JPH09290505A - Ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high speed, high reliable ink jet recording apparatus by applying an alternating electric field to a dot piezoelectric oscillator performing no ink discharge during recording, and preventing the nozzle foul from happening at the time of recording. SOLUTION: Although a high frequency alternating voltage is cut and a driving voltage is applied at carrying out ink discharge again, at this time, the time measuring of a timer circuit is reset to start time measuring again. Also, at the time of awaiting time measuring or like the period, a high frequency, alternating voltage applied to the piezoelectric oscillation 17 is cut. In this manner, by applying a high frequency, alternating electric field to the piezoelectric oscillator 17 performing no ink discharge for a long period of time and causing the piezoelectric oscillator 17 to vibrate minutely, since the ink within the ink chamber oscillates, any foul due to ink solidification never occurs in the ink nozzle part. Furthermore, a voltage applied is small and the piezoelectric oscillator 17 vibrates finely so that ink is not discharged from the ink chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus, and more particularly to a method for preventing nozzle clogging.

[0002]

2. Description of the Related Art With the rapid spread of personal computers in recent years, ink jet recording apparatuses have become the mainstay of output devices for personal computers. 2. Description of the Related Art An inkjet recording apparatus records liquid by ejecting liquid ink onto a recording medium to form dots, and various systems have been proposed and put into practical use. Inkjet recording system,
There is a method in which the volume of the ink chamber is changed and ink is ejected from the nozzle by utilizing the characteristic of the piezoelectric vibrator that deforms when an electric field is applied. A necessary characteristic of the liquid ink used in the ink jet recording apparatus is that it is dried and fixed immediately after being ejected onto the paper. Therefore, the ink jet recording apparatus uses low viscosity ink in which a coloring agent such as a dye or a pigment is dispersed in an alcohol solvent. When this ink is used, it easily fixes on the paper immediately, but when exposed to the air for a long time, the solvent in the ink evaporates and the colorant component solidifies, which easily causes clogging in the nozzles of the recording head. I have a problem.

[0003] In order to solve this problem, the prior art has been proposed.
As disclosed in JP-A-7-195701, by moving the inkjet head to a maintenance station equipped with the same type of ink as that used for recording and immersing it in the ink in the maintenance station To prevent it from drying out. In addition, Japanese Patent Laid-Open No. 7-2
No. 66580 describes that it is possible to recover even if clogging occurs by retracting the recording head outside the printing area and performing idle ejection. These conventional techniques are methods of performing recording by reciprocally moving a recording head having a plurality of nozzles in a direction perpendicular to the sheet passing direction by a carriage, and retreating the recording head to the outside of a printing area to prevent ink drying or It is possible to remove clogging. However, since the recording head in which a large number of nozzles are arranged in an array over the entire printing area is fixed, it is not possible to take a measure to prevent clogging by retracting the recording head out of the printing area like a carriage method. Further, in the case of the carriage method, since the recording head moves to perform image recording, ink can be ejected from other nozzles to perform printing on behalf of printing even if clogging occurs. On the other hand, in the case of the array head, printing cannot be performed at the position corresponding to the nozzle in which the clogging has occurred. Therefore, an image with white spots is formed at a position corresponding to the position of the clogged nozzle. In order to solve this problem, a method of removing the clogging can be considered, but in the case of an array head, many nozzles are arranged in the thousands, so clogging is frequent and it is difficult to detect the clogging point. It is difficult to carry out a method of removing clogging from the.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a high-speed and highly reliable ink jet recording apparatus free from printing defects by preventing nozzle clogging during recording. The purpose is to

[0005]

In order to achieve the above object, the present invention applies a high frequency alternating electric field to a piezoelectric vibrator of a dot which does not eject ink to the piezoelectric vibrator of each dot during recording. Then, the ink in the ink chamber is vibrated to form a flow of the ink in the ink chamber to prevent the ink from drying. Further, it is characterized in that the ink is prevented from being dried by covering the nozzle group of the recording head with a cleaning member during non-recording.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of an ink jet recording apparatus to which the present invention is applied. When a print command signal is sent from the host computer 1 such as a personal computer to the control circuit 3 via the interface 2, the control circuit 3 drives the motor driver 4 to print the recording paper 7 from the paper feed tray 6 by the transport motor 5. Transport to the start position. When a recording signal is sent from the host computer 1, the recording signal is converted into recording data for printing inside the control circuit 3. Then, the motor driver 4 is driven by the control circuit 3 and the array head 9 is driven via the head driver 8 to eject ink from the nozzles to perform image recording. When the image recording is completed, the recording paper 7 is ejected to the paper ejection tray 10. The cleaning member 11 wipes the ink scattered on the nozzle surface, and raises the space between the sheets during recording or the lower surface of the array head 9 during non-recording for cleaning.

FIG. 2 shows the appearance of the array head 9 and the arrangement of nozzles in the ink jet recording apparatus of the present invention. As shown in FIG. 2A, an independent ink cartridge 12 of four colors of yellow, magenta, cyan, and black is provided above the array head 9. When the ink is used up, each color can be replaced individually. As shown in FIG. 2B, a large number of nozzle groups are provided on the lower surface of the array head 9, and the diameter of the opening of each nozzle is several tens μm and 250 μm.
Are lined up at equal intervals. The resolution of this one row nozzle group is 100 dots / inch, and a resolution of 400 dots / inch can be obtained by arranging four rows of nozzle groups in a staggered manner as shown in the figure. This nozzle group is arranged for each of the four colors. Further, it is possible to obtain an arbitrary resolution by changing the pitch between nozzles and the number of rows.

FIG. 3 shows the internal structure of the array head 9. On a metal orifice plate 14 having a nozzle hole 13, a partition wall 15 made of a metal such as nickel is formed by an electroforming method or the like in order to separate the nozzle from an adjacent nozzle.
Is formed, and the common electrode 16 made of a metal common to all the nozzles is provided thereon to form an ink chamber. A piezoelectric oscillator 17 such as PZT is attached to the common electrode 16 for each ink chamber, and an individual electrode 18 such as gold is provided on the piezoelectric oscillator 17 by a printing method or the like. A pulse voltage of about 30 v, 200 μs is applied from the piezoelectric vibrator driving power source inside the control circuit 3 shown in FIG. 1 via the head driver 8 to the individual electrodes 18 of the piezoelectric vibrator 17 of the dots corresponding to the recording data. By applying a voltage to the individual electrodes 18,
An electric field is generated between the individual electrode 18 and the common electrode 16, and the electric field contracts the piezoelectric vibrator 17 in the direction A shown in the drawing.
It extends in the direction. Due to this deformation of the piezoelectric vibrator 17, the common electrode 16 bends downward and the volume in the ink chamber becomes small. As a result, the ink in the ink chamber is pushed out and ejected as droplets from the nozzle 13.

Since the array head 9 has the nozzles 13 that are formed by dividing the entire printing area into recording dots, the nozzles 1 that do not eject ink for a long time depending on the image.
There are three. If ink is not ejected for a long time, the nozzle 1
The ink is exposed to the air in the portion 3 to evaporate the solvent component in the ink. Since there is no circulating flow in the ink in the ink chamber, the ink in the portion exposed to the air solidifies and blocks the nozzle 13 and becomes clogged. No image is recorded at the printing position corresponding to the clogged nozzle 13, and all images after the clogging are defective images.

In order to solve this problem, according to the present invention, as shown in FIG. 1, a timer circuit inside the control circuit 3 measures the time after ink is ejected to each dot at the time of recording and regulates it. For the dots that have reached the time, the high-frequency AC power source inside the control circuit 3 causes the piezoelectric vibrator 17 to pass through the head driver 8 at a level of about 10 V for several pp and several hundred H.
A high frequency alternating voltage of z is applied.

FIG. 4 shows a timing chart of the voltage applied to the piezoelectric vibrator 17. The voltage applied to the piezoelectric vibrator of a certain dot will be described. From the control circuit 3 to the piezoelectric vibrator 17 of the dot corresponding to the recording data, a pulsed drive voltage is supplied from the piezoelectric vibrator drive power source through the head driver 8. Is applied. With this point as the starting point, a certain fixed time is measured by the timer circuit inside the control circuit 3. The specified time is about half the time taken for the nozzle surface to be clogged when the nozzle surface is exposed to the air after the ink is ejected from the nozzle 13. Since this time differs depending on the type of ink, it can be set arbitrarily. When the time measured by the timer circuit reaches a certain specified time, a high frequency AC voltage is applied to the piezoelectric vibrator 17. When ink is ejected again, the high frequency AC voltage is cut off and the drive voltage is applied. At this time, the time measurement of the timer circuit is reset and the time measurement is started again. Also, when waiting for recording, etc.
The high frequency AC voltage applied to the piezoelectric vibrator 17 is cut off. In this way, by applying a high-frequency alternating electric field to the piezoelectric vibrators 17 of the dots that do not eject ink for a long time and vibrating the piezoelectric vibrators 17 weakly, the ink in the ink chamber vibrates, so that in the nozzle portion 13. The ink does not solidify and clogging does not occur. Further, since the voltage applied at this time is small, the piezoelectric vibrator 17 vibrates weakly and ink is not ejected from the ink chamber.
In addition, the piezoelectric vibrators 1 for all dots that do not eject ink
Since the high frequency alternating electric field is not always applied to 7, the high frequency alternating electric field is selectively applied by measuring the time, so that the power consumption can be reduced.

The cleaning member 11 shown in FIG. 1 is on standby during recording and during non-recording such as when the main power of the apparatus is not turned on.
Goes up to the bottom surface of the array head 9 and covers the nozzle 13,
Since the ink is prevented from drying, unnecessary power is not consumed.

[0014]

According to the present invention, clogging of ink is prevented by vibrating the ink in the ink chamber by applying an alternating electric field of high frequency to the piezoelectric vibrator of the dot which does not eject ink for a long time during recording. High speed without printing defects,
It is possible to provide a highly reliable inkjet recording device.

[Brief description of drawings]

FIG. 1 is a block diagram of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram of an inkjet array head to which the present invention is applied.

FIG. 3 is an explanatory diagram of an internal structure of an inkjet array head to which the present invention has been applied.

FIG. 4 is a timing chart of voltages applied to the piezoelectric vibrator of the present invention.

[Explanation of symbols]

13 ... Nozzle, 14 ... Orifice plate, 15 ... Partition wall, 16 ... Common electrode, 17 ... Piezoelectric vibrator, 18 ... Individual electrode.

Claims (2)

[Claims] 1. An ink jet recording apparatus, wherein an electric field is applied to a piezoelectric vibrator to deform the piezoelectric vibrator, and the deformation is used to eject ink from an ink chamber from a nozzle to perform recording. An inkjet recording apparatus, characterized in that an alternating electric field is applied to a piezoelectric vibrator of dots which are not ejected. 2. The ink jet recording apparatus according to claim 1, wherein an alternating electric field is applied to a piezoelectric vibrator of a dot which does not eject ink for a predetermined time or more during recording.