JP2003072067A - Ink jet printing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter of an ink jet printing head which has superior filtration performance, can fully exert ink jet characteristics and has high reliability. SOLUTION: The filter is constituted of a part which includes two plates formed of the same material as a material of a member for forming channels and arranged so that mutual holes are prevented from overlapping in an ink flow direction, and a plate equipped with opening parts corresponding to each group of the holes and held between the two plates. A thickness of the held plate is made equal to a size desired to be filtered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head used in an ink jet recording apparatus, and more particularly to an ink jet print head for removing foreign matter mixed in from ink to be supplied and a supply path.

[0002]

2. Description of the Related Art Nozzles and foreign matter mixed from an ink supply path to an ink jet print head clog the nozzles, causing a problem that ink is not ejected. The nozzle diameter of the inkjet print head is φ50.
It is around μm, and recently high-definition image quality is required,
Furthermore, the required nozzle diameter is becoming smaller, and the above-mentioned problems are more likely to occur.

For this reason, in order to remove foreign substances, a filter has been provided between the ink reservoir (tank) for supplying ink and the inkjet print head, and many holes smaller than the foreign substances have been formed in the inkjet print head. It was equipped with a filter to prevent its failure.

In the case of a filter provided in the ink supply path to the ink jet print head, if the filter is clogged, only that portion needs to be replaced, but at the time of maintenance replacement of the ink jet print head, When a foreign substance is mixed in from the ink supply path connecting portion, there is a risk of causing a secondary failure of replacing the entire inkjet print head. Therefore, when replacing the inkjet print head, special tools are used, and measures such as careless avoidance of foreign matter are taken as a work only by a trained maintenance worker, but the convenience of maintenance is impaired.

Further, the filter provided in the ink jet print head is manufactured by Ni plating called electroforming because of the small size of the hole.

In this method, 1. It is necessary to manufacture the mold according to the size of the foreign matter to be filtered. 2. Since the hole diameter is determined by the shape of the mold and the plating thickness, it is important to control the plating solution. 3. When foreign matter of the plating solution adheres to the plating layer, it becomes a nucleus and is abnormally generated, and a desired hole diameter or shape cannot be obtained. This is because electrolysis concentrates on the nuclei, and the plating production rate becomes higher than that in other places.

Due to the above-mentioned problems in manufacturing, not only the management and working conditions of the plating solution but also the steps such as 100% inspection and selection are unavoidable. Therefore, the parts were expensive.

In electroformed products, the hole diameter is determined by the plating thickness. Therefore, the parts are very thin and difficult to handle. Further, since it becomes easier to bend by making a hole, an opening ratio (hole area / total area) of about 10% is appropriate. Since this opening ratio is inversely proportional to the flow path resistance when the ink passes, the ink ejection ratio (ink amount per unit time) cannot be increased, and the ejection performance is limited. In other words, due to the large flow path resistance, the ink supply amount is insufficient and steady ejection cannot be maintained, the appropriate amount of liquid to be ejected is insufficient, the print quality is deteriorated, and further progress causes ink ejection failure, causing serious printing defects. As a result, the performance was limited by lengthening the continuous discharge time and discharge cycle.

Ink jet print heads are made of stainless steel to prevent corrosion and deterioration of performance due to ink. The ink jet print head is usually assembled by bonding or brazing.

This agent and a curing agent are mixed and cured at room temperature. 2
Since the working time of the liquid adhesive is limited, the one-liquid adhesive is heated to 100 ° C. or higher to be cured. Even when the brazing material is used, heating is performed until the brazing material melts. In any case, since the filter and the other components are different materials, a difference in expansion coefficient occurs during heating, resulting in in-plane sagging deformation and overall warpage.

The contact angle showing the wettability with a liquid is larger in electroformed products than in stainless steel. This indicates that the wettability with the ink is poor, and even when the ink jet print head is filled with the ink, the air inside cannot be easily deaerated. Therefore, in order to improve the wettability in the flow path, the ink is devised so that it can be easily removed, but on the other hand, it is necessary to have water repellency so that the ink does not overflow from the nozzle at the time of ejection. Is extremely difficult. When adjustment with ink is not possible, the nozzle surface is subjected to a water repellent treatment to maintain the jetting performance, but the inkjet print head is therefore very expensive.

[0012]

Due to the large flow path resistance, the ink supply amount is insufficient and steady jetting cannot be maintained.
Insufficient amount of liquid to be ejected, deterioration of print quality, and further progress causes defective ink ejection, causing serious printing defects.Therefore, continuous ejection time and ejection cycle were lengthened to limit printing performance. .

The object of the present invention is to maintain the ink jetting characteristics permanently in an ink jet print head, eliminate the cause of impaired performance, make it possible to easily manufacture parts, have good assemblability and maintainability, and be inexpensive. And to provide an ink jet print head that does not deteriorate in performance due to ink.

[0014]

In order to solve the above-mentioned problems, the present invention provides a drive source, a pressure chamber provided with a vibrating plate that abuts against the drive source and is partially displaced by the power of the drive source, A nozzle for ejecting ink droplets in the pressure chamber, a restrictor for preventing backflow of ink from the pressure chamber, a plurality of individual flow paths having the restrictor are formed, and a common path through which each restrictor communicates is provided. In an ink jet print head in which the common path is laminated with thin plate-shaped members, between the two thin plates having the same material as the thin plate-shaped members and having a plurality of holes, and the two thin plates having the plurality of holes. The holding path is arranged between the common path and the plurality of restrictors so as to sandwich a holding thin plate for keeping the distance constant.

Further, the plurality of holes of the two thin plates are provided so that the holes do not overlap with each other when projected in the plate thickness direction. Furthermore, the holding thin plate has a partition. It is characterized by having.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an inkjet printhead according to the present invention.

In the ink ejection method, in FIG. 1, the power of the driving source 2 deforms the flow path wall 3 forming a part of the flow path, and the pressure in the pressure chamber 4 increases, so that the ink is ejected from the nozzle 1. . The restrictor 5 prevents the ink from flowing back from the pressure chamber 4. Ink enters the common path 6 through a connecting portion with an ink supply pipe (not shown), and the filter 7
And penetrates into individual channels.

As shown in FIG. 1, each flow path is generally formed of a plurality of thin plates and is generally made of stainless steel that can withstand the corrosion of ink. The filter 7 according to the present invention is also made of the same material. . Here, each thin plate is assembled as a laminated structure by heating or pressurizing with adhesive or a brazing material as described above. Although not described in detail, after that, the drive source 2 is assembled to form an inkjet print head. Further, the ink jet print head assembled with the brazing material has an unprecedented advantage that it can handle all kinds of ink, unlike the adhesive material.

The main causes of defective ink ejection are "the nozzle 1 is clogged with foreign matter" and "the pressure is not sufficiently generated due to the presence of bubbles in the flow path".

Since the filter 7 is provided in the ink jet print head and the stainless steel having a smaller contact angle than the electroformed Ni material is adopted, the inconvenience in maintenance is eliminated.
In addition, the wettability with ink is good, the air in the flow path can be easily removed, and because of the same kind of material, there is no deformation during heating and after cooling, and an accurate assembly can be obtained.

FIG. 2 shows a specific structure of the filter 7. The filter 7-1 and the filter 7-3 have a large number of holes 7a,
7c, and the holes 7a and 7c are arranged so as not to overlap each other in the plate thickness direction. The filter 7-2 selects a plate thickness that is substantially sandwiched between the filters 7-1 and 7-3 and is approximately equal to the size of the foreign matter to be filtered. A partition 7b is provided for each group of holes 7a, 7c. However, if the passage width of the filter 7-2 is narrow and the distance does not change, the partition wall 7b may be omitted.

As will be described later in detail, in order to satisfy the performance of the filter, it is not necessary to have a high precision for the hole diameter and shape, and it can be manufactured by inexpensive etching.

The ink passes through the holes 7a, changes its flow, and passes through the plurality of holes 7c. Two flows of ink passing through different holes 7a are shown by a solid line and a broken line.

FIG. 3 is a diagram for explaining the flow of ink passing through the filter.

FIG. 3 shows that the ink passes through the hole 7a and flows into the hole 7c near the downstream side. The hole 7
Even if the foreign matter passes through a, the foreign matter larger than the plate thickness of the filter 7-2 is prevented from passing through.

If the shape of the hole 7a or 7c is a circle that is easy to manufacture and the diameter is D = 0.3 mm, the area is A = 0.15 ² × π (mm ² ). As for the aperture ratio, the unit area is D × 2D (mm
² ), η1 = A / (D × 2D) ≈0.39.

Further, assuming that the ink in the plane direction when passing through the filter b flows radially to the downstream filter hole 7c over the entire circumference, its flow passage area B is 0.3 × π × t.
(Mm ² ) (t: plate thickness of the filter 7-2). Here, the area B is the side area of a cylinder having a height t with the area A as the bottom surface.

The minimum diameter of the foreign matter to be filtered is the nozzle diameter φ5.
When the thickness is 0 μm or less, the filter plate thickness is B = 0.3 × π × 0.045 when t = 45 μm in consideration of the error.
(Mm ² ), the aperture ratio is the same as the above unit area, and η
2 = B / (D × 2D) ≈0.24.

From this, it can be seen that the aperture ratio can be set to be sufficiently larger than the conventional aperture ratio (about 0.1) in both flow paths. Therefore, the configuration of the present invention reduces the flow path resistance due to the increased aperture ratio, and does not impair the ejection characteristics and the performance.

FIG. 4 shows a method for evaluating the filter performance. In the figure, the liquid at the head height, here, the value obtained by dividing the unit volume of pure water passing through the filter by the time, that is, the relationship between the flow rate and the head height is shown in FIG.

When the flow rate is 0.1 cc / sec, the water head height is 65 mm in the product of the present invention and 185 mm in the electroformed product, and the flow path resistance is lower in the product of the present invention. In other words, it has been proved that the flow path resistance is low, and there is no hindrance in injection characteristics and no deterioration in performance.

According to the above description, since the filtering performance of the filter is determined by the plate thickness of the filter 7-2, the mold is not required to be manufactured, and the plate thickness is simply selected. The plate thickness is manufactured by rolling, and high precision is guaranteed if the quality is normal.

[0033]

According to the present invention, it is possible to provide an inexpensive ink jet print head which can be assembled with high accuracy and can be used with any ink, has maintainability, high performance and reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inkjet printhead according to an example of the present invention.

FIG. 2 is a perspective view of the filter of the present invention.

FIG. 3 is a diagram illustrating the flow of ink passing through a filter.

FIG. 4 is a diagram illustrating a filter performance evaluation method.

FIG. 5 is a graph showing the relationship between flow rate and head height.

[Explanation of symbols]

1 is a nozzle, 2 is a drive source, 3 is a flow path wall, 4 is a pressure chamber, 5
Is a restrictor, 6 is a common flow path, and 7 is a filter.

Claims (3)

[Claims] 1. A pressure source provided with a driving source, a vibrating plate which is brought into contact with the driving source and partially displaces due to its power, a nozzle for ejecting ink droplets from the pressure chamber, and a pressure chamber from the pressure chamber. An ink jet print head in which a restrictor for preventing backflow of ink and a plurality of individual flow paths including the restrictor are formed, and a common path through which the restrictors communicate with each other is provided, and the common path is laminated by a thin plate member. The two thin plates made of the same material as the thin plate member and having a plurality of holes, and a holding thin plate for maintaining a constant distance between the thin plates are provided, and the thin plate and the holding thin plate serve as the common path. An inkjet printhead, wherein the inkjet printhead is arranged between the plurality of restrictors. 2. The ink jet print head according to claim 2, wherein the plurality of holes of the two thin plates are provided so that the holes do not overlap each other when projected in the plate thickness direction. 3. The ink jet print head according to claim 1, wherein the holding thin plate has a partition.