JPH06171080A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To ensure that a required amount of ink droplet weight is discharged efficiently by providing a first, a second and a third period when a voltage is changed in a direction where the volume of an ink pressure chamber is enlarged, a voltage is maintained at a constant level and a voltage is changed in a direction where the volume is diminished respectively, and setting the time of the second period to, at least, 1/4 of the intrinsic period Tc of an ink flow path system which is influenced by the acoustic volume of the ink pressure chamber. CONSTITUTION:The rise time t1 of a voltage pulse is a few times an intrinsic period Tc, and is almost the same as the intrinsic period Tm of an ink flow path system influenced by an acoustic volume due to the surface tension of an ink meniscus. Therefore, the ink meniscus returns to a nozzle opening taking a little more than the time of Tm/2 by oscillation of the intrinsic period Tm. During a period when a voltage is maintained at a constant level at time T1 before the return, the oscillation speed of the intrinsic period Tc for maintaining time t2 at 1/4min of the intrinsic period Tc is maximized, resulting in he rapid return of the meniscus to the nozzle opening. During the fall time, time t3 is almost the same as an intrinsic period Ta when the time t3 is determined by an oscillator, so that the oscillation of the period Ta which is specific is made constant by an oscillating overshoot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus for an on-demand type ink jet printer which discharges ink droplets in response to a print signal to form an ink image on a recording medium such as recording paper.

[0002]

2. Description of the Related Art As an ink jet recording apparatus in which the volume of an ink pressurizing chamber is changed by deformation of a piezoelectric element to form an ink droplet, a unimorph vibrator having a vibrating plate and a plate-shaped piezoelectric element is laminated in the ink pressurizing chamber. The conventional technology of constructing one side has been put to practical use. This vibrator is a flexural vibrator that is flexibly deformed in a direction orthogonal to the deformation direction of the piezoelectric element due to an applied voltage from the outside.

Further, as a driving method for controlling the formation of ink droplets and obtaining stable ink droplet ejection characteristics for such an ink jet recording apparatus, Japanese Patent Application Laid-Open No. 2-19 is known.
There is the prior art disclosed in the 2947 specification.

Further, as another structure for changing the volume of the ink pressurizing chamber by the deformation of the piezoelectric element, a vertical vibrator for deforming the vibration plate of the ink pressurizing chamber in the deformation direction of the piezoelectric element using a rod-shaped piezoelectric element is used. The conventional technique used is US Pat. No. 44.
No. 59601.

[0005]

A combination of an ink pressurizing chamber, an ink flow path system including a nozzle and an ink supply flow path communicating with the ink pressurizing chamber, and a vibrator system including a piezoelectric element and a vibrating plate of the pressurizing chamber is combined. The vibrating system governs the response of the inkjet recording apparatus and the ejection characteristics of ink droplets.

Comparing the two ink jet recording apparatuses described as the prior art from the viewpoint of this coupled vibration system, there is a big difference between the two. That is, in the system using the flexural vibrator, the vibrator is configured to be mounted on the ink pressurizing chamber, and therefore the response of the vibrator system is controlled by the acoustic capacity of the ink pressurizing chamber. Will be the response itself. On the other hand, in the system using the vertical vibrator, since the piezoelectric element is mechanically connected to a structure different from the ink pressurizing chamber, the vibrator responds separately from the response of the ink flow path system. Furthermore, in a system using a vertical vibrator, the vibration plate of the ink pressurizing chamber is fixed to another structure by the vertical vibrator, so the acoustic capacity of the ink pressurizing chamber is small, and the external input by the vertical vibrator is small. In contrast, the response of the ink flow path system is fast.

The present inventors have encountered the following problems in the process of researching and developing an ink jet recording apparatus using a vertical vibrator.

1) As in the case of pulling striking, which is one of the conventional methods of driving a flexural vibrator, when a pulse having a rise sufficiently faster than the natural period of the vibrator is applied to the piezoelectric element, the vibrator suddenly moves. Due to the motion, a large pressure vibration is generated in the ink pressurizing chamber, and due to the large negative pressure at this time, bubbles are generated in the ink pressurizing chamber over time, and the ink droplets are not formed. Further, the meniscus formed in the nozzle opening vibrates violently due to this large pressure vibration, and thus ink droplets may be ejected before the fall of the pulse that reduces the volume of the ink pressurizing chamber,
The ejection characteristics greatly changed due to a slight change in environment or pulse, and stable ejection characteristics and good print quality could not be obtained.

2) In the pulling striking, which is one of the conventional methods for driving a flexural vibrator, a rectangular pulse having a width of ½ of the natural period of the vibrator is applied to the piezoelectric element so that the vibration of the vibrator is increased. The amount of flexural displacement was maximized, and ink droplets of high speed were obtained at low voltage. On the other hand, in the ink jet recording apparatus using the vertical vibrator, the response speed of the ink flow path system, which is governed by the acoustic capacity of the ink pressurizing chamber, is lower than the response speed of the vibrator. Could not follow the movement of the oscillator, and ink droplets were not ejected.

Therefore, as a result of further research and development, the present inventors gradually changed the voltage for expanding the volume of the ink pressurizing chamber so as not to give a large vibration to the meniscus, so that the meniscus was in the vicinity of the nozzle opening. It has been found that, at the time of returning, by applying a rapid voltage change that reduces the volume of the ink pressurizing chamber, a sufficient ink drop weight and speed can be obtained at a low voltage.

However, if the change of the voltage pulse is delayed until the meniscus is reliably returned to the vicinity of the nozzle opening in this way, the width of one pulse becomes too long, and the repeated ejection frequency of the ink jet recording apparatus cannot be increased. We cannot meet the demand for faster recording.

Further, if the ink is ejected before the meniscus returns to the vicinity of the nozzle opening, there is a problem that the ejection speed and the weight of the ink droplet are greatly changed due to environmental changes and manufacturing variations. .

Further, when ink is ejected around the area where the meniscus returns to the vicinity of the nozzle opening, it becomes clear that the ejection shape and stability of ink droplets deteriorate.

Therefore, an object of the present invention is to solve these problems, and the purpose thereof is to control the response of the coupled vibration system. (1) Environmental changes such as temperature and humidity and manufacturing (EN) Provided is an inkjet recording apparatus which is not easily affected by an error or a change in drive voltage waveform and which has stable ink droplet ejection characteristics and responds at a high frequency.

(2) An object of the present invention is to provide an ink jet recording apparatus in which the shape of main ink droplets is good and the printing quality is excellent.

[0016]

An ink jet head of the present invention comprises an ink pressurizing chamber, a nozzle communicating with the ink pressurizing chamber, and a piezoelectric element for deforming the ink pressurizing chamber. In an ink jet recording apparatus that is driven by a voltage pulse to deform the ink pressurizing chamber and eject ink filling the ink pressurizing chamber as ink droplets from the nozzle, the voltage pulse is the volume of the ink pressurizing chamber due to the deformation of the piezoelectric element. The first period in which the voltage changes in the direction in which the voltage expands, the second period in which the voltage is held constant, and the third period in which the voltage changes in the direction in which the volume of the ink pressurizing chamber decreases due to the deformation of the piezoelectric element. The period t2 of the second period
Is equal to or more than ¼ of the natural period Tc of the ink flow path system that is governed by the acoustic capacity of the ink pressurizing chamber.

[0017]

When the ink jet recording apparatus shown in FIG. 1 is replaced with an equivalent electric circuit, it becomes as shown in FIG. In the figure, m [kg / m4] is inertance, c [m5 / N] is acoustic capacity, r [Ns / m5] is acoustic resistance, and U [m3 / s] is volume velocity. A vibrator system including the piezoelectric element 22 and the vibration plate 8 of the ink pressurizing chamber 5 to which the piezoelectric element 22 is connected,
The subscript 1 means the ink pressurizing chamber system of the portion to which the piezoelectric element 22 is not connected, the subscript 2 means the ink supply flow channel system, and the subscript 3 means the nozzle flow channel system. P [Pa] of the oscillator system is
The voltage pulse applied to the piezoelectric element 22 is converted into an equivalent pressure by the pressure applied from the outside. Also,〔〕
Units are inside. When the equivalent electric circuit of FIG. 2 is decomposed into circuits that are important in the inkjet recording apparatus, the three electric circuits shown in FIG. 3 are obtained. First, the meaning of these circuits will be described below.

FIG. 3 (i) shows a circuit having only a vibrator system.

[0019]

[Equation 1]

It has a natural period determined by the oscillator indicated by.

FIG. 3 (ii) shows a circuit composed of an ink pressurizing chamber, a nozzle flow channel system and an ink supply flow channel system. When viewed from the ink pressurizing chamber, the nozzle flow channel system and the ink supply flow channel system are connected in parallel. Has been done,

[0022]

[Equation 2]

It has a natural period of the ink flow path system which is governed by the acoustic capacity of the ink pressurizing chamber shown by.

FIG. 3 (iii) shows a series circuit of a nozzle flow channel system and an ink supply flow channel system.

[0025]

[Equation 3]

It has a natural period of the ink flow path system which is governed by the acoustic capacity due to the surface tension of the ink meniscus formed at the nozzle opening shown by. This circuit describes a flow of supplying ink from the common ink chamber 4 to the nozzle opening 2 through the ink supply flow path 6 and the ink pressurizing chamber 5 by the surface tension of the ink meniscus.

In order for the equivalent electric circuit of the entire system in which the elements of the ink jet recording apparatus shown in FIG. 2 are coupled to be decomposed into the electric circuits of the respective parts shown in FIG. 3, their natural periods must be separated from each other. There is.

In the ink jet recording apparatus shown in FIG. 1,

[0029]

[Equation 4]

Since the relationship of is satisfied, the operation of the present invention can be understood with the circuit of FIG.

The response when the voltage pulse shown in FIG. 4I is applied to the ink jet recording apparatus shown in FIG. 1 (that is, the response of the equivalent electric circuit) will be described. The voltage pulse is applied to the ink pressurizing chamber 5 by the deformation of the piezoelectric element 22 shown at time t1.
A first period in which the voltage changes in the direction in which the volume of
A second period in which the voltage shown at time t2 is held constant,
It is a third period in which the voltage changes in the direction in which the volume of the ink pressurizing chamber 5 is reduced by the deformation of the piezoelectric element 22 shown at time t3, and the voltage change is linear in each period. The response of the transducer tip displacement at this time is shown in Fig. 4 (ii).
FIG. 4 (iii) shows the response of the ink meniscus formed in the nozzle opening.

As is well known as the transient response of an electric circuit, when the voltage (pressure in the equivalent electric circuit) changes discontinuously at time 0, time T1 or time T2, it is proportional to the size of the discontinuity in the vibration system. , The motion of each natural period is excited.

In response to the displacement of the vibrator tip, the rise time t1 of the voltage pulse is sufficiently longer than the natural period Ta.
The oscillations excited by the discontinuities at time 0 and T1 are small, and the oscillator responds almost as the voltage pulse changes. At the trailing edge of the voltage pulse, the time t3 is approximately the same as the natural period Ta, so an overshoot that oscillates in the natural period Ta is seen due to the discontinuity at the time T2.

The motion of the ink excited by the displacement of the tip of the vibrator is taken as the response of the ink meniscus, and is shown in FIG.
This will be described using ii). Rise time t1 of voltage pulse
Is several times as long as the natural period Tc, and is about the same time as the natural period Tm. Therefore, due to the discontinuity at time 0, the vibration having the relatively small natural period Tc is superimposed on the vibration having the relatively large natural period Tm. . Due to the vibration of the natural period Tm, the ink meniscus returns to the nozzle opening after a little longer than Tm / 2. However, when the voltage pulse changes discontinuously at time T1 before the meniscus returns to the nozzle opening, and during the second period in which the voltage is held constant, the discontinuity excited at time 0 and the magnitude are equal. The opposite vibration is excited. Since the time t2 is sufficiently shorter than the natural period Tm, the movement of the ink meniscus during the second period is the natural period Tm.
The influence of the vibration of c becomes dominant. That is, the meniscus can be rapidly returned to the nozzle opening by this vibration, and this effect is most effectively exerted because the time t2 is 1/4 or more of the natural period Tc. This is because the vibration speed of Tc is maximized and the meniscus return amount is sufficiently increased. Further, if the time t2 is equal to or less than 3/4 of the natural period Tc, the meniscus is not drawn from the nozzle opening due to the vibration in the opposite direction, and the ink is quickly and stably formed at the time T2 which is the start of the third period. Can be returned to the nozzle opening. Therefore, a high response of the inkjet recording device can be obtained. Further, when the voltage change is linear as in the voltage pulse shown in FIG. 4 (i), as described above, the time 0 and the time T1 are
Discontinuities of equal magnitude and opposite sign,
The effects of environmental changes such as temperature and humidity and manufacturing errors are offset,
It also has the effect of making the characteristics constant.

[0035]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the construction of an ink jet recording apparatus to which the embodiment of the present invention is applied.

In FIG. 1, an ink pressurizing chamber 5 is formed in the flow path forming member 3 as an elongated linear cavity, and one end of the cavity communicates with the common ink chamber 4 via an ink supply flow path 6. ing. The flow path forming member 3 is sandwiched between the nozzle substrate 1 and the elastic plate 7 to form a flow path unit, and the other end of the ink pressurizing chamber 5 corresponds to the nozzle substrate 1 and the ink pressurizing chamber 5. Communicates with the formed nozzle 2.

The rod-shaped laminated piezoelectric element 22 serving as a drive source for ejecting ink droplets has one half of its longitudinal surface fixed to the vibrator substrate 21, and the non-fixed portion has the vibrator substrate 21.
It projects like a beam from. The laminated piezoelectric element 22 has an active portion having electrode layers 26 and 27 that alternately cross each other in a beam-shaped portion, one electrode layer 27 serving as an individual electrode, and the other electrode layer 26 serving as a common electrode. No external drive circuit to the electrode layers 29, 2 formed on the surface of the piezoelectric element 22
Connected via 8.

The flow path unit and the oscillator substrate 22 are fixed to each other by the head frame 11. Ink is supplied from an external ink tank (not shown) to the ink pressurizing chamber 5 via the common ink chamber 4 of the flow path unit.
A portion of the elastic plate 7 forming the wall of the ink pressurizing chamber 5 can be deformed as a vibrating plate 8 and has an island shape formed on the surface opposite to the ink pressurizing chamber 5 so as to correspond to the ink pressurizing chamber 5. Thick part 9
It is a diaphragm with. This island-shaped thick part 9
The beam-shaped tip of the laminated piezoelectric element 22 is bonded to the. The circumference 10 of the island-shaped thick portion 9 of the diaphragm 8 is thin.

When a voltage is applied between the individual electrode 27 and the common electrode 26 of the laminated piezoelectric element 22 from an external drive circuit (not shown), the active portion of the laminated piezoelectric element 22 contracts in the longitudinal direction, and ink is pressed. The diaphragm 8 of the chamber 5 is bent downward to expand the volume of the ink pressurizing chamber 5. Due to the expansion of the volume of the ink pressurizing chamber 5, the ink is supplied from the common ink chamber 4 to the ink pressurizing chamber 5 through the supply passage 6. When the voltage application between the individual electrode 27 and the common electrode 26 is released in the subsequent time, the active portion of the laminated piezoelectric element 22 expands to the original length to reduce the volume of the ink pressurizing chamber 5, and the pressure generated at this time. A part of the ink filling the ink pressurizing chamber 5 is ejected as an ink droplet from the nozzle 2 communicating with the ink pressurizing chamber 5. A vibrator that uses displacement in the piezoelectric strain direction of the piezoelectric element is called a vertical vibrator. In this embodiment, since the laminated piezoelectric element is used, the piezoelectric element drive voltage required for ink ejection can be suppressed to 30 V or less.

Next, the characteristics of this ink jet recording apparatus will be specifically described with reference to the equivalent electric circuit shown in FIG.

The inertance m of the ink flow path system is calculated as follows.
If the density of the ink is ρ, the cross-sectional area of the flow path orthogonal to the flow direction is S, and the coordinates taken in the flow direction are x,

[0043]

[Equation 5]

Is calculated by The constant κ is a coefficient that depends on the vibration frequency of the flow, and 1.4 is used here.

The calculation of the resistance r of the ink flow path system was carried out using the equation of laminar fluid friction described in the Mechanical Engineering Handbook edited by the Japan Society of Mechanical Engineers. For example, when the flow path is a circular tube with a diameter d, the viscosity of the ink is μ,

[0046]

[Equation 6]

Is calculated by

The compliance c1 of the ink pressurizing chamber is
It consists of the rigidity of the members forming the ink pressurizing chamber and the compressibility of the ink. It is difficult to describe the rigidity of the ink pressurizing chamber by an equation, and it is generally obtained numerically by a structural analysis method such as the finite element method.

The acoustic capacity c3 due to the surface tension of the ink meniscus is represented by the following formula: d is the diameter of the nozzle and σ is the surface tension of the ink.

[0050]

[Equation 7]

Calculated by

If the length c of the piezoelectric element is 1, the cross-sectional area of the piezoelectric element is s, and the elastic coefficient of the piezoelectric element is y, the compliance c0 of the oscillator system is

[0053]

[Equation 8]

The spring constant k described in the mechanical system of the oscillator system can be calculated by the

[0055]

[Equation 9]

It is obtained by conversion using. Here, α is the ratio of the displacement of the vibrator at that time to the volume of the ink pressurizing chamber changed by the diaphragm.

The inertance m0 of the oscillator system is such that the natural period of longitudinal vibration of a fixed-free rod is

[0058]

[Equation 10]

Therefore, m0 can be calculated using the equations 1 and 10. Here, in the calculation of the oscillator system, only the piezoelectric element was considered and the diaphragm was ignored. In fact, in the present embodiment, the diaphragm is much lighter than the piezoelectric element and has a small spring constant, so that the above equation can be used.

The typical shape of the ink jet recording apparatus shown in FIG. 1 to which this embodiment is applied has a nozzle opening with a diameter of 38 μm.
m, the length is 100 μm, and is tapered so as to spread toward the ink pressurizing chamber. The ink pressurizing chamber has a length of 1 mm, a width of 150 μm, and a height of 200 μm.
The shape is close to a rectangular parallelepiped. The ink supply flow path has a shape close to a rectangular parallelepiped having a length of 300 μm, a width of 70 μm, and a height of 50 μm. The piezoelectric element has a length of 4 mm and a width of 500.
The thickness is 80 μm.

The ink is prepared mainly with water, and has a specific gravity of 1, a viscosity of 2 mPa · s and a surface tension of 50 mN / m.

Table 1 shows the parameters of the equivalent electric circuit of FIG. 2 calculated using these numerical values.

[0063]

[Table 1]

Table 2 shows the natural periods calculated from the equations 1 to 3 and the experimentally measured natural periods using these numerical values.

[0065]

[Table 2]

The measurement method by experiment was carried out by using an impedance analyzer or a Doppler vibrometer in the oscillator system. Measurement of the ink flow path system, applying a sinusoidal input to the oscillator, when observing using a stroboscope that emits light in synchronization with the behavior of the ink meniscus in the nozzle opening at that time, for a specific frequency, It was confirmed by the large vibration of the ink meniscus. It could also be measured by observing the residual vibration of the ink meniscus after ink ejection by normal driving.

Next, the voltage pulse used in this embodiment will be described in detail.

In FIG. 4 (i), Vh is determined by the ink drop weight required for the ink jet recording apparatus.
In this embodiment, the weight per ink drop is 0.1 μm.
g was required and the Vh for that was 25V. The voltage fall time t3 is important in determining the velocity of the ink drop. The shorter t3 is, the faster the ink drop velocity is. However, when the natural period Ta of the vibrator system is shorter than the natural period Tc of the ink flow path system governed by the acoustic capacity of the ink pressurizing chamber as in the ink jet recording apparatus of this embodiment, t3 is set more than necessary. Even if it is shortened, the ink flow path system does not respond, and on the contrary, an excessive pressure change is generated or the vibration of the vibrator system overshoots to make the ink droplet unstable. Also, if t3 is not sufficiently shorter than the natural period Tc, the response of the flow path system becomes small, and the weight and velocity of the ink droplets decrease. Therefore, when the optimum value was obtained by an experiment, t3 of 6 μs to 9 μs was obtained. This can be said to be optimal when t3 is equal to or more than the natural period Ta of the oscillator system and is equal to or less than 1/2 of the natural period Tc when combined with the above-described action.

Next, by using the voltage waveform as shown in FIG. 5, the time t1 of the first period during which the voltage changes in the direction in which the volume of the ink pressurizing chamber expands is changed to change the ink meniscus of the nozzle opening. The time (return time) for the water to return to the nozzle opening was measured. The measurement results are shown in FIG. When t1 was 120 μs, the return time of the ink meniscus was equal to t1. This value is 1 / of the natural period Tm
The value was slightly larger than 2. When t1 is 120 μs or more, the meniscus return time is shorter than t1. this is,
The ink meniscus is hardly drawn from the nozzle opening, which means that the meniscus has already returned even though the volume of the ink pressurizing chamber is expanding. Under such conditions, the third voltage is changed so that the volume of the ink pressurizing chamber is reduced in order to eject the ink.
The time T2 that starts in the period is determined not by the meniscus return time but by the time t1 of the first period. Therefore, if t1 is set to 120 μs or more, the repetition frequency of ink ejection is lowered, which is a preferable driving state. is not.
Further, after a lapse of time from the return time, the ink meniscus slowly projects from the nozzle opening due to the movement of the natural period Tm. This maximum amount of protrusion is approximately Tm / 4 after the return time of the ink meniscus.
In the ink jet recording apparatus of the present embodiment, it is about 170 μs after the voltage pulse is applied. As a result of repeated experiments by the present inventors, the volume of the ink pressurizing chamber is rapidly reduced and ink droplets are ejected at such a slow speed of the natural period Tm with the ink meniscus protruding from the nozzle opening. Then, the ejected ink droplets became a state as shown in FIG. 7 (ii), which markedly deteriorated the print quality. This phenomenon is caused by stagnation of ink in the nozzle opening due to the slow protrusion of the meniscus, which is dragged by the ink ejected rapidly from the inside of the nozzle to form an unstable ink droplet. Further, since the slow ejection of the ink meniscus is greatly affected by the wettability of the nozzle openings, if the wettability around the nozzle openings of the nozzle substrate 1 is deteriorated by paper dust of the recording paper, ink droplets Flight bends and satellite ink drops will occur. Therefore, the time t1 + t2 should be less than the meniscus return time + Tm / 4 for this voltage pulse, and preferably less than the meniscus return time + Tm / 8.

In FIG. 6, t1 is 100 μs and 110 μ
In s, the return time of the meniscus is faster. This is because the voltage pulse is in the second period at time T1 as described above, so that the vibration of the natural period Tc of the ink flow path system, which is governed by the acoustic capacity of the ink pressurizing chamber, is excited and the meniscus is generated. This is due to the accelerated return of. Also,
It was confirmed that the return time in this case is not easily affected by environmental changes and manufacturing errors.

When t1 is further shortened, the meniscus retreats deeply from the nozzle opening, and therefore the meniscus did not return to the nozzle opening even with vibration due to discontinuity at time T1. However, when t1 is further shortened to, for example, 50 μs, t1 becomes close to Tc, so that vibration with a large amplitude of the natural period Tc is excited and the restoration of the meniscus is accelerated. However, this vibration is so large that it is difficult to control, and the ejection characteristics of the ink droplets change significantly due to environmental changes and manufacturing errors, which is not practical.

As described above, it is preferable that the first period during which the voltage changes in the direction in which the volume of the ink pressurizing chamber 5 expands is shorter than the time for the ink meniscus to recover (120 μs in the above example) by a maximum of Tc. There was found.

Next, FIG. 8 shows the result of measuring the ink drop weight by changing the time t2 of the second period with t1 set to 110 μs by the voltage pulse of FIG. 4 (i). From this result, there is a tendency that the characteristic becomes constant when t2 is ¼ or more of Tc. Further, in order to stabilize certain characteristics and make it difficult to be affected by various disturbances such as environmental changes and manufacturing errors, t2 should be set to 1/4 or more and 3/4 or less of Tc. When t2 is further increased, the ink weight increases, which seems to be effective. This is because the ink meniscus protrudes due to the vibration of the natural period Tm, which increases the ink weight, as described above. by. However, this state is not preferable because it is the flying state of the ink droplets in FIG. 7 (ii). Also, t2 is 1 of Tc
Fig. 7 shows a good flight condition at 10 µs, which is / 2.
Shown in (i).

In the embodiment described above, a trapezoidal wave that changes linearly is used as the voltage pulse. However, even if the trapezoidal wave is not a perfect trapezoidal wave, if it is a voltage pulse that changes nearly discontinuously at time 0 and time T1. The action and effect similar to those of the above-described embodiment are obtained.

[0075]

According to the above configuration of the present invention, it is possible to shorten the time required for the ink meniscus to return to the nozzle opening, and to repeatedly eject ink droplets while efficiently securing the necessary ink droplet weight. It has the effect of speeding up. At this time, there is an effect that it is possible to provide an ink jet recording apparatus that has good ink droplet ejection characteristics and that is not affected by disturbances such as manufacturing errors and environmental changes.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an inkjet recording apparatus to which an embodiment of the present invention is applied.

FIG. 2 is an equivalent electric circuit diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is an equivalent electric circuit diagram for explaining the operation of the embodiment of the present invention.

FIG. 4 is a graph of a voltage pulse and a response thereof according to an embodiment of the present invention.

FIG. 5 is a graph of voltage pulses illustrating an embodiment of the present invention.

FIG. 6 is a graph showing the behavior of meniscus, which explains an example of the present invention.

FIG. 7 is a diagram illustrating a flight state of ink droplets for explaining the effect of the present invention.

FIG. 8 is a graph showing the behavior of a meniscus for explaining the effect of the present invention.

[Explanation of symbols]

 1 Nozzle Substrate 2 Nozzle 3 Flow Forming Member 4 Common Ink Chamber 5 Ink Pressurizing Chamber 7 Elastic Plate 8 Vibrating Plate 9 Thick Island-Shaped Portion of Diaphragm 10 Thin Wall of Vibrating Plate 11 Head Frame 22 Piezoelectric Element t1 1st Time of period t2 time of second period t3 time of third period

Claims (3)

[Claims] 1. An ink pressurizing chamber, a nozzle communicating with the ink pressurizing chamber, and a piezoelectric element that deforms the ink pressurizing chamber, the piezoelectric element being driven by a voltage pulse, and the ink pressurizing unit being driven. In an ink jet recording apparatus that deforms a chamber and ejects ink that fills the ink pressurizing chamber as ink droplets from the nozzle, the voltage pulse is applied in a direction in which the volume of the ink pressurizing chamber expands due to the deformation of the piezoelectric element. It comprises a first period in which the voltage changes, a second period in which the voltage is held constant, and a third period in which the voltage changes in a direction in which the volume of the ink pressurizing chamber is reduced by the deformation of the piezoelectric element. The inkjet recording apparatus is characterized in that the time t2 of the second period is equal to or more than ¼ of the natural period Tc of the ink flow path system that is governed by the acoustic capacity of the ink pressurizing chamber. 2. The ink jet recording apparatus according to claim 1, wherein the time t2 of the second period is 3/4 or less of the natural period Tc. 3. The ink jet recording apparatus according to claim 1, wherein the voltage change in the first period is substantially linear.