JP2006256115A - Device and method for inspecting liquid ejection state - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform the inspection of the ejection state of an inkjet head in a good state of the head in a short time. <P>SOLUTION: The device for optically inspecting the ejection state of a plurality of inkjet heads has a means for executing preliminary ejection prior to the inspection of the ejection state, a means for inspecting the ejection state of the inkjet heads in order. Furthermore, the distance between the preliminary ejection position and the inspection position is substantially the same as the distance between the heads. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ejection state inspection device and 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 a means such as hitting, and a high-quality image can always be obtained.

  On the other hand, if ink is not ejected from the inkjet head for a long time, the ink in the head is evaporated and dried, and the thickened solid component in the ink may cause ink ejection failure. For this reason, in a conventional ink jet recording apparatus, prior to discharging ink to a print medium, a preliminary discharge is performed at a position different from the print medium, and printing is performed after the ink jet head is in a good state. is there. The same applies to the case where the ejection state of the ink jet head is inspected, and it is necessary to inspect after the ink jet head is in a good state.

However, the above-mentioned Patent Document 1 and Patent Document 2 do not disclose that preliminary ejection is performed at the time of ejection state inspection of an inkjet head, and on the other hand, the preliminary ejection and ejection state inspection are simply combined. If only the test is performed, there is a possibility that a considerable time is required for the inspection time.
JP-A-10-119307 Japanese Patent Laid-Open No. 11-78051

  The present invention has been made in view of such conventional problems, and provides an ejection state inspection apparatus and an ejection state inspection method for an inkjet head that performs inspection after the inkjet head is in a good state in a short time. With the goal.

  In order to achieve the above object, the apparatus of the present invention according to claim 1 is an apparatus for optically inspecting a discharge state of a plurality of ink jet heads, and means for pre-discharge prior to the inspection of the discharge state And means for sequentially inspecting the ejection state of the ink jet head.

  In order to achieve the above object, the apparatus of the present invention according to claim 2 is such that the distance between the preliminary ejection position and the ejection state inspection position is substantially the same as the distance between the plurality of inkjet heads. It is characterized by being.

In order to achieve the above object, the method of the present invention according to claim 3 is a method for optically inspecting a discharge state of a plurality of ink jet heads, and performing preliminary discharge prior to the inspection of the discharge state. Step, sequentially inspecting the ejection state of the inkjet head,
It is characterized by having.

  In order to achieve the above object, the method of the present invention according to claim 4 is such that the distance between the preliminary ejection position and the ejection state inspection position is substantially the same as the distance between the plurality of inkjet heads. It is characterized by being.

  According to the present invention, the preliminary ejection is performed before the ejection state of the inkjet head is inspected, so that the head can be in a good state and the inspection can be performed correctly, and the preliminary ejection position is inspected. Since the head is separated from the position by the distance of the head, there is no need to move an extra head carriage, and the inspection can be performed correctly in a short time.

  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. 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.

  Next, preliminary ejection performed prior to the above-described inspection of the ejection state of the inkjet head will be described.

  FIG. 5 is a top view showing a schematic configuration of the ink jet head ejection state inspection apparatus according to the first embodiment.

  As described with reference to FIG. 3, the inspection position B formed by the light emitting unit 32 and the light receiving unit 33 is a position for inspecting the ejection state of the inkjet head, and the ink droplets are ejected on this optical axis. Variations occur in the amount of light received by the light receiving unit 33, and the ejection state of ink droplets can be inspected. The position where the preliminary discharge is performed prior to the discharge state inspection is the position indicated by the dotted line C. The reason why the preliminary ejection is performed before the inspection is to improve the ejection state of the inkjet head by performing the preliminary ejection as described above. About several to several tens of firings for all the nozzles of the inkjet head ( It is preferable to strike (depending on ink jet head and ink characteristics).

  The reason why the preliminary ejection is not performed on the inspection position B is that the ink ejected by the preliminary ejection floats on the inspection position B, so that the inspection accuracy is reduced in a short period of time, and the floating ink is gradually received by the light emitting unit 32 and the light receiving unit. This is to prevent the inspection accuracy from deteriorating in the long term by being deposited on the portion 33. It is an important point of the present invention that the distance A between the inspection position B and the preliminary ejection position C is substantially the same as the physical interval between a plurality of ink jet heads, and the Nth head is the inspection position B. Since the (N + 1) th head to be inspected next is in the preliminary ejection position C, preliminary ejection is performed at the preliminary ejection position C without moving the head carriage after the completion of the inspection of the Nth head, and the distance thereafter The head carriage is moved by A and the N + 1th head is inspected. By doing so, it is possible to minimize the movement time of the head carriage while suppressing the influence of floating ink.

  Next, the inspection sequence of the ejection state of the inkjet head of the present invention will be described.

  FIG. 6 is a flowchart of the discharge state inspection according to the embodiment of the present invention.

  First, in step S1, the head carriage is moved so that the head to be inspected first approximately matches the preliminary ejection position. In step S2, preliminary ejection of the head is performed prior to the inspection, and in step S3, the head carriage is moved so that the head substantially coincides with the inspection position. In step S4, the ejection state of the head is inspected. At this time, the head to be inspected next is almost at the preliminary ejection position as described with reference to FIG. 5, and thus the head carriage is repeated without moving the head carriage, and when all the heads have been inspected. This sequence ends.

(Second Embodiment)
FIG. 7 is a top view showing a schematic configuration of an ink jet head ejection state inspection apparatus according to the second embodiment.

  By providing the partition plate 36 between the preliminary ejection position and the inspection position, it is possible to increase the accuracy of the ejection state inspection by adopting a configuration in which ink floating due to the preliminary ejection is less likely to flow around the inspection position.

  Further, as described above, the partition plate 36 may be provided to form an integrated unit, but it goes without saying that the unit for performing preliminary ejection and the unit for inspecting the ejection state may be separate units.

  In the ink jet head discharge state inspection method described here, the direction of the optical axis of the discharge state inspection apparatus and the direction of the nozzle row of the ink jet head are approximately aligned, and the head carriage is stopped at a predetermined position. The optical axis is arranged obliquely with respect to the direction of the nozzle row, and the preliminary discharge position is also arranged obliquely with respect to the nozzle row of the head in parallel with the optical axis. The same effect can be obtained by performing preliminary discharge and inspection of the discharge state while moving the carriage.

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 top view which shows schematic structure of the discharge state inspection apparatus of the inkjet head of the 1st Embodiment of this invention. It is a flowchart of the discharge state test | inspection of embodiment of this invention. It is a top view which shows schematic structure of the discharge state inspection apparatus of the inkjet head 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 Scan rail 6 Head carriage drive motor 7 Motor pulley 8 Driven pulley 9 Timing belt 14 Recording medium 20 Bus line 21 Image input unit 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 36 Partition plate

Claims (4)

An apparatus for optically inspecting a discharge state of a plurality of inkjet heads,
Means for preliminary discharge prior to the inspection of the discharge state;
Means for sequentially inspecting the ejection state of the inkjet head;
A discharge state inspection apparatus comprising:   The discharge state inspection apparatus according to claim 1, wherein a distance between the preliminary discharge position and a position where the discharge state is inspected is substantially the same as a distance between the plurality of inkjet heads. A method for optically inspecting a discharge state of a plurality of inkjet heads,
Performing preliminary discharge prior to the inspection of the discharge state;
Sequentially inspecting the ejection state of the inkjet head;
A discharge state inspection method comprising:   The ejection state inspection method according to claim 3, wherein a distance between the preliminary ejection position and the position where the ejection state is inspected is substantially the same as the distance between the plurality of inkjet heads.

Images