JPH0460023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an inkjet recording device, and more particularly to an inkjet recording device that performs recording by ejecting ink droplets from nozzles.

[Prior Art] In general, the diameter of the nozzle in the inkjet head of an inkjet recording device is several tens of micrometers, and ink droplets may not be ejected due to clogging of the nozzle due to dust or dirt, generation of air bubbles, etc. Since the conventional inkjet recording apparatus is provided with only the necessary minimum number of nozzles, it has the disadvantage that if any one of the nozzles fails to eject, it will result in a recording failure.

In addition, mechanisms have been proposed to recover from clogged nozzles as described above by manually or automatically pumping ink or suctioning ink from the ejection ports, but such mechanisms may prolong recording time or Otherwise, the recording operation is interrupted, which is inconvenient when recording work is being done in a hurry.

Furthermore, if such a recovery mechanism causes unrecoverable clogging or failure, the nozzle must be replaced, but in most inkjet recording devices, it may not be possible to replace individual nozzles. In most cases, the method is to replace the ink jet head as an assembly. Therefore, if even one nozzle suffers an irrecoverable failure, the entire expensive head assembly must be replaced, placing a heavy burden on the user.

[Purpose] The present invention has been made in view of the above points, and has a simple and inexpensive structure. It is an object of the present invention to provide a highly reliable inkjet recording device that can recover from problems and perform reliable recording operations.

[Example] Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 and FIG. 2 show an embodiment of the inkjet recording apparatus of the present invention. Here, a so-called head scanning type inkjet recording apparatus is used as an embodiment, in which a recording medium is scanned by moving an inkjet head.

FIG. 1 shows a front view of an inkjet head 1 of an inkjet recording apparatus of the present invention, and this inkjet head 1 has four main nozzles 2.
A to 2D are arranged at predetermined intervals along the main scanning direction of the ink jet head 1, which is indicated by an arrow in the figure. Further, corresponding to each of these main nozzles, spare nozzles 2A' to 2D' are connected to each main nozzle 2.
It is arranged a predetermined distance apart from A to 2D. That is, each preliminary nozzle is arranged in the main scanning direction, that is, in the head transport direction, with respect to the corresponding main nozzle.

Each nozzle shown in FIG. 4 is configured to be driven by ejection energy generating means such as a known piezo element or heating element to eject ink droplets, and this ejection drive is performed as shown in FIG. This is done by a control circuit.

That is, the head driver 3 generates a drive pulse for driving each nozzle in response to a drive signal applied externally, and this drive pulse is switched to the main nozzles 2A to 2D or the spare nozzle 2A by the ejection signal switcher 4. ' to 2D', and each nozzle of the ink jet head 1 is driven to eject. The head driver 3 is mainly composed of switching transistors, and the ejection signal switch 4 can be composed of a microcomputer, a discrete logic circuit, a gate circuit, a switch circuit, and the like.

A known ejection abnormality detector 6 is provided near the ink jet head 1 for mainly detecting ink failure, and the output of this ejection abnormality detector 6 is fed back to the ejection signal switch 4.
Unless a discharge failure is detected by this discharge abnormality detector 6, the discharge signal switch 4 will switch to the main nozzle 2A.
~2D is used to perform the recording operation, and when the ejection abnormality detector 6 detects an ink ejection failure, the ejection signal switcher 4 switches the output signal line to the main nozzle where the trouble occurred. Drive the corresponding spare nozzle.

Furthermore, a delay circuit 5 is attached to the ejection signal switching device 4, and the ejection signal switching device 4 delays the drive pulse by a time specified by the delay circuit 5 when driving the preliminary nozzles 2A' to 2D'. This delay time depends on the scanning speed of the inkjet head 1.
The distance between the main nozzle and the spare nozzle of the set is set equal to the time required to move.

The operation in the above configuration is performed as follows.

During a recording operation, the head driver 3 generates drive pulses necessary to drive each nozzle of the inkjet head 1 in response to drive signals applied from the outside as described above.

As long as no ejection failure such as non-ejection is detected by the ejection abnormality detector 6, the ejection signal switch 4 selects a necessary nozzle among the main nozzles 2A to 2D to perform printing. At this time, the ink jet head 1 scans in the direction of the arrow in FIG. 1, and at this time, each of the main nozzles 2A to 2D is driven one after another at a predetermined timing to eject ink onto the recording medium to form a desired dot. .

When the ejection abnormality detector 6 detects that an ejection failure has occurred in any of the nozzles, a spare nozzle corresponding to the main nozzle that has caused the ejection failure is selected and driven instead.

For example, when the main nozzle 2B causes a discharge failure and a detection signal is sent from the discharge abnormality detector 6 to the discharge signal switch 4, the discharge signal switch 4 switches the output signal line to select the spare nozzle 2B'. Ru. As a result, a drive pulse is applied to the spare nozzle 2B' instead of the main nozzle 2B, but at this time, the drive pulse to the spare nozzle 2B' is delayed by the time set in the delay circuit 5 and applied. .

Due to this delay, ink can be ejected from the preliminary nozzle 2B when the preliminary nozzle 2B' reaches the point on the recording medium where the main nozzle 2B is originally supposed to eject.

If the configuration is configured with redundancy in the number of nozzles as described above, it is possible to drive the corresponding spare nozzle when a problem occurs with any of the main nozzles that are regularly used. Since the spare nozzles are driven with a delay of the inkjet head scanning time corresponding to the interval between the spare nozzles, it is possible to reliably print dots at the same desired positions as those recorded by the main nozzles.
This switching can be done instantaneously, and there is no need to interrupt the recording operation and perform a recovery operation as in the conventional method, which saves recording time. Furthermore, even if one of the nozzles suffers a fatal failure, the spare nozzle can be continued to be used, reducing the burden on the user as there is no need to immediately replace the assembly, which is expensive as in the past. Can be done.

In the above embodiment, four main nozzles and four auxiliary nozzles are provided, but the number of nozzles is of course not limited to this. Furthermore, although the above description did not mention ink colors, it may be configured such that all four jets eject ink of the same color, or each of the four jets may eject different inks, such as yellow, magenta, cyan, etc.
Color recording may be performed by allocating and ejecting ink of four colors such as black.

In addition, the discharge abnormality detector 6 shown in the above embodiment
may be omitted. In this case, the ejection signal switch 4 may be configured with a dip switch or the like so that the operator can manually switch the signal line to the ink jet head 1 when a recording failure occurs.

In addition, even without providing a delay circuit, if the spare nozzles are arranged in the main scanning direction and are arranged so that the main nozzle performs printing first, when the main nozzle becomes unable to eject droplets, it can be immediately replaced. By switching the signal to the spare nozzle corresponding to the main nozzle, there is almost no deterioration in image quality.

In the above embodiment, the main nozzle performs main scanning, that is,
Although we have shown an example in which spare nozzles are arranged in the main scanning direction for each head and are arranged in the transport direction of the head, as shown in Fig. 3, the main nozzles are arranged in a direction different from the main scanning direction (in this example, at right angles). However, a spare nozzle may be provided for each of them. Further, as shown in FIG. 1, the spare nozzles do not have to be provided near the corresponding main nozzles.
For example, in the example of FIG. 1, the main and spare nozzles may be distributed among the eight nozzles shown, such as four on the right and four on the left. Alternatively, the four nozzles in the center may be used as main nozzles, and the two on the outside may be used as backup nozzles. When configured in this way, the scanning width of the head does not necessarily need to cover the entire recording width on the recording medium, but the main or spare nozzles currently in use are arranged so as to cover a predetermined recording width. Just do it.

The present invention can also be used in a so-called full-line multi-head inkjet recording device in which nozzles are provided over the entire main scanning width, and inkjet recording devices in which the head is fixed and the recording medium is transported.

Furthermore, the number of spare nozzles is not limited to one at a time, but it is of course possible to provide a large number of spare nozzles and to set the delay time in several stages.

[Effects] As is clear from the above description, according to the present invention, in an inkjet recording device that performs recording by ejecting ink droplets from nozzles, at least one spare nozzle is provided corresponding to each main nozzle. In addition, means for switching the drive signal to select and drive either the main or spare nozzle, and when driving the spare nozzle, a means for driving the spare nozzle for a scanning time corresponding to the distance from the corresponding main nozzle to the spare nozzle. Since the configuration is equipped with a means to adjust the nozzle drive timing, even if a problem occurs with the nozzle, the simple and inexpensive configuration allows the nozzle problem to be resolved without interrupting or prolonging recording work. Therefore, it is possible to provide an excellent inkjet recording device with high reliability, which can recover from errors and perform reliable recording operations.

[Brief explanation of the drawing]

FIG. 1 is a front view of an ink jet head used in the ink jet recording apparatus of the present invention, FIG. 2 is a block diagram of a drive control circuit of the ink jet recording apparatus of the present invention, and FIG. 3 is a front view of an ink jet head used in the ink jet recording apparatus of the present invention. It is a front view showing a different example. DESCRIPTION OF SYMBOLS 1... Ink jet head, 2A to 2D... Main nozzle, 2A' to 2D'... Spare nozzle, 3... Head driver, 4... Ejection signal switcher, 5... Delay circuit, 6... Ejection abnormality detector.

Claims (1)

[Scope of Claims] 1. In an inkjet recording device that performs recording by ejecting ink droplets from nozzles, at least one spare nozzle is provided corresponding to each main nozzle, and a drive signal is switched between the main and spare nozzles. Means for selecting and driving one of the nozzles, and means for adjusting the drive timing of the spare nozzle by a scanning time corresponding to the distance from the main nozzle to the corresponding spare nozzle when driving the spare nozzle. An inkjet recording device characterized by: 2. Ink ejection failure detection means is provided, and when an ejection failure is detected by the detection means, the switching means switches the drive signal from the main nozzle to the spare nozzle. The inkjet recording device described in .