JP2007223230A - Apparatus for discharging liquid droplet and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a recording liquid from leaking in a filling operation to a head tank after the air is sucked into a liquid supply route when a cartridge is replaced, which results from a supply pump being in an excessively negative pressure state because the supply pump is operated with the cartridge left in an empty state. <P>SOLUTION: An aeration flag is set when there is a good possibility of the air being mixed into a supply route. When the aeration flag is set, a liquid feed sequence to feed to the head tank 35 the air in the supply route such as a supply pump 241 and a supply tube 36, is executed, and an operation to fill the head tank with a liquid in a state of the head tank being opened to the air is restricted until a bubble in the head tank disappears. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and an image forming apparatus for ejecting liquid droplets, and more particularly to an apparatus and an image forming apparatus for ejecting liquid droplets for feeding liquid between two liquid storage units.

  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”). Is not intended to limit the material, but means that the liquid adheres, and the recording medium, recording medium, recording paper, transfer material, etc. are also used synonymously.) , Which are also referred to as ink droplets) are mounted on a sheet of paper, and a liquid ejection type image forming unit that performs image formation (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 means for supplying 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.
JP 2005-144709 A Japanese Patent No. 3372844

Further, in Patent Document 3, an ink tank and a manifold that distributes ink to an actuator of a print head are connected by a circulation flow path including an outward path and a return path, and ink is forcibly circulated in the circulation path. Thus, there is described an apparatus for performing a circulation purge to remove bubbles adhering to the wall surface of the ink flow path.
JP 2000-033714 A

  As described in the above-mentioned Patent Document 1 and the like, in a liquid supply apparatus that uses at least two liquid storage means, the second liquid storage means has no liquid in the main first liquid storage means. On the other hand, the supply pump is driven to replenish and supply the liquid. At this time, the supply pump continues to be driven until the liquid amount in the second liquid storage means reaches a specified amount, and the supply pump is driven for a predetermined time. Even if it cannot be detected that the amount of the liquid in the second liquid storage means has become the specified amount, the first liquid storage means is empty, so that the replacement of the first liquid storage means is instructed. Become.

  However, as described above, when it is not possible to detect that the liquid amount of the second liquid storage means has reached the specified amount even if the supply pump is driven for a predetermined time, it is detected that the first liquid storage means is empty. In this case, the supply pump is driven despite the fact that the first liquid storage means is empty. At this time, the negative pressure increases excessively in the supply pump. When the instruction for one liquid storage means is issued, the supply pump is in a strong negative pressure state.

  At this stage, when the first liquid storage means is replaced, the portion connecting the first liquid storage means and the supply pump (for example, the joint between the rubber plug and the hollow needle) is removed, and the first liquid storage means The air is sucked into the supply pump which is in negative pressure at the moment of removing. The air that has been sucked into the supply pump does not escape, and when a new first liquid storage means is mounted and the supply operation starts, the air is sent to the second liquid storage means through the tube. The liquid level in the second liquid storage means becomes foamy, and the foam increases. The bubbles in the second liquid storage means may cause the sensor that detects the liquid level of the second liquid storage means to malfunction.

  Therefore, when replenishing and supplying the liquid in a state in which the second liquid storage means is opened to the atmosphere, liquid leakage from the atmosphere opening mechanism occurs, or the valve means constituting the atmosphere opening mechanism becomes dirty and malfunctions. There is a problem of causing a slow leak.

  The present invention has been made in view of the above problems, and provides an apparatus and an image forming apparatus for discharging liquid droplets having a fail-safe function that allows the apparatus to operate without malfunction even when air enters the liquid supply path. The purpose is to do.

  In order to solve the above problems, the apparatus for ejecting liquid droplets according to the present invention has a high possibility that air has entered the liquid supply path from the first liquid storage means to the second liquid storage means. In some cases, the first liquid storage means is provided with means for supplying liquid to the second liquid storage means.

  Here, if the second liquid storage means does not become full even if the operation of supplying the liquid from the first liquid storage means to the second liquid storage means for a predetermined time is performed, air is mixed into the liquid supply path. It is preferable to assume that the possibility of having met is high. In addition, when the apparatus has not been used for a predetermined period, it is preferable that the possibility that air has entered the liquid supply path is high.

  In addition, when a predetermined time has elapsed after the operation of supplying the liquid from the first liquid storage unit to the second liquid storage unit, there is a high possibility that air has entered the liquid supply path. It is preferable that it disappears.

  Further, when there is a high possibility that air has entered the liquid supply path, it is preferable not to perform the liquid replenishment supply operation in a state where the second liquid storage means is open to the atmosphere. Further, when there is a high possibility that air has entered the liquid supply path, it is preferable not to perform the recovery operation of the liquid discharge head that accompanies droplet discharge.

  The image forming apparatus according to the present invention includes the apparatus for ejecting liquid droplets according to the present invention.

  According to the apparatus and the image forming apparatus for ejecting liquid droplets according to the present invention, there is a high possibility that air is mixed in the liquid supply path from the first liquid storage unit to the second liquid storage unit. In some cases, since the first liquid storage means is provided with means for supplying liquid to the second liquid storage means, the air mixed in the supply path is fed into the second liquid storage means. In this state, it is possible to wait until the bubbles in the second liquid storage means disappear.

  As a result, when the first liquid storage means is replaced, even if air is mixed in the supply path when left for a long period of time, etc., liquid leakage may occur from the atmosphere release mechanism in the replenishment supply operation in the atmosphere release state after the next time. In addition, it is possible to provide a fail-safe function for preventing the air release mechanism from becoming dirty and causing a slow leak, and the apparatus can be operated.

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 paper on which an image is recorded (formed) detachably mounted on the apparatus main body 1. A paper discharge tray 3 for stocking is provided. Further, the one end side of the front surface of the apparatus main body 1 (the side of the paper supply / discharge tray portion) has a cartridge loading portion 4 for loading an ink cartridge as a first liquid storage means. The upper surface of 4 is an operation / display unit 5 provided with operation buttons and a display.

  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, 10y (referred to as “ink cartridge 10” when colors are not distinguished) as recording liquid cartridges as the first liquid storage means 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.

  In addition, the carriage 33 is equipped with a head tank 35 for each color, which is a second liquid storage means 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 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.

  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. 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 blade 83 that is a blade member for wiping the ink, and 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. ing. 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 blade 83 and removed by the wiper cleaner 85, and the idle ejection to the idle ejection receiver 94. The discharged ink is discharged and stored in a waste liquid tank (not shown).

  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, the recording liquid is sucked from the nozzle by a suction pump (not shown) with the recording head 34 capped by the cap 82 (referred to as “nozzle suction” or “head suction”), and the thickened recording liquid and bubbles are discharged. Perform recovery action. 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 the sub-scan motor 304 via 303, and control such as sending print data to the print controller 302 is performed.

  The main control unit 301 receives a detection signal from a carriage position detection circuit 305 that detects the position of the carriage 23, and the main control unit 301 controls the movement position and movement speed of the carriage 23 based on the detection signal. To do. The carriage position detection circuit 305 detects the position of the carriage 23 by, for example, reading and counting the number of slits of an encoder sheet arranged in the scanning direction of the carriage 23 with a photosensor mounted on the carriage 23. The main scanning motor drive circuit 303 rotates the main scanning motor 24 according to the carriage movement amount input from the main control unit 301 to move the carriage 23 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 58 in accordance with the conveyance amount input from the main control unit 301 to rotate the conveyance roller 52 to move the conveyance belt 51 to a predetermined position at a predetermined speed. Move with.

  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 blade 83, and driving the suction pump 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 unit 24 via the supply pump drive circuit 311, and the head tank from the ink cartridge 10 loaded in the cartridge loading unit 4. Ink is replenished to 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, and the above-mentioned image data is transferred to the head drive circuit 310 as serial data, and the transfer clock and latch signal necessary for transferring the image data and confirming the transfer, drop control, etc. In addition to outputting a signal (mask signal) etc. to the head drive circuit 310, it comprises a D / A converter, a voltage amplifier, a current amplifier, etc. for D / A converting the pattern data of the drive signal stored in the ROM. Drive waveform generation means and drive waveform selection means to be given to the head driver, one drive pulse (drive signal) or a plurality of drive parameters. Scan to generate a composed drive waveform (drive signal) 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.

  Next, a liquid supply apparatus that supplies ink as a recording liquid to the recording head 34 in the image forming apparatus will be described with reference to FIG. FIG. 5 is a schematic explanatory view of the liquid supply apparatus.

  The ink cartridge 10 as the first liquid storage means is configured by storing a flexible ink bag 102 that stores ink, which is a liquid, in a cartridge case 101, and supplying ink inside the ink bag 102. Ink supply port portion 103 is provided. The ink supply port 103 has an elastic member such as rubber inside.

  The head tank 35 serving as the second liquid storage means includes a tank case 201 for storing the ink 200, a negative pressure generation means (not shown), for example, a negative pressure generation mechanism including a film and an elastic member, and the inside of the tank case 201 is opened to the atmosphere. The recording head 34 is attached to the lower part of the tank case 201, and the liquid level of the ink 200 contained in the upper part of the tank case 202 is in a predetermined position. A full tank detecting means (head tank full sensor) 312 constituted by two detection electrodes to be detected is provided.

  The supply pump unit 24 includes a supply pump 241 for supplying ink from the ink cartridge 10 to the head tank 35, and a cam for reciprocating the piston 242 of the supply pump 241 in the vertical direction (arrow direction) in FIG. 243, a gear 244 that rotates the cam 243, and a drive motor 245 that is a pump driving unit in which a gear 247 that rotates and drives the gear 244 is attached to the motor shaft 245a. The hollow needle 246 provided in the supply pump 241 is an ink cartridge. By inserting into an elastic member (for example, rubber plug) in the ink supply port 103 of the ten ink bags 102, the inside of the supply pump 241 and the inside of the ink bag 102 are jointed.

  The main control unit 301, which is a control means for controlling the operation / stop of the supply pump 241, is based on a detection signal from the head tank full sensor 312 when supplying ink from the ink cartridge 10 to the head tank 35. The rotational drive and stop of the drive motor 305 are controlled via the ink supply motor drive circuit 311.

  In this liquid supply apparatus, one end of the supply tube 36 is in the liquid supply direction of the supply pump 241 (the same as the reciprocating direction of the piston rod 242 in FIG. 4) with respect to the supply pump 241 as the liquid feeding means. They are connected by a joint portion 249 in the direction along.

  Next, in this liquid supply apparatus, when the head tank 35 is filled with the recording liquid (ink), the ink cartridge 10 is filled when the head tank 35 does not become full even if the supply pump 241 is operated until a predetermined time elapses. Next, description will be made on the mixing of air in the case of performing the process of handling no ink.

  When the ink bag 102 of the ink cartridge 10 is empty, nothing is sucked out. As the supply pump 241 continues to be driven, the pressure in the supply pump 241 increases as the negative pressure (negative pressure) increases. Become. For this reason, when an instruction to replace the ink cartridge 10 is issued, the supply pump 241 is in a strong negative pressure state.

  In order to replace the ink cartridge 10 in this state, the joint between the rubber plug of the ink supply port 103 and the hollow needle 246 of the supply pump 241 is temporarily removed. Air inhalation begins. The sucked air does not escape because the supply path from the supply pump 241 to the head tank 35 is a closed path, and when a new ink cartridge 10 is installed and the supply operation starts, the air passes through the tube 36. And sent to the head tank 35.

  As shown in FIG. 6, the air sent into the sub tank 35 in this manner becomes bubbles B on the ink liquid level in the head tank 35, and the bubbles B increase as the supply operation proceeds. Become. The bubbles B in the head tank 35 cause a misdetection result of the ink detection means 203, and when the filling operation is performed with the air release mechanism 204 opened with respect to the head tank 35, the full tank is detected. In some cases, the ink leaks out from the atmosphere release mechanism 204 to contaminate the recording head 34 or cause the recording head 34 to malfunction.

A process for dealing with a case where air (air) is likely to be mixed in the supply path to the head tank 35 will be described with reference to FIG.
In this image forming apparatus, when there is a high possibility that air (air) is mixed in the supply path to the head tank 35, processing for setting the air mixing flag (= 1) is performed.

  That is, as shown in FIG. 7, the head tank filling process for driving the supply pump 241 to fill the head tank 35 with the recording liquid from the ink cartridge 10 to the head tank 35 (this is the above-described atmospheric release filling). Normal filling, and there is also a filling operation that occurs in association with the head maintenance recovery operation.) When the supply pump 241 is driven and a predetermined time elapses before the filling is completed (timeout) In this case, since there is no recording liquid in the ink cartridge 10, it is assumed that air is likely to be mixed in the supply path as described above, and after setting the air mixing flag (= 1), Shift to cartridge replacement processing.

  Further, even when the apparatus is not used for a predetermined period (predetermined time), it is assumed that there is a high possibility that air (air) has mixed into the supply path such as the supply pump 241 and the supply tube 36, and the air mixing flag is set. The process of setting (= 1) is performed.

  That is, as shown in FIG. 8, when the power of the apparatus is turned on and the elapsed time from the power-off has reached a predetermined period (for example, 72 hours), the air mixing flag is set (= 1). After performing the process, the process proceeds to the process when the power is turned on. In this case, since the supply pump 241 has not been driven for a predetermined period, the supply pump 241 is treated as having a high possibility of air entering the supply path.

  Therefore, as shown in FIG. 9, when the air mixing flag is “1” (viewed in units of heads), this image forming apparatus determines whether or not the liquid feeding sequence has been performed.

  Here, if the liquid feeding sequence has not been performed, the liquid feeding sequence is performed, the air mixed in the supply pump 241 and the supply tube 36 is sent to the head tank 35 together with the recording liquid, and the liquid feeding time is stored. To do.

  In this liquid feeding sequence, for example, a larger amount of recording liquid than the normal filling amount is fed to the head tank 35 (overfilling), and the recording head 34 is capped with a cap 82 to perform nozzle suction. The negative pressure is formed in the head tank 35 by the above operation, and the operation of wiping the nozzle surface of the recording head 34 (the surface on which the nozzle for discharging droplets is formed) with the wiper blade 83 is performed a required number of times (2 to 3 times) This is an operation (sequence) in which the required cleaning operation is repeated and the recording head 34 is capped with the cap 82.

  On the other hand, if the air mixing flag is “1” and the liquid feeding sequence has been performed, a predetermined time until the bubbles due to the air sent into the head tank 35 disappear has elapsed from the liquid feeding time. If the predetermined time has elapsed, the air mixing flag is reset (= 0).

  As described above, when the possibility that air has entered the liquid supply path from the first liquid storage means to the second liquid storage means is high, the first liquid storage means to the second liquid storage means. By providing the means for supplying the liquid, the recording liquid leaks until the air in the supply path is sent to the second liquid storage means until the bubbles in the second liquid storage means disappear. Can be prohibited.

  In this case, the apparatus is used for a predetermined period when the second liquid storage means does not become full even if the liquid is replenished and supplied from the first liquid storage means to the second liquid storage means for a predetermined time. If there is no air, the possibility that air has entered the liquid supply path has become high, so even if air is mixed into the supply pump due to the replacement operation of the liquid storage means at the time of liquid supply timeout, the head The apparatus can be operated without failing (fail-safe function), and it is possible to cope with problems caused by air in the supply path, particularly in the pump.

  Therefore, as shown in FIG. 10, the image forming apparatus determines whether or not the air mixing flag is set (= 1) when a request to fill the atmosphere to the head tank 35 is made. If the air mixing flag = 1 is not set, the air release filling operation is performed. If the air mixing flag = 1, an alternative operation (for example, a normal filling operation) is performed. It should be noted that the air release filling operation can be waited until the air mixing flag = 1 is not reached.

  Further, as shown in FIG. 11, when the refreshing operation of the recording head 35 is requested, it is determined whether or not the air mixing flag is set (= 1), and the air mixing flag = 1 must be set. For example, a refreshing operation accompanied by droplet ejection from the recording head 35 is performed. If the air mixing flag = 1, an alternative operation (for example, cleaning operation) not involving droplet ejection from the recording head 35 is performed.

  In this way, until the bubbles due to the air sent into the head tank disappear, the open air filling and the refreshing operation are limited, so that the recording tank leaks due to the head tank full detection error and the head tank with respect to the recording head. Intrusion of bubbles can be reduced.

  The apparatus for ejecting liquid droplets according to the present invention is not limited to an image forming apparatus. The image forming apparatus is not limited to a printer having a single function configuration, and an image forming apparatus having a combined function such as a printer / facsimile / copying device. It may be. Further, the liquid is not limited to ink.

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 the present invention including an apparatus for discharging droplets according to the present invention. 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. It is a typical explanatory view showing an example of a liquid supply device in the same device. It is explanatory drawing explaining generation | occurrence | production of the bubble in the head tank of the liquid supply apparatus. It is a flowchart with which it uses for description of an example of a process in case the possibility that air has mixed in the supply path | route is high. It is a flowchart with which it uses for description of an example of a process in case the possibility that air has mixed in the supply path | route is high. It is a flowchart with which it uses for description of a process when the possibility that air has mixed into the supply path | route has arisen. It is a flowchart with which it uses for description of the process which restrict | limits open air filling, when possibility that air has mixed in the supply path | route is high. It is a flowchart with which it uses for description of the process which restrict | limits head recovery operation | movement when there is a high possibility that air mixed in the supply path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Apparatus main body 2 ... Paper feed tray 3 ... Paper discharge tray 4 ... Cartridge loading part 10k, 10c, 10m, 10y ... Ink cartridge 33 ... Carriage 34 ... Recording head 35 ... Head tank 36 ... Supply tube 51 ... Conveying belt 101 ... Cartridge case 102 ... Ink bag 241 ... Supply pump

Claims (7)

  In the apparatus for ejecting liquid droplets, the apparatus comprising the liquid supply means for replenishing and supplying the liquid from the first liquid storage means to the second liquid storage means for supplying the liquid to the liquid discharge head for discharging liquid droplets An operation of supplying liquid from the first liquid storage means to the second liquid storage means when there is a high possibility that air has entered the liquid supply path from the means to the second liquid storage means. An apparatus for ejecting liquid droplets, characterized by comprising means for performing.   2. The apparatus for ejecting liquid droplets according to claim 1, wherein the second liquid storage means is full even if an operation of replenishing and supplying the liquid from the first liquid storage means to the second liquid storage means for a predetermined time is performed. An apparatus for ejecting liquid droplets, characterized in that when there is no state, there is a high possibility that air has entered the liquid supply path.   The apparatus for ejecting liquid droplets according to claim 1 or 2, wherein when the apparatus has not been used for a predetermined period of time, there is a high possibility that air has entered the liquid supply path. A device that ejects liquid droplets.   4. The apparatus for ejecting liquid droplets according to claim 1, wherein a predetermined time has elapsed after the operation of supplying the liquid from the first liquid storage means to the second liquid storage means. An apparatus for ejecting liquid droplets, characterized in that the possibility that air has entered the liquid supply path is no longer high.   5. The apparatus for ejecting liquid droplets according to claim 1, wherein when there is a high possibility that air has entered the liquid supply path, the second liquid storage means is opened to the atmosphere. The apparatus for ejecting liquid droplets is characterized in that the liquid replenishment supply operation is not performed in the state of being performed.   6. The apparatus for ejecting droplets according to claim 1, wherein when the air is likely to be mixed into the liquid supply path, the recovery operation of the liquid ejection head accompanied by droplet ejection is performed. A device for ejecting droplets characterized by not performing the above. An image forming apparatus for forming an image on a medium by discharging liquid droplets from a liquid discharge head, comprising the apparatus for discharging liquid droplets according to any one of claims 1 to 6. .

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