JP5365779B2 - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus capable of decreasing positional shift of recording in the recording medium conveying direction with high accuracy. <P>SOLUTION: The inkjet recording apparatus has a conveying positional shift correcting means which performs a correction processing on the conveying positional shift by: recording a dot A on a sheet by using a predetermined nozzle of a recording head mounted on a carriage (Step S13); thereafter, rotating a roller by a predetermined distance L as its outer peripheral distance to convey the sheet by a conveying means (Step S14); detecting the conveying position of the dot A on the sheet by a sensor provided separately from the predetermined nozzle by the predetermined distance L on the downstream side in the conveying direction of the sheet (Step S15); obtaining a difference of the conveying distance from the detected conveying position of the dot A and a theoretical conveying position on the sheet, according to the rotating position of the roller (Step S16); and correcting and sets the amount of rotation of the roller when recording the image on the sheet, based on a relation between the rotating position of the roller and the difference of the conveying distance (Step S17 and S18). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image forming position control technique in an ink jet recording apparatus, and more particularly to control of a conveyance roller for conveying a recording medium.

  In an ink jet image forming apparatus (also referred to as an ink jet recording apparatus or a recording apparatus), ink is ejected from a recording head during reciprocation in the main scanning direction, and recording is performed on a recording medium. Then, the recording medium is transported in the sub-scanning direction using a transport roller, and an image is formed by repeating recording in the main scanning direction.

  In general, when a recording medium such as a sheet is conveyed by a conveyance roller or the like, the conveyance amount varies depending on the attachment state of the conveyance roller, the type of the recording medium, or the like. Thus, for example, Patent Document 1 discloses a technique for recording a plurality of test patterns using different correction values and determining a correction value for the carry amount based on the printing result. That is, a pattern that is an optimum printing result is selected from the printed test patterns, and parameters for driving the transport roller are determined.

However, in the technique disclosed in Patent Document 1 described above, the following problem occurs when there is a change in the conveyance amount within one rotation (one cycle) of the roller.
The first problem is that a correction value depending on the phase of the conveying roller when performing the adjustment operation is set, so that a different correction value is determined each time the adjustment operation is performed, resulting in stable image quality. There is a point that cannot be realized.
A second problem is that it is impossible to correct image formation unevenness called white streak or black streak due to fluctuation within one rotation of the roller.

  With respect to this problem, in Patent Document 2, in the recording apparatus, a conveying unit that conveys the recording medium by rotating a roller and a detecting unit that detects the conveyance amount of the recording medium conveyed by the rotation of the roller of one rotation or less. And an acquisition means for acquiring a conveyance amount of the recording medium with respect to a predetermined rotation amount of the roller by detecting the conveyance amount a plurality of times, and an acquisition medium based on the acquired conveyance amount of the recording medium with respect to the predetermined rotation amount of the roller. It has been proposed to reduce the positional deviation of the recording in the recording medium conveyance direction by setting the rotation amount of the roller when forming an image on the recording medium.

  However, in the technique disclosed in Patent Document 2 described above, a reference pattern for detecting a transport position deviation is recorded while moving the recording head in the main scanning direction, and the detection means is also in the main scanning direction in the same manner as the recording head. Since the density of the reference pattern is read while being moved, the transport amount to be set includes a movement error of the recording head and the detection means, and an accurate transport amount cannot be obtained. The deviation could not be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides an ink jet recording apparatus that can reduce a positional deviation of recording in a recording medium conveyance direction with high accuracy.

The present invention provided to solve the above problems is as follows.
[1] A recording head (recording head 34) having a nozzle array (nozzle array 34L) that discharges ink onto the recording medium (sheet P) and the recording head are mounted, and the recording medium is orthogonal to the nozzle array. A carriage (carriage 33) that scans in the direction, a conveying means (motor drive unit 128) that conveys the recording medium by rotating a roller (conveying roller R4), and a predetermined nozzle (in a nozzle row of the recording head in the carriage) is arranged from a predetermined nozzle 34n) at a position away only the predetermined distance of the recording medium conveyance direction downstream side, the area image sensor for detecting an image recorded on a record medium (pattern position detecting sensor 20), the predetermined nozzle The test image (dot A) is recorded on the recording medium in a state where the carriage scanning and the conveyance of the recording medium are stopped. After recording (step S13), the recording medium is conveyed by rotating the roller by a rotation angle corresponding to a predetermined distance by the conveying means (step S14), and then the test on the recording medium detected by the area image sensor. A difference in conveyance distance is obtained from the image conveyance position (step S15) and the theoretical conveyance position on the recording medium in correspondence with the rotation position of the roller (step S16), and the difference between the roller rotation position and the conveyance distance is obtained. Based on the relationship, a rotation amount of the roller when an image is recorded on the recording medium is corrected and set (steps S17 and S18), a conveyance position deviation correction unit (CPU 120) that performs conveyance position deviation correction processing, and Storage means (RAM 123) for storing the rotation amount of the roller set by the conveyance position deviation correction means in correspondence with the rotation position of the roller The ink jet recording apparatus provided with (FIGS. 1 to 4, 8, 12).
[2] The inkjet recording apparatus according to [1], wherein the conveyance position deviation correction process by the conveyance position deviation correction unit is repeatedly performed a predetermined number of times (step S19).
[3] The ink jet recording apparatus according to [1], wherein the test image is recorded at a central portion or an end portion in the main scanning direction of the transport roller (FIGS. 15A and 15B) .
[4 ] The conveyance position deviation correction unit is the same as detecting the first test image (dot A) by the area image sensor and recording the second test image (dot B) by the recording head. The inkjet recording apparatus according to [1], which is performed at a conveyance timing (step S15, FIG. 13).

  According to the present invention, the sensor for detecting the conveyance position deviation is provided downstream of the nozzle array of the recording head in the recording medium conveyance direction, so that the positional deviation of the conveyance of the recording medium corresponds to the rotation position of the conveyance roller. Therefore, it is possible to detect with high accuracy and to reduce the positional deviation of the recording in the recording medium conveyance direction.

FIG. 3 is a perspective explanatory view of the ink jet recording apparatus according to the present invention as viewed from the front side. It is principal part plane explanatory drawing of the mechanism part of the apparatus. It is the schematic which shows the structure of the conveyance mechanism of the apparatus. FIG. 2 is a control block diagram of the ink jet recording apparatus of FIG. 1. It is a figure which shows typically the fluctuation | variation of the conveyance amount in 1 period of conveyance rollers. FIG. 6 is a schematic diagram illustrating a difference in sheet conveyance amount depending on the shape of a conveyance roller. It is a figure which shows typically the change of the conveyance amount by the position (phase) of a conveyance roller. It is a perspective view which shows the relationship (1) with the recording head, the pattern position detection sensor, and sheet | seat in the inkjet recording device of this invention. It is a figure which shows roughly the structure of a pattern position detection sensor. It is a figure which shows the mode of the incident of the illumination light to the prism of a pattern position detection sensor. It is a figure which shows the state by which the dot on the sheet | seat was detected by the pattern position detection sensor. 5 is a flowchart illustrating a processing procedure for correcting a conveyance position deviation of a sheet with a period of one rotation of a conveyance roller in the inkjet recording apparatus of the present invention. It is a perspective view which shows the relationship (2) with the recording head in the inkjet recording device of this invention, a pattern position detection sensor, and a sheet | seat. It is a figure which shows the relationship between the dot detected by the pattern position detection sensor, and the dot of a theoretical value. FIG. 6 is a diagram illustrating a carriage arrangement position when performing correction processing of a sheet conveyance position deviation with one rotation of a conveyance roller in the inkjet recording apparatus of the present invention.

The configuration of the ink jet recording apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective explanatory view of the ink jet recording apparatus according to the present invention as viewed from the front side.
The ink jet recording apparatus is detachably mounted on the apparatus main body 1, a paper feed tray 2 for loading paper (hereinafter, also referred to as a sheet) that is a recording medium mounted on the apparatus main body 1, and the apparatus main body 1. And a paper discharge tray 3 for stocking paper on which images are recorded (formed). Further, a cartridge loading for loading an ink cartridge that protrudes from the front surface to the front side of the apparatus main body 1 and is lower than the upper surface is provided at one end side of the front surface of the apparatus main body 1 (side of the paper supply / discharge tray section). The cartridge loading unit 4 has an operation / display unit 5 provided with operation buttons and a display.

  The cartridge loading unit 4 contains a plurality of recording liquids (inks) that are different color materials, such as black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink. Ink cartridges 10k, 10c, 10m, 10y (referred to as “ink cartridge 10” when colors are not distinguished) from the front side to the rear side of the apparatus main body 1 A front cover (cartridge cover) 6 that is opened when the ink cartridge 10 is attached or detached is provided on the front side of the cartridge loading portion 4 so as to be openable and closable. Further, the ink cartridges 10k, 10c, 10m, and 10y are configured to be loaded side by side in a vertical state.

  Further, the operation / display unit 5 includes ink remaining amounts of the ink cartridges 10k, 10c, 10m, and 10y of the respective colors at the arrangement positions corresponding to the mounting positions (arrangement positions) of the ink cartridges 10k, 10c, 10m, and 10y of the respective colors. Are arranged for displaying the remaining amount display portions 11k, 11c, 11m, and 11y for each color (when the colors are not distinguished, they are referred to as “remaining amount display portion 11”). Further, the operation / display unit 5 is also provided with a power button 12, a paper feed / print resume button 13, and a cancel button 14.

Next, the mechanism part of the ink jet recording apparatus will be described with reference to FIG. FIG. 2 is an explanatory plan view showing the main part of the mechanism.
A carriage 33 is slidably held in the main scanning direction by a guide rod 31 and a stay 32 which are horizontally mounted on left and right side plates 41A and 41B constituting the frame 41, and a timing belt is held by a main scanning motor (not shown). 3 is moved and scanned in the directions of the left and right arrows (carriage main scanning direction) in FIG.

  As described above, the carriage 33 includes a recording head 34 including four droplet discharge heads that discharge ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). A plurality of ink ejection openings are arranged as nozzle rows in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  As an inkjet head constituting the recording head 34, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. It is possible to use a shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like provided as pressure generating means for generating a pressure for discharging a droplet.

  A driver IC is mounted on the recording head 34 and is connected to a control unit (not shown) via a harness (flexible print cable) 42.

  In addition, the carriage 33 is equipped with a recording head 34 and sub tanks 35 for each color for supplying ink of each color to the recording head 34 as image forming means. As described above, each color sub-tank 35 is supplementarily supplied with ink of each color from the ink cartridge 10 of each color mounted in the cartridge loading unit 4 in a one-to-one relationship via the ink supply tube 36 of each color. Is done. The cartridge loading unit 4 is provided with a supply pump 44 for feeding ink in the ink cartridge 10, and the ink supply tube 36 is engaged with the rear plate 41 C constituting the frame 41 in the middle of turning. It is held by a stop member 45.

  Further, as shown in FIG. 2, in the non-printing area on one side (right side in the figure) of the carriage 33 in the scanning direction (main scanning direction), the recovery means for maintaining and recovering the nozzle state of the recording head 34 A maintenance / recovery mechanism 81 is disposed.

  The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a to 82d (hereinafter referred to as “caps 82” when not distinguished from each other) for capping the nozzle surfaces of the recording head 34, and nozzle surfaces. A wiper blade 83 that is a blade member for wiping the ink, and an empty discharge receiver 84 that receives liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing. Here, the cap 82a is a suction and moisture retention cap, and the other caps 82b to 82d are moisture retention caps.

  In addition, as shown in FIG. 2, in the non-printing area on the other side (left side in the figure) of the carriage 33 in the scanning direction, liquid droplets that do not contribute to recording are discharged in order to discharge the recording liquid thickened during recording. An empty discharge receiver 88 that receives liquid droplets when performing empty discharge is disposed, and the empty discharge receiver 88 is provided with an opening 89 along the nozzle row direction of the recording head 34.

FIG. 3 shows a sheet (paper) transport mechanism in the ink jet recording apparatus according to the present invention. FIG. 3 shows a conveyance path of the sheet P from the paper stacking portion exit side of the paper feed tray 2 to the carriage 33.
The sheets P stacked on the paper stacking portion of the paper feed tray 2 are sent out one by one by the first roll pair R1, and are clutched by the second roller pair R2. Next, the sheet P clutched by the rotation of the second roller pair R2 is sent out, and at the same time, the leading edge and the trailing edge of the sheet P fed by the sheet feeding encoder 51 are detected. The sheet P that has passed through the third roller pair R3, which is a guide roller, is detected by the sheet feed outlet sensor 53 and the pre-registration sensor 54, while the sheet P positioned before the area where the carriage 33 is scanned. It is sent to a conveyance roller R4 as a conveyance means.

  The transport roller R4 is formed by a pair of rollers coming into contact with each other, and is configured to be rotationally driven in the transport direction (sub-scanning direction) of the sheet P through a timing by a sub-scanning motor (not shown). . Further, the rotation axis of any one of the transport rollers R4 includes an HP that detects when a specific point on the circumference of the cross section of the roller reaches a specific rotation angle position as an initial position (home position (HP)). A sensor 55 and a sub-scanning encoder 56 that detects the leading and trailing ends of the sheet P at the roller contact portion of the conveying roller R4 and detects the theoretical conveying distance from the rotation angle of the roller are provided.

  After the leading edge of the sheet P is detected by the roller contact portion of the transport roller R4, the sheet P is transported to the stage 57 below the carriage 33 by the rotational driving of the transport roller R4.

The stage 57 has a front suction fan and a rear suction fan that suck and fix the sheet P.
Further, the sheet P recorded by the recording head 34 is discharged to the discharge tray 3 through a predetermined discharge roller.

  In the ink jet recording apparatus configured as described above, the sheets P are separated and fed one by one from the sheet feed tray 2, and the fed sheets P are guided substantially vertically upward by the rollers R1, R2, and R3, and the transport roller It is sandwiched between R4 roller pairs and conveyed to the stage 57. Here, when the sheet P reaches a predetermined position, the rotation of the transport roller R4 is stopped, and the sheet P is fixed on the stage 57 by suction of the suction fan.

  Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped sheet P to record one line, and after the sheet P is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet P has reached the recording area, the recording operation is terminated and the sheet P is discharged onto the discharge tray 3.

  Further, during printing (recording) standby, the carriage 33 is moved to the maintenance / recovery mechanism 81 side, and the recording head 34 is capped by the cap 82 to keep the nozzles in a wet state, thereby preventing ejection failure due to ink drying. . Further, the recording liquid is sucked from the nozzle by a suction pump (not shown) with the recording head 34 capped by the cap 82 (referred to as “nozzle suction” or “head suction”), and the thickened recording liquid and bubbles are discharged. Perform recovery action. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. As a result, the stable ejection performance of the recording head 34 is maintained.

FIG. 4 is a control block diagram of the ink jet recording apparatus shown in FIGS.
The control unit 100 is a unit that controls the entire apparatus, a unit that controls the sheet conveyance operation and the movement operation of the carriage 33, a CPU 120 that also performs arithmetic processing, a program executed by the CPU 120, and other fixed data such as fonts. A ROM 121 for storing, and a RAM 123 used for a buffer for temporarily storing a work area used for calculation, image data, and the like, and also controls image processing for performing various signal processing and rearrangement and other overall devices (mechanism) It also has a function of processing input / output signals for control, memory control, and I / F control with the CPU 120.

  The control unit 100 also generates a host I / F 124 that receives a print job from a host PC that is a data processing apparatus such as a personal computer equipped with a printer driver, a drive waveform for driving the recording head 34, and the like. An image output control unit 125 that controls output, a digital I / O 126 that receives output signals from the digital sensor 112 mounted on the carriage 33 and the digital sensor 134 mounted on the apparatus body, and outputs control signals to various actuators 135; The output signal of the analog position sensor 136 such as a pattern position detection sensor 20 (details will be described later) arranged on the carriage 33 and an encoder sensor for acquiring the moving speed and position information of the carriage 33 in the main scanning direction is converted into a digital value. The ADC 127 to be converted and the carriage 33 are scanned. It includes a motor driving unit 128 for driving the sub scanning motor various motor 137 for rotating the conveyance roller R4 for conveying a main scanning motor and the sheet P in order, the. In controlling the mechanism of the inkjet recording apparatus, the control unit 100 appropriately monitors the outputs of the digital sensors 112 and 134, the pattern position detection sensor 20, and the analog sensor 136, and grasps and controls the operation state of each mechanism. It is carried out.

  Here, in the control unit 100, a print job including image data from the host PC side such as a data processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera is transmitted via a cable or a network. And received by the host I / F 124. Then, in accordance with the program stored in the ROM 121, the CPU 120 and the RAM 123 read and analyze the print data in the reception buffer included in the host I / F 124, perform data rearrangement processing, etc. The image data is transferred to the image output control unit 125, and the image data and the drive waveform are output from the image output control unit 125 to the head driver 34a at a required timing.

  The head driver 34a selectively records drive pulses constituting a drive waveform supplied from the image output control unit 125 based on image data (dot pattern data) corresponding to one line of the recording head 34 input serially. The recording head 34 is driven by applying the pressure to the pressure generating means of the head 34.

Here, a change in the conveyance amount of the sheet P by the conveyance roller R4 is considered.
As described above, the conveyance of the sheet P under the carriage 33 is realized by rotating the conveyance roller R4. For example, when the outer circumference of the conveying roller R4 is 129 mm, the recording medium is conveyed by 129 mm by rotating the roller once. However, in general, a slight shift in the conveyance amount occurs when the sheet P is conveyed by the conveyance roller. That is, even if the sheet P is transported by a predetermined amount, a sheet transport misalignment that causes a recording scheduled portion on the sheet P to deviate from the target position under the carriage 33 occurs.

This cause can be broadly divided into one caused by the condition (paper condition) of the sheet P to be conveyed and one caused by the conveyance roller R4 that conveys the sheet P.
First, the factors on the side of the sheet P are conditions under which the contact state and the friction state with the conveying roller R4 fluctuate. For example, the width (A0 to A5 size, etc.), thickness, friction coefficient, etc. The conveyance position deviation correction of the sheet P, which will be described later, is preferably performed for each sheet condition such as the size, thickness, type, and paper quality of the sheet P to be used because the condition of the conveyance roller R4 in the inkjet recording apparatus is fixed.

Next, factors on the transport roller R4 side will be described.
FIG. 5 is a diagram schematically illustrating a change in the conveyance amount in one roller period. In FIG. 5, the vertical axis represents the feed fluctuation amount, and the horizontal axis represents the sheet conveyance amount. As can be seen from the figure, the conveyance amount of the sheet P can be expressed by the following two components.

  The first is a fixed component (A in FIG. 5) within one rotation of the roller depending on the sheet type, the machine body, and the environment. The second is a fluctuation component (B in FIG. 5) having a cycle of one rotation of the roller depending on the roller accuracy, the deflection of the roller, and the attachment of the roller support member. That is, the sheet conveyance amount can be approximated by adding these two components.

  Incidentally, since the fixed component (A in FIG. 5) depends on the use environment, it is necessary to perform the registration adjustment in an environment where the recording operation is actually performed. On the other hand, since the fluctuation component (B in FIG. 5) depends on the individual, adjustment may be performed once at the time of shipment.

  FIG. 6 is a schematic diagram illustrating the difference in sheet conveyance amount depending on the cross-sectional shape of the conveyance roller R4.

  Assuming that the roller rotation angle for sheet conveyance is uniform, when the roller cross-sectional shape is a perfect circle, the conveyance amount when the roller is rotated by the angle “R” is shown in FIG. Thus, it is the same L0 at any position. However, when the roller cross section has an irregular shape, the conveyance amount when the roller is rotated by an angle “R” varies depending on the rotational position of the roller. For example, as shown in FIG. 6B, when the roller cross-sectional shape is an ellipse, the sheet is conveyed by L1 in rotation at a certain position. Further, the sheet P is conveyed by L2 at different positions. In this case, there is a relationship of L1> L0> L2, and sheet conveyance fluctuations depending on the roller cycle occur. The transport amounts L0, L1, and L2 substantially coincide with the arc length at the angle “R”.

  When there is such a variation in the sheet conveyance amount depending on the roller cycle, the actual image is affected. When there is a variation in the sheet conveyance amount depending on the roller cycle, it means that the landing position of the droplet is biased depending on the rotation position of the conveyance roller R4.

  In FIG. 6, the generation of the conveyance amount fluctuation component within one rotation of the roller has been described using the difference between whether the roller cross-sectional shape is a perfect circle or an ellipse. The factors that cause the fluctuation component are not only the cross-sectional shape of the roller, but also, for example, displacement (eccentricity) of the rotation axis of the conveyance roller R4, deflection of the conveyance roller R4, or expansion of the conveyance roller R4 due to the influence of ambient temperature or humidity Other factors can be considered.

Next, the influence on the recording due to the variation of the sheet conveyance amount depending on the roller cycle will be considered.
First, when the position of the conveying roller R4 is at L1 in FIG. 6B, the sheet conveyance becomes larger than usual, so that the recording is performed below the position where recording is actually desired (backward in the conveying direction). On the other hand, when the conveyance roller position is at L2 in FIG. 6B, the sheet conveyance is smaller than usual, so the image to be recorded is recorded above the ideal position (front in the conveyance direction). For this reason, a density difference occurs when an image having a uniform density is recorded. This unevenness is remarkably confirmed in a single image such as a background of a landscape image, which is an adverse effect of high-quality printing.

  By the way, normally, when adjusting the sheet conveyance amount, it means adjusting a fixed component (A in FIG. 5) depending on the sheet type, the machine body and the environment. In the conventional technique, the shift amount of the transport amount is derived using the adjustment pattern and used as the transport adjustment value. However, the position at which the adjustment value of the fixed component is acquired changes depending on the timing of performing the registration adjustment operation due to the influence of the above-described fluctuation component.

  FIG. 7 is a diagram schematically illustrating a change in the conveyance amount depending on the position (phase) of the conveyance roller R4. When the registration adjustment is performed at the position (1) in FIG. 7, an adjustment value larger than the fixed component is acquired, and an adjustment value smaller than the fixed component is acquired at the position (3). By deriving the conveyance amount adjustment value at the position (2) in FIG. 7, the amount corresponding to the fixed component can be derived almost correctly. However, since the fluctuation component depends on the roller accuracy in the conveying roller R4, the deflection of the roller, and the attachment of the roller support member as described above, it is generally difficult to specify this position.

  However, as described above, the variation in the conveyance amount varies with a period corresponding to one rotation of the conveyance roller. In particular, as shown in FIG. 5, when the fluctuation cycle can be approximated by one cycle of the sin function, the fluctuation amounts at the two points corresponding to 1/2 rotation of the transport roller have the same absolute value and are positive and negative. Can be understood to be the opposite fluctuation amount.

  In the present invention, such a change in the transport amount of the transport roller R4 is detected, and the driving of the transport roller R4 is controlled based on the detection result so that proper transport is performed. Hereafter, the principal part of this invention is demonstrated.

  FIG. 8 is a perspective view showing the relationship between the recording head 34 which is an ink discharge unit, the pattern position detection sensor 20 provided on the carriage 33, and the sheet P which is a recording medium in the ink jet recording apparatus of the present invention.

  In the ink jet recording apparatus according to the present invention, the carriage 33 is arranged at a position separated from the predetermined nozzle 34n of the nozzle row 34L of the recording head 34 by a predetermined distance L on the downstream side in the sheet P (recording medium) conveyance direction. A pattern position detection sensor 20 for detecting an image recorded in the recording medium. In FIG. 8, the pattern position detection sensor 20 is provided so as to correspond to one nozzle row 34 </ b> L, but a plurality of recording heads (that is, a plurality of nozzle rows) are provided by one pattern position detection sensor 20 provided on the carriage 33. ).

  Here, first, the sheet P is conveyed by the rotation of the conveying roller R4 immediately below the recording head 34, and a test image (dot A), which is a position detection pattern, is formed by ink discharge using at least the predetermined nozzle 34n. Next, the sheet P is conveyed by a predetermined distance L, and this conveyance amount (predetermined distance L) is controlled by position information of a sub-scanning encoder 56 mounted on a rotation shaft of a conveyance roller R4 (not shown). Then, the test image (dot A) on the sheet P is detected by the pattern position detection sensor 20, and the difference of the transport distance from the transport position of the test image and the theoretical transport position of the sheet P is determined by the transport roller R4. The conveyance position deviation is calculated in correspondence with the rotation position (details will be described later).

  The predetermined distance L may be a length obtained by equally dividing the outer peripheral length of one round of the transport roller R4 into a plurality of parts. For example, when the diameter of the transport roller R4 is 41 mmφ, the length obtained by dividing the outer peripheral length by 12 (that is, the transport distance when the transport roller R4 is rotated by 30 °, about 10 mm) is defined as the predetermined distance L.

  FIG. 9 is a diagram illustrating a schematic configuration of a pattern position detection sensor 20 that detects a test image that is a position detection pattern formed on the sheet P, and FIG. 10 is a diagram illustrating a state in which illumination light is incident on the prism. is there. The pattern position detection sensor 20 uses a two-dimensional image sensor 21 so that a light beam from an illumination light source 23 constituted by an LED as a light source does not directly enter the image sensor 21 by a light shielding member 22. The light beam from the illumination light source 23 enters the triangular prism 24 from the total reflection surface 24 a of the triangular prism 24, and is refracted as shown in FIG. 9 due to the influence of the refractive index of the triangular prism 24. Is led to the main surface 25 on which is formed. The reflected light from the main surface 25 is totally reflected by the total reflection surface 24a of the triangular prism 24 and passes through the imaging lens 26 and the reflection surface 27a of the triangular prism 27 to the image sensor 21 formed on the same member as the illumination light source 23. Led. Reference numeral 28 denotes a substrate. As the image sensor 21, for example, a CCD image sensor (Charge Coupled Device Image Sensor), which is a solid-state image sensor, may be used as an area image sensor.

This state will be described with reference to FIG. The luminous flux of the light source (LED) 23 enters the prism 24 from the inclined surface of the triangular prism 24. Assuming that the incident angle from the light source (LED) 23 to the inclined surface of the prism 24 is θ0, the penetration angle into the prism 23 is θ1, and the refractive index of the prism 24 is n1, the penetration angle θ1 is
θ1 = Sin−1 (1 / n1) sin θ0)
For example, when the incident angle θ0 = 60 degrees, θ1 = 35.3 degrees.

  Since the bottom surface 24b of the prism 24 is disposed substantially parallel to the main surface 25 and the inclined surface 24a has an angle of 45 degrees with respect to the bottom surface 25b, the illumination light hits the main surface 25 substantially perpendicularly. Become.

  Next, in FIG. 9, the diffused light of the illuminated pattern again enters the prism 24 almost perpendicularly, and is reflected at right angles by total reflection on the inner surface of the inclined surface 24 a of the triangular prism 24. Thus, since the optical axis is parallel to the main surface 25, the height is not increased unnecessarily in the height direction. The light beam reflected at right angles passes through the imaging lens 26, is reflected by the inclined surface 27 a of the triangular prism 27, and forms an image on the image sensor 21.

  FIG. 11 shows a state in which a test image (dot A) formed on the image sensor 21 in the pattern position detection sensor 20 and detected on the sheet P is detected. Note that a rectangular area surrounded by a dotted line is an area (detection area 25a) detected by the image sensor 21, and in the drawing, the upward direction from the bottom is the conveyance direction of the sheet P. Here, the sheet P is conveyed as the theoretical value, and the dot A is detected at the center of the detection area 25a (the intersection of the vertical and horizontal center lines).

  Note that the triangular prism 27 is a reflective surface by processing the slope 27a such as aluminum vapor deposition. Further, the triangular prism 27 may be a reflecting surface and does not need to be a triangular prism. When the optical axis is not folded back, when a lens 26 with a focal length of about 8 mm is used, the height H is required to be 40 mm or more. In this method, the size can be reduced to a height H of 20 mm, which is half or less. it can.

Next, a correction method and processing procedure for the conveyance position deviation of the sheet P in the inkjet recording apparatus of the present invention will be described.
FIG. 12 is a flowchart showing a processing procedure for correcting the conveyance position deviation of the sheet P with one rotation of the conveyance roller R4 in the inkjet recording apparatus of the present invention. Hereinafter, a conveyance position deviation correction method will be described in accordance with this procedure.

(S11) While transporting the sheet P, the transport roller R4 is moved to the initial position (HP) using the HP sensor 55.
(S12) Next, the carriage 33 is moved in the main scanning direction, and is arranged at a position where it is desired to measure the influence (conveyance position deviation) of the variation in the conveyance amount with one rotation of the conveyance roller R4 as a cycle.
(S13) The dot A, which is a test image, is recorded on the sheet P by using at least the predetermined nozzle 34n of the recording head 34 in the scanning stopped state (FIG. 8). At this time, recording may be performed by ejecting a plurality of times continuously from the predetermined nozzle 34n, or may be performed by ejecting once from a plurality of nozzles including the predetermined nozzle 34n. Moreover, the shape of the dot A should just be a shape which can be detected as a conveyance position with the pattern position detection sensor 20, for example, may be a round dot pattern.

(S14) Next, the conveying roller R4 is rotated by a predetermined distance L as its outer peripheral distance, and the sheet P is conveyed and stopped. At this time, since the rotation angle (for example, 30 °) in the transport roller R4 corresponding to the predetermined distance L is known, the sub-scanning encoder 56 is used to rotate the transport roller R4 for the rotation angle (30 °). Do.
(S15) The pattern position detection sensor 20 detects the center position of the dot A on the sheet P. That is, the pattern position detection sensor 20 detects the XY coordinate position of the center position of the dot A in the detection area 25a, and stores the XY coordinate position information in the RAM 123 of the control unit 100 shown in FIG. At this time, at least the predetermined nozzle 34n of the recording head 34 in the scanning stopped state is used to record the next test image dot B on the sheet P (FIG. 13). The method and shape for recording the dots B may be the same as those for the dots A.
(S16) The XY coordinate position information of the dot A detected in step S15 is compared with the theoretical value. That is, in the RAM 123, the theoretical value of the position detected when the center point (the origin of the XY coordinates) in the X axis and Y axis in the detection area 25a of the pattern position detection sensor 20 is not decentered in the transport roller R4. By storing the difference in the conveyance position of the position of the dot A detected in step S15 with respect to this theoretical value, the conveyance position deviation of the sheet P due to the eccentricity of the conveyance roller R4 can be detected. For example, this arithmetic processing may be performed by the CPU 120 in the control unit 100 of FIG.

FIG. 14 is a diagram showing how the dot position A is detected by the pattern position detection sensor 20.
For example, assuming that the sheet P is conveyed in an ideal state (for example, a state where the rotation axis of the conveyance roller R4 is not eccentric) as the conveyance roller R4 rotates, the sheet P is conveyed by a predetermined distance L. (Conveyance amount L ′ = L in FIG. 13). For this reason, the dot A that has been directly under the predetermined nozzle 34n moves by a predetermined distance L and comes directly under the pattern position detection sensor 20 that is the theoretical transport position. As a result, the detected dot A overlaps with the dot position of the theoretical value, the center position of the dot A becomes substantially the same as the center of the detection area 25a of the pattern position detection sensor 20, and the positional deviation from the theoretical value does not occur. The difference between the transport positions that has not occurred = 0 (FIG. 14A). On the other hand, if the transport roller R4 is decentered, the decentration directly leads to rotational unevenness, that is, variation in the transport amount. Therefore, the dot A displayed on the pattern position detection sensor 20 deviates from the theoretical dot position. The center position of A is shifted from the center of the detection area 25a (FIG. 14B). In FIG. 14B, the position of the dot A (the position of the black circle) shows the result of being transported a distance y ahead of the theoretical dot position (the position of the dotted circle).

(S17) A correction value is calculated based on the transport position deviation amount obtained in step S16 (difference in the transport position of the detected dot A with respect to the theoretical value). For example, it is a value that cancels out the transport position deviation amount (difference in the transport position of the detected dot A with respect to the theoretical value). For example, in the case of FIG. 14B, on the premise of the rotation angle of the transport roller R4 in step S14, the correction value -y is set so as to cancel the transport position deviation amount y.
(S18) In the rotational position of the transport roller R4 involved in the transport of the dot A (from step S11, the rotation section from the initial position of the transport roller R4 to a predetermined rotational angle) is set as the printing operation condition up to the previous time. The set amount of the transported sheet P (that is, the rotation angle (rotation amount) of the transport roller R4) is set to the transport amount (rotation amount) subjected to the eccentricity correction by reflecting the correction value calculated in step S17. The data is stored in the RAM 123 of the control unit 100.
Up to here, the conveyance position deviation correction process in one printing / conveying operation is completed.

(S19) Next, it is confirmed whether or not the rotation of the transport roller R4 so far has made one rotation or more from the initial position (HP).
When the transport roller R4 does not make one rotation (N in S19), the processing from step S14 to step S18 is performed. That is, the carriage 33 is not moved, and the sheet P is conveyed by rotating the conveying roller R4 by a predetermined distance L with the outer peripheral distance thereof as in Step S14. This time, the dot B is placed under the pattern position detection sensor 20. Therefore, the position information is detected, and the conveyance amount of the sheet P (that is, the rotation amount of the conveyance roller R4) set as the printing operation condition at the rotation position of the conveyance roller R4 involved in the conveyance of the dot B is set. The value is corrected and stored in the RAM 123. At the same time, the dot C as the next test image is recorded on the sheet P using at least the predetermined nozzle 34n. Such correction processing of the conveyance position deviation in one printing / conveying operation is performed a plurality of times until the rotation of the conveyance roller R4 reaches one rotation or more. For example, when one conveyance is the rotation angle 30 ° of the conveyance roller R4, the above correction process is performed 12 times.
Then, when the rotation of the transport roller R4 reaches one rotation or more from the initial position (HP) (Y in S19), the process is terminated.

  In the above description, the case where a test image is recorded by one recording head 34 has been shown. However, as long as it falls within the detection area 25a of the pattern position detection sensor 20, a plurality of recording heads 34 are used to record test images. It may be recorded.

  Further, the above processing is performed for each paper condition such as the size, thickness, type, and paper quality of the sheet P to be used, and when a temperature / humidity sensor is provided, whenever the ambient temperature and humidity of the transport roller R4 change. It is good to do.

  Further, the arrangement of the carriage 33 at this time may be the central portion or the end portion of the transport roller R4 in the main scanning direction. That is, when the central portion of the transport roller R4 touches the sheet P, it is preferable to arrange the carriage 33 at the central portion in the width direction of the sheet P (FIG. 15A) and transport the end portion of the sheet P. In this case, it is preferable to dispose the carriage 33 at the end in the width direction of the sheet P (FIG. 15B).

  Further, heretofore, the conveyance position deviation correction processing (processing for correcting a variation in the conveyance amount with one rotation of the conveyance roller R4 as a cycle) has been described at one location in the main scanning direction of the conveyance roller R4. In the case of a long roller corresponding to the A0 size, there is a possibility that fluctuations in the conveyance amount with one rotation of the conveyance roller R4 are different at different positions in the main scanning direction of the conveyance roller R4. . Therefore, as shown in FIG. 15C, the conveyance position deviation correction processing (processing for correcting the variation in the conveyance amount with one rotation of the conveyance roller R4 as a cycle) shown in FIG. 12 at a plurality of locations in the main scanning direction. It is preferable to set the correction amount according to the size of the sheet P to be used and perform the eccentricity correction of the transport roller R4. When performing correction processing of the conveyance position deviation (processing for correcting a variation in the conveyance amount with one rotation of the conveyance roller R4) at a plurality of positions in the main scanning direction of the conveyance roller R4, the sheet P is wasted. In order to prevent the sheet P from being moved, the sheet P is reversely fed after the conveyance position deviation correction process (process for correcting the conveyance amount fluctuation with one rotation of the conveyance roller R4) and the position of the position where the process is performed. It may be performed next (in the main scanning direction). In addition, when carrying position correction processing (processing for correcting fluctuations in the conveyance amount with one rotation of the conveyance roller R4) is performed at a plurality of locations in the main scanning direction of the conveyance roller R4, depending on the situation, An average value (average value in the main scanning direction) of correction values obtained in all the above processes, or a representative value that is maximum or minimum may be used as the correction value.

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Paper feed tray 3 Paper discharge tray 4 Cartridge loading part 5 Operation / display part 10, 10k, 10c, 10m, 10y Ink cartridge 11k, 11c, 11m, 11y Remaining quantity display part 12 Power button 13 Paper feed / Resume printing Button 14 Cancel button 20 Pattern position detection sensor 21 Image sensor 22 Light blocking member 23 Illumination light source 24, 27 Triangular prism 25 Main surface 25a Detection area 26 Imaging lens 28 Substrate 31 Guide rod 33 Carriage 34 Recording head 34a Head driver 34L Nozzle array 34n Predetermined nozzle 35 Sub tank 36 Ink supply tube 41 Frame 44 Supply pump 51 Paper feed encoder 53 Paper feed outlet sensor 54 Pre-registration sensor 55 HP sensor 56 Sub scanning encoder 57 Stage 8 DESCRIPTION OF SYMBOLS 1 Maintenance recovery mechanism 82,82a, 82b, 82c, 82d Cap 83 Wiper blade 84,88 Empty discharge receptacle 89 Opening 100 Control part 112 Digital sensor 120 CPU
121 ROM
123 RAM
124 Host I / F
125 Image output control unit 126 Digital I / O
127 ADC
128 Motor drive unit 135 Various actuators 136 Analog sensor 137 Various motors A, B dots (test image)
PC Printer driver R1, R2, R3 Roller R4 Transport roller

JP 2003-011344 A JP 2007-261262 A

Claims (4)

A recording head having a nozzle array for discharging ink onto the recording medium;
A carriage mounted with the recording head and scanning the recording medium in a direction perpendicular to the nozzle rows;
A conveying means for conveying the recording medium by rotating a roller;
Wherein arranged from a predetermined nozzle of the nozzle array in only distant but a predetermined distance of the recording medium conveyance direction downstream side of the recording head, and the area image sensor for detecting an image recorded on a record medium in said carriage,
A test image is recorded on the recording medium in a state where scanning of the carriage and conveyance of the recording medium are stopped using at least the predetermined nozzle, and then the roller is rotated by a rotation angle corresponding to a predetermined distance by the conveying unit. The recording medium is transported, and the difference in the transport distance from the transport position of the test image on the recording medium detected by the area image sensor and the theoretical transport position on the recording medium is made to correspond to the rotational position of the roller. Based on the relationship between the roller rotation position and the difference in conveyance distance, the conveyance position deviation correction processing is performed to correct and set the rotation amount of the roller when recording an image on the recording medium. Correction means;
Storage means for storing the rotation amount of the roller set by the conveyance position deviation correction means in correspondence with the rotation position of the roller;
An inkjet recording apparatus comprising:   The inkjet recording apparatus according to claim 1, wherein the conveyance position deviation correction process by the conveyance position deviation correction unit is repeatedly performed a predetermined number of times.   The inkjet recording apparatus according to claim 1, wherein the test image is recorded at a central portion or an end portion in the main scanning direction of the transport roller. 2. The inkjet according to claim 1, wherein the conveyance position deviation correction unit detects the first test image by the area image sensor and records the second test image by the recording head at the same conveyance timing. Recording device.

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