JP2000318178A - Ink jet recording device - Google Patents

Abstract

(57) Abstract: Provided is an ink jet recording apparatus provided with a non-discharge detecting means which can be sufficiently applied even when a distance between an ink jet head and a recording medium is extremely small. An ink jet printer that discharges ink droplets from nozzle holes (13a) formed at the tip of an ink jet head (10) is provided in the ink jet head (10) on the front side of the nozzle holes (13a) in the ink discharge direction. In addition, a pair of electrodes 21b opposed to each other with the nozzle hole 13a interposed therebetween, and a capacitance detection circuit 22 for detecting non-ejection of ink droplets by detecting a change in capacitance between the electrodes 21b. The ejection detection means 20 is mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for ejecting ink droplets from nozzle holes formed at the tip of an ink jet head, and more particularly, to ink jet recording capable of detecting non-ejection of ink droplets from nozzle holes. Related to the device.

[0002]

2. Description of the Related Art An ink jet recording apparatus such as an ink jet printer discharges ink droplets from an ink jet head mounted on a carriage to record characters and images on a recording medium such as paper. Usually, an ink cartridge filled with ink is attached to the head via a manifold having an ink supply path.

[0003] The ink jet head uses ink stored in a number of cavities provided in an aligned state,
An actuator composed of an electromechanical transducer, an electrothermal transducer, or the like is configured to eject ink droplets from nozzle holes formed at the tip of the head. Since the ink itself is also very easy to solidify, the ink near the nozzle hole that is in direct contact with the air solidifies and causes clogging of the nozzle hole, or foreign matter or bubbles enter the ink, causing ink droplets to drop. May cause printing failure due to non-ejection.

For this reason, this type of ink jet recording apparatus is provided with a non-discharge detecting means for detecting a non-discharge state of the ink droplet when the nozzle hole is clogged or the like and the non-discharge of the ink droplet occurs. Then, when the non-ejection detecting means detects the non-ejection of the ink droplet, for example, the clogging of the nozzle hole is eliminated by forcibly performing a purging process such as suctioning from the nozzle side of the inkjet head. There is something.

[0005] Such a non-discharge detecting means is disclosed, for example, in Japanese Patent Application Laid-Open No. Sho 59-120264. This non-discharge detecting means is provided at the front of the nozzle hole of the ink jet head in the ink discharging direction. The charging electrode and the induction electrode are sequentially arranged, and after the ink droplet ejected from the nozzle hole is charged by the charging electrode, an induction current generated when the charged ink droplet passes through the induction electrode is detected. Thus, it is detected whether or not the ink droplet has been ejected.

[0006]

By the way, in the non-discharge detecting means as described above, it is necessary to provide two kinds of electrodes, a charging electrode for charging and an induction electrode for detection, in front of the ink jet head in the ink discharging direction. However, in a typical ink jet printer, the distance between the ink jet head and the recording medium is generally as short as 1 mm or less, so it is impossible to accommodate two types of electrodes between them. There is a problem that it is not practical to apply the above-described technology to a type of inkjet recording apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording apparatus provided with a non-discharge detecting means which can be sufficiently applied even when the distance between an ink jet head and a recording medium is very small.

[0008]

Means for Solving the Problems and Effects There is provided an ink jet recording apparatus for discharging ink droplets from a nozzle hole formed at the tip of an ink jet head. Non-ejection of ink droplets by detecting a change in capacitance between a pair of electrodes provided on the front side of the nozzle holes of the ink jet direction in the ink ejection direction and facing each other across the nozzle holes, and detecting a change in capacitance between the electrodes. And a capacitance detection circuit for detecting the non-discharge detection.

In the ink jet recording apparatus having the above-described structure, only one type of electrode for detecting a change in capacitance is provided in front of the nozzle hole of the ink jet head in the ink ejection direction. Since non-ejection can be detected, there is no need to increase the distance between the inkjet head and the recording medium in order to provide electrodes, and the printing mechanism part is made compact, just like an inkjet recording device without non-ejection detection means. It is possible to do.

According to a second aspect of the present invention, the capacitance detecting circuit detects the capacitance between the electrodes in synchronization with an ejection signal of an ink droplet from the nozzle hole. In this way, non-ejection of ink droplets can be detected during printing by the inkjet recording device.If non-ejection of ink droplets is detected during printing, the printing operation is temporarily interrupted and purged. By restarting the printing operation after the processing, it is possible to always ensure a high-quality printing state with no missing dots. This eliminates the need for discarding the recording medium in the middle of printing and reprinting from the beginning when the print quality is reduced due to the non-ejection of ink droplets as in the conventional case, and wastes printing time and recording medium. Can be effectively prevented.

According to a third aspect of the present invention, there is provided an ink jet recording apparatus, wherein a hole or a cutout through which an ink droplet ejected from the nozzle hole passes is formed, and the electrode is provided on a peripheral edge of the hole or the cutout. By attaching the obtained electrode plate to the tip of the inkjet head, there is an effect that the structure for attaching the electrode to the inkjet head is simplified.

According to another aspect of the present invention, there is provided an ink jet recording apparatus comprising:
When a nozzle plate having a nozzle hole is provided, the electrode plate may be attached to the nozzle plate.

[0013] In particular, when the electrode plate is formed integrally with the nozzle plate as in the ink jet recording apparatus according to the fifth aspect, compared with the case where the nozzle plate and the electrode plate are individually attached, Since the overall thickness can be reduced, there is an effect that the printing mechanism is further compacted.

[0014]

Embodiments will be described below with reference to the drawings. As shown in FIG. 1, the inkjet printer 1 has a platen 3 between a pair of frames 2 (only one frame is shown in FIG. 1) via a shaft 3a.
The platen 3 is rotatably driven by a motor 4. A piezoelectric inkjet head 10 is arranged facing the platen 3, and the piezoelectric inkjet head 10 is mounted on a carriage 6 together with the ink cartridge 5. The carriage 6 is slidably supported by two guide rods 6 a disposed in parallel with the axis of the platen 3, and is coupled to a timing belt 8 stretched over a pair of pulleys 7. When the pulley 7 rotates, the carriage 6 moves along the platen 3.

As shown in FIG. 2, the ink-jet head 10 has a plurality of cavities 11a formed in a groove shape and a manifold 1 for supplying ink to each of the cavities 11a.
A cavity plate 11 formed with an ink flow path composed of 1b, a piezoelectric element 12 for pressurizing the ink stored in the cavity 11a, and a nozzle plate 13 formed with a plurality of nozzle holes 13a for discharging ink droplets. An electrode plate 21 is fixed to the front surface of the nozzle plate 13.

Piezoelectric element 12 as ink pressurizing means
Is made of a piezoelectric material formed in a sheet shape, and is joined to the upper surface side of the cavity plate 11 to close an opening at an upper portion of the ink flow path. This piezoelectric element 12
Is configured such that a driving voltage is applied by driving means (not shown), and when the driving voltage is applied, the piezoelectric element 1
2, presses the ink stored in the cavity 11a by deforming vertically in FIG.

The nozzle plate 13 is provided with each nozzle hole 1.
3a is fixed to the front end surfaces of the cavity plate 11 and the piezoelectric element 12 so that the nozzle holes 3a communicate with the cavities 11a of the cavity plate 11, and the ink in the cavity 11a is pressurized by the piezoelectric element 12. An ink droplet P is ejected from 13a.

As shown in FIGS. 2 and 3, the electrode plate 21 is formed with a plurality of holes 21a which are slightly larger so as to surround the respective nozzle holes 13a formed in the nozzle plate 13. A pair of electrodes 21b facing each other with the respective nozzle holes 13a interposed therebetween is provided on the periphery of each hole 21a.

As shown in FIG. 4, a capacitance detecting circuit 22 having an AC power supply 22a and a current detector 22b is connected to the pair of electrodes 21b provided for each of the nozzle holes 13a. The electrode 21b and the capacitance detection circuit 22 constitute a non-discharge detection unit 20 for ink droplets.

The capacitance detecting circuit 22 includes two electrodes 21.
b is detected as a change in the current value, and the change in the capacitance between the ink droplets P ejected from the nozzle hole 13a is detected.
Is detected by the current detector 22b as a change in the current value between the two electrodes 21b, which changes when passing between the pair of electrodes 21b, so that the ink droplet P is ejected from the nozzle hole 13a. It is possible to detect whether or not.

FIG. 5 is a block diagram showing a control system for driving the ink jet printer 1. As shown in FIG. As shown in FIG. 1, the inkjet printer 1 includes a head drive controller 32 for controlling the drive of the inkjet head 10, a carriage feed mechanism 41, and a purge mechanism 42.
The head drive controller 32 is based on image data to be printed stored in the image data storage unit 33 and a print timing signal output from the timing device 34. In addition to controlling a plurality of drivers 35 for applying drive signals to the plurality of piezoelectric elements 12 provided for each cavity 11a, the capacitance detection circuit 22 controls the electrodes in synchronization with the drive signals output from the drivers 35. 2
Non-ejection detecting means 2 so as to detect the capacitance between
0 is controlled. Each driver 35
Is connected to a power supply 36 capable of supplying a voltage sufficient to generate a drive signal.

A series of printing processes in the ink jet printer 1 configured as described above will be described with reference to a flowchart shown in FIG. The print processing illustrated in FIG. 6 is, for example, processing performed when a print instruction is received from an externally connected host device. When the printing process is started, first, image data to be subjected to the printing process is obtained (step S1), and the obtained image data is developed into bitmap data (step S2).

The bitmap data has a data format directly corresponding to each dot of the print image. Based on the bitmap data, the head drive controller 32 drives each driver 35 to execute actual printing. (Step S3). At this time, the head drive controller 32 outputs a detection command to the non-discharge detection means 20 so as to synchronize with the drive signal of the driver 35, and simultaneously detects whether or not the ink droplet has been properly discharged (step S4). .

If it is detected in step S5 that the ink droplet has not been ejected, the printing is temporarily interrupted (step S5).
6), the non-ejection channel and the non-ejection detection position are stored (step S7). Then, after performing the purge process (Step S8), the inkjet head 10 is returned to the non-ejection detection position (Step S9), and the process returns to Step S3 to execute printing again.

On the other hand, if no non-ejection of ink droplets is detected in step S5, printing is continuously performed, and a series of printing processes ends when printing has been performed for all bitmap data. .

As described above, the ink jet printer 1 is provided with only one type of electrode 21b for detecting a change in capacitance, in front of the nozzle hole 13a of the ink jet head 10 in the ink discharge direction. Since it is possible to detect non-ejection of droplets, compared to a conventional inkjet recording apparatus in which two types of electrodes such as a charging electrode and a detection electrode must be disposed in the ink ejection direction front side of the inkjet head, The distance between the recording medium and the recording medium can be kept small, and the printing mechanism can be made compact as in the case of an ink jet recording apparatus having no ejection failure detecting means.

Further, the ink jet printer 1 includes:
Driver 35 for ejecting ink droplets from nozzle holes 13a
By detecting the capacitance between the electrodes 21b in synchronization with the drive signal of, the non-ejection of the ink droplet is detected while printing is being performed, and if the non-ejection of the ink droplet is detected during printing,
Once the printing operation is interrupted and the purging process is performed, printing is performed again from the position where ink droplet non-ejection has occurred, so it is possible to always ensure a high quality printing state with no missing dots Becomes Therefore, when the print quality is deteriorated due to the non-ejection of ink droplets as in the related art, it is not necessary to discard the recording medium that has been printed halfway and to print again from the beginning. Waste can be effectively prevented.

Further, the ink jet printer 1 includes:
Hole 2 through which ink droplets ejected from nozzle hole 13a pass
Electrode plate 21 provided with electrode 21b on the periphery of 1a
Is applied to the tip of the inkjet head 10, so that the structure for attaching the electrodes to the inkjet head 10 is simplified, and the inkjet head provided with the electrodes can be manufactured efficiently. is there.

In this embodiment, as described above, a structure in which the separate electrode plate 21 having the electrode 21b is fixed to the front surface side of the nozzle plate 13 is adopted. As shown in FIG. It is also possible to use a nozzle plate 15 having a nozzle hole 15a, a hole 15b, and an electrode 15c in which an electrode plate portion is integrally formed,
By adopting such a configuration, it is possible to efficiently manufacture an ink jet head provided with electrodes, and to reduce the overall thickness as compared with a case where a nozzle plate and an electrode plate are separately mounted. Since it is possible, there is an effect that the printing mechanism can be made more compact.

The purging process executed during printing is as follows.
As in the normal purging process performed at the time of starting the printer or the like, the ink in the cavity 11a where the ejection failure has occurred is pressurized for a certain time (several seconds) or is suctioned from the outlet side of the nozzle hole 13a. The non-ejection channel may be recovered by forcibly ejecting the ink in the cavity 11a.

Although the purging process may be basically performed on the color portion where the non-ejection has occurred, it is also possible to perform the purging process for all the colors collectively or to recover only the non-ejection channel by so-called flushing. It is possible. When the purge process is performed for all the colors at once, the amount of ink discarded by the purge process increases, but the purge mechanism can be simplified. Conversely, when only the non-ejection channel is recovered, the drive circuit is used. Although complicated, the amount of ink discarded by the purge process can be minimized. Therefore, any method may be adopted in consideration of the advantages and disadvantages of each.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an ink jet recording apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing an inkjet head in the inkjet recording apparatus according to the first embodiment.

FIG. 3 is a perspective view showing the inkjet head according to the first embodiment.

FIG. 4 is a schematic configuration diagram showing a non-ejection detecting unit in the ink jet recording apparatus according to the embodiment.

FIG. 5 is a block diagram showing a control system for driving the above ink jet recording apparatus.

FIG. 6 is a flowchart showing a series of printing processes in the above ink jet recording apparatus.

FIG. 7 is a perspective view showing a modification of the ink jet head in the above ink jet recording apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet printer 10 Ink jet head 13 Nozzle plate 13a Nozzle hole 20 Non-discharge detection means 21 Electrode plate 21a Hole 21b Electrode 22 Electrostatic capacity detection circuit

Claims (5)

[Claims] 1. An ink jet recording apparatus for ejecting ink droplets from a nozzle hole formed at the tip of an ink jet head, comprising: By detecting a change in capacitance between the electrodes,
An ink jet recording apparatus, comprising: a non-discharge detection unit including a capacitance detection circuit for detecting non-discharge of an ink droplet. 2. The ink jet recording apparatus according to claim 1, wherein the capacitance detection circuit detects the capacitance between the electrodes in synchronization with an ejection signal of an ink droplet from the nozzle hole. . 3. An electrode plate having a hole or notch formed therein through which ink droplets ejected from said nozzle hole passes, and said electrode provided on the periphery of said hole or notch, is attached to the tip of said inkjet head. The ink jet recording apparatus according to claim 1. 4. The ink jet recording apparatus according to claim 3, wherein the ink jet head has a nozzle plate having a nozzle hole formed at a tip thereof, and the electrode plate is attached to the nozzle plate. 5. The ink jet recording apparatus according to claim 4, wherein the electrode plate is formed integrally with the nozzle plate.