JP2002120366A - Ink jet recorder and its head drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder and its head drive circuit in which a stabilized image quality can be obtained by altering a head drive waveform depending on the nozzle position of a print head thereby reducing crosstalk in an array or between arrays. SOLUTION: Nozzles N1-N96, for example, in the same nozzle array are divided into three groups of N1-N3 and N94-N96 (first group), N4-N10 and N87-N93 (second group) and N11-N86 (third group). Based on an external COM and nozzle designation signal group (enable signal ENA and designation signals A, B), COM1 is applied to the N1-N3 and N94-N96 (first group), COM2 is applied to the N4-N10 and N87-N93 (second group) and COM3 is applied to the N11-N86 (third group).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet recording apparatus such as an ink jet printer or an ink jet plotter. For more information,
The present invention relates to a recording head drive unit in an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, in an ink jet recording apparatus, for example, an ink jet printer, as shown in FIG.
The drive waveform signal generated by the waveform generation circuit 80 formed on the printer body 2 is output to the print head 10 mounted on the carriage. A plurality of pressure generating elements 1 for discharging ink droplets from nozzle openings by pressurizing ink in a pressure generating chamber are provided on the print head 10 side.
7, and a plurality of pressure generating elements 1 based on the print data.
7 is selected via the analog switch 16 and the like, and the head switch 18 turns on the analog switch 16.
The drive signal COM is applied to the pressure generating element 17 that has been operated. As a result, the pressure generating element 17 pressurizes the ink in the corresponding pressure generating chamber and discharges the ink from the nozzle opening as an ink droplet.

As shown in FIG. 9, a waveform generation circuit 80
A memory 81 for storing driving waveform data provided from the control unit 6 (see FIG. 8) and the like in the printer main body 2;
A first latch 82 for temporarily holding the drive waveform data read from the first latch 82; an adder 83 for adding the output of the first latch 82 to the output of a second latch 84 to be described later; , 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 further a voltage-amplified drive waveform signal. A current amplifier circuit 89 amplifies the current to the extent that the analog switch 16 can be driven and outputs it as a drive signal COM. Here, the memory 81 stores predetermined parameters for determining the waveform of the drive signal. As described later, the waveform of the drive signal COM is determined in advance by a predetermined parameter received from the control unit (not shown).

As shown in FIG. 8, the output side of a current amplifying circuit 89 of a waveform generating circuit 80 is connected to a plurality of analog switches 16 of a head driving circuit 18, and each analog switch 16 is connected to a corresponding pressure generating element 17. It is connected to the. Then, on the ejection surface of the print head, for example, CM
Y (in this example, K [black] is assumed to be [composite black] formed by synthesizing three colors CMY) corresponding to each of the three colors of Y and three colors (for example, 1 (96 nozzles in a row) are formed, and by vibrating the pressure generating elements provided corresponding to the plurality of nozzles, respectively, the ink in the pressure generating chamber is pressurized so that the ink is discharged from the plurality of nozzles. Discharge the droplet. The same drive signal COM is simultaneously applied to the one row of nozzles from the same head drive circuit 18 to each pressure generating element 17.

[0005]

However, as described above, in the conventional example in which the same drive signal COM is applied to the pressure generating elements of all the nozzles regardless of the nozzle position of the print head, the structure of the print head is different. In addition, it is inevitable that the weight, the ejection speed, and the like of the ink droplet to be ejected vary depending on the nozzle position. As a result, there is a problem that printing unevenness occurs and stable image quality cannot be obtained. Hereinafter, this problem will be described by dividing into variations in the same column and between columns.

A) Within the same row (crosstalk within a row) This is because, within the same row, the method of bonding the array of pressure generating elements to the housing of the print head and the rigidity of each part of the housing of the print head. As described above, the difference causes a problem in that the weight, the ejection speed, and the like of the ink droplet ejected vary depending on the nozzle position.

B) Between columns (cross-talk between columns) This is because the difference in the amount of heat generated between the different columns depends on, for example, where in the housing of the print head the array of pressure generating elements is bonded. As a result, there is a problem that the weight of the ink droplet, the ejection speed, and the like vary depending on the nozzle position. If the crosstalk between rows or crosstalk between rows exceeds a certain limit as described above, it is possible to prevent printing unevenness in the ink jet printing apparatus due to such factors to some extent by not using it as a head. However, in the inspection stage of the manufactured print head, it is inevitable that the yield of the print head that can be actually used is reduced due to such variations. Also,
It is conceivable that the print head is replaced in the same inkjet recording apparatus.

Accordingly, a first object of the present invention is to reduce the intra-row crosstalk and the inter-row crosstalk by changing the head drive waveform according to the nozzle position of the print head, and obtain a stable image quality. And a head drive circuit for the same.

Further, a second object of the present invention is to provide the above-mentioned first object.
Another object of the present invention is to make it possible to obtain a stable image quality even when a print head is replaced in an ink jet recording apparatus that achieves the above object.

A third object of the present invention is to provide a head drive circuit which can improve the yield of a print head.

[0011]

In order to solve the above-mentioned problems, according to the present invention, drive waveform supply means are provided independently according to the nozzle position of the print head, and different drive waveforms are simultaneously applied to the pressure generating elements. I made it.

That is, in the ink jet recording apparatus according to the first aspect, a plurality of nozzles provided at least in one row on the discharge surface of the print head, and a plurality of nozzles provided corresponding to the plurality of nozzles, respectively, A plurality of pressure generating elements for ejecting ink droplets from the plurality of nozzles by pressurizing the ink, and a driving waveform for driving each of the pressure generating elements, and generating the driving waveforms based on print data. And a drive waveform supply means for applying a drive waveform to any one of the pressure generating elements, wherein the drive waveform supply means is provided independently in accordance with each of the nozzle positions, and different drive waveforms are provided. That the different drive waveforms can be simultaneously applied to the pressure generating elements corresponding to the respective nozzle positions. And butterflies.

Further, in the ink jet recording apparatus according to the second aspect, the drive waveform supply means is configured to be capable of selecting each of the nozzle positions to which the drive waveform is applied.

Further, in the ink jet recording apparatus according to the third aspect, the driving waveform supply means is provided independently according to each nozzle position in the same row, and generates and applies different driving waveforms respectively. And

According to a fourth aspect of the present invention, in the ink jet recording apparatus, the plurality of nozzles are provided on a discharge surface of the print head so as to be positioned in a plurality of rows, and the drive waveform supply means is provided between each of the different rows. It is provided independently according to the nozzle position, and generates and applies different drive waveforms.

Further, in the ink jet recording apparatus according to the fifth aspect, the selection of the drive waveform applied by the drive waveform supply means and the nozzle position to be applied can be designated by a head ID.

According to a sixth aspect of the present invention, in the ink jet recording apparatus, the drive waveform supply means can change the applied drive waveform.

[0018]

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. In the present embodiment, the present invention is applied to an ink jet printer as an ink jet recording apparatus. FIG. 1 is a functional block diagram of the ink jet printer of the present embodiment.

In FIG. 1, an ink jet printer according to the present embodiment includes a printer main body 2, a carriage mechanism 12,
It comprises a paper feed mechanism 11 and a print head 10. The paper feed mechanism 11 includes a paper feed motor (not shown), a paper feed roller (not shown), and the like, and sequentially feeds a recording medium (not shown) such as printing paper to perform sub-scanning. The carriage mechanism 12 includes the print head 1
A carriage (not shown) on which the print head 10 is mounted, a carriage motor (not shown) for moving the carriage via a timing belt (not shown), and the like, and the main scanning of the print head 10.

The printer body 2 receives an interface 3 for receiving print data including multi-level hierarchical information from a host computer (not shown) or the like, and stores various data such as print data including multi-level hierarchical information. RAM4
A ROM 5 storing routines for performing various data processing, a control unit 6 including a CPU, an oscillation circuit 7, and transmitting print data SI developed into dot pattern data to the print head 10. And an interface 9 having a function.

Here, the print head 10 is circuit-connected to the printer main body 2 via a flexible flat cable (not shown).

In the present embodiment, a waveform generator 800 corresponding to the waveform generator 80 in the above-described conventional example has the configuration shown in FIG.
As shown in FIG. 7, the driving circuit includes a first waveform generation circuit 80A, a second waveform generation circuit 80B, and a third waveform generation circuit 80C, each of which has a drive waveform COM1 having a different voltage value and a different cycle. COM2 and COM3 are generated and output.

As shown in FIG. 1, in the ink jet printer of the present embodiment, the waveform generator 800
The OM & nozzle selection circuit 900 is connected. This C
As shown in FIGS. 2 and 3, the OM & nozzle selection circuit 900 is configured to receive the output of each of the first waveform generation circuit 80A, the second waveform generation circuit 80B, and the third waveform generation circuit 80C. Has become. A plurality of analog switches 16 are connected to the output side of the COM & nozzle selection circuit 900, as shown in FIGS.

Print data including multi-level hierarchical information sent from a host computer or the like is held in a reception buffer 4A inside the printer via the interface 3. The recording data held in the receiving buffer 4A is subjected to command analysis, and the control unit 6 executes processing for adding the print position, decoration type, size, font address, and the like of each character. Next, the control unit 6 develops and stores the analyzed data in the output buffer 4C as print image data. The RAM 4 is also provided with a work memory (work area) 4B for temporarily storing various work data and the like.

When print image data corresponding to one scan of the print head 10 is obtained, the print image data is transmitted to the print head 1 via the interface 9.
0 is serially transferred. The print head 10 has a large number of nozzle openings such as 96 nozzles in the sub-scanning direction, and discharges ink droplets from each nozzle opening at a predetermined timing. The print head 10 includes a head drive circuit 18 including a shift register 13, a latch circuit 14, a level shifter 15, and a plurality of analog switches 16. The print data developed into the print image data on the printer main body 2 side is serially transferred from the interface 9 to the shift register 13 in synchronization with the clock signal (CLK) from the oscillation circuit 7. The serially transferred print data (SI / print data) is temporarily latched by the latch circuit 14. The latched print data SI is transmitted to the level shifter 1 which is a voltage amplifier.
5, the voltage is raised to a voltage at which each analog switch 16 can be driven, for example, a predetermined voltage of about several tens of volts. The print data SI boosted to a predetermined voltage is given to the analog switch 16.

In the present embodiment, as shown in FIG. 3, nozzles of the same nozzle row, for example, N1 to N96 are connected to N1 to N3.
And N94 to N96 (first group), N4 to N10 and N87 to
N1 is divided into three groups N93 (second group) and N11 to N86 (third group), and COM1 is assigned to N1 to N3 and N94 to N96 (first group) based on an external COM & nozzle designation signal group described later. And COM2 is applied to N4 to N10 and N87 to N93 (second group), and N11 to N86 (third group).
Is applied to COM3.

In the present embodiment, in particular, the current state of crosstalk in a row is analyzed, and first, as described above, nozzles of the same nozzle row are grouped into three groups, and different drive signals COM1, 2, or 3 are respectively transmitted. It is considered that the application is preferable.

That is, when there are 96 nozzles in one row of nozzles,
The ink ejection speed when all the nozzles are turned on has characteristics as shown in FIG. 4 depending on the head structure. FIG.
6 is a graph showing a relationship between a nozzle position and a discharge speed (when all nozzles are on). As shown in FIG. 4, the ink velocities of about 10 nozzles at both ends are that the 11th to 86th nozzles have substantially the same ink velocity, but the ink is ejected at a higher velocity toward both ends. Tend. Therefore, COM1 of N1 to N3 and N94 to N96 (first group)
Sets the head drive voltage to COM3, for example, Δ10%, and sets COM of N4 to N10 and N87 to N93 (second group).
2 is to set the head drive voltage of COM3 to, for example, Δ5%, so that the ejection speed can be flattened.

On the other hand, as a result of analyzing the current state of intra-column crosstalk, the following problems were found. FIG. 5 is a graph showing the relationship between the ejection speed (Vm) crosstalk (C / T) and the number of ejection nozzles. As shown in FIG. 5, when there are 96 nozzles in one row, ejection is performed from the 48th nozzle in the center. When the ink speed to be performed is 100, the number of ejection nozzles is increased from the nozzle at the center (47th and 49th) to the nozzles at both ends (1st and 96th) with the 48th nozzle being ejected. As the ink jetting speed increases, the ink ejection speed of the forty-eighth nozzle changes.

In this case, 12
The speed was reduced from 100 up to around 100 nozzles (total of 24 nozzles) to 92, and the change was drastic. Since then, there has been no major change and it is stable at around 90. When ink discharge is started from both ends, about 100 is kept for each of about 36 nozzles (72 nozzles in total). However, when the number of discharges is increased further, the discharge speed rapidly decreases to about 90. Would.

That is, it is shown that the 48th nozzle at the center is greatly affected by the discharge of the ± 12 nozzles before and after the 48th nozzle, and that the nozzle farther away from the nozzle has little effect on the 48th nozzle. Is shown. This indicates that the ejection speed of the ink decreases as the number of on-nozzles near the ejection nozzle increases, and this tendency is remarkable in the central nozzle. As a result, when the print data when the print duty is low and the print data when the print duty is high are printed before and after,
Printing unevenness occurs in the image quality.

Therefore, as a modification of the present embodiment, although not shown, for example, 24 nozzles N37 to N60 (4
The driving voltage is slightly increased for the eighth nozzle (+11, -12 nozzles) (for example, +3 for COM2).
%), Set this to COM1, and set the remaining nozzles to C1.
By setting it to OM2, printing unevenness can be reduced.

Referring again to FIG. 3, the input side of each analog switch 16 is provided with a COM & nozzle selection circuit 90.
Drive signals (COM1 to COM3) from 0 are applied, and each piezoelectric vibrator as each pressure generating element 17 is connected to the output side of each analog switch 16.

The print data SI is stored in the analog switch 16.
Control the operation of. For example, during a period in which the print data applied to the analog switch 16 is “1”, the drive signals (COM1 to COM3) are applied to the pressure generating element 17, and the pressure generating element 17 expands and contracts according to this signal.
As a result, the ink in the pressure generating chamber is pressurized and discharged from the nozzle opening. On the other hand, during a period in which the print data applied to the analog switch 16 is “0”, the supply of the drive signals (COM1 to COM3) to the piezoelectric vibrator 17 is interrupted, so that ink droplets are not ejected.

FIG. 6 shows a specific circuit configuration of the head driver output section. As shown in FIG. 6, when the positive output (upper left of FIG. 6) and the negative output (lower left of FIG. 6) of the level shifter are H and L, respectively, the analog switches 16A and 16B
ON, ON. Therefore, the discharging current (1) and the charging current (2) flow to both of them based on the COM and the Vo potential.

Conversely, when the positive output (upper left of FIG. 6) and the negative output (lower left of FIG. 6) of the level shifter are L and H, respectively, the above is reversed, and the analog switches 16A and 16
B turns OFF, OFF, and maintains a high impedance state. The analog switches 16A and 16B have their back gate terminals connected to VHV and GND. COM
COM1 to CO output from the & nozzle selection circuit 900
M3 is input from each COM input terminal 45.

One example of the configuration of the COM & nozzle selection circuit 900 is shown in FIGS. COM & nozzle selection circuit 90
0, a plurality of logic units 50 as shown in FIG. 7A are provided corresponding to the respective analog switches 16 as shown in FIG.
The above-mentioned COM1 to COM3 are input to 0. Also,
As shown in FIGS. 3 and 7A, the enable signal ENA and the designation signals A and B are input to each logic unit 50. In addition, each logic unit 50 is configured as shown in FIG.
As shown in FIG. 2A, an output terminal 53 for the drive signal COM is provided.

The operation per nozzle will be described below. As shown in FIG. 7B, when ENA is H and the designation signals A and B are not input (x), the drive signal is in a high impedance state. ENA is L, designation signals A and B are L and L
, COM1 is output from the output terminal 53 and ENA
Is L and the designation signals A and B are L and H, the output terminal 53 outputs COM2. Further, when ENA is L and the designation signals A and B are H and L, the output terminal 53 outputs COM3. Thus, the COM & nozzle selection circuit 9
At 00, based on an external COM & nozzle designation signal group (enable signal ENA and designation signals A and B),
In the nozzles N1 to N96 of the same nozzle row, N1 to N
COM1 to N3 and N94-N96 (first group)
The drive signal COM and the nozzle to which it is output are arbitrarily set such that COM2 is applied to N4 to N10 and N87 to N93 (second group), and COM3 is applied to N11 to N86 (third group). Can be specified.

In the case where the above operation is actually performed with multiple nozzles (for example, 96 nozzles), the COM & nozzle selection circuit 900 assigns the COM & nozzles to each of the 96 logic units 50 corresponding to the number of nozzles. It is necessary to simultaneously apply a nozzle designation signal group (enable signal ENA and designation signals A and B). For this purpose, for example, the designation signals A, B, etc. to be applied to the 96 logic units 50 are serially transferred from an ASIC (semiconductor integrated circuit for specific application) (not shown) provided in the control unit 6 or the like. It is only necessary to cut out the same number as the number of nozzles and apply it to each logic unit 50.

In the ink jet printer of this embodiment, the drive waveform to be applied and the selection of the nozzle position to be applied can be designated by the head ID of the print head.
That is, as shown in FIG.
0a is affixed, and the label 10a has a head ID that typifies the characteristics of the head in both a number / symbol and a barcode format. When the head is mounted, for example, when a head ID is inputted by a personal computer based on the numbers and symbols, the head ID is stored in an EEPROM not shown in FIG. The COM & nozzle designation is performed according to the control program read by the CPU 5 and stored in the ROM 5 (see FIG. 1).

In the conventional example, the ink ejection becomes unstable with the driving waveform applied depending on the nozzle position due to the variation of the intra-row crosstalk and the inter-row crosstalk.
While stable image quality could not be obtained, the ink jet printer of the present embodiment can correct the drive waveform applied to each nozzle position by specifying the COM & nozzle as described above. Therefore, stable image quality can be obtained, and the yield of print heads that can be actually used can be improved. Even when the print head is replaced, a stable image quality can be obtained.

As described above, the present invention has been described with respect to the specific embodiments. However, the present invention is not limited to these embodiments, and may be applied to other embodiments within the scope of the claims.

For example, in the above embodiment, the nozzles N1 to N96 of the same nozzle row are set to N1 to N3 and N94 to N96.
(First group), N4 to N10 and N87 to N93 (second group)
Group) and N11 to N86 (third group), and a drive waveform to be applied and a nozzle position to be applied were selected based on an external COM & nozzle designation signal. In, it is also possible to vary the drive waveform to be applied. In this case, the first to third waveform generation circuits 80A to 80C described above are provided for each nozzle row.
The respective waveform generation circuits may be provided. In addition, such a configuration is combined with the configuration of the above embodiment,
Similarly, the drive waveforms to be applied can be made different between different nozzle rows according to the nozzle position.

In the above embodiment, a piezoelectric vibrator is used as the pressure generating element. However, the present invention is not limited to the piezoelectric vibrator, and a magnetostrictive element or the like may be used. Further, the present invention can be applied to a so-called bubble jet (registered trademark) type ink jet recording apparatus using a heating element as a pressure generating element.

[0045]

As described above, according to the present invention,
In the inkjet recording apparatus, by changing the head drive waveform according to the nozzle position of the print head, it is possible to reduce intra-row crosstalk and inter-row crosstalk and obtain stable image quality.

Further, in such an ink jet recording apparatus, a stable image quality can be obtained similarly even when the print head is replaced.

Further, conventionally, in the inspection stage of the manufactured print head, it is inevitable that the yield of the print head which can be actually used is reduced due to such variation. A head drive circuit (unit) that can improve the yield of the print head can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a waveform generation unit in the inkjet printer illustrated in FIG. 1;

FIG. 3 is a diagram showing a COM & nozzle selection circuit in the ink jet printer shown in FIG.

FIG. 4 is a graph showing a relationship between a nozzle position and a discharge speed (when all nozzles are on).

FIG. 5 is a graph showing a relationship between a discharge speed crosstalk and the number of discharge nozzles. _

FIG. 6 is a diagram showing a specific circuit configuration of a head driver output unit.

FIG. 7 is a diagram illustrating a configuration example of a COM & nozzle selection circuit.

FIG. 8 is a functional block diagram of a conventional inkjet printer.

FIG. 9 is a diagram showing a waveform generation circuit in the conventional ink jet printer shown in FIG.

[Explanation of symbols]

2 Printer body 6 Control unit 10 Print head 13 Shift register 14 Latch circuit 15 Level shifter 17 Pressure generating element 18 Head drive circuit 80 Waveform generation circuit 89 Current amplification circuit 16 Analog switch 800 Waveform generation unit 900 COM & nozzle selection circuit

Claims (10)

[Claims] A plurality of nozzles provided at least in a row on a discharge surface of a print head; and a plurality of nozzles provided corresponding to the plurality of nozzles, and the plurality of nozzles being pressurized by ink in a pressure generating chamber. A plurality of pressure generating elements for ejecting ink droplets from the nozzles, and a driving waveform for driving each of the pressure generating elements are generated, and the driving waveform is applied to any of the plurality of pressure generating elements based on print data. An ink jet recording apparatus comprising a head drive unit including a drive waveform supply unit, wherein the drive waveform supply unit is provided independently according to each of the nozzle positions, generates different drive waveforms, and generates the different drive waveforms. An ink jet recording apparatus capable of simultaneously applying pressure to pressure generating elements corresponding to respective nozzle positions. 2. An ink jet recording apparatus according to claim 1, wherein said drive waveform supply means is configured to select each of said nozzle positions to which said drive waveform is applied. 3. An ink jet recording apparatus according to claim 1, wherein said drive waveform supply means is provided independently according to each nozzle position in the same row, and generates and applies different drive waveforms. Characteristic inkjet recording device. 4. The ink jet recording apparatus according to claim 1, wherein the plurality of nozzles are provided on a discharge surface of the print head so as to be positioned in a plurality of rows, and the drive waveform supply means is provided between different rows. An ink jet recording apparatus, which is provided independently according to each nozzle position, and generates and applies different driving waveforms. 5. The ink jet recording apparatus according to claim 1, wherein a drive waveform applied by said drive waveform supply means and a nozzle position to be applied are selected by a head ID.
An ink jet recording apparatus characterized in that it can be designated by: 6. An ink jet recording apparatus according to claim 1, wherein said driving waveform supply means can change a driving waveform to be applied, respectively. 7. A plurality of nozzles provided at least in one row on a discharge surface of a print head, and a plurality of nozzles provided corresponding to the plurality of nozzles, respectively, by pressurizing ink in a pressure generating chamber. A plurality of pressure generating elements for ejecting ink droplets from the nozzles, and a driving waveform for driving each of the pressure generating elements are generated, and the driving waveform is applied to any of the plurality of pressure generating elements based on print data. A head drive unit including a drive waveform supply unit, wherein the drive waveform supply unit is independently provided in accordance with each of the nozzle positions, generates different drive waveforms, and associates the different drive waveforms with each nozzle position. A head drive unit capable of simultaneously applying pressure to a pressure generating element. 8. The head drive unit according to claim 7, wherein said drive waveform supply means is configured to select each of said nozzle positions to which said drive waveform is applied. 9. The head drive unit according to claim 7, wherein the drive waveform supply means is provided independently according to each nozzle position in the same row, and generates and applies different drive waveforms. Characteristic head drive unit. 10. The head drive unit according to claim 7, wherein the plurality of nozzles are provided on a discharge surface of the print head so as to be positioned in a plurality of rows, and the drive waveform supply means is provided between different rows. A head drive unit which is provided independently for each nozzle position and generates and applies different drive waveforms.