JP4155763B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus that conveys a print recording medium and forms an image thereon.
[0002]
[Prior art]
An ink jet recording apparatus that conveys a print recording medium and forms an image thereon includes an ink jet head (print head) and a pulley, gear, belt, and the like driven by a motor that conveys the print recording medium to the print head. Transporting means. In order to form an image at a predetermined position on the print recording medium, the print recording medium must be conveyed in synchronization with the timing at which ink is ejected from the print head.
[0003]
FIG. 6 is a schematic view showing an example of the configuration of an ink jet printer according to the prior art, in which 50 is an ink jet printer. The ink jet printer 50 includes a paper feed unit including a paper feed tray 56, a paper transport unit including a transport belt 52, a print head 51, a paper discharge unit, and the like.
[0004]
The paper supply unit supplies a print recording medium (hereinafter, exemplified by paper) to the printer body, and supplies paper by a pickup roller and a pickup roller for feeding the set paper in addition to the paper supply tray 56 for setting paper. It is composed of a conveyance roller or the like for guiding the sheet to the sheet conveyance unit. The paper transport unit includes a transport belt 52, a drive motor 55, a transport roller 54, a pulley, a gear, and the like, and transports the paper from the paper feed unit to the exit of the inkjet printer 50 through the placement part of the print head 51. In the configuration example illustrated here, the sheet conveyed from the sheet feeding unit is conveyed in the printing direction by the conveyance belt 52. The conveying belt 52 is charged by being charged with a high voltage, and by this charging, the sheet is electrostatically attracted on the conveying belt 52 and conveyed along with the feeding of the conveying belt 52. Further, the conveyance belt 52 is driven by a drive motor 55.
[0005]
The print head 51 is fixed to the carriage and moves with the carriage, and ejects ink to form an image on the paper. When the inkjet printer 50 is a full color specification, the print head 51 is composed of four color heads, a black head, a cyan head, a magenta head, and a yellow head, in order to form a full color image. The paper discharge unit stocks the paper on which the image has been formed, and includes a paper discharge roller that guides the paper to the paper discharge side, a paper discharge tray for stocking the discharged paper, and the like.
[0006]
In order to form an image at a predetermined position on the paper, a disk 57 is provided on the axis of the roller 54 for conveying the paper. On the circumferential edge of the disk 57, there is a slit portion 60 provided with marks such as slits at equal intervals, and an encoder sensor 53 that can read the marks such as slits as a signal is attached. When printing with the recording positions of the respective colors aligned in the sub-scanning direction, the signal of the encoder sensor 53 is read and printing is performed in synchronization.
[0007]
However, in the above-described prior art, the conveyance speed of the paper may vary from product to product due to variations in the shape of parts such as the conveyance roller 54, pulleys, and gears that constitute the conveyance means, and the paper is supplied by the paper supply unit. Although it is delivered to the transport means, the transport speed varies depending on the position of the transport belt, and the paper transport speed changes.
[0008]
As a printing apparatus that employs a printing timing determination method different from that of the above-described inkjet printer 50, Japanese Patent Application Laid-Open No. 11-170623 employs an encoder that transmits rotation from a roller in contact with the conveyance belt. There is described a printing apparatus that determines a printing timing using a signal from an encoder that rotates with conveyance as a clock signal. The publication also describes a printing apparatus that determines the printing timing by causing the encoder to act on a drive shaft that drives the conveyor belt, detecting the moving speed of the conveyor belt.
[0009]
However, since the signal is not directly detected from the conveyance belt that moves with the paper, the conveyance distance calculated from the detected signal is different from the actually conveyed distance. As a result, printing cannot be performed at an accurate position, color misregistration occurs in the sub-scanning direction, and image quality is degraded.
[0010]
Furthermore, this publication provides slits arranged at equal intervals (same as the resolution in the conveyance direction of the printer) on the entire circumference of the conveyance belt, and detects the reflected light of the light irradiated to the slits and passes the slits through. There is also described a printing apparatus in which a belt speed sensor that calculates a conveyance distance by measuring the distance is measured. In this printing apparatus, the paper sensor detects the leading edge of the conveyed paper, and simultaneously, the belt speed sensor counts the number of slits (clock number) of the conveying belt, and the ejection position of the image based on the transferred image data and the number of clocks. To decide.
[0011]
However, the method of generating a synchronization signal from the signal from the encoder of the conveyance roller that drives the conveyance means and printing based on the synchronization signal does not directly control printing using the output signal of the encoder. The transport distance calculated from the encoder signal is different from the actually transported distance. As a result, printing cannot be performed at an accurate position, color misregistration occurs in the sub-scanning direction, and image quality is degraded.
[0012]
[Problems to be solved by the invention]
The present invention has been made in view of the actual situation as described above, and provides an inkjet recording apparatus and a control method therefor capable of obtaining a high-quality image without color misregistration in the sub-scanning direction with a simple configuration. Its purpose is to provide.
[0013]
[Means for Solving the Problems]
The invention of claim 1 includes a conveyor belt of an endless provided with slits at regular intervals to the edge conveying the Printout recording medium, the printing head control according to the conveying speed of the print recording medium conveyed by the conveying belt a synchronization signal, read-directly from the conveyor belt by detecting the presence or absence of the slit, and an encoder sensor which outputs a pulse, the synchronization signal read by the encoder sensor, control for controlling the print head to print the image The slits are provided at equal intervals only on a part of the circumference of the conveyor belt, starting from the origin on the conveyor belt corresponding to the print start position. And the ink jet recording apparatus detects the origin of the conveyor belt by the encoder sensor, so that paper on the conveyor belt is detected. It is obtained by comprising the detection means for detecting at a predetermined position of the conveyor belt.
[0014]
According to a second aspect of the present invention, in the first aspect of the invention, the encoder sensor outputs, as the synchronization signal, a pulse whose phases of A phase and B phase are shifted, and the control means obtains from the A phase pulse. The print head is controlled based on the transport speed of the transport belt, and the B-phase pulse is used to detect the rotation direction of the transport belt .
[0015]
According to a third aspect of the present invention, in the first or second aspect of the present invention, when the control means doubles the resolution and prints by the print head, the pulse output from the encoder sensor is doubled and used. It is characterized by that.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
In the ink jet recording apparatus according to the present invention, the print head directly from the transport means for transporting the print recording medium so as to obtain a high-quality image having no color misregistration in the sub-scanning direction with a simple configuration. The control synchronization signal is read, and the print head is controlled to print an image based on the read synchronization signal. Hereinafter, an embodiment of the present invention will be described by taking an example of an ink jet printer as an ink jet recording apparatus.
[0018]
FIG. 1 is a schematic view showing a configuration example of an ink jet printer according to an embodiment of the present invention. In FIG. 1, 10 is an ink jet printer. The ink jet printer 10 includes a paper feed unit including a paper feed tray 16, a paper transport unit including a transport belt 12, a print head 11, a paper discharge unit, and the like.
[0019]
The paper feeding unit supplies a print recording medium (hereinafter, exemplified by paper) to the printer body, and feeds paper by a pickup roller and a pickup roller for feeding the set paper in addition to the paper feed tray 16 for setting the paper. It is composed of a conveyance roller or the like for guiding the sheet to the sheet conveyance unit. A sheet conveying unit as an example of a conveying unit includes a conveying belt 12, a drive motor 15, a conveying roller 14, a pulley, a gear, and the like. The sheet is conveyed from the sheet feeding unit to the exit of the inkjet printer 10 through the arrangement portion of the print head 11. Transport. In the configuration example illustrated here, the sheet conveyed from the sheet feeding unit is conveyed in the printing direction by the conveyance belt 12. The conveying belt 12 is charged by being charged with a high voltage, and by this charging, the sheet is electrostatically attracted on the conveying belt 12 and conveyed along with the feeding of the conveying belt 12. The conveyor belt 12 is driven by a drive motor 15.
[0020]
The print head 11 is fixed to the carriage and moves with the carriage, and ejects ink to form an image on a sheet. When the inkjet printer 10 is a full color specification, the print head 11 is composed of four color heads, a black head, a cyan head, a magenta head, and a yellow head, in order to form a full color image.
[0021]
The transport belt 12 transports the paper 1 on the transport belt 12 to the paper start position, where the print head 11 moves in the main scanning direction and prints an image. When printing for one line is completed, the transport belt 12, that is, the paper 1 is moved in the sub-scanning direction by the drive motor 15, and printing for the next line is performed. In this way, printing is performed in the main scanning direction and the sub-scanning direction. The paper discharge unit stocks the paper on which the image has been formed, and includes a paper discharge roller that guides the paper to the paper discharge side, a paper discharge tray for stocking the paper that has been discharged, and the like.
[0022]
FIG. 2 is a diagram showing an outline of the conveying belt in the ink jet printer of FIG. 1, and FIG. 3 is an enlarged view showing an outline of slits provided on the conveying belt of FIG.
The synchronization signal reading unit is a unit that directly reads a synchronization signal for controlling the print head corresponding to the conveyance speed of the print recording medium conveyed by the conveyance unit from the conveyance unit. A slit portion 20 is provided on the circumference. As shown in FIG. 3, the slit part 20 has slits 22 provided at equal intervals, and the synchronization signal reading means has a sensor for detecting the presence or absence of the slits 22 and reading the synchronization signal. The interval between the slits 22 is the same as the resolution in the sub-scanning direction of the ink jet printer, and the detection capability of the movement amount of the transport belt 12 is configured to be equal to the resolution. In this configuration example, as an example of this sensor, an encoder 13 that outputs a pulse as a synchronization signal of the conveyance speed of the sheet 1 conveyed by the conveyance belt 12 at the edge of the conveyance belt 12 is attached to the printer main body side. The encoder (also referred to as an encoder sensor) 13 can execute accurate position control in accordance with the actual conveyance speed.
[0023]
The encoders 13 read the slits 22 recorded at equal intervals on the conveying belt 12 conveyed by the drive motor 15, and the period of the above-described pulse changes according to the conveying speed. As will be described later, the control means drives the print head 11 in synchronization with the pulse of the output signal, controls the ink to be ejected, and prints on the recording paper 1.
[0024]
In addition, it is preferable to include means for detecting the origin of the conveyor belt 12 with a sensor such as an encoder 13. Here, the slits 22 are equidistant from the printing start position (origin), and are arranged so that the paper on the conveyor belt 12 can always be detected at a certain position on the conveyor belt 12. Therefore, as shown in FIGS. 2 and 3, the slit portion 20 is not provided on the entire circumference of the conveyor belt 12, but the portion from the print end position (end point) to the origin is a non-slit portion. 21 is preferable. The interval between the slits 22 is very close when the print head is a line head. By reading this interval with an encoder sensor, a signal synchronized with each line recorded by the line head can be obtained.
[0025]
Here, an ink ejection sequence by the print head 11 will be described in detail. Simultaneously with detecting the leading edge of the conveyed paper 1, the encoder 13 on the conveyor belt 12 is read and the number of pulses is counted. The ejection position of the image is determined by the transferred image data and the counted number of pulses. Since the number of pulses is equal to the resolution as described above, the subsequent image creation is performed by sending an ink ejection signal corresponding to the image signal to the print head 11 in synchronization with the detected pulse.
[0026]
FIG. 4 is a block diagram illustrating a control unit that controls the print head in the inkjet printer of FIG. Image data is transmitted from a personal computer (PC) 31, and an output signal from the encoder 13 is taken into the main control circuit 32. A trigger signal is generated based on this output signal, and a signal is sent to the head drive circuit 33 to give an ink ejection command to each ink-jet head 34. At the same time, the head drive circuit 33 sends a control signal to the motor driver 35 of the motor 36 that drives the print head 11.
[0027]
FIG. 5 is a timing chart showing the timing of driving the print head based on the output signal detected by the encoder in the ink jet printer of FIG.
First, the home position (origin) is detected by the encoder 13 as the origin signal 41, and the output signal of the encoder 13 is read. As the output signal of the encoder 13, pulses (phase A output signal 42 and phase B output signal 43, respectively) out of phase A and phase B are output. Normally, the control is based on the A-phase output signal 42, but the B-phase output signal 43 is used when detecting the rotation direction. In this way, a print trigger is generated in synchronization with the pulse signal of the encoder 13 and a timing for driving the print head 11 is generated. The print trigger I (44) indicates the print trigger when the encoder 13 pulse is used as it is, and the print trigger II (45) indicates the print trigger when the encoder 13 pulse is multiplied by 2 to double the resolution. Yes.
[0028]
In the present invention, a belt speed sensor based on a method of detecting reflected light and measuring the passing speed of a slit as in the prior art is not disposed. For example, as described in FIGS. By disposing a sensor such as the encoder 13 that can directly read the slit 22 of the belt 12, an image having no color misregistration in the sub-scanning direction can be formed with a simple configuration. That is, the synchronization signal is read from the conveyance belt 12 that conveys the paper 1, and printing of each color is performed in accordance with the actual conveyance speed, so that a high-quality image without color misregistration in the sub-scanning direction can be obtained.
[0029]
【The invention's effect】
According to the present invention, it is possible to obtain a high-quality image having no color misregistration in the sub-scanning direction with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration example of an inkjet printer according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an outline of a transport belt in the ink jet printer of FIG.
3 is an enlarged view showing an outline of a slit provided on the conveyor belt in FIG. 2;
4 is a block diagram illustrating a control unit that controls a print head in the ink jet printer of FIG. 1. FIG.
5 is a timing chart showing the timing for driving the print head based on the output signal detected by the encoder in the ink jet printer of FIG. 1. FIG.
FIG. 6 is a schematic diagram illustrating a configuration example of an inkjet printer according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Paper, 10 ... Inkjet printer, 11 ... Print head, 12 ... Conveyor belt, 13 ... Encoder, 14 ... Conveyor roller, 15 ... Drive motor, 16 ... Paper feed tray, 20 ... Slit part, 21 ... Non-slit part, 22 ... slit, 31 ... PC, 32 ... main control circuit, 33 ... head drive circuit, 34 ... inkjet head, 35 ... motor driver, 36 ... motor, 41 ... origin signal, 42 ... A phase output signal, 43 ... B Phase output signal 44... Print trigger I, 45.

Claims (3)

A conveyor belt of an endless provided with slits at regular intervals in the conveying and edge markings shaped recording medium, a synchronization signal for the print head control according to the conveying speed of the print recording medium conveyed by the conveying belt, of the slit whether read-directly from the conveyor belt by detecting an encoder sensor for outputting a pulse, the synchronization signal read by the encoder sensor, ink jet recording and control means for controlling the print head to print the image A device,
The slits are provided at equal intervals only in a part of the circumference of the conveyor belt, starting from the origin on the conveyor belt corresponding to the print start position,
The ink jet recording apparatus includes an detecting unit that detects the origin of the conveyor belt by the encoder sensor, and detects a sheet on the conveyor belt at a certain position of the conveyor belt. Recording device. The encoder sensor outputs, as the synchronization signal, a pulse in which the phases of the A phase and the B phase are shifted, and the control unit is configured to output the print head based on the conveyance speed of the conveyance belt obtained from the A phase pulse. 2. The ink jet recording apparatus according to claim 1 , wherein the B phase pulse is used to detect a rotation direction of the transport belt . Wherein, in the case where the resolution is doubled to printing by the print head, the ink jet recording apparatus according to claim 1, wherein the Rukoto used by 2 Tei multiplying the pulses the encoder sensor outputs .

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