JPS6070367A - Apparatus for detecting flight speed of ink droplet - Google Patents

Abstract

PURPOSE:To detect the flight speed of an indivisual ink droplet, in an ink jet recording apparatus, by processing the electrical change of a charging electrode with the flight of a charged ink droplet. CONSTITUTION:The ink droplet 3 injected from a nozzle 2 is charged by a charging electrode 5 and flied toward an ink droplet adhering body 10 as a charged ink droplet 3. As this ink droplet 3 approaches the charging electrode 5, an induced current is flowed to the charging electrode 5. A detection circuit 9 processes the change in the induced current flowing through the charging electrode 3 and respectively detects time when the ink droplet 3 passes the charging electrode 5 and time required in adhering the ink droplet 3 to the adhering body 10. Subsequently, the flight speed of the ink droplet 3 is calculated on the basis of both detected times. By this method, the flight speed of the individual ink droplet can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a detection device for detecting the flying speed of ink droplets in an inkjet recording apparatus.

Background of fbl Technology Currently, various methods have been proposed for inkgeno recording devices, and some of the methods have already been put into practical use.

For example, in an on-demand type inkjet recording device, a piezoelectric element (
This is a device that performs recording by driving a piezo element to eject ink droplets from the tip of an inkjet.

However, since the inkjet head itself runs at a constant speed, and recording is performed by ejecting ink droplets from the inkjet head, differences in the flight speed of ink droplets during ejection can cause disturbances in the recorded image. be exposed. Figure 1 illustrates this.
bl is a recorded diagram when ink droplets are deposited at different speeds, and it is clear that the recording quality of FIG. 1 fbl is lower than that of FIG. The arrow in Figure 1 indicates the direction of movement of the head.

Such problems are particularly noticeable in on-demand multi-nozzle inkjet recording devices; even if the driving conditions are the same, the ink droplet speed varies depending on the condition of each nozzle, which causes disturbances in the recorded image. This causes a significant deterioration in recording quality.

Therefore, in order to obtain high-quality recorded images, it is important to equalize the flying speed of ink droplets from each nozzle. Easy to use on equipment! It is desirable to have an ink droplet flight speed detection device that can be incorporated into

Conventionally, in the lower stage of detecting the flight speed of ink droplets, ink droplets are ejected at fixed time intervals, and the ink droplet ejection time is delayed by a fixed time. The condition of the ink droplet at this time is captured as a still image using an optical device such as a mirror and observed. By changing the delay time until the light is emitted, the position of the still image of the ink droplet changes.From this, the flying speed of the ink droplet can be determined by the following equation.

V=L/T However, ■: Flying speed of ink droplets L: Change in position of ink droplets T: Change in delay time However, this conventional method is difficult to calculate the average value of a large number of ink droplets in a steady state where they are continuously ejected. However, it is impossible to directly measure the flight speed of individual ink droplets. This method also applies to delay circuits, strobes,
This method requires expensive equipment such as a microscope, is complicated to operate, and has drawbacks such as a long detection time and a large amount of ink used for detection. Furthermore, in the case of a multi-nozzle inkjet head, positioning and focusing operations are required for each nozzle, which is extremely complicated.

(di Object of the Invention In view of the above-mentioned drawbacks, it is an object of the present invention to provide an ink droplet flying speed detection device capable of detecting the flying speed of individual ink droplets.Furthermore, another object of the present invention is Applicable to either B-nozzle or multi-nozzle, clause c1
An object of the present invention is to provide an ink droplet flying speed detection device that has a simple configuration and can detect ink droplet flight speed without requiring complicated operations.

(el) Structure of the Invention The purpose is to use an ink generator 1 for recording on a recording medium 1 by driving a piezoelectric element in response to an information signal and ejecting ink droplets from the tip of a nozzle to record on a recording medium 1. The droplet flying speed detection device comprises a charging electrode placed in a position that does not impede the flight of the ink droplet and a charging electrode facing the nozzle to generate one electric charge for the ink droplet ejected from the tip of the nozzle. The apparatus is equipped with an ink droplet (=J-depositing body) and a first stage of detection that detects from the charged electrode, and as the charged ink droplet flies and lands, it hits the charged electrode. Ink droplet flight in which the time at which the ink l+!i passes through the charged electrode and the time at which it adheres to the ink droplet adhesion body is detected from changes in the induced current, and the flying speed of the ink droplet is detected from both times. This is accomplished by a speed sensing device.

(fl　Embodiments of the invention An embodiment will be described in detail below with reference to one drawing.

FIG. 2 shows a schematic view of the flying part of an ink droplet flying speed detection device according to an embodiment of the present invention, in which the inkjet head 1 is composed of a nozzle 2 and a piezoelectric element 4 for ejecting an ink droplet 3 from the nozzle 2. It is configured. 5 is a charging electrode for charging the ink droplets 3; 6 is a power supply applied to the charging electrode 5; 7 is a filter for removing noise from the charging power supply 6; 8 is a resistor for blocking induced current; 9 is a In the detection circuit, reference numeral 10 denotes an ink droplet adhering body provided at a position facing the nozzle 2. In the detection device according to the present invention, the charged electrode 5 also serves as a detection electrode for detecting the induced current flowing as the ink droplets fly.

The ink droplet detection unit (charged electrode and ink droplet (1 adherent) or ink droplet adhering body 10 is arranged at the left end or right end outside the printing area of the inkjet printer 1-recording device, and when the ink droplet flying speed is detected, the ink droplet detector 10 1--Move No. 11 to the position of the ink drop detection section or the ink drop adhering body 10.

Now, in the case of on-demand type inkjet, -1
The pulse voltage is adjusted to the piezoelectric element 7-4 by information from the - position device.
is applied and converted into a pressure pulse.

This pressure is transmitted to the nozzle tip and the ink droplet 3 is sent to the nozzle 2.
More sprayed. At this time, from the charging power source 6, a number of 10 to 1
Since a voltage of 00 V is applied to the charged electrode 5, the charged electrode 5 and the nozzle 1 form a kind of capacitor, and the charge opposite to the voltage applied to the charged electrode 5 is discharged from the nozzle. Induced by ink before separation. The ink separates from the nozzle while retaining this charge, becomes a charged ink droplet 3, and flies toward the ink droplet (=J).

FIG. 3 shows a detailed configuration of the detection circuit 9 shown in FIG. 2. In FIG. In the figure, II is a capacitor for C cup 1, 12 is a resistor, 13 is a current-voltage conversion circuit, 1
4 is a 119 width amplifier, 15 is a low-pass filter, ]6 is a hesophagus circuit, 17, 19, and 21 are comparators, and 18 is a reference voltage.

20 is a differentiation circuit, 22 is a flip-flop, 23.2
6 is AND gate 24.25 is JK flip-flop.

A control circuit includes a counter 27, a clock 28, and a microprocessor 29.

The operation of detecting the flight speed of an ink droplet using the signal voltage waveforms of each part of the detection circuit shown in FIG. 3 and the detection circuit shown in FIG. 4 will be described. First, as the charged ink droplet 3 approaches the charging electrode 5, a charge having a polarity opposite to that of the charged ink droplet 3 is induced in the charging electrode 5. That is, as this charge is induced in the charged electrode 5, an induced current flows through the capacitor 11 and the resistor 12 in the detection circuit.

At this time, the resistor 8 serves to prevent the induced current from flowing toward the charging power source 6.

When the charged ink/Fj3 passes through the charging electrode 5, the induced charge gradually decreases, and an induced current in the opposite direction flows through the resistor 12 accordingly. Thereafter, when the charged ink droplet 3 reaches the ink droplet adhering body 10, the induced current becomes zero. Because this induced current changes, the resistor 12
The voltage across both ends changes accordingly, and a signal voltage as shown in FIG. 4 ta+ is generated.

The potential difference obtained by this current-voltage conversion circuit 13 is transferred to the amplifier 1.
4 is amplified approximately 100 times, and a low-pass filter 15 removes high-frequency noise to obtain a waveform signal shown in FIG.

The flight time of the ink droplet is calculated from the output voltage obtained as shown below, and the charged ink VF7J3 is used for this purpose.
Time to and charged ink l+'a passing through electrode set 5
3 is attached to the ink droplet adhering body 10 at time t1.

First, passing time t. is the point at which the direction of the induced current changes °
(There is. If the region of the output voltage waveform of the buffer circuit 16 that is equal to or higher than the zero voltage level is determined by the comparator 19, it is shown in FIG.
The waveform becomes C1. This waveform contains noise, and in order to remove it, the other lumberrator 17 supplies the voltage region 1 above the reference voltage IF 18 to the 41st ffl (
+ l), which makes Furinopso 1 Konoso 22
4 (the first logic of the waveform of C1)
0'' (OV level) point, that is, the passing time of the ink droplet.

Reset with . Then, the waveform shown in FIG. 4 (el) is obtained. If the JK flip-flop 24 is set at the falling edge of the output waveform of the flip-flop 22,
FIG. 4 (A waveform of fl is obtained, and this cent point is the passing time t.

Next, add 1 to the adhesion time. When the output waveform of the buffer circuit 16 is differentiated by the differentiating circuit 20, the voltage waveform changes from negative to positive at the attachment time t1 as shown in FIG. An output waveform including the attachment time t1 as shown in FIG. and the output of the comparator 21 are input, and the common part is extracted.In this way, the noise before the ink droplet 3 passes the charging electrode 5 is removed, and as shown in FIG.
) waveform is obtained. JK at the falling edge of this voltage waveform
When Furi, Buflo and Pu25 are reset, Figure 4 (J)
The waveform is I? The arrival time Ll is the arrival time Ll at this Reseno 11 point.

Next, JK flip-flop 2 on Antogame 1/26.
By inputting the outputs of 4 and 25 and drawing out the common part, the pulse width (corresponding to the time from when the ink droplet 3 passes through the charging electrode 5 to when the ink droplet 1) lands on the deposited body 10 is determined. t+to) is obtained in a waveform as shown in FIG. 4(k). The counter 27 calculates this pulse width (tB-co).
By counting the number of glue l cocks from the clock 28, the time 'I''-(t+to) is obtained.This is input to the control circuit 29, and the time given in advance (11) between the electrode 5 and the ink droplet adhering body 10 is obtained. From the distance δItD to the ink droplet flight speed V
= T/D is observed.

FIG. 5 shows another embodiment of the present invention, and is a schematic diagram of a flying part when an inkjet recording apparatus has a multi-nozzle head 31. There is one difference from Figure 2! The 11-electrode electrode 35 has a large hole through which charged ink droplets from each nozzle pass, and the ink droplet deposit 40 has a correspondingly large hole.

In the ink droplet flying speed detection device according to the present invention, the structure of the flying part is particularly simple. That is, by integrating the charging electrode and the detection electrode, there is an advantage in that the structure of the flying part is simple, and the detection circuit is also relatively simplified accordingly.

(gl Effects of the Invention As is clear from the above explanation, according to the present invention, the flight time of each ink droplet can be automatically detected and the flight speed can be calculated. It can be used for any purpose, is inexpensive, has a simple structure, and is easy to operate.
Detection rate is also high. Therefore, it can be used for the development of inkjet recording devices or as a testing device, and can also be incorporated into recording devices, making it an extremely effective detection device for improving the quality of recording.

[Brief explanation of drawings]

Figure 1 (al, (b+) is a diagram showing recorded images, Figure 2 is a schematic diagram of the flying part of a detection device according to an embodiment of the present invention, and Figure 3 is a detailed detection diagram of the embodiment shown in Figure 2. Diagrams containing circuits,
FIG. 4 is a diagram showing signal waveforms of each part of the detection circuit shown in FIG. 3, and FIG. 5 is a schematic diagram of a flying section of another embodiment. In the figure, 1.31 is an inkjet head, 2 is a nozzle,
3 is an ink droplet, 4 is a piezoelectric element, 5.35 is a charging electrode, 6
is a charging power source, 7 is a filter, and 8 is a resistor. 9 is a detection circuit, 10.40 is an ink droplet adhering body, 11 is a capacitor, 12 is a resistor, 13 is a current-voltage conversion circuit, 1
4 is an amplifier, 15 is a low-pass filter, 16 is a buffer circuit, I'7.19-, 21 is a comparator, 18
is the reference voltage. 20 is a differentiation circuit, 22 is a flip-flop, 23.2
6 is Antoge-I, 24.25 is JK flip-flop. 27 is a counter, 28 is a clock, and 29 is a control circuit. 111[! Q (Q) (b) -C -11-in w14 Figure A Blind Figure 5

Claims (1)

[Claims] An ink droplet flight speed detection device for an inkjet recording apparatus that drives a piezoelectric element in response to an information fa signal to eject ink droplets from a nozzle tip to record on a recording medium, the ink droplet flying speed detection device In order to charge the droplets, a charging electrode is provided at a position that does not impede the flight of the ink droplets, and an ink droplet is located at a position facing in one direction from the nozzle. detecting means for detecting the time at which the ink droplet passes through the charging electrode and the time at which the ink droplet adheres to the ink droplet adhering body based on the change in the induced current generated in the charging electrode as the electrified ink droplet flies and lands. An ink droplet flying speed detection device characterized in that a time is detected and a flying speed of an ink droplet is detected based on both times.