JP2009214397A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation device which can correct the registration gap of each color caused by the eccentric center of the drive roller of a conveying means in the image formation device which forms an ink discharge timing of a recording head in line with the conveyance state of the conveying means (conveyance state of a recording medium). <P>SOLUTION: The image formation device is equipped with a block 25 for computing the conveyance speed of the recording medium from turning radius change data of rotor of the conveying means, a block 26 for computing the conveyance speed per pixel from this conveyance speed and an image resolution in the subscan direction, a block 27 which computes a conveyance time lags by comparing this conveyance time with the ideal conveyance time per pixel according to the image resolution of this subscan direction, and a block 32 for forming a record timing for some one pixel of the recording medium in the subscan direction from these conveyance time lags, a datum point detecting signal of rotor, a criteria timing pulse and the image resolution in the subscan direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an ink jet printing apparatus.

  An ink jet printing apparatus which is one of image forming apparatuses is a non-contact printing process. For this reason, the recording medium and the ink ejection timing are likely to be out of synchronization, and as a result, the image is distorted or the density is uneven.

  As shown in FIG. 1, the main cause of the synchronization shift is a conveying belt driving roller constituting a conveying means (or a roller pair that directly conveys a recording medium instead of a roller that drives a belt). Is greatly affected by the eccentricity (deviation between the roller center and the rotation center). Further, as shown in FIG. 2, there is an influence that the radius of rotation from the center of the driving roller changes due to variations in the thickness (distance to the core) of the conveying belt constituting the conveying means. In particular, in a line type recording head printing system in which a recording medium is continuously conveyed at a constant speed and the recording heads are arranged in a direction perpendicular to the conveying direction, unlike a serial type printing machine, a plurality of It is difficult to employ correction means such as recording over and over, and image distortion and density unevenness are more likely to occur.

  Therefore, means for detecting the speed, moving distance (per unit time) and moving time (per unit distance) of the recording medium are provided in the means for conveying the recording medium, and the conveying state of the conveying means (recording) A synchronization method for generating the ink ejection timing of the recording head in accordance with the (medium feeding state) is considered and is already known (Patent Documents 1 to 3).

  FIG. 3 shows one conventional example (extracted from FIG. 1 of Patent Document 1). In this example, detection means (91) for directly detecting the conveyance speed is provided on the conveyance means (54) of the recording medium, and the recording of the recording head (63, 64, 65, 66) is performed based on the speed information. The timing is adjusted by the control unit (92).

  Further, in Patent Document 2, for the purpose of correcting the registration deviation of each color, a speed detecting means for generating a pulse corresponding to the transport speed and a means for counting the pulse are provided on the transport path of the transport means, A system in which the recording timing is generated and the recording medium and the recording head are synchronized, and the speed detection means is arranged upstream (recording medium conveyance path) from the recording head, or the speed detection means are homogeneous. A configuration is disclosed in which a pair of rollers are made of a medium having a diameter and rotate while sandwiching the belt from above and below.

  Further, in Patent Document 3, for the purpose of correcting registration shift of each color, a detection roller that rotates as the conveyance belt of the conveyance unit moves and a detection unit that detects the rotation amount of the detection roller are provided, A synchronization method that adjusts the recording timing, and the arrangement interval of multiple recording heads is an integral multiple of the outer circumference of the detection roller, or the detection roller is composed of a pickup roller and an encoder that rotate as the conveyor belt moves. Or a configuration in which the recording timing adjustment means of the recording head counts the pulses of the encoder.

  However, in the ink jet printing apparatus that generates the ink discharge timing of the recording head in accordance with the transport state of the transport unit (the feeding state of the recording medium), a new detection unit is used to detect the transport state of the transport unit. In addition to increasing the cost, it is necessary to provide an arrangement space on the conveying means, and it is necessary to extend the conveying distance (enlarge the conveying means), and finally the apparatus itself Affects the size of Further, since the detection means is provided on the conveyance means, it becomes a load on the conveyance means, and it may be necessary to improve the performance of a motor or the like that drives the conveyance means.

  Further, in the conventional method, since the pickup roller is installed on the conveying means, it is affected by a detection error due to the eccentricity of the pickup roller. For this purpose, a new error detection means is provided as a correction means (cost increase, configuration expansion).

  Further, the detection error itself has a three-stage structure of driving roller → conveying belt → pickup roller, and thus may be accumulated. In particular, in the configuration as described above, an accurate speed cannot be detected due to sliding with the pickup roller at the contact portion with the conveying means, which causes an error to be accumulated.

  As described above, in the conventional printing apparatus, in order to compensate for the registration deviation of each color due to the variation in the conveyance speed of the conveyance means, a new detection means is provided, which is accompanied by cost increase, expansion of the apparatus, and newly added means. There is a problem in that errors in the system accumulate, and erroneous speed detection is performed on the contrary, resulting in an increase in registration deviation of each color.

Japanese Patent No. 2820433 Japanese Patent No. 2918905 Japanese Patent No. 2945412

The present invention has been made in view of the above-described problems in the prior art. In an image forming apparatus that generates ink discharge timings of a recording head in accordance with the conveyance state of a conveyance unit (the feeding state of a recording medium), Image formation that can correct registration deviation of each color caused by eccentricity of the driving roller of the conveying means without providing an expensive and complicated conveying state detecting means on the conveying path to detect the conveying state of the means An object is to provide an apparatus.
It is another object of the present invention to provide an image forming apparatus capable of correcting a registration shift of each color caused by variations in the thickness (heart position) of the conveying belt of the conveying unit.

  The inventor has arranged an inkjet recording head in which a plurality of nozzles are arranged in a nozzle row direction which is a direction (main scanning direction) orthogonal to the recording medium conveyance direction, and configured as a line type recording head. In the (non-contact printing process), intensive studies were conducted for the purpose of achieving higher accuracy in the synchronization deviation (landing position accuracy) between the conveyance state of the recording medium and the ink ejection timing from the recording head, and the idea of the present invention It came.

The present invention provided to solve the above problems is as follows.
[1] A recording head having a nozzle array (recording head arrays 9 to 12) in which a plurality of nozzles that eject ink on a recording medium (recording medium 7) are arranged in at least one direction (main scanning direction); Conveying means (driving roller 4, driven roller 5, conveying belt 7, driving roller pair 4a, 4b, driven roller pair 5a, 5b) for conveying the recording medium in a direction orthogonal to the main scanning direction (sub-scanning direction) , A rotating body (driving roller 4) having a reference point (reference point 1) and driving the conveying means by rotating, and the rotation A reference point detection sensor (reference point detection sensor 2) for detecting a reference point of the body, and a reference timing pulse generating means for generating a reference timing pulse as a starting point of recording in the sub-scanning direction according to the image resolution in the sub-scanning direction ( Vice Scanning reference timing pulse generating means 3) and speed change data calculating means (speed change data) for calculating change data of the conveyance speed of the recording medium based on the rotation radius change data (drive roller rotation radius change data 20) of the rotating body. A transport time change data calculating means for calculating transport time change data per pixel from the transport speed change data and the image resolution in the sub-scanning direction with reference to the calculation block 25) and the reference point of the rotating body. The transport time change data calculation block 26) per pixel is compared with the transport time change data and the ideal transport time per pixel according to the image resolution in the sub-scanning direction, and the transport time shift amount is calculated. A transport time shift amount data calculation means (transport time shift amount data calculation block 27) for calculating, the transport time shift amount and the reference point detection sensor; Based on the quasi-point detection signal, the reference timing pulse, and the image resolution in the sub-scanning direction, sub-scanning recording timing generating means (sub-scanning recording timing) for generating recording timing in the sub-scanning direction for one pixel of the recording medium. And an image forming apparatus (FIG. 5).
[2] The image forming apparatus according to [1], wherein the image resolution in the sub-scanning direction is selected from a predetermined image resolution range.
[3] The image forming apparatus according to [2], wherein the rotation radius change data of the rotating body is data measured in advance.
[4] The image forming apparatus according to [1], further including a rotation radius change measurement sensor (rotation radius change measurement sensor 34) that measures rotation radius change data of the rotating body (FIG. 16). .
[5] The rotation radius change data of the rotating body is measured by the rotation radius change amount measurement sensor at all times at regular intervals, at any time other than during a print job, or at the time of starting up the image forming apparatus. The image forming apparatus according to [4].
[6] The image forming apparatus according to any one of [1] to [5], wherein the conveying unit is an endless belt (conveying belt 6) driven by the rotating body.
[7] The belt has a second reference point (conveying belt reference point 35) on the belt rotation circumference, and a second reference point detection sensor (belt reference inspection) that detects the second reference point of the belt. Output sensor 38), pulse counting means (conveyance belt address counter 45) for counting the reference timing pulse starting from the second reference point, and a specific pattern set in advance for a plurality of recording media (FIGS. 20 and 21) is driven in synchronism with a reference timing pulse for each predetermined pulse count value, and the print head is driven and printed (print head array control block 33), and the printed specific pattern Printing state measuring means (printing state measuring means 36) for measuring the printing state at predetermined intervals on the rotation circumference of the belt, and the printing state measurement result set in advance Print state variation amount calculating means (print state variation amount calculation block 42) for comparing the print state setting value and calculating the variation amount of the print state on the belt rotation circumference, and the variation amount as the pitch of the image resolution. Variation amount interpolation data calculation means (variation amount interpolation data calculation block 43) for calculating the variation amount interpolation data by performing interpolation according to the sub-scanning recording timing generation means, the variation amount interpolation data and the transport The image forming apparatus according to [6], wherein a recording timing in the sub-scanning direction for the one pixel is generated based on a time shift amount, the reference timing pulse, and the image resolution in the sub-scanning direction. FIG. 17, FIG. 18, FIG.
[8] The image forming apparatus according to [7], wherein the variation amount interpolation data calculation unit calculates variation amount interpolation data by a linear interpolation method or a polynomial approximation interpolation method (FIGS. 26 and 27). .

According to the present invention, in the image forming apparatus that generates the ink discharge timing of the recording head in accordance with the conveyance state of the conveyance unit (the feeding state of the recording medium), it is expensive to detect the conveyance state of the conveyance unit. Without providing a complicated conveyance state detection unit on the conveyance path, it is possible to correct the registration shift of each color caused by the eccentricity of the driving roller of the conveyance unit in a simple form. Further, the correction can be made without any adverse effects caused by the provision of new means.
That is, in order to correct registration deviation caused by the eccentricity of the drive roller of the transport unit, a detection unit for newly detecting the transport state is not provided on the transport unit, but a drive roller having a reference point; The detection means for detecting the reference point is provided in the conveyance means, and the dispersion of the conveyance state is calculated from the eccentricity data of the driving roller measured in advance, and the recording timing is generated. Can be corrected in a simple manner.
Further, according to the present invention, in an image forming apparatus that generates the ink discharge timing of the recording head in accordance with the conveyance state (recording medium feeding state) of the conveyance unit, it is expensive to detect the conveyance state of the conveyance unit. Thus, the registration deviation of each color caused by the variation in the thickness of the conveying belt (the core position) of the conveying means can be corrected in a simple form without providing the complicated conveyance state detecting means on the conveying path. Further, the correction can be made without any adverse effects caused by the provision of new means.
That is, the correction of the registration deviation accompanying the variation in the conveyance belt thickness (center position) of the conveyance means does not provide a detection means on the conveyance means for newly detecting the conveyance state, but conveys a reference point. A belt and a detecting means for detecting the reference point are provided in the conveying means, the position of the conveying belt is grasped from the conveying belt reference point, and a plurality of recording media exceeding the conveying belt circumferential length are conveyed. , Print a specific pattern set in advance corresponding to the position on the transport belt, measure the print state, grasp the amount of variation in the transport belt thickness (heart position) from the print state, calculate, Since the recording timing is generated, registration deviation of each color can be corrected in a simple form.

The image forming apparatus according to the present invention will be described below.
[First Embodiment]
FIG. 4 shows a schematic configuration of an ink jet printing apparatus as a first embodiment of an image forming apparatus according to the present invention.
In the ink jet printing apparatus of the present invention, a conveyance belt 6 is stretched around a driving roller (rotating body) 4 and a driven roller 5 to convey a recording medium 7 in a direction perpendicular to the main scanning direction (sub scanning direction). And a recording head having a recording head row (nozzle row) 9, 10, 11, 12 in which a plurality of nozzles for recording by discharging ink onto the recording medium 7 are arranged in at least one direction (main scanning direction). And a recording medium detection sensor 8 and a control unit 21 for controlling each unit of the apparatus.

  The drive roller 4 has a reference point 1 and is a rotating body that drives the conveying means by rotating. By providing a reference point detection sensor 2 that detects the reference point 1, a rotation circle of the drive roller 4 is provided. A specific position on the circumference can be detected. The driving roller 4 is connected to a sub-scanning reference timing pulse generating means 3 such as a rotary encoder that outputs a sub-scanning reference timing pulse 14, and the resolution is the maximum sub-scanning resolution that can be set by the printing apparatus. It has become. These reference point 1 and sub-scanning timing pulse generation means 3 can identify the position of the drive roller 4 on the rotation circumference.

  A control line 19 entering the control unit 21 is a signal output from a host computer (not shown) and is a signal for setting the sub-scanning resolution (image resolution in the sub-scanning direction) of the printing apparatus. The sub-scanning resolution is selected from a predetermined image resolution range. The control line 20 is rotation radius change data of the driving roller 4 and is radius data measured with the reference point 1 of the driving roller 4 as a starting point, and the resolution is the same as that of the sub-scanning reference timing pulse 14. Data 20 measured in pitch units of the maximum sub-scanning resolution that can be set by the apparatus. Alternatively, the rotation radius change data 20 of the driving roller 4 (see FIG. 6) that can be calculated by calculation from the measured maximum value, minimum value, and reference point phase information (phase shift amounts from the maximum value and minimum value). Both are data for one rotation of the driving roller 4.

  By these inputs, the control unit 21 starts from the sub-scanning resolution setting signal 19 and the reference point 1 of the driving roller 4 that drives the conveying means, and can calculate from the rotation radius change data 20 of the driving roller 4 of the conveying belt 6. Control of the recording head arrays 9 to 12 is performed so that the conveyance variation amount is obtained and the recording timing (ink ejection timing) of the recording head arrays 9 to 12 is shifted from the sub-scanning reference timing pulse signal 14 by the calculated variation amount. Control signals 15-18.

FIG. 5 is a block diagram showing control blocks in the control unit 21 of FIG. A control data processing procedure performed by the control unit 21 will be described with reference to FIG.
(S11) First, the rotation radius change data reception block 24 receives the rotation radius change data 20 of the drive roller 4 via a control line from the host computer. The drive roller rotation radius change data 20 is the radius change data of the drive roller 4 measured in advance in the printing device manufacturing process or the like at the maximum resolution pitch in the sub-scanning direction that can be set by the printing device, or the measurement maximum value, the measurement The minimum value and the phase information of the reference point 1 (maximum value, phase shift amount from the minimum value) are passed and expanded in the reception block 24 (the method is explained in FIG. 6), and then temporarily stored. The

Here, referring to FIG. 6, in the rotation radius change data reception block 24, the measurement maximum value, the measurement minimum value, and the phase information of the reference point 1 (the amount of phase deviation from the maximum value and the minimum value) of the driving roller 4 ) Will be described.
A broken line indicated by L ′ in FIG. 6A indicates the circumference of the drive roller 4, the point B indicates the center of the drive roller 4, and θ ′ is the reference point 1 centered on the point B. An angle (a recording medium entering side in the recording medium conveyance direction (sub-scanning direction) is 0 degree, and the rotation direction of the driving roller 4 is a plus angle). On the other hand, the point A indicates the rotation center of the drive roller 4, and Δx (= point A−point B) indicates the eccentricity. Further, the maximum radius rmax is from the point A to the L` broken line in the horizontal direction on the right side of the drawing, and the minimum radius rmin is shown from the L` broken line in the left direction on the drawing. At this time, if the theoretical radius value (measurement average value) of the driving roller 4 is r ′, the radius of the rotating body having a certain eccentricity is expressed by the following equations (1) and (2). Is done.

y = r` · sinθ` (1)
x = r`, cos [theta] `+ [Delta] x Expression (2)

Next, from the equations (1) and (2), the distance r from the point A to the reference point 1 is expressed by the following equation (3).
r = √ (x ^ 2 + y ^ 2)
= √ ((r ′ · cos θ ′ + Δx) ^ 2 + (r ′ · sin θ ′) ^ 2) (3)

Here, r ′ and Δx are as in equations (4) and (5).
r` = (maximum radius + minimum radius) / 2 Formula (4)
Δx = (maximum radius−minimum radius) Expression (5)

Further, the phase information (phase shift amount from the maximum value and the minimum value) of the reference point 1 is a parameter related to θ` in the above equation (3), and is maximum at a position rotated by 30 ° from the position of the reference point 1. When there is a radius, the expression (3) becomes the following expression (6).
r = √ ((r ′ · cos (θ′−30) + Δx) ^ 2 + (r ′ · sin (θ′−30)) ^ 2)
... Formula (6)

Therefore, an equation for calculating the turning radius change data from the measurement maximum value, the measurement minimum value, and the phase information of the reference point (phase shift amount from the maximum value and the minimum value) is expressed by the following equation (7) (FIG. 7). 6 (b)). Α is a rotation angle from the position of the reference point 1 to a position having a maximum radius, and α = 270 ° in FIG. 6B.
r = √ ((r ′ · cos (θ′−α) + Δx) ^ 2 + (r ′ · sin (θ′−α)) ^ 2) [mm]
... Formula (7)

As for the interval (resolution) for calculating the rotation radius change data of the driving roller 4, it is sufficient that the maximum resolution that can be printed by the printing apparatus is satisfied as the minimum unit. That is, in this embodiment, 600 dpi is the maximum resolution, and the driving roller 4 is configured so that the sub-scanning reference timing pulse generation unit 3 shown in FIG. 4 also outputs pulses at an interval equivalent to 600 dpi (0.0423 mm / dot). It is connected with. Therefore, the rotation radius change data is also calculated from the reference point 1 of the drive roller 4 at every 600 dpi pitch.
Thereafter, the calculation is performed for each of the intervals up to the conveyance speed change data, the conveyance time change data per pixel, and the conveyance time deviation amount data which will be sequentially described with reference to FIG. 5, and the result can be obtained.
The calculation interval may be equal to or greater than the maximum resolution of the printing apparatus, and is preferably a sub-scanning resolution that can be set by the printing apparatus and all the greatest common divisors.

(S12) Next, the temporary storage data is transferred to the speed change data calculation block 25, and the radius data is converted into speed data by the calculation formula (8) in FIG.

FIG. 7 is an explanatory diagram of a method for converting the rotation radius change data into the conveyance speed change data.
In FIG. 7, based on the rotation radius change data r shown in FIG. 6 (FIG. 7A), it is converted into the conveyance speed change data V at that radius (FIG. 7B).
Here, the calculation formula used for the conversion is the following formula (8).
V = 2 · π · r · R / 60 [mm / s] (8)
(Here, r represents rotation radius change data [mm], and R represents drive roller rotation speed [rpm].)

(S13) Next, the converted data is passed to the transport time change data calculation block 26 per pixel, and the speed data is converted into transport time change data per pixel by the calculation formula (9) in FIG. The Here, one pixel means the maximum resolution that can be set by the printing apparatus, and is 600 dpi in this embodiment.

FIG. 8 is an explanatory diagram of a method for converting the conveyance speed change data into the conveyance time change data per pixel.
In FIG. 8, based on the transport speed change data V shown in FIG. 7 (FIG. 8A), it is converted into transport time change data t at the transport speed (FIG. 8B).
Here, the calculation formula used for the conversion is the following formula (9).
t = (25.4 / Z) / V [s] (9)
(Here, Z indicates the maximum sub-scanning resolution [dpi] that can be set by the printing apparatus.)

(S14) Next, the converted data is transferred to the conveyance time deviation amount data calculation block 27 and converted into deviation amount data from the ideal conveyance time for each pixel by the calculation formula (10) in FIG. Next, the data is transferred to and stored in the transport time deviation amount data storage block 28.

FIG. 9 is an explanatory diagram of a method for converting the transport time change data per pixel into transport time shift amount data per pixel.
9, the transport time at that time is based on the transport time change data t shown in FIG. 8 (FIG. 9A) and the ideal transport time t0 that can be calculated from the maximum resolution that can be set by the printing apparatus. It is converted into deviation amount data Δt (FIG. 9B).
Here, the calculation formula used for the conversion is the following formula (10).
Δt = t−t0 [s] (10)
(Here, t0 indicates the period required per pixel when printing is performed at an ideal speed and discharge interval (period) at the maximum sub-scanning resolution [dpi] that can be set by the printing apparatus.)

(S15) In the transport time deviation amount data storage block 28, the data output operation is managed in addition to the storage operation so far, and the address counter operates in synchronization with the drive roller reference signal 13 and the sub-scanning reference timing pulse signal 14. In accordance with the address value generated by 29, the transport time deviation amount data is output to the sub-scanning recording timing pulse value addition / subtraction block 31.

(S16) In the sub-scanning recording timing pulse value addition / subtraction block 31, the sub-scanning recording timing ideal pulse value selected by the sub-scanning recording timing ideal pulse selection block 30 according to the sub-scanning resolution setting signal 19 received from a host computer (not shown), Based on the output data from the transport time deviation amount data storage block 28 and the sub-scanning resolution setting signal 19, the sub-scanning recording timing pulse count value is added or subtracted and output to the sub-scanning recording timing generation block 32.

(S17) The sub-scan recording timing generation block 32 counts the internal clock 23 using the detection signal of the recording medium 7 from the recording medium detection sensor 8 and the print permission signal 22 from the host computer as an operation permission condition, thereby sub-recording. A scan recording timing pulse is generated. Note that the count start trigger at this time is the sub-scanning reference timing pulse signal 14.

(S18) Next, the recording head array control block 33 outputs control signals 15 to 18 to the recording head arrays (nozzle arrays) 9, 10, 11, and 12 in synchronization with the generated sub-scan recording timing pulse. Print control.

  With the above configuration, in order to correct the registration deviation caused by the eccentricity of the driving roller 4 of the transport unit, a detection unit for newly detecting the transport state is not provided on the transport unit, but the reference point 1 is set. A drive roller 4 having a reference point detection sensor 2 for detecting the reference point 1 is provided in the transport means, and the dispersion of the transport state is calculated from the eccentricity data of the drive roller 4 measured in advance, and the recording timing Therefore, the registration shift of each color can be corrected in a simple form.

FIG. 10 shows another configuration example of the ink jet printing apparatus according to this embodiment.
In FIG. 10, the conveying means is not the conveying belt system in the ink jet printing apparatus shown in FIG. 4, but a conveying roller pair (4a, 4b, 5a, 5b). In the figure, the same components as those of the ink jet printing apparatus of FIG.
In this case, the rotating body (driving roller) in the present invention becomes the pair of rollers 4a and 4b on the upstream side of the recording head arrays 9 to 12 as the recording medium conveyance direction, and the reference point 1 and the sub-scanning reference timing pulse are applied to the driving roller 4a. The generation unit 3 is provided, and the reference point detection sensor 2 is arranged to be attached thereto. In addition, the processing procedure of the control data performed by the control unit 21 is the procedure S11 to S18 (FIG. 5).

Here, some citation examples of the rotation radius change data when calculating the transfer speed change data in the speed change data calculation block 25 are shown.
(Example 1)
A configuration in which the conveyance speed change data is calculated from the rotation radius change data at one point on the circumference of the drive roller 4.
FIG. 11 shows an example thereof, in which the rotation radius change data section to be cited is limited when calculating the conveyance speed change data. Here, the calculation is made using one point of the apex (the top in the height direction) of the driving roller 4 of the conveying means.

(Example 2)
As shown in FIG. 4, in the case of being constituted by the conveying belt 6 and the driving roller 4 that drives the conveying belt 6, it is within a range of 1/4 of the driving roller 4 that affects the recording medium conveying speed (0 to 90 degrees). The structure which calculates conveyance speed change data from the rotation radius change data of one point.
FIG. 12 shows an example of this, and the rotation radius change data section to be cited is limited when calculating the conveyance speed change data. Here, the calculation is made by using one point in the range of the region rotated 90 degrees in the rotation direction from the apex (the top in the height direction) of the driving roller 4 of the conveying means.

(Example 3)
As shown in FIG. 4, when the conveyor belt 6 and the driving roller 4 that drives the conveyor belt 6 are used, the average value of the rotation radius change data in the range of 1/4 on the circumference of the driving roller 4 is as shown in FIG. 4. In addition, when it is configured by the conveying belt 6 and the driving roller 4 that drives the conveying belt 6,
FIG. 13 shows an example thereof, and the rotation radius change data section to be cited is limited in calculating the conveyance speed change data. Here, the calculation is made using the average radius within the range of the region rotated 90 degrees in the rotation direction from the apex (the top in the height direction) of the driving roller 4 of the conveying means.

(Example 4)
As shown in FIG. 4, when the conveyance roller 6 and the driving roller 4 that drives the conveyance belt 6 are used, the rotation radius change at one point within the belt winding angle of the driving roller 4 that affects the recording medium conveyance speed. Configuration that calculates transfer speed change data from data.
FIG. 14 shows an example thereof, in which the rotation radius change data section to be cited is limited when calculating the conveyance speed change data. Here, the calculation is made by using one point within the winding angle of the conveying belt 6 in the driving roller 4 of the conveying means.

(Cited example 5)
As shown in FIG. 4, when the conveyor belt 6 and the driving roller 4 that drives the conveyor belt 6 are used, the conveyance speed change data is calculated from the average value of the rotation radius change data within the belt winding angle of the drive roller 4. Constitution.
FIG. 15 shows an example thereof, and the rotation radius change data section to be cited is limited when calculating the conveyance speed change data. Here, the calculation is made by using the average radius within the range of the winding angle of the conveyor belt 6 in the driving roller 4 of the conveyor.

Note that the inkjet printing apparatus of the present invention preferably includes a rotation radius change amount measuring sensor that measures rotation radius change data of the driving roller 4 that is a rotating body.
FIG. 16 shows a configuration of an ink jet printing apparatus including a rotation radius change amount measuring sensor. In the figure, the same components as those of the ink jet printing apparatus of FIG. 4 are denoted by the same reference numerals.
Here, a rotation radius change amount measuring sensor 34 for directly measuring the rotation radius of the driving roller 4 is provided inside the conveying means, and the control data processing procedure performed by the control unit 21 is based on the measured rotation radius. Reference is made instead of the turning radius change data 20 input from the host of FIG. 4, and the other steps are the same as those in steps S11 to S18 (FIG. 5). It is configured to do. It should be noted that the execution timing of the rotation radius change data of the drive roller 4 by the rotation radius change amount measurement sensor 34 is always at regular time intervals, except during a print job, immediately after starting the printing apparatus (when the power is turned on) ) Is preferably performed at any time.

[Second Embodiment]
FIG. 17 shows a schematic configuration of an ink jet printing apparatus as a second embodiment of the image forming apparatus according to the present invention. In the figure, the same components as those of the ink jet printing apparatus of FIG. 4 are denoted by the same reference numerals.
As shown in FIG. 17, in addition to the configuration of the inkjet printing apparatus shown in FIG. 4, the inkjet printing apparatus of the present invention uses an endless belt having a reference point 35 as a second reference point for the conveyor belt 6. A belt reference point detection sensor 38 as a second reference point detection sensor for detecting the reference point 35 is provided, and the sub-scanning reference timing pulse signal 14 from the sub-scanning reference timing pulse generating means 3 and its pulse signal are counted. The specific position on the conveyor belt 6 can also be specified by combining the pulse counting means (in the control unit 21).

  Further, the control unit 21 includes a printing control unit for outputting a preset specific pattern for printing and a specific pattern in synchronization with the pulse count, and a printing state for measuring the printing state in synchronization with the pulse count. A means for calculating the variation amount of the printing state from the signal from the measuring means 36 and the printing state measurement signal 37, a variation amount interpolation data calculating means for calculating the interpolation data in accordance with the sub-scanning resolution pitch, and a memory for storing it A sub-scanning resolution setting signal 19 and a reference point 35 of the conveyor belt as a starting point, a transport variation amount of the transport belt 6 that can be calculated is obtained, and the recording timing of the recording head arrays 9 to 12 is set to the sub-scan reference timing pulse signal 14. Therefore, the control signals 15 to 18 of the print head array are controlled so as to shift by the calculated variation amount.

  When the specific pattern is printed, control is performed by a conveyance belt correction control signal 40 output from the host so that the series of conveyance belt correction control is invalid.

  18 and 19 are block diagrams showing control blocks in the control unit 21 of FIG. A control data processing procedure performed by the control unit 21 will be described with reference to FIGS.

First, FIG. 18 shows a drive roller eccentricity correction control block in the control unit 21.
(S21) First, the rotation radius change data reception block 24 receives the rotation radius change data 20 of the drive roller 4 via a control line from the host computer. The drive roller rotation radius change data 20 is the radius change data of the drive roller 4 measured in advance in the printing device manufacturing process or the like at the maximum resolution pitch in the sub-scanning direction that can be set by the printing device, or the measurement maximum value, the measurement The minimum value and the phase information of the reference point 1 (maximum value, phase shift amount from the minimum value) are passed, developed in the reception block 24, and temporarily stored. The method is the same as step S11 in the first embodiment.

(S22) Next, the temporary storage data is transferred to the speed change data calculation block 25, and the radius data is converted into speed data by the calculation formula (8) in FIG.

(S23) Next, the converted data is passed to the transport time change data calculation block 26 per pixel, and the speed data is converted into transport time change data per pixel by the calculation formula (9) in FIG. The Here, one pixel means the maximum resolution that can be set by the printing apparatus, and is 600 dpi in this embodiment.

(S24) Next, the converted data is passed to the transport time deviation amount data calculation block 27 and converted into deviation amount data from the ideal transport time for each pixel by the calculation formula (10) in FIG. Next, the data is transferred to and stored in the transport time deviation amount data storage block 28.

(S25) In the transport time deviation amount data storage block 28, the data output operation is managed in addition to the storage operation so far, and the address counter operates in synchronization with the drive roller reference signal 13 and the sub-scanning reference timing pulse signal 14. In accordance with the address value generated by 29, the transport time deviation amount data is output to the sub-scanning recording timing pulse value addition / subtraction block 31 of FIG. 19 (control line 41).

FIG. 19 shows a conveyance belt correction control block in the control unit 21.
(S26) First, in the printing state variation calculation block 42, an address value (generated by the conveyor belt address counter 45) obtained by counting the sub-scanning reference timing pulse signal 14 with the conveyor belt reference signal 39 as a starting point. Value), the print state measurement result of the specific pattern (FIG. 20, FIG. 21: held in the specific pattern data storage block 46) printed out from the recording head row control block 33 is output from the print state measuring means 36. An output signal and a print state measurement signal 37 are captured.

20 and 21 show the specific pattern.
FIG. 20 shows an example of a specific pattern used for printing state measurement, and shows a pattern arranged every other pixel in the recording medium conveyance direction (sub-scanning direction). In the case of measuring the printing state using such a pattern, it may be a reflection density or a distance between line pitches.

  FIG. 21 shows an example of a specific pattern used for the print state measurement, as in FIG. 20. One pixel is arranged in the nozzle arrangement direction (main scanning direction) and the recording medium conveyance direction (sub-scanning direction). A checkered pattern arranged every other pattern is shown. In such a pattern, the print state measurement target is limited to the reflection density, but since a large area can be averaged and measured, there is a tendency that the measurement error of the measuring means is hardly affected. However, if the pattern has a print area ratio exceeding 50%, the print areas in pixel units overlap, and it is difficult to recognize minute differences.

Note that the printing interval of the specific pattern (= printing state measurement interval) is executed at regular intervals as shown in FIGS.
FIG. 22 is a diagram illustrating an example of a constant interval measured by the printing state measuring unit 36, and illustrates a configuration example of the conveying belt 6 and the driving roller 4 of the conveying belt. When such a conveying means is provided, the actual conveying speed of the recording medium 7 is within the range where the conveying belt 6 and the driving roller 4 are in contact with each other from the apex (the top in the height direction) of the driving roller 4 to the rotation direction. The average radius (distance to the core of the conveyor belt 6) within the region rotated 90 degrees is considered to be affected, and the interval, that is, the region rotated 90 degrees in the rotation direction from the apex of the drive roller 4 ( If the printing state is measured every 1/4 rotation), the fluctuation in the conveyance speed due to the variation in the thickness (center position) of the conveyance belt 6 can be grasped.

  FIG. 23 is a diagram showing an example of a constant interval measured by the printing state measuring unit 36 as in FIG. 22, and shows a configuration example of the transport belt 6 and the drive roller 4 of the transport belt. When such a conveyance means is provided, the actual conveyance speed of the recording medium 7 is an average radius within a range where the conveyance belt 6 and the driving roller 4 are in contact with each other, that is, a conveyance belt winding angle region (conveyance belt). If the printing state is measured every interval (1/4 rotation) rotated 90 degrees in the rotation direction from the apex of the driving roller 4, it is conveyed. Variations in the conveyance speed due to variations in the thickness (heart position) of the belt 6 can be grasped.

Further, the total total distance is executed until it becomes equal to or more than one round of the conveyor belt 6 as shown in FIG.
FIG. 24 is an explanatory diagram of the total total distance in which the printing state is measured by the printing state measuring unit 36, and is an image diagram in which the transport belt 6 is cut at one place and developed. The total distance for printing a specific pattern (FIGS. 20 and 21) set in advance and measuring the printing state is set to be equal to or more than one turn of the conveyor belt 6. Further, as shown in FIGS. 22 and 23, the specific pattern is printed by ejecting ink at a fixed interval target, but is not printed in the absence of the recording medium 7. Further, regarding the printing interval, printing is performed at a predetermined interval from the starting point of the reference point 35 of the conveyor belt 6.

  As shown in FIG. 25, the variation amount calculation method based on the print state measurement signal 37 measured in this way is obtained as an average value of all acquired data or a ratio to a preset expected value.

FIG. 25 is an explanatory diagram of a method for calculating the printing state variation amount data from the printing state measurement signal 37, and a method for calculating the printing state variation amount from the printing state measurement result performed in the printing state variation amount calculation block 42. Is shown. Plots (◯) in the figure are the print state measurement results (y1, y2,..., Yn) for each position (address) on the conveyor belt 6, and the one-dot chain line is the print state measurement results. All average values (yavg) are shown. Here, the print state measurement result shows the reflection density as an example.
In the printing state variation calculation block 42, relative to which level each measurement data (y1, y2,..., Yn) is based on the average value of all data or the preset expected value. Make a comparison. A value expressed by this ratio is a value when the sub-scan recording timing is generated. That is, as a result of a certain measurement point (y1), y1 = 0.8, the average value at that time (y
When avg) is y avg = 1.0, the printing state variation amount data is 0.8 (= 80%). In the sub-scanning recording timing pulse value addition / subtraction block 31 described later, the conveyance time deviation amount data is subtracted from the sub-scanning recording timing ideal pulse value, and 80% of the result (the ratio obtained by the printing state variation amount calculation block 42). ) As a sub-scanning recording timing pulse value and output to the sub-scanning recording timing generation block 32.

(S27) The calculation result is passed to the variation amount interpolation data calculation means 43, and becomes a data group for each maximum sub-scanning resolution pitch that can be set by the printing apparatus by the data interpolation method as shown in FIGS. In the same manner, the interpolation process is performed.

FIG. 26 shows an example of a method for calculating variation amount interpolation data from the printing state variation amount data shown in FIG. 25 as a method for calculating variation amount interpolation data from the printing state variation amount data. Here, variation amount interpolation data is calculated by linear interpolation connecting two data points with a straight line.
FIG. 27 shows an example of a method for calculating variation amount interpolation data from the printing state variation amount data shown in FIG. 25. Here, polynomial approximation interpolation (order) taking into account the distribution state of all data. Performs 6).

(S28) Here, the interpolated data for each maximum resolution pitch is stored in the variation amount interpolation data storage block 44.
The flow up to this point is a flow for acquiring data for carrying belt correction control. During this time, a variation amount interpolation data storage block 44 is used by a carrying belt correction control signal 40 from the host so as not to be affected by the carrying belt correction. Is configured to output a predetermined constant value.

Next, the case where the conveyance belt correction control signal 40 is canceled, that is, correction is started will be described (FIG. 19).
(S29) In the variation amount interpolation data storage block 44, an address value (a value generated by the conveyor belt address counter 45) obtained by counting the sub-scanning reference timing pulse signal 14 with the conveyor belt reference signal 39 as a starting point. In synchronization, the variation amount interpolation data is output to the sub-scanning recording timing pulse value addition / subtraction block 31.
(S2a) In the sub-scanning recording timing pulse value addition / subtraction block 31, the sub-scanning recording timing ideal pulse value selected by the sub-scanning recording timing ideal pulse selection block 30 according to the sub-scanning resolution setting signal 19 received from a host computer (not shown), Based on output data from the transport time deviation amount data storage block 28 shown in FIG. 18 (conveyance time deviation amount data from the control line 41), the variation amount interpolation data, and the sub-scan resolution setting signal 19, the sub-scan recording is performed. The timing pulse count value is added or subtracted and output to the sub-scanning recording timing generation block 32.
(S2b) The sub-scanning recording timing generation block 32 generates a sub-scanning recording timing pulse signal by counting the internal clock 23 using the recording medium detection sensor 8 and the print permission signal 22 from the host as an operation permission condition. The count start trigger at this time is the sub-scanning reference timing pulse signal 14.
(S2c) Next, the recording head array control block 33 outputs control signals 15 to 18 to the recording head arrays (nozzle arrays) 9, 10, 11, and 12 in synchronization with the generated sub-scan recording timing pulse. Print control.

  With the above configuration, in addition to the effects of the first embodiment, the correction of the registration deviation due to the variation in the thickness (heart position) of the conveying belt 6 of the conveying means is detected for newly detecting the conveying state. Rather than providing the means on the conveying means, a conveying belt 6 having a reference point 35 and a belt reference point detection sensor 38 for detecting the reference point 35 are provided in the conveying means, and the conveying belt reference point 35 is used as a starting point. The position of the conveyor belt 6 is grasped, a plurality of recording media exceeding the circumference of the conveyor belt 6 are conveyed, and a predetermined specific pattern is printed while corresponding to the position on the conveyor belt 6. Since the printing state is measured, the variation amount of the thickness (center position) of the conveying belt 6 is grasped and calculated from the printing state, and the recording timing is generated. The Shon deviation can be corrected in a simple form.

Although the image forming apparatus has been described as an embodiment of the present invention, the concept of the present invention can be applied to an image forming method.
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, changes, 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.

  As an application example of the present invention, in addition to an inkjet printing apparatus, an image forming apparatus using a conveyance belt, for example, an electrophotographic image forming apparatus can be cited.

FIG. 6 is an explanatory diagram of a synchronization deviation between conveyance and ink ejection timing due to eccentricity of a driving roller. FIG. 6 is an explanatory diagram of a synchronization shift between transport and ink discharge timing due to variations in the thickness of the transport belt. It is the schematic which shows the structure of the inkjet printing apparatus which has the conventional recording timing control function. 1 is a schematic diagram illustrating a configuration of an ink jet printing apparatus which is a first embodiment of an image forming apparatus according to the present invention. It is a block diagram which shows the control block in the control part 21 of FIG. It is explanatory drawing of the method of calculating the rotation radius change data in a rotation radius change data receiving block. It is explanatory drawing of the method of converting from rotation radius change data to conveyance speed change data. It is explanatory drawing of the method converted into conveyance time change data per pixel from conveyance speed change data. It is explanatory drawing of the method of converting into the conveyance time shift amount data per pixel from the conveyance time change data per pixel. It is the schematic which shows another structural example of the inkjet printing apparatus in the 1st Embodiment of this invention. It is explanatory drawing which shows the example 1 of rotation radius change data at the time of calculating conveyance speed change data. It is explanatory drawing which shows the example 2 of rotation radius change data at the time of calculating conveyance speed change data. It is explanatory drawing which shows the example 3 of rotation radius change data at the time of calculating conveyance speed change data. It is explanatory drawing which shows the example 4 of rotation radius change data at the time of calculating conveyance speed change data. It is explanatory drawing which shows the example 5 of rotation radius change data at the time of calculating conveyance speed change data. It is the schematic which shows the structure of an inkjet printing apparatus provided with the rotation radius variation | change_quantity measurement sensor in the 1st Embodiment of this invention. It is the schematic which shows the structure of the inkjet printing apparatus which is 2nd Embodiment of the image forming apparatus which concerns on this invention. It is a block diagram which shows the control block (1) in the control part 21 of FIG. It is a block diagram which shows the control block (2) in the control part 21 of FIG. It is a pattern diagram which shows the specific pattern (1) used for printing state variation | change_quantity calculation. It is a pattern diagram which shows the specific pattern (2) used for printing state variation | change_quantity calculation. It is the schematic which shows the example (1) about the fixed space | interval measured by a printing condition measurement means. It is the schematic which shows the example (2) about the fixed space | interval measured by a printing condition measurement means. It is explanatory drawing about the total total distance by which a printing state is measured by a printing state measurement means. It is explanatory drawing of the method of calculating printing state variation | change_quantity data from a printing state measurement signal. It is explanatory drawing of the method (linear interpolation) which calculates variation amount interpolation data from printing state variation amount data. It is explanatory drawing of the method (polynomial approximate interpolation) which calculates variation amount interpolation data from printing state variation amount data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reference point 2 Reference point detection sensor 3 Sub-scanning reference timing pulse generation means 4 Drive roller 4a, 4b Drive roller pair 5 Drive roller 5a, 5b Drive roller pair 6 Conveying belt 7 Recording medium 8 Recording medium detection sensor 9, 10, 11 , 12 Recording head row 13 Driving roller reference signal 14 Sub-scanning reference timing pulse signal 15, 16, 17, 18 Recording head row control signal 19 Sub-scanning resolution setting signal 20 Driving roller rotation radius change data 21 Control unit 22 Printing permission signal 23 Internal clock 24 Rotation radius change data reception block 25 Speed change data calculation block 26 Transfer time change data calculation block per pixel 27 Transfer time deviation amount data calculation block 28 Transfer time deviation amount data storage block 29 Address counter 30 Sub-scan recording timing Ideal Selection block 31 sub-scanning recording timing pulse value addition / subtraction block 32 sub-scanning recording timing generation block 33 recording head row control block 34 rotation radius change amount measuring sensor 35 transport belt reference point 36 printing state measuring means 37 printing state measuring signal 38 belt reference Point detection sensor 39 Conveyance belt reference signal 40 Conveyance belt correction control signal 41 Conveyance time deviation amount data (control line)
42 Print State Variation Amount Calculation Block 43 Variation Amount Interpolation Data Calculation Block 44 Variation Amount Interpolation Data Storage Block 45 Conveyance Belt Address Counter 46 Specific Pattern Data Storage Block 51 Cut Sheet 52 Registration Roller 54 Conveyance Belt 63 to 66 Recording Head 91 Speed Detector 92 Control unit

Claims (8)

A recording head having a nozzle array in which a plurality of nozzles for recording by discharging ink onto a recording medium is arranged in at least one direction (main scanning direction), and the recording in a direction orthogonal to the main scanning direction (sub-scanning direction). An image forming apparatus having a conveying means for conveying a medium,
A rotating body having a reference point and driving the conveying means by rotating;
A reference point detection sensor for detecting a reference point of the rotating body;
A reference timing pulse generating means for generating a reference timing pulse serving as a starting point of recording in the sub-scanning direction according to the image resolution in the sub-scanning direction;
Speed change data calculating means for calculating change data of the conveyance speed of the recording medium based on the rotation radius change data of the rotating body;
Transport time change data calculating means for calculating transport time change data per pixel from the transport speed change data and the image resolution in the sub-scanning direction with reference to the reference point of the rotating body,
A transport time shift amount data calculating means for calculating a transport time shift amount by comparing the transport time change data with an ideal transport time per pixel corresponding to the image resolution in the sub-scanning direction;
Based on the transport time shift amount, the reference point detection signal of the reference point detection sensor, the reference timing pulse, and the image resolution in the sub-scanning direction, the recording timing in the sub-scanning direction for one pixel of the recording medium is generated. Sub-scanning recording timing generating means,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the image resolution in the sub-scanning direction is selected from a predetermined image resolution range.   The image forming apparatus according to claim 1, wherein the rotation radius change data of the rotating body is data measured in advance.   The image forming apparatus according to claim 1, further comprising a rotation radius change amount measuring sensor that measures rotation radius change data of the rotating body.   The rotation radius change data of the rotating body is measured by the rotation radius change amount measurement sensor at all times at regular intervals, at any time other than during a print job, or when the image forming apparatus is activated. 5. The image forming apparatus according to 4.   The image forming apparatus according to claim 1, wherein the conveying unit is an endless belt driven by the rotating body. The belt has a second reference point on a belt rotation circumference;
A second reference point detection sensor for detecting a second reference point of the belt;
Pulse counting means for counting the reference timing pulse starting from the second reference point;
Print control means for driving and printing a recording pattern in synchronization with a reference timing pulse for each predetermined pulse count value with respect to a plurality of recording media;
A printing state measuring means for measuring the printing state of the printed specific pattern at predetermined intervals on the rotation circumference of the belt;
A printing state variation amount calculating means for comparing the printing state measurement result with a preset printing state setting value and calculating a variation amount of the printing state on the belt rotation circumference;
Variation amount interpolation data calculating means for calculating variation amount interpolation data by performing interpolation according to the pitch of the image resolution for the variation amount,
The sub-scanning recording timing generation unit generates a recording timing in the sub-scanning direction for the one pixel based on the variation amount interpolation data, the transport time shift amount, the reference timing pulse, and the image resolution in the sub-scanning direction. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 7, wherein the variation amount interpolation data calculation unit calculates variation amount interpolation data by a linear interpolation method or a polynomial approximation interpolation method.