JP2007229997A - Clogging prevention mechanism and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit a poor discharge of ink from a nozzle which is caused by the reduction of fluidity of ink due to pigments in the ink adhering or staying in an ink passage. <P>SOLUTION: The ink passage 33 is formed in interfaces 41a, 41b by adhering the first and second conductive passage members 41 and 42 with an insulating adhesive. Pigments G in the ink which flow in the ink passage 33 are dispersed in the ink in the state of being charged in minus. An alternative voltage of ±5 V at 50 Hz is applied between the first conductive passage member 41 and the second one 42 by a circuit 45 with an alternative power supply 44. Thereby, an alternating electric field is formed between the first conductive passage member 41 and the second one 42, and then the adhering or staying of the pigments is canceled by vibrating the pigments G which adhere or stay in the ink passage 33 in the direction of arrow mark. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a clogging prevention mechanism and an ink jet recording apparatus that prevent a decrease in fluidity of a solution, which occurs when a charged solute adheres to and stays in a solution flow path.

  Many ink flow paths and nozzles are formed in an ink jet head used in an ink jet printer or the like. Since these ink flow paths and nozzles are thin and small, clogging with ink tends to occur. When clogging occurs, ejection failure of ink ejected from the nozzles occurs, and the quality of an image formed on a sheet material such as paper is degraded by this ink.

  A technique for preventing ink clogging as described above has been proposed in Patent Document 1, for example. In the vicinity of the nozzle outlet, the ink medium (liquid component) in the ink evaporates, so that a solid component (for example, pigment) in the ink is deposited. The deposited solid component causes the nozzle to be clogged, and normal ink cannot be ejected from the nozzle.

  Therefore, in Patent Document 1, a DC voltage or an AC voltage is applied between the nozzle plate in which the nozzle is formed and the ink chamber provided on the upstream side of the nozzle plate, and adheres to the vicinity of the nozzle outlet. Solid components that cause clogging are removed.

Japanese Patent No. 3095905

  However, as a result of performing an endurance test of the inkjet head, the present applicant has confirmed that even when the clogging in the vicinity of the nozzle outlet described above is eliminated, ejection failure occurs with endurance. The main cause of this is that the pigment in the ink adheres to or stays on the wall surface of the ink flow path disposed upstream of the nozzles, thereby obstructing the flow of ink in the ink flow path. In other words, it was found that the fluidity of the ink was lowered. In addition, the adhesion and retention of the pigment on the wall surface of the ink flow path gradually occur even during normal use, unlike the solid component deposited near the nozzle outlet described above when the nozzle is not used. It will be.

  Here, since the technique of the above-mentioned patent document 1 aims at removing the solid component deposited in the vicinity of the nozzle outlet, it is essential that one of the two electrodes is a nozzle. It is difficult to apply to remove the pigment adhering to or staying on the wall surface in the ink flow path.

  In the above, the problem that the fluidity of the ink in the ink flow path is lowered by the pigment in the ink has been pointed out. However, such a problem is not limited to the case where the solution is ink, and the solute in the solvent. The same occurs for a general solution in which is dispersed.

  An object of the present invention is to provide a clogging prevention mechanism and an ink jet recording apparatus which remove solutes adhering to or staying in a solution flow path to prevent a decrease in fluidity of the solution. It is what.

  The invention according to claim 1 relates to a clogging prevention mechanism for removing the solute adhering and staying in a solution flow path through which a solution composed of a solvent and a solute dispersed in a charged state in the solvent flows. The clogging prevention mechanism according to the present invention includes two conductive flow path members that are in close contact with each other and that form the solution flow path on a boundary surface, and an insulation that bonds the two conductive flow path members at the boundary surface. An adhesive voltage and a circuit for applying an alternating voltage between the two conductive flow path members, and applying the alternating voltage between the two conductive flow path members by the circuit, An alternating electric field is formed between two conductive flow path members to vibrate the solute in the solution flow path.

  The invention according to claim 2 is the clogging prevention mechanism according to claim 1, wherein the solute is a pigment, the solution is ink, and the solution channel is an ink channel formed in an inkjet head. It is characterized by that.

  The invention according to claim 3 is the clogging prevention mechanism according to claim 1 or 2, characterized in that the conductive flow path member is formed in a layered manner on the surface of the insulating member.

  According to a fourth aspect of the present invention, there is provided an inkjet recording apparatus comprising: a conveying unit that conveys a sheet material to a printing unit; and an inkjet head that performs printing by ejecting ink from a nozzle to the sheet material conveyed to the printing unit. . The ink jet recording apparatus according to the present invention is characterized in that a clogging prevention mechanism according to claim 2 or 3 is provided for the ink jet head.

  According to the first aspect of the present invention, the two conductive flow path members that are in close contact with each other and form the solution flow path at the boundary surface are bonded to each other at the boundary surface by the insulating adhesive and are insulated from each other. Therefore, when an AC voltage is applied between the two conductive flow path members by a circuit, an alternating electric field in a direction perpendicular to the solution flow path is formed between them. Therefore, for example, a charged solute that adheres to or stays in the vicinity of the wall surface of the solution flow channel is forcibly vibrated by an alternating electric field between the two conductive members, and the attached state or the retained state is eliminated. . Thereby, the fluidity of the solution in the solution channel is recovered.

  According to the invention of claim 2, an alternating electric field in a direction perpendicular to the ink flow path is formed between the two by the alternating voltage applied between the two conductive flow path members. Therefore, for example, the pigment adhering to the wall surface of the ink flow path or staying in the vicinity of the wall surface is forcibly vibrated by the alternating electric field between the two conductive members, and the adhering state or the staying state is eliminated. Thereby, the fluidity of the ink in the ink flow path is recovered.

  According to the invention of claim 3, since the conductive flow path member is formed in a layer on the surface of the insulating member, the conductive flow path member is insulated by the insulating adhesive and the insulating member. Can do.

  According to the fourth aspect of the invention, it is possible to prevent ink ejection failure from the nozzles, which is caused by clogging of the ink flow path, and to prevent deterioration in image quality on the sheet material.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 shows an ink jet recording apparatus 10 to which a clogging prevention mechanism according to the present invention can be applied. FIG. 2 is a diagram of the inkjet recording apparatus 10 as viewed from the left side in the conveyance direction (arrow Ks direction) of the sheet material S (copy paper as a recording material, plastic film, envelope, etc.).

  As shown in the figure, an inkjet recording apparatus 10 includes a conveyance belt 11 that conveys a sheet material S, and a plurality of inkjet heads 12a, 12b, and 12c that perform printing on the surface of the sheet material S by ejecting ink from nozzles n. , 12d, and a transport guide 13 disposed so as to correspond to the inkjet heads 12a to 12d.

  As shown in FIG. 1, the conveyor belt 11 is stretched between a driving roller 14 and a driven roller 15, and the direction of the arrow R <b> 11 is accompanied by the rotation of the driving roller 14 in the direction of arrow R <b> 14 (counterclockwise) by the motor 16. Endlessly moved (rotated). A printing portion P is formed between the transport belt 11 and each of the inkjet heads 12a to 12d.

  A paper feed cassette 17 is disposed below the conveyor belt 11. The sheet material S stored in a stacked state in the paper feed cassette 17 is fed from the paper feed cassette 17 by the paper feed roller 18 and further separated one by one by the transport roller 20 and the retard roller 21 for preventing double feed, It is conveyed along the guide 22. Further, the sheet material S is supplied to the conveying belt 11 after the skew is corrected by the registration roller pair 23. At this time, the sheet material S is charged by the suction roller 24 to which a charging bias is applied, and is electrostatically attracted to and supported on the surface of the transport belt 11 (the sheet support surface 11a).

  The sheet material S carried on the surface of the conveyance belt 11 is supplied to the printing unit P as the conveyance belt 11 rotates in the direction of arrow R11, and printing is performed by inkjet heads 12a to 12d described later. After completion of printing, the sheet material S is separated from the conveying belt 11 and discharged to the paper discharge tray 25.

  Each of the inkjet heads 12a to 12d is formed long in the sheet passing width direction (left and right direction), and constitutes a so-called line head. In this embodiment, as shown in FIG. 1, the four inkjet heads 12a, 12b, 12c, and 12d are arranged at equal intervals from the upstream side to the downstream side along the transport direction. In this order, for example, an inkjet head that ejects ink of each color of black, yellow, magenta, and cyan.

  Each of the inkjet heads 12a to 12d has a flat head print surface N that faces the sheet carrying surface 11a of the above-described transport belt 11, and the head print surface N has a large number for ejecting ink. The nozzles n are aligned in a line along the sheet passing width direction. For example, when the resolution of the inkjet recording apparatus 10 is 600 dpi (dots / inch: number of dots per inch), the nozzle n has a diameter of about 20 μm and a pitch between adjacent nozzles of about 40 μm. . The nozzles arranged in a line may be arranged in a line in a line in the sheet passing width direction, or may be arranged in a staggered pattern in the sheet passing width direction.

  The inkjet recording apparatus 10 having the above-described configuration performs printing in units of lines by the inkjet heads 12a to 12d on the sheet material S carried and conveyed to the printing unit P by the conveyance belt 11, and performs four-color full-color printing as a whole. It can be carried out.

  In the above-described inkjet heads 12a to 12d, when clogging occurs in the ink flow path, ink ejection failure from the nozzle n occurs. As a result of clogging, the flow of ink in the ink flow path is disturbed and the fluidity of the ink is lowered. As a result, the ink is not ejected from the nozzle n, or even if ejected, the ejection speed is slowed down. The sheet material S does not land on the surface properly, and printing failure occurs.

  In this embodiment, the clogging of the ink flow path is prevented as follows.

  FIG. 2 schematically shows a longitudinal section of the black inkjet head 12a. In addition, since the inkjet heads 12b, 12c, and 12d of other colors have the same configuration, description thereof will be omitted.

  As shown in the figure, the ink jet head 12 a includes a downward nozzle n on a nozzle surface N facing the sheet carrying surface 11 a of the transport belt 11. A pressure chamber 30 is disposed on the upstream side of the nozzle n along the ink flow. One pressure chamber 30 is provided for each nozzle n, that is, one to one for the nozzle n. A vertical first ink flow path 31 is formed between the nozzle n and the pressure chamber 30. On the upstream side of the pressure chamber 30, a common ink common channel 32 is provided for each pressure chamber 30. Between the ink common flow path 32 and each pressure chamber 30, a second ink flow path 33 having a vertical flow path 33a and a horizontal flow path 33b is formed. Above the pressure chamber 30, a piezoelectric element 34 as a piezoelectric element is disposed, and an electrode 35 is connected to the piezoelectric element 34. When a voltage is applied to the electrode 35, the piezo element 34 is deformed and vibrates the ink in the pressure chamber. Thereby, ink is ejected from the nozzle n. Here, the second ink flow path 33 described above is formed narrower than the first ink flow path 31. This is because, when the second ink flow path 33 is thick, it becomes impossible to give the necessary ejection speed to the ink ejected from the nozzle n.

  In the present embodiment, a case where the clogging prevention mechanism according to the present invention is provided in the lateral flow path 33b of the second ink flow path 33 will be described as an example. When the pigment contained in the ink adheres to or stays in the second ink flow path 33, the fluidity of the ink flowing through the second ink flow path 33 decreases, and this causes the nozzle The discharge speed of ink from n becomes slow.

  FIG. 3 schematically shows a clogging prevention mechanism 40 according to this embodiment. This figure shows a longitudinal section obtained by cutting the transverse flow path 33b of the second ink flow path 33 shown in FIG. 2 in a direction orthogonal to the longitudinal direction (ink flow direction).

  As shown in the figure, the clogging prevention mechanism includes a first conductive channel member 41 and a second conductive channel member 42. In the boundary surfaces 41a and 42a of the first and second conductive flow path members 41 and 42, grooves having a substantially semicircular cross section are formed, respectively. A lateral flow path 33b (hereinafter simply referred to as “ink flow path 33”) of the second ink flow path 33 having a substantially circular cross-section is formed between 42a. The first and second conductive flow path members 41 and 42 are bonded to each other by an insulating adhesive 43 at the boundary surfaces 41a and 42a. The thickness of the insulating adhesive 43 is several μm. One end and the other end of a circuit 45 having an AC power supply 44 are connected to the first and second conductive flow path members 41 and 42, respectively. That is, the first conductive flow path member 41 functions as a first electrode, and the second conductive flow path member 42 functions as a second electrode. As the first and second conductive flow path members 41 and 42, for example, stainless steel can be used. Further, as the insulating adhesive 43, an adhesive that maintains adhesive strength over a long period of time and is excellent in solution resistance (ink resistance) is used.

  The ink flow path 33 has a diameter of, for example, about 10 μm, and ink used for printing of the inkjet recording apparatus 10 (see FIG. 1) flows through the ink flow path 33. The ink is a solution formed by dispersing the pigment G as a solute in a solvent (for example, water). The pigment G tends to be negatively charged when dispersed in a solvent.

  As described above, the clogging prevention mechanism according to the present embodiment is configured by the first and second conductive flow path members 41 and 42, the insulating adhesive 43, and the circuit 45. Among these, The first and second conductive flow path members 41 and 42 and the insulating adhesive 42 are also components of the inkjet head 12a. However, unlike this embodiment, when the first and second conductive flow path members 41 and 42 are not connected by the circuit 45, an adhesive that is not insulating is used instead of the insulating adhesive 43 described above. It is possible to use. In the present embodiment, in particular, the adhesive is used as the conductive adhesive 43 in order to use the first and second conductive flow path members 41 and 42 as the first and second electrodes, respectively, as described above. Instead of using the conductive adhesive 43, it is also possible to use a thin plate-like conductive member and adhere it to the first and second conductive flow path members 41,. However, in this case, the number of parts increases and the number of manufacturing steps also increases.

  As the above-described inkjet head 12a is used, the pigment G in the ink adheres to the wall surface A of the ink flow path 33 or stays in the vicinity of the wall surface A. As the cause, for example, the conductive flow path members 41 and 42 act as a ground for the charged pigment G, and the smoothness of the plane of the wall surface A is not sufficient with respect to the size of the pigment G. It is conceivable that the pigment G is easily caught on the surface irregularities.

  As described above, if the pigment G adheres or stays in the ink flow path 33, this interferes with the ink flowing in the ink flow path 33, and the fluidity of the ink decreases. As a result, the discharge speed of the ink from the nozzle n decreases, and discharge failure occurs.

  In this embodiment, an alternating voltage is applied between the first and second conductive flow path members 41 and 42 to form an alternating electric field in the ink flow path 33 in a direction perpendicular to the ink flow. Thus, the adhering or staying pigment G is vibrated along the electric field (in the direction of the arrow in FIG. 3), thereby preventing or eliminating the sticking or staying.

  FIG. 4 shows the experimental results of this embodiment as Example 1. An AC voltage having a voltage value of ± 5 V and a frequency of 50 Hz was applied to the first and second conductive flow path members 41 and 42 via the circuit 45 under the following conditions. An alternating voltage was applied for 1 minute every other hour for 10 days while the ink flow path 33 was filled with ink, and the rest were left unattended. The initial ink discharge speed from the nozzle n when the ink is circulated through the ink flow path 33 is measured to obtain the initial discharge speed in FIG. 4, and the ink discharge speed after 10 days is measured. It was. As a result, the initial discharge speed was 9.4 m / sec, and the discharge speed after standing was 9.3 m / sec. The measurement of the ejection speed employs a general method in which the flying state of the ink is photographed with a high-speed camera synchronized with the ejection signal.

  From the viewpoint of preventing the pigment from adhering to or staying in the ink flow path 33, it is effective to keep applying the AC voltage. However, in this case, a small amount of ions in the ink are deposited, or corrosion of the first and second conductive flow path members 41 and 42 acting as electrodes is promoted. Further, although depending on the viscosity of the ink and the temperature in the ink flow path 33, the ink fluidity starts to be affected after 90 to 150 minutes have passed in the state of being left. In other words, it was confirmed that adhesion and retention progressed as the fluidity of the ink changed.

  Considering the above, as a condition that is effective in preventing adhesion and staying and does not adversely affect the durability of the first and second conductive flow path members 41 and 42, 1 is set every 1 hour. It is preferable to apply an alternating voltage of about a minute.

  Here, the reason why the AC voltage is set to a voltage value of ± 5 V and a frequency of 50 Hz will be described. As for the voltage value ± 5V, the voltage applied to the above-described piezo element 34 (see FIG. 2) is 20 or more volts, and therefore when the absolute value of the voltage value of the AC voltage increases and approaches this value, the piezo element 34 Unnecessary effects will be given. Further, when the voltage value is high, the insulating adhesive 43 tends to cause dielectric breakdown. Further, in the present invention, a sufficient effect can be expected with a voltage value of ± 5 V for preventing the adhesion or retention of the pigment G in the ink flow path 33, and the voltage value of ± 5 V can be easily obtained in the ink jet recording apparatus 10. It is because it can be obtained. On the other hand, if the frequency is 50 Hz, if it is too high, not only the pigment G that is a solute but also the entire ink that is a solution is vibrated, and ink may be unnecessarily ejected from the nozzle n. Similarly to the case of the voltage value, a sufficient effect can be expected with a voltage value of 50 Hz for preventing the adhesion or retention of the pigment G in the ink flow path 33, and a frequency of 50 Hz can be easily obtained as a general power source. Because it can.

<Embodiment 2>
FIG. 5 schematically shows a clogging prevention mechanism 50 according to this embodiment. 2 is a vertical cross section obtained by cutting a horizontal flow path 33b (hereinafter simply referred to as “ink flow path 33”) of the second ink flow path 33 shown in FIG. 2 in a direction perpendicular to the longitudinal direction. Show. In addition, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is appropriately omitted.

  As shown in the figure, in the present embodiment, the first conductive flow path member 51 and the second conductive flow path member 52 are respectively formed in layers, and the first insulating member 53 and the second conductive flow path member 52 are respectively formed. Two insulating members 54 are provided on the surface. Further, the groove that becomes the ink flow path 33 is formed only on the second insulating member 54 side, and the first insulating member 53 side has a configuration like a cover of this groove. Then, by laminating the first and second conductive flow path members 51 and 52 of the first and second insulating members 53 and 54 with the insulating adhesive 43, respectively, on the boundary surface between them. An ink flow path 33 having a substantially rectangular cross section is formed. As in the first embodiment, one end and the other end of the circuit 45 having the AC power supply 44 are connected to the first and second conductive flow path members 51 and 52, respectively. That is, the first conductive flow path member 51 functions as a first electrode, and the second conductive flow path member 52 functions as a second electrode.

  Also in the second embodiment, the experiment was performed under the same conditions as in the first embodiment. That is, an AC voltage having a voltage value of ± 5 V and a frequency of 50 Hz was applied to the first and second conductive flow path members 51 and 52 through the circuit 45 under the following conditions. While the ink flow path 33 was filled with ink, an AC power supply was applied every 1 hour for 10 days, and the rest were left unattended. The initial ink discharge speed from the nozzle n when the ink was circulated through the ink flow path 33 was measured to obtain an initial discharge speed, and the ink discharge speed after 10 days was measured to be the discharge speed after standing. The results are shown in Example 2 in FIG. As shown in the figure, the initial discharge speed was 9.2 m / sec, and the discharge speed after being left was 9.2 m / sec. That is, also in this embodiment, by applying the AC voltage as described above, it was possible to prevent the adhesion and retention of the pigment G in the ink in the ink flow path 33.

<Comparative Example 1>
FIG. 4 shows Comparative Example 1. The comparative example 1 has the same configuration as the above-described first embodiment. However, unlike the first embodiment, nothing is performed without applying an AC voltage in a state where the ink flow path 33 is filled with ink. Then, the same measurement as in Example 1 was performed. In Comparative Example 1, the initial discharge speed of the ink from the nozzle n was 9.4 m / sec, but the discharge speed after being left decreased to 7.5 m / sec. As a result, the ink ejected from the nozzle n did not land properly on the sheet material P, and the image quality on the sheet material P was deteriorated.

<Embodiment 3>
In the third embodiment, the same measurement as that in the first embodiment is performed after applying the AC voltage for 1 minute after performing the measurement of the above-described comparative example 1. The results are shown as Example 3 in FIG. In both Comparative Example 1 and Example 3, the initial discharge speed was the same as 9.4 m / sec. On the other hand, the discharge speed after standing was 7.5 m / sec in Comparative Example 1, whereas it increased to 8.6 m / sec in Example 3, indicating that it was clearly improved.

  In the above first to third embodiments, the case where the cross-sectional shape of the ink flow path 33 is circular or rectangular has been described as an example. However, the present invention is subject to some restrictions on the cross-sectional shape of the ink flow path 33. is not. That is, the present invention can be applied to the ink flow path 33 having an arbitrary cross-sectional shape.

  The case where the clogging prevention mechanism according to the present invention is applied to the ink jet head of the ink jet recording apparatus has been described above as an example, but the present invention is not limited to this. The clogging prevention mechanism according to the present invention can be generally applied to a case where a solute dispersed in a charged state in a solvent is prevented from adhering or staying in a solution flow path. Examples of the solute in this case include metal particles, inorganic particles, organic particles such as polyester, and DNA other than the pigments used in the ink.

  The clogging prevention mechanism of the present invention is applied to an ink jet head of an ink jet recording apparatus to exemplify a mode of preventing clogging of an ink flow path. This can also be applied to the case where the solute dispersed in (1) is prevented from adhering or staying in the solution flow path.

It is the figure which looked at the inkjet recording device from the left side toward the sheet material conveyance direction. It is a figure which shows typically the longitudinal cross-section of an inkjet head. It is a figure which shows typically the longitudinal cross-section of the clogging prevention mechanism of Embodiment 1. FIG. 6 is a diagram comparing the initial ink ejection speed and the after-leaving ejection speed in Example 1, Example 2, Comparative Example 1, and Example 3. It is a figure which shows typically the longitudinal cross-section of the clogging prevention mechanism of Embodiment 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12a-12d ... Inkjet head, 33 ... 2nd ink flow path (ink flow path, solution flow path), 40, 50 ... Clogging prevention mechanism, 41, 51 ... 1st 1 conductive flow path member, 41a, 42a ... boundary surface, 42, 52 ... second conductive flow path member, 43 ... insulating adhesive, 44 ... AC power supply, 45 ... circuit, 53 , 54 ... Insulating member, G ... Pigment (solute), n ... Nozzle, S ... Sheet material

Claims (4)

In a clogging prevention mechanism for removing the solute that adheres and stays in a solution flow path through which a solution composed of a solvent and a solute dispersed in a charged state in the solvent flows.
Two conductive flow path members that are in close contact with each other and constitute the solution flow path on the boundary surface;
An insulating adhesive for adhering the two conductive flow path members at the boundary surface;
A circuit for applying an alternating voltage between the two conductive flow path members,
Applying an alternating voltage between the two conductive flow path members by the circuit to form an alternating electric field between the two conductive flow path members to vibrate the solute in the solution flow path;
A clogging prevention mechanism characterized by that. The solute is a pigment, the solution is ink, and the solution channel is an ink channel formed in an inkjet head.
The clogging prevention mechanism according to claim 1. The conductive flow path member is formed in a layer on the surface of the insulating member,
The clogging prevention mechanism according to claim 1 or 2, characterized by the above. In an inkjet recording apparatus comprising: a conveying unit that conveys a sheet material to a printing unit; and an inkjet head that performs printing by discharging ink from nozzles to the sheet material conveyed to the printing unit.
The clogging prevention mechanism according to claim 2 or 3 is provided for the inkjet head.
An ink jet recording apparatus.

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