JP2019014241A - Recording device - Google Patents

Abstract

To provide a recording device capable of preventing lowering of an image quality due to a speed difference between an upstream side roller pair and a downstream side roller pair.SOLUTION: A recording device includes: a first roller pair which is positioned on the upstream side of a recording head in a recording medium conveyance direction, conveys the recording medium to a discharge position of the recording head at a first conveyance speed, and is idled by pulling the sandwiching recording medium to the downstream side in the conveyance direction; a second roller pair which is positioned on the downstream side of the recording head and conveys the recording medium at a second conveyance speed higher than the first conveyance speed; a first rotation detection unit which detects information on the rotation speed of the roller of the first roller pair; and a control unit which controls the recording head so that the recording head performs discharge at a discharge timing based on the result of the rotation detection unit, when the second roller pair does not sandwich the recording medium and the first roller pair conveys the recording medium at the first conveyance speed, and the second roller pair sandwiches the recording medium and conveys the recording medium at the second conveyance speed and the first roller pair sandwiches the recording medium conveyed by the second roller pair and is idled.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a recording apparatus that records an image on a transported recording medium.

  In the recording medium transport path, ink is transferred from the recording head to a recording medium that is nipped and transported by a roller pair disposed upstream of the recording head and a roller pair disposed downstream of the recording head. There is a recording apparatus that forms an image on a recording medium by ejecting the ink. In such a recording apparatus, generally, the rotational speed of the downstream roller pair is set higher than the rotational speed of the upstream roller pair, and the nip of the downstream roller pair is set higher than the nip pressure of the upstream roller pair. The pressure is set low. As a result, when the recording medium is nipped and transported between both roller pairs, the recording medium is transported at the transport speed of the upstream roller pair having a high nip pressure, and the downstream speed is low although the rotational speed is fast. By sliding the pair of rollers on the recording medium, tension is applied to the conveyed recording medium to prevent the recording medium from being bent between the two roller pairs. However, in such a transport mechanism, when the trailing end of the recording medium passes through the upstream roller pair, the transport speed of the recording medium up to that time is due to the downstream roller pair having a higher rotational speed than the upstream roller pair. When the ink is ejected from the recording head, a large speed fluctuation of the recording medium occurs during the ejection of the ink from the recording head.

  On the other hand, in Patent Document 1, an encoder for detecting rotation is provided for each of the upstream and downstream roller pairs, and this occurs in both roller pairs when the trailing edge of the recording medium passes through the upstream roller pair. A speed difference is detected, and in response to the detection, the transport speed of the downstream roller pair is changed to a low speed equivalent to the transport speed of the upstream roller pair. In Patent Document 2, an encoder for detecting rotation is provided for each of the upstream and downstream roller pairs to detect the rotation of the roller pair. Immediately after the trailing edge of the recording medium passes through the upstream roller pair, The trailing edge of the recording medium at the virtual conveying speed V3 calculated from the conveying speed V1 of the upstream roller pair and the conveying speed V2 of the downstream roller pair without using the actual measured value of the encoder that cannot follow the rapid speed change. The discharge control is performed on the assumption that the sheet is being conveyed for a predetermined period before and after passing through the upstream roller pair.

JP-A-8-142431 JP 2013-59869 A

  However, as in Patent Document 1, in the configuration in which the speed difference between the two roller pairs is detected after the trailing edge of the recording medium passes through the upstream roller pair, and the conveyance speed by the downstream roller pair is switched, the conveyance speed is switched. In the meantime, the speed during switching may not be suitable for the ink ejection timing. That is, if the ink discharge timing is synchronized with the transport speed of the upstream roller pair after the switching, the ink discharge timing and the transport speed do not match until the speed switching is completed. As a result, the ink position on the recording medium may be displaced. In Patent Document 2, the discharge control is performed for a predetermined period before and after the trailing edge of the recording medium passes through the upstream roller pair, assuming that the recording medium is transported at the calculated virtual transport speed V3, but the transport speed V3 is calculated. Virtual speed. For this reason, the conveyance speed V3 may be different from the actual conveyance speed, and the ink discharge timing may not match the conveyance speed, and the ink position on the recording medium may be shifted.

  Therefore, the present invention has been made in view of the above problems, and provides a recording apparatus capable of preventing a reduction in image quality due to a speed difference between an upstream roller pair and a downstream roller pair. Objective.

  In order to achieve the above object, the present invention is based on a recording head for ejecting liquid onto a recording medium, and a drive that is positioned upstream of the recording head in the recording medium conveyance direction and transmitted via a one-way clutch. A first roller pair for nipping and conveying the recording medium to the discharge position of the recording head at a first conveying speed, and a first roller pair positioned downstream of the recording head in the conveying direction and faster than the conveying speed of the first roller pair unit. The second roller pair that sandwiches and conveys the recording medium to the downstream side in the conveyance direction at two conveyance speeds, the first rotation detection unit that detects the rotation amount of the rollers of the first roller pair, and the second roller pair perform recording. Before the medium is sandwiched, the first roller pair is transporting the recording medium at the first transport speed, and the second roller pair is sandwiching the recording medium transported at the second transport speed. One roller pair is Wang When you are idle by Ikuratchi, characterized in that it comprises a control unit first rotation detecting unit controls the recording head to perform the discharge operation at the ejection timing in accordance with the amount of rotation detected a.

  According to the present invention, it is possible to prevent deterioration in image quality due to the speed difference between the upstream roller pair and the downstream roller pair.

FIG. 2 is a schematic cross-sectional view showing a schematic configuration for conveying a recording medium of the recording apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a driving configuration of a conveyance roller pair and a discharge roller pair of the recording apparatus according to the first embodiment of the invention. FIG. 2 is a block diagram illustrating a configuration of a control system of the recording apparatus according to the first embodiment of the present invention. 3 is a flowchart of recording apparatus liquid discharge control according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating recording medium conveyance of the recording apparatus according to the first embodiment of the invention. 3 is a timing chart of the recording apparatus according to the first embodiment of the invention. It is a typical sectional view showing a schematic structure of a recording device concerning a 2nd embodiment of the present invention. It is a block diagram which shows the structure of the control system of the recording device which concerns on 2nd Embodiment of this invention. 6 is a flowchart illustrating liquid discharge control of a recording apparatus according to a second embodiment of the invention. It is a timing chart which shows the switching timing of two encoder recordings of the recording apparatus which concerns on 2nd Embodiment of this invention. FIG. 11 is an enlarged view of a part of FIG. 10, and is an explanatory diagram for explaining the timing for switching the recording speed of the first encoder to the recording speed of the second encoder. It is a typical sectional view showing a schematic structure which conveys a recording medium of a recording device concerning a 3rd embodiment of the present invention. It is a typical sectional view showing a schematic structure which conveys a recording medium of a recording device concerning a 4th embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of recording medium conveyance of the recording apparatus 300 according to the first embodiment.

  The sheet S as a recording medium is conveyed in the sheet conveying direction A, and forms an image by ejecting ink droplets from the recording head 1 serving as a recording unit to the sheet S in accordance with a signal based on image information. In the present embodiment, a so-called line printer in which nozzles that eject ink droplets in the sheet width direction are arranged and fixed on the recording head 1 and image formation is performed while the sheet S is continuously conveyed will be described as an example. In this embodiment, the recording head 1 is a recording head for ejecting black (Bk), cyan (C), magenta (M), and yellow (Y) inks in order to perform full-color printing on the sheet S. 1Bk, 1C, 1M, and 1Y. These are arranged side by side along the sheet conveying direction A. Note that the number of colors, that is, the number of recording heads can be arbitrarily determined, and will be referred to simply as “recording head 1” in the following.

  Next, the conveyance configuration of the sheet S will be described. From the upstream side in the transport direction on the right side of FIG. 1, the sheet rear end detection sensor 6, the transport roller pair (upstream roller pair) 100 as the first roller pair, the sheet front end detection sensor 5, the recording head 1, and A discharge roller pair (downstream roller pair) 200 which is a second roller pair is disposed. A platen 9 that is provided with a suction fan (not shown) and can suck the sheet S is disposed on the opposite side of the recording head 1. The conveyance roller pair 100 includes a conveyance roller 2 and a pinch roller 7, and the conveyance roller 2 is rotated by the drive of the conveyance motor 13 (see FIG. 2) and is rotated to a nip with the abutting pinch roller 7. A conveying force is applied to the sandwiched sheet S. The discharge roller pair 200 includes a discharge roller 4 and a spur 8. Like the transport roller pair 100, the discharge roller 4 is rotated by the drive transmitted by the transport motor 13, and is in contact with the spur 8 that contacts the spur roller 8. A conveying force is applied to the sheet S sandwiched in the nip. At this time, the conveyance speed of the sheet S by the rotation of the discharge roller 4 is set to a conveyance speed that is about 5% faster than the conveyance speed of the sheet S by the rotation of the conveyance roller 2. Thus, in the process of transporting the sheet S, after the leading edge of the sheet S reaches the discharge roller pair 200 from the transport roller pair 100, the sheet S is bent between the transport roller pair 100 and the discharge roller pair 200. Is suppressed. This conveyance speed difference is set to a limit value that does not cause the conveyance speed of the discharge roller pair 200 to be slower than the conveyance speed of the sheet S by the conveyance roller pair 100 due to component tolerances, or the conveyance speed of the sheet S by the discharge roller pair 200 is set to 10 % Speed may be increased.

  FIG. 2 is a schematic diagram illustrating a driving configuration of the transport roller pair 100 and the discharge roller pair 200. The transport roller 2 has a rubber layer 21 formed on the surface of a shaft 20 made of a metal such as SUS material and is rotatably supported by a bearing 19. The discharge roller 4 is formed by dividing a rubber layer 23 on the surface of a shaft 22 made of a metal such as SUS material, and is rotatably supported by a bearing 24. A code wheel 3 having slits having a pitch proportional to the resolution when forming an image is fixed to the transport roller 2 by a code wheel fixing member 14. The encoder sensor 12, which is an optical sensor, detects the slit of the code wheel 3, and can detect the rotational speed of the transport roller 2 based on the detection result. Further, the ink ejection timing of the recording head 1 is determined by detecting the slit of the code wheel 3 by the encoder sensor 12. Further, the transport roller 2 is fixed with a transport roller gear 16 that is driven and transmitted from the transport motor 13. A one-way clutch 18 is fixed to the conveyance roller gear 16, and the driving force of the conveyance motor 13 is transmitted to the conveyance roller 2 via the one-way clutch 18. When the leading edge of the sheet S reaches the discharge roller pair 200 and the sheet S is pulled by the discharge roller 4 at a faster speed than the conveyance roller 2 rotated by the conveyance roller gear 16, the conveyance of the conveyance roller pair 100 sandwiching the sheet S is performed. The roller 2 is released from the locked state with the one-way clutch 18, the drive transmission from the conveyance motor 13 is cut off, and the conveyance roller 2 rotates idly, thereby following the conveyance speed of the discharge roller 4 for conveying the sheet S. It is configured to be rotatable. That is, the conveyance roller pair 100 is idled by the one-way clutch when the sandwiched sheet S (recording medium) is pulled downstream in the conveyance direction. The sheet leading edge detection sensor 5 detects the leading edge of the sheet S to be transported, and is used to start image recording after the transport roller pair 100 transports the sheet S for a predetermined time. The sheet trailing edge detection sensor 6 is used for detecting the timing of changing the ink ejection control during printing according to the present invention.

  FIG. 3 is a block diagram illustrating a configuration of a control system of the recording apparatus according to the first embodiment. In FIG. 3, the CPU 101 of the control unit 104 of the recording apparatus 300 executes control processing of the operation of the recording apparatus 300, data processing, and the like. The ROM 102 stores programs for executing these processing procedures, and the RAM 103 as a storage unit is used as a work area or the like in the course of executing those processing. The CPU 101 controls the recording head 1 and the conveyance motor 13 via the corresponding recording head control circuit 1A and motor driver 13A, respectively.

  The CPU 101 of the control unit 104 receives output signals from the sheet leading edge detection sensor 5, the sheet trailing edge detection sensor 6, and the encoder sensor 12. The CPU 101 sends a signal to the motor driver 13A according to the program stored in the ROM 102, and controls the sheet S conveying operation. Further, the CPU 101 performs image recording control for ejecting ink from the recording head 1 via the recording head control circuit 1 </ b> A so as to eject ink according to the output signal of the encoder sensor 12. The RAM 103 is a storage unit that can temporarily store data being instructed by the CPU 101, operation results, and the like. In this embodiment, the ink on the sheet S that is conveyed while being sandwiched and conveyed by the discharge roller pair 200 that does not include a code wheel. The discharge timing is obtained and stored.

  FIG. 4 is a flowchart illustrating change in ink ejection control for image recording of the recording apparatus 300 according to the first embodiment of the present invention. Hereinafter, the operation of changing the speed of each roller or sheet S during image recording and the ink ejection control will be described with reference to this flowchart. FIG. 5 is a schematic sectional view showing recording medium conveyance of the recording apparatus according to the first embodiment of the present invention. FIG. 6 is a timing chart of the recording apparatus according to the first embodiment of the invention. First, as a premise, the standby position where the sheet S waits before the start of printing is an arbitrary position from the conveying roller pair 100 to the sheet leading edge detection sensor 5 as shown in FIG. When printing is started, the CPU 101 of the control unit 104 starts control for driving the carry motor 13 (see FIG. 3) (S400). Specifically, as shown in FIG. 5A, the conveying roller 2 has a sheet S conveying speed of 200 mm / s, and the discharge roller 4 has a sheet S conveying speed of 210 mm / s. Each is driven. From this standby position, the sheet S is conveyed in the sheet conveyance direction A at a conveyance speed of 200 mm / s by the conveyance roller 2.

  The CPU 101 of the control unit 104 determines whether the leading edge detection sensor 5 has detected the leading edge of the sheet S (S401). If the determination is affirmative, the code wheel 3 that rotates in synchronization with the rotation of the conveying roller 2 is detected. It is determined from the encoder sensor 12 that the predetermined number of pulses have been detected after detecting the leading edge of the sheet S (S402). If this determination is affirmative, ink ejection is started (S403). The ink is ejected in synchronization with the rotation of the transport roller 2 corresponding to a transport speed of 200 mm / s, that is, in synchronization with the pulse output from the encoder sensor 12, and the ink is ejected in synchronization with the encoder pulse at this time. The speed is the first recording speed.

  Further, the CPU 101 of the control unit 104 determines whether the sheet S has been conveyed a predetermined distance (a predetermined number of pulses) from the sheet leading edge detection sensor 5 (S404). In step S404, as shown in FIG. 5B, the distance until the leading edge of the sheet S conveyed by the conveying roller pair 100 reaches the discharge roller pair 200 is set as a predetermined distance. Here, as illustrated in FIG. 5B, when the sheet S is sandwiched between the pair of conveyance rollers 100 and the pair of discharge rollers 200, the discharge roller is faster than the conveyance speed of the sheet S by the conveyance roller pair 100. Since the conveyance speed of the sheet S by the pair 200 is faster, the sheet S is pulled by the discharge roller pair 200. At this time, since the one-way clutch 18 is interposed in the transmission path from the conveyance motor 13 to the conveyance roller 2, the conveyance roller pair 100 is idled by the driving of the conveyance roller gear 16 being blocked by the one-way clutch 18. Further, as shown in the timing chart of FIG. 6, the conveyance speed of the sheet S at this time follows the movement of the sheet S that is 210 mm / s, which is the conveyance speed by the discharge roller pair 200, and the conveyance roller pair 100. The conveyance speed due to is also 210 mm / s. On the other hand, the ink ejection at this time is synchronized with the rotation of the conveying roller 2 so that the conveying speed is 210 mm / s followed by the movement of the sheet S, that is, synchronized with the pulse output from the encoder sensor 12. (Step S405). The speed at the timing of ejecting ink in synchronization with the encoder pulse at this time is defined as the second recording speed. At that time, when an image is formed on the sheet S, the rotation speed of the transport roller 2 varies. However, the ink ejection during this time is synchronized with the encoder pulse output from the encoder sensor 12, that is, synchronized with the rotation of the transport roller 2. The amount of deviation basically does not occur, and even if it occurs, it is a level that cannot be judged visually.

  Next, the CPU 101 of the control unit 104 detects the number of pulses that the leading edge of the sheet S reaches the discharge roller pair 200 by the encoder sensor 12 that detects the code wheel 3 that rotates in synchronization with the rotation of the transport roller 2. Then, based on the number of encoder pulses detected during a period during which a predetermined amount of conveyance is performed and the time required for conveyance during that period, the conveyance speed of the idle conveyance roller pair 100, that is, the conveyance speed of the discharge roller pair 200 is determined. Is obtained (S406). That is, in this embodiment, as shown in FIG. 6, the ink discharge timing performed after the trailing edge of the sheet S passes through the sheet trailing edge detection sensor 6 and before the trailing edge of the sheet S passes through the conveyance roller pair 100. The asynchronous recording speed described below, which is switched by the switching control, is obtained in advance. Then, the CPU 101 stores the transport speed obtained in step S406 in the RAM 103 (S407). In the present embodiment, the CPU 101 calculates 210 mm / s, which is equal to the conveyance speed by the discharge roller 4, as the average value of the conveyance speed within a certain period, and stores this. The fixed period for obtaining the average value of the conveyance speed is preferably a period in which the discharge roller 4 that is the driving roller of the discharge roller pair 200 rotates at least once in consideration of the surface deviation of the discharge roller 4. The recording speed at which ink is ejected at a timing corresponding to the transport speed at this time is defined as an asynchronous recording speed. The ejection control at the asynchronous recording speed is not performed in synchronization with the pulse of the encoder sensor 12, but the ink ejection control is performed at the timing of the recording speed determined according to the sheet conveyance speed at that time. In the recording synchronized with the encoder pulse, the pulse width is variable according to the conveyance speed, and the ink ejection is also varied accordingly to cope with the change in the conveyance speed. However, in recording at the asynchronous recording speed, a fixed pulse corresponding to the obtained transport speed is generated, and ink is ejected from the recording head 1 for each predetermined pulse.

  In step S408, it is determined whether the trailing edge detection sensor 6 has detected the trailing edge of the conveyed sheet S. If the determination is affirmative, the process proceeds to step S409. If the determination is negative, the process is repeated until the sheet trailing edge detection sensor 6 detects it. In step S409, it is determined whether or not a predetermined number of pulses have been detected from the encoder sensor 12. If the determination is affirmative, the process proceeds to step S410. On the other hand, if the determination is negative, the sheet S is conveyed until a predetermined number of pulses are detected. The predetermined pulse at this time is the number of pulses conveyed for a distance from when the trailing edge of the sheet S is detected by the sheet trailing edge detection sensor 6 to when the sheet S leaves the conveying position by the conveying roller pair 100. In step S <b> 410, the ink ejection is switched to the ink ejection at the conveyance speed corresponding to the asynchronous recording speed stored in the RAM 103 at a predetermined position between the sheet trailing edge detection sensor 6 and the conveyance roller pair 100. Specifically, the recording is switched from the pulse next to the last pulse of recording synchronized with the encoder pulse when the switching command is received to recording at a fixed pulse, that is, asynchronous recording speed. Thereafter, as shown in FIG. 5C, when the trailing end of the sheet S passes through the pair of conveying rollers 100, the conveying roller 2 loses the rotation speed of 210 mm / s, which is the conveying speed through the sheet S, and the one-way clutch 18 Is connected, the drive by the original transport motor 13 is transmitted, and the transport speed returns to the rotational speed of 200 mm / s. At this time, the sheet S is conveyed by the discharge roller 4 at a conveyance speed of 210 mm / s. Thus, the sheet S is stored in the RAM 103 until the trailing edge of the sheet S passes through the conveying roller pair 100 and the conveying speed of the sheet S is changed from 210 mm / s to 200 mm / s due to the rotation of the conveying roller pair 100. Ink is ejected from the recording head 1 at an asynchronous recording speed corresponding to 210 mm / s, and an image is recorded.

  As described above, the CPU 101 of the control unit 104 switches from the ink ejection control based on the first recording speed and the second recording speed to the ink ejection control based on the asynchronous recording speed. Perform before exiting. By doing so, it is possible to maintain good printing accuracy from the leading edge to the trailing edge of the sheet S even in the conveyance of the sheet S by both the upstream and downstream roller pairs having a speed difference, and the upstream roller pair and the downstream side It is possible to prevent a reduction in image quality due to a speed difference with the roller pair.

  In the present embodiment, the second recording speed is stored after the leading edge of the sheet S reaches the discharge roller pair 200 based on the detection result of the encoder sensor 12. However, a sheet end detection sensor is newly arranged on the downstream side of the discharge roller pair 200 and is discharged by the sheet end detection sensor on the downstream side of the discharge roller pair 200 without using the code wheel 3 and the encoder sensor 12. It may be determined that the leading edge of the sheet S has reached the roller pair 200.

  In the switching to the asynchronous recording speed, the trailing edge of the sheet S is switched between the sheet trailing edge detection sensor 6 and the conveying roller pair 100. However, any position may be used as long as the trailing edge of the sheet S passes through the conveying roller pair 100, for example, the asynchronous recording speed may be obtained and switched immediately.

  Further, in the present embodiment, after the trailing edge of the sheet S passes through the conveyance roller pair 100, the average conveyance speed obtained when the sheet S is conveyed while being sandwiched between the conveyance roller pair 100 and the discharge roller pair 200 is used. Although the ink ejection control is performed as the asynchronous recording speed, the asynchronous recording speed is not limited to this average transport speed, and the encoder sensor 12 detects when the transport is carried between the transport roller pair 100 and the discharge roller pair 200. The CPU 101 acquires and stores the pulse in the RAM 103 during a period in which the discharge roller 4 that is the driving roller of the discharge roller pair 200 rotates at least once, and after the trailing edge of the sheet has passed through the conveyance roller pair 100, the conveyance speed is increased. The CPU 101 may perform ink ejection control by using the encoder pulse as the stored value as the asynchronous recording speed without obtaining it.

(Second Embodiment)
Next, a recording apparatus according to the second embodiment of the invention will be described. Note that description of portions similar to those of the first embodiment is omitted.

  FIG. 7 is a schematic cross-sectional view showing a schematic configuration of a recording apparatus according to the second embodiment of the present invention. In the second embodiment, a one-way clutch 18 is fixed to the conveyance roller gear 16 to which the rotation of the conveyance motor 13 is transmitted as in the first embodiment, and the driving force of the conveyance motor 13 is transmitted via the one-way clutch 18. It is transmitted to the conveyance roller 2. Moreover, in 2nd Embodiment, it is the structure of what is called a double encoder which attached the code wheel 10 to the discharge roller 4. FIG. The encoder sensor of the transport roller 2 is a first encoder sensor 3B (see FIG. 8), and the encoder sensor of the discharge roller 4 is a second encoder sensor 10B (see FIG. 8). In the second embodiment, the asynchronous recording speed may be obtained as in the first embodiment, and the ejection control may not be performed based on the obtained asynchronous recording speed.

  FIG. 8 is a block diagram showing the configuration of the control system of the recording apparatus according to the second embodiment of the present invention. In FIG. 8, the CPU 101 of the control unit 104 receives output signals from the sheet leading edge detection sensor 5, the first encoder sensor 3B as the first rotation detection unit, and the second encoder sensor 10B as the second rotation detection unit. Entered. The CPU 101 sends a signal to the motor driver 13A in accordance with the program stored in the ROM 102, and controls the sheet S conveying operation. Further, the CPU 101 performs recording control for ejecting ink from the recording head 1 via the recording head control circuit 1 </ b> A so as to eject ink according to the output signals of the first encoder sensor 3 </ b> B and the second encoder sensor 10 </ b> B. Do.

  FIG. 9 is a flowchart illustrating liquid discharge control of the recording apparatus according to the second embodiment. Hereinafter, the changing operation of the rotation speed of each roller during the image recording, the conveyance speed of the sheet S, and the ink discharge control will be described with reference to this flowchart.

  Here, in the second embodiment, the process is the same as in the first embodiment until the sheet S reaches the discharge roller pair 200 and is nipped and conveyed. However, the CPU 101 does not stop after the sheet S reaches the discharge roller pair 200. The ink ejection control is switched from the output signal of the first encoder sensor 3B to the output signal of the second encoder sensor 10B. The timing at which the CPU 101 switches the encoder sensor may be switched anywhere from the position where the leading edge of the sheet S exceeds the discharge roller pair 200 and before the trailing edge of the sheet S passes the conveying roller pair 100. It is desirable to switch after delaying a predetermined number of pulses from the start of conveyance by the roller pair and waiting for the conveyance speed of both roller pairs to stabilize.

  FIG. 10 is a timing chart for explaining the switching timing of two encoder recordings. The conveyance roller pulse signal shown in FIG. 10 performs image recording with the first encoder while the conveyance speed is increased when the leading edge of the sheet S reaches the discharge roller pair 200, as in the first embodiment. When the trailing edge of the sheet S passes through the conveyance roller pair 100, the driven state is canceled and the rotation speed of the conveyance roller 2 returns. However, before the rotation speed returns, the CPU 101 performs recording in synchronization with the first encoder. Switching to synchronous recording with the second encoder. The synchronous recording switching between the first encoder and the second encoder will be described with reference to FIG. FIG. 11 is an enlarged view of a part of FIG. 10, and is an explanatory diagram for explaining the timing for switching the recording speed of the first encoder to the recording speed of the second encoder. When the CPU 101 detects the width of the latest transport roller encoder pulse as X (μm), it switches at least one pulse by switching the recording control from the first encoder to the second encoder at the rise timing of the discharge roller encoder pulse. Switching in error is possible. If the image recording resolution is 1200 dpi, it is possible to suppress the error to about 22 μm at the maximum. This can improve the resolution and further reduce the switching error by dividing one pulse. It is.

  As described above, the ink ejection control synchronized with the first encoder 3B, which is the first recording speed, and the ink ejection control synchronized with the second encoder 10B, which is the second recording speed, are both synchronized during recording. Thus, it is possible to control the ink discharge, and to maintain the ink discharge with high accuracy for a sheet whose conveyance speed during recording changes midway. Thereby, it is possible to prevent the image quality from being deteriorated due to the speed difference between the upstream roller pair and the downstream roller pair.

(Third embodiment)
Next, a recording apparatus according to the third embodiment will be described. A description of the same parts as those in the first embodiment will be omitted.

  FIG. 12 is a schematic cross-sectional view showing a schematic configuration for transporting a recording medium of a recording apparatus according to the third embodiment of the present invention. In the third embodiment, a one-way clutch 18 is fixed to the conveyance roller gear 16 to which the rotation of the conveyance motor 13 is transmitted as in the first embodiment, and the driving force of the conveyance motor 13 is transmitted via the one-way clutch 18. It is transmitted to the conveyance roller 2.

  A third encoder 11 is arranged on the platen 9, and the control system is the same as in the first embodiment. The third encoder 11 may be disposed anywhere between the recording head 1 and the conveyance roller pair 100, but the disturbance during conveyance is reduced when the third encoder 11 is disposed in the vicinity of the recording head 1 as shown in FIG. It is possible to improve the conveyance accuracy. Thereby, it is possible to prevent the image quality from being deteriorated due to the speed difference between the upstream roller pair and the downstream roller pair.

(Fourth embodiment)
Next, a recording apparatus according to the fourth embodiment will be described. A description of the same parts as those in the first and second embodiments is omitted.

  FIG. 13 is a schematic cross-sectional view showing a schematic configuration for conveying a recording medium of a recording apparatus according to the fourth embodiment of the present invention. As a configuration, the second embodiment and the third embodiment are combined. The third encoder 11 disposed between the recording head 1 and the conveying roller pair 100 is used, and the second code wheel 10 is used as the discharge roller 4. The control system is the same as in the second embodiment. With this configuration, the ink discharge control synchronized with the third encoder 11 which is the first recording speed during the image recording, the ink discharge control synchronized with the second encoder 10B which is the second recording speed, Ink ejection control synchronized with the encoder is possible. Further, by disposing the third encoder 11 in the vicinity of the recording head 1 as shown in FIG. 13, disturbance during conveyance can be reduced, and conveyance accuracy can be improved. Thereby, it is possible to prevent the image quality from being deteriorated due to the speed difference between the upstream roller pair and the downstream roller pair.

DESCRIPTION OF SYMBOLS 1 Recording head 2 Conveyance roller 3 Code wheel 4 Discharge roller 5 Sheet front end detection sensor 6 Sheet rear end detection sensor 7 Pinch roller 8 Spur 9 Platen 10 Code wheel B
DESCRIPTION OF SYMBOLS 11 3rd encoder 12 Encoder sensor 13 Conveyance motor 14 Code wheel fixing member 15 Motor gear 16 Conveyance roller gear 17 Discharge roller gear 18 One-way clutch 19 Bearing 20 Conveyance roller shaft 21 Rubber member 22 Discharge roller shaft 23 Rubber member 24 Bearing 100 Conveyance roller pair 200 Discharge Roller vs. S sheet

Claims (7)

A recording head for discharging liquid onto a recording medium;
The recording medium is positioned upstream of the recording head in the recording medium conveyance direction and the drive is transmitted to convey the sandwiched recording medium to the ejection position of the recording head at a first conveyance speed. A first roller pair idling by being pulled downstream in the conveying direction;
A second roller pair positioned downstream of the recording head in the transport direction and transporting the recording medium while being sandwiched downstream of the transport direction at a second transport speed higher than the first transport speed;
A first rotation detection unit for detecting information relating to the rotation speed of the rollers of the first roller pair;
When the first roller pair is transporting the recording medium at the first transport speed without the second roller pair sandwiching the recording medium, and when the second roller pair sandwiches the recording medium, the second roller pair sandwiches the recording medium. When the first roller pair is nipping the recording medium conveyed by the second roller pair and is idling, the discharge timing is based on the detection result of the first rotation detection unit. And a control unit for controlling the recording head so as to perform an ejection operation.   The recording apparatus according to claim 1, wherein the drive is transmitted to the first roller pair via a one-way clutch.   In the control unit, the second roller pair sandwiches the recording medium and transports the recording medium at the second transport speed, and the first roller pair sandwiches the recording medium transported by the second roller pair and idles. The conveyance speed of the recording medium to be conveyed is obtained based on the detection result of the first rotation detection unit, and the first roller pair does not sandwich the recording medium based on the obtained conveyance speed. The recording apparatus according to claim 1, wherein the recording head controls ejection timing of the recording head onto a recording medium that is sandwiched and conveyed by the second roller pair.   The obtained transport speed is a speed at which the recording medium is transported when the driving roller of the second roller pair rotates at least once when the first roller pair is idling. The recording apparatus according to claim 3.   In the control unit, the second roller pair sandwiches the recording medium and transports the recording medium at the second transport speed, and the first roller pair sandwiches the recording medium transported by the second roller pair and idles. The information detected by the first rotation detection unit is stored, and based on the information, the first roller pair does not pinch the recording medium and the second roller pair pinches and conveys the recording medium. The recording apparatus according to claim 1, wherein ejection timing of the recording head to the recording medium to be controlled is controlled.   The information is information detected by the first rotation detection unit when the driving roller of the second roller pair rotates at least once when the first roller pair is idling. The recording apparatus according to claim 5, wherein:   A second rotation detection unit configured to detect information about a rotation speed of the roller of the second roller pair, and the control unit includes the first roller pair before the rear end of the sheet passes through the first roller pair; 2. The control is performed to change the detection result of the first rotation detection unit to the detection result of the second rotation detection unit when the engine is idling and to perform a discharge operation. Alternatively, the recording apparatus according to claim 2.

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