JP2008062499A - Discharge inspection device and discharge inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge inspection device and a discharge inspection method making it possible to correctly determine presence or absence of discharge of ink droplets by properly amplifying voltage change generated along with the discharge of the ink droplets. <P>SOLUTION: Output signals amplified by an amplifying circuit 69 amplifies the voltage change generated along with the discharge of a recording liquid by inputting the output signals to the amplifying circuit 69 only when the recording liquid is discharged at least for discharge inspection The voltage change of a recording head 30 is not transmitted to the amplifying circuit 69 as the output signals when the recording head 30 is not driven for discharging for the discharge inspection. Accordingly, the movement of the amplifying circuit 69 can be always in a stable movement condition, the presence or absence of the discharge can be correctly determined using the amplified output signals because the output signals are not transmitted to the amplifying circuit 69 even though large voltage change is generated in the voltage Ve of the recording head 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention utilizes the recording head voltage change that occurs when a recording liquid is ejected from a recording head having a predetermined potential to the counter electrode toward the counter electrode. The present invention relates to a discharge inspection technique for inspecting the presence or absence of liquid discharge.

  In an ink jet recording apparatus that discharges ink as one of the recording liquids from a recording head and prints an image or the like on printing paper, the image is not printed correctly unless ink droplets are discharged from a plurality of nozzles provided on the recording head. It will be. Therefore, a technique for inspecting whether or not an ink droplet is reliably ejected from a nozzle has been conventionally proposed. For example, when a charged ink droplet is ejected, a change in the voltage of the recording head with respect to the second electrode is detected. A technique for determining whether or not ink droplets are ejected is disclosed (see, for example, Patent Document 1 or Patent Document 2).

JP 59-178256 A JP 2004-195760 A

  As in the technique disclosed in Patent Document 1 or Patent Document 2, when inspecting whether or not ink droplets are ejected from the nozzles using voltage changes generated by ejecting charged ink droplets, the ink droplets are ejected. It is necessary to correctly detect the voltage change that occurs. By the way, the ink droplets ejected from the recording head are often small ink droplets for printing a high-definition image such as a photographic image. In many cases, the voltage change that occurs with the discharge of the ink is a small value. Inspecting whether or not ink droplets are ejected using such a small voltage change may result in poor inspection accuracy due to the small absolute value of the change amount of the voltage change. Therefore, it is often performed that the generated voltage change is amplified by an amplifier circuit, and the inspection is performed using the amplified voltage change.

  As the amplifier circuit, for example, an operational amplifier or the like is used, and the voltage signal at the input stage of the amplifier circuit is amplified about 100 to 1000 times. For this reason, when a signal having a large voltage is input to the input stage of the amplifier circuit, the amplified output signal is distorted or saturated, so that the voltage signal is in an unstable operation state where it is not amplified correctly. The amplifier circuit may take a considerable amount of time to recover from such an unstable operation state to a stable operation state in which amplification can be performed correctly again. Therefore, the discharge inspection cannot be performed correctly for the time until the amplifier circuit recovers to a stable operating state.

  Incidentally, as a factor for generating such a large voltage, a voltage generated due to electric field noise from the outside of the ink jet recording apparatus or electric field noise generated in the ink jet recording apparatus is assumed. In addition to this, for example, there is a case in which a fine vibration drive that generates a pressure for causing the ink to vibrate in the ink in the print head changes the voltage of the print head. The slight vibration drive is performed to suppress the increase in viscosity so that the viscosity of the ink to be discharged does not increase (thickening) and the ink cannot be discharged from the nozzle.

  The voltage that is actually applied to the recording head for micro-vibration driving is a voltage that is relatively much larger than the value of the voltage change (several tens to hundreds of microvolts) that occurs as the ink droplets are ejected. Often a value (about several volts). For this reason, the voltage of the recording head with respect to the second electrode is affected by the voltage applied to the recording head during micro-vibration driving. Furthermore, since such micro-vibration driving is normally performed for all nozzles provided in the recording head, the influence is large when the number of nozzles is large, and as a result, the voltage of the recording head is greatly changed. Will end up.

  However, in the conventional technique disclosed in Patent Document 1 or Patent Document 2, electric field noise from the outside of the ink jet recording apparatus, electric field noise generated in the ink jet recording apparatus, or micro vibration drive is generated. There is no disclosure about the voltage change of the recording head due to factors other than the ejection of ink droplets, such as the voltage change of the recording head to be performed, and therefore no specific disclosure has been made about a solution to such a problem.

  The present invention solves such a problem, and correctly amplifies a change in voltage generated along with the ejection of an ink droplet, thereby making it possible to correctly determine whether or not an ink droplet has been ejected. The purpose is to provide.

  In order to solve the above problems, the present invention utilizes a change in voltage of a recording head that occurs when a recording liquid is ejected from a recording head having a predetermined voltage to the counter electrode toward the counter electrode. A discharge inspection apparatus for performing a discharge inspection for inspecting whether or not the recording liquid is discharged from the recording head, wherein the recording liquid is generated by generating a first pressure for the discharge inspection. A first head driving unit for driving the recording head to discharge from the recording head; an output signal acquiring unit for acquiring a voltage change of the recording head as an output signal; and a signal for amplifying the output signal by a predetermined amplifier circuit An amplification unit; and a signal transmission unit that intermittently transmits the output signal to the signal amplification unit, wherein the signal transmission unit is a period during which the first head driving unit drives the recording head , The serial output signal, characterized in that transmitted to the signal amplifier.

  According to this configuration, when the recording liquid is being driven for ejection inspection, the voltage change of the recording head is transmitted as an output signal to the amplifier circuit. Accordingly, since the output signal when the recording head is driven to be ejected is transmitted to the amplifier circuit and input, the output signal amplified by the amplifier circuit reliably amplifies the voltage change that occurs as the recording liquid is ejected. become. On the other hand, when the recording head is not ejected for ejection inspection, the voltage change of the recording head is not transmitted as an output signal to the amplifier circuit. Therefore, even if a large voltage change occurs in the recording head voltage when the recording head is not driven to discharge, the output signal is not transmitted to the amplifier circuit, so that the operation of the amplifier circuit can always be in a stable operation state. As a result, since the output signal can be correctly amplified, it is possible to correctly determine whether or not ejection is performed using the amplified output signal.

  Here, the signal transmission unit may be configured by an electric circuit that electrically interrupts transmission of the output signal.

  By doing so, compared to a switch including a mechanical mechanism such as an electromagnetic relay, for example, the intermittent speed can be performed at a high speed, so that there is no delay with respect to the period during which ejection driving for ejection inspection is performed, The output signal can be appropriately transmitted to the amplifier circuit. Therefore, it is possible to correctly perform the discharge inspection.

  Moreover, it is preferable that the signal transmission unit is provided in an input stage of an amplifier circuit of the signal amplifier.

  When the physical distance from the recording head to the amplifier circuit is long, the output signal transmission path is inevitably long. In such a case, noise such as the above-described electric field noise from the outside is easily mixed in the transmission path, and therefore, the probability that a large voltage change is caused in the output signal is increased. Therefore, a signal transmission unit is configured at the input stage of the amplifier circuit. In this way, even if noise is mixed in the transmission path in this way, the output signal is not transmitted to the amplifier circuit, so that the amplifier circuit can always be in a stable operation state. Therefore, it is possible to correctly perform the discharge inspection.

  Furthermore, the ejection inspection apparatus of the present invention is a period in which the first head driving unit is not driving the recording head, and the recording head is placed in a predetermined period to generate the second pressure in the recording liquid. A second head driving unit for driving, and the signal transmission unit cuts off the output signal to the signal amplifying unit during the predetermined period when the second head driving unit is driving the recording head. It is good also as not transmitting.

  In some cases, the recording head is driven for purposes other than the ejection inspection during a period in which the recording head is not driven for ejection inspection. At this time, for example, if driving is performed to simultaneously discharge recording liquid from a plurality of nozzles provided in the recording head, a change in voltage generated along with the recording liquid discharge becomes large. It is assumed that it will change greatly. Therefore, the output signal is prevented from being transmitted to the amplifier circuit during the drive period of the recording head for purposes other than the ejection inspection in which such drive is assumed. In this way, the operation of the amplifier circuit can always be in a stable state. As a result, it is possible to correctly perform the discharge inspection.

  Here, the predetermined period may be a period before the start of the discharge inspection for inspecting whether or not the recording liquid is discharged.

  Alternatively, the predetermined period may be a period in the middle of a discharge inspection for inspecting whether or not the recording liquid is discharged.

  As a period for driving the recording head for purposes other than the ejection inspection, it is assumed that the ejection head is before or during the ejection inspection. For example, there are a case where a nozzle provided in a recording head is cleaned in order to reliably perform a discharge inspection, and a case where a recording liquid in the recording head is prevented from being thickened and prevented from being discharged from the nozzle. Therefore, during this period, by preventing the output signal from being transmitted to the amplifier circuit, the operation of the amplifier circuit can always be in a stable state. As a result, it is possible to correctly perform the discharge inspection.

  Here, the second pressure generated in the recording liquid by the second head driving unit may be a pressure within a range in which the recording liquid is not discharged from the recording head.

  A state in which the recording liquid is not ejected from the recording head occurs in a nozzle in which ejection driving for ejection inspection is not performed even during the ejection inspection or in a period before the ejection inspection. If such a state continues for a predetermined time, the recording liquid thickens as described above, and the recording liquid cannot be ejected from the nozzles provided in the recording head. For this reason, in order to suppress the thickening of the recording liquid, the recording head may be driven so that a pressure within a range in which the recording liquid is not discharged is generated in the recording liquid. At this time, the output signal is affected by the drive of the recording head. Therefore, during the period in which the recording head is driven in this way, the operation of the amplifier circuit can always be in a stable state by preventing the output signal from being transmitted to the amplifier circuit.

  Alternatively, the second pressure generated in the recording liquid by the second head driving unit may be a pressure for discharging the recording liquid from the recording head.

  During the discharge inspection or during the period before the discharge inspection, the recording liquid is discharged from the nozzles so that the recording liquid is not clogged in the nozzles provided in the recording head. In response to this, there is a case where flushing driving is performed in which the recording liquid is discharged from the recording head at a predetermined timing for recovery of the recording liquid discharge. For this reason, the recording head may be driven to generate a pressure in the recording liquid that can eject the recording liquid. At this time, the output signal is affected by the drive of the recording head. Therefore, during the period in which the recording head is driven in this way, the operation of the amplifier circuit can always be in a stable state by preventing the output signal from being transmitted to the amplifier circuit.

  The present invention can also be understood as a discharge inspection method. That is, by using a change in the voltage of the recording head that occurs when the recording liquid is discharged from the recording head having a predetermined voltage to the counter electrode toward the counter electrode, the recording liquid from the recording head A discharge inspection method for performing a discharge inspection for inspecting the presence or absence of discharge, wherein the recording head generates a first pressure in the recording liquid and discharges the recording liquid from the recording head for the discharge inspection. A first head driving step for driving the output head, an output signal acquisition step for acquiring a voltage change of the recording head as an output signal, a signal amplification step for amplifying the output signal by a predetermined amplifier circuit, and the output signal, A signal transmission step of intermittently transmitting to the signal amplification unit, wherein the signal transmission step includes at least a period during which the first head driving step drives the recording head. Characterized by transmitting the output signal to the signal amplification step.

  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. In addition, a process for realizing each function of the above-described discharge inspection apparatus may be added.

  Hereinafter, an example of a discharge inspection apparatus according to the present invention will be described using a recording apparatus as an embodiment equipped with the apparatus. FIG. 1 shows a schematic structure of an ink jet printer 10 as a recording apparatus in which a discharge inspection apparatus according to the present invention is incorporated. The inkjet printer 10 includes a carriage 20 mounted with ink cartridges 11 to 14 that store inks of Y (yellow), M (magenta), C (cyan), and K (black) as recording liquids. When the print medium 25 as a recording medium moves in the vertical direction of the drawing, ink droplets are ejected from the recording head 30 provided on the back side of the drawing of the carriage 20 and supported by the platen 28 from the back side of the drawing. A predetermined image or the like is printed on the printed medium 25.

  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. At this time, an image can be printed correctly by ejecting predetermined ink droplets corresponding to the image to be printed from a plurality of nozzles for ejecting each color ink provided in the recording head 30. 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, or at the end of the print job, the recording head A discharge inspection is performed on the plurality of nozzles provided at 30 to inspect whether 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.

  In the ejection inspection, for example, flushing driving or fine vibration driving described later may be performed on the recording head 30 at a predetermined timing, for example, during the ejection inspection or before the ejection inspection. The flushing drive is performed in order to recover the ink clogging of the nozzles provided in the recording head 30 or to prevent the ink surface state (meniscus) from being thickened at the tip of the nozzles. Is generated, and ink droplets are ejected from the nozzles. In addition, the fine vibration drive is a drive that generates a minute pressure within a range in which ink droplets are not ejected from the nozzles in the ink in the recording head 30 in order to prevent ink from being thickened and being unable to eject from the nozzles. Is the method.

  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 and the sub-control circuit operate in cooperation with each other by exchanging data between the 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. Further, the above-described ejection inspection inspection timing and the flushing drive and fine vibration drive execution timing are also stored in the processing routine program recorded 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 is a schematic diagram illustrating an apparatus configuration for determining whether ink droplets are ejected by using charged ink droplets and applying pressure to each of the plurality of nozzles provided in the recording head 30 to eject ink. FIG. 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 recording head 30 through a supply path (not shown) is ejected from the recording 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 recording head 30 using the connecting member 65. Of course, the portion to which the voltage Ve is applied in the recording head 30 is a portion (for example, the nozzle plate 34 (see FIG. 5)) that is electrically connected to the ink.

  In the present embodiment, the voltage applied to the recording 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 recording head 30 side to the electrode member 71 side between the electrode member 71 in the inspection box electrically connected to the frame 17. As a result, the recording head 30 is positively charged and the electrode member 71 is negatively charged.

  When the ink droplet 39 is ejected from the recording head 30, the ink droplet 39 is deprived of the positive charge charged from the recording head 30, and a positive charge flows through the resistor 64 to supplement the deprived positive charge. Therefore, a voltage drop occurs due to the positive charge flowing through the resistor 64 in this way, and the voltage of the recording head 30 changes (decreases). This change in voltage is acquired by the ASIC 61 via the capacitor 68 and amplified by an amplifier circuit described later formed in the ASIC 61. Then, the presence or absence of ejection is determined by comparing the amplified voltage change with a predetermined threshold.

  Each of the plurality of nozzles provided in the recording head 30 is formed with a pressure generating mechanism that generates pressure to eject ink for each nozzle. In the present 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. As a result, ink is ejected as ink droplets from the nozzles provided on the nozzle plate. Accordingly, by applying a voltage to the piezoelectric element corresponding to the nozzle to be inspected, it is possible to inspect whether or not an ink droplet has been 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 drive signal for the piezoelectric element. The driver substrate 31 is provided in the carriage 20 in the vicinity of the recording 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. 3 is an explanatory diagram for explaining a driving method of the piezoelectric element. In the present embodiment, the recording head 30 is provided with nozzle rows 35Y, 35M, 35C, and 35K corresponding to Y, M, C, and K, and each nozzle row has 180 nozzles from n = 1 to 180. Nozzle is formed. As described above, in the present embodiment, a total of 720 nozzles to be inspected are formed in the recording 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. In the main board 50, a total of four pulse signals of Pv, P1, P2, and P3 are sent in a section for printing an image corresponding to one pixel (also called a segment when the carriage 20 crosses one pixel interval). The original signal ODRV in which the unit signal (the balloon portion in FIG. 3) is repeatedly generated and the print signal PRTn are generated.

  The original signal ODRV includes a pulse signal Pv for causing the piezoelectric element to vibrate slightly so that the ink does not solidify in the nozzle, and pulse signals P1, P2 for ejecting one ink drop from the nozzle, respectively. P3. 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 print signal PRTn (n = 1 to 180) is a signal for specifying a nozzle signal for ejecting ink droplets from among the 180 nozzles for each YMCK nozzle row and selecting a pulse signal in the original signal ODRV. Therefore, the print signal PRTn is a signal for selectively supplying the nozzles by selecting the nozzles to eject ink and the pulse signals to be output based on the print data (the presence / absence of dots and their gradation values) at the time of printing. There is a signal for specifying a nozzle to eject ink for inspection and for selecting a pulse signal to be output at the time of ejection inspection. Further, in other cases, the signal is a signal for selecting a nozzle to be driven and a pulse signal necessary for driving in the case of micro vibration driving or flushing driving described later.

  These signals are output to the mask circuit provided on the driver board via the ASIC 61 as described above. The mask circuit is configured so that a pulse signal selected by the print signal PRTn among the original signals is output to a piezoelectric element corresponding to the nozzle that is also specified by the print signal PRTn. That is, the mask circuit is configured to output a pulse signal selected by the print signal PRTn among the pulse signals Pv, P1, P2, and P3 to the piezoelectric element corresponding to the selected nozzle to be inspected, and the mask. The circuit outputs the head drive signal DRVn. Thus, the head drive signal DRVn is generated. Of course, when the print signal PRTn is a signal that does not select all the pulse signals, the head drive signal DRVn is in a state where there is no pulse signal.

  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.

  Here, the CPU 51 functions as a first head drive unit according to the claims by causing the piezoelectric element to output a head drive signal DRVn in which the original signal ODRV is masked by the print signal PRTn for ejection inspection. Similarly, the CPU 51 outputs a head drive signal DRVn in which the original signal ODRV is masked by the print signal PRTn to a piezoelectric element corresponding to the nozzle to be driven in the case of micro vibration drive or flushing drive described later. It functions as the second head driving unit described. In the present embodiment, the CPU 51 uses the print signal PRTn input to the mask circuit provided on the driver board in this way for the ejection inspection and for other fine vibration driving or flushing driving, and the same mask circuit. Thus, the head drive signal DRVn masked with the original signal ODRV is outputted to function as the first head drive unit or the second head drive unit.

  Next, the discharge inspection performed by the discharge inspection apparatus incorporated in the inkjet printer 10 of the present embodiment will be specifically described with reference to FIG. FIG. 4 is a timing chart showing a case where one target nozzle for ejection inspection is selected and whether or not ink droplets are ejected is detected for each selected nozzle.

  First, a head drive signal DRV1 that outputs the pulse signals P1, P2, and P3 of the original signal ODRV from the discharge inspection start (time T = 0) to a period of two segments (until time T = t1) is generated by the print signal PRT1. . As a result, the piezoelectric element corresponding to the nozzle n = 1 is driven for a period of two segments. Thereafter, the state in which all the pulse signals are not output continues for two segments (time T = t1 to t2), and then the pulse signals P1, P2, and P3 among the original signals are also converted into two segments by the print signal PRT2. A head drive signal DRV2 output for a period (time T = t2 to t3) is generated. As a result, the piezoelectric element corresponding to the nozzle n = 2 is driven for a period of two segments. Thereafter, the state where all the pulse signals are not output continues for two segments (time T = t3 to t4).

  Basically, such driving is sequentially repeated after nozzle n = 3. In this way, the ejection inspection is performed by repeatedly driving the piezoelectric element between the two segments with respect to the inspection target nozzle and not driving the piezoelectric element between the two segments. In the present embodiment, for one inspection target nozzle of interest, a period of four segments in total, including two segments in which the piezoelectric element is driven and two segments in which the piezoelectric element is not driven, is inspected. This will be referred to as a nozzle discharge inspection period.

  By the way, in order to output the head drive signal without missing each pulse signal, it is necessary that the original signal ODRV and the print signals PRT1 and PRT2 are synchronized, as is apparent from the drawing. Therefore, in the present embodiment, it is assumed that the original signal ODRV and the print signal PRTn are synchronized with respect to the latch (LAT) signal. The LAT signal is normally used as one of the signals serving as a reference for various operations in the printer, and is a pulse signal having a predetermined pulse width that is output with a period of one segment. Of course, a signal other than the LAT signal (for example, a clock signal) may be used.

  Thus, when the piezoelectric element corresponding to the nozzle n = 1 is driven by the two-segment head drive signal DRV1 from the inspection start (T = 0) to the time t1, and ink droplets are ejected from the nozzle, recording is performed as described in FIG. Since the head 30 is positively charged, the charged ink droplet takes away the positive charge from the recording head 30. Then, the positive charge is replenished from the voltage generation circuit 62 through the resistor 64 in order to compensate for the lost positive charge. As a result, since a current flows through the resistor 64, the voltage of the recording head 30 decreases according to the number of ejections of the ink droplets 39.

  The magnitude of the decreasing voltage depends on the amount of positive charge taken away, and therefore approximately depends on the size (ink amount) of the ejected ink droplet 39. By the way, it is desirable that the voltage change is large in order to improve the accuracy of determination of the presence or absence of ejection in the ejection inspection. Therefore, in the present embodiment, the print signal PRTn is output so that the drive signals at the time of the ejection inspection are signals in which all the pulse signals P1, P2, and P3 exist between one segment.

  After that, the nozzle n = 1 is not driven to eject between the two segments from the time t1 to the time t2, so the ink droplet 39 is not ejected. As a result, the voltage between the recording head 30 and the electrode member 71 (hereinafter, “interelectrode voltage”) Gradually increases and then recovers to the voltage Ve applied at the start of the discharge inspection. In the present embodiment, the interelectrode voltage is treated as being recovered to the voltage Ve after two segments in this way.

  In this embodiment, such a discharge inspection period is set to 4 segments. However, the number of segments in which the piezoelectric elements are driven is not limited to 2 segments, and the number of segments in which the piezoelectric elements are not driven is also 2 segments. It is not limited to. Depending on the discharge conditions of the ink droplets, such as the amount of charge taken by one drop of ink and the number of discharges per segment, the voltage change between the measurement terminals is actually different. It is preferable to check in advance conditions that facilitate detection, such as the number of segments in which voltage recovery is reliably performed, and determine the number of these segments according to the conditions.

  In this embodiment, a segment where the piezoelectric element is not driven (also referred to as “off segment”) is provided so that the voltage of the recording head always decreases when ink droplets are ejected from the recording head. Although the voltage recovery of the voltage is performed, there is no problem even if the off segment is not provided. In this way, the time required for the discharge inspection can be shortened.

  When the off-segment is not provided, there is a case where the voltage does not change except when the voltage change of the recording head decreases when the ink droplet is ejected from the recording head. That is, even when ink droplets are ejected from the recording head, the positive charge replenished through the resistor 64 does not increase. Therefore, when no off-segment is provided, it is only necessary to determine the presence or absence of ejection in consideration of such a voltage change.

  Next, from time t2 to time t3 by the print signal PRT2, the head drive signal DRV2 between the two segments is output to the nozzle n = 2, and when the ink droplet is ejected, the voltage Ve is again adjusted in accordance with the ejection number of the ink droplet. The voltage drops gradually, and the voltage between the electrodes decreases as in the case of nozzle n = 1. Thereafter, since the nozzle n = 2 is not driven for two segments from time t3 to t4, no ink droplet is ejected. As a result, the voltage between the electrodes gradually increases and then recovers to the voltage Ve. Such a voltage change is repeatedly generated between the electrodes of the recording head 30 and the electrode member 71 each time an ink droplet is ejected. Of course, when no ink droplet is ejected, the voltage Ve does not change, so the voltage Ve does not change.

  Therefore, with respect to the voltage that changes in this way, the direct current component is cut through the capacitor 68 (FIG. 2), and an output signal having an amplitude voltage that adds or subtracts only the voltage change component is taken out. By the way, the voltage Ve applied to the recording head is usually higher than the operating voltage of the ASIC 61 (for example, several tens to hundreds of volts). Accordingly, only the voltage change can be input to the ASIC 61 via the capacitor 68, and therefore the withstand voltage value of the ASIC 61 can be suppressed.

  As shown in the lower part of FIG. 4, the extracted output signal has an approximately sine wave shape. The extracted output signal is amplified by an amplifier circuit. Here, the capacitor 68 functions as an output signal acquisition unit described in claims, and the amplifier circuit 69 functions as a signal amplification unit described in claims.

  In the present embodiment, the capacitor 68 is used as the output signal acquisition unit. However, the present invention is not limited to this, and an element having a capacitive coupling function equivalent to the capacitor may be used. In addition to a capacitor, a well-known differentiation circuit using an operational amplifier or a resistor may be configured, and this differentiation circuit may be used as an output signal acquisition unit. Of course, any circuit configuration may be used as long as the change in voltage of the recording head can be acquired as an output signal.

  The output signal is usually a low voltage having an amplitude of about several hundred microvolts. Therefore, the output signal is amplified by an amplification circuit so that the amplitude voltage of the output signal after amplification is about several volts. When an ink droplet is ejected, an output signal having a predetermined amount of voltage amplitude is generated on the negative side, so that the voltage value on the negative side of the amplified output signal is a voltage value equal to or greater than a predetermined threshold value. Whether or not ink droplets are ejected is determined by checking whether or not the ink droplets are present. In other words, if a voltage change occurs according to the ejection of the ink droplet, it can be determined whether or not the ink droplet is ejected.

  However, the voltage between electrodes may change in a considerable range due to electric field noise from the outside of the printer, electric field noise from the inside of the printer, or the like. Alternatively, in order to prevent the ink from thickening and being unable to be ejected from the nozzles before the start of the ejection inspection or during the ejection inspection, the ink in the recording head is subjected to a minute pressure within a range not ejected as ink droplets. Flushing drive that ejects ink droplets is performed in order to perform fine vibration drive to be generated, to recover ink clogging of the nozzle, or to prevent thickening of the ink surface state (meniscus) at the tip of the nozzle There are many cases.

  In the fine vibration drive, the pulse signal Pv is output to the piezoelectric elements for all the nozzles (720 in this embodiment) provided in the recording head, and a large voltage change may be given to the voltage of the recording head. Can happen. Similarly, in the flushing drive, since at least one pulse signal among the pulse signals P1 to P3 is output to the piezoelectric elements corresponding to the plurality of nozzles, a large voltage change is given to the voltage of the recording head. It can happen. This will be described with reference to FIG.

  FIG. 5 is a schematic diagram illustrating a configuration of a pressure generation mechanism that generates pressure for ejecting ink droplets for each of the plurality of nozzles provided in the recording 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 (expanded). Then, since the GND electrode side is physically fixed, the member 33 is pushed down in the direction of the arrow (the lower side in the drawing), and for example, the ink 38 supplied from the ink cartridge 11 is pressurized. Therefore, the voltage applied to the COM electrode of the piezoelectric element corresponding to the nozzle to be inspected can generate a pressure for ejecting ink droplets from the nozzle, or a minute pressure that does not eject ink droplets. That is, as described above, the fine vibration driving is performed when the pulse signal Pv is output between the GND electrode and the COM electrode of the piezoelectric element, and the flashing is performed when at least one pulse signal among the pulse signals P1 to P3 is output. Each drive is performed. Of course, in the ejection inspection, all the pulse signals P1 to P3 are output as described above.

  At this time, since the member 33 and the ink 38 are equivalently interposed as a capacitor between the COM electrode of the piezoelectric element 32 and the nozzle plate 34, a change in the voltage applied to the COM electrode passes through the capacitor. The voltage is electrically transmitted to the nozzle plate 34, and as a result, the voltage value of the recording head 30 is affected to change the voltage. By the way, although the pulse signals P1 to P3 have a larger voltage value than the pulse signal Pv, only one piezoelectric element corresponding to the nozzle to be inspected is driven one by one in the ejection inspection. Only the pulse signals P1 to P3 are output only to the COM electrodes. Therefore, the change that the pulse signals P1 to P3 give to the voltage value of the recording head during the ejection inspection is small.

  However, it is clear that only one pulse signal Pv for micro-vibration driving has little influence, but piezoelectric elements (720 in this embodiment) corresponding to all the nozzles provided in the recording head 30. When the pulse signal Pv is applied to the other, the degree of influence thereof becomes considerably large, and the voltage of the nozzle plate 34, that is, the voltage between the electrodes is greatly changed. Similarly, in the flushing drive, since at least one of the pulse signals P1 to P3 is applied to the plurality of piezoelectric elements, the degree of influence thereof is considerably increased, and the voltage of the nozzle plate 34, that is, the voltage between the electrodes is greatly changed. End up.

  When a large change occurs in the voltage between the electrodes as described above, the amplitude voltage of the output signal becomes considerably larger than the amplitude voltage of the output signal generated when the ink droplet is ejected. On the other hand, the amplification circuit is set so that the output signal generated when ink droplets are ejected can be appropriately amplified. If such an output signal has a large amplitude voltage, it is amplified by the amplification circuit. The amplified output signal is in a saturated state where the output is shaken, and the operation of the amplifier circuit becomes unstable. Once the amplifier circuit is in an unstable operation state, the unstable operation state may continue for a while and the output signal may not be amplified correctly during that time.

  In such a state, even if the output signal generated by the ejection of the ink droplet is input to the input stage of the amplifier circuit, the output signal cannot be correctly amplified. Therefore, the ink droplet ejection inspection is performed using the amplified output signal after amplification. It cannot be done correctly. Therefore, the ejection inspection apparatus of the present invention prevents an output signal having an amplitude voltage larger than the amplitude voltage of the output signal generated along with the ejection of the ink droplet from being input to the input stage of the amplification circuit, and uses the amplified output signal. The present invention provides a discharge inspection apparatus capable of correctly performing a discharge inspection.

  Hereinafter, an embodiment of the discharge inspection apparatus of the present invention will be described with reference to FIG. FIG. 6 is a schematic diagram illustrating a configuration of a discharge inspection apparatus as one embodiment. Note that FIG. 6 is basically the same as the apparatus configuration shown in FIG. 2, and therefore the same configuration is indicated by the same reference numeral.

  As shown in FIG. 6, in this embodiment, there is an electrical connection between the input stage (reference numeral B in the figure) of the amplifier circuit 69 provided in the ASIC 61 and the output stage (reference numeral A in the figure) of the capacitor 68. A switch 80 for interrupting the general connection is interposed. The switch 80 is turned on (connected) and turned off (cut off) by the control signal SW, and the output signal generated at the output stage of the capacitor 68 is connected to or cut off from the input stage of the amplifier circuit at a predetermined timing. Thus, the signal is transmitted to the amplifier circuit 69. The switch 80 and the control signal SW correspond to a signal transmission unit described in claims.

  Further, by providing the switch 80 in the output stage of the capacitor 68 in this way, the voltage Ve having the normally high voltage value is not applied to the switch 80, so that the switch 80 has a withstand voltage value corresponding to the change in voltage. A switch having a low withstand voltage value can be used.

  In the present embodiment, the switch 80 is a switch configured by an electric circuit that electrically connects and disconnects. The switch 80 is constituted by a well-known analog switch circuit composed of an inverter and a MOS transistor, for example, as shown in a balloon part in the figure, and the output stage A of the capacitor 68 and the input of the amplifier circuit are controlled by a control signal SW. The stage B is configured to be connected or disconnected. Incidentally, according to the configuration of the analog switch shown in FIG. 6, when the control signal SW outputs a high level signal (for example, a predetermined positive voltage), the analog switch is turned off and the output stage A of the capacitor 68 is turned off. And the input stage B of the amplifier circuit are cut off, and the analog switch is turned on when the control signal SW outputs a low level signal (for example, a voltage of 0 volts), and the output stage A of the capacitor 68 and the input of the amplifier circuit Stage B is connected. By using an analog switch that electrically connects and disconnects in this way, the connection and disconnection can be switched at a higher speed than when mechanically switching.

  Of course, besides electrically disconnecting the connection, the voltage change of the output signal is converted into a light change (for example, light amount), and the converted light is converted again into a voltage change by the light receiving unit, so that the output signal is sent to the amplifier circuit. The switch 80 may be configured using an optical system for transmission. In this case, if any one of the conversion from the voltage change to the light quantity change or the conversion from the light quantity change to the voltage change is not performed, the transmission of the output signal can be controlled. Of course, if the intermittent speed is high, a mechanical switch using an electromagnetic relay or the like may be employed.

  Next, how the switch 80 configured in this manner is controlled by the control signal SW in the discharge inspection in this embodiment will be described with reference to FIG. FIG. 7 is a timing chart showing the state of output of main signals related to ejection inspection. In this embodiment, as shown in the drawing, it is assumed that after the flushing drive is performed before the discharge inspection, the discharge inspection is performed in order from the first nozzle. Then, after the discharge inspection of the second nozzle, the discharge inspection is temporarily stopped and the fine vibration drive is performed, and then the discharge inspection is started again from the third nozzle. Of course, such a timing chart is set for the convenience of explaining the effect of the embodiment shown in FIG. 6, and the fine vibration driving is performed before the inspection or the flushing driving is performed during the discharge inspection. Needless to say, the driving is actually performed in various patterns. As described above, each signal is synchronized with the LAT signal as a reference.

  First, a head driving signal for flushing driving between two segments before ejection inspection is output to the inspection target nozzle and a predetermined nozzle other than the inspection target based on the print signal. In this embodiment, as shown in the figure, pulse signals P1 to P3 are output for two segments to all the nozzles provided in the recording head, and the flushing drive is performed. Of course, when a plurality of nozzles to be flushed are determined in advance, the plurality of nozzles are flushed. Needless to say, the pulse signal for the flushing drive and the output period (here, between two segments) are not limited to this.

  When all the nozzles are flushed in this way, as described above, the interelectrode voltage changes greatly, and the amplitude voltage of the output signal increases. For this reason, an output signal having a large amplitude voltage is input to the amplifier circuit. As a result, when the amplified output signal after amplification is not controlled by the control signal SW (described later), the output is saturated as described above, and the operation of the amplifier circuit becomes unstable. . Therefore, even after the flushing drive, the discharge inspection is started, and even if the output signal having a voltage change due to the discharge of the ink droplet from the first nozzle is input to the amplifier circuit, the amplifier circuit is in an unstable operation state. As a result, the amplified output signal that is output is not a signal obtained by correctly amplifying the input output signal as shown in the figure. It should be noted that the behavior of the amplified output signal (without SW control) shown in FIG. 7 is an example, and of course varies depending on the circuit configuration of the amplifier circuit, the amplitude voltage of the output signal input to the amplifier circuit, and the like.

  Thus, since the amplified output signal does not amplify the output signal correctly, in the example shown in FIG. 7, the ejection inspection cannot be performed correctly for the first nozzle. Of course, when the unstable operation state of the amplifier circuit continues for a longer time, it goes without saying that the second and subsequent nozzles cannot be correctly inspected for ejection. Therefore, in order to correctly perform the ejection inspection, it is necessary to avoid performing the ejection inspection for a time until the operation of the amplifier circuit is stabilized, and as a result, there is a problem that the inspection time becomes longer. Become.

  Further, in FIG. 7, even when all the nozzles are finely driven during the discharge inspection for the second and third nozzles during the discharge inspection, the control by the control signal SW (described later) is not performed. Since the amplitude voltage of the output signal becomes large, the amplified output signal is saturated, and the operation of the amplifier circuit becomes unstable. Therefore, for the third nozzle to be inspected, the amplifier circuit is in an unstable operation state even if an output signal having a change in inter-electrode voltage due to ink droplet ejection is input to the amplifier circuit. As a result, the amplified output signal that is output is not a signal obtained by correctly amplifying the input output signal, as shown in the figure.

  Thus, once an output signal having a large amplitude voltage accompanying a voltage change larger than the change in interelectrode voltage due to ink droplet ejection is input to the amplifier circuit, the amplifier circuit becomes unstable. After that, the amplifier circuit cannot amplify the output signal correctly for a while. As a result, the above-described problem that the ejection inspection cannot be performed correctly occurs.

  Therefore, in this embodiment, the switch 80 is controlled by the control signal SW so that the output signal is not input to the amplifier circuit during the flushing drive period or the fine vibration drive period. That is, as shown in FIG. 7, the control signal SW is output at a high level during the flushing drive period and the slight vibration drive period, and the switch 80 is turned off (broken line in the figure). The switch 80 is turned on (solid line in the figure) by setting SW to a low level output. By doing so, it is possible to prevent the output signal from being input to the amplifier circuit during a period when a large amplitude voltage is generated in the output signal. Therefore, the amplifier circuit does not enter an unstable operation state, and a stable amplification state is always maintained. Therefore, the output signal generated along with the ejection of the ink droplet is correctly amplified by the amplifier circuit, and is displayed on the lower side of FIG. It is output as an output signal after amplification as shown (with SW control). As a result, it is possible to correctly perform the ink droplet ejection inspection for the first nozzle and the third nozzle. In addition, since it is not necessary to wait for the time discharge inspection until the operation of the amplifier circuit is stabilized, the above-described problem that the inspection time becomes long can be solved.

  In the present embodiment, the control signal SW is output at a high level in synchronization with the output timing of the LAT signal during the segment period corresponding to the flushing drive period or the fine vibration drive period. Specifically, when a head drive signal is output from the mask circuit, the CPU 51 (see FIG. 1) determines whether it is flushing drive or fine vibration drive based on a processing routine program stored in the ROM 52. As described above, the inkjet printer 10 performs nozzle ejection inspection, flushing drive, and micro-vibration drive at predetermined timings in accordance with a processing routine program such as an ejection inspection program. Therefore, the CPU 51 determines this predetermined timing, and the control signal SW is set to a high level output in synchronization with the output timing of the LAT signal during the flushing drive and fine vibration drive periods.

  By outputting the control signal SW in this way, the switch 80 can be turned off for a period that matches the period of the flushing drive or the fine vibration drive. That is, since the switch 80 can be reliably turned off during a period in which a large amplitude voltage may be applied to the output signal, the on / off operation of the switch 80 can be effectively performed.

  As described above, according to the present embodiment, when the flushing drive or the micro vibration drive is performed before or during the discharge inspection, the amplification operation of the amplifier circuit is caused by these drives. In order not to be affected by the amplitude voltage of the output signal, a switch can be provided in the input stage to the amplifier circuit to control the input of the output signal. As a result, in the discharge inspection, by suppressing the voltage change due to factors other than the ink droplet discharge from being input to the amplification circuit, it is possible to correctly detect the voltage change caused by the ink droplet discharge. An inspection apparatus can be provided.

  Although the present invention has been described with respect to the discharge inspection apparatus mounted on the ink jet printer as one embodiment, the present invention is not limited to these embodiments and examples. Needless to say, the present invention can be implemented in various modes within the scope of the above. Hereinafter, a modification will be described.

(First modification)
In the above embodiment, the switching of the output signal is controlled by using one switch 80, but the switching may be performed by a plurality of switches. An analog switch used as an electrical switch may have a case where an output signal leaks depending on the characteristics of a configured circuit and a large amplitude voltage is input to an amplifier circuit. Therefore, in such a case, by using a plurality of analog switches, the insulation can be improved and this leakage can be suppressed.

  This modification is shown in FIG. In this example, two analog switches are connected in series to form a switch. These two switches 81 and 82 are controlled so as to be simultaneously in the off state (the state shown in the figure) when the control signal SW is at a high level, as in the above embodiment, and the output signal from the capacitor 68 Are not input to the amplifier circuit 69. Therefore, since the transmission of the output signal to the amplifier circuit 69 is suppressed by the two switches, the probability of reducing the leak amount of the output signal is increased. Of course, it can be expected that the leakage of the output signal can be further suppressed by configuring the switch using a plurality of analog switches greater than two.

  In the present modification, the potential between the switch 81 and the switch 82 may be controlled to be the ground potential when the switch 81 and the switch 82 are in the off state. An example of this is shown in FIG. As shown in the figure, when a switch 83 is provided between the potential between the two switches 81 and 82 and the ground potential, and the switch 81 and the switch 82 are simultaneously turned off (the state shown in the figure), The switch 83 is turned on (the state shown in the figure) to set the potential between the two switches 81 and 82 to the ground potential.

  In this way, when the output signal leaks from the switch 81, the leaked output signal can be supplied to the ground potential, that is, the “0 volt” side. Therefore, the output signal leaking from the switch 82 is further suppressed, and it can be expected that the leak amount of the output signal input to the amplifier circuit 69 is further suppressed.

  Note that the potential between the switch 81 and the switch 82 is set to the ground potential when the switch 83 is in the on state. However, the potential is not limited to the ground potential, and a leaked output signal can be suppressed. Any potential other than the ground potential can be used.

(Second modification)
In the above-described embodiment, when the on / off state of the switch 80 is used to control the intermittent state of the output signal, when the switch 80 is off, that is, when the output signal is cut off, the output stage A side of the capacitor 68 is determined in terms of potential. It is in a state where it is not connected to either. Therefore, the charge amount on the output stage A side of the capacitor 68 is held as it is, and when the switch 80 is turned on next time, the held charge amount is input to the amplifier circuit as an output signal. At this time, if the amount of charge held is large, the output signal becomes a signal having a large amplitude voltage, so that the operation of the amplifier circuit becomes unstable as described above. Therefore, as a modification, when the output signal is cut off, the output stage A side of the capacitor 68 may be grounded to the ground potential.

  This modification is shown in FIG. In this example, the switch 80 in FIG. 6 is replaced with a bistable switch 85. The switch 85 is controlled so as to be in an off state (state shown in the figure) when the control signal SW is at a high level as in the above embodiment, so that the output signal from the capacitor 68 is not input to the amplifier circuit 69. To. At the same time, the switch 85 electrically connects the output stage A side of the capacitor 68 to the frame 17 so as to be at the ground potential in this OFF state.

  In this way, it is expected that the charge held on the output stage A side of the capacitor 68 is neutralized by the charge from the ground potential and basically becomes the same potential as the ground potential. As a result, the amount of charge held in the capacitor 68 is reduced, and when the switch 85 is turned on and the output stage A of the capacitor 68 and the input stage B of the amplifier circuit 69 are connected, they are input to the amplifier circuit. It can be expected that the influence of the held charge amount on the amplitude voltage of the output signal is reduced. Accordingly, since the amplifier circuit operates stably from when the switch 85 is turned on, it is possible to immediately perform the discharge inspection.

  Further, in the present modification, when the switch 85 is in the OFF state, the potential of the input stage B of the amplifier circuit 69 may be controlled to be an intermediate potential with respect to the operating voltage of the amplifier circuit 69. An example of this is shown in FIG. As shown in the figure, when the switch 86 is provided and the switch 85 is turned off (the state shown in the figure), the switch 86 is turned on, so that the input stage B between the switch 85 and the amplifier circuit 69 is switched. The potential is set to an intermediate potential Vm with respect to the operating voltage of the amplifier circuit 69.

  In this way, when the switch 85 is turned on (the switch 86 is turned off) and the output stage A of the capacitor 68 and the input stage B of the amplifier circuit 69 are connected, the potential of the input stage of the amplifier circuit 69 is already present. Since it is almost the intermediate potential Vm of the operating voltage of the amplifier circuit, the amplitude voltage of the output signal can be correctly amplified on both the positive side and the negative side. Accordingly, since the amplifier circuit operates stably from when the switch 85 is turned on, it is possible to immediately perform the discharge inspection.

(Third Modification)
In the above embodiment, in the description of FIG. 7, when the flushing driving or the micro-vibration driving that greatly affects the amplitude voltage of the output signal is performed, the output signal is output using the switch 80 during the period during which the driving is performed. It was decided to block it so that it would not be input to the amplifier circuit. However, as described above, the voltage between electrodes may change in a considerable range due to electric field noise from the outside of the printer, electric field noise from the inside of the printer, or the like. In such a case, the amplitude voltage of the output signal may be greatly changed even if the flushing drive or the fine vibration drive is not performed. In particular, when the physical distance from the recording head 30 to the amplifier circuit 69 is long, the transmission path for transmitting the voltage change generated in the nozzle plate 34 to the amplifier circuit inevitably becomes long. In such a case, noise such as the above-described electric field noise from the outside is easily mixed in the transmission path, and therefore, the probability of changing the output signal is increased.

  Therefore, as a modification, the output signal is prevented from being input to the amplifier circuit even when the discharge inspection such as the flushing drive or the micro vibration drive is not performed when the discharge inspection is not performed. Also good. In other words, the output signal may be transmitted to the amplifier circuit only during the period during which the ejection inspection is performed. By doing so, the output signal is not transmitted to the amplifier circuit even when noise is mixed in the transmission path during the period when the ejection inspection is not performed, and thus the probability that the amplifier circuit is in a stable operation state is increased. Therefore, the probability of correctly performing the discharge inspection is increased.

  Specifically, in the present modification, for each target nozzle for discharge inspection, a discharge inspection period of a total of 4 segments, including 2 segments in which discharge drive is performed and the next 2 segments in which discharge drive is not subsequently performed, The output of the control signal SW is set to a low level output, and all other periods are set to a high level output. Thus, the switch is controlled so that the output signal is input to the amplifier circuit only during the ejection inspection period of each nozzle. Therefore, even when noise is mixed in the transmission path during the period when the ejection inspection is not performed, the output signal is not transmitted to the amplifier circuit, so that the probability that the amplifier circuit is in a stable operation state is increased.

  Further, in the present modification, the switch is controlled so that the output signal is input to the amplifying circuit only for the two-segment period in which the piezoelectric element for the ejection inspection is being driven for each ejection inspection target nozzle. It is good as well. In this way, even in the ejection inspection period of each nozzle, the output signal is amplified even if the voltage of the output signal changes greatly due to the noise described above during the period of two segments in which the piezoelectric element is not driven. Since the signal is not transmitted to the circuit, the amplifier circuit can be stably operated in the subsequent ejection inspection for the nozzle to be inspected. In this modification, the period during which the output signal is input to the amplifier circuit is only the two-segment period in which the piezoelectric element is driven. As described with reference to FIG. In this way, the amplitude voltage of the output signal, i.e., the negative voltage value is used for comparison with the threshold value. Presence / absence determination can be performed.

(Fourth modification)
In the above-described embodiment and each of the above-described modified examples, the switch is turned off when the output of the control signal SW is at a high level. However, in this modified example, when the output of the control signal SW is at a high level, It is also possible to turn on the switch. That is, the switch is turned on only during the ejection inspection period so that the output signal is input to the amplifier circuit. Specifically, the output of the control signal SW is an output obtained by inverting the output state shown in FIG. In this case, for example, if the switch is an analog switch shown in the balloon portion of FIG. 6, it can be realized by deleting the inverter to which the control signal SW is first input.

  In this way, only the ejection inspection period and the piezoelectric element driving period are grasped, and during that period, the control signal SW is set to the high level output, and the control signal SW is set to the low level output in all other periods. It will be good. Therefore, it is not necessary to determine a period other than the ejection inspection or the timing of the flushing drive or the fine vibration drive as described above. As a result, the CPU 51 only needs to determine the ejection inspection period and the piezoelectric element driving period for ejection inspection from the processing program recorded in the ROM 52, and the processing load is reduced.

(Other variations)
In the above-described embodiment, when a voltage for ejection inspection is applied between the recording head 30 and the electrode member 71, the recording head 30 side is applied to have a positive potential, but the electrode member 71 side has a positive potential. It is good also as applying. In this way, even when a high voltage cannot be applied to the recording head 30 side, such as in an ink jet printer having a configuration in which it is difficult to form a circuit that generates a high voltage near the recording head 30, it is possible to connect between measurement terminals. A voltage for discharge inspection can be applied. In this case, when the ink droplet is ejected, the amplitude voltage of the output signal is reversed. That is, in the above embodiment, when the ink droplets are ejected from the nozzles, the voltage fluctuates in the negative direction. In this case, the output signal voltage fluctuates in the positive direction. It is sufficient to set the threshold value on the plus side and perform the discharge determination.

  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 that discharges ink droplets onto a print medium using an ink jet printer has been described as one embodiment. However, the present invention is not limited to this. For example, an image, a figure, a character, etc. are recorded on a recording medium by discharging a recording liquid using an ink jet system, such as an ink jet recording apparatus which forms a wiring pattern by discharging a recording liquid onto a glass substrate or a resin substrate. The apparatus can be similarly implemented.

1 is a schematic structural diagram of an inkjet printer according to an embodiment of the present invention. The schematic diagram for demonstrating the structure of the discharge inspection apparatus as one Embodiment of this invention. FIG. 4 is an explanatory diagram illustrating a driving method for generating pressure on ink in a recording head. The timing chart of the main signals in the discharge inspection of this invention. FIG. 3 is a schematic diagram illustrating a configuration of a pressure generation mechanism for generating pressure in ink. The schematic diagram which shows the discharge test | inspection apparatus used as the Example of this invention. The timing chart of the main signals regarding the discharge inspection process in an Example. (A) (b) is a schematic diagram which shows the discharge inspection apparatus used as the 1st modification. (A) (b) is a schematic diagram which shows the discharge inspection apparatus used as the 2nd modification.

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 ... Recording head, 31 ... Driver board, 32 ... piezoelectric element, 33 ... member, 34 ... nozzle plate, 35 ... nozzle row, 38 ... ink, 39 ... ink droplet, 40 ... carriage motor, 41 ... carriage belt, 45 ... flexible board, 50 ... main board 50a ... main control circuit, 51 ... CPU, 52 ... ROM, 53 ... RAM, 54 ... flash memory, 55 ... I / F, 60 ... sub-board, 60a ... sub-control circuit, 61 ... ASIC, 62 ... voltage generation circuit 64: Resistance, 65: Connection member, 66: Connection member, 68: Capacitor, 69: Amplifier circuit, 0 ... inspection box, 71 ... electrode member, 72 ... ink absorber, 80～83,85,86 ... switch.

Claims (9)

By utilizing the change in voltage of the recording head that occurs when the recording liquid is discharged from the recording head having a predetermined voltage to the counter electrode toward the counter electrode, the recording liquid is discharged from the recording head. A discharge inspection apparatus for performing a discharge inspection for inspecting presence or absence,
A first head driving unit for driving the recording head to generate a first pressure in the recording liquid and to discharge the recording liquid from the recording head for the ejection inspection;
An output signal acquisition unit for acquiring a voltage change of the recording head as an output signal;
A signal amplifying unit for amplifying the output signal by a predetermined amplifier circuit;
A signal transmission unit that intermittently transmits the output signal to the signal amplification unit;
With
The ejection inspection apparatus, wherein the signal transmission unit transmits the output signal to the signal amplification unit while the first head driving unit is driving the recording head. The discharge inspection apparatus according to claim 1,
The discharge inspection apparatus according to claim 1, wherein the signal transmission unit includes an electric circuit that electrically interrupts transmission of the output signal. The discharge inspection apparatus according to claim 1 or 2,
The discharge inspection apparatus, wherein the signal transmission unit is provided in an input stage of an amplification circuit of the signal amplification unit. In the discharge inspection apparatus according to any one of claims 1 to 3,
A second head driving unit that drives the recording head for a predetermined period to generate a second pressure in the recording liquid during a period in which the first head driving unit is not driving the recording head; ,
The ejection inspection apparatus, wherein the signal transmission unit cuts off the output signal and does not transmit the output signal to the signal amplification unit during the predetermined period in which the second head driving unit is driving the recording head. In the discharge inspection apparatus according to claim 4,
The ejection inspection apparatus according to claim 1, wherein the predetermined period is a period before the start of ejection inspection for inspecting whether or not the recording liquid is ejected. The discharge inspection apparatus according to claim 4,
The ejection inspection apparatus according to claim 1, wherein the predetermined period is a period in the middle of ejection inspection for inspecting whether or not the recording liquid is ejected. The discharge inspection apparatus according to any one of claims 4 to 6,
The discharge inspection apparatus according to claim 2, wherein the second pressure generated by the second head driving unit in the recording liquid is a pressure within a range in which the recording liquid is not discharged from the recording head. The discharge inspection apparatus according to any one of claims 4 to 6,
The discharge inspection apparatus, wherein the second pressure generated by the second head driving unit in the recording liquid is a pressure for discharging the recording liquid from the recording head. By utilizing the change in voltage of the recording head that occurs when the recording liquid is discharged from the recording head having a predetermined voltage to the counter electrode toward the counter electrode, the recording liquid is discharged from the recording head. A discharge inspection method for performing a discharge inspection for inspecting presence or absence,
A first head driving step for driving the recording head to generate a first pressure in the recording liquid and to discharge the recording liquid from the recording head for the ejection inspection;
An output signal acquisition step of acquiring a voltage change of the recording head as an output signal;
A signal amplification step of amplifying the output signal with a predetermined amplification circuit;
A signal transmission step of intermittently transmitting the output signal to the signal amplification unit;
With
In the signal transmission step, the output signal is transmitted to the signal amplification step during the period when the first head driving step drives the recording head.

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