JPH0640034A - Driving method of ink-jet type printing head - Google Patents

Abstract

PURPOSE:To ensure reliability on the strength of an ink discharge mechanism, and to improve the quality of printing by preventing the driving of the discharge-pressure generating means of the ink discharge mechanism at both continuously disposed ends in a printing head. CONSTITUTION:The shapes and constitution of all of continuous ink discharge mechanisms are manufactured completely similarly up to end sections. Consequently, rigidity in the peripheries of ink chambers 618 is made the same entirely with the exception of the end-section ink chamber 618. The structure of the end-section ink chamber 618 is formed in a fine shape, and the high rigidity of the end-section ink chamber 618 also has an effect on the ink chambers 618 except an end section. Accordingly, at least one ink discharge mechanism is not driven at the time of the large effect, and a plurality of the ink discharge mechanisms are not driven from the end section, thus equalizing rigidity in the peripheries of a plurality of the ink chambers 618 driven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of an ink jet printer for forming ink images on a recording medium such as recording paper by ejecting ink droplets according to a print signal.

[0002]

2. Description of the Related Art There are many known types of recording heads for ink jet printers that eject ink droplets in response to a print signal.

First, as disclosed in Japanese Patent Application Laid-Open No. 2-238950, an ink flow path communicating with a nozzle, a partition wall for dividing the ink flow path individually, and a joint portion of the partition wall are deformed. The piezoelectric element is provided. FIG. 3 shows an exploded perspective view of an ink jet print head according to the prior art. In the figure, a plurality of piezoelectric elements 112 are provided on a base 111. One side surface of the piezoelectric element 112 is electrically connected to the signal electrode 113 on the fixed base 111, and the other side surface is electrically connected to the common electrode 114.
The electrodes 113 and 114 are connected to a drive circuit (not shown). A cover block 117 is provided on the side surface of the piezoelectric element 112, which is not fixed, via an elastic wall member 116. The cover block 117 is the elastic wall member 116.
An ink flow path 118 is formed between and. Nozzle 119
Are continuously formed on the nozzle substrate 117b and are arranged in a one-to-one correspondence with the continuous ink channels 118.

The principle of ink ejection is that a voltage is selectively applied to one of the continuous signal electrodes 113 via an external control circuit or drive circuit (not shown). The signal is sent to the ink flow path 118 for ejecting ink, and the ink flow path 118.
Is applied to the piezoelectric element 112 that is partially in contact with the partition wall 117a that forms the. Therefore, as shown in the partial cross-sectional view of FIG. 4, the corresponding piezoelectric element 112 is displaced in the direction of arrow A by the piezoelectric effect, causing the base portion 116a of the partition wall 117a to be deformed, and the partition wall 117a is displaced in the direction of arrow B. As a result, a pressure change is generated in the ink in the ink flow path 118, and an ink droplet is ejected from the nozzle.

The other one is, as shown in Japanese Patent Laid-Open No. 3-258550, separates the other end of the piezoelectric element whose one end is fixed to the base from the elastic wall forming the ink chamber and the ink chamber. It is configured to abut against the partition wall. FIG. 5 shows an exploded perspective view of an ink jet print head according to the prior art.
In the figure, a comb-shaped piezoelectric element 312 is provided on the base 311.
Is provided. Each side of the piezoelectric element 312 is electrically connected to the signal electrode 313 on the fixed base 311 and the other side is electrically connected to the common electrode 314.
3 and 314 are connected to the drive circuit 315.

A cover block 317 is disposed on the non-fixed side surface of the piezoelectric element 312 via an elastic wall member 316. The cover block 317 is an elastic wall member 316.
An ink chamber 318 and a nozzle 319 are integrally formed between and.

A drive circuit 3 is connected from an external control circuit (not shown).
A voltage is selectively applied to any of the signal electrodes 313 via 15. As shown in the partial cross-sectional view of FIG. 6a, the signal is a piezoelectric element 312a that comes into contact with an ink chamber 318 that ejects ink, and a piezoelectric element that comes into contact with a partition wall 317a that forms the ink chamber 318 and divides an adjacent ink chamber 318. Simultaneously applied to the element 312b. Therefore, the piezoelectric elements 312b, 312a, 312b are displaced in the same direction by the piezoelectric effect in the same direction, that is, the arrow C in FIG. 6A and the arrow C ′ in FIG. 6B, and a pressure change is generated in the ink in the ink chamber 318. A droplet is ejected from the nozzle 119.

7A and 7B are similar to those having the same structure.
As shown in (b), the piezoelectric element 312a and the piezoelectric element 312b
There is a driving method in which the and are reversely displaced to efficiently generate a pressure change in the ink in the ink chamber 318.

The other one is, as shown in Japanese Patent Publication No. 2-52625, in which an ink chamber having a nozzle is energized to expand the ink chamber to be filled with ink, and deenergized to compress the ink chamber. A piezoelectric element is provided so that ink droplets are ejected from the nozzle. FIG. 8 shows a sectional view of an ink jet print head according to the prior art. In the figure,
The other end of the piezoelectric element 612 whose one end is fixed to the base 611 is connected to the elastic wall member 616 of the container forming the ink chamber 618.
And is configured to abut on the leg portion 616a via the leg portion 616a. The leg portion 616a makes a translational movement along the bearing means of the cylindrical opening in the member adjacent to the member forming the elastic wall member 616.

According to the technique of the publication, the principle of ink ejection is as follows.
The piezoelectric element 612 is contracted to increase the volume of the ink chamber 618, and the piezoelectric element 612 is again expanded to expand the ink chamber 6.
The ink is ejected as droplets from the nozzle 619 by reducing the volume of 18 pieces.

In any of the above structures, ink is used so as to be ejected from all continuous nozzles.

[0012]

In the conventional ink jet type print head described above, the structural elements are made thinner and the rigidity is lowered as the structure is made higher in density. The generated stress at the time of ejecting the ink appears as vibration as a result for each of these constituent elements. However, in a continuous ink ejection mechanism formed of an ink chamber, a piezoelectric element, and a nozzle, the same shape is continuous, so its vibrations are dispersed and disappear,
Since the ink chamber is basically reinforced by the rigidity of the base, it is possible to obtain a good ink image ejected from the nozzle and good print quality.

However, at both ends of the continuous ink ejecting mechanism, for example, a partition for forming a nozzle or an ink chamber shown in a portion 117c of FIG. 4 or in another structure, a portion 317c of FIG. 5 and a portion 617c of FIG. The rigidity of the piezoelectric element and the rigidity of the piezoelectric element are completely different from those of the same component in the portion that continuously configures the ink ejection mechanism of the same shape. As a result, the dispersion of vibration due to the ink ejection pressure generation stress is 117 c and 317.
There is a problem in that it is biased in the direction of lower rigidity in the portions c and 617c, resulting in deterioration of strength of the close joint portion and the low-rigidity component.

Further, there is a problem in that the printing quality is deteriorated by the ejected ink image by the ink ejecting mechanism at both ends due to the deviation of the transmitting direction of the ink ejecting pressure generating stress.

Therefore, an object of the present invention is to provide an ink jet type print head which can secure strength reliability of an ink ejection mechanism and can obtain good print quality.

[0016]

In an ink jet type print head of the present invention, an ink chamber is composed of at least a partition wall for dividing the ink chamber individually and a wall forming a nozzle, and an ink discharge provided in the ink chamber. In an ink jet type print head in which the ink discharge mechanism of the same shape is continuously arranged to discharge the ink in the ink chamber from the nozzles by driving the pressure generating means, at both ends of the continuous arrangement,
It is characterized in that at least one ink ejection pressure generating means of the ink ejection mechanism is not driven.

[0017]

EXAMPLES The ink jet print head according to the present invention will be described in detail below with reference to examples. Here, a stable method of manufacturing an inkjet print head will be described. FIG. 2 is a perspective view showing the configuration of an embodiment of the present invention, in which each component is disassembled after assembly. FIG. 1 is a partial sectional view showing the same embodiment in more detail.

In these figures, 617b is a nozzle substrate. The nozzle substrate 617b includes a plurality of nozzles 61.
9 is provided. Reference numeral 617a is a partition wall. Partition 617a
Is sandwiched between the nozzle substrate 617b and the elastic wall member 616 to form an ink chamber 618. The elastic wall member 616, the partition wall 617a, and the nozzle substrate 617b are sequentially adhered to each other to form the ink chamber 618, and then adhered to the head frame 640. The detailed structure of the embodiment will be described with reference to FIG. Piezoelectric element 612 serving as a drive source for ink droplet ejection
About one side of a in the longitudinal direction thereof, one surface is fixed to the base 611, and the other half end, which is not fixed, is joined to the elastic wall member 616. In the Z direction of the piezoelectric element 612a, after the bonded body in which the elastic wall member 616, the partition wall 617a, and the nozzle substrate 617b are bonded to the head frame 640, the tip of the piezoelectric element 612a abuts on the elastic wall member 616. To match. The above is the schematic configuration.

On the other hand, as shown in FIG. 1, the ink chamber 618 filled with ink formed by the partition wall 617a, the nozzle substrate 617b, and the elastic wall member 616 has the partition wall 617a processed by etching glass, laminating thin metal plates, and photosensitivity. Although it can be formed by exposure of resin, injection molding of resin, or the like, in this embodiment, the photosensitive resin which is inexpensive in cost is used, and the partition wall 61 is used.
The nozzle substrate 617b covering the upper surface of 7a was formed by press working using a stainless steel plate of about 0.1 mm in which a plurality of ink chambers 618 were each provided with one nozzle 619. The nozzle substrate 617b can also be manufactured by an electroforming method of nickel. In addition, the partition 617a
As the elastic wall member 616 covering the lower surface of the above, a thin metal plate formed to a thickness of 5 μm or less by an electroforming method of nickel is used. The thin metal plate is preferable as it is thin in order to efficiently transmit the expansion and contraction of the piezoelectric element 612a to the ink chamber 618.
The ink in 18 should not seep out. When the ink exhibits conductivity, the thin metal plate can be replaced with a resin such as a film.

Here, the ink droplet ejection operation will be described with reference to FIG. An electric field is applied from a drive circuit (not shown) to one electrode 613 and the other electrode 614 of the piezoelectric element 612a in response to a print signal. The piezoelectric element 612a to which the electric field is applied tends to contract in the longitudinal direction (vertical direction in the figure). At this time, the lower half of the piezoelectric element 612a is fixed to the base 611 held by the head frame 640 and cannot be contracted and displaced. On the other hand, the upper half of the piezoelectric element 612a is
The elastic wall member 616 is pulled by the contracting force because the contracting displacement is performed without receiving any other constraint. Piezoelectric element 612a
The thin metal plate of the elastic wall member 616 that is pulled toward the bottom bends downward, and as a result, the volume of the ink chamber 618 expands. Then, the piezoelectric element 612 is discharged by applying no electric field and discharging.
a expands to a steady state, and the volume of the ink chamber 618 contracts at this time, so that ink droplets are ejected from the nozzle 619.

By the way, when the ink ejection state of the ink chamber 618 located at the end of the continuous ink chamber 618 is observed, the ejected ink amount and the ejected ink speed are not stable as compared with the other continuous ink chambers 618. There is. The cause of this phenomenon is that the portion 617c shown in the figure has an extremely large rigidity because there is no portion that causes low rigidity such as the thin partition wall portion of the partition wall 617a separating the ink chambers 618 or the nozzle 619 processing of the nozzle substrate 617b. It has become a part to have. Therefore, only the end ink chamber 618 has a different transfer conversion efficiency of the ink ejection generation pressure from the piezoelectric element 612a to the ink ejection.

On the other hand, the effect of not driving at least one ink ejecting mechanism at the end of the ink ejecting mechanism constituted by the continuous nozzle 619, the partition wall 617a and the piezoelectric element 612a, which is carried out in the present invention, will be described. All the continuous ink ejection mechanisms are made to have the same shape and configuration up to the end. Therefore, the rigidity around the ink chamber 618 is exactly the same except for the end ink chamber 618. However, in reality, the structure is minute and the high rigidity of the end ink chamber 618 affects the ink chambers 618 other than the end portion. Therefore, when the influence is large, at least one ink ejection mechanism is not driven, and a plurality of ink ejection mechanisms 618 are driven by not driving a plurality of ink ejection mechanisms from the end.
The rigidity of the surroundings can be equalized. As a result, it is possible to stably obtain the ejection amount and the ejection speed with the continuous ink ejection mechanism. With respect to this effect, the effect of the rigidity of the end ink chamber 618 on other ink chambers 618 in the structure in which the ink chambers 618 of the ink jet printing head shown in FIG. The print head has a structure in which the space between the ink chambers 618 is fixed to the piezoelectric element 612b, and since the rigidity of each ink chamber 618 is relatively stable, the other ink chambers 6 of the end ink chambers 618 are fixed.
The effect of rigidity on 18 is small. One ink chamber 6 at each end
The remaining 14 continuous ink chambers 618 that do not drive 18 are ± 5% even if the ejection amount and ejection speed that are the ink ejection characteristics are large.
It is stable and fits within the variations. However, when the end ink chambers 618 are driven at the same time, the ink ejection characteristics of up to 50% UP are exhibited compared to the other ink chambers 618, which is a factor that hinders the stabilization.

Further, as a phenomenon that is particularly different only in the end ink chamber 618, there is vibration of the nozzle substrate 617b when ejecting ink. In a continuous ink ejection mechanism, a very stable amount of the nozzle substrate 61 when ejecting ink except the end portion thereof
A displacement of 7b is observed. On the contrary, the ink chamber 6 at the end
No. 18 has almost no vibration. Therefore, the ink chamber 618 near the end is located at the boundary where the vibration of the nozzle substrate 617b is absorbed and diverged, and the structural strength is remarkably deteriorated due to the close contact between the nozzle substrate 617b, the partition 617a, and the elastic wall member 616.

[0024]

As described above, in the ink jet type print head of the present invention, at least one ink ejecting mechanism at the end of the ink ejecting mechanism having the same shape is not driven to eject ink from the piezoelectric element. The transfer conversion efficiency of generated pressure to ink ejection can be stably obtained, and high print quality is enabled. Further, since the dispersion disappears smoothly with respect to the vibration of the ink ejection generated stress applied to the ink chamber, it is possible to obtain an ink jet type print head having high strength reliability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inkjet print head for explaining the present invention.

FIG. 2 is an exploded perspective view of an ink jet print head for explaining the present invention.

FIG. 3 is an exploded perspective view showing an embodiment of a conventional ink jet print head.

FIG. 4 is a sectional view showing an example of a conventional ink jet print head.

FIG. 5 is an exploded perspective view showing another embodiment of a conventional ink jet print head.

FIG. 6 is a cross-sectional view showing another embodiment of a conventional ink jet print head.

FIG. 7 is a sectional view of a part similar to another embodiment of the conventional ink jet print head.

FIG. 8 is a cross-sectional view showing another embodiment of the conventional ink jet print head.

[Explanation of symbols]

 611 Base 612 Piezoelectric element 613 Signal electrode 614 Common electrode 616 Elastic wall member 617a Partition wall 617b Nozzle substrate 618 Ink chamber 619 Nozzle 640 Head frame

Claims (1)

[Claims] 1. The ink chamber comprises at least a partition wall for dividing the ink chamber individually and a wall for forming a nozzle, and the ink in the ink chamber is moved by driving an ink discharge pressure generating means arranged in the ink chamber. In an ink jet type print head in which ink ejection mechanisms of the same shape, which are ejected from nozzles, are continuously disposed,
A method for driving an inkjet print head, characterized in that at least one ink ejection pressure generating means of an ink ejection mechanism is not driven.