JPH07276647A - Ink jet printer - Google Patents

Abstract

PURPOSE:To obtain stable print quality even if the liquid droplet velocity of some of nozzles is different from that of the others. CONSTITUTION:A printing head 1 is engaged with a shaft 2 in an axial direction in a movable state. At least, two or more nozzles 10 are provided on the printing head 1. In addition, a measuring device 7 for measuring a liquid droplet velocity is provided, and a control device 8 recognizes a nozzle which affects print quality adversely and controls a printing operation in such a way that such a nozzle is not used for printing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer.

[0002]

2. Description of the Related Art Ink jet printers for ejecting ink from nozzles to print characters and pictures on a print medium are small in size and low in price, and have been dramatically installed in offices as computer printers. However, as a problem peculiar to an inkjet printer, there are cases where the nozzles are clogged, the characteristics of the ink jet drive device change, and the ink droplet speed changes. If printing is performed in these states, there is a drawback that the print quality is degraded.

[0003]

The conventional ink jet printer has a problem that the print quality is deteriorated due to the clogging of the nozzle and the characteristic change of the ink jet drive device. The present invention is to provide an inkjet printer having stable print quality.

[0004]

SUMMARY OF THE INVENTION The above object is to provide a nozzle in the printer itself for confirming the ink droplet velocity from the nozzle, detect the ink ejection velocity, and detect the nozzle that adversely affects the print quality by the ink ejection velocity. This is achieved by performing print control so that the printer itself automatically recognizes and nozzles that adversely affect print quality during printing operation are not used for printing during printing operation.

[0005]

In the ink jet printer configured as described above, the ink jet speed is detected by measuring the ink droplet speed by the CCD or the like, and the printer itself automatically recognizes the nozzles that adversely affect the print quality. However, during the printing operation, the printing control operation is performed so that the nozzles which adversely affect the printing quality are not used for the printing, if necessary.

[0006]

1 and 2 show an inkjet printer according to an embodiment of the present invention. In the figure, the print head 1 is locked by a shaft 2 so as to be movable in parallel in the axial direction. The print head 1 has at least two or more nozzles 10.
Ink 11 is ejected from the sheet onto the sheet 3. The ink 11 is ejected from the nozzle by an ink ejection drive device 12 having a drive element such as an electromechanical energy conversion element, and its drive timing is controlled by an ink ejection drive circuit 81 controlled by a signal from the control device 8. . The sheet 3 is conveyed by the belt 5 and the sheet feed rollers 51 and 52. This operation is also controlled by the control device 8. A measuring device 7 for measuring the ink droplet velocity is provided at a position outside the belt 5, and is operated by a measuring device drive circuit 82 controlled by a control device 8. The measuring device 7 is composed of a CCD or the like. In order to measure the speed of the ink 11 ejected from the nozzle 10, the print head 1 moves while performing position control so that the nozzle 10 is directly below the measuring device 7.

When printing, the print head 1 moves on the shaft 2 at a constant speed, ejects the ink 11 from the nozzles 10 and sprays the ink 11 onto the paper 3 at an appropriate timing. Further, after the paper 3 is conveyed by the belt 5 by a predetermined amount, the print head 1 is moved to spray the ink 11. An image is formed by repeating this process.

The droplet speed and print quality of the ink 11 will be described with reference to FIG. When the ink droplet speed is Vi, the moving speed of the print head 1 is Vp, and the distance from the nozzle to the paper is G, the distance L from the ejection of the ink 11 to the arrival of the paper is represented by the following equation. It

[0009]

[Equation 1]

Here, the moving speed Vp of the print head 1 is controlled to be a constant speed, and the distance G from the nozzle to the paper is adjusted in advance so as to be a constant value. Therefore, the distance L changes as the ink droplet speed Vi changes, so that the ink droplet speed Vi changes.
Is kept constant or there is no speed difference with other nozzles in order to obtain stable print quality.

Therefore, the droplet velocity of the ink 11 is regularly measured by the measuring device 7, and the control device 8 detects the nozzles which adversely affect the print quality and the nozzles from which the ink is not ejected.
By recognizing and changing the print control of the control device 8 so that these nozzles are not used during the printing operation, good print quality can be maintained.

An example of print control is shown below.

In normal printing, the ink 11 is jetted onto the paper 3 by the movement of the print head 1, and after a certain amount of paper is conveyed, the print head 1 moves and the ink 11 is sprayed on the paper 3 repeatedly. Form an image.
However, when the control device 8 recognizes that there is a nozzle that adversely affects the print quality, that nozzle is not used for printing, and therefore the portion on the paper 3 to which the ink is to be ejected is in the “white spot” state. ing. Before carrying out a steady and constant amount of paper conveyance, the paper feed amount output from the control device 8 is corrected so that the ink spray of that nozzle is supplemented by another normal nozzle, and the ink is printed on the "white spots" part with the normal nozzle. By spraying, good print quality can be maintained.

[0014]

According to the present invention, a nozzle that adversely affects print quality is recognized and the nozzle is not used for printing, so that stable print quality can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an inkjet printer according to the present invention.

FIG. 2 is a configuration block diagram showing an embodiment of an inkjet printer according to the present invention.

FIG. 3 is a schematic diagram illustrating ink droplet velocity and print quality.

[Explanation of symbols]

1 is a print head, 2 is a shaft, 3 is paper, 5 is a belt, 51 and 52 are paper feed rollers, 7 is a measuring device, 10
Is a nozzle, 11 is ink, 12 is an ink jet drive device,
Reference numeral 8 is a control device, 81 is an ink ejection drive circuit, and 82 is a measurement device drive circuit.

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Claims (1)

[Claims] 1. A nozzle having, independently for each nozzle, an ink ejection drive device and a drive circuit required for ejecting ink, and a measuring device for measuring a droplet velocity of ink ejected from the nozzle. In an inkjet printer, by measuring the ink droplet speed, it is detected whether the ink is not ejected from the nozzle or the droplet speed is different from that of other nozzles due to the change in the characteristics of the ejection drive device to improve the print quality. An ink jet printer characterized in that it is configured to recognize nozzles that have an adverse effect and, if necessary, perform printing control so that those nozzles that adversely affect print quality are not used for printing during printing operation.