JP2009241376A - Nozzle checking method of inkjet head, inkjet head, and inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a nozzle checking method of an inkjet head which enables a nozzle to be checked even during printing in a short time. <P>SOLUTION: In the inkjet head of an inkjet printer 1, a sensing coil 33 is arranged around each nozzle 25a, and an ink supplied to each nozzle 25a is magnetized with a pair of magnets 31, 32. If an ink liquid droplet is discharged, a magnetic flux density of the circumference of the nozzle 25a varies, and an induced current generates in the circumference of the sensing coil 33. It can be checked with the nozzle whether the ink liquid droplet is normally discharged from the nozzle 25a based on the output value from a sensing terminal 33a of the sensing coil 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

INDUSTRIAL APPLICABILITY The present invention can employ a nozzle check method for detecting whether or not each nozzle of an inkjet head is in a state where ink droplets cannot be ejected or ink droplets are insufficiently ejected, and the nozzle check method can be employed. The present invention relates to an inkjet head and an inkjet printer equipped with the inkjet head.

In an ink jet printer, each nozzle of an ink jet head may become clogged due to thickening of ink remaining in the nozzle, mixing of bubbles, adhesion of foreign matters, etc., and it may become impossible to eject ink droplets. . In addition, the nozzle may be partially clogged, resulting in a discharge failure state in which a sufficient amount of ink droplets cannot be discharged. When printing is performed using an ink jet head including a nozzle that has fallen into such a state (hereinafter referred to as a defective nozzle), the print quality deteriorates. Therefore, the ink jet head is regularly or at a predetermined timing. Nozzle check is performed to detect the presence or absence of defective nozzles.

Patent Document 1 discloses a printer that performs nozzle check and head cleaning as part of startup processing when power is turned on. In the nozzle check method disclosed herein, the inkjet head is returned to the home position, opposed to the counter electrode plate arranged there with a certain gap, and a high voltage is applied between the nozzle surface of the inkjet head and the counter electrode substrate. In this state, ink droplets are ejected toward the counter electrode, the voltage of the induced current generated on the counter electrode substrate by the charged ink droplets landed on the counter electrode substrate is detected, and the ink is detected based on the voltage value. It is determined whether or not a droplet has been ejected. As a nozzle check method, there is a method for detecting whether or not an ink droplet is ejected from a nozzle by an optical sensor, and a method for detecting by an image analysis using a CCD camera as disclosed in Patent Document 2. Are known.
JP 2007-7960 A Japanese Patent Laying-Open No. 2006-04138

In the conventional nozzle check method, the inkjet head is returned to the home position and is opposed to the counter electrode substrate disposed there, or the detection area of the optical sensor or CCD
After positioning in the imaging region of the camera, it is necessary to actually eject ink droplets from each nozzle. For this reason, it takes time for the nozzle check, and if the nozzle check is frequently performed, the print throughput is greatly reduced.

In addition, since it is necessary to actually eject ink droplets from each nozzle, it is necessary to process the ejected ink droplets. Therefore, the nozzle check cannot be performed during printing, and the position is out of the print area. It is necessary to carry out the operation while facing the head cleaning mechanism. For this reason, it is suitable for nozzle check of serial type inkjet head,
It is impossible or difficult to use for the nozzle check of the line inkjet head including the print region and extending in the paper width direction.

Furthermore, in the nozzle check method disclosed in Patent Document 1, since a high voltage is applied between the nozzle surface and the counter electrode substrate, it is necessary to take EMC measures so that noise does not enter the drive control circuit of the ink jet printer.

In view of such problems, an object of the present invention is to propose a nozzle check method for an ink jet head that can perform a nozzle check in a shorter time than in the past.

Another object of the present invention is to propose a nozzle check method for an ink jet head that can perform a nozzle check during printing.

Another object of the present invention is to propose a nozzle check method for an ink jet head that can perform nozzle check without actually ejecting ink droplets.

A further object of the present invention is to propose an ink jet head and an ink jet printer that can employ a new nozzle check method.

In order to solve the above problems, the nozzle check method of the inkjet head of the present invention is:
Magnetize the ink supplied to the nozzles of the inkjet head,
Discharging an ink droplet made of the magnetized ink from the nozzle, or vibrating an ink meniscus formed of the magnetized ink formed on the nozzle;
Detecting a change in magnetic flux in the vicinity of the nozzle generated by ejection of the ink droplets or vibration of the ink meniscus;
Based on the detected magnetic flux change, it is determined whether or not the ink droplet ejection state from the nozzle is normal.

Here, in the nozzle check method of the present invention, the magnetic flux change is detected using a detection coil or a magnetic sensor attached to a position in the vicinity of the nozzle in the inkjet head.

According to the present invention, since it is not necessary to move the ink jet head to a predetermined nozzle check position, the nozzle check time can be greatly shortened. Moreover, the nozzle check of a line inkjet head can be performed. Furthermore, when performing a nozzle check based on a magnetic flux change caused by the vibration of the ink meniscus, it is possible to avoid wasteful consumption of ink just for a nozzle check that is not involved in printing, and the ink droplets discharged Processing is also unnecessary.

Next, the nozzle check method of the present invention is characterized in that the nozzle check is performed during the printing operation of the recording medium. In this way, the nozzle check can be performed in real time, and it is not necessary to secure a dedicated time for the nozzle check, and the print throughput does not decrease even if the nozzle check is frequently performed. Further, it is possible to avoid wasteful consumption of ink only for the nozzle check, and it is not necessary to process the discharged ink droplets.

In the nozzle check method of the present invention, a detection coil or a magnetic sensor for detecting the magnetic flux change is arranged at a position different from the inkjet head, and the detection coil is positioned in the vicinity of the nozzle. It is also possible to determine the state of the nozzle after moving the inkjet head.

Next, the inkjet head of the present invention is
A nozzle for ejecting ink droplets;
In order to detect a magnetic flux change caused by magnetized ink droplets ejected from the nozzle or a magnetic flux change caused by vibration of a meniscus of magnetized ink formed on the nozzle, a position near the nozzle And a detection coil or a magnetic sensor arranged in the above.

Here, if the detection coil or the magnetic sensor is arranged so as to surround the nozzle concentrically, it is possible to detect a change in magnetic flux with high accuracy.

The inkjet head includes a head body including an ink pressure chamber for generating an ink pressure for ejecting the ink droplets from the nozzle, and a nozzle plate in which the nozzle is formed, In the case where the nozzle plate is joined to the head body and the nozzle communicates with the ink pressure chamber, the detection coil or the magnetic sensor may be disposed on the nozzle plate. When the nozzle plate is manufactured, a fine conductive coil pattern of the detection coil can be formed by photolithography, and a multilayer detection coil thin film can be easily formed. In addition, a thin film manufacturing method such as vapor deposition, sputtering, and CVD, a thick film manufacturing method such as sintering, or a combination of these, the conductive film pattern of the detection coil on the nozzle plate, and the magnetic material layer and the wiring pattern that conducts to it. Can also be formed.

Furthermore, the inkjet head is generally configured to include a plurality of the nozzles and a plurality of the detection coils or magnetic sensors arranged to detect the magnetic flux change of each nozzle.

Further, it is determined whether each nozzle is normal based on a magnet for magnetizing the ink supplied to the nozzle and / or an induced electromotive force generated in the detection coil or an output of a magnetic sensor. It can be set as the structure provided with the discrimination means.

Next, an ink jet printer according to the present invention includes an ink jet head having a detection coil or a magnetic sensor for detecting a change in magnetic flux, a magnet for magnetizing ink supplied to each nozzle of the ink jet head, and each detection coil. And a discriminating means for discriminating whether each nozzle is normal based on the generated electromotive force or the output of the magnetic sensor.

According to the ink jet printer of the present invention, since it is not necessary to move the ink jet head for the nozzle check, the nozzle check time can be shortened. In addition, when the nozzle check is performed during printing, it is not necessary to provide time for the nozzle check. further,
When performing a nozzle check during printing, and when performing a nozzle check by vibrating the ink meniscus, it is possible to avoid consuming ink only for the nozzle check,
Processing of ink droplets ejected at the time of nozzle check is also unnecessary.

Embodiments of an ink jet printer to which the present invention is applied will be described below with reference to the drawings.

(Overall configuration of inkjet printer)
FIG. 1 is a schematic configuration diagram of an ink jet printer. The overall configuration of the inkjet printer 1 is a general one, and only the main part is shown. In this ink jet printer 1, the ink jet head 2, the paper feed mechanism 4 including the platen 3 facing the ink jet head 2, and the ink jet head 2 are reciprocated in the direction along the platen 3 (main scanning direction). A carriage mechanism 5 and an ink supply mechanism 8 for supplying ink from an ink tank 7 to the inkjet head 2 via an ink tube 6 are provided. There is a head cleaning mechanism 10 at a position outside the printing area on the side of the platen 3.
The head cap 11 is disposed. A waste ink collection tube 12 is connected to the head cap 11, and the waste ink collection tube 12 communicates with a waste ink tank 14 via a pump 13. The recording paper 15 is conveyed along the platen 3 by the paper feeding mechanism 4, and the inkjet head 2 performs printing by ejecting ink droplets onto the surface of the recording paper on the platen 3 while reciprocating by the carriage mechanism 5.

FIG. 2A is an explanatory diagram illustrating a cross-sectional configuration of one nozzle of the inkjet head 2. The ink-jet head 2 is of an electrostatic drive type that generates a discharge pressure of ink droplets by changing the volume of an ink pressure chamber communicating with a nozzle by vibrating a diaphragm using electrostatic force. Of course, another drive type ink jet head that generates a discharge pressure using a piezoelectric element or the like may be used. The ink jet head 2 of this example is an edge eject type that ejects ink droplets from nozzles provided on the end face of the substrate, but a face that ejects ink droplets from nozzles provided on the upper surface of the substrate. It may be of an eject type.

The ink jet head 2 has a head main body portion 24 formed by laminating three substrates 21, 22, and 23, and a nozzle plate 25 attached to the front end surface of the head main body portion 24. An ink pressure chamber 26, an orifice 27 communicating with the ink pressure chamber 26, and a common ink chamber 28 are formed between the substrates 21 and 22, and the ink supply port 21 is provided in the common ink chamber 28.
Ink is supplied from the side of the ink tank 7 via a and the ink tube 6. Board 2
2, the bottom wall portion of the ink pressure chamber 26 is a diaphragm 26a that can be bent in the out-of-plane direction. The individual electrodes 29 formed on the surface of the semiconductor substrate 23 with a certain gap are opposed to each other below the diaphragm 26a. The communication hole 26 b on the front end side of the ink pressure chamber 26 communicates with a nozzle 25 a formed in the nozzle plate 25.

The intermediate substrate 22 functions as a common electrode 30 having conductivity. When a driving voltage is applied between the individual electrode 29 and the common electrode 30, the vibration plate 26a is vibrated by the electrostatic force generated between them, and the ink pressure is increased. The volume of the chamber 26 changes. The vibration plate 26a is once sucked toward the individual electrode 29 to expand the ink pressure chamber 26. Then, the ink pressure chamber 26 is contracted, and ink droplets can be ejected from the nozzles 25a by the pressure change at the time of contraction. .

Here, a pair of magnets 31 and 32 are disposed on the upper surface of the substrate 21 of the inkjet head 2. These magnets 31 and 32 are arranged on both sides of the ink supply port 21a in order to magnetize the ink flowing into the common ink chamber 28 from the ink supply port 21a. Magnet 31,
32 may be a permanent magnet or an electromagnet. In the case of an electromagnet, an AC magnetic field may be generated. The nozzle 2 is disposed on the inner surface 25b of the nozzle plate 25.
The detection coil 33 is arranged in a state surrounding 5a.

FIG. 2B is an explanatory view showing the inner surface 25 b of the nozzle plate 25. As can be seen from this figure, the conductive thin film is patterned around the nozzle 25a so as to surround the nozzle 25a, thereby forming the detection coil 33 wound in a spiral shape. A detection terminal 33 a that is an outer end of the detection coil 33 is drawn to the edge side of the nozzle plate 25.
The inner end 33b of the detection coil 33 is electrically connected to the nozzle plate 25, and the nozzle plate 25 is set to the ground potential. Therefore, the detection coil 33 changes the magnetic flux density around the nozzle that is generated when the magnetized ink droplet is ejected from the nozzle 25a, or when the meniscus of the magnetized ink formed on the nozzle 25a vibrates. The change in the magnetic flux density around the nozzle can be detected, and the induced electromotive force corresponding to the change in the magnetic flux density is taken out from the detection terminal 33a of the detection coil 33.

Next, FIG. 3 is a functional block diagram showing the control system of the ink jet printer 1 centering on the drive control system of the ink jet head 2. In FIG. 3, reference numeral 40 denotes a printer control circuit centered on a CPU. The printer control circuit 40 includes a RAM 44, a ROM 45, and a character generator ROM via internal buses 41, 42, 43 including an address bus and a data bus. A (CG-ROM) 46 is connected. Various control programs are stored in the ROM 45, and an ink jet for printing print data supplied from the host device (not shown) on the basis of the activated control program called from the ROM 45. Drive control of the head 2, drive control of the paper feed mechanism, and drive control of the carriage mechanism are performed. The RAM 44 is used as a working area in drive control, and CG-RO
A dot pattern corresponding to the input character is developed in M46.

Reference numeral 50 denotes a head drive control circuit, which outputs a drive signal, a clock signal, and the like to the head driver 60 under the control of the printer control circuit 40. Further, print data DATA is supplied via the data bus 61. The head driver 60 is composed of, for example, a gate array, generates a driving voltage pulse corresponding to an input driving signal, and applies this between the individual electrode 29 and the common electrode 30 to be driven, Ink droplets are ejected from the corresponding nozzle 25a. In order to generate the drive voltage pulse signal, the head driver 60 includes:
A ground voltage GND, a drive voltage Vn, and the like are supplied. These are generated from the drive voltage Vcc of the power supply circuit 70.

Here, reference numeral 80 denotes a nozzle check circuit (determination means), to which detection signals of the detection coils 33 of the inkjet head 2 are supplied, and drive voltage pulse signals for driving the nozzles 25a are provided. Supplied. The nozzle check circuit 80 includes each detection coil 33.
Based on the detection signal, it is determined whether each nozzle 25a is normal or defective. The determination result (nozzle check result) is supplied to the printer control circuit 40.

(Nozzle check operation)
The printer control circuit 40 of the ink jet printer 1 moves the ink jet head 2 to the home position facing the head cap 11 of the head cleaning mechanism 10 periodically or at a predetermined time, and performs a nozzle check.

In the nozzle check, a driving voltage pulse for ejecting ink droplets is supplied to each nozzle 25a. Since the ink is magnetized by the pair of magnets 31 and 32, when ink droplets are ejected from the nozzles 25a, the magnetic flux density around the nozzles changes, thereby causing an induced current in each detection coil 33. appear. If the nozzle 25a is clogged, ink droplets will not be ejected, or the ink droplet ejection amount will be insufficient.
The induced current generated in each detection coil 33 is smaller than that in the normal state. The same applies to an ink meniscus described later. Therefore, when the voltage value of the induced current output from the detection terminal 33a of the detection coil 33 is less than the predetermined threshold, it can be determined that the nozzle 25a is a defective nozzle. In the nozzle check circuit 80, the output of the detection coil 33 of each nozzle 25a is compared with a predetermined threshold value, and if the output is a value equal to or greater than the threshold value, it is determined that the nozzle 25a is normal, and not so. In this case, it is determined that the nozzle 25a is a defective nozzle.

The determination result (nozzle check result) is supplied to the printer control circuit 40. If a defective nozzle is detected based on the determination result, the printer control circuit 40 causes the head cleaning mechanism 10 to perform a head cleaning operation for recovering the defective nozzle of the inkjet head 2.

FIG. 4 is an explanatory diagram showing a waveform example of the drive voltage pulse at the time of printing and nozzle check. In this example, the pulse width W1 of the energization pulse Pw1 (1) (i = 1, 2, 3,...) Is set so that the ink droplet ejection operation is performed by the striking method. That is, when the diaphragm 26a is attracted to the individual electrode 29 by the electrostatic force generated by the drive voltage pulse V, the volume of the ink pressure chamber 26 is thereby reduced, and the ink meniscus of the nozzle 25a is drawn inward. When the ink meniscus is drawn to the maximum, the diaphragm 26a
The pulse width W1 of the energization pulse Pw1 (i) is set so that can return to the original state. With this setting, the nozzle 25 is determined by the ink pressure accompanying the increase in the volume of the ink pressure chamber 26a due to the return of the vibration plate 26a and the kinetic energy at the time of elastic return of the vibration plate itself.
Ink droplets are ejected from a.

It is also possible to eject ink droplets by a pushing method. In this case,
As shown in FIG. 4B, the energization pulse Pw2 (with a pulse width W2 larger than the pulse width W1)
i) (i = 1, 2, 3...) is used.

(Other embodiments)
In the nozzle check, the ink meniscus may be vibrated without actually ejecting ink droplets, and the change in magnetic flux generated along with this may be detected by the detection coil 33. In this case, as shown in FIG. 4C, an energization pulse Pw3 (i) having a pulse width W3 smaller than the energization pulse Pw1 in the pulling method may be used. Such energization pulse Pw3
When the driving voltage pulse V is applied, the application of the driving voltage pulse V is canceled before the diaphragm 26a is sufficiently attracted to the individual electrode 29 side. As a result, as shown in FIG. 4D, the ink meniscus 35 of the nozzle 25a only vibrates back and forth within the nozzle 25a, and no ink droplets are ejected.

When the ink meniscus vibrates, the magnetic flux density around the nozzle 25a changes accordingly, and an induction current proportional to the magnitude of the change is generated in the detection coil 33. Therefore, when the output of the detection coil 33 is equal to or greater than a predetermined value, it can be determined that the nozzle 25a is normal. On the other hand, when the ink in the nozzle 25a is in a thickened state, the vibration width of the ink meniscus is small. Further, when the nozzle 25a is completely clogged, the ink meniscus does not vibrate. In this case, since the output of the detection coil 33 is small, it can be determined that the nozzle 25a is a defective nozzle.

Next, in the above example, the inkjet head 2 is moved to a position facing the head cap 11 of the head cleaning mechanism 10, and nozzle check is performed at this position. In this case, when a defective nozzle is detected by the nozzle check, there is an advantage that a head cleaning operation such as immediately ejecting ink droplets from each nozzle 25a can be performed. However, in the method of the present invention, since the ejection of ink droplets during printing can be detected by the detection coil 33, nozzle check can be performed in parallel even during printing.

In this case, in the nozzle check circuit 80, for the nozzle 25a to which the drive voltage pulse V is applied (that is, the nozzle instructed to eject the ink droplet), is the detection output of the detection coil 33 equal to or greater than the threshold value? By determining whether or not, the quality of the nozzle 25a can be detected. When a defective nozzle is detected, head cleaning may be performed at a time point after the end of printing.

On the other hand, in the above example, a pair of magnets 31 and 32 are attached to the inkjet head 2 to magnetize the ink. A magnet may be disposed on the main body side of the inkjet printer 1. That is, the ink may be magnetized by being disposed in a portion of the ink supply path from the ink tank 7 to the inkjet head 2.

In the above example, the nozzle check circuit 80 is disposed on the ink jet printer 1 side, but it can also be mounted on the ink jet head itself.

Next, in the above example, the detection coil 33 is attached to the inkjet head 2.
It is also possible to arrange the detection coil on the front surface of the head cap 11 in the head cleaning mechanism 10. In this case, the inkjet head 2 is moved, each nozzle 25a is positioned on the corresponding detection coil 33, and the nozzle check is performed in this state.

In the above example, the detection coil 33 has been described as detecting the magnetic flux. However, a magnetic sensor made of a magnetic material or the like may be used.

Next, the above example is a case where the present invention is applied to a serial type ink jet head. The nozzle check method of the present invention can also be applied to a line-type inkjet head.

1 is a schematic configuration diagram of a serial type ink jet printer to which the present invention is applicable. It is a schematic block diagram of the inkjet head of FIG. It is a functional block diagram which shows the control system of the inkjet printer of FIG. It is explanatory drawing which shows the example of an electricity supply pulse and a drive voltage pulse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer, 2 Inkjet head, 3 Platen, 4 Paper feed mechanism, 5 Carriage mechanism, 6 Ink tube, 7 Ink tank, 8 Ink supply mechanism, 10 Head cleaning mechanism, 11 Head cap, 12 Waste ink collection tube, 13 Pump , 14 Waste ink tank, 15 Recording paper, 21, 22, 23 Substrate, 21
a Ink supply port, 24 head body, 25 nozzle plate, 25a nozzle, 26
Ink pressure chamber, 26a Diaphragm, 26b Communication hole, 27 Orifice, 28 Common ink chamber, 29 Individual electrode, 30 Common electrode, 31, 32 Magnet, 33 Detection coil, 33a
Detection terminal 33b Inner end 35 Ink meniscus 40 Printer control circuit 41
, 42, 43 Internal bus, 44 RAM, 45 ROM, 46 CG-ROM, 50 Head drive control circuit, 60 Head driver, 70 Power supply circuit, 80 Nozzle check circuit

Claims (11)

Magnetize the ink supplied to the nozzles of the inkjet head,
Discharging an ink droplet made of the magnetized ink from the nozzle, or vibrating an ink meniscus formed of the magnetized ink formed on the nozzle;
Detecting a change in magnetic flux in the vicinity of the nozzle generated by ejection of the ink droplets or vibration of the ink meniscus;
An ink jet head nozzle check method comprising: determining whether or not an ink droplet ejection state from the nozzle is normal based on the detected magnetic flux change. The nozzle check method according to claim 1,
A method for checking a nozzle of an ink jet head, comprising: detecting a change in the magnetic flux using a detection coil or a magnetic sensor attached to a position near the nozzle in the ink jet head. In the nozzle check method according to claim 1 or 2,
A nozzle check method for an ink jet head, wherein the nozzle state is determined during a printing operation on a recording medium. The nozzle check method according to claim 1,
A detection coil or a magnetic sensor for detecting the magnetic flux change is arranged at a position different from the inkjet head,
Moving the inkjet head so that the detection coil or magnetic sensor is positioned near the nozzle;
A nozzle check method for an ink jet head, wherein the state of the nozzle is determined thereafter. A nozzle for ejecting ink droplets;
In order to detect magnetic flux changes caused by magnetized ink droplets ejected from the nozzles, or magnetic flux changes caused by vibrations of the meniscus of magnetized ink formed on the nozzles, An ink-jet head having a detection coil or a magnetic sensor arranged. In the inkjet head according to claim 5,
The inkjet head according to claim 1, wherein the detection coil or the magnetic sensor is arranged in a state of concentrically surrounding the nozzle. The inkjet head according to claim 5 or 6,
A head body including an ink pressure chamber for generating ink pressure for discharging the ink droplets from the nozzle;
A nozzle plate on which the nozzle is formed,
The nozzle plate is joined to the head body, and the nozzle communicates with the ink pressure chamber.
An ink jet head, wherein the detection coil or the magnetic sensor is arranged on the nozzle plate. The inkjet head according to any one of claims 5 to 7,
A plurality of the nozzles;
An inkjet head comprising a plurality of the detection coils or magnetic sensors arranged to detect the magnetic flux change of each nozzle. The inkjet head according to any one of claims 5 to 8,
An ink-jet head comprising a magnet for magnetizing the ink supplied to the nozzle. The inkjet head according to any one of claims 5 to 9,
An ink jet head comprising: a determination unit that determines whether each nozzle is normal based on an induced electromotive force generated in the detection coil or an output of a magnetic sensor. An ink jet head according to any one of claims 5 to 8,
A magnet for magnetizing the ink supplied to each nozzle of the inkjet head;
An ink jet printer comprising: a determination unit that determines whether each nozzle is normal based on an induced electromotive force generated in each detection coil or an output of a magnetic sensor.

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