JP6709250B2 - Recording device - Google Patents

Description

The present invention relates to a recording device that records an image on a recording medium that is conveyed.

In the recording medium conveyance path, ink is ejected from the recording head with respect to the recording medium conveyed by being nipped by the roller pair arranged on the upstream side of the recording head and the roller pair arranged on the downstream side of the recording head. There is a recording apparatus that discharges the ink to form an image on a recording medium. 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 pressure of the downstream roller pair is higher than the nip pressure of the upstream roller pair. The pressure is set low. As a result, when the recording medium is nipped by both roller pairs and conveyed, the recording medium is conveyed at the conveyance speed of the upstream roller pair with a high nip pressure, and the rotation speed is high but the nip pressure is low. The roller pair on the side slides on the recording medium, thereby applying tension to the conveyed recording medium and preventing the recording medium from bending between the roller pairs. However, in such a transport mechanism, when the trailing edge of the recording medium passes through the upstream roller pair, the transport speed of the recording medium up to that point is higher than that of the upstream roller pair by the downstream roller pair. At the conveyance speed, a large fluctuation in the speed of the recording medium occurs while the ink is being ejected from the recording head, so that the recording position deviates and the image quality deteriorates.

On the other hand, in Patent Document 1, encoders for detecting rotation are provided on each of the upstream and downstream roller pairs, and when the trailing end of the recording medium passes through the upstream roller pair, it occurs in both roller pairs. A speed difference is detected, and in response to the detection, the conveyance speed of the downstream roller pair is changed to a low speed equivalent to the conveyance speed of the upstream roller pair. Further, in Patent Document 2, encoders for detecting rotation are provided on each of the upstream and downstream roller pairs to detect the rotation of the roller pairs, but immediately after the trailing end of the recording medium leaves the upstream roller pair. The rear end of the recording medium is a virtual transport speed V3 calculated from the transport speed V1 of the upstream roller pair and the transport speed V2 of the downstream roller pair without using the actual measurement value of the encoder that cannot follow a rapid speed change. The ejection 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 Japanese Unexamined Patent Application Publication No. 2004-242242, in the configuration in which the trailing edge of the recording medium passes through the upstream roller pair and then the speed difference between both roller pairs is detected to switch the transport speed by the downstream roller pair, the transport speed is switched. In the meantime, the speed during switching may not match 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. Further, in Japanese Patent Laid-Open No. 2004-242242, discharge control is performed assuming that the recording medium is conveyed at the calculated virtual conveyance speed V3 for a predetermined period before and after the trailing end of the recording medium passes through the upstream roller pair, but the conveyance speed V3 is calculated. It is a virtual speed. Therefore, the transport speed V3 may be different from the actual transport speed, and the ink ejection timing and the transport speed may not match and the ink position on the recording medium may be displaced.

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a recording apparatus capable of preventing deterioration of image quality due to a speed difference between an upstream roller pair and a downstream roller pair. To aim.

In order to achieve the above object, the present invention provides a recording head for ejecting a liquid onto a recording medium, and a drive which is located on the upstream side of the recording head in the conveyance direction of the recording medium and which is transmitted through a one-way clutch. A first roller pair that nips and conveys the recording medium to the ejection position of the recording head at a first conveying speed, and a first roller pair that is located downstream of the recording head in the conveying direction and that is faster than the conveying speed of the first roller pair unit. A second roller pair that nips and conveys the recording medium downstream in the conveyance direction at two conveyance speeds, a first rotation detection unit that detects the amount of rotation of the rollers of the first roller pair, and a second roller pair record. Before nipping the medium, when the first roller pair conveys the recording medium at the first conveying speed, and when the second roller pair nips the recording medium conveyed at the second conveying speed, And a control unit for controlling the recording head so as to perform an ejection operation at an ejection timing corresponding to the rotation amount detected by the first rotation detection unit when one roller pair is idling by the one-way clutch. Characterize.

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

FIG. 3 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 showing a drive configuration of a conveyance roller pair and a discharge roller pair of the recording apparatus according to the first embodiment of the present invention. It is a block diagram showing 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 ejection control according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing recording medium conveyance of the recording apparatus according to the first embodiment of the present invention. 3 is a timing chart of the recording apparatus according to the first embodiment of the present 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 showing a configuration of a control system of a recording apparatus according to a second embodiment of the present invention. 8 is a flowchart showing liquid ejection control of the recording apparatus according to the second embodiment of the present invention. 8 is a timing chart showing switching timings of two encoder recordings of the recording apparatus according to the second embodiment of the present invention. FIG. 11 is an enlarged view of a part of FIG. 10 and is an explanatory diagram illustrating a timing at which the recording speed of the first encoder is switched to the recording speed of the second encoder. FIG. 9 is a schematic cross-sectional view showing a schematic configuration for carrying a recording medium of a recording apparatus according to a third embodiment of the present invention. FIG. 11 is a schematic cross-sectional view showing a schematic configuration for conveying a recording medium of a recording device according to a fourth 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 showing a schematic configuration of recording medium conveyance of the recording apparatus 300 according to the first embodiment.

The sheet S, which is a recording medium, is conveyed in the sheet conveying direction A, and an ink droplet is ejected from the recording head 1 as recording means onto the sheet S according to a signal based on image information to form an image. In the present embodiment, a so-called line printer will be described as an example in which nozzles that eject ink droplets are arrayed and fixed to the recording head 1 in the sheet width direction, and the image is formed while the sheet S is continuously conveyed. 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 conveyance direction A. Note that the number of colors, that is, the number of recording heads can be arbitrarily set, and will be generically referred to as "recording head 1" below.

Next, the transport configuration of the sheet S will be described. From the upstream side in the transport direction, which is the right side on the paper surface of FIG. 1, the sheet trailing edge detection sensor 6, the transport roller pair (upstream roller pair) 100 that is the first roller pair, the sheet leading edge detection sensor 5, the recording head 1, and A discharge roller pair (downstream roller pair) 200, which is a second roller pair, is arranged. A platen 9 that is provided with a suction fan (not shown) and is capable of adsorbing the sheet S is disposed on the opposite side of the recording head 1. The transport roller pair 100 is composed of a transport roller 2 and a pinch roller 7. The drive of the transport motor 13 (see FIG. 2) is transmitted to the transport roller 2 to rotate the nip between the pinch roller 7 and the abutting roller. A conveying force is applied to the sandwiched sheet S. Further, the discharge roller pair 200 is composed of the discharge roller 4 and the spur 8, and like the transport roller pair 100, the discharge roller 4 is rotated by the drive transmitted by the transport motor 13, and is rotated to contact the spur 8. A conveying force is applied to the sheet S nipped in the nip. At this time, the transport speed of the sheet S by the rotation of the discharge roller 4 is set to a transport speed about 5% faster than the transport speed of the sheet S by the rotation of the transport roller 2. As a result, during the process in which the sheet S is conveyed, after the leading edge of the sheet S reaches the discharge roller pair 200 from the conveyance roller pair 100, the sheet S is bent between the conveyance roller pair 100 and the discharge roller pair 200. Is suppressed. This conveyance speed difference is set to a limit value at which the conveyance speed of the discharge roller pair 200 does not become slower than the conveyance speed of the sheet S by the conveyance roller pair 100 due to component tolerance, or the conveyance speed of the sheet S by the discharge roller pair 200 is 10%. % May be increased.

FIG. 2 is a schematic diagram showing a drive configuration of the transport roller pair 100 and the discharge roller pair 200. The conveying roller 2 has a rubber layer 21 formed on the surface of a shaft 20 made of metal such as SUS material, and is rotatably supported by a bearing 19. A plurality of discharge rollers 4 are formed by dividing a rubber layer 23 on the surface of a shaft 22 made of metal such as SUS material, and are rotatably supported by bearings 24. A code wheel 3 having slits having a pitch proportional to the resolution when forming an image is fixed to the conveying 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 rotation speed of the transport roller 2 based on the detection result. In addition, the encoder sensor 12 detects the slit of the code wheel 3 to determine the ink ejection timing of the recording head 1. Further, the transport roller 2 is fixed with a transport roller gear 16 which is drive-transmitted from the transport motor 13. A one-way clutch 18 is fixed to the transport roller gear 16, and the driving force of the transport motor 13 is transmitted to the transport roller 2 via the one-way clutch 18. When the leading end of the sheet S reaches the discharge roller pair 200 and the sheet S is pulled by the discharge roller 4 at a speed faster than the rotation of the transport roller 2 rotated by the transport roller gear 16, the transport roller pair 100 that holds the sheet S is transported. The roller 2 is released from the locked state with the one-way clutch 18, the drive transmission from the carry motor 13 is cut off, and the carry roller 2 idles to follow the carry speed of the discharge roller 4 for carrying the sheet S. It is configured to be rotatable. That is, when the sheet S (recording medium) to be sandwiched is pulled to the downstream side in the transport direction, the transport roller pair 100 idles due to the one-way clutch. The sheet leading edge detection sensor 5 is used to detect the leading edge of the conveyed sheet S and to start image recording after the pair of conveying rollers 100 conveys the sheet S for a predetermined period. The sheet trailing edge detection sensor 6 is used to detect the timing of changing the ink ejection control during printing according to the present invention.

FIG. 3 is a block diagram showing the configuration of the 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 operations of the recording apparatus 300, data processing, and the like. A program for executing those processing procedures is stored in the ROM 102, and the RAM 103, which is a storage unit, is used as a work area or the like in the process of executing those processing. The CPU 101 controls the recording head 1 and the carry motor 13 via the corresponding recording head control circuit 1A and motor driver 13A.

Output signals of the sheet front end detection sensor 5, the sheet rear end detection sensor 6, and the encoder sensor 12 are input to the CPU 101 of the control unit 104. Then, the CPU 101 sends a signal to the motor driver 13A in accordance with the program stored in the ROM 102 to control the conveyance operation of the sheet S. The CPU 101 also performs image recording control for ejecting ink from the recording head 1 via the recording head control circuit 1A so that ink is ejected according to the output signal of the encoder sensor 12. The RAM 103 is a storage unit in which the CPU 101 can temporarily store the data in the command, the calculation result, and the like, and in the present embodiment, the ink to the sheet S that is sandwiched and conveyed by the discharge roller pair 200 having no code wheel is used. The ejection timing is determined and stored.

FIG. 4 is a flowchart showing a 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 and the sheet S during image recording and the ink ejection control will be described with reference to this flowchart. Further, FIG. 5 is a schematic cross-sectional view showing the recording medium conveyance of the recording apparatus according to the first embodiment of the present invention. Further, FIG. 6 is a timing chart of the recording apparatus according to the first embodiment of the present invention. First, as a premise, the standby position where the sheet S stands by before printing is started is an arbitrary position from the conveyance roller pair 100 to the sheet front end detection sensor 5 with the sheet front end 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 transport roller 2 is configured to set the sheet S at a transport rate of 200 mm/s, and the discharge roller 4 is configured to set the sheet S at a transport rate of 210 mm/s. Each is driven. From this standby position, the sheet S is transported in the sheet transport direction A at a transport speed of 200 mm/s by the transport roller 2.

The CPU 101 of the control unit 104 determines whether the leading edge of the sheet S is detected by the sheet leading edge detection sensor 5 (S401), and if the determination is affirmative, the code wheel 3 that rotates in synchronization with the rotation of the transport roller 2 is detected. The encoder sensor 12 determines whether a predetermined number of pulses has been detected after the leading edge of the sheet S is detected (S402). If this determination is affirmative, ink ejection is started (S403). Ink ejection is performed in synchronization with the rotation of the conveyance roller 2 corresponding to the conveyance speed of 200 mm/s, that is, in synchronization with the pulse output from the encoder sensor 12, and the ink ejection timing is synchronized 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 (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 to a predetermined distance. Here, as shown in FIG. 5B, when the sheet S is nipped by both the transport roller pair 100 and the discharge roller pair 200, the discharge roller is faster than the transport speed of the sheet S by the transport roller pair 100. Since the conveyance speed of the sheet S by the pair 200 is higher, the sheet S is pulled by the discharge roller pair 200. At this time, since the one-way clutch 18 is interposed in the transfer roller 2 from the transfer motor 13 in the transfer roller 2, the transfer roller pair 100 rotates idly because the drive of the transfer roller gear 16 is blocked by the one-way clutch 18. In addition, as shown in the timing chart of FIG. 6, the transport speed of the sheet S at this time follows the movement of the sheet S at the transport speed of 210 mm/s by the discharge roller pair 200, and follows the transport roller pair 100. The transport speed due to is also 210 mm/s. On the other hand, the ejection of the ink at this time is in synchronization with the rotation of the transport roller 2 that makes the transport speed 210 mm/s which is made to follow the movement of the sheet S, that is, in synchronization 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, the rotational speed of the transport roller 2 changes while the image is formed on the sheet S. However, since the ink ejection during this period is in synchronization with the encoder pulse output from the encoder sensor 12, that is, in synchronization with the rotation of the conveyance roller 2, the ink ejection in the conveyance direction of the dots recorded on the sheet S is performed. Basically, the amount of deviation does not occur, and even if it occurs, it is insignificant, so it cannot be visually judged.

Next, the CPU 101 of the control unit 104 detects the number of pulses at which 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 in which a predetermined amount of conveyance is performed and the time required for the conveyance in that period, the conveyance speed of the idling conveyance roller pair 100, that is, the conveyance speed of the discharge roller pair 200. Is calculated (S406). That is, in the present embodiment, as shown in FIG. 6, the ink ejection timing that is performed after the trailing edge of the sheet S has passed the sheet trailing edge detection sensor 6 and before the trailing edge of the sheet S leaves the transport roller pair 100. The asynchronous recording speed, which will be described below, which can be 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 transport speed of the discharge roller 4, as the average transport speed within a certain period, and stores this. The constant period for obtaining the average value of the transport speed is preferably a period in which the discharge roller 4 which is the driving roller of the discharge roller pair 200 makes at least one rotation in consideration of the surface deviation of the discharge roller 4. A 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 of 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 obtained according to the sheet conveyance speed at that time. Incidentally, in the recording synchronized with the encoder pulse, the pulse width is variable according to the transport speed, and the ink ejection is also varied accordingly to respond to the change in the transport speed. However, in the case of 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 every predetermined pulse.

Further, in step S408, it is determined whether the sheet 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, while if the determination is negative, the process is repeated until the sheet trailing edge detection sensor 6 detects. In step S409, it is determined whether or not a predetermined number of pulses have been detected by the encoder sensor 12, and 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 that are conveyed 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 exits the transportation position by the transportation roller pair 100. Then, in step S410, ink ejection is switched at a predetermined position between the sheet trailing edge detection sensor 6 and the conveyance roller pair 100 at a conveyance speed timing corresponding to the asynchronous recording speed stored in the RAM 103. Specifically, the fixed pulse, that is, the recording at the asynchronous recording speed, is switched from the pulse next to the last pulse of the recording synchronized with the encoder pulse when the switching command is received. Then, as shown in FIG. 5C, when the trailing edge of the sheet S passes through the pair of transport rollers 100, the transport roller 2 loses the rotation speed of 210 mm/s, which is the transport speed through the sheet S, and the one-way clutch 18 Is connected, the original drive of the transport motor 13 is transmitted, and the transport speed returns to 200 mm/s. At this time, the sheet S is transported by the discharge roller 4 at a transport speed of 210 mm/s. Thus, by the time the trailing edge of the sheet S passes through the pair of transport rollers 100 and the transport speed of the sheet S due to the rotation of the pair of transport rollers 100 changes from 210 mm/s to 200 mm/s, it is stored in the RAM 103 and transported. Ink is ejected from the recording head 1 to record an image at an asynchronous recording speed corresponding to 210 mm/s.

As described above, the CPU 101 of the control unit 104 switches from the ink ejection control at the first recording speed and the second recording speed to the ink ejection control at the asynchronous recording speed, and the trailing end of the sheet S uses the conveyance roller pair 100. Do it before you leave. By doing so, it is possible to maintain good printing accuracy from the leading edge to the trailing edge of the sheet S even when the sheet S is conveyed by both the upstream side roller pair and the downstream side roller pair having a speed difference. It is possible to prevent the deterioration of image quality due to the speed difference between the roller pair.

In the present embodiment, the timing for storing the second recording speed is set after the leading edge of the sheet S reaches the discharge roller pair 200 according to the detection result of the encoder sensor 12. However, a sheet edge detection sensor is newly arranged on the downstream side of the discharge roller pair 200 so that the sheet edge detection sensor on the downstream side of the discharge roller pair 200 does not use 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.

Further, in 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 conveyance roller pair 100. However, it may be changed anywhere after the asynchronous recording speed has been obtained, as long as the trailing edge of the sheet S passes through the pair of transport rollers 100.

Further, in the present embodiment, after the trailing edge of the sheet S has passed through the pair of transport rollers 100, the sheet S is sandwiched between the pair of transport rollers 100 and the pair of discharge rollers 200 and is transported by the average transport speed determined when the sheet S is transported. Although the ink ejection control is performed as the asynchronous recording speed, the asynchronous recording speed is not limited to this average conveyance speed, and an encoder detected by the encoder sensor 12 when the paper is nipped and conveyed by the conveyance 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 drive roller of the discharge roller pair 200 makes at least one rotation, and after the trailing edge of the sheet leaves the transport roller pair 100, the transport speed is changed. The CPU 101 may control the ink ejection by setting the encoder pulse as the stored value as an asynchronous recording speed without obtaining it.

(Second embodiment)
Next, a recording apparatus according to the second embodiment of the present invention will be described. The description of the same parts as those in the first embodiment will be omitted.

FIG. 7 is a schematic cross-sectional view showing a schematic configuration of a recording device according to the second embodiment of the invention. In the second embodiment, as in the first embodiment, the one-way clutch 18 is fixed to the transport roller gear 16 to which the rotation of the transport motor 13 is transmitted, and the driving force of the transport motor 13 is supplied via the one-way clutch 18. It is transmitted to the transport roller 2. Further, the second embodiment has a so-called double encoder configuration in which the discharge roller 4 is provided with the code wheel 10. 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, unlike the first embodiment, it is not necessary to obtain the asynchronous recording speed and perform ejection control 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 the output signals of 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. Is entered. Then, the CPU 101 sends a signal to the motor driver 13A according to the program in the ROM 102 to control the sheet S carrying operation. Further, the CPU 101 performs recording control for ejecting ink from the recording head 1 via the recording head control circuit 1A so as to eject ink in accordance with the output signals of the first encoder sensor 3B and the second encoder sensor 10B. To do.

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

Here, in the second embodiment, the process is the same as that in the first embodiment until the sheet S reaches the discharge roller pair 200, and is nipped and conveyed. However, after the sheet S reaches the discharge roller pair 200, the CPU 101 , 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 from a position where the front end of the sheet S exceeds the discharge roller pair 200 to before the rear end of the sheet S passes through the transport roller pair 100. It is desirable to delay the conveyance by the roller pair by a predetermined number of pulses and wait for the conveyance speed of both roller pairs to stabilize before switching.

FIG. 10 is a timing chart explaining the switching timing of two encoder recordings. With the conveyance roller pulse signal shown in FIG. 10, when the leading edge of the sheet S reaches the discharge roller pair 200 as in the first embodiment, the first encoder performs image recording while the conveyance speed increases. When the trailing edge of the sheet S passes through the pair of conveyance rollers 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 synchronizes with the first encoder during recording. Switching to synchronous recording with the second encoder. Switching of the synchronous recording 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 of switching the recording speed of the first encoder to the recording speed of the second encoder. When the CPU 101 detects that the width of the most recent conveyance roller encoder pulse is X (μm), the recording control is switched from the first encoder to the second encoder at the rising timing of the discharge roller encoder pulse, so that at least one pulse is generated. Switching is possible in error. If the image recording resolution is 1200 dpi, it is possible to suppress the error to about 22 μm at maximum, which can improve the resolution and further reduce the switching error by dividing one pulse. Is.

As described above, during recording, the ink ejection control synchronized with the first encoder 3B having the first recording speed and the ink ejection control synchronized with the second encoder 10B having the second recording speed are both synchronized. The ink ejection control can be performed, and the ink ejection can be maintained with high accuracy on the sheet whose conveyance speed during recording changes midway. As a result, it is possible to prevent deterioration of image quality due to a speed difference between the upstream roller pair and the downstream roller pair.

(Third Embodiment)
Next, a recording device according to the third embodiment will be described. The 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 conveying a recording medium of the recording apparatus according to the third embodiment of the present invention. In the third embodiment, as in the first embodiment, the one-way clutch 18 is fixed to the conveyance roller gear 16 to which the rotation of the conveyance motor 13 is transmitted, and the driving force of the conveyance motor 13 is transmitted via the one-way clutch 18. It is transmitted to the transport roller 2.

The 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 arranged anywhere between the recording head 1 and the conveyance roller pair 100, but if the third encoder 11 is arranged near the recording head 1 as shown in FIG. 12, the disturbance during conveyance is reduced. It is possible to further improve the transportation accuracy. As a result, it is possible to prevent deterioration of image quality due to a speed difference between the upstream roller pair and the downstream roller pair.

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

FIG. 13 is a schematic cross-sectional view showing a schematic configuration for conveying a recording medium of a recording device according to the fourth embodiment of the present invention. The configuration is a combination of the second embodiment and the third embodiment, and the third encoder 11 arranged between the recording head 1 and the conveying roller pair 100 is used, and the discharge roller 4 is provided with the second code wheel 10. The control system is the same as that of the second embodiment. With this configuration, ink ejection control synchronized with the third encoder 11 having the first recording speed during image recording, ink ejection control synchronized with the second encoder 10B having the second recording speed, and Ink ejection control can be performed in synchronization with the encoder. Further, by disposing the third encoder 11 in the vicinity of the recording head 1 as shown in FIG. 13, it is possible to reduce disturbance during conveyance and improve conveyance accuracy. As a result, it is possible to prevent deterioration of image quality due to a speed difference between the upstream roller pair and the downstream roller pair.

1 Recording Head 2 Conveying Roller 3 Code Wheel 4 Discharging Roller 5 Sheet Leading Edge Detection Sensor 6 Sheet Trailing Edge Detection Sensor 7 Pinch Roller 8 Spur 9 Platen 10 Code Wheel B
11 Third encoder 12 Encoder sensor 13 Conveying motor 14 Code wheel fixing member 15 Motor gear 16 Conveying roller gear 17 Discharging roller gear 18 One-way clutch 19 Bearing 20 Conveying roller shaft 21 Rubber member 22 Discharging roller shaft 23 Rubber member 24 Bearing 100 Conveying roller pair 200 Discharging Roller pair S sheet

Claims (7)

A recording head for ejecting a liquid onto a recording medium,
The recording medium is positioned on the upstream side of the recording head in the conveyance direction of the recording medium, and the driving force is transmitted to convey the nipping recording medium to the ejection position of the recording head at the first conveying speed. A first roller pair that idles by being pulled to the downstream side in the transport direction;
A second roller pair located downstream of the recording head in the transport direction and configured to sandwich and transport the recording medium downstream in the transport direction at a second transport speed higher than the first transport speed;
A first rotation detection unit that detects information about the rotation speed of the rollers of the first roller pair;
When the first roller pair conveys the recording medium at the first conveying speed without the second roller pair sandwiching the recording medium, and when the second roller pair sandwiches the recording medium, the second roller pair holds the recording medium. At the ejection timing based on the detection result of the first rotation detection unit when the recording medium is conveyed at the conveyance speed and the first roller pair holds the recording medium conveyed by the second roller pair and is idling. A recording apparatus, comprising: a control unit that controls the recording head to perform an ejection operation. The recording apparatus according to claim 1, wherein the drive force is transmitted to the first roller pair via a one-way clutch. In the control unit, the second roller pair nips a recording medium and conveys the recording medium at the second conveying speed, and the first roller pair nips the recording medium conveyed by the second roller pair and idles. While the recording medium is moving, the conveyance speed of the recording medium to be conveyed is calculated based on the detection result of the first rotation detection unit, and the first roller pair does not nip the recording medium based on the calculated conveyance speed. The recording apparatus according to claim 1, wherein the ejection timing of the recording head onto the recording medium that is nipped and conveyed by the second roller pair is controlled. The obtained transport speed is a speed at which the recording medium is transported when the drive-side roller of the second roller pair makes at least one rotation while the first roller pair is idling. The recording device according to claim 3. In the control unit, the second roller pair nips a recording medium and conveys the recording medium at the second conveying speed, and the first roller pair nips the recording medium conveyed by the second roller pair and idles. The first rotation detection unit, the information stored in the first rotation detection unit is stored. Based on the information, the first roller pair does not hold the recording medium and the second roller pair holds the recording medium and conveys the recording medium. The recording apparatus according to claim 1, wherein the ejection timing of the recording head onto the recording medium is controlled. The information is information detected by the first rotation detection unit when the drive-side roller of the second roller pair makes at least one rotation while the first roller pair is idling. The recording apparatus according to claim 5, wherein the recording apparatus is a recording apparatus. A second rotation detection unit that detects information about the rotation speed of the rollers of the second roller pair is provided, and the control unit is configured to detect the information about the first roller pair before the trailing edge of the sheet passes through the first roller pair. 2. The discharge result is controlled by changing the detection result of the first rotation detection unit when the engine is idling to the detection result of the second rotation detection unit. Alternatively, the recording device according to claim 2.

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