JP2000351202A - Ink droplet ejection state detection apparatus and recording apparatus using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent reflected light from an object interposed between a light emitting source and a light receiving unit and accurately detect the presence or absence of ink ejection. SOLUTION: In order to prevent a light beam 7 emitted from a light emitting source 5 from being reflected by a bottom surface of a carriage 110 on which a recording head is mounted, entering an opening 9 and being caused by a light receiving unit 6, light is emitted so that reflection does not occur. The light shielding plate 7 is provided between the source 5 and the carriage 110. Thus, the pure / non-discharge state of the ink discharge element is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink droplet ejection state detecting device for a recording head used in an apparatus for recording an image by ejecting ink droplets, and a recording apparatus using the same.

[0002]

2. Description of the Related Art In an ink jet recording method, an image is obtained by directly discharging a fine ink droplet from a fine nozzle onto a print medium to perform printing. Unlike electrophotography, there are few intervening parts until an image is formed.
It has the major feature that the intended product can be obtained stably. However, if the ink is not ejected (clogging with dust or thickened ink, the ink droplets are ejected by the action of thermal energy, the disconnection of the heater, the ink droplets And the like, the nozzle opening is covered by the recording head), and white streaks may occur along the scanning direction of the print head.

On the other hand, a method of detecting non-ejection using a light emitting element (LED) and a light receiving element (photodiode) has been used. In this method, an ink droplet is ejected into a light beam from a light emitting element, and non-ejection is detected from an output signal of a light receiving element that receives the light. This method is called an optical non-discharge detection method. When performing non-discharge detection by this optical non-discharge detection method, since an ink droplet is small relative to a light beam, an opening (a pinhole, a slit, or the like) is provided in front of the light receiving sensor to perform non-discharge detection. I have.

To detect the non-ejection, the nozzles are sequentially driven to eject one drop into the light beam, and this is detected. The ejection signal is obtained at the ejection frequency interval of the ink droplet. On the other hand, the ink droplet includes a main droplet and a satellite, and two detection signals of the main droplet and the satellite are obtained for one ejection signal. At that time, since the satellite has a lower ejection speed, the satellite detection signal is obtained after the main droplet detection signal. Therefore, it is necessary that the detection signal of the satellite does not overlap with the detection signal of the main drop of the next ink drop. To this end, the light flux is brought as close as possible to the head (head carriage) to eject the ink drop. It is necessary to detect the discharge failure by shortening the distance from the light beam to the light beam.

[0005]

However, when the head is long in the nozzle row direction and the distance between the light receiving element and the light emitting element is long as in the case of an ink jet printing machine, the light is diffracted.
The end of the light flux is reflected by a part of the head or a head carriage on which the head is mounted, and the reflected light also enters the light receiving unit, thereby generating noise. When noise occurs, the ejection signal may be buried in the noise, and even if ejection is performed, it may be erroneously detected as non-ejection.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an ink capable of preventing reflected light from an object interposed between a light-emitting source and a light-receiving unit and accurately detecting the presence or absence of ink ejection. An object of the present invention is to provide a droplet discharge state detecting device and a recording device using the same.

[0007]

In order to solve this problem, for example, an ink droplet ejection state detecting device according to the present invention has the following arrangement. That is, a light emitting source and a light receiving section are provided with a recording head having a plurality of ink discharging elements therebetween, and the ink discharging elements are driven, and the state of the light flux from the light emitting source to the light receiving section is controlled by the ink discharging elements. An apparatus for detecting an ink ejection / non-ejection state, in which an object interposed between the light emitting source and the light receiving unit prevents reflected light from the light emitting source from reaching the light receiving unit. A light shielding member is provided at a predetermined position between the light emitting source and the light receiving unit.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

<Structure of Entire Apparatus> FIG. 10 shows an example of a schematic structure of an ink jet recording apparatus according to the embodiment.

In FIG. 1, reference numeral 1 denotes a cloth as a recording medium (print medium), which is unwound in accordance with the rotation of the unwind roller 11,
The transport unit 10 provided at a portion facing the printing unit 1000
After being conveyed in a substantially horizontal direction by 0, it is taken up by a take-up roller 21 via a feed roller 17 and a middle roller 19.

The transport section 100 generally includes transport rollers 110 and 120 provided on the upstream and downstream sides of the printer section 1000 in the transport direction of the cloth 1, and an endless belt-shaped transport belt wound between the rollers. 130, and a pair of platen rollers 140 provided to extend the transport belt 130 with an appropriate tension within a predetermined range so as to regulate the printing surface of the fabric flat when printing by the printer unit 1000, and to improve flatness. ing. Here, in this example, the transport belt 130 is made of a metal as disclosed in, for example, Japanese Patent Application Laid-Open No. H5-212851, and the surface thereof is partially enlarged as shown in the drawing. An adhesive layer (sheet) 133 is provided. Then, the fabric 1 is adhered to the transport belt 130 by the adhesive layer 133 by the attaching roller 150, and the flatness at the time of printing is secured.

The printing agent is applied by the printer unit 1000 in the area between the platen rollers 140 to the cloth 1 conveyed in such a state where the flatness is ensured. It is peeled off from the layer 133 and is wound up by the winding roller 21. The drying heater 60
A drying process is performed according to 0. The drying heater 600
Any suitable form, such as one that blows warm air onto the cloth 1 or one that irradiates infrared rays, can be used.

<Structure of Printer Unit> FIG. 11 is a perspective view schematically showing a printer 1000 and a transport system for the cloth 1.
FIG. 12 is a cross-sectional view showing a scanning system of the carriage. Hereinafter, the configuration of the printer unit 1000 will be described with reference to FIGS.

As shown in FIGS. 10 and 11, the printer unit 1000 is scanned in a direction different from the transport direction (sub-scanning direction) F of the cloth 1, for example, in the width direction S of the cloth 1 orthogonal to the transport direction F. It has a carriage 1010. 1
Reference numeral 020 denotes a support rail extending in the S direction (main scanning direction), and a slider 10 fixed to the carriage 1010.
12 is supported, and a slide rail 1022 for guiding is supported. Reference numeral 1030 denotes a motor serving as a driving source for performing main scanning of the carriage 1010. The driving force is transmitted to the carriage 1010 via a belt 1032 to which the carriage 1010 is fixed and other appropriate transmission mechanisms.

The carriage 1010 has a print head 1100 in which a large number of printing elements (ink ejection ports = nozzles) are arranged in a predetermined direction (in the present embodiment, the transport direction F).
Are held in a direction (main scanning direction S in this example) different from the above-mentioned predetermined direction, and in this example, they are held in two stages in the transport direction. In the print head 1100 of each stage, the color used for the printing agent having a different color and the number of print heads can be conveniently selected according to an image to be formed on the fabric 1 or the like, but are, for example, three primary colors of printing. Yellow (Y), magenta (M), and cyan (C), or black (Bk) added thereto can be used. Alternatively, instead of, or together with, a special color (metallic color such as gold or silver, vivid red or blue, etc.) that cannot be expressed or is difficult with the three primary colors, etc., can be used. Alternatively, even in the case of the same color, a plurality of printing agents may be used according to the density.

In this embodiment, a plurality of print heads 1100 arranged in the main scanning direction S are arranged as shown in FIG.
Two stages are provided in the transport direction F. The color, the number, the arrangement order, and the like of the printing agents used by the print heads in each stage may be the same in each stage or may be different depending on the image to be printed. Further, it is possible to print again the area printed by the main scanning movement of the one-stage print head by the next-stage print head (or to perform complementary thinned-out printing by the respective-stage print heads). It is also possible to perform high-speed printing by sharing print areas. Further, the number of print head stages is not limited to two, but may be one or three or more.

In this embodiment, the print head 1100
As an ink jet head, for example, a so-called bubble jet head proposed by the present applicant using a heating element that generates heat energy that causes film boiling of ink as energy used for discharging ink is used. . Then, with respect to the fabric 1 which is conveyed in a substantially horizontal direction by the conveyance unit 100, the ink ejection ports as the printing agent applying element are used in a state where the ink ejection ports face downward, so that the head difference between each ejection port is eliminated. The conditions are made uniform so that a good image can be formed, and a uniform recovery process can be performed on all the ejection openings.

In FIG. 12, capping means 122
0 is in contact with the ejection port surface of each print head 1100 during the non-printing operation, and suppresses the drying and mixing of foreign matter;
Alternatively, it is removed. Specifically, during a non-printing operation, the print head 1100 moves to a position facing the capping unit 1220. Then, the capping unit 1220 is driven in the cap direction by the driving unit 1210, and performs capping by pressing an elastic member or the like against the ejection port surface to protect the recording head 1100.

The clogging prevention means 1231 receives the discharged ink when the print head 1100 performs a discharge operation (preliminary discharge operation) for equalizing discharge conditions by ink refresh. The clogging prevention means 1231 is provided at a portion facing the print head outside the print area by the print head, and a liquid receiving member for absorbing and receiving the pre-discharged ink is provided between the capping means 1220 and the print area and between the capping means 1220 and the print area. It is located on the opposite side. Note that a liquid holding member is provided in the liquid receiving member, and a sponge-like porous member or the like is used as a material thereof.

A wiping means (wiping blade) 70 is provided between the capping means 1220 and the printing area so as to rub the discharge port surface of the print head 1100, and the wiping means adheres to the discharge port surface by the rubbing. We try to wipe off water drops and dust.

<Structure of Optical Discharge Detecting Apparatus> FIGS. 7, 8 and 9 show a schematic structure of a method for detecting a non-discharge head in the embodiment.

FIG. 7 is a sectional view for explaining a schematic configuration of the discharge failure detecting device. In the figure, ink droplets are ejected from the print head 2 of one color component of the print head 1100 and pass through the light flux 7 to prevent clogging.
Head to 231. The light beam 7 exits from the light source 5 and is
Through the light receiving sensor 6.

FIG. 8 is a perspective view for explaining a schematic configuration of the discharge failure detecting device. In FIG. 8, the print head 2
Has a number of nozzles on its lower surface,
231 is ejected, and the arrow 3 indicates the main scanning direction.
032 moves in the main scanning direction. Reference numerals 8 'and 8 "denote print media (fabrics) which are fed in the sub-scanning direction in the direction of arrow 4.
8 'is an area which has already been recorded by the print head 2,
8 "is an area to be printed.

The light emitting section 5 and the light receiving section (light receiving sensor) 6 are arranged on opposite sides of the head, and the light emitting section 5 generates a beam 7 so as to have a certain angle with the nozzle arrangement.

FIG. 9 is a conceptual diagram for determining whether there is a non-discharge nozzle. FIG. 9 shows the time on the horizontal axis and the output (voltage) from the light receiving unit 6 on the vertical axis. 6-a shows an output waveform from the light receiving unit 6. Reference numeral 6-b denotes a signal (encoder reference signal) detected from an encoder (not shown) with the movement of the carriage, and the individual nozzles of the print head 2 are driven in synchronization with this signal.

As shown in FIG. 7, the print head 2 drives the nozzles in order in synchronization with the signal from the encoder reference signal so that the ink droplet passes through the center of the beam 7, and sequentially prints the droplets one by one. Let it be discharged. By discharging with the encoder reference signal, each ink droplet can pass through the center of the light beam with high accuracy. For this reason, by performing the operation on the preliminary ejection box 4, no extra space is required, it is possible to incorporate it into a part of the printing sequence, and it is not necessary to reduce the printing speed. That is, the determination of non-ejection may be based on the speed of the scanning movement of the carriage during normal printing.

Since it is necessary to narrow the observation area in order to reduce the size of the luminous flux with respect to the ink droplet and increase the S / N of the output, the opening (pinhole, slit, etc.) 9 is formed by the light receiving sensor. It is provided in front. As shown in FIG. 9, a method of determining non-discharge is as follows. At a certain time t1, an encoder sends a discharge signal of an ink droplet to a nozzle based on a signal, and the voltage is changed from V2 (H) to V2 (L). Changes to If the nozzle is a healthy nozzle, an ink drop is ejected and the ink drop passes through the luminous flux,
The output waveform from the light receiving sensor changes at the time t3 to the voltage V1.
(L) to the voltage V1 (H) (V1 (H) -V
1 (L) is called an ejection signal level). At this time, time tl
Output from V to a certain time (for example, t4)
If it exceeds 1 (M), it is determined that ejection has occurred, and if it does not exceed 1 (M), it is determined that ejection has failed. By synchronizing with the ejection signal generated from the signal of the encoder, the timing of seeing the detection signal for each nozzle can be known, and erroneous detection due to a noise signal or the like can be prevented. In the case of non-ejection, the output waveform is the voltage V1 as shown by the dotted line (6-c) in FIG.
(L) is maintained.

<Discharge detection with one light shielding plate>
2 and 3 are cross-sectional views for explaining a schematic configuration of the discharge failure detection device according to the embodiment.

In FIG. 1, reference numerals 30 and 31 denote positions where light shielding plates are provided. FIG. 1 shows a state in which there is no light-shielding plate, FIG. 2 shows a state in which a light-shielding plate 30 is provided between the light-emitting portion and the carriage, and FIG. 3 shows a state in which a light-shielding plate 31 is provided between the carriage and the light-receiving portion. Each state is shown in the case where it is provided.

First, as shown in FIG. 1, when there is no light-shielding plate, as shown in FIG. 1, the upper end of the light flux 7 from the light emitting source 5 strikes the lower surface of the carriage 1010 and is reflected as indicated by a two-dot chain line. Light has entered the light receiving part. It can be seen that if the position where the light is reflected on the carriage can be moved toward the light receiving section, light can be prevented from being reflected on the carriage. Therefore, a light-shielding plate 30 is provided between the light-emitting unit and the carriage, and the light-shielding plate 30 shields a part of the upper end of the light flux 7 to prevent the upper end of the light flux from being reflected on the carriage so that reflected light is not generated. I do. FIG. 2 shows the situation at that time.

Even with this, it is possible to prevent reflected light from entering the light receiving section. If it is impossible to provide a light-shielding plate between the light-emitting unit and the carriage due to a mechanical configuration problem, by providing a light-shielding plate between the carriage and the light-receiving unit, the reflected light is completely blocked, It is also possible to prevent light from entering the light receiving unit. This is shown in FIG.

As shown in the figure, by providing the light shielding plate 31, the light reflected by the carriage (represented by a two-dot chain line) is completely shielded from light and does not enter the light receiving portion. FIG.
As can be seen, when a light shielding plate is provided between the light emitting unit and the carriage, it is more suitable to dispose the light shielding plate immediately before the carriage to prevent light from being reflected on the carriage. Also,
As can be seen from FIG. 3, when a light-shielding plate is provided between the light-receiving unit and the carriage, it is more appropriate to dispose the light-shielding plate immediately after the carriage to prevent the reflected light of the carriage from entering the light-receiving unit.

<Detection of Discharge with Two Light Shielding Plates> In particular, when the head is long in the nozzle row direction and it is impossible to completely block the reflected light with one light shielding plate, two light shielding plates are used. To shield the reflected light. The situation at this time is shown in FIGS.
Shown in FIG. 4 shows a state in which there is no light-shielding plate, FIG. 5 shows a case in which a light-shielding plate is provided only between the light-emitting source and the carriage, and FIG. This shows a state in which a light shielding plate is provided for each sheet.

As can be seen by comparing FIGS. 4 and 5, even if the light-shielding plate is provided only between the light-emitting portion and the carriage, the amount of reflected light entering the light-receiving portion can be reduced, but the light-receiving portion can be reduced completely. Light cannot be shielded. This is because the optical path length becomes longer because the head is longer in the nozzle row direction. FIG. 6 shows a state in which a light shielding plate is also provided between the carriage and the light receiving section in order to completely block the remaining reflected light. As can be seen from FIG. 6, the reflected light, which could not be prevented by the light shielding plate 30 alone, is completely shielded by providing the light shielding plate 31, and no reflected light enters the light receiving portion. In this case, the arrangement of the two light-shielding plates should be such that the light-shielding plate between the light-emitting unit and the carriage is located immediately before the carriage, and the light-shielding plate between the light-receiving unit and the carriage is located immediately after the carriage so that the reflected light is received by the light-receiving unit It is suitable for preventing light from entering.

As described above, according to this embodiment,
If a discharge failure detection device provided with a light-shielding plate is used, it is possible to prevent light from being reflected on the head carriage and from entering the light-receiving portion. Then, it is possible to prevent the occurrence of noise due to the reflected light, to prevent erroneous detection, and to reliably perform non-discharge detection.

The non-discharge detecting device in the above embodiment may be provided by the number of a plurality of recording heads or nozzle rows mounted on the carriage. Can be detected, and it is sufficient to provide one from the viewpoint of saving space. However, when a multi-stage carriage is provided as shown in FIG. 10, the number of stages is required.

In the embodiment, the reflection by the carriage has been described as an example. However, if there is a reflection from an object interposed between the light emitting unit and the light receiving unit, the same effect can be obtained by blocking the reflected light. The present invention is not limited by the above-described embodiment because the effects can be obtained.

[0038]

As described above, according to the present invention, it is possible to prevent reflected light from an object interposed between a light emitting source and a light receiving unit, and to accurately detect the presence or absence of ink ejection.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical path when a light shielding plate is not provided in an embodiment.

FIG. 2 is a diagram illustrating an optical path when a light shielding plate is provided between a head carriage and a light emitting source in the embodiment.

FIG. 3 is a diagram illustrating an optical path when a light shielding plate is provided between a head carriage and a light receiving unit in the embodiment.

FIG. 4 is a diagram illustrating an optical path when a head is long in the nozzle row direction and there is no light shielding plate.

FIG. 5 is a diagram illustrating an optical path when a light shielding plate is provided between a head carriage and a light emitting source when the head is long in the nozzle row direction.

FIG. 6 is a diagram illustrating an optical path when a light shielding plate is provided between the head carriage and the light emitting source and between the head carriage and the light receiving unit when the head is long in the nozzle row direction.

FIG. 7 is a cross-sectional view illustrating a schematic configuration of a discharge failure detection device.

FIG. 8 is a perspective view showing a schematic configuration of a discharge failure detection device.

FIG. 9 is a timing chart showing the relationship between the timing of sequentially discharging ink droplets from nozzles and the amount of light sensed by a light receiving element.

FIG. 10 is a cross-sectional configuration diagram of an ink jet printing apparatus to which the discharge failure detection device of the present invention is attached.

FIG. 11 is a perspective view showing a schematic configuration of a printing unit of the apparatus shown in FIG.

FIG. 12 is a side sectional view of the printing unit shown in FIG. 11;

Claims (7)

[Claims] 1. A light emitting source and a light receiving unit are provided between a recording head having a plurality of ink discharging elements, and the ink discharging elements are driven. An apparatus for detecting an ink ejection / non-ejection state of an ejection element, comprising: an object interposed between the light emitting source and the light receiving unit;
An ink droplet ejection state detecting device, wherein a light shielding member is provided at a predetermined position between the light emitting source and the light receiving unit so as to block reflected light from the light emitting source from reaching the light receiving unit. 2. The apparatus according to claim 1, wherein the object is a carriage on which a recording head is mounted. 3. The light-shielding member is provided between the recording head and the light-receiving unit at a position that prevents reflected light from the object from reaching the light-receiving unit. Item 3. The ink droplet ejection state detection device according to Item 1 or 2. 4. The light-shielding member according to claim 1, wherein the light-shielding member is provided at a position between the light-emitting source and the recording head, the light-shielding member being disposed at a position where the light flux is not irradiated to the object. Item 10. The ink droplet ejection state detection device according to item 8. 5. The light-shielding member has first and second members, and the first member is between the recording head and the light-receiving unit, and receives light reflected from the object by receiving the light. A second member is provided between the light emitting source and the recording head, and is provided at a position that prevents the object from being irradiated with the light flux. The ink droplet ejection state detection device according to claim 1 or 2. 6. A direction connecting the light emitting source and the light receiving section is provided at a predetermined angle with respect to a direction in which a plurality of ink ejection elements of the recording head are arranged. 5. The ink droplet ejection state detecting device according to claim 1, wherein the recording head is conveyed by a minute distance each time the ejection element is driven. 7. A recording apparatus comprising the ink droplet ejection state detection device according to claim 1, wherein an end of a range in which the recording head performs a scanning movement is provided. A recording device provided with the ink droplet ejection state detection device;