JPH0278567A - Discharge recovery method of ink jet recording head, and recording head and ink jet recorder adopting the same method - Google Patents

Abstract

PURPOSE:To reduce ink consumption for recovery of discharge and to achieve shortening of recovery time by a method wherein a pressurizing heater is established independently from a recording heater. CONSTITUTION:A bubble is generated by film boiling on a surface of an electrified recording heater 3 among the recording heaters when recording is performed. An ink drop springs out from a top of a liquid passage 2 by utilizing this bubble as pressure force, and flies toward recording paper. Then, in the case where recovery operation is performed, when electrification to the all recording heater 3 is stopped and a pressurizing heater 5 is electrified on a preliminary discharge signal emitted by a preliminary discharge signal generation means, a bubble is generated in a common liquid chamber 4, and pressure is applied to each inside of the liquid passage 2 by pressure due to its expansion. Air 14, a residual bubble 15, and ink in the liquid passage 2 are pushed out from a discharge port, and clogging can be removed. Besides, liquid pressure by the bubble generated with the pressurizing heater 5 presses a check valve, closes an outlet of ink supply part 7, and elevates delivery force of the ink by preventing a back flow of the ink.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an inkjet recording head recovery method in a recording head equipped with an ejection recovery means for recovering ink ejection failure from the ejection ports of the inkjet recording head, and The present invention relates to a recording head and an inkjet recording apparatus that employ this method.

[Conventional technology]

An inkjet recording device supplies ink into a recording head and has at least one ink droplet formed on the front surface of the recording head.
The driving elements provided corresponding to the two ink ejection ports are driven based on the print data signal, and the ink is ejected from the ink ejection ports to form flying droplets on the recording medium. It is used for recording by attaching it to

In the recording head of this type of inkjet recording apparatus, ejection failure occurs due to air being mixed into the liquid path communicating with the ink ejection opening, or due to adhesion of paper waste or thickened ink. In order to eliminate this ejection failure and stabilize ejection, for example, U
S P 4,600.931 Terasawa,
[JSP 4,123,761. As shown in K:mura, a gear pump or the like is installed in the ink supply path that communicates with the recording head and supplies ink to forcibly pressurize the ink and discharge air and foreign matter in the liquid path, or A pump mechanism or the like was provided to draw negative pressure from the discharge port and discharge air and foreign matter.

However, in the conventional recovery method for an inkjet recording head, it is necessary to discharge a large amount of ink in order to remove a small amount of air remaining in the liquid path or thickened ink in the ejection ports and the liquid path.

Furthermore, as a result of the time required to operate these drive systems (pumps, etc.), it is necessary to temporarily stop recording, and it cannot be said that efficient operation is being carried out.

In addition to the above configuration, for example, US P 3,925
,788 Kashio, US P 3+925+
789. Kashro, USP 4.1B3
,030 Kaieda et al, U.S.P.
4,176.363. Kasahara et al., a configuration has been proposed in which a drive element such as a piezo element for ejection is driven during non-recording to perform preliminary ejection.

[Technical problem to be solved by the invention]

However, in the configuration for performing preliminary ejection, since the drive element used for recording and the drive element used for preliminary ejection are used in combination, there are technical problems that need to be solved as will be described later.

The first technical issue is that in the preliminary ejection of the above configuration, the driving element is also used, which is effective in preventing clogging and defective ejection, but when re-recording after a long period of non-use, etc. If an ejection failure has already occurred, as is likely to happen, the effect of resolving this is not very effective.

Further, a configuration in which the preliminary ejection of the above configuration is performed by changing the driving conditions etc. is, for example, UA P 4,466.005 Yo
Shimura. However, with the configuration described in detail above, it may not be possible to completely recover the ejection because the drive element is also used, and furthermore, since the piezo element is used as the drive element, the technology that is effective may not be able to drive the drive element. There remains a technical problem in that the element, that is, the element that generates the energy used to eject ink, cannot simply be used as is in a configuration using a thermal energy generating means that generates thermal energy.

An object of the present invention is to provide an inkjet recording head recovery method that can improve the technical problems remaining in the conventional technology, reduce the amount of ink consumed for ejection recovery, and shorten the recovery time. That's true.

Another object of the present invention is to provide an inkjet recording apparatus that can extend the life of a recording driving element and perform good recording for a long period of time.

Still another object of the present invention is to provide an inkjet recording head that can restore the ejection ports of the recording head to a good ejection state.

Another object of the present invention is to provide an inkjet recording head that is compact and inexpensive, capable of good ejection recovery.

[Means for solving problems]

The invention according to claim 1 is provided with an ejection port for ejecting ink, and a recording energy generator communicating with the ejection port and generating energy for ejecting ink from the ejection port based on a recording signal. A recording head having a liquid path and a liquid chamber communicating with the liquid path and supplying ink to the acid liquid path is used to cause a state change in the ink provided in the liquid chamber and in the acid liquid chamber. A method for recovering ejection of an ink-side recording head, characterized in that ink is ejected from the ejection ports by driving a thermal energy generating means that generates thermal energy for generating bubbles during non-recording. This aims to achieve the above objectives.

The invention according to claim 2 provides an ejection port for ejecting ink;
A recording energy generator is provided corresponding to the ejection port to eject ink based on a recording signal, and a recording energy generator is provided upstream of the ink supply to the recording energy generator to cause a state change to the ink. generating bubbles by the second thermal energy generating means during non-recording, using a recording head having a second thermal energy generating means for generating thermal energy for generating bubbles;
The above object is achieved by a method for recovering ejection of an inkjet recording head, characterized in that ink is ejected from the ejection ports using the pressure generated when the bubbles are generated.

The invention according to claim 3 provides: ``an ejection port for ejecting ink; and a recording device that communicates with the ejection port and generates thermal energy as energy used to eject ink from the ejection port based on a recording signal. A liquid path provided with a first electrothermal converter, a liquid chamber communicating with the liquid path and supplying ink to the liquid path, and a liquid chamber provided within the liquid chamber to which a signal is applied during non-recording. A second device that generates thermal energy to cause a state change in the ink in the liquid chamber and generate bubbles.
The above object is achieved by an inkjet recording head characterized by comprising: an electrothermal transducer;

The invention according to claim 4 provides the following: "an ejection port for ejecting ink, a liquid path communicating with the ejection port, a liquid chamber communicating with the liquid path, and a first thermal energy generating body provided in the liquid path. , a second thermal energy generator provided in the liquid chamber, and a recording signal is input to the first thermal energy generator to eject ink from the ejection port to perform recording. and a preliminary ejection signal generating means for inputting a signal to the second thermal energy generating body to cause a state change in the ink to generate bubbles and eject the ink during non-recording. The above object is achieved by an inkjet recording apparatus characterized by comprising the following.

〔Example〕

The present invention will be specifically explained below with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an inkjet recording head to which the recovery method of the present invention is applied.

In FIG. 1, ■ is a recording head that is equipped with each member described later and discharges ink onto a recording paper or the like to form ink droplets;
2 is a plurality of liquid channels provided at the tip of the recording head 1; 3;
4 is a recording heater as an electrothermal transducer that is disposed at the bottom of each liquid path 2 and is energized during recording to generate thermal energy used for ink ejection; 4 is a recording heater at the bottom of each liquid path 2; a common liquid chamber that is communicated with one end and supplies ink to each;
5 is a pressurizing heater disposed at the bottom of the common liquid chamber 4 as shown in FIG. 2, 6 is a check valve provided in the ink supply section 7 for the common liquid chamber 4, and 8 is a recording heater 3. A flexible cable 9 has a built-in drive signal line connected to each of them, and 9 is a wiring section connected to the pressurizing heater 5.

The present invention can be suitably applied to an inkjet recording apparatus of the type in which a recording head and an ink tank for accommodating ink to be supplied to the head are integrally mounted removably on a carriage.

This is because in the above-mentioned type of apparatus, in which reduction in ink consumption and miniaturization of the apparatus are desired, it is desirable to limit the configuration of the recovery means.

Further, such a head may have an ink tank that is further detachable.

The common liquid chamber 4 is arranged at the boundary surface and is
When air bubbles are created in the common liquid chamber 4, the ink supply section 7
This prevents ink from flowing back to the side. When a plastic film, metal foil, or the like is used for the check valve 6, if the plate thickness is about 50 microns (μm), an excellent response to pressure fluctuations can be obtained.

In the above configuration, the common liquid chamber 4 and the liquid path 2 are filled with ink supplied from the ink supply section 7. During recording, the pressure heater 5 is not energized based on the signal generated by the recording signal generating means, and only the recording heater 3 is energized in accordance with the recording signal. Bubbles are generated on the surface of the recording heater 3 that is energized by the membrane, and the bubbles are used as pressure to cause ink droplets to fly out from the tip of the liquid path 2 and fly toward the recording paper. New ink is fed into the liquid path where air bubbles have been generated due to the negative pressure generated in the liquid path as the ink droplets fly, and ink corresponding to the decreased amount is supplied from the ink supply section 7 to prevent backflow. The common liquid chamber 4 is replenished via the valve 6.

Next, when performing a recovery operation, all of the recording heaters 3 are de-energized and the pressurizing heater 5 is energized based on the preliminary ejection signal generated by the preliminary ejection signal generating means. Bubbles are generated in the bubbles, and the pressure caused by the expansion applies pressure inside each of the liquid passages 2, and the third
YI! As shown in J, air 14 in the liquid path 2 from the discharge port,
The remaining air bubbles 15 and ink are pushed out and clogging can be eliminated. At the same time, the liquid pressure due to the bubbles generated by the pressurizing heater 5 presses the check valve 6 and ink supply section 7.
Closes the outlet of the ink, prevents backflow of ink, and increases ink discharging power.

In addition to the structure shown in Fig. 1, the check valve is formed of an elastic member whose tip end is closed by ink pressure, as shown in Fig. 4, and which removes dust contained in ink within the ink passage. It is also possible to adopt a structure in which a filter 11 is provided. By doing so, it is possible to remove dust that causes clogging of the discharge port and the liquid path to the common liquid chamber 4.

Further, the check valve may have a structure other than a valve mechanism as shown in FIG. That is, a heater 12 for backflow prevention (return check) is installed on the bottom of the common liquid chamber 4 near the outlet of the ink supply section 7.
It was designed to provide a. Note that 9 is a lead connected to the pressurizing heater 5 and the check heater 12. In this case, when the pressure heater 5 is energized, the non-return heater 12 is energized at a rate of about LQ psec to increase the heater temperature to several hundred layers, and the ink on the upper surface of the pressure heater 5 is brought to film boiling. As a result, air bubbles 13 are generated as shown in FIG. 6, and the outlet of the ink supply section 7 can be blocked. This bubble 13 disappears after 20 to 30 μsec by cutting off the power supply to the check heater 12, and subsequent ink can be supplied to the common liquid chamber 4 without any hindrance.

In the configuration shown in FIG. 5, as shown in FIG. 7, a narrow horizontal slit opening 28 is provided at the tip of the ink supply section 7
A non-return heater 1 having a length equal to or greater than its width dimension.
It is also possible to use a configuration in place of 2. With this configuration, the slit opening 28 can be closed even when the height of the bubbles generated by the non-return heater 17 is low;
Backflow to the ink supply section 7 can be prevented.

Next, the energization timing of the pressurizing heater 5 and the check heater 12 will be explained with reference to FIGS. 8 and 9.

FIG. 8 shows that the recording device automatically enters the recovery mode after a switch operation or a certain amount of ejection operation at the time of ejection failure, heats the pressurizing heater 5, operates the check valve 6 by the bubbles, and As shown in Figure 3, remove air, residual bubbles, etc. in the liquid path. When the pressurizing heater 5 is turned off, the generated bubbles begin to disappear, and negative pressure begins to occur in the common liquid chamber 4. This opens the check valve 6 and prevents the meniscus at the ejection port from retreating due to the meniscus holding force of the ejection port of about 50 μm, the liquid path, and the low flow resistance of the ink supply section with a large diameter relative to the ejection port diameter. are doing.

Next, the energization timing of the pressurizing heater 5 and the check heater 12 in the configuration shown in FIG. 5 will be explained with reference to FIG. 9.

When the recovery mode is turned on, the check heater 12 is energized by the check signal generating means, bubbles 13 are generated as shown in FIG. 6, and the ink supply to the common liquid chamber 4 is cut off. Next, the pressurizing heater 5 is energized, and a third
As shown in the figure, bubbles 16 are generated to force ink into each liquid path 2. At this point, the check heater 12 is turned off, and the ink supply section 7 and the common liquid chamber 4 are connected. Then, when the pressurizing heater 5 is turned off, the resulting air bubbles 16 disappear, a negative pressure is generated, and ink flows from the ink supply section 7 into the common liquid chamber 4. As a result, the pressure inside the common liquid chamber 4 is kept uniform while maintaining the meniscus of the discharge port.

Next, with reference to FIG. 10, the energization timing of the pressurizing heater 5 and the check heater 12 in the configuration shown in FIG. 5 will be explained.

When the recovery mode is turned on, the check heater 12 is energized, bubbles 13 are generated as shown in FIG. 6, and the ink supply to the common liquid chamber 4 is cut off. Next, the pressurizing heater 5 is energized to generate bubbles 16 in the common liquid chamber 4 as shown in FIG. 3, and ink is forced into each of the liquid channels 2. At this point, the check heater 12 is turned off, and the ink supply section 7 and the common liquid chamber 4 are communicated with each other. Then, when the pressurizing heater 5 is turned off, the resulting air bubbles 16 disappear, a negative pressure is generated, and ink flows from the ink supply section 7 into the common liquid chamber 4. As a result, the pressure inside the common liquid chamber 4 is kept uniform while maintaining the meniscus of the discharge port.

As described above, by controlling only the heater of the common liquid chamber 4 in response to an ejection failure of the recording head, ejection recovery can be achieved, and the amount of ink discharged from the ejection ports can be extremely reduced. Also, since it does not depend on the mechanical configuration, the recovery time depends only on the ink glue fill, making the operation time extremely fast and allowing the use of the recovery mode to be imperceptible to the user.

As shown in FIG. 10, when the non-return heater 12 is energized, the non-return heater 12 This makes it possible to prevent the bubbles 13 from overheating and to slightly delay the disappearance of the bubbles 13.

As a result, the pressurizing effect by the pressurizing heater 5 is enhanced, and the heating time can be easily controlled.

Similarly, by providing a short pulse P3 on the off side when energizing the pressurizing heater 5, it is possible to delay the disappearance of the bubbles 16 and prevent overheating. Since the main purpose of the pulses P2 and P3 is to maintain the temperature of the heater section, the heating energy does not need to be as large as the heating energy during bubble formation (on side).

In addition to controlling the current flow by changing the pulse width,
This is also possible by reducing the on-duty and reducing the voltage applied to the heater resistor.

In the recording heater 3, the input pulse conditions for forming ink droplets are USP 4,345,262.5hir.
at.

As shown in FIG. 2, the input cycle is controlled to be at least three times as long as the pulse of 0.1 μsec to 500 μsec, but according to this embodiment, the recording By using the pressurizing heater 5 separately from the pressurizing heater 3, it is possible to apply a signal that is not subject to the above-mentioned limitations, and there is an advantage that the range of selection of driving conditions for the pressurizing heater 5 is expanded.

FIG. 11 shows a schematic configuration of a control system for heater energization control. The output of a control section 26 is connected to the pressurizing heater 5, and this control section 26 is connected to a temperature detection thermistor ( The output signal of Th) 18 is used as a feed hack signal, and the energization time is controlled by the set time of the timer 27. Note that 19 is an ink supply source.

FIG. 12 shows the head position when ejection recovery is performed.

A platen 20 that conveys a recording paper 21 as a recording medium according to printing conditions is rotatably supported by the main body, and a guide shaft 22 is fixedly arranged parallel to the front of the platen 20. A carriage 23 is slidably engaged with the guide shaft 22, and is reciprocated on the guide shaft 22 according to the printing state using a carriage motor (not shown) as a drive source. The recording head 1 is mounted on the carriage 23, and ejection recovery is performed when the recording head 1 is at the home position (H, P). A wiping blade 24 has a plate-like elastic body that wipes away ink adhering to the head surface after completion of ejection recovery when the carriage 23 is moved.

As described above, since the discharge recovery operation according to the present invention is performed in an extremely short time, the time required for the discharge recovery operation can be completed within 1 second, even including the time for returning the carriage 7 23 to the home position. . Therefore, the user does not feel that recording has been interrupted.

FIG. 13 is a flowchart for automatically performing discharge recovery according to the present invention.

After the power is turned on, a recording operation is performed (step 31).
In the process, it is determined whether a time has come when a discharge recovery operation is necessary (step 32). When it is determined that recording has been completed for the reference time, the carriage 23 is returned to the home position (step 33), and the heater 5 (or the first
The heaters 12 and 5) are energized at the timing shown in the figure, and a discharge recovery operation is performed using the generated bubbles (step 34).Then, the carriage 23 is moved to the first
It moves to the right in FIG. 2, and in the process the head surface (near the ejection port) is cleaned by the blade 24 (step 35). After this process, the process returns to step 31 and the recording process is restarted.

In addition, in step 32, the judgment condition is "printing of the reference time", but it is also possible to stop printing the reference time, or to ensure that the "recording operation" in step 31 is performed after the power is turned on. However, a recovery operation having the same contents as step 34 may be inserted before step 31. In this way, even if there is a long period of non-use before the power is turned on, no ejection failure will occur during recording in step 31.

Furthermore, the condition for starting the recovery operation in step 32 is a predetermined number of sheets (
or number of pages) may be set as a condition for the completion of recording N.Furthermore, as shown in the NFS14 diagram, the removal of residual air generated by the recording heater 3 due to the rise in head temperature due to continuous use of the ejection port of the recording head may be set as a condition. For this purpose, we added an operation (step 36) between steps 32 and 33 to determine whether the head temperature exceeds the set temperature, so that even if the recording time does not reach the set value, the head temperature will recover when the head temperature rises. It can also be controlled to start an operation.

The drive of the pressurizing heater 5 is generally controlled so that preliminary discharge is performed a plurality of times during one recovery operation.

Therefore, the amount of thermal energy generated by the pressurizing heater 5 in one preliminary ejection operation is reduced by the amount of thermal energy generated by the recording heater 3 in one ejection operation.
If the material and film thickness of both heaters 5 and 3 are the same, the area of the recording heater k (k=1...N) is
When k is the area of the pressurizing heater 5, the following relationship is established.

Here, N represents the number of recording-like heaters 3.

Furthermore, more preferably, the number of times the preliminary ejection signal is applied can be reduced by the following.

Next, the position of the pressurizing heater 5 will be explained using FIG. 15.

The recording head schematically shown in FIG.
) is the type of head that ejects ink.

Here, when the length of the heat generating section in the discharge direction (arrow AA) is S, and the distance between the recording heater 3 and the pressurizing heater 5 is m, it seems that the relationship m≧S or m≧a is satisfied. It is desirable to determine the location of the heater.

This is because air bubbles generated by the heat generation of the recording heater 3 tend to stay within the length S of the recording heater 3.
According to the pressurizing heater 5 arranged in this way, the accumulated air bubbles can be effectively discharged through the discharge port, or the air bubbles can be discharged through the discharge port by the cavity sizing action of the pressurizing heater 5. Even if the air bubbles are not discharged, a strong function is to collect the air bubbles in the liquid chamber and exhaust them to the outside through a vent hole (not shown) or the like.

Furthermore, in a recording head to which the present invention can be applied, which discharges ink in a direction substantially perpendicular to the surface of the heat generating part of the recording heater (arrow BB in FIG. 16), the accumulation of air bubbles causes heat generation. Although it is not limited to the above-mentioned position because the position is rarely far away from the surface of the part, it is still preferable to provide the pressurizing heater at a similar position.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, by providing a pressurizing heater separately from a recording heater,
Without shortening the life of the recording heater, the ejection failure that could not be corrected by the conventional preliminary ejection operation was resolved, and a good ejection recovery operation could be performed.

Furthermore, since the pressurizing heater can have the desired structure and be freely placed near the recording heater, it is possible to generate pressurizing force in areas where air bubbles and foreign matter tend to accumulate, thereby discharging a large amount of ink. It was possible to significantly improve the efficiency of ejection recovery without causing any problems.

[Brief explanation of the drawing]

FIG. 1 is a top view of a cross section of an inkjet recording head in which the ejection recovery method according to the present invention is implemented, and FIG.
FIG. 3 is a schematic plan view showing details of the heater board of the recording head shown in FIG.
FIG. 4 is a schematic sectional view showing another example of the check valve shown in FIG. FIG. 6 is a schematic diagram for explaining the operation of the backflow prevention structure shown in FIG. 5, FIG. 7 is a schematic diagram showing another example of the backflow prevention structure shown in FIG. 9 is a timing chart showing the operation of the embodiment shown in FIG. 5, FIG. 10 is a timing chart showing another example of the timing shown in FIG. 9, and FIG. Block diagram showing the schematic structure of the control system for heater energization control, Part 1
FIG. 2 is a schematic diagram showing a part of an inkjet recording apparatus for performing ejection recovery according to the present invention, FIG. 13 is a flowchart showing automation of ejection recovery operation according to the present invention, and FIG.
FIG. 4 is a flowchart showing an example of automation of the ejection recovery operation according to the present invention, FIG. 15 is a schematic diagram illustrating the position of the pressurizing heater in the inkjet recording head that implements the ejection recovery method of the present invention, and FIG. 16 1 is a partially enlarged sectional view of an inkjet recording head of a type that discharges ink in a direction perpendicular to a recording heater. t---1---inkjet recording head, 2-
-Liquid path, 3-...-- Recording heater, 4--
---1 common liquid chamber, 5-----pressurizing heater, 6----1...-check valve, 7-----ink supply section, i o - -----・---m-Check valve, 12
−・・・−・・−・・− Check heater, 13.16 −
-----One bubble, l 7---One-way check heater. Agent Patent Attorney Yasushi Ooto Figure 3 Figure 4 Figure 5 Figure 8 Figure 9 P3 Figure 11 Figure 12

Claims (4)

[Claims] (1) A liquid path that is provided with an ejection port that ejects ink, and a recording energy generator that communicates with the ejection port and generates energy to eject ink from the ejection port based on a recording signal; Using a recording head having a liquid chamber that communicates with the liquid path and supplies ink to the liquid path, the recording head is provided in the liquid chamber and causes a state change in the ink in the liquid chamber to generate bubbles. 1. An ejection recovery method for an inkjet recording head, characterized in that ink is ejected from the ejection openings by driving a thermal energy generating means that generates thermal energy for the inkjet printing head during non-printing time. (2) An ejection port for ejecting ink, a recording energy generator provided corresponding to the ejection port for ejecting ink based on a recording signal, and a recording energy generator for ejecting ink from the recording energy generator. A second thermal energy generating means is provided on the upstream side of the supplied ink and generates thermal energy for causing a state change in the ink to generate bubbles. An ejection recovery method for an inkjet recording head, characterized in that bubbles are generated by the thermal energy generating means of item 2, and ink is ejected from the ejection ports using the pressure generated when the bubbles are generated. (3) An ejection port that ejects ink, and a first electricity for recording that communicates with the ejection port and generates thermal energy as energy used to eject ink from the ejection port based on a recording signal. A liquid path provided with a heat converter; a liquid chamber communicating with the liquid path and supplying ink to the liquid path; An inkjet recording head comprising: a second electrothermal converter that generates thermal energy for causing a state change in ink to generate bubbles. (4) an ejection port that ejects ink, a liquid path that communicates with the ejection port, a liquid chamber that communicates with the liquid path, a first thermal energy generator provided in the liquid path, and the liquid chamber. a second thermal energy generating body provided in the recording head; a recording signal for inputting a recording signal to the first thermal energy generating body and ejecting ink from the ejection opening to perform recording; and a preliminary ejection signal generating means for inputting a signal to the second thermal energy generator to cause a state change in the ink to generate bubbles and eject the ink during non-recording. An inkjet recording device characterized by: