Image forming system and method for controlling the image forming system

Abstract

To provide an image forming system that can prevent recurrence of jams caused by double feeding of paper. [Solution] The image forming system of the present invention comprises: an image forming unit that forms an image on paper; a paper feeding unit equipped with a plurality of paper feed trays for storing paper, which feeds paper to the image forming unit from one of the plurality of paper feed trays; a detection unit that detects the characteristics of the paper fed by the paper feeding unit; and a control unit that, in the event of a paper jam occurring during the execution of an image forming job, switches the paper feed tray that feeds paper to the image forming unit from one paper feed tray to another paper feed tray based on the characteristics of the paper detected by the detection unit.

Description

Technical Field

[0001] The present invention relates to an image forming system and a method for controlling the image forming system.

Background Art

[0002] In an image forming apparatus such as a printer, a phenomenon (jam) may occur where the paper is not correctly conveyed during the execution of a printing job.

[0003] In relation to this, Patent Document 1 below discloses a technique for measuring the physical property value of paper and setting paper conveyance control conditions when a paper jam occurs. The technique of Patent Document 1 measures the physical property value of paper by a media sensor provided in the paper conveyance path, and changes paper conveyance control conditions such as the paper conveyance speed and the interval between papers. According to this technique, re-occurrence of jams is prevented by adjusting the paper conveyance control conditions according to the physical property value of the paper.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there is a problem that jams (double-feed jams) caused by double-feed where sheets of paper stick together due to static electricity and are conveyed stacked cannot be eliminated even by adjusting the above paper conveyance control conditions.

[0006] The present invention has been made in view of the above problems. Therefore, an object of the present invention is to provide an image forming system and a method for controlling the image forming system that can prevent re-occurrence of jams caused by double-feed of paper.

Means for Solving the Problems

[0007] The above objectives of the present invention are achieved by the following means.

[0008] (1) An image forming system comprising: an image forming unit that forms an image on paper; a paper feeding unit equipped with a plurality of paper feeding trays for accommodating paper, which feeds paper to the image forming unit from one of the plurality of paper feeding trays; a detection unit that detects the characteristics of the paper fed by the paper feeding unit; and a control unit that, in the event of a paper jam occurring during the execution of an image forming job, switches the paper feeding tray that feeds paper to the image forming unit from one of the paper feeding trays to another paper feeding tray based on the characteristics of the paper detected by the detection unit.

[0009] (2) The image forming system according to (1) above, wherein if the characteristics of the paper detected by the detection unit satisfy predetermined conditions, the control unit switches the paper feed tray for feeding paper to the image forming unit from one paper feed tray to another paper feed tray.

[0010] (3) The image forming system according to (2) above, wherein if the characteristics of the paper detected by the detection unit satisfy the predetermined conditions, the control unit prompts the user to choose whether or not to switch the paper feed tray, and if the user chooses to switch the paper feed tray, the control unit switches the paper feed tray that supplies paper to the image forming unit from the first paper feed tray to the other paper feed tray.

[0011] (4) If the characteristics of the paper detected by the detection unit satisfy the predetermined conditions, the control unit prompts the user to choose whether to switch paper trays or change the state of paper stored in the paper trays, and if the user chooses to switch paper trays, the control unit switches the paper tray that supplies paper to the image forming unit from one paper tray to another paper tray, the image forming system according to (2) above.

[0012] (5) The image forming system according to any one of (1) to (4) above, wherein the characteristics of the paper include the moisture content or charge amount of the paper.

[0013] (6) The image forming system according to any one of (1) to (4) above, wherein the paper characteristics include at least one selected from paper size, basis weight, surface properties, stiffness, paper resistance value, and paper thickness.

[0014] (7) The detection unit is located between the paper feeding unit and the image forming unit in the image forming system according to any one of (1) to (4) above.

[0015] (8) The image forming system according to any one of (2) to (4) above, further comprising a storage unit for storing the characteristics of the paper detected by the detection unit.

[0016] (9) The image forming system according to (8) above, wherein the predetermined conditions are set or updated based on the characteristics stored in the memory unit.

[0017] (10) A control method for an image forming system, comprising: an image forming unit for forming an image on paper; a paper feeding unit comprising a plurality of paper feed trays for accommodating paper, which feeds paper to the image forming unit from one of the plurality of paper feed trays; and a detection unit for detecting the characteristics of the paper fed by the paper feeding unit, wherein, if a paper jam occurs during the execution of an image forming job, the control method for an image forming system switches the paper feed tray that feeds paper to the image forming unit from one of the paper feed trays to another paper feed tray based on the characteristics of the paper detected by the detection unit. [Effects of the Invention]

[0018] According to the present invention, jams caused by double feeding of paper are prevented from occurring again. [Brief explanation of the drawing]

[0019] The advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which are for illustrative purposes only and are not intended to define the limitations of the present invention. [Figure 1] It is a diagram showing a schematic configuration of an image forming system. [Figure 2] It is a flowchart showing the procedure of the jam prevention process according to the first embodiment. [Figure 3] It is a flowchart showing the procedure of the jam prevention process according to the second embodiment. [Figure 4] It is a flowchart showing the procedure of the jam prevention process according to the reference example.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments.

[0021] In the description of the drawings, the same elements are denoted by the same reference numerals, and duplicate descriptions are omitted. Also, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from the actual ratios. Further, the paper in the present embodiment includes printing paper and various films. In particular, the printing paper includes those manufactured using plant-derived mechanical pulp and / or chemical pulp. Also, the types of paper include glossy paper, matte paper, plain paper, high-gloss paper, coated paper, etc.

[0022] (First Embodiment) FIG. 1 is a diagram showing a schematic configuration of an image forming system 1 according to the first embodiment of the present invention.

[0023] As shown in FIG. 1, the image forming system 1 includes an image forming apparatus 10, a paper feeding apparatus 20, and a paper property detecting apparatus 30. Each apparatus is connected in the order of the paper feeding apparatus 20, the paper property detecting apparatus 30, and the image forming apparatus 10 along the conveyance direction of the paper 90 fed from the paper feeding apparatus 20.

[0024] <Image forming apparatus 10> The image forming apparatus 10 comprises a control unit 11, a storage unit 12, a communication unit 13, an operation display unit 14, a main paper feeding unit 15, a transport unit 16, an image forming unit 17, and a fixing unit 18. Each of these units is interconnected via a bus for exchanging signals.

[0025] The control unit 11 includes a CPU (Central Processing Unit) and performs control of the above-mentioned parts and various calculation processes according to the program.

[0026] The memory unit 12 consists of a ROM (Read Only Memory) for pre-storing various programs and data, a RAM (Random Access Memory) for temporarily storing programs and data as a working area, and a hard disk for storing various programs and data.

[0027] The communication unit 13 is an interface for communicating with other devices. For example, the communication unit 13 transmits and receives various data and signals with the paper feed device 20 and the paper characteristics detection device 30.

[0028] The operation display unit 14 is equipped with a touch panel, a numeric keypad, a start button, a stop button, etc., and is used for displaying various information and inputting various instructions.

[0029] The main paper feed unit 15 is equipped with multiple paper trays 151, 152, and 153 for storing the paper 90 used for printing, and feeds one sheet of paper 90 at a time from each paper tray.

[0030] The transport unit 16 includes a transport path 161, a plurality of transport roller pairs 162, and a drive motor (not shown) that drives the transport roller pairs 162, and transports paper 90 fed from the main paper feeding unit 15 or paper fed from the paper feeding device 20 along the transport path 161. The transport path 161 is provided with a plurality of photosensors (not shown) for detecting paper jams.

[0031] The image forming unit 17 forms an image on the paper 90 fed from the main paper feeding unit 15 or on the paper 90 fed from the paper feeding device 20. The image forming unit 17 forms an image on the paper 90 using, for example, a well-known electrophotographic image formation process that includes the steps of charging, exposure, development, and transfer.

[0032] The fixing unit 18 includes a heating roller and a pressure roller that are heated by a heater, and heats and pressurizes the paper 90 on which the image has been formed by the image forming unit 17 to fix the image to the paper 90.

[0033] <Paper feeder 20> The paper feeder 20 comprises a control unit 21, a storage unit 22, a communication unit 23, a paper feeding unit 24, and a transport unit 25. These units are interconnected via a bus for exchanging signals. Note that the parts of the paper feeder 20 that have the same functions as those of the image forming apparatus 10 will not be described.

[0034] The paper feed unit 24 is equipped with multiple paper feed trays 241, 242, and 243 for holding the paper 90 used for printing, and feeds one sheet of paper 90 at a time from each paper feed tray. The multiple paper feed trays 241, 242, and 243 can hold paper 90 of the same size and type.

[0035] Furthermore, a photosensor (not shown) for detecting paper jams is also provided in the transport path of the paper 90 within the paper feed device 20.

[0036] <Paper characteristics detection device 30> The paper characteristic detection device 30 comprises a control unit 31, a storage unit 32, a communication unit 33, a first detection unit 34, a second detection unit 35, a transport unit 36, and a paper discharge unit 37. These units are interconnected via a bus for exchanging signals. Note that the parts of the paper characteristic detection device 30 that have the same functions as those of the image forming apparatus 10 will not be described.

[0037] The first detection unit 34 is installed in the transport path (main transport path) from the paper feed device 20 to the image forming apparatus 10 and detects the characteristics of the paper 90 transported in the main transport path. The first detection unit 34 includes a size sensor 341, a paper thickness sensor 342, a moisture content sensor 343, and a basis weight sensor 344. The size sensor 341 includes a line sensor and detects the size of the paper from the scanned image data of the paper. The paper thickness sensor 342 mechanically measures the thickness of the paper based on the distance between two members that sandwich the paper. The moisture content sensor 343 irradiates the surface of the paper with two types of near-infrared light with different wavelengths and detects the moisture content of the paper from the ratio of the amount of reflected light received for the two types of near-infrared light. The basis weight sensor 344 detects the basis weight of the paper by measuring the transmittance and amount of reflected light transmitted through the paper.

[0038] The second detection unit 35 is located in a transport path (discharge path) that branches upward from the transport path leading from the paper feed device 20 to the image forming apparatus 10, and detects the characteristics of the paper 90 transported to the discharge path. The second detection unit 35 includes a stiffness sensor 351, a surface quality sensor 352, and a paper resistance sensor 353. The stiffness sensor 351 includes a load cell and acquires the pressure detected when the paper is bent as the stiffness of the paper. The surface quality sensor 352 detects the surface quality of the paper by irradiating light onto the surface of the paper and receiving the specularly reflected and scattered reflected light. The paper resistance sensor 353 electrically measures the paper resistance of the paper by applying a high voltage to the paper and measuring the current value.

[0039] The paper output unit 37 is equipped with a paper output tray from which the paper 90 transported to the output path is discharged, and the paper 90 that has passed through the second detection unit 35 is discharged to the outside.

[0040] Furthermore, a photosensor (not shown) for detecting paper jams is also provided in the transport path of the paper 90 within the paper characteristics detection device 30.

[0041] The detection results from each of the sensors 341-344 and 351-353 are transmitted from the paper characteristics detection device 30 to the image forming apparatus 10. The control unit 11 of the image forming apparatus 10 then controls the paper feeding operation of the paper feed device 20 based on the various detection results transmitted from the paper characteristics detection device 30.

[0042] The image forming apparatus 10, the paper feeder 20, and the paper characteristic detection device 30 may include components other than those described above, or may not include some of the components described above. For example, the paper characteristic detection device 30 may include an electrostatic sensor for detecting the amount of charge on the paper.

[0043] In the image forming system 1 configured as described above, if a paper jam occurs during the execution of a print job, the characteristics of the jammed paper 90 are detected. If the characteristics of the paper 90 meet predetermined conditions, the paper feed tray from which the paper 90 is supplied is switched. The operation of the image forming system 1 will be described below with reference to Figure 2.

[0044] Figure 2 is a flowchart showing the procedure for jam prevention processing performed by the image forming system 1. Jam prevention processing is performed when a jam occurs in the image forming system 1 during the execution of a print job in which an image is formed by the image forming apparatus 10 on paper 90 fed from the paper feeder 20. The processing shown in the flowchart in Figure 2 is realized by the control unit 11 of the image forming apparatus 10 controlling the image forming apparatus 10, the paper feeder 20, and the paper characteristic detection device 30 according to a program stored in the memory unit 12 of the image forming apparatus 10.

[0045] (Step S101) First, the image forming system 1 determines whether or not a jam has occurred. More specifically, the control unit 11 of the image forming apparatus 10 determines, for example, whether or not a phenomenon has occurred in which the paper is not transported correctly in the image forming system 1 while a print job is being executed. For example, if the paper is not detected by the photosensor on the transport path even after a predetermined time has elapsed since the paper was fed from the paper tray, it is determined that a jam has occurred. Note that the technology for detecting the occurrence of a jam is a well-known technology, so a detailed explanation will be omitted.

[0046] If it is determined that no jam has occurred (step S101: NO), the image forming system 1 waits until a jam occurs. On the other hand, if it is determined that a jam has occurred (step S101: YES), the image forming system 1 proceeds to the process in step S102.

[0047] (Step S102) If it is determined that a jam has occurred (step S101: YES), the image forming system 1 transports the jammed paper to the paper characteristic detection device 30. More specifically, the control unit 11 of the image forming apparatus 10 controls the transport units 16, 25, and 36 of the image forming system 1 to transport the jammed paper (jammed paper) to the paper characteristic detection device 30.

[0048] (Step S103) Next, the image forming system 1 detects the moisture content of the jammed paper. More specifically, the control unit 11 of the image forming system 1 controls the paper characteristics detection device 30 to detect the moisture content of the paper transported to the paper characteristics detection device 30 in step S102 using the moisture content sensor 343.

[0049] (Step S104) Next, the image forming system 1 determines whether the moisture content of the jammed paper is below a threshold. More specifically, the control unit 11 of the image forming apparatus 10 determines whether the moisture content of the paper detected in step S103 is below a predetermined threshold. Here, the threshold is a fixed value used to determine the possibility of double-feed jams occurring due to paper sticking together due to static electricity, and is set based on experiments, etc. Note that the lower the moisture content of the paper, the greater the amount of static electricity the paper has. Therefore, the lower the moisture content of the paper, the higher the possibility that the paper will stick together and cause a double-feed jam.

[0050] If the image forming system 1 determines that the moisture content of the jam paper is not below the threshold (step S104: NO), it assumes that the jam determined to have occurred in step S101 is unlikely to be a double-feed jam and proceeds to step S108. On the other hand, if the image forming system 1 determines that the moisture content of the jam paper is below the threshold (step S104: YES), it assumes that the jam determined to have occurred in step S101 is likely to be a double-feed jam and proceeds to step S105.

[0051] (Step S105) If the system determines that the moisture content of the jammed paper is below a threshold (step S104: YES), the image forming system 1 asks the user whether or not to switch paper trays. More specifically, the control unit 11 of the image forming apparatus 10 displays a selection screen on the touch panel of the operation display unit 14 prompting the user to choose whether or not to switch paper trays, and asks the user whether or not to switch the paper tray from which the paper is fed. At this time, the selection screen also displays supplementary information such as that there is a high possibility that a double feed jam has occurred due to static electricity in the paper, and that it is preferable to switch paper trays to prevent the double feed jam from occurring again.

[0052] (Step S106) Next, the image forming system 1 determines whether the user has selected to switch the paper feed tray. More specifically, the control unit 11 of the image forming apparatus 10 determines whether the user has selected to switch the paper feed tray through the selection screen displayed on the operation display unit 14 in the process of step S105.

[0053] If the system determines that the user has not selected to switch the paper tray (step S106: NO), the image forming system 1 proceeds to step S108. On the other hand, if the system determines that the user has selected to switch the paper tray (step S106: YES), the image forming system 1 proceeds to step S107.

[0054] (Step S107) If the system determines that the user has selected to switch paper trays (step S106: YES), the image forming system 1 switches the paper tray. More specifically, the control unit 11 of the image forming apparatus 10 controls the paper feed device 20 to switch the setting of the paper feed tray from the tray that contained the jammed paper to another paper feed tray.

[0055] (Step S108) Next, the image forming system 1 discharges the jammed paper. More specifically, the control unit 11 of the image forming apparatus 10 controls the paper characteristic detection device 30 to discharge the paper that was transported to the paper characteristic detection device 30 in step S102 to the outside from the paper discharge unit 37.

[0056] (Step S109) Then, the image forming system 1 resumes the print job and terminates processing. More specifically, the control unit 11 of the image forming system 1 resumes the print job that was interrupted due to the jam and terminates processing. In the resumed print job, paper 90 is fed to the image forming apparatus 10 from the same paper tray as before the jam occurred, or from a different paper tray than before the jam occurred.

[0057] As described above, according to the flowchart shown in Figure 2, if a jam occurs in the image forming system 1, the paper characteristic detection device 30 detects the moisture content of the jammed paper. If the moisture content of the jammed paper is below a predetermined threshold, it is considered highly likely that a double-feed jam has occurred, and the user is asked whether or not to switch paper trays. If the user selects to switch paper trays, the paper tray is switched, and paper is fed from the new paper tray. On the other hand, if the user does not select to switch paper trays, or if the moisture content of the jammed paper is not below the predetermined threshold, paper continues to be fed from the same paper tray as before the jam occurred.

[0058] As described above, according to the image forming system 1 of this embodiment, if the moisture content of the paper is low, there is a high possibility that a double feed jam has occurred due to the papers sticking together because of static electricity, and the paper feed tray is switched. With this configuration, since paper with different static charge states is fed from the new paper feed tray, the recurrence of a double feed jam is prevented.

[0059] Furthermore, multiple sheets of paper 90 placed in the same paper tray are highly likely to be similarly charged to each other. Therefore, if paper is fed again from the same paper tray without switching trays, there is a high probability that a double-feed jam caused by the charging of the paper 90 will occur again.

[0060] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figure 3. This embodiment is one in which the paper feed tray is switched when the paper size satisfies predetermined conditions. Except for the fact that the paper size is detected as a characteristic of the paper, the configuration of the image forming system 1 according to this embodiment is the same as that of the first embodiment, so a detailed explanation of the configuration of the image forming system 1 will be omitted.

[0061] Figure 3 is a flowchart showing the procedure for jam prevention processing according to this embodiment. The processing shown in the flowchart in Figure 3 is realized by the control unit 11 of the image forming apparatus 10 controlling the image forming apparatus 10, the paper feeder 20, and the paper characteristic detection device 30, according to a program stored in the storage unit 12 of the image forming apparatus 10.

[0062] (Steps S201~S202) The processes in steps S201 to S202 are the same as those in steps S101 to S102 in Figure 2, so their explanation will be omitted.

[0063] (Step S203) Next, the image forming system 1 detects the size of the jammed paper. More specifically, the control unit 11 of the image forming apparatus 10 controls the paper characteristics detection device 30 to detect the size of the paper (paper length in the paper transport direction) transported to the paper characteristics detection device 30 in step S202 using the size sensor 341.

[0064] (Step S204) Next, the image forming system 1 determines whether the size of the jammed paper is larger than the set size. More specifically, the control unit 11 of the image forming apparatus 10 determines whether the size (paper length) of the jammed paper detected in step S203 is larger than the size of the paper fed from the paper tray that is pre-stored in the storage unit 12 of the image forming apparatus 10. Note that if two sheets of paper are overlapping (double feeding), the overlapping misalignment of the paper will cause the paper size to be larger than the set size.

[0065] If the image forming system 1 determines that the size of the jam paper is less than or equal to the set size (step S204: NO), it determines that the jam that occurred in step S201 is not a double-feed jam and proceeds to step S209. On the other hand, if the image forming system 1 determines that the size of the jam paper is larger than the set size (step S204: YES), it determines that the jam that occurred in step S201 is a double-feed jam and proceeds to step S205.

[0066] (Step S205) If the system determines that the size of the jammed paper is larger than the set size (step S204: YES), the image forming system 1 asks the user whether to switch paper trays or change the paper arrangement in the paper tray. More specifically, the control unit 11 of the image forming apparatus 10 displays a selection screen on the touch panel of the operation display unit 14 prompting the user to choose, for example, to switch paper trays or to separate the stack of paper in the paper tray to change the paper arrangement.

[0067] (Step S206) Next, the image forming system 1 determines whether the user has selected to switch the paper feed tray. More specifically, the control unit 11 of the image forming apparatus 10 determines, through the selection screen displayed on the operation display unit 14 in step S205, whether the user has selected to switch the paper feed tray or to change the state of the paper contained in the paper feed tray.

[0068] If the system determines that the user has not selected to switch the paper tray (step S206: NO), the image forming system 1 proceeds to step S208, assuming that the user has selected to change the paper storage state in the paper tray. On the other hand, if the system determines that the user has selected to switch the paper tray (step S206: YES), the image forming system 1 proceeds to step S207.

[0069] (Step S207) If the system determines that the user has selected to switch paper trays (step S206: YES), the image forming system 1 switches the paper tray. More specifically, the control unit 11 of the image forming apparatus 10 controls the paper feed device 20 to switch the setting of the paper tray from which the paper is fed to another paper tray.

[0070] (Step S208) On the other hand, if the system determines that the user has not selected to switch the paper tray (step S206: NO), the image forming system 1 determines whether the change in the paper storage state has been completed. More specifically, for example, if the user removes the stack of paper from the paper tray, sorts it, returns the stack of paper to the paper tray, and then presses the completion button (not shown) displayed on the operation display unit 14, the control unit 11 of the image forming apparatus 10 determines that the change in the paper storage state has been completed.

[0071] If it is determined that the change in the paper loading state is not yet complete (step S208: NO), the image forming system 1 waits until the change in the paper loading state is complete. On the other hand, if it is determined that the change in the paper loading state is complete (step S208: YES), the image forming system 1 proceeds to the process in step S209.

[0072] (Steps S209~S210) The processing in steps S209 to S210 is the same as the processing in steps S108 to S109 in Figure 2, so the explanation is omitted.

[0073] As described above, according to the flowchart shown in Figure 3, if a jam occurs in the image forming system 1, the paper characteristic detection device 30 detects the size of the jammed paper. If the size of the jammed paper is larger than the set size, it is determined that a double-feed jam has occurred, and the user is asked whether to switch paper trays or change the paper loading state in the paper tray. If the user chooses to switch paper trays, the paper trays are switched, and paper is fed from the new paper tray. On the other hand, if the user chooses to change the paper loading state, the paper loading state of the same paper tray as before the jam occurs is changed to prevent double-feed jams, and paper is fed from the same paper tray. If the size of the jammed paper is less than or equal to the set size, it is determined that no double-feed jam has occurred, and paper continues to be fed from the same paper tray as before the jam occurred.

[0074] As described above, according to the image forming system 1 of this embodiment, if the paper size is larger than the set size, a double feed jam is detected, and the paper tray is switched. Alternatively, if the paper size is larger than the set size, a double feed jam is detected, and the user is prompted to change the paper storage state in the paper tray. With this configuration, the recurrence of double feed jams is prevented.

[0075] (Reference example) Finally, with reference to Figure 4, the jam prevention treatment according to the reference example will be explained. The jam prevention treatment according to the reference example is implemented by an image forming system 1 equipped with an anti-static device such as an ionizer in the paper feed device 20.

[0076] Figure 4 is a flowchart showing the procedure for jam prevention processing according to a reference example. The processing shown in the flowchart in Figure 4 is realized by the control unit 11 of the image forming apparatus 10 controlling the image forming apparatus 10, the paper feeder 20, and the paper characteristic detection device 30, according to a program stored in the memory unit 12 of the image forming apparatus 10.

[0077] (Steps S301~S304) The processes in steps S301 to S304 are the same as those in steps S101 to S104 in Figure 2, so their explanation is omitted. In step S304, if it is determined that the moisture content of the jam paper is not below the threshold (step S304: NO), the image forming system 1 determines that the jam determined to have occurred in step S301 is unlikely to be a double-feed jam and proceeds to step S306. On the other hand, if it is determined that the moisture content of the jam paper is below the threshold (step S304: YES), the image forming system 1 determines that the jam determined to have occurred in step S301 is highly likely to be a double-feed jam and proceeds to step S305.

[0078] (Step S305) If the image forming system 1 determines that the moisture content of the jammed paper is below a threshold (step S304: YES), it activates the static elimination device. More specifically, the control unit 11 of the image forming apparatus 10 activates, for example, the static elimination devices provided in each paper tray of the paper feeder 20 to eliminate static electricity from the paper placed in the paper trays.

[0079] (Steps S306~S307) The processes in steps S306 to S307 are the same as those in steps S108 to S109 in Figure 2, so their explanation will be omitted.

[0080] As described above, according to the flowchart shown in Figure 4, if a jam occurs in the image forming system 1, the paper characteristic detection device 30 detects the moisture content of the jammed paper. If the moisture content of the jammed paper is below a predetermined threshold, it is considered highly likely that a double-feed jam caused by static electricity in the paper has occurred, and static electricity removal is performed on the paper in the paper tray. With this configuration, the recurrence of double-feed jams is prevented.

[0081] The present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the claims.

[0082] For example, in the first embodiment described above, if the moisture content of the paper is below a predetermined threshold, the user is asked whether they wish to switch the paper tray, and if the user selects to switch the paper tray, the paper tray is switched. However, it is not always necessary to ask the user whether to switch the paper tray; the paper tray may be switched automatically if the moisture content of the paper is below a predetermined threshold.

[0083] Furthermore, in the first embodiment and reference example described above, the moisture content of the jammed paper was compared with a threshold (fixed value) that was set in advance based on experiments, etc. However, the threshold does not necessarily have to be a fixed value and may be a variable value that is updated as needed. If the threshold is a variable value, for example, the moisture content of the jammed paper detected in the process of step S103 is stored in the storage unit 12 of the image forming apparatus 10, and the threshold is updated based on the newly stored moisture content. Alternatively, the threshold can be initially set based on the moisture content of the paper when jamming occurs.

[0084] Furthermore, in the first embodiment and reference example described above, the moisture content of the jammed paper was detected. However, the paper whose moisture content is detected when jamming occurs is not limited to the jammed paper; it may be other paper fed from the same paper tray as the jammed paper, or other paper placed in the same paper tray that fed the jammed paper.

[0085] Furthermore, in the second embodiment described above, if the paper size was larger than the set size, the user was asked whether to switch paper trays or change the paper loading state in the paper tray. However, the above inquiry is not necessarily required, and the paper tray may be switched automatically if the paper size is larger than the set size.

[0086] Furthermore, in the embodiments and reference examples described above, when a jam occurs, the moisture content or paper size is detected as an example of the paper characteristics. However, the paper characteristics detected when a jam occurs are not limited to the moisture content or paper size; basis weight, surface quality, stiffness, paper resistance value, or paper thickness may also be detected. Alternatively, if the paper characteristic detection device 30 is equipped with an electrostatic sensor, the amount of charge on the paper may be detected. Note that the greater the amount of charge on the paper, the higher the possibility of the sheets sticking together, and the higher the possibility of a double feed jam. Also, the lower the basis weight of the paper, the higher the possibility of the sheets sticking together, and the higher the possibility of a double feed jam. Also, the lower the surface roughness of the paper, the higher the possibility of the sheets sticking together, and the higher the possibility of a double feed jam. Furthermore, for example, a double feed jam may be directly detected by detecting the paper thickness and comparing it with a set thickness, similar to the second embodiment.

[0087] Furthermore, the detection results from multiple sensors may be combined. Specifically, for example, the decision of whether or not to switch the paper tray may be made based on two values: the moisture content and the surface quality of the paper.

[0088] Furthermore, in the embodiments and reference examples described above, the paper characteristic detection device 30 is provided separately from the image forming apparatus 10 and the paper feed device 20. However, the paper characteristic detection device 30 may be provided integrally with the image forming apparatus 10, or integrally with the paper feed device 20.

[0089] Furthermore, in the embodiments and reference examples described above, various sensors for detecting the paper characteristics were provided within the paper characteristic detection device 30. However, for example, a moisture content sensor for detecting the moisture content of the paper may be provided in each paper tray of the paper feed device 20.

[0090] The processing units in the flowcharts of the embodiments described above are divided according to the main processing content in order to facilitate understanding of each process. The present invention is not limited by how the processing steps are classified. Each process can be further divided into more processing steps. Also, one processing step may perform even more processes.

[0091] The means and methods for performing various processing in the image forming system 1 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 (Universal Serial Bus) memory or a DVD (Digital Versatile Disc)-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. Furthermore, the program may be provided as a standalone application software, or it may be incorporated into the software of the image forming system 1 as a function of the device.

[0092] 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]

[0093] 1. Image forming system, 10 Image forming apparatus, 11,21,31 Control Unit, 12,22,32 storage section, 13, 23, 33 Communications Department, 14 Operation display section, 15 Main paper feed section, 151, 152, 153, 241, 242, 243 paper trays, 16, 25, 36 Conveyor section, 17 Image forming unit, 18 Fixing section, 20 Paper feed device, 24 Paper feed section, 30. Paper characteristics detection device, 34 First detection unit, 341 size sensor, 342 Paper thickness sensor, 343 Moisture content sensor, 344 basis weight sensor, 35 Second detection unit, 351 rigidity sensor, 352 surface sensor, 353 Paper resistance sensor, 37 Paper output section, 90 sheets of paper.

Claims

1. An image forming unit that forms an image on paper, A paper feeding unit is provided with multiple paper trays for holding paper, and paper is fed from one of the multiple paper trays to the image forming unit, A detection unit for detecting the characteristics of the paper fed by the aforementioned paper feeding unit, If a paper jam occurs during the execution of an image forming job, the control unit switches the paper feed tray that supplies paper to the image forming unit from one paper feed tray to another paper feed tray based on the characteristics of the paper detected by the detection unit. An image forming system having the following features.

2. The image forming system according to claim 1, wherein if the characteristics of the paper detected by the detection unit satisfy predetermined conditions, the control unit switches the paper feed tray for feeding paper to the image forming unit from one paper feed tray to another paper feed tray.

3. If the paper characteristics detected by the detection unit satisfy the predetermined conditions, the control unit performs a process to prompt the user to choose whether or not to switch the paper tray. The image forming system according to claim 2, wherein if the user chooses to switch paper trays, the control unit switches the paper tray that supplies paper to the image forming unit from one paper tray to another paper tray.

4. If the characteristics of the paper detected by the detection unit satisfy the predetermined conditions, the control unit prompts the user to choose whether to switch the paper tray or change the state of the paper stored in the paper tray. The image forming system according to claim 2, wherein if the user chooses to switch paper trays, the control unit switches the paper tray that supplies paper to the image forming unit from one paper tray to another paper tray.

5. The image forming system according to any one of claims 1 to 4, wherein the characteristics of the paper include the moisture content or charge amount of the paper.

6. The image forming system according to any one of claims 1 to 4, wherein the paper characteristics include at least one selected from paper size, basis weight, surface properties, stiffness, paper resistance value, and paper thickness.

7. The image forming system according to any one of claims 1 to 4, wherein the detection unit is disposed between the paper feeding unit and the image forming unit.

8. The image forming system according to any one of claims 2 to 4, further comprising a storage unit for storing the characteristics of the paper detected by the detection unit.

9. The image forming system according to claim 8, wherein the predetermined conditions are set or updated based on the characteristics stored in the memory unit.

10. A control method for an image forming system comprising: an image forming unit for forming an image on paper; a paper feeding unit equipped with a plurality of paper feed trays for accommodating paper, which feeds paper from one of the plurality of paper feed trays to the image forming unit; and a detection unit for detecting the characteristics of the paper fed by the paper feeding unit, A control method for an image forming system, which, when a paper jam occurs during the execution of an image forming job, switches the paper feed tray that supplies paper to the image forming unit from one paper feed tray to another paper feed tray based on the characteristics of the paper detected by the detection unit.

Images