JP2010111061A - Liquid ejector and ejection inspecting method - Google Patents

Abstract

When there is a nozzle row having a weak detection signal, by increasing the detection signal only for this nozzle row, it is possible to improve the inspection accuracy when inspecting whether or not liquid is discharged from the nozzle opening. A liquid discharge apparatus and a discharge inspection method are provided.
An electrical change is detected between a recording head, a drive signal generation circuit, a cap member that receives liquid ejected from a nozzle opening of the recording head, and a nozzle plate and a cap member of the recording head. A discharge inspection device 32 and a CPU 26 for inspecting the presence or absence of liquid discharge from the nozzle opening. The ejection test drive pulse is generated based on the information stored in the head information storage unit 31 based on the magnitude of the electrical change of the preliminary test performed in advance for the nozzle row.
[Selection] Figure 1

Description

  The present invention relates to a liquid discharge apparatus such as an ink jet printer and a discharge inspection method, and in particular, a liquid discharge that discharges liquid from a nozzle opening by supplying a drive signal and operating a discharge drive unit. The present invention relates to a liquid ejection apparatus including a head, and an ejection inspection method thereof.

  For example, a liquid ejection apparatus is an apparatus that includes a liquid ejection head capable of ejecting liquid and ejects various liquids from the liquid ejection head. As a typical example of this liquid ejection apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejection head is provided, and liquid ink is recorded on recording paper or the like from a nozzle opening of the recording head. An image recording apparatus such as an ink jet printer (hereinafter simply referred to as a printer) that records an image or the like by ejecting and landing on a medium (ejection target) can be given. In recent years, liquid ejecting apparatuses have been applied not only to this image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for a color filter such as a liquid crystal display.

  For example, in the above printer, when ink is not ejected from any one of a plurality of nozzle openings, that is, when a so-called dot dropout occurs, an image on a recording medium is not printed correctly. Therefore, a technique for inspecting whether ink is reliably discharged from all nozzle openings has been proposed. For example, Patent Document 1 discloses a technique for inspecting whether or not ink is ejected by charging ink, causing the ink to fly between electrodes, and detecting a voltage change between these electrodes. .

JP 2008-168526 A

  However, in the above technique, the liquid discharge head includes a plurality of nozzle arrays, and the detection signal in a certain nozzle array may be low. In this case, if the drive voltage supplied to all the nozzle arrays is increased, In other words, the nozzle row that has generated a sufficient detection signal makes the discharge unstable, and in any case, there is a problem that the dot missing inspection accuracy cannot be sufficiently obtained.

  The present invention has been made in view of such circumstances, and the purpose of the present invention is to increase the detection signal only for this nozzle row when there is a nozzle row with a weak detection signal, so that the liquid from the nozzle opening can be reduced. An object of the present invention is to provide a liquid ejection apparatus and an ejection inspection method capable of improving the inspection accuracy when inspecting the presence or absence of ejection.

The present invention has been proposed in order to achieve the above-described object, and includes a plurality of nozzle groups each including a plurality of nozzle openings, and a liquid discharge head that discharges liquid from the nozzle openings by driving the discharge drive unit;
A drive signal generator for generating a drive pulse for driving the ejection driver;
A liquid receiving portion that is disposed opposite to the nozzle forming surface of the liquid discharge head and receives the liquid discharged from the nozzle opening;
Electricity between the conductive portion and the liquid receiving portion when the liquid is discharged from the nozzle opening toward the liquid receiving portion with a voltage applied between the conductive portion and the liquid receiving portion of the liquid discharge head. A discharge inspection unit that inspects whether or not liquid is discharged from the nozzle opening by detecting a change, and
The drive signal generation unit can generate the ejection inspection drive pulse used in the ejection inspection process by the ejection inspection unit for each nozzle group, and can vary the ejection inspection drive pulse for each nozzle group. It is characterized by occurring.
The “conductive portion” means a member having conductivity and a portion that comes into contact with the liquid in the liquid discharge head.

  According to this configuration, the drive signal generation unit can generate the ejection inspection drive pulse used in the ejection inspection process by the ejection inspection unit for each nozzle group, and the ejection inspection drive pulse for each nozzle group. Therefore, it is possible to supply drive pulses suitable for the inspection for each nozzle group, thereby eliminating variations in detection sensitivity for each nozzle group and increasing the determination accuracy.

In the above configuration, the ejection inspection drive pulse is set so that the ejection speed of the ejected liquid is higher than the ejection speed of the liquid ejected by the normal drive pulse used in other than the ejection inspection process. Features.
Note that “other than the ejection inspection process” means a process mainly performed by the liquid ejection device, for example, an ink jet printer which is a kind of the liquid ejection device, which ejects ink to a recording medium (ejection target) such as recording paper. On the other hand, it means a printing process for printing an image or text.

  According to this configuration, since the ejection inspection is performed using the inspection driving pulse that is higher than the flying speed of the liquid ejected by the normal driving pulse, the detection is performed in comparison with the configuration in which the ejection inspection is performed using the normal driving pulse. It becomes possible to increase the amplitude (detection voltage) of the signal. Thereby, the detection sensitivity can be improved, and the determination accuracy of the presence or absence of ejection can be improved. Further, since the amplitude of the detection signal can be increased, it is possible to reduce the number of times the liquid is discharged from one nozzle opening at the time of inspection. As a result, it is possible to reduce the amount of liquid consumed in the ejection inspection.

  Further, it is desirable that the ejection inspection drive pulse is different for each nozzle group in accordance with the type of liquid ejected from the nozzle opening of the nozzle group.

In the above-described configuration, the ejection inspection drive pulse includes an expansion element that expands a pressure generation chamber that communicates with the nozzle opening, an expansion hold element that maintains an expansion state of the pressure generation chamber by the expansion element for a certain period of time, and an expanded pressure A discharge element for discharging liquid from the nozzle opening by contracting the generation chamber,
The drive signal generation unit changes the time width of at least one of the expansion element, the expansion hold element, and the discharge element, so that the liquid fly when discharged using the discharge inspection drive pulse. It is desirable to adopt a configuration in which the speed is made constant regardless of the environmental temperature.

  According to this configuration, the drive signal generator changes the time width of at least one of the expansion element, the expansion hold element, and the discharge element, so that the liquid at the time of discharge using the discharge inspection drive pulse is changed. Since the flying speed can be made uniform for all nozzle groups, fluctuations in the flying speed of the liquid can be prevented regardless of the solid difference of the nozzle groups, thereby contributing to an improvement in ejection determination accuracy.

The drive signal generator may increase the electrical change for the nozzle group ejected using the ejection test drive pulse by increasing the drive voltage of the ejection test drive pulse.
The “drive voltage” means a potential difference between the lowest potential and the highest potential of the drive pulse.

  According to this configuration, the drive signal generator corrects the drive voltage of the nozzle group so that the amount of liquid ejected using the ejection inspection drive pulse is made uniform, so that the liquid ejection amount varies. This can be easily and reliably suppressed. Thereby, it becomes possible to contribute to the further improvement of the discharge determination accuracy.

  Further, the presence or absence of liquid ejection from the nozzle openings may be inspected by sequentially supplying drive pulses generated by the drive signal generator to the nozzle groups and detecting electrical changes in the nozzle groups.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet printer (hereinafter abbreviated as a printer) shown in FIG. 1 is exemplified as the liquid ejection apparatus of the present invention.

  As shown in FIG. 1, the printer 1 of the present embodiment includes an ink jet recording head (hereinafter referred to as a recording head 2) as a liquid ejection head mounted on a carriage 3. The printer 1 also includes a carriage moving mechanism 5 that reciprocates the carriage 3 in the main scanning direction, which is the width direction of the recording paper 4 (a type of recording medium or discharge target), and a sub-scanning direction orthogonal to the main scanning direction. A paper feed mechanism 6 that conveys the recording paper 4 to the platen, a platen 7 on which the recording paper 4 is placed, and a capping mechanism 8 that is provided at a position (home position) deviated from the platen 7 to one end in the main scanning direction And a controller 9 for controlling the entire printer 1.

  On the carriage 3, for example, ink cartridges 11 individually storing ink of each color of yellow (Y), magenta (M), cyan (C), and black (K) are detachably mounted. The ink of the cartridge 11 is supplied to the recording head 2. Further, a linear encoder 12 for detecting the position of the carriage 3 is disposed in the printer main body, and the position of the carriage 3 can be managed based on a detection signal from the linear encoder 12.

  As shown in FIG. 2, the recording head 2 includes a nozzle plate 15 in which the nozzle openings 13 are formed, a flow path forming plate 17 that forms an ink flow path including a pressure generation chamber 16 that communicates with the nozzle openings 13, and a pressure. A flexible diaphragm 18 that seals the opening of the generation chamber 16 and a piezoelectric element 19 bonded to the upper surface of the diaphragm 18 are provided. The nozzle plate 15 has a plurality of nozzle openings 13 for discharging inks of cyan (C), magenta (M), yellow (Y), and black (K) in the sub-scanning direction (180 in this embodiment). The nozzle row 14 is formed in a row. And this nozzle row 14 is provided in total 4 rows (14C, 14M, 14Y, 14K) corresponding to each color.

  Further, the recording head 2 includes a plurality of mask circuits 22 provided on the head driving substrate 21 corresponding to the plurality of piezoelectric elements 19 that respectively drive the nozzle openings 13. Then, a voltage (drive signal) is applied from the mask circuit 22 to the piezoelectric element 19 to drive the expansion and contraction of the piezoelectric element 19, thereby expanding or contracting the volume of the pressure generation chamber 16, and ink in the pressure generation chamber 16. Ink is ejected from the nozzle opening 13 by controlling the pressure fluctuation. The mask circuit 22 is supplied with the drive signal COM and the print signal PRTn generated by the drive signal generation circuit 25 of the controller 9 (a kind of drive signal generation unit in the present invention; see FIG. 1). Note that n at the end of the print signal PRTn is a number for specifying the nozzles included in the nozzle row. In this embodiment, since the nozzle row is composed of 180 nozzles, n is any number from 1 to 180. It becomes a numerical value.

  As shown in FIG. 1, the controller 9 is configured as a microprocessor centered on a CPU 26 (which functions as a discharge inspection unit in the present invention together with a discharge inspection device 32 described later), and a ROM 27 that stores various processing programs. A RAM 28 that temporarily stores and saves data, a flash memory 29 that can write and erase data, an interface (I / F) 30 that exchanges information with external devices, and the printer And a head information storage unit 31 that stores information of the recording head 2 attached to the head. The head information storage unit 31 stores information unique to the recording head 2, specifically, ejection characteristics for each nozzle row, and based on the information regarding the ejection characteristics for each nozzle row, the inspection drive pulse Pt. Is corrected. Details of this point will be described later. Note that the discharge characteristic information stored in the head information storage unit is measured as a preliminary inspection of the discharge speed and the discharge amount when a standard drive pulse is supplied after the recording head 2 is manufactured. Then, a deviation between the measured value (electrical change, one example of which is a detection voltage described later) and a standard value is calculated, and is mounted on a printer and shipped as head solid information. The head solid information is preferably configured to be transmitted by issuing an ID to the recording head.

  The ROM 27 stores processing programs for a main routine, a discharge inspection routine, and a print processing routine, which will be described later. The RAM 28 is provided with a print buffer area, and print data sent from the external device via the I / F 30 is stored in the print buffer. In addition to a position signal from the linear encoder 12 being input to the controller 9 via an input port (not shown), a print job output from an external device is input via the I / F 30. Further, from the controller 9, a control signal to the recording head 2 (including the mask circuit 22 and the piezoelectric element 19), a control signal to the carriage moving mechanism 5, a driving signal to the paper feeding mechanism 6, and an operation to the capping mechanism 8. Control signals and the like are output via an output port (not shown), and print status information of an external device is output via the I / F 30.

  As shown in FIG. 2, the drive signal generation circuit 25 mainly includes a first ejection pulse P1, a second ejection pulse P2, and a third ejection pulse P3 in a section for one pixel (one ejection cycle or one recording cycle). A drive signal COM having one drive pulse as a repeating unit is output to the mask circuit 22. Hereinafter, these ejection pulses P1 to P3 are collectively referred to as normal drive pulses P as appropriate. The normal drive pulse P is a drive pulse used in a normal recording mode (print mode) in which an image, text, or the like is printed on the recording paper 4 by ejecting ink from the nozzle openings 13. The drive signal generation circuit 25 generates an inspection drive signal COM ′ used in a discharge inspection routine described later. The inspection drive signal COM ′ is a drive signal including an inspection drive pulse Pt in which the flying speed of ink is increased as compared with the normal drive pulse P. When the drive signal COM (COM ′) and the print signal PRTn are input, the mask circuit 22 makes a necessary pulse from the drive signal COM (COM ′) based on these signals as a drive pulse DRVn toward the piezoelectric element 19. Selectively output.

FIG. 3 shows a normal drive pulse P (FIG. 3A) in the drive signal COM generated by the drive signal generation circuit 25 and an inspection drive pulse Pt (FIG. 3B) in the inspection drive signal COM ′. It is a wave form diagram explaining a structure.
As shown in FIG. 3A, the normal drive pulse P has a first pre-expansion element p11 that raises the electric potential with a constant gradient from the reference electric potential VB to the maximum electric potential VH, and a rear end electric potential of the first pre-expansion element p11. A first expansion hold element p12 that maintains a certain maximum potential VH for a certain period of time, a first discharge element p13 that drops a potential with a relatively steep gradient from the maximum potential VH to the minimum potential VL, and a minimum potential VL that maintains a certain period of time. The first contraction hold element p14, the first intermediate expansion element p15 that increases the potential with a constant gradient from the lowest potential VL to the intermediate potential VM between the lowest potential VL and the reference potential VB, and maintains the intermediate potential VM for a certain period of time And a first return expansion element p17 for returning the potential with a constant gradient from the intermediate potential VM to the reference potential VB.

  Further, as shown in FIG. 3B, the inspection drive pulse Pt of the inspection drive signal COM ′ is composed of the same waveform elements as the normal drive pulse P, and from the reference potential VB to the maximum potential VH. A second pre-expansion element p21 that increases the potential at a constant gradient, a second expansion hold element p22 that maintains the maximum potential VH that is the rear end potential of the second pre-expansion element p21 for a certain period of time, and a minimum potential from the maximum potential VH A second discharge element p23 that drops the potential with a relatively steep gradient to VL, a second contraction hold element p24 that maintains the lowest potential VL for a certain time, and a potential that rises with a constant gradient from the lowest potential VL to the intermediate potential VM The second intermediate expansion element p25, the second intermediate hold element p26 that maintains the intermediate potential VM for a certain period of time, and the potential is restored with a constant gradient from the intermediate potential VM to the reference potential VB. And a second return expansion element p27 Metropolitan that.

  When the drive pulses P and Pt are supplied to the piezoelectric element 19, the following effects are obtained. First, when the pre-expansion elements p11 and p21 are supplied to the piezoelectric element 19, the piezoelectric element 19 contracts, and accordingly, the pressure generating chamber 16 corresponds to the maximum potential VH from the reference volume corresponding to the reference potential VB. Expands to maximum volume. Thereby, the meniscus exposed to the nozzle opening 13 is drawn into the pressure generating chamber side. The expansion state of the pressure generating chamber 16 is maintained constant throughout the supply period of the expansion hold elements p12 and p22.

  When the discharge elements p13 and p23 are supplied to the piezoelectric element 19 following the expansion hold elements p12 and p22, the piezoelectric element 19 expands, whereby the pressure generating chamber 16 corresponds to the minimum potential VL from the maximum volume. Shrinks rapidly to minimum volume. The ink in the pressure generating chamber 16 is pressurized by the rapid contraction of the pressure generating chamber 16, and thereby, several pl to several tens of pl of ink are ejected from the nozzle opening 13. The contraction state of the pressure generation chamber 16 is maintained for a short time over the supply period of the contraction hold elements p14 and p24, and thereafter, the intermediate expansion elements p15 and p25, the intermediate hold elements p16 and p26, and the return expansion elements p17 and p27. Are sequentially supplied to the piezoelectric element 19, and the pressure generating chamber 16 returns from the volume corresponding to the lowest potential VL to the reference volume corresponding to the reference potential VB.

  Thus, the normal drive pulse P and the test drive pulse Pt have the same basic function for ejecting ink. However, both are set so that the flying speeds of the ink ejected from the nozzle openings 13 are different from each other by being applied to the piezoelectric element 19. Specifically, the ink flying speed Vmt when ejected using the inspection drive pulse Pt in the ejection inspection routine is higher than the ink flying speed Vm ejected using the normal drive pulse P in the normal recording mode. It is getting higher. More specifically, at least one of the waveform elements of the time width t21 of the second preliminary expansion element p21, the time width t22 of the second expansion hold element p22, and the time width t23 of the second ejection element p23 is set as a normal drive pulse. By shortening or lengthening the corresponding waveform element in P as a reference, the flying speed of ink when using the inspection drive pulse Pt is increased. In the present embodiment, the time width t23 of the second discharge element p23 is slightly longer than the time width t13 of the first discharge element p13, whereas the time width t21 of the second preliminary expansion element p21 is the first preliminary time. It is shorter than the time width t11 of the expansion element p11, and the time width t22 of the second expansion hold element p22 is shorter than the time width t12 of the first expansion hold element p12.

  FIG. 4 is a graph showing changes in the ink flying speed Vmt when the time width t22 of the second expansion hold element p22 is changed. As shown in this graph, it can be seen that if the time width t22 is changed, the ink flying speed Vmt increases or decreases. Here, the flying speed of the ejected ink varies depending on the state of the meniscus at the ejection timing, specifically, the position and movement speed of the meniscus. The period of the pressure vibration generated by expanding the ink in the pressure generating chamber 16 by the second preliminary expansion element p21 that excites the pressure vibration is called the natural vibration period Tc of the pressure generating chamber determined for each liquid ejecting head. The state of the meniscus depends on the pressure vibration excited by the ink in the pressure generation chamber 16. That is, the meniscus vibrates according to the natural vibration period Tc, and the flying speed of the ink changes. Accordingly, the ink flying speed Vmt can be increased by setting the time width of each waveform element in consideration of the natural vibration period Tc.

  With the inspection driving pulse Pt set in this way, the ink flying speed Vmt can be increased by several tens of percent with respect to the ink flying speed Vm by the normal driving pulse P. Also, there was no significant change in the amount of ink ejected. That is, it is possible to increase only the flying speed while suppressing a change in the amount of ejected ink.

  Here, in the printer 1, each of the nozzle arrays formed on the recording head 2 does not necessarily have the same ejection characteristics, and some nozzle arrays have ejection speeds lower than other nozzle arrays. If a nozzle row having a low ejection speed is included, the voltage for detecting the droplets ejected from the nozzle row becomes weak and the detection sensitivity becomes low. In order to eliminate such an inconvenience, the ejection inspection drive pulse Pt is made different from the ejection inspection drive pulse Pt that supplies the other nozzle rows to increase the ejection speed of the nozzle row.

  By the way, if it is attempted to increase the inspection sensitivity of the nozzle row having a low discharge speed by increasing the discharge speed of all the nozzle rows of the recording head 2, the discharge speed of the other nozzle rows becomes too high and the flight direction is greatly bent. Since inconveniences such as satellites become excessively large, the ejection speed is increased only for nozzle rows having a low ejection speed, thereby raising the inspection sensitivity. That is, the head information storage unit 31 stores information on the magnitude of the electrical change in the preliminary inspection performed in advance for each nozzle group (nozzle row). This is generated by correcting the ejection test drive pulse for the row, and driving the piezoelectric element 19 with this corrected drive pulse to make the flight speed uniform (increasing the voltage of the nozzle row having a low test voltage).

  For this reason, the drive signal generation circuit 25 functions as drive signal correction means, and corrects the test drive pulse Pt based on the head information from the head information storage unit 31. Specifically, as described above, at least one of the waveform elements of the time width t21 of the second preliminary expansion element p21, the time width t22 of the second expansion hold element p22, and the time width t23 of the second discharge element p23 is set. By shortening or lengthening the ink, the ink flying speed Vmt ′ when ink is ejected using the corrected inspection driving pulse Pt is the ink when the uncorrected inspection driving pulse Pt is used at the reference temperature. The flight speed is set to be equal to Vmt. That is, the ejection inspection driving pulse Pt is corrected so that the flying speed of ink is uniform in all the nozzle arrays without being greatly affected by the difference in the ejection characteristics of the nozzle arrays. For example, the ink flying speed is increased by making the time width t21 of the second preliminary expansion element p21 and the time width t22 of the second expansion hold element p22 shorter than before correction.

The correction of the drive signal is not limited to a method of increasing the ejection speed to increase the inspection sensitivity, and the drive voltage Vd (potential difference between the minimum potential VL and the maximum potential VH) of the inspection drive pulse Pt may be corrected. That is, for example, by increasing the drive voltage Vd of the test drive pulse Pt from the reference value based on the information stored in the head information storage unit 31, the amount of ink ejected from the nozzle openings 13 is increased. Align to the appropriate value. As described above, the inspection sensitivity is increased by correcting the drive voltage Vd of the inspection drive pulse Pt to increase the ink ejection amount. In this case, for example, by adjusting the time width of each element of the pulse so as to further increase the flight speed to the test drive pulse in which the drive voltage Vd is increased so as to increase the amount of ejected ink, the ink amount and The flight speed may be adjusted together.
The correction of the inspection drive pulse Pt may be adjusted in consideration of the balance between the ejected ink amount and the flying speed.

  Here, adjusting the flying speed of the ink ejected by the inspection drive pulse Pt is not limited to the configuration exemplified in this embodiment. For example, all the waveform elements of the time width t21 of the second preliminary expansion element p21, the time width t22 of the second expansion hold element p22, and the time width t23 of the second ejection element p23 are represented by the corresponding waveform elements in the normal drive pulse P. The time width of the waveform element may be changed as a reference, or the time width of any one of the waveform elements may be changed. Also, for example, it is possible to adjust the flight speed by changing the reference potential VB without changing the time width of each element. Specifically, the ink flying speed can be further increased by setting the reference potential VB lower than the reference potential before correction. Further, ink flying can be performed by changing the ratio t21: t22 without changing the total time (t21 + t22) of the time width t21 of the second preliminary expansion element p21 and the generation time t22 of the second expansion hold element p22 before and after correction. The speed Vmt can also be adjusted. That is, the ink flying speed can be increased by increasing the generation time t21 and shortening the generation time t22 while maintaining t21 + t22.

  In each of the above embodiments, the drive pulses P and Pt shown in FIG. 3 are given as an example of the drive pulse in the present invention. However, the shape of the pulse is not limited to that illustrated. At least an expansion element that preliminarily expands the pressure generation chamber 16, an expansion hold element that maintains the expansion state of the pressure generation chamber 16 for a predetermined time, and a discharge that contracts the pressure generation chamber 16 and discharges ink from the nozzle opening 13 As long as the driving pulse has elements, one having an arbitrary waveform can be used.

  Next, an ejection inspection routine (ejection inspection process) that is an inspection of whether or not ink is normally ejected from each nozzle opening 13 in the printer 1 having the above-described configuration will be described.

The discharge inspection apparatus 32 that performs the discharge inspection routine functions as a discharge inspection unit in the present invention together with the CPU 26, and as shown in the schematic diagram of FIG. 5, the liquid provided in the capping mechanism 8 disposed at the home position. A voltage is applied between the cap member 33 as a receiving portion, an inspection region 34 provided inside the cap member 33, and the nozzle region 15 (a kind of conductive portion in the present invention) of the recording region 2 and the inspection region 34. Is constituted by a voltage application circuit 35 for applying voltage and a voltage detection circuit 36 for detecting the voltage of the inspection region 34. The cap member 33 is a tray-like member having an open upper surface, and is made of an elastic member such as an elastomer. An ink absorber 37 is disposed inside the cap member 33. The ink absorber 37 includes an upper absorber 37a and a lower absorber 37b, and a mesh electrode member 38 is disposed between the absorbers 37a and 37b. The upper absorbent body 37a is made of a conductive sponge so as to have the same potential as the electrode member 38. This sponge is highly permeable so that the landed ink droplets can move downward quickly. In this embodiment, an ester urethane sponge is used. The surface of the upper absorbent body 37a corresponds to the inspection region 34. The lower absorbent body 37b has a higher ink holding power than the upper absorbent body 37a, and is made of a nonwoven fabric such as felt. The electrode member 38 is formed as a lattice mesh made of a metal such as stainless steel. For this reason, the ink once absorbed by the upper absorber 37a is absorbed and held by the lower absorber 37b through the gap between the grid-like electrode members 38.
One or both of the upper absorbent body 37a and the lower absorbent body 37b may be omitted.

  The voltage application circuit 35 includes a DC power source (for example, several hundred [V]) and a resistance element (for example, several [MΩ]) of the printer body so that the electrode member 38 is a positive electrode and the nozzle plate 15 of the recording head 2 is a negative electrode. Both are electrically connected to each other. Here, since the electrode member 38 is in contact with the conductive upper absorber 37 a, the surface of the upper absorber 37 a, that is, the inspection region 34 is also at the same potential as the electrode member 38. The voltage detection circuit 36 integrates and outputs the voltage signal of the electrode member 38, an inverting amplification circuit 41 that inverts and amplifies the signal output from the integration circuit 40, and the inverting amplification circuit 41. And an A / D conversion circuit 42 for A / D converting the signal output from the controller 9 and outputting the converted signal to the controller 9 side. The integrating circuit 40 outputs a larger voltage change by integrating the voltage change (a kind of electrical change) due to the flight / landing of a plurality of ink droplets. The inverting amplifier circuit 41 inverts the sign of the voltage change and amplifies and outputs the signal output from the integrating circuit at a predetermined amplification factor. The A / D conversion circuit 42 converts the analog signal output from the inverting amplification circuit 41 into a digital signal and outputs it as a detection signal to the controller 9 side.

  In the discharge inspection routine using the discharge inspection apparatus 32 having the above-described configuration, first, the recording head 2 is positioned above the cap member 33, and the cap member 33 causes the ink discharged from the recording head 2 to land on the inspection region 34. The inspection area 34 is raised to a possible position by the elevating mechanism of the capping mechanism 8 so as to face the nozzle forming surface (nozzle plate 15) of the recording head 2 in a non-contact state. Ink is ejected from the nozzle opening 13 by driving the piezoelectric element 19 using the above-described inspection drive pulse Pt in a state where a voltage is applied between the nozzle plate 15 and the electrode member 38 by the voltage application circuit 35. Is done. In this embodiment, since the nozzle plate 15 is a negative electrode, as shown in FIG. 6A, a part of the negative charge of the nozzle plate 15 moves to the ink, and the discharged ink is negatively charged. To do. As the ink droplet approaches toward the inspection region 34 of the cap member 33, positive charges increase in the inspection region 34 (the surface of the upper absorber 37a) due to electrostatic induction. As a result, the voltage between the nozzle plate 15 and the electrode member 38 becomes higher than the initial voltage value when ink is not ejected due to the induction current flowing by electrostatic induction. Thereafter, as shown in FIG. 6B, when the ink droplet lands on the upper absorber 37a, the positive charge of the upper absorber 37a is neutralized by the negative charge of the ink. As a result, the voltage between the nozzle plate 15 and the electrode member 38 is lower than the initial voltage value. Thereafter, the voltage between the nozzle plate 15 and the electrode member 38 returns to the initial voltage value.

  FIG. 7 is a diagram illustrating an example of a waveform of a detection signal output from the voltage detection circuit 36 of the ejection inspection device 32. Since the amplitude of the detection signal due to the ink droplet for one shot is extremely small, the ink is ejected a plurality of times through one nozzle opening 13 at the time of inspection. As a result, the detection signal becomes an integral value of the detection voltage by the ink for a plurality of shots by the integration circuit 40, and is further inverted and amplified by the repetitive amplification circuit 41, and thus has a sufficiently large output waveform for inspection. Since the signal output from the voltage detection circuit 36 passes through the inverting amplification circuit 41, the direction of the amplitude is reversed.

In this manner, for each nozzle row 14, the discharge inspection is sequentially performed for each nozzle opening 13 constituting the nozzle row 14, and the detection signal as the inspection result from the discharge inspection device 32 is stored in the RAM 28 of the controller 9. Accumulate. At this time, the waveform of the inspection drive pulse Pt used for the ejection inspection of each nozzle group is generated differently for each nozzle group, and the piezoelectric element of the corresponding nozzle group is driven.
The CPU 26 of the controller 9 functions as an amplitude acquisition unit and acquires the amplitude of the received detection signal. Specifically, the maximum value and the minimum value of the detection signal are detected, and the potential difference between them is acquired as the amplitude of the detection signal. Then, the CPU 26 determines whether the ink is normally ejected from each nozzle opening 13 based on the amplitude (detection voltage) of the detection signal. Here, if no ink is ejected from the nozzle opening 13 or the amount of ejected ink is extremely smaller than a specified amount (designed target ink amount), the amplitude of the detection signal Is smaller than that in the normal case, that is, when a predetermined amount of ink is ejected from the nozzle opening 13 or becomes a value close to zero, so whether or not the amplitude of the detection signal falls below a predetermined threshold value. Based on the above, it can be determined whether or not the ink is normally ejected from the nozzle opening 13.

FIG. 8 is a graph showing the relationship between the ink flying speed (ink flying speed Vmt when ejected using the inspection drive pulse Pt) and the amplitude of the detection signal (detection voltage (V)). As shown in the figure, the detection voltage (V) depends on the flying speed of the ink, and the detection voltage (V) tends to increase as the flying speed increases. Here, the charged ink moves at a velocity Vmt in the electric field between the electrodes at a constant interval x (that is, in the case of the present embodiment, between the nozzle plate 15 and the inspection region 34) and lands on the inspection region 34. In this case, if the charge changes by dQ at time dt, the current I flowing at that time is expressed by the following equation (1). Here, the direction of current (positive or negative) is not considered.
I = Vmt × dQ / dx (1)
Therefore, from the above equation (1), the higher the ink flying speed Vmt, the larger the generated current I. Accordingly, the detected voltage (V) also increases.

  In the printer 1 according to the present invention, since the ejection inspection routine is performed using the inspection drive pulse Pt that can increase the flying speed Vmt of the ink as compared with normal printing, the ejection inspection is performed using the normal drive pulse P. Compared with the configuration, the amplitude (detection voltage (V)) of the detection signal can be increased. Thereby, the detection sensitivity can be improved, and the determination accuracy of the presence or absence of ejection can be improved. Further, since the amplitude of the detection signal (detection voltage (V)) can be increased, the number of ink ejections for one nozzle opening 13 at the time of inspection can be reduced. As a result, it is possible to reduce the amount of ink consumed in the ejection inspection.

Further, in the printer 1 according to the present invention, the waveform of the ejection test drive pulse Pt is varied for each nozzle row to correct the test drive pulse so as to complement the ejection properties of the nozzle row. Even so, it is possible to suppress a decrease in determination accuracy by the complement. That is, since the ink flying speed Vmt when ejected using the ejection inspection drive pulse Pt is increased and the speeds of all the nozzle arrays are made to be within a certain range, the difference in ink flying speed between the nozzle arrays is reduced. Thus, it is possible to contribute to the improvement of the discharge determination accuracy.
Further, since the ejection characteristics are raised by correcting the drive voltage Vd of the ejection test drive pulse Pt for the nozzle row inferior in ejection characteristics, the entire recording head, that is, all of the recording heads are obtained without instability. It is possible to improve the ejection determination accuracy with this nozzle row.

  Actually, the fluctuation of the detection signal amplitude (detection voltage V) accompanying the change in the ejected ink amount is smaller than the fluctuation of the amplitude accompanying the change in the flying speed Vmt. Therefore, when the test drive pulse Pt is provided separately from the normal drive pulse P, the test drive pulse Pt is adjusted so that only the flight speed is adjusted without adjusting the ink discharge amount according to the temperature. It may be what you did. Further, it is preferable that the normal drive pulse used for the printing process is adjusted so that the ink discharge amount is aligned at least according to the temperature.

  On the other hand, the test drive pulse Pt may be used in common with the normal drive pulse P. In this case, if the amount of ejected ink fluctuates, the print quality is lowered. Therefore, it is desirable to adjust the variation in the amplitude of the detection signal by adjusting the ink ejecting amount and the flying speed. In this case, it is desirable that the flying speed is set to a flying speed that is as fast as possible at a flying speed at which the bending in the flying direction and the mist formation of the satellite do not occur so that a desired print quality can be obtained.

  The ejection inspection drive pulse may be different for each nozzle group depending on the type of liquid ejected from the nozzle opening of the nozzle group. For example, a standard ejection test drive pulse is supplied for a relatively low-viscosity ink, and a corrected ejection different from the standard ejection test drive pulse is used for an ink having a higher viscosity than this ink. Inspection drive pulses may be supplied so that the flight speeds are uniform. With this configuration, it is possible to supplement the ejection characteristics resulting from the type of liquid, and it is possible to inspect all colors of ink in the same way.

  The plurality of types of inks having different viscosities may be the same type of ink and different ink colors (for example, black ink and color ink), or different types of ink (for example, dye ink and pigment). Ink) or other types of inks with different viscosities.

  The reason why the inspection voltage varies depending on the type of ink is not limited to the viscosity of the ink. As shown in FIG. 6, since a detection voltage is generated by the movement of an ink droplet having a charge in an electric field, even if the flying speed of the ink does not change, it can be obtained depending on the conductivity of the ink. The magnitude of the detection voltage is different. For this reason, the type of ink may be ink with different conductivity (for example, water-based ink or oil-based ink).

Furthermore, not only when the type of liquid discharged for each nozzle group is different, but even when discharging the same liquid, when manufacturing processes and parts together in the manufacturing process for each nozzle group, There are cases where the ejection characteristics differ from nozzle group to nozzle group, and in particular, when Tc varies from nozzle group to liquid group, the liquid flying speed differs and the magnitude of the detection voltage varies. Therefore, the inspection drive pulse Pt may be changed for each nozzle group in accordance with the individual difference in ejection characteristics for each nozzle group. That is, the magnitude of the detection voltage differs depending on the nozzle group due to the difference in solids or the type of liquid to be ejected, but the magnitude of the detection voltage is adjusted by changing the inspection drive pulse Pt. It is.
For at least two nozzle groups, the inspection drive pulse Pt may be changed for each nozzle group.

In addition, this invention is not limited to above-described embodiment, A various deformation | transformation is possible based on description of a claim.
For example, in the above embodiment, the configuration using the cap member 33 of the capping mechanism 8 as the liquid receiving portion in the present invention has been exemplified. However, the present invention is not limited to this, and an independent liquid receiving portion dedicated for ejection inspection is provided. Also good.
Further, in the above-described embodiment, the example in which the electrode member 38 is electrically connected so that the electrode plate 38 is a positive electrode and the nozzle plate 15 of the recording head 2 is a negative electrode is shown, but the present invention is not limited to this example. It is also possible to adopt a configuration in which both positive and negative are reversed. One of the positive electrode and the negative electrode may be a GND potential (ground potential) whose potential is substantially zero. Further, the conductive portion in the recording head is not limited to the nozzle plate 15 and may be other members as long as it has conductivity and has a portion that contacts the ink in the recording head 2. Further, although the configuration in which the voltage detection circuit for detecting the electrical change is connected to the electrode member 38 in the cap member 33 is illustrated, the voltage detection circuit may be connected to the conductive portion in the recording head.

  In the above embodiment, the so-called longitudinal vibration mode piezoelectric element 38 is exemplified as the ejection driving unit in the present invention. However, the present invention is not limited to this. For example, it may be provided for each pressure generating chamber 16 like a so-called flexural vibration mode piezoelectric element. Furthermore, not only the piezoelectric element, but also other ejection driving units such as a heating element can be used.

  The present invention can also be applied to liquid ejection devices other than the printer. For example, the present invention can be applied to a display manufacturing apparatus, an electrode manufacturing apparatus, a chip manufacturing apparatus, and the like.

FIG. 2 is a block diagram and a perspective view illustrating a schematic configuration of the printer. FIG. 3 is a schematic diagram illustrating a configuration of a recording head. (A) is a waveform diagram of a normal drive pulse, and (b) is a waveform diagram of an inspection drive pulse. It is a graph which shows the change of the flying speed of an ink when the time width of the expansion hold element of a drive pulse is changed. It is a schematic diagram explaining the structure of a discharge inspection apparatus. FIG. 3 is a schematic diagram illustrating the principle of ink ejection inspection. It is a figure which shows an example of the waveform of the detection signal output from the voltage detection circuit of a discharge inspection apparatus. It is a graph which shows the relationship between the flying speed of an ink, and a detection voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 13 ... Nozzle opening, 15 ... Nozzle plate, 16 ... Pressure generating chamber, 19 ... Piezoelectric element, 25 ... Drive signal generating circuit, 32 ... Discharge inspection apparatus, 33 ... Cap member, 34 ... Inspection area 35 ... Voltage application circuit 36 ... Voltage detection circuit 37 ... Ink absorber 38 ... Electrode member

Claims (8)

A plurality of nozzle groups each having a plurality of nozzle openings, and a liquid discharge head that discharges liquid from the nozzle openings by driving the discharge drive unit;
A drive signal generator for generating a drive pulse for driving the ejection driver;
A liquid receiving portion that is disposed opposite to the nozzle forming surface of the liquid discharge head and receives the liquid discharged from the nozzle opening;
Electricity between the conductive portion and the liquid receiving portion when the liquid is discharged from the nozzle opening toward the liquid receiving portion with a voltage applied between the conductive portion and the liquid receiving portion of the liquid discharge head. A discharge inspection unit that inspects whether or not liquid is discharged from the nozzle opening by detecting a change, and
The drive signal generation unit can generate the ejection inspection drive pulse used in the ejection inspection process by the ejection inspection unit for each nozzle group, and can vary the ejection inspection drive pulse for each nozzle group. A liquid discharge apparatus generated by   The ejection inspection drive pulse is set such that a flying speed of a liquid to be ejected is higher than a flying speed of a liquid ejected by a normal drive pulse used in other than the ejection inspection process. Item 2. The liquid ejection device according to Item 1.   The liquid ejection apparatus according to claim 1, wherein the ejection inspection drive pulse is different for each nozzle group according to a type of liquid ejected from a nozzle opening of the nozzle group. The ejection test drive pulse includes an expansion element that expands a pressure generation chamber that communicates with the nozzle opening, an expansion hold element that maintains the expansion state of the pressure generation chamber by the expansion element for a certain period of time, and contracts the expanded pressure generation chamber And a discharge element that discharges liquid from the nozzle opening,
The drive signal generation unit changes the time width of at least one of the expansion element, the expansion hold element, and the discharge element, thereby discharging the electrical when the discharge inspection drive pulse is used. The liquid ejection device according to claim 1, wherein the change is enhanced.   2. The drive signal generation unit increases the electrical change in a nozzle group ejected using the ejection inspection drive pulse by increasing a drive voltage of the ejection inspection drive pulse. The liquid discharge apparatus according to claim 3.   2. The presence or absence of liquid ejection from a nozzle opening is inspected by sequentially supplying drive pulses generated by the drive signal generation unit to the nozzle groups and detecting an electrical change of each nozzle group. The liquid discharge apparatus according to claim 1. A liquid receiving portion that receives the liquid discharged from the nozzle opening is disposed opposite to the nozzle forming surface of the liquid discharge head that discharges liquid from each of the plurality of nozzle openings constituting the nozzle group by driving the discharge driving portion. In a state where a voltage is applied between the conductive portion of the liquid discharge head and the liquid receiving portion, the liquid is discharged from the nozzle opening toward the liquid receiving portion between the conductive portion and the liquid receiving portion. A discharge inspection method for inspecting each nozzle group for the presence or absence of liquid discharge from a nozzle opening by detecting an electrical change,
A discharge inspection method, characterized in that, for each nozzle group, a drive pulse for discharge inspection used in the discharge inspection process is driven differently from other nozzle groups.   The ejection inspection method according to claim 6, wherein the ejection inspection drive pulse is inspected so that the electrical changes of the nozzle groups are aligned.

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