JP2010046806A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it takes an initial filling time to surely discharge bubbles when an ink is initially filled. <P>SOLUTION: The image forming apparatus controls as follows. When the ink is initially filled into a head 101 from an ink tank 81 by driving a suction pump 63 with a nozzle surface 104 of the head 101 of a recording head 51 sealed by a cap member 62, the image forming apparatus continuously drives the suction pump 63 until a set time t for the ink to reach the head 101 passes, whereby a continuous flow of the ink is generated from the ink tank 81 to the head 101. After the ink reaches the head 101, the image forming apparatus intermittently drives the suction pump 63 to generate an intermittent flow of the ink. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an ink supply apparatus in an image forming apparatus including a recording head that ejects 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 such an image forming apparatus (hereinafter, also simply referred to as “inkjet recording apparatus”), when initial filling is performed for supplying ink from an ink tank to a recording head for the first time, bubbles in the recording head and the ink supply path are removed. It is necessary to discharge reliably. 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.

  For example, as described in Patent Document 1, a valve unit is arranged in the ink flow path between the ink cartridge and the head, and the opening and closing of the valve unit can be controlled in conjunction with the head cleaning operation. Valve opening control is performed with the negative pressure accumulated by the pump, and the suction pump is continuously driven so that bubbles are discharged by the instantaneous fast flow of ink generated by opening the valve unit. Are known.

  In addition, as described in Patent Document 2, it is known that the pressure is changed in multiple stages by intermittent operation of the pump, and ink is discharged from the head ejection unit by suction or pressurization.

  Further, as described in Patent Document 3, a mode is provided that includes a print recovery means for maintaining and recovering the head by ink suction, in which the suction operation is intermittently performed a plurality of times, and the ink channel is filled with ink. It is known to perform a mode for continuously performing a suction operation.

JP 2007-98959 A JP 11-348318 A Japanese Patent No. 3484869

  However, conventionally, when the ink is initially filled in the recording head, since the ink is intermittently supplied from a state where the ink flow path is not filled, an instantaneous fast ink flow can be created. However, there is a problem that the flow rate of the sucked ink is not so large that it takes time to completely fill the ink flow path, and the initial ink filling time becomes longer and the waiting time of the user is prolonged. is there.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to shorten the filling time while maintaining the bubble discharging property when the ink is initially filled in the recording head.

In order to solve the above problems, an image forming apparatus according to the present invention includes:
A recording head for discharging droplets;
An ink tank for storing ink to be supplied to the recording head;
A cap member for sealing the nozzle surface of the recording head, and suction means connected to the cap member;
In a state where the nozzle surface of the recording head is sealed with the cap member, when the suction unit is driven to initially fill the recording head with ink from the ink tank, until the ink reaches the recording head, The suction unit is continuously driven to generate a continuous ink flow from the ink tank to the recording head, and after the ink reaches the recording head, the suction unit is intermittently driven to intermittently And a control means for controlling the generation of ink flow.

An image forming apparatus according to the present invention includes:
A recording head for discharging droplets;
An ink tank for storing ink to be supplied to the recording head;
A cap member for sealing the nozzle surface of the recording head, and suction means connected to the cap member;
Opening and closing means for opening and closing a suction path between the cap member and the suction means;
When the suction unit is driven and the recording head is initially filled with ink from the ink tank with the cap member sealed with the nozzle surface of the recording head, the recording unit is continuously driven while the recording unit is driven. Until the ink reaches the head, the opening / closing means is opened to generate a continuous ink flow from the ink tank to the recording head, and after the ink reaches the recording head, the opening / closing means is opened / closed. And a control means for controlling to generate intermittent ink flow repeatedly.

  In these image forming apparatuses according to the present invention, the flow path between the ink tank and the recording head includes a detecting unit that detects the presence or absence of ink in the vicinity of the inlet of the recording head. it can.

  According to the image forming apparatus of the present invention, when ink is initially filled, a continuous ink flow is generated from the ink tank to the recording head until the ink reaches the recording head, and the ink is applied to the recording head. Since the ink flow is intermittently generated after the arrival, the initial filling time can be shortened while maintaining the bubble discharge performance.

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 first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram for explaining the overall configuration of the image forming apparatus, and FIG. 2 is a plan explanatory view of the apparatus.
This image forming apparatus is a line type image forming apparatus, and includes an apparatus main body 1, a paper feed tray 2 on which paper P is stacked and fed, a paper discharge tray 3 on which printed paper P is discharged and stacked, and paper P A transport unit 4 that transports the paper from the paper feed tray 2 to the paper discharge tray 3, an image forming unit 5 that performs printing by ejecting liquid droplets onto the paper P transported by the transport unit 4, and a required timing after completion of printing. A cleaning device 6 that is a maintenance and recovery mechanism for maintaining and recovering each head of the image forming unit 5, a conveyance guide portion 7 that opens and closes the cleaning device 6, and an ink tank unit that supplies ink to each head of the image forming unit 5. 8 and a main tank unit 9 for supplying ink to the ink tank unit 8.

  The apparatus main body 1 includes front and rear side plates and stays (not shown), and the sheets P stacked on the sheet feed tray 2 are fed one by one to the transport unit 4 by the separation roller 21 and the sheet feed roller 22. Is done.

  The transport unit 4 includes a transport drive roller 41a, a transport driven roller 41b, and an endless transport belt 43 wound around these rollers 41a and 41b. A plurality of holes (not shown) are formed on the surface of the transport belt 43, and a suction fan 44 that sucks the paper P is disposed below the transport belt 43. Further, conveyance guide rollers 42a and 42b are respectively held on guides (not shown) on the conveyance driving roller 41a and conveyance driven roller 41b and are in contact with the belt 43 by their own weight.

  The conveyance belt 43 rotates around when the conveyance driving roller 41 a is rotated by a motor (not shown), and the paper P is sucked onto the conveyance belt 43 by the suction fan 44 and is conveyed by the rotation movement of the conveyance belt 43. The transport driven roller 41 b and the transport guide rollers 42 a and 42 b rotate following the transport belt 43.

  An image forming unit 5 including a recording head unit 50 including a plurality of recording heads 51 that discharge droplets to be printed on the paper P is disposed above the transport unit 4 so as to be movable in the arrow A direction. The image forming unit 5 is moved to above the cleaning device 6 during the maintenance / recovery operation (cleaning).

  The recording head unit 50 of the image forming unit 5 includes a plurality of recording heads 51y, 51m, 51c, 51k (hereinafter referred to as “yellow” (Y), magenta (M), cyan (C), and black (K)). When the colors are not distinguished from each other, the symbols without the sub-codes y, m, c, and k are used (the same applies to the other members).

  As shown in FIG. 3, each recording head 51 has 10 heads 101 </ b> A to 101 </ b> J arranged in a staggered manner in two rows on a head support member 100. As shown in FIG. 4, each head 101 has a nozzle surface 104 in which nozzle rows 103 in which a plurality of nozzles 102 for discharging droplets are arranged side by side are arranged in a zigzag manner. The configuration of the recording head unit 50 is not limited to these examples.

  In the image forming unit 5, a branching member 52, which is a branching unit that supplies ink of a required color to each recording head 51, is disposed above the recording head unit 50, and the supply between the branching member 52 and the recording head 51 is provided. Connected by a tube 53. An ink tank 81 of the ink tank unit 8 (only one ink tank is provided with a reference numeral for convenience of illustration) is disposed on the upstream side of the branching member 52, and the distributor 52 of the recording head 51 is connected via a supply tube 82. And a negative pressure is formed in each head 101 due to a water head difference between the ink tank 81 and each head 101 of the recording head 51. Further, the main tank unit 9 is disposed on the upstream side of the ink tank 81, and ink is supplied from the main tank 91 through the supply tube 92 to the ink tank 81.

  On the downstream side of the transport unit 4, a transport guide portion 7 that discharges the paper P to the paper discharge tray 3 is provided. The paper P guided and conveyed by the conveyance guide unit 7 is discharged to the paper discharge tray 3. The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper P and an end fence 32 that regulates the front end of the paper P.

  The maintenance / recovery mechanism (cleaning device) 6 includes four rows of cleaning means 61 corresponding to each recording head 51 of the image forming unit 5, and one cleaning means 61 includes ten heads 101 of the recording head 51. 10 cap members 62 corresponding to, and a wiper member (not shown). Note that the cap member 62 can be moved up and down independently. Further, below the cleaning unit 61, there is a suction pump 63 that is a suction unit for sucking ink from the nozzles 102 of the head 101 with the cap member 62 capping (sealing) the nozzle surface 104 of the head unit 100. Has been placed.

  In this image forming apparatus, after the printing is completed, when the recording head 51 that discharges the droplets is capped by the cleaning unit 61 and ink is sucked from the nozzles 102, or the nozzle surface 104 of the head of the recording head 51 is used. When the ink adhering to the toner is cleaned by the wiper member of the cleaning means 61, as shown in FIG. 5, after the printing is stopped, the entire transport unit 4 rotates in the direction of arrow B with the transport driven roller 41b as a fulcrum. By making the space between the image forming unit 5 larger than that at the time of image formation, a space for moving the image forming unit 5 is secured. At this time, the conveyance guide plate 71 of the conveyance guide portion 7 disposed on the upper portion of the cleaning device 6 is also rotated upward in the direction of the arrow C at the fulcrum 72, and the upper portion of the cleaning device 6 is opened.

  Then, after the transport unit 4 and the transport guide portion 7 are released (released), the image forming unit 5 moves in the paper passing direction (in the direction of arrow A), stops above the cleaning device 6, and the cleaning unit 61. Rises and shifts to a head cleaning operation (maintenance recovery operation) of each recording head 51.

Next, an ink supply system and an ink discharge system for the recording head in this image forming apparatus will be described with reference to FIG.
The ink tank 81 that stores ink to be supplied to the recording head 51 is arranged with a required water head difference from the recording head 51. In this case, the negative pressure (water head pressure) at the nozzle surface 104 (opening of the nozzle 102 to the nozzle surface 104) generated by the difference between the liquid level height of the ink tank 81 and the height of the recording head 51 (water head difference). ) Changes depending on the consumption of ink in the ink tank 81. Further, the ink tank 81 is provided with an atmosphere release path 83 that communicates with the atmosphere inside the tank, and an atmosphere release valve 84 that opens and closes the atmosphere release path 83. Normally, the ink tank 81 is in the atmosphere release state.

  Further, a main tank 91 for supplying ink to the ink tank 81 is provided, and ink is supplied from the main tank 91 to the ink tank 81 in accordance with a signal from a liquid level sensor such as an electrode pin (not shown) provided in the ink tank 81. To control the amount of ink in the ink tank 81 within a certain range. Note that ink is supplied from the main tank 91 to the ink tank 81 by a control means (not shown) such as an electromagnetic valve provided in an ink supply path (supply tube) 92 from the main tank 91 to the ink tank 81. The opening / closing control is performed based on the signal of the liquid level sensor.

  On the other hand, a branching member 52 is disposed as a branching unit that branches the ink supply path (flow path) with respect to each head 101 of one recording head 51. In addition, as shown in FIG. 1, the branch member 52y, 52m, 52c, and 52k are arrange | positioned with respect to each recording head 51y, 51m, 51c, and 51k, respectively.

A supply tube 82 is connected to one end of the branch portion 52 between the ink tank 81 and ink is supplied from the ink tank 81 via the supply tube 82.
.

  Further, in order to suck ink from the nozzle 102 of the head 101 of the recording head 51, the cleaning device 6 is connected to the cap member 62 that seals the nozzle surface 104 of the head 101, and the cap member 62 via the exhaust ink tube 64. And the suction pump 63 is driven in a state in which the nozzle surface 104 of the head 101 is sealed by the cap member 62, and the sealed space in the cap member 62 becomes negative pressure. Then, ink is sucked and discharged from the nozzle 102.

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 includes a main control unit (system controller) 501 including a microcomputer that also serves as a control unit according to the present invention that controls the entire image forming apparatus, an image memory, a communication interface, and the like. 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.

  Based on the print data signal received from the main control unit 501, the print control unit 502 generates data for driving the pressure generating means for ejecting the droplets from the recording head 51, and transfers the data. Various signals necessary for confirmation of transfer and the like are transferred to the head driver 503, and a storage unit as drive waveform data storage means, a D / A converter, a voltage amplifier and a current amplifier for D / A conversion of drive waveform data Drive waveform generation unit configured by the above and selection means for selecting a drive waveform to be given to the head driver 503, and generates a drive waveform configured by one drive pulse (drive signal) or a plurality of drive pulses (drive signal) Then, the output is output to the head driver 503 to drive and control the recording head 51.

  Further, the main control unit 501 drives and controls a paper feed motor 505 and a suction pump 63 that move the conveyor belt 43 around through a motor driver 504.

  Further, the main control unit 501 receives detection signals from the sensor group 506 including the ink liquid level detection means described above, and inputs / outputs various information and exchanges display information with the operation unit 507. .

Next, ink initial filling control by the control unit in this embodiment configured as described above will be described with reference to a timing chart shown in FIG.
First, when the recording head 51 is initially filled with ink, the nozzle surface 104 of the head 101 of the recording head 51 of the recording head unit 50 is capped (sealed) by the cap member 62 of the cleaning device 6. Further, the air release valve 84 of the ink tank 81 is closed.

  Here, as shown in FIG. 8A, when an ink filling start command is generated (turned on), as shown in FIG. 8B, the main control unit 501 has a set time t set in advance. The intermediate suction pump 63 is continuously driven (on). Thereby, an ink flow is continuously generated from the ink tank 81 to the recording head 51, and ink is supplied to each head 101 of the recording head 51. Here, the set time t is from when the suction pump 63 starts to be driven until the ink pumped from the ink tank 81 through the supply tube 82 fills the branch member 52 of the recording head 51 and reaches the head 101. It is time and has been obtained in advance through experiments.

  Then, after the set time t has elapsed, the main control unit 501 repeats driving and stopping of the suction pump 63 to drive intermittently (repeat on / off). This intermittent driving is performed for a preset number of times Nn. Accordingly, an ink flow is intermittently generated from the ink tank 81 to the recording head 51, and ink is supplied to each head 101 of the recording head 51.

  In this manner, the suction pump 63 is continuously driven until ink reaches the head 101 of the recording head 51 to generate a continuous ink flow from the ink tank 81 to the recording head 51, and the ink is supplied to the recording head 51. Is reached, the suction pump 63 is intermittently driven so as to generate an intermittent ink flow.

  Therefore, the ink can be continuously supplied until the ink reaches the recording head 51 and the ink in the supply tube 82 and the flow path in the branching member 52 can be filled in a short time. Then, after the ink reaches the recording head 51, the bubbles can be discharged by intermittent ink flow.

  In other words, even if intermittent ink filling is performed before ink reaches the inside of the recording head, there is no significant effect on the bubble discharge performance. Rather, if ink is intermittently supplied, ink reaches from the ink tank to the head. It will take time to make it happen. Therefore, in order to quickly reach the ink to the head, a continuous pump operation (suction) is performed, and when the ink reaches the head, intermittent ink supply is performed to create an instantaneous ink flow. To ensure that it is discharged.

  In this way, when ink is initially filled, a continuous ink flow is generated from the ink tank to the recording head until the ink reaches the recording head, and intermittently after the ink reaches the recording head. Since the ink flow is generated, the initial filling time can be shortened while maintaining the bubble discharge performance.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a schematic explanatory view of an ink supply system and a discharge system in the same embodiment, and FIG. 10 is a schematic side view of one recording head.
Here, an opening / closing valve (valve) 65 is provided between the cap member 62 of the cleaning device 6 and the suction pump 63 as opening / closing means for opening / closing a suction path formed by the exhaust ink tube 64. Further, in the supply path formed by the supply tube 53 between the branching member 52 of the recording head unit 50 and each head 101 of the recording head 51, the head 101 is detected by detecting the presence or absence of ink at the inlet of the head 101. Ink presence / absence detection means 66 including a transmission type photosensor for detecting that the ink has reached is provided. The opening / closing drive of the opening / closing valve 65 is performed by the main control unit 501 of the first embodiment described above, and a detection signal of the ink presence / absence detection means 66 is input to the main control unit 501.

Next, ink initial filling control by the control unit in this embodiment configured as described above will be described with reference to a timing chart shown in FIG.
First, when the ink is initially filled in the recording head 51, the nozzle surface 104 of each head 101 of the recording head 51 of the recording head unit 50 is capped (sealed) by the cap member 62 of the cleaning device 6. Further, the air release valve 84 of the ink tank 81 is closed.

  Here, as shown in FIG. 11A, when an ink filling start command is generated (turned on), the main control unit 501 opens the on-off valve (valve) 65 as shown in FIG. 11B. At the same time, as shown in FIG. 11C, the suction pump 63 is continuously driven (turned on). Thereby, an ink flow is continuously generated from the ink tank 81 to the recording head 51, and ink is supplied to each head 101 of the recording head 51.

  Then, as shown in FIG. 11 (d), from the time when it is detected that the ink presence / absence detecting means 66 has reached the inlet portion of the head 101 of the recording head 51, as shown in FIG. The control unit 501 repeatedly opens and closes the opening / closing valve 65. At this time, since the suction pump 63 is continuously driven, the opening and closing valve 65 is opened and closed, whereby an ink flow is intermittently generated from the ink tank 81 to the recording head 51, and the recording head 51. Ink is supplied to each head 101. The opening / closing drive of the opening / closing valve 65 is performed a predetermined number of times Nn.

  In this way, the ink pump 81 is continuously driven until the ink reaches the head 101 of the recording head 51, and the on-off valve 65 is opened to generate a continuous ink flow from the ink tank 81 to the recording head 51. After the ink reaches the recording head 51, the control is performed such that the on-off valve 65 is repeatedly opened and closed while the suction pump 63 is continuously driven to generate an intermittent ink flow.

  Therefore, the ink can be continuously supplied until the ink reaches the recording head 51 and the ink in the supply tube 82 and the flow path in the branching member 52 can be filled in a short time. Then, after the ink reaches the recording head 51, the bubbles can be discharged by intermittent ink flow.

  In other words, as described above, even if intermittent ink filling is performed before the ink reaches the inside of the recording head, the bubble discharge performance is not significantly affected. It takes time to make the ink reach the head. Therefore, in order to quickly reach the ink to the head, a continuous suction operation is performed, and when the ink reaches the head, intermittent ink supply is performed to create an instantaneous ink flow, thereby ensuring air bubbles. Let it drain.

  In this way, when ink is initially filled, a continuous ink flow is generated from the ink tank to the recording head until the ink reaches the recording head, and intermittently after the ink reaches the recording head. Since the ink flow is generated, the initial filling time can be shortened while maintaining the bubble discharge performance.

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

1 is a schematic front view illustrating an overall configuration of an example of an image forming apparatus according to a first embodiment of the present invention. Similarly it is principal part plane explanatory drawing. FIG. 2 is an explanatory plan view of a recording head. It is a plane explanatory view of a head. It is principal part explanatory drawing used for description at the time of cleaning operation | movement. FIG. 3 is a schematic explanatory diagram of an ink supply system and a discharge system. It is a functional block diagram explaining the outline | summary of a control part. 6 is a timing chart for explaining the ink initial filling control in the embodiment. It is a typical explanatory view of the ink supply system and discharge system in a 2nd embodiment of the present invention. FIG. 6 is a schematic side view of the same recording head. 6 is a timing chart for explaining the ink initial filling control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Apparatus main body 4 ... Conveyance unit (conveyance part)
5. Image forming unit 6. Cleaning device (maintenance and recovery mechanism)
DESCRIPTION OF SYMBOLS 7 ... Conveyance guide part 8 ... Ink tank unit 9 ... Main tank unit 50 ... Recording head unit 51 ... Recording head 54 ... Branch member 62 ... Cap 63 ... Suction pump 64 ... Waste ink tube (suction path)
65 ... Open / close valve 66 ... Ink presence / absence detecting means 81 ... Ink tank 91 ... Main tank 101 ... Head

Claims (3)

A recording head for discharging droplets;
An ink tank for storing ink to be supplied to the recording head;
A cap member for sealing the nozzle surface of the recording head, and suction means connected to the cap member;
In a state where the nozzle surface of the recording head is sealed with the cap member, when the suction unit is driven to initially fill the recording head with ink from the ink tank, until the ink reaches the recording head, The suction unit is continuously driven to generate a continuous ink flow from the ink tank to the recording head, and after the ink reaches the recording head, the suction unit is intermittently driven to intermittently An image forming apparatus comprising: a control unit that performs control to generate an ink flow. A recording head for discharging droplets;
An ink tank for storing ink to be supplied to the recording head;
A cap member for sealing the nozzle surface of the recording head, and suction means connected to the cap member;
Opening and closing means for opening and closing a suction path between the cap member and the suction means;
When the suction unit is driven and the recording head is initially filled with ink from the ink tank with the cap member sealed with the nozzle surface of the recording head, the recording unit is continuously driven while the recording unit is driven. Until the ink reaches the head, the opening / closing means is opened to generate a continuous ink flow from the ink tank to the recording head, and after the ink reaches the recording head, the opening / closing means is opened / closed. An image forming apparatus comprising: a control unit that performs control to repeatedly generate an intermittent ink flow.   3. The image according to claim 1, wherein the flow path between the ink tank and the recording head includes detection means for detecting the presence or absence of ink in the vicinity of the inlet of the recording head. Forming equipment.

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