JP3580065B2 - Ink jet recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving technique of an inkjet recording head using a piezoelectric vibrator of a longitudinal vibration mode or a longitudinal effect, and a flexurally deformed piezoelectric vibrating plate as a driving source.
[0002]
[Prior art]
The on-demand type ink jet recording head has a plurality of pressure generating chambers for generating ink pressure by piezoelectric vibrators and heating elements, a common ink chamber for supplying ink to each pressure generating chamber, and a nozzle opening communicating with each pressure generating chamber. And a driving signal is applied to the pressure generating chamber corresponding to the print signal to cause the ink droplet to fly from the nozzle opening to the recording medium.
[0003]
In such an ink jet recording head, there is a so-called bubble jet (registered trademark) type as a pressure generating means in which a resistance wire for generating Joule heat is provided in a pressure generating chamber, and ink droplets are ejected by utilizing the pressure for generating bubbles. .
[0004]
On the other hand, a piezoelectric vibrator, which is formed by alternately laminating a piezoelectric material and a conductive layer, and extends in the axial direction, that is, a piezoelectric vibrator utilizing a longitudinal vibration mode, expands and contracts a pressure generating chamber partially constituted by an elastic plate. In addition, a piezoelectric vibration type that sucks ink and discharges ink droplets is also known. The piezoelectric vibrator can be driven at a high speed, and has a characteristic that the pressure generating chamber can be repeatedly expanded and contracted at a high speed by being brought into contact with the pressure generating chamber.
[0005]
Such an on-demand type inkjet head has the following problems.
[0006]
After the pressure is generated in the pressure generating chamber and the ink droplet is ejected, the pressure fluctuation remains in the pressure generating chamber, and the meniscus in the nozzle vibrates and recovers to the steady position.
[0007]
However, when ink droplets are ejected at a high frequency, since the meniscus has not yet recovered to the steady position at the time of ink droplet ejection, the ejection amount and ejection speed of the ink droplets vary, and the ejection of the ink droplets becomes unstable. Therefore, the flying direction changes, ink mist is generated, and the printing quality is likely to be reduced. As a result, there is a problem that the response frequency of the ink jet recording head is prevented from being improved.
[0008]
As a countermeasure against such a problem, a driving method as disclosed in Japanese Patent Application Laid-Open No. 2-233258 has been proposed.
[0009]
This driving method is a technique of applying an auxiliary signal so that the meniscus pull-in is reduced after the application of a signal for ejecting ink droplets.
[0010]
According to this driving method, the first bubble is generated in the pressure generating chamber by the heating element when a signal is applied, and the ink droplet is caused to fly from the nozzle, and then the second bubble is generated at a time when the meniscus suction is maximized. By doing so, the pressure change due to the second bubble is generated so as to cancel the pressure change due to the generation of the first bubble and the flying of the ink droplet, and they interfere with each other. As a result, the pressure change acting on the meniscus is reduced, and the meniscus is sucked. And the recovery time is reduced.
[0011]
As a result, high-response driving becomes possible.
[0012]
Although this drive head is of a bubble jet (registered trademark) type, it is apparent that a piezoelectric vibration type has a similar effect in that pressure is generated in the pressure generating chamber.
[0013]
In other words, in the case of the piezoelectric vibration type, if the meniscus recovery time after the ink droplet ejection is slow, there is a problem that stable ejection is not performed because the meniscus is not recovered even when driving at a high frequency. Depending on the driving method, it has become possible to shorten the recovery time.
[0014]
[Problems to be solved by the invention]
However, in the process of recovering the meniscus, residual vibration having a resonance frequency (Helmholtz resonance frequency) unique to the pressure generating chamber accompanies.
[0015]
With the conventional driving method, even if an attempt is made to start ejection of ink droplets before the minute residual vibration is sufficiently suppressed, the formation of the ink droplets becomes unstable because the meniscus is not stable, and the ejected ink droplets may become unstable There is.
[0016]
Therefore, in the conventional ink jet recording head driving method, even if the meniscus recovery time can be shortened to achieve a high-frequency driving response, it is not expected to be effective in damping the minute residual vibration of the meniscus, and the ink droplets cannot be regenerated. There was a problem that it did not lead to stable ejection.
[0017]
In addition, the vibration cycle and amplitude of the meniscus vibration change depending on the dimensional variation of the flow path, the material and the physical properties of the ink.
[0018]
For this reason, there are also problems that the dimensional control of the flow path is strict, the range of selection of the flow path constituent material and the ink is narrowed, the manufacturing cost is increased, and the degree of freedom in design is reduced.
[0019]
In addition, if the environmental temperature changes, the meniscus vibration period and amplitude further change due to the change in the ink physical properties. Therefore, the fixed driving method cannot effectively suppress the residual vibration of the meniscus.
[0020]
For this reason, it is necessary to limit the environmental temperature range to be used, or to prepare a plurality of driving devices in order to perform separate driving for each environmental temperature, and the cost of the device itself increases. there were.
[0021]
The present invention has been made in view of such a problem, and an object thereof is to ensure stable ejection of ink droplets even at a high frequency drive, and to achieve dimensional variations of ink flow paths, physical properties of materials and inks. A new ink jet recording device that can secure stable ejection against changes in ink temperature and environmental temperature, and also keeps the ink jetting speed constant regardless of the drive frequency to keep the ink droplet landing position constant To provide.
[0022]
[Means for Solving the Problems]
An ink jet recording apparatus according to the present invention includes a pressure generating chamber that communicates with a common ink chamber via a nozzle opening and an ink supply port and has a Helmholtz resonance frequency of a period Tc, and a piezoelectric vibrator that contacts the pressure generating chamber. An inkjet recording head comprising: a pressure generating chamber that expands / contracts the pressure generating chamber by contracting / expanding the piezoelectric vibrator due to a potential change;
A first pulse for expanding the pressure generating chamber, a second pulse for contracting the expanded pressure generating chamber to eject ink droplets from the nozzle openings, and the pressure generating chamber after the second pulse. Driving pulse generating means for outputting a third pulse for expanding the pressure again;
Based on the environmental temperature detected by the environmental temperature detecting means and the duration of the second pulse, First pulse And a drive pulse control means for determining the applied potential ratio of the third pulse and determining the applied potential of the third pulse based on the applied potential ratio.
[0023]
Further, the duration of the second pulse and the duration of the third pulse are set to be the same, and the time from the start of the second pulse to the start of the third pulse is equal to the resonance cycle Tc of the pressure generating chamber. It is characterized in that the time is set to be substantially the same.
[0024]
Further, the drive pulse control means controls the third pulse start timing based on an environmental temperature.
[0025]
Further, the applied potential of the third pulse is lower than the applied potential of the first pulse.
[0026]
Further, the duration of the third pulse is constant regardless of the environmental temperature.
[0027]
[Action]
Based on the environmental temperature detected by the environmental temperature detecting means and the duration of the second pulse, First pulse And a driving pulse control means for determining the applied potential of the third pulse based on the applied potential ratio, so that the meniscus of the meniscus that changes according to the ambient temperature and the gradient of the second pulse is determined. Vibration suppression vibration can be applied with an optimal amount of vibration. As a result, the vibration of the meniscus can be effectively attenuated, and stable ejection of ink droplets can be ensured regardless of the ambient temperature and the inclination of the second pulse.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, details of the present invention will be described based on examples.
[0029]
FIG. 1 is a sectional view showing an ink jet recording head used in an ink jet recording apparatus according to one embodiment of the present invention.
[0030]
In the figure, reference numeral 1 denotes a nozzle plate in which the nozzle openings 2 are formed, reference numeral 7 denotes a flow path forming plate formed so that the pressure generating chamber 3, the common ink chamber 4, and the ink supply port 5 communicate with each other, and reference numeral 8 denotes an elastic plate. The ink flow path unit is integrally formed by sandwiching the flow path forming plate 7 between the nozzle plate 1 and the elastic plate 8.
[0031]
The piezoelectric vibrator 9 is formed by alternately laminating a piezoelectric material and a conductive material. The piezoelectric vibrator 9 contracts in a charged state in a direction perpendicular to the lamination direction of the conductive layer, and when the charged state is released, it is perpendicular to the lamination direction with the conductive layer. The other end is fixed to the fixed substrate 10 in a state where the inactive portion at the tip where no electrode is present is in contact with the elastic plate 8 in the region of the pressure generating chamber 3. Have been. .. Correspond to the pressure generating chambers 3, 3, 3,... And the nozzle openings 2, 2, 2,.
[0032]
The ink jet recording head configured as described above discharges ink droplets by the following drive.
[0033]
When a drive voltage is applied to the piezoelectric vibrator 9 to perform charging, the piezoelectric vibrator 9 contracts to deform the abutting elastic plate 8, thereby expanding the pressure generating chamber 3 and the common ink through the ink supply port 5. Ink flows into the pressure generating chamber 3 from the chamber 4.
[0034]
Next, the piezoelectric vibrator 9 is extended to its original state by the discharge and the elastic plate 8 is pressed, so that a pressure is generated in the pressure generating chamber 3 and the ink droplet is ejected from the nozzle opening 2.
[0035]
Further, the pressure generating chamber 3 is expanded again so that the ink droplets are not discharged by the subsequent charging.
[0036]
Hereinafter, the drive pulse generating means, the drive pulse control means, and the driving method of the present invention will be described in detail.
[0037]
FIG. 2 is a block diagram showing an ink jet recording apparatus according to one embodiment of the present invention.
[0038]
In the figure, the ink jet recording apparatus includes an ink jet recording head 100, a driving nozzle selecting means 110 for selecting driving of the piezoelectric vibrators 9, 9, 9,..., A driving pulse generating means 120 for generating a driving pulse, and a driving pulse. And an environmental temperature detecting means 140.
[0039]
The environmental temperature detecting means 140 detects the ambient environmental temperature and sends the environmental temperature data to the drive pulse control means 130.
[0040]
The drive pulse control means 130 generates a pulse width pw1 corresponding to the environmental temperature, based on the relation table between the pulse widths of the pulse control signals p1, p2, and p3 set in the means and the environmental temperature, and the applied potential and the environmental temperature. , Pw2, pw3, and the applied potential control signals v1, v2, v3 to the drive pulse generation means 120. The print data is sent to the drive nozzle selecting means based on a print signal from the outside.
[0041]
The drive pulse generator 120 generates a drive pulse having a desired peak and valley based on the plurality of pulse width control signals p1, p2, p3 and the applied potential control signals v1, v2, v3 sent from the drive pulse controller 130. .
[0042]
The generated driving pulse is selectively transmitted to the piezoelectric vibrator 9 belonging to the nozzle opening 2 where a dot is to be formed, via the driving nozzle selecting means 110. Thus, ink droplets are ejected from desired nozzle openings 2.
[0043]
In this embodiment, a driving nozzle selecting unit 110 and an environmental temperature detecting unit 140 are mounted on the inkjet recording head 100. The reason why the environmental temperature detecting means 140 is mounted on the inkjet recording head 100 is to detect the environmental temperature around the inkjet recording head 100 more accurately.
[0044]
FIG. 3 is a diagram illustrating the formation of a driving pulse of an inkjet recording head in an inkjet recording apparatus according to an embodiment of the present invention.
[0045]
The drive pulse of the ink jet recording head of the present invention is a step-like trapezoidal pulse composed of peaks and valleys as shown in FIG. 3A, a first pulse S1 for charging, a second pulse S2 for discharging, and a re-pulsing. It comprises a third pulse S3 for charging.
[0046]
In this embodiment, three pulse width control signals p1, p2, p3 and applied potential control signals v1, v2, v3 are set in the drive pulse control means 130. Each of them corresponds to the first pulse S1, the second pulse S2, and the third pulse S3 of the driving pulse, and depends on the application timing of each pulse control signal p1, p2, p3 and the pulse width pw1, pw2, pw3. The start timing and duration of each of the drive pulses S1, S2, S3 are determined, and the applied potential of each of the drive pulses S1, S2, S3 is determined by the applied potential control signals v1, v2, v3.
[0047]
In the present invention, the applied potential control signal v2 is set so that the applied potential becomes zero so that the second pulse becomes a discharge pulse.
[0048]
In each step of the drive pulse as described above, the following driving of the ink jet recording head is performed.
[0049]
When the first pulse control signal p1 is turned on, the pulse is charged to the peak potential (V1) indicated by the first applied potential control signal v1 in the time required for the pulse width pw1 and the piezoelectric vibrator is charged. 9 contracts at a constant rate. Accordingly, the pressure generating chamber 3 expands, and the ink in the common ink chamber 4 flows into the pressure generating chamber 3 via the ink supply port 5. After the end of the first pulse control signal p1, the potential is maintained at the peak potential, and the piezoelectric vibrator 9 also stops deforming and waits.
[0050]
Subsequently, when the second pulse control signal p2 is turned on, the discharge is performed to the potential zero specified by the second applied potential control signal v2 in the time required for the pulse width pw1 and the piezoelectric vibrator 9 Elongates. Accordingly, the pressure generating chamber 3 starts contracting, and the pressure is generated in the pressure generating chamber 3 so that ink droplets are ejected from the nozzle openings 2. After ink droplet ejection, the meniscus starts oscillating in the nozzle.
[0051]
Thereafter, when the third control pulse signal p3 and the third applied potential control signal v3 are turned on, the piezoelectric vibrator 9 is charged to the potential (V3) with the time required for the pulse width pw3 and slightly contracted. Then, the pressure generating chamber 3 expands. By this expansion, the vibration behavior of the meniscus vibrating in the nozzle is controlled, and the vibration of the meniscus is rapidly attenuated. After the end of the expansion, the potential is maintained at the potential (V3) until the next ink ejection signal comes.
[0052]
The inkjet recording apparatus of the present invention is driven by the driving method as described above. In the present invention, in particular, the drive pulse control is performed based on the environmental temperature detected by the environmental temperature detecting means 140, particularly the application timing and the applied potential of the third pulse. The means 130 can be adjusted and changed.
With this driving method, an arbitrary driving pulse can be formed, and the vibration of the meniscus after ink ejection can be rapidly attenuated effectively under any conditions.
[0053]
Hereinafter, a detailed adjustment and variation method of the application timing and the applied potential will be described.
[0054]
First, the application timing of the third pulse will be described.
[0055]
FIG. 4 is a diagram for explaining a driving pulse and a meniscus behavior of the ink jet recording head in the ink jet recording apparatus according to one embodiment of the present invention.
[0056]
Even if the third pulse is applied at an arbitrary timing, the vibration of the meniscus is not sufficiently suppressed. In order to effectively dampen the meniscus, it is preferable to apply the third pulse at the timing when the vibration of the meniscus generated by ink ejection moves to the pressure generating chamber 3 side most. As a result, the kinetic energy of the meniscus going to the nozzle at this point can be effectively attenuated, and the vibration of the meniscus is rapidly attenuated to return to a steady state in a short time as shown by the solid line L1 in FIG. Can be done.
[0057]
However, when charging is started and the pressure generating chamber 3 is expanded at the timing when the meniscus is moving to the pressure generating chamber 3 side or the nozzle opening 2 side, the kinetic energy of the meniscus is not sufficiently reduced, and the dashed line L2 in FIG. Since the vibration of the meniscus remains as described above, if the next ejection timing corresponds to the process in which the meniscus is drawn into the nozzle (the process indicated by the arrow in the dashed line L2 in the figure), the formation of the meniscus during the ejection of the ink droplets Becomes unstable, and as a result, mist is generated in the ejected ink droplets, and the ejection ink is likely to bend or shake.
[0058]
For this reason, under the driving frequency at which the next ink droplet is to be ejected at the above timing, stable ejection of the ink droplet cannot be sufficiently ensured, and ink ejection bends and mist are generated, which tends to cause deterioration in print quality. The problem arises.
[0059]
Therefore, care must be taken in setting the application timing of the third pulse.
[0060]
However, in the present invention, the optimal application timing of the third pulse is easily determined and set by means utilizing the Helmholtz frequency of the period Tc which is a typical meniscus vibration characteristic as described below.
[0061]
The representative value of the vibration characteristics of the meniscus will be described below.
[0062]
The ink jet recording head configured as shown in FIG. 1 has a compliance Ci due to the compressibility of the ink in the pressure generating chamber 3, an elastic plate 8 forming the pressure generating chamber 3, a nozzle plate 1, and a flow path configuration. Assuming that the rigidity compliance of the material such as the plate 7 itself is Cv, the inertance of the nozzle opening 2 is Mn, and the inertance of the ink supply port 4 is Ms, the Helmholtz resonance period Tc of the ink flow path is
Tc = 2π × √ ((Mn + Ms) / ((Ci + Cv) (Mn × Ms)))
Can be represented by
[0063]
Here, the compliance Ci is as follows, where V is the volume of the pressure generating chamber 3, ρ is the density of the ink, and c is the sound velocity in the ink.
Ci = V / (ρc ^Two )
It is.
[0064]
The rigidity compliance Cv of the pressure generating chamber 3 matches the static deformation rate of the pressure generating chamber 3 when a unit pressure is applied to the pressure generating chamber 3.
[0065]
To give a specific example, when the pressure generating chamber 3 having a length of 0.5 to 2 mm, a width of 0.05 to 0.2 mm, and a depth of 0.05 to 0.3 mm is formed, the Helmholtz resonance period is 5 to 20 μs (resonance). An inkjet recording head having a frequency of about 50 to 200 kHz) can be configured.
[0066]
The representative values shown above are largely related to the behavior characteristics of the residual vibration of the meniscus after ink droplet ejection.
[0067]
As shown in FIG. 4, the meniscus after the ejection of the ink droplet has a small vibration cycle (T) and a large cycle (Tm).
[0068]
As described above, the effect of the third pulse is most effective when the meniscus is drawn into the pressure generating chamber 3 side. For this reason, the timing of the third pulse at which the vibration of the meniscus can be effectively suppressed exists in a very small cycle T.
[0069]
That is, the third pulse is applied after a lapse of time corresponding to the oscillation period of T from the time of ink droplet ejection (that is, the time pw4 from the start of the second pulse to the start of the third pulse in FIG. 3 is substantially equal to T). Means that the meniscus can be effectively damped.
[0070]
The minute oscillation period (T) of the meniscus is the above-mentioned Helmholtz resonance period (Tc), that is, if the minute resonance period Tc can be confirmed by the above-described formula, the optimal third pulse application timing is easy. Can be set to
[0071]
The inventor has investigated the resonance period Tc of the ink jet recording head and the optimum application timing of the third pulse.
[0072]
FIG. 5 is a diagram showing the relationship between the resonance period Tc and the optimum application timing of the third pulse for stabilizing the ejection of ink droplets in the ink jet recording apparatus according to one embodiment of the present invention. In the figure, the optimum application timing of the third pulse is indicated by a time pw4 from the start of the second pulse to the start of the third pulse.
[0073]
As is apparent from FIG. 5, the resonance period Tc and the optimum application timing (pw4) of the third pulse are almost the same, and in the present invention, the Helmholtz resonance period (Tc), which is a representative value of the meniscus vibration characteristics, is set to It can be seen that the means to use makes it possible to easily determine and set the optimal application timing of the third pulse.
[0074]
If the duration pw3 of the third pulse is not the same as the duration pw2 of the second pulse, the resonance cycle Tc and pw4 do not match, but pw4 is a value slightly shifted with respect to the resonance cycle Tc. As long as the shift amount can be grasped, it is easy to set the resonance period Tc to a representative value.
[0075]
Next, the applied potential of the third pulse will be described.
[0076]
Regarding the applied potential (V3) of the third pulse, any applied potential may not be used. Depending on the vibration state of the meniscus after ink ejection, there is an applied potential appropriate to attenuate the vibration (see FIGS. 9 and 10 described later).
[0077]
For this reason, even if the third pulse is applied at the optimal timing, if the applied potential (V3) is inappropriate, the meniscus may not be sufficiently attenuated. This will be described below.
[0078]
FIG. 8 is a second diagram illustrating the relationship between the driving pulse of the ink jet recording head and the behavior of the meniscus in the ink jet recording apparatus according to one embodiment of the present invention.
[0079]
When the applied potential (V3) is too small, the oscillation of the meniscus is not sufficiently reduced as shown in the figure, and the effect of the third pulse is reduced by half (the dashed line in FIG. 8).
[0080]
Conversely, if the amount of applied potential (V3) is unnecessarily large, the third pulse will generate a vibrant vibration rather than attenuate the vibration of the meniscus, resulting in an adverse effect (see FIG. 8 dotted line).
[0081]
As a result, as in the case where the application timing is not appropriate, the formation of the meniscus during the ejection of the ink droplet becomes unstable, and the mist is likely to be generated in the ejected ink droplet, and the ejection of the ink droplet is likely to cause bending or ejection blur.
[0082]
For the above reasons, in order to effectively attenuate the meniscus with the third pulse, it is necessary to carefully set not only the application timing but also the applied potential (V3).
[0083]
Therefore, as described below, the present inventor experimentally investigated the optimum applied potential of the third pulse and decided based on it.
[0084]
The present inventor has investigated the optimal applied potential of the third pulse.
[0085]
FIG. 9 is a diagram showing the applied potential of the third pulse and the ink ejection state in the ink jet recording apparatus according to one embodiment of the present invention.
[0086]
In the figure, the applied potential (V3) is indicated by an applied potential ratio (V3 / V1) with respect to the peak potential (V1), and shows the ejection state of the ink droplet under the maximum driving frequency at each applied potential ratio.
[0087]
In this investigation, an inkjet recording head having a Helmholtz resonance period (Tc) of Tc = 6.0 μs was used, and the duration (pw2) of the second pulse was changed to pw2 = 3 μs, 9 μs, and 18 μs, and the meniscus after ink ejection was changed. The relationship between the applied potential ratio and the ejection state was arranged for each case by changing the vibration energy amount.
[0088]
As is clear from the figure, it is necessary to apply a third pulse at an optimum applied potential ratio for each pw2 in order to stably eject ink droplets. The shorter the pw2 is, the more the ink ejection energy becomes. It was found that it was necessary to increase the applied potential ratio as the vibration energy of the meniscus increased.
[0089]
Further, it was also confirmed that if the applied potential ratio was too high, rather than attenuating the meniscus vibration as described above, a vibrant vibration would be generated, which would have an adverse effect.
[0090]
Based on the above investigation results, the optimum applied potential of the third pulse was confirmed.
[0091]
In the head of this embodiment, the applied potential ratio is preferably set between 0.1 and 0.3. When the duration (pw2) of the second pulse is 3 μs, the applied potential ratio is about 0.2. ~ 0.3 is optimal.
[0092]
By the way, the vibration of the meniscus is, as defined by the above-mentioned equation, the compliance due to the compressibility of the ink, the rigidity of the pressure generating chamber 3 and the shape of the ink flow path such as the nozzle opening 2 and the ink supply port 4. The vibration period and vibration amplitude change with the change in inertance due to the size.
[0093]
The main factors that cause these fluctuations are variations in the shape of the ink flow path in manufacturing and changes in the environmental temperature. In particular, when the environmental temperature changes, not only the physical properties of the ink but also the pressure generation chamber 3 Since the stiffness of the constituent materials also changes, the fluctuation is relatively large.
[0094]
For this reason, the resonance oscillation period Tc and the oscillation energy change, and accordingly, the optimum application timing and applied potential of the third pulse also change.
[0095]
The inventor has investigated the optimum application timing of the third pulse and the change of the applied potential due to the environmental temperature.
[0096]
FIG. 6 is a diagram showing the relationship between the resonance period Tc and the ambient temperature in the ink jet recording apparatus according to one embodiment of the present invention. FIG. 7 is a diagram showing the relationship between the ambient temperature and the application timing of the optimal third pulse for stabilizing the ejection in the ink jet recording apparatus according to one embodiment of the present invention.
[0097]
Obviously, as the environmental temperature increases, the resonance period Tc also increases, and the optimum third pulse application timing pw4 changes accordingly.
[0098]
That is, if the driving is performed with the application timing fixed at a certain value, if the resonance period Tc changes due to a change in the environmental temperature, the optimal meniscus vibration is not performed and the ink droplet ejection becomes unstable. There is a possibility that it will be.
[0099]
On the other hand, the present inventor also investigated the relationship between the ambient temperature and the optimal applied potential of the third pulse.
[0100]
FIG. 10 is a second diagram showing the applied potential of the third pulse and the ink ejection state under each temperature environment in the ink jet recording apparatus according to one embodiment of the present invention. The way of reading the figure conforms to FIG.
[0101]
The figure shows the results of investigations at various environmental temperatures under high temperature (40 ° C.), normal temperature (25 ° C.), and low temperature (15 ° C.).
[0102]
As is clear from the figure, the optimum applied potential ratio (V3 / V1) at which the ink is stably ejected differs depending on the environmental temperature, and it is desirable that the higher the temperature, the higher the applied potential.
[0103]
This is because the viscosity of the ink changes depending on the temperature, and the attenuation state of the meniscus vibration changes.
[0104]
In other words, when the temperature is high, the viscosity of the ink decreases and the vibration of the meniscus after the ink discharge becomes more intense. Therefore, it is necessary to apply a higher applied potential to attenuate the ink. Since the viscosity is increased and the vibration of the meniscus after ink ejection is reduced, the meniscus can be sufficiently attenuated by applying a small applied potential.
[0105]
However, if added too much, stable ejection cannot be ensured.
[0106]
As is clear from the investigation results, the applied potential ratio of the third pulse is about 0.5 μs or more (that is, the applied potential of the third pulse is lower than the applied potential of the first pulse) from low temperature to high temperature. Becomes higher), the ink is not discharged stably. Therefore, it is preferable that the applied potential of the third pulse be lower than the applied potential of the first pulse.
[0107]
On the basis of the above investigation results, in the present embodiment, the environmental temperature detecting means 140 is provided, thereby detecting the environmental temperature, and the driving pulse output from the driving pulse generating means 130 through the driving pulse controlling means 130. The application timing and applied potential of the third pulse are changed.
[0108]
Specifically, when the environmental temperature is high, the application timing pw4 is long, and the applied potential ratio (V3 / V1) is large. When the environmental temperature is low, the application timing pw4 is short and the applied potential ratio is small.
[0109]
In the case of the ink jet recording head of FIGS. 7 and 10, as shown in FIG.
At low temperature (15 ° C) → normal temperature (25 ° C) → high temperature (40 ° C)
V3 / V1 = 0.15 → 0.25 → 0.35
pw4 = 6.0 μs → 7.0 μs → 8.0 μs
It is better to change.
[0110]
In the figure, both V3 / V1 and pw4 are linearly changed with respect to temperature, but the same effect can be obtained by changing stepwise in a certain temperature range.
[0111]
By the way, when changing the applied potential ratio, the duration of the third pulse was set to be the same as the duration of the second pulse, and was constant regardless of the environmental temperature.
[0112]
This is because, as described above in the description of the application timing, the meniscus vibrations caused by both pulses are generated at almost the same period by applying the pulses with the same duration, and both vibrations have the opposite phases. This is because, in the event that the duration of both pulses is not the same, the meniscus is more effectively damped than when the durations of both pulses are not the same.
[0113]
For this reason, the third pulse is determined by the duration of the second pulse, and it is desirable that the duration be constant even if the applied potential changes due to the environmental temperature.
[0114]
As described above, in the present embodiment, the third pulse is applied for the same duration as the second pulse, and both the application timing and the applied potential are adjusted according to the environmental temperature, so that the third pulse is generated by the ejection of the ink droplet. Even if the vibration of the meniscus changes due to the environmental temperature, the third pulse can cause the pressure generation chamber 3 to expand again with the optimum expansion amount at the stage where the meniscus has moved to the most. Can be effectively attenuated.
[0115]
As a result, the ink droplet ejection instability caused by poor attenuation of the kinetic energy of the meniscus is suppressed under any environmental temperature environment, and the meniscus is stopped at a fixed position regardless of the repetition frequency due to the rapid stop of the meniscus. The flying speed is stabilized because the ink droplets are ejected in the state where the ink droplets are ejected. Therefore, stable ejection can be ensured even at a high driving frequency.
[0116]
Finally, the operation at the time of preparation for printing start and at the time of printing end will be described.
[0117]
Before the printing is started, the driving pulse is charged to the potential (V3), and the piezoelectric vibrator 9 is slightly contracted to stand by until a printing signal is sent. The time required for charging to the potential (V3) may be such that ink droplets are not ejected by the drive, and there is no problem if the time is about the duration of the third pulse.
[0118]
On the other hand, when the print signal is no longer input, the drive pulse is discharged by a predetermined pulse from the potential (V3) to make the potential zero. There is no problem with this required time as long as ink droplets are not ejected by the drive.
[0119]
Although all the above embodiments have been described using an example of an ink jet recording head using a piezoelectric vibrator that contracts by charging, a piezoelectric vibrator of a longitudinal effect that expands by charging or a piezoelectric vibrating plate that bends and deforms into a unimorph or bimorph type. It is clear that the same effect is obtained when used.
[0120]
【The invention's effect】
As described above, according to the present invention, based on the environmental temperature and the duration of the second pulse, First pulse And a drive pulse control means for determining the applied potential of the third pulse based on the applied potential ratio, so that the vibration behavior of the meniscus is influenced by the environmental temperature and the continuation of the second pulse. Even if it changes with time, it is possible to apply vibration damping with an optimal amount of application. As a result, the vibration of the meniscus can be effectively attenuated, and stable ejection of ink droplets can be ensured regardless of the ambient temperature and the inclination of the second pulse.
[0121]
In addition, the rapid stopping of the meniscus allows the ink droplet to be ejected in a state where the meniscus is stopped at a fixed position even at a high driving frequency, so that the flying speed is stable, and the meniscus recovery time is shortened. The frequency is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an ink jet recording head used in an ink jet recording apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating an ink jet recording apparatus according to one embodiment of the present invention.
FIG. 3 is a diagram illustrating a driving pulse formation of an ink jet recording head in an ink jet recording apparatus according to an embodiment of the present invention.
FIG. 4 is a second diagram illustrating the relationship between the driving pulse of the ink jet recording head and the behavior of the meniscus in the ink jet recording apparatus according to one embodiment of the present invention.
FIG. 5 is a diagram illustrating a relationship between a resonance period Tc and an application timing of an optimal third pulse for stabilizing ejection of ink droplets in the ink jet recording apparatus according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a relationship between a resonance cycle Tc and an ambient temperature in the ink jet recording apparatus according to one embodiment of the present invention.
FIG. 7 is a diagram illustrating a relationship between an environmental temperature and an application timing of an optimal third pulse for stabilizing ejection in an inkjet recording apparatus according to an embodiment of the present invention.
FIG. 8 is a second diagram illustrating the relationship between the driving pulse of the ink jet recording head and the behavior of the meniscus in the ink jet recording apparatus according to one embodiment of the present invention.
FIG. 9 is a diagram showing an applied potential of a third pulse and an ink ejection state in the ink jet recording apparatus according to one embodiment of the present invention.
FIG. 10 is a second diagram illustrating an applied potential of a third pulse and an ink ejection state in the inkjet recording apparatus according to the embodiment of the present invention.
FIG. 11 is a diagram illustrating a setting table of an ambient temperature and an application potential of a third pulse, and a setting table of an environmental temperature and an application timing of a third pulse in the inkjet recording apparatus according to the embodiment of the present invention.
[Explanation of symbols]
1 Nozzle plate
2 Nozzle opening
3 Pressure generating chamber
4 Common ink chamber
5 Ink supply port
6 Ink channel
7 Flow path configuration plate
8 Elastic plate
9 Piezoelectric vibrator
10 Fixed board
100 inkjet recording head
110 Driving nozzle selection means
120 Drive pulse generating means
130 Drive pulse control means
140 Environmental temperature detection means

Claims (6)

A pressure generating chamber communicating with a common ink chamber through a nozzle opening and an ink supply port and having a Helmholtz resonance frequency of a period Tc; and a piezoelectric vibrator in contact with the pressure generating chamber; An ink jet recording head that expands and contracts the pressure generating chamber by contracting and expanding the child,
A first pulse for expanding the pressure generating chamber, a second pulse for contracting the expanded pressure generating chamber to eject ink droplets from the nozzle openings, and the pressure generating chamber after the second pulse. Driving pulse generating means for outputting a third pulse for expanding the pressure again;
The applied potential ratio between the first pulse and the third pulse is determined based on the environmental temperature detected by the environmental temperature detecting means and the duration of the second pulse, and the third pulse is determined based on the applied potential ratio. Drive pulse control means for determining the applied potential of
An inkjet recording apparatus comprising: The duration of the second pulse and the duration of the third pulse are set to be the same, and the time from the start of the second pulse to the start of the third pulse is equal to the resonance cycle Tc of the pressure generation chamber. 2. The ink jet recording apparatus according to claim 1, wherein the times are set to be substantially the same. 2. The ink jet recording according to claim 1, wherein the time from the start of the second pulse to the start of the third pulse is set to be long when the environmental temperature is high and to be short when the environmental temperature is low. apparatus. 2. The ink jet recording apparatus according to claim 1, wherein the drive pulse control means controls the third pulse start timing based on an environmental temperature. 2. The ink jet recording apparatus according to claim 1, wherein an applied potential of the third pulse is lower than an applied potential of the first pulse. 2. The ink jet recording apparatus according to claim 1, wherein the duration of the third pulse is constant irrespective of the environmental temperature.

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