JP2006168203A - Method for optimizing ejection state of inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of optimizing the ejection state of an inkjet head on the basis of the result of the ejection state inspection of an inkjet head. <P>SOLUTION: The method of optimizing the ejection state of an inkjet head comprises a step for inspecting the ejection state of an inkjet head, a step for judging whether or not changing the pulse to be applied to the inkjet head using the inspection result of the inspection, a step for changing the pulse to be applied to the inkjet head corresponding to the judgement, and a step for inspecting the ejection state of the inkjet head again when the pulse to be applied is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for optimizing the ejection state of an ink jet head, and more particularly to a method for optimizing a pulse to be applied so that each nozzle of the ink jet head ejects normally.

  Among image forming apparatuses, the inkjet recording apparatus has a relatively simple and inexpensive configuration for printing, and has recently been used in various applications ranging from personal use to industrial use. The demand for high stability is also increasing.

  In particular, in an inkjet recording apparatus for professional use and industrial use, it is important to print with a constant quality as well as high image quality.

However, due to an accidental failure due to the clogging of the nozzles of the inkjet head or disconnection of the heater, the ink droplets are not ejected normally even when a pulse is applied to the nozzles, and the dots of the image to be originally formed cannot be formed. Is present.
As a conventional technique for solving this problem, a method of inspecting whether or not a nozzle is normally ejected by ejecting an ink droplet for each nozzle between a light emitting element and a light receiving element and knowing whether or not the nozzle is ejecting normally is known. Yes (see, for example, Patent Document 1 and Patent Document 2).

  This method can detect abnormally ejected nozzles, for example, by performing a head cleaning operation so that ejection is in a normal state, or dots that should not be ejected by a nozzle that is not normal at the time of printing are changed to other normal ejected nozzles. It is possible to take measures such as hitting, and a high-quality image can always be obtained (see, for example, Patent Document 3 and Patent Document 4).

However, in these conventional techniques, when the number of nozzles whose discharge has weakened gradually increases due to the state of the head, the nozzles are not completely broken, but the head is often cleaned and consumes ink. However, if the discharge remained weak, it was not possible to return to normal discharge other than replacing the head.
JP-A-10-119307 Japanese Patent Laid-Open No. 11-78051 JP-A-8-25700 JP-A-11-77986

  The present invention has been made in view of such conventional problems, and an object thereof is to provide a method of performing an inspection of the ejection state of an inkjet head and optimizing the ejection state of the inkjet head based on the result. To do.

  In order to achieve the above object, the apparatus of the present invention according to claim 1 is a method for optimizing the discharge state of an inkjet head, the step of inspecting the discharge state of the inkjet head, and the inspection result of the inspection Determining whether or not to change the pulse applied to the inkjet head using the step, changing the pulse applied to the inkjet head in accordance with the determination, and again changing the applied pulse when the applied pulse is changed. And a step of inspecting the discharge state.

  As described above, according to the present invention, it is possible to optimize the ejection state of the inkjet head by a simple method using the inspection result of the ejection state of the inkjet head.

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

(First embodiment)
FIG. 1 is a schematic perspective view of an ink jet recording apparatus to which the present invention is applied.

  In the ink jet recording apparatus 1, reference numeral 2 denotes a head carriage. An ink jet head that has a recording element array in which a plurality of recording elements are arranged in the sub-scanning direction and ejects ink droplets is attached to the head carriage 2 by a recording head fixing lever 3. It is removable. The head carriage 2 is provided with a connector for positioning and mounting the recording head and transmitting a signal for driving the recording head and the like, and is electrically connected to the recording head. The head carriage 2 positions and mounts the ink tank 4 so that the recording head and the ink tank 4 communicate with each other to supply ink.

  A scanning rail 5 extends in the main scanning direction of the head carriage 2 and slidably supports the head carriage 2. The head carriage 2 scans the recording medium by reciprocating on the scanning rail 5 in the directions of arrows a and b via the head carriage driving motor 6, the motor pulley 7, the driven pulley 8 and the timing belt 9. At this time, the recording head can perform reciprocal recording. Reference numerals 10, 11, 12, and 13 denote conveyance roller pairs for nipping and conveying the recording medium.

  Reference numeral 14 denotes a recording medium such as paper, which is pressed against a platen (not shown) that regulates the recording surface of the recording medium 14 to be flat. The recording head mounted on the head carriage 2 protrudes downward from the head carriage 2 and is positioned between the recording medium transport rollers 11 and 13, and the nozzle forming surface of the recording head is pressed against the guide surface of the platen. It faces the medium 14 in parallel. The image data is transmitted from the electric circuit of the recording apparatus main body to the recording head via a flexible cable (not shown).

  FIG. 2 is a block diagram showing a system configuration of the ink jet recording apparatus according to the embodiment of the present invention.

  Reference numeral 20 denotes a bus line for transmitting an address signal, a control signal, and data inside the recording apparatus, and 21 is a data input unit for inputting an image signal and the like. Reference numeral 22 denotes a CPU that controls the entire recording apparatus based on various programs in the ROM 23. In the CPU 22, reference numeral 23 denotes a ROM which stores an error processing program, a recording operation program, a program for operating the CPU 22, and the like. Reference numeral 24 denotes a RAM used as a work area for various programs in the ROM 23 and a temporary save area during error processing.

  An image signal processing unit 25 performs signal processing of an input image signal obtained by the data input unit 21, and an operation unit 26 performs operations such as recording start. Reference numeral 29 denotes an ejection control unit that drives and controls the recording head based on the data processed by the image signal processing unit 25. The sub scanning unit 27 rotates the transport motor by a predetermined amount at a predetermined timing. The main scanning unit 28 rotates the head carriage driving motor 6 by a predetermined amount at a predetermined timing. Reference numeral 30 denotes a recording unit, which ejects ink onto the recording medium 14 by a recording head to form an image.

  FIG. 3 is a side view showing a schematic configuration of an inkjet head discharge state inspection apparatus used in the embodiment of the present invention. This apparatus is in a range in which the head carriage 2 can move, and is arranged so that the direction of the nozzle row of the ink jet head substantially coincides with the direction of the arrow A in FIG. 3 (not shown in FIG. 1).

  31 is an ink jet head, and 34 is an ink receiver for receiving and discharging ink droplets ejected from each nozzle for inspection. Reference numerals 32 and 33 denote a light emitting unit and a light receiving unit for optically detecting ink droplets ejected from each nozzle of the ink jet head in order to inspect the ejection state. The light emitting element that constitutes the light emitting unit is preferably an LED, a semiconductor laser, or the like, and the light receiving element that constitutes the light receiving unit uses a photodiode that matches the characteristics of the light emitting element. By ejecting ink droplets into the light emitted from the light emitting portion, the amount of light received by the light receiving portion varies, and it can be detected that the ink droplet has passed.

  However, the volume of ink droplets is as small as several picoliters, and when only one droplet is ejected, the amount of light varies little and the S / N ratio is small. Therefore, five dots are ejected continuously at a period of 15 kHz per nozzle. Considering the width of the optical axis emitted from the light emitting part and the temporal characteristics of the light receiving part, since the 15 kHz period is short in time, the fluctuation of light quantity for one dot is convoluted into five dots and sufficient S / N ratio can be obtained. In addition, it is possible to inspect the ejection state of all the nozzles by sequentially performing the inspection of the ejection state of one nozzle while changing the nozzles. However, in order to prevent the signals of the adjacent nozzles from overlapping, 5 in a cycle of 15 kHz. A pause period of 10 dots is provided after the dots are continuously ejected. That is, the inspection time per nozzle is about 1 msec.

  A signal as a result of inspecting the ejection state of the ink jet head by such a method is as shown in FIG. The upper signal is a reference signal for the discharge command, and the lower signal is a signal for the light receiving unit of the discharge state inspection device. Assuming that the signal between 0 and 1 msec is the Nth nozzle, the signal indicating the discharge state of the (N + 1) th nozzle is between 1 and 2 msec, and the signal between the N + 2 and the nozzle is between 2 and 3 msec. As can be seen from FIG. 4, in the (N + 2) th nozzle, the signal fluctuation level due to the passage of the ink droplet in the optical axis is hardly seen, and it is determined that the nozzle is not ejected normally. The ejection state inspection described above is sequentially performed for all nozzles, and is performed for each head when a plurality of heads are provided.

  As a result of the above-described ejection state inspection, it is possible to obtain information on whether ejection is normal for each nozzle. In the following, as a first embodiment, a method for optimizing the ejection state of the inkjet head based on this information will be described.

  FIG. 5 is a flowchart showing a sequence for optimizing the ejection of the ink jet head according to the first embodiment. First, in step S1, the above-described discharge state inspection is sequentially performed for all nozzles. Thereby, it is determined whether or not the ejection of each nozzle is normal. Next, in step S2, the result of this inspection is stored in the memory. When the total number of the results of the main inspection and the past inspection results becomes 3 or more, for example (S3), the discharge state history of each nozzle is checked. In this history check, for example, if it has been determined that the discharge has been performed three times in the past, the nozzle is healthy, and if it has been determined that no discharge has occurred in the past three times, the nozzle cannot be restored for some reason. (Dots to be hit by the nozzles determined to be unrecoverable when printing are printed by other normal ejection nozzles to be complemented). The other nozzles whose discharge state has changed in the past three times are determined to be nozzles whose discharge is unstable. For example, when such nozzles exceed 10% of the total nozzles (S4), The pulse applied for ejection is changed to a table that facilitates ejection (S5).

  This is because the response characteristics due to the same applied pulse change when the head is used continuously, and the total amount and speed of ink to be ejected change. By changing the pulse table in this way, it is possible again. The head can be in a normal state.

  Thereafter, in step S6, the history of past inspection results is cleared from the memory because the driving condition of the head changes due to the change of the pulse table and loses its meaning as a comparison target. Then, the ejection state is inspected again with the pulse table changed (S7), and the inspection result is stored in the memory (S8). Thereby, the history of the inspection result is accumulated for one time.

  Thereafter, this sequence is repeated, but each time the inspection result history is accumulated three times, it is determined whether or not to change the pulse table.

  Further, the sequence shown in FIG. 6 may be used. That is, in step S14, by adding a step for checking whether the pulse table is at the limit to be changed, if the pulse table cannot be changed any more, a message prompting the user to replace the head Can be displayed (S20) to notify the user when the head should be replaced.

  It goes without saying that the above-described inspection result history may be stored in a non-volatile memory so that it is not lost even when the printer power is turned off. In addition, the number of times the history is stored and checked is not limited to three, and the threshold for changing the pulse table is not limited to the unstable nozzle ratio of 10%. Furthermore, although this sequence is normally performed before the printing operation, it does not necessarily have to be before the printing operation.

(Second Embodiment)
Next, a method for optimizing the ejection state of the ink jet head according to the second embodiment will be described. In the first embodiment, the result of the discharge state inspection is a determination as to whether or not each nozzle is discharging. However, as shown in FIG. Time 40a (hereinafter referred to as “arrival time”) from the reference signal of the command until the ink droplet reaches the optical axis of the inspection apparatus, and the time during which the ink droplet is present on the optical axis and the amount of light varies. 40b (hereinafter referred to as “light blocking time”) may be used as a criterion for determination. In step S23 of FIG. 7, nozzles that have a long arrival time or a short light blocking time are counted up with respect to a predetermined reference value. A long arrival time or a short light blocking time indicates that the discharge of the nozzle is weakening. If the number of nozzles is, for example, 10% or more, the pulse table is changed and the discharge state is changed. To normalize. Note that the reason why the ejection / non-ejection information is stored in steps S22 and S27 is to cause dots that should not be shot by the nozzles that are not normal during printing to hit other normal ejection nozzles.

  The threshold for changing the pulse table is not limited to the nozzle ratio of 10%, which has a long arrival time or a short light blocking time. Furthermore, although this sequence is normally performed before the printing operation, it does not necessarily have to be before the printing operation. In addition, the reference values for the arrival time and the light shielding time described above may be determined in advance according to the type of ink, or initial values are acquired and stored when a new head is mounted, and then the initial values are obtained. Judgment may be made based on the fluctuation ratio from

  In the method for optimizing the ejection state of the ink jet head described here, the pulse table applied to the head is changed, but the same effect can be obtained even if the voltage value of the pulse is changed. Further, the pulse table to be applied does not necessarily have to be changed in units of heads. For example, when the head is divided into a plurality of blocks and an independent pulse table can be set for each block, the pulses are changed in such units. The change of the table may be controlled.

1 is a schematic perspective view of an ink jet recording apparatus to which the present invention is applied. 1 is a block diagram showing a system configuration of an ink jet recording apparatus to which the present invention is applied. 1 is a side view illustrating a schematic configuration of an ejection state inspection device for an inkjet head according to an embodiment of the present invention. It is a figure which shows the signal of the discharge state test | inspection of the inkjet head of embodiment of this invention. It is a flowchart of the discharge state optimization of the 1st Embodiment of this invention. It is a flowchart (another example) of the discharge state optimization of the 1st Embodiment of this invention. It is a flowchart of the discharge state optimization of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Recording head fixing lever 4 Ink tank 5 Scanning rail 6 Head carriage drive motor 7 Motor pulley 8 Driven pulley 9 Timing belt 14 Recording medium 20 Bus line 21 Image input part 22 CPU
23 ROM
24 RAM
25 Image signal processing unit 26 Operation unit 27 Sub-scanning unit 28 Main scanning unit 29 Discharge control unit 30 Recording unit 31 Head 32 Light-emitting unit 33 Light-receiving unit 34 Ink receiver 35 Nozzle

Claims (3)

A method for optimizing the ejection state of an inkjet head,
Inspecting the ejection state of the inkjet head; and
Determining whether to change the pulse applied to the inkjet head using the inspection result of the inspection; and
Changing a pulse to be applied to the inkjet head according to the determination;
Inspecting the ejection state of the inkjet head again when the applied pulse is changed; and
A method for optimizing the ejection state of an inkjet head, comprising: The step of determining includes
2. The method for optimizing the discharge state of an ink jet head according to claim 1, wherein whether or not each nozzle of the ink jet head can be discharged is used as a criterion for determination. The step of determining includes
The time from when the ink droplets ejected from each nozzle of the inkjet head at the time of the inspection receives the ejection command signal to reach the ejection inspection device, and the time that the ink droplet exists in the ejection inspection device are determined. The method for optimizing the discharge state of an ink jet head according to claim 1, wherein the method is used as a reference.

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