JP2009045848A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of reliably discharging bubbles and foreign matters in a common liquid chamber with a simple configuration by initial filling in a long head.
A liquid discharge head (1) is provided with a plurality of communication pipes (4a, 4b, 4c) communicating with a common liquid chamber (103). A supply path (7) connected to a pump (3) is connected to an ink flow control means (5). Branching paths 5a, 5b and 5b are formed which branch to correspond to 4b and 4c and lead to the respective communication pipes 4a, 4b and 4c. The branch pipes 5a, 5b and 5c are connected to the communication pipes 4a, 4b and 4c, respectively. Opening / closing means 8a, 8b, and 8c for individually opening and closing are provided, and the communication pipes 4a to 4c that supply ink by sequentially opening / closing the opening / closing means 8a, 8b, and 8c when performing initial filling are sequentially changed.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a liquid discharge head.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, or a multifunction machine of these, for example, a liquid ejection apparatus including a recording head constituted by a liquid ejection head (also referred to as a droplet ejection head) that ejects liquid droplets. The liquid is used while transporting the medium (hereinafter also referred to as “paper”, but the material is not limited, and the recording medium, recording medium, transfer material, recording paper, etc. are also used synonymously). In some cases, image formation (recording, printing, printing, and printing are also used synonymously) is made to adhere to the film.

  The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The term “meaning that a meaningful image such as a character or a figure or a meaningless image such as a pattern” is added to the medium. Further, the liquid is not limited to the recording liquid and the ink, and is not particularly limited as long as it is a liquid capable of forming an image (hereinafter, “ink” is a general term for liquid).

  An inkjet head as a liquid ejection head used in such an image forming apparatus includes a nozzle that ejects ink droplets, an individual liquid chamber that communicates with the nozzle, and a common liquid chamber that communicates with the individual liquid chamber via a fluid resistance unit. The pressure generating means generates pressure to pressurize the ink filled in the individual liquid chamber, and the ink droplets are ejected from the nozzles by applying pressure to the individual liquid chamber by the pressure generating means.

  In order to make such an ink jet head usable, first, a process of filling ink supplied from an ink cartridge or the like into a flow path from a common liquid chamber to an nozzle through an individual liquid chamber (this process) Is referred to as “initial filling”).

  If bubbles remain in the flow path during the initial filling, the ink droplet ejection performance is adversely affected. In particular, in recent years, in order to realize high-speed printing, inkjet heads tend to be longer and have more nozzles, and accordingly, the common liquid chamber has to be lengthened. It is becoming more difficult to completely discharge the ink and completely fill the flow path with ink. In addition to the bubbles, it is preferable that, for example, minute foreign matters mixed in the manufacturing process can be discharged together with the bubbles during the initial filling.

Therefore, for example, Patent Document 1 discloses that the cross-sectional area of the common liquid chamber is reduced as the distance from the ink supply pipe (hereinafter referred to as “connecting pipe”) decreases, so that the flow velocity at the end of the common liquid chamber is prevented and bubble discharge is promoted. It is described to do.
JP 2002-264329 A

Further, Patent Document 2 adopts a structure in which a flow path connecting an ink reservoir tank and a common liquid chamber is branched and ink is dispersed by a plurality of tributaries and supplied to the common liquid chamber. It is described that ink can be stably supplied even with an ink jet head.
Japanese Patent Laid-Open No. 2002-361892

On the other hand, a so-called ink circulation system is also known in which ink is circulated between an ink reservoir tank and an inkjet head (common liquid chamber) (see, for example, Patent Documents 3 to 6).
JP 2006-168023 A JP 2006-159722 A JP 2006-068904 A JP 2004-160907 A

  However, even with the configuration of Patent Document 1, a decrease in the flow velocity at a position farthest from the connecting pipe is unavoidable, and there is a problem that ejection failure is likely to occur in the nozzle communicating with the corresponding position. Further, in the configuration of Patent Document 2, ink that flows from the ink reservoir tank via each branch collides with the inside of the common liquid chamber, and stagnation with a slow ink flow velocity occurs in some places. There exists a possibility that it may stay, and there exists a subject that it is not preferable from a viewpoint of initial filling.

  On the other hand, in the ink circulation system, since a constant flow rate can be always maintained in the flow path, efficient bubble / foreign matter removal can be expected, but there is a problem that the apparatus becomes larger and the cost is increased due to the complicated flow path.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce ejection defects due to retention of bubbles and foreign matters in initial filling, and to ensure ejection stability.

  In order to solve the above problems, an image forming apparatus according to the present invention is configured to supply a liquid to a common liquid chamber while sequentially changing a plurality of connection pipes communicating with a common liquid chamber of a liquid discharge head and a communication pipe supplying liquid. And an initial filling means.

  Here, a plurality of opening and closing means for individually opening and closing the plurality of connecting pipes can be provided, and the opening and closing of the plurality of opening and closing means can be sequentially changed, and in this case, a region communicating with the plurality of connecting pipes in the common liquid chamber The liquid chamber side opening / closing means for dividing the liquid chamber side opening / closing means can be provided to open and close in conjunction with the opening / closing means of the communication pipe.

  In addition, a plurality of pump means for sucking and pressurizing the liquid may be provided in each of the plurality of connecting pipes, and the suction and pressurization of the plurality of pump means may be sequentially changed.

  According to the image forming apparatus of the present invention, the common liquid chamber is configured by sequentially changing the plurality of connection pipes communicating with the common liquid chamber of the liquid ejection head and the communication pipe through which the liquid flows by controlling opening and closing of the plurality of opening and closing means. Therefore, it is possible to reduce ejection failure due to retention of bubbles and foreign matters in the initial filling, and to secure ejection stability.

Embodiments of the present invention will be described below with reference to the accompanying drawings. A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic explanatory view of an ink supply system in the image forming apparatus of the embodiment, and FIG. 2 is an explanatory plan view for explaining the flow path configuration of the liquid ejection head.
In this image forming apparatus, a liquid discharge head 1 that discharges droplets, an ink tank (ink cartridge) 3 that contains ink to be supplied to the liquid discharge head 1, and ink in the ink tank 2 are pressure-fed to the liquid discharge head 1. A pump 3 and an ink flow control unit 5 that is interposed between the liquid discharge head 1 and the pump 3 and opens and closes a plurality of communication pipes 4 that communicate with the common liquid chamber of the liquid discharge head 1 are provided.

  As shown in FIG. 2, the liquid ejection head 1 includes a plurality of nozzles 101 that eject droplets, individual liquid chambers 102 that communicate with the nozzles 101, and individual liquid chambers 102 via fluid resistance units 104. And a common liquid chamber 103 for supplying ink, and pressure generating means (not shown) for generating energy for pressurizing the ink in the individual liquid chamber 102. By selectively driving each pressure generating unit of the liquid discharge head 1, it is possible to discharge the droplets from the nozzle 101 and discharge the droplets onto the conveyed paper to form an image.

  The liquid discharge head 1 is provided with a plurality of (in this case, three) communication pipes 4 a, 4 b, 4 c (referred to as “communication pipe 4” when not distinguished) that communicate with the common liquid chamber 103. . In this case, in the longitudinal direction of the common liquid chamber 103 (arrangement direction of the nozzles 101), the communication pipe 4a is set at one end (the left end), the communication pipe 4b is set at the center, and the other end (the right end). ) Is connected to the communication pipe 4c.

  The ink flow control means 5 branches the supply path 7 connected to the pump 3 corresponding to the communication pipes 4a, 4b, and 4c, and branch paths 5a, 5b, and 5b communicating with the communication pipes 4a, 4b, and 4c are formed. The branch paths 5a, 5b and 5c are provided with opening / closing means 8a, 8b and 8c for individually opening and closing the communication pipes 4a, 4b and 4c. The opening / closing means 8a, 8b, 8c are constituted by, for example, a shutter and are driven by a driving means (not shown).

FIG. 3 is a block explanatory diagram showing a part related to control relating to the initial filling of the apparatus.
The initial filling control means 21 controls the opening and closing means 8a to 8c by controlling the driving means 22a to 12d to perform opening and closing of the communication pipes 4a to 4b communicating with the common liquid chamber 103 when performing the initial filling. Control is performed to sequentially change. Note that the initial filling control means 21 also performs drive control of the pump 3. The initial filling control means 21 is configured as program firmware.

Next, an initial filling operation for the liquid ejection head in the embodiment configured as described above will be described with reference to FIG.
In this apparatus, the open / close means 8a to 8c that are opened by the initial filling control means 21 are controlled to open and close, thereby individually connecting the communication pipes 4a to 4c that supply ink to the common liquid chamber 103. Can be selected.

  For example, as shown in FIG. 4A, the shutter 8a is opened (illustrated by phantom lines), and the shutters 8b and 8c are blocked (illustrated by solid lines) to be supplied from the supply path 7. As shown by the arrow, the ink to be supplied is supplied to the common liquid chamber 103 from the communication pipe 4a at the left end and flows toward the right end. Similarly, when the shutter 8b is opened and the shutters 8a and 8c are shut off as shown in FIG. 4B, the ink supplied from the supply path 7 is connected to the central communication tube 4b as indicated by an arrow. Is supplied to the common liquid chamber 103 and flows toward the left and right ends. Similarly, when the shutter 8c is opened and the shutters 8a and 8b are shut off as shown in FIG. 4C, the ink supplied from the supply path 7 is connected to the right end communication tube 4b as indicated by an arrow. Is supplied to the common liquid chamber 103 and flows toward the left end.

  As a result of measuring the flow rate of the ink in the common liquid chamber 103 in each of these states, as shown in FIG. 5, in the longitudinal direction of the common liquid chamber, in the state of FIG. The flow velocity on the side is relatively fast and slows toward the right end, and as shown by the solid line in FIG. 4B, the flow velocity on both sides of the center is relatively fast and slows toward both sides. Thus, in the state of FIG. 4C, the flow velocity on the right end side is relatively fast as shown by the two-dot chain line, and becomes slower toward the left end portion.

  Accordingly, the ink flow control means 5 changes the connecting pipes 4a to 4c that selectively supply ink at the time of initial filling in order, and thereby the flow velocity is sufficient to discharge bubbles and foreign matters almost in the entire area of the common liquid chamber 103. Can be ensured, ejection failure due to retention of bubbles and foreign matters can be reduced, ejection stability can be ensured, and the initial printing failure rate can be reduced.

  For example, the shutters 8a to 8c of the ink flow control means 5 are opened in the order of shutter 8a → shutter 8c → shutter 8b every predetermined time after all the shutters 8a to 8c are opened for a predetermined time as shown in FIG. When the test printing is performed with the control sequence for changing the shutter to be changed (the other shutters are shut off) and test printing is performed, the initial printing failure rate (discharge failure rate when printing is performed for the first time after initial filling) Was significantly reduced. In this case, since the nozzle 101 at the endmost in the longitudinal direction of the common liquid chamber 103 has many ejection defects, when the nozzle 101 is not subjected to a printing test (non-driven), the initial printing defect rate is further increased. Declined.

  That is, for comparison, as shown in FIG. 7, in the case where only the central communication pipe 4b that is always open is used, the printing failure nozzle after the initial filling and the common liquid chamber at the location where the corresponding nozzle communicates. As a result of measuring the relationship with the flow velocity of ink, as shown in FIG. 8, the ink flow velocity takes a minimum value near the central portion of the common liquid chamber 103 into which ink flows from the connecting pipe 4b, and is maximal on the left and right sides of the central portion. The nozzle 101 communicating with a portion having a high flow velocity has a low initial printing failure rate, and conversely, the nozzle 101 communicating with a portion having a low flow velocity tends to have a high initial printing failure rate.

  Therefore, it is understood that the flow rate in the common liquid chamber at the time of initial filling and the initial printing defect rate for each nozzle are closely related. Therefore, as in the above-described embodiment, the initial printing defect rate can be reduced by ensuring a sufficient flow rate throughout the common liquid chamber during the initial filling.

  Thus, a plurality of connecting pipes communicating with the common liquid chamber of the liquid discharge head, and a means for filling the common liquid chamber with liquid while sequentially changing the communication pipes through which the liquid flows by controlling opening and closing of the plurality of opening and closing means. By providing the above, it is possible to reduce ejection failure due to retention of bubbles and foreign matters in the initial filling, and to secure ejection stability. In this case, the communication pipe can be opened and closed with a simple configuration by using the shutter means as the opening and closing means.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic explanatory diagram of a main part of the embodiment.
In the above-described embodiment, the ink flow control means 5 is configured to select only one connecting pipe for supplying ink from the plurality of connecting pipes 4a to 4c, whereas in this embodiment, the plurality of connecting pipes is selected. In this configuration, the flow rate is weighted with respect to 4a to 4c, and the ink can be supplied or the ink can be sucked from the common liquid chamber 103.

  That is, the ink flow control means 5 is provided with the micropumps 18a and 18c in the branch paths 5a and 5c communicating with the communication pipes 4a and 4c, so that the supply to the common liquid chamber 103 and the suction from the common liquid chamber 103 are performed. The supply flow rate and suction flow rate can be controlled at this time.

  Therefore, for example, when the flow rate supplied from the ink tank 2 is Q, the ink is supplied from the connection pipe 4a to the common liquid chamber 103 at a flow rate of 0.8Q by the pump 18a, and 0 is supplied to the connection pipe 4c by the pump 18c. When the ink is controlled to flow from the common liquid chamber 103 at a flow rate of 2Q, the flow velocity in the common liquid chamber 103 is as shown in FIG.

  That is, when the supply pipe 4a is simply supplied (in the case of FIG. 4 (a)), the flow velocity changes as shown by the one-dot chain line in FIG. 10, whereas the supply is made from the communication pipe 4a as described above. By performing suction from the tube 4c, as shown by a solid line in FIG. 10, the flow rate on the left end side of the common liquid chamber 103 is slightly reduced, but the flow rate on the right end portion can be increased.

  As described above, although the maximum flow velocity in the common liquid chamber is slightly reduced, it is possible to improve the region where the minimum flow velocity is achieved, and it is possible to discharge bubbles and foreign matters more reliably. In the above configuration, when supplying from the central communication pipe 4b, both the pumps 18a and 18c can perform suction to increase the flow velocity at the left and right ends.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 11 is a schematic explanatory diagram of a main part of the embodiment.
Here, in the common liquid chamber 103 of the liquid discharge head 1, liquid chamber side opening / closing means 9a and 9b such as shutters are provided to divide the area communicating with the connection pipes 4a to 4c with the central communication pipe 4b interposed therebetween. The opening and closing means 9a and 9b of the liquid chamber side are opened and closed in conjunction with the opening and closing means 8a to 8c of the communication pipes 4a to 4c by the initial filling control means 21 described above.

  Here, as shown in FIG. 12A, when the right opening / closing means (shutter) 9b is closed, the left shutter 9a is opened, and ink is supplied from the central communication tube 4b, the position in the longitudinal direction of the common liquid chamber 13 changes as shown by the solid line in FIG. 13, while the left opening / closing means (shutter) 9a is closed and the right shutter 9b is opened as shown in FIG. 12B, and the central communication tube 4b is opened. When the ink is supplied from the flow rate, the flow velocity at the position of the common liquid chamber in the longitudinal direction changes as shown by the broken line in FIG.

  As a result, the flow rate when ink is supplied from the central communication tube 4a can be increased (compared to the flow rate indicated by the solid line in FIG. 5).

  Therefore, for example, the shutters 8a to 8c of the ink flow control means 5 and the shutters 9a and 9b of the head 1 are opened for a predetermined time after all the shutters 8a to 8c, 9a and 9b are opened for a predetermined time as shown in FIG. Every time, the shutter 8b and the shutter 9b are simultaneously opened (the others are shut off), ink is supplied from the central communication tube 4b to the right side area of the common liquid chamber 103, and then the shutter 8b and the shutter 9a are simultaneously opened. (The others are shut off), ink is supplied from the central communication tube 4b to the left side region of the common liquid chamber 103, and then the shutter 8a and the shutters 9a, 9b are opened simultaneously (the others are shut off), and the left communication tube Ink is supplied from 4a to the common liquid chamber 103, then the shutter 8c and the shutters 9a and 9b are simultaneously opened (the others are shut off), and the ink is supplied from the right communication tube 4c to the common liquid chamber 103. When the test printing is performed by controlling the opening and closing with a control sequence for changing the shutter to be in the open state (the other shutters are shut off), the initial printing defect rate is significantly reduced as compared with the first embodiment. It was. In this case, the nozzle 101 at the extreme end with respect to the longitudinal direction of the common liquid chamber 103 is not subject to the print test (not driven).

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 15 is a schematic explanatory diagram of a main part of the embodiment.
In this embodiment, the communication pipes to the liquid ejection head 1 in the second embodiment are the left and right communication pipes 4a and 4c, and the ink flow control means 5 has a micropump 18a corresponding to each of the communication pipes 4a and 4c. 18b is arranged, and the opening / closing means 8a to 8c are omitted.

  Then, as shown in FIG. 16, pressurization (supply) and suction of the micropumps 18a and 18b are alternately repeated every predetermined time to perform initial filling, and test printing is performed, as compared with the first embodiment. The initial printing defect rate was significantly reduced.

FIG. 2 is a schematic explanatory diagram of an ink supply system of the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is an explanatory plan view for explaining the flow path configuration of the liquid ejection head. It is a block explanatory drawing used for description of the part which concerns on control of the initial filling operation | movement of the same apparatus. It is explanatory drawing which shows an example of the control sequence of the opening / closing means of an ink flow control means. It is explanatory drawing with which it uses for description of the open / close state of the opening / closing means and the ink filling supply from each communication pipe. It is explanatory drawing with which it uses for description of the relationship between the communicating pipe filled with ink and the flow velocity in a common liquid chamber longitudinal direction position. FIG. 6 is a schematic explanatory diagram for explaining a liquid ejection head of a comparative example. It is explanatory drawing which shows an example of the relationship of the ink filling supply of the same comparative example, the flow rate in the position of a common liquid chamber longitudinal direction, and the incidence rate of an initial expected printing defect. It is a principal part schematic explanatory drawing which shows 2nd Embodiment of this invention. It is explanatory drawing which shows an example of the relationship between the ink filling supply in the same embodiment, and the flow velocity in a common liquid chamber longitudinal direction position. FIG. 6 is a schematic explanatory diagram of an ink supply system of an image forming apparatus according to a second embodiment of the present invention. It is explanatory drawing with which it uses for description of the opening / closing control of the liquid chamber side opening / closing means in the embodiment. It is explanatory drawing which shows an example of the relationship of the flow velocity in the common liquid chamber longitudinal direction position at the time of performing the same opening / closing control. It is explanatory drawing which shows an example of the control sequence of the opening / closing means and liquid chamber side opening / closing means of the embodiment. It is a principal part schematic explanatory drawing which shows 4th Embodiment of this invention. It is explanatory drawing which shows an example of the control sequence of the pump of the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid discharge head 2 ... Ink tank 3 ... Pump 4a, 4b, 4c ... Communication pipe 5 ... Ink flow control means 7 ... Supply path 8a, 8b, 8c ... Opening / closing means (shutter)
9a, 9b ... Liquid chamber side opening / closing means (shutter)
18a, 18b ... Pump 101 ... Nozzle 102 ... Individual liquid chamber 103 ... Common liquid chamber

Claims (4)

In an image forming apparatus including a liquid discharge head that supplies liquid from a common liquid chamber to a plurality of individual liquid chambers that communicate with each of a plurality of discharge ports that discharge liquid.
A plurality of connecting pipes communicating with a common liquid chamber of the liquid discharge head;
An image forming apparatus comprising: means for initially filling the liquid into the common liquid chamber while sequentially changing the communication pipe for supplying the liquid.   2. The image forming apparatus according to claim 1, further comprising a plurality of opening / closing means for individually opening / closing the plurality of connecting pipes, wherein the opening / closing of the plurality of opening / closing means is sequentially changed.   3. The image forming apparatus according to claim 2, further comprising: a liquid chamber side opening / closing means that divides an area communicating with the plurality of connection pipes in the common liquid chamber, wherein the liquid chamber side opening / closing means is opened and closed. An image forming apparatus that opens and closes in conjunction with the means.   2. The image forming apparatus according to claim 1, wherein the plurality of connecting pipes are provided with a plurality of pump units that respectively perform suction and pressurization of liquid, and the suction and pressurization of the plurality of pump units are sequentially changed. An image forming apparatus.

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