JPS6245826B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink-on-demand type inkjet printer that prevents clogging of nozzles without inkjet during inkjet recording.

In an inkjet printer, an increase in ink viscosity at a nozzle due to evaporation of ink solvent makes it difficult to eject ink, resulting in inability to record and deterioration in print quality. Conventionally, long-term increases in ink viscosity have been prevented by covering the nozzles with lids to prevent ink drying when not in operation. However, since it is difficult to cover the nozzle during operation, ink is ejected from the nozzle at regular intervals to prevent a short-term increase in ink viscosity. At this time, in the deflection type inkjet printer, the ejected ink is deflected toward the ink collector and collected. Furthermore, since unnecessary ink cannot be collected in ink-on-demand printers, an ink absorbing device is provided at a position away from the recording medium, and the print head is moved to this position to eject ink. Ink absorption devices require measures such as pumping out ejected ink to prevent it from accumulating even after long-term operation.

The purpose of the present invention is to prevent clogging of the nozzle portion without using such an expensive and complicated ink collection and removal device, and to eject ink by moving the head to a predetermined position to prevent clogging of the nozzle. To provide an ink-on-demand type inkjet printer which prevents a decrease in printing speed due to the printing speed, has a simple configuration, and can print at high speed without clogging any of a plurality of nozzles.

This will be explained below using examples.

FIG. 1 is a diagram showing one embodiment of the present invention, and is shown in the vertical direction.
FIG. 2 is a block diagram for printing in a 24×24 dot matrix while serially moving a 24-nozzle multihead in the horizontal direction. 1 is a piezo that provides the driving force for ink ejection. In a steady state, a low-level input signal is applied to the base of the drive transistor 6, and there is no deflection, but when a high-level signal is applied during driving, a potential difference occurs between the electrodes on both sides. The resulting piezo flexes and ejects ink. There are 24 piezos arranged corresponding to the nozzles. Reference numeral 2 denotes a clock generating means for generating a clock which is a printing timing. 4 is a main control section which supplies an output signal to the character generator 3 to control printing. The character generator 3 is controlled by the main control section 4 and generates a print pattern signal in the form of a low level signal at the timing of the clock output signal of the clock generating means 2. The counter 5 counts the clock signal input from the clock generation means 2 to the character generator 3, and has output terminals corresponding to the number of nozzles, and there is a time lag from each output terminal. A low level signal is output. Reference numeral 20 denotes gate means for inputting the output signals of the character generator 3 and the counter 5 and generating an output signal obtained by performing a logical sum.

To explain the operation in the above configuration, the character generator 3 inputs the clock output of the clock generating means 2 and the output control signal of the main controller 4. A normal print pattern output signal (low level) is generated based on the print pattern.
This output signal is input to the base of the drive transistor 6 via the gate means 20, drives the drive transistor 6 which is fully turned up to +V, deflects the piezo, and ejects ink from the nozzle corresponding to the regular printing pattern. let As a result, ink is ejected from a predetermined nozzle, and printing is performed on the recording medium in accordance with the printing pattern of the character generator 3.

On the other hand, the counter 5 counts the clock signal of the clock generating means 2, outputs a low level signal every time it reaches a predetermined value, drives a specific drive transistor 6 via the gate means 20, and outputs a low level signal every time it reaches a predetermined value. Ink is ejected from each nozzle regardless of the regular printing pattern by the generator 3. In this case, since low-level output signals are generated from each output terminal of the counter 5 with a time lag, ink is always ejected from each of the 24 nozzles at regular time intervals.

In this way, each nozzle will eject ink at least every cycle counted by the counter 5,
Increase in ink viscosity at the nozzle portion can be suppressed. Furthermore, since the ink is ejected from each nozzle discretely, it is hardly noticeable to the human eye.

For example, FIG. 2 shows a print pattern printed with 24 nozzle heads. White circles 10 indicate regular printing patterns by the character generator, and black circles 11 indicate dots of injected ink to prevent an increase in ink viscosity due to the counter. Each dot is actually about 0.15
Since it has a diameter of mm, it is indistinguishable from dirt on the recording medium 12 and can be almost ignored.

Next, the operation of the counter 5 will be explained in more detail using FIGS. 3 and 4.

The signal 30 is applied to the counter 5 when the power is turned on, for example.
This is the signal input to the A signal 31 is a clock signal input from the clock generating means 2 to the counter 5. Signals 32, 33, 34, . . . are output from the counter 5 with a time lag and are input to the respective piezo drive transistors 6 via the gate means 20.

Here, as mentioned above, after the signal 30 is output, the signals 32, 33, and 34 are outputted in synchronization with the clock signal 31 with a time lag.

A specific example of the counter 5 is a ring counter using a shift register as shown in FIG. Published by Baifukan, first edition, 7th edition, April 30, 1971, pages 158-161, pages 172-175
) may be considered.

The operation of the counter 5 will be explained as follows. When signal 30 is output, clock signal 3
1, flip-flops 42, 43, 4
The signal 30 is taken in with a time lag in 4, . . . , and the signals 32, 33, 3
4, . . . are output with a time lag. Further, the Q output of the final stage flip-flop is inputted to the flip-flop 42 via an OR gate means 45. Therefore, the signals 32, 33, 34,
...will be generated cyclically.

Further, as shown in FIG. 3, the output signals 32, 33, 44 from the flip-flops 42, 43, 44
34 are output when a predetermined number of clock signals 31 are output. That is, the signal 32 is output in synchronization with the fall of the second clock, the signal 33 is output in synchronization with the fall of the third clock, and the signal 34 is output in synchronization with the fall of the fourth clock.
These are flip-flops 42, 43, 44,...
... are respectively synchronized with the clock signal 31,
This is because data is being imported.

In this embodiment, the counter 5 counts the clocks 2. That is, ink is ejected according to a printing timing signal. Therefore, if the head is left unused for a long period of time during incremental printing, the viscosity of the ink may increase because the print timing signal is not output and the drying prevention lid is not closed. As a countermeasure for this, it is possible to close the lid when no printing command is input even after a certain period of time has elapsed.

As another embodiment, a timer may be used instead of the counter 5, and ink may be ejected after a certain period of time has elapsed.

The present invention is particularly suitable for printing high-density dot matrices such as 24×24 and 32×32. When printing alphabetic characters, the printing pattern is divided into upper and lower parts for uppercase and lowercase letters.For example, when only uppercase letters are being printed, the lower nozzle is hardly used.In such cases, the present invention is particularly effective. . In some cases, it may be possible to eject ink only from nozzles that are unlikely to be used in order to prevent an increase in ink viscosity.

Furthermore, in this embodiment, ink is ejected independently of the print pattern, but the pause time or pause timing clock is counted for each nozzle, and ink is ejected only from nozzles that have been paused for a certain period of time or longer. Also good. In this way, the influence on print quality can be reduced.

The inkjet printer of the present invention described above does not require an expensive and complicated ink collection and removal device, and can prevent nozzle clogging.

In addition, it is not necessary to periodically move the head to the home position and eject ink from all nozzles to prevent clogging, and it is possible to prevent clogging while performing normal printing operations.
It becomes possible to speed up printing.

Further, although it is an ink-on-demand type, ink is ejected periodically from each nozzle while printing is performed by the counter 5 and the gate means 20, regardless of the printing pattern, so the nozzles are not clogged. At this time, since ink is ejected from each nozzle at different times,
It is almost unrecognizable on the recording medium and the regular print pattern is not damaged.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a print pattern diagram according to the embodiment of the present invention. FIG. 3 is a time chart showing the operation of the counter 5. FIG. 4 is a diagram showing a specific circuit configuration of the counter 5. DESCRIPTION OF SYMBOLS 1...Piezo, 2...Clock generating means, 3...Character generator, 5...Counter, 10...Regular printing dots, 11...Ejection dots for preventing increase in ink viscosity, 12...Recording medium.

Claims (1)

[Claims] 1. A main control unit 4, which includes a plurality of nozzles, and a clock generation means 2 that generates printing timing.
and a character generator 3 which is controlled by the output signal of the main control section 4 and receives the clock signal of the clock generating means to generate an output signal of a regular printing pattern, and a character generator 3 corresponding to each of the nozzles. In an ink-on-demand type inkjet printer, the ink-on-demand type inkjet printer is equipped with a drive transistor 6 which is provided with an output signal of the character generator 3 and ejects ink from the nozzle by inputting an output signal of the character generator 3. input and count clock signals, and when the counter value reaches a predetermined clock counter value corresponding to each of the plurality of nozzles, a clock signal with a time lag is input and counted from the plurality of output terminals corresponding to each of the plurality of nozzles. a counter 5 that generates a plurality of output signals; an output signal of the character generator 3 and an output signal of the output terminal of the counter 5 corresponding to each nozzle are inputted, and a logical sum is outputted; An inkjet printer characterized in that it is equipped with a gate means 20 which is used as an input signal for driving.