JPS596232B2 - Inkjet printer print monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a print monitoring device for an inkjet printer that forcibly gives a printing command to a nozzle when a missing dot in printing is detected.

In general, in printers such as impact printers or type wheel printers that use type to print, even if a missing character occurs, it is immediately obvious by looking at the printed recording paper.

However, inkjet printers that print pixel-separated characters using a plurality of dots do not have the above-mentioned printing omissions, but dot omissions occur. This missing dot cannot be easily detected just by looking at the recording paper, and in the worst case, it can lead to misidentification, such as when a missing dot occurs in the katakana "u" and becomes "wa". There is a high possibility that this will occur. The present invention has been made in consideration of these points, and is capable of reliably detecting missing dots, and at the time of detecting the missing dots, temporarily interrupting the printing operation based on the image information signal, which is a printing command given from the outside, and eliminating the missing dots. To provide a print monitoring device for an inkjet printer, which forcibly drives a nozzle until printing is performed on a dot that has been printed.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the structure of the head portion of an inkjet printer according to the present invention. A base 2 is provided in front of a nozzle 1, and a base 2 is provided on the base 2 so that ink droplets ejected from the nozzle 1 can be detected. It is constructed by attaching an optical sensor consisting of a pair of light emitting element 3 and light receiving element 4, such as a photocoupler.

Note that 5 in the figure indicates an electrostrictive vibrator that excites the nozzle 1 to eject ink droplets. Further, FIG. 2 shows an ink droplet ejection monitoring device that monitors whether or not missing dots have occurred during printing according to the detection output of the optical sensor 6, which takes the logical negation of the output of the optical sensor 6. A first binary counter 8 that counts the number of ink droplets ejected from the nozzle 1 according to the output B of the NOT circuit 7 and a head shown in FIG. 1 are driven according to the digital image signal S for each pixel. a second binary counter 10 that counts the number of pulses of the printing finger +A applied from the head drive circuit 9 to the head 1;
Comparison circuit 11 which compares each count output of these first and second binary counters 8 and 10 and generates a detection output F (exclusive OR output) when both output values are different.
and a comparison circuit 1 corresponding to the output A of the head drive circuit 9.
1, a control circuit 12 that sends a clock signal E to determine the timing of the comparison operation; a monostable multivibrator 13 that operates according to the output F of the comparison circuit 11; a head drive control circuit 14 which temporarily suspends the reading of the input digital image signal S given to the head drive circuit 9 from the head drive circuit 9, stops the carriage operation of the nozzle 1, and forcibly gives a printing command 2 to the head drive circuit 9; It is composed of.

The operation of the print monitoring device for a quick-jet printer according to the present invention configured as described above will be explained below with reference to the time chart shown in FIG.

First, when a digital image signal corresponding to the number of dots such as characters to be recorded is given to the head drive circuit 9, a pulse voltage of a printing command A is applied to the electrostrictive vibrator 5 of the head portion shown in FIG. As a result, the electrostrictive vibrator 5 is excited every three pulses to eject an ink droplet forming one printed dot from the nozzle 1, and the number of output pulses is counted by the counter 10.

When an ink droplet is ejected from the nozzle 1, the light that is constantly being sent from the light emitting element 3 of the optical sensor 36 to the light receiving element 4 is interrupted by the ink droplet, and the output of the light receiving element 4 momentarily becomes zero. By logically negating the result using the NOT circuit 7, a pulse-like detection output B is obtained each time an ink droplet is ejected. When the pulsed printing finger +A is output from the head drive circuit 9, the printing command A is also sent to the control circuit 12, where the pulsed voltage of the printing command A is applied to the head to actually eject. A clock signal E delayed by the time t until the ink droplet is detected by the optical sensor 16 is sent to the comparator circuit 11.

Note that the first counter 8, which counts the actual number of ink droplets ejected, and the second counter 10, which counts the number of pulses of the printing command A, each hold the current count value until the next pulse is sent. Use what you can. Further, these counters 8 and 10 are not limited to binary counters, and it goes without saying that ordinary universal counters that add and count input pulses may be used. Next, the comparator circuit 11, whose operation timing is set by the output E of the control circuit 12, operates the first and second
Read the count contents of counters 8 and 10 at the same time, compare the two count contents, and if they match, keep the output F at zero (L level), and if there is a difference in the count contents, output the comparison output. When F becomes H level, it is detected that missing dots in printing have occurred.

That is, as shown in the time chart of FIG. 4, if no ink droplets are ejected from the nozzle 1 and the output B of the optical sensor 6 is zero despite the printing command A (part a in the figure). ), the count content of the first counter 8 (in this embodiment, both the first and second counters 8, 10 are configured to produce a 4-bit encoded count output) and the count content of the second counter 8 As a result, the fifth dot to be printed will be missed without being printed. At that point, the comparator circuit 11 will detect the missing dot. Upon detection, an H level output F is generated. At this time, when the output F of the comparator circuit 11 changes from L level to H level,
Monostable multivibrator 13 has its input FOL-+H
A pulse signal G of a constant width is sent to the head drive control circuit 14 triggered by a change in the edge of the head.

As a result, the head drive control circuit 14 temporarily stops reading the input when there is an external digital image signal S input, and also stops the carriage operation of the head 1, so that ink droplets can be placed in the area where the missing dot has occurred. A printing command is forcibly given to the nozzle drive circuit 9 until the nozzle is injected. When an ink droplet is ejected from the nozzle 1 by this forced nozzle drive, it is detected by the optical sensor 6 and counted by the first counter 8, so that the contents of the comparison circuit 11 match. (The compulsory printing order is the second
(The output F of the monostable multivibrator 13 is not added to the counter 10) returns to the L level, and the output G of the monostable multivibrator 13 also becomes zero, and the above-mentioned forced control in the nozzle drive control circuit 14 is released. , the head drive circuit 9 continues to perform the printing operation or carriage operation based on the digital image signal S from the outside. As described above, in the print monitoring device for an inkjet printer according to the present invention, when a missing dot is detected, the nozzle is forcibly driven until an ink droplet is ejected, so that it is possible to perform high-quality printing without any missing dots. At the same time, it is possible to eliminate some clogging that occurs in the nozzle.

Note that if no ink droplets are ejected from the nozzle even after the above-mentioned forced drive is continued for a certain period of time, it is possible to assume that the ink is out or the head is malfunctioning, and the head drive control circuit 14 issues an alarm. . As described above, regarding the quick jet printer according to the present invention,
In addition to providing a sensor (not limited to an optical sensor, other electromagnetic detection devices may also be used) that detects in a pulsed manner whether or not ink droplets have been ejected at the tip of the nozzle of the head, A missing dot is detected by comparing the count value of the detected number of ink droplets ejected with the count number of the printing command given to the head and creating a difference between the two, and the ink droplet is ejected from the nozzle according to the detection signal. This device is equipped with an ink droplet ejection monitoring device that forcibly drives the nozzle until the ink droplet is ejected, regardless of the printing command given from the outside, and its simple configuration reliably prevents missing dots during printing. It has the excellent advantage of being able to print with good quality.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of the head portion in one embodiment of the present invention, FIG. 2 is a block diagram of the ink droplet ejection monitoring device in the same embodiment, and FIG. 3 is a signal diagram of each part of the ink droplet ejection monitoring device. This is a time chart. 1... Nozzle, 5... Electrostrictive vibrator, 6
(3,4)...Light sensor, 8,10...
... Binary counter, 9 ... Head drive circuit, 11 ... Comparison circuit, 12 ... Control circuit, 13 ... Monostable multivibrator, 14
...Nozzle drive control circuit.

Claims (1)

[Claims] 1. A sensor that is installed at the tip of the nozzle of the head and detects whether or not ink droplets are ejected in a pulsed manner, and a count of ink droplet ejection detected by the sensor and a count of printing commands given to the head. The ink droplet ejection monitoring device detects missing dots by comparing the numbers and creating a difference between the two, and in response to the detection signal, forcibly drives the nozzle until an ink droplet is ejected from the nozzle. Print monitoring device for configured inkjet printer.