JP2014034205A - Device for discharging droplet, and ink jet recorder using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for discharging droplets which can discharge in a stable size of the discharged droplet regardless of sheet speed variation and prevent shifting of a striking position.SOLUTION: A device includes: piezoelectric elements arranged so as to face each of a plurality of pressure chambers via a diaphragm; a sheet conveying encoder; and a control part which sets a period of timing for discharging droplets based on a sheet conveying encoder signal output by the sheet conveying encoder, and outputs a discharge timing signal being a signal of the discharge timing period and data on a drive waveform which drives the piezoelectric elements and corresponds to the discharge timing period. When a change of recording media conveying speed is generated, the control part performs a first correction for correcting the discharge timing so that an integer multiple of the frequency of the discharge timing signal is synchronized with a frequency of a resonant oscillation of the plurality of the pressure chambers, and a second correction for correcting inclination of the drive waveform so as to eliminate the shifting of a striking position of the droplets on the recording media caused by the first correction.

Description

  The present invention relates to a droplet discharge device that forms an image by discharging ink droplets, and an ink jet recording apparatus using the droplet discharge device.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, or a combination of these, for example, an ink jet recording apparatus is known. This ink jet recording apparatus ejects ink droplets from an ink jet recording head onto a recording medium such as paper or OHP to form a desired image.

  As an ink jet recording head (hereinafter also referred to as a recording head or a head), a piezoelectric element is used as pressure generating means for pressurizing ink in an ink flow path, and a diaphragm that forms the wall surface of the ink flow path is finely formed by the piezoelectric element. A so-called piezoelectric type in which ink drops are ejected by changing the volume in the ink flow path by vibration is known.

  Ink jet recording apparatuses using the recording head as described above have recently been increased in speed, and line scan type ink jet recording apparatuses have been proposed in order to achieve higher speeds. This apparatus uses a long inkjet recording head extending in the width direction of a recording paper (recording medium), and nozzle holes for discharging ink particles are arranged in a row along the width direction of the recording paper in the recording head. Is configured. With the recording head facing the recording paper surface, ink particles are ejected from the nozzle holes described above, and at the same time, the recording paper is continuously moved to perform main scanning. The main scanning means scanning in the moving direction of the recording paper, and a line in the main scanning direction of the recording paper facing each nozzle hole is called a main scanning line. By such control, recording dots are selectively formed on the scanning lines of the recording paper, and a recording image is formed on the recording paper.

  Such line scanning ink jet recording apparatuses include those using a continuous ink jet recording head and those using an on-demand ink jet recording head. An on-demand inkjet recording device is not as fast as a continuous recording device, but is suitable for providing a popular high-speed recording device because the ink system is very simple. ing. Patent Document 1 discloses a typical recording head used in an on-demand ink jet recording apparatus.

  In the case of a line scan type ink jet recording apparatus, a stable constant speed paper conveyance is normally performed after the recording medium is accelerated to a constant speed or before the deceleration starts so that the image quality can be stabilized. Print in the state. However, especially when printing on a continuous recording medium, the recording medium passing through the recording head during acceleration or deceleration is not printed and is wasted paper (waste paper), so printing is also performed during acceleration or deceleration. An ink jet recording apparatus that performs the above has also been introduced (see, for example, Patent Document 2).

  When printing is performed at a non-constant speed as described above, the landing position may be shifted due to the speed fluctuation of the recording medium. In order to prevent such landing position deviation, the ink jet recording apparatus of Patent Document 2 detects the conveyance speed of the recording medium, and sets the ink ejection timing based on this.

  However, since the ejection timing is set regardless of the frequency characteristics of the head (ink jet recording head), the ejection droplet speed and ejection droplet size of the ink may change, and the generation of satellites may increase. is there. The satellite is an unnecessary minute ink droplet generated accompanying the main ink droplet.

  In the ink jet recording apparatus using the piezoelectric recording head described above, after the recording medium conveyance speed reaches a constant speed due to the residual vibration generated in the ink due to the resonance frequency of the individual pressure generating chambers in the head. When the discharge timing is set according to the speed fluctuation, the discharge droplet speed and the discharge droplet size change. This phenomenon becomes remarkable in the high frequency region.

  In order to prevent this, Patent Document 3 discloses a technique for setting the above-described ejection timing in accordance with the Helmholtz frequency.

  However, there has been a problem that landing position deviation is inevitably caused by the discharge timing becoming discrete due to fluctuations in the conveyance speed of the recording medium. In particular, when printing is performed by transporting a recording medium at high speed, the influence of the deviation in the ejection timing on the deviation in the landing position becomes large.

  The present invention provides a liquid droplet ejection apparatus (inkjet recording head) and an inkjet recording apparatus that are capable of ejecting with a stable ejection droplet size regardless of the speed fluctuation of the recording medium and suppressing the deviation of the landing position. Objective.

  In order to achieve such an object, a droplet discharge device according to claim 1 includes a plurality of pressure chambers that communicate with a plurality of nozzles and store droplets, and a plurality of pressure chambers that form elastic walls of the pressure chambers. Detecting the moving distance of the recording medium on which the liquid droplets are landed, and the pressure generating element disposed so as to face each of the plurality of pressure chambers via the vibration plate, A paper transport encoder that outputs a paper transport encoder signal that is a signal of the period detected at the equiposition interval, and a period of droplet discharge timing are set based on the paper transport encoder signal output from the paper transport encoder, Control that outputs a discharge timing signal that is a signal of a discharge timing period and a drive waveform that drives a pressure generating element and that corresponds to the discharge timing period When the speed at which the recording medium is conveyed changes, the control unit causes the discharge timing so that an integral multiple of the frequency of the discharge timing signal is synchronized with the resonance vibration frequency of the plurality of pressure chambers. And a second correction for correcting the inclination of the drive waveform so as to eliminate the deviation of the landing position of the droplet on the recording medium caused by the first correction. .

  According to the present invention, ejection can be performed with a stable ejection droplet size regardless of the speed fluctuation of the recording medium, and deviation of the landing position can be suppressed.

1 is a schematic configuration diagram illustrating an example of an overall configuration of an on-demand line scanning inkjet recording apparatus to which the present invention is applied. It is explanatory drawing which shows the structure of the head part used for the inkjet recording device of embodiment. It is an enlarged plan view showing an example of an ink jet recording head used for a head portion. It is a disassembled perspective view of an inkjet recording head. It is a block diagram of an ink droplet ejection control unit according to an embodiment. It is a timing chart for demonstrating the ink drop control which concerns on the 1st correction | amendment of embodiment. It is a figure which shows an example of the drive waveform of an inkjet recording head. It is explanatory drawing which concerns on the 2nd correction | amendment of embodiment.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

  FIG. 1 is a schematic diagram showing the overall configuration of an on-demand line scanning inkjet recording apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the ink jet recording apparatus 1 is disposed between the paper supply unit 2 and the paper collection unit 13. A desired color image is formed by the ink jet recording apparatus 1 on the continuous paper m fed from the paper supply unit 2 at a high speed, and is wound and collected by the paper collection unit 13.

  The paper transport device in the ink jet recording apparatus 1 includes a regulation guide 3 for positioning the paper m supplied from the paper supply unit 2 in the width direction, an infeed unit 4 composed of a driven roller and a driving roller, and a tension of the paper m. The dancer roller 5 that moves up and down to output a position signal, the EPC (Edge Position Control) 6 that controls the meandering of the paper m, the meandering amount detector 7 that is used for the meandering amount feedback, and the speed at which the paper m is set. And an outfeed unit 11 composed of a driven roller and a driving roller that rotate at a constant speed, and a puller 12 composed of a driving roller and a driven roller for discharging the paper m to the outside of the apparatus.

  This sheet conveying apparatus is a tension control type conveying apparatus that detects the position of the dancer roller 5 and controls the rotation of the infeed unit 4 to keep the tension of the sheet m being conveyed constant.

  In the ink jet recording apparatus 1, a recording unit 8, a platen 9 provided so as to face the recording unit 8, and a drying unit 10 are provided.

  The recording means 8 has a line-shaped recording head in which printing nozzles are arranged over the entire printing width, and color printing is performed by black, cyan, magenta, and yellow recording heads, and the nozzle surface of each recording head is on the platen 9. Are supported with a predetermined gap. The recording unit 8 ejects ink droplets in synchronization with the paper conveyance speed, thereby forming a color image on the paper m.

  The drying unit 10 dries and fixes the ink to prevent the ink printed by the recording unit 8 from adhering to other parts. In this embodiment, the drying means 10 uses a non-contact drying apparatus, but may be a contact-type drying apparatus.

  Next, a droplet discharge apparatus according to an embodiment of the present invention will be described with reference to FIGS. The droplet discharge device (inkjet recording head, 15) according to the present embodiment forms a plurality of pressure chambers (18) that communicate with a plurality of nozzles (16) and store droplets, and elastic walls of the pressure chambers. A diaphragm (22) disposed over a plurality of pressure chambers, a pressure generating element (piezoelectric element, 28) disposed to face each of the plurality of pressure chambers via the diaphragm, and a droplet landing A paper transport encoder (33) for detecting a relative position between the recording medium to be conveyed and a means for transporting the recording medium at equal intervals and outputting a paper transport encoder signal that is a signal of the period detected at the equal positions And a droplet discharge timing period based on the sheet transfer encoder signal output from the sheet transfer encoder, and a discharge timing signal that is a signal of the discharge timing period and a pressure generating element. And a controller that outputs drive waveform data corresponding to the period of the ejection timing, and when the speed at which the recording medium is conveyed changes, the controller A first correction that corrects the discharge timing so that an integral multiple of the frequency of the discharge timing signal is synchronized with the frequency of resonance vibration of the plurality of pressure chambers, and a droplet on the recording medium caused by the first correction The second correction for correcting the inclination of the drive waveform is performed so as to eliminate the landing position deviation.

  In the present embodiment, the above-described control unit outputs a master controller 32 that outputs ink temperature, head characteristics, and drive waveform data that is selected in a matrix according to ejection droplet speed correction, which will be described later. The drive waveform data received from the master controller 32 is stored in the memory 34, and when the ejection timing signal is received, the drive waveform data is read from the memory 34 and output to the slave controller 35.

  FIG. 2 is an enlarged plan view showing an example of the configuration of the head portion constituting the recording means 8 of FIG. In the case of this embodiment, the head array (head portion) 14 is constituted by an assembly of a black head array 14K, a cyan head array 14C, a magenta head array 14M, and a yellow head array 14Y. Extends in a direction orthogonal to the conveyance direction (arrow direction) of the paper m.

  Each head array 14 is composed of a plurality of ink jet recording heads 15 arranged in a zigzag pattern, and in this embodiment, an example in which the ink jet recording heads 15 are arranged in a zigzag pattern in two rows each is shown. In this way, the inkjet recording head 15 is arrayed to ensure a wide print area width.

  FIG. 3 is an enlarged plan view showing an example of the inkjet recording head 15. As shown in the figure, the ink jet recording head 15 has a large number of nozzles 16 arranged in a staggered manner. In this embodiment, an example in which 64 nozzles 16 are arranged in two rows in a staggered manner is shown. ing. In this way, a large number of nozzles 16 are arranged in a staggered manner, thereby supporting high resolution.

  FIG. 4 is an exploded perspective view showing a configuration example of the ink jet recording head 15 described above. In the figure, 16 is a nozzle, 17 is a nozzle plate, 18 is a pressure chamber, 19 is a pressure chamber plate, 20 is a restrictor, 21 is a restrictor plate, 22 is a diaphragm, 23 is a filter, 24 is a diaphragm plate, and 25 is A common ink flow path, 26 is a housing, 27 is a piezoelectric element group, 28 is a piezoelectric element, and 29 is a support substrate.

  A nozzle plate 17 in which a large number of nozzles 16 are arranged in a staggered manner, a pressure chamber plate 19 formed by a pressure chamber 18 corresponding to each nozzle 16, a common ink flow path 25, and a pressure chamber 18 communicate with each other. A flow path substrate is formed by sequentially positioning and joining a restrictor plate 21 having a restrictor 20 that controls the flow rate of ink to a plate 18 and a diaphragm plate 24 having a diaphragm 22 and a filter 23. .

  The flow path substrate is joined to the housing 26 so that the filter 23 faces the opening of the common ink flow path 25. Reference numeral 31 denotes an ink introduction pipe connected to the common ink flow path 25 of the housing 26.

  A piezoelectric element group 27 configured by arranging a large number of piezoelectric elements 28 on a support substrate 29 is inserted from an insertion opening 30 provided in the housing 26, and the free ends of the piezoelectric elements 28 are bonded to the diaphragm 22. By fixing, the ink jet recording head 15 is configured.

  In FIG. 4, the number of nozzles 16, pressure chambers 18, restrictors 20, piezoelectric elements 28, and the like are reduced to simplify the drawing. Further, since the ink droplet ejection operation in the inkjet recording head 15 is the same as that of the conventional one, the description of the operation is omitted.

  The ink jet recording head 15 configured as described above has Helmholtz natural vibration controlled by compliance and inertance determined by the opening of the nozzle 16 and the shape of the pressure chamber 18 and the ink supply port formed by the restrictor 20. ing. In order to eject ink droplets from the inkjet recording head 15, an electrical signal is applied from an external driving power source to individual electrodes and common electrodes (not shown), and the piezoelectric element 28 is displaced.

  This displacement becomes a volume change of the pressure chamber 18 through the vibration plate 22 and a pressure change of the filled ink. This pressure change causes ink to be ejected as ink droplets from the orifice. In general, the pressure change is a method in which the volume of the pressure chamber 18 is expanded, the position of an ink tip called a meniscus in the nozzle 16 is once drawn in the direction of the pressure chamber 18, and the pressure chamber 18 is contracted to eject ink droplets. Many have been proposed.

  When the pressure chamber 18 is expanded, the meniscus is once pulled in the direction of the pressure chamber 18. Then, after the meniscus is drawn in most, it returns to its original position with Helmholtz natural vibration. The pressure chamber 18 is contracted in order to eject ink, but the timing is important for high-quality printing. This is because the size of the ink droplets ejected depending on the position of the meniscus is greatly influenced by the speed of the meniscus.

FIG. 5 is a block diagram of an ink droplet ejection control unit related to the ink ejection operation of the inkjet recording apparatus 1 according to the embodiment of the present invention.
As shown in the figure, the ink droplet ejection control unit includes a master controller 32, a paper transport encoder 33, and a drive waveform generation unit 39. Since the drive waveform generation unit 39 is arranged for each unit for outputting the drive waveform, a plurality of drive waveform generation units 39 may be provided for the head 15. In this embodiment, there are two rows of nozzles as shown in FIG. As a result, the head 15 has two circuits.

  Further, the drive waveform generation unit 39 includes a slave controller 35, a memory 34, a D / A converter 36, a voltage amplifier 37, and a current amplifier 38.

  As shown in the figure, the master controller 32 transmits drive waveform data indicating the shape of the drive waveform, ejection timing signals, and printing data indicating the ink droplet size of each nozzle 16 to each slave controller 35.

  Here, the ejection timing signal and the drive waveform data will be described. The ejection timing signal is set based on the paper transport encoder signal. For example, the paper transport encoder 33 detects the movement distance of the recording medium m on which the ink droplets are landed at equal position intervals, and outputs a paper transport encoder signal that is a signal with a period detected at the equal position intervals. The paper transport encoder 33 is composed of, for example, a paper transport encoder film (not shown) and a paper transport encoder sensor (not shown). The paper transport encoder sensor transports the paper as the inkjet recording head 15 moves. A plurality of slits arranged in the main scanning direction of the encoder film are optically detected. And the paper conveyance encoder signal which is a signal corresponding to the period of these slits is output.

Based on the paper transport encoder signal described above, the period of ink droplet ejection timing is set, and the ejection timing signal, which is a signal of the ejection timing period, and the drive waveform for driving the piezoelectric element 28, Drive waveform data corresponding to the cycle is output.
The drive waveform data described above is selected in a matrix form according to the ink temperature, the characteristics of the ink jet recording head 15, and the first and second corrections described later.

  The slave controller 35 once stores the drive waveform data received from the master controller 32 in the memory 34. When the slave controller 35 receives the ejection timing signal from the master controller 32, the slave controller 35 extracts the drive waveform data from the memory 34 and corrects the extracted drive waveform data to the correction value. And then output to the D / A converter 36.

  The D / A converter 36 converts the received corrected drive waveform data into an analog voltage and outputs it to the voltage amplifier 37. The voltage amplifier 37 amplifies the analog voltage and outputs it to the current amplifier 38. The current amplifier 38 amplifies the voltage-amplified analog signal and outputs it to the ink jet recording head 15 as a final drive waveform. The ink jet recording head 15 generates a waveform based on the printing data by means described later with reference to FIG. 6, and drives the piezoelectric element 28.

  The drive waveform generation unit 39 including a memory 34, a slave controller 35, a D / A converter 36, a voltage amplifier 37, and a current amplifier 38 is arranged for each unit that outputs a drive waveform. In this embodiment, FIG. As shown in the figure, since two nozzle rows are provided in one ink jet recording head 15, the drive waveform generator 39 has two circuits. That is, a common drive waveform is supplied from one drive waveform generation unit 39 to one nozzle row.

  Therefore, in the case of the head array 14 shown in FIG. 2, the drive waveform generation unit 39 is obtained by multiplying the number of inkjet recording heads 15 to be used by two circuits. That is, since 24 (6 × 4 =) inkjet recording heads 15 are arranged, it is assumed that the drive waveform generation unit 39 has 48 circuits that is twice as many.

  Next, the ink discharge timing in the ink jet recording head 15 of the ink jet recording apparatus 1 of the present embodiment will be described. FIG. 6 is a timing chart for explaining ejection control of droplets (ink, ink droplets) of the inkjet recording head 15 according to the first correction described later.

  Hereinafter, the first correction will be described. As shown in FIG. 6, the master controller 32 (FIG. 5) generates a meniscus synchronization signal P3 having the same frequency as the resonance vibration (Helmholtz frequency) of the pressure chamber 18 separately from the ejection timing signal P1 and the paper transport encoder signal P2. To do. When the paper conveyance is stable, the driving frequency (frequency of the ejection timing signal P1) is xHz, the frequency of the paper conveyance encoder signal P2 is yHz, the Helmholtz frequency (frequency of the meniscus synchronization signal P3) is zHz, and y = ax ( It is assumed that a is an integer, here a = 20), and z = bx (b is an integer, here b = 10).

  Here, a point in time when the paper conveyance speed is increased and the frequency of the paper conveyance encoder signal P2 is y × 1.33 Hz is shown in FIG. At this time, when the cycle of the paper transport encoder signal P2 and the cycle of the ejection timing signal P1 are set to be synchronized as described above, it is assumed that z ≠ cx × 1.33 (c is an integer). Since the frequency does not synchronize with the Helmholtz frequency, the ejection droplet speed and ejection droplet size vary. Therefore, the control unit (the master controller 32 in the present embodiment) corrects the ejection timing (first correction) in the following manner so that the drive frequency and the Helmholtz frequency are synchronized.

  The master controller 32 discharges so as to synchronize with the cycle of the nearest meniscus synchronization signal P3 (Helmholtz frequency) from the timing T1 when the pulse of the paper transport encoder signal P2 is detected a predetermined number of times (b = 10 in FIG. 7 described above). It is desirable for the sake of accuracy to perform the first correction for outputting the timing P1. This is because the number of times of the paper conveyance encoder signal P2 corresponding to one time of the ejection timing signal P1 preset when the speed is stable when the speed at which the recording medium m is conveyed changes. That is, the first correction is performed so that the timing synchronized with the frequency of the resonance vibration is set as the ejection timing at the timing closest to the counted timing.

  In the present embodiment, as an example in which the first correction can be easily performed, the master controller 32 detects the pulse of the paper transport encoder signal P2 a specified number of times (b described above, b = 20 in FIG. 7) T1. Thereafter, the timing T2 at which the first meniscus synchronization signal P3 is detected is output as the ejection timing P1. This is because the number of times of the paper conveyance encoder signal P2 corresponding to one time of the ejection timing signal P1 preset when the speed is stable when the speed at which the recording medium m is conveyed changes. In the first timing after the counted timing, the first correction is performed so that the timing synchronized with the frequency of the resonance vibration is set as the ejection timing.

  Similarly, the time point when the paper transport speed becomes slow and the paper transport encoder signal P2 pulse becomes y × 0.75 Hz is shown in FIG. Similarly, at this time, when it is assumed that the timing T3, which is the synchronization of the cycle of the paper transport encoder signal P2 and the cycle of the ejection timing signal P1, is z ≠ cx × 0.75 (c is an integer), the drive frequency Is not synchronized with the Helmholtz frequency.

  Therefore, similarly, the timing T4 at which the first meniscus synchronization signal P3 is detected after the timing T3 at which the pulse of the paper transport encoder signal P2 is detected a predetermined number of times (b = 20 in FIG. 7) is output as the ejection timing. To do. Through the processing as described above, the discharge timing is corrected so that the integral multiple of the frequency of the discharge timing signal P1 is synchronized with the resonant vibration frequency (Helmholtz frequency, meniscus synchronization signal P3) of the plurality of pressure chambers 18, that is, the first 1 correction can be performed.

  When the first correction described above, that is, the correction of the ink ejection timing setting in accordance with the Helmholtz frequency is performed, the ejection timing becomes discrete, and there is a concern that the landing position may actually shift. For this reason, in the present invention, a correction (second correction) for adjusting the slope of the drive waveform for driving the piezoelectric element (pressure generating element) 28 is performed in accordance with the first correction.

  First, an example of a drive waveform according to the embodiment of the present invention will be described with reference to FIGS. The drive waveform shown here is assumed to be a drive waveform constituting the cycle (one cycle) of the ejection timing signal P1 described above. In the present embodiment, a driving waveform and a waveform of a fine driving pulse when ejecting ink droplets of three sizes of large, medium, and small are shown.

  At the time of printing, the input image data is switched based on a control table (not shown), and a desired pulse is selected and output. For example, when printing a large dot, the print data applied to the switch circuit (not shown) at time S2, time S3, and time S4 in FIG. 4A is set to “1”, and from time S2 to time S4. By setting the print data to “0”, the first pulse, the second pulse, and the third pulse are supplied to the piezoelectric element as shown in FIG.

  When printing a medium-sized dot, the second pulse and the third pulse are supplied to the piezoelectric element as shown in FIG. 7C, and when printing a small-sized dot, as shown in FIG. 7D. Only the first pulse is supplied to the piezoelectric element to print a dot of the desired size. The fine drive pulse shown in FIG. 5 (e) realizes a function of stirring the ink by slightly vibrating the meniscus without ejecting the ink droplet. The drive pulse (first through second) for ejecting the ink droplet is realized. The voltage amplitude is lower than that of (three pulses).

  As described above, by correcting the ejection timing in accordance with the meniscus synchronization signal (Helmholtz frequency) P3, the meniscus of the nozzle 16 of the inkjet recording head 15 is caused by the residual vibration of the resonance frequency (Helmholtz frequency) generated in the pressure chamber 18. Even if the position fluctuates, the piezoelectric element 28 can be driven with the same phase with respect to the Helmholtz frequency. Therefore, even if the speed of the recording medium m being conveyed fluctuates, the ink droplet ejection speed and the ink droplet size Fluctuations can be suppressed. However, since the discharge timing becomes discrete, the landing positions are actually shifted.

  Therefore, according to the present invention, in accordance with the first correction described above, the inclination of the drive waveform is set so that the deviation of the landing position of the droplet on the recording medium caused by the first correction becomes zero. Correct.

Here, assuming that the paper speed is Vp and the deviation of the ejection timing is Δt, the landing position deviation Δx is expressed by the following equation (1).
Δx = Vp × Δt (1)

On the other hand, in this embodiment, it correct | amends so that it may be set to (DELTA) x = 0 by adjusting the discharge droplet speed. Assuming that the gap between the head and the paper is L, the specified ejection droplet velocity is Vj, and the ejection droplet velocity correction amount when Δx = 0 is ΔVj, Δx is expressed as the following equation (2), and ΔVj is It is expressed as the following equation (3).
Δx = Vp × Δt−Vp × L × [ΔVj / {Vj × (Vj + ΔVj)}] = 0 (2)
ΔVj = Vj ² × Vp × Δt / (Vp × L−Vj × Vp × Δt) (3)

  Next, correction (second correction) for adjusting the slope of the drive waveform described above in the present embodiment will be described with reference to FIG. FIG. 8A shows a drive waveform before the second correction, and FIG. 8B shows a drive waveform after the second correction.

  Here, when the inclination of the driving waveform is increased, the ejection droplet speed is increased, and when the inclination of the driving waveform is decreased, the ejection droplet speed is decreased. Further, when the inclination of the drive waveform is changed, the discharge droplet speed changes, but the change in the discharge droplet size is small. That is, it is possible to independently correct the ejection droplet speed. The above-described ejection droplet velocity is set according to the ejection droplet velocity correction amount obtained when Δx = 0 obtained from the above equation (3), and the drive waveform is corrected as indicated by the correction portion R in FIG.

  The slope of the drive waveform is increased after the second correction, as shown in the correction portion R of FIG. 8B, as compared to before the second correction in FIG. 8A. That is, when the ejection timing signal is output at the timing when the first meniscus synchronization signal P3 is detected after detecting the signal P1 of the paper transport encoder a specified number of times, the ejection timing is the ideal timing (the ejection timing of the ink at the ideal landing position). ), The actual landing position is delayed, so that the landing position can be corrected to a desired position by correcting the drive waveform and increasing the ejection droplet speed.

  As in this embodiment, when the drive waveform is composed of a plurality of pulses in the period of the ejection timing (when one dot is formed by a plurality of pulses), the drive waveform that is the second correction As shown in the correction portion R of FIG. 8, the adjustment of the inclination of is performed only for the last pulse of the plurality of pulses, so that the ejection droplet speed as a whole can be increased.

  As is clear from the above, according to the ink jet recording head 15 of the present embodiment, when a change occurs in the speed at which the recording medium is conveyed, the master controller 32 is an integer of the frequency of the ejection timing signal P2. A first correction that corrects the ejection timing so that the frequency is synchronized with the frequency of the meniscus synchronization signal P3 (Helmholtz frequency), and the recording medium m caused by the first correction accompanying the first correction. The second correction for correcting the inclination of the drive waveform is performed so that the landing position deviation of the ink droplet becomes zero. As a result, even if fluctuations occur in the speed of the recording medium m being conveyed, fluctuations in ink droplet ejection speed and ink droplet size can be suppressed, and landing positions caused by discrete ejection timings Deviation can be suppressed.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, since the relationship between the slope of the drive waveform and the ejection droplet velocity varies depending on the characteristics of the head and the drive waveform, it is possible to apply a suitable correction of the drive frequency and adjustment of the drive waveform depending on them. In addition, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Paper supply part 3 Regulation | regulation guide 4 Infeed part 5 Dancer roller 6 EPC (Edge Position Control)
7 Meandering amount detector 8 Recording means 9 Platen 10 Drying means 11 Outfeed part 12 Puller 13 Paper recovery part 14 Head part 15 Inkjet recording head (droplet ejection device)
16 Nozzle 17 Nozzle plate 18 Pressure chamber 19 Pressure chamber plate 20 Restrictor 21 Restrictor plate 22 Vibration plate 23 Filter 24 Diaphragm plate 25 Common ink flow path 26 Housing 27 Piezoelectric element group 28 Piezoelectric element (pressure generating element)
29 Support substrate 30 Insertion opening 32 Master controller (control unit)
33 Paper transport encoder 34 Memory 35 Slave controller 36 D / A converter 37 Voltage amplifier 38 Current amplifier 39 Drive waveform generation unit m Paper (recording medium)
P1 Discharge timing signal P2 Paper transport encoder signal P3 Meniscus synchronization signal

JP-A-11-78013 Japanese Patent No. 3635756 JP 2000-135829 A

Claims (6)

A plurality of pressure chambers communicating with a plurality of nozzles for storing droplets;
A diaphragm disposed across the plurality of pressure chambers to form an elastic wall of the pressure chamber;
A pressure generating element disposed to face each of the plurality of pressure chambers via the diaphragm;
A paper transport encoder that detects a movement distance of the recording medium on which the droplets are landed at equal position intervals, and outputs a paper transport encoder signal that is a signal of the period detected at the equal position intervals;
Based on the paper transport encoder signal output from the paper transport encoder, the droplet discharge timing period is set, and a discharge timing signal that is a signal of the discharge timing period and a drive for driving the pressure generating element A control unit for outputting drive waveform data corresponding to a period of the ejection timing, the waveform,
With
When a change occurs in the speed at which the recording medium is conveyed,
The controller is
A first correction for correcting the discharge timing such that an integral multiple of the frequency of the discharge timing signal is synchronized with the frequency of resonance vibration of the plurality of pressure chambers;
And a second correction for correcting an inclination of the drive waveform so as to eliminate a deviation of a landing position of the droplet on the recording medium caused by the first correction. . The first correction is:
When a change occurs in the speed at which the recording medium is conveyed,
At a timing closest to the timing of counting the number of times of the paper transport encoder signal corresponding to one time of the ejection timing signal, which is set in advance when the speed before the change in speed is stable, The liquid droplet ejection apparatus according to claim 1, wherein a timing synchronized with a frequency of the resonance vibration is set as a ejection timing. The first correction is:
When a change occurs in the speed at which the recording medium is conveyed,
The first timing after the timing of counting the number of times of the paper transport encoder signal corresponding to one time of the ejection timing signal, which is preset when the speed before the change in speed is stable 2. The droplet discharge device according to claim 1, wherein a timing synchronized with the frequency of the resonance vibration is set as a discharge timing.   2. The second correction is performed in the last pulse among the plurality of pulses when the drive waveform is composed of a plurality of pulses in the period of the ejection timing. The droplet discharge device according to claim 3.   5. The droplet discharge device according to claim 1, wherein the frequency of the resonance vibration is a Helmholtz frequency. 6.   An ink jet recording apparatus comprising the liquid droplet ejection apparatus according to claim 1.