Image forming apparatus, control method for image forming apparatus, and control program for image forming apparatus

Abstract

To provide an image formation apparatus which can reduce a frequency of apparatus stop or nozzle return processing following the malfunction of the nozzle.SOLUTION: An ink jet type image formation apparatus comprises: a malfunction nozzle detection unit which detects a malfunction nozzle that occurs in any of the plurality of nozzles in an ink jet head while a printing job is executed; a complementation setting unit which performs nozzle complementation setting for complementing the malfunction nozzle by a normal nozzle in the plurality of nozzles when the malfunction nozzle is detected; and a continuation execution control unit which suspends the printing job that is currently executed when the malfunction nozzle is detected and the nozzle complementation setting to the malfunction nozzle is impossible, and outputs an execution command of a continuation executable job that can normally execute printing by only using the normal nozzle in the other printing jobs that are accumulated in the storage unit and have not been executed.SELECTED DRAWING: Figure 7

Description

Technical Field

[0006] , , , ,

[0001] The present disclosure relates to an image forming apparatus, a control method for an image forming apparatus, and a control program for an image forming apparatus.

Background Art

[0002] There is known an inkjet type image forming apparatus that has an inkjet head in which a plurality of nozzles are arranged, and ejects ink from the nozzles to land on a recording medium, thereby recording an image, a structure, or the like on the recording medium.

[0003] In recent years, in this type of image forming apparatus, as the number of nozzles increases, the occurrence of ink operation failures (i.e., ink ejection failures) in the nozzles has become inevitable. In particular, during the execution of a printing job, operation failures that do not affect the image quality often occur in any of the many nozzles provided in the inkjet head. For example, a deviation in the ejection direction that does not cause a problem during normal image recording can occur in many nozzles.

[0004] From such a background, conventionally, in this type of image forming apparatus, when such an operation failure of a nozzle occurs, ink is ejected from a nozzle existing at a position adjacent to the malfunctioning nozzle in the inkjet head to complement the ejection operation of the malfunctioning nozzle (see, for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, in this type of image forming apparatus, it is common practice to register multiple print jobs in advance in a storage unit, and then to execute print jobs sequentially from among the multiple print jobs registered in the storage unit, thereby improving the efficiency of the operator's equipment operation.

[0007] In conventional image forming apparatuses, if a nozzle malfunction occurs during print job execution, the apparatus attempts to compensate for the malfunctioning nozzle's ejection operation using the adjacent nozzles in the inkjet head, as described above. However, in practice, nozzle compensation is often impossible, and situations arise where the apparatus must be completely shut down or nozzle recovery processing (i.e., maintenance processing) must be performed each time.

[0008] This situation has room for improvement from the standpoint of production efficiency.

[0009] This disclosure has been made in view of the above-mentioned problems, and aims to provide an image forming apparatus, a control method for the image forming apparatus, and a control program for the image forming apparatus that can reduce the frequency of apparatus shutdown or nozzle recovery processing due to nozzle malfunction. [Means for solving the problem]

[0010] The main disclosure that addresses the aforementioned issues is: An inkjet-type image forming apparatus that forms an image on a recording medium using an inkjet head having multiple nozzles, A print job registration unit that sequentially registers print jobs in the storage unit in response to a print command, When the aforementioned print job is being executed, an image reading unit reads the image formed on the recording medium using an image sensor, A malfunctioning nozzle detection unit detects a malfunctioning nozzle that occurs in any of the multiple nozzles while the print job is being executed, based on the image read and a pre-stored correct image. When the malfunctioning nozzle is detected, the complement setting unit performs nozzle complement settings to compensate for the malfunctioning nozzle using a normal nozzle among the plurality of nozzles, When the malfunctioning nozzle is detected, and it is not possible to perform nozzle compensation settings for the malfunctioning nozzle, the continuous execution control unit interrupts the currently running print job and outputs an execution command for a continueable job from among the other unexecuted print jobs stored in the storage unit that can be executed normally using only the normal nozzle. This is an image forming apparatus equipped with [a specific feature].

[0011] Also, in other situations, A control method for an inkjet-type image forming apparatus that forms an image on a recording medium using an inkjet head having multiple nozzles, A first process involves sequentially registering print jobs in the storage unit in response to a print command, During the execution of the aforementioned print job, a second process is performed in which the image sensor reads the image formed on the recording medium, A third process for detecting a malfunctioning nozzle that occurred in any of the multiple nozzles while the print job was being executed, based on the image read and a pre-stored correct image. When the malfunctioning nozzle is detected, a fourth process is performed to perform nozzle compensation settings to compensate for the malfunctioning nozzle using the normal nozzles among the plurality of nozzles, When the malfunctioning nozzle is detected, and it is not possible to perform nozzle compensation settings for the malfunctioning nozzle, a fifth process is performed which interrupts the currently running print job and outputs a command to execute a continueable job from among the other unexecuted print jobs stored in the storage unit that can be executed normally using only the normal nozzle. This is a control method for an image forming apparatus having [a specific feature / feature].

[0012] Also, in other situations, A control program for an inkjet type image forming apparatus that forms an image on a recording medium using an inkjet head having a plurality of nozzles, a first process of sequentially registering print jobs in a storage unit in response to a print command, a second process of reading, with an image sensor, an image formed on the recording medium when the print job is being executed, a third process of detecting a malfunctioning nozzle that has occurred in any of the plurality of nozzles while the print job is being executed based on the read image and a correct image stored in advance, a fourth process of performing nozzle compensation setting for compensating the malfunctioning nozzle with a normal nozzle among the plurality of nozzles when the malfunctioning nozzle is detected, a fifth process of interrupting the currently executing print job when the malfunctioning nozzle is detected and the nozzle compensation setting for the malfunctioning nozzle is impossible, and outputting an execution command for a continuously executable job that can be normally printed using only the normal nozzles among the other unexecuted print jobs stored in the storage unit, which is a control program for an image forming apparatus having the above.

Advantages of the Invention

[0013] According to the image forming apparatus according to the present disclosure, it is possible to reduce the frequency of apparatus stop or nozzle return processing due to nozzle malfunction.

Brief Description of the Drawings

[0014] [Figure 1] A diagram showing a schematic configuration of an image forming apparatus according to a first embodiment [Figure 2] A schematic diagram showing a configuration of a head unit according to a first embodiment [Figure 3] A block diagram showing a main functional configuration of an image forming apparatus according to a first embodiment [Figure 4] A diagram showing functional blocks of a control unit according to a first embodiment [Figure 5]Figure showing an example of a test image pattern for detecting malfunctioning nozzles [Figure 6] Flowchart showing an example of the operation of the control unit in an image forming apparatus according to the prior art [Figure 7] Flowchart showing an example of the operation of the control unit in an image forming apparatus according to the present embodiment [Figure 8] Figure showing the behavior of the printing execution operation of the image forming apparatus according to the present embodiment (Fig. 8B) and the behavior of the printing execution operation of the image forming apparatus according to the prior art (Fig. 8A) when a malfunctioning nozzle occurs in the head unit [Figure 9] Flowchart showing an example of the operation of the image forming apparatus according to the second embodiment

Mode for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same function are denoted by the same reference numerals, and redundant description is omitted.

[0016] (First Embodiment) [Schematic Configuration of Image Forming Apparatus] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to the first embodiment.

[0017] The image forming apparatus 1 is an inkjet type image forming apparatus that records an image on a recording medium P. The image forming apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharging unit 30, and a control unit 40.

[0018] Under the control of the control unit 40, the image forming apparatus 1 conveys the recording medium P stored in the paper feeding unit 10 to the image forming unit 20, ejects ink onto the recording medium P in the image forming unit 20 to record an image, and conveys the recording medium P on which the image is recorded to the paper discharging unit 30.

[0019] In detail, the image forming apparatus 1 records a color image on the recording medium P by superimposing and outputting four colors—yellow (Y), magenta (M), cyan (C), and black (K)—on the recording medium P at a predetermined number of recording gradations. In the following, the ink colors yellow (Y), magenta (M), cyan (C), and black (K) will be abbreviated as Y, M, C, and K, respectively.

[0020] As the recording medium P, various media capable of fixing ink deposited on its surface can be used, including paper such as plain paper or coated paper, as well as fabric or sheet-like resin.

[0021] The paper feeding unit 10 includes a paper feeding tray 11 for storing the recording medium P, and a media supply unit 12 for transporting and supplying the recording medium P from the paper feeding tray 11 to the image forming unit 20. The media supply unit 12 has a ring-shaped belt supported on its inside by two rollers, and the recording medium P is transported from the paper feeding tray 11 to the image forming unit 20 by rotating the rollers with the recording medium P placed on this belt.

[0022] The image forming unit 20 includes a transport unit 21, a transfer unit 22, a heating unit 23, a head unit 24, a fixing unit 25, a delivery unit 27, and the like.

[0023] The transport unit 21 holds the recording medium P placed on the transport surface of the cylindrical transport drum 211, and the transport drum 211 rotates around a rotation axis (cylindrical axis) extending in the T direction in Figure 1 (representing a direction perpendicular to the transport direction; the same applies hereinafter), thereby transporting the recording medium P on the transport drum 211 in the transport direction along the transport surface.

[0024] The transport drum 211 includes claws and an air intake (not shown) for holding the recording medium P on its transport surface. The recording medium P is held on the transport surface by its ends being pressed down by the claws and being drawn towards the transport surface by the air intake.

[0025] The transfer unit 22 is located between the media supply unit 12 and the transport unit 21 of the paper feeding unit 10. It holds one end of the recording medium P transported from the media supply unit 12 with the swing arm unit 221, picks it up, and transfers it to the transport unit 21 via the transfer drum 222.

[0026] The heating unit 23 is located between the position of the transfer drum 222 and the position of the head unit 24, and heats the recording medium P being transported by the transport unit 21 so that the recording medium P reaches a temperature within a predetermined temperature range. The heating unit 23 has, for example, an infrared heater, and energizes the infrared heater based on a control signal supplied from the control unit 40 to generate heat.

[0027] The head unit 24 records an image by ejecting ink onto the recording medium P from nozzle openings provided on the ink ejection surface facing the transport surface of the transport drum 211 at an appropriate timing corresponding to the rotation of the transport drum 211 in which the recording medium P is held.

[0028] The head unit 24 is arranged such that the ink ejection surface and the transport surface are separated by a predetermined distance. In the image forming apparatus 1 of this embodiment, four head units 24, each corresponding to one of the four ink colors Y, M, C, and K, are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium P in the order of the colors Y, M, C, and K.

[0029] The head unit 24 is used in a fixed position when recording images, and records images in a single-pass manner by sequentially ejecting ink at predetermined intervals (transport direction intervals) at different positions in the transport direction in accordance with the transport of the recording medium P.

[0030] Figure 2 is a schematic diagram showing the configuration of the head unit 24 according to this embodiment. Figure 2 shows the surface of the head unit 24 that faces the outer circumferential surface of the transport drum 211.

[0031] Here, the head unit 24 comprises four inkjet heads 240 attached to a mounting member 244. Each inkjet head 240 is provided with multiple image forming elements, each having a pressure chamber (not shown) for storing ink, a piezoelectric element (not shown) provided on the wall of the pressure chamber, and a nozzle 243. When a drive signal is input to deform the piezoelectric element, the pressure chamber deforms due to the deformation of the piezoelectric element, changing the pressure inside the pressure chamber, and ink is ejected from the nozzle 243 that communicates with the pressure chamber.

[0032] The four inkjet heads 240 are arranged in a staggered pattern so that the arrangement range of the nozzle rows in the T direction is seamlessly connected. The arrangement range of the nozzles 243 included in the head unit 24 in the T direction covers the width in the T direction of the area on the recording medium P transported by the transport drum 211 where the image is formed, and the head unit 24 is used fixed to the rotation axis of the transport drum 211 when the image is formed. In other words, the head unit 24 constitutes a line head capable of ejecting ink over the image-forming width in the T direction relative to the recording medium P.

[0033] The inkjet head 240 is equipped with an ink heating unit (not shown) that heats the ink stored inside the inkjet head 240, and ejects the heated, sol-like ink. When this sol-like ink is ejected onto the recording medium P, the ink droplets land on the recording medium P, and then, due to natural cooling, the ink quickly turns into a gel and solidifies on the recording medium P.

[0034] Furthermore, the configuration of the head unit 24 is not limited to the above configuration, as long as multiple recording elements (for example, piezoelectric elements) are provided at different positions in the T direction.

[0035] The fixing unit 25 has an energy ray irradiation unit that is arranged over the width of the transport unit 21 in the T direction, and irradiates the recording medium P placed on the transport unit 21 with energy rays such as ultraviolet light from the energy ray irradiation unit to cure and fix the ink ejected onto the recording medium P. The energy ray irradiation unit of the fixing unit 25 is arranged facing the transport surface in the transport direction from the position of the head unit 24 to the position of the transfer drum 271 of the delivery unit 27.

[0036] The inline scanner 26 has an image sensor and, under the control of the control unit 40, captures an image of the surface of the recording medium P at an appropriate timing and outputs the captured data to the control unit 40. As the image sensor, for example, a line sensor capable of capturing in RGB three colors is used, and it is possible to acquire a two-dimensional image by repeatedly capturing an image in accordance with the transport of the recording medium P.

[0037] The inline scanner 26 is positioned, for example, downstream of the fixing unit 25 on the transport unit 21, facing the recording medium P, and captures images formed on the recording medium P. The inline scanner 26 is capable of capturing images in each wavelength band of RGB (multiple wavelength bands).

[0038] The delivery unit 27 includes a belt loop 272 having a ring-shaped belt supported on the inside by two rollers, and a cylindrical transfer drum 271 that transfers the recording medium P from the transport unit 21 to the belt loop 272. The recording medium P transferred from the transport unit 21 to the belt loop 272 by the transfer drum 271 is transported by the belt loop 272 and sent to the paper discharge unit 30.

[0039] The cleaning unit 28 has, for example, a nonwoven fabric or a blade member, and cleans the nozzles 243 of the inkjet head 240 and the nozzle surface on which the nozzles 243 are located. The cleaning unit 28 may also have an ink tray or the like for collecting ink when ink is forcibly ejected from the nozzles 243.

[0040] The cleaning unit 28 operates, for example, under the control of the control unit 40. When the control unit 40 outputs an operation command related to maintenance processing, the cleaning unit 28 moves to a position facing the inkjet head 240 and performs a cleaning operation on the inkjet head 240.

[0041] The paper output unit 30 has a plate-shaped output tray 31 on which the recording medium P sent out from the image forming unit 20 by the delivery unit 27 is placed. The paper output unit 30 has multiple output trays 31 and is configured to switch to a different output tray 31 for each print job to which the printed recording medium P is output.

[0042] Figure 3 is a block diagram showing the main functional configuration of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 comprises a control unit 40, a head drive unit 50, a transport drive unit 60, an image processing unit 70, an input / output interface 80, an operation reception unit 90, and a storage unit 100.

[0043] The control unit 40 has a CPU 41 (Central Processing Unit), RAM 42 (Random Access Memory), and ROM 43 (Read Only Memory), and comprehensively controls the overall operation of the image forming apparatus 1. The control unit 40 receives print job data (i.e., image data) transmitted from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network) via the input / output interface 80, and causes the head drive unit 50, transport drive unit 60, and image processing unit 70, etc., to perform operations to form an image on the recording medium P based on this print job data (i.e., image data).

[0044] The CPU 41 reads various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various calculations.

[0045] RAM42 provides the CPU41 with a working memory space and stores temporary data. RAM42 may also include non-volatile memory.

[0046] ROM43 stores various control programs and setting data executed by the CPU41. Alternatively, rewritable non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory) or flash memory may be used instead of ROM43.

[0047] The head drive unit 50, based on the control of the control unit 40, supplies a drive signal corresponding to the image data to the recording elements of the head unit 24 at an appropriate timing, thereby causing the nozzles of the head unit 24 to eject an amount of ink corresponding to the pixel value of the image data.

[0048] The transport drive unit 60, based on control signals supplied from the control unit 40, supplies a drive signal to the transport drum motor provided on the transport drum 211, causing the transport drum 211 to rotate at a predetermined speed and timing. The transport drive unit 60 also supplies drive signals to motors that operate the medium supply unit 12, the transfer unit 22, and the delivery unit 27, based on control signals supplied from the control unit 40, causing the recording medium P to be supplied to the transport unit 21 and discharged from the transport unit 21.

[0049] The image processing unit 70 performs predetermined image processing on the image data stored in the storage unit 100 and stores the obtained image data in the storage unit 100. This image processing includes correction processing, which corrects the image data by applying a correction table (not shown) to the image data, as well as color conversion processing, gradation correction processing, pseudo-halftone processing, and so on.

[0050] The input / output interface 80 is connected to the input / output interface of an external device (e.g., a personal computer) and mediates the transmission and reception of data between the control unit 40 and the external device. For example, the input / output interface 80 acquires print job data (image data to be printed and setting data related to image recording) from the external device based on the control of the control unit 40, and also transmits status information to the external device. The input / output interface 80 includes one or more input / output interfaces that support various communication protocols, such as a LAN card.

[0051] The operation reception unit 90 receives user input and outputs it to the control unit 40. The operation reception unit 90 is composed of, for example, a touch sensor, a push button switch, and a numeric keypad, which are superimposed on the display screen.

[0052] The storage unit 100 stores print job data 100a, nozzle data 100b related to the nozzle state of the inkjet head 240, and test image pattern data 100c, etc., which are input from an external device via the input / output interface 80. For example, the storage unit 100 can be an HDD (Hard Disk Drive) or DRAM (Dynamic Random Access Memory).

[0053] The print job data 100a includes, for example, job identification information, image data to be printed, setting data related to image recording, and status data related to the status of the print job during execution (e.g., number of completed prints). The print job data 100a is configured such that if the print job is interrupted while it is being executed, the information related to the status of the print job (e.g., number of completed prints) is updated.

[0054] The storage unit 100, for example, registers print job data 100a related to a print command in order, associating it with job identification information, in response to a print command input from an external device, and stores and manages the print job data 100a for each print job. The storage unit 100 is configured to identify and store print job data 100a related to print jobs that have not been printed and print job data 100a related to print jobs that were interrupted during printing. The data structure in which the storage unit 100 stores and manages the print job data 100a has, for example, a queue structure, and is configured so that print job data 100a related to print jobs that have not been printed are retrieved in the order in which the print commands were issued, and print job data 100a related to print jobs that were interrupted during printing are retrieved in the order in which they were interrupted. Hereinafter, the storage area of ​​the storage unit 100 that stores print job data 100a related to a print command input from an external device will also be referred to as the "print queue," and the storage area of ​​the storage unit 100 that stores print job data 100a related to a print job that was interrupted during printing will also be referred to as the "stop queue."

[0055] The nozzle data 100b includes data relating to the status of each of the multiple nozzles 243 of the inkjet head 240 (malfunctioning nozzle or normal nozzle). The nozzle data 100b is generated, for example, by a malfunctioning nozzle detection process (described later).

[0056] Test image pattern data 100c is a test image used in the process of detecting a malfunctioning nozzle.

[0057] [Regarding the continuous execution process of print jobs] The continuous execution process of print jobs performed by the image forming apparatus 1 according to this embodiment will be described below with reference to Figures 4 to 8. The function for such continuous execution of print jobs is provided, for example, by the control unit 40.

[0058] Figure 4 shows the functional blocks of the control unit 40 according to this embodiment. The control unit 40 has the functions of a print job registration unit 40a, an image reading unit 40b, a malfunctioning nozzle detection unit 40c, a supplementary setting unit 40d, and a continuous execution control unit 40e.

[0059] The print job registration unit 40a sequentially registers print jobs in the storage unit 100 in response to print commands. The print job data 100a stored in the storage unit 100 are managed in a queue and executed in the order they were registered. The timing for each of the multiple nozzles 243 of the head unit 24 to perform ink ejection is determined from the image data of the print target stored in the print job data 100a.

[0060] The image reading unit 40b reads the image formed on the recording medium P (i.e., the image formed on the recording medium P by the ink ejected from the head unit 24) using the inline scanner 26 while a print job is being executed.

[0061] The malfunctioning nozzle detection unit 40c detects whether or not a malfunctioning nozzle has occurred among the multiple nozzles 243 of the head unit 24 while a print job is being executed, based on the image read by the image reading unit 40b (hereinafter referred to as the "read image") and the correct image previously stored in the storage unit 100.

[0062] The malfunctioning nozzle detection unit 40c, for example, when executing a print job, causes the image forming unit 20 to form a test image pattern in the margin area of ​​the recording medium P based on the test image pattern data 100c stored in the storage unit 100, and detects a malfunctioning nozzle by comparing the correct image with the read image with respect to this test image pattern. At this time, the malfunctioning nozzle detection unit 40c causes each of the multiple nozzles 243 of the head unit 24 to perform an ejection operation, and detects abnormalities in the test image pattern read by the image reading unit 40b to determine whether there is an ink ejection failure in each nozzle 243. The malfunctioning nozzle detection unit 40c then stores the operating status of each nozzle 243 as nozzle data 100b.

[0063] Figure 5 shows an example of a test image pattern for detecting a malfunctioning nozzle. Figure 5A shows the test image pattern to be printed by the head unit 24 (i.e., the correct image), and Figure 5B shows the test image pattern actually printed on the recording medium P (i.e., the read image).

[0064] As a test image pattern, as shown in Figure 5A, a separate line segment is recorded by each nozzle 243 so that it is possible to identify which nozzle 243 ejected the ink. For example, as shown in Figure 5A, each nozzle 243 draws a line segment extending in an independent transport direction. L(N1), L(N2)... represent the nozzle numbers of the multiple nozzles 243 of the head unit 24 that perform the ejection operation to draw the line segment in question.

[0065] In the malfunctioning nozzle detection process using the test image pattern, as shown in Figure 5B, nozzles 243 corresponding to areas V1 and V2 where no straight lines are drawn are determined to be experiencing ink ejection failure. Furthermore, if a straight line T1 thinner than it should be drawn, it is determined that the amount of ink ejected is insufficient. Additionally, a straight line F1 that is significantly deviated relative to the drawing position of surrounding straight lines is determined to have an inaccurate ejection direction.

[0066] Furthermore, as a method for detecting a malfunctioning nozzle by the malfunctioning nozzle detection unit 40c, in addition to the above method which uses a dedicated test image pattern as the correct image, a method which uses the image to be printed as the correct image and detects the malfunctioning nozzle by comparing the correct image with the read image may also be used.

[0067] When a malfunctioning nozzle is detected by the malfunctioning nozzle detection unit 40c, the complementary setting unit 40d performs nozzle complementary settings using a normal nozzle from among the multiple nozzles 243 of the head unit 24 to compensate for the malfunctioning nozzle.

[0068] The complementary setting unit 40d sets, for example, a normal nozzle located adjacent to a malfunctioning nozzle among the multiple nozzles 243 of the head unit 24 as a complementary nozzle in the nozzle data 100b. The information relating to the complementary nozzle set in the nozzle data 100b is read, for example, when a print job is executed, and when the ink ejection operation of the malfunctioning nozzle is performed as defined from the image data of the print job, the complementary nozzle performs the ink ejection operation on behalf of the malfunctioning nozzle.

[0069] For further details on the method for detecting a malfunctioning nozzle and the method for replacing a malfunctioning nozzle with a normal nozzle, please refer, for example, to Patent Document 1 or Patent Document 2, which are prior applications of this applicant.

[0070] The continuous execution control unit 40e controls the automatic and continuous execution of print jobs stored in the storage unit 100.

[0071] The continuous operation control unit 40e controls the operation of the image forming apparatus 1 by dividing it into the following four cases, depending on the nozzle state of each nozzle 243 of the head unit 24. 1) The continuous execution control unit 40e sequentially executes the print jobs that have been queued and managed in the storage unit 100 while no malfunctioning nozzles are detected in the head unit 24. 2) Furthermore, if a malfunctioning nozzle is detected in the head unit 24, the continuous execution control unit 40e will perform nozzle compensation settings for the malfunctioning nozzle in the compensation setting unit 40d, and then continue the currently running print job. 3) On the other hand, when a malfunctioning nozzle is detected in the head unit 24, if it is not possible to set nozzle compensation for the malfunctioning nozzle, the continuous execution control unit 40e interrupts the currently running print job and outputs an execution command for a continuously executable job (hereinafter referred to as the "continued executable job") that can be printed normally using only normal nozzles from among the other unexecuted print jobs stored in the storage unit 100. 4) On the other hand, when a malfunctioning nozzle is detected in the head unit 24, and it is not possible to set nozzle compensation for the malfunctioning nozzle, and there are no jobs that can be continued among the other unexecuted print jobs stored in the storage unit 100, the continuous execution control unit 40e interrupts the currently executing print job and outputs a command to perform maintenance processing to restore the malfunctioning nozzle.

[0072] The image forming apparatus 1 according to this embodiment is characterized in that, even when nozzle compensation settings for a malfunctioning nozzle are not possible, the continuous execution control unit 40e automatically identifies a job that can be continued from among other unexecuted print jobs stored in the storage unit 100, and executes such a job continuously. In other words, the image forming apparatus 1 according to this embodiment makes it possible to reduce the frequency of apparatus shutdowns or maintenance processes through this operation control of the continuous execution control unit 40e.

[0073] More specifically, if nozzle compensation settings are not possible for a malfunctioning nozzle (i.e., case 3) above), the continuous execution control unit 40e determines, for example, whether each of the other unexecuted print jobs stored in the storage unit 100 is a print job that can be continued, in the order in which they were registered, and executes the print jobs that are eligible for continued execution in order.

[0074] Here, the continuous execution control unit 40e is configured to queue the currently running print job when it interrupts the currently running print job and executes a job that can be continued (i.e., in case 3) above). Then, if the malfunctioning nozzle is restored to normal operation through subsequent maintenance processing, the continuous execution control unit 40e resumes printing in the order of the print jobs that were registered in the queue first.

[0075] Typically, the continuous execution control unit 40e switches the output tray 31 to which the printed recording medium P is ejected for each print job. This allows the user to smoothly remove the printed recording medium P from the output tray 31 for each print job without any hassle, even if print jobs are interrupted or switched while multiple print jobs are being executed consecutively. This process is achieved, for example, by associating and storing the job identification number assigned to the print job with the identification number of the output tray 31 when printing is executed.

[0076] The continuous execution control unit 40e determines whether a print job is a job that can be continued, based, for example, on the shape of the image to be printed in the print job under consideration and the position of the malfunctioning nozzle among the multiple nozzles 243. For example, the continuous execution control unit 40e determines that a print job is a job that can be continued if, in the print job under consideration, it is not necessary to use the ink color handled by the malfunctioning nozzle, and / or it is not necessary to eject ink to the ejection position handled by the malfunctioning nozzle.

[0077] Furthermore, when a command to perform maintenance processing is issued to the image forming apparatus 1 (control unit 40), for example, it will forcibly eject ink from a malfunctioning nozzle in the head unit 24, then move the cleaning unit 28 to the nozzle position of the head unit 24, and perform an operation to wipe the ejection port of the malfunctioning nozzle of the head unit 24.

[0078] The operation of the control unit 40 in the image forming apparatus 1 according to this embodiment (in particular, the operation of the continuous operation control unit 40e) will be explained below with reference to Figures 6 to 8, in comparison with the operation of the control unit 40 in the conventional image forming apparatus 1P.

[0079] Figure 6 is a flowchart illustrating an example of the operation of the control unit in a conventional image forming apparatus (referred to here as image forming apparatus 1P and control unit 40P to distinguish them from the image forming apparatus 1 and control unit 40 according to this embodiment). Figure 7 is a flowchart illustrating an example of the operation of the control unit 40 in the image forming apparatus 1 according to this embodiment.

[0080] First, with reference to Figure 6, an embodiment of a print job in a conventional image forming apparatus 1P will be described.

[0081] In step S101, the control unit 40P receives a print command from the user and, in response to the print command from the user, sequentially registers the print job in the storage unit 100 (print queue) along with the image data related to the print command.

[0082] In step S102, when the image forming apparatus 1P is ready for printing, the control unit 40P starts printing the print job registered in the storage unit 100.

[0083] In step S103, the control unit 40P sequentially performs the printing process for the print jobs registered in the storage unit 100 (print queue). At this time, the control unit 40P controls the image forming unit 20 to form a test image pattern on the recording medium P for detecting a malfunctioning nozzle, based on the print target image set for the print job as well as the test image pattern data 100c stored in the storage unit 100.

[0084] In step S103, the control unit 40P executes the print jobs that are queued and managed in the storage unit 100 in order. That is, the control unit 40P executes the print jobs stored in the storage unit 100 in the order in which the print commands were issued.

[0085] In step S104, the control unit 40P reads the test image pattern formed on the recording medium P using the inline scanner 26.

[0086] In step S105, the control unit 40P detects a malfunctioning nozzle among the multiple nozzles 243 of the head unit 24 by comparing the read image related to the test image pattern read by the inline scanner 26 with the correct image related to the test image pattern stored in the storage unit 100 beforehand. If no malfunctioning nozzle has occurred among the multiple nozzles 243 of the head unit 24 (S105: NO), the control unit 40P returns to step S103 and continues the printing process and the monitoring process for malfunctioning nozzles. On the other hand, if a malfunctioning nozzle has occurred among the multiple nozzles 243 of the head unit 24 (S105: YES), the process proceeds to step S106.

[0087] In step S105, the control unit 40P calculates the similarity between the read image and the correct image, for example, by pattern matching based on the test image pattern data 100c. If the similarity is above a threshold, it is determined that no malfunctioning nozzles have occurred; if the similarity is below the threshold, it is determined that malfunctioning nozzles have occurred.

[0088] In step S106, the control unit 40P identifies the location of a malfunctioning nozzle in the head unit 24. In step S106, the control unit 40P, for example, performs image analysis of the read image (see, for example, Figure 5B) to identify the position and density in the width direction of the line corresponding to each nozzle 243, and thereby identifies the location of the malfunctioning nozzle.

[0089] In step S107, the control unit 40P determines whether the malfunctioning nozzle can be compensated for by the normal nozzles among the multiple nozzles 243 of the head unit 24. If the malfunctioning nozzle can be compensated for by the normal nozzles among the multiple nozzles 243 of the head unit 24 (S107: YES), the control unit 40P proceeds to step S108. If the malfunctioning nozzle cannot be compensated for by the normal nozzles among the multiple nozzles 243 of the head unit 24 (S107: NO), the control unit 40P proceeds to step S109.

[0090] In step S107, the control unit 40P sets, for example, one of the multiple nozzles 243 of the head unit 24 that is adjacent in the width direction to the malfunctioning nozzle as a compensating nozzle. However, in cases where both adjacent nozzles 243 in the width direction are malfunctioning nozzles, it is not possible to compensate for the malfunctioning nozzle. Therefore, in step S107, the control unit 40P performs a case-by-case analysis for subsequent processing.

[0091] In step S108, the control unit 40P performs a compensation setting for the malfunctioning nozzle and returns to S103 to continue the currently running print job. In step S108, the compensation setting for the malfunctioning nozzle is performed, so in subsequent operations, the image data will determine that the compensation nozzle will dispense ink at the ejection position handled by the malfunctioning nozzle, and the compensation nozzle will dispense ink in place of the malfunctioning nozzle.

[0092] In step S109, the control unit 40P performs maintenance on the malfunctioning nozzle.

[0093] In step S109, the control unit 40P, for example, forcibly ejects ink from the malfunctioning nozzle in the head unit 24, then moves the cleaning unit 28 to the nozzle position of the head unit 24 to wipe the ejection port of the malfunctioning nozzle in the head unit 24.

[0094] In step S110, the control unit 40P determines whether the malfunctioning nozzle has recovered. If the malfunctioning nozzle has recovered (S110: YES), the unit returns to step S103 and resumes printing the currently running print job. On the other hand, if the malfunctioning nozzle does not recover (S110: NO), the operation of the image forming apparatus 1P is interrupted. Causes of nozzle 243 malfunction include those that can be recovered by the above maintenance process, such as clogging of the nozzle 243 or contamination of the ink flow path, as well as those that cannot be recovered by the above maintenance process, such as deterioration of the piezoelectric element or disconnection of the drive circuit. Step S110 is used to make such a determination.

[0095] In step S110, the control unit 40P, for example, forms a test image pattern on the recording medium P, similar to the processes in steps S103, S104, and S105, and determines whether the malfunctioning nozzle has recovered by comparing the read image of the test image pattern with the correct image.

[0096] Next, with reference to Figure 7, an embodiment of the printing job in the image forming apparatus 1 according to this embodiment will be described.

[0097] The processes from steps S101 to S108 in the flowchart of Figure 7 are the same as the processes from steps S101 to S108 in the flowchart of Figure 6. However, in step S107, if it is not possible to compensate for a malfunctioning nozzle (S107: NO), the control unit 40 in this embodiment interrupts the currently running print job, extracts a job that can be continued from among other unexecuted print jobs stored in the storage unit 100, and executes such jobs that can be continued without performing head maintenance.

[0098] Specifically, in step S111, if the malfunctioning nozzle cannot be compensated for (S107: NO), the control unit 40 in this embodiment determines whether there are any jobs that can be continued among the other unexecuted print jobs stored in the storage unit 100. In step S111, the control unit 40 determines whether the print job in question is a job that can be continued, based, for example, on the shape of the image to be printed in the print job in question and the location of the malfunctioning nozzle among the plurality of nozzles 243.

[0099] In step S111, if the control unit 40 finds that there are other unexecuted print jobs stored in the storage unit 100 that can be continued (S111: YES), it proceeds to step S112. On the other hand, if the control unit 40 finds that there are no other unexecuted print jobs stored in the storage unit 100 that can be continued (S111: NO), it interrupts the operation of the image forming apparatus 1.

[0100] In step S112, the control unit 40 interrupts the currently running print job and registers the print job in the stop queue of the storage unit 100.

[0101] In step S113, the control unit 40 starts printing the jobs that were extracted in step S111 that can be continued. Then, it returns to step S103 and executes the printing process again.

[0102] Furthermore, in this embodiment, if a malfunctioning nozzle occurs while executing a print job that was determined in step S111 to be a job that can be continued, and the malfunctioning nozzle cannot be compensated for, the control unit 40 similarly suspends the print job and registers it in the stop queue of the storage unit 100 (step S112). Then, it restarts the execution of the next print job that is a job that can be continued.

[0103] Figure 8 shows the behavior of the printing operation of the image forming apparatus 1 according to this embodiment (Figure 8B) and the behavior of the printing operation of the conventional image forming apparatus 1P (Figure 8A) when a malfunctioning nozzle occurs in the head unit 24.

[0104] Here, we illustrate a situation where, initially, four different print jobs are registered in the memory unit 100 (referred to as the first print job J1, the second print job J2, the third print job J3, and the fourth print job J4 in order of registration), and while these print jobs J1, J2, J3, and J4 are being executed consecutively, a malfunction of the nozzle 243, which cannot be configured for interpolation, occurs during the execution of the first print job J1 and the third print job J3.

[0105] Specifically, the "100" registered in the memory unit 100 in Figure 8 represents a single print job that prints 100 pages. Figure 8 shows a situation where, at the 40th page of the first print job J1, a malfunction occurred in the nozzle 243 that could not be adjusted for completion, and then, at the 20th page of the third print job J3, another malfunction occurred in the nozzle 243 that could not be adjusted for completion.

[0106] In Figure 8, the print queue represents a memory area in the storage unit 100 that stores print job data 100a related to print jobs that have not yet been printed, and the stop queue represents a memory area in the storage unit 100 that stores print job data 100a related to print jobs that were interrupted during printing.

[0107] As shown in Figure 6, the conventional image forming apparatus 1P is configured such that a maintenance process for the inkjet head 240 is activated whenever a malfunction occurs in the nozzle 243, which cannot be adjusted for complementary settings.

[0108] Therefore, as can be seen in Figure 8A, in the conventional image forming apparatus 1P, when a malfunction of nozzle 243 that cannot be interpolated occurs on the 40th sheet of the first print job J1, the first maintenance process is initiated. If the malfunctioning nozzle 243 recovers after this maintenance process, the remaining 60 sheets of the first print job J1 are printed. After the first print job J1 is completed, the second print job J2 is started in the order registered in the storage unit 100 (print queue), and after the second print job J2 is completed, the third print job J3 is started. When a malfunction of nozzle 243 that cannot be interpolated occurs again on the 20th sheet of the third print job J3, a second maintenance process is initiated. If the malfunctioning nozzle 243 recovers after this maintenance process, the remaining 80 sheets of the third print job J3 are printed. After the third print job J1 is completed, the fourth print job J4 is executed.

[0109] Thus, in the conventional image forming apparatus 1P, two maintenance processes are required before a series of prints are completed.

[0110] On the other hand, as shown in Figure 7, the image forming apparatus 1 according to this embodiment is configured such that when a malfunction occurs in the nozzle 243 that cannot be supplemented, and there are other unexecuted print jobs stored in the storage unit 100 (print queue) that can be continued, the currently executing print job is interrupted and the jobs that can be continued are executed continuously.

[0111] Therefore, as can be seen in Figure 8B, in the image forming apparatus 1 according to this embodiment, when a malfunction of the nozzle 243 that cannot be interpolated occurs on the 40th sheet of the first print job J1, the second print job J2, the third print job J3, and the fourth print job J4 are executed continuously without any maintenance processing on the inkjet head 240. After the fourth print job J4 is completed, maintenance processing is performed, and then the remaining 60 sheets of the first print job J1 and the remaining 80 sheets of the third print job J3, which are stored in the stop queue, are executed in order.

[0112] Thus, in the image forming apparatus 1 according to this embodiment, maintenance processing for the inkjet head 240 performed during the completion of a series of prints is only required once. In other words, the image forming apparatus 1 according to this embodiment makes it possible to reduce the frequency of apparatus stoppage or nozzle recovery processing due to malfunction of the nozzle 243 compared to the conventional image forming apparatus 1P.

[0113] (Second embodiment) The image forming apparatus 1 according to the second embodiment differs from the image forming apparatus 1 according to the first embodiment in that the continuous execution control unit 40e allows the user to choose whether to prioritize the execution of a job that can be continued or to perform maintenance processing to restore the malfunctioning nozzle to normal operation and then restart the currently running print job, based on the user's input operation to the operation reception unit 90, when it is not possible to set nozzle compensation for a malfunctioning nozzle.

[0114] Figure 9 is a flowchart showing an example of the operation of the image forming apparatus 1 according to this embodiment.

[0115] The basic print operation flow from steps S101 to S108 in the flowchart of Figure 9, and the continuous printing execution flow for jobs that can be continuously executed from steps S111 to S113, are the same as the processing in the flowchart of Figure 7.

[0116] However, in the flowchart of Figure 9, if a malfunctioning nozzle is detected in step S107 and it is not possible to replace the malfunctioning nozzle (S107: NO), a process is performed to accept a selection operation from the user (step S114). Specifically, in step S114, the control unit 40 according to this embodiment accepts a selection operation from the user regarding whether to prioritize "executing a job that can be continued" or "performing maintenance processing to restore the malfunctioning nozzle to normal and restarting the currently running print job".

[0117] Then, in step S114, if the user selects to execute a job that can be continued, the control unit 40 performs the continuous printing execution flow for jobs that can be continued from steps S111 to S113. If the user selects to perform maintenance processing, the control unit 40 performs the maintenance processing in step S109. Note that the processing in steps S109 and S110 is the same as the processing in Figure 6.

[0118] In this embodiment, if nozzle compensation settings are not possible for a malfunctioning nozzle, it is necessary to have the user perform a selection operation. Therefore, when a malfunctioning nozzle is detected, the control unit 40 (compensation setting unit 40d) preferably determines whether nozzle compensation settings are possible or not for that malfunctioning nozzle, and if nozzle compensation settings are not possible for that malfunctioning nozzle, it is preferable to inform the user of that fact.

[0119] As described above, the image forming apparatus 1 according to this embodiment is useful in that it can perform processing in cases where nozzle compensation settings for a malfunctioning nozzle are not possible, in accordance with the user's wishes. This allows, for example, the user to prioritize maintenance processing when they want to quickly complete a currently running print job, or to prioritize the continuous execution of jobs that can be continued when they want to reduce the frequency of device stoppages or nozzle recovery processing due to nozzle 243 malfunction.

[0120] (Third embodiment) In the image forming apparatus 1 according to the third embodiment, the continuous execution control unit 40e differs from the image forming apparatus 1 according to the first embodiment in that, when a print job is temporarily suspended and maintenance processing is performed while the print job is being executed by automatic or manual operation control, it first terminates the print job, and then resumes printing in order from the suspended print jobs registered in the stop queue of the storage unit 100.

[0121] In this type of image forming apparatus 1, there is generally a function that allows for the temporary suspension of a print job and the forced execution of maintenance processing while the print job is in progress. This forced execution of maintenance processing can be performed by the user through an input operation to the operation reception unit 90, or it may be performed automatically by the image forming apparatus 1 in an automatic inspection mode, etc. In such cases, some users may find it cumbersome to have a print job currently in progress postponed mid-print.

[0122] From this perspective, in the image forming apparatus 1 according to this embodiment, if maintenance processing is forcibly performed while a print job is being executed, first the print job is terminated, and then printing is resumed in order from the suspended print jobs registered in the stop queue of the storage unit 100.

[0123] As described above, the image forming apparatus 1 according to this embodiment is useful in that it can suppress the unnecessary division of print jobs.

[0124] Furthermore, the above embodiments are merely examples of how the present invention may be implemented, and the technical scope of the present invention should not be limited by them. In other words, the present invention can be implemented in various ways without departing from its gist or its main features. [Explanation of symbols]

[0125] 1. Image forming apparatus 10 Paper feed section 11 Paper feed tray 12 Media supply section 20 Image forming unit 21 Conveying section 22 Transfer Unit 23 Heating section 24 Head Units 240 inkjet heads 243 Nozzles 25 Fixing section 26 Inline Scanners 27 Delivery Department 28 Cleaning Department 30 Paper output section 31. Discharge tray 40 Control Unit 40a Print Job Registration Section 40b Image reading unit 40c Malfunctioning nozzle detection unit 40d Complementary Settings Section 40e Continuous Execution Control Unit 50 Head drive unit 60 Conveyor drive unit 70 Image Processing Unit 80 Input / Output Interfaces 90 Operation reception unit 100 Storage section

Claims

1. An inkjet-type image forming apparatus that forms an image on a recording medium using an inkjet head having multiple nozzles, A print job registration unit that sequentially registers print jobs in the storage unit in response to a print command, When the aforementioned print job is being executed, an image reading unit reads the image formed on the recording medium using an image sensor, A malfunctioning nozzle detection unit detects a malfunctioning nozzle that occurs in any of the multiple nozzles while the print job is being executed, based on the image read and a pre-stored correct image. When the malfunctioning nozzle is detected, the complement setting unit performs nozzle complement settings to compensate for the malfunctioning nozzle using a normal nozzle among the plurality of nozzles, When the malfunctioning nozzle is detected, and it is not possible to perform nozzle compensation settings for the malfunctioning nozzle, the continuous execution control unit interrupts the currently running print job and outputs an execution command for a continueable job from among the other unexecuted print jobs stored in the storage unit that can be executed normally using only the normal nozzle. Equipped with, When the continuous execution control unit interrupts the currently running print job and executes the continuously executable job, it queues the currently running print job in the second storage unit. If the malfunctioning nozzle returns to normal operation after subsequent maintenance, printing will resume in order from the print jobs that were previously queued in the second storage unit. Image forming apparatus.

2. The continuous execution control unit sequentially retrieves data of the print job to be judged from among the other unexecuted print jobs stored in the storage unit, and determines whether the print job is a print job that can be continued based on the appearance of the image to be printed in the print job and the position of the malfunctioning nozzle in the inkjet head. The image forming apparatus according to claim 1.

3. The continuous execution control unit determines that, in the print job subject to determination, if it is not necessary to use the ink color handled by the malfunctioning nozzle, the print job falls under the category of a job that can be continued. The image forming apparatus according to claim 2.

4. The continuous execution control unit determines that, in the print job subject to determination, if there is no need to eject ink to the ejection position handled by the malfunctioning nozzle, the print job is a job that can be continued. The image forming apparatus according to claim 2.

5. If the continuous execution control unit does not find any print jobs among the other unexecuted print jobs stored in the storage unit that are suitable for continuous execution, it will interrupt the currently executing print job and output a command to perform maintenance processing to restore the malfunctioning nozzle. The image forming apparatus according to claim 1.

6. It has an operation reception unit that accepts user input operations, The continuous execution control unit allows the user to choose whether to prioritize the execution of the job that can be continued when it is not possible to perform the nozzle compensation setting for the malfunctioning nozzle based on the input operation, or to perform maintenance processing to restore the malfunctioning nozzle to normal operation and then restart the currently running print job. The image forming apparatus according to claim 1.

7. When the malfunctioning nozzle is detected, the complementary setting unit determines whether or not it is possible to perform the nozzle complementary setting for the malfunctioning nozzle, and if it is not possible to perform the nozzle complementary setting for the malfunctioning nozzle, it notifies the user accordingly. The image forming apparatus according to claim 6.

8. The continuous execution control unit, when executing a print job by automatic or manual operation control, pauses the print job and performs the maintenance process, first terminates the print job, and then resumes printing in order from the print jobs queued in the second storage unit. The image forming apparatus according to claim 1.

9. The continuous execution control unit determines, for each of the other unexecuted print jobs stored in the storage unit, whether or not the print job is a continuously executable job, in the order in which it was registered in the storage unit, and executes the print jobs that are continuously executable jobs in order. The image forming apparatus according to claim 1.

10. The continuous execution control unit switches the output tray to which the printed recording medium is ejected for each print job to a different tray. The image forming apparatus according to claim 1.

11. A control method for an inkjet-type image forming apparatus that forms an image on a recording medium using an inkjet head having multiple nozzles, A first process involves sequentially registering print jobs in the storage unit in response to a print command, During the execution of the aforementioned print job, a second process is performed in which the image sensor reads the image formed on the recording medium, A third process for detecting a malfunctioning nozzle that occurred in any of the multiple nozzles while the print job was being executed, based on the image read and a pre-stored correct image. When the malfunctioning nozzle is detected, a fourth process is performed to perform nozzle compensation settings to compensate for the malfunctioning nozzle using a normal nozzle among the multiple nozzles. When the malfunctioning nozzle is detected, and it is not possible to perform nozzle compensation settings for the malfunctioning nozzle, a fifth process is performed which interrupts the currently running print job and outputs a command to execute a continueable job from among the other unexecuted print jobs stored in the storage unit that can be executed normally using only the normal nozzle. In the fifth process, if the currently running print job is interrupted and the continuously executable job is executed, the currently running print job is queued in the second storage unit, and when the malfunctioning nozzle returns to normal operation as a result of the maintenance process performed thereafter, printing is resumed in order from the print jobs that were first queued in the second storage unit, in the sixth process. A control method for an image forming apparatus having the following features.

12. A control program for an inkjet-type image forming apparatus that forms an image on a recording medium using an inkjet head having multiple nozzles, A first process involves sequentially registering print jobs in the storage unit in response to a print command, During the execution of the aforementioned print job, a second process is performed in which the image sensor reads the image formed on the recording medium, A third process for detecting a malfunctioning nozzle that occurred in any of the multiple nozzles while the print job was being executed, based on the image read and a pre-stored correct image. When the malfunctioning nozzle is detected, a fourth process is performed to perform nozzle compensation settings to compensate for the malfunctioning nozzle using a normal nozzle among the multiple nozzles. When the malfunctioning nozzle is detected, and it is not possible to perform nozzle compensation settings for the malfunctioning nozzle, a fifth process is performed which interrupts the currently running print job and outputs a command to execute a continueable job from among the other unexecuted print jobs stored in the storage unit that can be executed normally using only the normal nozzle. In the fifth process, if the currently running print job is interrupted and the continuously executable job is executed, the currently running print job is queued in the second storage unit, and when the malfunctioning nozzle returns to normal operation as a result of the maintenance process performed thereafter, printing is resumed in order from the print jobs that were first queued in the second storage unit, in the sixth process. A control program for an image forming apparatus.

Images