JP2015100982A - Inkjet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recorder capable of easily aligning an output image in a desired size, without deteriorating an image quality.SOLUTION: An inkjet recorder comprises: a carrying driving part for moving a recording medium at a predetermined moving speed along a carrying surface; an encoder for outputting a pulse signal corresponding to the moving speed and the direction of the recording medium; an inkjet head provided by arranging a plurality of nozzles and discharging ink to the recording medium opposed to these nozzles; and a control part for controlling the ink discharge timing from the nozzles. The timing control part executes ink discharge operation every predetermined counting frequency by counting pulse signals of the encoder, and expands or contracts a forming image in the carrying direction by irregularly increasing or reducing the predetermined counting frequency in response to the set expansion ratio or the contraction ratio.

Description

  The present invention relates to an ink jet recording apparatus.

  There is an ink jet recording apparatus that forms an image on a recording medium by ejecting ink from a plurality of nozzles while controlling timing from a plurality of nozzles. By ejecting ink from the nozzles at a frequency (frequency) according to the transport speed while transporting the recording medium at a predetermined speed, the ink can land on the recording medium at an appropriate interval in the transport direction. I can do it.

  However, conventionally, when ink is ejected at regular intervals, the image is partially enlarged or reduced from the desired size due to fluctuations in the conveyance speed of the recording medium, axial deviation of the rotary motor or rotary drum, unevenness of the conveyance surface, etc. There is a problem that. On the other hand, in Patent Document 1, when ink ejection timing is determined using a pulse signal from an encoder corresponding to the number of rotations of a motor that transports a recording medium, ink is ejected at a predetermined interval. It describes a technique for widening or narrowing the ink discharge interval by changing the number of rotations of the motor. Patent Document 2 discloses a technique for measuring the outer diameter of a rotating drum and changing the ink discharge timing with respect to a pulse signal in accordance with the measured value.

JP2013-139209A JP 2010-5859 A

  In an ink jet recording apparatus, the recording medium may be temporarily expanded or contracted slightly due to processing such as heating of the surface after double-sided printing or heating (ink drying) or fixing. In such a case, when an image is formed as it is with a conventional ink jet recording apparatus, there is a problem that the size of the drawing differs from the desired one when enlargement or shrinkage is eliminated thereafter.

  An object of the present invention is to provide an ink jet recording apparatus capable of easily aligning an output image to a desired size without degrading image quality.

In order to achieve the above object, the present invention described in claim 1
A conveyance drive unit that moves the recording medium along the conveyance surface at a predetermined movement speed;
An encoder that outputs a pulse signal corresponding to the moving speed and direction of the recording medium by the transport driving unit;
An inkjet head provided with a plurality of nozzles arranged and ejecting ink to a recording medium facing the nozzles;
A timing control unit for controlling the timing of ink ejection from the nozzles,
The timing control unit counts the encoder pulse signal and causes ink to be ejected every predetermined number of times, and irregularly increases the predetermined number of times according to a set enlargement ratio or reduction ratio. Alternatively, by reducing the size, the formed image is enlarged or reduced in the transport direction.

The invention described in claim 2 is the ink jet recording apparatus according to claim 1,
The transport unit can perform a transport operation for causing ink to be ejected to the same recording medium a plurality of times.
The timing control unit is characterized in that the formed image at the second and subsequent ink discharges is enlarged or reduced in accordance with a preset enlargement ratio or reduction ratio with respect to the first ink discharge.

The invention described in claim 3 is the ink jet recording apparatus according to claim 1 or 2,
The transport unit can transport the recording medium again after an image is formed on one surface of the recording medium, and form an image on another surface different from the one surface,
When the image is formed on the other surface, the number of counts is decreased once by a predetermined frequency.

Invention of Claim 4 is an inkjet recording device as described in any one of Claims 1-3,
The irregular timing and / or timing for increasing or decreasing the number of times of counting is determined using a random value.

The invention described in claim 5 is the ink jet recording apparatus according to claim 4,
Storage means for storing a random number table in which a predetermined number of random values are arranged;
The timing control unit is configured to count the number of counts based on a magnitude relationship between a threshold value determined according to a change frequency of a magnitude that increases or decreases the number of counts and a random value acquired from the random number table for each ink ejection. It is characterized by determining the timing to change

Invention of Claim 6 is an inkjet recording device as described in any one of Claims 1-5,
The timing controller is
Count the elapsed time since the output of the control signal indicating the ink discharge timing,
When the setting is made to change the counting number, if the elapsed time until the counting one time before the changed counting number is not within a predetermined reference time range, the change is performed next time. It is characterized by being postponed after the ink ejection timing.

The invention according to claim 7 is the ink jet recording apparatus according to any one of claims 1 to 6,
The image forming apparatus includes a fixing unit that outputs a predetermined energy line for fixing the ink to the landing surface of the ink that has landed on the recording medium.

  According to the present invention, in the ink jet recording apparatus, there is an effect that the output image can be easily aligned to a desired size without degrading the image quality.

It is the whole schematic diagram which looked at the ink jet recording device of this embodiment from the side. It is a block diagram which shows the internal structure of an inkjet recording device. It is a figure explaining the interval setting of an ink discharge. 5 is a flowchart illustrating a control procedure of image forming processing. It is a flowchart which shows the control procedure of a back surface printing process. It is a flowchart which shows the modification of the control procedure of a back surface printing process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall schematic view of an inkjet recording apparatus 1 according to the present embodiment as viewed from the side.

  The ink jet recording apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharge unit 30, a control unit 40 (timing control unit), and the like. In the inkjet recording apparatus 1, based on the control of the control unit 40, the image forming unit 20 uses ink supplied from an ink supply unit (not shown) to the recording medium P sent from the paper supply unit 10 to the image forming unit 20. After the image is formed, the recording medium P is discharged to the paper discharge unit 30.

  The paper feeding unit 10 holds the recording medium P on which image formation is performed, and supplies the recording medium P to the image forming unit 20 before image formation. The paper feed unit 10 includes a paper feed tray 11 and a supply unit 12.

  The paper feed tray 11 is a plate-like member provided so that one or a plurality of recording media P can be placed thereon. The paper feed tray 11 is provided so as to move up and down according to the amount of the recording medium P placed thereon, and is held at a position where the uppermost recording medium P is conveyed by the supply unit 12.

  The supply unit 12 is mounted on the paper feed tray 11 and a transport mechanism that transports the recording medium P on the belt 123 by rotating the annular belt 123 by a plurality of (for example, two) rollers 121 and 122. A delivery unit is provided for delivering the uppermost recording medium P to the belt 123. The supply unit 12 conveys the recording medium P delivered to the belt 123 by the delivery unit as the belt 123 rotates.

  The image forming unit 20 forms an image by ejecting ink onto the recording medium P. The image forming unit 20 includes a transport drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25 (fixing unit), a delivery unit 26, and the like.

  The conveyance drum 21 carries the recording medium P along a cylindrical outer peripheral surface (conveyance surface), and conveys the recording medium P as it rotates. The outer peripheral surface of the transport drum 21 faces the paper heating unit 23, the head unit 24, and the irradiation unit 25, and processing related to image formation is performed on the transported recording medium P.

  In the transport drum 21, the rotation shaft 211 is rotated at a predetermined speed by a rotation motor (not shown). An encoder 42 is provided on the rotation shaft, and generates a pulse signal corresponding to the rotation direction and rotation speed of the rotation shaft, that is, the moving speed of the recording medium P, and outputs the pulse signal to the control unit 40.

  The delivery unit 22 is provided at a position between the supply unit 12 of the paper feed unit 10 and the conveyance drum 21, and delivers the recording medium P conveyed by the supply unit 12 to the conveyance drum 21. The delivery unit 22 includes a swing arm 221 that supports one end of the recording medium P conveyed by the supply unit 12 and a cylindrical delivery drum 222 that delivers the recording medium P supported on the swing arm 221 to the conveyance drum 21. The recording medium P on the supply unit 12 is picked up by the swing arm unit 221 and transferred to the transfer drum 222 to guide the recording medium P in the direction along the outer peripheral surface of the transfer drum 21 to the transfer drum 21. Deliver.

  The paper heating unit 23 heats the recording medium P carried on the transport drum 21. The paper heating unit 23 includes, for example, an infrared heater and generates heat when energized. The paper heating unit 23 is provided in the vicinity of the outer peripheral surface of the transport drum 21 and on the upstream side of the head unit 24 in the transport direction of the recording medium P by the rotation of the transport drum 21. The heat generation amount of the paper heating unit 23 is controlled by the control unit 40 so that the recording medium P carried on the transport drum 21 and passing through the vicinity of the paper heating unit 23 has a predetermined temperature.

The head unit 24 ejects ink to the recording medium P carried on the transport drum 21 to form an image. The head unit 24 is individually provided for each color of C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, head units 24 corresponding to the respective colors Y, M, C, and K are provided in order from the upstream in the transport direction of the recording medium P that is transported as the transport drum 21 rotates.
The head unit 24 of this embodiment is provided with a length (width) that covers the entire recording medium P in a direction (width direction) perpendicular to the conveyance direction of the recording medium P. That is, the ink jet recording apparatus 1 is a one-pass line head type ink jet recording apparatus. The head unit 24 is formed by arranging a plurality of ink jet heads in which a plurality of nozzles are arranged on a surface facing the transport drum 21 in a predetermined pattern and holding the head on a support member (carriage).

  The irradiation unit 25 irradiates energy rays for curing and fixing the ink ejected on the recording medium P. The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp, and emits energy rays such as ultraviolet rays by causing the fluorescent tube to emit light. The irradiation unit 25 is provided in the vicinity of the outer peripheral surface of the transport drum 21 and on the downstream side of the head unit 24 in the transport direction of the recording medium P by the rotation of the transport drum 21. The irradiation unit 25 irradiates the recording medium P carried on the transport drum 21 and ejects the ink with energy rays, and cures the ink ejected onto the recording medium P by the action of the energy rays.

  As a fluorescent tube emitting ultraviolet rays, in addition to a low-pressure mercury lamp, a mercury lamp having an operating pressure of about several hundred Pa to 1 MPa, a light source usable as a germicidal lamp, a cold cathode tube, an ultraviolet laser light source, a metal halide lamp, a light emitting diode, etc. Is mentioned. Among these, a light source (for example, a light emitting diode) that can irradiate ultraviolet rays with higher illuminance and consumes less power is more desirable. However, in the irradiation unit 25, a part of the power consumption is converted into heat to generate heat, and the recording medium P on which the ink has been ejected is further heated. The energy rays are not limited to ultraviolet rays, and may be any energy rays having a property of curing ink according to the properties of the ink, and the light source is also replaced according to the wavelength of the energy rays.

  The delivery unit 26 transports the recording medium P irradiated with the energy rays from the irradiation unit 25 from the transport drum 21 to the paper discharge unit 30. The delivery unit 26 includes a conveyance mechanism that conveys the recording medium P on the belt 263 by rotating the annular belt 263 by a plurality of (for example, two) rollers 261 and 262, and the recording medium P from the conveyance drum 21. A cylindrical delivery drum 264 and the like are provided to the transport mechanism. The delivery unit 26 conveys the recording medium P transferred to the belt 263 by the transfer drum 264 by the belt 263 and sends it to the paper discharge unit 30. Further, the delivery unit 26 rotates the rollers 261 and 262 and the transfer drum 264 in the reverse direction so that the image forming surface of the recording medium P once discharged is supported on the transport drum 21 again in a direction in contact with the transport drum 21 to form an image. Image formation can be performed on another surface (back surface) different from the already completed one surface (front surface).

  The paper discharge unit 30 stores the recording medium P sent out from the image forming unit 20 by the delivery unit 26. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31 and the like, and the recording medium P after image formation is placed on the paper discharge tray 31.

  The control unit 40 controls the operation of each unit of the inkjet recording apparatus 1 and controls the overall operation. The control unit 40 includes a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, a RAM (Random Access Memory) 403, and the like (see FIG. 2). In the control unit 40, the program read from the ROM 402 by the CPU 401 is executed on the RAM 403, and various control processes are executed.

  FIG. 2 is a block diagram showing the internal configuration of the inkjet recording apparatus 1 of the present embodiment.

  In the inkjet recording apparatus 1, the control unit 40 is connected via a bus 49 to the conveyance drive unit 41, encoder 42, head drive unit 43, communication unit 44, operation display unit 45, storage unit 46, paper heating unit 23, irradiation unit 25, and the like. Connected with.

  In the control unit 40, the CPU 401 reads out and executes various programs and data corresponding to the processing contents from the ROM 402 and the storage unit 46, and controls the operation of each unit of the inkjet recording apparatus 1 according to the executed processing contents. To do. The RAM 403 temporarily stores various programs and data processed by the CPU 401. The ROM 402 stores various programs read by the CPU 401 and the like, initial setting data, and the like. This initial setting data includes a random number table that is used to determine the timing for performing an enlargement / reduction process described later.

  The transport drive unit 41 operates the paper feed unit 10, the transport drum 21 of the image forming unit 20, the delivery unit 22, the delivery unit 26, and the paper discharge unit 30 based on a control signal from the control unit 40, at an appropriate timing. The recording medium P is conveyed at the direction and speed.

  The encoder 42 detects the rotation operation of the transport drum 21 and outputs a pulse signal corresponding to the rotation direction and the rotation speed. The pulse signal is counted by the control unit 40, and the control unit 40 outputs the pulse signal to the head driving unit 43 as a control signal indicating the timing at which ink is ejected from the nozzle every predetermined number of counts.

The head driving unit 43 operates the head unit 24 based on the timing control signal from the control unit 40 and the image data to be image formed, and ejects ink from a plurality of nozzles at an appropriate timing, thereby recording the recording medium. An image is formed on P.
The control unit 40 outputs control signals to the transport driving unit 41, the head driving unit 43, the paper heating unit 23, and the irradiation unit 25 and operates them at appropriate timings, so that the recording medium P is subjected to the head unit 24 under appropriate conditions. The ink ejected onto the recording medium P is cured.

  The communication unit 44 controls communication between the inkjet recording apparatus 1 and an external device. A print job and various control signals transmitted from the external device are received via the communication unit 44 and sent to the control unit 40. The control unit 40 performs various processes for image formation according to the acquired print job. Note that processing such as image data analysis and rasterization may be performed by a CPU or memory for image processing provided separately from the control unit 40.

  The operation display unit 45 is, for example, a touch panel having a liquid crystal screen and a touch sensor. The control unit 40 outputs a display control signal to the liquid crystal driver to display a status, a menu, and the like on the liquid crystal screen. The touch sensor receives an input operation from the outside and outputs an input signal to the control unit 40. The control unit 40 performs various processes based on the input signal.

  The storage unit 46 stores image data to be formed, processing data thereof, and various settings related to image formation. The storage unit 46 includes, for example, a volatile memory that can be read and written at high speed, such as a RAM, and a nonvolatile memory or HDD (Hard Disk Drive).

Next, an operation related to double-sided printing in the inkjet recording apparatus 1 of the present embodiment will be described.
In double-sided printing in the inkjet recording apparatus 1, when an image is formed on the surface, the ultraviolet fluorescent tube of the irradiation unit 25 that irradiates the surface with ultraviolet rays generates heat, and the recording medium is temporarily heated and contracted. In consideration of this influence, when forming an image on the back surface, the image is reduced and output in the transport direction from the front surface. In the ink jet recording apparatus 1 of the present embodiment, the distance between the lines is reduced by narrowing the ink discharge time interval.

FIG. 3 is a diagram for explaining the ink discharge interval setting.
As shown in FIG. 3A, the encoder 42 outputs a pulse signal corresponding to the rotation speed of the transport drum 21, and this is used as a drive pulse. As shown in FIG. 3B, the control unit 40 outputs a control signal indicating the ink discharge timing every time the drive pulse is counted N times a predetermined number of times. By reducing the number N of counts to (N-1) times, the interval between ink discharges can be narrowed.

  The count N is, for example, about 100, and if it is decreased once every time, the interval changes by 1%, and fine adjustment cannot be performed. Therefore, by changing the number of counts to (N-1) times at a frequency corresponding to the reduction rate, the image can be reduced with higher accuracy. For example, the reduction rate is 99.5% by changing once in two times, and the reduction rate is 99.6% by changing twice in five times. Similarly, by changing the number of counts to (N + 1) times at a frequency corresponding to the enlargement rate, the image can be enlarged with higher accuracy.

  At this time, if the number of counts is changed in the same cycle, the image quality deteriorates due to factors such as density unevenness and moire. Therefore, the change in the number of counts is adjusted to be performed irregularly.

  FIG. 4 is a flowchart showing a control procedure of image forming processing executed by the control unit 40.

  This image forming process is started when a print job is input from the outside via the communication unit 44 or when an image forming command is detected by a user operation.

  The control unit 40 first acquires print setting information (step S101). This print setting information includes information on whether or not to perform back side printing and information on the type of recording medium. First, the control unit 40 executes image formation on the surface of the recording medium P (step S102). In this image formation on the surface, the control unit 40 outputs a control signal indicating the ink discharge timing every time the pulse signal output from the encoder 42 is counted a predetermined number of times (N times) and outputs the control signal to the head driving unit 43 for each line. Image formation is performed. Further, the control unit 40 converts the image data into a format suitable for image formation as necessary before causing the head driving unit 43 to perform image formation, and performs color correction and contours corresponding to the head driving unit 43. Perform processing such as correction.

  The control unit 40 determines whether or not the reverse side print setting is made in the print setting information (step S103). If the setting has not been made (“NO” in step S103), the control unit 40 discharges the recording medium P having an image formed on the surface (step S107), and ends the image forming process.

  If the reverse side printing setting has been made (“YES” in step S103), the control unit 40 changes the operation setting of the conveyance driving unit 41 to invert the recording medium P and reversely supply the recording medium P to the conveyance drum 21. (Step S104).

  The control unit 40 acquires the enlargement / reduction ratio for backside printing that is set in advance and stored in the storage unit 46 (step S105). And the control part 40 performs the back surface printing process which forms the image of the magnitude | size according to the said expansion / contraction rate on the back surface (step S106). The control unit 40 discharges the recording medium P (step S107) and ends the image forming process.

  FIG. 5 is a flowchart showing a control procedure of the back side printing process that is called and executed in the process of step S106.

When the back side printing process is called, the control unit 40 sets how often the predetermined number of counts (predetermined value) is changed based on the enlargement / reduction ratio (step S161). The control unit 40 sets a threshold according to this frequency (step S162). This threshold value is set so that the probability of a value equal to or higher than the threshold value corresponds to the frequency with respect to the maximum value of the random number table stored in the storage unit 46. For example, in the case where the random number value is in the range of 0 to 2 ¹⁵ −1 (32767) and the frequency is twice in five times, the probability that the random number value becomes larger than the threshold value is set to 19660, so 4.

  The control unit 40 acquires a random number value from the random number table in the storage unit 46 before starting counting related to the ink ejection timing of each line (step S163). The control unit 40 compares the acquired random number value with a threshold value, and determines whether or not the random number value is larger than the threshold value (step S164). When it is determined that the random number value is larger than the threshold value (“YES” in step S164), the control unit 40 adds (enlarges) or subtracts (reduces) 1 to a predetermined value for the line (step S165). . Then, the process proceeds to step S166. If it is determined that the random number value is not larger than the threshold value (“NO” in step S164), the process of the control unit 40 proceeds to step S166 as it is.

  When the process proceeds to step S166, the control unit 40 determines whether or not the count value has reached a predetermined value every time 1 is added to the count value (step S166). When it is determined that the predetermined value has not been reached (“NO” in step S166), the process of step S166 is repeated every time the count value is incremented by one.

  If it is determined that the predetermined value has been reached (“YES” in step S166), the control unit 40 outputs a timing signal indicating the ink ejection timing for this line to the head driving unit 43 (step S167).

  The control unit 40 determines whether or not the ink ejection to all the lines related to the back side printing has been completed (step S168). If it is determined that ink ejection has not ended ("NO" in step S168), the process of the control unit 40 returns to step S163. If it is determined that the ink ejection has ended (“YES” in step S168), the control unit 40 ends the back surface printing process and returns to the image forming process.

As described above, the inkjet recording apparatus 1 according to the present embodiment includes a transport drive unit 41, an encoder 42 that outputs a pulse signal corresponding to the moving speed and direction of the recording medium P by the transport drive unit 41, and a plurality of inkjet heads. A head unit 24 having line heads arranged and a control unit 40 that controls the timing of ink ejection from the nozzles of the inkjet head. The control unit 40 counts the pulse signal of the encoder 42 and outputs a control signal indicating the ink discharge timing to the head drive unit 43 every predetermined number of times to cause the head drive unit 43 to perform the ink discharge operation. At this time, the control unit 40 enlarges or reduces the formed image in the conveyance direction of the recording medium P by irregularly increasing or decreasing the predetermined number of times according to the set enlargement rate or reduction rate.
Therefore, it is easy to change the output frequency of the drive pulse itself or to reduce the size of the image to be formed by image processing before outputting it, and the image can be generated without causing color unevenness or moire. The image can be output in a desired size without deterioration.

  This makes it possible to fix an image formed by discharging liquid ink and then drying it with heat or curing it with a predetermined energy ray such as ultraviolet light. Therefore, in the case where the recording medium is transmitted and heated at the time of image formation, the present invention is used when the size of the recording medium slightly changes as the recording medium wets or dries depending on the material of the recording medium. By applying, an image having a desired image size can be formed after the deformation is eliminated.

  In addition, when an image is formed on a stretchable recording medium such as a cloth, even if the cloth is excessively stretched during wrinkling or the like, the present invention can be applied to perform a normal operation after image formation. An image of a desired size can be formed on the fabric that has returned to size.

  In addition, since the increase / decrease timing of the predetermined value related to the enlargement / reduction of the formed image is determined using the random number value, the positions where the intervals between the lines are changed easily and reliably are dispersed, and the image is hardly deteriorated.

  In addition, by storing the random number table in the storage unit 46 in advance, it is possible to easily and reliably change the distance between lines without providing a highly accurate random number generator.

  In particular, in the inkjet recording apparatus 1 that includes the irradiation unit 25 and fixes the ink by UV irradiation, the influence of the irradiation unit 25 that generates a large amount of heat is accurately estimated, and the output image at the time of backside printing is reduced. The image size can be aligned on the front and back in an appropriate and accurate manner.

[Modification]
FIG. 6 is a flowchart illustrating a modification of the control procedure of the back surface printing process.
In this modification, the back side printing process shown in FIG. 5 is the same except that the processes in steps S164 to S166 are changed to the processes in steps S180 to S185 and steps S190 to S195. Are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this back side printing process, after the random value is acquired in the process of step S163, the control unit 40 determines whether or not the count value is (predetermined value −1) (step S180). If it is determined that the count value is not (predetermined value-1) ("NO" in step S180), the process of step S180 is repeatedly executed until the count value becomes (predetermined value-1).

  When it is determined that the count value is (predetermined value −1) (“YES” in step S180), the control unit 40 has an enlargement / reduction ratio of less than 100%, that is, a reduction setting, and It is determined whether or not the random number value is larger than a threshold value (step S181). When it is determined that the setting is a reduction setting and the random value is larger than the threshold value (“YES” in step S181), the control unit 40 stores the setting for reducing the predetermined value in the storage unit 46 ( Step S183). Here, the storage unit 46 can store a predetermined maximum number of settings for decreasing the predetermined value. Alternatively, the number of times that the setting is stored may be counted and stored. Then, the process of the control unit 40 proceeds to the process of step S184.

  When it is determined that the setting is not reduced or the random value is not larger than the threshold (“NO” in step S181), the control unit 40 stores the setting for decreasing the predetermined value in the storage unit 46. It is determined whether or not there is (step S182). If it is determined that it is not stored (“NO” in step S182), the process of the control unit 40 proceeds to step S190. If it is determined that it is stored (“YES” in step S182), the process of the control unit 40 proceeds to step S184.

  In the process of step S184, the control unit 40 determines whether or not the elapsed time since the output of the control signal indicating the previous ink discharge timing is less than the reference interval (reference time) (step S184). If it is determined that it is not less than the reference interval (or more) (“NO” in step S184), the control unit 40 deletes one setting for reducing the predetermined value from the storage unit 46 (step S185), Thereafter, the processing of the control unit 40 proceeds to step S167. Further, the control unit 40 has already stored the maximum number of settings for decreasing the predetermined value, and when the maximum number is exceeded due to this addition, the process proceeds to step S167 in the same manner. I can do it.

  On the other hand, in the process of step S184, when it is determined that the elapsed time from the output of the control signal indicating the previous ink ejection timing to the present time is less than the reference interval (“YES” in step S184). ") The process of the control unit 40 proceeds to step S190. The control unit 40 waits until “1” is added to the count value (step S190), and then the processing of the control unit 40 proceeds to step S191.

The control unit 40 determines whether or not the enlargement / reduction ratio is 100% or more, that is, enlargement setting (including unity magnification), and whether the random number value acquired in the process of step S163 is greater than the threshold ( Step S191). When it is determined that the setting is an expansion setting and the random value is larger than the threshold value (“YES” in step S191), the control unit 40 stores the setting for increasing the predetermined value in the storage unit 46 (step S193). ). The storage unit 46 can store a predetermined maximum number similar to the setting for decreasing the predetermined value. Then, the process proceeds to step S194.
In the case of magnification, the change frequency of a predetermined value to "0", or the like is set a threshold for such 2 ¹⁵ may be associated with scaling the same process.

  When it is determined that the setting is not an enlargement setting or the random value is not larger than the threshold value (“NO” in step S191), the control unit 40 stores the setting for increasing the predetermined value in the storage unit 46. It is determined whether or not there is (step S192). If it is determined that it is not stored ("NO" in step S192), the process of the control unit 40 proceeds to step S167. If it is determined that it is stored (“YES” in step S192), the process of the control unit 40 proceeds to step S194.

  In the process of step S194, the control unit 40 determines whether or not the elapsed time since the output of the control signal indicating the previous ink discharge timing is longer than the reference interval (step S194). If it is determined that it is not longer than the reference interval (“NO” in step S194), the control unit 40 waits until “1” is added to the count value, and also increases the predetermined value from the storage unit 46. One setting is deleted (step S195). Thereafter, the processing of the control unit 40 proceeds to step S167. Further, the control unit 40 has already stored the maximum number of settings for increasing the predetermined value, and when the maximum number is exceeded due to this addition, the process proceeds to step S167 in the same manner. I can do it.

  On the other hand, in the process of step S194, if it is determined that the elapsed time from the output of the control signal indicating the previous ink ejection timing to the present is longer than the reference interval (“YES” in step S194), the control unit 40 The process proceeds to step S167.

As described above, in the back surface printing process according to the modification, the predetermined value is not necessarily changed randomly at the line where the random value exceeds the threshold value. Even if the acquired random number value exceeds the threshold value, if the time interval from the ink ejection timing to the previous line to the ink ejection timing to the main line is too short than the reference at the time of image reduction, or the image is enlarged If it is too long for the time reference, the line can be held after the next line without shortening or extending the timing. Accordingly, when the rotation speed of the transport drum 21 fluctuates in response to deformation such as contraction of the recording medium P, the ink ejection timing is controlled so that the enlargement ratio and the reduction ratio do not vary more than necessary. I can do it.
Note that the determination conditions related to the above-described time interval are not limited to the lower limit at the time of image reduction and the upper limit at the time of image enlargement, and the condition determination may be performed in a range having an upper limit and a lower limit.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, in the above-described embodiment, the reduction at the time of printing on the back side when forming an image on both sides has been described. However, the image formation on the second time is similarly performed in the image formation by the two-pass method related to the second printing. Such processing can be performed.

  In the above embodiment, the process of adding or subtracting 1 to the predetermined number of times N is performed at a predetermined frequency in the case where addition or subtraction is not performed (the magnitude of addition or subtraction is equal to 0). The case of execution has been described as an example, but is not limited thereto. For example, when an image is formed on a recording medium having a large expansion / contraction ratio, such as a cloth, the number of times of adding 1 to the number of counts N and the number of times of adding 2 to the number of counts N are mixed together at an appropriate ratio. The size can be adjusted with high accuracy when the rate is between 101% and 102%.

  In the above embodiment, an independent random number value is used for each ink ejection timing and compared with a threshold value related to increase / decrease of a predetermined value. However, an appropriate dither arrangement is prepared in advance and is similar to the dither processing. In addition, the previous error may be compared with the threshold while carrying over to the process at the next ink ejection timing.

  In the above embodiment, the LED for irradiating the ink fixing UV of the irradiation unit 25 is given as an example of the cause of the shrinkage of the recording medium. However, the ink (moisture) such as heating by the heater is dried, and the recording medium is The same applies to other factors that cause deformation.

In the above embodiment, the ink jet recording apparatus having the line head has been described. However, the present invention can be similarly applied to the reduction and enlargement in the transport direction even in the ink jet recording apparatus having the serial head. . In this case, with respect to the image formation in the width direction, the ink may be ejected without any change, or the ink ejection timing may be adjusted by using another process in combination.
In addition, details such as the specific configuration, arrangement, and processing procedure shown in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 10 Paper feed part 11 Paper feed tray 12 Supply part 121, 122 Roller 123 Belt 20 Image forming part 21 Conveyance drum 211 Rotating shaft 22 Delivery unit 221 Swing arm part 222 Delivery drum 23 Paper heating part 24 Head unit 25 Irradiation Unit 26 delivery unit 261, 262 roller 263 belt 264 delivery drum 30 paper discharge unit 31 paper discharge tray 40 control unit 41 transport drive unit 42 encoder 43 head drive unit 44 communication unit 45 operation display unit 46 storage unit 49 bus P recording medium

Claims (7)

A conveyance drive unit that moves the recording medium along the conveyance surface at a predetermined movement speed;
An encoder that outputs a pulse signal corresponding to the moving speed and direction of the recording medium by the transport driving unit;
An inkjet head provided with a plurality of nozzles arranged and ejecting ink to a recording medium facing the nozzles;
A timing control unit for controlling the timing of ink ejection from the nozzles,
The timing control unit counts the encoder pulse signal and causes ink to be ejected every predetermined number of times, and irregularly increases the predetermined number of times according to a set enlargement ratio or reduction ratio. Alternatively, by reducing the size, the formed image is enlarged or reduced in the moving direction of the recording medium by the transport driving unit. The transport driving unit can perform a transport operation for causing ink to be ejected to the same recording medium a plurality of times.
The said timing control part enlarges or reduces the formation image at the time of the second and subsequent ink discharges according to a preset enlargement ratio or reduction ratio with respect to the first ink discharge. Inkjet recording device. The transport driving unit can transport the recording medium again after an image is formed on one surface of the recording medium, and form an image on another surface different from the one surface,
3. The ink jet recording apparatus according to claim 1, wherein, when forming an image on the other surface, the number of times of counting is decreased by one at a predetermined frequency.   The inkjet recording apparatus according to any one of claims 1 to 3, wherein the irregular timing and / or magnitude for increasing or decreasing the number of counts is determined using a random number value. A storage unit for storing a random number table in which a predetermined number of random values are arranged;
The timing control unit is configured to count the number of counts based on a magnitude relationship between a threshold value determined according to a change frequency of a magnitude that increases or decreases the number of counts and a random value acquired from the random number table for each ink ejection. The ink jet recording apparatus according to claim 4, wherein a timing for changing is determined. The timing controller is
Count the elapsed time since the output of the control signal indicating the ink discharge timing,
When the setting is made to change the counting number, if the elapsed time until the counting one time before the changed counting number is not within a predetermined reference time range, the change is performed next time. The inkjet recording apparatus according to any one of claims 1 to 5, wherein the inkjet recording apparatus is postponed after the ink ejection timing.   The inkjet according to any one of claims 1 to 6, further comprising: a fixing unit that outputs a predetermined energy ray for fixing the ink to a landing surface of the ink that has landed on the recording medium. Recording device.

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