JP2008230069A - Inkjet recorder and method for controlling recording position - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the deterioration in recording quality caused by a deviation of recording position due to the deformation of a platen, in an inkjet recorder. <P>SOLUTION: A paper-to-paper detection unit 124 provided to a carriage is used to scan a platen. In this scanning, the paper-to-paper distance is measured with regard to each rib arranged in the scanning direction. The measurement of ribs is performed by dividing the measurement region into two, an upstream region and a downstream region so as to measure in the transfer direction of a recording medium. When the sub-scanning direction of the platen is deformed, the paper-to-paper distance differs according to nozzle position, so that the paper-to-paper distance is measured by dividing the same rib into two regions to store the measured results in each region. Then, recording position control for varying the ejection timing is performed corresponding to the paper-to-paper distance for each region of the rib. Thereby, even if there is a variation in the height of the rib caused by the deformation of the platen, the ejection timing is decided corresponding to the varied height, enabling the deviation of the ink hitting position to be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and a recording position control method, and more particularly to adjustment of a recording position when the distance between a recording head and a recording medium changes.

  2. Description of the Related Art Recording apparatuses that perform recording while scanning a recording head that ejects ink on a recording medium are applied to various image formations. In recent years, the resolution of images has been increased due to the high performance of digital cameras and the spread of single-lens reflex cameras. Accordingly, it is possible to record an image with higher resolution by reducing the ink discharge amount per one ink droplet. On the other hand, while recording media such as A3 and A3 Nobi are becoming larger, recording speed is increased by increasing the number of nozzles, driving frequency, and bi-directional recording. High throughput is obtained.

  For example, when performing bidirectional recording, it is necessary to adjust the recording positions of forward recording and backward recording. For this reason, a test pattern for recording position adjustment (bidirectional registration) is recorded, and this pattern is read by an optical sensor or adjusted by a user through visual judgment.

  However, it is possible to record at the correct recording position in bidirectional recording by adjusting the recording position. However, if the distance between the recording head and the recording medium (hereinafter also referred to as the inter-paper distance) fluctuates, recording at the adjusted recording position is possible. May not be possible. In other words, the ink droplets ejected from the recording head shift in the scanning direction due to the inertia of the recording head scanning before landing on the recording medium, but this deviation changes according to the distance between the sheets. The recording position adjustment includes the above-described deviation according to the assumed inter-paper distance, but if the inter-paper distance fluctuates from what is assumed, the landing position changes, resulting in a reduction in the quality of the recorded image. .

  Such a problem caused by the variation in the distance between papers is a problem that occurs not only in bidirectional recording but also in unidirectional recording. For example, if the inter-paper distance varies in the conveyance direction of the recording medium, the recording position is shifted between nozzles or recording areas arranged in the conveyance direction, and the image quality is lowered. Similarly, when a so-called full-line type recording head in which nozzles are arranged corresponding to the width of the recording medium is used, the recording position shifts and the same problem may occur.

  Causes of the inter-paper distance include curling of the recording medium and minute paper floating (cockling) due to the recording medium absorbing ink and expanding and contracting. In order to solve this problem, it is known that the recording medium is prevented from being lifted by pressing the recording medium against the platen (Patent Document 1). In addition, it is also known that a platen is provided with concave and convex ribs, and the recording medium is pushed down from above by a paper pressing plate to impart a wavy shape to stabilize the distance between the head and the recording medium. (Patent Document 2).

Japanese Patent Laid-Open No. 4-69264 JP 2003-251800 A JP-A-7-81190

  However, when the platen itself is deformed for some reason and the height of the platen becomes non-uniform, the distance between the sheets varies.

  For example, the distance between the recording head and the platen is determined by the scanning direction of the recording head (hereinafter also referred to as the main scanning direction) or the conveyance direction of the recording medium (hereinafter referred to as the main scanning direction). Hereinafter, it may be difficult to keep uniform in the sub-scanning direction). Further, platen undulation (deformation) may occur due to fluctuations in the environmental temperature of the recording apparatus.

  Even if the deformation of the platen is within the allowable tolerance at the time of shipment from the factory, after the environmental temperature changes significantly during transportation, etc., when the user purchases and comes to the platen, the platen is brought up to a level where an adverse effect appears on the image. The deformation of may be large. In addition, after the user purchases, there is a possibility that the above-described deformation may occur along with changes in environmental temperature and humidity.

  FIGS. 1A, 1B and 1C show such swells due to deformation of the platen. FIG. 1A is a diagram for explaining a change in the inter-paper distance due to waviness in the main scanning direction, and FIGS. 1B and 1C are diagrams for explaining a difference in the inter-paper distance in the sub-scanning direction. is there.

  As shown in FIG. 1A, the platen 10 is provided with ribs extending a certain length in the normal sub-scanning direction. In the example shown in the figure, ribs 11 and auxiliary ribs 11A corresponding to the reference position of the recording medium are provided. If the platen 10 is deformed due to any of the causes described above, the height of the rib 11 varies in the main scanning direction. As a result, the inter-paper distance A between the recording head and the recording medium 20 in the rib with fluctuation is different from the same inter-paper distance B in the rib without fluctuation. The same thing occurs in the sub-scanning. FIG. 1B shows a state where the platen is not deformed, and shows a case where there is no fluctuation in the height of the rib 11. In this case, the nozzle array of the recording head 105 has one end and the other end. There is no difference between the inter-paper distance I and the inter-paper distance II. On the other hand, FIG. 1C shows a state in which the platen is deformed and the rib 11 is deformed, and the height thereof is different in the sub-scanning direction. In this case, there is a difference in the inter-paper distance I and the inter-paper distance II between one end and the other end of the nozzle array of the recording head 105.

  The problem due to the deformation of the platen becomes more prominent as the size of the platen increases as the size of the recording apparatus increases or the size of the recording medium increases.

  Further, the influence of the displacement of the recording position due to the deformation of the platen described above differs depending on the image to be recorded. For example, when recording an image with a small amount of ink used per unit area, such as a monochrome image, the landing position shift is more noticeable than when recording a color image with a large amount of ink used. Degradation may be significantly reduced.

  FIG. 2A shows a dot arrangement in a case where an image having a uniform density is recorded using Bk ink predominantly like a monochrome image, and the platen is not deformed. FIG. 2B shows a dot arrangement in the case where an image having a uniform density is recorded using inks of three colors C, M, and Y, and the platen is not deformed. When the platen is not deformed, as shown in FIGS. 2A and 2B, the dots are uniformly arranged, and the image does not feel rough.

  On the other hand, FIGS. 3A and 3B show dot arrangements when the same image as that in FIGS. 2A and 2B is formed when the platen is deformed and the recording position is shifted. Is shown. As apparent from FIG. 3A, when the Bk ink is used predominantly, the number of dots forming this image is small, that is, the coverage is low. For this reason, when the inks of the three colors C, M, and Y shown in FIG. 3B are used, the recording position shift is conspicuous, and the influence on the image is affected. growing.

  An object of the present invention is to provide an ink jet recording apparatus and a recording position control method that can suppress a decrease in recording quality due to a shift in recording position due to deformation of the platen described above.

  To this end, in the present invention, in an ink jet recording apparatus that uses a recording head that ejects ink and ejects ink onto a recording medium that is transported on the platen, the recording medium corresponds to a plurality of positions on the platen. An inter-paper distance obtaining unit that obtains distance information with respect to the recording head, and an ejection timing that determines ink ejection timing with respect to a position on the recording medium corresponding to the position based on the distance information of each of the plurality of positions of the platen And determining means.

  Also, in a recording position control method in an ink jet recording apparatus that uses a recording head for ejecting ink and performs recording by ejecting ink onto a recording medium conveyed on the platen, the recording medium corresponds to a plurality of positions of the platen. And a paper distance acquisition step for acquiring distance information between the print head and the discharge information for determining the ink discharge timing for the position on the print medium corresponding to the position based on the distance information for each of the plurality of positions of the platen. And a timing determination step.

  According to the above configuration, the distance between the recording head and the platen or the recording medium is acquired corresponding to a plurality of positions on the platen, and the ink ejection timing of the recording head is determined based on the distance. Thereby, whatever the deformation of the platen is, it is possible to suppress the deterioration of the recording quality due to the deviation of the recording position caused by it.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 4 is a perspective view showing a main recording part of the ink jet recording apparatus according to the embodiment of the present invention.

  In FIG. 4, the recording medium 20 is supported by a recording medium feeding roller 202 and a rib on the platen 212 disposed in the recording area, and a spur 213, and the feeding roller 202 is driven by a sheet feeding motor 203, thereby causing an arrow. It is conveyed in the α sub-scanning direction. As the sheet feed motor 203, a stepping motor or a DC motor is used. In recent years, DC motors are often used for reasons such as quietness. In that case, a rotary encoder (not shown) is installed in the feed roller 202, and the sheet feed motor 203 is controlled based on an encoder signal obtained therefrom.

  A shaft 204 is provided in front of the feed roller 202 in parallel therewith. The carriage 108 is slidably guided by the shaft 204 and is reciprocated in the main scanning direction indicated by the arrow β via the belt 207 by the output of the carriage motor 107. Lubricating oil such as grease is applied between the shaft 204 and the carriage 108 in order to reduce mechanical load due to friction or the like.

  As the carriage motor 107, a stepping motor or a DC motor is used similarly to the sheet feeding motor 203. In recent years, DC motors are often used for reasons such as quietness. In that case, a linear encoder (not shown) is arranged on the carriage 205 and a linear encoder scale (not shown) is arranged in parallel with the shaft 204. The carriage motor 107 is controlled based on a signal obtained from the linear encoder. In addition, based on a signal obtained from the linear encoder, a timing for ejecting ink from the recording head 105 is also generated.

  A carriage 108 serving as a recording head moving unit is equipped with a recording head 105 and a tank 209 that stores recording ink. The recording head of this example is for a color image, and along the moving direction of the carriage 108, a black ink ejection head 105-BK, a cyan ink ejection head 105-C, a magenta ink ejection head 105-M, A head 105-Y for discharging yellow ink is disposed. Further, as the tank 209, a tank 209-BK for black ink (BK), a tank 209-C for cyan ink (C), a tank 209-M for magenta ink (M), and a tank for yellow ink (Y). 209-Y is mounted. Ink is supplied from these tanks to the heads corresponding to the respective colors. An ink ejection unit is provided on the front surface of the recording head 209, that is, the surface facing the recording surface of the recording medium 20 with a predetermined interval (for example, 0.8 mm). A plurality of (for example, 48 or 64) ink discharge ports are arranged in a vertical line along the direction intersecting the scanning direction of the carriage 108 in the ink discharge portion.

  The carriage 108 is provided with a paper interval detection unit (not shown), whereby the distance between the surface on which the nozzles of the recording head are arranged and the recording medium can be measured.

  In addition, a recording control unit including a control circuit (CPU, ASIC) of a recording apparatus, which will be described later with reference to FIG. Receive information and recorded data. The recording control unit controls driving of driving sources such as various motors in the recording apparatus based on these information and recording data. In addition, the recording control unit controls the recording head 105 via the head drive circuit, thereby ejecting ink from the ink ejection unit of the recording head 105 and recording an image on the recording medium 20. In other words, the operation of ejecting ink from the ink ejection unit while moving the recording head 105 in the main scanning direction and the operation of transporting the recording medium 20 by a predetermined amount in the sub-scanning direction are alternately repeated to thereby record the recording medium 20. Record the image on top.

  FIG. 5 is a block diagram showing a recording control unit of the ink jet recording apparatus shown in FIG. In the execution of the recording control described above with reference to FIG. 4, the recording control unit according to the present embodiment controls the recording position based on the scanning speed information of the recording head and the information on the distance between sheets (hereinafter also simply referred to as the information on the distance between sheets). Specifically, the discharge timing is controlled. FIG. 5 mainly shows a configuration for this purpose.

In FIG. 5, the recording data transferred from the host computer is received by the I / F unit 103 in the recording control unit 102 and then sent to the recording data generation unit 104. The recording data generation unit performs decompression of the compressed data, conversion of the data arrangement, etc., converts the received data into a format that can be recorded by the recording head 105 by the recording head, and sends the data to the recording data transfer unit 106. As the recording head, an ink jet recording head of a type that ejects ink using thermal energy can be used. The recording head causes film boiling of the ink in the ink flow path, and ejects ink droplets from the ink ejection port by the foaming energy.
On the other hand, an encoder 109 is mounted on the carriage 108 driven by the carriage motor 107 together with the recording head 105. The encoder 109 outputs a pulse signal every time the carriage 108 moves a certain distance. The pulse signal generated by the encoder 109 is sent to the edge trigger generation unit 111 after passing through the LPF unit 110 in the recording control unit 102 to remove noise. The edge trigger generator 111 detects a predetermined edge (encoder edge) in the received pulse signal and generates a trigger pulse. The trigger pulse generated by the edge trigger generation unit 111 is sent to the head position detection unit 112, the speed detection unit 113, and the edge trigger delay unit 114.

  The head position detection unit 112 detects the moving position of the recording head by counting the signal sent from the edge trigger generation unit 111 with an UP / DOWN counter, and sends information to the paper gap information acquisition unit 115. In the memory 116, information on the inter-paper distance acquired by the inter-paper distance acquisition process described later with reference to FIG. 11 and the like, and information on the scanning speed of the recording head are stored. The paper interval information acquisition unit 115 acquires the paper interval distance and the discharge speed information from the memory 116 as necessary, and updates the delay information according to the paper interval distance sent to the delay value calculation unit 117.

  The speed detector 113 measures the interval between trigger pulses generated by the edge trigger generator 111 and transfers the value to the delay value calculator 117 as the current scanning speed information. The scanning speed information detected by the speed detection unit 113 is also sent to a servo controller (not shown) that servo-controls the carriage motor 107 as necessary.

  In the memory 116, as described above, information on the inter-paper distance acquired by the inter-paper distance acquisition process described later with reference to FIG. 11 and the like is stored. In the present embodiment, the distance information stores the distance between sheets detected by the sheet interval detection unit 124 and the position on the platen. In other embodiments, the inter-paper distance information is set and input by the user.

  The speed detector 113 measures the interval between trigger pulses generated by the edge trigger generator 111 and transfers the value to the delay value calculator 117 as current speed information. The speed information detected by the speed detection unit 113 is also sent to a servo controller (not shown) that servo-controls the carriage motor 107 as necessary.

  The delay calculation unit 117 uses the paper gap information sent from the paper gap information acquisition unit 115 and the speed information sent from the speed detection unit 113, as will be described later, and the ink droplet landing position (recording position). The landing correction delay value for correcting is calculated. The edge trigger delay unit 114 delays the trigger pulse generated by the edge trigger generation unit 111 according to the landing correction delay value calculated by the delay calculation unit 117 and then records the recording timing generation unit 118 and the recording position detection unit. It outputs to 119. The recording timing generation unit 118 generates a recording timing signal obtained by converting the trigger pulse sent from the edge trigger delay unit 114 into a recording resolution, and sends the recording timing signal to the recording position information detection unit 119 and the recording data transfer unit 106. .

  The recording position information detection unit 119 generates position information related to the recording timing by counting signals sent from the edge trigger delay unit 114 and the recording timing generation unit 118 with an UP / DOWN counter. The position information regarding the recording timing detected by the recording position information detection unit 119 is sent to the recording position detection unit 120. The recording position detection unit 120 generates a recording start signal when the recording start position is detected from the position information, and generates a recording end signal when the recording end position is detected, and transfers the information to the recording data. Send to part 106. The recording data transfer unit 106 transfers the recording data generated by the recording data generation unit 104 to the recording head 105 in accordance with information from the recording timing generation unit 118 and the recording position detection unit 120. The recording head 105 ejects ink droplets toward the recording medium based on the information sent from the recording data transfer unit 106.

  The carriage 108 is provided with a paper interval detection unit 124 for detecting the paper interval in front of the nozzles in the scanning direction. This detection unit 124 sends a signal corresponding to the distance between sheets to the recording control unit in conjunction with the scanning of the carriage. The paper gap detection unit 124 detects the reflected light by irradiating the recording medium with laser light, and outputs a DC signal whose level changes depending on the paper gap. The paper gap detection unit 124 detects the paper gaps at a plurality of positions as will be described later. Note that the inter-paper distance described here is equivalent to the distance between the recording head and the platen. The paper gap information includes the paper gap distance and the position information on the platen.

  A configuration and principle for detecting the inter-paper distance from the reflected light from the recording medium will be described. The inter-paper detection unit 124 includes a light emitting unit that emits laser light and a line sensor that receives reflected light reflected by the recording medium. The line sensor includes a photodiode array arranged in a line.

  Next, a procedure for calculating the distance between the recording head and the recording medium will be described. As shown in FIG. 6, the laser light emitted from the light emitting unit E1001 toward the recording medium M6001 is reflected on the recording medium M6001. The arrow in FIG. 6 shows the center part of the optical path, and the optical path after reflection shown in the figure indicates the optical path of regular reflection light among the reflected light.

The specularly reflected light is received by the line sensor E1002, and the intensity of the amount of received light becomes maximum at P1 among the line sensors. If the position P1 at which the intensity of specular reflected light is maximized is known, the distance between the light emitting portion and P1 is known. Therefore, the distance G1 between the upper surface of the recording medium M6001 and the lower surface of the line sensor E1002 can be calculated from the following equation. .
G1 = L1 / 2 / tan θd

  FIG. 7 is a diagram illustrating a waveform of a signal generated by the encoder 109. The signals generated by the encoder are output by shifting the two waveforms of phase A and phase B by about 90 degrees in phase. Depending on the movement direction of the carriage, the leading phase (forward rotation) on the left side in the figure or the delayed phase (reverse rotation) on the right side in the figure is obtained. Therefore, the UP / DOWN operation of the position detection counter is switched to the detection point of the rising edge and the falling edge of the A phase at the fixed phase (Low level) of the B phase with the one side edge of the A phase as the detection point. Thus, the movement position of the carriage can be detected. More specifically, for example, at the low level of the B phase, the position detection counter is incremented every time a falling edge of the A phase is detected. Then, every time the A-phase falling edge is detected, the UP / DOWN operation of the position detection counter is switched so as to count down the position detection counter. Thus, the carriage movement position (recording head movement speed) can be detected from the count value of the position detection counter.

  The edge trigger generation unit 111 detects the edge of the encoder pulse as shown in FIG. 7 to generate a trigger pulse, and the speed detection unit 113 measures the interval (time) of the trigger pulse, thereby moving the carriage moving speed. Is detected.

  FIG. 8 is a diagram for explaining correction processing when the scanning speed of the recording head changes. In FIG. 8, the ink discharge speed is Vd, the distance between the recording head and the recording medium is d, and the reference speed of the recording head is Vs. The landing point when the recording head ejects at a predetermined timing when the reference scanning speed Vs is indicated by P. In this case, the delay time T of the ejection timing when the scanning speed changes to Vs (Vs <V) is obtained as follows.

The angle at which the ejected ink droplets fly when scanning at the reference speed V is θ, and the distance in the main scanning direction from the ink ejection position to the ink landing position P at that time is l, and the ink droplets when scanning at the scanning speed Vs Let θs be the flight angle. If the distance in the main scanning direction from the ink discharge position to the landing position P at that time is ls,
From tan θ = V / Vd = 1 / d, l = d * V / Vd Equation 1
From tan θs = Vs / Vd = ls / d, ls = d * Vs / Vd Equation 2
From Equation 1 and Equation 2, the difference in distance lx from each ink ejection position to the ink landing position P is:
lx = l−1s = (V−Vs) * d / Vd Equation 3
Here, the scanning speed of the recording head can be obtained by moving the edge interval of the encoder signal, that is, the distance of the encoder resolution. When the distance of the encoder resolution is Er, the time when the distance Er is moved with V is Tsta, and the time when the distance Er is moved with Vs is Ts.
V = Er / Tsta Equation 4
Vs = Er / Tss Equation 5
If the time required for the ink droplet to travel the distance d704 at the speed Vd is Td,
Vd = d / Td Equation 6
From Equation 3, Equation 4, Equation 5, and Equation 6, the time T required to move lx at the scanning speed Vs is
T = lx / Vs = (Tss−T) Td / Tsta Equation 7
Here, if A = Td / Tsat, Ts = (Tss−Tsta) * A Equation 8

  As is clear from FIG. 8, the landing position can be matched to the landing position P at the reference speed V by shifting (delaying) the ink ejection timing by the time T at the changed scanning speed Vs.

  That is, if the ejection speed Vd of the ink droplet and the reference scanning speed V of the recording head are known from Expression 8, the landing position can be corrected every time the changed speed Vs is detected. The parameter A = Td / Tsat in Equation 8 is proportional to Td. Since Td is the time required for the ink droplet to move the distance d at the velocity Vd, it is expressed as Td = d / Vd. That is, the parameter A is proportional to the reciprocal of the ink droplet ejection speed Vd, and correction corresponding to the ink droplet ejection speed change can be performed by controlling the parameter A according to the ink droplet ejection speed change. it can.

  FIG. 9 is a diagram for explaining correction when the distance between the recording head and the recording medium changes.

The scanning speed of the recording head is Vs, the ejection speed of the ink droplet is Vd, the angle at which the ink droplet flies is θ, the reference paper distance is d, and the distance from the ink ejection position to the ink landing position P at that time is l. . Further, the distance between the paper after the change is ds, and the distance from the ink ejection position to the ink landing position P at that time is ls. At this time,
tan θ = V / Vd = 1 / d = ls / ds Equation 9
From Equation 9: l = V * d / Vd Equation 10
ls = V * ds / Vd Equation 11
The difference lx in the distance from the ink ejection position to the landing position P in the inter-paper distance before and after the change is
lx = l−1s = V (d−ds) / Vd Equation 12
Assuming that the time required for the ink droplets to pass through the paper interval d at the ejection speed Vd is Td, and the time required for the ink droplets to pass through the paper interval ds is Tds,
Vd = d / Td = ds / Tds Equation 13
The time T required to move the landing deviation amount lx at the recording head scanning speed V is:
Tp = lx / V = V (d−ds) / (Vd * V)
= Td-Tds Equation 14

  Equation 14 shows the time required to pass the difference between the reference paper distance d and the changed paper distance ds at the ink droplet ejection speed Vd, and is proportional to the amount of change in the paper distance. . That is, it is proportional to the inverse of the ink droplet ejection speed. In other words, by applying the value of Expression 14 corresponding to the change amount between the papers and the change in the ejection speed of the ink droplets, it is possible to correct the landing position corresponding to the change in the distance between the papers.

  The delay value Tp due to the paper-to-paper variation shown in Expression 14 is related only to the change amount of the paper-to-paper distance and the ink droplet ejection speed, and is independent of the print head scanning speed. That is, the delay value due to the scanning speed variation of the recording head and the delay value due to the inter-paper variation are independent. Therefore, by reflecting the delay value Ts (FIG. 8; Expression 8) due to the fluctuation of the scanning speed and the delay value Tp (FIG. 9; Expression 14) due to the fluctuation of the inter-paper distance, the respective delay values are reflected. Corrections can be made accordingly.

  Note that when the present invention is applied, when the variation in the inter-paper distance due to the deformation of the platen is large and the variation in the scanning speed is not so high, the ejection timing delay due to the inter-paper distance variation shown in FIG. Of course, it is necessary to consider only. On the other hand, when there is an influence on the deviation of the landing position, for example, when there is a change in the discharge speed, the delay value due to the influence can be considered in the same manner as described above.

  FIG. 10 is a flowchart showing recording position control processing according to an embodiment of the present invention. This process is a process activated during the recording operation, and each acquisition timing described below is performed by determining whether there is a CPU interrupt in synchronization with the encoder signal, for example. Alternatively, a count circuit that counts signals input from the encoder signal may be provided, and it may be determined whether or not the respective acquisition timings have been reached based on the count value.

  First, when the operation start timing occurs (s901), it is determined whether the delay calculation mode is on or off (s902). Here, if the delay calculation mode is OFF, no operation is performed and the processing is terminated as it is (s903). If the delay calculation mode is ON, it is next determined whether or not it is the scanning speed information acquisition timing (s904). If it is determined that the scanning speed information acquisition timing is reached, the scanning speed information is acquired (s905), and whether the acquired scanning speed has changed by a predetermined value or more with respect to the scanning speed used for the calculation at that time. The determination (s906) is performed. If the acquired scanning speed has changed by more than a specified value, the delay time Ts is updated (s907) due to fluctuations in the scanning speed corresponding to the acquired scanning speed information.

  Next, it is determined whether it is the paper interval information acquisition timing (s908). In the case of the paper interval information acquisition timing, the paper interval information acquired in advance is acquired from the memory 116 (s909) and the delay time Tp ′ used for the correction calculation is updated (s910). To do.

  Further, it is determined whether or not it is the paper interval correction value update timing (s911). In this embodiment, in accordance with the fact that the distance between the sheets is acquired for each rib of the platen in the present embodiment, the discharge is performed at the timing based on the distance between the sheets updated at the discharge position corresponding to the rib. It is determined whether or not the timing has been met. In the case of the inter-paper correction value update timing, Tp is updated with Tp ′ (s912). Then, the delay time correction value is calculated (s913). The respective delay values Ts and Tp are obtained by the equations 8 and 14, respectively, as described above.

  FIG. 11 is a flowchart showing the inter-paper distance acquisition process according to an embodiment of the present invention. This process is performed in advance at a predetermined timing for subsequent recording operations when the recording operation is not performed, such as before the start of recording. Note that steps S1005 to S1007 shown in FIG. 11 are processing for acquiring the inter-paper distance, which will be described later as a second embodiment of the present invention, and are performed with the intervention of the user, and in the first embodiment of the present invention. Then, the process from step S1002 to step S1003 is executed.

  This process is activated when the user selects the inter-paper distance acquisition process via the user interface of the printer driver. Then, the user selects either automatic acquisition or manual acquisition through the user interface (S1101). When it is determined that automatic acquisition is performed (S1102), this embodiment is performed.

  That is, first, the recording medium on the platen is scanned by the paper interval detection unit 124 provided with the carriage 107, and the distance (inter-paper distance) between the recording head and the rib is measured at a position corresponding to each rib. (S1003). This emits laser light and measures the distance by detecting the laser light that is reflected from the recording medium on the ribs.

12A and 12B are diagrams for explaining the measurement range of the inter-paper distance.
As shown in FIG. 12A, the platen is scanned by the paper interval detection unit 124 provided in the carriage 108 at a position corresponding to the range in which the nozzles of the recording head 105 are disposed. In this scanning, the inter-paper distance is measured for each of the ribs I, II, III, IV,... N arranged in the scanning direction. In the present embodiment, this measurement is performed by dividing each rib into two areas, upstream and downstream, along the recording medium conveyance direction (paper discharge direction orthogonal to the scanning direction). As shown in FIG. 12B, when the platen is deformed in the sub-scanning direction, the inter-paper distance varies depending on the position of the nozzle. For this reason, the same rib is divided into two areas, and the measurement is stored for each divided area. These rib regions can be specified by position coordinates in the scanning direction and position coordinates in the sub-scanning direction. The areas divided by the ribs correspond to areas obtained by dividing the nozzle array of the recording head into two equal parts. In other words, the areas where ink ejected from the nozzle group divided in half correspond to the upstream portion and the downstream portion of the rib, respectively. The number of nozzles of the recording head used in this embodiment is 768, and the covering portion of the first to 385th nozzle groups from the downstream side in the transport direction is the downstream portion, that is, the odd (k) -th number shown in FIG. Corresponds to the region. The covering portion of the 385th to 768th nozzle groups indicates the even (k + 1) th rib region.

  The detection unit 124 detects the inter-paper distance at both ends in the sub-scanning direction of each of the (k) and (k + 1) areas of each rib. Then, the average value of the distance between the two ends is stored in the memory 116 as the distance between the respective (k) and (k + 1) areas (S1004). The inter-paper distance is stored in the memory together with the position information of the area in the rib.

  As described above, the inter-paper distance in the two areas of each rib is measured, and based on the inter-paper information including the inter-paper distance for each area of the rib and the position information of the area, the above-described FIG. Recording position control for determining the ejection timing is performed. As a result, even if the rib height fluctuates due to the deformation of the platen, the discharge timing (delay time) is determined according to the fluctuating height, which is caused by the fluctuation in the height of the recording medium due to the deformation of the platen. The deviation of the ink landing position can be suppressed.

(Second embodiment)
The second embodiment of the present invention relates to a form for determining the inter-paper distance based on the result of the user observing the pattern. As described above with reference to FIG. 11, when it is determined in step S1002 in FIG. 11 that the user manually sets the inter-paper distance, the processing of this embodiment is executed. First, a recording pattern is recorded on the recording medium corresponding to the rib position on the platen (S1005). Based on the recorded pattern, the user inputs the best pattern number for each rib area (S1006). When the printer driver accepts this input, the paper gap information corresponding to the number is stored in the memory (S1007).

  FIG. 13 is a flowchart showing details of the processing in steps S1005 to S1007. First, the user sets a recording medium in the recording apparatus main body, and starts recording a test pattern via a user interface by a printer driver (S1201). At this time, the user interface prompts the user to select the ink color for recording the test pattern and the size of the recording medium. In response to this, the user inputs information on the size and ink color of the recording medium (S1202, S1203). This is because the area on the platen through which the recording medium passes differs depending on the size of the recording medium, so that the inter-paper distance is acquired at the platen rib position through which the recording medium passes.

  After the input, a test pattern is recorded by the recording device (S1204). The pattern to be recorded can be a registration pattern for bidirectional recording by the recording head. For example, a pattern described in Patent Document 3 having a width corresponding to a predetermined number of pixels in the scanning direction can be a pattern that is shifted in units of pixels according to the adjustment value. This pattern is easier to determine visually than the determination based on the ruled line pattern, and can also determine a shift of one pixel or more.

  FIG. 14 is a diagram showing a state in which the pattern described in Patent Document 3 is used and recorded in correspondence with the position of the rib. In FIG. 14, a pattern element 1301, which is one unit of a pattern, is a pattern recorded by an upstream or downstream nozzle of the nozzle arrangement described in FIG. The numbers “+5” to “−5” attached to the left side of each row (in the horizontal direction in the figure) constituted by pattern elements indicate adjustment values for bidirectional registration. Here, the pattern of “0” value (default value) is recorded with a value set when shipped from the factory. Each pattern corresponding to “+5” to “−5” is recorded by shifting the ejection timing in the backward recording by one pixel while fixing the ejection timing in the forward recording. On the other hand, each row (in the vertical direction in the figure) constituted by pattern elements corresponds to a rib on the platen and a position in the scanning direction. In FIG. 14, each element 1301 of the “bidirectional registration pattern I” occupying the upper half of the pattern is recorded using the first (# 1) to 384th (# 384) nozzles which are the downstream nozzles. Is. Each element 1301 of the “bidirectional registration pattern II” occupying the lower half is recorded using the 385th (# 385) to 768th (# 768) nozzles which are the nozzles on the downstream side. .

  The method of recording this pattern is as follows. The recording medium 20 is conveyed in the direction of the arrow in the figure, and positioned so that the nozzles # 1 to # 384 of the recording head face the +5 recording position of the “bidirectional registration pattern I” on the recording medium 20. Then, the recording position of the recording medium is reciprocated by the recording head, and the pattern element 1301 is recorded at a position corresponding to each of the ribs I to k. Next, the recording medium 20 is conveyed to the next +4 recording position to the position where the nozzles # 1 to # 384 of the recording head are opposed to each other, and is similarly reciprocally scanned to pattern elements 1301 at positions corresponding to the respective ribs I to k. Record. By repeating this operation, each pattern element of the “bidirectional registration pattern I” is recorded. Next, the “bidirectional registration pattern II” is recorded in the same manner. In this case, the recording medium is positioned so that the nozzles # 385 to # 768 of the recording head face each other.

  Referring to FIG. 13 again, when the pattern is recorded, the user can select the pattern element 1301 in which the recording position is adjusted most for each rib in each of “bidirectional registration pattern I” and “bidirectional registration pattern II”. Select. Then, the value (adjustment value) is input together with the position information of the rib area (S1205). That is, the height of the recording medium on the rib is different according to the height of the rib, and the pattern element whose recording position is adjusted most differs according to the height of the recording medium. Accordingly, by defining the correspondence between the pattern element whose recording position is most adjusted in advance and the height (inter-paper distance) of the recording medium, the value of the pattern element whose recording position is most adjusted can be input. The distance between papers can be specified.

  When the user inputs an adjustment value corresponding to the selected pattern element, the paper gap information corresponding to the adjustment value is stored in the memory I16 (S1207). In the test pattern recording, one ink color is used as described above. However, the present invention is not limited to this, and a test pattern using a plurality of ink colors may be recorded. That is, at least one color ink may be used. In this case, when the test pattern recording by the first color and the input of each adjustment value are finished, the user is prompted to select either the second color or the end of the print adjustment on the printer driver (S1206). After the second ink color, the test pattern can be recorded and the adjustment value can be input as in the case of the first ink color.

  As described above, by inputting the adjustment value for registration adjustment, it is possible to acquire the inter-paper information including the inter-paper distance for each area of the rib and the position information of the area. Based on this information, the recording position control described above with reference to FIG. 10 is performed. As a result, even in this embodiment, even if the height of the rib varies due to the deformation of the platen, the discharge timing (delay time) is determined according to the varied height, and the height of the recording medium due to the deformation of the platen. Therefore, it is possible to suppress the deviation of the ink landing position due to the fluctuation of the ink.

  In this embodiment, test pattern recording and adjustment setting value acquisition in a plurality of colors are output to the user, observed, and the user selects and inputs the optimum conditions. I need. Furthermore, since it takes time from the output to the final setting, it is not advantageous in terms of time cost. Especially for beginner users who are unfamiliar with it, it is an incomprehensible and cumbersome task, and it is a method that is not preferable for customer satisfaction. However, by using a plurality of ink colors, it is possible to adjust the ejection timing of each ink color more accurately. For this reason, a user who is accustomed to some extent can make a precise adjustment in a satisfactory state, and therefore may give a better impression than the detection of the distance between the head platens by the sensor.

  Further, it is not necessary to calculate the ejection timing of the ink color used for recording the test pattern from the head platen distance, and it is possible to set the ejection timing directly from the test pattern setting value.

(Third embodiment)
Inter-paper distance information acquisition and ejection timing adjustment can be performed before recording starts as described above, when unpacking, or when a change in environmental temperature over a certain level is detected. Is possible. It is also possible to carry out both the direct detection method of the inter-paper distance by the inter-paper detection unit and the indirect detection method by bidirectional registration pattern recording. Immediately after the detection of the inter-paper distance by the inter-paper detection unit in the first embodiment, it is also possible to record the bidirectional registration adjustment pattern and derive the average value of both. Thereby, it is possible to set the ejection timing of each ink color from the more accurate acquisition of the distance information between the head platens and the ejection speed of the ink droplets.

(Fourth embodiment)
Although it will take time, it is not necessary to acquire distance information by recording the test patterns of all colors of ink mounted on the recording device and adjusting the ink droplet ejection timing at each platen rib position of each color. This makes it possible to adjust the recording position with very high accuracy.

(Fifth embodiment)
As shown in FIG. 15, when the distance between the sheets differs with respect to the sub-scanning direction, even when the carriage is inclined with respect to the sub-scanning direction as shown in FIG. Included if different. In this embodiment as well, as in the other embodiments, paper distance information by the platen area is acquired using direct means, indirect means, or both, and the ink droplet ejection timing is adjusted for each platen area. can do.

(Sixth embodiment)
When the rib is made of a material that can detect the rib of the platen by the sensor and the distance can be detected, the distance between the head and the platen rib may be regarded as the head platen distance. In this case, distance information acquisition and ink droplet ejection timing correction can be performed without a recording medium.

(A), (b), and (c) are the figures explaining the wave | undulation by the deformation | transformation of the platen in a printer. (A) is a diagram showing a dot arrangement when a monochrome image is recorded and the platen is not deformed, and (b) is a uniform density using inks of three colors of C, M, and Y. FIG. 6 is a diagram illustrating a dot arrangement when a simple image is recorded and the platen is not deformed. (A) is a diagram showing a dot arrangement when a monochrome image is recorded and the platen is deformed, and (b) is a uniform density using inks of three colors of C, M, and Y. FIG. 6 is a diagram illustrating dot arrangement when a simple image is recorded and the platen is similarly deformed. 1 is a perspective view showing a main recording part of an ink jet recording apparatus according to an embodiment of the present invention. It is a block diagram which shows the recording control part of the inkjet recording device shown in FIG. It is a figure explaining the detection structure of the distance between sheets of this embodiment, and a principle. It is a figure which shows the waveform of the signal which the encoder of this embodiment generate | occur | produces. FIG. 10 is a diagram for describing correction processing when the scanning speed of the recording head changes. FIG. 10 is a diagram illustrating correction when the distance between the recording head and the recording medium changes. It is a flowchart which shows the recording position control process which concerns on one Embodiment of this invention. It is a flowchart which shows the acquisition process of the distance between sheets concerning one Embodiment of this invention. (A) And (b) is a figure explaining the measurement range of the distance between paper concerning one Embodiment of this invention. It is a flowchart which shows the detail of the acquisition process of the distance between sheets by a user. 4 shows changes in ink droplets caused by fluctuations in the recording head scanning speed in the recording apparatus. It is a figure which shows the recording pattern used by the paper distance acquisition process which concerns on other embodiment of this invention. FIG. 10 is a diagram illustrating a distance between sheets when a recording head is tilted according to still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Platen 20 Recording medium 105 Recording head 108 Carriage 109 Encoder 111 Edge trigger production | generation part (edge detection part)
DESCRIPTION OF SYMBOLS 112 Head position detection part 113 Speed detection part 114 Edge trigger delay part 115 Paper gap information acquisition part 116 Memory 117 Delay value calculating part 118 Recording timing generation part 119 Recording position information detection part 124 Paper gap detection unit

Claims (12)

In an ink jet recording apparatus that uses a recording head that ejects ink and performs recording by ejecting ink onto a recording medium conveyed on a platen.
An inter-paper distance acquisition means for acquiring distance information between the recording medium and the recording head in correspondence with a plurality of positions of the platen;
An ejection timing determining means for determining an ink ejection timing for a position on a recording medium corresponding to the position based on the distance information of each of the plurality of positions of the platen;
An ink jet recording apparatus comprising:   2. The ink jet recording apparatus according to claim 1, wherein the recording medium is scanned by the recording head and recording is performed by ejecting ink from the recording head to the recording medium during the scanning.   The inter-paper distance acquisition means emits light at each of the plurality of positions of the platen and detects reflected light from the platen or the recording medium on the platen to detect distance information between the recording medium and the recording head. The inkjet recording apparatus according to claim 1, further comprising a detection unit.   The inter-paper distance acquisition means is a pattern recorded by each reciprocating scan of the recording head, and a pattern for adjusting the ejection timing of each reciprocating scan is set to a plurality of adjustment values for each of a plurality of positions of the platen. The inkjet recording apparatus according to claim 2, wherein the distance information between the recording medium and the recording head is acquired by recording correspondingly and receiving input of adjustment values for each of a plurality of positions of the platen. .   5. The plurality of positions of the platen are positions of ribs provided on the platen, and are divided into a plurality of positions in a direction perpendicular to the scanning direction of the recording head. Any one of the inkjet recording apparatuses.   6. The ink jet recording apparatus according to claim 4, wherein the pattern is recorded using at least one color ink among inks used in the ink jet recording apparatus.   6. The ink jet recording apparatus according to claim 4, wherein the pattern is recorded according to a size of a recording medium used for recording. In a recording position control method in an ink jet recording apparatus that performs recording by discharging ink onto a recording medium conveyed on a platen using a recording head that discharges ink,
An inter-paper distance acquisition step of acquiring distance information between the recording medium and the recording head in correspondence with a plurality of positions of the platen;
An ejection timing determining step for determining an ink ejection timing for a position on the recording medium corresponding to the position based on the distance information of each of the plurality of positions of the platen;
A recording position control method characterized by comprising:   9. The recording position control method according to claim 8, wherein the ink jet recording apparatus performs recording by scanning a recording medium with a recording head and discharging ink from the recording head to the recording medium during the scanning.   The inter-paper distance acquisition step detects the distance information between the recording medium and the recording head by emitting light at each of a plurality of positions of the platen and detecting reflected light with respect to the platen or the recording medium on the platen. 10. The recording position control method according to claim 8, further comprising a detection step.   The inter-paper distance acquisition step is a pattern recorded by each reciprocating scan of the recording head, and a pattern for adjusting the ejection timing of each reciprocating scan is set to a plurality of adjustment values for each of a plurality of positions of the platen. 10. The recording position control according to claim 9, wherein recording is performed correspondingly, and distance information between the recording medium and the recording head is acquired by receiving an input of an adjustment value for each of a plurality of positions of the platen. Method.   12. The plurality of positions of the platen are positions of ribs provided on the platen, and are each divided into a plurality of positions in a direction orthogonal to the scanning direction of the recording head. The recording position control method according to any one of the above.

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