KR100657952B1 - Ink-jet head having array of tilted printheads - Google Patents

Abstract

An inkjet head having a printhead array for printing an image by ejecting ink droplets on a print medium is disclosed. In the disclosed inkjet head, the printhead array has a plurality of printheads inclined at a first angle β with respect to a direction orthogonal to the transport direction of the print medium, each of the plurality of printheads in the transport direction of the print medium. Inclined at a second angle α with respect to. In addition, a plurality of the printhead array may be arranged in a direction orthogonal to the transport direction of the print medium. According to the present invention, since the length of each printhead can be shorter than the conventional one, the yield is increased in the manufacturing process of the printhead.

Description

Ink-jet heads with inclined printhead arrays {Ink-jet head having array of tilted printheads}

1 is a cross-sectional view showing a general configuration of a conventional piezoelectric inkjet printhead.

2 is a view showing an example of a conventional printhead array.

3 is a view showing another example of a conventional printhead array.

FIG. 4 is an enlarged view of a portion of the printhead array shown in FIG. 3.

5 is a plan view showing a printhead array of the inkjet head according to the present invention.

FIG. 6 is a plan view illustrating an inkjet head including a plurality of printhead arrays illustrated in FIG. 5.

7A and 7B are views showing a specific embodiment of the inkjet head according to the present invention in comparison with a conventional inkjet head.

<Explanation of symbols for main parts of the drawings>

100 ... inkjet head 101 ... nozzle

110 ... printhead 120 ... frame

The present invention relates to an inkjet head used in an inkjet printer, and more particularly, to an inkjet head capable of printing a high resolution image by arranging a plurality of printheads having a low cpi in an inclined state.

In general, an inkjet printhead is a device that prints an image of a predetermined color by ejecting a small droplet of printing ink to a desired position on a recording medium. Such inkjet printheads can be classified into two types according to ink ejection methods. One is a heat-driven inkjet printhead that generates bubbles in the ink by using a heat source and discharges the ink by the expansion force of the bubbles. The other is a piezoelectric inkjet printhead. It is a piezoelectric inkjet printhead which discharges ink by an applied pressure.

The general configuration of the piezoelectric inkjet printhead described above is shown in FIG. Referring to FIG. 1, the manifold 2, the restrictor 3, the pressure chamber 4, and the nozzle 5 constituting the ink flow path are formed inside the flow path forming plate 1. The piezoelectric actuator 6 is provided in the upper part of 1). Manifold (2) is a passage for supplying the ink flowing from the ink reservoir (not shown) to each of the pressure chamber (4), the restrictor (3) is the ink flow into the pressure chamber (4) from the manifold (2) It is a passage. The pressure chamber 4 is a place where the ink to be discharged is filled, and the volume thereof is changed by driving the piezoelectric actuator 6 to generate a pressure change for ejecting or inflowing ink. The upper wall of the pressure chamber 4 serves as the diaphragm 1a deformed by the piezoelectric actuator 6.

Referring to the operation of the piezoelectric inkjet printhead described above, when the diaphragm 1a is deformed by the driving of the piezoelectric actuator 6, the volume of the pressure chamber 4 is reduced, and accordingly, in the pressure chamber 4 The ink in the pressure chamber 4 is discharged to the outside through the nozzle 5 by the pressure change. Subsequently, when the diaphragm 1a is restored to its original shape by the drive of the piezoelectric actuator 6, the volume of the pressure chamber 4 is increased, and ink is discharged from the manifold 2 by the pressure change. It enters into the pressure chamber 4 via 3.

In a conventional general inkjet printer, the printhead reciprocates in a direction orthogonal to the conveying direction of the recording medium, for example, the paper width, i. However, such a conventional inkjet printer had a disadvantage of slow printing speed.

Therefore, in recent years, an inkjet printer capable of performing printing at high speed without reciprocating movement of the print head by arranging a plurality of print heads over the entire width direction of the paper has been developed. Such inkjet printers are also called wide format printers.

2 shows an example of a conventional printhead array used in the above wide format printer.

The inkjet head shown in FIG. 2 is a direction in which a plurality of printheads 10 are orthogonal to the conveying direction (Y direction) of the paper P on the frame 20, that is, the width direction of the paper P (X direction) ) Has a structure arranged in at least two columns. A plurality of nozzles 11 are arranged in the width direction (X direction) of the paper P in each of the arranged plurality of print heads 10. At this time, the print heads 10 arranged in the first column A ₁ and the print heads 10 arranged in the second column A ₂ are arranged to be staggered with each other.

As such, using the array of printheads 10 arranged in two rows, the ink droplets and the second row A discharged from the nozzles 11 of the printhead 10 arranged in the first row A ₁ . _The ink droplets ejected from the nozzles 11 of the printhead 10 arranged in ₂ ) print an image to form one line on the paper P. FIG.

Here, the resolution of the image to be printed is greatly influenced by the number of nozzles 11 per inch. The number of nozzles 11 per inch is generally expressed in channels per inch (cpi), and the resolution of the image is generally expressed in dots per inch (dpi). By the way, in the conventional printhead 10, the improvement of cpi depends on the development of the microfabrication gas and the actuator of the semiconductor substrate, and the speed of the development of such technology is sufficient to keep up with the recent trend of demanding higher resolution images. I'm not satisfied. For example, when an image is printed using an inkjet head having a structure in which the printhead 10 of approximately 120 cpi is arranged in two rows, the resolution of the image is only 120 dpi.

Therefore, when it is desired to print a high resolution image using the low cpi printhead 10, the number of arrangement of the printheads 10 must be increased. For example, as shown in FIG. 2, when printing an image using the printhead 10 arranged in four columns A ₁ , A ₂ , A ₃ , A ₄ , the resolution of the image is printed. It will have twice the dpi of the cpi of the head 10. If a 1200 dpi image is to be printed using a print head 10 of approximately 120 cpi, the print head 10 should be arranged in 20 rows. Meanwhile, in FIG. 2, the interval C between the nozzles 11 may be calculated as 1 inch / dpi, and the interval D between dots may be calculated as 1 inch / dpi.

However, when the printheads 10 are arranged in a plurality of rows in order to increase the resolution of the image, that is, the dpi, the size of the inkjet head becomes too large. In addition, the nozzles 11 of the printheads 10 arranged in different rows must be accurately aligned. As the number of arrays of the printheads 10 increases, the alignment error between the nozzles 11 increases. There is also.

In order to prevent this problem, as shown in Figs. 3 and 4, a method of arranging the printhead inclined has been proposed.

3 and 4 together, a plurality of printheads 30 are arranged in a row in the width direction (X direction) of the paper in the frame 40 of the inkjet head, and each of the plurality of printheads 30 is It is arrange | positioned inclined at the predetermined angle (alpha) with respect to the paper feed direction (Y direction). In this case, the spacing D between the dots formed on the paper P becomes much smaller than the spacing C between the nozzles 31, so that an image of dpi much higher than the cpi of the printhead 30 is obtained. Will be able to print.

In detail, since sin (α) = D / C, D = 1 / dpi, and C = 1 / cpi, sin (α) = cpi / dpi. Therefore, since dpi = cpi / sin (α), the dpi becomes higher as the inclination angle α of the printhead 30 with respect to the paper feed direction (Y direction) becomes smaller. Since α = sin ⁻¹ (cpi / dpi), for example, when a 1200 dpi image is to be printed using the 120 cpi printhead 30, the inclination angle α of the printhead 30 is approximately 5.74 °. In the case where a 1200 dpi image is to be printed using the 60 cpi printhead 30, the inclination angle α of the printhead 30 is approximately 2.87 °.

However, when the plurality of print heads 30 are inclined as described above, the length of each of the print heads 30 is gradually longer as the inclination angle α becomes smaller. Since the width t of the printhead 30 itself is required, and a predetermined distance is also required between the printheads 30 to mount the printhead 30 to the frame 40, any one printhead ( A predetermined distance G is required between the center line of the nozzle 30 provided at 30 and the center line of the nozzle 30 provided at the printhead 30 adjacent thereto. Then, the horizontal distance between the lowermost nozzle 31 of any one printhead 30 and the uppermost nozzle 31 of the printhead 30 arranged next to it should be adjusted to the interval D between dots.

In detail, the distance between the uppermost nozzle 31 and the lowermost nozzle 31 provided in the printhead 30 is L, and the horizontal interval between the uppermost nozzle 31 and the lowermost nozzle 31 is B. . Here, B is closely related to the width t of the printhead 30 and the gap G. Then, sin (α) = B / L and L = B / sin (α). Therefore, when B is fixed constantly, the distance L between the uppermost nozzle 31 and the lowermost nozzle 31 becomes longer as the inclination angle α of the printhead 30 with respect to the paper feed direction (Y direction) becomes smaller. Will be. Here, the printhead 30 includes a free space above the uppermost nozzle 31 and below the lowermost nozzle 31, and thus has a length longer than L.

As described above, when the length of each of the print heads 30 becomes long, the following problem occurs. As the length of each of the print heads 30 becomes longer, the defective rate increases during the manufacturing process, and thus the yield decreases, thereby increasing the manufacturing cost. In addition, the risk of damage in the handling process of the print head 30 also increases. In addition, since the number of the nozzles 31 provided in each of the print heads 30 increases, a deviation occurs easily in the pressure of the ink supplied to each nozzle 31, and thus a problem of deterioration of ink ejection performance is caused. Will occur.

The present invention was created to solve the above problems of the prior art, and in particular, by arranging a plurality of print heads inclined not only in the conveying direction of the paper but also in the width direction of the paper, the length of each of the print heads is shorter than in the related art. The object is to provide an inkjet head.

An inkjet head according to the present invention for achieving the above technical problem,

An inkjet head having a printhead array for printing an image by ejecting ink droplets on a print medium, the inkjet head comprising:

The printhead array has a plurality of printheads inclined at a first angle β with respect to a direction orthogonal to a transport direction of the print medium, each of the plurality of printheads with respect to a transport direction of the print medium. It is characterized by being disposed obliquely at a second angle α.

In the present invention, a plurality of printhead arrays may be arranged in parallel with a direction orthogonal to a conveying direction of the print medium or at a third angle θ. In this case, the first printhead provided in the next arranged printhead array is positioned below the last printhead provided in any one printhead array.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of description.

FIG. 5 is a plan view showing a printhead array of an inkjet head according to the present invention, and FIG. 6 is a plan view showing an inkjet head in which a plurality of printhead arrays shown in FIG. 5 are arranged.

5 and 6 together, the inkjet head 100 according to the present invention is for printing an image by ejecting ink droplets on a printing medium, for example, the paper (P), a plurality of printheads 110 It has an array of printhead arrays S.

Each of the plurality of printheads 110 is provided with a plurality of nozzles 101 for ejecting ink droplets on the paper P, and the plurality of printheads 110 are arranged and supported on the frame 120. do.

In the present invention, as shown in Figure 5, the printhead array (S) has a plurality of printheads 110 arranged in a constant form. Each of the plurality of print heads 110 is disposed to be inclined at a predetermined angle α with respect to the conveying direction (Y direction) of the paper P. In this case, the spacing D between the dots formed on the paper P becomes much smaller than the spacing C between the nozzles 101, so that the dpi of much higher dpi than the cpi of the printhead 110 is obtained. The image can be printed.

Specifically, as described above, since dpi = cpi / sin (α), the dpi becomes higher as the inclination angle α of the printhead 110 with respect to the conveying direction (Y direction) of the paper P becomes smaller. . Since the inclination angle α = sin ⁻¹ (cpi / dpi), the inclination angle α of the printhead 110 is set to approximately 5.74 °, for example, using the printhead 110 of 120 cpi. If you can print an image of 1200 dpi, that is, 1200 dpi, and you set the inclination angle α of the printhead 110 to approximately 2.87 °, you can use the 60 cpi printhead 110 to achieve 20 times that of 1200 dpi. Images can be printed.

In the printhead array S, the plurality of printheads 110 may have a predetermined angle with respect to the direction orthogonal to the conveying direction of the paper P, that is, the width direction (X direction) of the paper P. are arranged obliquely to β). At this time, the width direction (X direction) interval of the paper P between the lowermost nozzle 101 of any one printhead 110 and the uppermost nozzle 101 of the printhead 110 arranged next is The spacing D between one dots is adjusted.

As described above, when the plurality of print heads 110 are arranged to be inclined at a predetermined angle β with respect to the width direction (X direction) of the paper P, the length of each of the print heads 110 is 3 and 4. Compared with the conventional inkjet head shown in FIG. This will be described later with reference to FIGS. 7A and 7B.

As described above, when the length of each of the printheads 110 is shortened, the yield is increased in the manufacturing process of the printhead 110, and the risk of breakage in the handling process of the printhead 110 is lowered. In addition, since the number of nozzles 101 provided in each printhead 110 is reduced, and the pressure of ink supplied to the plurality of nozzles 101 is uniform, the ejection performance of the ink can be improved.

Meanwhile, as the inclination angle α of each of the print heads 110 becomes smaller, the arrangement angles of the plurality of print heads 110 need to be increased to keep the length of each of the print heads 110 shorter. There is a need. However, when the arrangement angle β of the plurality of printheads 110 is increased in this way, the length of the conveying direction (Y direction) of the paper P of the printhead array S becomes long, which is an inkjet head ( 110) It increases the size of the whole.

Therefore, in order to minimize the size of the entire inkjet head 110, as illustrated in FIG. 6, it is preferable to arrange a plurality of the printhead arrays S in the width direction (X direction) of the paper P. FIG. desirable. The first printhead 110 provided in the printhead array S arranged next may be disposed below the last printhead 110 provided in any one printhead array S. FIG. At this time, the lowermost nozzle 101 of the last printhead 110 provided in any one printhead array S and the uppermost nozzle of the first printhead 110 provided in the next printhead array S arranged therein. The width direction (X direction) interval of the sheet | seat P between 101 is matched with the space | interval D between said dots.

When arranged in the arrangement method as described above, as shown in Figure 6, a plurality of printhead array (S) having a plurality of printheads 110 in a constant form throughout the width direction of the paper (P) It is possible to implement the arrayed inkjet head 100.

Meanwhile, as the inclination angle α of each of the print heads 110 becomes smaller, the number of print heads 110 provided in each of the plurality of print head arrays S may be smaller. If the inclination angle α is very small, two print heads 110 may be provided in each of the print head arrays S, as shown in FIG. 7B. The plurality of printhead arrays S may be arranged at a predetermined angle θ with respect to the width direction (X direction) of the paper P. FIG.

7A and 7B are views showing a specific embodiment of the inkjet head according to the present invention in comparison with a conventional inkjet head. 7A is a view showing an embodiment of the conventional inkjet head shown in FIGS. 3 and 4, and FIG. 7B is a view showing a specific embodiment of the inkjet head according to the present invention.

7A and 7B, in order to print an image of 1200 dpi using the 120 cpi printheads 30 and 110, the inclination angle α with respect to the paper feed direction of each printhead 30 and 110 is 5.47. Set to °.

First, referring to FIG. 7A, in the conventional inkjet head, as described above, since the plurality of printheads 30 are arranged in the width direction of the paper, the length of each of the printheads 30 is assumed to be 7 mm. Becomes approximately 104 mm.

Next, referring to FIG. 7B, in the inkjet head according to the present invention, two printheads 110 constitute one printhead array S, and such printhead array S is the width of the paper. A plurality are arranged at a predetermined angle θ with respect to the direction. The inclination angle α of each of the print heads 110 is, as described above, relatively small as 5.47 °, and the arrangement angles of the two print heads 110 constituting one print head array S are ) Is relatively large.

As such, when the two printheads 110 constituting one printhead array S are arranged to be inclined with respect to the width direction of the paper, the width of each of the printheads 110 is assumed to be 7 mm. The length is approximately 59 mm.

In the overall size of the inkjet head 100 according to the present invention, the length of the paper conveying direction is approximately 137 mm, which is slightly increased compared to approximately 104 mm of the conventional inkjet head, but the length of each of the print heads 110 is as described above. It is about 57% shorter than the conventional inkjet head.

As described above, according to the present invention, each of the plurality of printheads is disposed to be inclined with respect to the conveying direction of the paper, so that not only the image of a higher dpi can be printed than the cpi of the printhead, By arraying inclined with respect to the width direction of the print head can be shorter than the conventional length of each.

Accordingly, the yield increases in the manufacturing process of the printhead, there is an advantage that the risk of breakage in the handling process of the printhead is lowered. In addition, since the pressure of the ink supplied to the plurality of nozzles provided in each printhead becomes uniform, there is an advantage in that the ejection performance of the ink is improved. In addition, it is possible to easily implement an inkjet head capable of printing an image of high dpi, such as 1200 dpi, using a printhead of low cpi, such as 60 cpi or 120 cpi.

While the preferred embodiments of the present invention have been described in detail, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

Claims (4)

delete An inkjet head having a printhead array for printing an image by ejecting ink droplets on a print medium, the inkjet head comprising: The printhead array has a plurality of printheads inclined at a first angle β with respect to a direction orthogonal to a conveying direction of the print medium, Each of the plurality of printheads is disposed to be inclined at a second angle α with respect to a conveying direction of the print medium, And the first angle β becomes larger as the second angle α becomes smaller. An inkjet head having a printhead array for printing an image by ejecting ink droplets on a print medium, the inkjet head comprising: The printhead array has a plurality of printheads inclined at a first angle β with respect to a direction orthogonal to a conveying direction of the print medium, Each of the plurality of printheads is disposed to be inclined at a second angle α with respect to a conveying direction of the print medium, And the plurality of printhead arrays are arranged in parallel with a direction orthogonal to a transfer direction of the print medium or at a third angle (θ). The method of claim 3, wherein An inkjet head, characterized in that the first printhead provided in the next arranged printhead array is located below the last printhead provided in any one printhead array.

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