JPS626991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink jetting device used for inkjet printing.

The construction of a conventional inkjet head of this type is shown in FIGS. 1a, 1b and 1c. 1st
The one shown in Figure a is the so-called ink-on-demand type, which applies a voltage to the electrostrictive vibrator 1 to excite the diaphragm 2 and apply pressure waves to the ink in the head to generate ink droplets. is injected from the nozzle 3. What is shown in Figure 1b is
The electrostrictive vibrator 1 generates pressure waves in the ink liquid, and ink droplets are ejected from the nozzle 3.
In all of these, ink liquid is simply supplied from an ink tank, and the supplied ink liquid is not pressurized.
Conventionally, these ink jet heads have had the following problems.

(1) Nozzle 3 is easily clogged. Once clogging occurs, it is difficult for the pressure waves generated by the electrostrictive vibrator 1 to break through the clogging and eject ink.

(2) If air enters the head from the nozzle 3, the jetting characteristics of ink droplets may change or jetting may become impossible. This also applies when air is mixed in the supplied ink liquid.

(3) Since the supplied ink liquid is not pressurized, there is a limit to the flow rate of the ink liquid, and there is a limit to increasing the ejection repetition frequency, that is, the ejection speed.

(4) Particularly in the ink jet head shown in Fig. 1b, the pressure wave excited by the vibrator 1 is
Since the ink droplets also propagate in the opposite direction, the ink droplet jetting efficiency is poor.

In the ink jet head shown in FIG. 1c, relatively high, constant pressure ink is supplied to the space (pressure chamber) between the ink jet nozzle 3 and the diaphragm 2, and the diaphragm 2 is integrally connected to the space (pressure chamber) between the ink jet nozzle 3 and the diaphragm 2. The electrostrictive vibrator 1 vibrates at a constant period due to continuous vibration energization of the electrostrictive vibrator 1,
Regular periodic pressure vibrations are superimposed on the ink supplied to the pressurizing chamber and ejected from the nozzle 3. As a result, the ink ejected from the nozzle 3 is separated into ink particles at regular intervals at a position that has advanced a predetermined distance from the nozzle 3. Ink particles are selectively charged by selectively applying a charging voltage between the charging electrode 4 and the ink in the pressurizing chamber in accordance with the timing of separation into ink particles. The charged ink is transferred to the upper and lower deflection electrodes 2.
In this example, the gutter 6
collides with the recording paper (not shown) behind the The uncharged ink particles advance straight into the gutter 6.

In the inkjet recording device shown in FIG. 1c,
Ink with a high enough pressure to fly ink particles to the gutter 6 and the recording paper behind it is supplied to the pressurizing chamber, and the ink is constantly ejected from the nozzle 3, so air is sucked into the pressurizing chamber from the nozzle 3. There's nothing to do. However, since the ink pressure is high, the vibration pressure by the electrostrictive vibrator 1 must be increased in order to form particles. Another problem is that it is difficult to control printing density.

The present invention facilitates the removal of clogging, prevents air from being sucked into the pressurized chamber from the nozzle, increases the ink jetting repetition frequency, improves the efficiency of pressurized ink jetting, and allows ink particles to be released at relatively low vibration pressure. It is an object of the present invention to provide an ink ejecting device that can perform ejection and facilitate control of printing density.

In order to achieve the above object, in the present invention,
a first liquid chamber communicating with the ink ejection nozzle; a second liquid chamber communicating with the first liquid chamber; an ink pressurizing means for supplying pressurized ink liquid to the second liquid chamber; A valve member that opens and closes an ink flow path connecting the second liquid chamber; and a vibration pressure is applied to the ink in the first liquid chamber, and when the vibration pressure is high, the second liquid chamber is expanded and the valve member is opened. vibrating means for driving the valve member toward the closing side and contracting the second liquid chamber when the valve member is at a low level;

According to this, the pressurized ink is supplied to the first liquid chamber, and the vibration means applies vibration pressure to the pressurized ink, so that clogging of the nozzle can be easily removed. In addition, the vibration means can eject ink droplets at a relatively low vibration pressure by the pressure applied to the ink by the ink pressurizing means, and the vibration means
When a low pressure is applied to the liquid chamber, the second liquid chamber is contracted, which offsets the low pressure in the first liquid chamber and eliminates the suction of air into the first liquid chamber through the nozzle;
Since the ink ejection efficiency by the vibration means is improved and the ink supply speed to the first liquid chamber is fast, the ink ejection repetition frequency can be set high. Since the vibrating means can eject ink droplets at a relatively low vibration pressure, the excitation force of the vibrating means can be set over a wide range from weak to strong, making it easy to control printing density.

FIG. 2a shows an embodiment of the invention. In FIG. 2a, a first liquid chamber 7 communicating with the ink jet nozzle 3 communicates with a second liquid chamber 9 via a pipe 8. In FIG. The first liquid chamber 7 and the second liquid chamber 9 are separated by a laminated diaphragm in which the first diaphragm 2, the electrostrictive vibrator 1, and the second diaphragm 10 are integrally joined. . The second diaphragm 10 has a needle valve-shaped projection 1.
0a (that is, a valve member), and an elastic O-ring 11 is fixed to the base member at a position facing the protrusion 10a. An ink flow path formed to penetrate this O-ring 11 is connected to a discharge port of a pressure pump 13 via a pipe 12. The inlet of the pressure pump 13 is the pipe 1
It is connected to the ink tank 15 via 4. When no voltage is applied to the electrostrictive vibrator 1, the electrostrictive vibrator 1, the first diaphragm 2, and the second diaphragm 10
In the illustrated state, the projection 1 of the second diaphragm 10
0a is in contact with the O-ring 11 with very little pressure.

To explain how the ink ejecting device shown in FIG. 2a is used, first, before driving the pressure pump 13, as shown in FIG. ) is applied to the electrostrictive vibrator 1. This causes the protrusion 10a to
Tighten ring 11. And pressure pump 13
When the discharge pressure reaches a set value, a voltage (hereinafter referred to as positive voltage) is applied to the electrostrictive vibrator 1 in a direction in which it extends toward the nozzle 3 based on the image signal. By applying this voltage, the electrostrictive vibrator 1,
A laminated diaphragm formed by integrally bonding the first diaphragm 2 and the second diaphragm 10 projects in the direction of the nozzle 3, passes through the gap between the O-ring 11 and the protrusion 10a, and connects the second liquid chamber 9 and the pipe. 1st through 8
Pressure due to the discharge pressure of the pressurizing pump 13 is applied to the liquid chamber, and the vibration pressure of the laminated diaphragm is also applied, and ink is ejected from the nozzle 3. When the voltage applied to the electrostrictive vibrator 1 is switched from a positive voltage to a reverse voltage, the protrusion 10a is pressed against the O-ring 11, thereby blocking the application of pressure to the first and second liquid chambers 7 and 9. At this time, the ink in the second liquid chamber is supplied to the first liquid chamber, and no ink is ejected from the nozzle 3. Therefore, by applying a pulsed positive voltage based on the image signal, ink particles are ejected from the nozzle 3, and the peak value of the positive voltage applied to the electrostrictive vibrator 1 is adjusted to correspond to the analog image signal level. By changing this, a printed record with density gradation can be obtained.

FIG. 3 shows another embodiment of the invention. In this embodiment, a nozzle 3 and a first liquid chamber are formed in the inkjet head 16, and a first electrostrictive vibrator 1 and a first diaphragm 2 are installed in the first liquid chamber 7. An integrally bonded laminated diaphragm applies pressure.
A valve structure is constituted by a base member 18 and a laminated diaphragm in which a second electrostrictive vibrator 17 and a second diaphragm 10 are integrally joined. It is connected to the first liquid chamber 7 of.

In this embodiment, a reverse voltage and a positive voltage are applied to the first electrostrictive vibrator 1 and the second electrostrictive vibrator 17 in synchronization, so that the protrusion 10a
When the head 16 is separated from the nozzle 3, the diaphragm of the head 16
The protrusion 10a extends in the direction of the O-ring 1.
When the head 16 is tightened, the diaphragm of the head 16 is operated so as to return to its original position. As a result, the ink ejecting operation is performed in this embodiment as well in the same manner as in the embodiment shown in FIG. 2a.

With the configuration and operation described above, the inkjet jetting device of the present invention has the following effects.

1. Since pressurized ink liquid is supplied to the head, the response frequency is high and the operating frequency can be increased to several tens of Kz or more.

2. Pressurized ink pressure and the pressure of the diaphragm are applied to the first liquid chamber communicating with the nozzle, so the ejected ink particles fly at a high speed, are resistant to disturbances such as air currents, and the recording position accuracy is improved to improve image quality. Quality improves. Furthermore, the distance between the recording paper surface and the nozzle can be increased.

3 When the diaphragm returns, the pressure causes the ink to flow from the second liquid chamber to the first liquid chamber, so the nozzle 3
The negative pressure (suction pressure) applied to is low, and there is little air suction.

4. As mentioned in 2 above, since the injection pressure is high, if the clogging is only mild, the clogging can be removed by the injection operation. Furthermore, the ink does not become incapable of ejection due to air bubbles in the ink liquid or air sucked in from the nozzle.

[Brief explanation of the drawing]

Figures 1a, 1b and 1c are cross-sectional views of conventional ink jet heads. FIG. 2a is a sectional view showing an embodiment of the present invention;
FIG. 2b is a waveform diagram showing the voltage applied to the electrostrictive vibrator. FIG. 3 is a sectional view showing another embodiment of the present invention. 1, 17... Electrostrictive vibrator, 2, 10... Vibration plate, (1+2+10 in Figure 2a: vibration means), (3rd
1+2 in the figure: Vibration means; first vibrator, 10+17:
2nd vibrator), 3... nozzle, 4... charging electrode, 5... deflection electrode, 6... gutter, 7... first
liquid chamber, 8, 12, 14... pipe, 9... second
liquid chamber, 10a...protrusion (valve member), 11...O
Ring, 13...Pump (ink pressurizing means), 1
5... Ink tank, 16... Knot, 17... Electrostrictive vibrator, 18... Base member.

Claims (1)

[Scope of Claims] 1. A first liquid chamber communicating with an ink jet nozzle; a second liquid chamber communicating with the first liquid chamber; an ink pressurizing means for supplying pressurized ink liquid to the second liquid chamber; ; A valve member that opens and closes an ink flow path connecting the ink pressurizing means and the second liquid chamber; and A vibration pressure is applied to the ink in the first liquid chamber, and when the vibration pressure is high, a valve member opens and closes the ink flow path connecting the ink pressure means and the second liquid chamber; An ink ejecting device comprising: vibrating means for widening and driving the valve member to the open side, and for contracting the second liquid chamber when the liquid chamber is low and driving the valve member to the closed side. 2. The vibration means is a flat vibrator with a vibration plate fixed to an electrostrictive vibrator, and the front surface of the flat vibrator is in contact with the first liquid chamber, and the back surface is in contact with the second liquid chamber. 2. The ink ejecting device according to claim 1, wherein the valve member is located on the back surface. 3. The vibration means is: a first vibrator, which is a flat plate-shaped vibrator made of an electrostrictive vibrator, the surface of which is in contact with the first liquid chamber; A second vibrator comprising: a flat plate-shaped vibrator having a plate fixed thereto, the surface of the flat plate-shaped vibrator being in contact with a second liquid chamber, and the valve member being positioned on the surface; An ink ejecting device according to claim 1.