JPS6137435A - Liquid-injection recording device - Google Patents

Abstract

PURPOSE:To increase the maximum frequency of driving pulses by simple constitution, cost thereof is low, and to conduct recording at high speed by providing a driving means effectively lowering the driving voltage of a generating element at the maximum frequency of driving pulses and using a filter with fine holes penetrating in the axial direction. CONSTITUTION:The form and structure of a filter 7 are formed to a columnar shape with a large number of fine holes 7a penetrating the whole approximately rectilinearly along the axial direction in a honeycomb manner, and the whole is shaped from ceramics. The diameter of the filter 7 takes size such as approximately 1mm., and the number of the holes 7a extend over several dozen or several hundreds, but optimum size and number of holes are selected according to the design, etc. of each device as these values. The filter 7 is formed to a honeycomb shape from ceramics having a high hydrophilic nature, bubbles are difficult to stay in the filter when they are taken into the filter 7, and bubbles are removed easily. Effective driving voltage is lowered only on maximum frequency, the quantity of ink injected when a meniscus slightly retreats from the noze of a nozzle is reduced, and there is no possibility of which bubbles are taken in from the outside after injection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid jet recording device, and more particularly, the present invention relates to a liquid jet recording device, and more specifically, a liquid jet recording device having a liquid jetting portion that discharges droplets of recording liquid by driving a jetting energy generating element by applying a driving pulse. The present invention also relates to a liquid jet recording device in which a filter is provided in a liquid flow path that supplies liquid to the liquid ejecting section.

[Prior art]

The conventional structure and operation of this type of so-called on-demand inkjet recording apparatus will be explained with reference to FIGS. 1 to 5.

FIG. 1 shows the configuration of the recording head of the above apparatus.

As shown in the figure, the ink ejection section of the recording head is formed by constricting the tip of a glass capillary 1 to form a nozzle section 2 having an ejection opening 2a with a diameter of several tens of micrometers.
A cylindrical piezoelectric element 3, which is the ejection energy generating element described above, is fitted and fixed onto the outer periphery of the ejection energy generating element. Piezoelectric element 3
is driven by a driving voltage applied through the lead wire L11L and contracts, and ink droplets are ejected from the ejection opening 2a of the nozzle portion 2 due to this pressurizing force.

On the other hand, a tube 4 for supplying ink to the glass tube 1 is connected to the rear end of the glass tube 1, and the rear end of this tube 4 is connected to the ink 6 in a sub-ink tank 5 for storing ink provided in the recording head. A filter 7 is fitted to the rear end of the tube 4.

This GIL Tough has the function of preventing air bubbles and dust from entering the gas capillary tube 1, and also blocking pressure waves generated within the glass capillary tube 1 when the piezoelectric element 3 is driven. Polyethylene particles of approximately 100 μm are sintered into a filter shape and then subjected to various hydrophilic treatments, which are widely used.

Further, the sub-ink tank 5 is connected to a main ink tank (not shown) via an ink supply tube 8.

The recording head configured as described above is mounted on a carriage (not shown), and scans the recording paper by driving the carriage and feeding the recording paper (not shown).

During this scanning, the piezoelectric element 3 is driven, causing ink droplets.

By ejecting from the ejection opening 2a of the nozzle section 2, dot recording is performed on the recording paper.

Next, FIG. 2 is a drive circuit diagram for driving the piezoelectric element 3 in FIG. 1. Here, the piezoelectric element 6 is configured as a capacitor. When a driving pulse P is input to the transistor Tr shown in the figure, the piezoelectric element 3 is rapidly charged to the voltage VNN through Tr and R1 as a capacitor. R1 is a limiting resistance! It is around 11100A. When the driving pulse P is interrupted, the charge stored in the piezoelectric element 6, which normally has a capacitance of several thousand picofarads, is transferred to the resistor R1.
, R2. This discharge operation is performed by the lead wire L.
Voltage between 2 and common ground■. FIG. 3 shows the waveform.

When recording with such a drive circuit, the drive voltage (2) at the piezoelectric element as shown in FIG. 4(A) is determined based on the timing signal t shown in FIG. 4(A). A waveform of

Here, in Figure 4), the part a is the highest frequency molecule max for driving the element, and the part b is fmax / 2.
It is.

In this way, the driving frequency is fmax and its 1/2°1/
The piezoelectric element 3 is driven at a frequency that varies from 3 to 1/4, but as the recording density increases or the scanning speed of the carriage increases, the period T to be driven in Figure 4 (B) increases.
As the fmax value becomes smaller and the fmax value becomes larger, the position of the ink meniscus within the nozzle portion 2 changes as shown in FIG.

That is, while the driving frequency is relatively low, the meniscus remains at position 9, and as the driving frequency increases, it retreats to position 10, which is a little inside instead of 9.

This is because the return of the meniscus of the ink 6 is carried out only by the force of the surface tension of the ink, and when ink ejection becomes frequent, the ink is ejected again before the meniscus returns to 9.

Further, if the filter 7 does not effectively block the pressure waves generated within the glass capillary 1 due to the drive of the piezoelectric element 3 described above, this also becomes a cause of the above-mentioned change in the position of the meniscus.

If continuous ejection is continued in a situation where the position of the meniscus has changed in this way, air bubbles are likely to be drawn into the nozzle from the outside after ink is ejected from the nozzle.

Furthermore, since the meniscus is driven at an unstable position, the amount of ink ejected changes, and the flying speed of the ink droplets also changes, which tends to hinder accurate landing.

Therefore, in order to perform proper recording, it is difficult to increase the recording speed by simply setting fmax high, and for the reasons mentioned above, conventionally fmax has been limited to approximately 3)G(z).

On the other hand, another reason why fmax cannot be set high as described above is that the characteristics of the conventional filter 7 are unstable.

That is, as mentioned above, with conventional filters made of sintered polyethylene particles, it is extremely difficult to numerically control filter characteristics such as ink permeability. Therefore, in order to increase the margin, there is a general tendency to set the liquid flow resistance to a larger value.

However, due to this, there have been cases where the droplet ejection energy is not used effectively. If air bubbles are still trapped in the filter.

The air bubbles change the properties of the filter, but once air bubbles are introduced into conventional filters, it is extremely difficult to remove them, and they cannot be removed without a special method such as extrusion at high pressure.

In this way, with conventional filters, not only the characteristics of the filter themselves are not sufficient, but also the characteristics are unstable, so the amount of ink supplied to the nozzle section 2 is also unstable, making it difficult to maintain the optimum value of fmax. Therefore, fmax is set low as a safety measure.

The above-mentioned problems are not limited to the conventional example described above, but are common to all liquid jet recording apparatuses of the type mentioned first.

〔the purpose〕

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to increase the maximum frequency of the drive pulses that drive the ejection energy generating elements of the print head using a simple and inexpensive structure in the above-mentioned type of liquid jet recording apparatus. [Summary of the Invention] In order to achieve the above objects. According to the present invention, there is provided a liquid ejecting section that ejects a droplet of recording liquid by driving an ejecting energy generating element by application of a drive pulse, and a filter is provided in a liquid flow path that supplies the liquid to the liquid ejecting section. The liquid jet recording device according to the present invention includes a driving means for effectively lowering the driving voltage of the generating element at the highest frequency of the driving pulse, and a filter having fine holes penetrating in the axial direction as the filter. The configuration used was adopted.

[Example] Hereinafter, an example in which the present invention is applied to the inkjet printer described in the conventional example described above will be described with reference to FIG. 6 and subsequent figures. Note that this embodiment differs from the conventional example only in the parts described below, and the explanation of other parts similar to the conventional example will be omitted.

First, in this embodiment, the filter 7 provided in the tube 4 that supplies ink to the ejection section of the recording head in the configuration of the inkjet printer described above is used as the filter 7 in FIG.
A filter 7 shown in FIG. Here, FIG. 6(4) is a perspective view of the entire filter 7, and FIG. 6(J3) is an enlarged plan view of a part of the upper surface in FIG. 6(G).

As shown in both figures, in this embodiment, the filter 7 is formed into a cylindrical shape having many fine holes 7a that penetrate almost straight through the whole along the axial direction in the shape of a lotus root, and the whole is made of ceramic. Formed.

The diameter of the filter 7 is, for example, about one diameter, and the number of holes 7a provided in the filter 7 is said to be several tens to several hundreds, but of course, these values are
The optimum size and number of holes are selected depending on the design of each device.

In this way, since the filter 7 is originally made of highly hydrophilic ceramic and is formed into a lotus root shape, air bubbles can be removed from the filter 7.
When air bubbles are taken into the filter, they are less likely to remain in the filter mouth, making it easy to remove air bubbles.

Further, the characteristics such as liquid permeability of the filter 7 can be freely designed and managed in a multivalued manner by setting the length of the filter and the diameter and number of holes.

Therefore, the characteristics of the filter 7 can be appropriately set according to the conditions when fmax is increased, and this molecule max
Since the margin width can be set small, sufficient child ma
x can be made high.

Furthermore, according to the filter 7 of this embodiment, the hydrophilic treatment can be omitted when manufacturing the filter 7. In addition, unlike conventional methods, the corners of the fitting part are less likely to be broken when fitting and fixing into the tube 4, and the process of removing the pieces from inside the recording head can be omitted, reducing the manufacturing cost of the recording head. I can figure it out.

Next, in this embodiment, a configuration is adopted in which the drive voltage of the piezoelectric element 3, which is the ejection energy generator described above, is effectively lowered when the frequency of the drive pulse is at its highest. This configuration will be explained with reference to FIG. 7(4), 2) and FIG. 8.

FIG. 7(a), ω) is the recording timing signal t of this embodiment.
and driving voltage V. shows the relationship with the waveform of As can be seen by comparing this with the conventional example shown in FIGS. 4(A) and 4(B), the drive voltage V. The next recording timing comes before the discharge drop curve of ' has not returned to the Nouss potential. - Also, in this embodiment, it is determined that when an interval corresponding to one timing pulse opens during continuous driving of fmax, the previous driving voltage returns to the original value.

In order to do this, in this embodiment, the discharge resistance R2 of the drive circuit shown in FIG. The constant is made thicker so that the voltage does not return to zero until the next recording timing only at the maximum frequency, so that the effective drive voltage value for the next piezoelectric element becomes low.

In this way, if the effective drive voltage is set to be low only at the highest frequency, the amount of ink ejected will decrease when the meniscus retracts a little from the nozzle tip, and there is a risk that air bubbles will be drawn in from the outside after ejection. do not have.

FIG. 8 shows the relationship between the frequency of the driving pulse of the piezoelectric element 6 and the ejection speed of the ink droplet when the driving voltage of the piezoelectric element 6 is high and low.
Curve H indicates the characteristics at a high drive voltage, and curve VL indicates the characteristics at a low drive voltage. As shown in the figure, the higher the driving voltage is, the higher the frequency becomes, the wider the variation in the injection speed becomes.

Generally, as the driving frequency increases, the position of the meniscus changes and the ejection speed of ink droplets changes, but as the effective voltage decreases, the degree of this also decreases. Therefore, by lowering the effective voltage only at fmax, this fluctuation range can be reduced.

The amount of reduction in effective voltage is determined as appropriate depending on the need, but is preferably about 10% at the time of maximum frequency driving.

In this way, by effectively lowering the drive voltage of the piezoelectric element 6 when the frequency of the drive nozzle is at its highest, it is possible to prevent the intake of air bubbles and fluctuations in the injection speed when driving at the highest frequency fmax, and fmax can be set high.

Moreover, this configuration can be realized in an extremely simple and inexpensive manner by changing the resistance value of the discharge resistor R2 of the drive circuit of the piezoelectric element 3 as described above.

Moreover, according to this configuration, the driving power of the piezoelectric element B can be reduced.

As described above, according to this embodiment, the maximum frequency fmax can be made significantly higher than that of the prior art due to the synergistic effect of the configuration of the driving means regarding the driving voltage of the piezoelectric element 6 and the configuration regarding the filter 7.

By the way, when we actually tested using the device of this example, fm
It has been confirmed that proper recording can be performed even when the ax is set to 61G-1z, which is twice the conventional value.

Note that the configuration of the present invention regarding the drive voltage of the filter 7 and the ejection energy generating element described above is not limited to the apparatus of the embodiment, but can be applied to all liquid jet recording apparatuses of the type mentioned at the beginning.

〔effect〕

As is clear from the above description, according to the liquid jet recording apparatus of the present invention, a means is provided for effectively lowering the driving voltage of the ejection energy generating element when the frequency of the driving pulse for driving the element is the highest. As a filter installed in the liquid flow path that supplies the recording liquid to the liquid discharge section, a ceramic filter having a large number of fine holes penetrating in the axial direction was used, so the above maximum frequency could be achieved with an extremely simple and inexpensive configuration. The excellent effect of high-speed recording can be obtained by setting the value high.

[Brief explanation of drawings]

1 to 5 illustrate a conventional inkjet recording device, in which FIG. 1 is a sectional view showing the structure of the recording head of the inkjet recording device, FIG. 2 is a driving circuit diagram of a piezoelectric element, and FIG. 3 is a waveform diagram of the drive voltage in the piezoelectric element in Figure 2, Figure 4 (B) is a waveform diagram of the timing signal and the drive signal of the piezoelectric element, respectively, Figure 5 is an explanatory diagram explaining the state of the meniscus, Figure 6 and the following are detailed explanations of the present invention. Figure 6 (5) is an overall perspective view of the filter;
Figure (B) is a partially enlarged plan view of the upper surface of Figure 6 (4), Figure 7
Figures (4) and (B) are waveform diagrams of the timing signal and drive signal of the piezoelectric element, respectively, and Figure 8 is a line explaining the relationship between the drive frequency and droplet ejection speed when changing the drive voltage applied to the piezoelectric element. It is a diagram. 1... Glass thin tube 2... Nozzle part 6... Piezoelectric element 4... Tube 5... Sub ink tank 6... Ink 7... Filter R2
...Discharge resistance patent applicant Canon Corporation Figure 1 Figure 2 Figure 3 Figure 4 (A) Figure 4 (B) O Figure 5 Figure 6 (A) Figure 6 (B) ) Figure 7 (A) Figure 7 (B) Figure 8/S1 Coffee @Weila

Claims (1)

[Claims] Liquid jet recording, comprising a liquid ejecting section in which an ejection energy generating element is driven by application of a drive pulse to eject droplets of recording liquid, and a filter is provided in a liquid flow path that supplies liquid to the liquid ejecting section. The apparatus is characterized in that it is equipped with a driving means that effectively lowers the driving voltage of the generating element at the highest frequency of the driving pulse, and that a filter having fine holes penetrating in the axial direction is used as the filter. A liquid jet recording device.