JP2006062118A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which reduces declining of a recording quality due to meandering of a transfer belt. <P>SOLUTION: The inkjet recorder is equipped with a recording head HD which has the configuration in which a plurality of head units HU1-HU4 with a recording width of an arrangement of a plurality of nozzles over a predetermined length are aligned in parallel to each other in a direction that intersects a transfer direction X so that the recording width intersects the transfer direction X of a recording medium P. An alignment position of each of the head units HU1-HU4 of the recording head HD is adjusted in accordance with a meandering amount of the transfer belt V. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus that performs recording on a recording medium placed on a conveyor belt, and more particularly to a technique for reducing deterioration in recording quality due to meandering of the conveyor belt.

In recent years, in order to increase the recording speed in an ink jet recording apparatus that records ink onto a recording medium by ejecting ink droplets from nozzles, a line type in which a large number of nozzles are arranged over a length longer than the width of the recording medium. An ink jet recording apparatus (hereinafter referred to as a line head type ink jet recording apparatus) provided with a recording head (hereinafter referred to as a line head) has been put into practical use.
In this line head type ink jet recording apparatus, the recording medium is conveyed continuously or intermittently with the recording surface facing the surface on which the nozzles of the line head are formed. Further, the line head selectively ejects ink droplets toward the recording surface of the conveyed recording medium based on information to be recorded from among a large number of arranged nozzles. That is, the line head type ink jet recording apparatus completes the recording on the recording medium only by moving the recording medium in one direction without moving the recording head. Hereinafter, in this specification, an ink jet recording apparatus that completes recording only by moving a recording medium without moving the recording head is generically referred to as a line type ink jet recording apparatus.

In this line-type ink jet recording apparatus, conventionally, a plurality of head units that discharge yellow, magenta, cyan, and black inks are inclined on a conveyance belt that conveys a recording medium with respect to the conveyance direction of the recording medium. A configuration arranged along a line is known (see, for example, Patent Document 1).
JP 2002-103598 A (page 9, FIG. 2, FIG. 4, FIG. 5 and FIG. 8)

  However, in the configuration of Patent Document 1, a plurality of head units that eject ink of one color are arranged along a line that is inclined with respect to the transport direction, and therefore, between the head units, the transport direction. Have a predetermined interval. That is, as shown in FIG. 7 (a), the two head units H1 and H2 adjacent to each other in the Y direction, which is a direction intersecting the recording medium transport direction X, have an interval X1 in the X direction. Yes. This interval X1 is necessary to avoid interference between the head units H1 and H2. In FIG. 7, symbol Dt indicates dots formed by ejecting ink droplets from the nozzles NZ of the head units H1 and H2 onto the recording surface of the recording medium, and is a boundary of recording between the head units H1 and H2. Each dot Dt is shown connected by a two-dot chain line.

  When the meandering phenomenon that the meandering belt meanders due to the accuracy of the components constituting the paper conveyance system occurs in the rotation of the conveyance belt, as shown in FIG. 7A, the head having an interval X1 in the X direction. The interval between the dots Dt at the boundary portion of the recording between the units H1 and H2 is greatly widened or becomes dense, resulting in uneven recording density, resulting in a decrease in recording quality. There is a problem to be solved.

  SUMMARY An advantage of some aspects of the invention is that it provides an ink jet recording apparatus capable of reducing deterioration in recording quality due to meandering of a conveyor belt.

  In order to solve the above-described problems, a first invention according to the present invention is directed to an ink droplet from a nozzle on a recording surface which is a surface opposite to a conveying surface of a recording medium which is placed on a conveying belt and conveyed. A plurality of head units having a recording width in which a plurality of the nozzles are arranged over a predetermined length, and the recording width is set in the conveyance direction of the recording medium. A recording head having a configuration in which the recording heads are aligned in parallel to each other in a direction intersecting the conveyance direction of the recording medium, and the alignment position of each head unit of the recording head is set to the meandering amount of the conveyance belt. An ink jet recording apparatus characterized by being adjusted accordingly is provided.

According to a second aspect of the present invention, there is provided an ink jet recording apparatus that performs recording by ejecting ink droplets from nozzles onto a recording surface that is a surface opposite to a transport surface of a recording medium that is placed and transported on a transport belt. A plurality of head units having a recording width in which a plurality of nozzles are arranged over a predetermined length are transported of the recording medium such that the recording width intersects the transporting direction of the recording medium. A recording head having a configuration aligned in parallel with each other in a direction crossing the direction, meandering detecting means for detecting the meandering amount of the conveyor belt, and the head unit based on the detected meandering amount. And a head moving means for moving the head unit within a range in which the plurality of head units do not overlap each other when viewed from a direction orthogonal to the recording medium conveyance direction. To provide an ink-jet recording apparatus according to.
According to the above configuration, the head unit transports the recording medium within a range where the head units do not overlap each other when viewed from a direction perpendicular to the recording medium transport direction based on the meandering amount detected by the meandering detection unit. Moved along the direction.

As described above, it is possible to change the interval between dots at the recording boundary between the head units without interference between the head units.
According to a third aspect, in the second aspect, the test pattern is read from the recording medium in which the ink droplets are ejected from the nozzles at least at the ends of the plurality of head units to form a test pattern. Reading means, the head moving means based on the read image information of the test pattern, among the dot intervals at the boundary between the head units adjacent to each other in the direction intersecting the conveyance direction of the recording medium An ink jet recording apparatus is provided, wherein the head unit is moved so as to perform either one of a decrease in the maximum value and an increase in the minimum value.
Here, the dot means a minimum unit of recording formed by ejecting ink droplets from the nozzles on the recording surface of the recording medium.

According to the above configuration, the head unit is based on the image information obtained by reading the test pattern so as to decrease the maximum value or increase the minimum value among the dot intervals at the boundary between the head units. Moved.
As described above, it is possible to move the head unit so as to reduce unevenness in the density of the recording that occurs when the dot interval is widened or becomes dense.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1A, which is a plan view, an ink jet recording apparatus 1 according to an embodiment of the present invention includes a gate roller GR, a paper transport unit CV, a recording head HD, a belt displacement meter DM, and dot positions. A reading unit SC and a paper discharge unit EJ are provided.
Here, the detail of each said structure is demonstrated.

As shown in FIG. 2A, which is a plan view of the paper transport unit CV, the paper transport unit CV includes a drive shaft DS to which power is transmitted from a transport unit drive motor (not shown) that drives the paper transport unit, and this drive. A driven shaft FS disposed parallel to the axis DS and on the upstream side of the drive shaft DS, and a conveyor belt V that spans the drive shaft DS and the driven shaft FS are provided.
Here, although not shown, the drive shaft DS and the driven shaft FS are rotatably held in the housing by bearings.

Further, although not shown, the driven shaft FS is applied with a force in the upstream direction in order to apply tension so as not to loosen the conveyor belt V that is stretched between the driven shaft FS and the drive shaft DS.
The conveyance belt V is rotated counterclockwise as viewed in FIG. 1B by the power of the conveyance unit drive motor, and the recording paper P placed on the conveyance belt V is moved in the X direction, which is the conveyance direction. Transport. The recording paper P placed on the conveyor belt V is placed on the conveyor belt V through a suction opening (not shown) formed in the conveyor belt V by a suction fan SF disposed inside the conveyor belt V. Adsorbed and conveyed so as not to deviate from the position placed on the conveyor belt V.

Further, the paper transport unit CV includes an index sensor IS that outputs an index signal serving as a reference for controlling the rotation of the transport belt V.
The index sensor IS is composed of, for example, an optical sensor including a light emitting element such as a photo interrupter and a light receiving element, and the index portion ID provided on the transport belt V blocks the optical axis between the light emitting element and the light receiving element. And changing the output voltage. The index signal uses the change in the output voltage, and the recording paper P is supplied to the paper transport unit CV, and each head unit HUi (i = 1 to 4) of the recording head HD described later performs recording. It is an opportunity to measure the timing.

As shown in FIGS. 1A and 1B, the recording head HD has a head unit HUi that directs nozzles that eject ink droplets toward the recording surface PP of the recording paper P on the paper transport unit CV. It is arranged.
The head unit HUi is shown in FIG. 3 (a), which is a diagram showing the details of part B in FIG. 1 (a), and is sandwiched between the spring SP and the laminated piezoelectric actuator PZ in the X direction, Is supported so as to be slidable in the X direction.

Here, the arrangement of the nozzles provided in the head unit HUi will be described. The head unit HUi is given the same reference numeral for convenience of explanation, but is the same, and here, the head unit HU1 will be described as an example.
In the head unit HU1, as shown in FIG. 3B, which is a bottom view, nozzles NZ for ejecting ink droplets are arrayed over an array distance KH. This arrangement distance KH is the recording width of the head unit HU1. In FIG. 3, in order to show the nozzles in an easy-to-understand manner, the size of the nozzles is exaggerated and the number is reduced. Further, as the head unit HUi, a head unit that applies pressure to ink by a piezoelectric element, a heating element, or the like and ejects ink droplets from the nozzle NZ can be employed.

Then, as shown in FIG. 1A, the recording head HD has a support frame FR in which these head units HUi are housed, with the recording width KH of the head unit HUi in the Y direction, and the X direction and the Y direction. Are arranged side by side at predetermined intervals.
That is, when the head units HU2 to HU4 are moved in the X direction and the recording widths KH of the head units HU1 to HU4 are aligned in the Y direction, recording in the Y direction in the inkjet recording apparatus 1 is performed as shown in FIG. Region KR is configured.

  The head unit HUi is biased toward the laminated piezoelectric actuator PZ by the above-described spring SP in the support frame FR, and moves along the X direction, that is, the conveyance direction of the recording paper P when the laminated piezoelectric actuator PZ is driven. Is done. At this time, the displacement of the head unit HUi in the X direction is measured by the head displacement meter LS disposed in the support frame FR, and the driving of the laminated piezoelectric actuator PZ is controlled. As the head displacement meter LS, a reflective laser displacement meter or the like can be employed.

The belt displacement meter DM is constituted by, for example, a reflective laser displacement meter, and measures the displacement of the transport belt V in the Y direction. By measuring the belt displacement meter DM, the amount of meandering of the conveyor belt V can be grasped.
The dot position reading unit SC is composed of an image information input device such as an optical scanner including an optical sensor such as a CCD. Read position. Based on the position of the read dot, it is possible to grasp the dot interval at the recording boundary.

Here, the connection of the control of each main part of the inkjet recording apparatus 1 described above will be described.
In addition to the main components described above, the ink jet recording apparatus 1 further includes a paper feeding unit KS that feeds the recording paper P to the gate roller GR as shown in FIG. 4 which is a block diagram.
Further, the ink jet recording apparatus 1 includes a paper feed control unit KSD that controls the paper feed unit KS, a gate roller control unit GRD that controls the gate roller GR, a suction control unit SFD that controls the suction fan SF, and an index sensor IS. A sensor control unit SD that controls the motor, a motor control unit MD that controls the transport unit drive motor M0, a head unit control unit HUD that controls each head unit HUi, and a paper discharge control unit EJD that controls the paper discharge unit EJ. , A belt displacement meter controller DMD for controlling the belt displacement meter DM, a dot position reading controller SCD for controlling the dot position reader SC, a head displacement meter controller LSD for controlling the head displacement meter LS, and a laminated piezoelectric actuator Multi-layer piezoelectric actuator controller PZD that controls PZ and recording information from external devices A recording information storage unit BF for storing the CPU, and a CPU that issues an operation command to each of the control units KSD, GRD, SFD, SD, MD, HUD, EJD, DMD, SCD, LSD, and PZD based on the recording information; It has.

Next, the recording operation in the inkjet recording apparatus 1 will be described below.
The inkjet recording apparatus 1 shown in FIG. 1 starts a recording operation when receiving recording information and a recording command from an external device.
When the recording operation is started, the CPU sends a conveyance unit drive command to the motor control unit MD, and the conveyance unit drive motor M0 is counterclockwise by the motor control unit MD when the conveyance belt V is viewed in FIG. The drive is controlled to rotate in the direction.

At the same time or later than this, the CPU sends a paper feed command for instructing the supply of the recording paper P to the gate roller GR to the paper feed controller KSD.
Upon receiving a paper feed command from the CPU, the paper feed control unit KSD controls the paper feed unit KS and supplies the recording paper P one by one from the paper cassette (not shown) in which a plurality of recording papers P are stored to the gate roller GR. Let

When the recording paper P is supplied, the gate roller GR corrects the inclination of the recording paper P with respect to the X direction and the positional deviation in the Y direction.
When the index part ID blocks the optical axis between the light emitting element and the light receiving element of the index sensor IS, an index signal is output from the index sensor IS to the CPU.
When the index signal is input, the CPU starts measuring the time for each head unit HUi to record on the recording paper P, and controls the gate roller control unit GRD to control the driving of the gate roller GR so that the recording paper P is loaded. The paper is sent to the paper transport unit CV.

At the same time or later than this, the CPU causes the suction control unit SFD to control the suction fan SF to start suction.
The recording paper P delivered to the paper transport unit CV is placed on the outer peripheral surface of the transport belt V rotated counterclockwise as viewed in FIG. 1B by driving the transport unit drive motor M0. Guided under unit HUi.

Then, the CPU sends a first recording command to the head unit controller HUD when it is time to start recording by the head unit HU1 within the measured time.
The head unit control unit HUD controls the head unit HU1 based on the first recording command, and records the recording width PP on the recording surface PP of the recording paper P continuously conveyed by the conveying belt V based on the recording information. The first recording is performed by selectively ejecting ink droplets from the plurality of nozzles NZ constituting the KH.

The CPU sequentially sends second, third, and fourth recording commands to the head unit controller HUD when it is time to start recording by the head units HU2, HU3, and HU4 within the time being measured.
The head unit control unit HUD controls each of the head units HU2 to HU4 based on the second, third, and fourth recording commands, and the second, third, and fourth recordings as in the first recording. To implement.

Based on the end of the fourth recording, the CPU causes the suction control unit SFD to control the suction fan SF to stop or weaken the suction.
When the fourth recording is finished, the recording on one recording paper P is finished, and the recording paper P is discharged out of the inkjet recording apparatus 1 by the paper discharge unit EJ controlled by the paper discharge control unit EJD.

Here, when the recording for all of the recording information has been completed, the recording operation is completed, and when there is unrecorded recording information, the CPU sends a new paper feeding command to the paper feeding control unit KSD. A new recording paper P is supplied to the gate roller GR, and the recording operation is continued until the recording of all the recording information is completed.
Next, the head unit position adjustment operation and process flow in the inkjet recording apparatus 1 will be described below. Here, an example will be described in which the maximum dot interval is narrowed at the recording boundary between the head units HUi.

The head unit position adjustment is performed by the CPU starting the head unit position adjustment process shown in FIG. 5 when the power supply of the inkjet recording apparatus 1 is turned on from OFF or when the user arbitrarily gives an instruction. Be started.
First, in step S1, a test recording process to be described later is performed, and the process proceeds to step S2.

Here, the test recording is a recording in which dots are formed by ejecting ink droplets at a predetermined cycle from all the nozzles NZ of the head unit HUi onto the recording surface PP of the recording paper P conveyed by the paper conveying unit CV. Say. In the test recording in the ink jet recording apparatus 1, the meandering amount of the conveying belt V is measured by the belt displacement meter DM along with the formation of dots.
Next, in step S2, a dot position reading command is output to the dot position reading control unit SCD, the dot position reading unit SC is made to read the dot position of the test recording result, and the process proceeds to step S3.

In this step S3, the dot position data is read and the process proceeds to step S4.
In step S4, all dot intervals ΔY in the Y direction are calculated, and the process proceeds to step S5.
In step S5, the maximum dot interval ΔYmax that is the maximum among the dot intervals ΔY is calculated, and the process proceeds to step S6.

Here, the maximum dot interval ΔYmax, which is the maximum among the dot intervals ΔY, is represented by C in the drawing, as schematically shown in FIG. 7A as an example of the result of test recording on the meandering recording paper P. This is the interval between dots.
In step S6, it is determined whether or not the maximum dot interval ΔYmax is within the allowable range. If it is determined that the maximum dot interval ΔYmax is within the allowable range (YES), the process ends, and it is determined that the allowable range is exceeded (NO). Then, the process proceeds to step S7.

In step S7, the belt displacement data obtained from the belt displacement meter DM in the test recording process described later is read, and the process proceeds to step S8.
In step S8, the movement amount ΔX of the head unit HUi that minimizes the maximum dot interval ΔYmax is calculated within the movable range of the head unit HUi in the X direction, and the process proceeds to step S9.

In step S9, the drive voltage Va applied to the laminated piezoelectric actuator PZ is set to an initial value, and the process proceeds to step S10.
In step S10, the multilayer piezoelectric actuator control unit PZD controls the drive so as to apply the drive voltage Va to the multilayer piezoelectric actuator PZ, and the process proceeds to step S11.

In step S11, the displacement measurement data ΔXa of the head displacement meter LS is read, and the process proceeds to step S12.
In this step S12, it is determined whether or not the displacement meter side data ΔXa matches the movement amount ΔX of the head unit HUi. If it is determined that they match (YES), the process is terminated and does not match (NO) ), The process proceeds to step S13.

In step S13, the voltage ΔVa is added to the current drive voltage Va, and the process proceeds to step S10 as a new drive voltage Va.
As shown in FIG. 6, in the test recording process in step S1, first, in step S31, a conveyance unit drive command is output to the motor control unit MD, and the conveyance belt V is rotated counterclockwise as viewed in FIG. Then, the conveyance section drive motor M0 is controlled so as to shift to step S32.

In step S32, a paper feed command is output to the paper feed controller KSD, the recording paper P is supplied to the gate roller GR, and the process proceeds to step S33.
In step S33, it is determined whether or not an index signal is input. If it is determined that the index signal is input (YES), the process proceeds to step S34. If it is determined that the index signal is not input (NO), the index signal is determined. Wait until is entered.

In step S34, the timer Tm1 is activated to start measuring the time Ta, and the process proceeds to step S35.
In step S35, a paper supply command is output to the gate roller control unit GRD, the recording paper P is supplied to the paper transport unit CV, and the process proceeds to step S36.
In step S36, the suction fan SF is activated by the suction control unit SFD, and the process proceeds to step S37.

In this step S37, it is determined whether or not the time Ta measured by the timer Tm1 has reached the predetermined time T1, and if it is determined that it has reached (YES), the process proceeds to step S38 and has not been reached (NO). If it is determined, the system waits until a predetermined time T1 is reached.
In step S38, a first recording command is output to the head unit controller HUD, and ink droplets are ejected from all the nozzles NZ of the head unit HU1 at a predetermined period to start forming dots Dt, and the process proceeds to step S39. .

In step S39, the belt displacement meter controller DMD controls the belt displacement meter DM to start taking in belt displacement data which is displacement meter side data in the Y direction of the conveyor belt V, and the process proceeds to step S40.
Here, the belt displacement data is obtained as time series data by sequentially storing the displacement meter side data of the belt displacement meter DM in a predetermined cycle together with the measurement time Ta of the timer Tm1 in a data storage unit (not shown) provided in the CPU. can get.

In step S40, it is determined whether or not the time Ta measured by the timer Tm1 has reached the predetermined time T2. If it is determined that the time Ta has reached (YES), the process proceeds to step S41 and is not reached (NO). If judged, it waits until the predetermined time T2 is reached.
In step S41, a second recording command is output to the head unit controller HUD, and ink droplets are ejected from all the nozzles NZ of the head unit HU2 at a predetermined period to start the formation of dots Dt, and the process proceeds to step S42. .

In this step S42, it is determined whether or not the time Ta has reached the predetermined time T3. If it is determined that the time Ta has reached (YES), the process proceeds to step S43, and if it is determined that it has not reached (NO), Wait until a predetermined time T3 is reached.
In step S43, a third recording command is output to the head unit controller HUD to cause the head unit HU3 to start forming dots Dt, and the process proceeds to step S44.

In this step S44, it is determined whether or not the time Ta has reached the predetermined time T4. If it is determined that the time Ta has reached (YES), the process proceeds to step S45, and if it is determined that it has not reached (NO), Wait until a predetermined time T4 is reached.
In step S45, a fourth recording command is output to the head unit controller HUD, the head unit HU4 is started to form dots Dt, and the process proceeds to step S46.

In this step S46, it is determined whether or not the fourth recording has ended. If it is determined that the recording has ended (YES), the process proceeds to step S47, and if it is determined that it has not ended (NO), Wait until the fourth recording is completed.
In step S47, the capturing of the belt displacement data is stopped, and the process proceeds to step S48.

In step S48, the timer Tm1 is reset, and the process returns to the head unit position adjustment process shown in FIG. 5 (return).
In the head unit position adjustment process shown in FIG. 5, when the minimum dot interval ΔYmin is increased, the minimum dot interval ΔYmin is calculated in step S5, and it is determined whether the minimum dot interval ΔYmin is within the allowable range in step S6. In step S8, the movement amount ΔX that maximizes the minimum dot interval ΔYmin within the movable range of the head unit HUi may be set.

In the present embodiment, the belt displacement meter DM corresponds to the meandering detecting means, and the laminated piezoelectric actuator PZ corresponds to the head moving means.
With the above, it is possible to change the interval between the dots Dt at the recording boundary between the head units HUi without interfering with each other, and the interval between the dots Dt is increased or becomes dense. This can reduce the unevenness of the recording density.
In addition, since the inkjet recording apparatus 1 includes the belt displacement meter DM and the dot position reading unit SC, the head unit HUi can be moved at a desired timing in the non-recording state.

1 is an external view showing a main configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 3 is an external view illustrating a paper transport unit of the ink jet recording apparatus according to the embodiment of the invention. FIG. 3 is a diagram illustrating a configuration of a recording head of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing a connection of control of main parts of the ink jet recording apparatus according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a flow of head unit position adjustment processing of the ink jet recording apparatus according to the embodiment of the invention. FIG. 4 is a diagram illustrating a test recording process flow of the ink jet recording apparatus according to the embodiment of the present invention. The figure explaining the effect of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet recording device, HU1-HU4 ... Head unit, HD ... Recording head, KH ... Recording width, DM ... Belt displacement meter, PZ ... Multilayer piezoelectric actuator, SC ... Dot position reading unit

Claims (3)

An inkjet recording apparatus that performs recording by ejecting ink droplets from nozzles onto a recording surface that is opposite to a conveyance surface of a recording medium that is placed on a conveyance belt and conveyed.
A plurality of head units having a recording width in which a plurality of the nozzles are arranged over a predetermined length are crossed with the recording medium conveyance direction so that the recording width intersects the recording medium conveyance direction. A recording head having a configuration aligned in parallel with each other in a direction to be
An ink jet recording apparatus, wherein an alignment position of each head unit of the recording head is adjusted according to a meandering amount of the conveying belt. An inkjet recording apparatus that performs recording by ejecting ink droplets from nozzles onto a recording surface that is opposite to a conveyance surface of a recording medium that is placed on a conveyance belt and conveyed.
A plurality of head units having a recording width in which a plurality of the nozzles are arranged over a predetermined length are crossed with the recording medium conveyance direction so that the recording width intersects the recording medium conveyance direction. A recording head having a configuration in which the recording heads are aligned parallel to each other;
Meander detection means for detecting the amount of meander of the conveyor belt;
Based on the detected meandering amount, the head unit is within a range in which the plurality of head units do not overlap each other when viewed from a direction perpendicular to the recording medium conveyance direction along the recording medium conveyance direction. An ink jet recording apparatus comprising: a head moving unit that moves the head. Image reading means for reading the test pattern from the recording medium in which the ink droplets are ejected from the nozzles at least at the ends of the plurality of head units to form a test pattern;
The head moving unit is configured to reduce a maximum value among dot intervals at a boundary portion between the head units adjacent to each other in a direction intersecting a conveyance direction of the recording medium based on read image information of the test pattern. The inkjet recording apparatus according to claim 2, wherein the head unit is moved so as to perform either one of the minimum value increases.

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