JP2018176563A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge head recovery mechanism that inhibits wear of a discharge port of an inkjet print head and a water repellent layer of the periphery thereof, sufficiently resolves contamination and color mixture due to attached ink mist and can maintain stable recording.SOLUTION: A liquid discharge head recovery mechanism includes: a cleaning mechanism for cleaning an inkjet print head surface while moving in a non-contact manner; and a control mechanism for performing suction when performing cleaning.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a configuration for recovering the performance of a droplet discharge head in an ink jet recording apparatus.

  Generally, a liquid discharge recording head has a plurality of nozzles provided to discharge ink as droplets, and an ink path independent for each nozzle, and the ink path is supplied with ink from a common liquid chamber, and is common The liquid chamber is externally supplied through an ink supply port. The supplied ink is distributed from the common liquid chamber to each independent ink path and nozzle.

  The ink path is provided with an energy application part for discharging ink and energy generation means for generating energy for droplet formation applied to the liquid in the application part.

  As a typical method of this energy generation means, there is a method using an electrothermal conversion element for the discharge of ink droplets.

  This is achieved by causing the ink liquid in the vicinity of the electrothermal transducer to boil instantaneously by giving an electric pulse as a recording signal to the electrothermal transducer, and causing rapid bubble growth caused by the phase change of ink droplets at that time. It is a method of discharging a droplet from the nozzle at high speed.

  The advantage of this method is that it has many practical advantages, such as simple structure and easy integration of nozzles for ejecting ink droplets.

  By the way, in the current ink jet recording method, when the ink droplet is discharged, fine ink particles are inevitably generated accompanying the main ink droplet. This is called an ink mist, and the ink mist adheres to the periphery of the nozzle on the nozzle formation surface, and when it is united, a liquid reservoir (hereinafter, ink reservoir) is formed.

  When ink droplets ejected from the nozzle come in contact with ink reservoirs at the edge of the nozzle opening in a state where the ink reservoir is formed by such ink mist on a part of the opening edge of the nozzle, they are mutually subjected to surface tension Gravitate. As a result, the ejection trajectory of the ink droplet ejected from the nozzle may be deviated, or the ink may be mixed with another ink in another nozzle row and mixed. In addition, when the ink mist adhering to the periphery of the nozzle is left, the solvent evaporates from there, the ink viscosity rises, the ink solidifies, and furthermore, the ink becomes a state of ejection failure due to the mixture of air bubbles, etc. I have a problem.

  Therefore, in order to ensure stable droplet discharge performance, a maintenance and recovery mechanism (maintenance device) is provided to maintain and recover the state of the recording head, and ink mist or the like from the nozzle formation surface (hereinafter referred to as the nozzle surface) of the recording head is provided. An ink reservoir is to be removed (Patent Document 2).

  A liquid repellent coating (hereinafter referred to as a water repellent layer) is formed on the nozzle surface of the recording head in order to improve discharge, but when performing head cleaning for maintenance, the nozzle surface using a blade There is a problem of causing deterioration of the water repellent layer by wiping the When the water repellent layer is deteriorated, the ink droplet removing property and the discharge are lowered with time, so that it is necessary to suppress the abrasion of the water repellent layer in order to prolong the life of the head. When the ink mist is left to stand, when the solvent evaporates and the viscosity of the ink droplet rises and the ink is solidified, the force pressing the member in contact with the nozzle surface of the recording head needs to be increased. The wear of the water repellent layer tends to increase. Even if it is not necessary to increase the contact pressure, depending on the wettability, the meniscus can not be maintained by the recovery of the recording head, and the dischargeability tends to be reduced.

  As means for solving these problems, there is one disclosed in Patent Document 1. In the printing function recovery mechanism described in this, a cleaning mechanism that performs cleaning while making an ink reservoir on the surface of the inkjet print head and moves without contact, and moves the ink used for cleaning to a place other than the discharge port Proposed a control mechanism to perform suction after the

  However, in the printing function recovery mechanism, since the ink overflowing on the nozzle surface is mixed with the ink in the other nozzle row to cause color mixing, it is considered that a preliminary ejection operation is also required after the nozzle surface scratching operation.

JP, 2006-212870, A JP, 2016-516, A

  The present invention further improves the printing function recovery mechanism as described in Patent Document 1, and it is an object of the present invention to provide a printing function recovery mechanism of an ink jet recording apparatus which does not require preliminary ejection. Do.

In order to achieve the above object, a droplet discharge head recovery mechanism according to the present invention is:
There is a pressure mechanism for applying pressure in the ink flow path of the recording head and causing the ink to overflow on the recording head nozzle surface, and a mechanism that performs cleaning with a suction cap that moves the overflowed ink noncontactingly to the nozzle surface It is a maintenance and recovery mechanism (maintenance device) that maintains and recovers the state of the recording head characterized by a mechanism that performs suction while moving.

  According to the droplet discharge head recovery mechanism of the present invention, the wear of the water repellent layer on the nozzle surface can be suppressed by using the above-described mechanism, and contamination and color mixing due to the attached ink mist can be sufficiently eliminated. Furthermore, since the increase in the viscosity of the ink droplet and the cleaning of the ink sticking can be solved, it is possible to maintain the stable recording by the ink jet print head.

FIG. 6 is a schematic view for explaining the droplet discharge head recovery mechanism in detail. It is an experimental result of the pressure waveform in the ink flow path at the time of ink supply and tube recovery. It is a model perspective view which shows the suction cap form in embodiment of this invention. FIG. 1 is a configuration diagram according to a first embodiment of the present invention. It is an experimental result of the cleaning in the combination of the clearance and the suction pressure.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  In the present invention shown in FIG. 1, the ink flow path 4 is provided in the upper part in the common liquid chamber 3, the ink supply port 10 for taking in the ink is provided upstream of the ink flow path 4, and the plasticity is provided above the ink supply port 10. The tube 7 is connected, and a pump or the like that generates pressure is provided in part.

  The ink flow path 4 will be described. The ink is supplied from the ink flow path 4 to the common liquid chamber 3 and flows from the common liquid chamber 3 to the ink path 9 branched into many. The ink passage 9 includes an element substrate provided with the discharge port 2 for discharging ink and the heating element 11.

  The ink supply will be described with reference to FIG. When ink is supplied to the ink flow path 4 at a speed of 0.45 g / min by the pressure pump 6, the pressure in the head flow path 4 rises, the meniscus is broken around 6 kPa, and when the ink is pushed out from the discharge port 2, the ink flow path The pressure in 4 falls.

  The pressure in the ink flow path 4 is stabilized at 3 kPa because the ink continues to be supplied even if the pressure in the ink flow path 4 decreases. At this time, the overflowed ink forms an ink reservoir 18 at the nozzle surface 22 and grows large. When the overflowing ink falls from the nozzle surface 22 by its own weight, the tube recovery operation is started.

  The ink mist 13 on the nozzle surface 22 is taken into the overflowing ink reservoir 18. Furthermore, since the ink whose viscosity has been lowered and the ink which has begun to evaporate and adhere are also taken into the ink reservoir 18 of the new high viscosity ink which overflows, the decrease in viscosity and the fixation are eliminated.

  The tube recovery will be described. The suction cap 15 is raised while the suction pump 14 is driven at -50 kPa, and the clearance with the nozzle surface 22 is set to 0.12 mm. It is desirable to set a position where the clearance does not contact even if the ink jet head 1 assembly tolerance varies.

  The shape of the suction cap 15 is shown in FIG. The nozzle surface 22 contact portion has a flat shape, and the outer side has a slope shape facing the nozzle surface 22 at an acute angle, and the inner side has a vertical shape. Further, the direction orthogonal to the nozzle row has a shape that can wipe the entire nozzle surface 22.

  Then, the suction cap 15 is moved at a speed of 5 mm / sec. As a result, when the suction operation is performed while sequentially switching the suctioned nozzle group, the meniscus is stretched from the discharge port 2 through which the suction cap 15 has passed, and the pressure in the ink flow path 4 starts to increase.

  It is important to set the speed at which the scan of suction cap 15 reaches the end position before the suction cap 15 passes and the stretched meniscus breaks. In addition, if the ink supply is not stopped at the same time as the scan arrives at the end point position, the pressure in the ink flow path 4 rises and the ejection port 2 meniscus is broken again.

  Color mixing can be prevented at the same time as the suction cap 15 scans while maintaining the clearance with the nozzle surface 22 while supplying ink, and scavenging of the ink reservoir 18 attached to the nozzle surface 22. Thereafter, the suction cap 15 is lowered and the suction pump 14 is stopped.

  The above-described implementation condition is the configuration when different ink is contained for each nozzle row, and the following first embodiment shows the configuration when the same ink is contained for each nozzle row.

  FIG. 4 shows a recovery method performed at the time of pre-shipment printing inspection in the first embodiment.

  The inkjet head 1 is installed at a predetermined position of the ink filling device. Where the filter 5 member of the ink jet head 1 is provided, the ink supply seal member 17 formed of an elastic material such as rubber operates and is connected to the filter 5 portion.

  The shaft 19 of the tube pump 6 connected to the ink supply seal member 17 is rotated, and the roller 20 rotates while crushing the tube 7. As a result, the plasticizing tube 7 is strained in a predetermined range, and the ink is extruded and the extruded ink is discharged from the plasticizing tube 7 to the ink supply port 10, the ink flow path 4, the common liquid chamber 3, the ink path 9. , And the outlet 2 in order.

  Even if the ink is filled up to the discharge port 2 and continues to be supplied by the tube pump 6 even if the pressure in the ink flow path 4 rises up to the discharge port 2 meniscus holding force, the discharge port 2 meniscus is destroyed and the ink is discharged from the discharge port 2 An ink reservoir 18 is formed on the nozzle surface 22.

  When the ink is discharged from the discharge port 2, the pressure in the ink flow path 4 is lowered, so it is desirable to select the ink supply capacity (maximum flow rate) from the tube pump 6 so as not to lower it.

  When the ink supply by the operation of the tube pump 6 is started, a pressure is generated in the ink flow path 4 from the plasticizing tube 7 to the discharge port 2. A pressure gauge 16 is installed between the plasticizing tube 7 and the ink supply seal member 17. The pressure is monitored and the tube pump 6 is stopped when the pressure reaches a predetermined value.

  For example, when the total area of the discharge port 2 for discharging 12 pl droplets is 0.34 mm 2, the pressure is 20 kPa. When the total area of the discharge ports 2 for discharging 5 pl droplets is 0.15 mm 2, the pressure is monitored at about 50 kPa.

  Even if the operation of the tube pump 6 is stopped, the residual pressure in the ink flow path 4 from the plasticizing tube 7 to the discharge port 2 causes the ink to come out from the discharge port 2, so the valve 25 is opened to release the pressure.

  The pipe connected to the valve 25 for releasing the residual pressure in the ink flow path 4 is connected to the ink tank 8 storing the ink, and the pipe tip is always in contact with the ink in the ink tank 8. By setting the water surface of the ink in the ink tank 8 at a position lower than the nozzle surface 22, the pressure in the ink flow path 4 can be reduced.

  When the pressure in the ink flow passage 4 becomes equal to or less than the pressure which does not break the meniscus, the valve 25 is closed and the ink supply seal member 17 connected to the filter 5 operates to separate from the filter 5.

  Thereafter, in a state where the suction pump 14 is driven, the suction cap 15 formed of an elastic material such as rubber is raised to a position where it does not contact the nozzle surface 22. Then, the suction cap 15 is moved in parallel with the nozzle row.

  The suction cap 15 scans and the ink reservoir 18 formed on the nozzle surface 22 can be sucked, scratched and removed.

  In practicing the present invention, three factors, namely, the clearance (mm) between the suction cap 15 and the nozzle surface 22, the suction pressure (kPa) and the scanning speed (mm / sec), are factors determining the cleaning state of the nozzle surface 22. It can be mentioned.

  In this example, the scanning speed was fixed at 15 [mm / sec], and experiments were performed using a combination of clearance and suction pressure. From the experimental results shown in FIG. 5, it was confirmed that if the clearance is set to 0.12 mm and the suction pressure is set to 50 kPa, a good cleaning state can be obtained even if the clearance and the suction pressure fluctuate up and down.

1 Ink jet head, 2 discharge port (nozzle), 3 common liquid chamber, 4 ink flow path,
5 filter, 6 pressure pump or tube pump, 7 plasticizing tube,
8 ink tanks, 9 ink paths, 10 ink supply ports, 11 heating elements,
12 joint rubber, 13 ink mist, 14 suction pump,
15 suction cap, 16 pressure gauge, 17 ink supply seal members,
18 ink reservoirs

Claims (2)

An ink jet recording apparatus that performs printing on a recording medium by discharging ink from the nozzles of an ink jet recording head, a filter is configured at a liquid introduction port of an ink supply path, and a flammable tube is disposed upstream of the liquid introduction port. The flammable tube is equipped with a tube pump, which supplies ink by means of the tube pump, which exerts pressure in the head ink flow path, and a pressure mechanism for overflowing the ink on the surface of the ink jet print head and its overflow In an inkjet recording apparatus that performs cleaning using the selected ink,
What is claimed is: 1. A droplet discharge head recovery mechanism comprising: a cleaning mechanism that performs cleaning while moving the surface of an inkjet print head in a non-contacting manner; and a mechanism that performs suction while moving.   The pressure mechanism scans the surface of the inkjet print head by non-contact suction while supplying ink, and in the operation of forming the meniscus in the head discharge port, the ink supply at the time of the scanning operation does not destroy the formed meniscus. The droplet discharge head recovery mechanism according to claim 1, wherein the ink is supplied.