JPH10226066A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the image quality from degrading by driving a piezoelectric element with an applying voltage varying smoothly with time based on a specified data and recording an image by flying ink droplets. SOLUTION: A head jet part drive section 105 comprises an inverted amplification circuit 1051, and a drive circuit 1052 wherein an image signal Vin is amplified through the inverted amplification circuit 1051 to produce a signal Vn which is then passed through the drive circuit 1052 to produce a smooth drive signal Vout for driving a piezoelectric element. The waveform comprises five waveforms having different maximum amplitude of 10, 15, 20, 25 and 30V wherein a larger amplitude is employed for printing a larger dot and dots of different size are printed by applying driving voltage of different amplitude to the piezoelectric element thus representing a half tone. Since the driving voltage varies smoothly with time, degradation of image quality can be prevented.

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, and more particularly, to an ink jet recording apparatus that drives a piezoelectric element to fly an ink droplet from a predetermined container to record an image.

[0002]

2. Description of the Related Art Conventionally, there is an ink jet printer using a piezoelectric element in a print head. In such a printer head, the ink in a predetermined closed space (ink channel) is pressurized by distortion of a piezoelectric element driven by application of a voltage. When the ink is pressurized, ink droplets (ink drops) fly from the nozzles provided in the ink channels toward the recording sheet.

Conventionally, a rectangular or trapezoidal pulse voltage has been known as a voltage applied to such a piezoelectric element. With these pulse voltages, the drop speed, the drop diameter, and the like are controlled by adjusting the rise time, the duration of the pulse amplitude, the fall time, the magnitude of the pulse amplitude, and the like.

[0004]

However, the rectangular or trapezoidal pulse voltage as described above is composed of a portion that changes linearly with time. That is,
The rise, continuation and fall of the rectangular or trapezoidal pulse voltage waveform are all changed linearly with time. The bent portion of such a straight line (for example, a rising end point, a falling start point, etc.)
In this case, discontinuous vibration occurs in the piezoelectric element. This discontinuous vibration is also transmitted to the ink in the ink channel, adversely affecting the flight of the ink droplets, generating noise such as satellites, curves, drop cracks, and landing scatter, and significantly lowering the image quality. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink jet recording apparatus capable of preventing a deterioration in image quality.

[0006]

According to the first aspect of the present invention, an image is recorded by applying a voltage based on predetermined data to drive a piezoelectric element to cause ink droplets to fly from a predetermined container. This is an ink jet recording apparatus, which is characterized in that a voltage is set to change smoothly with time based on data.

According to the first aspect of the invention, the voltage applied to the piezoelectric element is set to change smoothly with time. As a result, discontinuous vibration of the piezoelectric element does not occur as in the related art, and the flying of the ink droplets is not adversely affected, so that it is possible to prevent a decrease in image quality.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ink jet printer 1 according to one embodiment of the present invention will be described with reference to the drawings.
Will be described.

FIG. 1 is a perspective view showing a schematic configuration of an ink jet printer 1 according to a first embodiment of the present invention.

[0010] The ink jet printer 1 uses paper or OH.
A recording sheet 2 which is a recording medium such as a P sheet, and a printer head 3 which is an inkjet printer head
A carriage 4 for holding the printer head 3, swinging shafts 5 and 6 for reciprocating the carriage 4 in parallel with the recording surface of the recording sheet 2, and swinging shafts 5 and 6 for the carriage 4.
Drive motor 7 for reciprocating drive along
The timing belt 9 and the idle pulley 8 for changing the rotation of the carriage into a reciprocating motion of the carriage are included.

The ink jet printer 1 includes a platen 10 also serving as a guide plate for guiding the recording sheet 2 along the conveyance path, a paper pressing plate 11 for pressing the recording sheet 2 between the platen 10 and preventing floating. Recording sheet 2
Roller 12, spur roller 13 for discharging
A recovery system 14 that cleans the nozzle surface of the printer head 3 that discharges ink and recovers defective ink discharge to a good state.
Paper feed knob 1 for manually conveying recording sheet 2
5 is included.

The recording sheet 2 is supplied to a printer head 3 by a paper feed device such as a manual feed or a cut sheet feeder.
And the platen 10 are sent to the opposite recording unit. At this time, the rotation amount of a paper feed roller (not shown) is controlled, and the conveyance to the recording unit is controlled.

A piezoelectric element (PZT) is used in the printer head 3 as an energy source for flying ink. A voltage is applied to the piezoelectric element, causing distortion. This distortion changes the volume of the channel filled with ink. Due to this change in volume, ink is ejected from nozzles provided in the channel, and recording on the recording sheet 2 is performed.

The carriage 4 is driven by the drive motor 7, the idle pulley 8, and the timing belt 9 to perform main scanning in the digit direction of the recording sheet 2 (a direction crossing the recording sheet 2). Record the image for the line. Each time recording of one line is completed, the recording sheet 2 is fed in the vertical direction and sub-scanned, and the next line is recorded.

The image is recorded on the recording sheet 2 in this manner, and the recording sheet 2 that has passed through the recording section is discharged by a discharge roller 12 disposed downstream of the conveyance direction and a spur roller 13 pressed against the discharge roller 12. Is done.

FIGS. 2 to 4 are views for explaining the configuration of the printer head 3. FIG. FIG. 2 is a plan view of a surface of the printer head 3 having nozzles, and FIG.
FIG. 4 is a sectional view taken along the line III, and FIG. 4 is a sectional view taken along the line IV-IV of FIG.

The printer head 3 includes a nozzle plate 30
1, a partition 302, a diaphragm 303, and a substrate 304 are integrally laminated.

The nozzle plate 303 is made of metal or ceramic, has nozzles 307, and has a surface 318.
Has an ion-repellent layer. A thin film is used for the partition 302, and the nozzle plate 301 and the diaphragm 3
03.

The nozzle plate 301 and the partition 302
A plurality of ink channels 306 for accommodating the ink 305 and an ink inlet 309 for connecting each ink channel 306 to the ink supply chamber 308 are formed between them. The ink supply chamber 308 is connected to an ink tank (not shown).
05 is supplied to the ink channel 306.

Each ink channel 3 is provided on the vibration plate 303.
In addition, a plurality of piezoelectric elements 313 corresponding to 06 are included. The processing of the diaphragm 303 is performed by first setting the diaphragm 303 to the wiring portion 317.
Is fixed with an insulating adhesive to the substrate 304 having
Separation grooves 315 and 316 are formed by dicer processing, and the diaphragm 303 is cut off.
In addition, the division separates the piezoelectric element 313 corresponding to each ink channel 308, the piezoelectric element column 314 located between the adjacent piezoelectric elements 313, and the surrounding wall 310 surrounding them.

The wiring section 317 on the substrate 304 is individually connected to the common electrode side wiring section 311 connected to the ground and to all the piezoelectric elements 313 in the printer head 3 and to each piezoelectric element 313 in the printer head 3. And an individual electrode-side wiring portion 312 connected to the The common electrode side wiring portion 311 on the substrate 304 is connected to a common electrode in the piezoelectric element 313, and the individual electrode side wiring portion 312 is connected to an individual electrode in the piezoelectric element 313.

The operation of the printer head 3 having such a configuration is controlled by the control unit of the ink jet printer 1. Head discharge drive unit 105 of control unit
From (see FIG. 5), a predetermined voltage, which is a print signal, is applied between the common electrode and the individual electrode provided inside the piezoelectric element 313, and the piezoelectric element deforms in the direction of pressing the partition 302. The deformation of the piezoelectric element 313 is transmitted to the partition 302,
Accordingly, the ink 305 in the ink channel 306 is pressurized, and the ink drop flies toward the recording sheet 2 (see FIG. 1) via the nozzle 307.

FIG. 5 is a block diagram showing a schematic configuration of the control unit of the ink jet printer 1. As shown in FIG.

The control unit of the ink jet printer 1 is C
PU 101, RAM 102, ROM 103, data receiving unit 104, head ejection driving unit 105, head movement driving unit 106, paper feed driving unit 107, recovery motor driving unit 108, and various sensor units 109 Contains.

The CPU 101 that controls the entire system executes programs stored in the ROM 103 using the RAM 102 as necessary. The program includes a head ejection drive unit 105, a head movement drive unit 106, a paper feed drive unit 107 based on image data read from the data reception unit 104 which is connected to a host computer or the like and receives image data to be recorded. A part for controlling the various sensor units 110 and recording an image on the recording sheet 2;
A part for controlling the recovery system motor drive unit 108 and various sensor units 109 when necessary to recover the nozzle surface of the printer head 3 to a good state is included.

Under the control of the CPU 101, the head ejection drive unit 105 drives the piezoelectric element 313 of the printer head 3, and the head movement drive unit 106 drives the drive motor 7 that moves the carriage 4 holding the printer head 3 in the beam direction. , And the paper feed drive unit 107 drives the paper feed roller. Further, based on the control of the CPU 101, the recovery motor drive unit 108 drives a motor and the like necessary to recover the nozzle surface of the printer head 3 to a good state.

Next, the waveform of a pulse voltage applied to the piezoelectric element 313 of the printer head 3 by the head ejection drive unit 105 will be described.

FIGS. 6 to 9 show the above-described head ejection driving section 1.
FIG. 5 is a diagram for describing a schematic configuration of the drive unit and a drive voltage applied to a piezoelectric element by a head ejection drive unit.

FIG. 6 is a block diagram for explaining a schematic configuration of the head ejection drive unit 105. The head ejection drive unit 105 includes an inverting amplifier circuit 1051 and a drive circuit 1052. The image signal Vin input to the head ejection drive unit 105 is amplified to a signal Vn by the inverting amplifier circuit 1051, and then output as a voltage Vout for driving the piezoelectric element 313 by the drive circuit 1052.

FIG. 7 is a circuit diagram showing the inverting amplifier circuit 1051 of FIG. 6, and FIG. 8 is a circuit diagram showing the drive circuit 1052 of FIG. The image signal Vin as shown in FIG. 7 is amplified to a signal Vn by the inverting amplifier circuit 1051, and then outputted as a smooth drive voltage Vout by the drive circuit 1052 as shown in FIG.

FIG. 9 shows a waveform 1 of the drive voltage Vout of the piezoelectric element 313 output from the drive circuit 1052 shown in FIG.
FIG.

Waveform 1 is composed of five waveforms having different maximum amplitudes, and these waveforms are displayed with the voltage application start time aligned on a coordinate with the vertical axis representing voltage and the horizontal axis representing time from the start of voltage application. The maximum amplitudes of these waveforms are 10, 15, 20, 25, 30 in ascending order.
[V]. In these waveforms, dots having a larger diameter are printed as the amplitude becomes larger, and dots having different sizes are printed by applying drive voltages having different sizes to the piezoelectric elements, thereby expressing a halftone.

The voltage values of the five waveforms having different maximum amplitudes of the waveform 1 are smoothly changed without abrupt changes over time. More specifically, the voltage values in these waveforms are such that the rising gradually increases the gradient, decreases as the voltage approaches the maximum voltage, and decreases the gradient to 0 at the maximum voltage.
After reaching the maximum voltage, the voltage is changed so that the gradient is lowered without keeping the voltage constant, and the voltage value returns to 0 while gradually lowering the gradient. Such a waveform 1 is formed only of a curve that does not include a straight line portion and that changes smoothly. This effect will be described together with the driving voltage applied to the piezoelectric element in the printer head in the ink jet printer according to the second to seventh embodiments.

The driving voltages applied to the piezoelectric elements in the printer head in the ink jet printer according to the second to seventh embodiments will be described below, and their effects will be described.

FIG. 10 is a diagram showing a driving circuit of the piezoelectric element of the ink jet printer according to the second embodiment. This drive circuit shown in FIG. 10 is the drive circuit 1052 of the ink jet printer 1 of the first embodiment described with reference to FIG.
Corresponding to A rectangular signal Vn as shown in FIG.
Is output as a semi-elliptical drive voltage Vout.

The overall configuration of the printer other than the driving circuit of the piezoelectric element of the ink jet printer according to the second embodiment,
The configuration of the printer head, the configuration of the control unit, and the like are the same as those of the inkjet printer 1 of the first embodiment.

FIG. 11 is a diagram showing a waveform 2 of the drive voltage of the piezoelectric element output from the drive circuit shown in FIG.

Waveform 2 has 5 different maximum amplitudes and pulse widths.
These waveforms are displayed on a coordinate system in which the vertical axis represents voltage and the horizontal axis represents time from the start of voltage application, with the voltage application start time aligned. The maximum amplitude of these waveforms is
5, 10, 15, 2 in ascending order
0 and 25 [V]. In these waveforms, as in the case of the waveform 1, dots having a larger diameter are printed as the amplitude becomes larger, and dots having different sizes are printed by applying driving voltages having different sizes to the piezoelectric elements, so that halftones are printed. To express. Further, as in the case of the waveform 1, the voltage values of the five waveforms having different maximum amplitudes of the waveform 2 are all smoothly changed without being rapidly changed with respect to time.
It is semi-elliptical.

The waveforms 3 to 7 of the driving voltage of the piezoelectric element in the ink jet printer according to the embodiment of the present invention, which will be described with reference to FIGS. , Respectively, corresponding to the drive voltage waveforms of the piezoelectric elements. The overall configuration of the printer, the configuration of the printer head, the configuration of the control unit, and the like, other than the driving circuits for the piezoelectric elements of the inkjet printers of the third to seventh embodiments, are the same as those of the inkjet printers of the first and second embodiments. It is.

The ink-jet printers of the third to seventh embodiments have drive circuits as shown in FIGS. 8 and 10, like the ink-jet printers of the first and second embodiments. Description is omitted.

Hereinafter, waveforms 3 to 7 will be described.
FIG. 12 is a diagram showing a waveform 3 of the driving voltage of the piezoelectric element.
FIG. 13 is a diagram showing waveforms 4, 5, and 6. The waveform 3 includes five waveforms having different maximum amplitudes and pulse widths similarly to the waveform 2, and these waveforms are displayed in the same manner as the waveforms 1 and 2. Also, each of the waveforms 4 to 6 includes a plurality of waveforms as in the case of the waveforms 1 to 3, but only those having the largest maximum amplitude are displayed. The waveform 3 has a semicircular shape, and the waveforms 4 to 6 have a plurality of peaks and valleys, and their gradients are continuously changed, and have a smoothly continuous shape. Waveform 4 includes the maximum value, the minimum value, the maximum value and the three extreme values, and the waveform 5 includes the maximum value, the minimum value, the maximum value, the minimum value and the four extreme values,
Waveform 6 is the maximum value, the minimum value, the maximum value, the minimum value, the maximum value and 5
Contains one extreme value. In any of the waveforms 3 to 6, the voltage value changes smoothly with no rapid or linear change with time. In a driving voltage having a waveform having six or more extreme values, the driving frequency is 2 kHz.
Since it cannot be made z or more, the printing speed is practically inferior.

FIG. 14 is a diagram showing a waveform 7 of the drive voltage of the piezoelectric element. The waveform 7 includes a main pulse voltage 51 and a sub-pulse voltage 52. Main pulse voltage 51
Is applied to the piezoelectric element corresponding to the image signal Vin shown in FIG. 6, and the sub-pulse voltage 52 is applied to the piezoelectric element in order to suppress the fluctuation of the ink in the ink channel caused by the application of the main pulse voltage 51. Also in the waveform 7, the voltage value is smoothly changed without abrupt change over time.

Next, the effect of applying a drive voltage having waveforms 1 to 7 to the piezoelectric element will be described.

FIG. 15 is a diagram showing evaluation of printing by ink drops ejected from the piezoelectric element when a drive voltage having waveforms 1 to 8 is applied to the piezoelectric element. For printing here, the maximum amplitude of the waveforms 1 to 7 is 20 [V], and the shapes of the waveforms are similar to each other.

FIG. 15 shows an evaluation of printing with the waveform 8 for comparison with printing with these waveforms. A waveform 8 is a waveform of a driving voltage applied to the piezoelectric element in the conventional inkjet printer, and is a rectangular wave having a pulse width of 20 [μsec] and a pulse amplitude of 20 [V].

These printings are performed while changing the driving frequency of the piezoelectric element from 2 to 10 [kHz] in increments of 2 [kHz]. The five items of cracking, impact scattering, and responsiveness were evaluated.

Here, the satellite means that the flying of the ink drop corresponding to the print dot diameter is accompanied by the generation of a small ink drop, and the curve means that the flying direction of the ink drop deviates. In addition, drop cracking means that the tip of a flying ink drop is split into two, and landing scattering means that the ink drop scatters a fine ink drop after landing on a recording sheet. These are evaluations of images obtained by high-speed flash photography, video photography, and printing after attaching to recording paper. Furthermore, responsiveness, when the drive frequency is changed,
For the above four items, the range of frequencies in which the piezoelectric element can be operated without any practical problem is shown.

For each item, the symbol ◎ in FIG. 15 indicates that these did not occur, and the symbol 示 す indicates that these occurred within 2%. Further, for each item, the symbol △ indicates that these occurrences were 2 to 10%, and the symbol X indicates that these occurrences were 10%.

In each case, the symbols ◎ and ○ mean that there is no problem in printing, and the symbols △ and × mean that there is a practical problem in printing.

Reference is made to the evaluation of printing with waveforms 1 to 7 of the present embodiment and waveform 8 of the comparative example shown in FIG.

Regarding the satellite, the evaluation was × in the waveform 8, but in the waveforms 1 to 7, these were completely improved to evaluation ◎. Regarding the curves, the waveform 8 was evaluated as ○, but in the waveforms 1 to 7, these were completely improved to ◎.

Regarding the drop crack, the evaluation was × in the waveform 8, but in the waveform 1, the waveforms 4 to 6, these were completely improved to the evaluation ◎.
The waveform 7 is also improved to the evaluation ○ to a level having no practical problem. Regarding the impact scattering, the evaluation was △ in the waveform 8, but in the waveform 1, the waveforms 4 to 6, these were completely improved to the evaluation ◎, and the waveforms 2, 3, and 7 were also evaluated as ○. Has been improved to a level where there is no practical problem.

Further, regarding the responsiveness, in the waveform 8, 2
[KHz] or less, and the fluctuation of the ink in the ink channel did not stop.
Shows very good results of 10 [kHz] or more, and waveforms 1 to 6 also show good results of 2 to 10 [kHz].

With the driving voltage of the piezoelectric element having the above-described waveforms 1 to 7, the voltage value changes smoothly with time. This prevents discontinuous vibration of the piezoelectric element as in the related art, which does not adversely affect the flying of the ink drop, and can prevent a decrease in image quality.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an ink jet printer 1 according to a first embodiment of the present invention.

FIG. 2 is a plan view of a surface of the printer head 3 having nozzles for explaining the configuration of the printer head 3;

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a block diagram illustrating a schematic configuration of a control unit of the inkjet printer 1.

FIG. 6 is a block diagram illustrating a schematic configuration of a head ejection driving unit 105.

FIG. 7 is a circuit diagram showing the inverting amplifier circuit 1051 of FIG. 6;

FIG. 8 is a circuit diagram showing a driving circuit 1052 of FIG.

9 is a diagram illustrating a waveform 1 of a drive voltage Vout of the piezoelectric element 313 output from the drive circuit 1052 illustrated in FIG.

FIG. 10 is a diagram illustrating a driving circuit of a piezoelectric element of the ink jet printer according to the second embodiment.

11 is a diagram showing a waveform 2 of a drive voltage of the piezoelectric element output from the drive circuit shown in FIG.

FIG. 12 is a diagram showing a waveform 3 of a driving voltage of the piezoelectric element.

FIG. 13 is a diagram showing waveforms 4, 5, and 6 of the piezoelectric element.

FIG. 14 is a diagram showing a waveform 7 of a driving voltage of the piezoelectric element.

FIG. 15 is a diagram illustrating evaluation of printing by ink drops ejected from a piezoelectric element when a drive voltage having waveforms 1 to 8 is applied to the piezoelectric element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink jet printer 3 Printer head 105 Head discharge drive part 305 Ink 306 Ink channel 307 Nozzle 313 Piezoelectric element 1051 Inverting amplification circuit 1052 Drive circuit

Claims (1)

[Claims] 1. An ink jet recording apparatus for driving a piezoelectric element by applying a voltage based on predetermined data to fly an ink drop from a predetermined container to record an image, wherein the ink jet recording apparatus performs the recording based on the data. Wherein the voltage is set so as to smoothly change with time.