JP2001010049A - Method and apparatus for driving ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow high image quality and rapid recording to be compatible by preparing a driving voltage waveform to be applied to a vibration generating means for generating a pressure change in a pressure generating chamber in response to a diameter of a discharging ink droplet, and applying the waveform corresponding to ink droplets having different diameters at a predetermined time difference. SOLUTION: A driving voltage waveform is prepared in response to a diameter of a discharging ink droplet. That is, driving voltage waveform generators 41A to 41C for generating driving voltage waveforms for a small-diameter ink droplet, an intermediate-diameter ink droplet and a large-diameter ink droplet are provided, and connections of lines 44A to 44C to a piezoelectric vibrator 36 are switched by a switching circuit 43 provided between the lines 44A to 44C and the vibrator 36. Thus, discharging timing of the droplet in the waveform for discharging the droplet having the smallest diameter is fastened earlier than that of the waveforms having the other diameters to always discharge the droplet at suitable speed, thereby improving an image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for driving an ink-jet recording head in an ink-jet recording apparatus for recording characters and drawings on a recording medium such as paper by discharging fine ink droplets from nozzles.

[0002]

2. Description of the Related Art An actuator such as a piezoelectric vibrator is used to expand and contract a pressure generating chamber filled with ink.
A so-called drop-on-demand type ink jet recording apparatus that discharges ink droplets from the tip of a nozzle formed in a pressure generating chamber by a change in internal pressure is disclosed in, for example, Japanese Patent Publication No. 53-12138 and Japanese Patent Application Laid-Open No. 10-193587.
It is known in Japanese Patent Publication No.

FIG. 6 is a front view illustrating an example of a recording head of an ink jet recording apparatus known in the above-mentioned publications and the like.
FIG. 7 is a side view of the recording head of FIG. A plurality of pressure generating chambers 31 to be filled with ink are arranged side by side in a direction perpendicular to the plane of FIG. Behind the pressure generating chamber 31, each pressure generating chamber 3
1 are provided with a common ink tank 33, and are connected to the respective pressure generating chambers 31 by an ink supply path 34 so as to communicate with each other. Piezoelectric vibrators 36 for expanding and contracting each of the pressure generating chambers 31 are arranged in a comb blade shape corresponding to each of the pressure generating chambers 31. Further, a vibration plate 35 that is vibrated by driving the piezoelectric vibrator 36 is provided between the piezoelectric vibrator 36 and the pressure generating chamber 31.

When the piezoelectric vibrator 36 is driven, the vibration plate 35
Is vibrated to expand or contract the pressure generating chamber 31. Thus, the ink filled in the pressure generating chamber 31 is ejected from the opening of the nozzle 32 as an ink droplet 37.

[0005] By the way, from the demand for improvement of the recording image quality, it is required that this type of ink jet recording head also perform high-quality recording image quality.
It is necessary to express a smooth halftone. The method of performing gradation recording includes a method of forming one pixel (pixel) with a plurality of droplets while fixing the ink droplet diameter, and a method of changing the ink droplet diameter in multiple steps. There are two known methods for changing the concentration every time.

In order to obtain high image quality by the former method, it is necessary to extremely increase the recording resolution, and thus the number of dots required for recording is greatly increased, and the recording speed is disadvantageously reduced. On the other hand, in the latter method, since the density can be changed for each dot, there is an advantage that high image quality can be obtained at a relatively low recording resolution and the recording speed can be increased.

In order to change the ink droplet diameter in multiple stages, a plurality of types of drive voltage waveforms as shown in FIG. FIG. 9 is a graph showing driving voltage waveforms for generating three types of ink droplets of small diameter, medium diameter, and large diameter. FIG.
(B) is for medium diameter ink drops, and (c) of FIG. 9 is for large diameter ink drops. In FIGS. 9B and 9C, parts corresponding to the respective parts in FIG.
The same reference numerals as in (a) are used, and “′” or “″” is added to the right shoulder of the reference numerals.

In FIG. 9, the pressure generating chamber 31 expands at a voltage change portion where the graph is directed downward (portions indicated by reference numerals 51 and 53), and the pressure is increased at a voltage change portion where the graph is directed upward (portions indicated by 52 and 54). The generation chamber shrinks. As shown in FIG. 9 (c), the pressure generating chamber 31 is contracted for a relatively long time t3 ", the contracted state of the pressure generating chamber 31 is maintained for a relatively long time t4", and thereafter, the pressure generating chamber 31 is relatively long. When the pressure generating chamber 31 is expanded over time t7 ″, a large-diameter ink droplet is ejected from the nozzle opening.

On the contrary, as shown in FIG.
When the pressure generating chamber 31 is contracted in a short time t3 from the expanded state and switched to the expanded state in a short time, a small diameter ink droplet is ejected from the nozzle opening. FIG. 9B shows FIG.
FIG. 9B is an intermediate state between FIG. 9A and FIG. 9B, in which a medium diameter ink droplet is ejected from the nozzle opening. The method of changing the diameter of the ink droplet by changing the drive voltage waveform in this manner is also described in Japanese Patent Laid-Open No. Hei 10-193587 described above as a so-called meniscus control method.

However, since a large number of pressure generating chambers are closely arranged in parallel in the ink jet recording head as described above, and the piezoelectric vibrators are also provided in close proximity, vibration caused by driving of the piezoelectric vibrators is obtained. However, there is a problem that it is difficult to eject ink droplets of a desired diameter due to interference. In particular, as shown in FIG.
Are simultaneously driven (the direction in which the longitudinal vibration of the piezoelectric vibrator 36 is applied is indicated by an arrow), and the supporting member 37 provided between the piezoelectric vibrators 36 for supporting the piezoelectric vibrator 36 is vibrated as shown in FIG. In the direction indicated by the arrow. This deformation affects the other pressure generating chambers 31 and causes vibration loss, and the diameter and ejection speed of the ink droplets A vary for each nozzle 32, so that a high-quality recorded image cannot be obtained.

In order to solve such a problem of so-called crosstalk, the piezoelectric vibrator support member and the pressure generating chamber are so arranged that the piezoelectric vibrator does not affect other pressure generating chambers or cause vibration loss. In addition, it is preferable that members constituting the ink jet recording head be formed of a material having high rigidity. However, when the ink jet recording head is formed of a material having high rigidity, there is a problem that processing is difficult, the ink jet recording head becomes large, and the cost increases.
In Japanese Patent Application Laid-Open No. Hei 10-193587, adjacent piezoelectric vibrators are alternately driven in order to solve the problem of crosstalk. However, such a method has a problem that the recording time becomes longer. .

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and solves the problem of structural crosstalk of an ink jet recording head and does not increase the printing speed. An object of the present invention is to provide a driving method and a driving apparatus of an ink jet recording head capable of achieving both high image quality and high speed recording.

[0013]

According to a first aspect of the present invention, there is provided a pressure generating chamber, comprising: a plurality of pressure generating chambers filled with ink; and a nozzle provided in the pressure generating chamber to discharge the ink. A driving voltage waveform applied to the vibration generating means, wherein the driving voltage waveform applied to the vibration generating means is provided in correspondence with each of the pressure generating chambers and a vibration generating means for causing a pressure change in the pressure generating chamber. In this method, the drive voltage waveforms corresponding to the ink droplets having different diameters are prepared at predetermined time intervals according to the diameters of the ink droplets to be ejected.

According to this method, a drive voltage waveform is generated in accordance with the ink droplet, and the drive voltage waveform is applied to the vibration generating means provided for each pressure generating chamber with a time difference. Therefore, when an ink droplet is ejected from one of the pressure generating chambers, the vibration does not affect the other pressure generating chamber, so that an ink droplet having a desired diameter is generated in each of the pressure generating chambers, and a desired speed is obtained. It becomes possible to discharge from the nozzle. Further, since the drive voltage waveform is generated according to the ink droplet, it is possible to eject ink droplets of different diameters one after another in a very short time, and the recording time is not unnecessarily extended.

According to a second aspect of the present invention, there is provided a method of setting the drive voltage waveform such that an ink droplet having a smaller droplet diameter is ejected earlier. An ink droplet having a smaller droplet diameter has a smaller mass and is more affected by air resistance, and it takes a longer time to reach a recording medium. According to this method, the smaller the ink droplet diameter, the earlier the ink droplet is ejected. Therefore, it is possible to reduce the variation in the landing time on the recording medium due to the difference in the droplet diameter and improve the recording image quality. .

According to a third aspect of the present invention, there is provided a method as described above, wherein the driving voltage waveform at the time of discharging a small-diameter ink droplet includes one that draws a meniscus of a nozzle portion toward the pressure generating chamber before discharging the ink droplet. According to this method, it is possible to obtain ink droplets having a desired diameter with high accuracy, and to improve the recording image quality.

According to a fourth aspect of the present invention, a plurality of pressure generating chambers, an ink discharge nozzle provided in communication with the pressure generating chambers, and a vibration for changing the internal pressure of the pressure generating chambers are provided. A driving means for applying a driving voltage waveform to the vibration applying means, and ejecting ink droplets from the nozzles by the driving voltage waveform, wherein the diameter of the ejected ink droplet And a plurality of waveform generating means for generating the driving voltage waveform according to the diameter of the ink droplet. The driving voltage waveform corresponding to the ink droplet diameter generated by the waveform generating means is The driving voltage waveform is set so as to be generated at different ejection timings due to the difference in the driving voltage.

According to this configuration, a drive voltage waveform is generated according to the ink droplet, and the drive voltage waveform is applied to the vibration generating means provided corresponding to each pressure generating chamber with a time difference. Therefore, when an ink droplet is ejected from one of the pressure generating chambers, the vibration does not affect the other pressure generating chamber, so that an ink droplet having a desired diameter is generated in each of the pressure generating chambers, and a desired speed is obtained. It becomes possible to discharge from the nozzle. Further, since the drive voltage waveform is generated according to the ink droplet, it is possible to eject ink droplets of different diameters one after another in a very short time, and the recording time is not unnecessarily extended.

According to a fifth aspect of the present invention, the vibration applying means is a piezoelectric vibrator. When the vibration applying means is a piezoelectric vibrator, the size of the device can be reduced, and the generation of pressure waves in the pressure generating chamber can be controlled with high accuracy.

According to a sixth aspect of the present invention, the piezoelectric vibrator generates longitudinal vibration. As described above, by using the vertical vibration type piezoelectric vibrator, the size of the vibrator can be reduced as compared with the bending vibration type vibrator, and the nozzles can be arranged with high density.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and apparatus for driving an ink jet recording head according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a graph showing a driving voltage waveform according to the first embodiment of the method for driving an ink jet recording head of the present invention. FIG. 1A shows a driving voltage waveform for discharging a small-diameter ink droplet, and FIG. FIG. 1B shows a driving voltage waveform for ejecting a medium diameter ink droplet, and FIG. 1C shows a driving voltage waveform for ejecting a large diameter ink droplet.

The first feature of the recording method of the present invention is that a drive voltage waveform is prepared according to the droplet diameter of the ink droplet to be ejected, and the drive voltage waveform is generated so that the ejection timing of the ink droplet differs at different droplet diameters. It is in the point which did. The second feature is that the ejection timing of the ink droplet in the drive voltage waveform for ejecting the ink droplet having the smallest droplet diameter is earlier than the ejection timing of the drive voltage waveform of the ink droplet of another diameter.

As shown in the graph of FIG. 1A, when a small diameter ink droplet is ejected, the voltage V1 (V1 = 15) is applied.
V) to reduce the volume of the pressure generating chamber for time t1 (t2 = 2
(t2 = 4 μs), and then a voltage V2 (V2 = 10 V) is applied to contract rapidly at t3 (t3 = 2 μs). After maintaining the contracted state for t4 hours (t4 = 0.3 μs), t
After 5 hours (t5 = 2 μs), the voltage V3 (V3 = 15V) is applied to rapidly expand the volume of the pressure generating chamber 31 again. Then, the expanded state is maintained for time t6 (t6 = 8 μs), and the applied voltage is slowly returned to the reference voltage Vb (Vb = 20 V) at time t7 (t7 = 30 μs).

In the voltage change portion 11 at time t1 in the graph, the meniscus is rapidly drawn into the nozzle, and a concave meniscus is formed. In the drive voltage waveform of this embodiment, it was confirmed that the center of the meniscus was pulled to a position of about −50 to −45 μm at time t = t1 + t2. In the voltage change portion 12 at the time t3, a narrow liquid column is formed at the center of the concave meniscus by rapidly contracting the pressure generating chamber. In the voltage change portion 13 at the time t6, the meniscus is rapidly pulled back, so that the leading end of the liquid column separates early, and a small-diameter ink droplet is ejected.

In the drive voltage waveform of this embodiment, the time from the application of the voltage change (pressure change) to the start of the ejection of the small diameter ink droplet is t1 + t2 = 6 μs, and the voltage change related to the ejection ends. The time te (ejection timing) until the operation is completed is about 10.3 μs. In this embodiment, the droplet diameter is about 20 μm according to the driving voltage waveform of FIG.
m ink droplets were ejected at a droplet speed of 6 m / s.

As shown in FIG. 1B, when a medium diameter ink droplet is ejected, the ink droplet is miniaturized by meniscus control in the same manner as when a small diameter ink droplet is ejected. In the drive voltage waveform shown in FIG. 1B, the voltage V1 '
(V1 '= 15V) and t1' time (t1 '= 2
μs), the volume of the pressure generating chamber is rapidly expanded, and this state is maintained for a time t2 ′ (t2 ′ = 4 μs).
2 ′ (V2 ′ = 20 V) is applied and t3 ′ time (t3 ′
= 2 μs), the volume of the pressure generating chamber is rapidly contracted.

After time t4 '(t4' = 8 .mu.s), the applied voltage is slowly returned to the reference voltage Vb (Vb = 20 V) at time t7 '(t7' = 30 .mu.s). Each voltage change portion 11 ', 1 shown in the graph of FIG.
Reference numerals 2 'and 14' denote voltage changing portions 11, 12, and 14 in FIG. 1A when forming small-diameter ink droplets, respectively.
Corresponding to

Compared with the drive voltage waveform for discharging the small diameter ink droplet (FIG. 1A), the voltage change portion 1
Since the expansion of the pressure generating chamber immediately after 2 'is not as abrupt as when a small-diameter ink droplet is generated, the discharge amount of the ink droplet increases, and as a result, the diameter of the ink droplet increases. In the drive voltage waveform for the medium diameter ink droplet of the present embodiment, an ink droplet having a droplet diameter of about 30 μm was ejected at a droplet speed of 6 m / s (in the case of single nozzle ejection).

In the driving voltage waveform for a medium-diameter ink droplet of this embodiment, the time t0 'until the start of ejection is about 11 μm.
Since it is set to s, the voltage change (pressure change) for ejecting the medium diameter ink droplet starts after the ejection of the small diameter ink droplet ends (t0 '> te).

Therefore, even if there is a pressure generating chamber 31 for discharging medium-sized ink drops around the pressure generating chamber 31 for discharging small-sized ink drops, the drop velocity of the small-sized ink drops due to structural crosstalk. Of the ink droplets, and the occurrence of ejection failure can be prevented, and high stability can be achieved in the ejection of small-diameter ink droplets.

As shown in FIG. 1C, the driving voltage waveform for discharging a large-diameter ink droplet has a voltage V2 ″ (V
2 "= 22 V), the pressure generating chamber is contracted in a rising time (t3" = 10 [mu] s) longer than that for small and medium diameter ink droplets, and this state is maintained for t4 time (t4 = 15 [mu] s). Thereafter, the applied voltage is slowly returned to the reference voltage Vb (Vb = 20 V) at time t7 ″ (t7 ″ = 30 μs). In the drive voltage waveform of FIG.
A 0 μm ink droplet was ejected at a droplet speed of 7 m / s (single nozzle ejection).

In the driving voltage waveform for the large-diameter ink droplet, since t0 ″ = 11 ″ μs, the voltage change (pressure change) starts only after the ejection of the small-diameter ink droplet is completed. Pressure generating chamber 3 for ejecting small diameter ink droplets
Even if there is a pressure generating chamber 31 for discharging large-diameter ink droplets around 1, there is no reduction in the droplet speed of small-diameter ink droplets due to structural crosstalk, and no defective discharge occurs.

Next, the configuration of a driving device for applying the driving voltage waveform described in the above invention to the piezoelectric vibrator according to the ink droplet diameter will be described with reference to FIG. The driving voltage waveforms for the small-diameter ink droplet, the medium-diameter ink droplet, and the large-diameter ink droplet are respectively formed by separate waveform generating circuits 41.
A, 41B and 41C. The driving voltage waveform generated by each of the waveform generating circuits 41A, 41B, 41C is:
The driving voltage waveforms are the same as those shown in FIGS. Each of the drive voltage waveforms generated by each of the waveform generating circuits 41A, 41B, 41C is amplified by the amplifier circuit 42 and transmitted to the lines 44A, 44B, 44C.

Each piezoelectric vibrator 36 and lines 44A, 44
A switching circuit 43 is provided between B and 44C,
This switching circuit 43 is connected to the lines 44A, 44B, 4
The connection between 4C and the piezoelectric vibrator 36 is switched. And
The switching circuit 43 is connected to the line 4 based on the image data.
By switching between 4A, 44B, and 44C, the drive voltage waveform applied to each piezoelectric vibrator 36 is switched, and the diameter of the ink droplet ejected from the nozzle is switched, thereby performing gradation recording.

FIG. 3 is a view for explaining the operation of the driving device shown in FIG. 2. In FIG. 3, small, medium and large ink droplets A,
It is a side view which shows the state which discharged B and C. When the ejection of the small-diameter ink droplet A is performed based on the drive voltage waveform generated by the waveform generation circuit 41A (the state of FIG. 3A), the ejection is performed based on the drive voltage waveform generated by the waveform generation circuits 41B and 41C. As a result, the piezoelectric vibrator 36 is driven, and ink droplets B and C having medium and large diameters are simultaneously ejected from the nozzle 32 (FIG. 3B).

In this embodiment, the small diameter ink drop A, the medium diameter ink drop B, and the large diameter ink drop C
It is possible to always stably discharge at a driving frequency of 0 KHz, and even if the number of piezoelectric vibrators 36 to be driven at the same time or the discharge pattern is changed, there are no fluctuations in droplet speed and defective discharge that affect the recording image quality. It was confirmed that it did not occur.

On the other hand, a recording experiment was carried out using the conventional waveform (time, each parameter is the same as the waveform in FIG. 1) shown in FIG. 9 with the ink jet recording apparatus used in this embodiment. The ejection state of A clearly deteriorates. In particular, in an image pattern portion in which small-diameter ink droplet A, medium-diameter ink droplet B, and large-diameter ink droplet C are mixed, the landing position of small-diameter ink droplet A Large deviation or small diameter ink drop A
It was confirmed that ejection failure occurred.

In the conventional driving voltage waveform shown in FIG. 9, this is within the time (0 ≦) until the small diameter ink droplet A is ejected.
In a time range of t ≦ te), a voltage change (pressure change) for ejecting the medium-diameter ink droplet B and the large-diameter ink droplet C occurs, so that structural crosstalk greatly influences. is there. The ejection timings of the large-diameter ink droplets and the medium-diameter ink droplets shown in FIGS. 1B and 1C are shifted only by about 11 μs as compared with the conventional driving voltage waveform (FIG. 6). Has almost no effect on the ejection frequency. Specifically, stable ejection is possible even at the same drive frequency as the limit ejection frequency (15 KHz) in the conventional drive voltage waveform.

As described above, by using the driving method and the driving device of the present invention, it is possible to prevent the ejection of small-diameter ink droplets from becoming unstable due to structural crosstalk without lowering the ejection frequency. High quality image recording at high speed is possible. The drive voltage waveform when performing the droplet diameter modulation using the present invention is not limited to the drive voltage waveform shown in the present embodiment.

For example, even in the drive voltage waveform for a large-diameter ink droplet, a voltage changing process for making the meniscus slightly concave immediately before ejection may be added. Further, in the driving voltage pattern for medium-sized ink droplets of the present embodiment, the droplet diameter is made larger than that of the small-sized ink droplet without expanding the pressure generating chamber 31 immediately after the voltage change portion 12 '. By setting the change time (t1 ') large, it is also possible to increase the droplet diameter. It is also possible to increase the drop diameter without using meniscus control.

In this embodiment, the number of droplet diameter modulation steps is described as three, large, medium, and small. However, the number of droplet diameter steps is not limited to this, and two or four or more droplet diameter steps are set. Is also good. Further, in the present embodiment, the drive voltage waveform is set such that the small-diameter ink droplet is ejected before the medium-diameter ink droplet and the large-diameter ink droplet. The ejection timing of the ink droplets may be arranged after the ejection of the medium diameter ink droplets and the large diameter ink droplets. However, small-diameter ink droplets are more susceptible to air resistance than large-diameter ink droplets and medium-diameter ink droplets, and the droplet deposition time is likely to be slower. It is desirable to perform this before discharging large diameter ink droplets.

In this embodiment, the drive voltage waveform is set so that only small-diameter ink droplets are hardly affected by structural crosstalk. However, the small-diameter ink droplet and the medium-diameter ink droplet are set at the same ejection timing. Alternatively, the drive voltage waveform may be set so as to shift only the ejection timing of a large-diameter ink droplet that most easily causes structural crosstalk.

[Second Embodiment] FIG. 4 is a graph showing a driving voltage waveform according to a second embodiment of the driving method of the present invention, and FIG. 4 (a) is for discharging a small diameter ink droplet. 4 (b) is for ejecting medium diameter ink droplets, and FIG. 4 (c) is for ejecting large diameter ink droplets. In the second embodiment, a small diameter ink droplet is about 20 μm in diameter, and a medium diameter ink drop is about 30 μm in diameter.
m, a large diameter ink droplet was about 40 μm.

If the ejection timing is shifted according to the droplet diameter as in the present embodiment, there is an advantage that the maximum instantaneous current required for driving the piezoelectric vibrator can be reduced, and the cost of the drive circuit system can be reduced. The feature of the drive voltage waveform of the present embodiment is that all the ejection timings of the small-diameter ink droplet, the medium-diameter ink droplet, and the large-diameter ink droplet are set to be shifted.

The shapes and functions of the drive voltage waveforms for the small-diameter ink droplet, the medium-diameter ink droplet, and the large-diameter ink droplet are basically the same as those shown in FIG. However, in the graph of FIG. 4, the voltage change start time (t0 ′) of the driving voltage waveform for the medium diameter ink droplet (graph (b)) is 5 μs, and the driving voltage waveform for the large diameter ink droplet ((c)). The difference from the first embodiment (graph in FIG. 1) is that the voltage change start time (t0 ″) in the graph (graph) is set to be 13 μs.

In the drive voltage waveform for the medium-diameter ink droplet of the present embodiment, t0 '= 5 μs, so that the pressure generating chamber 31 is contracted by the voltage changing portion 22' at the timing of the small-diameter ink. This is after the application of the voltage for drop ejection (voltage change portions 11 to 13) is completed. Therefore,
Even if there is a pressure generating chamber for discharging medium-sized ink drops around the pressure generating chamber for discharging small-sized ink drops, the drop speed of small-sized ink drops may be reduced due to structural crosstalk,
Discharge failure can be prevented from occurring. It is possible to obtain high stability in discharging small diameter ink droplets.

In the driving voltage waveform of the present embodiment, the meniscus control process (voltage change portion 21 ') of the medium diameter ink droplet is performed during the discharge of the small diameter ink droplet. It is somewhat affected by crosstalk. However, since the voltage changing portion 21 'displaces the pressure actuator in the direction of expanding the pressure generating chamber, the structural crosstalk acts in the direction of increasing the droplet speed of the small diameter ink droplet. Therefore, the influence on the image quality can be suppressed as compared with the drop in the droplet speed of the small diameter ink droplet and the occurrence of the ejection failure.

In the drive voltage waveform for a large diameter ink droplet, t
Since 0 ″ = 13 μs, the voltage change is started only for the voltage change for discharging the small-diameter ink droplet and the medium-diameter ink droplet (the voltage change portions 21 to 23 and the voltage change portions 21 ′ to 21 ′). FIG. 5 is a side view of the recording head showing a state in which ink droplets are ejected from the nozzle 32. As shown in FIG. Ink drops A, B, C in order of diameter and diameter
Is discharged. Therefore, even if there is a pressure generating chamber 31 for discharging a large-diameter ink drop C around the pressure generating chamber 31 for discharging a small-diameter ink drop A or a medium-diameter ink drop B, the small-diameter ink The drop speed of the drop A and the medium diameter ink drop B does not decrease, and ejection failure does not occur.

Also in this embodiment, the drive voltage waveforms for the small-diameter ink droplet A, the medium-diameter ink droplet B, and the large-diameter ink droplet C are individually generated as shown in FIG. Generated by the circuits (41A, 41B, 41C). Then, gradation recording was executed by switching the drive voltage waveform applied to each piezoelectric vibrator 36 based on the image data. As a result, it was confirmed that stable ejection can always be performed at a driving frequency of 0.1 to 10 KHz, and no problem such as ejection failure occurs at all.

In the second embodiment, a small-diameter ink droplet A, a medium-diameter ink droplet B, and a large-diameter ink droplet C are ejected in this order, but structural crosstalk is prevented. Need not necessarily be discharged in this order.
However, since the influence of the structural crosstalk becomes more remarkable as the diameter of the ejected ink droplets becomes smaller, it is desirable to set so that the smaller the ejected droplet diameter is, the faster the ejection is performed, as in the present embodiment.

Although the embodiments have been described above, the present invention is not limited to the above embodiments.
For example, in the above embodiment, the laminated piezoelectric vibrator 36 in the longitudinal vibration mode using the piezoelectric constant d33 as the vibration generating means.
However, other types of piezoelectric generators, such as a longitudinal vibration mode vibration generator using a piezoelectric constant d31, a single-plate type piezoelectric vibrator, and a flexural vibration mode piezoelectric vibrator, may be used.

In the above embodiment, a Kaiser type ink jet recording head as shown in FIG. 6 was used.
The present invention can be similarly applied to an ink jet recording head having another structure such as a recording head in which a groove provided in a piezoelectric vibrator is used as a pressure generating chamber.

Further, the present invention can be applied to an ink jet recording head using an actuator other than the piezoelectric vibrator, for example, an actuator using electrostatic force or magnetic force. Further, in the above-described embodiment, an ink jet recording apparatus that performs recording of characters and figures by discharging colored ink on recording paper has been described as an example. However, the present invention is not limited to recording of characters and figures on recording paper. The ink is not limited to the colored ink.

[0054]

According to the present invention, a drive voltage waveform is generated in accordance with the diameter of an ink droplet, and the drive voltage waveform is applied to a vibration generating means provided for each pressure generating chamber with a time difference. As a result, when an ink droplet is ejected from one of the pressure generating chambers, the vibration does not affect the other pressure generating chamber, so that an ink droplet having a desired diameter is generated in each pressure generating chamber. It is possible to discharge from the nozzle at a speed of. Therefore, the recording image quality can be improved.

Further, since the drive voltage waveform is generated according to the ink droplet, it is possible to eject ink droplets of different diameters one after another in a very short time. Therefore, the recording time is not extended more than necessary.

[Brief description of the drawings]

FIG. 1 shows a driving method according to a first embodiment of the present invention,
1A is a driving voltage waveform for discharging a small-diameter ink droplet, FIG. 1B is a driving voltage waveform for discharging a medium-diameter ink droplet, and FIG. 1C is a large-diameter ink droplet. 6 is a graph showing a drive voltage waveform for causing the ejection of the ink.

FIG. 2 is a block diagram illustrating a driving path of an inkjet recording head according to an embodiment of the recording head of the present invention.

FIG. 3 is an explanatory view of the operation of the driving device of FIG. 2 and is a side view showing a state in which small-, medium-, and large-diameter ink droplets are ejected from nozzles.

FIG. 4 is a diagram illustrating a driving method according to a second embodiment of the present invention;
4A is a driving voltage waveform for discharging a small-diameter ink droplet, FIG. 4B is a driving voltage waveform for discharging a medium-diameter ink droplet, and FIG. 4C is a large-diameter ink droplet. 6 is a graph showing a drive voltage waveform for causing the ejection of the ink.

FIG. 5 is a side view of the recording head showing a state where ink droplets are ejected from nozzles.

FIG. 6 is a front view of an ink jet recording head according to a conventional example of the invention.

FIG. 7 is a side view of the recording head of FIG.

FIG. 8 is a side view of the recording head of FIG. 6, showing a state where adjacent piezoelectric vibrators are simultaneously driven.

9A and 9B are graphs showing driving voltage waveforms for generating three types of ink droplets of small diameter, medium diameter, and large diameter, wherein FIG. 9A is for a small diameter ink droplet, and FIG. FIG. 9C is for an ink droplet having a large diameter.

[Explanation of symbols]

Reference Signs List 31 pressure generating chamber 32 nozzle 33 ink chamber 34 ink supply path 35 diaphragm 36 piezoelectric vibrator (vibration generating means) 41A, 41B, 41C waveform generating circuit (waveform generating means) 42 amplifying circuit 43 switching circuit A, B, C ink drop

Claims (6)

[Claims] 1. A plurality of pressure generating chambers filled with ink, a nozzle provided in the pressure generating chamber, from which the ink is discharged, and a plurality of pressure generating chambers provided corresponding to each of the pressure generating chambers. In a method of driving an ink jet recording head having a vibration generating means for causing a pressure change, a drive voltage waveform applied to the vibration generating means is prepared according to a diameter of an ink droplet to be ejected, and ink droplets having different diameters are prepared. Wherein the drive voltage waveform corresponding to the above is applied with a predetermined time difference. 2. The method according to claim 1, wherein the drive voltage waveform is set such that the smaller the ink droplet diameter, the earlier the ink droplet is ejected. 3. The driving voltage waveform when a small-diameter ink droplet is ejected includes one that pulls a meniscus of a nozzle portion toward a pressure generating chamber before ejecting the ink droplet.
Or the driving method of the inkjet recording head according to 2. 4. A plurality of pressure generating chambers, an ink discharge nozzle provided in communication with the pressure generating chambers, and vibration applying means for applying vibration for changing the internal pressure of the pressure generating chambers. A driving voltage waveform is applied to the vibration applying means, and the driving voltage waveform ejects ink droplets from the nozzles. The driving device of the ink jet recording head is provided in accordance with the diameter of the ejected ink droplet. A plurality of waveform generating means for generating the drive voltage waveform corresponding to the diameter of the droplet, wherein the drive voltage waveform corresponding to the diameter of the ink droplet generated by the waveform generating means has different ejection timings depending on the difference of the ink droplet. A driving device for an ink jet recording head, wherein the driving voltage waveform is set so as to generate. 5. The driving apparatus according to claim 4, wherein the vibration applying unit is a piezoelectric vibrator. 6. The driving apparatus according to claim 5, wherein the piezoelectric vibrator generates longitudinal vibration.