JP5056326B2 - Inkjet printer - Google Patents

Description

  The present invention relates to an ink jet printer that performs a printing operation by ejecting droplets from nozzles.

  An ink jet printer records a desired character or image on a recording medium by conveying the recording medium such as recording paper and ejecting ink from a plurality of nozzles of an ink jet head to the recording medium. It is configured as follows. Ink jet heads of such ink jet printers use ink in nozzles when recording is not performed (no ink is ejected) for a long time or when nozzles that are not used frequently among a plurality of types of nozzles. May dry up and thicken, causing clogging.

  Therefore, in order to solve the above-described problem, a so-called flushing operation is performed in which ink is ejected from each nozzle regardless of printing, and ink having a high viscosity in the nozzle is discharged. For example, in the ink jet printer described in Patent Document 1, the print head (ink jet head) can reciprocate along a direction orthogonal to the conveyance direction of the recording paper, and an ink receiver disposed outside the conveyance path of the recording paper. After moving to a position facing the portion, the ink having increased viscosity is ejected from the nozzle toward the ink receiving portion as a flushing operation. The flushing operation is performed at any time before the start of printing or during printing in consideration of the time when printing is not performed and the time during which printing is left unattended and the time during which ink is not ejected during printing.

JP 2001-277543 A (FIG. 2)

  By the way, ink jet printers, for example, ink droplets ejected from nozzles to one dot, such as a mode for printing high-definition images such as photographs, and a printing mode that does not require high resolution such as FAX printing or solid printing. Multiple print modes with different volumes.

In general, it is desirable that the flushing amount in the flushing operation is such that the thickened ink in the nozzle disappears and the discharge is maintained in good condition, but a plurality of printing modes having different ink droplet volumes as in Patent Document 1 are used. In the ink jet printer having the above, since a uniform flushing amount of ink is ejected from the nozzle in any printing mode in the flushing operation before the printing operation, the droplet volume of the ink to be printed by the nozzle is small. When the flushing process is performed in accordance with the mode, if the mode for printing using the following print mode is larger drop volume often flushing amount more than necessary, resulting in wasted ink. Conversely, if the flushing operation is performed in accordance with the mode in which the droplet volume of the ink ejected from the nozzle is large, if the next printing mode is a mode for printing using a small droplet volume, the thickened ink in the nozzle In some cases, it is difficult to eject ink with a small volume.

  An object of the present invention is to provide an ink jet printer in which an optimal flushing amount is set for each printing mode to reduce ink consumption.

An ink jet printer of the present invention applies a liquid flow path including nozzles for ejecting liquid droplets, an energy element that applies ejection energy to the liquid in the liquid flow path, and a pulse signal that is a drive signal to the energy element. An ink jet printer having a driving unit and a control unit that controls the driving unit to eject droplets from the nozzles , wherein the nozzles are different colors from the first nozzles that eject black ink droplets. A plurality of second nozzles for ejecting ink droplets, and the control means has a plurality of different droplet volumes ejected from the nozzle for one dot when print data is input. One of the print modes is selected, a pulse signal corresponding to the selected print mode is output to the drive unit, and the print is output to the drive unit. And the pulse signal based on chromatography data is applied to the energy device, which ejects liquid droplets from the nozzle as a printing operation, wherein the plurality of printing modes, a black dot on the recording medium In this case, the first printing mode using a plurality of color inks ejected from the plurality of second nozzles without ejecting the black ink from the first nozzles, and the black in which the volume of droplets differs from the first nozzles. A second printing mode capable of ejecting color ink and ejecting color inks having different droplet volumes from the plurality of second nozzles, and the control means receives the print data. Flushing that ejects droplets from the nozzles before ejecting droplets according to the printing mode from the nozzles as the printing operation It includes flushing control means for causing the work, the flushing control means, wherein changing the flushing amount during the flushing operation according to a print mode of the printing operation performed immediately after the flushing operation, the first printing The amount of liquid droplets ejected from the first nozzle in the flushing operation performed before the mode is performed is ejected from the first nozzle in the flushing operation performed before the second printing mode is performed. you less than the amount of the liquid droplet.

According to the ink jet printer of the present invention, when the volume of a droplet ejected from a nozzle for one dot (one pixel) formed on a recording medium during a printing operation is different for each printing mode, the droplet volume of that printing mode Accordingly, the flushing amount at the time of the flushing operation performed before that can be changed. Thus, by optimizing the flushing amount according to the print mode, it is possible to reduce the flushing amount at the time of the flushing operation, which was wasted compared to the conventional case. In addition, since the flushing amount is reduced, the volume of the tray for the droplets ejected from the nozzles during the flushing operation can be reduced, so that the inkjet printer can be made compact.
In the plurality of printing modes, black ink having a constant droplet volume can be ejected from the first nozzle, and color ink having a constant droplet volume can be ejected from the plurality of second nozzles. The third print mode may be further included. In this case, the flushing control means performs the amount of liquid droplets ejected from the first nozzle in the flushing operation performed before the third print mode is performed before the first print mode is performed. In the flushing operation, the amount of droplets ejected from the first nozzle may be smaller.

  In addition, it is preferable that the flushing control unit increases the flushing amount during the flushing operation performed immediately before the droplet volume corresponding to the printing mode is reduced. According to this configuration, the smaller the volume of droplets ejected from the nozzle and the more easily affected by the thickened ink in the nozzle, the greater the flushing amount during the flushing operation performed immediately before. Thereby, the thickened ink in the nozzle is sufficiently discharged as the droplet volume is smaller, and a desired droplet having a smaller volume can be ejected from the nozzle. Further, when the volume of droplets ejected from the nozzles during a printing operation is large, there is no problem even if the flushing amount is reduced because the influence of ink thickening on ejection is small.

  In addition, it is preferable that the flushing control unit changes a flushing amount during the flushing operation by applying a pulse signal having a different pulse width depending on the printing mode from the driving unit to the energy element. According to this configuration, since the driving voltage of the pulse waveform applied from the driving means to the energy element is constant and only the pulse width is varied, the power supply configuration is simplified.

  In addition, the flushing control unit can change the flushing amount during the flushing operation by changing the number of ejections of the droplet during the flushing operation according to the volume of the droplet corresponding to the printing mode. preferable. According to this configuration, when the flushing amount during the flushing operation is changed, the number of droplets ejected from the nozzles is changed according to the volume of the droplets ejected from the nozzles in the printing mode performed immediately after that. . Since the number of ejection shots affects the number of times the energy element is driven, heat generated by driving the energy element can be reduced by changing the number of shots.

  Further, the flushing control unit causes the driving unit to apply the same signal as the pulse signal applied to the energy element in accordance with the printing mode during the printing operation to the energy element during the immediately preceding flushing operation. It is preferable. According to this configuration, by using the pulse signal used at the time of the printing operation as the pulse waveform used at the time of the flushing operation, it is possible to reduce the number of signal lines from the control means to the energy elements, and thus the flushing pulse signal is unnecessary. Therefore, the cost can be reduced.

  In addition, the flushing control unit outputs, to the driving unit, a pulse signal corresponding to a maximum volume droplet among the pulse signals applied to the energy element according to the printing mode during the printing operation. It is preferable that the energy element is applied during the flushing operation performed immediately before the operation. According to this configuration, the number of droplet ejections can be reduced by performing a flushing operation using a pulse signal that maximizes the volume of a droplet ejected from a nozzle having a large discharge energy. By reducing the number of times of driving, heat generation due to driving of the energy element can be reduced.

Moreover, it is preferable that the said control means is previously provided with the several different pulse waveform applied to an energy element corresponding to the droplet of a different volume ejected from the said nozzle with respect to said 1 dot. According to this, since it is only necessary to select a pulse waveform necessary for flushing or printing without complicating the power supply configuration and forming a plurality of pulse waveforms, the power supply configuration is simplified.

Furthermore, it is preferable that the print resolution differs among the plurality of print modes. According to this configuration, the volume of the droplet ejected from the nozzle can be changed by changing the print mode according to the print resolution.

  According to the present invention, the flushing amount at the time of the flushing operation is prevented by ejecting liquid droplets from the nozzle more than the flushing amount necessary for the printing operation corresponding to the printing mode performed immediately after the flushing operation, so that the flushing operation is not performed. Can be reduced. In addition, since the flushing amount is reduced, the volume of the tray for the droplets ejected from the nozzles during the flushing operation can be reduced, so that the inkjet printer can be made compact.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an inkjet printer that records (prints) desired characters or images on a recording sheet by ejecting ink droplets from the inkjet head onto the recording sheet. . The ink jet printer of the present invention can be applied not only as a single printer device but also as a printer of a multi-function device (MFD) having a copy function, a scanner function, a facsimile function, and the like. It is.

  FIG. 1 is a plan view showing a schematic configuration of the ink jet printer according to the present embodiment. As shown in FIG. 1, an inkjet printer 200 stores a carriage 202 configured to be reciprocally movable along one direction, an inkjet head 100 mounted on the carriage 202, sub tanks 204 a to 204 d, and ink. Ink cartridges 206a to 206d, and a tray 213 for receiving ink ejected from a nozzle 4 (to be described later) of the inkjet head 100 during a flushing operation.

  The carriage 202 is mounted across two guide shafts 217 extending in parallel in the left-right direction (scanning direction) in FIG. 1 and is configured to be able to reciprocate along the guide shaft 217. An endless belt 218 is connected to the carriage 202, and when the endless belt 218 is driven to travel by the carriage drive motor 219, the carriage 202 moves in the left-right direction as the endless belt 218 travels. It has become.

  An ink jet head 100 and four sub tanks 204 are mounted on the carriage 202. The inkjet head 100 reciprocates in the scanning direction together with the carriage 202, and from the nozzle 4 (see FIG. 3) provided on the lower surface (the surface on the opposite side of the paper surface in FIG. 1), the ink jet head 100 is moved in the scanning direction by a paper transport mechanism (not shown). Ink droplets are ejected onto the recording paper P transported in the intersecting paper feed direction (downward in FIG. 1). As a result, desired characters and images are recorded on the recording paper P.

  The four sub tanks 204 are arranged side by side along the scanning direction. These four sub tanks 204 are integrally provided with a tube joint 220. The four sub tanks 204a to 204d and the four ink cartridges 206a to 206d are connected to each other through flexible tubes 205a to 205d connected to the tube joints 220, respectively.

  The four ink cartridges 206a to 206d store, for example, four colors of ink of black, yellow, cyan, and magenta, respectively, and these ink cartridges 206a to 206d are placed on the ink jet printer main body side. The holder 207 is detachably attached.

  The four color inks stored in the four ink cartridges 206a to 206d are temporarily stored in the sub tanks 204a to 204d and then supplied to the inkjet head 100.

  The tray 213 is arranged in a region outside the printing region facing the recording paper P (right side in FIG. 1) (hereinafter also referred to as a flushing region) within the moving range of the carriage 202 in the scanning direction. When the carriage 202 moves to the flushing region during a flushing operation described later, the tray 213 faces the lower surface of the inkjet head 100 (the droplet ejection surface on which the plurality of nozzles 4 are arranged). Then, the ink ejected from the plurality of nozzles 4 is received as a flushing operation.

  Next, the inkjet head 100 will be described. FIG. 2 is a perspective view of the inkjet head.

  As shown in FIG. 2, in the inkjet head 100, a plate-type piezoelectric actuator 2 (energy element) is joined to the upper surface of a flow path unit 1 composed of a plurality of plates. A flexible flat cable 3 used for electrical connection with an external device is joined to the upper surface of the plate-type piezoelectric actuator 2, and a driver IC 5 is connected to the upper surface of the flexible flat cable 3. Then, ink droplets are ejected downward from a nozzle 4 (see FIG. 3) opened on the lower surface side of the flow path unit 1.

  Next, the flow path unit 1 will be described with reference to FIGS. FIG. 3 is an exploded perspective view of the flow path unit. FIG. 4 is an enlarged exploded perspective view of the flow path unit. 5 is a cross-sectional view taken along line AA in FIG. First, the flow path unit 1 will be described. As shown in FIG. 3, the flow path unit 1 includes a nozzle plate 11, a spacer plate 12, a damper plate 13, two manifold plates 14 a and 14 b, a supply plate 15, a base plate 16, and a cavity plate 17 in total from the lower layer. The thin flat plates are laminated so that the flat plate surfaces face each other, and are bonded and joined. Each of the plates 12 to 17 is made of 42% nickel alloy steel plate except for the nozzle plate 11 made of synthetic resin such as polyimide, and the plate thickness is about 50 μm to 150 μm.

  In the nozzle plate 11, a large number of nozzles 4 (nozzle diameter 20 μm) for ejecting droplets having a small diameter are formed at minute intervals along the longitudinal direction (X direction) of the nozzle plate 11. The nozzles 4 are arranged at appropriate intervals in five rows parallel to the longitudinal direction (X direction).

  As shown in FIG. 4, in the cavity plate 17, a plurality of pressure chambers 36 are arranged in five rows corresponding to the rows of nozzles 4. Each pressure chamber 36 is formed in an elongated shape in plan view so as to penetrate the plate thickness of the cavity plate 17, and is arranged such that its longitudinal direction is along a direction (Y direction) orthogonal to the row of nozzles 4. Yes.

  The distal end portion 36a in each pressure chamber 36 is connected to the base plate 16, the supply plate 15, the two manifold plates 14a and 14b, the damper plate 13 and the spacer plate 12 through a communication hole 37 having a small diameter. The nozzle plate 11 communicates with each nozzle 4.

  The base plate 16 adjacent to the lower surface of the cavity plate 17 is provided with a communication hole 38 connected to one end 36 b of each pressure chamber 36. The supply plate 15 adjacent to the lower surface of the base plate 16 is provided with a connection channel 40 for supplying ink from a common ink chamber 7 to be described later to each pressure chamber 36. Each connection channel 40 includes an inlet hole into which ink enters from the common ink chamber 7, an outlet hole opened so as to face the communication hole 38, and an inlet hole and an outlet hole. A throttle part having a small cross-sectional area so as to have the largest flow path resistance in the path 40 is provided. In order to eject the ink from the nozzle 4, the throttle portion prevents the ink from moving backward toward the common ink chamber 7 when the pressure chamber 36 receives the ejection pressure, and efficiently advances the ink toward the nozzle 4. It is for making it happen.

  In the two manifold plates 14a and 14b, five common ink chambers 7 extending along the bottom of each row of pressure chambers 36 are formed through the plate thickness. That is, as shown in FIGS. 3 and 5, two manifold plates 14a and 14b are stacked, and the upper surface is covered with the supply plate 15 and the lower surface is covered with the damper plate 13, so that a total of five common inks are obtained. Chamber 7 is formed.

  As shown in FIGS. 4 and 5, a damper chamber 45 isolated from the common ink chamber 7 is formed in a recessed manner on the lower surface side of the damper plate 13 adjacent to the lower surface of the manifold plate 14a. The formation positions and shapes of the damper chambers 45 are the same as those of the common ink chambers 7, as shown in FIG. The thin plate-like ceiling portion above the damper chamber 45 absorbs and attenuates the pressure variation by elastically deforming and vibrating even when the pressure variation generated in the pressure chamber 36 propagates to the common ink chamber 7 during ink ejection. This produces a damper effect that suppresses crosstalk in which pressure fluctuations propagate to other pressure chambers 36 via the common ink chamber 7.

  Further, as shown in FIG. 3, four ink supply ports 47 are formed at one end in the longitudinal direction of the cavity plate 17, the base plate 16, and the supply plate 15 so as to correspond to the upper and lower positions. . The ink supplied from the ink cartridge 6 through the tube 205 and the tube joint 220 is supplied from the ink supply port 47 to one end portion in the longitudinal direction of the common ink chamber 7.

  After the ink is supplied from the ink supply port 47 to the common ink chamber 7, as shown in FIG. 5, the ink is distributed to each pressure chamber 36 via the connection flow path 40 of the supply plate 15 and the through hole 38 of the base plate 16. Supplied. Then, as will be described later, when the drive unit 49 of the piezoelectric actuator 2 is driven, the ink passes from the inside of each pressure chamber 36 through the communication hole 37 to the nozzle 4 corresponding to the pressure chamber 36. That is, the ink supply port 47, the common ink chamber 7, the connection channel 40, the pressure chamber 36, and the nozzle 4 constitute a liquid channel through which ink flows.

  In the present embodiment, as shown in FIG. 3, four ink supply ports 47 are provided, whereas five common ink chambers 7, nozzles 4, and pressure chambers 36 are provided. Only the ink supply port 47a located on the left in FIG. 3 is configured to supply ink to the two common ink chambers 7 on the left in FIG. This is because black ink is set to be supplied to the ink supply port 47a, and the black ink is used more frequently than other color inks. Although not shown in FIG. 3, the black ink supplied to the two common ink chambers 7 is ejected from the row of the two pressure chambers 36 and the row of the two nozzles 4 correspondingly. The other ink supply ports 47b, 47c, and 47d are respectively supplied with yellow, magenta, and cyan inks individually, and ink colors from the corresponding common ink chambers 7 to the respective pressure chambers 36 and the nozzles 4 are provided. Each is supplied and injected. A filter 20 having a filtration portion 20a corresponding to the ink supply ports 47a, 47b, 47c, and 47d is attached to the upper surface of the flow path unit 1 with an adhesive or the like (see FIG. 2).

  Next, the piezoelectric actuator 2 will be described. 6 is a cross-sectional view taken along line BB in FIG. As shown in FIG. 6, the piezoelectric actuator 2 has a structure in which a total of nine piezoelectric sheets 41 to 43 each having a thickness of about 30 μm are laminated. In this piezoelectric actuator 2, a total of seven piezoelectric sheets 41 and piezoelectric sheets 42 are alternately stacked from the lower layer, and two piezoelectric sheets 43 are stacked on the upper layer. On the boundary surface between the even-numbered piezoelectric sheets 41 and 42 from the lower side, narrow individual electrodes 44 are arranged at locations facing the pressure chambers 36 in the flow path unit 1. A common electrode 46 common to the plurality of pressure chambers 36 is disposed on the boundary surface between the odd-numbered piezoelectric sheets 41 and 42 from the lower side.

  A plurality of surface electrodes 48 (surface individual electrodes 48a, surface common electrodes 48b, see FIG. 3) are formed on the upper surface of the piezoelectric actuator 2 (opposite the flow path unit 1) and on the upper surface of the uppermost sheet. The individual electrodes 44 and the common electrode 46 are connected to each other through electrical through holes. The surface electrode 48 is electrically connected to a driver IC 5 (driving means) that is a driving circuit on the flexible flat cable 3 (see FIG. 2). The common electrode 46 is electrically connected to the ground (GND). Then, pressure (jetting energy) is applied to the ink in the pressure chamber 36 from a portion of the piezoelectric sheets 41 and 42 sandwiched between the plurality of individual electrodes 44 and the common electrode 46 facing each pressure chamber 36 in the stacking direction. One driving portion 49 is formed.

  The polarization direction of the piezoelectric sheets 41 and 42 excluding the lowermost piezoelectric sheet 41 in the drive unit 49 is the thickness direction thereof. When a voltage is applied between the individual electrode 44 and the common electrode 46 to generate an electric field in the same direction as the polarization direction of the piezoelectric sheets 41 and 42, the piezoelectric sheet sandwiched between the electrodes 44 and 46 acts as an active layer, and the piezoelectric sheet Due to the longitudinal effect, it extends parallel to the polarization direction (vertical direction), and the volume of the pressure chamber 36 is reduced.

FIG. 7 is a diagram showing a pulse waveform of the drive signal. The drive signal 90 is a voltage signal applied to the surface individual electrode 48a of the piezoelectric actuator 2, and has three drive pulses P during one printing cycle in which ink is ejected to one dot. This drive pulse P applies pressure to the ink by so-called striking. That is, when ink is not ejected, the individual electrode 44 is held at a predetermined potential V ₀ , the volume of the pressure chamber 36 is reduced, and the volume of the pressure chamber 36 is reached at the timing of the falling edge Pa of the drive pulse P. Is increased, and then the volume of the pressure chamber 36 is decreased at the timing of the rising edge Pb of the drive pulse P to apply pressure to the ink in the pressure chamber 36 and eject the ink. Although specifically described later, by changing the number of drive pulses P during one printing cycle and the time (pulse width) from the falling edge Pa to the rising edge Pb in each drive pulse P, The droplet volume of ink ejected from the nozzle 4 is determined, and a plurality of inks with different droplet volumes can be ejected from the nozzle 4 without changing the nozzle diameter. Drive signals (waveform signals) having different droplet volumes of the plurality of inks are prepared in advance and stored in a ROM (Read Only Memory) of the control circuit 61 described later.

  Next, the electrical configuration of the inkjet printer 200 will be described. FIG. 8 is a schematic block diagram showing an electrical connection relationship between the control circuit and the inkjet head.

  The control circuit 60 (control means) is mounted on a main body side substrate (not shown) disposed in the casing of the ink jet printer 200 outside the carriage 202. As shown in FIG. 8, the control circuit 60 is electrically connected to a driver IC 5 that is a drive circuit for driving the inkjet head 100 (piezoelectric actuator 2) via various signal lines. Various signal lines include transfer signal lines such as waveform signals FIRE1 to FIRE6, VDD1, print signals SIN-1 to SIN-4, and transfer clock CLK.

  Although not shown, the control circuit 60 includes a print data storage unit for storing print data transferred from an external device such as a personal computer via an interface. The print data is not shown with the control circuit 60. Print signals SIN1 to SIN4 are generated by a CPU (Central Processing Unit). In addition, waveform signals having a plurality of different ink droplet volumes are formed in advance and stored in a ROM (not shown) configured in the control circuit 60 together with a control program for discharging various inks. Also, the ROM has a plurality of types of print modes prepared in advance corresponding to the resolution (pixels) to be printed (in this embodiment, there are four modes: a draft mode, a normal mode, a fine mode, and a photo mode). ) Is stored, and a waveform signal to be further used can be selected from the print mode selected by the user's operation. Waveform signals FIRE1 to FIRE6 are waveform signals that are used in the printing mode selected from a plurality of printing modes when print data is input to the control circuit, and are output to the drive circuit. Yes. Further, VDD1 is assigned a pulse waveform in which ink is not ejected from the nozzle 4, that is, always in a HIGH state.

  The drive circuit 5 includes a serial-parallel conversion circuit 61, a latch circuit 62, a waveform selection circuit 63, and a drive buffer 64.

  The serial-parallel conversion circuit 61 performs parallel conversion on the print signals SIN-1 to SIN-4 serially input from the control circuit 60 via the four signal lines and outputs them. The print signal is data including which waveform signal is selected for each of the plurality of nozzles 4 (drive unit 49). The latch circuit 62 outputs the data output in parallel by the serial-parallel conversion circuit 61 to the waveform selection circuit 63 simultaneously in synchronization with the transfer clock CLK. The waveform selection circuit 63 is a so-called multiplexer, and selects one waveform signal from the waveform signals FIRE1 to FIRE6 and VDD1 according to the data output from the latch circuit 62 and outputs the selected waveform signal to the drive buffer 64. The drive buffer 64 converts the waveform signal selected and input by the waveform selection circuit 63 into a voltage suitable for the actuator, amplifies it, and inputs it as a drive signal to each of the plurality of surface individual electrodes 48 of the piezoelectric actuator 2. Is displaced.

  Next, the printing operation of the inkjet printer 200 will be described in detail. FIG. 9 is an explanatory diagram of the print mode. As shown in FIG. 9, the ink jet printer 200 is set with four printing modes in which the droplet volume of ink ejected from the nozzle 4 for one dot on the recording paper P differs according to the printing resolution. That is, there are a Draft mode with a print resolution of 600 dpi × 150 dpi, a Normal mode with a print resolution of 600 dpi × 600 dpi, a Fine mode with a print resolution of 1200 dpi × 1200 dpi, and a Photo mode with a print resolution of 1200 dpi × 2400 dpi. The ink jet printer 200 is capable of ejecting a plurality of types of different volumes of ink from the nozzles 4 for each printing mode, and according to the resolution required for each printing mode, the plurality of types of droplets having different volumes. Printing is performed by forming dots using. In the inkjet printer 200 of the present embodiment, a total of nine types of droplets with different volumes can be ejected. These printing modes and a plurality of different ink droplet volume programs used in each mode are stored in advance in the ROM and executed by the control circuit 60.

  For example, in the Normal mode, the printing resolution is 600 dpi × 600 dpi, and the nozzle 4 that ejects black ink can eject ink of any volume of 24 pl, 7 pl, or 4 pl, and color ink (magenta, magenta, The nozzle 4 that ejects cyan and yellow) can eject ink having a volume of 16 pl, 5 pl, or 3 pl. Thus, a plurality of types of inks having different volumes can be ejected from the nozzles 4 in each printing mode, and a printing operation is performed by combining a plurality of different volumes of ink according to the printing purpose such as gradation printing or high image quality printing. be able to. The reason why the volume of droplets ejecting the color ink is smaller than the volume of droplets ejecting the black ink is to perform fine high-quality printing.

  The ink droplet volume ejected from the nozzle 4 is determined by the pulse waveform of the drive signal input to the surface individual electrode 48a of the piezoelectric actuator 2, as shown in FIG. As described above, the number of the drive pulses P during one printing cycle in the pulse waveform and the pulse width from the falling edge to the rising edge in each driving pulse P are different, so that the ink ejected from the nozzle 4 In the case of this embodiment, pulse waveforms corresponding to a total of nine types of droplets that can be ejected are shown in FIGS. 10 (a) to 10 (h). In order from FIG. 10A, pulse waveforms for ejecting ink of 24 pl, 16 pl, 14 pl, 10 pl, 7 pl, 5 pl, 4 pl, 3 pl and 1.5 pl from the nozzle 4 are stored in the ROM. Thus, since the drive voltage is constant and only the number of pulses and the pulse width need only be changed, there is no need to configure a plurality of drive buffers (power supply units) that can supply different voltages. It will be easy.

  As described above, the pulse waveform of the drive signal corresponding to the ink droplet volume that can be ejected from the nozzle 4 in one printing mode is assigned in advance to the waveform signals FIRE1 to FIRE6. When a print command designating a print mode or the like is input to 60, pulse waveforms corresponding to ejected droplets of different volumes in the print mode to be printed by this print command are assigned to the waveform signals FIRE1 to FIRE6.

  For example, when a print command in the Normal mode is input to the control circuit 60, a pulse waveform corresponding to 24 pl ink (FIG. 10 (a)) for FIRE1 (FIG. 10A), and a pulse waveform corresponding to 7pl ink for FIRE2 (FIG. 10). 10 (e)), FIRE3 corresponding to 4pl ink waveform (FIG. 10 (g)), FIRE4 corresponding to 16pl ink waveform (FIG. 10 (b)), FIRE5 corresponding to 5pl ink A pulse waveform (FIG. 10F) and a pulse waveform (FIG. 10H) corresponding to 3 pl of ink are assigned to FIRE6. FIRE1 to FIRE3 are assigned pulse waveforms corresponding to the black droplet volume, and FIRE4 to FIRE6 are assigned pulse waveforms corresponding to the color ink droplet volume. As described above, since the pulse waveform corresponding to the droplet volume of the ink ejected from the nozzle 4 is preliminarily assigned as the waveform signal, it is possible to easily select any one of the waveform signals from the nozzle 4 with the drive circuit. A desired volume of ink can be ejected.

  In the printing operation, first, based on the print data input from the PC of the print data recording unit, in which print mode and which volume of liquid droplets in that one print mode are ejected from the plurality of nozzles 4 respectively. Data is serially arranged as print signals SIN-1 to SIN-4 from the control circuit 60 and input to the serial-parallel conversion circuit 61. Data serially input to the serial-parallel conversion circuit 61 is converted into parallel data by the latch circuit 62 and input to the waveform selection circuit 63 all at once in synchronization with the transfer clock CLK.

  For a plurality of nozzles 4 that eject black ink, the waveform selection circuit 63 selects one waveform signal from the waveform signals FIRE1 to FIRE3 and VDD1, and outputs it to the drive buffer 64 to amplify it. As a drive signal, it is input to the surface individual electrode 48a of the piezoelectric actuator 2 corresponding to the plurality of nozzles 4 ejecting black ink. Further, the nozzle 4 that ejects color ink is amplified by selecting one waveform signal from the waveform signals FIRE4 to FIRE6 and VDD1 by the waveform selection circuit 63 and outputting it to the drive buffer 64. The driving signals are respectively input to the surface electrodes 48a of the piezoelectric actuator 2 corresponding to the plurality of nozzles 4 that eject the color ink. In this manner, when the drive signals are input to the plurality of surface electrodes 48, the volumes of the plurality of pressure chambers 36 respectively corresponding to the plurality of surface electrodes 48 change, and the plurality of pressure chambers 36 correspond to the plurality of pressure chambers 36. Each nozzle 4 ejects a desired volume of ink.

  Next, the flushing operation will be described. If a state where ink droplets are not ejected from the nozzle 4 continues for a long period of time, the ink in the nozzle dries and the viscosity of the ink increases. When ejecting droplets from the nozzle 4, ejection failure occurs. There is a possibility that it will occur, and before the printing operation, during printing, or when designated by the user, a flushing operation is performed to eject the thickened ink by ejecting ink outside the printing area.

  As in the printing operation, the control circuit 60 includes a flushing data storage unit that stores flushing data (not shown), and the flushing data is generated by the control circuit 60 and a CPU (not shown). Specifically, when a flushing command is input to the control circuit, the control circuit 60 drives a carriage motor (not shown) to move the carriage 202 to the right in FIG. As a flushing operation toward the tray 213, the same pulse waveform corresponding to the flushing data (the same drive waveform as that for printing is applied) is input to all nozzles a predetermined number of times. Ink is ejected from all the nozzles 4 and the thickened ink in the nozzles 4 is discharged. In the present embodiment, the thing related to the configuration for performing the flushing operation in the control circuit 60 constitutes the flushing control means.

  Here, in the present embodiment, during the flushing operation before the printing operation, the control circuit 60 determines the droplet ejection amount (flushing amount) from the nozzle 4 according to the printing mode during the printing operation performed immediately after that. It is supposed to change.

  That is, the flushing amount is determined for each printing mode for each of the printing modes stored in the ROM in accordance with the droplet volume of different ink ejected from the nozzle 4. The pulse waveform used for the flushing operation is the same as the drive waveform for printing, so select the multiple drive waveforms used in the immediately following print mode, and the flushing required for that print mode (necessary for resolution) In order to inject the quantity, it is injected a predetermined number of times (the number of flushing times).

  At this time, as a reference of the flushing amount necessary for each printing mode, the flushing amount that can maintain the nozzle state in which the smallest droplet volume ejected in each printing mode can be ejected from the nozzle, and the pulse waveform during the flushing operation is used. Used a pulse waveform for ejecting ink having the largest volume in the printing mode of the printing operation performed immediately thereafter. This is because the pulse waveform of the ink with the largest volume has a large ejection energy.

  In this way, among the plurality of types of ink droplets used in each printing mode immediately after the flushing operation, the thickened ink in the nozzles 4 is sufficiently applied so that the ink with the smallest droplet volume can be ejected from the nozzles 4. Since it can be discharged and the nozzle state without nozzle clogging can be maintained, desired ink with a small volume can be ejected well from the nozzle 4, and droplets with a larger volume can also be ejected. can do. In addition, since the pulse waveform of the ink with the largest volume is selected from the plurality of types of ink droplets used in each printing mode immediately after that, in order to eject a desired flushing amount, the ejection energy is large. The number of times of flushing can be reduced.

  Furthermore, since the pulse waveform at the time of the flushing operation uses the pulse waveform at the time of the printing operation performed immediately after that, the waveform signal (FIRE) for applying a voltage from the control circuit 60 to the piezoelectric actuator 2 is reduced. For example, the pulse waveform used during the flushing operation becomes unnecessary, and the cost can be reduced.

  Specifically, as shown in FIG. 10, for example, in the case of a printing operation in the Normal mode, a pulse waveform that ejects 24 pl that is the maximum droplet in the Normal mode is used during a flushing operation performed before the printing operation. The standard for the flushing amount required for the Normal mode is the flushing amount that allows the 3pl droplet, which is the smallest droplet, to be ejected satisfactorily during the printing operation. The ink droplet volume (24 pl) and the flushing amount (3pl ejection) The number of flashing shots is determined from (possible). The same applies to the other printing modes, and as shown in FIG. 11, the ink droplet volume ejected from the nozzle 4 at the time of the flushing operation performed immediately before the printing operation in each printing mode, the flushing number, and the flushing amount are determined. To do. In this way, by performing the flushing operation using the pulse waveform that maximizes the ink droplet volume ejected from the nozzle 4, the number of ink flushing is reduced, and the number of times the piezoelectric actuator 2 is driven is reduced. As a result, heat generated by driving the piezoelectric actuator 2 can be reduced.

  As described above, during the flushing operation before the printing operation, the flushing amount from the nozzle 4 is changed by changing the pulse width of the pulse waveform and the number of flashing occurrences according to the printing mode. As a result, the drive voltage of the pulse waveform applied from the control circuit 60 to the piezoelectric actuator 2 is constant and only the pulse width is changed. Therefore, it is necessary to configure a drive buffer (power supply unit) that supplies a different drive voltage. There will be no power supply configuration.

  In the Photo mode, high-resolution printing is required. Therefore, when printing black, color mixing is performed on the recording paper P using three color inks of magenta, yellow, and cyan without using black ink. Black dots are formed. That is, since black ink is not used during the printing operation, a pulse waveform for the printing operation is not required. However, in the inkjet printer, apart from the flushing operation before printing, the regular flushing operation is performed during the printing operation according to the time since the last flushing, and the Photo mode is selected. Even during the printing operation, the nozzle 4 that ejects the black ink is not used. Therefore, the black ink stays in the nozzle for a long time, and the black ink is also pulsed to eject the thickening ink. It has a waveform. Therefore, when the flushing operation is performed immediately before printing in the Photo mode, the pulse waveform used during the flushing operation during printing is used for the black ink (14pl, see FIG. 9). Each of the print modes has a pulse waveform for flushing during printing. In the flushing operation immediately before the printing operation in this printing mode, since the black ink is not ejected from the nozzle 4 during the printing operation, it is not necessary to discharge much thickened ink in the nozzle 4 that ejects the black ink. Therefore, there is no problem even if the flushing amount of the black ink ejected from the nozzle 4 during the flushing operation is reduced.

  According to the ink jet printer 200 in the embodiment described above, when the volume of the droplet ejected from the nozzle 4 with respect to one dot at the time of the printing operation is different for each printing mode, depending on the droplet volume in the printing mode, before that, It is possible to efficiently change the flushing amount during the flushing operation. Therefore, when the printing mode performed immediately after the flushing operation is performed in accordance with the printing mode in which the volume of ink droplets ejected from the nozzle 4 is small, the flushing amount is more than necessary and the ink is consumed wastefully. On the contrary, if the flushing operation is performed in accordance with the printing mode in which the ink droplet volume ejected from the nozzle 4 is large, the thickened ink in the nozzle 4 cannot be sufficiently discharged, and the ink having a small volume is ejected. It is no longer difficult to do so, and the flushing amount can be optimized for the immediately subsequent print mode. In addition, by optimizing the flushing amount according to the print mode as described above, the flushing amount during the flushing operation can be reduced as compared with the conventional case. Moreover, since the volume of the ink tray 213 for the ink ejected from the nozzles 4 during the flushing operation can be reduced by reducing the flushing amount, the inkjet printer 200 can be made compact.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, components having the same configuration as in the present embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  In this embodiment, the pulse waveform for the printing operation is used as the pulse waveform for the flushing operation. However, a separate waveform signal (FIRE) is prepared, and the flushing operation is performed using the pulse waveform of this waveform signal. Also good. At this time, by using this pulse waveform, the ink droplet volume ejected from the nozzle 4 is made larger than the ink droplet volume ejected during the printing operation, so that the number of ink flushing is reduced and the piezoelectric actuator is reduced. As the number of times of driving 2 decreases, the heat generated by driving the piezoelectric actuator 2 can be further reduced.

  In this embodiment, a plurality of pulse waveforms having different pulse widths and pulse numbers are formed in advance and stored in the ROM. However, the number of drive pulses and the pulse width are constant, and the nozzle 4 is changed by changing the drive voltage. The volume of ink droplets ejected from the ink may be changed.

  In the ink jet head of this embodiment, a piezoelectric actuator is used as an energy element for causing ink to be ejected from the nozzle to the flow path unit in which the flow path is formed, and this piezoelectric actuator is stacked on the flow path unit. However, the present invention is not limited to this. For example, thermal energy may be applied to the ink as an energy element, and the bubble pressure at the time of ink firing (at the time of boiling) caused by the ink phase change may be used for ink droplet ejection. The present embodiment can be applied to any configuration that includes a flow path unit for generating ink from a nozzle and an energy element for causing the ink to be ejected.

1 is a plan view illustrating a schematic configuration of an ink jet printer according to an embodiment. It is a perspective view of an inkjet head. It is a disassembled perspective view of a flow path unit. It is an expansion exploded perspective view of a channel unit. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. It is a figure which shows the pulse waveform of a drive signal. It is a schematic block diagram which shows the electrical connection relationship of a control circuit and an inkjet head. It is explanatory drawing of printing mode. It is a pulse waveform diagram according to the volume of the droplet ejected from the nozzle. It is a figure which shows the flushing amount in each printing mode.

Explanation of symbols

1 channel unit 2 piezoelectric actuator 4 nozzle 5 driver IC
60 Control Circuit 100 Inkjet Head 200 Inkjet Printer

Claims (9)

A liquid channel including a nozzle for ejecting liquid droplets, an energy element for applying ejection energy to the liquid in the liquid channel, a driving unit for applying a pulse signal as a driving signal to the energy element, and the driving unit In an inkjet printer having a control means for controlling the liquid and ejecting droplets from the nozzle,
The nozzle includes a first nozzle that ejects droplets of black ink, and a plurality of second nozzles that eject droplets of color inks of different colors,
The control means selects one of a plurality of print modes in which the volume of liquid droplets ejected from the nozzle is different for one dot when print data is input, and corresponds to the selected print mode. Output the pulse signal to the drive means, the drive means to apply the pulse signal based on the print data to the energy element, to eject a droplet from the nozzle as a printing operation,
In the plurality of printing modes, when forming black dots on the recording medium, a plurality of color inks ejected from the plurality of second nozzles are used without ejecting black ink from the first nozzle. A first printing mode and a second printing mode in which black inks having different droplet volumes can be ejected from the first nozzles and color inks having different droplet volumes can be ejected from the plurality of second nozzles. And
When the print data is input, the control means performs a flushing operation for ejecting droplets from the nozzles before ejecting droplets corresponding to the print mode from the nozzles as the printing operation. Including control means,
The flushing control means, wherein changing the flushing amount during the flushing operation according to a print mode of the printing operation performed immediately after the flushing operation, in the flushing operation performed before the first printing mode is performed wherein the amount of the liquid droplets jetted from the first nozzle, wherein less to Rukoto than the amount of droplets ejected from the first nozzle in the flushing operation is performed before the second printing mode is performed Inkjet printer. In the plurality of printing modes, black ink having a constant droplet volume can be ejected from the first nozzle, and color ink having a constant droplet volume can be ejected from the plurality of second nozzles. A third print mode is further included,
The flushing control means determines the amount of droplets ejected from the first nozzle in the flushing operation performed before the third printing mode is performed, and the flushing performed before the first printing mode is performed. 2. The ink jet printer according to claim 1, wherein the amount of liquid droplets ejected from the first nozzle in operation is smaller. 3. The ink jet printer according to claim 1, wherein the flushing control unit increases the flushing amount at the time of the flushing operation performed immediately before the droplet volume corresponding to the print mode is reduced. 2. The flushing control unit changes a flushing amount during the flushing operation by applying a pulse signal having a different pulse width according to the printing mode from the driving unit to the energy element. the ink jet printer according to any one of to 3. The flushing control means changes the flushing amount during the flushing operation by changing the number of ejections of the droplet during the flushing operation according to the volume of the droplet corresponding to the printing mode. The inkjet printer according to any one of claims 1 to 4 . The flushing control unit causes the driving unit to apply the same signal as the pulse signal applied to the energy element according to the printing mode during the printing operation to the energy element during the immediately preceding flushing operation. the ink jet printer according to any one of claims 1 to 5, wherein. The flushing control means sends a pulse signal corresponding to a maximum volume droplet among pulse signals applied to the energy element according to the printing mode to the driving means immediately before the printing operation. The ink jet printer according to claim 6 , wherein the energy element is applied during the flushing operation performed at the same time. The control means according to claim 1-7, characterized in that it comprises corresponding to different volumes of droplets to be ejected from the nozzle to the 1 dot, a plurality of different pulse waveforms to be applied to the energy device in advance An inkjet printer according to any one of the above. The inkjet printer according to any one of claims 1 to 8 , wherein a printing resolution is different among the plurality of printing modes.

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