JPH1170655A - Ink jet printer and method of driving recording head for ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer and a method of driving a recording head for an ink jet printer, which can appropriately control the flying speed of ejected ink droplets. SOLUTION: A nozzle opening for discharging ink droplets, an ink chamber communicating with the nozzle opening, an ink supply path for supplying ink to the ink chamber, and a piezoelectric element for expanding and contracting the ink chamber according to an applied voltage. Prepare. A first step (A to B) in which the ink chamber is expanded to draw meniscus in the nozzle opening toward the ink chamber, and a second step (B) in which the ink chamber is filled with ink and the meniscus is moved in the direction of the nozzle opening.
To C) and a third stroke (CD) in which the ink chamber is contracted to eject ink droplets, the change in the meniscus position and the periodic position change at the start of the third stroke. By appropriately selecting the speed, the size and the flying speed of the ink droplet ejected in the third stroke are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer for ejecting ink droplets from nozzle openings to record on a recording sheet and a method of driving a recording head for the ink jet printer.

[0002]

2. Description of the Related Art In recent years, an ink jet printer which discharges ink droplets from a nozzle opening communicating with an ink chamber and performs recording on recording paper has become widespread. In this type of printer, a method of stably reducing the ink droplet size for higher resolution, and a method of changing the ink droplet size between dots for expressing an intermediate gradation image have been studied. I have.

As one method for reducing the ink droplet size, an ink chamber is expanded so that a position of a tip of the ink called a meniscus in the nozzle is once drawn toward the ink chamber, and the meniscus is returned to the original position. A method has been proposed in which the ink chamber is contracted before returning to eject ink droplets from the nozzle openings.

For example, Japanese Patent Laying-Open No. 55-17589 proposes a method in which ink is ejected by a process of driving the displacement from the initial state to the direction of increasing the inner volume of the ink chamber and restoring the ink state to the initial state. . This publication describes that the particle diameter (droplet diameter) can be changed by changing the displacement amount (increase displacement amount of the inner volume of the ink chamber) in the suction stroke.

For example, Japanese Patent Laid-Open Publication No. Hei 2-6137 proposes a method of controlling the ink droplet size by changing the applied voltage when the pressure in the ink chamber is once reduced and then restored to the initial state. .

[0006] For example, see Japanese Patent Application Laid-Open No. 59-143652.
In the publication, a method of controlling an ink droplet size by applying an auxiliary pulse before a main pulse for discharging an ink droplet and changing a meniscus position in a nozzle is proposed.

For example, Japanese Patent Application Laid-Open No. Hei 5-16359 proposes a method of controlling an ink droplet size by applying an auxiliary pulse and then applying a main pulse in accordance with the cycle of a residual pressure wave in the ink chamber. ing.

On the other hand, in this type of ink jet printer, the recording head ejects ink droplets while moving in a direction perpendicular to the paper feed direction.
When the flying speed of the ejected ink droplets varies, the landing positions of the ink droplets also vary, and as a result, the quality of the recorded image is significantly deteriorated. Therefore, it is important to keep the flying speed of the ink droplet constant in order to obtain a high-quality recorded image.

The recording head is normally controlled so as to reciprocate at a constant speed by using a head carriage driving motor or the like. However, speed fluctuation due to mechanical factors and deviation of the distance from the recording head to the landing point are caused. Etc. may occur. In this case, an error occurs at the landing point of the ink droplet ejected from the recording head, which may be a factor that hinders high-quality image expression. Therefore, in order to correct these error factors, it is advantageous if the flying speed of the ink droplet can be appropriately controlled.

In this type of recording head, as described above, the ink chamber is once expanded, the meniscus position in the nozzle is once drawn in the direction of the ink chamber, and then the ink chamber is contracted to eject ink droplets. In this case, a vibration called Helmholtz's natural vibration occurs in the ink chamber along with the driving of the piezoelectric vibrating plate, and the position of the meniscus once drawn in the direction of the ink chamber is also adjusted. Vibrates at the frequency of natural vibration. For this reason,
The time at which the ink chamber is contracted greatly affects not only the size of the ink droplet but also the flying speed. Therefore, conventionally, various methods of driving the recording head which are hardly affected by such natural vibration have been studied.

For example, in the specification of US Pat. No. 4,646,106, there is proposed a driving method in which the ink chamber is contracted at the time when the leading end position of the ink is most retracted to discharge the ink droplet.

[0012] For example, Japanese Patent Application Laid-Open No. 8-26739 proposes an ink jet recording apparatus in which ink droplets are ejected within a period of 2/3 times the natural oscillation period of the meniscus.

[0013]

However, the above-mentioned Japanese Patent Application Laid-Open No. 55-17589 merely suggests that the droplet diameter can be changed by changing the displacement in the suction stroke. It is not clear how to specifically control the ink droplet size, and it is difficult to properly control the ink droplet size.

The method described in Japanese Patent Laid-Open No. 2-6137 controls the ink droplet size by changing the applied voltage when the pressure in the ink chamber is once reduced and then restored to the initial state. There is no suggestion about the control of the pull-in position of the ink tip in consideration of the ink filling, and it is practically difficult to accurately control the ink droplet size.

In each of the methods described in JP-A-59-143652 and JP-A-5-16359, a main pulse is applied after adjusting an ink tip position in a nozzle by an auxiliary pulse. is necessary. In this case, the pulse width of the auxiliary pulse and its peak value,
Alternatively, since the meniscus position changes depending on the time interval between the auxiliary pulse and the main pulse, it is necessary to adjust these parameters. Moreover, in the former publication, the relationship between the auxiliary pulse and the position of the ink droplet size is unclear, and in the latter publication, the relationship between the fluctuation cycle of the ink position and the ink droplet size is described. However, there is no specific description of the relationship between the ink tip position drawn into the nozzle and the ink droplet size, and it has been difficult in practice to appropriately control the ink droplet size by these methods. .

As described above, in the conventional ink jet printer, it is difficult to accurately control the ink droplet size, and it is not easy to improve the image quality such as high resolution and halftone image expression. .

Also, the above-mentioned US Pat. No. 4,646,106 is disclosed.
Although the method described in the specification and JP-A-8-267739 does not consider the meniscus position change speed or phase, it considers the existence of the natural vibration of the meniscus, It has been difficult to control the flying speed of the droplets sufficiently accurately to maintain a constant value. In addition, these proposals are to perform the ejection operation within a very limited range of the natural vibration of the meniscus, so that the obtained flying speed is naturally limited, and it is difficult to arbitrarily control the flying speed.

Further, the size of the ink droplet and the flying speed are simultaneously controlled, for example, by controlling the image density and gradation while correcting the landing position deviation caused by the instability of the running speed of the recording head as described above. It was difficult to do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet printer and a method of driving a recording head for an ink jet printer, which can appropriately control the size and the flying speed of the ejected ink droplet. Is to provide.

[0020]

An ink jet printer according to the present invention comprises a nozzle opening for discharging ink droplets, an ink chamber communicating with the nozzle opening, and an ink supply path for supplying ink to the ink chamber. A piezoelectric element for expanding or contracting the ink chamber in accordance with an applied voltage, and a first step of expanding the ink chamber by the piezoelectric element to draw the ink tip in contact with the outside air through the nozzle opening toward the ink chamber. A second step in which the ink is supplied from the ink supply path to the ink chamber to advance the tip end of the ink in the direction of the nozzle opening, and an ink droplet is ejected from the nozzle opening by contracting the ink chamber by the piezoelectric element. An ink jet printer comprising: a stroke control means for controlling a third stroke; By appropriately setting the position and periodic position change rate of the definitive ink tip, which is constituted so as to control the size and the flying speed of ink droplets ejected in the third step. The stroke control means can also control the size and the flying speed of the ink droplet by controlling the contraction amount and contraction speed of the ink chamber in the third stroke.

Here, the stroke control means, for example, changes the drawing amount of the ink tip portion in the first stroke while keeping the required time of the second stroke constant, and makes the drawing amount of the ink tip portion in the first stroke constant. In either case, the time required for the second stroke is changed while changing the amount of ink drawn in the first end and the time required for the second stroke. The position of the part and the periodic position change speed can be set appropriately. In particular, the stroke control means can perform the stroke control so that the periodic position change speed of the ink leading end portion at the start of the third stroke is constant. Further, the stroke control means sets the phase of the periodic position change of the ink tip portion at the start of the third stroke as appropriate to set the periodic position change speed of the ink tip portion at the start of the third stroke. In particular, by making the phase of the periodic position change of the ink tip at the start of the third stroke constant, the rate of change of the periodic position of the ink tip at the start of the third stroke can be reduced. It is possible to make it constant.

A method of driving a recording head for an ink jet printer according to the present invention comprises a nozzle opening for discharging ink droplets, an ink chamber communicating with the nozzle opening, and an ink supply path for supplying ink to the ink chamber. And a piezoelectric element for expanding or contracting an ink chamber according to an applied voltage, wherein the piezoelectric element expands the ink chamber to contact the outside air through a nozzle opening. A first step of drawing the ink tip toward the ink chamber, a second step of supplying the ink from the ink supply path to the ink chamber to advance the ink tip toward the nozzle opening, Controlling a third step of ejecting ink droplets from the nozzle openings by contracting the nozzles. By appropriately setting the position and periodic position change velocity of the ink tip at the beginning, but which is adapted to control the size and the flying speed of ink droplets ejected in the third step.

In the method of driving an ink jet printer or a recording head for an ink jet printer according to the present invention, the position of the ink tip and the periodic position change speed at the start of the third stroke, ie, at the start of ejection, are appropriately set. , The size and flying speed of the ink droplets are controlled. The position of the ink tip portion and the periodic position change speed at the start of the third stroke are, for example, the first
By changing at least one of the amount of ink drawn in at the stroke and the time required for the second stroke,
Set arbitrarily. In particular, when the periodic position change speed of the ink tip portion at the start of the third stroke is constant, the flying speed of the ink droplet is constant. The periodic position change speed of the ink tip at the start of the third stroke is set, for example, by the phase of the periodic position change of the ink tip at the start of the third stroke. By setting this phase to be constant, the periodic position change speed of the ink tip at the start of the third stroke is made constant.

[0024]

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

[First Embodiment] FIG. 1 shows a schematic configuration of a main part of an ink jet printer according to an embodiment of the present invention. The method of driving the recording head for an ink jet printer according to the embodiment of the present invention is embodied by the ink jet printer according to the present embodiment, and will be described below.

The ink jet printer 1 has a recording head 11 for discharging ink droplets onto a recording sheet 2 for recording, an ink cartridge 12 for supplying ink to the recording head 11, a position of the recording head 11, and recording. A head position / paper feed controller 13 for controlling the paper feed of the paper 2; a head controller 14 for controlling the ink droplet ejection operation of the recording head 11 by a head drive signal; and performing predetermined image processing on input image data. An image processing unit 15 that supplies the recording data to the head controller 14 and a system controller 16 that controls the head position / paper feed controller 13, the head controller 14, and the image processing unit 15 are provided. Here, the head controller 14 corresponds to “stroke control means” in the present invention.

FIG. 2 shows a perspective cross-sectional structure of the recording head 11 in FIG. 1, and FIG. 3 shows a cross-sectional structure of the recording head 11 in FIG. 2 viewed from the direction of arrow Z (FIG. 2). As shown in these drawings, the recording head 11 includes a nozzle plate 111a, a flow path plate 111b, and a vibration plate 111c which are sequentially stacked. These plates are made of, for example, glass or stainless steel, and are attached to each other by a method such as bonding with an adhesive (not shown) or melting and pressing the glass. In addition, these plates may be formed integrally.

On the upper surface side of the flow path plate 111b in the figure,
A concave portion is selectively formed, and the concave portion and the vibration plate 111c constitute a plurality of ink chambers 113 and a common flow channel 117 communicating with these ink chambers. The communicating portion between the common flow channel 117 and each of the ink chambers 113 is a squeezed channel, and has a structure in which the width of the flow channel increases from here toward the direction of each of the ink chambers 113. The portion of each ink chamber 113 on the side opposite to the side communicating with the common flow channel 117 has a structure in which the width of the flow channel gradually narrows, and the flow channel plate 111b at the end thereof is punched in the thickness direction. Channel hole 114 is provided. The passage hole 114 communicates with a minute nozzle opening 115 formed in the lowermost nozzle plate 111a, and an ink droplet is ejected from the nozzle opening 115. That is, each nozzle opening 1
The channel holes 14 and the ink chambers 113 are provided as a set for each of the 15 holes. Here, the ink chamber 113 corresponds to the “ink chamber” in the present invention, the tip of the nozzle opening 115 corresponds to the “nozzle opening” in the present invention, and the common flow channel 117 corresponds to the ink supply path in the present invention. I do.

As shown in FIG. 3, a lower electrode 121, a piezoelectric element (piezo element) 122 and an upper electrode 1 are formed on the vibration plate 111c in the area where each ink chamber 113 is formed.
23 are sequentially stacked. When the voltage of the head drive signal input from the head controller 14 of FIG. 1 is applied between the lower electrode 121 and the upper electrode 123, the piezoelectric element 122 bends and the volume of the ink chamber 113 increases (expands). Or decrease (shrink). Here, the piezoelectric element 122 corresponds to the “piezoelectric element” in the present invention.

In this embodiment, the recording head 11 includes
The plurality of nozzle openings 115 are arranged in two rows in a staggered (alternate) manner. Nozzle openings 115 in each row
Are equally spaced. Each nozzle opening 115 in one row
And the ink chambers 113 corresponding to the respective nozzle openings 115 in the other row,
5 are provided on opposite sides with respect to each other, forming a staggered arrangement. The nozzle openings 115 may be arranged at equal intervals only on a straight line, instead of being arranged in two lines in a staggered manner as described above.
Other arrangements may be used.

The common flow channel 117 communicates with the ink cartridge 12 shown in FIG. The ink cartridge 12 always supplies ink to each of the ink chambers 113 via the common flow channel 117 at a constant speed. The supply of the ink can be performed by using, for example, a capillary phenomenon. Alternatively, the ink may be supplied by providing a predetermined pressurizing mechanism in the ink cartridge 12 and pressurizing the ink. The recording head 11 records an image on the recording paper 2 by ejecting ink droplets while reciprocating in a direction perpendicular to the paper feeding direction of the recording paper 2 by a carriage driving motor (not shown) and a carriage mechanism associated therewith. It has become.

FIG. 4 shows the head controller 1 shown in FIG.
4 represents the circuit configuration of FIG. As shown in this figure, the head controller 14 is composed of a microprocessor or the like and controls the entire head controller 14, and a ROM (Read Only Memory) storing a program executed by the main controller 141. ) 142,
A work memory 143 composed of a RAM (Random Access Memory) or the like, which is used for predetermined calculations or temporary data storage by the main control unit 141, a drive voltage waveform storage unit 144 composed of a nonvolatile memory, and a timer function A counter 145, a digital / analog (D / A) converter 146 for converting digital data read from the drive voltage waveform storage section 144 into analog, and a D / A
And an amplifier 147 for amplifying the output of the converter 146 and outputting it as a head drive signal.

The drive voltage waveform storage section 144 stores data indicating a voltage waveform of a head drive signal for driving the recording head 11 (hereinafter, referred to as waveform data). This waveform data includes various types of drive voltage waveforms corresponding to the size and the flying speed of the ink droplet for forming each pixel dot, and more specifically, the lower electrode 121 and the upper electrode 121 in FIG. This is a digitized waveform of a voltage (waves A to E in FIG. 5A to be described later) applied to the electrode 123 and driving the piezoelectric element 122. Although only one head drive signal output from the head controller 14 is shown in FIG. 4, it actually corresponds to the number of the nozzle openings 115 (that is, the number of the piezoelectric elements 122) in FIG. A number of head drive signals are output in parallel.

The counter 145 is used as a reference clock for the operation timing of the printer by the system controller 16.
The timer is reset by a discharge timing clock (not shown) input from the controller, counts up from this reset point, and sends a time-up signal to the main controller 141 after a predetermined time determined by the above-mentioned waveform data has elapsed. Output. The time-up signal serves as a start trigger of the first stroke, as described later.

Next, the operation of the ink jet printer having the above configuration will be described.

First, the basic operation of the recording head 11 will be described with reference to FIG. Here, FIG. 5A shows an example of a driving voltage waveform applied between the lower electrode 121 and the upper electrode 123 of the recording head 11, and FIG. 5B shows main points A to F of the driving voltage waveform. 5C shows the state of the nozzle opening 115 at each of the points A to F. FIG. In FIG. 5C, the nozzle opening 115 is drawn upward for convenience of explanation.

Here, three operation steps of the recording head 11 will be defined. In FIG. 5A, first, the process of changing the drive voltage from the first voltage V1 to the voltage 0 (from A to B
Is the first step, and the time required for this is t1. Also, the process of waiting while holding the voltage 0 (from B to C)
Is the second step, and the time required for this is t2. Further, the process of changing the voltage from 0 to the second voltage V2 (from C to D) is referred to as a third process, and the time required for the process is referred to as t3. In the following description, the first voltage V1 is referred to as a pull-in voltage, and the second voltage V2 is referred to as an ejection voltage. In the present embodiment, the required time t3 in the third process
And the discharge voltage V2 is kept constant.

The recording head 11 is driven at a constant frequency (for example, about 1 to 10 kHz), and the ejection timing cycle T of the ink droplet (that is, the ejection timing clock of the ejection timing clock) corresponds to the driving frequency. period)
Is determined. Time points C and G, which are the start points of the third stroke, are synchronized with the above-described ejection timing clocks, and the first and second strokes are performed prior to each of these ejection timing clocks. I have.

First, at and before the time point A, as shown in a state P _A of FIG. 5B, the application of the voltage V1 to the piezoelectric element 122 causes the vibrating plate 112c to be slightly bent inward and to stand still. The ink chamber 113 is in a contracted state. At time A, the position of the meniscus (ink tip) in the nozzle opening 115 is as shown in FIG.
As shown in the state M _A , the nozzle opening 115 is located at the same position as the end of the nozzle opening 115 (hereinafter, referred to as an opening end).

Next, when the first step of reducing the drive voltage from the voltage V1 at the time A to the voltage 0 at the time B is performed, the voltage applied to the piezoelectric element 122 becomes 0,
2c there is no deflection of the ink chamber 113 is expanded (the state P _B in Figure 5 (b)). Therefore, the nozzle opening 11
Meniscus within 5 is drawn towards the ink chamber 113, the point B, for example retracted to the state of the M _B in FIG. 5 (c) (i.e., away from the open end).

However, the position of the meniscus thus pulled in thereafter vibrates in a waveform such as that shown in FIG. 7 described later. This is because, even after the voltage applied to the piezoelectric element 122 changes from V1 to 0, the deflection amount of the vibration plate 112c does not immediately become zero and stops, and the property of the ink filling the ink chamber 113 is not changed. This is because a minute vibration displacement of a specific frequency determined by the above remains.

FIG. 7 shows how the meniscus position changes after the pull-in operation of the first stroke.
This is an actual measurement value when the pull-in voltage V1 is 20 volts and the required pull-in time (that is, the required time of the first step) t1 is 7 μsec. However, this experiment was performed with the supply of ink to the ink chamber 113 stopped for convenience. Here, the horizontal axis represents the elapsed time when the start time of the first stroke is set to 0, and the unit is μsec. The vertical axis represents the meniscus position (displacement amount from the opening end) and is set to an arbitrary unit. From this figure, it is understood that the meniscus does not stop immediately at the end of the first stroke, but gradually attenuates while vibrating at a constant cycle. This vibration cycle is equal to the above-described vibration cycle of the vibration plate 112c, and is a unique value determined from the structure, material, properties of the ink, and the like of the ink chamber 113, and thus can be determined in advance by experiments. .

Next, during the time t2 from the time point B to the time point C, a second step of fixing the driving voltage to 0 and keeping the volume of the ink chamber 113 constant is performed. However, during this time, since the ink supply from the ink cartridge 12 is continuously performed, the meniscus position in the nozzle opening 115 is gradually displaced toward the opening end, and at the time C, for example, as shown in FIG. It advanced to the state of the M _C. In addition, since the meniscus is displaced at the natural oscillation period as shown in FIG. 7 described above, the position of the meniscus is eventually changed by the overlap of these two types of displacement, for example, as shown in FIG.
A locus as shown in (a) is drawn. In FIG. 10A, the horizontal axis represents time, and the vertical axis represents the position of the meniscus (the amount of displacement from the opening end). As shown in the figure, the meniscus position is rapidly displaced in the direction of the ink chamber 113 from the start of the retraction in the first stroke, and then gradually moves toward the opening end while vibrating at a constant cycle. It shows.

Next, a third step of rapidly increasing the drive voltage from the voltage 0 at time C to the ejection voltage V2 at time D is performed. This time point C is synchronized with the above-described ejection timing pulse (not shown). In this case, since a large discharge voltage V2 to the piezoelectric element 122 at the time point D is applied, the vibration plate 112c bends greatly inwardly as shown in state P _D of FIG. 5 (b), the ink chamber 113 is abruptly contracted I do. Therefore, as shown in state M _D in FIG. 5 (c),
The meniscus in the nozzle opening 115 is pushed at a stroke toward the opening end, and is discharged as an ink droplet from here. The ejected ink droplet flies in the air, and forms a recording sheet 2 (FIG. 1, FIG. 1).
(Fig. 2).

Thereafter, the driving voltage is reduced again to V1, and the vibration plate 112c is slightly bent inward to an initial state (state P _{E in} FIG. 5B), and this state is changed to the first state in the next ejection cycle. Maintain until the start point F of one stroke. At the time E immediately reduced to a driving voltage again V1, a state as shown in state M _E, substantially corresponding amount corresponding meniscus position in the drop volume ejected retracted shown in FIG. 5 (c) made but, by the filling of the ink thereafter performed (refilling), the meniscus position of the first stroke start point F of the next dispensing cycle, as shown in state M _F in FIG. 5 (c), the same as the open end Recover to position. The state at this time is the same as the state M _A at the time point A.

Thus, one cycle of the discharging operation is completed. Hereinafter, by repeating such a cycle operation in parallel for each nozzle opening 115, image recording on the recording paper 2 (FIGS. 1 and 2) is continuously performed.

Next, based on some experimental data, the relationship between the meniscus position and meniscus speed and the size and flight speed of the ink droplet will be considered, focusing on the natural vibration of the meniscus.

First, the relationship between the pull-in voltage V1 and the pull-in amount in the first step will be described with reference to FIG.

FIG. 6 shows the results of an experimental example for examining the relationship between the pull-in voltage V1 of the meniscus and the time required for the meniscus to advance. Here, the time required for the meniscus to advance is defined as the nozzle opening 1 by the pull-in voltage V1.
It is the time required for the meniscus drawn in the direction of the ink chamber 113 to advance again by ink supply and reach the open end. In this figure, the horizontal axis represents the pull-in voltage V1, and the unit is volt. The vertical axis represents the time required for advance, and the unit is microsecond (μsec). The experimental results show that the time required for pull-in, that is, the time corresponding to the required time t1 of the first step in FIG.
ec.

As is apparent from this figure, the increment of the required advance time increases almost in proportion to the pull-in voltage V1. Since the ink supply speed can be considered to be constant, it can be seen from the results of FIG. 6 that the meniscus position immediately after the drawing-in, that is, the meniscus drawing-in amount is determined according to the level of the drawing-in voltage V1. This means that the meniscus position at the time of ejection (at the start of the third stroke) can be indirectly adjusted by the pull-in voltage V1.

Next, the relationship between the natural vibration of the meniscus and the size and flying speed of the ink droplet will be described with reference to the experimental results shown in FIGS.

FIG. 7 shows the meniscus position after the pull-in time, while changing the required time t2 of the second stroke (ie, the time from the time of the meniscus pull-in of the first stroke to the start of the third stroke (discharge operation)). And the state of change in the diameter of the ejected ink droplets. In this figure, the horizontal axis represents the elapsed time when the start time of the first stroke is set to 0, and the vertical axis represents the ink droplet diameter (unit: μm) in addition to the meniscus position.
In this figure, a black triangle (▲) indicates a meniscus position, and a cross (x) indicates an ink droplet diameter.

FIG. 8 shows the result when the change in the flying speed of the ink droplet is examined while changing the required time t2 in the second stroke. In this figure, the horizontal axis represents the elapsed time (unit: μsec) when the start time of the first stroke is set to 0, and the vertical axis represents the flight of the ink droplet obtained when the third stroke is started at each elapsed time. Speed (unit: m / sec (meter / second)).

FIG. 9 is a superposition of FIGS. 7 and 8, wherein the horizontal axis represents the elapsed time when the start time of the first stroke is set to 0, and the vertical axis represents the meniscus position at each elapsed time. , And the diameter and flying speed of the ink droplet obtained when the third stroke is started at each elapsed time. In FIG. 9, a black triangle (▲) indicates the meniscus position, a cross (x) indicates the ink droplet diameter, and a black circle (●) indicates the flying speed of the ink droplet. 7 to 9
As shown in (2), the elapsed time from the end of the meniscus pull-in (here, when 7 μsec has elapsed) is the second elapsed time.
This is the required time t2 of the process.

As is apparent from FIG. 7, the deeper the meniscus position at the start of the third stroke, the smaller the diameter of the ejected ink droplet. For example, when the meniscus position is (−38), the ink droplet diameter is about 20 μm, and when the meniscus position is (−32), the ink droplet diameter is about 40 μm. Further, as is apparent from FIG. 8, the flying speed of the ink droplet changes at a substantially constant oscillation cycle. Further, as is apparent from FIG. 9, the flying speed of the ink droplet started the third stroke at the moment when the meniscus position was displaced the fastest in the pull-in direction (when the inclination of the meniscus position displacement curve became a negative maximum). In contrast, the maximum value is obtained, and conversely, the minimum value is obtained when the third stroke is started at the moment when the meniscus position is displaced fastest in the ejection direction (when the inclination of the meniscus position displacement curve becomes a positive maximum). That is, the fluctuation period of the flying speed of the ink droplet is the same as the period of the displacement speed of the meniscus, and the phase of both is approximately 1
It can be seen that the angle is shifted by 80 ° (ie, 周期 cycle). Also, from FIG. 9, three timings at which the flying speed of the ink droplet takes a substantially constant value (7 to 8 m / s) (12, 24, and 38 μsec after the start of pull-in)
It can be seen that the ink droplet diameters take different values, and that the longer the elapsed time, the larger the ink droplet diameter.

The above fact will be described conceptually with reference to FIG. Here, FIG. 10A shows a change curve of the meniscus position when ink is supplied as described above. FIG. 10B shows a meniscus position change speed curve obtained by differentiating the meniscus position change curve of FIG. 10A once. The horizontal axis represents time, and the vertical axis represents the meniscus position change speed (hereinafter, referred to as the meniscus position change speed). , Simply referred to as meniscus velocity). Here, the speed in the ink droplet ejection direction is defined as a (+) direction, and the speed in the meniscus pull-in direction is defined as a (-) direction. Further, FIG.
(B) represents the change in the flying speed of the ink droplet obtained when the third stroke is started at each point on the meniscus position change speed curve, in which the horizontal axis represents the start timing of the third stroke, and the vertical axis represents Represents the flying speed of the ink droplet. FIG. 10D shows a change in ink droplet size obtained when the third stroke is started at several points on the meniscus position change speed curve shown in FIG. The axis represents the start timing of the third stroke, and the vertical axis represents the ink droplet diameter. In these figures, both the horizontal axis and the vertical axis are expressed in arbitrary units.

As shown in FIG. 10B, the meniscus velocity changes at a specific oscillation period, and the amplitude of the change gradually decreases. Correspondingly, as shown in FIG. 10C, the flying speed of the ink droplet also changes at the same cycle as the oscillation cycle of the meniscus speed, and the change amplitude gradually attenuates.
Here, the phase of the change of the flying speed of the ink droplet is shifted from the phase of the change of the meniscus speed by about 周期 cycle, as described in FIG. For this reason, the flying speed of the ink droplet is smaller when discharging when the meniscus position changes in the pull-in direction than when discharging when the meniscus position changes in the discharging direction. However, it turns out that it becomes larger. Moreover,
The higher the speed of change in the pull-in direction, the higher the flying speed of the ink droplet. For example, when the meniscus velocity becomes maximum in the pull-in direction (for example, points P1 and P
When the third stroke is started at 2, P3, P4, etc., the flying speed of the ink droplets reaches a maximum value (for example, points Q1, Q2,
Q3, Q4, etc.), and conversely, the point in time at which the meniscus velocity becomes maximum in the ejection direction (for example, points P5, P6, P7, etc.)
When the third step is started, the flying speed of the ink droplet takes a minimum value (for example, points Q5, Q6, Q7, etc.).

As described above, the flying speed of the ink droplet is the third speed.
It can be seen that it is directly related to the meniscus velocity at the start of the stroke. Therefore, by appropriately setting (or selecting) the meniscus speed at the start of the third stroke, the flying speed of the ink droplet can be accurately controlled. In particular, the start point of the third stroke is the timing at which the meniscus velocity has a maximum value in the pull-in direction (either the point P1 or the point P2 in FIG. 10B).
If the first step is started so as to coincide with the above, it is possible to increase the flying speed of the ink droplets and to make the flying speed constant.

As described with reference to FIG. 9, the size of the ink droplet depends on the meniscus position at the start of the third stroke, and the smaller the meniscus is, the smaller the ink droplet size is. Therefore, for example, the timing Q at which the flying speeds of the ink droplets are maximized,
Since the meniscus position in 1, Q2, Q3, Q4, etc. changes from a deep position to a shallow position in order with the lapse of time as shown in FIG. The size of the ink droplet becomes larger as the ejection timing is later (S1 in FIG. 10D).
To S4). At the timing P8 when the meniscus speed becomes zero for the first time, the flying speed of the ink droplet is medium (Q8 in FIG. 10 (c)). The size is minimal.

As described above, the meniscus position after the retraction in the first stroke oscillates and changes at a specific period, and the size of the ejected ink droplet depends on the meniscus position at the start of the third stroke. Is dependent on the meniscus velocity at the start of the third stroke. Therefore, by appropriately setting (selecting) the meniscus position and the flying speed at the start of the third stroke while considering the natural vibration of the meniscus position, it is possible to arbitrarily and accurately control the size and the flying speed of the ink droplet. You can do it.

Incidentally, as described above, the size of the ink droplet depends on the meniscus position at the start of the third stroke.
The meniscus position at the start of the third stroke depends on the pull-in amount of the first stroke. That is, even if the time (the required time t2 of the second stroke) from the end of the first stroke attraction to the start of the third stroke is the same, the amount of attraction of the first stroke is changed to change the amount of the third stroke. The meniscus position at the start can be appropriately selected. On the other hand, the flying speed of the ink droplet changes according to the meniscus speed at the start of the third stroke as described above, and the amplitude of the meniscus speed changes depending on the amount of pull-in in the first stroke. Therefore, even if the time from the end of the first stroke pull-in to the start of the third stroke is the same, the meniscus speed at the start of the third stroke can be appropriately selected by changing the amount of pull-in in the first stroke. Can be. Therefore, the size and the flying speed of the ink droplet can be controlled by changing the pull-in amount in the first stroke. This will be further described with reference to FIG.

FIG. 11 shows changes in the meniscus position and meniscus velocity when the pull-in voltage V1 in the first stroke is changed while keeping the required time t2 in the second stroke constant. (A) of this figure shows the voltage waveform of the head drive signal, the horizontal axis represents time, and the vertical axis represents voltage. (B)
Represents the state of change of the meniscus position, the horizontal axis represents time, and the vertical axis represents the meniscus position (the distance from the opening end to the meniscus). (C) shows how the meniscus velocity changes, with the horizontal axis representing time and the vertical axis representing meniscus velocity.

Here, the locus 31 of the meniscus position and the meniscus speed change curve 35 shown by the solid line correspond to the voltage waveform 33 when the pull-in voltage is made smaller (V1 = V11), and the meniscus position shown by the broken line is shown. Locus 32
And the meniscus speed change curve 36 corresponds to the voltage waveform 34 when the pull-in voltage is made larger (V1 = V12). Here, as described above, the required time t3 and the discharge voltage V2 in the third step are constant. Also,
In the present embodiment, the required time t1 of the first step is described as being fixed to an appropriate value, but may be variable as needed.

As is apparent from FIGS. 11A and 11B, when the pull-in voltage is large, the meniscus is drawn deeply. On the other hand, since the ink supply speed is the same, the magnitude of the average inclination of the trajectories 31 and 32 when the meniscus position advances while vibrating toward the opening end at the average meniscus advance speed (FIG. 11B). ) Are equal. For this reason, as shown in FIG.
The meniscus position at the stroke start point C) is different even if the required time t2 of the second stroke is equal. In the example shown here, when the pull-in voltage V1 is large, it is as deep as x2, and when the pull-in voltage V1 is small, it is as shallow as x1. That is, the meniscus position at the start point C of the third stroke can be changed by changing the magnitude of the pull-in voltage V1.

As shown in FIG. 11B, the locus 32 of the meniscus position when the pull-in voltage V1 is large.
Is larger than the amplitude of the locus 31 of the meniscus position when the pull-in voltage V1 is small, and the fluctuation cycle in this case does not change. Therefore, the maximum slope of the meniscus position trajectory 32 is larger than the maximum slope of the meniscus position trajectory 31. As a result, as shown in FIG. It becomes larger than the amplitude of the curve 35. Therefore, even if the required time t2 of the second stroke (that is, the time from the pull-in end time B to the third stroke start time C) is equal, the meniscus speed at the third stroke start time C is different. In the example shown here, the pull-in voltage V1
Is large, a high speed vel2 is obtained in the pull-in direction, and when the pull-in voltage V1 is low, a low speed vel1 is obtained in the pull-in direction. That is,
The meniscus speed at the start point C of the third stroke can be changed by changing the magnitude of the pull-in voltage V1.

From these facts, the time required for the second stroke t
By changing the pull-in voltage V1 in the first step while keeping 2 constant, the size of the ink droplet and the flying speed can be controlled simultaneously.

Next, the overall operation of the ink jet printer 1 according to the present embodiment will be described with reference to FIG. Here, FIG. 12 shows the head controller 14 (FIG. 1).
3 shows the operation of the main part of one discharge cycle. Here, a description will be given assuming that the counter 145 (FIG. 4) of the head controller 14 has already been reset in the immediately preceding ejection cycle. Before the head drive signal is output in step S106 of FIG. 12, the discharge end point I of the previous discharge cycle (FIG. 5)
Is held as it is.

In FIG. 1, when print data is input to the inkjet printer 1 from an information processing device such as a personal computer (not shown), the image processing section 15 performs predetermined image processing (for example, compression) on the input data. After decompression, the data is sent to the head controller 14 as recording data.

Main control section 141 of head controller 14
In FIG. 4, when print data is input (Step S101; Y in FIG. 12), the size and the flying speed of the ink droplet for forming one target dot are determined based on the data. (Select) (Step S10)
2).

For example, it is determined to increase the ink droplet size to express a high density, and to reduce the ink droplet size when expressing a low density or high resolution. When expressing a natural image, an image having a density gradient, or the like, it is determined that the size of the ink droplet is different between adjacent dots as necessary.

Also, for example, when the traveling speed of the recording head is
If the speed error is to be corrected when the speed error slightly changes depending on the position on the travel stroke, the flying speed of the ink droplet is determined according to the coordinates of each dot in the stroke direction. . For example, when it is known that the carriage moving speed of the recording head 11 is slower near both ends compared to the center of the stroke, the flying speed of the ink droplets is slowed near both ends, and the ink speed is lower at the center. It is determined that the flying speed of the droplet is increased. On the other hand, when it is guaranteed that the moving speed of the recording head 11 is constant with high accuracy regardless of the position of the stroke, it is determined that the flying speed of the ink droplet is always kept constant. In these cases, how much the absolute value of the flying speed of the ink droplet is set depends on the recording head 11.
It is determined in advance in consideration of the distance between the sheet and the recording paper and other various conditions.

Next, the main control section 141 reads out the waveform data of the drive voltage waveform corresponding to the determined flying speed of the ink droplet from the drive voltage waveform storage section 144 (step S10).
3). As described with reference to FIG. 4, the drive voltage waveform storage unit 144 stores various types of waveform data according to the size and the flying speed of the ink droplet. In the present embodiment, for example, when the size and the flying speed of the ink droplet are changed according to the traveling position of the recording head 11 as described above, each dot has the pull-in voltage V1 corresponding to the determined flying speed. Read the waveform data. When the size and the flying speed of the ink droplet are controlled to be constant, only one type of predetermined waveform data is repeatedly read for all dots.

Next, based on the read waveform data, the main control section 141 discharges the start time H of the third stroke in the previous cycle (that is, the time when the counter 145 is reset and the count-up is started). A time τ from the time point) to the pull-in start time point C (the first stroke start time point) in the current cycle is obtained (step S104). As is apparent from FIG. 5, the time τ is determined from the discharge interval (cycle of the discharge timing clock) T to the first stroke and the second stroke.
It is obtained by subtracting the total time required for the process (t1 + t2). The processing of steps S101 to S104 described above is performed within a short time after time I in FIG. When the voltage V1 in the waveform data read this time (that is, the voltage at the time A) is different from the voltage at the time I in the previous ejection cycle, the voltage V1 is applied to the piezoelectric element 122 as soon as possible immediately after the reading. The value of the voltage V1 is changed to a new value read this time, and this value is held.

After that, the main control section 141 executes step S
Wait for the time τ obtained in step 104 to elapse (step S10
5). Then, when the time τ has elapsed and a time-up signal is input from the counter 145 at the time A (step S105; Y), the main control unit 141 starts outputting the read waveform data (step S106). This waveform data is converted into an analog signal by a D / A converter 146 and then amplified by an amplifier 147.
(A) is supplied to the recording head 11 as a head drive signal having a waveform as shown in A to E. In the recording head 11, the three strokes described with reference to FIG. 5 are performed based on the voltage waveform of the head drive signal, whereby ink droplets having the size and the flying speed specified by the waveform data are formed. Discharged. Then, at time E
In the subsequent period, preparation for the next ejection cycle, that is, processing such as determination of ink droplet size and the like based on input data and reading of waveform data (Steps S101 to S104) are performed. Thereafter, such a discharge operation and a discharge preparation process are repeated.

Now, after the output of the head drive signal is started in step S106, the starting point C of the third stroke is set.
(Step S107; Y), the counter 145 is reset here, and starts counting up for the next ejection cycle (step S108). Then, at the time point D in FIG. 5A, the third stroke ends (step S10).
9) Further, after the drive voltage is returned to V1 at the point E, the voltage V1 is held as it is or changed as described above until the start point F of the next ejection cycle arrives. During this time, the ink is filled (refilled) in the ink chamber 113 to prepare for the next ejection. This completes one ejection cycle.

As described above, in the present embodiment, the first step of pulling in the meniscus by the pull-in voltage V1 and the second step of supplying ink while maintaining the drive voltage at 0 to advance the meniscus position are unique. When the ink discharge operation is performed in three strokes of the third stroke in which the ejection voltage V2 is applied in accordance with the meniscus speed that fluctuates with the oscillation cycle of the ink drop, the pull-in voltage V in the first stroke
Since the meniscus position and the meniscus speed at the start of the ejection are appropriately set by changing 1, the size and the flying speed of the ink droplet can be arbitrarily controlled. Of course, by fixing the pull-in voltage V1, the size and the flying speed of the ink droplet can be made constant with high accuracy.

In the above description, the required time t3 (that is, the contraction speed of the ink chamber 113) and the magnitude of the ejection voltage V2 (that is, the contraction amount of the ink chamber 113) in the third step are constant. The parameters may also be changed. In general, the size and the flying speed of the ink droplet also change depending on the ejection voltage V2 and the required time t3 in the third stroke. For example, as the ejection voltage V2 increases, the size of the ink droplet increases, and the required time t
The smaller the number 3, the higher the flying speed of the ink droplet.
Therefore, if these parameters (V2, t3) are controlled in addition to the control of the pull-in voltage V1, more various controls can be performed, and the control range of the ink droplet size and the flying speed can be expanded. Is also possible.

[Second Embodiment] Next, another embodiment of the present invention will be described.

In the present embodiment, the meniscus position and the meniscus speed at the start of the third stroke are appropriately set by changing the length of the required time t2 of the second stroke while keeping the pull-in voltage V1 of the first stroke constant. Is what you do. here,
Since the position of the start time of the third stroke (that is, the start time of the ejection of the ink droplet) C is fixed in synchronization with the above-described ejection timing clock, it is necessary to change the length of the required time t2 of the second stroke. Needs to change the position of the start point A of the first step. In the present embodiment, the drive voltage waveform storage unit 144 of FIG. 4 previously stores second lengths having different lengths in accordance with the size and the flying speed of each ink droplet.
A plurality of types of waveform data having the required process time t2 may be stored, read out, and used.
Other configurations are the same as those in the first embodiment.

FIG. 13 shows changes in the meniscus position and the meniscus speed when the required time t2 in the second stroke is changed while the pull-in voltage V1 in the first stroke is kept constant. (A) of this figure shows the voltage waveform of the head drive signal, the horizontal axis represents time, and the vertical axis represents voltage. (B)
Represents the state of change of the meniscus position, the horizontal axis represents time, and the vertical axis represents the meniscus position (the distance from the opening end to the meniscus). Here, the locus 41 of the meniscus position shown by the solid line indicates that the time required for the second stroke is longer (t2 = t2).
The trajectory 42 of the meniscus position indicated by a broken line corresponds to the voltage waveform 43 when the required time of the second stroke is shorter (t2 = t22). Also in the present embodiment, the required time t1 in the first stroke, the required time t3 in the third stroke and the magnitude of the discharge voltage V2 are described as being constant.

As is clear from these figures, since the pull-in voltage V1 in the first stroke is equal, the meniscus position immediately after the pull-in is equal, but the required time t2 in the second stroke is equal.
Are different, the amount of meniscus advance from the end point B of the first stroke to the start point C of the third stroke is different. For this reason,
The meniscus position at the start point C of the third stroke differs.

Even if the required time t2 of the second stroke is different, since the waveforms of the trajectories 41 and 42 of the meniscus position are equal (FIG. 13B), the meniscus velocity curve 4
The waveforms of 5, 46 are also equal. However, since there is a phase difference corresponding to (t21−t22) between the trajectories 41 and 42 of the meniscus position, the same phase difference between the meniscus velocity curves 45 and 46 correspondingly exists. Exists. For this reason, as shown in FIG. 3C, even if the pull-in voltage V1 in the first stroke (that is, the amount of pull-in of the meniscus) is equal, the meniscus speed at the start point C of the third stroke is different.

In the example shown here, when the required time t2 of the second stroke is short, the meniscus position at the start point C of the third stroke is as deep as x2 ', and a large velocity vel2' is obtained in the pull-in direction. On the other hand, when the required time t2 of the second stroke is long, the meniscus position at the start point C of the third stroke is as shallow as x1, and a small velocity vel1 is obtained in the pull-in direction. Therefore, in this case, in the former combination, a smaller ink droplet size and a larger flying speed of the ink droplet can be obtained. However, depending on the setting of the required time t2 of the second stroke, the meniscus velocity change curves 45, 46
The magnitude relationship between the meniscus position and the meniscus speed at the start of the third stroke may be reversed due to the phase difference relationship between them, and the magnitude of the ink droplet size and the flying speed may be reversed. In any case, the meniscus position and the meniscus speed at the start of the third stroke C can be changed by changing the length of the required time t2 of the second stroke, whereby the size and the flying speed of the ink droplet can be changed. You can control it.

As described above, in the present embodiment, the first step of pulling in the meniscus by the pull-in voltage V1 and the second step of supplying ink while maintaining the drive voltage at 0 to move the meniscus position forward are unique. When the ink discharge operation is performed in three strokes of the third stroke in which the ejection voltage V2 is applied in accordance with the meniscus speed that fluctuates with the oscillation cycle of the third stroke, the ejection time is changed by changing the required time t2 of the second stroke. Since the meniscus position and the meniscus speed at the start are appropriately set, it is possible to arbitrarily control the size and the flying speed of the ink droplet.

Further, as described above, the size and the flying speed of the ink droplet depend on the required time t3 (the contraction speed of the ink chamber 113) and the magnitude of the ejection voltage V2 (the contraction amount of the ink chamber 113) in the third stroke. Changes, so the second
If these parameters (t3, V2) are controlled together with the control of the required time t2 of the stroke, more various controls can be performed, and the control range of the ink droplet size and the flying speed can be expanded. Is also possible.

[Third Embodiment] Next, still another embodiment of the present invention will be described.

In this embodiment, the meniscus position and the meniscus speed at the start of the third stroke are appropriately set by changing both the amount of meniscus drawn in in the first stroke and the required time t2 in the second stroke. is there. Here, since the position of the third stroke start time (ink droplet ejection time) C is fixed in synchronization with the above-described ejection timing clock, it is necessary to change the length of the required time t2 of the second stroke. Needs to change the position of the start point A of the first step. Therefore, in the present embodiment, the meniscus speed is actually adjusted by changing the magnitude of the pull-in voltage V1 in the first stroke and the position at the start point A of the first stroke. In the present embodiment, a plurality of types of waveforms in which different pull-in voltages V1 and second stroke required times t2 are combined in advance in the drive voltage waveform storage unit 144 of FIG. 4 according to the size and the flying speed of each ink droplet, respectively. What is necessary is just to store data, read it out, and use it. Other configurations are the same as those in the first embodiment.

FIG. 14 shows changes in meniscus position and meniscus velocity when the meniscus pull-in amount in the first stroke and the required time t2 in the second stroke are changed. (A) of this figure shows the voltage waveform of the head drive signal, the horizontal axis represents time, and the vertical axis represents voltage. (B) shows how the meniscus position changes, the horizontal axis represents time, and the vertical axis represents the meniscus position (the distance from the opening end to the meniscus). Here, the locus 51 of the meniscus position shown by the solid line
Means that the pull-in voltage in the first step is smaller (V1 = V1
1) and increase the time required for the second step (t2 =
Corresponding to the voltage waveform 53 in the case of t21), the trajectory 52 of the meniscus position indicated by the broken line increases the pull-in voltage in the first stroke (V1 = V12) and shortens the time required for the second stroke (t2). = T22) corresponding to the voltage waveform 54. In the present embodiment, the required time t1 in the first stroke, the required time t3 in the third stroke, and the discharge voltage V2 are also assumed to be constant.

As is apparent from these figures, in this example, both the pull-in voltage V1 in the first step and the required time t2 in the second step are set to be different from each other.
The trajectories 51 and 52 of the meniscus position shown in (b) have different amplitudes and phases, and as a result, the meniscus positions at the start point C of the third stroke also differ. FIG.
The meniscus velocity curves 55 and 56 shown in FIG.
Since the amplitude and the phase are different, the meniscus speed at the start point C of the third stroke is also different.

In the example shown here, when the pull-in voltage V1 in the first stroke is large and the required time t2 in the second stroke is short, the meniscus position at the start point C of the third stroke is as deep as x2 ″ and Large speed ve in the pull-in direction
l2 "is obtained, the pull-in voltage V1 in the first stroke is small, and the required time t2 in the second stroke is long, the meniscus position at the start point C of the third stroke is as shallow as x1, and the speed is small in the pull-in direction. Therefore, in this case, a smaller ink droplet size and a larger flying speed of the ink droplet can be obtained in the former combination, provided that the required time t2 of the second stroke is set. In some cases, the magnitude relation of the meniscus velocity at the start of the third stroke may be reversed due to the phase difference relation between the meniscus velocity change curves 55 and 56, so that the magnitude of the flying velocity of the ink droplet may be reversed. In any case, by changing both the pull-in voltage V1 of the first stroke and the required time t2 of the second stroke, the start of the third stroke is also possible. Can change the meniscus position and the meniscus velocity at C, thereby, it is possible to control the flying speed of the ink droplet.

As described above, in the present embodiment, the first step of pulling in the meniscus by the pull-in voltage V1 and the second step of supplying ink while maintaining the drive voltage at 0 to advance the meniscus position are unique. When the ink discharge operation is performed in three strokes of the third stroke in which the ejection voltage V2 is applied in accordance with the meniscus speed which fluctuates with the oscillation cycle of the first stroke, the pull-in voltage V1 of the first stroke and the required voltage of the second stroke Since the meniscus position and the meniscus speed at the start of the ejection are appropriately set by changing the time t2, the size and the flying speed of the ink droplet can be arbitrarily controlled.

Note that the pull-in voltage V1 in the first step and the second
By variously changing and combining the required time t2 of the stroke, the size and the flying speed of the ink droplet can be variously changed. For example, the pull-in voltage V1 in the first stroke is increased, and the required time t2 in the second stroke is increased.
Or, conversely, control can be performed such that the pull-in voltage V1 in the first stroke is reduced and the required time t2 in the second stroke is shortened. Thus, various controls can be performed.

Further, as described above, the size and the flying speed of the ink droplet depend on the magnitude of the ejection voltage V2 (shrinkage amount of the ink chamber 113) and the required time t3 (shrinkage speed of the ink chamber 113) in the third stroke. Also changes, so the first
The pull-in voltage V1 of the stroke and the required time t2 of the second stroke
If these parameters (V2, t3) are also controlled in addition to the above control, more various controls can be performed, and the control range of the ink droplet size and the flying speed can be expanded.

As is clear from FIG. 10B, the meniscus speed at the start of the third stroke can be set (or selected) by selecting the phase of the meniscus speed starting from the end of the retraction, for example. is there. Because the fluctuation period of the flying speed of the ink droplet is equal to the fluctuation period of the meniscus speed, if the phase is determined, the meniscus speed there is also determined. As a result, the flying speed of the ink droplet is also determined. However, in practice, the amplitude of the change in the meniscus velocity gradually attenuates as shown in FIG. 10B, so that even if the relative phases are the same, if the absolute phases are different (that is, an integer of the period) If there is a fold difference), the meniscus velocities will not be exactly equal. However, as long as the ejection operation is performed at an early timing immediately after the pull-in (the timing before about two or three cycles) where the attenuation amount is still small, specifying the relative phase and specifying the meniscus speed are almost the same. Will be. Therefore, within a range of about two to three cycles immediately after the pull-in, if the third stroke is started when the relative phase of the meniscus velocity reaches a predetermined value, the phase (2π) for one cycle Even if the ejection timing is changed by a phase equal to an integral multiple of the above, the flying speed of the ink droplet becomes substantially constant.

For example, when ejection is started at times P1 to P4 or the like at which the absolute phase becomes 2nπ (n is an integer) starting from the end of the pull-in, the flying speed of the ink droplet obtained at each of these timings (see FIG. 10
The speeds given at points Q1 to Q4 in (c)) are substantially equal. In particular, in this example, a flying speed close to the highest speed is obtained. In addition, at a plurality of timings having the same relative phase as described above, the ink droplet size is smaller when the third stroke is started at an earlier timing (FIG. 10D). Therefore, by appropriately selecting the timing for starting the third process,
It is possible to control the ink droplet size while keeping the flying speed of the ink droplets substantially constant.

On the other hand, when the absolute phase of the meniscus velocity at the start of the third stroke is fixed to only one (for example, 2π) (P in FIG. 10C).
2) It is possible to stabilize the flying speed of the ink droplet with high accuracy. However, in this case, the ink droplet size is also fixed (S1 in FIG. 10D).

In general, it is desirable that the flying speed of the ink droplet be higher. Therefore, in FIG. 10, the phase points P1 to P4 and the like at which the meniscus speed becomes maximum in the pulling direction are selected and described. It is also possible to select different phases according to. For example, it is also possible to select the phase points P8 to P13 at which the meniscus velocity becomes zero. In this case, the flying speed of the ink droplet is almost constant at a medium value, but on the other hand, as shown in FIG. 10A, the meniscus position corresponding to these timings (the meniscus position) R8 at which the extremum takes an extreme value in its natural vibration
To R13) are all different, so that control for finely changing the ink droplet size becomes possible. Of course, it is also possible to select another arbitrary phase and control the ink droplet size while keeping the flying speed of the ink droplet almost constant.

As described above, the present invention has been described with reference to some embodiments. However, the present invention is not limited to these embodiments, and can be variously modified within an equivalent range. For example, in each of the above embodiments, the holding voltage in the second step is set to 0.
V and the pull-in voltage V1 in the first step and the third
Although the discharge voltage V3 in the stroke is a voltage of the same polarity, the present invention is not limited to this.
Can be set to 0 V, and the holding voltage in the second stroke and the ejection voltage V2 in the third stroke can be voltages of opposite polarities.

In each of the above embodiments, the main control unit 141 of the head controller 14 reads out the waveform data from the drive voltage waveform storage unit 144 and obtains the flight speed of the designated ink droplet based on the waveform data. However, the present invention is not limited to this. However, the present invention is not limited to this. The hardware-based method of creating a head drive signal using a logic circuit is described. The control may be performed by a method.

In each of the above-described embodiments, the ink supply to the ink chamber 113 is always performed at a constant speed. However, for example, the ink supply to the ink chamber 113 may be performed during the second stroke and the refill period after the end of the third stroke. The ink supply may be performed only in one period. Further, for example, by providing a pressure mechanism in the ink cartridge 12 and performing pressure control,
The ink supply speed in the second stroke and the ink supply speed in the refill period after the end of the third stroke may be made different.

[0101]

As described above, according to the method for driving a recording head for an ink jet printer according to any one of claims 1 to 8, or the ink jet printer according to any one of claims 9 to 16, , Third
Appropriately set (select) the position of the ink tip and the periodic position change speed at the start of the process (the start of ejection)
In this way, the flying speed of the ink droplet is controlled by controlling the size and the flying speed of the ink droplet in accordance with the position of the ink tip and the speed of the periodic position change. It is also possible to simultaneously control the size of the ink droplet and the flying speed. Therefore, for example, the ink droplet size is changed for each dot while correcting the landing position deviation caused by the instability of the traveling speed of the recording head, the instability of the distance between the recording head and the landing position, and the like. Control the gradation, etc.
Control that was difficult in the past can be performed.

In particular, according to the ink jet printer described in claim 2 or the ink jet printer recording head driving method described in claim 10, the third
Since the contraction amount and contraction speed of the ink chamber in the process are also controlled, there is an effect that various control of the size and the flying speed of the ink droplets can be performed.

According to the ink jet printer of the sixth aspect or the method of driving the recording head for an ink jet printer of the fourteenth aspect, the periodic position change speed of the ink tip portion at the start of the third stroke is constant. Since the stroke control is performed as described above, it is possible to control the size of the ink droplet while keeping the flying speed of the ink droplet constant. For this reason, for example, when the recording head performs recording while traveling at a constant speed, it is possible to perform uniform density expression and intermediate gradation expression with high accuracy while reducing the landing position deviation of ink droplets. There is an effect that quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of an inkjet printer according to an embodiment of the present invention.

FIG. 2 is a perspective sectional view illustrating a configuration example of a recording head.

FIG. 3 is a cross-sectional view illustrating a structural example of a recording head.

FIG. 4 is a block diagram illustrating a configuration example of a head controller.

FIG. 5 is an explanatory diagram illustrating an example of an operation of a recording head.

FIG. 6 shows a meniscus pull-in voltage V in a first step.
FIG. 9 is a diagram illustrating the results of an experimental example for examining the relationship between No. 1 and the time required for the meniscus to advance.

FIG. 7 is a diagram illustrating a result of an experimental example for examining a state of a change in a meniscus position after the pull-in.

FIG. 8 is a diagram illustrating a result of an experimental example for examining a state of a change in a flying speed of an ink droplet when a time from a pull-in start time to a third stroke start time is changed.

9 is a diagram in which the experimental results shown in FIG. 7 and the experimental results shown in FIG. 8 are superimposed.

FIG. 10 is an explanatory diagram for explaining a relationship among a meniscus position, a meniscus speed, an ink droplet flying speed, and an ink droplet size.

FIG. 11 is a view for explaining a method of driving a recording head for an ink jet printer according to an embodiment of the present invention, and more specifically, a meniscus position when only the pull-in voltage in the first step is changed. FIG. 6 is a diagram illustrating a change in a meniscus velocity.

FIG. 12 is a flowchart for explaining the operation of a main controller of the head controller.

FIG. 13 is a view for explaining a method of driving a recording head for an ink jet printer according to a second embodiment of the present invention, and more specifically, in a case where only the time required for the second stroke is changed. It is a figure showing a change of a meniscus position and a meniscus velocity.

FIG. 14 is a view for explaining a method of driving a recording head for an ink jet printer according to a third embodiment of the present invention, and more specifically, a pull-in voltage of a meniscus in the first step and a voltage in the second step. It is a figure showing the change of the meniscus position and the meniscus speed when both the required times are changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ink-jet printer, 2 ... Recording paper, 11 ... Recording head, 12 ... Ink cartridge, 14 ... Head controller, 111c ... Vibration plate, 113 ... Ink chamber, 115 ... Nozzle opening, 117 ... Common flow path, 122 ...
Piezoelectric element, 141: main control unit, 144: drive voltage waveform storage unit, 145: counter, V1: pull-in voltage, V2 ...
Discharge voltage, t1 ... required time for first stroke, t2 ... required time for second stroke, t3 ... required time for third stroke

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Tanigawa 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Yuichiro Ikemoto 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hiroshi Tokunaga 6-35 Kitashinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (16)

[Claims] A nozzle opening for discharging ink droplets; an ink chamber communicating with the nozzle opening; an ink supply path for supplying ink to the ink chamber; A piezoelectric element for expanding or contracting; a first step of expanding the ink chamber by the piezoelectric element to draw an ink tip in contact with the outside air through the nozzle opening toward the ink chamber; A second step in which the ink tip is advanced in the direction of the nozzle opening by supplying ink to the ink chamber; and an ink droplet is ejected from the nozzle opening by contracting the ink chamber by the piezoelectric element. A stroke control means for controlling a third stroke to be performed, wherein the stroke control means comprises: By setting the position and periodic position change velocity of the ink tip at the start properly, ink jet printer, characterized by controlling the size and the flying speed of ink droplets ejected in the third step. 2. The method according to claim 1, wherein the stroke control means further comprises:
Controlling the amount of contraction of the ink chamber during the stroke to control the size of the ink droplet and controlling the contraction speed of the ink chamber to control the flying speed of the ink droplet. The inkjet printer according to claim 1. 3. The process according to claim 1, wherein the stroke control unit changes the amount of ink withdrawn at the tip of the ink in the first stroke while keeping the time required for the second stroke constant. 3. The ink jet printer according to claim 1, wherein the position of the unit and the periodic position change speed are appropriately set. 4. The ink jet printer according to claim 1, wherein the stroke control unit controls the second stroke while keeping the ink leading-edge amount in the first stroke constant.
3. The ink-jet apparatus according to claim 1, wherein the position of the ink tip and the periodic position change speed at the start of the third stroke are appropriately set by changing a time required for the stroke. Printer. 5. The process according to claim 1, wherein the stroke control means changes a retracted amount of the ink front end portion in the first stroke and a time required for the second stroke to change the position of the ink front end portion at the start of the third stroke. 3. The ink jet printer according to claim 1, wherein the speed of the periodic position change is set as appropriate. 6. A process according to claim 1, wherein said stroke control means controls the stroke such that a periodic position change speed of said ink leading end portion at the start of said third stroke is constant. 5. The inkjet printer according to any one of 5. 7. The ink control device according to claim 7, wherein the stroke control unit appropriately sets a phase of a periodic position change of the ink tip portion at a start time of the third stroke, thereby setting the ink tip portion at a start time of the third stroke. The ink jet printer according to any one of claims 1 to 5, wherein the position and the periodic position change speed are set. 8. The stroke control means according to claim 1, wherein the phase of the periodic change in the position of the ink tip at the start of the third stroke is constant, whereby the ink tip at the start of the third stroke is fixed. 8. The ink jet printer according to claim 7, wherein the periodic position change speed is made constant. 9. A nozzle opening for discharging ink droplets, an ink chamber communicating with the nozzle opening, an ink supply path for supplying ink to the ink chamber, and an ink supply passage for supplying ink to the ink chamber. A method for driving a recording head for an ink-jet printer, comprising: a piezoelectric element for expanding or contracting, wherein the ink chamber is expanded by the piezoelectric element, so that an ink tip that comes into contact with outside air through the nozzle opening is formed in the ink chamber. A second step of drawing ink in the direction of the arrow; a second step of supplying ink from the ink supply path to the ink chamber to advance the tip end of the ink in the direction of the nozzle opening; Controlling a third step of ejecting ink droplets from the nozzle opening by contracting the third step. An ink jet printer for controlling the size and flying speed of ink droplets ejected in the third step by appropriately setting the position of the ink tip portion and the periodic position change speed at the start time. Driving method of recording head. 10. The ink droplet size is controlled by controlling the contraction amount of the ink chamber in the third step, and the ink droplet contraction speed is controlled by controlling the contraction speed of the ink chamber. The method according to claim 9, wherein the flying speed is controlled. 11. The position and periodicity of the ink tip at the start of the third stroke by changing the amount of pull in of the ink tip in the first stroke while keeping the time required for the second stroke constant. 11. The method according to claim 9, wherein the position changing speed is set appropriately. 12. The method according to claim 12, wherein the time required for the second stroke is changed while keeping the amount of the ink leading end drawn in the first stroke constant. 11. The method according to claim 9, wherein the position changing speed is set appropriately. 13. The position and the periodic position change speed of the ink tip at the start of the third stroke by changing the amount of retraction of the ink tip in the first stroke and the time required for the second stroke. 11. The method of driving a recording head for an ink-jet printer according to claim 9, wherein is set as appropriate. 14. The process according to claim 9, wherein the stroke control is performed so that the periodic position change speed of the ink tip portion at the start of the third stroke is constant. Driving method of a recording head for an ink jet printer. 15. The position and the periodic position of the ink tip at the start of the third stroke by appropriately setting the phase of the periodic position change of the ink tip at the start of the third stroke. 14. The method according to claim 9, wherein the changing speed is set. 16. The periodic position change speed of the ink tip portion at the start of the third stroke by making the phase of the periodic position change of the ink tip portion constant at the start of the third stroke. The method according to claim 15, wherein the recording head is fixed.