JP5052426B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  An ink jet recording apparatus (ink jet printer) that performs printing by using a liquid ejecting apparatus that ejects (discharges) liquid to a recording medium (also referred to as a medium) as a recording head is very small from the nozzle of the recording head to the medium. An ink droplet is ejected to record an image such as a desired character or figure. Among this type of ink jet recording apparatus, there is a line printer that performs printing using a line head in which a plurality of nozzles are arranged in a line on a medium while the medium is conveyed by a belt. When printing by ejecting ink from a large number of nozzles of the line head to the media that is being conveyed in this way, if you are waiting without ejecting ink, use the opening at the tip of the nozzle. Liquid such as water in the ink evaporates, resulting in an increase in ink viscosity. For this reason, the ink may not be ejected normally when the ink is ejected next time. In order to prevent this, the line head of the ink jet recording apparatus needs to perform idle ejection (also referred to as preliminary ejection) for ejecting ink at a constant interval apart from image formation.

  Line printers can perform high-speed printing, and often perform large-scale printing at a time. Therefore, compared with a serial printer, it is necessary to repeat the idle ejection of ink for recovering the non-printing nozzles at an appropriate timing. Usually, the ink at the time of idle ejection is idlely ejected through a hole provided in a part of the conveyance belt that conveys the recording medium to a liquid receiving portion (waste liquid tank) that accommodates an idle ejection liquid provided below the conveyance belt. .

  For example, Patent Document 1 discloses a recording medium in an image recording apparatus (see FIG. 23) for the purpose of preventing the deterioration of the conveyance belt and the image recording accuracy and significantly reducing the manufacturing effort and cost. And a plurality of ink discharge ports 3a arranged in parallel along a direction perpendicular to the conveyance direction of the recording medium, and disposed above the conveyance path of the recording medium. In the image recording apparatus 1 including the line head 3, the transport belt 2 has a hole 2 </ b> A provided to face each of the ink discharge ports 3 a and is disposed below the transport path of the recording medium. An image recording apparatus including a waste ink collection container 4 that receives ink that has been preliminarily ejected and passed through a hole 2A from an ink ejection port 3a is disclosed.

  In Patent Document 2, for the purpose of providing an ink jet printer capable of reducing the number of parts required for maintenance work of the line head and improving workability, a line head having a plurality of discharge ports and a substantially flat plate shape are formed. A platen that contacts the recording medium on the surface facing the ejection port, and a plurality of openings are arranged at substantially equal intervals along the direction in which the ejection port is disposed on the portion facing the ejection port of the platen, and the platen is ejected from the platen. A platen moving mechanism that moves in the arrangement direction, a line head control unit that controls the drive of the line head so that the waste ink is discharged only from the discharge port that is located at a position facing the opening, and the discharge port across the opening And an ink receiving container that stores waste ink discharged from the discharge port during the maintenance operation of the line head through the opening. Recording apparatus is disclosed.

  If the waste ink collecting container 4 and the ink receiving container as described above are provided, the empty discharge liquid will not be directly scattered on the conveying belt or the recording medium, and the recording medium or the like will not be soiled. However, in the discharge liquid sprayed into the empty discharge receiving member, in addition to the main droplets that reach the lower portion of the empty discharge receiving member in a relatively large particle almost linearly and stay in the lower portion of the empty discharge receiving member as liquid, There is also a thing that becomes a mist and floats before reaching the lower part of the empty discharge receiving member. If this mist leaks from the idle discharge receiving member, the conveyor belt and the recording medium may be soiled.

  In particular, when waste ink discharged in the empty discharge receiving member accumulates, the level of waste ink in the empty discharge receiving member rises, and the space is reduced, the waste ink is scattered by the impact of empty discharge and mist is generated. The mist easily leaks out of the empty discharge receiving member, and the possibility of soiling the conveyance belt and the recording medium is increased. A line printer that performs mass printing has a large number of idle ejections and a large amount of idle ejection ink. For this reason, measures against leakage of ink mist from the idle discharge receiving member are an important issue.

  As one countermeasure, it is conceivable that the waste liquid tank portion of the empty discharge receiving member is enlarged to always secure a desired space in the empty discharge receiving member. However, when a line printer is used for commercial printing, the continuous printing time per time is long, the frequency of empty ejection for recovering the non-printing nozzles is increased, and the amount of waste liquid collected in the waste liquid tank is also increased. However, if the waste liquid tank is enlarged, the apparatus itself becomes large and handling of the waste liquid tank becomes difficult. Generally, when the waste liquid tank is full or nearly full, a method of replacing it with a new one is taken. When replacing the waste liquid tank, it is necessary to stop the apparatus. If the apparatus is stopped for replacement during continuous printing in commercial printing, there is a problem that work efficiency decreases.

  For this reason, various apparatuses and methods have been proposed for collecting mist accompanying ink that has been ejected preliminarily (preliminarily ejected). For example, Patent Document 3 discloses a case where the nozzle head of the line head 20 recovers the nozzle discharge performance when an image is formed by ejecting liquid onto the medium with the line head while the medium is transported by the transport unit. A liquid ejecting apparatus is disclosed that collects ink in a waste ink tank while sucking the discharged liquid by a pump 230 via a liquid receiving portion 21 and a tube 235 to create an air flow (see FIG. 24).

  Further, Patent Document 4 discloses a liquid ejecting apparatus that is considered to be an improved type relating to the mist processing of the liquid ejecting apparatus described in Patent Document 3. The liquid ejecting apparatus includes mist collecting means for sucking air containing mist from a liquid receiving portion through a duct with a fan and absorbing the mist with a mist absorbent.

Patent Document 5 discloses an ink jet recording apparatus that can effectively prevent ink contamination in the apparatus and ink contamination of a recording medium even when ink mist is generated during preliminary ejection or the like. This ink jet recording apparatus includes an ink container that receives ink preliminarily ejected from a recording head, a suction fan that sucks ink mist generated during ink ejection between the line head and the ink container, and a sucked ink mist. An absorption filter for absorbing ink is provided, and a suction fan is operated during preliminary discharge to suck ink mist and absorb it into the absorption filter.
JP 2003-341106 A JP 2004-09515 A JP 2006-159556 A JP 2007-229550 A JP 2005-014487 A

  The image forming apparatuses disclosed in Patent Documents 1 and 2 include a device that collects the main droplets of ink that has been ejected in an idle manner, but have not yet taken measures against contamination caused by mist generated due to the ejection of the ink. In addition, the image forming apparatuses disclosed in Patent Documents 3 to 5 have a structure for collecting mist generated from the ink ejected idle. However, in the image forming apparatuses disclosed in Patent Documents 3 and 4, when the empty discharge amount is larger than the ink storage amount of the liquid receiving portion, not only the ink mist easily leaks, but also the replacement of the waste ink tank Also become frequent. In this case, the primary stop of the image forming apparatus is forced. Further, since the image forming apparatus disclosed in Patent Document 5 sucks air containing mist from the space between the line head and the liquid receiving portion, the sucked mist contaminates the conveyance belt and the recording medium. There is a fear.

  In the future, the continuous printing amount of line printers will further increase, and the amount of idle ejection for recovering non-printing nozzles during one continuous printing tends to increase. In a limited apparatus space, the capacity of the liquid receiving part that receives the empty ejection droplets cannot be increased so much. If the liquid receiving member becomes full or nearly full, it may be forced to stop due to machine convenience, and may stop in the middle of continuous printing, resulting in a problem that work efficiency is reduced. For this reason, it is conceivable to reduce the number of empty discharges and the amount of empty discharges in accordance with the capacity of the liquid receiving part, but this is not preferable in terms of print quality.

  In addition, if the continuous printing period becomes longer, the number of empty ejections during one continuous printing, the number of idle ejections increases, and the influence of contamination on the conveyance belt and recording medium due to mist leakage accompanying it increases. There has been a growing need to deal with small mist leaks that have not been a problem in the past.

  In view of the above-described problems, an object of the present invention is to provide a mist liquid that is generated when empty discharge liquid is discharged from a line head to a liquid receiving portion in an image forming apparatus including a line head type liquid discharge apparatus. An object of the present invention is to provide an image forming apparatus that suppresses leakage to the outside of the receiving part and enables long-term continuous operation.

The present invention relates to an image forming apparatus including a line head in which a plurality of nozzles for forming an image by discharging liquid onto a recording medium is disposed, and a liquid receiving portion for storing empty discharged liquid discharged from the nozzles. The liquid receiving portion includes a sub tank that receives the empty discharge liquid discharged from the nozzle, and a main tank that is detachably coupled to the bottom of the sub tank and stores the empty discharge liquid. The sub tank includes an openable / closable door and an opening / closing device that opens / closes the door, and a discharge pressure control device that controls a discharge pressure of the empty discharge liquid from the nozzle according to an attachment / detachment state of the main tank; the image forming apparatus according to claim Rukoto includes an air ejection timing control device for controlling the.

  Preferably, the present invention includes an empty discharge hole forming member in which an empty discharge hole is formed between the nozzle and the sub tank. The empty discharge hole guides the empty discharge liquid discharged from the nozzle to the sub tank. An image forming apparatus.

  In a preferred aspect of the present invention, the image forming apparatus is characterized in that the sub tank has a liquid absorbent material disposed at the bottom.

  In a preferred aspect of the present invention, the image forming apparatus is characterized in that the opening / closing device is disposed outside a discharge path of an empty discharge liquid discharged from the nozzle.

  In a preferred aspect of the present invention, the opening / closing device includes a spring member.

The reference invention is an image including a line head in which a plurality of nozzles for discharging a liquid to a recording medium are arranged, and a liquid receiving portion having a discharge liquid receiving port for receiving an empty discharge liquid discharged from the nozzles. In the forming apparatus, the liquid receiving portion includes an attracting device that attracts, from the vicinity of the discharge liquid receiving port, mist of the empty discharge liquid that is discharged from the discharge liquid receiving port to the inside . An image forming apparatus.

A preferred reference invention is the reference image forming apparatus, wherein the attracting device includes a suction fan and a mist adsorbing member that adsorbs the attracted mist.

A preferred reference invention is the reference image forming apparatus, wherein the mist adsorbing member is disposed on a side surface in the vicinity of the discharge liquid receiving port.

A preferred reference invention is the image forming apparatus according to the reference , wherein the attracting device includes an electrode that attracts mist by the action of an electric field.

A preferred reference invention is the reference image forming apparatus including a mist adsorbing member that adsorbs the attracted mist.

A preferred reference invention is the reference image forming apparatus, wherein the liquid receiving portion includes a partition member therein.

A preferred reference invention is the reference image forming apparatus, wherein the attraction device includes an attraction timing control device that controls a timing at which the mist is attracted.

  According to the present invention, in an image forming apparatus equipped with a line head type liquid ejection device, leakage of mist generated outside the liquid receiving portion when empty ejection liquid is idly discharged from the line head to the liquid receiving portion. It is possible to provide an image forming apparatus that can suppress long-term continuous operation.

  Embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and the configuration, function, and the like can be changed, omitted, and integrated within the scope of the object of the present invention.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a printing unit which is a main part of the image forming apparatus of the present invention. FIG. 2 is a plan view of an empty discharge hole forming member (in this embodiment, the conveyance belt also serves as the empty discharge hole forming member) provided with a liquid receiving portion. FIG. 3 is a plan view of the liquid receiving portion in a state where the conveyance belt is removed in FIG. FIG. 4 is a cross-sectional view taken along the line AA in FIG.

  In FIG. 1, a sheet 104 is conveyed, for example, from left to right on a conveyance belt 105 having an electrostatic attraction force. Line heads 100, 101, 102, 103 in which a plurality of short heads equipped with ink ejection nozzles are arranged in a staggered manner so as to be orthogonal to the paper transport direction are disposed above the transport belt 105. Are arranged in order. In a normal printing process, when the paper 104 comes directly under the line heads 100, 101, 102, 103, the line heads 100, 101, 102, Ink is ejected from the sheet 103 and a predetermined image is formed on the sheet 104. When printing is continued for a predetermined period, the paper 104 is removed from the conveyor belt 105 and adhered to the nozzles of the short heads of the line heads 100, 101, 102, 103 by idle ejection to the idle ejection holes 106 on the conveyor belt 105. Remove the increased viscosity ink.

  As shown in FIGS. 2 to 4, below the conveying belt 105, it faces the line head 100, 101.102.103 in order to receive empty ejection droplets ejected from the line head 100, 101.102.103. Waste liquid tanks 120, 121, 122, and 123 serving as liquid receiving portions are respectively disposed at the positions. The conveying belt 105 is formed with empty discharge holes 106 that are slightly larger than the short head 100a so as to face the individual short heads. Each of the waste liquid tanks 120, 121, 122, 123 installed on the inner side of the conveyance belt 105 that circulates between the two conveyance rollers 107 is composed of a main tank and a sub tank arranged vertically. For example, the waste liquid tank 120 includes a lower main tank 120a and an upper sub tank 120b having an opening for receiving an empty discharge liquid. There is a waste liquid tank fixing member between the adjacent waste liquid tanks, and a recess is formed on the waste liquid tank side of the waste liquid tank fixing member. The waste liquid tank fixing rib and the waste liquid tank fixing member, which are formed at positions where both the main tank and the sub tank face the waste liquid tank fixing member, are engaged with each other, and the main tank and the sub tank are fixed to each other. Yes. Further, the position of the waste liquid tank is positioned at a position where the empty discharged liquid discharged from the line head can be accurately received.

  5 and 6 are explanatory views for explaining the structure of a waste liquid tank that is a liquid receiving portion. FIG. 5 is a view showing a state where the sub tank door is opened, and FIG. 6 is a view showing a state where the sub tank door is closed. 5 (a) and 6 (a) are side views of the waste liquid tank, FIGS. 5 (b) and 6 (b) are plan views of the waste liquid tank, FIG. 5 (c), and FIG. 6 (c). These are sectional views of a BB cross section of Drawing 5 (a) and Drawing 6 (a), respectively.

  As shown in FIGS. 5A and 5C, the bottom of the sub-tank 1000 has a door 1002 that also serves as a bottom member that can be opened and closed. In FIGS. 5A and 5C, the door 1002 is open. Represents. This door 1002 is a double door opening type that opens to the top (separated into right and left as shown in FIG. 5C), and is fixed to the sub tank 1000 by a hinge 1003, respectively. In the open state, the sub tank 1000 is housed in a recess including a step 1007 provided on the inner wall side so as not to protrude from the inner wall. In this way, empty discharge droplets discharged from above the waste liquid tank are smoothly guided to the bottom of the main tank 1001.

  As shown in FIGS. 5A and 5B, an open / close lever 1005 and a lever control device 1006 are installed outside the main tank 1001, and the open / close lever 1005 is connected to the end of the door 1002. is doing. The door is opened by lifting the open / close lever 1005 upward. A wall is extended to the outside of the sub tank 1000, an end of the door 1002 is extended along the extended wall, and a spring member is provided between the wall extended to the outside of the sub tank 1000 and the extended end of the door 1002. 1004 is arranged so that the open state of the door is maintained by the stress of the spring member 1004. Thus, by providing the opening / closing lever 1005, lever control device 1006, spring member 1004, etc. outside the waste liquid tank, contamination of the opening / closing lever 1005, lever control device 1006, spring member 1004 due to discharged liquid such as empty discharged droplets is prevented. This prevents malfunction due to contamination.

  FIG. 6 shows a state where the same waste liquid tank door 1002 as shown in FIG. 5 is closed. As shown in FIGS. 6A and 6B, the door 1002 biased by the spring member 1004 is closed when the opening / closing lever 1005 is lowered and the end of the door 1002 is rotated. It will be in a closed state and will form the bottom of the sub tank 1000. By using the spring member 1004 having a simple configuration, a door opening / closing structure can be obtained at low cost.

  In the state where the door 1002 shown in FIG. 5 is left open, the empty discharge liquid discharged from the nozzle above the waste liquid tank is received by the sub tank 1000 and stored in the main tank 1001 as it is. When the main tank 1001 is full, the printing of the image forming apparatus is continued as it is, and the door 1002 is closed and the main tank 1001 is replaced, or the main tank 1001 is removed and the waste liquid therein is discarded and reattached. Or Since the main tank 1001 can be detached from the sub tank 1000, if the empty discharge liquid is temporarily stored at the bottom of the sub tank 1000, there is no problem in the continuous operation of the image forming apparatus.

  When the main tank 1001 is full, the continuous operation of the image forming apparatus is continued while temporarily storing the empty discharge liquid only in the sub tank 1000, but when the main tank 1001 is replaced, the door 1002 of the sub tank 1000 is opened. Therefore, only a small amount of empty discharge liquid is accumulated in the sub tank 1000. For this reason, the waste liquid level in the waste liquid tank may always be considered to be lower than the bottom surface of the sub tank 1000, and since the empty discharge liquid is normally received in the waste liquid tank, the occurrence of mist abnormality and the empty discharge liquid of the generated mist Contamination of the conveying belt and the recording medium due to the backflow from the receiving port can be prevented.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is an explanatory view of a waste liquid tank in the image forming apparatus of the present invention corresponding to FIG. 7A is a side view of the waste liquid tank, FIG. 7B is a plan view, and FIG. 7C is a cross-sectional view taken along the line BB of FIG. 7A. The difference from FIG. 6 is that a liquid absorbing material 1009 is installed on the upper surface of the door 1002 of the waste liquid tank. The liquid absorbent material 1009 is preferably a material that absorbs and holds liquids such as ink, such as porous material rubber, plastic, ceramics, cloth, nonwoven fabric, fiberboard, and cardboard.

  By installing the liquid absorbing material 1009 on the upper surface of the door 1002 of the waste liquid tank, it is possible to prevent the dripping of empty discharged droplets from the sub tank 1000 when the main tank 1001 is removed and image formation is performed. At the same time, since the empty discharge droplets can be softly adsorbed, the effect of preventing the empty discharge droplets from colliding with the bottom plate of the sub-tank 1000 to become mist and leak from the waste liquid tank to be contaminated in the apparatus is improved. Further, if the liquid absorbent material 1009 is installed so as to cover the hinge 1003, the hinge 1003 can be prevented from being contaminated by the empty discharge liquid, and malfunction due to the hinge 1003 being contaminated can be prevented. Furthermore, it goes without saying that further contamination can be prevented by installing an ink intrusion prevention member between the liquid absorbent material 1009 and the hinge 1003.

  FIG. 8 is an enlarged view of a portion A (round portion) in FIG. 7C, and is an enlarged view of a joint portion when the door 1002 constituted by two members is closed. FIG. 8A shows a state in which the left door 1002a and the right door 1002b are configured, and the left door 1002a and the right door 1002b overlap each other. By doing so, it is possible to prevent the waste liquid of the empty discharge droplets accumulated from leaking downward. At this time, when the bottom of the sub-tank 1000 is closed, the right door 1002b and the left door 1002a are closed in this order.

  In FIG. 8B, in addition to the structure of FIG. 8A, the part where the liquid absorbent material 1009a and the liquid absorbent material 1009b installed in the door 1002a and the door 1002b are joined is also in a key state. By doing in this way, it can prevent that a waste liquid leaks below, and can further improve the dripping prevention effect. Needless to say, it is possible to prevent dripping even if either the bottom member or the waste liquid absorber is set to the key state. Further, since the waste liquid absorbent 1009 easily expands when absorbing the liquid, the space of the overlapping portion is narrowed according to the degree of absorption, and the dripping prevention effect is exhibited.

  FIG. 9 is a flowchart of image formation in the image forming apparatus of the present invention. FIG. 9 shows a flow of processing in a case where the main tank of the liquid receiving portion becomes full due to idle discharge during continuous printing. First, the process starts at S1 and a print job start is instructed at S2. When the start of the print job is instructed, if it is determined in S3 that it is not the time to perform the idle ejection during printing, the print job in S6 is executed as a normal print operation, and in S7, it is determined whether or not the print job is finished. If the print job ends, the process ends at S23. On the other hand, if it is not the end of the print job in S7, the printing is continued. Therefore, it is determined again in S3 whether or not it is the timing for performing the idle ejection during printing.

  If it is determined in S3 that it is the timing for performing the idle ejection during printing, the idle ejection during printing is performed in S4. Subsequently, in S5, it is determined whether or not the waste liquid tank is full. If it is determined that the waste tank is not yet full, the flow returns to the print job execution flow in S6 to continue printing. If it is determined in S5 that the waste liquid tank is full, the door control lever is operated by the lever control device in the machine body (not shown) in S10, the sub tank door is closed, and the sub tank is ready in S11. It is notified and displayed on the machine body and the host computer (hidden).

  Subsequently, when the machine main body receives notification of the completion of the sub tank preparation, the main tank replacement preparation sequence shown in S12 is activated to prepare the main tank in a replaceable state so as not to affect the print job. In S13, the host computer is notified that the main tank replacement is ready, and is displayed on the machine body and the host computer.

  Thereafter, the operator manually replaces the main tank. However, on the machine body side, it is always determined whether or not the main tank has been replaced in S14. If the main tank has not yet been replaced, the empty discharge interval during printing is determined in S15. The interval is set shorter than normal, and the setting is continued until the main tank replacement is completed and the normal state is restored. The normal state here refers to a state in which the main tank is replaced, the bottom door of the sub tank is opened, and empty discharge droplets during printing are received by the main tank.

  If it is determined in S16 that the idle ejection timing is reached, the idle ejection is executed at short intervals in S17, and if it is not the idle ejection timing, the print job is executed as it is. Shortening the idle discharge interval is to secure the empty discharge amount to prevent the ink from drying out along with reducing the single empty discharge amount in order to suppress the occurrence of mist due to collision of the empty discharge liquid with the bottom of the sub tank. It is to do. If it is determined in S19 that the print job is completed, the process returns to S13. If the print job has not ended, the process returns to S16, and the print job is continued while determining whether it is the idle ejection timing.

  If it is determined in S14 that the main tank replacement by the operator has been completed, the sub tank door is opened in S20, the empty discharge interval during printing is reset to the normal condition in S21, and the main tank preparation completion and the host are determined in S22. The computer is notified. Then, the process returns to the determination of the idle discharge execution timing in S3.

  By executing such a sequence, the print job is not interrupted at least because of machine convenience such as replacement of the waste liquid tank. In addition, since the replacement of the main tank does not require a long time, waste liquid does not accumulate in the sub tank. For this reason, the droplets ejected in an empty manner reach the waste liquid level in the main tank or the bottom surface of the sub tank while maintaining a normal distance, so that the generation of mist can be suppressed. Furthermore, since the space is always secured in the sub tank, it is possible to prevent the mist from leaking from the waste liquid tank. Although the main tank can be reused, it is desirable to replace the main tank at a certain frequency.

(Third embodiment)
In the third embodiment, in the image forming apparatus of the first embodiment or the second embodiment, a discharge pressure control device that adjusts the idle discharge pressure of the nozzle, and an idle discharge timing control device that adjusts the idle discharge interval. It has.

  When the sub-tank door is closed in S10 described with reference to the flowchart of FIG. 9, the distance from the nozzle surface of the line head to the landing surface of the empty discharged liquid in the waste liquid tank is shortened. In this state, if empty discharge is performed at the same discharge pressure as in the normal state, the empty discharge liquid that bounces off the sub tank door surface becomes mist, leaks from the sub tank, and may contaminate the nozzle surface, conveying device, recording medium, etc. There is a risk that normal quality printing cannot be maintained. In such a case, it is preferable to make the idle discharge pressure weaker from the viewpoint of preventing the occurrence of mist. Specifically, the number of idle ejection droplets may be reduced, or the peak value of the idle ejection waveform may be reduced. On the other hand, it is necessary to keep the nozzle state normal even under such idle discharge conditions. For that purpose, if the idle discharge is executed while the liquid on the nozzle surface is not very dry, the idle discharge pressure may be low. Specifically, the idle discharge interval may be shortened. Therefore, while the sub tank door is closed in order to replace the main tank, the idle discharge interval is shortened by the idle discharge timing control device, and the idle discharge pressure (empty discharge condition) is set by the nozzle discharge pressure control device. It is preferable to weaken. By adjusting the idle discharge pressure by the discharge pressure control device of the nozzle and adjusting the idle discharge interval by the idle discharge timing control device, it is possible to prevent the occurrence of mist or leakage of mist due to the splash of the empty discharge liquid on the sub tank door surface.

  Table 1 shows the relationship between the state of the waste liquid tank and the idle discharge timing with respect to the presence or absence of the main tank replacement request in S12 of FIG.

表１に示すように、メインタンクの交換要求がない場合は、通常印刷状態であり、サブタンクの扉は開放されており、ノズルから廃液面までの距離は比較的長く正常状態である。この為、ノズルの空吐出は通常のとおりであれば、ミストの異常発生や漏洩も起こらない。一方、メインタンクの交換要求がある場合は、サブタンクの扉は閉鎖され、ノズルから廃液面までの距離は短くなる。この為、ノズルの空吐出状態が通常のとおりであれば、ミストの異常発生や漏洩が起こる可能性がある。そこで、ノズルの空吐出圧力を弱めて、ミストの異常発生や漏洩が起こる可能性を低減している。空吐出圧力の低減法としては、空吐出液滴数を減らしたり、空吐出波形の波高を小さくしたりしてもよい。

As shown in Table 1, when there is no replacement request for the main tank, it is in a normal printing state, the sub tank door is opened, and the distance from the nozzle to the waste liquid surface is relatively long and normal. For this reason, if the idle discharge of the nozzle is normal, the occurrence of mist abnormality or leakage does not occur. On the other hand, when there is a request to replace the main tank, the door of the sub tank is closed, and the distance from the nozzle to the waste liquid surface is shortened. For this reason, if the idle discharge state of the nozzle is normal, mist abnormality may occur or leakage may occur. Therefore, the possibility of occurrence of mist abnormality or leakage is reduced by reducing the idle discharge pressure of the nozzle. As a method for reducing the empty discharge pressure, the number of empty discharge droplets may be reduced, or the wave height of the empty discharge waveform may be reduced.

(Fourth embodiment)
The fourth embodiment is different from the above-described embodiment in that the maintenance / recovery unit for the nozzle of the line head and the waste liquid tank communicate with each other. FIG. 10 is a diagram illustrating the relationship between the waste liquid tank and the maintenance / recovery unit. FIG. 10A is a diagram in which maintenance / recovery units 110, 111, 112, and 113 corresponding to the respective line heads are arranged adjacent to the line heads 100, 101, 102, and 103. The conventional maintenance / recovery units 110, 111, 112, and 113 are provided with a waste liquid tank that collects the waste liquid discharged from the line head during the maintenance / recovery operation. As shown in FIG. 10 (b), the maintenance / recovery unit in this embodiment does not have a waste liquid tank alone, but a waste liquid tank that is a liquid receiving portion for empty discharged liquid, particularly the main tank 120 shown in FIG. , 121, 122, 123. The main tanks 120, 121, 122, 123 may be arranged so as to correspond to the maintenance / recovery units 110, 111, 112, 113 and connected to the maintenance / recovery units 110, 111, 112, 113, respectively. By configuring the image forming apparatus in this way, the number of parts can be reduced, and the cost can be reduced and the failure can be reduced. In this case, it is needless to say that the main tank can be replaced during the print job.

(Fifth reference embodiment)
A fifth reference embodiment will be described with reference to FIGS. FIG. 11 is a plan view of the printing unit of the image forming apparatus of the fifth reference embodiment. FIG. 12 is a plan view of an empty discharge hole forming member (in this case, a conveyance guide) in this embodiment having a liquid receiving portion at the lower portion. FIG. 13 is a plan view of the liquid receiving portion from which the empty discharge hole forming member in FIG. 12 is removed. 14 is a cross-sectional view taken along the line AA in FIG. 11 (cross section AA in FIGS. 12 and 13). 15 is a cross-sectional view taken along the line BB in FIG. 11 (the cross section taken along the line BB in FIGS. 12 and 13). FIG. 16 is an explanatory diagram of the operation of mist attraction of the liquid receiving portion during idle ejection.

  As shown in FIG. 11, in this image forming apparatus, the sheet 104 on which an image is formed is discharged by a discharge roller 107b. Between the paper supply roller 107a and the paper discharge roller 107b, an empty discharge hole forming member (in this case, also serving as the conveyance guide 125) is disposed. When the paper 104 is transported on the transport guide 125 by the paper feed roller 107a and reaches the printing unit in which a plurality of short heads are arranged in the order of the line heads 100, 101, 102, and 103, the paper Ink is ejected toward 104 to form a predetermined image. A spur 108 is disposed between the line heads on the upper part of the conveyance guide 125 to prevent the paper from being twisted.

  FIG. 12 shows a conveyance guide 125 having liquid receiving portions 126, 127, 128, and 129 in the lower portion. The transport guide 125 is formed with an empty discharge hole 125a slightly larger than the short head so as to face each short head.

  FIG. 13 is a plan view of the liquid receiving portions 126, 127, 128, and 129 immediately below the transport guide 125. The liquid receiving part will be described with respect to the liquid receiving part 126. The suction ducts 132 are formed on both sides, and the suction ducts 132 are provided with a plurality of suction fans 133 as mist attracting means. At this time, the suction fan 133 is arranged so as to generate a uniform suction force with respect to each filter 131 which is a mist collecting member. At approximately the center of the liquid receiving portion 126, a partition plate 130 is disposed in parallel to the longitudinal direction of the line head so as to correspond to each short head. The partition plate may be arranged so as to be orthogonal to the longitudinal direction of the line head. Below the suction fan 133, a mesh back panel 134 for exhausting the airflow generated by the suction fan 133 is installed. The liquid receiving portions 127, 128, and 129 have the same structure as the liquid receiving portion 126.

  FIG. 14 is a cross-sectional view of the AA cross-sectional portion of the liquid receiving portion in FIG. 11 (only the cross-sectional portion is shown for simplification of the drawing). FIG. 15 is a cross-sectional view taken along the line B-B of the liquid receiving portion in FIG. 11 (only the cross-sectional portion is shown for simplification of the drawing). A partition plate 130 parallel to the longitudinal direction of the line head is provided in the upper central portion of each of the liquid receiving portions 126, 127, 128, and 129, and the empty discharge liquid discharged from the nozzle of the short head 102a is It has a structure in which it falls directly below the liquid receiving portions 126, 127, 128, and 129. As shown in FIGS. 13 to 15, a filter 131, which is a mist adsorbing member, is disposed on a portion of the side wall of each of the liquid receiving portions 126, 127, 128, and 129 that faces the partition plate 130 of the empty discharge liquid passage. Yes. A suction duct 132 and a plurality of suction fans 133 are installed on the side surfaces of the liquid receiving portions 126, 127, 128, and 129, and the liquid receiving portion is passed through the filter 131 from the liquid receiving portions 126, 127, 128, and 129. The suspended particles (ink mist) can be sucked together with the air in 126, 127, 128, and 129. The filter 131 is installed in the vicinity of the discharge liquid inlet of the liquid receivers 126, 127, 128, and 129, and the suction duct 132 and the suction fan 133 are arranged at the respective filter 131 portions. , 128 and 129 are arranged so as to be sucked by substantially the same suction force.

  FIG. 16 is a view for explaining the suction operation of suspended particles (ink mist) generated from the empty discharge liquid in the liquid receiver (for example, the liquid receiver 126). As shown in FIG. 16, the droplets ejected during the actual idle ejection operation are composed of main droplets 136a having a high ejection speed and suspended particles (ink mist 136b) having a slow ejection speed. Since the main droplet 136a having a high discharge speed can easily reach the bottom of the liquid receiving portion 126, a waste liquid 134 pool is formed, but the ink mist 136b having a low discharge speed is formed near the empty discharge liquid inlet 126a of the liquid receiving portion 126. Easy to float. If the air containing the ink mist 136b is sucked by the suction fan 133 through the filter 131, the ink mist 136b is sucked by the filter 131 and adsorbed to flow down to the bottom of the liquid receiving portion 126. . The filters 131 are provided in the vicinity of the respective empty ejection liquid inlets 126a. However, since the suction forces in the respective filters 131 are almost the same, the ink mist 136b ejected from each nozzle is caused by the nearby filter 131. Sucked.

FIG. 17 is a flowchart for explaining the idle ejection operation in the fifth reference embodiment. The ink mist 136b is easily affected by the turbulence of the atmosphere (due to the temperature difference of the atmosphere or the weak air current generated by the drive unit in the recording apparatus). Therefore, as shown in the operation flow of FIG. 17A, if the suction fan operation is started with a slight delay after the idle discharge operation is started, the main droplet 136a having a high discharge speed is formed in the liquid receiving portion. Only the ink mist 136b, which is accumulated at the bottom and has a low discharge speed, can be efficiently adsorbed to the filter 131. Specifically, the idle discharge operation flow will be described. After the idle discharge operation is started (S31), the idle discharge is started from the nozzle of the line head (S32), and after the time that the main droplet passes near the filter has passed. Then, the operation of the suction fan is started by delaying a predetermined timing so as to suck air from the filter (S33). When the idle ejection is completed (S34), after the ink mist 136b has been absorbed, the operation of the suction fan is terminated and stopped (S35).

  Depending on the operating environment (temperature and humidity) of the image forming apparatus, it is necessary to change the required empty discharge amount. In general, when the temperature is low and humidity is low, the amount of idle discharge for recovering the nozzle discharge performance increases. If the idle discharge amount is increased and the idle discharge is continuously performed, the next empty discharge will be performed before the ink mist is completely absorbed, making it difficult to efficiently adsorb only the ink mist to the filter. Become. Accordingly, in this case, as shown in FIG. 17B, by repeating the idle discharge operation and the fan suction operation alternately, main droplets having a high discharge speed are accumulated at the bottom of the liquid receiving portion, and the discharge speed is low. Only the ink mist can be efficiently adsorbed to the filter. In FIG. 17B, from the start of the idle discharge from the nozzle of the line head (S42) to the end of the operation of the suction fan (S45), the empty discharge from the nozzle of the line head in FIG. ) To the end of the operation of the suction fan (S35), but after the end of the operation of the suction fan (S45), it is determined whether or not the empty discharge amount has reached a predetermined discharge amount (S46). If the discharge amount is not the predetermined discharge amount, the flow returns to the idle discharge start (S42) and the flow from (S42) to (S46) is repeated. Then, when it is determined in (S46) that the empty discharge amount has reached the predetermined discharge amount, the empty discharge operation ends (S47).

  In addition, when a large amount of ink mist is adsorbed to the filter due to the idle ejection operation and clogging occurs and the suction force is reduced, the suction force can be recovered by replacing the filter with a new one or a cleaned product.

  The droplets ejected from a plurality of nozzles of a short head are generally composed of a main droplet having a high ejection speed and floating particles (ink mist) having a slow ejection speed. The main droplet having a high discharge speed reaches the liquid receiving portion first. Suspended particles (ink mist) with a slow discharge speed arrive at the liquid receiver after the main droplet, but due to the slow discharge speed, there is disturbance in the atmosphere (due to atmospheric temperature differences and the weakness caused by the drive unit in the recording device). Susceptible to airflow). Therefore, by providing a mist adsorbing member (filter, etc.) and an attracting device (fan, duct, etc.) for each short head on the side wall of the liquid receiver near the short head, suspended particles (ink mist) reaching the liquid receiver are It becomes possible to immediately adsorb to the mist adsorbing member without floating in the entire liquid receiving part, and by reducing the distance between the short head, the mist adsorbing member and the attracting device as much as possible, there is a slight variation in attracting force in the attracting device. Even when there is, the ink mist adsorption amount to the mist adsorption member can be made uniform, so that the effective period of the mist adsorption member and the period during which the mist adsorption member functions can be made uniform. If the effective period of the mist adsorbing member is uniform, when replacing the ink mist collecting member, all can be replaced with one replacement, so the replacement frequency is reduced and the image forming cost is reduced (replacement work, downtime) Since the time is reduced, a large number of printed sheets can be secured.)

(Sixth embodiment of reference )
An image forming apparatus according to a sixth reference embodiment will be described with reference to FIGS. FIG. 18 is a plan view of the printing unit of the image forming apparatus according to the sixth reference embodiment. FIG. 19 is a plan view of an empty discharge hole forming member (in this case, a conveyor belt) having a liquid receiving portion disposed in the lower portion. FIG. 20 is a plan view of the liquid receiving portion. 21 is a cross-sectional view taken along the line CC in FIG. Note that a line head is also shown above the transport belt. FIG. 22 is an explanatory diagram of the mist suction operation when the liquid receiving unit receives the empty discharge liquid.

  As shown in FIG. 18, the image forming apparatus of this embodiment ejects ink when the paper 104 is conveyed on the conveying belt 105 and reaches a position facing the line heads 100, 101, 102, 103. To form an image. This is the same as the conventional image forming apparatus. In addition, it is preferable that the conveyance belt 105 has a structure that sucks a sheet conveyed by an electrostatic force.

  As shown in FIG. 19, the idle discharge hole forming member (in this case, the conveyance belt 105) has an idle discharge hole 106 formed at a position facing the line heads 100, 101, 102, and 103. The empty discharge hole 106 is slightly larger than the short head, and all of the empty discharge liquid discharged from the nozzle portion of the short head passes therethrough.

  FIG. 20 is a diagram illustrating a state where the conveyance belt 105 of FIG. 19 is removed. As shown in FIG. 20, liquid receivers 137, 138, 139, and 140 are installed immediately below the conveyor belt 105 so as to correspond to the line heads 100, 101, 102, and 103, respectively. A plurality of mist attracting plates 142, which are mist attracting devices and mist attracting members, are installed on both side surfaces of the liquid receiving portions 137, 138, 139, 140 corresponding to the short heads of the line heads. 142 are grouped for each line head via the wiring 144 and connected to the charge charge unit 145 through the changeover switch 146. When charging the mist suction plate 142, the changeover switch 146 is connected to the charge charge unit 145, and when removing the charge from the mist suction plate 142, the changeover switch 146 may be connected to the ground side. The ink mist in the liquid receiving portions 137, 138, 139, 140 is attracted to the mist suction plate 142 charged with electric charge, and is attached to the mist suction plate 142 and removed. In addition, a mist adsorption | suction member is good also as a structure arrange | positioned on the front surface of a mist board as a mesh or a filter separately from the mist attraction board which is a mist attraction apparatus. Here, when charging from the charge charging unit, charging with a polarity different from the charge of the ink mist generated by the action of the transport belt 105 (electrostatic adsorption transport belt) can improve the mist collection efficiency. Since it improves, it is preferable.

  As shown in FIGS. 20 to 22, the mist adsorbing plate 142 is disposed on the side surface of the empty discharge liquid receiving port portion 137 a of the liquid receiving portion (for example, the liquid receiving portion 137) so as to face the partition plate 143. A plurality of partition plates 143 are arranged in the upper central portion of the liquid receiving portions 137, 138, 139, 140 in parallel with the longitudinal direction of the line heads 100, 101, 102, 103, corresponding to the short heads. . It is desirable that the partition plate 143 is an electrical insulator. The insulating partition plate 143 has an effect of weakening the influence of the electrostatic force of the mist adsorbing plates 142 adjacent to each other.

By using an electrostatic force as the attraction device, unlike the suction fan shown in the fifth reference embodiment, a suction duct becomes unnecessary, and the number of parts can be reduced. Further, since the space between the line heads can be narrowed, the apparatus can be miniaturized.

  In the image forming apparatus of this embodiment, if the mist suction plate 142 is detachable, the mist suction plate 142 is removed when a large amount of ink mist is adsorbed and the suction force (in this case, electrostatic force) due to electric charges is reduced. The suction power can be recovered by removing the mist adsorbed and cleaning it.

  The droplets ejected from the plurality of nozzles of the short head are generally composed of a main droplet 148a having a high ejection speed and an ink mist 148b having a slow ejection speed. For the droplets that have passed through the idle ejection hole 106 of the transport belt 105, the main droplet 148 a having a high ejection speed reaches the liquid receiving portion 137 first. The ink mist 148b having a low ejection speed reaches the liquid receiving portion with a delay from the main droplet 148a. However, since the particles are small and the influence of air resistance is large, the disturbance of the atmosphere (due to the atmospheric temperature difference or the drive unit in the recording apparatus) It is easily affected by the weak air flow that occurs. Therefore, by providing the mist suction plate 142 on the side wall of the liquid receiving part near the short head, the ink mist 148b that has reached the vicinity of the empty discharge liquid receiving inlet 137a on the upper side of the liquid receiving part 137 Can be immediately adsorbed to the ink mist adsorbing plate 142 without staying floating. In addition, by reducing the distance between the short head and the ink mist suction plate 142 as much as possible, even when the electrostatic force of the ink mist suction plate 142 varies slightly, the amount collected on the ink mist suction plate 142 can be made uniform, and the ink The lifetime of the mist suction plate 142 (period during which the ink mist collection mechanism functions) can be made uniform. Therefore, if the ink mist collecting member is replaced, all can be replaced with a single replacement, so the replacement frequency is reduced and the cost is reduced (replacement and downtime are reduced, so a large number of printed sheets is secured. it can.).

Plan view of printing section of image forming apparatus Plan view of an empty discharge hole forming member (in this case, a conveyor belt) provided with a liquid receiving portion Top view of liquid receiver AA sectional view in FIG. Side view (a), plan view (b), and BB cross-sectional view (c) of liquid receiving part in door open state Side view (a), plan view (b), and BB cross-sectional view (c) of liquid receiving part in door closed state Side view (a), plan view (b), and BB cross-sectional view (c) of a liquid receiving portion provided with a liquid absorbent Enlarged view of part A in FIG. Image forming flowchart in image forming apparatus of the present invention Schematic diagram showing the relationship between the line head maintenance and recovery unit and the liquid receiver Plan view of printing section of image forming apparatus Plan view of empty discharge hole forming member (in this case, transport guide) provided with a liquid receiving portion Top view of liquid receiver AA sectional view in FIG. BB sectional view in FIG. Operation explanatory diagram of liquid receiver Flow chart of empty discharge operation Plan view of printing section of image forming apparatus Plan view of an empty discharge hole forming member (in this case, a conveyor belt) provided with a liquid receiving portion Internal structure diagram of liquid receiver CC sectional view in FIG. Operation explanatory diagram of liquid receiver Example of conventional image forming apparatus (1) Example of conventional image forming apparatus (2)

Explanation of symbols

100, 101, 102, 103: Line head 100a: Short head 104: Paper 105: Conveying belt (empty ejection hole forming member)
106: Empty discharge hole 107: Conveying roller 107a: Paper feed roller 107b: Paper discharge roller 108: Spur 110, 111, 112, 113: Maintenance recovery unit 120, 121, 122, 123: Liquid receiving part (waste liquid tank)
120a: main tank 120b: sub tank 124: waste liquid tube 125: transport guide (empty discharge hole forming member)
125a: Empty discharge holes 126, 127, 128, 129: Liquid receiving portion 126a: Near empty discharge liquid inlet 130: Partition plate 131: Filter 132: Suction duct 133: Suction fan 134: Back panel 135: Waste liquid 136a: Main droplet 136b: Ink mist 137, 138, 139, 140: Liquid receiving part 137a: Empty discharge liquid inlet vicinity 141: Empty discharge liquid inlet 142: Mist adsorption plate 143: Partition plate 144: Wiring 145: Charge charge unit 146: Switch 147: Waste liquid 148a: Main droplet 148b: Ink mist 1000: Sub tank 1001: Main tank 1002, 1002a, 1002b: Door 1003: Hinge 1004: Spring member 1005: Open / close lever (open / close device)
1006: Lever control device 1007: Step 1008: Waste liquid 1009, 1009a, 1009b: Liquid absorbent

Claims (5)

An image forming apparatus comprising: a line head in which a plurality of nozzles for forming an image by discharging liquid onto a recording medium is disposed; and a liquid receiving portion for storing empty discharge liquid discharged from the nozzles,
The liquid receiving portion includes a sub tank that receives the empty discharge liquid discharged from the nozzle, and a main tank that removably couples to the bottom of the sub tank and stores the empty discharge liquid.
The sub tank includes a door that can be opened and closed and an opening and closing device that opens and closes the door .
Depending on detachment state of the main tank, the image forming, wherein a discharge pressure control unit for controlling the discharge pressure of the air discharge liquid, the Rukoto includes an air ejection timing control apparatus for controlling the air ejection timing from the nozzle apparatus.   The empty discharge hole forming member in which an empty discharge hole that guides empty discharge liquid discharged from the nozzle to the sub tank is formed between the nozzle and the sub tank. Image forming apparatus.   The image forming apparatus according to claim 1, wherein a liquid absorbing material is disposed at a bottom of the sub tank.   The image forming apparatus according to claim 1, wherein the opening / closing device is disposed outside a discharge path of an empty discharge liquid discharged from the nozzle.   The image forming apparatus according to claim 1, wherein the opening / closing device includes a spring member.

Images