JP5445214B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a recording head that discharges droplets and a sub tank that supplies liquid to the recording head.

  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.

  Such an image forming apparatus includes a sub tank (also referred to as a head tank or a buffer tank) that supplies ink to the recording head, and a main tank (also referred to as an ink cartridge) that is detachably attached to the apparatus main body. A method of supplying ink to a sub tank is known.

  With regard to conventional subtank control, for example, it is known to detect the ink remaining amount in a subtank and perform ink replenishment operation for the subtank according to the detection result (Patent Document 1).

JP 2005-059490 A

  By the way, for example, in order to eliminate bidirectional color differences or improve resolution, it has two heads or nozzle rows that discharge droplets of the same color, and each head or head row has a sub-tank. A configuration including a supply system that supplies ink of the same color to two subtanks may be employed.

  In this case, when the main tank is in the ink end (including ink near end) state, it is requested to replace the main tank. However, when the main tank is out of stock, it cannot be replaced immediately and printing is not possible. There is an inconvenience that it will be canceled.

  Therefore, it is conceivable to continue printing using the ink remaining in the subtank. However, even if the ink remaining in one subtank runs out in this way, there is sufficient ink remaining in the other subtank. Even in this case, there is an inconvenience that printing is stopped.

  SUMMARY An advantage of some aspects of the invention is that printing can be continued as long as possible even when a main tank is in an end state.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A plurality of heads that discharge droplets of the same color or a head having a nozzle row that discharges droplets of the same color;
A plurality of first tanks for storing liquid to be supplied to each head or each nozzle row for discharging the same color droplets;
A second tank containing liquid to be supplied to the plurality of first tanks containing liquid of the same color;
Reversible liquid feeding means for feeding a liquid between the first tank and the second tank;
Means for detecting a remaining amount of liquid in the first tank;
When the second tank is in an end state, after the liquid is recovered from the first tank having a relatively large amount of remaining liquid among the plurality of first tanks to the second tank, the remaining amount of liquid is relatively And means for controlling the liquid to be fed to the first tank with a small amount ,
When the difference between the remaining amount of liquid in the first tank having a relatively large amount of remaining liquid and the remaining amount of liquid in the first tank having a relatively small amount of remaining liquid is equal to or less than a predetermined amount, the control is not performed. <br/> Configuration.

According to the image forming apparatus of the present invention, since the liquid can be moved between at least two first tanks when the second tank is in the end state, even if the second tank is in the end state. Printing can be continued as much as possible.

1 is a schematic side view illustrating an overall configuration of a mechanism unit of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. It is a typical plane explanatory view showing an example of a sub tank. FIG. 4 is a schematic front explanatory view of FIG. 3. FIG. 3 is a schematic explanatory diagram for explaining an ink supply / discharge system. It is explanatory drawing with which it uses for description of the ink supply system from one main tank with respect to two subtanks. It is explanatory drawing with which it uses for description of an example of a supply pump. FIG. 4 is a main part explanatory view of a carriage and an apparatus main body side detection sensor for explaining subtank negative pressure detection operation, remaining amount detection operation, and full tank detection operation; It is a typical explanatory view similarly used for operation explanation of a displacement member of a sub tank. It is a schematic block explanatory drawing explaining the control part of the apparatus. It is explanatory drawing with which it uses for description of the ink movement operation | movement between the subtanks in this invention. FIG. 3 is an explanatory diagram for explaining ink movement control in the first embodiment of the present invention performed by the control unit. It is explanatory drawing with which it uses for description of the ink movement control in 2nd Embodiment of this invention which the same control part performs. It is explanatory drawing with which it uses for description of the ink movement control in 3rd Embodiment of this invention which the same control part performs. It is explanatory drawing with which it uses for description of the ink movement control in 4th Embodiment of this invention which the control part performs.

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 the overall configuration 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 four recording heads 34a and 34b (not distinguished from each other) that are liquid ejection heads for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). In some cases, 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. For example, the two nozzle rows of the recording head 34a discharge black (K) droplets, and the recording heads 34b, 34c, and 34d discharge, for example, each nozzle row. The colors of the droplets to be assigned are assigned in the order of Y, M, C, C, M, Y in the order from any one to the other in the main scanning direction. Alternatively, in the recording heads 34a to 34d, for example, the colors of the liquid droplets ejected from each nozzle row are arranged from any one to the other in the main scanning direction, and K, C, M, Y, Y, M, C, It can also be assigned in the order of K. In any case, it has a plurality of nozzle rows that discharge droplets of the same color.

  Further, the carriage 33 is mounted with sub tanks 35a to 35d (hereinafter referred to as “sub tanks 35” when not distinguished), which are first tanks for supplying ink of each color corresponding to the nozzle rows of the recording head 34. Yes. The sub-tank 35 is provided with a supply tube 36 for each color by a supply pump unit 24 from ink cartridges (main tanks) 10y, 10m, 10c, and 10k that are second tanks for each color that are detachably attached to the cartridge loading unit 4. Thus, the recording liquid of each color is replenished and supplied. Note that the sub tanks 35 a to 35 d are obtained by integrally providing two sub tanks for each nozzle row of one recording head 34.

  An encoder scale 91 is provided along the main scanning direction of the carriage 33, and an encoder sensor 92 that reads the encoder scale 91 is provided on the carriage 33, and the linear encoder 90 is configured by the encoder scale 91 and the encoder sensor 92. The position of the carriage 33 in the main scanning direction (carriage position) and the amount of movement are detected by the detection signal of the linear encoder 90.

  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 example of the sub tank 35 will be described with reference to FIGS. 3 is a schematic top view for explaining one nozzle row of the sub tank, and FIG. 4 is a schematic front view for one nozzle row of the sub tank.
The sub-tank 35 has a tank case 201 that forms an ink containing portion opened on one side for holding ink. The opening of the tank case 201 is sealed with a flexible film 203, and the inside of the tank case 201 is The film 203 is constantly urged outward by a spring 204 as an elastic member disposed on the outside. As a result, an outward biasing force is applied to the film 203 of the tank case 201 by the spring 204, so that a negative pressure is generated when the remaining amount of ink in the tank case 201 decreases.

  In addition, a displacement member (also referred to as a full-fill detection filler) is formed on the outside of the tank case 201. The displacement member includes a filler whose one end is swingably supported by a support shaft 202 and is urged toward the tank case 201. 205 is fixed to the film 203 by adhesion or the like, and the displacement member 205 is displaced in conjunction with the movement of the film 203. Therefore, the displacement amount of the displacement member 205 is detected by the full tank detection sensor 301 including an optical sensor arranged on the apparatus main body side. By detecting this, it is possible to detect the remaining amount of ink in the sub tank 35 and the like.

  A supply port 209 for supplying ink from the ink cartridge 10 is connected to the ink supply tube 36 at the upper portion of the tank case 201. An air release mechanism 207 that opens the inside of the sub tank 35 to the atmosphere is provided on the side of the tank case 201. The atmosphere release mechanism 207 includes a valve body 207b that opens and closes an atmosphere release path 207a communicating with the sub tank 35, a spring 207c that biases the valve body 207b to a closed state, and the like. Is opened by pushing the valve body 207b, and the sub tank 35 is opened to the atmosphere (a state communicating with the atmosphere).

  Electrode pins 208a and 208b for detecting the ink level in the sub tank 35 are attached. Since the ink has electrical conductivity, when the ink reaches the electrode pins 208a and 208b, a current flows between the electrode pins 208a and 208b, and the resistance value of the two changes. It is possible to detect that the air amount in the sub tank 35 has become a predetermined amount or more.

Next, an outline of the ink supply / discharge system will be described with reference to FIG.
First, ink is supplied from the ink cartridge 10 to the sub tank 35 through a supply tube 36 by a liquid supply pump 241 that is a liquid supply means of the supply unit 24. The supply pump 241 is a reversible pump configured by a tube pump or the like, and can perform an operation of supplying ink from the ink cartridge 10 to the sub tank 35 and an operation of returning ink from the sub tank 35 to the ink cartridge 10. Yes.

  Then, with the air release mechanism 207 of the sub tank 35 closed, the nozzle surface of the recording head 34 is capped with the suction cap 82 a of the maintenance / recovery mechanism 81, and the suction pump 811 of the maintenance / recovery mechanism 81 is driven to suck the suction tube 812. The ink in the sub tank 35 can be sucked by sucking the ink from the nozzle through the elastic member 204, and a negative pressure is formed in the sub tank 35 by the elastic member 204 pushing the flexible film 203 outward. The sucked waste ink is discharged to a waste liquid tank 813.

  In addition, ink in the sub tank 35 is consumed by discharging droplets that do not contribute to image formation from the recording head 34 toward the above-described empty discharge receiver 84 in a state where the atmosphere release mechanism 207 of the sub tank 35 is closed. Similarly, a negative pressure can be formed in the sub tank 35 by the elastic member 204 pushing the flexible film 203 outward.

Next, a supply system for two sub tanks that store ink of the same color will be described with reference to FIG.
As described above, this image forming apparatus includes a plurality of sub tanks 35 corresponding to a plurality of nozzle rows that discharge droplets of the same color. Here, as shown in FIG. 6, the two sub tanks 35 containing the same color ink are sub tanks 35A and 35B, and the main tank 10 and the sub tank 35A are connected via a reversible pump 241A and an on-off valve 242A, By connecting the tank 10 and the sub tank 35B via the reversible pump 241B and the on-off valve 242B, ink is supplied from the single main tank 10 to the two sub tanks 35A and 35B.

  As shown in FIG. 7, the tube pump constituting the reversible pump 241 has a flexible tube 401 wound around the tube support surface 400a inside the pump case 400, and an eccentric cam type pressing roller 402 is provided. By rotating around the support shaft 403, the pressure roller 402 handles the tube 401 in the rotational direction to feed liquid in the rotational direction of the pressure roller 401. By changing the rotational direction of the pressure roller 401, Forward / reverse feeding (supply and suction) can be performed. Note that a DC motor or the like is used as a driving source for driving the pressing roller 401.

Next, detection of the negative pressure (pressure) of the sub tank 35 and the ink remaining amount will be described with reference to FIGS.
Here, as shown in FIG. 8, on the apparatus main body side, when the carriage 33 moves in the main scanning direction, the above-described detection is performed at a position where the tip 205a of the displacement member (detection filler) 205 of each sub tank 35 passes. A sensor 301 is installed. Here, the position of the carriage 33 in the main scanning direction is detected by the encoder 90.

  Here, when the amount of ink in the sub tank 35 increases or decreases, the front end detection unit 205a of the detection filler 205 moves in the main scanning direction. Therefore, by detecting the position of the detection filler 205 at a predetermined position. The negative pressure state of the sub tank 35 and the remaining amount of ink can be detected.

  Specifically, when ink is supplied to the sub tank 35 from the state shown in FIG. 9A, the detection filler 205 is displaced by the distance a as shown in FIG. If the position where the detection sensor 301 detects the tip detection unit 205a is set to the full tank position, ink is supplied at a position where the carriage 33 is moved by a position corresponding to the distance a from the position shown in FIG. When the detection filler 205 is detected, it can be assumed that the ink filling to the sub tank 35 is completed to the full tank position.

  Similarly, if the detection filler 205 is set to be displaced within the range of the distance a when the negative pressure state of the sub tank 35 is within the normal range, the ink is excessively supplied to the sub tank 35. For example, when the sub tank 35 is in a positive pressure state, the film 203 bulges outward and the detection filler 205 is displaced beyond the normal range a. Therefore, even if the sub tank 35 is moved by a predetermined amount, it is detected by the detection sensor 305. The filler 205 cannot be detected. At this time, it can be detected that the negative pressure state of the sub tank 35 is abnormal. Similarly, when the sub tank 35 is in an over-negative pressure state (a state in which bubbles are sucked from the nozzle), the film 203 contracts inward, and similarly, the detection filler 205 is displaced beyond the normal range a. Also in this case, it can be detected that the negative pressure state is abnormal.

  In this way, by detecting the position (movement distance) of the sub tank 35 when the displacement member 205 is detected, the displacement amount of the displacement member 205 (corresponding to the displacement amount of the elastic member 204 inside the sub tank 35) or Since the displacement member 205 is displaced according to the pressure in the sub tank 35 and further according to the remaining amount of ink, the remaining amount of ink can also be detected.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit 500 controls the entire apparatus, a CPU 501 also serving as a control unit according to the present invention, a program executed by the CPU 501, a ROM 502 for storing other fixed data, and a RAM 503 for temporarily storing image data and the like. And a rewritable nonvolatile memory 504 for holding data while the apparatus is powered 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 for supplying, an air release solenoid 302 for opening and closing the air release mechanism 207 of the sub tank 35, a supply system drive unit 512 for driving the supply pumps 241 (241A, 241B), 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.

  Then, 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 the 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. The sensor group 515 input to the I / O unit 513 is also input with signals such as the full tank detection sensor 301 and the detection electrode pins 208a and 208b that detect the displacement member 205 of the sub tank 35 described above.

  The CPU 501 of the control unit 500 detects the pressure in the sub tank 35 by detecting the displacement member 205 based on the detection signal of the detection sensor 301, and is detected from the detection signals of the temperature sensor and humidity sensor included in the sensor group 515. As a storage means for storing the environmental temperature, humidity, etc. of the device, a rewritable storage means (memory) such as a battery backup RAM or NVRAM 504 is used, which can maintain the storage state even when the apparatus power is shut off.

Next, the ink collection and supply control between the sub tanks in the ink end state in the image forming apparatus will be described with reference to FIG.
First, when the main tank 10 is in an end state, as shown in FIG. 11A, for example, the remaining amount of the ink 700 in the sub tank 35A is a predetermined remaining amount (predetermined amount: this is “printable remaining amount”). In the following, it is assumed that the ink 700 exceeding the printable remaining amount remains in the sub tank 35B. Whether or not the remaining amount of ink in the sub tank 35 is less than or equal to the printable remaining amount depends on whether or not the ink consumption from the state in which the sub tank 35 is fully filled with ink has reached a predetermined value or more. Can be determined. This “ink consumption” (the amount of ink ejected from the head) is a value obtained by the sum of “the amount of ejected droplets × the number of ejected droplets”, and “the amount of ejected droplets” is It is a predetermined value (amount).

  At this time, as shown in FIG. 11B, the on-off valve 242B on the sub tank 35B side is opened, the supply pump 241B is driven in reverse, and the ink in the sub tank 35B is returned (collected) into the main tank 10. The recovery amount at this time can be managed by the number of rotations or the rotation time of the supply pump 241B since the amount of liquid supply per rotation of the supply pump 241B or the amount of liquid supply per unit time is known in advance. .

  Note that when performing the recovery operation, the supply pump 241B is driven in reverse to reduce the pressure in the supply path on the sub tank 35A side, so that the on-off valve 242A on the sub tank 35A side is closed.

  Thereafter, as shown in FIG. 11C, the on-off valve 242A on the sub tank 35A side is opened, the supply pump 241A is driven to rotate forward, and the ink collected in the main tank 10 is sent to the sub tank 35A.

  Thus, if the remaining amount of ink in the sub tank 35B is sufficient, a part of the sub tank 35B can be moved to the sub tank 35A, and the sub tanks 35A and 35B can be set to the remaining printable amount and printing can be continued.

  Note that the remaining printable amount means the amount of ink that can be printed on a predetermined sheet for one page in the next printing. In addition, when one page cannot be printed in the next printing, the amount of ink in the sub tank 35 is less than the amount of ink to be ejected to print one page, or the amount of ink in the sub tank 35 is too small. For example, the pressure in the sub tank 35 decreases (the negative pressure becomes too high), and normal droplet discharge cannot be performed.

  A plurality of first tanks that store liquids that are supplied to the heads or nozzle rows that discharge droplets of the same color, and a second that stores liquids that are supplied to the plurality of first tanks that store liquids of the same color. A tank, a reversible liquid feeding means for feeding a liquid between the first tank and the second tank, a means for detecting a remaining amount of liquid in the first tank, and the second tank in an end state. When the liquid is collected from the first tank having a relatively large amount of remaining liquid to the second tank, the liquid is discharged to the first tank having a relatively small amount of remaining liquid. By adopting a configuration that includes means for controlling the liquid feeding, when the second tank is in an end state, the liquid can be moved between at least two first tanks. Continue printing as much as possible even in the end state. Able to.

Accordingly, ink movement control (ink distribution control) in the first embodiment of the present invention will be described with reference to the flowchart of FIG.
First, when the main tank 10 is in an end state, the ink remaining amount A of the sub tank 35A and the ink remaining amount B of the sub tank 35B are added together and equally distributed to the sub tanks 35A and 35B ((A + B) / 2. )), It is determined whether or not the remaining ink amounts A and B of the sub-tanks 35A and 35B are equal to or greater than the printable remaining amount.

  At this time, if the remaining ink levels A and B of the sub tanks 35A and 35B are equal to or greater than the printable remaining capacity, is the remaining ink level A of the sub tank 35A greater than the remaining ink level B of the sub tank 35B (A> B)? Determine whether or not.

  If A> B, the pump 241A (denoted as pump A in the figure) is reversed and a part of the ink in the sub tank 35A is collected in the main tank 10, and the pump 241B (denoted as pump B in the figure) is corrected. When the ink recovered is supplied to the sub tank 35B and A> B is not satisfied, the pump 241B is reversed to recover a part of the ink in the sub tank 35B to the main tank 10, and the pump 241A is rotated forward to rotate the sub tank 35A. After the recovered ink is supplied to the printer, it shifts to a standby state.

  Further, if the ink remaining amount A, B in each of the sub tanks 35A, 35B does not exceed the printable remaining amount even after the ink is distributed (collected and supplied), the process proceeds to the ink out state process.

Next, ink movement control (ink distribution control) in the second embodiment of the present invention will be described with reference to the flowchart of FIG.
First, when the main tank 10 is in the end state, the absolute value (| A−B |) of the difference between the ink remaining amount A of the sub tank 35A and the ink remaining amount B of the sub tank 35B is equal to or less than a predetermined threshold C ( Whether or not | A−B | ≦ C) is determined.

  Here, the threshold value C is a value that cannot be adjusted even when the supply pump 241 is driven. For example, the threshold C is supplied when the pressure roller 402 of the tube pump constituting the supply pump 241 is rotated once. Amount. In addition, as the threshold value C, it is possible to use a liquid feeding amount when rotating a predetermined rotation amount other than this.

  When the absolute value (| A−B |) of the difference between the ink remaining amount A in the sub tank 35A and the ink remaining amount B in the sub tank 35B is equal to or less than a predetermined threshold C (| A−B | ≦ C) Transition to out of ink state. In other words, if the difference in the remaining amount of ink between the sub tanks 35A and 35B is about the same as the amount of liquid delivered when the pressure roller 402 of the tube pump constituting the supply pump 241 is rotated once, the remaining amount can be maintained even if the ink is moved. There is a high possibility that the sub-tanks 35A and 35B will not have a printable remaining amount only by switching the size relationship.

  Therefore, in such a case, useless operation is avoided by shifting to the out-of-ink state without collecting and supplying ink.

  On the other hand, when the absolute value (| A−B |) of the difference between the ink remaining amount A in the sub tank 35A and the ink remaining amount B in the sub tank 35B is not less than or equal to a predetermined threshold C (| A−B | ≦ C). The process proceeds to the same process as in the first embodiment.

Next, ink movement control (ink distribution control) in the third embodiment of the present invention will be described with reference to the flowchart of FIG.
In this embodiment, in addition to the “normal printing” mode in which image formation is performed while supplying ink from the main tank 10 to the sub tank 35, the main tank 10 is in an ink end state, and ink supply cannot be performed. This is an example having an “emergency printing” mode in which an image forming operation is performed by using the remaining ink in the sub tank 35 without setting “printing stop”.

  First, it is determined whether or not the ink remaining amount A in the sub tank 35A is larger than the ink remaining amount B in the sub tank 35B (A> B).

  If A> B, the pump 241A is reversed to collect a part of the ink in the sub tank 35A in the main tank 10, the pump 241B is rotated forward to supply the collected ink to the sub tank 35B, and A> B Otherwise, the pump 241B is reversed to collect a part of the ink in the sub tank 35B in the main tank 10, and the pump 241A is rotated forward to supply the collected ink to the sub tank 35A.

  Thereafter, the ink remaining amount A in the sub tank 35A and the ink remaining amount B in the sub tank 35B are added together and distributed equally to the sub tanks 35A and 35B ((A + B) / 2). As a result, the ink in each sub tank 35A and 35B It is determined whether the remaining amounts A and B are equal to or greater than the remaining printable amount.

  At this time, if the remaining ink amounts A and B of the sub tanks 35A and 35B are equal to or greater than the remaining printable amount, the process proceeds to a standby state in which normal printing is performed. On the other hand, if the remaining ink amounts A and B of the sub tanks 35A and 35B are not equal to or greater than the printable remaining amount, the emergency printing mode is entered.

Next, ink movement control (ink distribution control) in the fourth embodiment of the present invention will be described with reference to the flowchart of FIG.
Here, in the third embodiment, first, as in the second embodiment, when the main tank 10 is in the end state, the difference between the ink remaining amount A of the sub tank 35A and the ink remaining amount B of the sub tank 35B is determined. It is determined whether or not the absolute value (| A−B |) is equal to or less than a predetermined threshold C (| A−B | ≦ C).

  When the absolute value (| A−B |) of the difference between the ink remaining amount A in the sub tank 35A and the ink remaining amount B in the sub tank 35B is equal to or less than a predetermined threshold C (| A−B | ≦ C) As a result, the ink remaining amount A in the sub tank 35A and the ink remaining amount B in the sub tank 35B are added and distributed equally to the sub tanks 35A and 35B ((A + B) / 2). As a result, the ink remaining in each sub tank 35A and 35B The process proceeds to a process for determining whether the amounts A and B are equal to or greater than the remaining printable amount.

  The processing according to the present invention, such as the above-described liquid recovery between the sub-tanks, control related to supply (movement or distribution), and ink consumption calculation processing, 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, an example is described in which a plurality of first tanks containing liquids of the same color supply liquids to different nozzle arrays, but the present invention is similarly applied to cases where liquids are supplied to different heads. can do.

10 Ink cartridge (main tank, second tank)
33 Carriage 34, 34a to 34d Recording head (liquid ejection head)
35, 35a to 35d, 35A, 35B Sub tank (first tank)
81 Maintenance and recovery mechanism 201 Tank case (liquid container)
203 flexible member (flexible film)
205 ... Displacement member (detection filler)
241, 241A, 241B Supply pump 301 ... Detection sensor 500 ... Control unit 600 ... Host (information processing device)

Claims (1)

A plurality of heads that discharge droplets of the same color or a head having a nozzle row that discharges droplets of the same color;
A plurality of first tanks for storing liquid to be supplied to each head or each nozzle row for discharging the same color droplets;
A second tank containing liquid to be supplied to the plurality of first tanks containing liquid of the same color;
Reversible liquid feeding means for feeding a liquid between the first tank and the second tank;
Means for detecting a remaining amount of liquid in the first tank;
When the second tank is in an end state, after the liquid is recovered from the first tank having a relatively large amount of remaining liquid among the plurality of first tanks to the second tank, the remaining amount of liquid is relatively And means for controlling the liquid to be fed to the first tank with a small amount ,
When the difference between the remaining amount of liquid in the first tank having a relatively large amount of remaining liquid and the remaining amount of liquid in the first tank having a relatively small amount of remaining liquid is equal to or less than a predetermined amount, the control is not performed. An image forming apparatus characterized by the above.

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