JP5515634B2 - Image forming apparatus - Google Patents

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 machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . 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 ejection method is an apparatus that forms an image by ejecting 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 that an image having a meaning such as a character or a figure is imparted to the medium but also an image having no meaning such as a pattern is imparted to the medium (simply liquid. It also means that a droplet hits the 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 and the like are also included.

  In a liquid discharge type image forming apparatus (hereinafter, also simply referred to as “inkjet recording apparatus”), generally, bubbles, thickened ink, and the like are discharged from nozzles of a recording head in order to reduce ink discharge defects. Cleaning is done in a timely manner. This cleaning operation includes both a suction method that forcibly sucks and discharges ink from the nozzle, and a pressure method that forcibly supplies ink to the recording head and forcibly discharges ink from the nozzle. A combination is known.

  In such a recovery operation, one that changes the pressurizing time according to the ink temperature (ink viscosity) (Patent Document 1), one that changes the driving speed of the pressure pump (Patent Document 2), and the like are known. .

JP-A-11-188894 JP 2005-59461 A

  As described above, the viscosity of the ink is very temperature-dependent, and if the discharge control is performed under the same conditions, the ink viscosity increases at a low temperature and the flow path resistance of the supply path (including the inside of the head) increases, resulting in a room temperature environment. In comparison with, the amount of ink discharged from the head is reduced, and it is not possible to obtain the amount of ink discharged for recovery of the ejection state of the head. Further, when the temperature is high, the ink viscosity is lowered and the resistance is lowered, so that the discharge amount is increased and unnecessary ink is consumed.

  Therefore, this point can be solved by changing the pressurizing time and the driving conditions of the pressurizing pump according to the ink temperature (ink viscosity) as disclosed in Patent Documents 1 and 2.

  However, when a pressure-type ink tank that supplies ink to the head is used in which a flexible ink containing member (ink pack) is sealed and stored in a pressure case, the pressurized ink is used. Changing the remaining amount of ink in the pack changes the volume inside the tank case, and also changes the way the ink pack is crushed, which has the effect of affecting the amount of ink discharged when pressure is applied. is there.

  The present invention has been made in view of the above-described problems, and reduces the influence of the remaining amount of liquid in the liquid tank in the pressure recovery operation so that a reliable recovery operation can be performed while suppressing wasteful liquid consumption. The purpose is to do.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having nozzles for discharging droplets;
A replaceable main tank,
A sub-tank having a flexible bag-like ink pack that is supplied with liquid from the main tank and stores the liquid supplied to the recording head, and a pressure case in which the ink pack is sealed and stored;
A pressurizing unit that pressurizes the ink pack by supplying a pressurized gas between a pressurizing case of the liquid tank and the ink pack;
Opening and closing means provided in a gas supply path from the pressurizing means to the sub tank;
A remaining amount detecting means for detecting the remaining amount of liquid in the ink pack;
Control means for performing control to pressurize the inside of the sub tank by the pressurizing means and pressurize and supply the liquid to the recording head when performing the recovery operation of the recording head;
With
Providing a water head difference between the sub-tank and the recording head to generate a predetermined negative pressure on the recording head;
The ink pack is horizontally sealed and stored in the pressure case,
The remaining amount detecting means is
A detection member that partially contacts the ink pack and displaces in accordance with the position of the outer surface of the ink pack being crushed in the vertical direction according to the amount of liquid contained in the ink pack;
An upper limit detection sensor and a lower limit detection sensor disposed outside the pressure case,
The control means includes
When the upper limit detection sensor and the lower limit detection sensor detect the detection member to detect the upper limit position and the lower limit position, and when the lower limit position is detected, liquid supply from the main tank is started and the upper limit position is detected. Stop supplying liquid to the
Calculate the amount of liquid used from the printed image and the number of printed sheets,
When the liquid is supplied to the upper limit position by the remaining amount detecting means as a full tank state, the remaining liquid amount is calculated from the liquid amount in the full tank state and the used liquid amount,
During the pressurizing time corresponding to the remaining amount of liquid detected by the remaining amount detecting means, the opening / closing means is opened to control the supply of pressurized liquid from the pressing means to the sub tank.

  Here, the said control means can be set as the structure which correct | amends the said pressurization time according to environmental temperature.

According to the image forming apparatus of the present invention, it is possible to perform a reliable recovery operation while reducing the influence of the remaining amount of liquid in the main tank and suppressing wasteful liquid consumption.

1 is a schematic perspective view illustrating an overall configuration of an image forming apparatus according to the present invention. It is side surface schematic explanatory drawing similarly. Similarly it is principal part plane explanatory drawing. It is explanatory drawing similarly used for description of a maintenance recovery operation | movement. FIG. 6 is a schematic explanatory diagram for explaining the ink supply system. It is typical explanatory drawing with which it uses for description of the 1st example of residual amount detection means. It is typical explanatory drawing with which it uses for description of the 2nd example of residual amount detection means. It is block explanatory drawing which shows the outline | summary of a control part. It is a flowchart with which it uses for description of pressurization recovery operation. FIG. 6 is an explanatory diagram for explaining a relationship between an ink remaining amount, ink temperature, and ink discharge amount.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to the present invention will be described with reference to FIGS. 1 is a schematic perspective view for explaining the overall configuration of the image forming apparatus, FIG. 2 is a side view for explaining the same, and FIG.

  This image forming apparatus is opposed to a head unit 1 composed of a line-type recording head that discharges droplets, an ink supply unit 2 that supplies ink to the recording head of the head unit 1, and a recording head of the head unit 1. Are arranged on the downstream side of the conveyance unit 3 in the sheet conveyance direction, and are used for line-type recording of the head unit 1. A maintenance / recovery unit 5 as a maintenance / recovery means for performing head maintenance / recovery, a paper discharge unit 6, a position corresponding to the transport unit 3 along the paper transport direction, and a position corresponding to the maintenance / recovery unit 5 And a head moving means 7 that moves in both directions (in the direction of arrow A in FIG. 1).

  The head unit 1 comprises four rows of recording heads 11 configured by arranging a plurality of heads 11a for discharging droplets, that is, black (K), cyan (C), magenta (M), and yellow (Y). A plurality of recording heads 11y, 11m, 11c, and 11k that discharge inks that are liquids of respective colors (hereinafter, when colors are not distinguished, codes without sub-codes y, m, c, and k are used. The same applies to the members and the like.) Is arranged along the sheet conveyance direction and is held by the base member 12.

  The ink supply unit 2 that supplies ink of each color to the head 11a of each recording head 11 of the head unit 1 includes a main tank unit including a replaceable main tank (ink cartridge) 20 that stores ink of each color, which will be described later, and a main tank unit. A sub tank (ink tank) 21, which is a liquid tank to which ink is supplied from the tank via the ink supply tube 26, a pressure recovery device 27 that pressurizes the inside of the sub tank 21, and ink from the sub tank 21 via the supply tube 23. A branch portion (distribution member) 22 that supplies and supplies the supplied ink to each head 11 a via a supply tube 24 is provided, and is provided between each sub tank 21 and the recording head 11 of the head unit 1. A required negative pressure is generated in the recording head 11 by providing a water head difference.

  The head unit 1 is held by a base member 12. The base member 12 includes a first base member 12A that holds the head unit 1, and a second base member 12B that holds the first base member 12A so as to be movable at least in the vertical direction. It consists of and. On the second base member 12B, the sub tank 21 and the branching portion 22 of the ink supply unit 2 are also held.

  The second base member 12B is connected to a timing belt 74 wound around the driving roller 72 and the driven roller 72 of the head moving means 7, and the driving roller 72 is rotationally driven by the driving motor 75, thereby causing the sheet to move. It is moved along the transport direction. As a result, the head unit 1 is moved in both directions between the position corresponding to the transport unit 3 and the position corresponding to the maintenance / recovery unit 5 along the paper transport direction.

  In this way, the head unit 1 and the sub tank 21 of the ink supply unit 2 are also held on the base member 12 (here, the second base member 12B) and moved integrally, whereby the ink from the sub tank 21 to the recording head 11 is obtained. Problems such as changes in internal pressure due to deformation of the supply tube can be prevented.

  The transport unit 3 includes a transport belt 31 that transports the paper P separated from the paper feed unit 4 one by one by the separation roller 41 and the paper feed roller 42 to face the head unit 1. The conveyor belt 31 is an endless belt that is looped between the conveyor drive roller 32 and the conveyor driven roller 33, and a plurality of holes (not shown) are formed on the surface. An air suction fan (suction fan) 34 for sucking the paper P is disposed. Further, the transport unit 3 is provided with a gap adjusting means 35 that regulates a gap between the nozzle surface of the recording head 11 of the head unit 1 and the surface of the transport belt 41 (paper transport surface).

  The conveyance drive roller 32 is rotated by a motor (not shown), so that the conveyance belt 31 rotates. The sheet P is sucked onto the conveyance belt 31 by the suction fan 34 and is conveyed by the circular movement of the conveyance belt 31. Note that the suction of the sheet is not limited to suction, but may be configured to be held by electrostatic suction or adhesion.

  In this transport unit 3, the transport belt 31, the suction fan 34, the gap adjusting means 35 and the like are integrally rotated with the driven roller 33 on the upstream side in the paper transport direction as a fulcrum and the drive roller 32 on the downstream side in the paper transport direction is lowered. A home position (position indicated by a solid line in FIG. 2: first position) close to the recording head 11 (head unit 1) and a release position (position indicated by a broken line in FIG. 2: first position) that is separated from the recording head 10. 2 position) and can be displaced in the direction of arrow B. By adopting a configuration in which the downstream side in the paper conveyance direction of the conveyance unit 3 is lowered and released, it becomes easy to take out jammed paper in the case of a jam, and the head unit 1 is moved to the maintenance / recovery unit 5 side. The possibility of interference between the nozzle surface of the recording head 11 of the unit 1 and the conveying belt 31 can be prevented.

  The release mechanism 8 that displaces the transport unit 3 between the home position and the release position includes a transport unit release drive motor 81 and a sector gear 83 to which the rotation of the drive motor 81 is transmitted via a pinion 82. The transport unit release drive motor 81 and the pinion 82 are fixed to the base side (apparatus housing side) of the image forming apparatus, the sector gear 83 is fixed to the unit frame side of the transport unit 3 (not shown), and the sector gear 83 is rotated by the pinion 82 rotating. Moves, that is, the transport unit 3 is turned and displaced. Although a power transmission mechanism such as a timing belt or a gear is used from the conveyance belt release drive motor 81 to the pinion 82, the illustration is simplified.

  The maintenance / recovery unit 5 includes a cap member 51 for capping the nozzle surface of the recording head 11 and a wiper blade for wiping the nozzle surface (not shown). A conveyance guide member 9 covering the maintenance recovery unit 5 is disposed above the maintenance recovery unit 5, and the conveyance guide member 9 rotates in the direction of arrow C to open the maintenance recovery unit 5. And a position indicated by a solid line for guiding the sheet from the transport unit 3 can be taken.

  When the maintenance / recovery operation is performed, as shown in FIG. 4, the transport unit 3 is rotated to the release position in the arrow B1 direction, and the transport guide member 9 is rotated in the arrow C1 direction for maintenance recovery. The upper part of the unit 5 is opened, and the drive motor 75 of the head moving means 7 is driven, so that the head unit 1 is moved in the direction indicated by the arrow A1 along with the base member 12 and stops on the maintenance / recovery unit 5.

  The paper discharge unit 6 includes an end fence 61 and a side fence (not shown).

Next, an ink supply system in the image forming apparatus will be described with reference to FIG.
The sub tank 21 includes an ink pack 101 that is a flexible liquid storage member, and a tank case (pressure case) 102 in which the ink pack 101 is sealed and stored. Then, ink is supplied from the main tank 20 to the ink pack 101 of the sub tank 21 through the supply tube 26. Ink supply and supply stop from the main tank 20 to the sub tank 21 are performed by controlling the ink supply valve 103 to open and close.

  On the other hand, the pressurization recovery device 27 that pressurizes the inside of the sub tank 21 includes a pressurization pump 111 and a pressurization chamber 112 that stores a pressurization gas, and the inside of the pressurization chamber 112 pressurized by the pressurization pump 111. Is supplied into the pressurizing case 102 of the sub tank 21 (the space between the pressurizing case 102 and the ink pack 101) through the gas supply path 113. Supply and stop of the pressurized gas from the pressurizing chamber 112 to the sub tank 21 is performed by controlling opening and closing of a supply path on-off valve (pressurization valve) 114 including an electromagnetic valve as an opening / closing means provided on the gas supply path 113. .

  A pressure sensor 114 is provided between the pressurization chamber 112 and the pressurization pump 111, and an air release valve 115 that opens the interior to the atmosphere is provided in the pressurization chamber 112.

Next, different examples of the remaining amount detecting means for detecting the remaining amount of ink in the sub tank 21 will be described with reference to FIGS.
In the remaining amount detection means shown in FIG. 6, a detection filler (detection member) 104 that displaces following the change in the position of the outer surface of the ink pack 101 is provided in the pressure case 102, and the distance disposed outside the pressure case 102. By detecting the change (height) of the distance to the detection filler 104 by the detection sensor 105, the ink remaining amount of the ink pack 101 is detected by determining the collapsed state of the ink pack 101.

  In the remaining amount detection means shown in FIG. 7, a detection filler (detection member) 104 that displaces following the change in the position of the outer surface of the ink pack 101 is provided in the pressure case 102, and an upper limit that is disposed outside the pressure case 102. The detection filler 106 is detected by the detection sensor 106 and the lower limit detection sensor 107 to detect the upper limit position and the lower limit position. When the lower limit position is detected, the ink supply is started from the main tank 20 and the ink is detected when the upper limit position is detected. Stop supplying. Then, the amount of ink used is calculated from the printed image and the number of printed sheets, and when the ink is supplied up to the upper limit position, the full amount of ink is used. Calculate the amount.

Next, an overview of the control unit will be described with reference to the block explanatory diagram of FIG.
The control unit 500 is a main control unit (system controller) configured by a microcomputer, an image memory, a communication interface, and the like that also serves as a control unit that performs control related to the pressure recovery operation according to the present invention that controls the entire image forming apparatus. ) 501. The main control unit 501 sends print data to the print control unit 502 in order to form an image on a sheet based on image data transferred from an external information processing apparatus (host side) and various command information.

  The print control unit 502 generates data for driving pressure generating means for ejecting liquid droplets from the head of the head module (recording head) 51 based on the print data signal received from the main control unit 501. The data transfer and various signals necessary for the transfer confirmation are transferred to the head driver 503, and the storage unit as drive waveform data storage means, and the D / A converter for D / A converting the drive waveform data And a drive waveform generation unit composed of a voltage amplifier, a current amplifier, and the like, and a selection means for selecting a drive waveform to be given to the head driver 503, and is composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal). The drive waveform is generated and output to the head driver 503 to drive-control the recording head 11 of the head unit 1.

  The main control unit 501 also includes a drive motor (unit movement motor) 75 that moves the head unit 1 between an image forming position and a maintenance / recovery position via a motor driver 504, and a paper feed motor that moves the conveyor belt 31 around. 506, drive control of a fan motor 507 for driving the suction fan 34 is performed.

  The main control unit 501 performs drive control of the suction pump 52 of the maintenance / recovery unit 5 and the pressurization pump 111 of the pressurization / recovery device 27 via the driver 510, and the ink supply valve 103 via the driver 511. Then, drive control (opening / closing control) of the supply path opening / closing valve (pressurizing valve) 114 and the atmospheric release valve 116 is performed.

  The main control unit 501 also includes a detection signal from the remaining amount detection sensor 105 or the upper limit detection sensor 106 and the lower limit detection sensor 107, a detection signal from the pressure sensor 115, and a temperature sensor that detects the environmental temperature. Detection and detection signals from various sensors such as a detection signal from 512 are input. In addition, input / output of various information and exchange of display information are performed with the operation unit 513.

Next, the pressure recovery operation in this embodiment will be described with reference to the flowchart of FIG.
When performing the pressure recovery operation of each head 11 of the head unit 5, as described above, the unit moving motor 75 is driven to move the head unit 1 onto the maintenance recovery unit 5 and raise the maintenance recovery unit 5. The nozzle surface of the head 11a is capped by the cap 51.

  9 is started, the pressurization valve 114 and the air release valve 116 are shut off (closed), the drive of the pressurization pump 111 is started, and the pressure in the pressurization chamber 112 becomes a predetermined pressure. The driving of the pressurizing pump 111 is stopped.

  Thereafter, the remaining amount of ink in the sub-tank 21 is detected by the remaining amount detection sensor 105, and a predetermined standard pressurization time T0 is multiplied by a predetermined correction multiplier α according to the remaining amount of ink to obtain a remaining amount correction pressurization time. Tα is obtained.

  Further, the in-machine temperature (environment temperature) is detected by the temperature sensor 512, and the pressurization time Tβ is determined by multiplying the remaining amount correction pressurization time Tα by a correction multiplier β determined in advance according to the environmental temperature.

  Thereafter, the pressurization valve 114 is opened (opened), the pressurization valve 114 is opened for the pressurization time Tβ obtained by the correction, and the pressurization gas is supplied from the pressurization chamber 112 to the sub tank 21, and the pressurization time Tβ After the elapse of time, the atmosphere release valve 116 is opened to release the pressurization chamber 112 to the atmosphere, and the inside of the sub tank 21 is opened to the atmosphere, and then the pressurization valve 114 is shut off (closed).

  Then, after wiping the nozzle surface with a wiper member (not shown), the pressurizing valve 114 is opened.

  In this way, by setting the pressurization time during the pressurization recovery operation according to the ink remaining amount in the subtank and the environmental temperature, the amount of ink discharged from the subtank to the printhead can be controlled to be almost constant. Pressure recovery can be reliably performed while reducing ink consumption.

  That is, when the sub tank 21 is pressurized under the same conditions, as the remaining amount of ink in the ink pack 101 of the sub tank 21 increases, the amount of air in the pressure case 102 decreases as shown in FIG. Efficiency increases, ink discharge increases, and wasteful ink consumption occurs. On the contrary, when the remaining amount of ink decreases, the amount of air in the pressurizing case 102 increases, so the pressurization efficiency decreases, the ink discharge amount decreases, and an ink discharge amount that can be sufficiently recovered cannot be obtained. There is a fear.

  Further, as shown in FIG. 10B, the higher the ink temperature, the lower the ink viscosity, the lower the fluid resistance in the supply path from the sub-tank 21 to the recording head 11, the more the amount of ink discharged, and the wastefulness. Ink consumption will be performed. Conversely, when the ink temperature is lowered, the ink viscosity is increased, the fluid resistance in the supply path from the sub tank 21 to the recording head 11 is increased, the ink discharge amount is reduced, and the ink discharge amount that can be sufficiently recovered. May not be obtained.

  Therefore, as described above, the amount of ink discharged from the sub tank to the recording head can be controlled to be substantially constant by setting the pressurization time during the pressure recovery operation in accordance with the remaining ink amount in the sub tank and the environmental temperature. This makes it possible to reliably perform pressure recovery while reducing wasteful ink consumption.

  In this way, when performing the pressure recovery operation, the configuration is such that the remaining amount of liquid in the liquid tank is pressurized during the pressurization time, thereby reducing the effect of the remaining amount of liquid in the liquid tank and wasting. It is possible to perform a reliable recovery operation while suppressing excessive liquid consumption.

  In the above-described embodiment, an example in which the present invention is applied to a line type image forming apparatus has been described. However, the present invention can be similarly applied to a serial type image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Head unit 2 Ink supply part 3 Conveyance unit 4 Paper supply part 5 Maintenance recovery unit 6 Paper discharge part 7 Head moving means 8 Paper discharge unit cancellation | release mechanism 9 Conveyance guide member 11 Recording head 12 Base member 21 Sub tank 27 Pressure recovery apparatus 31 Conveying belt 32 Drive roller 33 Driven roller 34 Air suction fan (suction fan)
101 Ink pack (flexible liquid container)
DESCRIPTION OF SYMBOLS 102 Pressurization case 104 Detection filler 105 Distance detection sensor 111 Pressurization pump 112 Pressurization chamber 113 Gas supply path 114 Pressurization valve (opening-closing means)

Claims (2)

A recording head having nozzles for discharging droplets;
A replaceable main tank,
A sub-tank having a flexible bag-like ink pack that is supplied with liquid from the main tank and stores the liquid supplied to the recording head, and a pressure case in which the ink pack is sealed and stored;
A pressurizing unit that pressurizes the ink pack by supplying a pressurized gas between a pressurizing case of the liquid tank and the ink pack;
Opening and closing means provided in a gas supply path from the pressurizing means to the sub tank;
A remaining amount detecting means for detecting the remaining amount of liquid in the ink pack;
Control means for performing control to pressurize the inside of the sub tank by the pressurizing means and pressurize and supply the liquid to the recording head when performing the recovery operation of the recording head;
With
Providing a water head difference between the sub-tank and the recording head to generate a predetermined negative pressure on the recording head;
The ink pack is horizontally sealed and stored in the pressure case,
The remaining amount detecting means is
A detection member that partially contacts the ink pack and displaces in accordance with the position of the outer surface of the ink pack being crushed in the vertical direction according to the amount of liquid contained in the ink pack;
An upper limit detection sensor and a lower limit detection sensor disposed outside the pressure case,
The control means includes
When the upper limit detection sensor and the lower limit detection sensor detect the detection member to detect the upper limit position and the lower limit position, and when the lower limit position is detected, liquid supply from the main tank is started and the upper limit position is detected. Stop supplying liquid to the
Calculate the amount of liquid used from the printed image and the number of printed sheets,
When the liquid is supplied to the upper limit position by the remaining amount detecting means as a full tank state, the remaining liquid amount is calculated from the liquid amount in the full tank state and the used liquid amount,
An image characterized by controlling the supply of pressurized liquid from the pressurizing means to the sub-tank by opening the opening / closing means for a pressurizing time corresponding to the remaining liquid amount detected by the remaining capacity detecting means. Forming equipment.   The image forming apparatus according to claim 1, wherein the control unit corrects the pressurizing time according to an environmental temperature.

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