KR20050087929A - Method of driving inkjet printhead - Google Patents

Abstract

A method of driving an inkjet printhead is disclosed. In the driving method of the disclosed printhead, the driving pulse applied to the actuator is a main pulse applied at a main potential Vm of a degree capable of discharging ink droplets, and a predetermined time before the main pulse Vm. It has a preliminary pulse applied at a low preliminary potential Vp. According to the present invention as described above, by appropriately adjusting the T1, T2 and T3 sections of the preliminary pulse and the T4 section between the preliminary pulse and the main pulse, it is possible to effectively increase or decrease the speed and volume of the droplets discharged through the nozzle. .

Description

Method of driving inkjet printhead

The present invention relates to a method of driving an inkjet printhead, and more particularly, to a method of driving an inkjet printhead capable of adjusting the ejection speed and volume of ink droplets.

In general, an inkjet printhead is a device that prints an image of a predetermined color by ejecting a small droplet of printing ink to a desired position on a recording medium. Such inkjet printheads can be largely classified in two ways depending on the ejection mechanism of the ink droplets. One is a bubble jet inkjet printhead which generates bubbles in ink by using a heat source and ejects ink droplets by the expansion force of the bubbles. The other is ink due to deformation of the piezoelectric body using a piezoelectric body. A piezoelectric inkjet printhead which ejects ink droplets by a pressure applied thereto.

1 shows a structure of an inkjet printhead disclosed in US Pat. No. 6,074,033 as an example of a conventional piezoelectric inkjet printhead.

Referring to FIG. 1, the inkjet printhead has a pressure chamber 4 filled with ink to be discharged, and at one side of the pressure chamber 4 draws ink from the ink reservoir 10 into the pressure chamber 4. Ink supply passages 11 and 13 for supplying are connected. Ink discharge passages 8, 9, 14 are connected to the other side of the pressure chamber 4, and nozzles 7 for discharging ink are formed at ends of the ink discharge passages 8, 9, 14. And a diaphragm 2 is provided in the upper part of the pressure chamber 4, The piezoelectric plate which vibrates the diaphragm 2 and changes the volume of the pressure chamber 4 on this diaphragm 2, and provides the driving force for ink ejection. The actuator 3 is provided.

In the piezoelectric inkjet printhead having such a configuration, when a driving pulse having a predetermined driving voltage is applied to the piezoelectric actuator 3, the diaphragm 2 is bent due to the deformation of the piezoelectric actuator 3 and the pressure chamber 4 ) Volume is reduced. As a result, the ink in the pressure chamber 4 is discharged to the outside through the nozzle 7 by the pressure rise in the pressure chamber 4. Subsequently, when the driving pulse applied to the piezoelectric actuator 3 is removed, the diaphragm 2 is restored to its original shape, thereby increasing the volume of the pressure chamber 4. As a result of the pressure drop in the pressure chamber 4, ink flows from the ink reservoir 10 into the pressure chamber 4 through the ink supply passages 11 and 13 so that the pressure chamber 4 is filled with ink again. do.

2 shows a driving waveform applied to a method of driving a conventional inkjet printhead disclosed in US Pat. No. 6,074,033.

The waveform of the driving pulse shown in FIG. 2 includes a period t5 to t6 for applying a signal for expanding the pressure chamber to supply ink into the pressure chamber, and a signal for contracting the input chamber to discharge ink through the nozzle. Has a period between t1 and t3.

However, in the above-described conventional driving waveform, since the t1 section is continuously applied after the t6 section, there is a disadvantage in that the behavior of the ink due to the free vibration of the diaphragm cannot be finely adjusted. The conventional driving pulse having the above-described waveform is offset to a predetermined potential as a whole, so that the predetermined potential is continuously applied even in the t4 section in which the actuator is not driven. Accordingly, since the actuator and the diaphragm have a certain amount of deformation even when the actuator is not driven, there is a problem in that the stress remaining on the actuator and the diaphragm becomes greater than when no electric potential is applied, thereby increasing the possibility of breakage. In addition, since the maximum voltage applied in the t2 period is increased by the offset of the potential, there is a disadvantage in that durability of the electric circuit of the inkjet printhead is lowered and power consumption is increased.

The present invention has been created to solve the above problems of the prior art, and in particular, by using a drive waveform that can effectively control the speed and volume of the droplets discharged through the nozzle without having a potential offset, the optimum ink An object of the present invention is to provide a method of driving an inkjet printhead capable of exhibiting ejection performance.

An inkjet printhead driving method according to the present invention for achieving the above technical problem,

The driving of the inkjet printhead to apply a driving pulse to the actuator to change the volume of the ink-filled pressure chamber, thereby causing ink droplets to be discharged through the nozzles connected to the pressure chamber by the pressure change caused by the volume change of the pressure chamber. In the method,

The driving pulse is applied to a main pulse applied at a main potential Vm of a degree capable of discharging the ink droplets, and to a preliminary potential Vp lower than the main potential Vm before a predetermined time before the main pulse. It is characterized by including a preliminary pulse.

Here, the preliminary pulse includes a T1 section in which the potential increases from 0V to the preliminary potential Vp, a T2 section in which the preliminary potential Vp is kept constant, and the potential from the preliminary potential Vp. It consists of a T3 section that drops to 0V

Preferably, a T4 section in which a potential of 0 V is maintained is present between the preliminary pulse and the main pulse.

In the T1 section, the actuator is driven by the preliminary pulse to increase the pressure inside the pressure chamber.

In the T2 section, free vibration of the diaphragm is induced,

In the T3 section, vibration of the diaphragm is forcibly attenuated or resonated in the free vibration state of the diaphragm,

In the T4 section, an application time point of the main pulse may be determined.

According to the present invention, it is possible to effectively increase or decrease the speed and volume of the droplets discharged through the nozzle by the preliminary pulse applied before the main pulse, and the durability of the inkjet printhead is improved because it does not have a potential offset. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view for explaining a waveform of a driving pulse applied to the method of driving an inkjet printhead according to a preferred embodiment of the present invention.

Referring to FIG. 3, in the method of driving an inkjet printhead according to the present invention, a driving pulse applied to a piezoelectric actuator for discharging ink droplets includes a main pulse and a pre-pulse.

The main pulse is applied to the piezoelectric actuator at a main potential (Vm) of a degree capable of ejecting ink droplets, and the preliminary pulse is a preliminary potential (Vp) lower than the main potential (Vm) a predetermined time before the main pulse. It is applied to the piezo actuator.

The preliminary pulse is divided into a T1 section in which the potential rises from 0 V to a preliminary potential Vp, a T2 section in which the preliminary potential Vp is kept constant, and a T3 section in which the potential falls from the preliminary potential Vp to 0V. Is done. In addition, there is a T4 section in which a potential of 0 V is maintained between the preliminary and main pulses.

4 is a graph showing a specific example of a drive pulse and a displacement of the diaphragm by the drive pulse in the driving method according to the present invention.

3 and 4 together, the actuator is driven by a preliminary pulse in the T1 section to increase the pressure inside the pressure chamber. At this time, the preliminary potential Vp of the preliminary pulse is determined according to the pressure rise width in the set pressure chamber. That is, by adjusting the preliminary potential Vp of the preliminary pulse, it is possible to change the width of the pressure rise in the pressure chamber.

After the system consisting of ink, an actuator, and a diaphragm is excited in the T1 section, free vibration of the diaphragm is induced in the T2 section.

On the other hand, when a preliminary pulse is applied, the response delay of the diaphragm occurs due to the viscosity of the ink, etc. The response delay time (Td) and the free vibration period (Ts) of the diaphragm and the time corresponding to the T1 section and the T2 section are as follows. It can be determined by the equation (1).

T1 + T2 = Td + Ts × (n / 4) (n = 1,2,3,4)

In Equation 1 above, since the response delay time Td and the free vibration period Ts are determined by a system consisting of ink, an actuator, a diaphragm, and the like, depending on how much n is set, the phase in which the displacement of the diaphragm is changed in the T2 section is determined. It is determined whether it will end when it is in the

In the T3 section, the vibration of the diaphragm is forcibly attenuated or resonated in the free vibration state of the diaphragm. The time corresponding to the T3 section may be determined by Equation 2 below.

T3 = Ts × (n / 8) (n = 1,2,3,4,5,6,7,8)

In Equation 2 above, the vibration of the diaphragm may be forced attenuated or resonated depending on how much n is set, so that the behavior of the system when the main pulse is applied by adjusting the time corresponding to the T3 section, specifically, the amplitude of the diaphragm You can decide how much to do.

In the T4 section, the application time point of the main pulse is determined. The time corresponding to the T4 section may be determined by Equation 3 below.

T1 + T2 + T3 + T4 = Td + Ts × (m + n / 4) (m = 1,2,3 ..., n = 1,2,3,4)

In Equation 3 above, the time corresponding to the T4 section may be determined according to how much m and n are set, and thus, the main pulse is applied when the phase of the free oscillating diaphragm is in a state. . For example, in consideration of the response delay time Td of the diaphragm, when the main pulse number is applied at the time when the diaphragm falls, the displacement of the diaphragm increases, and thus the velocity and volume of the ink droplets discharged through the nozzle are increased. Will increase. On the contrary, when the main pulse number is applied at the time when the phase of the diaphragm rises, the displacement of the diaphragm decreases, thereby reducing the speed and volume of the ink droplets ejected through the nozzle.

As described above, according to the present invention, in consideration of the inherent vibration characteristics of the diaphragm in the inkjet printhead and the response delay time of the diaphragm due to the viscosity of the ink after application of a signal to the carrier pressure wave and the actuator in the pressure chamber, the ink It is possible to set the optimum driving waveform to effectively control the speed and volume of the droplets.

Meanwhile, the time applied to each section of the preliminary pulse shown in FIG. 4 is determined as follows according to the above equations, and a DC voltage of 12 Volt is used as the maximum potential, that is, the preliminary potential Vp.

T1 = 1㎲

T1 + T2 = Td (2㎲) + Ts (8㎲) = 10㎲ (In equation 1 above, n = 4)

T3 = Ts × 1/8 = 1㎲ (Equation 2 above, n = 1)

T1 + T2 + T3 + T4 = Td + 3 × Ts = 26㎲ (In equation 3 above, m = 2, n = 4)

The preliminary pulses to which the above times are applied are for increasing the volume and velocity of the droplets discharged through the nozzle, and the result will be described later with reference to the graph of FIG. 5.

FIG. 5 is a graph showing experimental results of ink droplet ejection performance when the driving pulse shown in FIG. 4 is applied to an actuator of the inkjet printhead.

The graph of FIG. 5 shows the volume and liquid of the droplets when the driving pulses having the preliminary pulses and the main pulses are applied by the driving method according to the present invention, and when the driving pulses having only the main pulses are applied as in the prior art. Compare and measure the speed of the enemy.

And, Table 1 below shows the experimental results numerically.

division Main pulse Spare Pulse + Main Pulse Increase Average velocity of droplets 4.12 m / s 5.61 m / s 36% Average volume of droplets 19.17 pℓ 21.28 pℓ 11%

Referring to the graph and table 1 of FIG. 5, when the preliminary pulse is applied before the main pulse as in the present invention, it can be seen that the velocity of the droplets discharged through the nozzle is increased by about 36% on average than when the main pulse is applied. have. The velocity of these droplets tends to increase proportionally as the driving frequency increases.

In addition, it can be seen that the volume of the droplets increased by an average of about 11% in the case of applying the preliminary pulse and the main pulse compared to the case of applying only the main pulse. In particular, when only the main pulse is applied, the volume of the droplet is decreased at the high driving frequency. However, when the preliminary pulse is applied before the main pulse as in the present invention, the volume of the droplet is maintained substantially constant even at the high driving frequency.

In summary, when the preliminary pulse is applied before the main pulse according to the present invention, the velocity and volume of the droplets discharged through the nozzle can be effectively controlled even by the maximum voltage of the main pulse, that is, the main potential Vm. You can increase it. On the contrary, in the case of discharging droplets having the same volume as in the prior art, the maximum voltage of the driving pulse, that is, the main potential Vm can be lowered than in the prior art. Therefore, durability of the inkjet printhead can be improved and power consumption can be reduced. On the other hand, as described above, it will be fully understood that the speed and volume of the droplet may be reduced by appropriately adjusting the T1 to T3 sections of the preliminary pulse and the T4 section between the preliminary pulse and the main pulse.

While the preferred embodiments of the present invention have been described in detail, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

As described above, according to the inkjet printhead driving method according to the present invention, by appropriately adjusting the T1 to T3 section of the preliminary pulse applied to the actuator before the main pulse, and the T4 section between the preliminary pulse and the main pulse, Since the speed and volume of the droplets ejected through the nozzle can be effectively increased or decreased, the ink ejection performance is improved.

In the case of discharging droplets of the same volume as in the prior art, the maximum voltage of the driving pulse, that is, the main potential Vm can be lowered as compared with the conventional one, and thus, the inkjet printhead is improved in durability and power consumption is reduced. .

In addition, since the drive pulse in the present invention does not have an offset of the potential, the potential is not applied while the actuator is not driven, so that the stress remaining on the actuator and the diaphragm becomes small, thereby improving durability.

1 is a cross-sectional view showing an example of a conventional piezoelectric inkjet printhead.

2 is a view showing an example of a drive waveform applied to a conventional method for driving an inkjet printhead.

3 is a view for explaining a waveform of a driving pulse applied to the method of driving an inkjet printhead according to a preferred embodiment of the present invention.

4 is a graph showing a specific example of a drive pulse and a displacement of the diaphragm by the drive pulse in the driving method according to the present invention.

FIG. 5 is a graph showing experimental results of ink droplet ejection performance when the driving pulse shown in FIG. 4 is applied to an actuator of the inkjet printhead.

Claims (5)

The driving of the inkjet printhead to apply a driving pulse to the actuator to change the volume of the ink-filled pressure chamber, thereby causing ink droplets to be discharged through the nozzles connected to the pressure chamber by the pressure change caused by the volume change of the pressure chamber. In the method, The driving pulse is applied to a main pulse applied at a main potential Vm of a degree capable of discharging the ink droplets, and to a preliminary potential Vp lower than the main potential Vm before a predetermined time before the main pulse. And a preliminary pulse. The method of claim 1, The preliminary pulse has a T1 section in which the potential rises from 0V to the preliminary potential Vp, a T2 section in which the preliminary potential Vp is kept constant, and the potential is lowered from the preliminary potential Vp to 0V. Loss consists of T3 sections, And a T4 section in which a potential of 0 V is maintained between the preliminary pulse and the main pulse. The method of claim 2, In the T1 section, the actuator is driven by the preliminary pulse to increase the pressure inside the pressure chamber. In the T2 section, free vibration of the diaphragm is induced, In the T3 section, vibration of the diaphragm is forcibly attenuated or resonated in the free vibration state of the diaphragm, In the T4 section, the time point of applying the main pulse is determined, the inkjet printhead driving method. The method of claim 3, wherein And adjusting the preliminary potential (Vp) of the preliminary pulse to change the pressure rise width in the pressure chamber. The method of claim 3, wherein When the response delay time of the diaphragm is called Td and the free vibration period of the diaphragm is called Ts, the times corresponding to the T1, T2, T3, and T4 sections are determined by the following equations. How to drive a printhead. T1 + T2 = Td + Ts × (n / 4) (n = 1,2,3,4) T3 = Ts × (n / 8) (n = 1,2,3,4,5,6,7,8) T1 + T2 + T3 + T4 = Td + Ts × (m + n / 4) (m = 1,2,3 ..., n = 1,2,3,4)