JP2009208248A - Recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording device achieving high-quality recording based on exact recording timing by exactly performing correction without being influenced by change of a phase difference between pulse signals from a plurality of encoders when switching the pulse signals therefrom. <P>SOLUTION: The phase difference between the pulse signals from the first and second encoders is detected continuously in a predetermined period, and a variation pattern of the detected phase difference in the predetermined period is stored. When switching a signal source from the first encoder to the second encoder, an actual phase difference between the pulse signals at a point of time when a phase is corrected is estimated from comparison of the variation of the phase difference detected at a point of time when a correction start signal is output with the stored variation pattern of the phase difference when correcting the pulse signal from the second encoder so that the phases of the pulse signals from the first and second encoders may match with each other by taking output of the correction start signal of the phase as a trigger. On the basis of the estimated phase difference, the phase of the pulse signal from the second encoder is corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording apparatus, and more particularly to a recording apparatus that can detect an accurate amount of movement of a recording medium conveyed on a conveying belt and perform high-quality recording.

  An ink jet recording apparatus that transports a recording medium by a transport belt has a top surface of a transport belt that is stretched around a plurality of rollers as a mounting surface of the recording medium, and is driven by rotating one of the rollers as a drive roller. The belt is rotated, and the recording medium placed thereon is conveyed. Image recording on a recording medium conveyed on the conveying belt is performed by ejecting ink from the recording head at an appropriate timing according to the position of the recording medium in the middle of conveyance, so that accurate recording on the recording medium is performed. Therefore, it is necessary to accurately detect the position of the recording medium from the start to the end of recording.

  Generally, the position of the recording medium conveyed on the conveyance belt can be detected by a pulse signal output from an encoder provided coaxially with a roller that stretches the conveyance belt (Patent Document 1). However, this method does not directly detect the position of the recording medium.

  On the other hand, it has been proposed to read the position of the recording medium by bringing the driven roller into contact with the surface of the recording medium and rotating the recording medium following the movement of the recording medium and providing an encoder coaxially with the driven roller. (Patent Document 2). According to this, the position of the recording medium can be directly detected.

  However, since the recording medium has a leading edge and a trailing edge, even if the position of the recording medium starts to be detected from the time when the leading edge passes through the nip between the driven roller having the encoder and the conveyor belt, the trailing edge is eventually driven. Since the roller is separated from the nip between the roller and the conveyor belt, an impact occurs when the driven roller collides with the conveyor belt at the time of separation, and an error occurs in the encoder pulse output from the encoder. The driven roller that is in contact with the surface of the recording medium needs to be in contact with the surface of the recording medium before recording in order to protect the recorded image. Therefore, the driven roller is generally disposed upstream of the recording head in the conveyance direction of the recording medium. The Therefore, when the rear end of the recording medium leaves the nip between the driven roller and the conveyor belt, recording is still being performed by the recording head, so the recording timing is shifted due to the detection error of the recording medium position, and the recorded image is May be disturbed.

  For this reason, in addition to the encoder provided on the driven roller that rotates in contact with the recording medium, for example, an encoder is provided on the drive roller of the conveyor belt, and the recording timing is controlled before the trailing edge of the recording medium is detached from the driven roller. By switching the signal source for switching to the encoder provided on the driving roller, the position of the recording medium is continued from the leading edge to the trailing edge without being affected by the error caused by the impact when the trailing edge of the recording medium is separated from the driven roller. It is conceivable to enable detection.

At this time, there may be a phase difference between the encoder pulses when the encoder is switched. Conventionally, a technique for correcting the phase difference between encoder pulses is known (Patent Document 3). It is considered that the problem of the phase difference at the time of switching the encoder can be solved by applying a technique for correcting.
JP 2005-219339 A JP 58-11861 A JP 2007-105970 A

  However, there is a new problem when correcting the phase difference between the encoder pulses when switching the encoder.

  That is, the phase difference between the encoder pulses output from two encoders provided at different positions is not always constant. For example, a roller generally has an outer diameter error (flare) slightly different in outer diameter with respect to the phase of the roller. Since the outer diameter error of a roller usually occurs during processing, it varies from roller to roller and is not necessarily uniform.

  FIG. 10 is a graph showing the phase difference of pulse signals from two encoders coaxially provided on the rotation shafts of two different rollers that rotate when the recording medium is conveyed, and the amount of change in the phase difference. Thus, even if each pulse signal is compared and its phase difference is detected, the phase difference always changes due to the outer diameter error of the roller. Moreover, since the circumferences of the rollers differ due to the outer diameter error of the rollers, this phase difference increases.

  FIG. 11 is a timing chart showing how the phase difference between the pulse signals EP1 and EP2 from the two encoders coaxially provided on the rotation shafts of two different rollers is corrected. Each pulse signal EP1, EP2 has a phase difference of Δt1, Δt2, Δt3, Δt4. Each of these phase differences is not constant due to the outer diameter error of the roller.

  Now, at a certain timing T, the encoder pulse signal for generating the recording timing is switched from the pulse signal EP1 to the pulse signal EP2. For this reason, the phase of the pulse signal EP2 at this timing T is matched with the phase of the pulse signal EP1. At this time, since the phase difference to be corrected is the phase difference Δt3 measured immediately before the timing T, the pulse signal EP2 ′ obtained by shifting the phase of the pulse signal EP2 by Δt3 is obtained as the pulse signal of the encoder after correction. become.

  However, since the actual phase difference between the pulse signals EP1 and EP2 immediately after the timing T is Δt4 (> Δt3), the pulse signal EP2 ′ is out of phase with the pulse signal EP1 by Δt4−Δt3. Will be corrected. In other words, even if the phase difference between the pulse signals of the two encoders is corrected at a certain timing, the phase difference changes due to the outer diameter error of the roller. There is a problem that inaccurate correction is performed due to the deviation. Normally, the recording timing is synchronized with the rising pulse of the encoder pulse signal, so if the correct phase cannot be corrected, the phase difference will remain slightly when the encoder pulse signal for controlling the recording timing is switched. As a result, the rising pulse of the pulse signal of the encoder is shifted, so that a slight shift occurs in the recording timing, and banding occurs in which the image is shifted only at a certain position, and a high quality image cannot be obtained.

  The encoder for detecting the position of the recording medium is not only provided coaxially with the rotating shaft of the roller as described above, but also, for example, an encoder formed by a linear scale at the end of the conveyor belt. As described above, the above-described rotational difference is caused by the difference in phase difference caused by the outer diameter error of the roller.

  Therefore, the problem of the present invention is to change the phase difference of each pulse signal when switching each pulse signal from a plurality of encoders for detecting the position of the recording medium in order to control the recording timing of the recording medium. It is an object of the present invention to provide a recording apparatus that can perform accurate correction without being affected and can perform high-quality recording based on accurate recording timing.

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

  According to the first aspect of the present invention, a conveying unit that conveys a recording medium, a recording unit that records an image on the recording medium conveyed by the conveying unit, and a position of the recording medium conveyed by the conveying unit are detected. A first encoder and a second encoder which are provided at different positions and output a pulse signal by rotating, and a recording timing control for controlling a recording timing by the recording unit according to the position of the recording medium Means, switching means for switching the signal source for controlling the recording timing in the recording timing control means to the first encoder or the second encoder according to the position of the recording medium, and the recording medium being conveyed And a phase between pulse signals respectively output from the first encoder and the second encoder. When the signal source is switched from the first encoder to the second encoder by the switching means, the output of the phase correction start signal is used as a trigger when the signal source is switched by the switching means. And a phase correction means for correcting the pulse signal output from the second encoder so that the phases of the pulse signals output from the encoder and the second encoder respectively match, A change amount pattern storage means for storing a change amount pattern of a phase difference detected by the phase difference detection means for a predetermined period; a phase difference change amount pattern detected continuously by the phase difference detection means for a predetermined period; and The point of time when correction is performed by the phase correction unit based on the comparison with the variation pattern of the phase difference stored in the variation pattern storage unit A phase difference predicting unit that predicts a phase difference between each of the pulse signals, and the phase correcting unit outputs a pulse output from the second encoder based on the phase difference predicted by the phase difference predicting unit. A recording apparatus that corrects the phase of a signal.

  According to a second aspect of the present invention, the phase difference predicting means changes between the phase difference last detected by the phase difference detecting means at the output time of the correction start signal and the phase difference appearing immediately before the phase difference. Based on the value of the amount, the value of the amount of change that appears next is predicted from the comparison with the amount of change pattern stored in the amount of change pattern storage means, and the predicted change amount and the output time point of the correction start signal 2. The recording apparatus according to claim 1, wherein a predicted value of the actual phase difference is calculated by adding the phase difference detected last by the phase difference detecting means.

  The invention according to claim 3 has period modulation means for modulating the period of the pulse signal output from the second encoder, and the variation pattern storage means is transmitted from the second encoder by the period modulation means. The phase difference variation pattern after modulation is performed so that the period of the output pulse signal coincides with the period of the pulse signal output from the first encoder. It is a recording apparatus of description.

  According to a fourth aspect of the present invention, on the upstream side of the recording unit in the conveyance direction of the recording medium, the surface of the recording medium conveyed by the conveying unit contacts the surface of the recording medium and rotates following the movement of the recording medium. A driven roller, wherein the first encoder is provided coaxially with a rotation shaft of the driven roller, and the conveying means includes a conveying belt stretched around a plurality of conveying rollers, and the second encoder The recording apparatus according to claim 1, wherein the recording apparatus is provided coaxially with a rotation shaft of any of the plurality of transport rollers.

  According to a fifth aspect of the present invention, the switching unit includes a signal source for controlling the recording timing in the recording timing control unit immediately before the trailing edge of the recording medium is released from contact with the driven roller. The recording apparatus according to claim 4, wherein the recording apparatus is switched to a second encoder.

  According to the present invention, when switching each pulse signal from a plurality of encoders for detecting the position of the recording medium in order to control the recording timing of the recording medium, it is influenced by the change in the phase difference of each pulse signal. Therefore, it is possible to provide a recording apparatus that can correct the image quality accurately and can perform high-quality recording based on accurate recording timing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a schematic configuration of the ink jet recording apparatus, and FIG. 2 is a block diagram showing an internal configuration of a main part of the ink jet recording apparatus.

  The belt conveyance device 1 shown in FIG. 1 is configured by an endless conveyance belt 13 stretched between two conveyance rollers 11 and 12. Here, one conveyance roller 11 is rotationally driven by a conveyance motor 14 controlled by the overall control unit 8 to rotate the conveyance belt 13 counterclockwise in the figure. The other transport roller 12 rotates following the rotation of the transport belt 13.

  A flat surface on the upper surface of the conveyance belt 13 is a conveyance surface 13a of the recording medium S, and the recording head 2 is arranged on the conveyance surface 13a with a predetermined interval. The recording head 2 has a large number of nozzles arranged on the surface facing the conveyance surface 13a, and ejects ink at an appropriate timing generated by the timing generation unit 7 according to the position of the recording medium S from each nozzle. The ink jet head records a predetermined image by causing ink to land on the recording medium S located below the recording medium S. Here, the recording head 2 has a length that extends over the entire width of the conveyor belt 13 and exemplifies a line head that is fixedly disposed on the conveyor belt 13, but the narrow head is conveyed. A shuttle type recording head that records an image by reciprocating along the width direction of the belt 13 may be used.

  On the transport surface 13 a of the transport belt 13, the driven roller 3 is disposed at a predetermined distance upstream of the recording head 2 in the transport direction of the recording medium S. The driven roller 3 is installed across the width direction of the transport belt 13 and is provided so as to press the transport surface 13a of the transport belt 13 with a predetermined pressing force. The driven roller 3 comes into contact with the upper surface of the recording medium S that is placed on the conveying surface 13 a and conveyed by the rotation of the conveying belt 13, and rotates following the conveying movement of the recording medium S.

  On the upstream side of the driven roller 3 in the transport direction of the recording medium S, the end detection sensor 4 is disposed above the transport surface 13a with a predetermined interval. The edge detection sensor 4 is composed of, for example, a reflection type optical sensor, and outputs an ON signal to the overall control unit 8 when the leading edge of the recording medium S passes thereunder. In addition, an OFF signal is output to the overall control unit 8 when the rear end of the recording medium S passes below.

  The driven roller 3 and the transport roller 11 are provided with a first encoder 5 and a second encoder 6, respectively. The first encoder 5 is provided coaxially with the rotation shaft of the driven roller 3, and the disk 5 a rotates with the rotation of the driven roller 3, and a pulse signal is detected by detecting a scale formed radially on the disk 5 a. Output to the timing generator 7. The second encoder 6 is provided coaxially with the rotation shaft of the transport roller 11, and the disk 6 a rotates with the rotation of the transport roller 11, and the pulse is detected by detecting the scale formed radially on the disk 6 a. The signal is output to the timing generator 7.

  The first encoder 5 and the second encoder 6 are preferably of the same manufacturer and the same standard (same model number). Further, it is preferable that the driven roller 3 provided with the first encoder and the transport roller 11 provided with the second encoder 6 have the same nominal diameter. This is because the phase difference between the pulse signals of the first encoder 5 and the second encoder 6 can be made as small as possible, and accuracy can be ensured in the subsequent phase correction.

  FIG. 3 is a block diagram showing details of the timing generation unit 7.

For the pulse signals output from the first encoder 5 and the second encoder 6, the phase difference between the pulse signals is continuously measured by the phase difference measuring unit 71 in the timing generation unit 7. For example, as shown in FIG. 4, phase differences ΔT ₁ , ΔT ₂ , ΔT ₃ ... Are generated between the pulse signal from the first encoder 5 and the pulse signal from the second encoder 6. Here, the difference between the rising pulses of the pulse signal is detected as a phase difference, but the difference between the falling pulses of the pulse signal may be detected as a phase difference. Each phase difference can be measured by counting clock pulses output from a clock pulse generator (not shown).

When the phase difference between the pulse signals is measured by the phase difference measuring unit 71, each value of the phase difference is output to the phase difference change amount measuring unit 72 one after another. The phase difference change amount measuring unit 72 calculates phase difference change amounts ΔT ₂ −ΔT ₁ , ΔT ₃ −ΔT ₂ ,... ΔT _n −ΔT _n−1 for each pulse signal sent from the phase difference measuring unit 71 one after another. measure. The amount of change in the phase difference has a certain period as shown in FIG. This is due to the outer diameter error of the driven roller 3 provided with the first encoder 5 and the conveying roller 11 provided with the second encoder 6.

  The amount of change measured by the phase difference change amount measuring unit 72 for a predetermined period is sent to and stored in the change amount pattern storage unit 73. This predetermined period is preferably one cycle of the driven roller 3 and the conveying roller 11, that is, during the rotation of these rollers once. This is because the outer diameter error of the roller repeats fluttering almost every cycle. The change amount of the phase difference stored in the phase difference change amount storage unit 73 is used when the phase correction unit 74 performs phase correction later.

  Note that the amount of change in phase difference stored in the change amount pattern storage unit 73 may be updated for each cycle of the driven roller 3 and the transport roller 11. In addition, the recording medium S is not always measured and stored every time the recording medium S is actually transported, but may be stored in advance as a default value. When the phase difference varies depending on the type (thickness) of the recording medium S, etc., a plurality of types of change amount patterns corresponding to the type of the recording medium S are stored and read out according to the type of the recording medium S. It is also preferable to use them.

  The pulse signal output from the first encoder 5 is sent to the switching unit 75, and the pulse signal output from the second encoder 6 is sent to the switching unit 75 via the phase correction unit 74.

The phase correction unit 74 uses the correction start signal sent from the overall control unit 8 as a trigger so that the phase of the pulse signal output from the second encoder 6 matches the phase of the pulse signal of the first encoder 5. to correct. This will be described with reference to FIGS. 4 and 5. Phase differences ΔT ₁ , ΔT ₂ , ΔT between the pulse signal output from the first encoder 5 and the pulse signal output from the second encoder 6 are described. ₃ ... exists. These phase differences are not constant. When one cycle of the driven roller 3 and the conveying roller 11 is compared, the phase difference variation pattern repeats with a predetermined cycle.

Now, when a correction start signal is output at a certain timing and this is used as a trigger to start phase correction, a pulse signal output from the first encoder 5 and a pulse signal output from the second encoder 6 It is measured that there is a phase difference of ΔT _n between them. However, the phase of the pulse signal of the second encoder 6 is actually corrected by a pulse signal (here, the pulse signal P _n from the second encoder 6 at the time when the correction start signal is output). Next pulse signal P _{n + 1} ). Here, even if the phase of the pulse signal P _{n + 1} is corrected by the measured phase difference ΔT _n at the time of the next pulse signal P _{n + 1} , the phase difference is already ΔT _{n + 1} (≠ ΔT _n ) at that time. Therefore, accurate phase correction is not performed.

  Therefore, when the correction start signal is output, the phase correction unit 74 corrects the phase by the following method.

First, before the output time of the correction start signal, the phase difference [Delta] T ₁ measured by the phase difference measurement unit _{71, ΔT 2, ΔT 3,} ... ΔT variation [Delta] T ₂ -.DELTA.T ₁ of _n, ΔT ₃ -ΔT _2, ... ΔT _n −ΔT _n−1 is calculated by the phase difference change amount measuring unit 72. Since the amount of change in the last phase difference at the time when the correction start signal is output is ΔT _n −ΔT _n−1 , the phase correction unit 74 outputs this to the change amount pattern storage unit 73 when the correction start signal is output. Compared with the stored variation pattern, the variation amount of the phase difference that appears next is predicted. For example, when the variation pattern stored in the variation pattern storage unit 73 is as shown in FIG. 5, the variation in the phase difference that appears next to ΔT _n −ΔT _n−1 is ΔT _{n + 1} −ΔT _n . It is predicted. Then, the predicted ΔT _{n + 1} −ΔT _n and the phase difference ΔT _n measured last when the correction start signal is output are added to calculate the predicted value ΔT _{n + 1} of the phase difference. The phase correction unit 74 corrects the phase of the pulse signal output from the second encoder 6 using the predicted value ΔT _{n + 1} as an actual phase correction value.

  The switching unit 75 is controlled by a switching command signal from the overall control unit 8, so that a signal source for generating a recording pulse in the recording pulse generation unit 76 is a pulse signal output from the first encoder 5. Or the pulse signal output from the second encoder 6 and subjected to phase correction by the phase correction unit 74 is switched.

  The recording pulse generation unit 76 generates the timing of the recording pulse based on the pulse signal output from the first encoder 5 or the pulse signal output from the second encoder 6 and subjected to phase correction by the phase correction unit 74. Then, the data is output to the recording head 2 in accordance with image data (not shown).

  Next, the conveyance and recording operation of the recording medium S will be described using the flowchart of FIG.

  First, after the conveyance motor 14 is driven by the overall control unit 8 and the conveyance roller 11 is rotated forward, the conveyance belt 13 is rotated (S1), and then the recording medium S is conveyed by the sheet feeding roller (not shown) on the conveyance surface of the conveyance belt 13. 13a (S2). The recording medium S placed on the transport surface 13a is transported by the transport belt 13, and eventually the end detection sensor 4 is turned on when the tip passes below the end detection sensor 4 (S3).

  When the end detection sensor 4 is turned on, the overall control unit 8 counts a predetermined number N1 of pulse signals output from the second encoder 6 provided on the transport roller 11 (S4). The predetermined number N1 is the amount of movement d of the recording medium S that is supposed to reach the nip between the driven roller 3 and the conveyor belt 13 after the leading edge of the recording medium S passes the end detection sensor 4 (FIG. 1). The number of pulse signals corresponding to the reference). If the pulse signal is counted by N1, the leading edge of the recording medium S reaches the nip between the driven roller 3 and the conveying belt 13, so that the moving amount (position) of the recording medium S is thereafter changed to the driven roller 3. This may be detected by a pulse signal output from the first encoder 5 provided.

  After counting this predetermined number N1, the overall control unit 8 sets the switching unit 75 so that the pulse signal output to the recording pulse generation unit 76 is from the first encoder 5, and the driven roller 3 is set to the recording medium. Acquisition of a pulse signal from the first encoder 5 generated when rotating while contacting the surface of S is started (S5).

  By obtaining the pulse signal from the first encoder 5, the pulse signals of both the first encoder 5 and the second encoder 6 are input to the timing generation unit 7. Therefore, in the timing generation unit 7, the phase difference measurement unit 71 and the phase difference change amount measurement unit 72 start measuring the phase difference between the pulse signals of the first encoder 5 and the second encoder 6, and follow The variation pattern of the phase difference for one cycle of the roller 3 and the conveyance roller 11 is stored in the variation pattern storage unit 73 (S6).

  When it is detected that the leading edge of the recording medium S has reached the recording position below the recording head 2 based on the pulse signal output from the first encoder 5 (S7), the timing generator 7 Using the pulse signal from the first encoder 5 as a signal source, image recording by the recording head 2 is started at a predetermined timing (S8).

  Thereafter, when the rear end of the recording medium S passes below the end detection sensor 4 and the end detection sensor 4 is turned off (S9), the overall control unit 8 includes a first roller provided on the driven roller 3. A predetermined number N2 of pulse signals output from the encoder 5 are counted (S10). The predetermined number N2 is the amount of movement d of the recording medium S that is supposed to reach the nip between the driven roller 3 and the conveyor belt 13 after the trailing edge of the recording medium S passes the end detection sensor 4 (see FIG. The value is smaller than the number of pulse signals corresponding to 1). If the pulse signal is counted by N2, the rear end of the recording medium S is positioned slightly in front (upstream) of the nip between the driven roller 3 and the conveying belt 13, and the recording medium S is still present. Is in a state of being pressed by the driven roller 3. This is because the phase correction is performed immediately before the rear end of the recording medium S is removed from the nip between the driven roller 3 and the conveyance belt 13 as much as possible. Thereby, the period during which the position of the recording medium S can be directly detected by the rotation of the driven roller 3 is lengthened, so that highly accurate position detection can be performed.

After counting the predetermined number N2, the overall control unit 8 outputs a correction start signal to the phase correction unit 74 of the timing generation unit 7 (S11). Upon receiving this correction start signal, the phase correction unit 74 receives the last phase difference change amount ΔT _n −ΔT _n−1 measured by the phase difference change amount measurement unit 72 up to that point in time as the change amount pattern storage unit. 73 compared with the stored variation pattern, predicts the change amount ΔT _{n + 1} -ΔT n phase difference appearing in the next, and ΔT _{n + 1} -ΔT n expected, the last at the output time point of the correction start signal A predicted value ΔT _{n + 1} is obtained by adding the phase difference ΔT _n (S12).

The phase correction unit 74 uses the predicted value ΔT _{n + 1} as an actual phase correction value, and corrects the phase of the pulse signal output from the second encoder 6 based on this value so as to be shifted by ΔT _{n + 1} (S13). ). Thereby, the phase of the pulse signal from the subsequent first encoder 5 and the phase of the pulse signal from the second encoder 6 coincide with each other.

  Thereafter, before the rear end of the recording medium S leaves the nip between the driven roller 3 and the conveyor belt 13, the overall control unit 8 outputs a switching command signal to the switching unit 75, and the recording pulse generation unit 76. The signal source of the panel signal to be output is switched from the first encoder 5 to the second encoder 6 (S14). The timing of this switching can be, for example, the time when the pulse signal from the first encoder 5 is counted by a predetermined number N3 from the time when the end detection sensor 4 is turned off. This predetermined number N3 is a pulse signal from the first encoder 5 corresponding to the amount of movement of the recording medium S that seems to be immediately before the trailing end of the recording medium S passes through the nip between the driven roller 3 and the conveyor belt 13. Number (where N3> N2).

  Thereafter, the recording medium S records an image based on the pulse signal output from the second encoder 6 provided on the transport roller 11 until the image recording is completed (S15).

  Thus, the signal source for controlling the recording timing is changed from the first encoder 5 to the second encoder 6 before the trailing end of the recording medium S passes through the nip between the driven roller 3 and the conveying belt 13. Can be switched. Moreover, when switching from the first encoder 5 to the second encoder 6, it can be corrected accurately without being affected by the change in phase difference of each pulse signal, and high-quality recording can be performed based on accurate recording timing. It can be carried out.

  In the above embodiment, the output timing of the correction start signal is after the pulse signal has been counted by a predetermined number N2 after the end detection sensor 4 is turned off, but between the driven roller 3 and the end detection sensor 4. By appropriately setting the separation distance, the time when the end detection sensor 4 is turned off can be set as the output timing of the correction start signal.

  Further, the second encoder 6 is not limited to the one provided coaxially with the conveyance roller 11, and for example, as shown in FIG. 7, the pulse is detected by detecting a linear scale 9 provided around the side end of the conveyance belt 13. The structure which outputs a signal may be sufficient.

  Incidentally, the driven roller 3 provided with the first encoder 5 and the transport roller 11 provided with the second encoder 6 may not necessarily have the same diameter. Further, the first encoder 5 and the second encoder 6 may not be the same manufacturer and the same standard (same model number). For this reason, the pulse signal output from the first encoder 5 and the pulse signal output from the second encoder 6 may be assumed not only to have a phase difference but also to have a period that does not match.

  FIG. 8 shows a timing generator 7 that is preferable when the periods between the pulse signals are different. In addition to the configuration shown in FIG. 3, the pulse signal output from the first encoder 5 and the second encoder 6 are shown. Has a period measuring unit 77 for measuring each period of the pulse signal output from.

  When the phase correction unit 74 receives the correction start signal and executes the phase correction, the pulse signal output from the second encoder 6 so that the periods of the pulse signals measured by the period measurement unit 77 coincide with each other. Modulate the period. For example, the outer diameter of the driven roller 3 provided with the first encoder 5 is d1, the number of pulse signals when the first encoder 5 makes one cycle is p1, and the conveyor belt 13 provided with the second encoder 6 is provided. The frequency of the pulse signal output from the second encoder 6 is (d2), where d2 is the outer diameter of the transport roller 11 taking the thickness of the second encoder 6 into account and p2 is the number of pulse signals when the second encoder 6 makes one cycle. Xp1) / (d1 * p2) times.

  FIG. 9 is a timing chart showing how the period of the pulse signal output from the second encoder 6 is modulated. The pulse signal output from the second encoder 6 has a longer period than the pulse signal output from the first encoder 5, and the period of each pulse signal is measured by the period measuring unit 77. Here, when the correction start signal is output, it is output from the second encoder 6 by multiplying the frequency of the pulse signal output from the second encoder 6 by (d2 × p1) / (d1 × p2). The period of the pulse signal is matched with the pulse signal output from the first encoder pulse 5. Thereafter, the phases of the pulse signals are matched as described above. Thereby, the mismatch of the period between each pulse signal can be corrected, and exact phase correction can be performed.

  The method of modulating the period in this way is performed by extracting the harmonic component of the pulse signal output from the second encoder 6. For this reason, in order to make the periods between the pulse signals coincide with each other, the value of (d2 × p1) / (d1 × p2) must be an integer. For this reason, it is preferable to appropriately set the outer diameter of each roller and the number of pulse signals when the encoder makes one rotation so that the value of (d2 × p1) / (d1 × p2) is an integer.

  When the second encoder 6 is configured to detect the linear scale 9 provided around the conveyor belt 13 as shown in FIG. 7, the first encoder 5 is used to match the period of each pulse signal. The outer diameter of the driven roller 3 provided is L1, the number of pulses when the first encoder 5 makes one cycle is p1, the circumference of the second encoder composed of the linear scale is L2, and the second encoder has one cycle ( The frequency of the pulse signal output from the second encoder may be multiplied by (L2 × p1) / (L1 × p2), where p2 is the number of pulses when the conveyor belt 13 is rotated once). .

  The above embodiment exemplifies an ink jet recording apparatus as the recording apparatus. However, the present invention can be applied to any recording apparatus that performs recording by conveying the recording medium S using the conveyance belt 13. For example, a toner image on the recording medium S is applicable. Or a recording apparatus such as an image forming apparatus that forms an exposure image by light exposure such as an LED light source or an organic EL.

Side view showing schematic configuration of inkjet recording apparatus Block diagram showing the internal configuration of the main part of the inkjet recording apparatus Block diagram showing details of timing generator Pulse signal timing chart Graph showing phase difference variation pattern Flow chart showing recording medium conveyance and recording operation Partial plan view of a conveyor belt showing another example of the second encoder The block diagram which shows the detail of the timing generation part which concerns on another aspect Timing chart of pulse signal when changing period Graph showing the phase difference of encoder pulses from two encoders coaxially provided on the rotation shafts of two different rollers that rotate when the recording medium is conveyed and the amount of change in the phase difference Timing chart showing how to correct the phase difference between pulses P1 and P2 from two encoders coaxially provided on the rotation shafts of two different rollers.

Explanation of symbols

1: Belt conveying device 11, 12: Conveying roller 13: Conveying belt 14: Conveying motor 2: Recording head 3: Driven roller 4: End detection sensor 5: First encoder 5a: Disk 6: Second encoder 6a: Disc 7: Timing generation unit 71: Phase difference measurement unit 72: Phase difference change amount measurement unit 73: Change amount pattern storage unit 74: Phase correction unit 75: Switching unit 76: Recording pulse generation unit 77: Period measurement unit 8: Overall Control unit 9: Linear scale

Claims (5)

Conveying means for conveying the recording medium;
Recording means for recording an image on the recording medium conveyed by the conveying means;
A first encoder and a second encoder, which are provided at different positions for detecting the position of the recording medium conveyed by the conveying means, and which output a pulse signal by rotating;
Recording timing control means for controlling the recording timing by the recording means in accordance with the position of the recording medium;
Switching means for switching the signal source for controlling the recording timing in the recording timing control means to the first encoder or the second encoder according to the position of the recording medium;
Phase difference detection means for continuously detecting a phase difference between pulse signals respectively output from the first encoder and the second encoder during conveyance of the recording medium;
When the signal source is switched from the first encoder to the second encoder by the switching means, pulses output from the first encoder and the second encoder, respectively, triggered by the output of a phase correction start signal A recording apparatus comprising: phase correction means for correcting the pulse signal output from the second encoder so that the phases of the signals match;
A change amount pattern storing means for storing a change amount pattern of a predetermined period of the phase difference detected by the phase difference detecting means;
From the comparison between the change amount of the phase difference detected continuously by the phase difference detection means for a predetermined period and the change pattern of the phase difference stored in the change pattern storage means, the phase correction means corrects the phase. Phase difference prediction means for predicting the actual phase difference between each pulse signal at the time of performing,
The recording apparatus, wherein the phase correction unit corrects the phase of the pulse signal output from the second encoder based on the phase difference predicted by the phase difference prediction unit.   The phase difference prediction means is based on the value of the amount of change between the phase difference last detected by the phase difference detection means at the output time of the correction start signal and the phase difference that appears immediately before the phase difference. The value of the change amount that appears next is predicted from the comparison with the change amount pattern stored in the change amount pattern storage means, and at the time of output of the predicted change amount and the correction start signal, the phase difference detection means finally The recording apparatus according to claim 1, wherein the predicted value of the actual phase difference is calculated by adding the detected phase difference to the phase difference. Periodic modulation means for modulating the period of the pulse signal output from the second encoder;
The change pattern storage means is modulated by the period modulation means so that the period of the pulse signal output from the second encoder matches the period of the pulse signal output from the first encoder. The recording apparatus according to claim 1, wherein a phase difference variation pattern is stored. A driven roller that contacts the surface of the recording medium conveyed by the conveying means and rotates following the movement of the recording medium upstream of the recording means in the conveying direction of the recording medium; The encoder is provided coaxially with the rotating shaft of the driven roller,
The conveyance means includes a conveyance belt stretched around a plurality of conveyance rollers, and the second encoder is provided coaxially with a rotation shaft of any of the plurality of conveyance rollers. Item 4. A recording apparatus according to item 1, 2 or 3.   The switching unit switches the signal source for controlling the recording timing in the recording timing control unit to the second encoder immediately before the rear end of the recording medium is released from contact with the driven roller. The recording apparatus according to claim 4.

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