JPH08169124A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE: To prevent inferior printing by simply removing air bubbles hard to remove in a recording head by applying an emission signal having frequency higher than that of the emission signal at the time of recording to an ink jet head at the time of the operation of a restoration system to emit ink. CONSTITUTION: A suction cap 4 is brought into contact with a recording head 1 and an emission signal is applied to the recording head. By making the frequency of the emission signal at this time higher than that of the emission signal at the time of recording, next air bubbling is started before a meniscus is returned and the meniscus communicates with an air bubble to be destructed. At this time, since negative head pressure is applied to the ink in the recording head, the ink retreats and the recording head becomes empty. A pump 5 is operated and the pressure in the cap 4 is reduced to suck ink and this ink is guided into the recording head through a supply tube 8. Therefore, the interior of the head becomes a bubble free state and stable printing becomes possible and printing inferiority can be reduced.

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, and more particularly to a liquid jet recording apparatus for recording by ejecting a recording liquid from an orifice of a recording head.

[0002]

2. Description of the Related Art Conventionally, as such a recording apparatus, a method is known in which an electrothermal converter is used to heat and boil a recording liquid, and the pressure causes the recording liquid to be ejected from a recording head to perform recording. . In such a recording device,
When the recording liquid is boiled, a gas component dissolved in the recording liquid may be deposited and may remain in the recording head without being redissolved. When this is repeated, residual bubbles grow,
It may enter the nozzle and hinder the discharge of the recording liquid. In particular, in a graphic printer having a higher printing duty than a character printer, bubbles grow at a high speed, and the probability of bubbles entering the nozzles increases. Until the bubble grows to a problem size, for example, in the case of a graphic printer, it is about 100% of A3 size.
The duty is 3 to 40 sheets, and this bubble must be removed before this. Almost all the conventional recording devices are provided with a means for removing this bubble. Generally, a cap is brought into close contact with the front surface of the recording head, and a negative pressure is generated in the cap by a pump, so that a negative pressure is generated in the recording head. A method of sucking the recording liquid and bubbles is known.

[0003]

However, in the above-mentioned conventional example, it is difficult to remove air bubbles in the stagnation in the recording head, especially small air bubbles. Further, even a large bubble is torn off and discharged, but most of it remains, and there is a problem that it grows again during the printing of several sheets and enters the nozzle.

FIGS. 4 (a) to 4 (c) are partially cutaway sectional views of the recording head to show the situation. In FIG.
Reference numeral 14 is a nozzle, 15 is a common liquid chamber, 16 is a bubble, 17 is a top plate, 18 is an electrothermal converter, 19 is a substrate, and 20 is a filter. The arrow indicates the flow of the recording liquid. The bubbles 16 shown in FIG. 4A grow as shown in FIG.
As shown in (c), it is split and a part thereof enters the nozzle 14.

The flow path of the recording head is divided into a nozzle portion for discharging the recording liquid, each of which has an electrothermal converter, and a common liquid chamber portion for storing the recording liquid supplied to the nozzle. Requires several tens to several hundreds times the volume of the nozzle portion, and therefore it is unavoidable that a sudden change in shape occurs between the nozzle portion and the common liquid chamber and a stagnation point occurs. Therefore, as a method for solving such a problem, as disclosed in Japanese Patent Laid-Open No. 63-224958, the elastic member of the cap is deformed while the cap is pressed against the recording head, and the air in the cap is removed. There is a method in which the ink is refilled in the recording head by pushing it into the recording head and sucking it with a pump in a state where the flow path is empty. However, this method requires a mechanism for deforming the elastic member of the cap, and has a problem that the configuration becomes complicated.

As another means, Japanese Patent Laid-Open No. 62-109.
As disclosed in Japanese Patent No. 655, there is a method in which a similar effect is obtained by providing a branch in the supply path and introducing air from the branch, but there is a problem that the mechanism is similarly complicated.

In view of the above problems, the present invention has an object to provide an apparatus capable of removing difficult-to-remove bubbles in a recording head by a simple method and preventing defective printing in advance.

[0008]

In order to achieve the above object, an ink jet recording apparatus according to the present invention comprises an ink jet head for performing recording by ejecting ink as droplets onto a recording medium by the action of an electrothermal converter. In an inkjet recording apparatus having an ink non-ejection recovery system for recovering non-ejection of ink of the inkjet head, an ejection signal having a frequency higher than an ejection signal during recording is supplied to the inkjet head when the recovery system is operated. In addition,
It is characterized by having a means for discharging.

[0009]

In the present invention, the ejection pulse having a higher frequency than that at the time of recording is applied immediately before the suction operation to reliably remove the difficult-to-remove bubbles in the recording head without using a complicated mechanism and reduce the print defect. can do.

[0010]

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

FIG. 1 is a schematic sectional view showing a first embodiment of the present invention. In the figure, 1 is a recording head, 2 is an ink cartridge, and 3 is an ink cartridge sensor. This sensor 3 is composed of a pair of electrodes in this example, and electrically contacts a resistor printed on the ink cartridge to form a closed circuit when the ink cartridge is inserted, and when it is not inserted. The circuit is opened and the presence or absence of the ink cartridge is transmitted to the CPU. The sensor may be another mechanism such as a spring switch. 4 is a suction cap, 5 is a pump, 6 is a cam 7
It is a motor for driving the pump 5 via the motor and for bringing the suction cap into close contact with the recording head via a gear (not shown), and operates by receiving a signal from the CPU. 8 is an ink supply tube for guiding the recording liquid to the recording head, 9 is a waste ink tube, 10 is a recording liquid, 11 is a remaining ink sensor, for example, a negative pressure sensor using a diaphragm, 13 is a waste ink reservoir, 13 is a sub tank.

FIG. 2 is a flow chart showing the actual operation in the configuration of FIG. During printing in step 2-1
When the time which is Step 2-2 has elapsed, Step 2-
In order to remove bubbles generated in the recording head in 3,
Move the recording head to the recovery position opposite the recovery system. Then, in step 2-4, the suction cap 4 is brought into contact with the recording head 1, and in step 2-5, an ejection signal (ejection pulse) is applied to the recording head 1. By setting the ejection signal at this time to a frequency higher than that at the time of recording, the next bubbling starts before the meniscus returns, and the meniscus and the bubbling communicate with each other to break the meniscus. At this time,
In general, since negative ink head pressure is applied to the ink inside the print head, the ink retreats and the inside of the print head becomes empty. As for such an ejection frequency, the maximum frequency during recording is 5
In the case of ˜6 kHz, it is 8 to 10 kHz. Further, it is more effective to apply the ejection signal to all the nozzles, not just some of the nozzles. It is sufficient to apply the ejection signal for several hundred pulses per nozzle, but there is no problem even if it is applied more.

Next, when the recording head is empty, the pump 5 is actuated in step 2-6 to make the inside of the cap 4 a negative pressure and perform suction. As a result, the ink is guided into the recording head through the supply tube 8 and the head is free of bubbles, which enables stable printing. The discharge-suction routine is performed a predetermined number of times as in step 2-7. Usually, most of the bubbles can be removed by carrying out once, but by repeating 3 to 5 times, it is possible to remove bubbles which are considerably difficult to remove.

The above operation is performed by the CPU controlling the operations of the head carriage, the cap, the thermoelectric converter and the like according to the program stored in the read-only memory.

It is more preferable that the above-mentioned operation is automatically performed at a time interval during which the user may timely perform the operation. Specifically, there are a method of performing the operation at a constant time interval by a timer, a method of counting the number of scans or the number of printed sheets and performing it when a certain number of scans (number of sheets) is reached, a method of performing each time the power is turned on, and the like.

The effect of using the present invention will be described with reference to FIG. 3 in comparison with a conventional example. The left half of FIG. 3 experimentally generated bubbles that hinder printing in the recording head.
After that, the result of printing after performing the conventional recovery operation. From this result, it can be seen that when solid printing of A4 is performed, discharge failure occurs at a probability of once or more on four sheets, and bubbles cannot be removed. Next, the result using the present invention is shown in the right half of FIG. After the bubbles are generated as described above, 5000 ejection pulses are applied at 10 kHz before suction, and this is repeated three times. Looking at this result, 10 sheets of A4 solid printing were performed and no discharge failure occurred. As described above, according to the present invention, bubbles that cannot be removed by the conventional recovery operation can be removed, and the printing reliability is improved.

More effectively, there are the following methods as means for removing bubbles. That is, this is a method of applying a pulse having a larger energy than that at the time of recording when applying the ejection pulse for the recovery operation. Larger foaming is obtained by applying more energy than during recording, and the meniscus breaks easily. To increase the energy, there is a method of increasing the pulse width or increasing the voltage. Considering the durability of the heater, the input energy is 30
% Up is appropriate, pulse width is 30%, and voltage is 15% up. Of course, the pulse width and the voltage may be changed at the same time.

(Others) In particular, the present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, particularly in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because such a system can achieve high density recording and high definition recording.

Regarding the typical structure and principle thereof, see, for example, US Pat. No. 4,723,129 and US Pat. No. 4,740.
What is done using the basic principles disclosed in 796 is preferred. This method is a so-called on-demand type,
It can be applied to any of the continuous type, but especially in the case of the on-demand type, it can be applied to the sheet holding the liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling, heat energy is generated in the electrothermal converter, and film boiling is caused on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal in a one-to-one correspondence
It is effective because bubbles can be formed inside. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. It is more preferable to make this drive signal into a pulse shape because bubbles can be immediately and appropriately grown and contracted, so that liquid (ink) ejection with excellent responsiveness can be achieved. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angle liquid passage) as disclosed in the above-mentioned respective specifications, US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
The structure using the specification of No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full-line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

In addition, even in the case of the serial type as in the above example, the recording head fixed to the apparatus main body or the electrical connection with the apparatus main body and the ink from the apparatus main body by being attached to the apparatus main body The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is integrally provided in the recording head itself is used.

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add an ejection recovery means of the recording head, a preliminary auxiliary means and the like because the effect of the present invention can be further stabilized. Specifically, heating is performed by using a capping unit, a cleaning unit, a pressure or suction unit for the recording head, an electrothermal converter or a heating element other than this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

Regarding the type and number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to control the temperature of the ink itself within the range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change from the solid state of the ink to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent No. 1260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as a form of the ink jet recording apparatus of the present invention, besides the one used as an image output terminal of an information processing apparatus such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. It may be a form or the like.

[0027]

As described above, according to the present invention,
By applying an ejection pulse having a higher frequency than that during recording just before the suction operation, it is possible to reliably remove bubbles that are difficult to remove in the recording head without using a complicated mechanism and reduce printing defects.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a recording apparatus embodying the present invention.

FIG. 2 is a flow chart illustrating the operation of the present invention.

FIG. 3 is a diagram showing the effect of the present invention in comparison with a conventional example.

FIG. 4 is a sectional view of a conventional recording head.

[Explanation of symbols]

 1 Recording Head 2 Ink Cartridge 3 Ink Cartridge Sensor 4 Cap 5 Pump 6 Motor 7 Cam 8 Supply Tube 9 Waste Liquid Tube 10 Recording Liquid 11 Ink Remaining Sensor 12 Waste Ink Reservoir 13 Sub Tank 14 Nozzle 15 Common Liquid Chamber 16 Bubble 17 Top Plate 18 Electrothermal converter 19 Substrate 20 Filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Misumi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Atsushi Arai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (4)

[Claims] 1. An ink jet head for performing recording by ejecting ink as droplets onto a recording medium by the action of an electrothermal converter, and an ink ejection failure recovery system for recovering ink ejection failure of the ink jet head. In an ink jet recording apparatus having:
An ink jet recording apparatus comprising a means for performing ejection by applying an ejection signal having a frequency higher than an ejection signal at the time of recording to the ink jet head. 2. The pulse width of the ejection signal during operation of the recovery system is longer than the ejection signal during recording.
The inkjet recording device according to item 1. 3. The ink jet recording apparatus according to claim 1, wherein the voltage of the ejection signal during the operation of the recovery system is higher than the voltage of the ejection signal during recording. 4. The ink jet recording apparatus according to claim 1, wherein the pulse width of the ejection signal during the operation of the recovery system is longer than the ejection signal during recording, and the voltage is higher than the recording signal during recording.