|Publication number||USRE41609 E1|
|Application number||US 12/078,811|
|Publication date||Aug 31, 2010|
|Filing date||Apr 4, 2008|
|Priority date||Jun 11, 2002|
|Also published as||US7245756, US20030228046|
|Publication number||078811, 12078811, US RE41609 E1, US RE41609E1, US-E1-RE41609, USRE41609 E1, USRE41609E1|
|Inventors||Hiroshi Inoue, Yukio Sugita|
|Original Assignee||Fujifilm Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Classifications (14), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a liquid ejection inspecting method, liquid ejection inspector and image forming apparatus. More particularly, the present invention relates to a liquid ejection inspecting method and liquid ejection inspector in which inspection of liquid ejection to check failure can be effected efficiently without waste of consumables, and an image forming apparatus for use with the liquid.
2. Description Related to the Prior Art
An ink jet printer is known as an image forming apparatus. A printhead includes an ink reservoir for storing ink. Ejection nozzles are connected with the ink reservoir, and caused by an ink supply unit to eject the ink to print an image on a recording medium. The ink jet printer of the type known so far has problems in that ink is dried and deposited on the inside of the ejection nozzles, or that the surplus ink may be scattered by the recording medium, and come back to and deposit on a surface of the printhead, to cause jamming of ink.
When jamming of ink occurs, there is ejection failure in which an amount of ejected ink decreases, or comes down to zero. Unevenness in the density or colors occurs in a streak shape in a recorded image, to lower the image quality remarkably. Therefore, it is necessary in an ink jet printer to detect the ejection failure at the ejection nozzles, and to eliminate the ejection failure in the case of occurrence.
To check the ejection failure, various methods are known. JP-A 8-332736 and 11-078051 disclose test printing to eject test ink to the recording medium and inspection of the shape and arrangement of droplets of the ink. JP-A 11-192726, EP-A 1059172 (corresponding to JP-A 2001-054954), and JP-A 2001-063083 disclose methods in which droplets of test ink are ejected, a beam of laser or other electromagnetic rays is applied to the droplets, to detect a shielded state of the beam at the droplets.
However, those known techniques have problems. In the first of those methods, a test pattern must be recorded together with a target image without any relation. Also, ink for test printing is required in a wasteful manner. A space in the recording medium for receiving droplets of the ink is required for the test printing. In the second of those methods, the same problem occurs in ink for test printing is required in a wasteful manner. Specifically, density in image recording has been higher in recent techniques for printing. The number of the ejection nozzles as arranged in the printhead has been high. This causes a shortcoming in requirement of much time for the detecting the ejection failure. If the ejection failure is checked in the course of the printing, productivity or efficiency in the printing becomes lower.
In view of the foregoing problems, an object of the present invention is to provide a liquid ejection inspecting method and liquid ejection inspector in which inspection of liquid ejection to check failure can be effected rapidly and efficiently without waste of consumables, and an image forming apparatus for use with the liquid.
In order to achieve the above and other objects and advantages of this invention, a liquid ejection inspecting method is provided for an ejection nozzle array including plural ejection nozzles for ejecting liquid. In the liquid ejection inspecting method, the ejection nozzles are photographed in the ejection nozzle array, to output image data. The image data is analyzed to output analysis result information. It is judged whether an ejecting state of the ejection nozzles is acceptable or unacceptable according to the analysis result information.
In the analyzing step, predetermined reference image data is used, to check the image data by comparison.
Furthermore, if the ejection nozzles are in the unacceptable state, the ejection nozzles are wiped to eliminate foreign material.
The photographing, analyzing, and judging steps are effected again after the eliminating step. Furthermore, if the unacceptable state is judged again in the judging step, an alarm signal is generated.
According to another aspect of the invention, an image forming apparatus comprises at least one ejection nozzle array including plural ejection nozzles for ejecting liquid. A pickup device photographs the ejection nozzles in the ejection nozzle array, to output image data. An analyzer stores reference image data, and outputs analysis result information according to the image data and the reference image data. A determining unit judges whether an ejecting state of the ejection nozzles is acceptable or unacceptable according to the analysis result information.
Furthermore, a foreign material elimination unit eliminates foreign material from the ejection nozzles.
The reference image data is used in a pattern recognition process, and the analyzer and the determining unit cooperate to judge one of acceptable and unacceptable states of the ejection nozzles by evaluating the image data in the pattern recognition process.
The elimination unit is operated at least when the unacceptable state is judged according to the analysis result information.
According to the analysis result information, the elimination unit is selectively operated for unacceptable ejection nozzles included in the ejection nozzles and of which the unacceptable state is judged.
The analyzer further calculates a blocked area where the foreign material blocks the ejection nozzles according to the image data. Furthermore, a control unit changes a driving parameter of the elimination unit according to the blocked area.
The elimination unit is a suction unit for sucking the liquid out of the ejection nozzles, and the driving parameter is at least one of a pressure of suction of the suction unit, a length of time of the suction, and a number of times of the suction.
The liquid is ink, and the ejection nozzle array constitutes a printhead of an ink jet type, is adapted to image recording to recording material, and extends in a first scan direction. Furthermore, a control unit moves one of the printhead and the recording material relative to a remaining one thereof at a small adjusting shifted amount in the first scan direction, the adjusting shifted amount being equal to a pitch between an unacceptable nozzle of which the unacceptable state is judged and an acceptable nozzle close thereto and of which the acceptable state is judged among the ejection nozzles, the control unit causing the acceptable nozzle to eject the ink instead of the unacceptable nozzle, so as to compensate for lowering of image quality due to the unacceptable state.
Furthermore, a mode selector sets a selected one of an elimination mode and a nozzle substitution mode, and when the elimination mode is set, operates the elimination unit, and when the nozzle substitution mode is set, causes the control unit to operate the acceptable nozzle included in the ejection nozzles for substitution.
Furthermore, a carriage moves the printhead relative to the recording material in a second scan direction. The pickup device is arranged beside a printing surface of the recording material in the second scan direction, and is opposed to the printhead moved by the carriage.
Furthermore, an image history memory stores image history data constituted by plural sets of image data obtained previously. The analyzer judges whether the image data is within a range of the image history data, and if the image data is within the range of the image history data, determines the acceptable state of an ejection nozzle corresponding to the image data, and if the image data is outside the range of the image history data, determines an ejection nozzle corresponding to the image data as a failure-expected nozzle, and processes the image data for the failure-expected nozzle, to output the analysis result information.
The pickup device photographs the failure-expected nozzle when operated again.
The analyzer determines a difference between the image data and the reference image data, the difference constituting the analysis result information. The determining unit stores information of a predetermined threshold value adapted to the pattern recognition process, compares the difference with the threshold value, judges the acceptable state if the difference is equal to or less than the threshold value, and judges the unacceptable state if the difference is more than the threshold value.
The pickup device comprises a CCD or CMOS.
The above objects and advantages of the present invention will become more apparent from the following detailed description when read in connection with the accompanying drawings, in which:
The printhead 2 has a nozzle arrangement surface 2a opposed to the recording material 5. A plurality of ejection nozzles 7 are arranged in the printhead 2. An ink chamber 6 is connected to each of the ejection nozzles 7. An ink reservoir 8 stores ink. A passageway is connected with the ink reservoir 8, and passes the ink to the ink chamber 6. An ink supply unit 9 is used to supply the ejection nozzles 7 with the ink from the ink reservoir 8, and fires the ejection nozzles 7 to record an image on the recording material by ejection of the ink.
Examples of the recording material 5 include printing paper, resin film such as an OHP (overhead projector) sheet, fabric, a surface of a product of metal, and the like. If the printer is a piezoelectric printing type, the ink supply unit 9 is a piezoelectric element for pressurizing the ejection nozzles 7. If the printer is a bubble jet printing type, the ink supply unit 9 is a heater for generating bubbles by heating ink in the ejection nozzles 7.
At the time of printing, a drive signal according to image data of an image is supplied to the ink supply unit 9 for each of the colors. Ink droplets of the number and sizes according to the image data are ejected toward the recording material 5. A full-color image is obtained by arrangement of the ink droplets on the recording material 5.
The pickup device 12 is constructed in a selectable manner between a normal pickup mode and a high image quality mode. When the normal pickup mode is set, the pickup device 12 picks up four nozzles among the ejection nozzles 7 and disposed inside a pickup region 21 at the broken line in FIG. 2. When the high image quality mode is set, each of the ejection nozzles 7 with its vicinity is picked up in enlargement by use of an enlarging lens in the pickup optical system 16. The image data obtained by picking up is transferred to an analyzer 32 which will be described later.
As the pickup device 12 is located in the marginal region 11, it is possible to photograph an image at any time irrespective of printing and not printing. The printing can be discontinued immediately upon detection of the failure in the ink ejection. Wasteful use of the ink can be suppressed specifically when a size of image data of an image is considerably great. Note that, in spite of the four nozzles photographed simultaneously in the present embodiment, it is possible to photograph three or less or five or more nozzles at one time. This is because the number of the photographable nozzles changes according to definition of the pickup device 12 and the density of arranging the nozzles. Also, the pickup clement 14 may be a line CCD sensor instead of the area CCD sensor. For the line CCD sensor, it is necessary to synchronize the operation of the sensor with the movement of the carriage 4.
There is a determining unit 33 for detecting failing ones of the nozzles as will be described later. The suction unit 13 operates for recovery of a normal state by eliminating failure in the ink ejection. The suction unit 13 includes a suction cap or head 17 and a suction pump 18. At the time of the recovering process, the suction cap 17 is tightly contacted on the nozzle arrangement surface 2a. The suction pump 18 is driven to suck the ink from out of the ejection nozzles 7. It is to be noted that the suction cap 17 may be separate from a protecting cap (not shown) which covers the nozzle arrangement surface 2a at the time of not printing. According to this, wasteful use of the ink can be reduced, because only a failing one of the ejection nozzles 7 with the jam of ink can be sucked selectively by use of the suction cap 17.
The analyzer 32 includes an image parameter compensator 35 and a pattern recognition unit 36. The image parameter compensator 35 subjects the image data to edge enhancement or other correction after the transfer from the pickup device 12. The pattern recognition unit 36 operates according to the known technique of the pattern recognition, and recognizes the image data after the correction.
The pattern recognition unit 36 is constituted by a reference image memory, and checks the image data from the pickup device 12 by comparison with reference image data stored previously. In
The failing nozzles among the ejection nozzles 7 according to the determination in the determining unit 33 are subjected to the recovering process which includes steps of sucking the ink in the suction unit 13, forcible ejection, heating the periphery of each nozzle, wiping with a blade of a wiper, and the like. In the case of the failure depicted in
In the case of failure of each of
In the case of failure of each of
Furthermore, if one or more of the ejection nozzles 7 have failure, remaining normal nozzles 7 can be substituted for the failing nozzles. The feeding speed of the recording material 5 can be lowered in the printing. After the printing at the low speed is completed, the recovering operation may be effected. In
Note that the pickup element 14 may be a CMOS (complementary metal-oxide semiconductor) sensor instead of the CCD sensor. Also, it is possible to apply laser light to the ejection nozzles 7, and obtain surface shape data of protruding and retracting shapes. The surface shape data can be checked by comparison with predetermined reference surface shape data, so as to detect failure in the ejection. Also, an ink jet printer of the invention may be a piezoelectric printing type. A pressurizing pump is provided in an ink supply passageway between the ink reservoir 8 and the printhead 2. At the time of the process for the recovery, the pressurizing pump is actuated to raise an inner pressure of the ink supply passageway. Piezoelectric elements are driven to eliminate foreign material by ejecting the ink. Otherwise, it is possible to eject the ink forcibly by raising amplitude of the voltage applied to the piezoelectric elements for the purpose of eliminating foreign material.
In the above embodiment, the printer is a serial printer. However, a printer according to the invention may be a line printer 71 of
A guide rod 73 is disposed between the printhead 72 and the recording material 5. A pickup device 74 and a suction unit 75 are supported on the guide rod 73 in a slidable manner in a direction X indicated by the arrow. The suction unit 75 is movable up and down in the direction Y. A nozzle arrangement surface 72a of the printhead 72 is contacted tightly by the suction unit 75, which subjects failing nozzles to the recovering process among the ejection nozzles 7. To detect failure in the ink ejection, the printhead 72 is shifted away so as to slide the pickup device 74 and the suction unit 75 along the guide rod 73. Note that it is possible to shift away a passageway for the recording material 5 instead of shifting the printhead 72.
Also, the liquid ejected according to the present invention may be other than the ink.
Although the present invention has been fully described by way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein.
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|US6431685 *||Aug 29, 2000||Aug 13, 2002||Canon Kabushiki Kaisha||Printing head and printing apparatus|
|US6460980 *||Mar 2, 1999||Oct 8, 2002||Hegedus Gyoergy||Liquid dispensing apparatus|
|US6471323 *||Aug 30, 2001||Oct 29, 2002||Canon Kabushiki Kaisha||Ink jet printing method and apparatus|
|US6547367||Jun 1, 2000||Apr 15, 2003||Canon Kabushiki Kaisha||Ink jet printing apparatus and a judgement method of an ink ejection state of an ink jet head|
|US6557984 *||Oct 28, 1999||May 6, 2003||Canon Kabushiki Kaisha||Ink-jet printing head and ink-jet printing apparatus|
|US6672704 *||Nov 15, 2001||Jan 6, 2004||Seiko Epson Corporation||Liquid ejecting apparatus and method of cleaning an ejection head|
|US6702419 *||May 3, 2002||Mar 9, 2004||Osram Opto Semiconductors Gmbh||System and method for delivering droplets|
|US6764159 *||Nov 1, 2002||Jul 20, 2004||Seiko Epson Corporation||Nozzle testing before and after nozzle cleaning|
|JP2001063083A||Title not available|
|JPH1178051A||Title not available|
|JPH08332736A||Title not available|
|JPH11192726A||Title not available|
|U.S. Classification||382/141, 358/502, 347/68, 382/112|
|International Classification||B41J29/393, B41J2/165, B41J2/01, G06K9/00|
|Cooperative Classification||B41J2/04536, B41J2/0451, B41J2/16579, B41J29/393|
|European Classification||B41J29/393, B41J2/165D|
|Feb 21, 2011||REMI||Maintenance fee reminder mailed|
|Apr 15, 2011||SULP||Surcharge for late payment|
|Apr 15, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Dec 24, 2014||FPAY||Fee payment|
Year of fee payment: 8