JP2001162793A - Method for driving ink jet recording head and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hit a desired pixel surely with a desired dot even when a line on a recording medium is printed through a plurality of times of main scanning with a recording head and different kinds of dot are ejected from the same nozzle opening. SOLUTION: A recording head comprising a pressure chamber and a pressure generating element is applied selectively with a plurality of kinds of drive pulse having different waveform created from a common drive signal and different kinds of dot are ejected selectively from the same nozzle opening. An ejection time difference or the time difference between the kinds of dot during the time required for ejection, after transmission of a signal commanding generation of a drive pulse before delivery of a dot, is then determined. When main scanning of the recording head is performed a plurality of times per one line on a recording medium, starting position on the time axis of the common drive signal is adjusted by a correction time determined based on the ejection time difference such that a plurality of dots, ejected in different times of main scanning, do not hit against the same pixel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an ink jet recording head and an ink jet recording apparatus, and more particularly to an ink jet recording head for printing one line on a recording medium by performing multiple main scans of the recording head. The present invention relates to a recording head driving method and an ink jet recording apparatus.

[0002]

2. Description of the Related Art Generally, an ink jet recording apparatus is
A recording head having a large number of nozzle openings formed in a line, a carriage mechanism for moving the recording head in the main scanning direction (the width direction of the recording medium), and sub-scanning a recording medium such as recording paper. Paper feed mechanism for moving the paper in the direction (paper feed direction).

The above-described recording head includes a pressure chamber communicating with the nozzle opening, and a pressure generating element for changing the ink pressure in the pressure chamber. Then, by supplying a drive pulse to the pressure generating element, the ink pressure in the pressure chamber is changed, and an ink droplet is ejected from the nozzle opening.

The above-mentioned carriage mechanism moves the recording head in the main scanning direction. During this movement, the recording head ejects ink droplets at the timing specified by the dot pattern data. Then, when the recording head reaches the end of the movement range, the paper feeding mechanism moves the recording medium in the sub-scanning direction. After the recording medium is moved, the carriage mechanism moves the recording head again in the main scanning direction, and the recording head ejects ink droplets during the movement.
It is to be noted that printing can be performed only on the outward path of the main scan of the recording head, or on both the outward path and the return path.

[0005] By repeating the above operation, an image based on the dot pattern data is recorded on the recording medium.

In the ink jet recording apparatus, a plurality of types of driving pulses having different waveforms generated from a common driving signal having a predetermined waveform are appropriately selected and applied to a recording head to thereby provide the same nozzle opening. There is a type in which dots of different types (for example, dots of different sizes) are appropriately selected and ejected. Here, the cycle (drive cycle) of the common drive signal defines the printing speed in the printing apparatus.

[0007] Further, the ink jet recording apparatus includes:
Some systems employ a method in which the main scanning of the recording head is performed a plurality of times per line on a recording medium. Such a system is called a "singling system" or a "multi-scan system".

For example, when the main scan of the print head is performed four times in the same row and one row is printed in four passes, if the drive cycle is T, the common drive signal of the second pass is displayed on the time axis. The start point is delayed by T / 4 seconds from the start point of the common drive signal in the first pass, and similarly, the start point of the common drive signal in the third pass is delayed by T / 4 seconds from the start point of the common drive signal in the second pass. The start point of the common drive signal of the fourth pass is delayed by T / 4 seconds from the start point of the common drive signal of the third pass. By shifting the start point of the common drive signal by T / 4 seconds for each pass in this way, it is possible to set so that printing of one line is completed in four passes.

[0009]

However, when a plurality of types of dots having different sizes and the like are ejected by using one type of common drive signal, the ejection timing changes between the dot types. The landing position of the dot differs depending on the type of the dot. For example, when ejecting dots of different sizes by appropriately selecting and generating a plurality of types of drive pulses from the common drive signal, the time axis of the waveform element extracted from the common drive signal when generating the drive pulse is generated. Since the position differs depending on the dot size, the ejection timing changes depending on the dot size.

Since the ejection timing varies depending on the type of dot as described above, when printing one line in a plurality of passes, the second dot is included in the pixels already printed by the preceding pass. (A type different from the first dot) may be printed.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described circumstances, and has as its object to print one line on a recording medium by a plurality of main scans of a recording head and use the same nozzle. It is an object of the present invention to provide a method of driving an ink jet recording head and an ink jet recording apparatus capable of reliably landing a desired dot on a desired pixel even when ejecting different types of dots from an opening.

[0012]

In order to solve the above-mentioned problems, the present invention provides a plurality of pressure chambers communicating with a plurality of nozzle openings for ejecting ink droplets, and a plurality of pressure chambers provided corresponding to the plurality of pressure chambers. A plurality of pressure generating elements, and a plurality of types of driving pulses having different waveforms generated from a common driving signal having a predetermined waveform are appropriately selected and applied to an ink jet recording head having the same nozzle. In a method of driving an ink jet recording head that appropriately selects and discharges different types of dots from an opening, the method includes the steps of: transmitting a signal instructing the generation of the drive pulse to a discharge time of the dot; An ejection time difference determining step of determining an ejection time difference that is a time difference between the printing head and the printing head main scanning is performed a plurality of times per line on a printing medium. The starting point position on the time axis of the common drive signal is determined by the correction time determined based on the ejection time difference so that the plurality of dots ejected in the main scanning one time do not land on the same pixel. And a starting point adjusting step of adjusting.

The correction time may be an integral multiple of a value obtained by dividing a driving cycle of the common driving signal by the number of main scans per row of the recording head.

Further, the plurality of nozzle openings can be classified into several nozzle groups, and the ejection time difference can be determined for each nozzle group.

The plurality of nozzle openings may form several nozzle rows, and each of the nozzle groups may correspond to each of the nozzle rows.

Further, the ink jet recording head can discharge a plurality of types of inks having different colors, and the nozzle openings having the same color of the discharged ink are classified into the same nozzle group. be able to.

The ink jet recording head is capable of discharging a plurality of types of inks of different colors, and the step of determining the discharge time difference and the step of adjusting the starting point are performed by the nozzle opening for discharging the ink of a specific color. It can be performed only for parts.

Further, the different types of dots may be dots of different sizes.

According to the present invention, there is provided an ink jet recording method comprising: a plurality of pressure chambers communicating with a plurality of nozzle openings for discharging ink droplets; and a plurality of pressure generating elements provided corresponding to the plurality of pressure chambers. A head and a plurality of types of drive pulses having different waveforms are appropriately selected and generated from a common drive signal having a predetermined waveform, and the drive pulses are applied to the pressure generating element to form different types of dots from the same nozzle opening. And a head drive device that appropriately selects and discharges the ink. The head drive device performs different scans when the main scan of the print head is performed a plurality of times per line on a print medium. In order to prevent the plurality of dots ejected in the main scanning from landing on the same pixel, the dot is sent from the time of transmission of the signal instructing the generation of the driving pulse. The correction time determined based on the discharge time difference is a time difference between dots kinds of discharge time required to discharge time of, characterized by adjusting the starting point position on the time axis of the common drive signal.

The correction time may be an integral multiple of a value obtained by dividing a driving cycle of the common driving signal by the number of main scans per row of the recording head.

Further, the discharge time difference may be determined for each of the nozzle groups after the plurality of nozzle openings are classified into several nozzle groups.

The plurality of nozzle openings may form several nozzle rows, and each of the nozzle groups may correspond to each of the nozzle rows.

Further, the ink jet recording head includes a plurality of nozzle openings for ejecting a plurality of kinds of inks of different colors for each color, and the nozzle openings having a common color of ejected ink. Can be classified into the same nozzle group.

Further, the ink jet type recording head is provided with a plurality of nozzle openings for discharging a plurality of kinds of inks of different colors, and the driving device is provided with the nozzle opening for discharging a specific color ink. , The start point on the time axis of the common drive signal can be adjusted.

Further, the different types of dots can be dots having different sizes.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of driving an ink jet recording head and an ink jet recording apparatus according to one embodiment of the present invention will be described.

FIG. 1 is a functional block diagram of an ink jet recording apparatus according to one embodiment of the present invention. The ink jet recording apparatus includes a printer controller 1 and a print engine 2. The printer controller 1 includes an interface 3 for receiving print data and the like from a host computer (not shown), a RAM 4 for storing various data, a ROM 5 for storing control routines for various data processing, and the like. A control unit 6 including a CPU, etc., an oscillation circuit 7, a drive signal generation circuit 9 for generating a common drive signal to be supplied to the printhead device 18 (including the printhead 8), and a dot pattern data (bitmap data) An interface 10 for transmitting the developed print data and common drive signals to the print engine 2 is provided.

The interface 3 receives, for example, any one of character code, graphic function, and image data or print data including a plurality of data from a host computer or the like. In addition, the interface 3 communicates a host computer with a viscous (BU)
SY) signal or acknowledge (ACK) signal. The RAM 4 is used as a reception buffer 4a, an intermediate buffer 4b, an output buffer 4c, a work memory (not shown), and the like. The print data from the host computer received by the interface 3 is temporarily stored in the reception buffer 4a. The intermediate buffer 4b stores the intermediate code data converted into the intermediate code by the control unit 6. Output buffer 4c
The dot pattern data after the grayscale data is decoded is developed in (2). This will be described later.

The ROM 5 stores various control routines executed by the control unit 6, font data, graphic functions, and the like.

The control section 6 reads out the print data in the reception buffer 4a and converts it into an intermediate code. Then, the control unit 6 stores the converted intermediate code data in the intermediate buffer 4b.
To memorize. Further, the control section 6 develops the intermediate code data read from the intermediate buffer 4b into dot pattern data with reference to font data and graphic functions in the ROM 5. The developed dot pattern data is stored in the output buffer 4c after necessary decoration processing is performed.

When dot pattern data corresponding to one line on the recording medium is obtained, the dot pattern data for one line is serially transmitted to the recording head device 18 including the recording head 8 via the interface 10. You. When one line of dot pattern data is output from the output buffer 4c, the contents of the intermediate buffer 4b are deleted, and the conversion for the next intermediate code is performed.

The print engine 2 includes a recording head device 1
8, a paper feed mechanism 11, and a carriage mechanism 12. The paper feed mechanism 11 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds a print recording medium such as a recording paper. That is, the paper feed mechanism 11 performs the sub-scan in the recording operation. The carriage mechanism 12 is used for the recording head device 1.
And a pulse motor for driving the carriage via a timing belt or the like. The carriage mechanism 12 performs main scanning in a printing operation.

The recording heads 8 constituting a part of the recording head device 18 are arranged in the sub-scanning direction in a large number (for example, 64).
The nozzle openings 13 (shown in FIG. 2) are formed, and ink droplets are ejected from each nozzle opening 13.

The print data (SI) developed into the dot pattern data corresponds to the clock signal (C
K), the data is serially transmitted to the selection signal generator 22 through the interface 10. The selection signal generator 22 generates a selection signal corresponding to print data by receiving a latch signal (LAT), and supplies the generated selection signal to a level shifter 23, which is a voltage amplifier. here,
The selection signal is a signal for selecting a necessary part from the common drive signal (COM) from the drive signal generation circuit 9.

The level shifter 23 outputs a switch signal to the switch circuit 24 based on the supplied selection signal. A common drive signal is input to the input side of the switch circuit 24, and the piezoelectric vibrator 25 constituting a part of the recording head 8 shown in FIG. 2 is connected to the output side of the switch circuit 24. The switch circuit 24 is connected when a switch signal is input.

The above-described piezoelectric vibrator 25 is a kind of the pressure generating element of the present invention. Further, the printer controller 1, the selection signal generator 22, the level shifter 23, and the switch circuit 24 constitute a head driving device according to the present invention.

The above print data controls the operation of the switch circuit 24. For example, during a period in which the print data is “1”, a selection signal is output from the selection signal generation unit 22 and
A switch signal is output from the level shifter 23. Thereby, the common drive signal is supplied to the piezoelectric vibrator 25, and the piezoelectric vibrator 25 is deformed according to the common drive signal. On the other hand, while the print data applied to the switch circuit 24 is “0”, the supply of the common drive signal to the piezoelectric vibrator 25 is cut off.

Then, with the deformation of the piezoelectric vibrator 25,
Ink droplets are ejected from the nozzle openings 13.

Next, the structure of the recording head 8 will be described in detail. The recording head 8 illustrated in FIG. 2 is a recording head 8 to which a piezoelectric vibrator 25 in a flexural vibration mode is attached.

The recording head 8 includes an actuator unit 32 in which a plurality of pressure chambers 31 are formed, and a channel unit 34 in which a nozzle opening 13 and a common ink chamber 33 are formed.
And a piezoelectric vibrator 25. The flow path unit 34 is joined to the front surface of the actuator unit 32, and the piezoelectric vibrator 25 is provided on the rear surface of the actuator unit 32.

The pressure chamber 31 expands and contracts with the deformation of the piezoelectric vibrator 25, and changes the ink pressure in the pressure chamber 31. Then, an ink droplet is ejected from the nozzle opening 13 by the change of the ink pressure in the pressure chamber 31. For example, the inside of the pressure chamber 31 is pressurized by rapidly contracting the pressure chamber 31, and an ink droplet is ejected from the nozzle opening 13.

The actuator unit 32 includes the pressure chamber 3
A pressure chamber forming substrate 35 in which a space for forming 1 is formed;
Lid member 36 joined to the front surface of pressure chamber forming substrate 35
And a vibrating plate 37 joined to the back surface of the pressure chamber forming substrate 35 to close the opening surface of the empty space. A first ink flow path 38 for communicating the common ink chamber 33 and the pressure chamber 31 and a second ink flow path 39 for communicating the pressure chamber 31 and the nozzle opening 13 are formed in the cover member 36. I have.

The flow path unit 34 includes an ink chamber forming substrate 41 in which a space for forming the common ink chamber 33 is formed, and a plurality of nozzle openings 13 formed in the ink chamber forming substrate 4.
1 and a supply port forming plate 43 bonded to the back surface of the ink chamber forming substrate 41.

A nozzle communication port 44 communicating with the nozzle opening 13 is formed in the ink chamber forming substrate 41. The supply port forming plate 43 has an ink supply port 45 that connects the common ink chamber 33 and the first ink channel 38, and a communication port 4 that connects the nozzle communication port 44 and the second ink channel 39.
6 is drilled.

Therefore, a series of ink flow paths from the common ink chamber 33 to the nozzle opening 13 through the pressure chamber 31 are formed in the recording head 8.

The piezoelectric vibrator 25 is formed on the opposite side of the pressure chamber 31 with the vibration plate 37 interposed therebetween. This piezoelectric vibrator 2
Reference numeral 5 denotes a flat plate. A lower electrode 48 is formed on the front surface of the piezoelectric vibrator 25, and an upper electrode 49 is formed on the rear surface so as to cover the piezoelectric vibrator 25.

At both ends of the actuator unit 32, connection terminals 50 whose base ends are electrically connected to the upper electrode 49 of each piezoelectric vibrator 25 are formed. The distal end face of the connection terminal 50 is formed higher than the piezoelectric vibrator 25. Then, a flexible circuit board 51 is joined to the end surface of the connection terminal 50, and supplies a drive waveform to the piezoelectric vibrator 25 via the connection terminal 50 and the upper electrode 49.

Although only two pressure chambers 31, two piezoelectric vibrators 25, and two connection terminals 50 are shown in the figure, a large number are provided corresponding to the nozzle openings 13.

In the recording head 8, when a driving pulse is inputted, a voltage difference is generated between the upper electrode 49 and the lower electrode 48. Due to this potential difference, the piezoelectric vibrator 25 contracts in a direction orthogonal to the electric field. At this time, since the lower electrode 48 of the piezoelectric vibrator 25 joined to the vibration plate 37 does not contract but only the upper electrode 49 side contracts, the piezoelectric vibrator 25 and the vibration plate 37 project toward the pressure chamber 31 side. So that the volume of the pressure chamber 31 is contracted.

When an ink droplet is ejected from the nozzle opening 13, for example, the pressure chamber 31 is rapidly contracted. That is, when the pressure chamber 31 is rapidly contracted, an increase in the ink pressure occurs in the pressure chamber 31, and an ink droplet is ejected from the nozzle opening 13 with the increase in the pressure. After the ink droplets are ejected, the upper electrode 49 and the lower electrode 48
Is eliminated, the piezoelectric vibrator 25 and the diaphragm 37 return to the original state. As a result, the inside of the contracted pressure chamber 31 expands, and ink is supplied from the common ink chamber 33 to the pressure chamber 31 through the ink supply port 45.

Next, the electrical configuration of the recording head device 18 will be described. As shown in FIG. 1, the recording head device 18 includes a selection signal generator 22, a level shifter 23, a switch circuit 24, a piezoelectric vibrator 25, and the like.

As shown in FIG. 3, the level shifter 23 includes a plurality of level shifter elements 23a to 23n provided corresponding to the nozzle openings 13. Similarly, the switch circuit 24 includes a plurality of switch elements 24a to 24n. In addition, the piezoelectric vibrator 25 also includes a plurality of piezoelectric vibrators 25a to 25a.
25n.

The selection signal from the selection signal generating section 22 is supplied to the level shifter elements 23a to 23n based on the print data.
Are selectively supplied to Switch elements 24a-2
4n, the connection state is selectively controlled based on this selection signal.

The common drive signal (COM) generated by the drive signal generation circuit 9 is input to each of the switch elements 24a to 24n. When the switch elements 24a to 24n are connected, the switch elements 24a to 24n are connected. A common drive signal is selectively supplied to the connected piezoelectric vibrators 25a to 25n.

As described above, in the recording head device 18, it is possible to control whether or not to input a common drive signal to the piezoelectric vibrator 25 based on the print data. For example, the switch circuit 24 is in the connected state during the period in which the print data is “1”, so that the common drive signal is supplied to the piezoelectric vibrator 25. Then, the piezoelectric vibrator 25 is deformed by the common drive signal. Further, since the switch is in a non-connected state during the period when the print data is “0”, the supply of the common drive signal to the piezoelectric vibrator 25 is cut off. During the period when the print data is “0”, each piezoelectric vibrator 25 holds the immediately preceding electric charge, and the last deformed state is maintained.

Next, the control of the recording head 8 will be described with an example of four gradations of "large dot", "medium dot", "small dot" and "non-print". Here, the “large dot” in the present embodiment means a relatively large dot formed by an ink droplet having the largest ink volume among the ejected ink droplets. "Medium dot" means a dot having a medium ink volume. “Small dot” means a relatively small dot formed by an ink droplet having the smallest ink volume among the ejected ink droplets.

FIG. 4 is a diagram showing the waveform of the common drive signal generated by the drive signal generation circuit 9. From the common drive signal shown in FIG. 4, a large dot drive pulse, a medium dot drive pulse, a small dot drive pulse, and an in-print minute vibration drive pulse are generated.

The drive signal generation circuit 9 generates this common drive signal at a predetermined drive cycle T. Note that this driving cycle T
Defines the printing speed in the recording device. The selection signal generator 22, the level shifter 23, and the switch circuit 24 generate a micro-vibration drive pulse, a small dot drive pulse, a medium dot drive pulse, and a large dot drive pulse from the common drive signal shown in FIG. I do.

As shown in FIG. 4, in this common drive signal, the waveform element constituting the in-print minute vibration drive pulse is divided into three, and a period T1 (P221 to P225) and a period T4 (P240 to P243) , And period T5 (P243
To P246). Further, the waveform element constituting the small dot drive pulse is divided into two,
(P225 to P228) and the period T6 (P247 to P228)
258). Further, the waveform element constituting the medium dot drive pulse is not divided and is not divided during the period T3 (P23).
0 to P240). Further, the waveform element constituting the large dot drive pulse is divided into two, and is divided into a period T4 (P240 to P243) and a period T7 (P26).
0 to P266). The waveform element in the period T4 is commonly used for the large dot drive pulse and the in-print fine vibration pulse.

A period TS between the period T2 and the period T3
1, the first connection elements (P228 to P229) are arranged. Similarly, a period TS between the period T5 and the period T6
In 2, a second connection element (P246 to P247) is arranged, and in a period TS3 between the period T3 and the period T4, a third connection element (P258 to P259) is arranged.

When a large dot drive pulse is generated, the fourth waveform element in the period T4 and the seventh waveform element in the period T7 are selected from the common drive signal and connected based on predetermined print data. Further, when generating the medium dot drive pulse, the third dot of the period T3 is determined based on the predetermined print data.
The waveform element is selected from the common drive signal. When generating the small dot drive pulse, the second waveform element in the period T2 and the sixth waveform element in the period T6 are selected from the common drive signal and connected based on predetermined print data. Further, when generating the in-print micro-vibration pulse, the first waveform element in the period T1, the fourth waveform element in the period T4, and the fifth waveform element in the period T5 are converted from the common drive signal based on predetermined print data. Select and connect to generate a micro-vibration pulse in the print.

As shown in FIG. 5, the large dot drive pulse slightly expands the pressure chamber 31 having the reference volume to cause the pressure chamber 31 to expand.
Expansion waveform elements (P241 to P243, P259 to P260) for holding a certain amount of ink inside and holding for a predetermined time
When a filling wave element to a pressure chamber 31 which is expanded by the expansion wave element further by a little more inflated filled with ink (P260~P262), second high order is set to slightly lower voltage level than the maximum potential V _H The voltage is rapidly increased from the lower voltage _VL to the voltage _VH ', and the nozzle opening 1
No. 3 discharge waveform element (P260-
P264) and a damping waveform element (P264 to P265) for suppressing waving of the meniscus immediately after ejection.

Also, the middle dot drive pulse has the lowest potential V
Expanding the pressure chamber 31 by lowering the voltage slightly along the medium voltage V _M to the second low voltage V _{L ',} which is set to a higher voltage level to the voltage gradient θ31 than _L, holding the expanded state Filling waveform element to be made (P230 to P232)
And the discharge waveform element (P
232 to P234), and withdrawal waveform elements (P234 to P236) for rapidly expanding the pressure chamber 31 and pulling the meniscus to the pressure chamber 31 side immediately before the portion that becomes an ink droplet by the supply of the ejection waveform element separates from the meniscus. , Damping waveform element to stop meniscus undulation immediately after ejection
(P236 to P239).

Further, the small dot drive pulse has a middle voltage V
Is slightly contracting the pressure chamber 31 by raising the voltage from _M to the high level voltage _{V H,} contraction wave element (P226~P228, P247~P248) for holding the contraction state, this contraction waveform element is contracted state holding Pressure chamber 3
Filling waveform element (P2
48 to P250), an ejection waveform element (P250 to P252) for contracting the expanded pressure chamber 31, and the pressure chamber 31 is rapidly expanded just before a portion that becomes an ink droplet by the supply of the ejection waveform element is separated from the meniscus. Waveform element (P252 to P25) that pulls the meniscus to the pressure chamber 31 side
4) and damping waveform elements (P254 to P257) for suppressing waving of the meniscus immediately after ejection.

Further, the in-print minute vibration pulse is composed of first minute vibration waveform elements (P221 to P224) and second minute vibration waveform elements (P241 to P245).

The above-mentioned large dot driving pulse is applied to the piezoelectric vibrator 2.
5, a large ink droplet having a large ink volume can be ejected as follows. First, medium voltage _{V M}
The voltage is dropped at a predetermined voltage gradient θ21 from (P241
~P242), reaches the second intermediate voltage _{V ML} of a substantially middle level of the medium voltage _{V M} and the low voltage _{V L,} the maintaining predetermined time Tc the second intermediate voltage _{V ML (P242~P26}
0). At this time, the pressure chamber 31 expands slightly more than the reference volume with the extension deformation of the piezoelectric vibrator 25, and the ink is filled in the pressure chamber 31 to some extent. Then, since the second middle voltage _VML is held for a sufficiently long time Tc, a steady state in which the vibration of the meniscus when the pressure chamber 31 is expanded sufficiently converges is achieved.

[0067] Next, further lowering the voltage at a predetermined voltage gradient θ22 from the second intermediate voltage _{V ML (P260~P2}
61) reaches the low voltage _{V L} to maintain this low voltage _{V L} predetermined time (P261~P262). At this time, the slightly expanded pressure chamber 31 further expands, and ink is filled in the pressure chamber 31. Next, along the steeply set voltage gradient θ23, the low voltage VL is switched to the second high voltage _VL .
_The voltage is rapidly increased to _H ′ (P262 to P26).
3) After holding the second high voltage V _H ′ for a predetermined time (P
263 to P264), the pressure chamber 31 is expanded from the second higher voltage V _H ′ so as to stop the waving of the meniscus in a short time, and returns to the reference volume (P264 to P265). At this time, the sudden deformation of the piezoelectric vibrator 25 causes the pressure chamber 31
Is rapidly contracted and ink droplets are ejected from the nozzle opening 13.

Also, the medium dot drive pulse is applied to the piezoelectric vibrator 2
5, ink droplets are ejected as follows. First, _'to lower the voltage to (P230~P231), second low voltage V _L' with a predetermined voltage gradient θ31 which is set so as not to eject ink droplets from the medium voltage V _M second low voltage V _L to When it reaches, the second lower voltage _VL 'is maintained for a predetermined time (P231 to P232). Thereby, the pressure chamber 31
Is filled with ink. Next, along the steeply set voltage gradient θ32, the second lower voltage _VL ′
The voltage is rapidly increased to the higher voltage V _H ′ (P232
ＰP234). At this time, the pressure chamber 31 contracts rapidly, and the ink pressure in the pressure chamber 31 increases. As the ink pressure increases, the center of the meniscus rises in the ejection direction.

At the timing immediately before the ink droplet portion separates from the meniscus, the steeply set θ
The voltage drops along the line 31 to the pull-in voltage _VA (P23
4-P235). As a result, the pressure chamber 31 rapidly expands, and the inside of the pressure chamber 31 becomes a negative pressure, and the peripheral portion of the meniscus is drawn into the inside of the pressure chamber 31. Therefore, the central portion of the meniscus is separated from the meniscus, and the central portion flies as an ink droplet. When the ink droplets are ejected, the voltage is raised and then lowered again, so that the pressure chamber 31
Are contracted and expanded to converge the vibration of the meniscus early (P236 to P239).

The small dot drive pulse is applied to the piezoelectric vibrator 2.
5, the medium voltage V _MFrom higher voltage V_H
The pressure chamber 31 is
Expands to secure an expansion allowance (P226 to P228, P
247-P248). After that, the medium dot explained earlier
The same operation as the driving pulse is performed (P248 to P25).
7). With this small dot drive pulse, the inside of the pressure chamber 31
Ink droplets with the meniscus pulled in
Discharge smaller ink droplets
Can be.

[0071] Also, in the case of supplying the vibrating pulse to the piezoelectric vibrator 25, the first micro-vibration waveform and the second micro-vibration waveform, the pressure chamber 31 is slightly from a reference volume corresponding to the medium voltage V _M Swell. Thereafter, the pressure chamber 31 returns to the reference volume after maintaining this expanded state for a predetermined time. As a result, the meniscus is slightly drawn into the pressure chamber 31, and then returns to the normal state. Therefore, the ink near the nozzle opening 13 is stirred.

In this embodiment, first, in the ejection time difference determination step, the dot type in the ejection required time from the transmission time of the signal for instructing the generation of the driving pulse shown in FIG. An ejection time difference, which is a time difference between the two, is determined. Here, the different types of dots mean, for example, dots having different sizes, and it can be seen from the waveform diagram of FIG. 5 that the ejection timing differs depending on the dot size.

As a specific method for determining the ejection time difference, for example, dots of different types are actually ejected onto a recording medium, and the amount of deviation of the impact position according to the type of dot (hereinafter referred to as “the impact deviation”). Amount) is calculated, and the ejection time difference is calculated from the landing deviation amount. For example, in a four-pass mode in which the print head scans four times per line on the print medium, as shown in FIG. 6, small dots S ejected from a specific nozzle opening 13a of the print head 8 have the same nozzle. It is assumed that, when viewed from the landing position (pixel 1) of the medium dot M when ejected from the opening 13a at the same timing as the command signal, the droplet lands on the next pixel (pixel 2) toward the main scanning direction. Here, if the drive cycle of the common drive signal is T seconds, the time corresponding to one pixel is T / 4 seconds in the 4-pass mode, so that the ejection time difference between the medium dot M and the small dot S Is T / 4 seconds.

Similarly, when the landing position of the large dot L lands on the next adjacent pixel (pixel 3) in the main scanning direction when viewed from the landing position of the medium dot M (pixel 1), The ejection time difference between the dot M and the large dot L is (T / 4) × 2 seconds.

The pixel 1 in FIG. 6 is printed in the first pass, the pixel 2 is printed in the second pass, the pixel 3 is printed in the third pass, and the pixel 4 is printed in the fourth pass.
In the first pass, dots are ejected from the nozzle openings 13a, in the second pass, dots are ejected from the nozzle openings 13b, in the third pass, and from the nozzle openings 13d in the fourth pass. You. By changing the nozzle opening used for each pass in this way, it is possible to prevent a decrease in image quality due to a difference in characteristics of each nozzle opening 13.

Further, there is a manufacturing error in the manufacture of the recording head 8, especially in the formation of the nozzle openings 13, so that even if the type of dot is the same, the landing deviation amount is different for each recording head 8. It is known that one recording head 8 differs for each nozzle row.

In consideration of such a manufacturing error,
It is desirable to classify the plurality of nozzle openings 13 into a plurality of nozzle groups according to a predetermined criterion and determine the ejection time difference for each nozzle group. In this case, the method of classifying the nozzle groups is as follows.

FIG. 7 is a diagram showing an example of a recording head 8 capable of discharging a plurality of colors of ink. The first head 101 is provided with a plurality of nozzle openings 13 for discharging black ink. ing. The second to fourth heads 102, 103, and 104 are provided with a plurality of nozzle openings 13 for discharging cyan, magenta, and yellow inks, respectively.

When the ejection time difference is determined for the recording head 8 shown in FIG. 7, each nozzle row X1, X2,... X8 in the recording head 8 is classified into each nozzle group, and The ejection time difference is determined for each row. Alternatively, a plurality of nozzle openings 13 having a common color of ink to be ejected
The groups Y1, Y2, Y3, and Y4 can be classified into the same nozzle group, and the discharge time difference can be determined for each nozzle group of each color.

After the ejection time difference for each type of dot is determined in the ejection time difference determination step as described above, in the start point adjustment step, the head driving device determines the time of the common drive signal based on the correction time determined based on the ejection time difference. Adjust the starting point on the axis. Specifically, when the main scanning of the recording head 8 is performed a plurality of times per line on the recording medium, a plurality of dots ejected in different main scanning times do not land on the same pixel. Next, the start point position on the time axis of the common drive signal is adjusted by the correction time determined as described above.

Here, the correction time can be set to an integral multiple of a value obtained by dividing the drive cycle T of the common drive signal by the number of main scans per row of the recording head 8. For example, the driving cycle T
Is 138 μs (frequency = 7.2 kHz, dot density = 3
60 dpi), in the case of the 4-pass mode in which the number of main scans per line of the print head is four, the correction time ΔT = (1
38/4) × n (n: integer).

When the landing positions of the small dot and the medium dot are shifted by one pixel in the 4-pass mode as shown in FIG. 6, the ejection time difference is recognized as T / 4 seconds and corrected. As shown in FIG. 8, when a small dot is ejected, the start position of the common drive signal on the time axis is viewed from the start position of the medium drive signal on the time axis as shown in FIG. It is adjusted to a time point earlier by T / 4 seconds, and the starting point position of the large dot common drive signal on the time axis is (T / 4) × when viewed from the start point position of the medium dot common drive signal on the time axis.
The adjustment is made two seconds earlier and applied to the piezoelectric vibrator 25 made of PZT.

If the point of adjusting the start point position on the time axis of the common drive signal is supplemented, the adjustment of the start point position is specifically performed by selecting a printing path.
In other words, when it is desired to land a medium dot on the pixel 1 shown in FIG. 6, as shown in the lowermost row in FIG. 8, (n + 2)
In the case where the medium dot is ejected toward the pixel 1 at the pass, and it is desired to cause the pixel 1 to land a small dot instead of the medium dot, as shown in the middle part of FIG. When a small dot is ejected toward the pixel 1 and a large dot is to be landed on the pixel 1 as well, a large dot is ejected toward the pixel 1 at the n-th pass as shown in the upper part of FIG. .

On the other hand, according to the conventional technique, regardless of the type of dot, discharge is performed to the pixel 1 shown in FIG. 6 in the n-th pass, to the pixel 2 in the (n + 1) -th pass, and to the pixel 3. Are ejected in the (n + 2) -th pass, and are ejected to the pixel 4 in the (n + 3) -th pass, and printing is performed in order according to the arrangement order of the pixels.

On the other hand, in the present embodiment, by adjusting the starting point position on the time axis of the common drive signal according to the type of dot as described above, it is possible to reduce the landing deviation amount due to the type of dot. Specifically, the landing deviation amount in the 1440 mode is set to 1/1440.
It can be suppressed within dpi.

In FIG. 6, for convenience, the landing deviation amount is an integral multiple (1 or 2 times) of the distance between pixels. However, in practice, the landing deviation amount is 1.2 times or 1.8 times the distance between pixels. In such a case, 1.2 times is approximated to 1 time, and
The correction time ΔT can be calculated after approximating 8 times to 2 times.

When the recording head 8 has a plurality of nozzle openings 13 for discharging a plurality of color inks as shown in FIG. 7, the discharge time difference determination step and the start point adjustment step are performed for all the color nozzles. It is also possible to carry out not only for the opening 13 but only for the nozzle opening 13 of a specific color.

As described above, according to the present embodiment, the starting point on the time axis of the common drive signal is adjusted according to the type of dot in consideration of the ejection time difference between the types of dot. Even when one line on the medium is printed by a plurality of main scans of the recording head 8 and different types of dots are ejected from the same nozzle opening 13, a desired type of dot is reliably landed on a desired pixel. It is possible to improve the image quality.

In the above embodiment, the recording head 8 using the flexural vibration mode piezoelectric vibrator 25 as a pressure generating element has been exemplified. However, the present invention is not limited to the flexural vibration mode piezoelectric vibrator 25, The present invention can also be applied to a recording head 62 using a piezoelectric vibrator 61 in the longitudinal vibration mode shown in FIG.

The recording head 62 has a base 63 made of synthetic resin and a flow path unit 64 attached to the front surface (corresponding to the left side in the figure) of the base 63. And
The flow path unit 64 includes a nozzle plate 66 having a nozzle opening 65 formed therein, a vibration plate 67, and a flow path forming plate 6.
And 8.

The base 63 is a block-shaped member provided with a housing space 69 opened at the front and back. In the housing space 69, the piezoelectric vibrator 6 fixed to the fixed substrate 70 is provided.
1 is accommodated.

The nozzle plate 66 is a thin plate-like member having a large number of nozzle openings 65 formed in the sub-scanning direction. Each nozzle opening 65 is opened at a predetermined pitch corresponding to the dot formation density. The diaphragm 67 has an island portion 71 as a thick portion with which the piezoelectric vibrator 61 contacts.
And a thin plate member 72 provided to surround the periphery of the island portion 71 and having elasticity.

The island portions 71 are provided in large numbers at a predetermined pitch so that one island portion 71 corresponds to one nozzle opening 65.

The flow path forming plate 68 includes a pressure chamber 73, a common ink chamber 74, and the pressure chamber 73 and the common ink chamber 7.
An opening for forming an ink supply path 75 that communicates with the nozzle 4 is provided.

Then, the nozzle plate 66 is disposed on the front surface of the flow path forming plate 68, and the vibration plate 67 is disposed on the rear side, and the flow path forming plate 68 is sandwiched between the nozzle plate 66 and the vibration plate 67. In this state, the flow path unit 64 is formed integrally by bonding or the like.

In the passage unit 64, a pressure chamber 73 is formed on the back side of the nozzle opening 65, and the pressure chamber 73 is formed.
The island portion 71 of the diaphragm 67 is located on the back side of the. The pressure chamber 73 and the common ink chamber 74 communicate with each other via an ink supply path 75.

The tip of the piezoelectric vibrator 61 is
1 is contacted from the back side, and in this contact state, the piezoelectric vibrator 6
1 is fixed to the base 63. Further, a common drive signal (COM), print data (SI), and the like are supplied to the piezoelectric vibrator 61 via a flexible cable.

The piezoelectric vibrator 61 in the longitudinal vibration mode has a characteristic that when charged, it contracts in the direction perpendicular to the electric field, and when discharged, it expands in the direction perpendicular to the electric field. Therefore, in the recording head 62, the piezoelectric vibrator 61 contracts rearward by being charged, and the island portion 71 is pulled back along with the contraction, and the contracted pressure chamber 73 expands. With this expansion, the ink in the common ink chamber 74 flows into the pressure chamber 73 through the ink supply path 75. On the other hand, the electric discharge causes the piezoelectric vibrator 61 to extend forward, the island 71 of the elastic plate 67 is pushed forward, and the pressure chamber 73 contracts. With this shrinkage, the pressure chamber 73
The ink pressure inside becomes high.

As described above, in the recording head 62, the relationship between the voltage level due to the charging and discharging of the piezoelectric vibrator 61 and the expansion and contraction of the pressure chamber 73 is opposite to that in the above-described embodiment.
Therefore, when this recording head 62 is used, the common drive signal and the drive waveform shown in the previous embodiment are used as the common drive signal and the drive waveform in which the polarity of the voltage is reversed at the intermediate voltage. For example, as shown in FIG. 10, the common drive signal and the drive waveform shown in FIGS. 4 and 5 are different from the common drive signal and the drive waveform in which the rising and falling directions of the voltage are reversed with respect to the intermediate voltage VM. Used.

That is, in the recording head 62, the pressure chamber 73 is filled with ink by increasing the voltage. Similarly, ejection of ink droplets is performed by lowering the voltage. Then, even when this recording head 62 is used, the same operation and effect as those of the above-described embodiment can be obtained.

In general, there are roughly two types of driving systems for an ink jet recording head, one of which is a pull driving system and the other is a push driving system.

FIG. 11 is a view for explaining the pulling drive method in the case of the recording head 62 shown in FIG. 9. In this method, the pressure chamber 31 in the standby state is neither in the expanded state nor in the contracted state. In the state of the reference volume, the piezoelectric vibrator 25 is contracted in the next decompression step so that the pressure chamber 3
1 is expanded, whereby the pressure chamber 31 is filled with ink. Next, in the pressurizing step, the piezoelectric vibrator 25 is extended to pressurize the pressure chamber 31, and in the subsequent pressure releasing step, ink droplets are ejected from the nozzle openings 13.

FIG. 12 is a diagram for explaining the push driving method in the case of the recording head 62 shown in FIG. 9. In this method, the pressure chamber 31 in the standby state is in the expanded state, and In the pressurizing step, the piezoelectric vibrator 25 is extended to pressurize the pressure chamber 31, and in the subsequent pressure releasing step, ink droplets are ejected from the nozzle openings 13.

Next, first and second modifications of the present embodiment will be described.

In the above embodiment, the starting point position on the time axis of the common drive signal is adjusted in accordance with the type of the dot in consideration of the ejection time difference between the types of the dot, so that the desired type of dot can be converted into the desired pixel. To make it land.

However, in the above-described embodiment, if a printing condition occurs such that two dots are ejected in the same driving cycle in the same pass, the common driving signal shown in FIGS. . In other words, as can be seen from FIG. 5, since the common drive signals from P226 to P257 are used to eject small dots, when small dot ejection is selected, medium dots or large dots are ejected. Cannot be generated.

On the other hand, as can be seen from FIG. 5, since the drive pulse for the medium dot and the drive pulse for the large dot do not interfere with each other, both the medium dot and the large dot are used in the same drive cycle of the same pass. Can be ejected.

Therefore, as a first modification of the above embodiment, the adjustment of the starting point position of the common drive signal is performed only when medium dots or large dots are ejected. By doing so, it is possible to land medium dots and large dots on desired pixels.

In this modification, when printing is performed in both directions in the main scanning direction of the recording head, the ejection timing of large dots is corrected in the forward direction and the ejection timing of medium and small dots is corrected in the forward direction. Instead, in the backward direction, the ejection timing of medium dots can be corrected, and the ejection timing of medium and small dots can not be corrected.

Further, as a second modified example of the above embodiment,
The waveform of the common drive signal shown in FIG. 4 may be changed as shown in FIG. 13 so that only medium dots and large dots are ejected. That is, the common drive signal shown in FIG. 13 is for generating a drive pulse for medium dots and a drive pulse for large dots that do not interfere with each other.
According to this modification, it is possible to cope with a case where both the medium dot and the large dot are selected in the same driving cycle in the same pass, so that the medium dot and the large dot can be landed on a desired pixel. it can.

[0111]

As described above, according to the present embodiment,
Since the starting point on the time axis of the common drive signal is adjusted in accordance with the type of dot in consideration of the ejection time difference between the types of dots, one line on the recording medium is scanned by the main scanning of the recording head a plurality of times. Even when printing and ejecting different types of dots from the same nozzle opening, it is possible to reliably cause a desired type of dot to land on a desired pixel, thereby improving image quality. .

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an ink jet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an ink jet recording head of the ink jet recording apparatus according to one embodiment of the present invention.

FIG. 3 is a block diagram showing a main part of a driving circuit of an ink jet recording head of the ink jet recording apparatus according to one embodiment of the present invention.

FIG. 4 is a common drive signal used in an embodiment of the present invention, which is a common drive signal for generating a large dot drive pulse, a medium dot drive pulse, a small dot drive pulse, and a fine vibration drive pulse in printing. FIG. 4 is a waveform diagram showing signals.

FIG. 5 is a waveform diagram showing a large dot drive pulse, a medium dot drive pulse, a small dot drive pulse, and a fine vibration drive pulse in print generated from the common drive signal shown in FIG.

FIG. 6 is an explanatory diagram for explaining a method of determining an ejection time difference in an ejection time difference determination step according to one embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining a method of determining an ejection time difference in an ejection time difference determination step according to one embodiment of the present invention.

FIG. 8 is a diagram showing a common drive signal for large, medium, and small dots whose start point position on the time axis has been adjusted by the start point adjustment step in one embodiment of the present invention.

FIG. 9 is a cross-sectional view showing another example of a recording head to which the present invention can be applied.

FIG. 10 is a waveform diagram showing a common drive signal of the recording head shown in FIG. 9, and a large dot drive pulse, a medium dot drive pulse, a small dot drive pulse, and a fine vibration drive pulse in printing generated from the signal.

FIG. 11 shows a driving method 1 of an ink jet recording head.
FIG. 3 is a diagram for explaining one of the pulling driving methods.

FIG. 12 shows a driving method 1 of the ink jet recording head.
FIG. 3 is a diagram for explaining a push driving method which is one of the methods.

FIG. 13 is a waveform chart showing a common drive signal used in a second modification of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer controller 2 Print engine 8, 62 Recording head 9 Drive signal generation circuit 13 Nozzle opening 22 Selection signal generation part 23 Level shifter 24 Switch circuit 25, 61 Piezoelectric vibrator 31 Pressure chamber L Large dot M Medium dot S Small dot X1 X8, Y1 to Y4 nozzle group

Claims (14)

[Claims] An ink jet recording head comprising: a plurality of pressure chambers communicating with a plurality of nozzle openings for discharging ink droplets; and a plurality of pressure generating elements provided corresponding to the plurality of pressure chambers. On the other hand, by appropriately selecting and applying a plurality of types of drive pulses having different waveforms generated from a common drive signal having a predetermined waveform, an ink jet type of appropriately selecting and discharging different types of dots from the same nozzle opening. In the method of driving a recording head, an ejection time difference determining step of determining an ejection time difference which is a time difference between dot types in a required ejection time from a transmission time point of a signal instructing generation of the drive pulse to a dot ejection time point; When the main scanning of the recording head is performed a plurality of times per one line on the recording medium, a plurality of the dots ejected in the different main scannings at different times are used. A start point adjusting step of adjusting a start point position on the time axis of the common drive signal by a correction time determined based on the ejection time difference so as to prevent landing on the same pixel. A method for driving an ink jet recording head. 2. The ink-jet method according to claim 1, wherein the correction time is an integral multiple of a value obtained by dividing a driving cycle of the common driving signal by the number of main scans per row of the recording head. Driving method of recording head. 3. The ink-jet recording method according to claim 1, wherein the plurality of nozzle openings are classified into several nozzle groups, and the ejection time difference is determined for each of the nozzle groups. Head driving method. 4. The ink jet recording head according to claim 3, wherein said plurality of nozzle openings form several nozzle rows, and each said nozzle group corresponds to each of said nozzle rows. Drive method. 5. The ink jet recording head is capable of discharging a plurality of types of inks of different colors, and classifies the nozzle openings having the same color of the discharged ink into the same nozzle group. 4. The method of driving an ink jet recording head according to claim 3, wherein: 6. The ink jet type recording head is capable of discharging a plurality of types of inks of different colors, and the discharging time difference determining step and the starting point adjusting step are performed by the nozzle opening for discharging a specific color ink. The method of driving an ink jet recording head according to claim 1, wherein the method is performed only for a unit. 7. The method according to claim 1, wherein the different types of dots are dots having different sizes. 8. An ink jet recording head comprising: a plurality of pressure chambers communicating with a plurality of nozzle openings for discharging ink droplets; and a plurality of pressure generating elements provided corresponding to the plurality of pressure chambers. A plurality of types of drive pulses having different waveforms are appropriately selected and generated from a common drive signal having a predetermined waveform, and the drive pulses are applied to the pressure generating element to appropriately select different types of dots from the same nozzle opening. And a head driving device that discharges the recording head, wherein the head driving device performs the main scanning of the recording head a plurality of times per line on a recording medium, In order to prevent the plurality of dots ejected in the main scanning from landing on the same pixel, the ejection of the dots from the transmission time of the signal instructing the generation of the drive pulse is performed. The correction time determined based on the discharge time difference is a time difference between dots kinds of discharge time required to point, an ink jet recording apparatus characterized by adjusting the starting point position on the time axis of the common drive signal. 9. The ink-jet system according to claim 8, wherein the correction time is an integral multiple of a value obtained by dividing a drive cycle of the common drive signal by the number of main scans per row of the print head. Recording device. 10. The apparatus according to claim 8, wherein the discharge time difference is determined for each of the nozzle groups after the plurality of nozzle openings are classified into several nozzle groups. The ink-jet recording apparatus as described in the above. 11. An ink jet recording apparatus according to claim 10, wherein said plurality of nozzle openings form several nozzle rows, and each of said nozzle groups corresponds to each of said nozzle rows. 12. The ink-jet type recording head comprises a plurality of nozzle openings for ejecting a plurality of kinds of inks of different colors for each color, wherein the nozzle openings having a common color of ejected ink are provided. 11. The ink jet recording apparatus according to claim 10, wherein the ink jet recording apparatuses are classified into the same nozzle group. 13. The ink-jet type recording head includes a plurality of nozzle openings for discharging a plurality of types of inks of different colors, and the driving device includes a nozzle opening for discharging a specific color ink. 13. The ink jet recording apparatus according to claim 8, wherein the adjustment of the start point position on the time axis of the common drive signal is performed only for. 14. The ink jet recording apparatus according to claim 8, wherein the different types of dots are different in size.