JP2005280192A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer that maintains a fixed printing throughput irrespective of whether defective nozzles exist or not. <P>SOLUTION: The line head type inkjet printer includes a plurality of printer heads arranged in different positions along a printing medium transfer direction. The printer heads have nozzles capable of discharging ink drops that are arranged in the direction intersecting the transfer direction and have a first command generation means to generate a discharge command to make the nozzles discharge ink drops, nozzle control means to control the nozzles on the basis of the discharge command, a defective nozzle detection means to detect defective nozzles incapable of discharging ink drops in accordance with the discharge command, and a second command generation means to generate a discharge command to cause the prescribed nozzles of a printer head different from a printer head containing the defective nozzles to discharge ink drops in place of a discharge command to cause the defective nozzles detected to discharge ink drops. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet printer including a plurality of printer heads in which a plurality of nozzles capable of ejecting ink droplets are arranged.

Conventionally, as an ink jet printer of this type, a line head type printer having a plurality of printer heads in which a plurality of nozzles are arranged in a direction orthogonal to a conveyance direction (hereinafter also referred to as “paper feeding direction”) of printing paper. Is known (for example, see Patent Document 1).
The printer described in Patent Document 1 further includes an auxiliary printer head (hereinafter also referred to as “auxiliary head”) that can move in a direction orthogonal to the paper feeding direction. If there is a defective nozzle that cannot eject ink due to clogging or the like, the auxiliary head is moved to a position corresponding to the defective nozzle, and printing is performed on the auxiliary head instead of the defective nozzle. And the like are prevented from occurring in the printed image.
Japanese Patent Laid-Open No. 02-276647

  However, in the conventional ink jet printer, when the printing is performed on the printing paper, the auxiliary head is moved to a position corresponding to the defective nozzle. Therefore, if there is a defective nozzle, the auxiliary head is moved. It takes time to make it happen. Therefore, for example, when there are a large number of defective nozzles, the time required for moving the auxiliary head becomes long, and as a result, there is a problem that the print throughput is reduced.

  The present invention aims to solve the above-mentioned unsolved problems of the conventional ink jet printer, and provides an ink jet printer capable of maintaining a constant print throughput regardless of the presence or absence of defective nozzles. This is the issue.

  In order to solve the above problems, an ink jet printer according to a first aspect of the present invention is a line head type ink jet printer including a plurality of printer heads arranged at different positions along a conveyance direction of a print medium, In the printer head, a plurality of nozzles capable of ejecting ink droplets are arranged in a direction intersecting the transport direction, and further, a first command generating unit that generates a discharge command for causing the plurality of nozzles to eject ink droplets; A nozzle control unit that controls the plurality of nozzles based on the ejection command, a defective nozzle detection unit that detects a defective nozzle that cannot eject an ink droplet according to the ejection command, and an ink droplet that is applied to the detected defective nozzle Instead of a discharge command for discharging, an ink droplet is applied to a predetermined nozzle of a printer head different from the printer head including the defective nozzle. Characterized in that a second command generating means for generating an ejection command for ejecting. Examples of defective nozzles include nozzles that are unable to eject ink due to clogging or the like, nozzles that have reduced ink ejection amount, and the like.

  The ink jet printer according to the second aspect of the invention is a serial head type ink jet printer including a plurality of printer heads arranged at different positions along a direction intersecting the transport direction of the print medium, The plurality of printer heads includes a plurality of nozzles capable of ejecting ink droplets arranged in the transport direction, a first command generation unit configured to generate a discharge command for causing the plurality of nozzles to eject ink droplets, Nozzle control means for controlling the plurality of nozzles based on the command, defective nozzle detection means for detecting a defective nozzle that cannot eject ink droplets according to the ejection command, and ejecting ink droplets to the detected defective nozzles Instead of an ejection command, ink droplets are ejected to a specified nozzle on a printer head that is different from the printer head that contains the defective nozzle. Characterized in that a second command generating means for generating a discharge command that.

Furthermore, in the ink jet printer according to the third invention, the predetermined nozzle is a nozzle corresponding to the same pixel as the defective nozzle.
In the ink jet printer according to the fourth aspect of the invention, the second command generation means replaces the ink droplets with the ink droplets instead of the ejection command for causing the defective nozzles detected by the defective nozzle detection means to eject ink droplets. An ejection command for ejecting ink droplets to a predetermined nozzle of a printer head different from the printer head including the defective nozzle is generated so that the same color or substantially the same color is printed.

Further, in the ink jet printer according to the fifth aspect of the present invention, the defective nozzle detection means is configured to detect the residual of the displaced diaphragm when the diaphragm is displaced so that ink droplets are ejected from the nozzle. The defective nozzle is detected based on vibration.
In the ink jet printer according to the sixth aspect of the invention, the defective nozzle detection unit causes the plurality of nozzles to eject ink droplets in order so that a predetermined test pattern is printed, and then the test pattern. When the printing state data is input, the defective nozzle is detected based on the input data.

  According to these first to sixth inventions, when each printer head is sequentially ejected with ink droplets while being moved relative to the print medium to be printed along the same path, that is, printing is performed on the print medium. When performing the above, ink droplets can be ejected instead of the defective nozzle to the nozzle of the printer head different from the printer head including the defective nozzle. Therefore, even if there is a defective nozzle, there is no need to make a new movement of the printer head, that is, a movement different from the movement of the printer head when there is no defective nozzle, and the print throughput is kept constant regardless of the presence or absence of the defective nozzle. be able to.

Hereinafter, a line printer which is an embodiment of an ink jet printer of the present invention will be described with reference to the drawings.
<Configuration of line printer>
FIG. 1 is a block diagram showing the internal configuration of the line printer of this embodiment. As shown in FIG. 1, a line printer 1 includes a CPU (Central Processing Unit) 2, a RAM (Random Access Memory) 3, a ROM (Read Only Memory) 4, an I / F (InterFace) 5, and a printing paper transport unit 6. The ink ejection unit 7 and the residual vibration detection circuit 8 are configured to be connected to each other by a bus 9.

Among these, when a print execution command (described later) is output from the I / F 5, the CPU 2 reads various programs and data stored in the ROM 4, expands these various programs in a work area provided in the RAM 3, A print execution process, which will be described later, is executed to control each unit so that information such as images and characters according to a print execution command (described later) is printed.
The RAM 3 forms a work area for developing various programs executed by the CPU 2 and also forms a memory area for storing data related to the various programs. Then, when a read request is output from the CPU 2, the RAM 3 outputs the stored data to the CPU 2 in response to the read request.

Furthermore, the ROM 4 stores various programs and data executed by the CPU 2. Then, when a read request is output from the CPU 2, the ROM 4 outputs various stored programs and data to the CPU 2 in response to the read request.
The I / F 5 is connected to a personal computer (not shown) that outputs data of information to be printed by the line printer 1. When the information data is output from the personal computer (not shown), the I / F 5 issues a command (hereinafter also referred to as “print execution command”) to cause the line printer 1 to print information corresponding to the data. It outputs to CPU2.

Further, as shown in FIG. 2, the printing paper transport unit 6 includes a driving roller 10 that can be rotationally driven by a servo motor (not shown), a driven roller 11 that is the same type as the driving roller 10 and that can rotate freely, and those rollers. And an endless belt 12 stretched between 10 and 11. Among these, the endless belt 12 has a mechanism (not shown) capable of attracting the printing paper 13 on the surface. The mechanism capable of attracting is, for example, a mechanism that charges the endless belt 12 in order to generate an electrostatic attracting force, or a suction from a plurality of holes in the endless belt 12 in order to generate a negative pressure attracting force. This is a mechanism for sucking air with a fan or the like.
Then, when a print control command (described later) is output from the CPU 2, the printing paper transport unit 6 attaches the printing paper 13 to the endless belt 12, and then drives the endless belt 12 to rotate at a constant speed. It is rotated and the attached printing paper 13 is conveyed.

  The ink ejection unit 7 includes seven printer heads 14 disposed above the endless belt 12. These printer heads 14 are arranged at different positions along the direction in which the printing paper is conveyed (hereinafter also referred to as “paper feeding direction”), and in order from the downstream side in the paper feeding direction, black Bk, cyan C A plurality of nozzles 15 capable of ejecting one of the light cyan LC, magenta M, light magenta LM, yellow Y, and dark yellow DY vertically downward are formed on the lower surface. Further, as shown in FIG. 3, the nozzles 15 of the same printer head 14 are arranged in a line in a direction orthogonal to the paper feed direction, and the nozzles 15 at different positions of the different printer heads 14 are arranged. Are arranged in a line in the paper feed direction. Further, the length of the printer head 14 in the direction orthogonal to the paper feeding direction is longer than the width of the printing paper 13. When the print control command (described later) is output from the CPU 2, the ink ejection unit 7 outputs the timing, the number of times, and the dot size (for example, L size, M size, and S size) according to the print control command (described later). The ink droplets are ejected to the nozzles 15 by size, and information corresponding to a print control command (described later) is printed on the printing paper conveyed by the endless belt 12.

Further, when a nozzle state detection command (described later) is output from the CPU 2, the residual vibration detection circuit 8 determines whether or not ink droplets can be appropriately ejected, that is, ink droplets having an arbitrary dot size at an arbitrary timing. Whether or not ejection can be performed a number of times is detected for each nozzle 15 and the detection result is output to the CPU 2. Hereinafter, the nozzle 15 that can properly eject ink droplets is referred to as a normal nozzle, and the nozzle that cannot eject ink droplets appropriately is referred to as a defective nozzle. Specifically, when an operation of ejecting ink droplets is performed by displacing the diaphragm by an actuator (not shown) of the ink ejection unit 7 and increasing or decreasing the pressure of the cavity (not shown) by the displacement, Whether residual vibration of a diaphragm (not shown) displaced by an actuator (not shown) is detected, and whether or not ink droplets are properly ejected based on the detected vibration pattern of the residual vibration Is detected.
<Contents of print execution processing>
Next, the print execution process executed by the CPU 2 will be described with reference to the flowchart of FIG. This print execution process is executed when a print execution command is output from the I / F 5. First, in step S101, information corresponding to the print execution command output from the I / F 5 is transferred to the printing paper. Print data that causes each nozzle 15 to eject ink droplets is generated at an appropriate timing, number of times, and dot size so as to be printed on the printing paper conveyed by the unit 6, and the generated print data is stored in the RAM 3. Let

Next, the process proceeds to step S102, which is also referred to as a command for detecting the operation state of each nozzle 15 (hereinafter referred to as a nozzle state detection command). ) Is output to the residual vibration detection circuit 8.
Next, the process proceeds to step S103, and whether or not there is one defective nozzle that cannot eject ink droplets according to the print data generated in step S101 based on the detection result of the operation state by the residual vibration detection circuit 8. If there is a defective nozzle (Yes), the process proceeds to step S104. If there is no defective nozzle (No), the process proceeds to step S105.

  In step S104, the information corresponding to the print execution command output from the I / F 5 is output from the residual vibration detection circuit 8 so that the information is printed by the normal nozzle 15 only on the printing paper conveyed by the printing paper conveyance unit 6. Based on the detected result, the print data generated in the step S101, that is, the print data stored in the RAM 3 is corrected, which will be described later, and then the step S105 is executed.

In step S105, a print control command for causing each nozzle 15 to eject ink droplets at a timing, number of times, and dot size corresponding to the print data stored in the RAM 3 is output to the printing paper transport unit 6 and the ink ejection unit 7. Then, this calculation process is terminated.
Next, the print data correction process executed in step S104 of the print execution process will be described with reference to the flowchart of FIG. In this print data correction process, first, in step S201, based on the detection result of the operation state by the residual vibration detection circuit 8, the print data generated in step S101, that is, the print data stored in the RAM 3, is used as a defective nozzle. Print data for instructing ejection of ink droplets is detected. Next, correction print data for causing the detected print data to print the same color or almost the same color as the ink droplet commanding ejection on the nozzle 15 of the printer head 14 different from the printer head 14 including the defective nozzle is generated. . Specifically, according to the interpolation color creation table of FIG. 6, the other nozzles 15 in the column in the paper feed direction including the defective nozzle, that is, the nozzles 15 corresponding to the same pixel among the pixels constituting the information to be printed on the printing paper 14. Print data for correction for causing the ink droplets to be discharged. For example, when the nozzle 15 that ejects black Bk ink droplets is a defective nozzle, the nozzles 15 that can eject cyan C, magenta M, and yellow Y are arranged in a row in the paper feed direction including the defective nozzle. Correction print data is generated by which each L-size ink droplet is ejected to the nozzle 15 at a timing when the spot where the ink droplet is landed is directly below. Further, for example, when the nozzle 15 that discharges cyan C ink droplets is a defective nozzle, among the nozzles 15 that can discharge light cyan LC, the nozzles 15 arranged in the row in the paper feed direction including the defective nozzle are The correction print data for ejecting the L size ink droplet twice is generated at the timing when the spot where the ink droplet is landed is directly below.

In step S202, the print data stored in the RAM 3 in step S101 is added to the ink droplets corresponding to the print data, and ink droplets corresponding to the correction print data generated in step S201 are added. After correcting the command to discharge, this calculation process is terminated.
<Operation of line printer>
Next, the operation of the line printer 1 of the present embodiment will be described based on a specific situation.

  First, it is assumed that data of information to be printed is output from a personal computer (not shown), and a print execution command corresponding to the data is output by the I / F 5. Then, the CPU 2 executes a print execution process, and as shown in FIG. 4, first, in step S101, print data for causing each nozzle 15 to eject ink droplets at an appropriate timing, number of times, and dot size is generated. The generated print data is stored in the RAM 3. In step S102, a nozzle state detection command is output, the residual vibration detection circuit 8 detects the operation state of each nozzle 15, and the detection result is output to the CPU 2.

Here, paper powder of the printing paper 13 adheres to three consecutive nozzles 15 that eject black Bk ink droplets, and these three nozzles 15 are defective nozzles that cannot properly eject ink droplets according to print data. Is detected. Then, the determination in step S103 is “Yes”, and the print data correction process is executed in step S104.
When the print data correction process is executed, as shown in FIG. 5, first, in step S201, based on the detection result of the operation state by the residual vibration detection circuit 8, the three print data stored in the RAM 3 are used. Print data for instructing the nozzle 15 to eject ink droplets is detected. Next, out of the nozzles 15 capable of ejecting cyan C, magenta M, and yellow Y ink droplets based on the print data, the nozzles 15 arranged in the row in the paper feed direction including the three nozzles 15 respectively. Each of the print data for correction is generated so that an L-size ink droplet is ejected once at a timing when the spot where the ink droplet is landed is directly below. In step S202, the print data stored in the RAM 3 is corrected to a command for ejecting ink droplets corresponding to the correction print data in addition to the ink droplets corresponding to the print data. The process ends, and the process returns to the print execution process.

  When the print execution process is returned, in step S105, a print control command corresponding to the print data stored in the RAM 3 is output, and the print execution process ends. Then, after the printing paper 13 is attached to the endless belt 12 by the printing paper transport unit 6, the driving roller is rotated at a constant speed, the endless belt 12 is rotated, and the attached printing paper 13 is transferred to the printer. It is conveyed below the head 14. At the same time, the ink ejection unit 7 ejects ink droplets to the nozzles 15 at the timing, number of times, and dot size according to the print control command, and information according to the print control command on the printing paper conveyed by the endless belt 12; That is, information corresponding to print data output from a personal computer (not shown) is appropriately printed.

  As described above, according to the line printer 1 of the present embodiment, ink droplets are ejected to the nozzles of the printer head 14 different from the printer head 14 including the defective nozzle instead of the defective nozzle. For this reason, even if there is a defective nozzle, there is no need to make a new movement in the printer head 14, that is, a movement different from the movement of the printer head 14 when there is no defective nozzle. Can be kept in. Further, for example, the manufacturing cost can be reduced as compared with a method in which an auxiliary head movable in a direction perpendicular to the paper feeding direction is provided and printing is performed by the auxiliary head instead of the defective nozzle.

  Incidentally, in a conventional method in which one printer head 14 is provided with a spare nozzle provided in parallel with the nozzle 15 and there is a defective nozzle, printing is performed on the spare nozzle by the printer head 14. When paper dust is applied, it adheres to both the nozzle 15 and the spare nozzle. For this reason, both the nozzle 15 and the spare nozzle become defective nozzles, and information cannot be printed appropriately.

  Further, in the conventional method, since the spare nozzle is provided, the apparatus becomes large and the manufacturing cost increases. Further, it is necessary to periodically flush the spare nozzle or perform a refresh operation by cleaning so that the ink is thickened, clogged due to drying, and the flight bend occurs. Therefore, a large amount of ink is consumed by flushing or cleaning, and the maintenance cost increases.

  Further, when there is a defective nozzle, the drive is switched so that the dot size of the ink droplets ejected by the normal nozzle adjacent to the defective nozzle is increased, and the range to be printed by the defective nozzle is also printed on the adjacent normal nozzle. In the conventional method to be performed, when the three consecutive nozzles 15 are clogged, the area to be printed by the central nozzle 15 cannot be printed, and the image quality is deteriorated due to density unevenness or streaks. End up.

  As described above, the CPU 2 in FIG. 1 and step S101 in FIG. 4 constitute the first command generation means described in the section of the claims. Similarly, the CPU 2, the printing paper transport unit 6 and the ink ejection unit 7 in FIG. Step S105 in FIG. 4 constitutes nozzle control means, CPU 2 and residual vibration detection circuit 8 in FIG. 1, steps S102 and S103 in FIG. 4 constitute defective nozzle detection means, and CPU 2 in FIG. 1 and steps in FIG. S104 and steps S201 and S202 in FIG. 5 constitute the second command generation means.

The ink jet printer of the present invention is not limited to the contents of the above embodiment, and can be appropriately changed without departing from the gist of the present invention.
For example, although an example in which a line head type ink jet printer is configured as the ink jet printer of the present invention has been shown, the present invention is not limited to this. For example, as shown in FIG. 7, the printer includes a plurality of printer heads 14 that are arranged at different positions along a direction orthogonal to the paper feed direction and in which a plurality of nozzles that can eject ink droplets are arranged in the paper feed direction. A serial head type ink jet printer may be configured.

Further, as shown in steps S101 and S102 of FIG. 4, the example in which the nozzle state detection command is output after the print data is generated has been described. However, the present invention is not limited to this, for example, before the print data is generated. A nozzle state detection command may be output.
Moreover, although the example which makes the residual vibration detection circuit 8 detect whether each nozzle 15 can discharge an ink drop appropriately was shown, it is not restricted to this. For example, after ejecting ink droplets to each nozzle 15 in order so that a predetermined test pattern is printed, the user inputs data on the print state of the test pattern, and the data is input based on the input data. A defective nozzle may be detected. Specifically, as shown in FIG. 8, first, a test consisting of a set of a plurality of straight lines is made by ejecting a predetermined number (for example, 100 shots) of ink droplets in order from the nozzle 15 at the right end facing the paper feed direction. Print the pattern. Next, for the printed test pattern, the number of the straight line that was not printed properly (for example, the number indicating the straight line in the paper feed direction and counting from the right end of the printing paper) The user inputs from a control panel (not shown). Then, when the number is input by the user, the nozzle 15 corresponding to the input number may be detected as a defective nozzle. At that time, if nozzles 15 that perform continuous discharge are provided every several nozzles (for example, every 10 nozzles), printing was not properly performed from a relatively long straight line printed by the nozzles 15 that perform continuous discharge. It is preferable because the number of straight lines can be counted, and the number of straight lines to be counted can be reduced compared with the method of counting the numbers in order from the end, and mistakes in counting can be suppressed.

It is a block diagram which shows the internal structure of one Embodiment of this invention. FIG. 2 is a perspective view illustrating an appearance of a printing paper transport unit in FIG. 1. It is explanatory drawing for demonstrating arrangement | positioning of a nozzle. It is a flowchart of a printing execution process. 6 is a flowchart of print data correction processing. It is explanatory drawing for demonstrating an interpolation color creation table. It is explanatory drawing for demonstrating the modification of this invention. It is explanatory drawing for demonstrating the modification of this invention.

Explanation of symbols

1 is a line printer, 2 is a CPU, 3 is a RAM, 4 is a ROM, 5 is an I / F, 6 is a printing paper transport unit, 7 is an ink ejection unit, 8 is a residual vibration detection circuit, 9 is a bus, and 10 is a drive Roller, 11 driven roller, 12 endless belt, 13 printing paper, 14 printer head, 15 nozzle

Claims (6)

A line head type ink jet printer including a plurality of printer heads arranged at different positions along a conveyance direction of a print medium,
The plurality of printer heads are arranged in a direction in which a plurality of nozzles capable of ejecting ink droplets intersect the transport direction,
Furthermore, a first command generation unit that generates a discharge command for discharging the ink droplets to the plurality of nozzles, a nozzle control unit that controls the plurality of nozzles based on the discharge command, and an ink droplet corresponding to the discharge command Instead of a defective nozzle detecting means for detecting defective nozzles that cannot eject ink and an ejection command for ejecting ink droplets to the detected defective nozzles, ink droplets are applied to predetermined nozzles of a printer head different from the printer head including the defective nozzles. An ink jet printer comprising: a second command generation unit that generates a discharge command to be discharged. A serial head type ink jet printer including a plurality of printer heads arranged at different positions along a direction intersecting a conveyance direction of a print medium,
In the plurality of printer heads, a plurality of nozzles capable of ejecting ink droplets are arranged in the transport direction,
Furthermore, a first command generation unit that generates a discharge command for discharging the ink droplets to the plurality of nozzles, a nozzle control unit that controls the plurality of nozzles based on the discharge command, and an ink droplet corresponding to the discharge command Instead of a defective nozzle detecting means for detecting defective nozzles that cannot eject ink and an ejection command for ejecting ink droplets to the detected defective nozzles, ink droplets are applied to predetermined nozzles of a printer head different from the printer head including the defective nozzles. An ink jet printer comprising: a second command generation unit that generates a discharge command to be discharged.   The inkjet printer according to claim 1, wherein the predetermined nozzle is a nozzle corresponding to the same pixel as the defective nozzle.   The second command generation means replaces the ejection command for causing the defective nozzles detected by the defective nozzle detection means to eject ink droplets, so that the same color or almost the same color as the ink droplets is printed. 4. The inkjet printer according to claim 1, wherein an ejection command for ejecting ink droplets to a predetermined nozzle of a printer head different from the printer head including the nozzle is generated. 5.   The defective nozzle detection unit detects the defective nozzle based on residual vibration of the displaced diaphragm when the diaphragm is displaced so that ink droplets are ejected from the nozzle. The ink jet printer according to claim 1.   The defective nozzle detection means is configured to input the test pattern print state data after sequentially ejecting ink droplets to the plurality of nozzles so that a predetermined test pattern is printed. The inkjet printer according to claim 1, wherein the defective nozzle is detected based on data.

Images