JP3156770U - Printing device - Google Patents

Abstract

The present invention relates to a printing apparatus for printing print data on paper using ink ejected from a plurality of nozzles in a recording head, and detects the presence of defective nozzles in the recording head before starting a printing operation. At the same time, it aims to detect which nozzle is a defective nozzle. A static head having a recording head having a plurality of nozzles for ejecting ink and at least two kinds of electrodes for detecting ink droplets of ink ejected from the plurality of nozzles. An electric sensor 6 and an electrostatic capacity detection unit 70 for detecting the electrostatic capacity between the two types of electrodes of the electrostatic sensor, and recording based on the change in the electrostatic capacity detected by the electrostatic capacity detection unit It is configured to detect, for each nozzle, whether ink is normally ejected from each nozzle on the head. [Selection] Figure 2

Description

  The present invention relates to a printing apparatus such as an ink jet printer for printing predetermined print data on a sheet using ink ejected from a plurality of nozzles installed in a recording head. In particular, the present invention relates to a printing apparatus having a nozzle clogging detection function for detecting nozzles in which clogging has occurred and ink has not been ejected normally.

  In general, in an ink jet printer, each nozzle of a recording head having a plurality of nozzles is clogged due to thickening of ink in the nozzle, mixing of bubbles, adhesion of dust from outside the nozzle, etc. It may become impossible to discharge normally. Normally, a nozzle in such a state is called a defective nozzle. If there is a defective nozzle, there will be a portion where ink is not ejected on the paper to be printed, so a printing failure state will occur. In order to prevent or eliminate this printing defect state, conventionally, when performing a printing operation for printing print data on paper, an operation called cleaning that continuously ejects ink from each nozzle of the recording head (Hereinafter, referred to as a nozzle cleaning operation).

  However, in the method of performing the nozzle cleaning operation as described above, it is not possible to know that there is a defective nozzle in a state where ink cannot be ejected normally until the actual printing operation is performed. The problem of consuming the money occurs.

  Incidentally, in some printing apparatuses, ink droplets ejected from the recording head are detected by an optical sensor, a direct current pulse or the like to determine whether or not the ink has fallen, and the nozzle cleaning operation is performed according to the determination result. There has also been a method of determining whether or not to do so. However, such a method causes a problem that the configuration becomes very complicated, and misjudgment occurs due to the influence of surrounding noise, ink droplets, etc., and ink is consumed wastefully. In addition, inconvenience may occur because it takes a long time to detect nozzle clogging and clean it.

  The present invention has been made in view of the above problems, and detects the presence of a defective nozzle in a recording head before starting a printing operation, and detects which nozzle in the recording head is a defective nozzle. It is an object of the present invention to provide a printing apparatus that can perform such a process.

  In order to solve the above problems, a printing apparatus of the present invention (for example, an ink jet printer) includes a recording head having a plurality of nozzles for ejecting ink used when printing print data on paper, An electrostatic sensor having at least two types of electrodes (also referred to as pads) for detecting ink droplets of ink ejected from the nozzle and a capacitance between the two types of electrodes of the electrostatic sensor are detected. Whether or not the ink is normally ejected from each nozzle on the recording head based on a change in capacitance detected by the capacitance detection unit. It is comprised so that it may detect for every nozzle.

  Preferably, in the printing apparatus of the present invention, the recording head is controlled so that a predetermined amount of ink can be ejected onto the electrostatic sensor one by one with respect to the nozzle. In particular, prior to the printing operation, it is desirable to control so that a predetermined amount of ink is ejected from each nozzle onto the electrostatic sensor.

  Further preferably, in the printing apparatus according to the present invention, the electrostatic sensor is capable of detecting a minute ink droplet or detecting the change in the capacitance with high accuracy. The gap between the seed electrodes is sufficiently narrow.

  Further preferably, in the printing apparatus of the present invention, the two types of electrodes of the electrostatic sensor are arranged substantially parallel to a surface of the recording head on which the nozzles are ejected.

  Further preferably, in the printing apparatus of the present invention, the two types of electrodes of the electrostatic sensor are disposed obliquely with respect to a surface of the recording head on which the nozzles are ejected. As a result, the ink ejected from the nozzle onto the electrostatic sensor easily flows down from the two types of electrodes of the electrostatic sensor.

  Further preferably, the printing apparatus of the present invention includes a residual ink removing unit that removes ink remaining on the two types of electrodes of the electrostatic sensor.

  Further preferably, in the printing apparatus according to the present invention, the capacitance detection unit is configured by a microprocessor (also referred to as MPU (Micro Processing Unit)) having a function of detecting a change in the capacitance or a part thereof. Is done.

  Further preferably, in the printing apparatus according to the present invention, the electrostatic capacitance detection unit may be configured such that the electrostatic capacitance before the ink is ejected from each nozzle between the two types of electrodes of the electrostatic sensor. The electrostatic capacity after the ink is ejected is compared, and the change in the electrostatic capacity before the ink is ejected and after the ink is ejected is greater than or equal to a predetermined threshold value. If it is determined that the ink is normally ejected from the corresponding nozzle and the capacitance does not change or the change in capacitance is less than a predetermined threshold, It is determined that the ink is not normally ejected from the nozzle.

  Further preferably, in the printing apparatus according to the present invention, the residual ink removing unit is configured to perform the capacitance detection operation of one nozzle by the capacitance detection unit and then perform the electrostatic sensor 2 described above. The ink remaining on the seed electrode is removed, and the ink is prepared for the operation of ejecting the ink from the next nozzle.

  Further preferably, in the printing apparatus of the present invention, when the detection operation of all the nozzles is completed, the ink is discharged based on the detection result of the capacitance of each nozzle by the capacitance detection unit. A defective nozzle determined not to be ejected normally is extracted, and a cleaning operation is performed to eliminate the clogging of the defective nozzle. Desirably, the cleaning operation of the defective nozzle is performed by automatically removing ink or dust adhering to the defective nozzle using a removing means such as a spatula, or by discharging ink from the nozzle a plurality of times. Performed by trying.

  If necessary, after the defective nozzle cleaning operation is performed in the printing apparatus of the present invention, the defective nozzle detection operation may be performed again for each nozzle.

  According to the present invention, it is possible to determine whether each nozzle in the recording head is a defective nozzle before executing the printing operation for printing the print data on the paper, so the printing operation is started. It becomes possible to perform the cleaning operation of the defective nozzles before the paper is used, and the paper is not wasted.

  Furthermore, according to the present invention, since it is possible to determine which nozzle in the recording head is a defective nozzle, it becomes possible to perform a cleaning operation only on the defective nozzle, which wastes ink. There is no longer to do.

1 is a schematic diagram illustrating an overall configuration of a printing apparatus according to an embodiment of the present invention. It is a block diagram which expands and shows the principal part of the printing apparatus which concerns on the Example of this invention. It is a perspective view which expands and shows a part of electrostatic sensor of FIG. It is a flowchart which shows the procedure of the nozzle clogging detection control which concerns on the Example of this invention.

Hereinafter, the configuration and operation of a printing apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings (FIGS. 1 to 4).
FIG. 1 is a schematic diagram illustrating an overall configuration of a printing apparatus according to an embodiment of the present invention. Here, as a printing apparatus 3 according to an embodiment of the present invention, a configuration of an ink jet printer that performs a printing operation using ink ejected by an ink jet method is representatively shown.

  In the printing apparatus 3 of FIG. 1, a plurality of recording heads 1 are provided for ejecting a plurality of color inks used when printing predetermined print data on a sheet S, respectively. Here, three recording heads 1 for ejecting three color inks of cyan, magenta, and yellow are illustrated, but the embodiment of the present invention is limited to only these three recording heads. There is nothing. Each recording head 1 is fixed to a lower portion of an ink supply unit 10 including an ink cartridge for storing the corresponding ink and a carriage for holding the ink cartridge. Each recording head 1 has a plurality of print head nozzles (see FIG. 2). Each of the ink supply unit 10 and the recording head 1 performs the printing operation for printing the print data on the paper S (that is, in the period of the print mode) by the ink cartridge transport unit 12 on the paper S. It is conveyed to a predetermined position.

  Further, in the printing apparatus 3 of FIG. 1, the nozzle clogging detection unit 2 that is an indispensable constituent element of the present invention is provided at a position outside the installation place of the paper S. The nozzle clogging detection unit 2 includes an electrostatic sensor (see FIG. 2) having a function of detecting ink droplets of mist-like ink ejected from a plurality of print head nozzles (see FIG. 2) in the recording head 1. And a capacitance detecting unit (see FIG. 2) for detecting the capacitance between the two types of electrodes (see FIG. 2) of the electrostatic sensor. The specific configuration of the nozzle clogging detection unit 2 will be described in detail with reference to FIG.

  Further, in the printing apparatus 3 of FIG. 1, a residual ink removing unit 8 that removes ink remaining on the two types of electrodes of the electrostatic sensor is provided at a position away from the installation location of the paper S. The residual ink removing unit 8 is configured after the capacitance detecting unit of the nozzle clogging detecting unit 2 detects the capacitance of one print head nozzle (that is, during the residual ink cleaning mode). The ink remaining on the two electrodes of the electrostatic sensor is removed as much as possible. As a result, even in the operation of ejecting ink from the next print head nozzle, it is possible to reliably detect the change in capacitance between the two types of electrodes. Preferably, in the residual ink removing section 8, in order to remove as much as possible the ink remaining on the two types of electrodes, the ink may be removed by contact with rubber or sponge, or air pressure or the like may be used. The ink may be removed. However, it should be noted that the residual ink removing unit 8 is not necessarily an essential component of the present invention, as will be described later.

  Further, in the printing apparatus 3 of FIG. 1, a host computer that comprehensively controls the operations of the recording head 1, the ink supply unit 10, the ink cartridge transport unit 12, the nozzle clogging detection unit 2 and the residual ink removal unit 8. A host device (not shown) such as a host computer is provided.

  FIG. 2 is an enlarged configuration diagram illustrating a main part of the printing apparatus according to the embodiment of the present invention, and FIG. 3 is an enlarged perspective view illustrating a part of the electrostatic sensor of FIG. FIG. 2 illustrates a specific configuration of the recording head 1 and a specific configuration of the nozzle clogging detection unit 2 that is an essential component of the present invention. Hereinafter, the same components as those described above are denoted by the same reference numerals.

  As shown in the configuration diagram of FIG. 3, for example, a plurality of print head nozzles (hereinafter simply referred to as nozzles) 4 having 300 to 400 slits are installed in each recording head 1. Furthermore, each nozzle in the plurality of nozzles 4 has a hollow portion for storing ink supplied from the ink supply unit 10 and a tip portion having a shape of a thin slit for ejecting mist-like ink by an ink jet method. And have. A nozzle fixing frame 14 is provided around each nozzle. Each nozzle fixing frame 14 is joined to each other by a joining portion 16, and is installed and fixed in the recording head 1 together with each nozzle 4. Further, the recording head 1 in which a plurality of nozzles are installed is fixed to the lower part of the ink supply unit 10 via a holding member 18.

  In the recording head 1 having the above-described structure, mist-like ink is ejected from the tip portion of each nozzle 4 and drops onto the electrostatic sensor 6 in the form of ink droplets 5. Here, the ink is sequentially ejected from the tip of each nozzle 4 in the recording head 1 toward the electrostatic sensor 6 in a time-series manner and at a constant cycle. Therefore, the recording head 1 is preferably controlled by a host device or the like so that a predetermined amount of ink can be ejected from the nozzles 4 onto the electrostatic sensor 6 one by one. . In particular, during a nozzle check mode period before the printing operation is performed, control is performed so that a predetermined amount of ink is ejected from each nozzle 4 onto the electrostatic sensor 6 one by one. desirable.

  In the embodiment of FIGS. 1 and 2, it is assumed that ink is ejected from each nozzle by the ink jet method, but it is also possible to eject ink from each nozzle by a method using a piezoelectric element. Further, in the embodiment of FIGS. 1 and 2, it is assumed that ink is ejected sequentially from each nozzle in a time-series manner and at a constant cycle, but it is also possible to eject ink from a plurality of nozzles simultaneously. .

  Further, as shown in FIG. 2, the nozzle clogging detection units 2 are arranged in an array or a grid in order to capture and detect ink droplets 5 of ink ejected from each nozzle 4. An electrostatic sensor 6 having seed electrodes (for example, an electrostatic sensor electrode 6a and an earth (GND) electrode 6b) and an electrostatic capacity between the electrostatic sensor electrode 6a of the electrostatic sensor 6 and the earth electrode 6b And a capacitance detecting unit 70 for detection. The electrostatic sensor electrode 6a and the ground electrode 6b of the electrostatic sensor 6 are separated from each other, a weak DC signal is applied to the electrostatic sensor electrode 6a, and the ground electrode 6b has a ground potential (a potential of 0V). ) Is set. The electrostatic sensor electrode 6a and the ground electrode 6b can be made of any metal such as copper (Cu) or aluminum (Al). Preferably, the electrostatic sensor electrode 6a and the ground electrode 6b are produced by forming a thin conductive pattern such as copper or aluminum on a printed wiring board (also called a PCB (Printed Circuit Board)).

  Preferably, in order to be able to detect minute ink droplets 6, the ink droplets 6 are arranged in an array or a grid as shown in an enlarged view in FIG. 3. Control is performed so as to fall in such a manner as to completely cover any gap between the electrode 6a and the ground electrode 6b. Therefore, it is desirable for the electrostatic sensor 6 to make the gap between the electrostatic sensor electrode 6a and the ground electrode 6b as narrow as possible. However, the electrostatic sensor electrode 6a is detected to such an extent that a change in the electrostatic capacitance between the electrostatic sensor electrode 6a and the ground electrode 6b (that is, the capacitance value (capacitance) C) of the electrostatic capacitance can be accurately detected. This is not the case as long as the gap between the ground electrode 6b and the ground electrode 6b can be sufficiently narrowed.

  Preferably, the electrostatic sensor electrode 6a and the ground electrode 6b of the electrostatic sensor 6 are disposed substantially parallel to the surface of the recording head 1 where each nozzle 4 is ejected. Alternatively, the electrostatic sensor electrode 6a and the ground electrode 6b of the electrostatic sensor 6 are disposed obliquely with respect to the surface of the recording head 1 where each nozzle 4 is ejected. In this way, the ink ejected from each nozzle and dropped onto the electrostatic sensor electrode 6a and the ground electrode 6b easily flows down from the electrostatic sensor electrode 6a and the ground electrode 6b. In this case, since no ink remains on the electrostatic sensor electrode 6a and the ground electrode 6b, it is not necessary to provide the above-described residual ink removing unit 8 (see FIG. 1).

  Further, as shown in FIG. 2, the capacitance detection device 7 including the capacitance detection unit 70 is a micro having a function of detecting a change in capacitance between the electrostatic sensor electrode 6a and the ground electrode 6b. It is constituted by a processor (MPU). Preferably, in the embodiment of FIG. 2, PSoC® (also referred to as Pissock®) from Cypress Semiconductor is used as the microprocessor. However, any type of capacitance detection device can be used as long as it has a function of accurately detecting a change in capacitance between the electrostatic sensor electrode 6a and the ground electrode 6b.

  Further, as shown in FIG. 2, the capacitance detection device 7 receives a detection voltage (Vsense) proportional to the capacitance between the electrostatic sensor electrode 6a and the ground electrode 6b of the electrostatic sensor 6. A capacitance detection unit 70, and a digital comparator 72 that compares the detected value (Csense) with a preset reference capacitance (Cref) are provided. Furthermore, the electrostatic capacitance detection device 7 determines, for each nozzle, whether or not ink is normally ejected from each nozzle 4 based on the comparison result by the digital comparator 72, and defective nozzles related to each nozzle 4. The controller 74 for notifying the host device of the information (Dout) and the like, and information such as defective nozzles related to the respective nozzles 4 are stored, and various types of information related to control of the nozzle clogging detection operation such as defective nozzles are stored. And a storage unit 76 that performs such operations. Preferably, the capacitance detection unit 70, the digital comparator 72, the control unit 74, and the storage unit 76 are integrated and mounted as an integrated circuit on one substrate, and are commercialized as a microprocessor including one semiconductor chip. Has been.

  More specifically, the digital comparator 72 has an electrostatic capacity before ink is ejected from each nozzle 4 (corresponding to a reference capacity (Cref)) and after ink is ejected from each nozzle 4. Comparing with the capacitance (corresponding to the detection capacitance (Csense)), if the change in capacitance before ink ejection and after ink ejection is greater than or equal to a predetermined threshold, For example, a digital “1” value is output, and the capacitance does not change at all between before the ink is ejected and after the ink is ejected, or a change in the capacitance is a predetermined threshold value. If it is less than, for example, a digital “0” value is output. When the digital comparator 72 confirms that the change in capacitance is equal to or greater than a predetermined threshold, the control unit 74 determines that the ink is normally ejected from the corresponding nozzle, If the digital comparator 72 confirms that the capacitance does not change or the change in capacitance is less than a predetermined threshold, the ink is not ejected normally from the corresponding nozzle. (That is, the corresponding nozzle is a defective nozzle) and various controls including nozzle clogging detection control for the defective nozzle are performed. The storage unit 76 is configured by a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores information such as defective nozzles regarding each nozzle 4. Save various information related to the control of the nozzle clogging detection operation such as a defective nozzle.

  Preferably, the function of the control unit 74 is to execute various programs (software) stored in a storage unit 76 formed of a memory such as a RAM or a ROM by a CPU (Central Processing Unit) of a general-purpose computer. This is realized by reading and executing. Instead of the storage unit 76, a memory such as a RAM or a ROM built in the CPU can be used.

  Preferably, in the embodiment of FIG. 2, the control unit 74 is configured so that when the nozzle clogging detection operation for all the nozzles 4 is completed, the control unit 74 is connected between the electrostatic sensor electrode 6 a and the ground electrode 6 b by the capacitance detection device 7. Based on the detection result of the change in capacitance, the defective nozzles that are determined not to eject ink normally are extracted, and the nozzle cleaning operation is performed to eliminate clogging of the defective nozzles. The recording head 1 and the like are controlled. Desirably, the cleaning operation of the defective nozzle is performed by automatically removing ink or dust adhering to the defective nozzle using a removing means such as a spatula, or by discharging ink from the nozzle a plurality of times. Performed by trying. In such a cleaning operation, after determining which nozzles in the recording head 1 are defective nozzles, ink ejection is attempted a plurality of times targeting only the defective nozzles. Ink is not wasted as in the case where ink ejection is attempted.

  Further, preferably, in the embodiment of FIG. 2, after the defective nozzle cleaning operation is performed, the control unit 74 performs the defective nozzle detection operation for each nozzle 4 again so as to perform the defective nozzle detection operation again. You may control the electric capacity detection apparatus 7 grade | etc.,.

  According to the embodiment of the present invention, a change in the capacitance between the two types of electrodes of the electrostatic sensor is detected for each nozzle by the capacitance detection unit during the nozzle check mode before executing the printing operation. As a result, it is possible to determine whether each nozzle in the recording head is a defective nozzle. Therefore, it is possible to perform a cleaning operation for the defective nozzle before starting the printing operation, and waste paper. There is no longer to do.

  Furthermore, according to the embodiment of the present invention, by detecting the change in capacitance between the two types of electrodes of the electrostatic sensor for each nozzle by the capacitance detection unit, which nozzle in the recording head is a defective nozzle. Therefore, it is possible to perform the cleaning operation only on the defective nozzle, and the ink is not wasted.

  FIG. 4 is a flowchart showing the procedure of nozzle clogging detection control according to the embodiment of the present invention. Here, a description will be given of a procedure for performing nozzle clogging detection control of a defective nozzle by operating a control unit configured by a CPU or the like.

  As shown in step S1 of the flowchart of FIG. 4, the control unit starts electrostatic discharge from one nozzle (for example, the nozzle of the Nth channel (N is a positive integer of 1 or more) channel) after starting the nozzle check mode. Ink is ejected onto the sensor.

  Next, as shown in step S <b> 2, the control unit scans the electrostatic sensor so that ink droplets falling on the electrostatic sensor electrode and the ground electrode of the electrostatic sensor are detected by the electrostatic sensor. Control.

  Further, as shown in step S3, a capacitance between the electrostatic sensor electrode and the ground electrode of the electrostatic sensor is detected by a capacitance detection unit such as a microprocessor.

  Further, as shown in step S4, the capacitance value after the ink is ejected from the nozzle of the Nth channel and the reference value (that is, before the ink is ejected from the nozzle of the Nth channel). Whether or not the capacitance value of the capacitance after the ink is ejected has changed with respect to the reference value (that is, the capacitance after the ink has been ejected). Whether or not the change in the capacitance value is equal to or greater than a predetermined threshold value).

  As a result of the determination in step S4, when it is determined that the capacitance value of the electrostatic capacity after the ink is ejected has changed with respect to the reference value, the process proceeds to step S5, and the ink is discharged from the nozzle of the Nth channel. It is determined that the ink is normally discharged, and nozzle information indicating that ink is normally discharged from the nozzle of the Nth channel is stored in the memory (for example, the capacitance value of the capacitance has changed). The digital “1” value shown is stored in memory).

  On the other hand, if it is determined as a result of determination in step S4 that the capacitance value of the electrostatic capacity after ink ejection has not changed with respect to the reference value, the process proceeds to step S6, and the Nth channel It is determined that the ink is not normally ejected from the nozzle (that is, the nozzle of the Nth channel is a defective nozzle), and nozzle information indicating that the ink is not ejected normally from the nozzle of the Nth channel is stored in the memory (For example, a digital “0” value indicating that the capacitance value of the capacitance has not changed is stored in the memory).

  Further, as shown in step S7, the electrostatic sensor electrode of the electrostatic sensor can be reliably detected even in the operation in which the ink is ejected from the nozzle of the next channel. In addition, cleaning of residual ink is performed to remove ink remaining on the ground electrode.

  As shown in step S8, it is determined whether or not the nozzle check regarding whether or not the ink is normally ejected from the nozzles of all the channels is completed.

  If it is determined as a result of the determination in step S8 that the nozzle check relating to whether or not the ink has been normally ejected from the nozzles of all channels has not been completed, the nozzle check has been completed as shown in step S9. A nozzle with no channel is selected, and the processing flow of steps S1 to S7 is repeated.

  On the other hand, if it is determined as a result of determination in step S8 that the nozzle check for all channels has been completed, the nozzle information for all channels is notified to the host device as shown in step S10. The nozzle check mode is completed by executing the processing flow of steps S1 to S10 as described above.

  The present invention has a simple configuration such as an electrostatic sensor or a microprocessor, and determines whether each nozzle in the recording head is a defective nozzle during a nozzle check mode period before executing a printing operation. And a printing apparatus such as an ink jet printer having a function of detecting which nozzle in the recording head is a defective nozzle.

DESCRIPTION OF SYMBOLS 1 Recording head 2 Nozzle clogging detection part 3 Printing apparatus 4 Print head nozzle 5 Ink droplet 6 Electrostatic sensor 6a Electrostatic sensor electrode 6b Ground (GND) electrode 7 Capacitance detection apparatus 8 Residual ink removal part 10 Ink supply part 12 Ink cartridge transport unit 14 Nozzle fixing frame 16 Joining unit 18 Holding member 70 Capacitance detection unit 72 Digital comparator 74 Control unit 76 Storage unit

Claims (10)

A recording head having a plurality of nozzles for ejecting ink used for printing print data on paper;
An electrostatic sensor having at least two types of electrodes for detecting ink droplets of ink ejected from the nozzle;
A capacitance detecting unit that detects a capacitance between the two types of electrodes of the electrostatic sensor;
Based on a change in capacitance detected by the capacitance detection unit, it is configured to detect for each nozzle whether or not the ink is normally ejected from each nozzle on the recording head. A printing apparatus.   The printing apparatus according to claim 1, wherein the recording head is controlled so that a predetermined amount of ink can be ejected onto the electrostatic sensor one by one with respect to the nozzles.   The electrostatic sensor sufficiently narrows the gap between the two types of electrodes to such an extent that a minute ink droplet can be detected or a change in the capacitance can be accurately detected. The printing apparatus according to claim 1 or 2.   4. The printing apparatus according to claim 1, wherein the two types of electrodes of the electrostatic sensor are disposed substantially parallel to a surface of the recording head from which the nozzles are ejected. 5.   4. The printing apparatus according to claim 1, wherein the two types of electrodes of the electrostatic sensor are disposed obliquely with respect to a surface of the recording head on which the nozzles are ejected. 5.   The printing apparatus according to claim 1, further comprising a residual ink removing unit that removes ink remaining on the two types of electrodes of the electrostatic sensor.   The printing apparatus according to claim 1, wherein the capacitance detection unit includes a microprocessor having a function of detecting a change in the capacitance or a part thereof.   The capacitance detection unit includes the capacitance before the ink is ejected from each nozzle between the two types of electrodes of the electrostatic sensor, and the static after the ink is ejected. If the change in the capacitance before the ink is ejected and after the ink is ejected is equal to or greater than a predetermined threshold, the ink is normal from the corresponding nozzle. If the electrostatic capacity does not change or the change in the electrostatic capacity is less than a predetermined threshold, the ink is normally ejected from the corresponding nozzle. The printing apparatus according to any one of claims 1 to 6, wherein it is determined that there is not.   The residual ink removing unit removes ink remaining on the two types of electrodes of the electrostatic sensor after the capacitance detecting operation of one nozzle by the capacitance detecting unit is performed, The printing apparatus according to claim 6, wherein the printing apparatus is prepared for an operation of ejecting the ink from the next nozzle.   A defective nozzle that has been determined that the ink has not been ejected normally based on the detection result of the electrostatic capacity of each nozzle by the electrostatic capacity detection unit when the detection operation of all the nozzles has been completed. The printing apparatus according to claim 1, wherein a cleaning operation for removing clogging of the defective nozzle is performed.

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