JP2001138498A - Method for driving head of ink-jet recording apparatus, ink-jet recording apparatus, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording apparatus capable of recording the quality of which is kept over a long period by setting driving conditions in consideration of the change in a pressure generation element with the passage of time and a method for driving the head of the apparatus. SOLUTION: In the ink-jet recording apparatus 1, the frequency of ink ejection from a nozzle opening 111 is monitored by an ejection frequency monitor part 461. When the ejection reaches a prescribed number of times, a wave form correction means 465 corrects the wave form of a driving signal COM to be applied on a pressure generation element 17. Accordingly, even when the element 17 changes with the passage of time, ink droplets are ejected from the nozzle opening 111 in proper conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording apparatus used as an ink-jet printer or an ink-jet plotter, a head driving method in the ink-jet recording apparatus, and a recording medium storing a program for implementing the head driving method. Things. More specifically, the present invention relates to a technique for compensating a temporal change of a head in an ink jet recording apparatus.

[0002]

2. Description of the Related Art In an ink jet recording apparatus used as an ink jet printer or an ink jet plotter, a nozzle opening, a pressure generating chamber communicating with the nozzle opening, and ink in the pressure generating chamber are pressurized with respect to a recording head. A plurality of pressure generating elements for ejecting ink droplets from the nozzle openings are formed.

In such a recording head, for example, a piezoelectric vibrator shown in FIG. 7 is used as a pressure generating element. In FIG. 7, on the surface of the first lid member 130,
The common electrode 131 serving as one pole, the pressure generating element 17 including a piezo element, and the driving electrode 134 are formed in this order. In the example shown here, the pressure generating element 1
7 constitutes a flexural vibration type actuator together with the first lid member 130.
For example, when charged by the drive signal COM shown in FIG. 8, the pressure generating element 17 contracts and the pressure generating chamber 113 contracts, so that the pressure in the pressure generating chamber 113 rises and the ink in the pressure generating chamber 113 becomes ink. Nozzle opening 1 as a drop
It is discharged from 11 to the outside.

[0004] In the ink jet recording apparatus thus configured, the drive signal COM is set to an optimal waveform in consideration of the characteristics of the pressure generating element 17 and the ink characteristics at the design stage.

[0005]

However, in an ink jet recording apparatus, when an ink droplet is ejected from a recording head, the pressure generating element 17 repeats expansion and contraction every time. During the repetition, the characteristics of the pressure generating element 17 change from the initial characteristics. As a result, while the ink droplets are repeatedly ejected, the weight of the ink droplets and the ejection speed of the ink droplets deviate from the initially set conditions, and there is a problem that the quality of recording changes.

[0006] In view of the above problems, an object of the present invention is to provide:
By setting the driving conditions in consideration of the time-dependent change in the pressure generating element, an ink jet recording apparatus capable of performing recording without changing the quality for a long period of time, a head driving method thereof, and this head driving method are implemented. To provide a recording medium in which a program for executing the program is stored.

[0007]

According to the present invention, there is provided a pressure generating chamber communicating with a nozzle opening, and an ink droplet is ejected from the nozzle opening by pressurizing ink in the pressure generating chamber. A print head on which a plurality of pressure generating elements are formed, a head drive unit for selecting which of the plurality of pressure generating elements to apply a drive signal based on print data, and a drive signal for generating the drive signal In an ink jet recording apparatus having a generation unit, an ejection number monitoring unit that monitors the number of ink ejections from the nozzle, and when the number of ink ejections from the nozzle opening exceeds a predetermined number in the monitoring result of the ejection number monitoring unit. And a waveform correcting means for correcting the waveform of the drive signal.

That is, according to the present invention, a pressure generating chamber communicating with a nozzle opening and a plurality of pressure generating elements for discharging ink droplets from the nozzle opening by pressurizing ink in the pressure generating chamber are formed in a recording head. In the head driving method for an ink jet recording apparatus, the number of times of ink ejection from the nozzle opening is monitored, and when the number of times of ink ejection from the nozzle opening exceeds a predetermined number in the monitoring result, the driving applied to the pressure generating element It is characterized in that the signal waveform is corrected.

In the present invention, the number of times of ink ejection from the nozzle opening is monitored, and when the number of times of ink ejection exceeds a predetermined number of times, the drive applied to the pressure generating element in consideration of a change in the characteristics of the pressure oscillator over time. Correct the signal waveform. For this reason, even if the ink droplets are ejected hundreds of millions of times, the ink weight and the ejection speed of the ink droplets can be maintained under the optimum conditions, so that the recording without any change in quality can be performed forever.

In the present invention, it is preferable that the waveform correction means corrects the waveform of the drive signal in multiple stages according to the number of times of ink ejection. As described above, when the drive signal is corrected in multiple stages according to the number of times of ink ejection,
The driving conditions for the pressure generating element are always maintained at the optimum conditions. Therefore, it is possible to perform recording in which the quality does not change forever.

In the present invention, the nozzle openings are divided into a plurality of groups, and the drive signal generating means is formed so as to output a signal having a different waveform for each group as the drive signal to the head drive means. And
The number-of-discharges monitoring means monitors the number of times of ink ejection for each group, and the waveform correction means monitors the number of times of ink ejection for each group by the number-of-discharges monitoring means. It is preferable to correct the waveform of the drive signal applied to the pressure generating element belonging to the above. As described above, when the waveform of the drive signal applied to the pressure generating element belonging to the group in which the number of times of ink ejection exceeds the predetermined number of times is corrected, even when the number of times of ink ejection from the nozzle opening greatly differs between the groups, Ink droplets can be ejected from the nozzle openings belonging to the group under the optimum conditions. For example, in an ink jet recording apparatus for color recording, the number of times of ink ejection greatly differs for each color of ink. Ink droplets can be ejected from the nozzle openings to which the ink droplets belong under optimum conditions.

In this case, the number-of-discharges monitoring means monitors the average number of times of ink ejection of each nozzle opening belonging to each of the groups, and the waveform correction means determines whether or not the average number of times of ink discharge exceeds a predetermined number of times. It is preferable to correct the waveform of the drive signal applied to the pressure generating element belonging to the above.

In the present invention, the nozzle openings may be formed, for example, in a plurality of rows. In such a case, the nozzle openings are grouped for each of the rows. In the present invention, the nozzle openings may be formed in each of a plurality of recording heads, and may be grouped for each of the recording heads.

In the present invention, the waveform correction means may include, for example, correction data storage means for storing correction data for correcting the waveform of the drive signal. The waveform of the drive signal is corrected based on the correction data stored in the correction data storage means.

Here, the correction data storage means may be formed on either the apparatus main body side or the recording head side.

In the present invention, the pressure generating element may include a piezoelectric vibrator that presses ink in the pressure generating chamber by performing flexural vibration by application of the driving signal. The waveform correcting means corrects the waveform of the drive signal to a waveform such that the weight of the ink droplet decreases when the number of times of ink ejection increases.

On the other hand, the pressure generating element may include a piezoelectric vibrator that presses ink in the pressure generating chamber by performing expansion and contraction vibration by applying the drive signal. In such a case, the waveform correction means
When the number of times of ink ejection increases, the waveform of the drive signal is corrected to a waveform that increases the ink droplet weight.

The head driving method according to the present invention may be implemented by either a hardware or software configuration in an ink jet recording apparatus. Further, the whole or a part of the program for implementing the head driving method according to the present invention may be a floppy disk or a CD-R.
If the program is stored in a recording medium such as an OM, the program stored in the recording medium is read by a computer, so that the head driving method according to the present invention can be performed under the control of the computer.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet recording apparatus to which the present invention is applied will be described with reference to the drawings.

(Overall Configuration of Inkjet Recording Apparatus) FIG. 1 is a perspective view showing a main part of the inkjet recording apparatus.

As shown in FIG. 1, in the ink jet recording apparatus 1, the carriage 101
Through the carriage motor 103 of the carriage mechanism 12
To the recording sheet 1 guided by the guide member 104.
05 is reciprocated in the paper width direction. A paper feed mechanism 11 using a paper feed roller 106 is formed in the inkjet recording apparatus 1. Carriage 10
1, an ink jet recording head 10 is attached to a surface facing the recording paper 105, in the example shown in FIG. The recording head 10 includes two ink cartridges 107 mounted on an upper portion of the carriage 101.
K, 107F, and the carriage 10
In accordance with the movement of No. 1, ink droplets are ejected onto the recording paper 105 to form dots, and images and characters are recorded on the recording paper 105. Here, the ink cartridge 107 </ b> K supplies the stored black (BK) ink to the recording head 10. On the other hand, the ink cartridge 107F is for color ink, and has a plurality of ink storage units 107C, 107M, and 107Y for storing the respective color inks. These ink storage units 107C, 107M, 1
07Y includes cyan (C), magenta (M),
Yellow (Y) ink is stored independently, and ink of each color is supplied to the recording head 10 independently.

A capping device 108 is provided in the non-recording area of the ink jet recording apparatus 1 to seal the nozzle openings of the recording head 10 during the pause of recording. Therefore, it is possible to suppress the ink from thickening or forming an ink film due to the solvent being scattered from the ink during the suspension of recording. Therefore, it is possible to prevent the nozzle from being clogged during the suspension of the recording. Further, the capping device 108 receives ink droplets from the recording head 10 due to a flushing operation performed during the recording operation. A wiping device 109 is disposed near the capping device 108, and the wiping device 109
By wiping the surface of 0 with a blade etc.,
It is configured to wipe off ink residue and paper powder attached thereto.

(Nozzle Arrangement) FIG. 2 is an explanatory diagram showing a nozzle arrangement formed on the recording head 10 shown in FIG. As can be seen from the figure, the nozzles 111 are formed in the recording head 10 for five rows (for five groups), and are grouped for each row. That is, the nozzle openings 111 eject three color inks of cyan (C), magenta (M), and yellow (Y), respectively.
Nozzle openings of one color group, black ink is ejected during monochrome printing, but ejection of ink droplets is stopped during color printing. Nozzle openings of the first black group (BK1) eject black ink during color printing and monochrome printing. Second
Of the black group (BK2). In addition,
When performing the flushing operation, all the nozzle openings 1
11 ejects ink droplets.

(Configuration of Control System) FIG. 3 is a functional block diagram of the ink jet recording apparatus 1 of the present embodiment.

In FIG. 3, the ink jet recording apparatus 1
Is composed of a print controller 40 and a print engine 5.

The print engine 5 includes a recording head 10
And the paper feed mechanism 11 and the carriage mechanism 1
2 is provided. The paper feed mechanism 11 sequentially feeds a recording medium such as recording paper to perform sub-scanning, and the carriage mechanism 12 causes the recording head 10 to perform main scanning.

The print controller 40 includes an interface 43 for receiving image data (recording information) including multi-value gradation information from a computer (not shown),
An input buffer 44A composed of a DRAM for storing various data such as recording information including multi-valued gradation information, an image buffer 44B, and an output buffer 4 composed of an SRAM.
4C, a ROM 45 storing routines for performing various data processing, a control unit 46 including a CPU and a memory, an oscillation circuit 47, and a drive signal generation unit 8 for generating a drive signal COM to the print head 10. And an interface 4 for transmitting print data and drive signals developed into dot pattern data to the print engine 5.
9 is provided.

In the present embodiment, the drive signal generating section 8 controls the cyan (C)
, Magenta (M), yellow (Y), first black group (BK1), and second black group (BK
The drive signals COM generated by the drive signal generators 8 formed in five groups as 2) and thus grouped are output to the recording head 10, respectively.

(Structure of Recording Head) The recording head 10
Ink droplets are ejected from each nozzle opening 111 at a predetermined timing, and a plurality of nozzle openings 111, a plurality of pressure generating chambers 113 communicating with each of these nozzle openings 111, and a plurality of A plurality of pressure generating elements 17 that pressurize ink and eject ink droplets from each nozzle opening 111 are formed.

Here, as described above, the nozzle openings 111 form three color groups for discharging three color inks of cyan (C), magenta (M), and yellow (Y) to the recording head 10. , Five rows (five groups) as nozzle openings for the first black group (BK1) and nozzle openings for the second black group (BK2). , The pressure generating chamber 113, the pressure generating element 17, and the switching element are formed in a 1: 1 relationship.
Therefore, the pressure generating chamber 113 and the pressure generating element 17 are also divided into five groups corresponding to the nozzle openings 111.

The recording head 10 has a head drive circuit 50 including a shift register 13, a latch circuit 14, a level shifter 15, and a switch circuit 16. The head drive circuit 50 also has a nozzle opening 111
Of the first black group (BK) for cyan (C), for magenta (M), for yellow (Y),
1) and a second black group (BK2).

(Ink Discharge Operation) In the ink jet recording apparatus 1 thus configured, the operation up to ink discharge is performed in the same manner in any group.

First, the print data SI developed into dot pattern data by the print controller 40 is:
The data is serially output to the head drive circuit 50 of the recording head 10 via the interface 49 in synchronization with the clock signal CLK from the oscillation circuit 47, serially transferred to the shift register 13 of the recording head 10, and sequentially set.
In this case, first, the data of the most significant bit in the print data SI of the nozzle is serially transferred, and when the serial transfer of the data of the most significant bit is completed, the data of the second highest bit is serially transferred. Hereinafter, similarly, data of lower bits are sequentially serially transferred.
When the print data of the bit is set in each element of the shift register 13 for all nozzles, the control unit 4
6 outputs a latch signal to the latch circuit 14 at a predetermined timing. With this latch signal, the latch circuit 14 latches the nozzle selection data set in the shift register 13. The nozzle selection data latched by the latch circuit 14 is applied to a level shifter 15 which is a voltage converter. When the recording data SI is, for example, “1”, the level shifter 15 converts the voltage into a voltage value that can be driven by the switch circuit 16, for example, several tens of volts. Then, the converted recording data SI is applied to each switching element of the switch circuit 16, and each element is connected.

Here, each switching element of the switch circuit 16 has a drive signal CO generated by the drive signal generator 8.
When M is applied and each switching element of the switch circuit 16 is connected, the drive signal COM is applied to the pressure generating element 17 connected to this element.

Therefore, in the recording head 10, whether or not the drive signal COM is applied to the pressure generating element 17 can be controlled by the nozzle selection data corresponding to the recording data SI. For example, nozzle selection data (print data S
In the period when I) is “1”, the elements of the switch circuit 16 are in the connected state, so that the drive signal COM can be supplied to the pressure generating element 17. Is displaced (deformed).

On the other hand, during the period when the recording data SI is "0", the elements of the switch circuit 16 are disconnected, so that the supply of the drive signal COM to the pressure generating element 17 is cut off. During the period when the nozzle selection data (print data SI) is “0”, each pressure generating element 17
Holds the previous charge, so that the previous displacement state is maintained.

Here, when the element of the switch circuit 16 is turned on and the drive signal COM is applied to the pressure generating element 17, the pressure generating chamber 113 communicating with the nozzle opening 111 is formed.
Is contracted and the ink in the pressure generating chamber 113 is pressurized, so that the ink in the pressure generating chamber 113 is ejected from the nozzle openings 111 as ink droplets to form dots on recording paper or the like.

FIG. 4 is a block diagram showing the configuration of the drive signal generator 8. As shown in FIG. FIG.
FIG. 4 is an explanatory diagram showing a process of generating each drive pulse included in a drive signal COM in a drive signal generation unit 8. FIG. 6 is a timing chart showing the timing of each signal when the drive signal generator 8 sets a potential difference (ΔV) in a memory using a data signal.

In FIG. 4, in the ink jet recording apparatus 1 of this embodiment, a waveform control section 462 configured as a part of the function of the control section 46 and various data for forming the drive signal COM are stored. Data storage unit 46
The drive signal COM having a predetermined waveform is generated by the drive signal generator 8 and the drive signal generator 8 that generates the drive signal COM under the control of the waveform controller 462.

The drive signal generator 8 includes a waveform controller 462
, A first latch 82 for reading out and temporarily storing the contents of the memory 81, an output of the first latch 82 and another second latch 84 described later. Adder 8 for adding the output of
3, a D / A converter 86 for converting the output of the second latch 84 into analog data, a voltage amplifying circuit 88 for amplifying the converted analog signal up to the voltage of the drive signal, and a voltage amplified by the voltage amplifying circuit 88 A current amplifying circuit 89 for amplifying the current of the driving signal COM is formed.

The waveform of the drive signal COM is determined by the waveform control unit 46.
2 is determined by the predetermined parameters received from the server.
That is, the drive signal generation unit 8 sends the clock signals 801, 802, 803 and the data signal 83 from the waveform control unit 462.
0, an address signal 810, 811, 812, 813, a reset signal 820 and an enable signal 840 are received. Here, the data output from the waveform control unit 462 is
It is defined by the waveform data recorded in the waveform data recording section 466 of the data storage section 468.

In the drive signal generator 8 configured as described above, as shown in FIG. 5, prior to generation of the drive signal COM, several data signals indicating the amount of voltage change of the waveform controller 462, The address of the data signal is synchronized with the clock signal 801, and the memory 8 of the drive signal generation unit 8
1 is output. As shown in FIG. 6, the data signal 830 is configured to exchange data by serial transfer using the clock signal 801 as a synchronization signal. That is, when transferring a predetermined amount of voltage change from the waveform control unit 462, first, a data signal of a plurality of bits is output in synchronization with the clock signal 801, and then the address for storing this data is set to the enable signal 840. They are output as address signals 810 to 813 in synchronization. Memory 81
Reads the address signal at the timing when the enable signal 840 is output, and writes the received data to the address. Since the address signals 810 to 813 are 4-bit signals, up to 16 types of voltage change amounts can be stored in the memory 81. Note that the most significant bit of the data is used as a code.

After the setting of the amount of voltage change for each address A, B,.
813, the first latch circuit 82 holds the amount of voltage change corresponding to the address B by the first clock signal 802. In this state, when the clock signal 803 is output next, the second latch circuit 84
And the output of the first latch circuit 82 is added to the output of the second latch circuit 84. That is, as shown in FIG. 5, once the voltage change amount corresponding to the address signal is selected, each time the clock signal 803 is received thereafter, the output of the second latch circuit 84 changes according to the voltage change amount. Increase or decrease. The slew rate of the drive waveform is determined by the voltage change amount ΔV1 stored in the address B of the memory 81 and the unit time ΔT of the clock signal 803. The increase or decrease is determined by the sign of the data stored at each address.

In the example shown in FIG. 5, the address A stores a value 0 as a voltage change amount, that is, a value for maintaining a voltage. Therefore, when the address A becomes valid by the clock signal 802, the waveform of the drive signal is maintained in a flat state with no increase or decrease. Further, the address C stores a voltage change amount ΔV2 per unit time ΔT in order to determine a slew rate of the drive waveform. Therefore, after the address C becomes valid by the clock signal 802, the voltage decreases by this voltage ΔV2.

As described above, only by outputting the address signal and the clock signal from the waveform control section 462, the drive signal CO
The waveform of M can be freely controlled. Therefore, with the recording head 10 having the configuration shown in FIG. 7, the drive signal COM having the waveform shown in FIG. 8 can be formed, and the waveform of the drive signal COM can be arbitrarily corrected by the data output from the waveform control section 462.

(Specific Structure of Inkjet Recording Head) FIG. 7 shows an example of a mechanical sectional structure of the recording head 10. FIG. 8 is a waveform diagram of the drive signal COM supplied to the print head of the type shown in FIG.

In the recording head 10 shown in FIG.
Is made of zirconia (Z) having a thickness of about 6 μm.
A common electrode 131 serving as one pole is formed on the surface of the thin plate, and a pressure generating element 17 made of PZT or the like is fixed on the surface of the common electrode 131 as will be described later. A drive electrode 134 made of a relatively flexible metal layer is formed.

The pressure generating element 17 constitutes a flexural vibration type actuator together with the first lid member 130.
When the pressure generating element 17 is charged, it contracts and the pressure generating chamber 1
The pressure generating element 17 is deformed so as to expand when the pressure generating element 17 is discharged and expands based on the volume of the pressure generating chamber 113.

The spacer 135 has a through hole formed in a ceramic plate made of, for example, zirconia having a thickness suitable for forming the pressure generating chamber 113 and having a thickness of, for example, 100 μm. Both sides are sealed by the lid member 130 to form the pressure generating chamber 113.

The second lid member 136 is also a ceramic plate made of zirconia or the like.
A communication hole 138 that connects the pressure generating chamber 7 with the pressure generating chamber 113 and a nozzle communication hole 139 that connects the nozzle opening 111 with the other end of the pressure generating chamber 113 are formed and fixed to the other surface of the spacer 135.

Each of these members 130, 135, and 136 is formed into a predetermined shape from a viscous ceramic material, and is laminated and fired to be assembled into the actuator unit 121 without using an adhesive. ing.

The ink supply port forming substrate 140 also serves as a fixed substrate for the actuator unit 121, and has a nozzle communication hole 1 connected to a common ink chamber 141 and a nozzle opening 111, which will be described later, at one end of the pressure generating chamber 113.
A common ink chamber 141 is formed by sealing the other surface with a nozzle plate 145.

The ink supply port forming substrate 140, the common ink chamber forming substrate 143, and the nozzle plate 14
5 are fixed to each other by adhesive layers 146 and 147 such as a heat-sealing film and an adhesive between them, and are combined in the channel unit 122.

The recording head 10 is formed by fixing the flow path unit 122 and the above-described actuator unit 121 by an adhesive layer 148 such as a heat-sealing film or an adhesive.

In the recording head 10 configured as described above, when the pressure generating element 17 is discharged, the pressure generating chamber 113 is discharged.
Expands, the pressure in the pressure generation chamber 113 decreases, and ink flows from the common ink chamber 141 into the pressure generation chamber 113. On the other hand, when the pressure generating element 17 is charged,
The pressure generation chamber 113 contracts, the pressure in the pressure generation chamber 113 increases, and the ink in the pressure generation chamber 113 is ejected to the outside through the nozzle openings 111 as ink droplets.

In FIG. 8, the drive signal COM for operating the pressure generating element 17 is such that the intermediate potential Vc is set at the time T1.
1 after a predetermined time (hold pulse 21
3) During the period Twd from time T11 to time T12, the voltage drops to the lowest potential VB at a constant gradient (discharge pulse 2).
14), the minimum potential VB is changed from time T12 to time T13.
(Hold pulse 21)
5) During a period Twc from time T13 to time T14, the voltage rises to a maximum potential VH with a constant gradient, and is increased at time Tc.
15 for a predetermined time (charging pulse 216), and thereafter, it falls again to the intermediate potential Vc before time T16 (discharge pulse 217).

According to such a drive signal COM, FIG.
In the recording head 10 described with reference to the above description, the meniscus of the ink after the ink droplet is ejected by the previously applied charge pulse is vibrated at a predetermined cycle by the ink surface tension while the hold pulse 213 is applied. Then, the vibration around the nozzle opening 111 is caused, and as the time elapses, the meniscus attenuates the vibration and eventually becomes stationary. Next, when the discharge pulse 214 is applied, the pressure generating element 17 bends in a direction to expand the volume of the pressure generating chamber 113, and a negative pressure is generated in the pressure generating chamber 113. As a result, the meniscus causes a movement toward the inside of the nozzle opening 111, and the meniscus causes the nozzle opening 11 to move.
1 is drawn inside. This state is maintained while the hold pulse 215 is being applied, and then, when the charging pulse 216 is applied, a positive pressure is generated in the pressure generating chamber 113, and the meniscus is pushed out from the nozzle opening 111, and the ink droplet is pushed out. Is discharged. Then, discharge pulse 2
17 is applied, the pressure generating element 17
3 is deflected in a direction to expand the volume, and a negative pressure is generated in the pressure generating chamber 113. As a result, the meniscus has the nozzle opening 11
Cause a movement towards the inside of 1. Then, after the vibration around the nozzle opening 111 is caused by the vibration at a predetermined cycle due to the ink surface tension, the meniscus returns to a stationary state again with a lapse of time while attenuating the vibration.

(Configuration for Performing Correction Corresponding to Temporal Change) In the recording head 10 configured as described above, the characteristic of the pressure generating element 17 changes while the ejection of the ink droplet from the nozzle opening 111 is repeated several hundred million times. I do. For example, as shown in FIG. 7, the piezoelectric vibrator (the pressure generating element 17) that performs bending vibration increases the ink weight and the ink droplet ejection speed as compared with the initially set levels as the number of ink ejections increases. Changes over time. When the piezoelectric vibrator (pressure generating element 17) shown in FIG. 7 is used, if the maximum potential VH of the drive signal COM (see FIG. 8) is lowered or the intermediate potential Vc is raised, the ink weight tends to be reduced. is there. When the piezoelectric vibrator (pressure generating element 17) shown in FIG. 7 is used, the maximum potential VH of the drive signal COM (see FIG. 8) is lowered or the periods Twh, Twd,
By increasing Twc, the ejection speed of ink droplets can be reduced.

Therefore, in the present embodiment, the waveform of the drive signal COM is corrected in accordance with the number of ejections of ink droplets in consideration of the features of the pressure generating element 17 described above.

That is, in the ink jet recording apparatus 1 of the present embodiment, as shown in FIGS. 3 and 4, the control unit 46 on the apparatus main body side monitors the number of ejections of ink droplets from the nozzle openings 111. Unit 461 and the recording head 10 based on the monitoring result by the ejection number monitoring unit 461.
A waveform correction means 465 for correcting the drive signal COM corresponding to a change with time of the (pressure generating element 17) is formed, and a data storage unit 468 storing correction data defining a correction condition by the waveform correction means 465 is formed. ing.

First, the number-of-discharges monitoring unit 461 obtains and monitors the number of discharges of ink droplets from the nozzle openings 111 based on the recording data SI that specifies the presence or absence of ink droplets.

In the case where color printing is performed and the case where monochrome printing is performed, the nozzle openings 111 used are different.
Are different from each other, the number of ejections of the ink droplets greatly differs depending on the group of the nozzle openings 111. Therefore, the ejection number monitoring unit 461, like the drive signal generation unit 8 and the head drive circuit 50, uses the first black group (BK) for cyan (C), magenta (M), yellow (Y).
5) for the first black group (BK2) and for the second black group (BK2).
The number of times of ink ejection from 1 is monitored.

In the same group, the number of times of ejection of ink droplets differs depending on the nozzle openings 111.
The ejection number monitoring unit 461 calculates the average number of ink ejections of the nozzle openings 111 belonging to each group, and monitors this as the number of ink ejections of each group.

The data storage section 468 stores waveform data for generating a drive signal COM of a basic waveform without correction with respect to a change over time. A correction data storage unit 467 for storing correction data for performing a predetermined correction for the change is formed.

Therefore, in the initial stage, the waveform control section 462 uses the waveform data stored in the waveform data storage section 466 to send the uncorrected drive signal CO to the drive signal generation section 8.
On the other hand, when it is necessary to correct the waveform of the drive signal COM while generating M, the waveform is corrected for the drive signal generation unit 8 using the correction data stored in the correction data storage unit 467. The generated drive signal COM is generated.

As described above, in the present embodiment, the correction data storage unit 467 and the waveform control unit 462 constitute the waveform correction unit 465. This waveform correction means 465
For example, when the piezoelectric vibrator shown in FIG. 7 is used as the pressure generating element 17, correction such as lowering the maximum potential VH of the drive signal COM (see FIG. 8) when the number of ejections increases is performed. This prevents the weight of the ink droplet and the ejection speed of the ink droplet from changing with time.

In the present embodiment, the number-of-discharges monitoring unit 46
1, the drive signal generator 8 and the head drive circuit 50 are for cyan (C), magenta (M), yellow (Y),
Are formed for the black group (BK1) and the second black group (BK2), the waveform correction unit 465 monitors the number of ink ejections for each group by the ejection number monitoring unit 461. The drive signal C corresponding to the group in which the number of ink ejections exceeds a predetermined number
Only the OM waveform is individually corrected. For example, the waveform correction unit 465 determines that the number of ejections of ink droplets from the nozzle openings 111 for the second black group (BK2) exceeds a predetermined number, and that the nozzle openings 111 other than those for the second black group (BK2). If the number of ejections of ink droplets from has not reached the predetermined number, the drive signal generation unit 8 corresponding to the second black group (BK2) generates a drive signal COM having a waveform that has been subjected to correction corresponding to aging. The drive signal COM having the waveform subjected to this correction is supplied to the second black group (BK
Output to the head drive circuit 50 corresponding to 2).

(Waveform Setting / Correction Processing) FIG. 9 is a flowchart showing the contents of processing for setting the waveform of the drive signal COM in consideration of the number of ink ejections in the ink jet recording apparatus 1 shown in FIG. Each process shown is performed based on a program stored in advance in the ROM 45 or the like. Here, when the number of times of ink ejection increases, the maximum potential V with respect to the drive signal COM shown in FIG.
The case where the correction for lowering H is performed will be described as an example. However,
If the correction is such that the weight of the ink droplets ejected from the nozzle opening 111 or the ejection speed of the ink droplets is appropriately maintained, the correction is not limited to the change of the maximum potential VH, but is, for example, the change of the intermediate potential Vc, or Period Tw
Even when the correction for changing h, Twd, and Twc is performed, basically, the same processing as the processing described below with reference to FIG. 9 can be used. In the present embodiment, the nozzle opening 11
Monitoring of the number of times of ink ejection and correction of the drive signal COM are also performed for each group in accordance with the grouping of 1. However, since correction for any group is performed by the same process, the following description is for one group. Only the correction processing for will be described.

In FIG. 9, in the ink jet recording apparatus 1 according to the present embodiment, when the power switch is turned on (step ST 1), the waveform control unit 462 first determines the ink based on the monitoring result of the ejection number monitoring unit 461. It is determined whether the number of ejections is less than 2 billion (step ST2).

In this step ST2, if the number of ink ejections is less than 2 billion, the waveform control section 462 sets so as to generate the drive signal COM in which the maximum potential VH remains the initial condition (step ST3). ), The waveform correction processing ends (step ST4). On the other hand, if the number of ink ejections is 2 billion or more in step ST2, the waveform control unit 462 determines that the number of ink droplet ejections is 60
It is determined whether the number is less than 100 million times (step ST5).

If the number of ink ejections is less than 6 billion in step ST5, the waveform controller 462 determines that the number of ink droplet ejections is currently between 2 billion and 6 billion, and A setting is made to lower the highest potential VH of COM by, for example, 5% from the initial condition (step ST6), and the waveform correction processing is ended (step ST4). On the other hand, if the number of ink ejections is 6 billion or more in step ST5, the waveform control unit 46
2 means that the number of ink droplet ejections in step ST7 is 1
Judge whether it is less than 5 billion times.

If the number of ink ejections is less than 15 billion in this step ST7, it is determined that the number of ink droplet ejections is currently between 6 billion and 15 billion.
The waveform control unit 462 sets the maximum potential VH of the drive signal COM to be reduced by 8% from the initial condition (step ST8), and ends the waveform correction processing (step ST8).
4). On the other hand, if the number of ink ejections is 15 billion times or more in step ST7, the waveform control unit 462
Means that the number of ink droplet ejections in step ST9 is 30
It is determined whether it is less than 100 million times.

If the number of ink ejections is less than 30 billion in step ST9, the waveform controller 462 determines that the number of ink droplet ejections is currently between 15 billion and 30 billion, COM's highest potential V
The setting for lowering H by 10% with respect to the initial condition is performed (step ST10), and the waveform correction processing ends (step ST4). On the other hand, if the number of ink ejections is 30 billion or more in step ST9, the waveform control unit 462 notifies that the print head 10 has reached the end of its life in step ST11, and performs the waveform correction processing. It ends (step ST4).

(Effect of this embodiment) As described above,
In the ink jet recording apparatus 1 of the present embodiment, the nozzle opening 1
11 is monitored, and when the number of times of ink ejection exceeds a predetermined number, the drive signal CO applied to the pressure generating element 17 is considered in consideration of the characteristic change of the pressure generating element 17.
Correct the M waveform. For this reason, even if the ink droplets are ejected hundreds of millions of times, the ink weight and the ink droplet speed can be maintained under the optimal conditions without being affected by the aging of the pressure generating element 17. It is possible to perform recording in which the quality does not change until the life is completely exhausted.

In the present embodiment, since the drive signal COM is corrected in multiple stages according to the number of times of ink ejection, the drive conditions for the pressure generating element 17 are always maintained at optimal conditions. Therefore, it is possible to perform the printing in which the quality does not change until the life of the print head 10 is completely exhausted.

Further, in this embodiment, the number of times of ink ejection from the nozzle openings 111 is monitored for each group, and the pressure generating elements 17 belonging to a group in which the number of times of ink ejection exceeds a predetermined number of times.
To correct the waveform of the drive signal COM to be applied. For this reason, even when the number of times of ink ejection from the nozzle openings 111 is greatly different between groups, ink droplets can be ejected from the nozzle openings 111 belonging to any group under the optimum conditions until the life of the recording head 10 is completely exhausted. Can be ejected. That is, in the ink jet recording apparatus 1 for color recording, the number of times of ink ejection greatly differs for each color of ink, but even in such a case, correction is performed in accordance with temporal change by grouping by color. Ink droplets can be ejected from the nozzle openings 111 belonging to any of the color groups under optimal conditions until the life of the recording head 10 is completely exhausted.

[Structure of Another Recording Head 10] FIG.
In the inkjet recording apparatus 1 shown in FIG. 1, an example of a mechanical cross-sectional structure of a recording head 10 using a piezoelectric vibrator that expands and contracts as a pressure generating element is shown. FIG.
FIG. 3 is a waveform diagram of a drive signal COM supplied to a print head 10 of this type.

In the recording head 10 shown in FIG. 10, nozzle openings 111 are formed in the nozzle plate 410, and the flow path forming plate 412 communicates with the through holes that define the pressure generating chambers 113 and communicates with the pressure generating chambers 113 on both sides. Two ink supply ports 4
14 and two common ink chambers 4 communicating with these ink supply ports 414, respectively.
15 are formed. Diaphragm 416
Is made of an elastically deformable thin plate, abuts against the tip of a pressure generating element 17 (pressure generating element) such as a piezo element,
It is fixed integrally with the nozzle plate 410 in a liquid-tight manner with the flow path forming plate 412 interposed therebetween, and forms a flow path unit 418.

The base 419 is formed with an accommodation chamber 420 for accommodating the pressure generating element 17 so as to be able to vibrate and an opening 421 for supporting the flow path unit 418, and exposing the tip of the pressure generating element 17 from the opening 421. Pressure generating element 1
7 is fixed by a fixed substrate 422. Also, base 419
The recording head 10 is assembled by fixing the channel unit 418 to the opening 421 in a state where the island portion 416a of the vibration plate 416 is in contact with the pressure generating element 17.

The driving signal COM for driving the pressure generating element 17 in the recording head 10 thus configured.
As shown in FIG. 11, after the voltage value starts from the intermediate potential Vc (hold pulse 311), at time T2
From 1 to time T22, the voltage rises to a maximum potential VH at a constant gradient (charging pulse 312), and from time T22 to time T2.
The maximum potential VH is maintained for a predetermined time until 3 (hold pulse 313). Next, after falling at a constant gradient from the time T23 to the time T24 to the lowest potential VB (discharge pulse 314), the lowest potential V from the time T24 to the time T25.
B is maintained for a predetermined time (hold pulse 315).
Then, from time T25 to time T26, the voltage value rises at a constant gradient to the intermediate potential Vc (charging pulse 31
6).

In the recording head 10 configured as described above, when the charging pulse 312 included in the drive signal COM is applied to the pressure generating element 17, the pressure generating element 17 bends in a direction to expand the volume of the pressure generating chamber 113. , A negative pressure is generated in the pressure generating chamber 113. As a result, the meniscus retracts from the nozzle opening 111. Next, the discharge pulse 31
4, the pressure generating element 17 is turned into the pressure generating chamber 113.
, And a positive pressure is generated in the pressure generating chamber 113. As a result, ink droplets are ejected from the nozzle openings 111. Then, after the hold pulse 315 is applied, the charging pulse 316 is applied to suppress the meniscus vibration.

In the recording head 10 configured as described above,
The characteristics of the pressure generating element 17 change as the ejection of the ink droplet from the nozzle opening 111 is repeated several hundred million times. However, as shown in FIG. 10, when a piezoelectric vibrator that performs expansion and contraction vibration is used as the pressure generating element 17, unlike the case where the piezoelectric vibrator shown in FIG. As the number of times increases, the ink weight and the ejection speed of the ink droplets decrease as compared with the initially set levels. Further, the piezoelectric vibrator (pressure generating element 17) shown in FIG. 10 can increase the ink weight by increasing the maximum potential VH or increasing the intermediate potential Vc in the drive signal COM shown in FIG. FIG.
The piezoelectric vibrator (pressure generating element 17) shown in FIG.
By increasing the maximum potential VH of the OM (see FIG. 11) or shortening the periods Twh, Twd, and Twc, the ejection speed of the ink droplets can be increased.

Accordingly, when the piezoelectric vibrator shown in FIG. 10 is used as the pressure generating element 17, the waveform correcting means 465 shown in FIG. 3 and FIG. At times, by performing correction such as increasing the maximum potential VH, a drive signal COM whose waveform is corrected so as to increase the weight of the ink droplet and the ejection speed of the ink droplet is generated.

[Other Embodiments] As shown in FIG. 12, since the recording heads 10 tend to have different characteristics for each head, the optimum driving waveform COM for each recording head 10 is provided. It is preferable to drive with. Therefore, a data storage unit 468 is formed on the apparatus main body side, and correction data for defining the optimum waveform of the drive signal COM when the recording head 10 is used is stored for the recording head 10. The part 469 may be formed in some cases. In such a case, the correction data corresponding to the above-described aging is also stored in the correction data storage unit 469 of the recording head 10, and when the inkjet recording apparatus 10 starts to be used, or when the recording head 10
Is exchanged, the data is transferred from the correction data storage section 469 formed on the recording head side to the correction data storage section 467 on the apparatus main body side. When such a configuration is employed, the drive signal COM having the optimum waveform for each recording head 10 can be used both in the initial stage of use and when performing correction corresponding to aging.

The correction data storage section 469 on the recording head side shown in FIG.
Of various data stored in the data storage unit 468 of the apparatus main body, identification data for specifying which data is to be used is stored, and the data specified by the identification data is actually used. The configuration may be such that a drive signal having a waveform suitable for the mounted recording head 10 is generated, and the drive signal COM is appropriately corrected.

Further, in the above-described embodiment, the configuration in which the nozzle openings 111 are grouped in each row on one recording head 10 has been described as an example. However, in an ink jet recording apparatus in which a plurality of recording heads 10 are mounted, Alternatively, the nozzle openings 111 may be divided into groups for each recording head, and the drive signal COM may be generated or corrected for each group.

Further, in the above embodiment, the nozzle opening 111
Has been described as an example, but the present invention may be applied to an inkjet recording apparatus in which such grouping is not performed.

Furthermore, in the above embodiment, an ink jet recording apparatus using a piezoelectric vibrator as a pressure generating element has been described as an example. However, the present invention is also applicable to an ink jet recording apparatus that generates pressure in a pressure generating chamber by heat. Applicable.

Further, the present invention may be embodied by either a hardware or software configuration in an ink jet recording apparatus. Also, if the whole or a part of the program for implementing the head driving method according to the present invention is stored in a recording medium such as a floppy disk or a CD-ROM, the program stored in the recording medium can be stored in a computer. The present invention can also be implemented under the control of a computer.

[0090]

As described above, in the ink jet recording apparatus and the head driving method thereof according to the present invention, the number of times of ink ejection from the nozzle opening is monitored, and when the number of times of ink ejection exceeds a predetermined number, the pressure is generated. It is characterized in that the waveform of the drive signal applied to the pressure generating element is corrected in consideration of the characteristic change of the element. Therefore, according to the present invention, even if the ink droplets are ejected hundreds of millions of times, the ink weight and the ink droplet speed can be maintained under the optimal conditions, so that the recording without changing the quality can be performed forever.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of an ink jet recording apparatus used in an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram showing a nozzle array formed on a print head of the ink jet printing apparatus shown in FIG.

FIG. 3 is a functional block diagram of the ink jet recording apparatus shown in FIG.

FIG. 4 is a block diagram of a drive signal generation unit and a waveform correction unit formed in the inkjet recording apparatus shown in FIG.

FIG. 5 is an explanatory diagram showing a process of generating each pulse included in the drive signal in the drive signal generation unit shown in FIG.

6 is a timing chart showing the timing of each signal when a voltage change amount is set in a memory based on a data signal in a drive signal generation unit shown in FIG. 4;

FIG. 7 illustrates an example of a mechanical cross-sectional structure of a recording head using a piezoelectric vibrator that bends and vibrates as a pressure generating element.

8 is a waveform diagram of a drive signal supplied to a print head of the type shown in FIG.

FIG. 9 shows a configuration of the ink jet recording apparatus shown in FIG.
9 is a flowchart illustrating processing for setting a waveform of a drive signal in consideration of the number of times of ink ejection.

FIG. 10 illustrates an example of a mechanical cross-sectional structure of a recording head using a piezoelectric vibrator that expands and contracts as a pressure generating element.

11 is a waveform diagram of a drive signal supplied to a print head of the type shown in FIG.

FIG. 12 is a block diagram illustrating an example in which a data storage unit that stores correction data for correcting a waveform with respect to a drive signal is mounted on a recording head side in an inkjet recording apparatus to which the present invention is applied.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 inkjet recording device 5 print engine 8 drive signal generation unit 10 recording head 13 shift register 14 latch circuit 15 level shifter 16 switch circuit 17 pressure generation element 46 control unit 50 head drive circuit 111 nozzle opening 113 pressure generation chamber 461 ejection frequency monitoring unit Ejection number monitoring means) 462 waveform control section 465 waveform correction means 466 waveform data storage sections 467, 469 correction data storage section (correction data storage section) 468 data storage section COM drive signal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C056 EA04 EB08 EB29 EB59 EC07 EC42 FA04 FA10 KD10 2C057 AF23 AF30 AG14 AG15 AG44 AL40 AM16 AN01 BA04 BA14

Claims (18)

[Claims] 1. An ink jet recording apparatus comprising: a pressure generating chamber communicating with a nozzle opening; and a plurality of pressure generating elements for discharging ink droplets from the nozzle opening by pressurizing ink in the pressure generating chamber. In the head driving method of the apparatus, the number of times of ink ejection from the nozzle opening is monitored, and when the number of times of ink ejection from the nozzle opening exceeds a predetermined number in the monitoring result, the waveform of a drive signal applied to the pressure generating element is changed. A method for driving a head of an ink jet recording apparatus, comprising: correcting. 2. The method according to claim 1, wherein the nozzle openings are divided into a plurality of groups, and the number of times of ink ejection is monitored for each group, thereby belonging to a group in which the number of times of ink ejection exceeds a predetermined number. A method of driving a head of an ink jet recording apparatus, wherein a waveform of the drive signal applied to the pressure generating element is corrected. 3. The pressure generation method according to claim 2, wherein the number of times of ink ejection is monitored as an average number of times of ink ejection of each nozzle opening belonging to each of the groups, and the average of the number of times of ink ejection exceeds a predetermined number. A method of driving a head of an ink jet recording apparatus, wherein a waveform of a drive signal applied to an element is corrected. 4. The method according to claim 1, wherein
The method of driving a head of an inkjet recording apparatus, wherein the correction of the drive signal is performed in multiple stages according to the number of times of ink ejection. 5. The method according to claim 1, wherein
The pressure generating element includes a piezoelectric vibrator that pressurizes ink in the pressure generating chamber by performing flexural vibration by applying the drive signal, and when the number of times of ink ejection increases, the waveform of the drive signal is changed to an ink droplet. A head driving method for an ink jet recording apparatus, wherein the waveform is corrected so as to reduce the weight. 6. The method according to claim 1, wherein
The pressure generating element includes a piezoelectric vibrator that pressurizes ink in the pressure generating chamber by performing expansion and contraction vibration by applying the driving signal, and when the number of times of ink ejection increases, the waveform of the driving signal indicates the ink droplet weight. A head driving method for an ink jet recording apparatus, wherein the waveform is corrected to increase the waveform. 7. A print head having a pressure generating chamber communicating with a nozzle opening, a plurality of pressure generating elements for discharging ink droplets from the nozzle opening by pressurizing ink in the pressure generating chamber, and print data. An ink jet recording apparatus comprising: a head driving unit that selects a driving signal to be applied to any one of the plurality of pressure generating elements based on the driving signal; and a driving signal generating unit that generates the driving signal. There are ejection number monitoring means for monitoring the number of ejections, and waveform correction means for correcting the waveform of the drive signal when the number of ink ejections from the nozzle openings exceeds a predetermined number in the monitoring result of the ejection number monitoring means. An ink jet recording apparatus, comprising: 8. The ink-jet recording apparatus according to claim 7, wherein the waveform correction means corrects the waveform of the drive signal in multiple stages according to the number of times of ink ejection. 9. The head drive unit according to claim 7, wherein the nozzle openings are divided into a plurality of groups, and the drive signal generation unit outputs a signal having a different waveform for each group as the drive signal. The number-of-discharges monitoring means monitors the number of times of ink ejection for each group, and the waveform correction means monitors the number of times of ink ejection based on the result of monitoring the number of times of ink ejection for each group by the number-of-discharges monitoring means. Wherein the waveform of the drive signal applied to the pressure generating elements belonging to a group exceeding a predetermined number of times is corrected. 10. The method according to claim 9, wherein the number-of-discharges monitoring means monitors the average number of ink discharges of each nozzle opening belonging to each of the groups, and the waveform correction means determines that the average number of ink discharges is a predetermined number of times. An ink jet recording apparatus, wherein the waveform of the drive signal applied to the pressure generating elements belonging to the group exceeding the waveform is corrected. 11. The ink jet recording apparatus according to claim 9, wherein the nozzle openings are formed in a plurality of rows and are grouped for each row. 12. The ink jet recording apparatus according to claim 9, wherein the nozzle openings are formed in each of a plurality of recording heads and are grouped for each of the recording heads. 13. The correction data storage device according to claim 7, wherein said waveform correction means includes correction data storage means for storing correction data for correcting a waveform of said drive signal. An ink jet recording apparatus for correcting a waveform of the drive signal based on the correction data stored by a means. 14. An ink jet recording apparatus according to claim 13, wherein said correction data storage means is provided on an apparatus main body side. 15. An ink jet recording apparatus according to claim 13, wherein said correction data storage means is provided on said recording head side. 16. The pressure generating element according to claim 7, wherein the pressure generating element includes a piezoelectric vibrator that presses ink in the pressure generating chamber by performing bending vibration by applying the drive signal, and An ink jet recording apparatus, wherein the correction means corrects the waveform of the driving signal to a waveform such that the weight of ink droplets decreases when the number of times of ink ejection increases. 17. The pressure generating element according to claim 7, wherein the pressure generating element includes a piezoelectric vibrator that presses ink in the pressure generating chamber by performing expansion and contraction vibration by applying the drive signal, and An ink jet recording apparatus, wherein the correcting means corrects the waveform of the drive signal to increase the ink droplet weight when the number of ink ejections increases. 18. A recording medium, wherein a program for executing the head driving method defined in any one of claims 1 to 6 is stored so as to be readable from a computer.