JPH09309206A - Ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the ink amount and the scattering speed of ink drops constant regardless of ink viscosity generated by the temperature fluctuation. SOLUTION: An ink jet recording device comprises a potential in which the voltage from a reference potential is varied by the temperature and a signal issuing means 30 for issuing a first signal for expanding a pressure generating chamber by the potential variation in the range of an intermediate potential to the reference potential, a second signal issued as the difference between the reference potential and the maximum potential and contracting the pressure generating chamber for jetting ink drops and a third signal for restoring the pressure generating chamber in the contracted state to the original state after jetting the ink drop. The intermediate potential is varied by the temperature to adjust the position of a meniscus at the time of jetting ink based on the second signal, and the flow path resistance up to a nozzle opening and the ink viscosity are offset each other to keep the weight and scattering speed of the ink drops constant regardless of the temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving technique of an ink jet recording head using a piezoelectric vibrator as a driving source.

[0002]

2. Description of the Related Art An ink jet recording head, which is partially formed of an elastic plate and which expands and contracts a pressure generating chamber communicating with a nozzle opening by a piezoelectric vibrator, sucks ink and discharges ink droplets. Since the ink droplets are ejected by the pressure, the ink amount of each ink droplet for printing is greatly affected by the change in the viscosity due to the temperature change, and the ink amount increases as the temperature rises as shown in FIG. However, there is a problem that the print quality varies. For this reason, a driving technique for keeping the ink amount constant by adjusting the magnitude and the changing speed of the signal of the piezoelectric vibrator when the pressure generating chamber is contracted according to the environmental temperature to eject the ink droplets. Is proposed.

[0003]

According to this, by changing the level of the signal applied to the recording head according to the temperature, it is possible to maintain the ink amount of the ink droplet constant regardless of the temperature. However, since the contraction speed and the contraction amount of the pressure generation chamber change, the flight speed of the ink droplets also fluctuates, and when the voltage level of the signal is lowered, the ink droplet speed decreases and it is transferred to the recording medium. However, there is a problem that an error occurs in the landing position of the ink and the print quality deteriorates. The present invention has been made in view of such a problem, and an object of the present invention is to suppress the fluctuation of the speed of the ink droplet as small as possible and to reduce the ink amount of the ink droplet regardless of the temperature change. An object of the present invention is to provide an ink jet recording apparatus that can be maintained constant.

[0004]

In order to solve such a problem, in the present invention, a pressure generating chamber communicating with a common ink chamber through a nozzle opening and an ink supply port,
An ink jet recording head including a piezoelectric vibrator that expands and contracts the pressure generating chamber, an intermediate potential at which the voltage from the reference potential changes with temperature, and the pressure generating chamber due to the potential change from the intermediate potential to the reference potential. A first signal for expanding the ink, a second signal generated as a difference between the reference potential and the highest voltage for contracting the pressure generating chamber for ejecting an ink droplet, and a pressure in a contracted state after ejecting the ink droplet. And a signal generating means for generating a third signal for returning the generating chamber to the original state.

[0005]

By changing the intermediate potential according to the temperature and adjusting the position of the meniscus at the time of ink ejection by the second signal, the flow path resistance up to the nozzle opening and the ink viscosity are canceled, and the ink is irrespective of the temperature. Keep the drop weight and flight speed constant.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows an embodiment of an ink jet recording head to which the present invention is applied, in a structure in the vicinity of a pressure generating chamber of one actuator unit, in which reference numeral 1 is a first lid, Thickness 9μ
It is composed of a thin plate of zirconia of about m, drive electrodes 3, 3 are formed on the surface so as to face the pressure generating chambers 2, 2, and piezoelectric vibrators 4, 4 made of PZT or the like are fixed on the surface. Is configured.

Numeral 5 is a spacer, which is formed by forming a through hole in a ceramics plate of zirconia (ZrO2) or the like having a thickness suitable for forming the pressure generating chambers 2 and 2, which will be described later. Both surfaces are sealed by the second lid 6 and the first lid 1 to form the pressure generating chambers 2, 2.

The pressure generating chambers 2, 2 are expanded and contracted by the flexural vibrations of the piezoelectric vibrators 4, 4 to expand and contract to supply ink.
The ink in the common ink chambers 8 and 8 is sucked through the nozzles to eject ink droplets from the nozzle openings 9 and 9.

Reference numeral 6 denotes the above-mentioned second lid, which is also a ceramic plate made of zirconia or the like, and nozzle communicating holes 10 communicating with the nozzle openings 9, 9 at the ends of the pressure generating chambers 2, 2 on the opposite side.
10 and communicating holes 11, 11 communicating with the ink supply ports 7, 7 on the outside.

Reference numeral 12 denotes an ink supply port forming substrate having nozzle communication holes 13 and 13 connected to the nozzle openings 9 and 9 on the central side of the pressure generating chambers 2 and 2, and a common ink chamber 8 on the outside. The ink supply ports 7 and 7 are connected to connect the pressure generating chambers 2 and 2.

A common ink chamber forming substrate 14 has a thickness suitable for forming the common ink chambers 8, for example, 15
A through hole corresponding to the shape of the common ink chamber 8 and a communicating hole 15, 15 connected to the nozzle opening 9, 9 on the outside of the plate material having corrosion resistance and rigidity such as 0 μm stainless steel.
Is formed by drilling.

A nozzle plate 16 is formed by forming a plurality of nozzle openings 9, 9 in a row, in this embodiment, two rows. Reference numeral 17 in the figure denotes a flexible cable that supplies a signal from an external circuit to the piezoelectric vibrators 4 and 4.

FIG. 2 shows an embodiment of a driving device for driving the above-mentioned recording head, which is designated by reference numeral 30 in the drawing.
In the signal generating circuit, as shown in FIG. 3, the intermediate potential Vc and the intermediate potential Vc, which become higher as the outside air temperature becomes higher.
Signal that drops from the reference potential Vs to the reference potential Vs
Is generated as the difference between the maximum voltage VH and the maximum potential VH, and the second signal for ejecting an ink droplet is generated as the difference between the maximum voltage VH and the intermediate potential Vc. It is configured to return to the state and to generate a third signal for sucking ink from the common ink chamber 8 to the pressure generating chamber 2. And the intermediate potential Vc
Can be controlled by the temperature from the temperature detecting means 31.

In this embodiment, when the outside air temperature is room temperature, the intermediate potential Vc has a value determined so that one ink droplet has an optimum amount for printing. When a print signal is input in this state, the piezoelectric vibrator 4 charged to the intermediate potential Vc is discharged by the first signal, and the pressure generating chamber 2 expands by an amount corresponding to the intermediate potential Vc. As a result, the meniscus M is drawn from the nozzle opening 2 by an amount corresponding to this expansion amount (FIG. 5).

When the predetermined time has passed, the reference potential Vs
And a second signal as a difference between the maximum potential VH and the pressure generating chamber 2 is contracted. At the time when the second signal is output, the meniscus once drawn into the pressure generating chamber 2 moves toward the nozzle opening 9 and reaches a position suitable for printing. , Ink droplets of an amount corresponding to the distance ΔL of the meniscus to the nozzle opening 9 are ejected, and fly at a predetermined speed.

After the ink droplets are ejected, the piezoelectric vibrator 4 is discharged by the third signal, and the pressure generating chamber returns to the original volume position in preparation for the next printing. Then, it is charged to the intermediate potential Vc again in time with the print signal. Hereinafter, printing is executed by repeating such steps.

When the outside air temperature is high and therefore the viscosity of the ink is lower than that at room temperature, the intermediate potential Vc is higher than that at room temperature. When a print signal is input in this state, the piezoelectric vibrator 4 charged to the intermediate potential Vc becomes the first
And the pressure generating chamber 2 expands more than at room temperature.

Therefore, the meniscus is drawn into the pressure generating chamber side more than at room temperature. When the predetermined time has elapsed, the second potential as the difference between the reference potential Vs and the highest potential VH
Signal is output to contract the pressure generating chamber 2. At the time when the second signal is output, the meniscus once drawn into the pressure generating chamber 2 is moving toward the nozzle opening 9, but since it is greatly drawn into the pressure generating chamber 2, the meniscus is drawn from the nozzle opening 9 Of the nozzle opening 9
The fluid resistance up to becomes large.

However, since the temperature is rising and the viscosity of the ink is decreasing, both factors are canceled out, the ink amount does not change, and the pressure received during ejection becomes constant. Therefore, an ink droplet having the same amount of ink as at room temperature flies at the same flight speed as at room temperature.

On the other hand, when the outside air temperature is low and therefore the viscosity of the ink is higher than that at room temperature, the intermediate potential VC is lower than that at room temperature. When a print signal is input in this state, the piezoelectric vibrator 4 charged to the intermediate potential Vc
Are discharged, and the expansion amount of the pressure generating chamber 2 becomes smaller than that at room temperature.

Therefore, the meniscus M is located closer to the nozzle opening side than at room temperature. When the predetermined time has elapsed, the second signal as the difference between the reference potential Vs and the highest potential VH is output to contract the pressure generating chamber 2. At the time when the second signal is output, the meniscus is already located in the vicinity of the nozzle opening 9 and the fluid resistance up to the nozzle opening 9 is small, but since the viscosity of the ink increases, both factors cancel each other out. As a result, the ink amount does not change and the pressure received during ejection is constant, so that an ink droplet with the same ink amount as at room temperature flies at the same flight speed as at room temperature.

Hereinafter, by changing the intermediate potential Vc according to the outside air temperature in this manner, the distance between the meniscus at the time of ink ejection and the nozzle opening is adjusted to cancel the resistance caused by the change in ink viscosity. , The ink amount of the ink drop and the flight speed are kept constant regardless of the temperature change.

In the above-described embodiment, the third signal is once lowered to the reference potential Vs and then the intermediate potential Vc for the next printing is applied, but it is shown in FIG. Even if the potential at the end of discharge is set to the intermediate potential Vc, it is apparent that the same action is achieved. That is, since the third signal is an operation for returning the pressure generating chamber 2 contracted by the ink droplet ejection to the original state in preparation for the next ink droplet ejection after the ink droplet ejection, it is related to the ink droplet ejection characteristics. Does not induce the movement of a meniscus.

Further, although the second signal is fixed to a constant value in the above-mentioned embodiment, it changes depending on the temperature,
For example, when the temperature at room temperature of 25 ° C. is set to 1, when the temperature is changed to 1.2 times at 15 ° C. and 0.9 times at 40 ° C., the ink amount of the ink droplet and the flying speed become constant. Easy to hold on. The ratio of the intermediate potential Vc to the second signal, for example, at room temperature of 25 ° C.
Of the first signal at this time at 15 ° C, and 0.3 times of the first signal at 40 ° C. Is desirable.

Further, by keeping the time tc for contracting the pressure generating chamber for ejecting the ink droplet as constant as possible, the ink droplet can be ejected when the meniscus moves to the optimum position. As a result, the ink amount of the ink droplet and the flight speed can be maintained constant regardless of the temperature change.

[0026]

As described above, in the present invention, the pressure generating chamber communicating with the common ink chamber through the nozzle opening and the ink supply port, and the piezoelectric vibrator for expanding and contracting the pressure generating chamber. An ink jet recording head comprising: a first signal for expanding the pressure generating chamber; a second signal for contracting the expanded pressure generating chamber to eject an ink droplet from the nozzle opening; After the ink droplet is ejected, there is provided a signal generating means for outputting a third signal which has a volume smaller than the expansion volume by the first signal and which expands the pressure generating chamber depending on the environmental temperature. The amplitude of the first signal that expands the generation chamber can be adjusted by the third signal that is the intermediate potential to change the amount of meniscus pull-in, and the amplitude of the second signal for ejecting ink droplets can be adjusted. Without changing the speed of the ink droplet as a constant, the quantity of ink droplets can be kept constant by adjusting the ink ejection ability of the head the position of the meniscus.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an ink jet recording head used in an ink jet recording apparatus of the present invention.

FIG. 2 is a block diagram showing an embodiment of the signal generating means of the present invention.

FIG. 3 is a waveform chart showing an embodiment of a signal in the above device.

FIG. 4 is a waveform chart showing another embodiment of a signal in the same device.

FIG. 5 is a diagram showing a behavior of a meniscus in the vicinity of a nozzle opening.

FIG. 6 is a diagram showing a relationship between an intermediate potential and a weight ratio of ink droplets.

FIG. 7 is a diagram showing a relationship between an ink temperature and an ink amount of an ink droplet.

[Explanation of symbols]

 2 Pressure generating chamber 4 Piezoelectric vibrator 8 Common ink chamber 9 Nozzle opening

Claims (3)

[Claims] 1. An ink jet recording head comprising a pressure generating chamber communicating with a common ink chamber through a nozzle opening and an ink supply port, and a piezoelectric vibrator for expanding and contracting the pressure generating chamber; An intermediate potential at which the voltage from the reference potential changes,
It is generated as a difference between the first signal that expands the pressure generating chamber due to the potential change from the intermediate potential to the reference potential and the reference potential and the highest voltage, and contracts the pressure generating chamber to eject an ink droplet. An ink jet recording apparatus comprising: a second signal; and a signal generating means for generating a third signal for returning the pressure generating chamber in a contracted state to the original state after ink droplets are ejected. 2. The ink jet recording apparatus according to claim 1, wherein the terminal potential of the third signal is the intermediate potential. 3. The ink jet recording apparatus according to claim 1, wherein the maximum voltage of the second signal changes with temperature, and the intermediate potential is set by the ratio of the maximum voltage.