JPS6070365A - Apparatus for detecting flight speed of ink droplet - Google Patents

Abstract

PURPOSE:To detect the flight speed of an individual ink droplet, in an ink jet recording apparatus, by processing the electrical change of charging electrode with the flight of charged ink droplets. CONSTITUTION:An droplet 2 injected from a nozzle 1 is charged by a charging power source 4 and flied toward a charging electrode 3 as the charged ink droplet 2. As the ink droplet 2 approaches the charging electrode 3, an induced current is flowed to the charging electrode 3. The change in this induced current is processed and time, when the ink droplet 2 passes the charging electrode 3, is detected to be supplied to a control circuit 19. Subsequently, the control circuit 19 calculates the flight speed of the ink droplet 2 on the basis of the time of the ink droplet 2 passing the charging electrode 3 and the injection time of the ink droplet 2 from the nozzle 1. By this method, the flight speed of the individual ink droplet 2 can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical outline of the invention (81) ``r'' The present invention relates to a detection device for detecting the flying speed of ink droplets entering an inkjet recording device.

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

Such an inkjet recording device, for example, is an on-demand type that drives a piezoelectric element installed in an inkjet head that runs at a constant speed according to information from a host device (for example, a computer) to print an inkjet recording device. This is a device that performs recording by ejecting ink droplets from the tip of the paper.

Due to the force and strength, the inkgeno 1 head itself runs at a constant speed, and recording is performed by ejecting ink droplets from the gutter to the inkgeno 1.
Differences in the flying speed of the ink during ejection appear as disturbances in the recorded image. Figure 1 illustrates this. Figure 1 (l) is a recorded diagram when a single ink droplet is deposited at a uniform speed, and Figure 1 (b) is a diagram when ink droplets are deposited at different speeds. Of the recording diagrams, it is clear that the recording quality in Figure 1 (bl) is lower.The arrows in the figure indicate the moving direction of the head.

Such problems are particularly noticeable in on-demand multi-nozzle inkjet recording devices, where even if the driving conditions are the same, the γC 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. Furthermore, it is desirable to have an ink droplet flight speed detection device that can be easily incorporated into an Ink Geno recording device.

(C1 Prior Art and Problems By the way, in the past, as a means for detecting the flying speed of ink droplets, ζ was used to eject ink droplets at constant ■η intervals and to delay the ink droplet ejection time by a certain period of time.)・When the robot emits light, the state of the ink droplets at this time is captured and observed as a still image using an optical device such as a microscope.

In this case, the position of the still image of the ink droplets is changed by changing the delay time from the ink droplet ejection time to the strobe light emission. From this, the flying speed of the ink droplet can be determined by the following formula.

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 based on the average of many 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 7F multi-nozzle ink jet, it is necessary to perform positioning and focusing operations for each nozzle, which is extremely complicated.

+dl OBJECTS 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. Another object of the present invention is to provide an ink droplet flying speed detection device that can be applied to either a single nozzle or multiple nozzles, has a simple configuration, and does not require complicated operations.

(141 Structure of the Invention The purpose of the Inkgeno I recording device is to record ink droplets on a recording medium by driving a piezoelectric element in response to an Il'7 signal and ejecting ink droplets from the tip of a nozzle. A charging electrode that is a flight speed detection device and is located close to the nozzle and at a position that does not interfere with the flight of ink droplets;
4 for charging the ejected ink droplet via the charging electrode;
It is equipped with a 11F electric means and a detection means also connected to the charging electrode, and detects the time when the ink droplet passes the closest position of the charging electrode from the electrical change of the 11F heavy electrode accompanying the flight of the charged ink droplet. The time and ink droplet are detected at the nozzle tip θ11.
This is achieved by the ink droplet flying speed detection device which detects the flying speed of the ink droplets based on the ejection time from 1 to 1.

(fl　Embodiments of the invention Examples will be described in detail below with reference to five drawings.

FIG. 2 is a schematic diagram of an ink droplet flight speed detection device according to an embodiment of the present invention, in which 1 is a nozzle, 2 is an ink droplet, 3 is a charging electrode, 4 is a charging power source, and 5 is a resistor. In the case of the on-demand type inkgeno 1-, a pulse voltage is applied to a piezo element (not shown) based on information from a host device and converted into a pressure pulse. This pressure is the nozzle tip +M
The ink droplet 2 is ejected from the nozzle 1.

At this time, since a voltage of several tens to several IOOV is applied to the charging electrode 3 from the N voltage source 4, the charging electrode 3 and the nozzle 1 form a kind of capacitor, and An electric charge having a polarity opposite to that of the applied voltage is induced in the ink before it flows through the nozzle. The ink separates from the nozzle while retaining this charge, becomes a charged inflow droplet 2, and flies toward a charging electrode 3.

Thus, ([i) As the electric ink 42 approaches the position closest to the charging electrode 3, the ink 'tFj
A charge having a polarity opposite to that of the capacitor 2 is induced, and an induced current flows through the capacitor 6. The charged ink droplet 2 exhibits the most induced current at its closest position, and beyond that point 1. On the contrary, it decreases. The capacitor 6 is a DC cut capacitor that prevents the charging voltage from the charging power source 4 from entering the detection circuit.

This induced current is detected by a detection circuit shown in FIG. 2, and the flight time is determined. The induced current flowing through the capacitor 6 is first converted into a voltage by a current-voltage conversion circuit consisting of an inversion circuit 7 and a resistor 8, and further amplified by an amplifier 9. The amplified signal waveform is shown in FIG.
is compared with the reference voltage] 2, and if the confidence υ- is larger than the reference voltage, it becomes the debt shown in Figure 3 (C1. Figure 3 (b
l indicates a signal passed through the low-pass filter 10.

The signal passing through this low-pass filter 10 is divided into two parts, one of which is used by a comparator 13 to detect the time at which the signal crosses the zero rail. Figure 3 (dl is comparator
This is the signal waveform output from the relay 13. The polarity of the output of the comparator 11 (signal output shown in FIG. 3 (C1)) is converted by the inverter 14 to generate a piezo drive signal (signal for ejecting ink droplets when voltage is applied to the piezo element) P.
is input to flip-flop 15 to which is added. The signal tel in FIG. 3 is the output signal from the flip-flop 15. Next, this is inputted to the flip-flop 16 together with the signal from the comparator 13 (signal shown as +d+ in FIG. 3) to obtain the signal shown in FIG. 3 (fl).

The signal shown in FIG. 3(f) is the flight time signal of the ink droplet to be detected.

During this signal application time, the counter 17 counts the number of clocks from the clock circuit 18.The count value obtained by the counter 17 is sent to the control circuit 19, and multiplied by the clock period. The flight time of the ink droplet is 1゛.Furthermore, if the distance between the nozzle 1 and the charging electrode 3 is D, then the average flight speed of the ink droplet is V = ]
) / ]' is marked. The control circuit 20 is comprised of a microprocessor, memory, etc., and outputs the flight speed (2) calculated in this way.

FIG. 4 is a schematic diagram of the flying portion when the inkjet head is a multi-nozzle 21. By making the charging electrode 23 sufficiently large to cover the multi-nozzle 21 and ejecting ink from each nozzle sequentially, it is possible to detect the flight time of an ink droplet with the same configuration as the single nozzle described above.

FIG. 5 is a diagram showing still another embodiment according to the present invention. What differs from FIG. and the control circuit 25. P]−
At the same time as a voltage pulse is applied to the element, the 11
AI)::I converts the input voltage similar to the voltage signal shown in FIG. Based on the captured memory data, the control circuit 25 executes flight y11.
Time and flight speed are calculated.

Since the ink droplet flying F, 1+ speed detection device according to the present invention detects the time when ink droplets are flying and passing, it can be integrated with the inkjet head and can be detected even during the operation of the recording device. This is something that has the advantage of being possible.

(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, and it can also be detected even when the inkjet/recording device is in operation. In addition, it can be used with either a single nozzle or multiple nozzles, and is inexpensive, has a simple structure, and is easy to operate.Therefore, it can be said to be extremely effective in improving the quality of recording.

[Brief explanation of the drawing]

Figure 1 (at, (bl) is a diagram showing a recorded image, Figure 2 is a schematic diagram of a detection device according to an embodiment of the present invention, Figure 3 is a signal waveform of each part of the detection circuit shown in Figure 2. Fig. 4 is a diagram showing the marking 1 of the front part of another embodiment, and Fig. 5 is a schematic diagram of the detection circuit of another embodiment. In the figure, 1 is a nozzle. , 2 is an ink droplet 23 is a bandffiffl
4 is a charging power source, 5 is a resistor, and 6 is a capacitor. 7 is an inverting circuit, 8 is a resistor, 9 is an amplifier, 10 is a low-pass filter, IL 13 is a comparator, 12 is a reference voltage, 14 is an inverter, 15.16 is a flip-flop, 17 is a counter, 18 is a clock circuit, 19 is Control circuit, 21 is a multi-nozzle, 23 is a charging electrode, 24
indicates an AD converter, and 25 indicates a control circuit. $1 Figure (Q) tb> Figure 2 #I3 Figure p

Claims (1)

[Claims] An ink droplet flight speed detection device for an inkjet recording device that drives a piezoelectric element in response to an information signal to eject an ink droplet from a nozzle tip to record on a recording medium, A charging m-pole provided at a position that does not impede the flight of the ink droplet, a charging means for electrifying the ejected ink droplet via the charging electrode, and a detection means also connected to the charging electrode. The time when the ink droplet passes the closest position to the charged electrode is detected from the electrical changes in the charged electrode as the ink droplet flies, and the flying speed of the ink droplet is determined based on this time and the time when the ink droplet is ejected from the nozzle tip. An ink droplet flying speed detection device, characterized in that it detects the flight speed of ink droplets.