JPS6315913B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for preventing clogging in an ink droplet ejecting device that controls the main part of an inkjet printer.

(B) Prior Art Ink droplet ejecting devices are currently classified into electric field control type, charge control type, on-demand type, etc. depending on the type of ink droplet ejection control. It is widely known that the biggest drawback common to all these ink droplet ejecting devices is that the orifice through which the ink droplets are ejected is clogged, and the following suggestions are available to prevent such clogging. is being done.

(a) Put a lid on the orifice (110847/1984
issue).

(b) Keep the area near the orifice humid to prevent it from drying out (Utility Model Publication No. 50-35624).

(c) Coat the orifice (nozzle) with anti-drying liquid (Japanese Patent Publication No. 54-24661).

(d) The ink itself is mixed with chemicals that do not dry, such as polyethylene glycol or ethylene glycol.

There is also a self-recovery method in which dried ink is removed by applying great pressure to the ink.

However, in the case of an on-demand type ink droplet ejecting device that ejects ink droplets by applying a minute pressure change to the ink near the orifice, as mentioned above, the ink droplets are ejected due to the minute pressurizing force. Once the clogging occurs, the clogging cannot be easily recovered by itself, and therefore, it is necessary to prevent the clogging in advance during non-printing operations.

(c) Problems to be Solved by the Invention The present invention attempts to prevent clogging of the orifice for ejecting ink droplets, which is the biggest drawback in the ink droplet ejecting device that controls the main part of an inkjet printer. It is something.

(d) Means for Solving Problems The method for preventing clogging in the ink droplet ejecting device of the present invention is to prevent clogging in the ink droplet ejecting device by
It covers a second orifice through which ink droplets ejected from the orifice pass and is ejected to the outside, and is connected to the front chamber located between the first orifice and the second orifice, and is connected to the first orifice. The ink is supplied from the first orifice to the front chamber with the air vent provided at a high position open, and the first orifice is covered with the filled ink.

(E) Function As mentioned above, during non-printing operation, ink droplets ejected from the first orifice cover the second orifice which is ejected to the outside, and cover the second orifice provided in front of the first orifice. By supplying ink from the first orifice to the chamber in front of the chamber with an open atmosphere opening that is connected to the chamber and provided at a higher position than the first orifice, the atmosphere opening that is opened is It acts as an exhaust port for the air stagnant in the front chamber that is pushed out as the air is supplied.

(f) Examples The method for preventing clogging of the present invention will be described below in detail with reference to the drawings for an on-demand type ink droplet ejecting device.

FIG. 1 shows a cross-sectional view of the ink droplet ejecting device during printing operation. In the figure, 1 is an on-demand type ink droplet ejecting device, and the ejecting device 1 curves in response to an image signal. A vibrating piezoelectric diaphragm 2, a horn-shaped pressure chamber 3 in which the piezoelectric diaphragm 2 is arranged at the opening on the long diameter side, and a thin plate-shaped vibrator 4 provided in the short diameter side of the pressure chamber 3 so as to be able to vibrate freely. , an ink chamber 5 that holds ink on the front surface of the vibrator 4, a front plate 6 that faces the vibrator 4 with the ink chamber 5 in between, and a vibration center of the vibrator 4 on the front plate 6. It has a first orifice 7 with a minute diameter bored at an opposite location, and further has a front chamber 8 provided in front of the first orifice 7, and a hole opened from the chamber 8 and the first orifice 7. The second orifice 10 has an opening diameter twice or more larger than that of the first orifice 7 through which the ink droplets 9 ejected from the orifice 7 pass.
Reference numeral 11 denotes an ink tank for supplying ink to the ink chamber 5 of the ink droplet ejecting device 1, and several hundred c.c. of ink is stored in a bag made of polymer film or the like with low air permeability. 12 is an ink supply pipe that connects the ink tank 11 and the ink chamber 5; 13 is an ink coupler inserted in the middle of the ink supply pipe 12;
The ink supply pipe 12 extending from the ink tank 1 is freely attachable, and ink can be replenished by replacing each ink tank 11. Reference numeral 14 denotes an air pump that appropriately adds an air flow 16 as indicated by the arrow to the chamber 8 and the ink tank 11 at the front of the ink droplet ejecting device 1 through the air supply pipe 15; A valve device provided in the air supply pipe 15 between the two is, for example, a three-way solenoid valve, and communicates with the air pump 14 and the front chamber 8 during the printing operation. A recording medium 18 is placed in front of the second orifice 10 of the ink droplet ejecting device 1 at a short distance, and is wound around a rotating drum 19 and main-scanned in the rotational direction.

FIG. 2 shows the state during non-printing operation, in which the second orifice 10 of the ink droplet ejecting device 1 is covered with a lid 20 made of an elastic material such as rubber.
During this non-printing operation, the first orifice 7 is covered with ink supplied to the front chamber 8. During such a non-printing operation, the ink droplet ejecting device 1 is located at a home position HP away from the recording medium 18 and the drum 19, as shown in FIG. In the figure, PP is a print position where the ink droplet ejecting device 1 is performing a printing operation by ejecting ink droplets 9, and the ink droplet ejecting device 1 is in the state as shown in FIG. SP is a standby position located between the print position PP and the home position HP, where the ink droplet ejecting device 1 waits for printing operation. The orifice 10 faces the gutter 21 as shown in FIGS. 4 and 5.

When an image signal is applied to the piezoelectric diaphragm 2 of the ink droplet ejecting device 1 at the print position PP, the piezoelectric diaphragm 2 suddenly curves and vibrates in its thickness direction, pressurizing the pressure chamber 3. This pressurization is carried out in pressure chamber 3.
Together with the horn shape, the pressure is amplified and propagated to the vibrator 4, causing the vibrator 4 to bend significantly.
That is, the piezoelectric diaphragm 2, the pressure chamber 3, and the vibrator 4
acts as a pressure changing means that rapidly changes the pressure on the ink in the ink chamber 5. Therefore, the ink chamber 5 receives a sudden pressure change from the vibrator 4.
The ink is pushed out from the first orifice 7,
The ink becomes an ink droplet 9 and is ejected from a coaxial second orifice 10 while being surrounded by an air flow 16. The ejection of the ink droplets 9 by the air flow 16 is described in more detail in Japanese Patent Laid-Open No. 51-37541, so a detailed explanation thereof will be omitted here.
These ink droplets 9 ultimately adhere to a recording medium 18 that is being rotated and scanned by a drum 19 to print images such as characters and figures.

After the printing operation is completed, the ink droplet ejecting device 1 passes through the standby position SP and returns to the home position HP. After returning, the second orifice 10 is closed to the lid body 2.
0 and the front chamber 8 is sealed off from the outside. Next, in order to supply ink to the front chamber 8 through the ink system from the ink tank 11 to the first orifice 7, the valve device 17 is switched to communicate the front chamber 8 with the outside air. This switching of the valve device 17 brings the front chamber 8 and the air pump 14 into a closed state. When the air pump 14 is operated in this state, the air flow 16 flows toward the ink tank 11 and pressurizes the ink in the ink tank 11. This pressure increase of the ink in the ink tank 11 is caused by the ink supply pipe 12,
The ink is transmitted through the ink connector 13 and further through the ink supply pipe 12 to pressurize the ink in the ink chamber 5.
Therefore, the pressure of ink in the ink chamber 5 near the first orifice 7 gradually increases compared to the pressure in the chamber 8 in front. When this pressure difference reaches a threshold value that breaks the equilibrium state of the ink in the first orifice 7, the ink flows out from the first orifice 7 into the forward chamber 8. When an electric signal is applied to the piezoelectric diaphragm 2 to cause the vibrator 4 to continuously vibrate in a curved manner in order to assist the flow of ink, the balance of the ink immediately collapses and the ink flows from the first orifice 7 into the front chamber 8. It starts to flow. Once the ink starts to flow, even if the application of the electrical signal to the piezoelectric diaphragm 2 is stopped, the pressure (air pressure) in the front chamber 8 is lower than the ink pressure in the ink chamber 5, so the ink supply will continue. Ru. Furthermore, such ink supply is achieved by opening the valve device 17, which is located at a higher position than the first orifice 7, which is the ink supply hole, and which currently communicates the front chamber 8 with the atmosphere, as shown in FIG. Mouth 17 out,
It acts as an exhaust port for the front chamber 8 pushed out by the ink supply. In this way, the first orifice 7 is covered with the supplied ink without leaving any air bubbles in the front chamber 8. This ink is supplied to the front chamber 8 or the air supply pipe 1 near the front chamber 8.
It is controlled by the detection output of the resistance detection means provided at 5.

In this embodiment, the body 22 of the ink droplet ejecting device 1 and the detection electrode 2 in the insulated air supply pipe 15 are used.
The resistance value between 3 and 3 is detected. That is, when the ink in the air supply pipe 15 rises and immerses the detection electrode 23, the resistance value between the body 22 and the detection electrode 23 is drastically reduced by the ink, and the completion of ink filling is detected.

Further, if the vibration of the piezoelectric diaphragm 2 is continued until the filling is completed, the ink filling is not only done quickly but also completely, so this method is usually adopted.

When the detection means detects that the front chamber 8 has been filled with ink, the air pump 14 stops operating and the pressure in the ink tank 11 gradually decreases. On the other hand, the front chamber 8 is in communication with the outside air via the air supply pipe 15, and when the pressure in the ink tank 11 decreases as described above in this state, the ink supplied and filled in the front chamber 8 is removed from the ink tank. Valve device 17 is closed for back flow towards 11. Therefore, the system of the front chamber 8 and the air supply pipe 15 is closed, and the backflow of ink is prevented by the so-called Torricelli principle.

As a result, when the ink droplet ejecting device 1 is in the home position during non-printing operation, the front chamber 8 is filled with ink, and the first orifice 7 is covered with the ink, preventing it from drying and getting dust. The main cause of clogging is prevented.

In this way, the ink droplet ejecting device 1, which had been supplied with ink into the front chamber 8 in the home position HP to prevent clogging of the first orifice 7, is moved to the standby position SP prior to the printing operation. Move and face the gutter 21. In this state, the valve device 17 is operated to establish communication between the air pump 14 and the front chamber 8, and to operate the air pump 14. Then, the ink filled in the front chamber 8 is pressurized from the outer circumferential direction by the air flow 16 as shown by the arrow in FIG. is discharged from. This discharged ink is captured by the gutter 21 disposed opposite to each other. When the ejection operation is completed, the air flow 16 is stopped, the ink is kept in equilibrium in the first orifice 7, and the ink drop ejecting device 1 is placed in a standby state as shown in FIG. Each time this ink is discharged, the second orifice 10 is cleaned by discharging even a small amount of ink coagulation that had adhered during the previous printing operation, and waits for the next printing operation.

The cleaning action described above is also performed on the first orifice 7 when ink is supplied from the first orifice 7 during non-printing operations.

FIG. 6 shows an ink supply operation during a non-printing operation in another embodiment of the present invention. That is, this corresponds to FIG. 2, which describes the previous embodiment. The difference from FIG. 2 is that the air intake port 24 of the air pump 14 is connected to a valve device 17 and an intake valve 25 that is closed when the valve device 17 is opened and opened when the valve device 17 is closed. In such a system, when the second orifice 10 is covered by the cover body 20, the valve device 17 shuts off the exhaust side of the air pump 14 and puts the front chamber 8 and the intake port 24 into communication. With,
In response to this operation, the intake valve 25 is closed.
Therefore, when the air pump 14 operates, the air pump 14 pressurizes the ink tank 11 with one air supply pipe 15 and exhausts the air in the front chamber 8 with the other, so that the pressure in the front chamber 8 decreases The pressure immediately becomes lower than that in chamber 5, and the first orifice 7
Ink flows out from the ink and is supplied. Further, the ink may be supplied by driving the piezoelectric diaphragm 2 as appropriate. Furthermore, even if only the front chamber 8 is evacuated by the air pump 14, the pressure inside the chamber 8 becomes low and ink flows out from the first orifice 7.

When the front chamber 8 is filled with ink in this way, the valve device 17 is closed and the front chamber 8 is filled with ink.
The first orifice 7 is covered with ink.

Incidentally, the ink droplet ejecting device 1 used in the present invention is not limited to the above-mentioned embodiment, but for example, the ink droplet ejecting device 1 used in the present invention is
Similar to the present invention, as disclosed in No. 109738, the first
An ink droplet ejecting device in which an air flow 16 is applied to the orifice 7 is desirable. Furthermore, even if the air flow 16 is not used, the ink tank 11 can be supplied with ink by pressurizing it with an appropriate pressurizing means, and the ink tank 11 can be pressurized with an appropriate pressurizing means, and the ink tank 11 can be pressurized with its own weight at the bottom of the front chamber 8 for ink discharge. This can be countered by providing an outlet for the water to flow out.

(G) Effects of the Invention As is clear from the above description, the method for preventing clogging in the ink droplet ejecting device of the present invention is such that the first orifice is connected to the front chamber provided in front of the first orifice, and the first orifice Since ink is supplied from the first orifice to the front chamber with the atmosphere release port provided at a higher position open, the air release port that is opened allows the air flow in the front chamber to be pushed out as the ink is supplied. As a result of acting as an exhaust port for air stagnant in the chamber, ink can be reliably supplied to the front chamber, and the first orifice covers the ink supplied to the front chamber. This eliminates clogging accidents mainly caused by ink drying. Furthermore, after ink is supplied to the chamber in front of the first orifice, when the atmosphere opening port is closed, the natural backflow of the ink supplied to the front chamber is prevented by the Trichie-tsuri principle, and the first orifice is securely filled. Can be coated. The supply of ink to the front chamber takes place via a first orifice, which is cleaned each time, so that the desired jet of ink droplets can be constantly obtained during the printing operation. Furthermore, if the first orifice is covered, even if an impact is applied to the ink droplet ejecting device or inkjet printer for some reason, air bubbles will not be sucked into the ink chamber, and even if air bubbles are sucked in, they will not be in the front chamber. Since the air bubbles in the lever are removed at least when the ink is discharged, it is therefore possible to substantially eliminate the air bubble suction accident, which was the biggest drawback along with clogging in on-demand ink droplet ejecting devices. .

[Brief explanation of the drawing]

1 to 5 are cross-sectional views and schematic diagrams for explaining each operation of one embodiment of the prevention method of the present invention, and FIG. 6 is a cross-sectional view for explaining another embodiment of the present invention. , 1 is an ink droplet ejecting device, 5 is an ink chamber, 7 is a first orifice, 8 is a front chamber, 10
is the second orifice, 11 is the ink tank, 14 is the air pump, 17 is the valve device, 17out is the atmosphere opening port,
20 is a lid, 21 is a gutter, and 23 is a detection electrode.

Claims (1)

[Scope of Claims] 1. An ink chamber filled with ink, a pressure change means for applying a pressure change to the ink chamber, and a first ink chamber for ejecting ink droplets from the ink chamber by the pressure change of the pressure change means. An ink droplet comprising an orifice, a front chamber provided in front of the first orifice, and a second orifice that is opened from the chamber and through which the ink droplet ejected from the first orifice passes. In the ejecting device, the second orifice is covered by a lid body when the ink droplet ejecting device is not in a printing operation, and the second orifice is connected to the front chamber and is provided at a higher position than the first orifice. An ink droplet ejecting device characterized in that ink is supplied from the first orifice to the chamber provided in the front with the atmosphere opening opened, and the first orifice is covered with the ink. How to prevent clogging. 2. After supplying ink to the chamber provided in the front, the atmosphere opening port is closed to retain the ink supplied to the chamber in the front, and the first orifice is covered with this ink. A method for preventing clogging in an ink droplet ejecting device according to claim 1.