JP2008062526A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation device shortening the time until starting an image formation by shortening the time required for an dummy discharge movement prior to starting the image formation. <P>SOLUTION: At starting a printing, an ink consumption is counted for every each nozzle train of a recording head 34. For the nozzle train whose ink consumption is less than a predetermined setting value at finishing the printing, the nozzle train is capped with a cap member 82 after executing the dummy discharge movement for discharging liquid droplets which do not contribute to the image formation from the nozzles of the nozzle train concerned. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image by discharging a liquid.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, or a multifunction machine of these, for example, a liquid (e.g., a liquid ejecting apparatus) including a recording head composed of a liquid ejecting head that ejects liquid droplets of recording liquid (liquid) is used. Hereinafter, although it is also referred to as “paper”, the material is not limited, and a recording medium as a liquid (hereinafter, referred to as “recording medium”, “recording medium”, “transfer material”, “recording paper” and the like is also used synonymously). Some of them perform image formation (recording, printing, printing, and printing are also used synonymously) by attaching the ink to the paper.

  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, etc. The term “not only” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. Further, the liquid is not limited to the recording liquid and ink, and is not particularly limited as long as it is a liquid capable of forming an image. Further, the liquid ejection apparatus means an apparatus that ejects liquid from a liquid ejection head, and is not limited to an apparatus that forms an image.

  In an image forming apparatus that includes such a liquid ejecting apparatus and ejects liquid droplets (droplets) to form an image, the recording head is ejected to maintain and recover the performance of the recording head. Recovery action is required. Therefore, in order to prevent thickening and sticking of the recording liquid in the vicinity of the nozzle hole due to natural evaporation of the ink, the recording liquid is discharged to prevent the recording liquid from being ejected due to a cap function that is covered with a highly-sealing cap member and bubbles generated in the nozzle. And a recovery recovery function that sucks and discharges the recording liquid from the nozzle of the head through the cap function, and wipes the residual recording liquid that adheres to the nozzle surface and causes the droplet flight state to change. For example, a wiping function for wiping off, and an empty discharge (preliminary discharge) function for discharging liquid droplets that do not contribute to image formation.

With regard to the idle ejection operation as the recovery operation by such a maintenance recovery mechanism, for example, Patent Document 1 discloses the duration of the non-recording state and the measurement result of the print amount of recording performed immediately before the non-recording state. It is described that the number of idle ejections is set and the idle ejection operation is performed before the start of the next recording with the set number of idle ejections.
Japanese Patent Laid-Open No. 01-281950

Patent Document 2 describes that the number of ejections per predetermined time is varied in accordance with the density of the ejected ink.
Japanese Patent Laid-Open No. 05-092579

Patent Document 3 describes that the state of bubbles inside a recording head is predicted from the number of printed sheets, and the number of droplets for preliminary ejection is changed based on the standing time after printing and the count value of the number of printed sheets. ing.
JP 09-193415 A

In Patent Document 4, immediately after the recording head is released from the capping unit, the amount of ink that causes the recording head to perform the flushing operation is determined based on the time that the recording head is sealed by the capping unit, and the idle ejection operation is performed. It is described that during the printing period, the idle discharge operation is performed by determining the time interval for performing the flushing operation based on the sealing time.
Japanese Patent No. 3491622

As for detection of ink consumption during image formation, there is a method as described in Japanese Patent Application Laid-Open No. H10-228707.
JP 2001-260375 A

  By the way, since image formation cannot be performed in the state where the idle ejection operation is performed, it is necessary to make the idle ejection operation time as short as possible in order to increase the printing speed. If the ejection operation is insufficient, the amount of empty ejection droplets is insufficient, and the process shifts to image formation without being able to recover from clogging, resulting in a reduction in image quality.

  In the conventional apparatus, as described above, since the idle ejection operation is performed immediately before starting the image formation or during the printing, the printing speed decreases as the number of the ejected droplets (the number of droplets) increases, and the printing starts. There is a problem that the rise time of the is long.

  For example, in the apparatus described in Patent Document 1, the number of times of idle ejection is set based on the measurement result of the print duration of the non-recording state and the recording amount performed immediately before the non-recording state. The idle discharge operation is performed before the start of the next recording by the number of ejections. However, since the ink in the nozzle is drying due to the continuation of the non-recording state, the nozzle is reliably recovered by performing the idle discharge before the start of recording. In order to do this, the number of empty ejection drops must be increased. As described in Japanese Patent Application Laid-Open No. H10-228707, the amount of ink to be ejected idle based on the sealing time is also increased since the ink in the nozzles is dried by increasing the sealing time. In order to reliably recover the nozzle by performing (flushing operation), it is necessary to increase the number of empty ejected droplets.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which the time required for the idle ejection operation before the start of image formation is shortened and the rise time until the start of image formation is shortened. To do.

  In order to solve the above-described problem, the image forming apparatus according to the present invention uses an amount of liquid ejected in accordance with the amount of liquid discharged during image formation based on the amount of liquid consumed during image formation. A configuration is provided that includes means for performing an empty ejection operation for ejecting droplets that do not contribute to formation.

  Here, a configuration in which an idle ejection operation is performed with an idle ejection amount corresponding to the liquid consumption during image formation, and the idle ejection operation is performed for nozzles or nozzle arrays in which the amount of liquid ejected during image formation is equal to or less than a preset value. A configuration in which the amount of droplets discharged is changed according to environmental conditions, a recording head that discharges liquid droplets of different colors, and a configuration that controls the idle discharge operation according to each color. it can.

  In addition, the image forming apparatus according to the present invention includes a unit that performs an idle discharge operation for discharging a droplet that does not contribute to the image formation at the end of the image forming operation based on the liquid consumption during the image formation.

  The image forming apparatus according to the present invention discharges a liquid droplet that does not contribute to image formation at the end of the image forming operation with an empty droplet amount corresponding to the liquid consumption amount during image formation based on the liquid consumption amount during image formation. In this configuration, it is possible to reduce the drying of the liquid until the start of the next image formation, and to reduce the time required for the idle discharge operation before the start of image formation. The rise time until the start of image formation can be shortened. Further, according to the image forming apparatus of the present invention, the means for performing the idle ejection operation for ejecting the liquid droplets that do not contribute to the image formation at the end of the image formation operation with the idle ejection droplet amount according to the liquid consumption during the image formation. Therefore, it is possible to reduce the drying of the liquid until the start of the next image formation, shorten the time required for the idle ejection operation before the start of image formation, and shorten the rise time until the start of image formation. .

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall configuration of the image forming apparatus, and FIG. 2 is an explanatory plan view of a main part of the apparatus.
This image forming apparatus is a serial type image forming apparatus, and main and slave guide rods 31 and 32 which are guide members horizontally mounted on the left and right side plates 21A and 21B of the apparatus main body 1 are used to move a carriage 33 which is a head holding member in the main scanning direction. The main scanning motor (not shown) moves and scans in the direction indicated by the arrow (carriage main scanning direction) via a timing belt.

  The carriage 33 is provided with recording heads 34a and 34b (which are liquid ejection heads according to the present invention for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). When not distinguished, it is referred to as “recording head 34”). A nozzle row composed of a plurality of nozzles is arranged along the sub-scanning direction (paper transport direction) perpendicular to the main scanning direction, and the droplet discharge direction is directed downward. Wearing.

  Each of the recording heads 34 has two nozzle rows. One nozzle row of the recording head 34a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 34b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets.

  Further, the carriage 33 is equipped with head tanks 35a and 35b (referred to as “head tank 35” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 34. The head tank 35 includes recording liquid cartridges 10y, 10m, 10c, and 10k that are detachably attached to the cartridge loading unit 4 and each color recording liquid via a supply tube 36 of each color by a supply pump unit 5. Is replenished.

  In addition, a plurality of recording heads composed of liquid ejection heads that are independent for each color or black and color may be used, or a liquid ejection head in which a plurality of nozzle arrays that eject liquid droplets of all colors are formed. You may use the recording head which consists of.

  On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feeding tray 2, a half-moon roller (feeding) that separates and feeds the papers 42 one by one from the paper stacking unit 41. A separation pad 44 made of a material having a large friction coefficient is provided facing the paper roller 43) and the paper feed roller 43, and the separation pad 44 is urged toward the paper feed roller 43 side.

  In order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34, a guide member 45 for guiding the paper 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. And a holding belt 48 which is a conveying means for electrostatically attracting the fed paper 42 and conveying it at a position facing the recording head 34.

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction). Further, a charging roller 56 that is a charging unit for charging the surface of the transport belt 51 is provided. The charging roller 56 is disposed so as to come into contact with the surface layer of the transport belt 51 and to rotate following the rotation of the transport belt 51. The transport belt 51 rotates in the belt transport direction when the transport roller 52 is rotationally driven through timing by a sub-scanning motor (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 spur 63 that is a paper discharge roller. And a paper discharge tray 3 below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, a maintenance / recovery mechanism 81 including a recovery means for maintaining and recovering the state of the nozzles of the recording head 34 is disposed in the non-printing area on one side in the scanning direction of the carriage 33.

  The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a and 82b (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface 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.

  Further, in the non-printing area on the other side of the carriage 33 in the scanning direction, there is an empty space for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is disposed, and the idle discharge receiver 88 includes an opening 89 along the nozzle row direction of the recording head 34.

  Next, an example of a droplet discharge head constituting the recording head in this image forming apparatus will be described with reference to FIGS. 3 is a cross-sectional explanatory diagram along the longitudinal direction of the liquid chamber of the head, and FIG. 4 is a cross-sectional explanatory diagram of the head along the lateral direction of the liquid chamber (nozzle arrangement direction).

  The droplet discharge head includes a flow channel plate 101 formed by anisotropic etching of a single crystal silicon substrate, a vibration plate 102 formed by nickel electroforming, for example, bonded to the lower surface of the flow channel plate 101, and a flow plate. A nozzle plate 103 bonded to the upper surface of the path plate 101 is bonded and stacked, and a nozzle communication path 105, a liquid chamber 106, and a liquid chamber, which are channels through which the nozzles 104 that discharge liquid droplets (ink droplets) communicate with each other. An ink supply port 109 communicating with a common liquid chamber 108 for supplying ink to 106 is formed.

  In addition, two rows (only one row is shown in FIG. 6) of stacked piezoelectric elements as electromechanical conversion elements that are pressure generating means (actuator means) for pressurizing ink in the liquid chamber 106 by deforming the diaphragm 102. An element 121 and a base substrate 122 to which the piezoelectric element 121 is bonded and fixed are provided. Note that a column portion 123 is provided between the piezoelectric elements 121. This support portion 123 is a portion formed simultaneously with the piezoelectric element 121 by dividing and processing the piezoelectric element member. However, since the drive voltage is not applied, the support portion 123 becomes a simple support.

  Further, an FPC cable 126 for connecting to a drive circuit (drive IC) (not shown) is connected to the piezoelectric element 121.

  The peripheral edge of the diaphragm 102 is joined to a frame member 130, and the frame member 130 serves as a through-hole 131 and a common liquid chamber 108 that house an actuator unit composed of the piezoelectric element 121 and the base substrate 122. A recess and an ink supply hole 132 for supplying ink from the outside to the common liquid chamber 108 are formed. The frame member 130 is formed by injection molding with a thermosetting resin such as an epoxy resin or polyphenylene sulfite, for example.

  Here, the flow path plate 101 is formed by, for example, subjecting the single crystal silicon substrate having a crystal plane orientation (110) to anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 105, Although a recess or a hole serving as the liquid chamber 106 is formed, the invention is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

  The vibration plate 102 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). Alternatively, a metal plate or a joining member between a metal and a resin plate may be used. it can. The piezoelectric element 121 and the support post 123 are bonded to the diaphragm 102 with an adhesive, and the frame member 130 is further bonded with an adhesive.

  The nozzle plate 103 forms a nozzle 104 having a diameter of 10 to 30 μm corresponding to each liquid chamber 106 and is bonded to the flow path plate 101 with an adhesive. The nozzle plate 103 is formed by forming a water repellent layer on the outermost surface of a nozzle forming member made of a metal member via a required layer. The surface of the nozzle plate 103 is the nozzle surface.

  The piezoelectric element 121 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 151 and internal electrodes 152 are alternately stacked. An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn out to different end faces of the piezoelectric element 121 alternately. In this embodiment, the ink in the liquid chamber 106 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element 121. However, the pressure in the d31 direction is used as the piezoelectric direction of the piezoelectric element 121. The ink in the liquid chamber 106 may be pressurized. Alternatively, a structure in which one row of piezoelectric elements 121 is provided on one substrate 122 may be employed.

  In the droplet discharge head configured as described above, for example, by lowering the voltage applied to the piezoelectric element 121 from the reference potential, the piezoelectric element 121 contracts, and the vibration plate 102 descends to expand the volume of the liquid chamber 106. As a result, the ink flows into the liquid chamber 106, and then the voltage applied to the piezoelectric element 121 is increased to extend the piezoelectric element 121 in the stacking direction, and the diaphragm 102 is deformed in the direction of the nozzle 104 to change the volume of the liquid chamber 106. / By contracting the volume, the recording liquid in the liquid chamber 106 is pressurized, and droplets of the recording liquid are ejected (jetted) from the nozzle 104.

  Then, by returning the voltage applied to the piezoelectric element 121 to the reference potential, the diaphragm 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. The recording liquid is filled in 106. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform.

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 200 is configured by a main control unit 201 configured by a microcomputer that also serves as a unit that controls the idle ejection operation according to the present invention, which controls the entire image forming apparatus, and a microcomputer that controls printing. A printing control unit 202.

  Then, the main control unit 201 includes a main scanning motor 213 and a conveyance roller 52 that move the carriage 33 in the main scanning direction in order to form an image on the paper 42 based on the print processing information input from the communication circuit 211. The sub-scanning motor 215 to be rotated is driven and controlled via the main scanning motor driving circuit 212 and the sub-scanning motor driving circuit 214, and control such as sending print data to the print control unit 102 is performed.

  The main control unit 201 receives a detection signal from a carriage position detection circuit 216 that detects the position of the carriage 33, and the main control unit 201 controls the movement position and movement speed of the carriage 33 based on the detection signal. To do. The carriage position detection circuit 216 moves the carriage 33 from a linear encoder 217 composed of, for example, an encoder sheet (linear scale) arranged in the scanning direction of the carriage 33 and a photosensor (encoder sensor) mounted on the carriage 33. The detection signal output in response is input, and the position of the carriage 33 is detected. The main scanning motor driving circuit 212 rotates the main scanning motor 103 in accordance with the carriage movement amount input from the main control unit 101 to move the carriage 33 to a predetermined position at a predetermined speed.

  The main control unit 201 receives a detection signal from a conveyance amount detection circuit 218 that detects the movement amount of the conveyance belt 51, and the main control unit 201 detects the movement amount and movement of the conveyance belt 51 based on the detection signal. Control the speed. The conveyance amount detection circuit 218 outputs a detection signal output in accordance with the rotation of the conveyance belt 51 from a rotary encoder 219 composed of, for example, an encoder wheel attached to the rotation shaft of the conveyance roller 52 and a photo sensor (encoder sensor). An input is made to detect the amount of movement of the conveying belt 51 (the amount of paper conveyed). The sub-scanning motor driving circuit 214 rotates the sub-scanning motor 215 in accordance with the conveyance amount input from the main control unit 201 and rotationally drives the conveyance roller 52 to bring the conveyance belt 51 to a predetermined position at a predetermined speed. Move.

  Further, the main control unit 201 performs control for charging the conveyance belt 51 by applying an AC bias to the charging roller 56 via the AC bias supply unit 221. The main control unit 201 rotationally drives the maintenance / recovery motor 224 of the maintenance / recovery mechanism 81 via the maintenance / recovery mechanism drive motor drive circuit 223, thereby raising and lowering the cap 82, raising and lowering the wiper blade 83, and a suction pump (not shown). Drive it.

  Further, the main control unit 201 takes in information stored in the non-volatile memory 226 provided in each liquid cartridge attached to a cartridge loading unit (not shown) through the cartridge communication circuit 225, performs necessary processing, It is stored and held in a nonvolatile memory (for example, EEPROM) 227 which is a main body storage means.

  Further, the main control unit 201 receives a detection signal from an environmental sensor 228 that detects environmental temperature and environmental humidity.

  The print control unit 202 generates a pressure for ejecting droplets of the recording head 34 based on a signal from the main control unit 201 and a carriage position and conveyance amount from the carriage position detection circuit 216 and the conveyance amount detection circuit 218. Data for driving the means is generated, and the above-described image data is transferred to the head drive circuit 210 as serial data, and the transfer clock and latch signal necessary for transferring and confirming the transfer of the image data, drop control, etc. In addition to outputting a signal (mask signal) etc. to the head drive circuit 210, 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 110.

  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 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.

  In this image forming apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and includes the transport belt 51 and the counter. It is sandwiched between the rollers 46 and transported. Further, the leading end is guided by the transport guide 37 and pressed against the transport belt 51 by the pressure roller 49, and the transport direction is changed by approximately 90 °.

  At this time, an AC bias voltage in which positive and negative electrodes are alternately repeated from the AC bias supply unit 221 to the charging roller 56 is applied, and the conveyor belt 51 is belt-shaped with a predetermined width between the positive electrode and the negative electrode in the sub-scanning direction. Alternately charged. When the paper 42 is fed onto the conveying belt 51 charged alternately with positive and negative electrodes, the paper 42 is attracted to the conveying belt 51 by electrostatic force, and the paper 42 is conveyed in the sub-scanning direction by the circular movement of the conveying belt 51. The

  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.

A first embodiment of the present invention applied to this image forming apparatus will be described with reference to the flowchart of FIG.
This control process is entered at the start of printing, and the ink consumption is counted for each nozzle row of the recording head 34 (in this example, for each different color). The consumption is counted by counting the number of droplets ejected from the recording head 34.

  Then, when printing is completed, it is determined whether or not the ink consumption amount of the first nozzle row is equal to or less than a predetermined set value. Confirm that you want to Although not shown, nozzles that perform the same process up to the second nozzle row, the third nozzle row,..., The nth nozzle row (the fourth nozzle row in the present embodiment) and perform the idle ejection operation. Confirm the column.

  Thereafter, droplets that do not contribute to image formation are ejected from the nozzles of all the determined nozzle rows (the number of droplets to be ejected may be set to a predetermined number of droplets or may be changed according to the amount of liquid consumption as described later. The empty discharge operation is performed and the cap member 82 is capped.

  In this way, in an image forming apparatus that forms an image with a recording head having nozzles that eject liquid droplets, droplets that do not contribute to image formation at the end of the image forming operation based on the liquid consumption during image formation Equipped with a means for performing the idle ejection operation to eject the ink, it is possible to reduce the number of droplets ejected in the idle ejection operation before the start of the next recording, and to shorten the first print (rise time until the start of image formation) Can do.

  That is, as in the comparative example shown in FIG. 7A, when the cap member is capped after printing and the idle ejection operation is performed before the start of the next printing, the ink remains even during capping. In the pre-printing empty discharge operation, the number of empty discharged droplets is changed according to the capping time.The longer the capping time, the more empty discharged droplets, The time T1 required for the discharge operation becomes longer. On the other hand, in the present invention, as shown in FIG. 7B, since the capping is performed after the idle discharge operation is performed after the printing is finished, the degree of drying during the capping is less than that in the comparative example. Therefore, even if the number of empty ejection droplets is changed according to the time of capping in the pre-printing idle ejection operation, the number of idle ejection droplets is relatively small, and the time T0 required for the idle ejection operation is a comparative example. In this case, the time is shorter than the time T1 (T0 <T1), so that the rise time until the start of printing can be shortened and the time until the first print can be shortened.

  Further, in this example, the ink consumption that is a criterion for performing the idle ejection operation is different for each nozzle row that ejects droplets of each color. For example, as shown in FIG. 8, the black (K) ink has a higher (larger) set value of the ink consumption for performing the idle ejection operation than the other colors (C, M, Y). If ink does not eject more drops than color ink, an idle ejection operation is performed. This is because the ease of drying varies depending on the type of ink color, and in this embodiment, the black (K) ink is easier to dry than the color (C, M, Y) ink. As a result, it is possible to reduce wasteful ink consumption associated with idle ejection.

  Also, since the degree of ink drying varies depending on the environmental conditions (environmental temperature, environmental humidity), for example, the lower the environmental humidity, the easier it is to dry, so as shown in FIG. Reduce as the environmental humidity increases. In this case, the setting value of the ink consumption is stored in a memory constituting the main control unit 201 in a table or the like, and the reference setting value of the ink consumption is read based on the detection result of the environmental sensor 228. What is necessary is just to compare with a count value.

Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG.
This control process is entered at the start of printing, and the ink consumption is counted for each nozzle row of the recording head 34 (in this example, for each different color). The consumption is counted by counting the number of droplets ejected from the recording head 34.

  Then, when printing is completed, it is determined whether or not the ink consumption amount of the first nozzle row is equal to or less than a predetermined set value. Is determined, and the number of droplets (empty droplets) ejected in accordance with the counted ink consumption is set. Here, the empty ejection droplet amount is set by performing (setting value−consumption amount), but since the consumption amount is counted by the number of ejection droplets, the setting value is also the number of droplets. Set by the number of empty droplets.

  Next, although not shown in the drawing, the same processing is performed up to the second nozzle row, the third nozzle row,..., The nth nozzle row (the fourth nozzle row in the present embodiment), and the nozzle that performs the idle ejection operation. The column is fixed and the number of empty ejection droplets (droplet amount) corresponding to the counted ink consumption is set.

  After that, for all the nozzles in the determined nozzle row, an empty discharge operation for discharging droplets that do not contribute to image formation is performed with the number of empty discharge droplets (drop amount) set for each nozzle, and capping is performed by the cap member 82. .

  In this way, by performing the idle ejection operation with the number of idle ejection droplets (empty ejection droplet amount) according to the liquid consumption during image formation, it is possible to more effectively perform idle ejection while reducing wasteful liquid consumption. Can do.

Next, a third embodiment of the present invention will be described with reference to the flowchart of FIG.
In each of the above embodiments, the idle discharge operation is performed in units of nozzle rows by looking at the consumption amount for each nozzle row, but in this third embodiment, the idle discharge operation is performed in units of nozzles by looking at the amount of consumption for each nozzle. Like to do.

  That is, this control process is entered at the start of printing, and the ink consumption is counted for each nozzle of the recording head 34. The consumption is counted by counting the number of droplets ejected from the nozzles of the recording head 34. The recording head 34 has n nozzle rows from the first to n-th nozzle rows, and each nozzle row has m nozzles from the first nozzle to the m-th nozzle.

  When the printing is finished, a part of the illustration is omitted, but whether the ink consumption amount for each of the first nozzle to the n-th nozzle in the first nozzle row to the n-th nozzle row is equal to or less than a predetermined set value. If the consumption amount is equal to or less than the set value, it is determined that the idle ejection operation is performed for the nozzle, and the number of idle ejection droplets (drop amount) corresponding to the counted ink consumption amount is determined. Calculate and set by calculating (setting value-consumption).

  Thereafter, for all the determined nozzles, an empty discharge operation for discharging droplets that do not contribute to image formation is performed with the number of empty discharge droplets (drop volume) set for each nozzle, and capping is performed by the cap member 82.

  In this way, it is determined whether or not to perform the idle ejection operation for each nozzle, and by setting the number of idle ejection droplets during the idle ejection operation, it is possible to perform idle ejection while further reducing wasteful liquid consumption. Can do.

  In the above embodiment, the printer configuration is described as the image forming apparatus according to the present invention. However, the present invention is not limited to this, and can be applied to an image forming apparatus such as a printer / fax / copier multifunction machine. . Further, the present invention can be applied to an image forming apparatus using a liquid other than ink, a recording liquid, a fixing processing liquid, or the like.

1 is a configuration diagram showing an outline of a mechanism part of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. FIG. 3 is an explanatory cross-sectional view along the longitudinal direction of the liquid chamber showing an example of a liquid discharge head that constitutes the recording head of the image forming apparatus. It is sectional explanatory drawing along the liquid chamber transversal direction of the head. FIG. 2 is a block explanatory diagram illustrating an overview of a control unit of the image forming apparatus. FIG. 3 is a flowchart for explaining the first embodiment of the present invention applied to the image forming apparatus. It is explanatory drawing with which it uses for description when not performing idle discharge after completion | finish of printing. It is explanatory drawing with which description of an example of the relationship between the color of ink and an ink consumption setting value is provided. It is explanatory drawing with which an example of the relationship between environmental humidity and an ink consumption amount setting value is provided. It is a flowchart with which it uses for description of 2nd Embodiment of this invention applied to the image forming apparatus. It is a flowchart with which it uses for description of 3rd Embodiment of this invention applied to the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Ink cartridge 33 ... Carriage 34 ... Recording head 84 ... Empty discharge receptacle 201 ... Main control part

Claims (5)

  In an image forming apparatus that forms an image with a recording head having a nozzle that ejects liquid droplets, based on the amount of liquid consumed during image formation, the amount of empty ejected droplets according to the amount of liquid consumed at the end of the image forming operation An image forming apparatus comprising: a unit that performs an empty ejection operation for ejecting droplets that do not contribute to image formation.   The image forming apparatus according to claim 1, wherein the idle ejection operation is performed only for a nozzle or a nozzle row in which the amount of liquid ejected during image formation is equal to or less than a predetermined set value.   3. The image forming apparatus according to claim 1, wherein the amount of the ejected droplets is changed according to an environmental condition. 4.   4. The image forming apparatus according to claim 1, further comprising: a recording head that ejects liquid droplets of different colors, wherein the idle ejection operation is controlled according to each color.   In an image forming apparatus that forms an image with a recording head having nozzles that eject liquid droplets, an empty space that ejects liquid droplets that do not contribute to image formation at the end of the image forming operation based on the amount of liquid consumption during image formation An image forming apparatus comprising means for performing an ejection operation.

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