JP2008137254A - Discharge checking apparatus and discharge inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge checking apparatus which can control an increase in ink viscosity during checking the discharge and, thereby, inhibit the time until the completion of the discharge inspection after its starting from getting longer, and to provide a discharge inspection method. <P>SOLUTION: The discharge checking apparatus is equipped with a fine oscillating voltage generation part for generating the fine oscillating voltage, a voltage application means for applying a the fine oscillating voltage for generating a fine oscillating pressure in a liquid to a pressure generation means. Two kinds of the fine oscillating voltages whose applying directions are different each other are generated by the fine oscillating voltage generation part. Concerning the nozzles of non-inspection object other than the nozzle to be inspected at checking the discharge, the two kinds of fine oscillating voltages are applied to the pressure generation means by the voltage applying part so that the nozzles of non-inspection object to which one of the two kinds of fine oscillating voltages is applied and the nozzles of non-inspection object to which the other fine oscillating voltage is applied may be intermixed. The discharge checking apparatus and the discharge inspection method are composed so as to meet the requirement. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge inspection apparatus and a discharge inspection method for performing a discharge inspection for inspecting whether or not liquid is discharged from a plurality of nozzles of a liquid ejecting head using a change in voltage generated in the liquid ejecting head.

  In an inkjet printer that ejects ink as one of the liquids from a liquid ejecting head and prints an image on printing paper, the image is printed correctly unless ink droplets are ejected from a plurality of nozzles provided on the liquid ejecting head. Will not be. Accordingly, a technique for inspecting whether or not an ink droplet is reliably ejected from a nozzle has been proposed in the past. For example, when a charged ink droplet is ejected using a liquid ejecting head as a first electrode, the second electrode is used. A technique for determining whether or not ink droplets are ejected by detecting a change in the voltage of the liquid ejecting head with respect to the above is disclosed (see Patent Document 1 or Patent Document 2).

JP 59-178256 A JP 2004-195760 A

  As in the techniques disclosed in Patent Document 1 and Patent Document 2, ink droplets are ejected from nozzles using a voltage change between the liquid ejecting head and the second electrode generated by ejecting charged ink droplets. When performing an ejection inspection for inspecting the presence or absence of ink, a voltage is applied to a pressure generation mechanism provided in the liquid ejecting head to generate a pressure for ejecting ink droplets in the ink. The pressure generating mechanism is usually configured by using a piezoelectric element, and applying a predetermined voltage to the piezoelectric element to drive the piezoelectric element to be deformed to generate pressure on the ink. The configuration of the pressure generating mechanism will be described in detail later.

  As is well known, the viscosity of ink increases with time (referred to as thickening). As a result of thickening, nozzle clogging may occur and ink droplets may not be ejected from the nozzles. In the ejection inspection, the ink corresponding to the inspection target nozzle to be subjected to the ejection inspection generates a pressure at which the ink droplet should be ejected from the nozzle, and therefore the ink vibrates due to the generated pressure. For this reason, the viscosity of the ink corresponding to the inspection target nozzle is suppressed. On the other hand, since the pressure to be ejected is not generated in the ink corresponding to the non-inspection target nozzle that is not the target of the ejection inspection, the ink corresponding to the non-inspection target nozzle is thickened as it is. Therefore, during discharge inspection, if the ink is caused to vibrate slightly by generating a minute pressure within a range where ink is not discharged from the nozzle for the non-inspection target nozzle, ink thickening is suppressed. be able to. For this reason, if a voltage for causing the ink to vibrate (referred to as a fine vibration voltage) is applied to the piezoelectric element, it is possible to suppress the thickening of the ink.

  However, if a micro-vibration voltage for micro-vibration of the ink is applied to the piezoelectric element, noise is generated, which affects the change in the voltage generated as the ink is ejected, and the ejection test cannot be performed correctly. To do. One of the factors that generate noise is that the ink interposed between the nozzle plate on which the nozzles are formed and the piezoelectric element is equivalent to a capacitor, so that the nozzle plate is in accordance with the voltage applied to the piezoelectric element. It is mentioned that a charge is induced. When this micro-vibration voltage is applied to the piezoelectric element corresponding to the non-inspection target nozzle provided in the liquid jet head, the amount of charge induced in the nozzle plate is the voltage applied to the piezoelectric element corresponding to each nozzle. Therefore, the micro-vibration voltage has an influence on the value of the voltage change generated when the ink droplet is ejected. As a result, the ejection inspection cannot be performed correctly.

  In order to avoid this state, when performing an inspection for the presence or absence of normal ink discharge, during the discharge inspection, the fine vibration drive for suppressing the increase in the ink viscosity is not performed, and the increase in the ink viscosity is suppressed. In this case, the ejection inspection is interrupted and the vibration is driven. Alternatively, the discharge inspection is performed within the time until the nozzle is thickened and the nozzle is clogged. Therefore, when performing a discharge inspection of all the nozzles provided in the liquid ejecting head, there is a problem that the time from the start of the discharge inspection to the end thereof becomes long.

  The present invention has been made in view of such a problem, and in a discharge inspection for inspecting whether or not ink is discharged from a nozzle, a discharge inspection apparatus and a discharge inspection capable of suppressing ink thickening during the discharge inspection Provide a method. This suppresses an increase in the time from the start to the end of the discharge inspection.

  In order to solve the above-described problem, the present invention provides a discharge inspection for performing a discharge inspection for inspecting whether or not liquid is ejected from a plurality of nozzles provided in a liquid ejecting head by using a change in voltage generated in the liquid ejecting head. A pressure generating means for generating pressure according to an applied voltage with respect to the liquid to be discharged from the plurality of nozzles, and a pressure in a range in which the liquid is not discharged from the plurality of nozzles. A fine vibration voltage generating unit for generating a fine vibration voltage for causing the liquid to generate a fine vibration pressure that is a pressure for finely vibrating the liquid; and the fine vibration for generating the fine vibration pressure in the liquid. A voltage application unit that applies a voltage to the pressure generating unit, the micro-vibration voltage generation unit generates two types of micro-vibration voltages having different application directions, and the voltage application unit For a non-inspection target nozzle other than the nozzle to be subjected to the discharge inspection at the time of the ejection inspection, the non-inspection target nozzle to which one of the two types of micro-vibration voltages is applied and the other micro-vibration voltage The two kinds of micro-vibration voltages are applied to the pressure generating means so that the non-inspection target nozzles to which are applied are mixed.

  According to this configuration, at the time of ejection inspection, the voltage application unit applies two types of micro-vibration voltages having different voltage application directions so as to be mixed in the non-inspection target nozzles. Accordingly, as described above, the charge induced by the micro-vibration voltage applied to the pressure generating mechanism is a mixture of positive charge and negative charge depending on the application direction. As a result, the positive charge and the negative charge cancel each other, so that a voltage generated in the liquid ejecting head is generated even if a fine vibration voltage is applied during ejection inspection in order to generate a fine vibration pressure in the liquid corresponding to the non-inspection target nozzle. It is possible to suppress the thickening of the liquid without greatly changing the. In addition, this makes it possible to suppress the thickening of the ink during the ejection inspection. Accordingly, since it is not necessary to provide a period for performing fine vibration driving for stopping the ejection inspection and suppressing the increase in the viscosity of the ink, it is possible to suppress an increase in the time from the start to the end of the ejection inspection. .

  Here, it is preferable that the two types of micro-vibration voltages have the same absolute value of the amount of potential change from the reference potential. In this case, since the absolute value of the potential change amount from the reference potential is the same, there is a high probability that the charge amounts having different polarities induced by two types of micro-vibration voltages having different application directions are the same. Accordingly, since the probability that the positive charge and the negative charge are canceled increases, it is possible to reduce the voltage change of the liquid ejecting head caused by the micro-vibration voltage applied to the pressure generating means during the discharge inspection.

  For the non-inspection target nozzles, the number of non-inspection target nozzles to which one of the two types of micro-vibration voltages is applied and the number of non-inspection target nozzles to which the other is applied are the same or one nozzle difference. It is preferable.

  In this way, when the number of non-inspection target nozzles is an even number, the induced positive charge and the negative charge are basically the same amount, so that they are induced by the micro-vibration voltage applied to all the non-inspection target nozzles. Charge is canceled out. When the total number of non-inspection target nozzles is an odd number, the amount of induced positive charge and negative charge is basically the same for all remaining non-inspection target nozzles leaving one non-inspection target nozzle. Therefore, the charges induced by the micro-vibration voltages applied to all the non-inspection target nozzles are only charges corresponding to the micro-oscillation voltage applied to one non-inspection target nozzle after cancellation. Therefore, it is possible to reduce the voltage change of the liquid ejecting head caused by the micro-vibration voltage applied to the pressure generating means during the ejection inspection.

  In addition, in the nozzles to which two types of micro-vibration voltages are applied, the application directions may be different between adjacent nozzles.

  In this way, since the induced positive charge and negative charge are adjacent to each other, the charge is offset between the adjacent positive charge and negative charge, which is caused by the micro-vibration voltage applied to the pressure generating means during the discharge inspection. The voltage change of the liquid ejecting head can be reduced.

  Moreover, it is preferable that a voltage application part applies two types of micro vibration voltages to a pressure generation means simultaneously.

  In this way, since the positive charge and the negative charge are simultaneously induced, the positive charge and the negative charge are canceled at the same timing. Therefore, the voltage of the liquid ejecting head generated by the micro-vibration voltage applied to the pressure generating means at the time of ejection inspection Change can be reduced.

  The present invention can also be understood as an inspection method. That is, a discharge inspection method for performing a discharge inspection for inspecting whether or not liquid is ejected from a plurality of nozzles provided in a liquid ejecting head using a change in voltage applied to the liquid ejecting head, Pressure generating means for generating a pressure in response to an applied voltage with respect to the liquid to be discharged from the nozzle, and a pressure within a range where the liquid is not discharged from the plurality of nozzles, and a pressure that slightly vibrates the liquid A fine vibration voltage generating step for generating a fine vibration voltage for generating the fine vibration pressure in the liquid and a fine vibration voltage for generating the fine vibration pressure in the liquid are applied to the pressure generating means. A voltage application step, wherein the micro-vibration voltage generation step generates two types of micro-vibration voltages having different application directions, and the voltage application step is performed during the discharge inspection. For non-inspection target nozzles other than the nozzle to be inspected, the non-inspection target nozzle to which one of the two types of microvibration voltages is applied and the non-inspection to which the other microvibration voltage is applied The two kinds of micro-vibration voltages are applied to the pressure generating means so that the target nozzle is mixed.

  According to the discharge inspection method of the present invention, it is possible to obtain the same operational effects as those of the discharge inspection apparatus of the present invention described above. This discharge inspection method may be executed in the discharge inspection apparatus having the various aspects described above, or may be executed in the discharge inspection apparatus having other aspects.

  Embodiments of the discharge inspection apparatus according to the present invention will be described below. FIG. 1 shows a schematic structure of an ink jet printer 10 as a recording apparatus incorporating a discharge inspection apparatus according to an embodiment of the present invention. The inkjet printer 10 includes a carriage 20 on which ink cartridges 11 to 14 that store inks of Y (yellow), M (magenta), C (cyan), and K (black) as liquids to be ejected are mounted. The print medium 25 as a recording medium is conveyed by repeating a predetermined amount of movement in the vertical direction of the drawing. Each time the printing medium 25 moves, the carriage 20 moves in the left-right direction of the drawing, and ink droplets are ejected from the liquid ejecting head 30 provided on the back side of the drawing of the carriage 20. A predetermined image or the like is printed on the print medium 25 supported by the printer.

  The carriage 20 is fixed to the carriage belt 41, and moves along the guide 21 fixed to the frame 17 as the carriage belt 41 is driven by the carriage motor 40. The print medium 25 is moved in the vertical direction of the drawing by a paper feed roller (not shown) driven by a drive motor 26 fixed to the frame 17. When the carriage 20 moves, a predetermined ink droplet corresponding to the image to be printed is ejected from a plurality of nozzles for ejecting each color ink provided in the liquid ejecting head 30 so that the image can be printed correctly. Therefore, an image cannot be printed correctly unless ink droplets are ejected.

  For this reason, in the inkjet printer 10, when the inspection timing to be inspected comes at a predetermined time such as when the power is turned on, before the start of the print job, in the middle of the print job, at the end of the print job, etc. A discharge inspection is performed on a plurality of nozzles provided in the head 30 to inspect whether or not ink droplets are discharged from the nozzles. In the ejection inspection, the carriage 20 is moved to the position of the inspection box 70 provided in the ink jet printer 10 and a predetermined ejection inspection process is performed to inspect whether ink droplets are ejected from each nozzle. If there is a non-ejection nozzle that does not eject ink droplets as a result of the inspection, the carriage is moved to the position of the cleaning box 18 provided in the inkjet printer 10 to suck ink in the nozzle. The nozzle is cleaned by performing the cleaning procedure.

  The main control of the series of operations described above is performed by a main control circuit 50a provided on the main board 50 attached to the frame 17 and a sub control circuit 60a provided on the sub board 60 attached to the carriage 20. Done. These substrates are connected by a flexible substrate 45, and the main control circuit 50a and the sub-control circuit 60a operate in cooperation by exchanging data between the respective substrates, thereby performing a predetermined ink droplet ejection test.

  The main control circuit 50a includes a CPU 51 for controlling various operations of the ink jet printer 10, a ROM 52 for recording a program related to these operations, and a RAM 53 for temporarily storing and reading data necessary for the operation. And an interface (I) for exchanging data between the flash memory 54 to which data can be written and erased and the sub-control circuit 60a, and exchanging information with an external device such as a personal computer (PC) 90 of the user. / F) 55.

  A processing routine program for the ejection inspection from the nozzle is stored in the ROM 52. A print job including print data to be printed is stored in the RAM 53. Note that the processing routine program for the ejection inspection from the nozzle may be input from the outside via the I / F 55 and downloaded to the RAM 53.

  On the other hand, the sub-control circuit 60a is provided with an ASIC 61 in which a logic circuit and the like for executing a predetermined operation relating to the discharge inspection are configured. Therefore, when the CPU 51 reads out the processing routine program recorded in the ROM 52 and exchanges various signal data with the ASIC 61, the CPU 51 and the ASIC 61 execute a predetermined operation to perform the discharge inspection.

  Next, the mechanism of the discharge inspection apparatus incorporated in the ink jet printer 10 will be specifically described with reference to FIG. FIG. 2 shows an apparatus configuration for determining whether ink droplets are ejected by using charged ink droplets, applying pressure to the ink to eject ink from each of a plurality of nozzles provided in the liquid ejecting head 30. It is a schematic diagram. When the carriage 20 moves to a predetermined position with respect to the inspection box 70, for example, ink supplied from the ink cartridge 11 to the liquid ejecting head 30 through a supply path (not shown) is ejected from the liquid ejecting head 30 as ink droplets 39.

  The ejected ink droplet 39 lands on the electrode member 71 provided in the inspection box 70. The electrode member 71 is made of a metal material such as a mesh-like SUS plate and serves as a landing receiving area for the ink droplets 39. The landed ink droplet 39 then passes through the electrode member 71 and is absorbed by the ink absorber 72 formed of sponge-like resin or the like. Thus, the electrode member 71 is configured not to deposit ink. The electrode member 71 is electrically connected to the frame 17 by a connection member 66.

  The ASIC 61 operates a voltage generation circuit 62 in which one end of the circuit is connected (grounded) to the frame 17 during discharge inspection, generates a predetermined voltage for the frame 17, and then passes a resistor 64 having a predetermined resistance value. Then, the voltage Ve is applied to the liquid jet head 30 using the connecting member 65. Of course, the portion to which the voltage Ve is applied in the liquid ejecting head 30 is a portion that is electrically connected to the ink. In this embodiment, the voltage Ve is applied to the nozzle plate 34 (see FIG. 3) that is in electrical conduction with the ink, and the voltage is the same as the voltage applied to the liquid ejecting head 30.

  In this embodiment, the voltage applied to the liquid ejecting head 30 is a positive potential with respect to the frame 17. Therefore, as described above, a voltage is generated in the direction of application from the liquid jet head 30 side to the electrode member 71 side between the electrode member 71 in the inspection box 70 electrically connected to the frame 17. As a result, the liquid ejecting head 30 is positively charged and the electrode member 71 is negatively charged.

  When the ink droplet 39 is ejected from the liquid ejecting head 30, the ink droplet 39 is deprived of the positive charge charged from the liquid ejecting head 30, and the positive charge flows through the resistor 64 to supplement the deprived positive charge. For this reason, a voltage drop occurs due to the positive charge flowing in the resistor 64 in this way, and the voltage of the liquid ejecting head 30 changes (decreases). This change in voltage is acquired by the ASIC 61 via the capacitor 68, and the presence or absence of ejection is determined by comparing the acquired change in voltage with a predetermined threshold.

  Each of the plurality of nozzles provided in the liquid ejecting head 30 is formed with a pressure generating mechanism that generates pressure on the ink for each nozzle. In this embodiment, the piezoelectric element is deformed when a voltage is applied to the piezoelectric element, and the ink supplied from the ink cartridge is pressurized. Therefore, by applying a voltage at which ink should be ejected as ink droplets to the piezoelectric element corresponding to the nozzle to be inspected, it is possible to inspect whether or not ink droplets are ejected from that nozzle. A specific configuration of the pressure generating mechanism will be described later with reference to FIG.

  A voltage for deforming the piezoelectric element is output from the driver substrate 31 as a head driving signal of the piezoelectric element. The driver substrate 31 is provided in the carriage 20 in the vicinity of the liquid ejecting head 30, is connected to the sub substrate 60 by a connection member (not shown), and operates in response to an output signal from the ASIC 61.

  Next, how the piezoelectric element corresponding to the nozzle is driven will be described. FIG. 4 is an explanatory diagram for explaining a driving method of the piezoelectric element. In this embodiment, the liquid jet head 30 is provided with nozzle rows 35Y, 35M, 35C, and 35K corresponding to Y, M, C, and K, and each nozzle row has n = 1 to 180 (n 180 indicates nozzle numbers). Thus, in this embodiment, a total of 720 nozzles to be inspected are formed in the liquid jet head 30. In order to eject ink droplets from the nozzles to be inspected, for each YMCK nozzle row, a head drive signal DRVn (n = 1 to 180) for driving the piezoelectric elements to be deformed with respect to the piezoelectric elements corresponding to the nozzles to be inspected. ) Is output.

  The head drive signal DRVn is generated as follows. On the main board 50, as shown in the balloons in FIG. 4, Pva and P1, P1, and P1, are shown in a section for printing an image corresponding to one pixel (also called a segment when the carriage 20 crosses one pixel interval). An original signal ODRVa in which unit signals having a total of four pulse signals of P2 and P3 are repeatedly present, an original signal ODRVb in which unit signals having a total of four pulse signals of Pvb and P1, P2, and P3 are present repeatedly, and a print signal PRTa and the print signal PRTbn are generated.

  5A shows the waveform of the voltage value of each pulse signal of the original signal ODRVa, and FIG. 5B is a diagram for explaining the waveform of the voltage value of each pulse signal of the original signal ODRVb. The original signal ODRVa shown in FIG. 5A is a pulse signal Pva for causing the piezoelectric element to vibrate slightly so that the ink does not harden in the nozzle, and ejects one ink drop from each nozzle. It has pulse signals P1, P2, and P3 to be used. A small size dot is formed on the print medium only by the pulse signal P1, a medium size dot is formed by the pulse signals P1 and P2, and a large size dot is formed by the pulse signals P1, P2 and P3, respectively.

  The original signal ODRVb shown in FIG. 5B is a pulse signal Pvb for causing the piezoelectric element to vibrate slightly so that the ink does not harden in the nozzle, and ejecting one ink drop from each nozzle. It has pulse signals P1, P2, and P3 to be used. The pulse signal Pvb is a waveform of a voltage value formed so that a voltage is generated in a direction different from the application direction of the pulse signal Pva included in the original signal ODRVa. That is, the pulse signal Pva has a waveform with a positive voltage value with respect to the GND potential (0 volt in this embodiment), and the pulse signal Pvb has a GND potential (0 volt in the present embodiment). ) Is a waveform of a negative potential voltage value. In this embodiment, it is assumed that the absolute value of the positive potential of the pulse signal Pva and the absolute value of the negative potential of the pulse signal Pvb are the same. Further, the pulse signals P1, P2, and P3 shown in the original signal ODRVb are waveforms having the same voltage value in the same application direction as the original signal ODRVa. In this embodiment, the reference potentials of the waveforms of the pulse signal Pva and the pulse signal Pvb (intermediate potential where the waveform is neither a peak nor a valley) are set to 0 volts (GND potential), but a potential having a plus or minus value. May be a reference potential.

  The print signals PRTa and PRTbn (n = 1 to 180) specify the nozzles that should eject ink droplets out of the 180 nozzles for each YMCK nozzle row, and specify either the original signal ODRVa or the original signal ODRVb. This is a signal for selecting and selecting a pulse signal in the selected original signal. Accordingly, the print signals PRTa and PRTbn are selectively supplied to the nozzles by selecting the nozzles that should eject ink and the pulse signals that should be output based on the print data (the presence / absence of dots and their gradation values) during printing. Although it is a signal, it is a signal for specifying a nozzle to eject ink for the inspection and for selecting a pulse signal to be output at the time of the ejection inspection. Further, in the fine vibration driving described later, it becomes a signal for selecting a nozzle to be driven and a pulse signal necessary for the driving.

  These signals are output to the mask circuit provided on the driver substrate 31 via the ASIC 61 as described above. The mask circuit selects the original signal ODRVa or the original signal ODRVb according to the print signals PRTa and PRTbn, and the pulse signal selected by the print signals PRTa and PRTbn from the selected one original signal is also the print signals PRTa and PRTbn. The circuit is configured so as to output to the piezoelectric element corresponding to the nozzle specified by. That is, when the original signal ODRVa is selected by the print signal PRTa, the mask circuit applies the piezoelectric signal corresponding to the selected nozzle to be inspected by the print signal PRTa out of the pulse signals Pva, P1, P2, and P3. The selected pulse signal is output, and is output from the mask circuit as a head drive signal DRVn. When the original signal ODRVb is selected by the print signal PRTbn, the mask circuit selects the piezoelectric signal corresponding to the selected nozzle to be inspected from the pulse signals Pvb, P1, P2, and P3 by the print signal PRTbn. The pulse signal is output and is output from the mask circuit as the head drive signal DRVn. Thus, the head drive signal DRVn is generated.

  In the ejection inspection, the head drive signal generated in this way is output to the piezoelectric element corresponding to the inspection target nozzle, and then the head drive signal is output to the corresponding piezoelectric element every time the next inspection target nozzle is selected. This procedure is repeated sequentially. By applying this procedure to all nozzle rows of YMCK, the corresponding piezoelectric elements are sequentially driven for all nozzles, and ejection inspection is performed.

  FIG. 3 is a schematic diagram illustrating a configuration of a pressure generation mechanism that generates a pressure for ejecting ink droplets for each of the plurality of nozzles provided in the liquid ejecting head 30. That is, when a voltage is applied between the GND electrode and the COM electrode provided at both ends of the piezoelectric element 32, the piezoelectric element 32 is deformed. In the present embodiment, the piezoelectric element 32 is configured to expand when a pulse signal having a ground potential on the GND electrode side and a positive potential on the COM electrode side is applied. Therefore, when a pulse signal having a positive potential is applied to the COM electrode, the GND electrode side is physically fixed. Therefore, the member 33 is pushed down in the direction of the arrow (the lower side in the drawing), for example, the ink 38 supplied from the ink cartridge 11 is removed. Pressurize. Conversely, when a pulse signal having a negative potential is applied to the COM electrode, the piezoelectric element 32 contracts, and the member 33 is pushed up in the direction opposite to the arrow direction (upper side in the drawing) to depressurize the ink 38.

  Accordingly, the voltage applied to the COM electrode of the piezoelectric element 32 corresponding to each nozzle can generate a pressure for ejecting the ink droplet 39 from the nozzle, or a minute pressure that does not eject the ink droplet 39 can be generated. . In other words, as described above, if the pulse signal Pva is output between the GND electrode and the COM electrode of the piezoelectric element, the ink 38 is pressurized and the fine vibration drive is performed. In addition, if the pulse signal Pvb is output between the GND electrode and the COM electrode of the piezoelectric element 32, the ink 38 is depressurized and fine vibration driving is performed. Therefore, the pulse signals Pva and Pvb are also fine vibration voltages. Further, in the discharge inspection, it is desirable that the voltage change is large in order to improve the accuracy of determination of the presence / absence of discharge, so that all the pulse signals of the pulse signals P1 to P3 are generated by the piezoelectric element 32 corresponding to the inspection target nozzle. Output to the COM electrode.

  At this time, since the ink 38 is equivalently interposed as a capacitor between the COM electrode of the piezoelectric element 32 and the nozzle plate 34, the voltage applied to the COM electrode is electrically connected to the nozzle plate via the capacitor. As a result, the voltage value of the liquid jet head 30 is affected and the voltage is changed. By the way, the pulse signals P1 to P3 have a larger voltage value than the pulse signals Pva and Pvb. However, in the ejection inspection, only the piezoelectric elements 32 corresponding to the inspection target nozzles are driven one by one. Only the pulse signals P1 to P3 are output to the COM electrodes of the two piezoelectric elements 32. Therefore, the change that the pulse signals P1 to P3 give to the voltage value of the liquid ejecting head during the ejection inspection is small.

  However, it is clear that only one pulse signal Pva or pulse signal Pvb for micro-vibration driving has little influence, but the piezoelectric elements 32 corresponding to all the nozzles provided in the liquid jet head 30. When only one of the pulse signal Pva or the pulse signal Pvb is applied to (720 in this embodiment), the degree of influence becomes considerably large.

  For example, if the pulse signal Pva is output between the GND electrode and the COM electrode of the piezoelectric element 32, the ink 38 is equivalently provided between the COM electrode of the piezoelectric element 32 and the nozzle plate 34 as described above. Since a positive potential is applied to COM because it is interposed as a capacitor, negative charges are generated in the nozzle plate 34, respectively. Accordingly, the voltage of the nozzle plate 34 is approximately proportional to the total amount of charges induced by the positive voltage applied to the piezoelectric element 32, and the voltage of the liquid ejecting head 30 is greatly changed to the negative side. Conversely, when the pulse signal Pvb is applied between the GND electrode and the COM electrode of the piezoelectric element 32 corresponding to all the nozzles provided in the liquid ejecting head 30, a negative potential is applied to the COM electrode. Therefore, positive charges are generated in the nozzle plate 34, respectively. Accordingly, the voltage of the nozzle plate 34 is approximately proportional to the total amount of charges induced by the negative voltage applied to the piezoelectric element 32, and the voltage of the liquid ejecting head 30 is greatly changed to a plus.

  If the voltage of the liquid ejecting head 30 is greatly changed to the plus side or the minus side in this way, a change in the voltage of the liquid ejecting head 30 that occurs when the ink droplet 39 is ejected is affected. Accordingly, during the period in which the voltage change between the electrodes when the ink droplet 39 is ejected is detected, either the pulse signal Pva or the pulse signal Pvb is applied to the piezoelectric elements 32 corresponding to all the nozzles that are not subjected to the ejection inspection. When only is applied, this state is reached, and the output signal cannot be detected correctly. As a result, the ejection inspection of the ink droplet 39 cannot be performed correctly.

  Therefore, in this embodiment, the pulse signal Pva is applied to the piezoelectric elements 32 corresponding to some of the nozzles that are not subjected to the ejection inspection during the ejection inspection period during which the ejection inspection of the ink droplets 39 is performed, and the rest By applying the pulse signal Pvb to the piezoelectric elements 32 corresponding to the nozzles, the positive charge induced in the nozzle plate 34 by the pulse signal Pva and the negative charge induced in the nozzle plate 34 by the pulse signal Pvb cancel each other. As a result, the voltage of the nozzle plate 34 is prevented from changing greatly.

  Next, the discharge inspection method performed by the discharge inspection apparatus of the present embodiment will be specifically described with reference to the time chart of FIG. In this embodiment, the original signal ODRVa is supplied to the nozzles with odd nozzle numbers, the original signal ODRVb is supplied to the nozzles with even nozzle numbers, and the print signal PRtan (n = 1, 3, 5...) And the print signal. It is assumed that it is selected by PRTbn (n = 2, 4, 6,...).

  The time chart shown in FIG. 6 shows the state of each signal such as an original signal and a print signal in each segment from time 0 to time t1, from time t1 to time t2, and from time t2 to time t3. From time 0 to time t1, a test is performed on the presence or absence of ejection for the inspection target nozzle with nozzle number n = 1. In the period from the time t2 to the time t3, it is shown that the ejection presence / absence inspection is performed for the nozzle to be inspected with the nozzle number n = 3.

  Incidentally, the LAT signal shown in FIG. 6 is a pulse signal having a predetermined pulse width that is output at a period of one segment in order to synchronize the original signal ODRVa, the original signal ODRVb, and the print signal PRTn.

  First, time 0 to time t1 will be described. The original signal ODRVa and the original signal ODRVb (see FIG. 4) generated by a circuit provided on the main board are output via the ASIC 61. As described above, the original signal ODRVa has the pulse signals Pva, P1, P2, and P3, and the original signal ODRVb has the pulse signals Pvb, P1, P2, and P3.

  The inspection target nozzle n = 1 is selected by the print signal PRTa = 1 of the inspection target nozzle shown in FIG. 6, and the pulse signals P1, P2, P3 are selected from the original signal ODRVa for the discharge inspection by the same print signal PRTa = 1. Then, the drive signal DRVn = 1 is generated, and the head drive signal DRVn = 1 is applied to the piezoelectric element 32 corresponding to the inspection target nozzle n = 1.

  At this time, since all the nozzles after nozzle number n = 2 are non-inspection target nozzles, the head drive signal DRVn in which the pulse signal Pva is selected by the print signal PRTa is generated for the odd-numbered nozzles, and the even number A head drive signal DRVn in which the pulse signal Pvb is selected by the print signal PRTbn is generated for the numbered nozzles. Then, the head drive signal DRVn is applied to the piezoelectric elements corresponding to the respective non-inspection target nozzles selected by the respective print signals PRTa and PRTbn. The timing at which the pulse signal Pva and the pulse signal Pvb are applied is the same.

  As described above, regarding the non-inspection target nozzle, the pulse signal Pva is applied to the piezoelectric element 32 for the odd-numbered nozzles, and the pulse signal Pvb is applied to the piezoelectric element for the even-numbered nozzles. Accordingly, since the pressure that slightly vibrates is applied to the ink 38 to be ejected from each nozzle as described above, the ink slightly vibrates and the thickening of the ink 38 is suppressed. On the other hand, as described above, the pulse signal Pva induces a negative charge on the nozzle plate 34, and the pulse signal Pvb induces a positive charge on the nozzle plate 34. Therefore, since the negative charge induced in the odd-numbered nozzles and the positive charge induced in the even-numbered nozzles have substantially the same charge amount, there is a high probability that they will cancel each other, and the negative charges are induced in the nozzle plate 34. The amount of electric charge is only the amount of electric charge induced in one nozzle. As a result, since there is no influence on the voltage change of the liquid jet head during the ejection inspection, the ejection inspection for the nozzle number n = 1 can be correctly performed.

  Next, during one segment from the time t1 to the time t2, the ejection inspection of the nozzle to be inspected with the nozzle number n = 2 is performed, and the piezoelectric element corresponding to the odd numbered nozzle among the non-inspection target nozzles for which the ejection inspection is not performed. A pulse signal Pva is applied to the element, and a head drive signal DRVn having the pulse signal Pvb is applied to the piezoelectric element corresponding to the even-numbered nozzle.

  Further, during one segment from time t2 to time t3, similarly, the ejection inspection of the nozzle to be inspected with the nozzle number n = 3 is performed, and it corresponds to the odd-numbered nozzle among the non-inspection target nozzles for which the ejection inspection is not performed The pulse signal Pva is applied to the piezoelectric element 32 to be applied, and the head drive signal DRVn having the pulse signal Pvb is applied to the piezoelectric element 32 corresponding to the even-numbered nozzle.

  Thereafter, although not shown in the figure, the pulse signal Pva is applied to the piezoelectric element 32 corresponding to the odd-numbered nozzle among the non-inspected nozzles at the same time while the discharge inspection of the inspection-target nozzle is performed. A head drive signal DRVn having a pulse signal Pvb is applied to the piezoelectric element 32 to be applied.

  According to the embodiment described above, the pulse signal Pva and the pulse signal Pvb having different voltage application directions can be obtained even if the micro-vibration driving is performed to slightly vibrate the ink 38 corresponding to the non-inspection target nozzle during the ejection inspection. Since they are mixed and applied to the piezoelectric element 32, the voltage of the nozzle plate 34 does not change greatly. Therefore, it is possible to accurately detect whether or not the ink droplet 39 is ejected by detecting a change in the voltage of the nozzle plate 34 when ejected from the inspection target nozzle. In the ejection inspection period, the pulse signal Pva and the pulse signal Pvb having different voltage application directions are mixedly applied to the piezoelectric elements 32 corresponding to the nozzles that are not subjected to the ejection inspection, so that the ink 38 is slightly vibrated. The thickening of the ink 38 can be suppressed.

  Further, since the viscosity increase of the ink 38 can be suppressed even during the ejection inspection period, it is not necessary to provide a period for stopping the ejection inspection and suppressing the viscosity increase of the ink 38. It can be suppressed that the time is long.

  Here, the relationship between the pressure generating means, the micro-vibration voltage generating unit, and the voltage applying unit described in the claims will be described.

  The pressure generating means corresponds to the pressure generating mechanism shown in FIG. When the head drive signal DRVn is applied to the piezoelectric element 32 constituting the pressure generating mechanism, the piezoelectric element 32 is deformed to generate pressure in the liquid in the pressure generating mechanism.

  The fine vibration voltage generation unit corresponds to a circuit and a mask circuit provided in the main board 50. From the original signals ODRVa and ODRVb generated in the main board 50, the mask circuit selects the pulse signals Pva and Pvb by the print signals PRTa and PRTbn also generated in the main board 50, thereby generating a fine vibration voltage. To do.

  The voltage application unit corresponds to print signals PRTa and PRTbn and a mask circuit. The piezoelectric elements 32 corresponding to the nozzles for which the print signals PRTa and PRTbn are targeted are selected, and two types of pulse signals having different voltage application directions, that is, the micro vibration voltages Pva and Pvb are applied.

  The present invention has been described with respect to the discharge inspection apparatus mounted on the ink jet printer as one embodiment. However, the present invention is not limited to such an embodiment, and various embodiments are within the scope of the present invention. Of course, it can be implemented. Hereinafter, a modification will be described.

(First modification)
In the above embodiment, for the non-inspection target nozzle, the pulse signal Pva is applied to the piezoelectric elements 32 corresponding to the odd-numbered nozzles, and the pulse signal Pvb is applied to the piezoelectric elements 32 corresponding to the even-numbered nozzles. It was. That is, the direction of the voltage applied to the piezoelectric element 32 differs between adjacent nozzles. In the present modification, the number of non-inspection target nozzles to which one of the two types of pulse signals is applied and the number of non-inspection target nozzles to which the other applied voltage is applied may be the same or a difference of one nozzle. .

  By doing this, the number of nozzles to which the micro-vibration voltage Pva is applied and the number of nozzles to which the micro-vibration voltage Pvb are applied are substantially the same, so the negative charge amount and the positive charge amount induced in the entire liquid ejecting head 30. Is offset. Accordingly, it is possible to correctly perform the discharge inspection on whether or not the ink 38 is discharged from the inspection target nozzle without affecting the voltage change of the liquid jet head 30 during the discharge inspection.

(Second modification)
Moreover, in the said Example, the voltage application part applied two types of applied voltages simultaneously to a pressure generation means. In the present modification, the timings at which the two types of micro-vibration voltages Pva and Pvb are applied to the pressure generating means do not necessarily have to be the same.

  Even if the timing at which the positive charge and the negative charge applied to the liquid ejecting head 30 are offset is offset within the ejection inspection time, the voltage change of the liquid ejecting head 30 is not affected, and the inspection is performed. It is possible to correctly perform the ejection inspection for the presence / absence of ejection of the ink 38 from the target nozzle.

(Third Modification)
In the above embodiment, the total number of nozzles provided in the liquid jet head 30 is an even number of 180 nozzles, and the number of nozzles to be inspected is one. For this reason, since the number of non-inspected nozzles is an odd number of 179, the difference between the number of nozzles with an odd nozzle number and the number of nozzles with an even nozzle number is one nozzle difference. In this modification, the total number of nozzles is an odd number (for example, 179), and the number of nozzles to be inspected is one. At this time, the number of non-inspection target nozzles is an even number. Alternatively, when the total number of nozzles is an even number and the number of nozzles to be inspected is an even number (for example, 2), the number of non-inspection target nozzles is an even number.

  As a result, in any case, since the number of non-inspection target nozzles is an even number, the number of nozzles to which the fine vibration voltage Pva is applied is equal to the number of nozzles to which the fine vibration voltage Pvb is applied. Accordingly, since the negative charge amount and the positive charge amount induced in the entire liquid ejecting head 30 are offset, the ink from the inspection target nozzle is not affected without affecting the voltage change of the liquid ejecting head 30 during the ejection inspection. It is possible to correctly perform the ejection inspection for the presence / absence of 38 ejections.

(Fourth modification)
Further, if it is in a range that does not affect the voltage change of the liquid ejecting head 30 at the time of ejection inspection, the ratio between the number of nozzles to which the minute vibration voltage Pva is applied and the number of nozzles to which the minute vibration voltage Pvb is applied is set to a predetermined value. It may be a ratio. For example, the ratio of the number of nozzles to which the minute vibration voltage Pva is applied and the number of nozzles to which the minute vibration voltage Pvb is applied may be 2 to 3.

  Further, when the ratio between the number of nozzles to which the micro-vibration voltage Pva is applied and the number of nozzles to which the micro-vibration voltage Pvb is applied is a predetermined ratio, the ratio between the absolute values of the micro-vibration voltage Pva and the micro-vibration voltage Pvb is You may change it. For example, when the ratio of the number of nozzles to which the micro-vibration voltage Pva is applied and the number of nozzles to which the micro-vibration voltage Pvb is applied is 2 to 3, the ratio is preferably 3 to 2. In this way, since the negative charge amount and the positive charge amount induced in the entire liquid ejecting head are offset, the ink from the inspection target nozzle is not affected without affecting the voltage change of the liquid ejecting head during the ejection inspection. It is possible to correctly perform the discharge inspection for the presence or absence of discharge.

(5th modification)
In the above embodiment, the micro-vibration voltage Pva or Pvb is applied to the piezoelectric elements 32 corresponding to all the non-inspection target nozzles other than the ejection inspection target nozzles, but the piezoelectric elements corresponding to some of the non-inspection target nozzles. A fine vibration voltage Pva or Pvb may be applied to 32.

  For example, since the ink 38 vibrates at the time of the ejection inspection for the nozzle subjected to the ejection inspection, the viscosity does not immediately increase. Therefore, if the elapsed time after the ejection inspection is within a predetermined time, the minute vibration voltage Pva or Pvb Need not be applied, and the fine vibration voltage Pva or Pvb may be applied to the other nozzles. In this way, since the number of nozzles to which the minute vibration voltage Pva or Pvb is applied is reduced, it is expected that the influence of noise is reduced.

(Other variations)
In the above embodiment, when a voltage for ejection inspection is applied between the liquid ejecting head 30 and the electrode member 71, the liquid ejecting head 30 side is applied so as to have a positive potential, but the electrode member 71 side becomes a positive potential. It is good also as applying. In this case, even when a high voltage cannot be applied to the liquid ejecting head 30 side, such as an inkjet printer having a configuration in which it is difficult to form a circuit that generates a high voltage near the liquid ejecting head 30, the measurement terminal can be used. A voltage for ejection inspection can be applied between them. In this case, when the ink droplet 39 is ejected, the amplitude voltage of the output signal is reversed. That is, in the above embodiment, when the ink droplet 39 is ejected from the nozzle, the voltage fluctuates in the negative direction. In this case, the output signal voltage fluctuates in the positive direction. For the above, a threshold value is set on the plus side and the ejection determination is performed.

  In the above embodiment, the piezoelectric element is driven to eject ink droplets from the nozzle. However, the ink is heated by applying a voltage to a heating resistor (for example, a heater) and the ink is generated by the generated bubbles. The ink droplets may be ejected by applying pressure. In this way, the nozzle inspection apparatus of the present invention can be applied to an ink jet printer that does not use a piezoelectric element.

  In the above embodiment, the discharge inspection apparatus incorporated in a recording apparatus that discharges ink droplets as a recording liquid onto a printing medium by an ink jet printer has been described as one embodiment. However, the present invention is not limited to this. Of course not. For example, an ink jet recording apparatus that forms a wiring pattern by discharging a recording liquid onto a glass substrate or a resin substrate, an ink jet recording apparatus that forms a color filter, or the total direction in which the liquid ejecting head is orthogonal to the conveyance direction of the print medium. The present invention can be similarly applied to an apparatus that records an image, a figure, a character, or the like on a recording medium by ejecting a recording liquid using an ink jet system, such as an ink jet printer that is arranged over the entire area.

1 is a schematic structural diagram of an ink jet printer according to an embodiment of the present invention. The schematic diagram for demonstrating the structure of the discharge inspection apparatus as one Example of this invention. FIG. 3 is a schematic diagram illustrating a configuration of a pressure generation mechanism for generating pressure in ink. Explanatory drawing for demonstrating the drive method of a piezoelectric element. The figure explaining the waveform of the voltage value of the original signal ODRVa and the original signal ODRVb in one Example of this invention. The time chart explaining the method of the discharge test | inspection in one Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet printer, 11-14 ... Ink cartridge, 17 ... Frame, 18 ... Cleaning box, 20 ... Carriage, 21 ... Guide, 25 ... Print medium, 26 ... Drive motor, 28 ... Platen, 30 ... Liquid ejecting head, 31 ... driver board, 32 ... piezoelectric element, 33 ... member, 34 ... nozzle plate, 35Y ... nozzle row, 35M ... nozzle row, 35C ... nozzle row, 35K ... nozzle row, 38 ... ink, 39 ... ink droplet, 40 ... carriage Motor 41... Carriage belt 45. Flexible board 50. Main board 51. CPU 52. ROM 53 53 RAM 54 Flash memory 55 I / F 60 Sub board 61 ASIC 62 ... Voltage generation circuit, 64 ... Resistance, 65, 66 ... Connection member, 68 ... Capacitor, 70 ...査 box, 71 ... electrode member, 72 ... ink absorber, 90 ... PC.

Claims (6)

A discharge inspection apparatus that performs discharge inspection for inspecting presence / absence of liquid discharge from a plurality of nozzles provided in a liquid ejecting head using a change in voltage generated in the liquid ejecting head,
Pressure generating means for generating pressure according to an applied voltage with respect to the liquid to be ejected from the plurality of nozzles;
A micro-vibration voltage generator that generates a micro-vibration voltage for causing the liquid to generate a micro-vibration pressure that is a pressure within a range in which the liquid is not discharged from the plurality of nozzles,
A voltage application unit that applies the micro-vibration voltage for generating the micro-vibration pressure to the liquid to the pressure generation unit;
The micro-vibration voltage generating unit generates two types of micro-vibration voltages having different application directions,
The voltage application unit is a non-inspection target nozzle to which one of the two types of micro-vibration voltages is applied to a non-inspection target nozzle other than the nozzle to be subjected to the ejection inspection during the ejection inspection. And a non-inspection target nozzle to which the other micro-vibration voltage is applied are mixed,
A discharge inspection apparatus, wherein the two kinds of micro-vibration voltages are applied to the pressure generating means. The discharge inspection apparatus according to claim 1,
The two types of micro-vibration voltages have the same absolute value of the amount of potential change from the reference potential. The discharge inspection apparatus according to claim 1 or 2,
For non-inspection target nozzles, the number of non-inspection target nozzles to which one of the two types of micro-vibration voltages is applied and the number of non-inspection target nozzles to which the other is applied are the same number or the number of one nozzle difference. Discharge inspection device characterized. The discharge inspection apparatus according to any one of claims 1 to 3,
In the nozzle to which the two kinds of micro-vibration voltages are applied, the application direction is different between adjacent nozzles. The discharge inspection apparatus according to any one of claims 1 to 4,
The discharge inspection apparatus, wherein the voltage application unit applies the two kinds of micro-vibration voltages simultaneously to the pressure generating means. A discharge inspection method for performing a discharge inspection for inspecting presence / absence of liquid discharge from a plurality of nozzles provided in a liquid ejecting head using a change in voltage generated in the liquid ejecting head,
Pressure generating means for generating pressure according to an applied voltage with respect to the liquid to be ejected from the plurality of nozzles;
A micro-vibration voltage generating step for generating a micro-vibration voltage for causing the liquid to generate a micro-vibration pressure, which is a pressure within a range in which the liquid is not discharged from the plurality of nozzles, and which finely vibrates the liquid;
A voltage application step of applying the micro-vibration voltage for generating the micro-vibration pressure to the liquid to the pressure generation unit,
The fine vibration voltage generating step generates two types of the fine vibration voltages whose application directions are different from each other,
In the voltage application step, a non-inspection target nozzle to which one of the two types of micro-vibration voltages is applied to a non-inspection target nozzle other than the nozzle to be subjected to the ejection inspection at the time of the ejection inspection. And the other two types of micro-vibration voltages are applied to the pressure generating means so that the other non-inspection target nozzle to which the micro-vibration voltage is applied is mixed.

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