JPH11254665A - Liquid ink marking engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for printing to prevent unevenness of printing characteristics of each nozzle and each printhead base. SOLUTION: A recording medium on a drum passes at least twice a printing bar 10 to complete an image. The bar 10 is moved to a lateral individual position by a positioning unit at each rotation of the drum. The bar 10 completes an image under the control of a controller to inject an ink droplet from a nozzle at each N pieces at the time of rotating N times of the drum and disposes the droplets on the medium in a chessboard pattern on the medium. By this printing method, the image on the medium is formed with the ink droplets injected from different nozzles or two different printhead bases 80, 82.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to ink jet marking devices, and more particularly to an ink jet marking engine having a print bar that can be positioned to improve image output.

[0002]

2. Description of the Related Art Liquid ink marking engines of the type frequently referred to as continuous flow or drop-on-demand, such as piezoelectric, acoustic, phase-change wax-based, and thermal systems, apply ink droplets to a recording medium. It has at least one printhead to fend. In the printhead, ink is contained in a plurality of droplet ejectors. By electrically addressing the droplet ejector, droplets of ink are ejected from an orifice or nozzle at the end of the droplet ejector as required.

In a thermal ink jet marking engine, the electrical address pulses are usually generated by a thermal transducer or resistor typically associated with one of the channels. Individual resistors are individually addressable to heat and vaporize the ink in the channels. When a voltage is applied to the selected resistor, a bubble grows in the corresponding channel, first bulging out of the channel orifice and then crushing the bubble. Then, the ink in the channel retracts, separates from the swelling ink, and forms a droplet that moves away from the channel orifice toward the recording medium, and hits the recording medium to cause a drop or drop of ink. A spot is placed. Then, the channel is refilled with ink by a capillary action of sequentially drawing ink from the liquid ink supply container.

[0004] The inkjet printhead may be incorporated into any of a carriage type printer, a partial width array type printer, or a page width type printer. Carriage type printers typically have a relatively small printhead with ink channels and nozzles. The printhead can be hermetically mounted on a disposable ink supply cartridge. The combined printhead and cartridge assembly is mounted on a carriage, which reciprocates and prints one swath (print width) at a time on a recording medium, such as paper or transparent film, which is stationary. (Having a height equal to the length of the column). When one swath is printed, the paper is stepped by a distance equal to the height of the printed swath or a portion thereof, with the next swath continuing or partially overlapping the already printed swath.
This procedure is repeated until the entire page has been printed.
In contrast, page-width printers have a stationary printhead, which is long enough to print at one time over the width or length of a sheet of recording media. During the printing process, the recording medium moves intermittently at a constant or varying speed, substantially perpendicular to the printhead length, past the pagewidth printhead. Page width inkjet printers are disclosed, for example, in US Pat.
92,959.

Various printers and methods are shown and described in the following disclosure, which may be related to certain aspects of the present invention.

[0006] US Pat.
No. 748,453 describes a method for arranging dots of liquid ink on a substrate. At least 2 lines of information
Printed in one pass, the dots of liquid ink are arranged in a checkerboard pattern (checkerboard pattern) at the selected pixel center, and in one pass only in the pixel areas that are diagonally adjacent.

US Pat. No. 5,057,854 to Pond et al. Describes a bar component module and a full width array printhead made from the bar component module. The bar component module includes a base bar having a length and a plurality of printhead subunits mounted on only one side of the base bar. This bar part module is used as a building block to form a full width staggered (alternating) array printhead.

[0008] US Patent No. 5-1 by Drake
No. 60,945 describes a page width thermal inkjet printhead for an inkjet printer. The printhead is of the type assembled from all functional subunits of a roofshooter type printhead.

[0009]

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, a recording medium having a print dimension that defines a maximum area for receiving liquid ink that moves along a recording medium path. Providing a liquid ink marking engine that places liquid ink to form an image. The marking engine extends over a portion of the recording medium that passes through the nozzle at least twice to place one swath (print width) of ink on the recording medium during movement of the recording medium along the recording medium path. An array of nozzles and a positioning device coupled to the array of nozzles for positioning the array of nozzles at a plurality of discrete locations to form an image.

[0010]

FIG. 1 shows an embodiment of the present invention. For example, an ink-jet marking device 8 is positioned to place ink on a curved recording medium placed on a rotating drum 11. The drum 11 is rotated in the direction of arrow 12 by a motor (not shown). Print bar 10 abuts to form an array of extended width, for example, in accordance with the technique described in U.S. Pat. No. 5,221,397, the contents of which are hereby incorporated by reference. Assembled from a plurality of modules or printhead dies 10A. In one example, printbar 10 has 7,200 nozzles or jets.
Having. As described in the aforementioned patent, the printhead die 10A combines a channel die containing an array or recess used as an ink supply channel, an associated ink reservoir, a heater die containing heating elements, and appropriate addressing circuitry. Formed. The combined channel die and heater die form a printhead die that abuts to form a print bar. The heating element is selectively applied to heat the ink contained in the channel and eject ink droplets from the associated nozzle. The ink channels are coupled into a common ink manifold 14, which is mounted along the top of the printbar 10 and sealingly communicates with the ink inlet of the channel die through the aligned openings. . The manifold 14 is supplied with a suitable ink, in this case black, from an ink container 16 via a flexible tubing 18 attached to the container. The print bar 10 is shown as a page width or large array of print bars, where the print bar is positioned and the number of nozzles is determined by the width and width of the recording medium as the recording medium passes through the print bar two or more times. The number is sufficient to place the ink over at least one dimension, including the length.
Partial width array printbars are also possible.

In addition to the printbar 10 for printing black ink, the color printhead assembly 20 includes a plurality of inkjet printheads 22, 2 for individually printing, for example, cyan, magenta, and yellow, respectively.
4 and 26. The ink attached to the printhead is stored in a printhead ink tank attached to and connected to the printhead itself, or via a flexible tubing (not shown) as shown in ink reservoir 16. The container allows the appropriate ink to be supplied to the associated printhead.
The assembly 20 is mounted on a movable carriage 28 driven by lead screws 30 and 31 and a drive motor 32. The carriage 28 has curved frame members 34 and 36, some of which have threaded openings through which lead screws 30 and 31 pass. Carriage 28 moves in direction 38. The construction of the printheads 22, 24, and 26 is conventional and is described, for example, in U.S. Pat. No. Re. 32,572 and U.S. Pat. It can be prepared as described in 774,530.

The printer of FIG. 1 can be operated as a monochrome printer using only the print bar 10 or as a color printer using the assembly 20 for disposing color inks or using a combination of both. However, the printer shown in FIG.
In order to minimize certain undesirable printing characteristics due to the multi-pass printing technique in which the print bar 10 is moved in discrete steps, the printer 8
A mechanism has been added to improve the image output from. For example, individual nozzles of the printhead die 10A may eject ink droplets with wrong orientation. Such erroneous orientation occurs when the ink drops are not ejected perpendicular to the front face of the printhead die, but are ejected in a bent manner. Also, droplet ejection from the printhead nozzles may be accompanied by unwanted satellite droplets. In addition to certain undesirable printing characteristics due to individual nozzles, the printing characteristics of one printhead die and another may vary. For example, all printhead nozzles of one printhead die may eject on average a slightly smaller drop than the average of all printhead nozzles of another printhead die, thereby reducing the image to the size of the ink drop. It will have related light and dark parts. Then
Although the entire image can be completed by one rotation of the drum 11, the output image printed during one rotation may have various printing defects described.

To reduce or eliminate such problems, print bar 10 is moved in direction 40 by a positioning device 42 that changes the position of print bar 10 during each rotation of drum 11. In one embodiment, the positioning device 42 has a cam 44 that is electrically activated and rotates on a spindle 46 driven by a motor 48. The cam 44 has an eccentric shape and has a rotation axis that is off the center of the cam. When the cam 44 rotates in contact with the contact member 50, the print bar is determined by the shape of the cam and the motor 48. It moves in the direction 40 by an amount determined by the amount of rotation of the cam. During printing, a resilient biasing system 52, including, for example, a spring, is located at the opposite end of the printbar so that the printbar 10 is held in a stable position.

To print an image, the controller 54
Receives a bitmap image from a print driver resident in a printer or an image generating device such as a personal computer, or from a combination of print drivers resident in both. The bit-mapped image is operated by the controller 54, and the print bar 10 and the print head assembly 2 are operated.
An appropriate signal is transmitted to 0. The drive signals generated by controller 54 are applied to drive and logic circuits on individual printhead dies 10A and individual printheads 22, 24, and 26, conventionally via wire bonds. The signal includes a pulse signal that is applied to a heating resistor or converter formed in the heater die. Controller 54 may take the form of a microcomputer having a central processing unit, a read-only memory that stores a complete program, and a random access memory. The controller 54 controls the rotation of the drum 11, the movement of the scanning carriage 20 by controlling the motor 32, and the cam 44 under the control of the motor 48.
Control other machine functions, such as the individual position of the print bar 10 determined by the rotation of. The print bar is stationary at each individual position during one revolution of the drum as the recording medium passes through the print bar once.

FIG. 2 shows a more detailed view of the printbar 10 and different positioning mechanisms for movement of the printbar 10. As shown, the print bar 10 has a plurality of printhead dies 10A, and as described above, each die has eight printhead nozzles 60 for illustrative purposes. The print head dies 10A abut each adjacent print head dies such that the nozzles are arranged along a single array axis. A printhead die joint 62 is located between them. The printhead die is mounted between a first substrate 64 and a second substrate 66. Other configurations are also possible. Ribbon cable 68 is coupled to one of the substrates 66 and supplies signals received from controller 54 to the individual printhead dies as described above. Other positioning mechanisms are also possible, including pneumatic or hydraulic.

A bar 70 fixed within a frame (not shown) of the printer is slidably positioned within a member 72 to allow the print bar 10 to move in the direction 40 of FIG. Bar 70 supports printbar 10 and allows movement of printbar 10 in direction 40. In this embodiment, the controller 54 is connected via a cable 76.
Move the print bar 10 to a discrete position for printing. As described above, at the opposite end of the print bar 10 is a spring mechanism 78 for holding the print bar in place.

Other positioning mechanisms for aligning the print bar 10 in multiple increments in the direction 40 include a stepper motor that advances a lead screw or a linear actuator with a position feedback device such as a linear encoder.

FIG. 3 shows a simplified schematic diagram of a printbar 10 having a first printhead die 80 and a second printhead die 82 for illustrative purposes. The nozzles of the individual printhead dies are arranged in a linear array as described above and are numbered from 1 to 8 to indicate a printing procedure according to the present invention. Each printhead die has four nozzles. First of print bar 10
In the print position A, the print bar 10 arranges ink drops from every other print nozzle, and in the first pass, on the recording medium 86 passing through the print bar 10 stationary at the position A, Every other ink drop is printed. For example, the recording medium 86 has a plurality of ink drops arranged in a plurality of rows 88. When the printbar 10 is positioned at position A, the first row 88 (1) has ink drops positioned by the printbar nozzles 1, 3, 5, and 7. These ink drops placed in the first pass of the recording medium are individually indicated by subscript A. Then, the second row 88 (2) contains the printbar 10
Nozzles 1, 2, 4, 6, and 8, which are incorporated herein by reference.
As described in U.S. Pat. No. 4,748,453 to T. al.), during one pass of the medium, the obliquely adjacent ink droplets have a known checkerboard pattern (checkerboard pattern). Then, the adjacent line of the recording medium is printed.

The print bar 10 whose recording medium is at the position A
Completes the first pass through the print bar 10
Is moved to position B and every other nozzle of the print bar 10 places an ink drop along a row already printed with ink drops during the first pass of the recording medium. For example, in the second pass where the printbar is located at position B, row 8
8 (1) is located at nozzles 1, 3, 5, and 7;
8 (2) is located at nozzles 2, 4, 6, and 8 (the ink drops located in the second pass are indicated by subscript B). The remaining portion of the recording medium 86 is printed and completed as such.

By slightly moving the print bar laterally by one jet (ejection port), about 42 microns at a resolution of 600 spi (spots per inch), one row of ink 90 is shown (shown in FIG. 1). It has a single column of ink drops composed of individual ink drops fired by two different jets or nozzles. As can be seen, rows 92 and 94 are comprised of ink jets ejected from a single nozzle, but are printed such that the area of these rows is outside the designated maximum print area of the recording medium. If the bars are long enough, there is no need to print such rows. In this example, the print bar may not only be wider than the maximum print area width, but also longer than the size of the media parallel to the print bar.

FIG. 4 shows another embodiment of the present invention in which the print bar 10 is moved laterally a distance of one-half the length of the printhead die. 2 shows a conventional nozzle and ink drop arrangement according to the prior art example. In this embodiment, the die joint 94 between the first and second printheads of the printbar differs with respect to the recording medium during image printing by moving the printhead about one-half the die length. Effectively moved into position. Such movement can improve printing in several ways and not only has the ability to produce an array of ink composed of ink drops from two different nozzles, but also, for example, a printhead die between nozzles 4 and 5. This effectively hides the irregular nozzle spacing between the nozzles on both sides of the die joint due to the contact. It is also possible to move the print bar 10 in other increments, for example a distance of one printhead die (length) divided by another number, to increase the number of drum revolutions to complete the image. . For example, for each rotation of the drum, the print bar 10 may
It is possible to move by a distance of / 4 and rotate the drum four times to complete the image. With two revolutions, the controller selects or activates every other nozzle that ejects every other ink drop, but with four revolutions, the controller determines that the ink drops while the recording medium passes through the print bar once. Is selected for every fourth nozzle for ejecting. In other words, when the image information requires ejection of ink droplets when the drum rotates N times, the nozzles every Nth nozzle are activated to arrange the ink droplets. If the length of the printhead die is selected as a decision parameter, the printbar is advanced in 1 / N times the length of the printhead die.

FIG. 5 illustrates a third printing method of the present invention in which the print bar 10 is moved laterally the full length of the printhead die. FIG. 3 shows a conventional nozzle and an ink droplet arrangement according to the preceding conventional example. In this embodiment, by moving the printhead approximately the entire length of the die, each row of nozzles on one die is composed of ink droplets from two different dies, and the amount or direction of the ink droplets is different. Average differences from die to die.
As shown in FIG. 5, a plurality of rows 100, 1
Alternate ink drops of one of 02, 104, and 106 each consist of ink drops from two different printhead dies. For example, row 100 is comprised of ink drops from nozzle 5 of second die 82 and nozzle 1 of first die 80. This printing method also has the effect of arranging adjacent ink droplets along one row of four columns with nozzles of different dies. For example, column 10
Row 108 with 0, 102, 104, and 106 is:
There is a drop from nozzle 2 next to the drop from nozzle 5, a drop from nozzle 7 next to it, and a drop from nozzle 4 next to it.

The printing method of FIG. 5 has additional advantages when printed using the page width staggered print bar 110 of FIG. In this print bar configuration, a plurality of printhead dies are staggered and arranged alternately on opposite sides of a substrate 112 defining a centerline. For example, die 114, die 116, and die 11
8 is installed on a first surface of the base 112, and the dies 120 and 122 are installed on a second surface of the base 112 opposite to the first surface. As can be seen, die 1
It can be seen that fourteen nozzles 124 are aligned with nozzles 126 of die 120. In addition, it can be seen that the vertices of the individual triangular nozzles are located at the furthest distance from the substrate.

This type of printbar has different behavior of satellite drops due to the apexes being located at different individual locations on opposite sides of the substrate, and the nozzle face systematically causes deflection of the ink drops. If so, the printing has certain disadvantages, including the concern that its deflection will be magnified by the stagger arrangement method, both of which are averaged out by the printing arrangement of FIG. further,
By providing a printhead with a staggered arrangement in which the jets at both ends of the staggered die overlap, perception of edge jet defects is reduced. In addition, such a printing arrangement can improve the manufacturing yield of individual dies because critical end jet parameters are substantially reduced or eliminated.

Although the present invention has been described in relation to particular embodiments in an ink jet environment, it will be apparent to those skilled in the art that many alternatives, modifications, and variations are possible. For example, the invention is not limited to the embodiments shown here, but is applicable to any type of inkjet printer having a page width printbar. For example, in one practical embodiment of the present invention, the printhead is a U.S. patent to Xerox Corporation, by Drake, incorporated herein by reference. No. 5,160,945, may have a roof shooter type printhead die. Also, page-width printheads of the piezoelectric, acoustic, and phase-change wax-based types, and printheads with rectangular, circular, or elliptical nozzles in which the nozzles are not triangular in configuration, are considered as well. ing. In addition, although the invention has been described with respect to configurations having a rotating drum, it is equally applicable to belt-type transport systems. Accordingly, this application is intended to cover all such alternatives, modifications, and variations as fall within the scope of the appended claims.

[Brief description of the drawings]

FIG. 1 is a perspective view of an ink jet printer of the present invention.

FIG. 2 is a perspective view of an inkjet print bar.

FIG. 3 is a diagrammatic view of a printing method according to the invention, wherein the print bar has been moved a distance of the nozzle spacing.

FIG. 4 is a diagram of another printing method according to the present invention, wherein the print bar has been moved a distance of one-half the length of the die.

FIG. 5 is a diagrammatic view of another printing method according to the invention, wherein the print bar has been moved a distance of the length of the die.

FIG. 6 is a perspective view of an inkjet print bar having print head dies arranged in a staggered arrangement.

[Explanation of symbols]

 Reference Signs List 8 inkjet printer 10 print bar 11 drum 42 positioning device 80, 82 print head die

Continuation of front page (72) Inventor Peter Jay. Nistrom United States 14580 New York Webster Glenwood Drive 62

Claims (1)

[Claims] 1. A printing device that moves along a recording medium path and has a printing dimension that defines a maximum printing area for receiving liquid ink.
What is claimed is: 1. A liquid ink marking engine for disposing liquid ink on a recording medium to form an image, the disposition of one swath of ink on the recording medium during movement of the recording medium along the recording medium path. An array of nozzles positioned to span a portion of a recording medium that passes through the nozzles at least twice; and an array of nozzles for positioning the array of nozzles at a plurality of discrete locations to form an image. A liquid ink marking engine having a positioning device coupled to the array.