JP2020069794A - Ink jet printer - Google Patents

Abstract

To provide an ink jet printer which prevents contamination of a printing sheet due to collection of ink accumulated on a side face of an ink jet head to a nozzle face by a suction operation of a conveyance section.SOLUTION: An ink jet printer includes: a conveyance belt 133 which has a plurality of suction holes and sucks and absorbs a printing medium by a suction operation through a suction hole and conveys the printing medium; an ink jet head which performs printing processing by discharging ink to the printing medium conveyed by the conveyance belt 133; a cleaning operation section 80 which performs a cleaning operation of the ink jet head; and a control section 70 which acquires cumulative time of the suction operation in a state in which the suction hole is opened, controls the cleaning operation section when the acquired cumulative time reaches a preset threshold, and performs the cleaning operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink onto a print medium.

  2. Description of the Related Art Conventionally, there has been proposed an inkjet printing apparatus that carries out printing by ejecting ink from an inkjet head onto a print medium while transporting the print medium such as paper or film.

  In an inkjet printing apparatus, ink may adhere to the nozzle surface of an inkjet head, or dust such as paper dust generated from printing paper may adhere. When ink adheres to the nozzle surface or paper dust is accumulated, ejection failure such as disturbance in ejection direction of ink from the nozzle or ejection failure may occur.

  In order to reduce such ejection failure, a cleaning operation is known in which ink is forcibly ejected from nozzles of an inkjet head, so-called purging is performed, and then a nozzle surface is wiped with a wiper (see, for example, Patent Document 1). ). As a result, the ink adhered to the nozzle surface and dust on the nozzle surface are removed by the wipe blade.

JP, 2007-301912, A

  Here, when the cleaning operation by the wipe as described above is performed, the ink and the like on the nozzle surface is removed, but when the nozzle surface of the inkjet head is wiped by the wiper, the ink protruding from the end of the wiper, It may collect on the side surface of the inkjet head. 10A to 10C are diagrams for explaining this phenomenon, and are views showing a vertical cross section of the inkjet head 100. FIG. 10A shows a state where the ink IK is accumulated on the side surface of the inkjet head 100, and the shaded portion is the accumulated ink IK.

  Then, from the state shown in FIG. 10A, when the print medium is sucked and conveyed by the conveying belt 103 by the suction operation through the suction hole 103a, as shown in FIG. There is a timing when the sheet interval between P1 and the next conveyed printing medium P2 is located directly below the inkjet head. At this time, due to the suction force of the suction operation through the suction holes 103a, the ink IK accumulated on the side surface of the inkjet head is attracted and drops downward as shown in FIGS. 10B and 10C, and the ink IK is discharged from the nozzle of the inkjet head. It was found that the phenomenon of gathering on the surface occurs.

  Then, in particular, when the number of printed sheets is large, or when the paper interval is enlarged with the increase of the processing time in a print job with a large amount of data, that is, when the print medium is located immediately below the inkjet head, suction is performed. It was found that the longer the cumulative operating time, the greater the amount of ink that collects on the nozzle surface and the higher the height of the ink droplets that collect on the nozzle surface. It was found that when the height of ink droplets collected on the nozzle surface became high, the ink droplets contacted with the conveyed print medium, causing a problem of contaminating the print medium.

  In view of the above circumstances, it is an object of the present invention to provide an inkjet printing apparatus that prevents the printing paper from being contaminated by the ink collected on the side surface of the inkjet head being collected on the nozzle surface by the suction operation of the transport belt. Is.

  An inkjet printing apparatus of the present invention has a plurality of suction holes, and a transport unit that suctions and transports a print medium by a suction operation through the suction holes, and ink to the print medium transported by the transport unit. An inkjet head that ejects and prints, a cleaning operation unit that performs an inkjet head cleaning operation, and a cumulative time of the suction operation when the suction holes are opened are acquired, and the acquired cumulative time is preset. And a control unit that controls the cleaning operation unit to perform the cleaning operation when the threshold value is reached.

  According to the inkjet printing apparatus of the present invention, the accumulated time of the suction operation in the state where the suction hole of the transport unit is opened is acquired, and the cleaning operation is performed when the acquired accumulated time reaches a preset threshold value. Since this is done, it is possible to prevent the ink accumulated on the side surface of the inkjet head from being contaminated on the print medium due to the ink collecting on the nozzle surface by the suction operation of the transport unit.

The figure which shows the schematic structure of one Embodiment of the inkjet printing apparatus of this invention. Plan view of an example of a head unit FIG. 3 is a perspective view showing a schematic configuration of an example of a cleaning operation unit. FIG. 3 is a plan view showing a schematic configuration of an example of a cleaning operation unit. Block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. Schematic diagram for explaining the printing operation of the inkjet printing apparatus shown in FIG. Schematic diagram showing a state in which the transport section and the cleaning operation section are in the cleaning position. Flowchart for explaining the relationship between the cleaning operation and the periodic cleaning operation according to the accumulated time of the suction operation time between sheets FIG. 6 is a diagram for explaining another example of the timing of performing the cleaning operation according to the accumulated time of the suction operation time between sheets. FIG. 3 is a diagram for explaining contamination of a print medium in a conventional inkjet printing device.

  Hereinafter, an embodiment of an inkjet printing apparatus of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of the present embodiment is characterized by controlling the cleaning operation of the inkjet head. First, the overall configuration of the inkjet printing apparatus will be described. FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus 1 of this embodiment. The up, down, left, and right directions indicated by arrows in FIG. 1 are the up, down, left, and right directions in the inkjet printing apparatus 1. In addition, the direction orthogonal to the paper surface of FIG. 1 is the front-back direction, the front direction of the paper surface is the front, and the back direction of the paper surface is the rear direction.

  As shown in FIG. 1, the inkjet printing apparatus 1 according to the present embodiment includes a side paper feeding unit 10, an internal paper feeding unit 20, a printing unit 30, a paper ejection unit 40, a reversing unit 50, and an operation panel 60. A control unit 70 and a cleaning operation unit 80.

  The side paper feed unit 10 is a paper feed tray 11 on which the print paper P is placed, and a primary paper feed unit that feeds out only the uppermost print paper P from the paper feed tray 11 and conveys it onto the paper feed conveyance path FR. 12 and a secondary paper feed unit 14 that carries the print paper P carried by the primary paper feed unit 12 onto the circulation carrier path CR.

  The internal paper feeding unit 20 is a primary paper feeding unit 21a on which the printing paper P is placed, and a primary paper feeding unit that feeds out only the uppermost printing paper P from the paper feeding base 21a and conveys it onto the paper feeding conveyance route FR. 22a, a paper feed table 21b on which the print paper P is placed, a primary paper feed section 22b for feeding only the uppermost print paper P from the paper feed tray 21b and carrying it to the paper feed path FR, The paper feed table 21c on which the paper P is placed, the primary paper feed section 22c for feeding only the uppermost print paper P from the paper feed tray 21c and carrying it to the paper feed transport path FR, and the print paper P are placed. It is provided with a paper feed tray 21d to be placed and a primary paper feed section 22d for feeding out only the uppermost printing paper P from the paper feed tray 21d and carrying it onto the paper feed carrying path FR.

  As described above, the printing paper P is conveyed from the side paper feeding unit 10 or the internal paper feeding unit 20 to the secondary paper feeding unit 14, and the printing paper P is further conveyed from the reversing unit 50 described later.

  Therefore, in front of the secondary paper feed unit 14 in the transport direction, the transport path of the print paper P fed from the internal paper feed unit 20 and the print paper P having one surface transported from the reversing unit 50 printed. There is a confluence point where the transportation route of No. 1 merges. A path on the paper feed mechanism side is referred to as a paper feed conveyance path FR, and other paths are referred to as a circulation conveyance path CR with reference to this confluence point.

  The printing unit 30 includes a head unit 31 provided with a plurality of inkjet heads, and a conveyance unit 32 provided so as to face the head unit 31.

  FIG. 2 is a plan view of the head unit 31. As shown in FIG. 2, the head unit 31 includes four line heads 28C, 28K, 28M and 28Y. The four line heads 28C, 28K, 28M and 28Y each include six inkjet heads 29 and are arranged in the left-right direction (the conveyance direction of the printing paper P). The four line heads 28C, 28K, 28M and 28Y eject inks of different colors. In the present embodiment, the line head 28C ejects cyan (C) ink, the line head 28K ejects black (K) ink, the line head 28M ejects magenta (M) ink, and 28Y ejects yellow (Y) ink.

  The printing paper P is subjected to printing processing by ejecting ink from a plurality of line heads 28C, 28K, 28M, 28Y while being conveyed right under the head unit 31 from left to right.

  The conveyor 32 includes an annular conveyor belt 133, intake fans 131 and 132, and a drive roller 134 and a driven roller 135 around which the conveyor belt 133 is wound.

  The transport belt 133 is provided with a plurality of suction holes. Further, the suction fans 131 and 132 are provided at positions facing the surface of the transport belt 133 on the back side of the transport path surface of the print paper P. As the intake fans 131 and 132 rotate, a suction force is generated in the suction holes of the conveyor belt 133.

  The printing paper P fed by the secondary paper feeding unit 14 is adsorbed onto the conveyance belt 133 by the suction operation by the rotation of the intake fans 131 and 132, and is conveyed at a predetermined conveyance speed by the rotation of the drive roller 134. The printing process is performed by the ink ejected from the head unit 31.

  The printing paper P printed by the printing unit 30 is conveyed on the circulation conveyance route CR by the conveyance rollers arranged on the circulation conveyance route CR. A switching mechanism 43 is provided on the circulatory transport path CR to switch between guiding the print paper P transported on the circulatory transport path CR to the paper discharge section 40 or recirculating on the circulatory transport path CR. There is. The switching mechanism 43 specifically switches between the transport path on the side of the paper discharge unit 40 and the transport path on the side of the reversing unit 50.

  The paper discharge unit 40 has a tray-shaped paper discharge base 41 protruding from the housing of the inkjet printing apparatus 1, and a pair of paper discharge rollers 42 for discharging the print paper P to the paper discharge base 41. Then, the printing paper P guided by the switching mechanism 43 to the conveyance path on the paper ejection unit 40 side is ejected to the paper ejection tray 41 by the paper ejection rollers 42.

  The reversing unit 50 conveys the print sheet P from the circulation conveyance path CR to the reversal table 51 and the reversal table 51 for reversing the print sheet P, and transfers the print sheet P conveyed to the reversal table 51 on the circulation conveyance path CR. And a reversing roller 52 for returning to.

  The printing paper P guided to the reversing unit 50 by the switching mechanism 43 is conveyed by the reversing rollers 52 from the circulation conveyance path CR to the reversing table 51, and is returned from the reversing table 51 to the circulation conveyance path CR again, so that the front and back are reversed. In this state, it is conveyed on the circulation conveyance route CR. Then, the front and back of the printing paper P is conveyed again toward the printing unit 30 by a plurality of rollers such as the conveyance rollers 53 provided on the circulation conveyance path CR.

  The cleaning operation unit 80 performs a cleaning operation by wiping the nozzle surface of the inkjet head 29. The nozzle surface is a surface where ink ejection ports of a large number of nozzles of the inkjet head 29 are arranged.

  The cleaning operation unit 80 is configured to be movable between a retracted position, which is the position of the cleaning operation unit 80 shown in FIG. 1, and a standby position (FIG. 6A) described later, by a predetermined actuator (not shown). Further, the cleaning operation unit 80 is arranged at a cleaning position (see FIG. 7) described later during the cleaning operation.

  As shown in FIGS. 3 and 4, the cleaning operation unit 80 includes an ink receiving member 46, a wiper unit 47, and a wiper drive unit 48. 3 and 4 are diagrams in a state where the cleaning operation unit 80 is arranged at the cleaning position.

  The ink receiving member 46 receives ink or the like that is removed from the nozzle surface of the inkjet head 29 and drops during the cleaning operation. The ink receiving member 46 is formed in a rectangular parallelepiped shape. A recess 46a for receiving ink is formed in the center of the ink receiving member 46. The recess 46a is formed to be larger than a region where the inkjet heads 29 of the line heads 28C, 28K, 28M, and 28Y are arranged in a plan view. The upper side of the ink receiving member 46 is open.

  The wiper unit 47 wipes the nozzle surface of the inkjet head 29. The wiper unit 47 includes a mount 49 and eight wipers 80A.

  The wiper 80A is attached to the attachment base 49. The mounting base 49 is formed in a rectangular parallelepiped shape. Screw holes 49 a and 49 b are formed in the mounting base 49. Threaded gears 54A and 54B, which will be described later, are passed through and screwed into the screw holes 49a and 49b, respectively. The mounting base 49 moves in the front-rear direction by the rotation of the screw gears 54A and 54B.

  The wiper 80A is a member that wipes the nozzle surface of the inkjet head 29. The wiper 80A is made of a material such as elastically deformable rubber and is formed in a rectangular plate shape. The lower end of the wiper 80A is fixed to the mount 49. As shown in FIG. 4, the eight wipers 80A are positioned on the extension line of each row along the front-rear direction of the staggered inkjet heads 29 when the cleaning operation unit 80 is disposed at the cleaning position. It is arranged.

  The upper end of the wiper 80A is located higher than the nozzle surface of the inkjet head 29 when the cleaning operation unit 80 is located at the cleaning position. When the wiper 80A is moved in the front-rear direction and comes into contact with the inkjet head 29, the wiper 80A is elastically deformed and the upper end portion slides (wipe) on the nozzle surface.

  The wiper drive unit 48 moves the wiper unit 47 in the front-rear direction. The wiper drive unit 48 includes a wiper motor 81, a drive belt 82, drive pulleys 83A and 83B, and screw gears 84A and 84B.

  The wiper motor 81 generates a rotational driving force for moving the wiper unit 47. The wiper motor 81 is arranged outside the rear wall of the ink receiving member 46. The wiper motor 81 has an output gear 81a. The output gear 81a transmits the rotational driving force of the wiper motor 81 to the drive belt 82. The output gear 81a is arranged at the center of the drive belt 82.

  The drive belt 82 transmits the rotational drive force transmitted from the wiper motor 81 to the drive pulleys 83A and 83B. The drive belt 82 is stretched around a drive pulley 83A and a drive pulley 83B.

  The drive pulleys 83A and 83B transmit the rotational driving force transmitted from the drive belt 82 to the screw gears 84A and 84B. The drive pulley 83A and the drive pulley 83B are spaced apart from each other in the left-right direction and arranged at the same height. The drive pulleys 83A and 83B are rotatably supported on the rear wall of the ink receiving member 46.

  The screw gears 84A and 84B move the wiper unit 47 in the front-rear direction by the rotational drive force transmitted from the drive pulleys 83A and 83B. The screw gears 84A and 84B extend over substantially the entire length of the recess 46a in the front-rear direction. The rear ends of the screw gears 84A and 84B are fixed to the drive pulleys 83A and 83B, respectively. The front ends of the screw gears 84A and 84B are rotatably supported by the front wall of the ink receiving member 46. As a result, the screw gears 84A and 84B rotate with the drive pulleys 83A and 83B, respectively.

  The operation panel 60 is composed of, for example, a touch panel, displays various input screens, and accepts input operations by the user.

  FIG. 5 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1 of this embodiment.

  The control unit 70 controls the entire inkjet printing apparatus 1, and includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, and the like. The control unit 70 controls the operation of each unit of the inkjet printing apparatus 1 by executing a program stored in advance in a storage medium such as a semiconductor memory or a hard disk and operating an electric circuit.

  In particular, the control unit 70 of the present embodiment determines the timing at which the cleaning operation unit 80 performs the cleaning operation, and controls the cleaning operation unit 80 so that the cleaning operation is performed at that timing. Specifically, in order to prevent the printing paper P from being contaminated by the ink collected on the side surface of the inkjet head 29 collecting on the nozzle surface, the control unit 70 is in a state in which the suction hole of the transport belt 133 is opened. The cumulative time of the suction operation is acquired, and when the acquired cumulative time reaches a preset threshold value, the cleaning operation unit 80 is controlled to perform the cleaning operation.

As a method of acquiring the above-described cumulative time, the control unit 70 of the present embodiment acquires information about the number of print sheets included in the print job when a print job to be printed output from a computer or the like is acquired, and The number of print sheets is acquired from the information on the number of print sheets. Then, the control unit 70 calculates the inter-sheet suction operation time T by calculating the following equation based on the number N between the print sheets, the distance D between the print sheets and the transport speed V of the print sheet P. .. Note that D / V is the time during which the space between the printing sheets passes immediately below the predetermined inkjet head 29.
T = N × D / V

  The distance D between the printing papers may be set in advance, or, for example, a sensor for detecting the edge of the conveyed printing paper P is provided, and the sensor detects the edge of the printing paper P to print the paper. The interval may be calculated. Also, the number of printed sheets or the number N between printing sheets, the distance D between printing sheets, and the transport speed V may be set and input by the user using the operation panel 60. Further, ± α time may be added to D / V based on the experimental result and the like.

  The control unit 70 calculates the inter-sheet suction operation time T each time a print job is input, and calculates and stores the cumulative time obtained by cumulatively adding the inter-paper suction operation time T. Then, when the accumulated time reaches a preset threshold value, the cleaning operation is performed.

  Since the inkjet printing apparatus 1 according to the present embodiment performs the cleaning operation when the cumulative time obtained by cumulatively adding the inter-paper suction operation time T reaches the threshold value, the ink accumulated on the side surface of the inkjet head 29 is used. However, it is possible to prevent the printing paper P from being contaminated by being collected on the nozzle surface by the suction operation of the transport unit 32. Further, it is possible to prevent the ink attached to the printing paper P from being transferred inside the apparatus, and it is possible to improve the maintainability such as cleaning. Furthermore, since only the cleaning operation unit 80 is controlled, it is not necessary to add a new configuration, and the above effect can be obtained without increasing the cost.

  If the threshold value is reached during the number of prints set in the print job, the control unit 70 may perform the cleaning operation at the end of the print job, or the threshold value is reached. It is also possible to calculate the number of prints to be performed, and when the print processing has been performed up to the calculated number of prints, interrupt the print processing, perform the cleaning operation, and then perform the print processing of the remaining number of prints.

  Further, the control unit 70 periodically performs the cleaning operation in addition to the cleaning operation according to the cumulative time of the inter-sheet suction operation time T described above. Specifically, the control unit 70 of the present embodiment performs the cleaning operation every time the number of printed sheets reaches a preset threshold number (for example, 1000 sheets).

  Even in this periodic cleaning operation, if the threshold number is reached in the middle of the number of prints set in the print job, the control unit 70 performs the cleaning operation when the print job ends. Alternatively, when the print processing is performed until the threshold number of sheets is reached, the print processing may be temporarily interrupted to perform the cleaning operation, and then the print processing of the remaining number of print sheets may be performed.

  Next, the printing operation of the inkjet printing apparatus 1 of the present embodiment will be described with reference to FIG.

  In the standby state before the start of the printing operation, the transport unit 32 and the cleaning operation unit 80 are arranged at the standby positions shown in FIG. 6A. The standby position of the transport unit 32 is below the line heads 28C, 28K, 28M and 28Y and below the printing position, which is the position of the transport unit 32 shown in FIG. The standby position of the cleaning operation unit 80 is a position on the transport unit 32 at the standby position.

  From the state of FIG. 6A, first, the control unit 70 moves the cleaning operation unit 80 to the retracted position, as shown in FIG. 6B. Next, as shown in FIG. 6C, the control unit 70 raises the transport unit 32 and moves it to the printing position. As a result, the cleaning operation unit 80 is retracted to the retracted position, and the transport unit 32 is placed at the printing position.

  After the transport unit 32 is arranged at the printing position, the unprinted printing paper P is fed from the paper feed tray 11 of the side paper feed unit 10 or one of the plurality of paper feed trays 21 a to 21 d to the secondary paper feed unit 14. Then, the printing paper P is transported to the transport unit 32 by the secondary paper feeding unit 14. Then, the printing paper P is subjected to a printing process by the ink ejected from the line heads 28C, 28K, 28M, and 28Y while being sucked by the carrying unit 32 and being carried. The printing paper P that has undergone the printing process is conveyed to the circulation conveyance path CR above the head unit 31. Then, in the case of single-sided printing, the printing paper P is guided by the switching mechanism 43 to the conveyance path on the paper ejection unit 40 side, and ejected to the paper ejection tray 41 by the paper ejection rollers 42.

  On the other hand, in the case of double-sided printing, the printing paper P is guided to the reversing unit 50 by the switching mechanism 43. The printing paper P guided to the reversing unit 50 is conveyed by the reversing rollers 52 from the circulation conveyance path CR to the reversal table 51, and is returned from the reversal table 51 to the circulation conveyance path CR again. Then, the printing paper P, the front and back sides of which have been reversed, is conveyed again toward the conveyance section 32 by a plurality of rollers such as the conveyance rollers 53 provided on the circulation conveyance path CR.

  Since the printing paper P has been reversed by the reversing unit 50, the unprinted surface faces upward. The printing paper P is printed on the unprinted surface by the ink ejected from the line heads 28C, 28K, 28M, and 28Y while being transported by the transport unit 32. Then, the double-sided printed printing paper P is conveyed to the paper ejection unit 40 by the circulation conveyance path CR, and is ejected to the paper ejection tray 41 in the paper ejection unit 40.

  When the printing of the number of prints set in the print job or the like is completed, the control unit 70 moves the transport unit 32 from the print position to the standby position. After that, the control unit 70 moves the cleaning operation unit 80 from the retracted position to the standby position.

  Next, the cleaning operation of the inkjet head 29 in the inkjet printing apparatus 1 of the present embodiment will be described.

  In the cleaning operation, when the cumulative time of the inter-sheet suction operation time T reaches a preset threshold value as described above, or the cumulative number of printed sheets from the previous cleaning operation becomes the threshold number of the periodic cleaning operation. When it arrives. Note that the relationship between the cleaning operation and the periodic cleaning operation according to the cumulative time of the inter-sheet suction operation time T will be described in detail later.

  When performing the cleaning operation, the control unit 70 arranges the transport unit 32 and the cleaning operation unit 80 at the cleaning position. Specifically, the control unit 70 lowers the transport unit 32 from the printing position to the standby position. Next, the control unit 70 moves the cleaning operation unit 80 from the retracted position to the standby position. Then, the control unit 70 raises the transport unit 32 to move the transport unit 32 and the cleaning operation unit 80 to the cleaning position shown in FIG. 7.

  The cleaning position of the transport unit 32 is above the standby position and below the printing position. The cleaning position of the cleaning operation unit 80 is a position on the transport unit 32 at the cleaning position.

  When the transport unit 32 and the cleaning operation unit 80 are placed at the cleaning position, the control unit 70 executes purging. Specifically, the control unit 70 controls the inkjet head 29 to generate a predetermined purge pressure and eject the ink from the nozzle. As a result, the ink is pushed out from the nozzle of the inkjet head 29, and the ink is attached to the nozzle surface.

  Then, the control unit 70 executes a wipe operation. Specifically, the control unit 70 drives the wiper motor 81 to start the forward movement of the wiper unit 47. Here, when the cleaning operation unit 80 moves to the cleaning position, the wiper unit 47 is in the initial position behind the rearmost inkjet head 29.

  When the wiper unit 47 moves forward and the wiper 80A contacts the inkjet head 29, the wiper 80A is pressed by the inkjet head 29 and elastically deforms. When the wiper unit 47 further moves forward in this state, the upper end of the wiper 80A slides (wipe) on the nozzle surface. As a result, the ink attached to the nozzle surface is removed together with dust on the nozzle surface.

  When the wiper 80 </ b> A moves to the front of the ink-jet head 29 that is the most forward, the control unit 70 stops the wiper motor 81. As a result, the wiper unit 47 stops. As a result, the wipe operation ends and the cleaning operation ends.

  When the printing operation is restarted after the cleaning operation is completed, the control unit 70 moves the cleaning operation unit 80 to the retracted position and the transport unit 32 to the printing position. Specifically, first, the control unit 70 lowers the transport unit 32 to move the transport unit 32 and the cleaning operation unit 80 from the cleaning position to the standby position. Further, the control unit 70 drives the wiper motor 81 to move the wiper unit 47 to the initial position.

  Next, the control unit 70 moves the cleaning operation unit 80 from the standby position to the retracted position. Then, the control unit 70 raises the transport unit 32 to move it from the standby position to the printing position. After that, the printing operation is restarted.

  When the printing operation is not restarted, the control unit 70 lowers the transport unit 32 after the cleaning operation is finished, and moves the transport unit 32 and the cleaning operation unit 80 from the cleaning position to the standby position. Further, the control unit 70 drives the wiper motor 81 to move the wiper unit 47 to the initial position. As a result, the inkjet printing apparatus 1 enters a standby state.

  Next, the relationship between the cleaning operation and the periodic cleaning operation according to the cumulative time of the inter-sheet suction operation time T will be described with reference to the flowchart shown in FIG.

  The control unit 70 monitors whether or not the number of printed sheets reaches a threshold number of sheets for performing the periodic cleaning operation, and whether or not the cumulative time of the inter-sheet suction operation time T reaches the threshold (S10).

  Then, when the threshold number of sheets for performing the periodic cleaning operation is reached, the control unit 70 controls the cleaning operation unit 80 to perform the above-described cleaning operation (S12).

  After performing the periodic cleaning operation, the control unit 70 resets the number of printed sheets counted to determine the timing of the periodic cleaning operation, and resets the cumulative time of the inter-sheet suction operation time T (S14). ). The reason why the cumulative time is reset is that the ink collected on the nozzle surface by the suction operation is removed by performing the periodic cleaning operation. In this way, when the periodic cleaning operation is performed before the cumulative time of the inter-sheet suction operation time T reaches the threshold value, resetting the cumulative time can prevent the cleaning operation from being unnecessarily increased. Therefore, it is possible to prevent a decrease in printing efficiency.

  On the other hand, when the accumulated time of the inter-sheet suction operation time T reaches the threshold value, the control unit 70 controls the cleaning operation unit 80 to perform the above-described cleaning operation (S16). Then, the control unit 70 resets the cumulative time after performing the cleaning operation according to the cumulative time (S18).

  In addition, when the timing of the cleaning operation according to the accumulated time and the timing of the periodic cleaning operation overlap, the periodic cleaning operation is preferentially performed and the accumulated time is reset. By resetting the cumulative time in this way, it is possible to prevent the cleaning operation from being unnecessarily increased, and prevent a decrease in printing efficiency.

  Further, in the inkjet printing apparatus 1 of the above-described embodiment, the cleaning operation may be performed every time the cumulative time of the inter-paper suction operation time T reaches the threshold value, or the cleaning operation according to the cumulative time may be performed once. After that, it is expected that the amount of ink adhering to the side surface of the inkjet head 29 will also decrease and the time until it collects on the nozzle surface again will become long. Therefore, the timing for performing the cleaning operation according to the accumulated time is set next. The threshold value of the cumulative time when determining may be set longer than the threshold value used this time. As a result, it is possible to prevent the number of cleaning operations from being unnecessarily increased, and it is possible to prevent a decrease in printing efficiency.

  Further, as shown in FIG. 9, the control unit 70 performs the cleaning operation according to the cumulative time once (for example, the first time after performing the periodic cleaning operation), and then the cumulative time reaches the threshold value. Even in this case, the cleaning operation according to the accumulated time is not performed until the periodic cleaning operation is performed, and the counting of the accumulated time of the suction operation is restarted from the time when the periodic cleaning operation is performed. Good. As a result, it is possible to prevent the number of cleaning operations from being unnecessarily increased, and it is possible to prevent a decrease in printing efficiency.

  Further, in the inkjet printing apparatus 1 of the above-described embodiment, the control unit 70, when the suction operation time between the print media conveyed by the conveyance unit 32, that is, D / V is shorter than a preset time, Since the amount of ink collected on the nozzle surface is expected to be small due to the suction operation, the cleaning operation according to the accumulated time may not be performed. As a result, it is possible to prevent the number of cleaning operations from being unnecessarily increased, and it is possible to prevent a decrease in printing efficiency.

  Further, in the inkjet printing apparatus 1 of the above-described embodiment, the user may switch between a mode in which the cleaning operation is performed according to the accumulated time and a mode in which the cleaning operation is not performed according to the accumulated time. The operation panel 60 may accept the mode switching by the user, for example.

  Further, in the inkjet printing apparatus 1 of the above-described embodiment, the cleaning operation is performed when the cumulative time of the inter-paper suction operation time T reaches the threshold value, but the threshold value may be changed. For example, the threshold value may be changed according to the distance between the head unit 31 (inkjet head 29) and the transport unit 32 (hereinafter referred to as the head gap).

  Specifically, the control unit 70 may change the head gap according to the type and thickness of the printing paper P. For example, when the relationship between the thickness T1 of plain paper, the thickness T2 of thick paper, and the thickness T3 of envelope is T1 <T2 <T3, the control unit 70 sets the head gap D1 for printing on plain paper and The print process may be performed by changing the head gap D2 for printing and the head gap D3 for printing on the envelope to D1 <D2 <D3, respectively. When the control unit 70 changes the head gap in this way, the wider the head gap, the smaller the influence of the suction operation of the transport unit 32 on the ink accumulated on the side surface of the inkjet head 29.

  Therefore, the control unit 70 may change the threshold so that the larger the head gap, the larger the threshold. As a result, the productivity can be improved without unnecessarily increasing the number of cleaning operations. The threshold value may be changed, for example, when the head gap is changed.

  When the control unit 70 changes the threshold value according to the head gap as described above, a table in which the head gap and the threshold value are associated with each other may be set in advance, or the size of the head gap may be set. A table in which the type information or the thickness information of the printing paper P that indirectly represents the threshold value is associated with the threshold value is set in advance, and the control unit 70 may determine the threshold value based on the information. Good. In addition, regarding the type information or the thickness information of the printing paper P, when it is included in the print job, the information may be acquired, or the user may set and input the operation panel 60. ..

  Further, in the above description, the threshold is changed according to the head gap, but the cumulative time of the inter-sheet suction operation time T may be changed instead of changing the threshold. Specifically, for example, when the head gap is large, the number of cleaning operations can be reduced by increasing the threshold value as described above. However, for example, a coefficient smaller than 1 (for example, 0.8 or the like) with respect to the accumulated time. ) Is compared with a threshold value (threshold value before change) to determine the timing of the cleaning operation, it is possible to perform substantially the same control as when the threshold value is increased. In this case, the control unit 70 may previously set a table in which the head gap and the coefficient by which the cumulative time is multiplied are associated with each other, or the type information or the thickness information of the printing paper P and the cumulative time. You may make it preset the table which matched with the coefficient by which is multiplied.

  Further, in the above description, the threshold value or the coefficient by which the cumulative time is multiplied is changed according to the size of the head gap, but the present invention is not limited to this, and the control unit 70 determines the amount of scratches on the surface of the inkjet head 29. The threshold value or the coefficient by which the cumulative time is multiplied may be changed depending on the related parameter. The surface of the inkjet head 29 may be scratched by the contact of the printing paper P, for example. When the number of such scratches on the surface of the inkjet head 29 increases, the amount of ink accumulated on the side surface of the inkjet head 29 increases, and the ink easily adheres to the printing paper P. Therefore, the control unit 70 preferably decreases the threshold value or increases the coefficient by which the cumulative time is multiplied as the amount of scratches on the surface of the inkjet head 29 increases. In this case, a value larger than 1 (for example, 1.2) is used as the coefficient by which the cumulative time is multiplied.

  In addition, since it is difficult to directly measure the scratches on the surface of the inkjet head 29, the control unit 70 acquires a parameter related to the amount of scratches on the surface of the inkjet head 29, and depending on the parameter, the threshold value or the accumulated time. Change the coefficient to be multiplied by. Specifically, the control unit 70 uses the total number of prints, the number of jams, the cumulative number of cleaning operations, or the like as a parameter related to the amount of scratches on the surface of the inkjet head 29.

  Since the scratches on the surface of the inkjet head 29 are caused by the contact of the printing paper P, the scratches on the surface of the inkjet head 29 tend to increase as the total number of printed sheets increases.

  Therefore, the control unit 70 preferably decreases the threshold value or increases the coefficient by which the cumulative time is multiplied as the total number of printed sheets increases.

  Further, since the surface of the inkjet head 29 is scratched by the printing paper P coming into contact with the surface of the inkjet head 29 when the user releases the jam of the printing paper P, the number of times the printing paper P is jammed increases. The number of scratches on the surface of the inkjet head 29 tends to increase.

  Therefore, it is preferable that the control unit 70 decrease the threshold value or increase the coefficient by which the cumulative time is multiplied, as the number of times the print sheet P is jammed. The number of times the print sheet P is jammed may be counted by the control unit 70 each time a jam occurs. Further, as the configuration of the jam detection unit that detects a jam, a known configuration can be used.

  Further, the scratches on the surface of the inkjet head 29 are also generated, for example, by performing a cleaning operation (wiping operation) with paper dust adhered to the surface of the inkjet head 29, and thus the inkjet head has a larger cumulative number of cleaning operations. The number of scratches on the surface of 29 tends to increase.

  Therefore, it is preferable that the control unit 70 decreases the threshold value or increases the coefficient by which the cumulative time is multiplied as the cumulative number of cleaning operations increases.

  As described above, the number of cleaning operations can be increased by changing the threshold value or the coefficient by which the cumulative time is multiplied according to the parameter related to the amount of scratches on the surface of the inkjet head 29, and thus the inkjet head 29 can be increased. It is possible to more reliably prevent the printing paper P from being contaminated by the ink accumulated on the side surface of the.

  In addition, for example, depending on the environment in which the inkjet printing apparatus 1 is used and the type of the printing paper P used by the user, the printing paper P may be easily deformed (curled or wavy). When the printing paper P is deformed, the printing paper P easily comes into contact with the ink that has run down from the side surface of the inkjet head 29 and has collected on the nozzle surface.

  Therefore, the control unit 70 may change the threshold value or the coefficient by which the accumulated time is multiplied according to the deformation state of the printing paper P.

  For example, when the humidity of the environment in which the inkjet printing apparatus 1 is used is outside the preset range, the printing paper P is easily deformed. Specifically, when the humidity is higher than the above range, the corrugation of the printing paper P is likely to occur. If the humidity is lower than the above range, the edge of the printing paper P is likely to be warped.

  Therefore, when the environmental humidity is outside the preset range, the control unit 70 preferably decreases the threshold value or increases the coefficient by which the cumulative time is multiplied. The environmental humidity may be measured by providing a known hygrometer. Further, the measurement of the environmental humidity may be performed, for example, at the timing of starting the print processing of the print job, and at that time, the control unit 70 may change the threshold value or the coefficient by which the cumulative time is multiplied.

  Further, when the water absorption of the printing paper P is high, the printing paper P is likely to be deformed. Therefore, the control unit 70 multiplies the threshold value or the cumulative time according to the type information (water absorption) of the printing paper P. The coefficient may be changed. Specifically, it is preferable that the control unit 70 decreases the threshold value as the water absorption of the printing paper P is higher, or increases the coefficient by which the cumulative time is multiplied. It is assumed that a table in which the type information (water absorbency) of the printing paper P and the coefficient for multiplying the threshold value or the cumulative time are associated with each other is set in the control unit 70 in advance. Regarding the type information (water absorption) of the printing paper P, if it is included in the print job, the information may be acquired, or the user may set and input the operation panel 60. .. Further, the control unit 70 may change the threshold value or the coefficient by which the accumulated time is multiplied, for example, at the start of the print processing of the print job.

  Alternatively, a floating detection unit that detects floating of the printing paper P is provided for the inkjet printing apparatus 1, and the control unit 70 sets a threshold value or a cumulative time according to the number of times the floating detection unit detects floating of the printing paper P. The coefficient to be multiplied may be changed. The floating detection unit is for detecting floating from the installation surface of the printing paper P of the transport unit 32. As the configuration of the floating detection unit, a known configuration such as a contact sensor or an optical sensor can be used. The deformation state of the printing paper P can be determined based on the number of times the floating detection unit detects the floating of the printing paper P. The control unit 70 determines that the deformation of the printing paper P is large and reduces the threshold value or multiplies the cumulative time when the number of times the floating detection unit detects the floating number is equal to or greater than a preset threshold number. Should be increased.

  Alternatively, the user may recognize the deformed state by observing the printing paper P, and manually change the threshold value or the coefficient by which the cumulative time is multiplied according to the deformed state. The change of the threshold value or the coefficient by which the accumulated time is multiplied may be performed using the operation panel 60, for example.

  As described above, the number of cleaning operations can be increased by changing the threshold value or the coefficient by which the cumulative time is multiplied according to the deformation state of the printing paper P. As a result, the ink accumulated on the side surface of the inkjet head 29 can be changed. It is possible to more reliably prevent the printing paper P from being contaminated.

  Further, the suction force of the transport unit 32 may be changed depending on the deformed state of the printing paper P, for example. Specifically, when the deformation of the printing paper P is large, the suction force of the transport unit 32 is increased, and when the deformation of the printing paper P is small, the suction force of the transportation unit 32 is weakened. When the suction force of the transport unit 32 is changed in this way, the stronger the suction force of the transport unit 32, the greater the influence of the suction operation on the ink accumulated on the side surface of the inkjet head 29.

  Therefore, the control unit 70 preferably decreases the threshold value or increases the coefficient by which the cumulative time is multiplied as the suction force of the transport unit 32 increases. Note that the threshold value or the coefficient by which the cumulative time is multiplied may be changed, for example, when the suction force of the transport unit 32 is changed.

  Regarding the change of the suction force, for example, when the intake fans 131 and 132 of the transport unit 32 are rotated by the supply of the drive voltage having a predetermined duty ratio, the suction ratio is changed by changing the suction ratio. Power can be changed. Therefore, for example, the higher the duty ratio of the drive voltage of the intake fans 131, 132, the stronger the suction force becomes, so the control unit 70 preferably reduces the threshold value or increases the coefficient by which the cumulative time is multiplied.

  As described above, when the suction force of the transport unit 32 is strong, the number of cleaning operations can be increased by decreasing the threshold value or increasing the coefficient by which the cumulative time is multiplied. It is possible to more reliably prevent the printing paper P from being contaminated by the ink accumulated on the side surface. On the contrary, when the suction force of the transport unit 32 is weak, the threshold value is increased or the coefficient by which the cumulative time is multiplied is decreased to improve productivity without wastefully increasing the number of cleaning operations. Can be made

Regarding the inkjet printing apparatus of the present invention, the following additional notes are disclosed.
(Appendix)

  In addition, in the inkjet printing apparatus of the present invention, the control unit controls the cleaning operation unit to periodically perform the cleaning operation in addition to the cleaning operation according to the cumulative time, and performs the periodic operation before the cumulative time reaches the threshold. When the general cleaning operation is performed, the cumulative time can be reset.

  Further, in the inkjet printing apparatus of the present invention, the cleaning operation includes a wiping operation of the inkjet head, and the control unit controls the cleaning operation unit to periodically perform the cleaning operation in addition to the cleaning operation according to the accumulated time. When the timing of the cleaning operation according to the accumulated time and the timing of the periodic cleaning operation overlap, the periodic cleaning operation is preferentially performed and the accumulated time can be reset.

  In addition, in the inkjet printing apparatus of the present invention, the control unit controls the cleaning operation unit to periodically perform the cleaning operation in addition to the cleaning operation according to the accumulated time, and performs the cleaning operation once according to the accumulated time. Even if the cumulative time reaches the threshold after performing the cleaning, the cleaning operation according to the cumulative time is not performed until the periodic cleaning operation is performed, and the suction operation is accumulated from the time when the periodic cleaning operation is performed. You can start counting time.

  Further, in the inkjet printing apparatus of the present invention, after performing the cleaning operation according to the accumulated time, the control unit sets a threshold longer than the threshold used this time, and uses the threshold to respond to the next accumulated time. The timing of the cleaning operation can be determined.

  Further, in the inkjet printing apparatus of the present invention, the control unit performs the cleaning operation according to the accumulated time when the time of the suction operation between the print media transported by the transport unit is shorter than the preset time. You can avoid it.

  Further, in the inkjet printing apparatus of the present invention, the control unit can change the cumulative time or the threshold value according to the distance between the transport unit and the inkjet head.

  Further, in the inkjet printing apparatus of the present invention, the control unit can change the cumulative time or the threshold value according to the parameter related to the amount of scratches on the surface of the inkjet head.

  Further, in the inkjet printing apparatus of the present invention, the control unit can change the cumulative time or the threshold value according to the deformation state of the print medium.

  Further, in the inkjet printing apparatus of the present invention, the control unit can change the cumulative time or the threshold value according to the suction force of the transport unit.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 10 Side paper feed section 11 Paper feed stand 12 Primary paper feed section 14 Secondary paper feed section 20 Internal paper feed sections 21a-21d Paper feed stands 22a-22d Primary paper feed sections 28C, 28K, 28M, 28Y line head 29 Inkjet head 30 Printing unit 31 Head unit 32 Conveying unit 40 Paper discharging unit 41 Paper discharging table 42 Paper discharging roller 43 switching mechanism 46 Ink receiving member 46a Recess 47 Wiper unit 48 Wiper driving unit 49 Mounting table 49a, 49b Hole 50 Reversing unit 51 Reversing base 52 Reversing roller 53 Conveying rollers 54A, 54B Screw gear 60 Operation panel 70 Control unit 80 Cleaning operation unit 80A Wiper 81 Wiper motor 81a Output gear 82 Driving belts 83A, 83B Driving pulleys 84A, 84B Screw gear 100 Inkjet Head 103 conveyor bell 103a suction holes 131 and 132 suction fan 133 conveying belt 134 drive roller 135 driven roller CR circulation path FR feeding conveyance path P printing paper P1 printing medium P2 print medium

Claims (7)

A transport unit having a plurality of suction holes, which suctions and transports the print medium by a suction operation through the suction holes;
An inkjet head that performs a printing process by ejecting ink onto the print medium that is transported by the transport unit,
A cleaning operation unit for performing the cleaning operation of the inkjet head;
A control unit that acquires the cumulative time of the suction operation in the state where the suction holes are opened, and controls the cleaning operation unit to perform the cleaning operation when the acquired cumulative time reaches a preset threshold value. And an inkjet printing apparatus including.   In addition to the cleaning operation according to the cumulative time, the control unit controls the cleaning operation unit to perform the cleaning operation periodically, and the periodic cleaning operation before the cumulative time reaches the threshold value. The ink jet printing apparatus according to claim 1, wherein the cumulative time is reset when performing the above. The cleaning operation includes a wiping operation of the inkjet head,
In addition to the cleaning operation according to the accumulated time, the control unit controls the cleaning operation unit to periodically perform the cleaning operation, and the timing of the cleaning operation according to the accumulated time and the periodic cleaning operation. 3. The inkjet printing apparatus according to claim 1, wherein the periodical cleaning operation is prioritized and the accumulated time is reset when the timing of the above is overlapped.   The inkjet printing apparatus according to claim 1, wherein the control unit changes the cumulative time or the threshold according to a distance between the transport unit and the inkjet head.   The inkjet printing apparatus according to claim 1, wherein the control unit changes the cumulative time or the threshold according to a parameter related to the amount of scratches on the surface of the inkjet head.   The inkjet printing apparatus according to claim 1, wherein the control unit changes the cumulative time or the threshold value according to a deformation state of the print medium.   The inkjet printing apparatus according to claim 1, wherein the control unit changes the cumulative time or the threshold according to the suction force of the transport unit.