JPH07299906A - Ink jet head - Google Patents

Abstract

PURPOSE:To realize an ink jet head capable of performing good printing generating no white stripe between lines causing the deterioration of printing quality without bringing about the increase of a printing time caused by the shift of paper feed quantity or the increase in the printing number of times due to the reduction of a paper feed pitch. CONSTITUTION:When printing is performed by an ink jet head wherein a second ink chamber adapted to the emission of ink droplets high in wt. is provided to at least one end of an ink chamber row having a large number of ink chambers arranged thereto, the second ink chamber is adapted in order to print the upper and lower end dots 10, 11 of the printing corresponding to one line and, therefore, the dots 10, 11 are larger than usual dots 12 in diameter. As a result, the connection parts B1 of lines become easy to overlap each other and a white stripe can be made hard to generate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an inkjet recording apparatus such as a printer that forms an ink image on a medium such as recording paper, and more specifically to an inkjet head.

[0002]

2. Description of the Related Art A plurality of ink chambers having nozzles are provided,
In an ink jet head of a type that ejects ink droplets from nozzles by increasing the pressure of the ink chamber by a pressure generating member composed of a piezoelectric element, if the ink chamber ejects the same color, ink is used to improve the printing quality than before. It is required that the drop weight be uniform.

However, in recent years, there is an increasing demand not only for printing a character having a size that fits within the width of the ink chamber array (text printing), but also for printing a scalable font or graphic (graphic printing). .

FIG. 10 is an example showing an ideal array of printed dots. One line is composed of 8 dots, and the dot pitch, that is, the interval between dots is A1. In the case of printing that does not fit in one line, it is assumed that the line is divided into several lines in advance, and after printing one line, the dot pitch of the connecting portion, that is, the upper end dot 10 is changed to the lower end dot 11.
One image is printed by performing paper feeding at the paper feeding pitch L1 so that the interval is B1 below and printing repeatedly. However, in the conventional case, the dot pitch A1 and the dot pitch B1 of the connecting portion are set to be equal.

Regarding the printing quality such as graphic printing, not only the ejection performance such as the variation of the ink droplet weight and the ejection bending of the nozzles of the ink jet head but also the improvement of the feeding accuracy so as to reduce the unevenness in feeding the printing paper, It is necessary to improve the mounting position accuracy such as the mounting angle of the inkjet head. However, there is a limit to the paper feed accuracy only by improving the accuracy of the paper feed gear, etc.,
Further, even when the mounting position adjustment in consideration of the assembly size variation of the head cannot be performed with sufficient accuracy, the dot pitch B1 at the connecting portion is likely to vary, and white streak-like unevenness is generated between the first line and the second line. It was a problem that it occurred. Therefore, in Japanese Patent Publication No. 1-235054 as shown in FIG. 11, the dot pitch B2 at the connecting portion is made smaller than the dot pitch A1, and the paper feed pitch L2 is set to the regular paper feed so that white lines are not generated between the lines. It was changed to be smaller than the pitch L1.

[0006]

However, since this is smaller than the regular paper feed pitch L1, the difference in the paper feed amount accumulates when the paper feed is repeated, and the paper is misaligned with the one printed by the regular paper feed. Occurs. Further, since the number of times of printing must be increased, there is a problem that the time required for printing is increased.

According to the present invention, by increasing the weight of ink droplets ejected from the ink chambers at the ends of the ink chamber row and increasing the diameter of the dots to be printed, white lines between lines which cause deterioration of print quality occur. It is to realize an inkjet head that can perform good printing.

[0008]

According to an ink jet head of the present invention, a plurality of first nozzles having an ink discharge amount W1 are arranged on one substrate in one or more rows, and the ink discharge amount W2 is provided at least at one end of the first nozzle row. A second nozzle having a relation of> W1 is arranged.

Further, the opening diameter of the second nozzle is larger than the opening diameter of the first nozzle.

Furthermore, a first ink chamber, which is a flow path for ink near the first nozzle, and a second ink flow path, which is a flow path for ink near the second nozzle, have a larger volume than the first ink chamber.
And an ink chamber.

Further, in an ink jet head having a first pressure generating member provided on the wall surface of the first ink chamber and pressurizing the first ink chamber, pressure is generated from the first pressure generating member on the wall surface of the second ink chamber. Large second
It is characterized by having a pressure generating member.

Further, in an ink jet head having a vibrating plate provided in the first ink chamber and transmitting a displacement pressure generated by the first pressure generating member, the vibrating plate having a rigidity smaller than that of the vibrating plate is used. It is characterized by having two ink chambers.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1 for the structure and operation of an inkjet recording apparatus, and an outline of the inkjet head 1 with reference to FIG.

The ink jet head 1 slides in the print digit direction along the guide shaft 13 and prints on the print paper 15 sent by the platen 14. At the time of cleaning, the cap 16 is brought into close contact with the nozzle forming substrate 2 of the inkjet head 1, and the ink is filled in the ink chamber 8 by suction from the nozzle 3 by the suction pump 17. After this, the unnecessary ink adhering to the nozzle forming substrate 2 is wiped off by the cleaner 18.

The ink filled in the plurality of ink chambers 8 arranged in rows is formed by the nozzles 3 formed on the nozzle base 2.
Therefore, the pressure generating member 9 pressurizes the ink chamber 8 to eject the ink. More specifically, the displacement of the pressure generating member 9 is transmitted to the vibrating plate 5 by the pulse voltage, and the thin thin film portion 6 of the vibrating plate 5 is deformed to bend in the ink chamber 8 and the volume eliminated by this bending. Ink can be ejected by the increase in the pressure of the ink chamber 8 accompanying the above.

The target value of the weight of the ejected ink droplet is determined in advance by the dot diameter required for printing,
The actual weight of the ink droplets ejected by the inkjet head 1 is slightly changed depending on the excluded volume of the ink in the ink chamber 8 due to the deflection of the vibrating plate 5 and the pressure increase value. Therefore, it is necessary to optimize design dimensions such as the opening diameter of the nozzle 3, the shape of the ink chamber 8, the shape of the vibration plate 5, the displacement pressure of the pressure generating member 9.

FIG. 3 is a sectional view of the ink jet head 1 according to the first embodiment of the present invention. The second ink chamber 8b is arranged at both ends of the first ink chamber 8a row, and the weight of the ejected ink droplet 7 is larger than that of the first ink chamber 8a.

FIG. 9 shows a schematic diagram of dots printed by using the ink jet head 1. The interval dot pitch of the printed dots is A1. Since the upper end dot 10 and the lower end dot 11 for printing one line are printed in the second ink chamber 8b, the diameter of the printed dot is larger than the printed normal dot 12 in the other first ink chamber 8a. . For this reason, even when the first line is printed, the paper is fed at the paper feed pitch L1, and the second line is printed, the line-to-line connecting portion is likely to overlap and white streaks are less likely to occur. When the normal dots 12 to be printed in the first ink chamber 8a are about 100 μm, the diameter of the printed dots in the second ink chamber 8b is 120 to 140.
If about μm is appropriate, white streaks are unlikely to occur and the print density does not become particularly high. In other words, even if the print paper is unevenly fed, or if the mounting position adjustment that takes into account variations in the head assembly dimensions cannot be performed with sufficient accuracy, white streaks between lines can be the cause of poor print quality. Good printing that does not occur is possible.

Further, since the paper is fed at the regular paper feeding pitch L1, there is no deviation even if the paper feeding is repeated. Further, since it is not necessary to increase the number of times of printing, there is no problem that the time required for printing increases.

In FIG. 9, the case where the second ink chamber 8b is arranged at both ends of the first ink chamber 8a row has been described, but in the case of an ink jet head in which the second ink chamber 8b is arranged at one end instead of both ends. Similarly, the dots in the connecting portions of the lines are likely to overlap with each other, and white streaks can be less likely to occur. Further, the ejection of ink by the end nozzles of the nozzle row can be selectively used depending on the print mode. That is, if the second ink chamber 8b is also used for printing in graphic printing for printing between lines and is not used for text printing, the second ink chamber 8b
It is not necessary to worry that dots with a large diameter for printing will adversely affect printing.

FIG. 4 is a sectional view of an ink jet head according to a second embodiment of the present invention. The opening diameter of the second nozzle 3b is designed to be larger than the opening diameter of the first nozzle 3a. Therefore, even if the displacement volume due to the displacement of the vibration plate 5 is about the same, the ejection efficiency of the ink is increased, and thus it is possible to eject a larger amount of the ink droplet than the first nozzle 3a. The first nozzle 3 in which a plurality of the second nozzles 3b are arranged
By arranging at the end of the a row, the upper end dot 10 and the lower end dot 11 of the print for one line become large, and white streaks hardly occur at the connecting portion between the lines.

FIG. 5 is a sectional view of an ink jet head according to a third embodiment of the present invention. The second ink chamber 8b is designed to be large in the width direction and the volume thereof is designed to be larger than the volume of the first ink chamber 8a. That is, the width of the diaphragm 5 is large,
Even if the displacement pressure of the pressure generating member 9 is about the same, the vibration plate 5
The amount of deflection is large. Therefore, the excluded volume of the vibration plate 5 of the second ink chamber 8b is large, and the weight of the ejected ink droplet is larger than that of the first nozzle 3a. By arranging the second nozzles 3b at the end of the array of the plurality of first nozzles 3a, the upper dot 10 and the lower dot 11 for printing one line become large, and white lines are less likely to occur in the connecting portion between the lines. Become.

FIG. 6 is a sectional view of an ink jet head according to a fourth embodiment of the present invention. The second pressure generating member 9b that pressurizes the second ink chamber 8b and the first pressure generating member 9a that pressurizes the first ink chamber 8a are also large, that is, the displacement pressure is designed to be large. Therefore, the excluded volume of the vibration plate 5 of the second ink chamber 8b is large, and the weight of the ejected ink droplet is larger than that of the first nozzle 3a. By arranging the second nozzles 3b at the end of the first nozzle row in which a plurality of second nozzles 3b are arranged, the upper end dot 10 and the lower end dot 11 of the print for one line become large, and white lines are less likely to occur at the connecting portion between the lines. .

FIG. 7 is a sectional view of an ink jet head according to a fifth embodiment of the present invention. The thickness of the second thin film portion 6b of the diaphragm 5 which is the wall surface of the second ink chamber 8b is designed to be thinner than the first thin portion 6a of the diaphragm 5 which is the wall surface of the first ink chamber 8a. For this reason, the second thin film portion 6b has a small rigidity and is easily bent, so that the displacement amount is large. Therefore the second
The displacement volume of the vibrating plate 5 in the ink chamber 8b is large, and the weight of the ejected ink droplet is larger than that of the first nozzle 3a. By arranging the second nozzles 3b at the end of the first nozzle row in which a plurality of second nozzles 3b are arranged, the upper end dot 10 and the lower end dot 11 of the print for one line become large, and white lines are less likely to occur at the connecting portion between the lines. .

FIG. 8 is a diagram showing the cleaning operation of the ink jet head 1 according to the sixth embodiment of the present invention. More specifically, the drawing shows a color ink jet head having a plurality of rows in which a plurality of nozzles 3 are arranged on a nozzle forming substrate 2, and these rows are capable of ejecting inks of different colors from the front side. is there. At the time of cleaning, since the cap 16 is brought into close contact with the nozzle forming base 2 to suck the ink, ink of different colors (mixed color ink 19) is attached to the surface of the nozzle forming base 2.
After this, the mixed color ink 19 is scraped off by the cleaner 18, but since the cleaner 18 is a soft material such as a rubber member, it bends in an arc shape in the traveling direction of the cleaner 18. Therefore, the mixed color ink 19 is cleaner 1
8 is scraped off in the direction of the arrow 20, that is, in the end direction of the nozzle row, but the closer the nozzle is to the end of the nozzle row, the more the mixed color ink 19 penetrates into the nozzle 3.
When the mixed color ink 19 enters the nozzle 3, the mixed color ink 19 is discharged by performing idle discharge after the cleaner 18 is wiped off. However, compared to the nozzles near the center, the nozzles near the edges are mixed with ink 19
Therefore, when the same number of blank discharges are performed, the ink is excessively discharged from the nozzle near the center before the mixed color ink 19 is discharged from the nozzle near the end.
In addition, increasing the number of idle discharges of the nozzles near the edge leads to an increase in cleaning time.

According to the embodiment of the present invention, it is possible to increase the weight of the ink droplets ejected from the end nozzles of the nozzle row, so that the mixed color ink 19 can be discharged in a short idle ejection time without discharging the ink more than necessary. Can be discharged. Therefore, it is particularly effective for a color inkjet in which nozzle rows are arranged so as to eject a plurality of colors on the same plane.

[0027]

The ink jet head 1 of the present invention is the first
It is characterized in that a second ink chamber 8b, which has a larger ink ejection amount than the first ink chamber 8a, is provided at the end of the row of ink chambers 8a. Therefore, even if the paper feed is uneven or the head mounting position is adjusted,
Since dots having a large diameter ejected from the second ink chamber 8b are printed, there is an effect that white lines are unlikely to occur. Further, since it is not necessary to reduce the paper feed pitch, it is possible to eliminate the problem that the paper feed does not shift and the time required for printing increases due to the increase in the number of times of printing.

Further, in a color ink jet in which nozzle rows are arranged so as to eject a plurality of colors on the same plane, when the Kunina operation after ink suction is performed, a large amount of mixed color ink 19 is mixed into the end nozzles of the nozzle rows. Therefore, more idle discharge is required, but the second line at the end of the nozzle row
Since the weight of the ink droplet ejected from the nozzle 3b is large, the mixed color ink 19 can be ejected in a short idle ejection time without ejecting the ink more than necessary.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inkjet recording apparatus.

FIG. 2 is a schematic diagram of an inkjet head.

FIG. 3 is a sectional view of an inkjet head according to a first embodiment of the present invention.

FIG. 4 is a sectional view of an inkjet head according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of an inkjet head according to a third embodiment of the present invention.

FIG. 6 is a sectional view of an inkjet head according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of an inkjet head according to a fifth embodiment of the present invention.

FIG. 8 is an operation diagram of cleaning an inkjet head according to a sixth embodiment of the present invention.

FIG. 9 is a schematic diagram of dots printed by the inkjet head according to the first embodiment of the present invention.

FIG. 10 is a schematic diagram of dots printed by an inkjet head according to an example of the prior art.

FIG. 11 is a schematic diagram of dots printed by an inkjet head according to an example of Japanese Patent Publication No. 1-235054 which is a conventional technique.

[Explanation of symbols]

 10 ... Top dot 11 ... Bottom dot 12 ... Normal dot L1 ... Paper feed pitch A1 ... Dot pitch B ... Dot pitch of connected part

Claims (5)

[Claims] 1. A plurality of first nozzles having an ink discharge amount W1 are arranged in one or more rows on the same substrate, and a second nozzle having a relationship of ink discharge amount W2> W1 is arranged at least at one end of the first nozzle row. An inkjet head characterized by the above. 2. From the opening diameter of the first nozzle, the second nozzle
The inkjet head according to claim 1, wherein the opening diameter of the nozzle is large. 3. A first ink chamber that is a flow path of ink near the first nozzle, and a second ink chamber that is a flow path of ink near the second nozzle and has a larger volume than the first ink chamber. The inkjet head according to claim 1, further comprising: 4. An ink jet head having a first pressure generating member provided on a wall surface of the first ink chamber and pressurizing the first ink chamber, wherein pressure is generated by the first pressure generating member on the wall surface of the second ink chamber. The inkjet head according to claim 1, further comprising a second pressure generating member having a large amount. 5. An inkjet head having a vibration plate provided in the first ink chamber and transmitting a displacement pressure generated by the first pressure generating member, wherein the vibration plate has a rigidity smaller than that of the vibration plate. The ink jet head according to claim 1, wherein two ink chambers are provided.