JP2001322265A - Drive controller and controlling method for ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive controller for ink jet head of such a type as one pixel is formed by ejecting ink liquid drops a plurality of times in which record quality does not deteriorate even when the environmental temperature is varies. SOLUTION: The drive controller 1 for an ink jet head 100 sets the number of pulses per pixel depending on the environmental temperature and controls the number of times for ejecting ink to stabilize ejection of ink liquid drop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control of an ink jet head of the type in which ink droplets are ejected from ink nozzles by vibrating a vibrating plate formed on a peripheral wall of an ink chamber communicating with the ink nozzles by electrostatic force. The present invention relates to a method and an apparatus. More specifically, the present invention relates to a method for controlling the driving of an ink-jet head in which one pixel is formed by discharging ink droplets a plurality of times in this type of ink-jet head. The present invention relates to a drive control method and apparatus for an inkjet head capable of performing a droplet discharge operation and ensuring a stable print density.

[0002]

2. Description of the Related Art An ink jet head of the type which discharges ink droplets by changing the volume of an ink chamber storing ink using electrostatic force is disclosed in, for example, Japanese Patent Application Laid-Open No.
-71882, 6-55732, 5-5060
What is described in each gazette of No. 1 is conventionally known.

In these ink jet heads,
In order to maintain the quality of the printed image at a constant level, it is necessary to stabilize the mass and the ejection speed of the ink droplets to be ejected, and further stabilize the mass of the ink droplets constituting one pixel.

[0004] In order to address these problems, an ink jet recording method for recording one pixel by discharging a plurality of ink droplets is disclosed in Japanese Patent Application Laid-Open No. 10-278309.

In JP-A-10-278309, the recording quality is improved by controlling the number of ink ejections according to the environmental temperature.

[0006]

However, these conventional methods for controlling the drive of an ink jet head employ the above-described electrostatic force to change the volume of an ink chamber in which ink is stored, thereby discharging ink droplets. When the present invention is applied to an ink jet head of a type which performs the following, there are further problems to be solved as follows.

When the ambient temperature around the ink jet head changes, the characteristics of the ink droplet mass fluctuation with respect to the change in the pulse width and voltage of the drive voltage pulse applied to the head change with the change in the viscosity of the ink. When the pulse width is fixed, even if the number of ejections is controlled and the total mass of a plurality of ink droplets forming one pixel is adjusted to a desired value, each ink droplet is unstable. An area with a pulse width that causes ejection occurs, and the size and density of the desired pixel cannot be kept constant, making it impossible to keep the quality of the printing result constant, or even making printing impossible. Had the problem that

[0008] In view of the above, an object of the present invention is to provide:
In an ink jet head of a type in which an ink chamber volume is increased or decreased to eject ink droplets from an ink nozzle, 1
When configuring a pixel by discharging ink droplets multiple times,
Inkjet head capable of stably ejecting each ink droplet and stably controlling the total mass of a plurality of ink droplets forming one pixel even when the ambient temperature around the inkjet head changes It is an object of the present invention to provide a drive control method.

Furthermore, it is possible to propose a drive control device capable of variously modulating the pixel size, performing gradation printing, and stably obtaining a high quality and beautiful printing result, and providing a printing device. Is to do.

[0010]

In order to solve the above-mentioned problems, the present invention provides an ink nozzle for discharging ink droplets, and an ink chamber communicating with the ink nozzle and holding ink. A diaphragm formed on a peripheral wall that defines the ink chamber and displaceable in an out-of-plane direction, and a counter electrode formed on each of the diaphragms. In a drive control method for an ink-jet head in which an electric signal is applied to deform the vibrating plate to discharge ink droplets from the ink nozzles, and one pixel is formed by discharging ink a plurality of times, the ambient environmental temperature of the ink-jet head is controlled. Temperature detecting step of detecting the temperature of the electric signal, and a first temperature compensation value for calculating a pulse number correction value of the pulsed electric signal based on the temperature detected in the temperature detecting step. And applying the pulse-shaped electric signal between the opposed electrodes with a correction pulse number obtained by adding the pulse number correction value to a preset pulse number initial value of the pulse-shaped electric signal. And a driving step.

The temperature detecting step detects the ambient temperature of the environment where the ink jet head is placed, and the first temperature compensation calculating step calculates a pulse number correction value in association with the detected ambient temperature, Applies a pulse-like electric signal between the counter electrodes with the number of correction pulses per pixel obtained from a preset pulse number initial value and a pulse number correction value associated therewith. That is, the temperature detection step and the first
The temperature compensation calculating step and the driving step, the number of pulses of the pulse-like electric signal applied between the counter electrodes per pixel can be changed in accordance with the surrounding environmental temperature, and the diaphragm per pixel can be changed. Can be changed, thereby changing the number of ejections of the ejected ink droplets and changing the mass of ejected ink per pixel. Therefore, even if the ambient temperature changes, the mass of ejected ink can be reduced. It is possible to maintain a substantially constant value.

An ink nozzle for discharging ink droplets, an ink chamber communicating with the ink nozzle and holding the ink, and an outer surface formed on a peripheral wall defining the ink chamber and extending in an out-of-plane direction. And a counter electrode formed on each of the vibrating plates. A pulse-like electric signal is applied between these counter electrodes to deform the vibrating plate, thereby causing the vibrating plate to deform from the ink nozzles. In a drive control apparatus for an ink jet head which discharges ink droplets and forms one pixel by plural times of ink discharge, a temperature detecting step of detecting a surrounding environmental temperature of the ink jet head, and a temperature detected in the temperature detecting step. A first temperature compensation value calculating step of calculating a pulse number correction value of the pulse-like electric signal based on the pulse-like electric signal; Characterized in that it comprises a driving step for applying the pulse-like electrical signal between the counter electrode correction pulse number of the pulse number correction value to the pulse number initial value Motoma' by adding the issue.

The number of ejections of ink droplets per pixel can be changed by the temperature detecting step, the first temperature compensation calculating step, and the driving step, so that even if the ambient temperature around the ink jet head changes, It is possible to easily realize a drive control device for an ink jet head that can maintain the mass of ejected ink at a substantially constant value. Therefore,
The mass of ink droplets that land on a recording medium, such as paper, is constant, and the print density on the recording medium can be made substantially constant. Stable printed products are not affected by the surrounding environmental temperature It is possible to propose an ink jet recording apparatus that can secure the position.

Further, the method and apparatus for controlling the driving of an ink-jet head according to the present invention calculate the pulse width correction value of the pulse-like electric signal based on the temperature detection step and the temperature detected in the temperature detection step. A second temperature compensation value calculation step, and the pulse-shaped electric signal is corrected by a pulse width correction value obtained by adding the pulse width correction value to a preset pulse width initial value of the pulse-shaped electric signal. And a driving step of applying a voltage between the opposed electrodes.

The temperature detecting step detects the ambient temperature of the environment where the inkjet head is placed, and the second temperature compensation calculating step calculates a pulse width correction value in association with the detected ambient temperature, Applies a pulse-like electric signal between the counter electrodes the number of times equal to the set number of correction pulses, the pulse width obtained from the preset pulse width initial value and the pulse width correction value associated therewith. That is, the temperature detecting step, the second temperature compensation calculating step, and the driving step
It is possible to change the pulse width of the pulse-like electric signal applied between the opposing electrodes in accordance with the surrounding environmental temperature, and it is possible to discharge in the pulse width region where ink droplets are stably discharged at each environmental temperature. Even when the ambient temperature changes, the flying state of the ejected ink droplet can be stably maintained. Therefore, it is possible to propose an ink jet recording apparatus that can secure stable print quality without being affected by the surrounding environmental temperature.

Further, the voltage waveform or the number of pulses of the pulse-like electric signal for performing the ink ejection a plurality of times is set for each pixel.

In addition, one or more pairs of pulse-like electric signals having different polarities of an electric field generated between the opposed electrodes due to the pulse-like electric signals for ejecting ink droplets from the ink nozzles are applied. It is characterized by.

This is a drive control method peculiar to an ink jet head of a type in which a different one or a plurality of pairs of pulse-like electric signals are applied, and an ink droplet is ejected by deforming a diaphragm using electrostatic force. It is also possible to cope with alternate driving in the forward and reverse directions, and even in an ink jet head using electrostatic force, it is possible to maintain the mass of ejected ink at a substantially constant value even when the surrounding environmental temperature changes. Therefore, it is possible to propose an ink jet recording apparatus that can secure stable print quality without being affected by the surrounding environmental temperature.

In addition, the temperature compensation value calculating step may include:
When the temperature detected in the temperature detection step is equal to or lower than the temperature at which the pulse number initial value of the pulsed electric signal is set, the pulse number correction value is calculated as a positive integer. I do.

In the temperature compensation value calculating step, when the temperature detected in the temperature detecting step is equal to or lower than the temperature at the time when the pulse number initial value is set, the pulse number correction value is calculated to be a positive integer, and the correction pulse is calculated. The number is corrected to a pulse number larger than the pulse number initial value. The viscosity of the ink used in the ink jet head changes with a change in the environmental temperature. The viscosity increases as the environmental temperature decreases. That is, the mass of the ejected ink droplets decreases, and the print density on the recording medium decreases. Therefore, when the environmental temperature decreases, the number of ejections of the ejection ink droplet is increased,
The print density can be kept from dropping and stable print density can be maintained. Therefore, it is possible to propose an ink jet recording apparatus that can secure stable print quality without being affected by the surrounding environmental temperature.

Further, in addition to the above, the first temperature compensation value calculating step includes a storage unit storing a correspondence table between the ambient environment temperature of the ink jet head and the pulse number correction value, and corresponds to the detected temperature. The pulse number correction value is retrieved and output from the correspondence table.

The storage unit provided in the first temperature compensation value calculation step stores a table in which the temperature and the pulse number correction value are associated with each other, and the first temperature compensation value calculation step is detected in the temperature detection step. The pulse number correction value corresponding to the detected temperature is retrieved from the correspondence table, and in the driving step, the pulse number of the corrected pulse number obtained from the retrieved pulse number correction value and the pulse number initial value is applied to the pulse-like electric signal between the counter electrodes. It is possible to change the number of ejections of the ejected ink droplets in accordance with the change in the environmental temperature when the voltage is applied.

Further, a pulse number correction value for each pixel,
By setting the pulse number initial value, the correspondence table can be easily created without being affected by changes in the pattern to be printed, characters, and the like.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of an ink jet head to be driven and controlled according to the present invention, and shows a flow path and a cross section of an actuator. As shown in FIG. 1, an ink jet head 100 of this type has a structure in which three semiconductor substrates 102 and 103 and a glass substrate 104 are stacked, and a plurality of ink nozzles 105 are provided on an intermediate semiconductor substrate 102. In addition, an independent ink chamber 106 communicating with each ink nozzle 105 is defined, and a bottom wall of each ink chamber 106 is formed as a vibration plate 107 capable of vibrating in an out-of-plane direction. Each vibrating plate 107 functions as a common electrode, and a counter electrode 109 is formed in a portion of the counter plate 108 defined by the lower semiconductor substrate 104 opposed thereto. Driving voltage (pulsed electric signal) between these electrodes
Utilizing the electrostatic force generated by applying
The vibration plate 107 is caused to vibrate (drive).
The volume of the ink chamber 106 increases or decreases due to the vibration of the vibration plate 107, whereby the ink droplets 110 are ejected from the ink nozzle 105 communicating with the ink chamber 106 based on the fluctuation of the ink pressure generated in the ink chamber 106. Is done.

In the ink jet head to be controlled according to the present invention, the flow path and the actuator shown in FIG. I have. 64
A character or an image is printed by selecting from the nozzles 105 and ejecting ink droplets and controlling the drive.

In the example of the ink jet head shown in FIG. 1, the distance between the counter electrode 109 and the vibration plate 107 is configured as an actuator, but this distance may be changed within the same actuator if necessary. It may have a structure. The counter electrode 109 has a stepped shape so that the counter electrode 109 and the diaphragm 107 are non-parallel,
By partially vibrating a part of the diaphragm 107,
Ink droplets with a smaller ink mass can be ejected, and the ink mass per pixel can be adjusted.

Further, the ink jet head 100 of this embodiment
Is a type in which the volume of an ink chamber communicated with a nozzle is changed by sucking and vibrating a diaphragm using electrostatic force to discharge ink droplets. Of course, it is also possible to employ a type in which the volume of the ink chamber communicated with the nozzle is changed using a piezoelectric element or the like to discharge the ink droplets. In the present embodiment, the face ejection type ejects ink droplets from nozzle holes provided on the upper surface of the substrate 103, but the edge eject type ejects ink droplets from nozzle holes provided at the end of the substrate.

FIG. 2 is a schematic block diagram of a drive control device for an ink jet head to which the present invention is applied. The ink jet head driven and controlled by the drive control device 1 shown in this figure is the same as that shown in FIG. 1, so the same reference numerals are given and the description thereof will be omitted.

The drive control device 1 for an ink jet head has an ink jet head control unit 2, and the ink jet head control unit 2 is mainly composed of a CPU. That is, print information is supplied to the CPU from the external device 3 via the bus. The CPU is connected to a ROM, a RAM, and a character generator 4 via an internal bus, and executes a control program stored in the ROM by using a storage area in the RAM as a work area. A control signal for driving the inkjet head is generated based on the character information generated from. The gate array 5 supplies a drive control signal corresponding to the print information to the head driver IC 9 by a control signal from the CPU, and also supplies a control signal for generating a drive voltage pulse to the drive voltage pulse generation circuit 6.

The drive voltage pulse generating circuit 6 is supplied with a control signal from the logic gate array 5, generates a drive voltage pulse, and supplies a drive pulse to the head driver IC 9.
In the drive voltage pulse generation circuit 6, a control signal as digital information is converted into an analog drive voltage pulse waveform by a D / A (digital-analog) converter. That is,
The drive voltage pulse generation circuit 6 generates a drive pulse waveform from a control signal relating to pulse signal waveform generation conditions such as the pulse width and voltage of the drive voltage pulse, the rise time and the fall time of the pulse. By forming the drive pulse generation circuit 6 with a D / A converter, the only way to generate a drive voltage pulse waveform with high accuracy is to increase the number of bits of the D / A converter used to increase the resolution of the waveform. So
It is possible to easily improve the accuracy of the drive voltage pulse waveform. The drive pulse generation circuit 6 may be constituted by an RC circuit. If the drive pulse generation circuit 6 is configured by an RC circuit, it is possible to make the circuit configuration less expensive than when the drive pulse generation circuit 6 is configured by a D / A converter.

The drive control signal and the drive voltage pulse are supplied to a head driver IC 9 formed on a head substrate 8 via a connector 7. The head driver IC 9 operates by being supplied with a driving voltage Vh of a high voltage system and a driving voltage Vcc of a logic circuit system from a power supply circuit 10, and switches between a driving voltage pulse and a GND potential according to the supplied driving control signal to thereby form an inkjet head. The voltage is applied between opposed electrodes corresponding to each of the 100 ink nozzles. As a result, ink droplets are ejected from the ink nozzle in which a potential difference is generated between the opposing electrodes due to the drive pulse.

FIG. 3 shows a voltage waveform of a drive pulse Pw which is a basic pulse of the drive voltage pulse Vp generated by the drive voltage pulse generation circuit 6.

In the present invention, the ink nozzle 10 to be driven is
5 discharges a plurality of times, k times in total, to form one pixel. The drive pulse Pw discharges one shot of ink droplets from the ink nozzle by one pulse application. Pwn (n = 1, 2,... K) is the pulse width of the drive voltage pulse Pw (n) for performing the n-th ejection, and Pwin (n = 1, 2,..., K−1) ) Is a drive voltage pulse Pw for performing the n-th and (n + 1) -th ejections.
This is the time interval between (n) and Pw (n + 1).

V (n) is the drive voltage of the drive pulse Pw (n). Here, Pwin is the natural oscillation cycle and P
It is set to be equal to or longer than the time interval of wn. The details are described below.

After the ejection when n = 1, that is, Pw
From the behavior of the meniscus immediately after the first ink droplet ejection after applying (1), it was originally impossible to apply Pw (2) to perform ejection by the conventional drive until the meniscus was restored. . However, in order to realize high-speed printing, it is necessary to apply and discharge Pw (2) without waiting for the meniscus to be restored.

Therefore, the method of setting the pulse interval time Pwin and the first, second and subsequent pulse width times Pwin
Regarding the setting of wn or the drive voltage V (n), each is individually set so that the ejection characteristics are optimal for the quality of the printing result.

The pulse interval time Pwin can be set as Pwin ≧ Pw (n) + T0, where T0 is a natural period. This is because, according to observations made by the inventors, the time required for an ink droplet to be ejected from an ink nozzle and being cut off corresponds to Pwn + T0. This is because it has been discovered that it is necessary for stable ejection of droplets. Here, T0 is a natural oscillation period when a voltage is applied to the ink flow path, and is an acoustic constant of ink in the ink flow path composed of the ink chamber and the ink nozzles. It is mainly determined by the compliance of the surrounding wall.

FIG. 3 shows a drive pulse Pw for performing two ejections.
And the driving waveforms are described. For example, Pwi1 = Pw1 + T0 is set to stably perform the second ink ejection by the drive pulse Pw (2) and minimize the difference between the first and second ejection times.

Pwcn (n = 1, 2,... K) is Pw
In the charging interval that regulates the charging time of (n), Pwdn (n
.., K) are discharge times that regulate the discharge time of Pw (n).

Among the waveforms of the driving pulse Pw, the driving pulse width Pwn largely depends on the dimensions of the flow path of the ink jet head. In the embodiment of the ink jet head shown in FIG. 1, the nozzle shape of the ink nozzle is circular, the diameter is 20 μm, the width of the ink chamber 106 is 45 μm, the length is 3 mm, and the depth is 178 μm. .
The width of the diaphragm 107 is 45 μm, which is the same as that of the ink chamber 106.
m, and the thickness is 0.8 μm. The interval between the diaphragm 107 and the counter electrode 109 is 0.175 μm.
A thermal oxide film is laid on the surface of the diaphragm 107 between the substrate and the counter electrode 109 (the thermal oxide film is not shown).
Even if a driving voltage is applied, it is not broken.

In the driving voltage pulse Vp shown in FIG.
When one pixel is formed by two ejections with the ink jet head shown in FIG. 1 and driven at 25 ° C. under the condition that the diaphragm 107 and the counter electrode 109 are in contact with each other, V (n) = V1
=, V2 = 27V, Pw1 =, Pw2 = 10 μsec,
Pwi1 = 50 μs, Pwc1 =, Pwc2 = 2 μs,
By setting Pwd1 = and Pwd2 = 1 μsec and performing drive control, it was possible to eject ink droplets.

Pwn is the time required for the diaphragm 107 to be displaced and the time from when the diaphragm 107 is displaced to when the pressure of the ink in the ink chamber 106 becomes the highest in the above-mentioned specifications of the flow path of the ink jet head. Is determined by In the embodiment of the ink jet head illustrated in FIG. 1, when the vibration plate 107 contacts the opposite electrode 109, Pw
(N) is determined by the time until the diaphragm 107 contacts the counter electrode 109 and the response time of the ink inside the ink chamber 106 while the diaphragm 107 contacts. Ink chamber 1 in contact
The response time 06 is determined by the compliance of the peripheral wall of the ink flow path and the inertance of the ink in the ink chamber 106. That is, most of them are determined by the dimensions of the ink chamber.

In an ink jet head having a structure and a control method in which the vibration plate 107 is in contact with the counter electrode 109, each Pwn does not change its value greatly, and is almost determined if the size of the ink flow path of the ink jet head is determined. It means you can do it. Further, in this case, Pw due to manufacturing variation of the ink jet head.
There is an advantage that the setting of Pwn is easy and the print quality can be stably ensured without n being largely changed.

In setting a plurality of drive voltage pulses to form one pixel, the drive voltage can be applied to the embodiment of alternate forward / reverse drive. The forward / reverse alternating drive is a method of driving an ink jet head in which ink droplets are ejected by deforming the vibration plate 107 using electrostatic force, and eliminates the influence of residual charges remaining on the vibration plate 107. This is a method for controlling the driving of an ink jet head which is performed for the purpose of always performing a good ink droplet discharging operation, and is another invention by the present applicant.

The first between the diaphragm 107 and the counter electrode 109
Diaphragm 107 in the first driving mode in which a voltage having a polarity of
Is deformed so that the ink droplets are ejected from the nozzles 105, and the diaphragm 107 and the counter electrode 1 are discharged at least once every time when the ink droplets are ejected by the first driving mode.
A method of driving an ink jet head in which a diaphragm 107 is deformed in a second driving mode in which a voltage having a second polarity opposite to the first polarity is applied during the period 09 to discharge ink droplets from the nozzles 105 In this case, the ink droplet ejection operation according to the first and second driving modes is alternately performed, and the ink droplet ejection operation according to the first and second driving modes is performed twice. This is a method for driving an ink-jet head, wherein one-dot printing is sequentially formed on a recording medium.

Since the difference between the driving pulse widths in the first driving mode and the second driving mode may cause the accumulation of electric charge, for example, the driving pulse width may be further increased between the diaphragm 107 and the counter electrode 109 for each driving path. Devise so that the polarity of the applied voltage is switched. Thus, the accumulation of the residual charge remaining on the diaphragm due to the difference in the drive pulse width between the first drive mode and the second drive mode is suppressed, and the effect thereof becomes practically negligible. In this case, it is preferable that the number of ejections for forming one pixel is an even number.

The drive voltage pulse Vp shown in FIG. 3 can be generated by using at least one D / A converter or RC circuit of the drive pulse generation circuit 6 described above.

FIG. 4 is a schematic block diagram showing the inside of the head driver IC 9 to which the present invention is applied, which is shown in the block diagram of FIG. The head driver IC 9 is a CMOS 64-bit output high withstand voltage driver that operates by being supplied with a high-voltage drive voltage Vh and a logic circuit drive voltage Vcc from the power supply circuit 10. The head driver IC 9 generates a drive voltage pulse and a GND by the supplied drive control signal.
The potential is switched and applied between opposed electrodes corresponding to each ink nozzle of the inkjet head 100.

In FIG. 4, reference numeral 91 denotes a 64-bit shift register which receives a 64-bit DI signal input from the logic gate array 5 as serial data,
X which is a basic clock pulse synchronized with the I signal
Data is shifted up by SCL pulse signal input,
This is a static shift register stored in a register in the shift register 91. As the DI signal, a control signal for ON / OFF of the selection information of each of the 64 nozzles is transmitted as serial data.

Reference numeral 92 denotes a 64-bit latch circuit which latches 64-bit data stored in the shift register 61 by a latch pulse LP and stores the data, and sends the stored data to a 64-bit inversion circuit 93 as a signal. This is the output clutch. In the latch circuit 92, the DI signal of the serial data is converted into a 64-bit parallel signal for outputting 64 segments for driving each nozzle.

The inverting circuit 93 outputs an exclusive OR of the signal input from the latch circuit 92 and the REV signal to the level shifter 94. The level shifter 94 is a level interface circuit that converts the voltage level of the signal from the inverting circuit 93 from a logic system voltage level (5 V level or 3.3 V level) to a head drive system voltage level (0 V to 45 V level).

The SEG driver 95 has a transmission transmission gate output of 64 channels. The input of the level shifter 94 causes the segment output of SEG1 to SEG64 to be applied to the drive voltage pulse Vp input or GND.
Output any of the inputs. COM driver is REV
In response to the input, either the drive voltage pulse Vp input or the GND input is output to COM.

Each of the signals XSCL, DI, LP and REV is a signal of a logic system voltage level, and is a signal transmitted from the logic gate array 5 to the head driver IC 9.

By configuring the head driver IC 9 in this manner, even when the number of segments to be driven (the number of nozzles) increases, the driving voltage pulse Vp for driving each nozzle of the head and GND are easily switched, and The aforementioned forward / reverse alternating drive can be easily realized.

FIG. 5 is a timing chart showing an embodiment of a drive control signal pulse and a drive voltage pulse signal in the method of driving an ink jet head according to the present invention.

In this embodiment, one pixel (one dot) is formed by a maximum of eight drive pulses. The driving pulses Pw are Pw (1) and Pw (2), Pw (3) and Pw (4),
w (5) and Pw (6) and Pw (7) and Pw (8) form a pair, respectively, and constitute a shot set Ss. The shot set Ss corresponds to Ss (1), Ss (2), Ss (3),
Ss (4). That is, according to the timing chart of the embodiment shown in FIG. 5, it is possible to discharge a maximum of eight shots of ink droplets, and to perform four types of pixel (dot) modulation including non-driving by four shot sets Ss. , And one pixel modulated by selecting the number of shot sets Ss of each ink droplet ejected from one ink nozzle by a series of drive voltage pulses Vp.

In this example, one shot set Ss is composed of two shots forming a pair, but one shot set can have any number of shots.
In this example, since the forward / reverse alternating drive is applied, the number of shots constituting one shot set is preferably an even number of shots. Further, in order to configure the finest gradation,
It is preferable that the number of shots constituting one shot set is two shots.

In addition to the forward / reverse alternating drive, the diaphragm 107
However, it is known that there is no problem even if one set shot is composed of three shots, such as forward / reverse and reverse / forward / backward. one of.

Selection of each shot set is performed by inputting a latch pulse LP from the gate array 5 to the head driver IC 9 for each shot set Ss, and selecting a segment output by inputting a DI signal.

In this example, the density of one pixel is highest when all the shot sets Ss from the shot sets Ss (1) to Ss (4) are selected. In this case, eight shots are selected. Is ejected from the ink nozzle (the ejection pattern of segment output 1).

The segment output 2 includes the segment output 1
The ejection pattern in which the density of the pixel is increased next to the ejection pattern of FIG. In segment output 2, shot set Ss
(3) Three shot sets Ss of Ss (3) and Ss (4) are selected. Since Ss (1) is not selected, the common electrode (COM) output and the segment output have the same potential and no ink droplet is ejected. In addition, in order to discharge ink droplets of six shots, shot sets Ss (1), Ss (3) and Ss (4), shot sets Ss (1), Ss (2) and Ss (4) are also provided. It is also possible to select a combination of shot sets Ss (1), Ss (2) and Ss (3).

In the case of non-driving, none of the shot sets is driven like the driving pattern shown in segment output 3.
In this case, the segment output is the same as the output of the common electrode (COM), the diaphragm is not driven, and no ink droplet is ejected.

On the other hand, referring to FIG. 2 again, the ink jet head control section 2 of the ink jet head drive control device 1 of this embodiment has a temperature detecting circuit 14. This temperature detection circuit 14 is connected via a connector 7 to a thermistor 15 which is a temperature detection element mounted on the surface of the head substrate 8. Therefore, a change in the ambient temperature around the inkjet head 100 is detected by the temperature detection circuit 14 as a change in the resistance value of the thermistor 15.
The detected change in the resistance value is detected by the temperature detection circuit 14 as A /
After the D conversion, the CPU via the input / output port I / O
Supplied to

The ROM previously stores a correspondence table between the ambient temperature of the ink jet head, the pulse width correction value dPw of the drive voltage, and the pulse number correction value dSs.

For example, as shown in the table of FIG. 6A, the ambient temperature, the thermistor resistance value, and the pulse width correction value dPw have a corresponding relationship. Similarly, in the table of FIG. And the correspondence between the thermistor resistance value and the pulse number correction value dSs.

CPU of inkjet head control unit 2
Causes the pulse width correction value dPw corresponding to the detected temperature to be retrieved and output from the correspondence table and developed in the RAM.
As a result, the pulse width Pw of the drive voltage of the ink jet head 100 is determined by the following equation: the ambient temperature of the ink jet head and the preset pulse width initial value Pws
Is calculated based on the following equation (1).

Pw = Pws + dPw (1) Similarly, the CPU of the inkjet head controller 2
Causes the pulse number correction value dSs corresponding to the detected temperature to be retrieved and output from the correspondence table and developed in the RAM.
As a result, the number Ss of pulses of the drive voltage of the inkjet head 100 is determined by the following equation:
Is calculated based on the following equation (2).

Ss = Sss + dSs (2) A concrete example of how the pulse width correction value for the ambient temperature is set is shown below.

The graph of FIG. 7 shows the mass of the ejected ink droplet per shot of the ink jet head 100 at each ambient temperature with respect to the pulse width of the driving voltage of the ink jet head to which the present invention is applied. At this time,
The pulse width initial value Pws is set to 9 μs near the pulse width at which the mass of the ink droplet reaches a peak value at an ambient temperature of 25 ° C. At an ambient temperature of 10 ° C., the pulse width at which the mass of the ink droplet has a peak value is about 9 μs, so the pulse width correction value dPw at 10 ° C. is set to −1 μs. At an ambient temperature of 40 ° C., the pulse width at which the mass of the ink droplet reaches a peak value is about 12 μsec.
Is set to 2 μsec. Similarly, when the pulse width correction value dPw other than the ambient temperature is set based on the result of the mass characteristics of the ink droplets other than the ambient temperature, the result is as shown in the table of FIG. By using the correspondence table, at each ambient temperature, ink droplets are ejected with a pulse width that is the peak value of the mass (or ink speed) of the ejected ink droplets of the inkjet head 100 with respect to the pulse width of the drive voltage. Although the mass of the ink droplet is different, stable ejection of the ink droplet is performed at each temperature.

FIG. 8 is a graph showing a case where one pixel (dot) has a three-set shot configuration when the present invention is not applied, in other words, a case where a six-shot configuration is used.
3 shows the mass of the ejected ink droplet per pixel of the inkjet head 100 at each ambient temperature with respect to the pulse width of the drive voltage. From 10 ° C. to 40 ° C., the difference between the masses of the ink droplets is about 12 ng, and it can be seen that the difference greatly varies.

As for the print quality required of a printer, if it is only enough to print recognizable characters, it is unlikely that a problem will occur. However, a printer which requires color printing and, moreover, a print quality similar to a photograph is required. It turns out that it cannot be used.

FIG. 9 is a graph showing the driving voltage when the initial value of the number of pulses constituting one pixel (dot) is a three-shot configuration when the present invention is applied, in other words, when a six-shot configuration is used. 5 shows the mass of the ejected ink droplet per pixel of the inkjet head 100 at each ambient temperature with respect to the pulse width of FIG. 10 ℃
Between 40 ° C. and 40 ° C., the mass difference of the ink droplets is about 3
ng, which indicates that the variation is small.

The following shows how the pulse number correction value for the ambient temperature is set.

The pulse number initial value Sss is set to 3 shot sets so that the desired ink droplet mass per pixel (about 42 ng) is obtained at 25 ° C. around the frequently used ambient temperature. . At an ambient temperature of 10 ° C., when the number of pulses is 3 shot sets, the mass of the ink droplet per pixel is about 33 ng, and when the number of pulses is 4 shot sets, it is about 44 ng. Therefore, the pulse width correction value dPs is set to 1 because the value is close to the ink droplet mass. In addition, ambient temperature 40
In ° C., when the number of pulses is set to 3 shots, the ink droplet mass per pixel is about 45 ng, and when the number of pulses is 4 shots set, it is about 60 ng.
The pulse width correction value dPs is set to 0 because the value is close to the desired ink droplet mass in the case of the three-shot set.
Similarly, from the result of the mass characteristics of the ink droplets other than the ambient temperature, the pulse number correction value dSs other than the ambient temperature is obtained.
Is set as shown in the table of FIG. As a result of using the correspondence table corresponding to this table, the mass of the ejected ink droplet per pixel of the inkjet head 100 in each ambient temperature with respect to the pulse width of the driving voltage falls within the range of about 42 ng to 45 ng, The effect of temperature changes can be kept small.

Considering the correspondence table between the set ambient temperature, thermistor resistance value, and pulse number correction value dSs, the correspondence table between the ambient temperature, thermistor resistance value, and pulse width correction value dPw is 0.1 μsec or less. By subtly resetting the pulse width correction value dPw in units of (1), it is also possible to minimize the influence of the change in the ambient temperature of the inkjet head.

As described above, in the ink jet head drive control device 1 of the present embodiment, the pulse width Pw and the pulse number Ss of the drive voltage of the ink jet head 100 are corrected based on the ambient temperature of the ink jet head 100. It is possible to always obtain a stable ink discharge characteristic by compensating for a change in the ink discharge characteristic caused by the change.

It is preferable that the sampling cycle for temperature detection is, for example, about 2 seconds. Further, the number of correction pulses dSs and the correction pulse width dPw are not changed during the printing process, but the correction value is changed at the time of printing the next process after the printing process.

Also, in order to suppress the appearance of print density due to frequent switching of the correction value near the correction value switching temperature at the time of correction, it is also effective to provide a hysteresis characteristic at the time of correction to obtain a good printing result. is there.

[0079]

As described above, in the method and apparatus for controlling the drive of an ink jet head according to the present invention, one pixel is formed in an ink jet head of a type in which ink droplets are ejected from ink nozzles by increasing or decreasing the volume of an ink chamber. In the case where the ink droplets are ejected a plurality of times, the pulse width Pw and the pulse number Ss of the drive voltage of the inkjet head 100 are corrected based on the ambient temperature of the inkjet head 100. By compensating for variations in the ejection characteristics, it is possible to always obtain stable ink ejection characteristics.

Further, by setting the number of pulses Ss in units of one pixel, the CPU can control the head driver IC.
9 becomes easier to handle the control signal.
Compensation of w and the pulse number Ss is also performed stably.

A drive control peculiar to an ink jet head of a type in which a different one or a plurality of pairs of pulse-like electric signals are applied to deform the vibration plate 107 by using an electrostatic force to discharge ink droplets. It is possible to cope with the method of alternate driving in the normal and reverse directions, and even in an inkjet head using electrostatic force, it is possible to always obtain stable ink ejection characteristics by compensating for variations in ink ejection characteristics caused by temperature changes. Become.

Further, the ambient temperature of the ink jet head and the pulse width correction value dPw of the driving voltage are stored in the ROM in advance.
Since the correspondence table with the pulse number correction value dSs is stored, the pulse width and pulse number of the drive voltage can be easily and stably controlled, and stable ink ejection characteristics can always be obtained. .

Further, the present invention proposes a drive control device capable of modulating the size of pixels in various ways, capable of performing gradation printing, stably obtaining a high quality and beautiful printing result, and providing a clear and beautiful printed image. It is possible to provide a simple printing apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an inkjet head to be controlled by a drive control device according to the present invention.

FIG. 2 is a schematic block diagram of a control system of a drive control device for an inkjet head to which the present invention is applied.

FIG. 3 is a signal waveform diagram showing a drive voltage pulse signal of an inkjet head to which the present invention is applied.

FIG. 4 is a schematic block diagram showing the inside of a driver IC shown in FIG. 2;

FIG. 5 is a timing chart illustrating a drive control method of an inkjet head to which the present invention is applied.

6A is a table showing a correspondence relationship between an ink jet head ambient temperature, a thermistor resistance value, and a pulse width correction value to which the present invention is applied, and FIG. 6B is a table showing an ink jet head ambient temperature and thermistor resistance value to which the present invention is applied; 9 is a table showing the correspondence between the pulse number correction value and the pulse number correction value.

FIG. 7 is a graph showing the mass characteristics of an ink droplet per shot with respect to a pulse width at each inkjet head ambient temperature of an inkjet head to which the present invention is applied.

FIG. 8 is a graph showing a mass characteristic of an ink droplet per pixel with respect to a pulse width at each inkjet head ambient temperature when the present invention is not applied.

FIG. 9 is a graph showing a mass characteristic of an ink droplet per pixel with respect to a pulse width at an ambient temperature of each inkjet head when the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink-jet head drive control device 2 Ink-jet head control unit 6 Drive pulse generating circuit 8 Head substrate 9 Head driver IC 14 Temperature detection circuit 15 Thermistor 100 Ink-jet head 105 Ink nozzle 106 Ink chamber 107 Vibration plate (electrode) 108 Opposite plate 109 Electrode 110 ink droplet

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasushi Matsuno 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 2C056 EA04 EB07 EB30 EB59 EC07 EC42 EC73 FA01 2C057 AF21 AG54 AL25 AM21 AM40 AR08 BA04 BA15 CA04

Claims (12)

[Claims] An ink nozzle for discharging ink droplets;
An ink chamber communicating with the ink nozzle and holding ink, a diaphragm formed on a peripheral wall defining the ink chamber and displaceable in an out-of-plane direction, and formed on each of the vibration plates A pulse-like electric signal is applied between these opposing electrodes to deform the vibrating plate, thereby ejecting ink droplets from the ink nozzles, and discharging one pixel a plurality of times. In the method for controlling the driving of an ink-jet head, a temperature detection step of detecting an ambient temperature of the ink-jet head, and a pulse number correction value of the pulse-like electric signal based on the temperature detected in the temperature detection step. A first temperature compensation value calculating step of calculating, and a pulse number correction value is added to a preset pulse number initial value of the pulse-like electric signal to obtain a value. A driving step of applying the pulse-like electric signal between the counter electrodes with the corrected number of correction pulses. 2. The temperature detecting step according to claim 1, further comprising: a second temperature compensation value calculating step of calculating a pulse width correction value of the pulsed electric signal based on the temperature detected in the temperature detecting step. And a driving step of applying the pulse-shaped electric signal between the counter electrodes with a correction pulse width determined by adding the pulse width correction value to a preset pulse width initial value of the pulse-shaped electric signal. And a driving control method for the inkjet head. 3. The ink-jet head according to claim 1, wherein the voltage waveform or the number of pulses of the pulse-like electric signal for performing the ink ejection a plurality of times is set for each pixel. Drive control method. 4. A pulse-shaped pulse signal according to claim 1, wherein a polarity of an electric field generated between said opposed electrodes by said pulse-shaped electric signal for ejecting ink droplets from said ink nozzle is different. A drive control method for an inkjet head, comprising applying an electric signal. 5. The temperature compensation value calculating step according to claim 1, wherein the temperature detected in the temperature detecting step is equal to or less than a temperature when an initial value of the number of pulses of the pulse-like electric signal is set. Wherein the pulse number correction value is calculated to be a positive integer. 6. The apparatus according to claim 1, wherein the first temperature compensation value calculation step includes a storage unit storing a correspondence table between the ambient environment temperature of the ink jet head and the pulse number correction value, Wherein the pulse number correction value corresponding to (c) is retrieved and output from the correspondence table. 7. An ink nozzle for discharging ink droplets,
An ink chamber communicating with the ink nozzle and holding the ink; a vibrating plate formed on a peripheral wall defining the ink chamber and displaceable in an out-of-plane direction; and a vibrating plate formed on each of the vibrating plates. A pulse-like electric signal is applied between these opposing electrodes to deform the vibrating plate and eject ink droplets from the ink nozzles, thereby discharging one pixel a plurality of times. In the inkjet head drive control device, a temperature detection step of detecting the ambient temperature of the inkjet head, and a pulse number correction value of the pulse-like electric signal based on the temperature detected in the temperature detection step. A first temperature compensation value calculating step of calculating, and a pulse number correction value is added to a preset pulse number initial value of the pulse-like electric signal to obtain a value. A drive step of applying the pulse-like electric signal between the opposed electrodes with the corrected number of correction pulses. 8. The temperature detecting step according to claim 7, wherein a second step of calculating a pulse width correction value of the pulsed electric signal based on the temperature detected in the temperature detecting step. And a driving step of applying the pulse-shaped electric signal between the counter electrodes with a correction pulse width determined by adding the pulse width correction value to a preset pulse width initial value of the pulse-shaped electric signal. And a drive control device for the inkjet head. 9. The ink-jet head according to claim 7, wherein the voltage waveform or the number of pulses of the pulse-shaped electric signal for performing ink ejection is set for each pixel. Drive control device. 10. A pair of pulse-like or plural pairs in which the polarity of an electric field generated between the counter electrodes by the pulse-like electric signal for ejecting ink droplets from the ink nozzles is different from each other. A drive control device for an inkjet head, which applies an electric signal. 11. The temperature compensation value calculating step according to claim 7, wherein the temperature detected in the temperature detecting step is equal to or lower than a temperature at which a pulse number initial value of the pulse-like electric signal is set. Wherein the pulse number correction value is calculated as a positive integer. 12. The method according to claim 7, wherein
The temperature compensating value calculating step includes a storage unit storing a correspondence table between the ambient temperature of the inkjet head and the pulse number correction value, and retrieves and outputs the pulse number correction value corresponding to the detected temperature from the correspondence table. A drive control device for an ink-jet head, characterized in that: