JP2008221467A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus equipped with a maintenance unit performing good cleaning in a short time without damaging a nozzle face of an inkjet head and capable of being reduced in size. <P>SOLUTION: The cleaning is performed by relatively moving the inkjet head and a suction part in the approximately orthogonal direction to the nozzle face while air near the nozzle face of the inkjet head is sucked. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus, and more particularly to a maintenance technique for an ink jet recording apparatus that prevents or eliminates clogging of nozzles and performs cleaning of an ink jet head.

  In an ink jet recording apparatus, forced suction for sucking ink from nozzles is performed in order to prevent nozzle clogging or to eliminate clogging when clogging occurs.

  In addition, cleaning is performed to remove ink and foreign matters adhering to the nozzle surface.

  In forced suction, the print head unit is generally set to a cleaning position outside the printing position, and ink is sucked by a suction pump.

  The cleaning is conventionally performed by wiping the blade or cloth on the nozzle surface, but the method of wiping the nozzle surface has a problem of damaging the nozzle surface.

  In particular, an inkjet head having a water repellent treatment on the nozzle surface has a problem in that the water repellent layer is peeled off by wiping, and the shape and direction of the liquid droplets ejected from the nozzle changes to deteriorate the image quality.

  In order to solve the problem in wiping type cleaning, it has been proposed to perform cleaning by blowing air to the nozzle surface or sucking air in the vicinity of the nozzle surface.

  That is, in Patent Document 1, an adjustment unit that adjusts the interval between the suction port and the nozzle surface is provided in a nozzle cleaning mechanism that performs cleaning by moving the suction tool along the nozzle surface and sucking air from the suction port. It has been proposed.

  In Patent Document 2, the suction member is brought into contact with the nozzle surface in an unsealed state, and suction is performed by suction means while the suction member is moved in the nozzle surface, so that an object attached to the nozzle surface is sucked together with air. A cleaning method for cleaning is proposed.

Patent Document 3 proposes a cleaning method in which a suction member is moved along a nozzle arrangement direction with respect to a nozzle to which a positive pressure is applied for cleaning.
JP 2003-127406 A JP 2004-306546 A JP 2005-1119024 A

In recent years, the need for a high-speed inkjet recording apparatus has increased, and an inkjet recording apparatus having a line head has been developed.

  However, the cleaning methods proposed in Patent Documents 1 and 3 have a problem that a long time is required for cleaning because the suction part that sucks ink together with air moves along the nozzle surface. Therefore, the throughput is deteriorated.

  Furthermore, during maintenance, pressurization is performed so that the ink flows out from the nozzles. However, the ink pushed out of the nozzles is discharged by the pressurization, and the discharged ink jumps at the discharged momentum and pollutes the inside of the apparatus. The body was necessary and unnecessary cost increase was necessary.

  Further, when the pressurization is finished, the ink surface is in the form of an ice column on the nozzle surface. If the suction member is moved along the nozzle surface in this state, as proposed in Patent Documents 1 to 3. In the cleaning method, there is a problem in that ink adheres to the side surface of the suction member and travels through the suction member to stain the inside of the apparatus.

  Also, if ink containing bubbles adheres to the nozzle surface, the bubbles will be sucked into the nozzle when the cleaning unit passes and the ink pressure at the nozzle becomes negative with respect to atmospheric pressure. There is a problem of generating discharge.

  Further, in an ink jet recording apparatus equipped with a line head, the head occupies a much larger space than that of a line scanning head type. Furthermore, there is a problem that the cleaning mechanism becomes large as a result of the movement distance of the cleaning member becoming longer.

  The present invention solves the above-mentioned problems in the conventional inkjet head cleaning technology, can be cleaned in a short time, has a high cleaning performance, can be reduced in size, and is in-machine using ink. An object of the present invention is to provide an ink jet recording apparatus in which contamination is prevented.

The object is achieved by the following invention.
1.
A maintenance device that has a nozzle surface having a plurality of ink discharge ports, forms an image with ink on a recording medium, and has a suction means and a suction portion, and sucks ink adhering to the nozzle surface In an ink jet recording apparatus capable of setting the ink jet head at a position facing the suction portion,
With the ink jet head set at the position, the moving means for relatively moving the ink jet head and the suction portion in a direction substantially perpendicular to the nozzle surface, and the suction means and the moving means are controlled. Having control means,
The control means includes
While moving the suction means, control is performed to move the inkjet head or the suction portion in a direction substantially perpendicular to the nozzle surface by the moving means, and the ink is sucked together with air by the suction means. Inkjet recording apparatus.
2.
2. The ink jet recording apparatus according to claim 1, wherein the control unit brings the ink jet head and the suction unit closer while operating the suction unit.
3.
3. The ink jet recording apparatus according to 1 or 2, wherein the suction unit does not contact the nozzle surface in a state closest to the nozzle surface.
4).
Pressurizing means for increasing the ink pressure at the ink discharge port, and the control means comprises:
4. The inkjet recording apparatus according to any one of items 1 to 3, wherein the pressure is applied by the pressure unit during suction by the suction unit.
5.
The control unit executes the suction of the suction unit, the movement of the ink jet head or the suction unit by the moving unit, and the pressurization by the pressurizing unit in parallel, and by stopping the pressurizing unit. 5. The ink jet recording apparatus according to item 4, wherein control is performed to stop the suction unit and the moving unit when a predetermined time elapses until the ink pressure at the ejection port reaches substantially atmospheric pressure.
6).
A pressure sensor for detecting an ink pressure in the ink passage;
The pressure sensor that performs the suction of the suction unit and the pressurization by the pressurizing unit in parallel and detects that the ink pressure at the discharge port has reached almost the atmospheric pressure by stopping the pressurizing unit. 5. The ink jet recording apparatus according to 4, wherein the suction unit and the moving unit are stopped and controlled based on a detection signal.
7).
The control means executes the suction of the suction means and the pressurization by the pressurizing means in parallel, and a predetermined time until the ink pressure at the discharge port reaches almost atmospheric pressure by the stop of the pressurizing means. 5. The ink jet recording apparatus according to item 4, wherein control is performed to start movement of the ink jet head or the suction unit by the moving means during the lapse of time.
8).
A pressure sensor for detecting an ink pressure in the ink passage;
The pressure sensor that performs the suction of the suction unit and the pressurization by the pressurization unit in parallel, and detects that the ink pressure at the discharge port has reached almost atmospheric pressure by the stop of the pressurization unit. 5. The ink jet recording apparatus according to claim 4, wherein control for starting movement of the ink jet head or the suction portion by the moving means is performed based on a detection signal.
9.
9. The ink jet recording apparatus according to item 7 or 8, wherein the control unit performs control to stop the suction unit after the operation of the moving unit is stopped.
10.
10. The ink jet recording apparatus according to any one of 1 to 9, wherein the ink jet head is a line head.

  In the present invention, since the maintenance device is arranged vertically below the head, the ink is sucked while moving the suction member in a direction substantially perpendicular to the nozzle surface in order to suck the ink in the shape of an ice column. In addition, maintenance can be performed without ink adhering to the side wall or the like of the suction member to contaminate the apparatus.

  Further, since vacuum is performed while pressurizing in the maintenance device arranged vertically below the head, the ink discharged from the nozzle by the pressurization is sucked together with the air by the maintenance device, so that pressurization can be performed without staining the periphery.

  For this reason, there is no extra absorber or an extra mechanism for discharging ink, so the cost of the apparatus is reduced, and there is no extra mechanism, so the user does not have to troublesome to replace the absorber. .

  In addition, because it moves in the vertical direction, cleaning within a short period of time is possible, and the suction time required for cleaning, such as removal of ink containing bubbles adhering to the nozzle surface, has been extended significantly. It is possible to secure without performing. Further, the moving distance of the maintenance device is extremely small, and the cleaning mechanism can be downsized.

  As a result, it is possible to provide a high-quality printed matter.

  Hereinafter, the present invention will be described with reference to the illustrated embodiments, but the present invention is not limited to the embodiments.

  FIG. 1 is a diagram showing an overall configuration of an ink jet recording apparatus according to an embodiment of the present invention.

  A recording medium P such as a recording sheet fed from a sheet feeding unit 1 having a sheet feeding cassette and a sheet feeding unit 1A that feeds recording media from the sheet feeding cassette one by one is transported by a transport belt 2A and a transport roller 2B. 2 and is discharged by a paper discharge roller 3A of the paper discharge unit 3.

  An image is formed by the print head unit 4 at a predetermined position in the conveyance path.

  The print head unit 4 is a unit that ejects ink to form an image on the recording medium P, and the structure thereof will be described later.

  Ink for forming an image is stored in an ink tank 5 and supplied from an ink supply system 6 to the print head unit 4.

  The print head unit 4 is movable as indicated by an arrow X so that it can be set at a print position indicated by A and a maintenance position indicated by B.

  In the maintenance position B, the print head unit 4 can move up and down as indicated by an arrow Y.

  At the time of printing, the print head unit 4 is set to the printing position A and performs printing on the recording medium P conveyed on the conveying belt 2A.

  Maintenance is executed prior to the start of printing or when a maintenance command is issued by an operator's operation.

  FIG. 2 shows the print head unit 4 and the maintenance device 7.

  When the print head unit 4 is at the maintenance position B in FIG. 1, it faces the maintenance device 7 as shown in FIG.

  The print head unit 4 includes a head substrate 40 and a plurality of inkjet heads 41A to 41L arranged in parallel in the row direction during printing on the head substrate 40, and is a line head on which lines in the row direction are printed by one printing operation.

  The ink jet heads 41A to 41L are arranged on four lines as shown in the figure, and the ink jet heads on the two lines form a pair and are arranged in two rows in a staggered manner. Done.

  The print head unit 4 moves up and down as indicated by an arrow Y by driving a head up / down motor 42 as a moving means.

  The maintenance device 7 has cap members 71A to 71L, a vacuum chamber 73, and a vacuum pump 76 provided on the substrate 70 so as to face the ink jet heads 41A to 41L.

  The cap members 71 </ b> A to 71 </ b> L constitute suction portions for sucking ink, each having a suction hole 72, and a vacuum pump 76 as a suction means is disposed near the inkjet heads 41 </ b> A to 41 </ b> L via the suction hole 72 and the vacuum chamber 73. Aspirate air.

  FIG. 3 shows an ink supply system.

  The ink supply system 6 includes an ink tube 61 that supplies ink from the ink tank 5 to the print head unit 4, an ink tube 62 that connects the print head unit 4 and the syringe pump 63, a syringe pump 63 as a pressurizing unit, and a syringe pump. A pressure motor 64 for driving the ink 63, an electromagnetic valve 65 for opening and closing the ink tube 61, and a pressure sensor 66 for detecting the ink pressure in the ink tube 62 are provided.

  FIG. 4 shows a waste liquid system for collecting ink from the maintenance device 7.

  The waste liquid system includes a vacuum chamber 73, a vacuum tube 74 communicating with the vacuum chamber 73, a gas-liquid separation unit 75, and a vacuum pump 76.

  By the operation of the vacuum pump 76, ink is sucked together with air from the suction holes 72 of the cap members 71 </ b> A to 71 </ b> L, the ink is sucked through the vacuum chamber 73 and the vacuum tube 74, and the ink is collected in the gas-liquid separator 75.

  FIG. 5 is a block diagram of a control system of the ink jet recording apparatus.

  In printing, the control means 10 sets the print head unit 4 to the printing position A in FIG. In the printing state, the electromagnetic valve 65 is open, and ink is supplied to the print head unit 4 from the ink tank 5. As shown in FIG. 1, the ink tank 5 is disposed below the inkjet head 41 of the print head unit 4. Accordingly, the ink pressure at the nozzles of the print head unit 4 is set to a level slightly lower than the atmospheric pressure.

  The control means 10 drives each nozzle of the print head unit 4 with an ink discharge signal corresponding to the image signal to discharge ink from the nozzle, thereby performing printing.

  At the time of maintenance, the control means 10 performs the maintenance by setting the print head unit 4 to the maintenance position B in FIG.

  The maintenance will be described below.

  Maintenance is performed in the process shown in FIG. FIG. 6 shows a cross section of the ink jet head and the cap member as seen from the surface S in FIG. In FIG. 6, the ink jet heads 41 </ b> A to 41 </ b> L in FIG. 2 are shown as the ink jet head 41, and the cap members 71 </ b> A to 71 </ b> L are shown as the cap member 71.

  The inkjet head 41 has a plurality of nozzles 411, and the ink discharge ports of the nozzles 411 are formed on the nozzle surface 412.

  The cap member 71 has a plurality of suction holes 72 and a vacuum chamber 73.

  In the first stage of maintenance shown in FIG. 6A, the inkjet head 41 is set to the cap member 71 with the widest distance between the nozzle surface 412 as the lower end surface and the upper end surface of the cap member 71 as D1. The

  In the first stage, the syringe pump 63 as the pressurizing means is driven by the motor 64 to increase the ink pressure in the nozzle 411 in the inkjet head 41.

  As a result, the ink is pushed out, and the ink Q is attached to the nozzle surface 412 forming the lower end surface of the inkjet head 41 as shown in FIG.

  The ink jet head 41 is moved downward, that is, in the Y direction perpendicular to the nozzle surface while continuing suction while the cap member 71 with respect to the ink jet head 41 is maintained in the horizontal direction, that is, in the X direction. Thus, the interval between the inkjet head 41 and the cap member 71 is reduced from D1 to D2.

  By this suction, the ink Q adhering to the inkjet head 41 is sucked together with the air in the vicinity of the inkjet head 41. By this suction, as shown in FIG. 6C, ink and bubbles adhering to the nozzle surface 412 are removed by suction and cleaned. Since the bubbles are sucked together at the same time as they are discharged at the time of cleaning pressurization, the bubbles do not remain on the nozzle surface, and the non-ejection due to the bubbles flowing back to the nozzle does not occur.

  In the state of FIG. 6C where the cleaning is finished, the upper surface of the cap member 71 is not in contact with the nozzle surface 412.

  Accordingly, since the nozzle surface 412 is not contacted during cleaning, the nozzle surface 412 is prevented from being damaged. The wear of the head can be prevented and the life of the head can be extended. Also, unlike the wiping method, the periphery of the nozzle is not rubbed, and the water repellent treatment near the nozzle hole is not peeled off. Decline can be prevented.

  The distance D1 between the inkjet 41 and the cap member 71 at the cleaning start stage is preferably 15 to 20 mm, and the distance D2 at the cleaning end stage is preferably 0.7 to 1.2 mm.

  The sucked ink is collected in the gas-liquid separation unit 75 through the vacuum chamber 73 and the vacuum tube 74.

  FIG. 7 is a timing chart of the operation of each part in the example of the maintenance process shown in FIG.

  Time t1 is a maintenance start time point when the printing state is switched to the maintenance process.

  In the printing state, the print head unit 4 is at a height H1 that forms a printing interval with respect to the cap member 71.

  When the maintenance is started, the print head unit 4 is lowered, and is set at a position of height H2 that forms an interval D1 (see FIG. 6) narrower than the print interval at time t2.

  Next, at time t3, the electromagnetic valve 65 is closed and the syringe pump 63 is activated by driving the pressurizing motor 64.

  As a result, the ink pressure at the nozzle 411 of the inkjet head 41 increases from V1 to the high pressure V3. The ink is pushed out from the nozzle 412 by the increase in the ink pressure. This pressure state is the state shown in FIG. The pressure V1 is an ink pressure at the time of printing, and is slightly lower than the atmospheric pressure as described above.

  When the pressurization is started, the head up / down motor 42 is activated to lower the print head unit 4 and the vacuum pump 76 is activated to suck ink and air in the vicinity of the cap member 71.

  As described above, the ink jet head 41 is lowered while the vacuum pump 76 performs suction, and the ink jet head 41 and the cap member 71 approach each other.

  In this configuration, since the inkjet head 41 and the cap member 71 are separated from each other at the start of maintenance, the ink that has been pressed and vigorously ejected does not spread between the nozzle surface and the ink receiving surface of the cap member 71. Therefore, the device is not soiled. Naturally, there is no need for anti-scattering materials such as absorbers, and unnecessary cost increases can be avoided.

  The syringe pump 63 stops at time t4, the ink pressure gradually decreases, and decreases to the atmospheric pressure V2 at time t5.

  The time during which the ink pressure at the nozzles decreases from V1 to V2 is constant in the apparatus, and the time interval t5-t4 is obtained in advance by measurement.

  A timer 10A provided in the control means 10 measures a time interval t5-t4.

  Due to the head up / down motor 42, the print head unit 4 has a height H2 at the start of the vacuum at the time interval t5-t3, that is, the height H3 at the stop of the vacuum from the state of FIG. , And descends to the state of forming the interval D2 in FIG.

  The driving speed of the head up / down motor 42 is set so that the print head unit 4 is lowered from the height H2 to H3 at the time interval t5-t4.

  At the vacuum stop and print head unit 4 descent stop time t5, the rotation of the head up-and-down motor 42 is reversed to raise the print head unit 4 and set it to the height H1 of the print state. Stop at.

  Simultaneously with the stop of the head vertical motor 42, the electromagnetic valve 65 opens the ink supply system.

  As a result of opening the electromagnetic valve 65, the ink pressure returns to the value V1 of the printing state slightly lower than the atmospheric pressure.

  With the operation shown in FIG. 7, the maintenance device 7 moves the cap member 41 up and down with the ink jet head 41 facing, sucks ink during the lowering operation, and cleans the ink jet head 41.

  As a result, the ink adhering to the nozzle surface of the ink jet head 41 in the form of an ice column does not adhere to the side surface of the suction portion and travels through the suction portion to contaminate the inside of the apparatus. There is no up.

  Further, since the vertical movement is made, the moving distance of the maintenance device is extremely small, and the cleaning mechanism can be downsized.

Furthermore, since the moving distance is short, the maintenance time can be shortened, and as a result, the throughput can be shortened.
Needless to say, the nozzle surface of the ink jet head 41 is well cleaned.

  FIG. 8 is a timing chart of the operation of each part in another example of the maintenance process.

  The head up / down motor 42 operates from the maintenance start time t1 to lower the print head 4 and set it to the height H2, and then until the solenoid valve 65, the syringe pump 63, and the vacuum pump 76 are started, as shown in FIG. Same as example.

  In FIG. 7, the print head 4 starts to descend at time t3, but in this example, the print head 4 continues to be at the height H2.

  At time t4, the syringe pump 63 stops, the ink pressure gradually decreases, and at time t5 when the ink pressure reaches atmospheric pressure, the head up / down motor 42 is activated to lower the print head 4.

  The vacuum pump 76 continues to operate without stopping at time t5.

  After the print head 4 reaches the height H3, the vacuum pump 76 continues to operate for a predetermined time and sucks ink. Then, at the time t7, the vacuum pump 76 stops and at the same time, the electromagnetic valve 65 opens. The stop time t7 of the vacuum pump 76 is set to an appropriate value in advance by experiments.

  As a result of opening of the electromagnetic valve 65, the ink pressure drops to V3, which is slightly lower than the low atmospheric pressure.

  Simultaneously with the stop of the vacuum pump 76, the head up / down motor 42 is operated at time t7 to raise the print head 4 to the height H1 during printing and return to the printing state.

  7 and 8, the time interval t5-t4 at which the ink pressure at the nozzles of the ink jet head 41 reaches the atmospheric pressure from the stop of the syringe pump 63 is obtained in advance by experiments as described above. By storing this time interval in a memory (not shown) in the control means 10, the control means 10 performs control at time t5. Instead of such time control, the ink pressure is changed. It is also possible to detect and control by ink pressure.

  That is, the pressure sensor 66 for detecting the ink pressure is provided in the ink tube 62 that connects the syringe pump 63 and the print head unit 62 in FIG. 3, and the pressure sensor 66 shows the pressure sensor 66 shown in FIGS. Control can be performed.

  In this control, the time t5 is the time when the pressure detected by the pressure sensor 66 reaches the atmospheric pressure.

  In the control example of FIG. 7, when the pressure detected by the pressure sensor 66 drops to a predetermined value, the vacuum pump 76 is stopped and the print head unit 4 is raised by the head vertical pump 42.

  In the control example of FIG. 8, when the pressure detected by the pressure sensor 66 drops to a predetermined value, the head vertical motor 42 lowers the print head unit 4 to the height H3.

  In the embodiment described above, the interval between the inkjet head and the suction unit is changed by moving the print head unit 4 in the Y direction. However, the inkjet head and the suction unit can be moved by moving the suction unit. It is also possible to adopt a configuration in which the interval is changed by moving.

1 is a diagram illustrating an overall configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is a figure which shows a print head unit and a maintenance apparatus. It is a figure which shows an ink supply system. It is a figure which shows the waste liquid system which collect | recovers ink from a maintenance apparatus. It is a block diagram of the control system of an inkjet recording device. It is a figure which shows a maintenance process. It is a timing chart of operation of each part in an example of a maintenance process. It is a timing chart of operation of each part in other examples of a maintenance process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Print head unit 5 Ink tank 6 Ink tube 7 Maintenance apparatus 10 Control means 41, 41A-41L Inkjet head 42 Head vertical motor 63 Syringe pump 66 Pressure sensor 71A-71L Cap member 411 Nozzle 412 Nozzle surface

Claims (10)

A maintenance device that has a nozzle surface having a plurality of ink discharge ports, forms an image with ink on a recording medium, and has a suction means and a suction portion, and sucks ink adhering to the nozzle surface In an ink jet recording apparatus capable of setting the ink jet head at a position facing the suction portion,
With the ink jet head set at the position, the moving means for relatively moving the ink jet head and the suction portion in a direction substantially perpendicular to the nozzle surface, and the suction means and the moving means are controlled. Having control means,
The control means includes
While moving the suction means, the moving means controls the movement of the inkjet head or the suction portion in a direction substantially perpendicular to the nozzle surface, and the suction means sucks ink together with air. Inkjet recording apparatus. 2. The ink jet recording apparatus according to claim 1, wherein the control unit brings the ink jet head and the suction unit closer while operating the suction unit. The ink jet recording apparatus according to claim 1, wherein the suction unit does not contact the nozzle surface in a state of being closest to the nozzle surface. Pressurizing means for increasing the ink pressure at the ink discharge port, and the control means comprises:
The inkjet recording apparatus according to any one of claims 1 to 3, wherein the pressure is applied by the pressure unit during suction by the suction unit. The control unit executes the suction of the suction unit, the movement of the ink jet head or the suction unit by the moving unit, and the pressurization by the pressurizing unit in parallel, and by stopping the pressurizing unit. 5. The ink jet recording apparatus according to claim 4, wherein control is performed to stop the suction unit and the moving unit when a predetermined time elapses until the ink pressure at the ejection port reaches substantially atmospheric pressure. A pressure sensor for detecting an ink pressure in the ink passage;
The pressure sensor that performs the suction of the suction unit and the pressurization by the pressurizing unit in parallel and detects that the ink pressure at the discharge port has reached almost the atmospheric pressure by stopping the pressurizing unit. The inkjet recording apparatus according to claim 4, wherein the suction unit and the moving unit are stopped and controlled based on a detection signal. The control means executes the suction of the suction means and the pressurization by the pressurizing means in parallel, and a predetermined time until the ink pressure at the discharge port reaches almost atmospheric pressure by the stop of the pressurizing means. 5. The ink jet recording apparatus according to claim 4, wherein control is performed to start the movement of the ink jet head or the suction portion by the moving means during the lapse of time. A pressure sensor for detecting an ink pressure in the ink passage;
The pressure sensor that performs the suction of the suction unit and the pressurization by the pressurization unit in parallel, and detects that the ink pressure at the discharge port has reached almost atmospheric pressure by the stop of the pressurization unit. 5. The ink jet recording apparatus according to claim 4, wherein control for starting movement of the ink jet head or the suction unit by the moving means is performed based on a detection signal. 9. The ink jet recording apparatus according to claim 7, wherein the control unit performs control to stop the suction unit after the operation of the moving unit is stopped. The inkjet recording apparatus according to claim 1, wherein the inkjet head is a line head.

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