JPH06218926A - Ink jet recording head and ink jet recorder using same - Google Patents

Abstract

PURPOSE:To enable high density recording to be carried out without performing high speed relative transfer between a medium to be recorded and a recording head in an ink jet recorder using the recording head which jets ink by concentration of waves being transmitted in the ink. CONSTITUTION:In a recording head 11, a plurality of piezoelectric elements 12 are arranged in a matrix state. A recessed state owing to concentration of waves is formed by impressing a specific voltage to a group of the piezoelectric elements in a part to which an ink liquid drop 15 is going to be jetted. Further, that part is vibrated by impressing a high frequency voltage. Thereby, the ink drop is jetted by vibration and concentration of the waves in the ink corresponding to the piezoelectric element group.

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 a type in which ink droplets are ejected from an ink surface by concentrating waves propagating in ink, and an ink jet recording apparatus using the head.

[0002]

2. Description of the Related Art A conventionally known recording apparatus using an ink jet recording head has many advantages such as low noise, low running cost, easy miniaturization, and easy colorization. It is used as an information output device in etc.

The ink jet recording head used here has a discharge port (orifice) having a diameter of 20 μm to 300 μm, and most of the decrease in reliability of the recording head is due to this orifice. For example, clogging of the orifice may occur, ink thickening or sticking in the orifice and its vicinity, deformation of the orifice shape, etc. In such a case, ejection failure such as reduction of ink ejection amount or ejection failure may occur. Further, since it is necessary to process the orifice with high precision, the recording head becomes relatively expensive.

In contrast to the recording head having such a structure, a so-called nozzleless recording head which does not use an orifice has been proposed. One of them is to eject ink droplets from the ink surface by concentration of waves propagating in ink. It is an acoustic inkjet recording head. The basic principle of this ink ejection is, for example, the IBM Technical Disclosure Bulletin (IBM Technical Di).
sclossure Bulletin, Vol. 16,
No. 4, 1973, Sep. , 1168-).

[0005]

However, such a so-called acoustic ink jet recording head has hitherto been ejected from one recording head because of the structure of concentrating the pressure wave propagating in the ink at a specific point in the recording head. Then, the number of dots that can be simultaneously recorded on the recording medium is only one. For this reason, at the time of recording, it is necessary to move the recording medium and the recording head relative to each other at a higher speed than in other types of inkjet recording apparatuses. Therefore, a special structure for high-speed movement is required, which causes problems such as enlargement of the device.

The present invention has been made to solve the above-mentioned conventional problems, and a first object thereof is to provide continuous positions on a recording medium without moving the recording medium at high speed. An object of the present invention is to provide a recording head and an inkjet recording device that can perform high-density recording.

A second object is to provide an ink jet recording apparatus capable of gradation recording by changing the volume of ink droplets to be ejected.

A third object of the present invention is to provide a recording head having a plurality of ink ejecting portions and an ink jet recording apparatus having the head.

[0009]

Therefore, according to the present invention,
In an inkjet recording head for ejecting ink by concentrating a pressure wave at a predetermined position on an ink liquid surface, an electromechanical conversion element that is deformable to generate the pressure wave, and includes a plurality of electric elements arranged in a predetermined array. Mechanical conversion element,
The plurality of electromechanical conversion elements are selectively driven, and each of the electromechanical conversion elements includes an electrode for enabling the deformation.

A recording head for ejecting ink by concentrating a pressure wave at a predetermined position on the ink surface, which is an electromechanical conversion element deformable to generate the pressure wave, has a predetermined arrangement. A plurality of electromechanical conversion elements, and a recording head having electrodes for selectively driving the plurality of electromechanical conversion elements, each of which enables the deformation. Driving means for selectively driving the plurality of electromechanical conversion elements via electrodes, and controlling the driving means to deform the electromechanical conversion element group involved in ink ejection into a concave shape, and at a frequency higher than the deformation. An injection control means for deforming the electromechanical conversion element group.

More preferably, the jetting means shifts the position of the electromechanical conversion element group involved in the jetting at any time,
The feature is that ink is ejected from continuous positions.

Further, the ejection control means is characterized in that the volume of the ejected ink is changed by controlling the degree of the concave change.

[0013]

According to the above construction, by selectively driving a plurality of electromechanical conversion elements having a predetermined arrangement,
Ink can be ejected continuously from a continuous portion of the recording head, or can be ejected from a large number of portions at the same time.

Further, the amount of ejected ink can be made variable by changing the driving mode.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic perspective view showing the main structure of an ink jet recording apparatus using a recording head according to an embodiment of the present invention.

In the figure, the recording medium 20 is a platen 2.
The platen 2 is conveyed so as to be wound around the platen 2.
The sheet is conveyed by the rotation of the sheet ejection roller 22 and the pair of sheet ejection rollers 22, and is ejected in the direction of arrow D in the figure. During this time, ink droplets are ejected from the recording head 11 toward the recording medium 20 as necessary, and characters such as ABC or other images are recorded. The recording head 11 that ejects ink droplets according to the above-described principle is fixed to the apparatus main body. The print data input from the host device or the like is converted into a signal for selectively driving the print head in the head drive circuit 24, and is supplied as a drive signal to the print head 11 via the cable 23.

2A and 2B are schematic top views of the recording head 11 shown in FIG.
It is a B sectional view.

Ink is supplied from the A side and discharged to the B side in FIG. 2 (a). The amount of ink in the recording head is detected by the first ink liquid level sensor 13 and the second ink liquid level sensor 14, and when it is less than a predetermined amount,
It is positively supplied from the A side by a mechanism (not shown). The ink level sensors 13 and 14 are reflection type photo sensors and are used to detect the presence or absence of ink of a set predetermined level.

The signal supplied from the head drive circuit 24 to the recording head 11 is applied to the piezoelectric element 12 in the recording head. The piezoelectric element 12 has a columnar shape as will be described later with reference to FIG.
As shown in (a), they are arranged in a matrix. Further, a thin film layer 17 is provided on the plurality of piezoelectric elements 12 arranged in this way. this is,
This is to prevent direct contact between the piezoelectric element and the ink and to achieve acoustic impedance matching so that the pressure wave generated by the vibration of the piezoelectric element is efficiently transmitted into the ink.

FIG. 2B shows the case where the ink droplet 15 is ejected. At this time, an appropriate voltage is applied to each piezoelectric element group in the lower part of the ink droplet 15 in advance so that each piezoelectric element is deformed into a concave shape, and a high frequency voltage is further applied at the time of ejection. Vibrate. Such a concave deformation of the piezoelectric element is for the pressure waves emitted from the piezoelectric element group due to the vibration of the piezoelectric element group to concentrate near the ink surface 16.

More specifically, the piezoelectric element 12 is driven by the head drive circuit 24 which controls the position of the upper surface of the piezoelectric element by applying a relatively low frequency voltage based on the input recording data. A concave shape is formed, and vibration is generated by applying a voltage having a relatively high frequency to resonate the ink. At this time, at the same time, the volume of the ejected ink droplets can be controlled by controlling the degree of concave deformation of the piezoelectric element 12. That is, by appropriately determining the degree of concave deformation, it is possible to maximize the volume of the ejected ink droplets, and when the degree of concave deformation deviates from this maximum time, or If the degree is less than the maximum, the volume of the ink droplet is small. If there is no concave deformation, ink droplets are not ejected even if the piezoelectric element is driven at the relatively high frequency. Since the volume control of the ink droplets as described above is possible, it is possible to control the size of the ink dot formed on the recording medium and perform gradation recording.

Such selective ink ejection is performed from the left side to the right side in FIG. 2A, that is, from the A side to the B side.
I will go to the side while shifting. By repeating this operation, the recording of the first scan is completed. Then, after the second scan, the same operation is repeated, and at the same time, the recording medium 20 is synchronously conveyed, and recording can be performed on the entire recording medium.

FIG. 3 is a schematic perspective view showing the shape of a piezoelectric element that can be used in the above embodiment.

As shown in the figure, the piezoelectric element has an elongated prismatic shape, and its electrodes 12A are attached to two opposing surfaces shown by diagonal lines. The direction of polarization is the same as the direction of the two electrodes. In this case, the strain of the piezoelectric element 12 occurs in the direction of the arrow F in the figure which is orthogonal to the electrode direction (longitudinal deformation).
As described above, a large number of such piezoelectric elements are two-dimensionally arranged in the recording head 11. In addition, a sealing material that also serves as an electrode insulation and a strength reinforcement of the piezoelectric element is sealed between the piezoelectric elements.

(Embodiment 2) In the above-mentioned Embodiment 1, the shape of the piezoelectric element is an elongated prismatic shape, and the piezoelectric element is strained in the direction orthogonal to the polarization direction. However, the present invention is not limited to this and, for example, FIG.
As shown in (3), a laminated piezoelectric element in which electrodes and piezoelectric elements are laminated may be used, and the strain may be applied in the same direction as the polarization direction (lateral direction). In this case, there is an advantage that the voltage value for changing the piezoelectric element group into a concave shape can be made relatively small.

(Third Embodiment) In the first embodiment, the number of ink droplets ejected from the recording head 11 is one at the same time, but it may be plural, for example, two.

FIG. 5 shows a case where two ink droplets are ejected at almost the same time. In order to do so, the head drive circuit 24 may control the voltage applied to the piezoelectric element group so that two ink droplets are ejected at the same time. Further, by such control, it is possible to eject more ink droplets simultaneously. In this case, attention may be paid to the interference of pressure waves by the piezoelectric element groups corresponding to each, and in some cases, a minute appropriate amount of time difference may be provided.

[0029]

As described above, according to the present invention, by selectively driving a plurality of electromechanical conversion elements having a predetermined arrangement, ink is continuously ejected from a continuous portion of the recording head. It is also possible to inject from multiple locations at the same time.

Further, the amount of ejected ink can be made variable by changing the driving mode.

As a result, it was possible to perform high-density recording at continuous positions on the recording medium without moving the recording medium at high speed.

Further, since the volume of ink droplets to be ejected can be changed, gradation recording is possible.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a main configuration of an inkjet recording apparatus using a recording head according to an embodiment of the invention.

2A and 2B are a schematic top view of the recording head shown in FIG. 1 and a cross-sectional view taken along line AB thereof.

FIG. 3 is a schematic perspective view of a piezoelectric element that can be used in the above embodiment.

FIG. 4 is a schematic perspective view of a piezoelectric element that can be used in the above embodiment.

FIG. 5 is a sectional view of a recording head showing ejection control according to another embodiment of the present invention.

[Explanation of symbols]

 11 Recording Head 12 Piezoelectric Element 12A Electrode 13 First Ink Liquid Level Sensor 14 Second Ink Liquid Level Sensor 15 Ink Liquid Drop 16 Ink Liquid Level 17 Film Layer 20 Recording Medium 21 Platen 22 Paper Ejection Roller 23 Cable 24 Head Drive Circuit

Claims (7)

[Claims] 1. An ink jet recording head for ejecting ink by concentrating a pressure wave at a predetermined position on an ink liquid surface, the electromechanical conversion element being deformable to generate the pressure wave, wherein a predetermined arrangement is provided. An ink jet characterized by comprising: a plurality of electromechanical conversion elements, and electrodes for selectively driving the plurality of electromechanical conversion elements, each of which is capable of causing the deformation. Recording head. 2. Each of the plurality of electromechanical conversion elements comprises:
2. An elongated piezoelectric element, which is deformed in the vertical direction by the driving.
The inkjet recording head according to 1. 3. Each of the plurality of electromechanical conversion elements comprises:
A piezoelectric element formed by laminating a plurality of piezoelectric elements and electrodes, wherein deformation is generated in the lateral direction in each of the piezoelectric elements to cause deformation in the laminated piezoelectric element. 1. The inkjet recording head according to 1. 4. A recording head for ejecting ink by concentrating a pressure wave at a predetermined position on an ink liquid surface, the electromechanical conversion element deformable to generate the pressure wave, the predetermined arrangement. A plurality of electromechanical conversion elements, and electrodes for selectively driving the plurality of electromechanical conversion elements, each of which is capable of causing the deformation, and a recording head comprising: Driving means for selectively driving the plurality of electromechanical conversion elements via electrodes, and controlling the driving means to deform the electromechanical conversion element group related to ink ejection into a concave shape, and at a frequency higher than the deformation. An ink jet recording apparatus comprising: an ejection control unit that deforms the electromechanical conversion element group. 5. The ink jet recording apparatus according to claim 4, wherein the ejecting unit ejects the ink from a continuous position by shifting the position of the electromechanical conversion element group related to the ejection at any time. 6. The ink jet recording apparatus according to claim 4, wherein the ejection control unit changes the volume of the ejected ink by controlling the degree of the concave change. 7. The ink jet recording apparatus according to claim 4, wherein the electromechanical conversion element group involved in the ejection is located at two or more locations at the same time.