JP2004167839A - Ink circulation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink circulation system adapted to efficiently deaerate ink of a line head type printing head. <P>SOLUTION: The ink circulation system has a printing head 1 where an ink discharge hole array of an equal or larger length to or than the width of an ink discharge region is arranged for discharging ink to the total width of the ink discharge region in a fixed state; a deaeration tub 2 for carrying out deaeration for the air dissolved in the ink; a piping path 4 comprising a supply passage 12 which couples the printing head 1 and the deaeration tub 2 to supply the ink from the deaeration tub 2 to the printing head 1, and a feedback passage 13 for feeding back the ink from the printing head 1 to the deaeration tub 2; and a pump 3 for circulating the ink between the deaeration tub 2 and the printing head 1 via the piping path 4. At least one of ends of the supply passage 12 and the feedback passage 13 is branched at the printing head 1 side of the piping path 4 and is connected to a predetermined plurality of positions of the printing head 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink circulation system for degassing air dissolved in ink, and in particular, branches at least one of an end of a supply path and an end of a return path on a print head side of a piping path for circulating ink. The present invention relates to an ink circulation system for efficiently degassing ink of a line head type print head by connecting the ink to a plurality of predetermined positions of the print head.
[0002]
[Prior art]
Conventional recording devices such as ink jet printers supply ink stored in an ink tank to a print head through a flexible ink supply tube, and move the print head in a left-right direction while moving ink droplets from an ink discharge hole of the print head. Is a serial head type in which an image is formed on a recording sheet by discharging the recording paper.
[0003]
In the case of a recording apparatus having an ink supply mechanism for supplying ink from the ink tank to the print head via the ink supply tube, air bubbles easily enter the ink, and the flow of the ink when the air bubbles enter the print head. In some cases, causing non-ejection of ink and causing poor printing.
[0004]
Here, the above-described causes of air bubbles entering the ink supply path include a case where air enters from a joint portion of the ink supply tube, a case where air penetrates through the ink supply tube, and a case where air originally dissolves in the ink. In some cases, air that has been deposited may be deposited. Further, in general, since the print head holds the inside of the ink flow path at a negative pressure so that a meniscus is stretched in the ink discharge hole, air may enter from the ink discharge hole due to vibration or impact during printing. .
[0005]
As described above, a deaeration system for removing (deaeration) air bubbles mixed in the ink supply path includes a system in which a dissolved gas in ink is transmitted through a gas-permeable membrane to be deaerated. (For example, see Patent Document 1). Also, there is an air vent valve provided in a sub-tank for temporarily storing ink, air bubbles are collected in the sub-tank, and when the pressure in the space in the sub-tank rises, the air vent valve is opened to deaerate (for example, Patent Document 1). 2). Further, a deaerator and a dissolved oxygen meter are connected to the ink supply path, and a circulation path for returning the ink that has passed through the deaerator to the ink tank is connected to the dissolved oxygen meter. When a certain amount of dissolved gas is contained, the ink is bypassed from an ink supply path and returned to an ink tank via a circulation path so that ink containing bubbles is not supplied to a print head. 3). Still further, the two ink tanks are connected to the print head through first and second ink paths that are independent of each other, and a pump is connected to one of the two ink tanks. In some cases, when air bubbles are mixed, a pump is driven to form a forced flow of ink in the print head to eliminate air bubbles in the other ink tank (for example, see Patent Document 4).
[0006]
[Patent Document 1]
JP-A-5-17712 (pages 2 to 4, FIG. 2)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 10-114081 (page 4, FIG. 4)
[Patent Document 3]
JP-A-11-42795 (pages 9 to 13, FIG. 1)
[Patent Document 4]
JP-A-4-6451 (page 3, FIG. 1)
[0007]
[Problems to be solved by the invention]
However, such a conventional degassing system is a serial head type that forms an image on recording paper by ejecting ink droplets from ink ejection holes to a predetermined width of an ink ejection area while moving a print head in the left-right direction. May be effective, but arrange the rows of ink ejection holes in a length equal to or greater than the width of the ink ejection area, and fix the print head with the entire width of the ink ejection area in a fixed state. Sufficient degassing could not be achieved even when applied directly to a line head type print head that ejects ink. That is, the line head type print head has a disadvantage that the dynamic negative pressure loss in the ink flow path is large because the ink flow path is long, and air flows backward from the ink discharge holes and mixes with the ink to generate bubbles. However, in the conventional degassing system, such a problem cannot be solved. In particular, in a large-sized line head corresponding to a large-sized recording paper such as A0 size, the ink flow path is long, so that the backflow of the air from the ink ejection holes is more likely to occur. There is no ink circulation system as a degassing system that efficiently eliminates the problem.
[0008]
Accordingly, it is an object of the present invention to provide an ink circulation system which addresses such a problem and efficiently degass ink of a line head type print head.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an ink circulation system according to the present invention has a configuration in which an array of ink ejection holes is arranged at a length equal to or longer than the width of an ink ejection region, and the entire width of the ink ejection region in a fixed state. A print head that discharges ink to the print head, a deaeration tank for deaeration of air dissolved in the ink, and a print head connected to the print head and the deaeration tank. And a return line for returning ink from the print head to the deaeration tank, and a pump for circulating ink between the deaeration tank and the print head through the pipe path. Wherein at least one of an end of a supply path and an end of a return path is branched on the print head side of the pipe path and connected to a plurality of predetermined positions of the print head. A.
[0010]
With such a configuration, a print in which ink ejection holes are arranged in a length equal to or longer than the width of the ink ejection region and ink is ejected over the entire width of the ink ejection region in a fixed state. At least one of the supply path of the piping path or the print head side end of the return path is branched and connected to a plurality of predetermined positions of the head, and ink is circulated between the deaeration tank and the print head by a pump through the piping path. Then, the air dissolved in the ink is deaerated in the deaeration tank. Thus, the dynamic negative pressure loss of the ink in the large-sized line head is reduced, and the air in the ink is efficiently deaerated.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory diagram showing a first embodiment of the ink circulation system according to the present invention. This ink circulation system is for deaeration of air dissolved in the ink, and includes a print head 1, a deaeration tank 2, a pump 3, and a piping 4. Here, a case of a single color will be described for convenience of explanation.
[0012]
The print head 1 prints by ejecting ink from a row of ink ejection holes to be described later onto the recording paper 5, and arranges the rows of ink ejection holes to have a length equal to or longer than the width of the ink ejection area. In a fixed state, ink is ejected over the entire width of the ink ejection area. The print head 1 is formed by connecting four unit print heads 1a each having a short row of ink discharge holes to form a row of ink discharge holes having a length equal to or longer than the width of an ink discharge area. Each of the unit print heads 1a is provided with an ink inlet 6 and an ink outlet 7. As an example of a specific connection of the unit print heads 1a, as shown in FIG. 2, four unit print heads 1a each having a length L provided with ink discharge holes aligned at 5136 dots at a pitch of 42.3 μm and adjacent units The ends of the print head 1a are staggered by overlapping each other by x = 8.33 mm, so that the ink is ejected over the entire width of the A0 size recording paper having a width W of about 844 mm while the print head 1 is fixed. Is made possible.
[0013]
The deaeration tank 2 shown in FIG. 1 temporarily stores ink and deaerates air (bubbles) in the ink, and discharges air deaerated from the ink to the atmosphere. Air communication hole 8 is provided on the upper surface thereof. The degassing tank 2 is disposed at a position h = 60 to 70 mm below the print head 1 so that the liquid level of the ink in the tank is lower than the ink discharge surface of the print head 1. The negative pressure of the print head 1 can be stably maintained by the pressure.
[0014]
Further, a pump 3 is connected to the deaeration tank 2. The pump 3 circulates the ink between the degassing tank 2 and the print head 1 via a pipe line 4, an outlet 3 a communicates with the degassing tank 2, and an inlet 3 b passes through an opening / closing valve 9. It communicates with a return path 13 described later. A replaceable ink tank 10 is connected to the inlet 3b. When the amount of stored ink in the degassing tank 2 falls below a predetermined level, the ink is detected by a sensor (not shown) and a pump is provided. 3 is driven so that ink can be replenished from the ink tank 10 to the deaeration tank 2.
[0015]
The pipeline 4 includes one supply path 12 for supplying the ink from the degassing tank 2 to the print head 1 and one return path 13 for returning the ink from the print head 1 to the degassing tank 2. 12 and the end of the return path 13 on the side of the print head 1 are branched into four to form branch paths 12a and 13a. The branch path 12a is connected to the ink inlet 6 of each unit print head 1a, and to the branch path 13a. Are connected to an ink outlet 7 to form a pipe line connected in parallel so that the ink flows into and out of the print head 1. Further, a filter 14 is inserted in the supply path 12 so that foreign matter mixed in the ink can be removed. The number of the branch paths 12a or 13a is not limited to four, and at least one of them may be provided in a plural number, and the number is arbitrary.
[0016]
Next, the operation of the ink circulation system thus configured will be described.
Normally, the print head 1, the deaeration tank 2 and the piping 4 shown in FIG. 1 are filled with ink, and the ink is supplied to the print head during the printing operation by the capillary force of the ink. Through the supply path 12 of the pipe line 4 at any time. At this time, the pump 3 has stopped. When the amount of stored ink in the degassing tank 2 falls below a predetermined amount, the amount is detected by a sensor (not shown) provided in the degassing tank 2, the opening / closing valve 9 is closed, and the pump 3 is driven to drive the ink. Ink is supplied to the deaeration tank 2 from the tank 10. The opening / closing valve 9 may be open or closed during the printing operation.
[0017]
Here, when air bubbles are mixed in the print head 1 or the pipe path 4 and ink discharge failure occurs, the pump 3 is driven with the open / close valve 9 opened. Then, ink is forcibly supplied to the print head 1 from the deaeration tank 2. At this time, the ink flows in the supply path 12 in the direction of arrow A, and reaches the branch path 12 a of the supply path 12 on the side of the print head 1. Then, the ink is diverted to the four branch paths 12a, flows from the ink inlet port 6 of each unit print head 1a into an ink channel (not shown) provided inside the unit print head 1a, and flows through each unit print head 1a. It flows in the directions of arrows B, C, D and E.
[0018]
The ink flowing in the unit print head 1a flows out of the ink outlet 7 into the branch path 13a, merges with the return path 13, flows in the direction of arrow F, passes through the opening / closing valve 9, the pump 3 and the deaeration tank 2 Return to By the circulation of the ink, the air bubbles mixed in the ink are carried to the deaeration tank 2 and are discharged into the deaeration tank 2 to a space provided above the ink surface. Then, the air is removed from the tank through the atmosphere communication hole 8 provided in the upper part of the deaeration tank 2.
[0019]
By the way, a dynamic negative pressure loss occurs between the ink inlet and the ink outlet of the print head 1 during ink ejection and ink circulation. Here, the dynamic negative pressure loss refers to the pressure difference between the upstream side and the downstream side of the ink flowing in the piping 4, and the dynamic negative pressure loss of the print head 1 indicates the dynamic negative pressure loss in the ink flow path. This dynamic negative pressure loss is 400 mmH ₂ It has been experimentally confirmed that when the temperature is equal to or higher than O, air enters through the ink ejection holes on the ink outlet side. On the other hand, the dynamic negative pressure loss in the print head 1 of FIG. 1 is determined between the ink inlet 6 and the ink outlet 7 of the unit print head 1a. For example, five ink droplets are formed by a pulse number modulation (PNM) method. 40 to 50 mmH ₂ It is about O. Further, even during ink circulation, the dynamic negative pressure loss of the unit print head 1a is 100 mmH. ₂ It is about O, and there is no risk of air entering through the ink ejection holes.
[0020]
According to the first embodiment, even if the print head 1 is a line head type print head 1 corresponding to a large-size recording paper 5, the print head 1 includes four unit print heads 1a having a short row of ink ejection holes. The branch path 12a of the supply path 12 and the branch path 13a of the return path 13 are connected to the ink inlet 6 and the ink outlet 7 provided in each unit print head 1a. Since the ink circulation system is configured in parallel, the ink flow path in the print head 1 is divided, the substantial ink flow path is shortened, and the dynamic negative pressure loss of the print head 1 can be reduced. Accordingly, it is possible to prevent the air from flowing backward from the ink ejection holes and to mix into the ink, and it is possible to solve the problem of the ink ejection failure due to the air entry and the printing failure due to the ink ejection failure.
[0021]
Further, the piping path 4 is branched into four ends of one supply path 12 and a return path 13 on the side of the print head 1 to form branch paths 12a and 13a, each of which is provided in each unit print head 1a. Since the connection is made to the ink inlet 6 and the ink outlet 7, only one deaeration tank 2 and one pump 3 are connected to the supply path 12 and the return path 13, respectively, which increases the cost of the ink circulation system. Can be suppressed.
[0022]
In the first embodiment, a parallel piping path is formed, but the present invention is not limited to this. For example, as shown in FIG. 3, each unit print head 1a is connected to four unit print heads 1a. With respect to the ink inlet 6 and the ink outlet 7 of the head 1a, the ink inlet 6 and the ink outlet 7 that are adjacent to each other are connected to each other, and the supply path is connected to the ink inlet 6 located at one side end of the print head 1. It is also possible to connect the return line 13 to the ink outlet 7 located at the other side end to form the serially connected pipe line 4.
[0023]
However, in this case, the dynamic negative pressure loss of the print head 1 occurs between the ink inlet 6 and the ink outlet 7 at both ends of the print head 1. Accordingly, in the print head 1 corresponding to the A0 size recording paper shown in FIG. 2, the ink flow path is substantially four times longer than that of the print head 1 of the first embodiment. About four times larger than that of the first embodiment, and about 160 mmH ₂ O, 400mmH with ink circulation ₂ It is about O. For this reason, the degree of negative pressure on the ink outlet 7 side at the side end portion of the print head 1 becomes large, and particularly when air circulates, air enters the print head 1 from the ink ejection holes on the ink outlet 7 side. It will be easier.
[0024]
Further, as shown in FIG. 4, an individual pipe line 4 is connected to each of the four connected unit print heads 1a, and a deaeration tank 2, a pump 3 and an ink tank 10 are connected to each of the pipe lines 4. It is also possible to form pipe lines connected in parallel. However, in this case, the deaeration tank 2, the pump 3, and the ink tank 10 are required in the same number as the number of unit print heads to be connected, which increases costs. 3 and 4, the on-off valve 9 is not shown.
[0025]
FIG. 5 shows a second embodiment of the ink circulation system according to the present invention. In this circulation system, the print head 1 arranges an array of ink ejection holes in a length equal to or longer than the width of the recording paper 5 of, for example, A0 size, and the ink ejection area of the recording paper 5 is fixed in a fixed state. The unit print head 1s is configured to eject ink over the entire width, and the four branch paths 12a at the unit print head 1s side end of the supply path 12 and the return path 13 are connected to the four unit print heads 1s. The ink inlet 6 and the four branch passages 13a are connected to the four ink outlets 7 to form a parallel-connected pipe 4 so that ink flows into and out of the print head 1s. The substantial ink flow path in the unit print head 1s is arranged between the ink inlet 6 and the ink outlet 7 which are close to each other as indicated by an arrow in the drawing.
[0026]
According to the second embodiment, even if the unit print head 1s is large and has a long ink flow path corresponding to the width of, for example, A0 size recording paper, the substantial ink inside the unit print head 1s is obtained. The flow path can be shortened, whereby the dynamic negative pressure loss can be reduced and the air can be prevented from flowing backward from the ink ejection holes and being mixed into the ink.
[0027]
FIG. 6 shows a third embodiment of the ink circulation system according to the present invention. This circulation system is a unit printing system in which the print head 1 is provided with a row of ink ejection holes of four colors of yellow (Y), magenta (M), cyan (C), and black (K) in correspondence with color printing. A plurality of heads 1a are connected to each other. Each of the heads 1a is provided with a separate deaeration tank, a pump, and an ink tank (not shown) corresponding to each color, and ink can be supplied to a row of ink ejection holes of the corresponding color via a pipe line. It has been like that. Each of the pipe paths includes supply paths 12Y, 12M, 12C, and 12K and return paths 13Y, 13M, 13C, and 13K, and ends of the supply paths 12Y to 12K and the return paths 13Y to 13K on the print head 1 side. Are branched to form a plurality of branch paths 12y, 12m, 12c, 12k and 13y, 13m, 13c, 13k, and four groups provided corresponding to the rows of the four color ink ejection holes of the print head 1. Are connected via the ink inlets 6y, 6m, 6c, 6k and the outlets 7y, 7m, 7c, 7k to form a parallel-connected piping path.
[0028]
According to the third embodiment, similarly to the first embodiment, a plurality of unit print heads 1a having a short row of ink ejection holes are connected to form a line head type print head corresponding to a large-size recording sheet. 1 and each unit print head 1a is provided with an ink inlet 6y-6k and an ink outlet 7y-7k, and the ink inlets 6y-6k and the ink outlets 7y-7k have supply paths 12Y-12K and feedback. By connecting the branched paths 12y to 12k and 13y to 13k of the paths 13Y to 13K, the ink flow path in the print head 1 can be substantially shortened and dynamic negative pressure loss can be reduced. Therefore, it is possible to prevent the air from flowing backward from the ink ejection holes and to mix into the ink, thereby eliminating the problem of the ink ejection failure and enabling the formation of a high-quality color image.
[0029]
FIG. 7 shows a fourth embodiment of the ink circulation system according to the present invention. In this circulating system, the print head 1 is provided with a row of ink ejection holes of four colors of Y, M, C, and K in parallel with a color print, with a length equal to or greater than the width of the recording paper. The unit print head 1s is configured to discharge ink over the entire width of the ink discharge area in the state, and separate deaeration tanks 2Y, 2M, 2C, 2K and pumps 3Y, 3M corresponding to each color. , 3C, 3K, and an ink tank (not shown) so that ink can be supplied to the rows of ink ejection holes of the corresponding colors via the piping 4. Then, the piping path 4 connects the two branch paths 12y to 12k of each color at the end of the supply paths 12Y to 12K and the return paths 13Y to 13K on the unit print head 1s side to the corresponding ink inlets 6y to 6k of the unit print head 1s. In addition, two branch paths 13y to 13k for each color are connected to the corresponding ink outlets 7y to 7k to form a parallel connection piping path.
[0030]
According to the fourth embodiment, as in the second embodiment, even if the unit print head 1s is large and has a long ink flow path, the substantial ink flow path inside the unit print head 1s is shortened. As a result, it is possible to reduce the dynamic negative pressure loss and to prevent the air from flowing backward from the ink ejection holes and entering the ink. Therefore, it is possible to form a high quality color image by eliminating the problem of defective ink ejection.
[0031]
FIG. 8 shows a fifth embodiment of the ink circulation system according to the present invention. In this circulation system, as shown in FIG. 9, the print head 1 is arranged so that the print head 1 corresponds to the color printing, and the rows 15y, 15m, 15c, 15k, and 15y 'of the ink ejection holes of four colors Y, M, C, and K. 15m ', 15c', and 15k 'are provided with a length equal to or greater than the width of the recording paper so that ink is ejected over the entire width of the ink ejection area in a fixed state. A plurality of heads 1a, 1a 'are connected to each other, and the ink ejection holes 15 of the pair of unit print heads 1a, 1a' are juxtaposed in such a manner that they are displaced from each other by P / 2 of the arrangement pitch P. As shown in FIG. 8, individual deaeration tanks 2 </ b> Y to 2 </ b> K, pumps 3 </ b> Y to 3 </ b> K, and ink tanks (not shown) are provided for the respective colors. The rows are provided with ink. The piping path 4 includes two branch paths 12y to 12k and 12y 'to 12k' for each color at end portions of the supply paths 12Y to 12K and the return paths 13Y to 13K on the side of the unit print heads 1a and 1a ', respectively. The corresponding ink inlets 6y-6k and 6y'-6k 'of 1a' and the two ink outlets 7y-7k and 7y'-7k of two branches 13y-13k and 13y'-13k 'of each color. 'To form a parallel connection pipeline. In FIG. 8, only one pair of the unit print heads 1a and 1a 'is shown for convenience of explanation.
[0032]
According to the fifth embodiment, the ink flow path can be shortened in the same manner as in the first embodiment, whereby the dynamic negative pressure loss is reduced, and bubbles flow backward from the ink ejection holes and enter the ink. Can be suppressed. Therefore, it is possible to form a high quality color image by eliminating the problem of defective ink ejection. Further, according to the fifth embodiment, the unit print head 1a 'is connected to the ink discharge holes 15 so that the space between the adjacent ink discharge holes of the unit print head 1a is complemented by the ink discharge holes 15 of the unit print head 1a'. By arranging them in a state shifted by P / 2 pitch of the arrangement pitch P, it is possible to form a high-definition image.
[0033]
FIG. 10 shows a sixth embodiment of the ink circulation system according to the present invention. In this circulation system, as shown in FIG. 11, the print head 1 has a pair of rows 15y to 15k of ink discharge holes of four colors of Y, M, C, and K corresponding to color printing, and the width of the recording paper and A plurality of unit print heads 1a are connected to each other so as to discharge ink over the entire width of the ink discharge area in a fixed state. The rows 15y to 15k of the ink ejection holes are arranged so as to be shifted from each other by P / 2 pitch of the arrangement pitch P of the ink ejection holes 15. The two branch paths 12y to 12k and 12y 'to 12k' of each color of the supply paths 12Y to 12K are respectively connected to the corresponding ink inlets 6y to 6k and 6y 'to 6k' of the unit print head 1a, and a pair of the same color. Ink flow paths are connected inside the unit print head 1a at the ink outflow side ends to provide one ink outflow port 7y to 7k for each color, and connected to return paths 13Y to 13K to be connected in parallel. Make up the road. FIG. 10 shows only one unit print head 1a for convenience of explanation.
[0034]
According to the sixth embodiment, similarly to the first embodiment, it is possible to reduce the dynamic negative pressure loss and to prevent the bubbles from flowing backward from the ink ejection holes 15 and entering the ink. Therefore, it is possible to form a high quality color image by eliminating the problem of defective ink ejection. Similarly to the fifth embodiment, the ink discharge holes 15y to 15k are arranged so that the pair of ink discharge holes 15y to 15k complement each other between the ink discharge holes 15 of the other ink discharge holes 15y to 15k. Are arranged in a state shifted by P / 2 pitch of the arrangement pitch P, it is possible to form a high-definition image.
[0035]
In the first to sixth embodiments, when the number of branch paths of the supply path is p and the number of branch paths of the return path is q, p ≧ 1, q ≧ 1, and p + q> 2. The pipeline is configured. This allows the number of ink inlets and ink outlets to be optimized with respect to dynamic negative pressure loss.
[0036]
In addition, the circulation of the ink may be performed by automatically driving the pump at the start of printing, at the elapse of a predetermined time, at the time of printing a predetermined number of sheets, or a combination thereof, or when ink non-ejection occurs. At this time, the operation may be performed by driving the pump manually.
[0037]
【The invention's effect】
Since the present invention is configured as described above, according to the first aspect of the present invention, the rows of the ink discharge holes are arranged in a length equal to or longer than the width of the ink discharge area, At least one of a supply path or a return path of the piping path on the print head side is branched and connected to a plurality of predetermined positions of the print head which discharges ink over the entire width of the ink discharge area. The ink can be circulated between the degassing tank and the print head by a pump via the, and air dissolved in the ink can be degassed in the degassing tank. Therefore, it is possible to reduce the dynamic negative pressure loss of the ink in the large-sized line head, suppress the intrusion of air from the ink ejection holes, and efficiently deaerate the air in the ink. As a result, high-quality printing can be performed while preventing defective ink ejection.
[0038]
According to the second aspect of the present invention, the numbers of ink inlets and ink outlets are optimized with respect to dynamic negative pressure loss by making the number of branches of the supply path and the return path of the pipe path different. can do. Therefore, invasion of air from the ink ejection holes can be suppressed.
[0039]
Further, according to the third aspect of the present invention, a plurality of unit print heads having a short row of ink discharge holes are connected to each other to have a row of ink discharge holes having a length equal to or longer than the width of the ink discharge area. By connecting the branched ends of the supply path and return path of the piping path to each of the unit print heads, the dynamic negative pressure loss of ink can be reduced even in a large line head, and air is discharged from the ink ejection holes. Intrusion can be suppressed. Accordingly, high-quality printing can be performed while preventing ink ejection failure.
[0040]
Furthermore, according to the fourth aspect of the present invention, since the degassing tank is arranged at a position lower than the print head, the negative pressure of the print head can be stably maintained due to the head difference.
[0041]
According to the invention according to claim 5, an air communication hole is provided on the upper surface of the degassing tank, and the air degassed from the ink temporarily stored in the degassing tank is discharged outside the degassing tank. By discharging the ink, the air in the ink can be easily degassed.
[0042]
Further, according to the invention according to claim 6, the print head is provided with individual ink flow paths corresponding to the inks of a plurality of colors, and each of the plurality of ink flow paths is degassed via a pipe. By connecting the tank and the pump, the air in the ink in the print head corresponding to the color printing can be efficiently deaerated. Thus, high-quality color printing can be performed by preventing ink ejection failure.
[0043]
Further, according to the invention according to claim 7, the pump is automatically driven at the start of printing, at the time of elapse of a predetermined time, at the time of printing a predetermined number of sheets, or at a time when these are combined, whereby the ink is circulated. In addition, the air in the ink is degassed, and printing can always be performed in an optimum state.
[0044]
According to the eighth aspect of the invention, by circulating the ink by driving the pump by manual operation at an arbitrary time, the ink circulation can be appropriately performed when an ink ejection failure occurs due to the generation of bubbles. By executing the process, the air in the ink is degassed, and the ink discharge failure can be treated, so that high quality printing can be always performed.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a first embodiment of an ink circulation system according to the present invention.
FIG. 2 is an explanatory diagram illustrating an example of connection of unit print heads.
FIG. 3 is an explanatory diagram showing a case where a pipe line is connected in series to a plurality of unit print heads connected to each other.
FIG. 4 is an explanatory diagram showing a configuration in which each of a plurality of connected unit print heads includes an individual deaeration tank, a pump, and an ink tank via a pipe line.
FIG. 5 is an explanatory diagram showing a main part of a second embodiment of the ink circulation system according to the present invention.
FIG. 6 is an explanatory diagram showing a main part of a third embodiment of the ink circulation system according to the present invention.
FIG. 7 is an explanatory diagram showing a fourth embodiment of the ink circulation system according to the present invention.
FIG. 8 is an explanatory diagram showing a fifth embodiment of the ink circulation system according to the present invention.
FIG. 9 is an explanatory diagram showing an arrangement state of a row of ink ejection holes in the fifth embodiment.
FIG. 10 is an explanatory diagram showing a main part of a sixth embodiment of the ink circulation system according to the present invention.
FIG. 11 is an explanatory diagram showing an arrangement state of rows of ink ejection holes in the sixth embodiment.
[Explanation of symbols]
1. Print head
1a, 1a ', 1s ... unit print head
2. Degassing tank
3. Pump
4 ... Piping line
8 ... Atmosphere communication hole
12, 12Y to 12K ... supply path
12a, 12y to 12k, 12y 'to 12k' ... branch road
13, 13Y to 13K ... return path
13a, 13y to 13k, 13y 'to 13k' ... branch road
15 ... Ink ejection hole
15y to 15k, 15y 'to 15k' ... rows of ink ejection holes

Claims (8)

A print head in which a row of ink ejection holes is arranged at a length equal to or greater than the width of the ink ejection area and ejects ink over the entire width of the ink ejection area in a fixed state; A deaeration tank for deaeration of air dissolved in the print head, a supply path connecting the print head and the deaeration tank to supply ink from the deaeration tank to the print head, and a deaeration tank from the print head. An ink circulation system comprising a piping path comprising a return path for returning the ink to the ink path, and a pump for circulating the ink between the degassing tank and the print head via the piping path,
An ink circulation system, wherein at least one of an end of a supply path and an end of a return path is branched on the print head side of the pipe path and connected to a plurality of predetermined positions of the print head. When the number of branches of the supply path is p and the number of branches of the return path is q,
p ≧ 1, q ≧ 1, p + q> 2
The ink circulation system according to claim 1, wherein the ink circulation system is formed to have the following relationship. The print head has a plurality of unit print heads having a short row of ink discharge holes, and has a row of ink discharge holes having a length equal to or longer than the width of the ink discharge area by connecting a plurality of unit print heads. 2. The ink circulation system according to claim 1, wherein branched ends of the supply path and the return path of the pipe path are connected to the respective sections. The ink circulation system according to claim 1, wherein the degassing tank is disposed at a position lower than the print head. The degassing tank is provided with an air communication hole on its upper surface, and discharges air degassed from the ink temporarily stored in the degassing tank to the outside of the degassing tank. The ink circulation system according to claim 1, wherein The print head has an individual ink flow path corresponding to a plurality of color inks, and the deaeration tank and the pump are connected to each of the plurality of ink flow paths via the piping path. The ink circulation system according to any one of claims 1 to 5, wherein: 7. The ink circulation according to claim 1, wherein the circulation of the ink is performed by automatically driving a pump when printing is started, when a predetermined time elapses, when a predetermined number of sheets are printed, or when these are combined. 3. The ink circulation system according to item 1. The ink circulation system according to any one of claims 1 to 6, wherein the circulation of the ink is performed by driving a pump manually at an arbitrary time.

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