JPS6145542B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ink jet head that jets ink from ink jet ports, and more particularly to an ink jet head that jets ink droplets in the same direction and substantially parallel from a plurality of ink jet ports.

PRIOR ART One of the typical ink jet heads is one in which an electrostrictive vibrator is electrically energized to apply pulse-like pressure to ink in an ink flow path communicating with an ink jetting port. An example of this is disclosed in Japanese Patent Application Laid-Open No. 48-9622. In this case, one circular electrostrictive vibrator with a relatively large area is disposed for one ink jet orifice, and the space occupied by the vibrator is large. It was difficult to integrate and arrange them in a relatively short pitch.

In addition, several (for example, seven) ink jet ports are densely arranged in the width of one line of characters, and the ink channels that communicate with them are distributed radially, and electrostrictive vibrators are installed in areas where the channels are widely spaced. Disposed inkjet heads have also been proposed. For example, it is disclosed in Japanese Patent Application Laid-Open No. 51-55239. In this head, since the ink flow path between the vibrator and the ink jetting port is long, the pressure loss is large and the ink flying distance cannot be increased.

The above two rows are of the so-called on-demand system, in which ink particles are ejected from the ink jet orifice at regular intervals by continuously driving a vibrator, and the ink in the head is connected to a charging electrode placed ahead of the ink jet orifice. In a so-called charged deflection type ink jet head, ink particles are selectively charged by selectively applying a voltage in association with recorded information between the ink and the ink, and the charged ink is deflected by a deflection electric field between deflection electrodes. For example, one line of character width is recorded using ink ejected from one ink ejection port. In this case, the entire width of one line can be recorded simultaneously by arranging a large number of ink jet ports at intervals of, for example, one line character width. However, even in charge deflection type ink jet heads, an electrostrictive vibrator is continuously driven to eject ink particles at regular intervals, and a sinusoidal pressure is applied to the ink flow path communicating with the ink ejection port.
Another challenge is to relatively shorten the distance between the vibrator and the ink jet orifice and arrange the electrostrictive vibrators at high density.

Purpose An object of the present invention is to arrange a large number of ink jetting ports in the same direction at high density in a straight line in parallel without particularly increasing the distance between the electrostrictive vibrator and the ink jetting ports.

Configuration In order to achieve the above object, in the present invention,
Three or more ink jet ports are arranged in parallel to each other on a straight line in a direction perpendicular to the ink jet direction of one ink jet port, and the ink jet ports are arranged between each ink jet port and an ink chamber. A space extending in the direction is divided by a plurality of electrostrictive vibrators into a plurality of ink flow paths each communicating with each ink ejection port.

According to this, the ink jetting direction is the same, a plurality of ink jetting ports are lined up in a direction perpendicular to the ink jetting direction, and each of the adjacent ink jetting ports has one ink flow path communicating with each other. Since two opposite sides of one ink flow path are composed of electrostrictive vibrators, the arrangement of the ink flow paths becomes high density, and as a result, ink jetting becomes difficult. The arrangement of the mouth also becomes denser. Even if the area of the electrostrictive vibrator is large, its spread is in a direction perpendicular to the direction in which the ink jet ports are arranged, and the spread in this direction is unrelated to the pitch of the ink jet ports. The pitch is only influenced by the thickness of the electrostrictive vibrator and the width of the ink flow path space (gap), and the ink jet ports can be arranged at an extremely short pitch.

In a preferred embodiment of the present invention, in order to make the electrostrictive vibrator thin and to increase ink pressure efficiency, the electrostrictive vibrator is a bimorph type electrostrictive vibrator in which two piezo element plates are joined via an electrode layer. The vibrators are arranged in a direction perpendicular to the ink jetting direction, and every other vibrator is shifted along the ink flow path from the ink chamber to the ink jetting port.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

FIG. 1a shows the external appearance and cross section of a first embodiment of the present invention. The head body 1 includes an ink chamber 1a,
n first ink channels 1bi (i=1 to n) each communicating with the ink chamber 1a, a second ink channel 1ci continuous to the first ink channel, and pressurization continuous to the second ink channel. A chamber 1di is formed, and ink is supplied from a pipe 3 to the ink chamber 1a. Ink ejection ports 2ai (i=1 to n) are formed in the nozzle plate 2 and communicate with each of the pressurizing chambers 1di.

Each pressurizing chamber 1di has a bimorph type electrostrictive vibrator 4
These bimorph electrostrictive vibrators 4ai are separated from each other by ai, and are joined to the head main body 1.

An enlarged perspective view of the bimorph electrostrictive vibrator 4ai is shown in FIG. 1b. This electrostrictive vibrator 4ai has a first electrode layer 6 between two thin plate-shaped piezo elements ₅₁ and ₅₂ .
₁ is formed, and an extraction electrode 6 ₁ a is joined to it from the side surface of the piezo elements 5 ₁ and 5 ₂ , and an electrode 6 ₂ is formed on the surface of the piezo elements 5 ₁ and 5 ₂ , and they are rotated to form an integral relationship as an electrode. The piezo elements 5 ₁ and 5 ₂ are connected to each other, and an extraction electrode 6 ₂ a is connected thereto from the side surface of the piezo elements 5 1 and 5 2 .

The electrostrictive vibrator 4ai having such a structure is installed in the ink jet head shown in FIG. 1a with the respective electrodes 6 ₁ and 6 ₂ insulated from the ink in the pressurizing chamber 1di.

The electrode _61a of each electrostrictive vibrator 4ai is connected to the lead wire 7i
The conductive pins 8bi are connected to the divided electrodes 8ai on the printed circuit board 8 through the conductive pins 8bi. An ink ejection activation voltage is applied to these pins 8bi via a connector (not shown). 9i is an insulating sleeve through which an electric lead 7i connected to the electrode 6 ₁ a passes. The electrodes 6 ₂ a of each electrostrictive vibrator 4ai are all connected in common to the ground terminal 10.

Several examples of how to use the ink jet head shown in FIG. 1a will now be described.

(1) Assuming that each of the ink jet ports 2ai is given a consecutive number in the order of its arrangement, and the electrostrictive vibrator 4ai is given a similar serial number, the printing signal assigned to the odd numbered ink jet port is A voltage is applied to the odd-numbered (or even-numbered) electrostrictive vibrators in the direction of reducing the volume of the pressurized chamber communicating with the nozzle, and then a voltage is applied to the printing signal assigned to the even-numbered ink nozzle. Based on this, a voltage is applied to even-numbered (or odd-numbered) electrostrictive vibrators. The applied voltage should have a steep rise and a slow fall, increase the pressurizing speed of the electrostrictive vibrator, and make the return speed slow. Thereafter, the same operation is repeated.

(2) Based on the printing signal assigned to the odd-numbered ink jetting port j, the volume of the pressurizing chamber communicating with the ink jetting port j between them is set on both sides of the electrostrictive vibrator number j and j+1. Then, based on the printing signal assigned to the even-numbered ink ejection ports, the volume of the pressurized chamber between them is applied to the k-th and k+1-th electrostrictive vibrators. Apply a decreasing voltage from both sides. The applied voltage should have a steep rise and a slow fall, increase the pressurizing speed of the electrostrictive vibrator, and make the return speed slow. below,
Repeat the same action.

(3) In (1) and (2) above, when the voltage applied to the electrostrictive vibrators in the first group (odd numbered) falls, voltage is applied to the electrostrictive vibrators in the second group (even numbered). , a voltage is applied to the first group of electrostrictive vibrators at the time of falling. Repeat the same process below.

(4) Voltages are sequentially applied to the electrostrictive vibrators in numerical order based on the imprint signal.

(5) When used as an inkjet head of a charge deflection type inkjet recording device, a first sine wave voltage of a fixed period is applied to the odd numbered electrostrictive vibrators, and a first sine wave voltage is applied to the even numbered electrostrictive vibrators. A second sine wave voltage having the same period and voltage as the wave voltage and 180 degrees out of phase with the first sine wave voltage is applied. In other words, odd numbered ink jet ports,
Ink is ejected alternately from even-numbered ink ejection ports.

When controlling printing density, it is sufficient to change the applied voltage level according to the density command signal, but since the voltage applied to the electrostrictive vibrator is generally relatively high, the voltage control circuit for controlling the level has a withstand voltage. From a point of view it becomes complicated and expensive. Therefore, in the ink jet head shown in Fig. 1a, by taking advantage of the feature that two electrostrictive vibrators are disposed in one ink flow path, an electric current is applied to one electrostrictive vibrator in accordance with the concentration command signal. It is preferable to shift the phase of the voltage applied to the other electrostrictive vibrator with respect to the voltage applied to the other electrostrictive vibrator. Such phase control is achieved by connecting, for example, several shift registers with different numbers of shift stages in parallel between the drive pulse generation circuit and the printing signal supply circuit, and selectively controlling one shift register according to the density level. This can be easily done by providing only the output to the drive pulse generation circuit.

FIG. 2 shows the main parts of a second embodiment of the present invention. In this case, every other electrostrictive vibrator 4ai is shifted toward the ink supply port. Since the odd-numbered and even-numbered electrostrictive vibrators facing each other are relatively shifted in the direction along the ink flow path, when a voltage is applied to both of them at the same time, the first embodiment shown in FIG. Although the pressurizing force is lower than in the case of the example, a voltage is first applied to the upstream electrostrictive vibrator, and when the pressure is propagated to the ink flow path between the downstream electrostrictive vibrator and the head body 1, the downstream By applying a voltage to the electrostrictive vibrator, a large pressurizing force is applied to the ink that has already started flowing toward the ink jet orifice.
That is, at the point when the peak of pressure due to the excitation of the electrostrictive vibrator on the upstream side reaches between the electrostrictive vibrator on the downstream side and the head body 1, the peak of pressure due to the excitation of the electrostrictive vibrator on the upstream side reaches the peak of pressure due to the excitation of the electrostrictive vibrator on the downstream side. By delaying the downstream excitation by a certain amount of time relative to the upstream excitation so as to be applied between the electrostrictive vibrator and the head body 1, high pressure is concentrated on the ink near the ink jet orifice.

In the case of this ink jet head, after the ink in the ink flow path is pressurized by the electrostrictive vibrator on the upstream side and begins to move in the direction of the ink jet port 2ai, the electrostrictive vibrator on the downstream side Since the ink can be squeezed out by applying pressure with the ink, the phase control mentioned above allows for a wide variation range from large diameter ink particles consisting of an extremely large amount of ink to small diameter ink particles consisting of an extremely small amount of ink. . Therefore, printing density control can be performed over a wide control range.

Effects As described above, the inkjet head of the present invention has
Three or more ink jetting ports are arranged in parallel on the same straight line with the same ink jetting direction, and pressurized chambers communicating with these ink jetting ports are divided by electrostrictive vibrators toward the ink jetting ports. Therefore, the area of the electrostrictive vibrator does not affect the arrangement pitch of the ink jet ports, and many ink jet ports can be arranged side by side at an extremely short pitch, making it easy to obtain a multi-nozzle head with a high-density nozzle arrangement. .

[Brief explanation of the drawing]

FIG. 1a is a perspective view showing the appearance and cross section of a first embodiment of the present invention. FIG. 1b is an enlarged perspective view showing the appearance of the electrostrictive vibrator shown in FIG. 1a.
FIG. 2 is a horizontal sectional view of a portion of a second embodiment of the present invention. 1: Head body, 1d ₁ : Pressurizing chamber (ink flow path), 2: Nozzle plate, 2ai: Ink injection port, 3: Pipe, 4ai: Electrostrictive vibrator, 5 ₁ , 5
₂ : piezo element board, 6 ₁ , 6 ₁ a, 6 ₂ , 6 ₂ a: electrode, 7i: lead wire, 8: printed circuit board, 8ai:
Split electrode, 8bi: conductive pin, 9i: insulating sleeve, 10: ground terminal.

Claims (1)

[Scope of Claims] 1. Three or more ink jet ports are arranged parallel to each other on a straight line in a direction perpendicular to the ink jet direction of one of the ink jet ports, and between each ink jet port and an ink chamber. An ink jet head in which a space extending in the direction in which the ink jet ports are arranged is divided by a plurality of electrostrictive vibrators into a plurality of ink flow paths each communicating with each ink jet port. 2. The ink jet head according to claim 1, wherein the electrostrictive vibrator is a bimorph type electrostrictive vibrator in which two piezo element plates are joined via an electrode layer. 3 The electrostrictive vibrators are aligned in the orthogonal direction to 1
3. An ink jet head according to claim 1, wherein the ink jet heads are arranged at intervals of one another along an ink flow path from an ink chamber to an ink jet orifice.