JP2015080878A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device capable of performing choke cleaning so that unnecessary air does not enter into an ink supply path without imposing any labor on a user.SOLUTION: An image formation device comprises: an ink cartridge for storing ink; a recording head including a liquid droplet discharge head having a plurality of nozzles for discharging the ink; a head tank for temporarily storing a predetermined amount of ink replenished from the cartridge by a negative pressure formed by ink discharge; opening/closing means that is provided between the cartridge and the tank and blocks or opens an ink supply path; a maintenance recovery mechanism for performing head suction; and a main control unit for controlling execution of cleaning for performing the head suction in a state of blocking the opening/closing means. The main control unit executes the cleaning when an aeration amount in the tank is equal to or greater than a criterion value and a remaining amount of ink in the cartridge is equal to or greater than a criterion amount.

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.

  In general, a printer / fax / copier or an image forming apparatus combining these functions includes, for example, a recording head composed of a liquid discharge head that discharges liquid droplets of a recording liquid, and a medium (hereinafter also referred to as “paper”). However, the material is not limited and means that the liquid adheres, and a recording medium, a recording medium, a recording paper, a transfer material, and the like are also used synonymously.) In the following, a liquid ejection type image forming unit for forming an image by attaching ink droplets to a sheet of paper (recording, printing, printing, and printing are also used synonymously) is known. .

  In such a liquid (droplet) discharge type image forming apparatus, the recording liquid is supplied to the recording head. The recording liquid is a recording liquid storage means that stores the recording liquid in a carriage on which the recording head is mounted. A cartridge is detachably mounted, and a recording liquid is supplied from the recording liquid cartridge to the recording head, and a small-capacity head tank (also referred to as a sub tank) is a second liquid storage unit that supplies the recording liquid to the recording head on the carriage. The large-capacity recording liquid cartridge (main tank) as the first liquid storage means is mounted on the apparatus main body side in a replaceable manner, and the recording liquid (ink) is supplied from the recording liquid cartridge on the apparatus main body side to the head tank. ) Is replenished and supplied.

  If air accumulates too much in the head tank, the air reaches the nozzle and multi-channel nozzle omission occurs. For this reason, a technique called choke cleaning is known in which head suction is performed with the choke valve in the ink supply path closed in order to remove the air in the head tank.

  Patent Document 1 includes a choke cleaning control, a normal cleaning control, and a nozzle defect detection function in order to efficiently perform nozzle recovery. When manual cleaning is instructed by a user, the number of nozzle defect channels is determined. A configuration for determining whether or not to perform chalk cleaning control is disclosed. By performing chalk cleaning, bubbles are discharged from the nozzle.

  Patent Document 2 discloses performing chalk cleaning in order to efficiently discharge bubbles in the ink supply path (including in the sub tank).

  However, in the conventional configuration in which the execution determination of the chalk cleaning is performed at the time of manual cleaning instruction from the user, it is not known whether the cleaning is necessary until nozzle missing occurs, and the manual cleaning instruction from the user is necessary. It was over. Further, when chalk cleaning is performed in a state where the ink remaining amount is low, there is a problem that air enters the ink supply path as much as ink cannot be put.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to perform chalk cleaning in an image forming apparatus so as not to bother a user and to prevent excessive air from entering an ink supply path.

To solve this challenge,
An ink cartridge for containing ink;
A recording head including a droplet discharge head having a plurality of nozzles for discharging ink;
A head tank that temporarily stores a predetermined amount of ink replenished from the ink cartridge by a negative pressure formed by ink ejection;
An opening / closing means provided between the ink cartridge and the head tank, for blocking or opening an ink supply path;
A maintenance recovery mechanism that performs head suction;
A main control unit that controls the execution of cleaning that performs head suction in a state where the opening / closing means is shut off, and
The main controller performs the cleaning when the amount of air mixed in the head tank is equal to or greater than a reference value and the remaining amount of ink in the ink cartridge is equal to or greater than a reference amount. A device is proposed.

  An image forming apparatus that does not require the user's effort and that does not allow excessive air to enter the ink supply path is realized.

FIG. 2 is a perspective explanatory view seen from the front side of an ink jet recording apparatus as an image forming apparatus according to an embodiment including an apparatus for discharging droplets. It is a side schematic block diagram explaining the whole structure of the mechanism part of the apparatus. It is principal part plane explanatory drawing of the mechanism part. It is block explanatory drawing which shows the outline | summary of the control part of the apparatus. FIG. 4 is a diagram illustrating an ink supply mechanism in the image forming apparatus. It is a figure which shows a negative pressure interlocking valve. It is a figure which shows a choke valve. It is a flowchart which shows the choke | suction suction process for extracting air from a head tank. It is a flowchart which shows the cleaning process for making a nozzle state favorable. FIG. 3 is a diagram illustrating an ink supply path in the image forming apparatus. It is a flowchart which shows the implementation judgment of chalk cleaning. It is a figure which shows the relationship between chalk suction frequency and the air quantity in a head tank.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory perspective view of an ink jet recording apparatus as an image forming apparatus according to the present invention as viewed from the front side.
The ink jet recording apparatus includes an apparatus main body 1, a paper feed tray 2 for loading paper loaded in the apparatus main body 1, and a sheet on which an image is recorded (formed) by being detachably mounted on the apparatus main body 1. A paper discharge tray 3 for stocking is provided. Furthermore, a cartridge loading unit 4 for loading an ink cartridge is provided on one end side of the front surface of the apparatus main body 1 (side of the paper supply / discharge tray unit). The operation / display unit 5 is provided with a display or the like.

  The cartridge loading unit 4 contains a plurality of recording liquids (inks) that are different color materials, such as black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Ink cartridges (main tanks) 10k, 10c, 10m, and 10y (referred to as “ink cartridge 10” when colors are not distinguished) are inserted from the front side of the apparatus main body 1 toward the rear side. A front cover (cartridge cover) 6 that is opened when the ink cartridge 10 is attached or detached is provided on the front side of the cartridge loading portion 4 so as to be openable and closable. Further, the ink cartridges 10k, 10c, 10m, and 10y are configured to be loaded side by side in a vertical state.

  Further, the operation / display unit 5 has the remaining amounts of the ink cartridges 10k, 10c, 10m, and 10y of each color at the arrangement positions corresponding to the mounting positions (arrangement positions) of the ink cartridges 10k, 10c, 10m, and 10y of the respective colors. The remaining amount display portions 11k, 11c, 11m, and 11y for each color for displaying the near end and the end are arranged. Further, the operation / display unit 5 is also provided with a power button 12, a paper feed / print resume button 13, and a cancel button 14.

Next, the mechanism part of the ink jet recording apparatus will be described with reference to FIGS. 2 is a schematic side view illustrating the outline of the mechanism, and FIG. 3 is an explanatory plan view of the main part.
A main guide rod 31 which is a main guide member horizontally mounted on the left and right side plates 21A and 21B constituting the frame 21 and a sub guide rod 32 hold the carriage 33 slidably in the main scanning direction, and a main scanning motor (not shown). Is moved and scanned in the direction indicated by the arrow in FIG. 3 (carriage main scanning direction) via the timing belt.

  As described above, the carriage 33 includes a recording head 34 including four droplet discharge heads that discharge ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). A plurality of ink ejection openings are arranged in a direction crossing the main scanning direction (paper feeding direction), and the ink droplet ejection direction is mounted downward. Note that it is also possible to employ one or a plurality of head configurations having nozzle arrays that eject droplets of each color.

  As an inkjet head constituting the recording head 34, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. It is possible to use a shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like provided as pressure generating means for generating a pressure for discharging a droplet.

  The carriage 33 is equipped with a head tank 35 for each color for supplying each color ink to each recording head 34. As described above, each color head tank 35 is supplementarily supplied with ink of each color from the ink cartridge 10 of each color mounted in the cartridge loading unit 4 via the supply tube 36 having flexibility of each color. The cartridge loading unit 4 is provided with a supply pump unit 24 which is a liquid feeding means for feeding ink in the ink cartridge 10.

  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.

  A guide 45 for guiding the paper 42, a counter roller 46, a conveyance guide member 47, and a tip pressurizing roller 49 are provided to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34. And a conveying belt 51 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. Further, a guide member 57 is disposed on the back side of the conveyor belt 51 in correspondence with a printing area by the recording head 34.

  The transport belt 51 rotates in the belt transport direction of FIG. 3 when the transport roller 52 is rotationally driven through timing by a sub-scanning motor (not shown).

  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 paper discharge roller 63 are provided. The paper discharge tray 3 is provided 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, as shown in FIG. 3, a maintenance / recovery mechanism 81 including a recovery means for maintaining and recovering the state of the nozzles of the recording head 34 is arranged in the non-printing area on one side of the carriage 33 in the scanning direction. Yes.

  The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a to 82d (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 83 that is a blade member for wiping the ink, an empty discharge receiver 84 that receives 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 suction pump 98 (FIG. 5). Here, the cap 82a is a suction and moisture retention cap, and the other caps 82b to 82d are moisture retention caps.

  Then, the waste liquid of the recording liquid generated by the maintenance / recovery operation by the maintenance / recovery mechanism 81, the ink discharged to the cap 82, the ink attached to the wiper 83 and removed by the wiper cleaner 85, and the idle ejection receiver 94 are idled. The ink is discharged and stored in the waste liquid tank 99 (FIG. 5).

  Further, as shown in FIG. 3, in the non-printing area on the other side in the scanning direction of the carriage 33, idle discharge is performed to discharge liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. An empty discharge receiver 88 for receiving the liquid droplets at the time is disposed, and the empty discharge receiver 88 is provided with an opening 89 along the nozzle row direction of the recording head 34.

  In the ink jet recording apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feeding tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and the transport belt 51 and the counter roller 46, and the leading end is guided by the conveying guide 37 and pressed against the conveying belt 51 by the tip pressing roller 49, and the conveying direction is changed by approximately 90 °.

  At this time, a charging voltage pattern in which a positive output and a negative output are alternately repeated from the AC bias supply unit of the control unit (not shown) to the charging roller 56, that is, an alternating voltage is applied and the conveying belt 51 alternates. That is, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction which is the circumferential direction. 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.

  Further, during printing (recording) standby, the carriage 33 is moved to the maintenance / recovery mechanism 81 side, and the recording head 34 is capped by the cap 82 to keep the nozzles in a wet state, thereby preventing ejection failure due to ink drying. . Further, with the recording head 34 being capped by the cap 82, the recording liquid is sucked from the nozzle by the suction pump 98 (FIG. 5) (referred to as "nozzle suction" or "head suction"), and the thickened recording liquid or bubbles Perform recovery action to discharge In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. As a result, the stable ejection performance of the recording head 34 is maintained.

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 controls the entire image forming apparatus, and includes a main control unit 301 configured by a microcomputer that also serves as a unit for performing control according to the present invention, and a print control unit configured by a microcomputer that controls print control. 302.

  The main control unit 301 then sets a main scanning motor driving circuit that moves the carriage 33 in the main scanning direction in order to form an image on the paper 42 based on the information of the printing process input from the communication circuit 300. A sub-scan motor that feeds the paper 42 is controlled to be driven via a sub-scan motor driving circuit 304 via 303, and control is performed such as sending print data to the print controller 302.

  The main control unit 301 receives a detection signal from a carriage position detection circuit 305 that detects the position of the carriage 33, and the main control unit 301 controls the movement position and movement speed of the carriage 33 based on the detection signal. To do. The carriage position detection circuit 305 detects the position of the carriage 33 by, for example, reading and counting the number of slits of an encoder sheet arranged in the scanning direction of the carriage 33 with a photosensor mounted on the carriage 33. The main scanning motor drive circuit 303 rotates the main scanning motor in accordance with the carriage movement amount input from the main control unit 301 to move the carriage 33 to a predetermined position at a predetermined speed.

  Further, the main control unit 301 receives a detection signal from a conveyance amount detection circuit 306 that detects the movement amount of the conveyance belt 51, and the main control unit 301 moves the movement amount and movement speed of the conveyance belt 51 based on the detection signal. To control. The conveyance amount detection circuit 306 detects the conveyance amount by, for example, reading and counting the number of slits of the rotary encoder sheet attached to the rotation shaft of the conveyance roller 52 with a photo sensor. The sub-scanning motor driving circuit 304 rotates the sub-scanning motor according to the conveyance amount input from the main control unit 301, and rotationally drives the conveyance roller 52 to bring the conveyance belt 51 to a predetermined position at a predetermined speed. Move.

  The main control unit 301 rotates the sheet feeding roller 43 once by giving a sheet feeding roller driving command to the sheet feeding roller driving circuit 307. The main control unit 301 rotationally drives the motor of the maintenance / recovery mechanism 81 via the maintenance / recovery mechanism drive motor drive circuit 308, thereby raising and lowering the cap 82, raising and lowering the wiper 83, and driving the suction pump 98 as described above. And so on.

  The main control unit 301 drives and controls a drive motor (supply motor) for driving the pump of the supply pump unit 24 via the supply pump drive circuit 311, and the head from the ink cartridge 10 loaded in the cartridge loading unit 4. Ink is replenished to the tank 35 (filled). At this time, the main control unit 301 controls replenishment supply (filling operation) based on a detection signal from the head tank full tank sensor 312 that detects that the head tank 35 is full. In this case, there are open air filling in which the air release mechanism 204 of the head tank 35 is opened to perform filling, and normal filling in which filling is performed with the air release mechanism 204 closed.

  Further, the main control unit 301 takes in information stored in the nonvolatile memory 316 which is a storage unit provided in each ink cartridge 10 mounted on the cartridge loading unit 4 through the cartridge communication circuit 314, and performs a necessary process. And stored in a non-volatile memory (for example, EEPROM) 315 which is a main body storage means.

  Further, the main control unit 301 receives a detection signal from an environmental sensor 313 that detects environmental temperature and environmental humidity.

  The print control unit 302 generates pressure for ejecting droplets of the recording head 34 based on the signal from the main control unit 301 and the carriage position and conveyance amount from the carriage position detection circuit 305 and the conveyance amount detection circuit 306. Data for driving the means is generated. The print control unit 302 transfers the above-described image data as serial data to the head driving circuit 310, and also transfers a transfer clock, a latch signal, and a droplet control signal (mask signal) necessary for transferring the image data and confirming the transfer. ) And the like are output to the head drive circuit 310. Further, the print control unit 302 supplies the drive signal pattern data stored in the ROM to a drive waveform generation unit and a head driver including a D / A converter, a voltage amplifier, a current amplifier, and the like that perform D / A conversion. Drive waveform selection means is included. The print control unit 302 generates a drive waveform including one drive pulse (drive signal) or a plurality of drive pulses (drive signal) and outputs the drive waveform to the head drive circuit 310.

  The head drive circuit 310 selectively selects a drive signal constituting a drive waveform supplied from the print control unit 302 based on image data corresponding to one row of the print head 34 that is input serially. The recording head 34 is driven by applying it to a driving element (for example, a piezoelectric element as described above) that generates energy for discharging the ink. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets (large dots), medium droplets (medium dots), and small droplets (small dots) can be distinguished. it can.

FIG. 5 is a diagram illustrating an ink supply mechanism in the image forming apparatus.
The ink cartridge 10 and the head tank 35 are connected via a check valve 90, a pump 91 of the supply pump unit 24, a check valve 95, a pressure buffer 96, a choke valve 97 as an opening / closing means, and a supply tube 36. A pump 91 that is a membrane pump includes a pump seat 93 and a diaphragm 94 and a pressing member 92 that presses them. A pressure buffer 96 that is a pressure buffer includes a buffer sheet 104. The head tank 35 has a pressurizing chamber 103 in which a positive pressure is applied upstream of the negative pressure interlocking valve 101 and a negative pressure chamber 102 in which a negative pressure is applied downstream. Further, a cap 82 is disposed below the recording head 34, and the nozzle suction is performed by the operation of the suction pump 98. The ink discharged to the cap 82 is stored in the waste liquid tank 99.

FIG. 6 is a view showing a negative pressure interlocking valve.
When ink is ejected from the recording head 34 from the state shown in FIG. 6A where ink is sufficient, the negative pressure in the head tank 35 increases and the flexible film 100 is recessed (FIG. 6B). . Then, the lever 105 is pushed by the pressing force of the film 100 and the spring 110 coupled thereto, and the negative pressure interlocking valve 101 provided at one end of the lever 105 opens against the spring 111, and the ink cartridge is opened through the opening. Ink is supplied from the 10 side. When ink is supplied, the film 100 swells, and the lever 105 returns to its original state, the negative pressure interlocking valve 101 is closed, and the supply of ink is stopped (FIG. 6C).

FIG. 7 is a view showing a choke valve.
The figure shows a state in which the choke valve 97 is shut off. The tip of the valve 106 is made of an elastic member, and the main body is made of a metal material. The valve body is always urged by a spring 107 in a direction to block the flow path. When the magnet 108 is brought close to the valve body, the valve body moves upward against the biasing force of the spring by the action of the magnetic force, leaves the flow path of the valve portion, and opens the flow path. Further, when the magnet is moved away, the magnetic force is lost and the valve 106 is closed. When the choke valve 97 is in the closed state, the closed state can be maintained by the spring force even if the supply motor 122 is stopped. In the state where the valve is closed, ink is not sent even if the supply motor 122 is moved. When the choke valve 97 is in the open state, the open state is maintained unless the magnet 108 is separated.

Ink end detection of the ink cartridge is performed as follows.
Referring to FIG. 5, when the ink cartridge 10 is empty, if the ink is consumed by ink ejection or head suction, the pressure in the pressure buffer 96 decreases. When the pressure in the pressure buffer 96 decreases, the filler (not shown) serving as the pressure detection means is displaced, and when the filler sensor (not shown) is crossed, the ink cartridge 10 is determined to be empty (ink end detection).

After the ink end of the ink cartridge 10 is detected, if the cartridge is removed from the apparatus main body 1 to replace the ink cartridge or the like, air enters the ink supply path as the pressure in the pressure buffer 96 decreases. Therefore, the cartridge replacement after the ink end detection has a larger air mixing amount than the cartridge replacement without the ink end detection.
According to the formula for calculating the air amount in the head tank, which will be described later, the ink end coefficient (Ce) is larger than the cartridge replacement coefficient (Cc), so that the air amount in the head tank can be calculated with a value closer to reality. .

Next, chalk cleaning will be described.
In the chalk cleaning, a “choke suction process” and a “cleaning process” described later are performed. Thereby, air can be extracted from the head tank 35. In normal cleaning, a “cleaning step” may be performed.

FIG. 8 is a flowchart showing a choke suction process for removing air from the head tank.
First, the cap 82 is raised by driving the suction pump 98, and the recording head 34 is covered with the cap (S1). Next, the choke valve 97 is closed by driving the supply motor 122 and the magnet 108 (S2). Then, the head is sucked by driving the suction pump 98 (S3). Then, the film 100 in the head tank shrinks, and the air in the film 100 is discharged from the head nozzle. Next, the choke valve 97 is opened by driving the supply motor 122 and the magnet 108 (S4). At this time, the choke valve opens, and at the same time, ink enters the shrunken film 100. Finally, it is determined whether or not the chalk suction from S2 to S4 is repeated. If repetition is necessary, the process returns to S2 (S5). For example, if the amount of air in the head tank when the choke cleaning is activated is 1 to 2 times the minimum value (reference value) of the activation condition, the number of repetitions is 1, 2 to 3 times, and the number of repetitions is 2; If it is 3, 4 to 5 times, the number of repetitions is 4, and if it is 5 times or more, the number of repetitions is 5.

FIG. 9 is a flowchart showing a cleaning process for improving the nozzle state.
First, pressure is continuously applied from the ink cartridge 10 toward the head tank 35 by driving the supply motor 122 so that the ink is supplied to the head tank 35 when the ink is discharged (S6). In addition, when the negative pressure interlocking valve 101 is in the closed state, ink is not fed. Next, the head is sucked by driving the suction pump 98 (S7). Thereby, ink is discharged and ink is supplied to the head tank when ink is discharged. Next, a wiping operation is performed (S8). That is, the cap 82 is lowered by driving the suction pump 98, and the carriage 33 is moved to the wiping start position by driving a main scanning motor (not shown). The wiper 83 is raised by driving the suction pump 98, and the carriage 33 is moved to the wiping end position by driving the main scanning motor. Next, the carriage 33 is moved to the capping position by driving the main scanning motor, and ink discharge (empty discharge / preliminary discharge) is performed (S9). This eliminates mixed-color ink in the vicinity of the nozzle. Then, suction within the cap is performed by driving the suction pump 98 (S10), and ink in the cap is removed to prevent color mixing during capping. Finally, capping is performed by driving the suction pump 98 (S11).

  Here, it is necessary to prevent the ink cartridge 10 from being emptied during the chalk cleaning, and excessive air from entering the ink supply path. When choke cleaning is performed in a state where the remaining amount of ink is nearly empty, ink end may be detected when the head is sucked in S3 in FIG. When the ink end is detected, ink cannot be supplied. Therefore, when the user pulls out the ink cartridge 10, the pressure buffer 96 is contracted, and extra air enters the supply path. Therefore, in order to prevent this, the condition 2 for performing the choke cleaning is that the remaining amount of ink exceeds the reference amount.

Here, an ink supply path in the image forming apparatus will be described with reference to FIG.
The black ink supply path is in the order of the black ink cartridge 10k, the supply pump unit 24, the head tank 35, the recording head 34, and the nozzle row 120k. The same applies to cyan, magenta, and yellow. A supply motor 122 for supplying ink is connected to the supply pump unit 24. The recording head 34 has nozzle rows 120k, 120c, 120m, and 120y corresponding to the respective colors. The cap 82 a can cover these nozzle rows, and the ink sucked from the nozzle rows by the suction pump 98 is discharged to the waste liquid tank 99.

Next, a method for calculating the air mixing amount in the head tank in the image forming apparatus will be described.
In order to calculate the air mixing amount (Va) for each head tank 35, the main control unit 301 sets the air mixing amount reset time, the ink end number (the number of ink ends after the count is reset), the cartridge for each head tank. The number of replacements (the number of cartridge replacements after the count is reset) is stored in the nonvolatile memory 315 as storage means.

The air mixing amount (Va) is calculated by the main control unit 301 by the following calculation formula (1).
Air mixing amount (Va) [cc] = air permeability coefficient (Cp) × (current time−air mixing amount reset time)
+ Ink end coefficient (Ce) x number of ink ends
+ Cartridge replacement coefficient (Cc) x cartridge replacement count
... (1)

Here, the information of each color communicating with each head tank is used for the ink end number and the cartridge replacement number, and the information of the recording head 34 is used for the air mixing amount reset time.
Since the chalk cleaning is performed on all the recording heads 34 at once, resetting of the black, cyan, magenta, and yellow ink end counts and cartridge replacement counts is performed when the recording head 34 is subjected to chalk cleaning. In addition, the writing timing of the air mixing amount reset time is performed when choke cleaning is performed on the recording head 34 in terms of the number of ink ends.

  The first term on the right side of Equation 1 is the amount of air that is considered to have naturally entered the head tank from the reset to the present. The second term is the amount of air considered to have entered the head tank in proportion to the number of ink ends. The third term is the amount of air considered to have entered the head tank in proportion to the number of cartridge replacements. Here, since the case where the cartridge is replaced without detecting the ink end is included, the number of ink ends is not necessarily equal to the number of cartridge replacements.

  For example, the air permeability coefficient (Cp) is 0.020 [cc] / month in consideration of the air permeability, the ink end coefficient (Ce) is 0.010 [cc] / time, and the cartridge replacement coefficient (Cc) is 0. 001 [cc] / time.

  In this way, the main control unit 301 can determine the amount of air in each head tank. Thus, in the present invention, as the condition 1 for performing the choke cleaning, it is used that the air is accumulated in the head tank more than the reference value (the amount of air that does not cause nozzle missing). Therefore, it does not take time for the user.

Next, another calculation method of the air mixing amount in the head tank in the image forming apparatus will be described.
In order to calculate the air mixing amount (Va) for each head tank 35, the main control unit 301 sets the air mixing amount reset time, the ink end number (the number of ink ends after the count is reset), the cartridge for each head tank. The number of replacements (the number of cartridge replacements since the count was reset) and the cumulative ink usage during the ink end detection are stored in the nonvolatile memory 315 as storage means.

The air mixing amount (Va) is calculated by the following calculation formula (2).
Air mixing amount (Va) [cc] = air permeability coefficient (Cp) × (current time−air mixing amount reset time)
+ Ink end coefficient (Ce) x number of ink ends
+ Cartridge replacement coefficient (Cc) x cartridge replacement count
+ Cumulative ink usage during ink end detection
... (2)

Here, the information of each color communicating with each head tank is used for the ink end count, the cartridge replacement count, and the cumulative ink usage amount during ink end detection, and the information of the recording head 34 is used for the air mixing amount reset time.
The black, cyan, magenta, and yellow ink end counts, cartridge replacement counts, and cumulative ink usage counts during ink end detection are reset when the recording head 34 is subjected to chalk cleaning. In addition, the writing timing of the air mixing amount reset time is performed when choke cleaning is performed on the recording head 34 in terms of the number of ink ends.

  The first term on the right side in Equation 2 is the amount of air that is considered to have naturally entered the head tank since the reset until the present. The second term is the amount of air considered to have entered the head tank in proportion to the number of ink ends. The third term is the amount of air considered to have entered the head tank in proportion to the number of cartridge replacements. Here, since the case where the cartridge is replaced without detecting the ink end is included, the number of ink ends is not necessarily equal to the number of cartridge replacements. For example, when the cartridge is removed after detecting the ink end, air flows into the pressure buffer in the negative pressure state. However, it is considered that the ink has entered the head tank when printing is continued using the ink in the pressure buffer. The amount of air produced is approximated by the cumulative amount of ink used during ink end detection.

  For example, the air permeability coefficient (Cp) is 0.020 [cc] / month in consideration of the air permeability, the ink end coefficient (Ce) is 0.010 [cc] / time, and the cartridge replacement coefficient (Cc) is 0. 001 [cc] / time.

In the present embodiment, for the convenience of the user, a mechanism is provided in which the user can continue to use ink even after ink end detection.
For example, when an ink end is detected during image formation (while writing), printing is continued using ink in an ink tank or the like to complete image formation. This is because when an image in the middle of writing is discharged, waste paper and waste ink are generated. In this way, the user can continue to use ink even after ink end detection.

In addition, for example, a mechanism is provided that allows ink to be used (printed) using ink for the pressure buffer even after ink end detection. This allows the image forming apparatus to be used until the user prepares a new ink cartridge. Since there is ink for the pressure buffer, the head tank pressure does not drop rapidly, and ink can be ejected for a while.
When the ink cartridge is removed, air corresponding to the buffer pressure replenishment amount enters the supply path. Therefore, after the ink end is detected, the amount of ink used is set as the air mixing amount.

  According to the present embodiment, since the accumulated ink use amount during the ink end detection is stored as information for predicting the air amount in the head tank, it is possible to calculate a more realistic head tank air mixing amount.

Next, the ink remaining amount will be described.
In the present invention, the ink remaining amount can be obtained by storing a given ink capacity for each color ink cartridge and subtracting the consumed amount therefrom. The accumulated ink consumption in each color ink cartridge is the sum of the ink amounts due to head suction and ejection.
That is, (ink remaining amount) = (ink capacity) − (ink consumption).

  Thus, in the present invention, the condition 2 for performing the chalk cleaning is that the remaining amount of the ink cartridge is equal to or more than the reference amount. This ensures that no extra air enters the supply path. Only when the conditions 1 and 2 are satisfied, the chalk cleaning is performed.

FIG. 11 is a flowchart showing the execution determination of chalk cleaning.
An execution decision is made at a timing when there is no cleaning instruction from the user. As the execution timing, for example, there is a regular timing (for example, a periodic idle ejection timing) when the image forming apparatus is turned on from power OFF, when an ink cartridge is replaced, and when the power is on.

  First, as the condition 1, the main control unit 301 determines whether or not air is accumulated in the head tank more than a reference value (the amount of air that does not cause nozzle missing) (S12). In the case of No, chalk cleaning is not performed. In the case of Yes, as condition 2, it is determined whether the remaining amount of the ink cartridge is equal to or larger than the reference amount (S13). In the case of No, chalk cleaning is not performed. In the case of Yes, chalk cleaning is performed (S14). After the choke cleaning is completed, the stored information related to the air amount in the head tank 35 is reset to zero (S15).

In S13, if the remaining amount of ink is less than the reference amount, the air will flow in, so choke cleaning is not performed. Since the chalk cleaning is not performed, the condition of the air amount in the head tank remains met.
Also, chalk cleaning is performed when the remaining ink condition is satisfied by cartridge replacement or the like. If the ink remaining condition is not satisfied even after the cartridge is replaced, choke cleaning is not performed.

  As the cartridge replacement timing, it is assumed that the user replaces the cartridge after the ink end is detected. However, depending on the situation of the user, it may be an arbitrary timing when no ink end has occurred.

  The reference value of the air amount in the head tank is desirably set to an air amount in a range where nozzle missing does not occur. Depending on the condition of the remaining amount of ink, choke cleaning may not be activated for a while even if the reference value is exceeded, so a value smaller than the amount of air that causes nozzle omission (for example, 1/2 or 1/3 thereof). Etc.). The reference value, which is the amount of air in the head tank, is preferably a value related to the head tank volume.

  On the other hand, the reference amount of the ink cartridge remaining amount may be set to a value equal to or larger than the ink consumption amount consumed in the chalk suction process of chalk cleaning, for example. This is because when the ink end is detected during the cleaning process, air is not mixed as much as during the choke suction process. Alternatively, the reference amount may be a value that is greater than or equal to the amount of ink consumed by chalk cleaning.

FIG. 12 is a diagram showing the relationship between the number of choke suctions and the amount of air in the head tank.
As the suction pressure (suction strength), −30 kPa, −50 kPa, and −70 kPa are used. As can be seen from the figure, the air in the head tank may not be completely removed by one choke suction. It can also be seen that the larger the suction pressure, the smaller the amount of air in the head tank.

  Therefore, in the present invention, as described above, the number of repetitions of S2 to S4 in the choke suction process is changed according to the air amount in the head tank. In other words, if the air amount in the head tank when the choke cleaning is activated is 1 to 2 times the reference value, the number of repetitions is 1, 2 to 3 times, the number of repetitions is 2, and if it is 3 to 4 times, the number of repetitions is 3, 4 to 5 times. If the number of repetitions is 4 and 5 times or more, the number of repetitions is set to 5. In addition to or in place of such a change in the number of suctions, the suction pressure may be changed.

  As described above, since at least one of the suction pressure and the number of times of suction of the choke cleaning is changed according to the amount of air in the head tank when the chalk cleaning is activated, the air in the head tank is removed with an appropriate suction pressure and suction amount. be able to. Furthermore, since the air amount after choke cleaning is stabilized, the air amount in the head tank can be calculated with a value closer to reality.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Ink cartridge 34 Recording head 35 Head tank 81 Maintenance recovery mechanism 97 Choke valve (opening-closing means)
301 Main control unit

JP 2010-058303 A JP 2012-126099 A JP 2007-223230 A

Claims (5)

An ink cartridge for containing ink;
A recording head including a droplet discharge head having a plurality of nozzles for discharging ink;
A head tank that temporarily stores a predetermined amount of ink replenished from the ink cartridge by a negative pressure formed by ink ejection;
An opening / closing means provided between the ink cartridge and the head tank, for blocking or opening an ink supply path;
A maintenance recovery mechanism that performs head suction;
A main control unit that controls the execution of cleaning that performs head suction in a state where the opening / closing means is shut off, and
The main controller performs the cleaning when the amount of air mixed in the head tank is equal to or greater than a reference value and the remaining amount of ink in the ink cartridge is equal to or greater than a reference amount. apparatus. The main control unit stores the air mixing amount reset time, the number of ink ends, and the number of cartridge replacements in a storage unit in order to determine the amount of air mixing in the head tank.
The main control unit
Air mixing amount (Va) = air permeability coefficient (Cp) × (current time−air mixing amount reset time)
+ Ink end coefficient (Ce) x number of ink ends
2. The image forming apparatus according to claim 1, wherein the amount of air mixed in the head tank is calculated based on: + cartridge replacement coefficient (Cc) × number of cartridge replacements. The main control unit stores the air mixing amount reset time, the number of ink ends, and the number of cartridge replacements in a storage unit in order to determine the amount of air mixing in the head tank.
The main control unit
Air mixing amount (Va) = air permeability coefficient (Cp) × (current time−air mixing amount reset time)
+ Ink end coefficient (Ce) x number of ink ends
+ Cartridge replacement coefficient (Cc) x cartridge replacement count
2. The image forming apparatus according to claim 1, wherein the amount of air contamination in the head tank is calculated based on the cumulative ink usage during the ink end detection.   The image forming apparatus according to claim 2, wherein the ink end coefficient (Ce) is larger than the cartridge replacement coefficient (Cc).   The said main control part changes at least one of the suction pressure of the said cleaning, and the frequency | count of suction according to the air mixing amount in a head tank at the time of the said cleaning implementation, The any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus according to one item.

Images