JP2006240119A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder capable of preventing a great amount of defective printed materials from being produced by checking a defective nozzle in a real time manner during the printing and immediately detecting the defective nozzle when occurring. <P>SOLUTION: An ink ejection defect detection mechanism has a photosensor which is provided to a portion outside of a recording region and has an optical path diagonally intersecting with a nozzle array of a recording head. The ink is ejected from all the nozzles on each movement of a carriage to a detection region and the photosensor detects whether or not there is defective ejection. When the defective ejection is detected, the printing is stopped and maintenance of the head is immediately carried out to recover the head, and then the printing is restarted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus.

  Conventional inkjet printers record an image by ejecting ink droplets onto a recording medium from a plurality of nozzles using a thermal method, a piezo method, or the like as an ejection signal based on an image signal. In an ink jet printer, ink may adhere to the vicinity of the nozzle discharge port due to ink drying or increase in viscosity when left unused for a long period of time, or impurities (dust) may adhere to the nozzle discharge port. The nozzle is clogged by the nozzle, and the nozzle ejection failure (hereinafter referred to as nozzle missing) is that ink droplets are not ejected from the nozzle ejection port even though the ink ejection signal is normally output from the drive circuit unit. Occurs. When the nozzles are missing, the printed characters and images are whitened to form white stripes, or the color quality of the recorded image is different due to insufficient ink coloring material, resulting in a decrease in print quality. As such a nozzle missing detection means, an optical detection means is disclosed (for example, see Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-133826 discloses a nozzle missing detection unit for a carriage-type inkjet printer that ejects ink in a direction (main scanning direction) perpendicular to the paper transport direction (sub-scanning direction). A photo sensor in which a light emitting element and a light receiving element are combined at a distance corresponding to the head width is arranged in the nozzle row direction, ejected one by one in order, the shadow of the ejected liquid droplets is detected by the photo sensor, An ink discharge state detection method for detection is disclosed.
JP 2003-165204 A

  However, in the conventional technique, it takes a long time to detect all the nozzles in the nozzle row in order to confirm whether or not the liquid droplets are detected each time one nozzle is ejected. In order not to lower the print productivity of the ink jet recording apparatus, the detection of nozzle shortage could be performed only once per fixed time. For this reason, when a nozzle shortage occurs, printing may be performed with the nozzle missing until the next nozzle shortage detection, and a defective printed matter may be generated.

  In addition, when an unattended operation is performed using the ink jet recording apparatus, a large amount of defective printed matter may be generated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus that detects nozzle shortage in real time while printing and immediately detects when a nozzle shortage occurs and prevents a large amount of defective printed matter from being generated.

  The object of the present invention can be achieved by the following constitution.

The invention according to claim 1
In an inkjet recording apparatus that ejects ink droplets onto a recording medium using an inkjet head having a nozzle row in which a plurality of nozzles are arranged in a straight line,
A detecting means arranged so that an optical path connecting the light emitting element and the light receiving element intersects the arrangement direction of the nozzle rows;
Moving means for relatively moving the inkjet head and the detection means in a direction orthogonal to the arrangement direction of the nozzle rows;
An ejection control unit that causes ink droplets to be ejected from the nozzle row and the ink droplets ejected from the nozzle row to be detected by the detection unit when the inkjet head is relatively moved by the moving unit; An ink jet recording apparatus characterized by comprising:

The invention according to claim 2
The inkjet head has a first nozzle row and a second nozzle row parallel to the first nozzle row,
The ejection control unit ejects ink droplets from the first nozzle row or the second nozzle row when the inkjet head is relatively moved by the moving unit, and ejected ink droplets. The inkjet recording apparatus according to claim 1, wherein:

The invention according to claim 3
The inkjet recording apparatus according to claim 1, comprising a plurality of the inkjet heads.

  According to the first aspect of the present invention, the inkjet head and the detection unit are relatively moved, and the inkjet head is moved from the inkjet head within a predetermined movement range including an optical path formed between the light emitting element and the light receiving element. Let the discharge occur. Since the optical path obliquely intersects the nozzle row in the movement range, the optical path can sequentially irradiate the liquid droplets discharged from all the nozzles. When this occurs, it is possible to immediately detect the occurrence of a large amount of defective printed matter.

  According to the second aspect of the present invention, when the inkjet head passes through the moving range, one of the nozzle rows is ejected, and the other nozzle rows are not ejected. It is possible to detect missing nozzles for each nozzle without overlapping and blocking the optical path.

  According to the third aspect of the present invention, since a plurality of the ink jet heads are provided, all the missing nozzles can be detected in the color print ink jet recording apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a front view schematically showing an ink jet printer which is an embodiment of an ink jet recording apparatus according to the present invention.

  The ink jet printer 1 is an ink jet printer using a serial printing method, and the ink jet printer 1 has a rod-shaped carriage rail 2 extending in the main scanning direction A. A carriage 3 is supported on the carriage rail 2 so as to reciprocate along the carriage rail 2. The carriage 3 reciprocates in the main scanning direction A by a carriage drive source 11 (see FIG. 3) as a moving means. It is designed to be driven. The ink jet printer 1 is provided with a recording medium transport mechanism 12 (see FIG. 3) for transporting the recording medium P in a direction orthogonal to the main scanning direction A.

  As shown in FIGS. 1 and 2, the carriage 3 is mounted with a recording head 4 formed with nozzles 42 for ejecting ink. The recording head 4 is, for example, yellow (Y), magenta ( M), cyan (C), and black (Bk) are ejected.

  A central portion of the movable range of the carriage 3 is a recording area Y for recording on the recording medium P. The recording area Y is provided with a platen 5 that supports the recording medium P from the non-recording surface side during a recording operation. In addition, the outer end of the recording area Y that is the movable range of the carriage 3 is a maintenance area Z in which the recording head 4 is maintained.

  A maintenance unit 6 is provided in the maintenance area Z. In the maintenance unit 6, a suction cap 61 as a cap member that covers the nozzle surface 41 of the recording head 4 corresponds to the recording head 4 at a position facing the recording head 4 when the carriage 3 moves to the maintenance area Z. There are as many as you want. Further, the maintenance unit 6 is provided with an empty discharge tray 62 that receives ink discharged when ink is discharged from the nozzle 42 in the vicinity of one end of the suction cap 61, and adjacent to this, the nozzle surface 41. A blade 63 for wiping off the ink remaining on is provided.

  An ink communication tube 66 that communicates with the inside of the suction cap 61 is provided on the bottom surface of the suction cap 61. A suction pump 64 that is a suction device is provided in the middle of the ink communication pipe 66, and a waste ink tank 65 that receives the sucked ink is provided at the lower end of the ink communication pipe 66.

  The range where the carriage 3 can move and the opposite side of the maintenance area Z across the recording area Y is a home position area X in which the recording head 4 waits at times other than during image recording and head maintenance operations. A moisturizing unit 7 is provided in the home position region X, and a moisturizing cap 71 for protecting the nozzle surface 41 of the recording head 4 from drying or the like corresponds to the recording head 4 at the time of non-image recording. There are as many as you want.

  In the home position region X, an optical sensor 8 is provided as a detecting means for detecting a discharge failure such as a missing nozzle.

  As shown in FIG. 2, the optical sensor 8 includes a light emitter 81 that includes a light emitting element that emits light such as infrared rays, and a light receiver 82 that includes a light receiving element that senses light emitted from the light emitter 81. When the ejection failure of the recording head 4 is detected, the light emitter 81 and the light receiver 82 are opposed to each other with a certain angle with respect to the scanning direction of the recording head 4 with the recording head 4 interposed therebetween. Has been placed.

  In addition, when detecting the ejection failure of the recording head 4, a tray 80 for receiving ink ejected from the nozzles 42 is provided at a position facing the nozzle surface 41.

  The nozzles 42 form a nozzle row A421 and a nozzle row B422. Nozzle rows A and B are arranged in a staggered manner, and have a structure in which ejection is performed by interpolation in the sub-scanning direction.

Next, the control device will be described with reference to FIG.
The optical sensor 8 as the ink ejection shortage detection mechanism is connected to a control device 100 including a CPU (Central Processing Unit) 100a that determines whether or not there is a nozzle shortage from the light transmission state. The control device 100 includes a ROM (Read Only Memory) 100b for storing various programs, and a RAM (Random Access Memory) 100c having a work area and a storage area for expanding information acquired by the CPU. Further, the input unit 9, the recording head 4, the carriage drive source 11, and the recording medium transport mechanism 12 are connected to the control device 100 via interfaces (not shown).
The CPU 100a performs various controls such as driving of the recording head 4 and the carriage 3 and head maintenance operation according to the acquired information and a program stored in the ROM 100b.

  Next, this embodiment will be described.

  The control device 100 moves the recording head 4 to the recording area Y by the moving means and drives the carriage 3 to reciprocate the recording head 4 in the main scanning direction A, and the recording medium transport mechanism 12 moves the recording medium P. By ejecting ink of a required color from the nozzles 42 of the recording head 4 based on the input information from the input unit 9 and predetermined image information while transporting in the sub-scanning direction orthogonal to the main scanning direction A, the recording medium An image is recorded on P. After the image printing, the carriage 3 temporarily stops over the optical sensor 8, changes its direction, and repeats the reciprocating motion that proceeds again toward the empty discharge tray 62.

  When the recording head 4 moves from the left stop position in FIG. 1 toward the center of the apparatus and passes through the optical sensor 8, the control device 100 causes all of the nozzle rows A 421 to be ejected by the discharge control means (not shown) included in the control device 100. By applying a drive pulse voltage to the piezo elements, ink is ejected from all the nozzles 42 of the nozzle array A421. At the same time, the optical sensor 8 as the ink shortage detection mechanism is activated to irradiate the ink ejected from the nozzles 42 of the nozzle array A421 with light rays from the light emitter 81, and the received light rays are received by the light receiver 82. However, the recording head 4 is moved so that each of the nozzles 42 of the nozzle array A421 is irradiated with the light beam from the light emitter 81.

  Conversely, when the recording head 4 moves from the center of the apparatus in FIG. 1 toward the left stop position and passes through the optical sensor 8, the control apparatus 100 causes all of the nozzle rows B422 to be ejected by the ejection control means as described above. By applying a driving pulse voltage to the piezo element, ink is ejected from all the nozzles 42 of the nozzle row B422. In the same manner as described above, the optical sensor 8 is operated to detect missing nozzles in the nozzle row B422.

  At this time, when the nozzle missing is not generated, the light emitted from the light emitter is blocked by the ink ejected from the nozzle 42 and does not partially reach the light receiver 82, but the nozzle missing occurs. The light reaches the light receiver 82 without being blocked by the ink. When the light receiver 82 receives a light beam from the light emitter 81, the information is transmitted to the CPU 100 a in the control device 100.

  When the CPU 100a determines from the information transmitted from the light receiver that a discharge failure such as a missing nozzle has occurred, the control device 100 controls the carriage drive source 11 to move the recording head 4 along the carriage rail 2. The recording head 4 is moved to the maintenance area Z, and the recording head 4 is maintained for recovery.

  Here, a method of detecting a droplet with the optical sensor 8 will be described.

  In FIG. 2, the light receiver 82 is accommodated in a shield case 83, and a detection hole 831 is opened in the shield case 83 at a position where the detection light D emitted from the light emitting element toward the light receiving element is irradiated. Yes. As a result, the light receiving surface of the light receiving element is light-shielded by the shield case 83, and the change in the amount of light only from the detection light D incident from the detection hole 831 can be captured.

  As shown in FIG. 4, the detection hole 831 has an elliptical shape whose length in the direction parallel to the moving direction (main scanning direction) of the recording head 4 is shorter than the length in the direction perpendicular thereto. For example, the major axis is 2 mm and the minor axis is 1 mm, and the major axis is provided along the direction of ink discharge from the recording head 4. As a result, the distance over which the droplets cast a shadow on the light receiving element is increased, and the short diameter is provided along the nozzle row, so that the influence of the droplets ejected from the distant nozzles is reduced.

  FIG. 5A shows a detection circuit diagram for detecting a missing nozzle from light received by the light receiver 82, and FIG. 5B shows an example of input / output waveforms of the comparator in the detection circuit of FIG. 5A. Indicates.

  The light amount signal received by the light receiver 82 is amplified by the current amplifying unit 84, and then only the variation is amplified by the AC amplifying unit 85, and unnecessary noise is removed by the mid-band filter 86. The middle band filter output 871 is input to the + input terminal of the comparator 87.

  On the other hand, the power supply voltage is divided by the variable resistor 88 and the fixed resistor 89, and the voltage (V 872) taken out from the variable terminal of the variable resistor 88 is input to the negative input terminal of the comparator 87.

  The comparator 87 output V873 becomes a high voltage (T1, T3) when the voltage at the + input terminal (middle filter output) V871 is higher than the voltage V872 at the −input terminal, and becomes a low voltage in the opposite case (T2). That is, when a nozzle shortage is detected, the Low voltage is obtained.

  The nozzle missing signal is taken into the CPU 100a of the control device 100, and as described above, maintenance is performed when nozzle missing is detected, and printing is continued when there is no nozzle missing.

  The V872 of the negative input terminal of the comparator 87 can be set by adjusting the variable resistor 88. The voltage V872 is set so that a sufficient margin can be obtained by comparing the state where there is no nozzle shortage and the state where nozzle shortage occurs.

  FIG. 6 shows an example of a flowchart showing a procedure for detecting missing nozzles.

  Nozzle missing detection processing is triggered by the carriage entering the optical sensor detection range.

  In step S1, the carriage movement direction is confirmed. When moving toward the maintenance area Z in FIG. 1 (step S1; YES), the process proceeds to step S11. When moving toward the home position area X (step S1; NO), the process proceeds to step S2.

  In step S2, the operation of the optical sensor is started.

  In step S3, the ejection control unit starts ejection of all the nozzles in the nozzle row A. At this time, the nozzle row B is not discharged.

  In step S4, the nozzle missing detection circuit in FIG. 5 is set to an enable state.

  In step S5, it is confirmed whether the carriage is in the optical sensor detection range. If the carriage is still in the detection range (step S5; YES), the detection operation is continued as it is. If the carriage moves out of the detection range (step S5; NO), the process proceeds to step S6.

  In step S6, the nozzle missing detection circuit in FIG. 5 is disabled.

  In step S7, the ejection of the nozzle row A is stopped.

  In step S8, the operation of the optical sensor is stopped.

In step S9, it is determined whether a nozzle shortage has occurred. If it has occurred (step S9; YES), a maintenance process is performed in step S10, and printing is continued after the maintenance is completed. If no missing nozzle is detected (step S9; NO), printing continues.
Steps S11 to S17 are for the case where the carriage movement direction is toward the home position. Step S2 to step S2 are performed except that when all the nozzles in nozzle row B are started to be discharged in step S12, the discharge is stopped in step S16. Since it is the same as that up to S8, the description is omitted.

  As described above, according to the present embodiment, the inkjet head and the detection unit are relatively moved, and the optical path connecting the light receiver and the light emitter of the optical sensor obliquely intersects the nozzle row in the movement range. The optical path can detect the liquid droplets discharged from all nozzles in sequence, detect the missing nozzles in real time while printing, and immediately detect when a missing nozzle occurs, preventing the occurrence of a large amount of defective printed matter. It becomes possible.

  In addition, according to the present embodiment, when the ink jet head passes through the movement range, one of the nozzle rows is ejected and the other nozzle rows are not ejected. It is possible to detect missing nozzles for each nozzle row without blocking the optical path.

  In addition, according to the present embodiment, by providing a plurality of inkjet heads, it is possible to detect missing nozzles in all nozzle rows in a color print inkjet recording apparatus.

  In addition, the detailed configuration and detailed operation of each component constituting the ink jet recording apparatus can be changed as appropriate without departing from the spirit of the present invention.

1 is a front view schematically showing an ink jet printer according to the present invention. It is a bottom view of the optical sensor and the recording head part in the present invention. It is a block diagram which shows the outline of the control apparatus concerning this invention. It is a front view of the shield case in which the optical receiver concerning this invention is accommodated. It is the detection circuit diagram which detects a nozzle missing from the light received with the light receiver concerning this invention, and the input-output waveform of the comparator in it. It is a flowchart which shows the procedure of the nozzle missing detection concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Carriage rail 3 Carriage 4 Recording head 41 Nozzle surface 42 Nozzle 421,422 Nozzle row 6 Maintenance unit 7 Moisturizing unit 8 Optical sensor 81 Light emitter 82 Light receiver 83 Shield case 831 Detection hole 87 Comparator

Claims (3)

In an inkjet recording apparatus that ejects ink droplets onto a recording medium using an inkjet head having a nozzle row in which a plurality of nozzles are arranged in a straight line,
A detecting means arranged so that an optical path connecting the light emitting element and the light receiving element intersects the arrangement direction of the nozzle rows;
Moving means for relatively moving the inkjet head and the detection means in a direction orthogonal to the arrangement direction of the nozzle rows;
An ejection control unit that causes ink droplets to be ejected from the nozzle row and the ink droplets ejected from the nozzle row to be detected by the detection unit when the inkjet head is relatively moved by the moving unit; An ink jet recording apparatus comprising: The inkjet head has a first nozzle row and a second nozzle row parallel to the first nozzle row,
The ejection control unit ejects ink droplets from the first nozzle row or the second nozzle row when the inkjet head is relatively moved by the moving unit, and ejected ink droplets. The inkjet recording apparatus according to claim 1, wherein: The inkjet recording apparatus according to claim 1, comprising a plurality of the inkjet heads.

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