) 11 is a diagram showing a schematic configuration of the surface property sensor 372. The surface property sensor 372 is a reflective (specular reflection, diffuse reflection) optical sensor that detects the surface property of the paper 90.

[0088] The surface property sensor 372 detects the surface property of the paper 90 based on the absolute values ​​of the intensities of the detected specular reflected light and scattered reflected light, and on the ratio between them.

[0089] An opening a11 is provided in the upper guide plate 3411 located on the right side of the second transport path 342, and an opening a21 is provided in the lower guide plate 3412 located on the left side. The opening a11 is substantially rectangular in shape, and the hole size is, for example, several tens of mm in both length and width (Z and Y directions). The opening a21 is disposed at a position corresponding to the opening a11, and is slightly larger than the opening a11. A pressing plate 729 of a pressing mechanism is disposed in the opening a21, and during measurement, the pressing plate 729 moves from the left side to the right side in FIG. 10 to press and fix the paper 90 against the upper guide plate 3411. When not measuring, the opening a11 is closed by a shutter (not shown). The opening a21 is also closed by the surface of the pressing plate 729, which is slightly retracted.

[0090] The surface property sensor 372 detects the surface property by locating the surface of the stopped paper 90 as the reference plane of the opening a11, irradiating the opening a11 with light as the irradiation area, and receiving the specular reflected light and the scattered reflected light. The reference plane corresponds to the inner surface of the upper guide plate 3421.

[0091] 11, the surface sensor 372 includes a housing 721, a light emitting unit 722, a collimating lens 723, and a plurality of light receiving units 724a and 724b (hereinafter, these are also collectively referred to as light receiving units 724), etc. The surface sensor 372 detects light irradiated from the light emitting unit 722 and reflected from the surface of the paper 90 with the light receiving unit 724a, and detects scattered reflected light with the light receiving units 724b, etc.

[0092] The arrangement angle of the light emitting unit 722 is set so that the incident angle of the irradiated light with respect to the reference plane is 75°. This incident angle of 75° is the angle used in the measurement of white paper glossiness according to JIS, and is an angle that is less affected by the color of the measured object. The reference plane is a virtual plane including the lower surface of the upper guide plate 3421, and during measurement, the surface of the paper 90, which is the measured object, is placed on the reference plane. The light emitting unit 722 is placed on the substrate b1. The light emitting unit 722 includes a light emitting element as a light source, such as an LED that emits light of a predetermined wavelength, and the irradiated light emitted from the light source (point light source) is made into approximately parallel light by the collimating lens 723 and irradiated to the irradiation area. In this embodiment, the wavelength of the light source of the light emitting unit 722 is preferably in the range of more than 405 nm and less than 525 nm, more preferably in the range of 445 nm to 500 nm, and most preferably around 465 nm. The irradiation area (first irradiation area) is an inner area in the opening a11 when viewed from the Z' direction, and the center (optical axis) of the irradiation area intersects with a reference plane parallel to the XY' plane at an intersection p1. A surface-emitting type LED or a bullet-shaped LED may be used as the light-emitting unit 722. When a bullet-shaped LED is used, a desired irradiation diameter (also called a beam diameter) can be obtained by designing a lens that matches the directivity of the bullet type. The light-emitting unit 722 and the light-receiving unit 724 are arranged along the width direction (Y direction), that is, they are on the same XY plane, and the irradiation light from the light-emitting unit 722 is along the width direction.

[0093] Each of the multiple light receiving units 724 includes a light receiving element such as a photodiode or a phototransistor, and includes a first light receiving unit 724a that receives specularly reflected light from the irradiated area, and one or more second light receiving units 724b that receive diffusely reflected light from the irradiated area. The first light receiving unit 724a is disposed at a reflection angle of 75° corresponding to the incident angle of 75° of the light emitting unit 722, and receives specularly reflected light. The second light receiving unit 724b can be disposed at any reflection angle except for the 75° position within a reflection angle range of 0° or more and less than 90°, and receives diffusely reflected light. The preferred positions for the arrangement are positions with reflection angles of 60°, 30°, and 0°, and more preferably, two positions at 60° and 30°, or one position at 60°. 11 shows an example in which a first light receiving unit 724a for receiving specularly reflected light with a reflection angle of 75° and a second light receiving unit 724b for receiving diffusely reflected light with a reflection angle of 30° are arranged. In these figures, the light receiving unit 724a is arranged on the board b2, and the light receiving unit 724b is arranged on the board b3. On the light receiving paths of the light receiving units 724a and 724b, openings a3 and a4 are provided in the housing 721. The openings a3 and a4 have the same structure. When viewed from the intersection point p1 side, the openings a3 and a4 are, for example, circular slits with a diameter of φ3 mm.

[0094] (Resistance sensor 373) 12 is a diagram showing a schematic configuration of the resistance sensor 373. The resistance sensor 373 applies a high voltage between the front and back of the paper 90 in a stationary state, and detects the electrical resistance (volume electrical resistance) of the paper 90 from the value of the current that flows.

[0095] As shown in FIG. 12, the resistance sensor 373 includes a detection roller 732 , an opposing roller 731 , and a high voltage power supply unit 733 .

[0096] The detection roller 732 is disposed so as to be able to come into contact with one surface side of the paper 90. The detection roller 732 is made of an elastic material, for example, conductive rubber.

[0097] The opposing roller 731 is disposed facing the detection roller 732 with the paper 90 sandwiched therebetween. The opposing roller 731 is disposed so as to be able to come into contact with the other surface side of the paper 90. The opposing roller 731 is made of, for example, a metal material. The opposing roller 731 is grounded.

[0098] The high-voltage power supply unit 733 is a unit for applying a high-voltage 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 configures an electric 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 a current that flows due to a voltage applied in the high-voltage power supply circuit.

[0099] The high-voltage power supply circuit is electrically connected to the detection roller 732 via an ammeter. The high-voltage power supply circuit is capable of applying a high voltage. A voltage is applied from the high-voltage power supply circuit via an ammeter to the detection roller 732. The high-voltage power supply circuit is capable of applying a high voltage of, for example, 1 kV to 5 kV. The method of applying the voltage in the high-voltage power supply circuit may involve applying one type of voltage to the paper 90, or may involve applying multiple types of voltages to the paper 90 by controlling them in multiple steps.

[0100] (Determination of control parameters) Hereinafter, the process of determining the control parameters using the paper characteristics acquired by the paper characteristic detection device 30 will be described with reference to FIGS.

[0101] 13 is a schematic diagram showing a control parameter determination method. In a conventional control parameter determination method, the detection data is first converted into paper type and basis weight and then classified, and the control parameters are determined. However, in the control parameter determination method of this embodiment, each control parameter is determined directly from the detection data of the paper characteristics. For example, the control unit 11 of the image forming apparatus 10 determines the fixing control parameters from the detection data of the paper characteristic sensors i-iii, and determines the transfer control parameters from the detection data of the paper characteristic sensors i, iii, and n. The paper characteristic sensors i-n correspond to any one of the sensors 351-354, 371-373 of the paper characteristic detection device 30 described above.

[0102] FIG. 14 is a diagram for explaining quality items in each process of the image forming processing and paper characteristics related to each quality item.

[0103] 14 shows the relationship between quality items such as fixing quality, secondary transfer quality, transport quality, and paper discharge quality present in each process such as the fixing process, transfer process, transport process, and static electricity removal process included in the image formation process, and the paper characteristics related to each quality item. Examples of paper characteristics detected by each paper characteristic sensor include size, paper thickness, basis weight, moisture content, stiffness, surface properties, resistance (volume resistance value), and bending strength.

[0104] "Size" detects the size of the paper by the sensor 1. For example, the size can be detected by analyzing the read image data obtained by the size sensor 351.

[0105] "Paper thickness" is obtained by detecting characteristics according to the thickness of the paper using sensor 2. "Paper thickness" is obtained, for example, by paper thickness sensor 352, which pinches the paper between two members and measures the distance between the two members.

[0106] "Basis weight" is obtained by detecting characteristics corresponding to the basis weight of the paper using sensor 3. "Basis weight" is obtained, for example, by basis weight sensor 353. "Basis weight" is obtained, for example, by measuring the attenuation (transmittance) of light passing through the paper using a transmissive or reflective optical sensor.

[0107] The "moisture content" is obtained by the sensor 4 detecting characteristics corresponding to the moisture content (also called water content) of the paper. The "moisture content" is obtained, for example, by the moisture content sensor 354. The "moisture content" is obtained, for example, by a water content sensor that optically detects the amount of light absorption of OH groups by a near-infrared method using light transmitted through the paper. The "moisture content" constitutes a value related to the paper moisture content.

[0108] The "rigidity" is obtained by detecting characteristics according to the rigidity of the paper using sensor 5. The "rigidity" is obtained, for example, by measuring the pressing force when the rear end of the free end of the paper is pressed using rigidity sensor 371. The "rigidity" constitutes a value related to the folding strength of the paper.

[0109] "Surface properties" are obtained by sensor 6 detecting characteristics corresponding to the smoothness of the surface of the paper. "Surface properties" is also called smoothness, and is obtained by surface properties sensor 372. "Surface properties" are obtained, for example, by irradiating the surface of the paper with light at an incident angle of 75 degrees, and optically detecting the specularly reflected light and diffusely reflected light from the paper surface with two sensors. "Surface properties" constitute a value related to the surface condition of the paper.

[0110] "Paper resistance" is obtained by the sensor 7 detecting characteristics corresponding to the electrical resistance inside or on the surface of the paper. "Paper resistance" is obtained, for example, by the resistance sensor 373. "Paper resistance" is obtained, for example, by measuring the voltage and the current that flows when a high voltage is applied to the paper. "Paper resistance" constitutes a value related to the volume resistance of the paper.

[0111] (Paper characteristic detection process) 15 is a flowchart showing the paper characteristic detection process executed by the image forming system 1000 and the paper characteristic detection device 30. Steps S11 to S16 are processes for preparing for printing, and step S17 and the following steps are processes for executing printing.

[0112] (Step S11) When a print job is input by an instruction sent from an external terminal such as a PC, the control unit 11 feeds and transports paper used in the print job based on the print job setting information of the input print job. For example, the control unit 11 feeds paper 90 (the first sheet on the paper feed tray 245) from the paper feed tray 245 of the paper feed device 20, and transports the paper 90 to the first transport path 341.

[0113] (Step S12) The control unit 31 controls the transport unit 34 and the first detection unit 35, and causes the first detection unit 35 to detect the paper characteristics of the paper 90 transported on the first transport path 341. When the first detection unit 35 detects the paper characteristics, the paper 90 is transported at a normal transport speed and is not stopped.

[0114] (Step S13) The control unit 31 controls the conveying unit 34 and the second detection unit 37 to branch the paper 90 and convey it to the second conveying path 342, and to cause the second detection unit 37 to detect the paper characteristics of the paper 90. When the second detection unit 37 detects the paper 90, the paper 90 is stopped once or multiple times.

[0115] (Step S14) The control unit 31 controls the conveying unit 34 to discharge the paper 90 whose paper characteristics have been detected onto the purge tray 349 .

[0116] (Step S15) The control unit 11 of the image forming apparatus 10 determines parameters for each process of the image forming unit 13 and the like by using a plurality of pieces of paper characteristic information obtained by the first and second detection units 35 and 37 through the processing of steps S12 and S13. Specifically, the control unit 11 determines control parameters for each process of fixing, transfer, transport / feed, and post-processing through the processing shown in FIG.

[0117] (Step S16) The control unit 31 determines whether to start execution of the print job, and if YES, the process proceeds to step S17. The determination of the start of execution may be made by the user pressing an execution start button, or may be made to start execution automatically when the process of step S15 ends.

[0118] (Step S17) The control unit 31 feeds and transports the paper 90 (the second sheet onward on the paper feed tray 245) set in the print job settings of the print job. If the print job settings are for multiple sheets, multiple sheets of paper 90 are continuously fed and transported. For example, the control unit 11 controls the paper feed device 20 to continuously feed and transport the paper 90 from the paper feed tray 245.

[0119] (Step S18) The control unit 31 controls the transport unit 34 and the first detection unit 35 to detect the paper characteristics of the paper 90 transported on the first transport path 341 by the first detection unit 35. As in step S12, when the first detection unit 35 detects the paper characteristics, the paper 90 is transported at the normal transport speed and is not stopped.

[0120] (Step S19) The control unit 11 judges whether each of the continuously conveyed sheets 90 is an inappropriate sheet based on the sheet characteristic information acquired in step S18. For example, this is the case when a sheet of paper of a size or type different from the size of the sheet 90 set in the print job setting is mixed in with the stack of sheets (outside the print job setting), or when the moisture content of the sheet 90 is significantly different from the moisture content of the previous sheets 90 (large change in sheet condition). For example, this is the case when a slip sheet of a different size is mixed in with the stack of sheets loaded in the sheet feed tray 245, or when the sheet feed tray 245 is mistakenly supplied with sheets 90 of a different size or type. The case where the moisture content is different is when a sheet of paper (not exposed to a high humidity environment) is added from another package on top of the stack of sheets (remaining sheets) in the sheet feed tray 245 that has been left in a high humidity environment for a long time.

[0121] When the conveyed paper is outside the print job settings due to the paper characteristics or the paper state changes significantly, the control unit 11 determines that the paper is outside the predetermined range (YES) and proceeds to step S20. On the other hand, when the conveyed paper is within the predetermined range (NO), the control unit 11 proceeds to step S21.

[0122] (Step S20) The control unit 31 controls the conveying unit 34 to cause the paper 90 (paper outside the specified range) being conveyed on the first conveying path 341 to branch at the branching unit s1, be guided to the second conveying path 342, and be discharged onto the purge tray 349. Furthermore, the control unit 31 may stop the print job being executed when a specified number or more of papers outside the specified range are detected consecutively. At this time, the control unit 11 may display information on the operation panel 15 to the effect that paper outside the specified range has been detected and / or that the print job has been stopped, as an alert to the user.

[0123] (Step S21) The control unit 11 continues the transport of the paper 90, and transports the paper 90 to the image forming unit 13 via the first transport path 341 and the transport path 141 to form an image. The paper on which the image has been formed is then discharged to the paper discharge tray 41 of the post-processing device 40.

[0124] (Step S22) If the print job is not completed (NO), the control unit 11 repeats the process from step S17 until the print job is completed. If the printing of the set number of sheets of the print job is completed (YES), the process ends (END).

[0125] In this manner, the paper characteristic detection device according to the present embodiment includes a first transport path along which paper is transported, a second transport path that branches off from the first transport path and transports paper to be purged without passing through an image forming unit, and a first detection unit that is disposed on the first transport path and is capable of detecting paper characteristic information corresponding to at least one of the basis weight, moisture content, paper thickness, and size of the paper. This allows the paper characteristic information of the paper being transported along the first transport path to be detected. In particular, since the paper characteristic information of the paper being transported along the first transport path is detected by the first detection unit while the paper is being transported at a normal transport speed without stopping the paper being transported along the first transport path, the paper characteristic information of the paper is continuously detected without reducing productivity. In addition, if a paper whose paper characteristic information is outside a predetermined range (inappropriate paper) is mixed in, the paper can be discharged without passing through the image forming unit by transporting the paper to the second transport path, which is a purging path. In addition, by placing the second detection unit on the second conveying path, which is a purge route that does not pass through the image forming unit, the effects of paper charging, etc. caused by detection by the second detection unit do not extend to the image forming unit, so there is no decrease in the reliability of the image formation operation.

[0126] The configuration of the paper characteristic detection device 30 and the image forming system 1000 equipped with the same described above are the main configurations described in order to explain the features of the above embodiment, but are not limited to the above configurations and can be modified in various ways within the scope of the claims. Furthermore, configurations equipped in general image forming devices are not excluded.

[0127] In the above-mentioned embodiment, the first detection unit is provided with four sensors, namely, a size sensor, a paper thickness sensor, a basis weight sensor, and a moisture sensor, but is not limited to this, and may have at least one of the four sensors. Furthermore, the first detection unit may have at least one sensor disposed downstream of the branching portion in the first conveying path. Similarly, in the above-mentioned embodiment, the second detection unit is provided with a stiffness sensor, a surface property sensor, and a resistance sensor, but is not limited to this, and may have at least one of the three sensors, but is not limited to this.

[0128] In addition, the means and methods for performing various processes in the paper characteristic detection device 30 and the image forming system 1000 according to the above-mentioned embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The above-mentioned program may be provided by a computer-readable recording medium such as a USB memory or a DVD (Digital Versatile Disc)-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded in the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. In addition, the above-mentioned program may be provided as a standalone application software, or may be incorporated into the software of the device as one of its functions. [Explanation of symbols]

[0129] 1000 Image forming system 10 Image forming device 11 Control section 13 Image forming section 20 Paper feeder 30 Paper characteristic detection device 31 Control Unit 32 Storage section 34 Conveyor 341 First Transport Path 342 Second Transport Path 349 Purge Tray s1 Branch 35 First detection unit 351 Size Sensor 352 Paper thickness sensor 353 Basis weight sensor 354 Moisture Sensor 37 Second detection section 371 Stiffness Sensor 372 Surface Sensor 373 Resistance Sensor 38 Environmental Sensors 39 Communications Department

Claims

1. a first transport path along which the paper is transported; a second conveying path that branches off from the first conveying path and conveys the paper to be purged without passing through an image forming unit; a second detection unit disposed on the second transport path for detecting paper characteristic information corresponding to the paper characteristics of the paper by pressing the paper or applying a voltage to the paper;

2. The paper characteristic detection device according to claim 1 , wherein the second detection unit detects paper characteristic information corresponding to at least one of stiffness and resistance of the paper.

3. The paper characteristic detection device according to claim 1, wherein the second detection unit detects the paper characteristic information by stopping the paper being transported along the second transport path, or detects the paper characteristic information while transporting the paper at a transport speed slower than the transport speed on the first transport path.

4. the second detection unit includes at least one of a stiffness sensor capable of detecting paper characteristic information corresponding to stiffness of the paper and a resistance sensor capable of detecting paper characteristic information corresponding to resistance of the paper, The paper characteristic detection device according to claim 1 , wherein the sensor of the second detection unit detects the paper characteristic information by stopping the paper being transported on the second transport path.

5. the second detection unit includes the stiffness sensor and the resistance sensor, The paper characteristic detection device according to claim 4 , wherein the stiffness sensor is disposed upstream of the resistance sensor in the second transport path.

6. The paper characteristic detection device according to claim 4 , further comprising a surface property sensor arranged in the second transport path, the surface property sensor being capable of detecting paper characteristic information corresponding to a surface property of the paper.

7. The paper characteristic detection device according to claim 6 , wherein the stiffness sensor is disposed upstream of the surface property sensor in the second transport path.

8. The paper characteristic detection device according to claim 1 , further comprising: a first detection unit disposed on the first transport path and capable of detecting paper characteristic information corresponding to the paper characteristics of the paper while transporting the paper.

9. The paper characteristic detection device according to claim 8 , wherein the first detection unit is capable of detecting paper characteristic information corresponding to at least one of a size, a thickness, a basis weight, and a moisture content of the paper.

10. The paper characteristic detection device according to claim 8 , wherein the first detection section detects the paper characteristic information of each of a plurality of sheets of paper that are continuously conveyed.

11. The paper characteristic detection device according to claim 8 , wherein the first detection unit detects paper characteristic information corresponding to at least one of the type of the paper and a change in a state of the paper.

12. The paper characteristic detection device according to claim 8 , wherein the first detection unit includes at least one of a size sensor, a paper thickness sensor, a basis weight sensor, and a moisture content sensor capable of detecting paper characteristic information corresponding to size, paper thickness, basis weight, and moisture content, respectively.

13. The paper characteristic detection device according to claim 12 , wherein the first detection unit includes the moisture sensor.

14. The paper characteristic detection device according to claim 12 , wherein the first detection unit includes at least one of the basis weight sensor, the paper thickness sensor, and the basis weight sensor.

15. the first detection unit includes the paper thickness sensor, the basis weight sensor, and the moisture sensor; The paper characteristic detection device according to claim 12 , wherein the basis weight sensor and the moisture sensor are disposed downstream of the paper thickness sensor in the first transport path.

16. the first detection unit includes the moisture sensor and the basis weight sensor, The paper characteristic detection device according to claim 12 , wherein the moisture sensor and the basis weight sensor are disposed at the same position in the transport direction and at different positions in a width direction perpendicular to the transport direction in the first transport path.

17. the first detection unit includes the size sensor and another sensor corresponding to other paper characteristic information different from the size; The paper characteristic detection device according to claim 12 , wherein the size sensor is disposed upstream of the other sensors in the first transport path.

18. 13. The paper characteristic detection device according to claim 12, wherein the size sensor is an image sensor and is capable of detecting the size of the paper in the transport direction and width direction from read image data obtained by reading the paper being transported.

19. The paper characteristic detection device according to claim 8 , wherein the first detection unit is disposed upstream of a branch point of the first transport path and the second transport path.

20. 2. The paper characteristic detection device according to claim 1, further comprising a moisture sensor for detecting paper characteristic information corresponding to the moisture content of the paper, and a resistance sensor for detecting paper characteristic information corresponding to the resistance of the paper, the moisture sensor being disposed upstream of the resistance sensor.

21. Further comprising an environmental sensor for measuring the surrounding environment; The paper characteristic detection device according to claim 1 , wherein the detection result of the paper characteristic information is corrected in accordance with the detection value of the environment sensor.

22. The paper characteristic detection device according to claim 1 , wherein the first transport path is a transport path connected to the image forming unit.

23. The second detection unit includes the stiffness sensor, the stiffness sensor is disposed on the second transport path extending vertically upward, and includes a pressing section that presses a rear end portion, which has become a free end, of the stopped paper from a side direction, and a pressure detection section that detects a pressing force of the pressing section on the paper.

5. The paper characteristic detection device according to claim 4.

24. The second detection unit includes the resistance sensor, The paper characteristic detection device according to claim 4 , wherein the resistance sensor includes a pair of rollers that contact the front and back sides of the paper, and measures the resistance of the paper by applying a voltage between the pair of rollers and measuring the current that flows.

25. The first detection unit includes the moisture sensor, The paper characteristic detection device of claim 12, wherein the moisture content sensor comprises first and second light-emitting units that each irradiate light of a predetermined wavelength onto the surface of the paper, and a light-receiving unit that receives light of each wavelength reflected from the surface of the paper.

26. 2. An image forming system comprising the paper characteristic detection device according to claim 1 and an image forming apparatus including the image forming unit, the image forming device is disposed downstream of the first transport path; Image forming system.

27. The paper feeder further includes a paper feed unit that feeds paper and a conveying unit, 27. The image forming system according to claim 26, further comprising a paper feed device that transports the paper fed from the paper feed section to the first transport path.

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