JPS647586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing clogging in an inkjet printer that controls the main parts of the inkjet printer.

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 of these ink droplet ejecting devices is that the orifice through which the ink droplets are ejected is clogged, and the following suggestions have been made to prevent such clogging. has been done.

(a) Cover the orifice.

(b) Keep the area near the orifice humid to prevent it from drying out.

(c) Mixing chemicals into the ink itself that prevents it from drying.

There is also a method of removing dried ink by applying great pressure to the ink.

However, none of the above methods could reliably eliminate clogging.

The present invention has been made in view of this point, and embodiments of the present invention will be described below in detail using an on-demand type ink droplet ejecting device.

FIG. 1 shows a sectional view of the ink droplet ejecting device during printing operation, and FIG. 2 shows a sectional view during non-printing operation. In both figures, 1 is an on-demand type ink droplet ejecting device, and the ejecting device 1 includes a piezoelectric diaphragm 2 that curves and vibrates in response to an image signal, and a piezoelectric diaphragm 2.
a horn-shaped pressure chamber 3 in which is arranged at the opening on the long diameter side;
A thin plate-like vibrator 4 is provided on 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 side of the vibrator 4, and the vibrator 4 sandwiching the ink chamber 5. , and a first orifice 7 with a minute diameter bored at a location opposite to the vibration center of the vibrator 4 in the front plate 6, and a first orifice 7 in front of the first orifice 7. a second orifice 8 which is opened from the chamber 8 and has an opening diameter twice or more larger than that of the first orifice 8 through which ink droplets 9 ejected from the first orifice 7 pass; It is equipped with an orifice 10. Reference numeral 11 denotes an ink tank that supplies ink to the ink chamber 5 of the ink droplet ejecting device 1, and the liquid level of the ink tank 11 is at a lower level than the lowest level of the ink chamber 5 during printing operation, and at least for a long time. During non-time printing operations, it is at a higher level than the top level. In order to make the height difference between the ink tank 11 and the ink droplet ejecting device 1 variable,
One or both of the ink tank 11 and the ink droplet ejecting device 1 are configured to be able to move up and down. 12
...Second orifice 1 of the ink droplet ejecting device 1
The recording medium is placed in front of the recording medium 0, is wound around a rotating drum 13, and is main-scanned in the rotational direction. 14
is a lid that covers the second orifice 10 during non-printing operation.

Figure 3 shows the positional relationship for each operation of the ink droplet ejecting device 1, and shows the home position HP during non-printing operation.
As shown in FIG. 2, the second orifice 10 is covered by the cover 14. SP is a standby position where the ink droplet ejecting device 1 waits for printing operation, and in this standby position SP, the second orifice 10 of the ink droplet ejecting device 1 is connected to the gutter 15 as shown in FIGS. 4 and 5. is facing.
PP is a print position in which the ink droplet ejecting device 1 is in a printing operation by ejecting ink droplets 9, and the ink droplet ejecting device 1 is in a state as shown in FIG.

In this embodiment, the chamber and ink tank 11 of the ink droplet ejecting device 1 are provided with an air flow 16 as shown by the arrow.
The ink droplets 9 ejected from the first orifice 7 are accelerated while being surrounded by the air flow 16, and fly through the second orifice 10.

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 vibrates in a curved manner in its thickness direction and pressurizes the pressure chamber 3. This pressurization is amplified together with the horn shape of the pressure chamber 3 and is 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 function as a pressure change means for rapidly applying a pressure change to the ink in the ink chamber 5. Therefore, the vibrator 4
The ink in the ink chamber 5 is forced out of the first orifice 7 and is ejected from the coaxial second orifice 10 while being surrounded by an air flow 16 and becoming an ink droplet 9. These ink droplets 9 ultimately adhere to a recording medium 12 that is being rotated and scanned by a drum 13 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 1.
4, the chamber 8 is isolated from the outside. Next, in order to supply ink to the chamber 8 through the ink system extending from the ink tank 11 to the first orifice 7, the height difference between the ink tank 11 and the ink droplet ejecting device 1 is adjusted by changing the height of one or both of them. By moving the ink tank 11, the liquid level of the ink tank 11 is maintained at a high level. Therefore, the ink in the ink tank 11 pressurizes the ink in the ink chamber 5 with static pressure based on the difference in liquid levels. When this pressurizing force breaks the equilibrium state of the ink in the first orifice 7, the ink flows out from the first orifice 7 into the chamber 8. To assist this flow of ink, when an electrical signal is applied to the piezoelectric diaphragm 2 while the airflow 16 is blocked, and the vibrator 4 is caused to continuously vibrate in a curved manner, the balance of the ink is disrupted and the ink flows from the first orifice 7. Ink flows out into chamber 8. Once the ink begins to flow, even if the application of the electric signal to the piezoelectric diaphragm 2 is stopped, the ink will not be supplied to the chamber 8 until the liquid levels of both sides become approximately the same level due to the static pressure on the ink tank 11 side. The process continues and the first orifice 7 is covered with ink in the chamber 8, as shown in FIG. Further, if the vibration of the piezoelectric diaphragm 2 is continued until the filling is completed, the ink filling is completed.

Therefore, the first orifice 7 is covered with ink in the chamber 8 during non-printing operations, thereby preventing clogging mainly due to drying and adhesion of dust.

On the other hand, the ink covering the first orifice 7 comes into contact with the atmosphere at the second orifice 10. Since the opening diameter is more than twice as large as that of the first orifice 7, clogging of the second orifice 10 does not occur.

The ink droplet ejecting device 1, which has been filled with ink in the chamber 8 at the home position HP, moves to the standby position SP and faces the gutter 15 prior to the printing operation. In this state, when the relative position of the ink droplet ejecting device 1 and the ink tank 11 is moved as much as possible so that the liquid level in the ink tank 11 is at a low level, and the air flow 16 is again applied to the chamber 8, the ink in the chamber 8 is reduced as shown in FIG. As shown in the above air flow 16
and is discharged from the second orifice 10. This discharged ink is captured by the opposing gutter 15. When the ejection operation is completed, the air flow 16 is stopped and the ink is balanced in the first orifice 7, and the ink droplet ejecting device 1
is in a waiting state. That is, the second orifice 10
is cleaned by the ink each time it is discharged and waits for the next printing operation.

In the above description, the embodiment in which the air flow 16 is also used has been described in detail, but the air flow 16 may not be used. In this case, the problem is the discharge of ink from the chamber 8, but a bypass path is formed that communicates the ink tank 11 with the chamber 8, and the ink is not only discharged but also supplied through this bypass path. Just tighten it. At this time, the surface of the chamber 8 facing the recording medium 12 during the printing operation also acts as a protective wall against ink overflow.

Further, the height difference between the ink droplet ejecting device 1 and the ink tank 11 is not limited to vertical movement, but may be rotational movement.

As is clear from the above description, the present invention is such that the first orifice of the ink droplet ejecting device that ejects ink droplets is configured such that the liquid level of the ink tank is set higher than the top of the ink chamber during non-printing operation. Ink is supplied from the first orifice into a chamber provided in front of the orifice, and the first orifice is covered with the ink in the chamber, so the above-mentioned first orifice is mainly caused by drying and adhesion of dust. Clogging of the orifice can be completely prevented.

[Brief explanation of the drawing]

The figures are a sectional view and a schematic diagram for explaining the prevention method of the present invention, in which FIG. 1 is a sectional view of an inkjet printer during printing operation, FIG. 2 is a sectional view during non-printing operation, and FIG. FIG. 3 is a schematic diagram showing the positional relationship of the inkjet printer according to its operation, and FIGS. 4 and 5 are cross-sectional views during standby. 1... Ink droplet ejecting device, 5... Ink chamber, 7
...First orifice, 8...Chamber, 10...Second
orifice, 11... ink tank, 14... lid body, 15... gutter, 16... air flow.

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 ejecting device comprising an orifice, a chamber provided in front of the first orifice, and a second orifice that is opened from the chamber and through which the ink droplets ejected from the first orifice pass. and a means for varying the height difference between the ink tank that supplies ink to the ink chamber and the ink droplet ejecting device, the liquid level of the ink tank being adjusted to the ink chamber during printing operation. The liquid level of the ink tank is set lower than the lowest level of the ink chamber, and the liquid level of the ink tank is set higher than the highest level of the ink chamber, at least during long periods of non-printing operation. 1. A method for preventing clogging in an inkjet printer, characterized in that the first orifice is covered with the supplied ink. 2. An air flow is added to the chamber, and during the printing operation, the air flow assists the ejection operation of ink droplets, and the ink filled in the chamber is discharged from the second orifice prior to the printing operation. A method for preventing clogging in an inkjet printer according to claim 1.