JPS61279561A - Multinozzle on-demand ink jet head - Google Patents

Abstract

PURPOSE:To reduce or prevent mutual interference or to make a device for preventing the interference operate in accordance with the degree of effect thereof, by providing a means to increase a volume in a common liquid ink chamber and an adjusting means to adjust an increased amount of the volume. CONSTITUTION:A vibration unit 21 is composed of an electrostrictive vibrator and an elastic vibration plate, and one end of the unit is fixed on a support 20, while the other end thereof is joined to a flexible wall of a common liquid ink chamber 10 through the intermediary of a connecting rod 22. When a prescribed pulse voltage is impressed on the vibration unit 21, it is warped in the direction of separation from the liquid chamber 10 with the support 20 acting as a fulcrum, so that the flexible wall 23 is displaced in the direction in which the volume of the common liquid ink chamber 10 is increased. The action of increasing the volume of the common liquid ink chamber 10 absorbs a leakage pressure wave onto this chamber 10 which is generated at the time of driving for jetting ink droplets. This vibration unit 21 operates in such a manner that the electrostrictive vibrator is elongated in the direction of thickness thereof and contracted in the longitudinal direction thereof when a plus potential is applied on the plus polarization side of the electrostrictive vibrator and a zero potential on the minus polarization side thereof, so that the vibration unit 21 is warped upward.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-nozzle on-demand inkjet head, and more particularly to a fluidic mutual interference prevention device in a multi-nozzle on-demand inkjet head.

Figure 10 is a cross-sectional view for explaining an example of a conventional on-demand inkjet head, and Figure 11 is a cross-sectional view of A in Figure 10 when the inkjet head shown in Figure 10 is made into a multi-nozzle. -A view seen from direction A, in the figure, 1 is a nozzle, 2 is a flow path, 3 is an ink pressurized liquid chamber, 4 is a diaphragm part, 5 is a connecting rod, 6 is a vibration unit, 7 is a support base, 8
1 is an ink supply side flow path, 9 is an ink supply tube, 10 is a common ink liquid chamber, and 11 is an ink supply hole. The volume of the chamber 30 is reduced and the ink pressure in the ink liquid chamber 3 is increased to eject ink droplets from the nozzle hole 1 to print two images of characters or the like on a recording paper (not shown) or the like. Since the on-demand inkjet head described above has a simple structure, it can be used for simple printers,
It is suitable for use in plotters, etc. However, when the on-demand inkjet head is driven to eject ink droplets, a leakage pressure wave is generated that simultaneously causes the ink to be ejected from the nozzle and also propagates the pressure wave to the ink supply side. Therefore, if only multiple nozzles are used, the pressure waves will propagate to other nozzles via a common ink chamber to each nozzle, and will affect the droplet ejection operation. In other words, they will interfere with each other.

To explain in more detail, in FIGS. 10 and 11, the vibration unit 6 consists of an electrostrictive vibrator and a diaphragm (usually an elastic metal plate). When a positive pulse for driving ink ejection is applied (0 polarization side is O potential), the electrostrictive vibrator contracts in the thickness direction and extends in the longitudinal direction.

The vibration unit 6 as a whole performs a downward displacement movement using the support base 7 as a fulcrum. This displacement is transmitted to the diaphragm 4 via the connecting rod 5.

As a result, the volume of the ink pressurized liquid chamber is rapidly reduced, and pressure is generated inside. This pressure causes ink droplets to be ejected from the nozzle hole 1, but at the same time, a portion of the pressure is also transmitted to the ink supply channel 8 side. This is a leakage pressure wave, and when a multi-nozzle head as shown in FIG. This will have an impact on the This occurs mutually and causes so-called mutual interference.

In order to prevent the above-mentioned mutual interference, for example, Japanese Patent Application Laid-Open No. 52-49034 discloses that an elastic wall is provided at the highest part of the common ink chamber of a multi-nozzle ink-on-demand head to prevent mutual fluid interference between nozzles. A technique has been disclosed in which the elastic wall absorbs pressure waves leaking toward the common ink chamber when each nozzle is driven. However, the disadvantage of this technique is that in order to absorb the leakage pressure waves, the stiffness of the elastic wall has to be very small, so the wall has to be very deep or the area of the elastic wall has to be made very small. The reason is that we have to make it bigger. Furthermore, making the wall thinner or increasing the area of the wall poses problems in terms of processing the head and miniaturizing the head. Further, the fact that the elastic wall must be provided at the highest part of the liquid chamber results in structural limitations, which is extremely inconvenient.

The present invention was made in view of the above-mentioned circumstances.
In particular, it is intended to reduce or prevent mutual interference, which is a problem in the multi-nozzle on-demand inkjet head as described above, or to operate the prevention device according to the degree of influence.

In order to achieve the above object, the present invention includes a large number of ink pressurizing liquid chambers, a large number of nozzles provided corresponding to each ink pressurizing liquid chamber, and a common ink pressurizing liquid chamber. In a multi-nozzle on-demand inkjet head having a common ink liquid chamber, the volume of each ink pressurized liquid chamber is reduced in accordance with a printing information signal to eject ink droplets from the nozzle. The present invention is characterized in that it includes means for increasing the volume of the chamber, or means for increasing the volume within the common ink liquid chamber, and adjusting means for adjusting the amount of increase in the volume. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a sectional view for explaining an embodiment of a multi-nozzle on-demand inkjet head according to the present invention;
Figure 2 is a plan view, in which 2o is a support stand, 21 is a vibration unit, 22 is a connecting rod, 23 is a flexible wall, and other parts include a first
The parts that have the same effect as those in Figures 0 and 11 are shown in Figure 10.
The same reference numerals as in FIG. 1 and FIG. 11 are provided.

In FIGS. 1 and 2, the vibration unit 21 consists of an electrostrictive vibrator and an elastic diaphragm, and one end is attached to a support base 2.
0, and the other end is connected to a flexible wall 23 of the common ink chamber 10 via a connecting rod 22. When a predetermined pulse voltage is applied to the vibration unit 21, the vibration unit 21 bends in a direction away from the liquid chamber 10 using the support base 20 as a fulcrum, and displaces the flexible wall 23 in a direction that increases the volume of the common ink liquid chamber 10. It is designed to let you do so. This common ink liquid chamber 10
The volume increasing operation absorbs the leakage pressure wave to the common ink liquid chamber 10 that occurs during ink droplet ejection driving.

As is well known, the operation of this vibration unit 21 is to apply a + potential to the 0 polarization side of the electrostrictive vibrator and 0 potential (0 to the 0 polarization side).
When 0 potential is applied to the 0 polarization side and 1 potential is applied to the e polarization side), the vibrator stretches in the thickness direction, contracts in the longitudinal direction, and the vibration unit 21 bends upward.

FIG. 3 is an electric circuit diagram for explaining an example of a drive circuit for driving the ink shared head according to the present invention, and FIG. 4 is a time chart for explaining its operation.
The printing signal Vs is input to the head ink droplet jetting drive circuit 30 and also to the monomultipipe lake 31, and the printing signal inputted to the head ink droplet jetting driving circuit 30 drives the vibration unit 6 of the head. Ink droplets are ejected from the nozzle, but at this time, a part of the pressure wave leaks into the common ink liquid chamber 10 as described above. On the other hand, the printing signal VS input to the monomulti 31 is an output pulse MMI having a predetermined pulse.

output. Furthermore, this output pulse MMI is input to the monomulti 32, which outputs an output pulse MM2 having a predetermined pulse width. This output pulse MM2 turns off the transistor 34 and turns on the transistor 35 via the inverter 33, and applies a pulse voltage Vpo close to the power supply voltage +HV to the electrostrictive vibrator unit 21 via the resistor 38. As a result, the vibration unit 21 moves the flexible wall 23 of the common ink chamber 10 into the common ink chamber 1o.
is displaced in the direction of increasing the volume of the nozzle, absorbs the leakage pressure wave, and reduces or prevents mutual interference between the nozzles. Note that when the output pulse MM2 disappears, the transistor 3
4 is ON, and transistor 35 is OFF.

The transistor 36 is turned on, and the voltage Vpo applied to the vibration unit 21 is transferred from the diode 39 to the transistor 36. disappears via the resistor 37.

The resistor 38 sets the rise time of the pulse voltage Vpo, and the resistor 37 sets the fall time of the pulse voltage Vpo.

Here, the mono multi 31 adjusts the timing of applying the pulse voltage Vpo to the vibration unit 21, and a delay element such as a shift register may be used (also, the mono multi 32 adjusts the timing of applying the pulse voltage Vpo to the vibration unit 21). The monomulti 32 can be omitted if the signal Vs is set to a predetermined pulse, but in this case, the vibration unit 21 and the pulse voltage Vpo A delay element such as a shift register may be used to determine the timing of adding Vs.Alternatively, a circuit may be configured to prepare a plurality of signals Vs whose phases are shifted and select any one of them.

The point is that the operation timing and operation time of the vibration unit 21 can be set to predetermined values. In addition, the vibration unit 21
may be constituted by a magnetostrictive vibrator, a bimetal equipped with a heat-sensitive element, or the like; in short, it may be an electromechanical transducer that displaces the flexible wall of the common ink chamber in response to a predetermined electric signal. Further, the flexible wall 23 of the imaging unit 21 does not need to be provided on the wall of the common ink chamber 10, and may be configured by extending a part of the common ink chamber 10, for example, as shown at 24 in FIG. You may do so. In short, when a multi-nozzle head is configured, the volume of the liquid filling part common to each nozzle (herein referred to as the common ink liquid chamber) is increased at a predetermined timing for a predetermined time, and each It may be configured to absorb pressure waves leaking when the nozzle is driven to eject ink droplets. It is clear from the above description that the present invention can be applied even if the common ink chamber is located outside the head.

5 and 6 are modified embodiments of the embodiment shown in FIGS. 1 and 2, respectively, and the embodiment shown in FIG. 5 has an integrated vibration unit 6 for driving ink droplet jetting. (
For example, when constructing a comb-teeth retractor, a part of the vibrating unit 21 is used as the vibration unit 21, which helps simplify the construction. Further, in the embodiment shown in FIG. 6, an electrostrictive vibrator 2 is attached to the flexible wall 23 of the common ink chamber
1 are directly joined, but in this case as well, as described above, an electromechanical transducer other than an electrostrictive vibrator may be used.

Therefore, in the embodiment described above, in order to absorb leakage pressure waves in a multi-nozzle on-demand inkjet head, the volume of the common ink liquid chamber 10 is increased to generate negative pressure when ink droplets are ejected, thereby preventing mutual interference. In other words, a pulse is applied to the vibration unit 21 after a predetermined time corresponding to the propagation time of the leakage pressure wave from the ink droplet ejection drive pulse (the method of applying this pulse is as follows).
), the flexible wall 23 of the common ink chamber 10 is displaced outward of the common ink chamber 10 using the support base 20 as a fulcrum. , which is designed to generate negative pressure, but depending on the number of nozzles in the multi-nozzle head that are in the ink droplet jetting state, the intensity of the pressure wave leaking into the common ink chamber differs, and the degree of mutual interference differs. Therefore, the head described above cannot necessarily sufficiently prevent this mutual interference.

FIG. 7 is an electric circuit diagram for explaining an embodiment of an inkjet head drive circuit that solves the above-mentioned problems, and FIG. 8 is a time chart. In this method, leakage pressure waves to the common ink chamber that occur when each nozzle is driven to eject ink droplets and cause mutual influence are absorbed by generating negative pressure by increasing the volume of the common ink chamber. Moreover, the volume increase amount of the common ink liquid chamber is changed in accordance with the number of nozzles in the ink droplet ejection drive state to sufficiently absorb the leakage pressure wave, and its configuration is as follows. , as shown in the figure, the print command signal generation circuit 41 of each nozzle; the signal Vs of the signal generation circuit 41;
1 to Vs7 to a predetermined voltage; an ink droplet ejection drive circuit 42; Ink droplet ejection vibration units 431 to 437.
Vibration unit 70 that causes a common ink chamber volume increase to absorb leakage pressure waves. A drive circuit 80 (composed of a multivibrator 59°60, an inverter 62, a transistor 63, 65°66, a resistor 64, 67.6B, and a diode 69) that drives the vibration unit 70, the printing command signal A signal latch circuit 44 that stores Vs1 to Vs7 while the drive circuit 80 is operating.
．． an adder circuit 90 that adds the output signals of the launch circuit 44;
(This adder circuit 90 includes resistors R5 to R12, (resistance value R), operational amplifier 54, resistor 53 (Ro), 55
(R+).

56 (Rz), and an operator @ unit 57, which adds the printing command signals Vsl to Vs 7, that is,
An additional voltage corresponding to the number of nozzles in the driven state is generated. a NOR circuit 5 that outputs a NOR output when any one or more of the printing command signals Vs1 to Vs7 is present;
8. When the operation of the drive circuit 80 is completed, the output pulse MMS
It is composed of a multi-by-break 61 and the like that outputs and resets the latch circuit 44. Since the leakage pressure wave occurs at the same time as the ink droplet ejection drive or after a delay, the timing for increasing the volume of the common ink chamber is determined by the multi-by-break 59. The volume increase operation time is determined by the multivibrator 60.

In this way, when driving ink droplet jetting, the pulse width MM is delayed by MMI from the dipping jetting driving pulse Vp corresponding to the number N of nozzles in the driving state.
2, the vibration unit 10
to drive.

FIG. 9 shows a modified embodiment of the embodiment shown in FIG.
Something that achieves the same purpose by changing a part of
In other words, the number of nozzles in the driving state is determined by the gate circuit 10.
0,101,102゜103.109,105 (in the illustrated example, the number of multi-nozzles is 3 to simplify the explanation), and in order to generate the corresponding voltage, the resistance is weighted. Container 106 (R
3).

107 (R2), 10B (R1) as transistor 2
01, 202, and 203.

The gates too, 101, and 102 determine when the number of nozzles in the driven state is two, the gate 103 determines when there are three, and the gate 104 determines when any one of them is activated.

As a result, one of the transistors 201, 202 and 203 is turned on, and the voltage divided by the RO of the resistor 64, that is, one of the transistors is applied to the unit 10 in accordance with the drive state and the number of nozzles. be done.

As is clear from the above description, according to the present invention, in a multi-nozzle on-demand inkjet head,
It absorbs leakage pressure waves that cause mutual interference, and can easily reduce or prevent mutual interference. Further, the mutual interference can be reduced depending on the degree of influence thereof, and there is an advantage that the objective can be achieved easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of an on-demand inkjet head according to the present invention, FIG. 2 is a plan view when a multi-nozzle structure is used, and FIG. 3 is an electric circuit showing an example of a head drive circuit. 4 are time charts, FIGS. 5 and 6 are plan views showing modified embodiments of the inkjet head shown in FIGS. 1 and 2, respectively, and FIG. FIG. 8 is a time chart, FIG. 9 is an electrical circuit diagram showing a modified embodiment of the embodiment shown in FIG. FIG. 11, which is a cross-sectional view for explaining an example of a demand inkjet head, is a plan view when the inkjet head shown in FIG. 10 is multiplied. 6... Vibration unit, 10... Common ink liquid chamber, 2
0... Support stand, 21... Vibration unit 23...
flexible wall.

Claims (5)

[Claims] (1) It has a large number of ink pressurizing liquid chambers, a large number of nozzles provided corresponding to each ink pressurizing liquid chamber, and a common ink liquid chamber common to the ink pressurizing liquid chambers. , a multi-nozzle on-demand inkjet head for ejecting ink droplets from the nozzles by reducing the volume of each pressurized ink chamber in accordance with a printing information signal, comprising means for increasing the volume of the common ink chamber; A multi-nozzle on-demand inkjet head characterized by: (2) The means for increasing the volume of the common ink chamber includes a vibration unit that displaces a flexible member disposed in contact with ink in a direction in which the volume of the common ink chamber increases; and the vibration unit The multi-nozzle on-demand inkjet head according to claim 1, further comprising a pulse drive circuit that applies a pulse voltage to the multi-nozzle on-demand inkjet head. (3) The multi-nozzle on-demand inkjet head according to claim (2), further comprising means for delaying the pulse for driving the vibration unit by a predetermined period of time from the ink droplet ejection drive pulse. (4) It has a large number of ink pressurizing liquid chambers, a large number of nozzles provided corresponding to each ink pressurizing liquid chamber, and a common ink liquid chamber common to the ink pressurizing liquid chambers. , in a multi-nozzle on-demand inkjet head that reduces the volume of each pressurized ink chamber in accordance with a printing information signal to eject ink droplets from the nozzle, means for increasing the volume within the common ink chamber; A multi-nozzle on-demand inkjet head, characterized in that it has an adjusting means for adjusting the amount of increase in volume. (5) The multi-nozzle on-demand inkjet head according to claim (4), wherein the adjusting means for adjusting the volume increase amount operates in response to the number of nozzles driven in the multi-nozzle on-demand inkjet head. Demand inkjet head.