JP2012051277A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that enlargement of an area of a filter causes a bubble to stay in a channel of a filter part during an initial filling and thereby reducing liquid-ejecting characteristics.SOLUTION: An apparatus performs a first filling operation that fills ink at a first flow velocity which is slower than a second flow velocity when the ink is filled from a filter unit 101 into a recording head 34, until the ink is filled into a filter downstream chamber 104b of the filter unit 101. After the first filling operation, the apparatus controls a second filling operation that fills the ink in the channel of a recording head 24 at the second flow velocity.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging droplets.

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid discharge recording method is an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply It also means that a droplet is landed on a medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials, resins and the like are also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  In such an image forming apparatus, it is necessary to surely discharge bubbles in the recording head or in the supply path when the initial filling for supplying ink from the ink tank to the recording head for the first time is performed. In particular, if bubbles remain in the recording head, normal droplet discharge cannot be performed from the discharge port (nozzle), and image defects such as white streaks appear in the image.

  Conventionally, it is known that after the inside of an ink flow path between an ink cartridge (ink tank) and a recording head is formed at a negative pressure, the pressure is released to atmospheric pressure to create an instantaneous ink flow to discharge bubbles. . As a method of repeating this negative pressure formation and release to the atmosphere, a valve (electromagnetic valve, etc.) is provided in the middle of the ink flow path to create a state where the negative pressure in the ink flow path by the suction pump is accumulated and the valve is opened. By controlling the valve and discharging bubbles by the instantaneous ink flow generated by opening the valve, or by intermittently performing the suction operation (drive) of the suction pump to create an instantaneous ink flow A method of discharging bubbles is known (Patent Document 1).

  Further, when a filter for filtering foreign matter is provided on the upstream side of the recording head, there is a filter chamber provided with means for inducing bubbles in a head tank located upstream of the filter in the liquid moving direction (patent) Reference 2).

JP 2007-98959 A JP 2010-131934 A

  By the way, when a filter is disposed on the upstream side of the recording head, in order to prevent the pressure loss in the filter portion from affecting the ink supply particularly when the ink flow rate is increased for high-speed printing, the area of the filter is reduced. There is a need to make it bigger.

  However, when the area of the filter is increased, there is a problem that, during initial filling, a flow rate difference of the liquid occurs between the upstream side and the downstream side of the filter when passing through the filter, and bubbles remain on the downstream side.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce residual bubbles during initial filling.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head for discharging droplets;
A filter unit having a filter chamber in which a filter for filtering the liquid supplied to the recording head is built; and
A cap member for capping the nozzle surface of the recording head;
A negative pressure generating chamber connected to the cap member via a suction path;
Opening and closing means for opening and closing a path between the cap member and the negative pressure generating chamber;
A negative pressure generating pump for bringing the negative pressure generating chamber into a negative pressure state;
Control the initial filling of the recording head with the liquid by operating the negative pressure generating pump with the open / close means closed and controlling the opening / closing means to open after the negative pressure generating chamber is in a negative pressure state. Control means for
The control means includes
Until the liquid is filled in the flow path of the filter unit, the liquid is filled at a first flow rate that is slower than a second flow rate when the liquid is filled from the filter unit into the recording head. A first filling operation is performed,
After the completion of the first filling operation, the second filling operation for filling the liquid into the flow path of the recording head at a second flow rate is controlled.

Here, a main tank that contains the liquid and is detachably attached to the apparatus main body,
A head tank that receives liquid supply from the main tank via a liquid supply path and supplies liquid to the recording head;
The head tank is provided with air release means for opening to the atmosphere,
The negative pressure generating chamber is brought into a negative pressure state, and the inside of the head tank is opened to the atmosphere by the atmospheric release means before the opening / closing means is opened.

  In addition, before performing the initial filling operation, the opening / closing means may be closed to place the negative pressure generating chamber in a negative pressure state.

  According to the image forming apparatus of the present invention, during the initial filling, until the liquid is filled in the flow path of the filter unit, the second flow rate when the liquid is filled into the recording head from the filter unit. A first filling operation for filling the liquid at a slow first flow rate is performed, and after the first filling operation is finished, a second filling operation for filling the liquid into the flow path of the recording head at the second flow rate is controlled. With this configuration, the inside of the filter portion can be filled without leaving bubbles on the downstream side of the filter at the time of initial filling, and the remaining bubbles at the time of initial filling can be reduced and stable image formation can be performed.

FIG. 3 is a side explanatory view illustrating a mechanism unit of an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the apparatus. FIG. 2 is a schematic explanatory diagram for explaining an ink supply / discharge system in the image forming apparatus. It is sectional explanatory drawing of a filter unit part. It is typical explanatory drawing with which it uses for description of the attraction | suction mechanism in 1st Embodiment of this invention. It is a typical explanatory view similarly used for operation explanation. It is block explanatory drawing with which the outline | summary of a control part is provided. It is a flowchart with which it uses for description of control of the initial filling operation | movement by a control part. It is a typical explanatory view for explaining the initial filling operation in the same manner. It is typical explanatory drawing with which it uses for description of a comparative example. It is typical explanatory drawing with which it uses for description of the suction mechanism in 2nd Embodiment of this invention. It is a typical explanatory view similarly used for operation explanation. It is typical explanatory drawing with which it uses for description of the suction mechanism in 3rd Embodiment of this invention. It is typical explanatory drawing in the initial stage filling used for description of 4th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining a mechanism part of the image forming apparatus, and FIG. 2 is an explanatory plan view of a main part of the apparatus.
This image forming apparatus is a serial type ink jet recording apparatus, and a carriage 33 is slidable in a main scanning direction by main and sub guide rods 31 and 32 which are guide members horizontally mounted on the left and right side plates 21A and 21B of the apparatus main body 1. It is held and moved and scanned in the carriage main scanning direction via a timing belt by a main scanning motor described later.

  The carriage 33 is provided with recording heads 34a and 34b composed of liquid ejection heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). The “recording head 34” is arranged in a sub-scanning direction orthogonal to the main scanning direction, and the ink droplet ejection direction is directed downward.

  Each of the recording heads 34 has two nozzle rows. One nozzle row of the recording head 34a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 34b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets.

  Further, the carriage 33 is equipped with head tanks 35a and 35b (referred to as “head tank 35” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 34. In the head tank 35, ink cartridges 10y, 10m, 10c, and 10k, which are main tanks of the respective colors that are detachably attached to the cartridge loading unit 4, are supplied to the head tank 35 through the supply tubes 36 of the respective colors by the supply unit 24. The recording liquid is replenished and supplied.

  On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feeding tray 2, a half-moon roller (feeding) that separates and feeds the papers 42 one by one from the paper stacking unit 41. A separation pad 44 made of a material having a large friction coefficient is provided facing the paper roller 43) and the paper feed roller 43, and the separation pad 44 is urged toward the paper feed roller 43 side.

  In order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34, a guide member 45 for guiding the paper 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. And a holding belt 48 which is a conveying means for electrostatically attracting the fed paper 42 and conveying it at a position facing the recording head 34.

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction). Further, a charging roller 56 that is a charging unit for charging the surface of the transport belt 51 is provided. The charging roller 56 is disposed so as to come into contact with the surface layer of the transport belt 51 and to rotate following the rotation of the transport belt 51. The transport belt 51 rotates in the belt transport direction when the transport roller 52 is rotationally driven through timing by a sub-scanning motor described later.

  Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 34, a separation claw 61 for separating the paper 42 from the conveying belt 51, a paper discharge roller 62, and a spur 63 that is a paper discharge roller. And a paper discharge tray 3 below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, a maintenance / recovery mechanism 81 for maintaining and recovering the nozzle state of the recording head 34 is disposed in the non-printing area on one side of the carriage 33 in the scanning direction. The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a and 82b (hereinafter referred to as “caps 82” when not distinguished from each other) for capping the nozzle surfaces of the recording head 34, and nozzle surfaces. A wiper member (wiper blade) 83 for wiping the recording medium, an empty discharge receiver 84 for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid, and a carriage And a carriage lock 87 for locking 33. A waste liquid tank 100 for storing waste liquid generated by the maintenance recovery operation is mounted on the lower side of the head recovery mechanism 81 in a replaceable manner with respect to the apparatus main body.

  Further, in the non-printing area on the other side of the carriage 33 in the scanning direction, there is an empty space for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is disposed, and the idle discharge receiver 88 includes an opening 89 along the nozzle row direction of the recording head 34.

  In this image forming apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and includes the transport belt 51 and the counter. It is sandwiched between the rollers 46 and conveyed, and the leading end is guided by the conveying guide 37 and pressed against the conveying belt 51 by the leading end pressing roller 49, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately repeated with respect to the charging roller 56, that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 51 alternates, that is, in a sub-scanning direction that is a circumferential direction. , Plus and minus are alternately charged in a band shape with a predetermined width. When the paper 42 is fed onto the conveyance belt 51 charged alternately with plus and minus, the paper 42 is attracted to the conveyance belt 51, and the paper 42 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 51.

  Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper discharge tray 3.

  When performing the maintenance and recovery of the nozzles of the recording head 34, the nozzle 33 performs the suction from the nozzles by moving the carriage 33 to a position facing the maintenance and recovery mechanism 81 which is the home position and performing capping by the cap member 82. By performing a maintenance and recovery operation such as idle ejection for ejecting droplets that do not contribute to image formation, image formation by stable droplet ejection can be performed.

Next, an ink supply / discharge system in the image forming apparatus will be described with reference to FIG.
The main tank (ink cartridge) 10 is detachably attached to the apparatus main body. Ink is supplied from the ink cartridge 10 to the head tank 35 via the supply tube 36 by the supply pump 241 of the supply unit 24.

  The recording head 34 and the head tank 35 are integrated (unitized) via a filter unit 101 that filters ink supplied from the head tank 35 to the recording head 34.

  The head tank 35 opens the inside of the container main body 201 to the atmosphere, the container main body 201 that stores ink therein, the detection filler 205 that forms the displacement of the flexible member that forms part of the wall surface of the container main body 201. An air release mechanism 207 and detection sensors 208a and 208b for detecting the remaining amount of ink in the container body 201 are provided. The atmosphere release mechanism 207 is opened and closed by the atmosphere release solenoid 301, and the detection filler 205 is detected by the full sensor 301.

  On the other hand, the suction mechanism 400 is connected to the suction cap 82 a that capping the nozzle surface of the recording head 34, and the waste liquid generated by the suction by the suction mechanism 400 is discharged to the waste liquid tank 406.

Next, the filter unit 101 will be described with reference to FIG. FIG. 4 is a cross-sectional explanatory view of the filter unit portion.
The filter unit 101 includes a first filter case 102 </ b> A and a second filter case 102 </ b> B, and a filter 103 is disposed therein. Ink from the head tank 35 is supplied to the upstream side of the filter 103. The supply flow path 105a and the filter upstream chamber 104a are formed, and the filter downstream chamber 104b and the supply flow path 105b to the recording head 34 are formed on the downstream side of the filter 103. That said.)

  The recording head 34 is supplied with ink into the common liquid chamber 343 through a supply port 342 provided in the head frame 341. Ink is supplied from the common liquid chamber 343 to the individual liquid chambers corresponding to the nozzles.

  In principle, the filter 103 can be attached to either the first filter case 102A or the second filter case 102B. However, when the filter 103 is welded or bonded, dust is generated from the joint. Since it is easy, it is preferable to attach to the 2nd filter case 102B.

  Further, the filter 103 is made of a sintered metal fiber nonwoven fabric, a twill-folded metal body, a resin mesh, or the like. In the case of a mesh structure, a mesh size capable of capturing particles having a particle size of 20 μm or less. Set. Thus, clogging is suppressed by reducing the movement resistance of liquid such as ink while preventing the passage of foreign matters of a certain size or larger and irregular foreign matters. Further, in the case of a resin filter, it is possible to eliminate the need for troublesome joining work such as welding, and the workability during assembly or replacement can be improved.

  The filter unit 101 has a configuration having a larger cross-sectional area than the supply path, and the ink flow rate per unit area in the filter 103 is smaller than the flow rate per unit area in the supply path, so that ink can be printed for high-speed printing. Even when the flow rate increases, the pressure loss in the filter unit 101 does not affect the ink supply.

Next, the suction mechanism in the first embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a schematic explanatory view for explaining the suction mechanism, and FIG. 6 is a schematic explanatory view for explaining the operation.
The suction mechanism 400 includes a negative pressure generation chamber 402 connected to the cap 82a via a suction path 401, and pressure opening / closing as an opening / closing means disposed between the cap 82a and the negative pressure generation chamber 402 to open and close the suction path 401. A valve 403, a discharge path 404 connected to the negative pressure generation chamber 403, and a vacuum pump 405 that sucks air in the negative pressure generation chamber 402 through the discharge path 404 to bring the negative pressure generation chamber 402 into a negative pressure state. And. The negative pressure generating chamber 402 has a sealed space 402c formed by a container body 402a and a lid member 402b.

  With this configuration, the air 471 in the container of the pressure generating chamber 402 is discharged by the vacuum pump 405 in a state where the pressure on-off valve 403 is closed. It becomes a negative pressure state.

  Thereafter, by opening the pressure on-off valve 403, the inside of the cap 82a is sucked and ink is sucked from the nozzles. The ink waste liquid that has been sucked and accumulated in the negative pressure generating chamber 402 through the suction path 401 is discharged from a drain path (not shown).

Next, an outline of the control unit of the image forming apparatus will be described with reference to a block diagram of FIG.
The control unit 500 temporarily stores a CPU 501 for controlling the entire apparatus, a program including a program for controlling an initial filling operation according to the present invention executed by the CPU 501, a ROM 502 for storing other fixed data, image data, and the like. RAM 503 for storing, rewritable nonvolatile memory 504 for holding data even while the power of the apparatus is shut off, image processing for performing various signal processing and rearrangement on image data, and other control of the entire apparatus And an ASIC 505 for processing input / output signals.

  Further, a print control unit 508 including a data transfer unit for driving and controlling the recording head 34 and a driving signal generating unit, a head driver (driver IC) 509 for driving the recording head 34 provided on the carriage 33 side, An AC bias is applied to the charging roller 56, a main scanning motor 554 that moves and scans the carriage 33, a sub-scanning motor 555 that rotates the conveyance belt 51, a motor drive unit 510 that drives the maintenance / recovery motor 556 of the maintenance / recovery mechanism 81. An AC bias supply unit 511 to supply, an air release solenoid 302 that opens and closes the air release mechanism 207 of the head tank 35, an opening / closing valve 403 of the suction mechanism 400, a solenoid drive unit 512 that drives the vacuum pump 405, and the like are provided.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  The CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. Note that generation of dot pattern data for image output is performed by the printer driver 601 on the host 600 side.

  The print control unit 508 transfers the above-described image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 509.

  The head driver 509 selectively selects droplets of the recording head 7 as drive pulses constituting a drive signal given from the print control unit 508 based on image data corresponding to one line of the recording head 34 inputted serially. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element) that generates energy to be discharged. At this time, by selecting a driving pulse constituting the driving signal, for example, dots having different sizes such as a large droplet, a medium droplet, and a small droplet can be sorted.

  The I / O unit 513 acquires information from various sensor groups 515 mounted on the apparatus, extracts information necessary for controlling the printer, and print control unit 508, motor control unit 510, AC bias supply unit Used to control 511. The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature and humidity in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 513 can process various sensor information. This

Next, the control of the initial filling operation performed by the CPU 501 (program) of the control unit 500 in this image forming apparatus will be described with reference to the flowchart of FIG. 8 and the explanatory diagram of FIG.
First, the cap 82a is moved to cap the nozzle surface of the recording head 34, and the atmosphere release mechanism 204 is opened.

  Then, the on-off valve 403 is closed and the vacuum pump 405 is driven (ON) to determine whether or not a predetermined time T1 has elapsed. Thereby, the air in the negative pressure generating chamber 402 is discharged, and the negative pressure corresponding to the air discharge amount for the predetermined time T1 (the negative pressure at this time is set as the negative pressure P1. The negative pressure P1 is, for example, −10 kPa to 30 kPa).

  Thereafter, when the predetermined time T1 has elapsed, the vacuum pump 405 is stopped (OFF), and the on-off valve 403 is opened. Thereby, the inside of the cap 82a is sucked, and the ink of the ink cartridge 10 is sucked to the recording head 34 side.

  As a result, the ink flows into the filter unit 101 at the first flow rate corresponding to the negative pressure P1, and the ink 700 fills the filter upstream chamber 104a of the filter unit 101 as shown in FIGS. Then, the ink 700 passes through the filter 103 and flows into the filter downstream chamber 104b side.

  Here, the first flow rate of the ink generated at the negative pressure P1 is made slower than the second flow rate when the ink is filled from the filter unit 101 to the recording head 34, so that the filter upstream chamber when passing through the filter 103. The difference in the flow velocity of ink between the filter 104a and the filter downstream chamber 104b is reduced, and the ink passes uniformly through the filter 103, so that bubbles remain in the filter downstream chamber 104b and the filter downstream chamber 104b is filled. Done. That is, a negative pressure P1 that is filled at a first flow rate P1 at which no bubbles remain in the filter downstream chamber 104b is generated (referred to as low pressure suction).

  In this case, after the negative pressure generating chamber 402 is brought into a negative pressure state by the vacuum pump 405, the on-off valve 403 is opened to prevent pressure fluctuation due to pulsation generated in the vacuum pump 405, and the negative pressure in the cap 82a. The initial liquid filling can be performed in a short time.

  Thereafter, the on-off valve 403 is closed again, the vacuum pump 405 is driven (ON), and it is determined whether or not a predetermined time T2 (T2> T1) has elapsed. As a result, the air in the negative pressure generating chamber 402 is discharged and the negative pressure corresponding to the air discharge amount for a predetermined time T2 is set to the negative pressure P2 (P2> P1). For example, -30 kPa to -100 kPa) is generated.

  As a result, the ink flows from the filter unit 101 to the recording head 34 at a second flow velocity corresponding to the negative pressure P2, and the common between the filter unit 101 and the recording head 34 as shown in FIGS. 9 (d) and 9 (e). Ink 700 is filled in the liquid chamber 343. At this time, by increasing the flow rate of the ink generated by the negative pressure P2, the recording head 34 is filled with ink in a short time (high pressure suction).

  In this case, the inside of the negative pressure generating chamber 402 is set to a high negative pressure as in normal initial filling and high pressure suction is performed, so that a common liquid chamber 342 of the recording head 34 is obtained as shown in FIG. The remaining bubbles Bu can be discharged without any problem.

  Thereafter, the air release mechanism 204 of the head tank 35 is closed, the capping of the cap 82a is released, the nozzle surface is wiped, and the recording head 34 performs the idle ejection for ejecting liquid droplets that do not contribute to image formation. Then, the nozzle surface of the recording head 34 is capped to complete the initial filling.

  In the above processing, when the negative pressure in the negative pressure generating chamber 402 is controlled, the vacuum pump 405 is controlled by the drive times T1 and T2, but the rotation speed R1 and R2 of the vacuum pump 405 or negative It is also possible to directly detect the pressure in the pressure generation chamber 402 and set the negative pressures P1 and P2.

Here, a comparative example in which the entire initial filling is performed at the second flow rate will be described with reference to FIG.
When the initial filling is performed at such a second flow rate, bubbles Bu may remain in the filter downstream chamber 104b of the filter unit 101 as shown in FIG. As shown in FIGS. 10B and 10C, this occurs because of a difference in flow velocity of the ink 700 passing through the filter 103, and particularly when the ink flow rate increases due to high-speed printing. This occurs remarkably when the area of the filter 103 is widened so that the pressure loss in the portion does not affect the ink supply.

  Normally, the mixed bubbles Bu are discharged by performing head suction from the nozzles of the recording head 34 in a state where the recording head 34 is capped by the suction cap 82a, but the bubbles Bu remaining in the filter downstream chamber 104b are buoyant. Therefore, as indicated by the arrow in FIG. 10D, ink is sucked through the filter surface without the bubble Bu, and the bubble Bu cannot be discharged.

  In addition, when printing a high duty image or the like, the bubble Bu prevents the flow of ink supply to the recording head 34 through the filter 103, so that the ink supply does not catch up and causes ejection failure. It will be.

  On the other hand, as in the above-described embodiment, until the ink is filled in the flow path of the filter unit 101, filling is performed at a first flow rate that is slower than the second flow rate when filling the recording head 34. As a result, the flow rate difference is reduced and ink can be filled into the flow path of the filter unit 101 without leaving bubbles.

  Thus, at the time of initial filling, until the liquid is filled in the flow path of the filter unit, the liquid is at the first flow rate that is slower than the second flow rate when the liquid is filled from the filter unit into the recording head. Since the first filling operation of filling the liquid into the flow path of the recording head at the second flow rate is controlled after the first filling operation is performed, the initial filling operation is controlled. At the time of filling, the inside of the filter portion can be filled without leaving bubbles on the downstream side of the filter, and the residual bubbles at the time of initial filling can be reduced and stable image formation can be performed.

Next, a suction mechanism according to a second embodiment of the present invention will be described with reference to FIGS. 11 is a schematic explanatory diagram for explaining the suction mechanism, and FIG. 12 is a schematic explanatory diagram for explaining the operation.
This embodiment is an example in which the negative pressure generating chamber is configured by an elastic tube. That is, the opening / closing valve 413 as an opening / closing means is disposed upstream of an elastically deformable tube (elastic tube) 410 connected to a cap (not shown), and the suction pump 415 is disposed at a position away from the opening / closing valve 413 by a predetermined distance. The portion of the elastic tube 410 upstream of the on-off valve 413 is a suction path 411, and the elastic tube 410 between the on-off valve 413 and the suction pump 415 is a negative pressure generating chamber 412. The elastic tube 410 forms a discharge path 414 on the downstream side of the suction pump 415.

  With this configuration, by operating the suction pump 415 with the on-off valve 413 closed as shown in FIG. 11, the air in the negative pressure generating chamber 412 is discharged as shown in FIG. As a result, the elastic tube 412 is deformed, and the inside 412a of the negative pressure generating chamber 412 of the elastic tube 410 rises to a high negative pressure. The negative pressure at this time is preferably in the range of about −10 kPa to −30 kPa for low pressure suction for filling the filter unit 101 and about −30 kPa to −100 kPa for high pressure suction for filling the recording head 34. .

  Therefore, when the on-off valve 413 is opened from this state as shown in FIG. 12B, the portion of the negative pressure generating chamber 412 of the elastic tube 410 is restored to its original shape by the elastic restoring force, and this restoration restores the inside of the cap. Becomes a negative pressure, and the ink corresponding to the volume change of the elastic tube 410 is sucked and filled in the filter unit 101 and the recording head 34.

Next, a suction mechanism according to a third embodiment of the present invention will be described with reference to FIG. FIG. 13 is a schematic explanatory diagram for explaining the suction mechanism.
The present embodiment is an example in which the negative pressure generating chamber is configured by a metal or resin bellows tube (a bellows-like member). That is, an opening / closing valve 423 as an opening / closing means is provided on the upstream side of the bellows pipe 420 connected to the cap, and the bellows portion on the downstream side of the opening / closing valve 423 is used as the negative pressure generation chamber 422, downstream of the negative pressure generation chamber 422. A suction pump 425 is disposed in the exhaust passage 424, and a discharge path 424 is formed on the downstream side of the suction pump 425.

  With this configuration, by operating the suction pump 425 with the on-off valve 423 closed as shown in FIG. 13 (a), negative pressure is generated in the bellows tube 420 as shown in FIG. 13 (b). Air in the bellows part that becomes the chamber 422 is discharged, and the bellows part that becomes the negative pressure generation chamber 422 contracts, and the negative pressure generation chamber 422 rises to a high negative pressure. The negative pressure at this time is preferably in the range of about −10 kPa to −30 kPa for low pressure suction for filling the filter unit 101 and about −30 kPa to −100 kPa for high pressure suction for filling the recording head 34. .

  Therefore, when the on-off valve 423 is opened from this state, the bellows portion that becomes the negative pressure generating chamber 422 of the bellows pipe 420 is restored to the original shape shown in FIG. The inside becomes a negative pressure, and the ink corresponding to the volume change of the bellows tube 420 is sucked and filled in the filter unit 101 and the recording head 34.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition, FIG. 14 is a schematic explanatory view during the initial filling for explaining the embodiment.
The present embodiment is an example in which the filter unit 101 is preliminarily filled with a filling liquid 701 that is not ink but a liquid that does not contain a color material. That is, in the manufacturing process of the image forming apparatus, any one of the first to third embodiments is performed, and the filling liquid 701 as the liquid is not left in the filter downstream chamber 104b of the filter unit 101 without bubbles remaining. The filter unit 101 and the recording head 34 are filled.

  In this way, the filter unit 101 and the recording head 34 are always filled with the filling liquid 701 at the time of physical distribution, and bubbles are generated by substituting the filling liquid 701 and the ink 700 at the initial filling of the image forming apparatus. Since the initial ink filling can be performed without entering, it is not necessary to mount a large-sized and high-cost suction pump, vacuum pump, or the like in the image forming apparatus, so that the image forming apparatus can be reduced in size and cost.

  Note that the processing according to the present invention, such as control related to the initial filling operation in the above-described embodiment, is executed by a computer using a program stored in the ROM 502. This program can be downloaded to the information processing apparatus (host 600) and installed in the image forming apparatus. Further, the above processing may be performed by a printer driver on the information processing apparatus (host 600) side. Furthermore, the image forming apparatus according to the present invention and an information processing apparatus or an image forming apparatus and an information processing apparatus having a program for performing processing according to the present invention can be combined to form an image forming system. In the above embodiment, the serial type image forming apparatus is described. However, the present invention can be similarly applied to a line type image forming apparatus.

10 Ink cartridge (main tank)
33 Carriage 34, 34a, 34b Recording head (liquid ejection head)
35 Head tank (sub tank)
81 Maintenance and recovery mechanism 82a Suction cap 101 Filter unit 103 Filter 104a Filter upstream chamber 104b Filter downstream chamber 343 Common liquid chamber 400 Suction mechanism 401
500 ... Control unit 600 ... Host (information processing device)

Claims (3)

A recording head for discharging droplets;
A filter unit having a filter chamber in which a filter for filtering the liquid supplied to the recording head is built; and
A cap member for capping the nozzle surface of the recording head;
A negative pressure generating chamber connected to the cap member via a suction path;
Opening and closing means for opening and closing a path between the cap member and the negative pressure generating chamber;
A negative pressure generating pump for bringing the negative pressure generating chamber into a negative pressure state;
Control the initial filling of the recording head with the liquid by operating the negative pressure generating pump with the open / close means closed and controlling the opening / closing means to open after the negative pressure generating chamber is in a negative pressure state. Control means for
The control means includes
Until the liquid is filled in the flow path of the filter unit, the liquid is filled at a first flow rate that is slower than a second flow rate when the liquid is filled from the filter unit into the recording head. A first filling operation is performed,
An image forming apparatus that controls a second filling operation of filling the liquid into the flow path of the recording head at a second flow rate after the first filling operation is finished. A main tank that contains the liquid and is detachably attached to the apparatus main body;
A head tank that receives liquid supply from the main tank via a liquid supply path and supplies liquid to the recording head;
The head tank is provided with air release means for opening to the atmosphere,
2. The image forming apparatus according to claim 1, wherein the negative pressure generating chamber is brought into a negative pressure state, and the atmosphere of the head tank is opened to the atmosphere by the atmosphere releasing means before the opening / closing means is opened.   3. The image forming apparatus according to claim 1, wherein the opening / closing means is closed and the negative pressure generating chamber is in a negative pressure state before performing the initial filling operation.

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