Recording head of an image forming apparatus, and image forming apparatus

Abstract

To provide a recording head for an image forming apparatus that enables appropriate determination of the pressure exerted on the nozzle of the recording head by the recording medium when a media attack occurs. [Solution] The recording head 24 of the image forming apparatus 1 according to the present invention comprises a head body portion 241, a nozzle row 24N formed on the lower surface of the head body portion 241 and having a plurality of nozzles 243 for ejecting ink arranged in a predetermined direction, and a plurality of pressure sensors 25 arranged on the lower surface of the head body portion 241 along the nozzle row 24N.

Description

Technical Field

[0001] The present disclosure relates to a recording head of an image forming apparatus and an image forming apparatus.

Background Art

[0002] Conventionally, an inkjet image forming apparatus that forms (records) an image on a recording medium (for example, paper) by discharging ink from a plurality of nozzles provided in a recording head is known.

[0003] Among such image forming apparatuses, in order to prevent the recording head from contacting the recording medium and damaging the recording medium or damaging the nozzle surface of the recording head when the recording head reciprocates, there is a function for detecting the contact state between the recording head and the recording medium. Incidentally, the contact between the recording head and the recording medium is mainly caused by wrinkles and warping generated in the recording medium during conveyance. Incidentally, the contact between the recording head and the recording medium is also referred to as "media attack".

[0004] For example, in Patent Document 1, a contact detection unit that is mechanically displaced by contact with a recording medium is provided in a recording head, and based on the displacement amount of this contact detection unit, the occurrence of media attack is estimated, and subsequent printing operations and maintenance operations are determined. An image forming apparatus is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the prior art image forming apparatus described in Patent Document 1, etc., the contact detection unit is configured to be located at only one location (or two locations, one upstream and one downstream in the transport direction) relative to the recording head. Therefore, in such an image forming apparatus, even if a media attack occurs, it is unclear at which location the contact between the nozzle surface of the recording head and the recording medium occurred.

[0007] In this regard, the inventors of the present invention, while diligently studying a more suitable control system for an image forming apparatus, have come to recognize the need to understand the pressure exerted on each nozzle of the recording head when a media attack occurs. This is because a media attack significantly affects the ink ejection state at each nozzle of the recording head.

[0008] This disclosure has been made in view of the above-mentioned problems. Specifically, the purpose of this disclosure is to provide a recording head for an image forming apparatus and an image forming apparatus that enable appropriate determination of the pressing state of the recording head against the nozzle by the recording medium when a media attack occurs. [Means for solving the problem]

[0009] The main disclosure that addresses the aforementioned issues is: A recording head for an inkjet image forming apparatus, The head body and A nozzle row is formed on the lower surface of the head body, in which multiple nozzles for ejecting ink are arranged along a predetermined direction, A plurality of pressure sensors are arranged along the nozzle row on the lower surface of the head body, This is a recording head equipped with [a specific feature / feature].

[0010] Also, in other situations, The recording head and, A processing unit that obtains detection values ​​related to the pressing from each of the plurality of pressure sensors and estimates the state of the pressing on each nozzle of the nozzle row, This is an image forming apparatus equipped with [a specific feature]. [Effects of the Invention]

[0011] According to the recording head described herein, in the event of a media attack, it is possible to appropriately determine the pressure exerted on the nozzle of the recording head by the recording medium. [Brief explanation of the drawing]

[0012] [Figure 1] Diagram showing the schematic configuration of an image forming apparatus according to one embodiment of the present invention. [Figure 2] Block diagram showing the main functional configuration of an image forming apparatus according to one embodiment of the present invention. [Figure 3] Diagram showing an example of the configuration of a recording head related to one embodiment of the present invention. [Figure 4] Diagram showing an example of the configuration of a recording head related to one embodiment of the present invention. [Figure 5] Diagram showing an example of the configuration of a recording head related to one embodiment of the present invention. [Figure 6] A diagram showing an example of the configuration of a pressure sensor according to one embodiment of the present invention. [Figure 7] A schematic diagram illustrating the operation of a pressure sensor according to one embodiment of the present invention. [Figure 8] This figure shows an example of the pressure distribution of the pressing force acting on the nozzle row, as detected by a pressure sensor according to one embodiment of the present invention. [Figure 9] This figure shows an example of a media attack detection flow by a sensor processing unit according to one embodiment of the present invention. [Figure 10] This figure shows an example of media attack data created by the processing of the sensor processing unit according to one embodiment of the present invention. [Figure 11] A diagram showing an example of nozzle state data related to one embodiment of the present invention. [Figure 12] This figure shows an example of the analysis processing flow for a faulty nozzle discharged by a control unit according to one embodiment of the present invention. [Figure 13] This figure shows an example of a processing flow for analyzing the cause of a media attack by a control unit according to one embodiment of the present invention. [Figure 14] FIG. showing an example of a processing flow for analyzing the necessity of nozzle maintenance and status confirmation by a control unit according to an embodiment of the present invention [Figure 15] FIG. showing an arrangement mode of a pressure sensor in a recording head according to Modification 1 [Figure 16] FIG. showing an arrangement mode of a pressure sensor in a recording head according to Modification 2

MODE FOR CARRYING OUT THE INVENTION

[0013] 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.

[0014] In each figure, a common orthogonal coordinate system (X, Y, Z) is shown to clarify the positional relationship of each component. In the figure, the plus direction of the X-axis represents the paper conveyance direction (hereinafter referred to as the "conveyance direction"). Also, the plus direction of the Y-axis represents the paper width direction (hereinafter referred to as the "width direction") orthogonal to the paper conveyance direction. The plus direction of the Z-axis represents the vertically upward direction (hereinafter referred to as the "upward direction").

[0015] <Overall Configuration of Image Forming Apparatus> Hereinafter, referring to FIGS. 1 to 2, first, the schematic configuration of an inkjet type image forming apparatus 1 (hereinafter abbreviated as the "image forming apparatus 1") according to an embodiment of the present invention will be described.

[0016] FIG. 1 is a diagram showing a schematic configuration related to image formation of the image forming apparatus 1. FIG. 2 is a block diagram showing the configuration of the control system of the image forming apparatus 1.

[0017] The image forming apparatus 1 includes, as a schematic configuration related to image formation, a paper feeding unit 10, an image forming unit 20, and a paper discharging unit 30.

[0018] The image forming apparatus 1, under the control of the control unit 40, transports the paper P stored in the paper feeding unit 10 to the image forming unit 20, where the image forming unit 20 ejects ink onto the paper P to record an image, and then transports the paper P with the recorded image to the paper discharge unit 30. Specifically, the image forming apparatus 1 records a color image on the paper P by overlaying and outputting four colors—yellow (Y), magenta (M), cyan (C), and black (K)—at predetermined recording gradations for each color.

[0019] In this embodiment, paper P, such as plain paper or coated paper, is shown as an example of a recording medium to be image-formed by the image forming apparatus 1. However, in addition to paper P, various sheet-like recording media capable of fixing ink deposited on the surface can be used as the applicable recording medium, such as cloth or sheet-like resin.

[0020] The paper feeding unit 10 includes a paper feeding tray 11 for storing paper P and a media supply unit 12 for transporting and supplying paper 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 the inside by two rollers, and transports paper P from the paper feeding tray 11 to the image forming unit 20 by rotating the rollers with paper P placed on this belt.

[0021] The image forming unit 20 includes a transport unit 21, a transfer unit 22, a heating unit 23, a recording head 24, a delivery unit 26, and a fixing unit 27.

[0022] The transport unit 21 holds the paper P placed on the paper-holding surface 211a of the cylindrical transport drum 211. The transport drum 211 then rotates around a rotation axis (cylindrical axis) that extends in the width direction of the paper P, thereby transporting the paper P on the transport drum 211 in the transport direction.

[0023] The transport drum 211 is equipped with claws and an air intake (not shown) for holding the paper P on its paper-holding surface 211a. The paper P is held on the paper-holding surface 211a by having its edges pressed down by the claws and being drawn towards the paper-holding surface 211a by the air intake.

[0024] The transfer unit 22 is located between the media supply unit 12 and the transport unit 21 of the paper feeding unit 10. The transfer unit 22 holds one end of the paper P transported from the media supply unit 12 with the swing arm 221, picks it up, and transfers it to the transport unit 21 via the transfer drum 222.

[0025] The heating unit 23 is located between the position of the transfer drum 222 and the position of the recording head 24, and heats the paper P being transported by the transport unit 21 so that the paper P reaches a temperature within a predetermined range. The heating unit 23 has, for example, an infrared heater, and energizes the infrared heater to generate heat based on a control signal supplied from the control unit 40.

[0026] The recording head 24 is positioned opposite the paper-holding surface 211a of the transport drum 211, and records an image on the paper P by ejecting ink onto the paper P at an appropriate timing corresponding to the rotation of the transport drum 211. The recording head 24 is positioned such that the lower surface from which ink is ejected and the paper-holding surface 211a of the transport drum 211 are separated by a predetermined distance.

[0027] In the image forming apparatus 1 according to this embodiment, four recording heads 24, each corresponding to one of the four ink colors Y, M, C, and K, are arranged at predetermined intervals in the order of Y, M, C, and K from the upstream side in the paper transport direction of the paper P. Since the four recording heads 24 according to this embodiment each have a similar configuration, they will be collectively referred to as "recording heads 24" below.

[0028] In the image forming apparatus 1 according to this embodiment, the recording head 24 is used in a fixed position when recording an image, and records an image 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 paper P.

[0029] The delivery unit 26 includes a belt loop 262 having a ring-shaped belt supported on the inside by two rollers, and a cylindrical transfer drum 261 that transfers the paper P from the transport unit 21 to the belt loop 262. The paper P transferred from the transport unit 21 to the belt loop 262 by the transfer drum 261 is then transported by the belt loop 262 and sent to the paper discharge section 30.

[0030] The fixing unit 27 is positioned across the entire width of the transport unit 21 and irradiates UV light onto the paper P placed on the transport unit 21 to cure and fix the ink ejected onto the paper P. The fixing unit 27 is positioned, for example, between the position of the recording head 24 and the position of the delivery drum 261 of the delivery unit 26 in the transport direction.

[0031] The paper output unit 30 has a plate-shaped paper output tray 31 on which the paper P sent out from the image forming unit 20 by the delivery unit 26 is placed.

[0032] The image forming apparatus 1 comprises, in its general configuration as a control system, a control unit 40, a nozzle defect inspection unit 50, a transport drive unit 60, an image processing unit 70, an input / output interface 80, and an operation display unit 90.

[0033] The control unit 40 includes a CPU 41, RAM 42, ROM 43, and storage unit 44, and comprehensively controls the overall operation of the image forming apparatus 1. The CPU 41 reads a program corresponding to the processing content from the ROM 43, loads it into the RAM 42, and works in cooperation with the loaded program to centrally control the operation of each block of the image forming apparatus 1. At this time, various data stored in the storage unit 44 are referenced.

[0034] Furthermore, the control unit 40 according to this embodiment has a function to analyze the cause of discharge failure nozzles, a function to analyze the cause of media attacks, and a function to maintain and manage the nozzles 243 in the recording head 24. The control unit 40 corresponds to the "analysis unit" of the present invention.

[0035] The storage unit 44 is an external storage device, such as a non-volatile semiconductor memory or a hard disk drive. The storage unit 44 stores print job data acquired via the input / output interface 80. The print job data includes, for example, image data to be printed and paper information to be used during printing.

[0036] Furthermore, the storage unit 44 according to this embodiment stores nozzle status data (see Figure 11) indicating a defective nozzle among the nozzles 243 provided on the recording head 24.

[0037] Furthermore, the storage unit 44 according to this embodiment stores media attack data (see Figure 10) from the pressure sensor 25 provided on the recording head 24.

[0038] The transport drive unit 60 operates under the control of the control unit 40 and 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 operates the media supply unit 12, the transfer unit 22, and the delivery unit 26 to supply paper to the transport unit 21 and discharge paper from the transport unit 21.

[0039] The image processing unit 70 performs predetermined image processing on the image data input from the input / output interface 80 and stores the obtained image data in the storage unit 44. This image processing includes correction processing to correct the image data, as well as color conversion processing, gradation correction processing, and pseudo-halftone processing.

[0040] 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. The input / output interface 80 is composed of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

[0041] The operation display unit 90 is composed of, for example, a liquid crystal display with a touch panel, and functions as both a display unit and an operation unit. The operation display unit 90 displays various operation screens, image status, operating status of each function, printing information, etc., according to display control signals input from the control unit 40. The operation display unit 90 is also equipped with various operation keys such as a numeric keypad and a start key, and accepts various input operations from the user and outputs operation signals to the control unit 40.

[0042] Furthermore, the operation display unit 90 displays, for example, information on the pressure distribution to the nozzle row of the recording head 24 (see Figure 9).

[0043] The nozzle failure inspection unit 50 inspects whether or not there are any ejection defects in the nozzles 243 within the recording head 24. The method of inspecting the nozzles 243 by the nozzle failure inspection unit 50 may be any conventionally known method. For example, the nozzle failure inspection unit 50 irradiates light onto the ejection position of each nozzle and determines whether or not each nozzle is in an ejection defect state by whether or not the irradiated light is blocked by the ink ejected from the nozzle. For details of the method of inspecting the nozzles 243 by the nozzle failure inspection unit 50, please refer to, for example, Japanese Patent Application Publication No. 2004-275801.

[0044] Here, the control unit 40 communicates via a bus with the nozzle drive unit 24b, the sensor processing unit 24a, and the in-head memory 24c provided on the recording head 24, and also controls the operation of the recording head 24.

[0045] The nozzle drive unit 24b is a driver IC that includes a drive circuit that drives the image forming elements of the recording head 24 based on a drive signal sent from the control unit 40. Specifically, the nozzle drive unit 24b amplifies the drive signal corresponding to the image data sent from the control unit 40 and supplies the drive signal to the image forming elements of the recording head 24 at an appropriate timing. This causes the nozzle 243 of the recording head 24 to eject an amount of ink corresponding to the pixel value of the image data.

[0046] The sensor processing unit 24a is a microcontroller that includes, for example, an amplification circuit, an AD conversion circuit, and a comparator circuit. The sensor processing unit 24a acquires detection signals related to pressure detection values ​​from each of the multiple pressure sensors 25 (see Figure 3) provided on the recording head 24, performs amplification processing and AD conversion processing on the detection signals, and then sends them to the control unit 40. The sensor processing unit 24a also compares the pressure detection values ​​acquired from the multiple pressure sensors 25 with a threshold value to determine whether or not a media attack has occurred. The sensor processing unit 24a corresponds to the "processing unit" of the present invention.

[0047] The in-head memory 24c consists of memory built into the recording head 24 and stores measurement data related to the pressing of multiple pressure sensors 25 (see Figure 3) (see Figure 10). In other words, in the image forming apparatus 1 according to this embodiment, the recording head 24 can be removed from the image forming apparatus 1, and maintenance and reverse engineering of the recording head 24 can be performed based on the measurement data stored in the in-head memory 24c.

[0048] <Regarding the configuration of the recording head> Figures 3, 4, and 5 show an example of the configuration of the recording head 24. Figure 3 shows the bottom surface of the recording head 24 (i.e., the surface facing the paper placement surface 211a). Figure 4 shows a side view at the position of FF in Figure 3. Figure 5 shows a perspective view of the bottom surface of each colored recording head 24. Note that only one recording head 24 is shown in Figures 3 and 4.

[0049] The recording head 24 comprises a carriage-like head body 241 and four nozzle plates 242 attached to the lower side of the head body 241. Each of the four nozzle plates 242 has multiple image forming elements arranged in a line along the width direction of the paper P, each having a pressure chamber for storing ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle 243 communicating with the pressure chamber. That is, the nozzles 243 formed on the lower side of the nozzle plates 242 are aligned at regular intervals along the width direction of the paper P.

[0050] When a drive signal is input to deform the piezoelectric element in this image forming element, the deformation of the piezoelectric element causes the pressure chamber to deform, changing the pressure inside the pressure chamber, and ink is ejected from the nozzle 243 that communicates with the pressure chamber. As a result, ink droplets corresponding to the pixel values ​​of the image data are ejected from the nozzle 243 toward the paper P at each of the four nozzle plates 242, and an image is formed on the paper P placed on the transport drum 211.

[0051] The four nozzle plates 242 are arranged in a staggered pattern so that their arrangement range in the width direction of the paper P (the direction of the nozzle rows of the nozzle plates 242) is seamlessly connected. The arrangement range of the nozzles 243 included in the recording head 24 in the extending direction covers the width of the area on the paper P that is transported by the transport drum 211 where the image is formed. The recording head 24 is fixed to the rotation axis of the transport drum 211 when forming the image. In other words, the recording head 24 constitutes a line head capable of ejecting ink over the image-forming width in the width direction of the paper P.

[0052] Hereinafter, the row of nozzles 243 formed on the lower surface of the nozzle plate 242 will be referred to as the "nozzle row 24N". The lower surface of the nozzle plate 242 (i.e., the portion on which the nozzle row 24N is formed) will be referred to as the "nozzle surface".

[0053] Furthermore, the recording head 24 has a plurality of pressure sensors 25 arranged along the nozzle row 24N on the lower side of the head body 241.

[0054] Each of the multiple pressure sensors 25 is configured independently and detects the pressure exerted by the paper P pushing up the lower surface of the recording head 24 at various positions in the width direction of the recording head 24 when the paper P comes into contact with the recording head 24 during printing. In other words, the multiple pressure sensors 25 detect the pressure acting on each nozzle 243 provided on the recording head 24.

[0055] As described above, in conventional image forming apparatuses, the contact detection unit is located in only one place relative to the recording head, making it unclear at what point contact occurred between the nozzle surface of the recording head and the recording medium when a media attack occurred.

[0056] Therefore, in the image forming apparatus 1 according to this embodiment, a plurality of pressure sensors 25 are arranged along the nozzle row 24N of the recording head 24, so that the contact points of media attacks can be identified and the contact distribution with respect to the paper width can be obtained. In addition, since the failure of the recording head 24 generally depends on the strength of the media attack on the paper P, the strength of the pressure at the contact position is also detected and can be used to determine the degree of damage to the nozzle 243. Furthermore, in the image forming apparatus 1 according to this embodiment, contact frequency information is also recorded, and the need for head replacement and whether printing is possible can be determined from this information.

[0057] Here, we will explain the details of the configuration of the pressure sensor 25.

[0058] Figure 6 shows an example of the configuration of the pressure sensor 25. Figure 7 is a schematic diagram showing the operation of the pressure sensor 25. Figure 8 shows an example of the pressure distribution of the pressing force acting on the nozzle row 24N, as detected by the pressure sensor 25.

[0059] In the image forming apparatus 1 according to this embodiment, the multiple pressure sensors 25 are arranged adjacent to the nozzle row 24N on the upstream side in the transport direction of the nozzle row 24N (see Figure 3). More specifically, six pressure sensors 25 are arranged along the nozzle row 24N on the upstream side in the transport direction of each nozzle plate 242, adjacent to the nozzle row 24N. Furthermore, the multiple pressure sensors 25 are arranged from one end to the other end of the nozzle row 24N. It is preferable that the multiple pressure sensors 25 are arranged such that the distance between each pressure sensor 25 and the nozzle row 24N is approximately the same, as shown in Figure 3.

[0060] Each of the multiple pressure sensors 25 is composed of a planar type sensor. The distance d1 between the contact portion 25a of one of the multiple pressure sensors 25 that is exposed on the lower side of the recording head 24 and the paper placement surface 211a is configured to be approximately the same as the distance d2 between the nozzle surface of the recording head 24 and the paper placement surface 211a (see Figure 4). As a result, when the paper P comes into contact with the recording head 24, the individual pressure sensors 25 do not deform the curved state of the paper P.

[0061] With this configuration, the pressure distribution in the paper width direction when the paper P is in contact with the multiple pressure sensors 25 of the recording head 24 becomes approximately the same as the pressure distribution in the paper width direction when the paper P is in contact with the nozzle row 24N of the recording head 24. In other words, this makes it possible to accurately detect the pressure distribution of the pressing force acting on each nozzle 243 of the nozzle row 24N when the paper P is in contact with the recording head 24 using the multiple pressure sensors 25.

[0062] The pressure sensor 25 according to this embodiment is composed of, for example, a resistive film type pressure sensor (see Figure 6). Specifically, the pressure sensor 25 is composed of, for example, a conductive pressure-sensitive ink layer 251 and a sensor electrode 252 facing each other vertically with a spacer in between. The pressure-sensitive ink layer 251 is integrally disposed with the contact portion 25a (for example, a cushioning material) on the back side of the contact portion 25a that is exposed on the lower side of the recording head 24. As the pressure-sensitive ink layer 251, a flexible resin material into which conductive particles are blended is used. The surface of the sensor electrode 252 facing the pressure-sensitive ink layer 251 is formed with fine irregularities. When the pressure-sensitive ink layer 251 is compressed by external pressure, the contact area between the sensor electrode 252 and the pressure-sensitive ink layer 251 increases, and the resistance value of the electrical path passing through the sensor electrode 252 and the pressure-sensitive ink layer 251 changes. The pressure sensor 25 detects this change in resistance and measures the pressure.

[0063] However, the specific structure of the pressure sensor 25 is arbitrary as long as it can constitute a planar sensor. For example, a strain gauge type pressure sensor or a capacitive type pressure sensor may be used instead of a resistive film type pressure sensor.

[0064] Here, each nozzle 243 in the recording head 24 is individually managed by assigning an identification number sequentially from the +Y direction to the -Y direction in the table data of the storage unit 44 (and the in-head memory 24c) (Nozzle No. N1 to Nozzle No. NN). Similarly, each pressure sensor 25 in the recording head 24 is individually managed by assigning an identification number sequentially from the +Y direction to the -Y direction in the table data of the storage unit 44 (and the in-head memory 24c) (Sensor No. P1 to Sensor No. PP). Furthermore, in the table data of the in-head memory 24c, each nozzle 243 in the recording head 24 is managed in association with one of a plurality of pressure sensors 25 located in a position suitable for detecting the pressure applied to that nozzle 243.

[0065] In the image forming apparatus 1 according to this embodiment, the pressure acting on each nozzle 243 in the recording head 24 during a media attack is stored as a pressure detection value detected by one of the multiple pressure sensors 25. This makes it possible to monitor the pressure state of all nozzles 243 in the recording head 24 using the multiple pressure sensors 25.

[0066] The detection signals from each pressure sensor 25 in the recording head 24 are processed by the sensor processing unit 24a (see Figure 9).

[0067] <Media attack monitoring processing by sensor processing unit 24b> The sensor processing unit 24b according to this embodiment has a media attack monitoring function.

[0068] Figure 9 shows an example of the media attack detection flow by the sensor processing unit 24a. Figure 10 shows an example of media attack data created by the processing of the sensor processing unit 24a.

[0069] Here, the processes S11 to S15 shown in Figure 9 are processes that the sensor processing unit 24a executes at predetermined intervals (e.g., 100 msec) according to a computer program while printing is in progress. The sensor processing unit 24a starts the process shown in the flowchart of Figure 9 upon receiving a print start command from the control unit 40.

[0070] In step S11, the sensor processing unit 24a acquires detection signals from all pressure sensors 25 provided on the recording head 24, performs amplification processing and AD conversion processing on the detection signals, and identifies the pressure detection value of each pressure sensor 25.

[0071] In step S12, the sensor processing unit 24a determines whether the pressure detection value of each pressure sensor 25 is above a preset threshold. That is, the sensor processing unit 24a determines whether a media attack is occurring based on the pressure detection value of each pressure sensor 25. If the pressure detection value of any of the pressure sensors 25 on the recording head 24 is above the threshold (S12: YES), the sensor processing unit 24a proceeds to step S13. On the other hand, if the pressure detection values ​​of all the pressure sensors 25 on the recording head 24 are below the threshold (S12: NO), the sensor processing unit 24a returns to step S11 and continues monitoring the pressure sensors 25.

[0072] Here, the threshold value set in the sensor processing unit 24a is a threshold value for determining, for example, whether a media attack is applying enough pressure to the nozzle 243 to cause a dispensing failure. Preferably, this threshold value can be changed based on the type of recording medium (in this case, paper P). This is because the amount of pressure required to cause a dispensing failure to the nozzle 243 in the event of a media attack varies depending on the type of recording medium, such as its rigidity and surface roughness.

[0073] In step S13, the sensor processing unit 24a identifies the location of the media attack within the nozzle row 24N based on the determination result in step S12.

[0074] In step S13, the sensor processing unit 24a identifies the identification number of the pressure sensor 25 whose pressure detection value is above a threshold among the pressure sensors 25 provided on the recording head 24. Then, by identifying the identification number of the nozzle 243 corresponding to the pressure sensor 25 that is above the threshold, the location of the media attack within the nozzle row 24N is identified.

[0075] In step S14, the sensor processing unit 24a stores the media attack location within the nozzle row 24N, along with the pressure detection value (i.e., measurement data) from the pressure sensor 25, as media attack data (Figure 10) in the head memory 24c.

[0076] In step S15, the sensor processing unit 24a transmits the media attack data stored in the head memory 24c to the control unit 40 on the main body side of the image forming apparatus 1, along with a display command for media attack occurrence notification.

[0077] In step S15, the control unit 40 stores the media attack data in the storage unit 44 within the control unit 40 in response to receiving media attack data from the sensor processing unit 24a. The control unit 40 then displays a media attack notification on the operation display unit 90. The information displayed on the operation display unit 90 at this time includes, for example, pressure distribution information within the nozzle row 24N of the recording head 24. The pressure distribution information within the nozzle row 24N associates the nozzle position where the media attack occurred with the detected pressure value, for example, as shown in the graph in Figure 8. However, the display format of the pressure distribution information is not limited to the format of the graph in Figure 8, and may be a list of the nozzle row 24N, an image of the nozzle row 24N, or any other format.

[0078] The sensor processing unit 24a repeatedly executes the processes S11 to S15 described above while printing is in progress, monitoring for the occurrence of a media attack. Then, upon receiving a print termination command from the control unit 40, the process shown in the flowchart in Figure 9 is terminated.

[0079] Furthermore, the media attack data stored in the head memory 24c is stored as separate table data for each media attack that occurs during printing (see Figure 10). Here, the media attack data is stored on a page-by-page basis during printing, and if media attacks are continuously detected within a single page, it is stored as a single media attack occurrence information. The duration of continuous media attacks within a single page is stored as the contact time in the media attack data.

[0080] Specifically, media attack data is stored in the print head memory 24c in association with the print job ID, paper type information, paper size information, pressure sensor number, contact nozzle position, contact occurrence time, contact duration, and pressure value applied to the contact nozzle.

[0081] Here, "paper type information" and "paper size information" are information that has been set in advance for the print job. Furthermore, the "pressure sensor number" is stored for the pressure sensor 25 that has been set in advance for the pressure sensor 25 that has been set in advance for the pressure sensor 25 that has been set in advance for the pressure sensor 25 that has been set in close proximity to the record head 24. Furthermore, the sensor number of the pressure sensor 25 is associated with the position of the nozzle 243 that is set in close proximity, and the "contact nozzle position" is stored for the position identified from the "pressure sensor number". Furthermore, the "contact occurrence time" is the time when the media attack occurred, which is identified by the time indicated by the timing unit (not shown) in the control unit 40 and stored. Furthermore, the "contact time" is the time for which the media attack was continuously detected and stored. Furthermore, the "pressure value to the contact nozzle" is the pressure detected value of the pressure sensor 25 that is associated with the contact nozzle position and stored.

[0082] <Analysis processing 1 by the control unit 40> The control unit 40 according to this embodiment has a function to analyze the cause of the occurrence of a faulty nozzle. For example, when the control unit 40 receives notification of a media attack from the sensor processing unit 24a, it determines whether or not a faulty nozzle has occurred due to the media attack.

[0083] In a printing head, several nozzles may become clogged and unable to eject ink due to various reasons such as increased ink viscosity or nozzle damage. When nozzles become clogged, dots may be missing in the printed image, causing unevenness and disconnections. From this perspective, image forming apparatuses generally perform a process to detect nozzle ejection failures in the printing head at the start of printing or during printing.

[0084] There are various methods for detecting nozzle ejection failures. For example, one method involves shining light onto the ejection position of each nozzle and determining whether each nozzle is in an ejection failure state based on whether the irradiated light is blocked by the ink ejected from the nozzle.

[0085] If a nozzle malfunction occurs, it is necessary to perform maintenance to resolve the malfunction as soon as possible. In determining the appropriate maintenance procedure, it is important to identify the cause of the nozzle malfunction and the location where the malfunction is occurring.

[0086] As mentioned above, causes of nozzle ejection failure include increased ink viscosity and nozzle damage, but temporary damage to the meniscus at the nozzle tip due to media attack can also cause nozzle ejection failure. However, in this case, the nozzle condition returns to normal once the recording medium passes under the recording head, so in the case of ejection failure caused by media attack, it is not necessary to interrupt printing or perform any maintenance on the recording head.

[0087] The inventors of this application have come to the realization that, from the perspective of clarifying how to deal with nozzle ejection failures, it is necessary to understand the pressure exerted by the recording head 24 on each individual nozzle 243 when a media attack occurs.

[0088] Therefore, when the control unit 40 according to this embodiment receives notification of a media attack, it compares the location of the media attack in the nozzle row 24N (Figure 10) with the nozzle with a discharge failure (Figure 11) in the nozzle row 24N. This determines whether or not a discharge failure caused by a media attack has occurred.

[0089] The control unit 40 then determines whether to continue or stop the printing operation based on the cause of the defective nozzles in the nozzle row 24N, and also determines how to perform maintenance on the defective nozzles.

[0090] Figure 11 shows an example of nozzle status data. Nozzle status data is data that stores, for example, the identification information of each nozzle 243 in the recording head 24 and the nozzle status related to whether the nozzle 243 is capable of dispensing or not.

[0091] This nozzle status data is acquired, for example, at an appropriate timing during printing by the operation of the nozzle failure inspection unit 50. The nozzle failure inspection unit 50, for example, irradiates light onto the ejection position of each nozzle and determines whether each nozzle is in an ejection failure state based on whether or not the irradiated light is blocked by the ink ejected from the nozzle. This nozzle status data is stored in the storage unit 44.

[0092] Figure 12 shows an example of the analysis process flow for defective nozzles by the control unit 40. Here, the processes S21 to S27 shown in Figure 12 are processes that the control unit 40 repeatedly executes at predetermined intervals (e.g., 100 msec) according to a computer program during printing.

[0093] In step S21, the control unit 40 determines whether or not it has received a notification of a media attack from the sensor processing unit 24a. If it has received a notification of a media attack (S21: YES), the control unit 40 proceeds to step S22. If it has not received a notification of a media attack (S21: NO), the control unit 40 terminates the process shown in the flowchart of Figure 12 without performing any further processing.

[0094] In step S22, the control unit 40 obtains media attack location information (Figure 10) among the nozzle array 24N from the media attack data stored in the storage unit 44.

[0095] In step S23, the control unit 40 obtains the location information of a defective nozzle among the nozzle row 24N (Figure 11) from the nozzle status data stored in the storage unit 44.

[0096] In step S24, the control unit 40 compares the media attack location in the nozzle row 24N with the nozzle location of a defective nozzle in the nozzle row 24N. That is, for nozzles 243 where the defective nozzle location and the media attack location coincide, it is possible to identify that the cause of the defective nozzle 243 is a media attack. As a result, the control unit 40 adds a predetermined identification code to the nozzle status data for the nozzles 243 where the defective nozzle location and the media attack location coincide, for example, as the cause of the defective nozzle.

[0097] In step S25, the control unit 40 determines whether the cause of all defective nozzles 243 in the nozzle row 24N is due to a media attack. That is, in step S25, it determines whether there are any defective nozzles 243 that require maintenance. If the cause of all defective nozzles 243 in the nozzle row 24N is due to a media attack (S25: YES), the control unit 40 proceeds to step S26. On the other hand, if any of the defective nozzles 243 in the nozzle row 24N are due to a media attack (S25: NO), the control unit 40 proceeds to step S27.

[0098] In step S26, the control unit 40 decides to continue printing. Here, since the cause of the faulty nozzle 243 is due to a media attack, no maintenance process is performed. This is because the faulty nozzle 243 will resolve itself once the paper P passes through.

[0099] In step S27, the control unit 40 stops printing and performs maintenance on the defective nozzle 243. In this case, the cause of the defective nozzle 243 is, for example, an increase in ink viscosity. Therefore, as maintenance for the defective nozzle 243, the control unit 40 performs, for example, forced ejection from the defective nozzle 243. After the maintenance of the defective nozzle 243 is completed, the control unit 40 resumes printing.

[0100] In this manner, when the control unit 40 receives notification of a media attack, it determines whether or not a defective nozzle 243 has been generated due to the media attack. Based on this determination, it then decides whether to continue or stop the printing operation, and also determines how to perform maintenance on the defective nozzle 243.

[0101] In other words, the control unit 40 according to this embodiment continues printing without stopping printing if a faulty nozzle 243 occurs solely due to a media attack. This prevents unnecessary stopping of printing when a faulty nozzle 243 occurs.

[0102] <Analysis processing 2 by the control unit 40> The control unit 40 according to this embodiment has a function to analyze the cause of a media attack. For example, the control unit 40 periodically checks the media attack data (Figure 10) and analyzes the cause of the media attack.

[0103] Media attacks occur due to wrinkles or lifting on the recording medium. In this regard, since media attack data is continuously acquired during printing, it may be possible to discover trends in the location of media attacks from the time-series data. For example, it may be discovered that media attacks are constantly occurring at the same location in the nozzle row 24N. In such cases, the cause of the media attack can be said to be a malfunction or damage to the transport mechanism of the transport unit 21 itself, rather than a temporary foreign object in the transport mechanism of the transport unit 21.

[0104] From this perspective, it is preferable that the control unit 40 has an analysis function that uses time-series media attack data (Figure 10) within a predetermined period to check for the occurrence of failures or damage to the transport mechanism of the transport unit 21 itself.

[0105] Figure 13 shows an example of a processing flow for analyzing the cause of a media attack by the control unit 40. The processes in steps S31 to S32 shown in Figure 13 are processes that the control unit 40 executes according to a computer program when the image forming apparatus 1 is started up, for example.

[0106] In step S31, the control unit 40 acquires time-series media attack data for a predetermined period from the storage unit 44. The control unit 40 then determines whether or not media attacks are continuously occurring at any nozzle position. In this case, the control unit 40 refers to, for example, the "contact nozzle position" information in the time-series media attack data for the predetermined period and determines whether or not these are the same each time. Here, whether or not it is continuous can be determined, for example, by whether or not the same contact nozzle position occurs without interruption in the time-series media attack data.

[0107] If a media attack is continuously occurring at any nozzle position (S31: YES), the control unit 40 proceeds to step S32. If a media attack is not continuously occurring at any nozzle position (S31: NO), the control unit 40 terminates the process shown in the flowchart of Figure 13 without performing any further processing.

[0108] In step S32, the control unit 40 displays a notification to the operation display unit 90 indicating that an abnormality has occurred in the transport mechanism.

[0109] This series of processes allows users to quickly detect any abnormalities in the transport mechanism. Furthermore, performing maintenance on the transport mechanism can help prevent media attacks from continuing.

[0110] <Analysis processing 3 by the control unit 40> The control unit 40 according to this embodiment has an analysis function for maintenance management of the nozzles 243 in the recording head 24. For example, the control unit 40 periodically checks media attack data (Figure 10) and performs maintenance management of the nozzles 243 in the recording head 24.

[0111] Media attacks can damage the nozzle 243. Therefore, if a certain number of media attacks occur on the nozzle 243, it is advisable to perform maintenance or check its condition.

[0112] From this perspective, it is preferable that the control unit 40 has a function to analyze the need for maintenance or condition check of the nozzle 243 using time-series media attack data (Figure 10) within a predetermined period.

[0113] Figure 14 shows an example of a processing flow for the control unit 40 to analyze the need for maintenance and condition checks of the nozzle 243. The processes in steps S41 to S42 shown in Figure 14 are processes that the control unit 40 executes according to a computer program when the image forming apparatus 1 is started up, for example.

[0114] In step S41, the control unit 40 acquires time-series media attack data (Figure 10) from the storage unit 44 for a predetermined period (for example, a predetermined period since the last maintenance of the nozzle 243). The control unit 40 then determines whether the cumulative number of contacts to any of the nozzles 243 is equal to or greater than a threshold number (for example, 10 times). At this time, the control unit 40 calculates the cumulative number of contacts by, for example, referring to the "contact nozzle position" information in the time-series media attack data for the predetermined period and accumulating the number of media attacks for each contact nozzle position. Here, the control unit 40 counts the number of media attacks as 1 for each media attack ID on the media attack data table data in Figure 10.

[0115] If the cumulative number of contacts with any nozzle 243 exceeds the threshold number (S41: YES), the control unit 40 proceeds to step S42. If the cumulative number of contacts with any nozzle 243 does not exceed the threshold number (S41: NO), the control unit 40 terminates the process shown in the flowchart of Figure 14 without performing any further processing.

[0116] In step S42, the control unit 40 displays a notification to the operation display unit 90 indicating that maintenance or status check of the nozzle 243 of the recording head 24 is required.

[0117] This series of processes allows the user to perform maintenance or check the condition of the nozzles 243 of the recording head 24 at the appropriate time. This prevents situations where printing continues with one of the nozzles 243 damaged.

[0118] [effect] As described above, the recording head of the image forming apparatus according to this embodiment is The head body and A nozzle row is formed on the lower surface of the head body, in which multiple nozzles for ejecting ink are arranged along a predetermined direction, A plurality of pressure sensors are arranged along the nozzle row on the lower surface of the head body, It is equipped with.

[0119] According to the recording head of the image forming apparatus of this embodiment, it is possible to detect the pressure acting on each nozzle in the recording head when the recording medium comes into contact with the recording head during printing.

[0120] This makes it possible to check whether a faulty nozzle in the recording head is caused by a media attack. In other words, this makes it possible to accurately identify the cause of the faulty nozzle in the recording head, allowing for more appropriate decisions on whether to continue or stop printing, or whether maintenance of the recording head is necessary.

[0121] Furthermore, the recording head of the image forming apparatus according to this embodiment makes it possible to understand the media attack status of each nozzle in the recording head, thereby enabling analysis of the cause of media attacks and maintenance management of each nozzle.

[0122] <Variation> In the above embodiment, a plurality of pressure sensors 25 are arranged within the recording head 24, on the upstream side of the nozzle row 24N in the transport direction, adjacent to the nozzle row 24N.

[0123] However, within the recording head 24, the placement of the multiple pressure sensors 25 can be changed as long as they can detect the pressure acting on each nozzle 243 provided on the recording head 24. That is, the multiple pressure sensors 25 only need to be arranged on at least one of the upstream or downstream sides of the nozzle row 24N with respect to the direction of movement of the paper P or the recording head 24.

[0124] Figure 15 shows a modified example 1 of the arrangement of the pressure sensor 25 inside the recording head 24.

[0125] In the embodiment shown in Figure 15, within the recording head 24, a plurality of pressure sensors 25 are arranged either upstream or downstream in the transport direction relative to the nozzle 243 that the pressure sensors 25 are monitoring.

[0126] Depending on the configuration of the recording head 24, the staggered arrangement of nozzle plates 242 may obstruct the placement of the pressure sensor 25 adjacent to the nozzle 243 to be monitored. In this regard, according to the configuration shown in Figure 15, the pressure sensor 25 can be placed adjacent to the nozzle 243 to be monitored either upstream or downstream in the transport direction.

[0127] However, in the configuration shown in Figure 15, the pressure distribution in the paper width direction when the paper P is in contact with the multiple pressure sensors 25 of the recording head 24 may not be substantially the same as the pressure distribution in the paper width direction when the paper P is in contact with the nozzle row 24N of the recording head 24. For this reason, it is preferable that the multiple pressure sensors 25 within the recording head 24 be in the configuration shown in Figure 3 in the above embodiment.

[0128] Figure 16 shows a modified example 2 of the arrangement of the pressure sensor 25 within the recording head 24. In the configuration shown in Figure 16, multiple pressure sensors 25 are provided only in the Y-colored recording head 24 of the four recording heads 24 of the image forming apparatus 1.

[0129] When a media attack occurs, it is presumed that the contact state between the paper P and each nozzle 243 of the recording head 24 will be the same for the Y, M, C, and K color recording heads 24. Therefore, in this configuration, multiple pressure sensors 25 are provided only for the Y color recording head 24.

[0130] This configuration is useful in that it allows the use of existing recording heads 24 for M color, C color, and K color recording heads 24 as they are.

[0131] However, in order to reliably grasp the pressure acting on each nozzle 243 within each recording head 24, it is preferable that the multiple pressure sensors 25 within the recording head 24 be arranged in the manner shown in Figure 3 of the above embodiment.

[0132] (Other embodiments) The present invention is not limited to the above embodiments and can be applied to various modified forms.

[0133] For example, in the above embodiment, the transport unit 21 was shown to be composed of a transport drum. However, in realizing the image forming apparatus 1 according to the present invention, the transport unit 21 may be composed of a transport belt.

[0134] Furthermore, in the above embodiment, the structure and control mode of the recording head 24 that performs image formation in a single-pass manner was shown for the image forming apparatus 1. However, in realizing the image forming apparatus 1 according to the present invention, a structure and control mode of the recording head that performs image formation in a multi-pass manner may be adopted.

[0135] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Industrial applicability]

[0136] According to the recording head described herein, it is possible to determine the pressure applied to each nozzle of the recording head in the event of a media attack. [Explanation of Symbols]

[0137] 1. Image forming apparatus 10 Paper feed section 20 Image forming unit 21 Conveyor Unit 211 Conveyor Drum 211a Paper placement surface 22 Transfer Unit 23 Heating Unit 24 recording heads 24a Sensor Processing Unit 24b Nozzle drive unit 24c Head memory 241 Head body 242 Nozzle Plate 243 Nozzle with dispensing problems 243 Nozzles 24N nozzle row 25 Pressure Sensor 25a Contacted part 251 Pressure-sensitive ink layer 252 Sensor electrodes 26 Delivery Units 261 Drums 262 Belt Loops 27 Fixing section 30 Paper output section 31 Paper output tray 40 Control Unit 44 Storage section 50 Nozzle Defect Inspection Section 60 Conveyor drive unit 70 Image Processing Unit 80 Input / Output Interfaces 90 Operation display section 100 Nozzle Defect Inspection Unit P paper

Claims

1. A recording head for an inkjet image forming apparatus, The head body and A nozzle row is formed on the lower surface of the head body, in which multiple nozzles for ejecting ink are arranged along a predetermined direction, Multiple pressure sensors are arranged along the nozzle row on the lower surface of the head body, A recording head equipped with a recording head.

2. Each of the aforementioned pressure sensors independently outputs a detected value related to pressing. A recording head according to claim 1.

3. Each of the aforementioned multiple pressure sensors is composed of a planar type sensor. A recording head according to claim 1.

4. The distance between the contact portion of the head body of one of the plurality of pressure sensors that is exposed on the lower surface and the mounting surface on which the recording medium is placed is configured to be approximately the same as the distance between the portion of the lower surface of the head body where the nozzle row is formed and the mounting surface described above. A recording head according to claim 3.

5. The plurality of pressure sensors are arranged on at least one of the upstream or downstream sides of the nozzle row with respect to the direction of movement of the recording medium or the recording head. A recording head according to claim 1.

6. The plurality of pressure sensors are arranged adjacent to the nozzle row, upstream of the nozzle row, with respect to the direction of movement of the recording medium or the recording head. A recording head according to claim 1.

7. The plurality of pressure sensors are arranged from one end to the other end of the nozzle row. A recording head according to claim 1.

8. It incorporates a storage unit for storing measurement data related to the pressing of the plurality of pressure sensors. A recording head according to claim 1.

9. A recording head according to claim 1, A processing unit that obtains detection values ​​related to the pressing from each of the plurality of pressure sensors and estimates the state of the pressing on each nozzle of the nozzle row, An image forming apparatus equipped with the following features.

10. The processing unit outputs information on the pressure distribution to the nozzle row based on the detected values ​​related to the pressing of the plurality of pressure sensors. The image forming apparatus according to claim 9.

11. The processing unit determines whether the detected value related to the pressing on each nozzle in the nozzle row is equal to or greater than a threshold, and based on the determination result, detects contact between the recording medium and the recording head. The image forming apparatus according to claim 9.

12. When the processing unit detects contact between the recording medium and the recording head, it causes the contact information to be displayed on the display unit along with information on the pressure distribution to the nozzle row. The image forming apparatus according to claim 9.

13. The system includes an analysis unit that compares measurement data relating to the pressing state of each nozzle in the nozzle row with nozzle state data indicating a defective nozzle in the nozzle row identified based on the ink ejection status, and determines whether or not a defective nozzle has occurred due to contact between the recording medium and the recording head. The image forming apparatus according to claim 9.

14. The analysis unit determines whether to continue or stop the printing operation based on the cause of the defective nozzle in the nozzle row, and also determines a maintenance procedure for the defective nozzle. The image forming apparatus according to claim 13.

15. The analysis unit determines, based on the time-series measurement data, that an abnormality has occurred in the transport mechanism that transports the recording medium of the image forming apparatus. The image forming apparatus according to claim 13.

16. The processing unit changes the threshold based on the type of recording medium. The image forming apparatus according to claim 10.

17. The processing unit counts the cumulative number of contacts or cumulative contact time of the recording medium with each nozzle in the nozzle row, and if the result of the count exceeds a threshold, it notifies a request for nozzle maintenance. The image forming apparatus according to claim 9.

18. The measurement data relating to the state of pressure applied to each nozzle in the nozzle row is stored in association with the media information of the recording medium. The image forming apparatus according to claim 9.

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