JP3925729B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a nozzle recovery means for a recording head.

  An image forming apparatus such as an ink jet printer has a recording head having a large number of nozzles, and forms an image on the recording paper by discharging ink from the nozzles of the recording head onto the recording paper. For some of the many nozzles, ink clogging, ink ejection amount (dot size to be ejected onto recording paper) or flight direction (droplet ejection position) is inappropriate due to ink drying, foreign matter adhesion, etc. There may be a case where a discharge failure occurs. Such defective ejection nozzles cause a deterioration in the quality of the recorded image, and thus a recording head recovery process is performed as necessary.

Conventionally, recovery means such as flushing (preliminary ink ejection from nozzles), wiping (wiping nozzles), and nozzle suction (sucking defective ink from nozzles) are formed on the recording paper transport belt. A technique is known in which the recovery process is performed by relatively moving and approaching through the opening (see Patent Document 1). In addition, a technique relating to preliminary ejection in which a plurality of nozzle maintenance openings are provided at predetermined intervals in the conveyance direction of the recording paper of the conveyance belt and ink is ejected to the openings (see Patent Document 2). .
JP 2001-287377 A JP 2001-113690 A

  However, in the line-type recording head in which the nozzles are arranged over the length corresponding to the entire width of the recording paper, the opening size of the opening needs to be larger than that of the recording paper. The apparatus has a drawback that the rigidity of the conveyor belt is lowered due to the large opening. In addition, preliminary ejection can be performed only in a specific opening area on the belt, and there is a problem that productivity is lowered.

  Further, the image forming apparatus described in Patent Document 2 has a problem that wiping and nozzle suction cannot be performed. Further, since the recording paper is simply placed on the conveying belt and conveyed, there is a drawback that the recording paper cannot be stably conveyed.

  The present invention has been made in view of such circumstances, while maintaining the rigidity of the medium support portion (conveyor belt), recovery processing such as nozzle flushing (preliminary ejection), wiping (wiping), nozzle suction, and the like, An object of the present invention is to provide an image forming apparatus capable of performing nozzle drying prevention processing such as capping and contributing to space saving by downsizing.

In order to achieve the above object, the present invention provides a plurality of line-type recording heads corresponding to each color ink in which a plurality of nozzles for ejecting ink are arranged over a length corresponding to the entire width of the recording medium, and the recording A recording medium conveying unit that conveys the medium while supporting it, and moves the recording head and the recording medium relative to each other, and a negative pressure generated by a negative pressure generating unit is provided over the entire surface of the medium supporting unit that supports the recording medium. A plurality of openings for adsorbing and supporting the recording medium using the recording medium are formed in a fixed arrangement pattern along the conveyance direction of the recording medium, and the plurality of openings are substantially perpendicular to the conveyance direction of the recording medium A plurality of openings arranged in a staggered manner so that at least one of the openings exists across the entire nozzle width region of the recording head when projected in a line Open A phase detection means for detecting the position of the portion, a discharge control means for pre-discharging ink from the recording head toward the opening in synchronization with the position of the opening based on the detection result of the phase detection means, preliminary discharge ink, an ink receiving said wiping member and the wiping member that wipes the nozzle surface of the recording head through the opening and the member for collecting through the opening, the nozzle through the opening A single unit nozzle recovery device comprising an advancing / retreating means for advancing or retreating from the surface, and a wipe for sliding the wipe member of the nozzle recovery device in the transport direction relative to the nozzle surface of the recording head and sliding means member, in a standby position where the nozzle surface and an opposed position not opposed to the nozzle surface of the recording head, the conveying direction of the nozzle recovery device Moving means for moving in the width direction of the recording medium orthogonal to the conveying direction and, based on the detection result of said phase detecting means, the wiping operation by the wiping member in synchronism with the position of the opening the nozzle recovery device Wipe control means for controlling, and at the time of image formation in which ink is ejected from the recording head while transporting the recording medium by the recording medium transporting means, the nozzle recovery device is retracted to the standby position, and the recording During the head recovery process, the nozzle recovery device is moved by the moving means to a position facing the nozzle surface at any one of the plurality of openings, and the recovery process is performed via the openings. It is characterized by carrying out.

  According to the present invention, since the openings are arranged in a staggered manner so that the openings exist over the entire nozzle width region of the recording head with respect to the medium support portion, the recovery process by the preliminary discharge can be performed on all the nozzles. The In addition, since the opening area per opening can be reduced by the openings arranged in a staggered pattern, it is possible to prevent a decrease in the rigidity of the medium support portion. Further, since the preliminary ejection can be performed in synchronization with the position of the opening, the recovery process can be performed without interrupting image formation if the preliminary ejection is performed while transporting the recording medium. In this case, recording medium detection means for detecting conveyance of the recording medium is provided upstream of the recording medium conveyance means, and phase detection means for detecting the position of the opening is provided. If the recording medium detection means and the phase detection means detect the respective positions of the recording medium being conveyed and the opening, the preliminary ejection can be performed while the recording medium is being conveyed. Further, if the ink receiving member is provided inside the recording medium conveying means, the installation space for equipment for recovery processing can be reduced, and the image forming apparatus can be miniaturized to save the installation space. According to the present invention, it is not necessary to form an ink receiving portion for preliminary ejection on the medium support portion, and a special surface treatment such as a liquid repellent treatment for the medium support portion can be eliminated. Here, the ink collected by the ink receiving member includes both ink to be reused and ink to be discarded.

The images forming apparatus of the present invention, together with a phase detector means for detecting the position of the opening provided, the discharge control means, based on the detection result of the phase detecting means, the opening in synchronization with the position of the opening Since the ink is preliminarily ejected from the recording head, the position of the opening can be detected and the ink preliminarily ejected.

According to the present invention, since the openings are arranged in a staggered manner so that the openings exist over the entire nozzle width region of the recording head with respect to the medium support portion, the recovery by the wipe member is performed for all the nozzles of the recording head. Can be processed. In addition, since the opening area per opening can be reduced by the openings arranged in a staggered pattern, it is possible to prevent a decrease in the rigidity of the medium support portion . Further, since the wiping can be performed in synchronization with the position of the opening, the recovery process can be performed without interrupting image formation if the wiping is performed while the recording medium is conveyed. In this case, recording medium detection means for detecting conveyance of the recording medium is provided upstream of the recording medium conveyance means, and phase detection means for detecting the position of the opening is provided. If the recording medium detection unit and the phase detection unit detect the respective positions of the recording medium being conveyed and the opening, wiping can be performed while the recording medium is being conveyed. Further, if the wipe member is provided inside the recording medium conveying means, the installation space for the recovery processing device can be reduced, and the image forming apparatus can be miniaturized. The wipe operation includes an advance / retreat movement operation and a sliding operation of the wipe member. As a specific mode of the advancing / retreating means of the wipe member, for example, when the present invention is applied to an image forming apparatus in which a recording medium is placed horizontally during image formation, the wipe member is moved up and down with respect to the nozzle surface. It is preferable to use an elevating device that advances or exits. As the sliding means wiping member, can be cited for the sliding of the wipe member single body along the nozzle surface.

The images forming apparatus of the present invention, together with a phase detector means for detecting the position of the opening provided, the wipe control means based on the detection result of the phase detection means, in synchronism with the position of the opening, wipes Since the wiping operation by the member is controlled, the position of the opening can be detected to reliably perform the wiping operation.

According to the present invention, a plurality of the openings are formed in a constant array pattern along the recording medium conveyance direction on the entire surface of the medium support unit that supports the recording medium. By utilizing the space between the media, that is, the space between the recording media, the recording head can be recovered without interrupting the image formation, and the productivity of image formation can be improved. Further, it is not necessary to position the mounting position of the recording medium on the medium support portion as in the prior art, and image formation can be performed without limiting the mounting position of the recording medium.

According to the present invention, the medium support portion that supports the recording medium is a vacuum suction belt that sucks and supports the recording medium using the negative pressure generated by the negative pressure generating means. If the recording medium is adsorbed to the reduced-pressure adsorbing belt through the suction holes, the recording medium can be reliably conveyed. Further, if the ink receiving member, the wipe member, the suction cap, and the like described above are provided in the suction chamber, the installation space for the apparatus for recovery processing can be reduced, and the image forming apparatus can be downsized. In particular, if the opening is also used as the suction hole, the ink preliminarily ejected from the recording head can be sucked by generating an air flow around the opening, so that the ink can be collected smoothly and the outside of the image forming apparatus Ink can be prevented from splashing.

According to the present invention, since one unit of the nozzle recovery device used for the recovery process is moved between the position facing the nozzle surface of the recording head and the standby position, the nozzle recovery device including the ink receiving member and the wipe member is opened. You can evacuate from the department. As a result, in an image forming apparatus that adsorbs the recording medium to the reduced-pressure adsorbing belt, the nozzle recovery device can be retracted from the opening to increase the opening space of the opening at the time of image formation. The

According to another aspect of the present invention, the ink receiving member is a suction cap that abuts the nozzle surface of the recording head through the opening to cover the nozzle and sucks ink from the nozzle. Features.
Wherein the ink receiving member connected to suction means (such as a suction pump is used), since the suction cap for sucking the ink of the ink receiving member this from the nozzle, there is no need to provide a suction cap.

  The “full-line type recording head” is usually arranged along a direction perpendicular to the relative feeding direction (conveying direction) of the recording medium. There may be a mode in which the recording head is disposed along an oblique direction with an angle. Further, the arrangement form of the nozzles in the recording head is not limited to a single line arrangement, and may be a matrix arrangement composed of a plurality of columns. Furthermore, a combination of a plurality of short recording head units having nozzle rows that are less than the length corresponding to the full width of the recording medium may constitute a nozzle row corresponding to the full width of the recording medium as a whole.

  Further, in this specification, “recording” represents a concept in a broad sense including character formation and image formation. “Recording medium” is a medium on which an image is formed by a recording head (called an image forming medium, a recording medium, an image receiving medium, recording paper, etc.), and is a resin such as continuous paper, cut paper, sticker paper, OHP sheet, etc. Regardless of sheet, film, cloth, and other materials and shapes, various media are included.

  Furthermore, if the state in which ink is not ejected from the nozzles of the recording head continues for a certain period of time, the ink solvent near the nozzles of the recording head evaporates and the viscosity of the ink in the vicinity of the nozzles increases. Ink cannot be ejected from the nozzles. In this specification, “preliminary discharge” (also referred to as “empty discharge”, “purge”, “spitting”, etc.) refers to the state before such a state, that is, within the range of viscosity that can be discharged by an actuator, It means that the ink is ejected by operating the actuator toward the ink receiver, and the ink having increased viscosity inside the nozzle is ejected. In addition, after cleaning the nozzle surface of the recording head with a wiping member such as a blade, the preliminary ejection is performed in order to prevent foreign matter from entering the nozzle by the blade.

  Further, if the increase in the viscosity of the ink in the nozzle exceeds a certain level, ink cannot be ejected by the preliminary ejection, and the suction operation described below is performed.

  That is, when the ink viscosity in the nozzle rises above a certain level, ink cannot be ejected from the nozzle even if the actuator is operated. If air bubbles are mixed in the ink in the nozzle or the pressure chamber, ink cannot be ejected from the nozzle even if the actuator is operated. In such a case, the suction means is brought into contact with the nozzle surface of the recording head, the ink in the pressure chamber is sucked with a pump or the like, and the operation of sucking and removing the ink mixed with bubbles or the thickened ink is performed.

  However, since the suction operation is performed on the entire ink in the pressure chamber, the ink consumption is large. Therefore, when the increase in viscosity is small, it is preferable to perform preliminary discharge as much as possible.

  According to the present invention, recovery processing such as nozzle flushing (preliminary ejection), wiping (wiping), nozzle suction, and nozzle drying prevention processing such as capping can be performed while maintaining the rigidity of the medium support portion (conveyor belt). Also, it can contribute to space saving by downsizing.

  Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of an ink jet image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 includes recording heads 12K, 12C, 12M, and 12Y (hereinafter simply referred to as recording heads 12) for each ink color (black (K), cyan (C), magenta (M), and yellow (Y)). A belt conveying unit 18 which is disposed to face the nozzle surface 14 of the recording head 12 and conveys the recording paper 16 by the belt 17 while maintaining the flatness of the recording paper 16, and the recording paper 16 is provided, and a paper discharge unit 22 that discharges recording paper on which an image has been formed to the outside. The paper discharge unit 22 is provided with a discharge tray 23 for collecting the recording paper 16 on which images have been formed.

  The recording head 12 is a so-called full-line head in which a line-type head having a length corresponding to the paper width of the recording paper 16 is fixedly arranged in a direction orthogonal to the paper feeding direction. A recording head 12 corresponding to each color ink is arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the conveyance direction (arrow A) of the recording paper 16. .

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited.

  A nozzle surface 14 is provided below each recording head 12, and a color image or the like is formed on the recording paper 16 by ejecting each color ink from the nozzles arranged on the nozzle surface 14 to the recording paper 16 while conveying the recording paper 16. Form.

  Roll paper (continuous paper) 26 is detachably set in the paper supply unit 20. Although the roll paper 26 is used as an example of the paper supply unit 20, a plurality of roll papers having different paper widths, paper quality, and the like may be provided together with the roll paper 26. Further, instead of the roll paper 26 or in combination with this, the paper may be supplied by a cassette 26A in which cut sheets are stacked and loaded. In this case, a supply roller 27 for conveying and supplying cut paper from the cassette 26A is provided.

  In the vicinity of the paper feeding unit 20, a drawing roller 21 that pulls out the recording paper 16 from the roll paper 26 is provided. The power of a motor 25, which will be described later, is transmitted to at least one of the drawing rollers 21, and the drawn recording paper 16 is conveyed from right to left in FIG. Here, reference numeral 24 denotes a cutter for cutting disposed between the rollers 21. The recording paper 16 drawn from the roll paper 26 by the cutter 24 is cut into a desired size. Note that a decurling unit (not shown) that removes the curling of the recording paper 16 due to being loaded on the roll paper 26 may be arranged near the cutter 24.

  The belt conveyance unit 18 has a structure in which an endless belt 17 is wound between rollers 30, 32, 34, and 36, and at least a portion facing the nozzle surface 14 of the recording head 12 forms a horizontal surface (flat surface). It is configured as follows. The power of a motor 37 (described later) is transmitted to at least one of the rollers 30, 32, 34, and 36 around which the belt 17 is wound, and the belt 17 is driven counterclockwise in FIG. The recording paper 16 adsorbed on the paper is conveyed from right to left in FIG.

  A suction chamber 40 is provided at a position facing the recording head 12 inside the belt 17 spanned between the rollers 30, 32, 34, and 36.

  Reference numeral 42 denotes a recording paper detection unit for reading the position and size of the recording paper 16, reference numeral 44 denotes a recording position detection unit for determining ink ejection timing to the recording paper 16, and reference numeral 46 denotes a phase for detecting the phase of the belt 17. Reference numeral 48 denotes a recording paper end detection unit for determining whether the recording paper 16 is jammed or the next paper is supplied.

  As shown in FIG. 2, a plurality of nozzle groups 50 (50 </ b> A, 50 </ b> B) are arranged in a staggered manner on the nozzle surface 14 below the recording head 12. Each nozzle group 50 includes nozzles 52 arranged in a straight line at a constant pitch (Δt) in a direction (main scanning direction) orthogonal to the transport direction. Further, the nozzle group 50A on the downstream side in the transport direction and the nozzle group 50B on the upstream side in the transport direction are arranged with their positions shifted by a half pitch (Δt / 2) with respect to the direction orthogonal to the transport direction. With the recording head 12 having such a structure, the nozzles 52 can be handled equivalently to those in which the nozzles 52 are arranged in a single straight line over the entire width region L1, and a high-density nozzle arrangement can be realized. As another embodiment of the recording head 12, as shown in FIG. 3, a plurality of divided recording heads 53 each having a nozzle group 50 may be arranged in a staggered manner. By adopting such a configuration, it becomes easy to construct a high-density, high-precision line head. Each divided recording head 53 is supported by a support structure (not shown).

  Here, when the nozzles are driven by a full line head having a nozzle row corresponding to the entire width of the paper (recording paper 16), (1) all the nozzles are driven simultaneously, (2) the nozzles are directed from one side to the other. (3) The nozzles are divided into blocks, and the nozzles are sequentially driven from one side to the other for each block, etc., but 1 in the paper width direction (direction perpendicular to the paper conveyance direction). Driving a nozzle that forms an image of a line (a line composed of a single line of dots or a line composed of a plurality of lines of dots) is defined as main scanning.

  On the other hand, by relatively moving the above-mentioned full line head and the paper, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the above-described main scanning is repeatedly performed. This is defined as sub-scanning.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. In other words, in the present embodiment, the conveyance direction of the recording paper 16 is the sub-scanning direction, and the direction orthogonal to it is the main scanning direction.

  As shown in FIG. 4A, the belt 17 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes 56 are formed along the conveying direction of the recording paper 16 on the entire belt surface of the belt 17. A plurality of staggered patterns are formed. Each suction hole 56 is disposed so as to face the position where the nozzle group 50 (see FIGS. 2 and 3) of the recording head 12 is disposed, and in particular, an end 58 in a direction orthogonal to the transport direction of the suction hole 56, and The end portions 59 of the adjacent suction holes 56 in the direction orthogonal to the transport direction are formed such that the respective end positions overlap by Δd along the transport direction. As a result, when the suction holes 56 are projected so as to be arranged in a direction substantially perpendicular to the transport direction, at least one of the suction holes 56 extends over the entire nozzle full width region (L1 in FIGS. 2 and 3). Will exist. Although the effective width L2 of the suction hole 56 and the full width region L1 have a relationship of L2 ≧ L1, since the recovery process is performed on all the nozzle groups 50 of the recording head 12, as shown in FIG. It is necessary to satisfy the overlap portion Δd ≧ 0. The formation interval of the suction holes 56 in the conveyance direction is not particularly limited, but it is preferable to set the formation interval so that the arrangement pattern is constant along the conveyance direction of the recording paper 16. In particular, in the recovery process of the recording head, which will be described later, one of the suction holes 56 is positioned between the trailing edge of the recording paper 16 being conveyed and the leading edge of the recording paper 16 being conveyed next. As shown in FIG. 4A, the suction holes 56 are desirably formed on the entire surface of the belt 17 at a predetermined interval.

  In FIG. 4A, the phase detection unit 46 is disposed at both ends of the belt 17 and detects the belt phase detection marks 17A and 17B formed at the both ends of the belt 17 to detect the position of the suction hole 56. To do. The position detection of the suction hole 56 by the phase detection unit 46 will be described later.

  In FIG. 5, the suction chamber 40 is provided with a fan 60, a nozzle recovery device 62, and the like. The fan 60 is attached to the floor surface of the suction chamber 40, and the air in the suction chamber 40 is exhausted to the outside of the suction chamber 40 by the fan 60.

  The nozzle recovery device 62 includes an ink receiver 66 and a wiping blade 68 disposed so as to face the recording head 12, and a lifting device 70 that moves the ink receiver 66 and the wiping blade 68 forward and backward relative to the recording head 12. Further, each lifting and lowering device 70 includes a moving device 71 that independently moves the recording paper 16 along the conveyance direction of the recording paper 16.

  In FIG. 6, the ink receiver 66 includes an adhesive pad portion whose upper edge is made of an elastic member such as rubber and whose upper portion is opened so as to cover the nozzle groups 50. An ink absorbing member 72 made of a porous member is provided inside the ink receiver 66. The ink absorbing member 72 is connected to the pump P via a suction tube attached to the ink receiver 66, and the ink absorbed by the ink absorbing member 72 by driving the pump P is collected in a collection container 74 (see FIG. 5). Collect by suction. Since the pump P and the collection container 74 are provided in the recording head 12 for each ink color, the collected ink for each color can be reused, and the drive of the pump P that does not perform suction is stopped. It is possible to prevent unnecessary driving of the pump.

  On the other hand, the wiping blade 68 is formed of an elastic member such as rubber and is supported by the lifting device 70 via the lifting shaft 73. The elevating device 70 can move the elevating shaft 73 up and down to raise and lower the wiping blade 68, whereby the wiping blade 68 can be advanced to a position in contact with the lower surface of the recording head 12. If the moving device 71 is driven while the wiping blade 68 is in contact with the lower surface of the recording head 12 to move the elevating device 70 along the transport direction, ink droplets or foreign matter adhering to the nozzle 52 or the nozzle surface 14 are removed. The tip of the wiping blade 68 can be wiped off. With this movement, the ink receiver 66 is also moved along with the wiping blade 68 in the transport direction.

  When the belt 17 is driven on the suction chamber 40 while the suction chamber 40 is suctioned by the fan 60 to make the inside of the suction chamber 40 have a negative pressure, air is sucked through the suction hole 56 of the belt 17. Suction can be performed inside the chamber 40. Therefore, when the recording paper 16 is disposed on the belt 17 so as to block the suction hole 56, the recording paper 16 is attracted to the belt 17. At the same time, the portion of the belt 17 where the suction holes 56 are not formed is sucked in the direction of the suction chamber 40 (downward in FIG. 5), and the belt 17 can be prevented from floating in the direction of the recording head 12. The clearance with the nozzle 52 is kept constant.

  FIG. 7 is a principal block diagram showing the system configuration of the image forming apparatus 10 of the present invention. The image forming apparatus 10 includes a communication interface 100, a system controller 102, a print control unit 110, a head driver 112, a sensor unit 114, a cutter 24, a nozzle recovery device 62, and the like.

The communication interface 100 is an interface unit that receives image data sent from the host computer 120. As the communication interface 100, a serial interface such as USB, IEEE 1394, Ethernet (registered trademark) , a wireless network, or a parallel interface such as Centronics can be applied. Image data sent from the host computer 120 is taken into the image forming apparatus 10 via the communication interface 100 and temporarily stored in the image memory 104. The image memory 104 is a storage unit that temporarily stores input image data. The image data is read and written through the system controller 102.

  The system controller 102 functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as a calculation device that performs various calculations. In other words, the system controller 102 includes a central processing unit (CPU) and its peripheral circuits, and controls each part of the communication interface 100, the image memory 104, the motor driver 106, the fan 60, etc. Communication control, read / write control of the image memory 74 and the like, and a control signal for controlling the conveyance of the recording paper 16 by the motor 25 (37), the fan 60 in the suction chamber, and the like.

  The ROM 105 stores programs executed by the CPU of the system controller 102 and various data necessary for control. The ROM 105 may be a non-rewritable storage unit or a rewritable storage unit such as an EEPROM. The image memory 104 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 106 is a driver (drive circuit) that drives the motors 25 and 37 in accordance with instructions from the system controller 102.

  The print controller 110 includes a discharge controller 110A, a wipe controller 110B, and a cap controller 110C. The ejection control unit 110A is a control unit for controlling the ejection operation (including the preliminary ejection operation) from the recording head 12, and functions as an “ejection control unit”. The wipe control unit 110B is a control unit for controlling the operation of the wiping blade 68 in the nozzle recovery device 62, and functions as a “wipe control unit”. The cap control unit 110C is a control unit for controlling the operation (advance and retreat with respect to the nozzle surface) of the ink receiver 66 (corresponding to the cap member) in the nozzle recovery device 62, and functions as a “cap control unit”.

  That is, the print control unit 110 is a control unit that controls each unit such as the head driver 112, the cutter 24, and the nozzle recovery device 62 based on the detection result from the sensor unit 114. Under the control of the system controller 102, the print control unit 110 performs processing such as various processes for generating a recording control signal from the image data in the image memory 104, and generates the generated recording control signal (image forming data). This is supplied to the head driver 112.

  The head driver 112 drives the recording head of each color (K, C, M, Y) of the recording head 12 based on the image formation data given from the print control unit 110.

  The sensor unit 114 provided in the print control unit 110 is a block including the recording paper detection unit 42, the recording position detection unit 44, the phase detection unit 46, and the recording paper end detection unit 48 (see FIG. 1). The detection result detected by each detection unit is provided to the print control unit 110. In the print control unit 110, predetermined calculation processing is performed in the print control unit 110 based on the detection result detected by each detection unit, and the processing result is provided to the system controller 102. That is, the cutting timing of the recording paper 16 by the cutter 24 is determined based on the detection result in the recording paper detection unit 42. Further, the ink discharge timing and the like are determined based on the detection result of the recording position detection unit 44, and based on the detection result of the phase detection unit 46, the position of the suction hole 56 of the belt 17 is detected and the belt 17 is detected. The placement position of the recording paper 16 is determined. Further, based on the detection result by the recording paper end detection unit 48, the paper jam determination of the recording paper 16, the supply timing of the next paper, and the like are determined.

  Here, the phase detection unit 46 detects the belt phase detection marks 17A and 17B formed at both ends of the belt 17 shown in FIG. The mark 17A is positioned at a position that is synchronized with the position where the suction hole 56 is formed, whereby the position of the suction hole 56 is detected by the phase detector 46A. Further, the mark 17B is formed, for example, at one position with respect to the belt, and the phase detection unit 46B detects the period of each rotation of the belt 17. The phase detector 46 and the recording paper detector 42 detect the positions of the conveyed recording paper 16 and the suction holes 56, and the recovery process of the recording head 12 is performed by a nozzle recovery device 62 described later.

  Next, the operation of the image forming apparatus 10 configured as described above will be described.

  In FIG. 7, image data to be printed is input from the host computer 120 via the communication interface 100 and stored in the image memory 104. The system controller 102 drives the motor 25 (37) via the motor driver 106, pulls out the recording paper 16 from the roll paper 26 shown in FIG. 1 and conveys it to the cutter 24. The system controller 102 causes the cutter 24 to cut the recording paper 16 to a paper size predetermined by the image data via the print control unit 110, and the cut recording paper 16 is sent to the belt conveyance unit 18. Next, the system controller 102 outputs a control signal to the motor driver 106 so that the recording paper 16 cut based on the detection result from the sensor unit 114 is placed on the belt 17. That is, the position of the recording paper 16 and the position of the suction hole 56 of the belt 17 are detected by the recording paper detection unit 42 and the phase detection unit 46, respectively, and the system controller 102 records the suction hole 56 based on the detection result. An instruction signal is output to the motor driver 106 so that the position is covered with the paper 16. In response to this, the motor 25 controls the rotation of the roller 21, and the motor 37 controls the rotation of the rollers 30, 32, 34, and 36.

  Further, the fan 60 is driven by the system controller 102, and air is sucked from the suction holes 56 of the belt 17. The recording paper 16 on the belt 17 is adsorbed and conveyed on the belt 17 by air suction of the suction holes 56.

  When the recording paper 16 is conveyed by the belt 17 and reaches the recording head 12, an image is formed on the recording paper 16. That is, the image data stored in the image memory 104 in FIG. 7 is sent to the print control unit 110 and converted into dot data for each ink color via the head driver 112. The head driver 112 captures this dot data and generates a drive control signal for the recording head 12. When the drive control signal generated by the head driver 112 is applied to the recording head 12, ink is ejected from the nozzle 52 onto the recording surface of the recording paper 16. Note that the recording head 12 controls the ink ejection timing from the recording head in synchronization with the conveyance speed of the recording paper 16 based on the detection result from the recording position detection unit 44 of the sensor unit 114, so that the recording paper 16 is conveyed. An image can be formed on the recording paper 16 without stopping the operation. The image-recorded recording paper 16 is continuously conveyed by the belt 17 and discharged from the paper discharge unit 22.

  Next, the recovery process of the recording head 12 by the nozzle recovery device 62 will be described. When printing is performed continuously, in order to remove defective ink from unused nozzles (unused dry ink or ink whose viscosity has changed), after a predetermined time or the number of printing times has elapsed, the following is shown: The recording head is recovered.

  When the recording operation is continuously performed until the predetermined time or the predetermined number of times is reached, the print control unit 110 detects the leading edge of the conveyed recording paper 16 by the recording paper detection unit 42 and the position of the suction hole 56. Is detected by the phase detector 46, and after the trailing edge of the recording paper 16 currently being conveyed passes through the recording head 12K, and when the suction hole 56 is positioned to face the recording head 12K, the head driver 112 is detected. The ink is preliminarily ejected from the nozzles (nozzles facing the positions of the suction holes 56) in the recording head 12K. That is, when a gap (between sheets) between the recording papers 16 is positioned at a position facing the recording head 12K and the suction hole 56 is positioned facing the recording head 12K, the suction holes between the sheets. Ink is preliminarily ejected from the nozzles of the recording head 12 </ b> K toward 56. The ejected ink is ejected onto the ink receiver 66 located below the suction hole 56 and is absorbed by the ink absorbing member 72.

  After the ejection failure recovery process of the recording head 12K is performed in this manner, the suction hole 56 between the papers is similarly shifted sequentially to the opposing position of the other recording heads 12 (12C, 12M, 12Y). Ink that does not contribute to printing is ejected toward the suction hole 56 between the papers, and recovery processing is performed by the recording head of each color. Accordingly, since the preliminary ejection can be performed in synchronization with the position of the suction hole 56 between the sheets, the recovery process of the recording head 12 can be performed without interrupting the image formation.

  The recovery process by the wiping blade 68 uses the gap between the trailing edge of the recording paper 16 currently being transported and the leading edge of the recording paper 16 to be transported next, similarly to the recovery process by the ink receiver 66 described above. This is performed when the suction hole 56 is positioned to face the recording head 12. The print controller 110 drives the lifting device 70 to advance the wiping blade 68 to the recording head 12 through the suction hole 56, and drives the moving device 71 to move the wiping blade 68 to the suction hole 56. The tip of the wiping blade 68 is slid with respect to the nozzle surface 14 by moving at the same speed as the conveying speed. As a result, defective ink or the like adhering around the nozzle 52 or the nozzle surface 14 can be removed. After the cleaning of the nozzle 52 is completed, the lifting shaft 73 of the lifting device 70 is lowered and the wiping blade 68 is retracted from the recording head 12. Thereafter, as the suction holes 56 are sequentially shifted to the opposing positions of the other recording heads 12, the nozzles are similarly disposed through the suction holes 56 by the respective wiping blades 68 disposed at the opposing positions of the recording heads 12. 52 is cleaned. Each of the wiping blades 68 is moved in the direction opposite to the transport direction by the moving device 71 after the nozzle 52 is cleaned, and returns to the original position (initial position). In this way, defective ink or the like adhering to the nozzle 52 or the nozzle surface 14 by the wiping blade 68 can be removed in synchronization with the position of the suction hole 56 between the papers, so that the image formation of the recording head 12 can be performed without interruption. Recovery process can be performed.

  The suction of the defective ink at the nozzle 52 is similarly performed through the suction hole 56 of the belt 17 as in the preliminary discharge and wiping. The elevator 70 is driven to advance the ink receiver 66 (the ink receiver 66 functions as a suction cap) to a position in contact with the lower surface of the recording head 12, and the pump P is driven while the ink receiver 66 is in close contact with the lower surface of the recording head 12. If the air inside the ink receiver 66 is sucked, the ink (defective ink) in the nozzle 52 can be sucked and removed by the ink receiver 66. At this time, the marks 17A and 17B are detected by the phase detector 46, and the driving of the belt 17 is stopped so that the suction hole 56 is located at the position facing the ink receiver 66. The removed ink is ejected by the ink absorbing member 72 and absorbed, and is collected in the collecting container 74 through the suction tube.

  The operation for preventing ink drying will be described. During non-printing, the ink receiver 66 is always brought into close contact with the lower surface of the recording head 12 by the elevating device 70 so that the nozzles 52 (nozzle group 50) of the recording head 12 are in ink. Cover with a receptacle 66. As a result, the nozzle 52 can be prevented from drying, so that the ink of the nozzle 52 can be prevented from being deteriorated, and dust and the like can be prevented from adhering to the nozzle 52.

  As described above, according to the image forming apparatus 10 according to the embodiment of the present invention, the recovery process can be performed without retracting the recording head 12 for all the nozzles. Further, the rigidity of the belt 17 can be prevented from being lowered by the suction holes 56 arranged in a staggered manner in the belt 17. Furthermore, since a device for recovery processing is installed inside the suction chamber 40 of the belt conveyance unit 18, the image forming apparatus can be downsized and the installation space can be saved.

  Here, the nozzle recovery device 62 is configured to move independently along the transport direction, but the nozzle recovery device 62 is moved in the transport direction with the respective positions of the nozzle 52 and the suction hole 56 facing each other in the transport direction. It is good also as a structure which drives collectively along. In addition, the nozzle recovery device 62 is configured to move. However, it is also possible to provide a mechanism for moving the belt conveyance unit 18 so that the entire belt conveyance unit 18 is moved along with the nozzle recovery device 62 along the conveyance direction. Even in such a configuration, the same effect as the present invention can be obtained.

Furthermore, in the image forming apparatus according to the present embodiment, the recording head recovery process is performed after a predetermined time or the number of times of recording. However, the present invention is not limited to this. For example, an existing line for detecting an ink ejection defect is used. A sensor may be provided in the vicinity of the recording head 12, and the above-described recovery processing of the recording head may be performed when an ejection failure is detected by the line sensor. In this case, there is no need to provide the nozzle recovery device 62 in each of the suction holes 56. For example, only one unit of the nozzle recovery device 62 can be moved in the suction chamber 40 in the transport direction and in the direction orthogonal thereto, resulting in defective discharge. Alternatively, the nozzle recovery device 62 may be moved to the recording head in which this is detected, and only the recording head performs recovery processing. In particular, if the nozzle recovery device 62 can be moved between the position where the recording head 12 faces and the standby position, the nozzle recovery device 62 can be retracted from the suction hole 56 during normal image formation. Accordingly, since a large opening space of the suction hole 56 can be secured during image formation, the suction force of the suction conveyance of the recording paper 16 can be increased and the conveyance stability of the recording paper 16 can be improved. Note that the retracted position is not limited to the suction chamber 40 inside or outside, have good if greater position can be secured open space of the suction holes 56.

  Next, a second embodiment of the image forming apparatus according to the present invention will be described using an image forming apparatus 150 shown in FIG. The image forming apparatus 150 is obtained by changing the configuration of the belt conveyance unit 18 and the nozzle recovery device 62 of the image forming apparatus 10 described above, and the same or similar members are denoted by the same reference numerals and description thereof is omitted. .

  The image forming apparatus 150 includes a recording head 12, a belt conveyance unit 154 disposed to face the recording head 12, a nozzle recovery device 156 disposed inside the belt conveyance unit 154, and the like.

  The belt conveyance unit 154 has a structure in which an electrostatic adsorption belt 162 is wound around the rollers 158 and 160. The electrostatic attraction belt 162 enables electrostatic attraction of the recording paper 16 by an electrostatic effect on the attraction surface. The electrostatic attraction belt 162 has an opening 163 having the same configuration as the suction hole 56. The power of the motor 37 (see FIG. 7) is transmitted to the rollers 158 and 160, and the electrostatic attraction belt 162 is driven in the counterclockwise direction in FIG. 1 and is adsorbed on the electrostatic attraction belt 162. 16 is conveyed from right to left in FIG.

  The nozzle recovery device 156 includes an ink receiver 66 and a wiping blade 68 disposed to face the recording head 12, a lifting device 70 that moves the ink receiver 66 and the wiping blade 68 forward and backward relative to the recording head 12, and a lifting device. And a moving device 71 that moves the recording paper 16 along the conveyance direction of the recording paper 16.

  While the lifting device 70 is driven to bring the wiping blade 68 into contact with the nozzle surface 14 of the recording head 12, the moving device 71 can be driven in synchronization with the suction hole 56 to move the lifting device 70 along the transport direction. For example, ink droplets or foreign matter adhering to the lower surface of the nozzle 52 or the recording head 12 can be wiped off with the tip of the wiping blade 68. After completion of cleaning, the wiping blade 68 is retracted from the recording head 12 by the lifting device 70, and then the lifting device 70 is moved in the direction opposite to the transport direction by the moving device 71 to return to the initial position.

  At the time of preliminary ejection, after the rear end of the recording paper 16 currently being conveyed passes through the recording head 12 and when the suction hole 56 is positioned to face the recording head 12K, the recording head is connected via the head driver 112. Ink is ejected from the nozzle facing the position of the suction hole 56 in FIG.

  Further, the suction of the nozzle is similarly performed through the suction hole 56 of the electrostatic adsorption belt 162 in the same manner as the preliminary discharge and wiping, and the ink receiver 66 is advanced to a position where it comes into contact with the lower surface of the recording head 12 by driving the lifting device 70. Then, the ink can be sucked and removed with the ink in the nozzle 52 by driving the pump while the ink receiver 66 is in close contact with the lower surface of the recording head 12.

  Reference numeral 151 denotes a pressing roller for attracting the recording paper 16 to the electrostatic attraction belt 162.

  As described above, according to the image forming apparatus 150 according to the embodiment of the present invention, the recovery process can be performed without interrupting the image formation, and the productivity can be improved. Further, since the electrostatic adsorption belt is used as the belt, the suction chamber 40 shown in the above embodiment can be omitted.

  In the figure, only one unit of the recording head 12 is shown, but a plurality of recording heads 12 for each ink color may be arranged along the transport direction. Alternatively, the image forming apparatuses 150 having the recording heads for the respective color inks may be arranged in series, and the recording paper 16 may be conveyed in series to the respective image forming apparatuses 150 to form a color image or the like on the recording paper 16. Good.

  In the image forming apparatuses 10 and 150 described above, the recording paper 16 is transported by the belt. However, the invention is not limited to this, and the opening is formed in the outer peripheral portion, and the recording paper 16 is transported by the outer peripheral surface. Possible rotating drums may be used. In this case, a nozzle recovery device is mounted in the rotary drum, and the recording head recovery process is performed by the nozzle recovery device through an opening formed in the outer peripheral portion of the rotary drum.

  The configuration of the image forming apparatus shown in the embodiment as described above is not limited to the above embodiment. For example, the wiping blade 68 is formed of an elastic member such as rubber, but the present invention is not limited to this, and a brush or the like may be used. Moreover, it is good also as a structure which wipes off and collects ink droplets or a foreign material, using the porous member comprised with sponge etc. as a wiping blade.

  2 and 3, the nozzle groups 50 of the recording heads 12 are arranged in a staggered manner. However, even in the case of a line head in which nozzles are arranged in one row, the phase detection unit 46A detects the mark 17A. Thus, preliminary ejection can be performed in synchronization with the position of the suction hole 56.

  Further, if the preliminary ejection is performed from the nozzle 52 after the cleaning by the wiping blade 68 is completed, the clogging of the nozzle 52 due to the cleaning of the wiping blade 68 can be removed.

1 is a side view showing an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view showing a recording head used in an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a perspective view showing another recording head used in the image forming apparatus according to the embodiment of the invention. FIG. 3 is a plan view of a belt used in the image forming apparatus according to the embodiment of the invention. Sectional drawing which shows the detailed structure of the nozzle recovery apparatus used for the image forming apparatus which concerns on embodiment of this invention 1 is a perspective view showing a detailed structure of a nozzle recovery device used in an image forming apparatus according to an embodiment of the present invention. 1 is a principal block diagram showing a system configuration of an image forming apparatus according to an embodiment of the present invention. Sectional drawing which shows the detailed structure of the nozzle recovery apparatus used for the image forming apparatus which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 150 ... Image forming apparatus, 12 ... Recording head, 16 ... Recording paper, 17 ... Belt, 17A, 17B ... Mark, 18, 154 ... Belt conveyance part, 40 ... Suction chamber, 42 ... Recording paper detection part, 44 ... Recording position detection unit, 46 ... phase detection unit, 48 ... recording paper end detection unit, 56 ... suction hole, 60 ... fan, 66 ... ink receiver (cap), 68 ... wiping blade, 70 ... lifting device, 71 ... movement Device 102 System controller 110 Print control unit 162 Electrostatic suction belt 163 Opening

Claims (2)

A plurality of line-type recording heads corresponding to each color ink in which a plurality of nozzles for ejecting ink are arranged over a length corresponding to the entire width of the recording medium;
A recording medium conveying unit that conveys the recording medium while supporting the recording medium and relatively moves the recording head and the recording medium. The entire surface of the medium supporting unit that supports the recording medium is provided with a negative pressure generating unit. A plurality of openings for adsorbing and supporting the recording medium using negative pressure are formed in a fixed arrangement pattern along the conveyance direction of the recording medium, and the plurality of openings are substantially orthogonal to the conveyance direction of the recording medium. Recording medium conveying means in which the plurality of openings are arranged in a staggered manner so that at least one of the openings exists across the entire nozzle width region of the recording head when projected so as to line up ,
Phase detection means for detecting the position of the opening;
Discharge control means for preliminarily discharging ink from the recording head toward the opening in synchronization with the position of the opening based on the detection result of the phase detection means;
The preliminary discharge ink, the wiping member and the wiping member that wipes the nozzle surface of the recording head through the opening and the ink receiving member for collecting through the opening, the through the opening A one-unit nozzle recovery device comprising an advancing / retreating means for advancing or retracting the nozzle surface;
A wipe member sliding means for sliding the wipe member of the nozzle recovery device in the transport direction with respect to the nozzle surface of the recording head;
Moving means for moving the nozzle recovery device in the transport direction and the width direction of the recording medium perpendicular to the transport direction at a position facing the nozzle surface of the recording head and a standby position not facing the nozzle surface ;
A wipe control means for controlling a wipe operation by the wipe member of the nozzle recovery device in synchronization with the position of the opening based on the detection result of the phase detection means;
Equipped with a,
The nozzle recovery device is retracted to the standby position at the time of image formation in which ink is ejected from the recording head while the recording medium is conveyed by the recording medium conveying means, and the nozzle recovery device is at the time of recovery processing of the recording head Is moved to a position facing the nozzle surface at the position of any one of the plurality of openings by the moving means, and a recovery process is performed through the opening. .   The image forming apparatus according to claim 1, wherein the ink receiving member is a suction cap that abuts the nozzle surface of the recording head through the opening to cover the nozzle and sucks ink from the nozzle. apparatus.

Images