JPH053835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a head cleaning method for an inkjet printer that cleans the vicinity of the nozzle of an ink head that ejects minute ink droplets.

(B) Prior Art FIG. 4 shows an inkjet printer equipped with a cleaning device for cleaning the vicinity of the nozzle of an ink head that ejects minute ink droplets. A cylindrical drum 19 supports the recording paper 18 by tightly winding it on its surface, and a guide rod 20 is arranged parallel to the axis of the cylindrical drum. The guide rod 20 is used to slidably mount a carriage 21. The carriage 21 has an arch shape extending parallel to the drum surface in the circumferential direction of the cylindrical drum 19, and has first to fourth ink heads 1a to 1d arranged and fixed in a dispersed manner on its inner surface. These first to fourth heads 1a
~1d can eject magenta, cyan, yellow, and black inks, respectively. Therefore, the rotation of the cylindrical drum 19 is used as the main scanning, and the movement of the carriage 21 is used as the sub-scanning. 4
A color image is recorded on the recording paper 18 by appropriately ejecting ink droplets from the heads 1a to 1d.

FIG. 5 shows the structure of each of the ink heads 1a to 1d. Such a head 1 itself is well known, and its structure and operation will be briefly described below. Piezoelectric vibrator 2
deforms in response to a recording signal, and when pressure is applied to the pressure propagation medium in the horn chamber 3, the thin plate 4 provided at the opening of the horn chamber protrudes toward the ink chamber 5 in contact with it. The ink chamber 5 is always filled with ink via the ink introduction pipe 12, and therefore the thin plate 4
Due to the protrusion of the ink, the ink in front of the protrusion protrudes from the ink nozzle 7, and then ejects as an ink droplet 9 from the air nozzle 10 located coaxially with the ink nozzle 7. Air is fed under pressure from an air pump (not shown) through the air introduction pipe 15 to the ink nozzle 7.
The air gathers at the center in the air chamber 8 provided between the air nozzle 10 and the air nozzle 10, and then blows out from the air nozzle 10 to form a high-speed air flow.
Aided by this flow, the ink droplets 9 have sufficient flying speed necessary for high-speed recording.

By the way, in this type of inkjet printer, since the ink head comes close to the recording paper 18 during the printing operation, the ink droplets generated when the ink droplets collide with the recording paper 18 bounce back onto the ejection surface and contaminate the ejection surface.

The ejection surfaces of the ink heads 1a to 1d are contaminated by adsorption of fibers and dust from the recording paper 18, and if the ink heads 1a to 1d are left unused for a long period of time, the ink heads 1a to 1d become contaminated.
This is one of the causes of nozzle clogging. In particular, with on-demand ink heads that eject ink droplets by applying a weak pressure change to the ink near the ink nozzle, as mentioned above, the ink droplets are ejected due to the weak pressing force, so the ink droplets are ejected from the recording paper. Even though only a gap of several millimeters is formed and there is a lot of bouncing of ink droplets, once clogging occurs, this clogging cannot be easily corrected by itself.

Therefore, an inkjet printer has been developed which is equipped with a cleaning member for the purpose of cleaning the ink head before it is left unused for a long time in order to prevent ink droplets from rebounding and adhering to the ink head and adhering to fibers and dust. It is disclosed in the publication number etc.

That is, as shown in FIG.
A cleaning device 30 including a cleaning member 31 integrally formed with a porous structure such as urethane foam or sponge is disposed between the print position and the home position of 1d, and each contact portion 31a
~31d is set to a wet state with water. Then, in the process of moving the ink heads 1a to 1d between the print position and the home position, the contact portion 31a of the cleaning member 31
31d and the ejection surfaces of the ink heads 1a to 1d are in sliding contact, and attached ink droplets, dust, etc. are removed and cleaned.

Now, in the above-mentioned inkjet printer, the intrusion of air bubbles into the inside of the ink head 1 is a problem similar to the clogging of the ink head. If air bubbles entered the ink head 1, it not only caused printing deterioration but also sometimes made it impossible to eject ink droplets.

Conventionally, when cleaning the ink head described above, in order to prevent air from entering the ink chamber 5, the air pump is shut off and the cleaning member 3 is turned off after the air pressure becomes completely zero.
1, the ejection surface of the ink head 1 was brought into sliding contact for cleaning. That is, it was generally thought that if the nozzle was closed while air was flowing out, the air pressure would increase and air bubbles would enter the ink chamber 5 of the ink head 1.

(c) Problems to be Solved by the Invention The purpose of cleaning the ejection surface of the ink head 1 is to remove ink droplets, dust, etc. that adhere to the print head during printing, and remove the ink droplets and dust that may interfere with dot formation or the direction of the ejected ink droplets. This is done to improve printing deterioration due to deviations in printing.

However, as described above, when cleaning by bringing the ejection surface of the ink head 1 into sliding contact with the cleaning member 31, dirt such as ink dust adhering to the ejection surface may be pushed into the inside of the ink head 1. When dust adheres to the inside of the ink head 1, ink accumulates based on the dust, reducing the diameter of the air nozzle, preventing dot formation, and causing printing defects such as unstable direction.

(d) Means for Solving Problems The present invention has an ink nozzle and an air nozzle coaxially arranged with an air layer in between, and ink droplets ejected from the ink nozzle are directed to the outer periphery of the air layer. A head cleaning method for an inkjet printer in which the ejection surface of an ink head, which is caused to fly from an air nozzle through an air flow supplied from an air flow generation source toward the air nozzle, is cleaned by slidingly contacting the jet surface of the ink head with a cleaning member. The present invention is characterized in that the cleaning member slides into contact with the ink head ejection surface while the air flow is ejected from the air nozzle.

(e) Effect When the airflow is ejected, the air pressure overcomes the pressing force of the cleaning member, and it is possible to prevent dust from flowing into the nozzle. Furthermore, the ink inside the ink head that is being pushed out by the air flow can be wiped off, thereby maintaining the cleanliness inside and outside the ink head.

In addition, since the nozzle is blocked off with a cleaning member, the pressure is thought to increase momentarily, but since the nozzle diameter of the ink nozzle of the on-demand ink head that is normally used is small, about 40 μm, the ink in this area The surface tension of can prevent air from flowing into the ink chamber.

(F) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Incidentally, the same parts as those in the conventional example are given the same reference numerals, and the description thereof will be omitted.

The inkjet printer used in the present invention includes an air chamber 8 of the ink head 1 and an ink tank 11.
air flow 1 through air supply pipes 15, 15, respectively.
An air pump 14 is provided to add air pressure 6 as appropriate. Further, a valve device 17 consisting of a three-way solenoid valve is provided in the air supply pipe 15 between the air pump 14 and the air chamber 5. Furthermore, the air supply pipe 15 is provided with a vent hole 35 that prevents the filled ink from flowing back when the air chamber 8 is filled with ink, in order to prevent clogging mainly caused by drying of the ink in the ink nozzle 7. It is provided.

Next, a cleaning method according to the present invention will be explained.

During the movement of the ink head 1, whose ejecting surface is covered with ink due to the printing operation or the discharge of ink as a clogging prevention liquid, during the movement process to the home position or print position,
It is configured to come into sliding contact with the protruding cleaning member 31. That is, the free ends 31a to 31d of the cleaning member 31 made of a flat elastic body such as rubber or foamed plastic protrude within the moving path connecting the print position and the home position of the ink head 1, and the free ends 31
The ejection surfaces of the ink heads 1 that are in the middle of movement come into sliding contact with a to 31d as shown in FIG. 2A to FIG. 2B.

In the present invention, during such a cleaning operation, that is, while the ink head 1 is moving, the air pump 14 is operated and the air flow 16 is ejected from the air nozzle 10 of the ink head 1, and the cleaning member 31 is brought into sliding contact to remove the ink that has adhered to the ejection surface. The ink 40 and the ink 41 pushed out from inside the air layer 5 are peeled off or wiped off for cleaning.

In this way, since the cleaning member 31 is brought into sliding contact with the airflow being ejected, adhered ink is not forced into the ink head 1.

In addition, the ink head 1 and the cleaning member 31
When they come into sliding contact, the air nozzle 10 is in a blocked state. Therefore, the air pressure momentarily increases, and a difference is created between the pressure from inside the ink chamber 4 that is applied to the ink boundary surface of the ink nozzle 7 and the air pressure from the air chamber 5, and the air pressure inside the ink chamber 4 increases. Pressure is applied in the direction in which air flows into. However, since the nozzle diameter of the ink nozzle 7 of currently used ink heads is usually as small as about 40 μm, the surface tension of the ink at the boundary between the end face of the ink and the inner wall of the nozzle causes air to flow into the ink chamber 4. The present inventor has confirmed that the inflow can be prevented. Furthermore, since pressure is applied to the air system and the ink system using the same air pump 14, while the cleaning member 31 is blocking the air nozzle 10 surface,
Both pressures can be balanced.

(G) Effects of the Invention As explained above, according to the present invention, the air flow ejected from the air nozzle prevents adhered ink, etc. from being pushed into the ink head during cleaning, and also removes the remaining ink head. Since the air current pushes out ink, etc., this residual ink, etc. can be wiped off, so that the inside and outside of the ink head can be reliably cleaned.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an inkjet printer used in the present invention, FIGS. 2A to 2C are schematic diagrams showing the cleaning operation of the present invention in each state, and FIG. 3 is an enlarged sectional view of the main part of an ink head. FIG. 4 is a perspective view of an inkjet printer equipped with a cleaning device, and FIG. 5 is a sectional view of a typical ink head. 1, 1a, 1b, 1c, 1d...ink head,
5... Ink chamber, 7... Ink nozzle, 8... Air chamber,
DESCRIPTION OF SYMBOLS 10... Air nozzle, 16... Air flow, 31... Cleaning member.

Claims (1)

[Claims] 1 An ink nozzle and an air nozzle are arranged coaxially with an air layer in between, and the ink droplets ejected from the ink nozzle are directed toward the air nozzle from the outer periphery of the air layer, and the air is supplied from an air flow source. A head cleaning method for an inkjet printer, in which the ejection surface of an ink head that is ejected from an air nozzle via an air flow is cleaned by sliding contact with a cleaning member, the method comprising the steps of:
A method for cleaning a head of an inkjet printer, characterized in that the cleaning member slides into contact with an ink head ejection surface.