JPH0243054A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To obtain good recording characteristics by returning a collapsed meniscus to a normal shape by making air pressure lower than ink pressure and allowing ink to flow out by generating pressure difference larger than holding force due to the surface tension of the meniscus of the ink. CONSTITUTION:When recording characteristics are deteriorated by the foreign matter 38 accumulated in the vicinity of an inner edge 33 or ink spread by the collapse of an meniscus, a cam 42 is rotated by 180 deg. to project a press rod 45 and a silicone tube 46 is pressed. When the silicone tube is pressed to make the resistance therein large, the pressure on the side of an air supply source 3 becomes high while the pressure on the side of an air chamber 9 becomes low to generate pressure difference. By making the pressure difference larger than the surface tension of the meniscus of the ink, the ink is allowed to flow out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inkjet recording apparatus that records characters, figures, images, etc. on a recording material by ejecting ink liquid from a minute opening.

2. Description of the Related Art Recently, inkjet recording apparatuses have been widely used in the fields of color printers, converter terminals, and the like. The configuration of this inkjet recording apparatus is described, for example, in Japanese Patent Laid-Open No. 62-55164. Hereinafter, a conventional inkjet recording apparatus and head will be explained with reference to FIG.

In FIG. 4, 13 is a body member. An insulating air nozzle plate 2 has air discharge ports 1 perforated therein, and an insulating ink nozzle plate 14 is disposed in parallel with the air nozzle plate 2. An ink discharge port 4 is bored opposite the outlet 1.

A convex portion 17 is provided around the ink discharge port 4 and extends in one direction of the air discharge port. Air flow flows into the air supply path 8 from the air supply source 3, is made uniform in the annular air chamber 9, and is distributed between the air nozzle plate 2 and the ink nozzle plate 14.
The air flows in from around the air layer 70 created by this, and flows out from the air outlet 1. Since this air flow changes rapidly near the air outlet 1, a rapid change in pressure gradient occurs in the space from the ink outlet 4 to the air outlet 1. On the other hand, an ink chamber 10 adjacent to the ink discharge port 4 communicates with an ink reservoir 11 via an ink supply path 6.
A constant pressure adjusted by a pressure adjustment mechanism 16 is applied to the ink in the ink reservoir 11 by air pressure from the air supply source 3. This means that when the inkjet recording device is not driven, the air pressure near the ink ejection port 4 and the ink pressure in the ink ejection port 4 or the ink chamber 1o are approximately equal, and the ink meniscus near the ink ejection port 4 is kept stationary. This is to adjust it accordingly.

The signal source 6 is connected to an electrode 12 provided around the air outlet 10 and an electrode 15 provided around the ink outlet 4 facing the ink chamber 1o. A potential difference is generated between the ink and the ink held near the ink ejection port 4. The electrostatic force caused by this potential difference causes an ink meniscus generated near the ink ejection port 4 to be stretched in the direction of the air ejection port 1. Furthermore, since there is a sudden change in the pressure gradient in the space from the ink discharge port 4 to the air discharge port 1, when the ink meniscus generated near the ink discharge port 4 is stretched beyond a certain length, the pressure gradient changes. It is accelerated by the change and flies from the air outlet 1.

A more detailed explanation of the vicinity of the ink discharge ports 4 will be given with reference to a partially enlarged sectional view of FIG. In order to prevent ink from adhering, the front end surface 34 and outer surface 3 of the convex portion 17 of the ink nozzle plate 14 near the air discharge port 1 and where the ink discharge port 4 is provided.
6 and its surrounding area 37 are covered with water- and oil-repellent coatings 19 and 18. The water- and oil-repellent coating film 18 has the function of repelling ink and stably holding the ink meniscus along the inner edge 33.

Problems that the invention aims to solve The problem will be explained with reference to the partially enlarged sectional view of FIG.

In conventional inkjet recording devices, when foreign matter 38 such as ink precipitates or dust in the ink reaches the ink meniscus, and foreign matter 2B that is not ejected together with the ink during recording accumulates near the inner edge 33, the ink meniscus A collapse occurs. If there is a broken meniscus portion 39, there is a problem that the amount of ink ejected changes or the direction of ejection is bent, resulting in deterioration of recording characteristics. In view of the above-mentioned deterioration of recording characteristics, the present invention aims to restore good recording characteristics by restoring the collapsed meniscus to its normal shape.

Means for Solving the Problems The technical solution of the present invention for achieving the above object is as follows:
It has a pressure adjustment means that can lower the air pressure than the ink pressure and generate a pressure difference that is greater than the holding force due to the surface tension of the ink meniscus.

Effect: The above-mentioned pressure adjusting means causes the air pressure to be lower than the ink pressure, and by creating a pressure difference greater than the holding force due to the surface tension of the meniscus of the ink, the ink flows out. Since the flowing ink has a large flow rate, foreign matter that has accumulated near the inner edge and ink that has spread due to the collapse of the meniscus can be attracted by the viscosity and removed to the outside of the head along the flow of ink. When the pressure difference is maintained for a certain period of time and then returned to a balanced steady state, the foreign matter and the wet and spread ink have been removed, so the normal meniscus is restored.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIG. The difference from the conventional configuration shown in FIG. 4 is that the silicon tube 46 made of an elastic member, which is a part of the air supply path 8 between the air chamber 9 and the air supply source 3, is held down to narrow the flow path and resist the internal resistance. By increasing the pressure, a pressure adjustment means is provided to create a difference between the pressure on the air supply source 3 side and the pressure on the air chamber 9 side. The pressure adjustment means includes a presser bar 45 that presses or does not press the silicone tube 46, a guide 44 that holds the presser bar 45, and a presser bar 46.
cam 42 and cam 4 for extending and retracting the
2, a pulse motor 40 for rotating the cam 42, and a drive circuit 41 for driving the pulse motor 4o.

In the steady state, the presser bar 46 is retracted and does not press the Silico 7 tube 46, and the ink pressure PI and air pressure PA near the ink ejection port 4 are approximately equal and balanced, and when not driven, the ink The settings are such that the meniscus is maintained. Here, the non-driving state is a state in which no recording signal is applied, and if a bias voltage is used, it is applied. If the recording characteristics deteriorate due to foreign matter 38 that has accumulated near the inner edge 33 or ink that has spread due to a collapsed meniscus, the cam 42 is rotated 180' to restore the ink meniscus to its normal shape. , and press the silicone tube 46. When the Silico 7 tube 46 is pressed down and the resistance inside the tube increases, the pressure on the air supply source 3 side becomes high and the pressure on the air chamber 9 side becomes low, creating a pressure difference. Since the pressure on the air supply source 3 side passes into the ink reservoir 11 and pushes the ink, the ink pressure PI increases as shown in FIG. 2, and the pressure on the air chamber 9 side passes into the vicinity of the ink discharge port 4. Therefore, the air pressure PA becomes lower,
By making the difference larger than the holding force due to the surface tension of the ink meniscus, the ink flows out as shown in FIG. The holding cam PB due to surface tension is attached to the ink ejection port 4.
If the 0 radius is r, then multiply by T 8PB=-CDSQ. However, ΔPB is a pressure unit, T is the surface tension of the liquid, and θ is the contact angle between the liquid and the ink ejection port 4. Here, r-25μm, θ=O
, consider the case when T = 40 dyn 7cm, 8P.
B# 0.033 kg/ca, so if a pressure difference greater than this is created, the ink will flow out. In a steady state where the ink pressure PI and air pressure PA are balanced, if a signal is applied to eject the ink, the diameter of the ejected ink is as narrow as approximately 1011 m and the flow rate is small, but the pressure difference causes the ink to flow out. In this case, the flow rate can be increased by increasing the pressure difference, so the flow rate can be increased to such an extent that the diameter of the jetted ink approaches the diameter of the ink ejection port 4. Therefore, if a large pressure difference is generated to cause a large amount of ink to flow out, the foreign matter 38 that has accumulated on the inner edge 33 and the ink that has spread due to the collapse of the meniscus will be attracted by viscosity, and the ink will flow along the ink flow. can be removed to the outside of the head. After maintaining the pressure difference for a certain period of time to completely remove the foreign matter 38, the cam 42 is rotated 1806 times and the presser bar 46 is retracted to return to a steady state in which the silicone tube 46 is not pressed. is removed, it is possible to restore the normal meniscus shape. The pressure difference may be generated periodically as necessary when the recording characteristics deteriorate or to maintain good recording characteristics.

According to this embodiment, by creating a pressure difference and causing ink to flow out, the inner edge 3, which is the cause of the collapse of the meniscus,
Since the foreign matter 38 accumulated in the vicinity of 3 can be removed and the meniscus can be restored to its normal shape, the recording characteristics that have deteriorated by 100 degrees can be restored to their original good condition, which is highly effective.

Effects of the Invention As described above, the present invention can restore the meniscus to its normal shape, so that recording characteristics that have deteriorated to a certain degree can be restored to their original good state.

Further, by periodically returning the meniscus to its normal shape, good recording characteristics can be maintained for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an inkjet recording apparatus according to an embodiment of the present invention, FIG. 2 is a pressure graph for explaining the operation of the embodiment of FIG. 1, and FIG. 3 is an operation of the embodiment of FIG. 1. FIG. 4 is a schematic diagram of a conventional inkjet recording apparatus, and FIGS. 6 and 6 are partially enlarged sectional views of the inkjet recording apparatus shown in FIG. be. 1...Air discharge port, 2...Air nozzle plate, 4...
Ink discharge port, 6... Signal source, 6... Ink supply path, 8... Air supply path, 9... Air chamber, 10... Ink chamber, 11... Ink reservoir, 12. 15... Electrode, 14... Ink nozzle plate, 17... Convex portion, 1B
, 19... Water- and oil-repellent coating film, 33... Inner edge, 34...
...front end surface, 36..outer surface, 37..periphery, 38..
・Foreign object, 40...Pulse motor, 41-°° drive circuit, 42...Cam, 43°°・Spring, 44...Guide, 46...Press bar, 46...Silicon tube.

Claims (4)

[Claims] (1) An air outlet that allows air to flow out, an ink outlet that is arranged opposite to the air outlet, and an electrostatic force that applies an electrostatic force that stretches the ink held within the ink outlet in the direction of the air outlet. means for supplying an air flow to flow out from the air discharge port, and a pressure of the air flow is smaller than the ink pressure at the ink discharge port, and the pressure difference with the ink pressure is equal to the surface tension of the ink meniscus. An inkjet recording apparatus characterized by comprising a pressure adjustment means for adjusting a first pressure greater than a holding force of the ink and a second pressure substantially equal to an ink pressure. (2) The inkjet recording apparatus according to claim 1, wherein the ink discharge orifice forming portion of the ink nozzle plate in which the ink discharge orifices are formed has a convex portion projecting in the direction of the air discharge orifices. (3) Water-repellent on the inner wall surface of the air nozzle plate that forms the air discharge port and its surrounding surface, as well as the surface of the ink nozzle plate that forms the ink discharge port on the side facing the air nozzle plate around the ink discharge port. The inkjet recording device according to claim 1, wherein an oil-repellent coating film is formed. (4) The pressure adjustment means includes a tube made of an elastic member forming a part of the air supply path, a rod-shaped member that presses the side surface of the tube, and a state in which the rod-shaped member presses the side surface of the tube and a state in which it does not press the tube. 2. The inkjet recording apparatus according to claim 1, further comprising means for switching.