JP2004167773A - Recording head, recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of an ink jet recording head such that all nozzles cannot be recovered to a sound state even if recovery operation is performed periodically, recovery operation may be performed uselessly under sound state, and it is difficult to detect soundness of all nozzles especially in a line printer having a wide recording head because a large scale intricate circuit is required. <P>SOLUTION: A microphone is built in a recording head and a sound incident to cavitation is measured on the output waveform from the microphone thus judging whether ejection is acceptable or not. Waiting time after applying a driving pulse before reading out the microphone output is set for each nozzle and the gain of an amplifier for the microphone output is set for each measuring nozzle thus judging acceptability of the nozzle with high reliability. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head and a recording apparatus having the ink jet recording head.
[0002]
More specifically, the present invention relates to a technique for detecting non-discharge of an ink nozzle.
[0003]
[Prior art]
An ink jet recording apparatus that supplies heat energy according to a driving pulse to ink to form bubbles by film boiling, and discharges the ink from a nozzle of a recording head onto a recording medium based on the formation of the bubbles to perform recording. An ink jet line head recording device (inkjet line printer) for fixing a line head in which a number of nozzles of a recording head are arranged perpendicularly to a sheet passing direction to convey and record a recording medium at a constant speed in order to improve speed is well known. Has been.
[0004]
In addition, in an ink jet recording apparatus, when recording is performed using liquid ink, if the recording head is not used for a long period of time, the recording head may be unhealthy (discharge, etc.) due to drying or thickening of the ink. In order to prevent the nozzle from being generated, the following measures have been mainly taken.
[0005]
To protect the printhead, cap the printhead when it is not printing (printing) to prevent the nozzles from drying out, and forcibly eject ink from the printhead nozzles if they have not been used for a long time. In addition, during recording, the recording head is moved to the capping mechanism in order to periodically discharge bubbles collected near the nozzles of the recording head during recording. The recording operation was performed in the cap to maintain the stability of the recording operation.
[0006]
However, even if the recovery operation is performed periodically, not all nozzles can always be recovered to a healthy state. Conversely, the recovery operation may be uselessly performed in a healthy state.
[0007]
Therefore, it is desirable to provide a recording apparatus provided with a mechanism for detecting non-ejection.
[0008]
However, accurately detecting whether all the nozzles of a recording head having a large number of ink nozzles, such as a line head recording device, are sound, is physically and circuitally complicated and large-scale, and is difficult to realize. there were.
[0009]
There is a method based on a method of converting a burst of ink ejected in a burst into an electrical signal.
(See, for example, Patent Document 1).
[0010]
[Patent Document 1]
JP-A-11-170569 (page 1, FIG. 1)
[0011]
[Problems to be solved by the invention]
However, in this method, there is a problem that the measurement is difficult unless the ejected ink droplet has a certain mass or more, and there is a concern that the method is easily affected by external noise.
[Means to solve the problem]
For this reason, according to the present invention, in an ink jet recording apparatus that performs recording by discharging ink droplets from a plurality of nozzles onto a recording medium using a recording head having a plurality of nozzles, a sound due to cavitation phenomenon that occurs when ink is heated and boils. Is converted into an electric signal, and a judging means for judging whether or not the ink is normally ejected from the converted electric signal at a timing synchronized with the drive pulse is provided.
[0012]
In addition, since a microphone element for sound wave measurement is incorporated in the recording head in a circuit manner and the measurement can be performed inside a sealed capping mechanism, reliability against external noise is high.
On the other hand, a plurality of microphone elements for converting sound due to the cavitation phenomenon into an electric signal can be provided for each fixed nozzle width.
[0013]
Further, when the determination means determines that non-ejection has occurred, a recovery operation can be performed.
[0014]
[Action]
By accurately detecting non-ejection of ink, recording stability and recording quality can be improved.
[0015]
Further, even when an unhealthy nozzle is accidentally generated, it is possible to prevent a large amount of useless paper from being generated.
[0016]
Further, useless recovery operation can be prevented.
[0017]
In particular, even with a recording head having many nozzles, such as a line printer using a line head in which the recording head is stationary during a recording operation, non-discharge can be detected more accurately with a simple configuration.
[0018]
【Example】
<Description of recording device>
FIG. 1 shows an example of an ink jet recording apparatus embodying the present invention.
FIG. 1A shows a standby state, in which a plurality of print heads (101K, C, LC, M, LM, 101Y) for color printing are capped (sealed) by a capping mechanism (102).
[0019]
Here, K: black, C: cyan, LC: light cyan, M: magenta, LM: light magenta, and Y: yellow. In the standby state, all motors and actuators are stopped.
[0020]
FIG. 1b shows a state during a recording operation, in which the capping mechanism (102) moves to the left, the recording head (101) moves in the vertical direction, and after moving to the recording position, keeps the stationary state. The recording medium (106) is picked one by one from the paper feeding unit (107) and fed to the main body (100).
[0021]
In the recording apparatus main body (100), the recording medium (106) sequentially passes under the recording heads (101K, C, LC, M, LM, and 101Y) at a constant speed by a transport belt (105) of a transport unit (104), and color printing is performed. Be recorded. Ink for recording is supplied from an independent ink cartridge (103) corresponding to each recording head to the recording head (101) via a tube (not shown).
[0022]
When the recording operation is completed, the operation returns to the standby state of FIG. 1A again.
FIGS. 2-1 to 2-3 show structural schematic diagrams of a recording head embodying the present invention.
[0023]
Each nozzle (202) is provided with a heating element (nozzle heater) (204) corresponding to the nozzle, and by applying a predetermined drive pulse to the nozzle heater (204) from a driver circuit, the ink in the nozzle is rapidly reduced. The ink (203) is selectively ejected from the nozzle (202) by the action of heating and boiling.
[0024]
A slight low-frequency vibration sound is generated in the nozzle due to the cavitation phenomenon at the time of rapid film boiling.
The nozzle heater (204) is patterned on, for example, a silicon substrate (205), and a part of a control circuit including a driver circuit is also patterned on an exposure surface (212) on the silicon substrate (205).
The silicon substrate (205) is structurally supported by the base plate (206).
[0025]
Each nozzle (202) is partitioned by a nozzle partition (207), and ink is supplied from a common liquid chamber (208). A recording head (101) is formed by closely contacting a member called a top plate (209) from above.
[0026]
The microphone element (201) is formed to have a structure in contact with the common liquid chamber (208) as shown in FIG. 2-2. The microphone element (201) is electrically connected to the silicon substrate (205) by bonding wires (210). ) Inject and insulate.
The microphone element (201) is preferably installed near the nozzle (202) in order to easily detect the sound due to the cavitation phenomenon.
A part of the vibration element including the conversion element is also patterned on the exposure surface (212) on the silicon substrate (205).
[0027]
When the nozzle heater (204) is heated and the ink in the vicinity follows a normal process of instantaneous boiling, growth of bubbles (ink ejection), and contraction of bubbles (ink refill), a cavitation phenomenon occurs. Since the microphone element (201) according to the present invention is in contact with the interior of the common liquid chamber of the ink, a good S / N ratio can be obtained.
After the conversion into an electric signal, if the output waveform exceeds a certain area, it can be determined that the ejection is normal.
[0028]
However, if the output does not reach the above range, it is determined that ejection has not been performed or that a fixed amount of ink droplets have not been ejected, and a recovery operation is executed.
[0029]
The recovery operation is performed by forcibly sucking ink from the nozzles, or by discharging tens to hundreds of ink droplets per nozzle in a relatively short time in a burst, and then wiping the vicinity of the nozzles with a cleaning blade (not shown). (Wiping) works.
In this embodiment, the recording head (101) has, for example, 2560 (# 1 to # 2560) nozzles and a nozzle pitch of 42.5 [μm], and therefore the resolution of the recording head (101) is 600 [dpi] (dot). / Inch), the maximum recording width is about 4.3 [inch].
[0030]
Next, a method of electrically converting vibration sound due to the cavitation phenomenon and a determination method will be described.
[0031]
FIG. 5 shows a signal waveform diagram output from the microphone (201).
[0032]
It is determined from the output waveform whether a normal ink droplet has been ejected from the nozzle. The time t from the application of the driving pulse hp to the nozzle heater (204) to the occurrence of the cavitation phenomenon to the peak value of the microphone output can be experimentally predicted by the energy applied to the nozzle heater (204), the distance between the nozzle and the microphone, and the like. Therefore, if the output near this time is larger than a preset threshold value e, it is determined that the ejection is normal, and if the output is smaller than the threshold e, it is determined that the ejection is defective.
[0033]
By judging the output from the drive pulse hp to the elapse of the time t, it is easy to eliminate the influence of external noise. Further, in the present embodiment, since the measurement is performed in the closed capping mechanism, more accurate results can be obtained.
Next, the process proceeds to measurement of the nozzle # 2, and the process is sequentially performed up to # 2560, and the quality of all nozzles is determined.
[0034]
Furthermore, in order to avoid the influence of noise, a method of obtaining a highly reliable result by repeatedly determining a certain number of times may be considered.
FIG. 4 is an electrical block diagram of a recording apparatus embodying the present invention.
[0035]
The host computer (300) transfers the recording data to be used for recording to the interface unit (302) of the recording apparatus and instructs the start of recording, and also instructs the number of recording media to be recorded and the type and size of the recording media. The command to be transferred can be transferred to the interface unit (302) and instructed.
[0036]
A CPU (Central Processing Unit) (301) is an arithmetic processing unit that performs overall control such as reception of print data of a printer, printing operation, and handling of a printing medium, and is controlled based on a control program stored in a ROM (303). Execute
After analyzing the received command, the CPU (301) develops bitmap image data of each color component of the print data in the image RAM (304) and draws the image data.
[0037]
As an operation process before recording, the CPU (301) mutually drives the capping motor (308) and the head motor (310) via the motor drive unit (307), and moves the recording head (101) from the capping position to the recording position. Move to
[0038]
Almost at the same time, the conveyance unit is driven by the paper feed motor (315) for feeding the recording medium (106) and the conveyance motor (309) to convey the recording medium (106) to the recording position.
[0039]
In order to determine the recording timing of the recording medium (106) conveyed at a constant speed, the leading edge position of the sheet is detected by sheet detecting means (not shown). In synchronization with the sheet conveyance, the CPU (301) sequentially reads out the image data of the corresponding color from the image RAM (304) and prints the corresponding color ink through the print head driving circuit (311). 101), and perform color recording.
[0040]
The operation panel (312) is a part for displaying a warning such as out-of-ink or the like and performing an operation such as reset. The operation of the CPU (301) is executed based on a processing program stored in the program ROM (303).
[0041]
A work RAM (305) is used as a work memory. An EEPROM (306) is a non-volatile memory for storing parameters unique to the apparatus, such as minute print position adjustment values between print heads.
The output of the microphone (201) is converted into a digital value by an AD converter (314) after being converted by a signal conversion circuit (313) composed of a noise filter, an amplifier, etc., and can be read almost in real time by a CPU (301). is there.
[0042]
The above control operation related to the nozzle check will be described with reference to the flowchart of FIG.
[0043]
First, if the printing operation is being performed, the operation is stopped (S401), and thereafter, the printing head is moved to the capping mechanism, the # 0001 nozzle is selected (S402), and ejection is performed (S403).
[0044]
The acoustic output of the cavitation generated at this time is waited for the propagation time tn (S405), and read out via the A / D converter (S405).
Since the waiting time tn set in S404 depends on the distance between the nozzle to be measured and the microphone, when the microphone (201) is set at the center of the nozzle row, as shown in FIG. Indicates a value.
These are stored in the table area of the ROM (303) in advance as a waiting time table.
If it is determined that the ejection has been normally performed as a result of the microphone output reading (S406-Yes), the nozzle NO is incremented (S407). If the ejection check of all the nozzles has not been completed (S408-No), the process returns to S403 and returns to S403. Start checking the nozzle.
If it is determined that the ejection is not performed normally as a result of the microphone output readout (S406-No), and if the defect is detected first (S409-No), the recovery operation of the recording head is executed (S410).
When the recovery operation is completed, the process returns to S402 to restart the check.
When the failure determination is repeated three times in S406 (S409-Yes), the CPU (301) suspends the operation because there is a possibility of permanent failure of the nozzle, and a display (not shown) on the operation panel (312). Outputs an alarm to
FIG. 6 shows a detailed example of the signal conversion circuit (313). If no discharge has occurred, the maximum value of the signal is output from the microphone (201) after time t in synchronization with the drive pulse.
[0045]
The output signal is amplified by an amplifier (501) to cut noise by a noise filter (502) and converted to a digital value by an AD converter (314).
[0046]
The CPU (301) reads the peak value of the acoustic signal output synchronized with the drive pulse.
[0047]
Here, the voltage amplification factor of the amplifier (501) with respect to the measurement nozzle will be described. Since the sound pressure attenuates in inverse proportion to the square of the distance from the measurement nozzle to the microphone (201), when the microphone (201) is arranged at the center of the recording head, when the nozzle # 1280 at the center is measured as shown in FIG. Is 0 [dB], a gain of less than 30 [dB] is required at both ends (# 0001, # 2560).
In the above correction, the CPU (301) controls the control terminal of the amplifier (501) with gain adjustment via a D / A converter (not shown). The voltage gain for the nozzle No (FIG. 9) is stored in a table format in the table area of the ROM (303) in advance.
[0048]
FIG. 7 shows another embodiment in which a plurality of microphones (201) are provided inside the recording head in order to increase the detection accuracy.
[0049]
In this example, for example, 2560 nozzles of the recording head are divided into nozzles # 1 to # 640, # 641 to # 1280, # 1281 to 1920, and # 1921 # 2560, and a microphone ( 201) are provided as four of 201a to 201d.
[0050]
Detection of non-discharge of the nozzles # 1 to # 640 is performed by the microphone 201a, # 641 to # 1280 201b, # 1281 to 1920 by 201c, and # 1921 to # 2560 by 201d.
[0051]
According to this configuration, since the microphone (201) is provided closer to the nozzle to be detected, detection accuracy can be improved.
[0052]
In this embodiment, the waiting time table corresponding to the nozzle number from the driving pulse to the nozzle heater to the reading of the microphone output is different from the table value in FIG. 8, but the creation method is the same.
Further, the voltage gain table of the amplifier (501) corresponding to the nozzle NO is also different from the table value of FIG. 9, but the concept regarding the creation is the same.
[0053]
【The invention's effect】
By providing conversion means for converting the sound of cavitation generated at the time of ink ejection into an electric signal, and determination means for judging whether or not ink is normally ejected from the converted electric signal at a timing synchronized with a drive pulse. In addition, it is possible to more accurately determine whether or not there is a nozzle in which a discharge failure occurs in a nozzle row of an inkjet recording head having a large number of nozzles, and it is possible to perform an appropriate recovery operation.
[0054]
In particular, in an ink jet line printer in which the recording head performs a recording operation in a stationary state, discharge failure can be detected more accurately with a simple configuration.
[0055]
According to the present invention, it is possible to further improve the recording quality and operation reliability of the ink jet recording system.
[0056]
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a recording apparatus embodying the present invention.
FIG. 2 is a schematic image diagram of detecting a discharge failure of a printing apparatus embodying the present invention.
FIG. 3 is an output signal waveform diagram of a microphone embodying the present invention.
FIG. 4 is an electrical block diagram of a recording apparatus embodying the present invention.
FIG. 5 is a control flowchart relating to ejection failure detection embodying the present invention.
FIG. 6 is an explanatory diagram of a signal conversion method for detecting discharge failure.
FIG. 7 is a schematic view showing another embodiment.
FIG. 8 is a diagram showing a waiting time for each nozzle from a nozzle driving pulse to reading of a microphone output value.
FIG. 9 is a diagram showing a voltage gain of an amplifier set for a nozzle to be measured.
[Explanation of symbols]
REFERENCE SIGNS LIST 100 recording device 101 recording head 102 capping mechanism 103 ink cartridge 104 transport unit 105 transport belt 106 recording medium 107 paper feed unit 201 microphone 202 nozzle 203 ink droplet 204 heating element (nozzle heater)
205 Silicon substrate 208 Common liquid chamber 209 Top plate 210 Bonding wire 211 Insulating member 300 Host computer 301 CPU
302 Interface section 303 Program ROM
304 Image RAM
305 Work RAM
306 EEPROM
307 Motor drive unit 308 Capping motor 309 Transport motor 310 Head U / D motor 311 Recording head drive circuit 312 Operation panel 313 Signal conversion circuit 314 A / D converter 315 Feed motor 501 Amplifier 502 Noise filter

Claims (18)

A plurality of nozzle heaters for heating ink to eject ink from a plurality of nozzles;
A driver for driving the plurality of nozzle heaters;
A recording head having a control circuit for controlling the driver, further comprising a sound wave detecting element that can be incorporated near the control circuit. The recording head according to claim 1, wherein a part of the sound wave detecting element is patterned together with the driver and the control circuit. A part of the sound wave detecting element is arranged so as to be in contact with a liquid chamber of a recording head,
The recording head according to claim 1. It is characterized by having a plurality of the sound wave detection element,
The recording head according to claim 1. A plurality of nozzles for discharging ink,
A recording head including a sound wave detection element arranged near the nozzle,
A reading unit for reading an output of the sound wave detecting element in synchronization with a drive pulse for driving the nozzle. 6. The recording apparatus according to claim 5, wherein the synchronization unit sets a delay time from the drive pulse. The recording apparatus according to claim 6, wherein the delay time is a value related to a position of a nozzle driven by the drive pulse. The recording apparatus according to claim 5, further comprising an amplifying means for amplifying an output of the sound wave detecting element. 9. The recording apparatus according to claim 8, further comprising a gain control means for controlling a gain of said amplification means. 10. The recording apparatus according to claim 9, wherein the gain controlled by the gain control means is a value related to the position of the driven nozzle. A plurality of nozzles for discharging ink,
A recording head including a sound wave detection element arranged near the nozzle,
A capping mechanism that caps the plurality of nozzles of the recording head and the sound wave detection element,
A reading unit for reading an output of the sound wave detecting element in synchronization with a drive pulse for driving the nozzle. 12. The recording apparatus according to claim 11, wherein the reading unit operates when the plurality of nozzles and the sound wave detecting element are capped. The recording apparatus according to claim 11, wherein the synchronization unit sets a delay time from the drive pulse. 14. The apparatus according to claim 13, wherein the delay time is a value related to a position of a nozzle driven by the drive pulse. 15. The printing apparatus according to claim 5, wherein a discharge level of a corresponding nozzle is determined based on a value read by the reading unit. 15. The recording apparatus according to claim 5, wherein the recovery operation of the recording head is performed when a value read by the reading unit does not reach a predetermined value. 17. A recording apparatus which outputs an alarm when a value read by the reading means does not reach a predetermined value even when the recovery operation according to claim 16 is executed a plurality of times. 18. The recording apparatus according to claim 5, wherein the sound wave detected by the sound wave detecting element is caused by a cavitation phenomenon occurring in a nozzle portion.

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