JPH0729435B2 - Inkjet printhead and printing apparatus - Google Patents

Description

The present invention relates to an inkjet printhead and a printing apparatus, and more particularly to an inkjet printhead and a printing apparatus capable of gradation recording.

[Prior Art] The inkjet recording method has many advantages such as extremely low noise during recording, easy colorization, and so-called plain paper recording. Is increasing. Among them, an inkjet recording method in which thermal energy is applied to a liquid, bubbles are generated in the liquid, and the liquid is ejected from an orifice due to a sharp volume change of the bubbles to perform recording, that is, an inkjet recording method using thermal energy is In particular, the device has been particularly noticed because it can be easily downsized and the orifices can be arranged at a high density.

[Problems to be Solved by the Invention] However, since the ink jet recording method using thermal energy uses the volume change of gas in the process leading to the generation and disappearance of bubbles for ejection, it depends on the recording signal. Although it is easy to eject liquid accurately,
It has been difficult to accurately control the amount of the ejected liquid in multiple stages.

Therefore, a plurality of thermal energy generators are provided for one discharge port (orifice) for discharging liquid, and the plurality of thermal energy generators are driven individually or simultaneously. An inkjet recording head capable of performing gradation recording has been proposed. However, such multiple thermal energy generators are
It is provided in the liquid flow path as a heat generating part reaching the orifice, but since this liquid flow path is minute, it must be arranged in the extending direction (discharging direction) of the flow path, and therefore the position from the orifice is Since they are different from each other, problems may occur in terms of liquid ejection efficiency. In particular, when the recording head is left for a while and the liquid or the viscosity in the vicinity of the orifice is increased, there is a problem that the reliable liquid ejection may not be performed when the recording is restarted.

[Means for Solving Problems] An object of the present invention is to provide an ink jet print head and a printing apparatus that solve these problems and can perform efficient and sufficient gradation recording at all times. .

A first embodiment of the present invention that achieves this object is provided with a plurality of ejection ports for ejecting a liquid, and an energy generation means for communicating with each of these ejection ports and for generating energy for ejecting the liquid. A plurality of liquid flow paths, a common liquid chamber for communicating the liquid flow paths together to supply the liquid to the liquid flow paths, and a common liquid chamber provided in the common liquid chamber and formed at the discharge port. An inkjet head is provided with a discharge amount adjusting means for repeatedly advancing / retracting the front end surface along the discharge direction of the liquid.

Further, a second aspect of the present invention is a plurality of liquids each provided with a plurality of ejection ports for ejecting a liquid, and an energy generating means for communicating with each of these ejection ports and for generating energy for ejecting the liquid. A flow path, a common liquid chamber for communicating the liquid flow paths together to supply a liquid to the liquid flow path, and a front end surface of the liquid provided in the common liquid chamber and formed at the discharge port. An ink jet print head having a discharge amount adjusting means for repeatedly moving forward and backward along the discharge direction of the liquid, and the energy generating means is driven according to the position of the tip surface of the liquid shaken by the discharge amount adjusting means. By so doing, there is provided an ejection control means for controlling the size of the droplet of the liquid ejected from the ejection port.

Here, it is possible to have an ultrasonic wave generating element as the discharge amount adjusting means, and it is effective that the energy generating means is means for generating heat energy.

[Operation] According to the present invention, the tip end surface of the liquid formed in the ejection port is repeatedly moved forward and backward along the ejection direction of the liquid by the ejection amount adjusting means, and accordingly, the ejection port is discharged more than the energy generating means. The volume of the liquid located in the liquid flow path on the side increases or decreases.

When the energy generation means is driven by the ejection control means, a droplet having a volume corresponding to the position of the tip surface of the liquid formed in the ejection opening at this time is ejected from the ejection opening. That is,
By controlling the drive timing of the energy generating means by the ejection control means in accordance with the position of the tip surface of the liquid formed at the ejection port, a liquid having a size corresponding to the position of the tip surface of the liquid formed at the ejection port is controlled. Drops are formed.

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

(First Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention, FIG. 1 is a perspective view showing an example of the constitution of an ink jet print head according to the present embodiment, and FIG. It is the sectional view including a drive part. In these figures, reference numeral 1 is a liquid flow path formed of a glass thin tube or the like, and a recording liquid (hereinafter, referred to as ink) 2 such as ink is introduced therein. 3 is a discharge port of the liquid flow path 1 formed on the side facing the recording medium, 4 is a common liquid chamber provided at the rear of the liquid flow path 1, and 5 is a discharge amount provided at the rearmost part of the common liquid chamber 4. The ultrasonic oscillator constitutes a part of the adjusting means. Reference numeral 6 denotes an ink supply port for introducing ink into the common liquid chamber 4, which communicates with an ink supply source such as a tank via a tube or the like (not shown).

7 is each discharge port (hereinafter referred to as an orifice) 3
A heating electrode as discharge energy generating means disposed in each liquid flow path 1 corresponding to the above, and 9 is a heating electrode driving device for supplying a heating signal to the heating electrode 7 to heat it, and in response to the driving signal. The ink 2 in the vicinity of the orifice 3 is heated and foams, and the ink 2 is discharged as droplets from the orifice 3 due to the rapid expansion thereof, and thus dot recording is performed. Reference numeral 13 supplies a high-frequency signal to the ultrasonic oscillator 5, and the tip surface of the ink 2 formed in the orifice 3 in response to this,
That is, it is a high-frequency signal generator that constitutes a part of the ejection amount adjusting means for repeatedly advancing and retracting the meniscus 8 along the ejection direction of the ink 2. Further, 14 is a phase shift device (phase shifter) arranged for the heating electrode driving device 9, and controls the timing of the driving signal supplied to the heating electrode 7 according to the position of the meniscus 8.

When a high-frequency signal is supplied to the ultrasonic oscillator 5, ultrasonic waves are generated, and the ultrasonic waves propagate in the ink 2 in the form of compression waves, so that the meniscus 8 moves forward and backward along the ejection direction of the ink 2. Are repeated alternately.

FIG. 3 (A) shows the change of the meniscus 8 due to the propagation of the compression wave when there is no foaming, that is, when the heating electrode 7 is not driven, in which the horizontal axis represents time t and the vertical axis represents the degree of concave shape of the meniscus 8. That is, it is the retracted position of the meniscus 8 toward the common liquid chamber 4 side (the + direction is retracted). Therefore, the amount of the ink 2 on the orifice 3 side of the heating electrode 7 is set to a target amount, and when the target amount is reached, a voltage is applied to the heating electrode 7 to eject the ink 2 to change the droplet diameter. Be able to control.

In this embodiment, specifically, the ultrasonic oscillator 5 is constantly driven and the position of the meniscus 8 (see FIG. 3A).
MA, MB, MC), the timing of applying the pulse voltage to the heating electrode 7 as shown in FIG.
It is changed by 14 to control the droplet diameter.

The specific operation is as follows.

4 (A) to 4 (F) show the operation of each part according to the present embodiment. In FIG. 4 (A), a drive voltage waveform applied to the ultrasonic oscillator 5 is shown, and in FIG. 4 (B), there is no foaming. A waveform showing the receding position of the meniscus 8, a waveform (C) of the driving voltage (pulse signal) applied to the heating electrode 7, a waveform (D) of the drawing showing the receding position of the meniscus 8 before and after the droplet discharge, FIG. 6E is a cross-sectional view showing a state in the vicinity of the orifice 3 before droplet ejection, FIG.
FIG. 6 is a cross-sectional view showing a state in the vicinity of the orifice 3 after discharging droplets.

When the meniscus 8 responds to the drive voltage change of the ultrasonic oscillator 5 with a phase relationship as shown in (B) in the figure, the phase difference Φ with a certain drive voltage value is 0 °, −90 ° and 90 °. At this time, if the meniscus 8 is located at the intermediate position, the frontmost position, and the rearmost position with respect to the orifice 3, for example, the drive voltage of the ultrasonic oscillator 5 is monitored, and the phase shifter 14 according to the desired droplet diameter is monitored. The drive voltage may be supplied to the heating electrode 7 at the timing shown in FIG.

By performing the drive in this way, (D) to
As shown in (F), when Φ = −90 °, the meniscus 8 immediately before ejection is the most forward of the orifice 3, so the volume of the ejected droplet 12 becomes maximum, and when Φ = 90 °, Since the meniscus 8 just before the ejection is most retracted, the volume of the ejected droplet 12 becomes the minimum, and when Φ = 0 °, the volume of the ejected droplet 12 becomes an intermediate value. Therefore, by changing the timing of applying the pulse signal to the heating electrode 7, the volume of the ejected droplet 12 changes,
It is possible to change the dot diameter and modulate the image density.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention, in which parts corresponding to those in the first embodiment are designated by the same reference numerals. In this example, unlike the above-described first example, the phase shifter 14 is provided on the ultrasonic oscillator 5 side.

In this embodiment, specifically, the heating electrode 7 is driven at a constant cycle, and the timing of the high frequency signal applied to the ultrasonic oscillator 5 with respect to the position of the meniscus 8 is changed by the phase shifter.
By shifting to 14, the meniscus position immediately before the drive signal is applied to the heating electrode 7 is changed. As a result, the droplet diameter could be controlled as in the first embodiment.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention, in which parts corresponding to those in the first and second embodiments are designated by the same reference numerals. In this example, unlike the above-described embodiment, the ultrasonic oscillator 5 is not provided in the head common liquid chamber 4, and the ink supply system, particularly the main tank as an ink supply source and the common liquid chamber 4 are provided. In a device having the sub tank 11 on the way, it is provided in the sub tank 11.

In FIG. 6, reference numeral 10 is a tube made of resin or the like for connecting the ink supply port 6 of the head and the sub tank 11 to each other. Further, in a recording apparatus in which a print head is mounted on a carriage and moved in the scanning direction and recording is performed in the process, the sub tank 11 can be placed on the carriage in the same manner as the head.

Also in this embodiment, the heating electrode 7 or the ultrasonic transducer 5 is used.
In contrast to the phase shifter 14 of the first or second embodiment,
If the drive timing is adjusted by providing the same, the same effects as those of the embodiments can be obtained, and the ultrasonic oscillator 5 does not have to be enclosed in the common liquid chamber 4. The advantage is that maintenance is easy.

According to the three embodiments described above, the retracted position of the meniscus can be controlled by the ultrasonic waves generated by the ultrasonic oscillator 5 provided in the common liquid chamber 4 or the sub tank 11.
As a result, the diameter of the ejected liquid droplets can be changed, so that the gradation of the image density can be modulated according to the change in the diameter of the dots formed on the recording medium.

In addition, according to the above-described three embodiments, it is possible to eject a droplet having a small droplet diameter even if the orifice 3 having a relatively large diameter is adopted, and compared with the case where the orifice 3 having a small diameter is used. It is possible to prevent clogging of the orifice 3 or the liquid flow path 1. Moreover, if the orifice 3 having a larger diameter than the droplet diameter is provided for preventing clogging, it is not necessary to use a complicated mechanism as an ink non-ejection recovery mechanism.

In addition, even when the physical properties of the ink 2 change and the position of the meniscus 8 changes due to changes in temperature and humidity, the change in droplet diameter is compensated by controlling the voltage application time to the heating electrode 7. Will be easier.

[Effects of the Invention] As described above, according to the present invention, it is possible to realize an ink jet print head and a printing apparatus which can always perform sufficient and reliable gradation recording efficiently.

[Brief description of drawings]

1 and 2 are respectively a perspective view and a cross-sectional view showing one structural example of an ink jet print head according to a first embodiment of the ink jet printing apparatus of the present invention, and FIGS. 3 (A) and 3 (B) are respectively. FIGS. 4A to 4F are perspective views for explaining the meniscus change and the drive signal application timing according to the first embodiment, and FIGS. 4A to 4F are diagrams for explaining the operation of each part according to the first embodiment. FIGS. 5, 5 and 6 are cross-sectional views showing second and third embodiments of the present invention, respectively. 1 ... Liquid flow path, 2 ... Ink (recording liquid), 3 ... Orifice (ejection port), 4 ... Common liquid chamber, 5 ... Ultrasonic oscillator, 6 ... Ink supply port, 7 ... Heating electrode, 8 ... Meniscus, 9 ... Heating electrode driver, 10 ... Supply tube, 11 ... Sub tank, 12 ... Drop, 13 ... High frequency signal oscillator, 14 ... Phase shifter.

Claims (6)

[Claims] 1. A plurality of liquid outlets for ejecting a liquid, and a plurality of liquid flow paths each provided with an energy generating means for communicating with each of these outlets and for generating energy for ejecting the liquid, A common liquid chamber for communicating the flow channels together to supply the liquid to the liquid channel, and a tip end surface of the liquid provided in the common liquid chamber and formed at the discharge port in the discharge direction of the liquid. An ink jet print head, characterized in that it has a discharge amount adjusting means for repeatedly advancing and retreating along. 2. The ink jet print head according to claim 1, wherein the discharge amount adjusting means has an ultrasonic wave generating element. 3. The ink jet print head according to claim 1, wherein the energy generating means is means for generating heat energy. 4. A plurality of ejection passages for ejecting a liquid, a plurality of liquid flow paths each provided with an energy generating means for communicating with each of these ejection openings and for generating energy for ejecting the liquid, and these liquid passages. A common liquid chamber for supplying liquid to the liquid flow channel in common with the liquid flow channel, and a front end surface of the liquid provided in the common liquid chamber and formed at the discharge port are used as a liquid discharge method. An inkjet print head having a discharge amount adjusting means for repeatedly advancing and retreating along the discharge head, and by driving the energy generating means in accordance with the position of the tip surface of the liquid shaken by the discharge amount adjusting means, An inkjet printing apparatus, comprising: an ejection control unit that controls a size of a liquid droplet ejected from an outlet. 5. The ink jet printing apparatus according to claim 4, wherein the ejection amount adjusting means has an ultrasonic wave generating element. 6. The ink jet printing apparatus according to claim 4, wherein the energy generating means is means for generating heat energy.