JP5754621B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a liquid ejection head that ejects ink droplets, and ejects ink droplets while conveying a medium. 2. Related Art There is an ink jet recording apparatus that forms an image by adhering to a sheet. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  The ink jet recording apparatus includes a detachable ink cartridge that can store a large amount of ink, and a head tank that temporarily stores the ink from the ink cartridge and supplies the ink to a droplet discharge head that discharges the droplet. And a sub-tank or a buffer tank). The head tank is made of a flexible member such as a resin film. The head tank includes an air release mechanism such as an openable / closable valve that opens or closes the inside of the head tank to the atmosphere or shuts off the atmosphere, and a liquid feeding unit that sends ink from the ink cartridge to the head tank. . Further, the head tank is provided with a liquid level detecting means for detecting the liquid level of the full ink in the head tank. In the ink jet recording apparatus having such a configuration, when the ink is filled from the ink cartridge to the head tank by performing the forward transfer liquid by the liquid feeding means, the liquid level for detecting that the head tank is full with ink. The ink filling operation is controlled based on the detection signal from the detection means. The ink filling operation includes the open air filling in which the open air valve of the air opening mechanism is opened to fill the head tank with ink before the start of printing or after the end of printing. There is a normal filling in which ink filling is performed by closing the open / close valve of the air release mechanism in order to fill the used ink amount as needed.

  In the ink jet recording apparatus, when the ink in the ink cartridge is supplied to the head tank by the liquid supply means and the ink in the ink cartridge becomes empty, the ink cartridge is empty and is supplied to the head tank by the liquid supply means. When the liquid feeding is continued, the inside of the flow path between the liquid feeding means and the ink cartridge mounting portion is in an overnegative pressure state. If the ink cartridge is replaced in this state, outside air may be sucked in and air bubbles may be mixed between the liquid feeding means and the ink cartridge mounting portion. Air that has been sucked in cannot be removed because the supply path from the liquid feeding means to the head tank is closed, and when a new ink cartridge is installed and ink filling operation starts, the air passes through the tube together with the ink. Will be sent to the head tank. When the image forming operation is performed in a state where bubbles are present in the head tank, the bubbles in the head tank are sent to the droplet discharge head, causing a discharge failure due to non-discharge of ink and reducing the image quality. Further, if ink is filled in the state in which the inside of the head tank is open to the atmosphere with air bubbles mixed, the liquid level rises and lifts the air bubbles existing above the liquid level. For this reason, ink adheres to the atmosphere release mechanism provided in the upper part of the head tank, and the attached ink is dried and solidified, so that the opening / closing valve of the atmosphere release mechanism cannot be driven.

  As a method related to an ink filling operation when air bubbles are mixed when the ink cartridge is pulled out at the time of replacing the ink cartridge, a method described in Patent Document 1 is known. In the method of Patent Document 1, when there is a high possibility that air has been mixed, an air mixing flag is set, and a liquid feeding sequence is performed in which air in the supply path is sent to the head tank. After the liquid feeding sequence, if it is within a predetermined time, the air mixing flag state (head tank foam state) is set. When the air mixing flag is canceled after the liquid feeding sequence is performed, the normal state is restored. At the time when the user uses the printer in the air mixing flag state and needs re-negative pressure formation in the normal state (timing that requires air release filling), the air release filling is not performed, and alternative operations (normal filling, cleaning, etc.) are performed. ing. As described above, in the invention described in Patent Document 1, ink filling by the above-described open air filling is limited until the bubbles in the head tank disappear.

  However, according to the method of the above-mentioned Patent Document 1, since the negative pressure is not formed regardless of the timing at which ink filling that requires opening to the atmosphere, that is, the situation where the negative pressure is required, the negative pressure of the head tank is not generated. There may be no pressure. Further, in the mounting method of the re-negative pressure forming method in the air mixed state, the head tank ink level is lowered every time the re-negative pressure is formed, and in the worst case, the ink in the head tank is emptied. For this reason, ink non-ejection due to ink shortage occurs, and printing failure occurs.

  In addition, a predetermined amount of ink in the head tank was sucked to bring the head tank into a negative pressure state. When this negative pressure was formed, the amount of ink in the head tank was such that the volume in the head tank disappeared, the volume of ink It is less than the prescribed amount. For this reason, the negative pressure value in the head tank becomes lower than the specified value by forming the predetermined negative pressure in the head tank with the ink liquid amount in the head tank being smaller than the specified amount. An ink jet recording apparatus places a liquid chamber in a recording head communicating with a head tank in a negative pressure state having a predetermined negative pressure value, supplies a recording voltage to a displacement member provided in the liquid chamber, and displaces the displacement member. Printing is performed by applying a specified displacement pressure to the internal pressure of the liquid chamber and ejecting ink from the nozzles of the recording head. As described above, if the specified displacement pressure is applied to the internal pressure of the liquid chamber by the displacement member while the negative pressure value in the head tank is already lower than the specified value from the beginning of printing, excess ink will be ejected by the insufficient negative pressure value. Normal ink ejection is not possible. Further, when the negative pressure value in the head tank is lower than the specified value, there is a problem that the ink meniscus liquid level at the nozzle cannot be maintained and the ink in the liquid chamber drips from the nozzle.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress the occurrence of printing failure due to ink non-ejection caused by ink shortage, and to cause ejection failure due to lack of negative pressure in the head tank. It is an object of the present invention to provide an image forming apparatus capable of preventing ink dripping from the nozzle ejection port caused by insufficient negative pressure.

In order to achieve the above object, a first aspect of the present invention provides a liquid droplet ejection head for ejecting liquid droplets, an ink cartridge for storing ink, a negative pressure in the liquid droplet ejection head, and the ink cartridge. A head tank composed of a flexible member that temporarily stores a predetermined amount of ink fed from the head, an openable air opening mechanism that opens the inside of the head tank to the air, and the ink cartridge to the head tank. Liquid transfer means for performing forward transfer liquid for supplying ink and reverse transfer liquid for supplying ink from the head tank to the ink cartridge, and liquid level detection means for detecting the liquid level of the ink in the head tank. If, in the image forming apparatus and a control Gosuru controller to each drive in the detection result the air opening mechanism on the basis of and the liquid feeding means of the liquid level detecting means, said head tank With bubbly determination means bubbles determines whether mixed, when it is determined that the air bubbles to the head tank by the bubbly determining means, wherein, the pre-Symbol head tank and the atmosphere In the blocked state, the forward transfer liquid is supplied to supply the ink to the head tank. After that, the inside of the head tank is opened to the atmosphere, the inside of the head tank is cut off from the atmosphere, and the inside of the head tank is turned into the atmosphere. Each drive of the air release mechanism and the liquid feeding means is controlled so that the reverse transfer liquid is performed in a blocked state to form a negative pressure in the head tank .
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a supply port for supplying ink to the head tank is provided, and the supply port is a liquid full of ink detected by the liquid level detection means. The supply port is installed at a position lower than the surface position and fills the head tank with ink by performing the forward transfer liquid by the liquid feeding means until the liquid level detecting means detects the liquid level full of ink. Is blocked at the ink liquid level.
Further, the invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the bubble mixing judgment unit is configured such that the liquid level detection unit does not perform the normal transfer liquid for a predetermined time by the liquid feeding unit. When the ink level is not detected, it is determined that bubbles are mixed in the head tank.
According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the bubble mixing judgment unit is configured such that when the image forming operation is not performed even after a predetermined time has elapsed, the bubbles are formed in the head. It is characterized in that it is mixed in the tank.
Further, the invention of claim 5 is the image forming apparatus according to claim 1 or 2, wherein the liquid feeding means is a tube pump.

In the present invention, when it is determined that air bubbles are mixed into the head tank by the air bubble mixing determination means, the liquid is transferred to the head tank together with the ink by performing the positive transfer liquid with the liquid supply means in a state where the inside of the head tank is shut off from the atmosphere by the air release mechanism. Air bubbles mixed in the supply path from the liquid means to the head tank are sent into the head tank. Ink filling does not stop even if the liquid level detector detects a full tank due to the presence of air bubbles sent into the head tank in the ink or on the ink level. An amount of ink is filled. The inside of the head tank can be brought into a negative pressure state of a predetermined negative pressure value by performing the reverse transfer liquid in a state where the inside of the head tank in which the prescribed amount of ink is stored is opened to the atmosphere and then shut off from the atmosphere . Thereby, the negative pressure state in the head tank becomes normal, and the liquid chamber in the recording head communicating with the head tank also has a specified negative pressure value, so that normal ink discharge is possible. In addition, since the negative pressure value in the head tank becomes a specified value, the meniscus level of the ink at the nozzle can be maintained, and the ink in the liquid chamber does not drip from the nozzle. Therefore, it is possible to suppress the occurrence of printing failure due to ink non-ejection caused by ink shortage, and to prevent ejection failure and ink dripping from the nozzles.

  According to the present invention, it is possible to obtain an excellent effect that it is possible to suppress the occurrence of printing failure due to ink non-ejection caused by ink shortage and to prevent ejection failure and ink dripping from the nozzle.

It is the perspective view which looked at the ink-jet recording device of this embodiment from the front. It is a principal part side view of the mechanism part of an inkjet recording device. It is a principal part top view of the mechanism part of an inkjet recording device. It is a block diagram which shows the outline | summary of the control part of an inkjet recording device. It is a perspective view which shows the structure of a head tank. It is a schematic plan view which shows the structure of a tube pump. FIG. 2 is a schematic explanatory diagram for explaining an ink supply system. It is a schematic sectional drawing which shows the structure of the head tank mounted in the droplet discharge head. It is a flowchart which shows the process for respond | corresponding to the case where possibility that air has mixed in the supply path | route with respect to a head tank is high. It is a flowchart which shows another process for respond | corresponding to the case where possibility that air mixed in the supply path | route with respect to a head tank is high. It is a flowchart which shows another process for respond | corresponding to the case where possibility that air mixed in the supply path | route with respect to a head tank is high. It is a flowchart which shows another process for respond | corresponding to the case where possibility that air mixed in the supply path | route with respect to a head tank is high. It is a flowchart which shows the operation | movement of the atmosphere open | filling operation | movement and the normal re-negative pressure formation flow. It is a flowchart which shows the operation | movement of the alternative re-negative pressure formation flow.

Hereinafter, an embodiment of an ink jet recording apparatus will be described as an image forming apparatus to which the present invention is applied.
FIG. 1 is a perspective view of the ink jet recording apparatus according to the present embodiment as viewed from the front. An inkjet recording apparatus 100 according to this embodiment shown in the figure includes an apparatus main body 101, a paper feed tray 102 for loading paper mounted on the apparatus main body 101, and a detachably mounted on the apparatus main body 101 to display an image. And a paper discharge tray 103 for stocking the recorded (formed) paper. Further, a cartridge loading for loading an ink cartridge that protrudes from the front surface to the front side of the apparatus main body 101 and is lower than the upper surface is provided at one end of the front surface of the apparatus main body 101 (side of the paper supply / discharge tray section). The cartridge loading unit 104 is provided with an operation / display unit 105 such as operation buttons and a display.

  The cartridge loading unit 104 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 110k, 110c, 110m, and 110y (referred to as “ink cartridge 110” when the colors are not distinguished) are recording liquid cartridges serving as recording liquid storage units from the front side to the rear side of the apparatus main body 101. A front cover (cartridge cover) 106 that is opened when the ink cartridge 110 is attached or detached is provided on the front side of the cartridge loading unit 104 so as to be openable and closable. Further, the ink cartridges 110k, 110c, 110m, and 110y are configured to be loaded side by side in the horizontal direction in a vertically placed state.

  Further, the operation / display unit 105 has the remaining amounts of the ink cartridges 110k, 110c, 110m, and 110y for the respective colors at the arrangement positions corresponding to the installation positions (arrangement positions) of the ink cartridges 110k, 110c, 110m, and 110y for the respective colors. The remaining amount display sections 111k, 111c, 111m, and 111y for each color for displaying the near end and the end are arranged. Further, the operation / display unit 105 is also provided with a power button 112, a paper feed / print resume button 113, and a cancel button 114.

  Next, the mechanism part of the ink jet recording apparatus will be described with reference to FIGS. 2 is a side view showing the outline of the mechanism, and FIG. 3 is a plan view of the main part.

  In the mechanism of the ink jet recording apparatus, the carriage 133 is slidably held in the main scanning direction by a guide rod 131 and a stay 132 which are guide members horizontally mounted on the left and right side plates 121A and 121B constituting the frame 121. The main scanning motor that is not moved moves and scans in the bidirectional carriage main scanning direction indicated by the arrow in FIG. 3 via the timing belt.

  As described above, the carriage 133 includes four droplet discharge heads 134a to 134d that discharge ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). The droplet discharge heads 134 are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet discharge direction facing downward. It is also possible to employ one or a plurality of head configurations having nozzle rows that eject ink droplets of each color.

  Here, the inkjet head constituting the droplet discharge head 134 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a temperature change. It is possible to use a shape memory alloy actuator that uses a metal phase change due to the above, an electrostatic actuator that uses an electrostatic force, and the like as pressure generating means for generating pressure for discharging droplets.

  Further, the carriage 133 is equipped with head tanks 135a to 135d for supplying ink of each color to the respective droplet discharge heads 134a to 134d. Each head tank 135a to 135d is filled with ink of each color from each color ink cartridge 110y, 110m, 110c, 110k mounted on the cartridge loading section 104 via a plastic ink supply tube 136 for feeding each color ink. Is done. The cartridge loading 104 is provided with a supply pump unit 124 for feeding ink in the ink cartridge 110, and the ink supply tube 136 is locked to the rear plate 121C constituting the frame 121 in the middle of turning. It is held by the member 125. The supply pump unit 124 can also send liquid in the reverse direction (reverse transfer liquid).

  On the other hand, as a paper feeding unit for feeding the paper 142 stacked on the paper stacking unit (pressure plate) 141 of the paper feed tray 102 in FIG. 2, half a month in which the paper 142 is separated and fed one by one from the paper stacking unit 141. A separation pad 144 made of a material having a large coefficient of friction is provided opposite to the roller (sheet feeding roller) 143 and the sheet feeding roller 143, and the separation pad 144 is urged toward the sheet feeding roller 143 side.

  In order to feed the sheet 142 fed from the sheet feeding unit to the lower side of the droplet discharge head 134, a guide member 145 that guides the sheet 142, a counter roller 146, a transport guide member 147, and a tip addition member. A pressing member 148 having a pressure roller 149, and a conveying belt 151 that is a conveying means for electrostatically attracting the fed sheet 142 and conveying it at a position facing the droplet discharge head 134. .

  The conveyor belt 151 is an endless belt, and is configured to wrap around the conveyor roller 152 and the tension roller 153 and circulate in the belt conveyance direction (sub-scanning direction). Further, a charging roller 156 that is a charging unit for charging the surface of the transport belt 151 is provided. The charging roller 156 is disposed so as to come into contact with the surface layer of the conveyor belt 151 and to rotate following the rotation of the conveyor belt 151. Further, a guide member 157 is disposed on the back side of the conveyance belt 151 so as to correspond to a printing area by the droplet discharge head 134.

  The transport belt 151 rotates in the belt transport direction of FIG. 2 when the transport roller 152 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 142 recorded by the droplet discharge head 134, a separation claw 161 for separating the paper 142 from the transport belt 151, a paper discharge roller 162, and a paper discharge roller 163, And a paper discharge tray 103 below the paper discharge roller 162.

  A double-sided unit 171 is detachably attached to the back surface of the apparatus main body 101. The duplex unit 171 takes in the paper 142 returned by the reverse rotation of the transport belt 151, reverses it, and feeds it again between the counter roller 146 and the transport belt 151. The upper surface of the duplex unit 171 is a manual feed tray 172.

  Further, as shown in FIG. 3, a maintenance / recovery mechanism 181 including a recovery means for maintaining and recovering the nozzle state of the droplet discharge head 134 is arranged in the non-printing area on one side of the carriage 133 in the scanning direction. doing.

  The maintenance / recovery mechanism 181 includes cap members (hereinafter referred to as “caps”) 182a to 182d (hereinafter referred to as “caps 182” when not distinguished) for capping each nozzle surface of the droplet discharge head 134. A wiper blade 183 that is a blade member for wiping the nozzle surface, an empty discharge receiver 184 that receives droplets when performing an empty discharge that discharges droplets that do not contribute to recording in order to discharge the thickened recording liquid, and the like It has. Here, the cap 182a is a suction and moisture retention cap, and the other caps 182b to 182d are moisture retention caps.

  Then, the waste liquid of the recording liquid generated by the maintenance / recovery operation by the maintenance / recovery mechanism 181, the ink discharged to the cap 182, the ink attached to the wiper blade 183 and removed by the wiper cleaner 185, and the idle ejection to the idle ejection receptacle 184 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 133, 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 188 for receiving the droplets at the time is disposed, and the empty discharge receiver 188 is provided with an opening 189 along the nozzle row direction of the droplet discharge head 134.

  In the ink jet recording apparatus of this embodiment configured as described above, the sheets 142 are separated and fed one by one from the sheet feed tray 102, and the sheet 142 fed substantially vertically upward is guided by the guide 145, and is conveyed by the conveying belt. 151 and the counter roller 146 are sandwiched and conveyed. Further, the leading end is guided by the conveying guide 137 and pressed against the conveying belt 151 by the leading end pressure roller 149, and the conveying direction is changed by about 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, which will be described later, to the charging roller 156 alternately, that is, an alternating voltage is applied and the conveying belt 151 is alternating. 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 sheet 142 is fed onto the conveying belt 151 that is alternately charged with plus and minus, the sheet 142 is attracted to the conveying belt 151, and the sheet 142 is conveyed in the sub-scanning direction by the circumferential movement of the conveying belt 151.

  Therefore, ink droplets are ejected onto the stopped paper 142 by driving the droplet ejection head 134 according to the image signal while moving the carriage 133 in the main scanning direction based on the main scanning position information by the linear encoder 137. Then, one line is recorded, and after the sheet 142 is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 142 has reached the recording area, the recording operation is terminated and the sheet 142 is discharged onto the discharge tray 103.

  During printing (recording) standby, the carriage 133 is moved to the maintenance / recovery mechanism 181 side, and the droplet discharge head 134 is capped by the cap 182 to keep the nozzles in a wet state, thereby preventing discharge failure due to ink drying. To prevent. In addition, with the cap 182 capping the droplet discharge head 134, the recording liquid is sucked from the nozzle by a suction pump (not shown) (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. Thereby, the stable ejection performance of the droplet ejection head 134 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 201 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. 202.

  The main control unit 201 then sets a main scanning motor driving circuit that moves the carriage 133 in the main scanning direction in order to form an image on the paper 142 based on the print processing information input from the communication circuit 200. The sub-scanning motor driving circuit 204 controls the driving of the paper 142 via a sub-scanning motor that feeds the paper 142, and performs control such as sending print data to the print control unit 202.

  The main control unit 201 receives a detection signal from a carriage position detection circuit 205 that detects the position of the carriage 133, and the main control unit 201 controls the movement position and movement speed of the carriage 133 based on the detection signal. To do. The carriage position detection circuit 205 detects the position of the carriage 133 by, for example, reading and counting the number of slits of an encoder sheet arranged in the scanning direction of the carriage 133 with a photosensor mounted on the carriage 133. The main scanning motor driving circuit 203 rotates the main scanning motor according to the carriage movement amount input from the main control unit 201 to move the carriage 133 to a predetermined position at a predetermined speed.

  Further, the main control unit 201 receives a detection signal from a conveyance amount detection circuit 206 that detects the movement amount of the conveyance belt 151, and the main control unit 201 moves the movement amount and movement speed of the conveyance belt 151 based on this detection signal. To control. The carry amount detection circuit 206 detects the carry amount by, for example, reading and counting the number of slits of the rotary encoder sheet attached to the rotation shaft of the carry roller 152 with a photo sensor. The sub-scanning motor driving circuit 204 rotates the sub-scanning motor in accordance with the conveyance amount input from the main control unit 201 and rotationally drives the conveyance roller 152 to bring the conveyance belt 151 to a predetermined position at a predetermined speed. Move.

  The main control unit 201 rotates the sheet feeding roller 143 once by giving a sheet feeding roller driving command to the sheet feeding roller driving circuit 207. The main control unit 201 rotates and drives the motor of the maintenance / recovery mechanism 181 via the maintenance / recovery mechanism drive motor drive circuit 208, thereby moving the cap 182 up and down, the wiper blade 183 up and down, and driving the suction pump as described above. And so on.

The main control unit 201 drives and controls a drive motor (supply motor) for driving the supply pump of the supply pump unit 124 via the supply pump drive circuit 211, from the ink cartridge 110 loaded in the cartridge loading unit 104. Ink is supplied to the head tank 135 as a positive transfer liquid. At this time, the main control unit 201 controls filling supply based on a detection signal from a head tank full sensor that detects that the head tank 135 is full. In this case, there are open air filling in which filling is performed with the open air mechanism 234 of the head tank 135 open, and normal filling in which filling is performed while the open air mechanism 234 is closed. Further, the ink can be reversely transferred from the head tank 135 to the ink cartridge 110 and returned. By performing the reverse transfer liquid while the air release mechanism 234 is closed, negative pressure can be generated in the head tank 135 without discarding ink.

  Further, the main control unit 201 takes in information stored in a non-volatile memory that is a storage unit provided in each ink cartridge 110 attached to the cartridge loading unit 104 through the cartridge communication circuit 214 and performs a necessary process. Then, it is stored and held in a nonvolatile memory (for example, EEPROM) 215 which is a main body storage means. The main control unit 201 receives a detection signal from an environmental sensor 213 that detects environmental temperature and environmental humidity.

  The print control unit 202 discharges droplets of the droplet discharge head 134 based on the signal from the main control unit 201 and the carriage position and conveyance amount from the carriage position detection circuit 205 and the conveyance amount detection circuit 206. Data for driving the pressure generating means is generated. Then, the above-described image data is transferred to the head driving circuit 210 as serial data. Further, in addition to outputting the transfer clock, latch signal, droplet control signal (mask signal), etc. necessary for the transfer of the image data and the confirmation of the transfer to the head drive circuit 210, the drive signal stored in the ROM A D / A converter that performs D / A conversion of the pattern data, a drive waveform generation unit that includes a voltage amplifier, a current amplifier, and the like, and a drive waveform selection unit that is provided to the head driver. A drive waveform composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) is generated and output to the head drive circuit 210.

  The head drive circuit 210 selectively selects a drive signal constituting a drive waveform supplied from the print control unit 202 based on image data corresponding to one row of the droplet discharge head 134 input serially. The droplet discharge head 134 is driven by applying to a drive element (for example, a piezoelectric element as described above) that generates energy for discharging the droplets 134. 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 perspective view showing the structure of the head tank of the ink jet recording apparatus. In the figure, a negative pressure lever 20-1 is provided in the head tank 20 and is provided in the head tank in which a negative pressure is generated by a spring 20-7 that biases the flexible member film 20-2. The lever operates following the film 20-2 that is displaced according to the amount of ink consumed. The supply port 20-3 is a supply port through which ink is supplied from the ink cartridges 110k to 110y of FIGS. 1 and 3 through the ink supply tube 136 of FIG. The atmosphere release pin 20-4 is a pin that opens the inside of the head tank 20 to the atmosphere as necessary. Further, a recording head 20-5 for ejecting ink droplets is attached below the head tank 20. A detection mechanism 20-6 for detecting ink or air is also provided.

  Here, the liquid feed pump of the liquid feed pump unit 124 used in the present invention does not have a complicated pump structure, and forward and reverse ink feed is possible by changing the rotation direction of the drive motor as shown in FIG. A tube pump 30 is employed. A rubber tube 31 for feeding liquid is circulated inside the pump of the tube pump 30. The rubber tube 31 is locally crushed by a pump rotor 32 built in the pump, and the pump rotor 32 is rotated. By moving the crushed point in the rotation direction, the ink is fed in the rotation direction of the pump rotor 32. Specifically, when the ink is forwardly transferred from the ink cartridge to the ink tank, the pump rotor 32 is rotated in the direction of arrow A. Conversely, when the ink cartridge is reversely transferred from the ink tank, the pump rotor 32 is rotated in the direction indicated by the arrow B. Here, in the rotation of the pump rotor 32, rotation in the rotation direction of the arrow A is referred to as normal rotation, and rotation in the rotation direction of the arrow B is referred to as reverse rotation. Therefore, the ink feeding direction can be controlled by controlling the rotation of the pump rotor 32 forward and backward. In addition, by using a tube pump with a simple configuration as the liquid feed pump, the pump configuration is small. Furthermore, since the pumping motor can be controlled by forward / reverse control for controlling the liquid feeding direction, piping is simplified. The structure of the tube pump may be an eccentric cam type other than the rotary roller type as shown in FIG.

  Next, a liquid supply apparatus that supplies ink as a recording liquid to the droplet discharge head 34 in this image forming apparatus will be described with reference to FIG. FIG. 7 is a schematic explanatory view of the liquid supply apparatus.

  The ink cartridge 110 that is the first liquid storage means stores a plastic ink bag 222 that stores ink, which is a liquid, in a cartridge case 221, and an ink supply for supplying internal ink to the ink bag 222. A mouth portion 223 is provided. The ink supply port 223 has an elastic member such as rubber inside. The supply pump unit 124 includes a supply pump 224 for supplying ink from the ink cartridge 110 to the head tank 135, a cam 226 for reciprocating the piston 225 of the supply pump 224 in the vertical direction in FIG. And a gear 228 for rotating the gear 227 and an ink supply motor 230 which is a pump drive means attached to the motor shaft 229. The hollow needle 231 provided on the supply pump 224 is connected to the ink of the ink cartridge 110. The inside of the supply pump 224 and the inside of the ink bag 222 are jointed by being inserted into an elastic member (for example, a rubber plug) in the ink supply port 223 of the bag 222.

  The head tank 135 serving as the second liquid storage means includes a tank case 233 for storing the ink 232, 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 233 being opened to the atmosphere. A droplet discharge head 134 is attached to the lower part of the tank case 233, and the liquid level of the ink 232 stored in the upper part of the tank case 233 is in a predetermined position. It is provided with a full tank detecting means composed of two detection electrodes 235 (only one is shown in the figure) for detecting this.

  The supply pump 224 uses the tube pump described in FIG. When the main control unit 201, which is a control unit for controlling the operation / stop of the supply pump 224, supplies ink from the ink cartridge 110 to the head tank 135, detection from the detection electrode 235 of the full tank detection unit. Based on the signal, the rotational drive and stop of the drive motor 230 are controlled via the supply pump motor drive circuit 211.

  In this liquid supply apparatus, one end of the ink supply tube 136 is in a direction along the liquid supply direction (forward transfer liquid direction) of the supply pump 224 with respect to the supply pump 224 of the supply pump unit 124 that is the liquid supply means. The joints 236 are connected. The other end of the ink supply tube 136 is connected to a supply port 300 provided in the head tank 135. The end of the supply port 300 extends to a position lower than the height of the end of the detection electrode 235 from the bottom of the tank case 233.

  Next, in this liquid supply apparatus, when the head tank 135 is filled with the recording liquid (ink), the head tank 135 does not become full even if the supply pump of the supply pump unit 124 is operated until a predetermined time elapses. Next, the mixing of air when the ink cartridge 110 is treated as having no ink will be described.

  When the ink bag 222 of the ink cartridge 110 is empty, there is nothing to be sucked out, and if the supply pump of the supply pump unit 124 is continuously driven, the pressure in the supply pump 224 of the supply pump unit 124 becomes negative (negative) Pressure) will increase. Therefore, when an instruction to replace the ink cartridge 110 is issued, the supply pump unit 124 is in a strong negative pressure state.

  When the ink cartridge 110 is replaced in this state, the joint between the rubber plug of the ink supply port 223 and the hollow needle 231 of the supply pump unit 124 is temporarily removed. Air inhalation begins. Since the supply path from the supply pump unit 124 to the head tank 135 is a closed path, the sucked air does not escape from the supply path. For this reason, when a new ink cartridge 110 is installed and the supply operation starts, air is sent to the head tank 135 through the ink supply tube 136.

  As shown in FIG. 8, the air sent into the head tank 135 in this way becomes bubbles 301 on the ink surface in the head tank 135, and the bubble diameter of the bubbles 301 increases as the supply operation proceeds further. Will go. The air bubbles 301 in the head tank 135 float above the ink liquid level, so that the head tank is filled up by touching the detection electrode 235 even though the amount of ink liquid is small. The detection result is output. Furthermore, when the filling operation is performed with the atmosphere release mechanism 234 opened with respect to the head tank 135, the ink is released to the atmosphere release mechanism 234 without the full tank being detected while the bubbles 301 are in contact with the detection electrode 234. May leak to the outside and contaminate the droplet discharge head 134 or cause the droplet discharge head 134 to malfunction.

  Accordingly, processing for dealing with a case where there is a high possibility that air (air) has entered the supply path to the head tank 135 will be described with reference to the operation flows shown in FIGS. In this image forming apparatus, when there is a high possibility that air (air) is mixed in the supply path to the head tank 135, processing for setting the air mixing flag (= 1) is performed.

In FIG. 9 showing the operation flow of this embodiment, when the supply pump of the supply pump unit 124 is driven and the head tank 135 is filled with ink from the ink cartridge 110 to the head tank 135, the supply is first performed. The supply pump 224 of the pump unit 124 is driven (step S101). When a predetermined time elapses (timeout) before the filling is completed (step S102; NO, step S103; YES), the ink cartridge 110 has run out of ink. It is treated that the possibility that air has been mixed is high, and the air mixing flag is set (= 1) (step S104). Thereafter, the process proceeds to cartridge replacement processing (step S105).

  Further, as shown in FIG. 10, the time from the end of the recording operation is measured (step S201; NO), and the apparatus is not used for a predetermined period (predetermined time) (step S202; YES), assuming that there is a high possibility that air (air) has been mixed into the supply path such as the supply pump 224 and the ink supply tube 136 of the supply pump unit 124, the process of setting the air mixing flag (= 1) is performed ( Step S203). In other words, when the device is turned on and the elapsed time from the power-off has reached a predetermined period (for example, 72 hours), after performing the process of setting the air mixing flag (= 1), Shifts to processing at power-on. In this case, since the supply pump 224 of the supply pump unit 124 has not been driven for a predetermined period, it is treated that there is a high possibility that air has entered the supply path.

  Therefore, as shown in FIG. 11, when the air mixing flag is “1” (viewed in units of heads) (step S301; YES), this image forming apparatus supplies ink from the ink cartridge 110 to the head tank 135. It is determined whether or not the liquid supply sequence for forward transfer liquid has been performed (step S302). If the liquid feeding sequence has not been performed (step S302; NO), the liquid feeding sequence is performed (step S303), and the air mixed in the supply pump 224 and the ink supply tube 136 of the liquid feeding pump unit 124 ( Air) is sent to the head tank 135 together with the ink, and the liquid feeding time is stored (step S304).

  This liquid feeding sequence is, for example, feeding (overfilling) a larger amount of recording liquid to the head tank 135 than the normal filling amount, and capping the droplet discharge head 134 with a cap 182 to perform nozzle suction. By performing (maintenance suction), a negative pressure is formed in the head tank 135. The operation of wiping the nozzle surface of the droplet discharge head 134 (the surface on which the nozzle for discharging droplets is formed) with the wiper blade 183 is repeated a predetermined number of times (2 to 3 times) to perform the required cleaning operation. This is an operation (sequence) for capping the droplet discharge head 134 with the cap 182.

  On the other hand, if the air mixing flag is “1” and the liquid feeding sequence has been performed (step S302; YES), a predetermined predetermined time until the bubbles due to the air sent into the head tank 135 disappear. It is determined whether or not the liquid feeding time has elapsed (step S305). If the predetermined time has elapsed from the liquid feeding time (step S305; YES), the air mixing flag is set to “0” (step S306).

  In this way, if the air mixing flag is “1”, the image forming apparatus is made to recognize that there is a high possibility that air is mixed in the supply path or the head tank 135. Therefore, it is possible to separate maintenance operations depending on whether the air is mixed or not.

  In addition, as shown in FIG. 12, when the air mixing flag is not “1” (step S401; NO), the atmospheric refilling operation as shown in FIG. S402, S403). When the air mixing flag is “1” (step S401; YES), an alternative re-negative pressure forming flow as shown in FIG. 14 is performed (step S404). This alternative re-negative pressure forming flow is an operation flow including a normal filling operation in a state where the atmosphere is shut off before the atmosphere is released. The reason for performing this alternative re-negative pressure forming flow is that if the alternative re-negative pressure forming flow is not performed, bubbles may reach the top of the head tank 135 and destroy the atmosphere release mechanism.

Next, the air release filling operation and the normal re-negative pressure forming flow operation will be described with reference to FIG. 13 showing the operation flow.
First, the inside of the head tank 135 is released to the atmosphere by the atmosphere release mechanism (step S501). Since the negative pressure is formed in the head tank 135, the head tank 135 formed of a flexible member such as a film swells slightly and the liquid level drops. After that, the negative pressure is formed in the head tank by blocking the air and reverse transfer liquid (or by maintenance suction). Then, ink is filled in an open state (step S502). Then, ink is filled until the detection electrode 235 detects the liquid level. This is a position where the opening of the supply port 300 is lower than the lower end of the detection electrode 235. That is, in FIG. 8, the height h1 of the lower end of the detection electrode 235 is higher than the height h2 of the opening of the supply port 300. Therefore, when the detection electrode 235 detects the liquid level, the liquid level is above the opening of the supply port 300. As a result, the ink blocks the opening of the supply port 300 to block the atmosphere (step S503). By performing reverse transfer liquid in a state of being cut off from the atmosphere, a negative pressure state of a predetermined pressure is formed in the head tank 135 (step S504).

Next, the operation of the alternative re-negative pressure forming flow will be described with reference to FIG. 14 showing the operation flow.
First, the forward transfer liquid is filled into the head tank 135 and ink is filled to the overfill position or the normal fill position (step S601). In the ink filling in a state where the atmosphere is cut off as in this case, the head tank 135 formed of a flexible member such as a film only swells, and the liquid level does not rise. For this reason, since the bubbles do not go to the upper part, there is no fear of breaking the air release mechanism 234. Thereafter, the inside of the head tank 135 is released to the atmosphere (step S602). At this time, since the ink is already filled, there is an effect of suppressing the decrease in liquid level as compared with the case where the ink is not filled. Thereafter, the atmosphere is shut off (step S603). By performing reverse transfer liquid while the atmosphere is shut off, a negative pressure state is formed in the head tank 135 (step S604).

  Since the liquid level does not drop during the above-described atmosphere refilling operation, the above normal re-negative pressure forming flow operation, and the above alternative re-negative pressure forming flow operation, the supply port 300 of the head tank 135 is blocked by ink. The negative pressure can be formed by the reverse transfer liquid. Since the negative pressure is generated by the reverse transfer liquid, the negative pressure can be formed without discharging the ink.

  As described above, according to the embodiment, when it is determined by the air mixing flag that the bubbles 301 are mixed in the head tank 135, the main control unit 201 does not open the head tank 135 to the atmosphere with the atmosphere release mechanism 234. In addition, the supply pump unit 124 of the liquid feeding means is controlled so as to perform the normal transfer liquid from the ink cartridge to the head tank. That is, since ink filling is performed in a state of being cut off from the atmosphere, the head tank 135 formed of a flexible member such as a resin film swells and can be filled with a predetermined amount of ink. During the printing operation, the ink amount in the head tank becomes a specified amount. Since the ink amount in the head tank 135 is a specified amount, negative pressure is formed in the head tank 135 at the initial stage of printing, the negative pressure value in the head tank becomes a specified value, and normal ink ejection is possible. Further, since the negative pressure value in the head tank 135 is a specified value, the meniscus liquid level of the ink at the nozzle can be maintained, and the ink in the liquid chamber does not drip from the nozzle.

  Further, according to the embodiment, as shown in FIGS. 7 and 8, the supply port 300 that supplies ink to the head tank 135 is a detection electrode that is a liquid level detection unit that detects the level of ink in the head tank. It is installed at a position lower than the liquid level of the ink detected by 235. That is, the height of the supply port 300 from the bottom of the head tank 135 is lower than the height of the detection electrode 235. Then, the ink is filled in the head tank 135 until the liquid level of the ink passes through the supply port 300 and closes the supply port 300 with the ink. In the state where the supply port 300 is blocked with ink, the reverse transfer liquid is performed, and the ink is returned from the head tank to the ink cartridge side so that the inside of the head tank can be in a negative pressure state. Therefore, the ink level does not decrease and the occurrence of printing defects is suppressed, and ink dripping from the nozzles of the recording head is prevented. Further, since the negative pressure is generated by the reverse transfer liquid, the negative pressure can be formed without discharging the ink.

  Further, according to the embodiment, as shown in FIG. 9, when the head tank does not become full even if the ink is transferred from the ink cartridge to the head tank for a predetermined time and the head tank does not become full, bubbles are mixed in the head tank. Judge. Further, as shown in FIG. 10, when the image forming operation is not performed even after a predetermined time has elapsed, it is determined that bubbles are mixed in the head tank.

DESCRIPTION OF SYMBOLS 20 Head tank 20-1 Negative pressure lever 20-2 Film 20-3 Supply port 20-4 Atmosphere release pin 20-5 Recording head 20-6 Detection mechanism 20-7 Spring 30 Tube pump 110 Ink cartridge 124 Supply pump unit 133 Carriage 134 Liquid droplet ejection head 135 Head tank 136 Ink supply tube 181 Maintenance / recovery mechanism 201 Main control unit 202 Print control unit 203 Main scanning motor drive circuit 204 Sub-scanning motor drive circuit 205 Carriage position detection circuit 206 Conveyance amount detection circuit 207 Feed roller Drive circuit 208 Maintenance drive mechanism motor drive circuit 209 Head drive circuit 210 Supply pump drive circuit 211 Head tank full sensor 212 Environmental sensor 213 Cartridge communication circuit 214 Non-volatile memory 215 Car Tredge EEPROM
224 Supply pump 234 Atmospheric release mechanism 235 Detection electrode 300 Supply port 301 Bubble

JP 2007-223230 A

Claims (5)

A droplet discharge head that discharges droplets, an ink cartridge that stores ink, a negative pressure is created in the droplet discharge head, and a predetermined amount of ink sent from the ink cartridge is temporarily stored to be flexible. A head tank composed of a conductive member, an openable / closable atmosphere opening mechanism for opening the inside of the head tank to the atmosphere, a positive transfer liquid for feeding ink from the ink cartridge to the head tank, and the ink from the head tank. and feeding means for performing a backward transfer liquid to feed the ink to the cartridge, the liquid level detection means for detecting the liquid level of the ink full of the head tank, on the basis of the detection result of the liquid level detecting means in the image forming apparatus and a control Gosuru controller to each drive of the atmosphere opening mechanism and the feeding means,
A bubble mixing judgment means for judging whether or not bubbles are mixed in the head tank;
When determined that the air bubbles to the head tank by the bubbly determining means, wherein, the pre-Symbol head tank to the head tank of the ink by performing the positive transfer liquid in a state of blocking the atmosphere After that, the inside of the head tank is opened to the atmosphere, the inside of the head tank is shut off from the atmosphere, and the reverse transfer liquid is applied in a state where the inside of the head tank is shut off from the atmosphere to An image forming apparatus characterized by controlling each drive of the air release mechanism and the liquid feeding means so as to form pressure . The image forming apparatus according to claim 1.
A supply port for supplying ink to the head tank is provided,
The supply port is installed at a position lower than the liquid level position of the ink full tank detected by the liquid level detection means, and the liquid supply means detects the liquid level of the ink full until the liquid level detection means detects the ink full liquid level. An image forming apparatus, wherein a normal transfer liquid is applied to fill the head tank with ink, and the supply port is blocked by an ink liquid surface. The image forming apparatus according to claim 1, wherein
The bubble mixing determining means determines that bubbles are mixed in the head tank when the liquid level detecting means does not detect the full ink level even if the liquid transfer means performs the normal transfer liquid for a predetermined time. An image forming apparatus. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the bubble mixing determining unit determines that bubbles are mixed in the head tank when the image forming operation is not performed even after a predetermined time has elapsed. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the liquid feeding means is a tube pump.

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