JP2009285900A - Line type head unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line type head unit of simple pipe arrangement, capable of reducing a cost, having excellent ink delivery even by a line type, and capable of enhancing print quality. <P>SOLUTION: In this line type head unit 200 provided with a plurality of heads 100, an ink reservoir part 51 has the first and second ink ports 53, 54 communicated with an inside of the ink reservoir part 51 to make ink flow therethrough, and the ink reservoir part 51 is provided, in its inside, with a filter part F for dividing the inside into an ink flow channel 51a communicated with the first and second ink ports 53, 54, to make ink flow therethrough, and an ink chamber 51b for introducing the ink into a head chip 1. An upper face of the filter F is arranged along a flowing direction of the ink, to form one face of the ink flow channel 51a, and the second ink port 54 of one head 100 is connected to the first ink port 53 of the other head 100, to communicate the ink flow channel 51a of each head 100. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a line type head unit in which a plurality of inkjet heads are provided.

2. Description of the Related Art Conventionally, an ink jet printer has been proposed and put into practical use as an image recording apparatus capable of recording an image on various recording media such as plain paper and plastic thin plate. The ink jet printer includes an ink jet head having an ink ejection port for ejecting ink. By ejecting ink as fine droplets from the ink ejection port of the ink jet head toward the recording medium, a predetermined amount is applied to the recording medium. An image is recorded.
For example, in a serial-type inkjet printer, a predetermined image is recorded on a recording medium by ejecting ink from the inkjet head toward the recording medium while moving the inkjet head mounted on the carriage in a predetermined scanning direction. It has become. A line-type inkjet printer records a predetermined image on a recording medium by ejecting ink from a line-type inkjet head onto a recording medium conveyed in a predetermined conveyance direction.

  In an inkjet head, for example, a piezoelectric element that is deformed by applying a voltage is disposed in an ink flow path that supplies ink to an ink discharge port, and ink is discharged from the ink discharge port by applying a voltage to the piezoelectric element. It is like that.

The line-type ink jet printer as described above is basically provided with a branch pipe connected to each ink jet head from a common ink supply port, and is configured to supply ink to each ink jet head (for example, Patent Document 1). However, in the case of the above-mentioned Patent Document 1, since a common flow path and branch piping connected to each inkjet head are required, the piping is complicated and it is difficult to make it compact. There is also a problem of high costs.
Therefore, an ink jet printer in which a plurality of nozzle heads communicate with respective ink pressure chambers via the same circulation path is known (for example, see Patent Document 2).
JP 2005-225098 A JP 2000-52566 A

However, in the case of Patent Document 2, no countermeasure is taken against contamination of foreign matters such as dust. If foreign matter is mixed, the nozzles of the nozzle heads are clogged, or dust and the like are ejected together with ink, resulting in a decrease in printing quality. May bring.
The present invention has been made in view of the above circumstances, and provides a line-type head unit that has simple piping and can be reduced in cost, is excellent in ink discharge even in a line system, and can improve printing quality. The purpose is that.

In order to solve the above problems, the invention of claim 1 includes an ink storage section that stores ink;
In a line type head unit comprising a plurality of inkjet heads provided with a head chip having a nozzle for discharging ink introduced from the ink reservoir,
The ink reservoir has two ink ports through which ink flows in communication with the ink reservoir,
In the ink reservoir, there is provided a filter that divides into an ink flow path through which ink flows in communication with the two ink ports and an ink chamber for introducing ink into the head chip,
One surface of the filter is arranged along the direction of ink flow to form one surface of the ink flow path,
One ink port of one ink jet head and one ink port of another ink jet head are connected to each other so that the ink flow passages of the respective ink jet heads communicate with each other.

According to the present invention, even when foreign matter such as dust is mixed, the foreign matter does not flow into the ink chamber because it is blocked by the filter. Therefore, it is excellent in ink discharge, and print quality can be improved. Further, even when foreign matter adheres to the filter, the foreign matter also flows and is removed as the ink flows through the ink flow path, and the filter can be prevented from being clogged.
Furthermore, since the ink flow paths of the respective ink jet heads can be made common, the structure is simple, and the size and cost can be reduced.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for carrying out the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is an external perspective view of the line type head unit 200. In the following description, the arrangement direction of the nozzles 11a of the inkjet head (hereinafter referred to as the head) 100 is the left-right direction, one direction orthogonal to the left-right direction is the front-rear direction, and the direction is orthogonal to both the front-rear direction and the left-right direction. Is the vertical direction.
The line type head unit 200 is mounted on an ink jet printer (not shown) and records an image on a transported recording medium by a line method. The line-type head unit 200 includes two line-type heads 100 in the front-rear direction along a width direction of the recording medium (a direction perpendicular to the recording medium conveyance direction: left-right direction) on a support member 201 that is long in the left-right direction. A plurality of columns are provided. The heads 100, 100 adjacent to each other along the left-right direction are alternately arranged so that the positions in the front-rear direction are shifted. The line-type head unit 200 is arranged in a zigzag pattern when viewed as a whole.

The first ink port 53 of the head 100 at the left end among the plurality of heads 100, 100,... In the first row is connected to an ink tank (not shown) via a connecting pipe 203. The second ink port 54 of the head 100 at the left end of the first row is connected to the first ink port 53 of the head 100 at the center of the first row via the connecting tube 202, and the second ink port 54 of the head 100 at the center of the first row is connected. The tube 202 is connected to the first ink port 53 of the head 100 at the right end of the first row. The second ink port 54 of the head 100 at the right end of the first row is connected to the first ink port 53 of the head 100 at the right end of the second row via the connecting tube 202, and the second ink of the head 100 at the right end of the second row. The port 54 is connected to the first ink port 53 of the head 100 in the center of the second row through the connecting tube 202, and the second ink port 54 of the head 100 in the center of the second row is connected to the left end of the second row through the connecting tube 202. Connected to the first ink port 53 of the head 100. The second ink port 54 of the head 100 at the left end of the second row is connected to a waste liquid portion (not shown) via a connecting pipe 204.
In this way, the plurality of heads 100, 100,... In the first row and the plurality of heads 100, 100,... In the second row have the first ink port 53 and the second ink port 54 connected in series. Yes.

Next, the configuration of the head 100 will be described.
2A is a perspective view of the head 100, FIG. 2B is a bottom view of the head 100, and FIG. 3 is an exploded perspective view of the head 100. In addition, illustration of the cover member 9 is abbreviate | omitted in FIG.

  The head 100 includes a head chip 1 that discharges ink from a nozzle 11a (see FIG. 5), a wiring board 2 on which the head chip 1 is disposed, and a driving circuit board that is connected to the wiring board 2 via a flexible board 3. 4, a manifold 5 that introduces ink into the channel 13 of the head chip 1 through the filter F, a housing 6 that houses the manifold 5 inside, and a cap that is attached so as to close the bottom surface opening 61 of the housing 6. A receiving plate 7 and a cover member 9 attached to the housing 6 are provided.

4A is a perspective view showing the head chip 1, the wiring board 2, the flexible board 3, and the drive circuit board 4, and FIG. 4B is a view of the head chip 1 from a different direction from FIG. 4A. FIG. 5 is an exploded perspective view schematically showing the head chip 1 and the wiring board 2.
In FIG. 5, for simplification of the drawing, the head chip 1 with one nozzle row and the wiring substrate 2 in which the electrode portion 21 is disposed only on the front side are schematically shown.

The head chip 1 is a substantially quadrangular prism-like member that is long in the left-right direction. On the lower surface of the head chip 1, there is disposed a nozzle plate 11 on which nozzles 11a (see FIG. 5) serving as ink ejection ports are formed.
A wiring substrate 2 is disposed on the upper surface of the head chip 1 so that the upper surface opening is exposed upward. Two flexible boards 3 and 3 connected to the drive circuit boards 4 and 4 are disposed at both edges along the left-right direction of the wiring board 2.

In the head chip 1, drive walls 12 and channels 13 made of piezoelectric elements are alternately arranged in parallel in the left-right direction.
An inlet and an outlet of each channel 13 are arranged on the upper surface and the lower surface of the head chip 1, respectively. Each channel 13 has a substantially rectangular cross section and is formed along the vertical direction. Each channel 13 is a straight type whose size and shape are substantially the same in the length direction (vertical direction) from the inlet to the outlet, and a plurality of channels 13, 13,... Are arranged in parallel to each other. Yes. Further, a nozzle plate 11 is disposed so that each nozzle 11 a communicates with the outlet of each channel 13.

A drive electrode 14 for driving the drive wall 12 is provided on the inner surface of each channel 13. The drive electrode 14 is an independent metal film for each channel 13 and is connected to the electrode portion 21 of the wiring board 2 attached to the upper surface of the head chip 1.
The head chip 1 ejects ink from the nozzles 11 a when the drive wall 12 repeats expansion and contraction based on the control signal input from the flexible substrate 3.

In the head chip 1 configured as described above, when adjusting the ink ejection amount, the length of the channel 13 and the drive wall 12 in the vertical direction (extending direction) is adjusted.
Accordingly, by changing the lengths of the channel 13 and the drive wall 12 in the vertical direction, the length of the entire head chip 1 in the vertical direction (ink ejection direction) also changes.

The wiring board 2 is formed in a substantially rectangular plate shape that is long in the left-right direction, and each width in the left-right direction and the front-rear direction is larger than the head chip 1. In addition, an opening 22 is formed at a substantially central portion of the wiring board 2.
The opening 22 is formed in a substantially rectangular shape elongated in the left-right direction, and the inlet of the channel 13 on the upper surface of the head chip 1 is exposed through the opening 22 with the head chip 1 attached to the wiring board 2. It has become so.
In addition, a predetermined number of electrode portions 21 connected to the drive electrodes 14 of the head chip 1 are provided at the edge of the opening 22 in the front-rear direction.

A flexible substrate 3 is disposed on both edges of the wiring substrate 2 on the front and rear direction side (see FIG. 3A).
The flexible substrate 3 has a plurality of wirings 31, 31,... Electrically connected to the drive circuit substrate 4. And the wiring 31 and the electrode part 21 of the wiring board 2 are each electrically connected.
As a result, a signal from the drive circuit board 4 is applied to the drive electrodes 14 in each channel 13 of the head chip 1 via the wiring 31 of the flexible board 3 and the electrode portion 21 of the wiring board 2.

  The lower end portion of the manifold 5 is fixed to the outer peripheral edge of the wiring board 2 by bonding. That is, the manifold 5 is disposed on the inlet side of the channel 13 of the head chip 1, and the head chip 1 is disposed via the wiring board 2.

6 (a) is a perspective view of the manifold 5, FIG. 6 (b) is a perspective view of the manifold 5 when viewed from a direction different from FIG. 6 (a) by 180 ° C., and FIG. FIG. 8 is a side sectional view schematically showing the manifold 5 and the head chip 1. In FIG. 7, the cover member 9 is not shown. In FIG. 8, the left-right direction is opposite to that of FIG.
The manifold 5 is a member formed of resin and stores ink to be introduced into the channel 13 of the head chip 1. Specifically, the manifold 5 includes a hollow main body 52 that constitutes an ink reservoir 51 that is long in the left-right direction, a first ink port 53 that causes ink to flow through the ink reservoir 51, a second ink port 54, and the like. A third ink port 55 and a cleaning bypass section 56 for cleaning ink that has passed through the filter F are provided.

  The main body 52 has a box shape with an open bottom surface, and a wiring board mounting portion 521 having a length and width larger than the bottom surface opening is provided at the edge of the bottom surface opening. The wiring board mounting portion 521 also has a box shape with the lower surface opened, and the wiring board 2 is mounted so as to close the lower surface opening. As a result, the ink reservoir 51 is formed inside the main body 52 and the wiring board mounting portion 521.

  A first ink port 53 and a second ink port 54 that protrude upward and communicate with the ink reservoir 51 are provided at two locations on the left and right of the upper surface of the main body 52. Further, a cleaning bypass portion 56 that protrudes upward and communicates with the ink storage portion 51 is provided outside the first ink port 53 on the upper surface of the main body portion 52, and the ink that protrudes upward is provided outside the second ink port 54. A third ink port 55 that communicates with the reservoir 51 is provided.

The cleaning bypass unit 56 flows the ink in the ink chamber 51b that has passed through the filter F to the outside in order to clean and remove the foreign matter in the channel 13 of the head chip 1. The cleaning bypass unit 56 is closed with a seal or a cap after cleaning and removing foreign matter in the channel 13.
The second ink port 54 removes dust and bubbles by flowing the ink in the ink flow passage 51a to the outside, and supplies the ink to the first ink port 53 of the other head 100 via the connecting pipe 202. It is like that.
The third ink port 55 removes bubbles and the like by flowing ink in the ink chamber 51b to the outside.

A filter F for removing dust and the like in the ink is provided between the main body 52 and the wiring board mounting portion 521 in the ink reservoir 51. The upper surface of the filter F is arranged along the direction of ink flow from the first ink port 53 to the second ink port 54 to form one surface of the ink flow passage 51a. Specifically, the filter F is disposed substantially perpendicular to the four side wall surfaces forming the main body portion 52 and substantially horizontal to the upper surface of the main body portion 52. By arranging the filter F in this way, the inside of the ink reservoir 51 is vertically divided into two, the upper part being an ink flow path 51a and the lower part being an ink chamber 51b.
The upstream end of the ink flow passage 51 a communicates with the first ink port 53, and the downstream end communicates with the second ink port 54. Further, the ink chamber 51b guides ink to the head chip 1 through the filter F from the ink flow passage 51a. One end of the ink chamber 51 b communicates with the cleaning bypass unit 56, and the other end communicates with the third ink port 55 via the filter F. The ink chamber 51b is common to all the channels 13.
As shown in FIG. 1, the second ink port 54 of one head 100 and the first ink port 53 of another head 100 are connected by a connecting pipe 202, respectively. The flow passage 51a communicates in series.

In designing the flow path of the ink flow path 51a according to the present invention, the viscosity, density, head driving frequency, resolution, droplet volume, nozzle diameter, number of connected heads, and connection mode of ink used ( The design value changes depending on the loop shape, the state stopped at the end, etc., but when designing a general inkjet head, this range does not take any value depending on the design, but other actual structural design Should be designed with constraints in mind.
Assuming that the current general ink and head are used, values of ink viscosity of 5 to 20 cp, nozzle diameter of 20 to 50 micrometers, droplet volume of 100 pl or less, driving frequency of 50 kHz or less, and resolution of 600 dpi or less are applied. . The number of heads in this range requires that the pressure loss at the maximum flow rate of the path be lower than the meniscus break value of the nozzle. In a typical line type head unit design, the maximum is about 500 mm, and at a resolution of 360 dpi, the number of nozzles is about 7000 nozzles. Become. For example, when a head having about 1000 nozzles is connected, the number of heads is 7. When the ink circulation path is used, the necessary cross-sectional area of the tube is preferably 20 square millimeters or more and 80 square millimeters or less. When the cross-sectional area of the ink circulation path is small (less than 20 square millimeters), when the flow rate is maximized, the pressure loss value exceeds the meniscus pressure resistance of the nozzle, causing a meniscus break, and ink ejection becomes impossible. If the cross-sectional area of the ink circulation path becomes too large (exceeds 80 square millimeters), bubbles in the flow path are difficult to escape, particularly when ink is introduced.

  FIG. 9 is a diagram showing the relationship between the cross-sectional area of the ink flow passage 51a and the pressure loss value when the six heads 100, 100,... Are connected in series. As is apparent from FIG. 9, when the cross-sectional area of the ink flow passage 51a is 28.3 square millimeters (Φ6), the pressure loss value is 20 cm, and a sufficient flow-path cross-sectional area is ensured even when the ink flow rate is increased. Ink discharge is good. On the other hand, when the cross-sectional area of the ink flow passage 51a is 12.6 square millimeters (Φ4), the pressure loss value becomes 108 cm, and when the ink flow rate increases, the meniscus pressure resistance of the head is exceeded, and the meniscus breaks. As a result, ink ejection failure occurs. Note that the pressure loss value is calculated by a well-known general calculation formula, and the meniscus pressure resistance is about 40 cm. The calculation conditions in FIG. 9 are a droplet volume 42pl, an ink viscosity of 20 cp, a driving frequency of 7.4 kHz, and a tube length (between heads) of 200 mm.

As shown in FIGS. 2 and 7, the housing 6 is a member formed by die casting using aluminum as a material, and is formed in a hollow shape with an open bottom surface. The housing 6 houses a manifold 5 in which the head chip 1, the wiring board 2, and the flexible board 3 are attached.
Insertion holes 63 and 64 through which the first ink port 53 and the second ink port 54 are inserted at positions corresponding to the first ink port 53 and the second ink port 54 at two positions on the left and right sides of the upper surface of the housing 6. Is formed. The third ink port 55 and the cleaning bypass unit 56 are also inserted into positions corresponding to the third ink port 55 and the cleaning bypass unit 56 outside the insertion holes 63 and 64 on the upper surface of the housing 6. Insertion holes 65 and 66 are formed.
The first ink port 53, the second ink port 54, and the third ink port 55 inserted through the insertion holes 63 to 66 are slidably inserted up and down by joints 81, 82, and 83.

A cap receiving plate 7 is attached to the edge of the bottom opening 61 of the housing 6 so as to close the bottom opening 61.
The cap receiving plate 7 is formed in a substantially rectangular shape that is long in the left-right direction, and a nozzle opening 71 that exposes the nozzle plate 11 is formed in a substantially central portion thereof.

  Two board insertion openings 62 through which the two drive circuit boards 4, 4 connected to the manifold 5 and the flexible boards 3, 3 are inserted are formed at a substantially central portion in the left-right direction of the housing 6. The board insertion openings 62 and 62 are closed by attaching a cover member 9 to the housing 6.

Next, the operation of this embodiment will be described.
In the head 100 configured as described above, the wiring substrate 2 is attached to the upper surface of the head chip 1, so that the drive electrode 14 of each channel 13 of the head chip 1 and the electrode portion 21 of the wiring substrate 2 are electrically connected. Connecting.
When a signal related to ink ejection is sent to the head 1, the signal reaches the connection electrode of the head chip 1 and thus the drive electrode 14 from the wiring of the flexible substrate 3 through the electrode portion 21 of the wiring substrate 2. Then, the ink supplied from the first ink port 53 is introduced into the channel 13 through the ink flow passage 51a, the filter F, and the ink chamber 51b. At this time, the drive wall 12 formed by the piezoelectric element undergoes shear deformation and pressure is applied to the ink in the channel 13, so that ink is ejected from the nozzles 11 a formed on the nozzle plate 11. Ink flowing through the ink flow path 51a is supplied from the first ink port 53 of the other head 1 to the ink flow path 51a via the second ink port 54, and thus the heads connected in series in this way. 1 is sequentially supplied to each ink flow path 51a.

As described above, in the present embodiment, the filter F that is divided into the ink flow passage 51a and the ink chamber 51b is provided in the ink reservoir 51, and the upper surface of the filter F is arranged along the ink flow direction. Since one surface of the flow passage 51a is formed, even when foreign matter such as dust is mixed, the foreign matter does not flow into the ink chamber 51b because it is blocked by the filter F. Therefore, it is excellent in ink discharge, and print quality can be improved. Further, even when foreign matter adheres to the filter F, the foreign matter also flows and is removed together with the ink flowing through the ink flow passage 51a, so that the filter F can be prevented from being clogged.
Furthermore, since the second ink port 54 of one head 100 and the first ink port 53 of the other head 100 are connected and the ink flow passage 51a of each head 100 communicates, The ink flow path 51a of each head 100 can be made common and ink can be ejected satisfactorily without the need for a path and a branch pipe. Therefore, the structure is simple, and compactness and cost reduction can be achieved.
In addition, by setting the flow passage cross-sectional area of the ink flow passage 51a to a predetermined size, a sufficient flow cross-sectional area can be secured even when the ink flow rate is increased due to the line formation of the head 100, and ink discharge is also good. It becomes.

In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can change suitably.
For example, the above-described head 100 is configured to supply ink from the first ink port 53 and discharge ink from the second ink port 54. However, the present invention is not limited thereto, and ink is supplied from the second ink port 54. A configuration may be adopted in which ink is discharged from the first ink port 53. Therefore, in the connection between the heads 100 in FIG. 1, the connecting pipe 204 may be connected to the ink tank and the connecting pipe 203 may be connected to the waste liquid portion.
Further, as a method of connecting the heads 100, the heads 100 adjacent in the left-right direction are connected in FIG. 1, but the heads 100 adjacent in the front-rear direction in FIG. 1 may be connected to each other.
In addition, the third ink port 55 and the cleaning bypass unit 56 are not essential components and may not be provided.

It is a perspective view of a line type head unit of an embodiment to which the present invention is applied. (a) is a perspective view of an inkjet head, (b) is a bottom view of the inkjet head. It is a disassembled perspective view of an inkjet head. (a) is a perspective view showing a head chip, a wiring board, a flexible substrate, and a drive circuit board, and (b) is a perspective view when the head chip is viewed from a direction different from FIG. 4 (a). It is a disassembled perspective view which shows a head chip and a wiring board typically. (a) is a perspective view of a manifold, (b) is a perspective view when the manifold is viewed from a direction different from FIG. 6 (a) by 180 ° C. FIG. FIG. 2 is a side sectional view of the ink jet head of FIG. 1. It is the sectional side view which showed the manifold and the head chip typically. FIG. 6 is a diagram illustrating a relationship between a cross-sectional area of an ink circulation path and a pressure loss value when a plurality of heads are connected in series.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head chip 11a Nozzle 51 Ink storage part 51a Ink flow path 51b Ink chamber 53 First ink port 54 Second ink port 100 Inkjet head 200 Line type head unit F Filter

Claims (1)

An ink reservoir for storing ink;
In a line type head unit comprising a plurality of inkjet heads provided with a head chip having a nozzle for discharging ink introduced from the ink reservoir,
The ink reservoir has two ink ports through which ink flows in communication with the ink reservoir,
In the ink reservoir, there is provided a filter that divides the ink flow path through which ink flows in communication with the two ink ports and the ink chamber that introduces ink into the head chip,
One surface of the filter is arranged along the direction of ink flow to form one surface of the ink flow path,
One ink port of one ink jet head and one ink port of another ink jet head are connected to each other so that the ink flow path of each ink jet head communicates. Type head unit.

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