JPH05201004A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To eliminate problems relating to a high-accuracy assembly near an air feed system or an air delivery port and ink delivery port and achieve reduction in costs. CONSTITUTION:A concave portion 203 which is symmetrical with respect to its center axis is formed on a thin plate 202 made of insulating material and an ink delivery port 204 symmetrical with respect to its center axis is formed on the central bottom of the portion 203. A first electrode 206 having hole diameter smaller than the hole diameter of the concave portion 203 is formed around said portion on the surface of the plate 202, while a second electrode 207 is formed around the port 204 on the rear surface of the plate 202, and each of the electrodes is connected to a signal source 211. The ink delivery port 204 is connected to an ink tank 209 through an ink chamber 205 and an ink feed pipe 208.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for ejecting ink from minute openings to record characters, figures and the like on an object to be recorded.

[0002]

2. Description of the Related Art Conventionally, as an ink jet recording apparatus for ejecting ink from a minute opening by utilizing an air flow and an electrostatic force, for example, JP-A-57-120452 and JP-A-59-146860 are known. A configuration as described in the publication is known.

A conventional ink jet recording apparatus will be described below with reference to FIG. In FIG. 6, an air nozzle plate 102 made of an insulating material is attached to the tip surface of the outer wall of the body member 101, and an ink nozzle plate 103 made of an insulating material is attached to the tip surface of the inner wall. An air chamber 104 is formed between the outer wall and the inner wall of the body member 101, and the air nozzle plate 102 and the ink nozzle plate 103 are formed.
An air flow path 105 communicating with the air chamber 104 is formed between them. In addition, inside the ink nozzle 103,
The ink chamber 106 is formed. Ink nozzle plate 10
An ink ejection port 107 is formed in the center of the nozzle 3, and an air ejection port 108 is formed in the air nozzle plate 102 so as to face the ink ejection port 107. Air nozzle plate 102
On the surface of the first electrode 10 around the air outlet 108.
9 is formed, and the second electrode 114 is formed on the back surface of the ink nozzle plate 103 around the ink ejection port 107. The air chamber 104 is connected to an air supply source 112 by an air supply pipe 110, and the ink chamber 106 is connected to an ink supply source 113 by an ink supply pipe 111. The first electrode 109 and the second electrode 114 are connected to the signal source 11
Connected to 5.

Next, the operation of the above conventional example will be described. The air from the air supply source 112 is sent to the air chamber 104 and flows into the air flow path 105 as an air layer at a constant flow velocity while causing a sharp bend, and this air is discharged from the air discharge port 10.
8 and the ink ejection port 107, while flowing out from the air ejection port 108 while making a sharp bend. On the other hand, ink is supplied to the ink chamber 106 from the ink supply source 113, and a constant pressure is applied to the ink in the ink supply source 113 and the ink chamber 106 by the air pressure sent from the air supply source 112. ing. As a result, when the ink jet recording apparatus is not recording, the air pressure near the ink ejection port 107 generated by the air flow and the ink ejection port 1
The ink pressures in 07 are almost equal, and the ink ejection port 107
The meniscus of the ink that occurs on the surface is kept stationary.
Then, when a potential difference is generated by the voltage applied from the signal source 115 to the first electrode 109 and the second electrode 114, the meniscus of the ink generated in the ink ejection port 107 due to the electrostatic force due to this potential difference causes the air ejection port 108. Is stretched in the direction of. In the air flow path 105 from the ink ejection port 107 to the air ejection port 108, a rapid change in the pressure gradient is caused by the air flow, so the ink ejection port 1
The ink meniscus 07 is rapidly accelerated when it is stretched for a certain length or more, and is ejected from the air ejection port 108.

[0005]

An ink jet recording apparatus utilizing such an air flow and electrostatic force is driven at a relatively low voltage (500 V or less) in spite of using electrostatic force, and has a responsiveness. It is excellent (10 to 20 kHz) and capable of forming fine dots (20 to 30 μm φ) and is extremely excellent in recording characteristics.

However, there are some problems other than the recording characteristics. First of all, the air supply source 112,
The point is that an air supply system including the air supply pipe 110 is required. Due to the existence of such an air supply system, the cost is surely increased accordingly. further,
Air supply system reliability problems occur. That is, the problem of dust existing in the supply air, the problem of constant air pressure, etc. correspond to this. To accommodate these,
A method of using a filter or detecting air pressure and applying electrical feedback is used,
As a result, the device becomes more complicated and the cost is further increased.

Secondly, there is a problem in the construction method that the distance between the air flow paths 105 must be kept constant. Especially in the case of a multi-nozzle, the space between the air flow paths 105 is 100 μm.
Weakness, good parallelism, and variation between nozzles must be within a few μm. In addition, this interval is equal to
The air pressure in the vicinity of the ink ejection port 107 increases as the distance increases, as the air pressure in the vicinity of 07 increases.
The ink meniscus formed at the ink ejection port 107 approaches the pressure in 6 and is not held in a shape that is pushed out to the air ejection port 108 side, and the ink ejection amount and responsiveness decrease. On the other hand, if this interval becomes narrow, both the ink ejection amount and the responsiveness increase, but the ejection becomes unstable. Therefore, it is necessary to maintain an optimum air flow path interval that can balance these.

The present invention solves the problems caused by the existence of the air supply system in the conventional ink jet recording apparatus, and provides a low cost ink jet recording apparatus having a simple structure and easy assembly. The purpose is to

[0009]

In order to solve the above problems, the present invention eliminates the air supply system, forms a concave portion on the front surface side of the thin plate, and penetrates the back surface side of the thin plate at the center bottom thereof. An ink ejection port is formed, and a first electrode whose inner edge projects toward the center of the concave portion is provided around the concave portion, and a second electrode is provided around the ink ejection port to connect both electrodes to a signal source. The ink discharge port is communicated with the ink tank via the ink chamber and the ink supply pipe.

[0010]

According to the present invention, with the above-described structure, a signal voltage is applied between the concave portions on the front and back of the thin plate and both electrodes provided around the ink ejection port, whereby the ink is extended from the ink ejection port to form a thin plate. The ink can be ejected to the outside through the concave portion, and at the same time, highly accurate assembly is not required, and the cost of the inkjet recording apparatus can be reduced.

[0011]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic partial sectional view of an ink jet recording apparatus according to an embodiment of the present invention. In FIG. 1, 201 is a body member and 202 is a thin plate, both made of an insulating member. On the surface side of the thin plate 202, a central axis symmetric shape, in this embodiment, a circular concave portion 203.
An ink ejection port 204 having a central axis symmetrical shape, which is a circular shape penetrating the back surface, which is circular in this embodiment, is formed coaxially with the concave portion 203 at the center bottom portion thereof. Ink ejection port 20
4 communicates with an ink chamber 205 formed by a body member 201 and a thin plate 202. A first electrode 206 having a hole diameter smaller than the hole diameter is formed around the concave portion 203 on the front surface of the thin plate 202, and on the back surface of the thin plate 202 around the ink ejection port 204, the hole diameter is smaller than the hole diameter. A second electrode 207 having a large hole diameter is formed, and each is connected to the signal source 211. Ink ejection port 204
Are connected to an ink tank 209 via an ink supply pipe 208 connected to the ink chamber 205. An air vent hole 210 is formed in the upper part of the ink tank 209. The recording paper 2 is relatively close to the front of the thin plate 202.
Twelve are arranged. The diameter of the ink ejection port 204 is set to several tens of μm, and the diameter of the concave portion 203 is set to be slightly larger than that of the ink ejection port 4.

Next, the operation of the above embodiment will be described. From the signal source 211 to the first and second electrodes 206, 2
When a signal voltage is applied to 07, an electrostatic force acts on the ink meniscus formed in the ink ejection port 204, and the inner edge of the first electrode 206 protruding toward the center of the concave portion 203 has a central axis symmetric shape. The ink is ejected on the central axis of the ink ejection port 204 toward the first electrode 206 and flies from the hole of the first electrode 206. The flying ink is the recording paper 2
Attached to 12 and recorded. When the recording paper 212 is too far away from the thin plate 202, the ink flying from the hole of the first electrode 206 is attracted to the first electrode 206 again and returns.
It adheres to the thin plate 202 and the first electrode 206. Therefore, the distance between the recording paper 212 and the first electrode 206 needs to be narrow enough to prevent the ink from returning. Other factors that affect the recording characteristics are the shape and hole diameter of the ink ejection port 204, the shape of the concave portion 203, the hole diameter and depth, and the thin plate 20.
The dielectric constant of 2, the hole diameter of the first electrode 206, the physical properties of the ink, and the like are included, and these conditions are optimized according to the purpose of use of the apparatus.

The inner edge of the first electrode 206 projects toward the center of the concave portion 203 because the electrode is provided with a projecting portion to strengthen the electric field, and the electrostatic attraction action of ink is generated by the first electrode 206 and the ink. This is to make the meniscus dominant. This means that the hole diameter of the concave portion 203 depends on the first electrode 20.
6 and the hole diameter of the ink discharge port 204, if ink, dust, or the like adheres to the wall surface of the concave portion 206, or if burrs or the like are present on the side surface of the concave portion during head production, these Even if the electric field distribution in the concave portion changes due to the influence of, the electrostatic attraction direction on the ink meniscus can be stabilized on the central axis. Therefore, the hole diameter of the ink ejection port 204 is several tens of μm, the hole diameter of the first electrode 206 is about 1 to 10 times that of the ink ejection port 204, and the hole diameter of the concave portion 203 is 1 to 20 of the ink ejection port 204. About double. The difference in hole diameter between the first electrode 206 and the ink ejection port 204 is preferably as small as possible, but the stability of ink ejection is reduced by the thin plate 20.
Since it is also related to the thickness and dielectric constant of 2, the optimum hole diameter is set according to the system. Further, the hole diameter of the concave portion 206 is preferably as large as possible, but the hole diameter is optimally set in consideration of the mounting density when the multi-nozzle is used.

FIG. 2 shows the first electrode 206 and the concave portion 203.
An example of dimension setting of the hole diameter is shown. That is, from the center axis of the ink ejection port 204 and the center of the front end thereof, the first electrode 2
Assuming that the angle formed by the inner edge of 06 is θ ₁ and the angle formed by the inner edge of the first electrode and the front end corner of the concave portion 203 with respect to the center of the front end of the ink ejection port 204 is θ ₂ , as shown in FIG. , The response frequency has a small peak below θ ₂ / θ ₁ = 1 and the ejection stability (the deviation in the ink ejection direction is ± 5 °
The probability of falling within θ ₂ / θ ₁ = 1 is sharply decreased from around 1, and as shown in FIG. 4, the probability that ink will collide with the first electrode 206 is θ ₁ = 15 ° or less. Since it rapidly increases, θ ₁ and θ ₂ are preferably in the following ranges. 0 <θ ₂ / θ ₁ ≦ 1 and θ ₁ ≧ 15 °

FIG. 5 shows the essential parts of another embodiment of the present invention.
An ink-repellent coating film 213 for repelling ink is formed on the surfaces of the recesses 203 and the first electrode 206 so as to prevent excess ink from adhering as much as possible. However, when the material of the thin plate 202 already has ink repellency such as Teflon, such a coating film 213 becomes unnecessary.

Regarding the recording characteristics of the ink jet recording apparatus according to the above embodiment, the responsiveness and the driving voltage are slightly disadvantageous as compared with the conventional example shown in FIG. 6, but due to the simplification of the structure, cost and assembly are improved. This is extremely advantageous in the construction method.

[0017]

As described above, according to the present invention, the air supply system is eliminated, the concave portion is formed on the front surface side of the thin plate, and the ink discharge port penetrating to the rear surface side of the thin plate is formed at the central bottom portion thereof. A first electrode whose inner edge protrudes toward the center of the concave portion is provided around the concave portion, and a second electrode is provided around the ink ejection port to connect both electrodes to a signal source, and the ink ejection port is connected to the ink source. Since it is connected to the ink tank through the chamber and the ink supply pipe, it is possible to realize an electrostatic suction type inkjet recording device having a simple structure and excellent advantages in terms of cost, assembly method and reliability. The effect is extremely large.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional schematic configuration diagram of an inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a thin plate according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram for setting dimensions in an embodiment of the present invention.

FIG. 4 is a characteristic diagram for setting dimensions in an embodiment of the present invention.

FIG. 5 is a partially enlarged sectional view of another embodiment of the present invention.

FIG. 6 is a partial cross-sectional schematic configuration diagram showing an example of a conventional inkjet recording apparatus.

[Explanation of symbols]

 201 body member 202 thin plate 203 concave portion 204 ink ejection port 205 ink chamber 206 first electrode 207 second electrode 208 ink supply tube 209 ink tank 210 air vent hole 211 signal source 212 recording paper 213 ink repellent coating film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor and Shuko Matsu Matsushita Giken Co., Ltd. 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture

Claims (1)

[Claims] 1. A concave portion formed on the front surface side of a thin plate made of an insulating material, an ink discharge port formed through the back surface side in the central portion of the bottom of the concave portion, and the concave portion on the surface of the thin plate. A first electrode formed on the periphery of the thin plate and having an inner edge protruding toward the center of the concave portion; a second electrode formed on the back surface of the thin plate around the ink ejection port; and the first and second electrodes.
An ink jet recording apparatus comprising: a signal source connected to the electrode, an ink chamber communicating with the ink ejection port, and an ink tank communicating with the ink chamber via an ink supply pipe.