JP2017007196A - Inkjet image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet image formation device capable of making an ink stick to a nozzle surface of an inkjet head that is inclined against a vertical line, with no provision of new pressurizing and discharging means of ink.SOLUTION: An inkjet image formation device includes an inkjet head which contains a nozzle for discharging ink in an ink chamber and an actuator for changing a volume of the ink chamber according to a drive waveform, for recording an image by discharging an ink droplet from the nozzle by the actuator, and a maintenance station which performs maintenance with the inkjet head. A nozzle surface of the inkjet head is inclined against a vertical line, and the maintenance station includes a cap for covering the nozzle surface of the inkjet head and an absorbing body which is filled in the cap. The inkjet image formation device discharges an ink droplet from the inkjet head into the cap, so that the ink sticks to the nozzle surface.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an inkjet image forming apparatus.

  2. Description of the Related Art As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet type image forming apparatus using an ink jet head (recording head) that ejects ink droplets is known.

  The line head engine in the ink jet system is configured by arranging the ink jet heads to form a line extending over almost the entire width of the recording medium. The ink supplied from the main tank is supplied to each inkjet head via the sub tank and the ink distribution pipe. These inkjet heads simultaneously discharge ink to form an image.

  Such an inkjet image forming apparatus includes a maintenance station for stabilizing the ejection of each inkjet head. As an example of the maintenance station, Patent Document 1 describes that ink droplets are periodically ejected from a nozzle to an ink receiving mechanism in order to prevent ejection failure due to ink thickening. Further, Patent Document 2 describes a mechanism for mechanically rubbing (wiping) the nozzle surface using a wiper as a mechanism for cleaning ink adhering to the nozzle surface.

  By the way, in an inkjet image forming apparatus, a conveyance unit that conveys a recording medium includes a straight path method in which the recording medium is conveyed on an endless belt and a drum winding pass method in which the recording medium is wound around a drum and conveyed. . In the case of the straight path method, the inkjet head is usually installed so that the nozzle surface is horizontal. On the other hand, in the case of the drum winding pass method, since the inkjet head is installed along the circumference of the drum, the nozzle surface is inclined with respect to the vertical line.

  When the wiping operation of the inclined nozzle surface is performed by the maintenance station, the ink flows in the lower direction of the inclination, and the ink does not adhere to the nozzle surface. Further, when the wiping operation is performed in a dry state without ink, the water repellency of the nozzle surface is drastically decreased, which causes a decrease in ink wiping property during the wiping operation and a decrease in ejection stability of the inkjet head.

  As a countermeasure, it is conceivable to newly provide a pressure discharge means for adhering ink to the nozzle surface of the ink jet head. However, this is not a good idea because the cost of the pressure discharge means itself and the discharge ink increase.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet image forming apparatus capable of adhering ink to a nozzle surface of an ink jet head inclined with respect to a vertical line without newly providing an ink pressure discharge means.

  An object of the present invention is to provide an inkjet which has a nozzle for ejecting ink in an ink chamber and an actuator for changing the volume of the ink chamber in accordance with a driving waveform, and ejects ink droplets from the nozzle by the actuator to record an image. An inkjet image forming apparatus comprising a head and a maintenance station that maintains the inkjet head, wherein a nozzle surface of the inkjet head is inclined with respect to a vertical line, and the maintenance station includes a cap that covers the nozzle surface; and the cap This is solved by an inkjet image forming apparatus comprising an absorber filled therein, ejecting ink droplets from the inkjet head into the cap, and depositing ink on the nozzle surface.

  According to the inkjet image forming apparatus of the present invention, ink can be attached to the nozzle surface inclined with respect to the vertical line using the inkjet head. Accordingly, since a smooth wiping operation can be performed, the ink repellency and the ejection stability of the inkjet head can be maintained without reducing the water repellency of the nozzle surface. Further, there is no need to separately provide a pressure discharge means for the ink, so there is no cost.

It is a schematic diagram of a general line type inkjet image forming apparatus. 1 is a partially enlarged view of a line-type inkjet image forming apparatus (drum winding pass method) that is an example of the present embodiment. It is the schematic (the 1) of the drum part of a drum winding pass system, (a) shows the state at the time of printing, (b) shows the state at the time of a maintenance. It is the schematic (the 2) of the drum part of a drum winding pass system, (a) shows the state at the time of printing, (b) shows the state at the time of a maintenance. It is the schematic of the inkjet head and maintenance station which concern on this embodiment. It is the schematic which shows the state of the inkjet head at the time of a maintenance, and a maintenance station based on 1st Embodiment. It is the schematic which shows the state of the inkjet head at the time of a maintenance, and a maintenance station based on 2nd Embodiment. It is a schematic diagram explaining the main droplet and satellite discharged from a nozzle hole. It is a schematic diagram which shows the state of the airflow when discharging in a cap. It is the schematic which shows the state of the inkjet head at the time of a maintenance, and a maintenance station based on 3rd Embodiment.

(First embodiment)
FIG. 1 is a schematic diagram of a general line-type inkjet image forming apparatus. In this line-type inkjet image forming apparatus, an inkjet head that ejects droplets from nozzles has a line configuration that covers almost the entire width of the recording medium.

  The line-type inkjet image forming apparatus 1 includes an apparatus main body 10, a paper feed tray 11 that stacks and feeds recording media, a transport unit 12 that transports recording media, and a head that discharges and prints droplets on the recording media. Unit 13. The line-type inkjet image forming apparatus 1 also includes a cleaning device 14 that cleans the nozzles of each head, and a paper discharge tray 15 that discharges and stacks printed recording media.

  The recording media P stacked on the paper feed tray 11 are fed to the transport unit 12 one by one by the separation roller 17 and the paper feed roller 18.

  The conveyance unit 12 includes a conveyance driving roller 19, a conveyance driven roller 20, and an endless belt 21 wound around these rollers. A plurality of holes are formed on the surface of the endless belt 21. A suction fan 22 that sucks the recording medium P is disposed below the endless belt 21, and the recording medium P is conveyed while being sucked onto the endless belt 21. Further, conveyance guide rollers 23 and 24 are arranged above the conveyance driving roller 19 and the conveyance driven roller 20, respectively. When the conveyance drive roller 19 is driven by a motor, the conveyance driven roller 20 and the conveyance guide rollers 23 and 24 are driven to convey the recording medium P. Such a configuration is called an air suction straight path method.

  A paper discharge tray 15 is disposed on the downstream side of the transport unit 12. The paper discharge tray 15 includes a pair of side fences 28 that restrict movement of the recording medium P in the width direction, and an end fence 29 that restricts the leading end of the recording medium P.

  A head unit 13 is disposed on the transport unit 12. In the head unit 13, head modules 13a, 13b, 13c, and 13d are arranged for each color. In these head modules, a plurality of inkjet heads are arranged in a staggered manner over almost the entire width of the recording medium. Each inkjet head is connected by a coupling or the like so that it can be replaced in the event of a failure.

  The head modules 13a, 13b, 13c, and 13d eject black (K), magenta (M), cyan (C), and yellow (Y) inks, respectively. A main tank 25 is disposed above these head modules and is connected to a distribution pipe 26 via a supply tube 16. Each color ink in the main tank 25 is supplied to the corresponding head module via the distribution pipe 26.

  Further, the head unit 13 can move in a direction perpendicular to the sheet passing surface of the recording medium, and when the head unit 13 is cleaned, the head unit 13 is raised to the extent that a cleaning device 14 described below can be placed under the head unit 13.

  The cleaning device 14 is disposed on the transport unit 12 and can move in the transport direction of the recording medium. The cleaning device 14 includes cleaning means 14a, 14b, 14c, and 14d corresponding to the head modules 13a, 13b, 13c, and 13d. Suction pumps 27a, 27b, 27c, and 27d for sucking ink of the corresponding head modules 13a, 13b, 13c, and 13d are disposed below the respective cleaning units 14a, 14b, 14c, and 14d.

  Cleaning of each head module by the cleaning device 14 includes capping each head module and sucking ink, and cleaning ink adhering to the nozzle surface of the inkjet head with a wiper blade. At the time of cleaning, first, the head unit 13 is raised in a direction away from the recording medium (arrow A) to secure an insertion space for the cleaning device 14. Next, the cleaning device 14 slides to the lower part of the head portion 13 (arrow B), and when the head portion 13 is lowered, cleaning is started. When the cleaning is completed, the head unit 13 is again retracted upward, and the cleaning device 14 returns to the initial position. Then, the head unit 13 returns to the initial position and is ready for printing.

  FIG. 2 is a partially enlarged view of a line-type inkjet image forming apparatus (drum winding pass system) which is an example of the present embodiment. In the drum winding pass method, the recording medium P is wound around a rigid drum 30 and conveyed, and printing is performed by a plurality of inkjet heads 31 arranged on the circumference of the drum 30. As shown in FIG. 2, the plurality of inkjet heads 31 are arranged so that the nozzle surfaces thereof are inclined more greatly with respect to the vertical line at the both ends of the array. Such a configuration is called a drum winding pass method.

  In the case of the air suction straight path method shown in FIG. 1, the conveyance accuracy (positioning of the recording medium) deteriorates due to variations in the thickness and elongation of the endless belt 21 and lateral displacement and floating of the belt itself. There is. On the other hand, in the drum winding pass method, since the recording medium P is wound around the rigid drum 30, there is little misalignment in the conveyance direction / paper width direction, skew distortion, and floating of the recording medium P (head cap fluctuation). There is an advantage.

  The present invention is directed to such a drum winding pass type line-type inkjet image forming apparatus.

  FIG. 3 is a schematic diagram (part 1) of a drum portion of a drum winding pass method, where (a) shows a state during printing, and (b) shows a state during maintenance. As shown in FIG. 3, the drum portion includes a drum 30, a plurality of inkjet heads 31, and a plurality of maintenance stations 38. The maintenance station 38 is a device that maintains the inkjet head 31 and includes a wiper that wipes the nozzle surface, a cap that prevents the nozzle surface from drying, a suction mechanism that sucks waste ink in the cap, and the like.

  At the time of printing (a), the plurality of inkjet heads 31 are on the circumference of the drum 30, and the plurality of maintenance stations 38 are waiting behind the inkjet heads 31. Next, at the time of maintenance (b), the plurality of inkjet heads 31 are moved above the circumference of the drum 30, and the plurality of maintenance stations 38 are arranged below the nozzle surfaces of the inkjet heads 31. The maintenance station 38 performs maintenance of the inkjet head 31.

  4A and 4B are schematic diagrams (part 2) of the drum portion of the drum winding pass method, in which FIG. 4A shows a state during printing, and FIG. 4B shows a state during maintenance. The same components as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The drum 30 portion shown in FIG. 4 differs from the drum 30 portion shown in FIG. 3 in that a plurality of maintenance stations 38 are fixed and a plurality of inkjet heads 31 are moved instead. Specifically, at the time of printing (a), a plurality of inkjet heads 31 are arranged on the circumference of the drum 30. At the time of maintenance (b), the plurality of inkjet heads 31 move so that the nozzle surface is on the maintenance station 38.

  3 and 4 show two examples of the drum portion of the drum winding pass system, but the present invention is not limited to this.

  Hereinafter, characteristic portions of the present invention will be described.

  FIG. 5 is a schematic diagram of the inkjet head and the maintenance station according to the present embodiment. The ink jet head 31 includes an ink chamber 32, nozzles that eject ink, a control unit 33 that generates a drive waveform, and an actuator 34 that changes the volume of the ink chamber according to the drive waveform. Here, the nozzle surface 35 of the inkjet head 31 is disposed so as to be inclined with respect to the vertical line.

  The control unit 33 is configured by a computer including a CPU, ROM, RAM, I / O, and the like, and generates a drive waveform (voltage waveform) for driving the actuator 34. The speed and amount of ink ejected from the nozzles can be adjusted according to the amplitude and period of the drive waveform. The control unit 33 may be a computer that controls the entire image forming apparatus.

  The actuator 34 is, for example, a laminated piezoelectric element. The actuator 34 is deformed by applying a drive waveform (voltage waveform) from the control unit 33, and simultaneously changes the volume of the ink chamber 32. Thereby, the ink in the ink chamber 32 is discharged from the nozzle.

  The maintenance station 38 includes a cap 40 covering the nozzle surface 35, an absorber 41 filled in the cap 40, a suction hole provided in a lower portion of the cap 40, a tube 42 connected to the suction hole, and a nozzle surface. The wiper etc. which wipe 35 are provided. The tube 42 is connected to a suction unit such as a suction motor that sucks ink in the cap 40.

  FIG. 6 is a schematic diagram illustrating a state of the inkjet head and the maintenance station during maintenance according to the first embodiment. 6, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the maintenance station 38 (cap 40) is brought into contact with the nozzle surface 35 of the inkjet head 31. However, the absorber 41 has a positional relationship such that a gap is generated between the nozzle surface 35 and the absorber 41. If ink droplets are ejected from the inkjet head 31 in this state, the ink is held in the gap portion between the nozzle surface 35 and the absorber 41, and the ink can adhere to the nozzle surface 35.

  In addition, it is desirable that the drive waveform when ejecting ink droplets has a higher frequency than the drive waveform used during printing. Since the interval at which the ink droplets are ejected is shortened, the ink can be quickly held in the gap portion between the nozzle surface 35 and the absorber 41, and therefore the maintenance time can be shortened.

  Further, the absorber 41 can normally hold ink in the gap portion between the nozzle surface 35 and the absorber 41, and has such properties (material, density, etc.) that the ink in the gap portion is absorbed in a short time when ink is absorbed. It is desirable to have.

  If the nozzle surface 35 is wiped with a wiper or the like after the ink is attached to the nozzle surface 35, the entire nozzle surface 35 is wetted with the ink, so that the ink on the nozzle surface 35 can be removed smoothly. After the wiping operation, ink in the cap 40 is sucked from the suction holes provided in the lower portion of the cap 40 to prevent ink leakage from the cap 40.

  As described above, in the present embodiment, ink droplets are ejected into the cap 40 in a state where the nozzle surface 35 and the cap 40 are in contact with each other, and ink is attached to the nozzle surface 35 inclined with respect to the vertical line. If the nozzle surface is wetted with ink before the wiping operation, a smooth wiping operation can be performed, and a rapid decrease in the water repellency of the nozzle surface can be prevented. Accordingly, it is possible to maintain the ink wiping property and the ejection stability of the inkjet head. Further, there is no need to separately provide a pressure discharge means for discharging ink, so that no cost is required.

  Further, in the present embodiment, the drive waveform for ejecting ink droplets has a higher frequency than the drive waveform used for printing, and therefore the interval at which ink is ejected is shortened. Therefore, the maintenance time can be shortened.

(Second Embodiment)
FIG. 7 is a schematic diagram illustrating a state of the inkjet head and the maintenance station during maintenance according to the second embodiment. 7, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The present embodiment is characterized in that ink droplets are ejected from the inkjet head 31 into the cap 40 in a state where the maintenance station 38 (cap 40) and the nozzle surface 35 are separated from each other. In this case, it is possible to adhere to the nozzle surface 35 mist generated when ink droplets are ejected, ink rebounding against the absorber 41 in the cap 40, and the like.

  At this time, it is desirable that the drive waveform when ejecting ink droplets has a higher frequency than the drive waveform used during printing. Mist generated at the time of ink discharge can be quickly attached to the nozzle surface 35. Further, it is desirable that the drive waveform has a larger amplitude than the drive waveform used during printing. Also in this case, mist or the like can be quickly attached to the nozzle surface 35, and more mist can be generated.

  In addition, after the wiping operation of the nozzle surface 35, the ink in the cap 40 is sucked through the tube 42 from the suction hole provided in the lower portion of the cap 40.

  Here, the mist is an ink droplet ejected from the nozzle of the ink jet head 31 that does not land on the place where it should land, but forms a floating mist. However, satellites that land on the side of the main droplet as shown in FIG. 8 are not called mist. On the other hand, drops that are scattered on the paper surface and things that stain the inside of the apparatus are also mist.

  One of the main factors that cause mist is a satellite as shown in FIG. 8 and does not occur under driving conditions in which no satellite is generated. Accordingly, when it is desired to generate mist and adhere ink to the nozzle surface 35 as in this embodiment, it is desirable to use a drive waveform having a higher frequency and a larger amplitude than the drive waveform used during printing. As a result, the speed of the ink droplets can be increased so that the satellites or the main droplets do not merge.

  There are other factors that cause mist. The speed of the satellite is lost due to air resistance and floats to become mist, or the ejected ink hits the absorber 41 in the cap 40 and scatters to become mist. In addition, when ink is ejected, scattering different from normal droplets may occur and become mist, or a main droplet having a size almost equal to that of a satellite may become mist.

  FIG. 9 is a schematic diagram showing a state of airflow when ink droplets are ejected into the cap. As shown in FIG. 9, since the inkjet head 31 and the cap 40 are separated from each other, an air flow generated by ink ejection flows out of the cap 40. The generated mist rides on the airflow, so that the ink can adhere to the nozzle surface 35.

  As described above, in the present embodiment, in a state where the nozzle surface 35 and the cap 40 are separated from each other, ink droplets are ejected and suspended in the cap 40 (mist), and ink is applied to the nozzle surface 35 inclined with respect to the vertical line. Adhere. The present embodiment is particularly advantageous when applied to an apparatus configuration in which ink tends to mist (for example, an inkjet head configuration, ink type, etc.).

(Third embodiment)
FIG. 10 is a schematic diagram illustrating a state of the inkjet head and the maintenance station during maintenance according to the third embodiment. 10, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The present embodiment is further characterized by comprising switching means 43 that contacts or separates the nozzle surface 35 of the inkjet head 31 and the cap 40. As the switching means 43, for example, a slide mechanism driven by a stepping motor or the like can be used. By the switching means 43, the maintenance station 38 can be moved in the direction of the double arrow in the figure, and the nozzle surface 35 and the cap 40 can be brought into contact with or separated from each other.

  In the case of contact, the ink is attached according to the procedure shown in the first embodiment, and when it is separated, the ink is attached according to the procedure shown in the second embodiment. Depending on the device configuration (for example, the configuration of the ink jet head, the type of ink, etc.), it may or may not be a mist. In the present embodiment, since the procedure of ink attachment can be selected, ink can be attached to the nozzle surface 35 more efficiently according to the apparatus configuration.

  The present invention has been described with reference to a plurality of embodiments. These embodiments are examples, and various modifications (such as combining the first to third embodiments) may be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Line type inkjet image forming apparatus 10 Apparatus main body 11 Paper feed tray 12 Conveyance part 13 Head part 13a, 13b, 13c, 13d Head module 14 Cleaning device 14a, 14b, 14c, 14d Cleaning means 15 Paper discharge tray 16 Supply tube 17 Separation Roller 18 Feed roller 19 Transport drive roller 20 Transport driven roller 21 Endless belt 22 Suction fan 23, 24 Transport guide roller 25 Main tank 26 Distribution pipe 27a, 27b, 27c, 27d Suction pump 28 Side fence 29 End fence 30 Drum 31 Inkjet Head 32 Ink chamber 33 Control section 34 Actuator 35 Nozzle surface 38 Maintenance station 40 Cap 41 Absorber 42 Tube 43 Switching means
P Recording medium

JP 2013-67155 A JP 2013-52616 A

Claims (6)

An ink jet head for recording an image by ejecting ink droplets from the nozzle by the actuator, the nozzle for ejecting ink in an ink chamber, and an actuator for changing the volume of the ink chamber according to a drive waveform; In an inkjet image forming apparatus comprising a maintenance station for maintaining an inkjet head,
The nozzle surface of the inkjet head is inclined with respect to the vertical line,
The maintenance station includes a cap that covers the nozzle surface, and an absorber filled in the cap.
An ink jet image forming apparatus, wherein ink droplets are ejected from the ink jet head into the cap, and ink is adhered to the nozzle surface.   The inkjet image forming apparatus according to claim 1, wherein a drive waveform when ejecting ink droplets from the inkjet head into the cap has a higher frequency than a drive waveform used during printing.   The inkjet image forming apparatus according to claim 1, wherein a drive waveform when ejecting ink droplets from the inkjet head into the cap has a larger amplitude than a drive waveform used during printing.   The ink is held on the absorber in the cap in a state where the nozzle surface and the cap are in contact with each other, and the held ink is attached to the nozzle surface. The inkjet image forming apparatus according to Item.   4. The ink according to claim 1, wherein the nozzle surface and the cap are separated from each other, and ink is ejected and floated in the cap so that the floating ink is attached to the nozzle surface. The inkjet image forming apparatus described in 1. Comprising switching means for contacting or separating the nozzle surface and the cap;
When the nozzle surface and the cap are brought into contact, the ink is held in the absorber in the cap, and the held ink is attached to the nozzle surface,
4. The method according to claim 1, wherein when the nozzle surface and the cap are separated from each other, ink is ejected and floated in the cap, and the floating ink is attached to the nozzle surface. The inkjet image forming apparatus described.