JPH022011A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To prevent the generation of the jet impossibility of ink due to the drop of the liquid level of the ink by providing a means for detecting the transition of the height of the liquid level of the ink in a liquid chamber and a means for raising the liquid level of the ink in the liquid chamber. CONSTITUTION:A pair of electrodes 17 are provided in a liquid chamber 10 and the voltage divided according to the resistance value between said electrodes is inputted to a comparator 11 to be compared with reference voltage VRf. A control apparatus 12 reads the output of the comparator 11 and the resistance value between the electrodes 17 provided in the liquid chamber 10 of a recording head 14 becomes 'LARGE'. That is, it is judged that the voltage between these electrodes is larger than the reference voltage VRf. When said resistance does not become 'LARGE, the liquid level of ink is not falling and, therefore, recording operation is continued. When the resistance value reaches 'LARGE', the liquid level of the ink is falling and, therefore, a pump 13 is driven to such the liquid chamber 10 and the liquid level of the ink is raised. Then, on the basis of the resistance value between the electrodes 17, it is judged whether the liquid level of the ink is raised to repeat the same operation.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to printing on a recording material such as paper by ejecting droplets of ink (recording liquid) from an orifice (ink discharge port) provided in a recording head. The present invention relates to an inkjet recording device that performs recording by attaching the film to an inkjet recording device.

(Prior Art) An inkjet recording device that performs recording by ejecting ink, which is a recording liquid, as small droplets from an ink discharge port and making the recording by having these droplets adhere to the recording surface, generates noise during recording. It has the advantage of being able to perform non-impact recording with almost no impact, high-speed recording, and being able to record on plain paper.

As a recording head mounted on this inkjet recording apparatus, one having a configuration as shown in FIGS. 2(A) and 2(B), for example, is known.

This recording head has an orifice 7 on a substrate 1, an ink flow path 6, an energy acting part provided in a part of this flow path, and an energy acting part located in the acting part, and ink flowing from the orifice 7 to the ink. The ink in the flow path 6 is heated and bubbles are generated by applying electricity to the electrothermal converter 8 through the electrode 3. The ink is ejected from the orifice 7 due to the pressure caused by the bubbles generated by the wrinkles.

In addition to the electrothermal converter, other types of energy generating means such as a piezoelectric element are also used as the energy generating means.

(Problems to be Solved by the Invention) However, in a print head configured to utilize thermal energy for ejecting ink droplets as described above, temperature rise within the print head due to continuous printing operations is unavoidable. The bubbles generated in the flow path gradually accumulate, and further
), the liquid comes to stay in the liquid chamber 10. Furthermore, as the amount of retained gas increases, the ink liquid level in the liquid chamber 10 falls, and as shown in FIG. Atmospheric air enters the liquid chamber 10 from the 7 side, which promotes a drop in the ink liquid level, making it impossible to eject ink from all orifices.

Further, even in print heads using other ejection energy generating means such as piezoelectric elements, the ink liquid level within the liquid chamber may drop due to continuous printing operations, and similar problems have occurred.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus that does not become incapable of ejecting ink due to a drop in the ink level in the liquid chamber as described above.

[Means to solve the problem]

The inkjet recording apparatus of the present invention has a mechanism that prevents the inability to eject ink or the occurrence of ejection failure due to the drop of the ink liquid level in the liquid chamber described above.

The prevention mechanism of the recording apparatus of the present invention includes a means capable of detecting changes in the height of the ink liquid level in the liquid chamber, and a means for detecting changes in the height of the ink liquid level detected by the ink liquid level detecting means. It is configured to include means (ink liquid level recovery means) capable of raising the ink liquid level in the chamber.

That is, in the inkjet recording apparatus of the present invention, the ink level detection means detects a falling state of the ink level in the liquid chamber, and the ink level approaches a height at which ink cannot be ejected. At this point, the ink level is raised by the ink level recovery means, and ink ejection failure due to a drop in the ink level is automatically prevented.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

Note that in each of the following methods, a method is used that uses thermal energy as energy for ink ejection, but the present invention is not limited to this, and other methods such as piezoelectric elements may be used. It can also be suitably applied.

Example 1 FIG. 1 shows an example of an inkjet recording apparatus according to the present invention.

The recording head 14 performs a recording operation by generating bubbles in the ink in the flow path 6 and ejecting the ink from the orifice 7 by energizing the electrothermal transducer 8, which is an ejection energy generating means. Figure 2 (A) and (B
) has the structure shown below.

A pair of electrodes 17 are provided in the liquid chamber IO, and a voltage divided according to the resistance value between these electrodes is input to the comparator 11 and compared with a reference voltage VRf.

Here, the reference voltage VRf is the resistance value between the pair of electrodes 2, that is, the resistance value is small because ink exists between the pair of electrodes 8i17, or the ink liquid level is lower than the installation position of the electrodes 17. It is set in advance so that it can be determined whether the resistance value between these electrodes is large.

A control device 12 in the form of an MPU (microprocessor unit) controls the pump 13 according to the output of the comparator 11.
It has the function of driving the ink liquid level and raising it again.

With the configuration described above, as will be explained below, it is possible to effectively prevent the inability to eject ink due to a drop in the ink liquid level.

FIG. 4 is a flowchart showing an example of the control procedure.

First, after a power-on reset operation, the control device 12 performs a recording operation for one line in step S1 by receiving a print start command from the host device or by pressing a test print switch (both not shown).

Next, the process moves to step S2, and the control device 12 uses the comparator! Read the output of the liquid chamber lO of the recording head 14.
It is determined whether the resistance value between the electrodes 17 provided within the electrode 17 is "large", that is, whether the voltage between these electrodes is greater than the reference voltage VRf.

If it is not "large", the ink level has not fallen (it has not approached the dangerous liquid level height that would cause ink to fail to be ejected from the orifice 7), so step S again
Return to I and continue the recording operation.

On the other hand, in step S2, if the resistance value is r large, it is determined that the ink level has fallen and is approaching the dangerous level, that is, the ink is about to become incapable of ejecting. Therefore, the process moves to step S3, and the pump 13 is driven according to a command from the control device 12 to fill the liquid chamber l.
Suction O to raise the ink level.

Further, the process returns to step S2, and it is determined whether the ink level has risen based on the resistance value between the electrodes 17, and the same operation is repeated thereafter.

Note that the pair of electrodes 17 may be provided at a position higher than the ink liquid level at which ink ejection failure occurs, but in order to keep the frequency of ink level recovery processing low, it is necessary to place the electrodes 17 at a position higher than the ink liquid level at which ink ejection failure occurs. It is preferable to install it at a position that is close to the height and can reliably prevent the ink level from dropping to the dangerous ink level level.

Example 2 FIG. 5 shows another embodiment of the invention.

In the configuration of Embodiment 1, the height of the ink liquid level is detected using the resistance value between the electrodes 17 provided in the liquid chamber 10, but in the embodiment shown in FIG. Similar detection is performed in a configuration in combination with transistor 16.

In other words, when the ink level is rising, the light emitting diode and phototransistor are absorbed by the ink and the phototransistor is turned off, and when the ink level is falling, the light emitting diode is turned off. The light is reflected from the substrate surface and enters the phototransistor, which is set to turn on. Further, the collector output of the phototransistor is pulled up by a resistor and inputted to a comparator 11, where it is compared with a reference voltage VRf. Here, VRf is set in advance so that it is smaller than the collector output when the ink level rises and the phototransistor is off, and larger than the collector output when the ink level falls and the phototransistor is on. This makes it possible to determine whether the ink level is high or low.

Example 3 FIG. 6 shows another embodiment of the invention.

The apparatus of this embodiment is provided with a flow path 6a that is not involved in the recording operation, so that the ink liquid level in the liquid chamber IO can be raised by a suction operation from the orifice 7 side using the flow path 6a. This is what I did.

The present invention is not limited to the configurations of the embodiments described above, and may take various forms.

For example, to detect whether the ink level has dropped, a check is performed every time one line of recording is completed, but it is also possible to use a timer to check whether the ink level has dropped at regular intervals. can.

Furthermore, in order to raise and restore the ink liquid level, a method such as increasing the ink pressure from the ink supply side to expel air bubbles from the liquid chamber may be used.

〔Effect of the invention〕

The inkjet recording apparatus of the present invention is provided with a detection means for detecting the position of the ink liquid level in the liquid chamber and a recovery means for raising the ink liquid level, thereby preventing ink ejection failure due to a drop in the ink liquid level. be done. Therefore, by using the inkjet recording apparatus of the present invention, highly reliable and stable recording operations can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 (
A) is a partial sectional view of the main part of the inkjet recording head in a plane vertically traversing the flow path, FIG. 2(B) is a developed perspective view showing a part of the main part of the inkjet recording head in cross section, (C) and FIG. 3 are diagrams for explaining the transition of the ink liquid level in the liquid chamber of the inkjet recording head,
FIG. 4 is a flowchart showing the process of controlling the ink level in the configuration of FIG. 1, and FIGS. 5 and 6 are block diagrams showing other embodiments of the present invention. 11------Comparator 12------M
P U+ 3------Pump 14...
... Recording head 17 ... Electrode

Claims (1)

[Claims] 1) An orifice for ejecting ink, a flow path that communicates with the orifice and has a portion where energy acts on the ink to eject the ink, and a liquid chamber that can store the ink supplied to the flow path. In an inkjet recording apparatus configured with an inkjet recording head having: a means for detecting changes in the height of the ink liquid level in the liquid chamber; and a means for detecting changes in the height of the ink liquid level detected by the detection means. An inkjet recording apparatus comprising means for raising the ink liquid level in the liquid chamber accordingly.