JP2003175604A - Method of ejecting ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of ejecting ink capable of suppressing occurrence of a satellite drop. <P>SOLUTION: Two piezoelectric elements 116a, 116b are provided in each ink chamber 114 corresponding to a nozzle 118. While the ink chamber 114 is in the contraction condition by the displacement of one piezoelectric element 116a after the ejection of an ink drop is started by one piezoelectric element 116a, the other piezoelectric element 116b is displaced to further contract the ink chamber 114. As a result, a tail of the ink drop can be cut in an early stage so that the occurrence of a satellite drop can be suppressed. In particular, the occurrence of the satellite drop can be markedly effectively suppressed by starting the displacement of the piezoelectric element 116b at a time point when the piezoelectric element 116a is mostly displaced. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION The present invention relates to a nozzle
Ink jet that ejects ink droplets from the
The present invention relates to a method for discharging ink used in a printer. [0002] 2. Description of the Related Art In recent years, from a nozzle portion communicating with an ink chamber,
An ink jet that ejects ink droplets and records on recording paper
Printers have become widespread. Conventionally, this type of ink jet
In a printer, one piezoelectric element corresponds to one nozzle.
An element was provided. This piezoelectric element is, for example,
The outer wall of the ink chamber to which ink is supplied through the
The voltage of the applied drive signal is fixed to the diaphragm
Deflection according to the waveform changes the volume of the ink chamber and ejects it.
Discharge pressure, and this discharge pressure causes
Ink droplets could be ejected. In this type of ink jet printer,
Is the discharge pressure by changing the volume of the ink chamber as described above.
Is generated, so that the
The ink that has flowed into a columnar shape (in a trailing form)
Time difference between the head and tail of the flying ink
And speed differences occur. Therefore, the leading main ink droplet
Is accompanied by a small satellite-like unwanted ink droplet (hereinafter, referred to as
Called satellite drops. ) Occurs and this appears on the recording paper
An undesired printing result is caused by landing.
In this case, a dark image to be recorded with relatively large ink droplets
Then, the generation of satellite drops has a great effect on the image quality
Not given, but expresses low density image or halftone image
When printing with small ink droplets as in
Significant reduction in image quality due to generation of terite drops
Is expected. Therefore, especially for small size
The generation of satellite droplets when discharging droplets is large.
Problem. [0004] To address this problem,
Such measures have been proposed. For example, Japanese Patent Application Laid-Open No. 7-760
No. 87 discloses one piezoelectric element for one nozzle.
And the rate of change of the discharge voltage applied to this piezoelectric element.
A method of ejecting ink droplets by switching between two stages has been proposed.
Have been. This method was initially used as shown in FIG.
The discharge voltage is increased with a voltage change speed v1 of 1,
From the middle, the second voltage change speed v2 which is larger than v1
Thus, the discharge voltage is increased. Note that FIG.
The vertical axis represents voltage, and the horizontal axis represents time. According to this method
For example, follow the top of the ink that was ejected earlier
The ink will continue to be ejected,
The speed difference between the head and tail of the pillar is reduced,
Satellite drops are less likely to occur. Further, for example, Japanese Patent Application Laid-Open No. Sho 59-133067
In the publication, one piezoelectric element is provided for one nozzle.
Two independent voltage pulses are applied to this piezoelectric element.
A method of ejecting ink droplets by applying a voltage has been proposed. This
First, as shown in FIG. 10, the first pulse
P1 is added to the piezoelectric element to generate a first pressure fluctuation, and
Injection of ink droplets from the nozzle starts, and then the first pulse
After terminating Lus P1, ink droplets are ejected from the nozzles.
Before the second pulse P2 is applied to the piezoelectric element,
Force fluctuation is caused. FIG.
At 0, the vertical axis represents voltage and the horizontal axis represents time. According to this method
If the ink column ejected from the nozzle breaks early,
Satellite drops are less likely to occur. Incidentally, for example, Japanese Patent Application Laid-Open No.
In the publication, two pressure generating means are provided for one nozzle.
And the superposition of vibrations from these two pressure generating means.
To vibrate the ink to eject ink droplets
There has been proposed an ink droplet ejection device having such a configuration. [0007] SUMMARY OF THE INVENTION
In the method described in JP-A-7-76087,
The first voltage change speed v1 is higher than the second voltage change speed v2.
You must make it smaller. For this reason, the entire discharge stroke
The voltage was changed at a high voltage change speed v2 over
The flying speed of the ejected ink drops is lower than in the case
I have to do it. The drop in the flying speed of the ink drops
Such as the deterioration of the linearity of the flight route and the dispersion of the flight speed
This causes instability of ejection, causing print dot misalignment.
As a result, the print quality may be deteriorated. The above-mentioned Japanese Patent Application Laid-Open No. Sho 59-133067
In the method described in the publication, the first pulse P1 is terminated.
Then, after a certain time interval Ti, the second pulse P2
Is applied, so that this time interval Ti
If it is large, the trail of the ink column becomes longer and satellite drops
Is difficult to prevent. On the other hand, the time interval Ti is small.
The piezoelectric element cannot follow the voltage change,
No longer available. Generally, piezoelectric elements have unique vibration characteristics.
And can not operate at a frequency higher than its natural frequency
It is. This is because a piezoelectric element with a high natural frequency
It is thought that this can be solved by manufacturing
There is a limit to increasing the natural frequency.
Also lead to higher costs with manufacturing technology difficulties.
So it is not realistic. Also, in the description of the above publication,
The second pulse P2 is higher than the voltage value V1 of the first pulse P1.
Is smaller than the voltage value V2 of the ink column.
To make the tail part catch up with the head part and unite
Is smaller than the voltage value V1 of the first pulse P1 by the second pulse
It is necessary to increase the voltage value V2 of P2. Place
However, increasing the voltage applied to the piezoelectric element
Life of vibrator driven by vibrator and this piezoelectric element
As well as the residual vibration increases,
It is expected that the wave number characteristics will deteriorate. Further, Japanese Patent Laid-Open Publication No.
The ink drop ejection device described in the report is effective with a small power input.
The purpose is to discharge ink droplets efficiently.
To achieve this goal, two pressure generating means
While applying high-frequency drive signals,
By changing the phase difference and amplitude of the frequency drive signal,
The ink from the pressure generating means is superposed
Vibrating, thereby ejecting ink droplets
I have. That is, this ink droplet ejection device is a satellite
It is not intended to prevent the formation of drops,
There is no configuration for that. Also such suggestions
Nor. As described above, conventionally, the ejected ink droplet
Flight speed, equipment life, or frequency characteristics
Without the deterioration of the characteristics and the natural vibration of the piezoelectric element.
Generation of satellite droplets without being restricted by characteristics
It was difficult to sufficiently suppress the The present invention has been made in view of such a problem.
Therefore, its purpose is to overcome the problems mentioned above
Satellite droplets when ejecting ink droplets.
It is another object of the present invention to provide a method of discharging a clear ink. [0012] DISCLOSURE OF THE INVENTION Ink discharge according to the present invention
The ejection method is to change the volume of the ink chamber,
Ink in the ink chamber from the nozzle communicating with the ink chamber.
This is a method of discharging ink droplets,
To determine the size of the ink drop
Ink meniscus to retract the ink meniscus position
The retraction process and the ink meniscus retraction process
Start contraction of the ink chamber from the varnish position, and from the nozzle
A first ink chamber contraction step of discharging ink droplets;
The ink chamber shrunk in the ink chamber shrinking step of
Therefore, after the first ink chamber contraction step is started, the ink chamber
At or near the time of the largest displacement in the contraction direction
In the first ink chamber contraction step, the ink
A second ink chamber contraction step for initiating further chamber contraction;
Is included. In the method of discharging ink according to the present invention,
Ink mechanism that retracts the meniscus position of the ink in the
The meniscus is positioned by the varnish retreat process
The size of the ink droplet ejected from the nozzle is determined.
You. Next, the menu determined in the ink meniscus retreating process
With the scas position as the initial position, the contraction of the ink chamber starts.
Then, the ejection of the ink droplet from the nozzle starts. And in
When the working chamber is displaced the most in the direction of its contraction or
Near the first ink chamber contraction step
Further contraction of the link chamber is initiated. [0014] Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. FIG. 1 shows an ink according to an embodiment of the present invention.
1 shows a schematic configuration of a main part of a jet printer.
In the present embodiment, a multi-nozzle having a plurality of nozzles
An inkjet printer with a head will be described.
However, the present invention relates to a single nozzle having a single nozzle.
Also applicable to inkjet printers equipped with
Noh. In addition, the inkjet device according to the embodiment of the present invention.
The driving apparatus and method of a recording head for a printer
Realized by the inkjet printer according to the embodiment
Therefore, the description will be made below. This ink jet printer 1 is used for recording.
Recording head that performs recording by discharging ink droplets on paper 2
11 and ink for supplying ink to the recording head 11
Cartridge 12, position of recording head 11, and recording paper
Head position and paper feed control to control paper feed
Ink of the recording head 11 by the drive signal 21 and the drive signal 21.
A head controller 14 for controlling a droplet discharge operation;
Performs predetermined image processing on the image data
Image processing to be supplied to the head controller 14 as 22
Unit 15 and control signals 23, 24 and 25 respectively.
Head position / paper feed controller 13, head control
System controller for controlling the controller 14 and the image processing unit 15
And a roller 16. FIG. 2 is a perspective view of the recording head 11 in FIG.
FIG. 3 shows the recording head 11 in FIG.
It shows a sectional structure viewed from the direction of arrow Z. this
As shown in these figures, the recording head 11 has a thin nozzle
Plate plate 111 and laminated on nozzle plate 111
Flow path plate 112 and the flow path plate 112
And a vibrating plate 113 which is layered.
You. Each of these plates is, for example, an adhesive (not shown).
Are attached to each other. The upper surface of the flow path plate 112 is selectively
Recesses are formed, and these recesses and the vibrating plate 1 are formed.
13, a plurality of ink chambers 114 and their ink
And a common channel 115 communicating with the cooling chamber. Joint
The communicating portion between the flow path 115 and each ink chamber 114 is a narrow path.
From here toward the direction of each ink chamber 114
Therefore, the structure is such that the width of the flow path is widened. Each Inn
The vibration plate 113 just above the
A pair of piezoelectric elements 1 each composed of, for example, a piezo element or the like.
16a and 116b are fixed at a fixed distance from each other
I have. The upper and lower surfaces of each piezoelectric element 116a, 116b
The electrodes (not shown) are stacked and arranged.
Drive signals from the head controller 14 (FIG. 1) are applied to the electrodes
Is applied to each of the piezoelectric elements 116a and 116b, and
By flexing the moving plate 113, the ink chamber 114
Increase (expand) or decrease (shrink) the volume of
Can be done. Here, the ink chamber 114 is
This corresponds to the “ink chamber” in the present invention. In the present embodiment, the piezoelectric element 116
a and 116b are displacement amounts (hereinafter, referred to as “the same applied voltage”).
It is called displacement capacity. ) Are configured to be equal
You. Therefore, in the present embodiment, the piezoelectric elements 116a,
116b have the same material, thickness and area.
You. This results in the same volume change for the same applied voltage
To the ink chamber 114. However, two
By changing the area and thickness of the piezoelectric elements 116a and 116b,
You may comprise so that the displacement capability of both may differ. A common channel 115 in each ink chamber 114
In the part opposite to the side that communicates with the
The flow path plate 1 at the end
12 is provided with a channel hole 117 drilled in the thickness direction.
ing. The passage hole 117 is provided in the lowermost nozzle
Connected to the fine nozzles 118 formed on the plate 111.
Ink droplets are ejected from the nozzles 118
It has become so. In the present embodiment, the recording head 1
1, a paper feed direction (arrow in FIG. 2) of the recording paper 2 (FIG. 1)
Along X), a plurality of nozzles 118 are formed at equal intervals in a row.
Has been established. However, other arrangements (for example, staggered
Column array). The common channel 115 is provided with the ink reservoir shown in FIG.
Communicates with the cartridge 12 (not shown in FIGS. 2 and 3)
are doing. Then, the ink cartridge 12
Through the same flow path 115, the ink chamber 114 is always kept at a constant speed.
Ink is supplied. This ink supply
Feeding can be performed using, for example, capillary action.
However, in addition, a predetermined pressurizing machine
It may be performed by providing a structure and applying pressure. The recording head 11 having such a configuration is shown in FIG.
Carriage drive motor and its associated carriage
The ridge mechanism makes the recording paper 2 perpendicular to the paper feed direction X.
Ink droplets while reciprocating in the direction Y (FIG. 2)
As a result, an image is recorded on the recording paper 2.
ing. The head controller 14 shown in FIG.
For example, although not shown, a microprocessor
And the program executed by this microprocessor is
ROM (Read Only Memory)
Used for predetermined calculations and temporary data storage by Sessa
RAM (Random Access Me)
mory), a driving waveform storage unit including a non-volatile memory,
Digital data read from the drive waveform storage
Digital to analog conversion (D / A)
Converter and an amplifier that amplifies the output of the D / A converter.
And a pump. Here, the drive waveform storage unit
The piezoelectric elements 116a and 116 of each nozzle of the recording head 11
b of the drive signals 21a and 21b for driving
Waveform data indicating each voltage waveform is stored in a set.
These waveform data are stored, for example, in various parameters shown in FIG.
Various meters (time and voltage parameters)
It was created by setting it to an appropriate value. However, each group
Between the motion signal 21a and the drive signal 21b,
Such a constant relationship is maintained. These waveform data
Read out by the microprocessor respectively, D /
After being converted to analog signal by A converter,
Drive signals 21a and 21b which are amplified and have the same number as the number n of nozzles
Are output as a set. The head controller 14
Is not limited to the configuration described above.
It is also possible to adopt such a configuration. Each of the drive signals among the set of drive signals
21a is applied to the piezoelectric element 116a of the corresponding nozzle.
Each drive signal 21b is transmitted to the piezoelectric element 11 of the corresponding nozzle.
6b. In FIG. 1, n
The set of drive signals 21a and 21b is collectively referred to as drive signal 21.
I draw it. FIG. 4 shows one cycle of each of the drive signals 21a and 21b.
5 shows an example of a minute (T) waveform. In this figure
(A) shows the drive signal 21a and (b) shows the drive signal 21b.
You. Here, the vertical axis represents voltage, the horizontal axis represents time, and the time is a figure.
From left to right. Of these,
The motion signal 21a generates a pressure for ejecting ink droplets.
Drive signal for the
Voltage Vp and discharge voltage Va
I have. The drive signal 21b is a satellite at the time of ink droplet ejection.
Auxiliary drive signal for generating pressure to suppress the generation of droplets
Signal, a reference voltage of 0 V, a drop-in voltage Vp and a supplementary voltage.
An auxiliary voltage Vb can be taken. A set of drive signals 21a and 21b
Is calculated for each ejection cycle by the head controller 14.
It is switched as appropriate and supplied to the corresponding nozzle
It has become. Here, referring to FIG. 5, drive signal 21a
Will be described. FIG. 5 shows a driving signal
And the piezoelectric element 116a to which the drive signal is applied.
Behavior and the position of the ink tip in the nozzle 118
(Hereinafter referred to as meniscus position)
It represents. (A) of this figure shows that the drive signal 21a is
It represents almost one cycle of the generalized waveform, and FIG.
A drive signal having a waveform as shown in FIG.
Represents a change in the state of the ink chamber 114 when the ink chamber 114 is applied.
FIG. 4C shows the meniscus in the nozzle 118 at that time.
Represents the change in the position of the In FIG. 5A, first, the drive voltage is
Step of changing the reference voltage 0V to the pull-in voltage Vp (from A
B) as the first previous step, and the pull-in voltage Vp is set for a certain time.
The process to be held (from B to C) is defined as a second previous process.
Further, the drive voltage is changed from the pull-in voltage Vp1 to the reference voltage 0V.
Process (from C to D) is the first process.
The required time is defined as t1. Also, hold the reference voltage 0V
And the waiting process (from D to E) is the second process,
Is required to be t2. Furthermore, from the reference voltage 0V
The process of changing the discharge voltage Va (from E to F) is the third process.
It is a process, and the time required for this is t3. In this embodiment, at the start of the third stroke
The point E, which is a point, is the timing at which the ejection starts.
Prior to this timing, the first pre-stroke and the second pre-
The stroke, the first stroke, and the second stroke are performed
ing. First, at time A and before,
Since the voltage applied to the piezoelectric element 116a is 0 V, FIG.
State P in (b)_AAs shown in FIG.
Indeed, the volume of the ink chamber 114 is the maximum.
At time A, the meniscus position in the nozzle 118
The position is the state M in FIG._AOpen the nozzle as shown in
It must be located at a position receded by a predetermined distance from the mouth end
I do. Next, from the voltage 0V at the time point A to the pull-in at the time point B
First before slowly increasing the drive voltage to voltage Vp
When the stroke is performed, the vibration plate 113 bends inward, and
The ink chamber 114 contracts (state P in FIG. 5B)._B). This
The contraction speed of the ink chamber 114 at the time of
Therefore, the decrease in the volume of the ink chamber 114 is caused by the nozzle 1
At the same time as the meniscus position in 18 is advanced,
Also causes backflow of ink to the indicated common channel 115
You. At this time, the ratio between the ink advance amount and the reverse flow rate is mainly
The flow path resistance in the nozzle 118 and the ink chamber 114
Ratio with channel resistance in a narrow path connecting with common channel 115
It is determined by optimizing this,
State M of (c)_BAs shown in the figure, the menisca at time point B
Nozzle position without protruding from the nozzle opening end.
It can be set to be almost the same position as the mouth end
You. Next, during the period from time B to time C, the drive power
By maintaining the pressure at the pull-in voltage Vp, the capacity of the ink chamber 114 is reduced.
A second pre-stroke is performed to keep the product constant. However, during this time
The ink supply from the ink cartridge 12 is continuously
So that the meniscus in the nozzle 118
The position is displaced toward the end of the nozzle opening.
For example, the state M in FIG._CAs shown by the nozzle opening
Advance to a position slightly protruding from the end. Next, from the pull-in voltage Vp at the time point C to the time point B,
Perform the first step of reducing the drive voltage to the reference voltage 0V
And the applied voltage to the piezoelectric element 116 becomes zero,
The deflection of the rate 113 is eliminated, and the ink chamber 114 expands.
(State P in FIG. 5B) _D). Therefore, the nozzle 1
Meniscus in 18 is drawn in the direction of ink chamber 114
At the time point D, for example, the state M in FIG._DPointing out toungue
Retreat (ie away from the nozzle opening end)
). Note that the pull-in voltage, which is the potential difference between time C and time D,
By changing the magnitude of Vp, the
This changes the amount of varnish that is drawn in.
It is possible to control the size of the droplet. Ink drop
The size depends on the meniscus position at the start of ejection,
The deeper the scas position, the smaller the ink droplet size
It is. Next, at time t2 from time D to time E,
During this time, the driving voltage is fixed to the reference voltage 0V and the vibration plate 1
The ink chamber 1 is maintained by maintaining the deflection of the ink chamber 13c.
A second stroke is performed to keep the volume 14 constant (see FIG. 5C).
State P_D~ P_E). However, during this time, the ink cartridge
Since the ink supply from the nozzle 12 is performed continuously,
Meniscus position in nozzle 118 is toward nozzle opening end
At time E, for example, the state M in FIG._E
Move forward to the position shown in. The time required for the second process
By changing t2, the advance amount of the meniscus position is changed.
And adjust the meniscus position at the start of the third stroke.
Can be adjusted.
It is possible to control the size of the droplet. Next, from the voltage 0 V at the time point E to the discharge at the time point F,
A third step of rapidly increasing the drive voltage to the voltage Va is performed.
U. Here, the time point E corresponds to the discharge start time as described above.
Mining. At this time, the vibration plate
113 is the state P in FIG._FInside as shown
Large deflection, the ink chamber 114 contracts rapidly,
State M in FIG. 5 (c)_FAs shown in FIG.
The meniscus is pushed at a stroke toward the nozzle opening end,
From here, ink droplets are ejected. Ejected ink
Drops fly in the air and land on recording paper 2 (Figure 2)
You. Thereafter, the drive voltage was maintained at the discharge voltage Va.
At the point G when the predetermined time has elapsed, the reference voltage is again reduced to 0V.
Decrease. As a result, at the time point H, the state shown in FIG.
P_HAs shown in FIG.
Return to the normal state. This state is defined as a state before the first discharge operation.
It is maintained until the starting point I of the process. Drive voltage to 0V again
At time H immediately after the decrease, the state shown in FIG.
M_HAs shown in the figure, the volume of the ejected ink droplet and the
A volume corresponding to the sum of the increase in the volume of the
Only the meniscus position is retracted, but
The next ejection by the ink filling (refill)
Menis at the start I of the first previous step in the operation
The residue position is in the state M in FIG._IAs shown in
State M at time A_AWill be the same as Thus, one ejection operation is completed.
You. Hereinafter, such a cycle operation is performed for each nozzle 118.
The recording paper 2
Image recording on (FIG. 2) is performed continuously. In this embodiment, in the second step,
The required time t2 is that the meniscus drawn in the first stroke is
It is assumed that it is less than the time required to reach the chisel opening end,
The ejection voltage Va in the third step is sufficient to eject ink droplets.
It is assumed that it is within the range. FIG. 4 (a)
The time required for the steps other than the above steps CD, DE and EF
Are described as follows. AB = τ
1, BC = τ2, FG = t4, GH = t5. Next, returning to FIG. 4 again, the drive signal 21b
Will be described. In the present embodiment, the drive signal
The portions A to D in 21b are the same wave as the drive signal 21a.
It has a shape. On the other hand, the required time t for the 0V holding process DE '
6 is larger than the required second stroke time t2 of the drive signal 21a.
Drive signal 21b is assisted from the reference voltage 0V
The time point E 'at which the voltage starts rising to the voltage Vb is determined by the drive signal 21
a time td from the discharge start timing te (time E)
Only late. In FIG. 4B, the drive signal 21
Step E ′ in which b changes from the reference voltage 0 V to the auxiliary voltage Vb
The time required for F 'is t7, and the drive signal 21b is set to the auxiliary voltage Vb.
From the point of time F 'when the holding of the auxiliary voltage Vb ends
The time required until G 'is t8, and the driving signal 21b is an auxiliary voltage.
When the process G'H 'for changing from Vb to the reference voltage 0V is required
The interval is denoted by t9. Here, as described later,
The point that the interval td is appropriately set is one feature of the present invention.
However, this will be described later. Next, the ink jet printer 1 shown in FIG.
The overall operation will be briefly described. In FIG. 1, a personal computer (not shown)
Print data from an information processing device such as a computer
When input to the printer 1, the image processing unit 15
Image processing (for example, compressed
Data expansion, etc.) and print data 2
2 is sent to the head controller 14. The head controller 14 controls the recording head 1
Print data 22 for n dots corresponding to the number of nozzles of 1
When acquired, based on these print data 22, n
For each of the nozzles, the
The droplet size is determined, and from this determination result,
Each set of drive signals 21a and 21b to be supplied is selected.
For example, when expressing high density, increase the ink droplet size.
Drive waveforms (t2, Va are large and Vp
Select a set of waveforms with small
For high resolution expression, reduce the ink droplet size.
Drive waveforms (t2 and Va are small and Vp is large
Waveform). Also expresses subtle intermediate gradations
The size of the ink drop between adjacent dots.
And, for example, between each nozzle
If the ink ejection characteristics vary in
A set of drive waveforms that can be corrected is selected. Now, the head controller 14 has n dots.
Drive signals (ie, supplied to n nozzles 118)
After selecting the set of drive signals to
In the imaging, each nozzle 1 in the recording head 11 is
The selected drive signal 21 is applied to the 18 piezoelectric elements 116a.
a and the piezoelectric element 11 of each nozzle 118
6b is supplied with the selected drive signal 21b. Each
The piezoelectric element 116a in the skull is supplied with the supplied drive signal.
Each step as described in FIG. 5 according to the voltage waveform of 21a
And eject ink droplets. At this time, the pressure of each nozzle
The electric element 116b is a voltage wave of the supplied drive signal 21b.
Displaced according to the shape as described later,
An operation for assisting the discharge operation is performed. Next, referring to FIG. 4, FIG. 6 and FIG.
Characteristic of the ink jet printer according to the present embodiment
The operation will be described. As described in the related art section,
Sate, an incidental ink droplet that is generated when a droplet is ejected
Light droplets generate ejection pressure by piezoelectric elements and
Droplet ejection occurs frequently in the method of discharging droplets,
Between the head and tail of the flying ink
From the beginning to the tail due to time differences and speed differences that occur
Is separated, and the tail part becomes fine ink droplets.
it is considered as. In the present embodiment, such a satellite
In order to prevent the generation of droplets, as shown in FIG.
Signal 21a at time E (discharge start timing te).
By raising the pressure from 0V and changing it to the discharge voltage Va
While the ink chamber 114 is contracted, the drive signal 2
1a maintains the ejection voltage Va, and the ink chamber 114 contracts.
, The driving signal 21b is assisted from the reference voltage 0V.
The ink chamber 114 is further contracted by rising to the voltage Vb.
I try to make it. This point will be further explained with reference to FIG.
I will tell. FIG. 6 shows the voltage waveforms of the drive signals 21a and 21b.
The relationship between the change in the displacement of the piezoelectric elements 116a and 116b
It represents. More specifically, FIG.
21B shows a waveform of a main part of the piezoelectric element 116a.
(C) shows the waveform of the main part of the drive signal 21b.
(D) shows the displacement of the piezoelectric element 116b. here,
The horizontal axis indicates time, and the vertical axes in (a) and (c)
Indicates voltage, and the vertical axis in (b) and (d) indicates displacement.
Show. As shown in FIGS. 6A and 6B, the piezoelectric
The element 116a receives the drive signal 21a starting from the time point E.
Displaced in the direction to shrink the ink chamber 114 with increasing voltage
I do. Then, the piezoelectric element 116a is electrically driven by the inertial force.
When the pressure overshoots the point F when the pressure reaches the discharge voltage Va
The maximum displacement state is obtained at the point P, where the ink chamber 114 is in the maximum displacement state.
It is in a contracted state. On the other hand, as shown in FIGS.
As described above, the drive signal 21b indicates that the piezoelectric element 116a has the maximum displacement.
At the time point P (ie, time point E '), the reference voltage
Since it starts to rise from V to the auxiliary voltage Vb,
Accordingly, the piezoelectric element 116b further contracts the ink chamber 114.
Displaced in the direction to make it. And the piezoelectric element 116b is
With the same inertial force as above, the voltage reaches the auxiliary voltage Vb.
Maximum displacement state at time P 'when overrun from time F'
And the ink chamber 114 is in the most contracted state. like this
In the present embodiment, however, the piezoelectric element 116a
The time required to reach the large displacement point P is defined as a delay time td.
You have set. At time E, the discharge voltage Va of the drive signal 21a becomes
The applied piezoelectric element 116a changes in the ink chamber contraction direction.
Pressure to generate pressure in the ink chamber 114,
This pressure pushes the ink out of the nozzle 118. This
At this point, the ink pushed out from the nozzle 118
It has a tail and is in the state of an ink column. one
On the other hand, the drive signal 21b at the time of the maximum displacement of the piezoelectric element 116a
The piezoelectric element 116b to which the auxiliary voltage Vb of
Displaced in the ink chamber contraction direction,
Generate new pressure. And with this new pressure
Ink column already being pushed out of the nozzle 118
Is boosted. For this reason, the tail at the top of the ink column
The parts catch up and the two are integrated into a single ink drop
At the same time, discontinuity occurs in the ink flow,
The pillar is then cut off shortly after the tail. This
The tail of the ink column is prevented from extending long,
The generation of site drops is suppressed. It should be noted that the piezoelectric element 116a is provided with a discharge voltage Va.
While the vibration is maintained, the driving signal 21a
Changes from the discharge voltage Va at the time point G to the reference voltage 0V at the time point H.
When it changes, the displacement of the piezoelectric element 116a returns to 0, and furthermore,
Then, a natural vibration that attenuates gradually is performed. Similarly, the piezoelectric element
116b is a characteristic vibration while the auxiliary voltage Vb is maintained.
When the drive signal 21b is the auxiliary voltage Vb at the time point G '
Changes to the reference voltage 0V at the time point H ′, the piezoelectric element 1
The displacement of 16b returns to 0, and then gradually decreases.
Perform vibration. FIG. 7 shows the case where the delay time td is variously changed.
This represents the ejection state of ink droplets. (A) of this figure
Sets the delay time td to 14, 15, 16 μsec, respectively.
The change at the time of cutting the tail of the ink droplet when set to
(B) shows a case where the piezoelectric element 116a is driven by the drive signal 21a.
And the delay time td.
When set to 14, 15, 16μsec respectively
36 μsec after the discharge start timing te
It represents the state of the ink droplet. Note that the piezoelectric
The thickness of the elements 116a and 116b is 25 μm,
The thickness of the gate 113 is 25 μm and the drive shown in FIG.
Time parameters and voltage parameters of the motion signals 21a and 21b.
The parameters are set as follows. The time parameter
The unit of data is μsec.
Are in volts. Τ1 = 30, τ2 = 10, t1 = 9, t2 = 2, t3 = 4, t4 = 20, t5 =
8, t6 = 17, t7 = 4, t8 = 20, t9 = 8, td = 15, Vp = 35, Va = 30, Vb = 30 As shown in FIG. 7A, the delay time td
Are set to 14, 15, and 16 μsec, respectively.
Each cutting timing of the ink droplet is determined by an ejection start timing t
e from 31.2, 29.2, 31.6 μsec respectively
It has just passed. Also, as shown in FIG.
36 μsec from the discharge start timing te
Looking at the state after the elapse, the delay time td is set to 14,1.
In any case of 5, 16 μsec,
The tail of the droplet is the same as when the ejection was performed only with the piezoelectric element 116a.
It has been cut off earlier. In particular, when the delay time td is 15
The length of the ink droplet when set to μsec is the delay time td
Is shorter than when each is set to 14, 16 μsec.
It's getting worse. As described above, the drive signal 21b is supplied to the piezoelectric element
The tail of the ink droplet by applying it to the tip 116b
The timing can be advanced, and the generation of satellite drops is suppressed.
It turns out that it is. Particularly, the delay time td is reduced to 15 μsec.
If set, the tail of the ink drop will be cut off earliest,
It is found that the generation of satellite droplets can be suppressed most effectively.
You. In the present embodiment, the delay of 15 μsec
The delay time is the maximum after the piezoelectric element 116a starts displacing.
It is almost equal to the time required to reach the displacement position
You. That is, by the ejection voltage Va of the drive signal 21a,
When the displacement of the piezoelectric element 116a becomes maximum, the drive signal
Rises the auxiliary voltage Vb of the piezoelectric element 116b
Control to start the displacement of
Since the generation of site drops can be suppressed most effectively
is there. As described above, according to the present embodiment, each node
Two piezoelectric elements for each ink chamber 114 corresponding to the chirping
116a and 116b, and one piezoelectric element 1
16a, the ejection of ink droplets is started.
The ink chamber 114 contracts due to the displacement of the electric element 116a.
While the other piezoelectric element 116b is displaced,
Since the ink chamber 114 was further contracted,
The tail of the ink drop can be cut off early,
It becomes possible to suppress generation of tereite droplets. In particular,
When the piezoelectric element 116a is displaced the most, the piezoelectric element
By starting the displacement of 116b, the satellite drops
Can be most effectively suppressed. The present invention has been described with reference to the embodiments.
However, the present invention is not limited to this embodiment, and may be variously modified.
It is possible. For example, in the example shown in FIG.
When the piezoelectric element 116b is displaced the most, the piezoelectric element 116b changes.
Position, but the present invention is not limited to this.
The ink chamber 114 is in a contracted state
(Ie, after time E in FIG. 6B).
Before the point H), the displacement of the piezoelectric element 116b is started.
Even if this is done, a considerable effect can be obtained. Further, each time parameter and
The setting values of the voltage and voltage parameters are limited to the values exemplified above.
However, it can be changed as appropriate. For example, the real
In the embodiment, both driving signals 21a and 21b are used.
Although the pull-in voltage is the same Vp, both may be different.
No. In the above-described embodiment, the discharge pressure
Using the piezoelectric element 116a on the ink supply side as a raw means
Along with the nozzle as a pressure generation means for preventing satellite drops
Side piezoelectric element 116b is used,
Conversely, the piezoelectric element 1 on the nozzle side serves as a discharge pressure generating means.
16b, and a pressure generating means for preventing satellite drops
As the step, the piezoelectric element 116a on the ink supply side is used.
It may be. In the above embodiment, one nozzle
Has been described for the case where two piezoelectric elements are provided.
However, three or more piezoelectric elements are provided for one nozzle,
These piezoelectric elements are divided into those for ejection and those for suppressing satellite drops.
The drive signal 21a for ejection is added to the piezoelectric element for ejection.
Satellite drops on the piezoelectric element for suppressing satellite drops
The drive signal 21b for suppression may be applied.
In this case, the displacement abilities of three or more piezoelectric elements are equal to each other.
It may be better or different. Like this
This allows for finer control of satellite droplets
You can take control. In the above embodiment, one nozzle
In addition to providing one ink chamber 114 for 118,
Two piezoelectric elements 1 corresponding to this one ink chamber 114
16a and 116b are provided, for example, as shown in FIG.
As shown in FIG.
Ink chambers 114a and 114b,
The piezoelectric elements 116a, 1
16b may be provided. Note that FIG.
This represents a state in which a part of the head 11 is viewed from directly above.
2, the same elements as those shown in FIG.
The illustration of the vibration plate 113 is omitted.
According to the configuration shown in this figure, one ink chamber 114a
The behavior of the piezoelectric element 116a in the other ink chamber 11
4b has little effect on the state of the piezoelectric element 116b.
a, 116b can reduce crosstalk between them.
As a result, higher-precision printing quality can be obtained. [0061] As described above, according to the first aspect of the present invention,
According to the ink ejection method, the ink ejected from the nozzle
In order to determine the size of the drop, the size of the ink in the nozzle is
Ink meniscus retraction process for reversing the position of scass
And the meniscus determined in the ink meniscus retreating process
The contraction of the ink chamber starts from the position, and the ink drop from the nozzle
A first ink chamber shrinking step of discharging ink, and a first ink
To further shrink the ink chamber shrunk in the chamber shrinking process
After the first ink chamber contraction step starts, the ink chamber
At or near the point of maximum displacement in the chamber contraction direction
In addition, the ink chamber is overlapped with the first ink chamber shrinking step.
And a second ink chamber contraction step for starting contraction of the ink.
The ink drops early before the ink drops have long tails.
Can suppress the generation of incidental ink droplets.
Quality of recorded images can be prevented.
There is an effect that. In particular, use small ink droplets
Such as faint or halftone images that need to be
In images susceptible to important incidental ink droplets
Also, it is possible to effectively prevent the image quality from deteriorating. Ma
In addition, the flying speed of the ejected ink
There is no shortening or deterioration of frequency characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a schematic configuration of an inkjet printer according to an embodiment of the present invention. FIG. 2 is a perspective sectional view illustrating a structural example of a recording head. FIG. 3 is a cross-sectional view illustrating a configuration example of a recording head. FIG. 4 is a diagram illustrating an example of a waveform of a drive signal output from a head controller in FIG. FIG. 5 is a diagram for explaining the relationship between the ejection drive signal waveform shown in FIG. 4 and the state of the ink chamber and the change in the meniscus position in the nozzle. 6 is a diagram illustrating an example of a relationship between a drive signal waveform illustrated in FIG. 4 and a displacement amount of a piezoelectric element. 7 is a diagram illustrating an example of an ink droplet ejection state according to the drive signal waveform illustrated in FIG. FIG. 8 is a plan view illustrating a modification of the recording head used in the ink jet printer according to the present embodiment. FIG. 9 is an explanatory diagram illustrating a driving method of a conventional inkjet printer. FIG. 10 is an explanatory diagram for explaining a driving method of another conventional inkjet printer. [Description of Signs] 1 ... Inkjet printer, 11 ... Recording head, 14
... head controller, 21a, 21b ... drive signal, 2
2: Print data, 113: Vibration plate, 114: Ink chamber, 115: Common flow path, 116a, 116b: Piezoelectric element, 118: Nozzle, Vp: Pull-in voltage, Va: Discharge voltage, Vb: Auxiliary voltage, td: Delay Time, te: discharge start timing.

   ────────────────────────────────────────────────── ─── Continuation of front page    F-term (reference) 2C057 AF28 AF39 AG15 AG44 AM15                       AM17 AM21 AM22 AN01 AR08                       AR18 BA04 BA14 CA01

Claims (1)

1. A method of discharging ink in the ink chamber as ink droplets from a nozzle communicating with the ink chamber by changing the volume of the ink chamber. An ink meniscus retreating step of retreating the position of the ink meniscus in the nozzle in order to determine the size of the ink droplet to be discharged; A first ink chamber contraction step of ejecting ink droplets from the nozzles; and after the first ink chamber contraction step starts, in order to further contract the ink chamber contracted in the first ink chamber contraction step. At or near the time when the ink chamber is most displaced in the contraction direction, the first ink chamber contraction step is superimposed on Ejecting method of ink; and a second ink chamber contraction step of initiating a further contraction of the ink chamber.