JPH0160428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for stabilizing initial printing in an inkjet printer that ejects minute ink droplets.

(b) Prior art Figure 1 shows a basic device of this type. A cylindrical drum 1 is supported with recording paper 2 tightly wound around its surface, and a guide rod 3 is arranged parallel to the axis of the cylindrical drum. The guide rod 3 is for slidably mounting the arm 4. The arm 4 has an arch shape extending parallel to the drum surface in the circumferential direction of the cylindrical drum 1, and has first to fourth ink jet heads 5a to 5d dispersively arranged and fixed on its inner surface. These first to fourth heads 5a to 5d are capable of ejecting magenta, cyan, yellow, and black inks, respectively.Therefore, the rotation of the cylindrical drum 1 is used as the main scanning, and the movement of the arm 4 is used as the subscanning. A color image is printed on the recording paper 2 by appropriately ejecting ink from the first to fourth heads 5a to 5d in accordance with the signal.

FIG. 2 shows the structure of each of the ink heads 5a to 5d. Such heads themselves are well known, and their structure and operation will be briefly described below. Piezoelectric vibrator 10
deforms in accordance with the recording signal, and when pressure is applied to the pressure propagation medium 12 in the horn chamber 11, the thin plate 13 provided at the opening of the horn chamber deforms the ink chamber 14 in contact with it.
protrude to the side. The ink chamber 14 is always filled with ink 25 via an ink introduction pipe 15.
Therefore, due to the protrusion of the thin plate 13, the ink in front of the protrusion protrudes from the first orifice 16, and then ejects as an ink droplet 18 from the second orifice 17, which is coaxial with the first orifice 16. Air fed under pressure from the air introduction pipe 19 gathers in the center within the air chamber 20 provided between the first orifice 16 and the second orifice 17, and then flows into the second orifice.
The ink droplets 18 are ejected from the orifice 17 to form a high-speed air flow, and the ink droplets 18 are assisted by this flow and have a sufficient flying speed necessary for high-speed printing.

Incidentally, in inkjet printers, the orifice of the ink head tends to become clogged during non-printing operations. As an effective method for preventing this, the invention of Japanese Patent Application No. 112727/1983 was made. In general terms, this method, during non-printing operation, closes the second orifice 17 by closely contacting the pad to the front surface 21 of the ink head shown in FIG. 1
Ink is introduced at high pressure through the ink hole 5 and the air chamber 20 is also filled with ink, thereby preventing the ink near the second orifice 17 from drying out and preventing the orifice from clogging. Incidentally, at the start of printing, the ink must be discharged from the air chamber 20, but this is done by force-feeding air again from the air introduction pipe 19. That is, at this time, the ink in the air chamber 20 is pressurized from the outer circumferential direction and is discharged from the second orifice 17 at the center.

Referring again to FIG. 1, during the non-printing operation, the arm 4 stops at the home position at the left end of the guide rod 3. The home position is provided with the opening/closing device 6 that operates when filling the air chamber 20 with ink as described above. The opening/closing device 6 includes first and second support pieces 7 and 8 that cooperate to form an approximate arch.
, and near the top of the first support piece 7 are first and second
First and second pads 9 facing heads 5a and 5b
a, 9b, and a third support piece 8 near the top of the second support piece 8.
Third and fourth pads 9c and 9d are provided, respectively, facing the fourth heads 5c and 5d.

When the printing operation is completed and the arm 4 is located at the home position, first, the first and second support pieces 7 and 8
are rotated outward from each other around their respective lower ends, whereby the first to fourth pads 9a to 9d close the orifices of the corresponding first to fourth heads 5a to 5d, respectively. Subsequently, the air chamber 20 is filled with ink as described above.

Prior to the printing operation, the first and second support pieces 7, 8
is rotated inwardly so that each pad is separated from the orifice of each head, and then the arm 4 is positioned on the gutter 30, which is the waste ink collecting means. At this position, ink is discharged from the air chamber 20 of each head, and the discharged ink is collected in the gutter 30. Thereafter, the arm 4 reciprocates through the cleaning position on the side of the gutter 30, and then the recording paper 2
Move to the specified position above. A plurality of cleaning members 31, 31, . . . are erected at the cleaning position, and these members wipe the front surface 21 of each head that comes into contact with them and remove ink adhering to the surface.

Although inkjet printers can overcome the conventional problem of clogging by being equipped with a clogging prevention mechanism, the air chamber 20
Some of the ink filled in the ink chamber 14 may not be discharged to the gutter 30 and may enter the ink chamber 14 or
A small amount of ink remains on the wall surface of the air chamber 20 near the second orifices 16, 17, resulting in a new drawback that the initial printing becomes unstable.

Therefore, a method has been attempted to solve this new drawback by performing test printing several times before printing the image.

However, according to such test printing, the winding operation of the recording paper 2 around the cylindrical drum 1, the ejection operation of the ink droplets 18, and the recording paper 2 are completed until the printing is stabilized.
The printing operation, in which one cycle is the paper ejection operation, has to be repeated several times, which increases the waiting time until the start of printing and wastes the recording paper 2.

(c) Purpose of the Invention The present invention has been made for the purpose of shortening the waiting time until printing starts and preventing wasted use of the recording paper 2 in an inkjet printer equipped with such a clogging prevention mechanism. It is something.

(d) Structure of the Invention The inkjet printer of the present invention, which is equipped with a clogging prevention mechanism, discharges the filled ink that had been used to prevent clogging to an unnecessary ink recovery means prior to the printing operation, and then removes the ink from the inkjet printer. The ink in the chamber is pressurized to cause the filled ink that has flowed back into the ink chamber from the front chamber to flow out from the first orifice to the unnecessary ink collecting means, and then by supplying an ejection signal to the unnecessary ink collecting means. Head first
The ink is forcibly ejected from the orifice.

(E) Embodiment FIG. 3 shows the main parts of an inkjet printer according to the present invention, and 40 is a replaceable unit that supplies ink to the ink heads 5a to 5d detailed in FIG. 2 through an ink introduction pipe 15. An ink cartridge, 41 is an air pump that pumps air flow to the air chambers 20 of the ink heads 5a to 5d, and 42 is a first air introduction pipe 19 that connects the air pump 41 and the air chambers 20. solenoid valve, 43
The above air pump 41 and ink cartridge 40
A second solenoid valve 45 is installed in a second air introduction pipe 44 that connects the first air introduction pipe 1.
9 is a third solenoid valve that opens into the air chamber 20 only during the ink filling operation.

As shown in FIG. 4, in the home position of the ink heads 5a to 5d, the air chambers 20 are filled with ink to prevent clogging mainly caused by drying of the first orifice 16. In this state, the rubber pads 9a to 9, which are integrally molded with the flat head 46 and the legs 47 raised from the center thereof,
d comes into close contact with the orifice surfaces of the ink heads 5a to 5d due to the biasing of the support pieces 7 and 8 toward the head side,
The second orifice 17 is liquid-tightly closed.

The ink heads 5a to 5d, whose air chambers 20 have been filled with ink, are moved to the gutter 30 prior to the printing operation by the movement of the arm 4 supporting the heads.
As shown in FIG.
5' is discharged from the second orifice 17. Such a discharge operation is performed by opening only the first solenoid valve 42 and operating the air pump 41 at timing _T1 , as shown in the timing chart of FIG. That is, the air flow generated by the air pump 41 is added to the air chambers 20 of the ink heads 5a to 5d via the first air introduction pipe 19, and pressurizes the filled ink 25' from around it.
The filled ink 25' is discharged from the second orifice 17 in the open state toward the gutter 30 and collected.

At timing _T2 after the ejection operation is completed, the ink chamber 1 is discharged through the first orifice 16 by this ejection operation.
The first solenoid valve 42 is closed to discharge the filling ink 25' that has flowed back into the interior of the solenoid valve 4, and the second solenoid valve 42 is closed.
3 to connect the air pump 41 and the ink cartridge 40. That is, the pressure of the ink contained in the ink cartridge 40 increases due to the addition of airflow, and this pressure increase propagates through the ink introduction pipe 15 and pressurizes the ink within the ink chamber 14. When the ink in the ink chamber 14 is pressurized in this way, the pressure balance between the ink and air, which was in equilibrium in the first orifice 16, is disrupted, and the ink flows from the first orifice 16 into the gutter 3.
It is forced to flow out to 0. The ink that is forced to flow out is the ink near the first orifice 16, in other words, the filled ink 25' that has flowed back.

Next, at timing _T3 , the first solenoid valve 42 is opened and a continuous ejection signal is supplied to the ink heads 5a to 5d. Such a continuous ejection signal is mainly supplied to remove the filling ink 25' remaining on the wall of the air chamber 20 by vibrations and air flow applied to the wall as shown in FIG. .
Naturally, ink droplets 18 are forcibly ejected from the first orifice 17, pass through the second orifice 17, and are captured by the gutter 30. This operation ends at timing _T4 , and the initialization of the ink heads 5a to 5d for printing is completed. That is, after this operation is completed, the ink heads 5a to 5d are moved from the gutter 30 to the printing position facing the recording paper 2 wound around the cylindrical drum 1 by the movement of the arm 4.

In the above embodiment, after the filled ink 25' is discharged into the gutter 30, the ink is forced to flow out mainly for the purpose of discharging the filled ink 25' that has flowed back, and the remaining ink is removed from the wall of the air chamber 20. Although the ink ejection is performed by forcibly ejecting ink droplets for the purpose of removing the ink 25', a configuration may be adopted in which at least one of these is performed.

(f) Effects of the Invention As is clear from the above description, the present invention is directed to an unnecessary ink collecting means prior to a printing operation to remove the filled ink that had been used to prevent clogging of the first orifice during non-printing operations. After the ink is discharged, the ink in the ink chamber is pressurized to cause the filled ink that has flowed back into the ink chamber from the front chamber to flow out from the first orifice to the unnecessary ink recovery means, and then by supplying an ejection signal. Since the ink is forcibly ejected from the first orifice toward the unnecessary ink collecting means, the ink droplet ejecting operation can be stabilized without unnecessary operations, and the waiting time until printing starts can be shortened. At the same time, unnecessary consumption of recording paper can be avoided.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic configuration of an inkjet printer according to the present invention, FIG. 2 is a sectional view showing an example of an ink head, FIG. 3 is a block diagram showing an embodiment of the invention, and FIG. Figures 5 and 7
The figures are cross-sectional views showing each operation of the present invention, and FIG. 6 is a timing chart of the present invention. 5a to 5d... Ink head, 16, 17...
First and second orifices, 20...Air chamber, 30
... Gutter, 40 ... Ink cartridge, 41
……air pump.

Claims (1)

[Claims] 1. A chamber is formed in front of a first orifice that ejects the ink filled in the ink chamber as ink droplets, and the chamber is filled with ink during non-printing operation, and the first An initial printing stabilization method in an inkjet printer equipped with a clogging prevention mechanism for discharging the filled ink from a second orifice that is coaxially opened to separate an orifice and a chamber, the method comprising: After the ink is discharged toward the unnecessary ink collecting means, the ink in the ink chamber is pressurized to cause the filled ink that has flowed back into the ink chamber from the front chamber to flow out from the first orifice to the unnecessary ink collecting means. A method for stabilizing initial printing in an inkjet printer, characterized in that, by subsequently supplying an ejection signal, ink is forcibly ejected from a first orifice toward an unnecessary ink collecting means.