JPS58194566A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To make it possible to carry out diagnosis in good preciseness by a simple circuit, by a method wherein the diagnostic signal of an intermittent alternating wave form is recorded in place of an image signal and the state of an ink jet head is judged from the shape of the obtained diagnostic recorded pattern. CONSTITUTION:In place of an image signal, the diagnostic signal of an intermittent alternating wave form with amplitude of 0-220V and frequency of 2- 32kHz is inputted and a diagnostic recording pattern is recorded by recording paper 34. In the diagnosis of an ink jet head, an ink emission impossible state can be directly judged because the pattern is not satisfactorily recorded and, because the delay of response is generated in the ink jet head having air bubbles present therein, an emission starting point does not come to a straight line while an emission finishing point does not come to a straight line when a trailing phenomenon is generated. For example, it is understood that the delay of emission response is generated with respect to a signal with frequency of 10kHz and voltage of 60V and 80V in a part (a) while the trailing phenomenon is generated with respect to a signal with frequency of 20kHz and voltage of 180V in a part (b). By this method, the state of the head can be diagnosed in good preciseness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an inkjet recording apparatus using an ink-on-demand type inkjet head that ejects ink droplets only when necessary, and more specifically, a method for diagnosing the condition of the inkjet head. Marriage related to Nishikyu equipment.

Ink-on-demand type inkjet heads (hereinafter simply referred to as inkjet heads) are, for example,
As described in Japanese Patent No. 45698, when an image signal is input, ink droplets of the same size are ejected in response to that signal, and the ink recovery mechanism, high-voltage power supply, etc. are inexpensive, and the structure is simple. It has advantages such as small size 11@ quantity.

Japanese Unexamined Patent Publication No. i52-82462 describes an inkjet head that achieves continuous printing of k2 records and improved gradation by making the ejected ink fly with airflow. There is.

FIG. 1 shows the structure of an inkjet head with an added air flow. Pressure is applied to the ink 2 in the ink tank 1 by an air supply source 8, and the pressure is regulated by an air regulating valve 4.5.

The pressurized ink 2 passes through the ink supply pipe 6 and enters the external ink i18 from the ink inflow lower part. This external ink 11B has an ink nozzle 9 and is in communication with the internal ink 1iill IK via a coupling passage IO. A piezoelectric element 18 to which the diaphragm 12 is fixed is attached behind this internal ink ff1ll, and the drive circuit 1
By applying an electrical signal from 4, the diaphragm 12 deforms, increasing the pressure in the internal ink chamber 11 and forcing ink droplets out of the ink nozzle 9. Air from the air supply source 8 passes through the air supply pipe 15 and enters the air jj1174c from the air inlet 16. This air 1jl17 has an air nozzle 18 formed in its medium heat, from which the air is blown out. The ink droplets pushed out from the ink nozzle 9 fly on the airflow flowing out from the air nozzle 18 and adhere to the recording paper.

In this inkjet head, the ink nozzle 9
Failures of the inkjet head may occur, such as drying of nearby ink, clogging due to adhesion of dust, and instability of ink ejection characteristics due to air bubbles entering the external ink ii8 and internal ink chamber 11. . Although various countermeasures have been proposed for these obstacles, the reality is that none can completely solve them. Therefore, it is desirable to take measures to prevent the above-mentioned failures, as well as to appropriately examine the condition II of the inkjet head and repair or replace any failures that have occurred. Furthermore, the recording quality depends on the ejection characteristics of the inkjet head, and the ejection characteristics also change depending on the characteristics of the ink used and the m-boundary area. Therefore, in order to maintain a constant recording quality, it is recommended to attach the inkjet head to the device, drive it, check in advance whether the inkjet head is suitable for the device, and select (select) the inkjet head. The preferred one is Amano. Furthermore, at least Jl for each color
In an apparatus that uses 1 inkjet head to record 1/1 intermediate color, it is required that each inkjet head has the same ejection characteristics.
Being able to select inkjet heads based on the ejection characteristics t-X is beneficial in improving the appearance of color darkness.

The present invention is based on the above background and aims to provide an inkjet recording apparatus capable of diagnosing the condition of an inkjet head.

Problems with inkjet heads range from severe cases where ink cannot be ejected due to ink drying or clogging, to mild cases where small air bubbles get mixed into the ink chamber and ejection becomes unstable only at a specific frequency, and these various conditions are the same. It is desirable to be able to perform diagnosis using a method and with the inkjet head attached to the device. Therefore, the present invention combines normal recording and N-
A diagnostic signal of an intermittent cross IF waveform is recorded instead of an image signal, and the state of the inkjet head is determined from the shape of the resulting recorded pattern for cutting nine eyelids.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of an apparatus for generating diagnostic signals for an inkjet head, and shows an example in which the apparatus is added to a four-color inkjet recording apparatus. There are eight input signals from the inkjet recording device: a print start signal (a), a line synchronization signal (b), and a pixel clock signal () and ). When the print start signal (A) turns ON, the clearing of the 2-line counter 20 is canceled and the counter starts counting the line synchronization signal (B). The D/A converter 21 outputs an analog voltage (e) proportional to the value of the binary counter 20, and outputs an analog voltage (e) proportional to the value of the binary counter 20.
The frequency of the output (to) of the converter) 22 is controlled. V
If the relationship between the input voltage of the CO 22 and the number of output cycles IN is in the form 1, the value of 2 cycles/20, that is, the output w8 wave number of the VCO 22 increases in proportion to the amount of movement in the scanning.

On the other hand, since the two-way counter 28 is cleared by the line periodic signal (b), the signal counts the pixel clock (c) during the OF k' period (main scanning recording period). The contents of the 2-over counter 28 are sent to a latch circuit 86 and latched at a predetermined period. This means that when a certain bit of the binary counter 28 reaches a predetermined level, the latch circuit 86
All you have to do is latch it. The signal latched by the latch circuit 86 is converted into an analog signal by the D/A conversion@24,
The signal is input to an analog switch 88 that switches at a predetermined cycle. This analog switch 88 is synchronized with the latch circuit 86), and during the period when the latch circuit 86 is latching, the output of the D/A converter 24 is transferred to the analog multiplier 24.
If the voltage is too low or too low for 5, and the latch is released, it is grounded. Consequently, this analog switch 88 outputs a rectangular wave signal (chi) whose voltage gradually increases.

The analog multiplier 26 multiplies and combines two signals (H) and (H) whose frequency and amplitude change respectively for sub-scanning and main-scanning eclipse, thereby producing an inkjet head diagnostic signal whose frequency and amplitude change two-dimensionally. Outputs (su). The signal selection switch 26 is configured so that one of the eight diagnostic signals (su) of the -g & signal signal port of the zero inkjet head can be selected independently for each color, and the diagnostic signal can be applied to the desired inkjet head. ing. The analog image signals Vy, Vm, Vc, and Vb are yellow, magenta, cyan, and black liligIl signals, respectively, and the amplifier! After the ink is amplified in step 7, it is supplied to inkjet heads 28 to 81 provided for each color.

These inkjet heads 28 to 81 are arranged close to a rotating drum 82, and the rotating drum 82 is arranged in the direction of arrow 1.
For each rotation in the main scanning direction indicated by iI88, the arrow 918
The ink droplet is moved intermittently at a constant pitch in the sub-scanning direction perpendicular to 8 and discharges ink droplets toward the paper 84.

FIG. 8 schematically shows a timing chart and waveforms of each part in FIG. 2, and each symbol corresponds to that in FIG. 2. The signal (G) indicates a diagnostic signal, and the amplitude rises stepwise in the main scanning direction with a pause period in between, and the frequency gradually changes from 'I+...fn' in the sub-scanning direction. 9 (Figure 4 shows the diagnostic turn recorded with the diagnostic signal (G), and the vertical axis, horizontal axis, and scale are shown for convenience of explanation. The amplitude is θ ~ 220
V, the frequency varies by I from 2 to 82 KHz, and this is the recording pattern for nine cases.

Diagnosis of the inkjet head is performed by looking at this recording pattern. In other words, since the grain pattern cannot be satisfactorily recorded in a state in which ink cannot be ejected, this can be determined immediately. In an inkjet head with air bubbles,
Because a response delay occurs, the edge connecting the ejection start point at each head applied voltage must be straight! If IK does not occur and a trailing phenomenon occurs, the line connecting the ejection end points will not become a straight line. In the part indicated by the sign star, the frequency is about 10 KHz and the voltage is 6.
There is a delay in the ejection response for the signals of 0■ and 80■, and the frequency is 20KHz in the part already indicated by the code.
It can be seen that the ground pulling phenomenon occurs for a signal with a voltage of 180V.

In the above example, a recording apparatus having one inkjet head was described, but in an apparatus for drawing a color image, at least one inkjet head is used for each color. In this case, the added circuitry for generating diagnostic signals can be used in common, and each inkjet head can be diagnosed individually or all at once.

Another use of the inkjet head diagnostic pattern is to select inkjet heads.

The recording pattern shown in FIG. 4 includes patterns related to the basic characteristics of the inkjet head. In other words, the wave number characteristics of the lowest ejection voltage, the bending of the ejection current/reverse flow, the generation state of satellite particles, etc. can be viewed as a pattern, and inkjet heads can be sorted based on the shape of this pattern and the degree of manufacturing unevenness. It is. This sorting of inkjet heads is useful for recording apparatuses having a large number of inkjet heads.

In addition, Ie surrounded by a dotted line in the 2nd record pattern in Figure 4
Since no voltage is applied to the inkjet head by the area limiter, pattern recording is not performed. This is because if a high voltage is applied with a low frequency signal, the amount of ink ejected will be excessive and there is a risk of cavitation or air bubbles entering the inkjet head. It depends on Arutoto. With ink-on-demand inkjet heads, the amount of ink ejected remains within a certain range regardless of the drive frequency #)
Regardless of the drive frequency, if an excessive drive voltage is applied to achieve an excessive discharge amount, cavitation and air bubbles will occur as described above.

Further, the upper limit of the frequency that changes in the sub-scanning direction must be 1.5 times the frequency used when recording characters, etc., but it is not allowed to exceed the natural vibration frequency of the inkjet head. The behavior of the inkjet at the natural vibration frequency is very unstable, and there is a risk of cavitation and bubble inclusion as described above.

The inkjet head shown in Fig. 1 uses a signal obtained by modulating a sine wave of approximately 20 KHz with an image signal when recording characters, drawings, etc.; It is also possible to use a drive signal form with a waveform of 1, as detailed in Japanese Patent Publication No. 5 G-45698. In the case of such a drive signal type, the number of repeated S waves of the rectangular wave (or during the pulse) in the sub-scanning direction is
By applying a signal whose rectangular wave amplitude changes in the main scanning direction, the inkjet head can be diagnosed. Furthermore, it is possible to use a signal whose amplitude changes in the sub-scanning direction and whose frequency changes in the main scanning direction.

In FIG. 3, a voltage divider in the i11 signal circuit is used to obtain a rectangular wave signal whose voltage gradually increases. In some inkjet color drawing devices that use four colors of ink to perform 1IIr tone color printing, the voltage applied to the head is divided into, for example, seven stages to control the size of the ejected inkjet a. For this purpose, if the resistor voltage divider in the signal line circuit is used as a # disconnection device for all heads, it is possible to test the ejection %9' performance of the head under the applied voltage that is practically applied. This has the advantage of simplifying circuit disconnection. FIG. 2 illustrates a diagnostic circuit for a head that ejects magenta ink. A constant voltage circuit 40 and a voltage divider 41 are included in the drawing circuit.
．． Analog switch circuits 42 are included, and these circuits 4
0, 41, and 42 are selectively used by switching them with changeover switches 261 and 261 that are interlocked with the signal selection switch 26. The constant voltage circuit 40 outputs the maximum drawing voltage Vmm a
For example, 7 levels of partial pressure values Vmmax, Vml, V
ml, @1111 Vm6, and Vmmin can be set. These partial pressure values Vmmax, VmH
, VmlΦ・* Vm6. Vmmin is set in the drawing circuit by adjusting the variable resistors 41a to 41g in advance so that the scale II expression during drawing becomes narrow due to the applied voltage of the magenta head being 1%. The nine plurality of voltages output from the divided voltage @41 are input to the analog switch circuit 42, the applied voltages are sequentially selected by the digital number 1 from the signal selection switch 48, and input to the analog multiplier 25 via the buffer circuit 44. be done.

The # base lock signal ()・) is frequency-divided by a dividing period 45, and then input to a two-way counter 46, and the line synchronization signal (
It counts up until it is reset by Rono. On the other hand, the output of the frequency divider 45 is input to the gate circuit 47 which outputs an AND gate to each line, so even if the output of the d frequency divider 46 is "H", it is a binary signal. The contents of the counter 46 are sent to the signal selection switch 48 through the gate circuit 47, and the gate circuit 47 is closed during the period when the output of the frequency divider 46 is "L".

Signal changeover switches 26, 26', 26N are iiiIIIg
I! If recording is selected, press signal selection switch 4.
8 sends the digital image symbol read from the image file (not shown) to the analog switch circuit 42, so the head applied voltage Vmm a x for drawing.

Vml, Vm1@1111 Vm6, Vmm
In is selected appropriately, strange 1m! # (not shown) is modulated at a drawing frequency (for example, 20 KHz), and then supplied to the inkjet head via an amplifier 27 to perform drawing. - At the time of diagnosis, which is performed immediately before the recording or every predetermined period, the signal selection switch 26, 26',
2B' to #IIl'rl#, binary counter 46
The contents of are sent to the analog switch circuit 42. Therefore, during diagnosis, the head applied voltages Vmmln, Vm5, Vm4, *I used during drawing
The rectangular wave signals (chi) of @Vml and Vmmax are sequentially output from the analog switch circuit 42, and the changeover switch 2
6', is input to the analog multiplier 25 via the buffer circuit 44, is multiplied by the output signal of VC022 (Heko), becomes a diagnostic signal, and is sent to the selector switch 26.
7, it is input to the magenta head 29, which is driven to record a diagnostic pattern as shown in FIG.

Note: If the frequency is around 20KHz, the irises 6
The head showing the diagnostic pattern illustrated in the figure exhibits a so-called grounding phenomenon (# & 6 Pj'r in the figure) at around 20 KHz of the WM signal frequency and the applied voltage Vm2. There is a fee to replace the head with another one without any defects, but there are no defects near the minimum applied voltage Vmin, so for example, regarding Figure 4a, it would be a trap to overlook it in practical diagnosis. be.

The present invention having the above-mentioned configuration can accurately interrupt the state of the inkjet head by simply adding a relatively simple circuit to the inkjet recording apparatus, and
It can also be used as an inkjet head selection means. Furthermore, diagnosis is easy because the diagnostic pattern can be recorded using the same operations as in normal layout. Furthermore, in normal recording, the inkjet head is often driven suddenly or a voltage is applied suddenly. Since the present invention uses a diagnostic signal with an intermittent alternating waveform and uses the same voltage as in normal recording, it is possible to obtain a diagnostic pattern recorded in a manner similar to normal recording.

A simple 4-way station WJ1 diagram is an LR view showing the structure of an ink-on-demand inkjet and head, and Figures 2 and 5 are from this book@
A block diagram showing an embodiment of the invention, #! Figure 8 is a timing chart and waveform diagram of each part showing the operation state of Figure 2, and Figure 4
FIG. 6 is an explanatory diagram showing an example of a diagnostic node.

2...Ink 8...Air supply source 8...External ink chamber 11...Inner ink chamber 18...Piezoelectric element 20.28.46...Binary counter 21.24... D/A converter 22--VCOt5 fist/e analog multiplication value 27...
Amplifiers 28 to 81-@・Inkjet head 82...Rotating drum 84...Drop recording paper 86...-Latch circuit 40...Writing voltage circuit 41-Red・Voltage divider 42...゛Analog switch circuit procedure Amendment dated July 5, 1988, Director General of the Japan Patent Office 1, Table of Case 7r, 1988 Patent Application No. 78012 3, Relationship with the person making the amendment Patent Applicant Address: 8210 Nakaf, Minamiashigara City, Kanagawa Prefecture Name
(520) Fuji Photo Film Co., Ltd. 4, Agent voluntary 6, Amendment 1 Number of inventions increased from the above 7, Subject of amendment (1) “Detailed description of the invention” column of the specification (1)
#4 Correct "Signal (J)" on page 7, lK, 18th line of the specification to "Signal (D)".

(2) In the 16th line of page 7 of the specification, "(He), (C) are multiplied and combined" is amended to "(H), (D) are multiplied and matched."

(3) Correct "1 signal (su)" on page 7, line 18 of the specification to "signal (g)."

(4) Correct "signal (su)" on page 7, line 20 of the specification to "signal (g)".

(5) “Square wave signal (Q)” in line 6 of specification No. 15jj
" is corrected as "square wave signal (d)".

(6) In page 15, line 1θ of the specification, "(su)tonite" is amended to "(g)tonette".

(7) 2nd r! jA and Figure 5 are corrected as shown in the attached sheet.

that's all

Claims (3)

[Claims] (1) Ink-on-demand lid In an inkjet recording device using an inkjet head, a diagnostic circuit that generates a diagnostic signal with an intermittent alternating waveform is provided, and the amplitude changes stepwise with a pause period in one scanning direction, and the other An inkjet recording apparatus characterized in that a frequency changes in a scanning direction to record a diagnostic pattern, and the condition of an inkjet head is diagnosed from the shape of this diagnostic pattern. (2) The inkjet recording apparatus according to claim 1, wherein the amplitude of the diagnostic signal is determined according to a voltage selectively taken out from a voltage dividing finger made up of a plurality of resistors. (3) The inkjet recording apparatus according to claim 1, wherein the resistor is a variable resistor.