JP2006212875A - Method for inspecting ejection condition of inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inspecting an ejection condition of an inkjet head capable of performing the inspection accurately in a short period by a simple method. <P>SOLUTION: The method for optically inspecting the ejection condition of an inkjet head comprises a step of sequentially inspecting the ejection condition of each of nozzles of the inkjet head in a one-by-one manner and a step of checking an inspection unit after the above inspection according to the inspection result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ejection state inspection method for an inkjet head, and more particularly to a method for inspecting whether each nozzle of an inkjet head is ejected normally or not.

  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 nozzle clogging 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.

  To solve this problem, for example, as disclosed in Patent Document 1, Patent Document 2, and the like, ink droplets are ejected for each nozzle between the light emitting element and the light receiving element, and the nozzle ejects normally due to fluctuations in the amount of light. A method for inspecting whether or not a device is in progress is well known.

  With this method, it is possible to detect nozzles that are not ejected normally.For example, a head cleaning operation is performed so that ejection is normal. It is possible to take measures such as hitting, and a high-quality image can always be obtained.

  However, when the inspection unit does not operate normally, for example, when the light emitting element can no longer emit light normally, the light receiving element is not ink but the nozzle of the inkjet head is not clogged. Since fluctuations in the amount of light associated with the passage of droplets cannot be obtained, there has been a problem of erroneously determining that the ink jet head is defective.

For this problem, it is possible to perform a single check of the inspection unit before inspecting the ejection state of the inkjet head, and confirm that it is normal and then proceed to inspection of the ejection state of the inkjet head. Actually, the frequency at which the inspection unit does not operate normally is very small compared with the frequency at which the inspection of the discharge state is performed, so that the inspection time becomes longer if a single check of the inspection unit is performed each time. End up.
JP-A-10-119307 Japanese Patent Laid-Open No. 11-78051

  The present invention has been made in view of such conventional problems, and an object thereof is to provide a discharge state inspection method for an ink jet head that can be inspected in a short time and with high accuracy by a simple method.

  In order to achieve the above object, the apparatus of the present invention according to claim 1 is a method for optically inspecting an ejection state of an inkjet head, and sequentially inspecting the ejection state of the inkjet head one nozzle at a time. And checking the inspection unit after the inspection according to the result of the inspection.

  According to the present invention, when the number of nozzles for which ejection signals are not obtained as a result of the ejection state inspection of the ink jet head is very large, the inspection unit can check whether the head is normal by performing a single check of the inspection unit. It is possible to determine whether or not it is normal, and it is possible to reduce the inspection time as compared with the case where the inspection unit is checked before each inspection.

  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 the inkjet head ejection state inspection apparatus according to the embodiment of the present invention. This apparatus is in a range in which the head carriage 2 is movable, 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 each of the light receiving elements that constitute 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 a few picoliters, and when only one droplet is ejected, the variation in light quantity is small 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 unit and the temporal characteristics of the light receiving unit, the period of 15 KHz is short in time. Therefore, the fluctuation in the amount of light for one dot is convoluted into five dots and sufficient S / The 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 in order. However, in order to prevent the signals of 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, one 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. If 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 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 ink droplet passage in the optical axis is hardly seen, and it is determined that the nozzle is not ejected normally.

  In general, the number of nozzles that do not discharge normally is small. However, when the inspection unit itself is not normal, for example, when the light emitting element is unable to perform normal light emission, the normality described above is applied to almost all nozzles. A signal waveform similar to that of a non-nozzle is obtained. Since it is impossible to distinguish whether the inspection unit is not normal or most of the nozzles of the inkjet head are not normal from the signal waveform alone, check the operation of the inspection unit before inspection to confirm that it is normal. If so, it can be determined that the inkjet head is not normal. However, since checking the inspection unit every time before the inspection has a very low probability of the inspection unit being broken, the operation sequence becomes redundant simply by increasing the inspection time unnecessarily. The present invention can solve this problem, and a sequence for inspecting the ejection state of the ink jet head according to the first embodiment will be described below.

  FIG. 5 is a flowchart showing a sequence for inspecting the ejection state 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 tentatively determined whether or not the discharge of each nozzle is normal. Next, in step S2, it is checked whether or not the number of abnormal nozzles is N or more. This N is desirably a sufficiently large number that cannot occur when the ink jet head or the inspection unit is normal. When the number of nozzles that are not normal is smaller than N, there is no possibility that the inspection unit is abnormal, so the ejection state of each nozzle of the inkjet head is determined as it is (S4), and the ejection state of the inkjet head is inspected Exit. If the number of nozzles that is not normal is N or more, there is a possibility that the inspection unit is abnormal. In step S3, a single check of the inspection unit is performed (described later). As a result of checking the inspection unit, if the inspection unit itself is normal in step S5, it is determined that the head is abnormal and a head error is determined (S6). If the inspection unit is abnormal, an inspection unit error is detected. (S7). For example, if these results are displayed on the operation panel, the operator can determine whether to replace the head or call a service person. Further, in most normal cases, the sequence of steps S1, S2, and S4 in FIG. 5 can be performed, and there is an advantage that it is not necessary to check the inspection unit prior to the inspection of the inkjet head every time.

  Next, the single check of the inspection unit in step S3 in FIG. 5 will be described with reference to FIG. First, at step S8, the light emitting unit is turned on, and at step S9, it is checked whether or not the received light amount has changed. If it fluctuates, both the light emitting unit and the light receiving unit are operating, so it is determined that the inspection unit is normal (S10). If it does not fluctuate, either the light emitting unit, the light receiving unit, or both operate normally. Therefore, it is determined that the inspection unit is abnormal (S11). Moreover, the method of the single check of the inspection unit may be as shown in FIG. That is, even if it is determined in step S13 that the amount of received light has fluctuated, it is determined in step S14 whether the value is appropriate, and if it is not appropriate, the light emission amount is adjusted to an appropriate value (S16), The adjustment value is stored (S17), and the light emitting unit is caused to emit light based on the stored adjustment value at the next inspection of the inkjet head. With such a sequence, it is possible to suppress a decrease in inspection accuracy of the ink jet head due to deterioration of the light emitting element or adhesion of dirt, and more accurate inspection can be performed.

  It goes without saying that the light emission amount adjustment value may be held in a nonvolatile memory so that the adjustment value is not lost even when the printer power is turned off.

(Second Embodiment)
Next, as a second embodiment, a case will be described in which the head cleaning operation is performed when it is determined that the inspection unit is normal by the single check of the inspection unit.

  FIG. 8 is a flowchart showing a sequence for inspecting the ejection state of the ink jet head according to the second embodiment. Steps S19 to S23 are as described in the first embodiment. In this embodiment, if it is determined in step S23 that the inspection unit is normal, a head cleaning operation is executed in step S24. This is because even if the inspection unit is normal, there is a possibility that bubbles or the like may be mixed in the head and the ink is not normally ejected. Then, in step S26, the ejection state is re-inspected. If the number of nozzles in which the inkjet head is not ejected normally is N or more even after the cleaning is performed in step S27, it can be determined that this is not due to the mixing of bubbles. According to this sequence, more detailed state check and recovery can be performed by cleaning the head.

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 result of the discharge state test | inspection of the inkjet head of embodiment of this invention. It is a flowchart of the discharge state test | inspection of the 1st Embodiment of this invention. It is a flowchart of an inspection unit single body check of the present invention. It is a flowchart of the test | inspection unit single-piece | unit check by another method of this invention. It is a flowchart of the discharge state test | inspection 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 optically inspecting an ejection state of an inkjet head,
Sequentially inspecting the ejection state of the inkjet head one nozzle at a time;
Checking the inspection unit after the inspection according to the result of the inspection;
A method for inspecting an ejection state of an inkjet head, comprising: The step of checking the inspection unit includes:
The method for inspecting an ejection state of an ink jet head according to claim 1, further comprising a step of adjusting a light emission amount of a light emitting unit of the inspection unit.   The inkjet head ejection state inspection method according to claim 1, wherein when the inspection unit is determined to be normal by the inspection unit check, the inkjet head cleaning operation is performed.

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