Image forming apparatus and management system

Abstract

To enable a user to discriminate a failure caused by mixing sheets in a storage part when a failure occurs in an image forming apparatus.SOLUTION: An image forming apparatus 100 according to the present invention includes a detection device 33 which is disposed on a conveyance path and detects characteristic values indicating physical characteristics (basis weight and surface property) of a sheet being transferred along the conveyance path from a storage part toward an image forming part (secondary transfer part). The control unit 200 acquires boundary information indicating boundaries between different types of sheets in a sheet bundle housed in a storage unit based on changes in characteristic values detected by the detection device 33 while each sheet of the sheet bundle is transferred sequentially from the storage unit. When a failure occurs in the image forming apparatus 100, the control unit 200 discriminates a failure caused by mixed loading in which a plurality of kinds of sheets are loaded in the storage unit based on the acquired boundary information.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and a management system. [Background technology]

[0002] Recently, in the market for image forming devices such as laser printers, there are an increasing number of opportunities for vendors to enter into contracts such as maintenance contracts for image forming devices with users. For vendors (maintenance vendors) who perform maintenance management of image forming devices under such contracts, it is desirable to be able to efficiently resolve a malfunction that occurs in the image forming device without requiring a service technician to visit the location where the image forming device is installed. For example, if a malfunction occurs due to a mixture of different types of sheets in a sheet storage unit, the malfunction can be resolved without requiring a service technician to resolve the mixed sheet state in the sheet storage unit by encouraging the user to resolve the mixed sheet state in the sheet storage unit.

[0003] Patent Document 1 proposes a technology for controlling the temperature of a fixing unit in an image forming apparatus that fixes an image on a sheet to a fixing temperature corresponding to the sheet type detected by a media sensor. This technology can prevent fixing failures caused by multiple types of sheets being mixed in a sheet storage unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-33013 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional technology, when a malfunction occurs due to the mixed loading of multiple types of sheets in the sheet storage unit (for example, a sheet jam in the conveying path), it is not possible to determine that the cause of the malfunction is the mixed loading of sheets. In such a case, it is not possible to prompt the user to resolve the mixed loading of sheets in the sheet storage unit, and for example, a maintenance management company may be forced to call in a service representative to resolve the malfunction.

[0006] Therefore, the present invention provides a technique that, when a malfunction occurs in an image forming apparatus, makes it possible to determine whether the malfunction is caused by mixed stacking of sheets in a storage unit. [Means for solving the problem]

[0007] An image forming apparatus according to one embodiment of the present invention comprises a storage section in which a stack of sheets is stored, an image forming means for forming an image on a sheet transported from the storage section through a transport path, a detection means arranged on the transport path for detecting a characteristic value indicating a physical characteristic of a sheet being transported along the transport path from the storage section to the image forming means, an acquisition means for acquiring boundary information indicating the boundaries between different types of sheets in the stack of sheets stored in the storage section based on a change in the characteristic value detected by the detection means while each sheet of the stack of sheets is transported in sequence from the storage section, and a discrimination means for discriminating, when a malfunction occurs in the image forming apparatus, a malfunction occurring due to mixed loading of multiple types of sheets in the storage section based on the boundary information acquired by the acquisition means.

[0008] An image forming apparatus according to another aspect of the present invention comprises a storage section in which a stack of sheets is stored, an image forming means for forming an image on a sheet transported from the storage section through a transport path, a first sensor arranged near a bend on the transport path for detecting a sheet being transported along the transport path from the storage section to the image forming means, an acquisition means for acquiring boundary information indicating boundaries between different types of sheets in the stack of sheets stored in the storage section based on a change in the time required for the sheet to be transported in a predetermined section of the transport path measured using the output of the first sensor, and a discrimination means for discriminating, when a malfunction occurs in the image forming apparatus, a malfunction caused by mixed loading of multiple types of sheets in the storage section based on the boundary information acquired by the acquisition means. Effect of the Invention

[0009] According to the present invention, when a malfunction occurs in an image forming apparatus, it is possible to determine whether the malfunction is caused by mixed stacking of sheets in a storage unit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a cross-sectional view showing an example of a hardware configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a block diagram showing an example of a schematic control configuration of the image forming apparatus. [Diagram 3] FIG. 4 is a cross-sectional view showing an example of a configuration in the vicinity of a storage unit and a paper feed unit. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of a detection device. [Diagram 5] 11A and 11B are diagrams illustrating an example of a mixed state of sheets in a storage unit. [Figure 6] FIG. 4 is a diagram showing an example of distribution of characteristic values ​​indicating the basis weight and surface properties of a sheet. [Figure 7] FIG. 13 is a diagram showing an example of a mixed-loading index value Z obtained based on the output of a detection device. [Figure 8] 10 is a flowchart showing an example of a processing procedure for determining the cause of a malfunction that has occurred in an image forming apparatus. [Figure 9]FIG. 11 is a cross-sectional view showing a configuration example of the vicinity of a storage unit and a paper feed unit (second embodiment). [Figure 10] FIG. 11 is a diagram showing an example of a change in time t until a sheet reaches a conveyance sensor on a conveyance path (second embodiment). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0012] [First embodiment] As an example of an image forming apparatus according to an embodiment of the present disclosure, an electrophotographic laser beam printer (LBP) will be described. However, the image forming apparatus is not limited to a laser beam printer, and may be other types of image forming apparatus such as a printer, a copier, a facsimile machine, an inkjet printer, etc.

[0013] <Configuration of Image Forming Apparatus> FIG. 1 is a cross-sectional view showing an example of a hardware configuration of an image forming apparatus 100 according to an embodiment of the present disclosure. The image forming apparatus 100 is configured to form an image on a recording material by an electrophotographic method. The image forming apparatus 100 is configured as an in-line type laser beam printer that employs an intermediate transfer method, and is capable of forming a full-color image. The image forming apparatus 100 uses an intermediate transfer belt as an intermediate transfer body. The image forming apparatus may be configured as a laser beam printer that employs a direct transfer method in which a toner image is transferred from a photosensitive body (photosensitive drum) to a recording material without using an intermediate transfer body (intermediate transfer belt). The recording material on which an image is formed may be called a sheet, recording paper, recording medium, paper, transfer material, transfer paper, etc. An example in which an image is formed on a sheet will be described below.

[0014] The image forming apparatus 100 includes image forming units 30Y, 30M, 30C, and 30K, which form images (toner images) of different colors. The image forming units 30Y, 30M, 30C, and 30K are arranged in a line from the upstream side to the downstream side in the moving direction R1 of the surface of the intermediate transfer belt 8 that carries the toner image. The image forming units 30Y, 30M, 30C, and 30K form images using toner of each color, yellow, magenta, cyan, and black, respectively. The image forming units 30Y, 30M, 30C, and 30K have the same configuration. The letters Y, M, C, and K given to the reference numbers indicate the toner colors of yellow (Y color), magenta (M color), cyan (C color), and black (K color), and are omitted when matters common to each color are described.

[0015] The image forming section 30 includes a process cartridge 40 that is detachably attached to the image forming apparatus 100. The process cartridge 40 includes a photosensitive drum 1, a charging roller 2, a developing unit 20 including a developing roller 3, a cleaning blade 4, and a waste toner container 24. The developing unit 20 includes the developing roller 3. The image forming section 30 further includes a primary transfer roller 6 and a laser unit 7. The primary transfer roller 6 is disposed inside the intermediate transfer belt 8 at a position facing the photosensitive drum 1 with the intermediate transfer belt 8 interposed therebetween. The laser unit 7 is disposed below the process cartridge 40.

[0016] The photosensitive drum 1 is an image carrier that carries an electrostatic latent image and a toner image formed by developing the electrostatic latent image with toner. The photosensitive drum 1 is driven to rotate at a predetermined peripheral speed (circumferential velocity) in the direction of the arrow (clockwise direction) shown in FIG.

[0017] The charging roller 2 uniformly charges the surface of the photosensitive drum 1 by applying a predetermined charging voltage from a power source (not shown). The laser unit 7 exposes the photosensitive drum 1 based on an image signal (image data) to form an electrostatic latent image on the surface of the photosensitive drum 1. The developing roller 3 develops the electrostatic latent image formed on the photosensitive drum 1 using a developer (toner) supplied from a toner container in the developing unit 20, thereby forming a toner image on the photosensitive drum 1. Specifically, a predetermined developing voltage is applied to the developing roller 3 from a power source (not shown), so that the toner on the developing roller 3 moves to and adheres to the photosensitive drum 1. As a result, the electrostatic latent image on the photosensitive drum 1 is developed into a toner image.

[0018] The image forming apparatus 100 includes a flexible, endless intermediate transfer belt 8 disposed in a position facing each photosensitive drum 1. The intermediate transfer belt 8 is stretched around a drive roller 9 for rotating the intermediate transfer belt 8 and a driven roller 10 for applying an appropriate tension to the intermediate transfer belt 8. The intermediate transfer belt 8 is rotated in the direction of arrow R1 (counterclockwise direction) while in contact with the photosensitive drum 1 by a driving force transmitted to the drive roller 9 by a drive motor (not shown). The intermediate transfer belt 8 moves at a speed corresponding to the circumferential speed of the photosensitive drum 1.

[0019] A primary transfer roller 6 is disposed inside the intermediate transfer belt 8 as a transfer member for transferring a toner image from the photosensitive drum 1 to the intermediate transfer belt 8. A primary transfer voltage is applied to the primary transfer roller 6 by a power source (not shown), so that the toner image formed on the photosensitive drum 1 is transferred onto the intermediate transfer belt 8 at a transfer position (primary transfer section). For example, a positive polarity voltage is applied to the intermediate transfer belt 8 via the primary transfer roller 6, so that a negative polarity toner image is transferred from the photosensitive drum 1 onto the intermediate transfer belt 8. At that time, the four color toner images of Y, M, C, and K formed on the photosensitive drums 1Y, 1M, 1C, and 1K, respectively, are transferred onto the intermediate transfer belt 8 in a sequentially overlapping manner.

[0020] The toner image formed on the intermediate transfer belt 8 is transported to a secondary transfer unit 17, which is a contact portion between the intermediate transfer belt 8 and a secondary transfer roller 11, as the intermediate transfer belt 8 rotates. In the secondary transfer unit 17, the toner image on the intermediate transfer belt 8 is transferred to the sheet S that has been transported from a storage unit (sheet storage unit) 13 along a transport path.

[0021] The storage unit 13 stores sheets S in a stacked state. The paper supply unit 12 includes a pickup roller 121, a feed roller 122, and a separation roller 123. The pickup roller 121 is configured to perform a pickup operation of feeding the sheets S stacked in the storage unit 13 toward the conveying path. The feed roller 122 is configured to convey the sheets S fed from the storage unit 13 to the conveying path toward the registration roller pair 16. The separation roller 123 is configured to perform a sheet separation operation so that the sheets S fed from the storage unit 13 are conveyed one by one by the feed roller 122.

[0022] The image forming apparatus 100 includes a detection device 33 disposed on the transport path from the paper feed unit 12 to the pair of registration rollers 16. The detection device 33 detects a characteristic value (physical property value) indicating a physical property of a sheet transported on the transport path. In this embodiment, the detection device 33 is configured to detect physical property values ​​indicating the basis weight and surface properties of the sheet as the physical property values ​​of the sheet. An example of the configuration of the detection device 33 will be described later with reference to FIG. 4.

[0023] The sheet S transported to the registration roller pair 16 is transported by the registration roller pair 16 to a secondary transfer unit 17 at a speed corresponding to the rotation speed of the intermediate transfer belt 8 at a predetermined control timing. A secondary transfer voltage is applied to the secondary transfer roller 11 by a power source (not shown), so that the toner image on the intermediate transfer belt 8 is transferred onto the sheet S at the secondary transfer unit 17. For example, a positive voltage is applied to the sheet S via the secondary transfer roller 11, so that a negative toner image is transferred from the intermediate transfer belt 8 onto the sheet S.

[0024] The sheet S onto which the toner image has been transferred in the secondary transfer section 17 is conveyed to a fixing unit 18. The fixing unit 18 includes a fixing roller 18a which is a heating member, and a pressure roller 18b which is a pressure member disposed opposite the fixing roller 18a. The fixing unit 18 applies heat and pressure to the sheet S while the sheet S passes through the contact portion between the fixing roller 18a and the pressure roller 18b, thereby performing a fixing process in which the transferred toner image is fixed onto the sheet S. The sheet S which has been subjected to the fixing process is discharged onto a discharge tray 50 by a pair of discharge rollers 19.

[0025] The toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 8 is removed by the cleaning blade 4. The cleaning blade 4, in contact with the photosensitive drum 1, collects the toner on the photosensitive drum 1 into a waste toner container 24. In addition, the toner remaining on the surface of the intermediate transfer belt 8 after the toner image is transferred from the intermediate transfer belt 8 to the sheet S, and the paper powder moved from the sheet S to the intermediate transfer belt 8 during the transfer are removed by the cleaning blade 31. The cleaning blade 31, in contact with the intermediate transfer belt 8, collects the toner and paper powder on the intermediate transfer belt 8 into a waste toner container 32.

[0026] In this embodiment, the image forming section 30, the secondary transfer section 17, and the fixing unit 18 function as an example of an image forming unit that forms an image on a sheet transported from the storage section 13 through a transport path.

[0027] 2 is a block diagram showing a schematic control configuration example of the image forming apparatus 100. The image forming apparatus 100 further includes a control unit 200, an operation unit 211, and a communication interface (I / F) 212. The control unit 200 controls the operation of the devices in the image forming apparatus 100, thereby controlling the operation of the entire image forming apparatus 100.

[0028] The control unit 200 includes a processor (CPU), a ROM, and a RAM. The ROM is a non-volatile storage device that stores programs such as a control program for controlling the operation of the image forming apparatus 100. The RAM is a volatile storage device that is used as a temporary storage area for programs and data, and as a working area for the CPU. The CPU controls the operation of each device (image forming unit 30, etc.) of the image forming apparatus 100 by reading the programs stored in the ROM into the RAM and executing them.

[0029] The operation unit 211 includes an input unit and a display unit. The input unit has input devices such as a touch panel and hard keys, and receives various operations from the user. The display unit has a display device such as a liquid crystal display, and outputs (displays) various information to the user. The communication I / F 212 is an interface for communicating with external devices via a network.

[0030] The communication I / F 212 may be configured as an interface for wired communication, or may be configured as an interface for wireless communication (for example, wireless LAN communication). As shown in FIG. 2, the communication I / F 212 is capable of communicating with external devices such as a host computer 220 and a management device 230 via a network. As will be described later, the management device 230 is an information processing device (server device) that manages the image forming device 100. In this embodiment, the management device 230 is capable of communicating with the image forming device 100 via a network, and is an example of a management device that manages the image forming device 100, and the image forming device 100 and the management device 230 can constitute a management system.

[0031] When the control unit 200 receives a print job from the host computer 220, it expands the printing data included in the print job into image data that can be used for image formation. The control unit 200 has a function of performing image processing such as bitmapping of character codes or halftoning of images on the image data received from the host computer 220. The control unit 200 controls the image forming units 30Y, 30M, 30C, and 30K to perform an image forming operation for forming an image on the sheet S based on the expanded image data.

[0032] <Example of sheet feeding operation> With reference to Fig. 3, an example of a sheet feeding operation will be described in which a plurality of different types of sheets are stacked (mixed) in storage section 13, and then sheets are sequentially fed from storage section 13 by sheet feed section 12. Fig. 3 is a cross-sectional view showing an example of the configuration of storage section 13 and the vicinity of sheet feed section 12 of image forming apparatus 100. Note that in this specification, "mixed" refers to stacking a plurality of different types of sheets in the same storage section (storage cabinet).

[0033] FIG. 3(A) shows a state in which sheets (a stack of sheets) of plain paper 1 and sheets (a stack of sheets) of plain paper 2 are mixed in the storage section 13. In this example, the stack of sheets of plain paper 1, which is a different sheet type from the plain paper 2, is stacked on top of the stack of sheets of plain paper 2 that was previously stacked in the storage section 13. Furthermore, sheets of plain paper 1 and sheets of plain paper 2 are each stacked in units of several tens of sheets. This results in a state in which multiple different types of sheets, namely plain paper 1 and plain paper 2, are mixed in the storage section 13 (mixed state), as shown in FIG. 3(B).

[0034] Here, the image forming apparatus 100 of this embodiment has, as fixing temperature control modes of the fixing unit 18, a plain paper mode corresponding to plain paper, and a thick paper mode corresponding to thick paper. In the thick paper mode, a fixing temperature higher than the fixing temperature used in the plain paper mode is used. Plain paper 1 and plain paper 2 are both classified in the "plain paper" category and correspond to the same fixing temperature control mode (plain paper mode). On the other hand, plain paper 1 and plain paper 2 have different physical characteristics (basis weight, surface properties, etc.), and for this reason are defined as different types of sheets. The basis weight of a sheet is the mass per unit area of ​​the sheet (units are [g / m 2 ]).

[0035] FIG. 3B shows a state immediately before the feeding of sheets from the storage unit 13 is started. After the image forming operation is started, the control unit 200 first lowers the pickup roller 121 in the direction of the arrow shown in FIG. 3B. Then, the control unit 200 operates the lift-up plate 131 in the storage unit 13 to rotate in the direction of the arrow shown in FIG. 3B. As a result, the sheets of plain paper 1 and 2 stacked on the lift-up plate 131 are lifted, and the sheet of plain paper 1 abuts against the pickup roller 121. When the top sheet S of the sheet stack stacked in the storage unit 13 abuts against the pickup roller 121, the control unit 200 stops the operation of the lift-up plate 131. This determines the feeding position from which the sheets are fed.

[0036] Thereafter, the control unit 200 causes the pickup roller 121 to start a pickup operation for sending the topmost sheet S of the sheets stacked in the storage unit 13 toward the conveying path. The sheet S sent out from the storage unit 13 by the pickup roller 121 is conveyed to a nip portion between the feed roller 122 and the separation roller 123. The feed roller 122 conveys the sheet S sent out from the storage unit 13 toward the pair of registration rollers 16 on the conveying path. At that time, the separation roller 123 performs a sheet separation operation so that the sheets are conveyed one by one even when multiple sheets are sent out from the storage unit 13. Through such a paper feeding operation by the paper feeding unit 12, the sheets of plain paper 1 are fed in order from the storage unit 13.

[0037] 3C shows a state in which the number of remaining sheets of plain paper 1 in storage section 13 is reduced, and all the remaining sheets are transported (taken out) together as a sheet stack ST from storage section 13 to the nip between feed roller 122 and separation roller 123. This state occurs because the coefficient of friction μ between sheets of plain paper 1 and sheets of plain paper 2 is small. When the number of remaining sheets of plain paper 1 is reduced to a certain number (for example, about 10 sheets), a state occurs in which the transport force of pickup roller 121 acting on those sheets exceeds the friction force generated at the boundary between sheets of plain paper 1 and sheets of plain paper 2. As a result, a state occurs in which all the remaining sheets of plain paper 1 are taken out together from storage section 13.

[0038] 3C, the sheet stack ST is transported by a distance x from the storage unit 13 and is sandwiched between the feed roller 122 and the separation roller 123. The distance x corresponds to the distance from the leading edge of the plain paper 2 sheets stacked in the storage unit 13 to the nip between the feed roller 122 and the separation roller 123. Also, due to the thickness of the sheet stack ST, the feed roller 122 and the separation roller 123 are separated from each other. In this state, if the sheets continue to be fed from the storage unit 13, the separation roller 123 will not be able to perform its original function of separating the sheets and transporting them one by one.

[0039] Fig. 3(D) shows a state immediately before a jam (paper jam) occurs after another sheet is fed from the state of Fig. 3(C). If separation of the sheets by separation roller 123 is not performed normally, sheet S2, which is fed next to preceding sheet S1, is carried downstream in the conveying direction along with the conveyance of sheet S1, as shown in Fig. 3(D). In this example, sheet S2 stops with its leading edge advanced a distance y downstream in the conveying direction from the position of the nip portion between feed roller 122 and separation roller 123.

[0040] In this state, when the feed roller 122 starts conveying the sheet S2, the sheet interval defined as the interval between the rear end of the preceding sheet S1 and the front end of the succeeding sheet S2 becomes shorter than the designed interval by a distance y. In this way, when the sheet interval becomes shorter and falls below the designed allowable value, the image forming apparatus 100 (controller 200) determines that it is difficult to continue the image formation process, stops the image formation operation, and notifies the occurrence of a malfunction. In this case, the image forming apparatus 100 (controller 200) notifies the occurrence of a malfunction in the form of a sheet jam (paper jam) during conveyance.

[0041] In this way, if a user of the image forming device 100 mixes multiple different types of sheets in the storage section 13, as shown in Figure 3 (A), this may cause a jam (problem) to occur when the sheets are fed.

[0042] <Detection device configuration example> Next, a configuration example of the detection device 33 will be described with reference to Figs. 4(A) to (C). As shown in Fig. 1, the detection device 33 has a transmitting unit 34 and a receiving unit 35 arranged at positions facing each other across the conveying path. Fig. 4(A) is a three-view diagram (front view, top view, side view) showing a configuration example of the transmitting unit 34. Fig. 4(B) is a three-view diagram (front view, top view, side view) showing a configuration example of the receiving unit 35. Fig. 4(C) shows a configuration example of the entire detection device 33 including the pressing roller 36 in the AA cross section of Fig. 1.

[0043] In the detection device 33 of this embodiment, the transmitting unit 34 has an electric board 34A and an ultrasonic transmitter 34US arranged on the board. The receiving unit 35 has an ultrasonic receiver 35US and a light irradiator 35G. As shown in FIG. 4(C), the ultrasonic transmitter 34US and the ultrasonic receiver 35US are arranged at positions facing each other. In addition, a pressing roller 36 is arranged at a position facing the light irradiator 35G. The pressing roller 36 is pressed against the light irradiator 35G by being urged toward the light irradiator 35G by an urging member 36S.

[0044] The control unit 200 determines the type of the sheet based on characteristic values ​​indicating the physical characteristics of the sheet (surface property and basis weight in this embodiment) detected by the detection device 33. The control unit 200 further determines image formation conditions based on the results of the determination of the type of the sheet. The image formation conditions include, for example, the sheet conveying speed, the voltage applied to the secondary transfer roller 11 (secondary transfer voltage), the fixing temperature of the fixing unit 18, and the like.

[0045] The ultrasonic transmitter 34US has a piezoelectric element and an electrode terminal. The ultrasonic transmitter 34US is configured to generate ultrasonic waves by applying a pulse voltage of a predetermined frequency to the electrode terminal to oscillate the piezoelectric element. The ultrasonic waves generated by the ultrasonic transmitter 34US propagate through the air and reach the sheet being conveyed along the conveying path, causing the sheet to vibrate due to the ultrasonic waves. The ultrasonic waves generated by the ultrasonic transmission unit 34US are further propagated to the ultrasonic reception unit 35US via the sheet.

[0046] The ultrasonic receiver 35US has a piezoelectric element and an electrode terminal. The piezoelectric element of the ultrasonic receiver 35US generates an output voltage at the electrode terminal according to the amplitude of the received ultrasonic wave. This output voltage changes according to the transmittance of the ultrasonic wave when it passes through the sheet. For a sheet with a large basis weight, the transmittance of the ultrasonic wave is small, and the output voltage of the ultrasonic receiver 35US is small. On the other hand, for a sheet with a small basis weight, the transmittance of the ultrasonic wave is large, and the output voltage of the ultrasonic receiver 35US is large. The detection device 33 outputs the output voltage of the ultrasonic receiver 35US as a detection result of a characteristic value indicating the basis weight of the sheet. In addition, the light irradiation unit 35G is configured to irradiate light to the sheet being transported on the transport path and optically detect a characteristic value indicating the surface property of the sheet based on the distribution characteristic of the reflected light.

[0047] In the image forming apparatus 100 of this embodiment, the control unit 200 obtains detection results of characteristic values ​​indicating the basis weight and surface properties of the sheet from the detection device 33 as characteristic values ​​indicating the physical characteristics of the sheet before starting image formation on the sheet. The control unit 200 determines the type of the sheet on which the image is to be formed based on the detection results by the detection device 33, and determines the image formation conditions based on the determination results of the sheet type. Furthermore, the control unit 200 controls the image forming units 30 (30Y, 30M, 30C, 30K), the secondary transfer unit 17, the fixing unit 18, etc. so that the image is formed according to the determined image formation conditions.

[0048] <Detection device output example> Fig. 5 shows an example of a mixed state of sheets in the storage unit 13, which is the premise of the following description. In this example, four different types of sheets are mixed in the storage unit 13. Specifically, as shown in Fig. 5, a sheet stack of thick paper 2 is stacked at the bottom, and a sheet stack of thick paper 1, plain paper 2, and plain paper 1 are stacked in order on top of that.

[0049] K1, K2, and K3 indicate the number of counts (page counts) obtained by counting the sheets fed (conveyed) in order, with the topmost sheet of all sheets stacked in the storage unit 13 as the reference (page count = 1). K1 is the page count corresponding to the bottommost sheet (last sheet fed) of the stack of plain paper 1, and indicates the boundary (mixed boundary) between the stack of plain paper 1 and the stack of plain paper 2. K2 is the page count corresponding to the bottommost sheet of the stack of plain paper 2, and indicates the boundary (mixed boundary) between the stack of plain paper 2 and the stack of thick paper 1. K3 is the page count corresponding to the bottommost sheet of the stack of thick paper 1, and indicates the boundary (mixed boundary) between the stack of thick paper 1 and the stack of thick paper 2. (In this specification, the boundaries between sheet stacks each composed of different types of sheets are also referred to as "mixed boundaries.") Thus, K1, K2, and K3 indicate the positions of the mixed boundaries in the sheet stacks stacked (stored) in the storage section 13. In this example, 30 sheets each of plain paper 1, plain paper 2, thick paper 1, and thick paper 2 are stacked in the storage section 13 (a total of 120 sheets are stacked). In this case, K1=30, K2=60, and K3=90.

[0050] Fig. 6 shows an example of distribution of characteristic values ​​indicating the basis weight and surface properties of the sheets detected by the detector 33 while the mixed sheets shown in Fig. 5 are fed in order from the storage unit 13 and conveyed along the conveying path. Note that transmittance is used as the characteristic value indicating the basis weight.

[0051] As shown in FIG. 6, the transmittances of thick paper 1 and thick paper 2, which correspond to the thick paper mode as the fixing temperature control mode, are distributed in a region smaller than the transmittances of plain paper 1 and plain paper 2, which correspond to the plain paper mode. In this manner, the characteristic value (transmittance) indicating the basis weight of a sheet varies depending on the thickness of the sheet. A smaller transmittance indicates a thicker sheet, and a larger transmittance indicates a thinner sheet. Based on the detection result of such characteristic value indicating basis weight by the detection device 33, it is possible to determine whether the type of the sheet being transported is a type corresponding to the thick paper mode (thick paper 1 and thick paper 2) or a type corresponding to the plain paper mode (plain paper 1 and plain paper 2).

[0052] Furthermore, the characteristic values ​​indicating the surface properties of plain paper 1 and thick paper 1 are distributed in a region corresponding to a rougher state than the characteristic values ​​of plain paper 2 and thick paper 2. On the other hand, the characteristic values ​​indicating the surface properties of plain paper 2 and thick paper 2 are distributed in a region corresponding to a smoother state than the characteristic values ​​of plain paper 1 and thick paper 1. Here, in this example, the sheets of plain paper 1 and thick paper 1 are sheets with large surface irregularities, such as bond paper. On the other hand, the sheets of plain paper 2 and thick paper 2 are sheets with few surface irregularities, such as coated paper. The detection results of the characteristic values ​​indicating the surface properties of the sheets, shown in FIG. 6, reflect the surface properties of such sheets.

[0053] Based on the detection result of the characteristic value indicating such surface properties by the detector 33, it is possible to determine, for example, whether the type of the sheet being conveyed is thick paper 1 or thick paper 2, or plain paper 1 or plain paper 2. That is, as shown in Fig. 6, based on the detection result of the characteristic value indicating the basis weight of the sheet and the detection result of the characteristic value indicating the surface properties of the sheet, it is possible to determine whether the type of the sheet is one of four types (plain paper 1, plain paper 2, thick paper 1, and thick paper 2).

[0054] <Getting mixed loading index value> In the image forming apparatus 100 of this embodiment, the control unit 200 acquires (determines) a mixed loading index value, which will be described below, based on the detection result of the characteristic value indicating the physical characteristics of the sheet, which is output from the detection device 33. The mixed loading index value is an index value of the mixed loading state of the sheets in the storage unit 13, and can be used to identify the mixed loading boundary and to determine whether or not mixed loading of sheets has occurred in the storage unit 13.

[0055] 7 shows an example of acquiring the mixed load index value Z based on the detection results of characteristic values ​​indicating basis weight and surface properties by the detection device 33. The mixed load index value Z is acquired as follows. In this example, as shown in FIG. 5, an example of acquiring the mixed load index value Z is shown in which a total of 120 sheets including four different types of sheets are stacked (mixed) in the storage unit 13, and all of the sheets are fed in order from the storage unit 13 to perform the image formation process.

[0056] First, a variance value across a predetermined number of sheets is obtained for the characteristic value indicating the basis weight of the sheet, which is detected (output) by the detection device 33. Furthermore, a moving average value X across a predetermined number of sheets is obtained for the obtained variance value. In this example, the predetermined number is 10 sheets. In this case, a total of 110 moving average values ​​(X10, X11, ..., X120) are obtained for a total of 120 sheets to be processed. Note that, for example, X10 is the moving average value corresponding to the 10th sheet, and X120 is the moving average value corresponding to the 120th sheet.

[0057] Similar processing is performed on the characteristic values ​​indicating the surface properties of the sheets detected (output) by the detection device 33. Specifically, a variance value of the characteristic values ​​indicating the surface properties of the sheets across a predetermined number of sheets is obtained. Furthermore, a moving average value Y across the predetermined number of sheets is obtained for the obtained variance value. In this example, since the predetermined number is 10 as described above, a total of 110 moving average values ​​(Y10, Y11, ..., Y120) are obtained for a total of 120 sheets to be processed. Note that, for example, Y10 is the moving average value corresponding to the 10th sheet, and Y120 is the moving average value corresponding to the 120th sheet.

[0058] The mixed loading index value Z is calculated as a composite value of the moving average values ​​X and Y. In this embodiment, the sum of the moving average values ​​X and Y (i.e., Z 10 =X10+Y10,Z 11 =X11+Y11, ...) is calculated as the mixed load index value Z. Note that the mixed load index value Z is not limited to the sum of the moving average value X and the moving average value Y for each sheet, and for example, the product or quotient of the moving average value X and the moving average value Y may be used.

[0059] In this manner, in this embodiment, for each sheet conveyed from the storage unit 13, the variance value of the characteristic values ​​detected by the detection device 33 over a predetermined number of consecutive sheets including the sheet is calculated. Furthermore, the moving average value of the calculated variance values ​​is calculated as an index value for the mixed state of sheets in the storage unit 13 (mixed index value).

[0060] 7 shows an example of the change in the mixed load index value Z obtained (determined) as described above with respect to the count number (page count) obtained by sequentially counting the sheets fed from the storage unit 13. As shown in Fig. 7, it can be seen that the mixed load index value Z increases significantly when the page count exceeds page counts K1, K2, and K3, which correspond to the positions of the mixed load boundary. This is because the type of sheet being conveyed changes at the mixed load boundary, causing greater variation in the characteristic values ​​indicating the basis weight and surface properties of the sheets detected by the detection device 33 (i.e., the variance value increases).

[0061] <Judgment based on mixed loading index value> Next, a description will be given of the determination by the control unit 200 based on the above-mentioned mixed loading index value Z. As described above, the mixed loading index value Z changes significantly at the mixed loading boundary compared to the count number (page count) obtained by sequentially counting the sheets fed from the storage unit 13. Therefore, it is possible to identify the mixed loading boundary and determine whether or not mixed loading of sheets has occurred in the storage unit 13 based on the change in the mixed loading index value Z relative to the page count.

[0062] Specifically, as shown in FIG. 7, the mixed index value Z K1 and the mixed index value Z corresponding to the next sheet to be fed. K1+1 The difference Δ between these is calculated. Δ=Z K+1 -Z K Furthermore, when the difference Δ exceeds a predetermined threshold T1 (Δ>T1), the page count K1 is identified as the position of the mixed sheet boundary, and it is determined that mixed sheets have occurred in the storage unit 13.

[0063] In this way, for the sheets conveyed in order from the storage section 13, the mixed index value Z K1 and a mixed sheet index value Z corresponding to the succeeding sheet to be conveyed from the storage unit 13 after the preceding sheet. K1+1 When the difference Δ between the preceding sheet and the preceding sheet exceeds a predetermined threshold, the preceding sheet is identified as a boundary (mixed load boundary). In this example, as described above, boundary information indicating the boundary (mixed load boundary) is acquired by counting the sheets fed in sequence from the storage unit 13 (e.g., K1, K2, and K3). The acquired boundary information may indicate the boundary (mixed load boundary) by time information based on the timing of feeding the sheets fed in sequence from the storage unit 13 or the timing detected by the detection device 33.

[0064] When mixed sheets are loaded in the storage unit 13, the sheets among the stored sheet stack that may cause a jam are sheets that are transported together from the storage unit 13 due to the mixed loading of sheets, such as the sheet stack ST shown in Fig. 3C. For this reason, in this embodiment, a page count section in which a jam may occur due to the mixed loading of sheets is specified, such as section a, section b, and section c shown in Fig. 7.

[0065] Specifically, these sections are identified as sections between the page counts K1, K2, and K3 indicating the position of the mixed-load boundary in the sheet stack stored in the storage unit 13, which are a predetermined number of sheets (in this example, 10 sheets, the same as in FIG. 3) before the page counts K1, K2, and K3 indicating the position of the mixed-load boundary. For example, section a is identified (set) as the section K1-10≦a≦K1, section b as the section K2-10≦b≦K2, and section c as the section K2-10≦c≦K2.

[0066] In this way, when each sheet of the sheet stack is transported in sequence from the storage section 13, the range (section a, section b, and section c) that includes the sheet located at the boundary indicated by the boundary information (page counts K1, K2, and K3) and a predetermined number of consecutive sheets (10 sheets in this example) fed from the storage section 13 immediately before that sheet is identified as the range (section) of sheets where a jam may occur due to mixed sheets.

[0067] 3C (the number of sheets transported together from the storage section 13 to the nip between the feed roller 122 and the separation roller 123) varies depending on the type of stacked sheets. This is because the coefficient of friction between different types of sheets varies depending on the surface properties of those sheets. For this reason, the above-mentioned predetermined number defining the sections a, b, and c is not limited to 10 sheets, but can be determined depending on the type of sheets.

[0068] By using the page count intervals (intervals a, b, and c) in which a jam may occur due to mixed loading of sheets in the storage unit 13, it is possible to determine a malfunction (jam) caused by mixed loading of sheets among malfunctions (jams) that occur in the image forming apparatus 100. For example, when a jam occurs in a sheet corresponding to the page count of interval a, b, or c in Fig. 7, the control unit 200 determines that the cause of the jam that has occurred is (highly likely to be) mixed loading of sheets in the storage unit 13. In this way, it is possible to determine a malfunction (jam) that occurs due to mixed loading of sheets in the storage unit 13 based on the relationship between the position of the mixed loading boundary in a series of sheet bundles fed in order from the storage unit 13 and the timing of the jam occurrence in the sheet bundle.

[0069] In addition, the position of the mixed-loading boundary and the section in which a jam may occur due to mixed sheets can be determined not only based on the page count, but also based on the elapsed time from the start of feeding of the topmost sheet of all sheets stacked in the storage section 13 (i.e., the first sheet of a series of sheets fed in sequence from the storage section 13).

[0070] In addition, the accuracy of the above-mentioned determination can be improved based on the relationship between the position of the mixed sheet boundary and the storage unit that is the feed source of the jammed sheet. For example, when the image forming apparatus 100 has a plurality of storage units each capable of storing sheets, the control unit 200 may be configured to perform the following process. Specifically, even if a jam occurs with a sheet fed from a storage unit other than the storage unit in which it has been determined that mixed sheet loading has occurred, the control unit 200 does not determine that mixed sheet loading is the cause of the jam. On the other hand, when a jam occurs with a sheet fed from the storage unit in which it has been determined that mixed sheet loading has occurred, it is determined that mixed sheet loading is the cause of the jam (highly likely).

[0071] <Determining the cause of the problem> Fig. 8 is a flowchart showing an example of a procedure for determining (specifying) the cause of a malfunction that has occurred in image forming apparatus 100. In this example, when a sheet jam occurs as a malfunction in image forming apparatus 100, a process for determining whether the malfunction is caused by mixed stacking of sheets in storage unit 13 will be described. When control unit 200 starts execution of an image forming process, for example, it starts execution of the process according to the procedure in Fig. 8.

[0072] In S101, the control unit 200 judges whether or not some malfunction has occurred in the image forming apparatus 100. Examples of malfunctions that may occur include a sheet jam (paper jam) in the conveying path, a temperature problem in the fixing unit 18, an abnormality in the rotation speed of the photosensitive drum 1, or an abnormality in the rotation speed of the intermediate transfer belt 8. The control unit 200 judges the operation state (e.g., a malfunction occurrence state) of the image forming apparatus 100 based on the position information of the sheet and the operation information of each device. For example, when the control unit 200 detects that the sheet being conveyed does not reach a predetermined position by a pre-expected timing based on the position information of the sheet, the control unit 200 judges that a sheet jam has occurred. In response to the judgment that a malfunction (e.g., a sheet jam) has occurred, the control unit 200 stops the operation (image forming operation) of the image forming apparatus 100.

[0073] The control unit 200 repeats the determination process of S101 until it determines that a malfunction has occurred (detects the occurrence of a malfunction). When it determines that a malfunction has occurred (detects the occurrence of a malfunction), the control unit 200 advances the process from S101 to S102.

[0074] In S102, the control unit 200 judges whether or not mixed loading of sheets has occurred in the storage unit 13 based on the characteristic value indicating the physical characteristics of the sheets (in this embodiment, basis weight and surface property) detected by the detection device 33. Specifically, the control unit 200 acquires (determines) a mixed loading index value (described with reference to FIG. 7) based on the detection result output from the detection device 33. The control unit 200 further judges whether or not mixed loading of sheets has occurred in the storage unit 13 using the mixed loading index value as described above. The control unit 200 also identifies a mixed loading boundary in the sheet bundle stored in the storage unit 13 using the mixed loading index value. In this way, the control unit 200 acquires boundary information indicating a boundary between different types of sheets in the sheet bundle stored in the storage unit 13 based on a change in the characteristic value detected by the detection device 33 while each sheet of the sheet bundle is conveyed in order from the storage unit 13.

[0075] In S102, when the control unit 200 determines that mixed sheets have not occurred in the storage unit 13, the control unit 200 ends the process according to the procedure of Fig. 8. On the other hand, when the control unit 200 determines that mixed sheets have occurred in the storage unit 13, the control unit 200 advances the process from S102 to S103.

[0076] In S103, the control unit 200 determines whether the cause of the malfunction is mixed loading of sheets in the storage unit 13. As described above, this determination process can be performed based on the relationship between the timing of the malfunction (jam) occurrence (the jammed sheet) and the mixed loading boundary in a series of sheet stacks fed in order from the storage unit 13. In S103, if the control unit 200 determines that the cause of the malfunction is not mixed loading of sheets in the storage unit 13, it ends the process according to the procedure in Fig. 8. On the other hand, if the control unit 200 determines that the cause of the malfunction is mixed loading of sheets in the storage unit 13, it advances the process from S103 to S104.

[0077] In S104, the control unit 200 performs a notification process to notify the user that the mixed stacking of sheets in the storage unit 13 is the cause of the malfunction, and ends the process according to the procedure in Fig. 8. In this notification process, as described below, the result of determining (identifying) the cause of the malfunction may be notified, as well as troubleshooting (i.e., a method of resolving the malfunction) based on the determined cause.

[0078] In addition, if the control unit 200 determines that no mixed loading of sheets has occurred in the storage unit 13 ("NO" in S102), or if it determines that the cause of the malfunction is not mixed loading of sheets ("NO" in S103), it may report information indicating that no malfunction caused by mixed loading of sheets has occurred.

[0079] <Notification of the cause of the malfunction> In the image forming apparatus 100 of this embodiment, the control unit 200 can perform the following process as a notification process (S104). The control unit 200 notifies the malfunction determination result (S103) by displaying it on the operation unit 211 (display unit) of the image forming apparatus 100, or by transmitting it to an external device (management device 230) that can communicate with the image forming apparatus 100 via a network.

[0080] 2, the image forming apparatus 100 is communicably connected to a management apparatus 230 via a network. The management apparatus 230 may be, for example, a terminal apparatus (information processing apparatus) such as a PC of an IT manager in an office, or a terminal apparatus or server apparatus of a maintenance and management company. The management apparatus 230 may have a monitoring tool for monitoring the operation of the image forming apparatus 100 based on information received from the image forming apparatus 100. The monitoring tool may operate as one of the processes on the management apparatus 230.

[0081] The control unit 200 may display operation information indicating the operation state of the image forming apparatus 100 and malfunction information including information on the malfunction that has occurred on an operation unit 211 (display unit) in the image forming apparatus 100, or may transmit the operation information to the management device 230 via a network. The management device 230 may display the information received from the image forming apparatus 100 on a display unit (not shown) of the management device 230. Furthermore, when the control unit 200 executes the above-mentioned determination process (FIG. 8) and identifies that the cause of the jam that has occurred is mixed stacking of sheets in the storage unit 13, it displays information indicating the identified cause and information indicating troubleshooting on the operation unit 211 in the image forming apparatus 100.

[0082] The management device 230 may, for example, notify the user of the image forming device 100 from a remote location of a method for solving the malfunction based on the information received from the image forming device 100. The method for solving the malfunction includes, for example, a notification for encouraging the user to solve the mixed state of sheet bundles in the storage unit 13. Furthermore, based on the received information, the management device 230 may perform a process for providing a worn out regular replacement unit in the image forming device 100, or may perform a process for instructing the dispatch of a maintenance management company to repair the broken part of the image forming device 100.

[0083] As described above, the image forming apparatus 100 of the present embodiment includes a detection device 33 that is disposed on the transport path and detects characteristic values ​​indicating physical characteristics (basis weight and surface properties) of a sheet being transported on the transport path from the storage unit 13 to the image forming unit (secondary transfer unit 17). The control unit 200 acquires boundary information indicating boundaries between different types of sheets in the sheet stack stored in the storage unit 13 based on changes in the characteristic values ​​detected by the detection device 33 while each sheet of the sheet stack is transported in order from the storage unit 13. When a malfunction occurs in the image forming apparatus 100, the control unit 200 determines whether the malfunction occurs due to a mixture of multiple types of sheets being stacked in the storage unit 13 based on the acquired boundary information.

[0084] In this manner, in the present embodiment, in the image forming apparatus 100, a malfunction caused by a mixture of multiple types of sheets being stacked in the storage unit 13 is determined based on boundary information acquired based on changes in the characteristic values ​​of the sheets detected by the detection device 33. This makes it possible to identify (determine) the cause of a malfunction caused by a mixture of multiple types of sheets (e.g., a sheet jam). This makes it possible to prompt the user of the image forming apparatus 100 to carry out appropriate troubleshooting.

[0085] For example, a maintenance company can deal with a malfunction (jam) that has occurred by encouraging a user of the image forming apparatus 100 to check and resolve the mixed state of sheet bundles in the storage unit 13 (storing only one type of sheet), without requiring a service call. This makes it possible to efficiently resolve malfunctions.

[0086] In the present embodiment, an example has been described in which the mixed index value is obtained using the characteristics indicating the sheet's basis weight and surface properties as characteristic values ​​indicating the physical properties of the sheet, but characteristic values ​​indicating characteristics other than basis weight and surface properties may be used. Also, a characteristic value corresponding to one characteristic may be used, or characteristic values ​​corresponding to three or more characteristics may be used. Also, the cause of a malfunction occurring in the image forming apparatus 100 may be identified by an external device (e.g., a server device) capable of communicating with the image forming apparatus 100.

[0087] [Second embodiment] In the first embodiment, an example has been described in which the mixed load index value is calculated based on a characteristic value indicating a physical characteristic of a sheet, which is detected by the detection device 33. In the second embodiment, an example will be described in which the mixed load index value is calculated using a transport sensor provided on the sheet transport path. In the following, the same reference symbols are used for parts that overlap with the first embodiment, and explanations thereof will be omitted.

[0088] 9 is a cross-sectional view showing an example of the configuration of the storage unit 13 and the paper feed unit 12 of the image forming apparatus 100, and shows an example of a mixed state of sheets in the storage unit 13, which is the premise of the following description. In this example, two different types of sheets are mixed in the storage unit 13. Specifically, as shown in FIG. 9, a stack of thick paper 1 sheets is stacked at the bottom, and a stack of plain paper 1 sheets is stacked on top of that. K4 shown in FIG. 9 is a page count corresponding to the bottom sheet (the sheet fed last) of the stack of plain paper 1 sheets, and indicates the boundary (mixed boundary) between the stack of plain paper 1 sheets and the stack of thick paper 1 sheets.

[0089] The sheet fed from the storage section 13 is conveyed by the feed roller 122 through the conveying path formed by the conveying guide, guided to the nip of the conveying roller pair 60, and detected by the conveying sensor 61. The conveying sensor 61 is disposed near the nip of the conveying roller pair 60 and near the bent portion of the conveying path. The sheet that has passed the position of the conveying sensor 61 is conveyed by the conveying roller pair 60 along the conveying path formed by the conveying guide, and reaches the position of the registration roller pair 16. A registration shutter 62 is disposed near the nip of the registration roller pair 16. The registration shutter 62 corrects the skew of the sheet conveyed along the conveying path. Thereafter, the sheet is conveyed by the registration roller pair 16 to the secondary transfer section 17 on the downstream side in the conveying direction at a predetermined control timing.

[0090] A clearance of, for example, about 3 to 4 mm is formed in the conveying path in the sheet thickness direction in the image forming apparatus 100. Such a clearance is provided so that the image forming apparatus 100 can stably convey various types of sheets having different thicknesses, from thin sheets to thick sheets. If the clearance in the sheet thickness direction of the conveying path is extremely narrow, the conveying resistance increases in the conveying path, especially when conveying thick sheets. As a result, the conveying of the sheet is delayed, and the possibility of jamming increases. Conversely, if the clearance in the sheet thickness direction of the conveying path is extremely wide, the sheet flutters in the conveying path, especially when conveying thin sheets. As a result, the timing at which the sheet reaches the conveying sensor 61 also varies, making it difficult to control the conveying of the sheet. Therefore, as described above, a clearance of, for example, about 3 to 4 mm is generally formed as the clearance in the sheet thickness direction of the conveying path.

[0091] However, even if a clearance of about 3 to 4 mm is formed in the conveying path in the sheet thickness direction, when sheets with different basis weights are conveyed, each sheet does not necessarily pass through the same path in the conveying path. For example, when a thick sheet with high rigidity is conveyed, after the start of conveying by the feed rollers 122, the sheet tends to pass through the shortest path connecting the nip part of the roller pair on the conveying path to the nip part of the next roller pair. On the other hand, in the case of plain paper or thin paper, the rigidity of the sheet is relatively low, so after the start of conveying by the feed rollers 122, the sheet passes through a path that moves along the conveying guide.

[0092] Therefore, the time required from when the pickup roller 121 starts picking up the sheet until the sheet reaches the transport sensor 61 differs between when the sheet is a plain paper sheet and when the sheet is a thick paper sheet. That is, the required time changes depending on the type of the sheet being transported (the physical characteristics of the sheet).

[0093] 10 shows an example of the change in time t from when the sheet starts to be fed until it reaches the transport sensor 61 on the transport path. The vertical axis shows the time (time t) required from the start of the pickup operation until the sheet reaches the transport sensor 61, and the horizontal axis shows the page count. This example corresponds to the case where a stack of thick paper 1 and a stack of plain paper 1 are mixed and fed one by one starting from the top sheet, as shown in FIG.

[0094] In this embodiment, the control unit 200 measures the time (time t) required for conveying a sheet in a predetermined section of the conveying path (in this example, the section from the position of the storage unit 13 to the position of the conveying sensor 61) using the output of the conveying sensor 61. The control unit 200 acquires boundary information indicating the boundaries between different types of sheets in the sheet stack stored in the storage unit 13 based on the change in the measured time (time t).

[0095] Specifically, the time t corresponding to the sheet with page count K4 shown in FIG. 10 is tK4, and the time t K4 and the time t corresponding to the next sheet (page count K4+1) to be fed. K4+1 The difference Δ between is calculated using the following formula: Δ=|t K4+1 -t K4 | Furthermore, when the difference Δ exceeds a predetermined threshold T (Δ>T2), the page count K1 is determined to be a mixed-loading boundary, and it is determined that mixed loading of sheets has occurred in the storage unit 13. In this way, when a significant change occurs in the time t, it is determined that mixed loading of sheets has occurred in the storage unit 13. In addition, the page count K4 at this time is acquired as boundary information indicating the mixed-loading boundary.

[0096] When mixed sheets are present in the storage unit 13, a page count section (section d in FIG. 10) in which a jam may occur due to mixed sheets is identified, as in the first embodiment. That is, section d is set as K4-10≦d≦K4. As in the first embodiment, by using the page count section (section d) in which a jam may occur due to mixed sheets, it is possible to identify malfunctions (jams) caused by mixed sheets among malfunctions (jams) occurring in the image forming apparatus 100.

[0097] The registration shutter 62 also serves as a registration transport sensor and is used to detect the transport timing of the sheet. Therefore, instead of the time t until the sheet reaches the transport sensor 61, the time required for the sheet to be transported from the transport sensor 61 to the registration shutter 62 (registration transport sensor) may be used.

[0098] Similar to the first embodiment (FIG. 8), the image forming apparatus 100 (control unit 200) of this embodiment performs a process of determining (specifying) the cause of a malfunction that has occurred in the image forming apparatus 100. In this embodiment, when a malfunction such as a jam occurs in the page count of the above-mentioned section d, a notification process (S104) is performed, assuming that the cause of the malfunction is mixed stacking of sheets in the storage unit 13.

[0099] Note that even if no malfunction has occurred, if it is determined that the sheet stack stored in the storage unit 13 has been mixed, a notification process may be performed on the determination result. In this case, it is possible to notify that the image forming apparatus 100 is being used in a state in which the sheet stack stored in the storage unit 13 has been mixed, even though no malfunction has occurred in the image forming apparatus 100. This makes it possible to notify the user or the maintenance company that a malfunction may occur due to mixed sheets in the storage unit 13. This can lead to a warning or to the prevention of malfunctions.

[0100] As described above, the image forming apparatus 100 of this embodiment includes a transport sensor 61 (first sensor) that is disposed near a bent portion on the transport path and detects a sheet being transported on the transport path from the storage unit 13 to the image forming unit (secondary transfer unit 17). The control unit 200 acquires boundary information indicating boundaries between different types of sheets in the sheet stack stored in the storage unit 13 based on a change in the time required for the sheet to be transported in a predetermined section of the transport path, which is measured using the output of the transport sensor 61. When a malfunction occurs in the image forming apparatus 100, the control unit 200 determines whether the malfunction occurs due to a mixture of multiple types of sheets being stacked in the storage unit 13 based on the acquired boundary information.

[0101] In this embodiment, the above-mentioned predetermined section is a section on the transport path from the position of the storage unit 13 to the position of the transport sensor 61 (first sensor). Alternatively, the predetermined section may be a section on the transport path from the position of the transport sensor 61 (first sensor) to the position of the registration shutter 62 (second sensor).

[0102] According to this embodiment, similarly to the first embodiment, when a malfunction (e.g., a sheet jam) occurs due to the mixed stacking of multiple types of sheets, it is possible to identify (distinguish) such a cause. This makes it possible to prompt the user of the image forming apparatus 100 to carry out appropriate troubleshooting.

[0103] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0104] The disclosure of this specification includes the following image forming apparatus and management system. (Item 1) An image forming apparatus, a storage section in which a sheet stack is stored; an image forming unit for forming an image on a sheet conveyed from the storage unit through a conveying path; a detection unit arranged on the conveying path and configured to detect a characteristic value indicating a physical characteristic of the sheet being conveyed along the conveying path from the storage unit to the image forming unit; an acquisition unit that acquires boundary information indicating boundaries between different types of sheets in the sheet bundle stored in the storage unit based on a change in a characteristic value detected by the detection unit while each sheet of the sheet bundle is conveyed in sequence from the storage unit; a determination unit that, when a malfunction occurs in the image forming apparatus, determines whether the malfunction occurs due to a mixture of a plurality of types of sheets being stacked in the storage unit based on the boundary information acquired by the acquisition unit; and An image forming apparatus comprising: (Item 2) 2. The image forming apparatus according to claim 1, further comprising a notification means for notifying the result of the defect determination by the determination means by displaying the result on a display unit of the image forming apparatus or by transmitting the result to an external device capable of communicating with the image forming apparatus via a network. (Item 3) 3. The image forming apparatus according to claim 1, wherein the discrimination unit discriminates a defect occurring due to the mixed stacking based on a relationship between a timing at which the defect occurred and the boundary in the sheet stack indicated by the boundary information. (Item 4) The image forming apparatus according to item 3, wherein the discrimination means, when each sheet of the sheet stack is transported in sequence from the storage section, identifies a range including the sheet located at the boundary indicated by the boundary information and a predetermined number of consecutive sheets fed from the storage section immediately before the sheet, as a range of sheets in which a jam may occur due to the mixed loading. (Item 5) 5. The image forming apparatus according to claim 4, wherein when a jam occurs in a sheet included in the range among the sheet stack stored in the storage section, the discrimination unit identifies the mixed stack as the cause of the jam. (Item 6) The acquisition means includes: calculating a variance value of the characteristic values ​​detected by the detection means for each sheet conveyed from the storage unit over a predetermined number of consecutive sheets including the sheet, and calculating a moving average value of the calculated variance values ​​as an index value of the mixed state of the sheets in the storage unit; identifying the boundary of the sheet stack stored in the storage unit based on a change in the index value corresponding to the sheets conveyed in sequence from the storage unit; 6. The image forming apparatus according to any one of items 1 to 5. (Item 7) 7. The image forming apparatus according to claim 6, wherein the acquisition means identifies a preceding sheet as the boundary when a difference between the index value corresponding to a preceding sheet transported in sequence from the storage section and the index value corresponding to a succeeding sheet transported from the storage section after the preceding sheet exceeds a predetermined threshold value. (Item 8) 8. The image forming apparatus according to claim 7, wherein the boundary information indicates the boundary by a count value obtained by counting the sheets fed in sequence from the storage unit. (Item 9) 8. The image forming apparatus according to claim 7, wherein the boundary information indicates the boundary by time information based on timing of sheet feeding for sheets fed in sequence from the storage unit or timing detected by the detection unit. (Item 10) 10. The image forming apparatus according to any one of items 1 to 9, wherein the detection unit detects a characteristic value indicating a basis weight of the sheet. (Item 11) 11. The image forming apparatus according to any one of items 1 to 10, wherein the detection unit detects a characteristic value indicating a surface property of the sheet. (Item 12) 3. The image forming apparatus according to claim 2, wherein the notification unit notifies the user of the malfunction determination result and troubleshooting for eliminating the malfunction based on the determination result. (Item 13) An image forming apparatus, a storage section in which a sheet stack is stored; an image forming unit for forming an image on a sheet conveyed from the storage unit through a conveying path; a first sensor disposed near a bent portion on the conveying path and configured to detect a sheet being conveyed along the conveying path from the storage unit toward the image forming means; an acquiring unit that acquires boundary information indicating boundaries between different types of sheets in the sheet stack stored in the storage unit based on a change in a time required for conveying the sheets in a predetermined section of the conveying path, the change being measured using an output of the first sensor; a determination unit that, when a malfunction occurs in the image forming apparatus, determines whether the malfunction occurs due to a mixture of a plurality of types of sheets being stacked in the storage unit based on the boundary information acquired by the acquisition unit; and An image forming apparatus comprising: (Item 14) Item 14. The image forming apparatus according to item 13, wherein the predetermined section is a section from a position of the storage unit on the transport path to a position of the first sensor. (Item 15) a second sensor disposed on the conveying path downstream of the first sensor in a sheet conveying direction, the second sensor detecting the sheet being conveyed on the conveying path from the storage unit toward the image forming means, Item 14. The image forming apparatus according to item 13, wherein the predetermined section is a section from the position of the first sensor to the position of the second sensor on the transport path. (Item 16) An image forming apparatus according to item 1 or 13, a management device capable of communicating with the image forming apparatus via a network and managing the image forming apparatus; A management system comprising: The image forming apparatus further comprises a notifying unit that notifies the management apparatus of a result of the malfunction determined by the determining unit.

[0105] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0106] 100: image forming apparatus, 12: paper feed section, 13: storage section (sheet storage section), 16: pair of registration rollers, 30: image forming section, 33: detection device, 200: control section, 211: operation section, 212: communication I / F, 230: management device

Claims

1. An image forming apparatus, a storage section in which a sheet stack is stored; an image forming unit for forming an image on a sheet conveyed from the storage unit through a conveying path; a detection unit arranged on the conveying path and configured to detect a characteristic value indicating a physical characteristic of the sheet being conveyed along the conveying path from the storage unit to the image forming unit; an acquisition unit that acquires boundary information indicating boundaries between different types of sheets in the sheet bundle stored in the storage unit based on a change in a characteristic value detected by the detection unit while each sheet of the sheet bundle is conveyed in sequence from the storage unit; a determination unit that, when a malfunction occurs in the image forming apparatus, determines whether the malfunction occurs due to a mixture of a plurality of types of sheets being stacked in the storage unit based on the boundary information acquired by the acquisition unit; and An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, further comprising a notification means for notifying the result of the defect determination made by the determination means by displaying the result on a display unit of the image forming apparatus or by transmitting the result to an external device capable of communicating with the image forming apparatus via a network.

3. 3. The image forming apparatus according to claim 1, wherein the determining unit determines whether a defect occurs due to the mixed stacking based on a relationship between a timing at which the defect occurs and the boundary in the sheet stack indicated by the boundary information.

4. 4. The image forming apparatus according to claim 3, wherein the discrimination means, when each sheet of the sheet stack is transported in sequence from the storage section, identifies a range including the sheet located at the boundary indicated by the boundary information and a predetermined number of consecutive sheets fed from the storage section immediately before that sheet as a range of sheets in which a jam may occur due to the mixed loading.

5. 5. The image forming apparatus according to claim 4, wherein when a jam occurs in a sheet included in the range among the sheet bundle stored in the storage section, the discrimination unit identifies the mixed stack as the cause of the jam.

6. The acquisition means includes: calculating a variance value of the characteristic values ​​detected by the detection means for each sheet conveyed from the storage unit over a predetermined number of consecutive sheets including the sheet, and calculating a moving average value of the calculated variance values ​​as an index value of the mixed state of the sheets in the storage unit; identifying the boundary of the sheet stack stored in the storage unit based on a change in the index value corresponding to the sheets conveyed in sequence from the storage unit; 3. The image forming apparatus according to claim 1 or 2.

7. 7. The image forming apparatus according to claim 6, wherein the acquisition means identifies a preceding sheet as the boundary when a difference between the index value corresponding to a preceding sheet transported in sequence from the storage section and the index value corresponding to a subsequent sheet transported from the storage section after the preceding sheet exceeds a predetermined threshold value.

8. The image forming apparatus according to claim 7 , wherein the boundary information indicates the boundary by a count value obtained by counting the sheets fed in order from the storage unit.

9. The image forming apparatus according to claim 7 , wherein the boundary information indicates the boundary by time information based on timing of feeding the sheets fed in sequence from the storage unit or timing detected by the detection unit.

10. 3. The image forming apparatus according to claim 1, wherein the detection means detects a characteristic value indicating a basis weight of the sheet.

11. 3. The image forming apparatus according to claim 1, wherein the detection means detects a characteristic value indicative of a surface property of the sheet.

12. 3. The image forming apparatus according to claim 2, wherein the notification unit notifies the user of the result of the malfunction determination and of troubleshooting for eliminating the malfunction based on the result of the determination.

13. An image forming apparatus, a storage section in which a sheet stack is stored; an image forming unit for forming an image on a sheet conveyed from the storage unit through a conveying path; a first sensor disposed near a bent portion on the conveying path and configured to detect a sheet being conveyed along the conveying path from the storage unit toward the image forming means; an acquiring unit that acquires boundary information indicating boundaries between different types of sheets in the sheet stack stored in the storage unit based on a change in a time required for conveying the sheets in a predetermined section of the conveying path, the change being measured using an output of the first sensor; a determination unit that, when a malfunction occurs in the image forming apparatus, determines whether the malfunction occurs due to a mixture of a plurality of types of sheets being stacked in the storage unit based on the boundary information acquired by the acquisition unit; and An image forming apparatus comprising:

14. The image forming apparatus according to claim 13 , wherein the predetermined section is a section from a position of the storage unit to a position of the first sensor on the transport path.

15. a second sensor disposed on the conveying path downstream of the first sensor in a sheet conveying direction, the second sensor detecting the sheet being conveyed on the conveying path from the storage unit toward the image forming means; The image forming apparatus according to claim 13 , wherein the predetermined section is a section from the position of the first sensor to the position of the second sensor on the transport path.

16. The image forming apparatus according to claim 1 or 13, a management device capable of communicating with the image forming apparatus via a network and managing the image forming apparatus; A management system comprising: The image forming apparatus further comprises a notification unit that notifies the management apparatus of a result of the malfunction determined by the determination unit.

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